Polydopamine-based Advanced Lithium–sulfur Batteries

 Renjie Chen

 Beijing Institute of Technology

Abstract: The main problems plaguing Li-S batteries from being commercial are poor cycle life, which caused by the insulating nature of S and the shuttle effect associated with the dissolution of intermediate lithium polysulfides. To address these issues, we use polydopamine as “nano-binder” to glue carbon and sulfur at nanoscale, forming a stable double-shelled sulfur cathode (Fig. 1).This approach prevents carbon black from detaching from cathode surface during cycling and provides conductive agents for their reutilization. The hierarchical double-shelled structure can act as physical and conductive barrier to effectively trap the polysulfides and reutilize the migrating polysulfides. This “nano-binder” decorated structure exhibits a long cycle performance of 2500 cycles at 0.5 C, with only 0.014% capacity loss per cycle.

Besides, we also proposed a systematic modification of sandwiched cathode and polydopamine-coated separator to synergistically mitigate the shuttle effect and improve the performance of lithium sulfur batteries (Fig. 2). The sandwiched cathode with PD membranes around each sulfur particle can form physical barriers and allow it from deforming, so that the secondary particles are not ruptured during cycling. The PD-coated separator can increase the binding force between separator and lithium polysulfides. This systematic effect plays key roles in suppressing polysulfides shuttle, facilitating ion diffusion, keeping the cathode structure stable, leading to uniform lithium deposition and attributing to form solid electrolyte interphase.

Fig. 1 SEM and TEM images show the morphology of double-shelled cathode.

Fig. 2 Schematic of the systematic effect of lithium sulfur batteries.

Biography: Renjie Chen is a Professor in the School of Material Science & Engineering at Beijing Institute of Technology (BIT). His research focuses on electrochemical energy storage and conversion technology. He was a post-doctoral fellow in Department of Chemistry at Tsinghua University and a visiting professor in Department of Materials Science and Metallurgy at University of Cambridge. As the principal investigator, Prof. Chen successfully hosted a National Natural Science Foundation, National High Tech 863 project. He has (co-) authored 188 research papers and filed 58 patents and patent applications.