Thermal Management Material for High Density Electric Batteries

Charging and discharging inefficiencies of spaceborne and airborne battery cell designs result in significant heat dissipation. A closely packed battery of these cells poses a heat removal problem. The efficient removal of this energy is critical inmaintaining target operation temperatures. Thermal pyrolytic graphite (TPG) is a highly aligned crystalline graphite with an in-plane thermal conductivity of 1700 W/mK. Encapsulating TPG within carbon fiber encapsulant results in a high conductivity, lowdensity material system. The isotropic in-plane conductivity of the TPG will increase the composite thermal performance by 300% over typical Kll00/Polymer composites. In addition to high specific conductivity, the proposed material system can havetailored thermal expansion and stiffness properties. In Phase I, k Technology Corporation (kTC) demonstrated the feasibility of using the carbon fiber composite encapsulated TPG material as a lithium-ion battery packaging material. This was accomplishedthrough the development and evaluation of material samples and the demonstration of a specific design. kTC has demonstrated an encapsulated TPG battery bracket with a measured conductivity of 1060 W/mK and a density of 2.1 g/cm2. The stiffness of thepanels were also evaluated and found to be, on average 2.6 times greater than aluminum. Phase II will pursue advanced development of this material and design techniques, which will include the qualification of a flight battery bracket assembly. Futurecommercial aircraft and spacecraft platforms are dependent on proven, successful new technologies to reduce weight and improve reliability. Novel materials will allow for increased payloads with higher reliability. These payoffs will support the trendtoward smaller less expensive systems.