Ultrafast high-temperature sintering of high-entropy oxides with refined microstructure and superior lithium-ion storage performance

Abstract

High-entropy oxides (HEOs) have received significant attention because of their tunable mechanical properties and wide-range of functional applications. However, the conventional method used for sintering HEOs requires a prolonged processing time, which results in excessive grain growth, thereby compromising their performance. Here, an ultrafast high-temperature sintering (UHS) strategy was adopted and the rock-salt composite (Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)O was selected as a model material. The experimental parameters were tuned to illustrate the influence of the applied current and soaking time on the densification process and resulting grain size. Additionally, the electrochemical performance of UHS-synthesized microparticles as the anode material in lithium-ion batteries was investigated. The results show that the ultrafast heating rate results in fine grains with a diameter of ~6–8 μm and a density of 95%, which are, respectively, much smaller and similar to those obtained using the conventional sintering method (25 μm and 96%). Moreover, the high surface area and reactivity of the microparticles, as well as their sluggish diffusion effect and structural stability, contribute to an outstanding performance with high capacity (336 mAh/g at 1 A/g) and ultralong cyclability (1000 cycles). This novel technique offers valuable insights into the densification process of HEOs and other materials and can thus broaden their application range.