DEPENDENCE OF THE ELECTROCHEMICAL INTERCALATION OF LITHIUM IN CARBONS ON THE CRYSTAL-STRUCTURE OF THE CARBON

The voltage, V(x) and reversible capacity, x(max) of Li/LixC6 electrochemical cells depends on the choice of carbon used as the electrode. We have developed a structural model for disordered carbons and a corresponding structure refinement program for powder X-ray data which allows accurate quantification of the structural parameters (lattice constants, basal plane particle size, probability of turbostratic disorder, etc.) describing disordered carbons. The structural model is used to fit the diffraction patterns of hard and soft carbons, treated at different temperatures, and the structural parameters are then obtained. The structural data is then correlated to V(x) and x(max) to determine how the carbon structure influences the intercalation of lithium. We are able to understand, qualitatively, the variation in both x(max) and V(x) with heat treatment temperature and with the types of disorder present in the two classes of carbon. V(x) and x(max) are also measured for lithium intercalation in boron substituted carbon (B0.05C0.95). We are able to make general statements about which classes of carbons are most suitable as anodes in lithium ion cells and give some suggestions for future research directions.