Spherical Metal Oxides with High Tap Density as Sulfur Host to Enhance Cathode Volumetric Capacity for Lithium–Sulfur Battery

Effective hosts of sulfur are essential for the application of lithium-sulfur batteries. However, various refined nanomaterials or carbon-based hosts possess low density, high surface area, and large porosity, leading to undesirable reduction on both gravimetric and volumetric energy densities. Herein, spherical metal oxides with high tap density are introduced as carbon-free hosts of sulfur for the first time. The ternary oxides show a superior synergistic effect of adsorption and electrocatalytic conversion of soluble intermediate polysulfides. Besides, oxide microspheres can build stable conductive frameworks and open channels in porous electrodes for fast transport of electrons and active diffusion of electrolyte. Such a synergistic effect and unique structural feature of porous electrodes are favorable for achieving good utilization and stable cycle performance of the sulfur cathode. Typically, the S/LiNi_0.8Co_0.1Mn_0.1O₂ composite exhibits good cycle stability with a low capacity decay rate (0.057% per cycle) during 500 cycles at 0.1 C. Importantly, due to the high tap density (1.81 g cm^-3), the S/LiNi_0.8Co_0.1Mn_0.1O₂ composite delivers a larger volumetric capacity (1601.9 mAh cm^-3_-composite), almost 2.3 times of S/carbon composite (689.4 mAh cm^-3_-composite). Therefore, this work provides a feasible strategy to reach long life and high volumetric capacity of cathode based on metal oxides as sulfur hosts.