A flexible, integrated film battery configuration for ultrafast sodium ion storage

Abstract

Flexible sodium-ion battery (SIB) design is hampered by the incompatible component integration at the device level, especially in consideration of the sluggish Na⁺ diffusion kinetics, complex assembly technology and the electrode pulverization upon mechanical loadings. Herein, we develop a scalable spin-coating approach, through casting the cathode and anode slurries onto the both sides of an AlO_x modified polyethylene (AlO_x-MPE) separator, to construct a layer-stacked thin film battery configuration. The composite anode involves hierarchical structure design by vertically anchoring metallic phase (1T) MoS₂ nanosheets on an interconnected nitrogen-doped carbon framework (namely 1T-MoS₂/NCF). For the cathode part, NASICON-type NaVPO₄F was directly integrated with the AlO_x-MPE separator as the current-collector-free electrode. Upon the precise tuning of the areal capacity ratio of negative to positive electrodes (N/P ratio), the film battery prototype delivers a robust cyclability in the different deformation states as well as a maximized power output of ∼1049 W kg⁻¹. This integrated, thin-film battery configuration demonstrates tremendous potential in future flexible electronics.