Ellipsoid-like Li4Ti5O12–TiO2 composites constructed by nanocrystals for lithium ion batteries

Abstract

Porous ellipsoid-like Li₄Ti₅O₁₂–TiO₂ composites with a unique micro/nano structure have been successfully fabricated via a facile sol–gel route followed by calcination. The porous ellipsoid-like particles with micro/nano structures are formed through phase-separation induced by poly(ethylene oxide) (PEO), which are constructed using numerous nanocrystals with sizes of about 50–100 nm consisting of lithium titanate, anatase and rutile. The resultant Li₄Ti₅O₁₂–TiO₂ composite shows a superior rate capability and cycling stability in comparison with pure Li₄Ti₅O₁₂, which delivers a reversible capacity over 92 mA h g⁻¹ at 10C after 100 cycles as well as an acceptable rate capacity of 89 mA h g⁻¹ at a high rate of 30C. The excellent electrochemical performance of the Li₄Ti₅O₁₂–TiO₂ composite is attributed to the unique micro/nano and multiphase structures. The micro/nano structure enhances the structure stability and shortens the diffusion distance for both electron and lithium ions. Moreover, the abundant phase interfaces and grain boundaries store extra lithium ions and guarantee rapid lithium insertion/extraction kinetics.