Enhancing the lithium storage capability of TiO2 thin film for all-solid-state microbatteries via amorphous-crystalline heterostructure design

Abstract

TiO2 is regarded as a promising anode for all-solid-state thin film lithium-ion microbatteries due to its high temperature tolerance, good chemical stability, and desirable structural stability. However, its application in thin film batteries has been plagued by its low actual capacity and poor rate capability. Herein, a TiO2 thin film with a unique amorphous-crystalline heterostructure (AC-TO) is prepared by magnetron sputtering at room temperature. The heterostructure design of AC-TO not only takes advantage of faster Li+ diffusion of an amorphous phase and higher electric conductivity of a crystalline phase but also reaps the benefit of fast ion transport, fast electron transfer, and additional lithium storage at the hetero-interfaces, resulting in boosted lithium storage performance. When tested in all-solid-state thin film lithium batteries, the AC-TO based device exhibits an obviously higher reversible specific capacity (204 at 50 mA g−1) than the amorphous TiO2 based device (103 mAh g−1) and the crystalline anatase based device (147 mAh g−1), as well as good rate capability (73 at 1600 mA g−1) and excellent cycling stability (nearly no capacity loss after 400 cycles). This work provides an instructive structural regulation strategy for developing advanced thin-film electrodes for all-solid-state microbatteries.