JP2013191484A - Negative electrode active material layer, manufacturing method therefor and nonaqueous electrolyte secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode active material layer which can enhance the discharge rate characteristics of a negative electrode, and the cycle characteristics, in a nonaqueous electrolyte secondary battery using lithium titanate as a negative electrode active material.SOLUTION: A negative electrode consists of a negative electrode active material layer containing at least a negative electrode active material and a binder, and a collector to which the negative electrode active material layer is bonded. The negative electrode active material contains lithium titanate, and a plurality of holes having a bore diameter of 10-2000 nm are formed in the binder contained in the negative electrode active material layer bonded to the collector.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery using lithium titanate as a negative electrode active material.

  Lithium ion storage batteries are currently widely used as power sources for mobile devices. Moreover, since a lithium ion storage battery is high energy density compared with the existing nickel-cadmium storage battery and nickel-hydrogen storage battery, it is anticipated also as large sized power supply uses, such as an electric vehicle and electric power storage. In particular, non-aqueous electrolyte secondary batteries using lithium titanate as a negative electrode active material are attracting attention because of their good cycle characteristics and high safety (Patent Document 1).

Japanese Patent Laid-Open No. 10-255796

Lithium titanate is an extremely stable negative electrode active material because it does not expand or contract with lithium ion insertion / extraction reactions.
However, since the expansion / contraction associated with the lithium ion insertion / desorption reaction does not occur, the agitation action of the electrolyte inside the battery does not occur, resulting in a problem that the discharge rate characteristic representing the internal resistance of the battery deteriorates.

  Accordingly, an object of the present invention is to provide a negative electrode active material layer capable of improving the discharge rate characteristics of the negative electrode and improving the cycle characteristics in a nonaqueous electrolyte secondary battery using lithium titanate as the negative electrode active material. That is. Moreover, the objective of this invention is providing the manufacturing method of this negative electrode active material layer, and the nonaqueous electrolyte secondary battery using this negative electrode active material layer.

The inventor of the present invention provides a nonaqueous electrolyte secondary battery using lithium titanate as a negative electrode active material, by subjecting the negative electrode active material layer to a porous treatment, thereby providing excellent discharge rate characteristics and a simple manufacturing process. The present inventors have found that a secondary battery can be obtained and have completed the present invention.
That is, the present invention is used for a non-aqueous electrolyte secondary battery that includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, and the negative electrode includes at least a negative electrode active material and a binder, A negative electrode active material layer is attached to the binder, and the negative electrode active material contains titanium oxide, and the binder contained in the negative electrode active material layer attached to the current collector has a pore diameter of 10 nm or more. The present invention provides a negative electrode active material layer for a non-aqueous electrolyte secondary battery in which a plurality of holes of 2000 nm or less are formed.

In addition, the present invention provides a first solution included in the solution in which the binder is dissolved or dispersed after the mixture containing the solution in which the binder is dissolved or dispersed and the negative electrode active material is formed on the current collector. A method for producing a negative electrode active material layer for a non-aqueous electrolyte secondary battery, in which the solvent A is extracted with a second solvent B that is compatible with the solvent A is provided.
In general, as a method for producing an electrode in a non-aqueous electrolyte secondary battery, a method of applying a paste containing an active material and a binder to a current collector and drying it has been performed. According to this method, the active material can be attached to the strip-shaped current collector by utilizing the properties of the binder. However, as described above, lithium titanate is unlikely to expand or contract due to lithium ion insertion / extraction reactions. Therefore, when the negative electrode active material containing lithium titanate is covered with a dense binder, The movement of ions between the electrodes is hindered.

  Therefore, in the present invention, by adopting a structure in which a plurality of pores having a diameter of 10 nm or more and 2000 nm or less are formed in the binder forming the negative electrode active material, insertion of lithium ions of the negative electrode active material containing lithium titanate is performed. It was decided to facilitate the desorption, facilitate the movement of lithium ions between the electrodes, and improve the discharge rate characteristics of the battery.

  ADVANTAGE OF THE INVENTION According to this invention, the negative electrode active material layer which improved the discharge rate characteristic of the negative electrode and improved cycling characteristics can be provided. In addition, a non-aqueous electrolyte secondary battery using the negative electrode active material layer can be provided.

The horizontal axis represents the current value corresponding to the discharge rate (unit: C), and the vertical axis represents 100% of the discharge capacity at the current value equivalent to 0.1 C. It is the graph which plotted the discharge capacity value. Each of Example 6-10 and Comparative Examples 3 and 4 where the current value corresponding to the discharge rate (unit: C) is taken on the horizontal axis and the discharge capacity at a current value equivalent to 0.1 C is taken on the vertical axis. It is the graph which plotted the discharge capacity value. It is the photograph which observed the cast film | membrane of Example 4 by SEM. It is the photograph which observed the cast film of the comparative example 1 by SEM.

Embodiments of the present invention will be described below. The scope of the present invention is defined by the scope of the claims, and is intended to include any modifications within the scope and meaning equivalent to the scope of the claims.
<1. Negative electrode>
The negative electrode used in the nonaqueous electrolyte secondary battery of the present invention is composed of at least a negative electrode active material and a current collector. The negative electrode active material may contain a binder (binder) (hereinafter, a mixture of the negative electrode active material and the binder is referred to as a “negative electrode active material mixture”). The negative electrode active material mixture may contain a conductive additive as necessary.

In the nonaqueous electrolyte secondary battery of the present invention, lithium titanate is used as the negative electrode active material. In lithium titanate, lithium ion insertion / extraction reaction proceeds at 0.4 V (vs. Li ⁺ / Li) or more and 2.0 V (vs. Li ⁺ / Li) or less, so aluminum is used as a current collector material. be able to. However, the present invention is not limited to this, and copper, titanium, nickel, chromium, or an alloy thereof may be used as the current collector material.

The lithium titanate preferably has a spinel structure. The spinel structure is characterized by small expansion and contraction of the active material in the lithium ion insertion / extraction reaction. Lithium titanate is represented by Li ₄ Ti ₅ O ₁₂ as a molecular formula, but may contain a trace amount of elements other than lithium and titanium, such as Nb.
Lithium titanate preferably has a half width of (400) plane of powder X-ray diffraction by CuKα rays of 0.5 ° or less. If it is larger than 0.5 °, the crystallinity of lithium titanate is low, and the stability of the electrode may be lowered.

The lithium titanate preferably has a lithium content of 90% or more in the 8a site according to the Rietveld analysis by X-ray diffraction. If it is less than 90%, since there are many defects in the crystal of lithium titanate, the stability of the electrode may be lowered.
Lithium titanate can be obtained by heat-treating a lithium compound and a titanium compound at 500 ° C. or more and 1500 ° C. or less. When the temperature is less than 500 ° C or higher than 1500 ° C, it tends to be difficult to obtain lithium titanate having a desired structure. In order to improve the crystallinity of lithium titanate, after the heat treatment, reheating treatment may be performed again at 500 ° C. or higher and 1500 ° C. or lower. The temperature of the reheating treatment may be the same as or different from the temperature of the first treatment. The heat treatment may be performed in the presence of air or in the presence of an inert gas such as nitrogen or argon. Although it does not specifically limit in heat processing, For example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln etc. can be used.

As the lithium compound, for example, lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium oxalate, lithium halide and the like can be used. These lithium compounds may be used alone or in combination of two or more.
Although it does not specifically limit as a titanium compound, For example, titanium oxides, such as titanium dioxide and a titanium monoxide, can be used.

The compounding ratio of the lithium compound and the titanium compound may be about lithium / titanium atomic ratio Ti / Li = 1.25, but may have some width depending on the properties of the raw materials and heating conditions.
The surface of lithium titanate may be covered with a carbon material, a metal oxide, a polymer, or the like in order to improve conductivity or stability.
The particle size of lithium titanate is preferably 0.5 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less from the viewpoint of handling. The particle diameter is a value obtained by measuring the size of each particle from SEM and TEM images and calculating the average particle diameter.

The specific surface area of lithium titanate is preferably 0.1 m ² / g or more and 50 m ² / g or less because a desired output density is easily obtained. The specific surface area is preferably calculated by measurement using a mercury porosimeter or BET method.
The bulk density of lithium titanate is preferably 0.2 g / cm ³ or more and 2.0 g / cm ³ or less. In the case of less than 0.2 g / cm ³ tend to be economically disadvantageous because it requires a large amount of solvent in the step of preparing the slurry described below, 2.0 g / cm ³ greater than the later of conductive agent, a binder Mixing with the material tends to be difficult.

  As described above, the negative electrode active material preferably contains a binder. The binder is not particularly limited, but for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber, polyimide, and derivatives thereof may be used. it can. From the viewpoint that the active material and the current collector exhibit good adhesion, and as a result, a battery having excellent cycle characteristics can be obtained, PVdF, polyimide, or PTFE is preferably used.

  The binder is preferably dissolved or dispersed in a non-aqueous solvent from the viewpoint of easy production of the negative electrode. The non-aqueous solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, ethyl acetate, and tetrahydrofuran. These solvents correspond to “first solvent A”. You may add a dispersing agent and a thickener to these.

  In the present invention, the amount of the binder contained in the negative electrode active material mixture is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 2 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the negative electrode active material. It is. Within the above range, the adhesion between the negative electrode active material and the conductive additive can be maintained, and sufficient adhesion with the current collector can be obtained. As a result, the cycle characteristics of the obtained battery are good. Become.

  The negative electrode may contain a conductive additive as necessary. Although it does not specifically limit as a conductive support material, A carbon material or / and a metal microparticle are preferable. Examples of the carbon material include natural graphite, artificial graphite, vapor-grown carbon fiber, carbon nanotube, acetylene black, ketjen black, and furnace black. Examples of the metal fine particles include copper, aluminum, nickel, and an alloy containing at least one of these. Further, the fine particles of inorganic material may be plated. These carbon materials and metal fine particles may be used alone or in combination of two or more.

  The amount of the conductive additive contained in the negative electrode is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 1 part by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the negative electrode active material. If it is this range, the electroconductivity of a negative electrode will be ensured. Further, the adhesiveness with the binder is maintained, and the adhesiveness with the current collector can be sufficiently obtained. When using a larger amount of conductive aid than 30 parts by weight, the volume occupied by the conductive aid increases and the energy density tends to decrease.

The thickness of the current collector is preferably 0.01 mm or more and 5.0 mm or less. When the thickness is less than 0.01 mm, it is difficult to carry the negative electrode active material mixture.
The metal used for the current collector of the present invention is preferably copper, aluminum or an alloy thereof. Since the specific gravity is 70% smaller than the copper used in the conventional current collector, the weight of the battery can be reduced, and as a result, the energy density is improved. Although not particularly limited, high-purity aluminum represented by JIS standards 1030, 1050, 1085, 1N90, 1N99, or the like, or an alloy of aluminum and titanium, an alloy of aluminum and chromium, an alloy of aluminum and copper, or aluminum and nickel Or three or more kinds of composite alloys containing aluminum.

  The method for producing a negative electrode in the embodiment of the present invention is produced by supporting a negative electrode active material mixture comprising a negative electrode active material, a conductive additive, and a binder on a current collector. Due to the ease of the production method, a negative electrode active material, a conductive additive, a binder, and a solvent are used to produce a slurry. After the obtained slurry is filled and applied to the outer surface of the current collector, the solvent is removed to remove the negative electrode. The method of producing is preferable.

  When preparing the slurry, although not particularly limited, it is preferable to use a ball mill, a planetary mixer, a jet mill, and a thin-film swirl mixer because the negative electrode active material, the conductive additive, the binder, and the solvent can be mixed uniformly. . The method of kneading the slurry is not particularly limited, and after mixing the negative electrode active material, the conductive additive, and the binder, a solvent may be added and kneaded, or the negative electrode active material, the conductive additive, the binder, And the solvent may be mixed together and kneaded.

The solid content concentration of the slurry is preferably 30 wt% or more and 80 wt% or less. If it is less than 30 wt%, the viscosity of the slurry tends to be too low, whereas if it is higher than 80 wt%, the viscosity of the slurry tends to be too high, and it may be difficult to form an electrode described later.
The solvent used for the slurry is preferably a non-aqueous solvent. The non-aqueous solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, ethyl acetate, and tetrahydrofuran. The solvent used for this slurry is the same as the solvent in which the binder described above is dissolved or dispersed. Moreover, you may add a dispersing agent and a thickener to these.

In the method for forming pores of 10 nm to 2000 nm in the negative electrode binder of the present invention, a slurry containing at least a binder and a negative electrode active material dissolved or dispersed in the first solvent A is applied to the current collector. Then, after immersing the coated product in the second solvent B, a method of forming by removing the solvent A and the solvent B is exemplified.
The solvent B is preferably compatible with the solvent A and a poor solvent for the solvent A. Although the solvent B will not be specifically limited if the said conditions are satisfy | filled, It is preferable that it is the water effective with respect to any non-aqueous solvent.

The pore diameter of the binder can be controlled by the immersion time and / or temperature in the solvent B.
The immersion time is preferably 5 seconds or more and 15 minutes or less, more preferably 7 seconds or more and 13 minutes or less, and particularly preferably 10 seconds or more and 10 minutes or less. When the time is less than 5 seconds, there is a possibility that no hole is formed in the binder. When the time is longer than 15 minutes, a hole larger than the desired diameter is formed, and the battery characteristics may be deteriorated.

  The temperature of the solvent B is preferably higher than the melting points of the solvent A and the solvent B and lower than the boiling point. When the temperature is lower than the melting point, since the solvent A and the solvent B are in a solid state, no hole is formed in the binder. On the other hand, when the temperature is higher than the boiling point, the solvent is vaporized and handling becomes difficult. The temperature of the solvent B is 5 ° C. or more and less than 80 ° C., more preferably 10 ° C. or more and less than 70 ° C., and particularly preferably 10 ° C. or more and less than 60 ° C., because pores having a desired diameter can be obtained and handling is easy. When the temperature is less than 5 ° C., pores larger than the desired diameter are formed, and the battery characteristics may be deteriorated. On the other hand, when the temperature is 80 ° C. or higher, pores larger than the desired diameter are formed, and the battery characteristics may be deteriorated.

  The method for supporting the negative electrode active material layer on the current collector is not particularly limited. For example, the slurry is applied by a doctor blade, a die coater, a comma coater, etc., and the solvent is removed, or after being attached to the current collector by spraying. A method of removing the solvent and a method of removing the solvent after impregnating the current collector in the slurry are preferable. The method for removing the solvent is preferable because it is easy to dry using an oven or a vacuum oven. Examples of the atmosphere include room temperature or high temperature air, an inert gas, and a vacuum state. The formation time point of the negative electrode may be before or after forming the positive electrode described later.

  When the negative electrode active material, conductive additive and binder mixture are not dispersed in the solvent, a ball mill, planetary mixer, jet mill, thin film is used to uniformly mix the negative electrode active material, conductive additive and binder. It is preferable to carry the mixture on the current collector after preparing the mixture using a swirling mixer. The method of supporting the mixture on the current collector is not particularly limited, but a method of pressing the mixture after applying the mixture to the current collector is preferable. When pressing, it may be heated. Moreover, you may compress a negative electrode using a roll press machine etc. after negative electrode preparation. The negative electrode may be compressed before or after the above-described positive electrode is formed.

  In the embodiment of the present invention, the thickness T of the negative electrode is preferably 0.05 mm or more and 5 mm or less. When the size is smaller than 0.05 mm, it is difficult to increase the size of the battery. When the size is larger than 5 mm, it is difficult to penetrate the electrolyte into the electrode, and in addition, the ion diffusion distance is increased. There is a tendency that the performance as is not obtained. More preferably, it is 0.1 mm or more and 3 mm or less, and if the thickness is within this range, the substance diffusion tends to proceed easily. Further, the thickness T of the negative electrode is preferably x mm thicker over the entire surface of the current collector than the thickness of the current collector. Here, “x” is preferably in the range of more than 0 mm and 2 mm or less. When “x” is 0 mm, the current collector is exposed from the negative electrode, and the later-described separator tends to be destroyed. When it is thicker than 2 mm, the negative electrode active material mixture may fall off. In addition, you may cover with the below-mentioned separator in order to prevent drop-off.

The density of the negative electrode is preferably 1.0 g / cm ³ or more and 4.0 g / cm ³ or less. If it is less than 1.0 g / cm ³ , the contact with the negative electrode active material and the conductive additive becomes insufficient, and the electronic conductivity may decrease. On the other hand, when it is larger than 4.0 g / cm ³ , an electrolyte solution described later hardly penetrates into the negative electrode, and lithium conductivity may be lowered.
The negative electrode may be compressed. The compression method is not particularly limited, and can be performed using, for example, a roll press or a hydraulic press. The electrode may be compressed before or after the positive electrode is formed.

In the embodiment of the present invention, the negative electrode preferably has an electric capacity of 1 mAh or more and 50 mAh or less per rectangular parallelepiped having a square with a unit area of 1 cm ² as a bottom and a thickness T of the negative electrode as a height. If it is less than 1 mAh, the size of the battery may be large. On the other hand, if it is more than 50 mAh, it may be difficult to obtain a desired output density. The electric capacity of the negative electrode can be calculated by measuring charge / discharge characteristics after preparing the negative electrode and then preparing a half battery using lithium metal as a counter electrode.

<2. Positive electrode>
The positive electrode used in the nonaqueous electrolyte secondary battery of the present invention is composed of at least a positive electrode active material layer and a current collector. The positive electrode active material layer includes at least a positive electrode active material, preferably further includes a binder, and optionally includes a conductive aid.
The positive electrode active material is not particularly limited, but is preferably a lithium manganese compound because of excellent cycle stability.

The lithium manganese compound, for _{example, Li 2 MnO 3, Li a} M b Mn 1-b N c O 4 (0 <a ≦ 34,0 ≦ b ≦ 0.5,1 ≦ c ≦ 2, M is 2 At least one selected from the group consisting of elements belonging to Group 13 and belonging to the third and fourth periods, N is at least one selected from the group consisting of elements belonging to Groups 14 to 16 and belonging to the third period), Li _{1 + x} M _y Mn _2−x−y O ₄ (0 ≦ x ≦ 0.34, 0 <y ≦ 0.6, M is at least 1 selected from the group consisting of elements belonging to Groups 2-13 and belonging to the 3rd to 4th periods. A lithium manganese compound represented by Species). Here, M is at least one selected from elements belonging to Groups 2 to 13 and belonging to the 3rd to 4th periods, but Al, Mg, Zn, Ni, Co, Fe and Cr are preferred, Al, Mg, Zn, Ni and Cr are more preferred, and Al, Mg, Zn and Ni are even more preferred. Further, N here is preferably Si, P, or S because the effect of improving the stability is large.

Especially, since the stability of the positive electrode active material is high, Li _{1 + x} M _y Mn _2−xy O ₄ (0 ≦ x ≦ 0.34, 0 <y ≦ 0.6, M is a group 2 to 13 and A lithium manganese compound represented by at least one selected from the group consisting of elements belonging to the third to fourth periods is particularly preferable. When x <0, the capacity of the positive electrode active material tends to decrease. Further, when x> 0.34, there is a tendency that many impurities such as lithium carbonate are included. When y = 0, the stability of the positive electrode active material tends to be low. Further, when y> 0.6, a large amount of impurities such as M oxide tends to be contained.

The lithium manganese compound preferably has a spinel structure. This is because in the case of the spinel structure, the expansion and contraction of the active material in the reaction of insertion / extraction of lithium ions is small.
The lithium manganese compound preferably has a half width of 0.5 ° or less on the (400) plane of powder X-ray diffraction by CuKα rays. When it is larger than 0.5 °, the crystallinity of the positive electrode active material is low, and thus the stability of the electrode may be lowered.

The lithium manganese compound preferably has a lithium content of 90% or more in the 8a site according to the Rietveld analysis by X-ray diffraction. If it is less than 90%, there are many defects in the crystal of the positive electrode active material, and the stability of the electrode may be lowered.
The particle size of the lithium manganese compound is preferably 0.5 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less from the viewpoint of handling. The particle diameter here is a value obtained by measuring the size of each particle from the SEM and TEM images and calculating the average particle diameter.

The specific surface area of the lithium manganese compound is preferably 0.1 m ² / g or more and 50 m ² / g or less because a desired output density is easily obtained. The specific surface area can be calculated by measurement by the BET method.
The bulk density of the lithium manganese compound is preferably 0.2 g / cm ³ or more and 2.0 g / cm ³ or less. When the amount is less than 0.2 g / cm ³ , a large amount of solvent is required when preparing a slurry described later, which is economically disadvantageous. When the amount is greater than 2.0 g / cm ³ , the conductive auxiliary material and binder described later are used. Mixing tends to be difficult.

  The lithium manganese compound can be obtained by heat-treating a lithium compound, a manganese compound, and if necessary, a compound of M and a compound of N at 500 ° C. or higher and 1500 ° C. or lower. When the temperature is lower than 500 ° C. or higher than 1500 ° C., a positive electrode active material having a desired structure may not be obtained. The heat treatment may be a heat treatment by mixing a lithium compound and a manganese compound, and if necessary, an M compound or an N compound, or after the heat treatment of the manganese compound and the M compound or the N compound, the lithium compound You may heat-process. In order to improve the crystallinity of the positive electrode active material, after the heat treatment, reheating treatment may be performed again at 500 ° C. or higher and 1500 ° C. or lower. The temperature of the reheating treatment may be the same as or different from the initial temperature. The heat treatment may be performed in the presence of air or in the presence of an inert gas such as nitrogen or argon. Although it does not specifically limit in heat processing, For example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln etc. can be used.

As the lithium compound, for example, lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium oxalate, lithium halide and the like can be used. These lithium compounds may be used alone or in combination of two or more.
As the manganese compound, for example, manganese oxide such as manganese dioxide, manganese carbonate, manganese nitrate, manganese hydroxide and the like can be used. These manganese compounds may be used alone or in combination of two or more.

As the compound of M, for example, carbonate, oxide, nitrate, hydroxide, sulfate and the like can be used. The amount of _{Li a M b Mn 1-b} N c O 4 and _Li 1 ₊ x _{M y Mn} contained in the _{2-x-y O 4} M can be controlled by the amount of the compound of M in the heat treatment. One type of M compound may be used, or two or more types may be used.
As the N compound, for example, a simple substance, an oxide, an oxo acid and a salt thereof can be used. The amount of _{Li a M b Mn 1-b} N c O 4 and _{Li 1 + x M y Mn 2} -x-y O 4 contained in the N can be controlled by the amount of compound of N in the heat treatment. One type of N compound may be used, or two or more types may be used.

For example, Li _{1 + x} M _y Mn _2−xy O ₄ (0 ≦ x ≦ 0.34, 0 <y ≦ 0.6, M is a group consisting of elements belonging to Groups 2 to 13 and belonging to the third to fourth periods. At least one selected from the group consisting of lithium compound, manganese compound and M compound, the atomic ratio of lithium, manganese and M is 1 + x (lithium) and 2-x, respectively. -Y (manganese) and y (M), provided that 0 ≦ x ≦ 0.34 and 0 <y ≦ 0.6. For example, when preparing a positive electrode active material with an atomic ratio of 1.5 of Mn / Li, the blending ratio is set to around 1.5 depending on the properties of the raw materials and heating conditions, but some width may be allowed.

The surface of the positive electrode active material may be covered with a carbon material, a metal oxide, a polymer, or the like in order to improve conductivity or stability.
A binder may be mixed in the positive electrode active material mixture. What was illustrated by the binder used for the negative electrode active material layer mentioned above is applicable similarly. The binder is preferably dissolved or dispersed in a non-aqueous solvent or water from the viewpoint of easy production of the positive electrode. As the non-aqueous solvent, those exemplified above for the non-aqueous solvent can be similarly applied. You may add a dispersing agent and a thickener to these.

  In the present invention, the amount of the binder contained in the positive electrode active material mixture is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 2 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. It is. As the binder material, PVdF or PTFE is preferably used from the viewpoint that the active material and the current collector exhibit good adhesion and, as a result, a battery having excellent cycle characteristics can be obtained. If it is the said range and the said binder material kind, the adhesiveness of a positive electrode active material and a conductive support agent will be maintained, adhesiveness with a collector can fully be acquired, and cycling characteristics will improve as a result.

  The positive electrode may contain a conductive additive as necessary. Although it does not specifically limit as a conductive support material, A carbon material or a metal microparticle is preferable. Examples of the carbon material include the same carbon materials that can be contained in the negative electrode. Examples of the metal fine particles include aluminum and aluminum alloys. Further, the fine particles of inorganic material may be plated. These carbon materials and metal fine particles may be used alone or in combination of two or more.

  The amount of the conductive additive contained in the positive electrode is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 1 part by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. If it is this range, the electroconductivity of a positive electrode will be ensured. Further, the adhesiveness with the binder is maintained, and the adhesiveness with the current collector can be sufficiently obtained. On the other hand, when a larger amount of conductive aid than 30 parts by weight is used, the volume occupied by the conductive aid increases and the energy density tends to decrease.

The positive electrode binder may be formed with holes in the same manner as applied to the negative electrode binder.
As the current collector used for the positive electrode of the non-aqueous electrolyte secondary battery of the present invention, those exemplified for the current collector used for the negative electrode described above (except for copper) and foil-like ones can be similarly applied.
The non-aqueous electrolyte secondary battery of the present invention is manufactured by, for example, supporting a positive electrode active material layer including a positive electrode active material, a conductive additive, and a binder on a current collector. Then, a method of producing a positive electrode by preparing a slurry with a positive electrode active material, a conductive additive, a binder and a solvent, filling and applying the obtained slurry to the outer surface of the current collector, and then removing the solvent. preferable. Alternatively, the mixture of the positive electrode active material, the conductive additive and the binder may be supported on the current collector without being dispersed in the solvent.

In the preparation of the negative electrode, the method for preparing the slurry, the solid content concentration of the slurry, the solvent used for the slurry, the method for supporting the active material layer on the current collector, and the compression of the electrode can be similarly applied to the preparation of the positive electrode. .
The thickness of the positive electrode is not particularly limited, but is preferably 0.05 mm or more and 5 mm or less. When it is smaller than 0.05 mm, it is difficult to increase the size, and when it is larger than 5 mm, it becomes difficult to penetrate the electrolyte into the electrode, and in addition, the diffusion distance of ions becomes large. There is a tendency that performance cannot be obtained. More preferably, it is 0.1 mm or more and 3 mm or less. If the thickness is within this range, the material diffusion tends to proceed easily. Further, the thickness of the positive electrode is preferably x mm thicker than the thickness of the current collector. Here, “x” is preferably in the range of more than 0 mm and 2 mm or less. In the case of 0 mm, the current collector is exposed from the positive electrode active material mixture and tends to break the separator described later. If it is thicker than 2 mm, the positive electrode active material mixture may fall off. Moreover, you may cover with the below-mentioned separator in order to prevent drop-off.

In the present invention, the density of the positive electrode active material layer is preferably 1.0 g / cm ³ or more and 4.0 g / cm ³ or less. If it is less than 1.0 g / cm ³ , the contact with the positive electrode active material and the conductive additive becomes insufficient, and the electronic conductivity may be lowered. On the other hand, when it is larger than 4.0 g / cm ³ , an electrolyte solution described later hardly penetrates into the positive electrode, and lithium conductivity may be lowered. The positive electrode may be compressed to a desired thickness and density. The compression method is not particularly limited, and can be performed using, for example, a roll press, a hydraulic press, or the like. The electrode may be compressed before or after the positive electrode is formed.

In the present invention, the electric capacity per 1 cm ² of the positive electrode is preferably 1 mAh or more and 50 mAh or less. If it is less than 1 mAh, it may be difficult to obtain a desired output density, whereas if it is more than 50 mAh, the size of the battery may be increased. Calculation of the electric capacity per 1 cm < ² > of a positive electrode can be calculated by measuring a charging / discharging characteristic after producing a half cell which made lithium metal a counter electrode after producing a positive electrode. The electric capacity per 1 cm ^{2 of the} positive electrode is not particularly limited, but can be controlled by a method of controlling by the weight of the positive electrode formed per unit area of the current collector, for example, the coating thickness at the time of the positive electrode coating described above.

<3. Capacity ratio and area ratio of negative electrode to positive electrode>
The ratio of the electric capacity of the positive electrode and the electric capacity of the negative electrode in the nonaqueous electrolyte secondary battery of the present invention preferably satisfies the following formula (1).
0.7 ≦ B / A ≦ 1.3 (1)
However, in Formula (2), A shows the electric capacity per 1 cm < ² > of positive electrodes, and B shows the electric capacity per 1 cm < ² > of negative electrodes.

When B / A is less than 0.7, the potential of the negative electrode may become a lithium deposition potential during overcharge, while when B / A is greater than 1.3, the negative electrode activity that does not participate in the battery reaction may occur. Side reactions may occur due to the large amount of substances.
Although the area ratio of the positive electrode to the negative electrode in the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, it is preferable to satisfy the following formula (2).

1 ≦ D / C ≦ 1.2 (2)
(However, C represents the area of the positive electrode, and D represents the area of the negative electrode.)
When D / C is less than 1, for example, when B / A = 1 as described above, the capacity of the negative electrode is smaller than that of the positive electrode, so that the potential of the negative electrode may become a lithium deposition potential during overcharge. On the other hand, if D / C is greater than 1.2, the negative electrode active material not involved in the battery reaction may cause a side reaction because the portion of the negative electrode that is not in contact with the positive electrode is large. Although control of the area of a positive electrode and a negative electrode is not specifically limited, For example, in the case of slurry coating, it can carry out by controlling the coating width.

The area ratio between the separator and the negative electrode used in the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, but preferably satisfies the following formula (3).
1 ≦ F / E ≦ 1.5 (3)
(However, E represents the area of the negative electrode, and F represents the area of the separator.)
When F / E is less than 1, the positive electrode and the negative electrode are in contact with each other, and when F / E is greater than 1.5, the volume required for the exterior increases, and the output density of the battery may decrease.

<4. Separator>
Examples of the separator used in the nonaqueous electrolyte secondary battery of the present invention include porous materials and nonwoven fabrics. The material of the separator is preferably one that does not dissolve in the organic solvent that constitutes the electrolytic solution. Specifically, a polyolefin polymer such as polyethylene or polypropylene, a polyester polymer such as polyethylene terephthalate, cellulose, or glass. Inorganic materials.

The thickness of the separator is preferably 1 to 500 μm. If it is less than 1 μm, it tends to break due to insufficient mechanical strength of the separator and cause an internal short circuit. On the other hand, when it is thicker than 500 μm, the load characteristics of the battery tend to be reduced due to the increase in the internal resistance of the battery and the distance between the positive and negative electrodes. A more preferable thickness is 10 to 50 μm.
<5. Non-aqueous electrolyte>
The non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but a polymer is impregnated with an electrolytic solution in which a solute is dissolved in a non-aqueous solvent, or an electrolytic solution in which a solute is dissolved in a non-aqueous solvent. A gel electrolyte or the like can be used.

  The non-aqueous solvent preferably includes a cyclic aprotic solvent and / or a chain aprotic solvent. Examples of the cyclic aprotic solvent include cyclic carbonates, cyclic esters, cyclic sulfones and cyclic ethers. Examples of the chain aprotic solvent include chain carbonates, chain carboxylic acid esters and chain ethers. In addition to this, a solvent generally used as a solvent for non-aqueous electrolytes such as acetonitrile may be used. More specifically, dimethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, 1,2-dimethoxyethane, sulfolane, dioxolane, propionic acid Methyl and the like can be used. These solvents may be used alone or as a mixture of two or more. However, in view of the ease of dissolving the solute described below and the high conductivity of lithium ions, a mixture of two or more of these solvents. Is preferably used. A gel electrolyte in which an electrolyte is impregnated in a polymer can also be used.

The solute is not particularly limited. For example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiBOB (Lithium Bis (Oxalato) Borate), LiN (SO ₂ CF ₃ ) _2, etc. are dissolved in the solvent. It is preferable because it is easy to do. The concentration of the solute contained in the electrolytic solution is preferably 0.5 mol / L or more and 2.0 mol / L or less. If it is less than 0.5 mol / L, the desired lithium ion conductivity may not be exhibited. On the other hand, if it is higher than 2.0 mol / L, the solute may not be dissolved any more. The non-aqueous electrolyte may contain a trace amount of additives such as a flame retardant and a stabilizer.

<6. Non-aqueous electrolyte secondary battery>
The positive electrode and the negative electrode of the nonaqueous electrolyte secondary battery of the present invention may have a form in which one type of electrode is formed on one side or both sides of the current collector, the positive electrode on one side of the current collector, and the other side A form in which a negative electrode is formed, that is, a bipolar electrode may be used.
When a bipolar electrode is used, it is necessary to prevent a liquid junction between the positive electrode and the negative electrode through the current collector. For this reason, the bipolar electrode itself has a structure that does not allow liquid to pass between the surface on the positive electrode side and the surface on the negative electrode side.

In the case of a bipolar electrode, a separator is disposed between the positive electrode side and the negative electrode side of the opposing bipolar electrode, and the periphery of the positive electrode and the negative electrode is prevented in order to prevent liquid junction from the layer in which the positive electrode side and the negative electrode side face each other. An insulating material is disposed on the part.
The nonaqueous electrolyte secondary battery of the present invention may be one obtained by winding or laminating a separator disposed between the positive electrode side and the negative electrode side. The positive electrode, the negative electrode, and the separator are impregnated with a nonaqueous electrolyte that is responsible for lithium ion conduction. However, when a non-aqueous electrolysis gel is used, the electrolyte may be impregnated in the positive electrode and the negative electrode, or may be in a state only between the positive electrode and the negative electrode. If the positive electrode and the negative electrode are not in direct contact with the gel electrolyte, it is not necessary to use a separator.

The amount of the nonaqueous electrolyte used in the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, but is preferably 0.1 mL or more per 1 Ah of battery capacity. If it is less than 0.1 mL, the conduction of lithium ions accompanying the electrode reaction may not catch up, and the desired battery performance may not be exhibited.
The nonaqueous electrolyte may be added to the positive electrode, the negative electrode, and the separator in advance, or may be added after winding or laminating a separator disposed between the positive electrode side and the negative electrode side. When using a gel-like non-aqueous electrolyte, it may be gelled after impregnation with a monomer, or may be placed between the positive electrode and the negative electrode after gelling in advance.

  The non-aqueous electrolyte secondary battery of the present invention may be wound with a laminate film after winding the laminate or a plurality of laminates, and may be rectangular, elliptical, cylindrical, coin-shaped, button-shaped, or sheet-shaped. It may be packaged with a metal can. The exterior may be provided with a mechanism for releasing the generated gas or the like. Further, a mechanism for injecting an additive for recovering the function of the deteriorated nonaqueous electrolyte secondary battery from the outside of the battery may be provided. The number of stacked layers can be stacked until a desired battery capacity is exhibited.

  The nonaqueous electrolyte secondary battery of the present invention can be formed into an assembled battery by connecting a plurality of the nonaqueous electrolyte secondary batteries. The assembled battery of the present invention can be produced by appropriately connecting in series or in parallel according to a desired size, capacity, and voltage. Moreover, it is preferable that a control circuit is attached to the assembled battery in order to confirm the state of charge of each battery and improve safety.

<Example 1>
(Preparation of hole diameter confirmation sample)
A cast membrane for confirming the hole diameter was produced as follows.
First, a polyvinylidene fluoride (PVdF) solution (5 wt%, NMP solution as “first solvent A”) was applied to a glass plate using a doctor blade having a clearance of 300 μm. Next, after the glass plate coated with PVdF was immersed in deionized water as “second solvent B” for 10 seconds, the supernatant was removed. Finally, a cast film for confirming the hole diameter was prepared by drying in an oven (radiation type) at 120 ° C. As a result of SEM observation of this cast film, it was confirmed that a plurality of holes having a hole diameter of 10 to 100 nm were formed.

(Preparation of negative electrode)
The negative electrode active material Li ₄ Ti ₅ O ₁₂ was produced by the method described in the literature (Journal of Electrochemical Society, 142, 1431 (1995)).
That is, first, titanium dioxide and lithium hydroxide are mixed so that the molar ratio of titanium and lithium is 5: 4, and then this mixture is heated at 800 ° C. for 12 hours in a nitrogen atmosphere to obtain a negative electrode active material. Produced.

  100 parts by weight of the negative electrode active material, 6.8 parts by weight of a conductive additive (acetylene black), and a polyvinylidene fluoride (PVdF) binder (KF7305, manufactured by Kureha Chemical Co., Ltd.) (solid content concentration 5 wt%, NMP solution) ) Was mixed with a solid content of 6.8 parts by weight to prepare a slurry. This slurry was applied to an aluminum foil (thickness 20 μm) using a doctor blade having a clearance of 300 μm, and then immersed in deionized water (25 ° C.) from which most of ions dissolved in water were removed for 10 seconds. Then, the negative electrode (single-sided coating) by which the binder which can see the surface of a negative electrode active material layer was made porous by vacuum-drying at 150 degreeC was produced.

<Example 2>
A cast membrane for confirming the pore size and a negative electrode were prepared in the same manner as in Example 1 except that the sample was immersed in deionized water (25 ° C.) for 30 seconds. As a result of SEM observation of this cast film, it was confirmed that the cast film was made porous in a pore diameter range of 10 to 400 nm.
<Example 3>
A cast membrane for pore diameter confirmation and a negative electrode were prepared in the same manner as in Example 1 except that the sample was immersed in deionized water (25 ° C.) for 1 minute. As a result of SEM observation of the cast film, it was confirmed that the cast film was made porous in the pore diameter range of 200 to 1000 nm.
<Example 4>
A cast membrane for confirming the pore size and a negative electrode were prepared in the same manner as in Example 1 except that the sample was immersed in deionized water (25 ° C.) for 5 minutes. As a result of SEM observation of this cast film, it was confirmed that the cast film was made porous in a pore diameter range of 300 to 1200 nm. The photograph which observed the cast film | membrane of this Example 4 by SEM is published in FIG.

<Example 5>
A cast membrane for pore diameter confirmation and a negative electrode were produced in the same manner as in Example 1 except that the membrane was immersed in deionized water (25 ° C.) for 10 minutes. As a result of SEM observation of this cast film, it was confirmed that the cast film was made porous in a pore diameter range of 300 to 2000 nm.
<Example 6>
A cast membrane and a negative electrode for confirming the pore size were prepared in the same manner as in Example 1 except that a dimethylformamide solution of polyimide synthesized from biphenyltetracarboxylic acid and diaminodiphenyl ether (solid content concentration 5 wt%) was used as the binder. did. As a result of SEM observation of the cast film, it was confirmed that the cast film was made porous in the pore diameter range of 10 to 200 nm. This dimethylformamide corresponds to “first solvent A”.

<Example 7>
A cast membrane and a negative electrode for confirming the pore size were prepared in the same manner as in Example 2 except that a dimethylformamide solution of polyimide synthesized from biphenyltetracarboxylic acid and diaminodiphenyl ether (solid content concentration 5 wt%) was used as the binder. did. As a result of SEM observation of this cast film, it was confirmed that the cast film was made porous in a pore diameter range of 10 to 500 nm.

<Example 8>
A cast film and a negative electrode for confirming the pore size were prepared in the same manner as in Example 3 except that a dimethylformamide solution of polyimide synthesized from biphenyltetracarboxylic acid and diaminodiphenyl ether (solid content concentration: 5 wt%) was used as the binder. . As a result of SEM observation of the cast film, it was confirmed that the cast film was made porous in a pore diameter range of 100 to 1200 nm.

<Example 9>
A cast membrane and a negative electrode for confirming the pore size were prepared in the same manner as in Example 4 except that a dimethylformamide solution of polyimide synthesized from biphenyltetracarboxylic acid and diaminodiphenyl ether (solid content concentration 5 wt%) was used as the binder. did. As a result of SEM observation of this cast film, it was confirmed that the cast film was made porous in a pore diameter range of 200 to 1500 nm.

<Example 10>
A cast membrane and a negative electrode for confirming the pore size were prepared in the same manner as in Example 5 except that a dimethylformamide solution of polyimide synthesized from biphenyltetracarboxylic acid and diaminodiphenyl ether (solid content concentration 5 wt%) was used as the binder. did. As a result of SEM observation of this cast film, it was confirmed that the cast film was made porous in the pore diameter range of 500 to 2000 nm.

<Comparative Example 1>
A cast membrane for pore diameter confirmation and a negative electrode were prepared in the same manner as in Example 1 except that the sample was not immersed in deionized water (25 ° C.). As a result of SEM observation of this cast film, it was confirmed that it was not made porous. FIG. 4 shows a photograph of the cast film of Comparative Example 1 observed by SEM.
<Comparative example 2>
A cast film for confirming the pore size and a negative electrode were prepared in the same manner as in Example 1 except that the film was immersed in deionized water (80 ° C.) for 10 minutes. As a result of SEM observation of this cast film, it was confirmed that the cast film was made porous in a pore diameter range of 3000 to 10000 nm.

<Comparative Example 3>
A cast membrane for pore diameter confirmation and a negative electrode were prepared in the same manner as in Example 5 except that the sample was not immersed in deionized water (25 ° C.). As a result of SEM observation of this cast film, it was confirmed that it was not made porous.
<Comparative example 4>
A cast membrane for pore diameter confirmation and a negative electrode were produced in the same manner as in Example 5 except that the membrane was immersed in deionized water (80 ° C.) for 10 minutes. As a result of SEM observation of this cast film, it was confirmed that the cast film was made porous in a pore diameter range of 3000 to 10000 nm.

<Charge / discharge test>
In order to evaluate the capacity of the negative electrode, the following charge / discharge test was conducted. Here, “discharge” is defined as lithium insertion reaction into lithium titanate, “charge” and lithium elimination reaction from lithium titanate.
Each of the electrodes described above was punched out to 16 mmΦ to produce a working electrode. Li metal was punched out to 16 mmΦ as a counter electrode. Using these electrodes, the working electrode (single-sided coating) / separator (polyolefin-based porous membrane, thickness 25 μm) / Li metal was laminated in this order in a test cell (HS cell, manufactured by Hosen Co., Ltd.) 0.15 mL of an electrolyte (ethylene carbonate / dimethyl carbonate = 3/7 vol%, LiPF ₆ 1 mol / L) was added to prepare a half-cell.

  The half-cell was allowed to stand at 25 ° C. for one day, and then connected to a charge / discharge test apparatus (HJ1005SD8, manufactured by Hokuto Denko). This half-cell is equivalent to 0.1 ° C. at 25 ° C. (corresponding to a discharge rate “1C” is a current value at which the half-cell is discharged at a constant current and discharge is completed in one hour. The equivalent value is the current value at which discharge is completed in 10 hours). The constant current discharge (end voltage: 1.0 V) and constant current charge (end voltage: 2.0 V) are repeated five times. The discharge capacity at the second time was the discharge capacity corresponding to 0.1 C of the negative electrode. Here, the “discharge capacity” refers to a value “TI” obtained by multiplying the time T from the start of the discharge of the battery to the end of the discharge by the current I. The discharge capacity (TI value) increases as the internal resistance of the battery decreases.

Similarly, this half-cell was discharged at a constant current of 0.5 C, 1.0 C, 2.0 C, and 5.0 C at 25 ° C. (end voltage: 1.0 V) to obtain a current corresponding to 0.1 C. The constant current charge (end voltage: 2.0V) was performed by the value. Charging / discharging was repeated 5 times, and the discharge capacity at the fifth time was set to a discharge capacity corresponding to 0.5C; 1.0C; 2.0C and 5.0C.
The discharge capacities at current values corresponding to 0.5C; 1.0C; 2.0C and 5.0C, where the discharge capacity at a current value corresponding to 0.1C is 100, were calculated and compared.

  FIG. 1 is a graph in which the current value corresponding to the discharge rate (unit: C) is plotted on the horizontal axis, and the discharge capacity values are plotted with the discharge capacity at a current value corresponding to 0.1 C as 100 on the vertical axis. is there. From this graph, in Examples 1 to 5, the rate at which the discharge capacity when a large current, for example, a current corresponding to 5.0 C is applied, decreases from the discharge capacity when a current corresponding to 0.1 C is applied, is a comparative example. It can be seen that it is lower than 1 and 2. In particular, the rate of decrease in the order of Example 1 → 5 → 4 → 3 → 2 is low, and Example 2 immersed in deionized water (25 ° C.) for 30 seconds is about 83%, and the rate of decrease is the highest. Low (represents that a large current can flow through the electrode for a long time). Even if the immersion time is longer or shorter than this, the discharge capacity is slightly reduced.

Further, in Comparative Example 1 which was not immersed in deionized water (25 ° C.), the discharge capacity when a current corresponding to 5.0 C was passed was greatly reduced from the discharge capacity when a current corresponding to 0.1 C was passed. ing. This indicates that the internal resistance of the electrode is large and that a large current cannot flow for a long time.
In Comparative Example 2, which was immersed in high-temperature (80 ° C.) deionized water for 10 minutes, the pore diameter range was 3000 to 10000 nm, which was an order of magnitude larger than in the examples. The discharge capacity at high current is too low to be measured. This is presumably because the pores became too large, the structure of lithium titanate and the conductive additive was cut off, the electron conduction path of the whole negative electrode was cut off, and as a result, the resistivity of the negative electrode itself increased.

  2, as in FIG. 1, the horizontal axis represents the current value corresponding to the discharge rate (unit: C), and the vertical axis represents each discharge capacity value when the discharge capacity at a current value corresponding to 0.1 C is 100. Is a graph in which is plotted. From this graph, in Examples 6 to 10, the rate at which the discharge capacity when a large current, for example, a current corresponding to 5.0 C is applied, decreases from the discharge capacity when a current corresponding to 0.1 C is applied, is a comparative example. It can be seen that it is lower than 3 and 4. Particularly, the rate of decrease in the order of Example 6 → 10 → 9 → 8 → 7 is low, and Example 7 immersed in deionized water (25 ° C.) for 30 seconds is about 83%, and the rate of decrease is the highest. Low (represents that a large current can flow through the electrode for a long time). Even if the immersion time is longer or shorter than this, the discharge capacity is slightly reduced. In particular, in Example 6 (10 seconds) in which the immersion time was shortened, the discharge capacity was lowered.

Further, in Comparative Example 3 which was not immersed in deionized water (25 ° C.), the discharge capacity was greatly reduced from the discharge capacity when a current corresponding to 0.1 C was passed.
In Comparative Example 4 immersed in high-temperature (80 ° C.) deionized water for 10 minutes, the range of the pore diameter is 3000 to 10,000 nm, which is an order of magnitude larger than that of the example. The discharge capacity at high current is too low to be measured.

Claims (7)

Used in a non-aqueous electrolyte secondary battery composed of a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte,
The negative electrode is composed of a negative electrode active material layer containing at least a negative electrode active material and a binder, and a current collector to which the negative electrode active material layer is attached,
A non-aqueous electrolyte secondary in which the negative electrode active material contains titanium oxide, and a plurality of pores having a pore diameter of 10 nm or more and 2000 nm or less are formed in a binder contained in the negative electrode active material layer attached to the current collector Negative electrode active material layer for battery.   The negative electrode active material layer for a nonaqueous electrolyte secondary battery according to claim 1, wherein the binder is a polymer compound.   The negative electrode active material layer for nonaqueous electrolyte secondary batteries according to claim 1 or 2, wherein the titanium oxide is lithium titanate having a spinel structure. A method for producing a negative electrode active material layer for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3,
After forming a solution in which the binder is dissolved or dispersed and the mixture containing the negative electrode active material on a current collector, the first solvent A contained in the solution in which the binder is dissolved or dispersed is The manufacturing method of the negative electrode active material layer for nonaqueous electrolyte secondary batteries extracted with the 2nd solvent B compatible with the solvent A.   The method for producing a negative electrode active material layer for a non-aqueous electrolyte secondary battery according to claim 4, wherein the second solvent B is water. The nonaqueous electrolyte secondary battery which contains the negative electrode active material layer for nonaqueous electrolyte secondary batteries of any one of Claims 1-3 in a negative electrode. An assembled battery formed by connecting a plurality of the nonaqueous electrolyte secondary batteries according to claim 6.