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Boston College team demonstrates nanonet-based heterostructure strategy for high-performance Li-ion cathode materials; high-power and high-capacity vanadium oxide electrode

Zhou
Schematic illustrations of the TiSi2/V2O5 heteronanostructure design. The TiSi2 nanonet is directly grown on a current collector; V2O5 is deposited onto TiSi2 by a hydrolysis process. Upon annealing at 500 °C in O2, V2O5 nanoparticles form. Credit: ACS, Zhou et al. Click to enlarge.

Using a highly conductive two-dimensional TiSi2 nanonet technology they had earlier developed, a team from Boston College has synthesized a vanadium oxide (V2O5)-based cathode material that demonstrates a specific capacity of 350 mAh/g, a power rate of 14.5 kW/kg, and capacity retention of 78% after 9,800 cycles of repeated charge/discharge. In a paper published in the journal ACS Nano, they note that these results demonstrate “a cathode material significantly better than V2O5 of other morphologies.”

The strategy of having multiple components at the nanoscale—heteronanostructures—offers a critical advantage of achieving desired electronic and ionic properties on the same material by tailoring the constituent components, the team suggests in its paper.

Nanoscale materials are expected to contribute significantly to realizing an important goal in the lithium ion battery research of achieving high capacity and power rate and long cycle lifetime simultaneously...How to solve these issues in a concerted fashion, however, remains a challenge because they are intricately correlated at relevant length scales (e.g., charge and ionic behaviors at the nanoscale). Here we present a strategy that has the potential to meet this challenge.

...The key to our design is the capability to control the features of materials on multiple levels concurrently. At the atomic scale, we use Ti-doping to stabilize V2O5 upon lithiation and delithiation, which dramatically improves the cycle lifetime. At the nanoscale, the material is composed of more than one component, each designed for a specific function, the TiSi2 nanonet for charge transport, the Ti-doped V2O5 nanoparticle as the ionic host, and the SiO2 coating as a protection to prevent Li+ from reacting with TiSi2, which otherwise would lead to the destruction of the nanostructures. The strategy of having multiple components at the nanoscale offers a critical advantage of achieving desired electronic and ionic properties on the same material by tailoring the constituent components.

—Zhou et al.

Zhou et al. say that their work, compared to other work using nanostructures, is distinguished by at least three features:

  1. The two-dimensional TiSi2 nanonet inorganic framework is highly unique. The combination of mechanical strength and flexibility exhibited by the nanonet may be ideal for energy storage applications, they suggest.

  2. The seemingly complex design is realized through simple chemical synthesis, without the involvement of catalysts or templates.

  3. The combined power rate, specific capacity, and cycle lifetime render the nanonet-based nanostructure one of the highest performing cathode materials.

They used V2O5 to demonstrate the design principle because the addition of the conductive framework (TiSi2 nanonets) “is particularly useful to solve the key issues of poor conductivity and slow Li+ diffusion that limit the performance of V2O.

Zhou2
Charge capacity and Coulombic efficiency TiSi2/V2O5 heteronanostructures. (a) After the initial decay during the first 40 cycles, the heteronanostructure exhibits stability for up to 600 cycles, fading only 12% (rate: 300 mA/g). The reversible decrease of capacity between the 180th and 210th cycles (14 mAh/g, or 4.4%) are the result of controlled temperature change from 30.0 to 28.0 °C. One data point for every 10 cycles is shown. (b) The rate-dependent specific capacities. 1C: 350 mA/g. Credit: ACS, Zhou et al. Click to enlarge.

Ti-doping stabilizes V2O5, and the SiO2 layer shields TiSi2 from the electrolyte. More critically, Zhou et al. concluded, the unique two-dimensional nanonet platform bridges different length scales from the nanoscale to the micro/macro scale.

By introducing a dedicated charge transporter, we were able to separate charge and ionic behaviors and thereby obtain unprecedented high power and high capacity on a cathode material that can be cycled extensively. We emphasize our strategy is highly modular, and other high performance cathode compounds (such as LiFePO4) should be readily integrated into the nanonet-based design. Our results demonstrated that advanced functional materials can be obtained by simple chemical synthesis. This approach should be highly complementary to existing efforts of finding highly performing compounds as battery electrode materials.

—Zhou et al.

Resources

  • Sa Zhou, Xiaogang Yang, Yongjing Lin, Jin Xie, and Dunwei Wang (2011) A Nanonet-Enabled Li Ion Battery Cathode Material with High Power Rate, High Capacity, and Long Cycle Lifetime. ACS Nano doi: 10.1021/nn204479n

Comments

Darius

IMHO any reason avoiding range extender option. Why to be afraid of small range extender's which will eliminate need of redundant electric infrastructure cost and fast charging need and will facilitate market penetration of EV. ICE small Wankel type 30 kW range extender could weight as much as 60 lbs and compensate fast charging need and BIG BIG battery need!!!! And still 90% of population will be able to travel 90% of their distance using el. power. The rest of distance could be covered using domestically produced synthetic fuel - ethanol, methanol, DME or biodyzel which suites for Wankel. I should remind you that 10% of gasoline is renewable already.

yoatmon

@Anne:
I was not deliberating on todays proven technology when I made those statements in my previous comment. There are several prototypes in the pipeline which will be entering the market in 3 to 5 years. Lab models exist but have to be scaled up for industrial production. One of these is the Li Air and Graphene with its astonishing prroperties is just being scratched on the surface. In another 15 to 20 years, no one will remember anymore what Li was once used for.

@ Davemart:
Fast charging on the road will not be accomplished in the same mannner as charging at home overnight. Charging stations will have to be boosted with battery blocks in the MW range. With the right battery, suited for quick charging, there is no time problem while charging. Surely a 50 to 100 kW charge will force a normal grid to its knees but not a MW battery block buffered from the grid.

cujet

Interestingly enough, I drive quite a bit for work (hate commercial flight), hence my comment about interstate travel. There are very many days where I am expected to travel more than 200 miles. And very common days include home to office, to other airport, to a vendor to office to home. Plug in hybrids are what I would need. Hence my serious interest in battery technology. The Volt, unfortunately, falls short.

kelly

"ICE small Wankel type 30 kW range extender could weight as much as 60 lbs and compensate fast charging need and BIG BIG battery need!!!! And still 90% of population will be able to travel 90% of their distance using el. power."

I think Darius 'hit the nail on the head' and, quoting the 8 Million Dollar Man, "We have the technology".

SJC

The Volt EREV set the tone for PHEVs. It can go about 40 miles on a charge, maybe we only need 20 miles on a charge to be useful. Lots of people do errands on the weekends and would never need to use any gasoline. During the week commuting, just being able to plug in every night and get 40+ mpg saves LOTS of fuel.

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