Electric aircraft may be the future of specialties. In theory, electric aircraft are quieter, cheaper and more environmentally friendly than traditional aircraft. If an electric aircraft can fly 1,000 kilometers on a single charge, it can complete nearly half of today's commercial flight missions and reduce global special carbon emissions by 15%. The same goes for electric cars. In fact, electric cars are not only environmentally friendly, they are also better cars. The motor is almost silent and responds quickly to the driver's commands. Charging your car is much cheaper than burning oil. Electric vehicles have few moving parts and are cheaper to maintain. Why haven’t electric cars become popular yet? Because batteries are so expensive, the upfront cost of buying an electric car is greater than a similar gasoline car. Unless you drive your car all the time, the gas money saved won't be enough to cover the upfront cost. Simply put, electric cars are still not economical enough. In terms of weight or volume, current batteries cannot yet be used to power passenger aircraft. Humanity needs a breakthrough in battery technology before they can really take off. Battery-powered portable devices have changed our lives, but batteries are limited by physical principles. In 1799, mankind invented the first battery. Since then, we have continued to study it for more than two centuries, but scientists still cannot fully understand what is going on inside the device. We just know that if we want batteries to change our lives again, there are three issues that need to be solved: power, energy and safety. There is no universal lithium battery. Every lithium battery has two poles: a cathode and an anode. The anode of most lithium batteries is made of graphite, but the cathode is made of a variety of different materials, depending on where the battery is used. From the picture below, you can see the impact of different cathode materials on battery performance. The Challenge of Power Many times, we often use “Energy” and “Power” interchangeably, but when it comes to batteries, the meanings of the two are a little different. Power represents the rate of energy release. We call it power. If you want a business jet to fly 1,000 kilometers on a single charge, you need a powerful battery that can release enough energy in a very short time, especially when taking off. Therefore, it is not enough to store a large amount of energy in a battery, but it must also be released very quickly. If you want to solve the power problem, you need to have a deep understanding of the internal structure of some commercial batteries. We always hype new battery technology, mostly because we don't get a deep look at the internal details. The most common chemical used in the batteries we use is lithium ion. Most experts believe that no other chemical can defeat lithium in the next 10 years or more. Lithium-ion batteries have two electrodes (cathode and anode), a separator (a material that conducts ions rather than electrons, preventing short circuits) in the center, and an electrolyte (usually a liquid). It allows lithium ions to flow back and forth between the two poles. When a battery charges, ions flow from the cathode to the anode, and when the battery discharges, the ions move in the opposite direction. We might as well imagine it as two pieces of bread, the left one is the cathode and the right one is the anode. We might as well assume that the cathode is composed of nickel, manganese, and cobalt sheets (NMC), and the anode is composed of graphite, which is equivalent to superposing carbon atoms layer by layer. In the discharge state, NMC bread will have a lithium-ion sandwich between the interlayers. When the battery charges, lithium ions are extracted from the interlayer and forced through the liquid electrolyte. The separator ensures that only lithium ions can pass through the graphite layer. When the battery is fully charged, there are no longer any lithium ions in the cathode; they are all neatly arranged between the graphite blocks. When the battery releases power, lithium ions flow back toward the cathode until the anode is free of any lithium ions. At this point we have to charge the battery again. Essentially, the power of a battery is determined by how fast it can process. It's not that simple to speed things up. Lithium ions are extracted from the cathode, and if the speed is too fast, the layer will be damaged. Because of this, the longer the use of mobile phones, notebooks, and electric cars, the shorter the battery life is. Every time it is charged or discharged, the "bread cubes" become fragile. Many companies are looking for better solutions. One idea is to replace the electrode layer with a structurally stronger material. For example, Swiss battery company Leclanché is developing a technology that uses lithium iron phosphate (LFP) as the cathode, which has an olivine structure, and lithium titanate oxide (LTO) as the anode, which has a spinel structure. Using such materials to make batteries allows lithium ions to flow more efficiently. At present, Leclanché has installed its own battery into a driverless forklift, which can be charged to 100% in 9 minutes. Compared with the Tesla Super Charger, it takes about 10 minutes to charge a Tesla car to 50%. In the UK, Leclanché is deploying its own batteries into fast-charging electric vehicles. The battery is installed at a charging station and slowly draws power from the grid until it is fully charged. When the car pulls into the station, the battery will quickly charge the car's battery. When the car leaves, the battery at the charging station starts charging again. Leclanché’s research proves to us that it is entirely possible for humans to find better battery chemicals and increase battery power. But so far, humans have not found a battery that releases energy fast enough to meet the needs of business aircraft. Some startups are developing small planes that can seat up to 12 people that can be equipped with batteries with lower energy density, or electric hybrid aircraft that use fuel when taking off and batteries when cruising. Unfortunately, although there are many companies researching it, none of the technologies are close to commercial use. Venkat Viswanathan, a battery expert at Carnegie Mellon University, said the batteries needed for pure electric business aircraft may take decades to develop. The Energy Challenge Model 3 is Tesla’s cheapest car, starting at $35,000. A car equipped with a 50-kilowatt-hour battery costs about $8,750, accounting for 25% of the total price of the car. Compared with previous years, such costs have dropped a lot. According to a report by Bloomberg New Energy Finance, the average cost of lithium-ion batteries in 2018 was approximately US$175 per kilowatt-hour, compared with approximately US$1,200 in 2010. The U.S. Department of Energy calculates that once battery costs fall to $125 per kilowatt-hour, the cost of owning and operating an electric vehicle will be lower than that of a gasoline-powered vehicle, at least in most parts of the world. This does not mean that electric vehicles will completely defeat gasoline vehicles in all market segments and major markets. For example, battery-powered long-range trucks are not yet suitable. However, if this turning point is reached, it will become easier for everyone to choose electric vehicles, because it will be acceptable from an economic point of view. One way to reach this tipping point is to increase the energy density of batteries and squeeze more kilowatt-hours into the battery pack. Theoretically, what we can do in terms of battery chemistry is to either enhance the energy density of the cathode, enhance the energy density of the anode, or both. Among commercially available materials, the cathode with the highest energy density is NMC811 (the numbers represent the ratio of nickel, manganese and cobalt). But the electrodes are still not perfect. The biggest problem is that the battery has a relatively small number of charge and discharge cycles, and then becomes useless. However, experts predict that within the next five years, industry researchers will solve the NMC811 problem. If this is done, the energy density of batteries using NMC811 will increase by 10% or more. Still, a 10% improvement isn't a lot. There have been a lot of innovations over the past few decades and the energy density of the cathode has really improved, but now the opportunity lies in the anode. Graphite still dominates when making anodes. Cheap, reliable and energy dense are its advantages. However, compared with other potential anode materials, such as silicon and lithium, graphite is relatively fragile when stacked. In theory, silicon absorbs lithium ions better than graphite. Because of this, some companies try to squeeze some silicon into graphite when designing anodes; Tesla CEO Musk once said that his company is developing such batteries. It would be a big step forward to create commercially viable silicon anodes made entirely of silicon. However, because silicon has some characteristics of its own, it is difficult to do so. When graphite absorbs lithium ions, the volume does not change much. If it is a silicon anode, it will expand to four times its original size under the same conditions. What a shame, you can't just enlarge the case to accommodate the expansion, which also destroys the silicon anode's "solid electrolyte membrane" (SEI). You can think of SEI as a protective layer, it protects the anode, just like iron builds rust, which is called iron oxide, it protects. When there is an extra layer on the outside, the reaction with oxygen slows down. Under rust, the iron oxidizes more slowly and becomes stronger internally. When a battery is first charged, the electrode forms its own "rust" layer, known as SEI, separating the uncorroded parts of the electrode from the rest. SEI blocks other chemical reactions, prevents electrode corrosion, and ensures that lithium ions can move as smoothly as possible. If a silicon anode is introduced, when we use the battery to charge other devices, SEI will decompose every time and form again every time it is charged. During each charging cycle, some silicon is consumed. Eventually, the silicon consumption reaches a certain level, and then the battery is no longer usable. Over the past 10 years, some startups have been looking for solutions. For example, SilaNano found a way to encapsulate silicon atoms in nanoshells with many "empty rooms" inside. In this way, the SEI will be formed outside the shell, and the expansion of silicon atoms occurs inside, so the SEI will not be destroyed during each charge and discharge cycle. SilaNano, which has a valuation of $350 million, has said the technology will be available in devices as soon as 2020. There is also Enovix, which introduces special manufacturing technology to place the 100% silicon anode in an extremely physical pressure environment, forcing it to absorb as few lithium ions as possible. In this way, the expansion of the anode will be limited to prevent SEI damage. Enovix has received investment from Intel and Qualcomm, and it is expected that the batteries it develops will be used in devices in 2020. Judging from the research of these companies, silicon anodes cannot achieve the theoretical high energy density. But both companies say their electrodes perform better than graphite anodes. Third parties are testing the batteries. Safety Challenges: Modifying molecules in order to charge more energy may affect safety. Since their invention, lithium-ion batteries have caused trouble because of fires. In the 1990s, Canada's MoliEnergy began to use lithium iron batteries for mobile phones and officially commercialized them. However, in the real world, the batteries posed a fire hazard, and Moli was forced to recall the products, and the company eventually filed for bankruptcy. Some of the company's assets were acquired by Taiwanese companies, and Moli itself still sells lithium batteries under the brand name E-One Moli Energy. Recently, Samsung Galaxy Note7 was also recalled due to battery fire. The phone is equipped with lithium-ion batteries. During the 2016 recall, Samsung lost $5.3 billion. Lithium-ion batteries still pose a fire hazard because most of them use flammable liquids as electrolytes. It's unfortunate that liquids can transport ions easily, but they can easily catch fire. One way is to use solid electrolytes. But solid electrolytes also have other disadvantages. Solids are harder, so if you think about it, if you throw a die into water and sand, it will touch a lot more surface in the water than in the sand. Currently, solid-state electrolyte lithium-ion batteries are only used in low energy consumption environments, such as connected sensors. In order to expand the application range of solid-state batteries, everyone generally has two options: one is high-temperature solid polymer, and the other is room-temperature ceramics. Let’s explain them in turn: High-temperature solid polymers: Polymers are very long molecular chains connected together. This material is common in everyday applications, and plastic bags are made of polymers. Some polymers become liquid-like when heated, but they are not as flammable as liquid electrolytes. In other words, they have high ionic conductivity, like liquid electrolytes, but without the risk of flammability. Unfortunately, polymers also have their limitations. They can only work above 105 camera degrees and are not suitable for mobile phones. However, we can introduce it into household batteries to store grid power. At least two companies are developing, one is SEEO in the United States, and the other is Bollor in France. They are both developing new solid-state batteries that use high-temperature polymers as electrolytes. Room temperature ceramics: In the past 10 years, two ceramics have proven to us that its ionic conductivity is as good as liquids at room temperature, one is LLZO (lithium, lanthanum, zirconium oxide), and the other is LGPS (lithium, germanium, phosphorus sulfide).

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