Preparation and High-rate Lithium-ion Storage of Hollow Sphere Perovskite High-entropy Oxides Assisted by Deep Eutectic Solvents
In recent years,high-entropy oxides(HEOs)have attracted much attention as high-performance anode materials for lithium-ion batteries(LIBs)due to their four effects.In this study,lattice distortions and oxygen vacancies are modulated through morphology and defect modulation strategies.Perovskite-type La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3,La(Li1/6Co1/6Cr1/6Fe1/6Mn1/6Ni1/6)O3,and La(Na1/6Co1/6Cr1/6Fe1/6Mn1/6Ni1/6)O3 HEO nanocrystalline powders are synthesized through solid state reaction method assisted by deep eutectic solvents using metal nitrate as the metal source,glucose and urea as the deep eutectic solvents.The results show that the as-prepared HEOs exhibit a single perovskite phase which are hollow spherical porous structure with chemical and microstructure homogeneity.The lithium-ion storage performance shows that the La(Li1/6Co1/6Cr1/6Fe1/6Mn1/6Ni1/6)O3 electrode possesses the highest specific capacity(reversible specific capacity of 410.0 mAh·g-1 for 100 cycles at 200 mA·g-1)as well as the outstanding rate performance(342 mAh·g-1 at 100 mA·g-1 and 169.43 mAh·g-1 at 3000 mA·g-1 with a capacity retention rate of 49.4％).Although La(Li1/6Co1/6Cr1/6Fe1/6Mn1/6Ni1/6)O3 ex-hibts a smaller DLi+,the appropriate lattice distortions,oxygen vacancies and higher specific area give it a higher conductivity(0.072 S·cm-1)as well as a lower electrochemical impedance,thereby leading to the improved specific capacity and rate per-formance.This work provides new design concepts and ideas for developing advanced anode materials for high-performance LIBs.
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