Penn State team devises solution for fast charging of Li-ion batteries at cold temperatures
13 July 2018
Fast charging is seen as a solution for range and recharging time issues for EVs. However, a critical barrier to fast charging is temperature. Fast charging in cold or even cool temperatures brings the risk of lithium plating—the formation of metallic lithium that drastically reduces battery life and even results in safety hazards.
Now, a team from Penn State has devised an approach that enables 15-min fast charging of Li-ion batteries in any temperatures (even at −50 °C) while still preserving remarkable cycle life (4,500 cycles, equivalent to >12 y and >280,000 miles of EV lifetime), thus making EVs truly weather-independent. A paper on their work is published in Proceedings of the National Academy of Sciences (PNAS).
Fundamentally, lithium plating is affected by the rate of ion conduction and diffusion in the electrolyte, lithium diffusion in graphite particles, and reaction kinetics at graphite surfaces. Key parameters governing these processes all follow the Arrhenius law and drop substantially with temperature. As such, a plug-in hybrid EV (PHEV) cell that can withstand a 4-C charge without lithium plating at 25 °C can only allow a 1.5-C charge at 10 °C and C/1.5 at 0 °C to prevent lithium plating, which explains the long recharge time of today’s EVs at low temperatures.
To enhance fast charging ability, research in the literature has been focusing on improving anode materials such as coating graphite with an amorphous silicon nanolayer and developing new materials like lithium titanate and graphene balls, and on developing new electrolytes and additives. LiBs, however, are well known for their trade-off nature among key parameters. Improving one property without sacrificing another is always nontrivial. For instance, electrolyte with superior performance at low temperatures is quite often unstable at high temperatures. … It is extremely difficult, if possible at all, to develop materials with a high rate for charging while preserving durability and safety over a wide range of temperatures.
Here, we make an attempt to free battery science from trade-offs. Specifically, we present a cell structure that can be actively controlled to achieve lithium plating-free (LPF) fast charging in any ambient temperatures, enabling a paradigm shift of the relation between cycle life and temperature, from the Arrhenius correlation of conventional LiBs to a horizontal line insensitive to temperature.
—Yang et al.
The Penn State team uses a rapid internal fast-heating step prior to charging. The self-heating LiB structure has thin nickel (Ni) foils embedded inside a cell that can create immense and uniform heating.
The Ni foil becomes an inherent component of a single cell along with electrodes and electrolyte. It serves as an internal heating element, as well as an internal temperature sensor; the introduction of Ni foils only adds 0.5% weight and 0.04% cost to a conventional LiB single cell.
In their study, the team used 9.5-Ah pouch cells with graphite anode, LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode, and a cell-level energy density of 170 Wh/kg.
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| Schematic of the self-heating lithium-ion battery structure. Two pieces of thin nickel (Ni) foils are inserted into the cell, each located at ¼ cell thickness from cell surfaces. Each Ni foil is coated with thin polyethylene terephthalate for electrical insulation, and sandwiched between 2 single-sided anode layers. One ends of the two Ni foils are welded with tabs of anode layers and connected to the negative terminal; the other ends of the two Ni foils are welded and extend outside to form a third terminal, named activation (ACT) terminal. A switch is added between positive and ACT terminals. Yang et al. Click to enlarge. |
With the internal Ni foil, the team demonstrated the cell could be charged to 80% state of charge in 15 min even at −50 °C (beyond cell operation limit). Further, the cell sustained 4,500 cycles of 3.5-C charging in 0 °C with <20% capacity loss—a 90× boost of life compared with a baseline conventional cell— and equivalent to >12 y and >280,000 miles of EV lifetime under this extreme usage condition, i.e., 3.5-C or 15-min fast charging at freezing temperatures.
In comparison, cells with identical battery materials charged at 0 °C only sustained 50 cycles before losing 20% capacity.
… the present LPF cell holds great promise for next-generation EVs, as it can modulate cell internal temperature almost instantaneously on demand.
—Yang et al.
Resources
Xiao-Guang Yang, Guangsheng Zhang, Shanhai Ge, Chao-Yang Wang (2018) “Fast charging of lithium-ion batteries at all temperatures,” PNAS doi: 10.1073/pnas.1807115115
I think this an important advance, which also helps in a way which is perhaps not obvious.
The big penalty with BEVs in energy and emissions is in the very high level of energy embodied in building the batteries.
'Further, the cell sustained 4,500 cycles of 3.5-C charging in 0 °C with <20% capacity loss—a 90× boost of life compared with a baseline conventional cell— and equivalent to >12 y and >280,000 miles of EV lifetime under this extreme usage condition, i.e., 3.5-C or 15-min fast charging at freezing temperatures.'
Most are not going to be so heavily punished, so that assuming calendar life is OK the average life of a battery will be very high.
That transforms the average lifetime energy equation.
My objections to long range BEVs are not arbitrary, but based on solid potentially answerable issues:
Lifetime energy use.
Cost
Getting the electricity from renewables when you need it.
This goes some way to answering the first of those, but in my view long range BEVs are nowhere near for the other two, and FCEVs can answer them.
And temperature resistant batteries will help them a lot......
Posted by: Davemart | 13 July 2018 at 03:46 AM
How many years will it take to move that technology from the Lab to PHEVs/BEVs?
Posted by: HarveyD | 13 July 2018 at 05:17 AM
So if the battery is too cold to charge, heat the battery up to optimal temperature first. No-brainer, though I would divert the charging power to heaters rather than using battery power and possibly over-discharging the battery.
Posted by: Engineer-Poet | 13 July 2018 at 05:18 AM
Harvey:
Unless there are any gotchas, it sound do-able relatively soon to me, much quicker than solid state and so .
Not really practical for the small cylindricals Tesla use, I would have thought though,
Posted by: Davemart | 13 July 2018 at 06:06 AM
4500 cycles is an impressive number, but I find myself wondering whether you could not achieve the same results by building a a temperature controlled battery compartment (pack)? I also expect an energy cost to maintaining the temperatures at optimal using this method could be fairly substantial?
There must be some BEV's currently being operated in moderate climates where the battery temperature is always near optimal and I wonder if their battery degradation in similar to what is reported in this study.
280 k miles over 4500 cycles equates to 62 miles per cycle or a 20 kwh battery pack. Most packs for BEV's will be 40+ so there would potentially be way more miles of life than the rest of the car is capable if it is built to today's standards.
Posted by: Calgarygary | 13 July 2018 at 06:22 AM
Just warm the battery box, no problem.
Posted by: SJC | 13 July 2018 at 07:24 AM
SJC:
Well, they did not previously warm the battery box, so there would seem to be gotchas, maybe related to what you use to warm the box
Here is more technical information:
http://www.pnas.org/content/pnas/suppl/2018/06/21/1807115115.DCSupplemental/pnas.1807115115.sapp.pdf
Posted by: Davemart | 13 July 2018 at 09:15 AM
You put heating in the pack run by the grid, you don't need to modify every cell.
Posted by: SJC | 14 July 2018 at 06:38 AM
I've looked into it a bit more now, or more accurately a hugely informed expert has answered my questions, and he mentioned heating pads etc just as you said.
Another issue is the ongoing load, both to keep the battery at optimum temperature in the cold, and to heat the cabin.
It come out to 5-6KW, a very substantial load greatly decreasing range.
So it would be great if somehow, magically, that heat could be provided without impacting range.
Fortunately a fuel cell does just that, from its 'waste' heat.
Even though I look at battery advances with hope, I still end up coming back to what a fine technology fuel cells are.
Posted by: Davemart | 14 July 2018 at 01:22 PM
You don't have to heat the battery in operation. It has some amount of self-heating from resistive losses. All you have to do is keep that heat from escaping.
If you keep the people warm and the glass clear it doesn't really matter what temperature the cabin is.
You don't ask if it impacts anything else.
Surprise, so does an ICE... and we have everything we need to support ICEs already in place, rather than having to build an expensive new infrastructure from scratch. Use an ICE as your range extender; that's what a PHEV is.
Of course, the FCEV would be of very limited usefulness until that infrastructure was in place. In the mean time most people waiting on the "practical" FCEV would still drive ICEVs rather than switching to PHEVs. Doesn't this look suspiciously like diversionary defensive propaganda from the oilcos?
Posted by: Engineer-Poet | 14 July 2018 at 05:11 PM
You can insulate the battery to reduce heat losses,
That increases weight and bulk though, and does not help the cabin,
Sure, you can use an ICE, but that does not address the pollution issue, especially in the cold, and is a lot less efficient than fuel cells.
The infrastructure build out is happening right now, with for instance over 100 going in in South Korea, an area abou the size of that between. SF and LA.
Battery only people had better start finding some new excuses to dismiss whole fields of technology.
Posted by: Davemart | 15 July 2018 at 06:34 AM
Most of the objections can be overcome, that is the nature of progress.
Posted by: SJC | 15 July 2018 at 06:54 AM
Posted by: Engineer-Poet | 15 July 2018 at 08:38 AM
I don't dismiss fields of technology, preferring to look at criteria to meet or improve.
The Bosch diesel system perhaps running on synfuels or part syn fuels might go a long way to meeting or approaching targets for reducing pollution, be OK in the cold, and be able to run at least partly through renewables.
Alternatively much better batteries may come along - I have been hopeful since 2009, but although progress has been made, it is proving a tough nut to crack and both the cold and the drain from automation which uses a lot of power, aside from cost, remain very difficult other than for city runabouts.,
And I have long been an advocate of hybrids, but if the infrastructure can be run out, and it is being, replacing the ICE in it with a fuel cell is better in just about every measurable metric.
There are no breakthroughs needed, and Toyota reckon they can build fuel cell hybrids by 2025 at no more cost than any other hybrid,
That sounds ambitious, particularly in view of the need for a CF tank, but in the past at least it has proven unwise to bet against Toyota production engineering.
At the moment the only way we know to produce decent range and zero pollution in the cold is with fuel cells, so trying to rule them out seems not very sensible.
Posted by: Davemart | 15 July 2018 at 09:09 AM
Building out a trillion dollars in new infrastructure to achieve zero pollution under one specific set of conditions (which are the opposite of the ones which produce significant photochemical smog) is silly. It's doubly silly when the least-cost source of your new fuel is the same old fuel (natural gas) being peddled by the same old interests that have been ruling the roost for decades. You don't see this propaganda for what it is yet?
Electricity is always going to be way cheaper than either petroleum or hydrogen. Going electric means a lot less money changes hands and almost none of it passes through oilcos any more except for what goes to natural gas. You can tell what the oilcos fear because they never mention it, never give it any visibility: nuclear power and PEVs.
Hydrogen? They love hydrogen. They're all set up and ready to control hydrogen. Meet the new boss, same as the old boss.
If you want zero pollution, try a PHEV with an electrically preheated catalyst and something like DME for starting fuel. DME produces no soot and has a lower flammability limit of something like 2.7% in air. Fire up lean and burn any CO in an already-hot catalyst and you're good. Do this and we can skip the $trillion infrastructure project and get moving TODAY, not 15 years from now.
Posted by: Engineer-Poet | 15 July 2018 at 09:58 AM
EP:
You prefer to compare real solutions which we can do to fantasy ones based on nuclear reactors which aren't being built, at least in the West.
Let me know when they are building them in quantity.
And let me know when batteries can perform without massive loss of capacity in the cold, and at reasonable lifetime energy costs and money.
They can't without new technology.
BTW, I have nothing against DME, nor do I preclude anything.
Posted by: Davemart | 15 July 2018 at 12:44 PM
You think we "can do" HFCEVs everywhere? At $2.67 million per service station? There are over 110,000 service stations in the US today; you are talking $300 billion just for dispensing.
The beauty of PHEVs is that we already have almost everything we need.
Two AP1000s still going up at Vogtle. China's first AP1000 is already on the grid. It can certainly be done; France's grid emitted 58 gCO2/kWh last year, compared to Germany's 560 grams. Mass "renewable" power based on hydrogen for energy buffers? Nobody's done that anywhere, ever. The whole point of "renewables" is stranding the US on the "natural gas bridge" to nowhere.
Won't happen as long as the politics insist that wind and PV can do everything, despite all the evidence that they can't. Nuclear is frozen out despite providing 60% of our emissions-free electricity. Include nuclear under "renewables" for incentives, portfolio standards and grid priority and you'd see that change overnight.
BTW, the first-ever EPR went on the grid last month too. Also in China.
This entire post is about avoiding loss of capacity in the cold, by warming up the battery. So simple, but overlooked. Cycle life went WAY up too, or didn't you notice?
Nickel foil with a PETF insulator is new technology?The cost is no big deal even today, at least for PHEVs. Pack prices are headed for $200/kWh, so 10 kWh per vehicle only adds $2000. You get a host of benefits along with it, starting with massive fuel economy improvements even in engine mode. But perhaps most unappreciated is that most of your "fuel" comes from a plug, and you plug in wherever you are. You are no longer tied to filling stations for mobility.
The real irony? Where renewablistas want us to be... I've already been for 5 years now. But according to them, I'm "doing it wrong."
Posted by: Engineer-Poet | 15 July 2018 at 01:58 PM
"And let me know when batteries can perform without massive loss of capacity in the cold, and at reasonable lifetime energy costs and money.
They can't without new technology."
There are a number of companies using Tesla models S as taxies. A number of these cars have already passed 200,000 miles on the original battery with only about a 7% capacity loss. Additionally these cars routinely use the Tesla high speed chargers. One of the these taxie services is in Finland which has extremely cold winters. Driving rang is reduced by about 20% at or below 0C.
https://www.teslarati.com/tesla-model-s-400k-km-250k-mi-7-percent-battery-degradation/
https://cleantechnica.com/2018/07/15/tesla-range-plotted-relative-to-speed-temperature-graphs/
https://www.teslarati.com/tesla-model-s-400k-km-250k-mi-7-percent-battery-degradation/
Tesla already has temperature controlled batteries and many tesla owners take advantage of rapid charging stations on long trips and cold weather doesn't kill the batteries. We don't need any new technology .
What we have now is already better than any hydrogen fuel cell cars that have ever been made. Also fuel cells need to be heated at freezing temperatures otherwise ice will damage the fuel cells.
Posted by: Steven F | 15 July 2018 at 08:54 PM
Both BEVs and FCEVs can be adapted to operate with increased efficiency in cold weather areas. Current FCEVs can already do it while keeping the driver/passengers in comfort. BEVs lose 40% range in the same cold areas. Short range BEVs simply stop being driven on very cold days.
Another acceptable/possible solution are PHEVs with larger batteries (up to 100+ Km range) and a very small FC as range extender. To refill with H2 and recharge batteries on very long trips will cease to be a problem very soon as many more clean H2 stations are being installed.
Posted by: HarveyD | 16 July 2018 at 04:54 PM
The extended-range capability of the FC range extender is useless if the H2 network isn't where the vehicle needs to go. Chicken/egg. On the other hand, electricity is already almost everywhere you need to go and liquid fuels are much more portable than H2.
Give it up. Hypedrogen is a mirage. There's no way to get to it, and it's a stalking-horse for the Oilco's anyway. Go HEV and then PHEV right now and just keep making batteries bigger over time. That is the most effect for the least effort, soonest.
Posted by: Engineer-Poet | 16 July 2018 at 05:02 PM
With H2 buses and trucks there can be adequate refueling. H2 can be made at the point of fueling using MSR of renewable methane. The cost per kg of H2 is less that way and the carbon is neutral.
Posted by: SJC | 18 July 2018 at 08:52 PM
There isn't nearly enough "renewable" methane. In other words, it would just be another way of running on fossil fuel.
Also, you mean SMR, steam methane reforming. MSR is molten salt reactor.
Because the fallback is fossil methane, and methane leaks create more greenhouse effect than coal, your "green" hydrogen bus would actually be worse for the climate than a coal-fired plant charging a battery bus. And so ironic for someone using the Tesla logo as their avatar to be pushing hypedrogen.Posted by: Engineer-Poet | 19 July 2018 at 09:11 AM