Dean Wheeler and Brian Mazzeo of Brigham Young University (Provo, UT) have developed a new surface probe that can accurately measure electronic conductivity of intact electrodes. Measuring conductivity of intact thin-film electrodes (still attached to current collector) is difficult, and prior methods have not been sufficiently accurate and robust. The new method uses four small parallel lines to contact the surface with controlled applied pressure. The method also allows simultaneous measurement of bulk film conductivity and contact resistance between the film and the current collector.
The probe device is fabricated using semiconductor clean room techniques. A computer model is used to interpret the experimental results and obtain local values of the two properties.
A computer-controlled fixture allows the probe to be scanned across the surface of the electrode sample, allowing a local conductivity map to be created. In effect, “hot” and “cold” conductivity spots can be identified so that electrode process quality can be improved. The technology has been validated with several commercially produced electrodes and is being adopted by A123 to improve their electrode production processes.
|Photograph of fabricated device with inset of the micro-four-line probe region
|Local map of conductivity of cathode film attached to aluminum current collector