Bilayered Nanostructured V₂O₅·<i>n</i>H₂O for Metal Batteries

Bilayered V 2 O 5 · n H 2 O prepared by sol–gel synthesis is generally assumed amorphous due to lack of long‐range structural order. However, at the nanoscale, a well‐organized repetition of bilayers is found and thus V 2 O 5 · n H 2 O can be considered a nanostructured material. Synthesis route affects the morphological and structural characteristics of V 2 O 5 · n H 2 O and, depending on the drying method used, xerogel and aerogel are obtained. The reduced structural order, the large interlayer space and the short diffusion length that this class of material offer are the key factors that allow V 2 O 5 · n H 2 O to reversibly host cations that are different in charge and dimensions. These properties make bilayered V 2 O 5 · n H 2 O materials almost unique for the wide range of applicability in metal batteries. Herein, a panoramic of the most common V 2 O 5 · n H 2 O synthesis methods and the peculiar characteristics of this material is given. A survey of the most important findings on the use of bilayered V 2 O 5 · n H 2 O for metal batteries is reported focusing on Li‐, Na‐ and Mg‐batteries. The increased number of publications recently divulgated confirms the renewed interest on V 2 O 5 · n H 2 O for energy storage and thus an updated rationalization of the findings can be helpful to guide further technological development and research activity in the field.