Density functional investigation of the interaction of H2O with spinel Li1-xMn2O4 surfaces: Implications for aqueous Li-ion batteries

Aqueous lithium-ion batteries are receiving a lot of attention as large-scale energy storage technology owing to their low-cost, environmentally friendly, and safe behavior in comparison to commercial organic Li-ion batteries. However, aqueous batteries suffer fast degradation due to the interaction of water with electrodes. The O loss has often been claimed to deteriorate the electrode materials and the voltage window accessible for the cathode and anode is limited by aqueous electrolyte decomposition through O2 evolution at the cathode and H2 evolution at the anode. In this work, we use density functional theory simulations to unveil the behavior of spinel Li1-xMn2O4 as cathode material for aqueous Li-ion batteries exploring the Li1-xMn2O4 electrode deterioration at the surface level. The surface stability, O vacancy formation, interaction with water, and oxygen evolution reaction have been investigated at different Li concentrations, suggesting that a partially lithiated (011) surface can produce O2 at low overpotential, and (001) termination can favor the presence of O and OOH intermediates anchored to the surface at 1.23 V, without generating O2. Our work reveals the pros and cons of this material as a cathode for aqueous electrolytes and the importance of surface termination.

Automated summary

Aqueous lithium-ion batteries are promising large-scale energy storage technology due to their low-cost and environmentally friendly nature. However, the interaction between water and electrodes leads to fast degradation of the batteries. In this study, density functional theory simulations were used to investigate the behavior of Li1-xMn2O4 as a cathode material for aqueous batteries. The results reveal that a partially lithiated (011) surface can produce O2 at low overpotential, while a (001) termination can facilitate the presence of O and OOH intermediates at 1.23 V without generating O2. The study highlights the pros and cons of using Li1-xMn2O4 as a cathode material and the importance of surface termination in aqueous electrolytes.