Capacity intermittent titration technique (CITT): A novel technique for determination of Li+ solid diffusion coefficient of LiMn2O4

The capacity intermittent titration technique (CITT) has been developed on basis of the ratio of the potentio-charge capacity to the galvano-charge capacity (RPG) method to determine continuously the solid diffusion coefficient D of the intercalary species within insertion-host materials. In experiment, CITT is based on the capacity response of galvano–potentio-charge in a small voltage region. In theory, CITT is based on the linear equations of D versus q (value of RPG) in different range of q. By the CITT, the Li+ solid diffusion coefficients within LiMn2O4 have been determined at different voltages and different galvano-charge currents. Results shows that the order of magnitude of D varies non-linearly with the “W” shape from 10−9 to 10−11 cm2 s−1 in the voltage range from 3.3 to 4.3 V. The galvano-charge current also leads to the error due to the semi-conductive character of LiMn2O4, and the maximal error may reach as much as one order of magnitude. In addition, the main approximations that lead to errors of CITT are qualitatively analyzed.