Composite solid electrolyte and preparation method and application thereof

Abstract

The invention discloses a composite solid electrolyte and a preparation method and application thereof, and relates to the technical field of lithium metal batteries and solid electrolyte materials. The composite solid electrolyte comprises a three-dimensional porous oxide electrolyte framework and a PEGA-based electrolyte which is subjected to in-situ polymerization in the electrolyte framework; the three-dimensional porous oxide electrolyte framework forms a continuous lithium ion transmission channel, so that the agglomeration problem of oxide electrolyte particles is solved; a three-dimensional porous oxide electrolyte framework is directly constructed on a positive electrode, and PEGA-based electrolyte is polymerized in situ in the three-dimensional porous oxide electrolyte framework, so that high ionic conductivity, high lithium ion transference number and excellent cycle stability are realized; the prepared composite solid electrolyte can also be used as a diaphragm, and the design can reduce impedance introduced by an inert diaphragm and improve the overall battery performance; and the preparation process is simplified, so that the preparation method is compatible with the existing lithium ion battery production process and has industrialization potential.

Description

Technical Field

[0001] This invention relates to the field of lithium metal battery and solid electrolyte material technology, and more specifically, to a composite solid electrolyte, its preparation method and application. Background Technology

[0002] Currently, lithium-ion batteries (LIBs) are widely used in electric vehicles and energy storage systems, but the liquid organic electrolytes they use pose safety hazards such as flammability and leakage, and also have limited energy density. Solid-state electrolytes (SEs), due to their non-flammability and high stability, are considered an important direction for the development of next-generation batteries.

[0003] In existing technologies, solid electrolytes are mainly classified into organic types (such as PEO-based), inorganic types (such as LATP and LLZO), and composite types (CSEs). Among them: Organic electrolytes (such as PEO and PEGA) have flexibility and low interfacial impedance, but low ionic conductivity and insufficient mechanical strength, making it difficult to suppress lithium dendrites.

[0004] Inorganic electrolytes (such as NASICON-type LATP) have high ionic conductivity and mechanical strength, but they are brittle and unstable at the lithium metal interface.

[0005] Composite electrolytes (CSEs) combine the advantages of both inorganic particles and organic matrices. However, in existing methods, LATP particles tend to aggregate in polymer matrices, leading to discontinuous ion transport and limiting performance.

[0006] Existing studies have attempted to construct three-dimensional porous inorganic frameworks (such as electrospun LLZO nanofibers and sol-gel LLTO skeletons), but these methods are complex, difficult to scale up, and have poor reproducibility.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The purpose of this invention is to provide a composite solid electrolyte, its preparation method, and its application, so as to solve or improve the above-mentioned technical problems.

[0009] This invention is implemented as follows: In a first aspect, embodiments of the present invention provide a composite solid electrolyte comprising a three-dimensional porous oxide electrolyte framework and a PEGA-based electrolyte polymerized in situ within the electrolyte framework; By mass percentage, the electrolyte framework comprises the following components: 10wt%-35wt% of oxide-type electrolyte, 60wt%-85wt% of solvent, 2wt%-8wt% of binder and 0.5wt%-5wt% of lithium salt; The PEGA-based electrolyte comprises the following components: 30wt%-55wt% polyethylene glycol methyl ether acrylate, 5wt%-20wt% crosslinking agent, 10wt%-30wt% channel optimizer, 5wt%-20wt% plasticizer, 1wt%-5wt% interface stabilizer, 10wt%-25wt% lithium salt, and 0.5wt%-3wt% thermal initiator.

[0010] Secondly, embodiments of the present invention provide a method for preparing a composite solid electrolyte as described above, comprising the following steps: Preparation of electrolyte framework: The oxide electrolyte, solvent, binder and lithium salt are mixed in proportion to prepare a slurry; the slurry is coated on the surface of the base film or positive electrode to prepare the electrolyte framework; Preparation of PEGA-based electrolyte: PEGA-based electrolyte is prepared by mixing polyethylene glycol methyl ether acrylate, crosslinking agent, channel optimizer, plasticizer, interface stabilizer, lithium salt and thermal initiator in proportion. A composite solid electrolyte was prepared by injecting a PEGA-based electrolyte into an electrolyte framework and reacting it at a temperature of 55℃-65℃ for 2.5h-3.5h.

[0011] Thirdly, embodiments of the present invention provide a lithium-ion battery, comprising a composite solid electrolyte as described above or a composite solid electrolyte prepared by the aforementioned preparation method, a positive electrode material, and a lithium metal sheet. The cathode material comprises, by mass percentage, 75wt%-85wt% LiFePO4, 8wt%-12wt% conductive agent, and 8wt%-12wt% binder.

[0012] Fourthly, embodiments of the present invention provide an application of the lithium-ion battery as described above in the fields of electric vehicles and energy storage systems.

[0013] The present invention has the following beneficial effects: The composite solid electrolyte, its preparation method, and its application provided in the embodiments of the present invention have the following characteristics: (1) A composite solid electrolyte that can be prepared on a large scale is provided. By directly constructing a three-dimensional porous oxide electrolyte framework on the positive electrode and polymerizing PEGA-based electrolyte in situ therein, high ionic conductivity, high lithium-ion transference number and excellent cycle stability are achieved. (2) The three-dimensional porous oxide electrolyte framework forms a continuous lithium-ion transport channel, which solves the problem of agglomeration of oxide electrolyte particles; (3) The composite solid electrolyte can also serve as a separator. This design can reduce the impedance introduced by the inert separator and improve the overall battery performance. (4) The simplified preparation process makes it compatible with existing lithium-ion battery production processes and has industrialization potential. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the structure of a composite solid electrolyte; Figure 2 The image shows the SEM image of the composite solid electrolyte prepared in Example 1. Figure 3 The image shows the elemental mapping of the cross-sectional SEM image of the composite solid electrolyte prepared in Example 1, corresponding to the energy dispersive spectroscopy (EDS) analysis. Figure 4 The results are from the cycle performance test of the full battery. Figure 5 These are the results of electrochemical impedance spectroscopy. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0017] The composite solid electrolyte provided in this invention combines the high ion conductivity of a three-dimensional LATP framework with the flexibility of a polymer matrix, forming a continuous lithium-ion transport network while avoiding the aggregation problem of inorganic particles in the polymer matrix. Its simplified preparation process makes it compatible with existing lithium-ion battery manufacturing processes, giving it industrialization potential. Specific implementation methods are as follows: In a first aspect, embodiments of the present invention provide a composite solid electrolyte comprising a three-dimensional porous oxide electrolyte framework and a PEGA-based electrolyte polymerized in situ within the electrolyte framework; By mass percentage, the electrolyte framework comprises the following components: 10wt%-35wt% of oxide-type electrolyte, 60wt%-85wt% of solvent, 2wt%-8wt% of binder and 0.5wt%-5wt% of lithium salt; The PEGA-based electrolyte comprises the following components: 30wt%-55wt% polyethylene glycol methyl ether acrylate, 5wt%-20wt% crosslinking agent, 10wt%-30wt% channel optimizer, 5wt%-20wt% plasticizer, 1wt%-5wt% interface stabilizer, 10wt%-25wt% lithium salt, and 0.5wt%-3wt% thermal initiator.

[0018] It should be noted that the design concept of the electrolyte framework also serving as a separator reduces the impedance introduced by the inert separator, improving overall battery performance; it also possesses good mechanical strength and provides continuous ion transport channels. Specifically, the oxide-type electrolyte used exists in a three-dimensional framework form, providing continuous ion channels, which is superior to traditional particle-filled CSEs.

[0019] A composite solid electrolyte exhibiting high ionic conductivity, high lithium-ion transference number, and excellent cycle stability was successfully prepared by in-situ polymerization of PEGA-based electrolyte within a three-dimensional porous oxide electrolyte framework supported by the cathode. The prepared composite solid electrolyte possesses the following characteristics: (1) High performance indicators: room temperature ionic conductivity reaches 0.22 mS·cm -1 (1) The lithium-ion transference number is 0.60, which is much higher than that of traditional PEO-based electrolytes; (2) Strong interface stability: FEC and TMU optimize the interface to form a stable SEI rich in LiF and Li2O, which suppresses lithium dendrites; (3) Simple and scalable process: PVDF / NMP slurry coating and thermal polymerization are adopted, and the process is compatible with existing lithium-ion battery production lines; (4) Dual-functional framework: The oxide electrolyte framework is both an ion conductor and a separator, which reduces interface impedance.

[0020] In an optional embodiment, the D of the oxide-type electrolyte 50 The wavelength range is 200nm-800nm, and it is selected from LATP (Li 1.3 Al 0.3 Ti 1.7 (PO4)3), LAGP (Li 1.5 Al 0.5 Ge 1.5 (PO4)3), LiTi2(PO4)3 and LLZO (Li7La3Zr2O) 12 At least one of the following. Oxide electrolytes provide high ionic conductivity and mechanical strength to the electrolyte framework.

[0021] It should be noted that the LATP (Li) used in the implementation method 1.3 Al 0.3 Ti 1.7 (PO4)3) belongs to the high-purity NASICON type.

[0022] In an optional embodiment, the solvent is selected from at least one of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), acetone, and tetrahydrofuran (THF); the solvent is used to dissolve the binder, lithium salt, and disperse the oxide-type electrolyte. The purity of NMP is >99%.

[0023] And / or, the binder is selected from at least one of polyvinylidene fluoride (PVDF), PVDF-HFP, polyacrylonitrile (PAN) and PMMA; the binder can ensure the dispersion and film formation of oxide-type electrolyte particles in the slurry.

[0024] And / or, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(fluorooxalateborate) (LiDFOB), LiClO4, and LiPF6. The lithium salt is used to provide migratable lithium ions.

[0025] In an optional embodiment, the molecular weight of polyethylene glycol methyl ether acrylate (PEGMEA) is 200-2000; PEGMEA serves as the polymer electrolyte matrix, providing it with flexibility and good lithium salt solubility.

[0026] And / or, the crosslinking agent is polyethylene glycol diacrylate (PEGDA), with a molecular weight of 400-2000. PEGDA is used to enhance the stability of the polymer network.

[0027] During the polymerization reaction, if the amount of PEGDA is high, the material will be hard and brittle, with a low swelling rate and poor permeability. If the crosslinking density is too high, it may cause large internal stress during polymerization, or even cracking. If the amount of PEGMEA is high, the material will be soft and elastic with a high swelling rate. If the proportion of PEGMEA is too high and the amount of PEGDA is too low, it may lead to insufficient crosslinking, forming a weak gel with very poor mechanical strength, or even failing to form a stable three-dimensional network (dissolving or excessive swelling and disintegrating).

[0028] In an optional embodiment, the channel optimizer is selected from at least one of tetrahydrofurfuryl acrylate (THFA), cyclohexyl methacrylate (CHMA), and isobornyl acrylate (IBOA); the channel optimizer is beneficial for improving lithium-ion transport channels and reducing polymer crystallinity.

[0029] And / or, the plasticizer is selected from at least one of tetramethylurea (TMU), ethylene carbonate (EC), propylene carbonate (PC), 1,2-dimethoxyethane (DME), and NMP derivatives; the plasticizer is used to reinforce Li + It improves the solubility and increases the ionic conductivity.

[0030] The interface stabilizer is selected from at least one of fluoroethylene carbonate (FEC), ethylene carbonate (VC), and lithium oxalate borate (LiBOB); it is used to improve the interface stability of lithium anodes.

[0031] And / or, the thermal initiator is azobisisobutyronitrile (AIBN), which initiates free radical polymerization at a temperature of 55℃-65℃ to prepare PEGA-based electrolyte.

[0032] Secondly, embodiments of the present invention provide a method for preparing a composite solid electrolyte as described above, comprising the following steps: Preparation of electrolyte framework: The oxide electrolyte, solvent, binder and lithium salt are mixed in proportion to prepare a slurry; the slurry is coated on the surface of the base film or positive electrode to prepare the electrolyte framework; Preparation of PEGA-based electrolyte: PEGA-based electrolyte is prepared by mixing polyethylene glycol methyl ether acrylate, crosslinking agent, channel optimizer, plasticizer, interface stabilizer, lithium salt and thermal initiator in proportion. A composite solid electrolyte was prepared by injecting a PEGA-based electrolyte into an electrolyte framework and reacting it at a temperature of 55℃-65℃ for 2.5h-3.5h.

[0033] It should be noted that stirring was used during the preparation of the electrolyte framework to ensure complete dissolution of all substances and a more thorough reaction. The specific preparation process is as follows: First, 2wt%-8wt% of binder and 60wt%-85wt% of solvent are mixed in a specific ratio and stirred at 1200rpm-1800rpm until completely dissolved. The stirring time is adjusted according to the actual amount of material being processed. Then, 0.5wt%-5wt% of lithium salt is added and stirred until uniformly dissolved. Next, 10wt%-35wt% of oxide-type electrolyte is added. Through auxiliary stirring and ultrasonic treatment, the oxide-type electrolyte is evenly distributed in the solution, finally obtaining a stable slurry.

[0034] The slurry was uniformly coated on the surface of the substrate membrane and dried at 55℃-65℃ for 10h-13h. As the solvent evaporated, a three-dimensional porous electrolyte framework with a diameter of 25μm-35μm and a pore size of 0.7μm-1.5μm was formed.

[0035] The preparation of PEGA-based electrolytes specifically includes the following process: 30wt%-55wt% of polyethylene glycol methyl ether acrylate as the matrix, 5wt%-20wt% of polyethylene glycol diacrylate as the crosslinking agent, and 10wt%-30wt% of channel optimizer, 5wt%-20wt% of plasticizer, 1wt%-5wt% of interface stabilizer and 10wt%-25wt% of lithium salt were mixed and stirred under assisted stirring at 1000 rpm-1500 rpm and ultrasonically dispersed to ensure uniformity of the system. Then, 0.5wt%-3wt% of thermal initiator was added to obtain PEGA-based electrolyte.

[0036] A PEGA-based electrolyte is injected into an electrolyte framework and allowed to stand for a period of time to ensure full penetration into the pores of the electrolyte framework. Then, a thermal polymerization reaction is carried out to obtain a composite solid electrolyte. In this process, the electrolyte framework is completely immersed in the PEGA-based electrolyte system.

[0037] It should be noted that the prepared composite solid electrolyte is an amorphous polymer-ceramic composite solid electrolyte.

[0038] In an optional embodiment, the porosity of the base membrane is 40%-90% and the thickness is 5μm-30μm; it is selected from any one of cellulose membrane (CM), polyethylene membrane (PE), polypropylene membrane (PP) and polyimide membrane (PI); And / or, the positive electrode is selected from any one of LiFePO4, LiCoO2, LiNiO2, NCM / NCA and LiMn2O4.

[0039] In an optional embodiment, before obtaining the electrolyte framework, the process further includes drying at a temperature of 55°C-65°C for 10-13 hours. The obtained electrolyte framework has a thickness of 25μm-35μm and a pore size of 0.7μm-1.5μm.

[0040] Thirdly, embodiments of the present invention provide a lithium-ion battery, comprising a composite solid electrolyte as described above or a composite solid electrolyte prepared by the aforementioned preparation method, a positive electrode material, and a lithium metal sheet. The cathode material comprises, by mass percentage, 75wt%-85wt% LiFePO4, 8wt%-12wt% conductive agent, and 8wt%-12wt% binder.

[0041] In an optional embodiment, carbon black is used as the conductive agent and PVDF is used as the binder; in other embodiments of the present invention, the types of conductive agent and binder can be reasonably replaced according to actual needs.

[0042] In an optional implementation, the assembly process of the lithium-ion battery is as follows: The positive electrode material, carbon black, and PVDF were mixed and ground into a slurry at a mass ratio of 80:10:10. The slurry was then uniformly coated onto an aluminum foil current collector. After air drying at 55℃-65℃ and vacuum drying at 110℃-130℃, the positive electrode sheet, denoted as LFP, was obtained. The active material loading of the positive electrode sheet was approximately 2.56 mg·cm³. -2 In other embodiments of the present invention, the amount of raw materials used in the slurry varies, resulting in differences in the active material of the final positive electrode sheet. The specific amount should be adjusted according to actual needs.

[0043] Then, using lithium metal sheets as the negative electrode, and composite solid electrolyte / separator, a CR2032 coin cell is assembled.

[0044] It should be noted that the composite solid electrolyte prepared by this invention can also serve as a separator. This design can reduce the impedance introduced by the inert separator and improve the overall battery performance.

[0045] Fourthly, embodiments of the present invention provide an application of the lithium-ion battery as described above in the fields of electric vehicles and energy storage systems.

[0046] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0047] Example 1 This embodiment provides a composite solid electrolyte, which is prepared by the following steps: (1) Preparation of electrolyte framework Mix 25 wt% of the binder polyvinylidene fluoride (PVDF) and 75 wt% of the solvent N-methylpyrrolidone (NMP) at 1200-1800 rpm until completely dissolved. Adjust the stirring time according to the actual amount of material being processed. Then add 2 wt% of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and continue stirring until homogeneous. Finally, add 18 wt% of the oxide electrolyte LATP (Li... 1.3 Al 0.3 Ti 1.7 (PO4)3, high-purity NASICON type, D 50 =500 nm), through auxiliary stirring and ultrasonic treatment, the oxide electrolyte is uniformly distributed in the solution, and finally a stable slurry is obtained.

[0048] The slurry was uniformly coated on the surface of a cellulose membrane and dried at 60°C for 12 hours. As the solvent NMP evaporated, a three-dimensional porous electrolyte framework with a diameter of 30 μm and a pore size of 1 μm was formed, denoted as p-LATP.

[0049] (2) Preparation of PEGA-based electrolyte 40 wt% polyethylene glycol methyl ether acrylate (PEGMEA, molecular weight 500) was used as the matrix, 10 wt% polyethylene glycol diacrylate (PEGDA, molecular weight 400) was used as the crosslinking agent, and mixed with 20 wt% channel optimizer tetrahydrofurfuryl acrylate (THFA), 10 wt% plasticizer tetramethylurea (TMU), 3 wt% interface stabilizer fluoroethylene carbonate (FEC), and 15 wt% lithium salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The mixture was then stirred at 1200 rpm and ultrasonically dispersed to ensure uniformity. Subsequently, 2 wt% thermal initiator azobisisobutyronitrile (AIBN) was added to obtain the PEGA-based electrolyte, denoted as PPTTLF electrolyte.

[0050] (3) Preparation of composite solid electrolyte The PPTTLF electrolyte obtained in step (2) was injected into the three-dimensional porous LATP framework obtained in step (1) and allowed to stand for a period of time to ensure that it fully penetrated into the pores. Then, a thermal polymerization reaction was carried out at 60°C for 3 hours to obtain the composite solid electrolyte, denoted as PPTTLF@p-LATP. The electrolyte framework was completely immersed in the PEGA-based electrolyte system. A schematic diagram of the composite solid electrolyte structure is shown below. Figure 1 .

[0051] Example 2 This embodiment provides a composite solid electrolyte, the preparation steps of which are the same as those in Example 1, the only difference being: (1) Preparation of electrolyte framework The electrolyte framework contained 8 wt% PVDF, 67 wt% NMP, and 25 wt% LATP, with no LiTFSI added.

[0052] Example 3 This embodiment provides a composite solid electrolyte, the preparation steps of which are the same as those in Example 1, the only difference being: (2) Preparation of PEGA-based electrolyte The PEGA-based electrolyte contains 30 wt% PEGMEA, 20 wt% PEGDA, 10 wt% THFA, 10 wt% TMU, 25 wt% LiTFSI, 5 wt% FEC, and 3 wt% AIBN.

[0053] Example 4 This embodiment provides a composite solid electrolyte, the preparation steps of which are the same as those in Example 1, the only difference being: (2) Preparation of PEGA-based electrolyte The PEGA-based electrolyte contains 25 wt% LiTFSI and no other lithium salts or interface stabilizers are added.

[0054] Example 5 This embodiment provides a composite solid electrolyte, the preparation steps of which are the same as those in Example 1, the only difference being: (2) Preparation of PEGA-based electrolyte No interface stabilizers were added to the PEGA-based electrolyte. The raw material formulation includes the following: PEGMEA 45 wt%, PEGDA 10 wt%, THFA 20 wt%, TMU 15 wt%, LiTFSI 10 wt% and AIBN2 wt%.

[0055] Test Example 1 This test example uses the composite solid electrolyte prepared in Example 1 as an example for SEM morphology testing and analysis and EDS analysis. The SEM morphology testing and analysis are shown in [link to SEM analysis]. Figure 2 Energy dispersive spectroscopy (EDS) analysis can be found in [link to EDS analysis]. Figure 3 .

[0056] from Figure 2 It can be seen that the p-LATP (three-dimensional porous electrolyte framework) formed by NMP volatilization has uniform and numerous pores with a pore size of approximately 1 μm, which is conducive to the permeation of PPTTLF monomer precursors. The dense fibrous structure of the positive electrode LFP provides tight support for p-LATP. At the same time, the thickness of p-LATP is approximately 30 μm, which is competitive for high-energy LMBs.

[0057] from Figure 3 It can be seen that the LFP-supported p-LATP exhibits a distinct layered structure, and the Fe and Ti elements in the corresponding layers of the LFP-supported p-LATP are relatively uniformly distributed. This proves that the p-LATP and LFP cathode have excellent structural stability and integrity during the preparation process.

[0058] Test Example 2 This test example uses the composite solid electrolyte prepared in Example 1 as an example to assemble a battery and conduct performance tests.

[0059] The battery assembly process is as follows: During battery assembly, the positive electrode is prepared by mixing and grinding LiFePO4, carbon black, and PVDF in a mass ratio of 80:10:10 to form a slurry. This slurry is then uniformly coated onto an aluminum foil current collector. After air drying at 60 ℃ and vacuum drying at 120 ℃ for 12 hours, an active material loading of approximately 2.56 mg·cm³ is obtained. -2The positive electrode is a lithium metal sheet. A composite solid electrolyte is used to assemble a CR2032 coin cell.

[0060] In the performance testing, electrochemical impedance spectroscopy (EIS) was performed as follows: Using a CHI650D electrochemical workstation, the EIS curves of Li / Li before and after polarization were calculated in the frequency range of 1 MHz to 0.1 Hz to obtain the CSE interfacial resistance (R0) before and after the 10 mV potentiostatic chronoamperometry test; the test results are shown below. Figure 4 .

[0061] from Figure 4 It can be seen that the composite solid electrolyte prepared in Example 1 has an ionic conductivity of 0.22 mS·cm at room temperature. -1 By applying a 10 mV bias voltage to a Li / CSE / Li symmetric cell and calculating the interface impedance before and after EIS, the lithium-ion transference number was found to be 0.60.

[0062] The linear scan voltammetry test is as follows: the scan rate is 1 mV·s. -1 The scanning range was 2.5 V-6 V; the test results showed that the electrochemical stability window of the composite solid electrolyte prepared in Example 1 could reach 4.5 V.

[0063] The cycle performance was tested as follows: at 0.05 mA·cm -2 Constant current cycling tests of Li / CSEs / Li symmetric cells were performed on a LAND CT2002A battery tester. The current was 0.05 mA·cm⁻¹ at room temperature. -2 @ 0.05 mA·h·cm -2 and 0.1 mA·cm -2 @ 0.1 mA·h·cm -2 Test results are shown below. Figure 5 .

[0064] from Figure 5 It can be seen that the Li / Li symmetric cell at 0.1 mA·cm -2 It can cycle stably for 1645 hours without significant increase in voltage polarization; the initial capacity of the Li / LFP full cell at 0.5C rate is 146.7 mAh·g. -1 After 300 cycles, the capacity retention rate is still 96.9%, and after 500 cycles, the retention rate is 85.8%, with a coulomb efficiency of approximately 99.5%.

[0065] Test Example 3 This test example performs performance tests on the composite solid electrolytes prepared in Examples 1-5. The relevant data are shown in Table 1. The test items and corresponding test methods are as follows: Thickness: Sample thickness is typically measured using a digital micrometer or a non-contact optical profilometer. Before testing, the sample must be equilibrated under standard environmental conditions (e.g., 23°C, 50%RH) to avoid the influence of environmental factors. For solid electrolytes, multiple measurements should be taken at different locations, and the average value and standard deviation recorded. If an optical profilometer is used, a certain area can be scanned to obtain a thickness distribution map, thereby evaluating thickness uniformity.

[0066] Room temperature ionic conductivity: Ionic conductivity is determined by electrochemical impedance spectroscopy (EIS). Typically, the electrolyte sample is pressed into a disc, sandwiched between stainless steel blocking electrodes, and a small AC perturbation (e.g., 5–10 mV) is applied at room temperature, covering a frequency range from 1 MHz to 0.1 Hz. The resistance value is obtained from the real intercept of the Nyquist plot. Combined with sample thickness With area Calculate conductivity The results are expressed in S / m or mS / cm.

[0067] Interface impedance: Using a symmetrical battery structure (such as Li|electrolyte|Li), EIS testing is performed after the battery has been left to stand at a constant temperature for a period of time. The resistance corresponding to the high-frequency semicircle in the Nyquist plot is the interface impedance, which is usually normalized to the area resistance. ).

[0068] Porosity: determined by solvent absorption method. First, weigh the dried sample. Then immerse it in a suitable solvent until saturated, wipe off the surface solvent, and weigh the wet mass. According to the formula Calculate the porosity, where Solvent density, This represents the sample volume.

[0069] 1C Initial Capacity (mAh / g, NCM811): Charge and discharge tests were performed at a 1C current within a specified voltage window (e.g., 2.8–4.3 V). Charging was performed in constant current / constant voltage mode, and discharging in constant current mode. The initial discharge capacity was recorded, and the specific capacity (mAh / g) was calculated based on the mass of the positive electrode active material.

[0070] 0.2C→1C rate retention rate (%): First, discharge at a 0.2C current to obtain the reference capacity. Then discharge with a 1C current to obtain the capacity. The formula for calculating the leverage retention rate is as follows: This indicator reflects the material's kinetic properties and ion transport capabilities at high magnification.

[0071] Capacity retention rate (%) after 200 charge-discharge cycles at 1C at 25 ℃: The capacity of the first cycle was recorded after 200 charge-discharge cycles at 1C at room temperature. With the capacity of the 200th cycle The formula for calculating capacity retention is as follows: This test reflects the cycling stability and lifespan characteristics of materials and is an important indicator for evaluating the long-term performance of batteries.

[0072] Penetration / Short Circuit Suppression: The penetration test is typically conducted under full charge conditions, where a steel needle is used to pierce the battery cell at a specified speed, and the occurrence of fire, explosion, or casing rupture is observed. The short circuit test monitors the temperature and voltage changes of the battery cell under external short circuit conditions. If the battery cell does not exhibit thermal runaway during the test, it indicates good suppression capability.

[0073] Self-discharge: Self-discharge is evaluated by the capacity loss during rest. After fully charging the cell, it is left to rest at room temperature for a certain period of time (e.g., 7–14 days), and then a discharge test is performed to compare the capacity difference before and after resting. The self-discharge rate can be calculated as the percentage of capacity loss relative to the initial capacity. This indicator reflects the energy retention capability of the cell during the resting process.

[0074] Table 1 Performance Data

[0075] As shown in Table 1, Example 1 exhibits the best performance in terms of room temperature conductivity, cycle retention, and interface impedance, with a capacity retention of 92% and an interface impedance of only 120 Ω·cm. 2 Compared to Examples 2–5, Example 1 showed an increase in ionic conductivity of approximately 1.9–4.4 times at room temperature, a decrease in interfacial impedance of 40%–60%, and an increase in capacity retention of 10–24 percentage points after 200 cycles.

[0076] In summary, the composite solid electrolyte preparation method provided by this invention employs slurry coating and thermal polymerization, a process compatible with existing lithium-ion battery production lines. Based on a three-dimensional porous oxide electrolyte framework supported by the positive electrode, pores are formed specifically through the drying of PVDF / NMP slurry, avoiding complex processes and enabling large-scale production. The three-dimensional framework provides continuous ion channels, preventing particle agglomeration, which is superior to traditional particle-filled CSEs. In-situ polymerization of PEGA-based electrolyte within the oxide electrolyte framework forms an amorphous polymer-ceramic composite structure, possessing both high ionic conductivity and mechanical strength. The resulting composite solid electrolyte can also function as a separator; this design reduces the impedance introduced by inert separators, improving overall battery performance. The use of interface stabilizers and plasticizers helps regulate the SEI composition, suppress lithium dendrites, and improve the stability of the lithium metal anode.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite solid electrolyte, characterized in that, Includes a three-dimensional porous oxide electrolyte framework and a PEGA-based electrolyte polymerized in situ within the electrolyte framework; The electrolyte framework comprises, by weight percentage: 10wt%-35wt% of an oxide-type electrolyte, 60wt%-85wt% of a solvent, 2wt%-8wt% of a binder, and 0.5wt%-5wt% of a lithium salt. The PEGA-based electrolyte comprises the following components: 30wt%-55wt% polyethylene glycol methyl ether acrylate, 5wt%-20wt% crosslinking agent, 10wt%-30wt% channel optimizer, 5wt%-20wt% plasticizer, 1wt%-5wt% interface stabilizer, 10wt%-25wt% lithium salt, and 0.5wt%-3wt% thermal initiator.

2. The composite solid electrolyte according to claim 1, characterized in that, The oxide-type electrolyte D 50 The wavelength ranges from 200 nm to 800 nm, and it is selected from at least one of LATP, LAGP, LiTi2(PO4)3 and LLZO.

3. The composite solid electrolyte according to claim 1, characterized in that, The solvent is selected from at least one of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, acetone, and tetrahydrofuran; And / or, the adhesive is selected from at least one of polyvinylidene fluoride, PVDF-HFP, polyacrylonitrile and PMMA; And / or, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(fluorooxalateborate), LiClO4, and LiPF6.

4. The composite solid electrolyte according to claim 1, characterized in that, The molecular weight of the polyethylene glycol methyl ether acrylate is 200-2000; And / or, the crosslinking agent is polyethylene glycol diacrylate, and the molecular weight of the crosslinking agent is 400-2000.

5. The composite solid electrolyte according to claim 1, characterized in that, The channel optimizer is selected from at least one of tetrahydrofurfuryl acrylate, cyclohexyl methacrylate and isobornyl acrylate; And / or, the plasticizer is selected from at least one of tetramethylurea, ethylene carbonate, propylene carbonate, 1,2-dimethoxyethane and NMP derivatives; The interface stabilizer is selected from at least one of fluoroethylene carbonate, ethylene carbonate and lithium oxalate borate. And / or, the thermal initiator is azobisisobutyronitrile.

6. A method for preparing a composite solid electrolyte as described in any one of claims 1-5, characterized in that, Includes the following steps: Preparation of electrolyte framework: An oxide electrolyte, solvent, binder and lithium salt are mixed in proportion to prepare a slurry; the slurry is coated on the surface of a base film or positive electrode to prepare an electrolyte framework; Preparation of PEGA-based electrolyte: PEGA-based electrolyte is prepared by mixing polyethylene glycol methyl ether acrylate, crosslinking agent, channel optimizer, plasticizer, interface stabilizer, lithium salt and thermal initiator in proportion. The PEGA-based electrolyte was injected into the electrolyte framework and reacted at 55℃-65℃ for 2.5h-3.5h to obtain a composite solid electrolyte.

7. The preparation method according to claim 6, characterized in that, The porosity of the base membrane is 40%-90%, and the thickness is 5μm-30μm; it is selected from any one of cellulose membrane, polyethylene membrane, polypropylene membrane, and polyimide membrane. And / or, the positive electrode is selected from any one of LiFePO4, LiCoO2, LiNiO2, NCM / NCA and LiMn2O4.

8. The preparation method according to claim 6, characterized in that, Before obtaining the electrolyte framework, the process further includes drying at a temperature of 55℃-65℃ for 10h-13h. The obtained electrolyte framework has a thickness of 25μm-35μm and a pore size of 0.7μm-1.5μm.

9. A lithium-ion battery, characterized in that, Includes the composite solid electrolyte as described in any one of claims 1-5 or the composite solid electrolyte prepared by the preparation method as described in any one of claims 6-8, a positive electrode material, and a lithium metal sheet; The cathode material comprises, by mass percentage, 75wt%-85wt% LiFePO4, 8wt%-12wt% conductive agent, and 8wt%-12wt% binder.

10. An application of the lithium-ion battery as described in claim 9 in the fields of electric vehicles and energy storage systems.

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