CAM-7/LTO LITHIUM-ION CELLS FOR BATTERIES WITH HIGH CHARGE/DISCHARGE PERFORMANCE AT EXTREME LOW TEMPERATURE

TIAX is developing laminated prismatic lithium-ion (Li-ion) cell technology capable of rapid charging at low temperature (to -50 °C) to replace current lead-acid vehicle batteries. The novel cells are based on TIAX’s high energy, high power CAM-7 cathode material, high rate capability lithium titanate (LTO) anode material, and novel electrolyte formulation, and target cell-level energy content greater than 90 Wh/kg and 250 Wh/l. CAM-7 cathode material promises significant boost in power and run time of Li-Ion batteries for a wide range of DoD applications, and is now being commercialized by a separate company, CAMX Power, which is scaling up production in a 50 metric ton per year plant installed in Massachusetts. Proceedings of the 2012 Ground Vehicle Systems Engineering and Technology Symposium (GVSETS) INTRODUCTION Military applications can require rechargeable batteries to operate in extreme environments with temperatures as low as -50 °C or as high as 70 °C. These temperature extremes extend beyond those to which current commercial Li-ion technology is constrained, and are a major hindrance to replacement of current lead-acid vehicle battery technologies with much lighter, more compact Liion batteries. Prismatic laminate type lithium-ion rechargeable cells are of particular interest to the military because of their potential for dual-use application in both military and commercial automotive vehicles. Operational temperature limitations of Li-ion batteries are related to the electrolytes and materials they use. At low temperatures, performance is hampered by low electrolyte conductivity and poor electrochemical kinetics associated with ion-desolvation processes [1]. Low-temperature charge acceptance capability is particularly poor because the graphitic carbon anodes used in Li-ion cells are particularly prone to plating lithium metal when charged at low temperature: a condition giving rise to rapid fade and serious safety concerns. At high temperatures, Li-ion battery lifetime is compromised by thermal instability of the electrolytes and of electrode surface films they form, and by the electrolytes’ reactivity with the charged electrode materials; in particular by decomposition reactions at the graphitic carbon anode [2]. Furthermore, the high-temperature decomposition reactions of Li-ion electrolytes result in the formation of non-condensable gaseous products. This gassing results in swelling of prismatic pouch cells thereby limiting their use, although they are otherwise very advantageous for their light weight and flexible form factor. Accordingly, in a TARDEC-sponsored program, TIAX is developing low-temperature-capable, laminated prismatic lithium-ion cell technology employing TIAX’s high energy, high power CAM-7 cathode material, high rate capability lithium titanate (LTO) anode material, and novel electrolyte formulation. CAM-7 provides the highest energy content and rate capability (Figure 1) of any market-ready cathode material, and therefore minimizes the cost to cell energy content incurred by use of high rate charging-capable LTO anode. Commercially available nanostructured LTO is used for its high rate capability and its high potential vs. Li, enabling it to be lithiated at high rate and low temperature without plating lithium metal. Novel electrolyte provides outstanding performance at low temperatures and suppresses electrolyte gassing in foil laminatepackaged cell designs.