“One stone two birds” design for hollow spherical Na 4 Fe 3 ( PO 4 ) 2 P 2 O 7 /C cathode enabled high‐performance sodium‐ion batteries from iron rust

Abstract Sodium‐ion battery (SIB) is considered as a revolutionary technology toward large‐scale energy storage applications. Developing cost‐effective cathode material as well as economical synthesis procedure is a key challenge for its commercialization. Herein, we develop a facile and economic strategy to simultaneously remove rust from the surface of carbon steel and achieve porous and hollow spherical Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 /C (HS‐NFPP/C). Benefiting from the desirable structure that fastens the electronic/ionic transportation and effectively accommodates the volume expansion/contraction during discharge/charge process, the as‐prepared cathode exhibits outstanding rate capability and ultralong cycle life. An extraordinarily high‐power density of 32.3 kW kg −1 with an ultrahigh capacity retention of 89.7% after 10 000 cycles are achieved. More significantly, the 3 Ah HC||HS‐NFPP/C full battery manifests impressive cycling stability. Therefore, this work provides an economical and sustainable approach for the massive production of high‐performance Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 cathode, which can be potentially commercialized toward SIB applications. image