Unraveling New Role of Binder Functional Group as a Probe to Detect Dynamic Lithium-Ion De-Solvation Process toward High Electrode Performances

Binder plays a pivotal role in the development of lithium-ion batteries as it must be used to adhere electrode materials on current collectors tightly to guarantee stability. Then, many binder molecules have been designed to enhance the adhesion capability, and conductivity, and/or form a robust solid electrolyte interphase layer for better performance. However, the binder effect on the lithium-ion (i.e., Li+) de-solvation on the electrode surface has never been reported before. Herein, it is reported that the binder can influence the Li+ (de-)solvation process significantly, where its functional group can serve as a probe to detect the dynamic Li+ (de-)solvation process. It is discovered that different binder functional groups (e.g., *─COO− versus *─F) can affect the Li+-solvent arrangement on the electrode surface, leading to different degrees of side-reactions, rate capabilities, and/or the tolerance against Li+-solvent co-insertion for the graphite anode, such as in the propylene carbonate-based electrolyte. A molecular interfacial model related to the electrolyte component's behaviors and binder functional group is proposed to interpret the varied electrode performance. This discovery opens a new avenue for studying the interactions between the binder and electrolyte solvation structure, in turn helping to understand electrode performances underlying the micro-structures.