Transient heat and mass transfer modeling aspects of rechargeable lithium/polymer electrolyte batteries

Rechargeable lithium/polymer electrolyte batteries have the potential for higher energy density than existing lithium-ion type batteries. However, lithium/polymer batteries have limited cycle life. Discharge capacity is extremely sensitive to temperature and discharge rate, and potential safety problems exist and are related to battery temperature distribution. This dissertation addresses several of these battery performance limiting issues by modeling fundamental heat and mass transfer processes that occur during lithium/polymer battery operation.; A transient, three dimensional heat transfer and generation model was developed and applied to a single lithium/poly(ethylene oxide)/titanium disulfide cell. This model can be used to predict the cell temperatures for a new type of thermal battery, namely, a lithium/polymer thermal battery.; Fundamental processes that occur at the lithium/polymer electrolyte interface were determined and a diffusion-limited reaction model was proposed to explain the interfacial resistance growth with time. The addition of alumina to the poly(ethylene oxide) polymer electrolyte reduces the magnitude and growth rate of the interfacial resistance mainly by serving as a diluent.; The cell voltage and discharge capacity as a function of discharge rate for a room temperature rechargeable lithium/polymer electrolyte/lithium manganese oxide cell were accurately simulated by a simple diffusion-limited reaction model and by a transient, two-dimensional mass transfer and generation model. The importance of using the intrinsic lithium chemical diffusion coefficient in modeling lithium insertion cathode materials is addressed.