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With the wide application of electric vehicles in recent years, the development of new tools and the design of new materials are the key factors for the future breakthroughs in battery energy storage technology. The development of new tools will help uncover the basic processes that lead to battery failure and provide powerful guidance for better material design.
The synergy between these two themes will not only lead to practical applications in the short term, but also help stabilize long-term solutions for high-energy battery materials.
Yuzhang Li, an assistant professor at UCLA's School of Engineering, and his team have scored some big wins over the years, such as capturing the first atomic-scale image of the cause of a lithium-ion battery fire, allowing for the development of safer batteries. It has also developed a commercially licensed method for using graphene cage encapsulation technology to improve battery stability, which has been patented. In addition to batteries, there are also promising results in metal-organic frameworks and atomic insights into the imaging of gas molecules.
Silicon batteries that don't charge properly? Graphene cage packaging technology to help achieve
High-energy lithium-ion batteries have chemical components such as silicon, lithium metal and sulfur that facilitate the transition from fossil fuels to renewable energy sources such as solar and wind power. Silicon has more than 10 times the capacity of conventional battery materials, but because the material breaks and loses electrical contact during charge and discharge, the broken particles become inactivated and the battery can no longer be charged.
In 2013, Li began studying materials science and engineering at Stanford University, and his first research project was on graphene and silicon materials. "Because the research project had to use electron microscopy to look at the atomic layers of materials like graphene, I gained a lot of operational experience. Not everyone is going to be able to use the electron microscope well, so I had put in a year or two before that to learn how to operate the instrument skillfully."
The project began with Li's extensive research into how silicon cells fail. Silicon particles are a low-cost alternative, but unlike silicon nanoparticles, they suffer inevitable particle breakage during the electrochemical cycle, making it difficult to cycle steadily in real-world batteries.
So Li and his team investigated a way to use synthetic multilayer graphene "cages" to encapsulate silicon particles (about 1-3μm). The graphene cage acts as a mechanically strong and flexible buffer film during the cycle of charging, maintaining electrical connectivity at the particle and electrode levels even as the particles expand and burst in the cage. In addition, the chemically inert graphene cage forms a stable solid electrolyte interface, thus minimizing irreversible lithium ion consumption and rapidly improving Coulomb efficiency in the early cycle.
"We wanted to see if we could make silicon work with cheap materials that are not nanoscale," Li told Deeptech. "This is very difficult because the large silicon particles will break during the battery charging and discharging."