Core-Shell Nanorod Arrays of Crystalline/Amorphous TiO2 Constructed by Layer-by-Layer Method for High-Performance Electrochromic Electrodes

In this paper, core-shell nanorod arrays of crystalline/amorphous TiO2 (c/a-TiO2) are demonstrated for the comprehensive enhancement of electrochromic performance. The amorphous TiO2 (a-TiO2) shell was conformally deposited on the surface of single-crystalline TiO2 nanorod arrays (c-TiO2) core via a facile layer-by-layer method, which ensures the high-quality contact between the core and shell. The optimal c/a-TiO2 core-shell structure with 13 nm a-TiO2 layer combines the assets of distinct porous morphology in c-TiO2 and high charge density in a-TiO2, possessing notably larger optical contrast (43%) and higher coloration efficiency (16.2 cm2C−1) than c-TiO2 (18%, 8.8 cm2C−1) at 800 nm. Compared to the pristine c-TiO2, c/a-TiO2 shows lower threshold voltage and faster response speed due to the low energy barrier and rapid ion migration in the a-TiO2 shell during lithium insertion/extraction. Moreover, the c/a-TiO2 nanostructures can offer outstanding cycling stability in different potential windows upon extensive electrochemical cycling.

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