Material and structural design of a new binder for high energy and high power lithium ion batteries

The rapid growth of large-scale energy storage systems, such as electric vehicles, has significantly increased the demand for high-performance lithium-ion batteries. To meet these demands, it is essential to optimize every component of the battery, including electrode materials, electrolytes, and binders. Conventional lithium-ion battery binders typically consist of an insulating polymer combined with a conductive additive. However, this random distribution of conductive particles and active materials often leads to poor electron and ion transport, limiting battery performance. Moreover, when high-capacity materials are used, the mechanical stresses from electrochemical reactions can compromise the stability of the binder system, reducing the battery’s cycle life. Therefore, developing a new binder system that ensures stable, low-resistance, and continuous pathways across the entire electrode is crucial.

Recently, Professor Yu Guihua (corresponding author) and Dr. Shi Wei from the University of Texas at Austin were invited to contribute to the prestigious journal *Accounts of Chemical Research*, published by the American Chemical Society. Based on their recent work on the synthesis, application, and mechanism of advanced binder systems for lithium-ion batteries, they provided a comprehensive review of the latest developments in material and structural design. The article also discusses simulation techniques and advanced characterization methods for studying binder behavior, offering insights into the future of multifunctional battery adhesives (Figure 1).

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

The article begins by discussing the use of insulating polymers rich in carboxyl groups as effective binders. These polymers offer strong bonding with active materials, maintaining structural stability during electrochemical reactions, which results in high capacity and excellent cycle performance (Figure 2a). However, traditional insulating polymer-based binders still require conductive additives, which limits further improvements in energy density. In contrast, conductive polymer-based binders serve dual purposes—adhesion and conductivity—and have been widely explored for next-generation batteries.

In various studies, researchers have modified the molecular structure of conductive polymers by introducing different functional groups, enhancing mechanical and swelling properties without compromising electrical performance (Figure 2b). Professor Yu's group developed a three-dimensional conductive polymer gel by adjusting the microstructure of the polymer, which was then applied as a battery binder (Figure 2c). This flexible structure not only improves electron and ion transport but also enhances electrode stability and ensures more uniform distribution of active particles.

The paper further explores the mechanisms behind these binder systems, incorporating computational simulations and advanced characterization techniques. It outlines key design principles for future binder development, emphasizing the importance of both functionality and adaptability.

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

Looking ahead, the article highlights the potential of multifunctional battery binders. By integrating molecular design and composite material synthesis, binders can now possess additional functions such as self-healing, flexibility, and environmental responsiveness. Self-healing binders have already shown promise in extending battery life. For instance, Professor Yu’s team recently developed a conductive and self-healing composite gel, which could serve as a next-generation binder to enhance battery performance (Figure 3). Similarly, other advanced binders with improved mechanical and environmental properties are being explored for flexible and smart safety batteries.

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