Binder Chemistry: Unlocking scalable high-areal-capacity Li battery cathodes

Key Words: Li batteries, Cathodes, High areal capacity, Binders, Bottlebrush polymers

Achieving high-energy-density Li batteries is of paramount importance in expediting the advent of smart energy era. Major research approaches implemented to achieve this goal have focused on the synthesis and modification of electrode active materials and electrolytes. In addition to these materials-based works, much attention should be devoted to designing high-areal-capacity (leading to high-energy-density) electrode sheets as a facile architectural strategy. To achieve the high areal-capacity electrode sheets (= areal-mass-loading × specific capacity of electrode active materials), the areal-mass-loading should be maximized while stably maintaining the specific capacity of electrode active materials. A formidable challenge facing the high-areal-mass-loading electrode sheets is the inhomogeneous redox reaction in their through-thickness direction.

Here, we present new binder approaches beyond a conventional PVdF binder, which include the amphiphilic bottlebrush polymeric binders and cationic polymeric binders. Particularly, the cationic polymer binders suppressed the solvent-drying-induced crack evolution of electrodes and improved the dispersion state of electrode components owing to its surface charge-driven electrostatic repulsion and mechanical toughness, thus enabling the fabrication of high-areal-capacity cathodes with 5 times the capacity of a conventional PVdF-based cathode. This new binder chemistry strategy proposed herein opens a new route toward scalable high-mass-loading electrodes with redox homogeneity, which lie far beyond those achievable with previously reported electrode sheets based on conventional neutral binders.

Image

Fig. (a) Schematic depicting the structural superiority of the BBP binder over the PVdF binder [ref.1]. (b) Specific capacity of the c-IPN cathode (vs. control cathode) as a function of mass loading [ref.2].

Reference

1. S. Y. Lee et al., Amphiphilic bottlebrush polymeric binders for high-mass-loading cathodes in lithium-ion batteries Advanced Energy Materials (2021) 2102109.
2. S. Y. Lee et al., Regulating electrostatic phenomena by cationic polymer binder for scalable high-areal-capacity Li battery electrodes Nature Communications 14 (2023) 5721.