NiCo<sub>2</sub>O<sub>4</sub>/CNF Separator Modifiers for Trapping and Catalyzing Polysulfides for High-Performance Lithium–Sulfur Batteries with High Sulfur Loadings and Lean Electrolytes
Jin‐Xia Lin, Ximing Qu, Xiaohong Wu, Jun Peng, Shiyuan Zhou, Jun‐Tao Li, Yao Zhou, Yuxue Mo, Mei-Jiao Ding, Ling Huang, Shi‐Gang Sun
Abstract
The shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPSs) restrict the practical application of lithium–sulfur (Li–S) batteries. Herein, we introduce nickel cobaltite/carbon nanofiber (NiCo2O4/CNF) composites as a chemical trapper and conversion accelerator for LiPSs. The experiment and density functional theory indicate that polar NiCo2O4 can strongly trap polysulfides through Ni–S and Co–S bonds. The CNF network provides structural stability and serves as a second barrier for polysulfides. Systematic studies on the solid(sulfur)–liquid(polysulfides)–solid(sulfide) conversion reactions qualitatively and quantitatively demonstrate that the well-designed NiCo2O4/CNF interface with strong polysulfides affinity, affluent polar nucleation sites, and fast Li+/e– transport can noteworthily catalyze the liquid-phase conversion of LiPSs and the solid-phase deposition of lithium sulfide (Li2S) and protect the lithium anode as well. Thus, the NiCo2O4/CNF-based batteries can exhibit a high rate capability of 870 mAh g–1 at 5 C and excellent cycling performance evidenced by a capacity retention of 95% after 200 cycles at 0.1 C with a sulfur loading of 6.3 mg cm–2. Further increasing the sulfur loading to 7.9 mg cm–2 and with a lean electrolyte/sulfur (E/S) ratio of 7.2 μL mgs–1, the Li–S battery can deliver a high areal capacity of 8.1 mAh cm–2.