Phosphorus-doped torreya shell-derived hard carbon anodes for ultra-low capacity decay rate of sodium-ion batteries

Hard carbon anodes for sodium-ion batteries (SIBs) still suffer from poor initial coulombic efficiency and an ambiguous Na+ storage mechanism. Here, we proposed a novel phosphorus-doped torreya shell-derived hard carbon (P-TSHC) as an anode for SIBs via a feasible two-step carbonization technique. Effects of P contents in hard carbon on porous structure, plane d-spacing, and electrochemical properties were investigated. In particular, P-TSHC15 exhibits the most excellent electrochemical performance with a superior rate capability up to 8 A g-1 and an ultra-low capacity decay rate of 0.075 % per cycle within 1000 cycles at 1 A g-. 1 This should be mainly attributed to P-doping, which expands the interlayer spacing for better Na+ accommodation in mesoporous filling mechanism, generates more defects and specific surface areas, and provides transport channels for Na+, thereby increasing the low-voltage plateau capacity. This work will provide a route for further property optimization of biomass hard carbon for SIBs.