Polycrystalline Vanadium Oxide Nanorods: Growth, Structure and Improved Electrochemical Response as a Li-Ion Battery Cathode Material

Abstract

Thermally removing amine molecules that serve as chemical templates for vanadium oxide nanotubes is demonstrated to significantly improve the performance when tested as a cathode material in Li-ion battery cells. Capacity fading issues associated with blocked intercalation sites on the (010) faces of layered vanadium oxide that form the nanotubes are prevented. Thermal treatment of the nanotubes up to 600 • C is shown to cause a specific conversion from nanotubes to polycrystalline nanorods and removal of the organic template. The conversion process was monitored by thermogravimetric analysis, X-ray diffraction, transmission electron microscopy and infra-red spectroscopy. In a potential window of 4.0-1.2 V drawing 30 μA (C/30), the nanorods show improved specific capacities of ∼280 mAh g −1 with a modest 6% capacity fade compared to ∼8 mAh g −1 with 62% capacity fade for the VONTs. The improvements in specific capacity and cycling performance are due to the successful removal of amine molecules and conversion to nanorods containing nanoscale crystals. The cathode material also demonstrated enhanced energy densities (∼700 W h kg −1 ) compared to composites of the same overall weight, without conductive carbon additives or polymeric binders. In recent years there has been a significant increase in the desire and need to improve the performance and cycle life of commercial rechargeable lithium ion batteries.1-6 The advent of smart phones and tablet devices has highlighted the limitations of current generation lithium ion batteries. Rechargeable lithium ion batteries still hold great promise for use in powering electric and hybrid electric vehicles and continue to be crucial in medical and handheld portable devices. 7However it is vital that factors such as power and energy density, coulometric efficiency and rate performance are improved upon in order to meet demands for improved performance in advanced Liion batteries (∼400 Wh/kg). 1,4,[7][8][9] It is no surprise that nanostructured materials are attracting significant attention because of their novel properties and their potential applications in a wide range of devices such as biological and gas sensors, 10-18 field effect transistors 19,20 and as electrode materials for next generation high energy density batteries. 21-23 Nanostructured cathode electrodes offer improved energy storage capacity and charge-discharge kinetics, as well as better cyclic stabilities.24 This is, in part, due to the increased surface area in direct contact with the electrolyte, and better electronic and ionic conductivity, and shorter distances for cation diffusion as compared with bulk materials. 25 Nanostructured electrodes are also able to better accommodate volume changes associated with cyclic intercalation and deintercalation of lithium ions into and from the host lattice. This reduces pulverization issues associated with bulk materials and consequently improves cycle life. 62 Nanostructures such as vanadium oxide nanotubes (VONTs) and nanorods are particularly attractive in prin...

V2O3 Polycrystalline Nanorod Cathode Materials for Li‐Ion Batteries with Long Cycle Life and High Capacity Retention

“…V 2 O 3 poly‐NRs were prepared by annealing vanadium oxide (V 2 O 3 nanotubes (VONTs) as previously reported . Briefly, VONTs were synthesized via hydrothermal treatment of a vanadium oxide xerogel mixed with nonylamine.…”

“…Despite the structure defining role of the amines in the synthesis of the VONTs, they are detrimental to their electrochemical performance . We have previously reported on the poor electrochemical performance of as prepared VONTs, which achieved capacities <10 mAh g −1 . We demonstrated that the amine molecules which occupy the majority of the possible lithium intercalation sites within the VONTs are responsible for the poor cycling performance and that removing the amines via thermal treatment can significantly improve electrochemical performance.…”

“…While as‐synthesized VONTs exhibit poor electrochemical performance, they are quite useful in providing nanorod or nanowire‐type structures with nanoscale features after various post‐treatments. Thermal treatment of VONTs in a N 2 atmosphere results in a specific structural conversion V 2 O 5 to V 2 O 3 polycrystalline nanorods (poly‐NRs) during annealing . Previous studies have detailed the reduction of various V 2 O 5 samples to V 2 O 3 via annealing in inert atmospheres, such as the reduction of a V 2 O 5 gel via annealing in H 2 and the formation of V 2 O 3 nanocrystals by thermal reduction of V 2 O 5 thin films …”

Carbon-Coated Honeycomb Ni-Mn-Co-O Inverse Opal: A High Capacity Ternary Transition Metal Oxide Anode for Li-ion Batteries

“…These demands have necessitated studies into the development of active materials with higher specific capacities and enhanced cycle-lives678. From the perspective of anode materials for Li-ion applications, these can be broadly divided into three classes based on the reactions occurring during lithiation/delithiation namely; intercalation mode, alloying mode and conversion mode materials91011.…”

3D Vanadium Oxide Inverse Opal Growth by Electrodeposition

“…The layered geometry of orthorhombic crystalline V 2 O 5 makes it ideally suited to the reversible intercalation of mobile guest species, 21,22 such as Li + and other cations. [23][24][25][26] While the lattice structure is theoretically maintained upon mild intercalation, phase changes are known to occur and the interlayer van der Waals spacing characteristic of its layered orthorhombic crystal structure can become deformed at lower voltages (higher Li mole fraction). 27,28 Large particle sizes can also limit the solid state diffusional rate of cation insertion.…”