Lithium intercalation and deintercalation processes in Li4Ti5O12 and LiFePO4

We have studied the kinetics of electrochemical lithium intercalation and deintercalation processes at different currents in lithium iron phosphate and lithium titanate based composite materials containing fine carbon particles. The results demonstrate that lithium intercalation and deintercalation processes in the electrode materials are characterized by an overvoltage: 4 and 2 mV, respectively, for a cell with a lithium titanate based electrode and 4 and 24 mV for a lithium iron phosphate based cell. Li4Ti5O12 solubility in Li7Ti5O12 is 1.1% (the limit of the solid solution at Li4.03Ti5O12), and Li7Ti5O12 solubility in Li4Ti5O12 is 2.5% (the limit of the solid solution at Li6.93Ti5O12). The conductivity of the phosphate and titanate solid solutions involved in the lithium intercalation and deintercalation processes has been determined.