“Zero-strain” K2SrV4O12 as a high-temperature friendly Li+-storage material

Abstract

Heat generated during the use of lithium-ion batteries usually causes the aging of Li+-storage materials, significantly limiting their applications in large-scale electronic equipment and hot situations. Here, we develop K2SrV4O12 with a rich V-valence variation as a high-temperature friendly anode material and demonstrate for the first time that the “zero-strain” behavior greatly benefits high-temperature cyclability. In its special crystal structure, electrochemical active VO4 tetrahedron layers are fully surrounded by inactive layers consisting of KO6 octahedra and SrO8 square antiprism decahedra. The opposite volume changes of KO6 and SrO8 polyhedra effectively accommodate the volume expansions originating from Li+ storage and V-ion-size increase during lithiation. This superior volume-buffering capability enables its “zero-strain” behavior with negligible unit-cell-volume changes at not only 25 °C (maximum 0.066%) but also 60 °C (maximum 0.42%). Consequently, K2SrV4O12 nanowires exhibit superior cyclability (135.4% capacity retention over 1000 cycles at 4 A g−1) at 60 °C. Additionally, this material at 60 °C shows a larger reversible capacity and higher rate performance than those at 25 °C due to its better high-temperature electrochemical activity, and a proper average working potential. Therefore, K2SrV4O12 nanowires can be a promising anode material suitable for high-temperature operation.