UT Austin team devises new strategy for safe, low-cost, all-solid-state rechargeable Na or Li batteries suited for EVs
13 December 2016
Researchers at the University of Texas at Austin, including Prof. John Goodenough, known around the world for his pioneering work that led to the invention of the rechargeable lithium-ion battery, have devised a new strategy for a safe, low-cost, all-solid-state rechargeable sodium or lithium battery cell that has the required energy density and cycle life for a battery that powers an all-electric road vehicle.
As reported in their paper in the RSC journal Energy & Environmental Science, the cells use a solid glass electrolyte having a Li+ or Na+ conductivity σi > 10-2 S cm-1 at 25°C with a motional enthalpy ΔHm ≈ 0.06 eV, which promises to offer acceptable operation at lower temperatures. The glass also has a surface that is wet by metallic lithium or sodium, which allows reversible plating/stripping of an alkali-metal anode without dendrites, and an energy-gap window Eg > 9 eV that makes it stable on contact with both an alkali-metal anode and a high-voltage cathode without the formation of an SEI.
The glass also contains electric dipoles that endow it with a large dielectric constant. Optimal properties are only obtained after aging, which requires more than 10 days at 25°C, but only a few minutes at 100°C.
With this glass, a rechargeable battery with a metallic lithium or sodium anode and an insertion-compound as cathode may require a polymer or liquid catholyte in contact with the cathode. However, the team notes, the all-solid-state metal-plating batteries are simpler to fabricate at lower cost and offer much higher energy densities, longer cycle life, and acceptable charge/discharge rates.
To fabricate test cells for their study, the researchers took Na+ and Li+ glass electrolytes and introduced them into either a fiberglass sheet or a thin sheet of recycled paper from a slurry of the glass particle sin ethanol. They heated the membranes to outgas the ethanol and reform the solid glass electrolyte without grain boundaries, then pressed these against an anode of Li or Na foil contacting a stainless-steel cell container.
The electrolyte membrane was 0.06 mm thick. The cathode consisted of a redox center (an S8, or ferrocene Fe(C5H5) molecule or MnO2 particle) embedded in a mix of electrolyte and carbon contacting a Cu current collector.
This cathode composite was pressed against the electrolyte membrane in a coin-cell configuration. The sealed cell was then aged. None of the components were optimized before the electrochemical performance measurements.
|
|
| Schematic of an all-solid-state Li-S cell with the glass electrolyte; during discharge the metallic-lithium anode is plated on the cathode carbon-copper composite current collector. Click to enlarge. |
The ability to plate/strip reversibly an alkali-metal anode from a solid electrolyte invites a complete rethink of rechargeable-battery strategies. With the Li-glass and Na-glass electrolytes, we have demonstrated in this paper one possible new strategy in which the cathode consists of plating the anode alkali-metal on a copper-carbon cathode current collector at a voltage V > 3.0 V. Replacement of a host insertion compound as cathode by a redox center for plating an alkali-metal cathode provides a safe, low-cost, all-solid-state cell with a huge capacity giving a large energy density and a long cycle life suitable for powering an all-electric road vehicle or for storing electric power from wind or solar energy.
—Braga et al.
Resources
Maria Helena Braga, Nicholas S. Grundish, Andrew J. Murchison and John B Goodenough (2016) “Alternative Strategy for a Safe Rechargeable Battery” Energy Environ. Sci. doi: 10.1039/C6EE02888H
Could be important but reality is that less than 1% of these inventions make it into a real world product and it takes like 5 to 10 years before it is even possible. New battery tech coming before 2018 in real BEVs is the following 3 BEVs from Tesla, Faraday and Lucid and the story is here
https://electrek.co/2016/12/13/lucid-motors-first-electric-car-battery-pack-bigger-tesla-range/
Posted by: Account Deleted | 13 December 2016 at 03:35 AM
This could become an important early step in the development of improved SS lithium batteries? Can it be mass produced at a competitive price by 2022 or so? Will Toyota reach the same conclusion?
Posted by: HarveyD | 13 December 2016 at 07:39 AM
@Henrik,
You are correct 2018 technology is already in production. This technology is really for the 2022 time frame or later. This is also about the Anode and Electrolyte where as I pointed out was the flaw in Dr. Whitacre's study which only focused on the Cathode. Dr. Goodenough (who is still a great researcher, contributed with actually making Lithium Ion batteries practical) has included Sodium metal anodes as well (the area of his current research).
Lucid will make an announcement this week about their 2018 car. It should be interesting. The Samsung SDI 21700 battery has a long life > 4000 cycles (check their website) and Lucid has technology to handle repeated high energy charges and repeated high performance runs based on their Formula E battery.
Again no one knows what battery technology will look like in 2022, 6 years is still a long way off.
Posted by: Account Deleted | 13 December 2016 at 07:42 AM
@gryf I totally agree. I also expect the next jump in battery performance to be an anode invention. Startup Solidenergy also has an interesting anode breakthrough.
See http://www.greencarcongress.com/2015/01/20150131-solidenergy.html
Posted by: Account Deleted | 13 December 2016 at 09:28 AM
In reading this in more detail, Dr. Goodenough is not only rethinking the metal anode with a glass electrolyte, but also the cathode.
I could not get free access to this paper, however in another article with open access (Goodenough, "Batteries and a Sustainable Modern Society", Electrochem. Soc. Interface Fall 2016 volume 25, issue 3, 67-70, doi: 10.1149/2.F05163if), Dr.Goodenough discusses a cathode architecture that confines the charged Sulfur (S8) particles in mesoporous conductive fibers. Basically an all-solid-state cell with the glass electrolyte, a metallic-lithium anode, and a sulfur relay embedded in a carbon/glass mix on a copper current collector plates which is the strategy in this paper.
This approach if successful would lead to low cost, long cycle life energy storage.
Posted by: Account Deleted | 14 December 2016 at 08:48 PM
yes, yes but Where is the battery 300-400wh/kg?. 2050?.
Posted by: Centurion | 15 December 2016 at 03:07 AM
A few more details. These same authors: Braga, Murchison, etc, are involved in PATHION work to develop LiRAP-based solid-state electrolytes for Li-sulfur and sodium-ion batteries (see http://www.greencarcongress.com/2015/04/20150428-pathion.html). The earlier paper uses a Li3ClO-based glass electrolyte. The PATHION web site points out that a lithium-sulfur battery could achieve specific energy levels up to 800 Wh/kg.
The Li3ClO-based glass electrolyte could be used with current cathode technology (NCA or NMC based) to achieve 300-400 Wh/kg cell level energy densities with Lithium anodes for the next generation batteries in the 2020 timeframe.
Posted by: Account Deleted | 15 December 2016 at 07:16 AM
Many thanks for the info, gryf.
That sounds one of the more interesting approaches.
Posted by: Davemart | 15 December 2016 at 03:29 PM
yw
Posted by: Account Deleted | 16 December 2016 at 07:13 AM