JP2010262798A - Method of manufacturing positive electrode for nonaqueous electrolyte battery, the nonaqueous electrolyte battery, and the positive electrode for nonaqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode for a nonaqueous electrolyte battery that can fully suppress unevenness of the surface of the positive electrode, able to inhibit the positive electrode from contacting the negative electrode, even if a solid electrolyte is fully made thin, and uses the solid electrolyte that can prevent deficiency of the solid electrolyte, and to provide a method of manufacturing the electrode. <P>SOLUTION: The method of manufacturing the positive electrode for nonaqueous electrolyte battery by using the solid electrolyte includes a precursor sol solution filling process to fill a precursor sol solution of a positive electrode material with a positive electrode active material powder as a main substance in the concave part on the surface of a molding having unevenness on its surface; and a heat treatment process to heat-treat the molding filled with the precursor sol solution. The positive electrode manufactured by this manufacturing method uses the nonaqueous electrolyte battery, where the surface filled with the precursor sol solution of the positive electrode material is arranged to face the solid electrolyte and also uses a sintered body as the molding. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a positive electrode for a non-aqueous electrolyte battery using a solid electrolyte, and in particular, a positive electrode manufacturing method with suppressed surface roughness, a non-aqueous electrolyte battery using the positive electrode manufactured by the manufacturing method, and a non-aqueous electrolyte battery. This relates to the positive electrode.

  Non-aqueous electrolyte batteries using lithium (Li) or lithium alloy as the negative electrode and solid electrolyte as the electrolyte have features such as no volatilization of organic solvents at abnormally high temperatures and no risk of liquid leakage. Therefore, it is widely used as a power source for small electric devices such as mobile phones and notebook computers.

A non-aqueous electrolyte battery using a solid electrolyte is formed as a laminate in which a positive electrode, a solid electrolyte, and a negative electrode are sequentially laminated, and the positive electrode is a lithium composite oxide such as lithium cobalt oxide (LiCoO ₂ ) that is a positive electrode active material. A sintered body obtained by sintering powder mainly composed of an object is used. (Patent Document 1)

  In order to increase the volume capacity density, the thickness of the positive electrode and the negative electrode is large, while the thickness of the solid electrolyte that does not contribute to the battery capacity is designed to be as small as possible.

  However, the surface of the sintered body or the like usually has unevenness (steps), and when the thickness of the solid electrolyte is too small, the unevenness is not sufficiently covered with the solid electrolyte and exposed, so when forming the laminate The exposed part of the positive electrode comes into contact with the negative electrode, causing a short circuit. For example, in the case of the sintered body, the surface roughness Ra value is usually 0.5 to 5 μm, and in order to suppress a short circuit, the thickness of the solid electrolyte must be sufficiently large, Incurs a decline. In addition, the unevenness often causes defects in the solid electrolyte, and when performing a charge / discharge cycle, that is, when the battery is driven, it tends to cause dendrite growth of lithium as a negative electrode. The lithium dendrite generated from the negative electrode grows through the solid electrolyte and may cause a short circuit between the positive electrode and the negative electrode, resulting in poor cycle characteristics.

  In order to solve the above problem, for example, a method of reducing the surface roughness by polishing the surface of the sintered body is employed.

Japanese Patent No. 3427570

  However, since there are voids inside the sintered body, in the method of polishing the surface of the sintered body or the like, the voids are exposed and remain as recesses on the surface of the sintered body after polishing. For this reason, there was a limit to making the thickness of the solid electrolyte sufficiently small. In addition, there is still a possibility that a defect may occur in the solid electrolyte with the recess as a base point.

  Therefore, the present invention can sufficiently suppress unevenness on the surface of the positive electrode, suppress contact between the positive electrode and the negative electrode even if the thickness of the solid electrolyte is sufficiently small, and can suppress generation of defects in the solid electrolyte. It is an object of the present invention to provide a positive electrode for a non-aqueous electrolyte battery using a solid electrolyte, a manufacturing method thereof, and the like.

  The present invention has been made for the purpose of solving the above-mentioned problems, and is filled with a precursor sol solution of a positive electrode material in a concave portion facing a solid electrolyte such as a positive electrode sintered body and subjected to heat treatment. Thus, the surface roughness of the facing surface is reduced. The invention of each claim will be described below.

A method for producing a positive electrode for a non-aqueous electrolyte battery according to the present invention is as follows.
A method for producing a positive electrode for a non-aqueous electrolyte battery using a solid electrolyte, comprising:
A precursor sol solution filling step of filling a precursor sol solution of a positive electrode material into a concave portion of a surface of a molded body mainly having a positive electrode active material powder and having irregularities on the surface;
A heat treatment step of heat-treating the molded body filled with the precursor sol solution.

  In the present invention, the recesses on the surface of the molded body having irregularities are filled with a fluidized positive electrode material precursor sol solution and heat-treated, so that the recesses can be efficiently and sufficiently filled with the positive electrode material. . As a result, the concave portion does not remain on the surface of the molded body as in the prior art, and the surface roughness can be reduced more effectively than in the prior art. For this reason, even when the thickness of the solid electrolyte is sufficiently small, a short circuit due to contact between the positive electrode and the negative electrode can be suppressed. Moreover, generation | occurrence | production of the defect of a solid electrolyte can be suppressed.

  Moreover, since the heat treatment product of the precursor sol solution exhibits a function as a positive electrode such as a positive electrode active material, the volume capacity density can be improved.

  The “molded body” referred to in the present invention is not limited to a sintered body, a molded body molded by pressure molding, and a molded body molded by a green sheet method that is applied onto a substrate and dried to form a sheet. Is included. In addition, a thin film formed by a vapor deposition method such as a vapor deposition method or a sputtering method is also included in a thin film having unevenness reflecting the unevenness of the surface of the substrate.

  The precursor sol solution only needs to be filled in the recesses on at least one surface of the molded body. The present invention is particularly effective when the Ra value of the surface of the molded body is 0.5 μm or more.

  The “precursor of positive electrode material” refers to a substance that generates a positive electrode active material that exhibits the action and effect of a positive electrode by heat treatment. An example of a precursor of lithium cobaltate is lithium alkoxide or salt as a lithium source, specifically, lithium alkoxides such as lithium ethoxide, lithium methoxide, lithium butoxide, lithium nitrate, lithium carbonate, etc. Mention may be made of organic acid salts such as inorganic salts, lithium oxalate and lithium acetate. Further, as a cobalt source, cobalt alkoxides and salts, specifically, cobalt alkoxides such as cobalt ethoxide, cobalt diisopropoxide and cobalt dibutoxide, inorganic salts such as cobalt nitrate and cobalt carbonate, cobalt oxalate, acetic acid Mention may be made of organic acid salts such as cobalt.

  As the precursor sol solution, a sol solution in which the fine particles of the positive electrode material precursor are dispersed in alcohol, water, or a mixed solvent of water and alcohol, such as ethanol and methanol, is preferably used.

  As a method for filling the concave portion of the surface of the molded body with the precursor sol solution of the positive electrode material, for example, a coating method in which the precursor sol solution is applied to the surface of the sintered body by spin coating, dip coating, blade method, or the like. Can be mentioned. The viscosity of the precursor sol solution is appropriately adjusted to an optimal value according to the above filling method and the like.

  The heat treatment is preferably performed until the solvent or the like in the precursor sol solution is evaporated or decomposed by heating, and the precursor of the positive electrode material exhibits the function and effect of the positive electrode of the battery.

The positive electrode active material powder used in the present invention has a general formula LiMO ₂ or LiM ₂ O ₄ (where M is one or more of Mn, Fe, Co, Ni, Al, and Mn, Fe in M , Co, Ni, and Al ratios of 50 at% or more) can be preferably used. Specifically, LiCoO ₂ , LiNiO ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiMn ₂ O ₄ , LiMn _1.9 Mention may be made of powders such as Co _0.1 O ₄ and LiFePO ₄ .

  In addition, this invention is especially effective when manufacturing the positive electrode for non-hydrolyzed batteries using a solid electrolyte using the molded object which consists of a sintered compact with large surface roughness Ra value.

The nonaqueous electrolyte battery according to the present invention is
A non-aqueous electrolyte battery using a solid electrolyte in which a positive electrode manufactured by the positive electrode manufacturing method for a non-aqueous electrolyte battery is used,
The positive electrode is disposed so that the surface filled with the precursor sol solution faces the solid electrolyte.

  In the present invention, since a positive electrode having a sufficiently small surface roughness Ra is used, it is possible to provide a nonaqueous electrolyte battery in which occurrence of a short circuit is sufficiently suppressed while reducing the thickness of the solid electrolyte. it can.

  And since generation | occurrence | production of a short circuit is fully suppressed, the yield of a product can be improved compared with the past. In addition, by reducing the thickness of the solid electrolyte, it is possible to provide a nonaqueous electrolyte battery having excellent characteristics with high volume capacity density and low battery resistance.

Examples of the solid electrolyte of the nonaqueous electrolyte battery according to the present invention include sulfides such as Li—P—S—O composed of Li, P, S, and O, and Li—P— composed of Li ₂ S and P ₂ S _5. It is composed of an S amorphous film or a polycrystalline film. Also, since it is suitable for the formation of thin films for the formation of solid electrolytes, PVD methods such as vacuum deposition, sputtering, ion plating, and laser ablation, and CVD such as thermal CVD and plasma CVD The method is preferably used.

A buffer layer made of LiNbO ₃ or the like may be provided between the positive electrode and the solid electrolyte.

The positive electrode for a non-aqueous electrolyte battery according to the present invention is
It is manufactured by the method for manufacturing a positive electrode for a non-aqueous electrolyte battery using a sintered body as the molded body.

  Since the sintered body functions as a positive electrode without using a conductive additive or a binder, the packing density of the positive electrode active material can be increased as compared with a molded body other than the sintered body, such as pressure molding. In the present invention, the packing density of the positive electrode active material can be increased as described above, and the thickness of the solid electrolyte can be sufficiently reduced by using a sintered body having a sufficiently small surface roughness Ra value. Therefore, it is possible to provide a positive electrode for a non-aqueous electrolyte battery suitable for manufacturing a battery having a particularly high volume capacity density.

  According to the present invention, unevenness on the surface of the positive electrode is sufficiently suppressed, and even when the thickness of the solid electrolyte is sufficiently reduced, contact between the positive electrode and the negative electrode can be suppressed, and the occurrence of defects in the solid electrolyte can be suppressed. It is possible to provide a positive electrode for a non-aqueous electrolyte battery that can be produced and a method for producing the same.

It is a figure which shows notionally the filling method of the precursor sol solution of the positive electrode material to the recessed part of the molded object surface in one Example of this invention. It is a figure which shows typically the structure of the laminated body of the nonaqueous electrolyte battery using a solid electrolyte.

  Hereinafter, the present invention will be described based on embodiments. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

In this example, a molded body made of a sintered body of LiCoO ₂ powder was prepared, and then a heat treatment was performed by filling a concave portion on the surface of the molded body with a precursor sol solution of a positive electrode material containing Li and Co. This is an example of producing a positive electrode for a non-aqueous electrolyte battery using a solid electrolyte.

1. Fabrication of molded body and measurement of surface roughness First, fabrication of a molded body and measurement of surface roughness will be described.
(1) Preparation of LiCoO ₂ powder LiOH (lithium hydroxide) and Co (CH ₃ COO) ₂ (cobalt acetate) are weighed in equimolar amounts, put into distilled water, stirred and mixed thoroughly, and then dried. A precursor powder of a positive electrode active material was obtained. The precursor powder was formed into a 20 mmφ × 1 mmt pellet, calcined at 900 ° C. × 5 h, and then pulverized to obtain LiCoO ₂ powder. When the particle size of the obtained LiCoO ₂ powder was measured by a laser scattering method, the volume distribution center particle size D50 = 4 μm. The obtained powder was pulverized using a jet mill (manufactured by Nisshin Engineering Co., Ltd.) to obtain a LiCoO ₂ powder having a volume distribution center particle size D50 = 1 μm.

(2) Production of molded body A predetermined amount of the LiCoO ₂ powder was put into a molding die and pressed at 50 MPa to obtain a molded body before sintering. The obtained pre-sintered molded body was sintered in the atmosphere at 970 ° C. × 3 h, and after the obtained sintered body was processed to a predetermined thickness, the surface was polished with # 1200 abrasive paper to obtain a 16 mmφ × 0.1 mmt A disk-shaped compact of LiCoO ₂ powder was produced. When the surface roughness (Ra value) of the produced molded body was measured with a stylus profilometer, Ra was 0.5 μm.

2. Preparation of Precursor Sol Solution of Positive Electrode Material and Filling of Recesses on Surface of Molded Body Next, filling of the precursor sol solution of positive electrode material into the recesses on the surface of the sintered compact will be described with reference to FIG. FIG. 1 is a diagram conceptually illustrating a method of filling a precursor sol solution of a positive electrode material into a concave portion on the surface of a molded body using a spin coating method. In FIG. 1, 31 is a molded body, 80 is a dropper in which a precursor sol solution of a positive electrode material is stored, 32 is a precursor sol solution of a positive electrode material being dropped from the dropper 80, 33 Is a precursor sol solution that spreads thinly on the surface of the molded body 31 after dropping. 30 is a positive electrode, and 90 is a heater.

(1) Preparation of precursor sol solution of positive electrode material After introducing equimolar amounts of LiOC ₂ H ₅ (ethoxylithium) and Co (Oi-C ₃ H ₇ ) ₂ (di-isopropoxycobalt) into ethanol The mixture was stirred to prepare ethanol solutions containing 10 mol% of each. Next, ethanol was evaporated to prepare a positive electrode material precursor sol solution in which the viscosity was adjusted to 100 mPa · s so that appropriate application was performed.

(2) Filling the concave portion on the surface of the compact with the precursor sol solution of the positive electrode material The prepared precursor sol solution was applied to the surface of the compact 31 of the LiCoO ₂ powder by a spin coating method and filled in the concave. Specifically, the LiCoO ₂ powder compact 31 is rotated at 200 rpm in a horizontal state, and as shown in FIG. 1 (1), the precursor sol solution 32 is dropped on the surface of the rotating compact, A thin coating was applied to the entire surface of the molded body 31 by centrifugal force.

(3) Heat treatment and measurement of surface roughness of positive electrode Next, as shown in (2) of FIG. 1, it was dried in air at 25 ° C. for 10 hours. Thereafter, as shown in FIG. 1 (3), heat treatment was performed at 700 ° C. for 3 hours in the atmosphere to produce a positive electrode 30 in which the product (LiCoO ₂ ) and the molded body obtained by heat treatment were integrated. When the surface roughness of the produced positive electrode was measured with a stylus profilometer, Ra = 0.1 μm.

(Comparative example)
The molded body produced by the same method as in the example was used as it was as the positive electrode except that the concave portion on the surface of the molded body was not filled with the precursor sol solution of the positive electrode material.

3. Performance Evaluation Next, production of a non-aqueous electrolyte battery using a solid electrolyte produced using the positive electrodes of Examples and Comparative Examples (hereinafter, “non-aqueous electrolyte battery using a solid electrolyte” is also simply referred to as “battery”) The performance evaluation will be described.
(1) Production of Battery Using the positive electrode of the above example and the positive electrode of the comparative example, 100 batteries were produced by the following method, and the occurrence of short circuit was examined. Note that the batteries of the examples and comparative examples have the same materials, dimensions, and manufacturing methods other than the positive electrode.

  FIG. 2 is a diagram schematically showing the configuration of the battery stack. In FIG. 2, 10 is a solid electrolyte layer, 15 is a buffer layer, 20 is a negative electrode, 25 is a negative electrode current collector layer, 30 is a positive electrode, and 35 is a positive electrode current collector layer. . Hereinafter, the respective layers will be briefly described focusing on the production thereof.

I. Positive electrode current collector layer The positive electrode current collector layer 35 is made of a thin plate made of SUS304 having a thickness of 0.5 μm, performs current collection when the positive electrode 20 is electrically connected to the outside, and also supports the layers. Also serves as a

B. Buffer layer The buffer layer 15 is made of LiNbO ₃ on the surface of the positive electrode 30 by excimer laser ablation (surface with Ra value of 0.1 μm in the example, surface with Ra value of 0.5 μm in the comparative example). Was formed by vapor deposition to a thickness of 20 nm. At this time, the temperature condition is adjusted so that the deposited LiNbO ₃ becomes amorphous, and after the film formation, the oxygen is annealed by holding at 400 ° C. × 0.5 hr in an atmospheric furnace to constitute the buffer layer. Was diffused into the positive electrode 30.

C. Solid Electrolyte Layer The solid electrolyte layer 10 was formed by forming an Li—PS—S layer on the buffer layer 15 by excimer laser ablation. At this time, the raw materials lithium sulfide (Li ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) were adjusted so that the Li / P (molar ratio) was 2: 1. The thickness is 5 μm.

D. Negative electrode The negative electrode 20 was formed by depositing Li on the solid electrolyte layer 10 to a thickness of 1 μm by resistance heating vapor deposition.
E. Negative electrode current collector layer The negative electrode current collector layer 25 collects current when the negative electrode 20 is electrically connected to the outside, and also serves as a substrate that supports each layer together with the positive electrode current collector layer 35. Yes, the negative electrode 20 was covered with a SUS304 foil having a thickness of 0.5 μm.

  The battery main body described above was packaged to obtain a button-type battery having a thickness of 1 mm and a diameter of 16 mm.

(2) Situation of occurrence of short circuit When the positive electrode of the comparative example was used, the number of batteries in which the positive electrode and the negative electrode were short-circuited was ten. On the other hand, when the positive electrode of the example was used, occurrence of a short circuit was not recognized. From this result, the effectiveness of the present invention was confirmed.

(Other embodiments)
As the precursor sol solution, lithium methoxide, lithium butoxide, lithium nitrate, lithium carbonate, lithium oxalate, lithium acetate, etc. are used as the lithium source, cobalt ethoxide, cobalt butoxide, cobalt nitrate, cobalt carbonate, cobalt oxalate, Even when cobalt acetate was used and methanol was used as a solvent, a positive electrode having a smooth surface was obtained.

DESCRIPTION OF SYMBOLS 10 Solid electrolyte layer 15 Buffer layer 20 Negative electrode 25 Negative electrode collector layer 30 Positive electrode 31 Molded body 32, 33 Precursor sol solution 35 Positive electrode collector layer 80 Dropper 90 Heater

Claims (3)

A method for producing a positive electrode for a non-aqueous electrolyte battery using a solid electrolyte, comprising:
A precursor sol solution filling step of filling a precursor sol solution of a positive electrode material into a concave portion of a surface of a molded body mainly having a positive electrode active material powder and having irregularities on the surface;
A method for producing a positive electrode for a non-aqueous electrolyte battery, comprising: a heat treatment step of heat-treating a molded body filled with the precursor sol solution. A nonaqueous electrolyte battery using a solid electrolyte in which a positive electrode manufactured by the method for manufacturing a positive electrode for a nonaqueous electrolyte battery according to claim 1 is used,
A non-aqueous electrolyte battery, wherein a positive electrode is disposed such that a surface filled with the precursor sol solution faces the solid electrolyte.   A positive electrode for a non-aqueous electrolyte battery, which is manufactured by the method for manufacturing a positive electrode for a non-aqueous electrolyte battery according to claim 1 using a sintered body as the molded body.

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