2015 年 81 巻 825 号 p. 14-00637
Lithium-ion battery is a rechargeable battery with high energy density, and it is fabricated by laminating of electrodes with separator. In fabrication process, it is important for evaluation of contact state of laminated electrodes to estimate current density between the electrodes. This paper describes a novel technique to estimate the current density by using magnetic sensor. This technique applies an inverse analysis on magnetic flux density induced around the lithium-ion battery impressed with inspection current. In the inverse analysis, boundary element method for thin plate is applied to derive the observation equation relating the current density to the magnetic flux density. Then truncated singular value decomposition is applied on the observation equation. In order to demonstrate the validity of the proposed technique, numerical simulations have been performed by using a model consisted with the electrodes and separator. In the numerical simulations, the correct distribution of the current density was given in advance, and the direct analysis was applied to obtain the simulation data of the magnetic flux density. Then the inverse analysis was applied on the simulation data. The results show that the correct distribution of the current density can be obtained by the proposed technique. In addition, though the estimation accuracy is lower when fewer number of decimals of the magnetic flux density data is utilized, the tendency of the correct distribution can be obtained due to the truncation of the rank of the singular value matrix.
