Toyota researchers develop Li–O2/CO2 battery with very high discharge capacity

Discharge curves of the Li–O2/CO2 batteries with various ratio of CO2 in O2/CO2 mixed gas at 25 °C (current density: 0.2 mA cm-2). Inset shows CO2 ratio dependence on relative capacities as compared with the Li–O2 battery (CO2 0%). Credit: RSC, Takechi et al. Click to enlarge.

Researchers at the Advanced Battery Lab, Toyota Central R&D Laboratories, Inc., have developed a new advanced gas-utilizing battery using a mixture of O₂ and CO₂ and featuring a very high discharge capacity of up to almost three times that of a non-aqueous Li–air (O₂) battery. A paper on their work was published in the Royal Society of Chemistry journal Chemical Communications.

Although the new battery has to be a primary battery (i.e., non-rechargeable) due to the difficulty of electrochemical decomposition of
Li₂CO₃ in the cathode, its very high discharge capacity offers the potential for an alternative energy source with the use of
CO₂-rich gas such as exhaust gas from vehicles or factories, the researchers conclude. Additionally, the basic mechanism of this battery can in
principle be extended to non-lithium systems.

Because of its potential very high energy density, Li–air (O₂) chemistry is one of the promising candidates looked to for providing the significant improvement in batteries required to meet the demands of future vehicles, electronics and other applications. (Earlier post.) The oxygen reduction at the cathode (air electrode) is the most important process in the battery. However, the team of Kensuke Takechi, Tohru Shiga and Takahiko Asaoka explain, the reduced oxygen forms superoxide anion
radical species (O₂^•- in non-aqueous electrolyte. A subsequent reaction between O₂ and Li⁺ leads to final discharge products: Li₂O₂, Li₂O, and/or the decomposed compounds of solvent in the electrolyte