Preparation method and application of polymer lithium-conducting glue solution and solid-state lithium battery

Abstract

The invention discloses a preparation method and application of a polymer lithium-conducting glue solution and a solid-state lithium battery, and the preparation method comprises the following steps: adding a lithium salt and a polymer monomer into a solvent according to a mass ratio of (5-10): (3-5) to form a mixed solution; adding an initiator, uniformly stirring to obtain a mixture glue solution, and carrying out heat treatment to obtain a polymer lithium-conducting glue solution; the initiator is selected from one or a mixture of two or more of azodiisobutyronitrile, benzoyl peroxide, potassium persulfate and ammonium persulfate in any proportion; the interface material which is formed in situ in the battery and has excellent mechanical property and lithium conducting capacity is used for reducing the operation pressure of the solid-state battery and improving the electrochemical performance of the solid-state battery.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a preparation method and application of a polymer lithium-conducting gel and a solid-state lithium battery. Background Art

[0002] Solid-state batteries are regarded as an important development direction of the next generation of energy storage technology due to their high energy density and safety. However, solid-state batteries still face many challenges in practical applications, among which interface contact problems and operating pressure requirements are key factors restricting their performance improvement. Traditional solid-state batteries usually use rigid solid electrolytes (such as oxides, sulfides or polymer electrolytes), which have poor physical contact with electrode materials, resulting in high interface impedance and low lithium ion transfer efficiency. To solve this problem, existing technologies mainly improve the interface contact between electrodes and electrolytes by high-temperature sintering or applying external high pressure (usually >10MPa). However, high-temperature sintering can easily lead to material decomposition and interface side reactions, and high stack pressure not only increases the mechanical complexity of the battery system, but also accelerates interface degradation, affecting the cycle life and safety of the battery.

[0003] In recent years, researchers have tried to alleviate the interface contact problem by introducing flexible interface layers or gel electrolytes. For example, some studies have used polymer-ceramic composite electrolytes or in-situ polymerization technology to enhance interface adhesion and reduce interface impedance. However, these methods often cannot take into account both mechanical properties and ionic conductivity: insufficient mechanical strength of polymer materials may cause deformation or short circuit of the battery during cycling, while excessive cross-linking will reduce ion mobility. In addition, existing gel electrolytes usually need to be pre-polymerized before battery assembly, which makes it difficult to fully infiltrate and fill the microscopic pores between the electrode and the electrolyte, resulting in insufficient interface contact. These factors make it difficult for solid-state batteries to operate stably at low stack pressures (<2MPa) and to perform large rate charge and discharge (>3mAh / cm2) under conditions of large electrode surface capacity. 2 ,>0.2C). Insufficient interface contact makes the ion transfer efficiency low, further aggravates the polarization effect, and seriously restricts the performance improvement and wide application of solid-state batteries. To solve these problems, the present invention provides a new lithium-conducting gel technology. This technology obtains a gel system with extremely strong electrode wettability and interface adhesion by rationally designing the gel composition and structure, and induces it to form a bonding system with excellent lithium conductivity and mechanical strength after in-situ solidification and gelation inside the battery, so that the solid-state battery can be used at low stack pressure (<1MPa) and high surface capacity (>3mAh / cm 2 ) and high rate conditions (>0.2C), it can still work stably in cycles, significantly improving the overall performance of solid-state batteries. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a preparation method and application of a polymer lithium-conducting gel and a solid-state lithium battery.

[0005] The technical solution adopted by the present invention is: a method for preparing a polymer lithium-conducting gel, comprising the following steps:

[0006] Adding lithium salt and polymer monomer into a solvent in a mass ratio of 5-10:3-5 to form a mixed solution;

[0007] Add initiator and stir evenly to obtain mixture glue, and then heat treat to obtain polymer lithium conductive glue;

[0008] The initiator is one or a mixture of two or more of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, and ammonium persulfate in any proportion.

[0009] Furthermore, the mixed solution also includes a coupling agent and a diluent. The coupling agent is one or two or more of 3-(triethoxysilyl)propyl methacrylate, 3-chloropropyltrimethoxysilane, aminosilane, and titanate coupling agent, mixed in any proportion; the diluent is one or two or more of ethylene carbonate, dimethyl carbonate, 1,3-dioxolane, ethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, and fluoroethylene glycol dimethyl ether, mixed in any proportion.

[0010] Furthermore, the lithium salt is one or a mixture of two or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonylimide) and lithium bis(fluorosulfonylimide) in any proportion;

[0011] The polymer monomer is one or two or more of polyethylene glycol diacrylate, polymethyl methacrylate, polyethylene oxide, polyacrylonitrile, and polyethylene glycol diglycidyl ether mixed in any proportion;

[0012] The mass ratio of lithium salt, polymer monomer, solvent and initiator is 5-10:3-5:85-90:0.01-0.2.

[0013] A polymer lithium-conducting gel.

[0014] An application of a polymer lithium-conducting gel, wherein the lithium-conducting gel is used to prepare a solid-state lithium battery.

[0015] A solid-state lithium battery obtained from a polymer lithium-conducting gel has an operating pressure of 0.1-1 MPa and an ion conductivity of a solid electrolyte membrane greater than 0.8×10-3 S / cm.

[0016] A method for preparing a solid-state lithium battery comprises the following steps:

[0017] S1: injecting the mixed glue into the solid-state lithium battery shell;

[0018] The injection process is as follows:

[0019] Inject for 5 minutes at a pressure of 0 to 30 kPa;

[0020] Inject for 10 minutes at a pressure of 30 to 60 kPa;

[0021] Inject for 15 minutes at a pressure of 60 to 90 kPa;

[0022] S2: Heat treatment. The heat treatment process is as follows:

[0023] Keep warm at 20-30℃ for 12h;

[0024] Raise the temperature to 60°C at 0.5°C / min and keep warm for 4 hours; raise the temperature to 80°C at 0.2°C / min and keep warm for 20 hours;

[0025] Cool down to room temperature at 0.1℃ / min.

[0026] Furthermore, the negative electrode material in the solid-state lithium battery is one or two or more of graphite, silicon dioxide, deposited silicon carbon, lithium metal, and lithium alloy mixed in any proportion; the positive electrode material is one or two or more of lithium iron phosphate, lithium iron manganese phosphate, ternary material, and lithium cobalt oxide mixed in any proportion; the solid electrolyte is one or two or more of oxides, sulfides, and polymers mixed in any proportion.

[0027] Furthermore, the negative electrode surface capacity of the solid-state lithium battery is 1 to 5.5 mAh / cm 2 The compaction density of the pole piece is 0.5~1.2g / cm 3 ; Positive electrode surface capacity is 1~4.5mAh / cm 2 The compaction density of the pole piece is 2.5~3.5g / cm 3 The area of the positive and negative electrodes is 10 to 100 cm 2 .

[0028] Furthermore, the injection amount of the polymer lithium conductive gel is 1 to 6 g / Ah.

[0029] Beneficial effects of the present invention:

[0030] (1) The present invention directly injects the lithium conductive glue after the dry battery cell is assembled and before the battery cell is sealed, and induces a polymerization reaction through a simple heat treatment to form an adhesive that has both excellent mechanical properties and lithium ion conductivity, and has the advantage of simple process;

[0031] (2) The lithium-conducting gel of the present invention can effectively infiltrate and adhere to the positive and negative electrodes and the solid electrolyte membrane, and is compatible with a wide range of positive and negative electrode materials and solid electrolytes, forming a good interface contact, and can achieve a high total surface area (>3mAh / cm 2 ) Maximum rate charge and discharge cycle (>0.2C) of solid-state battery systems;

[0032] (3) The lithium-conducting gel obtained by the present invention can generate uniform cohesive force inside the battery, replacing the external high-voltage effect, significantly reducing the stack pressure required for the solid-state battery during the cycle to ≤1 MPa, and improving the cycle life of the battery and the battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 1 is a diagram of the lithium conductive gel obtained in Example 1 of the present invention, a is the polymer lithium conductive gel, b is the lithium conductive gel after heat treatment, and c is the lithium conductive gel after heat treatment in Comparative Example 1.

[0034] Figure 2 The first cycle capacity-voltage curves of the solid-state lithium battery obtained in Comparative Example 1 and Example 1 of the present invention are shown in Figure 1. a is the curve obtained in Comparative Example 1, and b is the curve obtained in Example 1.

[0035] Figure 3 The EIS curves of the solid-state lithium batteries obtained in Example 1 and Comparative Example 1 of the present invention are shown.

[0036] Figure 4 Schematic diagram of the cycle curves of the solid-state lithium battery obtained in Example 1 of the present invention and the battery of Comparative Example 2. DETAILED DESCRIPTION

[0037] A method for preparing a polymer lithium-conducting gel comprises the following steps:

[0038] Adding lithium salt and polymer monomer into a solvent in a mass ratio of 5-10:3-5 to form a mixed solution; the solvent is an ester or ether solvent;

[0039] After adding the initiator and stirring evenly, a mixture glue is obtained, and after heat treatment, a polymer lithium conductive glue is obtained; the mass ratio of lithium salt, polymer monomer, solvent and initiator is 5-10:3-5:85-90:0.01-0.2.

[0040] The initiator is selected from one or more of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, and ammonium persulfate, mixed in any proportion. The lithium salt is one or more of lithium hexafluorophosphate, lithium bistrifluoromethanesulfonyl imide, and lithium bisfluorosulfonyl imide, mixed in any proportion. The polymer monomer is one or more of polyethylene glycol diacrylate, polymethyl methacrylate, polyethylene oxide, polyacrylonitrile, and polyethylene glycol diglycidyl ether, mixed in any proportion. Coupling agents and diluents can also be added, and the added amount is 0.02% to 0.05% of the mass of the main raw materials (including the total mass of lithium salts and polymer monomers). The addition of coupling agents and diluents can reduce the viscosity of the precursor glue, enhance electrode wetting, promote the adsorption of the precursor glue on the electrode particles, and enhance the interface compatibility between the glue and the battery components.

[0041] The polymer lithium-conducting gel obtained in the present invention can be polymerized with a relatively low amount of added polymer monomers to form a solid electrolyte membrane with good mechanical properties (>0.5N / m) and lithium-conducting properties (>0.8×10-3S / cm).

[0042] The contents of lithium salt, polymer monomer, and other components in the present invention cannot be changed. The above proportions ensure the stability of the prepolymer solution and the performance after polymerization: 5-10% lithium salt constructs efficient ion channels, ensuring the solid electrolyte membrane conductivity >0.8×10⁻³ S / cm; 3-5% monomer forms a continuous phase network, imparting an interfacial bonding strength >0.5 N / m; 85%-90% solvent balances fluidity and curing shrinkage; and 0.02-0.05% coupling agent and diluent reduce the adhesive's viscosity and promote interfacial compatibility. The critical ratios of these components produce a synergistic effect, giving the adhesive excellent lithium conductivity, mechanical properties, and interfacial stability, resolving the technical challenge of traditional formulations that struggle to balance conductivity and mechanical strength.

[0043] A method for preparing a solid-state lithium battery comprises the following steps:

[0044] S1: Inject the mixed gel into the solid-state lithium battery shell; through the program-controlled adjustable vacuum injection technology, inject the polymer lithium conductive gel into the electrode / electrolyte interface to form a step-by-step infiltration effect.

[0045] The injection process is as follows:

[0046] Inject for 5 minutes under a pressure of 0 to 30 kPa; in the initial stage, allow the mixture glue to gradually penetrate the electrode macropores.

[0047] Inject for 10 minutes at a pressure of 30 to 60 kPa; in the middle stage, promote the solution to enter the secondary pores of the electrode.

[0048] The injection process was carried out for 15 minutes at a pressure of 60-90 kPa. The final stage ensured that the solution completely filled the nanoscale gaps at the electrode / electrolyte interface. The entire injection process was carried out in a dry environment with a humidity of <0.01 ppm.

[0049] S2: Heat treatment. The heat treatment process is as follows:

[0050] Keep the temperature at 20-30°C for 12 hours; after heating to the required temperature, maintain the temperature fluctuation within ±1°C to achieve molecular-level interfacial wetting of the solution.

[0051] Raise the temperature to 60°C at 0.5°C / min and keep warm for 4 hours; raise the temperature to 80°C at 0.2°C / min and keep warm for 20 hours; ensure that the degree of polymerization reaches 85-92%.

[0052] Cool down to room temperature at 0.1℃ / min to fully eliminate the interface stress.

[0053] The negative electrode material in solid-state lithium batteries is one of graphite, silicon oxide, deposited silicon carbon, lithium metal, and lithium alloy. The negative electrode surface capacity of solid-state lithium batteries is 1 to 5.5 mAh / cm 2 The compaction density of the pole piece is 0.5~1.2g / cm 3 ; Positive electrode surface capacity is 1~4.5mAh / cm 2 The compaction density of the pole piece is 2.5~3.5g / cm 3 The area of the positive and negative electrodes is 10 to 100 cm 2 The injection amount of polymer lithium conductive gel is 1 to 6 g / Ah.

[0054] The negative electrode material in the solid-state lithium battery is one or two or more of graphite, silicon oxide, deposited silicon carbon, lithium metal, and lithium alloy mixed in any proportion; the positive electrode material is one or two or more of lithium iron phosphate, lithium iron manganese phosphate, ternary material, and lithium cobalt oxide mixed in any proportion; the solid electrolyte is one or two or more of oxides (such as lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide or lithium titanium aluminum phosphate), sulfides (lithium phosphorus sulfur chloride, lithium germanium phosphorus sulfur, etc.) and polymers (polyethylene oxide, polycarbonate) mixed in any proportion.

[0055] Example 1

[0056] First, prepare the polymer lithium conductive gel.

[0057] Lithium hexafluorophosphate and polyethylene glycol diacrylate are added to a solvent in a mass ratio of 8:4 to form a mixed solution; the solvent is an ether solvent;

[0058] After adding an initiator azobisisobutyronitrile and stirring evenly, a mixture glue is obtained, and after heat treatment, a polymer lithium conductive glue is obtained; wherein the mass ratio of lithium hexafluorophosphate, polyethylene glycol diacrylate, solvent and azobisisobutyronitrile is 8:4:87:0.1.

[0059] A method for preparing a solid-state lithium battery comprises the following steps:

[0060] S1: injecting the mixed glue into the solid-state lithium battery shell, wherein the solid-state lithium battery negative electrode adopts graphite negative electrode material, the positive electrode adopts NCM811 ternary positive electrode material, and the solid electrolyte is an oxide-coated polyethylene solid electrolyte membrane;

[0061] The injection process is as follows:

[0062] Inject for 5 minutes at a pressure of 15 kPa;

[0063] At a pressure of 45 kPa, inject for 10 minutes;

[0064] At a pressure of 80 kPa, inject for 15 minutes;

[0065] S2: Heat treatment, the heat treatment process is as follows

[0066] Keep warm at 25℃ for 12h;

[0067] Raise the temperature to 60°C at 0.5°C / min and keep warm for 4 hours; raise the temperature to 80°C at 0.2°C / min and keep warm for 20 hours;

[0068] Cool down to room temperature at 0.1℃ / min.

[0069] The solid-state lithium battery obtained in Example 1 operates stably under low stack pressure (<1MPa) and performs high-rate charge and discharge (>3mAh / cm 2 ,0.4C), the cycle was stable, showing good electrochemical performance.

[0070] Example 2

[0071] First, prepare the polymer lithium conductive gel.

[0072] Lithium hexafluorophosphate and polyethylene glycol diacrylate are added to a solvent in a mass ratio of 5:5 to form a mixed solution; the solvent is an ether solvent;

[0073] An initiator, azobisisobutyronitrile, is added and stirred to obtain a mixture glue, which is then subjected to heat treatment to obtain a polymer lithium conductive glue; wherein the mass ratio of lithium hexafluorophosphate, polyethylene glycol diacrylate, solvent and azobisisobutyronitrile is 5:5:90:0.1.

[0074] A method for preparing a solid-state lithium battery comprises the following steps:

[0075] S1: injecting the mixed glue into the solid-state lithium battery shell, wherein the solid-state lithium battery negative electrode adopts lithium metal negative electrode material, the positive electrode adopts NCM811 ternary positive electrode material, and the solid electrolyte is a sulfide-coated polyethylene solid electrolyte membrane;

[0076] The injection process is as follows:

[0077] Inject for 5 minutes at a pressure of 30 kPa;

[0078] At a pressure of 60 kPa, inject for 10 minutes;

[0079] At a pressure of 90 kPa, inject for 15 minutes;

[0080] S2: Heat treatment. The heat treatment process is as follows:

[0081] Keep warm at 30℃ for 12h;

[0082] Raise the temperature to 60°C at 0.5°C / min and keep warm for 4 hours; raise the temperature to 80°C at 0.2°C / min and keep warm for 20 hours;

[0083] Cool down to room temperature at 0.1℃ / min.

[0084] The solid-state lithium battery obtained in Example 2 operates stably under low stack pressure (<1MPa) and performs high-rate charge and discharge (>3mAh / cm 2 ,0.5C), the cycle was stable and showed good electrochemical performance.

[0085] Example 3

[0086] First, prepare the polymer lithium conductive gel.

[0087] Lithium bis(trifluoromethanesulfonyl)imide and polyethylene oxide are added to a solvent in a mass ratio of 8:4 to form a mixed solution; the solvent is an ether solvent;

[0088] An initiator, potassium persulfate, is added and stirred to obtain a mixture glue, which is then heat-treated to obtain a polymer lithium conductive glue; wherein the mass ratio of lithium bis(trifluoromethanesulfonylimide), polyethylene oxide, solvent and potassium persulfate is 10:3:85:0.2.

[0089] A method for preparing a solid-state lithium battery comprises the following steps:

[0090] S1: injecting the polymer lithium conductive gel into the solid-state lithium battery shell, wherein the solid-state lithium battery negative electrode adopts deposited silicon carbon negative electrode material, the positive electrode adopts NCM811 ternary positive electrode material, and the solid electrolyte is an oxide-coated polyethylene solid electrolyte membrane;

[0091] The injection process is as follows:

[0092] Inject for 5 minutes at a pressure of 2 kPa;

[0093] Inject for 10 minutes at a pressure of 30 kPa;

[0094] At a pressure of 60 kPa, inject for 15 minutes;

[0095] S2: Curing the lithium conductive glue. The curing process is as follows:

[0096] Keep warm at 20℃ for 12h;

[0097] Raise the temperature to 60°C at 0.5°C / min and keep warm for 4 hours; raise the temperature to 80°C at 0.2°C / min and keep warm for 20 hours;

[0098] Cool down to room temperature at 0.1℃ / min.

[0099] The solid-state lithium battery obtained in Example 2 operates stably under low stack pressure (<1MPa) and performs high-rate charge and discharge (>3mAh / cm 2 ,0.4C), the cycle was stable, showing good electrochemical performance.

[0100] Comparative Example 1

[0101] The other steps of this comparative example are the same as those of Example 1, except that in the preparation of the polymer lithium conductive gel, the mass ratio of lithium hexafluorophosphate, polyethylene glycol diacrylate, solvent and azobisisobutyronitrile is 8:12:87:0.1.

[0102] Comparative Example 2

[0103] The other steps of this comparative example are the same as those of Example 1, except that no diluent is contained in the preparation of the polymer lithium-conducting gel.

[0104] In order to facilitate the observation of the morphology of the polymer lithium conductive gel after heat treatment, the polymer lithium conductive gel obtained in Example 1 and Comparative Example 1 was treated according to the heat treatment system in the solid-state lithium battery preparation method in Example 1, without injecting it into the battery. The obtained lithium conductive gel was as follows: Figure 1 As shown, a is a picture of the lithium conductive glue solution before heat treatment in Example 1, b is a picture of the lithium conductive glue solution obtained in Example 1 after heat treatment, and c is a picture of the lithium conductive glue solution obtained in Comparative Example 1 after heat treatment.

[0105] As can be seen from the figure, the lithium-conducting glue obtained in Example 1 is transparent and viscous after heat treatment, while the lithium-conducting glue obtained in Comparative Example 1 is white and turbid and has no viscosity.

[0106] The solid-state lithium battery obtained in Example 1 and Comparative Example 1 was subjected to the first cycle charge and discharge test at a rate of 0.05C. The curves are as follows: Figure 2 As shown, Figure 2 a is the result of comparative example 1, and b is the result of example 1. As can be seen from the figure, under the condition of high polymer monomer addition, the ICE of the first cycle capacity-voltage curve of the battery is 79.0%, while the ICE of the curve obtained in example 1 is 87.1%, that is, under low stack pressure (<1MPa) and high areal capacity (>3mAh / cm 2 ) test conditions, the lithium-conducting gel prepared by the present invention can enable the solid-state lithium battery to achieve a higher first coulombic efficiency and show better electrochemical performance.

[0107] The EIS curves of the solid-state lithium batteries obtained in Example 1 and Comparative Example 1 are as follows: Figure 3 As shown in the figure, it can be seen that the ohmic resistance of the solid electrolyte membrane prepared in Example 1 is less than the ohmic resistance of the solid-state lithium-ion battery prepared in Comparative Example 1. The known conductivity is calculated by the following formula:

[0108]

[0109] Where d is the thickness of the solid electrolyte membrane, R0 is the ohmic resistance, and S is the area of the solid electrolyte membrane. From this, it can be calculated that the ionic conductivity of the solid electrolyte membrane prepared in Example 1 with a low polymer monomer addition is much greater than the ionic conductivity of the solid electrolyte membrane prepared in Comparative Example 1 with a high polymer monomer addition, and its ionic conductivity is >0.8×10-3 S / cm.

[0110] The solid-state lithium battery cycle curves obtained in Example 1 and Comparative Example 2 are as follows: Figure 4 As shown, Figure 4 a is the result of comparative example 2, and b is the result of embodiment 1. It can be seen from the figure that the capacity retention rate of the solid-state lithium battery containing a diluent in the lithium-conducting gel obtained in embodiment 1 is greater than 85% after 300 cycles; the capacity retention rate of the solid-state lithium battery without a diluent in the lithium-conducting gel obtained in comparative example 2 is only 85% after 120 cycles, and the capacity continues to decay, that is, at low stack pressure (<1MPa) and high areal capacity (>3mAh / cm 2 ) and high rate (0.4C) test conditions, the lithium-conducting gel prepared by the present invention can significantly improve the cycle stability of solid-state lithium batteries and show better electrochemical performance.

[0111] The present invention achieves molecular-level wetting of the electrode / electrolyte interface by optimizing the ratio and preparation process, and reduces the interface contact impedance by more than 60%. The specially designed polymer monomer combination significantly improves the interface bonding strength (>0.5N / m), effectively suppressing the interface stratification during the cycle; the in-situ formed lithium-conducting gel produces uniform cohesion, stably controlling the battery working pressure at 1.0±0.2MPa, while avoiding the interface stress concentration caused by volume shrinkage of traditional polymer materials; the elastic modulus is adjustable, perfectly matching the pressure requirements of different solid-state battery systems. The vacuum gradient injection process used increases the solution filling efficiency by 90% and reduces the production cost by 30%. Multi-stage temperature-controlled polymerization ensures a conversion rate of >99% and a residual monomer content of <50ppm, which is fully compatible with the existing stacking / winding process and does not require additional equipment investment.

[0112] The solid-state lithium battery obtained by the present invention has a room temperature ionic conductivity of the solid electrolyte membrane exceeding 0.8×10-3S / cm, which can support the stable operation of the battery at a rate of 0.5C. More importantly, the lithium-conducting gel enables the battery to maintain excellent performance under low stack pressure (<1MPa), breaking through the limitations of traditional solid-state batteries. Its unique interface stability greatly reduces interface side reactions, allowing the battery to maintain high surface capacity (>3mAh / cm 2 ) and high compaction (negative electrode>1.1g / cm 3 , positive electrode>3.1g / cm 3 Specifically, the battery's initial coulombic efficiency reached 87%, and its capacity retention remained above 85% after 300 cycles, far exceeding that of traditional solid-state battery systems.

[0113] This invention directly injects a mixture into the battery during preparation. After heat treatment, it polymerizes in situ to form a lithium-conducting gel with excellent mechanical properties and lithium conductivity. This innovative solution addresses two key challenges of solid-state batteries: poor interface contact and high operating pressure requirements. After polymerization, the lithium-conducting gel exhibits excellent mechanical properties and high ionic conductivity. It effectively bonds the electrode and electrolyte to form a low-impedance interface and, through cohesion, reduces the battery's operating pressure to below 1 MPa.

Claims

1. A method for preparing a polymer lithium-conducting gel, characterized in that: The following steps are involved: Adding lithium salt and polymer monomer into a solvent in a mass ratio of 5-10:3-5 to form a mixed solution; Add initiator and stir evenly to obtain mixture glue liquid, and obtain polymer lithium conductive glue liquid after heat treatment; The initiator is one or a mixture of two or more of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, and ammonium persulfate in any proportion.

2. The method for preparing a polymer lithium conductive gel according to claim 1, wherein: The mixed solution also includes a coupling agent and a diluent. The coupling agent is one or a mixture of two or more of 3-(triethoxysilyl)propyl methacrylate, 3-chloropropyltrimethoxysilane, aminosilane, and titanate coupling agent in any proportion. The diluent is one or a mixture of two or more of ethylene carbonate, dimethyl carbonate, 1,3-dioxolane, ethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, and fluoroethylene glycol dimethyl ether in any proportion.

3. The method for preparing a polymer lithium conductive gel according to claim 1, wherein: The lithium salt is one or a mixture of two or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonylimide) and lithium bis(fluorosulfonylimide) in any proportion; The polymer monomer is one or two or more of polyethylene glycol diacrylate, polymethyl methacrylate, polyethylene oxide, polyacrylonitrile, and polyethylene glycol diglycidyl ether mixed in any proportion; The mass ratio of lithium salt, polymer monomer, solvent and initiator is 5-10:3-5:85-90:0.01-0.

2.

4. The lithium-conducting polymer gel obtained by any one of the preparation methods of claims 1 to 3.

5. The use of the polymer lithium conductive gel as claimed in claim 4, characterized in that: The lithium-conducting gel is used to prepare solid-state lithium batteries.

6. A solid-state lithium battery obtained by using the polymer lithium conductive gel according to claim 4, characterized in that: The working pressure of the solid-state lithium battery is 0.1-1 MPa, and the ion conductivity of the solid electrolyte membrane is greater than 0.8×10-3 S / cm.

7. A method for preparing a solid-state lithium battery according to claim 6, characterized in that: The following steps are involved: S1: injecting the mixed glue into the solid-state lithium battery shell; The injection process is as follows: Inject for 5 minutes at a pressure of 0 to 30 kPa; Inject for 10 minutes at a pressure of 30 to 60 kPa; Inject for 15 minutes at a pressure of 60 to 90 kPa; S2: Heat treatment. The heat treatment process is as follows: Keep warm at 20-30℃ for 12h; Raise the temperature to 60°C at 0.5°C / min and keep warm for 4 hours; raise the temperature to 80°C at 0.2°C / min and keep warm for 20 hours; Cool down to room temperature at 0.1℃ / min.

8. The method for preparing a solid-state lithium battery according to claim 7, characterized in that: The negative electrode material in the solid-state lithium battery is one or two or more of graphite, silicon oxide, deposited silicon carbon, lithium metal, and lithium alloy mixed in any proportion; the positive electrode material is one or two or more of lithium iron phosphate, lithium iron manganese phosphate, ternary material, and lithium cobalt oxide mixed in any proportion; the solid electrolyte is one or two or more of oxides, sulfides, and polymers mixed in any proportion.

9. The method for preparing a solid-state lithium battery according to claim 7, wherein: The negative electrode surface capacity of the solid-state lithium battery is 1 to 5.5 mAh / cm 2 The compaction density of the pole piece is 0.5~1.2g / cm 3 ; Positive electrode surface capacity is 1~4.5mAh / cm 2 The compaction density of the pole piece is 2.5~3.5g / cm 3 The area of the positive and negative electrodes is 10 to 100 cm 2 .

10. The method for preparing a solid-state lithium battery according to claim 7, characterized in that: The injection amount of the polymer lithium conductive gel is 1-6 g / Ah.

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