Microwave solvothermal synthesis of high entropy oxide on carbon nanotubes towards high-performance lithium-ion battery anode

Abstract

Transition metal oxide (TMO) anodes with multielectron transfer mechanism exhibit high theoretical capacity for lithium-ion batteries. However, the huge volume changes of TMOs during the lithiation/delithiation process limit their commercialization. High entropy oxides (HEOs) with unique component and structure adjustability demonstrate attractive lithium storage potential. While the inherently poor electrical conductivity of oxides remains a problem. Herein, the amorphous HEOs grown in situ on the surface of carbon nanotubes (CNTs) through simple and rapid microwave solvothermal method followed by heat treatment. The composite shows high capacity and excellent cycle and rate performance. The HEO@CNT-60 with an optimal amount of CNTs added maintains a specific capacity of 560.1 mAh g⁻¹ after 500 cycles at a current density of 1 A g⁻¹ with the capacity retention rate of 86.4 %. The improved charge transfer kinetics and Li⁺ diffusion rate together with the pseudocapacitance contributions are the main reason for the excellent electrochemical performance, which is related with the uniformly dispersed nanoscale active materials, the entropy stabilization mechanism, the synergistic effect of multiple transition metal elements and abundant oxygen vacancies, the good electrical conductivity of CNTs, and the tight heterogeneous interfaces between HEOs and CNTs. This report suggests a strategy to further exploit the lithium storage potential of high entropy oxides.