A tailorable and stable lithium-oxygen battery with close to theoretical charge-discharge overpotential

Rechargeable lithium-Oxygen batteries (LOBs) are attractive alternatives to lithium ion batteries due to their high theoretical energy density. However, a large charge-discharge overpotential is usually accompanied, which reduces the energy efficiency and the cycling life. Redox mediators can be introduced in LOBs to reduce the overpotential by effectively decomposing the discharged product, lithium peroxide. Here, we propose 10-ethylphenoxazine as an active additive in the electrolyte to reduce the overpotential to 0.3 V and increase the energy efficiency to 90.4%. The 10-ethylphenoxazine is believed to favor the formation of stable solid electrolyte interface layer on the lithium anode, which benefits the even accumulation of the Li⁺ on the anode surface to prevent the formation of dendrite and improve the stability of Li foil against the attack of soluble species in the electrolyte. In addition, by utilizing a self-supporting graphene aerogel as the cathode, the LOB can be tailored to different sizes and shapes. The tailorable LOB features the low charging-discharging overpotential of 0.3 V and can be stably cycled for 93 times. With its excellent tailorability and stable electrochemical performance, the current LOB holds a promising future to power portable electronic devices with individualized sizes and shapes.