New Sn-based composites as anode materials for Li-ion batteries

A new strategy was developed to synthesize tin-composite materials. The Sn:BPO4 and Sn:CaSiO3 composites were obtained by solid state reaction, but the BPO4 and CaSiO3 matrices were synthesized by solid state reaction and sol–gel method, respectively. These materials are characterized by X-ray diffraction, 119Sn Mössbauer spectroscopy and electrochemical tests. The results show that these new materials are efficient during electrochemical cycling (500 mAh g−1), because of a good dispersion of Sn particles into the matrix. From the second cycle, charge and discharge reversibility is linked to both reversible LiXSn alloy forming and the modification of the tin particle surface showed by Conversion Electron Mössbauer spectroscopy (CEMS) which allows us to characterize the sample surface. The irreversible capacity observed for the first charge/discharge cycle is due to tin oxide reduction and passivation of the anode surface by electrolyte solution decomposition (SEI layer).