In this talk, the research on nanostructure electrode materials for lithium-air batteries and sodium-ion batteries will be reported.

Rechargeable Li-O₂ batteries are considered to be one of the most promising systems for meeting today’s stringent requirements as the power source for electric vehicles. The theoretical specific energy of the Li-O₂ battery is 3,505 Wh kg^‑1, which is almost ten times higher than that of Li-ion batteries (387 Wh kg^-1).The electrochemical performance of lithium – oxygen (Li-O₂) batteries awaits dramatic improvement in the design of porous cathode electrodeswith sufficient spaces to accommodate the discharge products and discovery of effective cathode catalysts to promote both oxygen reduction reactions and oxygen evolution reactions. I will report the synthesis of porous graphene with different pore size architectures as cathode catalysts for Li-O₂ batteries. Porous graphene materials exhibited significantly higher discharge capacities than that of non-porousgraphene. Furthermore, porous graphene with pore diameter around 250 nm showed higher discharge capacity than the porous graphene with the small pores(about 60 nm), indicating that large macropores can efficientlyincrease the discharge capacity than the smaller pores. Moreover, It was discovered that addition of ruthenium (Ru) nanocrystals to porous graphenepromotes the oxygen evolution reaction. The Ru nanocrystal decorated porous graphene exhibited an excellent catalytic activity ascathodes in Li-O₂ batteries with a high reversible capacity of 17,700mAh g^-1, a low charge/dischargeoverpotential (about 0.355 V), and a long cycle life up to 200 cycles (under thecurtainingcapacity of 1,000 mAh g^-1).^[1]

Sodium-ion batteries are being considered as a promising system for stationary energy storage and conversion, owing to the natural abundance of sodium. It is important to develop new cathode and anode materials with high capacities for sodium-ion batteries. Herein, we report the synthesis of β-MnO₂nanorods with exposed tunnel structures by a hydrothermal method. The as-prepared β-MnO₂nanorods have exposed {111} crystal planes with a high density of (1 × 1) tunnels, which leads to facile sodium ion insertion and extraction. When applied as cathode materials in sodium ion batteries, β-MnO₂nanorodsexhibited good electrochemical performance with a high initial Na-ion storage capacity of 350 mA h g^-1. β-MnO₂nanorods also demonstrated a satisfactory high-rate capability as cathode materials for sodium-ion batteries.^[2]Furthermore, single crystalline bilayered vanadium oxide nanobelts were synthesized by a simple solvothermal method, which exhibited a high capacity of 231.4 mA h g^-1 at the current density of 80 mA g^-1.^[3]For anodes,through in-situ synthesis approach, WS₂@graphene nanocomposites^[4] were synthesized. The WS₂@graphene nanocomposite exhibited a high reversible sodium storage capacity of about 590 mA h g^-1,good cyclability and a satisfactory high rate performance.