Molten salt synthesis of carbon anode for high-performance sodium-ion batteries

•Carbon materials were prepared in an easy, efficient and low-temperature way.•Molten salt promoted the reaction effectively in dynamics.•Carbon materials presented the characteristics of highly porous and disordered.•Carbon materials exhibited excellent performance superior to many carbon anodes.•CO2 can be utilized as a raw material to synthesize carbon materials. Preparation of high-performance anode materials in a convenient, efficient and environment friendly way is a challenge for the commercialization of sodium-ion batteries (SIBs). Herein, a carbon material was fabricated via a facile reaction between CaC2 and CaCO3 in CaCl2NaCl molten salt. The microstructure of the carbon materials was systemically characterized and the electrochemical performance was investigated. By optimizing temperature and duration, the carbon product has porous and disordered structures. These characteristics facilitate the reversible capacity of Na storage. The optimized carbon anode exhibits excellent rate capabilities (179 and 129 mAh·g−1 at 5 and 20 A·g−1, respectively) and high reversible capacities (295 mAh·g−1 at a low current density of 0.1 A·g−1). The carbon anode also presents attractive stability with 0.0275% capacity decay per cycle at 5 A·g−1 over 1000 cycles. Furthermore, the utilization of this route to transform CO2 to high-performance carbon anode was evaluated.