Treated FeS2 samples were prepared by natural FeS2 samples which were ground first, heated in nitrogen and then washed in acid. The levels of impurity elements, primarily present asmetallic oxides and sulfides, are higher in the natural FeS than those in the treated sample. Scan-ning electron microscopy shows that the grain sizes of treated FeS:, particles are smaller than thoseof natural FeS2 particles. The electrochemical performance of Li/treated FeS2 cells is attributed tothe smaller grain sizes and higher purity of treated FeS particles in comparison to the natural FeSsample.

Improvement of elevated-temperature performance of LiL02Cr0. 1MnLg04 cathode material by silicious sur- face modification was studied. The Lil0Cr0. 1lMnl. 904 cathode material was treated by silanes coupling agent and then heated at 580℃ to remove organic material. The structures of the modified and unmodified Li1. 02Cr0. lMn1. g04 were characterized by SpectraPlus, SEM and XRD. The results show that the surface layer of Li1. 02Cr0. 1Mnl. 904 ma- terial is found to be rich in silicious compound. X-ray diffraction show that all the samples have perfect spinel structure. The electrochemical characterization of modified Li1. 02Cr0. 1Mnl904 cathode material was tested. The cycle stability of charge/discharge at 55℃ is improved. The results of the charge/discharge curves show that the modi- fied LiCralMnl. 904 has better performance than those unmodified according to the inhibition of decline of reversible capacity of spinel Li1. 02Cr0. 1Mnl. 904. Therefore, cycle performance is improved so obviously that 86. 03% of the initial capacity is preserved after 100 cycles.

Some rare earth doping spinel LiMn2-RE, Oa(RE=La, Ce, Nd) cathode materials for lithium ion batteries were synthesized by the solid-state reaction method. "File structure characteristics of these produced samples were investi-gated by XRD, SEM, and particle size distribution analysis. According to the microstructure and charge-discharge testing, the effect of doping rare earth on stabilizing the spinel structure was analyzed. Through a series of doping experiments, it is shown that when the doping content x within the range of 0. 01～0. 02 the cycle performance of the materials is greatly improved. The discharge capacity of the sample LiMnl 9sLao. o204, LiMnl 9sCe0 0204 and LiMni 98Nd0 0204 remain 119. 1, 114. 2 and 117. 5mAh'g-i after 50 cycles.

Olivine-type LiFePO4/C composite cathode materials were synthesized by a solid-state reaction methodin an inert atmosphere. The glucose was added as conductive precursors before the formation of the crystallinephase. The effects of glucose content on the properties of as-synthesized cathode materials were investigated. Thecrystal structure and the electrochemical performance were characterized by X-ray diffraction (XRD), scanningelectron microscopy (SEM), laser particle-size distribution measurement and electrochemical performance testing. The material has a single crystal olivine structure with grain-sizes ca. 100-200rim. SEM micrographs and thecorresponding energy dispersive spectrometer (EDS) data confirm that the carbon particulates produced by glucosepyrogenation are uniformly dispersed among the LiFePO4 grains, ensuring a good electronic contact. Impedancespectroscopy was used to investigate the ohmic and kinetic contributions to the cell performance. It is found thatincreasing the carbon content leads to a reduction of the cell impedance due to the reduction of the charge transferresistance. The galvanostaticaUy charge and discharge tests show that the material obtained by adding 10% C (bymass) gives a maximum discharge capacity of 140.8mA. h. g, 1 at the same rate (C/10). The material also displaysa more stable cycle-life than the others.

SEM). The electrochemical properties of composite electrolyte membranes were studied. The ionic conductivityof the polymer electrolyte composed of 75wt. % 1MLiBF4 in ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC:DMC=1:1by weight) was about 2.6×10−3 S cm−1 at ambient temperature. The electrochemical window of the polymer electrolyte was about 4. 6Vdetermined from the linear sweep voltammetry plot. The lithium ion polymer batteries were assembled by sandwiching gel polymer electrolytebetween LiCoO2 cathode and mesophase carbon fibre (MPCF) anode. Charge-discharge test results display that lithium ion batteries withthese gel polymer electrolytes have good electrochemical performance.