According to NASA's official website, the energy density of the solid-state battery successfully developed by NASA has reached 500Wh/kg, which is almost twice the energy density of the current best electric vehicle battery - Tesla's 4680 lithium battery has an energy density of about 300Wh/kg.
In April 2021, NASA announced its e Solid-state Architecture Batteries for Enhanced Rechargeability and Safety, The SABERS division will develop solid-state batteries for electric aircraft, which have a higher energy density and are smaller than existing lithium-ion batteries with liquid electrolytes, so that they can continue to be used after impact and have a lower risk of fire.
It is understood that NASA's solid-state battery is a sulfur-selenium battery, and its electrolyte material uses cheap and easily available sulfur, and the battery also uses the "porous graphene" material previously developed by NASA, which has good conductivity and light quality. Since the solid-state lithium battery has no liquid electrolyte, it reduces the risk of liquid fire and explosion.
In addition, in the packaging of the battery, unlike the ordinary lithium-ion battery single package, NASA's solid-state battery stacks the cells together in a single housing, which reduces the weight of the battery by 30% to 40%."SABERS has experimented with new materials for batteries that have made remarkable progress in discharging. 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 five, bringing the researchers closer to their goal of powering large vehicles." NASA said in its press release.
Electric aircraft and NASA's Advanced Air mobility program will be the main beneficiaries of the new battery technology.
Solid state battery standing in the air
Coincidentally, recently, another news on solid-state batteries has also aroused wide public attention.
According to a number of domestic media reports, Li Xin, a Chinese professor from Harvard University, and his student Ye Luhan, developed a new solid-state battery that can be reused 10,000 times, with the fastest charging speed of 3 minutes, compared to the current best solid-state battery cycles of 2000-3000 times.
Their paper, published in May 2021 in the journal Nature (www.nature.com), describes how this new solid-state battery works. In the paper, the researchers said that they have prepared a multi-layer lithium metal solid state battery with interface stability, so as to achieve a stable cycle at ultra-high current density and inhibit dendrite penetration phenomenon.
The multi-layer design of the battery is characterized by sandwiching the unstable electrolyte between the stable solid electrolyte, forming a "sandwich" structure, and by achieving good local crack decomposition in the unstable electrolyte layer, inhibiting the growth of any lithium dendrites.
As shown in the figure above, from left to right, the "sandwich" battery structure is distributed as lithium metal negative → graphite →LPSCI→LGPS→LPSCI→ single crystal LiNi0.8Mn0.1Co0.1O2 (nickel-Mangano-cobalt 811) positive electrode. The graphite is between the lithium metal cathode and the first layer of solid electrolyte, which is mainly used for thermal insulation.
According to the paper, the first layer of solid electrolyte sandwiczed on both sides is Li5.5PS4.5Cl1.5 (LPSCI), which is characterized by a relatively stable performance against lithium metal, but is prone to lithium dendrite penetration. Its presence can stabilize the main interface of the lithium metal and graphite layers and reduce the overall overpotential.
The second electrolyte sandwiczed in the middle is Li10Ge1P2S12 (LGPS), which has poor stability to lithium metal, but is not easy to penetrate lithium dendrites. The intermediate electrolyte can be replaced with Li9.54Si1.74(P0.9Sb0.1)1.44S11.7Cl0.3(LSPS) to achieve similar performance.
Lithium dendrites can pass through graphite and the first electrolyte, but are intercepted when they reach the second electrolyte. Usually lithium metal solid state batteries repeatedly charge and discharge, ceramic particles will frequently produce micron or submicron cracks. Once the crack is formed, the phenomenon of lithium dendrite penetration and short circuit is difficult to avoid. This layer of solid electrolyte in the middle of the "sandwich" makes the lithium dendrites unable to Pierce the entire battery, thus avoiding short circuits and even fires in the positive and negative terminals of the battery.
Not only in terms of safety, the technology uses lithium metal as a negative electrode and LiNi0.8Mn0.1Co0.1O2 as a positive electrode to show excellent cycling performance. Under discharge rates of 1.5C (0.64mAcm-2) and 20C (8.6mAcm-2), the capacity retention rates reached 81.3% and 82% after 2000 and 10000 cycles. In addition, the battery's micron-scale cathode material is capable of achieving specific power of 110.6 kW/kg and specific energy of up to 631.1 watt-hours/kg.
To further their research into solid-state batteries, the two researchers have set up a battery startup, Adden Energy, with Ye as chief technology officer. This year, Adden Energy reportedly raised $5.15 million (about 35.7 million yuan).
