I am a scientist by training, so let me give you a primer on lithium ion construction. The thin polymer prismatic cells (flat rectangular shaped) batteries used in consumer electronics are made of a flammable oil based plastic polymer case, filled with an oily electrolyte that is also flammable, the carbon in the cathode is flammable, and the lithium cobalt sponge anode is also flammable. This means that in order to prevent the batteries from catching fire, manufactures employ a series of special safety measures. Exploding cell phone, hover boards, laptops, and electric vehicles have made the news along with the Boeing 787 dreamliner for battery related lithium ion fires! Many things must be done carefully to ensure this problem does not continue!
The Galaxy Note 7 has been exploding while charging lately, which caused me to write about this. My wife's father is living with us, and he just bought one, so we have to be careful with charging it now, I warned him of the recall. The problem is so bad that samsung is recalling nearly 8 million handsets for a battery swap. I am reminded of the Takata airbag recall that is pending for my Honda CR-Z :( It seems that mistakes are in all things human! The engineering microporous anode cathode separator film is what failed inside the Note 7 battery, allow a short circuit to form in the core of the cell, causing the electrolyte, an oily unstable fluid to off gas with heat, which forms a positive feedback loop called thermal runaway, which often leads to Venting with Flame, or a battery fire!
Current Safety measures used in well made Lithium Ion battery cells & packs
1. Pressure expansion disconnect that electrically disconnects the battery from the BMS and load if expansion of the cell propagates beyond a certain limit. Many people have seen a swollen phone battery from an old Samsung cell phone with a removable battery. RC hobby people also are familiar with swollen lithium polymer cells. If this safety measure malfunctions, the polymer case can rip open, allowing moisture laden air into the battery, which will cause venting with flame as the water reacts with the anodes cobalt lithium sponge, which then sets the electrolyte and polymer separator film on fire, which then sets the cathode and polymer case on fire, the BMS gets cooked, thermal runaway propagates, and you end up with a battery fire!
2. A BMS or battery management system to prevent charging beyond 4.26v per cell, and to prevent draining the cells below 2.9v, while also reducing the charge current when the cell is almost fully charged. Sadly most usb chargers are not smart, so they continue to trickle charge the battery, forcing more lithium ions back into the anode, which causes it to gradually swell a little more with each 100% charge camped on the charger cycle. Leaving a cell phone constantly plugged into the charger will cook the battery and increase your odds of a battery fire substantially. I recommend charging phones when they get to 30%, and unplugging them when they get to 80%, then every 20 days or 500 hours, giving a saturation charge to 100% and draining to to 15% to reformat the set points in the BMS so the battery display % on the phone is more accurate! If the BMS malfunctions a battery fire can occur, this means only high quality Made in Germany, Made in the USE or Made in Japan BMS's should be used. The QAQC from most chinese factories is not sufficient to produce a reliable large batch of BMS controllers at the scale needed to supply cell phone OEM's.
3. Water cutoff detection that disconnect the cell when saturated with water, because water can cause a violent reaction to occur in the anode.
4. Temperature monitoring that cuts off charging if the cell exceeds 122 deg F for any reason. High temperature will cause the battery to fail faster, reducing the performance of the battery faster, causing you to lose run time faster. Lithium ion likes 70 deg F, no colder than 50 deg F, and no hotter than 80 deg F, if you go outside those ranges, it will cause accelerated damage to the battery. Leaving your phone in direct sun for example while it is on is a great way to cook the phone and battery faster.
5. Some manufacturers bake in a BFR flame suppression layer in the polymer case of prismatic cells to suppress flame propagation and prevent a dangerous cell failure from occurring.
6. In 18650 cells, like the ones used in the Model S, the case of the battery is made of high grade stainless steel alloys, which can withstand great temperatures and pressures without failing, if the end seals, gaskets, and case crimping is done intelligently with great care and quality. This causes high grade aerospace cells to cost more, as there are more quality control steps and procedures to insure cell performance and safety over the life of the cell. This contrasts with goals like the Gigafactory, to church out cheaper cells by the billions.
7. The manufacturing of Lithium Ion cells must be done in a clean room to ensure that dust or other chemical contaminates floating in the air are not integrated into the active material foils, oils, or layers used in the manufacturing. Coal dust contamination in cheap chinese 18650's made in an open dirty room were the cause of those Hoverboard fires that were all over the news recently!
Better Quality = Higher Costs
Cheap is often the wrong ideas, quality at a higher cost is often safer! Higher quality goods require more care in their design and manufacturing, including and specifically the engineering done on the manufacturing process, especially in chemically engineered high performance battery applications. Fires and explosions can occur when a lead acid battery is improperly charged, boiling out the sulfuric acid into a cloud of hydrogen gas fuming with acid vapor, and the explosion can blow the top off a car battery violently! Car manufactures spent a lot of time with their OEMs to design alternators that will not overcharge the lead acid battery used in almost all vehicles for starting, lighting, and accessory load balancing.
Lithium batteries come in more than 100 different chemistries
Although almost all of them are Lithium Cobalt, Lithium Manganese, Lithium Titanate
, Lithium NMC or NCA, and Lithium Silicon Nano-wire, Lithium Iron Phosphate, Lithium Sulfur, Lithium Aluminum, Lithium Cobalt Nickel, or some combo of anode and cathode tech based on about 12 common recipes used in industrial lithium ion battery manufacturing.
Lithium sulfur is the most interesting one currently. Oxis Energy currently manufactures fault tolerate fire proof Li-S batteries that have 2x better energy density than the best Lithium Ion Cobalt batteries!
Lithium sulfur batteries have been used in long range Drones since about 2006, made by Qinetiq, a UK defense contractor specialized at building long flight endurance drones for aerospace & defense! They make the DJI drones that cost between $1000 and $5000 look cheap by comparison! Boeing Defense Systems also has some cool drones that use Lithium Sulfur batteries!
I have a pair of Casio G-Shock solar watches, and a pair of Citizen Eco-Drive watches that use 23 year life Lithium Titanate batteries for the energy storage!!!!! I was hopeful to see Lithium Titanate and Lithium Iron Phosphate, the two durable long life Lithium Ion batteries make a bigger splash in the electric bike market, electric vehicle market, electric scooter market, laptop markets, and other applications where a long life battery is awesome, like in hybrid vehicles! Speaking of which Toyota figured out how to make NiMH last 50,000 cycle and 20 years, by computer controlling the batteries to stay between 30 and 80%, never fully charging or fully discharging them. There are similarly Nickel Hydrogen space satellite batteries that go more than 40,000 cycles and last up to 25 years, used every day 24/7 in space! The key to long life with NiMH and Lithium Ion is 30 to 80 % state of charge! Time you charge, never leave your mobile phone on the charger for more than 2 hours and you will enjoy good battery performance and long battery life! It is also much safer to shallow charge the batteries between 30 & 80%.
I am not sure why the engineers at Boeing missed out of this fact with the Dreamliner! I am an environmental scientist who has been informally studying batteries for 28 years, and I knew that Lithium Cobalt Carbon was a bad choice for the extreme thermal cycling encounter in commercial aircraft applications. I wonder if the people in charge of the battery on the Dreamline were smoking burning battery fumes when they decided to use the most unsafe of all battery chemistries, made in China no less, the FAA approval cell pack was made in small batches by a bespoke battery builder in the UK! Boeing should have used high quality cells made in the UK, Germany, Japan or the USA. Rose electronics builds awesome battery energy packs for aerospace and custom bespoke energy storage applications. The supplier of the final Boeing Dreamliner battery, Chinese PRC manufacturing subsidiary of GS Yuasa, a Japanese battery conglomerate behemoth, completely screwed up the BMS controller and cell manufacturing QA: QC that ultimately gave rise to the Dreamliner battery failures. I think the executives at GS Yuasa and the executives of the manufacturing in China should all be deeply ashamed of themselves! Similarly I think Samsung needs to do extensive internal auditing to correct whatever series of mistakes they made that gave rise to the battery failures. I believe the FTC and NATO should ban China from making Lithium Ion cell outside of a clean room factory, require that all battery manufacturers in China be audited by a competent third party battery manufacturing expert from another country, who is personally audited to prevent bribery and collusion from happening. Chinese manufacturing firms are notorious for cutting corners to reduce manufacturing costs to improve profit margins, but thats about as intelligent as running a generator in a windowless non-ventilated room, when it comes to manufacturing safe lithium ion batteries!
My History with Batteries
I started studying NiCD batteries as a child, long used in power tool packs that I disassembled and reassembled into 3.6v packs to build super long run time batteries for my cordless panasonic home phone handset, taped onto the back with Kapton tape, I was an unusual child, very interested in power and electricity, heat and chemistry. Later I started experimenting with NiMH in high school, becoming interested in RC aircraft. It was during this phase that I learned about LiPo batteries used in higher performance RC aircraft applications. I got a cool 12v in battery charger that can charge NiCD, NiMH, Lithium Ion/Polymer cells, with automatic voltage regulation to account for different pack voltages, made by Hobby Co in the USA. In college I spent a lot of time online reading about battery chemistries, innovations made in battery designs, and discovered the NiZn zebra cells and chargers, along with gaining a deeper understanding of why electric vehicles were not happening sooner, circa 2000.
When I was 14 years old I got a CD video disc at a RiteAid about the future of electric vehicles, and put it in the CD-ROM drive of my home built computer! It seemed from the video at that time, in 1995, that Toyota was going to be the leader, having released the Rav4 EV, and then GM launched the EV1, upgrading its battery from PbA to NiMH after 2 years on the market, gas prices sinking, the EV1's were collected and crushed, angering me and many others who were looking forward to cool electric vehicles without a foul toxic tail pipe emission problem common to all fossil fuel engine vehicles. Nissan ended up being first to market with a mass produced affordable electric car in 2010 with the launch of the Nissan Leaf! In 2005 I bought a new Toyota Prius after doing 650 hours of online research while I was in college. I learned more about the Prius than most people will ever know, and how Toyota was excluded from the PNGV program, a $2 billion US federal stimulus package given to the US automakers to build a passenger sedan that achieves 80 MPG by the year 2000. Toyota was insulted by not being invited to participate, so they secretly began developing the Prius program in Japan in 1993. The first Toyota Prius was launched in 1997 in Japan! In 2015 I purchase another hybrid after returning the leased Nissan Leaf S to Nissan of Bellevue. This time I went with a sport hybrid called a Honda CR-Z, with a 6sp manual, it was what I really wanted when I got the Prius back in 2005! Today we operate both of these hybrids, looking forward to affordable 300mi per charge electric vehicles and a much better charging infrastructure in the future. No doubt Tesla Motors has lit a fire under the market to accelerate the deployment of long range electric vehicles that normal people can afford with the launch of the Tesla Model 3, which is coming up next!
Lithium Ion Battery Functioning Principle
Lithium Ion batteries move lithium ions between the Anode and Cathode when they are charged and discharged. The Lithium Ions are doing the electron movement that gives current output to the battery, the anode and cathode forming the collecting plates that absorb and give up lithium ions when they are soaking up or giving off electric power, DC energy that consumer electronic use to operate. Battery energy storage systems based on Lithium Ion are what give the Tesla Model S P100D is power! To be safe, the battery pack has to be very carefully assembled with high quality components in a clean room when the cells are manufactured, and in a clean brightly lit room of intelligent people when the cells are assembled into a pack, even if robots are doing it, skilled staff are needed to perform auditing of the machines, maintenance of the machines, calibration of the machines, repair of the machines, making sure that everything is being done to a high level of perfection to insure good performance and safety in the resulting battery pack!
When the battery is fully charged, the lithium ions are jammed into the cathode, when you use your consumer electronics, lithium migrates out of the cathode, into the electrolyte, through tiny pores in the separator film, and they stick to the surface areas of the porous anode sponge, usually Lithium Cobalt. When you recharge the battery, electrons are forced into the carbon cathode, releasing the lithium ions from the anode, pushing them backwards through the electrolyte and film separator until they become part of the graphite or hard carbon cathode. The charging process is destructive to the cell because side reaction that occur in the electrolyte, and the swelling and shrinking of the anode upon lithium ion absorption and discharge cause physical damage to the composition of the anode sponge, causing it to break off, or shed into the electrolyte. This cause the internal resistance of the cell to increase, so the battery heats up more when you charge it. All lithium common lithium ion cells fail via a mixture of chemical side reactions and mechanical swelling shrinking damage to the anode sponge. Similarly the lithium ions can plate the carbon in the cathode if you over charge a device above 100% state of charge via a BMS failure. The BMS is designed to prevent this from happening, but they often fail, especially low quality BMS controllers made in China, by flimsy corporations that lack intelligent staff and management, and or are so overrun by greed that they are willing to take foolish shortcuts to make more money in the manufacturing of lithium ion batteries, BMS controllers, separator films, or electrolyte fluid mixtures. Hover boards were catching fire all over the world because of problems with battery manufacturing defects done in the PRC! I do not like the PRC because they harass one of my favorite countries in Asia, Japan, and one of my other favorite countries, Taiwan. I love Japan, Taiwan and South Korea! I also love America, Germany, the UK, Ireland, Holland, France, Norway, Sweden, and other intelligent countries like Brazil, and the Czech Republic! I am afraid that the PRC will partner with Russia to create a dystopian future, like the reality of life today in North Korea! The PRC has proven over and over again that they do not care about over population, pollution, currency manipulation, senseless killing of their own people, public safety, or product quality. Amazingly Apple produces almost all of it products in China, but are only able to do so by strictly supervising the entire manufacturing process from materials processing to final production, Foxconn or Hon Hai Precision Co. Ltd. in the case of mass manufacturing, Apple even resorted to building the Mac Pro in Texas for better quality control! Thats awesome. The iMac i am producing this blog posting on, along with all of my other computers, made in China :( On the positive side, some of my home spun machines are made entirely of components made in Taiwan :) I had picked Asus parts, Seagate parts, and Intel parts made outside of the PRC :) I will support the PRC when the central government of the PRC is composed of honest moral ethical kind people who are fair and reasonable! In the case of the iMac I had not choice, other than to not buy it.... so be it. At least the majority of the money went to the engineers in Cupertino California!
|How Lithium Ions Move In Lithium Ion Battery Cells|