Full paperLiquid exfoliation of interlayer spacing-tunable 2D vanadium oxide nanosheets: High capacity and rate handling Li-ion battery cathodes

- Large quantities of high quality, two-dimensional (2D) vanadium pentoxide (V2O5) nanosheet (NS) have been exfoliated in environmental friendly solvents.
- Large-area, flexible and binder-free V2O5 NS/SWCNT hybrid electrodes have been efficiently fabricated through programmed aerosol printing technique.
- The interlayer spacing of 2D orthorhombic V2O5 NS can be well manipulated, ranging from 4.4Å to 11.5 Å in ethanol and water-based colloidal solutions, respectively.
- The SWCNT further improves the reversible phase transition reactions of the V2O5 NS and maintains the structural integrity of the electrodes.
- The flexible printed V2O5 NS/SWCNT electrode has demonstrated a high discharge capacity of 370 mA h g−1 at 0.05 C, high energy density (1110 W h kg−1) and power density (4350 W kg−1), etc.

With a layered crystal structure and good Li+ storage performance, vanadium pentoxide (V2O5) is potentially a high-energy and cost-effective cathode material for Li-ion batteries (LiBs). Networks of two-dimensional V2O5 nanosheets (2D V2O5 NS), with large interlayer distance, are ideal for enhancing the Li+ diffusion kinetics and thus for building high power LiBs. However, the lack of a simple, scalable and environmentally friendly route to nanosheet production still hinders the development of V2O5 applications. Here we demonstrate, liquid-phase exfoliation (LPE) of commercial V2O5 powder in environmental friendly solvents (water and ethanol) to achieve large quantities of 2D V2O5 NS dispersions. The V2O5 NS are of high-quality whose interlayer spacing can be well manipulated, ranging from 4.4Å to 11.5 Å in ethanol and water (forming NS xerogel), respectively. Ultrasonic aerosol printing of V2O5 NS xerogel/single-wall carbon nanotube (SWCNT) blended dispersions resulted in large-area, flexible, and binder-free hybrid electrodes, which showcase a high discharge capacity of 370 mA h g−1 at 0.05 C, high energy density (555 W h kg−1) and power density (2175 W kg−1), etc. These properties can be attributed to the synergistic effects between the expanded hydrated NS and the conductive SWCNT matrix; the latter improves the reversible phase transition reactions of the NS, enhances the ion diffusion kinetics, maintains the electrode's mechanical integrity and provides electron transport pathways. The Li+ storage mechanism was investigated, suggesting the capacity was majorly contributed by the non-diffusion controlled process (pseudocapacitive). We believe the LPE/aerosol printing approach is environmentally green, general and scalable, and could be extended to other layered transitional metal oxides or dichalcogenides for fabrication of corresponding flexible, binder-free, conductive composites for energy storage systems.

Large quantities of two-dimensional V2O5 orthorhombic nanosheets have been exfoliated in environmental friendly solvents. The interlayer distance of the nanosheets can be well manipulated. The large-area, binder-free, flexible V2O5/SWCNT composite, which can be efficiently fabricated through an aerosol printing technique, well explores the synergistic effects of broadened interlayer distance of V2O5 and electrical, mechanical properties of SWCNT. As a result, high capacity and excellent energy and power density Li-ion batteries have been achieved.470