Lihong Shi

Studies on Capacity Loss and Capacity Fading of Nanosized SnSb Alloy Anode for Li-Ion Batteries

Nanosized SnSb alloy exhibits much higher reversible capacity as an anode active material for Li-ion batteries. However, rather large capacity loss at the first charge and discharge cycle as well as capacity fading during cycling for pure nanosized alloy has been observed. These phenomena originate from the following factors: the decomposition reaction of surface oxide and the formation of solid electrolyte interphase on the surface of alloy, the irreversible trapping of Li ions by host atoms, serious aggregation of alloy particles during electrochemical cycling, and the existence of an impure phase. Several strategies have been proposed to overcome these drawbacks, including surface modification, addition of dispersant, and coating on stable frame cores, such as mesophase carbon microbeads, to form composite materials

Nano-alloy anode for lithium ion batteries

The features related to nano-alloy anode for Li ion batteries are summarized in this paper mainly based on our recent studies on nano-SnSb. Electrochemical agglomeration, irreversible trapping of inserted ions by host lattice, and unstable solid electrolyte interphase (SEI) film are highlighted. A strategy that pinning nano-alloy particles on the surface of micrometer-sized carbon particles is introduced, in which all components are active for Li storage.

Improving the Performances of LiCoO2 Cathode Materials by Soaking Nano-Alumina in Commercial Electrolyte

The electrochemical and thermal performances of commercial LiCoO2 as cathode material of lithium-ion batteries were improved by soaking the nano-Al2O3 in commercial LiPF6/ ethylene carbonate/ dimethyl carbonate electrolyte. The acidity of the new electrolyte is much higher than that of the original ( commercial ) electrolyte. These observations cannot be explained with traditional models of performance improvement by surface coating/ modification. A solid superacid model was proposed based on extended and comprehensive analyses. This model disagrees with previous improvement mechanisms and predicts that some other nanocompounds can also be used as additives for improving the performances of LiCoO2 cathode materials. (c) 2006 The Electrochemical Society.

Electrochemical performance of Ni-deposited graphite anodes for lithium secondary batteries

The Raman-active vibron modes of solid nitrogen have been investigated by coherent anti-Stokes Raman scattering (CARS) spectroscopy to 22 GPa at room temperature. Frequencies and linewidths were measured with an accuracy of 0.1 to 0.2 cm(-1). From the pressure dependence of the linewidths a dynamical model for the transitions between the delta, delta (loc), and epsilon phases has been developed. These phase transitions are characterized by different degrees of ordering of the N(2) molecules. The processes can be described by an increase in the orientational order with increasing pressure and a decrease in number in the rotational degrees of freedom at the phase transitions coupled with changes in crystal structure. A structural model for the delta (loc) phase is given, in which the delta-delta (loc)-epsilon transition sequence arises from a group/subgroup relationship and can therefore be considered ferroelastic in nature. Sample annealing was found to have a significant effect on the results