I sure wish I had found this when I started researching batteries! You managed to summarize hours of material into an entertaining 23 minute video. Thanks and well done!
@@BillyWu Dear Billy, I have noticed with other explanations Lithium Nickel Oxide is used in the cathode and in others Lithium, Nickel cobalt oxide is used. Is there more than one technology? It is also asserted that the microporous membrane allows the passage of lithium ions but not electrons. Is this just because of the electric field between anode and cathode?
@@exsollertan7366 Good question! Yes, there are quite a few different cathode options each with their pros and cons. NMC (lithium nickel manganese cobalt oxide) is one of the most popular, with researchers aiming to reduce cobalt due to cost and ethical sourcing. For the separator, we need this to prevent the anode and cathode from touching since this would cause a short-circuit and damage the battery, yet we also need the electrolyte to connect the 2 electrodes, as the battery needs this to operate.
A very nice and concise presentation. You must have spent a lot of time to compress the vast amount of material into easily digestible material. It is commendable that you have put it for free on you tube. There is nothing more valuable than sharing knowledge.
The best battery basics video on TH-cam, thank you Prof Billy Wu on such an insightful video. Your vocabulary is spectacular as well, keep up the great work !!.
It's just mind blowing...a great effort towards knowledge sharing..a very reliable and knowledgeful resource to learn about battery basics....kudos Dr. Billy...keep up the good work
Hello Dr Wu. Great insight. I just have one question at 6:07 minutes in the figure . On the left side when you are describing the full cell packaging i believe the direction of the current is wrong. Inorder to light the bulb the electron will flow from negative terminal (anode) to positive terminal (cathode).
I build home made batteries. Very difficult to get a cheap chemistry that does self discharge within a few days. I'd welcome any ideas you may have for a home builder. Good video. Take care Bret
Hi Professor Wu, very informative video! I was thinking about the hexagonal representation of different chemistries on slide 8. Should Voltage be there as a parameter? Maybe its included in the power term? For Li-Sulfur chemistry, how will the hexagonal map look like? Maybe better than NMC/NCA?
Thanks Kunal. Good question. Voltage is important and is somewhat captured in the specific energy of the material as this will be related to the product of the nominal voltage and the specific capacity of the material. Li-sulfur will have better specific energy than NMC and very good cost since sulfur is quite cheap. However, the lifetime of these devices are quite poor due to instabilities in the lithium and also power rate is quite poor since sulfur is not a very good electrical conductor.
Very informative video on battery basics! Thanks a lot Dr. Wu! Can you make a similar type of video explaining the working of the ANSYS Fluent battery Model (E-chemistry Models)??
@@BillyWu So happy that this kind of great content is not hidden behind a paywall and enough condensed that one does not need to read a great number of papers to get such an overview about the current state of the technology. You're doing humanity a great service sir.
Thanks. For batteries to have good lifetime, we need the materials to be as stable as possible. Lithium-ion batteries work by moving lithium-ions between an anode and cathode. When we insert lithium-ions into the structure we call this process intercalation. We can think of this like lithium-ions being books and the electrode materials being the bookshelf. In the case of the cathode, one of the most common cathode chemistries is NMC (Lithium Nickel Manganese Cobalt Oxide). This forms a layered crystal structure, similar-ish to the bookshelf analogy. These elements have the right blend of properties to form this structure but also give a good electrical potential when inserted.
Slides like no. 5 are very useful when comparing results reported in different papers. But, there are just too many parameters to keep track of! The papers use variety of different parameters like energy density, power density, aerial capacity, volumetric capacity, voltage variations, driving range etc. to quantify the battery/electrode performance. I think it should be made mandatory to narrow down the performance to a fixed set of metric parameters. That would make it easy to assess the potential of any new technology. Prof. Wu, can you provide such 'now' and 'future' data for all possible metric parameters? Also, how are the 'future' values determined? Is it based on comparison to IC engines?
Nice comments Kunal. You're right that there are many different parameters. Unfortunately, it is a complex space and in reality we need to consider all of these together. Again these metrics can be made to look better if you look at a single one. For example it's relatively straightforward to make a high energy cell or high power cell but difficult to get all into the same cell at low cost. I know a range of people are working on standards for these metrics to make them more transparent and comparable, so that would be my hope for the future.
The electrons can flow in either direction (from/to the positive/negative terminals) depending on whether the battery is being charged or discharged. This is driven by the potential applied to the battery and the need to maintain charge neutrality in the battery, i.e. when a lithium-ion comes out of the anode/cathode, another lithium-ion has to be intercalated into the opposite electrode and an electron is needed to balance the charge.
Hi Billy I am still a bit confused about the process of the charging of the Li-ion cell. When a lithium ion cell is connected to a DC source, the electric field applied forces the lithium ions to move from the cathode through the electrolyte to the graphite anode. Meanwhile electrons move through the outside circuit and again end up in the graphite. These electrons would be same number as the lithium ions. Presumably therefore the lithium ions have now recovered their charge, and the cell become electrically neutral. But it obviously isnt! So what have I missed? . John F
Good question and perhaps the best explanation for this is with another video. The Limiting Factor has a really nice visualisation of this at the atomic level to help describe what is happening with the lithium-ions, electrons and electrode materials, as well as how this relates to the potential of the electrode. th-cam.com/video/4-1psMHSpKs/w-d-xo.html
@@BillyWuHi Billy Thanks for that. The reference you gave is excellent and complements your own explanation explanation. The way I now visualise it is a) In the cathode, the LI+ ions and the PO4- ions share the electrons but the electrons are rather loosely bound. b) An applied dc voltage drives the Li+ ions across the electrolyte to the anode at the same time pulling the electrons off the cathode through the external circuit where they mate with the Li+ at the anode. So when the cell is charged, the cathode becomes strongly electronegative while the anode is neutral. John F
Thanks and definitely. I made this video a few years ago but lots of new developments and I think LFMP has a lot of potential. Low cost materials with superior capacity to LFP. Definitely one to look out for.
Linden's Handbook of Batteries is a good start (www.amazon.co.uk/Lindens-Handbook-Batteries-Thomas-Reddy/dp/007162421X). Also consider the MOOC from Gregory Plett and his associated book. mocha-java.uccs.edu/ECE5710/index.html and mocha-java.uccs.edu/BMS1/
Can someone explain what is meant by the accessible capacity being decreased at lower voltages? Based on the graphs shown around ~20:00, it looks like the maximum Amp Hour Capacity is reached when the voltage dips all the way to 2V? Is it meant that, although current capacity approaches to near it's maximum as voltage goes down, higher charge rates lead to relatively lower current capacities at the same voltage?
Ah is a measure of amps integrated over time (eg 2A at 1hr is 2 Ah). But at the end of the day it is total energy delivered by the battery that matters, and total energy is Wh, or current * voltage integrated over time. I think he is saying when you get down to 2V, the energy being delivered is much less than at 3V for the same delivered current integrated over time. 1A over 1-hour at 3V delivers 3Wh, but 1A over 1-hour at 2V delivers only 2Wh.
Good question. We normally operate batteries between certain voltage limits (e.g. 4.2 V-2.7 V) to avoid damage to the battery. This limit can change depending on the chemistry (usually lithium-iron phosphate has lower limits). If we increase the discharge current, then the voltage drop of the battery increases (Voltage drop=Current*Resistance). This can mean that you reach the lower voltage cut-off sooner and therefore not be able to extract as much capacity. This will also depend on other factors but broadly high currents and low temperatures make it harder to get all the charge from your battery.
Great presentation Professor, are nuclear energy generation on a smaller scale, nuclear fusion will be considered as a source of potential energy generation once further safety & R&D has been conducted on utilizing Uranium 238 or Cobalt 60?
Good question. My take is that nuclear energy is an important consideration for a future energy system. A practice fusion system is still many decades away, but fission systems are likely needed for base load. Smaller modular fission reactors could be an approach to address the large capital needed to get them set up.
Thank you for a great lecture. I wonder if you wouldn't mind answering a question - do you think it is feasible for batteries at some point to reach energy density parity with thermal engines operating on hydrocarbon fuels ~ 10 MJ/kg. This means the battery pack for a BEV would have to increase by a factor of roughly 10 compared to the state of the art today (Tesla).
In theory a lithium-air battery which has the highest energy density would get you to about 5-11 kWh/kg but that's the theoretical value and in practice this would be much lower due to the other supporting components. Hydrogen has an energy density of about 33 kWh/kg which is very attractive but again needs considerations of the fuel cell and the volumetric energy density isn't as good. I think in the short term we see a pathway to >400 Wh/kg with reasonable lifetime and maybe 500 Wh/kg but the metal air systems still have challenges.
Good question. Whilst we call these lithium-ion batteries the amount of lithium in them is actually quite minimal by mass. This normally exists in the cathode and the electrolyte with most of it in the cathode when manufactured. Here, the main precursors are lithium carbonate and lithium hydroxide. Not many batteries use pure lithium metal anodes though many are exploring due to higher energy density
Dr Dr Wu In your excellent video the examples you give show are cylindrical cells, not much larger than AA cells. I have found suppliers offering Prismatic Cell LiFePO4 Cells from EVE offering 280 Ah at 3.2 v giving 896Wh. I presume that the capacity is dependent on the area of the anode and cathode, i.e the amount of Li ions that can be generated. And that a so called prismatic cell/battery will have more area for the electrodes. Is that broadly correct? Best wishes John
Thanks John. Yeah, that's right. The most common cells are generally the 18650 cells which have a diameter of 18 mm and length of 65 mm. Usually these have a capacity of around 3 Ah. There are other sizes which are bigger and thus offer larger capacities since they have more active material or electrode area. Putting multiple smaller cells in parallel can create the same effect as a single cell, though there are pros and cons of either approach. Smaller cells being easier to manufacture, thermally manage and being a bit safer. Larger cells generally requiring less pack assembly with fewer welds, and in theory having more energy density since you have less packaging material, though can be more dangerous if not handled correctly.
@@BillyWu Thanks Billy for your patience in answering these questions. We are faced (threatened ?) with the construction of a 400MW/2000MWh BESS in the middle of residential area not far from us. It seems that the company would use prismatic cells each of which would contribute 800 Wh of energy about 250 Ah. This is about 80 times larger than the 18650 cells. The only other BESS of comparable size is the 400MW/1600MWh facility at Moss Landing California, which is situated miles from anywhere. Thanks again and best wishes - John
@@exsollertan7366 Yeah, at the GWh scale, use of smaller 18650 cells starts to become quite challenging in terms of integrating that number of cells. Larger cells are more attractive there for that reason but both still have pros and cons. Of course, any suitably designed/manufactured system should still maintain a good level of safety
Great question. The low temperatures will increase the resistance of the battery which unfortunately will decrease the efficiency. A thermal management system might well be needed to keep the battery in it's optimum temperature range (~10-30°C) but pre-heating often consumes energy, leading to lower system efficiency.
Can you explain reduced battery capacity when cold? If I charge a battery with say 100Ah, and it gets cold, how exactly is the capacity reduced? Is the Ah reduced, (eg I can only get 95Ah out), or does the voltage drop faster resulting in less Wh out? I do believe the ESR increases, so if pulling higher currents more power is lost in the ESR. But if pulling low current, say 0.05C, ESR increase would have a small impact on ability to get energy out.
Great question and there are a number of causes of reduced accessible capacity at low temperatures. Normally we impose voltage limits (4.2 V-2.7 V) to avoid damaging the battery and if these are hit then the battery normally stops. You're right that at low temperatures, the resistance of the battery often increases since the electrochemical reactions are slower. This means for the same current at higher temperatures, there will be more resistance and you will hit the lower voltage cut-off sooner. The other reason is that at lower temperatures lithium-ions move slower through the electrode materials. This means its more difficult to effectively squeeze these lithium-ions out of the electrodes which results in lower accessible capacity.
Hi there I enjoyed your video. One thing is not clear to me though; when a Li Ion battery is discharging the LI ions must flow from the anode to the cathode how do the ion's overcome the 3.7v potential ???? and if you can point me to paper that talks about this that would be great!! - well no reply from Billy so this is not the guy to ask questions of
Sorry, I don't check the comments that often. The voltage of a battery is made up of the difference between the anode and the cathode. The overall cell voltage varies from 4.2 V (fully charged) to 2.7 V (fully discharged) for most battery chemistries. The 3.7 V quoted number is the nominal (~average) voltage of discharge. This series of talks from nanoHUB-U on rechargable batteries gives a great overview of the fundamental science th-cam.com/video/ghbiKe45s2c/w-d-xo.html&ab_channel=nanohubtechtalks
Thanks. I recommend Gregory Plett's excellent course on battery modelling. It's available online for free also! Modeling, Simulation, and Identification of Battery Dynamics mocha-java.uccs.edu/ECE5710/index.html Battery Management and Control mocha-java.uccs.edu/ECE5720/index.html
Great question! The safety differences come in part due to the thermal stability of the cathode materials. LFP has something called a olivine crystal structure and NCA is a layered material. This is basically how the atoms stack up with some more thermally stable than others. Whilst LFP has a lower capacity because of this it is more stable with it more difficult for the oxygen in the materials to decompose which is one of the safety issues. This paper gives an excellent review on safety and thermal runaway "Thermal runaway mechanism of lithium ion battery for electric vehicles: A review" www.sciencedirect.com/science/article/abs/pii/S2405829716303464
Bugging me for a while now is "why do manufacturers make single-layer cells instead of 2-layer cells"? If they adhered anode graphite to both sides of the anode metal sheet, cathode nickel to both sides of the cathode metal sheet, and jellyrolled round batteries with one additional separator sheet, they would have, on packaging and pumping in electrolyte, a cell with just slightly lower current but double the voltage, with slightly less anode and cathode metal sheet than a single-layer cell. A 1.8 times increase of energy density.
Good question. Many battery electrodes are actually coated on both sides to improve cell level energy density (though most of the time for simplicity we just show a single side coating. This reduces some of the need for current collectors as they can be shared. On the point about voltage, in most cases connecting cells in series in the same electrolyte can lead to its decomposition and hence poor lifetime so is not generally done, however there are bipolar cell designs for solid-state batteries where you can isolate the electrolyte a bit better to mitigate this issue
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I sure wish I had found this when I started researching batteries! You managed to summarize hours of material into an entertaining 23 minute video. Thanks and well done!
Glad to hear it was useful
Hello Brandan, I am just starting my research on batteries. I would like to connect with you and seek some guidance.
@@BillyWu Dear Billy, I have noticed with other explanations Lithium Nickel Oxide is used in the cathode and in others Lithium, Nickel cobalt oxide is used. Is there more than one technology? It is also asserted that the microporous membrane allows the passage of lithium ions but not electrons. Is this just because of the electric field between anode and cathode?
@@exsollertan7366 Good question! Yes, there are quite a few different cathode options each with their pros and cons. NMC (lithium nickel manganese cobalt oxide) is one of the most popular, with researchers aiming to reduce cobalt due to cost and ethical sourcing. For the separator, we need this to prevent the anode and cathode from touching since this would cause a short-circuit and damage the battery, yet we also need the electrolyte to connect the 2 electrodes, as the battery needs this to operate.
@@BillyWu are the slides available freely? Is there any link?
now this is getting epic. Definitely one of the cleanest presenters on youtube.
Thanks Evan. Appreciate the comment
Excellent 101 on batteries - simple, clean and organized! Thank you!
Glad it was helpful!
A very nice and concise presentation. You must have spent a lot of time to compress the vast amount of material into easily digestible material. It is commendable that you have put it for free on you tube. There is nothing more valuable than sharing knowledge.
Thanks for the comment. Appreciate it and glad to hear it was useful
EXCELLENT, comprehensive and thorough video, presented in a succinct and straightforward fashion. Thanks so much!
Glad you enjoyed it!
Very useful information for someone likes me who has zero knowledge on battery. Thank you for the effort
Glad it was helpful!
The best battery basics video on TH-cam, thank you Prof Billy Wu on such an insightful video. Your vocabulary is spectacular as well, keep up the great work !!.
Thanks! New video on solid-state batteries coming soon
👍Well done! Most of the important Li battery attributes explained in a short video, best I've come across.
Thanks!
Thank you Dr. Wu for the very informative video. I’m also a PhD student at Imperial.
Thanks. Glad you found it useful
Very informative. Trustworthy source. Thank you. 🙏
Thanks. Glad to hear it was useful
It's just mind blowing...a great effort towards knowledge sharing..a very reliable and knowledgeful resource to learn about battery basics....kudos Dr. Billy...keep up the good work
Thanks. Glad to hear it was useful
great and useful stuff, summaries bunch of material in a short time, really appreciate your effort.
Thanks. Glad to hear it was useful
Beautiful intro to Li ion batteries from a 360 dég point of view
Thanks!
I wish I could Like this video several times. Very informative Dr Wu. Thank you many times. I'll instead share this on several platforms.
Thanks for the comments. Appreciate it and glad it was helpful
Prof. Wu, thank you very much for this Lecture.
Glad it was helpful!
Hi Dr. Billy - Covered all aspects of battery design! Very nice consolidated demonstration. Thank you Sir!
Glad it was helpful!
Dr Billy wu, highly useful stuff.
Thanks for sharing the knowledge on batteries.
Great to hear it was useful
Hi Dr.Bill Wu good to watch your TH-cam videos.
It's very informative.
What an awesome channel!! You've got my subscription for learning more on battery technology
Thanks! Appreciate it
Touch of a class talk. Impressed.
Thanks
best presentation I have seen on Li-ion tech on youtube . hats off :)
Thanks a lot
Hi Prof. Wu...very nice and clean presentation and was really useful information. Thanks
Glad it was helpful!
Very informative presentation! Thanks a lot Dr. Wu!
Thank you for the video, I am starting to work with batteries and it is really helpful!
Glad it was helpful!
Thank you very much for this talk. It is excellently presented. Well done!
Glad it was helpful!
Hello Dr Wu. Great insight. I just have one question at 6:07 minutes in the figure . On the left side when you are describing the full cell packaging i believe the direction of the current is wrong. Inorder to light the bulb the electron will flow from negative terminal (anode) to positive terminal (cathode).
Thanks Ali. You're right! I never noticed that till now :)
Highly fact density. A good presentation. Thank you.
Glad it was helpful!
I build home made batteries. Very difficult to get a cheap chemistry that does self discharge within a few days.
I'd welcome any ideas you may have for a home builder.
Good video.
Take care
Bret
Hi Professor Wu, very informative video! I was thinking about the hexagonal representation of different chemistries on slide 8. Should Voltage be there as a parameter? Maybe its included in the power term? For Li-Sulfur chemistry, how will the hexagonal map look like? Maybe better than NMC/NCA?
Thanks Kunal. Good question. Voltage is important and is somewhat captured in the specific energy of the material as this will be related to the product of the nominal voltage and the specific capacity of the material. Li-sulfur will have better specific energy than NMC and very good cost since sulfur is quite cheap. However, the lifetime of these devices are quite poor due to instabilities in the lithium and also power rate is quite poor since sulfur is not a very good electrical conductor.
Great overview of the battery basics! Thanks for sharing.
Glad it was helpful!
very educative & many thanks for sharing
Thanks. Glad to hear it was helpful
Thank you, very informative
Glad it was helpful!
I like this summary. Very insightful.
Thanks
Very informative video on battery basics! Thanks a lot Dr. Wu! Can you make a similar type of video explaining the working of the ANSYS Fluent battery Model (E-chemistry Models)??
You are GREAT...!!! Never stop making your fantastic vids..!
Thanks. Appreciate the comment :)
Very clear presentation! Thanks for the lecture :)
Thanks
Thanks Dr. Wu, this was very interesting and well explained
Glad it was helpful!
@@BillyWu So happy that this kind of great content is not hidden behind a paywall and enough condensed that one does not need to read a great number of papers to get such an overview about the current state of the technology. You're doing humanity a great service sir.
Very informative video. Could you please enlighten me on the reason behind selecting Transition metals for cathode chemistry?
Thanks. For batteries to have good lifetime, we need the materials to be as stable as possible. Lithium-ion batteries work by moving lithium-ions between an anode and cathode. When we insert lithium-ions into the structure we call this process intercalation. We can think of this like lithium-ions being books and the electrode materials being the bookshelf. In the case of the cathode, one of the most common cathode chemistries is NMC (Lithium Nickel Manganese Cobalt Oxide). This forms a layered crystal structure, similar-ish to the bookshelf analogy. These elements have the right blend of properties to form this structure but also give a good electrical potential when inserted.
Nice and informative Talk
Please make a general video on Sodium ion battery (Cathodes and anodes)... How it is comparable to Li ion battery..
Definitely
Excellent video, well done and extremely informative.
Thanks. Glad to hear it was helpful
Perfect. Thank you!
Glad it helped!
How can I cite your work in research paper?
Slides like no. 5 are very useful when comparing results reported in different papers. But, there are just too many parameters to keep track of! The papers use variety of different parameters like energy density, power density, aerial capacity, volumetric capacity, voltage variations, driving range etc. to quantify the battery/electrode performance. I think it should be made mandatory to narrow down the performance to a fixed set of metric parameters. That would make it easy to assess the potential of any new technology.
Prof. Wu, can you provide such 'now' and 'future' data for all possible metric parameters? Also, how are the 'future' values determined? Is it based on comparison to IC engines?
Nice comments Kunal. You're right that there are many different parameters. Unfortunately, it is a complex space and in reality we need to consider all of these together. Again these metrics can be made to look better if you look at a single one. For example it's relatively straightforward to make a high energy cell or high power cell but difficult to get all into the same cell at low cost. I know a range of people are working on standards for these metrics to make them more transparent and comparable, so that would be my hope for the future.
At 4:37 why are electrons depicted as flowing from the positive terminal to the negative terminal? Is this suppose to represent current instead?
The electrons can flow in either direction (from/to the positive/negative terminals) depending on whether the battery is being charged or discharged. This is driven by the potential applied to the battery and the need to maintain charge neutrality in the battery, i.e. when a lithium-ion comes out of the anode/cathode, another lithium-ion has to be intercalated into the opposite electrode and an electron is needed to balance the charge.
Thank for this usefull and detailed video !
Glad it was helpful!
Hi Billy I am still a bit confused about the process of the charging of the Li-ion cell. When a lithium ion cell is connected to a DC source, the electric field applied forces the lithium ions to move from the cathode through the electrolyte to the graphite anode. Meanwhile electrons move through the outside circuit and again end up in the graphite. These electrons would be same number as the lithium ions. Presumably therefore the lithium ions have now recovered their charge, and the cell become electrically neutral. But it obviously isnt! So what have I missed? . John F
Good question and perhaps the best explanation for this is with another video. The Limiting Factor has a really nice visualisation of this at the atomic level to help describe what is happening with the lithium-ions, electrons and electrode materials, as well as how this relates to the potential of the electrode. th-cam.com/video/4-1psMHSpKs/w-d-xo.html
@@BillyWuHi Billy
Thanks for that. The reference you gave is excellent and complements your own explanation explanation.
The way I now visualise it is
a) In the cathode, the LI+ ions and the PO4- ions share the electrons but the electrons are rather loosely bound.
b) An applied dc voltage drives the Li+ ions across the electrolyte to the anode at the same time pulling the electrons off the cathode through the external circuit where they mate with the Li+ at the anode.
So when the cell is charged, the cathode becomes strongly electronegative while the anode is neutral.
John F
But Watt about energy?
Excellent video
Thanks internet stranger. Hopefully the video will charge interest in the subject
thanks for this video...very informative
Thanks
nice informative ..........thank you sir
Thanks. Glad to hear it was useful
Thank you
excellent presentation
Thanks!
Very good content.
Thx a lot!!
Thanks! Glad it was helpful
Please upload the vedio of heart of Na-ion Batteries also ...nice vedio
Thanks! Am working (very slowly) on a sodium-ion video
@@BillyWu please fast go ahead sir ,I am waiting 😊😛🙏
Thanks Dr Wu! How we can quantify the power density of a battery? Imax*Vnom?
Great video - thanks. What about the LFMP cathode, does this feature in the future roadmap?
Thanks and definitely. I made this video a few years ago but lots of new developments and I think LFMP has a lot of potential. Low cost materials with superior capacity to LFP. Definitely one to look out for.
@@BillyWu Thanks Billy. Really appreciate your quick answer 🙏🙏🙏
This is some serious shit, need to watch at least twice to absorb all the info, btw did you see my 2nd life storage project/product?
Thanks. Just had a quick look. Looks interest. Hope the project goes well
thank you great video, very clear :)
Glad to hear it was useful
Dr, I saw both videos, those are very nice and informative. Can you suggest book name to understand Li as element in detail. Thanks.
Linden's Handbook of Batteries is a good start (www.amazon.co.uk/Lindens-Handbook-Batteries-Thomas-Reddy/dp/007162421X). Also consider the MOOC from Gregory Plett and his associated book. mocha-java.uccs.edu/ECE5710/index.html and mocha-java.uccs.edu/BMS1/
🔋 Thanks Billy.
Thanks!
Thanks so much for your support. Hope that this content is useful
Can someone explain what is meant by the accessible capacity being decreased at lower voltages? Based on the graphs shown around ~20:00, it looks like the maximum Amp Hour Capacity is reached when the voltage dips all the way to 2V? Is it meant that, although current capacity approaches to near it's maximum as voltage goes down, higher charge rates lead to relatively lower current capacities at the same voltage?
Ah is a measure of amps integrated over time (eg 2A at 1hr is 2 Ah). But at the end of the day it is total energy delivered by the battery that matters, and total energy is Wh, or current * voltage integrated over time. I think he is saying when you get down to 2V, the energy being delivered is much less than at 3V for the same delivered current integrated over time. 1A over 1-hour at 3V delivers 3Wh, but 1A over 1-hour at 2V delivers only 2Wh.
Good question. We normally operate batteries between certain voltage limits (e.g. 4.2 V-2.7 V) to avoid damage to the battery. This limit can change depending on the chemistry (usually lithium-iron phosphate has lower limits). If we increase the discharge current, then the voltage drop of the battery increases (Voltage drop=Current*Resistance). This can mean that you reach the lower voltage cut-off sooner and therefore not be able to extract as much capacity. This will also depend on other factors but broadly high currents and low temperatures make it harder to get all the charge from your battery.
Very good Billy!
Thanks
great information pack
Thanks!
Great presentation Professor, are nuclear energy generation on a smaller scale, nuclear fusion will be considered as a source of potential energy generation once further safety & R&D has been conducted on utilizing Uranium 238 or Cobalt 60?
Good question. My take is that nuclear energy is an important consideration for a future energy system. A practice fusion system is still many decades away, but fission systems are likely needed for base load. Smaller modular fission reactors could be an approach to address the large capital needed to get them set up.
Thank you for a great lecture. I wonder if you wouldn't mind answering a question - do you think it is feasible for batteries at some point to reach energy density parity with thermal engines operating on hydrocarbon fuels ~ 10 MJ/kg. This means the battery pack for a BEV would have to increase by a factor of roughly 10 compared to the state of the art today (Tesla).
In theory a lithium-air battery which has the highest energy density would get you to about 5-11 kWh/kg but that's the theoretical value and in practice this would be much lower due to the other supporting components. Hydrogen has an energy density of about 33 kWh/kg which is very attractive but again needs considerations of the fuel cell and the volumetric energy density isn't as good. I think in the short term we see a pathway to >400 Wh/kg with reasonable lifetime and maybe 500 Wh/kg but the metal air systems still have challenges.
@@BillyWu very interesting thanks for the feedback. 👍
Great Job!
Thanks!
👍🏻
excellent
Thanks
Is pure lithium (LI) or lithium oxide or LCE used in BEVs and PHEVs?
Good question. Whilst we call these lithium-ion batteries the amount of lithium in them is actually quite minimal by mass. This normally exists in the cathode and the electrolyte with most of it in the cathode when manufactured. Here, the main precursors are lithium carbonate and lithium hydroxide. Not many batteries use pure lithium metal anodes though many are exploring due to higher energy density
@@BillyWu appreciate the response!
🖤 thank you very helpful
Glad it was helpful!
Dr Dr Wu In your excellent video the examples you give show are cylindrical cells, not much larger than AA cells. I have found suppliers offering Prismatic Cell LiFePO4 Cells from EVE offering 280 Ah at 3.2 v giving 896Wh. I presume that the capacity is dependent on the area of the anode and cathode, i.e the amount of Li ions that can be generated. And that a so called prismatic cell/battery will have more area for the electrodes. Is that broadly correct? Best wishes John
Thanks John. Yeah, that's right. The most common cells are generally the 18650 cells which have a diameter of 18 mm and length of 65 mm. Usually these have a capacity of around 3 Ah. There are other sizes which are bigger and thus offer larger capacities since they have more active material or electrode area. Putting multiple smaller cells in parallel can create the same effect as a single cell, though there are pros and cons of either approach. Smaller cells being easier to manufacture, thermally manage and being a bit safer. Larger cells generally requiring less pack assembly with fewer welds, and in theory having more energy density since you have less packaging material, though can be more dangerous if not handled correctly.
@@BillyWu Thanks Billy for your patience in answering these questions. We are faced (threatened ?) with the construction of a 400MW/2000MWh BESS in the middle of residential area not far from us. It seems that the company would use prismatic cells each of which would contribute 800 Wh of energy about 250 Ah. This is about 80 times larger than the 18650 cells. The only other BESS of comparable size is the 400MW/1600MWh facility at Moss Landing California, which is situated miles from anywhere. Thanks again and best wishes - John
@@exsollertan7366 Yeah, at the GWh scale, use of smaller 18650 cells starts to become quite challenging in terms of integrating that number of cells. Larger cells are more attractive there for that reason but both still have pros and cons. Of course, any suitably designed/manufactured system should still maintain a good level of safety
@@BillyWu Thanks again for responding so quickly. Best wishes John
As a denizen of Canada, how would our rather nasty winter temperatures going to affect battery efficiency?
Great question. The low temperatures will increase the resistance of the battery which unfortunately will decrease the efficiency. A thermal management system might well be needed to keep the battery in it's optimum temperature range (~10-30°C) but pre-heating often consumes energy, leading to lower system efficiency.
Can you explain reduced battery capacity when cold? If I charge a battery with say 100Ah, and it gets cold, how exactly is the capacity reduced? Is the Ah reduced, (eg I can only get 95Ah out), or does the voltage drop faster resulting in less Wh out? I do believe the ESR increases, so if pulling higher currents more power is lost in the ESR. But if pulling low current, say 0.05C, ESR increase would have a small impact on ability to get energy out.
Great question and there are a number of causes of reduced accessible capacity at low temperatures. Normally we impose voltage limits (4.2 V-2.7 V) to avoid damaging the battery and if these are hit then the battery normally stops. You're right that at low temperatures, the resistance of the battery often increases since the electrochemical reactions are slower. This means for the same current at higher temperatures, there will be more resistance and you will hit the lower voltage cut-off sooner. The other reason is that at lower temperatures lithium-ions move slower through the electrode materials. This means its more difficult to effectively squeeze these lithium-ions out of the electrodes which results in lower accessible capacity.
Hi there I enjoyed your video. One thing is not clear to me though; when a Li Ion battery is discharging the LI ions must flow from the anode to the cathode how do the ion's overcome the 3.7v potential ???? and if you can point me to paper that talks about this that would be great!! - well no reply from Billy so this is not the guy to ask questions of
Sorry, I don't check the comments that often. The voltage of a battery is made up of the difference between the anode and the cathode. The overall cell voltage varies from 4.2 V (fully charged) to 2.7 V (fully discharged) for most battery chemistries. The 3.7 V quoted number is the nominal (~average) voltage of discharge. This series of talks from nanoHUB-U on rechargable batteries gives a great overview of the fundamental science th-cam.com/video/ghbiKe45s2c/w-d-xo.html&ab_channel=nanohubtechtalks
Hello Dr. Wu, excellent video. Can you recommend a book who is just getting started into LIBs and their thermal management? Thanks.
Thanks. I recommend Gregory Plett's excellent course on battery modelling. It's available online for free also!
Modeling, Simulation, and Identification of Battery Dynamics
mocha-java.uccs.edu/ECE5710/index.html
Battery Management and Control
mocha-java.uccs.edu/ECE5720/index.html
What makes LFP safer than NCA? or vice versa. A source would be enough
Great question! The safety differences come in part due to the thermal stability of the cathode materials. LFP has something called a olivine crystal structure and NCA is a layered material. This is basically how the atoms stack up with some more thermally stable than others. Whilst LFP has a lower capacity because of this it is more stable with it more difficult for the oxygen in the materials to decompose which is one of the safety issues. This paper gives an excellent review on safety and thermal runaway "Thermal runaway mechanism of lithium ion battery for electric vehicles: A review" www.sciencedirect.com/science/article/abs/pii/S2405829716303464
@@BillyWu Thank you for the explanation. Excellent video
Does lithium have the same "memory effect" as nickel-cadmiun?
Nope. Lithium-ion batteries don't suffer from the "memory effect" that was found in older batteries so you can use these straight out the box.
Bugging me for a while now is "why do manufacturers make single-layer cells instead of 2-layer cells"?
If they adhered anode graphite to both sides of the anode metal sheet, cathode nickel to both sides of the cathode metal sheet, and jellyrolled round batteries with one additional separator sheet, they would have, on packaging and pumping in electrolyte, a cell with just slightly lower current but double the voltage, with slightly less anode and cathode metal sheet than a single-layer cell.
A 1.8 times increase of energy density.
Good question. Many battery electrodes are actually coated on both sides to improve cell level energy density (though most of the time for simplicity we just show a single side coating. This reduces some of the need for current collectors as they can be shared. On the point about voltage, in most cases connecting cells in series in the same electrolyte can lead to its decomposition and hence poor lifetime so is not generally done, however there are bipolar cell designs for solid-state batteries where you can isolate the electrolyte a bit better to mitigate this issue
this is peak youtube
Mr. Wu please contact me to discuss potential sustainable replacements. Ray
Elections flow externally from cathode to anode 😂, otherwise ok 👍
too boring to pick up any understanding. next time give it some life - not like reading a text-book.
go less words per minute, half as much.