关键词: 高熵氧化物, 钙钛矿结构, 固相反应法, 锂离子电池负极材料, 电化学性能

Abstract: Perovskite-type (ABO3) oxides have attracted great attention as one of the most promising energy storage materials owing to the advantage of good electric conductivity and electrochemical activity. However, severe volume change for conventional metal oxides during the electrochemical reaction processes is likely to result in severe polarization of the electrodes and inferior kinetic properties as well as fast capacity fading. Transition-metal-based high-entropy oxides (HEOs) are an emerging kind of single-phase solid solution materials, which exhibit improved lithium storage properties and excellent cycling stability due to the multi-principal synergistic effect and entropy stabilization. In this work, transition metal-based perovskite-type La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 HEO lithium-ion batteries (LIBs) anode material are prepared by solid-state reaction method and compared with the conventional binary perovskite-type LaCoO3. The crystal structure, microstructure, and elemental composition of HEOs are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) in detail. The electrochemical properties of LIBs anode are elucidated. XRD results show that the impurity phase in the perovskite structure disappears gradually and the crystallinity increases with the increase of reaction temperature from 750℃ to 950℃ and sintering time from 30 min to 4 h. SEM/EDS results confirm the as-synthesized spherical powder has a homogeneous distribution throughout the entire particle at the micrometer level. The electrochemical performance study illustrates that the La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 anode material delivers higher specific capacity, excellent cycle stability, and rate performance than LaCoO3 mainly due to the entropy-stabilized crystal structure and the multi-principal synergistic effect. The reversible specific capacity of La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 is 331 mAh/g after 100 cycles at 200 mA/g currrent density, which is fairly approximate to the theoretical capacity of 332 mAh/g, while the reversible specific capacity of LaCoO3 is only 185 mAh/g. Moreover, the capacity retention rates of La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 and LaCoO3 are 72.5% and 61.6% at 1000 mA/g. This strategy on high entropy chemistry not only opens new insights into the development of advanced electrode materials but also provides a new design concept and strategy for the low content cobalt or free cobalt direction of electrode materials.

Key words: high-entropy oxide, Perovskite structure, solid-state reaction, anode material of lithium ion battery, electrochemical performance