The Synthesis Of Advanced Solid Polymer Electrolytes And Their Applications In Lithium Batteries

Replacing conventional liquid electrolytes with solid polymer electrolytes has been recognized as a promising method to enhance the safety coefficiency of lithium batteries.However,the design of an ideal polymer electrolyte simultaneously possessing high ionic conductivity,low electrode/solid electrolyte interfacial resistance and robust mechanical properties still remains an enormous challenge.In this work,the preparation processes of novel polymer electrolytes were systematically studied,meanwhile their electrochemical performances and interfacial properties were characterized.Firstly,the application of solid electrolyte based on nitrile materials for lithium-ion batteries was investigated.The gelation mechanism of cyanoethyl polyvinyl alcohol?PVA-CN?-based gel polymer electrolyte was revealed,and a graphite electrode/gel polymer electrolyte interface with less resistance was fabricated during the battery formation process.Furthermore,a hierarchical all-solid-state electrolyte based on nitrile materials?SEN?was prepared via in situ synthesis method.PVA-CN framework was embedded in succinonitrile?SN?based solid electrolyte,which was filled in a polyacrylonitrile?PAN?based electrospun fiber membrane to form this novel electrolyte.The structure similarity of the raw materials and the hierarchical structure design ensured the electrolyte with high conductance,high lithium ion transference number,favorable mechanical strength,excellent safety and good flexibility.Moreover,the in situ synthesis method provided an excellent contact and affinity between electrolyte and electrodes,which greatly reduced the interfacial resistance and led to an outstanding electrochemical performance for the assembled solid cells.Secondly,a SiO₂ hollow nanosphere-based composite solid electrolyte?SiSE?was presented for lithium metal batteries.Cross-linked tripropylene gycol diacrylate?TPGDA?framework was in situ polymerized in carbonate-based liquid electrolyte,which was absorbed in a SiO₂ hollow nanosphere layer to form this hierarchical electrolyte.The prepared solid electrolyte exhibited high conductivity,excellent safety,remarkable suppression for lithium dendrite growth and enhanced cycle life.When the SiSE was in situ fabricated on the cathode and applied to lithium metal batteries,the obtained cells showed a significant improvement in cycling stability,mainly attributed to the stable electrode/electrolyte interface and remarkable suppression for lithium dendrite growth by the SiSE.Thirdly,considering the aggravated shuttle effect caused by the large specific surface area of lithiated silicon nanoparticles which severely decreasing the cycling stability of lithiated silicon-sulfur batteries,we presented a novel lithiated silicon-sulfur battery exploiting an optimized solid-like electrolyte?OSE?.This electrolyte was fabricated by integrating ether-based liquid electrolyte with SiO₂ hollow nanosphere layer to suppress the shuttle effect and fluoroethylene carbonate?FEC?additive to optimize the anodic solid electrolyte interface?SEI?.The prepared batteries exhibited enhanced cycle life,low flammability and strong recovery ability against short-circuit.Finally,based on the incombustibility of ionic liquid/poly?ionic liquid?materials,a high-safety hierarchical poly?ionic liquid?-based solid electrolyte?HPILSE?was designed.The prepared electrolyte showed high ionic conductivity,low electrode/solid electrolyte interfacial resistance,good mechanical strength and superior cycle performances in LiFePO₄/Li and Na_0.9[Cu_0.22Fe_0.30Mn_0.48]O₂/Na polymer cells.