The Effects of Cycling and Storage Conditions on Li-Ion Battery Health, Rate Capability, and Recyclability

Abstract

In this thesis the effects of environmental and cycling conditions on the capacity retention and rate capability of 1100mAh LiFePO4 (LFP) pouch batteries are tested and quantified. Particular emphasis is placed on characterizing harmful effects brought by conditions involving high and low temperatures, storage at varying states of charge, fast and slow cycle rates, and combinations of these factors. The batteries and cycling data are analyzed with multiple imaging, characterization, and electrochemical analysis techniques to determine how the different abuse factors impact the damage and long-term decay of individual component performance. Emphasis is placed on the characterization of bulk ion transport, as well as interfacial conductance and phase changes. This analysis is used to draw conclusions regarding possible avenues of non-destructive recycling of cells with major damage of a single component. This paper concludes with the discussion of the highest potential avenues for effective and efficient recycling, reaching the final conclusion that the most promising path forward is in electrolyte replacement to restore bulk ion transport in damaged or spent cells that suffer from poor diffusive performance but perhaps have not lost the majority of their cycleable lithium inventory, due to the remarkable restoration of ionic diffusivity in a badly damaged test cell.