A solid-state battery, its preparation method and application

Abstract

The present invention relates to the technical field of lithium-ion batteries, and discloses a solid-state battery, a preparation method thereof, and an application thereof. The solid-state battery includes stacked battery elements, and each battery element includes a positive electrode, a negative electrode, and a composite electrolyte disposed between the positive electrode and the negative electrode; the composite electrolyte includes a first electrolyte and second electrolytes disposed on both sides of the first electrolyte, the first electrolyte is a solid electrolyte membrane, and the second electrolyte is obtained by curing an electrolytic solution containing an additive. The solid-state battery provided by the present invention combines a solid electrolyte and a liquid electrolytic solution containing an additive organically, can significantly enhance the interfacial impedance between the electrolyte and the positive electrode and between the electrolyte and the negative electrode, and thus obtains a solid-state battery with excellent cycle stability performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a solid-state battery, a preparation method thereof, and an application thereof. Background Art

[0002] To date in social development, the energy issue remains one of the important issues faced by human development. Developing a clean, pollution-free, and recyclable new energy system has become an important topic explored by scientists today. Among many energy technologies, lithium-ion batteries are widely used in consumer electronics products, energy storage devices, and electric vehicles due to their advantages such as high energy density, good rate performance, and long service life, and have become green energy storage and conversion devices with great development potential at present.

[0003] With the wide use of lithium-ion batteries, safety issues have also emerged one after another. Safety accidents such as fires and explosions caused by batteries in various products such as mobile phones and electric vehicles have been increasing continuously. The safety issue has become the main factor restricting the further application of lithium-ion batteries.

[0004] Traditional lithium-ion batteries use organic liquid electrolytes, which contain a large amount of organic solvents. They are volatile at high temperatures, have poor thermal stability, and are prone to combustion and fire, which are important factors for the safety hazards of lithium-ion batteries.

[0005] In addition, the use of organic liquid electrolytes also limits the energy density of lithium-ion batteries. The next generation of lithium batteries generally uses high-voltage cathode materials, and the electrochemical window of the existing electrolyte technology system is relatively narrow (<4.8V), making it difficult to match high-energy-density high-voltage cathode materials.

[0006] On the negative electrode side, it is also a future development trend to replace the current graphite with high-energy-density lithium metal. However, the electrolyte will undergo side reactions with lithium metal during battery use, producing dangerous organic salts and being prone to the generation of lithium dendrites. The continuous growth of lithium dendrites will pierce the separator and cause internal short circuit of the battery and then fire. Therefore, the matching of organic liquid electrolytes and lithium metal negative electrodes will have serious safety hazards.

[0007] Solid-state batteries use solid electrolytes and have advantages such as high safety, high energy density, and excellent high-temperature performance, and are considered the most promising technical solution. Solid electrolytes have a wide electrochemical window, have high strength to prevent the piercing of lithium dendrites, can match high-voltage cathodes and lithium metal negative electrodes with higher energy density, and at the same time have the characteristics of non-volatility, no leakage, and non-flammability, eliminating the possibility of combustion from the root and having high safety performance.

[0008] However, solid-state batteries prepared by traditional methods have poor cycle performance, which hinders the development of solid-state battery technology.

[0009] CN113363572A discloses a composite solid electrolyte, a preparation method thereof, and a solid-state battery. This method combines an inorganic electrolyte and a polymer electrolyte to form a composite electrolyte with a sandwich structure. However, the solid-state battery using this composite electrolyte is prone to uneven current distribution.

[0010] CN113471408A discloses a preparation method of a composite cathode for a all-solid-state battery, a composite cathode, and a all-solid-state battery. This method involves coating a solid electrolyte on an electrode interface. This method is difficult to prepare, expensive, and cannot be matched with current lithium battery equipment.

[0011] Therefore, it is of great significance to develop a solid-state battery with a simple preparation process and high cycle stability. Summary of the Invention

[0012] The object of the present invention is to solve the problem of poor cycle performance of solid-state batteries in the prior art.

[0013] The inventors found through research that the poor cycle performance of existing solid-state batteries is mainly because the contact between the electrolyte and the positive electrode sheet is uneven, which hinders the diffusion of lithium ions at the interface, resulting in a significant increase in interface impedance. Moreover, during the research process, the inventors also found that by using a first electrolyte as the main framework and injecting a liquid electrolyte at the same time, particularly by controlling the minimum thickness and maximum thickness of the solidified liquid electrolyte, the contact efficiency between the electrolyte and the electrode can be greatly improved, thereby obtaining a solid-state battery with high cycle stability. Based on this, the inventors completed this solution.

[0014] To achieve the above object, in the first aspect of the present invention, a solid-state battery is provided. The solid-state battery includes stacked battery units. Each battery unit includes a positive electrode, a negative electrode, and a composite electrolyte disposed between the positive electrode and the negative electrode. The composite electrolyte includes a first electrolyte and second electrolytes disposed on both sides of the first electrolyte. The first electrolyte is a solid electrolyte membrane, and the second electrolyte is obtained by curing a liquid electrolyte containing additives. Based on the total mass of the electrolyte, the content of the additives is 0.05 - 1 wt%. The additives contain catalytic functional groups, and the catalytic functional groups are selected from at least one of -OH, -OLi, -ONa, -COOH, -CHO, -OK, ester group, -NH, -CONH2, -CN, -SO4, sulfonic acid group, and alkenyl.

[0015] Preferably, the amount of the electrolyte is controlled so that the minimum distance between the two surfaces of the second electrolyte along the stacking direction of the battery unit is not less than 1 μm and the maximum distance is not greater than 10 μm.

[0016] Preferably, the conditions for the curing treatment include at least: a temperature of 85 - 200 °C, a pressure of 0.8 - 2 MPa, and a time of 0.1 - 0.5 h.

[0017] Preferably, the average thickness of the solid electrolyte membrane is 80 - 120 μm.

[0018] The second aspect of the present invention provides a method for preparing the solid - state battery, and the method includes:

[0019] (1) In the presence of a first solvent, the solid electrolyte, the binder, and the lithium salt are subjected to a first contact mixing to obtain a first mixed solution, and the first mixed solution is poured into a mold for drying treatment to obtain a solid electrolyte membrane;

[0020] (2) Stack the positive electrode sheet, the solid electrolyte membrane, and the negative electrode sheet in sequence to obtain a bare battery cell;

[0021] (3) In the presence of a second solvent, an electrolyte solution containing an additive is introduced into the bare battery cell for formation treatment, and the battery cell after the formation treatment is subjected to air extraction treatment.

[0022] Preferably, in step (1), the mass ratio of the amounts of the solid electrolyte, the binder, and the lithium salt used is 1:0.1 - 1:0.05 - 0.2.

[0023] Preferably, in step (1), the solid electrolyte is selected from oxide solid electrolytes containing at least one of NASICON structure, LISICON structure, perovskite - type structure, and garnet - type structure.

[0024] Preferably, in step (1), the binder is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene copolymer, polyethylene oxide, polyethylene oxide derivatives, polyacrylonitrile, polyacrylonitrile derivatives, polyvinyl chloride, and polyvinyl fluoride.

[0025] Preferably, in step (1), the conditions for the drying treatment include at least: a vacuum degree of negative pressure 300 Pa to negative pressure 100 Pa, a temperature of 80 - 120 °C, and a time of 12 - 30 h.

[0026] Preferably, in step (3), the conditions for the air extraction treatment include at least: a pressure of negative pressure 0.5 MPa to negative pressure 0.1 MPa.

[0027] The third aspect of the present invention provides the application of the solid - state battery described in the first aspect in energy storage devices, electric vehicles, and electronic products.

[0028] The solid-state battery provided by the present invention combines a solid electrolyte and a liquid electrolyte containing additives organically, which can significantly enhance the interfacial impedance between the electrolyte and the positive electrode and between the electrolyte and the negative electrode, thereby obtaining a solid-state battery with excellent cycle stability performance. Description of the Drawings

[0029] Figure 1 It is a schematic cross-sectional structure diagram of a battery element of the solid-state battery provided by the present invention.

[0030] Description of the Reference Numerals

[0031] Detailed Embodiments

[0032] In the present disclosure, the endpoints and any values in the disclosed ranges are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0033] In the present invention, unless otherwise stated, the room temperature or normal temperature both represent 25 ± 2 °C.

[0034] As described above, the first aspect of the present invention provides a solid-state battery, which includes battery elements stacked. Each battery element includes a positive electrode, a negative electrode, and a composite electrolyte disposed between the positive electrode and the negative electrode; the composite electrolyte includes a first electrolyte and second electrolytes disposed on both sides of the first electrolyte. The first electrolyte is a solid electrolyte membrane, and the second electrolyte is obtained by curing a liquid electrolyte containing additives; based on the total mass of the liquid electrolyte, the content of the additives is 0.05 - 1 wt%; the additives contain catalytic functional groups, and the catalytic functional groups are selected from at least one of -OH, -OLi, -ONa, -COOH, -CHO, -OK, ester group, -NH, -CONH2, -CN, -SO4, sulfonic acid group, and alkenyl.

[0035] The following combines Figure 1 The preferred specific embodiments of the solid-state battery of the present invention are described in detail with reference to the structures shown.

[0036] The solid-state battery includes battery elements 100 arranged in a stacked manner. Each battery element 100 includes a positive electrode sheet 1, a negative electrode sheet 2, and a composite electrolyte disposed between the positive electrode sheet 1 and the negative electrode sheet 2. The composite electrolyte includes a solid electrolyte membrane 3 and second electrolytes 4 disposed on both sides of the solid electrolyte membrane 3. The second electrolytes 4 are obtained by curing an electrolyte solution containing additives.

[0037] According to a particularly preferred specific embodiment, the additives are selected from at least one of acrylamide and ethyl methacrylate.

[0038] Preferably, the amount of the electrolyte solution is controlled such that the minimum distance between two surfaces of the second electrolyte along the stacking direction of the battery elements is not less than 1 μm and the maximum distance is not greater than 10 μm. The inventors have found that by adopting the specific embodiment in this preferred case, a solid-state battery with more excellent cycle stability can be obtained.

[0039] Preferably, the conditions of the curing treatment at least include: a temperature of 85 - 200 °C, a pressure of 0.8 - 2 MPa, and a time of 0.1 - 0.5 h.

[0040] Preferably, in the electrolyte solution, the concentration of the electrolyte salt is 0.1 - 2 mol / L.

[0041] Preferably, in the electrolyte solution, the electrolyte salt is selected from at least one of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluoromethanesulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0042] Preferably, the organic solvent in the electrolyte solution is selected from at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), γ-hydroxybutyrolactone (GBL), methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.

[0043] Preferably, the average thickness of the solid electrolyte membrane is 80 - 120 μm.

[0044] As described above, the second aspect of the present invention provides a method for preparing the solid-state battery. The method includes:

[0045] (1) In the presence of a first solvent, a solid electrolyte, a binder, and a lithium salt are brought into first contact and mixed to obtain a first mixed solution, and the first mixed solution is poured into a mold and dried to obtain a solid electrolyte membrane;

[0046] (2) Stack the positive electrode sheet, the solid electrolyte membrane, and the negative electrode sheet in sequence to obtain a bare battery cell;

[0047] (3) In the presence of a second solvent, introduce an electrolyte containing an additive into the bare battery cell for formation treatment, and perform air extraction treatment on the battery cell after the formation treatment.

[0048] Preferably, in step (1), the first solvent is dimethylacetamide.

[0049] Preferably, in step (1), the conditions for the first contact mixing include at least: the stirring speed is 100 - 1000 rpm, the temperature is 20 - 40 °C, and the time is 6 - 10 h.

[0050] Preferably, in step (1), the mass ratio of the amounts of the solid electrolyte, the binder, and the lithium salt is 1:0.1 - 1:0.05 - 0.2.

[0051] Preferably, in step (1), the solid electrolyte is selected from oxide solid electrolytes containing at least one of NASICON structure, LISICON structure, perovskite structure, and garnet structure.

[0052] According to a particularly preferred specific embodiment, in step (1), the solid electrolyte is lithium aluminum titanium phosphate.

[0053] Preferably, in step (1), the binder is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene copolymer, polyethylene oxide, polyethylene oxide derivatives, polyacrylonitrile, polyacrylonitrile derivatives, polyvinyl chloride, and polyvinyl fluoride.

[0054] According to a particularly preferred specific embodiment, in step (1), the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

[0055] Preferably, in step (1), the conditions for the drying treatment include at least: the vacuum degree is from - 300 Pa to - 100 Pa, the temperature is 80 - 120 °C, and the time is 12 - 30 h.

[0056] Preferably, in step (2), the material of the positive electrode sheet is selected from at least one of lithium iron phosphate, nickel cobalt manganese ternary positive electrode material, and nickel cobalt aluminum ternary positive electrode material.

[0057] According to a particularly preferred specific embodiment, in step (2), the material of the positive electrode sheet is lithium iron phosphate.

[0058] Preferably, in step (2), the material of the negative electrode sheet is selected from at least one of graphite, silicon - carbon negative electrode material, hard carbon, lithium, lithium - indium alloy, and lithium - aluminum alloy.

[0059] According to a particularly preferred specific embodiment, in step (2), the material of the negative electrode sheet is graphite.

[0060] The present invention has no special requirements for the preparation methods of the positive electrode sheet and the negative electrode sheet, and the preparation can be carried out by using methods known in the art.

[0061] The present invention has no special requirements for the preparation method of the battery cell, and it can be carried out by using methods known in the art. Exemplarily, it can be prepared by a stacking or winding method.

[0062] In the present invention, the electrolyte is solidified during the formation treatment, that is, the conditions of the formation treatment at least include: the vacuum degree is 0.8 - 2 MPa, the temperature is 80 - 120 °C, and the time is 12 - 30 h. The inventors have found that by adopting the specific embodiment in this preferred case, the prepared solid-state battery has more excellent cycle stability.

[0063] According to a particularly preferred specific embodiment, in step (3), the second solvent is ethanol.

[0064] Preferably, in step (3), the amount of the second solvent accounts for 0.05 - 0.2 wt% of the amount of the electrolyte.

[0065] Preferably, in step (3), the conditions of the air extraction treatment at least include: the pressure is from negative pressure 0.5 MPa to negative pressure 0.1 MPa.

[0066] As described above, the third aspect of the present invention provides the application of the solid-state battery described in the first aspect in energy storage devices, electric vehicles, and electronic products.

[0067] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, various raw materials and instruments used are commercially available products.

[0068] Solid electrolyte: Lithium aluminum titanium phosphate, purchased from Shenzhen Kejing Zhida Technology Co., Ltd.;

[0069] Binder: Polyvinylidene fluoride, grade Akema LBG, purchased from Dongguan Taotao Plastic Raw Materials Co., Ltd.;

[0070] Lithium salt: Lithium bis(trifluoromethanesulfonyl)imide, purchased from Aladdin Reagent Co., Ltd.;

[0071] First solvent: Dimethylacetamide, purchased from Aladdin Reagent Co., Ltd.;

[0072] Positive electrode sheet: Lithium iron phosphate, polyvinylidene fluoride, and conductive carbon black are mixed in N,N-dimethylformamide at a mass ratio of 8:1:1, uniformly coated on aluminum foil with a thickness of 100 μm, dried at 100 °C for 2 h, and then cut into circular electrode sheets with a size of 5×4 mm;

[0073] Negative electrode sheet: Graphite, polyvinylidene fluoride, and conductive carbon black are mixed in N,N-dimethylformamide at a mass ratio of 8:1:1, uniformly coated on copper foil with a thickness of 80 μm, dried at 100 °C for 2 h, and then cut into circular electrode sheets with a size of 5.2×4.2 mm;

[0074] PP / PE / PP three-layer microporous composite membrane separator: Model 2300, purchased from Celgard;

[0075] In the following examples, the electrolyte salt in the electrolyte is lithium hexafluorophosphate with a concentration of 1 mol / L, and the organic solvents are a combination of ethylene carbonate and dimethyl carbonate with a mass ratio of 1:1.

[0076] Example 1

[0077] This example provides a method for preparing a solid-state battery, including the following steps:

[0078] (1) Dissolve a solid electrolyte (the amount of the solid electrolyte is 5 g), a binder, and a lithium salt in a first solvent at a mass ratio of 1:0.5:0.1, perform a first contact mixing to obtain a first mixed solution, and pour the first mixed solution into a polytetrafluoroethylene circular mold for drying treatment to obtain a solid electrolyte membrane with an average thickness of 100 μm;

[0079] Among them, the conditions for the first contact mixing are: stirring speed is 300 rpm, temperature is room temperature, and time is 8 h;

[0080] The conditions for the drying treatment are: vacuum degree is -100 Pa, temperature is 100 °C, and time is 24 h;

[0081] (2) Stack the positive electrode sheet, the solid electrolyte membrane, and the negative electrode sheet in sequence, weld the electrode tabs, and wind them into a standard 26650 cylindrical battery cell through a winding machine;

[0082] (3) Introduce 5 g of an electrolyte containing 1 wt% acrylamide and 0.1 wt% ethanol into the cell for formation treatment. The minimum distance between the two surfaces of the formed second electrolyte along the stacking direction of the battery element is 2 μm, and the maximum distance is 5 μm. After the formation capacity is completed, assemble and mold it, then perform a degassing treatment on the cell, and finally encapsulate it to obtain a solid-state battery S1;

[0083] Among them, the conditions for the formation treatment are: temperature is 100 °C, pressure is 1.5 MPa, and time is 0.5 h;

[0084] The conditions for the air extraction treatment are: the pressure is a negative pressure of 0.1 MPa.

[0085] Example 2

[0086] This example provides a method for preparing a solid-state battery, including the following steps:

[0087] (1) Dissolve a solid electrolyte (the amount of the solid electrolyte is 5 g), a binder, and a lithium salt in a first solvent according to a mass ratio of 1:0.6:0.2, perform a first contact mixing to obtain a first mixed solution, and pour the first mixed solution into a polytetrafluoroethylene circular mold for drying treatment to obtain a solid electrolyte membrane with an average thickness of 100 μm;

[0088] Among them, the conditions for the first contact mixing are: the stirring speed is 300 rpm, the temperature is room temperature, and the time is 8 h;

[0089] The conditions for the drying treatment are: the vacuum degree is a negative pressure of 300 Pa, the temperature is 100 °C, and the time is 24 h;

[0090] (2) Stack the positive electrode sheet, the solid electrolyte membrane, and the negative electrode sheet in sequence, weld the tab, and wind them into a standard 26650 cylindrical battery cell through a winding machine;

[0091] (3) Introduce 5 g of an electrolyte solution containing 0.5 wt% acrylamide and 0.1 wt% ethanol into the cell for formation treatment. The minimum distance between the two surfaces of the formed second electrolyte along the stacking direction of the battery element is 3 μm, and the maximum distance is 5 μm. After the formation capacity is completed, assemble and mold it, then perform air extraction treatment on the cell, and finally encapsulate it to obtain the solid-state battery S2;

[0092] Among them, the conditions for the formation treatment are: the temperature is 120 °C, the pressure is 1.0 MPa, and the time is 0.5 h;

[0093] The conditions for the air extraction treatment are: the pressure is a negative pressure of 0.1 MPa.

[0094] Example 3

[0095] This example provides a method for preparing a solid-state battery, including the following steps:

[0096] (1) Dissolve a solid electrolyte (the amount of the solid electrolyte is 5 g), a binder, and a lithium salt in a first solvent according to a mass ratio of 1:0.8:0.05, perform a first contact mixing to obtain a first mixed solution, and pour the first mixed solution into a polytetrafluoroethylene circular mold for drying treatment to obtain a solid electrolyte membrane with an average thickness of 100 μm;

[0097] Among them, the conditions for the first contact mixing are: the stirring speed is 300 rpm, the temperature is room temperature, and the time is 8 h;

[0098] The conditions for the drying treatment are: the vacuum degree is -200 Pa, the temperature is 100 °C, and the time is 24 h;

[0099] (2) Stack the positive electrode sheet, the solid electrolyte membrane, and the negative electrode sheet in sequence, weld the electrode tabs, and wind them into a standard 26650 cylindrical battery cell by a winding machine;

[0100] (3) Introduce 5 g of the electrolyte containing 1 wt% ethyl methacrylate and 0.1 wt% ethanol into the cell for formation treatment. The minimum distance between the two surfaces of the formed second electrolyte along the stacking direction of the battery element is 1 μm, and the maximum distance is 8 μm. After the formation capacity is completed, assemble and mold it, then perform air extraction treatment on the cell, and finally encapsulate to obtain the solid-state battery S3;

[0101] Among them, the conditions for the formation treatment are: the temperature is 90 °C, the pressure is 0.8 MPa, and the time is 0.5 h;

[0102] The conditions for the air extraction treatment are: the pressure is -0.1 MPa.

[0103] Example 4

[0104] This example prepares the solid-state battery according to the method of Example 1. The difference is that in step (3), the minimum distance between the two surfaces of the formed second electrolyte along the stacking direction of the battery element is 0.5 μm, and the maximum distance is 5 μm.

[0105] The remaining steps are the same as those in Example 1.

[0106] Obtain the solid-state battery S4.

[0107] Example 5

[0108] This example prepares the solid-state battery according to the method of Example 1. The difference is that in step (3), the temperature of the formation treatment is 150 °C.

[0109] The remaining steps are the same as those in Example 1.

[0110] Obtain the solid-state battery S5.

[0111] Comparative Example 1

[0112] This comparative example prepares the solid-state battery according to the method of Example 1. The difference is that no electrolyte is added;

[0113] The specific operation steps include:

[0114] (1) Dissolve a solid electrolyte (the amount of the solid electrolyte is 5 g), a binder, and a lithium salt in a first solvent at a mass ratio of 1:0.5:0.1, conduct a first contact mixing to obtain a first mixed solution, and pour the first mixed solution into a polytetrafluoroethylene circular mold for drying treatment to obtain a solid electrolyte membrane with an average thickness of 100 μm;

[0115] Among them, the conditions for the first contact mixing are: the stirring speed is 300 rpm, the temperature is room temperature, and the time is 8 h;

[0116] The conditions for the drying treatment are: the vacuum degree is -100 Pa (negative pressure), the temperature is 100 °C, and the time is 24 h;

[0117] (2) Stack the positive electrode sheet, the solid electrolyte membrane, and the negative electrode sheet in sequence, weld the tab ears, and wind them into a standard 26650 cylindrical battery cell through a winding machine;

[0118] (3) Subject the battery cell to formation treatment. After the formation capacity is completed, assemble and form it, then conduct air extraction treatment on the battery cell, and finally encapsulate it to obtain a solid-state battery DS1.

[0119] Comparative Example 2

[0120] This comparative example prepares a solid-state battery according to the method of Example 1. The difference is that a Celgard 2300 PP / PE / PP three-layer microporous composite membrane separator is used to replace the solid electrolyte membrane.

[0121] The remaining steps are the same as those in Example 1.

[0122] A solid-state battery DS2 is obtained.

[0123] Comparative Example 3

[0124] This comparative example prepares a solid-state battery according to the method of Example 1. The difference is that in step (3), the additive in the electrolyte is 2 wt% acrylamide.

[0125] The remaining steps are the same as those in Example 1.

[0126] A solid-state battery DS3 is obtained.

[0127] Test Example

[0128] Test the cycle stability of the solid-state batteries prepared in the examples and comparative examples. The specific test results are shown in Table 1.

[0129] The specific test conditions are as follows: At 25°C, a battery test system (Land-CT2001A, purchased from Wuhan Blue Electric Co., Ltd.) is used to test the solid-state battery. The first-week discharge specific capacity and Coulomb efficiency of the battery at a current density of 0.2C are tested respectively, as well as the discharge specific capacity after 300 cycles. The test voltage range is 2.2 - 3.65V, and the capacity retention rate is calculated.

[0130] Among them, the calculation formula for the capacity retention rate is: (discharge specific capacity after 300 cycles / first-week discharge specific capacity) × 100%.

[0131] Table 1

[0132]

[0133] It can be seen from the results in Table 1 that the solid-state battery provided by the present invention has more excellent cycle stability performance.

[0134] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A solid-state battery, characterized in that, The solid-state battery includes battery cells arranged in a stacked manner. Each battery cell includes a positive electrode, a negative electrode, and a composite electrolyte disposed between the positive electrode and the negative electrode. The composite electrolyte includes a first electrolyte and second electrolytes disposed on both sides of the first electrolyte. The first electrolyte is a solid electrolyte membrane, and the solid electrolyte contained in the solid electrolyte membrane is selected from oxide solid electrolytes containing at least one of NASICON structure, LISICON structure, perovskite structure, and garnet structure. The second electrolyte is obtained by curing an electrolyte solution containing an additive and ethanol. Based on the total mass of the electrolyte solution, the content of the additive is 0.5 - 1 wt%, and the content of the ethanol is 0.05 - 0.2 wt%. The additive is acrylamide and / or ethyl methacrylate. Control the amount of the electrolyte solution so that the minimum distance between the two surfaces of the second electrolyte along the stacking direction of the battery cells is not less than 1 μm and the maximum distance is not greater than 8 μm. The average thickness of the solid electrolyte membrane is 80 - 120 μm. The conditions of the curing treatment at least include: temperature of 90 - 120 °C, pressure of 0.8 - 2 MPa, and time of 0.1 - 0.5 h.

2. A method for preparing the solid-state battery according to claim 1, characterized in that, This method includes: (1) In the presence of a first solvent, the solid electrolyte, a binder, and a lithium salt are brought into first contact and mixed to obtain a first mixed solution, and the first mixed solution is poured into a mold for drying treatment to obtain a solid electrolyte membrane. (2) The positive electrode sheet, the solid electrolyte membrane, and the negative electrode sheet are stacked in sequence to obtain a bare battery cell. (3) In the presence of a second solvent, an electrolyte solution containing an additive is introduced into the bare battery cell for formation treatment, and the battery cell after the formation treatment is subjected to a degassing treatment.

3. The method according to claim 2, wherein In step (1), the mass ratio of the amounts of the solid electrolyte, the binder, and the lithium salt is 1:0.1 - 1:0.05 - 0.

2.

4. The method according to claim 2 or 3, characterized in that, In step (1), the binder is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene copolymer, polyethylene oxide, polyethylene oxide derivatives, polyacrylonitrile, polyacrylonitrile derivatives, polyvinyl chloride, and polyvinyl fluoride.

5. The method according to claim 2 or 3, characterized in that, In step (1), the conditions of the drying treatment at least include: vacuum degree from negative pressure of 300 Pa to negative pressure of 100 Pa, temperature of 80 - 120 °C, and time of 12 - 30 h.

6. The method according to claim 2 or 3, characterized in that, In step (3), the conditions of the degassing treatment at least include: pressure from negative pressure of 0.5 MPa to negative pressure of 0.1 MPa.

7. Application of the solid-state battery according to claim 1 in energy storage devices, electric vehicles, and electronic products.

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