Composite solid-state polymer electrolyte membrane and preparation method thereof, and solid-state lithium ion battery
By anchoring boron-containing groups on the surface of inorganic fillers and forming a three-dimensional cross-linked network, the problems of low ionic conductivity and high-pressure oxidative decomposition of PEO-based solid polymer electrolytes are solved, thereby improving the mechanical strength and electrochemical stability of solid-state batteries.
Patent Information
- Application Number
- CN202610426605.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-02
- Publication Date
- 2026-06-30
AI Technical Summary
PEO-based solid polymer electrolytes have high crystallinity at room temperature, resulting in poor ionic conductivity. They are also prone to oxidation and decomposition under high voltage conditions, leading to performance degradation in solid-state batteries.
By chemically modifying the surface of inorganic fillers with boron-containing silane coupling agents, boron-containing groups are anchored on the surface of the inorganic fillers. Combined with hydrogen-extractable photoinitiators and multifunctional unsaturated monomers, composite solid polymer electrolyte membranes are prepared to form a three-dimensional cross-linked network.
The mechanical strength of the electrolyte membrane was improved, the risk of lithium dendrite puncture was suppressed, and the ion conduction and electrochemical stability window were optimized under high voltage conditions, reducing the risk of oxidative decomposition.
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Abstract
Description
Technical Field
[0001] This application relates to the field of electrochemical energy storage technology, specifically to a composite solid polymer electrolyte membrane and its preparation method, and a solid lithium-ion battery. Background Technology
[0002] Solid-state batteries (such as solid-state lithium-ion batteries) possess excellent safety and high energy density, making them a key direction for next-generation energy storage technology, and solid-state electrolytes have become a research hotspot. Among them, polyethylene oxide (PEO)-based solid polymer electrolytes have advantages such as good flexibility, good interfacial contact with electrodes, and ease of processing and molding. However, the high crystallinity of PEO-based solid polymer electrolytes at room temperature leads to poor ionic conductivity, and their electrochemical stability window is narrow. They are also prone to oxidative decomposition under high-voltage conditions, resulting in performance degradation of solid-state batteries. Summary of the Invention
[0003] In view of this, this application provides a composite solid polymer electrolyte membrane and its preparation method, as well as a solid lithium-ion battery, to solve the above-mentioned technical problems.
[0004] To achieve the above objectives, in a first aspect, this application provides a method for preparing a composite solid polymer electrolyte membrane, comprising the following steps: chemically modifying the surface of an inorganic filler using a borosilicate coupling agent to anchor boron-containing groups onto the surface of the inorganic filler, thereby preparing a modified filler; dissolving polyethylene oxide, lithium salt, hydrogen-extractable photoinitiator, and multifunctional unsaturated monomer in an organic solvent to prepare a precursor solution; dispersing the modified filler in the precursor solution to prepare a composite slurry; and after the composite slurry is formed into a film, initiating a crosslinking reaction by ultraviolet light irradiation to form a three-dimensional crosslinked network, thereby preparing the composite solid polymer electrolyte membrane.
[0005] Based on the first aspect, in some embodiments, the surface of the inorganic filler is chemically modified using a boron-containing silane coupling agent to anchor boron-containing groups onto the surface of the inorganic filler. This includes the following steps: hydrolyzing the boron-containing silane coupling agent under acidic conditions to generate boron-containing silanol groups, and condensing the boron-containing silanol groups with the hydroxyl groups on the surface of the inorganic filler to form Si-OM covalent bonds, wherein M is a metal element in the inorganic filler, thereby anchoring the boron-containing groups onto the surface of the inorganic filler.
[0006] Based on the first aspect, in some embodiments, the amount of borosilicate coupling agent used is 10%-20% of the mass of the inorganic filler.
[0007] Based on the first aspect, in some embodiments, the amount of hydrogen-extractable photoinitiator used is 1%-2% of the mass of polyethylene oxide.
[0008] Based on the first aspect, in some embodiments, the amount of the multifunctional unsaturated monomer is 5%-10% of the mass of the polyethylene oxide.
[0009] Based on the first aspect, in some embodiments, the amount of modified filler used is 5%-15% of the mass of polyethylene oxide.
[0010] Based on the first aspect, in some embodiments, the intensity of the ultraviolet light irradiation is 50 mW / cm². 2 -100 mW / cm 2 The irradiation time is 10 min-30 min.
[0011] Based on the first aspect, in some embodiments, the inorganic filler includes lithium lanthanum zirconium oxide.
[0012] Based on the first aspect, in some embodiments, the borosilicate coupling agent includes a silane compound containing a borate ester group and / or a borosilicate group.
[0013] Based on the first aspect, in some embodiments, hydrogen-extractable photoinitiators include benzophenone compounds.
[0014] Based on the first aspect, in some embodiments, the multifunctional unsaturated monomer includes multifunctional acrylate compounds.
[0015] Based on the first aspect, in some embodiments, the oxygen-lithium molar ratio of polyethylene oxide to lithium salt is (10-20):1.
[0016] Secondly, this application provides a composite solid polymer electrolyte membrane, prepared according to the above-described preparation method; the composite solid polymer electrolyte membrane includes a polymer matrix, a modified filler, and a lithium salt, wherein the polymer matrix includes polyethylene oxide and a three-dimensional cross-linked network structure bonded to polyethylene oxide.
[0017] Thirdly, this application provides a solid-state lithium-ion battery, which includes the aforementioned composite solid-state polymer electrolyte membrane.
[0018] Compared with traditional solutions, this application has the following advantages:
[0019] In this application, by anchoring boron-containing groups to the surface of inorganic fillers via covalent bonds, it is beneficial to avoid the aggregation or migration of boron-containing components in the solid polymer matrix due to physical blending, thereby helping to maintain stable interfacial protection during long-term cycling. Simultaneously, the use of hydrogen-extractable photoinitiators to prepare the PEO polymer matrix allows for the polymerization of multifunctional unsaturated monomers under ultraviolet light irradiation without end-group modification of polyethylene oxide, forming a three-dimensional cross-linked network bonded to the polyethylene oxide backbone. This helps improve the mechanical strength of the electrolyte membrane and suppress the risk of lithium dendrite puncture. When the composite solid polymer electrolyte membrane prepared by this method is applied to solid-state batteries, under high-voltage conditions, the anchored boron-containing groups can preferentially oxidize and decompose, facilitating the in-situ formation of an interfacial film rich in inorganic boron and oxygen components on the positive electrode surface. This further promotes ion conduction, and the synergistic effect of the improved mechanical strength brought by the three-dimensional cross-linked network structure helps reduce the risk of oxidative decomposition of the electrolyte under high voltage, thereby improving the electrochemical stability window. Detailed Implementation
[0020] To facilitate understanding of the technical solutions of this application, a more comprehensive description of the technical solutions will be provided below. The technical solutions of this application can be implemented in many different forms and are not limited to the embodiments described herein. Rather, the purpose of providing these embodiments is to make the disclosure of the technical solutions of this application more thorough and comprehensive.
[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0022] To address the shortcomings of traditional PEO-based solid polymer electrolytes, such as poor room-temperature ionic conductivity and susceptibility to oxidation and decomposition under high-voltage conditions, related technologies have attempted to improve their mechanical strength by using UV curing to prepare a PEO polymer matrix. However, due to the saturated structure of the PEO backbone and the lack of active double bonds, traditional photoinitiators struggle to directly induce cross-linking of the PEO backbone. This makes it difficult for added multifunctional monomers to react with the PEO chain and form a true interpenetrating or grafted network, resulting in limited mechanical reinforcement. Furthermore, relying on end-group modification of PEO is costly and involves complex processes. Related technologies have also attempted to improve the mechanical strength and ionic conductivity of solid polymer electrolytes by introducing inorganic nanofillers (such as LLZO and Al2O3) through physical blending, or by adding small molecule additives (such as LiBOB) to construct high-voltage protective films. However, traditional physically blended small molecule additives have low diffusion coefficients in the solid polymer matrix, making it difficult to effectively migrate to the positive electrode interface. Moreover, they are prone to aggregation and loss under long-term cycling or high temperatures, leading to unsustainable high-voltage protection. Meanwhile, inorganic fillers typically contain hydroxyl groups on their surface, which readily react with lithium salts to produce HF, easily corroding the electrode interface. Physical mixing makes it difficult to eliminate undesirable interfacial side reactions.
[0023] Based on this, one embodiment of this application provides a method for preparing a composite solid polymer electrolyte membrane, comprising the following steps:
[0024] Step 1: Chemically modify the surface of inorganic fillers using boron-containing silane coupling agents to anchor boron-containing groups onto the surface of the inorganic fillers, thereby preparing modified fillers.
[0025] In the above steps, by anchoring the boron-containing groups to the surface of the inorganic filler in the form of covalent bonds, it is beneficial to avoid the agglomeration or migration of boron-containing components in the solid polymer matrix due to physical blending, thereby helping to maintain a stable interface protection function during long-term cycling.
[0026] In some embodiments, the surface of inorganic fillers is chemically modified using boron-containing silane coupling agents to anchor boron-containing groups onto the surface of the inorganic fillers. This includes the following steps: hydrolyzing the boron-containing silane coupling agent under acidic conditions to generate boron-containing silanol groups; the boron-containing silanol groups condense with hydroxyl groups on the surface of the inorganic fillers to form Si-OM covalent bonds, where M is a metal element in the inorganic filler. This anchors the boron-containing groups onto the surface of the inorganic filler. Acidic hydrolysis of the boron-containing silane coupling agent forms stable covalent bonds between the boron-containing groups and the inorganic fillers, which enhances the fixation effect of the boron-containing components in the polymer matrix and reduces the risk of detachment or phase separation under long-term cycling or high-temperature conditions. Simultaneously, the formation of Si-OM covalent bonds covers the active hydroxyl groups on the surface of the inorganic fillers, helping to reduce the possibility of side reactions between the fillers and lithium salts to generate HF, thereby reducing the risk of electrode interface corrosion.
[0027] In some embodiments, the amount of borosilicate coupling agent used is 10%-20% of the mass of the inorganic filler. For example, the amount of borosilicate coupling agent relative to the mass of the inorganic filler can be 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, or any value within the range of any two of the above values. Controlling the amount of borosilicate coupling agent within the above range is beneficial for forming a uniform and moderately dense boron-containing group modification layer on the surface of the inorganic filler, thereby promoting an effective covalent anchoring effect and reducing multilayer adsorption or free residue when there is a large amount of coupling agent. This helps maintain the dispersion stability of the filler and the uniformity of subsequent crosslinking reactions.
[0028] In some embodiments, the inorganic filler comprises lithium lanthanum zirconium oxide. Using lithium lanthanum zirconium oxide as the inorganic filler provides excellent lithium-ion conductivity and electrochemical stability. Combined with covalent anchoring modification of boron-containing groups, it is beneficial to improve the ionic conductivity of the electrolyte membrane while utilizing the anchored boron-containing components to form a protective interfacial film under high voltage, thus helping to further extend the operating voltage window of the electrolyte. Understandably, when the inorganic filler comprises lithium lanthanum zirconium oxide, the M in the covalent Si-OM bond includes Zr and / or La.
[0029] In some embodiments, the borosilicate coupling agent comprises a silane compound containing borate ester groups and / or borane groups. The aforementioned borosilicate coupling agent can form a covalent bond with the surface of the inorganic filler through the silane end, and can expose the boron-containing functional end to the outside of the filler. This facilitates the preferential participation of the boron-containing groups in the interfacial reaction under high-voltage charge-discharge conditions, generating an inorganic interfacial film rich in boron and oxygen components in situ, thereby improving the high-voltage withstand capability of the cathode interface.
[0030] Step 2: Dissolve polyethylene oxide, lithium salt, hydrogen-extractable photoinitiator and multifunctional unsaturated monomer in an organic solvent to prepare a precursor solution.
[0031] In the above steps, the PEO polymer matrix is prepared using a hydrogen-extractable photoinitiator. This allows for the polymerization of multifunctional unsaturated monomers initiated by ultraviolet light irradiation without the need for end-group modification of polyethylene oxide. This forms a three-dimensional cross-linked network bonded to the polyethylene oxide backbone, which helps to improve the mechanical strength of the electrolyte membrane and suppress the risk of lithium dendrite puncture.
[0032] In some embodiments, the amount of hydrogen-extractable photoinitiator used is 1%-2% of the mass of polyethylene oxide. For example, the amount of hydrogen-extractable photoinitiator relative to the mass of polyethylene oxide can be 1%, 1.05%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95%, 2%, or any value within the range of any two of the above values. Controlling the amount of hydrogen-extractable photoinitiator within the above range helps to generate sufficient active free radicals under ultraviolet light irradiation to initiate the polymerization reaction of polyfunctional unsaturated monomers, forming a structurally stable three-dimensional cross-linked network, while reducing the risk of adverse effects on the ionic conductivity or interfacial stability of the electrolyte membrane due to initiator residue.
[0033] In some embodiments, the amount of the multifunctional unsaturated monomer is 5%-10% of the mass of polyethylene oxide. For example, relative to the mass of polyethylene oxide, the amount of the multifunctional unsaturated monomer can be 5%, 5.25%, 5.5%, 5.75%, 6%, 6.25%, 6.5%, 6.75%, 7%, 7.25%, 7.5%, 7.75%, 8%, 8.25%, 8.5%, 8.75%, 9%, 9.25%, 9.5%, 9.75%, 10%, or any value within the range of any two of the above values. Controlling the amount of the multifunctional unsaturated monomer within the above range is beneficial for forming a three-dimensional network structure with a moderate crosslinking density, which improves the mechanical strength of the electrolyte membrane while maintaining the mobility of polymer chain segments, thereby balancing the mechanical properties and ion conductivity of the membrane.
[0034] In some embodiments, hydrogen-extracting photoinitiators include benzophenone compounds. Benzophenone photoinitiators can effectively extract hydrogen atoms from the ether bonds of the polyethylene oxide backbone under ultraviolet light irradiation, generating macromolecular free radicals, which initiate the polymerization reaction of multifunctional unsaturated monomers. This facilitates the chemical bonding between polyethylene oxide and the crosslinked network without altering the end-group structure of polyethylene oxide, simplifying the process and improving the stability of the crosslinked structure.
[0035] In some embodiments, the multifunctional unsaturated monomer includes multifunctional acrylate compounds. Multifunctional acrylate compounds contain multiple polymerizable unsaturated bonds, which can rapidly form a three-dimensional cross-linked network under free radical initiation conditions. Furthermore, the covalent connection between these compounds and the polyethylene oxide chains, formed through a hydrogen extraction reaction, helps enhance the structural integrity of the polymer matrix, thereby improving the electrolyte membrane's resistance to lithium dendrite penetration and its antioxidant mechanical properties.
[0036] In some embodiments, the oxygen-lithium molar ratio of polyethylene oxide to lithium salt is (10-20):1. For example, the oxygen-lithium molar ratio of polyethylene oxide to lithium salt can be 10:1, 10.5:1, 11:1, 11.5:1, 12:1, 12.5:1, 13:1, 13.5:1, 14:1, 14.5:1, 15:1, 15.5:1, 16:1, 16.5:1, 17:1, 17.5:1, 18:1, 18.5:1, 19:1, 19.5:1, 20:1, or any value within the range of any two of the above values. Controlling the oxygen-lithium molar ratio of polyethylene oxide to lithium salt within the above range is beneficial for forming an appropriate amount of lithium-ion transport channels in the polyethylene oxide matrix, balancing ionic conductivity and polymer chain mobility, and also helps maintain the compatibility and reactivity of the system during the crosslinking reaction.
[0037] Step 3: Disperse the modified filler in the precursor solution to prepare the composite slurry.
[0038] In some embodiments, the amount of modified filler is 5%-15% of the mass of polyethylene oxide. For example, the amount of modified filler relative to the mass of polyethylene oxide can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, or any value within the range of any two of the above values. Controlling the amount of modified filler within the above range helps to form a good filler dispersion system in the polymer matrix, utilizes the anchored boron-containing groups to form a protective interfacial film at the positive electrode interface, and reduces the risk of obstructed ion transport paths or increased membrane brittleness when there is a large amount of modified filler.
[0039] Step 4: After the composite slurry is formed into a film, it is irradiated with ultraviolet light to initiate a cross-linking reaction, forming a three-dimensional cross-linked network, and thus preparing a composite solid polymer electrolyte membrane.
[0040] In some embodiments, the intensity of the ultraviolet light irradiation is 50 mW / cm². 2 -100 mW / cm 2 The irradiation time is 10-30 minutes. For example, the intensity of ultraviolet light irradiation can be 50 mW / cm². 2 52 mW / cm 2 55 mW / cm 2 58 mW / cm 2 60 mW / cm 2 62 mW / cm 2 65 mW / cm 2 68 mW / cm2 70 mW / cm 2 72 mW / cm 2 75 mW / cm 2 78 mW / cm 2 80 mW / cm 2 82 mW / cm 2 85 mW / cm 2 88 mW / cm 2 90 mW / cm 2 92 mW / cm 2 95 mW / cm 2 98 mW / cm 2 100 mW / cm 2 The UV irradiation time can be any value within the range of any two of the above values: 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, or any value within the range of any two of the above values. Controlling the UV irradiation within the above parameter range is beneficial for the full activation of hydrogen-extracting photoinitiators, enabling the effective extraction of hydrogen atoms from the polyethylene oxide backbone and initiating cross-linking polymerization of multifunctional unsaturated monomers to form a uniform and stable three-dimensional network structure. Simultaneously, it reduces the risk of thermal damage to the polymer matrix or side reactions when the irradiation intensity is high.
[0041] An embodiment of this application also provides a composite solid polymer electrolyte membrane, prepared according to the above-described preparation method; the composite solid polymer electrolyte membrane includes a polymer matrix, a modified filler, and a lithium salt, wherein the polymer matrix includes polyethylene oxide and a three-dimensional cross-linked network structure bonded to polyethylene oxide.
[0042] In this application, the boron-containing groups in the composite solid polymer electrolyte membrane are covalently fixed to the surface of the inorganic filler, which facilitates the uniform distribution and long-term stability of the boron-containing components in the membrane phase and reduces the risk of additive migration or loss in traditional physical blending systems. The chemical bonding between the polyethylene oxide and the three-dimensional cross-linked network helps improve the mechanical strength of the membrane and inhibit lithium dendrite growth. Under high-voltage charge-discharge conditions, the anchored boron-containing groups can form an interface film rich in inorganic boron and oxygen components in situ at the positive electrode interface, which helps to further promote ion conduction. Furthermore, the synergistic effect of the improved mechanical strength brought by the three-dimensional cross-linked network structure helps to reduce the risk of oxidative decomposition of the electrolyte under high voltage and broadens the battery's operating voltage range.
[0043] One embodiment of this application also provides a solid-state lithium-ion battery, which includes the above-described composite solid-state polymer electrolyte membrane.
[0044] In this application, the solid-state lithium-ion battery uses the aforementioned composite solid-state polymer electrolyte membrane. When charged to high voltage, the anchored boron-containing groups in the electrolyte membrane can preferentially participate in the positive electrode interface reaction to form a stable inorganic boron-oxygen interface layer. This helps to suppress side reactions between the electrolyte and the positive electrode, and improves the capacity retention and cycle stability of the battery during high-voltage cycling. At the same time, the three-dimensional cross-linked network structure inside the electrolyte membrane works synergistically with the covalently anchored filler to help reduce interfacial impedance and enhance the mechanical stability of the membrane, thereby reducing the risk of internal short circuits in the battery.
[0045] The present application will be described below through specific embodiments and comparative examples. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.
[0046] Example 1:
[0047] A composite solid polymer electrolyte membrane, the preparation method of which includes:
[0048] Step 1: 5 g of cubic phase lithium lanthanum zirconium oxide nanoparticles were dispersed in 100 mL of anhydrous ethanol, 1 mL of deionized water was added, the pH was adjusted to 4.5 with acetic acid, and then 0.5 g of triethoxysilylpropylboronate was added as a borosilicate coupling agent. The mixture was refluxed at 70 °C for 12 h. After the reaction was completed, the unreacted coupling agent was removed by centrifugation and washing. After vacuum drying, the modified filler with boron-containing groups anchored on the surface was obtained.
[0049] Step 2: Take 1 g of polyethylene oxide with a molecular weight of 600,000 and 0.17 g of lithium bis(trifluoromethanesulfonyl)imide (controlling the oxygen-lithium molar ratio to 15:1), dissolve them in 20 mL of acetonitrile, then add 0.01 g of benzophenone as a hydrogen-extractable photoinitiator and 0.05 g of pentaerythritol triacrylate as a multifunctional unsaturated monomer, stir evenly to obtain the precursor solution.
[0050] Step 3: Take 0.1 g of the above modified filler and disperse it in the above precursor solution, ultrasonically disperse and magnetically stir for 12 h to form a uniform composite slurry.
[0051] Step 4: The above composite slurry is cast onto a polytetrafluoroethylene mold, the solvent is evaporated at 50 °C for 2 hours, and then it is irradiated under ultraviolet light with a wavelength of 365 nm and a light intensity of 50 mW / cm². 2Irradiation with light for 20 min initiates a cross-linking reaction to form a three-dimensional cross-linked network, followed by vacuum drying at 80 °C for 24 h to obtain a composite solid polymer electrolyte membrane.
[0052] Example 2:
[0053] A composite solid polymer electrolyte membrane, the preparation method of which includes:
[0054] Step 1: 5 g of cubic phase lithium lanthanum zirconium oxide nanoparticles were dispersed in 100 mL of anhydrous ethanol, 1 mL of deionized water was added, the pH was adjusted to 4.5 with acetic acid, and then 1 g of triethoxysilylpropylboronate was added as a borosilicate coupling agent. The mixture was refluxed at 70 °C for 12 h. After the reaction was completed, the unreacted coupling agent was removed by centrifugation and washing. After vacuum drying, the modified filler with boron-containing groups anchored on the surface was obtained.
[0055] Step 2: Take 1 g of polyethylene oxide with a molecular weight of 600,000 and 0.17 g of lithium bis(trifluoromethanesulfonyl)imide (controlling the oxygen-lithium molar ratio to 15:1), dissolve them in 20 mL of acetonitrile, then add 0.01 g of benzophenone as a hydrogen-extractable photoinitiator and 0.08 g of pentaerythritol triacrylate as a multifunctional unsaturated monomer, stir evenly to obtain the precursor solution.
[0056] Step 3: Take 0.15 g of the above modified filler and disperse it in the above precursor solution, ultrasonically disperse and magnetically stir for 12 h to form a uniform composite slurry.
[0057] Step 4: The above composite slurry is cast onto a polytetrafluoroethylene mold, the solvent is evaporated at 50 °C for 2 hours, and then it is irradiated under ultraviolet light with a wavelength of 365 nm and a light intensity of 50 mW / cm². 2 Irradiation with light for 20 min initiates a cross-linking reaction to form a three-dimensional cross-linked network, followed by vacuum drying at 80 °C for 24 h to obtain a composite solid polymer electrolyte membrane.
[0058] Example 3:
[0059] A composite solid polymer electrolyte membrane, the preparation method of which includes:
[0060] Step 1: 5 g of cubic phase lithium lanthanum zirconium oxide nanoparticles were dispersed in 100 mL of anhydrous ethanol, 1 mL of deionized water was added, the pH was adjusted to 4.5 with acetic acid, and then 1 g of trimethyl borate silane derivative was added as a borosilicate coupling agent. The mixture was refluxed at 70 °C for 12 h. After the reaction was completed, the unreacted coupling agent was removed by centrifugation and washing. After vacuum drying, the modified filler with boron-containing groups anchored on the surface was obtained.
[0061] Step 2: Take 1 g of polyethylene oxide with a molecular weight of 600,000 and 0.17 g of lithium bis(trifluoromethanesulfonyl)imide (controlling the oxygen-lithium molar ratio to 15:1), dissolve them in 20 mL of acetonitrile, then add 0.01 g of benzophenone as a hydrogen-extractable photoinitiator and 0.08 g of pentaerythritol triacrylate as a multifunctional unsaturated monomer, stir evenly to obtain the precursor solution.
[0062] Step 3: Take 0.15 g of the above modified filler and disperse it in the above precursor solution, ultrasonically disperse and magnetically stir for 12 h to form a uniform composite slurry.
[0063] Step 4: The above composite slurry is cast onto a polytetrafluoroethylene mold, the solvent is evaporated at 50 °C for 2 hours, and then it is irradiated under ultraviolet light with a wavelength of 365 nm and a light intensity of 50 mW / cm². 2 Irradiation with light for 20 min initiates a cross-linking reaction to form a three-dimensional cross-linked network, followed by vacuum drying at 80 °C for 24 h to obtain a composite solid polymer electrolyte membrane.
[0064] Comparative Example 1:
[0065] A composite solid polymer electrolyte membrane is prepared by means of: using unmodified virgin lithium lanthanum zirconium oxide powder as filler, and simultaneously adding borosilicate coupling agent in a free manner. Specifically, 0.1 g of unmodified lithium lanthanum zirconium oxide powder and 0.05 g of triethoxysilylpropylborate liquid are directly added to a precursor solution. The preparation of the precursor solution, mixing of the composite slurry, film formation, and UV curing steps are the same as in Example 1, i.e., the precursor solution is prepared using polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide, benzophenone, and pentaerythritol triacrylate; the filler and free additive are dispersed and cast into a film; a crosslinking reaction is initiated by UV irradiation; and finally, the composite solid polymer electrolyte membrane is obtained by vacuum drying.
[0066] Comparative Example 2:
[0067] A composite solid polymer electrolyte membrane is prepared by using unmodified virgin lithium lanthanum zirconium oxide powder as filler without adding any borosilicate coupling agent. Specifically, 0.1 g of unmodified lithium lanthanum zirconium oxide powder is directly added to a precursor solution. The preparation of the precursor solution, mixing of the composite slurry, film formation, and UV curing are all the same as in Example 1, i.e., the precursor solution is prepared using polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide, benzophenone, and pentaerythritol triacrylate; the filler is dispersed and cast into a film; a crosslinking reaction is initiated by UV irradiation; and finally, the composite solid polymer electrolyte membrane is obtained by vacuum drying.
[0068] Comparative Example 3:
[0069] A composite solid polymer electrolyte membrane is prepared by means of: surface modification of lithium lanthanum zirconium oxide powder with a common silane coupling agent without introducing boron-containing groups. The preparation method of the modified filler is the same as in Example 1, except that a boron-free aminosilane coupling agent (KH550) is used instead of a boron-containing silane coupling agent. Specifically, 5 g of lithium lanthanum zirconium oxide powder is dispersed in anhydrous ethanol, deionized water is added and the pH is adjusted to 4.5, 0.5 g of KH550 is added, and the mixture is refluxed at 70 °C for 12 h. After centrifugation and washing, the mixture is vacuum dried to obtain a surface-modified aminosilane modified filler. The preparation of the precursor solution, mixing of the composite slurry, film formation, and UV curing steps are the same as in Example 1. Specifically, 0.1 g of the modified filler is dispersed in the precursor solution, and the mixture is cast into a film, subjected to UV irradiation to initiate a crosslinking reaction, and vacuum dried to obtain the composite solid polymer electrolyte membrane.
[0070] The testing method for this application is as follows:
[0071] 1. Ionic conductivity: The ionic conductivity at 25 °C and 60 °C was calculated by electrochemical impedance spectroscopy (EIS) of the assembled stainless steel sheet / electrolyte membrane / stainless steel sheet blocking battery.
[0072] 2. Electrochemical window: A half-cell of Li / electrolyte membrane / stainless steel sheet was assembled and linear sweep voltammetry (LSV) was performed at a scan rate of 0.5 mV / s, recording a current density of 0.1 mA / cm². 2 The voltage at that time.
[0073] 3. Battery cycle performance: Assembled Li / electrolyte membrane / NCM811 full cell (area capacity 1.5 mAh / cm³) 2 ), calculate the capacity retention rate by cycling 100 times at a rate of 0.5 C within a voltage range of 2.8V-4.3V.
[0074] 4. Interface impedance: Assemble a symmetrical Li / electrolyte membrane / Li cell, let it stand for 24 h, test the EIS, and record the interface impedance value.
[0075] The composite solid polymer electrolyte membranes obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to the above-mentioned performance tests. The test results are shown in Table 1.
[0076] Table 1. Performance test results of the composite solid polymer electrolyte membranes of Examples 1-3 and Comparative Examples 1-3 of this application
[0077]
[0078] Please refer to Table 1. In Examples 1-3 of this application, by anchoring boron-containing groups to the surface of inorganic fillers in the form of covalent bonds, it is beneficial to avoid the aggregation or migration problems of boron-containing components in the solid polymer matrix due to physical blending, thereby helping to maintain a stable interface protection function during long-term cycling. Simultaneously, the PEO polymer matrix prepared using a hydrogen-extractable photoinitiator allows for the polymerization of multifunctional unsaturated monomers initiated by ultraviolet light irradiation without end-group modification of polyethylene oxide, forming a three-dimensional cross-linked network bonded to the polyethylene oxide backbone. This helps to improve the mechanical strength of the electrolyte membrane and suppress the risk of lithium dendrite puncture. When the resulting composite solid polymer electrolyte membrane is applied to solid-state batteries, under high-voltage conditions, the anchored boron-containing groups can preferentially oxidize and decompose, which is beneficial to the in-situ formation of an interface film rich in inorganic boron and oxygen components on the positive electrode surface. This further promotes ion conduction, and the synergistic effect of the improved mechanical strength brought by the three-dimensional cross-linked network structure helps to reduce the risk of oxidative decomposition of the electrolyte under high voltage, thereby improving the electrochemical stability window.
[0079] Compared to the embodiments of this application, Comparative Example 1 introduces unmodified original lithium lanthanum zirconium oxide powder through traditional physical blending. The free additives are prone to phase separation and interfere with ion transport channels, resulting in poor ionic conductivity and high interfacial impedance of the resulting composite solid polymer electrolyte.
[0080] Compared to the embodiments of this application, the lithium lanthanum zirconium oxide powder added in Comparative Example 2 did not introduce boron-containing groups. The resulting composite solid polymer electrolyte had a lower ionic conductivity than the embodiments of this application, and a higher initial interfacial impedance. The applied battery had poorer electrochemical performance and a narrower electrochemical stability window. This indicates that the modified filler of this application, by introducing boron-containing groups on the surface of the inorganic filler, helps to improve filler dispersion and promotes the formation of amorphous regions.
[0081] The initial interfacial impedance of Examples 1-3 of this application is significantly lower than that of Comparative Examples 1 and 2, indicating that the chemical bonding layer effectively reduces the interfacial contact resistance and the crosslinking network inhibits the excessive growth of the interfacial side reaction layer.
[0082] Compared to the embodiments of this application, Comparative Example 3 uses KH550 modified lithium lanthanum zirconium oxide powder. Although it forms group modification on the surface of inorganic filler, the group is mainly amino and does not contain boron. The electrochemical stability window of the resulting composite solid polymer electrolyte is not as good as that of the embodiments of this application. This indicates that the modified filler of this application introduces boron-containing groups, which can preferentially oxidize and decompose under high voltage conditions. This is beneficial to the in-situ formation of an interface film rich in inorganic boron and oxygen components on the positive electrode surface, which helps to reduce the risk of oxidative decomposition of the electrolyte under high voltage, thereby improving the electrochemical stability window.
[0083] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0084] The embodiments described above are merely illustrative of several implementations of the technical solution of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the technical solution of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.
Claims
1. A method for preparing a composite solid polymer electrolyte membrane, characterized in that, Includes the following steps: Modified fillers are prepared by chemically modifying the surface of inorganic fillers with boron-containing silane coupling agents to anchor boron-containing groups onto the surface of the inorganic fillers. A precursor solution was prepared by dissolving polyethylene oxide, lithium salt, hydrogen-extractable photoinitiator, and multifunctional unsaturated monomer in an organic solvent. The modified filler is dispersed in the precursor solution to prepare a composite slurry; After the composite slurry is formed into a film, it is irradiated with ultraviolet light to initiate a cross-linking reaction, forming a three-dimensional cross-linked network, thus preparing the composite solid polymer electrolyte membrane.
2. The preparation method according to claim 1, characterized in that, The method of chemically modifying the surface of the inorganic filler with the boron-containing silane coupling agent to anchor the boron-containing groups to the surface of the inorganic filler includes the following steps: hydrolyzing the boron-containing silane coupling agent under acidic conditions to generate boron-containing silanol groups, wherein the boron-containing silanol groups condense with the hydroxyl groups on the surface of the inorganic filler to form Si-OM covalent bonds, wherein M is a metal element in the inorganic filler, thereby anchoring the boron-containing groups to the surface of the inorganic filler.
3. The preparation method according to claim 1, characterized in that, The amount of the borosilicate coupling agent is 10%-20% of the mass of the inorganic filler.
4. The preparation method according to claim 1, characterized in that, The amount of the hydrogen-extractable photoinitiator is 1%-2% of the mass of the polyethylene oxide.
5. The preparation method according to claim 1, characterized in that, The amount of the multifunctional unsaturated monomer is 5%-10% of the mass of the polyethylene oxide.
6. The preparation method according to claim 1, characterized in that, The amount of the modified filler is 5%-15% of the mass of the polyethylene oxide.
7. The preparation method according to claim 1, characterized in that, The intensity of the ultraviolet light irradiation is 50 mW / cm². 2 -100 mW / cm 2 The irradiation time is 10 min-30 min.
8. The preparation method according to claim 1, characterized in that, The preparation method satisfies at least one of the following conditions: (1) The inorganic filler includes lithium lanthanum zirconium oxide; (2) The borosilicate coupling agent includes silane compounds containing borate ester groups and / or borosilicate groups; (3) The hydrogen-extractable photoinitiator includes benzophenone compounds; (4) The multifunctional unsaturated monomers include multifunctional acrylate compounds; (5) The oxygen-lithium molar ratio of the polyethylene oxide to the lithium salt is (10-20):
1.
9. A composite solid polymer electrolyte membrane, characterized in that, Prepared according to the preparation method according to any one of claims 1-8; The composite solid polymer electrolyte membrane includes a polymer matrix, the modified filler, and the lithium salt, wherein the polymer matrix includes the polyethylene oxide and a three-dimensional cross-linked network structure bonded to the polyethylene oxide.
10. A solid-state lithium-ion battery, characterized in that, The solid-state lithium-ion battery includes the composite solid-state polymer electrolyte membrane as described in claim 9.