Battery

Abstract

To provide a battery capable of suppressing an increase in resistance in a battery containing an Si-based active material.SOLUTION: The battery includes an electrode body in which a positive electrode mixture layer, an electrolyte layer, and a negative electrode mixture layer containing an Si-based active material are laminated, wherein a voltage at a capacity of 10 mAh / g in terms of weight of the positive electrode mixture layer is 2.5 V or more and 3.07 V or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a battery containing a Si-based active material as an electrode active material. [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 includes a Si-based active material and that can suppress an increase in resistance. [Means for solving the problem]

[0006] During the initial charge of a battery, the reaction potential is fixed, resulting in a plateau at a specific voltage. The inventors discovered that the lower the voltage behavior at the initial charge of 10 mAh / g (weight equivalent) of the positive electrode composite layer before the plateau, the better the durability. This is presumed to be due to the progress of electrolyte reduction at around 3 V, and further investigation revealed that this generally correlates with the amount of remaining solvent.

[0007] The present application discloses a battery including an electrode body formed by laminating a positive electrode composite layer, an electrolyte layer, and a negative electrode composite layer containing a Si-based active material, wherein the voltage when the capacity of the positive electrode composite layer is 10 mAh / g converted into weight is 2.5 V or more and 3.07 V or less.

[0008] The positive electrode active material contained in the positive electrode mixture layer may be a ternary or NCA type.

[0009] The amount of residual solvent in the negative electrode mixture layer may be 0.2 or less.

[0010] The battery may be an all-solid-state battery in which the electrolyte layer contains a solid electrolyte. [Effects of the Invention]

[0011] According to the battery of the present disclosure, in a battery containing a Si-based active material, the battery performance, particularly the increase in resistance, can be suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating the layer structure of a solid-state battery 10. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] [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 y Li-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:

[0018] 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.

[0019] 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).

[0020] [Electrolytes] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] [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.

[0025] 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.

[0026] 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.

[0027] [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.

[0028] 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))

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 IB 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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 Cis, 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.

[0042] 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.

[0043] [solvent] In addition, a solvent is used in synthesizing the material for the negative electrode composite layer (the synthesis 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 2. Battery characteristics The battery of this embodiment can have the following features in addition to the above-mentioned features. 2.1.Voltage In this embodiment of the battery, when the battery capacity converted into weight of the positive electrode composite layer is 10 mAh / g, the voltage is 2.5 V or more and 3.07 V or less. This makes it possible to suppress an increase in resistance. If this voltage is greater than 3.07 V, the increase in resistance becomes significant. On the other hand, if the voltage is less than 2.5 V, the average voltage of the battery decreases, which may result in a decrease in energy density. In addition, the battery may fall into an overdischarge state, which may cause deterioration of the positive and negative electrodes.

[0049] 2.2.Residual solvent amount The amount of residual solvent in the negative electrode composite layer is preferably 0.2% or less. This can suppress an increase in resistance. There is no particular lower limit for the amount of residual solvent, but it is preferably 10 ppm. Furthermore, the amount of residual solvent is preferably 0.1% or less. If the amount of residual solvent is high, there is a concern that battery performance may deteriorate. On the other hand, if the amount of residual solvent is too low, there is a concern that costs may increase in the mass production process. [Example]

[0050] 3. Working Example In the examples, the amount of remaining solvent in the negative electrode mixture layer was changed to examine the increase in resistance.

[0051] 3.1. 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 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] 3.2. Test Methods and Evaluation The fabricated electrode body was restrained using a restraining jig with bolt torque to achieve a specified restraining pressure, and the volume expansion rate was calculated from the amount of change in the restraining pressure when it was charged at a constant current and constant voltage up to 4.05 V at a 10-hour rate (1 / 10C). The battery was then discharged to 2.5 V at a 1-hour rate (1C), charged at a constant current and low voltage to 4.05 V at a 3-hour rate (1 / 3C), and then discharged at a constant current and low voltage to 2.5 V at a 3-hour rate (1 / 3C) to determine the initial capacity.

[0057] The evaluation was carried out based on "voltage at 10 mAh / g," "resistance increase," and "amount of remaining solvent." [Voltage at 10mAh / g] "Voltage at 10 mAh / g" refers to the voltage when the weight-equivalent capacity of the positive electrode composite layer is 10 mAh / g. This value was measured by constant current charging at a 10-hour rate (1 / 10C) and the voltage when the weight-equivalent capacity of the positive electrode composite layer reached 10 mAh / g. [Resistance Increase] The battery was subjected to charge-discharge tests to obtain the resistance increase. Specifically, the battery was first CCCV charged at 0.1C to 4.05V and then discharged at 1C to 2.5V. The battery was then CCCV charged at 1 / 3C to 4.05V and CCCV discharged at 1 / 3C to 3.6V, followed by a 5-second discharge at 6C. The initial resistance was calculated using the DCIR method from the voltage drop. The battery was then CCCV discharged at 1 / 3C to 2.5V. This cycle was then repeated 100 times: CC charging at 1 / 3C to 4.05V and CC discharging at 1 / 3C to 2.5V. The resistance after charge-discharge was then measured. The difference between the resistance after charge-discharge and the initial resistance was calculated as a percentage (%), representing the resistance increase. [Remaining solvent amount] A gas chromatography / mass spectrometry (GC / MS) device (7250GC / Q-TOF (Agilent)) was used to measure the "remaining solvent amount (%)." More specifically, after the negative electrode composite layer was produced, it was powdered, dissolved and extracted in ethanol, and then measured. The conditions were a temperature increase of 1°C / min up to 500°C, with a titration volume of 1 μL. Measurement can also be performed using thermal evolved gas analysis or gas chromatography.

[0058] 3.5.Results The evaluation results are shown in Table 1.

[0059] [Table 1]

[0060] As can be seen from these results, the increase in resistance could be suppressed by keeping the voltage at 3.07 or less when the capacity of the positive electrode composite layer was 10 mAh / g in terms of weight conversion. This is also related to the amount of remaining solvent. [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 battery including an electrode assembly formed by laminating a positive electrode mixture layer, an electrolyte layer, and a negative electrode mixture layer containing a Si-based active material, The voltage at 10 mAh / g, which is the capacity of the positive electrode mixture layer converted into weight, is 2.5 V or more and 3.07 V or less. battery.

2. The battery according to claim 1 , wherein the positive electrode active material contained in the positive electrode mixture layer is a ternary or NCA-based positive electrode active material.

3. 3. The battery according to claim 1, wherein the amount of residual solvent in the negative electrode mixture layer is 0.2 or less.

4. 3. The all-solid-state battery according to claim 1, wherein the electrolyte layer comprises a solid electrolyte.

Images