Method for making composite solid-state electrolyte layers and the product made therefrom

Abstract

A method for preparing a composite solid electrolyte layer and its product. The composite solid electrolyte layer is bonded to a positive electrode plate and includes a polymer fiber membrane with interlaced fibers and interconnected pores defined by the fibers, a solid polymer attached to the fibers and filling the pores, oxide ceramic particles with positive charges on their surfaces and located in each pore, and an ionic liquid distributed in the solid polymer and on the oxide ceramic particles. The ionic liquid contains a flame-retardant ionic plasticizer with a thermal decomposition temperature higher than 200°C, lithium ions, and anions. After the positive electrode plate, the composite solid electrolyte layer, and the negative electrode plate are assembled into a solid-state battery and during actual operation, the positive charge on the surface of the oxide ceramic particles can attract anions to promote the dissociation of lithium ions and anions and enhance the free migration of lithium ions in the composite solid electrolyte layer.

Claims

1. A method for preparing a composite solid electrolyte layer, comprising the following steps: Step (a) mixing a first lithium salt, a flame-retardant ionic plasticizer, and an additive to form an ionic liquid containing lithium ions and anions, wherein the flame-retardant ionic plasticizer has a thermal decomposition temperature higher than 200°C; Step (b) dissolving a solid polymer and a second lithium salt in an organic solvent to form a polymer solution containing lithium ions and anions; Step (c) mixing a plurality of oxide ceramic particles with the ionic liquid of step (a) to form an ionic gel containing the oxide ceramic particles with positive surface charges, lithium ions, and anions; Step (d) mixing the ionic gel with the polymer solution to form a composite material containing the oxide ceramic particles with positive surface charges, lithium ions, and anions; Step (e) introducing the composite material into an introducer to form a mixed solution. Step (f) involves injecting the mixed solution between a polymer fiber membrane and a positive electrode plate, allowing the mixed solution to penetrate into a plurality of interconnected pores of the polymer fiber membrane and flow through these pores to a surface of the positive electrode plate, thereby forming a preform. The preform includes the positive electrode plate, the polymer fiber membrane, and the mixed solution flowing to the surface of the positive electrode plate and distributed within the pores of the polymer fiber membrane. Step (g) involves subjecting the preform to vacuum drying to remove the organic solvent and the introducing agent from the mixed solution, thereby... A composite solid electrolyte layer is prepared and adhered to the surface of the positive electrode plate. The composite solid electrolyte layer includes a polymer fiber membrane, solid polymers attached to a plurality of interlaced fibers of the polymer fiber membrane and filling the pores therein, oxide ceramic particles located in the pores of the polymer fiber membrane and carrying a positive charge on their surfaces, and an ionic liquid distributed in the solid polymers and on the oxide ceramic particles. The ionic liquid in step (g) contains a flame-retardant ionic plasticizer, lithium ions, and anions. When the composite solid electrolyte layer attached to the positive electrode plate and a negative electrode plate are assembled into a solid-state battery and the solid-state battery is actually in operation, the positive charge on the surface of the oxide ceramic particles can attract the anions in the composite solid electrolyte layer, thereby promoting the dissociation of lithium ions and anions in the composite solid electrolyte layer and enhancing the free migration of lithium ions in the composite solid electrolyte layer.

2. The manufacturing method as described in claim 1, wherein, The thermal decomposition temperature of this flame-retardant ionic plasticizer is higher than 200℃ and lower than or equal to 500℃.

3. The manufacturing method as described in claim 2, wherein, The flame-retardant ionic plasticizer is selected from an ionic compound consisting of the group consisting of: pyrrolidinyl bis(fluorosulfonyl)imine salt, pyrrolidinyl bis(trifluoromethanesulfonyl)imine salt, imidazolyl bis(fluorosulfonyl)imine salt, imidazolyl bis(trifluoromethanesulfonyl)imine salt, and combinations thereof.

4. The manufacturing method as described in claim 1, wherein, The first lithium salt and the second lithium salt are selected from lithium salts of the group consisting of: lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiOTf), lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (LiFTFSI), lithium perchlorate (LiClO4), and combinations thereof; the additive is selected from salts of the group consisting of: lithium difluorooxalateborate (LiDFOB), lithium dioxalateborate (LiBOB), lithium nitrate (LiNO3), lithium difluorophosphate (LiPO2F2), and combinations thereof.

5. The manufacturing method as described in claim 1, wherein, The solid polymer is selected from a group consisting of: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polypropylene carbonate (PPC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), polyimide (PI), and combinations thereof.

6. The manufacturing method as described in claim 1, wherein, The delivery agent is an organic solvent selected from a carbonate or an ether.

7. The manufacturing method as described in claim 6, wherein, The carbonates are selected from a group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), dimethyl carbonate (DMC), 1,2-dimethoxyethane (DME), and combinations thereof.

8. The manufacturing method as described in claim 1, wherein, The vacuum drying process is carried out at a temperature below 100°C.

9. A composite solid electrolyte layer, adhered to a surface of a positive electrode plate, comprising: a polymer fiber membrane including a plurality of interleaved fibers and a plurality of interconnected pores defined by the fibers; a solid polymer attached to the fibers of the polymer fiber membrane and filling the pores; a plurality of oxide ceramic particles, each oxide ceramic particle having a positively charged surface and located in the pores of the polymer fiber membrane; and an ionic liquid distributed in the solid polymer and on the oxide ceramic particles, the ionic liquid containing a flame-retardant ionic plasticizer, lithium ions and anions, wherein the flame-retardant ionic plasticizer has a thermal decomposition temperature higher than 200°C; wherein... When the composite solid electrolyte layer attached to the positive electrode plate and a negative electrode plate are assembled into a solid-state battery and the solid-state battery is actually in operation, the positive charge on the surface of the oxide ceramic particles can attract the anions in the composite solid electrolyte layer, thereby promoting the dissociation of lithium ions and anions in the composite solid electrolyte layer and enhancing the free migration of lithium ions in the composite solid electrolyte layer.

10. The composite solid electrolyte layer as claimed in claim 9, wherein, The thermal decomposition temperature of this flame-retardant ionic plasticizer is higher than 200℃ and lower than or equal to 500℃.

11. The composite solid electrolyte layer as claimed in claim 10, wherein, The flame-retardant ionic plasticizer is selected from an ionic compound consisting of the group consisting of: pyrrolidinyl bis(fluorosulfonyl)imine salt, pyrrolidinyl bis(trifluoromethanesulfonyl)imine salt, imidazolyl bis(fluorosulfonyl)imine salt, imidazolyl bis(trifluoromethanesulfonyl)imine salt, and combinations thereof.

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