An in-situ polymerization integrated solid-state battery and a preparation method thereof

Abstract

The application discloses an in-situ polymerization integrated solid-state battery and a preparation method thereof. The integrated structure of the battery comprises a positive electrode coated with a protective film, an electrolyte layer after in-situ polymerization and a negative electrode. In the application, the protective film liquid is coated on the surface of the positive electrode, and the positive electrode coated with the protective film is obtained after drying. The in-situ solidification liquid is injected into the assembled battery, and after standing, the electrolyte fully infiltrates the electrode / protective film and electrolyte / electrode interface, and polymerization is induced to form an integrated solid-state battery. In the application, the integrated battery structure avoids ensuring normal work by increasing a pressurizing mold; flexible contact is realized at each interface, and the interface impedance can be fully reduced. The application also provides a preparation method of the in-situ polymerization integrated solid-state battery, and the method is suitable for the existing lithium ion battery production process and equipment, and can be quickly cut in for batch production.

Description

Technical Field

[0001] This invention belongs to the field of all-solid-state battery technology, and particularly relates to an in-situ polymerized solid-state battery with integrated positive and negative electrodes and its preparation method. Background Technology

[0002] Solid-state batteries are widely regarded as the ultimate solution for next-generation power batteries due to their high safety and high energy density. However, the industrialization of solid-state batteries is not a simple process; the industry generally adopts a gradual strategy from "semi-solid" to "quasi-solid" and then to "all-solid." Currently, semi-solid-state batteries have become the main form of industrialization. The commercialization of all-solid-state batteries still faces two major challenges: firstly, gaps exist in the solid-solid contact between the solid electrolyte and the electrodes, leading to high interfacial resistance and affecting ion transport—this is the most critical technical bottleneck; secondly, the current cost of all-solid-state batteries is as high as $400-800 / kWh, 3-5 times that of liquid batteries, and new production processes also require huge equipment investments. Currently, the industry mainly uses three routes: sulfide, oxide, and polymer. Among them, the polymer route has the advantages of excellent processing performance, high compatibility with existing battery production processes, and relatively low cost. However, its complex process and low ionic conductivity remain significant challenges to commercialization.

[0003] CN110048158A proposes a method for preparing an in-situ polymerized bilayer polymer electrolyte membrane. This method involves in-situ polymerization of two different polymer monomers onto both sides of a porous membrane framework to prepare a bilayer polymer electrolyte membrane for assembling all-solid-state batteries. CN117276686B proposes a method for preparing a localized cationic in-situ polymerized solid-state battery. This method uses a pre-polymerized membrane prepared by cationic polymerization on a supporting polymer membrane as a separator. After assembly, an in-situ polymerization solution is injected, and cationic polymerization is carried out at room temperature to obtain an all-solid-state battery. CN108493486B proposes a... The preparation method of in-situ polymerized solid-state batteries uses a polypropylene film as a separator to assemble the battery. It uses LITFSI, LiNO3, dimethoxymethane, dioxolane, isoprene tetraacrylate, allyl hydroxyethyl ether, and initiator AIBN as electrolytes injected into the battery, followed by heating and polymerization to obtain a solid-state battery. The methods reported above all involve preparing a film outside the cell or assembling the battery using commercially available film materials, and then injecting a mixture containing polymerizable monomers and initiators for polymerization. The process of preparing the film outside the cell is complex, and the electrolyte-electrode interface impedance of batteries assembled using film materials is relatively high, which is detrimental to battery performance. Although CN114335716A does not use a separator and prepares an in-situ polymerized solid-state battery with a multilayer electrolyte structure through in-situ polymerization, it requires mixing pre-placed monomers with a slurry. This process introduces various chemically active substances, which may cause complex physicochemical reactions, thus affecting the performance of the slurry and increasing the difficulty of slurry preparation and subsequent processes. Summary of the Invention

[0004] Purpose of the invention: To address the technical problems of high interface impedance, poor process compatibility, and high cost in existing solid-state batteries, this invention provides an in-situ polymerized integrated solid-state battery and its preparation method. This invention uses in-situ polymerization to prepare an integrated battery, avoiding rigid contact at the interface, thereby improving interface impedance and cycle stability. At the same time, this method is compatible with existing lithium-ion battery production processes and equipment, allowing for rapid market entry and mass production.

[0005] Technical Solution: The present invention discloses an in-situ polymerized integrated solid-state battery. The battery adopts an integrated structure, which includes a positive electrode coated with a protective film, an in-situ polymerized electrolyte layer, and a negative electrode. The in-situ polymerized electrolyte layer is formed by initiating polymerization inside the cell with an in-situ curing liquid, and it bonds the positive electrode and the negative electrode coated with the protective film together. Furthermore, the protective film and the in-situ polymerized electrolyte layer, as well as the in-situ polymerized electrolyte layer and the negative electrode, form flexible and continuous contact interfaces. The three are tightly bonded into an inseparable whole through a polymerization reaction.

[0006] The protective film is formed by coating the positive electrode surface with a film-forming solution and then drying it, and includes a binder, a plasticizer, and a lithium salt.

[0007] The in-situ curing liquid includes a crosslinking agent, a polymerizing monomer, an initiator, and a lithium salt.

[0008] In some embodiments, the film-forming liquid contains 20-90 wt% binder, 1-60 wt% plasticizer, and 1-60 wt% lithium salt.

[0009] The in-situ curing liquid contains a crosslinking agent with a mass fraction of 0.1-60 wt%, a polymeric monomer with a mass fraction of 20-90 wt%, an initiator with a mass fraction of 0.001-20 wt%, and a lithium salt with a mass fraction of 1-60 wt%.

[0010] In some embodiments, the adhesive comprises one or more of polyvinylidene fluoride homopolymer and polyvinylidene fluoride copolymer;

[0011] The plasticizer includes one or more of the following: ester group, ether group, cyano group, and phosphorus-containing group.

[0012] The crosslinking agent includes one or more of acrylates, epoxy groups, isocyanates, mercapto groups, and cyano groups;

[0013] The polymerization monomers include one or more of the following: ester monomers, carbonate monomers, sulfone monomers, isocyanate monomers, amide monomers, nitrile monomers, and fluorinated monomers;

[0014] The initiator includes one or more of azo initiators, peroxide initiators, and organometallic compound initiators;

[0015] The lithium salt includes one or more of the following: inorganic halides, borates, imine salts, and carborane salts.

[0016] In some embodiments, the binder includes one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), and polyvinylidene fluoride-trifluoroethylene copolymer (TrFE). This type of binder is chosen because it possesses excellent chemical stability, thermal stability, and bonding properties, enabling the formation of a uniform and dense protective film on the positive electrode surface. Simultaneously, it exhibits good compatibility with the subsequent in-situ polymerized electrolyte layer, promoting interfacial fusion.

[0017] In some embodiments, the plasticizer includes one or more of vinylene carbonate (VC), ethylene carbonate (EC), dioctyl adipate (DOA), tetraethylene glycol dimethyl ether (TEGDME), polyethylene glycol dimethyl ether (PEGDME), crown ether, succinate (SN), adiponitrile (ADN), trimethyl phosphate (TMP), and hexaphosphoric triamine (HPT). The plasticizer improves the flowability and film-forming properties of the film-forming solution, while also reducing the crystallinity of the protective film, promoting the dissociation of lithium salts, and improving the transport efficiency of lithium ions in the protective film. Furthermore, some plasticizers also possess flame-retardant and interface-stabilizing functions.

[0018] In some embodiments, the crosslinking agent includes one or more of polyethylene glycol methacrylate (PEGMA), polyethylene glycol diacrylate (PEGDA), methyl methacrylate (MMA), phosphorus / nitrogen-containing flame-retardant acrylate monomers, polyethylene glycol (PEG), polyethylene oxide (PEO), isocyanurate derivatives, trimethylolpropane tris(3-mercaptopropionate) (TMPMP), pentaerythritol tetra-3-mercaptopropionate (PETMP), and polyacrylonitrile (PAN). The crosslinking agent can form a three-dimensional network structure during the polymerization reaction, improving the mechanical strength, thermal stability, and electrochemical stability of the in-situ polymerized electrolyte layer, while simultaneously enhancing the adhesion between the electrolyte layer and the protective film and the negative electrode, ensuring the stability of the integrated structure.

[0019] In some embodiments, the polymer monomers include methyl methacrylate (MMA), butyl methacrylate (BMA), vinyl acetate (VAc), 1,4-butanediol diacrylate (BDDA), 1,6-hexanediol diacrylate (HDDA), ethoxylated trimethylolpropane triacrylate (ETPTA), pentaerythritol triacrylate (PETA), pentaerythritol tetraacrylate (PET4A), high-functionality acrylates, diethyl terephthalate (DMT), dimethyl allyl diacrylate, diethyl allyl malonate, and vinylene carbonate. Esters (VC), ethylene ethylene carbonate (VEC), allyl methyl carbonate, methyl vinyl sulfone (MVS), ethyl vinyl sulfone (EVS), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isoflurone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), acrylamide (AM), N-methylmaleamide, N-ethylmaleamide, caprolactam, butyrolactam, acrylonitrile (AN), 1-cyclohexeneacetonitrile, hexafluorobutyl methacrylate (HFBMA), and trifluoroethyl methacrylate (TFEMA). The polymerizable monomers are the foundation for forming the in-situ polymerized electrolyte layer. Their structure and properties directly affect the ionic conductivity, mechanical strength, and electrochemical stability of the electrolyte layer. This invention selects various types of polymerizable monomers, allowing for formulation adjustments based on actual needs to optimize the electrolyte layer's performance.

[0020] In some embodiments, the initiator includes one or more of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), dimethyl azobisisobutyrate (AIBME), benzoyl peroxide (BPO), dicumyl peroxide (DCP), potassium persulfate (KPS), di-tert-butyl peroxide (DTBP), stannous octoate (Sn(Oct)2), stannous trifluoromethanesulfonate (Sn(OTf)2), tetrabutyl titanate (TBT), tetrabutyl zirconate (TBZ), tributyltin oxide (TBTO), trialkyltin alkoxides, and dialkyltin oxides. The initiator can decompose under specific conditions (such as heating, light exposure, etc.) to generate active free radicals or ions, initiating the polymerization reaction of the monomers. The type and amount of initiator must be strictly controlled to ensure a mild and uniform polymerization reaction, avoiding the formation of pores or defects in the electrolyte layer due to excessively rapid reaction rates.

[0021] In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) (LiBOB), lithium difluorophosphate (LiPO2F2), and lithium perchlorate (LiClO4). Lithium salts provide the lithium-ion source for the battery, and their degree of dissociation and ion migration rate directly affect the battery's electrochemical performance. This invention selects various lithium salts with high dissociation and high stability, which can be matched according to the system characteristics of the film-forming solution and the in-situ curing solution to ensure efficient lithium-ion transport throughout the battery system.

[0022] In some embodiments, the thickness of the protective film is 1 μm-1 mm, preferably 10 μm-500 μm; the thickness of the in-situ polymerized electrolyte layer is 5 μm-5 mm, preferably 20 μm-1 mm. If the protective film is too thin, it cannot provide effective protection and interface modification; if it is too thick, it will increase the resistance to lithium-ion transport. The thickness of the in-situ polymerized electrolyte layer needs to be adjusted according to the overall design and performance requirements of the battery to ensure that it can effectively isolate the positive and negative electrodes while ensuring rapid lithium-ion transport.

[0023] In some embodiments, the positive electrode is selected from one of the following: ternary cathode materials (such as NCM523, NCM622, NCM811, etc.), lithium iron phosphate cathode (LFP), lithium cobalt oxide cathode (LCO), and lithium manganese oxide cathode (LMO); the negative electrode is selected from one of the following: graphite negative electrode, silicon-based negative electrode (silicon-carbon composite negative electrode, silicon-oxygen composite negative electrode, etc.), lithium titanate negative electrode (LTO), and hard carbon negative electrode. The battery structure and preparation method of the present invention have no special limitations on the positive and negative electrode materials and are compatible with various existing commercial or research and development electrode materials, thus having wide applicability.

[0024] On the other hand, the present invention also discloses a method for preparing an in-situ polymerized integrated solid-state battery, comprising the following steps:

[0025] S1. Prepare a film-forming solution by coating the surface of the normally prepared positive electrode with the film-forming solution and drying it to obtain a positive electrode with a protective film.

[0026] S2. Assemble the positive electrode with the protective film from step S1 and the normally prepared negative electrode into a battery cell.

[0027] S3. Prepare an in-situ curing solution, inject it into the cell, and let it stand to initiate polymerization to obtain an integrated solid-state battery.

[0028] The film-forming liquid contains a binder, a plasticizer, and a lithium salt;

[0029] The in-situ curing solution contains a crosslinking agent, a polymerizing monomer, an initiator, and a lithium salt.

[0030] In some embodiments, the drying temperature in step S1 is 40-200 °C, the drying time is 1-240 hours, and the protective film thickness is 1 μm-1 mm.

[0031] In some embodiments, the settling time in step S3 is 1-120 hours; the polymerization initiation temperature is 10-100 °C; and the polymerization time is 1-240 hours.

[0032] Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) Excellent interface performance and significantly reduced impedance: This invention forms an integrated structure by coating a protective film on the surface of the positive electrode and then injecting an in-situ curing liquid for in-situ polymerization. The protective film and the surface of the positive electrode are tightly bonded through the coating and drying process. The in-situ curing liquid fully wets the protective film, the surface of the positive electrode and the surface of the negative electrode before polymerization. After polymerization, the in-situ polymerized electrolyte layer formed forms a flexible and continuous contact interface with the protective film and the negative electrode, which completely eliminates the gap between solid-solid contacts in traditional solid-state batteries, significantly reduces interface impedance, and improves ion transport efficiency and battery cycle stability.

[0034] (2) No additional pressure mold required, high structural stability: The integrated structure tightly bonds the positive electrode, the in-situ polymerized electrolyte layer and the negative electrode into an inseparable whole. The battery can be kept stable during charging and discharging without the need for an additional pressure mold, which simplifies the battery packaging and usage process and avoids problems such as electrode damage or electrolyte layer rupture caused by improper pressure.

[0035] (3) Compatible with existing production processes and easy to mass-produce: In the preparation process of this invention, the preparation of the positive electrode and the negative electrode adopts the conventional lithium-ion battery production process. The steps such as film coating, cell assembly, and in-situ curing liquid injection can all be realized by existing lithium-ion battery production equipment. There is no need to make large-scale modifications to the production line, which reduces the equipment investment cost and allows for rapid mass production. This solves the problem of poor compatibility of existing solid-state battery processes.

[0036] (4) The process is simple and controllable, and the cost advantage is obvious: This invention does not require the pre-preparation of electrolyte membrane outside the cell, nor does it require mixing of polymer monomers with electrode slurry, which simplifies the production process and reduces process control points; at the same time, the raw materials used are all commonly used materials in the battery industry, which are widely available and cost controllable, avoiding the use of rare precious metals or special customized materials, further reducing the production cost of batteries.

[0037] (5) Flexible material selection and wide applicability: This invention has no special restrictions on positive and negative electrode materials and is compatible with various electrode materials such as ternary materials, lithium iron phosphate, graphite, and silicon-based materials; the composition of the film-forming liquid and the in-situ curing liquid can be flexibly adjusted according to the battery performance requirements, which can adapt to the requirements of different application scenarios for battery energy density, rate performance, safety performance, etc., and has wide applicability. Attached Figure Description

[0038] Figure 1 This is a CV curve diagram of a conventional liquid lithium-ion battery.

[0039] Figure 2 Charge-discharge curves for a conventional liquid lithium-ion battery;

[0040] Figure 3 This is a CV curve diagram of the battery in Embodiment 1 of the present invention;

[0041] Figure 4 This is a charge-discharge curve of the battery in Embodiment 1 of the present invention;

[0042] Figure 5 This is a CV curve diagram of the battery in Embodiment 2 of the present invention;

[0043] Figure 6 This is a charge-discharge curve of the battery in Embodiment 2 of the present invention;

[0044] Figure 7 This is a CV curve of the battery in Embodiment 3 of the present invention;

[0045] Figure 8 This is a charge-discharge curve of the battery in Embodiment 3 of the present invention;

[0046] Figure 9 This is a CV curve of the battery in Embodiment 4 of the present invention;

[0047] Figure 10 This is a charge-discharge curve of the battery in Embodiment 4 of the present invention;

[0048] Figure 11 This is a CV curve of the battery in Embodiment 5 of the present invention;

[0049] Figure 12 This is a charge / discharge curve of the battery in Embodiment 5 of the present invention.

[0050] In the attached figures, the horizontal axis of the CV curve represents potential (V vs. Li⁺ / Li), and the vertical axis represents current (A); the horizontal axis of the charge-discharge curve represents capacity (mAh / g), and the vertical axis represents voltage (V). As can be seen from the figures, the CV curve of the in-situ polymerized integrated solid-state battery prepared in this invention exhibits symmetrical peaks and stable peak currents, indicating good electrochemical reversibility; the charge-discharge curves show stable plateaus and high capacity retention, demonstrating superior electrochemical performance compared to conventional liquid lithium-ion batteries. Detailed Implementation

[0051] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship shown, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0053] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0055] Example 1

[0056] (1) Dissolve 0.6g PVDF, 0.086g SN and 0.171g LiTFSI in 10g N-methylpyrrolidone to obtain a film-forming solution; coat the film-forming solution onto the surface of the positive electrode with a coating thickness of 100 μm, and bake at 80℃ for 24 h to obtain a positive electrode with a protective film.

[0057] (2) Dissolve 0.72 g LiTFSI and 0.297 g PEGDA into 2.97 g VEC, then add 0.0297 g AIBN and stir to dissolve to obtain in-situ curing solution.

[0058] (3) Assemble the positive electrode with protective film prepared in (1) and the negative electrode into a battery cell.

[0059] (4) Inject the in-situ curing liquid prepared in (2) into the cell in (3), let it stand for 8 h, heat it to 80℃ and keep it for 24 h to initiate polymerization, and obtain an in-situ polymerized integrated solid-state battery.

[0060] Example 2

[0061] (1) Dissolve 0.6g PVDF, 0.086g SN and 0.171g LiTFSI in 10g N-methylpyrrolidone to obtain a film-forming solution; coat the film-forming solution onto the surface of the positive electrode with a coating thickness of 75 μm, and bake at 80℃ for 48 h to obtain a positive electrode with a protective film.

[0062] (2) Dissolve 0.72 g LiTFSI and 0.0148 g PEO to 2.97 g VEC, then add 0.0297 g AIBN and stir to dissolve to obtain in-situ curing solution.

[0063] (3) Assemble the positive electrode with protective film prepared in (1) and the negative electrode into a battery cell.

[0064] (4) The in-situ curing liquid prepared in (2) is injected into the cell in (3), left to stand for 24 h, heated to 80°C and held for 48 h to initiate polymerization, and an in-situ polymerized integrated solid-state battery is obtained.

[0065] Example 3

[0066] (1) Dissolve 0.6g PVDF, 0.086g SN and 0.171g LiTFSI in 10g N-methylpyrrolidone to obtain a film-forming solution; coat the film-forming solution onto the surface of the positive electrode with a coating thickness of 75 μm, and bake at 80℃ for 48 h to obtain a positive electrode with a protective film.

[0067] (2) Dissolve 0.72 g LiTFSI and 0.0148 g PAN to 2.97 g VEC, then add 0.0297 g AIBN and stir to dissolve to obtain in-situ curing solution.

[0068] (3) Assemble the positive electrode with protective film prepared in (1) and the negative electrode into a battery cell.

[0069] (4) The in-situ curing liquid prepared in (2) is injected into the cell in (3), left to stand for 24 h, heated to 80°C and held for 48 h to initiate polymerization, and an in-situ polymerized integrated solid-state battery is obtained.

[0070] Example 4

[0071] (1) Dissolve 0.086g SN and 0.171g LiTFSI in 10g PVDF N-methylpyrrolidone solution (0.6% PVDF) to obtain film-forming solution; coat the film-forming solution onto the surface of the positive electrode with a coating thickness of 75 μm, and bake at 90℃ for 24 h to obtain a positive electrode with a protective film.

[0072] (2) Dissolve 0.725 g LiTFSI and 0.6 g PEGDA into 3 g AN, then add 0.015 g AIBN and stir to dissolve to obtain in-situ curing solution.

[0073] (3) Assemble the positive electrode with protective film prepared in (1) and the negative electrode into a battery cell.

[0074] (4) The in-situ curing liquid prepared in (2) is injected into the cell in (3) and left to stand at 25°C for 96 h. During the standing process, the electrolyte is slowly initiated to polymerize, and an in-situ polymerized integrated solid-state battery is obtained.

[0075] Example 5

[0076] (1) Dissolve 0.086g SN and 0.171g LiTFSI in 10g PVDF N-methylpyrrolidone solution (0.6% PVDF) to obtain film-forming solution; coat the film-forming solution onto the surface of the positive electrode with a coating thickness of 75 μm, and bake at 90℃ for 24 h to obtain a positive electrode with a protective film.

[0077] (2) Dissolve 0.879 g LiTFSI and 0.6 g PEGDA in 3 g mixed solvent (VEC to AN mass ratio is 1:1), then add 0.06 g AIBN and stir to dissolve to obtain in-situ curing solution.

[0078] (3) Assemble the positive electrode with protective film prepared in (1) and the negative electrode into a battery cell.

[0079] (4) The in-situ curing liquid prepared in (2) is injected into the cell in (3) and left to stand at 25°C for 96 h. During the standing process, the electrolyte is slowly initiated to polymerize, and an in-situ polymerized integrated solid-state battery is obtained.

[0080] Performance testing

[0081] Electrochemical performance tests were conducted on the in-situ polymerized integrated solid-state batteries prepared in Examples 1-5 above and on conventional liquid lithium-ion batteries (control group, using the same positive and negative electrodes, and the electrolyte being a 1 mol / L LiPF6 EC / DEC / DMC (volume ratio 1:1:1) solution). The test conditions are as follows:

[0082] 1. Cyclic voltammetry (CV) test: A three-electrode system was used, with lithium metal as the counter electrode and reference electrode. The scan voltage range was 2.0-4.3V, and the scan rate was 0.1mV / s.

[0083] 2. Charge and discharge test: The Blue Battery test system is used, with a charge and discharge voltage range of 2.8-4.3V and a current density of 0.1C.

[0084] The test results are shown in Figure 1-12, and the detailed analysis is as follows:

[0085] As can be seen from the CV curves (Figures 1, 3, 5, 7, 9, 11), the CV curves of the conventional liquid lithium-ion batteries in the control group have a wider peak shape and a relatively smaller peak current, indicating that their interface impedance is larger. In contrast, the CV curves of the solid-state batteries prepared in Examples 1-5 of this invention have a sharper and more symmetrical peak shape, and the peak current is significantly greater than that of the control group, indicating that the integrated structure of this invention effectively reduces the interface impedance and improves the electrochemical reversibility.

[0086] As can be seen from the charge-discharge curves (Figures 2, 4, 6, 8, 10, and 12), the charge-discharge platform of the conventional liquid lithium-ion battery in the control group is not stable enough, with an initial discharge specific capacity of approximately 150 mAh / g. In contrast, the solid-state batteries prepared in Examples 1-5 of this invention have a stable charge-discharge platform, with initial discharge specific capacities all above 160 mAh / g. Among them, the initial discharge specific capacity of Example 5 reaches 175 mAh / g, and the capacity retention rate is excellent. This indicates that the battery structure and preparation method of this invention can significantly improve the energy density and cycle stability of the battery.

[0087] Furthermore, the solid-state battery prepared in Example 1 was subjected to cycle life testing. Under 0.1C charge-discharge conditions, the capacity retention rate was 92.5% after 100 cycles, which is much higher than the 83.2% of the conventional liquid lithium-ion battery in the control group, further demonstrating that the battery of the present invention has excellent cycle stability.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An in-situ polymerized integrated solid-state battery, characterized in that: The battery adopts an integrated structure, which includes a positive electrode coated with a protective film, an in-situ polymerized electrolyte layer, and a negative electrode. The in-situ polymerized electrolyte layer is formed by initiating polymerization inside the cell with an in-situ curing liquid, and it bonds the positive and negative electrodes coated with the protective film together. The protective film is made of a film-forming liquid, which includes an adhesive, a plasticizer, and a lithium salt; The in-situ curing liquid includes a crosslinking agent, a polymerizing monomer, an initiator, and a lithium salt.

2. The in-situ polymerized integrated solid-state battery according to claim 1, characterized in that: The film-forming solution contains 20-90 wt% binder, 1-60 wt% plasticizer, and 1-60 wt% lithium salt. The in-situ curing liquid contains a crosslinking agent with a mass fraction of 0.1-60 wt%, a polymeric monomer with a mass fraction of 20-90 wt%, an initiator with a mass fraction of 0.001-20 wt%, and a lithium salt with a mass fraction of 1-60 wt%.

3. The in-situ polymerized integrated solid-state battery according to claim 1, characterized in that: The adhesive includes one or more of polyvinylidene fluoride homopolymer and polyvinylidene fluoride copolymer; The plasticizer includes one or more of the following: ester group, ether group, cyano group, and phosphorus-containing group. The crosslinking agent includes one or more of acrylates, epoxy groups, isocyanates, mercapto groups, and cyano groups; The polymerization monomers include one or more of the following: ester monomers, carbonate monomers, sulfone monomers, isocyanate monomers, amide monomers, nitrile monomers, and fluorinated monomers; The initiator includes one or more of azo initiators, peroxide initiators, and organometallic compound initiators; The lithium salt includes one or more of the following: inorganic halides, borates, imine salts, and carborane salts.

4. The in-situ polymerized integrated solid-state battery according to claim 3, characterized in that: The adhesive includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, and polyvinylidene fluoride-trifluoroethylene copolymer.

5. The in-situ polymerized integrated solid-state battery according to claim 3, characterized in that: The plasticizer includes one or more of the following: vinylene carbonate, ethylene carbonate, dioctyl adipate, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, crown ether, succinate, adiponitrile, trimethyl phosphate, and hexaphosphoric triamine.

6. The in-situ polymerized integrated solid-state battery according to claim 3, characterized in that: The crosslinking agent includes one or more of polyethylene glycol methacrylate, polyethylene glycol diacrylate, methyl methacrylate, phosphorus / nitrogen flame retardant acrylate monomers, polyethylene glycol, polyethylene oxide, isocyanurate derivatives, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra-3-mercaptopropionate, and polyacrylonitrile.

7. The in-situ polymerized integrated solid-state battery according to claim 3, characterized in that: The polymer monomers include methyl methacrylate, butyl methacrylate, vinyl acetate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, high-functionality acrylates, diethyl terephthalate, dimethyl allyl diacrylate, diethyl allyl malonate, vinylene carbonate, ethylene ethylene carbonate, methyl allyl carbonate, methyl vinyl sulfone, ethyl vinyl sulfone, toluene diisocyanate, diphenylmethane diisocyanate, isoflurane diisocyanate, hexamethylene diisocyanate, acrylamide, N-methylmaleamide, N-ethylmaleamide, caprolactam, butyrolactam, acrylonitrile, 1-cyclohexeneacetonitrile, hexafluorobutyl methacrylate, and trifluoroethyl methacrylate.

8. The in-situ polymerized integrated solid-state battery according to claim 3, characterized in that: The initiator includes one or more of the following: azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, dicumyl peroxide, potassium persulfate, di-tert-butyl peroxide, stannous octoate, tin trifluoromethanesulfonate, tetrabutyl titanate, tetrabutyl zirconate, tributyltin oxide, trialkyltin alkoxide, and dialkyltin oxide.

9. The in-situ polymerized integrated solid-state battery according to claim 3, characterized in that: The lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium difluorophosphate, and lithium perchlorate.

10. A method for preparing an in-situ polymerized integrated solid-state battery as described in any one of claims 1-9, characterized in that: Includes the following steps: S1. Prepare a film-forming solution by coating the surface of the normally prepared positive electrode with the film-forming solution and drying it to obtain a positive electrode with a protective film. S2. Assemble the positive electrode with the protective film from step S1 and the normally prepared negative electrode into a battery cell. S3. Prepare an in-situ curing solution, inject it into the cell, and let it stand to initiate polymerization to obtain an integrated solid-state battery. The film-forming liquid contains a binder, a plasticizer, and a lithium salt; The in-situ curing solution contains a crosslinking agent, a polymerizing monomer, an initiator, and a lithium salt.

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