Influence of solvation structure on interphase components for tin phosphide anode in potassium-ion batteries

With high theoretical capacity, tin phosphide (Sn₄P₃) has recently garnered attention as the anode for potassium-ion batteries (PIBs). However, its application is limited by the rapid capacity decay, which is highly correlated with the stability of solid electrolyte interphase (SEI). Here, we explore how the solvation structure of electrolytes affects the interphase components for the Sn₄P₃ anode, thus determining the cycle stability. The decomposition of FSI⁻ and ester solvents, particularly EC, may result in the SEI layer being enriched with poly(CO₃) and K-F, leading to a more stable cycling capability of K/Sn₄P₃ batteries in the KFSI-EC:DMC:EMC electrolyte. Moreover, a compact and uniform SEI layer promotes cycle stability. Theoretical analysis of the solvation structure epitomizes that the KFSI-EC:DMC:EMC electrolyte can generate a stable SEI layer due to K⁺ interacting more with FSI⁻ anions and EC solvent. The finding of this work helps us comprehend how SEI layer components affect the capacity of Sn₄P₃ anodes in PIBs.