From smart phones to laptops, from electric cars to e-cigarettes, lithium-ion batteries are powering a wide range of electronics. However, as the potential of lithium has been developed to the extreme, researchers are working hard to find the next battery breakthrough.
If you read this article on your smartphone, it means you are holding a "bomb." Under the shield, lithium (a very volatile metal that ignites when in contact with water) is being broken down and reconstituted in a powerful chemical reaction that provides the modern world with no Or lack of motivation.
Lithium is being used in mobile phones, tablets, laptops, and smart watches, and is found in our e-cigarettes and electric cars. It is light and soft, and is an energy-intensive substance, making it the perfect source of power for portable electronics. However, as consumer technology becomes more powerful, lithium-ion battery technology has always struggled to keep pace. Now, just as the world is addicted to lithium, scientists are rushing to reinvent batteries that power the world.
Huge illuminated screens, faster processing speeds, fast data connections, and slim design are all that make it difficult for many smartphones to support the entire day. Sometimes, mobile phone users even have to charge multiple times. After two years of use, the battery life of many devices will be drastically shortened and have to be thrown into the garbage. The huge advantage of lithium is also its biggest weakness. It is unstable and may explode. The energy of a lithium-ion laptop battery is similar to that of a grenade. Mike Zimmerman, founder and CEO of Ionic Materials, said: "There is a smartphone in the pocket like a kerosene in your pocket."
Zimmerman witnessed the burning effect at his company research laboratory in Woburn, Massachusetts. In one experiment, a machine drives a nail through a battery pack, and the battery pack expands rapidly, like a popcorn in a microwave oven, and then emits a bright flash. Battery research over the past 50 years has always been a tightrope between performance and safety, pushing energy as much as possible without pushing lithium to extremes.
We are doing this now. It is predicted that by 2022, the global battery market will reach 25 billion US dollars. But consumers believe that in one survey after another, battery life is the most popular feature of smartphones. With the popularity of 5G networks with higher energy consumption in the next decade, the problem will only become more and more serious. And for those who can solve the problem, they will get huge returns.
Ionic Materials is just one of dozens of companies that are embarking on an epic competition that fundamentally rethinks battery issues. However, the competition was plagued by wrong start, painful litigation and failed startups. But after a decade of slow development, hope is still there. Scientists from start-ups, universities and well-funded national laboratories around the world are using sophisticated tools to find new materials. They seem to be about to dramatically increase the energy density and battery life of smartphone batteries and create more environmentally friendly and safer devices that will be recharged in seconds and are sufficient for continuous use throughout the day.
The battery generates electricity by decomposing chemicals. Since the Italian physicist Alessandro Volta invented the battery in 1799 to solve the debate about frogs, each battery has the same key components: two metal electrodes - with The negatively charged negative electrode and the positively charged positive electrode are separated by a substance called an electrolyte. When the battery is connected to the circuit, the metal atoms in the negative electrode react chemically. They lose an electron, become a positively charged ion, and are attracted to the positive electrode through the electrolyte. At the same time, electrons (also with a negative charge) will flow to the positive electrode. But it does not pass through the electrolyte, but instead travels through the circuit outside the battery to power the devices it connects.
The metal atoms on the negative electrode will eventually run out, which means the battery is running out of power. But in a rechargeable battery, this process can be reversed by charging, forcing ions and electrons back into place, ready to start the cycle again. Electrodes made of pure metal cannot withstand the constant pressure of atoms to enter and exit without collapse, so rechargeable batteries must use a combination of materials to maintain the shape of the negative and positive electrodes through repeated charge cycles. This structure can be compared to an apartment building with a "room" for reactive elements. The performance of a rechargeable battery depends to a large extent on how fast you can get in and out of these rooms without causing the building to collapse.
In 1977, young British scientist Stan Whittingham worked at the Exxon plant in Linden, New Jersey. He built a negative electrode and used aluminum to form the walls of an apartment block. And the floor", using lithium as the active material. When he charges the battery, lithium ions move from the positive electrode to the negative electrode and precipitate in the gap between the aluminum atoms. When discharged, they move in the other direction and return to the space on the positive side through the electrolyte.
Whittingham invented the world's first rechargeable lithium battery, which is enough to power a too negative watch. But when he tries to increase the voltage (making more ions in and out) or trying to make a bigger battery, they will continue to burn. In 1980, American physicist John Goodenough, who worked at Oxford University, made a breakthrough. Goodnow is a Christian who served as a US Army meteorologist in the Second World War. He is also an expert in metal oxides. He suspects that there is definitely something in the body that can provide a stronger cage for lithium than the aluminum compound used by Whitingham.
Goodnow advised two postdoctoral researchers to systematically explore the periodic table and compare lithium with different metal oxides to see how much lithium can be extracted from them before they collapse. In the end, they identified a mixture of lithium and cobalt, the latter being a blue-gray metal throughout central Africa. Lithium cobalt oxide can withstand the limits of half of the lithium being pulled out. When it is used as a positive electrode, this represents a big step forward in battery technology. Cobalt is a lighter, less expensive material that is suitable for both small and large equipment and is superior to other materials on the market.
Today, Goodnow's positive pole appears in almost all of the handheld devices on Earth, but he has not made a penny. Oxford University refused to apply for a patent, and he himself gave up this right. But it changed what might happen. In 1991, after 10 years of tinkering, Sony combined Goodnow's lithium cobalt oxide positive electrode with carbon negative electrode to try to improve the battery life of its new CCD-TR1 camera. This is the first rechargeable lithium-ion battery for consumer products that has changed the world.
Gene Berdichevsky was the seventh employee of Tesla. When the electric car company was founded in 2003, the battery energy density has steadily increased for ten years, with an annual increase of about 7%. But by the end of 2005, Berdychevsky found that the performance of lithium-ion batteries began to stabilize. In the past seven or eight years, scientists have had to do their best to fight for even 0.5% improvement in battery performance.
The progress at the time was mainly due to improvements in engineering and manufacturing. Berdychevsky said: "After 27 years of modern chemical reactions, they continue to be refining." The materials are more pure, and battery manufacturers have been able to make more active materials by making each layer thinner. Load the same space. Berdychevski called it "sucking air out of the jar." But it also has its own risks. Modern batteries consist of an extremely thin alternating layer of electrolyte, electrolyte and anode material that is tightly integrated with the copper and aluminum charge collectors to carry the electrons out of the battery and where they are needed.
In many high-end batteries, the plastic diaphragm is located between the positive and negative electrodes to prevent contact and short-circuit, and is only 6 microns thick (about 1/10 of the thickness of human hair), which makes them susceptible to crush damage. . This is why the airline's security video now warns that if your phone falls into the mechanism, don't try to adjust the seat.
Every improvement in lithium-ion batteries requires trade-offs. Increasing energy density reduces safety, and introducing fast charging may reduce the cycle life of the battery, which means that the performance of the battery drops even faster. The potential of lithium ions is approaching its theoretical limits. Since Goodnow's breakthrough, researchers have been trying to find the next leap, including systematically examining the four main components of the battery—positive, negative, electrolyte, and separator—and using increasingly complex tool.
Clare Grey is a student at Goodnow at Oxford University. He has been studying lithium-air batteries, using oxygen in the air as another electrode. In theory, these batteries offer huge energy densities, but let them charge reliably and last for more than a few dozen cycles, which is already difficult in the lab, not to mention dirty in the real world. Unpredictable in the air.
Although Gray claims to have made a breakthrough recently, due to the above issues, the research group's attention has mainly turned to lithium-sulfur batteries. It provides a cheaper and more powerful alternative to lithium ions, but scientists are always trying to stop the cathodes that form on the positive electrode, and the sulfur on the negative electrode dissolves due to repeated charging. Sony claims to have solved the problem and hopes to bring consumer electronics with lithium-sulfur batteries to market by 2020.
At the University of Manchester, material scientist Xuqing Liu is one of those who are trying to squeeze more energy out of a carbon negative. He combines two-dimensional materials similar to graphene to enlarge the surface area and thus increase the lithium atom. Quantity. Liu Xuqing likened it to the number of pages that added a book. The university also invests in dry labs that will allow researchers to safely and easily exchange different components to test different combinations of electrodes and electrolytes.
It is incredible that even Goodnow himself is studying this issue. Last year, at the age of 94, he published a paper describing a battery that is three times the capacity of existing lithium-ion batteries. This is widely questioned. One researcher said: "If someone other than Goodnow published this article, I might want to marry her."
However, despite the publication of thousands of papers, billions of dollars in funding, and dozens of startups established and funded, the basic chemical functions of most of our consumer electronics products have remained almost unchanged since 1991. There is nothing to replace the combination of lithium cobalt oxide and carbon in terms of cost, performance and portability of consumer electronics. The iPhoneX's battery is almost identical to Sony's first camcorder.
Therefore, in 2008, Berdychevsky left Tesla and began to focus on studying new battery chemistry. He is particularly interested in finding alternatives to graphite anodes, which he believes are the biggest obstacle to making better batteries. Berdychevsky said: "The use of graphite has been around for six or seven years, and it is now basically used in the thermodynamic capacity of batteries." In 2011, he and Tesla's former colleague Alex Ya Alex Jacobs and Gleb Yushin, a professor of materials science at the Georgia Institute of Technology, co-founded Sila Nanotechnologies. They have an open layout in the Bay Area office in Alameda, a conference room named after the Atari game, and an industrial laboratory filled with furnaces and gas pipes.
After investigating all possible solutions, the three men theoretically determined that silicon is the most promising material. They only need to make the technology work. Many people tried before them, but they all ended in failure. However, Berdychevsky and his colleagues are optimistic about their success. A silicon atom can attach 4 lithium ions, which means that a silicon negative electrode can store 10 times more lithium than a graphite negative electrode of similar weight. This potential means that the National Academy of Sciences is interested in silicon anode materials, as are startups backed by venture capital firms such as Amprius, Enovix and Envia.
When lithium ions adhere to the negative electrode while the battery is charging, it expands slightly and then shrinks again during use. During repeated charging cycles, this expansion and contraction destroys the solid electrolyte interface layer, which is a protective substance that forms plaque on the surface of the negative electrode. This damage can cause side effects and consume some of the lithium in the battery. Berdychevsky said: "It is trapped in useless garbage."
Over time, this is the main reason why smartphones are beginning to lose energy quickly. The graphite anode expands and contracts by about 7%, so it can complete about 1000 charge and discharge cycles before performance begins to plummet. This is equivalent to a smartphone that lasts for two years and is charged every day. But because silicon particles can absorb so much lithium, they swell much more (at up to 400%) when charged. Most silicon anodes break after several charge cycles. For more than five years in the lab, Sila Nanotechnologies has created a nanocomposite to solve the expansion problem.
Berdychevski explained that if the graphite anode is an "apartment area", then all the "rooms" are the same size and are tightly packed together. After 30,000 iterations (different columns and room combinations), they form a negative electrode, where each layer has enough space for the silicon atoms to expand as they acquire lithium. He said: "We trap the extra space inside the building." This solves the expansion problem while keeping the outer dimensions and shape of the negative pole stable.
Berdychevsky said that the first generation of materials that Sila Nanotechnologies will provide to manufacturers next year will increase energy density by 20% and eventually increase by 40%, while also improving safety. He said: "Silicon can keep you away from the edge, you can vacate 1% or 2% of the space to really improve your safety." Most importantly, it can also be directly converted into an existing design. As Asian battery manufacturers compete to increase factory capacity and prepare for the electric vehicle era, Berdychevsky believes that any product that is incompatible with current production processes may be excluded. He said: "If there is no technology that can replace lithium ions, it will usher in countless user groups when it goes on the market."
When the battery is fully charged and discharged, lithium ions dance between the two electrodes, and sometimes they are difficult to return. Conversely, especially when the batteries are charging too fast, they will accumulate on the outside of the electrodes, gradually forming dendritic branches, like the stalactites at the top of the cave. Eventually, these dendrites, which look like frosted on the glazing, can extend through the electrolyte, penetrate the membrane, and create a short circuit by touching the opposite electrode.
As the distance between the layers gets closer, the risk increases and the likelihood of errors increases. As Samsung discovered last year, mistakes can cause damage and are costly. Tiny manufacturing defects have caused internal short circuits in the Galaxy Note7 mobile phone battery. On some devices, the negative and positive electrodes eventually contact each other, and this catastrophic recall event is estimated to have caused Samsung to lose 3.4 billion euros. Zimmerman of Ionic Materials explains: "When this happens, the battery becomes very hot and the liquid electrolyte will escape and eventually cause a fire and explosion."
Because this situation is very dangerous, in fact, there is not much lithium in lithium-ion batteries, only about two percent. But if there is a way to safely release pure metal lithium from a metal cobalt oxide cage, as Whitingham tried in the 1970s, it could add ten times the energy density. This is known as the "Holy Grail" of battery research, and Zimmerman may have discovered it.
He believes that electrolytes are actually the biggest obstacle to increasing the energy density of batteries. Instead of using substances immersed in liquid electrolytes, gels and polymers are used, but they are still generally flammable and do not help prevent rapid heat escape. Zimmerman himself admits that he is not a "battery control." His major is in materials science, especially in polymers. He taught at Bell Labs and Tufts University for 14 years before starting a business.
At the beginning of the 21st century, Zimmerman began to take an interest in rechargeable batteries. At the time, some people were trying to move from liquid electrolytes to solid electrolytes. Senior energy storage scientist Donald Highgate explains: "In principle, because solid-state electrolyte batteries are safer, you can make it work harder. For the same application, you can use smaller batteries." Most of them are ceramic or glass products, so they are very brittle and difficult to mass produce. ”
Plastics have been used in cells for separators, that is, portions that are located in the middle of the electrolyte to prevent electrode contact. Zimmerman believes that if he can find the right material, he can abandon the liquid electrolyte and separator, and replace it with a layer of solid plastic, which is fireproof and prevents growth between the two layers. Density. Through Ionic Materials, Zimmerman created a polymer with a new conduction mechanism that mimics how electrons pass through the metal. This is the first solid polymer that conducts lithium ions at room temperature. The materials are flexible, low cost, and can withstand a variety of tests.
In one experiment, they sent the raw materials to the ballistics lab, where they were usually used to test bulletproof vests and shoot them with 9mm bullets. Two wires connect the battery (flat silver bag) to the Samsung tablet, which is carefully removed. After the bullet hit, the battery blasted like a volcano. In the slow motion, you can see plastic and metal squirting from the crater, like lava. However, there was no explosion inside the battery, no explosion or fire. The device remains on for each collision. Zimmerman said: "We have always thought that polymers will make it safer, and we never expected the battery to continue to work."
According to Zimmerman, this polymer will drive the development of lithium metal and accelerate the adoption of new battery chemistries such as lithium-sulfur or lithium-air. But the long-term future may not be just lithium. Liu Xuqing, a researcher at the University of Manchester, said: "This improvement does not match the speed of improvement in equipment performance. We need a revolution."
In the huge Harvard Science and Innovation Park in Oxfordshire, where John Goodenough signed an agreement to abandon his patent breakthrough in the lithium ion field, Stephen Voller A piece of carbon fiber similar in size and shape to the beverage cup. Waller is an amiable Manchester City fan, nearly 50 years old. Prior to joining Netscape, the first browser brand, he worked as a software engineer at IBM. After the company was acquired by AOL, Waller was increasingly disappointed with the limitations of laptop battery life, so he decided to take some measures.
Waller’s first idea was to use hydrogen fuel cells to extend battery cruising time, but its volatility proved to be a challenge that portable electronics could not overcome. He said: "It is quite difficult to get hydrogen through the airport security." Then, through Oxford University acquaintances, Waller heard about some exciting research, including extremely fast charging materials that are more like supercapacitors. When a battery chemically stores energy, the supercapacitor can place it in an electric field, just like the static collection on a balloon.
The problem with supercapacitors is that they don't store as much energy as a battery, and the amount of electricity quickly leaks out. If you don't use it often, lithium-ion batteries can last up to 2 weeks, while supercapacitors can only last for hours. Many in the industry believe that combining supercapacitors with batteries may benefit smart phones and other power-hungry consumer technology products. According to Highgate, supercapacitors can be used to make hybrid phones that can be fully charged in one or two minutes, and can also be used as spare lithium-ion batteries. He said: "If you can charge very quickly, you can put it on the induction loop and charge it while you stir the coffee."
Waller believes that he can do better. In 2013, he founded ZapGo, a company that is developing carbon-based batteries that charge as fast as supercapacitors, but with similar charging times as lithium-ion batteries. By November 2017, the company had grown to 22 employees at the Appleton Labs in Rutherford and the offices in Charlotte, North Carolina. Its first consumer battery will be used in third-party products launched at the end of this year, including booster starters for cars and electric scooters with charging times reduced from 8 hours to 5 minutes.
The piece of carbon fiber that Waller holds in his hand is a battery that uses a solid electrolyte and does not catch fire. The two electrodes are made of a thin layer of aluminum covered with nanostructured carbon to increase the surface area. Waller said: "You want it to look like the Himalayas." Although under the microscope, it is more like the outline of the city skyline. The key to ZapGo technology is to increase efficiency and reduce leakage, primarily by ensuring that the electrolyte seamlessly matches the carbon skyline above it, just like a Velcro.
The biggest advantage of carbon-based batteries is longevity. Because ZapGo's battery storage is more like a balloon than a traditional battery. As Waller said "no chemical reaction," he claims that the new battery can last 100,000 discharge cycles, which is 100 times that of lithium-ion batteries. Even if you charge your phone every day, you can use it for 30 years. The current third-generation ZapGo battery is not yet powerful enough to run a smartphone, but because the materials used do not provide the barrier to increase the voltage, Waller expects that the battery will be put into use in 2022, that is, "iPhone15".
This requires changing the charging infrastructure. Many of the bombings were blamed on cheap third-party chargers that didn't have the electronics needed to stop the explosion. For ZapGo's battery, or any supercapacitor-based system, you need a charger to do the opposite – pick up and store energy from the grid and send it to your phone in a short time. In the lab, Waller's team has built laptop-sized power supplies, but they are working hard to make it smaller and more efficient.
Many people, including Sam Cooper of the Dyson Institute of Design and Engineering, question whether these companies really want to implant accessories that last for so long. Cooper said: "The mobile phone company has a clear profit incentive, that is, to let the old equipment stop production in the next release. For this reason, the competition to develop better batteries may not exist at all." Waller admitted that ZapGo holds Among the approximately 30 patents, one method can artificially reduce the life of the battery and prevent them from continuing to be used for 30 years. He said: "We will not do this, but if the customer is willing, we have the ability to provide them."
Carbon-based energy storage technology has another major advantage over the prior art. It can actually be used as an external structure for mobile phones. Waller did not design a battery that fits the current phone design, but is preparing for the future of flexible screens and foldable devices. In the 5G network, all our data comes from the cloud, and battery life becomes more important.
Waller walked along the narrow corridor of his office and walked under the negative light of the afternoon, passing through the shadow of the Diamond Light Source, a huge ring-shaped building that looked like an alien spacecraft landed in the Oxfordshire countryside. Internally, researchers are using accelerated beams to study potential battery materials on a microscopic scale, exploring why lithium-sulfur batteries fail, and finding alternative materials to get the negative and positive electrodes, which have plagued the field for nearly 30 years. .
Waller waved his smartphone in the air, lamenting the flaws in lithium-ion batteries, and it was these flaws that prompted him and hundreds of others to join this high-risk race in order to reinvent these flawless but flawed battery. He said: "We all have to develop strategies to deal with this situation, whether it is a back-clip battery or two mobile phones, this is crazy, things should not be like that."