Ameliorating the Fire Risk of Energy Storage Devices.

[NNadir]

The paper I will discuss in this link from the primary scientific literature is this one:

Promising and Reversible Electrolyte with Thermal Switching Behavior for Safer Electrochemical Storage Devices (Xu et al, ACS Appl. Mater. Interfaces, 2018, 10 (8), pp 7171–7179)

As I frequently point out energy storage wastes energy, a consequence of the inviolable second law of thermodynamics, a law of physical science that all the wishful thinking in the world cannot repeal.

Nevertheless, like so called "renewable energy" itself, the idea of energy storage is inexplicably popular, perhaps because even the most enthusiastic and delusional partisans of so called "renewable energy" recognize, at least in the back of their minds if not consciously, that there are times when the wind does not blow at night. Since they are under the erroneous opinion that so called "renewable energy" is "green" and sustainable, they like to pretend that there is a simple solution in energy storage, and do all kinds of cheering for absurd stuff like Elon Musk's crappy car for billionaires and millionaires.

So called "renewable energy" has not worked; it is not working and it will not work to address climate change or reduce the use of dangerous fossil fuels.

On the other hand, energy storage devices are in fact commercial and work quite well, and are utilized on a grand scale in all sorts of devices, the overwhelming majority of them being portable devices even though, again, they waste energy. The idea of making portable devices however into utility scale devices, while already in some marginal practice to support the marginal and insignificant so called "renewable energy" devices is dubious, especially when one considers that large scale devices, since they waste energy, they can and sometimes do, exhibit heat exchange problems that can become uncontrolled and lead to fires and even explosions.

News item: Lithium-Ion Battery on Delta Air Lines Flight Explodes, Catches Fire

The ignition of batteries brought down UPS Flight 6 in Dubai, killing both pilots, one by asphyxiation, the other being killed when he couldn't land the plane because of smoke. It was covered in the wonderful if scary Smithsonian Channel Show Air Disasters.

News Item: Why the Fire that Incinerated a Tesla Was Such a Nightmare to Put Out

Reducing this risk is the topic of the paper cited at the beginning of this post.

Some commentary from the introduction to the paper:

Advanced electrochemical devices, such as supercapacitors, lithium-ion batteries, and nickel−metal hydride batteries, have been large-scale applied in energy storage because of their properties such as high power and energy densities,1,2 stable cycling performance, and long cycle life.3−8 Delivering energy at high rates, however, could cause security issues with respect to considerable amounts of gases and heat generated by ultrafast charging and discharging processes, especially in some extreme conditions such as short circuiting and overcharging, thus resulting in catastrophic burning or explosion.9,10 With the increasing oil crisis and continuous development of new energy vehicles, safety problems of large battery packs with high specific energy density are in urgent need of technical breakthroughs.

A series of exothermic reactions leading to a rapid rise in temperature and to thermal runaway can be initiated in addition to the charge/discharge cycle, including the thermal pyrolysis of electrodes and evolution of oxygen and hydrogen between the electrode/electrolyte interface, which in turn increases the internal cell temperature and pressure.11 Accordingly, effective suppression of thermal runaway is the premise of achieving safety application and plays a very important role in the research studies of high-energy storage devices.12

You hear people talking as if battery storage and so called "renewable energy" are already mainstream. They are not. They are trivial and if one believes these scientists - contempt for scientists and engineers is very popular on both political extremes - there are serious technical "breakthroughs" required.

The question that should arise in people's minds is therefore a question of time. It's 2018. We're at close to 412 ppm for the concentration of the dangerous fossil fuel waste carbon dioxide in the planetary atmosphere. We cannot continue - if, in spite of all evidence, we want to have any hope of elevating our ghastly impoverished moral standing - to bet the future on hopes for "breakthroughs." We're out of time to wait for them.

Nevertheless, the authors are doing what good scientists do, they are working to solve the problem that the existing problem represents. Their work involves "thermoresponsive polymers." The idea is to shut down the device before it gets too hot and catches fire or explodes. (It's better to have your swell Tesla car stall and be even more useless than it is to have it catch fire and kill people.)

They describe the current state of affairs:

Recently, researchers proposed to develop smart reversible electrolytes based on thermoresponsive polymers, which have unique lower-critical solution temperature (LCST), to cope with the issue of thermal runaway. The migrations of conductive ions in the reversible electrolytes exhibit temperature dependence due to the phase separation of LCST polymers, thus providing or inhibiting conductive paths to achieve the thermoreversible protection. To date most of the research studies have focused on poly(N-isopropylacrylamide)-based copolymers because of its extensive mature application in biomedicine.23,24 However, their actual applications in electrochemical energy storage are restricted by the low LCST at around 32−34 °C and complicated synthesis with low productivity. Although commercial thermoplastic elastomer Pluronic [poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide)] have been dissolved in the electrolyte to shutdown the electrochemical devices upon heating, the high concentration up to 30 wt % influences the electrochemical properties at room temperature and increases the cost.25

Then they discuss their approach:

Here, methyl cellulose (MC) is used as a stimuli-responsive material in the smart electrolyte because of its thermoreversible gelation property in aqueous solution at elevated temperatures. MC, a type of modified cellulose with a portion of hydroxyl groups substituted by hydrophobic groups, has been increasingly investigated as separators or binder materials instead of synthetic polymers for electrochemical devices owing to its characteristics such as abundance, regeneration, and low cost.26−31 In this study, MC molecules exist as randomly isolated chains in the electrolyte below the LCST when ions can move in the interspaces freely, enabling a high ionic conductivity, which is not possible with conventional flameretardant additives. When temperature increases, the electrolyte undergoes a thermally activated sol−gel transition, which results in a decreased ion concentration and broken circuit because the hydrophobic segment in MC molecular chains is tangled to inhibit the motion of ions. This process is reversible and returns to high conductivity after cooling, as shown in Figure 1. We chose MC as the stimuli-responsive material in reversible electrolytes based on the following considerations: (1) MC solution exhibits relatively proper transition temperatures, so that system can be shutdown before or at the early stage of thermal runaway; (2) it is sensitive to temperature change in abnormal conditions and low concentration (∼2 wt %), making it a cost-effective system; (3) it is inert and stable within the electrochemical environment, having little impact on the electrochemical performance.

Methyl cellulose can be obtained of course from wood and other biological materials and to the extent biological sources are used, this material might represent economically viable sequestration of atmospheric carbon, probably in amounts that would be trivial compared to our 35 billion ton dumping practices in use today, but perhaps meaningful in a world where carbon dumping was arrested by the expanded development and embrace of nuclear energy.

They then produce a graphic showing how their system is designed to work:



The caption:

Figure 1. (a) Schematic illustration of the smart electrolyte with reversible thermoresponsive gelation properties for electrochemical energy storage devices. The system works normally at room temperature because of the free migration of ions in the interspaces. On heating, the hydrophobic crosslinked network leads to the sol−gel transition and absence of moving ions from solution, thus effectively shutting down the device above the LCST. Upon cooling, the electrolyte reversibly transforms to solution and recovers its ion motion. (b) Structures of MC, showing hydrophilic and hydrophobic groups. (c) Digital photograph of a MC solution below and above the LCST. (d) FTIR of pure MC and the mixture solution of MC and 1 M H2SO4-based electrolyte before and after 10 CV cycles, respectively.

Here are the cyclic voltammetry (CV) curves showing the reversibility of charge and discharge, a property essential to make a viable battery:



The caption:

Figure 2. Electrochemical properties of AC electrodes in 2 wt % MC-based electrolyte (1 M H2SO4). The CV curves were performed at scan rates of 10, 50, and 100 mV/s on AC electrodes at (a) 25 and (b) 70 °C. The charge/discharge characteristics in reversible electrolyte using a current density of 3 A g−1 at (c) RT, 25 °C and (d) HT, 70 °C.

They test the shutdown of current in terms of heat responsiveness:



The caption:

Figure 4. (a)Temperature-dependent CV tests of the system based on electrolyte with 1 wt % MC solution. (b) Storage modulus G′ (black) and loss modulus G″ (red) as a function of temperature in heating processes for a 1 wt % MC solution. (c) Illustrative DSC trace for 1 wt % MC solution on heating. (d) The temperature-dependent G′ value curves for MC with different concentrations.

The DSC curve, curve C, is a differential scanning calorimetry curve, which shows the transition temperature at which the electrolyte converts from a liquid into a gel. This temperature is comfortably low.

And finally, a nice picture of stuff in their lab by which they do the testing:



The caption:

Figure 6. (a) Illustration of thermal switching behavior of the coin cell supercapacitor using 1 wt % MC solution-based electrolyte: digital photographs show the decreased light intensity of the LED while heating to 70 °C. (b) The reversible specific capacitance summary of thermal-responsive supercapacitor cycling between 25 °C and shutdown. (c) Ionic conductivity response to temperature of 1 wt % MC solution-based electrolyte.

Interesting work, I think. If we must waste energy by storing it, let's try to do it safely at least.

Now of course, I fully recognize that our concept of "safety" is a function of selective attention. I recall a mindless fool here, for example - whose happily made it to my "ignore" list - who focused on the "major news" that a tunnel at the Hanford Nuclear Weapons site collapsed, which in his tiny brain "proved" that nuclear energy was "unsafe," while so called "renewable energy" was without risk.

And of course, people couldn't care less if Tesla cars for billionaires and millionaires catch fire, or if computer batteries bring down planes.

I submit that this kind of thinking is the reason we are at 412 ppm and out of time. It didn't have to be this way, but it is.

All this said, I applaud the fact that these Chinese scientists, if not the general public here in the United States and indeed around the world, are paying attention to risks that are real as opposed to those that are inflated.


Have a pleasant Sunday afternoon.

[hunter]

1. I'm curious how it compares to lithium iron phosphate batteries.

https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery

Lithium iron phosphate batteries are currently considered the most "foolproof" of common lithium battery chemistries.

They're increasingly being used as drop-in replacements for heavy lead acid batteries.

[NNadir]

2. I plainly confess that I don't know about lithium iron phosphate batteries. Many widely used Li...

...batteries use fairly flammable ketones as electrolytes. If I recall correctly, methyl ethyl ketone is a common one.

The idea behind the technology reported in the OP is to "freeze" out the electrolytes before they get too hot, which they can do in a runaway discharge.

The journals I read often have a lot of comment and papers about batteries, and I have attended several lectures on the subject, but its not a central focus of my interests, since, again, energy storage is generally wasteful and my interest is in improving the use of energy as opposed to wasting it.

So a lot of what's written about batteries escapes my eye or slips out of my brain, except for the purpose of ridiculing the strange enthusiasm among us on the left for Musk's stupid car for billionaires and millionaires.

For some reason though, this paper caught my eye. I'm always interested in phase transitions, and my kid took a class last semester on the thermodynamics of materials, so that might have something to do with it.

This is a journal by the way, that is massively rich with papers, so rich that I can't really keep up with it. I read fast, but not that fast.

I'm sorry I can't be much help here.

[Eko]

3. You just cant seem to escape using the straw man argument can you?

"Now of course, I fully recognize that our concept of "safety" is a function of selective attention. I recall a mindless fool here, for example - whose happily made it to my "ignore" list - who focused on the "major news" that a tunnel at the Hanford Nuclear Weapons site collapsed, which in his tiny brain "proved" that nuclear energy was "unsafe," while so called "renewable energy" was without risk."

Might I suggest using your vaunted research skills to show where it was said that "renewable energy" was without risk."? Here is a link to help you out.


https://www.democraticunderground.com/1127109489

[hunter]

4. Tesla is using the flammable lithium cobalt batteries because less dangerous and more ethically...

... sourced alternative battery chemistries are at least 14% heavier than lithium nickel cobalt aluminum oxide (NCA) batteries.

These car battery packs are totally inappropriate for home use, but what the heck, Elon Musk has got himself a "gigafactory." You can hang his batteries on the wall of your garage.

Oooo awwww...

NNadir has already posted on the evils of the cobalt mining industry.

https://upload.democraticunderground.com/1127116904

You were there.

The engineering of these Tesla battery packs is quite involved... they almost make nuclear power look easy. It takes some mad engineering skills to make an electric car like this that doesn't spontaneously combust.

http://evtv.me/2018/05/tesla-model-3-gone-battshit/

My favorite part of the new Tesla battery packs are the explosive fuses; fuses that literally have explosives in them to disconnect the battery pack should anything goes wrong as determined by the sophisticated computer monitor system.

[Eko]

5. I dont see how that is a response,

as you didn't address a single thing I said.

[hunter]

6. It's the grok of the thing.

https://en.wikipedia.org/wiki/Grok