Electrochemical properties of vanadium oxide aerogels

Abstract

Aerogels are well-known mesoporous materials whose low density and high surface area result from synthesis methods that enable the pore solvent to be removed without collapsing the solid network phase. The interconnected porosity provides both molecular accessibility and rapid mass transport via diffusion, and for these reasons transition metal oxide aerogels are gaining increased interest as intercalation electrode materials for lithium-ion batteries. The present paper reviews recent research on vanadium oxide aerogels that has been directed at establishing both their fundamental properties and unique ways of incorporating these materials into electrode structures. The experiments used to determine the fundamental electrochemical properties of vanadium oxide aerogels involve the use of a sticky-carbon electrode that is designed to both hold the material and serve as the current collector. The results show that these materials combine elements of both capacitor and battery behavior as the materials possess both high specific capacitance (.2000 F/g) and high capacity for lithium incorporation (.450 mAh/g). The unique morphology of the vanadium oxide aerogel has led us to consider alternate electrode structures because traditional methods may compromise the mesoporous, high surface area morphology. One approach has involved the incorporation of single wall carbon nanotubes as the electronically conducting network. The resulting nanocomposites effectively retain the aerogel morphology and exhibit excellent electrochemical properties. These electrodes are especially effective at high discharge rates. Another approach has involved the preparation of aerogel electrodes that possess an inverted opal structure. The fabrication route is based on combining the templating of polystyrene spheres with sol-gel synthesis and leads to materials that possess a hierarchical pore structure. This architecture is also effective at retaining high lithium capacity at high current densities. q

Facile synthesis of vanadia aerogels with controlled V3+/V4+ ratio

“…Materials: V 2 O 5 Á nH 2 O wet gel was obtained by a conventional technique based on acid-catalyzed hydrolysis of vanadium (V) oxytripropoxide (VO(OC 3 H 7 ) 3 ) [5]. A corresponding xerogel was synthesized by drying of the wet gel at 60-90 1C in air for 3-5 h. The wet gel or the xerogel were then put into an autoclave and the primary solvent (the mixture of the acetone and ethanol (10, 20 or 30 vol.%), Table 1) was added (the fill factor was 80-90 vol.%).…”

“…Among the plethora of cathode materials of various compositions [2], vanadium oxide aerogels attract special interest due to their unique structure [3], high discharge capacity (up to $ 1000 mAh/g mAh/g [4]) and their ability to be recharged rapidly due to their large surface area [5]. In practice, these aerogels are generally used as matrices for composites containing highly conductive organic or inorganic additives [6,7].…”

“…The choice of the solvent greatly affects the composition and microstructure of thus obtained materials [12,[15][16][17]. In vanadium oxides aerogels synthesis, V 2 O 5 Á nH 2 O wet gel is generally used as a precursor [3][4][5][6][7]. This compound contains vanadium in both V 4 þ and V 5 þ oxidation states [18].…”

Facile synthesis of self-standing binder-free vanadium pentoxide-carbon nanofiber composites for high-performance supercapacitors

“…A high specific capacitance could be achieved through inclusion of small quantity of metal oxide into conductive and porous carbonaceous materials with high surface area [31,32]. The effects of deposition of thin V 2 O 5 layer on carbonaceous materials have been studied by many researchers [33][34][35]. Yang and co-workers have synthesized metal oxide/CNF composites by deposition of Ni-Co binary oxide nanosheets on CNF surface and exploit their pseudo-capacitive performance with good cyclic properties [36].…”

In-situ preparation of PEDOT/V 2 O 5 nanocomposite and its synergism for enhanced capacitive behavior

“…The SC values reported vary from 290 F g -1 to 350 F g -1 depending on the pH. High surface area V 2 O 5 aero gels immobilized on the carbon electrode has been studied by Dong et al 6 for supercapacitor applications. Nanoporous vanadium oxide has been synthesized by Reddy et al 7 and have obtained SC of about 214 F g -1 in 2 M KCl.…”