Enhanced Cathode–Electrolyte Interfaces Formation via Lithium-Phytate Chelation for an Aqueous-Processed LiNi_0.7Mn_0.25Al_0.05O₂ High-Voltage Cathode

Emerging nickel-rich, cobalt-free LiNi0.7Mn0.25Al0.05O2 (LNMA7255) high-voltage layered oxide cathodes offer significant advantages in reducing costs and enhancing energy density of lithium batteries. However, their vulnerable interface at deep state-of-charge (SoC) is prone to severe capacity fading and structural instability, especially when processed in aqueous environments. We introduce lithium phytate (LP) as an eco-friendly, aqueous-based slurry additive combined with sodium carboxymethyl-cellulose and styrene-butadiene rubber (CMC-SBR) binders to address these challenges. By chelating with transition-metal (TM) ions on the surface lattice, this LP binder not only enhances the resilience of the cathode–electrolyte interface (CEI) formation, but also effectively suppresses parasitic interfacial side reactions and inhibits the detrimental H2–H3 phase-transition at 4.6 V. Herein, a comprehensive analysis using X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and high-resolution-transmission electron microscopy (HR-TEM) was employed as critical surface-sensitive tools for examining CEI formation and performing depth profiling of CEI species on the LNMA7255 cathode fabricated with different binder engineering, before and after cycling. In particular, the electrochemical lithium battery performance of an aqueous-processed LP-chelated LNMA7255 electrode delivers an impressive initial capacity of 213 mAh g–1 at 0.2 C, along with a remarkable capacity retention of 97% after 200 cycles. The enhanced cycling performance is attributed to a highly stabilized CEI formation that suppresses the electrode corrosion and lattice reconstruction. Based on these findings, rational guidelines are provided for the interface design and selection of high-voltage Co-free NMA cathode binders.