Yolk‐Shell Construction of Na3V2(PO4)2F3 with Copper Substitution Microsphere as High‐Rate and Long‐Cycling Cathode Materials for Sodium‐Ion Batteries

diffusion process in the bulk phase. The robust electrochemical performance suggests that developing the unique yolk-shell structure with the collaboration of interface and bulk crystal properties is a favorable strategy to design cathode material with a high performance for sodium-ion batteries.