On-site conversion reaction enables ion-conducting surface on red phosphorus/carbon anode for durable and fast sodium-ion batteries

Abstract

The practical applications of high-capacity alloy-type anode materials in sodium-ion batteries (SIBs) are challenged by their vast volume effects and resulting unstable electrode–electrolyte interphases during discharge–charge cycling. Taking red phosphorus (P)/carbon anode material as an example, we report an on-site conversion reaction to intentionally eliminate the volume effect-dominated surface P and yield an ionically conducting layer of Na3PS4 solid-state electrolyte on the composite. Such a surface reconstruction can significantly suppress the electrode swelling and simultaneously enable the activation energy of interfacial Na+ transfer as low as 36.7 kJ mol−1, resulting in excellent electrode stability and ultrafast reaction kinetics. Consequently, excellent cycling performance (510 mA h g−1 at 5 A g−1 after 1000 cycles with a tiny capacity fading rate of 0.016% per cycle) and outstanding rate capability (484 mA h g−1 at 10 A g−1) are achieved in half cells. When coupled with Na3V2(PO4)3 cathode, the full cells exhibit 100% capacity retention over 200 cycles at 5C with an average Coulombic efficiency of 99.93% and a high energy density of 125.5 W h kg−1 at a power density of 8215.6 W kg−1 (charge or discharge within ∼49 s). Remarkably, the full cell can steadily operate at a high areal capacity of 1.9 mA h cm−2, the highest level among red P-based full SIBs ever reported.