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Abstract: A series of polypyrrole-LiFePO4 (PPy-LiFePO4) composites were synthesised by polymerising pyrrole monomers on the surface of LiFePO4 particles. AC impedance measurements show that the coating of polypyrrole significantly decreases the charge-transfer resistance of LiFePO4 electrodes. The electrochemical reactivity of polypyrrole and PPy-LiFePO4 composites for lithium insertion and extraction was examined by charge/discharge testing. The PPy-LiFePO4 composite electrodes demonstrated an increased reversible capacity and better cyclability, compared to the bare LiFePO4 electrode. [Copyright &y& Elsevier]

Abstract: Several Sn-coated MCMB (mesocarbon microbeads) graphite anode materials were prepared by microencapsulating nanosize Sn particles in MCMB. The nanosized tin particles are homogeneously dispersed in MCMB graphite matrix via electroless in situ chemical reduction. X-ray diffraction and EDS measurement confirms the presence of Sn in MCMB matrix. A systematic electrochemical testing has been performed on the Sn-coated MCMB graphite electrodes. The tin-coated MCMB graphite electrodes demonstrated an improvement in lithium storage capacity. The reaction process of lithium intercalation and de-intercalation in MCMB structure and lithium alloying with tin has been identified by cyclic voltammetry measurement. The micro-encapsulation of Sn in MCMB graphite can enhance the electrochemical properties of MCMB graphite anodes. [Copyright &y& Elsevier]