Tin-oxide-based binder-free lightweight nanostructured anode with high reversible capacity and cyclability for lithium-ion batteries, manifesting the interfacial effect

Abstract

Advancements in lithium-ion batteries (LIBs) that deliver higher storage capacity, energy density, and power density are essential to meet the growing power demands of modern technologies. The increasing use of lightweight micro-devices in flexible and portable electronics—such as wearable health monitors, implanted medical devices, smart cards, and IoT sensors—further emphasizes the need for miniaturization of energy storage. This report describes a high-performance, lightweight, binder-free tin-oxide (SnO₂)-based nanostructured thin-film anode on a copper (Cu) current collector for rechargeable LIBs, with lithium foil as the counter electrode. Importantly, the fabrication process of this binder-free electrode does not involve any binder, conductive agent or other additional inactive components (unlike the typical electrode preparation method), which results in improved energy density by reducing the effective weight of the LIB. Furthermore, it eliminates weak interaction and interface issues between binder and electrode material, thus minimizing the possibility of self-aggregation of active materials, besides providing increased accessibility of the electrolyte to the active material. The fabricated half-cell exhibits significantly high reversible capacities of 1430 mAh g⁻¹ and about 1200 mAh g⁻¹ after 100 and 500 cycles, respectively, at a current density of 0.3 A g⁻¹ (0.2C), excellent cyclability, rate performance (∼800 mAh g⁻¹ at 3 A g⁻¹ at 110 cycles) and stability with a high Coulombic efficiency (98–99%), as tested in the 0.02 to 1.8 V window. Activation of the electrode was achieved by a controlled post-deposition annealing process of optimized SnO₂ film on Cu, providing a suitable nanostructured hierarchical morphology and conformation involving an SnO₂–Cu interface, which facilitates good electrical contact and enhanced electron/ion transport kinetics, yielding high cyclability, rate performance and stability, preventing pulverization. Moreover, it introduces an extra interfacial charge storage phenomenon via Cu/Li₂O nanocomposites, resembling capacitive characteristics. Stable capacity involving SnO₂ dealloying–alloying along with the interface induced extra lithium storage capability, which contributed to accomplishing the observed high specific capacity of the electrode. This study provides an insight into the design of an advanced lightweight electrode for next-generation energy storage devices.