VO₂ Nanowires Assembled into Hollow Microspheres for High-Rate and Long-Life Lithium Batteries

Abstract

Development of three-dimensional nanostructures with high surface area and excellent structural stability is an important approach for realizing high-rate and long-life battery electrodes. Here, we report VO₂ hollow microspheres showing empty spherical core with radially protruding nanowires, synthesized through a facile and controllable ion-modulating approach. In addition, by controlling the self-assembly of negatively charged C₁₂H₂₅SO₄^– spherical micelles and positively charged VO²⁺ ions, six-armed microspindles and random nanowires are also prepared. Compared with them, VO₂ hollow microspheres show better electrochemical performance. At high current density of 2 A/g, VO₂ hollow microspheres exhibit 3 times higher capacity than that of random nanowires, and 80% of the original capacity is retained after 1000 cycles. The superior performance of VO₂ hollow microspheres is because they exhibit high surface area about twice higher than that of random nanowires and also provide an efficient self-expansion and self-shrinkage buffering during lithiation/delithiation, which effectively inhibits the self-aggregation of nanowires. This research indicates that VO₂ hollow microspheres have great potential for high-rate and long-life lithium batteries