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NNadir

(33,368 posts)
Tue Dec 29, 2020, 01:57 AM Dec 2020

Design of Lithium Battery Electrolytes to Prevent the Batteries from Bursting into Flame.

(Note: Graphics in this post, and many of my earlier posts, may not be visible in Google Chrome, but should be visible in Microsoft Edge, Firefox, and Android.)

The paper, a review article, that I'll discuss in this post is this one: Design Strategies of Safe Electrolytes for Preventing Thermal Runaway in Lithium Ion Batteries (Xiaolu Tian, Yikun Yi, Binren Fang, Pu Yang, Te Wang, Pei Liu, Long Qu, Mingtao Li, and Shanqing Zhang, Chemistry of Materials 2020 32 (23), 9821-9848)

As I often point out, a battery is a device that wastes energy, loses energy, owing to the Second Law of Thermodynamics, which despite any nonsense spouted by the likes of say, Amory Lovins, cannot be repealed by Congress, or by journalists at "Clean Technica" or any other body or person engaged in wishful thinking as an approach to address the complete and total destruction of this planet's atmosphere, which is ongoing, continuous, and accelerating.

The Second Law of Thermodynamics, simply stated as dS/dt > 0, involves entropy (S) which for the universe as a whole is monotonically increasing over time (t). Entropy shows up most prominently as heat. which is discharged into the surroundings, on Earth, our atmosphere, in a form that cannot be entirely recovered as mechanical or chemical, or electrochemical chemical work. Therefore, we know that batteries waste energy simply by touching them when they are charging and discharging. They are warmed when we do this; and this paper is about when the heating goes beyond "warming" into "hot" to the point of causing a fire or explosion.

This issue famously arose in the case with the Samsung Galaxy Note 7 cell phones, which had to be recalled, after being banned on aircraft because their batteries spontaneously caught fire, apparently causing a number of injuries. There have been a number of fires in batteries in Tesla cars, which are designed to help millionaires and billionaires pretend that they care about the environment, even though they don't.

The paper cited here is about lithium battery fires and approaches to designing electrolytes that are fire resistant or even fire proof.

From the introduction to the paper, which begins with a sentence that I personally find dubious:

Renewable and clean energy resources are urgently needed due to the shortage of traditional fossil energy and serious environmental pollution. The wide exploration of new energy prompts the fast development of energy storage devices.(1?5) The lithium ion battery is a promising representative of energy storage equipment among portable electronic devices and energy storage fields due to its advantages of low cost, high energy density, weak self-discharge effect, and long service life.(6?19,19) In recent years, the demand for LIBs is rapidly increasing in the market of electric vehicles, digital products, and mobile electronic devices because of the aggravation of environmental pollution and the guidance of governmental policies.(20?22) There is no doubt that LIBs are bringing great changes and convenience to environmental improvement and people’s daily lives, but at the same time, their safety problems have aroused much attention and remain to be solved urgently...(23?27)


I often argue, flying in the face of popular opinion, that so called "renewable energy" is neither clean, nor in fact, renewable. Since I assert these things to be truths, I believe that we don't "need" them at all. We have a superior option to climate change gas free energy, and have broad experience with it extending over more than half a century.

Nevertheless, there is a widespread belief that claims that batteries, along with a massive increase in the number of copper wires connecting batteries to things like wind turbines and solar cells, will save the day. This idea has been massively funded in the 21st century, to the tune of trillions of dollars.

It is, however, a fact that the rate of accumulation of the dangerous fossil fuel waste carbon dioxide in the planetary atmosphere has accelerated all through the same 21st century during which this faith based article has been widely accepted.

Facts matter.

As this statement is a fact, it is obvious that wires, solar cells and wind turbines, along with all the trillions of dollars thrown at them have not addressed climate change, are not addressing climate change, and, as I often argue, will not address climate change.

Despite half a century of hype, batteries remain a relatively trivial form of energy storage on the scale at which energy is consumed by humanity, around 600 ExaJoules per year. Below, I'll look at some real time (CAISO) data in that so called "renewable energy" nirvana, fire prone California, that graphically and explicitly - words often associated with obscenities - gives some sense of the scale of grid battery use to maintain power to the grid. It is nonetheless useful to consider what the consequences of them becoming a significant form of energy storage might be, assuming we can find enough slaves in the world to dig enough cobalt ores for the manufacture of them.

The authors continue:

...The heat accumulation in LIBs is dominated by heat generation and dissipation. Commercial LIBs work on the delivery of lithium ions in liquid electrolyte between the cathode of lithium alloy metal oxide and the graphite anode, which leads to heat generation because of the current thermal effect.(28) When LIBs work at lower rates, the heat generated by the thermal effect can be dissipated spontaneously. However, during the high rate charge–discharge process of LIBs, especially in those batteries equipped in electronic devices, the heat generation rate is significantly larger than the heat dissipation rate which results in a heat accumulation, and the heat accumulation can lead to an increase of internal temperature to over 300 °C. The high temperature may further lead to thermal runaway: combustion or explosion problems caused by the flammable organic liquid electrolyte with low thermal stability.(29?31) Moreover, the uneven deposition of lithium ions on the electrode/electrolyte interface may cause the growth of lithium dendrites, which further leads to a piercing effect and internal short circuit; also also a huge thermal effect and the decomposition of battery components arise, including SEI film decomposition, anode/solvent reactions, separator melt, and cathode breakdown reactions.(32?38) In addition to internal chemical reaction factors, external factors such as overheating, overcharging, and short circuits caused by mechanical shock can also lead to thermal runaway of LIBs.(26,39) Anyway, the instability of internal components such as the flammable organic electrolyte is the immediate cause of thermal runaway issues, and as a result, electrolytes with high conductivity, nontoxicity, nonflammability, and good interfacial compatibility with electrodes to suppress lithium dendrite growth are the keys to deal with thermal runaway risks.(40?42)...


The authors summarize the current state of affairs in a few sentences:

2. Thermal Runaway Mechanism

The source of thermal runaway issues is internal exothermic reactions including the following (Figure 1): 1. Improper operation, such as overcharge, causes a constant Li stripping reaction at the cathode and, thus, leads to cathode breakdown and the release of oxygen, which prompts the oxidation of organic carbonate solvent and massive heat generation.(47) 2. Excessive Li plating on the anode results in the growth of lithium dendrite, causing internal circuits and reactions between Li and carbonate solvent that can generate a large amount of gas and heat.(33,35,48) 3. The unstable SEI film decomposes at high temperatures and releases heat.(49,50) 4. The oxidation of carbonate solvent typically includes ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate(DMC), and diethyl carbonate (DEC), and the decomposition of lithium salt such as LiPF6 is easily triggered under high temperature and high voltage conditions, which further contributes to heat generation.(27,51?53) All these reactions can increase the internal pressure and the temperature of LIBs, bringing about severe thermal runaway risks...


"SEI" here, refers to "solid electrolyte interphase" (or sometimes interface), which is described in more detail here (for one case) and elsewhere: Solid Electrolyte Interphase Film on Lithium Metal Anode in Mixed-Salt System(Sho Eijima et al 2019 J. Electrochem. Soc. 166 A5421) The nature of the SEI will depend on the nature of the electrolyte.

Ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate(DMC), and diethyl carbonate (DEC) are all, by the way, products of the dangerous fossil fuel industry. In general - although many alternatives are being developed, including carbon dioxide - organic carbonates are manufactured by the use of phosgene, a war gas that was widely used in the the First World War to kill huge numbers of soldiers fighting for...fighting for...fighting for...well...who knows what? Phosgene is made by reacting carbon monoxide obtained generally from either dangerous coal and/or dangerous natural gas, with chlorine, which is made industrially by electrolysis of salt solutions in continuous processes that run 24/7 whether the sun is shining or not, whether the wind is blowing or not.

Now it turns out that phosgene can be used safely, at least with careful attention to its handling; I’ve done it myself, but it’s very clear that fossil fuels cannot be used safely, because, as familiarity breeds contempt, their familiar use invites sloppiness and contempt for safety. Some results of this attitude is the fact that dangerous fossil fuel waste (aka “air pollution”) kills millions of people every year and climate change has advanced so far that we literally have people dropping dead from overheating on a rising scale.

Figure 1, to which the text from the paper refers:



The caption:

Figure 1. Schematic of the classification of thermal runaway stages of LIBs.


Some more text from the paper:

...Up to now, there have been fairly thorough studies on the thermal stability and the decomposition mechanism of LIBs components.(54,55)

Richard et al. observed that the initial decomposition temperature of the SEI membrane was about 80 °C through accelerating rate calorimeter (ARC) experiment.(56) It is found that the equations of the SEI membrane decomposition reaction is as follows:



...



(LiOCOCH2)2 is the lithium salt of ethylene glycol dicarbonate.

...As the temperature further rises, the chemical properties of each component material inside the battery become more active. The protection of the anode will be lost when the decomposition of the SEI film reaches a certain level, and the lithium embedded in the anode will undergo a further exothermic reaction with the electrolyte. Biensan et al. studied the reactions between the electrolyte and the lithium anode, which contributed to the exothermic peak of up to 120 °C.(57) The anode/electrolyte reaction is as follows: (58)


...


C2H6 is of course the highly flammable gas ethane.

...The polyethylene (PP) separator begins to melt when the temperature further reaches 130–140 °C, leading to short circuits risks between electrodes.(59) As the anode/electrolyte reaction continuously contributes to heat accumulation, the cathode material decomposes and releases oxygen. Lithium cobalt oxide (LCO) is the earliest cathode material for LIBs, with a decomposition temperature of around 150 °C: (60)



I often in this space rail against the unsustainability of cobalt mining as well as its moral cost but will skip it here. God created the internet so you can find answers to moral questions that you might wish to avoid.

The release of oxygen and the heat of decomposition of LiPF6 can cause the organic carbonates to combust.

For commercial 1 M LiPF6-EC-DEC-DMC organic electrolyte, the solvent components can be oxidized at over 200 °C by the oxygen released from cathode decomposition, while LiPF6 decomposes to produce PF5 which facilitates the electrolyte decomposition in turn...


The standard combustion reactions of the various carbonates used in lithium batteries are shown in the text. These are the reactions one sees when a lithium battery bursts into flame, the flames often having a reddish tint from the flame emission of lithium.

This is a rather long paper, as it is a review article, and I obviously can't reproduce much of it here. It is available to subscribers and when and if university libraries again become available to the public at large, in them. Perhaps it is useful to show some pictures from the text and outline the strategies for addressing lithium battery fires.

One strategy is the use of flame retardants. A note about flame retardants: They are designed to be thermally stable, and thus represent persistent compounds. Many of them have been discovered to face toxicological issues and their use in the fabric and electronic industries have led in some cases to intractable environmental issues owing to contamination of water supplies and in solid matrices such as soil and dust. An example, the brominated diphenyl ether compounds represent a huge hazard in particular in the recycling of electronic components, an activity that is dangerous enough to have required bourgeois types in the so called "first world" to outsource this activity to poor people, while still feeling all smugly "green" about themselves.

Recently, there has been a trend to replace these with other types of flame retardants, notably phosphate esters and organophosphates. I'm not sure all these are that great either. Phosphate esters as a class include certain neurotoxins, which is why they are found in many insecticides. These statements may represent innuendo of a sort, but then again, without having looked too deeply into the matter, I believe I've come across some noise as to whether phosphate esters, as flame retardants actually are all that much of an improvement on polybrominated diphenyl ethers.

Apparently though, phosphate esters can help the SEI in lithium batteries maintain its integrity.



The caption:

Figure 2. (a) Molecular structure and functionalities of diethyl(thiophen-2-ylmethyl)phosphonate (DTYP). (b) Photographs of base and 0.5% DTYP-containing electrolytes before and after storage in the electrolytes. (c) Flammability of the PE membrane with base and DTYP-containing electrolytes. (d) Cycling performance of LiNi0.5Mn1.5O4 electrodes in the electrolytes after storage at room temperature at 0.5 C for the first three cycles and at 1 C for the subsequent cycles between 3 and 4.9 V, followed by a constant potential of 4.9 V until the current reached 0.1 C. Adapted with permission from ref (77). Copyright 2018 Royal Society of Chemistry.


A recently reported additive for an electrolyte is a cyclic phoshazene, ethoxy-(pentafluoro)-cyclotriphosphazene, PFN. What the toxicology profile of this interesting compound may be is probably unknown. It apparently prevents flame without compromising battery performance:



Figure 3. (a) Photographs of the flammability testing of the electrolytes: the base electrolyte 1 M LiPF6/EC+DEC+DMC (1:1:1, v/v/v) and the same electrolyte with 5 wt % PFN additive. (b) TEM images of LiNi0.5Mn1.5O4 electrodes with PFN additive after 100 cycles and without PFN additive after 100 cycles. (c) Electrochemical impedance spectra of LiNi0.5Mn1.5O4 in base and 5 wt % PFN-containing electrolyte before cycling and after 100 cycles. Reprinted with permission from ref (102). Copyright 2018 Elsevier.


Reference 102 is this one: Fluorinated phosphazene derivative – A promising electrolyte additive for high voltage lithium ion batteries: From electrochemical performance to corrosion mechanism (Jianwen Liu, Xin Song, Lai Zhou, Shiquan Wang, Wei Song, Wei Liu, Huali Long, Lixin Zhou, Huimin Wu, Chuanqi Feng, Zaiping Guo, Nano Energy 46 (2018) 404–414) This compound, it would seem on inspection, is made from hydroquinone, isobutylene, and 1-methoxy-2-chloroethane, pretty much all products of the dangerous fossil fuel industry.



Apparently this additive helps protect the SEI via polymerization. A graphic from that paper:



The caption:

Fig. 6. (a-e) Illustration of the mechanism of PFN additive decomposition on the surface of the electrode; schematic diagrams of (f) damaged CEI and exposed particles formed due to corrosion without PFN additive; and (g) uniform CEI formed due to corrosion suppression with PFN additive.


It is not, of course, entirely clear how this polymer, or its degradation products might effect that exercise about electronic components that always generates lots of "I'm green!" handwaving, recycling. If you look into this matter, given the massive scale of these distributed components, the recycling of batteries is in now way a "slam dunk" exercise. To wit: There are a lot of unaddressed and unanswered questions, as well as some well known issues in safety and toxicology.

The paper refers to a proposed additive, DBBB, 2,5-ditert-butyl-1,4-bis(2-methoxyethoxy)benzene to prevent overcharge, another issue in flammability:



The caption:

Figure 4. (a) Redox mechanism of DBBB additive in LIBs. (b) Charging voltage profile as a function of the SOC for graphite/C-LFP pouch cells without (STD Cell) and with 0.4 M DBBB additive (DBBB Cell). (c) The 1st, 400th, and 700th cycle voltage profiles for graphite/C-LFP pouch cells with 0.4 M DBBB additive cycled with 100% overcharge. (d) Charge capacity, discharge capacity retention, and Coulombic efficiency for graphite/C-LFP pouch cells with 0.4 M DBBB additive cycled with 100% overcharge. Reprinted with permission from ref (119). Copyright 2018 American Chemical Society.


I would guess that DBBB is made from hydroxyquinone, isobutylene, and 1-chloro-2-methoxyethane, all products of the dangerous fossil fuel industry.

There is a lot of discussion beyond these, aqueous electrolytes, solid electrolytes, etc., etc., but the fact remains that right now, the overwhelming majority of lithium batteries are flammable, and moreover, it is not entirely clear that the components are either, beyond flammability, safe, and sustainable. The main source of the common carbonates is dangerous fossil fuels.

And yet, and yet, and yet... ...we hear that batteries are "green" and that they will help so called "renewable energy" address climate change, this after half a century in which vast expenditures on so called "renewable energy" have failed miserably to do anything at all about climate change.

Looking at this full and admittedly interesting paper, which I do not have the time to explore any deeper than this, I'm not entirely convinced that the "cure" for these obvious limitations to batteries is worse than the problem themselves. I really can't find the time to discuss it all that much further, but it's there; it's there. There's a problem, a big problem, with our "green" fantasies, and we are not even close to recognizing them.

The extent to which batteries are currently serving the grid is limited. Recently in this space, I referred to the CAISO data for the California electricity grid, California being a so called "renewable nirvana" where the power company has gone bankrupt because it couldn't prevent all those wires linking all those solar cells and all those wind turbines from sparking and causing catastrophic fires.

It's about to become 2021, leaving that horrid year 2020 behind. For the week beginning December 20, 2020 the average concentration of the dangerous fossil fuel waste carbon dioxide was 414.60 ppm, 24.33 ppm higher than it was in the same week of 2010.

I've been hearing about how batteries would save the world with so called "renewable energy" my whole adult life. I'm not young. I'm old. I'm disgusted with what my generation is leaving behind.

On 12/22/20, according to the CAISO data, the peak power demand in California was 28,901 MW at 5:48 pm, after the sun went down. At that moment, the wires connecting California's solar infrastructure was consuming, not producing, about 40 MW of electricity, that is the power output was negative, -40 MW.

At 21:00 hours, 9:00 pm, California time, midnight here in New Jersey, I downloaded a set of graphics reflecting the sources of energy in that state, which includes all of the batteries serving the grid, as of 2020, in a week where the concentration of carbon dioxide was, again, 24.33 ppm higher than it was 10 years before, half a century into the cheering for the idea that so called "renewable energy" and batteries would save the day.

Here's what all the batteries connected to the grid in that so called "renewable energy" nirvana in California were doing:



When, when, when do we get serious?

I wish you the happiest of New Years.
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Design of Lithium Battery Electrolytes to Prevent the Batteries from Bursting into Flame. (Original Post) NNadir Dec 2020 OP
And the trillions if not more thrown at Nuclear energy Eko Dec 2020 #1
Cool to see some (NPF2)x chemistry ... eppur_se_muova Dec 2020 #2
I can't say it's chemistry around which I have much experience, any practical experience at all. NNadir Dec 2020 #3

Eko

(7,170 posts)
1. And the trillions if not more thrown at Nuclear energy
Tue Dec 29, 2020, 02:21 AM
Dec 2020

for decades has not addressed climate change and is not addressing climate change.

eppur_se_muova

(36,227 posts)
2. Cool to see some (NPF2)x chemistry ...
Tue Dec 29, 2020, 09:37 AM
Dec 2020

I haven't seen much of them since I first saw them suggested as polymer precursors years ago. But then, I've been away from Chem Depts and libraries for way too long now.

Of course, batteries which don't ignite would be desirable whatever the scale and intent of their use, so the "justification" introducing their paper seems a touch superfluous.

NNadir

(33,368 posts)
3. I can't say it's chemistry around which I have much experience, any practical experience at all.
Tue Dec 29, 2020, 11:11 AM
Dec 2020

It's interesting to see fairly complex structures for the first two group 15 elements, and at least, at long last, I have come to be appreciate the beauty of those 3rd period elements silicon, phosphorous and sulfur. My deepest familiarity with the latter two basically derives from biochemistry.

In organic chemistry, on a few rare occasions, I messed around with the higher phosphorous halides, no big deal there.

At one point in my career, I was involved in industrial Vilsmeier type chemistry, at least peripherally, where the counter ion was PF6-. We left that project because of exotherms making it problematic on an industrial scale. This ion shows up fairly frequently in the ionic liquid literature. One part of this battery paper showed it decomposing to give HF; but I didn't end up discussing it, because the paper was too rich for a blog post. That isn't a good thing, and certainly wouldn't be desirable if one were trying to extinguish an industrial scale battery fire.

How the phosphorous fluorine bond in PFN would behave in high temperatures, I couldn't say. The authors of the Nano Energy paper are, of course, recommending it as a flame retardant, so there's that.

There were a lot of other fluorine bonds in this paper. Fluorine bonds in general are proving to be incredible environmental problems, particularly in water and in air.

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