Nanostructured all-solid-state supercapacitor based on Li1.4Al0.4Ti1.6(PO4)3 ceramic electrolyte

Kurzfassung

Lithium aluminum titanium phosphate (LATP) is a NASION-type lithium-ion conductor, which belongs to one of the most promising solid electrolytes. High ionic conductivity at ambient temperatures and sufficiently high electrochemical stability are outstanding parameters compared to well established types of solid electrolytes [1]. These features make LATP very useful in solid state batteries and various sensors. Moreover, a novel application has been identified recently [2] employing LATP as electrolyte for manufacturing of all-solid-state supercapacitors. Advantages of solid electrolyte supercapacitors include the following: they prevent problems related to electrolyte leakage; they are non-flammable, typically enable a very long shelf life and can operate in a wide temperature range (no electrolyte freezing or boiling occur). In the present research, Li1.4Al0.4Ti1.6(PO4)3 has been synthesized by sol-gel process and used as both separator and ion conductor. Three device architectures have been examined including two with nanostructured electrodes which incorporate single-wall carbon nanotubes (SWCNTs). Herein, the SWCNTs are mixed with LATP by using ultrasonic and ball milling processes. The scanning electron microscope images reveal a more homogeneous SWCNT/LATP composite acquired by ball milling than ultrasonication, which ensures that the individual CNTs are distributed uniformly throughout the LATP and well-separated from each other [3]. Finally the solid state supercapacitors are sintered at a temperature of 750°C under N2 atmosphere. Cyclic voltammetry and electrochemical impedance spectroscopy demonstrate that these devices develop reversible double layer capacitance. The maximum capacitance of 329.5mF/g is measured by using a device of nanostructured electrodes prepared form the ball milling mixing procedure. . Explanations for the improved conductivity when using SWCNTs for the electrode layers are given from electrochemical impedance spectroscopy.