Improved impedance spectroscopy technique for status determination of production Li/SO3 batteries

The authors address the development of a technique to provide reliable two-terminal impedance measurements on graduation cells. The technique´s value as a quality control tool and field tester were criteria during its development. Accuracy and measurement time are two areas of concern. An impedance spectroscopy measurement system was set up using a Hewlett Packard HP9836 computer with hard drive and printer, a Schlumberger I286 electrochemical interface and a Schlumberger I250 frequency response analyzer. Since the concentration was on two terminal cells the working electrode of the electrochemical interface was connected to reference electrode 2 and the counter electrode was connected to reference electrode 1. Routine impedance measurements have been made on lithium/sulphur dioxide (Li/SO₂) cells using an equivalent electric circuit approach. The data obtained show that network analysis for production batteries can be achieved quickly and accurately