Achieving Low Overpotential Li–O₂ Battery Operations by Li₂O₂ Decomposition through One-Electron Processes

Abstract

As a promising high-capacity energy storage technology, Li-O2 batteries face two critical challenges, poor cycle lifetime and low round-trip efficiencies, both of which are connected to the high overpotentials. The problem is particularly acute during recharge, where the reactions typically follow two-electron mechanisms that are inherently slow. Here we present a strategy that can significantly reduce recharge overpotentials. Our approach seeks to promote Li2O2 decomposition by one-electron processes, and the key is to stabilize the important intermediate of superoxide species. With the introduction of a highly polarizing electrolyte, we observe that recharge processes are successfully switched from a two-electron pathway to a single-electron one. While a similar one-electron route has been reported for the discharge processes, it has rarely been described for recharge except for the initial stage due to the poor mobilities of surface bound superoxide ions (O2(-)), a necessary intermediate for the mechanism. Key to our observation is the solvation of O2(-) by an ionic liquid electrolyte (PYR14TFSI). Recharge overpotentials as low as 0.19 V at 100 mA/g(carbon) are measured.

Electrolytes for Rechargeable Lithium–Air Batteries

“…Meanwhile, a PYR 14 TFSI/TEGDME mixed electrolyte exhibited enhanced kinetics with a low overpotential compared with pure TEGDME electrolyte . Interestingly, a single‐electron mechanism was observed for a mixture of PYR 14 TFSI and DME during the charging process . PYR 14 TFSI stabilized the O 2 − species and promoted the single‐electron reaction, which lowered the overpotential to 0.19 V. Recently, a mixed EMIBF 4 /DMSO (1:3) electrolyte was used in a Li–air battery with an MoS 2 cathode and protected Li anode .…”

New Electrode and Electrolyte Configurations for Lithium‐Oxygen Battery

“…[22][23][24][25] Advantageously,t he structure of ILs can be endlessly modified [26,27] to tune their physicalchemicalp roperties, leading to favorable characteristics such as low vapor pressure, thus, low-flammabilitya nd remarkable thermals tability, high electrochemical stability, andh igh ionic conductivity. [28,29] The use of IL electrolytes in Li/O 2 batteries is favored by al ow OER average potential, [30,31] fast ORR kinetics, [32] good stability against O 2 À C nucleophilic attack, [33] and enhanced ORR/OER reversibility. [34][35][36][37] The choice of ap roperc omposite electrode for supporting the oxygen redox processesi so fk ey importancef or determining the cell performance.…”

A mesoporous tungsten carbide nanostructure as a promising cathode catalyst decreases overpotential in Li–O2 batteries

“…It is known that Li 2 O 2 as discharge product with small size oen exhibits better electrochemical property with low overpotential. 46,47 In previous studies, charge voltage plateaus reduced as the decrease of Li 2 O 2 size, which was attributed to the decrease of polarization and enhancement of oxidation reaction rate of Li 2 O 2 .…”