WO2013002369A1

WO2013002369A1 - Non-aqueous electrolyte secondary cell, and method for producing same

Info

Publication number: WO2013002369A1
Application number: PCT/JP2012/066695
Authority: WO
Inventors: 晃宏河北; 毅小笠原
Original assignee: 三洋電機株式会社
Priority date: 2011-06-30
Filing date: 2012-06-29
Publication date: 2013-01-03

Abstract

The main purpose of the present invention is to provide a non-aqueous electrolyte secondary cell and a method for producing same, wherein it is possible to inhibit the deterioration of the charge-discharge cycle properties at high temperatures even when a newly-formed surface is created on the surface or in the interior of the negative electrode. A negative electrode active material layer containing negative electrode active material particles having silicon particles therein is formed on the surface of a negative electrode collector, the negative electrode active material layer being characterized by being provided therein with: a bonding binder for bonding the negative electrode active material particles with one another, and the negative electrode active material particles with the negative electrode collector; a negative electrode which contains a covering binder for covering a portion of the surfaces of the negative electrode active material particles such that the covering binder is present on the surface and in the interior of the negative electrode; a positive electrode containing a positive electrode active material having the particles of a lithium transition metal complex oxide therein; a separator disposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte.

Description

Non-aqueous electrolyte secondary battery and manufacturing method thereof

The present invention relates to a non-aqueous electrolyte secondary battery and a method for manufacturing the same, and more specifically to a negative electrode using a material containing silicon, a silicon alloy, or the like as a negative electrode active material, and an improvement in the method for manufacturing the same.

In recent years, mobile information terminals such as mobile phones, notebook computers, tablets, etc. are rapidly becoming smaller and lighter, and batteries for driving power sources are required to have higher capacities. Lithium ion batteries that charge and discharge when lithium ions move between the positive and negative electrodes along with charge and discharge have high energy density and high capacity. Widely used.

Here, the mobile information terminal has a tendency to further increase the power consumption with enhancement of functions such as a video playback function and a game function. As a purpose, further increase in capacity and performance are strongly desired. In consideration of the above, the discharge of the nonaqueous electrolyte secondary battery can be achieved by using an aluminum alloy, silicon, silicon alloy, or tin alloy having a higher lithium storage amount per unit volume than the graphite material as the negative electrode active material. Attempts have been made to increase capacity.

However, in the non-aqueous electrolyte secondary battery using the negative electrode active material, the negative electrode active material is pulverized or negative electrode active material due to the large volume change of the negative electrode active material during insertion and extraction of lithium. May be detached from the negative electrode current collector. For this reason, as a result of destroying the current collection structure in the negative electrode, there was a problem that the electron conductivity inside the negative electrode was lowered and the charge / discharge cycle characteristics were lowered.

Therefore, in order to exhibit high current collection in the electrode, a proposal has been made to sinter and dispose a negative electrode active material layer including a negative electrode active material composed of a material containing silicon and a polyimide binder in a non-oxidizing atmosphere. (See Patent Document 1 below). With such a configuration, the binding force between the negative electrode active material particles and between the negative electrode active material and the negative electrode current collector is improved, and it is described that the charge / discharge cycle characteristics can be improved.

In addition, a proposal has been made that a layer containing a binder having a high strength of 5 to 70 Mp, a filler such as silica, and lithium imide is provided on a porous active material layer containing a metal-based active material (see Patent Document 2 below). ). With such a configuration, the layer formed on the outermost surface of the negative electrode can mechanically suppress the expansion of the negative electrode (negative electrode active material) present in the layer and improve the cycle life. Is described.

Japanese Patent Laid-Open No. 2002-260637 JP 2009-135104 A

However, the current collection (electron conductivity) in the negative electrode and the expansion and contraction from the negative electrode surface mechanically are suppressed by the above technique, because a large volume change occurs in the silicon during charge and discharge. There has been a problem that the deterioration of charge / discharge characteristics due to cracking and oxidation of the particle surface is still large particularly at high temperatures. Specifically, when a crack occurs on the surface of the silicon particle, a very active new surface appears, and a reductive decomposition reaction of the nonaqueous electrolyte occurs on this new surface. Further, when the potential of the negative electrode is increased at the end of discharge, silicon and the non-aqueous electrolyte react with each other on the new surface, and the silicon is oxidized and inactivated. Therefore, when a material containing silicon or a silicon alloy is used as the negative electrode active material, it is necessary to improve the negative electrode on the premise that a new surface is generated.

In the present invention, a negative electrode active material layer including negative electrode active material particles containing silicon and / or silicon alloy particles is formed on a surface of a negative electrode current collector, and the negative electrode active material layer includes the negative electrode active material. A binder for fixing the particles and the negative electrode active material particles and the negative electrode current collector; and a coating binder for covering a part of the surface of the negative electrode active material particles. Is present on the negative electrode surface and inside the negative electrode, a positive electrode containing a positive electrode active material containing lithium transition metal composite oxide particles, a separator disposed between the positive electrode and the negative electrode, and non-water And an electrolyte.

According to the present invention, there is an excellent effect that the cycle characteristics can be dramatically improved.

It is a front view of the test battery which concerns on embodiment of this invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1.

With the above configuration, the negative electrode active material particles or the negative electrode active material particles and the negative electrode current collector are firmly fixed by the fixing binder. Therefore, it can suppress that negative electrode active material particles or the negative electrode active material particles and a negative electrode collector peel. In addition, since the coating binder for coating the surface of the negative electrode active material particles is present on the negative electrode surface and inside the negative electrode, even if a new surface is generated on the negative electrode surface and inside the negative electrode, It can suppress that electrolyte and a negative electrode active material particle contact. Therefore, the reductive decomposition reaction of the nonaqueous electrolyte can be suppressed, and even when the potential of the negative electrode becomes high at the end of discharge, silicon reacts with the nonaqueous electrolyte on the new surface, and silicon is oxidized. Inactivation of silicon due to the above can be suppressed.

The amount of the binder for fixing and the binder for coating is not limited. However, if the amount of each binder is too small, the above-mentioned effects may not be sufficiently exhibited, while the amount of each binder is large. If too much, the charge / discharge reaction may be hindered. Accordingly, the proportion of the binder for fixing in the negative electrode is preferably 2 to 20% by mass, particularly 4 to 10% by mass, based on the negative electrode active material. Further, the ratio of the coating binder in the negative electrode is preferably 0.01 to 20% by mass, and particularly preferably 0.1 to 10% by mass with respect to the negative electrode active material. This is because by restricting in this way, not only the above-mentioned functions and effects are sufficiently exhibited, but also excellent discharge performance can be obtained.

The coating binder is preferably present more on the negative electrode surface than in the negative electrode.
Since the surface of the negative electrode is more likely to come into contact with the non-aqueous electrolyte than the inside of the negative electrode, the negative electrode active material is more likely to deteriorate on the negative electrode surface than in the negative electrode. Therefore, if the ratio of the coating binder is controlled to be higher on the negative electrode surface than in the negative electrode, deterioration of the negative electrode active material can be suppressed without increasing the amount of the coating binder in the negative electrode. .

A polyimide resin is preferably used as the fixing binder.
Since the polyimide resin has a large binding force, the negative electrode active material particles or the negative electrode active material particles and the negative electrode current collector are more firmly fixed.

The polyimide resin is preferably a heat-treated polyamic acid, and particularly preferably has a structure shown in Chemical Formula 1 below.
As a method for producing the polyimide resin, there is a catalyst method in addition to a heat treatment method. However, when the catalytic method is used, there is a concern that the catalyst may be mixed into the electrode and adversely affect the battery characteristics. Therefore, it is preferable to use a heat treatment method as in the embodiment.

The coating binder is preferably other than a polyimide resin. For example, a fluorine polymer, a diene polymer, a styrene polymer, an ester polymer, an olefin polymer, a cellulose polymer, or the like can be used. One or a mixture of two or more can be used. More specifically, at least one selected from the group consisting of PVdF, acrylate copolymer, styrene butadiene rubber, PTFE, polyacrylonitrile and cellulose is desirable.

It is desirable that the coating binder is not heat-treated or has a heat treatment temperature of 150 ° C. or lower even when heat-treated. This is because if the heat treatment is performed at a temperature exceeding 150 ° C., the coating binder may be decomposed, and if heat treatment is performed in an atmosphere containing oxygen in consideration of productivity, the heat treatment is performed at 150 ° C. This is because silicon may be oxidized if heat treatment is performed at a temperature higher than.

An inorganic particle layer containing inorganic particles is desirably formed on the surface of the negative electrode active material layer, and the thickness of the inorganic particle layer is desirably 4 μm or more and 25 μm or less.
Thus, if the inorganic particle layer is formed on the surface of the negative electrode active material layer, the contact between the nonaqueous electrolyte and the negative electrode active material particles can be further suppressed on the new surface. Moreover, it is preferable to regulate the thickness of the inorganic particle layer to 4 μm or more and 25 μm or less for the following reason. If the thickness is less than 4 μm, the inorganic particle layer may be deformed due to the expansion and contraction of the negative electrode active material. On the other hand, if the thickness exceeds 25 μm, the amount of active material for both positive and negative electrodes decreases accordingly, so that the battery capacity decreases. It is because it may invite.
In addition, as the inorganic particles, oxides or phosphate compounds using titanium or aluminum, silicon, magnesium or the like conventionally used alone or plurally, and those whose surfaces are treated with hydroxide or the like are used. be able to.

The positive electrode preferably contains a compound containing at least one element selected from the group consisting of rare earth, zirconium, aluminum, magnesium, titanium, tungsten, niobium, and tantalum. It is desirable that a compound containing at least one element selected from the group consisting of rare earth, zirconium, aluminum, magnesium, titanium, tungsten, niobium, and tantalum is fixed on the particle surface of the object.

In such a configuration, even when the reductive decomposition product of the nonaqueous electrolyte generated on the new surface of the negative electrode active material particles made of silicon or a silicon alloy diffuses and migrates to the positive electrode during charge and discharge at high temperature, The reductive decomposition product can be prevented from being oxidatively decomposed on the surface of the lithium transition metal composite oxide particles. Therefore, cycle deterioration due to the positive electrode can be suppressed.
In addition, the electrolytic solution may be decomposed even on the surface of the lithium transition metal composite oxide, particularly when the positive electrode potential becomes high [4.40 V (vs. Li / Li ⁺ ) or more, particularly 4.45 V (vs. Li / Li ⁺ )] is remarkably decomposed, and the product due to the decomposition of the electrolyte moves to the negative electrode. Since the decomposition product that has moved to the negative electrode tends to be reduced on the surface of the negative electrode active material, the negative electrode active material is oxidized by the reduced decomposition product, causing cycle deterioration due to the negative electrode. However, if the compound is fixed to the lithium transition metal composite oxide, decomposition of the electrolytic solution on the surface of the lithium transition metal composite oxide can be suppressed.

The reason why such an effect is exhibited is that the transition metal contained in the lithium transition metal composite oxide acts as a catalyst, so that when the electrolytic solution decomposition material from the electrolytic solution or the negative electrode diffuses, the lithium transition metal It becomes easy to be decomposed on the surface of the composite oxide. However, if a compound such as rare earth, zirconium, aluminum, or magnesium is fixed on the surface of the lithium transition metal composite oxide, the surface of the lithium transition metal composite oxide is not in contact with the electrolytic solution or the electrolytic solution decomposition material. It is because it can suppress that an electrolyte solution etc. decompose | disassemble.
Here, the element of the compound is particularly preferably a rare earth element. The reason for this is that rare earth can exhibit the effect of reducing the catalytic properties of the lithium transition metal composite oxide most.

Examples of the rare earth elements include yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Among them, lanthanum, neodymium, samarium, Erbium and ytterbium are preferred. Among these, erbium, neodymium, and samarium are particularly preferable, and erbium is most preferable. This is because neodymium, samarium, and erbium (particularly erbium) can reduce the catalytic properties of the lithium transition metal composite oxide and extremely suppress the reaction between the electrolytic solution and the lithium transition metal composite oxide.

As the form of the above compound, hydroxides, oxyhydroxides, oxides, carbonate compounds, phosphate compounds, halides, and mixtures thereof can be used. Hydroxides and carbonate compounds are preferred. This is because the finer particles can be selectively fixed to the surface of the lithium transition metal composite oxide.

The rare earth hydroxide or oxyhydroxide is, for example, a method of adding a solution in which a rare earth compound is dissolved in a solution in which a lithium transition metal composite oxide is dispersed, or a method of spraying directly on a lithium transition metal composite oxide. It is obtained by heat-treating after having obtained a fixed hydroxide.
When the heat treatment is performed, the rare earth hydroxide fixed to a part of the surface changes to a rare earth oxyhydroxide or a rare earth oxide. Further, when the hydroxide is fixed, when the atmosphere is changed to a carbon dioxide atmosphere or the lithium transition metal composite oxide powder is dispersed in a solution in which carbon dioxide is dissolved, a rare earth carbonate compound is mainly obtained.

The rare earth hydroxide or oxyhydroxide is, for example, in the case of adding a solution in which a rare earth compound is dissolved to a solution in which a lithium transition metal composite oxide is dispersed. It is preferable to maintain the pH of the solution from 6 to 13, and particularly preferably from 6 to 10. When the pH is less than 6, the transition metal in the lithium transition metal composite oxide is likely to be eluted, and when the pH is more than 10, the rare earth hydroxide or the like is likely to be precipitated due to a part of the electrolyte. There exists a possibility that the effect which suppresses a decomposition reaction may fall.

Examples of the rare earth compound dissolved in the solution used when fixing the rare earth hydroxide or carbonate compound include rare earth acetates, rare earth nitrates, rare earth sulfates, rare earth oxides, or rare earth chlorides. Can be used.
When heat treatment is performed on a surface of which a rare earth hydroxide or carbonate compound is fixed, an oxyhydroxide or oxide is obtained. However, in general, the temperature at which a rare earth hydroxide or oxyhydroxide becomes a stable oxide is 500 ° C. or more. When heat treatment is performed at such a temperature, a part of the rare earth compound fixed on the surface is lithium. It diffuses inside the transition metal complex oxide. As a result, there is a possibility that the effect of suppressing the decomposition reaction of the electrolytic solution on the surface of the lithium transition metal composite oxide is lowered. Therefore, it is preferable that the temperature is lower than 500 ° C. when the heat treatment is performed.

Further, the amount of the rare earth compound fixed to a part of the surface of the lithium transition metal composite oxide is 0.01% by mass or more and less than 0.5% by mass with respect to the lithium transition metal composite oxide in terms of rare earth elements. It is preferable. When the amount is less than 0.01% by mass, the amount of the rare earth compound adhered to the surface is too small, so that the effect of fixing the rare earth compound may not be sufficiently exhibited. The surface of the oxide is excessively covered with a compound that is difficult to directly participate in the charge / discharge reaction, and the discharge performance may be deteriorated. Further, the amount of the rare earth compound to be fixed is more preferably 0.3% by mass or less. This is because, if regulated in this way, not only the fixing effect of the rare earth compound can be obtained, but also excellent discharge performance can be obtained.

A step of preparing a negative electrode mixture slurry by mixing negative electrode active material particles containing silicon and / or silicon alloy particles, amic acid, and a solvent, and applying the negative electrode mixture slurry on the negative electrode core A step of preparing a negative electrode precursor by drying to remove the solvent, a step of heat-treating the negative electrode precursor after the drying in a non-oxidizing atmosphere to polyimidize the amic acid, and the polyimidation Between the step of impregnating the negative electrode precursor having been finished with a solution containing a coating binder to produce a negative electrode, and the positive electrode including the negative electrode and a positive electrode active material containing lithium transition metal composite oxide particles And a step of disposing a separator.
By such a method, a nonaqueous electrolyte secondary battery using a polyimide resin as a binder for fixing in the negative electrode can be produced.

(Other matters)
(1) As the positive electrode active material, for example, a lithium-containing transition metal composite oxide can be used. Specifically, lithium cobalt oxide, lithium composite oxide of Ni—Co—Mn, Ni—Mn—Al An olivine-type transition metal oxide containing lithium composite oxide, Ni—Co—Al composite oxide, iron, manganese, etc. (expressed as LiMPO ₄ , M is selected from Fe, Mn, Co, Ni) Illustrated. These may be used alone or in combination. In addition, the lithium-containing transition metal composite oxide may contain a substance such as Al, Mg, Ti, Zr or the like, or may be contained in the grain boundary.

The Ni—Co—Mn lithium composite oxide has a known composition such that the molar ratio of Ni, Co, and Mn is 1: 1: 1 or 5: 3: 2. In particular, it is preferable to use a material in which the ratio of Ni or Co is larger than that of Mn so that the positive electrode capacity can be increased.
When only the same type of positive electrode active material is used or when different types of positive electrode active materials are used, the positive electrode active material may have the same particle size or different particle sizes. May be.

(2) As the solvent for the nonaqueous electrolyte used in the present invention, a conventionally used solvent can be used. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, propionic acid Compounds containing esters such as ethyl and γ-butyrolactone, compounds containing sulfone groups such as propane sultone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxane, 1,4 -Compounds containing ethers such as dioxane and 2-methyltetrahydrofuran, butyronitrile, valeronitrile, n-heptanenitrile, succinonitrile, glutaronitrile, adiponitrile, pimeronite Le, 1,2,3-propanetriol-carbonitrile, 1,3,5-pentanetricarboxylic carbonitrile compounds containing nitrile such as nitrile or can be used compounds comprising an amide such as dimethylformamide. In particular, a solvent in which a part of these H is substituted with F is preferably used. Further, these can be used alone or in combination, and a solvent in which a cyclic carbonate and a chain carbonate are combined, and a solvent in which a compound containing a small amount of nitrile or a compound containing ether is further combined is preferable. .

On the other hand, conventionally used solutes can be used as the solute of the non-aqueous electrolyte, and LiPF ₆ , LiBF ₄ , LiN (SO ₂ F) _2, LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiPF _6-x (C _n F _2n-1 ) _x [where 1 <x <6, n = 1 or 2], and the like, in addition, a lithium salt having an oxalato complex as an anion Illustrated. Examples of the lithium salt having the oxalato complex as an anion include LiBOB [lithium-bisoxalate borate] and a lithium salt having an anion in which C ₂ O ₄ ²⁻ is coordinated to the central atom, for example, Li [M (C ₂ O ₄ ) _x R _y ] (wherein M is a transition metal, an element selected from groups IIIb, IVb, and Vb of the periodic table, R is selected from a halogen, an alkyl group, and a halogen-substituted alkyl group) Group, x is a positive integer, and y is 0 or a positive integer). Specifically, there are Li [B (C ₂ O ₄ ) F ₂ ], Li [P (C ₂ O ₄ ) F ₄ ], Li [P (C ₂ O ₄ ) ₂ F ₂ ], and the like. However, it is most preferable to use LiBOB in order to form a stable film on the surface of the negative electrode even in a high temperature environment.
In addition, the said solute may be used not only independently but in mixture of 2 or more types. The concentration of the solute is not particularly limited, but is preferably 0.8 to 1.7 mol per liter of the electrolyte.

(3) The inorganic particle layer may be formed not only on the surface of the negative electrode active material layer but also on the surface of the separator or the surface of the positive electrode active material layer. In this case, the inorganic particle layer is formed by directly applying the inorganic particle-containing slurry to the surface of the positive electrode active material layer or the surface of the separator, or by forming a sheet formed of inorganic particles on the surface of the active material layer or the surface of the separator. It can form by sticking to.

(4) As a separator used for this invention, the separator conventionally used can be used. Specifically, not only a separator made of polyethylene, but also a material in which a layer made of polypropylene is formed on the surface of a polyethylene layer, or a material in which a resin such as an aramid resin is applied to the surface of a polyethylene separator is used. Also good.
(5) As the negative electrode active material, silicon oxide [SiO _x (0 <x <2, particularly preferably 0 <x <1)] may be used in addition to the silicon and the silicon alloy. Accordingly, the silicon includes silicon in silicon oxide represented by SiO _x (0 <x <2) (SiO _x = (Si) _{1−1 / 2x} + (SiO ₂ ) _{1 / 2x} ). .

Hereinafter, the present invention will be described in more detail based on the following examples. However, the present invention is not limited to the following examples, and can be implemented with appropriate modifications without departing from the scope of the present invention. It is a thing.
[First embodiment]
Example 1
[Production of positive electrode]
(1) Preparation of lithium transition metal composite oxide Li ₂ CO ₃ and CoCO ₃ were mixed in a mortar so that the molar ratio of Li and Co was 1: 1, and then 800 in an air atmosphere. By heat-treating at ° C for 24 hours and further pulverizing, a lithium cobaltate powder (average particle size of 17 µm) represented by LiCoO ₂ was obtained.

(2) Coating of erbium compound by wet method After adding 1000 g of the above lithium cobaltate to 3 liters of pure water and stirring to prepare a suspension in which lithium cobaltate was dispersed, erbium nitrate was added to this suspension. A solution in which 1.85 g of pentahydrate was dissolved was added. In addition, when adding the liquid which melt | dissolved the erbium nitrate pentahydrate to suspension, 10 mass% sodium hydroxide aqueous solution was added and pH of the solution containing lithium cobaltate was kept at 9. Next, the suspension was filtered with suction, and further washed with water. The powder obtained was heat-treated (dried) at 120 ° C. Furthermore, this powder was heat-treated at 300 ° C. for 5 hours in air. Thereby, the positive electrode active material powder which the erbium compound fixed to the surface of lithium cobaltate was obtained. In the erbium compound, most of the erbium hydroxide was changed to erbium oxyhydroxide during the heat treatment.

When the obtained positive electrode active material powder was observed with a scanning electron microscope (SEM), an erbium compound having an average particle diameter of 100 nm or less was uniformly fixed in a state of being uniformly dispersed on the surface of lithium cobalt oxide. It was recognized that In addition, when the adhesion amount of the erbium compound was measured by ICP, it was 0.07 mass% with respect to lithium cobaltate in terms of erbium element.

(3) Production of positive electrode NMP (N-methyl-2-pyrrolidone) as a dispersion medium, positive electrode active material powder produced as described above, carbon black (acetylene black) powder having an average particle size of 30 nm as a positive electrode conductive agent, Polyvinylidene fluoride as a positive electrode binder was added so that the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder was 95: 2.5: 2.5, and then kneaded to obtain a positive electrode mixture slurry. Prepared.

Next, this positive electrode mixture slurry was applied to both surfaces of an aluminum foil (thickness 15 μm, length 402 mm, width 50 mm) as a positive electrode current collector (the length of the coating part was 340 mm on the front side and on the back side) 270 mm and the width of the coated part were both 50 mm), dried, and rolled to produce a positive electrode. In the portion where the positive electrode active material layer was formed on both surfaces, the amount of the positive electrode active material layer on the positive electrode current collector was 48 mg / cm ² , and the thickness of the positive electrode was 148 μm. In addition, an aluminum plate was connected to the uncoated portion of the positive electrode active material layer at the end of the positive electrode as a positive electrode current collecting tab.

(Production of negative electrode)
(1) Production of silicon negative electrode active material First, a polycrystalline silicon lump was produced by a thermal reduction method. Specifically, the silicon core installed in the metal reaction furnace (reduction furnace) is heated by heating to 800 ° C., and purified with the purified high purity monosilane (SiH ₄ ) gas vapor. By flowing a gas mixed with hydrogen, polycrystalline silicon was deposited on the surface of the silicon core, thereby producing a polycrystalline silicon lump produced in a thick rod shape.

Next, the polycrystalline silicon lump was pulverized and classified to prepare polycrystalline silicon particles (negative electrode active material particles) having a purity of 99%. In the polycrystalline silicon particles, the crystallite size was 32 nm, and the median diameter was 10 μm. The crystallite size was calculated by the Scherrer equation using the half width of the silicon (111) peak in powder X-ray diffraction. The median diameter was defined as the diameter at which the cumulative volume reached 50% in the particle size distribution measurement by the laser diffraction method.

(2) Preparation of negative electrode mixture slurry NMP as a dispersion medium has the negative electrode active material particles, graphite powder having an average particle size of 3.5 μm as a negative electrode conductive agent, and a molecular structure represented by the following chemical formula 1. Precursor varnish of thermoplastic polyimide resin having a glass transition temperature of 300 ° C. (resin that becomes a binder for fixing by heat treatment at 400 ° C. described later) (solvent: NMP, concentration: polymerization by heat treatment + polyimide resin after imidization) 47% by mass) of the negative electrode active material powder, the negative electrode conductive agent powder, and the polyimide resin after imidization (the negative electrode active material particles and the negative electrode active material particles and the negative electrode current collector are fixed) The negative electrode mixture slurry was prepared by mixing so that the mass ratio to the binder was 89.5: 3.7: 6.8.

Here, the precursor varnish of the polyimide resin is composed of 3,3 ′, 4,4′-benzophenone tetracarboxylic acid diethyl ester represented by the following chemical formula 2, chemical formula 3, and chemical formula 4, and m-phenylenediamine represented by chemical formula 5 below. And can be made from In addition, 3,3 ′, 4,4′-benzophenone tetracarboxylic acid diethyl ester represented by the above Chemical Formula 2, Chemical Formula 3, and Chemical Formula 4 is 3,3 ′, 4,4′-benzophenone tetracarboxylic acid represented by Chemical Formula 6 below. It can be prepared by reacting dianhydride with 2 equivalents of ethanol in the presence of NMP.

(3) Production of Negative Electrode As a negative electrode current collector, a copper alloy foil having a thickness of 18 μm (C7025 alloy foil having a composition of 96.2% by mass of Cu, 3% by mass of Ni, and 0.65% by mass of Si) , Mg 0.15% by mass), electrolytic copper so that the surface roughness Ra (JIS B 0601-1994) is 0.25 μm and the average peak spacing S (JIS B 0601-1994) is 1.0 μm. The roughened one was used. The negative electrode mixture slurry was applied to both surfaces of the negative electrode current collector in air at 25 ° C., dried in air at 120 ° C., and then rolled in air at 25 ° C. The obtained product was cut into a rectangle having a length of 380 mm and a width of 52 mm, and then heat-treated in an argon atmosphere at 400 ° C. for 10 hours to obtain a negative electrode precursor having a negative electrode active material layer formed on the surface of the negative electrode current collector. Produced. The amount of the negative electrode active material layer on the negative electrode current collector was 5.6 mg / cm ² and the thickness of the negative electrode was 56 μm. Moreover, the nickel plate as a negative electrode current collection tab was connected to the edge part of a negative electrode precursor.

Finally, the negative electrode precursor is dipped into a solution obtained by diluting a dispersion solution of ethyl acrylate-acrylonitrile copolymer with pure water, and further moisture is removed in air at 90 ° C. Then, a negative electrode in which an ethyl acrylate-acrylonitrile copolymer (binder for coating) covering the negative electrode active material particles was prepared. Here, the ratio of the coating binder to the silicon of the negative electrode active material layer is 1.9% by mass, and since the dipping method is used as described above, the surface of the negative electrode is more coated than the inside of the negative electrode. The percentage of binder was increased. When the dip method is used, if the viscosity of the dip solution is too high, the amount of the coating binder in the negative electrode is reduced. On the other hand, if the viscosity of the dip solution is too low, the amount of the coating binder in the negative electrode is excessive with respect to the negative electrode surface. It will not change. In consideration of this, it is necessary to define the viscosity of the dip solution.

(Preparation of non-aqueous electrolyte)
1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a solvent in which fluoroethylene carbonate (FEC), propylene carbonate (PC) and methyl ethyl carbonate (MEC) are mixed at a volume ratio of 10:10:80. Then, 0.4% by mass of carbon dioxide gas was dissolved in this solution to prepare a non-aqueous electrolyte.

(Production of electrode body)
One positive electrode, one negative electrode, and two polyethylene microporous membranes (thickness 20 μm, length 450 mm, width 54.5 mm, piercing strength 340 g, porosity 39%) The positive electrode and the negative electrode were opposed to each other with a separator. Next, it was wound in a spiral shape with a winding core having a diameter of 18 mm. At this time, both the positive electrode tab and the negative electrode tab were arranged so as to be located on the outermost peripheral portion in each electrode. Thereafter, the winding core was pulled out to produce a spiral electrode body, and this spiral electrode body was further crushed to produce a flat electrode body.

[Production of battery]
The flat electrode body and the non-aqueous electrolyte were inserted into an aluminum laminate outer package in a CO ₂ atmosphere at 25 ° C. and 1 atm to produce a flat non-aqueous electrolyte secondary battery. In addition, the design capacity | capacitance at the time of charging the said secondary battery to 4.35V is 1000 mAh.
The battery thus produced is hereinafter referred to as battery A1.

As shown in FIGS. 1 and 2, the nonaqueous electrolyte secondary battery 11 has a specific structure in which a positive electrode 1 and a negative electrode 2 are arranged to face each other with a separator 3 therebetween. A flat electrode body 9 composed of the separator 3 is impregnated with a non-aqueous electrolyte. The positive electrode 1 and the negative electrode 2 are connected to a positive electrode current collector tab 4 and a negative electrode current collector tab 5, respectively, and have a structure capable of charging and discharging as a secondary battery. In addition, the electrode body 9 is arrange | positioned in the storage space of the aluminum laminate exterior body 6 provided with the closing part 7 by which the periphery was heat-sealed. In the figure, reference numeral 8 denotes a spare chamber for minimizing the influence of the gas generated by the decomposition of the electrolyte etc. on the charge / discharge.

(Example 2)
In preparing the negative electrode, CMC was used as a coating binder instead of ethyl acrylate-acrylonitrile copolymer (specifically, a solution in which CMC was dissolved in water was used instead of a dispersion solution of ethyl acrylate-acrylonitrile copolymer). A battery was prepared in the same manner as in Example 1 except that the negative electrode precursor was dipped in this solution) and the ratio of CMC to silicon in the negative electrode active material layer was 2.0 mass%. .
The battery thus produced is hereinafter referred to as battery A2.

(Example 3)
A battery was fabricated in the same manner as in Example 2 except that the ratio of CMC to silicon in the negative electrode active material layer was 1.0% by mass.
The battery thus produced is hereinafter referred to as battery A3.

(Example 4)
When preparing the negative electrode, PVdF (polyvinylidene fluoride) was used as a coating binder instead of ethyl acrylate-acrylonitrile copolymer (specifically, PVdF was replaced with NMP instead of a dispersion solution of ethyl acrylate-acrylonitrile copolymer). In the same manner as in Example 1 except that the negative electrode precursor was dipped in this solution and the ratio of PVdF to silicon in the negative electrode active material layer was 5.7% by mass. A battery was produced.
The battery thus produced is hereinafter referred to as battery A4.

(Example 5)
When preparing the negative electrode, PTFE (polytetrafluoroethylene) was used as a coating binder instead of ethyl acrylate-acrylonitrile copolymer (specifically, PTFE instead of a dispersion solution of ethyl acrylate-acrylonitrile copolymer). A battery was prepared in the same manner as in Example 1 except that a dispersion solution was prepared and the negative electrode precursor was dipped in this solution.
The battery thus produced is hereinafter referred to as battery A5.

(Example 6)
When preparing the negative electrode, SBR (styrene butadiene rubber) was used instead of the ethyl acrylate-acrylonitrile copolymer as the coating binder (specifically, instead of the ethyl acrylate-acrylonitrile copolymer dispersion solution, SBR dispersion) A battery was prepared in the same manner as in Example 1, except that a John solution was prepared and the negative electrode precursor was dipped in this solution) and the ratio of SBR to silicon in the negative electrode active material layer was 2.1% by mass. Was made.
The battery thus produced is hereinafter referred to as battery A6.

(Example 7)
When preparing the negative electrode, polyacrylonitrile was used as a coating binder instead of ethyl acrylate-acrylonitrile copolymer (specifically, polyacrylonitrile was dissolved in NMP instead of a dispersion solution of ethyl acrylate-acrylonitrile copolymer). A battery was prepared in the same manner as in Example 1 except that a solution was prepared and the negative electrode precursor was dipped in this solution) and the ratio of polyacrylonitrile to silicon in the negative electrode active material layer was 1.8% by mass. Was made.
The battery thus produced is hereinafter referred to as battery A7.

(Comparative example)
A battery was produced in the same manner as in Example 1 except that no coating binder was used in the production of the negative electrode.
The battery thus produced is hereinafter referred to as battery Z.

(Experiment)
For the batteries A1 to A7, Z described above, after initial charge / discharge (charge / discharge at the first cycle) at 25 ° C. under the following conditions (A), charge / discharge at 45 ° C. under the following conditions (B) (Charge / discharge after the second cycle) was repeated, and the capacity retention rate after 40 cycles [shown in the following formula (1)] was examined. The results are shown in Table 1.

(A) Initial charging / discharging conditions and charging conditions at 25 ° C. After performing constant current charging at a current of 50 mA for 4 hours, charging is performed at a current of 200 mA until the battery voltage reaches 4.35 V. Constant voltage charging was performed until the current value reached 50 mA at a voltage of .35 V.
-Discharge conditions Constant current discharge was performed until the battery voltage became 2.75 V at a current of 200 mA.

(B) Charging / discharging conditions / charging conditions at 45 ° C. Constant current charging is performed until the battery voltage reaches 4.35 V at a current of 1000 mA, and further constant voltage charging is performed until the current value reaches 50 mA at a voltage of 4.35 V. Went.
-Discharge conditions Constant current discharge was performed until the battery voltage became 2.75 V at a current of 1000 mA.

Capacity retention ratio = (discharge capacity at the 40th cycle / discharge capacity at the first cycle) × 100 (1)

As is clear from Table 1, the batteries A1 to A7 containing the coating binder on the negative electrode surface or inside the negative electrode were charged at a higher temperature than the battery Z containing no coating binder on the negative electrode surface or inside the negative electrode. It can be seen that the capacity retention rate after repeating the discharge cycle is dramatically increased.

This is because the coating binder is contained on the negative electrode surface or inside the negative electrode, so that even if a new surface is formed during charging and discharging at high temperature, contact with the electrolyte on the new surface is suppressed. Therefore, it is considered that even if the potential becomes high at the end of discharge, the new surface can be prevented from being excessively oxidized.

[Second Embodiment]
(Example)
A battery was fabricated in the same manner as in Example 1 of the first example except that an inorganic particle layer containing alumina (AKP3000) particles was formed on the surface of the negative electrode active material layer. The inorganic particle layer was formed by coating the surface of the negative electrode active material layer with a solution in which alumina (AKP3000) and ethyl acrylate-acrylonitrile copolymer were dispersed, and drying at 90 ° C.
The battery thus produced is hereinafter referred to as battery B.

(Experiment)
The battery B was charged and discharged under the same conditions as in the experiment of the first example, and the capacity retention rate was examined. The results are shown in Table 2. In this experiment, not only the capacity retention rate after 40 cycles [shown in the above formula (1)] but also the capacity maintenance rate after 55 cycles [shown in the following formula (2)] were examined. For reference, the results of the battery A1 are also shown.

Capacity maintenance ratio = (discharge capacity at 55th cycle / discharge capacity at 1st cycle) × 100 (2)

As is apparent from Table 2, the surface of the negative electrode active material layer is made to contain a coating binder on the negative electrode surface or inside the negative electrode, as compared with the battery A1 in which the coating binder is contained only on the negative electrode surface or inside the negative electrode. It is recognized that the battery B having the inorganic particle layer formed thereon has a higher capacity retention rate after repeated charge / discharge cycles at a high temperature. In particular, it is recognized that the capacity retention ratio is further increased when charging and discharging are repeated many times (after 55 cycles in the above experiment).
This is because, when an inorganic particle layer is formed on the surface of the negative electrode active material layer, a network composed of inorganic particles and a binder is also formed in the inorganic particle layer, so that the negative electrode surface that is most in contact with the electrolytic solution is in contact with the electrolytic solution. This is because this can be further suppressed. Therefore, even if the potential becomes high at the end of discharge, it is considered that the new surface can be further prevented from being oxidized excessively.

[Third embodiment]
Example 1
The first embodiment described above except that the erbium compound was not fixed to the surface of lithium cobalt oxide (average particle size 17 μm) and the non-aqueous electrolyte prepared as described below was used when producing the positive electrode. A battery was fabricated in the same manner as in Example 4.
The preparation of the non-aqueous electrolyte is 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) with respect to a solvent in which fluoroethylene carbonate (FEC) and methyl ethyl carbonate (MEC) are mixed at a volume ratio of 20:80. After dissolving, 0.4 mass% carbon dioxide gas was dissolved in this solution.
The battery thus produced is hereinafter referred to as battery C1.

(Example 2)
A battery was produced in the same manner as in Example 1 of the third example except that a positive electrode active material having an erbium compound fixed to the surface of lithium cobaltate was used when producing the positive electrode. The fixing method of the erbium compound was performed in the same manner as in Example 1 of the first example. Therefore, most of the erbium compound was erbium oxyhydroxide. Moreover, when the fixed amount of the erbium compound was measured by ICP, it was 0.07 mass% with respect to lithium cobaltate in terms of erbium element.
The battery thus produced is hereinafter referred to as battery C2.

(Example 3)
When the positive electrode was produced, the heat treatment temperature was changed to 300 ° C. to 120 ° C., and the third embodiment was carried out except that the erbium compound (mostly erbium hydroxide) was fixed to the surface of the lithium cobalt oxide particles. A battery was fabricated in the same manner as in Example 2. In addition, when the fixed amount of the erbium compound was measured by ICP, it was 0.07% by mass in terms of erbium element with respect to lithium cobaltate (mol% in terms of erbium element is erbium in Example 2 of the third example). The same amount).
The battery thus produced is hereinafter referred to as battery C3.

(Example 4)
When making the positive electrode, except that the erbium compound (mostly erbium carbonate) was fixed to the surface of the lithium cobaltate particles by continuously bubbling carbon dioxide in the suspension in which lithium cobaltate was dispersed, A battery was fabricated in the same manner as in Example 2 of the third example. In addition, when the fixed amount of the erbium compound was measured by ICP, it was 0.07% by mass in terms of erbium element with respect to lithium cobaltate (mol% in terms of erbium element is erbium in Example 2 of the third example). The same amount).
The battery thus produced is hereinafter referred to as battery C4.

(Example 5)
When preparing the positive electrode, except that samarium nitrate hexahydrate was used instead of erbium nitrate pentahydrate, and the samarium compound (mostly samarium oxyhydroxide) was fixed to the surface of the lithium cobalt oxide particles. A battery was fabricated in the same manner as in Example 2 of the third example. When the amount of samarium compound fixed was measured by ICP, it was 0.06% by mass in terms of samarium element with respect to lithium cobaltate (mol% in terms of samarium element is erbium in Example 2 of the third example). The same amount).
The battery thus produced is hereinafter referred to as battery C5.

(Example 6)
When producing the positive electrode, neodymium nitrate hexahydrate was used instead of erbium nitrate pentahydrate, and a neodymium compound (mostly neodymium oxyhydroxide) was fixed on the surface of the lithium cobalt oxide particles. A battery was fabricated in the same manner as in Example 2 of the third example. When the amount of adhering neodymium compound was measured by ICP, it was 0.06% by mass in terms of neodymium element with respect to lithium cobaltate (mol% in terms of neodymium element was erbium in Example 2 of the third example). The same amount).
The battery thus produced is hereinafter referred to as battery C6.

(Example 7)
When producing the positive electrode, except that ytterbium nitrate trihydrate was used instead of erbium nitrate pentahydrate, and the ytterbium compound (mostly ytterbium oxyhydroxide) was fixed on the surface of the lithium cobalt oxide particles. A battery was fabricated in the same manner as in Example 2 of the third example. In addition, when the adhesion amount of the ytterbium compound was measured by ICP, it was 0.07% by mass in terms of ytterbium element with respect to lithium cobaltate (mol% in terms of ytterbium element is erbium in Example 2 of the third example). The same amount).
The battery thus produced is hereinafter referred to as battery C7.

(Example 8)
When producing the positive electrode, lanthanum nitrate hexahydrate was used instead of erbium nitrate pentahydrate, and the lanthanum compound (mostly lanthanum oxyhydroxide) was fixed to the surface of the lithium cobalt oxide particles. A battery was fabricated in the same manner as in Example 2 of the third example. When the amount of the lanthanum compound fixed was measured by ICP, it was 0.06% by mass in terms of lanthanum element with respect to lithium cobaltate (mol% in terms of lanthanum element is erbium in Example 2 of the third example). The same amount).
The battery thus produced is hereinafter referred to as battery C8.

Example 9
Example of the above third example, except that when the positive electrode was produced, the heat treatment temperature was changed to 300 ° C. to 500 ° C., and the lanthanum compound (mostly lanthanum oxide) was fixed to the surface of the lithium cobalt oxide particles. A battery was produced in the same manner as in Example 8. When the amount of the lanthanum compound fixed was measured by ICP, it was 0.06% by mass in terms of lanthanum element with respect to lithium cobaltate (mol% in terms of lanthanum element is erbium in Example 2 of the third example). The same amount).
The battery thus produced is hereinafter referred to as battery C9.

(Example 10)
When producing a positive electrode, lithium cobaltate is used by using zirconium oxynitrate dihydrate (zirconyl nitrate) instead of erbium nitrate pentahydrate and changing the heat treatment temperature to 400 ° C. instead of 300 ° C. A battery was fabricated in the same manner as in Example 2 of the third example except that a zirconium compound (mostly zirconium oxide) was fixed to the surface of the particles. In addition, when the adhesion amount of the zirconium compound was measured by ICP, it was 0.04% by mass in terms of zirconium element with respect to lithium cobaltate (mol% in terms of zirconium element was erbium of Example 2 of the third example). The same amount).
The battery thus produced is hereinafter referred to as battery C10.

(Example 11)
When producing the positive electrode, by using aluminum nitrate nonahydrate instead of erbium nitrate pentahydrate and changing the heat treatment temperature to 300 ° C. to 120 ° C., on the surface of the lithium cobalt oxide particles, A battery was fabricated in the same manner as in Example 2 of the third example except that an aluminum compound (mostly aluminum hydroxide) was fixed. In addition, when the adhesion amount of the aluminum compound was measured by ICP, it was 0.01% by mass in terms of aluminum element with respect to lithium cobaltate (mol% in terms of aluminum element is erbium in Example 2 of the third example). The same amount).
The battery thus produced is hereinafter referred to as battery C11.

(Comparative example)
A battery was produced in the same manner as in Example 1 of the third example except that the coating binder was not used when producing the negative electrode.
The battery thus produced is hereinafter referred to as battery Y.

(Experiment)
Charging / discharging of C1 to C11 and Y was performed under the same conditions as in the experiment of the first example, and the capacity retention rate after 40 cycles was examined. The results are shown in Table 3.

As is clear from Table 3, when the battery C1 and the battery Y in which the compound is not fixed to the surface of the lithium cobalt oxide are compared, the battery C1 containing PVdF as a binder for covering the negative electrode contains PVdF. It is recognized that the capacity maintenance rate is higher than that of the battery Y that is not used.

In addition, the batteries C2 to C11 in which the compounds containing Er, Sm, Nd, La, Yb, etc. are fixed on the surface of the lithium cobalt oxide have an extremely high capacity retention rate compared to the battery C1 in which the compounds are not fixed. It is recognized that In particular, the effect is large in the batteries C2 to C6 in which the compound containing Er, Sm, and Nd is fixed to the surface of the lithium cobalt oxide. Furthermore, when the batteries C2, C5, and C6 in which the compounds fixed on the surface of the lithium cobalt oxide are all oxyhydroxides are compared, the capacity maintenance rate of the battery C2 is high. Therefore, it can be seen that the compound fixed on the surface of lithium cobaltate is most preferably a compound containing Er.

In addition, even if the compound fixed on the surface of the lithium cobaltate is a hydroxide, an oxyhydroxide, a carbonate compound, or an oxide, since the effect is expressed, the compound is in any state. However, when the batteries C2 to C4 in which the metal element contained in the compound is Er are compared, the batteries C3 and C4 in which the compound is a hydroxide or a carbonate compound are the batteries C2 in which the compound is an oxyhydroxide. Compared to the above, the capacity retention rate is reduced by 0.8 to 1.0%. Further, when comparing the batteries C8 and C9 in which the metal element contained in the compound is La, the battery C9 in which the compound is an oxide has a capacity maintenance ratio of 2 compared to the battery C8 in which the compound is an oxyhydroxide. .7% decrease. Therefore, the state of the compound is preferably a hydroxide or a carbonate compound rather than an oxide, and more preferably an oxyhydroxide rather than a hydroxide or carbonate compound.

[Fourth embodiment]
Example 1
A battery was fabricated in the same manner as in Example 8 of Example 3 except that the pH of the solution in which lithium cobaltate was dispersed was set to 11.4 when the lanthanum compound was fixed.
The battery thus produced is hereinafter referred to as battery D1.

(Example 2)
A battery was fabricated in the same manner as in Example 8 of Example 3 except that the pH of the solution in which lithium cobaltate was dispersed was set to 10.0 when the lanthanum compound was fixed.
The battery thus produced is hereinafter referred to as battery D2.

(Example 3)
A battery was fabricated in the same manner as in Example 8 of Example 3 except that the pH of the solution in which lithium cobaltate was dispersed was adjusted to 8.0 when the lanthanum compound was fixed.
The battery thus produced is hereinafter referred to as battery D3.

(Example 4)
A battery was fabricated in the same manner as in Example 8 of Example 3 except that when the lanthanum compound was fixed, the pH of the solution in which lithium cobaltate was dispersed was 7.0.
The battery thus produced is hereinafter referred to as battery D4.

(Example 5)
A battery was fabricated in the same manner as in Example 8 of Example 3 except that the pH of the solution in which lithium cobaltate was dispersed was 6.0 when the lanthanum compound was fixed.
The battery thus produced is hereinafter referred to as battery D5.

(Experiment)
With respect to D1 to D5, charging and discharging were performed under the same conditions as in the experiment of the first example, and the capacity retention rate after 40 cycles was examined. The results are shown in Table 4. In Table 4, the result of the battery C8 is also shown.

As is clear from Table 4, it is recognized that the batteries D2 to D4 and C8 have a higher capacity retention rate than the batteries D1 and D5. Therefore, it can be seen that the pH when the lanthanum compound is fixed on the surface of lithium cobaltate is preferably 7 to 10. This is because if the pH exceeds 10, the lanthanum compound may be uniformly dispersed on the surface of the lithium cobalt oxide and may not be fixed, whereas if the pH is less than 7, a part of the cobalt in the lithium cobalt oxide will be eluted. It is.

The present invention can be applied to, for example, a drive power source of a mobile information terminal such as a mobile phone, a notebook computer, and a tablet, and particularly to a use requiring a high capacity. In addition, it can be expected to be used in high output applications that require continuous driving at high temperatures and applications where the battery operating environment is severe, such as HEVs and electric tools.

1: Positive electrode 2: Negative electrode 3: Separator 4: Positive electrode current collector tab 5: Negative electrode current collector tab 6: Aluminum laminate exterior body 9: Electrode body

Claims

A negative electrode active material layer including negative electrode active material particles containing silicon and / or silicon alloy particles is formed on the surface of the negative electrode current collector, and the negative electrode active material layer includes the negative electrode active material particles and the negative electrode active material particles. A binder for fixing the negative electrode active material particles and the negative electrode current collector, and a coating binder for coating a part of the surface of the negative electrode active material particles are contained. A negative electrode present inside the negative electrode;
A positive electrode including a positive electrode active material containing particles of a lithium transition metal composite oxide;
A separator disposed between the positive electrode and the negative electrode;
A non-aqueous electrolyte,
A non-aqueous electrolyte secondary battery comprising:
2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the coating binder is present more on the surface of the negative electrode than in the negative electrode.
The non-aqueous electrolyte secondary battery according to claim 1, wherein a polyimide resin is used as the fixing binder.
The non-aqueous electrolyte secondary battery according to claim 3, wherein the polyimide resin is a heat-treated polyamic acid.
The non-aqueous electrolyte secondary battery according to claim 3 or 4, wherein the polyimide resin has a structure shown in Chemical Formula 1 below.
The nonaqueous electrolyte secondary battery according to any one of claims 3 to 5, wherein the coating binder is other than a polyimide resin.
The nonaqueous electrolyte secondary battery according to claim 6, wherein the coating binder is at least one selected from the group consisting of PVdF, acrylate copolymer, styrene butadiene rubber, and cellulose.
The non-aqueous electrolyte secondary battery according to claim 6 or 7, wherein the coating binder is not heat-treated or has a heat treatment temperature of 150 ° C or lower even when heat-treated.
The nonaqueous electrolyte secondary battery according to any one of claims 1 to 8, wherein an inorganic particle layer containing inorganic particles is formed on a surface of the negative electrode active material layer.
The nonaqueous electrolyte secondary battery according to claim 9, wherein the inorganic particle layer has a thickness of 4 μm or more and 25 μm or less.
11. The positive electrode according to claim 1, wherein the positive electrode contains a compound containing at least one element selected from the group consisting of rare earth, zirconium, aluminum, magnesium, titanium, tungsten, niobium, and tantalum. 2. The nonaqueous electrolyte secondary battery according to item 1.
A compound containing at least one element selected from the group consisting of rare earth, zirconium, aluminum, magnesium, titanium, tungsten, niobium, and tantalum is fixed to the particle surface of the lithium transition metal composite oxide. The nonaqueous electrolyte secondary battery according to claim 11.
13. The nonaqueous electrolyte secondary battery according to claim 12, wherein a compound containing at least one element in the rare earth is fixed to the particle surface of the lithium transition metal composite oxide.
The non-aqueous electrolyte 2 according to claim 13, wherein a compound containing at least one element selected from the group consisting of Nd, Sm, and Er is fixed to the particle surface of the lithium transition metal composite oxide. Secondary battery
The compound fixed to the particle surface of the lithium transition metal composite oxide is at least one compound selected from the group consisting of oxides, hydroxides, oxyhydroxides, carbonate compounds, phosphate compounds, and fluorides. The nonaqueous electrolyte secondary battery according to any one of claims 12 to 14,
Mixing negative electrode active material particles containing silicon and / or silicon alloy particles, amic acid, and a solvent to prepare a negative electrode mixture slurry;
After applying the negative electrode mixture slurry on the negative electrode core, drying and removing the solvent to produce a negative electrode precursor;
Heat-treating the dried negative electrode precursor in a non-oxidizing atmosphere to polyimidize the amic acid;
Impregnating the negative electrode precursor having undergone the above-mentioned polyimidation into a solution containing a coating binder, and producing a negative electrode;
Disposing a separator between the negative electrode and a positive electrode including a positive electrode active material containing particles of a lithium transition metal composite oxide;
The manufacturing method of the nonaqueous electrolyte secondary battery characterized by the above-mentioned.