High-entropy spinel-structured (VCrNiCoMn)3O4 anode for Li-ion batteries

In the quest for improved battery performance, high entropy transition metal oxides (HEO-TM) have emerged as potential candidates for lithium-ion battery (LIB) anodes due to their high capacity resulting from multi-electron transfer redox reactions. This study a synthesized spinel high-entropy oxide (VCrNiCoMn)₃O₄ using a surfactant-assisted hydrothermal method and subjected it to annealing at different temperatures. XRD analysis revealed that the stabilized spinel phase formed at 1223 K. The (VCrNiCoMn)₃O₄ demonstrated a significant discharge capacity of 1269 mAh g⁻¹, accompanied by a charge capacity of 1030 mAh g⁻¹. After 1000 cycles, it achieved a reversible capacity of 733 mAh g⁻¹. Furthermore, superior rate performance was observed, demonstrating a high reversible capacity of 394 mAh g⁻¹ at a scanning rate of 2 mV s⁻¹. The superior performance was attributed to multivalent species, including vanadium, which stabilizes charge transfer, facilitates redox reactions, enhances electrical properties, and improves structural stability. Vanadium's ability to transition through multiple oxidation states reduce volume expansion, improve structural rigidity, and contribute to cycling stability. Moreover, Kinetic analysis showed that the lithiation reaction was dominated by the Faraday mechanism, while delithiation involved both capacitive and Faraday contributions. These results suggest that incorporating vanadium into high-entropy oxides can optimize electrochemical properties for long-life lithium-ion batteries.