Effect of polyacrylic binder solution pH on silicon electrode performance

Poly (acrylic acid) (PAA) and its analogue poly (ethylene-alt-maleic acid) (PEaMAc) are evaluated as a binder for silicon anodes. The effect of binder solution pH on slurry processability and electrochemical performance is evaluated. Rheological measurements indicate stronger binder–Si interactions at low pH, resulting in fewer cracks in the electrode and, consequently, higher electronic conductivity within the electrode. Thermogravimetric analysis evidences increasing active material oxidation with increasing pH. Electrochemical data further confirm enhanced silicon oxidation and highlight the electrochemical inactivity of SiO 2 . Unwanted oxidation was identified as a major factor responsible for the reduced specific capacity of the cell. As a result, both binders perform best at pH 5, where silicon oxidation is minimized. At this pH, Si||Li cells employing PEaMAc deliver average capacities of 2585 mAh g −1 at C/10 and 1012 mAh g −1 at 3C, outperforming PAA (2442 mAh g −1 at C/10 and 755 mAh g −1 at 3C). The superior performance of PEaMAc was attributed to an improved Li + transport along its polymeric backbone. Overall, low pH favors strong binder–Si interactions yielding high quality electrodes. It also prevents unwanted Si oxidation, which strongly affects cell performance. Finally, PEaMAc is identified as a promising alternative to PAA. • PAA and PEaMAc evaluated as binders for silicon anodes. • Effect of slurry pH: high pH drives Si oxidation, reducing cell capacity. • Both binders perform best after processing at pH 5. • PEaMAc delivers better performance than PAA. • PEaMAc's enables faster Li + transport than PAA.