Lithium vanadium oxides and vanadates have wide attention as cathode materials for Li ion battery applications, but there has been limited study on other cations substituted vanadium compounds, which could have favorable electrochemical properties. Here we report the synthesis and electrochemical properties of aggregated K0.25V2O5 nanobelts and the optimization of the crystalline structure for fast Li ion insertion. We propose a partial melting and self-alignment mechanism to produce the aggregated nanobelts. This material can deliver a high discharge capacity of 232mAh −1 at 100mAg−1 and high rate capability. It also exhibits superior long-term cycling performance with no capacity fading over 800 cycles at high current density of 1, 1.5, and 2Ag−1. Remarkably, although some work has been devoted to potassium vanadates, there is little work introducing this class of materials with super long lifespan. The results demonstrate that the as-prepared K0.25V2O5 would be a potential candidate for LIBs.