Stable Voltage Cutoff Cycle Cathode with Tunable and Ordered Porous Structure for Li-O₂ Batteries

Ordered porous RuO₂ materials with various pore structure parameters are prepared via a hard-template method and are used as the carbon-free cathodes for Li-O₂ batteries under the voltage cutoff cycle mode. The influences of pore structure parameters of porous RuO₂ on electrochemical performance are systematically studied. Results indicate that specific surface area and pore size determine the specific capacity and round-trip efficiency of Li-O₂ batteries. Too small pores cause pore blockage and hinder the diffusion pathways of Li⁺ and O₂ , thereby causing small specific capacity and high overpotentials. Too large pores weaken the mechanical property of porous RuO₂ , thereby causing the rapid decrease in capacity during electrochemical reaction. The Li-O₂ battery based on the RuO₂ cathode with an average pore size of 16 nm (RuO₂ -16) exhibits a high round-trip efficiency of ≈75.6% and an excellent cycling stability of up to 70 cycles at 100 mA g^-1 with a voltage window of 2.5-4.0 V. The superior performance of RuO₂ -16 can be attributed to its optimal pore structure parameters. Furthermore, the in situ differential electrochemical mass spectrometry test demonstrates that RuO₂ can effectively reduce parasitic reactions compared with carbon materials.