Synthesis of Cobalt Sulfide Multi‐shelled Nanoboxes with Precisely Controlled 2‐5 Shells for Sodium‐Ion Batteries

We report the synthesis of cobalt sulfide multi‐shelled nanoboxes through metal‐organic framework (MOF)‐engaged complex anion conversion and exchange processes. The polyvanadate ions transformed from metavanabate ions in alkaline media first react with cobalt‐based zeolitic imidazolate framework‐67 (ZIF‐67) nanocubes to form ZIF‐67/cobalt polyvanadate yolk‐shelled particles. Afterwards, the as‐formed ZIF‐67/cobalt polyvanadate yolk‐shelled particles are gradually converted to cobalt divanadate multi‐shelled nanoboxes by a solvothermal treatment under neutral condition. The number of shells in the range of 2 – 5 can be easily controlled by varying the temperature. Finally, the cobalt sulfide multi‐shelled nanoboxes are produced through the ion‐exchange reaction with S2‐ ions and a subsequent annealing treatment. The as‐obtained cobalt sulfide multi‐shelled nanoboxes exhibit enhanced sodium storage properties when evaluated as anodes for sodium‐ion batteries. For example, a high specific capacity of 438 mAh g‐1 can be retained after 100 cycles at the current density of 500 mA g‐1 for the triple‐shelled nanoboxes.

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