Exploiting Super-Lithiation in 3D Mesostructured Polyimide Electrodes: Towards Practical Organic Batteries

Abstract

Recent developments in redox-active organic molecules appear to be providing sustainable and cost-effective electrode materials as potential alternatives to conventional metal-based electrodes for lithium-ion batteries (LIBs). However, utilization of the organic battery electrodes in practical applications has been quite limited. The rational design principles of the electrode structure would be beneficial in concurrently achieving practical performance demands of high energy, fast charging rate, and long-term cyclability. In this work, we conceive a lithographic fabrication strategy for realizing a 3D mesostructured organic electrode that exploits a ‘super-lithiation’ phenomenon of nearly all unsaturated C=C bonds in multi-carbonyl polyimide. The polyimide layer grown on the ordered porous nickel current collector which is prepared via proximity-field nanopatterning (PnP), generates promoted super-lithiation and shows a much higher specific capacity of 1300 mAh g−1 compared to that of the 2D electrode (270 mAh g−1). We attribute the high electrochemical activity to fast reaction kinetics through the efficient pathways for Li-ions and electrons within the electrode, as well as pathways for rapid transport of ions within the interconnected, electrolyte-filled porous network. The effect of the 3D structure is further corroborated by the unprecedented high-rate capability (achieved rates up to 400 C) and 83% capacity retention at 10 C (15 A g−1) after 250 cycles. Finally, the full electrode-basis capacity reaches 2800 mAh cm−3, surpassing the target lines required to meet the energy density target of 1500 Wh L−1 (on half-cell level) for hybrid electric vehicles. Our findings suggest that our strategic electrode design may contribute to spurring the commercialization of organic electrodes for practical systems in near future. Furthermore, the 3D nickel with the continuous, periodic porous network used in this study is expected to accommodate the severe volume expansion and induce uniform Li deposition as an effective current collector. It could be further studied for the development of Si- and Sn-based anodes for advanced LIBs or dendrite-free Li anode for lithium-metal batteries.