Comparative Assessment of Commercial High Energy and High Power Lithium-ion Batteries

This work aims to investigate the fundamental characteristics of Lithium-ion (Li-ion) battery cells, which are generally distinct by their energy and power capability. The commercial high energy and high power Li-ion battery cells were characterised their physical, electrical and chemical properties. Physical properties, such as geometry and capacity of each cell were measured. Electrical properties, such as internal resistances, power characteristics were also tested. The results on energy and power densities of each battery cell and power-to-energy ratio (P/E ratio) could be simultaneously obtained. The cells were subsequently disassembled in order to characterise their internal properties. The thicknesses of electrodes, separator and current collectors were measured. The morphology of cathode and anode was observed by the scanning electron microscope (SEM) as well as the visible particle size. Chemical analysis was conducted by energy dispersive spectroscopy to identify the chemistry of the electrodes. Finally, all the characteristics measured and obtained were explained in relation with the P/E ratio. It was found that battery cells with high energy tended to have high internal resistances, large particle size of active materials in both cathode and anode. The cells contained the thick cathode and anode and thin current collectors and separator due to the benefit of high amount of energy capacity coatings. Conversely, the battery with high power tended to show the opposite characteristics. The relationship between these properties versus P/E ratio was attempted to develop. It showed a well-correlated result for some extents. However, due to the difference of battery chemistries and different manufacturer, it was still hard to make a strong correlation between the properties and P/E ratio, which need to be more clarified.