Kia is using lithium-ion polymer battery cells supplied by SK Inovation in the battery pack for the new Soul EV (earlier post). The pack, featuring an energy density of 200 Wh/kg (on the high end of specific energy ratings for current EVs), is the result of a three-year joint development program between Kia Motors Corporation and SK Innovation in Korea. The Soul EV offers a driving range of around 200 km (124 miles) on a single charge.
Engineers from Kia developed the pack with 192 SK lithium-ion polymer battery cells in eight modules, for a total capacity of 27 kWh. The pack incorporates advanced thermal control technology to maintain individual cells at optimum temperature and structural design to enhance crash worthiness.
Nickel-rich NCM (nickel-cobalt-manganese) cathode material is used in the mass production of the battery cells for Soul EV. High performance electrolyte additive and anode materials were also developed to meet various performance requirements (such as safety and lifecycle), while maintaining high energy density.
|One of the SK Innovation cells. Click to enlarge.|
In addition, a special safety & secure separator is used in the Kia Soul EV’s battery cells. The separator determines the safety and the charge/discharge speed of the battery. It has improved thermal resistance, which helps to keep the cell secure from exposure to heat or fire by preventing the shrinking of the separator if the temperature of the cell increases beyond normal levels.
Together, the low electrical resistance battery cell, proper battery system thermal control and accurate state-of-charge calculation improve the charging performance, thereby enabling a fast charge time of 25 minutes (100 kW DC) or 33 minutes (50 kW DC). Full recharge time, depending on power source, takes up to five hours (6.6 kW AC).
The electrolyte additive used in the Soul EV will prevent the degradation of battery performance at both low and high temperatures, expanding the temperature range of the battery usage and reducing the fluctuation of the driving range according to the weather.
The Soul EV features a battery heating system which warms-up the battery while the car is plugged into the grid, prior to use. This helps to maintain optimum battery performance regardless of external temperature.
For maximum active safety the battery module is fitted with an overcharge protection device that cuts the high voltage circuit if ever the battery cell swelling phenomenon should occur due to overcharging.
Optimization of the raw materials used to create the cathode morphology control and surface coating, the anode surface coating and electrolyte additive, plus the excellent mechanical strength of the separator, provide for the durability and safety of the cell.