Two LiCoO2 dense film electrodes were prepared on both surfaces of a lithium ion-conducting glass ceramics, and electromotive force measurements were, preformed between the film electrodes under mechanical compressive and tensile stresses by four-point bending tests. Electromotive force appeared immediately after applying the stress and disappeared after releasing the stress. The larger stress was applied, the larger electromotive force was observed. These results clearly demonstrated that the lithium chemical potential in the LiCoO2 electrode varies under mechanical stress. The influence of the mechanical stress on the lithium chemical potential was discussed based on the relation between the CoO2 interlayer distance and the lithium concentration in LiCoO2. (C) 2015 Elsevier B.V. All rights reserved.