Effects of surface density and compaction density on properties of fast charge lithium ion battery

The effects of cathode bulk density and compaction density on fast charge and cycle properties of the soft package battery, which was prepared by using LiCoO₂ as cathode material, were studied. The morphology and structure of the cathode materials were investigated by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) techniques. The prepared battery was charged at high rate 6 C (discharged at 1 C) to test its electrochemical properties. With the adding cathode surface density, the discharge specific capacity and the cycle performance diminish accompanied with increasing resistance. When the bulk density is increased from 150 g/m² to 220 g/m², the battery capacity retention ratio falls from 89.06 % to 60.45 % after 1000 cycles. The cycle performance of LiCoO₂ battery increases first and then drops with the adding compaction density. Appropriate increasing of press density can effectively reduce the resistance and shorten the migration path of Li⁺, which improves the battery's cycle performance. The capacity retention ratio for the battery charged at 6 C and discharged at 1 C with compaction density of 3.32 g/cm³ is 91.50 % after 500 cycles.