[en] ZnS/C composites were synthesized by a combined precipitation with carbon coating method. Morphology and structure of the as-prepared ZnS/C composite materials with carbon content of 4.6 wt%, 9.3 wt% and 11.4 wt% were characterized using TEM and XRD technique. TEM observation demonstrated that the ZnS/C (9.3 wt% C) composite showed excellent microstructure with 20-30 nm ZnS nanoparticles uniformly dispersed in conductive carbon network. Electrochemical tests showed that the ZnS/C (9.3 wt% C) composite presented superior performance with initial charge and discharge capacity of 1021.1 and 481.6 mAh/g at a high specific current of 400 mA/g, after 300 cycles, the discharge capacity of ZnS/C electrode still maintained at 304.4 mAh/g, with 63.2% of its initial capacity. The rate capability and low temperature performance of the ZnS/C (9.3 wt% C) composite were compared with commercial MCMB anode. The results showed that the ZnS/C (9.3 wt%) composite exhibited much better cycle capability and low temperature performance than MCMB anode. ZnS/C composite seems to be a promising anode active material for lithium ion batteries. Intercalation mechanism of the ZnS/C composites for lithium ion insertion-extraction is proposed based on the ex situ X-ray diffraction analysis incorporating with its electrochemical characteristics.

[en] Olivine compounds LiFe_1-xMn_xPO₄ (0.0 ≤ x ≤ 0.3) for cathodes of secondary lithium-ion batteries were synthesized via a mechanoactivation-assisted solid-state reaction. The optimal manganese content and electrochemical performance of the as-synthesized powders were investigated by XRD, EDX mapping, cyclic voltammetry, and charge-discharge characterizations. According to XRD and EDX mapping results, phase-pure compounds with olivine structure were formed after the calcination under nitrogen atmosphere at 700 ^oC for 20 h. Among the various LiFe_1-xMn_xPO₄ under test, LiFe_0.8Mn_0.2PO₄ showed the highest electrical conductivity, which reached a value of 3.49 x 10^-5 S cm^-1 at room temperature, more than 5 orders higher than that of pristine LiFePO₄ (1.08 x 10^-10 S cm^-1). Without the carbon coating, pristine LiFe_0.8Mn_0.2PO₄ showed discharge capacity of ∼123 and 100 mAh g^-1 at 0.1 and 1 C rates, respectively. It means about 91% and 74% of the Fe²⁺ in LiFe_0.8Mn_0.2PO₄ is electrochemically utilizable correspondingly. For a comparison, they are only 65% and 15% for the pristine LiFePO₄ prepared by a similar process. LiFe_1-xMn_xPO₄ also showed stable cycling performance within the 50 cycles under test. It suggests manganese lightly doped LiFePO₄ could be practical cathode materials for high-rate lithium-ion batteries.