Currently highest energy density battery! Beat the Tesla 4680, break the power battery energy density ceiling, and fill 80% in 6 minutes. Amprius completed its first batch of lithium batteries with an energy density of 450Wh/kg, promoting the commercial landing of electric aircraft. With the addition of silicon nanowire technology from Stanford, Amprius may stir up a pool of spring water in the power battery industry.
Wen 丨 wisdom driving network Huang Huadan
50% higher energy density than Tesla 4680!
According to foreign media news, the American startup Amprius has produced its first batch of high-energy density lithium batteries, and its battery energy density has reached 450 Wh/kg and 1150 Wh/L.
As a reference, the high-profile Tesla 4680 battery, as a representative of the current high energy density and low-cost battery, has a cell energy density of about 300Wh/kg.
The data shows that the general energy density of ternary lithium batteries in 2021 hovers around 150Wh/kg.
As the name suggests, the higher the energy density, the smaller the weight or volume of the battery storing the same amount of charge, depending on the unit used.
Under the premise that the space or weight of a car leaves for the battery is determined, the higher the energy density, the more power is stored, and the longer the mileage.
As far as the current situation is concerned, energy density is almost the most obvious breakthrough in the current battery industry, and even the electric vehicle industry.
But it won't be easy to achieve this breakthrough.
And Amprius, a little-known startup, how can it achieve a qualitative leap?
The secret lies in the silicon nanowire anode material used by Amprius.
Why is the use of silicon nanowire anode materials that can achieve a significant increase in energy density?
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Principles of silicon nanowire technology
To answer this question, let's first look at the structure of lithium-ion power batteries.
Lithium-ion power batteries are generally composed of negative collector, negative electrode, diaphragm, positive electrode, positive collector, polar ear, electrolyte, insulating sheet, shell and so on.
The operating principle of lithium battery is:
When charging, the lithium atoms on the positive electrode are stripped of their electrons, oxidized into lithium ions, and then moved in the electrolyte, ran to the negative electrode, and combined with the electrons flowing through the external power supply, reduced to lithium atoms, embedded in the micropores of the negative electrode material.
Discharge, on the other hand, is the opposite process. The lithium atom embedded in the negative electrode material removes the electrons, is oxidized into lithium ions, returns to the electrolyte, moves to the positive electrode, combines with the flowing electrons, and reduces to lithium atoms again.
Therefore, increasing the amount of lithium atoms embedded in the positive and negative electrode materials can also increase the storage capacity of the entire battery cell.
Cathode materials are common nickel cobalt manganese oxide lithium and lithium iron phosphate, which is often referred to as ternary lithium batteries and lithium iron phosphate batteries.
The current negative electrode material is mainly graphite, and some use lithium titanate and silicon-based materials.
At present, the gram capacity of graphite-based carbon anode materials reaches 360mAh/g, which is very close to the theoretical gram capacity (372mAh/g), and there is little room for improvement.
The gram capacity of the silicon-based anode material reaches 3500mAh/g, and its lithium storage capacity is almost 10 times that of the carbon material.
Theoretically, the energy density of lithium batteries using silicon-based anode materials can reach ten times that of lithium batteries of carbon materials.
The problem is that the silicon put into the battery expands by absorbing positively charged lithium atoms during charging, and then shrinks as lithium is drawn out of the silicon during use. This expansion/contraction cycle usually causes silicon (usually in the form of particles or thin films) to pulverize, reducing battery performance.
To solve this problem, Amprius used silicon nanowire technology.
What is Silicon Nanowire Technology?
Amprius' silicon nanowire technology is to grow silicon nanowires directly on the cell electrode, which expands to four times the normal volume after absorbing lithium atoms, but unlike the general silicon structure, the silicon material of this structure can release stress well through axial expansion, and will not cause cracking or damage of the nanowires, thus preventing the powdering of the electrode.
In addition, the negative electrode thickness using silicon nanowires is only half the thickness of the negative electrode of the carbon material.
Since silicon is the material with the best energy density, the use of 100% silicon means that the highest energy density can be achieved for lithium-ion batteries.
What's more, Amprius' silicon nanowire batteries have excellent cycle life, which has been proven in the actual use of multiple organizations, including national laboratories and major aerospace companies.
Amprius' first silicon nanowire lithium batteries will be supplied to a high-altitude pseudo-satellite company.
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Origins and Applications
Amprius' silicon nanowire technology originated at Stanford.
In 2007, Yi Cui, then an assistant professor in Stanford's Department of Materials Science and Engineering, published a paper titled "High-performance lithium battery anodes using silicon nanowires" in Nature Nanotechnology, detailing the application of silicon nanowire technology in lithium batteries.
In 2008, Cui Yi and Senior Venture Capital Partner Mark Platshon co-founded Amprius. Its board of directors includes Nobel laureate and former U.S. Energy Secretary Steven Chu.
Today, Cui Yi, who is only in his forties, is not only a tenured professor at Stanford, but also the founder of four startups.
Headquartered in Silicon Valley, Amprius has established a large battery factory in Wuxi with Wuxi Industrial Development Group, a government-owned investment company, to establish Ambris (Wuxi) Co., Ltd.
Amprius' investors include Silicon Valley venture capital firms Trident Capital and Kleiner Perkins, Chinese private equity firm SoftBank Saifu, Stanford University, Airbus and others. In addition, former Google CEO Eric Schmidt is also one of the company's investors.
The company's current CEO, Dr. Kang Sun, served as Honeywell's vice president and helped form JA Solar Limited, which is now the world's largest manufacturer of solar panels.
In December 2021, Amprius announced a breakthrough in battery charging efficiency, achieving a charge rate of 0% to 80% in just 6 minutes. The company is working towards mass production of batteries in the hundreds of MWh per year and expects to begin mass production in 2024.
Its COO, Jon Bornstein, said lithium batteries with a high energy density of 450Wh/kg will support aerospace products with higher power requirements, including new eVTOL aircraft (Electric Vertical Takeoff and Landing, also known as flying cars) that extend flight life. In addition, he said that Amprius expects to produce the first 500 Wh/kg batteries later this year.
Bornstein also said Amprius is developing batteries for drone applications and has signed a contract with an undisclosed airline. Previously, Amprius had supplied batteries to Airbus' Zephyr solar drones.
In addition, according to Fortune, the U.S. military is also using Amprius' battery to test its application on wearable devices.
The Airbus contract is both a lifeline and a warning sign for Amprius. "We've offered Airbus sky-high prices,... This price is not sustainable. CEO Sun Kang said.
If it is to be applied on a large scale in passenger cars, the high cost is obviously unacceptable.
Before Tesla Battery Day in August 2020, Musk said on Twitter that Tesla would mass-produce batteries with a longer life and a 50% increase in energy density in 3-4 years, which is 400wh/kg, when the Panasonic 2170 battery cell used by the Model 3 had an energy density of 260wh/kg.
Subsequently, Tesla used the silicon nanowire structure diagram as a background picture on the registration page of the Battery Day event on September 19.
Coupled with the fact that Amprius' company address was opposite Tesla, speculation about Tesla's acquisition of Amprius was a flurry of speculation.
But on Battery Day, the technology was not unveiled.
Musk even said bluntly on Twitter that nothing happened between Tesla and Amprius.
For Musk, cost is always one of the top factors to consider.
According to Huabao Securities data, the current 420-450mAh/g capacity of silicon-based anode material (made of silicon-based materials mixed with graphite) market price is between 110,000-150,000 / ton, the median value is about 120,000 / ton, while the price of high-end graphite is only 7-8 million / ton.
Perhaps when the cost of using silicon-based materials as anode materials can be controlled to be comparable to graphite, something will eventually happen between Amprius and Tesla.
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The Future of Power Batteries: Solid-State Batteries or Silicon Nanowires Anode?
The industry generally believes that the current development of lithium-ion batteries has reached its limit. If you want to further increase the range, you must make a big innovation in technology.
Like the silicon nanowire anode battery released by Amprius, the purpose of the industry's previous heat transfer solid-state batteries was to increase energy density.
It is generally believed that the energy density of liquid lithium batteries reaching 300Wh/kg is already a very outstanding performance, while solid-state batteries can generally reach 300-400Wh/kg.
The biggest difference between solid-state batteries and current mainstream traditional lithium-ion batteries is the electrolyte, which replaces the electrolyte and separator of traditional lithium-ion batteries with solid electrolytes.
In addition to the high energy density, solid-state batteries have higher safety because the solid electrolyte can inhibit lithium dendrites, is not easy to burn, is not easy to burst, has no electrolyte leakage, and does not react at high temperatures.
Moreover, because the solid electrolyte solves the problem of the solid electrolyte interface membrane formed by the liquid electrolyte during the charge and discharge process and the lithium dendrite phenomenon, it can also greatly improve the cycle and service life of the lithium battery.
However, although the advantages of solid-state batteries are very obvious, their disadvantages are also fatal, and directly lead to the difficulty of mass production of solid-state batteries.
Since the connection between the solid electrolyte and the electrode material is in a solid state, the effective contact between the electrode and the electrolyte is weak. Moreover, the transmission power of ions in solid matter is low, which will cause the problem of excessive interfacial impedance.
Another problem remains the high cost.
The industry generally believes that solid-state power batteries need to achieve large-scale mass production, at least after 2025.
Today, Amprius has successfully produced the first generation of lithium batteries with an energy density of 450Wh/kg with its silicon nanowire technology.
Although it may not be possible to achieve low-cost mass production, it undoubtedly provides another possible solution for the industry.
How the power battery will develop in the future, let us wait and see.
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