Interface Stability Design And Performance Research Of PEO-based Solid-state Lithium Metal Battery

The solid-state electrolyte?SSE?is an effective solution to the leaked,unstable and flammble issues of organic liquid electrolyte.Meanwhile,the SSE offers wide working temperature,processibility,and high energy density and thus attracts widespread attention.However,poor interfacial compatibility of electrolyte and eletrode has great impact on electrochemical performance of all-solid-state batteries.Unstable interface of PEO/Li potential results in severe short-circuit issues,which limit their practical application.To solve above problems,we have modificed PEO-based electrolyte with novel additives,constructing stable interface of PEO/Li via in situ reaction for superior electrochemical performance.?1?Construction of I-modified interface.With the addition of trace amounts of iodine?I₂?into PEO-Li TFSI electrolyte,there is a conversion from I₂ to I₃^-and homogeneously distributed I₃^-can further complex with PEO.In-situ Raman has verfied that Li I is formed via in-situ reaction of I₃^-and Li.Cryogenic transmission electron microscopy has revealed that I-rich SEI mainly consists of organic ROCO₂Li and inorganic Li₂O,effectively inhibiting the side reaction.Reduced Li₂O content contributes to fast interfacial transport of Li ions,achieving uniform Li deposition.With the addition of 1wt.%I₂,the Li Fe PO₄/Li cells exhibit higher capacity(150.1m Ah g^-1at 0.5 C),excellent cycling stability?96.5%after 400 cycles?at 50 ^oC.?2?Construction of Mg-modified interface.With the addition of trace Mg?TFSI?₂into PEO-Li TFSI electrolyte,a Mg-modified interface is constructed via the simple in-situ irreversible electrochemical reduction of Mg²⁺,which can be further by cyclic voltammetry test.Moreover,traces of crystalline Mg were observed in the interface between PEO and Li by cryogenic transmission electron microscopy,lowering barrier for Li⁺diffusion and nucleation over potential and achieving uniform Li deposition and a long-term stability.The Mg-modified Li electrode enables the full Li Fe PO₄/Li cells with superior cycling lifespan of more than 450 cycles without capacity loss.