Effect of the size-selective silver clusters on lithium peroxide morphology in lithium–oxygen batteries

Abstract

Lithium-oxygen batteries have the potential needed for long-range electric vehicles, but the charge and discharge chemistries are complex and not well understood. The active sites on cathode surfaces and their role in electrochemical reactions in aprotic lithium-oxygen cells are difficult to ascertain because the exact nature of the sites is unknown. Here we report the deposition of subnanometre silver clusters of exact size and number of atoms on passivated carbon to study the discharge process in lithium-oxygen cells. The results reveal dramatically different morphologies of the electrochemically grown lithium peroxide dependent on the size of the clusters. This dependence is found to be due to the influence of the cluster size on the formation mechanism, which also affects the charge process. The results of this study suggest that precise control of subnanometre surface structure on cathodes can be used as a means to improve the performance of lithium-oxygen cells.

Realizing the Embedded Growth of Large Li2O2 Aggregations by Matching Different Metal Oxides for High‐Capacity and High‐Rate Lithium Oxygen Batteries

“…Then, the adsorbed LiO 2 * undergoes a second reduction or disproportionation to form Li 2 O 2 as sur‐seeds (“sur‐seeds” represent the seeds formed through surface, Equation (S11) in Figure S8 of the Supporting information) 55. Simultaneously, in the bulk electrolyte, LiO 2sol transforms to Li 2 O 2 through disproportionation (Equation (S12) in Figure S8 of the Supporting information) 12. When Li 2 O 2 cluster reaches a supersaturated state, solid Li 2 O 2 deposits on the electrode surface as sol‐seeds (“sol‐seeds” represent the seeds formed through solution) 6, 19.…”

“…Han and co‐workers reported that Li 2 O 2 with large sheet‐like morphology provided a higher capacity than the small Li 2 O 2 nanoparticles 11. Amine and co‐workers also found that large Li 2 O 2 toroids delivered higher capacity than Li 2 O 2 film 12. Thus, a large size is a desirable feature for Li 2 O 2 in Li‐O 2 batteries.…”

Computational Studies of Solubilities of LiO2and Li2O2in Aprotic Solvents

“…2 A through-solution mechanism was also proposed involving heterogeneous nucleation from a supersaturated solution of LiO 2 . 10 There is other evidence that LiO 2 is soluble in the electrolyte prior to deposition on the surface based on a quartz microbalance study. 14 Results from several research groups suggest that the composition and morphology of the discharge products have a significant effect on charging overpotential and rechargeability of the Li-O 2 battery.…”

“…10,15,16 Therefore, understanding the chemistry and growth mechanism of discharge products in the cell is crucial for improving Li-O 2 battery. The study and modeling of nucleation and crystal growth requires knowledge of bulk solubility.…”

“…14 Results from several research groups suggest that the composition and morphology of the discharge products have a significant effect on charging overpotential and rechargeability of the Li-O 2 battery. 10,15,16 Therefore, understanding the chemistry and growth mechanism of discharge products in the cell is crucial for improving Li-O 2 battery. The study and modeling of nucleation and crystal growth requires knowledge of bulk solubility.…”