Multifunctional Cyclized Polyacrylonitrile (cPAN) as a Coating for Sb-Based Anodes in Sodium-Ion Batteries

Conversion electrodes, such as antimony (Sb), are high energy density electrode materials for sodium-ion batteries (NIBs). These materials are limited in their performance due to the mechanical instability of these systems resulting from volume expansion of the material during cycling. Stabilizing conversion materials using a conductive polymer binder (CPB) protective layer is an effective way to enhance the performance of these materials. There is, however, a lack of a clear understanding of how CPBs affect the (de)insertion and surface chemistry of these systems. Herein, we report the systematic investigation of the effects on Na-ion (de)insertion chemistry of a cyclized-polyacrylonitrile (cPAN) layer on Sb-based conversion electrodes in NIBS. Through electrochemical characterization, it was determined that the inclusion of a cPAN layer increases the achievable capacity of the electrode system due to the storage of Na ions by the cPAN layer and facilitates Na-ion transport to the Sb active material at early cycles by reducing the charge transfer resistance of the ensemble electrode.