JP2012094354A - Lithium ion secondary battery, and battery pack - Google Patents

Abstract

A lithium ion secondary battery capable of satisfying a demand for high speed charge / discharge and a battery pack using the same are provided.
A positive electrode plate having a positive electrode active material layer on a positive electrode current collector, a negative electrode plate having a negative electrode active material layer on a negative electrode current collector, and a separator provided between the positive electrode plate and the negative electrode plate; In the lithium ion secondary battery comprising at least an electrolyte solution containing a non-aqueous solvent, the positive electrode active material layer contains positive electrode active material particles and metal oxides, and the positive electrode current collector and the positive electrode active material particles Is fixed by a metal oxide, the positive electrode active material particles are fixed by a metal oxide, and the negative electrode active material layer contains a lithium titanium composite oxide.
[Selection] Figure 1

Description

  The present invention relates to a lithium ion secondary battery and a battery pack.

  Lithium ion secondary batteries have a high energy density and high voltage, and there is no phenomenon that the battery capacity gradually decreases when the battery is charged before it is completely discharged, which is called the memory effect during charging and discharging. To portable devices, notebook computers, portable devices, and so on.

Currently, as a measure to prevent global warming, efforts to reduce CO ₂ emissions are being carried out on a global scale. By reducing the dependence on oil and allowing it to travel with a low environmental load, it can greatly reduce CO ₂ emissions. There is an urgent need to develop and promote next-generation clean energy vehicles represented by plug-in hybrid vehicles and electric vehicles that can contribute. If lithium-ion secondary batteries can be used as the driving force for these next-generation clean energy vehicles, there is no need to rely on gasoline, which can greatly contribute to CO ₂ reduction and greatly contribute to the prevention of global warming. be able to. On the other hand, in order for a lithium ion secondary battery to be used as a driving force for a next-generation clean energy vehicle, it is necessary to satisfy the demand for faster charge / discharge.

  Currently, various lithium ion secondary batteries that have been proposed include a positive electrode plate, a negative electrode plate, a separator, and a non-aqueous electrolyte. The positive electrode plate is generally provided with an electrode active material layer in which positive electrode active material particles are fixed to the surface of a current collector such as a metal foil. The negative electrode plate is generally provided with an electrode active material layer in which graphite is fixed as negative electrode active material particles on the surface of a current collector such as copper or aluminum.

  In order to manufacture the electrode plate which is the positive electrode plate or the negative electrode plate, first, the electrode active material particles which are the positive electrode active material particles or the negative electrode active material particles, the resin binder, or further, the conductive material or other materials as necessary. The material is kneaded and / or dispersed in a solvent to prepare a slurry-like electrode active material layer forming liquid. And an electrode plate provided with an electrode active material layer is formed by applying an electrode active material layer forming liquid on the current collector surface, then drying to form a coating film on the current collector, and pressing (for example, Patent Document 1 or Patent Document 2).

  At this time, the electrode active material particles contained in the electrode active material layer forming liquid are particulate metal compounds dispersed in the liquid, and as such, are applied to the surface of the current collector, dried, and pressed. Even if it is done, it will be hard to adhere to the surface of the current collector, and will peel off from the current collector immediately. Therefore, when forming the electrode active material layer, a resin binder is added to the electrode active material layer forming liquid, and the electrode active material particles are fixed on the current collector by the resin binder, and the electrode active material The particles are fixed to each other.

JP 2006-310010 A JP 2006-107750 A

  However, when a lithium ion secondary battery is formed using the positive electrode plate and the negative electrode plate formed by the methods proposed in Patent Document 1 and Patent Document 2, the request for speeding up charging and discharging is satisfied. I can't let you. The following (1) and (2) can be mentioned as this factor. (1) Graphite as negative electrode active material particles contained in the negative electrode active material layer cannot make lithium ions in and out at high speed because of its structure. (2) The positive electrode plate formed by the method proposed in Patent Documents 1 and 2 is configured such that the current collector, the positive electrode active material particles, and the positive electrode active material particles are fixed only by a resin binder. Have taken. As a result, the resin binder acts to inhibit the desolvation reaction, and the rate characteristics are lowered.

  Moreover, in order to meet the demand for higher charge / discharge speed as a whole lithium ion secondary battery, it is not only necessary to improve the rate characteristics of either electrode plate, but both electrode plates (positive electrode plate / negative electrode plate). It is necessary to improve the rate characteristics. However, at present, there is no lithium ion secondary battery including both electrode plates with excellent rate characteristics.

  The present invention has been made in view of such a situation, and by satisfying the demand for speeding up of charge and discharge by making both the positive electrode plate and the negative electrode plate into positive electrode plates and negative electrode plates having excellent rate characteristics. It is an object of the present invention to provide a lithium ion secondary battery that can be used, and to provide a battery pack that exhibits the effects of the lithium ion secondary battery.

  The present invention for solving the above problems includes a positive electrode plate having a positive electrode active material layer on a positive electrode current collector, a negative electrode plate having a negative electrode active material layer on a negative electrode current collector, the positive electrode plate and the negative electrode plate, A lithium ion secondary battery comprising at least a separator provided between and an electrolyte containing a nonaqueous solvent, wherein the positive electrode active material layer contains positive electrode active material particles and a metal oxide. The positive electrode current collector and the positive electrode active material particles are fixed by the metal oxide, the positive electrode active material particles are fixed by the metal oxide, and the negative electrode active material layer is formed of a lithium titanium composite. It contains an oxide.

  Further, the metal oxide may be a metal oxide exhibiting a lithium ion insertion / release reaction, and the metal oxide is one or more selected from cobalt, nickel, manganese, iron, and titanium. A composite oxide of the above metal and lithium may be used.

  In addition, the positive electrode active material layer may include a portion where adjacent crystal oxides are connected by a continuous crystal lattice.

  In addition, the present invention for solving the above-described problems includes at least a storage case, a lithium ion secondary battery including a positive electrode terminal and a negative electrode terminal, and a protection circuit having an overcharge and overdischarge protection function. In the battery pack in which the lithium ion secondary battery and the protection circuit are housed, the lithium ion secondary battery is a lithium ion secondary battery having the above characteristics.

  In the lithium ion secondary battery of the present invention, in the positive electrode plate, the positive electrode current collector and the positive electrode active material particles are fixed by a metal oxide, and the positive electrode active material particles are also fixed by a metal oxide. In the negative electrode plate, a lithium titanium composite oxide is contained in the negative electrode active material layer. With this configuration, both the positive electrode plate and the negative electrode plate can improve rate characteristics, and the lithium ion secondary battery as a whole can meet the demand for faster charge / discharge.

  Moreover, according to the battery pack of this invention, the battery pack with which the effect of said lithium ion secondary battery was achieved can be provided.

It is the schematic which shows an example of the lithium ion secondary battery of this invention. It is sectional drawing of the positive electrode plate for lithium ion secondary batteries of this invention. It is a cyclic voltammogram which shows the result of the cyclic voltammetry test using the metal oxide which shows lithium ion insertion elimination reaction. It is a cyclic voltammogram which shows the result of the cyclic voltammetry test using the metal oxide which does not show lithium ion insertion elimination reaction. It is a sectional exploded view showing an example of a battery pack of the present invention.

(Lithium ion secondary battery)
Hereinafter, the lithium ion secondary battery of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing an example of the lithium ion secondary battery 100 of the present invention.

  As shown in FIG. 1, a lithium ion secondary battery 100 of the present invention includes a positive electrode plate 10 in which a positive electrode active material layer 2 is provided on one side of a positive electrode current collector 1, and a negative electrode combined therewith. The current collector 55 includes a negative electrode plate 50 in which a negative electrode active material layer 54 is provided on one surface side, and a separator 70 provided between the positive electrode plate 10 and the negative electrode plate 50. The container is housed in a container constituted by 82 and sealed in a state in which the nonaqueous electrolytic solution 90 is filled in the container. Here, in the lithium ion secondary battery 100 of the present invention, the positive electrode active material layer 2 contains positive electrode active material particles and a metal oxide, and the positive electrode current collector 1 and the positive electrode active material particles are a metal oxide. The positive electrode active material particles are fixed to each other with a metal oxide, and the negative electrode active material layer 54 contains a lithium titanium composite oxide. Hereinafter, a specific configuration of the lithium ion secondary battery 100 of the present invention will be described.

<< Positive electrode plate >>
Next, the positive electrode plate 10 constituting the lithium ion secondary battery 100 of the present invention will be described with reference to FIG. 2A and 2B are cross-sectional views of the positive electrode plate for a lithium ion secondary battery of the present invention.

  As shown in FIGS. 2A and 2B, the positive electrode plate 10 includes a positive electrode current collector 1 and a positive electrode active material layer 2 formed on the positive electrode current collector 1, and a positive electrode active material layer 2. Contains positive electrode active material particles 21 and metal oxides 22. The positive electrode current collector 1 and the positive electrode active material particles 21 are fixed by a metal oxide 22, and the positive electrode active material particles 21 are also fixed by a metal oxide 22. Hereinafter, the positive electrode current collector 1 and the positive electrode active material layer 2 will be described more specifically.

<Positive electrode current collector>
The positive electrode current collector 1 used in the present invention is not particularly limited as long as it is generally used as a positive electrode current collector of a positive electrode plate for a lithium ion secondary battery. For example, a positive electrode current collector formed of a simple substance such as an aluminum foil or a nickel foil or an alloy can be preferably used. Note that the positive electrode current collector 1 used for the positive electrode plate 10 is subjected to surface processing on the surface on which the positive electrode active material layer 2 is scheduled to be formed (the surface of the positive electrode current collector 1) as necessary. Body 1 may be sufficient. As the positive electrode current collector 1 whose surface is processed on the surface, a positive electrode current collector in which a conductive substance is laminated on the surface of a material having a current collecting function, chemical polishing treatment, corona treatment, oxygen plasma treatment are used. Examples thereof include a positive electrode current collector made. That is, the positive electrode current collector 1 has not only a current collector formed of only a material having a current collecting function, but also a surface on which a substance for ensuring conductivity is laminated, or some surface treatment. Also included are those made.

<Positive electrode active material layer>
The positive electrode active material layer 2 contains the positive electrode active material particles 21, the positive electrode current collector 1, the positive electrode active material particles 21, and the metal oxide 22 for fixing the positive electrode active material particles 21 to each other.

  The layer thickness of the positive electrode active material layer 2 is not particularly limited, and is generally about 300 nm to 200 μm. In particular, according to the present invention, the presence of the metal oxide 22 can improve rate characteristics without increasing the thickness of the positive electrode active material layer 2, and can further reduce the thickness of the positive electrode active material layer 2. It is.

  Moreover, it is preferable that the positive electrode active material layer 2 has voids to such an extent that the nonaqueous electrolyte solution can permeate, and the porosity is preferably 10% or more and 70% or less. The porosity can be measured with Autopore IV 9500 manufactured by Shimadzu Corporation. Hereinafter, the positive electrode active material particles 21 and the metal oxide 22 will be specifically described.

(Positive electrode active material particles)
The positive electrode active material particles 21 can be appropriately selected and used as chargeable / dischargeable positive electrode active material particles, and the positive electrode active material particles 21 are not particularly limited. Examples of such positive electrode active material particles 21 include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFeO ₂ , Li ₄ Ti ₅ O ₁₂ , LiFePO ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O. ₂ , cathode active material particles such as lithium transition metal composite oxides such as LiNi _0.80 Co _0.15 Al _0.05 O ₂ .

Among these positive electrode active material particles 21, LiMn ₂ O ₄ can be used particularly preferably. Since LiMn ₂ O ₄ has particularly high rate characteristics among various positive electrode active materials, the rate characteristics are further improved in combination with the fixation by the metal oxide, which is a feature of the present invention, and charge / discharge is achieved. Can be accelerated.

  The particle diameter of the positive electrode active material particles 21 is not particularly limited, and those having an arbitrary size can be appropriately selected and used. However, as the particle diameter of the positive electrode active material particles is smaller, the surface area per unit weight can be increased and the rate characteristics can be improved. Therefore, when higher rate characteristics are required, the positive electrode active material particles 21 have a small particle size, specifically less than 10 μm, preferably 5 μm or less, particularly preferably 1 μm or less.

  In addition, the particle diameter of the positive electrode active material particle 21 shown in the present invention and the present specification and the lithium titanium composite oxide described later is an average particle diameter (volume-median particle diameter) measured by laser diffraction / scattering particle size distribution measurement. : D50). The particle diameter of the core 11 is determined by identifying the measured electron microscope observation data using a particle recognition tool, and displaying a graph of particle size distribution based on the shape data acquired from the recognized particle image. It can be created and calculated from this particle size distribution graph. The particle size distribution graph can be created, for example, by using an image analysis type particle size distribution measurement software (manufactured by Mount Tech Co., Ltd., MAC VIEW) based on an electron microscope observation result.

(Metal oxide)
As shown in FIG. 2, the positive electrode active material layer 2 constituting the positive electrode plate 10 contains a metal oxide 22, and the positive electrode current collector 1 and the positive electrode active material particles 21 are fixed by the metal oxide 22. The positive electrode active material particles 21 are also fixed to each other by the metal oxide 22.

  As the metal oxide 22, any metal oxide 22 that can fix the positive electrode current collector 1 and the positive electrode active material particles 21 and can fix the positive electrode active material particles 21 to each other is appropriately selected and used. can do.

As such a metal oxide 22, a metal element generally understood as a metal, for example, Li, Be, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe , Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Cs, Ba, Hf, Ta, W, Re , Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Fr, Ra, Ce, etc., and one or more metals selected from cobalt, nickel, manganese, iron, and titanium And complex oxides of lithium, such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFeO ₂ , Li ₄ Ti ₅ O ₁₂ , LiFePO ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _0.9 Co _0.1 O ₂ , LiNi _0.80 Co _{0 And} lithium transition metal composite oxides such as _.15 Al _0.05 O ₂ .

  The metal oxide 22 may be a metal oxide 22 that does not show a lithium ion insertion / release reaction, or may be a metal oxide 22 that shows a lithium ion insertion / release reaction. When the metal oxide 22 contained in the positive electrode active material layer 2 is a metal oxide that does not exhibit a lithium ion insertion / release reaction, the lithium ions and the metal oxide may react electrochemically. As a result, no expansion or reaction product associated with the electrochemical reaction of the metal oxide occurs, and as a result, deterioration due to expansion or deficiency of the metal oxide 22 in the positive electrode active material layer 2 can be suppressed. There are advantages. On the other hand, when the metal oxide 22 contained in the positive electrode active material layer 2 is a metal oxide that exhibits a lithium ion insertion / release reaction, the metal oxide 22 itself can also function as an active material. Therefore, there is an advantage that the capacity of the positive electrode plate 10 can be increased.

The presence or absence of a lithium ion insertion / elimination reaction of the metal oxide can be confirmed by an electrochemical measurement (cyclic voltammetry: CV) method. The CV test will be described below. For example, if the electrode potential is within the appropriate voltage range of the active material, for example, lithium ions are assumed as alkali metal ions, and LiMn ₂ O ₄ is used as the metal oxide, after sweeping from 3.0 V to 4.3 V, again The operation of returning to 3.0 V is repeated about three times. The scanning speed is preferably 1 mV / second. For example, in the case of LiMn ₂ O ₄ , as shown in FIG. 3, an oxidation peak corresponding to the lithium ion elimination reaction of LiMn ₂ O ₄ appears in the vicinity of about 3.9 V, and insertion of lithium ions in the vicinity of about 4.1 V. A reduction peak corresponding to the reaction appears, whereby the presence or absence of a lithium ion insertion / extraction reaction can be confirmed. Further, as shown in FIG. 4, when no peak appears, it can be determined that there is no lithium ion insertion / extraction reaction. In the present invention, the fact that the metal oxide does not exhibit a lithium ion insertion / elimination reaction does not mean the electrical properties unique to the metal oxide, but the metal oxide contained in the positive electrode active material layer. 22 means that no lithium ion insertion / release reaction is exhibited in a voltage range suitable for the positive electrode active material particles contained in the positive electrode active material 2. This is because it is important that the metal oxide does not substantially insert and desorb lithium ions in the positive electrode plate.

  In the present invention, when the positive electrode current collector 1 and the positive electrode active material particles 21 are fixed by the metal oxide 22, and the positive electrode active material particles 21 are also fixed by the metal oxide 22, Includes two aspects. The first fixing mode is between the adherends (for example, between the positive electrode active material particles 21 and the positive electrode current collector 1, between the positive electrode active material particles 21, or when using a conductive material, the conductive material and the positive electrode. This is a mode in which the metal oxide 22 is interposed between the active material particles 21 and between the conductive material particles, and the both are fixed. In the second fixing mode, the objects to be bonded are in direct contact with each other, and the objects to be bonded are fixed to each other by the presence of the metal oxide 22 surrounding the contact portion. In the present invention, in the positive electrode active material layer, either one of the first fixing mode and the second fixing mode, or both modes are present. In particular, as the particle diameter of the positive electrode active material particles 21 contained in the positive electrode active material layer becomes smaller, the second fixing mode tends to increase.

  The metal oxide 22 may be present in the positive electrode active material layer in such a shape that the objects to be bonded are fixed in the first fixing mode or the second fixing mode. There is no particular limitation on the size and shape. For example, the metal oxide 22 is in the form of fine particles, and a large number of fine particle-like metal oxides 22 are one surface of the positive electrode active material particles 21 or the entire surface or a part of the aggregate. May be present so as to surround.

  In particular, as shown in FIG. 2B, the positive electrode active material layer 2 preferably includes a portion where adjacent metal oxides 22 are connected by a continuous crystal lattice. With this configuration, film adhesion can be improved and rate characteristics can be improved. As described above, the metal oxide 22 in the present invention is for fixing the positive electrode active material particles 21 on the positive electrode current collector 1, and as shown in FIG. It is presumed that the film adhesiveness of the positive electrode active material layer 2 is improved by including at least a portion where the crystal lattices are connected to each other at least partially. And it seems that this improvement in film adhesion contributes to the improvement in rate characteristics.

  Further, from the viewpoint of improving the film adhesion of the positive electrode active material layer 2, it is more desirable that the portion where the crystal lattices of adjacent metal oxides 22 are continuous exist significantly in the positive electrode active material layer 2. In the present invention, whether or not the crystal lattice of the metal oxides is continuous can be confirmed by observing the crystal lattice of the cross section of the adjacent metal oxide in the positive electrode active material layer with a transmission electron microscope. .

  In order to configure the positive electrode active material layer of the present invention to include a portion where the crystal lattices of adjacent metal oxides 22 are continuous, the positive electrode plate of the present invention can be manufactured according to the manufacturing method of the present invention described later. desirable. That is, in the production method of the present invention, a positive electrode active material layer forming liquid is applied onto a positive electrode current collector to form a coating film, and a positive electrode active material layer is formed from the coating film by performing means such as heating. To do. At that time, on the positive electrode current collector, the metal element-containing compound present around the positive electrode active material particles undergoes reactions such as thermal decomposition and oxidation, and a metal oxide is generated around the positive electrode active material particles. . At this time, if a part of the adjacent metal oxides (or their precursors) are joined, the crystal growth of the two tends to proceed simultaneously at the joined part. As a result of crystal growth proceeding simultaneously in the joint portion, the positive electrode active material layer of the present invention is configured to include a portion where crystal lattices in adjacent metal oxides are continuous.

  Further, the metal oxide 22 may be non-particulate and may be a continuous body that fills the space between the positive electrode active material particles 21 and the positive electrode current collector 1 and between the positive electrode active material particles 21 leaving a void. . Alternatively, the metal oxide 22 may form a continuous coating layer in the form of a film, a pleat, or a hump that surrounds two or more aggregates of the positive electrode active material particles 21. Further, when the surface of the metal oxide 22 is observed at the level of a scanning electron microscope, for example, the surface is observed in a smooth state, the innumerable protrusions are dense, the one between particles, or these The surface condition is not limited at all. That is, the metal oxide 22 in the present invention surrounds at least a part of the positive electrode active material particles 21 and the metal oxides 22 are connected to each other or the metal oxide 22 is a continuous body. What is necessary is just to comprise the positive electrode active material layer 2 by connecting the metal oxide 22 in the vicinity of the positive electrode current collector 1 to the surface of the positive electrode current collector 1.

  In addition, the present invention does not prohibit the use of a resin binder as a so-called binder material, and the resin binder and the metal oxide 22 are used in combination, thereby forming the positive electrode current collector 1 and the positive electrode active material. The material particles 21 and the positive electrode active material particles 21 may be fixed to each other. In the case where the resin binder and the metal oxide 22 are used in combination, the rate characteristic increases as the ratio of the metal oxide 22 to the total mass of the resin binder and the total mass of the metal oxide 22 increases. Will improve. Considering such points, the ratio of the metal oxide 22 to the total mass of the resin binder and the metal oxide 22 is preferably in the range of 50 to 100% by mass. Of course, even if it is outside this range, it goes without saying that the rate characteristics are improved by the amount of the metal oxide 22 contained.

  In the present invention, the mixing ratio of the positive electrode active material particles 21 and the metal oxide 22 contained in the positive electrode active material layer 2 is not particularly limited, but the content of the metal oxide 22 is too small. In such a case, the positive electrode current collector 1, the positive electrode active material particles 21, and the positive electrode active material particles 21 may not be able to increase the adhering strength to a desired level, and the improvement in rate characteristics may be sufficiently satisfied. There is a risk that it will not be possible. Therefore, considering this point, the mass ratio of the metal oxide 22 is preferably 1 part by mass or more and 100 parts by mass or less when the mass ratio of the positive electrode active material particles 21 is 100 parts by mass.

  Further, the positive electrode active material layer 2 may be composed of only the positive electrode active material particles 21 and the metal oxide 22, but may be formed by adding further additives without departing from the spirit of the present invention. Also good. For example, according to the present invention, good conductivity can be exhibited without using a conductive material exemplified by a conductive carbon material such as carbon black, but better conductivity is desired. Depending on the case or the type of active material particles, a conductive material may be used.

(Method for manufacturing positive electrode plate)
As described above, the positive electrode plate 10 of the present invention includes the positive electrode active material layer 2 provided on the positive electrode current collector 1, and the positive electrode active material layer 2 includes the positive electrode active material particles 21 and the metal oxide 22. The positive electrode current collector 1, the positive electrode active material particles 21, and the positive electrode active material particles 21 are fixed to each other by the metal oxide. If it can take such a structure, there will be no limitation in particular about the manufacturing method of the positive electrode plate 10, However, In this invention, the positive electrode plate mentioned above can be manufactured with a sufficient yield with the following method. Hereinafter, a preferable manufacturing method will be specifically described.

  A preferable manufacturing method of the positive electrode plate 10 described above includes an application step and a heating step. Hereinafter, each step will be described.

(Coating process)
In the coating step, a positive electrode active material layer forming liquid containing the positive electrode active material particles 21 described above and one or two or more metal element-containing compounds that become the metal oxide 22 by heating is used as a positive electrode. This is a step of forming a coating film on at least a part of the current collector 1.

  The metal element-containing compound is a precursor of the metal oxide 22 that fixes the positive electrode active material particles 21, the positive electrode current collector 1, and the positive electrode active material particles 21 to each other. Therefore, any metal element-containing compound capable of becoming the metal oxide 22 when applied to the substrate in a state of being added to the positive electrode active material layer forming liquid and heated.

  As the metal element-containing compound, a lithium element-containing compound and one or more metal element-containing compounds containing any metal element selected from cobalt, nickel, manganese, iron or titanium are preferably used. Can do. The metal element-containing compound may be an inorganic metal element-containing compound in which no carbon is contained in the compound, or an organometallic element-containing compound constituted by containing carbon in the compound. Also good. In the present invention and the present specification, the inorganic metal element-containing compound and the organic metal-containing compound may be simply referred to as a metal element-containing compound.

  Examples of the metal element-containing compound include carbonates, chlorides, nitrates, sulfates, perchlorates, acetates, phosphates, bromates and the like of other metal elements such as lithium element or cobalt. it can. Among them, in the present invention, carbonates, chlorides, nitrates, and acetates are preferable because they are easily available as general-purpose products. In particular, nitrate is preferably used because it has good film forming properties for a wide variety of positive electrode current collectors.

For example, as the metal element-containing compound for generating LiCoO ₂ as the metal oxide 22, a Li element-containing compound and a Co element-containing compound can be used as a main raw material in combination. Combinations of raw materials can also be used. Examples of the Li element-containing compound include lithium carbonate, lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, lithium nitrate, and lithium phosphate. Examples of the Co element-containing compound include cobalt carbonate, cobalt (II) chloride hexahydrate, cobalt (II) formate dihydrate, cobalt (III) acetylacetonate, and cobalt (II) acetylacetonate dihydrate. , Cobalt (II) acetate tetrahydrate, cobalt (II) oxalate dihydrate, cobalt (II) nitrate hexahydrate, cobalt (II) ammonium hexahydrate, cobalt (III) nitrite Examples thereof include sodium and cobalt (II) sulfate heptahydrate. The combination ratio (Li: Co = X: 1) of the Li element-containing compound and the Co element-containing compound used as the main raw material is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.

The metal oxide 22 The metal element-containing compounds to produce LiNiO _2, Li-element-containing compound, and a Ni element-containing compound can be used in combination as the main raw material, and further, other optionally Combinations of raw materials can also be used. Examples of the Li element-containing compound are the same as in the case of producing LiCoO ₂ described above. Examples of the Ni element-containing compound include nickel carbonate, nickel (II) chloride hexahydrate, and nickel (II) acetate. Tetrahydrate, nickel (II) perchlorate hexahydrate, nickel (II) bromide trihydrate, nickel (II) nitrate hexahydrate, nickel (II) acetylacetonate dihydrate, Examples thereof include nickel (II) hypophosphite hexahydrate and nickel (II) sulfate hexahydrate. The combination ratio (Li: Ni = X: 1) of the Li element-containing compound and Ni element-containing compound used as the main raw material is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.

Further, as the metal element-containing compounds to produce LiMn ₂ O ₄ as the metal oxide 22 may be used in combination Li element-containing compound, and a Mn element-containing compound as main components, further, if necessary Other raw materials can also be used in combination. Examples of the Li element-containing compound are the same as in the case of producing LiCoO ₂ described above. Examples of the Mn element-containing compound include manganese carbonate, manganese (III) acetate dihydrate, and manganese (II) nitrate. Examples include hexahydrate, manganese (II) sulfate pentahydrate, manganese (II) oxalate dihydrate, and manganese (III) acetylacetonate. The combination ratio (Li: Mn = X: 1) of the Li element-containing compound and the Mn element-containing compound used as the main raw material is not particularly limited, but is preferably 0.5 ≦ X <1, 0.5 ≦ More preferably, X ≦ 0.6.

The metal as the metal element-containing compounds to produce LiFeO ₂ as an oxide 22, Li-element-containing compound, and Fe to element-containing compound can be used in combination as the main raw material, further, other optionally These raw materials can also be used in combination. Examples of the Li element-containing compound are the same as in the case of producing LiCoO ₂ described above. Examples of the Fe element-containing compound include iron (II) chloride tetrahydrate, iron (III) citrate, and acetic acid. Examples include iron (II), iron (II) oxalate dihydrate, iron (III) nitrate nonahydrate, iron (II) lactate trihydrate, and iron (II) sulfate heptahydrate. . The combination ratio (Li: Fe = X: 1) of the Li element-containing compound and the Fe element-containing compound used as the main raw material is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.

Further, as the metal element-containing compound for producing Li ₄ Ti ₅ O ₁₂ as the metal oxide 22, a Li element-containing compound and a Ti element-containing compound can be used in combination as main raw materials, and further necessary Depending on the case, other raw materials may be used in combination. Examples of the Li element-containing compound are the same as in the case of producing LiCoO ₂ described above, and examples of the Ti element-containing compound include titanium tetrachloride and titanium acetylacetonate. The combination ratio (Li: Ti = X: 1) of the Li element-containing compound and the Ti element-containing compound used as the main raw material is not particularly limited, but is preferably 0.8 ≦ X <2, and 0.8 ≦ More preferably, X ≦ 1.2.

  In the positive electrode active material layer forming liquid described above, the ratio of the total amount of one or more metal element-containing compounds added in the solvent is 0.01 to 5 mol / L, particularly 0.1 to 5 mol / L. 2 mol / L is preferred. By setting the concentration to 0.01 mol / L or more, the positive electrode current collector 1 and the positive electrode active material layer 2 generated on the current collector surface can be satisfactorily adhered, and the positive electrode active material particles 21 Is secured. Moreover, by setting the concentration to 5 mol / L or less, it is possible to maintain a good viscosity that allows the positive electrode active material layer forming liquid to be satisfactorily applied to the surface of the positive electrode current collector 1. A film can be formed.

  Further, the positive electrode active material layer forming liquid may be blended with a conductive material, an organic substance that is a viscosity adjusting agent of the positive electrode active material layer forming liquid, or other additives within the scope of the present invention. Good. The solvent for dissolving the metal element-containing compound may be any solvent that can dissolve the metal element-containing compound, and a conventionally known solvent can be appropriately selected and used. For example, water, lower alcohols such as NMP (N-methyl-2-pyrrolidone), methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, 2-butanol, t-butanol, acetylacetone, diacetyl And ketones such as benzoylacetone, ketoesters such as ethyl acetoacetate, ethyl pyruvate, ethyl benzoylacetate and ethyl benzoylformate, toluene, ethylene glycol, diethylene glycol, polyethylene glycol, and mixed solvents thereof.

  The method for coating the positive electrode active material layer forming liquid on the positive electrode current collector 1 is not particularly limited, and a general coating method can be appropriately selected and used. For example, the positive electrode active material layer forming liquid can be applied to an arbitrary region on the surface of the positive electrode current collector by printing, spin coating, dip coating, bar coating, spray coating, or the like. In addition, when the surface of the positive electrode current collector is porous, has a large number of irregularities, or has a three-dimensional structure, it can also be applied manually other than the above method. . Note that the positive electrode current collector used in the present invention can be further improved in film formability of the positive electrode active material layer by performing corona treatment, oxygen plasma treatment, or the like in advance as necessary.

  Moreover, there is no limitation in particular about the coating amount of a positive electrode active material layer formation liquid, However, It is preferable to apply in the range in which the thickness after a heating becomes the thickness of the positive electrode active material layer demonstrated above.

(Heating process)
The heating step is a step of heating the coating film formed in the coating step described above to evaporate the solvent and generating the metal oxide 22 from the metal element-containing compound. Specifically, it is a step of thermally decomposing the metal element-containing compound to generate the metal oxide 22. Then, the positive electrode plate 10 in which the positive electrode current collector 1, the positive electrode active material particles 21, and the positive electrode active material particles 21 are fixed to each other by the metal oxide 22 is manufactured through the heating step.

  About the heating temperature in a heating process, what is necessary is just the temperature which can thermally decompose the metal element containing compound used, Therefore Therefore, according to these kind, it can set suitably.

  In addition, the heating method is not particularly limited as long as the heating method or the heating apparatus can heat the coating film at a temperature at which the metal element-containing compound is thermally decomposed. For example, a method of using any one of a hot plate, an oven, a heating furnace, an infrared heater, a halogen heater, a hot air blower, etc., or a combination of two or more can be mentioned.

  Further, the heating atmosphere in the heating step is not particularly limited, and can be appropriately determined in consideration of the material used for manufacturing the positive electrode plate, the heating temperature, the oxygen potential of the metal element, and the like. For example, an air atmosphere is preferable in that a special atmosphere adjustment is not necessary and the heating process can be easily performed. In particular, when an aluminum foil is used as the positive electrode current collector, the heating step can be preferably performed because there is no possibility that the aluminum foil is oxidized even if the heating step is performed in an air atmosphere.

  On the other hand, when a copper foil is used as the positive electrode current collector, it is not desirable because it is oxidized when the heating step is performed in an air atmosphere. Therefore, in such a case, it is preferable to heat in an inert gas atmosphere, a reducing gas atmosphere, or a mixed gas atmosphere of an inert gas and a reducing gas. In the case where the heating step is performed in an atmosphere that does not contain sufficient oxygen gas, when a positive electrode active material made of a metal oxide is generated in the positive electrode active material layer, the metal element in the metal element-containing compound Oxidation needs to be realized by the combination of oxygen and metal elements in the compound contained in the positive electrode active material layer forming liquid. Therefore, it is necessary to use a compound containing oxygen element in the compound to be used. There is.

  In the present invention, the inert gas atmosphere or the reducing gas atmosphere is not particularly limited to a specific atmosphere, and can be appropriately carried out under these conventionally known atmospheres. Examples of the inert gas atmosphere include argon gas, Examples of the nitrogen gas and reducing gas atmosphere include hydrogen gas, carbon monoxide gas, or a gas atmosphere in which the inert gas and the reducing gas are mixed.

<< Negative Electrode Plate >>
Next, the negative electrode plate 50 constituting the lithium ion secondary battery 100 of the present invention will be described. The negative electrode plate 50 includes a negative electrode active material layer 54 formed on the negative electrode current collector 55, and the negative electrode active material layer 54 contains a lithium titanium composite oxide. The present invention improves the rate characteristics of the negative electrode plate 50 by including in the negative electrode active material layer 54 a lithium-titanium composite oxide from which lithium ions can be easily taken in and out. Is combined with the positive electrode plate 10 having excellent rate characteristics as described above, it is possible to obtain extremely excellent charge / discharge characteristics at a high rate. Hereinafter, the negative electrode current collector 55 and the negative electrode active material layer 54 will be described more specifically.

<Negative electrode current collector>
There is no limitation in particular about the negative electrode collector 55, The conventionally well-known negative electrode collector 55 used for the negative electrode plate for lithium ion secondary batteries can be selected suitably, and can be used. For example, a negative electrode current collector formed of a simple substance such as an aluminum foil, a nickel foil, or a copper foil or an alloy can be preferably used. Similarly to the positive electrode current collector 1, the negative electrode current collector 55 includes a material in which a material for ensuring conductivity is laminated on the surface and a material on which some surface treatment is performed.

  The thickness of the negative electrode current collector 55 is not particularly limited as long as it is a thickness that can generally be used as a negative electrode current collector of a negative electrode plate for a lithium ion secondary battery, but is preferably 5 to 200 μm, and more preferably 10 to 50 μm. It is more preferable.

<Negative electrode active material layer>
The negative electrode active material layer 54 formed on the negative electrode current collector 55 is composed of a particulate lithium titanium composite oxide and a binder material, and the particulate lithium titanium composite oxide is composed of a binder material. As a result, the particulate lithium titanium composite oxide is also fixed to the negative electrode current collector 55 by the binder. Thereby, the negative electrode plate 50 including the negative electrode active material layer 54 is formed on the negative electrode current collector 55.

  The layer thickness of the negative electrode active material layer 54 is not particularly limited, but the layer thickness is preferably 50 μm to 150 μm in order to obtain a high capacity while improving rate characteristics. By setting the layer thickness of the negative electrode active material layer 2 in this range, the distance between the negative electrode active material layer 54 and the negative electrode current collector 55 can be shortened, and the impedance of the negative electrode plate 50 can be lowered.

  Moreover, it is preferable that the negative electrode active material layer 54 has a void to such an extent that the electrolytic solution can permeate. The porosity is not particularly limited as long as the electrolyte solution can permeate, but if the porosity is less than 10%, the electrolyte solution may not penetrate and it may be difficult to perform smooth charge and discharge. There is. Considering this point, the porosity of the negative electrode active material layer 54 is preferably 10% or more. On the other hand, when the porosity is larger than 70%, the volume energy density cannot be increased, which may hinder the downsizing of the lithium ion secondary battery. Considering this point, the porosity is preferably 70% or less. The porosity can be measured with Autopore IV 9500 manufactured by Shimadzu Corporation.

(Lithium titanium composite oxide)
The negative electrode active material layer 54 constituting the negative electrode plate 50 contains a lithium titanium composite oxide. The lithium-titanium composite oxide allows easy entry and exit of lithium ions, and according to the negative electrode plate 50 including the negative electrode active material layer 54 containing the lithium-titanium composite oxide, the rate characteristics of the negative electrode plate can be improved.

The lithium titanium composite oxide is a composite oxide containing a lithium element and a titanium element, and examples thereof include Li ₄ Ti ₅ O ₁₂ and Li ₂ Ti ₃ O ₇ . Among these, Li ₄ Ti ₅ O ₁₂ has a spinel structure, and lithium ions can be taken in and out particularly fast. Therefore, Li ₄ Ti ₅ O ₁₂ can be particularly preferably used as the lithium titanium composite oxide contained in the negative electrode active material layer 54.

  The shape of the lithium titanium composite oxide is not particularly limited, and for example, a scale shape, a flat shape, a spindle shape, or a spherical shape can be used. Further, the particle size of the particulate lithium titanium composite oxide is not particularly limited, and a material having an arbitrary size can be appropriately selected and used in consideration of the thickness of the designed negative electrode active material layer 54 and the like. Can do. As with the positive electrode active material particles described above, the rate and configuration can be improved by reducing the particle diameter of the lithium titanium composite oxide. The particle diameter of the lithium titanium composite oxide is preferably less than 10 μm, preferably 5 μm or less, and particularly preferably 1 μm or less.

(Binder)
There are no particular limitations on the particulate lithium-titanium composite oxide, the negative electrode current collector 55, and the binder for fixing the particulate lithium-titanium composite oxide to each other, and a conventionally known resin binder such as PVdF resin is used. Metal compounds such as metals and metal oxides can be used alone or in combination. A method of manufacturing a negative electrode plate in which the negative electrode current collector 55, the lithium titanium composite oxide, and the lithium titanium composite oxide are fixed to each other with a metal or a metal compound such as a metal oxide will be described later.

  In the lithium ion secondary battery of the present invention, lithium in the positive electrode active material 2 in the positive electrode plate 10 oozes out into the electrolytic solution, solvates with the electrolytic solution, diffuses into the electrolytic solution in the form of lithium ions, and the negative electrode plate To the negative electrode active material layer. The lithium ions are considered to be desolvated and inserted between the layers of the lithium-titanium composite oxide to give electrons. Although details of the mechanism of desolvation of lithium ions solvated in the electrolyte solution in the negative electrode plate 50 and electron donation are still unclear, the smaller the interfacial charge transfer resistance in the negative electrode active material layer 54, the more the solvent is removed. It is considered that the sum reaction is performed smoothly and the discharge rate characteristics in the negative electrode plate 50 are improved. In consideration of such points, the binder for fixing the negative electrode current collector 55 to the particulate lithium titanium composite oxide and the lithium titanium composite oxide is preferably a metal or a metal oxide. . By fixing the lithium titanium composite oxide, the negative electrode current collector 55, and the lithium titanium composite oxide to each other with a metal or metal oxide, there is no inhibitory effect on the desolvation reaction, and the transfer of electrons is very smooth. As a result, the rate characteristics can be further improved in combination with the improvement of the rate characteristics by the lithium titanium composite oxide.

  Furthermore, in the present invention, as described above, the positive electrode plate 10 fixes the positive electrode current collector 1, the positive electrode active material particles 21, and the positive electrode active material particles 21 with the metal oxide 22. The heat resistance can be improved by using a metal or metal oxide as the binding material of the negative electrode plate 50.

  As metal compounds such as metals and metal oxides as the binder, alkali metals, alkaline earth metals, transition metals belonging to the fourth period of the periodic table, and metal oxides thereof can be preferably used. Alkali metals and alkaline earth metals are stable even when used in the negative electrode plate 50 of a lithium ion secondary battery because of their low redox potential. In addition, transition metals belonging to the fourth period of the periodic table are chemically stable, can form a plurality of oxidation numbers, and form a plurality of complexes even with the same element. Therefore, the convenience as the metal contained in the negative electrode plate 50 is high. Examples of such metals or metal oxides include copper, nickel, lithium, and oxides thereof.

(Other materials)
The negative electrode active material layer 54 may be composed only of the lithium titanium composite oxide and the binder material described above, but may be formed by adding further additives without departing from the gist of the present invention. . For example, in the present invention, it is possible to exert good conductivity without using a conductive material, but depending on the case where better conductivity is desired or depending on the type of negative electrode active material particles, the conductive material may be It may be used.

(Method for manufacturing negative electrode plate)
Below, an example of the manufacturing method for manufacturing the negative electrode plate 50 of this invention is demonstrated. As a manufacturing method of the negative electrode plate 50 of the present invention, there are a method using a conventionally known resin binder as a binding material and a method using a metal or metal oxide as a binding material. This will be specifically described below.

(1) Method for producing negative electrode plate using resinous binder as binding material As a method for producing negative electrode plate using resinous binder as binder, a conventionally known method is appropriately selected. Can be used. For example, the negative electrode plate 50 can be manufactured by applying and drying a negative electrode active material layer forming liquid containing a lithium titanium composite oxide and a resin binder on the negative electrode current collector 55. it can.

  Examples of the resin binder include polyester resin, polyamide resin, polyacrylate resin, polycarbonate resin, polyurethane resin, cellulose resin, polyolefin resin, polyvinyl resin, fluorine resin, and polyimide resin. Among these, a fluororesin is preferable as a resin binder, and polyvinylidene fluoride is particularly preferable.

  The negative electrode active material layer forming liquid is prepared by mixing lithium-titanium composite oxide, a suitably selected resin binder, and other components as necessary. For example, lithium-titanium composite oxide and an appropriately selected binder are put into an organic solvent such as toluene, methyl ethyl ketone, N-methyl-2-pyrrolidone, or a mixture thereof, and further conductive as necessary. The material is added and prepared by dissolving or dispersing with a disperser such as a homogenizer, ball mill, sand mill or roll mill. The blending ratio at this time is preferably such that the total amount of the lithium-titanium composite oxide and the binder is about 40 to 80 parts by mass when the entire negative electrode active material layer forming liquid is 100 parts by mass. Further, the blending ratio of the lithium titanium composite oxide and the resin binder may be the same as before, and the lithium titanium composite oxide: binding material = 5: 5 to 9: 1 (mass ratio). Is preferred.

  The method for coating the negative electrode active material layer forming liquid on the negative electrode current collector 55 is not particularly limited, and a general coating method can be appropriately selected and used. For example, the negative electrode active material layer forming liquid can be applied to an arbitrary region on the surface of the negative electrode current collector by a printing method, spin coating, dip coating, bar coating, spray coating, or the like. In addition, when the surface of the negative electrode current collector is porous, has a large number of irregularities, or has a three-dimensional structure, it can be manually applied in addition to the above method. . Note that the negative electrode current collector used in the present invention can be further improved in film formability of the negative electrode active material layer by performing corona treatment, oxygen plasma treatment, or the like in advance, as necessary.

  Further, the coating amount of the negative electrode active material layer forming liquid is not particularly limited, but it is preferable that the coating is performed in such a range that the thickness after heating becomes the thickness of the negative electrode active material layer 54 described above. .

  As a heat source in drying after coating, hot air, infrared rays, microwaves, high frequencies, or a combination thereof can be used. In addition, after drying, the obtained negative electrode active material layer 54 may be pressed, and the uniformity can be improved by pressing.

(2) Method for producing negative electrode plate using metal or metal oxide as binder material (i) Negative electrode plate using metal oxide as binder material Negative electrode plate using metal oxide as binder material A negative active material layer forming liquid is prepared using a lithium titanium composite oxide, a binder precursor containing a metal element, a solvent, and, if necessary, the other materials described above. After coating on the body 55, it can be manufactured by heating.

  The binder precursor used for the preparation of the negative electrode active material layer forming liquid is a precursor containing a metal element, such as a chloride, carbonate, nitrate, acetate, perchlorate, phosphate of a metal element. , Metal salts such as bromate, and hydrates of these metal salts. Among them, chlorides, carbonates, nitrates, and acetates are easily available as general-purpose products, and these binder substance precursors are dissolved in a solvent, and the negative electrode active material layer forming liquid is placed on the negative electrode current collector 55. When coating is applied to form a coating film and heated, chlorine ions, carbonate ions, nitrate ions and acetate ions can be easily eliminated from the coating film, and these can be used particularly preferably.

  Specific examples of these binder precursors include, for example, when the metal element is copper, copper chloride, copper (II) carbonate, copper nitrate, copper acetate, copper acetate (II) monohydrate. When the metal element is nickel, nickel chloride, nickel carbonate, nickel nitrate, nickel acetate, nickel (II) nitrate hexahydrate, nickel acetate (II) tetrahydrate, etc. When the metal element is lithium, lithium chloride, lithium carbonate, lithium nitrate, lithium acetate, lithium acetate trihydrate, and the like can be given.

  The solvent for dissolving the binder precursor is not particularly limited as long as it can dissolve the precursor, and the same solvent as described in the method for producing the resin binder is used. be able to.

  In the negative electrode active material layer forming liquid described above, the total ratio of one or more binder materials added to the solvent is 0.01 to 20 mol / L, particularly 0.1. 10 mol / L is preferable. By setting the concentration to 0.01 mol / L or more, the negative electrode current collector 55 and the negative electrode active material layer 54 formed on the surface of the current collector 55 can be satisfactorily adhered, and the lithium titanium composite oxide Is sufficiently fixed to the current collector. In addition, by setting the concentration to 20 mol / L or less, the negative electrode active material layer forming liquid can maintain a good viscosity enough to be applied to the surface of the negative electrode current collector 55, and a uniform coating film Can be formed.

  The method for coating the negative electrode active material layer forming liquid containing the binder precursor on the negative electrode current collector 55 is not particularly limited, and is the same as the negative electrode active material layer forming liquid containing the resin binder described above. A coating method can be appropriately selected and used. The same applies to the thickness of the coating amount.

  By heating the binder precursor contained in the negative electrode active material layer forming liquid, a coating containing a lithium titanium composite oxide and a metal oxide formed by oxidizing the binder precursor metal by a chemical reaction is included. A film is formed. In the formed coating film, a metal oxide is formed so as to cover the surface of the lithium titanium composite oxide, and the lithium oxide composite oxide, the negative electrode current collector 55, and the lithium titanium composite oxide are formed by this metal oxide. Objects are fixed to each other, and the negative electrode plate 50 is manufactured.

  In addition, for the drying of the negative electrode active material layer forming liquid, the same method as the method for manufacturing a negative electrode plate using the resin binder described above can be used. The heating temperature only needs to be equal to or higher than the temperature at which the metal contained in the binder precursor can be oxidized, and varies depending on the type of metal contained in the binder precursor, but usually ranges from 120 ° C to 800 ° C. It is.

(Ii) Negative electrode plate using a metal as a binding material As described above, the metal oxide as a binding material is subjected to a reduction treatment to reduce the metal oxide to a metal. The negative electrode plate 50 in which the current collector 55, the lithium titanium composite oxide, and the lithium titanium composite oxide are fixed to each other can be manufactured.

  As a reduction treatment method, a reduction treatment method in which a reduction treatment is performed in a hydrogen plasma atmosphere, a reduction gas obtained by diluting hydrogen, carbon monoxide, or the like with hydrogen, carbon monoxide, or an inert gas such as nitrogen, helium, argon, or the like. And a reduction treatment method in which reduction is performed in the reducing gas atmosphere can be suitably used. As the reducing gas, one kind of reducing gas may be used alone, or two or more kinds of gases may be mixed and used.

  Further, the negative electrode plate 50 formed through the reduction treatment does not contain an oxide in the negative electrode active material layer 54, and does not cause a reduction reaction during initial charging. Thereby, it is possible to prevent the charge reaction from being hindered by the reduction reaction during the initial charge and the initial charge / discharge efficiency from being lowered.

<< Separator >>
There is no limitation in particular about the separator which comprises the lithium ion secondary battery 100 of this invention, A conventionally well-known separator can be suitably selected and used in the field | area of a lithium ion secondary battery. Examples of such a separator include a polyethylene porous film.

(Non-aqueous electrolyte)
The non-aqueous electrolyte 90 used in the lithium ion secondary battery of the present invention is not particularly limited as long as it is generally used as a non-aqueous electrolyte for a lithium ion secondary battery. A nonaqueous electrolytic solution dissolved in a solvent is preferably used.

Examples of the lithium salt include inorganic lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, and LiBr; LiB (C ₆ H ₅ ) ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiC ( Organic compounds such as SO ₂ CF ₃ ) ₃ , LiOSO ₂ CF ₃ , LiOSO ₂ C ₂ F ₅ , LiOSO ₂ C ₄ F ₉ , LiOSO ₂ C ₅ F ₁₁ , LiOSO ₂ C ₆ F ₁₃ , and LiOSO ₂ C ₇ F ₁₅ Typical examples include lithium salts.

  Examples of the organic solvent used for dissolving the lithium salt include cyclic esters, chain esters, cyclic ethers, and chain ethers.

  As a structure of the lithium ion battery 100 manufactured using the positive electrode plate 10, the negative electrode plate 50, the separator 70, and the nonaqueous electrolytic solution 90, a conventionally known structure can be appropriately selected and used. For example, the structure which winds said positive electrode plate 10 and the negative electrode plate 50 in the shape of a spiral via the separator 70, and accommodates in a battery container is mentioned. As another aspect, a structure in which the positive electrode plate 10 and the negative electrode plate 50 cut into a predetermined shape are stacked and fixed via a separator 70, and this is housed in a battery container may be employed. In any structure, after the positive electrode plate 10 and the negative electrode plate 50 are accommodated in the battery container, the lead wire attached to the positive electrode plate is connected to the positive electrode terminal provided in the outer container, while being attached to the negative electrode plate. The lead wire is connected to a negative electrode terminal provided in the outer container, and the battery container is filled with a non-aqueous electrolyte and then sealed to produce a lithium ion secondary battery.

(Battery pack)
Next, a battery pack 200 configured using the lithium ion secondary battery 100 of the present invention will be described with reference to FIG. FIG. 5 is a schematic exploded view showing an example of the battery pack 200 of the present invention.

  As shown in FIG. 5, the battery pack 200 includes a lithium ion secondary battery 100 housed in a resin container 36 a, a resin container 36 b, and an end case 37. Further, a protective circuit board 34 for preventing overcharge and overdischarge between one end face of the lithium ion secondary battery and a face including the positive electrode terminal 32 and the negative electrode terminal 33 and the end case 37. Is provided.

  The protection circuit board 34 includes an external connection connector 35. The external connection connector 35 is connected to an external connection window 38a provided in the resin container 36a and an external connection window 38b provided in the end case 37. Inserted and connected to external terminals. The protection circuit board 34 is equipped with a charge / discharge safety circuit (not shown) for controlling charge / discharge, a wiring circuit for connecting the external connection terminal and the lithium ion secondary battery 100, and the like.

  The battery pack 200 can appropriately select a configuration of a conventionally known battery pack, except that the lithium ion secondary battery 100 of the present invention is used. Although not shown, the battery pack 200 includes a positive electrode lead plate connected to the positive electrode terminal 32, a negative electrode lead plate connected to the negative electrode terminal 33, and an insulator between the nonaqueous electrolyte secondary ground 100 and the end case 37. Etc. may be provided as appropriate.

  Note that the lithium ion secondary battery 100 of the present invention has a function of blocking the excessive current, monitoring the battery temperature, and the like in addition to the above-described protection circuit, in addition to the mode of use for the battery pack, and the protection circuit is a lithium ion battery. You may use for the aspect attached integrally to a secondary battery. In such an embodiment, the battery pack can be used as a secondary battery having a protection function and a protection circuit without constituting a battery pack, and is highly versatile. In addition, some aspects demonstrated above are only illustrations, or use of the lithium ion secondary battery 100 of this invention is not limited at all.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. Hereinafter, unless otherwise specified, parts or% is based on mass.

Example 1
<Preparation of positive electrode plate 1>
Li (CH ₃ COO) · 2H ₂ O: 10 g and Mn (CH ₃ COO) ₂ · 4H ₂ O: 24 g were added to methanol: 35 g and mixed to obtain a raw material liquid for producing a metal oxide. Next, polyethylene glycol 200: 10 g in the above raw material liquid, lithium manganate (LiMn ₂ O ₄ ) particles: 40 g as positive electrode active material particles, graphite HS-100: 5 g as a conductive material, carbon fiber (manufactured by Showa Denko KK, VGCF) ): 0.5 g was added, and the positive electrode active material layer forming liquid 1 was prepared by kneading with an Excel auto homogenizer (Nihon Seiki Seisakusho Co., Ltd.) at a rotational speed of 7000 rpm for 15 minutes.

Next, an aluminum plate having a thickness of 15 μm was prepared as a positive electrode current collector, and the positive electrode active material layer forming liquid 1 prepared above was applied in an amount such that the coating amount after drying was 110 g / m ^2. A coating film for forming a positive electrode active material layer was formed on one side of the body with an applicator. Subsequently, the coating film was pressed using a roll press machine (manufactured by Sank Metal Co., Ltd .: mechanical type 1 ton) under the conditions of applied pressure: 0.1 ton / cm and pressing speed of 10 mm / second. Thereafter, the current collector on which the positive electrode active material layer-forming coating film was formed was placed in a normal temperature electric furnace (Muffle furnace, Denken, P90) and gradually increased from room temperature to 500 ° C. over 3 hours. To obtain a positive electrode plate 1 having a positive electrode active material layer laminated on a positive electrode current collector.

<Preparation of negative electrode plate 1>
Spinel type lithium titanate (Li ₄ Ti ₅ O ₁₂ ) powder is prepared as a negative electrode active material, the negative electrode active material: 90% by mass, graphite HS-100: 5% by mass as a conductive material, polyvinylidene fluoride (PVdF resin) ): 5% by mass, N-methyl-2-pyrrolidone (NMP) was added thereto so that the solid content ratio was 62%. The solid content ratio was gradually reduced while NMP was added thereto using an Excel auto homogenizer. This slurry was further mixed with a bead mill using a zirconia ball having a diameter of 1 mm as a medium to obtain a negative electrode active material layer forming liquid 1.

Next, the negative electrode active material layer forming liquid 1 was applied to one side of a negative electrode current collector made of aluminum foil having a thickness of 15 μm with an applicator in an amount such that the coating amount after drying was 66 g / m ^2, and dried. The negative electrode plate 1 was obtained by roll pressing with a roll heated to ° C.

<Preparation of non-aqueous electrolyte>
LiBF ₄ as an electrolyte was dissolved at a concentration of 1 mol / L in an organic solvent obtained by mixing 20% by volume of ethylene carbonate (EC) with γ-butyllactone (GBL) to obtain a nonaqueous electrolytic solution.

<Production of coin cell>
The positive electrode plate and the negative electrode plate produced by the above method are each cut to φ15 mm, placed in a coin cell so as to sandwich the separator, and the non-aqueous electrolyte produced by the above method is injected. A test cell was obtained.

(Example 2)
A test cell of Example 2 was obtained in the same manner as Example 1 except that instead of the negative electrode plate 1, a negative electrode plate 2 produced by the following method was formed.

(Preparation of negative electrode plate 2)
Li (CH ₃ COO) · 2H ₂ O: 5 g of pure water: 5 g and titanium chelating agent (Ti (Oi-C ₃ H ₇ ) ₂ (C ₆ H ₁₄ O ₃ N) ₂ ) : 20 g is mixed, and these are added to methanol: 35 g and mixed. Further, polyethylene glycol 200: 10 g, spinel-type lithium titanium composite oxide (Li ₄ Ti ₅ O ₁₂ ) powder as a negative electrode active material: 40 g, By adding graphite HS-100: 5 g as conductive material and carbon fiber (manufactured by Showa Denko KK, VGCF): 0.5 g, and kneading with an Excel auto homogenizer (Nihon Seiki Seisakusho Co., Ltd.) at a rotational speed of 7000 rpm for 15 minutes. A negative electrode active material layer forming liquid 2 was prepared.

Next, an aluminum plate having a thickness of 15 μm was prepared as a negative electrode current collector, and the negative electrode active material layer forming liquid 2 prepared above was applied in an amount such that the coating amount after drying was 62 g / m ^2. A coating film for forming a negative electrode active material layer was formed on one side of the body with an applicator. Subsequently, the coating film was pressed using a roll press machine (manufactured by Sank Metal Co., Ltd .: mechanical type 1 ton) under the conditions of applied pressure: 0.1 ton / cm and pressing speed of 10 mm / second. Thereafter, the negative electrode current collector having a negative electrode active material layer forming coating film formed thereon was placed in a normal temperature electric furnace (muffle furnace, manufactured by Denken, P90), and from room temperature to 500 ° C. over 3 hours. By gradually heating, a negative electrode plate 2 having a negative electrode active material layer laminated on a negative electrode current collector was obtained.

(Example 3)
A test cell of Example 3 was obtained in the same manner as Example 1 except that the positive electrode plate 2 produced by the following method was used instead of the positive electrode plate 1 of Example 1.

<Preparation of positive electrode plate 2>
Li (CH ₃ COO) · 2H ₂ O: 10 g and Mn (CH ₃ COO) ₂ · 4H ₂ O: 24 g were added to methanol: 35 g and mixed to obtain a raw material liquid for producing a metal oxide. Next, polyethylene glycol 200: 10 g in the above raw material liquid, lithium cobaltate (LiCoO ₂ ) particles: 40 g as positive electrode active material particles, graphite HS-100: 5 g as a conductive material, carbon fiber (Showa Denko KK, VGCF): 0.5 g was added, and the positive electrode active material layer forming liquid 2 was prepared by kneading with an Excel auto homogenizer (Nihon Seiki Seisakusho Co., Ltd.) at a rotation speed of 7000 rpm for 15 minutes.

Next, an aluminum plate having a thickness of 15 μm was prepared as a positive electrode current collector, and the positive electrode active material layer forming liquid 2 prepared above was applied in an amount such that the coating amount after drying was 76 g / m ^2. A coating film for forming a positive electrode active material layer was formed on one side of the body with an applicator. Subsequently, the coating film was pressed using a roll press machine (manufactured by Sank Metal Co., Ltd .: mechanical type 1 ton) under the conditions of applied pressure: 0.1 ton / cm and pressing speed of 10 mm / second. Thereafter, the current collector on which the positive electrode active material layer-forming coating film was formed was placed in a normal temperature electric furnace (Muffle furnace, Denken, P90) and gradually increased from room temperature to 500 ° C. over 3 hours. To obtain a positive electrode plate 2 having a positive electrode active material layer laminated on a positive electrode current collector.

Example 4
A test cell of Example 4 was obtained in the same manner as Example 1 except that instead of the positive electrode plate 1 of Example 1, the positive electrode plate 3 produced by the following method was used.

<Preparation of positive electrode plate 3>
Li (CH ₃ COO) · 2H ₂ O: 10 g and Co (No ₃ ) ₂ · 6H ₂ O: 29 g were added to methanol: 35 g and mixed to obtain a raw material liquid for producing a metal oxide. Next, polyethylene glycol 200: 10 g in the above raw material liquid, lithium cobaltate (LiCoO ₂ ) particles: 40 g as positive electrode active material particles, graphite HS-100: 5 g as a conductive material, carbon fiber (Showa Denko KK, VGCF): 0.5 g was added, and the positive electrode active material layer forming liquid 3 was prepared by kneading with an Excel auto homogenizer (Nihon Seiki Seisakusho Co., Ltd.) at a rotational speed of 7000 rpm for 15 minutes.

Next, an aluminum plate having a thickness of 15 μm was prepared as a positive electrode current collector, and the positive electrode active material layer forming liquid 3 prepared above was applied in an amount such that the coating amount after drying was 76 g / m ^2. A coating film for forming a positive electrode active material layer was formed on one side of the body with an applicator. Subsequently, the coating film was pressed using a roll press machine (manufactured by Sank Metal Co., Ltd .: mechanical type 1 ton) under the conditions of applied pressure: 0.1 ton / cm and pressing speed of 10 mm / second. Thereafter, the current collector on which the positive electrode active material layer-forming coating film was formed was placed in a normal temperature electric furnace (Muffle furnace, Denken, P90) and gradually increased from room temperature to 500 ° C. over 3 hours. To obtain a positive electrode plate 3 having a positive electrode active material layer laminated on a positive electrode current collector.

(Example 5)
A test cell of Example 5 was obtained in the same manner as Example 1 except that the positive electrode plate 4 produced by the following method was used instead of the positive electrode plate 1 of Example 1.

<Preparation of positive electrode plate 4>
The positive electrode plate 1 is immersed in a dipping tank filled with a resin mixture prepared by using a PVdF resin as a resin material and mixing with an NMP solvent so that the concentration of PVdF is 0.1%. The resin mixed solution was sufficiently infiltrated into the voids. Thereafter, the positive electrode plate 1 was taken out from the immersion layer, placed in an oven heated to 150 ° C., and dried for 15 minutes to remove the solvent of the resin mixed solution. As a result, the positive electrode plate 4 in which the resin binder remained in the positive electrode active material layer was obtained.

(Example 6)
A test cell of Example 6 was obtained in the same manner as Example 1 except that the positive electrode plate 5 produced by the following method was used instead of the positive electrode plate 1 of Example 1.

<Preparation of positive electrode plate 5>
The positive electrode plate 1 is immersed in a dipping tank filled with a resin mixture prepared by using a PVdF resin as a resin material and mixing with an NMP solvent so that the concentration of PVdF is 5%. The above resin mixture was sufficiently infiltrated into the resin. Thereafter, the positive electrode plate 1 was taken out from the immersion layer, placed in an oven heated to 150 ° C., and dried for 15 minutes to remove the solvent of the resin mixed solution. As a result, the positive electrode plate 5 in which the resin binder remained in the positive electrode active material layer was obtained.

(Comparative Example 1)
A test cell of Comparative Example 1 was obtained in the same manner as Example 1 except that the positive electrode plate 1 and negative electrode plate 1 of Example 1 were changed to the positive electrode plate 6 and the negative electrode plate 3 produced by the following method.

<Preparation of positive electrode plate 6>
Lithium manganate (LiMn ₂ O ₄ ) powder is prepared as a positive electrode active material, this positive electrode active material: 90% by mass, graphite HS-100: 5% by mass as a conductive material, polyvinylidene fluoride (PVdF resin): 5% % N-methyl-2-pyrrolidone (NMP) was added thereto so that the solid content ratio was 62%. The solid content ratio was gradually reduced while NMP was added thereto using an Excel auto homogenizer. This slurry was further mixed by a bead mill using a zirconia ball having a diameter of 1 mm as a medium to obtain a positive electrode active material layer forming liquid 4.

Next, the positive electrode active material layer forming liquid 4 was applied to one side of a positive electrode current collector made of aluminum foil having a thickness of 15 μm with an applicator in an amount such that the coating amount after drying was 117 g / m ^2, and dried. The positive electrode plate 6 was obtained by roll pressing with a roll heated to ° C.

<Preparation of negative electrode plate 3>
The negative electrode is the same as the negative electrode plate 1 except that graphite is used as the negative electrode active material, a copper foil having a thickness of 10 μm is used as the negative electrode current collector, and the coating amount after drying is 32 g / m ^2. Plate 3 was obtained.

(Battery characteristics evaluation)
Charging test:
The test cells of Examples 1 to 6 and Comparative Example 1 were charged with a constant current at a constant current until the voltage reached 2.8 V (end-of-charge voltage) in an environment of 25 ° C., and the voltage was 2.8 V. In order to prevent the voltage from exceeding 2.8 V, the current (discharge rate: 1 C) is reduced until it becomes 5% or less, and charging is performed at a constant voltage, and after full charging, 10 Paused for a minute. Here, “1C” means a current value (current value that reaches the discharge end voltage) at which constant current discharge is performed using the test cells of Examples 1 to 6 and discharge ends in 1 hour. Means that.

Discharge test:
Thereafter, the fully charged test cell of each example was subjected to a constant current (discharge rate :) until the voltage changed from 2.8 V (full charge voltage) to 1.1 V (discharge end voltage) in an environment of 25 ° C. 1C), constant current discharge, cell voltage (V) on the vertical axis, discharge time (h) on the horizontal axis, a discharge curve is created, and discharge of the working electrode (positive electrode plate of Examples 1 to 6) The capacity (mAh) was determined and converted to a discharge capacity (mAh / g) per unit active material mass of the working electrode.

  In the test cell of Comparative Example 1, a discharge test and a charge test were performed with the charge end voltage set to 4.2 V and the discharge end voltage set to 2.5 V.

  Subsequently, the test cell of each example was subjected to a constant current discharge test at a constant current (discharge rate: 1C, discharge end time: 1 hour), and the discharge capacity of the working electrode at the 1C rate was determined. Was converted to a discharge capacity (mAh / g). Next, based on the constant current discharge test at 1C rate, 5 times constant current (discharge rate 5C, discharge end time: 12 minutes), 10 times constant current (discharge rate 10C, discharge end time: 6 minutes), 40 A constant current discharge test at a double constant current (discharge rate 40C, discharge end time: 90 seconds) was performed to determine the discharge capacity (mAh) of the working electrode at each discharge rate, and the discharge capacity per unit active material mass (mAh / Converted to g).

<Calculation of discharge capacity maintenance rate (%)>
In order to evaluate the discharge rate characteristics of the test cells of Examples and Comparative Examples, each discharge capacity (mAh / g) per unit active material mass at each discharge rate obtained as described above was used. The discharge capacity retention rate (%) was determined. Table 1 shows the discharge capacity (mAh / g) and discharge capacity retention rate (%) per unit mass obtained by the above discharge test.

  As can be seen from the above table, each of the lithium ion secondary batteries of Examples 1 to 6 of the present invention takes an aspect in which the positive electrode active material particles are fixed with a metal oxide in the positive electrode plate, Moreover, in the negative electrode plate, since the lithium-titanium composite oxide was contained in the negative electrode active material layer, an excellent discharge capacity retention rate was obtained. On the other hand, in both the positive electrode plate and the negative electrode plate, Comparative Example 1, which is outside the scope of the present invention, has a lower discharge capacity retention rate than the Examples. From this, according to the lithium ion secondary battery of this invention, the request | requirement of the speeding-up of charging / discharging can fully be satisfy | filled.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode collector 2 ... Positive electrode active material layer 10 ... Positive electrode plate 21 ... Positive electrode active material particle 22 ... Binder material 32 ... Positive electrode terminal 33 ... Negative electrode terminal 34 ... Protection circuit board 35 ... External connector 36a, 36b ... Resin container 37 ... End case 38a, 38b ... External connection window 50 ... Negative electrode plate 54 ... Negative electrode active material Layer 55 ... Negative electrode current collector 70 ... Separator 81, 82 ... Exterior 90 ... Non-aqueous electrolyte 100 ... Lithium ion secondary battery 200 ... Battery pack

Claims (5)

A positive electrode plate comprising a positive electrode active material layer on a positive electrode current collector;
A negative electrode plate comprising a negative electrode active material layer on a negative electrode current collector;
A separator provided between the positive electrode plate and the negative electrode plate;
A lithium ion secondary battery comprising at least an electrolyte solution containing a non-aqueous solvent,
The positive electrode active material layer contains positive electrode active material particles and a metal oxide,
The positive electrode current collector and the positive electrode active material particles are fixed by the metal oxide, and the positive electrode active material particles are fixed by the metal oxide,
The lithium ion secondary battery, wherein the negative electrode active material layer contains a lithium titanium composite oxide.   The lithium ion secondary battery according to claim 1, wherein the metal oxide is a metal oxide exhibiting a lithium ion insertion / release reaction.   The metal oxide is a composite oxide of at least one metal selected from cobalt, nickel, manganese, iron, and titanium, and lithium. Lithium ion secondary battery.   4. The lithium according to claim 1, wherein the positive electrode active material layer includes a part of adjacent metal oxides connected by a continuous crystal lattice. 5. Ion secondary battery. A storage case, at least a lithium ion secondary battery having a positive electrode terminal and a negative electrode terminal, and a protection circuit having an overcharge and overdischarge protection function, the lithium ion secondary battery and the protection circuit being stored in the storage case In the battery pack configured as
The battery pack, wherein the lithium ion secondary battery is the lithium ion secondary battery according to any one of claims 1 to 4.

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