All-solid-state battery and method for preparing same

Abstract

The present invention provides an all-solid-state battery and a preparation method thereof. The preparation method includes the following steps: (1) spraying and curing an electrolyte layer on the surface of a pole piece to obtain a pole piece with an electrolyte layer attached to the surface, where the pole piece is a positive pole piece and a negative pole piece; (2) isostatically compressing and combining the positive pole piece and the negative pole piece with the electrolyte layer obtained by spraying and curing to obtain an all-solid-state battery; both the positive pole piece and the negative pole piece are prepared by a dry method, and the raw material for spraying is a solid electrolyte material; the number of times of spraying and curing is multiple. The preparation method provided by the present invention realizes that no solvent is used during the preparation process, the electrode layer and the electrolyte layer of the pole piece have high interfacial contact, and the electrolyte layer has high density and high ionic conductivity, effectively solving the problems of large interfacial contact impedance between the electrode layer and the electrolyte layer and insufficient conductivity of the electrolyte layer, optimizing the preparation process of the all-solid-state battery, and improving the cycle life of the all-solid-state battery.

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] All-solid-state batteries have attracted much attention due to their safety and high energy density. In the past few years, the ionic conductivity in some all-solid-state lithium-ion batteries has reached 10 -3 ~10 -2 S / cm, indicating that the rapid transport of lithium ions is no longer a major problem. At present, all-solid-state batteries mainly include polymer all-solid-state batteries, oxide all-solid-state batteries, and sulfide all-solid-state batteries.

[0003] However, there are huge challenges at the interface between the solid electrolyte and the electrode. In the cell structures and processes of all-solid-state batteries reported so far, the electrolyte layer is mostly formed by wet coating. However, it is difficult to select a binder in the wet process. At the same time, only non-polar solvents can be used. Usually, highly toxic solvents such as toluene are reported to be used, and the price is also very expensive. These factors directly limit the wet coating process of sulfide electrolytes. On the other hand, the electrodes and the solid electrolyte membranes are prepared separately, the process is complex, and it is difficult to control the interfacial internal resistance. The longer the preparation time of the sulfide electrolyte, the worse its air stability. Therefore, it is necessary to optimize the electrode manufacturing process to solve the above problems.

[0004] CN113394463A discloses "Sulfide-based solid electrolyte all-solid-state battery and preparation method thereof". The preparation method of the sulfide-based solid electrolyte all-solid-state battery is to coat a solid electrolyte membrane on the inner surface of the positive electrode layer and form a film, and the positive electrode layer, the negative electrode layer, and the solid electrolyte membrane are adhered together by pressing to produce an all-solid-state battery. However, xylene is used as a solvent to prepare the electrolyte slurry in this document, and the drying process after slurry coating may reduce the density of the electrolyte layer and affect the battery life.

[0005] CN111628139A discloses a method for preparing an electrode of an all-solid-state battery by a wet process. The method comprises the following steps: (1) providing a basic electrode, which comprises a current collector and an electrode material layer coated on the surface of the current collector, and the electrode material layer comprises 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 basic electrode, and removing the solvent to obtain the electrode; wherein, the first solid electrolyte is a sulfide-based solid electrolyte and is soluble in the solvent, and the second solid electrolyte is an inorganic solid electrolyte and is insoluble in the solvent. This document forms a solid-state battery electrode with multiple sulfide electrolyte layers in situ by mixing the electrolyte and the solvent and coating the obtained composite electrolyte suspension on the surface of the basic electrode, realizing 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. And after the electrolyte is soaked in an alcohol solvent, its ionic conductivity decreases, affecting the electrochemical performance of the all-solid-state battery.

[0006] Therefore, how to improve the contact between the solid-solid interface of the all-solid-state battery electrode and the electrolyte layer is a technical problem to be solved urgently. Summary of the Invention

[0007] The purpose of the present invention is to provide an all-solid-state battery and a preparation method thereof. The present invention obtains an electrolyte layer by spraying on the surface of the electrode for multiple times, and the electrode is also prepared by a dry process, realizing that no solvent is used during the preparation process. The electrode layer and the electrolyte layer of the prepared electrode have high interfacial contact, the electrolyte layer has high density and high ionic conductivity, which can effectively solve the problems of large interfacial contact impedance between the electrode layer and the electrolyte layer and insufficient conductivity of the electrolyte layer, and at the same time optimize the preparation process of the all-solid-state battery and improve the cycle life of the all-solid-state battery.

[0008] To achieve the purpose of this invention, the following technical solutions are adopted:

[0009] In the first aspect, the present invention provides a preparation method of an all-solid-state battery, and the preparation method comprises the following steps:

[0010] (1) Spraying and curing an electrolyte layer on the surface of the electrode to obtain an electrode with an electrolyte layer attached to the surface, and the electrode is a positive electrode and a negative electrode;

[0011] (2) Isostatically compressing and combining the positive electrode and the negative electrode with the electrolyte layer obtained by spraying and curing in step (1) to obtain the all-solid-state battery;

[0012] Wherein, both the positive electrode and the negative electrode are prepared by a dry process, and the raw material for spraying is a solid electrolyte material; the spraying and curing are carried out for multiple times, such as 2 times, 3 times, 4 times, 5 times or 6 times, etc.

[0013] In the present invention, an electrolyte layer is sprayed on the surfaces of both the positive electrode plate and the negative electrode plate respectively, and the number of spraying times is at least two for both. The number of spraying times on the positive electrode plate and the negative electrode plate can be the same or different.

[0014] The type of solid electrolyte can be selected from any one or a combination of at least two of sulfide electrolytes, oxide electrolytes, polymer dielectrics, or composite electrolytes.

[0015] In the present invention, an electrolyte layer is obtained by spraying on the surface of the electrode plate multiple times, and the electrode plate is also prepared by a dry process, realizing that no solvent is used during the preparation process. The electrode layer and the electrolyte layer of the prepared electrode plate have high interfacial contact, the electrolyte layer has high density and high ionic conductivity, which can effectively solve the problems of large interfacial contact impedance between the electrode layer and the electrolyte layer and insufficient conductivity of the electrolyte layer. At the same time, the preparation process of the all-solid-state battery is optimized, and the cycle life of the all-solid-state battery is improved.

[0016] By spraying the electrolyte powder evenly on the surface of the electrode plate and then curing by rolling, not only can the tight combination between the solid electrolyte particles and the electrode layer particles be realized, greatly improving the interfacial contact and reducing the interfacial impedance, but also the layer-by-layer spraying can make the solid electrolyte particles contact tightly, enhancing the density and increasing the ionic conductivity. Based on the above advantages, the cycle life of the solid-state battery can be optimized.

[0017] And after multiple spraying and curing, an electrolyte layer with a certain thickness can be formed on the surface of the electrode plate. Compared with the wet coating method, on the one hand, the processing is convenient and the process is simple. The preparation of the electrolyte layer also does not require the participation of a solvent, further reducing the solvent consumption in the production process and avoiding the decrease in the conductivity of the electrolyte layer caused by solvent volatilization.

[0018] In the present invention, if the number of spraying and curing is only one, that is, spraying and curing are carried out once on the surfaces of the positive electrode plate and the negative electrode plate, the tight combination between the solid electrolyte particles and the electrode layer particles or the tight contact between the solid electrolyte particles cannot be realized, and it is difficult to obtain an electrolyte layer with high ionic conductivity.

[0019] In the present invention, the raw material used for spraying is a pure solid electrolyte, and no binder needs to be added, which can avoid the influence of the addition of other auxiliary additives on the ionic conductivity of the electrolyte layer. If a binder is added to the raw material for spraying, it will affect the performance of the ionic conductivity of the solid electrolyte.

[0020] Preferably, in step (1), at least two layers of electrolyte layers are attached to the surface of the electrode plate.

[0021] Preferably, in the electrode sheet with an electrolyte layer on its surface in step (1), the median particle size of the solid electrolyte in the electrolyte layer in direct contact with the surface of the electrode sheet is the smallest.

[0022] In the present invention, the median particle size of the solid electrolyte in the electrolyte layer in direct contact with the surface of the electrode sheet is the smallest, which is beneficial to the embedding of electrolyte particles into the electrode layer during the spraying and rolling processes, optimizing the interfacial contact between the electrode layer and the electrolyte layer. If solid electrolyte particles of the same particle size are used during the layer-by-layer spraying process, if they are all small particles, the ionic conductivity of the electrolyte layer will be low due to the high grain boundary resistance of the particles in the case of small particles; if they are all large particles, the interfacial contact will be poor in the case of large particles. If the median particle size of the solid electrolyte in the electrolyte layer in direct contact with the surface of the electrode sheet is the largest, it will lead to a large interfacial impedance problem caused by the incomplete embedding of the solid electrolyte particles and the electrode layer particles.

[0023] Preferably, the median particle size D50 of the solid electrolyte in the electrolyte layer in direct contact with the surface of the electrode sheet is 3 to 5 μm, such as 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, etc.

[0024] Preferably, the median particle size D50 of the solid electrolyte in the electrolyte layer not in direct contact with the surface of the electrode sheet is 4 to 30 μm, such as 4 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, 28 μm or 30 μm, etc.

[0025] Preferably, during the spraying and curing of the electrode sheet in step (1), the pressure for the first curing is 0.18 to 0.38 MPa, such as 0.18 MPa, 0.2 MPa, 0.23 MPa, 0.25 MPa, 0.28 MPa, 0.3 MPa, 0.33 MPa, 0.35 MPa or 0.38 MPa, etc.

[0026] In the present invention, if the pressure for the first curing is too small, it will directly lead to a poor interfacial contact between the electrolyte layer and the electrode layer and an increase in the interfacial impedance; if the pressure for the first curing is too large, it will cause overpressure of the first electrolyte layer and inability to be embedded with the second electrolyte layer.

[0027] Preferably, during the spraying and curing of the electrode sheet in step (1), the pressure for non-first curing is 0.1 to 0.35 MPa, such as 0.1 MPa, 0.13 MPa, 0.15 MPa, 0.18 MPa, 0.2 MPa, 0.23 MPa, 0.25 MPa, 0.28 MPa, 0.3 MPa, 0.33 MPa or 0.35 MPa, etc.

[0028] In the present invention, if the pressure value for non-first curing is too small, it is difficult to meet the requirement of high density of the solid electrolyte layer. If it is too large, cracks will occur in the electrolyte layer.

[0029] Preferably, the temperature of the isostatic pressing in step (2) is 25 to 80 °C, such as 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C or 80 °C, etc.

[0030] Preferably, the pressure of the isostatic pressing in step (2) is 300 to 1000 MPa, such as 300 MPa, 400 MPa, 500 MPa, 600 MPa, 700 MPa, 800 MPa, 900 MPa or 1000 MPa, etc.

[0031] Preferably, the method for dry preparation of the electrode sheet includes:

[0032] Performing high-speed shearing on the active material, solid electrolyte, conductive agent and binder to obtain an electrode sheet slurry, and roll-pressing to obtain the electrode sheet.

[0033] In the preparation process of the electrode sheet of the present invention, the binder is mixed and fibrillated by high-speed shearing, and then the positive and negative electrode sheet films are obtained by roll-pressing. Compared with the wet coating process, the process is simple, no solvent is required in the preparation process, the participation of the solvent in the electrode sheet processing is reduced, the drying process is shortened, and the production efficiency and safety are improved.

[0034] In the present invention, when preparing the positive electrode sheet, it is the positive electrode active material, and when preparing the negative electrode sheet, it is the negative electrode active material. Both the positive electrode active material and the negative electrode active material are conventional technical choices. The positive electrode active material includes but is not limited to nickel-cobalt-manganese ternary materials, lithium iron phosphate, lithium cobaltate, lithium manganate, nickel-cobalt-aluminum ternary materials or lithium-rich manganese-based lithium-containing oxides, etc.; the negative electrode active material can be selected from any one or at least two combinations of graphite, silicon-based negative electrode, silicon-carbon negative electrode, lithium titanate and metallic lithium or Li-In alloy; the binder and the conductive agent are also conventional technical choices, that is, the corresponding material types suitable for preparing the positive electrode sheet or the negative electrode sheet are applicable. For example, the binder includes but is not limited to polyvinylidene fluoride or polytetrafluoroethylene, etc., and the conductive agent can be selected from any one or at least two combinations of Super P, conductive fiber, graphene or conductive graphite.

[0035] As a preferred technical solution, the preparation method includes:

[0036] (1) Spraying and curing the electrolyte layer on the surface of the electrode sheet. The number of times of spraying and curing is multiple. The pressure for the first curing is 0.18 to 0.38 MPa, and the pressure for non-first curing is 0.1 to 0.35 MPa, to obtain an electrode sheet with at least two layers of electrolyte layer on the surface. The electrode sheet is a positive electrode sheet and a negative electrode sheet;

[0037] (2) Isostatically press and composite the positive electrode sheet and the negative electrode sheet obtained by spraying and curing to form the electrolyte layer in step (1) at a pressure of 300-1000 MPa at 25-80 °C to obtain the all-solid-state battery;

[0038] Among them, both the positive electrode sheet and the negative electrode sheet are prepared by a dry method, and the raw material for spraying is a solid electrolyte material; the median particle size of the solid electrolyte in the electrolyte layer in direct contact with the surface of the electrode sheet is the smallest.

[0039] In a second aspect, the present invention provides an all-solid-state battery, and the all-solid-state battery is prepared by the preparation method of the all-solid-state battery as described in the first aspect.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] In the present invention, the electrolyte layer is obtained by spraying on the surface of the electrode sheet multiple times. The preparation process of the electrolyte layer does not require solvents and binders, which greatly retains the ionic conductivity of the solid electrolyte. Moreover, the electrode sheet is also prepared by a dry method, realizing that no solvents are used in the whole process of preparing the solid-state battery. The electrode layer and the electrolyte layer of the prepared electrode sheet have high interfacial contact, the electrolyte layer has high density and high ionic conductivity, which can effectively solve the problems of large interfacial contact impedance between the electrode layer and the electrolyte layer and insufficient conductivity of the electrolyte layer. At the same time, the preparation process of the all-solid-state battery is optimized, the cycle life of the all-solid-state battery is improved, and the preparation method is simple and suitable for mass production. For the all-solid-state battery provided by the present invention, the D50 of the solid electrolyte in the electrolyte layer in contact with the surface of the electrode sheet is the smallest, and when the first curing pressure is in the range of 0.18-0.38 MPa, its AC impedance is below 3.26 Ω. At 0.5C, after cycling more than 108 times, its capacity will decay to 80%. Description of the Drawings

[0042] Figure 1 It is an internal cross-sectional view of the all-solid-state battery provided in Example 1.

[0043] Figure 2 For Figure 1 A partial enlarged schematic view at location A in

[0044] Figure 3 It is a spraying device diagram of the spraying method provided in Example 1.

[0045] 1-unwinding device, 2-guiding device, 3-first spraying device, 4-first rolling device, 5-thickness measuring device, 6-second spraying device, 7-second rolling device, 8-thickness measuring device, 9-guiding device, 10-winding device. Detailed Embodiments

[0046] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only helpful for understanding the present invention and should not be regarded as specific limitations on the present invention.

[0047] Example 1

[0048] This example provides a preparation method for an all-solid-state battery. The preparation method is as follows (the preparation process is carried out at an environmental dew point of -50°C):

[0049] (1) Preparation of positive and negative electrode sheets: The positive electrode material is NCM811, the negative electrode material is graphite, and the solid electrolyte is Li6PS5Cl (LPSC); the solid electrolyte and the positive electrode material are weighed according to a mass ratio of 3:7, the binder is polyvinylidene fluoride, and the mass ratio is 1%. After high-speed shearing (rotation speed 20000 rpm), rolling, and compounding with a current collector, a single-sided positive electrode sheet is formed. The solid electrolyte and the negative electrode material are weighed according to a mass ratio of 4:6, the binder is polyvinylidene fluoride, and the mass ratio is 1%. The above substances are subjected to high-speed shearing (rotation speed 20000 rpm), rolling, and compounding with a current collector to form a single-sided negative electrode sheet;

[0050] (2) Electrolyte (LPSC) spraying: Spray a first electrolyte layer on the positive electrode surface, with D50 being 3.5 μm, the first curing pressure being 0.28 MPa, and the thickness of the first electrolyte layer being 8 μm; perform spraying of the second electrolyte layer, with D50 being 14.0 μm, the second curing pressure being 0.20 MPa, and the thickness of the electrolyte layer being 20 μm; spray a first electrolyte layer on the negative electrode surface, with D50 being 3.5 μm, the first curing pressure being 0.28 MPa, and the thickness of the first electrolyte layer being 7 μm; perform spraying of the second electrolyte layer, with D50 being 14.0 μm, the second curing pressure being 0.20 MPa, and the thickness of the electrolyte layer being 18 μm;

[0051] (3) Battery preparation: Cut the positive and negative electrode sheets loaded with the electrolyte layer into a size of 3*3 cm, assemble a single-piece soft-pack battery cell, and perform secondary vacuum packaging and then isostatic pressing at room temperature with a pressure of 350 MPa to complete the preparation of the all-solid-state battery cell.

[0052] Figure 1 The internal cross-sectional view of the all-solid-state battery provided in Example 1 is shown, Figure 2 which is Figure 1 a partial enlarged schematic view of the area A in Figure 1 Combined with Figure 2It can be seen that the particles in the middle electrolyte layer are tightly combined with each other, and the interface between the electrode layer and the electrolyte layer has good contact without obvious gaps, indicating that the preparation method provided by the present invention enables the electrode layer and the electrolyte layer to have high interface contact, and the electrolyte layer has high density and high ionic conductivity, which can effectively solve the problems of large interface contact impedance between the electrode layer and the electrolyte layer and insufficient conductivity of the electrolyte layer.

[0053] Figure 3 FIG. is a spraying device diagram of the spraying method provided in Example 1. In step (2) of Example 1, the electrolyte layer is realized by Figure 3 the spraying device in.

[0054] Example 2

[0055] This example provides a preparation method for an all-solid-state battery. The preparation method is as follows (the preparation process is carried out at an environmental dew point of -50°C):

[0056] (1) The preparation methods of the positive electrode sheet and the negative electrode sheet are the same as those in Example 1;

[0057] (2) Electrolyte (LPSC) spraying: Spray a first electrolyte layer on the positive electrode surface, with D50 being 5.0 μm, the first curing pressure being 0.3 MPa, and the thickness of the first electrolyte layer being 10 μm; conduct the spraying of the second electrolyte layer, with D50 being 20.2 μm, the second curing pressure being 0.25 MPa, and the thickness of the electrolyte layer being 19 μm; spray a first electrolyte layer on the negative electrode surface, with D50 being 5.0 μm, the first curing pressure being 0.3 MPa, and the thickness of the first electrolyte layer being 9 μm; conduct the spraying of the second electrolyte layer, with D50 being 20.2 μm, the second curing pressure being 0.25 MPa, and the thickness of the electrolyte layer being 20 μm;

[0058] (3) Battery preparation: Cut the positive and negative electrode sheets loaded with the electrolyte layer into a size of 3*3 cm, assemble a single-piece soft-pack battery cell, and perform isostatic pressing at 40°C after secondary vacuum packaging, with a pressure of 350 MPa, and the all-solid-state battery cell is prepared.

[0059] Example 3

[0060] This example provides a preparation method for an all-solid-state battery. The preparation method is as follows (the preparation process is carried out at an environmental dew point of -50°C):

[0061] (1) The preparation methods of the positive electrode sheet and the negative electrode sheet are the same as those in Example 1;

[0062] (2) Electrolyte (LPSC) spraying: Spray the first electrolyte layer on the positive electrode surface with a D50 of 3.5 μm, a first curing pressure of 0.25 MPa, and a first electrolyte layer thickness of 6 μm; perform the second electrolyte layer spraying with a D50 of 7.5 μm, a second curing pressure of 0.2 MPa, and an electrolyte layer thickness of 20 μm; perform the third electrolyte layer spraying with a D50 of 15.0 μm, a third curing pressure of 0.2 MPa, and an electrolyte layer thickness of 35 μm; spray the first electrolyte layer on the negative electrode surface with a D50 of 3.5 μm, a first curing pressure of 0.25 MPa, and a first electrolyte layer thickness of 9 μm; perform the second electrolyte layer spraying with a D50 of 15.0 μm, a second curing pressure of 0.2 MPa, and an electrolyte layer thickness of 30 μm;

[0063] (3) Battery preparation: Cut the positive and negative electrode plates loaded with the electrolyte layer into a size of 3*3 cm, assemble a single-piece soft-pack battery cell, and perform isostatic pressing at 60 °C with a pressure of 400 MPa after secondary vacuum packaging to complete the preparation of the all-solid-state battery cell.

[0064] Example 4

[0065] The difference between this example and Example 1 is that in step (2) of this example, the first curing pressure in the positive electrode plate is 0.15 MPa, the first electrolyte layer is 10 μm, the second pressure remains unchanged, and the electrolyte layer thickness is 25 μm; the first curing pressure of the negative electrode is set to 0.15 MPa, the first electrolyte layer is 11 μm, the second pressure remains unchanged, and the electrolyte layer thickness is 23 μm.

[0066] The remaining preparation methods and parameters are the same as those in Example 1.

[0067] Example 5

[0068] The difference between this example and Example 1 is that in step (2) of this example, the solid electrolytes of the first electrolyte layer and the second electrolyte layer of the positive and negative electrode plates are interchanged, that is, the D50 of the first electrolyte layer is 14.0 μm and the D50 of the second electrolyte layer is 3.5 μm.

[0069] The remaining preparation methods and parameters are the same as those in Example 1.

[0070] Example 6

[0071] The difference between this example and Example 1 is that in step (2) of this example, the median particle size of the solid electrolyte in the first electrolyte layer of the positive electrode plate is the same as that in the second electrolyte layer, and the median particle size of the solid electrolyte in the first electrolyte layer of the negative electrode plate is the same as that in the second electrolyte layer.

[0072] The remaining preparation methods and parameters are the same as those in Example 1.

[0073] Example 7

[0074] The difference between this example and Example 1 is that the cathode material is LiCoO2, the anode material is silicon material, and the solid electrolyte is Li 10 GeP2S 12 (LGPS), and the solid electrolyte in the electrolyte layer is also LGPS.

[0075] The remaining preparation methods and parameters are the same as those in Example 1.

[0076] Comparative Example 1

[0077] The difference between this comparative example and Example 1 is that in step (2) of this comparative example, LPSC slurry is prepared and coated on the surfaces of the cathode and anode plates. The specific preparation process of the LPSC slurry: Using xylene as the solvent, weigh LPSC powder (D50 is 3.5μm) and polyvinylidene fluoride (PVDF), with a mass ratio of 98:2. Add the solvent in small amounts and multiple times while keeping stirring until a stable slurry is obtained. After multiple coatings, electrolyte layers with a thickness of 30μm are finally formed on the cathode and anode plates respectively.

[0078] The remaining preparation methods and parameters are the same as those in Example 1.

[0079] Comparative Example 2

[0080] This comparative example uses a pure wet method to prepare an all-solid-state battery, and the method is as follows:

[0081] Preparation of the cathode plate: NCM811 is the active material, LPSC is the solid electrolyte, VGCF is the conductive agent, and PVDF is the binder, in a mass ratio of 68.6:29.4:1:1. Then use xylene as the solvent to make a slurry of the above materials (the solid content of the slurry is 60%), and uniformly coat it on the carbon-coated aluminum foil. After hot rolling at 80°C, the cathode plate is obtained and reserved;

[0082] Preparation of the anode plate: Graphite, LPSC and polyacrylic acid PAA are in a mass ratio of 80:18:2. Then use isobutyl isobutyrate as the solvent to make a slurry of the above materials (the solid content of the slurry is 55%), and uniformly coat it on the carbon-coated copper foil. After hot rolling at 80°C, the anode plate is obtained and reserved;

[0083] Preparation of the electrolyte layer: The preparation of the LPSC slurry is the same as that in Comparative Example 1, and electrolyte layers with a thickness of 30μm are respectively coated on the cathode and anode plates;

[0084] Battery preparation: The same as Example 1.

[0085] Comparative Example 3

[0086] The difference between this comparative example and Example 1 is that in step (1) of this comparative example, both the positive electrode sheet and the negative electrode sheet are spray-coated and cured once, that is, no subsequent spray-coating treatment is performed after the first curing.

[0087] The remaining preparation methods and parameters are the same as those in Example 1.

[0088] The all-solid-state batteries provided in Examples 1-7 and Comparative Examples 1-3 were subjected to impedance tests and electrochemical performance tests, and the results are shown in Table 1.

[0089] Impedance test: The AC impedance was tested at room temperature using an electrochemical workstation.

[0090] Electrochemical performance test: The cycle performance test was carried out on a 3*3 cm single-piece soft-pack battery cell, with a voltage window of 3.0-4.25 V and test conditions of 0.5C / 0.5C.

[0091] Table 1

[0092]

[0093] Comparing Example 1 and Example 4, too small a first curing pressure directly leads to poor interfacial contact between the electrolyte layer and the electrode layer, large interfacial impedance, and thus poor cycling performance.

[0094] Comparing Example 1 and Example 5, the median particle size of the electrolyte in the first electrolyte layer (the electrolyte layer in direct contact with the surface of the electrode sheet) is too large, resulting in poor contact between particles, increased AC impedance of the battery, and poor cycling performance of the battery cell.

[0095] Comparing Example 1 and Example 6, it can be shown that the median particle size in the first electrolyte layer is the smallest, which is more conducive to eliminating interfacial impedance.

[0096] Comparing Example 1 and Comparative Example 1, during the preparation process of the electrolyte layer, the volatilization of the auxiliary additives and solvents in the slurry during wet coating has a greater impact on the internal resistance of the battery, indicating that the spray coating in the present invention has obvious advantages.

[0097] Comparing Example 1 and Comparative Example 2, compared with the method for preparing an all-solid-state battery by wet process, the method provided by the present invention can effectively reduce the interfacial impedance and improve the cycling performance of the battery.

[0098] Comparing Example 1 and Comparative Example 3, the AC impedance of the electrolyte layer formed by one-time spray coating is significantly greater than that of multiple spray coatings, indicating that the particle stacking / embedding during one-time spray coating is not as good as that of multiple spray coatings, resulting in a large impedance, which seriously affects the cycling performance of the battery.

[0099] In summary, the present invention obtains an electrolyte layer by spraying on the surface of the electrode sheet multiple times, and the electrode sheet is also prepared by a dry method, realizing that no solvent is used throughout the battery preparation process. The electrode layer and the electrolyte layer of the prepared electrode sheet have high interfacial contact, the electrolyte layer has high density and high ionic conductivity, which can effectively solve the problems of large interfacial contact impedance between the electrode layer and the electrolyte layer and insufficient conductivity of the electrolyte layer. At the same time, the preparation process of the all-solid-state battery is optimized, and the cycle life of the all-solid-state battery is improved. For the all-solid-state battery provided by the present invention, the D50 of the solid electrolyte on the surface of the electrode sheet in the electrolyte layer is the smallest, and when the first curing pressure is in the range of 0.18 to 0.38 MPa, its AC impedance is below 3.26 Ω. At 0.5C, after cycling more than 108 times, its capacity will decay to 80%.

[0100] The applicant declares that the above description is only the specific implementation manner 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 any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing an all-solid-state battery, characterized in that, The preparation method includes the following steps: (1) Spraying and curing an electrolyte layer on the surface of the electrode sheet to obtain an electrode sheet with an electrolyte layer attached to the surface, where the electrode sheet is a positive electrode sheet and a negative electrode sheet; The pressure for the first curing is 0.18 - 0.38 MPa, and the pressure for non-first curing is 0.1 - 0.35 MPa; (2) Isostatically compressing the positive electrode sheet and the negative electrode sheet with an electrolyte layer obtained by spraying and curing in step (1) to obtain the all-solid-state battery; Among them, both the positive electrode sheet and the negative electrode sheet are prepared by a dry method, the raw material for spraying is a solid electrolyte material; the number of times of spraying and curing is multiple.

2. The preparation method of the all-solid-state battery according to claim 1, wherein In step (1), at least two electrolyte layers are attached to the surface of the electrode sheet.

3. The method for preparing an all-solid-state battery according to claim 1, wherein Among the electrode sheets with an electrolyte layer attached to the surface in step (1), the median particle size of the solid electrolyte in the electrolyte layer in direct contact with the surface of the electrode sheet is the smallest.

4. The preparation method of the all-solid-state battery according to claim 3, wherein The median particle size D50 of the solid electrolyte in the electrolyte layer in direct contact with the surface of the electrode sheet is 3 - 5 μm.

5. The preparation method of the all-solid-state battery according to claim 3, wherein The median particle size D50 of the solid electrolyte in the electrolyte layer not in direct contact with the surface of the electrode sheet is 4 - 30 μm.

6. The method for preparing an all-solid-state battery according to claim 1, wherein, The temperature of the isostatic pressing in step (2) is 25 - 80 °C.

7. The method for preparing an all-solid-state battery according to claim 1, wherein The pressure of the isostatic pressing in step (2) is 300 - 1000 MPa.

8. The method for preparing an all-solid-state battery according to claim 1, characterized in that, The method for preparing the electrode sheet by the dry method includes: High-speed shearing the active material, solid electrolyte, conductive agent and binder to obtain an electrode sheet slurry, and roll-pressing to obtain the electrode sheet.

9. The method for preparing an all-solid-state battery according to claim 1, wherein The preparation method includes: (1) Spraying and curing an electrolyte layer on the surface of the electrode sheet, the number of times of spraying and curing is multiple, the pressure for the first curing is 0.18 - 0.38 MPa, and the pressure for non-first curing is 0.1 - 0.35 MPa, to obtain an electrode sheet with at least two electrolyte layers attached to the surface, where the electrode sheet is a positive electrode sheet and a negative electrode sheet; (2) Isostatically compressing the positive electrode sheet and the negative electrode sheet with an electrolyte layer obtained by spraying and curing in step (1) at 25 - 80 °C under a pressure of 300 - 1000 MPa to obtain the all-solid-state battery; Among them, both the positive electrode sheet and the negative electrode sheet are prepared by a dry method, the raw material for spraying is a solid electrolyte material; the median particle size of the solid electrolyte in the electrolyte layer in direct contact with the surface of the electrode sheet is the smallest.

10. A all-solid-state battery, characterized in that, The all-solid-state battery is prepared by the preparation method of the all-solid-state battery according to any one of claims 1 - 9.

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