Electrochemically dynamic environment in lithium-ion batteries and water electrolysis often makes phase transition of electrode unpredictable. Lithium-ion insertion kinetics fundamentally hinges upon phase transformation behavior during (dis)charging at high cycling rates. Ni-rich NCM, one of the most widely investigated cathodes, shows strong phase-separating behavior as cycling rate increases. However, the origin of phase separation remains unclear and inconsistent, complicating quantitative analysis. On the other hands, surface reconstruction of electrocatalysts during water electrolysis determines the active species and the catalytic performance. However, rationally modulating the dynamic surface restructuring and generating active surface species remain tremendous challenges. In the first part of my talk, I will present how we can redirect the detrimental two-phase behavior to single-phase at a fast cycling rate during lithium-ion battery operation. [1] Electrochemically manipulating the lithium-ion distribution within the NCM particles could effectively induce facile lithium diffusion and solid-solution phase behavior. The second half of my talk will present a novel cationic redox-tuning method to redirect the in-situ surface reconstruction of a transition-metal-oxide electrocatalyst for the oxygen evolution reaction (OER). [2] Cl-doping lowered the potential to trigger in situ cobalt oxidation and lithium leaching, which induced the surface of LiCoO1.8Cl0.2 to transform into a self-terminated amorphous (oxy)hydroxide phase during the OER. We further demonstrated that surface-restructured LiCoO1.8Cl0.2 outperformed many state-of-the-art OER catalysts and demonstrated remarkable stability.

Manipulating phase transformation during electrochemical reactions: Lithium-ion batteries and battery-inspired electrocatalysis

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