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