Shejun Hu

Facile spray drying synthesis of porous structured ZnFe2O4 as high-performance anode material for lithium-ion batteries

Porous ZnFe2O4 nanorods have been successfully prepared by a simple spray-drying process followed by sintering. The structure and morphology of the samples were characterized by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The porous structured ZnFe2O4 materials are successfully used as potential anode material for lithium-ion batteries. Electrochemical results show that the anodes exhibit good cycling performance and rate capability. The anode exhibits initial discharge capacity of approximately 1459xa0mAhxa0g−1 with an initial coulombic efficiency of 77.8% at a constant density of 100xa0mAxa0g−1. The discharge capacity of the ZnFe2O4 retained 1458xa0mAxa0hxa0g−1 after 120 cycles at the current rate of 100xa0mAxa0g−1 and 456xa0mAxa0hxa0g−1 could be obtained at the current density of 5000xa0mAxa0g−1 after 200 cycles. The discharge capacities can still be as high as 778xa0mAhxa0g−1 at a high rate of 3000xa0mAxa0g−1. Such remarkable electrochemical properties could be ascribed to the unique porousxa0morphology with large surface area and porosity that were beneficial to facilitate the diffusion of Li ions and electrolyte into the electrodes, meanwhile prevent volume expansion/contraction during lithiation/dislithiation processes.

Performance and mechanism research of hierarchically structured Li-rich cathode materials for advanced lithium-ion batteries

The hierarchically structured cathode material Li1.165Mn0.501Ni0.167Co0.167O2 (LMNCO) is successfully synthesized via a facile ultrasonic-assisted co-precipitation method with a two-step heat treatment by adopting graphene and carbon nanotubes (CNTs) as functional framework and modified material. The structure and electrochemical performance degeneration mechanism were systematically investigated in this work. The obtained LMNCO microspheres possess a hierarchical nano-micropore structure assembled with nanosized building blocks, which originates from the oxidative decomposition of the transition metal carbonate precursor and carbonaceous materials accompanied with the release of CO2 (but still remain carbon residue). What’s more, the positive electrode exhibits enhanced specific capacities (276.6xa0mAhxa0g−1 at 0.1xa0C), superior initial coulombic efficiency (80.3xa0%), remarkable rate capability (60.5xa0mAhxa0g−1 at 10xa0C) and high Li+ diffusion coefficient (~10−9xa0cm2xa0s−1). The excellent performances can be attributed to the pore structure, small particle sizes, large specific surface area and enhanced electrical conductivity. (1xa0Cxa0=xa0250xa0mAxa0g−1).

The design and synthesis of polyhedral Ti-doped Co3O4 with enhanced lithium-storage properties for Li-ion batteries

Polyhedral Ti-doped Co3O4 nanoparticles with a diameter of about 100–300xa0nm have been easily synthesized by a co-heat precipitated method. The structure and morphology of the materials were characterized by X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. The electrochemical measurements were implemented on half coin cells. Galvanostatic charge, discharge performance, cyclic voltammetry and impedance measurement were utilized to investigate the electrochemical properties. The Ti-doped Co3O4 electrodes showed superior performance compared with the undoped Co3O4 electrodes, including the enhanced rate capability, and better capacity retention. At current densities of 500xa0mAxa0g−1, the Ti-doped Co3O4 electrodes exhibited initial capacities of 1173.6 and 849.0 mAhxa0g−1, and the capacities were maintained at 850.3 and 838.6 mAhxa0g−1 after 120 cycles. These excellent electrochemical properties can be attributed to the nanoscale structure and Ti doping.