Enhancing performance of NiCo Sulfide composite cathode by Mn doping in Li-S batteries

Abstract

A sulfurophilic Ni-Co bimetallic sulfide (NiCo2S4) with Mn doping is synthesized as the electrocatalyst for the cathode of lithium-sulfur batteries. The characterization showed that the incorporation of Mn into the NiCo2S4 effectively altered the size and crystallinity of the particles. The NiCoMn-S/CNT composite were further produced as the sulfur host by combining the Mn-doped NiCo2S4 with space-rich CNTs. This structure physically restricts polysulfides and improves the redox reaction kinetics of polysulfide conversion. Therefore, the NiCoMn-S/CNT@S (4:6) as optimal ratio enables stable cycling with an initial capacity of ∼1149 mAh g−1 at 0.2 C and a lower capacity fade rate (∼0.08% per cycle upon 500 cycles) at 0.5 C. Additionally, the cathode with a sulfur loading of 2.1 mg cm−2 delivers a reversible areal capacity (597.2mAh g−1) over 200 cycles. The results indicate that doping metallic ions into the NiCo2S4 lattice is an effective strategy for enhancing the electrochemical performance of the material in lithium-sulfur batteries.