Nasa Solid-state Battery Major Breakthrough: Energy Density Of About Twice The Tesla 4680 Battery

Recently, NASA said that its research and development of solid-state batteries for aviation has made a major breakthrough.

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

In April 2021, NASA announced that its Improved Solid-State Battery Recharge Efficiency and Safety program (e Solid-state Architecture Batteries for Enhanced Rechargeability and Safety, "SABERS ") department will develop solid-state batteries for electric aircraft, compared to existing liquid electrolyte lithium-ion batteries, which have a higher energy density, smaller battery size, the ability to continue to use after impact, and lower risk of fire.

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

In addition, in the battery package, unlike ordinary lithium-ion batteries in a single package, NASA's solid-state batteries stacked cells together in a single shell, a method that reduces the weight of the battery by 30-40 percent.

"SABERS has experimented with new materials for the batteries that have made significant progress in discharging them. In 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 five, bringing the researchers one step closer to their goal of powering large vehicles." NASA said in its press release.

According to the release, electric aircraft and NASA's Advanced Air Mobility Program will be the primary beneficiaries of the new battery technology.


By no coincidence, another piece of news about solid-state batteries has also recently sparked widespread public attention.

According to several media reports, Xin Li, a professor from Harvard University, and his student Luhan Ye, have developed a new solid-state battery that can be reused 10,000 times and recharged in as little as 3 minutes, compared to the current best solid-state batteries, which have a cycle count of 2,000-3,000 times.

A related paper by the two, published in the journal Nature (www.nature.com) in May 2021, describes the principle of this new solid-state battery. In the paper, the researchers state that they have prepared a multilayer structured lithium metal solid-state cell with interfacial stability, which enables stable cycling at ultra-high current densities and suppresses dendrite penetration.

The multilayer design of the cell features a "sandwich" structure with an unstable electrolyte sandwiched between a stable solid electrolyte, and any lithium dendrite growth is inhibited by achieving good local decomposition of cracks in the unstable electrolyte layer.

According to the figure above, from left to right, the "sandwich" cell structure is distributed as lithium metal anode → graphite → LPSCI → LGPSCI → LPSCI → single crystal LiNi0.8Mn0.1Co0.1O2 (Ni-Mn-Co811) anode. Graphite is sandwiched between the lithium metal cathode and the first solid electrolyte layer and is mainly used for thermal insulation.

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

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

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 battery is repeatedly charged and discharged many times, and micron or submicron cracks are frequently generated in the ceramic particles. Once the cracks are formed, lithium dendrite penetration and short circuiting are difficult to avoid. "The solid electrolyte layer in the middle of the sandwich prevents lithium dendrites from penetrating the entire battery, thus avoiding a short circuit or even a fire at the positive and negative electrodes of the battery.

Not only the safety is improved, but the technology uses lithium metal as the negative electrode and LiNi0.8Mn0.1Co0.1O2 as the positive electrode to demonstrate excellent cycle performance. Its capacity retention rate reached 81.3% and 82% after 2000 and 10,000 cycles at 1.5C (0.64mAcm-2) and 20C (8.6mAcm-2) discharge multiplier conditions. In addition, the micron-level cathode material of the cell is capable of achieving a specific power of 110.6 kW/kg and a specific energy of up to 631.1 Watt-hour/kg.

To further their research on solid-state batteries, two researchers have formed a battery startup, Adden Energy , with Luhan Ye as chief technology officer. This year, Adden Energy reportedly raised $5.15 million.

Looking around the world, solid-state batteries are not a brand new product. In traditional liquid lithium batteries, lithium ions move from positive to negative to positive again as the battery completes the charging and discharging process. The principle of solid-state battery is the same, except that its electrolyte is solid.

Back in 2017, Fisker, an electric vehicle company based in Anaheim, California, released a patent for a solid-state battery with a one-minute charge and an 800-kilometer range. Founder Henrik Fisker said the company's solid-state battery would be in mass production by 2023 and cost one-third the price of a traditional lithium battery. In 2021, however, Henrik Fisker said it had completely abandoned its solid-state battery plans.

In October 2011, Bollore Group began commercializing its own electric car "Bluecar" and electric bus "Bluebus In October 2011, Bollore Group started to equip its electric car "Bluecar" and electric bus "Bluebus" with solid-state batteries made by BatScap, and put them into 2,900 electric vehicles. However, the capacity of this solid-state battery pack is only 30KWh, and the energy density is only 110Wh/kg.

In the industry's view, the industrialization of solid-state lithium batteries still presents considerable challenges from a technical point of view.

The first is the low ionic conductivity of the solid-state electrolyte, especially in low-temperature environments. The second is the high interfacial resistance at the solid-solid interface of the electrode-electrolyte. In addition, the new materials used in solid-state batteries, such as pre-lithiated silicon carbon negative electrode or future lithium metal negative electrode, high nickel cathode, solid-state electrolyte, completely overturn the current liquid lithium battery system, and the production cost is much higher than the current corresponding materials, so the road to cost reduction is extremely difficult and long.

It is understood that there are three mainstream systems of 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 temperature ionic conductivity and ease of processing. However, it has very low ionic conductivity at room temperature, which limits its development. For example, the French Bollore brand solid-state battery has chosen the polymer system, and in order to make the electric car work properly at room temperature, the Bollore Group has purposely equipped each car with a heater to warm up the battery system to 60℃ to 80℃ before starting.

The oxide system has the advantage of good overall performance, but the interfacial resistance between the electrodes is higher than that of the polymer system. The thin-film products require harsh process technology and are difficult to produce on a large scale in terms of cost and scale. Non-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 Time. However, the development progress of sulfide system is at the most elementary level, with production environment restrictions and safety issues being the biggest obstacles and the highest risk of not being able to commercialize mass production.

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

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

Mercedes-Benz reached a strategic agreement this year with Massachusetts-based solid-state battery startup Factorial Energy to invest about $1 billion in the company to support solid-state battery research and development, and to begin testing prototypes in 2022 and achieve small-volume production within five years.

The VW Group invested $100 million in QuantumScape, a Silicon Valley-based solid-state battery startup, in 2018 and an additional $200 million in 2020. This year, the VW Group announced it will use solid-state batteries in its electric vehicles by 2025.

In Japan and South Korea, Toyota partnered with solid-state lithium battery creator Ilika in 2008, and plans to launch hybrid vehicles with solid-state batteries in 2025. Mitsubishi, Nissan, Panasonic and other companies have also accelerated the layout of solid-state batteries. It is understood that Toyota currently holds 1,331 patents related to solid-state batteries worldwide, ranking first in the world, and Panasonic ranks second with 272.

In China, NIO Motors released a solid-state battery with a lithium energy density of 150Wh/kg at Nio Day on January 9 last year, and it plans to achieve mass production in the fourth quarter of 2022. CATL previously said that the company's first-generation solid-state lithium battery has roughly the same energy as the current lithium-ion battery and is expected to be launched in 2025, and the second-generation solid-state battery is expected to be launched after 2030.