Nitrogen and Phosphorus Co-Doped Hard Carbon Materials as High-Performance Anode for Sodium Ion Batteries

Abstract The negative electrode of sodium ion batteries (SIBs) has always faced severe challenges in the commercialization process. At present, the commercial negative electrode capacity of sodium ion batteries is only 300–350 mA h g−1, with 1000 cycles capacity retention rate of less than 80%, making it difficult to apply to high profit downstream industries such as new energy vehicles and 3C digital that require strict energy density and lifespan. To improve capacity, increase the first Coulomb efficiency, and enhance performance under high current density, we have prepared a nitrogen phosphorus codoped hard carbon material. Phosphorus groups are doped in the material to achieve sodium storage, at the same time, coating phenolic resin for material modification. At the same time, nitrogen and carbon nanotube (CNT) structures are added during the preparation process to make it have good conductivity. CMC binder and ether-based electrolyte are used to solve the problem of low first Coulomb efficiency by reducing excessive reaction between the negative electrode and the electrolyte. In actual testing, this material has a capacity of 365 mA h g−1 and a capacity retention rate of 112% under long cycles.