Insight into the Effect of Cu²⁺ Doping on Cu_<i>x</i>Nb_2–<i>x</i>O_{5–3/2<i>x</i>} for High-Power Lithium-Ion Batteries

Abstract

Though Nb2O5 has great potential as a high-power anode, it still performs poorly because of its structural issue and insufficient electronic/ionic conductivity. Hence, an effective strategy that combines ion doping and structure regulation boosting the electrochemical properties of CuxNb2–xO5–3/2x (x = 0, 0.1, 0.2, and 0.3) toward high-power Li-ion batteries is demonstrated. A more open-tunnel-like crystalline skeleton comes from the Wadsley–Roth shear structure with enhanced structural stability, and larger lattice parameters are realized by Cu2+ doping, which infers rapid Li+ transport. The structure regulation of CuxNb2–xO5–3/2x was carried out by the accurate control of the Cu2+ doping amount to search for the best crystal fault tolerance. The electronic properties of Nb2O5 with different Cu contents are revealed by DFT calculations. Meanwhile, benefiting from the reinforced intrinsic electronic/ionic conductivity, Cu0.2Nb1.8O4.7 presents the prime electrochemical property. At 20 C, the specific capacity can reach 201.22 mA h·g–1 and maintain a capacity retention of 109.4% after 3000 cycles. The apparent Li+ diffusion coefficient of Cu0.2Nb1.8O4.7 can achieve 1.11 × 10–12 cm2·s–1, which is 2 orders of magnitude higher than that of Nb2O5. These results provide tremendous support for the widespread application of CuxNb2–xO5–3/2x.