Conventional catalyst designs have largely focused on thermodynamic properties, such as adsorption energy, to optimize catalytic activity. Now, however, a research team from the Institute of Metal Research of the Chinese Academy of Sciences has challenged the conventional thermodynamics-based framework for catalyst design in lithium batteries.
The team, led by Prof. LI Feng, Prof. SUN Zhenhua, and CAS Member CHENG Huiming, proposed a new principle for electrochemical systems that focuses on the declining efficiency of solid-phase electron transport, opening new avenues for electrocatalyst design.
The study was published in Nature Catalysis on April 15.
The practical deployment of lithium–sulfur and lithium–oxygen batteries has been limited—despite their high theoretical energy densities—by the sluggish and incomplete conversion of insulating solid intermediates such as Li2S2 and Li2O2. Unlike gas- or liquid-phase reactions, these solid intermediates continuously deposit on the electrode/catalyst surface during battery cycling, blocking electron and ion transport pathways and leading to premature reaction termination.
To address this limitation, the researchers performed large-scale density functional theory calculations on 351 dual-atom catalysts. Their results revealed that during the initial reaction stage, thermodynamic energy barriers dominated the nucleation kinetics of Li2S2. However, as insulating solid intermediates accumulated, electron transport rapidly became the rate-determining step.
According to the study, the proportion of electrons near the Fermi level showed a much stronger correlation with catalytic activity than thermodynamic energy barriers during the mid-to-late stages of solid-phase conversion.
Based on this insight, the researchers designed a homonuclear cobalt–cobalt dual-atom catalyst known as DA-CoCo. This catalyst significantly enhances charge transport in solid intermediates through strong orbital coupling, effectively extending catalytic activity from the passivated catalyst surface to the intermediate surface and enabling efficient ion and electron transport.
Under practical conditions, an ampere-hour-scale lithium–sulfur pouch cell incorporating DA-CoCo achieved a specific energy of 459 Wh kg-1, validating the new design principle in practical complex systems.
This work extends the fundamental understanding of rate-determining solid-phase reactions in redox chemistry while pointing to new approaches for the design of electrocatalysts for use in energy storage systems.
