Small Anatase TiO₂ Nanoparticles Grown On Carbon Nanocages As Anodes For High Performance Sodium And Lithium Ion Batteries

For supporting electric tools,portable devices and automobiles,lithium ion batteries（LIBs）have gradually become one kind of main-stream products in the power source markets.Anode material is not only an indispensable part of batteries,but also have a profound impact on the performance and cost of batteries.Among them,titanium dioxide is regarded as the most potential material to replace graphite-based anodes due to its good stability,low volume expansion（3-4%）,high safety and low cost.However,its poor intrinsic electronic conductivity and slow Li⁺/Na⁺diffusion in TiO₂ limit its practical applications.In this work,Ultra-small（4-15nm）anatase TiO₂ nanoparticles（TiO₂NPs）were successfully deposited on the carbon nanocage（CNC）frameworks（TiO₂/CNCs）as anodes for lithium and sodium ion batteries.Due to the high specific surface area(950 m² g^-1)and mesopore volume(1.6 cm³ g^-1)of CNCs,more sites are available for depositing of TiO₂ on the surface of the CNC framework.Thus,TiO₂ NPs were prepared with ultra-small sizes（average diameter of～7 nm）,leading to high specific surface area(300 m² g^-1)and mesopore volume(0.4 cm³ g^-1)of TiO₂/CNCs,which enhanced storage of Li⁺/Na⁺and shortened the diffusion path of Li⁺/Na⁺towards high performance anodes for LIBs(471 m Ah g^-1 at current density of0.1 A g^-1;180 m Ah g^-1 at 3 A g^-1)and SIBs(250 m Ah g^-1 at current density of 0.1 A g^-1;115m Ah g^-1 at 3 A g^-1)with high cycle stability(capacity retention:93%and 91%for LIBs and SIBs,respectively,after 1500 cycles at current density of 5 A g^-1).Because of novel nanostructure,such TiO₂/CNCs could be extended to the fabrication of various types of functional nanomaterials for wide applications in energy storage,fuel cells,catalysis or supercapacitors.