This article offers insight into the role of binders in the overall performance of a dual-ion battery (DIB). Replacing sodium carboxymethyl cellulose (CMC) with poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) enhances the interfacial stability of a graphite positive electrode in a DIB. Electrochemical testing combined with X-ray photoelectron spectroscopy (XPS) and operando pressure measurements highlight that PVdF-HFP suppresses parasitic reactions at the cathode-electrolyte interface (CEI), in sharp contrast with CMC. However, CMC causes less interfacial resistance and is hence beneficial in terms of rate capability.