Battery

Abstract

To provide a battery capable of suppressing performance degradation in a battery containing an Si-based active material.SOLUTION: In an aging method of a battery including an electrode body formed by laminating a positive electrode mixture layer, an electrolyte layer, and a negative electrode mixture layer containing a Si-based active material, the amount of an organic solvent contained in the negative electrode mixture layer is set to 0.2 mass% or less, and aging treatment is performed for 10 cycles or more as initial aging treatment.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to batteries. [Background technology]

[0002] Patent Document 1 discloses a negative electrode mixture containing porous Si as an electrode active material and a binder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-167083 Summary of the Invention [Problem to be solved by the invention]

[0004] In batteries containing Si-based active materials, it is not easy to suppress an increase in resistance due to problems such as durability, and improvements in this suppression are desired.

[0005] Therefore, an object of the present disclosure is to provide a battery that can suppress performance degradation in a battery that includes a Si-based active material. [Means for solving the problem]

[0006] Typically, batteries deteriorate most rapidly in the early stages. This is because the reaction during charging in the early stages is significantly different from that during other periods. For this reason, an aging treatment is performed to improve performance by charging and discharging the battery under different conditions for the first few cycles (for convenience, this aging treatment under these conditions may be referred to as the "initial aging treatment"). After extensive research into this initial aging treatment, the inventors have found that deterioration can be suppressed by combining the amount of remaining solvent with the conditions of this initial aging treatment. Although this is not entirely clear, it is thought that this is because, when residual solvent is present, deterioration progresses significantly over multiple cycles, and then the progression of deterioration slows down as the remaining solvent disappears.

[0007] The present application discloses an aging method for a battery having an electrode body formed by stacking a positive electrode composite layer, an electrolyte layer, and a negative electrode composite layer containing a Si-based active material, in which the amount of organic solvent contained in the negative electrode composite layer is 0.2 mass% or less, and 10 or more cycles of aging treatment are performed as an initial aging treatment.

[0008] The initial aging treatment may be CC charging and discharging at 60° C., 0.3 C, and from 0% to 100% SOC.

[0009] The electrolyte layer may include a solid electrolyte. [Effects of the Invention]

[0010] According to the battery of the present disclosure, the battery performance, particularly the capacity retention rate, can be improved in a battery containing a Si-based active material. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating the layer structure of a solid-state battery 10. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1. Battery configuration FIG. 1 illustrates a diagram of a solid-state battery (all-solid-state battery) according to one embodiment. Here, an all-solid-state battery is used as a typical example, but the present disclosure does not necessarily have to be an all-solid-state battery and can be applied to any battery having an electrode assembly and an exterior housing that seals it (for example, a solid-state battery (semi-solid battery) containing a solid electrolyte and an electrolytic solution, or a battery that is entirely made of an electrolytic solution). FIG. 1 illustrates the layer structure of an electrode assembly 11 included in a solid-state battery. A solid-state battery is formed by sealing such an electrode assembly 11 in an exterior housing. For example, an electrode assembly 11 that is roughly rectangular in plan view is enclosed in an exterior housing that is also roughly rectangular in plan view. In this case, a positive terminal extends from the positive electrode current collector of the electrode assembly 11, and a negative electrode terminal extends from the negative electrode current collector, with their tips protruding from the exterior housing. The components of the laminate 11 and their relationships will be described in more detail below.

[0013] The electrode body 11 has a positive electrode current collector 12, a positive electrode composite layer 13, an electrolyte layer 14, a negative electrode composite layer 15, and a negative electrode current collector 16. In this embodiment, the positive electrode current collector 12, the positive electrode composite layer 13, the electrolyte layer 14, the negative electrode composite layer 15, and the negative electrode current collector 16 are stacked in this order to form a unit element 11a, and a plurality of unit elements 11a are stacked to form the electrode body 11 (only one unit element 11a is shown in FIG. 1). As described above, a positive electrode terminal is electrically connected to the positive electrode current collector 12 of the electrode body 11, and a negative electrode terminal is electrically connected to the negative electrode current collector 16 of the electrode body 11.

[0014] 1.1. Positive electrode current collector The positive electrode current collector 12 is laminated on the positive electrode composite layer 13 and collects current from the positive electrode composite layer 13. In this embodiment, the positive electrode current collector 12 is a rectangular foil in plan view and can be composed of a positive electrode current collector foil, which is a metal foil, and a conductive resin layer or a carbon layer laminated on the positive electrode current collector foil. The carbon layer is laminated on the positive electrode composite layer 13, so that the positive electrode current collector 12 is laminated on the positive electrode active material layer 13. Examples of materials constituting the positive electrode current collector include metal foil materials such as stainless steel, nickel, chromium, gold, platinum, aluminum, iron, titanium, and zinc. These metal foils may also be plated or vapor-deposited with nickel, chromium, carbon, etc. The conductive resin layer may be made of a resin in which a conductive material is dispersed, and the carbon layer may be made of a material containing carbon.

[0015] 1.2. Positive electrode composite layer The positive electrode mixture layer 13 has the above-described positive electrode current collector 12 laminated on one surface and the electrolyte layer 14 laminated on the other surface. In this embodiment, the positive electrode mixture layer 13 has a rectangular sheet shape in a plan view. The positive electrode mixture layer 13 is a layer containing at least a positive electrode active material. Furthermore, the positive electrode mixture layer may contain at least one of an electrolyte, a conductive additive, and a binder, as necessary. The thickness of positive electrode mixture layer 13 is not particularly limited, but can be set to 1 μm or more and 100 μm or less, and more preferably 30 μm or more and 100 μm or less.

[0016] [Cathode active material] The positive electrode active material may be, for example, an oxide active material. Examples of the oxide active material include ternary (Li(Ni x Co y Mn z )O2), NCA system (Li(Ni x Co y Al z )O2), LiCoO2, LiMnO2, LiNiO2, LiVO2, Li 1+x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4 and other spinel-type active materials, LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4 and other olivine-type active materials, Li 1+x Mn 2-x-y M yLi-Mn spinel active material substituted with different elements, represented by O4 (M is one or more selected from Al, Mg, Co, Fe, Ni, and Zn), Li x TiO y Examples include:

[0017] A coating layer containing a Li-ion conductive oxide may be formed on the surface of the active material, because this can suppress the reaction between the active material and the solid electrolyte (especially the sulfide solid electrolyte). Examples of Li-ion conductive oxides include LiNbO3 and Li4Ti5O 12 , Li3PO4. The thickness of the coating layer is, for example, 1 nm or more and 30 nm or less.

[0018] The positive electrode active material may be, for example, particulate. The average particle size (D50) of the positive electrode active material is not particularly limited, but may be, for example, 10 nm or more, or 100 nm or more. On the other hand, the average particle size (D50) of the positive electrode active material is, for example, 50 μm or less, or may be 20 μm or less. The average particle size (D50) can be calculated, for example, from measurements using a laser diffraction particle size distribution analyzer or a scanning electron microscope (SEM).

[0019] [Electrolyte] The electrolyte contains at least a solid electrolyte in all-solid-state batteries and semi-solid-state batteries, but contains a liquid electrolyte (electrolyte) in semi-solid-state batteries and batteries that use only an electrolyte solution.

[0020] Examples of solid electrolytes include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes, as well as organic polymer electrolytes such as polymer electrolytes. Examples of sulfide solid electrolytes include solid electrolytes containing Li, X (where X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. The sulfide solid electrolyte may further contain at least one of O and a halogen element. Examples of halogen elements include F, Cl, Br, and I. The sulfide solid electrolyte may be glass (amorphous) or glass ceramics. Examples of sulfide solid electrolytes include Li2S-P2S5, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2, and Li2S-P2S5-GeS2.

[0021] The electrolyte preferably contains a supporting salt and a solvent. Examples of supporting salts (lithium salts) for the lithium ion conductive electrolyte include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3. Examples of solvents used in the electrolyte include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The electrolyte preferably contains two or more solvents.

[0022] The mass ratio of the positive electrode active material to the electrolyte is preferably 85 / 15 to 30 / 70 (positive electrode active material / electrolyte), and more preferably 80 / 20 to 50 / 50.

[0023] [Conductive additives / binders] Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF). Examples of binders include rubber-based binders and fluoride-based binders.

[0024] 1.3. Electrolyte layer The electrolyte layer 14 is a layer formed between the positive electrode composite layer and the negative electrode composite layer, and contains at least an electrolyte. The electrolyte may be a solid electrolyte alone, or may also contain a liquid electrolyte (electrolytic solution). Specific examples of the solid electrolyte and electrolytic solution are the same as those described above for the positive electrode composite layer. The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 300 μm or less, and even more preferably 1 μm or more and 100 μm or less.

[0025] 1.4.Negative electrode composite layer Negative electrode mixture layer 15 is a layer containing at least a negative electrode active material, and may contain at least one of an electrolyte, a conductive additive, and a binder. The electrolyte, conductive additive, and binder are the same as those in the above-mentioned positive electrode mixture layer. The thickness of negative electrode mixture layer 15 is not particularly limited, but can be set to 1 μm or more and 100 μm or less, and more preferably 30 μm or more and 100 μm or less.

[0026] [Negative electrode active material] The negative electrode active material in this embodiment contains Si. The negative electrode active material is usually in the form of particles. The active material may be primary particles or secondary particles formed by aggregation of primary particles.

[0027] The negative electrode active material in this embodiment has voids inside the primary particles. The void ratio is, for example, 4% or more, and may be 10% or more. The void ratio is, for example, 40% or less, and may be 20% or less. The void ratio can be determined, for example, by the following procedure. First, a cross section of an electrode layer containing an active material is obtained by ion milling. The cross section is then observed with a scanning electron microscope (SEM) to obtain a photograph of the particles. From the obtained photograph, the silicon portion and the void portion are clearly distinguished using image analysis software and binarized. The areas of the silicon portion and the void portion are determined, and the void ratio (%) is calculated using the following formula. Porosity (%) = 100 × (area of ​​void part) / ((area of ​​silicon part) + (area of ​​void part))

[0028] Specific image analysis and porosity calculation can be performed as follows. For example, Fiji ImageJ bundled with Java 1.8.0_172 (hereafter referred to as Fiji) is used as image analysis software. A secondary electron image and a backscattered electron image from the same field of view are combined to create an RGB color image. Then, to remove noise from each pixel, the resulting RGB image is blurred using the Fiji function "Median (filter size = 2)." Next, Fiji is used to distinguish between silicon and void areas in the SEM image, and the void volume is calculated from the area ratio between the silicon and void areas.

[0029] In RGB color imaging, since both the secondary electron image and the backscattered electron image are expressed in grayscale, for example, the brightness x of each pixel in the secondary electron image is assigned to the red value, and similarly the brightness y of the backscattered electron image is assigned to the green value. This results in an RGB image where, for example, R = x, G = y, B = (x + y) / 2 for each pixel.

[0030] The average particle size (D50) of the primary particles is, for example, 50 nm or more, or may be 100 nm or more, or 150 nm or more. On the other hand, the average particle size (D50) of the primary particles is, for example, 3000 nm or less, or may be 1500 nm or less, or may be 1000 nm or less. Furthermore, the average particle size (D50) of the secondary particles is, for example, 1 μm or more, or may be 2 μm or more, or may be 5 μm or more. On the other hand, the average particle size (D50) of the secondary particles is, for example, 60 μm or less, or may be 40 μm or less. The average particle size (D50) can be determined, for example, by observation using an SEM. A large number of samples is preferable, for example, 20 or more, or may be 50 or more, or may be 100 or more.

[0031] The negative electrode active material in this embodiment preferably has a silicon clathrate crystalline phase. The silicon clathrate crystalline phase may be a silicon clathrate I crystalline phase or a silicon clathrate II crystalline phase. In such a silicon clathrate crystalline phase, a polyhedron (cage) including a pentagon or hexagon is formed by a plurality of Si elements. This polyhedron has a space inside that can encapsulate metal ions such as Li ions. The insertion of metal ions into this space can suppress volume changes due to charge and discharge. In particular, in all-solid-state batteries, a high confining pressure is generally required to suppress volume changes due to charge and discharge. However, the use of this active material can reduce the confining pressure, thereby suppressing the need for a large confining jig.

[0032] The active material in the present disclosure may or may not have a silicon clathrate II crystalline phase. In the former case, the active material may have a silicon clathrate II crystalline phase as the main phase. The "main phase" means that the peak belonging to that crystalline phase has the highest diffraction intensity among the peaks observed in X-ray diffraction measurement. Furthermore, the term "not having a crystalline phase" means that no peak of that crystalline phase is confirmed in X-ray diffraction measurement.

[0033] The silicon clathrate type II crystalline phase usually belongs to the space group (Fd-3m). In X-ray diffraction measurement using CuKα radiation, the silicon clathrate type II crystalline phase exhibits typical peaks at 2θ = 20.09°, 21.00°, 26.51°, 31.72°, 36.26°, and 53.01°. These peak positions may vary within a range of ±0.50°, ±0.30°, or ±0.10°, respectively.

[0034] In the silicon clathrate II crystal phase, the peak at 2θ=20.09°±0.50° is defined as Peak A, and the peak at 2θ=31.72°±0.50° is defined as Peak B. The intensity of Peak A is defined as I A and the intensity of peak B is I B On the other hand, the maximum intensity at 2θ=22° to 23° is defined as IM. Since peaks of crystalline phases related to Si do not usually appear in the range of 2θ=22° to 23°, this can be used as a reference.

[0035] I A / I M The value of I is preferably greater than 1. A / I M When the value of is 1 or less, it can be determined that the silicon clathrate type II crystal phase is not substantially formed. A / I M The value of I is, for example, 1.75 or more, and may be 1.80 or more. A / I M The value of is, for example, 10 or less, and may be 5 or less.

[0036] I B / I M The value of I is preferably greater than 1. B / I M When the value of is 1 or less, it can be determined that the silicon clathrate type II crystal phase is not substantially formed. B / I M The value of I is, for example, 1.35 or more, and may be 1.40 or more, while I B / I M The value of is, for example, 7 or less, and may be 4 or less.

[0037] The active material of this embodiment may or may not have a silicon clathrate I crystalline phase. In the former case, the active material may have a silicon clathrate I crystalline phase as the main phase. The silicon clathrate I crystalline phase usually belongs to the space group (Pm-3n). In X-ray diffraction measurement using CuKα radiation, the silicon clathrate I crystalline phase has typical peaks at 2θ=19.44°, 21.32°, 30.33°, 31.60°, 32.82°, 36.29°, 52.39°, and 55.49°. These peak positions may vary within a range of ±0.50°, ±0.30°, or ±0.10°, respectively.

[0038] The active material in this embodiment may or may not have a diamond-type Si crystalline phase. In the diamond-type Si crystalline phase, a tetrahedron is formed by a plurality of Si elements. Since the tetrahedron does not have a space inside that can encapsulate metal ions such as Li ions, the diamond-type Si crystalline phase is less able to suppress volume changes due to charge and discharge than the silicon clathrate crystalline phase. On the other hand, the diamond-type Si crystalline phase has higher structural stability than the silicon clathrate crystalline phase.

[0039] The active material of this embodiment may have a diamond-type Si crystalline phase as a main phase. The diamond-type Si crystalline phase has typical peaks at 2θ=28.44°, 47.31°, 56.10°, 69.17°, and 76.37° in X-ray diffraction measurement using CuKα radiation. These peak positions may vary within a range of ±0.50°, ±0.30°, or ±0.10°, respectively.

[0040] When peak C at 2θ=28.44°±0.50° is observed as a peak of the diamond-type Si crystalline phase, the intensity of peak C is calculated as I C I A / I C is, for example, greater than 1, may be 1.5 or greater, may be 2 or greater, or may be 3 or greater. B / I C The preferred range of I A / I C The preferred range is the same as that of the above.

[0041] The composition of the negative electrode active material in this embodiment is not particularly limited, but may be Na x Si 136 It is preferable that the formula is represented by (0≦x≦24). x may be 0 or greater than 0. On the other hand, x may be 20 or less, 10 or less, or 5 or less. The active material in this embodiment may contain an unavoidable component (e.g., Li). The composition of the active material can be determined by, for example, EDX, XRD, XRF, ICP, or atomic absorption spectrometry. The compositions of other compounds can be measured in a similar manner. In general, an unavoidable oxide film is formed on the surface of the active material. Therefore, the active material may contain a trace amount of O (oxygen). The active material may also contain a trace amount of C (carbon) derived from the manufacturing process.

[0042] [solvent] In addition, a solvent is used when preparing the material for the negative electrode composite layer (the preparation method is exemplified in the Examples), and this solvent may remain in the negative electrode composite layer. Examples of the solvent include diisobutyl ketone, butyl butyrate, butyl acetate, dibutyl ether, dodecane, undecane, decane, octane, hexane, and heptane. The amount of remaining solvent will be explained later.

[0043] 1.5. Negative electrode current collector Negative electrode current collector 16 is laminated on negative electrode composite layer 15 to collect current from negative electrode composite layer 15. In this embodiment, negative electrode current collector 16 is a rectangular foil in plan view, and can be made of, for example, stainless steel, copper, nickel, carbon, aluminum, or alloys thereof. Alternatively, these may be plated or vapor-deposited with nickel, chromium, or carbon.

[0044] 1.6. Positive and negative terminals The positive electrode terminal and the negative electrode terminal are electrically conductive members, and serve as terminals for electrically connecting each electrode to the outside. One end of the positive electrode terminal is electrically connected to the positive electrode current collector 12, and the other end penetrates the exterior body and is exposed to the outside. One end of the negative electrode terminal is electrically connected to the negative electrode current collector 16, and the other end passes through the exterior body and is exposed to the outside.

[0045] 1.7.Exterior body The exterior body is made of a rectangular sheet-like member in a plan view, and includes, for example, a first sheet and a second sheet. The electrode assembly 11 is enclosed between the first sheet and the second sheet, and the outer peripheral edge of the first sheet and the outer peripheral edge of the second sheet are joined and sealed. Therefore, this exterior body is bag-shaped, and the electrode assembly 11 is enclosed and sealed inside.

[0046] The first and second sheets can be made of a laminate film. Here, a laminate film is a film having a metal layer and a sealant layer. Examples of metals used in the laminate film include aluminum and stainless steel, and examples of materials used in the sealant layer include thermoplastic resins such as polypropylene, polyethylene, polystyrene, and polyvinyl chloride.

[0047] 2. Battery characteristics The battery of this embodiment can have the following features in addition to the above-mentioned features. The amount of residual solvent in the negative electrode mixture layer is preferably 0.2 mass % or less, which, when combined with the initial aging treatment described below, can increase the capacity retention rate. Although there is no particular lower limit to the amount of residual solvent, it is preferably 0.001% by mass, more preferably 0% by mass, and even more preferably 0.1% by mass or less.

[0048] 3. Initial aging treatment Because battery degradation is greatest in the initial stage, the first few cycles are subjected to charging and discharging under conditions different from normal charging and discharging (aging treatment) to improve performance. Specifically, in this embodiment, the first 10 or more cycles are subjected to aging treatment under conditions different from normal charging and discharging. Here, the aging treatment performed under specified conditions for the first 10 or more cycles is sometimes referred to as the initial aging treatment. This, combined with the amount of remaining solvent described above, can increase the capacity retention rate of the battery. The number of cycles should be 10 or more, but is more preferably 20 or more. On the other hand, the upper limit of the number of cycles is not particularly limited, but is preferably 50 or less.

[0049] The aging conditions under the above-mentioned predetermined conditions for each cycle may be set appropriately according to the characteristics of the battery as long as they are different from normal charging and discharging conditions, but for example, CC (constant current) charging and discharging can be performed from 0% to 100% SOC (state of charge) at 60°C and a C rate of 0.3C. The temperature and C rate may be changed, but a range of 1 / 100C to 1C in the range of 25°C to 60°C is desirable. [Example]

[0050] 4. Working Example In the examples, the capacity retention rate was examined by changing the amount of remaining solvent in the negative electrode mixture layer and the initial aging conditions.

[0051] 4.1. Preparation of the electrode body [Preparation of positive electrode composite layer] A polypropylene container was filled with a 5% by mass solution of butyl butyrate, vinylidene fluoride resin binder, and LiNi with an average particle size (D50) of 6 μm as the positive electrode active material. 1 / 3 Co 1 / 3 Mn 1 / 3 O2, Li2S-P2S5-based glass ceramic as a sulfide solid electrolyte, and vapor-phase carbon fiber as a conductive additive were added to a container and stirred for 30 seconds using an ultrasonic disperser (UH-50, manufactured by SMT). The container was then shaken for 3 minutes using a shaker (TTM-1, manufactured by Shibata Scientific Co., Ltd.), followed by another 30 seconds using the ultrasonic disperser. After another 3 minutes of shaking using the shaker, the mixture was applied to an aluminum foil (manufactured by Showa Denko) using an applicator by the blade method. The coated material was dried on a hot plate at an appropriate temperature for 30 minutes.

[0052] [Preparation of negative electrode composite layer] To prepare the negative electrode mixture layer, first, a Si active material was synthesized. Metallic Li and Si powders were weighed out in a molar ratio of 4:1 and mixed in a mortar under an Ar atmosphere at room temperature for 0.5 hours to react with each other, yielding Li4Si. The resulting Li4Si was reacted with ethanol under an Ar atmosphere. The resulting reaction product is believed to contain Si and CH3CH2OLi. The reaction product was filtered, and the filtered solid was dried at 120°C for more than 3 hours to obtain powdered porous Si. The obtained porous Si was used to prepare a Na-Si alloy, using NaH as the Na source. The NaH was previously washed with hexane. NaH and porous Si were weighed out to a molar ratio of 1.05:1 and mixed using a cutter mill. The mixture of NaH and porous Si was heated in a heating furnace under an Ar atmosphere at 475°C for 40 hours to obtain a powdered Na-Si alloy. Using the resulting Na-Si alloy and AlF3 as a sodium trap, silicon clathrate was produced by solid-phase synthesis. The Na-Si alloy and AlF3 were weighed out at a molar ratio of 1:0.35 and mixed using a cutter mill to obtain the reaction material. The resulting powdered reaction material was placed in a stainless steel reaction vessel and heated in a heating furnace under an Ar atmosphere at 310°C for 60 hours. The resulting reaction product is believed to contain the desired active material and by-products NaF and Al. The reaction product was washed with a mixed solvent of HNO3 and H2O in a volume ratio of 10:90. This removed any by-products. After washing, the mixture was filtered and the filtered solid was dried at 120°C for at least 3 hours to obtain the powdered active material. Five grams of the resulting material was weighed out, washed in HF solution for 1 hour, filtered, and then dried at 120°C for at least 3 hours to obtain the Si active material.

[0053] Next, a negative electrode mixture layer was produced using the obtained active material made of Si. A 5% by weight solution of butyl butyrate, vinylidene fluoride resin binder, carbon fiber by vapor phase deposition as a conductive additive, the above-mentioned Si active material synthesized as the negative electrode active material, Li2S-P2S5-based glass ceramic as a sulfide solid electrolyte, and diisobutyl ketone as a solvent for slurry preparation were added to a polypropylene container and stirred for 30 seconds using an ultrasonic disperser (UH-50, manufactured by SMT). The container was then shaken for 30 minutes using a shaker (TTM-1, manufactured by Shibata Scientific Co., Ltd.). The coating was applied to Cu foil (manufactured by UACJ) as the negative electrode current collector using an applicator by the blade method. The coated electrode was dried as follows for each example. Comparative Example 1: 1 hour at 170°C Comparative Example 2: After 1 hour at 170°C, an additional 1 hour at 200°C Comparative Example 3: After 1 hour at 170°C, an additional 1 hour at 200°C in a vacuum environment Comparative Example 4: 1 hour at 170°C Example 1: 1 hour at 170°C, followed by an additional 1 hour at 200°C Example 2: After 1 hour at 170°C, an additional 1 hour at 200°C in a vacuum environment

[0054] [Preparation of solid electrolyte layer] A 5% by mass solution of heptane, a butadiene rubber binder, and a Li2S-P2S5-based glass ceramic sulfide solid electrolyte were placed in a polypropylene container and stirred for 30 seconds using an ultrasonic disperser (UH-50, manufactured by SMT). The container was then shaken for 30 minutes using a shaker (TTM-1, manufactured by Shibata Scientific Co., Ltd.). The electrode was then coated onto an Al foil using a blade method with an applicator. The coated electrode was then dried for 30 minutes on a hot plate at the appropriate temperature.

[0055] [Preparation of electrode body] The positive electrode composite layer and the solid electrolyte layer were laminated in this order, and the laminate was set in a roll press and pressed at a pressure of 100 kN / cm and a temperature of 165°C to obtain a laminate of the positive electrode composite layer and the solid electrolyte layer. The above-mentioned negative electrode composite layer and Cu foil as the negative electrode current collector layer were set in a roll press and pressed at a pressing pressure of 60 kN / cm and a pressing temperature of 25°C to obtain a laminate of the negative electrode composite layer and the negative electrode current collector layer. Furthermore, the laminate of the negative electrode active material layer and the negative electrode current collector layer was laminated on the laminate of the positive electrode composite layer and the solid electrolyte layer, and the laminate was set in a flat uniaxial press and pressed at 200 MPa and 120°C for 1 minute to obtain an electrode body (battery).

[0056] 4.2. Test Method The fabricated electrode body was restrained using a restraining jig with bolt torque to achieve a specified restraining pressure, discharged to 2.5 V at a 1-hour rate (1C), charged at a constant current / constant voltage to 4.05 V at a 3-hour rate (1 / 3C), and then discharged at a constant current / constant voltage to 2.5 V at a 3-hour rate (1 / 3C) to determine the initial capacity. Next, as an initial aging treatment, charge and discharge were carried out under different conditions for each example. Specifically, the conditions were as follows. Comparative Example 1: 3 cycles of charging and discharging at 0.3C in the voltage range of 2.5V-4.05V Comparative Example 2: 3-cycle charge / discharge at 0.3C in the voltage range of 2.5V-4.05V Comparative Example 3: 3 cycles of charging and discharging at 0.3C in the voltage range of 2.5V-4.05V Comparative Example 4: 20 cycles of charging and discharging at 0.3C in the voltage range of 2.5V-4.05V Example 1: 20 cycles of charging and discharging at 0.3C in the voltage range of 2.5V-4.05V Example 2: 20 cycles of charging and discharging at 0.3C in the voltage range of 2.5V-4.05V After the initial aging treatment, a durability test was performed in which the battery was discharged to 2.5 V at a 1-hour rate (1C), charged at a constant current and constant voltage at a 3-hour rate (1 / 3C) to 4.05 V, and then discharged at a constant current and constant voltage at a 3-hour rate (1 / 3C) to 2.5 V. This charge-discharge cycle was repeated 100 times, and the capacity retention rate relative to the initial capacity was calculated.

[0057] Evaluation The evaluation was carried out based on the "amount of remaining solvent," "number of aging cycles," and "capacity maintenance rate." A gas chromatography / mass spectrometry (GC / MS) device (7250GC / Q-TOF (Agilent)) was used to measure the "amount of remaining solvent." More specifically, the negative electrode composite layer was prepared, powdered, dissolved in ethanol, and extracted for measurement. The temperature was raised to 500°C at a rate of 1°C / min, and the titration volume was 1 μL. The "number of cycles" is as described above. The "capacity retention rate" is a value expressed as a percentage (%) obtained by dividing the capacity after the durability test by the initial capacity described above, by charging the battery at a constant current / constant voltage up to 4.05 V at a 3-hour rate (1 / 3C) and discharging it at a constant current / constant voltage down to 2.5 V at a 3-hour rate (1 / 3C) after the durability test to determine the capacity after the durability test.

[0058] 4.4.Results The evaluation results are shown in Table 1.

[0059] [Table 1]

[0060] As can be seen from the results, the capacity retention rate can be increased by adjusting both the amount of remaining solvent and the number of cycles. [Explanation of symbols]

[0061] 11... Electrode body, 12... Positive electrode current collector, 13... Positive electrode active material layer, 14... Solid electrolyte layer, 15... Negative electrode active material layer, 16... Negative electrode current collector

Claims

1. A method for aging a battery having an electrode assembly in which a positive electrode mixture layer, an electrolyte layer, and a negative electrode mixture layer containing a Si-based active material are stacked, the method comprising: the amount of organic solvent contained in the negative electrode mixture layer is 0.2% by mass or less, As the initial aging treatment, the aging treatment is performed for 10 cycles or more. Battery aging method.

2. 2. The battery aging method according to claim 1, wherein the aging treatment performed in the initial aging treatment is CC charge / discharge at 60°C, 0.3 C, and from 0% to 100% SOC.

3. The method for aging a battery according to claim 1 or 2, wherein the electrolyte layer comprises a solid electrolyte.

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