Hierarchically structured Ti3C2Tx MXene paper for Li-S batteries with high volumetric capacity

Due to the low density of sulfur and the large portion of carbon-based materials used as conducting network and lithium polysulfide (LiPS) host, the practical volumetric energy density of lithium-sulfur (Li-S) batteries barely rivals the Li-ion batteries. Here, MXene (Ti3C2Tx)-based membrane with unique 3D hierarchical structure, high electronic conductivity, abundent active binding sites, fast ion transport, and high affinity for lithium polysulfides has been developed as a new host material to improve the electrochemical performance of Li-S batteries. With a density of 2.2 g cm(-3), a MXene-based cathode containing 4.0 mg cm(-2) sulfur delivers a high volumetric capacity of 2.7 Ah cm(-3) after 200 cycles. Based on operando XRD and ex-situ XPS results, we find that the Ti-OH bonds present on the surface of MXene membrane can effectively trigger the LiPS transformation. Furthermore, alpha-S-8, as the stable charge product, is first reported in MXene-based host along with its possible important role in curtailing active mass loss and enhancing cycling capability. Our results reveal that 2D MXene with rationally-designed architecture enable high volumetric capacity Li-S batteries for practical applications.