JP2008282667A - Cathode active material for lithium ion secondary battery using organic electrolyte - Google Patents

Abstract

Provided are a positive electrode active material and a battery for a non-aqueous battery excellent in thermal stability, high load characteristics, and cycle characteristics.
A nickel lithium composite oxide (positive electrode active material 1) represented by formula 1 and a lithium manganese composite oxide (positive electrode active material 2) represented by formula 2 are mixed at 80:20 to 90:10. A battery comprising a positive electrode active material mixed at a mixing ratio (mass ratio). [Formula 1] Li _x Ni _(1-yz) Co _y Mn _z A _a O ₂ (A is at least one element of Mg and Al, 0 ≦ a ≦ 0.05. X, y, and z are each 0.05 ≦ x ≦ 1.15, 0.10 ≦ y + z ≦ 0.70, 0.00 ≦ z ≦ 0.40) [Formula 2] Li _s Mn _2−t M ′ _t O ₄ (s is 0.9 ≦ s, t is within the range of 0.01 ≦ t ≦ 0.15, M ′ is Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, At least one of B, Ga, In, Si, and Ge)
[Selection] Figure 1

Description

  The present invention relates to a positive electrode active material obtained by mixing a nickel lithium composite oxide and a lithium manganese composite oxide, and a battery using the same.

  2. Description of the Related Art In recent years, the demand for batteries as a power source for portable electronic devices has increased due to the development of electronic devices and the progress toward miniaturization accompanying the progress of semiconductor integrated technology. The battery is required to be a secondary battery that can be charged and discharged with small size, light weight and long life. Small secondary batteries with these characteristics include nickel metal hydride batteries, nickel-cadmium batteries, lithium ion secondary batteries, etc. Among them, lithium ion secondary batteries having a high voltage and high energy density of 4V class consume a large amount. There is also an increasing demand for portable electronic devices that have electric power and cannot be handled by primary batteries.

  As a feature of the above lithium ion secondary battery, a positive electrode having a higher oxidation-reduction potential and a negative electrode having a lower oxidation-reduction potential than other batteries are combined to produce a battery having a large capacity, that is, a high energy density. It is in a point that can be done. However, in actual batteries, there are many electronic devices that are used not only in a normal temperature environment but also in a wide environment from a low temperature to a high temperature, and this energy density changes depending on how it is used. For example, it can be taken out when discharging with a large current The amount of electricity decreases, and the voltage decreases due to internal resistance.

  Currently, lithium cobalt composite oxide is mainly used as a positive electrode active material for lithium ion secondary batteries. Although this positive electrode active material has an advantage of high average discharge potential, cycle characteristics are not good. In addition, when the power is discharged at a low temperature, the voltage drops drastically. For example, when a personal computer is turned on in a cold region, there is a problem of low temperature characteristics that it does not start due to insufficient output.

  In addition to the above problems, the lithium cobalt composite oxide has a problem that the deterioration rate of the high duty cycle characteristics is high and the cell capacity is low. As a method for solving these problems, the use of a nickel-lithium composite oxide having a large capacity has been studied. However, this nickel-lithium composite oxide has a high capacity, but its thermal stability is inferior to that of lithium cobalt oxide. Therefore, studies such as adding a spinel type lithium manganese composite oxide for the purpose of ensuring cell safety have been reported (Patent Documents 1 to 4).

JP 2002-110253 A JP 2003-142091 A JP 2006-252894 A JP 2006-252895 A

  However, conventional positive electrode materials are not sufficient in improving thermal stability, high load characteristics, cycle characteristics and ensuring cell safety, and further development has been demanded. The present invention has been made in view of such problems, and it is possible to ensure safety while improving thermal stability, high load characteristics, and cycle characteristics as compared with a positive electrode material mixed with a conventional nickel-based positive electrode active material. An object of the present invention is to provide a positive electrode active material and a battery using the same.

  The battery of the present invention is used for a positive electrode containing a positive electrode active material formed by mixing a nickel lithium composite oxide and a lithium manganese composite oxide, thereby improving thermal stability, high load characteristics, and cycle characteristics, Safety can be secured.

The battery according to the present invention is a battery including an electrolyte solution together with a positive electrode and a negative electrode. The positive electrode is a nickel-lithium composite oxide represented by Formula 1 (hereinafter referred to as positive electrode active material 1) and Formula 2. Containing a positive electrode active material formed by mixing a lithium manganese composite oxide represented by the following (hereinafter referred to as positive electrode active material 2) at a mixing ratio (mass ratio) of 80:20 to 90:10. The battery is characterized.
[Formula 1]
Li _x Ni _(1-yz) Co _y Mn _z A _a O ₂
In Formula 1, A represents at least one element of Mg and Al, and 0 ≦ a ≦ 0.05. x, y, and z are in the ranges of 0.05 ≦ x ≦ 1.15, 0.10 ≦ y + z ≦ 0.70, and 0.00 ≦ z ≦ 0.40, respectively.
[Formula 2]
_{Li s Mn 2-t M't} O 4
In Equation 2, the value of s is in the range of 0.9 ≦ s, the value of t is in the range of 0.01 ≦ t ≦ 0.15, and M ′ is Fe, Co, Ni, Cu, Zn, Al, Sn, Cr. , V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge.

  According to the battery of the present invention, in the present invention, a nickel-based active material in which cobalt and manganese are dissolved is used to ensure load characteristics and cycle characteristics, and spinel manganese having high thermal stability is mixed at a specific ratio. As a result, the thermal stability, high load characteristics, and cycle characteristics can be improved and safety can be ensured as compared with conventional nickel-based active materials.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a cross-sectional configuration of the secondary battery according to the first embodiment of the present invention. This secondary battery is a so-called lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium. This secondary battery is a so-called cylindrical type, and a wound electrode body 20 in which a belt-like positive electrode 21 and a negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. have. The battery can 11 is made of, for example, iron plated with nickel, and has one end closed and the other end open.
Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14, and a heat sensitive resistance element (PTC element) 16 are interposed via a gasket 17. It is attached by caulking, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound electrode body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. A positive electrode lead 25 made of aluminum or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

  The positive electrode active material layer 21B includes a nickel lithium composite oxide (positive electrode active material 1) represented by formula 1 and a lithium manganese composite oxide (positive electrode active material 2) represented by formula 2 in an amount of 80:20 to 90. : Mixed at a mixing ratio (mass ratio) of 10. This is because if the positive electrode active material is used, safety can be ensured while improving thermal stability, high load characteristics, and cycle characteristics.

The positive electrode active material 1 is a nickel lithium composite oxide represented by Formula 1.
[Formula 1]
Li _x Ni _(1-yz) Co _y Mn _z A _a O ₂
In Formula 1, A represents at least one element of Mg and Al, and 0 ≦ a ≦ 0.05. x, y, and z are in the ranges of 0.05 ≦ x ≦ 1.15, 0.10 ≦ y + z ≦ 0.70, and 0.00 ≦ z ≦ 0.40, respectively.
The positive electrode active material 1 contains lithium and nickel or cobalt as essential constituent elements, and the basic structure is a crystal structure having a hexagonal layered structure. Furthermore, cycle characteristics and high load characteristics can be improved by including at least one element of Mg and Al.
The positive electrode active material 1 is preferably secondary particles. This is because, when the particles are primary particles, the charge / discharge efficiency does not increase, and the cell capacity is significantly reduced.

The positive electrode active material 2 is a lithium manganese composite oxide represented by Formula 2.
[Formula 2]
_{Li s Mn 2-t M't} O 4
In Equation 2, the value of s is in the range of 0.9 ≦ s, the value of t is in the range of 0.01 ≦ t ≦ 0.15, and M ′ is Fe, Co, Ni, Cu, Zn, Al, Sn, Cr. , V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge. Among these, Al is particularly preferable from the viewpoint of high load characteristics.
The positive electrode active material 2 contains lithium, manganese, and oxygen as essential constituent elements, and the basic structure is a cubic crystal structure. Note that the composition of lithium varies depending on the state of charge and discharge, and the value of s represents a value in a complete discharge state.

  The average particle diameter of the particles of the positive electrode active material 1 is preferably within a range of 30 μm or less, and more preferably within a range of 10 to 30 μm. Further, the average particle diameter of the positive electrode active material 2 particles is preferably within a range of 30 μm or less, and more preferably within a range of 10 to 30 μm. By setting the average particle diameter of the positive electrode active material 1 and the positive electrode active material 2 within this range, the positive electrode active material 1 and the positive electrode active material 2 can be sufficiently mixed, the electrode filling density is increased, and the cell This is because the capacity can be improved.

The particle size ratio of 50% cumulative average particle diameter (D50 ₍₁₎ ) of the positive electrode active material 1 and 50% cumulative average particle diameter of the positive electrode active material 2 (D50 ₍₂₎ ) is 0.17 ≦ D50 ₍₂₎ / D50 ₍₁₎ ≦ 0.67 is preferable. This is because by setting the ratio of the cumulative average particle diameters of the positive electrode active material 1 and the positive electrode active material 2 within this range, a high electrode packing density can be obtained and the cell capacity can be improved.

  As a method for synthesizing the positive electrode active material 1, for example, hydroxides such as nickel, cobalt, and manganese serving as a transition metal source are prepared and mixed in accordance with each composition, and LiOH serving as a lithium source is mixed therewith, and oxygen The method of baking at 600-1100 degreeC in atmosphere is mentioned.

  As a method for synthesizing the positive electrode active material 2, for example, an oxide containing manganese is prepared and mixed in accordance with each composition, LiOH as a lithium source is mixed therewith, and fired at 700 to 900 ° C. in an oxygen atmosphere. The method of doing is mentioned.

Examples of the starting material of the transition metal source used for the synthesis of the positive electrode active material 1 and the positive electrode active material 2 include, for example, transition metal hydroxides, transition metal carbonates, nitrates and sulfates, and a plurality of transition metals. Examples include complex transition metal hydroxides and carbonates. Examples of the starting material for the lithium source include LiOH, Li ₂ O, Li ₂ CO ₃ and LiNiO ₃ .

  The positive electrode active material layer 21B may also contain a conductive material such as a carbon material and a binder such as polyvinylidene fluoride, if necessary, and further mix one or more other positive electrode active materials. May be included.

  The negative electrode 22 has, for example, a structure in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces. The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. Examples of the shapes of the positive electrode current collector 21A and the negative electrode current collector 22B include a net shape such as a foil shape, a mesh, and an expanded metal.

  The negative electrode active material layer 22B includes, for example, any one or more of negative electrode materials capable of inserting and extracting lithium as a negative electrode active material. Examples of the negative electrode material capable of inserting and extracting lithium include a material containing tin or silicon as a constituent element. This is because tin and silicon have a large ability to occlude and release lithium, and a high energy density can be obtained.

  Examples of such a negative electrode material include a simple substance of tin, an alloy, and a compound thereof, and a material having at least a part of one kind or two or more phases of a simple substance of silicon, an alloy, and the compound thereof. In the present invention, alloys include those containing a plurality of metal elements and a plurality of metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. Some of the structures include a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them.

  As an alloy of tin, for example, as a second constituent element other than tin, among the group consisting of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing containing at least 1 sort (s) of these is mentioned. As an alloy of silicon, for example, as a second constituent element other than silicon, among the group consisting of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing containing at least 1 sort (s) of these is mentioned.

  As the negative electrode material, for example, a material containing another metal element or other metalloid element capable of forming an alloy with lithium as a constituent element can be used. Examples of such metal elements or metalloid elements include magnesium, boron, aluminum, gallium, indium, germanium, lead, bismuth, cadmium, silver, zinc, hafnium, zirconium, yttrium, palladium, and platinum. .

  Moreover, as a negative electrode material, for example, carbon such as pyrolytic carbon, coke (pitch coke, needle coke, petroleum coke), graphite (natural graphite, artificial graphite, graphite), glassy carbon, carbon fiber, activated carbon, etc. Materials. You may make it use together these carbon materials and the negative electrode material mentioned above. The carbon material has very little change in crystal structure due to insertion and extraction of lithium. For example, when used together with the negative electrode material described above, a high energy density and excellent cycle characteristics can be obtained. It is also preferable because it functions as a conductive agent.

Among the negative electrode materials, a graphite material having at least one physical property of a specific surface area of 1.0 to 6.0 m ² / g and a bulk density of 0.5 to 1.3 g / cm ³ is particularly preferable. This is because the use of a graphite material having the physical properties makes it possible to produce a cell having a more excellent discharge capacity and cycle characteristics. The spheroidization degree of the graphite material having the physical properties is preferably in the range of 0.8 to 1.0. This is because by setting the spheroidization degree of the graphite material within this range, it is possible to improve the filling property of the negative electrode, and to produce a cell with more excellent discharge capacity and cycle characteristics.

  Further, as the negative electrode material, a polymer such as polyacetylene or polypyrrole capable of inserting and extracting lithium can be used as a fired organic polymer compound (phenol resin, furan resin or the like fired at an appropriate temperature).

  The negative electrode active material layer 22B may include other materials that do not contribute to charging, such as a conductive agent, a binder, and a viscosity modifier. Examples of the conductive agent include graphite fiber, metal fiber, and metal powder. Examples of the binder include fluorine-based polymer compounds such as polyvinylidene fluoride, and synthetic rubbers such as styrene butadiene rubber and ethylene propylene diene rubber. Examples of the viscosity modifier include carboxymethyl cellulose.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is made of, for example, a porous film made of a synthetic resin made of woven fabric, non-woven fabric, polytetrafluoroethylene, polypropylene, polyethylene, or the like, or a multi-hard film made of ceramic. A structure in which a porous film is laminated may be used.

  The separator 23 is impregnated with an electrolytic solution. The electrolytic solution includes, for example, a solvent and an electrolyte salt dissolved in the solvent. Examples of the solvent include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, γ-butyrolactan, diethyl ether, tetrahydrofuran, 2-methyl-tetrahydrofuran, 1,3-dioxolane, sulfolane, acetonitrile, dimethyl carbonate, diethyl carbonate, Examples include dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and the like. These solvents may be used alone or in combination of two or more.

  Moreover, as long as it is a material which has lithium ion electroconductivity, both an inorganic solid electrolyte and a polymer solid electrolyte can be used as a solid electrolyte. Examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. The polymer solid electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. Examples of the polymer compound include ether polymers such as poly (ethylene oxide) and cross-linked polymers, poly (methacrylate) esters, and the like. Acrylates and the like can be used alone or in the molecule by copolymerization or mixing.

  Furthermore, it is preferable to use a gel electrolyte containing an electrolytic solution and a polymer compound because high ion conductivity can be obtained and battery leakage can be prevented. As the matrix of the gel electrolyte, various polymers can be used as long as they can be gelated by absorbing the non-aqueous electrolyte. For example, fluorine-based polymers such as poly (vinylidene fluoride) and poly (vinylidene fluoride-co-hexafluoropropylene), ether-based polymers such as poly (ethylene oxide) and cross-linked products, and poly (acrylonitrile) Can be used. In particular, it is desirable to use a fluorine-based polymer from the viewpoint of redox stability. By containing an electrolyte salt, ionic conductivity is imparted.

Examples of the electrolyte salt include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiCl, and LiBr. . Any one of these electrolyte salts may be used alone, or a plurality of them may be mixed and used.

  For example, the secondary battery can be manufactured as follows.

  First, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like positive electrode mixture. A slurry is obtained. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 21 </ b> A, and then the solvent is volatilized. Further, the positive electrode active material layer 21 </ b> B is formed by compression molding using a roll press machine or the like, thereby producing the positive electrode 21.

  Moreover, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like negative electrode mixture slurry. Subsequently, after applying the negative electrode mixture slurry to the negative electrode current collector 22A and drying the solvent, the negative electrode active material layer 22B is formed by compression molding using a roll press or the like, and the negative electrode 22 is manufactured.

  Next, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip portion of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip portion of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, the electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through the gasket 17. Thereby, the secondary battery shown in FIG. 1 is completed.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and inserted in the negative electrode 22 through the electrolyte layer 24. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted into the positive electrode 21 through the electrolyte layer 24. Here, since the positive electrode 21 contains the positive electrode active material 1 and the positive electrode active material 2 in the above-described proportions, a highly safe battery having excellent thermal stability, high load characteristics, and cycle characteristics is manufactured. It is possible.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the case where the positive electrode and the negative electrode are wound has been described. However, a plurality of positive electrodes and negative electrodes may be stacked or folded. Furthermore, the positive electrode material of the present invention can be applied to, for example, a battery of a cylindrical type, a square type, a coin type, a button type, etc. using a can as an exterior member. Furthermore, the negative electrode of the present invention can be applied not only to secondary batteries but also to primary batteries.

  Further, specific examples of the present invention will be described. However, the present invention is not limited to the examples, and can be appropriately modified and implemented without changing the gist thereof.

[Examples 1-1 to 1-7, Comparative Examples 1-1 to 1-7 (NCM, NCA composition condition definition)]
<Examples 1-1 to 1-4>
In Examples 1-1 to 1-4, the molar ratios of commercially available lithium hydroxide, nickel hydroxide, cobalt hydroxide, and manganese hydroxide are x = 1.15 and 0.10 ≦ y + z as shown in Table 1. ≦ 0.70, 0.00 ≦ z ≦ 0.40, prepared and mixed so as to be fired in the air, and the general formula Li _x Ni _(1-yz) Co _y Mn _z A lithium composite oxide represented by _a O ₂ (the positive electrode active substance 1) was prepared.

When the obtained powder sample of the positive electrode active material 1 was measured by the X-ray diffraction method, it was identified as a substance having a structure substantially equivalent to LiNiO ₂ . There was no peak that could be confirmed except for LiNiO ₂ , indicating that this sample is a single layer. The 50% cumulative particle size of the positive electrode active material 1 was adjusted to 15 μm, and the 50% cumulative particle size of the positive electrode active material 2 was adjusted to 5 μm.

The positive electrode active material 1 produced as described above and the positive electrode active material 2 represented by the general formula LiMn _1.90 Al _0.10 O ₄ have a mass ratio of positive electrode active material 1: positive electrode active material 2 = 90: 10. Mixed. 90% by mass of the mixed positive electrode is mixed with 7% by mass of graphite as a conductive agent and 3% by mass of polyvinylidene fluoride (PVdF) as a binder, and dispersed in N-methyl-2-pyrrolidone (NMP) to form a positive electrode mixture. A slurry was obtained. The obtained positive electrode mixture slurry was dried and re-pulverized, and then pressed with a hydraulic press so that the area density was constant, to produce a coin-type green compact.

  At the same time, a positive electrode mixture slurry produced with the same composition as described above was uniformly applied to both sides of a 15 micron thick strip-shaped aluminum foil, dried, and then compressed with a roller press to obtain a strip-shaped positive electrode. As a negative electrode active material, 10% by mass of PVdF was mixed with 90% by mass of powdered artificial graphite and dispersed in NMP to obtain a negative electrode mixture slurry. This negative electrode mixture slurry was uniformly applied on both sides of a copper foil having a thickness of 12 microns, and dried and then compressed with a roller press to obtain a strip-shaped negative electrode.

  The belt-like positive electrode and the belt-like negative electrode produced as described above were wound many times through a porous polyolefin film to produce a spiral electrode body. This electrode body was accommodated in an iron battery can plated with nickel, and insulating plates were arranged on both upper and lower surfaces of the electrode body.

  Next, the aluminum positive electrode lead is led out from the positive electrode current collector and welded to the protrusion of the safety valve that is electrically connected to the battery lid, and the nickel negative electrode lead is led out from the negative electrode current collector to obtain a battery can. Welded to the bottom.

On the other hand, the electrolyte solution was prepared by dissolving LiPF ₆ in a mixed solution in which the volume mixing ratio of ethylene carbonate and methyl ethyl carbonate was 1: 1 so as to have a concentration of 1 mol / dm ³ .

  Finally, after injecting the electrolyte into the battery can incorporating the above electrode body, the safety can, the PTC element and the battery lid are fixed by caulking the battery can through the insulating sealing gasket, and the outer diameter is A cylindrical non-aqueous electrolyte secondary battery having a height of 18 mm and a height of 65 mm was produced.

The following physical properties were evaluated for the non-aqueous electrolyte secondary battery produced as described above.
(Initial capacity)
After charging at an ambient temperature of 25 ° C., a charging voltage of 4.20 V, a charging current of 1000 mA, and a charging time of 2.5 hours, the battery is discharged at a discharge current of 750 mA and a final voltage of 3.0 V, and the initial capacity (m / Ah) Asked.
(Capacity maintenance rate)
Charging / discharging was repeated at an environmental temperature of 25 ° C., the discharge capacity at the 150th cycle was measured, and the maintenance ratio (%) with respect to the initial capacity was determined.
(Voltage drop)
The battery in the third cycle was subjected to output discharge at 0 ° C. and 20 W from a charging voltage of 4.2 V, and the voltage drop (V) at that time was recorded.

<Comparative Examples 1-1 to 1-4>
In Comparative Examples 1-1 to 1-4, as shown in Table 1, the molar ratio of lithium hydroxide, nickel hydroxide, cobalt hydroxide, and manganese hydroxide was x = 1.15, 0.10 ≦ y + z ≦ 0. Lithium composite oxide (positive electrode active material) represented by Li _x Ni _(1-yz) Co _y Mn _z A _a O ₂ so as to be out of the range of .70, 0.00 ≦ z ≦ 0.40 Except for producing 1), a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1-1, and its physical properties were evaluated.

<Examples 1-5 to 1-7>
In Example 1-5～1-7, aluminum hydroxide, the molar ratio of magnesium carbonate as a _{a = 0.05, Li x Ni (} 1-y-z) Co y Mn z A a O 2 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that a lithium composite oxide (positive electrode active material 1) represented by the following formula was produced.

<Comparative Examples 1-5 to 1-7>
In Comparative Example 1-5～1-7, aluminum hydroxide, as a molar ratio a = 0.10 magnesium _carbonate, in _{Li x Ni (1-y-} z) Co y Mn z A a O 2 A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that the lithium composite oxide (positive electrode active material 1) represented was produced, and its physical properties were evaluated.

  Table 1 shows the results of evaluating the physical properties of the batteries produced in Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-7.

As can be seen from Table 1, the molar ratio of lithium hydroxide, nickel hydroxide, cobalt hydroxide, and manganese hydroxide is x = 1.15, 0.10 ≦ y + z ≦ 0.70, 0.00 ≦ z ≦ 0. Examples 1-1 to 1-4 in which a lithium composite oxide (positive electrode active material 1) represented by the chemical formula Li _x Ni _(1-yz) Co _y Mn _z A _a O ₂ was prepared within the range of 40. Then, compared with Comparative Examples 1-1 to 1-4 outside this range, higher values were obtained for the initial capacity, capacity retention rate, and voltage drop.

Further, a lithium composite oxide (positive electrode active material 1) represented by Li _x Ni _(1-yz) Co _y Mn _z A _a O ₂ where _a molar ratio of aluminum hydroxide and magnesium carbonate is a = 0.05. In Examples 1-5 to 1-7 in which A was prepared, the initial capacity, the capacity retention ratio, and the voltage drop were higher than those in Comparative Examples 1-5 to 1-7 in which a = 0.10. Obtained.

That is, the chemical formula Li _x Ni _(1-yz) Co _y Mn _z A _a O ₂ (where A represents at least one element from Mg and Al, and 0 ≦ a ≦ 0.05. X, y , Z is in the range of 0.05 ≦ x ≦ 1.15, 0.10 ≦ y + z ≦ 0.70, 0.00 ≦ z ≦ 0.40) (positive electrode) By using a positive electrode including an active material 1) and a lithium manganese composite oxide (positive electrode active material 2) represented by the chemical formula LiMn _1.90 Al _0.10 O ₄ , cycle characteristics and low-temperature output characteristics are greatly improved. I understood that.

[Examples 2-1 and 2-2, Comparative Examples 2-1 and 2-3 (regulation of mixing ratio)]
<Example 2-1>
In Example 2-1, as in Example 1-4, positive electrode active material 1 (Li _1.15 Ni _0.30 Co _0.30 Mn _0.40 O ₂ ) and positive electrode active material 2 (LiMn _1.90 Al _A non-aqueous electrolyte secondary battery was prepared with a mixing ratio of _0.10 O ₄ ) of 90:10, and its physical properties were evaluated. The 50% cumulative particle size of the positive electrode active material 1 was adjusted to 15 μm, and the 50% cumulative particle size of the positive electrode active material 2 was adjusted to 5 μm.
The cell maximum temperature and capacity recovery rate were evaluated by the following methods.
(Maximum cell temperature)
The cell maximum temperature (° C.) was measured by measuring the cell maximum temperature at 23 ° C. and 15 W output discharge. A lower cell temperature at the time of high output is better.
(Capacity recovery rate)
The capacity recovery rate (%) was determined by measuring the capacity retention rate before and after storing a 50% discharged cell in a 45 ° C. environment for 2 months.

<Example 2-2>
In Example 2-2, a nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 2-1, except that the mixing ratio (mass ratio) of the positive electrode active material 1 and the positive electrode active material 2 was set to 80:20. It was prepared and its physical properties were evaluated.

<Comparative Examples 2-1 to 2-3>
In Comparative Examples 2-1 to 2-3, except that the mixing ratio (mass ratio) of the positive electrode active material 1 and the positive electrode active material 2 was changed outside the range of 80:20 to 90:10 as shown in Table 2. A nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 2-1, and the physical properties thereof were evaluated.

  Table 2 shows the results of evaluating the physical properties of the batteries produced in Examples 2-1 and 2-2 and Comparative Examples 2-1 to 2-3.

  As shown in Table 2, in Examples 2-1 and 2-2 in which the mixing ratio (mass ratio) of the positive electrode active material 1 and the positive electrode active material 2 was 80:20 to 90:10, 80:20 to 90 : Compared with Comparative Examples 2-1 to 2-3 outside the range of 10, high values were obtained for the initial capacity, the capacity retention rate, the voltage drop, and the maximum packing density of the electrodes. That is, by making the mixing ratio (mass ratio) of the positive electrode active material 1 and the positive electrode active material 2 within the range of 80:20 to 90:10, the packing density of the electrode is improved, and the charge / discharge capacity and cycle characteristics are excellent. It was found that a cell can be produced.

  Moreover, in Example 2-1 and 2-2, it turned out that a capacity | capacitance recovery maintenance factor is high when it preserve | saves at high temperature in a semi-discharge state compared with Comparative Examples 2-1 to 2-3. That is, it was found that a cell having excellent storage characteristics can be obtained by setting the mixing ratio (mass ratio) of the positive electrode active material 1 and the positive electrode active material 2 within the range of 80:20 to 90:10. In Comparative Examples 2-1 to 2-3 in which the mixing ratio (mass ratio) of the positive electrode active material 1 and the positive electrode active material 2 was outside the range of 80:20 to 90:10, the addition ratio of Mn was high, and the semi-discharge state This is because Mn elutes when stored at a high temperature, and capacity deterioration after storage increases.

  In Example 2-1, in which the ratio (mass ratio) between the positive electrode active material 1 and the positive electrode active material 2 was 90:10, the ratio (mass ratio) between the positive electrode active material 1 and the positive electrode active material 2 was 80:20. In comparison with Example 2-2, high values were obtained for the initial capacity, capacity retention ratio, voltage drop, maximum filling density of the electrode, and capacity recovery maintenance ratio. That is, the mixing ratio (mass ratio) of the positive electrode active material 1 and the positive electrode active material 2 is in the range of 80:20 to 90:10, and the ratio of the positive electrode active material 2 to the positive electrode active material 1 is reduced as much as possible. It was found that a cell excellent in charge / discharge capacity, cycle characteristics, and storage characteristics can be produced.

[Examples 3-1 to 3-9 (regulation of particle size and particle size ratio)]
<Example 3-1>
In Example 3-1, as in Example 2-2, the 50% cumulative particle size (D50 ₍₁ ) of the positive electrode active material 1 (Li _1.15 Ni _0.30 Co _0.30 Mn _0.40 O ₂ ). ₎ ) Is 15 μm, the 50% cumulative particle size (D50 ₍₂₎ ) of the positive electrode active material 2 (LiMn _1.90 Al _0.10 O ₄ ) is 5 μm, and a non-aqueous electrolyte secondary battery is manufactured. Evaluated.

<Examples 3-2 to 3-4>
In Examples 3-2 to 3-4, as shown in Table 3, the 50% cumulative particle diameter of the positive electrode active material 1 was set in the range of 5 to 20 μm, and the 50% cumulative particle diameter (D50 ₍ D50 _{( 1) The} particle size ratio of 50% cumulative particle size (D50 ₍₂₎ ) of positive electrode active material 2 was changed within the range of 0.17 ≦ D50 ₍₂₎ / D50 ₍₁₎ ≦ 0.67 Produced a nonaqueous electrolyte secondary battery in the same manner as in Example 3-1, and evaluated its physical properties.

<Examples 3-5 to 3-9>
In Examples 3-5 to 3-9, as shown in Table 3, the 50% cumulative particle size of the positive electrode active material 1 is outside the range of 5 to 20 μm, or the 50% cumulative particle size of the positive electrode active material 1 The particle size ratio of 50% cumulative particle size (D50 ₍₂₎ ) of (D50 ₍₁₎ ) and positive electrode active material 2 is outside the range of 0.17 ≦ D50 ₍₂₎ / D50 ₍₁₎ ≦ 0.67 Except for the above, non-aqueous electrolyte secondary batteries were produced in the same manner as in Example 3-1, and the physical properties thereof were evaluated.

  In Table 3, the result of having evaluated the physical property of the battery produced in Examples 3-1 to 3-9 is shown.

As can be seen from Table 3, the 50% cumulative particle size of the positive electrode active material 1 is in the range of 5 to 20 μm, and the 50% cumulative particle size (D50 ₍₁₎ ) of the positive electrode active material ₁ and 50 of the positive electrode active material 2 In Examples 3-1 to 3-4, in which the particle size ratio of the% integrated particle size (D50 ₍₂₎ ) is in the range of 0.17 ≦ D50 ₍₂₎ / D50 ₍₁₎ ≦ 0.67, The 50% cumulative particle size of the substance 1 is out of the range of 5 to 20 μm, or the 50% cumulative particle size (D50 ₍₁₎ ) of the positive electrode active material ₁ and the 50% cumulative particle size (D50 _{( 2)} Compared to Examples 3-5 to 3-9 in which the particle size ratio of ₎ was outside the range of 0.17 ≦ D50 ₍₂₎ / D50 ₍₁₎ ≦ 0.67, the initial capacity and capacity retention rate High values were obtained for the voltage drop, and the maximum packing density of the electrodes. Moreover, it is difficult to control the 50% cumulative particle size of the positive electrode active material 2 to a particle size of less than 5 μm, and when it is 25 μm or more, the initial capacity is reduced due to the decrease in filling property.

That is, if the particle size of the positive electrode active material 1 is reduced too much, the filling capacity of the electrode is reduced, so that the cell capacity is reduced. Conversely, if the particle size is increased too much, the voltage drop at low temperature output is increased. I understood. In addition, when the 50% cumulative average particle size ratio between the positive electrode active material 1 and the positive electrode active material 2 is within a range where D50 ₍₂₎ / D50 ₍₁₎ is larger than 0.67, the electrode packing density does not increase and the cell capacity decreases. I found out that

[Examples 4-1 to 4-19, Comparative Examples 4-1 to 4-18 (regulation of additive elements and addition amount)]
<Example 4-1>
In Example 4-1, as in Example 2-2, the additive element (M ′) of the positive electrode active material 2 (LiMn _1.90 M ′ _t O ₄ ) was Al, and the addition amount (t) was set to 0.00. A non-aqueous electrolyte secondary battery was prepared as No. 10 and its physical properties were evaluated.

<Examples 4-2 to 4-19>
As shown in Table 4, Example 4-1 except that the additive element (M ′) of the positive electrode active material 2 was changed and the addition amount was changed within the range of 0.01 ≦ t ≦ 0.15. Similarly, non-aqueous electrolyte secondary batteries were produced and their physical properties were evaluated.

<Comparative Examples 4-1 to 4-18>
In Comparative Examples 4-1 to 4-18, as shown in Table 4, the additive amount (t) of the additive element (M ′) in the positive electrode active material 2 is out of the range of 0.01 ≦ t ≦ 0.15. A non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 4-1, except that the physical properties were changed.

  Table 4 shows the results of evaluating the physical properties of the batteries produced in Examples 4-1 to 4-19 and Comparative Examples 4-1 to 4-18.

As shown in Table 4, the additive amount t of the additive element (M ′) of the positive electrode active material 2 (Li _1.90 Mn _2−t M′tO ₄ ) is within the range of 0.01 ≦ t ≦ 0.15. In Examples 4-1 to 4-19, a high value was obtained for the initial capacity in comparison with Comparative Examples 4-1 to 4-18 outside this range. Further, as can be seen from Example 4-1 and Example 4-7, when the additive element (M ′) of the positive electrode active material 2 is Al, high values are obtained for the initial capacity, capacity retention rate, and voltage drop. It was.

That is, by setting the addition amount t of the additive element M ′ of (Li _1.90 Mn _2−t M′tO ₄ ) of the positive electrode active material 2 within the range of 0.01 ≦ t ≦ 0.15, the capacity is increased. It turns out that it can improve. Further, it was found that Al is particularly preferable as the additive element M ′.

[Examples 5-1 to 5-10 (regulation of negative electrode active material)]
<Example 5-1>
In Example 5-1, as in Example 2-2, the positive electrode active material 1 was Li _1.15 Ni _0.30 Co _0.30 Mn _0.4 O ₂ ) and the positive electrode active material 2 was Li _1.90. The specific surface area is 1.0 m ² / g, the bulk density is 1.2 g / cm ³ , and the degree of spheroidization is Mn _1.90 Al _0.10 O _4. A non-aqueous electrolyte secondary battery was prepared using a negative electrode active material adjusted to 0.8, and its physical properties were evaluated.

<Examples 5-2 to 5-8>
In Examples 5-2 to 5-8, as shown in Table 5, at least one of the specific surface area and the bulk density of the graphite-based material used for the negative electrode was changed to a specific surface area of 1.0 to 6.0 m ² / g and a bulk density. The nonaqueous electrolytic solution was the same as in Example 5-1, except that the sphericity was changed within the range of 0.5 to 1.3 g / cm ³ and the sphericity was changed within the range of 0.8 to 1.0. A secondary battery was prepared and its physical properties were evaluated.

<Examples 5-9 and 5-10>
In Examples 5-2 to 5-8, as shown in Table 5, at least one of the specific surface area and the bulk density of the graphite-based material used for the negative electrode was set to a specific surface area of 1.0 to 6.0 m ² / g and a bulk density of 0. It was changed outside the range of 5-1.3 g / cm ³ . Moreover, the nonaqueous electrolyte secondary battery was produced similarly to Example 5-1 except having changed as shown in Table 5, and the physical property was evaluated.

  Table 5 shows the results of evaluating the physical properties of the batteries produced in Examples 5-1 to 5-10.

As shown in Table 5, at least one of the specific surface area and bulk density of the graphite-based material used for the negative electrode is within the range of a specific surface area of 1.0 to 6.0 m ² / g and a bulk density of 0.5 to 1.3 g / cm ³ . In Examples 5-1 to 5-5, which were adjusted so that the sphericity was adjusted within the range of 0.8 to 1.0, compared with Examples 5-9 and 5-10, High values were obtained for the initial capacity and capacity retention rate.

That is, the graphite material used for the negative electrode satisfies at least one physical property of a specific surface area of 1.0 to 6.0 m ² / g and a bulk density of 0.5 to 1.3 g / cm ³ , and a sphericity of 0.8 It was found that by setting the content within a range of ˜1.0, it was possible to improve the filling property of the negative electrode, and it was possible to produce a cell with more excellent discharge capacity and cycle characteristics.

It is a disassembled perspective view showing the structure of the secondary battery which concerns on one embodiment of this invention. It is sectional drawing along the II line of the winding electrode body shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20 ... Winding electrode body, 21 ... Positive electrode, 21A , ... Positive electrode current collector, 21B ... Positive electrode active material layer, 22 ... Negative electrode, 22A ... Negative electrode current collector, 22B ... Negative electrode active material layer, 23 ... Separator, 24 ... Center pin, 25 ... Positive electrode lead, 26 ... Negative electrode lead

Claims (10)

A battery comprising an electrolyte solution together with a positive electrode and a negative electrode,
The positive electrode is
Mixing ratio (mass) of nickel lithium composite oxide (positive electrode active material 1) represented by Formula 1 and lithium manganese composite oxide (positive electrode active material 2) represented by Formula 2 is 80:20 to 90:10. A battery comprising a positive electrode active material mixed in a ratio).
[Formula 1]
Li _x Ni _(1-yz) Co _y Mn _z A _a O ₂
(In Formula 1, A represents at least one element of Mg and Al, and 0 ≦ a ≦ 0.05. X, y, and z are 0.05 ≦ x ≦ 1.15 and 0.10 ≦, respectively. (Y + z ≦ 0.70, 0.00 ≦ z ≦ 0.40.)
[Formula 2]
_{Li s Mn 2-t M't} O 4
(In Equation 2, the value of s is 0.9 ≦ s, the value of t is in the range of 0.01 ≦ t ≦ 0.15, and M ′ is Fe, Co, Ni, Cu, Zn, Al, Sn, (At least one of Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge is used.)   2. The battery according to claim 1, wherein a 50% cumulative average particle diameter of the positive electrode active material 1 is in a range of 10 to 30 μm.   The battery according to claim 1, wherein the positive electrode active material 2 has a 50% cumulative average particle diameter in the range of 5 to 20 μm. The particle size ratio of 50% cumulative average particle size (D50 ₍₁₎ ) of the positive electrode active material 1 and 50% cumulative average particle size (D50 ₍₂₎ ) of the positive electrode active material 2 is 0.17 ≦ D50 ₍₂₎ The battery according to claim 1, wherein / D50 ₍₁₎ ≦ 0.67. The negative electrode is made of a graphite material having at least one physical property of a specific surface area of 1.0 to 6.0 m ² / g and a bulk density of 0.5 to 1.3 g / cm ^3. 1. The battery according to 1.   The battery according to claim 1, wherein the spheroidization degree of the graphite-based material is in a range of 0.8 to 1.0. Mixing ratio (mass) of nickel lithium composite oxide (positive electrode active material 1) represented by Formula 1 and lithium manganese composite oxide (positive electrode active material 2) represented by Formula 2 is 80:20 to 90:10. Ratio)).
[Formula 1]
Li _x Ni _(1-yz) Co _y Mn _z A _a O ₂
(In Formula 1, A represents at least one element of Mg and Al, and 0 ≦ a ≦ 0.05. X, y, and z are 0.05 ≦ x ≦ 1.15 and 0.10 ≦, respectively. (Y + z ≦ 0.70, 0.00 ≦ z ≦ 0.40.)
[Formula 2]
_{Li s Mn 2-t M't} O 4
(In Equation 2, the value of s is 0.9 ≦ s, the value of t is in the range of 0.01 ≦ t ≦ 0.15, and M ′ is Fe, Co, Ni, Cu, Zn, Al, Sn, (At least one of Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge is used.)   The positive electrode active material according to claim 7, wherein a 50% cumulative average particle size of the positive electrode active material 1 is in a range of 10 to 30 μm.   The positive electrode active material according to claim 7, wherein a 50% cumulative average particle diameter of the positive electrode active material 2 is in a range of 5 to 20 μm. The particle size ratio of 50% cumulative average particle size (D50 ₍₁₎ ) of the positive electrode active material 1 and 50% cumulative average particle size (D50 ₍₂₎ ) of the positive electrode active material 2 is 0.17 ≦ D50 ₍₂₎ The positive electrode active material according to claim 7, wherein / D50 ₍₁₎ ≦ 0.67.

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