Does Electrode Calendering Always Help? Tradeoffs in V2O5 Cathodes for Sodium-Ion Batteries

Abstract Vanadium pentoxide (V2O5) is a promising cathode material for sodium-ion batteries due to its high capacity and layered structure that accommodates Na+ intercalation. Despite this potential, how electrode processing, particularly calendering, affects its electrochemical performance remains insufficiently understood. Here, we systematically investigate V2O5 cathodes with and without calendering using complementary electrochemical and structural characterization. Calendering improved electrode compactness, reduced microcracking, and lowered ohmic resistance, collectively yielding higher initial specific capacity. It slightly improves performance from the second cycle onward but does not substantially mitigate the first-cycle capacity loss. Although calendering reduces charge-transfer resistance upon cycling, calendering exceeding an optimal pressure restricts Na+ transport, reflecting the tradeoff between densification and ion diffusion. Overall, our results demonstrate that calendering is not universally beneficial: while it enhances mechanical integrity and initial electrochemical performance, excessive densification raises interfacial resistance and compromises ionic transport. Careful optimization of calendering conditions is therefore essential for unlocking the full potential of next-generation sodium-ion batteries.