On the evaluation of the factors influencing the rate capability of a LiCoO2|Li battery

The influence of compaction on the porosity and electrochemical properties of LiCoO2 positive electrodes, in lithium ion batteries, discharged at different rates is studied. The results show that at discharge rate lower than 1 C, the capacity increased as electrode density increased. However, at discharge rates greater than 2 C, the capacity showed an inverse relation to the density. The indication is that the inter particle contact resistance, which decreases with increase in compaction, is the key factor determining the discharge efficiency at a rate below 1 C. However, at discharge rates above 2 C, other factors such as conductivity in the liquid phase and contact area between active particles and electrolyte (wettability) would govern the discharge capacity, in addition to the inter-particle contact resistance. A compromise between all the above factors, required for better battery performance, translates to a recommended electrode density between 3.4 g/cm3 and 3.2 g/cm3.

► At discharge rates greater than 2 C, the capacity showed an inverse relation to the density.
► The inter particle contact resistance decreases with increasing in compaction.
► The conductivity, contact area and wettability govern the charge capacity at discharge rates above 2 C.
► Recommended electrode density between 3.4 g/cm3 and 3.2 g/cm3.