Study On High Current Discharge Ability Of 18650 Lithium-ion Batteries

18650 lithium-ion(Li-ion) batteries were used as studying objects. The influence on initial charge/discharge capacity, high current discharge ability, battery resistance due to the change of the composition of liquid electrolytes, cathode active materials and battery designs were investigated by testing 18650 batteries in terms of FT-IR, XRD, et al.The results show that the high current discharge ability is strongly influenced by electrolyte. High conductivity of electrolytes is in favor of the high current discharge ability of the lithium-ion batteries. The electrolyte having the highest conductivity ( 12.0mS/cm ) in the experiment shows excellent high current discharge ability. Discharged at 8C, the retention of discharge capacity is 99.5% of that at 1C, the discharge platform is about 3.3V, and the resistance of the battery is 39.5m? after discharging. Also, the high conductivity is helpful to minimize the polarization of batteries during initial high current discharge period.Among three cathode active materials, LiCoxM1-xO2, LixMnO4 and LiNixCoyMn1-x-yO2, the LiCoxM1-xO2/LixMnO4 blend material shows the best high current discharge ability. The retention of discharge capacity at 8C, 9C, 10C is 99.5%,93.4%,93.1% of that at 1C respectively, and the discharge platform is about 3.3V, 3.15V, 3.05V, which is obviously higher than that of LiCoxM1-xO2, LiCoxM1-xO2/LiNixCoyMn1-x-yO2 blend material and LixMnO4/LiNixCoyMn1-x-yO2 blend material. LiCoxM1-xO2 takes the second place, while LiCoxM1-xO2/ LiNixCoyMn1-x-yO2 blend material and LixMnO4/LiNixCoyMn1-x-yO2 blend material are worse.Changing internal design helps improve the high discharge ability of Li-ion batteries. The increasing of electrode ears can raise the discharge platform notably, minimize the polarization of batteries during initial high current discharge period, and diminish the battery resistance. The battery surface temperature rises somewhat calmly. Besides, the different cathode and anode capacity designs also play an important role on the high current discharge ability of the batteries. When the ratio of cathode and anode capacity is 1:1.30, the battery shows excellent discharge ability. Discharged at 8C, 9C, 10C, the retention of discharge capacity is about 99.5%, 99%, 96.2% of that at 1C respectively.