One-pot synthesis of porous nickel–manganese sulfides with tuneable compositions for high-performance energy storage

Mixed-metal compounds, especially for the sulfides, have been investigated as a very attractive type of electroactive materials for supercapacitors. In this work, we demonstrate nickel‒manganese (Ni‒Mn) sulfides are very attractive for supercapacitors with promising electrochemical performance. The Ni‒Mn sulfides with different Ni to Mn ratios have been synthesized via a facile one-pot hydrothermal method, which show a similar structure of interconnected particles and are very porous in microstructure. And then, the Ni‒Mn sulfides are investigated by three-electrode measurements and demonstrate strong synergy between Ni and Mn. The Ni‒Mn sulfide with a Ni to Mn ratio of 2:1 demonstrates superior performance of 1068 F g^‒1 at 1 A g^‒1. Lastly, The Ni‒Mn sulfide with a Ni to Mn ratio of 2:1 are used as positive electrode for two-electrode test, and the asymmetric supercapacitor shows both high energy and power densities combined with excellent cycling stability. Our work demonstrates that the Ni‒Mn sulfides are also very electrochemical active for supercapacitors and their performance can be tuned by changing the Ni to Mn ratio.