This Small Business Innovation Research (SBIR) Phase I project aims to develop novel high energy/power density polymer based cathode material for Li-ion battery. There is great demand for inexpensive, lightweight, and environmentally friendly Li-ion batteries for emerging applications such as plug-in hybrid and electric vehicles and efficient utilization of intermittent renewable energy. The most desired improvements on the current LIB technology include higher energy/power density, better safety characteristics, and more renewable synthesis of battery materials. The greatest challenges of LIBs mainly lie with the cathode. Transition metal oxides and phosphates are currently the dominant cathode materials, but their specific capacities of below 200 mAh/g limit their energy density. These materials are non-renewable and energy-intensive to produce, and they can evolve oxygen gas during cycling, which raises great safety concerns. To address these issues, this project will develop a high energy/power density polymer cathode with stable cycling and excellent rate performance at a lower cost compared to conventional cathode in LIBs. The polymer cathode synthesis can utilize renewable biomass resources and consist of eco-efficient processes, making sustainable Li-ion batteries possible. The use of polymer cathodes may also improve thermal safety of Li-ion batteries compared with conventional cathode materials.
The broader impact/commercial potential of this project is that the high energy/power density polymer cathode will significantly improve the performance of cathode in conventional LIBs with the utilization of environmental friendly material. If successful, it is anticipated that the proposed polymer cathode will have a higher gravimetric energy density than that of conventional cathodes, such as LiCoO2, LiFePO4 and LiMn2O4. Eco-efficient synthesis processes using inexpensive, renewable resources should also lead to a production cost below that of conventional cathodes. Particularly, the merits of the polymer cathode, including high energy density, lightweight, high flexibility and environmentally friendly will make the products highly competitive in the military market.
Li-ion batteries recently meet the development bottleneck because of the energy-density limitation of the conventional intercalation-based inorganic cathode materials (e.g., LiCoO2 and LiFePO4), and the large-scale use of transitional metal oxide electrode materials can bring the resources and environmental issues. As an alternative, organic electrode materials have attracted more and more interest due to their high electrochemical performance, resource sustainability, environmental friendliness, structure diversity, flexibility and so on. Herein, we synthesized novel polymer and polymer-CNT composites through a simple in situ polymerization. The highly dispersed CNT in the nanocomposite drastically enhanced the electronic conductivity and allowed the electrochemical activity of polymer cathode to be efficiently utilized. New Poly(anthraquinone)-CNT composite shows a stable discharge capacity of 245 mAh/g under 0.2 C rate, and only 1% capacity fading during as long as 500 cycles. Compared to the pure polymer, the composites possess much higher active material utilization ratios and superior ultrafast-charge and -discharge ability with a specific capacity of 135 mAh/g at 50 C. The finding of the research shows that novel polymers and polymer-CNT composites involving reversible redox reactions are promising candidates as electrode materials for the new generation of "green lithium batteries". The organic electrode can be used for the next generation of cheap, green, sustainable and versatile energy storage devices beyond conventional Li-ion batteries.
