Structural engineering and high entropy effect toward improved mechano-electrochemical performance in lithium batteries

The inferior structure/electrochemistry stability due to the volume expansion and the less lithium storage active sites of transition metal oxide (TMO) are critical issue hindering their commercialization. The rational design to utilize the combined advantages of both structure and composition is a key strategy to address these challenges. Here, the (FeCoNiMnCrMg)₂O₃ high entropy oxide (HEO) with different morphologic structures are developed through integrating molecule and microstructure engineering. The morphologic structure of high entropy oxide transforms from solid spheres to multishelled core–shell spheres, and then to hollow spheres, which is governed by a thermally induced non-uniform shrinkage process coupled with Kirkendall effect diffusion due to the different calcination temperature. Even with the incorporation of various metallic ions, the high entropy oxide with a homogeneous single-phase solid solution maintained their shape and uniformity in size due to the ability of metal ions to coexist on the same lattice point. Benefiting from the meticulous control of both compositional and geometric factors, the hollow high entropy oxide exhibited a significantly high specific capacity (1722.1 mAh·g⁻¹ after 200 cycles at 1 A·g⁻¹) and long-life span for lithium storage (2158.7 mAh·g⁻¹ over 900 cycles at 4 A·g⁻¹). The collaborative lattice and consistent volume demonstrated in this study offer significant potential in directing the development of materials for advanced energy storage solutions.

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