Mitigating Swelling of the Solid Electrolyte Interphase using an Inorganic Anion Switch for Low‐temperature Lithium‐ion Batteries

Inclusion of difluorophosphate anion in the primary solvation sheath of a weakly-solvated electrolyte helps to switch the swelling properties of solid electrolyte interphase (SEI) on a graphite (Gr) composite anode. By forming a low-swelling, Li₃PO₄-enriched SEI, reversible Li⁺ (de)intercalation was enabled at a stable Gr-electrolyte interface, contributing to improved low-temperature electrochemical performance of a Li-ion battery.

Abstract

In overcoming the Li⁺ desolvation barrier for low-temperature battery operation, a weakly-solvated electrolyte based on carboxylate solvent has shown promises. In case of an organic-anion-enriched primary solvation sheath (PSS), we found that the electrolyte tends to form a highly swollen, unstable solid electrolyte interphase (SEI) that shows a high permeability to the electrolyte components, accounting for quickly declined electrochemical performance of graphite-based anode. Here we proposed a facile strategy to tune the swelling property of SEI by introducing an inorganic anion switch into the PSS, via LiDFP co-solute method. By forming a low-swelling, Li₃PO₄-rich SEI, the electrolyte-consuming parasitic reactions and solvent co-intercalation at graphite-electrolyte interface are suppressed, which contributes to efficient Li⁺ transport, reversible Li⁺ (de)intercalation and stable structural evolution of graphite anode in high-energy Li-ion batteries at a low temperature of −20 °C.

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