UV-Curable Binders for Lithium-Ion Batteries

Polymer binder is one of the essential components of the composite electrodes used in today’s lithium-ion batteries (LIBs). Due to their chemical inertness, binders are less extensively studied than the active electrode materials in LIB research. Nevertheless, the performance of the entire battery relies heavily on the physical and chemical properties of these “inactive” polymer materials. In a typical electrode making process, a high molecular weight polymer (e.g., PVDF) is mixed with the active materials in the presence of a high boiling point solvent (e.g., NMP) to form a homogeneous slurry. The solvent was then removed from the electrode laminate and recovered―a process that requires significant energy input and capital cost. We recently developed a new process that utilizes ultraviolet (UV) curing to fabricate LIB electrodes, with low molecular weight, UV-curable oligomers serving as the binder precursor. Electrodes with excellent mechanical properties can be prepared using this new process. In the present study, electrode laminates of LiNi_1/3Mn_1/3Co_1/3O₂ (NMC) cathode with a polysiloxane acrylate (PSA) oligomer-based binder were prepared and evaluated electrochemically in NMC/Li and NMC/graphite cells. The cycling and C-rate performance of these UV-cured electrodes were comparable to that of conventional PVDF-based electrodes. The main advantage of this new approach is its high production speed with lower energy input and less solvent consumption than in traditional processes. Furthermore, a wide range of functional, reactive oligomers may potentially be utilized as binder precursors in this UV-curing process, allowing for easy tuning of the binder structure to deliver electrodes with desired physical and electrochemical properties.