Xianwen Wu

Nanosilica/carbon composite spheres as anodes in Li-ion batteries with excellent cycle stability

Because of its high capacity, relatively low operation potentials, abundance and environmental benevolence, silica is a promising anode material for high-energy lithium-ion batteries. In this work, to enhance the conductivity of silica and ensure robust connection between silica particles and the host structure in the anode, nanosilica/carbon composite spheres have been fabricated via the in situ copolymerization of formaldehyde and resorcinol on the surface of nanosilica particles, followed by carbonization in an inert atmosphere. The electrochemical properties of the as-prepared composite as an anode for lithium-ion batteries are evaluated. When cycled at a current density of 100 mA g−1 with a voltage window of 0.0–3.0 V the nanosilica/carbon composite spheres present a stable capacity of about 620 mA h g−1 (calculated from the mass of the nanosilica/carbon composite spheres), and the capacity retention is nearly 100% after 300 cycles. Moreover, at different current densities, the as-prepared composite exhibits high capacity and excellent cycle stability. The good electrochemical performance is attributed to the relatively small volume variation of silica nanoparticles, existence of pores/voids in the composite and robust connection between silica nanoparticles and the carbon matrix.

Green-low-cost rechargeable aqueous zinc-ion batteries using hollow porous spinel ZnMn2O4 as the cathode material

Rechargeable aqueous zinc-ion batteries (ZIBs) have been receiving much attention recently due to their potential large-scale applications for energy storage, although only a few cathode materials have been reported as the intercalation hosts for divalent Zn2+ ions. Here, we report competitive ZIBs based on hollow porous ZnMn2O4 as the cathode and zinc as the anode. ZnMn2O4 is firstly prepared through a solvothermal carbon template dispersed by polyvinyl pyrrolidone, followed by an annealing process. The galvanostatic charge–discharge measurement demonstrates that a reversible discharge capacity of 106.5 mA h g−1 at 100 mA g−1 after 300 cycles can be achieved with no capacity decay after the addition of 0.05 mol L−1 of MnSO4 into the electrolyte. Meanwhile, it exhibits a high capacity of 70.2 mA h g−1 at a large current density of 3200 mA g−1. The excellent cycle and rate performances are attributed to the synergistic effect of the deficient spinel structure of hollow porous ZnMn2O4 with residual carbon distribution and the inhibition of Mn dissolution during the charge/discharge process.

Enhanced electrochemical performances of Li 2 MnO 3 cathode materials by Al doping

Al-doped Li2MnO3 (Li2Mn0.9Al0.1O3) lithium-rich layered oxide is prepared and investigated as cathode material for lithium-ion batteries (LIBs). X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) analyses reveal that the Al element is distributed in the sample homogenously. The Al-LMO sample exhibits a great improvement on the rate capability and cycling stability compared to the LMO sample. The differential capacity versus voltage (dQ/dV) results reveal that Al doping would be to prevent the first charge phase transformation from a layered phase to a cubic spinel-like phase and also slowdown the rate of transformation upon cycling. Electrochemical impedance spectroscopy (EIS) results confirm that Al doping decreases the charge-transfer resistance and improves the electrochemical reaction kinetics.

Cryptomelane-Type KMn8O16 as Potential Cathode Material — for Aqueous Zinc Ion Battery

Aqueous battery has been gained much more interest for large-scale energy storage fields due to its excellent safety, high power density and low cost. Cryptomelane-type KMn8O16 confirmed by X-ray diffraction (XRD) was successfully synthesized by a modified hydrothermal method, followed by annealed at 400°C for 3 h. The morphology and microstructure of as-prepared KMn8O16 investigated by field-emission scanning electron microscopy (FE-SEM) with the energy spectrum analysis (EDS) and transmission electron microscopy (TEM) demonstrate that one-dimensional nano rods with the length of about 500 nm constitute the microspheres with the diameter about 0.5~2 μm. The cyclic voltammetry measurement displays that the abundant intercalation of zinc ions on the cathode takes place during the initial discharge process, indicating that cryptomelane-type KMn8O16 can be used as the potential cathode material for aqueous zinc ion batteries. The electrode shows a good cycling performance with a reversible capacity of up to 77.0 mAh/g even after 100 cycles and a small self-discharge phenomenon.