Laser Surface Structuring of Polyelectrolyte Complex Cathodes for Zinc‐Ion Batteries

ABSTRACT Aqueous zinc‐ion batteries (AZIBs) are attractive post‐lithium energy storage systems; however, their performance is often limited by slow cathode kinetics and inefficient Zn 2+ transport at the electrode‐electrolyte interface. Herein, we report a continuous‐wave laser surface modification strategy for precisely tailoring the surface architecture of composite polyelectrolyte complex (CPEC) cathodes composed of MnO 2 and carbon black. Leveraging the digitally controlled and highly tunable nature of laser processing, surface modification was optimized through laser power and scanning parameters, allowing for uniform surface structuring without altering the bulk composition. Laser treatment under a wet environment produced controlled surface roughening with negligible mass loss (< 3%), thereby preserving the dense, ion‐conducting CPEC framework. Surface analyses revealed enhanced exposure of electrochemically active MnO 2 domains and a 50%–54% reduction in water contact angle, indicating improved interfacial wettability. Electrochemical testing demonstrated 67% and 58% increases in current and power densities for stoichiometric (1:1) CPEC, while non‐stoichiometric CPEC (1:2) showed the highest laser‐induced enhancement (40%–50%), with nearly unchanged specific capacity at 1 mA cm −2 . These results establish laser surface engineering as a simple, controllable, and chemistry‐neutral approach for optimizing polymer‐based cathodes in AZIBs.