Composite solid electrolyte membrane, preparation method and solid lithium battery

Abstract

The invention belongs to the technical field of solid electrolyte preparation, and particularly relates to a composite solid electrolyte membrane, a preparation method and a solid lithium battery. Wherein the composite solid electrolyte membrane comprises a solid electrolyte three-dimensional composite skeleton, and a crown ether functional polymer, a lithium salt and an additive which are arranged on the surface of the solid electrolyte three-dimensional composite skeleton; the solid electrolyte three-dimensional composite skeleton is prepared from a solid electrolyte modified by polyamide acid PAA and polydopamine PDA. According to the solid electrolyte three-dimensional composite skeleton membrane constructed by the invention, the solid electrolyte is modified by PDA, and the surface of the solid electrolyte is compounded by the crown ether functional polymer, the lithium salt, the combined additive FEC and the inorganic filler to form the composite solid electrolyte membrane, so that the synergism of ionic conduction efficiency, interfacial compatibility and structural stability is realized, and therefore, the solid electrolyte three-dimensional composite skeleton membrane can be used for preparing the composite solid electrolyte membrane. And the cycle performance and the safety performance of the battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte preparation technology, and particularly relates to a composite solid electrolyte membrane, its preparation method, and a solid lithium battery. Background Technology

[0002] Lithium-ion batteries have been widely used in consumer electronics, electric vehicles, and distributed energy storage due to their advantages such as high energy density, long cycle life, and high design flexibility. However, traditional liquid lithium-ion batteries use liquid electrolytes, which can cause lithium metal to form dendrites during cycling and react with the electrolyte, leading to safety issues such as instability of the solid electrolyte interphase (SEI), lithium dendrite penetration of the separator, short circuits, and even thermal runaway. Furthermore, the flammability and leakage properties of liquid electrolytes further exacerbate the safety risks of lithium metal batteries under high energy density conditions.

[0003] To address the aforementioned issues, solid-state electrolytes, due to their excellent thermal stability and mechanical strength, can effectively suppress dendrite formation and prevent electrolyte leakage, and are considered an effective way to replace liquid electrolytes and improve the safety of lithium metal batteries. Existing solid-state electrolytes mainly include three categories: inorganic solid-state electrolytes, organic polymer solid-state electrolytes, and organic-inorganic composite solid-state electrolytes. Inorganic solid-state electrolytes have high ionic conductivity and excellent mechanical properties, but they are brittle, have poor interfacial contact, are complex to process, and are expensive. Polymer solid-state electrolytes have good flexibility, good interfacial contact with electrodes, and can be molded at low cost, but they suffer from low ionic conductivity, insufficient mechanical strength, and limited high-voltage resistance, making it difficult to meet the long-term stable operation requirements of high-energy-density lithium metal batteries.

[0004] To overcome these shortcomings, researchers have proposed introducing inorganic reinforcing phases into polymer electrolytes to prepare composite solid electrolytes, i.e., organic-inorganic composite solid electrolytes have become the mainstream research. However, existing composite solid electrolytes still have many shortcomings: on the one hand, the interfacial compatibility between inorganic solid electrolytes and organic polymer matrices is poor, easily generating interfacial impedance and reducing ion conduction efficiency; on the other hand, the mechanical support capacity of composite electrolytes is limited, and they are prone to deformation during battery charging and discharging, failing to effectively suppress lithium dendrite puncture, thus still posing safety risks.

[0005] Three-dimensional fiber skeleton materials are widely used to enhance the supporting performance of composite solid electrolytes due to their unique porous structure, high specific surface area and excellent mechanical strength. They can also form a continuous ion transport network in the polymer matrix, which helps to achieve efficient ion migration and improve the overall mechanical properties and thermal stability of the system.

[0006] While existing composite solid-state electrolytes have improved in terms of ionic conductivity and mechanical properties, they still generally suffer from problems such as poor interfacial contact, low ion transference number, and insufficient structural stability, making it difficult to achieve long cycle life and high safety in high-voltage lithium metal batteries. Therefore, designing a composite solid-state electrolyte that combines high ionic conductivity, excellent interfacial stability, and mechanical strength has become a key technical problem that urgently needs to be solved in the current lithium metal battery field. Summary of the Invention

[0007] This invention provides a composite solid electrolyte membrane, its preparation method, and a solid-state lithium battery, addressing the problems of low ionic conductivity, poor interfacial stability, and insufficient mechanical strength in existing technologies. A three-dimensional framework with high ionic conductivity regions is constructed by combining ceramic solid electrolyte particles with a polyimide phase. A polycrown ether polymer lithium salt precursor is infiltrated into this three-dimensional framework and solidified to form a continuous interfacial ion transport pathway, enhancing the lithium-ion migration rate. Nano-silica, as an inorganic filler, significantly improves the electrolyte's conductivity and ion transference number. This invention is suitable for producing high-energy-density lithium metal batteries and all-solid-state lithium batteries, meeting the demand for high-safety and long-life batteries.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, this application provides a composite solid electrolyte membrane, comprising a three-dimensional composite framework of a solid electrolyte and crown ether functionalized polymer, lithium salt and additives disposed on the surface of the three-dimensional composite framework of the solid electrolyte. The solid electrolyte three-dimensional composite framework is prepared from a solid electrolyte modified with polyamic acid (PAA) and polydopamine (PDA).

[0009] The preparation method of the solid electrolyte three-dimensional composite skeleton is as follows: a polyamic acid (PAA) solution is mixed with a solid electrolyte powder modified with polydopamine (PDA) to form an electrospinning solution. After obtaining a fiber membrane using an electrospinning device, the fiber membrane is dried under vacuum to obtain the solid electrolyte three-dimensional composite skeleton. The electrospinning solution is a solid electrolyte modified with polyamic acid (PAA):PDA with a mass ratio of (5-9):(1-5), preferably, the mass ratio of PAA:PDA modified solid electrolyte is 7:3.

[0010] The polyamic acid PAA is prepared in the following manner: under a nitrogen atmosphere, 2,2'-diaminodiphenyl ether ODA is added to N,N-dimethylacetamide DMAc, and pyromellitic dianhydride PMDA is added. The mixture is stirred and reacted to obtain a polyamic acid PAA solution. Preferably, the mass ratio of polyamic acid (PAA):N,N-dimethylacetamide (DMAc):N,N-dimethylacetamide (DMAc):pyromellitic dianhydride (PMDA) is 15:1:1.

[0011] The solid electrolyte modified with polydopamine (PDA) includes a solid electrolyte and a polydopamine layer coated on the surface of the solid electrolyte. Preferably, the solid electrolyte modified with polydopamine PDA is prepared by the following method: aminotris(hydroxymethyl)methane and dopamine hydrochloride are dissolved in methanol, solid electrolyte powder is added, the mixture is stirred continuously, pure oxygen gas is continuously introduced into the reaction system, dopamine self-polymerizes, and after the reaction is completed, the solid electrolyte modified with polydopamine PDA is obtained by drying. Preferably, the solid electrolyte is a ceramic solid electrolyte, and more preferably LLZTO.

[0012] The crown ether functionalized polymer is prepared by the following method: under nitrogen protection, a polycarboxylated polymer is dissolved in an organic solvent, a catalyst and a carboxyl activator are added and stirred to form an activation intermediate of the carboxyl group; a monool crown ether compound is slowly added to the activation solution to react, so that the carboxyl part of the polycarboxylated polymer reacts with the hydroxyl part of the crown ether alcohol to obtain the crown ether functionalized polymer. Preferably, the ratio of the polycarboxylated polymer: catalyst: carboxyl activator: monool crown ether compound is 50:0.5:11.5:4.5.

[0013] The monool crown ether compound is one of 2-hydroxymethyl-12-crown-4, 2-hydroxymethyl-18-crown-6, or benzo-12-crown-4-2-methanol; Preferably, the polycarboxylated polymer is one of polyacrylic acid (PAA), polymethacrylic acid (PMAA), or polymaleic acid (PMA); Preferably, the catalyst is a 4-dimethylaminopyridine DMAP carboxyl activator; Preferably, the carboxyl activator is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride EDC·HCl; Preferably, the ratio of the crown ether functionalized polymer to the lithium salt is (1-2):1, and preferably, the lithium salt is lithium bis(fluorosulfonyl)imide (LiTFSI).

[0014] The additive is a mixture of organic and inorganic additives. Preferably, the organic additive accounts for 1-5 wt% of the mass of the crown ether functionalized polymer and the lithium salt mixture; Preferably, the inorganic additive accounts for 10-30 wt% of the mixture of the crown ether functionalized polymer and the lithium salt; Preferably, the organic additive is fluoroethylene carbonate (FEC); Preferably, the inorganic additive is nano-silica (SiO2).

[0015] In a second aspect, this application provides a method for preparing the composite solid electrolyte membrane described above, characterized by comprising the following steps: casting a crown ether polymer composite electrolyte liquid onto the surface of a three-dimensional composite skeleton of a solid electrolyte, and performing scraping and curing to obtain a three-dimensional fiber skeleton reinforced composite solid electrolyte membrane. The crown ether polymer composite electrolyte solution is prepared by dissolving the crown ether functionalized polymer, the lithium salt, and the additives in an organic solvent; The organic solvent is one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, or N-methyl-2-pyrrolidone.

[0016] In a third aspect, this application provides a solid-state lithium battery, which is encapsulated from the aforementioned composite solid-state electrolyte membrane, positive electrode, and negative electrode. The positive electrode is composed of a positive electrode active material, a conductive agent super P, a binder PVDF and an additive LiTFSI, and a solvent N-methylpyrrolidone NMP. Preferably, the mass ratio of positive electrode active material: conductive agent Super P: binder PVDF: additive LiTFSI is 80:10:8:2; Preferably, the positive electrode active material includes one or more of lithium cobalt oxide (LCO), lithium iron phosphate (LFP), and lithium nickel cobalt manganese oxide (NCM). The negative electrode is one or more of lithium metal or lithium metal alloy negative electrodes.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This application focuses on the preparation of high-performance composite solid electrolyte membranes. By constructing a three-dimensional composite framework of polyimide / solid electrolyte, a solid electrolyte modified with polydopamine (PDA), and crown ether functionalized polymers, combined with inorganic fillers, a synergistic improvement in ion conduction efficiency, interfacial compatibility, and structural stability is achieved, offering the following advantages: (1) Three-dimensional fiber composite skeleton improves interface stability Solid electrolyte powder was surface-coated and modified using polydopamine (PDA). The hydroxyl and amino functional groups abundant in PDA significantly improved the interfacial bonding between the solid electrolyte and polyamic acid (polyimide precursor). The polyimide / solid electrolyte three-dimensional fiber skeleton prepared by electrospinning has both high mechanical strength and continuous three-dimensional pore structure, providing stable support for the subsequent penetration and solidification of electrolyte solution.

[0018] (2) Crown ether functionalized polymers enhance ion conduction performance This innovative method utilizes a monool crown ether (2-hydroxymethyl-12-crown-4) and a polycarboxyl polymer (polyacrylic acid) to prepare branched crown ether functionalized polymers via esterification. Leveraging the lithium-ion complexing properties of the crown ether macrocycle, it achieves lithium-ion chelation. + Highly selective complexation, improving Li + Migration number. The combined additive FEC optimizes the interface, promotes the formation of a robust CEI film containing nitrogen derivatives and LiF to improve cycling, participates in lithium ion coordination and preferentially reduces it on the lithium anode side, promoting the formation of a stable SEI film. At the same time, the inorganic filler nano-SiO2 assists in promoting the dissociation of lithium salt and suppressing anions, enhancing the Li+ transport capacity, and significantly improving the ionic conductivity and ion migration number of the electrolyte.

[0019] In summary, the three-dimensional fiber composite skeleton structure provides a continuous inorganic-organic interface ion transport channel, which significantly improves ion conductivity and reduces the interfacial impedance of lithium-ion transport. At the same time, the three-dimensional support of the skeleton combined with the flexibility of the crown ether polymer composite electrolyte balances the mechanical strength and interfacial contact of the electrolyte membrane, meeting the requirements for high safety and long life battery. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the preferred embodiments.

[0021] Example 1: 1.3D Fiber Composite Skeleton Preparation (1) Under a nitrogen atmosphere, 150.00 g of N,N-dimethylacetamide (DMAc) was added to a 250 mL three-necked flask, followed by 9.79 g of 2,2'-diaminodiphenyl ether (ODA). After mechanical stirring until completely dissolved, 10.66 g of pyromellitic dianhydride (PMDA) was added in portions under an ice-water bath. After mechanical stirring for 24 h, a PAA solution was obtained and stored in a sealed container at low temperature.

[0022] (2) 72.6 mg of aminotris(hydroxymethyl)methane (Tris) and 120 mg of dopamine hydrochloride (dopamine·HCl) were dissolved in 60 mL of methanol to form a transparent solution. 5 g of solid electrolyte powder was slowly added while stirring at 400 rpm. After the solid electrolyte powder was added, the solution gradually changed from colorless to light brown. Pure oxygen gas was then continuously introduced into the reaction system to promote the oxidative self-polymerization of dopamine. The reaction was carried out at room temperature for 16 h, with constant stirring to ensure uniform reaction. After the reaction, the product was collected by filtration, washed twice with methanol to remove unreacted dopamine and byproducts, and then dried in a vacuum oven (60 °C). The dried powder changed from white to brown, indicating that a polydopamine (PDA) coating layer was successfully formed on the surface of the solid electrolyte powder. This PDA layer is rich in hydroxyl and amino functional groups, which can significantly improve the interfacial compatibility and chemical bonding ability between the solid electrolyte and the polymer matrix. (3) After drying the PDA-modified solid electrolyte powder, it is mixed with PAA solution to form an electrospinning solution with a mass ratio of PAA:PDA-modified solid electrolyte = 7:3. (4) Electrospinning equipment was used, with a voltage of 18 kV and a liquid pushing rate of 0.6 mL·h. -1 Collection distance 20cm, roller speed 300r·min -1 The moving platform moves at a speed of 1 cm·s -1 Spinning was performed under specific conditions, and the resulting fiber membrane was collected. (5) The obtained fiber membrane was dried at 60°C until the residual solvent was removed, and then vacuum dried at 200°C for 2 hours to obtain a three-dimensional composite skeleton of polyimide / solid electrolyte with a three-dimensional structure.

[0023] 2. Preparation of crown ether polymer composite electrolyte Branched crown ether functionalized polymers were prepared by esterification of 2-hydroxymethyl-12-crown-4 with polyacrylic acid.

[0024] (1) Dissolving the polymer: Under nitrogen protection, dissolve 5.0 g of polyacrylic acid in 50 ml of dry organic solvent N,N-dimethylformamide (DMF) and stir until completely dissolved to form a homogeneous polymer solution. The solution should be kept anhydrous to avoid hydrolysis of the carboxyl-activated intermediate.

[0025] (2) Carboxyl activation: Under nitrogen protection, 0.05 g of 4-dimethylaminopyridine (DMAP) catalyst and 1.15 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) were added to the polyacrylic acid solution. The mixture was stirred for 1 h to allow the carboxyl groups to form an activation intermediate.

[0026] (3) Crown etherification reaction: Under nitrogen protection, 0.45 g of 2-hydroxymethyl-12-crown-4 was slowly added to the activation solution. The reaction was stirred at room temperature to 40°C for 24 h to allow the carboxyl group of polyacrylic acid to undergo esterification with the crown ether alcohol.

[0027] (4) Post-processing and purification: After the reaction is completed, the generated precipitate byproducts are removed by filtration, the filtrate is evaporated by rotary evaporation to remove the solvent, and the crude product is obtained. Unreacted small molecules and byproducts are removed by washing twice with ethanol, and the product is dried under vacuum at 60°C for 12 hours to obtain crown-etherified polyacrylic acid polymer.

[0028] (5) The obtained crown-etherified polyacrylic acid polymer is mixed with dry bis(fluorosulfonyl)imide lithium salt (LiTFSI) at a mass ratio of 1:1. 3 wt% of fluoroethylene carbonate (FEC) and 20 wt% of nano-silica (SiO2) are added to the mixture and uniformly dissolved in dry organic solvent (DMF). The weight of the solvent is 3 times the mass of the crown-etherified polyacrylic acid polymer, lithium salt, and additive mixture. After being ultrasonically dispersed uniformly at 60°C, a crown-ether polymer composite electrolyte solution is formed.

[0029] 3.3D fiber skeleton reinforced composite solid electrolyte membrane preparation The polyimide / solid electrolyte three-dimensional composite skeleton was immersed in ethanol and dried to remove any possible impurities. Next, the polyimide / solid electrolyte three-dimensional composite skeleton was laid flat on a glass plate surface, and a DMF solution of crown ether polymer composite electrolyte was poured onto the surface of the modified polyimide (PI) skeleton. After being coated by scraping, it was transferred to a 60°C hot plate for curing, resulting in a 3D fiber skeleton-reinforced composite solid electrolyte membrane.

[0030] 4.3D fiber skeleton reinforced composite solid electrolyte membrane lithium battery fabrication Lithium nickel cobalt manganese oxide (NCM) (molecular formula LiNi) 0.8 Co 0.1 Mn 0.1 O2), conductive agent Super P, binder PVDF, and additive LiTFSI are mixed in N-methylpyrrolidone (NMP) at a mass ratio of 80:10:8:2. After uniform mixing, the slurry is coated onto aluminum foil and dried in a vacuum oven at 80°C for 24 hours. The dried electrode sheet is cut into 10mm diameter discs and stored for later use. The negative electrode uses one or more of lithium metal or lithium metal alloy negative electrodes, which are conventional commercial electrode materials. The battery assembly process is mainly as follows: the composite electrode sheet, solid electrolyte, Li electrode, stainless steel sheet, and spring sheet are assembled into the CR2032 button cell in the following order. To achieve good interfacial contact and ion conduction between the electrolyte and the composite electrode sheet, 1.0 μL·mAh -1Electrolyte was dropped onto the surface of the composite electrode (1M LiTFSI EC / DEC=1:1, v / v, LFP; 1.2M LiPF6 EC / EMC=3:7, v / v, NCM).

[0031] Example 2: In Example 2, an electrospinning solution with a mass ratio of PAA:PDA modified solid electrolyte = 5:5 was formed, and the remaining steps were consistent with those in Example 1.

[0032] Example 3: In Example 3, an electrospinning solution with a mass ratio of PAA:PDA modified solid electrolyte = 9:1 was formed, and the remaining steps were consistent with those in Example 1.

[0033] Example 4: In Example 4, the obtained crown-etherified polyacrylic acid polymer was mixed with dry LiTFSI lithium salt at a mass ratio of 2:1, and the remaining steps were the same as those in Example 1.

[0034] Example 5: In Example 5, 5% wt of FEC was added, and the remaining steps were the same as those in Example 1.

[0035] Example 6: In Example 6, 1% wt of FEC was added, and the remaining steps were consistent with those in Example 1.

[0036] Example 7: In Example 7, 30% wt of nano-SiO2 was added, and the remaining steps were consistent with those in Example 1.

[0037] Example 8: In Example 8, 10% wt of nano-SiO2 was added, and the remaining steps were consistent with those in Example 1.

[0038] Comparative Example 1: In Comparative Example 1, only PAA electrospinning solution was formed, and the remaining steps were consistent with those in Example 1.

[0039] Comparative Example 2: In Comparative Example 2, FEC was not added, and the remaining steps were consistent with those in Example 1.

[0040] Comparative Example 3: In Comparative Example 3, no nano-SiO2 was added, and the remaining steps were consistent with those in Example 1.

[0041] Comparative Example 4: PEO, LiTFSI, nano-SiO2, and FEC were thoroughly mixed in a mass ratio of 5:5:2:0.3 and magnetically stirred at 50°C for 6 hours to form a homogeneous solution. The stirred slurry was then uniformly coated onto a polytetrafluoroethylene plate and allowed to stand at room temperature for 60 minutes. Afterward, it was heated at 50°C under an argon atmosphere for 2 hours to allow the solvent to evaporate, and then vacuum dried at 40°C for 12 hours to obtain the composite electrolyte membrane. The battery preparation process was consistent with that in Example 1.

[0042] (2) Composite solid electrolyte membrane and battery testing: a. Ionic conductivity test A clean, smooth stainless steel sheet (SS) was used as the blocking electrode, with the electrolyte sandwiched between two SSs and sealed within a coin cell. The assembled cell was placed in a 60°C oven for 1 hour to ensure adequate interface contact. After cooling to room temperature, the cell was connected to an electrochemical workstation using a coin cell clamp, and AC impedance spectra were recorded at different temperatures. The frequency range was 0.1 Hz to 1 MHz, and the AC amplitude was 10 mV. The ionic conductivity of the corresponding electrolyte was calculated.

[0043] b. Electrolyte-Li Electrode Interface Stability Test An electrolyte was sandwiched between two Li electrodes and sealed in a coin cell casing to assemble a Li||Li battery. The assembled battery was placed in a 60°C oven for 1 hour to ensure full interface contact. After cooling to room temperature, the battery was placed in a 25°C oven, and the symmetrical battery was connected to a battery testing system using 0.1 mA·cm². -2 The current density was used to test the stability of the Li electrode interface at a temperature of 25°C.

[0044] c. Assembly and testing of solid-state batteries After assembling the batteries, allow them to stand for approximately 6 hours, then place them in a 60°C oven for 1 hour to ensure full interface contact. Once cooled to room temperature, perform charge-discharge tests using a battery testing system. Capacity testing was conducted at 0.1C rate with a voltage window of 2.7-4.2V, and cycle testing was performed at 0.5C rate with a voltage window of 2.7-4.2V at a test temperature of 25°C.

[0045] The test results are shown in Table 1:

[0046] As can be seen from Table 1: (1) As can be seen from Examples 2-3 and Example 1, different mass ratios of PDA-modified solid electrolyte powder after drying and PAA solution were used. According to the experimental results in the table, the optimal mass ratio of polyamic acid PAA:PDA-modified solid electrolyte is 7:3. If too much modified solid electrolyte is added, the ionic conductivity does not increase substantially, but if too little is added, the ionic conductivity will be too low. This indicates that an appropriate amount of solid electrolyte is added to form more interfacial ionic activity, which can significantly improve the interfacial compatibility and chemical bonding ability between the solid electrolyte and the polymer matrix, and reduce the interfacial impedance. However, too much does not help ion transport, thus affecting the battery capacity and cycle performance.

[0047] (2) As can be seen from Examples 4 and 1, crown-etherified polyacrylic acid polymers are used in different mass ratios with dry LiTFSI lithium salt. Insufficient lithium salt addition will lead to a decrease in ionic conductivity, an increase in impedance, and affect the transport of lithium ions, thereby reducing the capacity of the cathode material and deteriorating the cycle performance.

[0048] (3) As can be seen from Examples 5 and 7 and Example 1, the difference between Examples 5 and 7 is that the amount of FEC added is too much and too little, respectively. Compared with Example 1, the ionic conductivity, lithium interface stability and cycling performance are reduced to varying degrees. This is because if FEC, as a dual film-forming additive, forms a film that is too thin, it will not provide sufficient protection for the electrolyte membrane and will be decomposed, which will reduce the cycling stability; conversely, if the film is too thick, it will reduce the ionic conductivity and increase the impedance, which will also reduce the cycling stability.

[0049] (4) As can be seen from Examples 6 and 8 and Example 1, the different proportions of nano-SiO2 content in Examples 6 and 8 have varying degrees of impact on ionic conductivity, capacity, and cycle life compared to Example 1. This is because nano-SiO2, as an inorganic filler, is Lewis acidic, which restricts anion movement and promotes lithium salt dissociation. The residual groups on the surface can also inhibit polycrown ether crystallization, thus doubly improving lithium-ion conductivity. If the amount of nano-SiO2 added is too small, it will lead to a decrease in the ionic conductivity of the electrolyte membrane, and the capacity and cycle performance will also decrease accordingly. If the amount added exceeds 20%wt, it will hinder ion transport, which will also reduce the performance.

[0050] (5) As can be seen from Comparative Example 1 and Example 1, Comparative Example 1 did not add PDA-modified solid electrolyte. Compared with Example 1, the ionic conductivity, lithium interface stability, capacity and cycle life were significantly reduced. This is because the solid electrolyte acts as an ionic conductor in the three-dimensional framework, and together with the polycrown ether polymer, it improves the ionic conductivity, thereby improving the battery performance.

[0051] (6) As can be seen from Comparative Example 2 and Example 1, Comparative Example 2 did not add FEC. Compared with Example 1, the ionic conductivity, lithium interface stability and cycling performance were reduced, and the interface lacked the protection of film-forming additives.

[0052] (7) As can be seen from Comparative Example 3 and Example 1, Comparative Example 3 did not add nano SiO2. Compared with Example 1, the ionic conductivity, capacity and cycle life were reduced. Due to the lack of inorganic filler SiO2, the polymer electrolyte was prone to crystallization and agglomeration, the lithium salt was not completely dissociated, and the lithium ion transport performance was reduced.

[0053] (8) As can be seen from Comparative Example 4 and Example 1, Comparative Example 4 uses a PEO polymer electrolyte and lacks a three-dimensional framework support. Compared with Example 1, its ionic conductivity, lithium interface stability, capacity, and cycle life are all reduced. The polymer electrolyte membrane is soft and has poor resistance to lithium dendrites, making it easily broken down during cycling. At the same time, the lithium-ion transport path is relatively simple, unlike Example 1 which has the support of a three-dimensional lithium-ion transport network. Therefore, it exhibits low lithium-ion conductivity and deteriorated battery performance.

[0054] In summary, the three-dimensional fiber composite framework structure of this application provides a continuous inorganic-organic interface ion transport channel, significantly improving ionic conductivity, enhancing the mechanical properties of the electrolyte, and greatly increasing its hardness. It also possesses the ability to resist lithium dendrite formation. Specifically, PDA-functionalized LLZTO improves the mixing uniformity with polyimide, effectively preventing agglomeration and forming more interfacial ion activity. This significantly improves the interfacial compatibility and chemical bonding ability between the solid electrolyte and the polymer matrix, reducing interfacial impedance. The crown ether polymer system enables the control of Li... + Highly selective complexation, improving Li + The migration number, combined with the additive FEC to promote the formation of a robust CEI film of nitrogen-containing derivatives and LiF to improve cycling, participates in lithium-ion coordination and preferentially reduces on the lithium anode side, promoting the formation of a stable SEI film, protecting the polymer and lithium salt under high voltage. Simultaneously, the inorganic filler nano-SiO2 promotes lithium salt dissociation and suppresses anions, enhancing LiF's ability to migrate. + The three-dimensional fiber skeleton reinforced and supported composite solid electrolyte membrane has high safety, high flexibility and excellent ionic conductivity, making it suitable for lithium metal batteries.

[0055] The above description is merely an example of the embodiments of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A composite solid electrolyte membrane, characterized in that, It includes a three-dimensional composite framework of a solid electrolyte and crown ether functionalized polymers, lithium salts, and additives disposed on the surface of the three-dimensional composite framework of the solid electrolyte; The solid electrolyte three-dimensional composite framework is prepared from a solid electrolyte modified with polyamic acid (PAA) and polydopamine (PDA).

2. The composite solid electrolyte membrane according to claim 1, characterized in that, The preparation method of the solid electrolyte three-dimensional composite skeleton is as follows: a polyamic acid (PAA) solution is mixed with a solid electrolyte powder modified with polydopamine (PDA) to form an electrospinning solution. After obtaining a fiber membrane using an electrospinning device, the fiber membrane is dried under vacuum to obtain the solid electrolyte three-dimensional composite skeleton. The electrospinning solution is a solid electrolyte modified with polyamic acid (PAA):PDA with a mass ratio of (5-9):(1-5), preferably, the mass ratio of PAA:PDA modified solid electrolyte is 7:

3.

3. The composite solid electrolyte membrane according to claim 2, characterized in that, The polyamic acid PAA is prepared in the following manner: under a nitrogen atmosphere, 2,2'-diaminodiphenyl ether ODA is added to N,N-dimethylacetamide DMAc, and pyromellitic dianhydride PMDA is added. The mixture is stirred and reacted to obtain a polyamic acid PAA solution. Preferably, the mass ratio of N,N-dimethylacetamide (DMAc): 2,2'-diaminodiphenyl ether (ODA): pyromellitic dianhydride (PMDA) is 15:1:

1.

4. The composite solid electrolyte membrane according to claim 2, characterized in that, The solid electrolyte modified with polydopamine (PDA) includes a solid electrolyte and a polydopamine layer coated on the surface of the solid electrolyte. Preferably, the solid electrolyte modified with polydopamine PDA is prepared by the following method: aminotris(hydroxymethyl)methane and dopamine hydrochloride are dissolved in methanol, solid electrolyte powder is added, the mixture is stirred continuously, pure oxygen gas is continuously introduced into the reaction system, dopamine self-polymerizes, and after the reaction is completed, the solid electrolyte modified with polydopamine PDA is obtained by drying. Preferably, the solid electrolyte is a ceramic solid electrolyte, and more preferably LLZTO.

5. The composite solid electrolyte membrane according to claim 1, characterized in that, The crown ether functionalized polymer is prepared by the following method: under nitrogen protection, the polycarboxyl polymer is dissolved in an organic solvent, a catalyst and a carboxyl activator are added and stirred to form an activated intermediate of carboxyl groups; The monool crown ether compound is slowly added to the activation solution to react, so that the carboxyl group -COOH in the polycarboxyl polymer reacts with the hydroxyl group -OH in the monool crown ether compound to obtain the crown ether functionalized polymer; Preferably, the mass ratio of the polycarboxyl polymer: catalyst: carboxyl activator: monool crown ether compound is 50:0.5:11.5:4.

5.

6. The composite solid electrolyte membrane according to claim 5, characterized in that, The monool crown ether compound is one of 2-hydroxymethyl-12-crown-4, 2-hydroxymethyl-18-crown-6, or benzo-12-crown-4-2-methanol; Preferably, the polycarboxylated polymer is one of polyacrylic acid (PAA), polymethacrylic acid (PMAA), or polymaleic acid (PMA); Preferably, the catalyst is a 4-dimethylaminopyridine DMAP carboxyl activator; Preferably, the carboxyl activator is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride EDC·HCl.

7. The composite solid electrolyte membrane according to claim 1, characterized in that, The ratio of the crown ether functionalized polymer to the lithium salt is (1-2):1, and preferably, the lithium salt is lithium bis(fluorosulfonyl)imide (LiTFSI).

8. The composite solid electrolyte membrane according to claim 1, characterized in that, The additive is a mixture of organic and inorganic additives. Preferably, the organic additive accounts for 1-5 wt% of the mass of the crown ether functionalized polymer and the lithium salt mixture; Preferably, the inorganic additive accounts for 10-30 wt% of the mixture of the crown ether functionalized polymer and the lithium salt; Preferably, the organic additive is fluoroethylene carbonate (FEC); Preferably, the inorganic additive is nano-silica (SiO2).

9. A method for preparing a composite solid electrolyte membrane according to any one of claims 1-8, characterized in that, The process includes the following steps: casting crown ether polymer composite electrolyte liquid onto the surface of a solid electrolyte three-dimensional composite skeleton, and then curing it by scraping to obtain a three-dimensional fiber skeleton reinforced and supported composite solid electrolyte membrane. The crown ether polymer composite electrolyte solution is prepared by dissolving the crown ether functionalized polymer, the lithium salt, and the additives in an organic solvent; The organic solvent is one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, or N-methyl-2-pyrrolidone.

10. A solid-state lithium battery, characterized in that: It comprises a composite solid electrolyte membrane as described in any one of claims 1-8, a positive electrode, and a negative electrode encapsulated thereon. The positive electrode is composed of a positive electrode active material, a conductive agent super P, a binder PVDF and an additive LiTFSI, and a solvent N-methylpyrrolidone NMP. Preferably, the mass ratio of positive electrode active material: conductive agent Super P: binder PVDF: additive LiTFSI is 80:10:8:2; Preferably, the positive electrode active material includes one or more of lithium cobalt oxide (LCO), lithium iron phosphate (LFP), and lithium nickel cobalt manganese oxide (NCM). The negative electrode is one or more of lithium metal or lithium metal alloy negative electrodes.

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