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

The sodium storage performance of NiS2 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 NiS2 in carbon framework is more effective in buffering for the volume expansion and enhancing the electronic conductivity of sodium‐ion batteries. In this work, NiS2 decorated with bifunctional carbon (NiS2@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 NiS2@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 NiS2@C@C are also remarkable. Extraordinarily, the excogitation of NiS2 decorated with bifunctional carbon is also significant for the preparation of similar materials. Through the sulfuration of nickel dimethylglyoxime wrapped with polyaniline, bifunctional carbon decorated NiS2 (NiS2@C@C) is prepared. Benefitting from the ingenious design, the sodium storage performance of NiS2@C@C electrodes is greatly superior to undecorated NiS2 electrodes. This work might supply an effective excogitation for the practical application of transitional metal sulfides in sodium‐ion batteries.