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UMD researchers report solution to high interfacial impedance hampering developing of high-performance solid-state Li-ion batteries

Garnet-type solid-state electrolytes (SSEs) for Li-ion batteries offer a range of attractive benefits, including high ionic conductivity (approaching 1 mS cm−1 at room temperature); excellent environmental stability with processing flexibility; and a wide electrochemical stability window. However, development of high-performance solid-state Li-ion batteries (SSLiBs) using these materials has been hobbled by the the major challenge of the high solid–solid interfacial impedance between the garnet electrolyte and electrode materials.

Now, team of researchers at the University of Maryland Energy Research Center and A. James Clark School of Engineering report a solution to this problem. In a paper in Nature Materials, the researchers report effectively addressing the large interfacial impedance between a lithium metal anode and the garnet electrolyte by using ultrathin aluminium oxide (Al2O3) coating placed by atomic layer deposition.

With the garnet composition Li7La2.75Ca0.25Zr1.75Nb0.25O12 (LLCZN) as the electrolyte material of choice (due to its reduced sintering temperature and increased Li-ion conductivity), the team observed a significant decrease of interfacial impedance from 1,710 Ω cm2 to 1 Ω cm2 at room temperature—effectively negating the lithium metal/garnet interfacial impedance.

Experimental and computational results showed that the oxide coating enables wetting of metallic lithium in with the garnet electrolyte surface and the lithiated-alumina interface allows effective lithium ion transport between the lithium metal anode and garnet electrolyte.

Characterizations of garnet solid-state electrolyte/Li metal interface. a, Schematic of the wetting behavior of garnet surface with molten Li. b, SEM images of the garnet solid-state electrolyte/Li metal interface. Without ALD-Al2O3 coating, garnet has a poor interfacial with Li metal even on heating. With the help of ALD-Al2O3 coating on garnet, Li metal can uniformly bond with garnet at the interface on heating. Inset are photos of melted Li metal on top of the garnet surface clearly demonstrating classical wetting behaviour for the ALD-treated garnet surface. Credit: Han et al. Click to enlarge.

The researchers also demonstrated a working cell with a lithium metal anode, garnet electrolyte and a high-voltage cathode by applying the newly developed interface chemistry.

This is a revolutionary advancement in the field of solid-state batteries—particularly in light of recent battery fires, from Boeing 787s to hoverboards to Samsung smartphones. Our garnet-based solid-state battery is a triple threat, solving the typical problems that trouble existing lithium-ion batteries: safety, performance, and cost.

—Liangbing Hu, co-corresponding author

Bruce Dunn, a UCLA materials science and engineering professor who was not involved in the research said the the work by the UMD team “effectively solves the lithium metal–solid electrolyte interface resistance problem, which has been a major barrier to the development of a robust solid-state battery technology”.

In addition, the high stability of these garnet electrolytes enable the team to use metallic lithium anodes, which contain the greatest possible theoretical energy density. Combined with high-capacity sulfur cathodes, this all solid-state battery technology offers a potentially unmatched energy density that far outperforms any lithium-ion battery currently on the market.

Lithium-ion battery pioneer John B. Goodenough, Virginia H. Cockrell Centennial Chair in Engineering at the University of Texas (who was also unaffiliated with the study) :

Xiaogang Han et al. report that deposition of an ultrathin layer of Al2O3 on a dense garnet-based solid Li+ electrolyte by atomic-layer deposition allows dendrite-free plating/stripping of a lithium anode with a small impedance to Li+ transport across the lithium/garnet interface. This [finding] is of considerable interest to those working to replace the flammable liquid electrolyte of the lithium-ion rechargeable battery with a solid electrolyte from which a lithium anode can be plated dendrite-free when a cell is being charged.

The polycrystalline garnet-derived oxide Li7La3Zr2O12 has a bulk Li+ conductivity σLi ≈ 10-4 S cm-1 and is stable on with lithium metal at room temperature; the flammable liquid electrolyte has a σLi ≃ 10-1 S cm-1, but a lithium anode forms dendrites (whiskers) during charge of a rechargeable battery and the dendrites can grow across a thin liquid electrolyte to the cathode to give an internal short-circuit that ignites the electrolyte. Although a bulk σLi ≈ 10-3 S cm-1 can be obtained with a garnet by suitable doping, initial attempts to plate lithium from the garnet resulted in anode dendrites that penetrated the garnet grain boundaries to reach the cathode. This observation reinforced a generally held assumption that dendrites are inevitably formed on a lithium anode during plating and that blocking the dendrites by a solid electrolyte would result in a high impedance to Li+ transfer across the anode/electrolyte solid/solid interface. In addition, with more than three Li+ per formula unit, the electrolyte Li+ leaves the solid to react with oxide species in the grain boundaries of the garnet to create a large grain-boundary impedance to Li+ transport.

The [University of Maryland research team] has overcome these problems with two important innovations: first, the composition of the garnet framework was changed to allow fabrication at lower temperatures of a dense polycrystalline solid with tight grain boundaries while retaining a σLi ≈ 10-3 S cm-1; second, application of an ultrathin interphase Al2O3 film between the anode and the garnet electrolyte is shown to prevent the formation of dendrites on plating a lithium anode; therefore, a lithium/garnet interface can be fabricated so as to give a bonded interface with a low impedance to Li+ transport. Reaction of the Al2O3 interphase with Li+ from both the electrolyte and the anode transforms the thin Al2O3 interphase to a Li+ conductor.

The ability to plate a dendrite-free alkali-metal anode from a solid electrolyte can be accomplished where the alkali metal wets the electrolyte surface; it has recently been achieved by several groups with different solid electrolytes, but plating at high currents can be a problem. An electrolyte σLi ≈ 10-3 S cm-1 is not high enough for such a test or for high-power batteries; the problems of fabricating a low-impedance cathode/electrolyte interface and of a thin ceramic solid electrolyte of sufficient mechanical properties for a large-area membrane have yet to be solved.

This work was supported by the US Department of Energy ARPA-E RANGE (entitled “Safe, Low-Cost, High-Energy-Density, Solid-State Li-Ion Batteries”) and EERE (entitled “Overcoming Interfacial Impedance in Solid-State Batteries”).


  • Xiaogang Han, Yunhui Gong, Kun (Kelvin) Fu, Xingfeng He, Gregory T. Hitz, Jiaqi Dai, Alex Pearse, Boyang Liu, Howard Wang, Gary Rubloff, Yifei Mo, Venkataraman Thangadurai, Eric D. Wachsman & Liangbing Hu (2016) “Negating interfacial impedance in garnet-based solid-state Li metal batteries” Nature Materials (2016) doi:



This will be a cracker if there are no 'gotchas'.

Its a shame they don't specify the energy density, but it has to be something over 1,000 Wh/Kg I would have thought, which is a whole different ball game.

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We need to see battery cells for sale in volume at a non-prohibitive price with this tech before we can celebrate anything. Having one working cell and tests and computer simulations does not prove commercial viability. The most important discoveries in battery tech are those that are not announced because they are made by for-profit companies like Panasonic and LG that need to do extensive and time consuming validation and file patent applications etc before they will start making their new batteries.

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I may add the other news by Huawei Watt Lab below is more interesting because it comes from a battery maker and is far more specific with cycle numbers and temperature. Shows they are years ahead in terms of commercialization than this highly unspecific news from UMD.


This is obviously early stage research and should be evaluated as such.
I am not sure what I have said which can fairly be interpreted otherwise.

Nor is it apparent why the prospects for the very different stage developments at Huawei alter of affect those of this technology in any way, or vice versa.

They are different subjects, and different technologies.

Account Deleted

Davemart I was just making a general comment. Not addressing or criticising you at all.



Apologies for the missreading!

As known to the regular readers here, and acknowledged by Davemart, a pathway to solid state lithium metal batteries is a game changer, even though current Li-Ion energy densities already provide such a significant level of utility. Personal electronics and cars will be the volume markets, but perhaps more significant is the opportunity to create entirely new markets that did not exist (or are profoundly transformed) based on the opportunity.


The pre lithiation idea was good as well.
The first charge creates the barrier, that is eliminated.

Account Deleted

There is no doubt that an effective solution to the dendrite problem will be a breakthrough for solid state batteries with higher energy density. However, UMD is not alone to claim such a breakthrough. There is Solid Energy that are in the initial stage of launching limited volume production.

However, it is taking time and they seem to be delayed all the time.

They claim 400wh/kg for their cells which will be a record for a stable solid cell.

I am sure that Panasonic and LG are also working feverishly on it and once they start making them it is game over for the startups. It reduces to a volume game once the tech is doable in a real product.

I agree that much higher wh/kg and we will start to see batteries for applications not yet imagined. If we could get over 500wh/kg battery electric airplanes and hexa copters could become a big thing. Add fully auto piloted tech and it will become a new important way of personal transportation. Not to mention killer robots for war and exoskeletons.


This does appear to be important research (If you would like additional information check
This is next generation battery tech and it has been reviewed by both Goodenough and Dunn. It takes some time before Material Science develops into commercial products. Dr. Goodenough LiCO cathode was patented in 1980 and Sony introduced the batteries in 1991.
There are many companies that are looking into Solid state and Lithium-Sulfur batteries, e.g. Dyson, BASF, and many others. Interesting to note that Sony is no longer in the battery business even though they invented the first generation battery.
The Huawei research is interesting too since it involves Graphene. Fisker Nanotech claims their EV batteries will use Graphene.
The 2018 EV batteries are already in production, might put some in my future E-Bike (check out BMZ 3Tron battery system that uses Samsung 21700 batteries. These are planned for the Lucid Motors Air EV (Tesla will use a Panasonic version).

Dr. Strange Love

The problem is the conductivity of the electrolyte they chose. It is too low at just 10^-3 S/cm^2. The liquid electrolyte works much better before dendrite short circuit occurs. The periodic chart is the limit. Li is as simple as it gets in the alkali metal group, and is limited in its bonding arrangements given its [He]2s1 noble configuration.

The lead acid battery didn't change much several decades after it was first used.


Actually Lead Acid batteries have changed quite a lot since Gaston Plante's original design in 1859. The sealed lead acid emerged in the 1970's and the most common are gel, also known as valve-regulated lead acid (VRLA), and absorbent glass mat (AGM). The Firefly Carbon Foam VRLA AGM GEL battery was invented in 2000 at Caterpillar and extended Lead Acid Battery life greatly. The Ultra Battery was developed by CSIRO in Australia, its key feature is the combination of the high-performance carbon ultracapacitor with the lead-negative electrode.
The only thing that cannot change is the maximum energy density of the Lead-Sulfuric Acid chemistry which could exceed 167 W-hrs/kg though is typically 30-40 W-hrs/kg.


True all solid electrolytes have low ionic conductivity compared to to organic liquid electrolytes. However, it still looks like this problem could be resolved. Check "Review—Solid Electrolytes in Rechargeable Electrochemical Cells", John B. Goodenough*,z and Preetam Singh, Journal of Electrochemical Society, 2015 volume 162, issue 14, A2387-A2392, doi: 10.1149/2.0021514jes (or


AGM is what powered the Tzero ancestor to the Tesla roadster.

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