Surface Behaviors of Conductive Acetylene Black for Lithium-Ion Batteries at Extreme Working Temperatures

The surface physical and chemical behaviors of conductive additive acetylene black (AB) are studied after the samples are cycled at different working temperatures (-20, 20, and 60 degrees C). Working at low temperature (-20 degrees C), AB shows high polarization and poor electrochemical property. In addition, plenty of inorganic compounds are formed on the surface of AB. For comparison, the surface film on AB after being worked at 60 degrees C is comprised of an outer organic layer and an inner inorganic layer. Moreover, it consumes large electrical energy and results in irreversible trapped lithium for surface film formation. Furthermore, much more organic components can induce lower thermal stability of conductive additive. During repeated electrochemical cycles, the surface structure of AB experiences a series of changes of surface electrolyte decomposition products. It is found that the organic polymer in outer layer will decompose into other stable species, and partial surface fluorides in the inner layer will transform into other fluorides. The working temperature has a great effect on the final transformation products.