JP2007042302A - battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery capable of improving energy density and charge / discharge efficiency.
An open circuit voltage in a fully charged state is in a range of 4.25 V to 6.00 V, and a positive electrode 21 has Li _a Co _1-b M1 _b O _2-c (M1 is Mn, Ni, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Ga, Y, Zr, Nb, Mo, Sn, Ca, Sr, W. 0.9 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.3, −0.1 ≦ c ≦ 0.1), and Li _w Ni _x Co _y Mn _z M2 _1-xyz O _2-v (M2 represents Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Ga, Y, Zr, Nb, Mo, Sn, Ca, Sr, W. −0.1 ≦ v ≦ 0. 1,0.9 ≦ w ≦ 1.1, 0 <x <1, 0 <y <0.7, 0 <z <0.5, 0 ≦ 1-xyz ≦ 0.2) A second having an average composition represented by It contains the electrode material.
[Selection] Figure 1

Description

  The present invention relates to a battery using a plurality of types of positive electrode materials.

  In recent years, with the widespread use of portable information electronic devices such as mobile phones, video cameras, and notebook computers, the performance, size, and weight of the devices are rapidly developing. The power source used for these devices is a disposable primary battery or a rechargeable secondary battery. However, because of the good balance of economy, high performance, small size and light weight, the secondary battery is used. There is an increasing demand for batteries, particularly lithium ion secondary batteries. In addition, these portable information electronic devices are being further improved in performance and size, and lithium ion secondary batteries are also required to have higher energy density.

  In order to increase the energy density, it is important to use a positive electrode having a high discharge capacity per unit volume. For example, as the positive electrode active material, lithium (Li), cobalt (Co), nickel (Ni), manganese (Mn), etc. A composite oxide in which the transition metal is dissolved is used. In these positive electrode active materials, characteristics such as electric capacity, reversibility, operating voltage, and safety can be obtained by changing the type of transition metal.

For example, a secondary battery using an R-3m rhombohedral rock salt layered composite oxide such as LiCoO ₂ exhibits a relatively high capacity density of 140 mAh / g to 160 Ah / g and a high value of 2.5 V to 4.2 V. Good reversibility is exhibited in the voltage region, and further excellent chargeability is exhibited. Moreover, the secondary battery using LiNiO ₂ or the like shows a high capacity density of 180 mAh / g to 200 Ah / g, but on the other hand, the thermal stability is not sufficient, and due to the decomposition reaction of the electrolyte during the charge / discharge cycle, The problem that the life performance and storage performance are not sufficient is a problem. Furthermore, in a secondary battery using a complex oxide using relatively inexpensive manganese as a raw material, for example, a secondary battery using LiMn ₂ O ₄ , the capacity density is as low as 100 mAh / g to 120 Ah / g, Further, a secondary battery using orthorhombic LiMnO ₂ has a problem of low capacity density.

  By the way, the conventional lithium ion secondary battery uses lithium cobaltate for the positive electrode and a carbon material for the negative electrode, and the end-of-charge voltage is 4.1V to 4.2V. In the lithium ion secondary battery designed with the end-of-charge voltage in this way, the positive electrode active material such as lithium cobaltate used for the positive electrode utilizes a capacity of about 50% to 60% with respect to its theoretical capacity. Not too much. For this reason, it is theoretically possible to utilize the remaining capacity by further increasing the charging voltage, and it is known that the energy density can be increased by actually setting the charging voltage to 4.30 V or higher. (For example, refer to Patent Document 1).

  However, when the charging voltage is increased, the oxidizing atmosphere in the vicinity of the positive electrode becomes strong, and there is a problem that the positive electrode active material collapses or elutes, and the electrolyte or the separator easily deteriorates.

On the other hand, the lithium-nickel-cobalt-manganese composite oxide has high thermal stability even when the charge voltage is increased, and the discharge capacity is set to 160 mAh by setting the charge end voltage to 4.30 V or more, for example. / G to 200 mAh / g (see Non-Patent Document 1, Patent Documents 2 and 3).
"Chemistry Letters" 2001, p642-643 International Publication No. WO03 / 0197131 Pamphlet Japanese Patent No. 2561556 Japanese Patent No. 3244314

  However, the lithium-nickel-cobalt-manganese composite oxide has a problem that it is difficult to increase the energy density because the filling property with respect to the positive electrode is low and the discharge capacity per unit volume is low.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a battery that can improve energy density and charge / discharge efficiency.

  A battery according to the present invention is a battery in which a positive electrode having a positive electrode active material layer and a negative electrode having a negative electrode active material layer are arranged to face each other via a separator, and the open circuit in a fully charged state per pair of positive electrode and negative electrode The voltage is in the range of 4.25 V to 6.00 V, and the positive electrode active material layer includes the first positive electrode material having the average composition shown in Chemical Formula 1 and the second positive electrode material having the average composition shown in Chemical Formula 2. And a positive electrode material.

(Chemical formula 1)
Li _a Co _1-b M1 _b O _2-c
(In the formula, M1 is manganese, nickel, magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), From zinc (Zn), gallium (Ga), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W) Represents at least one of the group consisting of a, b and c in the range of 0.9 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.3, −0.1 ≦ c ≦ 0.1. Within.)

(Chemical formula 2)
Li _w Ni _x Co _y Mn _z M2 _1-xyz O _2-v
(Wherein M2 is at least one selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, gallium, yttrium, zirconium, niobium, molybdenum, tin, calcium, strontium, and tungsten. The values of v, w, x, y and z are −0.1 ≦ v ≦ 0.1, 0.9 ≦ w ≦ 1.1, 0 <x <1, 0 <y <0.7. , 0 <z <0.5, 0 ≦ 1-xyz ≦ 0.2.)

  According to the battery of the present invention, since the open circuit voltage at the time of full charge is in the range of 4.25V to 6.00V, a high energy density can be obtained. In addition, since the first positive electrode material having the average composition shown in Chemical Formula 1 and the second positive electrode material having the average composition shown in Chemical Formula 2 are mixed and used, the energy density is further increased. In addition, the charge / discharge efficiency can be improved.

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

  FIG. 1 shows a cross-sectional structure of a secondary battery according to an embodiment of the present invention. This secondary battery uses lithium as an electrode reactant. This secondary battery is a so-called cylindrical type, and a pair of strip-like positive electrode 21 and strip-like negative electrode 22 are arranged opposite to each other through a separator 23 inside a substantially hollow cylindrical battery can 11. It has a wound wound electrode body 20. 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 (Positive Temperature Coefficient; 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.

  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. Although not shown, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil. The positive electrode active material layer 21B includes, for example, a positive electrode material that can occlude and release lithium as a positive electrode active material.

  The positive electrode material capable of inserting and extracting lithium includes a first positive electrode material having an average composition shown in Chemical Formula 1 and a second positive electrode material having an average composition shown in Chemical Formula 2. This is because the first positive electrode material can increase the filling amount in the positive electrode active material layer 21B and can increase the energy density. In addition, with only the first positive electrode material, when the charging voltage is increased, the positive electrode material, the electrolyte, or the separator deteriorates, and the charge / discharge efficiency decreases. However, by mixing the second positive electrode material, It is because deterioration of the is suppressed.

(Chemical formula 1)
Li _a Co _1-b M1 _b O _2-c
(In the formula, M1 is a group consisting of manganese, nickel, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, gallium, yttrium, zirconium, niobium, molybdenum, tin, calcium, strontium, and tungsten. The values of a, b and c are in the range of 0.9 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.3, −0.1 ≦ c ≦ 0.1. Note that the composition of lithium differs depending on the state of charge and discharge, and the value of a represents the value in a fully discharged state.

(Chemical formula 2)
Li _w Ni _x Co _y Mn _z M2 _1-xyz O _2-v
(Wherein M2 is at least one selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, gallium, yttrium, zirconium, niobium, molybdenum, tin, calcium, strontium, and tungsten. The values of v, w, x, y and z are −0.1 ≦ v ≦ 0.1, 0.9 ≦ w ≦ 1.1, 0 <x <1, 0 <y <0.7. , 0 <z <0.5, 0 ≦ 1-xyz ≦ 0.2 Note that the composition of lithium varies depending on the state of charge and discharge, and the value of w is a value in a fully discharged state. Represents.)

  The ratio by mass ratio of the first positive electrode material and the second positive electrode material (first positive electrode material: second positive electrode material) is preferably in the range of 5: 5 to 9: 1, more Preferably it is 7: 3 to 9: 1. This is because when the proportion of the first positive electrode material is small, the energy density is lowered, and when the proportion of the first positive electrode material is large, the charge / discharge efficiency is lowered.

The density of the mixed powder of the first positive electrode material powder and the second positive electrode material powder may be 3.0 g / cm ³ or more when pressed at a pressure of 1 t / cm ^3. Preferably, it is more preferably 3.2 g / cm ³ or more. This is because when the positive electrode 21 is produced by compression molding, the capacity per unit volume can be increased by optimizing the particle size distribution of the powder. To give a specific example, when the particle size distribution of the powder is wide and the ratio of the powder having a small particle size is 20% by mass to 50% by mass, the particle size distribution of the powder having a large particle size is used. It is possible to optimize by narrowing.

A powder of a first cathode material, the specific surface area by BET (Brunauer Emmett Teller) method of mixing powders of the powder of the second cathode material, 0.05 m ² / g or more 10.0 m ² / g or less It is preferable that it is in the range of 0.1 m ² / g or more and 5.0 m ² / g or less. This is because within this range, even if the battery voltage is increased, the reactivity between the positive electrode material and the electrolytic solution can be reduced.

As a positive electrode material capable of inserting and extracting lithium, in addition to these positive electrode materials, other positive electrode materials may be mixed and used. Examples of other positive electrode materials include lithium-containing compounds such as lithium oxide, lithium phosphorus oxide, lithium sulfide, or an intercalation compound containing lithium, and a mixture of two or more of these may be used. Examples of such a lithium-containing compound include a lithium composite oxide having a spinel structure shown in Chemical Formula 3, or a lithium composite phosphate having an olivine structure shown in Chemical Formula 4, and specifically. Is Li _d Mn ₂ O ₄ (d≈1) or Li _e FePO ₄ (e≈1).

(Chemical formula 3)
_{Li p Mn 2-q M4 q} O r F s
(In the formula, M4 represents at least one selected from the group consisting of cobalt, nickel, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, calcium, strontium, and tungsten. p, q, r, and s are values in the range of 0.9 ≦ p ≦ 1.1, 0 ≦ q ≦ 0.6, 3.7 ≦ r ≦ 4.1, and 0 ≦ s ≦ 0.1. (Note that the composition of lithium varies depending on the state of charge and discharge, and the value of p represents the value in a fully discharged state.)

(Chemical formula 4)
Li _t M5PO ₄
(Wherein M5 represents at least one selected from the group consisting of cobalt, manganese, iron, nickel, magnesium, aluminum, boron, titanium, vanadium, niobium, copper, zinc, molybdenum, calcium, strontium, tungsten and zirconium. (T is a value in the range of 0.9 ≦ t ≦ 1.1. Note that the composition of lithium varies depending on the state of charge and discharge, and the value of t represents a value in the complete discharge state.)

In addition to these, examples of the positive electrode material capable of inserting and extracting lithium include inorganic compounds not containing lithium, such as MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , NiS, and MoS.

  The positive electrode active material layer 21B may include a conductive agent and a binder as necessary. Examples of the conductive agent include carbon-based materials such as acetylene black, graphite, and ketjen black. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyamide, carboxymethyl cellulose, and acrylic resin.

  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. Although not shown, the negative electrode active material layer 22B may be provided only on one surface of the negative electrode current collector 22A. The anode current collector 22A is made of, for example, a metal foil such as a copper foil.

  The negative electrode active material layer 22B includes one or more negative electrode materials capable of inserting and extracting lithium as a negative electrode active material.

  In this secondary battery, the electrochemical equivalent of the negative electrode material capable of inserting and extracting lithium is larger than the electrochemical equivalent of the positive electrode 21, and lithium metal is deposited on the negative electrode 22 during charging. It is supposed not to.

  In addition, this secondary battery is designed so that the open circuit voltage (that is, the battery voltage) at the time of full charge is in the range of 4.25V to 6.00V. Therefore, even if the positive electrode active material is the same as that of the battery having an open circuit voltage of 4.20 V at the time of full charge, the amount of lithium released per unit mass is increased. Accordingly, the positive electrode active material and the negative electrode active material And the amount has been adjusted. As a result, a high energy density can be obtained. In particular, the effect of using the first positive electrode material and the second positive electrode material described above is high when the open circuit voltage during complete charging is in the range of 4.25 V to 4.50 V.

  Examples of the negative electrode material capable of inserting and extracting lithium include non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, and fired organic polymer compounds , Carbon materials such as carbon fiber or activated carbon. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. An organic polymer compound fired body is a carbonized material obtained by firing a polymer material such as a phenol resin or a furan resin at an appropriate temperature, and part of it is non-graphitizable carbon or graphitizable carbon. Some are classified as: Examples of the polymer material include polyacetylene and polypyrrole. These carbon materials are preferable because the change in crystal structure that occurs during charge and discharge is very small, a high charge and discharge capacity can be obtained, and good cycle characteristics can be obtained. In particular, graphite is preferable because it has a high electrochemical equivalent and can provide a high energy density. Further, non-graphitizable carbon is preferable because excellent characteristics can be obtained. Furthermore, those having a low charge / discharge potential, specifically, those having a charge / discharge potential close to that of lithium metal are preferable because a high energy density of the battery can be easily realized.

  When a carbon material is used as the negative electrode material capable of inserting and extracting lithium, the area density ratio of the positive electrode active material layer 21B to the negative electrode active material layer 22B (area density of the positive electrode active material layer 21B / negative electrode active material layer) The area density of 22B is preferably in the range of 1.70 to 2.10. This is because when the area density is large, metallic lithium is deposited on the surface of the negative electrode 22, and charge / discharge efficiency or safety is lowered. In addition, when the area density ratio is small, the negative electrode material that does not participate in the reaction with lithium as the electrode reactant increases, and the energy density decreases.

  Examples of the negative electrode material capable of inserting and extracting lithium include materials capable of inserting and extracting lithium and containing at least one of a metal element and a metalloid element as a constituent element. . This is because a high energy density can be obtained by using such a material. In particular, the use with a carbon material is more preferable because a high energy density can be obtained and excellent cycle characteristics can be obtained. The negative electrode material may be a single element, alloy or compound of a metal element or metalloid element, or may have at least a part of one or more of these phases. In the present invention, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist.

  Examples of the metal element or metalloid element constituting the negative electrode material include magnesium, boron, aluminum, gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin, lead (Pb), Bismuth (Bi), cadmium (Cd), silver (Ag), zinc, hafnium (Hf), zirconium, yttrium, palladium (Pd), or platinum (Pt) can be used. These may be crystalline or amorphous.

  Among these, as the negative electrode material, a material containing a 4B group metal element or a semimetal element in the short-period type periodic table as a constituent element is preferable, and at least one of silicon and tin is particularly preferable as a constituent element. This is because silicon and tin have a large ability to occlude and release lithium, and a high energy density can be obtained.

  Examples of the tin alloy include, as the second constituent element other than tin, silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony (Sb), and chromium. The thing containing at least 1 sort (s) of the group which consists of 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.

  Examples of the tin compound or silicon compound include those containing oxygen (O) or carbon (C), and may contain the second constituent element described above in addition to tin or silicon.

Examples of the negative electrode material capable of inserting and extracting lithium further include other metal compounds or polymer materials. Examples of other metal compounds include oxides such as MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ ), sulfides such as NiS and MoS, and lithium nitrides such as LiN _3. Examples include polyacetylene, polyaniline, and polypyrrole.

  The negative electrode active material layer 22B may contain a conductive agent and a binder as necessary. Examples of the conductive agent include graphites such as artificial graphite and expanded graphite, carbon blacks such as acetylene black, ketjen black, channel black and furnace black, conductive fibers such as carbon fiber and metal fiber, copper powder or Examples thereof include metal powders such as nickel powder, and organic conductive materials such as polyphenylene derivatives, among which acetylene black, ketjen black or carbon fiber is preferable. The addition amount of the conductive agent is preferably in the range of 0.1 to 30 parts by mass with respect to 100 parts by mass of the negative electrode material, and is in the range of 0.5 to 10 parts by mass. More preferred. As the conductive agent, one kind may be used alone, or a plurality of kinds may be mixed and used. Examples of the binder include polytetrafluoroethylene and polyvinylidene fluoride, and one kind may be used alone, or a plurality kinds may be mixed and used.

  The separator 23 has, for example, a base material layer and at least a part of the surface facing the positive electrode 21, more preferably the entire surface facing the positive electrode 21, more preferably a surface layer provided on both surfaces. ing. As a base material layer, it is comprised by the porous film made from synthetic resins, such as a polypropylene or polyethylene, for example, It may be set as the structure which laminated | stacked these 2 or more types of porous films. Among these, a porous film made of polyolefin is preferable because it is excellent in short-circuit preventing effect and can improve the safety of the battery due to the shutdown effect. In particular, polyethylene is preferable as a material constituting the base material layer because it can provide a shutdown effect within a range of 100 ° C. or higher and 160 ° C. or lower and is excellent in electrochemical stability. Polypropylene is also preferable, and any other resin having chemical stability can be used by copolymerizing or blending with polyethylene or polypropylene.

  The surface layer includes at least one of polyvinylidene fluoride and polypropylene. Thereby, chemical stability improves and the fall of charging / discharging efficiency by generation | occurrence | production of a micro short circuit is suppressed. In addition, when forming with a surface layer polypropylene, it is good also considering a base material layer as a single layer by forming with a polypropylene.

  The thickness of the surface layer facing the positive electrode 21 is preferably in the range of 0.1 μm or more and 10 μm or less. This is because if the thickness is small, the effect of suppressing the occurrence of micro-shorts is low, and if the thickness is large, the ion conductivity decreases and the volume capacity decreases.

  The pore diameter of the separator 23 is preferably in a range that does not allow eluate from the positive electrode 21 or the negative electrode 22 to permeate, and specifically in the range of 0.01 μm to 1 μm. Moreover, the thickness of the separator 23 is, for example, in the range of 10 μm to 300 μm, and preferably in the range of 15 μm to 30 μm. This is because if the thickness is small, a short circuit may occur, and if the thickness is large, the filling amount of the positive electrode material decreases. The porosity of the separator 23 is determined by electron and ion permeability, material, or thickness, but is generally in the range of 30% by volume to 80% by volume, more preferably 35% by volume to 50% by volume. Within the following range. This is because if the porosity is low, the ionic conductivity is lowered, and if it is high, a short circuit may occur.

  The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. This electrolytic solution contains a solvent and an electrolyte salt dissolved in the solvent.

  As the solvent, cyclic carbonates such as ethylene carbonate or propylene carbonate can be used, and it is preferable to use one of ethylene carbonate and propylene carbonate, particularly a mixture of both. This is because the cycle characteristics can be improved.

  As the solvent, in addition to these cyclic carbonates, it is preferable to use a mixture of chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate or methylpropyl carbonate. This is because high ionic conductivity can be obtained.

  It is preferable that the solvent further contains 2,4-difluoroanisole or vinylene carbonate. This is because 2,4-difluoroanisole can improve discharge capacity, and vinylene carbonate can improve cycle characteristics. Therefore, it is preferable to use a mixture of these because the discharge capacity and cycle characteristics can be improved.

  In addition to these, examples of the solvent include butylene carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3- Dioxolane, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropironitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N-dimethyl Examples include imidazolidinone, nitromethane, nitroethane, sulfolane, dimethyl sulfoxide, and trimethyl phosphate.

  A compound obtained by substituting at least a part of hydrogen in these non-aqueous solvents with fluorine may be preferable because the reversibility of the electrode reaction may be improved depending on the type of electrode to be combined.

As electrolyte salt, lithium salt is mentioned, for example, 1 type may be used independently, and 2 or more types may be mixed and used for it. Lithium salts include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, LiBr or the like. Among them, LiPF ₆ is preferable because it can obtain high ion conductivity and can improve cycle characteristics.

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

  First, for example, a first positive electrode material and a second positive electrode material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and this positive electrode mixture is mixed with N-methyl-2-pyrrolidone or the like. A paste-like positive electrode mixture slurry is prepared by dispersing in a solvent. Next, the positive electrode mixture slurry is applied to the positive electrode current collector 21 </ b> A, the solvent is dried, and the positive electrode active material layer 21 </ b> B is formed by compression molding using a roll press or the like, thereby forming the positive electrode 21.

  Further, for example, a negative electrode 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. Make it. Next, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, the solvent is dried, and the negative electrode active material layer 22B is formed by compression molding with a roll press machine or the like, and the negative electrode 22 is manufactured.

  Subsequently, 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 of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip 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 a gasket 17. Thereby, the secondary battery shown in FIG. 1 is formed.

  In this secondary battery, when charged, lithium ions are released from the positive electrode active material layer 21B, and the negative electrode material that can occlude and release lithium contained in the negative electrode active material layer 22B via the electrolytic solution. Occluded. Next, when discharging is performed, lithium ions stored in the negative electrode material capable of inserting and extracting lithium in the negative electrode active material layer 22B are released, and are inserted into the positive electrode active material layer 21B through the electrolytic solution. . Here, since the first positive electrode material and the second positive electrode material are included in the positive electrode 21, even if the open circuit voltage at the time of full charge is increased, the energy density becomes higher and the charge / discharge efficiency is improved. Is done.

  As described above, according to the secondary battery according to the present embodiment, the open circuit voltage at the time of full charge is in the range of 4.25 V or more and 6.00 V or less, so that a high energy density can be obtained. In addition, since the first positive electrode material and the second positive electrode material are mixed and used, the energy density can be further increased and the charge / discharge efficiency can be improved.

  In particular, the ratio by mass ratio of the first positive electrode material and the second positive electrode material (first positive electrode material: second positive electrode material) should be within a range of 5: 5 to 9: 1. If the negative electrode active material layer 22B contains a carbon material, the area density ratio of the positive electrode active material layer 21B to the negative electrode active material layer 22B (area density of the positive electrode active material layer 21B / area density of the negative electrode active material layer 22B) If the value is in the range of 1.70 or more and 2.10 or less, a higher effect can be obtained.

  Furthermore, if at least a part of the separator 23 on the positive electrode side is made of at least one of polyvinylidene fluoride and polypropylene, the charge / discharge efficiency can be further improved.

  Furthermore, specific examples of the present invention will be described in detail.

(Examples 1-1 to 1-7)
First, lithium hydroxide (LiOH) and a coprecipitated hydroxide represented by Co _0.98 Al _0.01 Mg _0.01 (OH) ₂ are mixed at a molar ratio of lithium and the other metal elements of Li: (Co + Al + Mg) = The mixture was mixed at 1: 1, and this mixture was heat-treated in air at 800 ° C. for 12 hours to produce a first positive electrode material having an average composition represented by LiCo _0.98 Al _0.01 Mg _0.01 O ₂ . Next, the obtained first positive electrode material was pulverized to have a BET specific surface area of 0.44 m ² / g, an average particle diameter of 6.2 μm, and a BET specific surface area of 0.20 m ² / g, Those having an average particle diameter of 16.7 μm were prepared, and these were mixed at a mass ratio of 15:85.

The molar ratio of lithium hydroxide and the coprecipitated hydroxide represented by Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ to the total of lithium and other metal elements is Li: (Ni + Co + Mn) = 1: 1. The mixture was heat-treated in air at 1000 ° C. for 20 hours to produce a second positive electrode material having an average composition represented by LiNi _0.5 Co _0.2 Mn _0.3 O ₂ . Next, the obtained second positive electrode material was pulverized. The specific surface area by BET after pulverization was 0.38 m ² / g, and the average particle size was 11.5 μm.

  In addition, when the X-ray-diffraction measurement by CuK (alpha) was performed about the produced 1st positive electrode material and 2nd positive electrode material, it was confirmed that both have R-3m rhombohedral layered rock salt structure.

Subsequently, the secondary battery shown in FIGS. 1 and 2 was produced using the produced first positive electrode material and second positive electrode material. First, a positive electrode mixture was prepared by mixing the first positive electrode material and the second positive electrode material, ketjen black as a conductive agent, and polyvinylidene fluoride as a binder. At that time, in Examples 1-1 to 1-7, the ratio between the first positive electrode material and the second positive electrode material was changed as shown in Table 1. The ratio of ketjen black and polyvinylidene fluoride in the positive electrode mixture was the same. Next, this positive electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, which is applied to both surfaces of a positive electrode current collector 21A made of a strip-shaped aluminum foil having a thickness of 20 μm, and dried. The positive electrode active material layer 21B was formed by compression molding with a press machine, and the positive electrode 21 was produced. At that time, in Examples 1-1 to 1-7, the positive electrode active material layer 21B had the same area density and the same pressure applied by a roll press. When the volume density of the positive electrode active material layers 21B of Examples 1-1 to 1-7 was examined, Example 1-1 was 3.6 g / cm ³ , Example 1-2 was 3.6 g / cm ³ , and example 1-3 3.5 g / cm ^3, example 1-4 3.4 g / cm ^3, example 1-5 3.35 g / cm ^3, example 1-6 3.3 g / cm ³ Example 1-7 was 3.2 g / cm ³ . The results are shown in Table 1. Subsequently, a positive electrode lead 25 made of nickel was attached to the positive electrode current collector 21A.

Further, as a negative electrode material, a granular artificial graphite powder having a BET specific surface area of 0.58 m ² / g, a vapor-grown carbon fiber as a conductive agent, and polyvinylidene fluoride as a binder are mixed to prepare a negative electrode mixture. Prepared. Next, this negative electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry, which is applied to both surfaces of a negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 12 μm, and dried. The negative electrode active material layer 22B was formed by compression molding with a press machine, and the negative electrode 22 was produced. When the volume density of the negative electrode active material layer 22B was examined, it was 1.80 g / cm ³ . Subsequently, a negative electrode lead 26 made of nickel was attached to the negative electrode current collector 22A. At that time, the amounts of the positive electrode material and the negative electrode material were adjusted, and the open circuit voltage at the time of full charge was 4.40 V, and the capacity of the negative electrode 22 was designed to be represented by a capacity component due to insertion and extraction of lithium. The area density ratio of the positive electrode active material layer 21B to the negative electrode active material layer 22B is as shown in Table 1.

  After each of the positive electrode 21 and the negative electrode 22 was prepared, a microporous membrane separator 23 was prepared, and the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 were laminated in this order, and this laminate was wound many times in a spiral shape. A jelly roll type wound electrode body 20 was produced. The separator 23 had a thickness of 20 μm and a three-layer structure in which a polypropylene layer was provided on both sides of the polyethylene layer. Further, in each of Examples 1-1 to 1-7, the lengths of the positive electrode 21 and the negative electrode 22 in the winding direction were adjusted so that the outer diameter of the wound electrode body 20 was 17.19 mm.

After producing the wound electrode body 20, the wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15. The wound electrode body 20 was housed inside the battery can 11. Thereafter, an electrolytic solution is injected into the battery can 11 and the battery lid 14 is caulked to the battery can 11 via the gasket 17, whereby Examples 1-1 to 1-7 have an outer diameter of 18 mm and a height of 65 mm. A cylindrical secondary battery was obtained. In the electrolytic solution, LiPF ₆ as an electrolyte salt was added to a solvent prepared by mixing 15% by mass of ethylene carbonate, 12% by mass of propylene carbonate, 5% by mass of ethyl methyl carbonate, 67% by mass of dimethyl carbonate, and 1% by mass of vinylene carbonate. What was dissolved so that it might become 5 mol / kg was used.

As Comparative Example 1-1 with respect to Examples 1-1 to 1-7, the first positive electrode material was not used, and only the second positive electrode material having an average composition represented by LiNi _0.5 Co _0.2 Mn _0.3 O ₂ was used. Except for this, secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-7. Further, as Comparative Example 1-2, the other examples were used except that the second positive electrode material was not used and only the first positive electrode material having an average composition represented by LiCo _0.98 Al _0.01 Mg _0.01 O ₂ was used. Secondary batteries were fabricated in the same manner as 1-1 to 1-7. Also in Comparative Examples 1-1 and 1-2, the volume density of the positive electrode active material layer 21B was examined in the same manner as in Examples 1-1 to 1-7, and each was as shown in Table 1.

  Furthermore, as Comparative Examples 1-3 to 1-11, the ratio between the first positive electrode material and the second positive electrode material was changed as shown in Table 1, and the open circuit voltage during full charge was 4.20 V. A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-7 except that the amounts of the positive electrode material and the negative electrode material were adjusted so that Also in Comparative Examples 1-3 to 1-11, the volume density of the positive electrode active material layer 21B was examined in the same manner as in Examples 1-1 to 1-7, and each was as shown in Table 2.

The obtained secondary batteries of Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-11 were charged and discharged at 25 ° C., and the discharge capacity at the fifth cycle and the discharge capacity at the 200th cycle were maintained. The rate and discharge capacity were examined. At that time, charging was performed at a constant current of 2400 mA up to the upper limit voltage, and then the charging current was attenuated to 10 mA at the upper limit voltage, and discharging was performed at a constant current of 2400 mA until the terminal voltage reached 3.0V. The upper limit voltage was 4.40 V in Examples 1-1 to 1-7 and Comparative Examples 1-1 and 1-2, and 4.2 V in Comparative Examples 1-3 to 1-11. The capacity maintenance rate at the 200th cycle was determined as the ratio of the discharge capacity at the 200th cycle to the discharge capacity at the second cycle (discharge capacity at the 200th cycle / discharge capacity at the second cycle) × 100 (%). The obtained results are shown in Tables 1 and 2. The discharge capacity is a value per 1 g or 1 cm ³ of the positive electrode active material layer 21B, and was obtained by the battery discharge capacity (mAh) / the amount of the positive electrode active material layer 21B (g or cm ³ ).

  As shown in Table 1, according to Examples 1-1 to 1-7 using a mixture of the first positive electrode material and the second positive electrode material, comparative examples using only the second positive electrode material Compared to 1-1, the volume density of the positive electrode active material layer 21B was improved, and thereby the discharge capacity per unit volume could be improved. Moreover, according to Examples 1-1 to 1-7, the discharge capacity retention ratio could be improved as compared with Comparative Example 1-2 using only the first positive electrode material. On the other hand, as shown in Table 2, in Comparative Examples 1-3 to 1-11 in which the open circuit voltage during full charge was 4.20 V, the first positive electrode material and the second positive electrode material were mixed. However, the improvement of the discharge capacity maintenance rate was not seen.

  That is, even if the open circuit voltage during full charge is higher than 4.20 V, if the first positive electrode material and the second positive electrode material are mixed and used, the discharge capacity and the discharge capacity maintenance rate It was found that both can obtain high values.

  Further, as the ratio of the first positive electrode material was decreased, the volume density of the positive electrode active material layer 21B decreased, and the discharge capacity per unit volume tended to decrease. That is, the ratio by mass ratio of the first positive electrode material and the second positive electrode material (first positive electrode material: second positive electrode material) is preferably in the range of 5: 5 to 9: 1. More preferably, it was found to be 7: 3 to 9: 1.

(Examples 2-1 and 2-2)
Except that the average composition of the second positive electrode material was LiNi _0.33 Co _0.33 Mn _0.33 O ₂ and the ratio of the first positive electrode material and the second positive electrode material was changed as shown in Table 3, Secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-7. The molar ratio of nickel, cobalt, and manganese in the second positive electrode material is 1: 1: 1. Note that the second positive electrode material contains lithium hydroxide and a coprecipitated hydroxide represented by Ni _0.33 Co _0.33 Mn _0.33 (OH) ₂ , and the molar ratio of lithium to the total of other metal elements is Li: The mixture was prepared so that (Ni + Co + Mn) = 1: 1, and the mixture was heat-treated in air at 1000 ° C. for 20 hours and then pulverized. The specific surface area by BET of the second positive electrode material after pulverization was 0.42 m ² / g, and the average particle size was 10.3 μm. When the X-ray diffraction measurement by CuKα was performed also for the second positive electrode material, it was confirmed that both had an R-3m rhombohedral layered rock salt structure. Also, in Examples 2-1 and 2-2, the volume density of the positive electrode active material layer 21B was examined in the same manner as in Examples 1-1 to 1-7. It was.

As Comparative Example 2-1 with respect to Examples 2-1 and 2-2, the first positive electrode material was not used, and only the second positive electrode material having an average composition represented by LiNi _0.33 Co _0.33 Mn _0.33 O ₂ was used. Except for this, a secondary battery was fabricated in the same manner as in Examples 2-1 and 2-2. Also in Comparative Example 2-1, when the volume density of the positive electrode active material layer 21B was examined in the same manner as in Examples 1-1 to 1-7, it was as shown in Table 3.

  For the obtained secondary batteries of Examples 2-1 and 2-2 and Comparative Example 2-1, charge and discharge were performed in the same manner as in Examples 1-1 to 1-7, and the discharge capacity at the fifth cycle, In addition, the discharge capacity retention ratio and discharge capacity at the 200th cycle were examined. The results are shown in Table 3 together with the results of Comparative Example 1-2.

  As shown in Table 3, according to Examples 2-1 and 2-2, compared with Comparative Example 2-1 using only the second positive electrode material, as in Examples 1-1 to 1-7. Thus, the discharge capacity per unit volume could be improved, and the discharge capacity retention rate could be improved as compared with Comparative Example 1-2 using only the first positive electrode material. That is, it has been found that it is preferable to use a mixture of the first positive electrode material shown in Chemical formula 1 and the second positive electrode material shown in Chemical formula 2.

(Examples 3-1 to 3-4)
Except that the amounts of the positive electrode material and the negative electrode material were adjusted so that the open circuit voltages at the time of full charge were 4.25 V, 4.35 V, 4.45 V, and 4.50 V, other than that of Example 1-2 Similarly, a secondary battery was produced. As Comparative Example 3-1 with respect to Examples 3-1 to 3-4, except that the amounts of the positive electrode material and the negative electrode material were adjusted so that the open circuit voltage at the time of full charge was 4.20 V. A secondary battery was fabricated in the same manner as in Example 1-2. For Examples 3-1 to 3-4 and Comparative Example 3-1, the volume density of the positive electrode active material layer 21B was examined in the same manner as in Example 1-2. The results were as shown in Table 4, respectively. It was.

  The obtained secondary batteries of Examples 3-1 to 3-4 and Comparative Example 3-1 were charged and discharged in the same manner as in Example 1-2, and the discharge capacity at the fifth cycle and the 200th cycle The discharge capacity retention rate and the discharge capacity were investigated. The results are shown in Table 4 together with the results of Example 1-2.

  As shown in Table 4, as the open circuit voltage during full charge was increased, the discharge capacity at the fifth cycle was improved, and the discharge capacity at the 200th cycle was improved and then decreased. That is, it was found that the energy density can be improved if the open circuit voltage at the time of full charge is made higher than 4.20V. In addition, it was found that if the voltage is in the range of 4.25 V to 4.45 V, a high capacity can be obtained even after 200 cycles, and in particular, 4.40 V is preferable.

(Examples 4-1 to 4-5)
A secondary battery was fabricated in the same manner as in Example 1-2, except that the area density ratio of the positive electrode active material layer 21B to the negative electrode active material layer 22B was changed. For the obtained secondary batteries of Examples 4-1 to 4-5, charging and discharging were performed in the same manner as in Example 1-2, and the discharge capacity at the fifth cycle, the discharge capacity maintenance rate at the 200th cycle, and The discharge capacity was examined. The results are shown in Table 5 together with the results of Example 1-2.

  As shown in Table 5, as the area density ratio of the positive electrode active material layer 21B to the negative electrode active material layer 22B is lowered, the amount of the positive electrode active material filled in the battery is reduced, so that the discharge capacity per unit volume is reduced. Tended to decline. That is, it was found that the area density ratio of the positive electrode active material layer 21B to the negative electrode active material layer 22B is preferably 1.70 or more.

(Examples 5-1 to 5-5)
A secondary battery was fabricated in the same manner as in Example 1-2 except that the configuration of the separator 23 was changed. As the separator 23, a single layer film of polyethylene was used in Example 5-1, and a single layer film of polypropylene was used in Example 5-2. The thickness of the separator 23 in each of Examples 5-1 and 5-2 was set to 20 μm as in Example 1-2. Moreover, in Examples 5-3 to 5-5, the thing of the 3 layer structure which provided the polypropylene layer on both surfaces of the polyethylene layer similarly to Example 1-2 was used, and the thickness was changed with 15 micrometers, 23 micrometers, or 30 micrometers. It was.

  As Comparative Examples 5-1 and 5-2 with respect to Examples 5-1 to 5-5, except that the amounts of the positive electrode material and the negative electrode material were adjusted so that the open circuit voltage at the time of full charge was 4.20 V Other than that, a secondary battery was fabricated in the same manner as in Example 5-1 or Example 1-2.

  For the obtained secondary batteries of Examples 5-1 to 5-5 and Comparative Examples 5-1 and 5-2, charging and discharging were performed in the same manner as in Example 1-2, and the discharge capacity at the fifth cycle was In addition, the discharge capacity retention ratio and discharge capacity at the 200th cycle were examined. The results are shown in Table 5 together with the results of Example 1-2.

  As shown in Table 6, according to Examples 5-1 to 5-5, the capacity could be improved as compared with Comparative Examples 5-1 and 5-2. Also, the capacity of Examples 1-2, 5-2 to 5-5 in which a polypropylene single layer film or a polypropylene layer was used as a surface was higher than Example 5-1 using a polyethylene single layer film. The maintenance rate was obtained. Furthermore, as the thickness of the separator 23 was increased, the capacity retention ratio was improved, but the capacity decreased because the filling amount of the positive electrode active material was decreased.

  That is, it has been found that it is more preferable if at least a part of the separator 23 on the positive electrode 23 side is made of polypropylene in a battery having an open circuit voltage higher than 4.20 V during full charge. Moreover, it turned out that it is preferable to make the thickness of the separator 23 into the range of 15 micrometers or more and 30 micrometers or less.

(Examples 6-1 and 6-2)
A secondary battery was fabricated in the same manner as in Example 1-2, except that the configuration of the negative electrode 22 was changed. In Example 6-1, a negative electrode active material layer 22B having a thickness of 5.0 μm made of silicon was formed on the negative electrode current collector 22A by a sputtering method, and the negative electrode 22 was produced. In Example 6-2, a negative electrode 22 was produced in the same manner as in Example 1-2 except that a copper tin alloy containing 55% by mass of copper and 45% by mass of tin was used as the negative electrode material.

  As Comparative Examples 6-1 to 6-4 with respect to Examples 6-1 and 6-2, except that only the first positive electrode material or the second positive electrode material was used, Example 6-1 or Example 6 was otherwise used. A secondary battery was produced in the same manner as in Example-2.

  For the obtained secondary batteries of Examples 6-1 and 6-2 and Comparative Examples 6-1 to 6-4, charging and discharging were performed in the same manner as in Example 1-2, and the discharge capacity at the fifth cycle was In addition, the discharge capacity retention ratio and the discharge capacity at the 200th cycle were examined. The results are shown in Table 7 together with the results of Example 1-2 and Comparative Examples 1-1 and 1-2.

  As shown in Table 7, if the first positive electrode material and the second positive electrode material are mixed and used, even if other negative electrode materials are used, both the discharge capacity and the discharge capacity retention ratio are high. I found out that

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the secondary battery having a winding structure has been described. However, the present invention is similarly applied to a secondary battery having a structure in which the positive electrode and the negative electrode are folded or stacked. be able to. In addition, the present invention can also be applied to a so-called coin type, button type, or square type secondary battery.

  Further, although cases have been described with the above embodiment and examples where an electrolytic solution is used, the present invention can also be applied to cases where other electrolytes are used. Examples of other electrolytes include so-called gel electrolytes in which an electrolytic solution is held in a polymer compound, or electrolyte salts dispersed in a polymer compound having ion conductivity.

It is sectional drawing showing the structure of the secondary battery which concerns on one embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery 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 (4)

A battery in which a positive electrode having a positive electrode active material layer and a negative electrode having a negative electrode active material layer are arranged to face each other via a separator,
The open circuit voltage in a fully charged state per pair of positive electrode and negative electrode is in the range of 4.25V to 6.00V,
The positive electrode active material layer includes a first positive electrode material having an average composition shown in Chemical Formula 1 and a second positive electrode material having an average composition shown in Chemical Formula 2.
(Chemical formula 1)
Li _a Co _1-b M1 _b O _2-c
(In the formula, M1 is manganese (Mn), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe). , Copper (Cu), zinc (Zn), gallium (Ga), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) And at least one member selected from the group consisting of tungsten (W), and the values of a, b, and c are 0.9 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.3, and −0.1 ≦ c. Within the range of ≦ 0.1.)
(Chemical formula 2)
Li _w Ni _x Co _y Mn _z M2 _1-xyz O _2-v
(Wherein M2 is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn) , Gallium (Ga), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W) The values of v, w, x, y and z are -0.1 ≦ v ≦ 0.1, 0.9 ≦ w ≦ 1.1, 0 <x <1, 0 <y. <0.7, 0 <z <0.5, 0 ≦ 1-xyz ≦ 0.2.   A ratio (first positive electrode material: second positive electrode material) based on a mass ratio between the first positive electrode material and the second positive electrode material is in a range of 5: 5 to 9: 1. The battery according to claim 1. The negative electrode active material layer includes a carbon material,
The area density ratio of the positive electrode active material layer to the negative electrode active material layer (area density of the positive electrode active material layer / area density of the negative electrode active material layer) is in the range of 1.70 to 2.10. The battery according to claim 1. The battery according to claim 1, wherein at least a part of the separator on the positive electrode side is made of at least one of polyvinylidene fluoride and polypropylene.

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