Unlocking High-Voltage Aqueous LiNi_0.5Mn_1.5O₄ Cathodes Through Binder-Collector Interfacial Design

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}O₄ (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.