Heteroepitaxy-Induced Rutile VO2 with Abundantly Exposed (002) Facets for High Lithium Electroactivity

Research on VO2 cathodes for lithium ion batteries has been mainly focused on the VO2 (B) phase. However, rutile VO2 (M/R) has rarely been studied because of the intrinsically low lithium activity resulting from the highly anisotropic nature of lithium accommodation. Here, we demonstrate that heteroepitaxial engineering can be an effective strategy for activating the anisotropic electrode and developing kinetically superior electrodes. Appropriate lattice mismatch between the active material (VO2) and conductive support (Sb:SnO2) yields a coherent interface, where tensile strain aids preferential growth along the rutile c-axis as well as expansion in the ab plane and thereby the exposure of reactive (002) facets. The VO2-Sb:SnO2 electrode exhibits high reversible capacity (350 mA h g(-1) at 100 mA g(-1)) and ultrafast rate capability (196 mA h g(-1) at 2000 mA g(-1)) with structural stability, which represents record-high performance compared with previous VO2 reports, including those on other polymorphs such as VO2 (A) and VO2 (B).