Nanocomposite of Nb-based binary phase for lowering the activation energy of Li⁺ intercalation as an anode for high-performance aqueous dual-ion batteries

Aqueous dual-ion batteries have good safety, environmental compatibility, and low cost due to the use of an aqueous electrolyte. However, water electrolysis occurs during charging at high potential, resulting in a poor cyclic stability of aqueous dual-ion batteries. Hence, novel anode materials are urgently needed to be developed for aqueous dual-ion batteries with low water electrolysis. A niobium-based binary-phase composite material is reported with a capacity of 135 mA h g⁻¹ at a current density of 0.2 mA cm⁻² and with excellent reversibility in the potential range of −1.3-0 V vs. Ag/AgCl. The activation energy of Li⁺ intercalation was obviously decreased because of the formation of an interface, which enhanced the Li⁺ intercalation reaction between FeNbO₄ and MoNb₁₂O₃₃. In addition, the lower amount of Fe²⁺ in the lattice of MoNb₁₂O₃₃ caused localized compressive strain, which promoted fast Li⁺ diffusion in MoNb₁₂O₃₃. A full dual-ion battery of 3.0 V was constructed using the binary-phase niobium-based composite for the anode, and demonstrated a high cycle stability and an average coulombic efficiency of 91% over 300 cycles. Furthermore, considering both the electrolyte and electrode materials, the theoretical energy density of this dual-ion battery was estimated to be 250 W h kg⁻¹, which is close to that of the current Li-ion rechargeable battery.