Mixed-phase enabled high-rate copper niobate anodes for lithium-ion batteries

The advancement of rapid-response grid energy storage systems and the widespread adoption of electric vehicles are significantly hindered by the charging times and energy densities associated with current lithium-ion battery technology. In state-of-the-art lithium-ion batteries, graphite is employed as the standard negative electrode material. However, graphite suffers from polarization and deteriorating side-reactions at the high currents needed for fast charging. Transition metal-oxide anodes are attractive alternatives due to their enhanced power density. However, often these anodes make use of toxic or scarce elements, significantly limiting their future potential. In this work, we propose a new, facile solid-state synthesis method to obtain non-toxic, abundant, mixed-phase copper niobate (Cu_xNb_yO_z) anodes for lithium-ion batteries. The material consists of various phases working synergistically to deliver high electrochemical capacities at exceptional cycling rates (167 mA h g⁻¹ at 1C, 95 mA h g⁻¹ at 10C, 65 mA h g⁻¹ at 60C and 37 mA h g⁻¹ at 250C), large pseudocapacitive response (up to 90%), and high Li⁺ diffusion coefficient (1.8 × 10⁻¹² cm² s⁻¹), at a stable capacity retention (99.98%) between cycles. Compared to graphite, at a comparable energy density (470 W h L⁻¹), the composite material exhibits a 70 times higher power density (27 000 W L⁻¹). These results provide a new perspective on the role of non-toxic and abundant elements for realizing ultrafast anode materials for future energy storage devices.