Boosting Initial Coulombic Efficiency of Coal-Based Carbon Anodes with Cross-Linked Polymeric Binder for Sodium-Ion Batteries

Benefiting from abundant resources, low price, and high carbon content, coal is considered as one of the most promising precursors of carbon-based anode materials for sodium-ion batteries. However, the application of coal-based carbon anode materials has been enormously restricted due to its poor sodium storage capacity and low initial Coulombic efficiency (ICE). In this work, a cross-linked polymeric binder [sodium alginate (SA)/ poly(acrylic acid) (PAA)] combining the molecular structure advantages of SA and PAA has been successfully designed. The SA/PAA binder has a strong interaction with coal-based carbon materials through covalent bonds, which can validly reduce its defect sites and inhibit the decomposition of the electrolyte. In addition, the cross-linking structure of the SA/PAA binder improves the bonding capacity and mechanical property of the coal-based carbon anode materials, significantly enhancing their rate and cycling performance. Simultaneously, the inclusion of a binder with Na-ions can compensate for the irreversible loss of sodium in coal-based carbon anode materials, thereby achieving higher ICE (82.08%) and reversible capacity (361.4 mA h g-1 at 0.1C). Therefore, the SA/PAA binder can be considered as a candidate binder for sodium-ion batteries, considering its desirable mechanical properties and electrochemical performances.