Li4Ti5O12 spinel is a popular zero-strain negative insertion material capable of acting as a host for both Li+ and Na+ ions. For efficient electrochemical activity, it is key to produce Li4Ti5O12 spinel in nanoscale morphology with reduced diffusion barrier. Here, we report (ultrasonic) sonochemical synthesis as a novel energy-miser route to achieve spherical 100–150nm spinel particles with restricted annealing for just 2h. Synchrotron diffraction analysis reveals the formation of phase-pure spinel product. The resulting Li4Ti5O12 yields desirable (de)intercalation of Li+ (at 1.55V) and Na+ (at 0.9V) ions with excellent electrochemical properties.