| Garnet type solid-state electrolytes have attracted great attention in the research of solid-state batteries due to their advantages of high lithium-ion conductivity and wide electrochemical window.However,there are still some problems to be solved,such as high interface impedance and poor processability.In order to solve these problems,the composite solid electrolyte(CSEs)with high lithium ion conductivity,high safety and high interface stability was prepared by the combination of garnet solid electrolyte and PVDF HFP.In addition,it was modified by nitrogen dielectric barrier discharge(DBD)plasma.Specifically,the following studies have been carried out:(1)First,the Al-doped Garnet-type solid electrolyte was prepared by cold isostatic pressing-high temperature solid phase method,and the effects of sintering temperature and Al doping on its performance were explored.The prepared Li6.3Al0.15La3Zr1.75Ta0.25O12(Al-LLZTO)solid electrolyte has Li+conductivity of4.14×10-4 S/cm and an activation energy as low as 0.11 e V at room temperature.Due to the doping of Al element,the density of the solid electrolyte is increased and more lithium vacancies are introduced.(2)Second,the different mass ratios between PVDF-HFP and Al-LLZTO and the influence of Li TFSI on the performance of CSEs were explored.50 wt.%CSEs without Li TFSI has the lowest interface impedance of 784?.On this basis,the interface impedance decreases significantly with the addition of Li TFSI,and the conductivity reaches 371×10-5 S/cm at room temperature.And it has high electrochemical window(5 V)and lithium ion migration number(0.42).Moreover,the specific capacity of the LFP|CSEs|Li battery is reduced from 145 m Ah/g to 136m Ah/g after 200 cycles at 1 C,and the specific capacity retention rate is 93%.Among them,Al-LLZTO and Li TFSI reduce the crystallinity of PVDF-HFP and increase the carrier concentration.(3)On the basis of the previous chapters,nitrogen DBD plasma was used to modify CSEs,and the effects of different treatment time(0 s,10 s,30 s,5 min)on CSEs were explored.The CSEs showed the best performance at 10s.The interface impedance of the CSEs is reduced and the lithium ion conductivity is 7.35×10-5 S/cm.The lithium ion migration number of CSEs is 0.45.XPS results show that Li3N is formed on the surface of the composite electrolyte after nitrogen DBD treatment,which is conducive to the transport of Li+.And the specific capacity of LFP|CSEs|Li battery increases to158 m Ah/g at 0.1 C,and the battery specific capacity retention rate is 95%after 200cycles at 1 C.The above research results provide a new strategy for the modification of Garnet solid electrolyte,and provide a new idea for improving the high-efficiency electrochemical performance of solid-state battery. |
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