Conjugated polymers as promising electrode materials for lithium-ion batteries

Abstract

After the competition of almost half a century, lithium-ion battery (LIB) has become the most important energy storage device in modern society and industry. However, with the still fast-growing demand of batteries with different requirements, such as energy storage device in electric vehicles, traditional inorganic LIBs have exposed their drawbacks, many of the components are toxic and hard to degrade/recycle, lack of the raw resources and high cost in manufacturing process. LIBs with organic materials as electrodes has attracted more interest from researchers under this background. Organic materials as electrode materials have great flexibility in design, because of their rich chemistry in carbon backbones as well as eco-friendly for environmental protection and potentially cost-effective as many organic compounds can be obtained from recycled products and biomass

The main objective of this project is to synthesize novel conjugated polymers as high-performance electrode materials for lithium-ion batteries. All experiments focus on the design, synthesis, characterization, and validation of the electrochemical mechanisms and performance of these materials. Various methods are employed to enhance the battery performance of these materials and to identify the reasons behind their high performance, ultimately leading to new strategies for seeking high-performance electrode materials.

In detail, a brief introduction is provided followed by hypothesis, scope, overview and outcomes of the research. Then, the history of organic materials as electrode materials for rechargeable batteries is reviewed, with a focus on the mechanisms and current research status of conjugated molecules and polymers as electrode materials, highlighting them as the most promising electrodes candidates. Subsequently, various characterization and electrochemical testing methods are introduced in the following chapter to obtain information about the morphology, chemical structure, and electrochemical performance of these polymers as electrode materials, thereby understanding their working principles and enhance performance for further study.

In the first part of the study, two ion-in-conjugation polymers were successfully synthesized, and both demonstrate good performance as cathode materials for LIBs. In the second part of the study, a polymer with a 2D structure was synthesized, and its unique laddered structure greatly enhance the stability as electrode material. Additionally, its distinctive bifunctionality enables it to be applied as both electrodes in LIBs, which exhibits excellent performance in all-plastic battery. Finally, a summary is provided to discuss the results of these polymers and recommendations are proposed for further study and unresolved challenges.