Nickel Chelate Derived NiS₂ Decorated with Bifunctional Carbon: An Efficient Strategy to Promote Sodium Storage Performance

The sodium storage performance of NiS 2 suffer from low initial coulombic efficiency and poor cycling stability which are ascribed to the volume expansion and collapse of the structure during the charge/discharge transformation process. Compared with composites, encapsulating NiS 2 in carbon framework is more effective in buffering for the volume expansion and enhancing the electronic conductivity of sodium‐ion batteries. In this work, NiS 2 decorated with bifunctional carbon (NiS 2 @C@C), where nickel dimethylglyoxime and polyaniline are employed as the precursor and carbon source, respectively, are obtained. Since the introduced carbon layer suppresses the volume expansion and enhances both the electronic conductivity and charge transfer of Na + , the attained NiS 2 @C@C displays outstanding sodium storage performance. At a current density of 0.1 A g −1 , a high reversible specific capacity of 580.8 mAh g −1 remains even after 100 cycles. The first coulombic efficiency (79.65%) and rate performance (448 mAh g −1 at 1.6 A g −1 ) of NiS 2 @C@C are also remarkable. Extraordinarily, the excogitation of NiS 2 decorated with bifunctional carbon is also significant for the preparation of similar materials.