NaCrO2/Coffee Waste–derived Nitrogen‐doped Carbon Composite as High‐Performance Cathode Material for Sodium Ion Batteries

Sodium‐ion batteries (NIBs) are promising alternatives to lithium‐ion batteries for large‐scale energy applications such as energy storage systems, owing to the earth‐abundance and low cost of sodium resources. Among layered oxide cathode materials for NIBs, O3‐type NaCrO2 has attracted considerable attention owing to its electrochemically active Cr3+/4+, which is unlike that of LiCrO2, and potential for carbon coating with a high thermal stability. In this study, we propose a new facile and eco‐friendly method for applying nitrogen‐doped carbon to NaCrO2 using coffee waste as a carbon source. The synthesized O3‐type NaCrO2/coffee waste–derived N‐doped carbon composite exhibits an outstanding electrochemical performance as an NIB cathode material. The sodium/composite cell achieved a 73.7% capacity retention after 500 charge/discharge cycles and an approximate 50% discharge capacity duri…