Electrochromic materials are attractive for applications like smart windows and thermal management which can modulate transmittance from visible to near-infrared wavelengths. Lithium titanate has been proven to be a potential electrochromic cathode material, but its application prospects in the field of smart windows still lack data support. In this work, Li₄Ti₅O₁₂ thin films with high transmittance and good crystallinity were prepared by Sol-Gel spin coating. The electrochromic properties of the films were characterized by different methods. It is found that all Li₄Ti₅O₁₂ thin films are very sensitive to the test conditions, such as scanning rate, displaying excellent dual band modulation property. Also, the thickness has a significant effect on the initial state transmittance, modulation amplitude, response time, voltage window and cycle durability of the Li₄Ti₅O₁₂ thin films. The colored and bleached response time of the 450 nm Li₄Ti₅O₁₂ is 19.1 and 8.9 s, respectively, while the transmittance modulation is 45% in the visible light region (550 nm). The performance of the films have not been significantly degraded after 20000 s continuous cycle. It is worth mentioning that the transmittance modulation in the near infrared band (1000 nm) is as high as 80%, showing excellent energy saving potential. Finally, Glass/FTO/Li₄Ti₅O₁₂/LiNbO₃/NiO_x/ITO, an all-solid-state inorganic electrochromic device with good cycle performance from gray to blue was successfully assembled. Above data demonstrate that lithium titanate is a strong competitive material for the popularization of electrochromic smart window.