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

Abstract

A novel composite electrode material has been prepared by easy and inexpensive route. Nanocrystalline grains of the tin-based phases CoSn 2, CoSn and SnO 2 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 Li y CoSn x phases are formed, while some grains of CoSn and CoSn 2 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.