What is the next generation of lithium-ion batteries?

Recently, Tesla and NiO's battery spontaneous combustion incidents occurred frequently, 18650 pack builder and everyone's focus on lithium batteries has shifted from the range to the safety issue. From the point of view of consumers, we certainly want to have a low price, long battery life, good performance, high safety of the perfect battery, but this does not conform to the laws of physics. Battery research is like playing a balance, requiring constant coordination and compromise between several dimensions. Often, changing metrics in one area affects other areas.

I recently came across an article on Linkedin by Bill Gates. battery manufacturing machine He says few inventions have changed people's lives as much as the battery. At the same time, a growing number of inventors and investors are working to build better batteries. On April 8, 2019, his reposted article "How We can achieve the Next Big Breakthrough in battery Technology" was published, which contains some of the latest information. I translated the original into Chinese for your reference! Click on the link at the end of this article to read the original article.

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Electric cars could be the future of aviation in China. li ion battery construction In theory, they will be quieter, cheaper, and cleaner than the corporate-owned planes our country now has. Electric aircraft that can be recharged 1,000 kilometers (620 miles) at a time today could be directly used to solve half of all commercial aircraft flying safely, reducing the carbon emissions of global development aviation by about 15 percent.

The same goes for electric cars. Electric cars aren't just cleaner versions of their pollution-emitting Cousins. Basically, it's a better car: its engine is quieter and reacts faster to the driver's decisions. The cost of charging an electric car is far less than the cost of paying for the same amount of gas. Electric cars can be built with a small number of moving parts, making maintenance cheaper.

So why aren't electric cars widespread yet? That's because batteries are expensive, making the upfront cost of electric vehicles much higher than comparable gas-powered vehicles. Plus, unless you drive a lot, the gas savings don't always offset the higher upfront costs. In a word, electric cars are not cost-effective.

Similarly, current batteries cannot store enough weight or volume of energy to power an airliner. Fundamental breakthroughs are still needed before battery technology becomes a reality.

Battery-powered portable devices have changed our lives. However, if we can cheaply make batteries that are safer, more powerful, and have a higher energy density, then those batteries are more likely to be destroyed. No laws of physics preclude their existence.

However, despite more than two centuries of closely related research since the first battery technology was invented in 1799, scientists still don't fully understand the basic workings of learning what exactly goes on inside these information devices. What we do know is that in order for batteries to once again truly make a difference to our lives, there are basically three major issues students need businesses to address: electricity, energy, and security.

There is no one size that fits all lithium-ion batteries

Each battery has two electrodes: a cathode and an anode. The anode of most lithium-ion batteries is made of graphite, but the cathode is made of a variety of materials, depending on the purpose of the battery. Below, you can see how different cathode materials change the performance of the battery type in six ways.

Energy challenge

In general, people use "energy" and "energy" interchangeably, but it's important to distinguish between them when it comes to batteries. Power is the rate at which energy is released.

A powerful battery can release a large amount of energy in a short period of time, enough to support the takeoff of a commercial jet and keep it flying at an altitude of 1,000 kilometers, especially at the moment of takeoff. So it's not just about being able to store a lot of energy, it's also about being able to release it quickly.

To meet the energy challenge itself, we need to understand what is actually inside commercial batteries. These studies may sound a little stiff, but bear with them. New battery management technologies are often overstated, one reason being that most people don't know enough about the details of batteries.

Our most advanced battery chemistry right now is lithium-ion. Most experts believe that no other chemical will destroy lithium ions for at least a decade or more. Lithium-ion batteries have two electrodes (cathode and anode), a separator (a material that conducts ions instead of electrons to prevent short circuits), and an electrolyte (usually a liquid) that allows lithium ions to flow back and forth between the electrodes. When a battery is charged, ions move from the cathode to the anode; When the battery is energized, the ions move in the opposite direction.

Inside a lithium-ion battery

Imagine two slices of bread. Each piece of bread is an electrode: the cathode on the left and the anode on the right. Let's assume that the cathode is made up of nickel, manganese and cobalt (NMC) sheets - one of the best of its kind - and the anode is made up of graphite, which is basically made up of laminated sheets or sheets of carbon atoms.

In the discharge state, that is, after the energy is exhausted, the NMC bread is sandwiched between each slice of bread by lithium ions. When the battery is charged, each lithium ion is extracted from between the sheets and forced through through the liquid electrolyte. The separator acts as a checkpoint to ensure that only lithium ions pass through the graphite layer. When the battery is fully charged, the cathode layer of the battery does not leave behind lithium ions, but is neatly sandwiched between the graphite layers. As the battery energy is consumed, the lithium ions return to the cathode until no lithium ions remain at the anode. The battery needs to be recharged.

The energy capacity of a battery basically depends on how fast this process occurs. But increasing speed is not easy. Extracting lithium ions from the cathode bread too quickly can cause defects in the chip and eventually rupture. This is one of the reasons why the longer we use our smartphones, laptops or electric cars, the longer their battery life. Each charge and discharge weakens the bread.

Many companies are constantly trying to learn how to solve our social problems. One idea is to replace the layered electrodes with sturdier materials. For example, Leclanch_, a 100-year-old Swiss battery management company, is working on an important technology that uses a lithium iron phosphate (LFP) with an "olivine" structure as a cathode and a lithium titanate (LTO) with a "spinel" structure as an anode. These data structures are even better at handling the liquid assets of lithium ions moving in and out of materials.

Leclanch e currently uses batteries in an automated warehouse forklift that can be charged to 100% in nine minutes. By comparison, the best Tesla superchargers can charge a Tesla car's battery to about 50 percent in 10 minutes. Leclanch e is also deploying its batteries in the UK for use in fast-charging electric vehicles. These batteries are located at charging stations and slowly absorb small amounts of electricity from the grid over a long period of time until they are fully charged. Then, when the car is pulled in, the dock battery quickly charges the car battery. As the bus left, the station's batteries began to recharge.

Efforts like Leclanche's show that it is possible to fix battery chemistry to boost its power. However, no one has yet made a battery powerful enough to quickly release the energy needed for commercial aircraft to overcome gravity. Startups are looking to build small aircraft (which can seat up to 12 people). Such aircraft can use relatively low power battery-intensive or electric hybrid aircraft. In this type of aircraft, it is difficult to lift jet fuel, and the battery acts as a taxi.

But no company has invested in this near-commercial sector. Moreover, according to Venka Viswanathan, a battery expert at Carnegie Mellon University, the technological leap needed for an all-electric commercial aircraft could be decades away.

Energy challenge

The Tesla Model 3 is the company's most affordable car, with a starting price of $35,000. It uses a 50 KWH battery and costs about $8,750, or 25 percent of the total price of the car.

Compared to China not so long ago, this is still a very surprising expense for us. According to Bloomberg New Energy Finance, the average time cost control for developing lithium-ion power batteries globally in 2018 was about $175 /kWh, down from nearly $1,200 /kWh in 2010.

The US Department of Energy says that once battery costs fall below $125 per kilowatt-hour, the cost of owning and using an electric car will be lower than gas-powered cars in most parts of the world. That doesn't mean EVs will beat gasoline-powered cars in all segments of the market, for example, long-haul trucks that don't yet have an electric solution. But it was a turning point. People are starting to like electric cars because, in most cases, they are more economical.

One way to achieve this is to increase the energy density of the battery, putting more electricity into the pack without lowering the price. In theory, battery chemists could achieve this by increasing the energy density of the cathode or anode, or both.

In commercial applications, the cathode with the highest energy density is NMC811(each number represents the ratio of nickel, manganese, and cobalt in the mixture). It's not perfect. The biggest problem is that it can only withstand a relatively short charge-discharge life cycle until it stops working. But experts predict that industrial research and development will solve NMC 811's problems within the next five years. When this happens, batteries using NMC811 will have an energy density of 10% or more.

But a 10% increase is not that big. A series of innovations over the past few decades have pushed the energy density of cathodes higher and higher, and the anode is the largest opportunity for energy density.

Graphite has always been the dominant anode material. It is relatively inexpensive, reliable, and the energy distribution density can be relatively high, especially compared to current cathodic protection material technologies. But it is quite weak compared to other potential anode materials, such as silicon and lithium.

For example, silicon is theoretically better at absorbing lithium ions than graphite. That's why many battery companies are trying to incorporate some silicon into their anode designs, and Tesla CEO Elon Musk has said the company is already incorporating silicon into its lithium-ion batteries.

An even bigger step would be to develop a commercially viable anode made entirely of silicon. But the nature of this element makes it difficult to implement. When graphite absorbs lithium ions, its volume changes very little. However, under the same conditions, the silicon anode expands to four times its original volume.

Unfortunately, you can't make the box bigger just to accommodate the expansion, which destroys the silicon anode's "fast ion conductor interface," or SEI.

You can think of the SEI as the protective layer that the anode creates for itself, similar to the way iron forms rust, aka iron oxide, to protect itself from the elements: When you leave a newly forged iron outside, it will slowly react with the oxygen in the air and rust. Below the rust layer, the rest of the iron does not suffer the same fate, thus preserving the structural integrity.

At the end of the battery's first charge, the electrodes form our own "rust" layer, and the SEI separates the unpolarized part of the electrode from the electrolyte. The SEI prevents additional learning of chemical reactions that consume electrodes, ensuring that our nation's lithium-ion technology can flow as smoothly as possible.

But with a silicon anode, the SEI breaks down every time a battery is used to power a device, and the SEI changes every time the battery is charged. A small amount of silicon is consumed during each charging cycle. Eventually, the silicon dissipates to the point where the battery no longer works.

Over the past decade, a handful of Silicon Valley start-ups have been grappling with this problem. Silanano's method, for example, encapsulates silicon atoms in a nanoscale shell with many cavities. Thus, the SEI forms on the outside of the shell, and the silicon atoms expand inside the shell without destroying the SEI after each charge-discharge cycle. The $350 million company says its technology will power the devices by 2020.

Enovix, on the other hand, uses a special manufacturing technique that puts a 100 percent silicon anode under enormous physical pressure, forcing it to absorb less lithium, which limits the expansion of the anode and prevents the SEI from breaking. The company, which has investments from Intel and Qualcomm, expects its batteries to be in devices by 2020.

These trade-offs mean that silicon anodes cannot achieve the theoretically high energy density. However, both companies say their anodes perform better than graphite anodes. Third parties are currently testing batteries from both companies.

Batteries are already big business, and the market is growing. This money has attracted many entrepreneurs with more ideas. However, the failure rate of battery management startups is higher than that of software companies, although Chinese software development companies are known for their high failure rate. This is us because this kind of material as well as scientific innovation is difficult.

So far, battery chemists have found that when they try to improve one performance, such as energy density, they have to compromise another, such as safety. This balancing act means that progress on all fronts is slow and fraught with problems.

But as more attention is paid to MIT's Mingjiang problem, he estimates that there are three times as many battery scientists in the United States as there were a decade ago, and that the chances of success will increase. The potential for batteries is still huge, but given the challenges ahead, it's best to treat every claim about new batteries with skepticism.

cylindrical lithium-ion batteries clarification

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