Flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation and preparation method thereof

Abstract

The invention relates to a flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation and a preparation method thereof. The preparation method of the flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation comprises the following steps: mixing a compound containing a boric acid ester fragment, a compound containing a phosphate ester fragment, a cross-linking agent and a lithium salt, adding an initiator, and carrying out a polymerization reaction to obtain the flame-retardant polymer electrolyte material. According to the flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation and the preparation method thereof, three functional molecular fragments are subjected to covalent crosslinking through in-situ free radical copolymerization to construct a three-dimensional network, and an all-solid-state polymer electrolyte with flame retardance, high ionic conductivity and stable interface is obtained.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials technology, specifically relating to a flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation and its preparation method. Background Technology

[0002] With the rapid development of electric vehicles and the aviation industry, the demand for high-energy-density batteries has surged. Traditional graphite anode lithium-ion batteries can no longer meet this demand. Lithium metal anodes have become a key direction for improving energy density due to their low redox potential (-3.04 V vs. standard hydrogen electrode) and high specific capacity (3860 mAh / g). However, liquid electrolyte (LE) based lithium metal batteries (LMBs) have risks of uncontrolled lithium dendrite growth, short cycle life and thermal runaway. The fundamental reasons are: (1) Imbalance in interfacial ion distribution: LE Dynamic reconstruction of the solvated sheath hinders interfacial migration, leading to concentration gradient collapse; (2) Space charge layer (SCL) distortion: Anion dissipation induces local electric field enhancement, driving Preferential deposition at micro-protrusions; (3) SEI layer heterogeneity: cracking of the SEI layer formed by solvation sheath decomposition exacerbates the uneven interface flux and accelerates dendrite growth.

[0003] While polymer electrolytes (such as polyester-based electrolytes) can reduce leakage risk, they still face three major bottlenecks: low dielectric constants lead to high ion pair binding energies, making lithium salt cleavage difficult; anion migration dominates polarization, resulting in low lithium ion transference number (LTL). The lithium salt exhibits several drawbacks: low efficiency, vigorous side reactions with lithium metal, poor interfacial stability, and unresolved flammability. While various targeted strategies have been proposed to overcome these shortcomings, including incorporating inorganic fillers, mixing organic materials, editing molecular structures, forming gel electrolytes through binding with liquid electrolytes, and designing new salts, these strategies all have limitations in practical applications. They still cannot simultaneously achieve excellent lithium salt dissociation capacity and high efficiency. Polyester-based solid electrolytes possess stable lithium metal properties, high voltage stability, and excellent flame retardancy. Therefore, a simple and scalable strategy is urgently needed to improve the overall performance of these electrolytes.

[0004] In view of this, the present invention proposes a new electrolyte material, which is a flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation. It achieves flame retardancy, high ionic conductivity and interface stability through Lewis acid-base synergistic effect, and is suitable for high energy density lithium metal batteries (such as electric vehicles and aircraft power systems). Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing flame-retardant polymer electrolyte materials based on Lewis acid-base synergistic regulation. The method employs a "Lewis acid-base synergistic regulation" strategy to construct flame-retardant polymer electrolytes (BE-P-Es) with covalent crosslinking of ternary molecular fragments through in-situ polymerization, thereby simultaneously solving the aforementioned bottlenecks.

[0006] To achieve the above objectives, the technical solution adopted is as follows:

[0007] A method for preparing a flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation comprises: mixing a compound containing borate ester fragments, a compound containing phosphate ester fragments, a crosslinking agent, and a lithium salt, then adding an initiator and carrying out an in-situ polymerization reaction to obtain the flame-retardant polymer electrolyte material.

[0008] Furthermore, the compound containing the borate ester fragment is one of allyl borate pinacol ester, propenyl borate diisopropyl ester, and but-1-ene-4-borate pinacol ester;

[0009] The compound containing the phosphate ester fragment is one of 3-butenylphosphocarboxylic acid ethyl ester, 2-(diethoxyphosphoryl)acetic acid allyl ester, 2-methacrylate ethoxyethyl phosphate, vinyl phosphate diethyl ester, and polyphosphocholine glycol acrylate.

[0010] The crosslinking agent is at least one of 1,4-butanediol diacrylate, diallyl phthalate, N,N'-methylenebisacrylamide, N,N'-methylenebismethylacrylamine, diallyl isocyanurate, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 1,3-diallylurea.

[0011] Furthermore, the molar ratio of the compound containing the borate ester fragment, the compound containing the phosphate ester fragment, and the crosslinking agent is 1:1 to 10:0.2.

[0012] Furthermore, the lithium salt is at least one selected from lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalateborate), and lithium difluorooxalateborate.

[0013] The molar ratio of the lithium salt to the compound containing the borate ester fragment, the compound containing the phosphate ester fragment, and the crosslinking agent is 1 mol / g.

[0014] Furthermore, the initiator is a thermal initiator;

[0015] The in-situ polymerization reaction is carried out at a temperature of 65-70℃.

[0016] Furthermore, the thermal initiator is 2,2'-azobis(isobutyronitrile) (AIBN).

[0017] The in-situ polymerization process is as follows: first, mix at 65°C for 2 hours, then react at 70°C for 6 hours.

[0018] Furthermore, the amount of the thermal initiator is 0.8-1.2 wt% of the compound containing borate ester fragments, the compound containing phosphate ester fragments, and the crosslinking agent.

[0019] Another objective of this invention is to provide a flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation, prepared using the above-described method, exhibiting a room-temperature ionic conductivity > S / cm, lithium-ion transference number >0.5.

[0020] Another objective of this invention is to provide a polymer solid-state battery that retains >90% of its capacity after 200 cycles at a cutoff voltage of 4.2 V and a temperature of 30 °C, and shows no signs of dendrite penetration.

[0021] To achieve the above objectives, the technical solution adopted is as follows:

[0022] A polymer solid-state battery comprising the aforementioned flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation.

[0023] Furthermore, the polymer solid-state battery also includes a positive electrode material and a negative electrode active material;

[0024] The cathode material is LiNi. x Co y M 1-x-y One or more of O2, LiCoO2, LiMn2O4, and LiFePO4; the LiNi x Co y M 1-x-y In O2, M is either Mn or Al, 0.2 <x<0.9,0.1<y<0.5;

[0025] The negative electrode active material is metallic lithium or a lithium alloy.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention discloses a flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation and its preparation method. It employs a "functional molecular assembly" strategy, splicing molecular fragments together through in-situ polymerization to construct a novel flame-retardant electrolyte. First, boron ester-rich molecular fragments (BEs) are prepared. The electron-deficient boron in these fragments acts as Lewis acid sites, adsorbing lithium salt anions from the solvent and releasing free lithium ions, thus increasing the lithium-ion transference number. Further, functional phosphate ester molecular fragments (Ps) are selected. The P=O group acts as a Lewis basic site, coordinating with lithium ions to form secondary transport channels. This fragment is also rich in phosphorus, endowing the electrolyte with excellent flame-retardant properties. In addition, diene molecular fragments (Es) rich in ester groups are selected. The C=O in these fragments can coordinate with lithium ions, assisting lithium-ion conduction. Simultaneously, these fragments can also act as crosslinking agents to construct a continuous conduction network, providing continuous jumping sites for lithium ions. The BE-P-Es electrolyte prepared by this invention exhibits excellent ionic conductivity and lithium-ion transference number, and demonstrates good lithium metal compatibility in lithium-symmetric batteries. This electrolyte material, when applied in solid-state batteries, exhibits a wide voltage window, excellent flame retardancy, and good interface stability, thus improving battery cycle life. Specific advantages include:

[0028] (1) Improving lithium-ion transport number and ionic conductivity: In the technical solution of this invention, by introducing Lewis acidic borate ester fragments, anions in lithium salts (such as...) are effectively anchored. This inhibits its migration and significantly increases the lithium-ion transference number (LTV). ⁺ >0.6), significantly higher than traditional polymer electrolytes (typically 0.2-0.4). Simultaneously, phosphate esters and ester-based crosslinking agents provide abundant... Coordination sites are used to construct continuous ion transport channels, thereby increasing the room temperature ionic conductivity to > S / cm meets the practical application requirements of solid-state batteries.

[0029] (2) Excellent interface stability and lithium metal compatibility: In the technical solution of the present invention, a high-quality SEI layer rich in B and P is formed on the lithium metal surface through the synergistic effect of Lewis acid and base, thereby improving interface stability.

[0030] (3) Excellent flame retardant performance and thermal stability: In the technical solution of the present invention, the phosphate ester fragment is rich in phosphorus, which effectively quenches the combustion chain reaction, enables the electrolyte to have self-extinguishing performance, significantly improves the thermal safety of the battery, and reduces the risk of thermal runaway.

[0031] (4) Good mechanical properties and processing adaptability: In the technical solution of the present invention, by adjusting the number of double bonds and crosslinking density in the crosslinking agent, the mechanical strength of the electrolyte membrane is taken into account, and the electrode structure with different thickness and shape is adapted. Attached Figure Description

[0032] Figure 1 Synthetic route diagram for BE-P-Es electrolyte;

[0033] Figure 2 The electrostatic potential and band structure diagrams of the polymer monomers ABE and DEBP are shown.

[0034] Figure 3 The binding energy of oxygen and lithium ions in the polymer monomers BDDA and DEBP;

[0035] Figure 4 Linear sweep voltammetry (LSV) spectra of Examples 1-3;

[0036] Figure 5 Polarization curves of the Li / BE-P-Es-1 / Li symmetric cell at 10 mV for Example 1 (Inset: Electrochemical impedance spectroscopy analysis of the Li / BE-P-Es-1 / Li symmetric cell before and after polarization).

[0037] Figure 6 Impedance spectra of Example 1 at different temperatures;

[0038] Figure 7 Rate performance of the full cell assembled in Example 1 at different current densities;

[0039] Figure 8 The long-cycle performance of the full cell assembled in Example 1 at different current densities;

[0040] Figure 9 Cycling performance of the full cell assembled in Example 2 under 1C conditions;

[0041] Figure 10 Cycling performance of the full cell assembled in Example 3 under 1C conditions;

[0042] Figure 11 The cycle performance of the full cell assembled in Comparative Example 1 under 1C conditions;

[0043] Figure 12 The cycle performance of the full cell assembled in Comparative Example 2 under 1C conditions. Detailed Implementation

[0044] To further illustrate the present invention's flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation and its preparation method, and to achieve the intended objectives of the invention, the following, in conjunction with preferred embodiments, details the specific implementation, structure, features, and effects of the flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation proposed in this invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.

[0045] The following will provide a more detailed description of the flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation and its preparation method, with reference to specific embodiments:

[0046] This invention provides a flame-retardant polymer electrolyte material synergistically regulated by Lewis acids and bases. This material is a novel polymer electrolyte covalently assembled from borate esters (Lewis acids), phosphate esters (Lewis bases), and ester-based diene crosslinking agents. Figure 1 A three-dimensional network is formed through in-situ polymerization, in which boronic acid esters anchor anions to enhance lithium-ion migration, and phosphate esters construct secondary networks. The electrolyte provides a transport channel and imparts flame retardancy, while the ester-based crosslinking agent offers continuous coordination sites. The electrolyte exhibits a room-temperature ionic conductivity > S / cm, electrochemical window 4.8V. The all-solid-state battery, matched with a high-nickel cathode and lithium metal anode, retains >92% capacity after 100 cycles. The technical solution adopted in this invention is as follows:

[0047] A method for preparing a flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation comprises: mixing a compound containing borate ester fragments, a compound containing phosphate ester fragments, a crosslinking agent, and a lithium salt, then adding an initiator and carrying out an in-situ polymerization reaction to obtain the flame-retardant polymer electrolyte material.

[0048] In the above technical solution, the compound containing the phosphate ester fragment contains at least one P=O group, and the P=O group is related to... The coordination energy is <-1.5 eV. The crosslinking agent contains at least two C=C double bonds and one C=O group, wherein the C=O group is... Its coordination energy is <-1.0 eV.

[0049] Preferably, the compound containing the borate ester fragment includes, but is not limited to, allyl borate pinacol ester, allyl borate diisopropyl ester, and but-1-ene-4-borate pinacol ester;

[0050] The compounds containing phosphate fragments include, but are not limited to, one of 3-butenylphosphocarboxylic acid ethyl ester, 2-(diethoxyphosphoryl)acetic acid allyl ester, 2-methacrylate ethoxyethyl phosphate, vinyl phosphate diethyl ester, and polyphosphocholine glycol acrylate.

[0051] The crosslinking agent includes, but is not limited to, at least one of 1,4-butanediol diacrylate, diallyl phthalate, N,N'-methylenebisacrylamide, N,N'-methylenebismethylacrylamine, diallyl isocyanurate, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 1,3-diallylurea.

[0052] More preferably, the molar ratio of the compound containing the borate ester fragment, the compound containing the phosphate ester fragment, and the crosslinking agent is 1:1 to 10:0.2.

[0053] Preferably, the lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalateborate), and lithium difluorooxalateborate.

[0054] The molar ratio of the lithium salt to the compound containing the borate ester fragment, the compound containing the phosphate ester fragment, and the crosslinking agent is 1 mol / g.

[0055] Preferably, the initiator is a thermal initiator;

[0056] The in-situ polymerization reaction is carried out at a temperature of 65-70℃.

[0057] More preferably, the thermal initiator is 2,2'-azobis(isobutyronitrile) (AIBN).

[0058] The in-situ polymerization process is as follows: first, mix at 65°C for 2 hours, then react at 70°C for 6 hours.

[0059] More preferably, the amount of the thermal initiator is 0.8-1.2 wt% of the compound containing borate ester fragments, the compound containing phosphate ester fragments, and the crosslinking agent.

[0060] In the above technical solution, the cross-linked network is formed through free radical in-situ polymerization under a thermal initiator. The degree of polymerization is controlled by adjusting the reaction time at different reaction temperatures. Furthermore, the mechanical strength and chain segment mobility can be controlled by adjusting the number of double bonds in the Es segments and the spacing between cross-linking sites.

[0061] A flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation is prepared using the above-described preparation method.

[0062] A polymer solid-state battery comprising the aforementioned flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation.

[0063] Preferably, the polymer solid-state battery further includes a positive electrode material and a negative electrode active material;

[0064] The cathode material is LiNi. x Co y M 1-x-y One or more of O2, LiCoO2, LiMn2O4, and LiFePO4; the LiNi x Co y M 1-x-y In O2, M is either Mn or Al, 0.2 <x<0.9,0.1<y<0.5;

[0065] The negative electrode active material is metallic lithium or a lithium alloy.

[0066] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0067] Example 1.

[0068] Combination Figure 1 The specific operating steps are as follows:

[0069] (1) Allylboronic acid pinacol ester (ABE, 0.1 mol), diethyl 3-butenylphosphonate (DEBP), 1,4-butanediol diacrylate (BDDA), and LiTFSI were added sequentially to a reaction flask. After the LiTFSI dissolved, the thermal initiator azobisisobutyronitrile (AIBN) (1.0 wt% relative to the sum of ABE, DEBP, and BDDA) was added, and the mixture was stirred at 65 °C for 2 h to prepare a prepolymerization solution.

[0070] The molar ratio of ABE, DEBP, and BDDA is 1:5:0.2.

[0071] The molar ratio of LiTFSI to ABE, DEBP, and BDDA is 1 mol / g.

[0072] (2) The prepolymer solution was immersed in a PE membrane (diameter: 19 mm) and further polymerized at 70 °C for 6 h to obtain a polymer electrolyte material, denoted as BE-P-Es-1.

[0073] A lithium metal battery was assembled using 5 mg NCM811 as the positive electrode, the aforementioned polymer electrolyte material as the electrolyte, and Li as the negative electrode, and then electrochemical tests were performed.

[0074] Example 2.

[0075] The specific operating steps are as follows:

[0076] (1) Allylboronic acid pinacol ester (ABE, 0.1 mol), diethyl 3-butenylphosphonate (DEBP), 1,4-butanediol diacrylate (BDDA), and LiTFSI (1 mol) were added sequentially to the reaction flask. After the LiTFSI dissolved, the thermal initiator azobisisobutyronitrile (AIBN) (1.0 wt% relative to the sum of ABE, DEBP, and BDDA) was added, and the mixture was stirred at 65 °C for 2 h to prepare a prepolymerization solution.

[0077] The molar ratio of ABE, DEBP, and BDDA is 1:10:0.2.

[0078] The molar ratio of LiTFSI to ABE, DEBP, and BDDA is 1 mol / g.

[0079] (2) The prepolymer solution was immersed in a PE membrane (diameter: 19 mm) and further polymerized at 70 °C for 6 h to obtain a polymer electrolyte material, denoted as BE-P-Es-2.

[0080] A lithium metal battery was assembled using 5 mg NCM811 as the positive electrode, the aforementioned polymer electrolyte material as the electrolyte, and Li as the negative electrode, and then electrochemical tests were performed.

[0081] Example 3.

[0082] The specific operating steps are as follows:

[0083] (1) Allylboronic acid pinacol ester (ABE, 0.1 mol), diethyl 3-butenylphosphonate (DEBP), 1,4-butanediol diacrylate (BDDA), and LiTFSI (1 mol) were added sequentially to the reaction flask. After the LiTFSI dissolved, the thermal initiator azobisisobutyronitrile (AIBN) (1.0 wt% relative to the sum of ABE, DEBP, and BDDA) was added, and the mixture was stirred at 65 °C for 2 h to prepare a prepolymerization solution.

[0084] The molar ratio of ABE, DEBP, and BDDA is 1:1:0.2.

[0085] The molar ratio of LiTFSI to ABE, DEBP, and BDDA is 1 mol / g.

[0086] (2) The prepolymer solution was immersed in the PE membrane (diameter: 19 mm) and further polymerized at 70 °C for 6 h to obtain the polymer electrolyte material, denoted as BE-P-Es-3.

[0087] A lithium metal battery was assembled using 5 mg NCM811 as the positive electrode, the aforementioned polymer electrolyte material as the electrolyte, and Li as the negative electrode, and then electrochemical tests were performed.

[0088] Example 4.

[0089] The operating steps of Example 4 are the same as those of Example 1, except for the selection of the compound containing the borate ester fragment, the compound containing the phosphate ester fragment, and the crosslinking agent. See Table 1 for details.

[0090] Table 1

[0091]

[0092] Example 5.

[0093] The operation steps of Example 5 are the same as those of Example 1, except for the selection of lithium salt. See Table 2 for details.

[0094] Table 2

[0095]

[0096] Example 6.

[0097] The operating steps of Example 6 are the same as those of Example 1, except for the amount of thermal initiator used. See Table 3 for details.

[0098] Table 3

[0099]

[0100] Comparative Example 1.

[0101] This comparative example provides a polymer electrolyte material, which is prepared in a manner that is basically the same as that in Example 1, except that allylboronic acid pinacol ester (ABE) was not added in step 1.

[0102] Comparative Example 2.

[0103] This comparative example provides a polymer electrolyte material, which is prepared in a manner that is basically the same as that in Example 1, except that ethyl 3-butenylphosphonate (DEBP) is not added in step 1.

[0104] Example 7: Performance Testing

[0105] 1. The electrostatic potential and band structure of monomers ABE and DEBP in Example 1 were detected and characterized, and the results are as follows: Figure 2 As shown.

[0106] Figure 2 The electrostatic potential (a) and band structure diagram (b) of the polymer monomers ABE and DEBP are shown.

[0107] Electrostatic potential distribution diagram ( Figure 2 a) This study revealed unique charge distribution characteristics on the surfaces of ABE and DEBP molecules, showing the simultaneous presence of significant negative potential regions and positive potential sites. The negative potential regions can interact with... Coordination occurs, and the positive potential sites effectively anchor lithium salt anions, thereby synergistically weakening ion pair interactions, promoting lithium salt dissociation, and thus reducing concentration polarization and increasing lithium ion transport number. (Band structure diagram) Figure 2 b) shows that the ABE and DEBP units have lowest unoccupied molecular orbital (LUMO) levels of -0.19 eV and -0.21 eV, respectively, and relatively high highest occupied molecular orbital (HOMO) levels. The wide HOMO-LUMO band gap indicates that these two molecules possess excellent thermodynamic structural stability and antioxidant capacity. Furthermore, DFT calculations show ( Figure 3In DEBP containing phosphate ester fragments, the P=O group and The coordination energy is -2.72 eV, while the C=O group in the crosslinking agent BDDA and... The coordination energy is -2.01 eV. Both DEBP and BDDA monomers can provide abundant lithium binding sites, expanding... Transmission path.

[0108] 2. Electrical properties

[0109] The solid-state lithium metal batteries assembled from the polymer electrolytes prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to electrochemical tests.

[0110] Test method:

[0111] A battery was assembled using 5 mg of active NCM811 as the positive electrode, a prepared polymer electrolyte as the test electrolyte, and a Li sheet as the negative electrode, and then subjected to electrochemical testing. Its charge-discharge performance and cycle stability were tested. Charge-discharge test conditions: 0.2C, 1C, 2C, 4C, 5C; Cycling test condition: 1C.

[0112] Test results are available Figure 4-12 .

[0113] Figure 4 Linear sweep voltammetry (LSV) spectra of Examples 1-3 are shown. The results indicate that the electrolytes prepared in Examples 1-3 all exhibit excellent oxidative stability, with electrochemical stability windows exceeding 4.0 V. This not only surpasses the approximately 3.8 V oxidative decomposition limit of traditional polyethylene oxide (PEO)-based electrolytes but also meets the operating voltage requirements of the cathode. Among them, the BE-P-Es-1 electrolyte (Example 1, ...) Figure 4 a) Exhibits the widest electrochemical stability window (4.9 V), significantly better than BE-P-Es-2 (4.7 V, Figure 4 b) with BE-P-Es-3 (4.3 V, Figure 4 c). This result confirms the potential of the BE-P-Es-1 electrolyte for high-voltage lithium metal battery (LMB) applications.

[0114] Figure 5 The polarization curves of the Li / BE-P-Es-1 / Li symmetric cell in Example 1 at 10 mV are shown in the inset (electrochemical impedance spectroscopy analysis of the Li / BE-P-Es-1 / Li symmetric cell before and after polarization). The results indicate that the lithium-ion transference number of the BE-P-Es-1 electrolyte ( The lithium transport efficiency (LTH) is as high as 0.68, a significant improvement over traditional polyether-based electrolytes. This performance optimization can be attributed to the selective anchoring effect of electron-deficient boron centers in the polymer matrix on anions. This effect effectively promotes the dissociation kinetics of lithium salts by weakening the Coulomb interaction between lithium ions and anions, thereby significantly improving the lithium ion transport efficiency and transport number.

[0115] Figure 6 The impedance spectra of Example 1 at different temperatures are shown; the results indicate that the BE-P-Es-1 electrolyte exhibits good impedance at temperatures between 30-60°C. o It exhibits excellent ion conductivity across a wide temperature range. Specifically, at 30°C... o Under C testing conditions, its ionic conductivity reaches as high as 2.8 mS / cm, which is significantly better than that of traditional solid electrolyte systems.

[0116] Figure 7 This study systematically investigated the rate performance of the Li|BE-P-Es-1|NCM811 full cell assembled in Example 1 at different current densities. The electrochemical performance evolution of the Li|BE-P-Es-1|NCM811 full cell was examined over a wide rate range from 0.2C to 5C. Rate performance tests showed that the battery system exhibited excellent discharge specific capacity (190 mAh / g) at a low rate of 0.2C. Even under the harsh conditions of a high rate of 5C, its discharge specific capacity remained at 106 mAh / g, demonstrating excellent rate tolerance. Notably, the coulombic efficiency remained stable above 98% across the entire rate range, and the polarization curve showed minimal fluctuations, indicating a highly reversible lithium-ion insertion / extraction process in the cathode material. Furthermore, when the test rate was reduced from 5C to 1C, the discharge specific capacity completely recovered to its initial level, fully demonstrating the excellent structural stability and electrochemical reversibility of the electrode material's crystal structure during high-rate cycling.

[0117] Figure 8 The long-cycle performance of the full cell assembled in Example 1 at different current densities was evaluated; this study systematically evaluated the Li|BE-P-Es-1|NCM811 full cell at 0.2C ( Figure 8 a) and 1C ( Figure 8 b) Long-cycle stability and electrochemical reversibility at two rate options. At a rate of 0.2C ( Figure 8 a) After the first 5 cycles of activation, the discharge specific capacity of the battery stabilized at approximately 168 mAh / g; after 100 cycles, the capacity retention was approximately 95% (>160 mAh / g), demonstrating excellent long-term cycle stability. The coulombic efficiency remained constant at 100% throughout the entire cycle range without significant fluctuations, indicating that the electrode / electrolyte interface was highly stable during long-term charge and discharge, and that the lithium-ion insertion / extraction reaction in the positive electrode active material exhibited extremely high reversibility, with side reactions being almost negligible. Under relatively high 1C rate conditions ( Figure 8(b) After activation, the initial discharge specific capacity of the battery is approximately 165 mAh / g. After 500 deep cycles, the capacity retention rate remains as high as approximately 94% (>155 mAh / g), and the coulombic efficiency remains stable at around 99% with minimal fluctuation. This result further confirms that the battery system still possesses excellent structural stability and electrochemical reversibility under high-rate long-cycle conditions. A stable and low-resistance interface layer is formed between the BE-P-Es-1 electrolyte, the NCM811 cathode, and the lithium metal anode, effectively suppressing side reactions and active lithium loss during cycling.

[0118] Figure 9 Cycling performance of the full cell assembled in Example 2 under 1C conditions; Figure 9 This study presents the long-term cycling performance of the Li|BE-P-Es-2|NCM811 full cell at 1C rate. After the first 5 activation cycles, the discharge specific capacity of this battery system stabilizes at approximately 155 mAh / g; after 300 cycles, the capacity retention is approximately 90% (>140 mAh / g), demonstrating good long-term cycling stability. Figure 9 b shows the voltage-specific capacity curves of the battery at the 1st, 100th, 200th, and 300th cycles. It can be seen that as cycling progresses, the charge-discharge curves do not show a significant increase in polarization voltage or a decrease in the discharge plateau, indicating that the BE-P-Es-2 electrolyte membrane has excellent compatibility with the electrode interface. It maintains stable ion transport channels and interfacial impedance characteristics throughout the long cycling process, effectively suppressing concentration polarization and interfacial side reactions.

[0119] Figure 10 Cycling performance of the full cell assembled in Example 3 under 1C conditions; Figure 10 This study presents the long-term cycling performance of the Li|BE-P-Es-3|NCM811 full cell at 1C rate. After the first 5 activation cycles, the discharge specific capacity of the battery system stabilizes at approximately 153 mAh / g; after 400 cycles, the capacity retention is as high as approximately 98% (>135 mAh / g), demonstrating excellent long-term cycling stability. Figure 10 b shows the voltage-specific capacity curves of the battery at 1, 100, 200, 300, and 400 cycles. It can be seen that even after 400 deep cycles, the charge-discharge curves remain highly consistent, the polarization voltage does not increase significantly, and the discharge plateau does not decay. This indicates that the BE-P-Es-3 electrolyte membrane and electrode interface possess excellent chemical / electrochemical stability, maintaining stable ion transport kinetics throughout the long cycling process and effectively suppressing interfacial impedance growth and active lithium loss.

[0120] Figure 11 The cycle performance of the full cell assembled in Comparative Example 1 under 1C conditions; Figure 10This study demonstrates the long-term cycling performance degradation behavior of a Li|NCM811 full cell based on the electrolyte of Comparative Example 1 at 1C rate. After activation in the first 5 cycles, the discharge specific capacity of this battery system stabilized at approximately 142 mAh / g; however, after 150 cycles, the capacity rapidly decreased to below 80 mAh / g, with a capacity retention of only 53%, exhibiting significant capacity degradation. This result contrasts sharply with the BE-P-Es series electrolyte systems, indicating that the electrolyte of Comparative Example 1 failed to form a stable electrode / electrolyte interface during cycling, making it difficult to effectively suppress interfacial side reactions and active material structural degradation, leading to rapid reversible capacity loss.

[0121] Figure 12 The cycle performance of the full cell assembled in Comparative Example 2 under 1C conditions; Figure 11 This study demonstrates the long-term cycling performance evolution of the Li|NCM811 full cell based on Comparative Example 2 electrolyte at 1C rate. After the first 5 activation cycles, the discharge specific capacity of this battery system stabilized at approximately 150 mAh / g; however, after 140 cycles, the capacity decayed to 115 mAh / g, with a capacity retention of only 76%, exhibiting a significant capacity degradation trend. Compared to the BE-P-Es series electrolyte systems, the cycling stability of Comparative Example 2 electrolyte is significantly insufficient, indicating defects in its ion conduction characteristics or interfacial chemical stability, making it difficult to effectively maintain the integrity of the electrode structure and the reversibility of the electrochemical reaction, thus leading to continuous capacity decay.

[0122] The results show that the electrolyte materials prepared in Examples 1-3 of this invention, when applied to solid-state lithium metal batteries, can solve the problem of low performance of polymer electrolytes. Problems include low ionic conductivity, interfacial instability, and flammability.

[0123] As can be seen from the embodiments, this invention discloses a flame-retardant polymer electrolyte material synergistically regulated by Lewis acids and bases, its preparation method, and its application in all-solid-state lithium metal batteries. This electrolyte constructs a three-dimensional network by covalently crosslinking three functional molecular fragments through in-situ free radical copolymerization: a Lewis acid borate ester fragment containing an electron-deficient boron center, which can effectively anchor... Anions release free radicals This increases the lithium-ion migration rate. >0.6; Lewis basic phosphate fragments containing P=O bonds, and Coordination forms secondary transport channels and imparts excellent flame retardant properties; the multi-double-bonded ester diene crosslinking agent containing C=O groups provides continuous coordination spacing, reducing... Jumping energy barriers and modulating mechanical strength. The resulting BE-P-Es electrolyte has a room temperature ionic conductivity > S / cm, electrochemical window ≥4.5 V, self-extinguishing and flame-retardant. The all-solid-state battery assembled with a high-nickel cathode and lithium metal anode maintains >90% capacity retention after 500 cycles at 4.2V and 30℃, with reduced interfacial impedance and no obvious dendrites. This strategy simultaneously addresses the low S / cm of the polymer electrolyte. It addresses challenges such as low ionic conductivity, interface instability, and flammability, making it suitable for high-energy-density power batteries and aviation power supplies.

[0124] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation, characterized in that, The preparation method is as follows: a compound containing borate ester fragments, a compound containing phosphate ester fragments, a crosslinking agent, and a lithium salt are mixed, an initiator is added, and an in-situ polymerization reaction is carried out to obtain the flame-retardant polymer electrolyte material.

2. The preparation method according to claim 1, characterized in that, The compound containing the borate ester fragment is one of allyl borate pinacol ester, propenyl borate diisopropyl ester, and but-1-ene-4-boronate pinacol ester; The compound containing the phosphate ester fragment is one of 3-butenylphosphocarboxylic acid ethyl ester, 2-(diethoxyphosphoryl)acetic acid allyl ester, 2-methacrylate ethoxyethyl phosphate, vinyl phosphate diethyl ester, and polyphosphocholine glycol acrylate. The crosslinking agent is at least one of 1,4-butanediol diacrylate, diallyl phthalate, N,N'-methylenebisacrylamide, N,N'-methylenebismethylacrylamine, diallyl isocyanurate, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 1,3-diallylurea.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the compound containing the borate ester fragment, the compound containing the phosphate ester fragment, and the crosslinking agent is 1:1 to 10:0.

2.

4. The preparation method according to claim 1, characterized in that, The lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalateborate), and lithium difluorooxalateborate. The molar mass ratio of the lithium salt to the compound containing the borate ester fragment, the compound containing the phosphate ester fragment, and the crosslinking agent is 1 mol / g.

5. The preparation method according to claim 1, characterized in that, The initiator is a thermal initiator; The in-situ polymerization reaction is carried out at a temperature of 65-70℃.

6. The preparation method according to claim 5, characterized in that, The thermal initiator is 2,2'-azobis(isobutyronitrile); The in-situ polymerization process is as follows: first, mix at 65°C for 2 hours, then react at 70°C for 6 hours.

7. The preparation method according to claim 5, characterized in that, The amount of the thermal initiator is 0.8-1.2 wt% of the compound containing borate ester fragments, the compound containing phosphate ester fragments, and the crosslinking agent.

8. A flame-retardant polymer electrolyte material based on Lewis acid-base synergistic regulation, characterized in that, It is prepared by any one of the preparation methods described in claims 1-7.

9. A polymer solid-state battery, characterized in that, The flame-retardant polymer electrolyte material containing the Lewis acid-base synergistic regulation as described in claim 8.

10. The polymer solid-state battery according to claim 9, characterized in that, The polymer solid-state battery also includes a positive electrode material and a negative electrode active material; The cathode material is LiNi. x Co y M 1-x-y One or more of O2, LiCoO2, LiMn2O4, and LiFePO4; the LiNi x Co y M 1-x-y In O2, M is either Mn or Al, 0.2 <x<0.9,0.1<y<0.5; The negative electrode active material is metallic lithium or a lithium alloy.

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