Double-Net Enclosed Sulfur Composite as a New Cathode in Lithium Sulfur Batteries

Abstract

Tremendous attempts have been tried on confinements of lithium polysulfides to kinetically slow down the “shuttling effect” in lithium sulfur batteries. Nonetheless, to avoid the thermodynamic loss of sulfides, a stronger physical/chemical bonding displays a more effective way to mitigate the sulfur “flow away” process. In this article, we created a double-net matrix, which is composed of activated carbon (AC) embedded by a mesoporous silicon oxide cap. The oxide cap not only “traps” the sulfide molecules but also chemically bonds the molecules to delay the dissolution, resulting in high-capacity retention and improved rate performance. The capacity as high as 980 mAh/g at 0.2 C of the battery using the double-net enclosed sulfur composite as cathode was retained after 300 cycles. A high-capacity retention of 780 mAh/g after 1000 cycles with a Coulombic efficiency of >99.5% was also achieved. In parallel, a wide range of sulfur ratios up to ∼73% in the composite led to a high loading of active material, thus enabling a high energy density. The battery showed high-capacity retention after 300 cycles with the sulfur loadings of 4 and 5 mg/cm2, respectively. The improved capability of cycling, rate, and Coulombic efficiency of Li–S battery using industry available both AC and sulfur pave the pathway in mass production as a high-energy-storage system.