Systematic investigation of the Binder's role in the electrochemical performance of tin sulfide electrodes in SIBs

Binders play a significant role in the electrochemical performance of electrodes in batteries, especially for high capacity conversion/alloying-type electrodes. However, the effects of binders on the electrochemical performance of the conversion/alloying-type anodes in sodium ion batteries are not widely investigated. In this work, we use SnS2 as a model anode and comparatively investigate the performance of six different types of binders in SnS2 electrodes of sodium ion batteries by half-cell testing. The binders are sodium carboxymethyl cellulose (CMC-Na), sodium polyacrylate (PAA-Na), CMC-Na-PAA-Na (1:1, wt%, denoted as PAA-CMC), sodium alginate (ALG-Na), PVDF, PTFE. The PAA-CMC binder electrodes exhibit outstanding cycling and rate performance, delivering a reversible capacity of 400 mAh g(-1) at the current density of 100 mA g(-1) within 70 cycles. Our results indicate that the binder with a large fraction of carboxylate and hydroxyl groups, which lead to stronger hydrogen bonds and/or covalent chemical bonds with the carbon black and active materials, is advantageous for the electrochemical performances of SnS2 electrodes. The synergistic interactions among the binder and the surface of both the active materials of SnS2 and the conductive additive of ketjen black have been also schematically proposed in this study.