The exploration of a CuNb₃O₈ Li⁺-storage anode compound

ABSTRACT

Niobates are regarded as prospective Li⁺-storage anode candidates due to the rich chemistry of niobium and crystal-structural openness. However, the exploration of niobates is still insufficient. In this study, we explore CuNb₃O₈ with a large theoretical capacity is 341.9 mAh g^–1 as a high-performance anode compound. The reversible redox reaction among Nb⁵⁺, Nb⁴⁺ and Nb³⁺ during lithiation/delithiation is confirmed by ex-situ XPS, and a large reversible capacity of 231.8 mAh g^–1 and safe lithiation potential of 1.53 V are achieved at 0.1 C. An intercalation-type Li⁺-storage mechanism is confirmed by in-situ XRD after the first lithiation process, guaranteeing the good cyclability from the second discharge–charge cycles. The Li⁺ diffusivity in CuNb₃O₈ is systematically and carefully studied. The galvanostatic intermittent titration technique tests show large Li⁺ diffusion coefficients of 1.2 × 10^–12/1.5 × 10^–12 cm² s^–1 during lithiation/delithiation, and the corresponding values obtained through the cyclic voltammetry technique are similar (2.2 × 10^–12/3.0 × 10^–12 cm² s^–1). Additionally, CuNb₃O₈ is successfully coupled with LiFePO₄, and the resultant CuNb₃O₈//LiFePO₄ full cell also exhibits good electrochemical properties, demonstrating the practicability of CuNb₃O₈ for large-scale energy-storage applications.

KEYWORDS:

• CuNb₃O₈
• anode
• Li⁺ diffusivity
• In-situ XRD
• electrochemical property

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by National Natural Science Foundation of China [51762014].