Carbothermal synthesis of Sn-based composites as negative electrode for lithium-ion batteries

The composite [Sn–BPO4/xC] to be used as negative electrode material for the storage of electrochemical energy was obtained by dispersing electroactive tin species onto a BPO4 buffer matrix by carbothermal reduction of a mixture of SnO2 and nanosized BPO4. This composite material was thoroughly characterized by X-ray diffraction, Scanning Electron Microscopy, 119Sn Mössbauer spectroscopy and Raman spectroscopy. The electrochemical tests of this new material highlight its very interesting electrochemical properties, i.e., a discharge capacity of 850 mAh g−1 for the first cycle and reversible capacity around 585 mAh g−1 at C/5 rate. These electrochemical performances are attributed to the very high dispersion and stabilisation of tin metal particles onto the BPO4 matrix. The irreversible capacity observed for the first charge/discharge cycle is due the reduction of interfacial SnII species and to the passivation of the anode surface by liquid electrolyte decomposition (formation of the SEI layer).