Ultra-high-rate lithium-sulfur batteries with high sulfur loading enabled by Mn2O3-carbonized bacterial cellulose composite as a cathode host

Abstract

Lithium-sulfur batteries have received significant attention due to their high specific capacity and natural abundance of the sulfur cathode. However, the notorious issue of higher-order lithium-polysulfides dissolution causes inferior cycling and poor electrochemical performance. To overcome the challenge, here, biodegradable and environmentally friendly carbonized bacterial cellulose (CBC) is used as the sulfur host. Further, Mn2O3 is incorporated in bacterial cellulose using hydrothermal synthesis and investigated as a sulfur host. The composite is prepared by a facile encapsulation “melt-diffusion” strategy. The high electronic conductivity of the CBC provides an efficient pathway to carry out redox reactions, and Mn2O3 helps to restrain and convert higher-order lithium-polysulfides to lower-order lithium-polysulfides. Further, the first-principle density functional theory calculation is performed to investigate and understand the role of carbon (CBC) and Mn2O3 in the host material. The lithium-sulfur cell with Mn2O3@CBC cathode host delivers a significantly high initial reversible capacity of 1150 mAh g−1(cathode) (i.e., 1450 mAh g−1(sulfur)) at 0.1 C. It retains a reversible capacity of 254 mAh g−1(cathode) (i.e., 554 mAh g−1(sulfur)) even at the ultra-high rate of 15.0 C. Furthermore, to achieve a practical high energy density and its commercial adoption, we tested lithium-sulfur cells with high areal sulfur loading of 4.2 mg cm−2. The cell shows promising electrochemical performance for long 500 cycles with a capacity retention of 70%. The cell performance is competitive and superior to the current state-of-the-art lithium-sulfur cells reported in the literature.