Impedance Spectroscopy of Industrial Batteries

The successful application of the Impedance Spectroscopy for measurement and quality control of batteries should obey a number of specific requirements, correspondent to the nature of the batteries as objects under investigation. Batteries are nonlinear and non-stationary large statistical systems with distributed parameters in macro- and micro-scale. Processes of charge and mass-transfer take place in their electrodes, changing the chemistry and the habitus of the active electrode materials.  Starting with the very first successful measurement of a small Lead-acid battery in 1976 [1], we developed a set of complementary techniques providing for reliable measurements of battery impedances, data handling and analysis. The techniques for inductive errors evaluation and correction, for the 4-Dimentional data treatment [2] of the evolving battery State of Charge will be discussed in details. Special attention will be given to the interpretation of the battery impedance as a property of a fuzzy system with un-known parameters distribution. The Differential Impedance Analysis which solves this problem and the related Spectral Transforms are powerful tools for batteries evaluation and quality control [3]. These techniques will be illustrated with practical examples of impedance measurements of large industrial Lead-acid and Li-ion batteries and stacks fabricated by different technologies and for different purposes.  Some related side phenomena as: (i) presence and destruction of the passive layer; (ii) increased inductance of stacks as well as impedance observation of local in-homogeneities in Li-ion batteries will be also discussed.  References  1. M. Keddam, Z. Stoynov, H. Takenouti, J. Appl. Electrochem. 7 (1977) 539. 2. Z. Stoynov in: C. Julien, Z. Stoynov (Eds.), Materials for Lithium- ion Batteries, Kluver Academic Publishers, 3/85 (2000) 359. 3. Z. Stoynov and D. Vladikova, in Encyclopedia of Electrochemical Power Sources, edited by U. Garche ( Elsevier, 2009) pp. 632-642.