Entropy-induced high-density grain boundaries in Co-free high-entropy spinel oxides for highly reversible lithium storage.

Transition metal oxides (TMOs) with high discharge capacity are considered as one of the most promising anodes for lithium-ion batteries. However, the practical utilization of TMOs is largely limited by cycling stability issues arising from volume expansion, structural collapse. In this study, we synthesized a high-entropy spinel oxide material (FeCrNiMnZn)3O4 using a solution combustion method. With the implementation of five cations through high-entropy engineering, the agglomeration and expansion of the electrode materials during charging and discharging are suppressed, and the cycling stability is enhanced. The results demonstrate that entropy-induced high-density grain boundaries and the reversibility of spinel structure contribute to improved capacity and cycling stability. Herein, (FeCrNiMnZn)3O4 provides a high capacity (1374 mAh g-1) at 0.1 A g-1 and superior cycling stability (almost 100 %) during 200 cycles with a current density of 0.5 A g-1. The study provides valuable understanding for designing the high entropy oxides anode electrodes.

Rational design of NiO/NiSe2@C heterostructure as high-performance anode for Li-ion battery.

Biphasic or multiphase heterostructures have promising futures in advanced electrode materials for energy-related applications because of their desirable synergistic effects. Here we prepared a rational NiO/NiSe2@C heterostructure microsphere through carbonization, selenization, and oxidation using Ni-MOF as a precursor. Electrochemical studies were conducted to examine the Li+ storage characteristics, and density functional theory (DFT) was utilized to comprehend the underlying mechanism. When employed as the anode for LIBs, the NiO/NiSe2@C showed a high specific capacity and long-term cyclic stability, with a specific capacity of 992 mAh g-1 for 600 cycles at a current density of 0.2 A g-1. The NiO/NiSe2@C exhibits a significantly enhanced lithium-ion diffusion coefficient ( [Formula: see text] ) value. The DFT results show that an electron-rich area forms at the NiO/NiSe2 heterointerface, where the metalloid selenium transfers electrons to the oxygen atoms. The lithiation reactions were improved dramatically by redistributing interfacial charges, which can trigger a built-in electric field that dramatically promotes the capacitance contribution of electrode materials, enhances the lithium storage capacity, and accelerates the ion/electron transmission. The rational synthesis of NiO/NiSe2@C heterostructure can provide an idea for designing novel heterostructure anode materials.