## ZSW develops process for Li-ion batteries with extended cycle life; 10,000 charge cycles

##### 04 June 2013

Scientists at the Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW) (Center for Solar Energy and Hydrogen Research Baden-Württemberg) have developed Li-ion batteries that have already demonstrated a very high cycle life of more than 10,000 full cycles with retention of more than 85% of original capacity. The cells have a power density of 1,100 W/kg.

The active materials for the batteries exclusively originate from German companies. ZSW designed the cells, developed the manufacturing process and produced a small sample series in the 18650 format. The technology has also created the basis for manufacturing large-size pouch and prismatic cells. The Lithium-ion batteries are intended for use in electric vehicles and as solar power storage systems.

After 10,000 complete charging and discharging cycles with a complete charge and discharge cycle per hour (2 C), our lithium batteries still have more than 85 % of the initial capacity. That also provides excellent prospects for a long calendar life.

—Dr. Margret Wohlfahrt-Mehrens, Head of the Accumulator Material Research Department in Ulm

In a 2012 paper (Tran et al.) published in the Journal of Power Sources, ZSW researchers noted that electrode manufacturing for lithium-ion batteries is based on a complex process chain with several influencing factors and that a proper tailoring of the electrodes can greatly improve both the electrochemical performances and the energy density of the battery.

In that paper, which specially investigated an NCA cathode material (LiNi0.8Co0.15Al0.05O2) they showed that electrode thickness, the degree of compacting, and the conductive agent type and mixing ratio have a strong impact on the electrochemical performances of the composite electrodes, especially on their behavior at high C-rates.

The ZSW researchers outlined the basics for optimizing cycling stability through the balancing of anode and cathode in a presentation later that year at the Honolulu PRiME 2012 meeting of The Electrochemical Society.

The balancing of electrodes means that the electrodes must be adjusted because the complete lithium is introduced by the positive electrode. Otherwise, when the electrodes are not adjusted this could lead to a lithium deposition on the surface of the negative electrode. Therefore the negative electrode (anode) was oversized to avoid the lithium deposition on the anode surface. The balancing of the electrode must be performed as accurately as possible. A high oversizing of the anode leads to a loss of energy density of the complete cell. One the other hand an oversizing of the cathode results in lithium deposition on the anode surface.

The problems with the accurately balancing of the electrodes are the different kinetics of the electrodes, the irreversible losses which can not be exactly recorded with half cell measurements, etc.

—Wilka et al.

The small cells are produced semi-automatically in a plant in the ZSW Laboratory for Battery Technology (eLaB) in Ulm. The cell development has been funded by the German Federal Ministry of Education and Research (BMBF) and the German Federal Ministry of Economics and Technology (BMWi). Such research contracts enable interested companies to have new materials and processes evaluated without having to stop their own production.

In a next stage, the researchers at ZSW want to develop electrodes for large prismatic lithium cells together with partners from industry.

It’s essential to master the currently demonstrated cell technology before going on to produce large cells.

—Margret Wohlfahrt-Mehrens

Wohlfahrt-Mehrens says that although further research and development work is necessary for the technology’s implementation in large cells, upscaling is in principle possible.

Resources

This people may have found the way to produce the impossible high performance battery, Many posters, like Kit P, will be highly disappointed.

GM has had the Envia the record setting high performance battery for 15 months, but it seems EV batteries have to be publicly SOLD for months/years before people are allowed to use them.

Tesla uses NCA type of cell in 18650 format. This could mean that this type of cell has a good future road-map.

“Many posters, like Kit P, will be highly disappointed. ”

Why would I be disappointed? I work in the power industry, we dream of capturing market share. Twenty years of disappoint with claims of the EV industry makes me skeptical.

Let me know when batteries stop being inefficient, heavy, expensive, and failure prone. In May I saved $400 by not driving a BEV. Did not even had to buy gas. Loaned my PU to someone moving. It cam back with a full tank of gas. If someone saves$10,000 on fuel using an EV only to have to replace a $20,000 battery, that is not a bargain. If these batteries can go 20 years or more, they go for the life of the car. Saving$40,000 over 20 years pays for the original price of the car.

>>>>"Let me know when batteries stop being inefficient, heavy, expensive, and failure prone."

You are hereby informed (let you know) of the above as of now, this moment. See also the previous article about recent development at Stanford University about Lithium battery with 5,000 charging cycles.

Harvey D's seemingly wildly optimistic prediction about BEV is now vindicated. And perhaps even sooner than what he predicted. Cheers, HD!

“You are hereby informed ..”

Really! So what do they cost? How much do they weigh? What is the efficiencies for charging and discharging? What is the failure frequencies for all the components?

Roger as most who post here do not understand the difference between useful information and BS. If it sounds to good to be true, it not true. I will be buying a car not a process. What data provide me reasonable assurance that I can save money over the life of the car then I will be buying a BEV. It will not be in my lifetime.

To be fair, battery "breakthroughs" have been announced every few weeks for at least the past decade. They rarely make it to production.

I think we would get an entirely different perspective on the state of battery tech if companies wrote press releases like this: "new Li-ion batteries fail heat-cycle testing," "new cathode chemistry disappoints," you get the idea.

Not the sort of thing that will reel-in investors, but a reasonable explanation for the hundreds of "breakthrough" batteries that never made it to market.

1,100 W/kg (should be Wh/kg?) and 10,000 cycles sounds great, but let's not count our chickens just yet.

@Bernard,
I believe they actually did mean 1,100 W/kg because they specifically called out power density. That is very good, but not "great". Of course, the fact they didn't mention Wh/kg means it was probably weak in that area LOL

Yes, there have been too many rosy predictions and breakthroughs announced. You just have to keep in mind that many of them are seeking funding, as you point out, so you just have to put your own filters on these announcements.

But just a few days ago, there was another announcement that was much more in line with production ready, next gen batteries coming: http://www.greencarcongress.com/2013/05/oxis-20130531.html

And even the one with Yi Cui and company was also exciting because "Stanford scientists used a battery fabrication process to make novel silicon/hydrogel electrodes"...even though it's a bit more on the early research side. But doing work on existing fab equipment is a great way to get to market one day and show it's practical and could be cost effective. http://www.greencarcongress.com/2013/06/bao-20130604.html#comments

I would just point to the organization, which is Center for Solar Energy and Hydrogen Research Baden-Württemberg. I doubt they are talking about car batteries. You see, thicker electrodes (and thus higher energy densities) and higher cycle numbers can be achieved when charging and dischargeing currents are lower. Not very good for EVs, but just fine for solar storage. The higher energy density also means lower cost, and higher cycle numbers means lower cost of storage overall because of the increased utilization. It has always been amazing to me that the solar industry and government solar people seem oblivious to the nuances. I guess the solar folks have had enough success to build in their own set of useless yesmen morons promoted to support the big bosses ineptitude, like every other old business or government department in the US.

bernard,

Why are people always looking for breakthroughs? Because it makes for an exciting story? Because it fuels the hope?

Do not overinterpret these research findings. Usually they only apply to a part of the battery (cathode, anode or electrolyte), and then only to one aspect (energy density, cycle life, heat tolerance, power density, price).

These research findings are just a step along the slow but steady path towards better batteries. All these findings and the understanding that comes with it contribute to gradually improving batteries. They have done so over the past decades and will continue to do so in the foreseeable future.

If you look at the semiconductor field, these kind of 'breakthroughs' are reported frequently. Did it lead to a breakthrough cpu? No, there has been a steady flow of faster, cheaper and more energy efficient cpu's. Forget about the breakthroughs. The steady progress over the past decades has made possible the current crop of EV's which were a pipe dream only 15 years ago.

15 years ago was the era of the EV-1, reportedly costing $80,000 to produce. The Tesla Model S is far cheaper to produce and incomparable to the EV-1, beating it by a wide margin in every respect. We'll get there sooner than you think. Without miracle breakthrough. But the EV-1 got 6.0 miles per kwh (on a driving cycle, not constant speed) and the Tesla Model S only gets 3.5. The EV-1 cost$80,000 because only a few were made. Actually I would compare the Leaf to the EV-1 - about the same weight, similar range (75 miles), but the Leaf also gets only 3.5 miles per kwh. It seems like 15 years later, the new BEVs, with 5 times better batteries, would have better, not worse milage.

@Zhukova
It's not just weight. The EV-1 was both lightweight AND aerodynamic. The EV-1 weighed 2,908 lb to the Tesla Model S's 4,647.3 lb and the Leaf is a box compared to the EV-1's Frontal Area of 1.9468 square meters (21.025 square feet) X Cd 0.188 = Drag Factor (CdA) 0.366 square meters (3.9528 square feet)

BTW the Leaf still weighs 3,291 lb to the EV-1's 2,908 lb.

I don't see how 10% lower weight than Leaf translates into 70% better mileage. Drag factor isn't going to make more than 5% difference for an EPA style combined cycle driving test. I think something else like power electronics or cooling system has something to do with it.

Are you sure S model Tesla only weighs 4,647lb? I think it's more like 4,900. That would explain the low mileage. The Volt gets barely 3 miles per kwh, but it has to lug around the dead weight of the ICE power train.

“I don't see how 10% lower weight than Leaf translates into 70% better mileage. ”

That is correct. It takes a certain amount of 'work' to move a mass from point A to point B. The amount of energy that is needed to move the BEV depends primarily on the efficiencies of the coal-based generation, how far away that power is being produced, and how inefficient the batteries are.

A light weight golf cart that go short distances with a few batteries makes a great deal of sense. One person driving to work in a $40k-$105 5 passenger car with a half to a full ton of batteries is not very clever.

"The amount of energy that is needed to move the BEV depends primarily on the efficiencies of the coal-based generation..."

I don't know what you mean by "That is correct." We weren't talking about the well-to-wheel efficiency. We were talking only about the rated or measured mileage, which only depends on the energy stored in the batteries and the distance traveled.

10% lower weight isn't going to give 70% increased milage in anything. Perhaps if you measured the mileage only during acceleration, or only going uphill, it might be true, but that's an absurd proposition. The work required to move a car from point a to b, when not accelerating, is mostly due to friction, not weight.

I've talked with people who drove EV1's including the guy who ran the EV charging program for Georgia Power back in the 90's. People claim that they really did get about 6 miles/kWh, but I wonder how they would have stacked up on the same test the Model S runs today for those EPA ratings.

People are probably remembering with fondness the best case scenarios and the EV1 was an aerodynamic dream for highway speed travel. ai_vin gave the salient points that would make the difference there: CdA of 1.9468m^2 for the Model S vs 0.366m^2 for the EV1 is a HUGE difference.

I'll have to give a couple of the guys a call and ask them to be honest with themselves and talk about the average vs best case for the EV1. If they really did get an everyday 6 miles/kWh then Zhukova has a very valid question.

Thanks Dave.

You see Zhukova it's not just the 10% lower weight, you also have 530% better aerodynamics. People too often overlook the benefits of streamlining. Even just reducing your Cd works wonders, for just $400 this guy halved his Cd and doubled his mpg; http://www.aerocivic.com/ A modern Class 8 truck gets 5.5-6.5 mpg. This one; http://www.airflowtruck.com/ gets 13.4 mpg. Right, a 10% reduction in weight PLUS a 530% reduction in air drag. “I don't know what you mean by "That is correct." ” A small change in weight is not going to make a large change mileage. “is mostly due to friction ” It depend on how fast you are driving. My light PU does better in town than on the highway while the Corolla does better on the highway. If you are going to drive very far at highway speeds, you need to add lots of weight for batteries. That means the BEV will do very poorly in stop and go driving. The problem with modeling is they may not match real life experience. For posters who worry too much about the current USA's power generation mix (i.e too many dirty coal fired power plants) for future BEVs, we may have the solution. We currently have an average surplus of 5,000 mega-watt or 5,000,000 KW of clean hydro power we could export (24/7) to USA's east coast States at about$0.05/KWh. Within 5 years we could easily double that at about \$0.08/KWh.

Unfortunately, USA's authorities do not like clean hydro energy and have shown a strong preference for fossil fuel based power plants while continuously blaming China for doing the same.

It is a rather funny world. In a 'Moneycracy' talks/words do not always match reality. Higher profits at all cost is the rule.

It is time to switch to cleaner ways (starting with cleaner e-energy, BEVs etc) before the majority suffers from avoidable industrial diseases, such as cancers, autism; Alzheimer and other brain diseases; from too much metal (iron, copper and zinc) in our industrial food, over polluted air and water etc.

The comments to this entry are closed.