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Given its safer working potential and higher theoretical capacity, Li3VO4 has become a potential alternative anode material to graphite. However, the hydrophilicity, low electrical conductivity, and unsatisfactory reaction kinetics of the Li3VO4 anode pose a challenge. In this paper, a graphene-wrapped Li3VO4@rGO hybrid was prepared using a novel efficient uniform rotation solvothermal (URS) method. Graphene with high electrical conductivity accelerates the reaction kinetics of the anode material to improve its rate performance. The URS method restrains the agglomeration of particles to shorten the diffusion paths of Li+. The uniform reaction obtained by this method and the lamellar shape of graphene synergistically enlarge the specific surface area of Li3VO4 to supply additional active sites for the extraction/insertion of Li+. Therefore, Li3VO4@rGO–R exhibits superior cycling performance (249.5 mA h g−1 after 4000 cycles at 5 A g−1) and rate performance (243.3 mA h g−1 at 10 A g−1). This study provides a versatile and efficient method for enhancing the electrochemical performance of anode materials. [ABSTRACT FROM AUTHOR]

Ingenious morphology design and doping engineering have remarkable effects on enhancing conductivity and reducing volume expansion, which need to be improved by transition metal oxides serving as anode materials for lithium-ion batteries. Herein, S0.15–Fe2O3@C nano-spindles with a hierarchical porous structure are obtained by carbonizing MIL-88B@PDA and subsequent high-temperature S-doping. Kinetic analysis showed that S-doping increases capacitive contribution, enhances charge transfer capability and accelerates Li+ diffusion rate. Therefore, the S0.15–Fe2O3@C electrode exhibits superior lithium storage performance with a remarkable specific capacity of 1014.4 mA h g−1 at 200 mA g−1, ultrahigh rate capability of 513.1 mA h g−1 at 5.0 A g−1, and excellent cycling stability of 842.3 mA h g−1 at 1.0 A g−1 after 500 cycles. Moreover, the size of S0.15–Fe2O3@C particles barely changed after 50 cycles, indicating an extremely low volume expansion, related to the carbon shell, fine Fe2O3 nanoparticles, abundant voids inside, and improved kinetics. This strategy can be applied to other metal oxides for synthesizing anodes with high-rate capability and low volume expansion. [ABSTRACT FROM AUTHOR]

In this study, we adopt a facile two-step annealing strategy to synthesize different structural 3D Fe2O3 micro-cubes and 3D Fe3O4 micro-cubes using Prussian blue (PB) as a precursor. Importantly, the effect of the annealing temperature on the structural evolution of the products is systematically investigated. In the first step, the 3D Fe2O3 cubes are synthesized by annealing PB in air. With the increasing temperature, the morphology of 3D Fe2O3 changes from the cube with pores on surface to the hollow cube assembled by nanosheets (HCNSs), which is caused by the higher gas generation and overflow. In the second step, 3D Fe3O4 cubes are obtained by annealing 3D Fe2O3-HCNSs in the atmosphere of Ar/H2. With the increasing temperature, the morphology of 3D Fe3O4 changes from the hollow cube assembled by nanosheets to the hierarchical porous hollow cube assembled by fine nano-particles (denoted as HCNPs), an interesting micro/nano-structure that is obtained by recrystallization and reduction. When the temperature is excessive, the building blocks become larger and the 3D structures collapse. Furthermore, we evaluate the electrochemical performance of 3D hierarchical porous Fe3O4-HCNPs as the anode materials for Li-ion batteries. They exhibit enhanced electrochemical performance, characterized by a large reversible capacity of 1193.6 mA h g−1 at a current density of 100 mA g−1 and a high rate capacity of 942.1 mA h g−1 at 1000 mA g−1. This superior performance is due to the unique structural advantages of 3D hierarchical porous Fe3O4-HCNPs, including abundant meso/micro-pores, hollow structure and robust structural stability. [ABSTRACT FROM AUTHOR]

Hydrothermal synthesis of high-performance LiFePO4 nanocrystals in pure water represents a green and sustainable approach to fabricate model cathode materials for lithium ion batteries. However, fundamental and technological hurdles in terms of yield and cost remain to be overcome, though strenuous efforts have been devoted to this challenging approach. Herein, we report a microwave-assisted hydrothermal strategy that enables scalable green synthesis of high-performance LiFePO4 nanocrystals using inexpensive chemical reagents, namely, lithium hydroxide, ferrous sulfate and phosphoric acid in pure water without involving any organic solvents or surfactants. Three critical issues regarding the hurdles are simultaneously addressed. First, the dream of recycling the lithium source, the most valued reagent, in the hydrothermal synthesis comes true, which substantially reduces synthesis cost; second, to the best of our knowledge, a record high volume specific yield of more than 1.3 mol L−1 is achieved. Third, the as-synthesized phase-pure LiFePO4 nanocrystals exhibit excellent electrochemical properties including high capacity and long cyclability. [ABSTRACT FROM AUTHOR]

In this study, ilmenite-type NaNbO3 microplates were prepared by a facile surfactant-free method, using NaAc and KOH as a sodium resource and as a mineralizer, respectively. The effects of each reactant were identified, and the formation process and crystallization pathway of ilmenite-type NaNbO3 microplates were explored based on the phase constitution, microstructure and chemical compositional analysis. The indispensable roles of K ions, which participated in the formation of layered KNN-hydrate intermediates, were revealed. Ilmenite-type NaNbO3 microplates were formed by the dissolution of these intermediates and subsequent recrystallization into K-containing NaNbO3, followed by the ion-exchange between K and Na ions. Meanwhile excess K ions would hinder the release of K ions associated with the dissolution of intermediates, thus preventing the formation of ilmenite-type NaNbO3. Moreover, the morphological evolution of ilmenite-type NaNbO3 microplates from platelets to octahedra was interpreted in terms of their intrinsic structure and KOH concentration. [ABSTRACT FROM AUTHOR]