Evaluation of Saft Ultra High Power Lithium Ion Cells (VL5U)

摘要

We evaluated Saft Ultra High Power (UHP) cells (Saft designation VL5U) to determine their rate capability, low temperature performance, storage, and cycle life. The energy and power density at 5 A (1C) were 45 Wh/kg and 55 W/kg, respectively; at 1000 A (200C) were 25 Wh/kg and 10 kW/kg, respectively; and at a 500 A rate, the energy densities were 35, 29, and 29 Wh/kg at 20, -20, and -40 deg C, respectively, and the power densities were 4.3, 3.9, and 3.6 kW/kg, respectively. The VL5U showed a high rate of self-discharge (tested at 70 deg C). Our cycling testing showed that high rate cycling degrades the cell faster than high temperature cycling, revealing significant self-heating at high rates of discharge. These results indicate the cell design is immature; further development will remediate the high self-discharge rates and the self- heating during high rate discharge. Pulse discharge testing using a capacitive load showed that, at an output voltage of 2 V, a pulsed current of 8750 A may be achieved. The minimum cell resistance from the pulse testing was measured to be about 0.23 megohm.