Self-standing oxygen-deficient α-MoO3-x nanoflake arrays as 3D cathode for advanced all-solid-state thin film lithium batteries

Abstract

Compared with the planar two-dimensional (2D) all-solid-state thin film batteries (TFBs), three-dimensional (3D) all-solid-state TFBs with interdigitated contact between electrode and electrolyte possess great advantage in achieving both high energy and power densities. Herein, we report a facile fabrication of vertically aligned oxygen-deficient α-MoO3-x nanoflake arrays (3D MOx) using metal Mo target by direct current (DC) magnetron sputtering. By utilizing the 3D MOx cathode, amorphous lithium phosphorus oxynitride solid electrolyte, and lithium thin film anode, 3D solid-state TFBs have been successfully fabricated, exhibiting high specific capacity (266 mAh g−1 at 50 mA g−1), good rate performance (110 mAh g−1 at 1000 mA g−1), and excellent cycle performance (92.7% capacity retention after 1000 cycles) in comparison with the 2D TFBs using the planar MOx thin film as cathode. The superior electrochemical performance of the 3D TFBs can be attributed to the 3D architecture of the cathode, maximizing the cathode/electrolyte interface while retaining the short Li+ diffusion length. The charge/discharge measurements of the 3D MOx cathode in liquid electrolyte, however, exhibit fast capacity fading, demonstrating the advantage of using transition metal oxide as cathode in solid-state batteries. Keywords: Thin film batteries, All solid-state Li batteries, MoO3, Nanoflake arrays, 3D cathode