Nanomechanical properties of polymer binders for Li-ion batteries probed with colloidal probe atomic force microscopy. (July 2019) - Nguyen, Quang Dang
Abstract: The nanomechanical properties of various polymer binders for lithium-ion batteries were assessed using colloidal probe atomic force microscopy (AFM) in air and in electrolyte. The reduced elastic moduli determined for polyacrylic acid (PAA), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), and polyvinylidene fluoride (PVDF) were 3.3 ± 1.3, 1.1 ± 0.4, 1.4 ± 0.4, 5.0 ± 2.5, and 1.4 ± 0.6 GPa in air, respectively, and 210 ± 70, 220 ± 130, 410 ± 150, 140 ± 50, and 5.4 ± 2.6 MPa after immersion in electrolyte for 14 h. The results suggest that the effect of friction on force-indentation data should be considered, particularly for measurements in air. It was shown that PAA, PAN, PVA, and CMC are more advantageous than PVDF in terms of mechanical properties. Also, PAA and CMC are preferred due to their enhanced adhesion properties resulting from lower surface roughness and greater work of adhesion. The outcomes provide information to help understand the effects of electrolyte on material properties of polymer binders, which is useful to improve the electrochemical stability of the electrode. Also, the approach used in this work may aid in more accurate measurement of mechanical properties using AFM. Highlights: Effect of electrolyte on the surface structures of polymer binders for lithium-ion batteries. Significant decrease in elastic modulus of polymer binders in electrolyte. Determination of the work of adhesion of polymer binders. Effect of friction on force-indentation data of polymer binders in air. Significant decrease in frictional properties of polymer binders in electrolyte.