Collaborative Research: Next-Generation Simultaneously Ion- and Electron-Conducting Block Copolymer Binders for Battery Electrodes
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Rechargeable lithium ion batteries help to enable sustainable energy systems by storing electricity generated by intermittent renewable resources such as wind and solar energy, or by powering zero-emission electric vehicles charged by electricity from renewable resources. Lithium-ion batteries are comprised of a variety of materials for storing and releasing ions, transporting electrical charge, and maintaining mechanical integrity. Binder materials, although representing less than 10% of the battery by weight, are an important component for maintaining adhesion between the different materials. This collaborative project will develop a new class of binding materials based on polymers that are both conductive and electrochemically active, enhancing both mechanical and electrochemical properties. The scientific research will establish the principles for the design of electroactive polymeric binders for lithium ion batteries. The key innovation is that the polymer material will be designed at the molecular level to enable these electroactive properties. When properly designed at the molecular level, these polymers have potential to improve the stability and performance of a wide range of battery electrodes. The educational activities associated with this project will provide opportunities for community college students to work on the development of conjugated polymers for energy storage. Furthermore, outreach activities to K-12 students from diverse and underrepresented groups are planned through Chemistry Open House, Empowering Leadership Alliance, Schlumberger Energy Institute, and the Sally Ride Festival.In lithium ion battery systems, polymeric binders provide adhesion with various electrode components and stabilize contact with the current collector. However, current binders are electronically inactive. Substantial improvements in electrode performance and capacity may be possible through the molecular design of electroactive polymeric binders. Towards this end, polymeric binders that are ion-conducting, electron-conducting, and redox-active as well as mechanically stable, are needed. The goal of this research is to develop and understand the functionality of the polymer materials needed to enable these properties. The research plan will consider polymers that contain electronically conductive backbones, side chains for self-doping and ionic conductivity, and redox-active carbonyl groups. The research plan has three objectives. The first objective is to synthesize co-polymers that conduct both ions and electrons simultaneously, and characterize their resulting structural, physiochemical, and electrochemical properties. The second objective is to characterize the electrochemical/mechanical properties of hybrid anodes containing a silicon base material and polymer binders developed under the first objective. The third objective is to incorporate redox-active groups into the polymer backbone and examine their role on conductive polymer binder properties. Through this approach, this work seeks to establish the fundamental properties that influence conductivity, mechanical integrity, and electrochemical activity of the polymeric materials to suggest design rules for electroactive binders that are compatible with a broad range of electrode materials.