Synergistic Effect of 3D Electrode Architecture and In Situ Carbon Coating on the Electrochemical Performance of SnO₂ Anodes for Sodium-Ion Batteries

SnO 2 , owing to its high theoretical capacity of 1378 mAh g −1 and low sodium insertion potential, is one of the attractive anode materials for Sodium-ion batteries (SIBs). However, extensive volume expansion (∼300 %), significant capacity loss, particle agglomeration, and low conductivity (1.82 × 10 −8 S cm −1 ) of SnO 2 limit its commercial applications. In this work, SnO 2 nano-particles have been synthesized via a one-step hydrothermal method. Subsequently, 3D electrode architecture is developed using pitch-coated SnO 2 nanomaterial onto carbon fiber (CF) current collector to mitigate the inherent challenges of SnO 2 anode. Compared to the conventional SnO 2 electrode, the optimized CF-SnO 2 - carbon composite electrodes show an excellent second-cycle stable capacity of 843 mAh g −1 at 30 mA g −1 with 95 % capacity retention after 100 cycles. This CF-SnO 2 -carbon composite electrode further delivers a stable capacity of 419 mAh g −1 at 300 mA g −1 , having 80 % capacity retention after 200 cycles, and shows excellent C-rate performance. Conductive CF backbone and carbon coating accommodate the volume expansion of the active material, acting as a buffer matrix and reducing the electrode pulverization. This work entails a carbon fiber-based electrode engineering approach to fabricate a binder-less metal current collector-free freestanding electrode as a potential anode for SIBs.