Direct measurement of current distribution in lithium-ion cells by magnetic field imaging

Inhomogeneous current distribution in lithium-ion cells is a major reason for degradation. A method to measure the locally resolved current distribution is to map the magnetic field caused by the current flowing in the cell. This paper presents an unshielded measurement setup using anisotropic magnetoresistive (AMR) sensors to map the magnetic field of a cell during operation. Moreover, it proposes an algorithm to calculate the two-dimensional current distribution from magnetic field data. The achieved accuracy of the current density is 227 mA cm−2 at a local resolution of 4 mm2.