Thermal Management Using Graphene and Carbon-Nanotubes
- Author(s): Goli, Pradyumna
- Advisor(s): Balandin, Alexander A
- et al.
This dissertation investigates the application of graphene and carbon nanotubes (CNTs) for thermal management of high-power batteries and interconnects. The research is focused on three applications: (i) thermal phase change materials (PCMs) with graphene fillers for thermal management of battery packs; (ii) CNTs incorporated in the battery electrodes; (iii) graphene coatings for copper (Cu) interconnects. In this study, lithium-ion (Li-ion) batteries were used for testing the proposed approaches. The graphene solutions for synthesis of graphene PCMs were obtained by the liquid-phase exfoliation. The graphene coatings on Cu films were grown by the chemical vapor deposition (CVD). In the first part of the dissertation, it is demonstrated that thermal management of Li-ion batteries can be drastically improved using PCM with graphene fillers. Incorporation of graphene to the hydrocarbon-based PCM allowed one to increase its thermal conductivity by more than two orders of magnitude while preserving its latent heat storage ability. A combination of the sensible and latent heat storage together with the improved heat conduction outside of the battery pack leads to a significant decrease in the temperature rise inside the Li-ion battery pack. I the second part of the dissertation, it is shown that thermal properties of Li-ion battery electrodes can be improved by incorporation of CNTs. The electrodes were synthesized via an inexpensive scalable filtration method, which can be extended to commercial electrode-active materials. The measurements reveal that the in-plane (cross-plane) thermal conductivity of the cathodes with the highest battery capacity was ~50 W/mK (3 W/mK) at room temperature. These values are up to two-orders-of-magnitude higher than those for conventional electrodes based on carbon black. The highest in-plane thermal conductivity achieved in the carbon-nanotube-enhanced electrodes was ~141 W/mK. In third part of the dissertation, it is demonstrated that graphene coating can strongly increase the thermal conductivity of Cu films as compared to the reference Cu and annealed Cu films. The observed improvement of thermal properties of graphene coated Cu films results primarily from the changes in Cu morphology during graphene CVD rather than from graphene's action as an additional heat conducting channel. The obtained results are important for thermal management of advanced batteries and downscaled computer chips.