Tungsten-Doped Vanadium Oxide Composites Fabricated with APT for Lithium Battery Application

Lithium-ion batteries (LIBs) have played an important role as the main source of power for various industries such as electric vehicles (EV) and solar energy storage tanks. LIBs have many advantages such as long cycle life, high power density and relatively low discharge speed. As the electric vehicles (EV) is growing massively in China and USA, however, the storage capacity has limited the driving range greatly.

Different methods had been applied to extend the storage capacity which include surface modification, stabilization of lattice structure by mixed metal composites, and the use of nanoparticles to increase surface area. Vanadium based oxides (Vox) have received much attention due to their diverse chemical structure and high specific charge capacity as high as 200 mAh/g. Unfortunately, they possess the drawbacks of irreversible structural changes and poor electrical conductivities.

To enhance the electrochemical performance, various loading percentage of tungsten (W) was introduced to prepare tungsten-doped vanadium oxide composites (VO2/Wx). The optimum percentage of W incorporated inside the VO2 lattice showed the best lithium storage performance.

The tungsten-doped vanadium oxide composites were fabricated from ammonium paratungstate (APT) for lithium battery application.VO2/Wx as below:

Calculated amount of ammonium paratungstate (APT) (11.4 mg, 0.0036 mmol) was mixed with V2O5 (0.2 g, 1.1 mmol) in water (50 mL) and sonicated for 30 min. Citric acid monohydrate (0.3 g, 1.4 mmol) was added to the above mixture and heated at 75 °C to form a dark green solution. After one hour, the mixture was transferred to 100 mL Teflon lined stainless steel autoclave, sealed, heated at 200 °C for 12 h and cooled to room temperature. The black solid obtained after centrifugation was washed with copious amounts of water (3 × 100 mL), followed by methanol (2 × 100 mL) and dried at 60 °C overnight. Elemental analysis and energy-dispersive X-ray (EDX) spectroscopic studies showed the presence of vanadium, tungsten, and oxygen in the black solid.

To sum up, tungsten-doped vanadium oxide composites were fabricated from ammonium paratungstate (APT) for lithium battery application.The lithium storage performance of VO2 has improved remarkably by increasing the loading of W to an optimal level, which influence the intercalation/ deintercalation of lithium ions into the expanded lattices of VO2. Morphological changes observed for the VO2/Wx composites led to an improved surface area of the electrode materials. VO2/W4 (3 wt% of W) composite showed a maximum capacity of 381 mAh/g at 0.1C rate with good cycling stability compared with 259 mAh/g of VO2.

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