JP2016081790A - Method for manufacturing all-solid type secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an all-solid type secondary battery manufacturing method which enables the manufacturing of an all-solid type secondary battery with enhanced cycle characteristics.SOLUTION: An all-solid type secondary battery manufacturing method comprises the steps of: an assembly step for assembling a battery having positive and negative electrodes, and a sulfide solid electrolyte layer disposed therebetween; an initial charging step for initially charging the battery thus assembled with a constant current and a constant voltage; a constant-voltage charging step for charging the battery with a constant voltage subsequently to the initial charging step; and an initial discharging step for initially discharging the battery with a constant current and a constant voltage subsequently to the constant-voltage charging step. The constant-voltage charging step is a step for charging the battery with the constant voltage while applying a binding pressure of 0.1-10 MPa to the battery under a temperature environment of 40-60°C; the capacity charged in the constant-voltage charging step is 5-10% of a discharge capacity of the battery identified when the battery is initially discharged with the constant current and the constant voltage without performing the constant-voltage charging step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing an all-solid secondary battery.

  A metal ion secondary battery having a solid electrolyte layer using a flame retardant solid electrolyte (for example, a lithium ion secondary battery or the like. Hereinafter, it may be referred to as an “all solid state secondary battery” or “all solid state battery”). Has advantages such as easy to simplify the system for ensuring safety.

As a technique related to a nonaqueous electrolyte secondary battery using an electrolytic solution, which is different from such an all-solid secondary battery, for example, Patent Document 1 discloses an assembly process for assembling a battery and an initial charging process for charging the assembled battery. And leaving the charged battery in a state where the open circuit potential of the positive electrode is 3.90 V to 4.88 V (vs. Li / Li ⁺ ) for 3 to 720 hours. A method for manufacturing a water electrolyte secondary battery is disclosed.

JP 2005-108682 A

  In Patent Document 1, a protective film referred to as SEI (Solid Electrolyte Interface) is formed on the electrode at an early stage during initial charging and discharging through the above leaving step. It is described that it is possible to suppress the decomposition of the electrolytic solution on the surface, and as a result, it is possible to suppress the swelling of the battery. As described above, in the non-aqueous electrolyte secondary battery using the electrolytic solution, the idea of forming SEI in the leaving step and thereby suppressing the swelling of the battery is known. However, in the all-solid-state secondary battery, the concept of film formation at the time of initial charging is not known. On the other hand, an all-solid secondary battery has a problem in that the capacity of the battery decreases after repeated charging and discharging, so that the battery usage time tends to be short. In order to extend the usage time of the all-solid secondary battery, it is desired to suppress the capacity reduction after repeated charge and discharge, that is, to improve the cycle characteristics of the all-solid secondary battery.

  Then, this invention makes it a subject to provide the manufacturing method of the all-solid-state secondary battery which can manufacture the all-solid-state secondary battery which improved cycling characteristics.

  The present inventors assembled an all-solid-state secondary battery, performed the first constant current constant voltage charging intended to charge the reversible capacity that can be taken out from the battery, and then further, a predetermined pressure under a predetermined temperature environment. The constant voltage charge intended to charge the irreversible capacity that cannot be removed from the battery was performed. As a result, it has been found that a film can be formed on the surface of the positive electrode active material, and the cycle characteristics can be improved. The present invention has been completed based on this finding.

In order to solve the above problems, the present invention takes the following means. That is,
The present invention relates to an assembling process for assembling a battery having a positive electrode and a negative electrode, and a sulfide solid electrolyte layer disposed therebetween, and for the battery assembled in the assembling process, the first constant current and constant voltage charging is performed. An initial charging step to be performed, a constant voltage charging step for performing constant voltage charging for the battery following the initial charging step, and an initial constant current constant voltage discharging for the battery following the constant voltage charging step. The constant voltage charging step is a step of performing constant voltage charging while applying a constraint pressure of 0.1 MPa to 10 MPa to the battery in a temperature environment of 40 ° C. to 60 ° C. And the capacity | capacitance charged by the said constant voltage charge process is 5 to 10% of the discharge capacity of the battery specified when performing the first constant current constant voltage discharge without performing this constant voltage charge process. It is characterized by A method for manufacturing an all-solid secondary battery.

Here, “the discharge capacity of the battery specified when performing the first constant current and constant voltage discharge without performing the constant voltage charging step” refers to performing the constant voltage charging step after performing the first charging step. The capacity taken out from the battery when the constant current constant voltage discharge is performed for the first time, more specifically, after performing the initial charging process, the constant current constant voltage without performing the constant voltage charging process first. The amount of electricity that is taken out of the battery before reaching the end voltage at 0.01 C when discharged.
A constant voltage for the purpose of charging the capacity that cannot be removed (for the irreversible capacity) following the initial charging process for the purpose of charging the capacity that can be taken out (for the reversible capacity) By performing the charging step, a film can be formed on the surface of the positive electrode active material. Then, the constant-voltage charging process is performed at the initial constant-current constant-voltage discharge without passing through the constant-voltage charging process while applying a restraining pressure of 0.1 MPa to 10 MPa in a temperature environment of 40 ° C. to 60 ° C. By adopting a step of performing constant voltage charging for charging a capacity corresponding to 5% to 10% of the discharged capacity, it is possible to form a film in a form capable of improving cycle characteristics. Therefore, by adopting such a form, it becomes possible to manufacture an all-solid-state secondary battery with improved cycle characteristics. In the present invention, the current value at the time of ending the initial charging step can be set as appropriate based on the fact that the initial charging step is a step of charging the reversible capacity. .01C.

In the present invention, LiNi _x Co _y Mn _(1-xy) O ₂ (where 0 <x <1, 0 <y <1, 0 <x + y <1) is used as the positive electrode active material. It may be included. For example, by adopting such a form, it is possible to form a film having a form capable of improving cycle characteristics on the surface of the positive electrode active material. Therefore, for example, by adopting such a form, it becomes possible to manufacture an all-solid secondary battery with improved cycle characteristics.

  Moreover, in the said invention, it is preferable that the surface of a positive electrode active material is coat | covered with lithium niobate. For example, by adopting such a form, it becomes possible to manufacture an all-solid-state secondary battery in a form that easily improves cycle characteristics.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the all-solid-state secondary battery which can manufacture the all-solid-state secondary battery which improved cycling characteristics can be provided.

It is a figure explaining the manufacturing method of the all-solid-state secondary battery of this invention. It is a figure explaining the all-solid-state secondary battery. It is a figure explaining the relationship between battery voltage and charging current, and time. It is a figure which shows the relationship between the termination capacity of a constant voltage charge process, and a capacity | capacitance ratio. It is a figure which shows the relationship between the temperature of a constant voltage charging process, and a capacity | capacitance ratio. It is a figure which shows the relationship between the restraint pressure in a constant voltage charge process, and a capacity | capacitance ratio.

  The present invention will be described below with reference to the drawings. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below.

  FIG. 1 is a diagram for explaining a method for producing an all-solid secondary battery of the present invention. The manufacturing method of the present invention shown in FIG. 1 includes an assembly process (S11), an initial charging process (S12), a constant voltage charging process (S13), and an initial discharging process (S14).

1. Assembly process (S11)
The assembly process (hereinafter sometimes referred to as “S11”) is a process of assembling a battery having a positive electrode and a negative electrode, and a sulfide solid electrolyte layer disposed therebetween. An example of the battery 20 assembled in S11 is shown in FIG. In FIG. 2, descriptions of terminals and exterior bodies provided in the battery 20 are omitted. 2 includes a positive electrode current collector 21, a positive electrode 22 connected to the positive electrode current collector 21, a negative electrode current collector 25, a negative electrode 24 connected to the negative electrode current collector 25, A sulfide solid electrolyte layer 23 disposed between the positive electrode 22 and the negative electrode 24. Terminals (not shown) are connected to the positive electrode current collector 21 and the negative electrode current collector 25, and the battery 20 is accommodated in an exterior body (not shown).

2. Initial charging process (S12)
The initial charging step (hereinafter may be referred to as “S12”) is a step of performing the initial constant current / constant voltage charging on the battery 20 assembled in S11. The constant current and constant voltage charging performed in S12 is performed for the purpose of charging the amount of electricity (reversible capacity) taken out from the battery 20 as in the conventional battery. The form of S12 is not particularly limited as long as it is a step of performing constant-current constant-voltage charging for the purpose of reversible capacity charging. S12 is a step of performing constant voltage charging while reducing the current value after performing constant current charging until reaching a predetermined voltage, and current at the time of ending constant voltage charging (when ending S12) The value can be, for example, 0.01C.

3. Constant voltage charging process (S13)
In the constant voltage charging step (hereinafter sometimes referred to as “S13”), following S12, a restraint pressure of 0.1 MPa to 10 MPa is applied to the battery 20 in a temperature environment of 40 ° C. to 60 ° C. However, this is a step of performing constant voltage charging. By performing S13 in a temperature environment of 40 ° C. or more and 60 ° C. or less, the battery 20 capable of improving the cycle characteristics can be manufactured in a short time. In addition, by performing S13 while applying a restraining pressure of 0.1 MPa or more and 10 MPa or less to the battery 20, it is possible to form a film uniformly on the surface of the positive electrode active material, and thus it is possible to improve cycle characteristics. The battery 20 can be manufactured. The method for applying the constraint pressure in S13 is not particularly limited, and for example, a configuration in which the constraint pressure is applied to the battery 20 using a hydraulic press machine or the like can be used.
In this invention, S13 is complete | finished when the capacity | capacitance equivalent to 5%-10% of the discharge capacity of the battery specified when performing the first constant current constant voltage discharge without performing S13 is charged. By setting the capacity increased in S13 (hereinafter sometimes referred to as “end capacity”) within the range of 5% to 10%, the cycle characteristics of the battery 20 can be improved. The termination capacity of S13 may be appropriately determined from the above 5% to 10%.
In S13 performed subsequent to S12, the amount of electricity that cannot be taken out from the battery 20 (irreversible capacity) is charged. By slowly charging at constant voltage in S13, a dense film can be formed on the surface of the positive electrode active material, and as a result, cycle characteristics can be improved. FIG. 3 shows the relationship between battery voltage and charging current and time in S12 and S13. Since S13 is a step of performing constant voltage charging following S12, as shown in FIG. 3, the current value at the start of S13 is the current value at the end of S12.

4). First discharge process (S14)
The initial discharge step (hereinafter may be referred to as “S14”) is a step of performing an initial constant-current / constant-voltage discharge for the battery 20 following S13. The constant current and constant voltage discharge performed in S14 is performed for the purpose of taking out the amount of electricity accumulated in the battery 20 in S12. The form of S14 is not particularly limited as long as it is a step of performing constant current and constant voltage discharge. S14 is a step of performing constant voltage discharge while reducing the current value after performing constant current discharge until a predetermined voltage is reached, and the current when the constant voltage discharge is terminated (when S14 is terminated). The value can be, for example, 0.01C.

  Subsequent to S12, through S13 in which constant voltage charging is performed under conditions of a predetermined temperature, restraining pressure, and final capacity, a coating film in a form capable of improving cycle characteristics on the surface of the positive electrode active material Can be formed. Therefore, by using the form having S11 to S14, it is possible to provide a method for manufacturing an all-solid-state secondary battery that can manufacture the battery 20 with improved cycle characteristics.

  If S11 is a process of assembling the battery 20, the form is not particularly limited. S11 can be set as the process of assembling the battery 20 through the process shown below, for example.

  The positive electrode 22 is, for example, a slurry-like positive electrode composition prepared by dispersing a substance (for example, a positive electrode active material, a sulfide solid electrolyte, a conductive material, etc., which is the same hereinafter) constituting the positive electrode 22 in a liquid. The product can be produced by applying it to the surface of a separately prepared positive electrode current collector 21, drying it, and pressing it at a predetermined pressure. In addition, it is also possible to produce the positive electrode 22 by pressing a mixture produced by mixing the substances that constitute the positive electrode 22.

  As the positive electrode current collector 21, a metal that can be used as a current collector of an all-solid-state secondary battery can be used. As such a metal, a metal containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. Materials can be exemplified.

Moreover, as a positive electrode active material contained in the positive electrode 22, the positive electrode active material which can be used with an all-solid-state secondary battery can be used suitably. Examples of such a positive electrode active material include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium nickel cobalt manganese composite oxide (LiNi _x Co _y Mn _(1-xy) O ₂ (however, In addition to layered active materials such as 0 <x <1, 0 <y <1, 0 <x + y <1)), olivine-type active materials such as olivine-type lithium iron phosphate (LiFePO ₄ ), and spinel-type lithium manganate A spinel active material such as (LiMn ₂ O ₄ ) can be exemplified. The shape of the positive electrode active material can be, for example, particulate or thin film. The average particle diameter (D ₅₀ ) of the positive electrode active material is, for example, preferably from 1 nm to 100 μm, and more preferably from 10 nm to 30 μm. Further, the content of the positive electrode active material in the positive electrode layer is not particularly limited, but is preferably 40% or more and 99% or less in mass%, for example.

Further, the positive electrode 22 can appropriately contain a sulfide solid electrolyte that can be used in an all-solid secondary battery using a sulfide solid electrolyte. Examples of such sulfide solid electrolytes include Li ₂ S—SiS ₂ , LiI—Li ₂ S—SiS ₂ , LiI—Li ₂ S—P ₂ S ₅ , LiI—Li ₂ S—P ₂ O ₅ , LiI—. Examples include Li ₃ PO ₄ —P ₂ S ₅ , Li ₂ S—P ₂ S ₅ , Li ₃ PS _{4, and the} like. The sulfide solid electrolyte may be crystalline, non-crystalline, or glass ceramic.

From the viewpoint of making it easy to prevent an increase in battery resistance by making the high resistance layer difficult to form at the interface between the positive electrode active material and the sulfide solid electrolyte, the positive electrode active material contained in the positive electrode 22 is an ion It is preferably coated with a conductive oxide. Examples of the lithium ion conductive oxide that coats the positive electrode active material include a general formula Li _x AO _y (A is B, C, Al, Si, P, S, Ti, Zr, Nb, Mo, Ta, or W). And x and y are positive numbers). Specifically, Li ₃ BO ₃ , Li ₂ CO ₃ , LiAlO ₂ , Li ₄ SiO ₄ , Li ₃ PO ₄ , Li ₂ SO ₄ , Li ₄ Ti ₅ O ₁₂ , Li ₂ ZrO ₃ , LiNbO ₃ , Li ₂ Examples thereof include MoO ₄ and Li ₂ WO ₄ . The lithium ion conductive oxide may be a complex oxide. As the composite oxide covering the positive electrode active material, any combination of the above lithium ion conductive oxides can be employed. For example, Li ₄ SiO ₄ —Li ₃ BO ₃ , Li ₄ SiO ₄ —Li ₃ PO ₄ etc. can be mentioned. Further, when the surface of the positive electrode active material is coated with an ion conductive oxide, the ion conductive oxide only needs to cover at least a part of the positive electrode active material, and covers the entire surface of the positive electrode active material. Also good. In addition, the thickness of the ion conductive oxide covering the positive electrode active material is, for example, preferably from 0.1 nm to 100 nm, and more preferably from 1 nm to 20 nm. The thickness of the ion conductive oxide can be measured using, for example, a transmission electron microscope (TEM).

  Further, the positive electrode 22 can appropriately contain a conductive material that improves conductivity. Such conductive materials include vapor grown carbon fiber, acetylene black (AB), ketjen black (KB), carbon nanotube (CNT), carbon nanofiber (CNF) and other carbon materials, as well as all-solid secondary A metal material that can withstand the environment when the battery is used can be exemplified.

  Moreover, the positive electrode 22 can contain a binder as appropriate. Examples of such a binder include acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), and the like.

  When the positive electrode 22 is produced using a slurry-like positive electrode composition prepared by dispersing the positive electrode active material, the sulfide solid electrolyte, and the conductive material in a liquid, heptane or the like is exemplified as a usable liquid. A nonpolar solvent can be preferably used. Further, the thickness of the positive electrode 22 is, for example, preferably from 0.1 μm to 1 mm, and more preferably from 1 μm to 100 μm. Moreover, in order to make it easy to improve the performance of the battery 20, the positive electrode 22 is preferably manufactured through a pressing process. In the present invention, the pressing pressure when producing the positive electrode 22 can be about 100 MPa.

  On the other hand, the negative electrode 24 is a negative electrode prepared separately by, for example, preparing a slurry-like negative electrode composition prepared by dispersing a material (for example, a negative electrode active material and a sulfide solid electrolyte) to constitute the negative electrode 24 in a liquid. It can be manufactured through a process in which it is applied to the surface of the current collector 25, dried, and then pressed at a predetermined pressure. In addition, the negative electrode 24 can be manufactured by pressing a mixture prepared by mixing the substances that constitute the negative electrode 24.

  Here, the negative electrode current collector 25 can be made of a metal that can be used as a current collector of an all-solid secondary battery. As such a metal, a metal containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. Materials can be exemplified.

Moreover, as a negative electrode active material contained in the negative electrode 24, the negative electrode active material which can be used with an all-solid-state secondary battery can be used suitably. Examples of such a negative electrode active material include a carbon active material, an oxide active material, and a metal active material. The carbon active material is not particularly limited as long as it contains carbon, and examples thereof include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of the oxide active material include Nb ₂ O ₅ , Li ₄ Ti ₅ O ₁₂ , and SiO. Examples of the metal active material include In, Al, Si, and Sn. Further, a lithium-containing metal active material may be used as the negative electrode active material. The lithium-containing metal active material is not particularly limited as long as it is an active material containing at least Li, and may be Li metal or Li alloy. Examples of the Li alloy include an alloy containing Li and at least one of In, Al, Si, and Sn. The shape of the negative electrode active material can be, for example, particulate or thin film. The average particle diameter (D ₅₀ ) of the negative electrode active material is, for example, preferably from 1 nm to 100 μm, and more preferably from 10 nm to 30 μm. In addition, the content of the negative electrode active material in the negative electrode layer is not particularly limited, but is preferably 40% or more and 99% or less in mass%, for example.

  The negative electrode 24 can appropriately contain a sulfide solid electrolyte that can be used in an all-solid secondary battery using a sulfide solid electrolyte. As such a sulfide solid electrolyte, the sulfide solid electrolyte that can be contained in the positive electrode 22 can be exemplified.

  Further, the negative electrode 24 can appropriately contain a conductive material that improves conductivity. As such a conductive material, the said conductive material which can be contained in the positive electrode 22 can be illustrated.

  Moreover, the negative electrode 24 can contain a binder as appropriate. As such a binder, the said binder which can be contained in the positive electrode 22 can be illustrated.

  When a negative electrode layer is prepared using a slurry-like negative electrode composition prepared by dispersing the negative electrode active material and sulfide solid electrolyte in a liquid, heptane or the like is exemplified as a liquid in which the negative electrode active material or the like is dispersed. A nonpolar solvent can be preferably used. Further, the thickness of the negative electrode 24 is, for example, preferably from 0.1 μm to 1 mm, and more preferably from 1 μm to 100 μm. Moreover, in order to make it easy to improve the performance of the battery 20, the negative electrode 24 is preferably manufactured through a pressing process. In this invention, the pressure at the time of pressing the negative electrode 24 can be about 400 MPa, for example.

  Moreover, as the sulfide solid electrolyte contained in the sulfide solid electrolyte layer 23, a sulfide solid electrolyte that can be used in an all-solid secondary battery can be appropriately used. As such a sulfide solid electrolyte, the above-mentioned sulfide solid electrolyte that can be contained in the positive electrode 22 and the negative electrode 24 can be exemplified. In addition, the sulfide solid electrolyte layer 23 can contain a binder that binds the sulfide solid electrolytes together from the viewpoint of developing plasticity. As such a binder, the said binder etc. which can be contained in the positive electrode 22 or the negative electrode 24 can be illustrated. However, from the viewpoint of making it possible to form a sulfide solid electrolyte layer 23 having a sulfide solid electrolyte uniformly dispersed and preventing excessive aggregation of the sulfide solid electrolyte in order to facilitate high output. The binder contained in the sulfide solid electrolyte layer 23 is preferably 5% by mass or less. Further, when the sulfide solid electrolyte layer 23 is manufactured through a process of applying the slurry solid electrolyte composition prepared by dispersing the sulfide solid electrolyte or the like in a liquid to the positive electrode 22 or the negative electrode 24, the sulfide solid electrolyte layer 23 is prepared. Examples of the liquid for dispersing the electrolyte and the like include heptane and the like, and a nonpolar solvent can be preferably used. The content of the sulfide solid electrolyte material in the sulfide solid electrolyte layer 23 is mass%, for example, 60% or more, preferably 70% or more, and particularly preferably 80% or more. Although the thickness of the sulfide solid electrolyte layer 23 varies greatly depending on the configuration of the battery, for example, it is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less.

  When assembling the battery 20 having the positive electrode 22, the negative electrode 24, and the sulfide solid electrolyte layer 23 that can be produced in this manner, for example, the positive electrode 22 is formed on one surface of the positive electrode current collector 21, and the negative electrode A negative electrode 24 is formed on one surface of the current collector 25, and a sulfide solid electrolyte layer 23 is formed on the surface of the negative electrode 24. Thereafter, the positive electrode 22, the sulfide solid electrolyte layer 23, and the negative electrode current collector formed on the surface of the positive electrode current collector 21 so that the sulfide solid electrolyte layer 23 is disposed between the positive electrode 22 and the negative electrode 24. By laminating the negative electrode 24 formed on the surface of the body 25, a laminate having the positive electrode current collector 21, the positive electrode 22, the sulfide solid electrolyte layer 23, the negative electrode 24, and the negative electrode current collector 25 is formed. And the battery 20 can be assembled by passing through processes, such as accommodating and sealing this laminated body in an exterior body. As an exterior body that houses the laminate, a laminate film that can be used in an all-solid secondary battery can be appropriately used. Examples of such a laminate film include a resin laminate film, a film obtained by depositing a metal on a resin laminate film, and the like.

  The present invention will be further described with reference to examples.

(1) Synthesis of sulfide solid electrolyte Li ₂ S (manufactured by Nippon Kagaku Kogyo Co., Ltd.) and P ₂ S ₅ (manufactured by Aldrich) are used as starting materials, 0.756 g of Li ₂ S, and P ₂ S ₅ of 1. 2344 g was weighed and mixed for 5 minutes in an agate mortar. Thereafter, 4 g of heptane was added, and a sulfide solid electrolyte was obtained by mechanical milling for 40 minutes using a planetary ball mill (Pulverisette-7, manufactured by Fritsch).

(2) Production of Battery As the positive electrode active material, lithium cobalt manganate LiNi _3/5 Co _1/5 Mn _1/5 O ₂ whose surface was coated with LiNbO ₃ was used. Moreover, the vapor growth carbon fiber (made by Showa Denko KK) was used for the electrically conductive material. 12.03 mg of the positive electrode active material, 0.51 mg of the conductive material, and 5.03 mg of the sulfide solid electrolyte synthesized by the method described above were weighed, and a mixture thereof was used as the positive electrode mixture.
Graphite (manufactured by Mitsubishi Chemical Corporation) was used as the negative electrode active material. 9.06 mg of the negative electrode active material and 8.24 mg of the sulfide solid electrolyte synthesized by the method described above were weighed, and a mixture thereof was used as the negative electrode mixture.
By weighing 18 mg of the sulfide solid electrolyte synthesized by the above-mentioned method into a ceramic mold having a hollow cross-sectional area of 1 cm ² with the axial direction as the normal direction, the sulfide is pressed by pressing at 98 MPa. A solid electrolyte layer was prepared. Next, 17.57 mg of a positive electrode mixture was placed on one side of the sulfide solid electrolyte layer thus prepared, and pressed at 98 MPa to prepare a positive electrode. Furthermore, 17.3 mg of the negative electrode mixture was put on the side opposite to the side where the positive electrode mixture was put, and pressed at 490 MPa to prepare a negative electrode. Thereafter, a battery (all-solid secondary battery) was manufactured through a process in which the positive electrode current collector (Al foil) was brought into contact with the positive electrode and the negative electrode current collector (Cu foil) was brought into contact with the negative electrode.

(3) Characteristic evaluation (capacity retention rate measurement after repeated charge / discharge)
<Example 1>
The battery manufactured by the above-described method is charged with a constant current up to 4.4V at 1C, and then charged with a constant voltage at 4.4V while gradually reducing the current value to a termination current value of 0.01C. (First charging step). Thereafter, a capacity equivalent to 5% of the initial discharge capacity of Comparative Example 1 described later is applied in a 40 ° C. environment while applying a 1 MPa restraining pressure with a hydraulic press (manufactured by Riken Seiki Co., Ltd., hydraulic press MS2). Constant voltage charging was performed while gradually decreasing the current value from 0.01 C at 4.4 V (constant voltage charging step). Then, constant current discharge was performed to 3.0V at 1C, and then constant voltage discharge was performed at 3.0V while gradually reducing the current value to a final current value of 0.01C (initial discharge process).
Thereafter, constant current charging was performed up to 4.4V at 2C, and then constant voltage charging was performed at 4.4V while gradually reducing the current value to the end current value of 0.02C (second charging step) ). Then, constant current discharge was performed to 3.0V at 2C, and then constant voltage discharge was performed at 3.0V while gradually reducing the current value to the end current value of 0.02C (second discharge process) ).
The battery that has completed the second discharge process is charged at a constant current of up to 4.4 V at 2 mA, and then charged and discharged at a constant current of up to 3.0 V at 2 mA for one cycle. Discharge was performed. After performing the constant current discharge of the 200th cycle, charge / discharge under the same conditions as the second charging step and the second discharging step, and the discharge capacity specified by the discharging under the same conditions as the second discharging step Was the discharge capacity after repeated use of Example 1. Then, using the initial discharge capacity of Comparative Example 1 described later, capacity ratio (%) = 100 × discharge capacity after repeated use of Example 1 / initial discharge capacity of Comparative Example 1 The ratio was determined.

<Comparative Example 1>
The first charging step and the first discharging step are performed in the same manner as in Example 1 except that the constant voltage charging step is not performed, and further, the second charging step and the second discharging step are performed in the same manner as in Example 1. It was. The discharge capacity specified in the second discharge process was used as the first discharge capacity of Comparative Example 1.
Thereafter, in the same manner as in Example 1, the discharge capacity after repeated use of Comparative Example 1 was obtained, and the capacity ratio (%) = 100 × discharge capacity after repeated use of Comparative Example 1 / initial discharge capacity of Comparative Example 1 Thus, the capacity ratio of Comparative Example 1 was obtained.

<Comparative Example 2>
The discharge capacity after repeated use of Comparative Example 2 was determined in the same manner as in Comparative Example 1, except that the battery was left for 24 hours after the completion of the initial charging process (aging) and then the initial discharge process was performed. Capacity ratio (%) = 100 × discharge capacity after repeated use of Comparative Example 2 / initial discharge capacity of Comparative Example 1 The capacity ratio of Comparative Example 2 was determined.

<Example 2>
The discharge capacity after repeated use of Example 2 was determined in the same manner as in Example 1 except that the constant voltage charging process was performed until the capacity corresponding to 7% of the initial discharge capacity of Comparative Example 1 increased. Capacity ratio (%) = 100 × discharge capacity after repeated use of Example 2 / first time discharge capacity of Comparative Example 1 The capacity ratio of Example 2 was determined.

<Example 3>
The discharge capacity after repeated use of Example 3 was determined in the same manner as in Example 1 except that the constant voltage charging step was performed until the capacity corresponding to 9% of the initial discharge capacity of Comparative Example 1 increased. Capacity ratio (%) = 100 × discharge capacity after repeated use of Example 3 / first time discharge capacity of Comparative Example 1 The capacity ratio of Example 3 was determined.

<Example 4>
The discharge capacity after repeated use of Example 4 was determined in the same manner as in Example 1 except that the constant voltage charging process was performed until the capacity corresponding to 10% of the initial discharge capacity of Comparative Example 1 increased. Capacity ratio (%) = 100 × discharge capacity after repeated use of Example 4 / initial discharge capacity of Comparative Example 1 The capacity ratio of Example 4 was determined.

<Example 5>
The discharge capacity after repeated use of Example 5 was determined in the same manner as in Example 2 except that the temperature during the constant voltage charging step was changed to 50 ° C., and the capacity ratio (%) = 100 × Example 5 The capacity ratio of Example 5 was obtained from the discharge capacity after repeated use / the initial discharge capacity of Comparative Example 1.

<Example 6>
The discharge capacity after repeated use of Example 6 was determined in the same manner as in Example 5 except that the temperature during the constant voltage charging step was changed to 60 ° C., and the capacity ratio (%) = 100 × Example 6 The capacity ratio of Example 6 was determined from the discharge capacity after repeated use / the initial discharge capacity of Comparative Example 1.

<Example 7>
The discharge capacity after repeated use of Example 7 was determined in the same manner as in Example 5 except that the constraint pressure in the constant voltage charging step was changed to 0.1 MPa, and the capacity ratio (%) = 100 × Example 7 The capacity ratio of Example 7 was determined from the discharge capacity after repeated use / the initial discharge capacity of Comparative Example 1.

<Example 8>
The discharge capacity after repeated use of Example 8 was determined in the same manner as in Example 5 except that the constraint pressure in the constant voltage charging step was changed to 2 MPa, and the capacity ratio (%) = 100 × repeated use of Example 8 The capacity ratio of Example 8 was determined from the subsequent discharge capacity / the initial discharge capacity of Comparative Example 1.

<Example 9>
The discharge capacity after repeated use of Example 9 was determined in the same manner as in Example 5 except that the constraint pressure in the constant voltage charging step was changed to 4 MPa, and the capacity ratio (%) = 100 × repeated use of Example 9 The capacity ratio of Example 9 was determined from the subsequent discharge capacity / the initial discharge capacity of Comparative Example 1.

<Example 10>
The discharge capacity after repeated use of Example 10 was determined in the same manner as in Example 5 except that the constraint pressure in the constant voltage charging step was changed to 8 MPa, and the capacity ratio (%) = 100 × repeated use of Example 10 The capacity ratio of Example 10 was determined from the subsequent discharge capacity / the initial discharge capacity of Comparative Example 1.

<Example 11>
The discharge capacity after repeated use of Example 11 was determined in the same manner as in Example 5 except that the constraint pressure in the constant voltage charging step was changed to 10 MPa, and the capacity ratio (%) = 100 × repeated use of Example 11 The capacity ratio of Example 11 was obtained from the subsequent discharge capacity / the initial discharge capacity of Comparative Example 1.

<Comparative Example 3>
The discharge capacity after repeated use of Comparative Example 3 was determined in the same manner as in Example 1 except that the constant voltage charging step was performed until the capacity corresponding to 2% of the initial discharge capacity of Comparative Example 1 increased. Capacity ratio (%) = 100 × discharge capacity after repeated use of comparative example 3 / initial discharge capacity of comparative example 1 The capacity ratio of comparative example 3 was determined.

<Comparative example 4>
The discharge capacity after repeated use of Comparative Example 4 was determined in the same manner as in Example 1 except that the constant voltage charging step was performed until the capacity corresponding to 4% of the initial discharge capacity of Comparative Example 1 increased. Capacity ratio (%) = 100 × Discharge capacity after repeated use of Comparative Example 4 / First discharge capacity of Comparative Example 1 The capacity ratio of Comparative Example 4 was determined.

<Comparative Example 5>
The discharge capacity after repeated use of Comparative Example 5 was determined in the same manner as in Example 1 except that the constant voltage charging step was performed until the capacity corresponding to 12% of the initial discharge capacity of Comparative Example 1 increased. Capacity ratio (%) = 100 × discharge capacity after repeated use of Comparative Example 5 / initial discharge capacity of Comparative Example 1 The capacity ratio of Comparative Example 5 was determined.

<Comparative Example 6>
The discharge capacity after repeated use of Comparative Example 6 was determined in the same manner as in Example 1 except that the constant voltage charging step was performed until the capacity corresponding to 15% of the initial discharge capacity of Comparative Example 1 increased. Capacity ratio (%) = 100 × Discharge capacity after repeated use of Comparative Example 6 / First discharge capacity of Comparative Example 1 The capacity ratio of Comparative Example 6 was determined.

<Comparative Example 7>
The discharge capacity after repeated use of Comparative Example 7 was determined in the same manner as in Example 2 except that the temperature during the constant voltage charging step was changed to 25 ° C., and the capacity ratio (%) = 100 × Comparative Example 7 The capacity ratio of Comparative Example 7 was obtained from the discharge capacity after repeated use / the initial discharge capacity of Comparative Example 1.

<Comparative Example 8>
The discharge capacity after repeated use of Comparative Example 8 was determined in the same manner as in Example 2 except that the temperature during the constant voltage charging step was changed to 35 ° C., and the capacity ratio (%) = 100 × Comparative Example 8 The capacity ratio of Comparative Example 8 was determined from the discharge capacity after repeated use / the initial discharge capacity of Comparative Example 1.

<Comparative Example 9>
The discharge capacity after repeated use of Comparative Example 9 was determined in the same manner as in Example 2 except that the temperature during the constant voltage charging step was changed to 70 ° C., and the capacity ratio (%) = 100 × Comparative Example 9 The capacity ratio of Comparative Example 9 was determined from the discharge capacity after repeated use / the initial discharge capacity of Comparative Example 1.

<Comparative Example 10>
The discharge capacity after repeated use of Comparative Example 10 was determined in the same manner as in Example 2 except that the temperature during the constant voltage charging step was changed to 80 ° C., and the capacity ratio (%) = 100 × Comparative Example 10 The capacity ratio of Comparative Example 10 was determined from the discharge capacity after repeated use / the initial discharge capacity of Comparative Example 1.

<Comparative Example 11>
The discharge capacity after repeated use of Comparative Example 11 was determined in the same manner as in Example 5 except that no constraint pressure was applied in the constant voltage charging step (the constraint pressure was set to 0 MPa), and the capacity ratio (%) = The capacity ratio of Comparative Example 11 was determined from 100 × discharge capacity after repeated use of Comparative Example 11 / initial discharge capacity of Comparative Example 1.

<Comparative Example 12>
The discharge capacity after repeated use of Comparative Example 12 was determined in the same manner as in Example 5 except that the constraint pressure in the constant voltage charging step was changed to 12 MPa, and the capacity ratio (%) = 100 × repeated use of Comparative Example 12 The capacity ratio of Comparative Example 12 was determined from the subsequent discharge capacity / the initial discharge capacity of Comparative Example 1.

(4) Results FIG. 4 shows the results of the capacity ratios of Examples 1 to 4 and the capacity ratios of Comparative Examples 1 to 6. As described above, since the constant voltage charging process was not performed in Comparative Example 1 and Comparative Example 2, it was assumed that the capacity increased in the constant voltage charging process was 0% in Comparative Example 1 and Comparative Example 2, and the results are shown in FIG. showed that. As shown in FIG. 4, the capacity ratio of Example 1 is 68%, the capacity ratio of Example 2 is 70%, the capacity ratio of Example 3 is 71%, and the capacity ratio of Example 4 is 71%. there were. In contrast, the capacity ratio of Comparative Example 1 is 60%, the capacity ratio of Comparative Example 2 is 61%, the capacity ratio of Comparative Example 3 is 61%, the capacity ratio of Comparative Example 4 is 62%, and the capacity ratio of Comparative Example 5 Was 61%, and the capacity ratio of Comparative Example 6 was 57%. That is, Examples 1 to 4 in which the final capacity of the constant voltage charging process is 5% or more and 10% are compared with Comparative Examples 1 to 4 in which the final capacity of the constant voltage charging process is less than 5%, The capacity ratio was larger than those of Comparative Examples 5 and 6 in which the final capacity of the charging process exceeded 10%. From this result, it was found that an all-solid-state secondary battery with improved cycle characteristics can be manufactured by performing a constant voltage charging step with a termination capacity of 5% to 10%.

  The results of the capacity ratios of Example 2, Example 5, Example 6, and Comparative Examples 7 to 10 are shown in FIG. As described above, Example 2, Example 5, Example 6, and Comparative Examples 7 to 10 had different temperatures when performing the constant voltage charging process. As shown in FIG. 5, the capacity ratio of Example 2 was 70%, the capacity ratio of Example 5 was 72%, and the capacity ratio of Example 6 was 72%. On the other hand, the capacity ratio of Comparative Example 7 was 61%, the capacity ratio of Comparative Example 8 was 62%, the capacity ratio of Comparative Example 9 was 55%, and the capacity ratio of Comparative Example 10 was 35%. That is, Example 2, Example 5 and Example 6 in which the temperature of the constant voltage charging step was set to 40 ° C. or more and 60 ° C. or less were Comparative Example 7 and Comparative Example in which the temperature of the constant voltage charging step was less than 40 ° C. 8 and the capacity ratio was larger than those of Comparative Examples 9 and 10 in which the temperature of the constant voltage charging step was higher than 60 ° C. From this result, it was found that an all-solid-state secondary battery with improved cycle characteristics can be manufactured by performing the constant voltage charging step in a temperature environment of 40 ° C. or higher and 60 ° C. or lower.

  The results of the capacity ratios of Example 5, Examples 7 to 11, Comparative Example 11, and Comparative Example 12 are shown in FIG. As mentioned above, Example 5, Example 7 thru | or Example 11, the comparative example 11, and the comparative example 12 differed in the restraint pressure provided at the constant voltage charging process. As shown in FIG. 6, the capacity ratio of Example 5 is 72%, the capacity ratio of Example 7 is 66%, the capacity ratio of Example 8 is 74%, the capacity ratio of Example 9 is 78%, and the Example The capacity ratio of 10 was 80%, and the capacity ratio of Example 11 was 80%. On the other hand, the capacity ratio of Comparative Example 11 was 55%, and the capacity ratio of Comparative Example 12 was 51%. That is, in Example 5 and Examples 7 to 11 in which the constraining pressure applied in the constant voltage charging process is 0.1 MPa or more and 10 MPa or less, the constraining pressure applied in the constant voltage charging process is less than 0.1 MPa. The capacity ratio was larger than Comparative Example 11 and Comparative Example 12 in which the constraining pressure applied in the constant voltage charging step exceeded 10 MPa. From this result, it was found that an all-solid-state secondary battery with improved cycle characteristics can be manufactured by performing a constant voltage charging step in which the constraint pressure is 0.1 MPa or more and 10 MPa or less.

20 ... Battery (All-solid secondary battery)
DESCRIPTION OF SYMBOLS 21 ... Positive electrode collector 22 ... Positive electrode 23 ... Sulfide solid electrolyte layer 24 ... Negative electrode 25 ... Negative electrode collector

Claims (3)

An assembly step of assembling a battery having a positive electrode and a negative electrode, and a sulfide solid electrolyte layer disposed between the positive electrode and the negative electrode;
For the battery assembled in the assembly process, the first constant current constant voltage charging, an initial charging process,
Following the initial charging step, the battery is subjected to constant voltage charging, a constant voltage charging step,
Following the constant voltage charging step, for the battery, performing an initial constant current constant voltage discharge, an initial discharge step,
Have
The constant voltage charging step is a step of performing constant voltage charging while applying a constraint pressure of 0.1 MPa to 10 MPa to the battery in a temperature environment of 40 ° C. to 60 ° C., and
The capacity charged in the constant voltage charging step is 5% to 10% of the discharge capacity of the battery specified when performing the first constant current constant voltage discharge without performing the constant voltage charging step.
A method for producing an all solid state secondary battery. The positive electrode includes LiNi _x Co _y Mn _(1-xy) O ₂ (where 0 <x <1, 0 <y <1, 0 <x + y <1) as a positive electrode active material, The manufacturing method of the all-solid-state secondary battery of Claim 1. The method for producing an all-solid-state secondary battery according to claim 2, wherein the surface of the positive electrode active material is coated with lithium niobate.