Combating climate change: Recyclable batteries remove CO₂ from the atmosphere

The urgent need to reduce CO₂ emissions to ensure a sustainable future cannot be emphasised enough. By investing in carbon capture, utilisation and storage (CCUS) technologies, renewable energy and energy efficiency measures, we can significantly reduce emissions. Metal CO₂ batteries (MCBs) offer a unique opportunity as they capture CO₂ and convert it into electrical energy - enabling both energy storage and emissions reduction.

However, MCBs are associated with considerable challenges. The specific reaction requirements of CO₂ (low solubility, high overvoltage) and the formation of by-products present major hurdles and make these batteries largely unexplored to date. The anode material (typically Li, Na, K or Mg) is either scarce, safety-critical or both. The cathode, in turn, must be able to efficiently and selectively catalyse CO₂ reduction to the desired product in order to ensure high capacities, good cycle stability and effective charge/discharge processes.

In contrast to today's rechargeable lithium-ion batteries, whose recyclability is largely unexplored despite their long-standing market presence, the chemistry of such a new and promising battery technology should ideally be fully recyclable. This requires (1) aqueous electrolytes, (2) carbon-based materials from renewable sources as cathodes and (3) transition metals as anodes (e.g. Fe, Zn or Al). Such cathode materials are amorphous but require impurities (non-carbon atoms) to achieve high activity and selectivity.

To achieve this, a deep understanding of which carbon centres catalyse the conversion of transition metal ions into carbonates via CO₂ reduction is necessary. This knowledge is particularly lacking in transition metal CO₂ batteries (TMCBs), which are still in their early stages, as most of the research to date has focussed on lithium chemistry.