How Do the Four Core Factors of High Entropy Affect the Electrochemical Properties of Energy-Storage Materials?
High-entropy materials (HEMs) are extremely popular for electrochemical energy storage nowadays. However, the detailed effects of four core factors of high entropy on the electrochemical properties of HEMs are still unclear. Here, a high-entropy La 1/4 Ce 1/4 Pr 1/4 Nd 1/4 Nb 3 O 9 (HE-LaNb 3 O 9 ) oxide is prepared through multiple rare-metal-ion substitution in LaNb 3 O 9 , and uses HE-LaNb 3 O 9 as a model material to systematically study the effects of the four core factors of high entropy on electrochemical energy-storage materials. The high-entropy effect lowers the calcination temperature for obtaining pure HE-LaNb 3 O 9 . The lattice distortion in HE-LaNb 3 O 9 leads to its decreased unit-cell-volume variations, which benefits its cyclability. Based on the restrained diffusion arising from the lattice distortion, the Li + diffusivity of HE-LaNb 3 O 9 at room temperature (25 °C) is limited, which causes its lowered rate capability. However, the Li + diffusivity of HE-LaNb 3 O 9 at high temperature (60 °C) becomes faster than that of LaNb 3 O 9 , which is attributed to the alleviated lattice distortion at the high-temperature, resulting in higher rate capability. The cocktail effects in HE-LaNb 3 O 9 enable its larger electronic conductivity, better electrochemical activity, more intensive Nb 5+ ↔ Nb 3+ redox reaction, and larger reversible capacity. The insight gained here can provide a guide for the rational design of new HEMs with good energy-storage properties.
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