| Solid state lithium batteries?SSLBs?are considered as promising chemical energy storage technologies,and cause widespread research,for they can meet the requirements of high energy density and high security.As an important part of the batteries,solid state electrolyte is a key to the development of SSLB technologies.Organic-inorganic composite solid electrolytes?CSEs?exhibit both flexibility and mechanical strength,show a great comprehensive performance.When the development of inorganic all solid-state lithium battery technology is not yet mature today,CSEs can be used as transitional SSLB technologies,during the progression from traditional liquid lithium ion battery to inorganic all solid-state lithium battery.With highest ionic conductivity of 10-410-2 S·cm-1 and many excellent features,sulfide solid electrolyte is most hopeful to be applied to inorganic all solid-state lithium battery.In this paper,the preparation and electrochemoical performances of solid electrolyte for SSLBs was studied.The contents are presented as below.?1?The garnet type Li6.4La3Zr1.4Ta0.6O12?LLZTO?powder was composited with poly?ethylene oxide??PEO?by solution-casting method,to prepare CSE membranes with different LLZTO contents.When mass fraction of LLZTO particles was 19.1 wt%,the CSE showed the best comprehensive performance,with ionic conductivity of 2.83×10-4 S·cm-1 at 50?and activation energy of 0.523 eV.At the same time,PEO8-LiTFSI-19.1wt%LLZTO had a wide electrochemical stability window of about 4.62 V,and exhibited interfacial stability against Li metal,as the interfacial resistance remained at a stable value of 61?after stored at 50?for 26days.?2?PEO8-LiTFSI-19.1wt%LLZTO was applied to Ni-rich cathode material?NCM622?.Electrolyte-modified cathode electrodes were prepared by single-step wet chemical process.The PVDF-SCN-LiTFSI electrolyte coated on surface of NCM622 particles,and provided more ion transport channels between the active material particles,forming a highly conductive network.As a result,the polarization was decreased and the kinetic performance was improved in the modified cathode electrode.NCM622|CSE|Li solid state lithium batteries showed good rate performance and cycling stability at 50?.The Coulombic efficiency of the battery was close to 100%,and kept stable for more than 100 cycles,meantime,capacity fading of the battery was retarded.?3?The preparation of Li3PS4 sulfide solid electrolyte was explored preliminarily.The ionic conductivity of electrolyte synthesized by useing NMF was 1.04×10-6 S·cm-1.The white powder prepared by useing THF was heat treated at 140?,of which the ionic conductivity was 1.18×10-5S·cm-1.The sulfide solid electrolyte prepared by high-energy ball milling method exhibited higher ionic conductivity(>10-4 S·cm-1).In consequence,high-energy ball milling was the best preparation process.The best ball milling time was 14h,after which the ionic conductivity of prepared Li3PS4glass was 3.13×10-4 S·cm-1.Li3PS4 glass transformed to glass-ceramic phase with a increased ionic conductivity of 6.87×10-4 S·cm-1 after heat treatment at 245?.The Li3PS4 glass-ceramic showed good electrochemical stability. |
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