A semi-interpenetrating polymer solid-state electrolyte, a solid-state lithium battery and a preparation method

Abstract

This invention provides a semi-interpenetrating polymer solid electrolyte, a solid-state lithium battery, and a preparation method thereof, belonging to the field of lithium-ion battery electrolyte technology. The electrolyte comprises the following components: a cross-linked network component, a first initiator, a linear structure component, a second initiator, a lithium salt, and additives. This invention utilizes the aforementioned semi-interpenetrating polymer solid electrolyte, solid-state lithium battery, and preparation method. By designing the molecular structures of the cross-linked network and the linear polymer, and controlling the component ratio and interpenetration degree, a semi-interpenetrating polymer electrolyte system with excellent mechanical properties, high room-temperature ionic conductivity, and a stable electrode interface is constructed. This provides a new strategy for resolving the contradiction between the mechanical and electrochemical performance of electrolytes in solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery electrolyte technology, and in particular relates to a semi-interpenetrating polymer solid electrolyte, a solid lithium battery, and a preparation method thereof. Background Technology

[0002] Solid-state lithium batteries are considered a crucial development direction for next-generation energy storage systems due to their high energy density and inherent safety. Solid-state electrolytes, as key materials, must possess high ionic conductivity, good mechanical properties, electrode compatibility, and stable interfacial characteristics. Currently, mainstream solid-state electrolyte technologies are mainly divided into three categories: inorganic ceramic / glass electrolytes, solid polymer electrolytes, and organic-inorganic composite electrolytes, but all still face unresolved bottlenecks.

[0003] Inorganic solid electrolytes (such as sulfides and oxides) have high room temperature ionic conductivity (10⁻⁶). -3 ~10 -2 However, its intrinsic brittleness and high modulus lead to poor interfacial contact with the electrode, and it is prone to interfacial peeling due to stress changes during cycling, resulting in a significant increase in interfacial impedance. At the same time, its poor processing performance makes it difficult to prepare large-area, thin-layer electrolyte membranes on a large scale.

[0004] Traditional solid polymer electrolytes (such as polyethylene oxide systems) have good flexibility and excellent interfacial contact properties, but their room temperature ionic conductivity is generally low (typically <10). -4 Its strength is insufficient (S / cm), and its mechanical strength is insufficient to suppress lithium dendrite growth; its electrochemical window is narrow, which limits its application in high-voltage cathode systems.

[0005] Although organic-inorganic composite electrolytes can combine the advantages of inorganic fillers and polymer matrices, they often face problems such as poor interfacial compatibility, discontinuous ion transport channels, and easy agglomeration of fillers, resulting in limited improvement in ionic conductivity and insufficient interfacial stability during long-term cycling. Summary of the Invention

[0006] The present invention aims to provide a semi-interpenetrating polymer solid electrolyte, a solid-state lithium battery, and a preparation method thereof. By designing the molecular structure of the cross-linked network and the linear polymer, and controlling the component ratio and interpenetration degree of both, a semi-interpenetrating polymer electrolyte system with excellent mechanical properties, high room temperature ionic conductivity, and stable electrode interface is constructed, providing a new strategy for resolving the contradiction between the mechanical and electrochemical performance of electrolytes in solid-state batteries. This method not only forms continuous and rapid ion transport channels and a stable three-dimensional framework, thus breaking the traditional trade-off between ionic conductivity and mechanical properties, but also further improves the interfacial compatibility and long-term cycling stability of the electrolyte and electrode through in-situ polymerization and the introduction of functional additives.

[0007] This electrolyte system, while maintaining good processability and interfacial contact, significantly improves room-temperature ionic conductivity and dendrite growth suppression, providing a promising material solution for developing high-performance, high-safety solid-state lithium batteries.

[0008] To achieve the above objectives, the present invention provides a semi-interpenetrating polymer solid electrolyte, comprising the following components: The cross-linked network component, the first initiator, the linear structure component, the second initiator, the lithium salt, and the additives; wherein the molar ratio of the number of moles of the first initiator to the sum of the number of moles of double bonds in the cross-linked network component is (5~10):1000, and the molar ratio of the second initiator to the linear structure component is (1~2):1000; the mass ratio of the cross-linked network component, the first initiator, the linear structure component, and the second initiator is (1~2):(1~2). The total volume ratio of lithium salt to cross-linked network component, first initiator, linear structure component, and second initiator is (1~4 mol): 1 L; The volume ratio of the additive to the total volume of the cross-linking network component, the first initiator, the linear structure component, and the second initiator is (1~10):100.

[0009] Preferably, the crosslinking network components include a main crosslinking agent, a reinforcing agent, and a compatibilizer; wherein the molar ratio of the main crosslinking agent, the reinforcing agent, and the compatibilizer is (4~1):(1~3):(5~6). The main crosslinking agents include polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, and tetra-arm polyethylene glycol acrylate; Reinforcing agents include methyl methacrylate, ethyl methacrylate, and styrene monomer; Compatibilizers include ethylene carbonate, vinylene carbonate, and diethylene glycol allyl carbonate monomers.

[0010] Preferably, the first initiator includes azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, azoisobutylcyanoformamide, and dimethyl azobisisobutyrate.

[0011] Preferably, the linear structural component includes 1,3-dioxolane and 1,3-dioxane.

[0012] Preferably, the second initiator includes lithium difluorooxalate borate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0013] Preferably, the lithium salt includes lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium perchlorate.

[0014] Preferably, the additives include fluoroethylene carbonate, difluoroethylene carbonate, hexafluoroglutaric anhydride, ethylene sulfate, and propylene sulfite.

[0015] Preferably, the thickness of the solid electrolyte membrane is 30-300 μm.

[0016] A method for preparing a semi-interpenetrating polymer solid electrolyte includes the following steps: The main crosslinking agent, reinforcing agent, compatibilizer and first initiator are mixed and stirred evenly to obtain a first transparent solution; A second initiator was added to the linear structure component solution and stirred until homogeneous to obtain a second transparent solution. The first transparent solution and the second solution are mixed evenly, and then lithium salt and additives are added in sequence. After mixing evenly, a precursor solution is obtained. The precursor solution is cured by heating to 50~90℃ for 1~12h to prepare a semi-interpenetrating polymer solid electrolyte.

[0017] A solid-state lithium battery comprising a semi-interpenetrating polymer solid electrolyte is prepared by assembling a CR2032 button cell, with a lithium sheet as the negative electrode and a glass fiber membrane as the separator. 20-100 μL of electrolyte precursor solution is injected into both sides of the glass fiber separator, with lithium iron phosphate or NCM811 as the positive electrode, to complete the battery assembly. The assembled battery is then heated to 50-90°C and cured for 1-12 h, and the semi-interpenetrating solid-state battery is obtained by in-situ polymerization.

[0018] Therefore, the present invention employs the above-mentioned semi-interpenetrating polymer solid electrolyte, solid-state lithium battery, and preparation method, and the technical effects are as follows: The glass transition temperature of the semi-interpenetrating polymer network is -33.4℃.

[0019] The LFP / Li full cell assembled based on a semi-interpenetrating network retains 80% of its capacity after 300 cycles at 2C.

[0020] The NCM / Li full cell assembled based on a semi-interpenetrating network retains 70% of its capacity after 100 cycles at 0.5C. Attached Figure Description

[0021] Figure 1 The DSC curves for the semi-interpenetrating polymer electrolyte are shown. Figure 2 The cycling performance of the LFP / SIPN / Li battery in Example 1 at a 2C current density; Figure 3 The rate performance of the LFP / SIPN / Li full cell in Example 1; Figure 4 The cycling performance of the NCM811 / SIPN / Li battery in Example 1 at a current density of 0.5C is shown. Figure 5The cycling performance of the LFP / SIPN / Li battery with a mass ratio of 2:1 for the first transparent solution and the second transparent solution in Example 2 is shown at a current density of 2 C. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0024] Reagent source: Polyethylene glycol diacrylate, CAS No.: 26570-48-9, AR, average molecular weight ~600, purchased from Aladdin Reagent Co., Ltd. Methyl methacrylate, CAS No.: 80-62-6, GC, ≥99.5%, purchased from Aladdin Reagent Co., Ltd. Ethylene carbonate, CAS No.: 4427-96-7, AR, ≥99%, purchased from Aladdin Reagent Co., Ltd. Azobisisobutyronitrile, CAS No.: 78-67-1, AR, ≥98%, purchased from Aladdin Reagent Co., Ltd.; 1,3-Dioxolane, CAS No.: 497-26-7, 99.8%, ultra-dry solvent, water ≤30 ppm, J&K Seal bottle, purchased from Bailingwei Technology Co., Ltd.; Lithium difluorooxalate borate, CAS No.: 409071-16-5, AR, ≥99%, purchased from Aladdin Reagent Co., Ltd. Lithium bis(trifluoromethanesulfonylimide), CAS No.: 90076-65-6, 7, AR, ≥99%, purchased from Aladdin Reagent Co., Ltd. Fluoroethylene carbonate, CAS No.: 114435-02-8, AR, ≥99.5%, purchased from Aladdin Reagent Co., Ltd.

[0025] Example 1 Preparation of a solid electrolyte based on a semi-interpenetrating polymer network (SIPN-1). The crosslinking component consists of polyethylene glycol diacrylate (PEGDA), methyl methacrylate (MMA), and ethylene ethylene carbonate (VEC) monomers. Among them, PEGDA is the main crosslinking agent, MMA is the reinforcing agent, and VEC is the compatibilizer.

[0026] All the following processes were carried out in a glove box filled with argon gas, with O2 and H2O contents both below 0.1 ppm.

[0027] PEGDA, MMA, VEC and the first initiator azobisisobutyronitrile (AIBN) were mixed and stirred at room temperature to obtain a first transparent solution, which is the precursor solution of the crosslinking part.

[0028] The molar ratio of monomers added to PEGDA, MMA and VEC is 2:6:2; The molar ratio of the first initiator AIBN molars to the sum of the molar numbers of the double bonds of the cross-linking structural components (PEGDA, MMA, and VEC) is 5:1000. A second initiator, lithium difluorooxalate borate (LiDFOB), was added to the linear structural component 1,3-dioxolane (DOL), and the mixture was stirred at room temperature to obtain a second transparent solution, which is the precursor solution of the linear portion.

[0029] The ratio of LiDFOB to DOL was 0.2 mol: 1 L.

[0030] After the first transparent solution and the second transparent solution are mixed evenly at a mass ratio of 1:1, lithium salt bis(trifluoromethanesulfonyl)imide (LiTFSI) and additive fluoroethylene carbonate (FEC) are added and mixed evenly to obtain a precursor solution. The precursor solution is then heated to 60°C and cured for 4 hours to prepare a semi-interpenetrating polymer solid electrolyte.

[0031] The ratio of the amount of lithium salt LiTFSI added to the sum of the volumes of the first transparent solution and the second transparent solution is 1 mol: 1 L. The volume ratio of the added FEC additive to the sum of the volumes of the first and second transparent solutions is 5:100. The precursor solution was cured at 60°C for 4 hours to prepare a semi-interpenetrating polymer solid electrolyte. The semi-interpenetrating polymer network solid electrolyte sample was labeled SIPN-1. DSC testing was performed on SIPN, as shown... Figure 1 As shown, the results indicate that the glass transition temperature of the semi-interpenetrating polymer network is -33.4 °C. The lower T... g This indicates that SIPN-1 has strong segmental mobility at room temperature, which is conducive to the rapid migration of lithium ions and provides a structural basis for high ionic conductivity.

[0032] Subsequently, CR2032 button cells were assembled in a glove box, with lithium foil as the negative electrode, a glass fiber membrane as the separator, and LFP or NCM811 as the positive electrode. 50 μL of the precursor solution was injected onto both sides of the glass fiber separator to complete the battery assembly. The assembled battery was then heated to 60°C for 4 hours for curing, and a semi-interpenetrating polymer solid-state battery was prepared via in-situ polymerization. Battery performance testing was performed as follows. Figure 2 , Figure 3 and Figure 4 As shown. Figure 2 The results show that the LFP / SIPN-1 / Li full cell assembled based on a semi-interpenetrating network retains up to 80% of its capacity after 300 cycles at 2 C. Figure 3 The rate performance of the LFP / SIPN-1 / Li full cell was measured, and the results show that the solid-state battery exhibits excellent rate performance. Figure 4 The image shows the cycle-capacity diagram of the NCM / SIPN-1 / Li full cell assembled based on a semi-interpenetrating network at 0.5C. The results indicate that the capacity retention of the cell reaches 70% after 100 cycles. These results demonstrate that the solid-state battery assembled from SIPN-1 exhibits excellent electrochemical performance.

[0033] Example 2 Preparation of solid electrolyte based on semi-interpenetrating polymer network (SIPN-2). The difference between this example and Example 1 is: The mass ratio of the first transparent solution to the second transparent solution is 2:1.

[0034] The solid electrolyte sample based on the semi-interpenetrating polymer network is labeled SIPN-2.

[0035] CR2032 button cells were assembled in a glove box, using lithium foil as the negative electrode, a glass fiber membrane as the separator, and LFP or NCM811 as the positive electrode. 50 μL of the precursor solution was injected onto both sides of the glass fiber separator, with LFP as the positive electrode, to complete the battery assembly. The assembled battery was then heated to 60°C and cured for 4 hours, followed by in-situ polymerization to obtain a semi-interpenetrating polymer solid-state battery. Battery performance testing was performed as follows. Figure 5 As shown, the LFP / SIPN-2 / Li full cell exhibits excellent cycling performance at a 2C current density, and retains 70.0% of its capacity after 200 cycles. Figure 5 As shown.

[0036] Example 3 Preparation of solid electrolyte based on semi-interpenetrating polymer network (SIPN-3). The difference between this example and Example 1 is: The molar ratio of monomers added to PEGDA, MMA and VEC is 1:3:6; The ratio of the amount of lithium tetrafluoroborate, the second initiator, to the amount of DOL added is 0.2 mol: 1 L; The ratio of the number of moles of lithium salt LiTFSI added to the sum of the volumes of the first and second solutions is 4 mol: 1 L; The additive is hexafluoroglutaric anhydride; The precursor solution was cured by heating to 50°C for 12 h to prepare a semi-interpenetrating polymer solid electrolyte.

[0037] The solid electrolyte sample based on the semi-interpenetrating polymer network is labeled SIPN-3.

[0038] Subsequently, CR2032 button cells were assembled in a glove box, with lithium foil as the negative electrode, glass fiber membrane as the separator, and LFP or NCM811 as the positive electrode. 20 μL of the precursor solution was injected onto both sides of the glass fiber separator to complete the battery assembly. The assembled battery was then heated to 50 °C for a curing reaction for 12 h, and a semi-interpenetrating polymer solid-state battery was prepared by in-situ polymerization.

[0039] Example 4 Preparation of solid electrolyte based on semi-interpenetrating polymer network (SIPN-4). The difference between this example and Example 1 is: The main crosslinking agent is polyethylene glycol dimethacrylate, which has an average molecular weight of 750. The molar ratio of the main crosslinking agent, reinforcing agent, and compatibilizer is 4:1:5; The first initiator is azobisisovalerate; The linear structural component is 1,3-dioxane; The additive is vinyl sulfate; The precursor solution was cured by heating to 90°C for 1 hour to prepare a semi-interpenetrating polymer solid electrolyte.

[0040] The solid electrolyte sample based on the semi-interpenetrating polymer network is labeled SIPN-4.

[0041] Subsequently, CR2032 button cells were assembled in a glove box, with lithium foil as the negative electrode, glass fiber membrane as the separator, and LFP or NCM811 as the positive electrode. 100 μL of the precursor solution was injected onto both sides of the glass fiber separator to complete the battery assembly. The assembled battery was then heated to 90°C for 1 hour for curing, and a semi-interpenetrating polymer solid-state battery was prepared via in-situ polymerization.

[0042] Example 5 Preparation of solid electrolyte based on semi-interpenetrating polymer network (SIPN-5). The difference between this example and Example 1 is: The main crosslinking agent is ethoxylated trimethylolpropane triacrylate, which has an average molecular weight of 693. The molar ratio of the main crosslinking agent, reinforcing agent, and compatibilizer is 1:3:6; The ratio of the amount of lithium hexafluorophosphate, the second initiator, to the amount of DOL added is 0.2 mol: 1 L; The additive is propylene sulfite; The solid electrolyte sample based on the semi-interpenetrating polymer network is labeled SIPN-5.

[0043] Example 6 Preparation of solid electrolyte based on semi-interpenetrating polymer network (SIPN-6). The difference between this example and Example 1 is: The reinforcing agent used is ethyl methacrylate; The molar ratio of the main crosslinking agent, reinforcing agent, and compatibilizer is 4:2:4; The second initiator is lithium tetrafluoroborate; The additive is difluoroethylene carbonate; The lithium salt is lithium difluorosulfonylimide; The solid electrolyte sample based on the semi-interpenetrating polymer network is labeled SIPN-6.

[0044] Example 7 Preparation of solid electrolyte based on semi-interpenetrating polymer network (SIPN-7). The difference between this example and Example 1 is: The reinforcing agent is styrene; The compatibilizer used is vinylene carbonate; The first initiator is dimethyl azobisisobutyrate; The molar ratio of the first initiator, dimethyl azobisisobutyrate, to the sum of the molar numbers of the double bonds of the cross-linking structural components (PEGDA, styrene, and vinylene carbonate) is 10:1000. The lithium salt is lithium perchlorate; The mass ratio of the first transparent solution to the second transparent solution is 1:2; The solid electrolyte sample based on the semi-interpenetrating polymer network is labeled SIPN-7.

[0045] Example 8 Preparation of solid electrolyte based on semi-interpenetrating polymer network (SIPN-8). The difference between this example and Example 1 is: The main crosslinking agent is four-arm polyethylene glycol acrylate; The compatibilizer is diethylene glycol allyl carbonate; The first initiator is azoisobutyl cyanoformamide; The molar ratio of the first initiator, azoisobutyl cyanoformamide, to the sum of the molar numbers of the double bonds in the cross-linking structural components (tetra-arm polyethylene glycol acrylate, MMA, and diethylene glycol allyl carbonate) is 10:1000. The mass ratio of the first transparent solution to the second transparent solution is 1:2.

[0046] The solid electrolyte sample based on the semi-interpenetrating polymer network is labeled SIPN-8.

[0047] Therefore, this invention employs the aforementioned semi-interpenetrating polymer solid electrolyte, solid-state lithium battery, and preparation method. By designing the molecular structure of the crosslinked network and the linear polymer, and controlling the component ratio and interpenetration degree of the two, a semi-interpenetrating polymer electrolyte system with excellent mechanical properties, high room temperature ionic conductivity, and stable electrode interface is constructed, providing a new strategy for resolving the contradiction between the mechanical and electrochemical properties of electrolytes in solid-state batteries.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A semi-interpenetrating polymer solid electrolyte, characterized in that, Includes the following components: The cross-linked network component, the first initiator, the linear structure component, the second initiator, the lithium salt, and the additives; wherein the molar ratio of the number of moles of the first initiator to the sum of the number of moles of double bonds in the cross-linked network component is (5~10):1000, and the molar ratio of the second initiator to the linear structure component is (1~2):1000; the mass ratio of the cross-linked network component, the first initiator, the linear structure component, and the second initiator is (1~2):(1~2). The total volume ratio of lithium salt to cross-linked network component, first initiator, linear structure component, and second initiator is (1~4 mol): 1 L; The volume ratio of the additive to the total volume of the cross-linking network component, the first initiator, the linear structure component, and the second initiator is (1~10):

100.

2. The semi-interpenetrating polymer solid electrolyte according to claim 1, characterized in that, The crosslinking network components include a main crosslinking agent, a reinforcing agent, and a compatibilizer; wherein the molar ratio of the main crosslinking agent, the reinforcing agent, and the compatibilizer is (4~1):(1~3):(5~6). The main crosslinking agents include polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, and tetra-arm polyethylene glycol acrylate; Reinforcing agents include methyl methacrylate, ethyl methacrylate, and styrene monomer; Compatibilizers include ethylene carbonate, vinylene carbonate, and diethylene glycol allyl carbonate monomers.

3. The semi-interpenetrating polymer solid electrolyte according to claim 1, characterized in that, The first initiator includes azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, azoisobutylcyanoformamide, and dimethyl azobisisobutyrate.

4. The semi-interpenetrating polymer solid electrolyte according to claim 1, characterized in that, The linear structural components include 1,3-dioxolane and 1,3-dioxane.

5. The semi-interpenetrating polymer solid electrolyte according to claim 1, characterized in that, The second initiator includes lithium difluorooxalate borate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

6. The semi-interpenetrating polymer solid electrolyte according to claim 1, characterized in that, Lithium salts include lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium perchlorate.

7. The semi-interpenetrating polymer solid electrolyte according to claim 1, characterized in that, The additives include fluoroethylene carbonate, difluoroethylene carbonate, hexafluoroglutaric anhydride, ethylene sulfate, and propylene sulfite.

8. The semi-interpenetrating polymer solid electrolyte according to claim 1, characterized in that, The film thickness of the solid electrolyte is 30-300 μm.

9. The method for preparing a semi-interpenetrating polymer solid electrolyte according to claim 1, characterized in that, Includes the following steps: The main crosslinking agent, reinforcing agent, compatibilizer and first initiator are mixed and stirred evenly to obtain a first transparent solution; A second initiator was added to the linear structure component solution and stirred until homogeneous to obtain a second transparent solution. The first transparent solution and the second solution were mixed evenly, and then lithium salt and additives were added in sequence and mixed evenly to obtain the precursor solution. The precursor solution was cured by heating to 50-90℃ for 1-12 hours to prepare a semi-interpenetrating polymer solid electrolyte.

10. A solid-state lithium battery comprising the semi-interpenetrating polymer solid electrolyte of claim 1, characterized in that, Assemble CR2032 button cells with lithium foil as the negative electrode and glass fiber membrane as the separator. Inject 20-100 μL of electrolyte precursor solution into both sides of the glass fiber separator. The positive electrode is lithium iron phosphate or NCM811. Complete the battery assembly. Then heat the assembled battery to 50-90℃ for 1-12 h to cure. Prepare a semi-interpenetrating solid-state battery by in-situ polymerization.

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