WO2014199782A1 - Anode active material for electrical device, and electrical device using same - Google Patents

Abstract

Provided is an anode active material for an electrical device such as a lithium ion secondary battery and having high cycling durability. The anode active material for an electrical device contains an alloy represented by chemical formula (1): Si_xSn_yM_zA_a, where in chemical formula (1), M is at least one metal selected from the group consisting of Ti, Zn, C, and a combination thereof, A is unavoidable impurities, and x,y,z, and a represent mass% values, where 0 < x < 100, 0 < y < 100, 0 < z < 100, 0 ≤ a < 0.5, and x+y+z+a = 100. A carbon material is carried at the surface of the alloy.

Description

Negative electrode active material for electric device, and electric device using the same

The present invention relates to a negative electrode active material for an electrical device, and an electrical device using the same. The negative electrode active material for an electric device according to the present invention and an electric device using the same are, for example, driving power sources and auxiliary power sources for motors of vehicles such as electric vehicles, fuel cell vehicles and hybrid electric vehicles as secondary batteries and capacitors. Used for

In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide is strongly desired. In the automobile industry, there are high expectations for reduction of carbon dioxide emissions by the introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs), and electric devices such as motor drive secondary batteries hold the key to their practical application Development is actively conducted.

As a motor drive secondary battery, it is required to have extremely high output characteristics and high energy as compared with a consumer lithium ion secondary battery used for a mobile phone, a notebook personal computer and the like. Therefore, a lithium ion secondary battery having the highest theoretical energy among all the batteries has attracted attention, and is currently being rapidly developed.

In general, a lithium ion secondary battery comprises a positive electrode obtained by applying a positive electrode active material etc. on both sides of a positive electrode current collector using a binder, and a negative electrode obtained by applying a negative electrode active material etc. on both sides of a negative electrode current collector using a binder Are connected via the electrolyte layer and stored in the battery case.

Heretofore, carbon / graphite based materials which are advantageous in terms of the life and cost of charge / discharge cycles have been used for the negative electrode of lithium ion secondary batteries. However, in the case of a carbon / graphite negative electrode material, charge and discharge are performed by insertion and extraction of lithium ions into the graphite crystal, so the charge and discharge capacity of 372 mAh / g or more of theoretical capacity obtained from LiC ₆ which is the maximum lithium introduction compound There is a drawback that can not be obtained. For this reason, it is difficult to obtain the capacity and energy density that satisfy the level of practical use of the vehicle application with the carbon / graphite based negative electrode material.

On the other hand, a battery using a material that is alloyed with Li for the negative electrode is expected to be a negative electrode material for use in vehicles because the energy density is improved as compared to conventional carbon / graphite based negative electrode materials. For example, the Si material occludes and releases _4.4 mol of lithium ion per mol as in the following reaction formula (A) in charge and discharge, and in Li ₂₂ Si ₅ (= Li _4.4 Si), the theoretical capacity is 2100 mAh / g. Furthermore, it has an initial capacity as high as 3200 mAh / g when calculated per Si weight.

However, a lithium ion secondary battery using a material that is alloyed with Li for the negative electrode has a large amount of expansion and contraction at the negative electrode during charge and discharge. For example, the volume expansion when occluding Li ions is about 1.2 times in the case of a graphite material, while in the case of Si material, when Si and Li are alloyed, it changes from an amorphous state to a crystalline state and a large volume change There is a problem of reducing the cycle life of the electrode to cause (about 4 times). In the case of the Si negative electrode active material, the capacity and the cycle durability are in a trade-off relationship, and there is a problem that it is difficult to improve the cycle durability while exhibiting a high capacity.

In order to solve such problems, a negative electrode active material for a lithium ion secondary battery including an amorphous alloy having a formula; Si _x M _y Al _z has been proposed (for example, JP-A-2009-517850 (International Publication 2007/064531))). Here, in the formula, x, y, z represent atomic percent values, x + y + z = 100, x 55 55, y <22, z> 0, M is Mn, Mo, Nb, W, Ta, Fe, Cu, It is a metal consisting of at least one of Ti, V, Cr, Ni, Co, Zr, and Y. In the invention described in JP-A-2009-517850, it is described that, in addition to the high capacity, a good cycle life is exhibited by minimizing the content of the metal M in the paragraph “0008”. .

However, the formula described in JP-T 2009-517850 Patent Publication (WO _{2007/064531);} For Si _x M y Al _z lithium ion secondary battery using the anode having an amorphous alloy having a good Although it can be said that it can show cycle durability, it can not be said that cycle durability is sufficient.

Then, the objective of this invention is providing the negative electrode active material for electric devices, such as a lithium ion secondary battery which has high cycle durability.

The present inventors diligently studied to solve the above-mentioned problems. As a result, it is found that the above-mentioned problems can be solved by using a ternary Si alloy which is a combination of predetermined elements and has a predetermined composition and further supporting a carbon-based material on the surface of the alloy. The present invention has been completed.

That is, the present invention relates to a negative electrode active material for an electric device. At this time, the negative electrode active material for an electric device has the following chemical formula (1):

(In the above chemical formula (1),
M is at least one metal selected from the group consisting of Ti, Zn, C, and a combination thereof,
A is an unavoidable impurity,
x, y, z and a represent the values of mass%, where 0 <x <100, 0 <y <100, 0 <z <100 and 0 ≦ a <0.5, x + y + z + a It is = 100. )
It is characterized in that it contains an alloy represented by Another feature is that the carbon-based material is supported on the surface of the alloy.

BRIEF DESCRIPTION OF THE DRAWINGS It is the cross-sectional schematic which represented typically the outline | summary of the lamination | stacking flat non-bipolar lithium ion secondary battery which is one typical embodiment of the electric device which concerns on this invention. In FIG. 1, 10 is a lithium ion secondary battery (stacked battery); 11 is a negative electrode current collector; 12 is a positive electrode current collector; 13 is a negative electrode active material layer; 15 is a positive electrode active material layer; Reference numeral 17 denotes an electrolyte layer, 19 denotes a single cell layer, 21 denotes a power generation element, 25 denotes a negative electrode current collector plate, 27 denotes a positive electrode current collector plate, and 29 denotes a battery exterior material (laminated film). BRIEF DESCRIPTION OF THE DRAWINGS It is the perspective view which represented typically the external appearance of the lamination-type flat lithium ion secondary battery which is typical embodiment of the electric device which concerns on this invention. In FIG. 2, 50 represents a lithium ion secondary battery (laminated battery); 57 represents a power generation element; 58 represents a negative electrode current collector; 59 represents a positive electrode current collector; and 52 represents a battery exterior material (laminate film) Respectively. It is a ternary composition chart which plots and shows the alloy component formed into a film by the reference example A with the preferable composition range of the Si-Sn-Ti type-alloy which comprises the negative electrode active material for electric devices of this invention. It is a ternary composition figure which shows the more preferable composition range of the Si-Sn-Ti type-alloy which comprises the negative electrode active material for electric devices of this invention. It is a ternary composition figure which shows the further more preferable composition range of the Si-Sn-Ti type | system | group alloy which comprises the negative electrode active material for electric devices of this invention. It is a ternary composition diagram which shows the especially preferable composition range of the Si-Sn-Ti type | system | group alloy which comprises the negative electrode active material for electric devices of this invention. It is a figure which shows the influence of the negative electrode active material alloy composition which acts on the initial stage discharge capacity of the battery obtained by the reference example A. It is a figure which shows the influence of the negative electrode active material alloy composition on the discharge capacity maintenance factor of the 50th cycle of the battery obtained by the reference example A. FIG. It is a figure which shows the influence of the negative electrode active material alloy composition on the discharge capacity maintenance factor of the 100th cycle of the battery obtained by the reference example A. FIG. It is a ternary composition chart which plots and shows the alloy component formed into a film by the reference example B with the preferable composition range of Si-Sn-Zn type alloy which comprises the negative electrode active material for electric devices of this invention. It is a ternary composition figure which shows the more preferable composition range of Si-Sn-Zn type alloy which comprises the negative electrode active material for electric devices of this invention. It is a ternary composition figure which shows the further more preferable composition range of the Si-Sn-Zn type alloy which comprises the negative electrode active material for electric devices of this invention. It is a ternary composition figure which shows the especially preferable composition range of the Si-Sn-Zn type alloy which comprises the negative electrode active material for electric devices of this invention. It is drawing which shows the influence of the negative electrode active material alloy composition on the initial stage discharge capacity of the battery obtained by the reference example B. FIG. It is drawing which shows the relationship between the discharge capacity maintenance factor of the 50th cycle of the battery obtained by the reference example B, and an anode active material alloy composition. It is a figure which shows the relationship of the discharge capacity maintenance factor of a 100th cycle of the battery obtained by the reference example B, and an anode active material alloy composition. It is a ternary composition chart which plots and shows the alloy component formed into a film by the reference example C with the preferable composition range of the Si-Sn-C type | system | group alloy which comprises the negative electrode active material for electric devices of this invention. It is a ternary composition figure which shows the more preferable composition range of the Si-Sn-C type | system | group alloy which comprises the negative electrode active material for electric devices of this invention. It is a ternary composition figure which shows the further more preferable composition range of the Si-Sn-C type | system | group alloy which comprises the negative electrode active material for electric devices of this invention. It is a ternary composition figure which shows the especially preferable composition range of the Si-Sn-C type | system | group alloy which comprises the negative electrode active material for electric devices of this invention. It is a figure which shows the influence of the negative electrode active material alloy composition on the initial stage discharge capacity of the battery obtained by the reference example C. FIG. It is a figure which shows the influence of the negative electrode active material alloy composition on the discharge capacity maintenance factor of the 50th cycle of the battery obtained by the reference example C. FIG. It is a figure which shows the influence of the negative electrode active material alloy composition on the discharge capacity maintenance factor of the 100th cycle of the battery obtained by the reference example C. FIG. It is a color photograph which shows the mapping result by Auger electron spectroscopy of the carbon-coated Si alloy of Example 7.

Hereinafter, embodiments of a negative electrode active material for an electric device of the present invention and an electric device using the same will be described with reference to the drawings. However, the technical scope of the present invention should be determined based on the description of the claims, and is not limited to the following embodiments. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Also, the dimensional proportions of the drawings are exaggerated for the convenience of the description, and may differ from the actual proportions.

Hereinafter, the basic configuration of an electrical device to which the negative electrode active material for an electrical device of the present invention can be applied will be described using the drawings. In the present embodiment, a lithium ion secondary battery is described as an example of the electric device. In the present invention, the “electrode layer” means a mixture layer containing a negative electrode active material, a binder, and, if necessary, a conductive auxiliary, but is also referred to as a “negative electrode active material layer” in the description of this specification. Sometimes. Similarly, the electrode layer on the positive electrode side is also referred to as a “positive electrode active material layer”.

First, a negative electrode for a lithium ion secondary battery, which is a representative embodiment of a negative electrode including the negative electrode active material for an electric device according to the present invention, and a lithium ion secondary battery using the same High energy density, high power density can be achieved. Therefore, the lithium ion secondary battery using the negative electrode active material for a lithium ion secondary battery of the present embodiment is excellent for use as a driving power supply or an auxiliary power supply of a vehicle. As a result, it can be suitably used as a lithium ion secondary battery for driving power supply of a vehicle. In addition to this, it is sufficiently applicable to lithium ion secondary batteries for mobile devices such as mobile phones.

That is, the lithium ion secondary battery to be a target of the present embodiment may be one using the negative electrode active material for the lithium ion secondary battery of the present embodiment described below, and the other constituent requirements will be described. It should not be particularly limited.

For example, when the lithium ion secondary battery is distinguished by form and structure, it can be applied to any conventionally known form and structure such as a laminated (flat) battery and a wound (cylindrical) battery. It is a thing. By employing a laminated (flat type) battery structure, long-term reliability can be secured by seal technology such as simple thermocompression bonding, which is advantageous in terms of cost and workability.

In addition, when viewed from the electrical connection form (electrode structure) in a lithium ion secondary battery, it can be applied to both non-bipolar (internal parallel connection type) batteries and bipolar (internal series connection type) batteries. It is a thing.

When it distinguishes with the kind of electrolyte layer in a lithium ion secondary battery, the solution electrolyte type battery using solution electrolytes, such as non-aqueous electrolyte solution, in the electrolyte layer, the polymer battery using polymer electrolyte in the electrolyte layer, etc. It can be applied to any of the conventionally known electrolyte layer types. The polymer battery is further divided into a gel electrolyte type battery using a polymer gel electrolyte (also simply referred to as a gel electrolyte), and a solid polymer (all solid) type battery using a polymer solid electrolyte (also simply referred to as a polymer electrolyte). Be

Therefore, in the following description, a non-dipolar (internal parallel connection type) lithium ion secondary battery using the negative electrode active material for a lithium ion secondary battery of the present embodiment will be described in a very simple manner using the drawings. However, the technical scope of the lithium ion secondary battery of the present embodiment should not be limited to these.

<Overall structure of battery>
FIG. 1 schematically shows the entire structure of a flat (stacked) lithium ion secondary battery (hereinafter, also simply referred to as “stacked battery”), which is a representative embodiment of the electrical device of the present invention. It is the cross-sectional schematic represented.

As shown in FIG. 1, the laminated battery 10 of this embodiment has a structure in which a substantially rectangular power generating element 21 in which the charge and discharge reaction actually proceeds is sealed inside a laminate sheet 29 which is an exterior body. . Here, in the power generation element 21, the positive electrode in which the positive electrode active material layer 15 is disposed on both sides of the positive electrode current collector 12, the electrolyte layer 17, and the negative electrode active material layer 13 on both sides of the negative electrode current collector 11. It has the structure which laminated | stacked the negative electrode. Specifically, the negative electrode, the electrolyte layer, and the positive electrode are stacked in this order so that one positive electrode active material layer 15 and the negative electrode active material layer 13 adjacent thereto face each other via the electrolyte layer 17. .

Thus, the adjacent positive electrode, the electrolyte layer, and the negative electrode constitute one unit cell layer 19. Therefore, it can be said that the stacked battery 10 shown in FIG. 1 has a configuration in which a plurality of unit cell layers 19 are stacked and electrically connected in parallel. In addition, although the positive electrode active material layer 15 is arrange | positioned in any one side only at the positive electrode collector of the outermost layer located in the both outermost layers of the electric power generation element 21, an active material layer may be provided in both surfaces. . That is, the current collector having the active material layer on both sides may be used as it is as the current collector of the outermost layer instead of the current collector having the active material layer provided on only one side. In addition, by reversing the arrangement of the positive electrode and the negative electrode from FIG. 1, the outermost negative electrode current collector is positioned in both outermost layers of the power generation element 21, and one side of the outermost negative electrode current collector or The negative electrode active material layer may be disposed on both sides.

The positive electrode current collector 12 and the negative electrode current collector 11 are attached to the positive electrode current collector plate 27 and the negative electrode current collector plate 25 respectively, which are conducted to the respective electrodes (positive electrode and negative electrode), and held between the ends of the laminate sheet 29 And the structure of being derived to the outside of the laminate sheet 29. The positive electrode current collector plate 27 and the negative electrode current collector plate 25 are ultrasonically welded to the positive electrode current collector 12 and the negative electrode current collector 11 of each electrode via the positive electrode lead and the negative electrode lead (not shown), respectively, as necessary. Or may be attached by resistance welding or the like.

The lithium ion secondary battery described above is characterized by the negative electrode. Hereinafter, main components of the battery including the negative electrode will be described.

<Active material layer>
The active material layer 13 or 15 contains an active material, and further contains other additives as needed.

[Positive electrode active material layer]
The positive electrode active material layer 15 contains a positive electrode active material.

(Positive electrode active material)
As a positive electrode active material, for example, metal lithium, lithium-transition metal complex oxide, lithium-transition metal phosphate compound, lithium-transition metal sulfate compound, solid solution type, ternary system, NiMn type, NiCo type, spinel Mn type Etc.

Examples of lithium-transition metal complex oxides include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni, Mn, Co) O ₂ , Li (Li, Ni, Mn, Co) O ₂ , LiFePO ₄ and What has some of these transition metals substituted by other elements etc. are mentioned.

As a solid solution system, xLiMO ₂ · (1-x) Li ₂ NO ₃ (0 <x <1, M is an average oxidation state of 3+, N is one or more transition metals having an average oxidation state of 4+), LiRO _2- LiMn ₂ O ₄ (R = transition metal element such as Ni, Mn, Co, Fe, etc.) and the like.

Examples of the ternary system include nickel-cobalt-manganese (composite) positive electrode materials and the like.

Examples of the NiMn-based material include LiNi _0.5 Mn _1.5 O _{4 and the} like.

The NiCo system, Li (NiCo) _{O 2,} and the like.

LiMn ₂ O ₄ etc. are mentioned as spinel Mn type | system | group.

General formula disclosed in JP 2012-185913 A: Li _{(2-0.5x) y} □ _{(2-0.5x) (1-y)} Mn _1-x M _1.5x O ₃ (wherein, Li is lithium, □ is a pore in the crystal structure, Mn is manganese, M is Ni _α Co _β Mn _γ (Ni is nickel, Co is cobalt, Mn is manganese, α, β and γ are 0 <α 0.5 ≦ 0 ≦ β ≦ 0.33, 0 <γ ≦ 0.5 is satisfied, and x and y have a relationship of 0 <x <1.00 and 0 <y <1.00. And a layered transition metal oxide whose crystal structure is attributed to the space group C2 / m may be used as a positive electrode active material.

In some cases, two or more positive electrode active materials may be used in combination. Preferably, in view of capacity and output characteristics, a lithium-transition metal complex oxide is used as a positive electrode active material. Of course, positive electrode active materials other than those described above may be used. When the optimum particle size is different in expressing the unique effects of each active material, the particle sizes optimum for expressing the unique effects of each material may be blended and used. It is not necessary to make the particle size uniform.

The average particle size of the positive electrode active material contained in the positive electrode active material layer 15 is not particularly limited, but is preferably 1 to 30 μm, more preferably 5 to 20 μm from the viewpoint of achieving high output. In the present specification, unless otherwise specified, “particle diameter” refers to active material particles (observation using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM)). Of the distances between any two points on the contour line of a surface), this means the largest distance. Further, in the present specification, unless otherwise stated, the value of “average particle diameter” may be within a few to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). A value calculated as an average value of particle diameters of particles observed in The particle sizes and average particle sizes of other components can be defined in the same manner.

The positive electrode active material layer 15 can include a binder.

(Binder)
The binder is added for the purpose of binding the active materials or the active material and the current collector to maintain the electrode structure. Although it does not specifically limit as a binder used for a positive electrode active material layer, For example, the following materials are mentioned. Polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile (PEN), polyacrylonitrile, polyimide, polyamide, polyamideimide, cellulose, carboxymethyl cellulose (CMC), ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene butadiene Rubber (SBR), isoprene rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and hydrogenated product thereof, styrene / isoprene / styrene block copolymer and Thermoplastic polymers such as hydrogen additive, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene, hexafluoropropyl Copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene Fluorine resin such as copolymer (ECTFE), polyvinyl fluoride (PVF), vinylidene fluoride-hexafluoropropylene fluororubber (VDF-HFP fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluorocarbon Rubber (VDF-HFP-TFE fluororubber), Vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), Vinylidene fluoride-pentafluoropropylene-tet Fluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride-perfluoromethylvinylether-tetrafluoroethylene-based fluororubber (VDF-PFMVE-TFE-based fluororubber), vinylidene fluoride-chlorotrifluoroethylene And vinylidene fluoride-based fluororubbers such as C-based fluororubbers (VDF-CTFE fluororubbers) and epoxy resins. Among them, polyvinylidene fluoride, polyimide, styrene butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, polyamide, and polyamideimide are more preferable. These suitable binders are excellent in heat resistance, and furthermore, the potential window is very wide and stable to both the positive electrode potential and the negative electrode potential, and can be used for the active material layer. These binders may be used alone or in combination of two or more.

The amount of the binder contained in the positive electrode active material layer is not particularly limited as long as it can bind the active material, but preferably 0.5 to 15% by mass with respect to the active material layer And more preferably 1 to 10% by mass.

The positive electrode (positive electrode active material layer) can be prepared by any method of kneading, sputtering, vapor deposition, CVD, PVD, ion plating, and thermal spraying, in addition to the usual method of coating (coating) slurry. It can be formed.

[Anode active material layer]
The negative electrode active material layer 13 contains a negative electrode active material.

(Anode active material)
The negative electrode active material essentially contains a predetermined alloy.

By applying an alloy of ternary Si _x Sn _y M _z A _a and supporting a carbon-based material on the surface of the alloy, miniaturization by expansion and contraction of the negative electrode active material at the time of charge and discharge and an electrolyte and The effect of suppressing the reaction of As a result, the negative electrode using the negative electrode active material according to the present invention has a useful effect of having high cycle durability.

Alloy In the present embodiment, the alloy is represented by the following chemical formula (1).

In the above chemical formula (1), M is at least one metal selected from the group consisting of Ti, Zn, C, and a combination thereof. Moreover, A is an unavoidable impurity. Furthermore, x, y, z and a represent the values of% by weight, where 0 <x <100, 0 <y <100, 0 <z <100 and 0 ≦ a <0.5 , X + y + z + a = 100. Further, in the present specification, the above-mentioned "unavoidable impurities" mean those which are present in the raw material in the Si alloy or are inevitably mixed in the manufacturing process. Although the inevitable impurities are unnecessary originally, they are trace amounts and are allowable impurities because they do not affect the characteristics of the Si alloy.

In the present embodiment, as the negative electrode active material, Sn, which is the first additive element, and M, which is the second additive element (at least one metal selected from the group consisting of Ti, Zn, C, and a combination thereof) are used. By being selected, during Li alloying, it is possible to suppress the amorphous-crystalline phase transition and improve the cycle life. In addition, as a result, the capacity is higher than that of a conventional negative electrode active material, for example, a carbon-based negative electrode active material.

Here, to suppress the phase transition between amorphous and crystalline during Li alloying, when Si and Li are alloyed in the Si material, the amorphous state is transformed to the crystalline state and a large volume change (about 4 times) is obtained. This is because the particles themselves are broken and the function as an active material is lost. Therefore, by suppressing the phase transition between amorphous and crystal, it is possible to suppress the collapse of the particles themselves, maintain the function (high capacity) as an active material, and improve the cycle life. By selecting such first and second additive elements, it is possible to provide a Si alloy negative electrode active material having high capacity and high cycle durability.

As mentioned above, M is at least one metal selected from the group consisting of Ti, Zn, C, and combinations thereof. Therefore, _{hereinafter, Si x Sn y Ti z A} a, the _{Si x Sn y Zn z A a} , and _{Si x Sn y C z A a} Si alloy will be described respectively.

_[Si x _Sn y _Ti z _Si alloys represented by _{A a]}
The _Si x _Sn y _Ti z _{A a,} as described above, and Sn is a first additional element, by selecting the Ti as the second additional element, when Li alloying, amorphous - crystalline phases Transition can be suppressed to improve cycle life. In addition, as a result, the capacity is higher than that of a conventional negative electrode active material, for example, a carbon-based negative electrode active material.

In the composition of the above alloy, the x, y, and z are the following formula (1) or (2):

It is preferable to satisfy That is, from the viewpoint of improving the characteristics of the negative electrode active material, as indicated by symbol A in FIG. 3, the first region is 35% by mass or more and 78% by mass or less of silicon (Si), 7% by mass or more It is preferable that the region contains 30% by mass or less of tin (Sn) and more than 0% by mass and 37% by mass or less of titanium (Ti). Further, as indicated by symbol B in FIG. 3, the second region is 35% by mass or more and 52% by mass or less Si, 30% by mass or more and 51% by mass or less Sn, more than 0% by mass and 35% by mass or less It is preferable that the region contains Ti. When the content of each component is in the above range, an initial discharge capacity of over 1000 Ah / g can be obtained, and the cycle life can also exceed 90% (50 cycles).

From the viewpoint of further improving the characteristics of the negative electrode active material, the content of titanium is preferably in the range of 7% by mass or more. That is, as indicated by the symbol C in FIG. 4, the first region is 35% by mass or more and 78% by mass or less of silicon (Si), 7% by mass or more and 30% by mass or less of tin (Sn), 7% by mass or more It is preferable that the region contains titanium (Ti) of 37% by mass or less. In addition, as indicated by symbol D in FIG. 4, the second region is 35% by mass or more and 52% by mass or less Si, 30% by mass or more and 51% by mass or less Sn, and 7% by mass or more and 35% by mass or less Ti It is preferably a region containing That is, the x, y, and z are the following formula (3) or (4):

It is preferable to satisfy As a result, as shown in the later-described reference example, the discharge capacity retention rate after 50 cycles can be 43% or more.

And from the viewpoint of securing better cycle durability, as shown by the symbol E in FIG. 5, the first region is 35% by mass or more and 68% by mass or less of Si, and 7% by mass or more and 30% by mass or less It is preferable that it is an area | region containing Sn and 18 mass% or more and 37 mass% or less Ti. In addition, as indicated by symbol F in FIG. 5, the second region is 39% by mass or more and 52% by mass or less Si, 30% by mass or more and 51% by mass or less Sn, and 7% by mass or more and 20% by mass or less Ti It is desirable that the region contains That is, the x, y, and z are the following formula (5) or (6):

It is preferable to satisfy

And, from the viewpoint of the initial discharge capacity and cycle durability, it is particularly preferable that the negative electrode active material of the present embodiment contains an alloy of a region indicated by symbol G in FIG. 6 and the balance is an unavoidable impurity. In addition, the area | region shown with code | symbol G is an area | region containing 46 mass% or more and 58 mass% or less Si, 7 mass% or more and 21 mass% or less Sn, and 24 mass% or more and 37 mass% or less Ti. That is, the x, y, and z are expressed by the following equation (7):

It is preferable to satisfy

As described above, A is an impurity (an unavoidable impurity) other than the above three components derived from the raw material and the manufacturing method. It is preferable that a is 0 ≦ a <0.5, and 0 ≦ a <0.1.

[Si alloy represented by Si _x Sn _y Zn _z A _a ]
As described above, the above-mentioned Si _x Sn _y Zn _z Aa is a phase transition between amorphous and crystalline when Li is alloyed by selecting Sn as the first additive element and Zn as the second additive element. Can be suppressed to improve the cycle life. In addition, as a result, the capacity is higher than that of a conventional negative electrode active material, for example, a carbon-based negative electrode active material.

In the composition of the above alloy, it is preferable that x is more than 23 and less than 64, y is 4 or more and 58 or less, and z is more than 0 and less than 65. Note that this numerical range corresponds to the range indicated by the symbol X in FIG. And this negative electrode active material of Si alloy is used for the negative electrode of an electric device, for example, the negative electrode of a lithium ion secondary battery. In this case, the alloy contained in the negative electrode active material absorbs lithium ions at the time of charge of the battery, and releases lithium ions at the time of discharge.

More specifically, although the negative electrode active material is a negative electrode active material of a Si alloy, tin (Sn) as a first additive element and zinc (Zn) as a second additive element are added thereto. It is a thing. And, by appropriately selecting Sn as the first additive element and Zn as the second additive element, when alloying with lithium, suppressing the phase transition of amorphous-crystal and improving the cycle life Can. In addition, the capacity can be made higher than that of the carbon-based negative electrode active material.

And Si (Si-Sn-Zn system) alloy provided with a good cycle life even after 100 cycles after 50 cycles by optimizing the composition range of Sn and Zn which are the 1st and 2nd addition elements respectively The negative electrode active material can be obtained.

At this time, in the above-described negative electrode active material made of a Si—Sn—Zn-based alloy, when x is more than 23, the first cycle discharge capacity can be sufficiently secured. In addition, when y is 4 or more, a good discharge capacity maintenance rate at the 50th cycle can be sufficiently secured. When the above x, y and z are in the above range, cycle durability is improved, and a good discharge capacity maintenance rate (for example, 50% or more) at the 100th cycle can be sufficiently secured.

From the viewpoint of further improving the above-mentioned characteristics of the Si alloy negative electrode active material, in the composition of the above alloy, the symbols of FIG. 11 shown by 23 <x <64, 4 ≦ y <34, 2 <z <65 It is desirable to make the range shown by A. Furthermore, it is desirable to set the range indicated by symbol B in FIG. 11 that satisfies 23 <x <44, 34 <y <58, and 0 <z <43. As a result, as shown in Table 2, a discharge capacity retention rate of 92% or more in 50 cycles and over 55% in 100 cycles can be obtained. Then, from the viewpoint of securing better cycle durability, it is desirable to set the range indicated by symbol C in FIG. 12 that satisfies 23 <x <64, 4 <y <34, and 27 <z <61. In addition, it is desirable to set the range indicated by symbol D in FIG. 12 that satisfies 23 <x <34, 34 <y <58, 8 <z <43. This improves the cycle durability, and as shown in Table 2, it is possible to obtain a discharge capacity retention rate exceeding 65% in 100 cycles.

Furthermore, the range indicated by the symbol E in FIG. 13 satisfying 23 <x <58, 4 <y <24, 38 <z <61, and 23 <x <38, 24 ≦ y <35, 27 <z <53 are satisfied. The range indicated by the symbol F in FIG. 13, the range indicated by the symbol G in FIG. 13 that satisfies 23 <x <38, 35 <y <40, 27 <z <44, or 23 <x <29, 40 ≦ y <58, It is desirable to set the range indicated by the symbol H in FIG. 13 that satisfies 13 <z <37. This improves the cycle durability, and as shown in Table 2, it is possible to obtain a discharge capacity retention rate exceeding 75% in 100 cycles.

As described above, A is an impurity (an unavoidable impurity) other than the above three components derived from the raw material and the manufacturing method. It is more preferable that a is 0 ≦ a <0.5, and 0 ≦ a <0.1.

[Si alloy represented by Si _x Sn _y C _z A _a ]
As described above, the above-mentioned Si _x Sn _y C _z A _a is an amorphous-crystalline phase during Li alloying by selecting Sn as the first additive element and C as the second additive element. Transition can be suppressed to improve cycle life. In addition, as a result, the capacity is higher than that of a conventional negative electrode active material, for example, a carbon-based negative electrode active material.

In the composition of the above-mentioned alloy, x is preferably 29 or more. Note that this numerical range corresponds to the range indicated by the symbol A in FIG. By having the above composition, not only high capacity can be expressed, but also after 50 cycles, high discharge capacity can be maintained after 100 cycles.

In order to further improve the characteristics of the negative electrode active material, it is preferable that x is 29 or more and 63 or less, y is 14 or more and 48 or less, and z is 11 or more and 48 or less. This numerical range corresponds to the range indicated by the symbol B in FIG.

And from the viewpoint of securing better cycle durability, it is preferable that x is 29 or more and 44 or less, y is 14 or more and 48 or less, and z is 11 or more and 48 or less. Note that this numerical range corresponds to the range indicated by the symbol C in FIG.

Furthermore, it is preferable that x is 29 or more and 40 or less, and y is 34 or more and 48 or less (therefore, 12 ≦ z ≦ 37). This numerical range corresponds to the range indicated by the symbol D in FIG.

As described above, A is an impurity (an unavoidable impurity) other than the above three components derived from the raw material and the manufacturing method. It is preferable that a is 0 ≦ a <0.5, and 0 ≦ a <0.1.

(Supporting carbon-based material on Si alloy surface)
The Si alloy according to the present invention is characterized in that a carbon-based material is supported (coated) on the surface thereof. Lithium ion using a negative electrode active material including a Si alloy (hereinafter, also simply referred to as "carbon-supported Si alloy" or "carbon-coated Si alloy") in which a carbon-based material is supported (coated) on the surface having such features Electrical devices such as secondary batteries have high cycle durability.

As used herein, "supported" or "coated" means that the carbon-based material is chemically or physically bonded to the surface of at least a part of the Si alloy. In addition, whether or not the carbon-based material is supported (coated) on the surface of the Si alloy, the carbon-based material adheres to the alloy particles in the carbon-supported Si alloy (negative electrode active material) manufactured or collected (separated) from the electrode. It can be confirmed by observation in the state of being carried out, and the case where the coverage of the alloy by the carbon-based material is 15 mol% or more is defined as the state where “the carbon-based material is supported (coated) on the surface of Si alloy”. For this reason, the conductive support agent is not supported by the negative electrode active material, or by the alloy carbon material depending on the simple mixing with the negative electrode active material, the conductive support agent (carbon-based material) and the binder as conventionally done. It is supported only at a coverage of less than 15 mol%. In addition, the support (coating | cover) state to the alloy surface of a carbon-type material can be easily confirmed by well-known means, such as a scanning electron microscope (SEM).

The detailed reason why the cycle durability of the electrical device using the Si alloy having the above characteristics is improved is unknown, but the following reasons can be considered.

As described above, since the Si alloy has a high degree of expansion and contraction at the time of charge and discharge, deterioration in cycle durability is considered to be a problem due to micronization, reaction (oxidation) with the electrolytic solution accompanying surface area increase. Further, the formulas described in the above Patent Document _1: The Si _x M lithium ion secondary battery using the anode having an amorphous alloy having a y Al _{z, wherein:} even amorphous alloy having a Si _x M y Al _z As with the high purity Si active material, expansion and contraction can not be sufficiently suppressed. For this reason, the specific surface area of the active material is increased by the miniaturization of the active material (particles) due to expansion and contraction at the time of charge and discharge, and the decomposition of the electrolyte is promoted, and the side reaction is generated by the depletion of the electrolyte and the decomposition of the electrolyte. An object is generated and interferes with the conductivity.

Further, since the amorphous alloy described in Patent Document 1 contains Si (semiconductor), sufficient conductivity can not be ensured. For this reason, when using the said amorphous alloy as an active material, addition of a conductive support agent is needed, but it is difficult to disperse | distribute uniformly by addition of the conventional conductive support agent, and the conductivity is locally high It often has a structure in which the active material and the low active material are mixed. For these reasons, it has been difficult for the prior art to maintain high cycle characteristics.

On the other hand, in the present invention, an alloy (particles) of Si _x Sn _y M _z A _a (M = Ti, Zn, C, or a combination thereof) is applied, and the surface of the alloy (particles) is carbon-based Load (cover) the material. Therefore, the reactivity of the alloy (particle) surface with the electrolyte can be suppressed by the presence of the carbon-based material on the alloy surface, so excessive decomposition reaction of the electrolyte and generation of a side reaction product accordingly It becomes possible to suppress. Also, unlike the conventional method of adding a conductive aid, since a carbon-based material having high conductivity is present on the surface of the alloy (particles), the conductivity of the alloy (particles) is secured, and the conductivity of the entire alloy is high. Can be granted. Thereby, for example, when applied to a lithium ion secondary battery, it has the effect of promoting equalization of the charging depth of the alloy particles at the time of Li ion insertion, resulting in excessive Li ion insertion and deterioration easily Alloy particles can be excluded.

That is, in the negative electrode active material according to the present invention, since the carbon-based material, not the alloy particles, contacts the electrolytic solution, the decomposition reaction of the electrolytic solution (particularly by silicon) can be suppressed and the carbon-based material is present on the outermost surface. The conductivity can be improved by the Therefore, the negative electrode active material according to the present invention can improve cycle characteristics, and further, initial capacity and cycle characteristics.

The above mechanism is speculation, and the present invention is not limited to the above mechanism.

The carbon-based material is supported (coated) on the surface of the alloy (particles). Here, the coverage (loading) of the alloy by the carbon-based material is not particularly limited. In consideration of the effect of improving cycle characteristics (cycle durability), the effect of improving conductivity, etc., the coverage of the carbon material of the alloy is preferably 50 to 400 mol%, more preferably 100 to 400 mol%. Still more preferably, it is 250 to 400 mol%.

In the present specification, “coverage (loading) of carbon-based material of alloy” is a value measured and calculated by the following method. In addition, in this specification, "the coverage (support ratio) (mol%) by the carbon-type material of an alloy" is also only called "carbon coverage (mol%)."

<Measurement of coverage (loading) of carbon-based material of alloy>
The carbon coverage of the alloy on which the carbon-based material is supported is measured by using Auger electron spectroscopy under the following measurement conditions to measure the molar ratio of silicon and the molar ratio of carbon.

Next, using the molar ratio of silicon and the molar ratio of carbon measured above, the molar ratio of carbon to the molar ratio of silicon is calculated according to the following equation, and the obtained values are shown as carbon coverage (Table 4 below). It is referred to as "carbon coverage to silicon" (mol%) in the inside.

Here, the method of controlling the coverage (loading) of the alloy by the carbon-based material to the above preferable range is not particularly limited. Specifically, a method is used in which an alloy and a carbon-based material are mixed in appropriate proportions and then treated physically or chemically to bond (support) the carbon-based material to the alloy surface chemically or physically. it can.

In the above method, the mixing ratio of the alloy and the carbon-based material is not particularly limited. Specifically, the carbon-based material is preferably 1 to 25 parts by weight, more preferably 5 to 25 parts by weight, based on 100 parts by weight of the total amount of the alloy and the carbon-based material. Particularly preferably, it is mixed with the alloy in a proportion of 10 to 25 parts by weight. According to such a mixing ratio, the coverage (loading) of the alloy with the carbon-based material can be easily controlled to the above-described preferable range. Moreover, according to such a mixing ratio, the carbon-based material can be uniformly supported (coated) on the alloy surface.

The carbon-based material is not particularly limited, and a carbon-based material generally used as a conductive aid can be used. Specifically, acetylene black, furnace black, carbon black, channel black, graphite and the like can be mentioned. Among these, from the viewpoint of supportability, the carbon-based material preferably has low crystallinity in which insertion or desorption of Li ions hardly occurs or does not occur, and it is more preferable to use acetylene black or carbon fiber. Further, the shape of the carbon-based material is also not particularly limited, and may be in the form of particles or fibers. The form of particles is preferred from the viewpoint of ease of supporting, and the form of fibers is preferred from the viewpoint of conductivity. The size of the carbon-based material is also not particularly limited. For example, when the carbon-based material is in the form of particles, the average particle diameter (secondary particle diameter) is preferably 10 to 200 nm, more preferably 20 to 150 nm. When the carbon-based material is in the form of fibers, the diameter is preferably 20 to 500 nm, more preferably 50 to 300 nm, and the length is preferably 5 to 20 μm, more preferably 8 to It is 15 μm. With such a size, the carbon-based material can be easily supported on the alloy surface. Moreover, if it is such a magnitude | size, carbon-type material can be uniformly carry | supported by the alloy surface.

Further, in the above method, the physical or chemical treatment method for chemically or physically bonding (supporting) the carbon-based material to the alloy surface is not particularly limited, and the carbon-based material in the alloy can be obtained by shearing. A method of embedding at least a part, a method of chemically bonding through a functional group on the surface of an alloy and a carbon-based material, and the like can be mentioned. More specifically, mechanochemical methods, liquid phase methods, sintering methods, vapor phase deposition (CVD) methods and the like can be mentioned.

Physical or chemical processing conditions for chemically or physically bonding (supporting) the carbon-based material to the alloy surface are not particularly limited, and can be appropriately selected according to the method used. For example, in the case of using the mechanochemical method, the rotational speed (processing rotational speed) is preferably 3000 to 8000 rpm, more preferably 4000 to 7000 rpm. The load power is preferably 200 to 400 W, more preferably 250 to 300 W. The treatment time is preferably 10 to 60 minutes, more preferably 20 to 50 minutes. Under such conditions, the carbon-based material can be supported (coated) on the alloy surface at the above-mentioned preferable coverage (loading). In addition, carbon-based materials can be uniformly supported on the alloy surface.

(D50 value of secondary particle diameter of Si alloy)
The size of the Si alloy according to the present invention is not particularly limited, but the D50 value of the secondary particle diameter obtained by the laser diffraction method is preferably more than 0.01 μm and less than 20 μm. An electrical device such as a lithium ion secondary battery using a negative electrode active material containing a Si alloy of such a size has high cycle durability. The D50 value of the secondary particle diameter is preferably 0.4 to 10 μm, more preferably 2.5 to 7 μm, from the viewpoint of cycle durability. With an alloy particle of such a size, the carbon-based material can be efficiently supported on the surface of the alloy particle, and the expansion and contraction of the alloy can be suppressed to effectively separate the supported carbon-based material from the alloy surface. Control and prevention.

In the present invention, the D50 value is calculated based on particle size distribution data calculated by a laser type particle size distribution meter, D50; median diameter, that is, particle diameter of intermediate value is calculated, and that value is adopted. In the present invention, the laser type particle size distribution analyzer uses a laser diffraction / scattering type particle size distribution measuring apparatus (manufactured by Horiba, Ltd., model: LA-920).

(Si alloy)
The shape of the Si alloy is not particularly limited, and may be spherical, elliptical, cylindrical, polygonal columnar, scaly, indeterminate, or the like.

Method of Producing Alloy The method of producing the alloy having the composition formula Si _x Sn _y M _z A _a according to the present embodiment is not particularly limited, and production may be performed using various conventionally known production methods. it can. That is, since there is almost no difference in alloy state and characteristics depending on the manufacturing method, any and all manufacturing methods can be applied.

Specifically, for example, there are a solid phase method, a liquid phase method, and a gas phase method as a method for producing the particle form of the alloy having the composition formula Si _x Sn _y M _z A _a (alloying treatment method). , Mechanical alloy method, arc plasma melting method, etc. can be used.

In addition, the Si alloy according to the present invention may be subjected to a pulverization treatment and / or a calcination treatment, if necessary, after the above-mentioned alloying treatment (for example, mechanical alloy method).

When the pulverizing treatment is performed after the alloying treatment, the pulverizing conditions are not particularly limited, but the pulverizing treatment can be carried out usually at a speed of 400 to 800 rpm for 5 minutes to 100 hours, preferably 30 minutes to 4 hours.

Further, the firing conditions in the case of performing the firing treatment after the alloying treatment or after the pulverizing treatment are not particularly limited. In addition, the BET specific surface area of Si alloy falls by performing a baking process. The firing temperature is preferably 80 to 300 ° C. in consideration of the BET specific surface area of the obtained Si alloy. The firing time is preferably 0.5 to 3 hours. By performing the firing treatment under such conditions, the BET specific surface area of the Si alloy can be appropriately adjusted.

In the method of producing in the form of the above particles, a binder and, if necessary, a conductive auxiliary agent and a viscosity adjusting solvent are added to the particles (carbon-supporting Si alloy) to prepare a slurry, and the slurry electrode is prepared using the slurry. It can be formed. Therefore, it is excellent in that it is easy to mass-produce (mass production) and easy to put to practical use as a battery electrode.

As mentioned above, although the predetermined | prescribed alloy essentially contained in the negative electrode active material layer was demonstrated, the negative electrode active material layer may contain the other negative electrode active material. As negative electrode active materials other than the above-mentioned predetermined alloy, natural graphite, artificial graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon or carbon such as hard carbon, pure metal such as Si or Sn, or the above predetermined composition Alloy based active material out of the ratio, or TiO, Ti ₂ O ₃ , TiO ₂ , or SiO ₂ , metal oxides such as SiO ₂ , SiO, SnO ₂ , lithium such as Li _4/3 Ti _5/3 O ₄ or Li ₇ MnN And complex oxides of lithium and transition metals, Li-Pb alloys, Li-Al alloys, Li and the like. However, from the viewpoint of sufficiently exhibiting the function and effect exhibited by using the above-mentioned predetermined alloy as the negative electrode active material, the above-mentioned predetermined alloy (carbon-supporting Si alloy) accounts for 100% by mass of the total amount of the negative electrode active material. The content is preferably 50 to 100% by mass, more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass, particularly preferably 95 to 100% by mass, and most preferably It is 100% by mass.

Subsequently, the negative electrode active material layer 13 contains a binder.

(Binder)
The binder is added for the purpose of binding the active materials or the active material and the current collector to maintain the electrode structure. There is no particular limitation on the type of the binder used in the negative electrode active material layer, and those described above as the binder used in the positive electrode active material layer can be used similarly. Therefore, the detailed description is omitted here.

Although the amount of binder contained in the negative electrode active material layer is not particularly limited as long as it can bind the active material, it is preferably 0.5 to the negative electrode active material layer. It is 20% by mass, more preferably 1 to 15% by mass.

(Requirements common to positive and negative electrode active material layers 15 and 13)
The requirements common to the positive and negative electrode active material layers 15 and 13 will be described below.

The positive electrode active material layer 15 and the negative electrode active material layer 13 contain, as necessary, a conductive additive, an electrolyte salt (lithium salt), an ion conductive polymer, and the like.

Conductive Support Agent In the carbon-supported Si alloy according to the present invention, a carbon-based material is previously supported (coated) on the surface of the alloy. For this reason, the negative electrode active material layer according to the present invention does not have to contain a conductive aid. Here, the conductive support agent refers to an additive compounded to improve the conductivity of the positive electrode active material layer or the negative electrode active material layer. Examples of the conductive aid include carbon materials such as carbon black such as acetylene black, graphite and vapor grown carbon fiber. When the active material layer contains a conductive additive, an electronic network inside the active material layer is effectively formed, which can contribute to the improvement of the output characteristics of the battery.

When the negative electrode active material layer or the positive electrode active material layer contains a conductive additive, the content of the conductive additive mixed into the active material layer is preferably 1% by mass or more, more preferably the total amount of the active material layer. Is 3% by mass or more, more preferably 5% by mass or more. In addition, the content of the conductive additive mixed into the active material layer is 15% by mass or less, more preferably 10% by mass or less, and still more preferably 7% by mass or less based on the total amount of the active material layer is there. The following effects are expressed by defining the compounding ratio (content) of the conductive aid in the active material layer in which the electron conductivity of the active material itself is low and the electrode resistance can be reduced by the amount of the conductive aid within the above range Ru. That is, without inhibiting the electrode reaction, the electron conductivity can be sufficiently ensured, the reduction of the energy density due to the reduction of the electrode density can be suppressed, and the energy density can be improved by the improvement of the electrode density. .

In addition, a conductive binder having both the functions of the conductive aid and the binder may be used instead of the conductive aid and the binder, or one or both of the conductive aid and the binder may be used in combination. . A commercially available TAB-2 (manufactured by Takasen Co., Ltd.) can be used as the conductive binder.

Electrolyte salt (lithium salt)
Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like.

Ion Conducting Polymers Ion conducting polymers include, for example, polyethylene oxide (PEO) based and polypropylene oxide (PPO) based polymers.

The compounding ratio of the components contained in the positive electrode active material layer and the negative electrode active material layer is not particularly limited. The compounding ratio can be adjusted by appropriately referring to known knowledge of non-aqueous solvent secondary batteries.

There is no particular limitation on the thickness of each active material layer (active material layer on one side of the current collector), and conventionally known findings on batteries can be referred to appropriately. As an example, the thickness of each active material layer is usually about 1 to 500 μm, preferably 2 to 100 μm, in consideration of the purpose of use of the battery (power emphasis, energy emphasis, etc.) and ion conductivity.

<Current collector>
The current collectors 11 and 12 are made of a conductive material. The size of the current collector is determined according to the use application of the battery. For example, if it is used for a large battery where high energy density is required, a large-area current collector is used.

The thickness of the current collector is also not particularly limited. The thickness of the current collector is usually about 1 to 100 μm.

The shape of the current collector is not particularly limited. In the laminated battery 10 shown in FIG. 1, a mesh shape (expanded grid etc.) or the like can be used besides the current collector foil.

When the thin film alloy is directly formed on the negative electrode current collector 12 by sputtering or the like, it is desirable to use a current collector foil.

There is no particular limitation on the material constituting the current collector. For example, a metal or a resin in which a conductive filler is added to a conductive polymer material or a nonconductive polymer material may be employed.

Specifically, as the metal, aluminum, nickel, iron, stainless steel, titanium, copper and the like can be mentioned. Besides these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plated material of a combination of these metals can be preferably used. In addition, it may be a foil in which a metal surface is coated with aluminum. Among them, aluminum, stainless steel, copper, and nickel are preferable from the viewpoint of electron conductivity, battery operation potential, adhesion of the negative electrode active material by sputtering to a current collector, and the like.

Examples of the conductive polymer material include polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, and polyoxadiazole. Such a conductive polymer material has sufficient conductivity even without the addition of a conductive filler, and thus is advantageous in facilitating the manufacturing process or reducing the weight of the current collector.

As the nonconductive polymer material, for example, polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), polyimide (PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA) And polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), or polystyrene (PS). Such non-conductive polymeric materials can have excellent voltage or solvent resistance.

A conductive filler may be added to the above-mentioned conductive polymer material or non-conductive polymer material as required. In particular, when the resin to be the base of the current collector is made of only a non-conductive polymer, the conductive filler is necessarily essential to impart conductivity to the resin.

The conductive filler can be used without particular limitation as long as it is a substance having conductivity. For example, metals, conductive carbon and the like can be mentioned as materials excellent in conductivity, potential resistance, or lithium ion blocking properties. The metal is not particularly limited, but at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, Sb, and K or a metal thereof Preferably, it contains an alloy or a metal oxide. Moreover, there is no restriction | limiting in particular as electroconductive carbon. Preferably, it contains at least one selected from the group consisting of acetylene black, vulcan, black pearl, carbon nanofibers, ketjen black, carbon nanotubes, carbon nanohorns, carbon nanoballoons, and fullerenes.

The addition amount of the conductive filler is not particularly limited as long as it can impart sufficient conductivity to the current collector, and is generally about 5 to 35% by mass.

<Electrolyte layer>
A liquid electrolyte or a polymer electrolyte may be used as the electrolyte constituting the electrolyte layer 17.

The liquid electrolyte has a form in which a lithium salt (electrolyte salt) is dissolved in an organic solvent. Examples of the organic solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), Carbonates such as methyl propyl carbonate (MPC) are exemplified.

As the lithium _{salt, Li (CF 3 SO 2)} 2 N, Li (C 2 F 5 SO 2) 2 N, LiPF 6, LiBF 4, LiAsF 6, LiTaF 6, LiClO 4, LiCF 3 SO 3 , etc. A compound that can be added to the active material layer of the electrode can be employed.

On the other hand, polymer electrolytes are classified into gel electrolytes containing an electrolyte solution and intrinsic polymer electrolytes not containing an electrolyte solution.

The gel electrolyte has a configuration in which the above-mentioned liquid electrolyte (electrolyte solution) is injected into a matrix polymer made of an ion conductive polymer. Use of a gel polymer electrolyte as the electrolyte is excellent in that the fluidity of the electrolyte is lost and the ion conduction between each layer can be easily blocked.

Examples of the ion conductive polymer used as a matrix polymer include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers of these. Electrolyte salts such as lithium salts can be well dissolved in such polyalkylene oxide polymers.

The proportion of the liquid electrolyte (electrolyte solution) in the gel electrolyte should not be particularly limited, but is preferably about several mass% to about 98 mass% from the viewpoint of ion conductivity and the like. The present embodiment is particularly effective for a gel electrolyte containing a large amount of electrolyte solution in which the ratio of the electrolyte solution is 70% by mass or more.

When the electrolyte layer is composed of a liquid electrolyte, a gel electrolyte or an intrinsic polymer electrolyte, a separator may be used for the electrolyte layer. Specific examples of the separator (including a non-woven fabric) include, for example, a microporous film made of a polyolefin such as polyethylene and polypropylene, a porous flat plate, and a non-woven fabric.

The intrinsic polymer electrolyte has a constitution in which a support salt (lithium salt) is dissolved in the above-mentioned matrix polymer, and does not contain an organic solvent which is a plasticizer. Therefore, when the electrolyte layer is composed of an intrinsic polymer electrolyte, there is no concern of liquid leakage from the battery, and the reliability of the battery can be improved.

A gel electrolyte or a matrix polymer of an intrinsic polymer electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. may be performed on a polymerizable polymer (eg, PEO or PPO) for forming a polymer electrolyte using an appropriate polymerization initiator. A polymerization treatment may be applied.

<Current collector and lead>
A current collector may be used for the purpose of extracting current outside the battery. The current collector plate is electrically connected to the current collector and the leads, and is taken out of the laminate sheet which is a battery exterior material.

The material which comprises a current collection board is not restrict | limited in particular, The well-known high-conductivity material conventionally used as a current collection board for lithium ion secondary batteries may be used. As a constituent material of the current collector plate, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS) and alloys thereof are preferable, more preferably aluminum from the viewpoint of light weight, corrosion resistance and high conductivity. Copper is preferred. The same material may be used for the positive electrode current collector plate and the negative electrode current collector plate, or different materials may be used.

The positive electrode terminal lead and the negative electrode terminal lead are also used as needed. As materials of the positive electrode terminal lead and the negative electrode terminal lead, terminal leads used in known lithium ion secondary batteries can be used. The heat-resistant insulation property does not affect the product (for example, automobile parts, especially electronic devices etc.) because the portion taken out from the battery exterior material 29 contacts with peripheral devices or wiring to cause electric leakage. It is preferable to coat with a heat-shrinkable tube or the like.

<Battery material>
A known metal can case can be used as the battery exterior material 29, and a bag-like case using a laminate film containing aluminum that can cover the power generation element can be used. As the laminate film, for example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used, but it is not limited thereto. A laminate film is desirable from the viewpoint of being excellent in high output and cooling performance and being suitably usable for a battery for large-sized devices for EV and HEV.

The above lithium ion secondary battery can be manufactured by a conventionally known manufacturing method.

<Appearance configuration of lithium ion secondary battery>
FIG. 2 is a perspective view showing the appearance of a laminated flat lithium ion secondary battery.

As shown in FIG. 2, the laminated flat lithium ion secondary battery 50 has a rectangular flat shape, and the positive electrode current collector plate 59 for taking out electric power from both sides thereof and the negative electrode collector The electric plate 58 is pulled out. The power generation element 57 is wrapped by the battery exterior material 52 of the lithium ion secondary battery 50, and the periphery thereof is heat-fused, and the power generation element 57 draws the positive electrode current collector plate 59 and the negative electrode current collector plate 58 to the outside. It is sealed tightly. Here, the power generation element 57 corresponds to the power generation element 21 of the lithium ion secondary battery (stacked battery) 10 shown in FIG. The power generation element 57 is formed by stacking a plurality of unit cell layers (single cells) 19 each including the positive electrode (positive electrode active material layer) 13, the electrolyte layer 17, and the negative electrode (negative electrode active material layer) 15.

In addition, the said lithium ion secondary battery is not restrict | limited to the thing (laminated cell) of the laminated | stacked flat shape. In a wound type lithium ion battery, one having a cylindrical shape (coin cell) or one having a prismatic shape (square cell), or such one obtained by deforming such a cylindrical shape into a rectangular flat shape Furthermore, there is no particular limitation, such as cylindrical cells. In the case of the cylindrical or prismatic shape, a laminate film may be used as the exterior material, or a conventional cylindrical can (metal can) may be used, and the like. Preferably, the power generation element is coated with an aluminum laminate film. Weight reduction can be achieved by the form.

Further, the removal of the positive electrode current collector plate 59 and the negative electrode current collector plate 58 shown in FIG. 2 is not particularly limited. The positive electrode current collector plate 59 and the negative electrode current collector plate 58 may be drawn out from the same side, or the positive electrode current collector plate 59 and the negative electrode current collector plate 58 may be divided into a plurality and taken out from each side. For example, it is not limited to what is shown in FIG. Further, in the winding type lithium ion battery, the terminal may be formed using, for example, a cylindrical can (metal can) instead of the current collector plate.

As described above, the negative electrode and the lithium ion secondary battery using the negative electrode active material for a lithium ion secondary battery of the present embodiment are large in such as electric vehicles, hybrid electric vehicles, fuel cell vehicles and hybrid fuel cell vehicles. It can be suitably used as a capacitive power source. That is, it can be suitably used for a vehicle drive power supply or an auxiliary power supply where high volume energy density and high volume output density are required.

In addition, although the lithium ion battery was illustrated as an electric device in the said embodiment, it is not necessarily restricted to this, It is applicable also to the secondary battery of another type, and also a primary battery. Moreover, it can apply not only to a battery but to a capacitor.

The invention is further described in detail by means of the following examples. However, the technical scope of the present invention is not limited to the following examples.

First, as a reference example, performance evaluation was performed on the Si alloy represented by the above-mentioned chemical formula (1) which constitutes the negative electrode active material for an electric device according to the present invention.

(Reference example A): Performance evaluation of Si _x Sn _y T _{z a a} [1] Preparation of negative electrode As a sputtering apparatus, a ternary DC magnetron sputtering apparatus of independent control system (manufactured by Daiwa Instruments Industry Co., Ltd., combinatorial sputter coating apparatus A gun-sample distance: about 100 mm) on a substrate (current collector) made of nickel foil with a thickness of 20 μm, under the following conditions, a thin film of negative active material alloy having each composition By depositing each of the films, 40 negative electrode samples were obtained (Reference Examples 1-1 to 1-26 and Reference Examples 1′-1 to 1′-14).

(1) Target (manufactured by High Purity Chemical Laboratory Co., Ltd., Purity: 4 N)
Si: 50.8 mm diameter, 3 mm thickness (with 2 mm thick oxygen free copper backing plate)
Sn: 50.8 mm diameter, 5 mm thickness Ti: 50.8 mm diameter, 5 mm thickness.

(2) Film forming conditions Base pressure: up to 7 × 10 ^-6 Pa
Sputtering gas type: Ar (99.9999% or more)
Sputtering gas introduction amount: 10 sccm
Sputtering pressure: 30 mTorr
DC power supply: Si (185 W), Sn (0 to 40 W), Ti (0 to 150 W)
Pre-sputtering time: 1 min.
Sputtering time: 10 min.
Substrate temperature: room temperature (25 ° C.).

That is, using the Si target, the Sn target, and the Ti target as described above, the sputtering time is fixed at 10 minutes, and the power of the DC power source is changed in the above range, respectively, thereby forming an amorphous alloy on the Ni substrate. A thin film was formed to obtain a negative electrode sample provided with alloy thin films of various compositions.

In the reference example 1-17, DC power supply 1 (Si target): 185 W, DC power supply 2 (Sn target): 30 W, DC power supply 3 (Ti target) in the reference example 1-17. : 150W. Further, in the reference example 1'-2, DC power supply 1 (Si target): 185 W, DC power supply 2 (Sn target): 22 W, DC power supply 3 (Ti target): 0 W. Furthermore, in Reference Example 1'-7, DC power supply 1 (Si target): 185 W, DC power supply 2 (Sn target): 0 W, DC power supply 3 (Ti target): 30 W.

The component compositions of these alloy thin films are shown in Table 1 and FIG.

(3) Analysis method Composition analysis: SEM, EDX analysis (JEOL), EPMA analysis (JEOL)
Film thickness measurement (for sputter rate calculation): Film thickness meter (Tokyo Instruments)
Membrane state analysis: Raman spectroscopy (Bruker).

[2] Preparation of Battery: Each negative electrode sample obtained as described above is opposed to a counter electrode made of lithium foil (made by Honjo Metal Co., Ltd., diameter 15 mm, thickness 200 μm) via a separator (Celgard 2400 made by Celgard) After that, CR2032 coin cells were manufactured by injecting an electrolyte.

In the mixed nonaqueous solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 1: 1, the concentration of 1 M of LiPF ₆ (lithium hexafluorophosphate) is used as the electrolytic solution. What was dissolved so that it might be used was used.

[3] Charge / Discharge Test of Battery The following charge / discharge test was performed on each of the batteries obtained as described above.

That is, using a charge / discharge tester (HJ0501SM8A manufactured by Hokuto Denko Co., Ltd.), in a thermostatic bath (PFU-3K manufactured by Espec Corp.) set to a temperature of 300 K (27 ° C.) In the process of inserting Li into a certain negative electrode, charging was performed from 2 V to 10 mV at 0.1 mA as a constant current / constant voltage mode. Then, in the discharge process (Li desorption process from the above-mentioned negative electrode), it was set as constant current mode and discharged from 0.1 mA and 10 mV to 2V. The above charge / discharge cycle was repeated 100 times as one cycle.

Then, the discharge capacity at the 50th and 100th cycles was determined, and the maintenance rate for the discharge capacity at the first cycle was calculated. The results are shown in Table 1 together. Under the present circumstances, discharge capacity has shown the value computed per alloy weight. Note that “discharge capacity (mAh / g)” is per pure Si or alloy weight, and when Li reacts with Si-Sn-M alloy (Si-M alloy, pure Si or Si-Sn alloy) Indicates the capacity of the In addition, what is described as "initial capacity" in the present specification corresponds to "discharge capacity (mAh / g)" of the initial cycle (first cycle).

The “discharge capacity maintenance rate (%)” at the 50th or 100th cycle represents an index of “how much capacity is maintained from the initial capacity”. The formula for calculating the discharge capacity retention rate (%) is as follows.

The results are shown in Table 1 together. Further, FIG. 7 shows the relationship between the discharge capacity at the first cycle and the alloy composition. Furthermore, in FIG. 8 and FIG. 9, the relationship between the discharge capacity maintenance rate at 50 cycles and 100 cycles and the alloy composition is shown, respectively. In addition, discharge capacity has shown the value computed per alloy weight.

As a result of the above, the battery of Reference Example A (see Table 1) using an Si-Sn-Ti alloy as a negative electrode active material, each component being in a specific range, that is, in a range A or a range B shown in FIG. , As shown in FIG. 7, with an initial capacity of at least 1000 mAh / g. Then, as shown in FIGS. 8 and 9, it was confirmed that the discharge capacity retention ratio of 91% or more after 50 cycles and 43% or more even after 100 cycles.

(Reference Example B): Performance Evaluation of Si _x Sn _y Zn _z A _a [1] Preparation of Negative Electrode “Ti: 50.8 mm diameter, 5 mm thickness” of the target in (1) of Reference Example A It changed to 50.8 mm diameter and 3 mm thickness. Furthermore, “Ti (0 to 150 W)” of the DC power supply in (2) was changed to “Zn (0 to 150 W)”. With the exception of the above changes, 46 negative electrode samples were prepared in the same manner as in Reference Example A (Reference Examples 2-1 to 2-32 and Reference Examples 2′-1 to 2′-14).

That is, the sputtering time was fixed to 10 minutes using the Si target, the Sn target and the Zn target as described above, and the power of the DC power source was changed in the above range. Thus, an alloy thin film in an amorphous state was formed on a Ni substrate to obtain a negative electrode sample provided with alloy thin films of various compositions.

Regarding the DC power supply in the above (2), if a few examples of sample preparation conditions are shown, in Reference Example 2-4, the DC power supply 1 (Si target) is 185 W, the DC power supply 2 (Sn target) 22 W, the DC power supply 3 (Zn target) was 100 W. Further, in the reference example 2'-2, the DC power supply 1 (Si target) is 185 W, the DC power supply 2 (Sn target) is 30 W, and the DC power supply 3 (Zn target) is 0 W. Furthermore, in the reference example 2'-5, the DC power supply 1 (Si target) is 185 W, the DC power supply 2 (Sn target) is 0 W, and the DC power supply 3 (Zn target) is 25 W.

The component compositions of these alloy thin films are shown in Table 2. The analysis of the obtained alloy thin film was performed by the same analysis method and analyzer as in Reference Example A.

[2] Production of Battery A CR2032 coin cell was produced in the same manner as in Reference Example A.

[3] Charge / Discharge Test of Battery The charge / discharge test of the battery was conducted in the same manner as in Reference Example A. The results are shown in Table 2 together.

As a result of the above, in the battery of Reference Example B (see Table 2) in which the Si-Sn-Zn-based alloy in which each component is within the specific range, that is, within the range X shown in FIG. As shown at 14, it has an initial capacity of at least 1000 mAh / g. And, as shown in FIG. 15 and FIG. 16, the negative electrode active material of the Si—Sn—Zn alloy within the range X of FIG. 10 discharges by 92% or more after 50 cycles and more than 50% even after 100 cycles. It was confirmed that the capacity retention rate was shown (see Reference Examples 2-1 to 2-32).

(Reference Example C): Performance Evaluation of Si _x Sn _y C _z A _a [1] Preparation of Negative Electrode “Ti: 50.8 mm diameter, 5 mm thickness” of the target in (1) of Reference Example A is “C: The diameter was changed to 50.8 mm diameter and 3 mm thickness (with a 2 mm thick oxygen free copper backing plate). Also, “Ti (0 to 150 W)” of the DC power supply in (2) was changed to “C (0 to 150 W)”. Except for the above changes, 34 negative electrode samples were prepared in the same manner as in Reference Example A (Reference Examples 3-1 to 3-22 and Reference Examples 3'-1 to 3'-12).

In the reference example 3-16, the DC power supply 1 (Si target) is 185 W, the DC power supply 2 (Sn target) is 35 W, and the DC power supply 3 (C target) in Reference Example 3-16. ) Was 110W. Further, in the reference example 3'-2, the DC power supply 1 (Si target) is 185 W, the DC power supply 2 (Sn target) is 22 W, and the DC power supply 3 (C target) is 0 W. Furthermore, in the reference example 3'-7, the DC power supply 1 (Si target) is 185 W, the DC power supply 2 (Sn target) is 0 W, and the DC power supply 3 (C target) is 30 W.

The component compositions of these alloy thin films are shown in Table 3 and FIG.

[2] Production of Battery A CR2032 coin cell was produced in the same manner as in Reference Example A.

[3] Charge / Discharge Test of Battery The charge / discharge test of the battery was conducted in the same manner as in Reference Example A. The results are shown in Table 3 together.

As a result of the above, in the battery of Reference Example C (see Table 3) using an Si-Sn-C based alloy containing 29% by mass or more of Si, that is, in the range B shown in FIG. Have an initial capacity of at least 1000 mAh / g as shown in FIG. And, as shown in FIG. 22 and FIG. 23, the negative electrode active material of the Si—Sn—C alloy within the range B shown in FIG. 18 is 92% or more after 50 cycles and 45% or more after 100 cycles. It was confirmed that the discharge capacity retention rate of the above was shown (see Reference Examples 3-1 to 3-22).

Next, as an example, performance evaluation is performed on a negative electrode for an electric device having a negative electrode active material layer using, as a negative electrode active material, a Si alloy (Si ₆₀ Sn ₂₀ Ti ₂₀ ) manufactured in the same manner as the reference example A The

Among the Si ₆₀ Sn ₂₀ Ti ₂₀ and alloys used in the present invention (Si _x Sn _y Ti _z A _a , Si _x Sn _y Zn _z A _a , and Si _x Sn _y C _z A _a , Also for Si ₆₀ Sn ₂₀ Ti ₂₀ ), the same or similar results as in the following example using Si ₆₀ Sn ₂₀ Ti ₂₀ can be obtained. The reason is that it is the coating of the carbon-based material on the alloy that is important for improving the cycle durability of the Si alloy. Moreover, in addition to the coating of the carbon-based material on the alloy, the progress of the amorphization of Si in the active material is considered to be important for the improvement of the cycle durability of the Si alloy, Ti, Zn and C (second The additive element) is for alloying the Si material to facilitate advancing the amorphous state. Therefore, it is considered that the cycle durability is improved as the amorphous state of Si progresses even in Si _x Sn _y Zn _z A _a and Si _x Sn _y C _z A _a using Zn and C other than Ti. . That is, when an alloy having such similar characteristics is used, similar results can be obtained even if the type of alloy is changed.

Example 1
[Manufacturing of Si alloy]
The Si alloy was manufactured by mechanical alloying (or arc plasma melting). Specifically, using a German Fritsch planetary ball mill P-6, the zirconia ground ball and each raw material powder of each alloy are charged into a zirconia ground pot and alloyed at 600 rpm for 24 hours (alloy Treatment), followed by grinding treatment at 400 rpm for 1 hour. The average particle size (D50) of the obtained Si alloy was 6 μm.

[Fabrication of negative electrode]
Mechanochemical composite of 75 parts by mass of the Si alloy manufactured above (Si ₆₀ Sn ₂₀ Ti ₂₀ , average particle size (D50): 6 μm) and 25 parts by mass of acetylene black (average particle size: 30 nm) as a carbon material The carbon-supporting treatment was performed for 30 minutes under conditions of a processing rotational speed of 6000 rpm and a load power of 300 W using a chemical conversion apparatus (manufactured by Hosokawa Micron). Moreover, about the carbon coating | coated state, it observed by the scanning electron microscope (SEM). The carbon coverage of the carbon-coated Si alloy obtained here was measured using the following Auger electron spectroscopy, and the results are shown in Table 4 below.

A negative electrode slurry was obtained by mixing 85 parts by mass of the carbon-coated Si alloy manufactured above as a negative electrode active material and 15 parts by mass of polyamideimide as a binder and dispersing in N-methylpyrrolidone. Next, the obtained negative electrode slurry is uniformly coated on both sides of a negative electrode current collector made of copper foil so that the thickness of the negative electrode active material layer is 30 μm, and dried in vacuum for 24 hours to obtain a negative electrode. Obtained.

[Production of positive electrode]
Li _1.85 Ni _0.18 Co _0.10 Mn _0.87 O ₃ which is a positive electrode active material was produced by the method described in Example 1 (paragraph 0046) of JP 2012-185913A. Then, 90 parts by mass of the positive electrode active material, 5 parts by mass of acetylene black as a conductive additive, and 5 parts by mass of polyvinylidene fluoride as a binder are mixed and dispersed in N-methylpyrrolidone to obtain a positive electrode slurry. The Next, the obtained positive electrode slurry was uniformly coated on both surfaces of a positive electrode current collector made of aluminum foil so that the thickness of the positive electrode active material layer was 30 μm, and dried to obtain a positive electrode.

[Production of battery]
The positive electrode produced above and the negative electrode were made to oppose, and the separator (polyolefin, 20 micrometers of film thickness) was arrange | positioned between this. Next, a laminate of a negative electrode, a separator, and a positive electrode was disposed on the bottom side of a coin cell (CR2032, material: stainless steel (SUS316)). Furthermore, a gasket is attached to maintain insulation between the positive electrode and the negative electrode, the following electrolytic solution is injected by a syringe, a spring and a spacer are laminated, and the upper side of the coin cell is overlapped and sealed by caulking. The lithium ion secondary battery was obtained.

In addition, as the said electrolyte solution, the hexafluorophosphoric acid which is a supporting salt in the organic solvent which mixed ethylene carbonate (EC) and diethyl carbonate (DEC) in the ratio of EC: DEC = 1: 2 (volume ratio) is mentioned. Lithium (LiPF ₆ ) was used at a concentration of 1 mol / L.

(Example 2)
A negative electrode and a battery were produced in the same manner as in Example 1 except that the amounts of acetylene black as the Si alloy and the carbon-based material were changed to 80 parts by weight and 20 parts by weight, respectively. The carbon coverage of the obtained carbon-coated Si alloy was measured using the following Auger electron spectroscopy, and the results are shown in Table 4 below.

(Example 3)
A negative electrode and a battery were produced in the same manner as in Example 1, except that the amounts of the Si alloy and acetylene black (carbon-based material) were changed to 85 parts by weight and 15 parts by weight, respectively. The carbon coverage of the obtained carbon-coated Si alloy was measured using the following Auger electron spectroscopy, and the results are shown in Table 4 below.

(Example 4)
A negative electrode and a battery were produced in the same manner as in Example 1 except that the amounts of the Si alloy and acetylene black (carbon-based material) were changed to 90 parts by weight and 10 parts by weight, respectively. The carbon coverage of the obtained carbon-coated Si alloy was measured using the following Auger electron spectroscopy, and the results are shown in Table 4 below.

(Example 5)
A negative electrode and a battery were produced in the same manner as in Example 1 except that the amounts of the Si alloy and acetylene black (carbon-based material) were changed to 95 parts by weight and 5 parts by weight, respectively, in the production of the negative electrode. The carbon coverage of the obtained carbon-coated Si alloy was measured using the following Auger electron spectroscopy, and the results are shown in Table 4 below.

(Example 6)
A negative electrode and a battery were produced in the same manner as in Example 1 except that the amounts of the Si alloy and acetylene black (carbon-based material) were changed to 99 parts by weight and 1 part by weight, respectively, in the production of the negative electrode. The carbon coverage of the obtained carbon-coated Si alloy was measured using the following Auger electron spectroscopy, and the results are shown in Table 4 below.

(Example 7)
In the preparation of the negative electrode, a carbon material (a carbon fiber having a diameter of 200 nm and a length of 10 μm) produced by a vapor deposition method was used as a carbon-based material in place of acetylene black. A negative electrode and a battery were produced. The carbon coverage of the obtained carbon-coated Si alloy was measured using the following Auger electron spectroscopy, and the results are shown in Table 4 below. Moreover, the mapping result obtained by the measurement of the Auger-electron spectroscopy of the obtained carbon-coated Si alloy is shown in FIG.

(Comparative example 1)
A Si alloy (Si ₆₀ Sn ₂₀ Ti ₂₀ , average particle size (D50): 6 μm) was produced in the same manner as in [Production of Si alloy] in Example 1.

90 parts by mass of the Si alloy (carbon non-coated) manufactured above and 10 parts by mass of acetylene black were dry mixed. The carbon coverage of the Si alloy obtained after dry mixing was measured using the following Auger electron spectroscopy, and the results are shown in Table 4 below.

85 parts by mass of the mixture obtained above, which is a negative electrode active material, and 15 parts by mass of polyamideimide as a binder were mixed and dispersed in N-methylpyrrolidone to obtain a negative electrode slurry. Next, the obtained negative electrode slurry is uniformly coated on both sides of a negative electrode current collector made of copper foil so that the thickness of the negative electrode active material layer is 30 μm, and dried in vacuum for 24 hours to obtain a negative electrode. Obtained.

(Comparative example 2)
A Si alloy (Si ₆₀ Sn ₂₀ Ti ₂₀ , average particle size (D50): 6 μm) was produced in the same manner as in [Production of Si alloy] in Example 1.

95 parts by mass of the Si alloy (carbon non-coated) manufactured above and 5 parts by mass of acetylene black were dry mixed. The carbon coverage of the Si alloy obtained after dry mixing was measured using the following Auger electron spectroscopy, and the results are shown in Table 4 below.

85 parts by mass of the mixture obtained above, which is a negative electrode active material, and 15 parts by mass of polyamideimide as a binder were mixed and dispersed in N-methylpyrrolidone to obtain a negative electrode slurry. Next, the obtained negative electrode slurry is uniformly coated on both sides of a negative electrode current collector made of copper foil so that the thickness of the negative electrode active material layer is 30 μm, and dried in vacuum for 24 hours to obtain a negative electrode. Obtained.

<Performance evaluation>
[Measurement of coverage (carbon coverage) of carbon alloy by Si alloy]
Carbon coverage measured the molar ratio of silicon, and the molar ratio of carbon using Auger electron spectroscopy on the following measurement conditions.

Next, using the molar ratio of silicon and the molar ratio of carbon measured above, the molar ratio of carbon to the molar ratio of silicon is calculated according to the following equation, and the obtained values are shown as carbon coverage (Table 4 below). It is referred to as "carbon coverage to silicon" (mol%) in the inside.

[Average particle size of Si alloy (D50)]
The particle size distribution data is measured using a laser diffraction / scattering type particle size distribution measuring apparatus (manufactured by Horiba, Ltd., model: LA-920), and based on the data, the average particle size of Si alloy (D50; median Calculate the diameter).

[Evaluation of cycle durability]
The cycle durability of each of the lithium ion secondary batteries produced above was evaluated by the following method. Each battery is charged to 4.2 V in a constant current constant voltage system (CCCV, current: 0.1 C, 20 hours ending) in an atmosphere of 30 ° C., and after resting for 10 minutes, a constant current (CC, current : Discharged to 2 V at 0.1 C) and allowed to rest for 10 minutes after discharge. Under the same charge and discharge conditions as in the first cycle, this charge and discharge process is the first cycle, and in the second and later cycles, charge and discharge are both 0.5 C (CCCV in charge ends in 4 hours). Charge and discharge test for up to 50 cycles. The ratio of the discharge capacity at the 50th cycle to the discharge capacity at the first cycle (discharge capacity retention ratio [%]) is shown in Table 4 below.

From the results in Table 4 above, it is understood that the negative electrode active material in which the surface of the Si alloy is supported by the carbon-based material exhibits high energy density and high cycle durability.

This application is based on Japanese Patent Application No. 2013-123981 filed on June 12, 2013, the disclosure of which is incorporated by reference in its entirety.

Claims (22)

The following chemical formula (1):

(In the above chemical formula (1),
M is at least one metal selected from the group consisting of Ti, Zn, C, and a combination thereof,
A is an unavoidable impurity,
x, y, z and a represent the values of mass%, where 0 <x <100, 0 <y <100, 0 <z <100 and 0 ≦ a <0.5, x + y + z + a It is = 100. )
A negative electrode active material for an electric device comprising an alloy represented by
A negative electrode active material for an electric device, wherein a carbon-based material is supported on the surface of the alloy. The negative electrode active material for an electric device according to claim 1, wherein a coverage of the alloy by a carbon-based material is 50 to 400 mol%. The negative electrode active material for an electric device according to claim 2, wherein a coverage of the alloy by a carbon-based material is 100 to 400 mol%. The negative electrode active material for an electric device according to claim 3, wherein a coverage of the alloy by a carbon-based material is 250 to 400 mol%. M is Ti,
The x, y and z may be the following formula (1) or (2):

The negative electrode active material for an electric device according to any one of claims 1 to 4, wherein The x, y and z may be the following formula (3) or (4):

The negative electrode active material for electric devices of Claim 5 which satisfy | fills. The x, y and z may be the following formula (5) or (6):

The negative electrode active material for electric devices of Claim 6 which satisfy | fills. The x, y, and z may be the following formula (7):

The negative electrode active material for an electric device according to claim 7, wherein Said M is Zn,
The negative electrode active material for an electric device according to any one of claims 1 to 4, wherein x is more than 23 and less than 64, y is 4 or more and 58 or less, and z is more than 0 and less than 65. The negative electrode active material for an electric device according to claim 9, wherein y is less than 34. The negative electrode active material for an electric device according to claim 9, wherein x is less than 44 and y is 34 or more. The negative electrode active material for an electric device according to claim 10, wherein z is more than 27 and less than 61. The negative electrode active material for an electric device according to claim 11, wherein x is less than 34. The negative electrode active material for an electric device according to claim 12, wherein y is less than 24 and z is more than 38. The negative electrode active material for an electric device according to claim 12, wherein x is 24 or more and less than 38. The negative electrode active material for an electric device according to claim 11, wherein the x is less than 38, the y is less than 40, and the z is more than 27. The negative electrode active material for an electric device according to claim 11, wherein x is less than 29 and y is 40 or more. Said M is C,
The negative electrode active material for an electric device according to any one of claims 1 to 4, wherein x is 29 or more. The negative electrode active material for an electric device according to claim 18, wherein the x is 63 or less, the y is 14 or more and 48 or less, and the z is 11 or more and 48 or less. The negative electrode active material for an electric device according to claim 19, wherein x is 44 or less. 21. The negative electrode active material for an electric device according to claim 20, wherein x is 40 or less and y is 34 or more. An electrical device comprising the negative electrode active material for an electrical device according to any one of claims 1 to 21.

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