Solvent-free synthesis of morphology-controllable nickel sulfides in one-pot plasma reactions for high-performance lithium-ion batteries

Nickel sulfides (NS) occupy a vital position in the fields of catalysis and energy storage by virtue of their outstanding functional properties. Currently, NS are usually synthesized in solid-state sulfidation and gas-sulfidation methods that require long preparation periods and high energy consumption and wet chemistry approaches involving toxic reagents or solvents and tedious processing steps. Here, taking advantage of microwave plasma triggered by corona discharge, NS with controllable morphology can be synthesized in an ordinary household microwave oven within minutes by a solvent-free one-pot plasma reaction. The plasma with inherent high energy can significantly accelerate reaction kinetics, thereby shortening the synthetic process and cutting the energy costs. When used as freestanding lithium-ion battery cathodes, the synthesized stone-forest-like NS deliver high rate capacity and superior cycling stability simultaneously. This green method can also realize morphology-controllable synthesis of copper sulfides, and it can be foreseen that this eco-friendly, high-efficiency and low-cost strategy can be extended to other metal sulfides and other metal compounds such as phosphides, carbides and selenides, opening new avenues for green synthesis and materials design.