Battery cell and method of manufacturing the same, battery device, power consuming device, energy storage device

Abstract

The application provides a battery monomer and a manufacturing method thereof, a battery device, a power utilization device and an energy storage device. The manufacturing method of the battery monomer comprises the following steps: preparing a polymer electrolyte film; sequentially stacking a positive electrode sheet, the polymer electrolyte film and a negative electrode sheet, and then putting the stacked sheet or the wound sheet into a shell after a stacking treatment or a winding treatment to obtain an initial battery cell; and performing a formation process on the initial battery cell to obtain the battery monomer. By combining a phosphazene skeleton with intrinsic flame-retardant characteristics and reversible borate dynamic covalent bonds, and by synergistically introducing ionic liquids and inorganic fast ion conductors, a multifunctional polymer electrolyte system with self-repairing capability, high ionic conductivity, excellent electrochemical stability and intrinsic flame retardancy is constructed, so that the following effects can be achieved simultaneously: significant improvement of room temperature conductivity, self-repairing after damage, effective widening of an electrochemical window and fundamental improvement of safety performance, thereby providing key material support for the practicalization of high-performance solid-state batteries.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a battery cell and its manufacturing method, a battery device, an electrical device, and an energy storage device. Background Technology

[0002] With the rapid development of electric vehicles and large-scale energy storage systems, the demand for high-safety, high-energy-density battery systems is becoming increasingly urgent. Solid-state batteries are considered an important development direction for next-generation energy storage technology due to their potential advantages in safety and energy density. In solid-state battery systems, the solid electrolyte is the core component for realizing its performance advantages. Polymer electrolytes have attracted widespread attention due to their good flexibility, ease of processing, and interfacial compatibility with electrodes, and have unique advantages in achieving large-scale production and application.

[0003] However, the development of polymer electrolytes still faces many technical challenges. While traditional polyethylene oxide (PEO)-based electrolytes possess good lithium-ion conductivity, their ionic conductivity is low at room temperature due to crystallization, typically requiring temperatures above 60°C to reach practical levels. To address this issue, researchers have modified polymer electrolytes using various strategies such as copolymerization, crosslinking, plasticization, and inorganic filler composites. Although these methods improve room-temperature ionic conductivity to some extent, they often come at the cost of other performance characteristics. More importantly, polymer electrolytes can develop microcracks during long-term cycling due to stress concentration and volume changes. The propagation of these cracks leads to increased interfacial impedance, loss of active materials, and ultimately, battery performance degradation. Summary of the Invention

[0004] This application provides a battery cell and its manufacturing method, battery device, power supply device, and energy storage device, which at least helps to achieve an optimized balance of multiple properties such as ion conduction, self-healing, flame retardancy, and electrochemical stability.

[0005] This application provides a method for manufacturing a single battery cell, comprising:

[0006] The preparation steps for the polymer electrolyte membrane include:

[0007] A phosphazene precursor is subjected to a nucleophilic substitution reaction with a boric acid compound to obtain a nucleophilic substitution product. Then, a polyol and a lithium salt are added to the nucleophilic substitution product to react and obtain a prepolymer solution. The phosphazene precursor includes a halogen group, and the boric acid compound includes a boric acid component and a substituted functional group that can undergo a substitution reaction with the halogen group.

[0008] The ionic liquid is added to the prepolymer solution and mixed, and then ionic conductor particles are added and dispersed to obtain a coating slurry;

[0009] The coating slurry is formed into a film and then crosslinked and cured to obtain the polymer electrolyte membrane;

[0010] The positive electrode, the polymer electrolyte membrane and the negative electrode are stacked in sequence and then placed into the housing after being processed by stacking or winding to obtain the initial battery cell.

[0011] The initial cell is subjected to a formation process to obtain the battery cell.

[0012] Optionally, the phosphazene precursor is selected from one or more of hexachlorocyclotriphosphazene, octachlorocyclotetraphosphazene, and linear polydichlorophosphazene.

[0013] Optionally, the boric acid component is selected from one or more of arylboronic acid, alkylboronic acid, heterocyclic boronic acid and their derivatives; the substituted functional group is selected from one or more of amino, hydroxyl and carboxyl groups.

[0014] Optionally, the degree of substitution of the prepolymer in the prepolymer solution is 30% to 90%.

[0015] The degree of substitution (DS) refers to the proportion of a specific functional group in a molecule that is replaced by another functional group. Specifically, the total number of reactive halogen groups on the phosphazene precursor is the first quantity, and the halogen groups replaced by boric acid compounds are the second quantity. The proportion of the second quantity to the first quantity is expressed as the degree of substitution.

[0016] The specific calculation method is: DS = (B / A) × 100%;

[0017] Where A is the total number of moles of reactive halogen groups (such as P-Cl) on the phosphazene precursor, and B is the number of moles of halogen groups replaced by boric acid compounds.

[0018] The detection methods include: elemental analysis: determining the decrease in chlorine content; 31 P NMR: Phosphorus chemical shift change and peak integral; FTIR: P-Cl characteristic peak (~580 cm⁻¹) -1 The ion weakens, and a new bond (PNC) appears.

[0019] Optionally, the molecular weight of the boric acid component is 100 g / mol to 500 g / mol.

[0020] Optionally, the polyol is selected from one or more of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran glycol.

[0021] Optionally, the number-average molecular weight of the polyol is 200 g / mol to 2000 g / mol.

[0022] Optionally, the molar ratio of boric acid groups in the boric acid component to hydroxyl groups in the polyol is 1:0.5 to 1:2.

[0023] The molar ratio of boric acid groups to hydroxyl groups in the boric acid component is n(boric acid group - B(OH)2):n(hydroxyl group - OH equivalent). If the polyol is a diol (such as PEG-400), then n(OH equivalent) = 2 × n(diol molecule). If the polyol is a triol or polyol, it is calculated based on the actual number of hydroxyl groups. This ratio controls the crosslinking density and dynamic bond density, which can affect the balance between self-healing ability and mechanical properties.

[0024] Optionally, the ratio of the number of borate ester bonds in the polymer electrolyte membrane to the number of hydroxyl groups in the polyol is 3% to 25%.

[0025] Optionally, the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium bis(oxalate)borate.

[0026] Optionally, the ionic liquid is selected from one or more of imidazole ionic liquids, pyrrolidine ionic liquids, piperidine ionic liquids, and quaternary ammonium ionic liquids.

[0027] Optionally, the content of the ionic liquid in the coating slurry is 5wt% to 50wt%.

[0028] Optionally, the film-forming method includes casting, blade coating, or spin coating; the curing method includes thermal curing, photocuring, or wet curing.

[0029] Optionally, the thickness of the polymer electrolyte membrane is 10 μm to 500 μm.

[0030] Optionally, the particle size of the ion conductor particles is 30 nm to 500 nm. The particle size distribution is expressed as D... 90 / D 10 The value is less than 3.0, and can be less than 2.0.

[0031] Optionally, the ion conductor particles include garnet-type, NASICON-type, perovskite-type, and sulfide-type solid electrolytes.

[0032] Optionally, the solid electrolyte includes at least one of LLZO, LLZTO, LATP, and LLTO.

[0033] The surface of ion conductor particles can be modified, such as by hydroxylation, fluorination, or silanization, to improve their interfacial compatibility with the polymer matrix.

[0034] Optionally, the crosslinking density of the polymer electrolyte membrane is 3% to 25%, specifically 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, and any range between two of these, such as 6% to 18%, 8% to 15%, 10% to 12%.

[0035] Crosslinking density is a key parameter affecting electrolyte performance, defined as the ratio of the molar number of effective bifunctional crosslinking sites forming borate ester bonds to the total equivalent number of reactive hydroxyl groups, such as: Crosslinking density = (Y / X) × 100%, where Y is the hydroxyl equivalent consumed in forming borate ester bonds, and X is the total equivalent number of reactive hydroxyl groups in the system. This crosslinking density is determined by... 11 B NMR, 1 The determination can be made by ¹H NMR combined with the internal standard method, or by quantitative analysis of the area ratio of characteristic peaks of BO and OH using FTIR. It can also be verified by gel fraction and swelling ratio.

[0036] Optionally, the molar ratio of lithium ions in the lithium salt to ether oxygen units in the polyol [Li + The [EO] value is 0.02~0.12, specifically selectable values ​​are 0.02, 0.03, 0.04, 0.045, 0.05, 0.055, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, and any range between these values, such as 0.03~0.09, 0.04~0.07, 0.045~0.055. The ether oxygen unit interacts with Li through the lone pair electrons on the oxygen atom. + Coordination, forming Li + Transmission channel, [Li + The significance of the [EO] / [E] ratio lies in controlling the lithium salt concentration and coordination environment, thereby affecting ionic conductivity and transport number.

[0037] EO (-CH2-CH2-O-, Ethylene Oxide units) mainly originate from the polyether segments in the polyol component, such as:

[0038] PEG (polyethylene glycol): Each -CH2-CH2-O- repeating unit is 1 EO unit; PEG-400: approximately 8 to 9 EO units; PEG-600: approximately 13 to 14 EO units.

[0039] PPG (polypropylene glycol): -[CH2-CH(CH3)-O]-, does not contain standard EO but contains ether oxygen;

[0040] PTHF (polytetrahydrofuran): -(CH2)4-O-, containing ether oxygen but not a standard EO structure.

[0041] Optionally, the preparation method of the polymer electrolyte membrane includes steps such as precursor synthesis, mixing and dispersion, film formation and curing, and post-treatment. Precursor synthesis is carried out under an inert atmosphere at a reaction temperature of 20℃~100℃, specifically 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, and 100℃, with a reaction time of 2h~24h, specifically 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, and 2h. 0h, 21h, 22h, 23h, 24h; the mixing and dispersion adopts the solution method, and the solvent is selected from acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, etc., with a solid content of 20%~60%, specifically 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%; the dispersion time is 0.5h~4h, specifically 0.5h, 1h, 1.5h, 2h, 2.5h. The film formation time is 3h, 3.5h, and 4h; film formation is achieved through methods such as casting, blade coating, and spin coating, with wet film thickness ranging from 50μm to 1000μm, specifically 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, and 1000μm; curing can be achieved through thermal curing, photocuring, or moisture curing. The curing temperature is 40℃~120℃, specifically 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, and 120℃; the curing time is 0.5h~24h, specifically 0.5h, 1h, 2h, 3h, 5h, 8h, 10h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, and 24h. The final film thickness is 10μm~500μm, specifically 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 150μm, 200μm, 300μm, 400μm, and 500μm; post-treatment includes vacuum drying at a temperature of 30℃~90℃, specifically 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, and 90℃; the residual moisture content in the membrane is controlled to be 100ppm~1000ppm.

[0042] The self-healing function of this polymer electrolyte membrane is based on the dynamic reversible properties of borate ester bonds. Under conditions of increased temperature (40℃~80℃) or the presence of trace amounts of moisture (100ppm~1000ppm) in the environment, the exchange rate of borate ester bonds is significantly enhanced, with activation energies of 15kJ / mol~25kJ / mol. When cracks or damage occur in the material, the borate ester bonds at the fracture interface can react again with adjacent hydroxyl groups, and combined with the movement of polymer chain segments, crack closure and performance recovery are achieved. Within 24 hours at room temperature, the morphology recovery rate can reach over 90%, and the conductivity recovery rate can reach over 80%.

[0043] Unless otherwise specified, the content of each component in the polymer electrolyte membrane of this application is based on the total solid mass after solvent removal (dry film mass), and the sum of the mass percentages of each component is 100%. The specific contents are as follows:

[0044] Phosphazene-boronate polymer (polymer matrix formed after prepolymer curing): 40%~70%;

[0045] Lithium salts: 2%~15%;

[0046] Ionic liquids: 20%~35%;

[0047] Ion conductor particles: 5%~10%.

[0048] The criteria for determining the completion of membrane crosslinking include rapid determination methods, precise determination methods, and industrial-scale rapid determination methods. The rapid determination methods include: 1. A gel fraction ≥ 85% is considered satisfactory; 2. After swelling in the electrolyte solvent for 24 hours, the swelling ratio no longer changes significantly, indicating satisfactory performance; 3. In FTIR detection, the -OH peak (3400 cm⁻¹) is present. -1 The -BOC peak was significantly reduced (1350 cm⁻¹). -1 If the condition appears and reaches the platform level, it is considered to have met the standard. Precise determination methods include: 1. Through... 11 1. B NMR detection showed that the tetrahedral boron content reached 30%~60% within the target range; 2. Rheological properties reached the target range (1×10⁻⁶). 4 Pa~5×10 5 (Pa), and is stable. An industrial-scale rapid judgment method uses two indicators: gel fraction and swelling ratio, i.e., gel fraction ≥ 85% and swelling ratio 150%~350%.

[0049] This application also provides a battery cell, which is manufactured using the battery cell manufacturing method described above, comprising:

[0050] The housing includes a positive electrode, a polymer electrolyte membrane, and a negative electrode located within the housing, with the polymer electrolyte membrane situated between the positive and negative electrode.

[0051] This application also provides a battery device, including the battery cell as described above, wherein the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

[0052] In another aspect, this application provides an electrical device that includes a battery device as described above, the battery device being used to provide electrical energy.

[0053] This application also provides an energy storage device, which includes a battery device as described above, the battery device being used to store electrical energy.

[0054] The technical solution provided in this application has at least the following advantages:

[0055] This application combines an intrinsically flame-retardant phosphazene skeleton with reversible borate ester dynamic covalent bonds, and synergistically introduces ionic liquids and inorganic fast ionic conductors to construct a multifunctional polymer electrolyte system with self-healing ability, high ionic conductivity, excellent electrochemical stability and intrinsic flame retardancy. It can simultaneously achieve a significant improvement in room temperature conductivity, self-repair after damage, effective widening of the electrochemical window and fundamental improvement in safety performance, providing key material support for the practical application of high-performance solid-state batteries.

[0056] The battery cells provided in this application can be widely used in electrical devices requiring high energy density and long cycle life, including high-end electric vehicle battery systems, portable electronic devices, and large-scale energy storage power stations. These battery cells are expected to overcome existing bottlenecks, achieving comprehensive improvements in energy density, cycle life, and safety performance, enabling high-capacity battery cells suitable for long-term energy storage applications, such as energy storage systems that can operate continuously for 4 to 8 hours at rated power. This provides key technological support for the development of next-generation high-performance electrochemical energy storage systems. Attached Figure Description

[0057] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 The flowchart corresponds to the manufacturing method of the battery cell provided in the embodiments of this application. Detailed Implementation

[0059] As can be seen from the background technology, existing polymer electrolyte technologies mainly include linear polymer electrolytes, cross-linked polymer electrolytes, and composite polymer electrolytes. Linear polymer electrolytes, such as PEO, bind to Li through ether oxygen segments. + The coordination of PEO enables ion transport, and its working principle is based on a chain segment motion-assisted ion hopping mechanism. In this system, lithium ions form coordination complexes with ether oxygen groups, and migration between different coordination sites is achieved through localized movement of polymer chain segments. To suppress PEO crystallization and improve room temperature performance, researchers have developed copolymers of PEO with other monomers, such as PEO-PPO block copolymers, which increase the proportion of amorphous regions by disrupting chain segment regularity.

[0060] Crosslinked polymer electrolytes form three-dimensional network structures through chemical or physical crosslinking. Chemical crosslinking systems typically employ UV curing or thermosetting to transform polymer precursors containing crosslinkable groups into insoluble and infusible network structures. While this structure improves mechanical strength and dimensional stability, the presence of crosslinking points restricts chain segment movement and may reduce ionic conductivity. Physical crosslinking systems, on the other hand, utilize non-covalent interactions such as hydrogen bonds and ionic interactions to construct reversible networks, which can be reorganized under certain conditions.

[0061] Composite polymer electrolytes improve their overall performance by introducing inorganic fillers into the polymer matrix. Commonly used inorganic fillers include inert oxides such as Al₂O₃, SiO₂, and TiO₂, as well as fast ion conductors such as LLZO, LLTO, and LATP. The mechanisms of action of these fillers include inhibiting polymer crystallization, providing additional ion transport pathways, and improving mechanical properties. The dispersion state of the filler has a significant impact on the performance of the composite electrolyte, and surface modification is often required to improve the compatibility between the filler and the polymer matrix. Some studies have also introduced ionic liquids as plasticizers, using their low volatility and high ionic conductivity to improve the room temperature performance of the electrolyte; however, excessive ionic liquids can lead to a decrease in mechanical strength.

[0062] Existing polymer electrolyte technologies face several interconnected technical challenges in practical applications. First, there is an inherent contradiction between ion conductivity and mechanical properties. Improving ion conductivity typically requires increasing chain segment mobility or adding plasticizers, but this leads to a decrease in modulus, affecting the electrolyte's ability to inhibit lithium dendrite growth. Conversely, while increasing crosslinking enhances mechanical properties, it restricts ion transport paths, resulting in decreased conductivity. This "seesaw" effect makes it difficult for current technologies to simultaneously meet the requirements of high conductivity and high mechanical strength.

[0063] Secondly, existing electrolytes lack effective self-healing mechanisms. Traditional static cross-linked networks cannot recover once cracks are formed, and even physical networks constructed using supramolecular forces have relatively limited self-healing capabilities. Although supramolecular forces are reversible, their strength is insufficient, making them prone to failure under battery operating conditions. Systems based on thermally reversible covalent bonds require higher temperatures to activate the repair process, making them unsuitable for the normal operating temperature range of batteries. More importantly, the repair process is often accompanied by a decrease in ionic conductivity, affecting battery performance.

[0064] Third, high-voltage stability still needs improvement. Most polymer electrolytes exhibit poor performance at high voltages (>4.3V vs Li / Li). + Oxidative decomposition occurs, and the resulting byproducts not only consume active lithium but also form a high-resistivity layer on the electrode surface, limiting the application of high-voltage cathode materials. Although this can be improved by adding stabilizers, this may affect other performance characteristics. Furthermore, safety concerns cannot be ignored. While solid-state electrolytes avoid the leakage risks of liquid electrolytes, most organic polymers remain flammable, potentially exacerbating safety hazards in the event of thermal runaway.

[0065] Finally, interface issues are a key factor limiting the application of polymer electrolytes. The interfacial contact between the polymer electrolyte and the electrode gradually deteriorates during cycling, especially in electrode material systems with large volume changes. The initiation and propagation of microcracks not only increase interfacial impedance but can also become the starting point for lithium dendrite growth, severely affecting the cycle life and safety of the battery. These intertwined problems indicate the need to develop novel polymer electrolytes with multifunctional integrated properties from a system-wide perspective of materials design.

[0066] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0067] In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0068] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0069] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0070] This application provides a method for manufacturing a single battery cell, such as... Figure 1 As shown, it includes:

[0071] S1. Preparation of polymer electrolyte membrane, the preparation steps include:

[0072] A phosphazene precursor is subjected to a nucleophilic substitution reaction with a boric acid compound to obtain a nucleophilic substitution product. Then, a polyol and a lithium salt are added to the nucleophilic substitution product to react and obtain a prepolymer solution. The phosphazene precursor includes a halogen group, and the boric acid compound includes a boric acid component and a substituted functional group that can undergo a substitution reaction with the halogen group.

[0073] The ionic liquid is added to the prepolymer solution and mixed, and then ionic conductor particles are added and dispersed to obtain a coating slurry;

[0074] The coating slurry is formed into a film and then crosslinked and cured to obtain the polymer electrolyte membrane;

[0075] S2. The positive electrode, the polymer electrolyte membrane and the negative electrode are stacked in sequence and placed into the housing after being stacked or wound to obtain the initial cell.

[0076] S3. Perform a formation process on the initial cell to obtain the battery cell.

[0077] This application constructs a multifunctional polymer electrolyte system with self-healing capabilities, high ionic conductivity, excellent electrochemical stability, and intrinsic flame retardancy by combining the intrinsically flame-retardant phosphazene framework with reversible borate ester dynamic covalent bonds and synergistically introducing ionic liquids and inorganic fast ionic conductors (i.e., ionic conductor particles). This system simultaneously achieves a significant increase in room temperature conductivity, self-repair after damage, effective widening of the electrochemical window, and fundamental improvement in safety performance, providing key material support for the practical application of high-performance solid-state batteries. Specifically, this can also be reflected in the following aspects:

[0078] 1) Fundamental differences in technical approaches: Existing technologies mostly use static cross-linked networks, which cannot be repaired once damaged; This application achieves a balance between structural stability and self-healing ability through a dual design of PN permanent network + BO dynamic network. Traditional methods improve performance through a single strategy, often at the expense of other aspects; This application adopts a multi-component synergistic strategy to simultaneously optimize ion conduction, mechanical strength, self-healing and flame retardant properties. Existing self-healing systems mostly require external stimulation or special conditions; This application can achieve self-healing at room temperature and ambient humidity.

[0079] 2) Core technological advantages: Innovative ion conduction mechanism: A three-phase synergistic transport network consisting of polymer phase, ionic liquid phase, and LLZTO local fast ion microregions has been constructed, breaking through the limitations of traditional single transport paths; Unique self-healing mechanism: Utilizing the temperature / humidity dual response characteristics of borate ester bonds, the repair conditions are mild and compatible with the battery operating environment; Improved intrinsic safety: The phosphazene skeleton provides intrinsic flame retardancy, eliminating the need for additional flame retardants and avoiding negative impacts on electrochemical performance.

[0080] 3) Significant improvement in overall performance: The room temperature ionic conductivity is more than an order of magnitude higher than that of traditional PEO-based electrolytes; it has excellent self-healing ability, with a performance recovery rate of more than 80% within 24 hours; the electrochemical window is widened to above 4.5V, making it suitable for high-voltage cathode materials; the limiting oxygen index (LOI) value is greater than 26%, exhibiting good flame retardant properties; the mechanical strength and ionic conduction are optimized and balanced, and the Young's modulus is kept within a suitable range.

[0081] 4) Advantages of industrial application: The preparation process is compatible with existing coating production lines, making it easy to scale up production; the raw materials are widely available and the cost is controllable; the self-healing properties extend battery life and improve economic efficiency; the multi-functional integration reduces the use of additional additives and simplifies the formulation system.

[0082] In this application, for the cathode system, the cathode active material can be selected from various material systems such as layered oxides, spinel structures, polyanionic types, and lithium-rich manganese-based materials. Layered oxides include LiCoO2 and LiNi. x Co y Mn z O2(NCM) series, LiNi x Co y Al z O2 (NCA), etc., among which NCM811, NCM622, and NCM523 are selected according to different energy density and stability requirements. Spinel structural materials such as LiMn2O4 and LiNi 0.5 Mn 1.5O4 exhibits good thermal stability and rate performance. Polyanionic cathodes such as LiFePO4, LiMnPO4, and Li3V2(PO4)3 demonstrate excellent cycle stability and safety. Lithium-rich manganese-based materials, such as xLi2MnO3·(1-x)LiMO2, show promise due to their high specific capacity. The cathode formulation comprises 85wt%~97wt% active material, 1wt%~8wt% conductive agent, and 2wt%~7wt% binder. The conductive agent is selected from carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, etc., and can be used alone or in combination. The binder can be a polymer with certain ionic conductivity, such as polyvinylidene fluoride (PVDF) or polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP). The cathode current collector uses aluminum foil with a thickness of 10μm~20μm; carbon-coated aluminum foil can be used to improve interfacial properties.

[0083] For anode systems, in lithium-ion batteries, anode active materials include graphite-based materials, silicon-based materials, tin-based materials, and lithium titanate. Natural graphite and artificial graphite are the most mature anode materials, exhibiting good cycle stability. Silicon-based materials include nano-silicon, silicon-carbon composites, and SiO₂. x While theoretically high capacity is desirable, the volume expansion issue needs to be addressed through structural design. Lithium titanate (Li4Ti5O4) 12 It exhibits excellent cycle stability and safety, making it suitable for applications with high lifespan requirements. For lithium metal batteries, lithium metal foil can be used directly as the negative electrode, with a thickness of 20μm~100μm. To improve the cycle stability of the lithium metal negative electrode, strategies such as three-dimensional current collectors, artificial SEI layers, and lithium alloys can be employed. In the negative electrode formulation, the active material content is 90wt%~97wt%, the conductive agent is 0~5wt%, and the binder is 3wt%~8wt%. The binder can be an aqueous system such as a combination of sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR), or polyacrylic acid (PAA), etc. The negative electrode current collector uses copper foil with a thickness of 6μm~12μm.

[0084] The self-healing polymer electrolyte membrane of this application is prepared using a continuous process. First, HCCP and 3-aminophenylboronic acid undergo a nucleophilic substitution reaction in acetonitrile solvent. The reaction is carried out at 50℃~70℃ for 6h~8h under nitrogen protection, with the degree of substitution controlled at 45%~55%. Then, PEG-400 diol and LiTFSI are added, and the reaction is continued for 2h~4h to form a prepolymer solution.

[0085] EMIM-TFSI ionic liquid was added to the prepolymer solution at a set ratio and dispersed for 30 min at 2000 rpm to 5000 rpm using a high-speed disperser. LLZTO nanoparticles were pre-dispersed in acetonitrile to form a 10 wt% slurry, which was then gradually added to the bulk solution and dispersed for another 1 h to finally obtain a coating slurry with a solid content of 40% to 45%.

[0086] The slurry was uniformly coated onto the release PET substrate using a slot coating method at a speed of 2-10 m / min, with the wet film thickness controlled at 200-250 μm. The coated wet film then entered a hot air drying zone, controlled in three stages: pre-drying at 60°C, main drying at 80°C, and post-drying at 70°C, with a total residence time of 5-10 minutes. The dried film then entered a hot pressing zone, where it was treated at 80-90°C and 0.5-1.0 MPa for 2-3 minutes to promote the completion of the borate ester crosslinking reaction.

[0087] The resulting polymer electrolyte membrane has a thickness of 100μm~150μm and is cut, packaged, and stored in a drying chamber (dew point ≤ -40℃). The membrane material has good flexibility and can adapt to roll-to-roll continuous production processes.

[0088] Battery assembly using the polymer electrolyte membrane of this application is carried out in a dry chamber environment (dew point ≤ -40℃). For pouch cells, a stacking process is used, in which the positive electrode, polymer electrolyte membrane, and negative electrode are stacked sequentially, with the number of stacks determined according to the capacity design. After stacking, the cells are compounded in a hot press at a temperature of 70℃~90℃, a pressure of 3MPa~5MPa, and a time of 3min~5min, to ensure good interfacial contact between the electrolyte and the electrode.

[0089] The composite battery cell assembly is encased in an aluminum-plastic film and undergoes top-side sealing, electrolyte injection (if necessary, a small amount of liquid electrolyte is added), and vacuum sealing. The sealed battery is then activated by standing at 45°C for 12-24 hours, followed by formation. Formation employs a stepped current strategy: charging to 3.0V at 0.05C, to 3.6V at 0.1C, and to the upper limit voltage at 0.2C (this upper limit voltage is determined by the cutoff voltage of the selected cathode material; for example, 4.3V for NCM811 and 3.65V for LFP), with constant voltage at each stage until the current drops to 0.02C. After 3-5 pre-cycles, the battery is ready for normal use.

[0090] When a small amount of liquid electrolyte needs to be added, the injection volume should be within 20% of the designed injection volume, typically 0.1 g / Ah to 0.5 g / Ah. The following liquid electrolytes can be selected:

[0091] Formula A (carbonate-based system), solvent is EC:DMC:DEC=1:1:1 (volume ratio), lithium salt is 1.0M~1.5M LiPF6, additive is VC (1wt%~3wt%) + FEC (3wt%~5wt%).

[0092] Formula B (ether-based system, suitable for lithium metal anodes) uses DOL:DME = 1:1 (volume ratio) as solvent, 1.0M LiTFSI as lithium salt, and LiNO3 (0.1M~0.5M) as additive.

[0093] Optionally, the phosphazene precursor is selected from one or more of hexachlorocyclotriphosphazene, octachlorocyclotetraphosphazene, and linear polydichlorophosphazene.

[0094] Optionally, the boric acid component is selected from one or more of arylboronic acid, alkylboronic acid, heterocyclic boronic acid and their derivatives; the substituted functional group is selected from one or more of amino, hydroxyl and carboxyl groups.

[0095] Optionally, the degree of substitution of the prepolymer in the prepolymer solution is 30% to 90%.

[0096] Optionally, the molecular weight of the boric acid component is 100 g / mol to 500 g / mol.

[0097] Optionally, the polyol is selected from one or more of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran glycol.

[0098] Optionally, the number-average molecular weight of the polyol is 200 g / mol to 2000 g / mol.

[0099] Optionally, the molar ratio of boric acid groups in the boric acid component to hydroxyl groups in the polyol is 1:0.5 to 1:2.

[0100] Optionally, the ratio of the number of borate ester bonds in the polymer electrolyte membrane to the number of hydroxyl groups in the polyol is 3% to 25%.

[0101] Optionally, the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium bis(oxalate)borate.

[0102] Optionally, the ionic liquid is selected from one or more of imidazole ionic liquids, pyrrolidine ionic liquids, piperidine ionic liquids, and quaternary ammonium ionic liquids.

[0103] Optionally, the content of the ionic liquid in the coating slurry is 5wt% to 50wt%.

[0104] Optionally, the film-forming method includes casting, blade coating, or spin coating; the curing method includes thermal curing, photocuring, or wet curing.

[0105] Optionally, the thickness of the polymer electrolyte membrane is 10 μm to 500 μm.

[0106] This application also provides a battery cell, which is manufactured using the battery cell manufacturing method described above, comprising:

[0107] The housing includes a positive electrode, a polymer electrolyte membrane, and a negative electrode located within the housing, with the polymer electrolyte membrane situated between the positive and negative electrode.

[0108] Battery cells can be classified into cylindrical cells, prismatic cells, and pouch cells according to their type.

[0109] This application also provides a battery device, including the battery cell as described above, wherein the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

[0110] In another aspect, this application provides an electrical device that includes a battery device as described above, the battery device being used to provide electrical energy.

[0111] Electrical devices include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0112] This application also provides an energy storage device, which includes a battery device as described above, the battery device being used to store electrical energy.

[0113] Energy storage devices include, but are not limited to, residential energy storage cabinets, commercial energy storage cabinets, energy storage containers, energy storage racks, energy storage power stations, energy storage battery packs, or portable energy storage systems. Energy storage devices may also include energy management systems (EMS), battery management systems (BMS), and power conversion systems (PCS).

[0114] The following are specific embodiments illustrating this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0115] To verify the technical effectiveness of the self-healing polymer electrolyte based on the phosphazene skeleton and dynamic crosslinking of borate esters proposed in this application, a series of examples and comparative examples (as shown in Tables 1-1 and 1-2) were designed to systematically investigate the influence of the phosphazene precursor substitution degree, the dynamic crosslinking density of borate esters, the ionic liquid content, the inorganic filler content, and the substitutability of each component on the comprehensive performance of the electrolyte. The example system covers 16 examples and 14 comparative examples, with Example 1 serving as a representative example, Comparative Examples 1 to 7 used to verify the necessity of each core technical feature, and Comparative Examples 8 to 14 used to verify the rationality of the key parameter range. All examples were completed under uniform preparation process conditions to ensure the reliability of the performance comparison. The core technical idea of ​​this application lies in constructing a "permanent crosslinking-dynamic crosslinking" dual-network system: the phosphazene skeleton provides intrinsic flame retardancy and structural stability through the P=N main chain, the dynamic reversible bonds of the borate ester endow the material with self-healing ability, and the ionic liquid and LLZTO filler synergistically construct a three-phase ion transport network. Through systematic formulation design and performance characterization, this application aims to reveal the mechanism of action of various technical elements on conductivity, mechanical strength, self-healing ability, flame retardant performance and cycle stability, and to establish the optimal parameter window, so as to provide technical support for the industrial application of high-safety and long-life solid-state battery electrolytes.

[0116] The raw materials used in the embodiments of this application are all commercially available analytical grade or battery grade reagents, as detailed below:

[0117] Hexachlorocyclotriphosphazene (HCCP, molecular formula N3P3Cl6, purity ≥ 99%) was used as the main phosphazene precursor; octachlorocyclotetraphosphazene (N4P4Cl8, purity ≥ 98%) was used in some examples to verify the substitutability of the precursor; linear polydichlorophosphazene (average molecular weight approximately 15,000, purity ≥ 95%) was used as an optional phosphazene precursor. All reagents were dried in a vacuum drying oven at 80°C for 12 hours before use to remove adsorbed moisture.

[0118] 3-Aminophenylboronic acid (molecular weight 137 g / mol, purity ≥ 98%), as the main boric acid compound, has its amino group undergoing a nucleophilic substitution reaction with the chlorine atom of the phosphazene precursor, while the boric acid group is used to subsequently form dynamic borate ester bonds with polyols; 4-Carboxyphenylboronic acid (molecular weight 166 g / mol, purity ≥ 97%) was used to verify the substitutability of boric acid compounds; phenylboronic acid (molecular weight 122 g / mol, purity ≥ 98%) served as a control boric acid compound. All boric acid compounds were vacuum dried at 40 °C for 24 h before use.

[0119] Polyethylene glycol (PEG-400, average molecular weight 400 g / mol, hydroxyl value 270 mg KOH / g ~ 290 mg KOH / g), as the main polyol component, provides ether oxygen units for lithium-ion coordination transport and simultaneously forms reversible borate ester bonds with borate groups; polyethylene glycol (PEG-600, average molecular weight 600 g / mol) was used to verify the effect of polyol molecular weight; polypropylene glycol (PPG-400, average molecular weight 400 g / mol) was used to verify the substitutability of polyol types; polytetrahydrofuran (PTHF-650, average molecular weight 650 g / mol) was used as an optional polyol. All polyols were dehydrated to a water content of less than 50 ppm using a molecular sieve (3 Å) before use.

[0120] Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, purity ≥ 99.5%, battery grade) was used as the main lithium salt; lithium bis(fluorosulfonyl)imide (LiFSI, purity ≥ 99.9%, battery grade) was used to verify the substitutability of lithium salts and broaden the electrochemical window. All lithium salts were stored and weighed before use in a glove box (argon atmosphere, H2O < 0.5 ppm, O2 < 0.5 ppm).

[0121] 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (EMIM-TFSI, purity ≥ 99%, electrochemical grade) was used as the main ionic liquid component to enhance room-temperature ionic conductivity and plasticize the polymer matrix; 1-butyl-1-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt (Pyr14-TFSI, purity ≥ 99%) was used to verify the substitutability of ionic liquid types; 1-Ethyl-3-methylimidazolium bis(fluoromethanesulfonyl)imide salt (EMIM-FSI, purity ≥ 99%) served as an ionic liquid with a high electrochemical window. All ionic liquids were degassed under high vacuum (< 1 Pa) for 12 h before use and stored in a glove box.

[0122] Lithium lanthanum zirconium tantalum oxide (LLZTO, chemical formula Li) 6.4 La3Zr 1.4 Ta 0.6 O 12 It has a cubic garnet structure, a grain size of 70nm~90nm, and a specific surface area of ​​approximately 12m². 2 / g~15m 2 LLZTO powder (with a purity of ≥99.5%) is used as a fast ion conductor filler. Before use, the LLZTO powder is calcined in a tube furnace at 650°C in air for 2 hours to remove surface-adsorbed moisture and carbon dioxide, and then stored in a glove box for later use. In some examples, LLZTO with a particle size of 50 nm or 100 nm is used to verify the particle size effect.

[0123] N-Methylpyrrolidone (NMP, anhydrous grade, water content less than 100 ppm) was used as the main solvent for slurry preparation; N,N-dimethylformamide (DMF, anhydrous grade) and N,N-dimethylacetamide (DMAc, anhydrous grade) were used as optional solvents. Triethylamine (TEA, purity greater than or equal to 99%) was used as a catalyst or acid-binding agent for partial substitution reactions. Epoxy resin (bisphenol A type, epoxy value 0.48 equivalents / 100g~0.54 equivalents / 100g) and its curing agent (aliphatic amine) were used for the preparation of the static crosslinking network in Comparative Example 4. All solvents were dehydrated by molecular sieve treatment before use.

[0124] The preparation of the polymer electrolyte membrane involves a substitution reaction carried out in a three-necked flask equipped with a mechanical stirrer, a reflux condenser, and a nitrogen protection device. Taking Example 1 as an example, 10.0 g (28.8 mmol, containing 6 reactive P-Cl bonds, with a total P-Cl equivalent of 172.8 mmol) of hexachlorocyclotriphosphazene (HCCP) was weighed into the flask and dissolved in 80 mL of anhydrous NMP. The degree of substitution is defined as the percentage of the equivalent of P-Cl bonds substituted by the boric acid compound relative to the total P-Cl bond equivalent in each batch. For example, for hexachlorocyclotriphosphazene (containing 6 P-Cl bonds per molecule), a degree of substitution of 50% means that an average of 3 P-Cl bonds are substituted per molecule, i.e., 3 mol of boric acid compound is required per mole of phosphazene. For a 50% substitution degree, the required P-Cl equivalent is 86.4 mmol (172.8 mmol × 0.5), therefore 86.4 mmol (11.83 g) of 3-aminophenylboronic acid is needed. This is dissolved in NMP (40 mol), and 12.0 mL (86.4 mmol, as an acid-binding agent) of triethylamine (TEA) is added dropwise to the phosphazene solution. After the addition is complete under ice bath conditions, the reaction system is heated to room temperature and then reacted at 60 °C for 12 h. The hydrochloric acid generated during the reaction is neutralized by triethylamine to form triethylamine hydrochloride (solid or viscous liquid). The reaction is maintained under a nitrogen atmosphere to prevent water and oxygen from entering. After the substitution reaction is complete, the system is cooled to room temperature, and the triethylamine hydrochloride precipitate is removed by filtration or centrifugation to obtain a clear liquid containing the phosphazene-boronic acid intermediate. PEG-400 is then slowly added dropwise to this clear liquid, the amount calculated based on the target crosslinking density: the crosslinking density is defined as the percentage of the number of moles of boric acid groups involved in the crosslinking of the borate ester to the total number of moles of boric acid groups. For a crosslinking density of 12%, 10.37 mmol (86.4 × 0.12) of the 86.4 mmol boric acid groups participate in crosslinking, forming a cyclic borate ester at a 1:1 molar ratio of boric acid to diol, requiring approximately 10.4 mmol (4.16 g) of PEG-400. In practice, to ensure sufficient crosslinking and retain some free PEG to enhance flexibility, the total amount of PEG-400 added can be adjusted to 1.2 to 1.5 times the theoretical amount required for the target crosslinking density, approximately 5 g to 6 g for Example 1. PEG-400 is stirred and mixed evenly at room temperature to obtain a homogeneous solution containing incompletely crosslinked phosphazene-boronate ester prepolymer. This solution can be used directly for subsequent slurry preparation, or partially concentrated under vacuum at 40°C to a solid content of approximately 30% to 35% and stored for later use (it can be stored sealed in a glove box at 4°C for one week).

[0125] Crosslinking density is defined as the percentage of molar borate groups participating in the crosslinking of borate esters to the total molar borate groups, and is controlled by adjusting the amount of polyol added. For example, a crosslinking density of 12% means that approximately 12% of the borate groups form borate ester crosslinking points with the polyol, while the remaining borate groups remain in a free state or form intramolecular rings. For embodiments where the degree of substitution is controlled, the amounts of 3-aminophenylboronic acid and TEA are adjusted according to the P-Cl equivalent ratio. Based on 28.8 mmol HCCP: Example 2 (40% substitution) required 69.1 mmol (9.47 g) of 3-aminophenylboronic acid and 69.1 mmol of TEA; Example 3 (70% substitution) required 120.9 mmol (16.56 g) of 3-aminophenylboronic acid and 120.9 mmol of TEA; Comparative Example 8 (25% substitution) required 43.2 mmol (5.92 g) of 3-aminophenylboronic acid and 43.2 mmol of TEA; Comparative Example 9 (95% substitution) required 164.2 mmol (22.49 g) of 3-aminophenylboronic acid and 164.2 mmol of TEA. While maintaining a crosslinking density of 12%, the amount of PEG-400 used should be adjusted accordingly based on the actual number of borate groups in each example (the theoretical crosslinking requirement is calculated based on 12% of the number of borate groups, and the actual amount used is 1.2 to 1.5 times the theoretical amount). For examples where the boric acid compound or polyol is changed (e.g., 4-carboxyphenylboronic acid is used in Example 13, and PPG-400 is used in Example 14), the corresponding components are replaced while maintaining the same reaction molar ratio. For examples using different phosphazene precursors (e.g., octachlorocyclotetraphosphazene is used in Example 12), the amount of boric acid compound needs to be adjusted according to the number of reactive halogen groups in the precursor.

[0126] The prepolymer solution (or concentrate diluted with NMP to a suitable concentration) obtained above was transferred to the container of a planetary mixer, and lithium salt, ionic liquid, and LLZTO filler were added sequentially. Taking Example 1 as an example, LiTFSI (5.2% of the total mass based on the final dry film mass, corresponding to a lithium ion to ether oxygen unit molar ratio of approximately 0.05), EMIM-TFSI (27.5%), and LLZTO (7%) were added to the prepolymer solution. The order of addition of all components was as follows: first, lithium salt was added and stirred at low speed (300 rpm) for 20 minutes to ensure complete dissolution; then, ionic liquid was added and mixed at medium speed (600 rpm) for 15 minutes; finally, LLZTO powder was added in batches and dispersed at high speed (1200 rpm) for 30 minutes. To ensure uniform dispersion of LLZTO filler, ultrasonic treatment (400W power, pulse mode: 2s on, 2s off) was used to assist dispersion for 15 minutes, followed by degassing under vacuum conditions (-0.09 MPa) for 20 minutes to remove air bubbles. The final slurry has a solid content of 40wt% to 45wt% and a viscosity of approximately 3000mPa·s to 5000mPa·s (25℃, shear rate 10 / s), suitable for blade coating or slot coating processes.

[0127] For the comparative example without ionic liquid (Comparative Example 5), the ionic liquid addition step was omitted, and the remaining components were increased proportionally to maintain a constant total solids content. For the comparative example without LLZTO (Comparative Example 6), the filler addition and ultrasonic dispersion steps were omitted. For the static crosslinking comparative example (Comparative Example 4), epoxy resin and its curing agent were added to the slurry to replace the borate ester dynamic crosslinking system, and the amount of curing agent was calculated based on an epoxy equivalent ratio of 1:1.

[0128] Electrolyte membranes were prepared on polytetrafluoroethylene (PTFE) substrates using a doctor blade coating method. The prepared slurry was poured onto the PTFE substrate and uniformly coated using a doctor blade (with adjustable gap, wet film thickness set to 200 μm~250 μm). The membrane was then pre-dried in a 40°C ventilated oven for 1 hour to evaporate most of the solvent. The pre-dried membrane was then transferred to a programmed temperature oven for staged curing: the first stage was held at 60°C for 2 hours to promote the slow evaporation of residual solvent; the second stage was heated to 80°C and held for 3 hours to promote the borate ester crosslinking reaction; the third stage was optionally held at 70°C under vacuum (-0.09 MPa) for 2 hours to further remove residual solvent and promote the crosslinking reaction to equilibrium. After curing, the electrolyte membrane was slowly cooled at room temperature and then peeled off from the PTFE substrate to obtain a self-supporting flexible electrolyte membrane.

[0129] Comparative Example 1 (Conventional PEO-based Electrolyte): Without using phosphazene precursors and boric acid compounds, PEO (average molecular weight 600,000) was used as the polymer matrix. A slurry was prepared with the same lithium salt, ionic liquid, and LLZTO content. After coating, it was dried at 60°C without a crosslinking curing step. Comparative Example 2 (Linear Polymer Without Dynamic Crosslinking): The phosphazene-boric acid substituted product was synthesized according to the formulation of Example 1, but without the addition of polyol PEG-400, maintaining the system as a linear polymer. Subsequent slurry preparation, coating, and curing steps were the same as in Example 1. Comparative Example 3 (Terminated Boric Acid Groups): After the substitution reaction was completed and before adding the polyol, a terminating agent such as trimethylchlorosilane was added to terminate the boric acid groups into borosilicate ethers, preventing them from forming borate ester bonds with the polyol. Subsequent operations followed the E1 procedure. Comparative Example 4 (Static Crosslinking): A permanent crosslinking network was constructed using epoxy resin and aliphatic amine curing agents to replace the dynamic crosslinking of borate esters. The remaining components remained unchanged. The curing temperature after coating needs to be increased to 120°C and maintained for 4 hours to ensure that the epoxy groups react fully. Comparative Example 7 (phosphazene-free skeleton) uses PEO or other phosphazene-free polyether polymers as the matrix, retains the dynamic crosslinking of 3-aminophenylboronic acid and PEG-400 borate ester, and the remaining components are the same as in Example 1, used to control the contribution of the phosphazene skeleton to the flame retardant properties.

[0130] The characterization and testing methods for the polymer electrolyte membranes and battery cells obtained in each embodiment and comparative example are as follows (as shown in Tables 2-1, 2-2, and 2-3):

[0131] The cured electrolyte membrane was cut into 1cm × 1cm cubes, and its initial mass was measured (accuracy 0.1mg). It was then immersed in an excess of NMP solvent (solvent volume more than 50 times the membrane volume) and allowed to stand at 25°C for 24 hours. During immersion, uncrosslinked soluble components (including unreacted monomers, oligomers, ionic liquids, lithium salts, etc.) dissolved. After immersion, the membrane sample was removed, the surface solvent was blotted dry with filter paper, and then dried to constant weight in a vacuum oven at 60°C. The gel fraction reflects the degree of crosslinking in the system; a higher value indicates a more complete crosslinked network. The crosslinking density (8%~15%) selected in this application typically corresponds to a gel fraction in the range of 85%~98%. In this application, the gel fraction is calculated based on the overall membrane mass (including LLZTO filler) and is used for process window comparison and engineering evaluation of crosslinked network integrity, rather than a strict stoichiometric indicator. The cured electrolyte membrane was cut into 1cm × 1cm cubes, and its initial mass was measured. It was then immersed in a mixed solvent of ethylene carbonate and dimethyl carbonate (volume ratio 1:1) and allowed to swell and reach equilibrium at 25°C for 24 hours. The membrane sample was removed, the surface solvent was quickly blotted dry with filter paper, and the swollen mass was immediately measured. The swelling ratio reflects the tightness of the cross-linked network and the solvent absorption capacity. The optional swelling ratio range in this application is 150%–350%, and more preferably 200%–280%. The swelling ratio is also based on the total membrane mass (including LLZTO filler) and is used to characterize the system's absorption capacity of the electrolyte and the tightness of the network.

[0132] The electrolyte membrane was cut into circular pieces with a diameter of 16 mm (corresponding to an area of ​​2.01 cm²). 2 The electrolyte was sandwiched between two stainless steel barrier electrodes to form a stainless steel-electrolyte-stainless steel symmetric cell. AC impedance spectroscopy was performed using an electrochemical workstation at a constant temperature of 25°C, with a frequency range of 0.01 Hz to 1,000,000 Hz and an AC amplitude of 10 mV. The bulk resistance was read from the intersection of the semicircle in the high-frequency region of the Nyquist plot with the real axis. The electrolyte membrane thickness was measured using a micrometer (average of 5 points), typically ranging from 80 μm to 120 μm. The measured thickness of each sample was used to calculate the conductivity. For temperature-dependent testing, conductivity was measured at three temperature points: -10°C, 25°C, and 60°C, with each temperature held for 30 minutes before testing. All data are based on the average of 3 to 5 parallel sample tests, with a typical error range of ±5% to ±10%.

[0133] The oxidative decomposition potential of the polymer electrolyte membrane was determined using linear sweep voltammetry. A lithium-electrolyte membrane-stainless steel battery was assembled, with stainless steel as the working electrode and lithium metal as the counter and reference electrode. At 25°C, the current was scanned from the open-circuit potential to 6.0 V (relative to the lithium metal potential) at a scan rate of 0.5 mV / s, and the current versus voltage curve was recorded. When the current density suddenly increased (typically defined as exceeding 10 μA / cm²), the voltage was recorded. 2 The potential corresponding to the oxidation decomposition initiation potential is the upper limit of the electrochemical stability window of the electrolyte. In this application, the oxidation decomposition potential of all electrolytes is greater than or equal to 4.8V (relative to the lithium metal potential), making it suitable for high-voltage cathode materials.

[0134] The Bruce-Vincent method was used to determine the lithium-ion transference number. A lithium-electrolyte membrane-lithium symmetric battery was assembled, and the initial interfacial resistance was obtained by AC impedance spectroscopy at 25°C. Subsequently, a constant DC polarization voltage of 10 mV was applied, and the current-time curve was recorded. After the current reached steady state (typically 2-4 hours), the steady-state current was recorded, and AC impedance spectroscopy was performed again under polarization to obtain the steady-state interfacial resistance. This method assumes that the electrode process is pure ion transport and can effectively assess the contribution of lithium ions to the total ionic conductivity of the electrolyte.

[0135] The tensile properties of the electrolyte membrane were tested using a universal testing machine. The polymer electrolyte membrane was cut into standard dumbbell-shaped specimens (effective test section length 25 mm, width 4 mm), and both ends of the specimen were fixed to clamps with a clamping distance of 20 mm. Under conditions of 25°C and 50% relative humidity, the specimen was stretched at a constant rate of 10 mm / min until fracture. Tensile strength (maximum stress at fracture), Young's modulus (the slope of the linear segment of the stress-strain curve, typically taken as the slope within the strain range of 0.5% to 2%), and elongation at break (the percentage of strain at fracture) were obtained from stress-strain curves. Five parallel specimens were tested for each sample, and the average value and standard deviation were reported.

[0136] The polymer electrolyte membrane was cut into 20mm × 20mm squares. A straight incision of approximately 10mm in length, completely penetrating the membrane thickness, was made in the middle of the membrane using a scalpel. The damaged membrane sample was placed under specified repair conditions: for room temperature repair, it was left to stand at 25°C for 24 hours; for accelerated repair, it was left to stand at 60°C for 2 hours. After repair, the incision area was observed using an optical microscope (50x magnification). The residual crack width was measured at 1mm intervals along the incision direction, and the average residual width was calculated. The morphology recovery rate was defined as the percentage of the difference between the initial width and the residual width divided by the initial width, where the initial width was the width measured immediately after the incision was made (typically approximately the blade thickness, 0.3mm~0.5mm).

[0137] A complete polymer electrolyte membrane was assembled into a stainless steel-electrolyte-stainless steel symmetric cell, and its initial ionic conductivity was tested. The cell was then disassembled, and a complete severance damage was created in the middle of the electrolyte membrane. The two membrane parts were aligned and bonded together and repaired under specified conditions (room temperature, 24 h or 60°C, 2 h). After repair, the cell was reassembled, and the conductivity after repair was tested. The conductivity recovery rate was defined as the percentage ratio of the repaired conductivity to the initial conductivity. This indicator directly reflects the reconnection capability of the dynamic cross-linked network at the microscopic interface and is a key indicator for evaluating self-healing functionality. A similar testing procedure to the conductivity recovery rate was used, but a tensile test was employed to evaluate the recovery of mechanical properties. After testing the tensile strength of the complete membrane, a complete severance damage was created, followed by repair under specified conditions. After repair, a tensile test was performed again to obtain the repaired strength. The strength recovery rate was defined as the percentage ratio of the repaired strength to the initial strength. To verify the repeatability of self-healing, multiple cut-repair-test cycles were performed on the same sample, and the change in recovery rate after each cycle was recorded.

[0138] The limiting oxygen index (LOI) test was conducted according to the national standard GB / T2406.2-2009. The electrolyte membrane was cut to standard dimensions (150mm × 10mm × membrane thickness) and vertically fixed to the sample holder of the oxygen indexer. The oxygen concentration in the oxygen-nitrogen mixture was adjusted, the top of the sample was ignited, and the combustion behavior was observed. The limiting oxygen index is defined as the minimum volume percentage of oxygen required to maintain stable combustion of the material (burning time greater than 5 seconds or burning length greater than 50mm). At least five parallel samples were tested, and the average value was reported. An LIO of 26% or higher is generally considered to have good flame retardant properties, and an LIO of 28% or higher is considered close to non-combustible. For thin film samples whose thickness does not meet the standard requirements, multi-layer stacking (3 to 5 layers) can be used to achieve the required test thickness, and the test results are converted to the equivalent performance of a single layer. A vertical burning test was conducted according to the UL-94 standard. The electrolyte membrane was cut into standard 125mm × 13mm samples, held vertically, and ignited from the bottom with a standard flame (propane or methane, flame height 20mm). After 10 seconds, the flame was removed, and the combustion behavior of the samples was recorded (including combustion time, whether dripping occurred, whether it ignited the absorbent cotton, etc.). Based on the combustion behavior, the samples were graded as V-0 (optimal, combustion time less than 10s and no dripping), V-1 (combustion time less than 30s and no dripping), V-2 (combustion time less than 30s but dripping), or HB (continuous combustion, flammable). Five parallel samples were tested for each sample.

[0139] A lithium-electrolyte membrane-lithium symmetric battery was assembled and subjected to constant current charge-discharge cycle testing at 25°C, with the current density set at 0.1 mA / cm². 2 Each charge / discharge cycle takes 0.5 hours (corresponding to a capacity of 0.05 mAh / cm³). 2Record the overpotential (half the voltage difference between the charge and discharge plateaus) for each cycle, for 200 consecutive cycles. A stable overpotential (variation less than 20%) indicates a stable electrolyte-lithium metal interface with no significant side reactions or interfacial impedance growth. This test is used to evaluate the compatibility and interfacial stability of the electrolyte and the lithium metal anode. Using ternary cathode materials (NCM811 or LFP) and lithium metal anodes, coin cells (CR2032) or small pouch cells (typical capacities 50mAh to 200mAh) are assembled. Charge at a constant current of 0.2C to the upper voltage limit (4.3V for NCM811, 3.65V for LFP), then charge at a constant voltage until the current drops to 0.05C; discharge at a constant current of 0.2C to the lower voltage limit (2.8V for NCM811, 2.5V for LFP). Perform 200 charge-discharge cycles at 25°C, recording the discharge capacity for each cycle. Capacity retention is defined as the ratio of the discharge capacity at the 200th cycle to the discharge capacity at the 2nd cycle (the 1st cycle is the formation cycle and is usually not included). This test is used to evaluate the cycle life and capacity decay rate of the electrolyte in practical battery applications.

[0140] To systematically verify the contribution of the four technical features proposed in this application—phosphazene skeleton, dynamic crosslinking of borate ester, ionic liquid, and LLZTO filler—to the overall performance of the electrolyte, this application designed a series of comparative examples. By removing or replacing key technical elements one by one, the mechanism of action of each component and its synergistic effect are clearly revealed (as shown in Tables 3-1, 3-2, and 4). Example 1 represents an optional technical solution of this application, using a formulation with 50% substitution degree of phosphazene-borate ester polymer, 12% dynamic crosslinking density, 27.5 wt% ionic liquid, and 7 wt% LLZTO, achieving an ionic conductivity of 1.35 × 10⁻⁶ at room temperature. -3 The conductivity was 82% (S / cm), Young's modulus was 450 MPa, conductivity recovery rate (room temperature 24h) was 82%, limiting oxygen index was 28.5%, and the overpotential of the lithium-lithium symmetric battery after 200 cycles at 0.1 mA / cm was only 45 mV. As a control, Comparative Example 1 used a traditional PEO-based electrolyte (without phosphazene framework, without dynamic cross-linking), which, although containing the same proportion of ionic liquid and LLZTO filler, had a room temperature conductivity of only 3.50 × 10⁻⁶. -4 The S / cm (only 26% of Example 1), Young's modulus of 280 MPa (37% lower than Example 1), complete lack of self-healing ability (both conductivity and strength recovery rates are 0%), limiting oxygen index of only 18.5% (far below the flame retardant standard), and overpotential of up to 125 mV after 200 cycles of the symmetrical battery (nearly three times that of Example 1). This comparison clearly shows that this application, by introducing a phosphazene skeleton and dynamic cross-linking network, has achieved a comprehensive breakthrough in conductivity, mechanical strength, self-healing ability, flame retardant performance, and interface stability, and has significant technical advantages over traditional PEO-based electrolytes.

[0141] Dynamic cross-linked networks are the core element for achieving self-healing functionality. Comparative Example 2, by not adding polyols to maintain the system as a linear polymer (uncross-linked), exhibits a room temperature conductivity of 8.25 × 10⁻⁶. -4 The Young's modulus was only 80 MPa (82% lower than Example 1), and self-healing ability was completely absent. This result indicates that although linear polymers have high chain segment mobility (which is beneficial for ion transport), the lack of cross-linking network support leads to severely insufficient mechanical strength and the inability to achieve interfacial rebonding at crack sites. Comparative Example 3 prevented the formation of borate ester bonds by end-capping boric acid groups. Although it preserved the structural integrity of the phosphazene skeleton, its Young's modulus dropped to 280 MPa (only 62% of Example 1) due to the inability to form a dynamic cross-linking network, and its self-healing ability was also zero. To further highlight the advantages of dynamic cross-linking compared to traditional static cross-linking, Comparative Example 4 used epoxy resin to construct a permanent cross-linking network. Comparative Example 4 had a Young's modulus as high as 1500 MPa (3.3 times that of Example 1) and a tensile strength of 72 MPa, showing excellent mechanical rigidity, but the elongation at break was only 65% ​​(250% in Example 1), indicating that the material became brittle. More importantly, the room temperature conductivity of Comparative Example 4 dropped significantly to 4.85 × 10⁻⁶. -4 The S / cm ratio (only 36% of Example 1) is due to the highly permanently cross-linked network severely restricting the movement of polymer chains and ion migration. Furthermore, Comparative Example 4 completely lacks self-healing capabilities; once the membrane suffers mechanical damage or interfacial cracking, it cannot be repaired through dynamic bond rearrangement. This comparison clearly reveals the core value of the dynamic cross-linking strategy of this application: while ensuring sufficient mechanical strength, the reversible breakage-reconnection mechanism of borate ester bonds maintains the dynamics of ion transport channels (beneficial for high conductivity) and achieves spontaneous repair after damage.

[0142] The ionic liquid EMIM-TFSI plays a dual role in the system of this application: on the one hand, it has high ionic conductivity (the conductivity of pure EMIM-TFSI at 25°C is approximately 10). -2 (S / cm) can directly contribute to ion transport channels; on the other hand, it acts as a plasticizer, lowering the glass transition temperature of the polymer and enhancing chain segment mobility. In Comparative Example 5, after removing the ionic liquid, the room temperature conductivity decreased to 5.25 × 10⁻⁶. -4The S / cm (only 39% of Example 1) and Young's modulus slightly increased to 550 MPa (due to the disappearance of plasticizing effect leading to system hardening), but more notably, its room temperature self-healing ability also decreased (conductivity recovery rate 62%, strength recovery rate 55%, a decrease of 24% and 27% respectively compared to Example 1). This phenomenon can be explained by the microscopic mechanism of dynamic cross-linking repair: the breaking and reconnection process of borate ester bonds requires sufficient chain segment mobility. Ionic liquids reduce the energy barrier of chain segment mobility through plasticizing, thus achieving faster repair kinetics at room temperature. Notably, the self-healing ability of Comparative Example 5 at 60°C (conductivity recovery rate 80%, strength recovery rate 74%) is close to that of Example 1 at the same temperature (88% and 82%), indicating that the increase in temperature can partially compensate for the chain segment mobility limitation caused by the absence of ionic liquid. In addition, the limiting oxygen index of Comparative Example 5 increased to 29.2% (higher than 28.5% of Example 1), which may be due to the ionic liquid itself changing the pyrolysis path of the system during thermal decomposition.

[0143] The introduction of inorganic filler LLZTO is intended to utilize its high lithium-ion conductivity (the intrinsic conductivity of cubic garnet-type LLZTO is approximately 10). -3 The construction of fast ion microdomains (S / cm) and Lewis acidic surface sites (lanthanum ions, zirconium ions) promotes lithium salt dissociation. Comparative Example 6: After removal of LLZTO, the room temperature conductivity is 8.95 × 10⁻⁶. -4 The S / cm (66% of Example 1) decreased the lithium-ion transference number from 0.52 in Example 1 to 0.46. This result indicates that although the direct bulk conductivity contribution of the LLZTO filler is limited (approximately 3v / v%~4v / v% at a 7wt% volume fraction, not reaching the percolation threshold), the Lewis acid sites on its surface enhance the dissociation of the lithium salt and the free migration ability of lithium ions through interaction with TFSI anions, thereby significantly increasing the lithium-ion transference number. Furthermore, the interfacial impedance (reflected by the overpotential of the symmetrical cell) of Comparative Example 6 was 72mV (higher than 45mV in Example 1), indicating that the LLZTO filler acts as a bridge and buffer between the polymer electrolyte and lithium metal interface, reducing interfacial polarization.

[0144] Phosphazene skeletons possess intrinsic flame-retardant properties due to their P=N main-chain structure. This is because phosphorus and nitrogen form a dense char layer and release non-combustible gases (such as nitrogen oxides and phosphorus oxides) during thermal decomposition, thereby isolating oxygen and heat transfer. Comparative Example 7 uses a PEO-based polymer to replace the phosphazene skeleton but retains the borate ester dynamic crosslinking, ionic liquid, and LLZTO filler. Its limiting oxygen index is only 18.5% (comparable to the phosphazene-free control of Comparative Example 1), far lower than the 28.5% of Example 1. Its UL-94 rating is HB (flammable) instead of V-1, indicating that polyether polymers themselves have extremely poor flame-retardant properties in the absence of added flame retardants. Furthermore, Comparative Example 7 has a room temperature electrical conductivity of 3.25 × 10⁻⁶. -4 The S / cm (only 24% of Example 1) and Young's modulus decreased to 180 MPa (40% of Example 1), indicating that the phosphazene skeleton not only imparts flame retardancy to the material, but its rigid main chain structure also provides important mechanical support. It is noteworthy that Comparative Example 7 still exhibits a certain degree of self-healing ability (65% room temperature conductivity recovery and 58% strength recovery), proving that the dynamic crosslinking mechanism of borate esters can function on different polymer matrices, but its overall performance is inferior to that of the phosphazene-based system.

[0145] Based on clarifying the necessity of each core technical feature, this application further explores the optimal window for key parameters. The degree of substitution of the phosphazene precursor directly affects the density of boric acid groups, thereby affecting the dynamic crosslinking density and self-healing ability. Example 2 (substitution degree 40%), Example 1 (substitution degree 50%), and Example 3 (substitution degree 70%) form a continuous parameter gradient, with room temperature conductivity of 1.18 × 10⁻⁶, respectively. -3 S / cm, 1.35×10 -3 S / cm, 1.28×10 -3 The S / cm ratio shows a trend of first increasing and then decreasing. This phenomenon can be understood as follows: when the substitution degree is too low (e.g., 40% in Example 2), the density of boric acid groups is insufficient, the dynamic cross-linking network is incomplete, resulting in limited mechanical strength and self-healing ability; when the substitution degree is moderate (e.g., 50% in Example 1), the density of boric acid groups is sufficient to form a stable cross-linking network, while still retaining sufficient chain segment movement freedom, achieving the best balance between conductivity and mechanical properties; when the substitution degree is too high (e.g., 70% in Example 3), the excessive boric acid groups lead to an increase in cross-linking point density, restricting chain segment movement, and the conductivity begins to decrease, but the mechanical strength continues to increase (Young's modulus increases from 450 MPa in Example 1 to 520 MPa in Example 3, but elongation decreases from 250% to 220%). Comparative Examples 8 (substitution degree 25%) and 9 (substitution degree 95%) further verified the rationality of the parameter range. The room temperature conductivity of Comparative Example 8 is 5.85 × 10⁻⁶. -4The S / cm (only 43% of Example 1), Young's modulus dropped to 260 MPa (58% of Example 1), and self-healing ability decreased significantly (room temperature conductivity recovery rate 38%, strength recovery rate 32%). Comparative Example 9 had a Young's modulus as high as 820 MPa, but the elongation at break dropped sharply to 120% (48% of Example 1), and the material became brittle and lost its flexibility.

[0146] The dynamic crosslinking density of borate ester is the core control parameter of this application's technical solution, directly determining the balance point of the material's mechanical strength, ion transport capacity, and self-healing kinetics. The room temperature conductivity of Examples 4 (crosslinking density 8%), 1 (crosslinking density 12%), and 5 (crosslinking density 15%) is 1.28 × 10⁻⁶. -3 S / cm, 1.35×10 -3 S / cm, 1.25×10 -3 The S / cm, Young's modulus were 320 MPa, 450 MPa, and 680 MPa, respectively, and the elongation at break were 290%, 250%, and 180%, respectively. This data clearly shows the regulatory effect of crosslinking density on performance: at low crosslinking density (8%), the chain segments have greater freedom of movement, which is beneficial for ion transport (relatively high conductivity), but insufficient mechanical support (lower modulus); at medium crosslinking density (12%), a stable and moderately tight crosslinking network is formed, providing sufficient mechanical strength while ensuring high conductivity, representing the optimal balance point; at high crosslinking density (15%), mechanical strength is significantly improved, but ion transport begins to be hindered (conductivity decreases slightly), and the material's flexibility decreases. Comparative Examples 10 (crosslinking density 3%) and 11 (crosslinking density 22%) further highlight the necessity of the selectable window. The crosslinking network of Comparative Example 10 is too loose; although the room temperature conductivity is as high as 1.05 × 10⁻⁶, it still exhibits poor performance. -3 The S / cm ratio was close to 78% of Example 1, thanks to the highly free movement of chain segments, but the Young's modulus was only 150 MPa (33% of Example 1), the swelling ratio was as high as 485% (far exceeding the reasonable range), and the gel fraction was as low as 58%, indicating that there were a large number of uncrosslinked or oligomer components in the system, and the self-healing ability was also severely insufficient (room temperature conductivity recovery rate 42%, strength recovery rate 35%). Comparative Example 11 represents the extreme case of over-crosslinking, with a Young's modulus as high as 1100 MPa (2.4 times that of Example 1), but the room temperature conductivity dropped sharply to 7.85 × 10⁻⁶. -4 S / cm (58% of Example 1), with an elongation at break of only 55% (the material is extremely brittle).

[0147] The content of the ionic liquid EMIM-TFSI directly affects the balance between the room temperature conductivity and mechanical properties of the electrolyte. The room temperature conductivity of Examples 6 (20% ionic liquid content), 1 (27.5% ionic liquid content), and 7 (35% ionic liquid content) was 1.15 × 10⁻⁶. -3 S / cm, 1.35×10 -3 S / cm, 1.48×10 -3 The S / cm conductivity showed a monotonically increasing trend with increasing ionic liquid content, due to the high conductivity and plasticizing effect of the ionic liquid itself enhancing polymer chain segment movement. However, the Young's modulus showed the opposite trend, reaching 580 MPa, 450 MPa, and 380 MPa respectively. Excessively high ionic liquid content led to over-plasticization of the system, resulting in a significant decrease in mechanical strength. Comparative Examples 12 (8% ionic liquid content) and 13 (55% ionic liquid content) defined the boundaries of a reasonable window. The excessively low ionic liquid content in Comparative Example 12 resulted in a room temperature conductivity of only 7.85 × 10⁻⁶. -4 S / cm (58% of Example 1), although the Young's modulus is as high as 640 MPa (the material is relatively hard), the room temperature repair rate is reduced, and the time required to reach the same recovery rate is prolonged. Comparative Example 13 represents the extreme case with a high ionic liquid content, and its room temperature conductivity is as high as 1.25 × 10⁻⁶. -3 S / cm (close to 93% of Example 1), but Young's modulus dropped sharply to 120 MPa (27% of Example 1), the material almost lost its self-supporting ability, and the swelling ratio was as high as 385% (the system was close to a gel state).

[0148] LLZTO filler enhances the ion transport performance and interfacial stability of electrolytes through its high lithium-ion conductivity and surface Lewis acidic sites; however, excessively high content can lead to filler agglomeration and decreased conductivity. The room temperature conductivity of Examples 8 (5 wt% LLZTO), 1 (7 wt% LLZTO), and 9 (10 wt% LLZTO) was 1.25 × 10⁻⁶. -3 S / cm, 1.35×10 -3 S / cm, 1.42×10 -3 The S / cm values ​​and lithium-ion transference numbers were 0.50, 0.52, and 0.54, respectively, and the overpotentials of the symmetric cells were 52 mV, 45 mV, and 40 mV, respectively. These data indicate that within the range of 5 wt% to 10 wt%, increasing the LLZTO content positively promotes conductivity, transference number, and interfacial stability, and has not yet reached the critical point where filler agglomeration leads to performance degradation. Comparative Example 14 (LLZTO content 18 wt%) clearly demonstrates the negative effects of excessive filler. The room temperature conductivity of Comparative Example 14 decreased to 6.15 × 10⁻⁶. -4S / cm (only 46% of Example 1) is because the excessive filler content causes LLZTO particles to agglomerate in the polymer matrix, forming dead zones for ion transport and increasing interfacial scattering.

[0149] The lithium salt concentration was characterized by the molar ratio of lithium ions to ether oxygen units. This ratio reflects the coordination relationship between lithium ions and the ether oxygen units of the polyether segment, directly affecting the degree of dissociation and ionic conductivity of the lithium salt. The room temperature conductivity of Examples 10 (ratio 0.03), 1 (ratio 0.05), and 11 (ratio 0.09) was 1.15 × 10⁻⁶. -3 S / cm, 1.35×10 - 3 S / cm, 1.28×10 -3 The S / cm ratio and the overpotentials of the symmetrical cells were 65mV, 45mV, and 52mV, respectively. This data indicates that there is an optimal ratio (approximately 0.05): when the ratio is too low, the lithium-ion concentration is insufficient; although the degree of lithium salt dissociation is high, the total carrier concentration is low, resulting in limited conductivity. When the ratio is moderate, the lithium-ion concentration and degree of dissociation reach an optimal balance, with the highest conductivity and the lowest interface overpotential. When the ratio is too high, although the lithium-ion concentration increases, the excess lithium salt leads to the formation of ion pairs and aggregates, causing the effective carrier concentration to decrease, conductivity to begin to decrease, and interface polarization to increase.

[0150] To broaden the scope of technical protection of this application and verify the universality of the technical solution, this application designs a series of component substitution examples. Example 12 uses octachlorocyclotetraphosphazene to replace hexachlorocyclotriphosphazene in E1. While maintaining a substitution degree of 50% and keeping the other components unchanged, the room temperature conductivity of Example 12 is 1.28 × 10⁻⁶. -3 The flame retardant properties were: S / cm (95% of Example 1), Young's modulus of 440 MPa (98% of Example 1), self-healing ability (80% room temperature conductivity recovery and 73% strength recovery) comparable to Example 1, and limiting oxygen index of 28.2% (slightly lower than Example 1 but still maintaining excellent flame retardant properties). These results indicate that different cyclic phosphazene precursors can achieve similar performance at the same degree of substitution. Example 13 used 4-carboxyphenylboronic acid instead of 3-aminophenylboronic acid in Example 1. The room temperature conductivity of Example 13 was 1.28 × 10⁻⁶. -3 The S / cm (95% of Example 1), Young's modulus of 455 MPa (101% of Example 1), and self-healing ability are comparable to Example 1. Example 14 uses polypropylene glycol PPG-400 instead of polyethylene glycol PEG-400 in Example 1. The room temperature conductivity of Example 14 is 1.18 × 10⁻⁶. -3The S / cm (87% of Example 1) and Young's modulus were 400 MPa (89% of Example 1), with slightly lower self-healing ability than Example 1. Example 15 used lithium bis(fluorosulfonyl)imide (LiFSI) instead of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in Example 1. Example 15 achieved a room temperature conductivity of 1.45 × 10⁻⁶. -3 S / cm (107% of Example 1), the electrochemical window widened to 5.4V (5.3V relative to the lithium metal potential in Example 1), the lithium-ion transference number was 0.53 (0.52 in Example 1), and the overpotential of the symmetric cell decreased to 42mV (45mV in Example 1).

[0151] Self-healing capability is one of the core technical highlights of this application. To further verify the self-healing mechanism and performance of the borate ester dynamic crosslinking network, this application designed a specific self-healing verification example 16. After standing at room temperature (25°C) for 24 hours, Example 16 exhibited excellent self-healing capability: the morphology recovery rate reached 95% (observed by optical microscopy, the initially completely severed crack almost completely closed after 24 hours), the electrical conductivity recovery rate reached 85%, and the strength recovery rate reached 78%. More importantly, after three cut-repair cycles, the electrical conductivity recovery rate of Example 16 remained above 80%, and the strength recovery rate remained above 72%, indicating that the self-healing capability is repeatable and will not significantly decrease due to repeated damage. This result experimentally verifies the reversibility and stability of the borate ester dynamic crosslinking network: the borate ester bonds can undergo a dynamic equilibrium of breakage and reconnection at room temperature. When the film is mechanically damaged and a new fracture interface is generated, the exposed borate groups and hydroxyl groups at the interface achieve interface rebonding through diffusion and bond exchange mechanisms.

[0152] To evaluate the kinetics of self-healing and simulate accelerated repair scenarios that may be encountered in practical applications (such as temperature rise during battery charging and discharging), Example 16 underwent accelerated self-healing testing at 60°C. At 60°C, Example 16 achieved a morphology recovery rate of 95% (comparable to 24 hours at room temperature), a conductivity recovery rate of 92% (significantly higher than 85% at 24 hours at room temperature), and a strength recovery rate of 85% (significantly higher than 78% at 24 hours at room temperature) in just 2 hours. This result indicates that increasing the temperature can significantly accelerate the kinetics of the borate ester exchange reaction and shorten the repair time. Accelerated repair at 60°C is particularly suitable for in-situ self-healing of batteries during operation: when microcracks develop in the battery due to cycling or external forces, the temperature rise during charging and discharging (typically reaching 40°C~60°C) can promote spontaneous repair of the electrolyte membrane, thereby extending battery life. The borate ester exchange reaction can also occur spontaneously in a dry environment; temperature rise is the main driving force promoting repair. This characteristic makes the self-healing electrolyte of this application particularly suitable for application in closed battery systems. Furthermore, in Example 16, after five cut-repair cycles at 60°C, the conductivity recovery rate remained above 88%, further demonstrating the repeatability and stability of the self-healing capability.

[0153] To clearly verify that the self-healing ability originates from the dynamic cross-linking of borate esters rather than other factors, Comparative Example 4 used an epoxy static cross-linking network as a control. Under the same repair conditions (room temperature, 24h or 60℃, 2h), Comparative Example 4 showed absolutely no self-healing ability: morphology recovery rate was 0% (no change in crack width), conductivity recovery rate was 0% (the cut film could not regain conductivity), and strength recovery rate was 0% (unable to withstand any tensile load). This result clearly demonstrates that once a permanent cross-linked network breaks, it is irreversible and cannot be rebonded through heat treatment or static resting. Besides single-cycle repair performance, the impact of self-healing ability on the long-term cycle stability of the battery is also crucial for evaluating its practical value. Example 16 exhibited excellent cycle stability in full-cell cycle testing (NCM811-lithium, 0.2C rate, 25℃), achieving a capacity retention of 92.5% after 200 cycles (slightly higher than the 91.8% of Example 1). In contrast, although Comparative Example 4 had excellent initial performance (high mechanical strength), it could not repair the microcracks and interface damage generated during the cycling process. Its capacity retention rate was only 88.5% after 200 cycles, and the capacity decay rate accelerated in the later stages of cycling.

[0154] Through systematic examples and comparative studies, this application clearly verifies the technical advantages of self-healing polymer electrolytes based on phosphazene skeletons and dynamic crosslinking of borate esters. Compared with traditional PEO-based electrolytes, optional example E1 of this application shows a 286% improvement in room temperature ionic conductivity, a 61% improvement in Young's modulus, a 10% expansion of the electrochemical window, a 54% improvement in limiting oxygen index, a 64% reduction in overpotential of lithium-lithium symmetric batteries, and a 22% improvement in capacity retention after 200 cycles of the full cell. More importantly, Example 1 exhibits excellent self-healing capabilities (82% conductivity recovery and 75% strength recovery at room temperature after 24 hours), a function completely absent in traditional electrolytes. This application achieves a comprehensive breakthrough in the safety, electrochemical performance, mechanical properties, and functionality of solid-state electrolytes through the synergistic innovation of "phosphazene skeleton + dynamic crosslinking + ionic liquid + fast ion filler". Common self-healing strategies in existing literature include supramolecular hydrogen bonding networks, Diels-Alder reactions, and metal coordination bonds. While supramolecular hydrogen bond networks can achieve rapid self-healing at room temperature, the relatively weak hydrogen bond strength typically results in low mechanical strength, making them unsuitable for use as self-supporting electrolyte membranes. Diels-Alder reactions, while providing higher mechanical strength, require high-temperature bond exchange reactions (typically above 80°C), hindering room-temperature self-healing. Metal coordination bonds can achieve room-temperature self-healing, but the introduction of metal ions may affect lithium-ion transport and pose potential electrochemical stability risks. In contrast, the borate ester dynamic crosslinking mechanism of this application offers advantages including low activation energy (rapid exchange at room temperature), moderate bond energy (providing sufficient mechanical support), electrochemical inertness (borate ester bonds are stable over a wide electrochemical window), and environmental friendliness.

[0155] All raw materials used in this application are commercially available chemicals. The synthesis route and preparation process are simple and controllable (one-step replacement of reaction, slurry preparation, coating, and curing), suitable for large-scale production. The curing process uses conventional heat treatment (60℃~80℃, 3h~4h), requiring no special equipment or harsh conditions, and is compatible with existing electrolyte membrane production lines. In terms of technological maturity, this application has completed the entire chain of research from material design, formulation optimization, performance characterization to application verification. The formulation in Example 1 achieved a capacity retention rate of 91.8% in NCM811-lithium full cells after 200 cycles, approaching the requirements for practical application.

[0156] In summary, the core technological innovations of this application can be summarized as follows: Firstly, a dual-network synergistic design of dynamic crosslinking between the phosphazene backbone and borate ester was proposed and realized for the first time. The phosphazene backbone provides a permanent structural framework, intrinsic flame retardancy, and mechanical support, while the dynamic bonds of the borate ester endow the material with rapid self-healing capabilities at room temperature. Secondly, the influence of five key parameters—phosphazene substitution degree, borate ester crosslinking density, ionic liquid content, LLZTO filler content, and the lithium-ion to ether-oxygen unit ratio—on the comprehensive performance of the electrolyte was systematically revealed. Thirdly, a three-phase ion transport network was constructed through the synergistic effect of the ionic liquid and LLZTO filler, achieving an ionic conductivity of 10 at room temperature. -3 It exhibits excellent ion transport performance on the order of S / cm and a lithium-ion transference number greater than or equal to 0.5; it verifies that the dynamic cross-linking mechanism of borate ester can achieve efficient and repeatable self-repair at room temperature, and the repair time can be shortened to 2h by heating to 60℃, which is particularly suitable for in-situ self-repair of batteries during operation.

[0157] Table 1-1

[0158]

[0159] Table 1-2

[0160]

[0161] In Tables 1-1 and 1-2, the verification objectives of each example and comparative example are as follows: Example 1, Gold Standard (all parameters can be selected); Example 2, Lower Limit Verification of Substitution Degree; Example 3, Upper Limit Verification of Substitution Degree; Example 4, Lower Limit Verification of Crosslinking Density; Example 5, Upper Limit Verification of Crosslinking Density; Example 6, Lower Limit Verification of Ionic Liquid Content; Example 7, Upper Limit Verification of Ionic Liquid Content; Example 8, Lower Limit Verification of LLZTO Content; Example 9, Upper Limit Verification of LLZTO Content; Example 10, [Li + [EO] Lower limit verification; Example 11, [Li + [EO] Upper limit verification; Example 12, phosphazene precursor replaceability; Example 13, boric acid compound replaceability; Example 14, polyol replaceability; Example 15, lithium salt replaceability; Example 16, self-healing performance verification; Comparative Example 1, comparison with conventional technology; Comparative Example 2, no need for dynamic crosslinking; Comparative Example 3, necessity of boric acid groups; Comparative Example 4, superiority of dynamic crosslinking; Comparative Example 5, necessity of ionic liquid; Comparative Example 6, necessity of LLZTO filler; Comparative Example 7, necessity of phosphazene skeleton; Comparative Example 8, substitution too low; Comparative Example 9, substitution too high; Comparative Example 10, crosslinking density too low; Comparative Example 11, crosslinking density too high; Comparative Example 12, ionic liquid content too low; Comparative Example 13, ionic liquid content too high; Comparative Example 14, LLZTO content too high.

[0162] Table 2-1

[0163]

[0164] Table 2-2

[0165]

[0166] Table 2-3

[0167]

[0168] Table 3-1

[0169]

[0170] Table 3-2

[0171]

[0172] Table 4

[0173]

[0174] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A method for manufacturing a single battery cell, characterized in that, include: The preparation steps for the polymer electrolyte membrane include: A phosphazene precursor is subjected to a nucleophilic substitution reaction with a boric acid compound to obtain a nucleophilic substitution product. Then, a polyol and a lithium salt are added to the nucleophilic substitution product to react and obtain a prepolymer solution. The phosphazene precursor includes a halogen group, and the boric acid compound includes a boric acid component and a substituted functional group that can undergo a substitution reaction with the halogen group. The ionic liquid is added to the prepolymer solution and mixed, and then ionic conductor particles are added and dispersed to obtain a coating slurry; The coating slurry is formed into a film and then crosslinked and cured to obtain the polymer electrolyte membrane; The positive electrode, the polymer electrolyte membrane and the negative electrode are stacked in sequence and then placed into the housing after being processed by stacking or winding to obtain the initial battery cell. The initial battery cell is subjected to a formation process to obtain the battery cell; The substituted functional group is selected from one or more of amino, hydroxyl, and carboxyl groups.

2. The method for manufacturing a single battery cell according to claim 1, characterized in that, The phosphazene precursor is selected from one or more of hexachlorocyclotriphosphazene, octachlorocyclotetraphosphazene, and linear polydichlorophosphazene.

3. The method for manufacturing a single battery cell according to claim 1, characterized in that, The boric acid component is selected from one or more of arylboronic acid, alkylboronic acid, heterocyclic boronic acid and their derivatives.

4. The method for manufacturing a battery cell according to claim 1 or 3, characterized in that, The degree of substitution of the prepolymer in the prepolymer solution is 30% to 90%.

5. The method for manufacturing a battery cell according to claim 1 or 3, characterized in that, The molecular weight of the boric acid component is 100 g / mol to 500 g / mol.

6. The method for manufacturing a single battery cell according to claim 1, characterized in that, The polyol is selected from one or more of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran glycol.

7. The method for manufacturing a battery cell according to claim 1 or 6, characterized in that, The number-average molecular weight of the polyol is 200 g / mol to 2000 g / mol.

8. The method for manufacturing a single battery cell according to claim 1, characterized in that, The molar ratio of boric acid groups to hydroxyl groups in the polyol is 1:0.5 to 1:

2.

9. The method for manufacturing a single battery cell according to claim 1, characterized in that, The ratio of the number of borate ester bonds in the polymer electrolyte membrane to the number of hydroxyl groups in the polyol is 3% to 25%.

10. The method for manufacturing a single battery cell according to claim 1, characterized in that, The lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium bis(oxalate)borate.

11. The method for manufacturing a single battery cell according to claim 1, characterized in that, The ionic liquid is selected from one or more of imidazole ionic liquids, pyrrolidine ionic liquids, piperidine ionic liquids, and quaternary ammonium ionic liquids.

12. The method for manufacturing a battery cell according to claim 1 or 11, characterized in that, In the coating slurry, the content of the ionic liquid is 5wt%~50wt%.

13. The method for manufacturing a single battery cell according to claim 1, characterized in that, The film-forming method includes casting, blade coating, or spin coating; the curing method includes thermal curing, photocuring, or wet curing.

14. The method for manufacturing a single battery cell according to claim 1, characterized in that, The thickness of the polymer electrolyte membrane is 10μm to 500μm.

15. A single battery cell, characterized in that, Prepared by the manufacturing method of any one of claims 1 to 14, comprising: The housing includes a positive electrode, a polymer electrolyte membrane, and a negative electrode located within the housing, with the polymer electrolyte membrane situated between the positive and negative electrode.

16. A battery device, characterized in that, The battery device includes one or more of the following: battery cell as described in claim 15, battery device including battery module, battery pack, and energy storage battery.

17. An electrical device, characterized in that, The electrical device includes the battery device as described in claim 16, the battery device being used to provide electrical energy.

18. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 16, the battery device being used to store electrical energy.

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