Structure Engineering of Polymers Used in Lithium-ion Battery Electrodes for Improved Performance
Doctor of Philosophy
In this work, we focused on different applications of polymer in Lithium-ion battery electrodes, with an emphasis in structure engineering of polymers in order to provide a better understanding in the fundamental relationship between polymer structure, electrode composition, battery properties and performance. We first studied self-doped polymeric binder, PFP, in V2O5 cathodes. This fully water-processable, thermally annealed hybrid electrode shows steady cycling performance even when it is annealed at 400°C. We believe this is because the addition of 5 wt% PFP as binder helps suppress the crystallization of V2O5 xerogel and avoid the disruption of its layered structure. Then we discussed using conjugated polymer PNDI-T2EG as the active materials in electrode. We demonstrated that modification of conjugated polymer side-chains had a significant impact on the electrochemical performance of nano-composite electrodes, in particular enabling excellent performance at high charge-discharge rates. By attaching OEG side-chains, electrodes demonstrate exceptional rate performance at high charge-discharge rate, high mass loading, and high active material content. As a continued study, we look at a series of PNDI-based polymer with different ratios of OEG side-chains. All these works help to demonstrate that structure engineering of polymers is an efficient strategy when researching for the next better materials used for battery development.
Conjugated polymer; lithium-ion Battery; organic electrode