Consolidating the Vulnerable Interphase of Ni-Rich Layered Cathode by Multifunctional Water-Based Binder

Ni-rich layered oxides hold significant promise as cathodes for lithium-ion batteries. Nevertheless, the susceptibility of their interphase at deep state-of-charge (SoC) imposes substantial limitations on their practical viability. Herein, we propose a water-based composite binder of dextran sulfate sodium-co-poly(acrylic acid) lithium (DSS-co-PAA(Li)) to address this dilemma. Capitalizing on the robust coordination bond interaction between the sulfate acid groups of DSS chains and transition-metal (TM) ion on the surface lattice, this functionally designed binder not only augments the cohesiveness within the electrode architecture but also effectively suppresses the vigorous reaction involving the highly labile Ni4+ and lattice O at the interphase. This attenuation is achieved by mitigating the undesirable phase transition and widening the energy gap between the Ni 3d and O 2p band of NCM811. Consequently, the NCM811 cathode with DSS-co-PAA(Li) binder yields an enhanced initial Coulombic efficiency (ICE) of 93.3% and capacity retention of nearly 90% after 200 cycles.