Synergistic strategy of the phosphorus anode decorated by LiF and combined with KFSI-based electrolyte against shuttle effect of dissoluble polyphosphides for boosting potassium-storage performance

Abstract

Phosphorus is a promising anode material for potassium-ion batteries due to the highest theoretical-specific capacity among all the proposed anode materials. So far, it is considered to have similar disadvantages to silicon anode, such as poor electronic conductivity and huge volumetric change, thus, lots of efforts have been devoted to synthesizing phosphorus/carbon hybrids. However, the electrochemical performance is still unsatisfied, due to the unclear capacity decay mechanism. Here we reveal that soluble potassium polyphosphides are generated during potassiation process and shuttle to the counter electrode where the side effects occur, leading to the loss of active phosphorus and the failure of counter electrode. To address this issue, we developed the P/CNT-LiF electrode in combination with the replacement of conventional KPF 6 by potassium bis(fluorosulfonyl)imide (KFSI) in electrolyte, in which KFSI contributes to the formation of stable and tough solid electrolyte interface (SEI), meanwhile LiF can prevent polyphosphides from diffusing to the electrolyte before and after the formation of SEI. Thus, the thin, stable and uniform SEI layer can be generated at the surface of the electrode particles, inhibiting the polyphosphides’ shuttle, contributing to the improved initial coulomb efficiency (73.7%) and reversible specific capacity (507.6 mAh g −1 after 100 cycles at 50 mA g −1 ).