Regulation Of Solvation Structure And Solid-Electrolyte Interface On Ether-Based Electrolyte For Sodium-Ion Battery

Ether-based electrolytes have great application potential in Sodium-ion batteries due to the excellent modification capability of solid-electrolyte interface and compatibility with graphite.However,the universal high-voltage instability of ether-based electrolytes makes it difficult to cooperate with various cathode materials.The strong oxidative tendency limits the voltage window and application in high-energy-density sodium-ion batteries.Focusing on the high-voltage oxidation of ether-based electrolytes and continuous deterioration of cathode-electrolyte interface（CEI）,this paper proposed the feasibility of NaNO₃ as an additive in representative 1.0 M NaOTf in DEGDME electrolyte through Frontier Molecular Orbital Theory by density functional theory（DFT）calculations.The addition of trace amount of NaNO₃（≈0.0428 M）changed the solvation structure of sodium ion,inducing the in-situ formation of Na₃N/NaF-riched CEI according to the preferential decomposition of anions,which effectively improved the high voltage stability of ether electrolytes to achieve stable cycling between 2～4 V.The general applicability of this addition method on improving the anti-oxidant capability was evaluated in different cathodes and ether-based electrolytes through comprehensive electrochemical test.Moreover,a design strategy of regulating solvation structure with anions-mediating advantageous CEI generation-improving electrochemical performance was raised.On this basis,the ether electrolytes with different anions were prepared in TEGDME,and the interface modification was carried out by controlling the decomposition of the anion-solvent cluster.The preferred 1.0 M NaPF₆ in TEGDME electrolyte was tested in Na₃V₂（PO₄）₃（NVP）cathode and full battery composed of NVP and graphite,which showed fast interfacial kinetics and excellent rate capability.64%capacity retention was preserved at a current density of 30 C(1 C≈118 m A g^-1)in full battery.Compared with hard carbon-ester electrolyte system,the rate performance was significantly improved.This provides a strategy of solvation-mediated interfacial engineering for solving the problem of compatibility with high-voltage cathodes.The simple and easy method with the advantages of in-situ construction has valid potential on industrial production.