Cyanoethylated Carboxymethyl Chitosan as Water Soluble Binder with Enhanced Adhesion Capability and electrochemical performances for LiFePO4 Cathode

Cyanoethylated carboxymethyl chitosan (CN-CCTS) has been synthesized through a straightforward cyanoethylation reaction by reacting CCTS with acrylonitrile in NaOH aqueous solution. CN-CCTS shows improved adhesion strength of 0.047 N/cm as compared with 0.013 N/cm for CCTS after introducing cyanoethyl group in the chemical structure of CCTS. The electrochemical performances of LiFePO4 electrode with CN-CCTS binder have been investigated and compared with those using water soluble sodium carboxymethyl cellulose (CMC) and non-aqueous polyvinylidene difluoride (PVDF) binder. LiFePO4 electrode with CN-CCTS exhibits better cycling stability and rate capability, retaining 56.3% capacity of C/5 at 5C rate as compared with 48.4% and 32.8% for CMC and PVDF, respectively. Cyclic voltammetry and electrochemical impedance spectroscopy measurement reveal that LiFePO4 electrode with CN-CCTS has a more favorable electrochemical kinetics than that with CMC and PVDF, thus better rate capability. (C) 2015 Elsevier Ltd. All rights reserved.