Quan-Feng Dong

Three-dimensional porous Cu6Sn5 alloy anodes for lithium-ion batteries

Abstract Three-dimensional porous Cu6Sn5 alloy electrodes were prepared by electroplating using copper foam as the current collector. The micro-holes and small islands on surface of the Cu6Sn5 alloy largely increased the surface area of the electrode, and significantly improved the ability of the electrode in buffering the volume change in the process of charge/discharge when the Cu6Sn5 alloy was employed as the anode in a lithium-ion battery. Galvonostatic charging/discharging results demonstrated that the initial discharge (lithiation) and charge (delithiation) specific capacities of the Cu6Sn5 alloy electrode were 620 mAh·g−1 and 560 mAh·g−1, respectively. It demonstrated that the Cu6Sn5 alloy electrode exhibited a large initial coulomb efficiency (90.3%) and good capacity retention. Scanning electron microscopy (SEM) results illustrated that the Cu6Sn5 alloy deposited on copper foam substrate was more stable than that on a conventional copper substrate, and displayed no obvious exfoliation after 50 charge/discharge cycles.

Impedance studies of spinel LiMn2O4 electrode/electrolyte interfaces

The formation process of solid electrolyte interphase(SEI) film on spinel LiMn2O4 electrode surface was studied by electrochemical impedance spectroscopy(EIS) during the initial storage in 1 mol/L LiPF6-EC:DMC:DEC electrolyte and in the subsequent first charge-discharge cycle. It has been demonstrated that the SEI film thickness increased with the increase of storage time,and spontaneous reactions occurring between spinel LiMn2O4 electrode and electrolyte can be prevented by the SEI film. In the first charge-discharge cycle succeeding the storage, the electrolyte oxidation coupled with Li-ion insertion is evidenced as the main origin to increase the resistance of SEI film. The results also confirm that the variations of the charge transfer resistance(Rct) with the electrode potential(E) can be well described using a classical equation. Keywords Li-ion batteries; SEI film; Electrochemical impedance spectroscopy; Spinel LiMn2O4

Preparation and characterization of a novel composite microporous polymer electrolyte for Li-ion batteries

A novel composite microporous polymer electrolyte composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and mesoporous SBA-15 was prepared. The composite solid polymer electrolyte (CSPE) exhibits ionic conductivity as high as 0.30 mS·cm −1 with a composition of SBA-15 : PVdF-HFP=3 : 8 at room temperature. Infrared transmission spectroscopic results suggested that the mechanism of micropore formation is similar to that of the phase inversion. X-ray diffraction (XRD) results demonstrated that the addition of SBA-15 inhibits the crystallization of PVdF-HFP, while the SBA-15 preserves well its ordered mesoporous structure during the course of preparation. The Li/CSPE/MCF of half-cell was assembled, and it showed a good electrochemical and cyclability performance during charge-discharge cycles.

Influence of Temperature on the Performance of a Graphite Electrode

The first lithiation of a graphite electrode in 1 mol.L-1 LiPF6-EC(ethylene carbonate)∶DEC(diethyl carbonate)∶DMC(dimethyl carbonate) electrolyte at 25 and 60 ℃,and in 1 mol.L-1 LiPF6-EC∶DEC:DMC+5%VC(vinylene carbonate) electrolyte at 60 ℃ were investigated by electrochemical impedance spectroscopy(EIS) combined with cyclic voltammetry(CV).It was found that deterioration of the graphite electrode′s electrochemical performance was mainly caused by the unstable solid electrolyte interphase(SEI) film on the electrode′s surface in 1 mol.L-1 LiPF6-EC:DEC:DMC electrolyte at 60 ℃.However,the use of VC as an additive to the above electrolyte significantly improved the electrochemical performance of the graphite electrode,which was attributed to an improvement in the stability of the SEI film that formed on the graphite electrode′s surface.