Enhancing Co/Co2VO4 Li-ion battery anode performances via 2D–2D heterostructure engineering

Abstract

High-capacity Co₂VO₄ has become a potential anode material for lithium-ion batteries (LIBs), benefiting from its lower output voltage during cycling than other cobalt vanadates. However, the application of this new conversion-type electrode is still hampered by its inherent large volume variation and poor kinetics. Here, a 2D–2D heterostructure building strategy has been developed to enhance the electrode performance of Co₂VO₄ through construction of Co/Co₂VO₄ nanocomposites converted from the in situ phase separation of Co₂V₂O₇·3.3H₂O nanosheets. Co/Co₂VO₄ based on face-to-face contact exhibits the optimized stacking configuration, where Co nanocrystals give gaps of several nanometers between stacked Co₂VO₄ nanosheets, enabling full contact with the electrolyte, a shorter transport path of lithium ions and more reactive sites. With this design, Co/Co₂VO₄ anodes deliver outstanding reversible capacity (750 mA h g⁻¹ at 1 A g⁻¹) with ultrahigh capacity retention rate, and excellent cycle stability at high rate (520 mA h g⁻¹ at 5 A g⁻¹ retained after 400 cycles). An “active center's charge transfer—capacity compensation” model was proposed based on capacity analysis, XPS depth analysis and HRTEM observation to uncover the fundamental reason of the excellent cycle performance. This in situ 2D–2D heterostructure constructing strategy may open up the possibility for designing high-performance LIBs.