Study on Electrochemical Mechanism Simulation and Characterization of Lithium Batteries

The rapid development of large-scale energy storage applications such as electric vehicles puts higher demands on the performance of lithium-ion batteries . The development of high performance battery systems requires optimization of each battery component, including electrode materials, electrolytes, and binders. The binder system of a conventional lithium ion battery consists of a mixture of an insulating polymer and a conductive additive. When preparing battery electrodes, the conductive phase and active material are randomly distributed, often resulting in poor electron and ion transport capabilities. When high capacity electrode materials are used, the high stresses generated by electrochemical reactions can disrupt the mechanical integrity of conventional binder systems, resulting in reduced cycle life of the battery. Therefore, it is critical to design a new binder system that provides a stable, low-resistance, continuous internal path to connect all areas of the electrode.

Recently, he was invited to the famous journal of the American Chemical Society (ACS), Accounts of Chemical Research, Professor Yu Guihua (corresponding author) and Dr. Shi Wei of the University of Texas at Austin. Dr. Zhou Xingyi is based on the recently published new lithium ion battery. The synthesis, application and mechanism research of the binder system systematically summarizes the latest developments in the material and structural design of high-performance binder systems, analyzes the simulation and characterization methods for studying the electrochemical mechanism of binders, and finally looks into the future. The development of multifunctional battery adhesives (Figure 1).

Fig.1 Material and structure design and mechanism study of new lithium ion battery binder

The article first introduces the application of insulating polymers with rich carboxyl groups in battery binders. They provide a strong bond with the active material, allowing the electrode material to remain structurally stable during the electrochemical reaction, resulting in high capacity and excellent cycle performance (Figure 2a). However, insulating polymer based binder systems still require the use of conductive additives, which hinders further increases in battery energy density. In contrast, multi-functional binders based on conductive polymers can be used for both adhesion and conduction, and have been extensively studied.

In a series of studies, the researchers introduced the molecular structure of the conductive polymer by introducing different functional groups on the main chain, which improved the mechanical and swelling properties of the binder without affecting the electrical properties (Fig. 2b). ). Yu Guihua's research group developed a conductive polymer gel with a three-dimensional network structure by regulating the microstructure of conductive polymers and applied it to battery binders (Fig. 2c). The structure and properties of the conductive polymer gel are highly adjustable, and the three-dimensional structure not only promotes the transport of electrons and ions in the electrode, but also improves the stability of the electrode and improves the uniform distribution of the active particles.

The article continues to introduce the work of the binder mechanism research, including the simulation calculation and the application of advanced characterization methods, and summarizes the design guidelines for the new binder system in the future.

Figure 2 (a) Application of an insulating polymer with a rich carboxyl group in a battery binder. (b) Modulation of the molecular structure of the conductive polymer binder by introducing different functional groups on the main chain. (c) Synthesis of conductive polymer gels and their application in a new generation of battery binders

The article also looks into the future synthesis and application of multi-functional battery binders. Through molecular design and synthesis of composite materials, more functions can be introduced into battery binder systems, including self-healing properties, flexibility, tensile properties, and environmental responsiveness. It has been proven that adhesives with self-healing properties can effectively improve battery life. Recently, Yu Guihua's research group has developed a composite gel material with both conductive and self-healing properties, which can be used as a future multi-functional battery binder to improve battery performance (Figure 3). Similarly, other new binders with excellent mechanical properties and environmental responsiveness can be used to develop flexible batteries and self-regulating safety batteries.

Figure 3 Synthesis of adhesive with self-healing properties and prospective applications in battery binders

Related work was published in the form of monographs at the Accounts of Chemical Research.