asheng Hu

Polyimide matrix-enhanced cross-linked gel separator with three-dimensional heat-resistance skeleton for high-safety and high-power lithium ion batteries

To develop a kind of gel polymer electrolyte with high ion conductivity and good mechanical strength and thermal stability, a polyimide (PI) matrix-enhanced cross-linked gel separator is designed and fabricated by a simple dip-coating and heat treatment method. The PI nonwoven substrate provides high-temperature thermal stability for the gel separator and the crosslinked gel part yields enhanced affinity with the liquid electrolyte. Besides, the cross-linked polymer network could solve the issue of long-term durability of the composite separator in batteries. The gel separator shows better cyclability and rate capability than the traditional PP separator, implying a promising potential application in high-power, high-safety lithium ion batteries. The preparation process is compatible with the traditional manufacturing process of nonwoven membranes, and can be easily converted into continuous production on the industrial scale.

Porous membrane with high curvature, three-dimensional heat-resistance skeleton: a new and practical separator candidate for high safety lithium ion battery

Separators with high reliability and security are in urgent demand for the advancement of high performance lithium ion batteries. Here, we present a new and practical porous membrane with three-dimension (3D) heat-resistant skeleton and high curvature pore structure as a promising separator candidate to facilitate advances in battery safety and performances beyond those obtained from the conventional separators. The unique material properties combining with the well-developed structural characteristics enable the 3D porous skeleton to own several favorable properties, including superior thermal stability, good wettability with liquid electrolyte, high ion conductivity and internal short-circuit protection function, etc. which give rise to acceptable battery performances. Considering the simply and cost-effective preparation process, the porous membrane is deemed to be an interesting direction for the future lithium ion battery separator.

Composite membrane with ultra-thin ion exchangeable functional layer: a new separator choice for manganese-based cathode material in lithium ion batteries

A composite membrane with an ultra-thin ion exchangeable layer is specially designed as a separator in lithium ion batteries with manganese-based cathode materials. The composite membrane features a Mn2+ capture function which originates from the ion exchanging process, especially at high temperature, and is proven to help to alleviate the capacity decay of lithium ion batteries effectively. The enhanced thermal stability, improved wettability and higher lithium ion transference number of the composite membrane further suggest its promising application in lithium ion batteries.

Improving the cyclability performance of lithium-ion batteries by introducing lithium difluorophosphate (LiPO2F2) additive

The cyclability of lithium-ion batteries (LIBs) is often affected by the components of the solid electrolyte interphase (SEI) layer which is generated from electrochemical decomposition of electrolyte. Here, lithium difluorophosphate (LiPO2F2) is studied in this work. When 1.6 wt% LiPO2F2 additive is incorporated into the reference electrolyte, the capacity retention of graphite/Li half-cell is increased from 82.53% to 98.04% and the capacity retention of LiCoO2/Li half-cell is increased from 89.60% to 97.53% after 160 cycles. Electrochemical impedance spectroscopy (EIS) indicates that the SEI layer containing LiPO2F2 can decrease the surface impedance of cells in the last stage cycle. In situ atomic force microscopy (AFM), DFT calculations and X-ray photoelectron spectroscopy (XPS) results show that LiPO2F2 is deposited on the surface of both LiCoO2 and graphite electrodes, which effectively protects the graphite anode and suppresses the degradation of the cathode during the long-term cycling of LIBs.

Evaluation of the dissolved oxygen-related electrochemical behavior of pure titanium in acidic fluoride-containing solutions

AbstractThe effects of dissolved oxygen (DO) on the corrosion behavior of pure titanium in acidic fluoride-containing acids (pH = 0.6–2.0) were evaluated by electrochemical methods, such as open circuit potential (OCP) measurements, potentiodynamic polarization tests, and electrochemical impedance spectroscopy (EIS), combined with surface characterization by X-ray photoelectron spectroscopy (XPS). The results showed that DO affected the anodic kinetic parameters, except the passive current density, by decreasing the maximum anodic current density as well as influencing its dependence on pH and the fluoride concentration. However, DO had no detectable contribution to the total cathodic process at potentials in the active region of titanium. The critical fluoride concentration for the corrosion of titanium was consistently determined by means of three kinds of electrochemical methods. The critical value increased with the DO content, and its dependence on pH was also affected by DO, which were attributed to the effects of DO on the anodic parameters. Additionally, multiple corrosion potentials were discovered under some specific conditions with DO, which resulted from the non-negligible contribution of ORR to the total cathodic current density at relatively higher potentials. Graphical Abstractᅟ

Effects of dissolved oxygen on the electrochemical corrosion behavior of pure titanium in fluoride-containing weakly acidic solutions

AbstractThe effects of dissolved oxygen (DO) on the electrochemical behavior of titanium in fluoride-containing weakly acidic solutions (pH = 5.0) were evaluated quantitatively by electrochemical methods, such as open circuit potential (OCP) measurements and potentiodynamic polarization tests, combined with corrosion morphology observation. The results showed that the electrochemical behavior changed from spontaneously passive to active-passive behavior with increasing the fluoride concentration irrespective of the DO content. DO was found to increase the critical fluoride concentration for the corrosion of titanium due to the increased limiting diffusion current density of oxygen reduction reaction and decreased maximum anodic current density caused by DO. But the corrosion rate of titanium would be accelerated by DO once the fluoride concentration exceeded the critical value. Moreover, corrosion products were observed on the surface when the fluoride concentrations were high enough and titanium was in the active state, which altered the electrochemical behavior of titanium further, such as facilitating the occurrence of OCP oscillation. Graphical abstractᅟ