All-solid-state battery and preparation method thereof

Abstract

The present invention provides an all-solid-state battery and a preparation method thereof. The preparation method comprises the following steps: dry-pressing a solid electrolyte in a mold to obtain a solid electrolyte block, stacking the solid electrolyte block and the positive electrode sheet, performing secondary pressing, cutting to obtain a positive electrode sheet covered with a solid electrolyte layer, stacking the negative electrode sheet on the surface of the solid electrolyte layer, and hot pressing to obtain the all-solid-state battery; wherein the positive electrode sheet and the negative electrode sheet are both prepared by wet pulping. The present invention adopts a method combining wet preparation of positive and negative electrode sheets with dry preparation of electrolyte layers, which achieves close contact between active materials and electrolyte layers, and can effectively control the thickness of the electrolyte layer, and can also avoid the problem of decreased conductivity of the electrolyte sheet due to the presence of solvent molecules, thereby achieving the purpose of improving battery performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries and relates to an all-solid-state battery and a preparation method thereof. Background Art

[0002] Lithium secondary batteries are widely used in various fields due to their high energy density and excellent electrochemical performance. Currently, commercial lithium-ion batteries generally use organic liquid electrolytes, which inevitably introduce volatile, flammable, and explosive organic liquids into the battery system, posing serious safety hazards to the battery system. Compared with liquid electrolytes, the use of all-solid-state electrolytes replaces the electrolyte and diaphragm in the liquid battery system, eliminating the safety hazards of the battery, and is more in line with the future development needs of electric vehicles and large-scale energy storage. Therefore, the research and development of all-solid-state lithium secondary batteries has become one of the mainstream trends.

[0003] At present, the preparation of solid-state batteries is divided into two types: wet method and dry method. For example, CN111628139A discloses a wet method for preparing all-solid-state battery electrodes. The method comprises the following steps: (1) providing a base electrode, the base electrode comprising a current collector, and an electrode material layer coated on the surface of the current collector, the electrode material layer comprising an active material; (2) mixing a first solid electrolyte, a second solid electrolyte and a solvent to obtain a composite electrolyte suspension, coating the suspension on the surface of the base electrode, and removing the solvent to obtain the electrode; wherein the first solid electrolyte is a sulfide-type solid electrolyte and is soluble in the solvent, and the second solid electrolyte is an inorganic solid electrolyte and is insoluble in the solvent. The document obtains a solid-state battery electrode with multiple sulfide electrolyte layers in situ by mixing an electrolyte and a solvent, and coating the composite electrolyte suspension on the surface of the base electrode, thereby achieving good contact between the electrolyte layer and the electrode material layer. However, a large amount of alcohol substances are used in the electrolyte preparation process, which are toxic. In addition, after the electrolyte is soaked in an alcohol solvent, its ionic conductivity decreases, affecting the electrochemical performance of the solid-state battery.

[0004] For example, CN103956458A discloses a dry process for preparing all-solid-state batteries. The composite positive electrode is composed of a positive electrode active material, an inorganic solid electrolyte and an oxidative conductive additive; the preparation method comprises the following steps: (1) mixing the positive electrode active material, the inorganic solid electrolyte and the oxide conductive additive and then ball milling them, and then pressing them into a ceramic sheet after drying; (2) sintering the ceramic sheet to obtain a composite positive electrode. Although the composite positive electrode can be used to prepare all-solid-state lithium-ion batteries, the preparation method is a dry process, which makes the interface bonding between the inorganic solid electrolyte and the active material in the composite positive electrode poor, and the production process is difficult, which limits its large-scale application.

[0005] Therefore, how to make the active material in the all-solid-state battery in close contact with the electrolyte layer without affecting the ionic conductivity of the electrolyte is a technical problem that needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to provide an all-solid-state battery and a method for preparing the same. The present invention adopts a method combining a wet method for preparing positive and negative electrode sheets with a dry method for preparing electrolyte layers, thereby achieving close contact between the active material and the electrolyte layer, while effectively controlling the thickness of the electrolyte layer, and avoiding the problem of decreased conductivity of the electrolyte sheet due to the presence of solvent molecules, thereby achieving the purpose of improving battery performance.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing an all-solid-state battery, the preparation method comprising the following steps:

[0009] The solid electrolyte is dry-pressed in a mold to obtain a solid electrolyte block, the solid electrolyte block is stacked with a positive electrode sheet, and a second pressing is performed, and the positive electrode sheet covered with a solid electrolyte layer is cut, and a negative electrode sheet is stacked on the surface of the solid electrolyte layer, and a hot pressing treatment is performed to obtain the all-solid-state battery;

[0010] Wherein, the positive electrode sheet and the negative electrode sheet are both prepared by wet pulping.

[0011] In the present invention, the shape of the solid electrolyte block obtained after dry pressing can be adjusted according to actual needs, and can be either regular or irregular shapes, such as a circle, a regular or irregular polygon, etc.

[0012] The present invention adopts a method combining wet preparation of positive and negative electrode sheets with dry preparation of electrolyte layers, thereby achieving close contact between the active material and the electrolyte layer, while effectively controlling the thickness of the electrolyte layer and avoiding the problem of decreased conductivity of the electrolyte sheet due to the presence of solvent molecules, thereby achieving the purpose of improving battery performance.

[0013] In the present invention, dry pressing is used to prepare electrolyte blocks, replacing wet mixing, thereby reducing the use of organic solvents and reducing the harm of organic matter to the environment and humans. In addition, there is no solvent immersion during the preparation of the electrolyte layer, and there is no organic solution residue in the electrolyte, thereby maximizing the electrolyte ion conductivity. Compared with the wet method, the electrolyte sheet is prepared by pressing, and there is no solvent between the particles, the density is higher, and the risk of battery short circuit is reduced.

[0014] Preferably, the dry pressing pressure is 100-1000 MPa, for example, 100 MPa, 150 MPa, 200 MPa, 250 MPa, 300 MPa, 350 MPa, 400 MPa, 450 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa or 1000 MPa, etc.

[0015] In the present invention, if the pressure of dry pressing is too small, the particles inside the electrolyte block will not be in close contact, and the lithium ion conduction will be blocked. If the pressure is too large, the electrolyte block will be brittle and cracks will easily appear inside.

[0016] Preferably, the weight of the solid electrolyte is greater than 200 mg, for example, 210 mg, 250 mg, 300 mg, 350 mg, 400 mg, 450 mg or 500 mg.

[0017] Preferably, the size of any side of the cross section of the solid electrolyte block is ≥1 cm, for example, 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm or 10 cm.

[0018] Preferably, the thickness of the solid electrolyte block is ≥1 cm, for example, 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm or 10 cm.

[0019] Preferably, the cutting method includes wire saw cutting and / or laser cutting.

[0020] In the present invention, the above-mentioned cutting method is adopted to replace solvent immersion, so that an extremely thin electrolyte sheet can be obtained, the thickness of the electrolyte layer can be reduced, and the energy density of the battery can be improved.

[0021] Preferably, the thickness of the solid electrolyte layer obtained after cutting is ≥1μm, for example, 1μm, 2μm, 3μm, 4μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm, etc., preferably 4-50μm.

[0022] In the present invention, the thickness of the electrolyte layer after cutting is in the range of 4 to 50 μm, which can have both good lithium ion conductivity and mechanical processing performance. If the thickness is too thin, it is easy to cause the electrolyte to rupture during the pressing process of the pole piece, resulting in a decrease in the battery yield. If the thickness is too thick, the lithium ion transmission capacity will be limited, and the production cost of the battery will increase, and the energy density of the battery will decrease.

[0023] Preferably, the secondary pressing pressure is 50-200 MPa, for example, 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa, 100 MPa, 110 MPa, 120 MPa, 130 MPa, 140 MPa, 150 MPa, 160 MPa, 170 MPa, 180 MPa, 190 MPa or 200 MPa, etc., preferably 100-150 MPa.

[0024] In the present invention, the secondary pressing pressure is within the range of 100-150 MPa, which can achieve good contact between the electrolyte sheet and the surface of the electrode sheet, ensure the integrity of the electrolyte sheet, and improve the production yield of the battery.

[0025] Preferably, the temperature of the hot pressing treatment is 60-120°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C or 120°C.

[0026] Preferably, the environment of the heat pressing treatment is a vacuum environment.

[0027] Preferably, the pressure of the hot pressing treatment is 300-1000 MPa, for example, 300 MPa, 400 MPa, 500 MPa, 600 MPa, 700 MPa, 800 MPa, 900 MPa or 1000 MPa.

[0028] Preferably, the heat pressing treatment time is 300 to 1800 s, for example, 300 s, 500 s, 800 s, 1000 s, 1300 s, 1500 s or 1800 s.

[0029] In the present invention, after stacking the negative electrode sheet, a hot pressing treatment is used, which is more conducive to promoting the contact between the electrolyte sheet and the surface layers of the positive and negative electrode sheets, and the parameters of the hot pressing treatment are within the above range, thereby reducing the grain boundaries between the electrolyte layer and the positive and negative electrode sheet layers, thereby achieving the effect of reducing the battery impedance.

[0030] Preferably, the method for preparing the positive electrode sheet comprises:

[0031] The positive electrode active material, solid electrolyte, conductive agent, binder and solvent are mixed to obtain positive electrode slurry, and the positive electrode slurry is coated on the surface of the positive electrode collector and dried to obtain the positive electrode sheet.

[0032] In the present invention, the positive electrode active materials are all conventional positive electrode materials, including but not limited to nickel-cobalt-manganese ternary materials, lithium iron phosphate, lithium cobalt oxide, lithium manganate, nickel-cobalt-aluminum ternary materials or lithium-rich manganese-based lithium-containing oxides; the binder is selected from the conventional binder types for preparing positive electrode plates, including but not limited to polyvinylidene fluoride or polytetrafluoroethylene; the type of solid electrolyte used in preparing the positive electrode plate can be selected from any one of sulfide electrolytes, oxide electrolytes, polymer dielectrics or composite electrolytes, or a combination of at least two; the solvent can be selected from any one of isobutyl isobutyrate, xylene or N-methylpyrrolidone, or a combination of at least two; the conductive agents are all conventional conductive agents, for example, can be selected from any one of Super P, conductive fiber, graphene or conductive graphite, or a combination of at least two.

[0033] Preferably, the positive electrode slurry is prepared in an environment with a dew point of less than -50°C, such as -51°C, -55°C, -58°C or -60°C.

[0034] Preferably, the drying temperature is 60-150°C, for example 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C.

[0035] Preferably, the drying time is 30 to 600 s, for example, 30 s, 50 s, 100 s, 150 s, 200 s, 250 s, 300 s, 350 s, 400 s, 450 s, 500 s, 550 s or 600 s.

[0036] Preferably, the method for preparing the negative electrode sheet comprises:

[0037] The negative electrode active material, solid electrolyte, conductive agent, binder and solvent are mixed to obtain negative electrode slurry, and the negative electrode slurry is coated on the surface of the negative electrode current collector and dried to obtain the negative electrode sheet.

[0038] In the present invention, the negative electrode active material can be selected from any one or a combination of at least two of graphite, silicon-based negative electrode, silicon-carbon negative electrode, lithium titanate and metallic lithium or Li-In alloy; the types of binder, solvent, solid electrolyte and conductive agent are all selected according to conventional technology, and their types are listed in the positive electrode sheet.

[0039] Preferably, the drying temperature is 60-250°C, for example, 60°C, 100°C, 130°C, 150°C, 180°C, 200°C, 230°C or 250°C.

[0040] Preferably, the drying time is 30 to 600 s, for example, 30 s, 50 s, 100 s, 150 s, 200 s, 250 s, 300 s, 350 s, 400 s, 450 s, 500 s, 550 s or 600 s.

[0041] As a preferred technical solution, the preparation method comprises:

[0042] Solid electrolytes weighing more than 200 mg are dry-pressed in a mold at a pressure of 100 to 1000 MPa to obtain solid electrolyte blocks with a thickness of ≥1 cm, the solid electrolyte blocks are stacked with positive electrode sheets, and secondary pressing is performed at a pressure of 100 to 150 MPa, and wire saw cutting is performed to obtain positive electrode sheets covered with solid electrolyte layers, wherein the thickness of the solid electrolyte layer is 4 to 50 μm, and negative electrode sheets are stacked on the surface of the solid electrolyte layer, and hot pressing is performed at a pressure of 300 to 1000 MPa for 300 to 1800 s in a vacuum environment of 60 to 120° C. to obtain the all-solid-state battery;

[0043] Wherein, the preparation method of the positive electrode sheet comprises:

[0044] In an environment with a dew point of less than -50°C, a positive electrode active material, a solid electrolyte, a conductive agent, a binder and a solvent are mixed to obtain a positive electrode slurry, the positive electrode slurry is coated on the surface of a positive electrode current collector, and dried at 60 to 150°C for 30 to 600 seconds to obtain the positive electrode sheet;

[0045] The method for preparing the negative electrode sheet comprises:

[0046] The negative electrode active material, solid electrolyte, conductive agent, binder and solvent are mixed to obtain negative electrode slurry, the negative electrode slurry is coated on the surface of the negative electrode collector, and dried at 60 to 250° C. for 30 to 600 seconds to obtain the negative electrode sheet.

[0047] In a second aspect, the present invention provides an all-solid-state battery, which is prepared by the preparation method of the all-solid-state battery as described in the first aspect.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention adopts a method combining wet preparation of positive and negative electrode sheets with dry preparation of electrolyte layers. The dry preparation of electrolyte layers avoids the use of toxic solvents, reduces the internal impedance of the battery, and can effectively control the thickness of the electrolyte layer. It can also avoid the problem that the conductivity of the electrolyte sheet decreases due to the presence of solvent molecules, thereby improving the reversible capacity and cycle life of the solid-state battery. The all-solid-state battery provided by the present invention has a sulfide electrolyte system, and the first discharge specific capacity at 0.1C can reach more than 125.4mAh / g, and the first efficiency can reach more than 68.1%. Under the oxide electrolyte system, its discharge specific capacity and first efficiency are also significantly improved, and the first discharge specific capacity at 0.1C can reach more than 122mAh / g, and the first efficiency can reach more than 78%. The pressure in the preparation of the solid electrolyte block and the thickness of the solid electrolyte layer after cutting are further adjusted. When the sulfide electrolyte system is used, the first discharge specific capacity at 0.1C can reach more than 138.2mAh / g, and the first efficiency can reach more than 76.4%. It is also obvious from the above data that the dry-wet mixing method provided by the present invention is applicable to all-solid-state batteries under different systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A comparison chart of the charge and discharge curves of the all-solid-state batteries provided in Example 1 and Comparative Examples 1-2.

[0051] Figure 2 Schematic diagram of an exemplary preparation of an all-solid-state battery.

[0052] ①-pressure module, ②-mold, ③-solid electrolyte block, ④-cutting equipment, ⑤-positive electrode active material layer, ⑥-aluminum foil, ⑦-base, ⑧-support. DETAILED DESCRIPTION

[0053] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0054] For example, Figure 2 A schematic diagram of preparing an all-solid-state battery in the following embodiment is shown. Figure 2 It can be seen that the solid electrolyte powder is pressurized by the pressure module ① in the mold ② to obtain a solid electrolyte block ③, and then a thinner solid electrolyte layer can be obtained by using a cutting device ④ (wire saw cutting).

[0055] Example 1

[0056] This embodiment provides a method for preparing an all-solid-state battery, and the preparation method is as follows:

[0057] 20 g of sulfide electrolyte Li6PS5Cl was placed in a mold and dry-pressed at 100 MPa to obtain a circular solid electrolyte block with a thickness of 1.5 cm (circular diameter of 1.5 cm), the circular solid electrolyte block and the positive electrode sheet (NCM811) were stacked and placed, and secondary pressing was performed at a pressure of 100 MPa, and wire saw cutting was performed to obtain a positive electrode sheet covered with a solid electrolyte layer (the thickness of the solid electrolyte layer was 10 μm); then a negative electrode sheet (artificial graphite) was stacked on the surface of the solid electrolyte layer, and hot-pressed at a pressure of 500 MPa for 600 s under a vacuum environment (80° C.) to obtain the all-solid-state battery;

[0058] The preparation method of the positive electrode sheet is as follows:

[0059] In an environment with a dew point of -55°C, 0.3g of polyvinylidene fluoride (PVDF) was uniformly dispersed in 12g of isobutyl isobutyrate, and stirred at a speed of 1000rpm for 2h to form a glue solution S1; 7g of NCM811 (D50 is 13μm) and 0.2g of conductive carbon black (SP) were added to the glue solution S1 and stirred for 120min to obtain S2; 2.5g of Li6PS5Cl (D50 is 10μm) was added to S2 and continued to stir for 30min to obtain S3; S3 was coated on an aluminum foil with a thickness of 10um to obtain a positive electrode plate, and the plate was placed in an oven at 90°C and baked for 10min to obtain a dry positive electrode plate;

[0060] The preparation method of the negative electrode sheet is as follows:

[0061] In an environment with a dew point of -55°C, 0.15g of polyvinylidene fluoride (PVDF) was uniformly dispersed in 12g of isobutyl isobutyrate and stirred at 1000rpm for 2h to form glue S4; 3.5g (D50 is 13μm) of graphite and 0.05g of SP were added to the glue S4 and stirred for 120min to obtain S5; 1.3g of Li6PS5Cl (D50 is 10μm) was added to S5 and continued to stir for 30min to obtain S6; S6 was coated on a copper foil with a thickness of 8μm to obtain a negative electrode sheet, and the sheet was placed in an oven at 90°C and baked for 10min to obtain a dry negative electrode sheet.

[0062] Example 2

[0063] This embodiment provides a method for preparing an all-solid-state battery, and the preparation method is as follows:

[0064] 25 g of oxide electrolyte Li7La3Zr2O 12Put it into a mold, dry-press it at 500 MPa to obtain a square solid electrolyte block with a thickness of 2 cm (the side length of the square cross section is 2 cm), stack the square solid electrolyte block and the positive electrode plate (lithium iron phosphate), perform secondary pressing at a pressure of 150 MPa, and perform laser cutting to obtain a positive electrode plate covered with a solid electrolyte layer (the thickness of the solid electrolyte layer is 50 μm); then stack the negative electrode plate (artificial graphite) on the surface of the solid electrolyte layer, and perform hot pressing at a pressure of 800 MPa for 350 seconds under a vacuum environment (80° C.) to obtain the all-solid-state battery;

[0065] The preparation method of the positive electrode sheet and the negative electrode sheet is consistent with that of Example 1 (the active material of the positive electrode sheet is lithium iron phosphate, and the solid electrolyte in the positive and negative electrode sheets is an oxide electrolyte Li7La3Zr2O 12 ).

[0066] Example 3

[0067] The difference between this embodiment and embodiment 1 is that the dry pressing pressure in this embodiment is 1000 MPa, and the thickness of the solid electrolyte layer is 4 μm.

[0068] The rest of the preparation methods and parameters were the same as those in Example 1.

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that the dry pressing pressure in this embodiment is 50 MPa.

[0071] The rest of the preparation methods and parameters were the same as those in Example 1.

[0072] Example 5

[0073] The difference between this embodiment and embodiment 1 is that the pressure of dry pressing in this embodiment is 1100 MPa.

[0074] The rest of the preparation methods and parameters were the same as those in Example 1.

[0075] Example 6

[0076] The difference between this embodiment and embodiment 1 is that the thickness of the solid electrolyte layer in this embodiment is 60 μm.

[0077] The rest of the preparation methods and parameters were the same as those in Example 1.

[0078] Comparative Example 1

[0079] This comparative example provides a method for preparing an all-solid-state battery, and the preparation method is as follows:

[0080] (1) In an environment with a dew point of -55°C, 0.3 g of polyvinylidene fluoride (PVDF) was uniformly dispersed in 12 g of isobutyl isobutyrate and stirred at a speed of 1000 rpm for 2 h to form a glue solution S1; 7 g of NCM811 (D50 was 13 μm) and 0.2 g of conductive carbon black (SP) were added to the glue solution S1 and stirred for 120 min to obtain S2; 2.5 g of Li6PS5Cl (D50 was 10 μm) was added to S2 and continued to stir for 30 min to obtain S3; S3 was coated on an aluminum foil with a thickness of 10 um to obtain a positive electrode plate, and the plate was placed in an oven at 90°C and baked for 10 min to obtain a dry positive electrode plate;

[0081] (2) adding 10 g of sulfide electrolyte Li6PS5Cl powder and 0.05 of binder PVDF to 2 g of isobutyl isobutyrate solution to prepare electrolyte slurry S4; coating S4 evenly on the positive electrode sheet with a coating thickness of 100 μm, and then baking in an oven at 90° C. for 20 min; obtaining a dry positive electrode sheet coated with electrolyte;

[0082] (3) Covering the surface of the electrolyte layer with a negative electrode plate, and hot pressing the plate at a pressure of 500 MPa for 600 seconds under a vacuum environment (80°C) to obtain the all-solid-state battery; wherein the preparation method of the negative electrode plate is as follows: in an environment with a dew point of -55°C, evenly dispersing 0.15g of polyvinylidene fluoride (PVDF) in 12g of isobutyl isobutyrate, and stirring at a speed of 1000rpm for 2h to form a glue solution S5; adding 3.5g (D50 is 13μm) of graphite and 0.05g of SP to the glue solution S5 and stirring for 120min to obtain S6; adding 1.3g of Li6PS5Cl (D50 is 10μm) to S6 and continuing to stir for 30min to obtain S7; coating S7 on a copper foil with a thickness of 8μm to obtain a negative electrode plate, and baking the plate in an oven at 90°C for 10min to obtain a dry negative electrode plate.

[0083] Comparative Example 2

[0084] This comparative example provides a method for preparing an all-solid-state battery, and the preparation method is as follows:

[0085] 20 g of sulfide electrolyte Li6PS5Cl was placed in a mold and dry-pressed at 100 MPa to obtain a circular solid electrolyte block with a diameter of 1.5 cm. The circular solid electrolyte block was stacked with a positive electrode plate (NCM811), and secondary pressing was performed at a pressure of 100 MPa. A wire saw was performed to obtain a positive electrode plate covered with a solid electrolyte layer (the thickness of the solid electrolyte layer was 10 μm); then a negative electrode plate (artificial graphite) was stacked on the surface of the solid electrolyte layer, and hot-pressed at a pressure of 500 MPa for 600 s under a vacuum environment (80° C.) to obtain the all-solid-state battery;

[0086] The preparation method of the positive electrode sheet is as follows:

[0087] In a glove box, 7g NCM811 (D50 is 13μm), 0.2g conductive carbon black (SP), 0.3g polyvinylidene fluoride (PVDF) and 2.5g Li6PS5Cl (D50 is 10μm) were mixed in a mortar and ground for 15min to obtain S1; S1 was rolled to make the material adhere to a 10um aluminum foil with a thickness of 100um to obtain a positive electrode sheet S2, and the sheet S2 was placed in an oven at 90°C and baked for 10min to obtain a dry positive electrode sheet for standby use;

[0088] The preparation method of the negative electrode sheet is as follows:

[0089] In a glove box, 3.5 g (D50 is 13 μm) of graphite, 0.05 g of SP, 0.15 g of polyvinylidene fluoride (PVDF) and 1.3 g of Li6PS5Cl (D50 is 10 μm) were mixed in a mortar and ground for 15 min to obtain S3. S3 was rolled to make the material adhere to an 8 μm copper foil to obtain a negative electrode sheet S4. The sheet was placed in an oven at 90°C and baked for 10 min to obtain a dry negative electrode sheet for later use.

[0090] Figure 1 The figure shows the charge and discharge curve comparison of the all-solid-state battery provided by Example 1 and Comparative Examples 1-2. Figure 1 It can be seen that under the same charge and discharge test conditions, the charge capacities of Example 1, Comparative Example 1, and Comparative Example 2 are 176.9 mAh / g, 165.5 mAh / g, and 104.9 mAh / g, respectively, and the discharge capacities are 140.4 mAh / g, 130.1 mAh / g, and 66.5 mAh / g, respectively, and the first coulombic efficiencies are 79.5%, 78%, and 63.5%, respectively. The electrochemical performance of the all-solid-state battery obtained by the preparation method provided by the present invention has been significantly improved. The first discharge capacity of the battery is the reversible capacity of the battery, which determines the energy density of the battery.

[0091] The all-solid-state batteries provided in Examples 1-6 and Comparative Examples 1-2 were subjected to electrochemical performance tests under the following test conditions: 0.1C current charge and discharge, with a cut-off voltage of 2.50-4.25V, and the first charge specific capacity and first coulombic efficiency were measured. The results are shown in Table 1.

[0092] Table 1

[0093]

[0094] From the data results of Example 1 and Examples 4 and 5, it can be seen that when preparing solid electrolyte blocks, the dry pressing pressure is too small, which is not conducive to the structural compactness of the electrolyte layer, affects the ionic conductivity of the electrolyte and thus leads to low battery capacity. If the dry pressing pressure is too high, cracks may occur in the internal structure of the electrolyte sheet, resulting in an increase in battery side reactions and a low initial coulombic efficiency of the battery.

[0095] From the data results of Example 1 and Example 6, it can be seen that if the thickness of the solid electrolyte layer is too large, the lithium ion transmission distance between the positive and negative electrodes will be increased, so that the polarization of the battery increases during the charge and discharge process, and the battery capacity and coulomb efficiency are low. Therefore, the method provided by the present invention effectively obtains a thinner solid electrolyte layer.

[0096] From the data results of Example 1 and Comparative Example 1, it can be seen that the pure wet method for preparing the solid-state battery in Comparative Example 1 has the problem of solution molecules remaining inside the electrolyte, which significantly reduces the lithium ion conductivity of the electrolyte.

[0097] From the data results of Example 1 and Comparative Example 2, it can be seen that the solid-state battery prepared by the pure dry method in Comparative Example 2 has poor discharge specific capacity and initial efficiency, and is difficult to use normally.

[0098] In summary, the all-solid-state battery prepared by the dry-wet mixing method provided by the present invention ensures the maximum performance of the ionic conductivity of the electrolyte; and the battery has a high first coulombic efficiency and a high first discharge capacity, which greatly improves the energy density of the battery. The all-solid-state battery provided by the present invention, when the sulfide electrolyte system is used, the first discharge specific capacity at 0.1C can reach more than 125.4mAh / g, and the first efficiency can reach more than 68.1%. Under the oxide electrolyte system, its discharge specific capacity and first efficiency are also significantly improved, and the first discharge specific capacity at 0.1C can reach more than 122mAh / g, and the first efficiency can reach more than 78%. The pressure in the preparation of the solid electrolyte block and the thickness of the solid electrolyte layer after cutting are further adjusted. When the sulfide electrolyte system is used, the first discharge specific capacity at 0.1C can reach more than 138.2mAh / g, and the first efficiency can reach more than 76.4%. It is also obvious from the above data that the dry-wet mixing method provided by the present invention is applicable to all-solid-state batteries under different systems.

[0099] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing an all-solid-state battery, characterized in that: The preparation method comprises the following steps: The solid electrolyte is dry-pressed in a mold to obtain a solid electrolyte block, the solid electrolyte block is stacked with a positive electrode sheet, and a second pressing is performed, and the positive electrode sheet covered with a solid electrolyte layer is cut, and a negative electrode sheet is stacked on the surface of the solid electrolyte layer, and a hot pressing treatment is performed to obtain the all-solid-state battery; The size of any side of the cross section of the solid electrolyte block is ≥1 cm; The thickness of the solid electrolyte block is ≥1 cm; Wherein, the positive electrode sheet and the negative electrode sheet are both prepared by wet pulping.

2. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The dry pressing pressure is 100-1000 MPa.

3. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The weight of the solid electrolyte is greater than 200 mg.

4. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The cutting method includes wire saw cutting and / or laser cutting.

5. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The thickness of the solid electrolyte layer obtained by cutting is ≥1 μm.

6. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The thickness of the solid electrolyte layer obtained by cutting is 4 to 50 μm.

7. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The secondary pressing pressure is 50-200 MPa.

8. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The secondary pressing pressure is 100-150 MPa.

9. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The temperature of the hot pressing treatment is 60-120°C.

10. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The environment of the heat pressing treatment is a vacuum environment.

11. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The pressure of the hot pressing treatment is 300-1000 MPa.

12. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The heat pressing treatment time is 300 to 1800 seconds.

13. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The method for preparing the positive electrode sheet comprises: The positive electrode active material, solid electrolyte, conductive agent, binder and solvent are mixed to obtain positive electrode slurry, and the positive electrode slurry is coated on the surface of the positive electrode current collector and dried to obtain the positive electrode sheet.

14. The method for preparing an all-solid-state battery according to claim 13, characterized in that: The positive electrode slurry is prepared in an environment with a dew point of less than -50°C.

15. The method for preparing an all-solid-state battery according to claim 13, characterized in that: The drying temperature is 60-150°C.

16. The method for preparing an all-solid-state battery according to claim 13, characterized in that: The drying time is 30 to 600 seconds.

17. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The method for preparing the negative electrode sheet comprises: The negative electrode active material, solid electrolyte, conductive agent, binder and solvent are mixed to obtain negative electrode slurry, and the negative electrode slurry is coated on the surface of the negative electrode current collector and dried to obtain the negative electrode sheet.

18. The method for preparing an all-solid-state battery according to claim 17, characterized in that: The drying temperature is 60-250°C.

19. The method for preparing an all-solid-state battery according to claim 17, characterized in that: The drying time is 30 to 600 seconds.

20. The method for preparing an all-solid-state battery according to claim 1, characterized in that: The preparation method comprises: A solid electrolyte with a weight of more than 200 mg is dry-pressed in a mold at a pressure of 100 to 1000 MPa to obtain a solid electrolyte block with a thickness of ≥1 cm, the solid electrolyte block is stacked with a positive electrode plate, and a secondary pressing is performed at a pressure of 100 to 150 MPa, and a wire saw is cut to obtain a positive electrode plate covered with a solid electrolyte layer, wherein the thickness of the solid electrolyte layer is 4 to 50 μm, a negative electrode plate is stacked on the surface of the solid electrolyte layer, and a hot pressing treatment is performed at a pressure of 300 to 1000 MPa for 300 to 1800 seconds in a vacuum environment of 60 to 120° C. to obtain the all-solid-state battery; Wherein, the preparation method of the positive electrode sheet comprises: In an environment with a dew point of less than -50°C, a positive electrode active material, a solid electrolyte, a conductive agent, a binder and a solvent are mixed to obtain a positive electrode slurry, the positive electrode slurry is coated on the surface of a positive electrode current collector, and dried at 60 to 150°C for 30 to 600 seconds to obtain the positive electrode sheet; The method for preparing the negative electrode sheet comprises: The negative electrode active material, solid electrolyte, conductive agent, binder and solvent are mixed to obtain negative electrode slurry, the negative electrode slurry is coated on the surface of the negative electrode collector, and dried at 60 to 250° C. for 30 to 600 seconds to obtain the negative electrode sheet.

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