Construction of robust solid-electrolyte interphase via electrode additive for high-performance Sn-based anodes of sodium-ion batteries

Alloy-based Sn anode for sodium-ion batteries has attracted tremendous attention due to its low working voltage, high specific capacity, and good availability. Its application is hindered, however, by inferior cycling stability due to its huge volume changes and unstable solid-electrolyte interphase (SEI) film. Herein, tetraphenylphosphonium bis(trifluoromethanesulfonyl)imide (TPPTFSI) is introduced into the electrode and spontaneously adsorbed on the surfaces of commercial Sn microparticles (μ-Sn) to improve the electrochemical performance of the Sn anode. In the first cycle, the TPP+ component of TPPTFSI decomposes to form an organic component of the SEI film, thereby enhancing its flexibility. Meanwhile, the TFSI− component is converted into an inorganic constituent of the SEI, improving its robustness and ionic conductivity. Therefore, the cycling performance of the μ-Sn is enhanced significantly. The modified electrode, TPPTFSI-Sn, delivers a capacity of 619.7 mAh g−1 after 2000 cycles at 2.0 A g−1, while the control sample can only survive for 30 cycles. Importantly, the full cell also exhibits excellent performance, including rate performance and cycling stability. Its simple operation and remarkable electrochemical performance improvement indicate the promising prospects of this strategy for advanced electrodes in SIBs.