Tunable and Well-Defined Bimodal Porous Model Electrodes for Revealing Multiscale Structural Effects in the Nonaqueous Li-O2 Electrode Process

Porous architecture is key in the nonaqueous lithium-oxygen (Li-O-2) electrode process, which is attracting huge interest because of its application in reversible energy storage with high theoretical energy density. However, it is still challenging to understand the optimal porous structure to obtain high reversibility of the reaction. One main reason is because of instability and undefined porous structures of standard electrodes consisting of carbonaceous materials, and this issue hinders from unveiling the fundamental mechanism in the complicated electrode process. Here, we developed a new synthetic strategy to design monolithic electrodes of pure metallic nickel with controlled bimodal porous structures. The present work aims to investigate the fundamental effects of the bimodal macroporous structure in the Li-O-2 electrode process under carbon-/binder-free stable model electrodes. As the result, we found that, depending on the multiscale structural configurations, the bimodal macroporous structure gave significant influences to key properties, such as the efficiency of redox-mediators, discharge overpotential, and cycling life. This work indicates that the rational design of stable and conductive porous materials is one of the promising approaches to investigate highly complicated electrochemical reactions in porous electrodes and suggest new guidelines for further development of hierarchically structured electrodes toward advanced electrochemical systems.

Automated summary

The study shows that the bimodal macroporous structure significantly influences key properties of the Li-O-2 electrode process, such as the efficiency of redox-mediators, discharge overpotential, and cycling life. Rational design of stable and conductive porous materials is promising for investigating highly complicated electrochemical reactions in porous electrodes.