Unlocking High‐Voltage Aqueous LiNi 0.5 Mn 1.5 O 4 Cathodes Through Binder‐Collector Interfacial Design

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Lithium‐ion battery performance and sustainability increasingly depend on “inactive” components such as polymer binders and current collectors. Replacing conventional N‐methyl‐2‐pyrrolidone/polyvinylidene fluoride processing with water‐based manufacturing requires binders that combine mechanical cohesion, interfacial stability, and ionic transport, together with current collectors resistant to corrosion and high‐voltage degradation. Here, two aqueous binder formulations—sodium carboxymethyl cellulose (NaCMC) + SX8684(A)‐64 and NaCMC + TRD202A—are investigated in LiNi 0 . 5 Mn 1 . 5 O 4 (LNMO) cathodes cast on bare and carbon‐coated aluminum foils. Spectroscopic and thermogravimetric analyses identify SX8684(A)‐64 as a single‐phase polymethacrylate with minimal swelling (~2%–3% mass uptake), whereas TRD202A exhibits a hybrid acrylic/fluoropolymer architecture, multistage degradation, and pronounced gel‐like swelling (>30%). Morphological analysis shows porosities of 67%–71% and tortuosities of 2.4–3.7, with TRD202A on carbon‐coated aluminum producing the most open and least tortuous architecture. Intermittent current interruption measurements confirm that this configuration provides the lowest resistance, while delivering >100 mAh g −1 at 5 C, >45 mAh g −1 at 15 C, and >80% capacity retention over 100 cycles. These results demonstrate the importance of co‐designing binder chemistry and current‐collector surfaces for scalable, sustainable aqueous LNMO cathodes.