Li₂MoO₄ Tailored Anion-enhanced Solvation Sheath Layer Promotes Solution-phase Mediated Li-O₂ Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• High overpotential in Lithium-Oxygen Batteries (LOBs) is caused by slow charge transfer kinetics.
• Lithium bromide (LiBr) redox mediators reduce overpotential but cause anode corrosion and shuttle effects, lowering efficiency.
• Existing redox mediators in LOBs face challenges with stability and anode compatibility.

Purpose of the Study:

• To develop a stable and efficient redox mediator system for Lithium-Oxygen Batteries (LOBs).
• To mitigate the issues of anode corrosion and shuttle effects associated with traditional LiBr mediators.
• To enhance the cycling stability and energy efficiency of LOBs through electrolyte modification.

Main Methods:

• Introduction of lithium molybdate (Li2MoO4) into a LiBr-containing electrolyte for LOBs.
• Analysis of the anion-enhanced Li+ solvation sheath layer and solid electrolyte interphases (SEI) formation on the Li anode.
• Evaluation of Li2MoO4's adsorption capabilities for oxygen, lithium peroxide, and bromine species.
• Testing of LOB performance, including cycling stability and energy efficiency.

Main Results:

• Formation of a robust, anion-derived SEI on the Li anode, effectively preventing corrosion from soluble bromine species and reactive oxygen species.
• Li2MoO4 demonstrated strong adsorption of O2/LiO2 and Br-related species, promoting solution-phase Li2O2 growth/decomposition and inhibiting shuttle effects.
• LOBs with the modified electrolyte achieved remarkable cycling stability of 415 cycles and a high energy efficiency of 86.2%.

Conclusions:

• The addition of Li2MoO4 to LiBr-based electrolytes significantly enhances the stability and efficiency of Lithium-Oxygen Batteries.
• The robust SEI layer and improved adsorption properties are key to mitigating traditional mediator-related drawbacks.
• This approach offers a promising pathway for the practical application and sustainable development of advanced LOB systems.