A Janus binder favors interfacial protection and mechanical stabilization for Li-rich layered oxide cathodes

Abstract

Ensuring the structural stability of Li-rich layered oxides (LLOs) during charge/discharge processes is critical for achieving high-energy-density Li-ion batteries (LIBs). Herein, carrageenan is introduced as a Janus binder, effectively removing residual alkalis on the surface of LLOs and forming an in situ stable interfacial protective layer to mitigate the dissolution of transition metals. Hydroxyl groups enhance intermolecular hydrogen bonding, provide robust adhesion and boost mechanical stability during long-term cycling. This dual functionality suppresses interfacial side reactions, maintains uniform porosity, and facilitates efficient Li⁺ transport. Remarkably, after 550 cycles at 2 C, the LLO cathodes using the carrageenan binder achieve a capacity retention ratio of 100% and an exceptionally low voltage decay rate of 0.598 mV per cycle, significantly outperforming conventional polyvinylidene fluoride binders, which retain only 45.7% and exhibit a voltage decay rate of 1.597 mV per cycle. This study highlights carrageenan as a Janus binder with the potential to revolutionize high-energy-density LIB technology.