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Local electric current reconstruction theory for non-destructive inspection inside battery cell using magnetic field measurement


Improvements in the performance of lithium-ion batteries has recently been accelerating, and quality management has become an essential issue. In order to inspect the spatial uniformity of the electric current density distribution inside a rechargeable battery, we have developed an electric-current imaging system. This system equips a highly sensitive magnetic field sensor to measure the magnetic field around an operating battery cell. In this paper, we discuss how to derive electric current image theoretically inside a battery cell using experimentally-obtained magnetic field image measured outside it, and show the local electric-current reconstruction theory for the non-destructive inspection. With this theory, it is possible to determine whether or not electric current is concentrated at a specific area inside a battery cell. This nondestructive inspection procedure could contribute to higher quality management for cutting-edge lithium-ion batteries.