Sodium Phytate\nCross-Linked Polyacrylic Acid as Multifunctional\nAqueous Binder Stabilizes LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub> to 4.6 V

Nickel-rich layered oxides are promising candidates for\nnext-generation\nlithium-ion batteries. However, nickel-rich cathodes largely suffer\nfrom poor cyclability due to interfacial instability and intergranular\ncracking, particularly under high voltages and elevated temperatures.\nHerein, a multifunctional binder (PAA–PN) derived from the\ncross-linking of sodium phytate (PN) and poly(acrylic acid) (PAA)\nwas designed to stabilize the LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub> (NCM811) working under a cutoff voltage of\n4.6 V. The PAA–PN promotes the formation of dual protective\nlayers, consisting of an outer stable cathode electrolyte interface\nand an inner thin rock-salt phase on the NCM811 surface, effectively\nmitigating electrolyte decomposition, transition-metal dissolution,\nand phase-fatigue issues. Additionally, the robust elastic PAA–PN\ncross-linking network and chelation of PAA–PN with the NCM811\nsurface effectively inhibit intergranular cracking. Benefiting from\nthese multifunctional advantages, NCM811 cathodes with PAA–PN\nbinder achieve capacity retention of 95.1% (25 °C) and 84.7%\n(45 °C) after 100 cycles at 4.6 V, respectively.