<i>In-Operando</i> Cross-sectional Observation of Graphite Anode with Deposited Lithium and Measurement of Internal Cell Resistance

By In-Operando cross-sectional observation of laminated Li-ion cells, morphology of deposited Li on surface of graphite anode and reaction distribution of anode was investigated. During 20C-CCCV charge, we observed 2 types of deposited Li as follows; Li whisker and Li dendrite under different conditions of constant voltage charging current, and found that Li dendrite decreased Li-ion concentration of electrolyte solution in anode. With electrochemical impedance spectroscopy, it was determined that Li dendrite increased ohmic resistance of a cell and charge transfer resistance of anode, while there was no affection by Li whisker. These results suggest that Li dendrite depresses the charge reaction of graphite anode, and Li whisker does not affect charge reaction.