Effect of binder on the electrochemical, mechanical, and thermal properties of hard carbon anodes in Na-ion batteries

A polymer binder is one of the critical components of metal-ion battery electrodes, and the choice of the appropriate polymer should be based on a comprehensive analysis of several key factors. In this study, for the first time, we compared the thermal, electrochemical, and mechanical stability of hard carbon (HC) electrodes depending on the binder used: polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), sodium carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), or sodium alginate (Alg). Thermal stability studies using differential scanning calorimetry (DSC) demonstrated that during thermal decomposition, all electrodes in the charged state release more heat than charged HC powder. The corresponding increase in enthalpy depends on the thermal stability of the polymer itself. Among the binders tested, the CMC/SBR combination seems to be the most promising for practical applications in electrodes, as it provides good cyclability, strong adhesion, and a relatively low thermal effect.