Polyacrylonitrile and cobalt-tin compounds based composite and its electrochemical properties in lithium ion batteries

A novel composite electrode material has been prepared by easy and inexpensive route. Nanocrystalline grains of the tin-based phases CoSn2, CoSn and SnO2 are embedded in an amorphous layer based on the polyacrylonitrile (PAN) polymer. Maximum reversible capacities around 600 mAh/g are observed. The PAN-based layer and the oxygen atoms contribute to stabilize the intermetallic phases upon electrochemical cycling, thus improving capacity retention. The mechanisms of the reactions are explored by using X-ray diffraction (XRD) and Mössbauer spectroscopy. In the first discharge process, the cassiterite phase is destroyed and amorphous LiyCoSnx phases are formed, while some grains of CoSn and CoSn2 remained unaffected. Lithium-tin intermetallic phases are not detected. In the charge process, the segregation of tin-based phases into Co-rich and Co-poor regions takes place.