Chemical reactions in lithium batteries

[Sunking]

It's the nature of charging. You're right: the charger is fairly "dumb," and the chemical reaction inside the battery limits the amount of current that can flow.

How dumb can you be? Pretty dumb if you are a pretender.

Lithium Ion batteries are not a chemical reaction pretender. It is Ion exchange. Ignore Nebster, he is dangerous and does not know what he is talking about and I will prove it right now. Pretenders giving dangerous advice and pretending they know what they are talking about get banned. Ask Karrak! Take notice Nebster you are being watched by moderators. I suggest you leave and haunt Arizona Wind & Sun forum where they welcome pretenders, advocates, and salesman.

OK let's answer your question with some facts. The IMax Charger is a very Smart Charger, it is a Hobby Charger made to charge any battery type
Here is what that DUMB CHARGER can do:

Feature summary

• Accepts AC input from 100-240 V or DC input from 11 to 18 volts.
• Charges 2 to20 Volt Pb batteries.
• Charges 1 to 15 NIMHor NiCd cells.
• Charges 1 to 6 LiPo, Li-ion, or LiFe cells.
• Integrated independent lithium battery balancer for 2 to 6 cells.
• Fast charge and storage mode for lithium batteries.
• Charge current range from 0.1 to 5.0 A . 50 watt max
• Discharge current range from 0.1 to 1.0 A . To measure battery capacity, 5 watt max
• Delta-peak sensitivity (automatic charge termination using delta-peak voltage detection).
• Input power monitor to prevent damage to a car battery when charging in the field.
• Charge-current limiting (NiMH, NiCd).
• Stores up to five user-created program settings.
• Cyclic charging/discharging.
• Temperature monitoring.
• 16 x 2 character LCD display.

So much for Nebster, he is as dumb as his charger, and here is the dangerous part Nebster has no clue about.

Your IMax has a built-in Active Balance Charger, and all good Balance Charger for Lithium Ion batteries have to Terminate the Charge when full or they go into Thermal Runaway and catch fire. You did not say what AH capacity the battery is, but generically you charge a Li battery at 1C. Example 1 Amp on a 1 AH battery. It uses a CC/CV algorithm and when the cells reach full charge voltage (3.6 to 4.2 depending on type,, it wil hold the voltage until Charge Current Tapers to C/10 or 0.1 Amps then turns off. If not Smoke on the Water and BOOM. However C/10 is pretty conservative and to get to 100% SOC, which you do not want to do with any lithium battery, terminate charge at C/30 or 3% of C (AH capacity). So the charger is smart enough to terminate but easily fooled because it it is not smart enough to read the battery AH capacity label printed on the battery. which is your job.

Now here is where you should pay close attention because you could be over charging the crap out of your battery, because you you are not telling the charger what AMp Hour Capacity or what rate to charge it at. Most all the Hobby Chargers by default assume if you set charge current to say 1-Amp assume it is a 1-Amp Charger, and wil terminate at C/10 or 0.1 Amps as you have described. So where is the problem you might ask?

You have not said what Amp Hour capacity your battery is. What i fit is say 10 AH? Your charger does not know unless you tell it. It thinks it is a 1 AH battery and wil not cut-off unti charge current tapers to 0.1 Amps or C/100 which means you are over charging the battery and risk Thermal Runaway and fire. Your charge is actual pretty smart, but garbage in = garbage out and with lithium can = Fire.

You can go one of two ways with this. Since I wear suspenders and a belt for safety. First check the max charge rate from the battery manufacture. It should likely say C/2 or 1 C. On say a 2500 mah battery would be 1.25 amps @ C/2 or 2.5 amps or 1C. Set your charger for that value. At 1C the charge will terminate @ .25 amps C/10, or @ .12 Amps C/20.

The other method is again from the battery manufactures cut sheet. That dumb IMax charger is programmable and you can make your own algorithm from the anufacture cut sheet. It may say something like: Charge at 4.2 volts, limit charge current to 3 amps, and terminate at 0.1 Amps aka C/33 or 3%.

So much for the ganja smoking Nebster in Colorado. I bet his businesses card name is: DUNNO CHIT, Ben Dover, or Dewey-Cheatum & Howe.

[Sunking]

I C. Thanks. No wonder I've heard people saying the Lithium battery chargers are simpler than the old Lead Acid ones.

Yes that is true up to a point. Difference is a Pb charger does not have to shut off, and most of the battery Pb chargers can use up to 6 phases or modes. Lithium chargers are simple 2 modes, CC/CV and shut off when complete to keep them from going BOOM.

[Ampster]

You've got to do a bit better than one sentence in terms of information if you expect to convince me of the rightness of your cause, but maybe that's just me.

Does this one sentance definition work for you?
"on-exchange reaction, any of a class of chemical reactions between two substances (each consisting of positively and negatively charged species called ions) that involves an exchange of one or more ionic components"
Source:
https://www.britannica.com/science/i...hange-reaction

[Ampster]

You've got to do a bit better than one sentence in terms of information if you expect to convince me of the rightness of your cause, but maybe that's just me.

Google "ion exchange". I did and found the following one sentence definition from Brittanica:

"Ion-exchange reaction, any of a class of chemical reactions between two substances (each consisting of positively and negatively charged species called ions) that involves an exchange of one or more ionic components"

[Sunking]

Again, this is incorrect. Ion exchange is a type of chemical reaction..

It is ot a chemical reaction and proves you do not know what you are talking about, just like the Imax Charger you have no clue about. The electrolyte in an Ion Battery is there as a conductor pathway. There is no chemical reaction as there is in a Pb battery changing from lead dioxide to lead sulfate. The electrolyte in a Li battery is just a conductor for Ions to exchange between Anode and Cathode. The electrolyte in Li batteries does not change state from one chemical to another. It is just a path for the ion exchange to happen like a road or conveyor belt.

[Ampster]

I wonder if it would be worthwhile for the moderator to put the parts of this thread that discuss ionic exchange and chemical reactions into another thread. Or, alternatively I could start a new discussion.
I would like to pursue parts of this discussion to illustrate some of the differences between Pb and Lithium, particularly as they relate to safety. Perhaps the title could be "Chemical Reactions in Lithium Batteries"? I am not as interested in continuing the flame war above but in my mind when a Lithium battery lights on fire there is a chemical reaction and the events leading up to that might illustrate where the dangers are and possibly how to avoid that kind of event.

[sdold]

I wonder if it would be worthwhile for the moderator to put the parts of this thread that discuss ionic exchange and chemical reactions into another thread.

Done. All: Keep it civil, thanks, I have a low tolerance threshold for nonsense today.

[Ampster]

Thanks. As I mentioned I don't want to continue the debate about chemical reactions versus ionic exchange. The issue may be one of thermodynamics and the question is what causes Lithium batteries to heat up? I think we can all agree that most if not all electrolytes in Lithium batteries are flammable and that is what creates those fireworks. I am not a chemist but my understanding is that that fire is a chemical reaction ( or rapid oxidation?). What I don't completely understand is the process that generates the heat in the first place. I know it happens when Lithium batteries are overcharged. Any thoughts?

[SunEagle]

Thanks. As I mentioned I don't want to continue the debate about chemical reactions versus ionic exchange. The issue may be one of thermodynamics and the question is what causes Lithium batteries to heat up? I think we can all agree that most if not all electrolytes in Lithium batteries are flammable and that is what creates those fireworks. I am not a chemist but my understanding is that that fire is a chemical reaction ( or rapid oxidation?). What I don't completely understand is the process that generates the heat in the first place. I know it happens when Lithium batteries are overcharged. Any thoughts?

Heat is a by product of either chemical reactions, friction, "losses", energy transfer, etc. to name a few. Also just about any battery will get hot if it is discharged or charged too fast. My guess it has something to do with the internal resistance between points A & B but I am not totally sure.

[Ampster]

Heat is a by product of either chemical reactions, friction, "losses", energy transfer, etc. to name a few. Also just about any battery will get hot if it is discharged or charged too fast. My guess it has something to do with the internal resistance between points A & B but I am not totally sure.

Yes, I should have mentioned discharge as well. 8 years ago when I first discovered Lithium batteries, I learned that lesson rather quickly. I had purchase some 18650"s and replaced the cells in a Dwalt 18v battery. I put that battery in a sawzall and handed the sawzall to some workers that were doing some demolition for me. I could hear that sawzall flying through the wood like it never did before. After the battery ran down I could feel it was warm when I took it out of the tool. Luckily I set it on a concrete slab and in a few minutes it was smoking and had melted the plastic. It never caught on fire but it was a good lesson.

[PNjunction]

What I don't completely understand is the process that generates the heat in the first place. I know it happens when Lithium batteries are overcharged. Any thoughts?

Exceeding the manufacturer's ratings for charge current is just one issue, and a daisy chain of events happen:

Too much current causes an ion-storm within the cell, as they can't "intercalate" fast enough. That is, ions can't move through the electrolyte, and then the SEI layer to the opposing plate fast enough due to the over-current condition. This "ion storm" boils the electrolyte raising it's temperature. Which in turn sets the active materials on fire because they have been heated up enough to release oxygen.

Speaking of electrolyte, when charging beyond it's current rating, not only does an ion storm occur, but active material is pulled into the electrolyte contaminating it, making the cell performance drop, but also UNSAFE for use.

Many newbies don't realize that this over-current condition exists *well below* the manufacturer's ratings when the cells are over-discharged! An over discharged cell should be recharged back near the nominal voltage with about 1/100th of the manufacturer's rating until somewhat near the nominal voltage. If not, the ion-storm and inability to intercalate fast enough causes problems.

And this is not even taking into consideration any quality issues of the cells themselves - such as fly by night manufacturers not even taking the time to do proper "plate offsets" to ward against dendrite growth.

Dendrites, when fed enough current, are really good electrolyte cookers, and the chain of events follows.

Note that the 3.2v nominal LiFeP04 active materials may not themselves catch on fire, (due to iron phosphate not releasing any oxygen), but cell abuse can make their electrolytes boil off dramatically and cause cell failure.

In the end, this is just physics - the end user should simply not exceed the manufacturer's ratings. In other words, it would be foolish of me to try and make a motorcycle Lifepo4 lithium starter battery out of AA-sized garden solar light LFP batteries, since the materials are not designed for high-current applications, like a Headway LFP cell is. (or say an A123 cell etc)

You may not like it but Sunking is right - there is NO *initial* chemical reaction when using a lithium battery - it is only when it is operated beyond its ratings, >> which makes it no longer a properly operating battery << that chemical reactions happen that start fires.

*Disclaimer - yes, there ARE negative "aging" chemical reactions that take place even when treating a cell properly - provided you are operating the cells within the manufacturer's specifications, but you will want to be clear about normal operating conditions, and exceeding those conditions, where massive chemical reactions take place. Those massive chemical reactions are not part of the norm, so be clear recognizing the two different conditions.

[PNjunction]

Shorter answer about chemical reactions:

Back in the day, Li-ion batteries were touted as "solid state" batteries. No chemical reaction.

For the sake of conversation, consider another solid-state component: electrolytic capacitor. It too has positive and negative plates, along with electrolyte. We (the circuit) charges and it discharges, much like a battery but on a much smaller scale.

Yes, the capacitor has normal "aging" chemical reactions, but for normal usage, it is considered a solid-state component. Or, if taken out beyond it's specifications, it is no longer a capacitor but something *else* - a firecracker.

It may be helpful to think of a li-ion battery in much the same manner from a "solid state" standpoint and not having any chemical reactions, *under normal usage*.

[nebster]

You may not like it but Sunking is right - there is NO *initial* chemical reaction when using a lithium battery - it is only when it is operated beyond its ratings, >> which makes it no longer a properly operating battery << that chemical reactions happen that start fires.

You've written a lot of great things in your post, but I'm sorry: electrochemists and I will not agree with you, sunking, or others on this statement. It is not a matter of liking or not liking, or of opinion: the science here is very clear. When charging and discharging, a lithium-ion chemistry cell has a pair of half reactions, one at each electrode, that together form a reversible redox reaction.

Redox reactions are at the heart of all batteries, including all the forms of lithium-ion cells that we use today.

Lithium-ion redox reactions experience ionic intercalation, wherein the electrode molecules are arranged in a structured form (usually a grid or lattice) and the ions intersperse themselves within this grid. The fact that the molecules retain their layered structure is interesting, but the fact that they do does not mean that there is no reaction. The very chemical composition of the anode and cathode in a lithium-cell changes when the reaction flows in either direction.

Please take a look at this section from an inorganic chem textbook where intercalation reactions are discussed. You can see that the title of the section includes the word "reaction," you can see half-reactions for several examples discussed, and you can also check out how they use the original LCO lithium-ion cell reaction from Goodenough's group as an example, too!

https://chem.libretexts.org/Textbook_Maps/Inorganic_Chemistry/Book%3A_Inorganic_Chemistry_(Wikibook)/Chapter_08%3A_Ionic_and_Covalent_Solids_-_Structures/8.4%3A_Layered_structures_and_intercalation_reacti ons

I'm not really sure what else to say, so I'll just reiterate that this is a reversible chemical reaction in every sense of the term. Yes, there are other reactions that can also occur when the battery is moved outside of its normal, reversible operating regime. Some of those reactions are not reversible or fully reversible, of course, and some of them are highly exothermic and thus can pose great danger. You have done a great job describing how some of those manifest.

But to suggest that the battery itself "doesn't have a reaction" when it's charging or discharging is simply nonsense, or at best an attempt to redefine the term for some reason.

Finally, the redox reaction's rate limits -- what chemical engineers would call "kinetics" -- are what raise the internal resistance and thus the reaction voltage... and, thus, in many common setups help the charger decide when to stop. I wrote that same answer (with a lot less words, not thinking this was something controversial to anyone here!) in the original post from the original question from the newcomer, who was wondering why his charger in CV would deliver fewer and fewer amps over time.

[SunEagle]

Yes, I should have mentioned discharge as well. 8 years ago when I first discovered Lithium batteries, I learned that lesson rather quickly. I had purchase some 18650"s and replaced the cells in a Dwalt 18v battery. I put that battery in a sawzall and handed the sawzall to some workers that were doing some demolition for me. I could hear that sawzall flying through the wood like it never did before. After the battery ran down I could feel it was warm when I took it out of the tool. Luckily I set it on a concrete slab and in a few minutes it was smoking and had melted the plastic. It never caught on fire but it was a good lesson.

I have some 20V batteries for my Black and Decker weed wacker. They have a thermal set point that will not allow me to recharge it if it has gotten too hot while discharging. Until a red warning light on the charger goes off the battery will not be charged until it has cooled down. Seems like a useful safety for an Li battery.

[Mike90250]

I think the "textbook" is pushing the notion of "reaction". Most lay persons will think of a reaction where 2 things are mixed and a 3rd novel item develops or something disappears. There's even some contradiction in the text :
"The lithium ion battery is a "rocking chair" battery, so named because charging and discharging involve moving Li⁺ ions from one side to the other"
The ions move back and forth, packing themselves in between layers. The chemicals in the layers don't change into something else, they are simply ion rich. Eventually physical changes occur as the battery ages, but that change is a side effect of imperfections, not the mechanism of the battery function.

Anyway, this is interesting, seeing how subtle differences in understanding brought this discussion this far.