Green Car Congress  
Home Topics Archives About Contact  RSS Headlines

« BP acquiring upstream portion of Clean Energy’s renewable gas business for $155M | Main | PNNL team finds electrolyte additive enables fast charging, stable cycling Li-metal batteries »

Print this post

Goodenough and UT team report new strategy for all-solid-state Na or Li battery suitable for EVs; plating cathodes

1 March 2017

A team of engineers led by John Goodenough, professor in the Cockrell School of Engineering at The University of Texas at Austin and co-inventor of the lithium-ion battery, has developed 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. An open-access paper on the work is published in the RSC journal Energy & Environmental Science.

The cells use a solid glass electrolyte having a Li+ or Na+ conductivity >10-2 S cm-1 at 25 ˚C with a motional enthalpy ≈ 0.06 eV, which promises to offer acceptable operation at lower temperatures. Using the new glass, the cathode consists of plating the anode alkali-metal (e.g., (lithium, sodium or potassium) on a copper–carbon cathode current collector at a voltage of more than 3.0 V. Replacing a conventional host insertion compound as a cathode by a redox center for plating an alkali-metal cathode provides a safe, low-cost, all-solid-state cell with a large capacity resulting in high energy density and a long cycle life.

The solid glass electrolyte also has a surface that is wet by metallic lithium or sodium, which allows the reversible plating/stripping of an alkali-metal anode without dendrites, and an energy-gap window > 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.

Traditional rechargeable batteries use a liquid electrolyte and an oxide as a cathode host into which the working cation of the electrolyte is inserted reversibly over a finite solid-solution range. The energy-gap “window” Eg = 1.23 eV of an aqueous electrolyte restricts rechargeable batteries with a long shelf life to a voltage V ≲ 1.5 V. The organic-liquid electrolyte of the lithium-ion battery has an energy-gap window Eg ≈ 3 eV, but its LUMO is below the Fermi level of an alkali-metal anode, it is flammable, and it is not wet by an alkali-metal anode; therefore, the anode of a rechargeable battery having an organic-liquid electrolyte does not contain an alkali-metal component lest anode dendrites form and grow across the electrolyte to the cathode during charge to short-circuit the battery cell with incendiary consequences.

Moreover, if the battery cells have an anode with a chemical potential (Fermi level) EF < 1.3 eV below the EF of lithium metal, a passivating solid/electrolyte interphase (SEI) is formed on the anode to prevent reduction of the electrolyte on contact with the anode. If the Li-ion battery is fabricated in a discharged state, as may be required for high-voltage cathodes, the Li+ of the SEI layer comes from the cathode, further restricting the operational capacity of the cathode. The carbon anodes of the Li-ion batteries that today power hand-held and portable devices have a low volumetric capacity and restrict the rate of charge since metallic lithium is plated on the carbon at higher charging voltages; also, oxide cathodes providing a cell voltage V 4 4.3 V versus lithium tend to be unstable if overcharged.

Therefore, the multiple cells of a large-scale battery stack require an expensive management system. Attempts to develop Li-alloy anodes have generally failed to provide the volumetric energy density required for portable batteries. Finally, sodium is cheaper than lithium and widely available from the oceans, which makes a sodium battery preferable to a lithium battery, but insertion hosts for Na+ have lower capacities than insertion hosts for Li+.

In this paper, we report 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.

—Braga et al.

The all-solid-state metal-plating batteries with the cathode strategy are simpler to fabricate at lower cost and offer much higher energy densities, longer cycle life, and acceptable charge/discharge rates, the researchers said.

For the study reported in EES, the UT team fabricated Li+ and Na+ glass electrolytes. Cathodes consisted of a redox center (an S8 or ferrocene molecule or an MnO2 particle) embedded in a mix of electrolyte and carbon contacting a copper current collector. The cathode composite was pressed against the electrolyte membrane in a coin-cell configuration.

Braga
Schematic representation of a plating cathode: the plating process on discharge with a redox center, the electrode energies, and the EDL capacitances at electrode/electrolyte interfaces are shown. Braga et al. Click to enlarge.

The researchers demonstrated that their new battery cells have at least three times as much energy density as today’s lithium-ion batteries. The UT Austin battery formulation also allows for a greater number of charging and discharging cycles—more than 1,200 cycles with low cell resistance.

Additionally, because the solid-glass electrolytes can operate, or have high conductivity, at -20 degrees Celsius, this type of battery in a car could perform well in subzero degree weather. This is the first all-solid-state battery cell that can operate under 60 degree Celsius.

Braga began developing solid-glass electrolytes with colleagues while she was at the University of Porto in Portugal. About two years ago, she began collaborating with Goodenough and researcher Andrew J. Murchison at UT Austin. Braga said that Goodenough brought an understanding of the composition and properties of the solid-glass electrolytes that resulted in a new version of the electrolytes that is now patented through the UT Austin Office of Technology Commercialization.

Goodenough and Braga are continuing to advance their battery-related research and are working on several patents. In the short term, they hope to work with battery makers to develop and test their new materials in electric vehicles and energy storage devices.

This research is supported by UT Austin, but there are no grants associated with this work. The UT Austin Office of Technology Commercialization is actively negotiating license agreements with multiple companies engaged in a variety of battery-related industry segments.

Resources

  • M. H. Braga, N. S. Grundish, A. J. Murchison and J. B. Goodenough (2017) “Alternative strategy for a safe rechargeable battery” Energy Environ. Sci., 10, 331-336 doi: 10.1039/C6EE02888H

March 1, 2017 in Batteries, Li-Sulfur, Solid-state | Permalink | Comments (6)

Comments

A times 3 density gain over present Li batteries and nonflammable would be outstanding...however, it's still in the Lab; so we'll see. Based on the data, that would give a current 3,000 lb Leaf about a 300 miles range.

At 3 times current batteries energy density (i.e. 600 Wh/Kg instead of 200 Wh/Kg) most short range (100 miles) BEVs could become extended range BEVs with 300 to 350 miles between refills.

Mega factories could be fully automated?

It just prove that my seal of disapproval for current evs was righteous. So stick to small gas car for the moment and goverment under trump and pruit administration should cancel all ev subsidies.

Interesting article. Excerpt:
Since the glass electrolyte is not reduced by the anode, no
anode-electrolyte interphase (SEI) is formed, and since the
electrolyte is wet by the anode, no anode or cathode dendrites are formed. Moreover, wetting of the electrolyte by the alkali metal anode allows volume changes at both the anode and the cathode during cycling to be accommodated by pressure from a spring at the back of one of the current collectors since the volume change of the electrodes is constrained to be perpendicular to the electrode electrolyte interface. The absence of an SEI on both electrodes and elimination of a large 3D insertion particle volume change and/or small active electrode particles that limit volumetric capacity provide a simplified, low-cost structure in which the principal sources of capacity fade on cycling are not present. The result is a cheaper cell with a large volumetric capacity and a long cycle life. The cell voltages and rates are acceptable.

Can't believe gorr is still around spouting his nonsense after all these years.

Is it not a double-layer ionic capacitor rather than a battery? The amount electric charge stored in the capacitor is directly proportional to the lithium metal deposited or stripped from the electrodes.

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Working...
Your comment could not be posted. Error type:
Your comment has been posted. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

Working...

Post a comment

Green Car Congress © 2017 BioAge Group, LLC. All Rights Reserved. | Home | BioAge Group