Co 2 B 2 O 5 as an anode material with high capacity for sodium ion batteries

In this work, a flake-structured Co2B2O5 material was obtained by a simple sol–gel method and researched for use in sodium ion batteries firstly. When serving as anode material for sodium ion batteries, it exhibits the high initial reversible capacity of 466 mAh·g−1 at a current density of 100 mA·g−1. Through the recombination of carbon nanotubes (CNTs), the composite Co2B2O5/CNTs delivers the initial reversible capacity of 464 mAh·g−1, and 324 mAh·g−1 is obtained after 60 cycles under the current density of 100 mA·g−1. When under the current density of 1000 mA·g−1, a capacity of 236 mAh·g−1 is obtained for Co2B2O5/CNTs while 160 mAh·g−1 for Co2B2O5. Moreover, the sodium storage behavior of Co2B2O5 is identified by kinetic analysis. The higher Na+ capacitive contribution of Co2B2O5/CNTs could account for the enhanced rate performance. The results indicate that Co2B2O5 is a promising anode material for sodium ion batteries.