Highly Stable Free‐standing Cobalt Niobate with Orthorhombic Structure as Anode Material for Li‐ion Batteries

Abstract

The current and future energy demands require high‐performance batteries with stable long‐term cycling, high capacities, and fast‐charging capabilities. In recent years, niobate compounds have gained significant research interests due to their attractive properties suited for battery applications. In this work, cobalt niobate, CoNb2O6, was synthesized via a simple and scalable solid‐state mechanochemical method through high‐energy ball milling, mechanical treatment (pellet formation), and calcination at 900 °C. The resulting product is a pure, columbite‐type (orthorhombic) cobalt niobate based on XRD findings. Electrochemical testing in a half‐cell against Li/Li+ of the as‐prepared free‐standing cobalt niobate anode material revealed a highly reversible process of lithiation (discharge) and delithiation (charge), with increasing pseudocapacitive behavior at higher scan rates. At 0.1 A g−1, the observed initial discharge capacity was about 900 mAh g−1. The synthesized CoNb anode material displayed an impressive rate performance, which involved increased stability at elevated current densities. During prolonged cycling tests, the anode material displayed extremely stable cycling vs Li/Li+, even at 2 A g−1, delivering a specific capacity of 700 mAh g−1 in the initial cycle, followed by a relatively constant capacity of 150 mAh g−1 throughout the majority of 5000 cycles completed. Post‐mortem analysis illustrated the reversibility of the cobalt niobate anode material and confirmed the growth and partial breakdown of the SEI film. With the results obtained from this work, cobalt niobate is full of potential as an anode material for Li‐ion battery applications.