High-Rate and Long-Cycle Cathode for Sodium-Ion Batteries: Enhanced Electrode Stability and Kinetics via Binder Adjustment

Sodium-ion batteries (SIBs) are heralded as promising candidates for grid-scale energy storage systems due to their low cost and abundant sodium resources. Excellent rate capacity and outstanding cycling stability are always the goals for SIBs. Up to now, nearly all attention has been focused on the control of morphology and structure of electrode materials, but the influence of binders on their performance is neglected, especially in cathode materials. Herein, using Na₃V₂(PO₄)₂O₂F (NVPOF) as a cathode material, the influence of four different binders (sodium alginate, SA; carboxymethylcellulose sodium, CMC; poly(vinylidene fluoride), PVDF; and poly(acrylic latex), LA133) on its electrochemical performance is studied. As a result, when using SA as the binder, the electrochemical performance of the NVPOF electrode is improved significantly, which is mainly because of the high water solubility, rich carboxyl and hydroxyl groups, and high adhesive and cohesive properties of the SA binder, leading to the uniform distribution of active materials NVPOF and carbon black in electrodes, good integrity, low polarization, and superior kinetic properties of the NVPOF electrodes, as demonstrated by scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic intermittent titration technique. More importantly, when coupled with a hard carbon anode, the fabricated sodium-ion full cells also exhibit excellent rate performance, thus providing a preview of their practical application. This work shows that the battery performance can be improved by matching suitable binder systems, which is believed to have great importance for the further optimization of the electrochemical performance of SIBs.