| Solid-state lithium-ion batteries have improved safety and energy density compared to conventional liquid batteries.Although inorganic solid electrolytes have high ionic conductivity,their high interfacial impedance and poor processability limit their applications.Polyvinylidene fluoride-hexafluoropropylene polymer?PVDF-HFP?has good interfacial contact,but its room temperature conductivity is low.In this paper,an oxide solid electrolyte Li6.4La3Zr1.4Nb0.6O12?LLZNO?and a sulfide solid electrolyte Li7P3S11?LPS?were prepared by solid state reaction,and were composited as inorganic fillers with polymer electrolytes PVDF-HFP/LITFSI.The composite polymer electrolyte having excellent properties is obtained.The garnet solid electrolyte Li6.4La3Zr1.4Nb0.6O12 was synthesized by solid state reaction.The room temperature ionic conductivity was 1.3×10-4 S·cm-1.It is then compounded in a different ratio with the polymer electrolyte PVDF-HFP/LITFSI.When the recombination ratio is 1 wt.%,its ionic conductivity reaches the highest(6.97×10-5S·cm-1)and the electrochemical window is greater than 5 V.At the same time,the polymer electrolyte modified by LLZNO has good stability to lithium interface and inhibition of lithium dendrite.More intriguingly,such polymer electrolyte based LiFePO4/Li battery showed prominent cycling stability.Tested at different rates,LLZNO composite polymer electrolyte has good rate performance and cycle stability.The sulfide solid electrolyte Li7P3S11 was obtained by ball milling and heat treatment,and sintering at 220 ? for 1 h gave an LPS room temperature ionic conductivity of 1.592×10-4S·cm-1.Different ratios of LPS were compounded with the polymer electrolyte PVDF-HFP/LITFSI by solution casting.The ionic conductivity,mechanical properties and electrochemical properties of the polymer electrolyte obtained after compounding have been greatly improved.Among them,the 1 wt.%composite ratio of LPS electrolyte ionic conductivity increased the most,and the room temperature ionic conductivity increased from 9.54×10-6 S·cm-1 to 6.78×10-5 S·cm-1.The ionic conductivity is increased by two orders of magnitude.At the same time,the ion migration number is 0.48,which are higher than the liquid electrolyte 0.38,and the LPS composite polymer electrolyte exhibits excellent ability to inhibit metal lithium dendrites.The electrochemical stability window is greater than 4.5 V.PVDF-HFP/LITFSI-1 wt.% LPS was assembled into a lithium-sulfur battery.After the interface modification,the battery performance test was carried out at 25 ? at a cycle rate of 0.1 C.The specific capacity of the first cycle was 969 mAh/g and after 100 cycles the specific capacity was maintained at 573.8 mAh/g.This experiment combines the advantages of inorganic solid electrolyte LLZNO\LPS and polymer electrolyte PVDF-HFP,and greatly improves the performance of polymer electrolyte PVDF-HFP.This work provides a new idea for the development of solid electrolytes. |
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