Insight into the Effect of Cu<sup>2+</sup> Doping on Cu<sub><i>x</i></sub>Nb<sub>2–<i>x</i></sub>O<sub>5–3/2<i>x</i></sub> for High-Power Lithium-Ion Batteries
Mingru Su, Meiqing Li, Xi Long, Yingying Lei, Xueli Chen, Aichun Dou, Panpan Zhang, Yu Zhou, Yunjian Liu
Abstract
Though Nb 2 O 5 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 Cu x Nb 2– x O 5–3/2 x ( 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 Cu 2+ doping, which infers rapid Li + transport. The structure regulation of Cu x Nb 2– x O 5–3/2 x was carried out by the accurate control of the Cu 2+ doping amount to search for the best crystal fault tolerance. The electronic properties of Nb 2 O 5 with different Cu contents are revealed by DFT calculations. Meanwhile, benefiting from the reinforced intrinsic electronic/ionic conductivity, Cu 0.2 Nb 1.8 O 4.7 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 Cu 0.2 Nb 1.8 O 4.7 can achieve 1.11 × 10 –12 cm 2 ·s –1, which is 2 orders of magnitude higher than that of Nb 2 O 5 . These results provide tremendous support for the widespread application of Cu x Nb 2– x O 5–3/2 x .