| The rapid development of the global economy makes the human demand for non-renewable energy increasing day by day,and the large consumption of oil and coal causes energy exhaustion and environmental pollution and other problems,so it is urgent to find clean renewable energy.However,the conversion and storage of renewable energy is unstable and costly,so the development of efficient energy storage equipment has been paid attention by scientists.Lithium-ion batteries because of their long cycle life and high energy density,has been widely used in People’s Daily life to use electric equipment,but because of the traditional liquid lithium-ion batteries have flammable,leakage and other safety problems,so solid-state batteries have received more and more attention,but its own existence of some problems,For example,the problem of poor contact between solid electrolyte and electrode interface limits its wide application.Firstly,by adjusting the ratio of N-butyl-n-methylpyrrole di（trifluoromethylsulfonyl）imide salt(Pyr14TFSI)to polyvinylidene fluoride（PVDF）and lithium bistrifluoromethylsulfonimide（Li TFSI）,Pyr14TFSI in PVDF-based solid electrolyte with a mass content of 40 wt%,Solid-state batteries offer the best performance.Secondly,the Pyr14TFSI/Li TFSI/PVDF solid electrolyte is combined with the lithium lanthanum zirconium tantalum oxygen solid electrolyte(Li6.4La3Zr1.4Ta0.6O12,LLZTO)to increase its mechanical properties and ionic conductivity.At the same time,in order to improve the capacity retention rate of solid state battery,the PAN-based solid state electrolyte was prepared and the laminated double solid electrolyte was constructed together with it.Through the characterization of physical and chemical properties of the material,electrochemical properties and battery performance tests,it was found that the laminated double-layer solid electrolyte has excellent cycling properties and rate properties under high pressure conditions.At room temperature,the reversible cycle capacity of 103 m Ah g-1is still maintained after 100 cycles of 3～4.5 V at 1 C rate,and the ionic conductivity at 30°C is 2.3×10-4S cm-1.Lithium stability was tested at a current density of 0.2 m A cm-2,and stable polarization voltage was maintained after 950 h.Finally,the optimized Pyr14TFSI/Li TFSI/PVDF solid electrolyte was combined with lithium difluoroxalate borate（Li DFOB）to increase the interface stability between it and the positive electrode.At the same time,in order to reduce the interface impedance between electrolyte/electrode and electrolyte/electrolyte,the PEO solid electrolyte was prepared and the graded double solid electrolyte was constructed together with it.Through physicochemical properties,electrochemical properties and battery performance tests,it is found that the graded double-layer solid electrolyte has low interface impedance and cycle stability.At room temperature,the reversible cycle capacity of 115 m Ah g-1was maintained after 200 cycles of 3～4.3 V at 1 C rate,and the ionic conductivity was 9.9×10-4S cm-1at 30°C.In addition,the reduction of DFOB-anion to B-O and B-F bonds from XPS analysis proves that the presence of CEI layer reduces the occurrence of side reactions at the interface.In this paper,the introduction of Pyr14TFSI,LLZTO and Li DFOB into PVDF-based polymer electrolyte effectively improved the interface compatibility and stability of PVDF-based solid electrolyte,and improved the cycle life and capacity retention rate of solid state battery through the double-layer structure design. |
