Self-Healing in Li-Ion Battery Electrodes

Battery lifetime relies on the electrical and mechanical integrity of its electrodes. A common cause of degradation of performance in Li-ion batteries is the capacity loss in negative electrode due to extensive mechanical cracking. During the regular operation of a battery, subsequent charging and discharging cycles induce high, cycling mechanical stress in graphite and silicon based electrodes resulting in crack initiation and growth. In this study, we introduce a microcapsule based autonomous healing approach to restore functionality across the through-cracks in battery electrodes. We use a custom designed battery cell, by which we observe a double clamped negative electrode in-situ during subsequent cycles, capture cracking by a CCD camera and assess mechanical failure/healing through capacity data. We incorporate microcapsules with a conductive core within or on the electrode to deliver their contents at the damage zone. The electrode design involves a mechanically vulnerable region to shorten the experiment time and to enable us to predict the crack location. We induce a capacity loss based on mechanical failure and then assess the effectiveness of autonomous restoration of battery capacity during its regular operation.