Stress in carbon film electrodes during Li+ electrochemical intercalation

The mechanical deformation of thin films and membrane carbon electrodes during galvanostatic charge-discharge cycles has been measured by a simple optical technique. We have considered the deformations of coke and of graphite membrane electrodes to be due to the variations in the volume of grains and to the surface forces resulting from the electrochemical double layer. For such composite electrodes the minimum stress can be associated with the potential of zero charge of the electrode. The results show that the stress Is due mainly to variations of volume in nonporous electrodes, to surface forces, and to the presence of passivating layers in very porous electrodes. The stress observed in the membrane electrodes after Li+ intercalation consists of an irreversible compressive tension and results in a permanent deformation of the electrodes.