Design of High Power Lithium Ion Battery for HEV Application

An 8Ah prismatic lithium ion cell with high current charge and discharge ability has been developed. Due to the safety and cost issues, the power type Li-ion cell was designed by using LiMn₂O₄ and carbon as cathode and anode materials, respectively. Specific power, discharge rate capability and safety performance of the battery is enhanced through the receipt of material system, electrodes design and new conducting mechanism for the cell structure. The internal resistance of the cell is lower than 2mΩ. The performance tests show the specific power of the new developed cell is over 2000W/kg at 80% SOC. For the rate capability characteristic at room temperature (25 ^oC), the cell can be retained 93.6% of its initial capacity when discharge at 15C rate (120A). Safety tests including nail penetration, external short circuit and overcharge are investigated. The results show neither explosion nor fire under all safety test conditions. A 14.4V battery module including 4 cells in series and integrated battery management system (BMS) has been developed. The BMS is capable of monitoring cell condition (voltage, temperature and current), charge/discharge management and safety protection. 10 modules (40 cells) are connected in series to achieve a 144V battery system for HEV. The discharge power of this battery system is higher than 12.5kW at 50%SOC, which meets the requirements of HEV applications.