Preparation And Performance Study Of Chloride-modified Poly(Ethylene Oxide)-based Solid-state Electrolytes

All-solid state lithium batteries（ASSLBs）are considered as a promising energy storage device due to their excellent energy density and safety performance.Solid-state electrolyte is the core component of ASSLBs and plays an essential role in the safety and electrochemical performance of the cells.The ideal solid electrolyte should possess high ionic conductivity and ionic transfer number,excellent mechanical properties,wide electrochemical window and good electrode interface compatibility.However,single solid electrolytes,such as inorganic solid electrolytes（ISE）and polymeric solid electrolytes（SPE）,can hardly meet the above requirements at the same time.Composite solid electrolytes（CSE）present a broad application because they combine the advantages of ISE and SPE.Therefore,CSEs with interfacial stability and high electrochemical properties are prepared by adding chlorides with poly（ethylene oxide）（PEO）.In addition,in order to eliminate the influence of uneven distribution of inorganic fillers in the polymer,a homogeneous CSE without particle aggregation is further prepared by in-situ coupling method.Firstly,the chloride superionic conductor Li₂Zr Cl₆（LZC）is innovatively introduced into the PEO matrix by solution casting method.The as-prepared electrolyte provides high ionic conductivity of 5.98×10^-4 S cm^-1 at 60°C and high Li ion transference number of 0.44 since LZC is crucial in improving ionic conductivity and enhancing mechanical strength.More importantly,the interaction between LZC and PEO is investigated using FT-IR and Raman spectra,which is conducive to inhibit the decomposition of PEO and beneficial to the even deposition of Li ions.The Li Fe PO₄||Li ASSLB with 1%LZC-added composite electrolyte（CPE-1%LZC）demonstrates excellent cycling performance with a capacity of 145.4 m Ah g^-1 after 400 cycles at 0.5C.This work combines the advantages of chloride and polymer electrolyte,exhibiting great potential in the next generation of all-solid-state lithium metal batteries.Moreover,to solve the problems of the interface compatibility at the inorganic/polymer phase and the agglomeration of inorganic particles in the polymer,inorganic-polymer composite electrolytes is prepared by in situ coupling reaction.The inorganic component is combined to the polymer chain by chemical bonds,providing a high speed channel for Li⁺transport.The prepared electrolyte exhibits a high ionic conductivity of6.4×10^-4 S cm^-1 and a wide electrochemical window（5.1 V）.The CSEs ran stably for more than 4000 h in Li||Li symmetrical cells.XPS characterization demonstrates that the cycled Li/electrolyte interface generates a Li F-rich SEI layer that can help suppress the penetration of lithium dendrites into electrolyte.In addition,the assembled Li Fe PO₄||Li cells present favorable cycling performance with a capacity retention of84.9%after 500 cycles at the rate of 0.5 C.NCM622||Li cells achieve the capacity of153 m Ah g^-1 at 0.1 C,confirming that the electrolyte is capable of operating at high voltages.