High‐Energy Sodium Ion Batteries Enabled by Switching Sodiophobic Graphite into Sodiophilic and High‐Capacity Anodes

Abstract Owing to the crustal abundance of sodium element, sodium ion batteries (SIBs) are considered a promising complementary to lithium‐ion battery for stationary energy storage applications. The cointercalation chemistry enables the use of cost‐effective graphite as anodes, whereas the low capacity (<130 mAh g −1 ) and high redox potential (>0.6 V vs. Na/Na + ) of graphite significantly limit the energy density of SIBs. Herein, we induce the high‐capacity Na metal into sodiophilic ternary graphite intercalation compounds ( t ‐GICs) via co‐intercalation and deposition reactions, thereby achieving Na/ t ‐GIC anodes with high capacities and low working voltage (0.18 V). The new anodes exhibit high coulombic efficiencies of above 99.7 % over 550 cycles and a high‐rate capacity of 588.4 mAh g −1 at 6 C (10 min per charge). When it is paired with Na 3 V 2 (PO 4 ) 2 F 3 (NVPF) cathodes, the SIBs demonstrate a high energy density of 259 Wh kg −1 both electrodes surpassing that of commercial LiFePO 4 //graphite batteries. The outstanding anode performance is attributed to the tailored sodiophilicity of graphite through manipulating the ether solvents and the in situ generated space among t ‐GIC flakes to stably accommodate Na metal. Our findings for stable Na plating/striping on sodiophilic graphite materials provide an effective approach for developing advanced SIBs.