Expanded Graphite Inserted by Few Red Phosphorus for Improved Sodium Storage at Room Temperature and Low Temperatures

Abstract Sodium‐ion batteries are experiencing a rapid development as one of the most promising candidates to replace lithium‐ion batteries. Carbonaceous materials attract widespread attention because of the successful commercialization. Among them, expanded graphite with a long‐range‐ordered layered structure and a high specific surface area gain further exploration and modification as potential materials. Expanded graphite inserted by few red phosphorus was prepared by oxidation/reduction process and vapor deposition process and exhibited a high reversible specific capacity of 418 mAh g⁻¹ at a current density of 100 mA g⁻¹ and 296 mAh g⁻¹ with the retention of 83.3% after 1000 cycles at the current density of 500 mA g⁻¹ at room temperature. At −10 °C, a reversible capacity of 228 mAh g⁻¹ with a retention of nearly 100% after 100 cycles was obtained. At a low temperature of −50 °C, a specific capacity of more than 50 mAh g⁻¹ remains, indicating actual availability under extreme cold conditions.