Nanosized Co Encapsulated in Porous Carbon for Ultra‐Stable Sodium‐Ion Batteries

Cobalt‐based compounds have been extensively studied due to their relatively high theoretical capacity as anode materials for sodium‐ion batteries (SIBs). However, the requirement for strong conductivity and excellent cycling stability is still an urgent challenge for the energy‐storage system. To address these problems, metal–organic‐framework‐74‐derived porous rod‐shaped nanostructure Co/C materials are designed as advanced anode materials for SIBs, which is beneficial for the reaction kinetics of SIBs. Moreover, the efficient synergistic utility of the nanostructure and the rich mesopores of Co/C materials provides the ion‐diffusion paths and active sites for the transfer and storage of Na + , which contributes to the energy‐storage ability. The indurative structure of the carbonization electrode material can alleviate the influence of volume change due to Na + insertion/extraction. Therefore, the Co/C anode exhibits a high Coulombic efficiency of 94.3% at 0.1 A g −1 . After 300 cycles, the Na + ‐storage capacity is 200.4 mAh g −1 , and the Coulombic efficiency is 99.0%, where the capacity retention rate is up to 88.2%. Herein, insight is provided into the role of porous Co/C material in improving the kinetics of Na + reaction, supplying an effective strategy for the rational design of key materials for high‐performance rechargeable batteries.