Simultaneous Catalytic Construction of Closed‐Pore‐Rich Hard Carbon Anode and Generation of Na _0.67 Ni _0.2 Fe _0.2 Mn _0.6 O ₂ Cathode for Sodium‐Ion Batteries

Sodium‐ion battery (SIB) has been regarded as a promising electrochemical device for stationary energy storage, whereas its widespread application is still hindered by relatively lower energy density and unredeemed cost‐effectiveness. High‐capacity anode materials are one of the bottlenecks limiting the improvement of energy density of SIBs, while tuning the closed porous structure is the most efficient approach to boost the plateau capacity. Unfortunately, simple and practical closed‐pore‐forming strategies remain scarce. Herein, a transition metal oxide catalytic strategy to prepare closed‐pore‐rich hard carbon anode for the first time while simultaneously transforming the catalyst into layered oxide cathode is reported. The abundant closed‐pore structure provides an augmented array of sites for sodium ion storage, thereby contributing to a heightened plateau capacity and Coulombic efficiency. Hence, the obtained anode delivers a reversible capacity of 301.6 mAh g −1 with a high initial coulombic efficiency of 92.3%. Note that a capacity retention of 98.4% is achieved after 300 cycles. In particular, a full cell constructed by the above closed‐pore‐rich hard carbon anode and layered oxide cathode demonstrates favorable energy density and cycling stability. This work is believed to provide a green and sustainable route for achieving high‐performance SIB electrode materials.