Two-dimensional materials and hierarchical nanostructured composites for sodium / lithium battery anodes

More and more sodium/lithium-ion battery anode materials are being developed with the aims of high energy density, high cycling stability, and excellent rate capability, in which two-dimensional (2D) and hierarchical nanostructured materials are showing promise due to their shortened paths for sodium ion transportation and their larger surface areas for sodium ion absorption. Moreover, 2D materials (e.g. graphene) have been proved to be excellent supporting and conducting agents in anodes due to their high electrical conductivity and structural stability. Synergetic effects between the graphene and the active materials are generally observed. This doctoral work is focused on the recent progress in the use of 2D active materials and of composites consisting of both 2D supports and active materials as anodes. Based on the manner of energy storage, their electrochemical performance for energy storage is discussed in terms of four subprojects, including (1) enhanced sodium-ion battery performance by a structural phase transition from 2D hexagonal-SnS2 to orthorhombic-SnS; (2) enhanced charge transfer in SnS/SnO2 heterostructures: towards high rate capability for sodium ion batteries; (3) a surface engineering and design strategy for surface‐amorphized hierarchical nanostructured TiO2@graphene hybrids for high power Li‐ion battery electrodes; and (4) highly ordered dual porosity mesoporous hierarchical nanostructured cobalt oxide for sodium‐ion batteries. The main challenges and perspectives on 2D energy storage materials are also discussed.