Correlating Catalyst Design and Discharged Product to Reduce Overpotential in Li‐CO₂ Batteries

Abstract

Li‐CO2 batteries with dual efficacy for greenhouse gas CO2 sequestration and high energy output have been regarded as a promising electrochemical energy storage technology. However, battery feasibility has been hampered by inferior electrochemical performance due to large overpotentials and low cyclability primarily caused by the difficult decomposition of ultra‐stable Li2CO3 during charge. The use of cathode catalysts has been highlighted as a promising solution and catalyst properties, as well as the nature of discharge products, are closely correlated with electrochemical performance. Here, the catalyst design strategies that include active site enrichment, electrical transport enhancement, and mass transfer improvement are summarized. Catalyst effects on product decomposition are then subsequently introduced, while product geometry and chemical composition will be explored, with an emphasis on the formation/decomposition of Li2C2O4 instead of Li2CO3. Building on previous research, future directions that facilitate improvements in catalyst design are put forward to reinforce the fundamental development of Li‐CO2 batteries.

Revealing the absence of carbon in aprotic Li–CO2 batteries: a mechanism study toward CO2 reduction under a pure CO2 environment

“…However, we do not exclude the possibility for eqn (12) to occur due to its calculated potential. 32 We consider that eqn (12) is kinetically poor but thermodynamically allowed. Therefore, eqn (12) should not be the dominating reaction in Li–CO 2 batteries.…”

“…The other reason is that the disproportionation reaction of Li 2 C 2 O 4 (eqn (13)) is thermodynamically unfavored since the Gibbs free energy of Li 2 C 2 O 4 is lower than that of CO 2 . 32 The Li 2 CO 2 species is unstable and thus does not benefit the forward reaction thermodynamically. Eqn (13) is also not able to be driven through potential change since it is a pure chemical reaction.…”

Recent Advances in Rechargeable Li–CO2 Batteries

“…During discharge, increasing accumulation of carbonate on the cathode leads to enlarged impedance and high overpotential for decomposition of discharge products. On the contrary, the intermediate, Li 2 C 2 O 4 , is thermally unstable, environmentally friendly, and nonoxidative; it is considered to replace conventional discharge product Li 2 CO 3 …”

“…On the contrary, the intermediate, Li 2 C 2 O 4 , is thermally unstable, environmentally friendly, and nonoxidative; it is considered to replace conventional discharge product Li 2 CO 3 . 52 With the help of a copper complex catalyst, the CO 2 reduction potential is around E(CO 2 (g)/C 2 O 4 2− ) = −0.03 V versus normal hydrogen electrode (NHE), and its oxidation occurs at E(C 2 O 4 2− /CO 2 (g)) = +0.81 V versus NHE, thereby decreasing overpotential and improving energy efficiency. 53 Oxalate salt formed does not react with other components in the system, such as porous carbon and electrolyte, during the charging process.…”

Recent Advances in Synthesis and Applications of Single‐Atom Catalysts for Rechargeable Batteries

“…The metal-CO 2 batteries are of two types based on the electrolytes: non-aqueous and aqueous. For metal-CO 2 batteries, the overall reaction can be described as with typical discharge products of metal carbonates and carbon: for example in LiÀ CO 2 battery, 4Li + 3CO 2 $ 2Li 2 CO 3 + C. [163,164] For the accommodation discharge products (metal carbonates) the cathode should have the large surface area.…”