Electrochemical Studies Of Vanadium Oxides For Use In Lithium Batteries

Vanadium oxides of varying stoichiometries have been studied for their potential use in rechargeable solid state lithium batteries. Deposits of hydrated diammonium hexavanadates have been prepared electrochemically on various conducting anode substrates. Coherent electrodeposits of highly oriented, crystalline M{dollar}\sb4{dollar}V{dollar}\sb6{dollar}O{dollar}\sb{lcub}16+\delta{rcub}{dollar}, where M = NH{dollar}\sb4{dollar}, K, Rb and Cs and 0.00 {dollar}\u3c\delta\u3c{dollar} 0.10, have also been made for the first time electrochemically on various conducting cathode substrates. Also, mixed crystalline phases of formula M{dollar}\sb{lcub}4-X{rcub}{dollar}N{dollar}\sb{lcub}X{rcub}{dollar}V{dollar}\sb6{dollar}O{dollar}\sb{lcub}16+\delta{rcub}{dollar}, where M, N = NH{dollar}\sb4{dollar}, K, Rb and Cs, M {dollar}\not={dollar} N and 0.00 {dollar}\u3c\delta\u3c{dollar} 0.13, have been made. The mechanism of formation of a deposit at the anode involves formation of a hydrated V{dollar}\sb2{dollar}O{dollar}\sb5{dollar} sol in a pH gradient at the anode, and subsequent electrophoretic deposition of the sol as an oriented crystalline deposit. The sol spreads to the cathode by convection, migration and diffusion, where the particles adhere with evidence of nucleation and growth on the cathode. These electrodeposits have been studied using both electrochemical and non-electrochemical techniques to determine their structure, stoichiometry and use as reversible insertion electrodes.;The deposits containing NH{dollar}\sb4\sp+{dollar} can be decomposed to crystalline V{dollar}\sb2{dollar}O{dollar}\sb5{dollar} by heating in air, or to non-stoichiometric V{dollar}\sb6{dollar}O{dollar}\sb{lcub}13{rcub}{dollar} by heating in argon or in vacuum at 300{dollar}\sp\circ{dollar}C for several hours, with retention of their orientation on the substrate. The first step of the thermal decomposition involves loss of 2NH{dollar}\sb3{dollar} + H{dollar}\sb2{dollar}O. In the second step, on heating in air, recrystallization and oxidation of V(IV) to V(V) is observed with the addition of 1/2 O to form V{dollar}\sb2{dollar}O{dollar}\sb5{dollar}. This oxidation is not seen on heating under reduced O{dollar}\sb2{dollar} partial pressure and reduction continues until V{dollar}\sb6{dollar}O{dollar}\sb{lcub}13+\delta{rcub}{dollar} is formed, where {dollar}\delta{dollar} is a function of how much residual O{dollar}\sb2{dollar} is left exposed to the deposit. Lithium could be reversibly inserted into and removed from the V{dollar}\sb2{dollar}O{dollar}\sb5{dollar} form of the deposit up to a mole ratio Li/V{dollar}\sb2{dollar}O{dollar}\sb5{dollar} = 1.2. For non-stoichiometric V{dollar}\sb6{dollar}O{dollar}\sb{lcub}13{rcub}{dollar} the ratio of Li/V{dollar}\sb6{dollar}O{dollar}\sb{lcub}13{rcub}{dollar} = 4.4. However, electrodes that were not decomposed inserted only a small amount of lithium, {dollar}\u3c{dollar}1% of total V.;Single-cell batteries consisting of a Li anode, a polymer electrolyte such as MEEP, PEO or tetraglyme (supported in Celgard) and a vanadium pentoxide cathode have been studied. The batteries show favorable cycle lifetimes and high cathode capacity

Study of Mex(VO3)2 vanadates, (Me = Co, Ni, Mn, 1 < x < 2) for lithium rechargeable cells

Transition metal vanadates, Mex(VO3)2.2H2O, where Me = Co, Ni and Mn and 1.0 < x < 2.0, were found to reversibly insert lithium. The efficiency of reversible insertion depended on both the transition metal present and the stoichiometric ratio of Me:V in the vanadate structure. The Ni and Co vanadates gave the highest specific capacities using lithium metal coin cells, with initial specific capacities above 0.7 A h/g (1.0 W h/g) when x is near 1.0. The operating voltage of these materials was in the range of 1.0 to 2.0 V. Lithium ion coin cells using LiCoO2 coupled with the vanadates, were also examined. These were found to deliver about 200 mA h/g, with average voltages of 2.5 to 2.0 V for values of x from 1.1 to 1.2.Peer reviewed: YesNRC publication: Ye

Diffusion of lithium in electrodeposited vanadium oxides

Using a novel electrodeposition/thermal process, V6O13+y, 0 < y < 2, bronzes were directly fabricated into a coin cell without the use of binders or electronic conductors. Transport properties of lithium insertion and removal from V2O5 and nonstoichiometric (ns) V6O13+y bronzes, were examined by electrochemical methods in asymmetrical Li/LixV6O13+y cells. Diffusion coefficients in the range 0.2\u20135.0 710 128 cm2 s 121 were found for insertion and removal steps in the range, x = 0\u20131.0. The transport of lithium ions from the vanadium oxides is similar to the insertion process. These bronze cathodes have similar transport properties to composite cathodes, making them potentially useful for electrochromic displays and microbatteries. \ua9 2004 Elsevier B.V. All rights reserved.Peer reviewed: YesNRC publication: Ye

Use of pure and cobalt-added aluminum vanadates as cathodes in lithium rechargeable cells

Peer reviewed: YesNRC publication: Ye

An integrated approach towards electric drive transportation in Canada

This paper presents a collective perspective on the evolution of electric mobility in Canada and the recommended process to build momentum within the government. Also discussed is the rationale for the integration of efforts, as well as the overall future direction of the industry. This paper also summarizes specific electric drive transportation activities of the seven departments and the EMC, which include the creation of a national directory of electric mobility resources and a Technology Roadmap (TRM) currently underway. Technology roadmapping is then explored in more detail, highlighting its ability to engage government and industry to work together to define goals to achieve electric drive transportation and identify pathways to address technology, market and regulatory needs. Clearly, the core strength of the TRM process lies within the interdependencies and influence that each department has on outcomes. And lastly, the paper outlines long-term perspectives; one common goal of these diverse departments is the development of an enhanced R&D base of electric drive technologies for the transfer and commercialization of these new technologies in Canada, with the potential for export sales worldwide.Peer reviewed: YesNRC publication: Ye