Construction And Performance Study Of Polymer Solid-state Electrolyte For Lithium Metal Battery

Lithium metal batteries have emerged as one of the most promising next-generation battery systems,attributed to their high energy density and power endurance.Nevertheless,liquid organic electrolytes,which are currently used in these batteries,pose significant risks,such as leakage and explosion.Thus,it is crucial to explore intrinsically safe and efficient electrolyte materials for the development of lithium metal batteries.Polymer solid electrolytes（SPE）present a viable alternative over liquid electrolytes,as they offer improved thermal stability,interface protection,and dendrite growth inhibition.However,the ionic conductivity of the polymer solid electrolyte at room temperature is low,the interface impedance between the electrolyte and the electrode is large,and the overall cycle performance of the polymer solid-state battery remains to be solved.Therefore,this paper examines the impact of different additives on the interface and overall performance of polymer electrolytes to address the challenges and build a safe and stable battery system.Firstly,a novel PVDF-HFP-based SPE by introducing[Li（G4）₁][TFSI]and Li BOB into the polymer matrix was successfully prepared.The SIL with unique solvated structure modifies the membrane morphology and provides favorable ionic transport kinetics along the polymer matrix.The additional Li BOB is found to further regulate the Li⁺coordination environment by competing with TFSI^-.The ionic conductivity of the electrolyte at room temperature is as high as 2.18×10^-3 S cm^-1,the lithium ion transfer number is 0.86,and superior electrochemical stability window is 5.7 V.Consequently,the assembled solid-state LFP|Li battery delivers a high capacity of 143.2 m Ah g^-1 and a capacity retention of as high as 95.9%after 500 cycles at a rate of 0.5 C at RT.Secondly,the electrolyte was prepared by incorporating SIL and polysulfide Li₂S₆ into the polymer matrix PEO.To reduce the interface resistance between the electrolyte and the cathode,the electrolyte slurry was directly cast onto the cathode surface using the solution casting method,allowing in-situ formation of the electrolyte.The S₆^2-in polysulfides has a strong interaction with the groups on the PEO segment,which reduces the crystallinity of the polymer and improves the electrochemical stability window.Ionic conductivity of the polymer solid electrolyte can reach 6.05×10^-4 S cm^-1 at room temperature.In addition,Li₂S₆ on the electrolyte surface reacts with lithium to form a thin Li₂S/L₂S₂ interface layer,which effectively reduces the Li⁺interface transfer impedance,regulates lithium ion deposition,and improves the cycle stability of the battery.The optimized LFP@ELGS|Li battery leverages the advantages of polysulfide and in-situ formation electrolyte,exhibiting an initial discharge specific capacity of158.91 m Ah g^-1 at 0.2 C rate and an average coulombic efficiency of 99.98%.Remarkably,the LFP@ELGS|Li battery retains 98.48%of its capacity after being cycled 100 cycles.Finally,a feasible design strategy of cathode/electrolyte integrated solid-state lithium-sulfur battery is proposed.The design utilizes the good solubility of polymer PEO to Li₂S₆,which is incorporated into a slurry containing active polysulfides to form a PEO electrolyte slurry.Using the solution casting method,the slurry is integrated into the porous conductive carbon cathode,creating a novel dual-conductive framework that facilitates efficient electron/ion transfer.This unique structural design improves the problem of poor solid-solid interface contact between traditional SC cathode and solid-state electrolyte,and improves the utilization of active materials.In addition,the active materials in the form of Li₂S₆ are added to the PEO electrolyte to promote the dissociation of Li TFSI,thus enhancing formation of Li F-rich SEI layers on the surface of the lithium anode.This process regulates the deposition of Li⁺.Further,the electrode/electrolyte integrated solid-state lithium-sulfur battery is demonstrated to have a discharge specific capacity of 1593 m Ah g^-1 at 60℃,with the reversible capacity remaining above 610 m Ah g^-1 after 180 cycles.