Rate capability fade of 18650 Li-ion cells

The rate capability of 18650 lithium-ion cells was studied in the paper. The experimental results showed that the reversible capacity declined to 89.5, 85.8 and 81.2% of the initial capacity after 300 cycles at discharge rate of 0.5, 1 and 2C, respectively. The XRD and SAED analysis indicated that at a high current density partial positive electrode material LiCoO2 transformed gradually from well-layered structure to rock salt cubic crystal. Upon the cycling, the degradation of cathode materials' structure and much thicker negative film on anode electrode surface contributed to the rate capability fade.