Wenze Wang,Qian Zhang,Liting Yang,Guisheng Liang,Xuhui Xiong,Yifeng Cheng,Limin Wu,Chunfu Lin,Renchao Che
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.
Currently, addressing the challenges posed by the low energy density of lithium titanate (LTO), a prevalent anode material in lithium slurry batteries (LSBs), is crucial for ensuring high stability, storage capacity, and cycle stability, thereby facilitating the commercialization of LSBs. In this study, a heterostructure (LTO-TOB) was created by integrating nano-TiO2(B) (bronze phase) onto the surface of commercial LTO. The coated TiO2(B) layer significantly increases the specific surface area and wettability, guaranteeing fantastic stability. The pseudo-capacitance lithium storage ability of TiO2(B) boosts the power of the electrochemical reaction. The extra interface in the crystalline phase and the presence of oxygen vacancies serve not just as lithium storage sites, but also accelerate the Li+ diffusivity and enhance the electron conductivity. Furthermore, the diffusion mechanism of lithium ions within LTO-TOB anolyte was examined by using a designed in situ Raman cell. The engineered LTO-TOB anolyte assembled reactor boasts a substantial specific capacity of 209.12 mA h g−1 at 0.5C, coupled with remarkable cycle steadiness (with a mere 0.095% capacity loss per 100 cycles). The reactor exhibits favorable electrochemical characteristics in both intermittent mode and static long-term cyclic mode, thereby highlighting the significance of surface heterostructure modification as a key approach in advancing the progress of LSBs.
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