Visualizing the Battery Degradation through Non-destructive Methods on Predicting the State of Health (SoH) of Second Life Batteries (SLB)

Ever since the vehicle electrification era had started, lithium-ion batteries become the sole fore runner in powering the Electric Vehicles (EV). Vehicle electrification contributed vastly in public transportation which further promoted the surge in usage of EV in recent days. The EVs are deployed in different climatic environment, and user defined handling which lead the battery to undergo non-uniform degradation as it undergoes a series of charge and discharge cycles. State of Health (SoH) is an indicator to quantify the battery health. When the SoH of lithium-ion batteries deployed in EV application reaches 80% of its nominal capacity, then the battery is said to be reached its End of Life (EoL) in EV application. Such batteries, when translated in to second life applications, its SoH estimation at second life is vital information on defining the operating points of the Second Life Battery (SLB). The SoH estimation of SLB is expected to be non-destructive in nature. This article deals with the SoH estimation of pouch cells that underwent lab level testing for 100 charge and discharge cycles. The battery degradation from cycle 1 to 100 is visualized through Incremental Capacity Differential Voltage (ICDV) method. Based on the degradation modes observed in the battery, the Health Indicators (HI) were summarized and the insights on dominant degradation phase can be visualized through bifurcating the operating voltage of the cell in to a particular zones of interest. This voltage band in particular, caters preliminary insights regarding the battery degradation and the same information can be translated to second life thereby reducing the cycle life testing time and efforts.