High Electrochemical Performance of Monodisperse NiCo₂O₄ Mesoporous Microspheres as an Anode Material for Li-Ion Batteries

Binary metal oxides have been regarded as ideal and potential anode materials, which can ameliorate and offset the electrochemical performance of the single metal oxides, such as reversible capacity, structural stability and electronic conductivity. In this work, monodisperse NiCo₂O₄ mesoporous microspheres are fabricated by a facile solvothermal method followed by pyrolysis of the Ni_0.33Co_0.67CO₃ precursor. The Brunauer–Emmett–Teller (BET) surface area of NiCo₂O₄ mesoporous microspheres is determined to be about 40.58 m² g^–1 with dominant pore diameter of 14.5 nm and narrow size distribution of 10–20 nm. Our as-prepared NiCo₂O₄ products were evaluated as the anode material for the lithium-ion-battery (LIB) application. It is demonstrated that the special structural features of the NiCo₂O₄ microspheres including uniformity of the surface texture, the integrity and porosity exert significant effect on the electrochemical performances. The discharge capacity of NiCo₂O₄ microspheres could reach 1198 mA h g^–1 after 30 discharge–charge cycles at a current density of 200 mA g^–1. More importantly, when the current density increased to 800 mA·g^–1, it can render reversible capacity of 705 mA h g^–1 even after 500 cycles, indicating its potential applications for next-generation high power lithium ion batteries (LIBs). The superior battery performance is mainly attributed to the unique micro/nanostructure composed of interconnected NiCo₂O₄ nanocrystals, which provides good electrolyte diffusion and large electrode–electrolyte contact area, and meanwhile reduces volume change during charge/discharge process. The strategy is simple but very effective, and because of its versatility, it could be extended to other high-capacity metal oxide anode materials for LIBs

Direct Synthesis of Few-Layer F‑Doped Graphene Foam and Its Lithium/Potassium Storage Properties

Heteroatom-doped graphene is considered a potential electrode materials for lithium-ion batteries (LIBs). However, potassium-ion batteries (PIBs) systems are possible alternatives due to the comparatively higher abundance. Here, a practical solid-state method is described for the preparation of few-layer F-doped graphene foam (FFGF) with thickness of about 4 nm and high surface area (874 m²g^–1). As anode material for LIBs, FFGF exhibits 800 mAh·g^–1 after 50 cycles at a current density of 100 mA·g^–1 and 555 mAh·g^–1 after 100 cycles at 200 mA·g^–1 as well as remarkable rate capability. FFGF also shows 165.9 mAh·g^–1 at 500 mA·g^–1 for 200 cycles for PIBs. Research suggests that the multiple synergistic effects of the F-modification, high surface area, and mesoporous membrane structures endow the ions and electrons throughout the electrode matrix with fast transportation as well as offering sufficient active sites for lithium and potassium storage, resulting in excellent electrochemical performance. Furthermore, the insights obtained will be of benefit to the design of reasonable electrode materials for alkali metal ion batteries