Today's mobile world is inseparable from the lithium-ion battery, which is currently the best choice for rechargeable batteries. Last year, consumers bought 5 billion lithium-ion batteries used for laptop computers, cameras, mobile phones and electric powered cars. Joint Research Centre energy storage Argonne National Laboratory (JCESR) head George Crabtree (George Crabtree) said, "This is the best ever battery technology." However, Crabtree's goal is far more than that.
In 1991, Sony introduced the first commercial version of the lithium-ion battery, compared with today's lithium-ion battery energy density (energy per unit mass stored) already has more than doubled, while the price is only the original 1 / 10. However, the energy density of the lithium-ion battery has reached the limit. Many researchers believe that lithium-ion battery improvements, but also the maximum energy density is further increased by 30%. This means that the lithium-ion battery can never be like a tank of petrol, as electric vehicles make continuous driving 800 kilometers, can not let the "electric tiger" life-like smart phones for many days.
2012, JCESR sought information from the US Department of Energy to $ 120 million in funding for research beyond lithium-ion battery technology for Asia, the Americas and Europe, many research teams and companies are looking beyond lithium-ion battery and replace new technology .
[Lithium - sulfur battery]
In early 2013, chemical engineer Elton Cairns (Elton Cairns) think that they have developed a new chemical battery, only the size of a coin. To July 2013, his battery has been in the US Lawrence Berkeley National Laboratory experienced a 1500 charge-discharge cycles, and the battery capacity is lost only half. This performance, which can be comparable to the best lithium-ion batteries. Cairns-based lithium battery - sulfur (Li-S) technology, the price of materials used is very low, the theoretical energy density is five times more than lithium-ion battery.
Lithium - sulfur battery is one of the main advantages is that the lithium-ion batteries lose "Invalid weight." In a typical lithium-ion battery, the multilayer graphite electrodes occupy a large volume, and these electrodes are basically just used to adsorb lithium ions. These lithium ions through the electrolyte flowing to multilayer metal oxide electrode. Like all batteries, the electrons must flow through an external circuit to balance the positive and negative charges, resulting in a current. To charge the battery, it shall be to reverse the flow of electrons through the applied voltage, which also makes lithium-ion back on the graphite electrode.
Lithium - sulfur batteries, a place of pure lithium metal multilayer sheet of graphite electrodes. This piece is both a lithium electrode, but also a source of lithium ions. When the battery is discharged, lithium sheet when the battery is charging, it restitution. The metal oxide electrode is also cheaper, lighter replaced by sulfur. Lithium sulfur adsorption stronger, sulfur atom may be bonded to each of two lithium atoms, and in the lithium ion battery, a lithium atom binding to need more than one metal atom. All this makes the lithium - sulfur battery in terms of both cost and weight has obvious advantages.
Some researchers questioned the academic recognition may not be converted into a commercial success. In the laboratory, researchers generally use a large number of small amounts of sulfur and an electrolyte, so more easy to study, but can not be produced in high energy density batteries. In PolyPlus company (a battery manufacturing company, located in Cairns 5 km west of laboratory places) Lithium - sulfur batteries for more than 20 years, Steve Visco (Steve Visco) said, adding sulfur and the electrolyte will decrease battery easier broken, in order to produce at low cost can withstand the test temperature throughout the year of commercialization of the battery is quite difficult.
At least one company - the UK Oxis Energy - optimistic about lithium - sulfur battery prospects. The company claims that they have created can be charged and discharged 900 times large lithium - sulfur battery energy density of current lithium-ion batteries comparable. Oxis Energy is working with the US Lotus Engineering Company, in 2016. They hope to develop batteries for electric vehicles, the energy density will reach 400 Wh / kg.
[] The magnesium battery
As the world's lightest metal, lithium has a huge weight advantage. But some researchers believe that the next generation of battery you should use heavier elements, such as magnesium. Each charge carries only one lithium ion, and divalent magnesium ions can carry two charges, which means you can release energy doubled. However, magnesium also has its own problems. Lithium-ion can easily through the electrolyte and the electrode, and the charge of carrying two magnesium ions moving slowly, like a walk through the viscous syrup.
Argonne National Laboratory researcher Peter Qiu Pasi battery (Peter Chupas) is working with JCESR, he used a variety of high-energy X-ray bombardment electrolyte magnesium, magnesium to study why it's great resistance. As of now, he and his colleagues found that magnesium ions can strongly attracted to the surrounding oxygen in the solution, in order to attract a large group of solvent molecules, which makes magnesium ions becomes heavy.
Materials scientist at the Lawrence Berkeley National Laboratory Christine Persson (Kristin Persson) is an analog of the internal structure of the battery with potential new supercomputer, she is trying to from about 2 000 kinds of electrolyte solution, to find a better combination electrode and electrolytic solution, so that the magnesium ions can more smoothly through the electrolyte.
Persson and MIT materials scientist Herb Rand Cede (Gerbrand Ceder) established Pellion technology company, to develop this high-capacity magnesium battery. The company remained silent on its progress, currently only published a research paper on the electrode. By the end of 2013 showed that a large number of patent disclosure, Pellion technology company is developing a more open electrode structure that helps magnesium ions flow. Including Toyota, LG, Samsung and Hitachi, the major electronics companies, we are developing similar batteries, but these companies are rarely disclose the relevant progress.
[Oxygen battery]
Winfried Wilke (Winfried Wilcke) claiming to be "very happy owner of a Tesla S electric car owners," he said, it made him realize that this car electric car battery research is a priority.
Initially, Wilke is concerned that high energy density electrochemical storage theoretical limit - the oxidation reaction of lithium and oxygen. Compared with other types of batteries, this "breathing" lithium - oxygen battery has a huge weight advantage, because one of the main starting material - oxygen, do not have to be loaded into the cell. Theoretically, lithium - energy density of oxygen (Li-O) batteries comparable gasoline engine, higher than the current electric vehicle battery energy density 10 times.
In driving his Tesla S electric cars with more than 000 one thousand meters after 22, Wilke on the car's battery life provided by 400 km of satisfaction. He said that the real problem is money, the cost of battery electric vehicles in more than $ 500 per kilowatt-hour, "the real reason electric cars will not be accepted by the public, not the energy density, but the price." So, Wilke now more optimistic about one of sodium-based, less expensive fuel cells. According to theoretical predictions, sodium - energy density of oxygen (Na-O) are lithium batteries - half the oxygen of the battery, however, it has been five times higher than lithium-ion batteries, and sodium cheaper than lithium. Therefore, Wilke said hopefully, sodium - oxygen battery might cost close to $ 100 per kilowatt-hour, which is JCESR other research institutions that consumers can afford the price.
[Flow battery]
Materials MIT chemist Donald Saduo Wei (Donald Sadoway) believes that the future of the battery is more like a smelter. He envisions a container as large as the box, each box has 20 as big as refrigerators steel unit, containing molten metal and the salt is heated to 500 for.
Such batteries can never use in the car, it is impossible to beat in the lithium-ion battery energy density of such indicators. However, when the power grid energy storage, or without having to consider the portability of application scenarios, the size of the battery is irrelevant. At this time, people need a battery, do not have small and light, strong energy, but rather at a lower cost and less maintenance, storage and release can be more or less power. JCESR hope that this battery can be charged and discharged 7000 times, you can use about 20 years.
Sa Duowei working on another technique, he used two layers of molten metal (because of different densities and is divided into upper and lower layers) as an electrode, an intermediate layer of molten salt separated places as an electrolyte. As the ions move in the meantime, two of the molten metal layer or expansion, or contraction, in order to achieve the storage and release of energy. All this is a liquid, so after thousands of charge-discharge cycles, it will not appear as broken as the solid electrode.
Some research groups are developing less aggressive flow battery. Such a fuel cell is composed of two liquids, ion transport between the two liquids, separated by a thin film. The liquid fuel can be stored in external storage battery box, and then pumped when needed, therefore, only need to use a larger storage tank can store large amounts of electrical energy. However, this requires a battery of pumps and valves. Saduo Wei said that these devices will face maintenance problems.
In the commercial flow battery, the liquid fuel film on both sides have used vanadium ions, vanadium and films but are very expensive. The world's largest flow battery is installed in a wind farm in China, according to Zhang Huamin, Dalian Institute of Chemical Physics of the Chinese Academy of Sciences estimates that the battery may cost as much as $ 1000 per kilowatt-hour. Harvard University materials scientist Michael Aziz (Michael Aziz) said, "the cost of vanadium alone had a high unbearable."
In January, the team announced Aziz cheap quinones (quinones, a class of organic compounds) can be used for flow batteries, which can be a standard liquid electrode (such as bromine) with use. Aziz battery system has been charged and discharged more than 100 times, performance is still strong. He hoped that the cost of such a battery can be reduced to less than $ 100 per kilowatt-hour. However, Aziz said, "The battery system is now just a toy laboratory fume hood only, only large-scale production in order to know how high the true cost." (Author: Richard van Norden / Richard Van translation: Zhaoxu Dan)
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