Electrochemical analysis of thin film electrolytes and electrodes for application in rechargeable all solid state lithium microbatteries

• Published in: Electrochimica acta 1997, Vol.42 (20), p.3375-3384
• Main Authors: Birke, P., Weppner, W.
• Format: Article
• Language: English
• Subjects: Applied sciences; coulometric titration; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; impedance analysis; magnetron sputtering; Microbatteries; stoichiometric width
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/S0013-4686(97)00190-4

The suitability of two important electrochemical experimental methods, impedance spectroscopy and coulometric titration of ion insertion and extraction compounds, has been examined for the investigation of thin film electrolytes and electrodes. These solid electrolytes and electrodes are employed in rechargeable lithium microbatteries which may be integrated into microchips and may serve as power sources for microstructures such as micromotors fabricated by the LIGA technique. Thin solid lithium electrolyte films with thicknesses of the order of 1 μm have been rf-sputtered from a 4″ × 1 4″ uniaxially hot pressed LiBO 2 target. The ionic conductivity σ of the resulting thin solid electrolyte films and their activation energy E A have been determined by impedance spectroscopy. The investigation of thin solid electrolyte films required the development of a special experimental setup. Thin electrode films with thicknesses in the range of several hundred nm were sputtered from 4″ × 1 4″ uniaxially hot pressed C and Li 4Fe 0.5− Ti 45.O 11.75 targets. Coulometric titration experiments allow us to conclude that lithium can be reversibly inserted into and extracted from bulk graphite like carbon according to Li + 6 C → LiC 6 at nearly 0 V vs Li while in the case of bulk Li 4Fe 0.5Ti 4.5O 11.75 2.5 Li per formula unit can be reversibly inserted and extracted at 2.3 V vs Li according to the reduction of iron and at 1.55 V vs Li due to the reduction of titanium. In the present paper we present the effect of thin film electrodes on coulometric titration curves.