The promise of eco-friendly batteries

26 October 2022

Unconventional phase nanostructures may signal a breakthrough for the new generation of meta-gas batteries

The metal-carbon dioxide battery is a promising energy conversion and storage technology that works by capturing and recycling carbon dioxide (CO2). The major drawback to these environmentally friendly batteries has been their limited energy efficiency. Co-led by the City University of Hong Kong, a research team discovered a way to overcome this problem by introducing an unconventional phase nanomaterial as a catalyst, improving battery energy efficiency up to 83.8%. The study reveals a novel design of catalysts for the new generation of meta-gas batteries that can contribute to carbon neutral goals.

A promising energy storage technology, metal-CO2 batteries offers durable electricity for electronics, and enables CO2 fixation without extra energy consumption from an external circuit to convert CO2 greenhouse gas emissions into value-added products. In particular, the lithium-carbon dioxide battery has high theoretical energy density, making it a promising candidate for next-generation high-performance energy conversion and storage technology. However, metal-CO2 batteries suffer from sluggish reaction kinetics. This causes large over-potential, low energy efficiency, poor reversibility, and limited cycling stability.

Schematic illustration of the aprotic Li-CO2 battery.

“Researchers commonly consider morphology, size, constituents and distribution of metal-based components in composite cathode catalysts to be the main concerns that lead to differences in battery performance,” said Dr Fan Zhanxi, Assistant Professor in the Department of Chemistry at CityU, and one of the leaders of the study. “But we found preparing novel catalysts with unconventional phases to be a feasible and promising strategy to boost the energy efficiency and performance of metal-gas batteries, especially since traditional modification strategies for catalysts have encountered long-term technical hurdles.”

Fan and his team selected suitable elements to construct their unconventional phases and studied the effect of the crystal phase of catalysts on the reaction kinetics of aprotic metal-gas electrochemistry. The team synthesized iridium nanostructures with an unconventional 4H/face-centred cubic heterophase by controlling the growth kinetics of internal resistance on gold templates. In their experiments, the catalyst with the heterophase demonstrated a lower charge plateau and higher energy efficiency up to 83.8% during cycling in aprotic Li-CO2 batteries compared with other metal-based catalysts.

“This study reveals the great potential of phase engineering of catalysts in metal-gas electrochemistry. It opens up a new direction to design catalysts for developing sustainable electrochemical energy conversion and storage systems,” concluded Fan.

The findings were recently published in the scientific journal The Proceedings of the National Academy of Sciences