Regulation of Li2S Deposition and Dissolution to Achieve an Efficient Bidirectional Lithium–Sulfur Battery

Abstract

Promoting the sulfur reduction reaction (SRR) and sulfur evolution reaction (SER) kinetics is crucial for practical lithium–sulfur batteries. However, the electrode will be passivated by insulated Li₂S if blindly accelerated the SRR kinetics, meanwhile, the high activation energy of Li₂S will lead to premature the oxidation of Li₂S (SER), achieving limited catalyst. Here, a nano-nickel nitrogen-doped carbon gel material (CG/Ni) induces the instantaneous nucleation, further endows Li₂S fast ion/electron transfer, resulting porous 3D growth instead single lateral growth. Therefore, CG/Ni material avoids being passivated, accelerating the SRR kinetics. Meanwhile, CG/Ni decreases the delithiation barrier, thus, facilitating the Li₂S dissociation. Both experiments and theory calculation prove that CG/Ni achieves efficient bidirectional catalysis. Consequently, CG/Ni cathode delivers a low-capacity decay ratio of 0.047% per cycle for 900 cycles at 5 C. This work unlocks a bidirectional catalyst and provide new insight for high-efficiency lithium–sulfur batteries.