Atomic-level image of a fire in a lithium battery was observed for the first time, and a cryo-electron microscope changed battery research 'big killer'

by:CTECHi     2021-07-05

With the widespread application of electric vehicles in recent years, the development of new tools and the design of new materials are key factors for future breakthroughs in battery energy storage technology. The development of new tools will help reveal the basic processes leading to battery failure and provide strong guidance for better material design.

The synergy between these two themes will not only bring practical applications in the short term, but also help stabilize long-term solutions for high-energy battery materials.

University of California, Los Angeles (UCLA) School of Engineering Assistant Professor Li Yuzhang and his team have achieved many important achievements for several years. For example, the cause of the fire of a lithium battery was captured for the first time. Atomic-level images provide a guarantee for the development of safer batteries. It has also developed a commercially licensed method of using graphene cage encapsulation technology to improve battery stability, and has applied for a patent. In addition to batteries, there have been promising research results in metal-organic frameworks and atomic insights for imaging gas molecules.

The silicon battery cannot be charged stably? Graphene cage encapsulation technology helps to realize the high-energy lithium battery chemical components such as silicon, metal lithium, sulfur, etc. can promote the transformation from fossil fuels to renewable energy (solar, wind) . The capacity of silicon is more than 10 times that of traditional battery materials. However, during the charging and discharging process, the silicon material will break and lose electrical contact, so that the broken particles lose activity and the silicon battery cannot be recharged.

In 2013, Li Yuzhang began to study materials science and engineering at Stanford University. His first research project was graphene and silicon materials. 'Because research projects must use electron microscopes to observe the atomic layers of graphene and other materials, I have accumulated a lot of operating experience. Not everyone can use electron microscopes well, so I have invested a year or two before that Come learn to operate the instrument proficiently.'

The project started with Li Yuzhang’s extensive research on how silicon batteries fail. Silicon particles are a low-cost alternative, but they are different from silicon nanoparticles. Differently, silicon particles suffer from unavoidable particle breakage during the electrochemical cycle, so it is difficult to achieve stable cycles when used in actual batteries.

Therefore, Li Yuzhang and his team studied a method of using synthetic multilayer graphene 'cage' to encapsulate silicon particles (about 1-3μm). The graphene cage acts as a high mechanical strength and soft buffer film during the cycle of charging. Even if the particles expand and rupture in the cage, it can maintain electrical connectivity at the particle and electrode level. In addition, the chemically inert graphene cage forms a stable solid electrolyte interface, thereby minimizing irreversible lithium ion consumption and rapidly increasing the Coulomb efficiency in early cycles.

Li Yuzhang told DeepTech, “We want to see if we can make silicon work from cheap materials that are not nano-level. This is very difficult because of the large silicon particles. It will rupture during battery charging and discharging.'

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