Silicene oxide: a potential Battery500 cathode for sealed non-aqueous lithium–oxygen batteries

The lithium-oxygen battery with high energy density holds a promising roadmap for future Eco society. However, its practical implementation is burdened by the sluggish cathodic kinetics and the severely polarized overpotential as well as the open-cell architecture. In this work, an emerging silicene oxide (SiO) material is predicted and evaluated as a potential cathode for sealed lithium-oxygen battery by first-principles/molecular dynamics simulations. Lithium is revealed to be chemisorbed on the surface of SiO with large binding energies, and afterward a semiconductor-to-metal transition (SMT) occurs in the system. Such an SMT switch can facilitate the charge transport and Li diffusion on the SiO surface (~0.29 eV barrier), achieving a specific capacity of 609.11 mA h g⁻¹ and an energy density of 359.37 W h kg⁻¹. Moreover, a van der Waals heterostructure consisting of silicene oxide and graphene (Si₂O₂/G) is established for further improving battery performance. Such a heterostructure exhibits larger Li binding energy and higher open-circuit voltage due to the synergistic effect. Assisted by the solvent effect, the Si₂O₂ and Si₂O₂/G cathodes respectively present the energy densities as high as 804.03 W h kg⁻¹ and 564.89 W h kg⁻¹, providing great potentials for the demand of Battery500 consortium. This work proves the potential of Si₂O₂ as a cathode for sealed lithium-oxygen batteries and opens up interesting possibilities in the rational design of new cathode structures based on two-dimensional (2D) lightweight materials.