Recently, NASA said it has made a major breakthrough in the development of solid-state batteries for aviation.

NASA introduced on its official website that the energy density of the solid-state battery that NASA has successfully developed so far has reached 500Wh/kg, almost twice the energy density of the best current electric car battery - Tesla's 4680 lithium battery has an energy density of about 300Wh/kg.

In April 2021, NASA announced that its e Solid-state Architecture Batteries for Enhanced Rechargeability and Safety ("SABERS") program would develop solid-state batteries for electric aircraft, with higher energy density than existing liquid electrolyte lithium-ion batteries, which are smaller in size and can be used after a shock. ") division will develop solid-state batteries for electric airplanes, which will have higher energy density, smaller battery size, the ability to continue use after shock, and a lower risk of fire compared to existing liquid electrolyte lithium-ion batteries.

It is understood that NASA's solid-state batteries for sulfur and selenium batteries, the electrolyte material using cheap and easy to obtain sulfur, the battery also utilizes NASA's previously developed "porous graphene" material, conductivity is good, the quality is also lighter. Because solid-state lithium batteries do not have a liquid electrolyte, thus reducing the risk of liquid fire and explosion.

In addition, in terms of battery packaging, unlike ordinary lithium-ion batteries that are individually packaged, NASA's solid-state batteries stack cells together in a single enclosure, a method that has resulted in a 30%-40% reduction in battery weight.

"SABERS has experimented with new materials for batteries that have made significant advances in discharge. Over the past year, the team has managed to increase the battery's discharge rate by a factor of 10 and subsequently by a factor of 5, bringing the researchers one step closer to their goal of powering large vehicles." NASA said in its press release.

Electric aircraft and NASA's Advanced Air Mobility Program are described as the main beneficiaries of the new battery technology.

Solid-state batteries on the cusp

Not coincidentally, another piece of news about solid-state batteries has recently sparked widespread public attention.

According to a number of domestic media reports, Chinese professor Li Xin from Harvard University and its students Ye Luhan, the development of a new solid-state batteries can be reused 10,000 times, the fastest charging speed of 3 minutes, compared to the current best solid-state battery cycle times of 2,000-3,000 times.

The pair's related paper, published in May 2021 in Nature (www.nature.com), describes the principles of this new solid-state battery. In the paper, the researchers said they prepared a multilayer structured lithium-metal solid-state battery with interfacial stability, which enabled stable cycling at ultra-high current densities and suppressed dendrite infiltration.

The multi-layer design of the battery is characterized by sandwiching the unstable electrolyte between the stable solid electrolyte, constituting a "sandwich" structure, and inhibiting the growth of any lithium dendrites by achieving a well-cracked local decomposition in the unstable electrolyte layer.

According to the figure above, from left to right, the structure of the "sandwich" battery is distributed as Li-Metal Anode → Graphite → LPSCI → LGPS → LPSCI → Monocrystalline LiNi0.8Mn0.1Co0.1O2 (Nickel-Manganese-Cobalt 811) Positive Electrode. Graphite is between the lithium metal anode and the first layer of solid electrolyte, mainly used for heat insulation.

According to the paper description, the first solid electrolyte layer sandwiched between the two sides is Li5.5PS4.5Cl1.5 (LPSCI), which is characterized by behaving more stably towards lithium metal but is prone to lithium dendrite penetration. Its presence stabilizes the main interface between the lithium metal and graphite layers and reduces the overall overpotential.

The second layer of electrolyte sandwiched in the middle is Li10Ge1P2S12 (LGPS), which is less stable to lithium metal but less prone to lithium dendrite penetration. The electrolyte in the middle can be replaced with Li9.54Si1.74(P0.9Sb0.1)1.44S11.7Cl0.3 (LSPS), which also achieves similar performance.

Lithium dendrites can pass through graphite and the first electrolyte layer, but are intercepted when they reach the second electrolyte layer. The usual lithium-metal solid-state batteries are repeatedly charged and discharged many times, and micron- or submicron-sized cracks are frequently generated in the ceramic particles. Once cracks are formed, lithium dendrite penetration and short circuits are difficult to avoid. "Sandwich" in the middle of the layer of solid electrolyte, so that lithium dendrites can not pierce the entire battery, thus avoiding the battery positive and negative electrode short circuit or even fire.

In addition to improved safety, the technology demonstrates excellent cycling performance with lithium metal as the anode and LiNi0.8Mn0.1Co0.1O2 as the positive electrode. The capacity retention rate is 81.3% and 82% after 2,000 and 10,000 cycles at discharge multipliers of 1.5C (0.64mAcm-2) and 20C (8.6mAcm-2), respectively, and the battery's micron-sized cathode material realizes a specific power of 110.6 kW/kg and a specific energy of up to 631.1 Watt-hours/kg.

To further their research on solid-state batteries, two researchers have founded a battery startup, Adden Energy, with Luhan Yeh as chief technology officer. This year, Adden Energy reportedly raised $5.15 million (about 35.7 million yuan).

What's so hard about getting solid-state batteries on board?

Looking around the world, solid-state batteries are not a brand new product. Traditional liquid lithium batteries, lithium ions from the positive pole to the negative pole and then to the positive pole of the movement process, the battery to complete the charging and discharging process. The principle of solid-state batteries is the same, except that their electrolyte is solid.

Back in 2017, Fisker, an American electric car company based in Anaheim, California, released a patent for a solid-state battery with a range of 800 kilometers on a one-minute charge. Founder Henrik Fisker said the company's solid-state batteries would be mass-produced in 2023 at a third of the price of conventional lithium batteries. In 2021, however, Henrik Fisker said it had abandoned its solid-state battery program altogether.

Currently, the only company in the world that has commercialized solid-state batteries for power is the French Bollore Group, which began using solid-state batteries made by BatScap in its self-developed electric car "Bluecar" and electric bus "Bluebus" in October 2011, with a total of 2,900 vehicles. In October 2011, the Bollore Group began using solid-state batteries made by BatScap in its self-developed electric car "Bluecar" and electric bus "Bluebus," putting a total of 2,900 electric vehicles into service. However, the capacity of this solid-state battery pack is only 30KWh, and the energy density is only 110Wh/kg.

In the view of industry insiders, the industrialization of solid-state lithium batteries, from a technical point of view, there are still not small challenges.

The first is the low ionic conductivity of the solid electrolyte, especially at low temperatures. The second is the high interfacial resistance at the solid-solid interface of the electrode-electrolyte. In addition, solid-state batteries using pre-lithiated silicon-carbon anode or future lithium metal anode, high nickel anode, solid-state electrolyte and other new materials, completely subvert the current liquid lithium battery system, the production cost is much higher than the current corresponding materials, the road to cost reduction is extremely arduous and long.

It is understood that there are three mainstream systems for solid-state electrolyte materials: polymers, such as lithium hexafluorophosphate doped into PEO; oxides, such as lithium-steel zirconium oxide (LLZO), NASICON, etc.; and sulfides, such as LPSX (X=Cl,Br,I).

Of these three material routes, the polymer system has the advantage of high ionic conductivity at high temperatures and ease of processing. However, it has extremely low ionic conductivity at room temperature, which restricts its development. For example, the French Bolloré brand solid-state batteries on the choice of polymer system, in order to make the electric car can work normally at room temperature, Bolloré Group deliberately equipped with a heater for each car, before starting the battery system to warm up to 60 ℃ to 80 ℃.

The advantages of the oxide system are good overall performance, but the interfacial resistance between the electrodes is higher than that of the polymer system. Thin-film products are technically demanding and difficult to produce on a large scale. Non-thin film products are currently the most reliable solution for electric vehicle batteries.

The advantage of the sulfide system is that the ionic conductivity is comparable to that of liquid electrolytes, which is the technology route chosen by Japanese and Korean companies Toyota, Honda, Samsung and Chinese battery giant Ningde Times. However, the development of the sulfide system is in its infancy, with production environment restrictions and safety issues being the biggest obstacles, and the risk of not being able to commercialize mass production is also the highest.

Despite the difficulties, however, in the pursuit of the future of lithium battery energy density and safety on the road, solid-state batteries are still pinned high hopes. It is understood that, at present, there are about 50 manufacturing enterprises, startups and universities and research institutes around the world are committed to the advancement of solid-state battery technology.

In Europe and the United States, BMW Group 2022 invested $130 million in Solid Power, a Colorado-based solid-state battery startup, with plans to launch prototypes equipped with solid-state batteries by 2025 and mass production by 2030.

Mercedes-Benz reached a strategic agreement this year with Factorial Energy, a solid-state battery startup in Massachusetts, U.S., and will invest an amount of about 1 billion U.S. dollars in it to support solid-state battery research and development, and start testing prototypes in 2022, and realize small batch production within five years.

Volkswagen Group injected $100 million in 2018 and an additional $200 million in 2020 into QuantumScape, a solid-state battery startup company based in Silicon Valley. This year, VW Group announced it would use solid-state batteries in its electric vehicles by 2025.

Japan and South Korea, Toyota in 2008 with solid-state lithium battery creator Ilika (Ilika) launched a cooperation, its plan in 2025 to launch the use of solid-state batteries hybrid vehicles. Mitsubishi, Nissan, Panasonic and other companies have also accelerated the layout of solid-state batteries. It is understood that at present, Toyota has 1331 global patents related to solid-state batteries, ranking first in the world, Panasonic 272 ranked second.

On the domestic front, Azalea Automobile released solid-state batteries with a lithium energy density of 150Wh/kg at Nio Day on January 9 last year, and it plans to realize mass production in the fourth quarter of 2022. Ningde Times previously said that the company's first generation of solid-state lithium batteries with roughly the same energy as current lithium-ion batteries is expected to be launched in 2025, the second generation of solid-state batteries is expected to be launched after 2030. In addition to this, domestic companies such as Vonergy, Hive Energy, Ganfeng Lithium, etc. have also announced the layout of solid-state batteries.

(Source of the article: Surfing News)

[Zhongshun New Energy Marketing Department December 17, 2022 Responsibility: Xiao Zheng]

Reprinted for the purpose of transmitting more information, and does not mean that we agree with its views and is responsible for its authenticity.