Li-ion batteries (LIBs) as an energy storage device have been established as a leading and a promising candidate for automotive and aerospace applications. But to meet the various application requirements, the energy and power density of LIBs need to be optimized for a given electrode material by controlling its porosity and thickness. Changes in electrode thickness and porosity affect the electrochemical performance of LIBs. Thus we employ a mathematical model to study and optimize the electrochemical performance of Graphite/ LiNi_0.6Co_0.2Mn_0.2O₂LIB cells with different cathode thicknesses and porosities. A non-linear least square method is used to provide a better understanding of the different porosities and thicknesses on Li-ion transport in both liquid and solid phases. Ragone plots are generated for the various cell designs where the specific energy and average specific power are evaluated. The LIB cells are optimized  for discharge times ranging from 10 h to 2 min in order to map the maximum performance of this electrode chemistry under wide operating range. The study allows us to ascertain the ability of this chemistry to be used in a particular application.

The solid phase Li-ion diffusion coefficient decreased with an increase in current rate. The salt concentration gradient increased with an increase in cathode thickness and porosity at high rate. Based on the experimental data and simulation results from this study, it can be concluded that both solution and solid phase diffusion limitation are the major limiting factors during high rate discharges in thick and less porous electrodes. The optimized designs derived in this work are expected to be starting point for battery manufacturers and to help decrease the time to commercialization.

References

1. W. A. Appiah, J. Park, L. Van Khue, Y. Lee, J. Choi, M.-H. Ryou and Y. M. Lee, Electrochimica Acta, 187,  422 (2016).

2. P. Arora, M. Doyle, A. S. Gozdz, R. E. White and J. Newman, Journal of power Sources, 88, 219 (2000).

3. V. Srinivasan and J. Newman, Journal of the Electrochemical Society, 151, A1530 (2004).

Acknowledgement

This work was supported by the Sebang Global Battery.