Solid-state battery electrode sheet and method of making same
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ANHUI LIKE NEW MATERIAL TECHNOLOGY CO LTD
- Filing Date
- 2025-08-08
- Publication Date
- 2026-07-24
AI Technical Summary
The poor ionic conductivity of the binder in the positive electrode of a solid-state battery leads to low ion transport efficiency, which affects battery performance.
A self-healing layer is formed by prepolymerizing methacrylate and azobisisobutyronitrile in N-methylpyrrolidone, adding lithium iron phosphate, conductive carbon black and polyvinylidene fluoride, mixing them and forming a complex network with polyvinylimidazole ionic liquid, improving lithium ion transport through hydrogen bonding, and undergoing polymerization reaction during vacuum drying.
It improves the ionic and electronic conductivity of solid-state battery electrodes, enhances the mechanical properties and safety of the battery, and improves the rate performance and capacity utilization of the battery.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery electrode technology, specifically relating to a solid-state battery electrode and its preparation method. Background Technology
[0002] Solid-state batteries, as a novel energy storage device, have attracted significant attention in recent years. Unlike traditional liquid lithium batteries, all materials in solid-state batteries exist in a solid state, including the cathode material, anode material, and solid electrolyte. Compared to liquid lithium-ion batteries, all-solid-state lithium-ion batteries offer significant advantages in energy density and safety. Their energy density can typically reach or exceed that of liquid lithium batteries, while safety risks are greatly reduced. This makes solid-state batteries a promising candidate for applications in numerous fields, including portable electronic devices, electric vehicles, and energy storage systems, and they are expected to become one of the mainstream development directions for future energy storage technologies.
[0003] However, the fabrication of positive electrode sheets for solid-state batteries still faces numerous challenges. Positive electrode sheets in solid-state batteries are typically manufactured using a slurry and coating process. During this process, a binder is added to the raw material mixture to ensure the continuity and integrity of the positive electrode sheet. However, most conventional binders lack ionic conductivity, which limits the ion transport efficiency within the battery. When the polymer binder is dissolved in a solvent and dried, it often coats the surface of the raw material powder particles, forming a relatively dense binder film. Due to the complexity of the internal structure and the uneven distribution of pores in the electrode sheet, this binder coating makes it difficult for the electrolyte to fully penetrate and uniformly distribute within the pores of the active material. This not only limits the efficiency of ion conduction within the battery, making the transport paths of ions and electrons between particles tortuous and obstructed, but also leads to a significant decrease in the ionic and electronic conductivity of the solid electrolyte positive electrode sheet. Ultimately, this reduction in conductivity severely impacts the battery's rate performance and capacity, significantly affecting its overall performance. Furthermore, in conventional wet slurry coating processes, a large amount of binder is often required to ensure the mechanical strength and structural stability of the electrode. This further exacerbates the binder's coating on the particle surface, making the aforementioned problems even more prominent. Therefore, improving the properties and application methods of binders, as well as optimizing the electrode manufacturing process, to enhance the ionic and electronic conductivity of the battery, thereby improving its rate performance and capacity, has become an important research direction in the current development of solid-state battery technology. Summary of the Invention
[0004] The purpose of this invention is to provide a solid-state battery electrode and its preparation method, so as to solve the problem that poor ion transport performance in solid-state battery electrodes affects battery performance.
[0005] The objective of this invention can be achieved through the following technical solutions: The first aspect of this application provides a method for preparing a solid-state battery electrode, comprising the following steps: Under nitrogen protection, methacrylate and azobisisobutyronitrile were added to N-methylpyrrolidone, stirred and mixed, and then heated to 60-70℃ for prepolymerization for 1-2 hours to obtain a mixture. After grinding lithium iron phosphate, conductive carbon black and polyvinylidene fluoride evenly, they are added to N-methylpyrrolidone and stirred to obtain positive electrode slurry; A mixed solution is obtained by mixing the mixed solution, the positive electrode slurry and the polyvinylimidazole ionic liquid. The mixed solution is coated on the surface of the current collector and then vacuum dried at a temperature of 80-120℃ for 12-48 hours to obtain the solid-state battery electrode.
[0006] In this invention, the polymethyl methacrylate (PMMA) introduced in situ contains abundant ester bonds, allowing lithium ions to migrate via coordination / dissociation with the oxygen atoms of the ester groups. The imidazole ring in the polyvinylimidazole ionic liquid promotes the dissociation of lithium salts, thereby providing more free lithium ions. The oxygen-containing groups in PMMA can act as hydrogen bond acceptors. When blended with the imidazole ring, the hydrogen bond donor and acceptor can interact to form hydrogen bonds. This hydrogen bonding enables the electrolyte to have self-healing capabilities. That is, during battery charging / discharging, when cracks or breaks occur in the electrolyte, the hydrogen bonding allows the molecules at the crack to recombine into an elastic self-healing layer. This self-healing layer can effectively reduce defects caused by lithium dendrites and improve the stability and safety of the battery. In other words, both synergistically improve the ionic conductivity, excellent mechanical properties, and good safety performance of the solid-state battery electrode.
[0007] Furthermore, the coating thickness is 20-30 μm.
[0008] Furthermore, the current collector is an aluminum foil with a thickness of 1-3 μm.
[0009] Furthermore, the mass ratio of methacrylate, lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and polyvinylimidazole ionic liquid is 0.25-0.75:8:1:0.25-0.75:0.25-0.50.
[0010] Furthermore, the conductive agent is a carbon material with conductive properties, and the conductive agent is at least one of conductive carbon black and graphene.
[0011] Furthermore, the cathode material is one of lithium iron phosphate, lithium cobalt oxide, and lithium manganese iron phosphate.
[0012] Furthermore, the amount of azobisisobutyronitrile added is 0.1% to 1% of the mass of methacrylate, and 0.1% to 0.3% can be added after mixing the mixture, positive electrode slurry, and solid electrolyte slurry to improve the conversion rate.
[0013] The amount of N-methylpyrrolidone added to the mixture is 30% of the mass of methacrylate; The amount of N-methylpyrrolidone added to the positive electrode slurry is 30% of the mass of lithium iron phosphate.
[0014] Furthermore, the polyvinylimidazole ionic liquid is prepared by the following steps: Vinylimidazolium bromide, divinylbenzene, and azobisisobutyronitrile were added to methanol and reacted under nitrogen protection at 60-70°C for 12-24 hours with stirring. After the reaction, the mixture was washed with anhydrous diethyl ether and dried under vacuum to obtain an intermediate product. The intermediate product was then added to an aqueous LiTFSI (lithium bis(trifluoromethanesulfonylimide)) solution for ion exchange to obtain a polyvinylimidazolium ionic liquid. Divinylbenzene was introduced as a crosslinking agent into the synthesis system of the polyimidazolium-based ionic liquid. Its role was to construct a three-dimensional network structure through free radical polymerization. This crosslinking structure generates micropores and mesopores after polymerization, thereby significantly improving the adsorption capacity of the material and providing abundant active sites and diffusion channels, indirectly affecting the electrochemical performance of the electrode.
[0015] Further, the vinylimidazolium ion bromide is at least one of 1-vinyl-3-ethylimidazolium bromide and 1-vinyl-3-butylimidazolium bromide.
[0016] Furthermore, the molar ratio of vinylimidazole ion bromide to divinylbenzene is 3:0.5-1; the amount of azobisisobutyronitrile added is 0.8-1% of the mass of vinylimidazole ion bromide. The ratio of vinylimidazole ion bromide to methanol is 0.15-1 g:10 mL.
[0017] The mass fraction of the LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) aqueous solution was 0.2 g / L; the volume ratio of the intermediate product to the LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) aqueous solution was 0.1-0.2 g: 100 mL.
[0018] The second aspect of this application provides a solid-state battery electrode, which is prepared by the above steps.
[0019] The beneficial effects of this invention are: This invention provides a method for preparing solid-state battery electrodes. In this method, methacrylate is first prepolymerized as a raw material, and then polymethyl methacrylate (PMMA) is prepared in situ during the subsequent drying process of the solid-state battery electrode. This forms a complex interpenetrating network of PVDF and PMMA segments with polyvinylidene fluoride (PVDF), reducing interfacial voids. The PVDF segments (crystalline phase) provide mechanical support, while the PMMA segments (amorphous phase) promote lithium-ion transport. During this process, solution blending improves the uniformity of PVDF and PMMA at the molecular size, disrupts the crystallinity of the polymer within the system, and further promotes ion transport.
[0020] The significant chemical differences between polyvinylidene fluoride (PVDF) and polyvinylimidazole (PVMA) ionic liquids can easily lead to microphase formation, reducing system homogeneity and affecting ion transport. This invention addresses this by introducing PMMA segments and using solution blending to improve the molecular-scale homogeneity of PVDF and PMMA, disrupting the crystallinity of the polymer within the system, and further promoting ion transport. Furthermore, the oxygen-containing groups in PMMA act as hydrogen bond acceptors; when blended with imidazole rings, the hydrogen bond donors and acceptors interact to form hydrogen bonds, which can endow the electrolyte with self-healing capabilities. Finally, the improved mixing effect of PMMA, PVDF, and PVMA ionic liquids reduces interfacial resistance and synergistically enhances the electrochemical performance of solid-state battery electrodes. Detailed Implementation
[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0022] The following is a detailed description of a solid-state battery electrode and its preparation method according to an embodiment of this application.
[0023] The following is a detailed description with reference to specific examples.
[0024] Example 1
[0025] This embodiment provides a method for preparing a solid-state battery electrode, including the following steps: Under nitrogen protection, methacrylate and azobisisobutyronitrile (AIB) were added to N-methylpyrrolidone (N-methylpyrrolidone), stirred and mixed, and then heated to 60°C for prepolymerization for 1.5 h to obtain a mixture. The amount of AIB added was 0.5% of the mass of methacrylate. The amount of N-methylpyrrolidone added to the mixture was 30% of the mass of methacrylate. Lithium iron phosphate, conductive carbon black, and polyvinylidene fluoride were ground evenly and then added to N-methylpyrrolidone and stirred to obtain a positive electrode slurry. The amount of N-methylpyrrolidone added to the positive electrode slurry was 30% of the mass of lithium iron phosphate. A mixed solution was prepared by mixing the mixed solution, positive electrode slurry, and polyvinylimidazole ionic liquid. This mixed solution was then coated onto the surface of an aluminum foil and vacuum-dried at 80°C for 24 hours to obtain a solid-state battery electrode. The coating thickness was 25 μm, and the aluminum foil thickness was 2 μm. The mass ratio of methacrylate, lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and polyvinylimidazole ionic liquid was 0.25:8:1:0.75:0.4.
[0026] The polyvinylimidazole ionic liquid is prepared by the following steps: Vinylimidazolium bromide, divinylbenzene, and azobisisobutyronitrile were added to methanol and reacted at 70°C for 24 h under nitrogen protection. After the reaction, the mixture was washed with anhydrous diethyl ether and dried under vacuum at 50°C to obtain an intermediate product. The intermediate product was then subjected to ion exchange in an aqueous solution of lithium bis(trifluoromethanesulfonyl)imide. After stirring at room temperature for 72 h, the precipitate was collected by filtration and dried under vacuum at 60°C to remove residual water, yielding a polyvinylimidazolium ionic liquid. The mass fraction of the lithium bis(trifluoromethanesulfonyl)imide aqueous solution was 0.2 g / L; the ratio of the intermediate product to the lithium bis(trifluoromethanesulfonyl)imide aqueous solution was 0.1 g: 100 mL. The vinylimidazolium bromide was 1-vinyl-3-ethylimidazolium bromide.
[0027] The molar ratio of vinylimidazole ion bromide to divinylbenzene is 3:0.5; the amount of azobisisobutyronitrile added is 1% of the mass of vinylimidazole ion bromide. The molar ratio of vinylimidazole ion bromide to methanol is 1g:10mL.
[0028] Example 2
[0029] The difference between this embodiment and Example 1 is that the mass ratio of methacrylate, lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and polyvinylimidazole ionic liquid is 0.5:8:1:0.5:0.4. The polyvinylimidazole ionic liquid is prepared in the same manner as in Example 1.
[0030] The remaining raw materials and preparation process are the same as in Example 1.
[0031] Example 3
[0032] The difference between this embodiment and Example 1 is that the mass ratio of methacrylate, lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and polyvinylimidazole ionic liquid is 0.75:8:1:0.25:0.4. The polyvinylimidazole ionic liquid is prepared in the same manner as in Example 1.
[0033] The remaining raw materials and preparation process are the same as in Example 1.
[0034] Example 4
[0035] The difference between this embodiment and Example 1 is that the mass ratio of methacrylate, lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and polyvinylimidazole ionic liquid is 0.25:8:1:0.75:0.3. The polyvinylimidazole ionic liquid is prepared in the same manner as in Example 1.
[0036] The remaining raw materials and preparation process are the same as in Example 1.
[0037] Example 5
[0038] The difference between this embodiment and Example 1 is that the mass ratio of methacrylate, lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and polyvinylimidazole ionic liquid is 0.25:8:1:0.75:0.50. The polyvinylimidazole ionic liquid is prepared in the same manner as in Example 1.
[0039] The remaining raw materials and preparation process are the same as in Example 1.
[0040] Example 6
[0041] The difference between this embodiment and Example 1 is that the vinylimidazolium ion bromide used in the preparation of the polyvinylpyrazole ionic liquid is 1-vinyl-3-butylimidazolium bromide.
[0042] The remaining raw materials and preparation process are the same as in Example 1.
[0043] Comparative Example 1
[0044] The difference between this comparative example and Example 1 lies in the preparation process: Under nitrogen protection, methacrylate and azobisisobutyronitrile (AIB) were added to N-methylpyrrolidone (N-methylpyrrolidone), stirred and mixed, and then heated to 60°C and reacted for 12 hours to obtain a mixture. The amount of AIB added was 0.5% of the mass of methacrylate. The amount of N-methylpyrrolidone added to the mixture was 30% of the mass of methacrylate. Lithium iron phosphate, conductive carbon black, and polyvinylidene fluoride were ground evenly and then added to N-methylpyrrolidone and stirred to obtain a positive electrode slurry. The amount of N-methylpyrrolidone added to the positive electrode slurry was 30% of the mass of lithium iron phosphate. A mixed solution was prepared by mixing the mixed solution, positive electrode slurry, and polyvinylimidazole ionic liquid. This mixed solution was then coated onto the surface of an aluminum foil and vacuum-dried at 80°C for 24 hours to obtain a solid-state battery electrode. The coating thickness was 25 μm, and the aluminum foil thickness was 2 μm. The mass ratio of methacrylate, lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and polyvinylimidazole ionic liquid was 0.25:8:1:0.75:0.4. The polyvinylimidazole ionic liquid was prepared using the same method as in Example 1.
[0045] The remaining raw materials and preparation process are the same as in Example 1.
[0046] Comparative Example 2
[0047] The difference between this embodiment and Example 1 is that no polyvinylimidazole ionic liquid is added, while the other raw materials and preparation process remain the same as in Example 1.
[0048] Comparative Example 3
[0049] The difference between this embodiment and Example 1 is that divinylbenzene is not added during the preparation of the polyvinylimidazole ionic liquid, while the other raw materials and preparation process remain the same as in Example 1.
[0050] Test case
[0051] Peel test: The adhesive strength of the mixed adhesive in the electrode was analyzed using a universal testing machine. The electrode was cut into 15mm × 40mm strips and fixed to a copper plate. Then, 3M transparent tape was used to adhere the electrode to the copper plate and folded 180°. The electrode was clamped by upper and lower fixtures. Finally, the tape was pulled 180° using the universal testing machine. The peel speed was set to 10mm / min. The average peel strength of the mixed adhesive in the positive electrode prepared in Examples 1-6 and Comparative Examples 1-3 was recorded.
[0052] Polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide were added to acetonitrile to obtain a solid electrolyte slurry. The ratio of polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide, and acetonitrile in the solid electrolyte slurry was 3.3:1:2. The solid electrolyte slurry was coated onto the surface of the positive electrode sheets prepared in Examples 1-6 and Comparative Examples 1-3. After drying, a solid electrolyte film layer with a coating thickness of 130 μm was formed on the surface of the positive electrode sheet. A coin cell solid-state battery was prepared using a lithium sheet as the negative electrode. The assembly process was carried out in an argon glove box. The battery capacity and cycle performance were measured. The cycle performance was recorded after 100 cycles of constant current charging at 0.05C to 3.95V, constant voltage charging at 3.95V, resting for 5 min, and then constant current discharging at 0.05C to 2.75V.
[0053] The results are shown in Table 1 below: Table 1
[0054] As can be seen from Table 1 and Examples 1-6, appropriately increasing the amount of methyl methacrylate can improve the cohesiveness of the mixed adhesive. However, the amount of methyl methacrylate should not be too high, as too much will result in low crystallinity of the system and reduce peel strength. Appropriately increasing the amount of polyvinylimidazole ionic liquid can enhance the interfacial compatibility between the mixed adhesive and the current collector, thereby indirectly improving the peel strength.
[0055] As shown in Example 1 and Comparative Example 1, polymethyl methacrylate (PMMA) is prepared through in-situ polymerization, forming a complex interpenetrating network of PVDF and PMMA segments with polyvinylidene fluoride (PVDF), reducing interfacial porosity. The PVDF segments (crystalline phase) provide mechanical support, while the PMMA segments (amorphous phase) promote lithium-ion transport, thereby increasing battery capacity. As shown in Example 1 and Comparative Example 2, the absence of an ionic liquid reduces peel strength, battery capacity, and cycle stability. Because polyvinylimidazole ionic liquids have good ionic conductivity, appropriately increasing its dosage can improve the ionic conductivity of the electrolyte, promote lithium-ion transport, and thus increase battery capacity. Improving electrolyte stability and ion transport performance, and appropriately increasing its dosage helps suppress lithium dendrite growth, improving battery cycle stability. In Comparative Example 3, the absence of divinylbenzene as a crosslinking agent affected the formation of the crosslinked structure of the polyvinylimidazole ionic liquid, which was detrimental to overall performance improvement.
[0056] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a solid-state battery electrode, characterized in that, Includes the following steps: Under nitrogen protection, methyl methacrylate and azobisisobutyronitrile are added to N-methylpyrrolidone, stirred and mixed, and then heated to 60-70℃ for prepolymerization for 1-2 hours to obtain a mixture; the positive electrode material, conductive agent and polyvinylidene fluoride are ground evenly and then added to N-methylpyrrolidone and stirred to obtain the positive electrode slurry. A mixed solution is prepared by mixing a mixture of a liquid, a positive electrode slurry, and a polyvinylidene ionic liquid. The mixed solution is then coated onto the surface of a current collector and vacuum dried at 80-120℃ for 12-48 hours to obtain a solid-state battery electrode. The mass ratio of methyl methacrylate, positive electrode material, conductive agent, polyvinylidene fluoride, and polyvinylidene ionic liquid is 0.25-0.75:8:1:0.25-0.75:0.25-0.
50. The polyvinylimidazole ionic liquid is prepared by the following steps: Vinylimidazolium bromide, divinylbenzene, and azobisisobutyronitrile were added to methanol and stirred at 60-70°C for 12-24 hours under nitrogen protection. After the reaction was completed, the mixture was washed with anhydrous diethyl ether and dried under vacuum to obtain an intermediate product. The intermediate product was then added to an aqueous solution of lithium bis(trifluoromethanesulfonylimide) for ion exchange to obtain a polyvinylimidazolium ionic liquid.
2. The method for preparing a solid-state battery electrode according to claim 1, characterized in that, The coating thickness is 20-30μm.
3. The method for preparing a solid-state battery electrode according to claim 1, characterized in that, The current collector is made of aluminum foil with a thickness of 1-3 μm.
4. The method for preparing a solid-state battery electrode according to claim 1, characterized in that, The conductive agent is at least one of conductive carbon black and graphene.
5. The method for preparing a solid-state battery electrode according to claim 1, characterized in that, The cathode material is one of lithium iron phosphate, lithium cobalt oxide, and lithium manganese iron phosphate.
6. The method for preparing a solid-state battery electrode according to claim 1, characterized in that, The amount of azobisisobutyronitrile added is 0.1% to 1% of the mass of methyl methacrylate.
7. The method for preparing a solid-state battery electrode according to claim 1, characterized in that, The vinylimidazolium ion bromide is at least one of 1-vinyl-3-ethylimidazolium bromide and 1-vinyl-3-butylimidazolium bromide.
8. The method for preparing a solid-state battery electrode according to claim 1, characterized in that, The molar ratio of vinylimidazole ion bromide to divinylbenzene is 3:0.5-1; The amount of azobisisobutyronitrile added is 0.8-1% of the mass of vinylimidazolium bromide ions; The mass fraction of the lithium bis(trifluoromethanesulfonyl)imide aqueous solution is 0.15-0.2 g / L; the ratio of the intermediate product to the lithium bis(trifluoromethanesulfonyl)imide aqueous solution is 0.1-0.2 g: 100 mL.
9. A solid-state battery electrode, characterized in that, Prepared by the preparation method according to any one of claims 1-8.