DSC investigation of exothermic reactions occurring at elevated temperatures in lithium-ion anodes containing PVDF-based binders

Differential scanning calorimetry (DSC) has been used to measure the thermal interactions between several binder materials and representative anode carbons both in the presence of cell electrolyte (EC:DEC/1M LiPF6 + 2 wt.% vinylene carbonate) and after washing/drying. Binders consisting of homo- or copolymers of vinylidene fluoride (VDF) were examined as well as other fluorinated and non-fluorinated binder materials. The heat evolved by the reactions of these materials was compared to that arising from other exothermic phenomena occurring in charged anodes at elevated temperatures. A matrix of anode material combinations was designed to investigate the role of carbon structure, carbon surface area, state of charge, binder level and presence of electrolyte. The temperature and magnitude of the exothermic reactions were measured up to 375degreesC and average enthalpy values were obtained over several duplicate samples to allow good quantitative comparison of the material reactions. The exothermic anode reactions were sensitive to the state of charge and presence of electrolyte. The magnitude of the reactions increased with increasing surface area of the carbon particles. However, similar reaction enthalpies were seen for all binder materials and binder levels. (C) 2004 Elsevier B.V. All rights reserved.