Apr 25 2017
Schematic of vertically aligned and connected ceramic channels for enhancing ionic conduction. In the left figure, ceramic particles are randomly dispersed in the polymer matrix, where ion transport is blocked by the polymer matrix with a low conductivity. In the right one, vertically aligned and connected structure facilitates ion transport, which can be realized by the ice-templating method. Credit: Image courtesy of Yuan Yang/Columbia Engineering
A new method capable of leading to the production of lithium batteries that are bendable and safer with longer battery life, providing new possibilities such as flexible smartphones, has been developed by Yuan Yang, assistant professor of materials science and engineering at Columbia Engineering.
In his new techniques, Yang uses ice-templating to control the structure of the solid electrolyte for lithium batteries that are employed in grid-level energy storage, electric vehicles, and portable electronics. The study features in the April 24 online issue of Nano Letters.
Currently, liquid electrolyte is used in commercial lithium batteries, and it is an established fact that liquid electrolyte is highly flammable, causing safety issues with a few electronic devices and some laptops. Yang’s team explored the concept of using solid electrolyte as a substitute for the liquid electrolyte in order to make all-solid-state lithium batteries. The researchers were interested in using ice-templating in order to fabricate vertically aligned structures of ceramic solid electrolytes, which are highly conductive and provide rapid lithium ion pathways. The aqueous solution was cooled with ceramic particles from the bottom and the ice was allowed to grow and push away and concentrate the ceramic particles. The team then applied a vacuum to convert the solid ice to a gas, leaving a vertically aligned structure. This ceramic structure was finally combined with polymer to provide flexibility and mechanical support to the electrolyte.
In portable electronic devices, as well as electric vehicles, flexible all-solid-state lithium batteries not only solve the safety issues, but they may also increase battery energy density for transportation and storage. And they show great promise in creating bendable devices.
Yuan Yang, Assistant Professor, Materials Science and Engineering, Columbia Engineering
In earlier studies, researches used either fiber-like ceramic electrolytes that are not vertically aligned or randomly dispersed ceramic particles in polymer electrolyte. “We thought that if we combined the vertically aligned structure of the ceramic electrolyte with the polymer electrolyte, we would be able to provide a fast highway for lithium ions and thus enhance the conductivity,” says Haowei Zhai, Yang’s PhD student and the paper’s lead author. “We believe this is the first time anyone has used the ice-templating method to make flexible solid electrolyte, which is nonflammable and nontoxic, in lithium batteries. This opens a new approach to optimize ion conduction for next-generation rechargeable batteries.”
Additionally, the team explains that this new technique could in principle enhance the energy density of batteries: By using the solid electrolyte, the negative electrode of the lithium battery, now a graphite layer, could be replaced by lithium metal, and this indeed could enhance the battery’s specific energy by 60% to 70%. Yang and Zhai next plan to work on optimizing the qualities of the combined electrolyte and then assembling the flexible solid electrolyte together with battery in order to build a prototype of a full lithium battery.
This is a clever idea. The rationally designed structure really helps enhance the performance of composite electrolyte. I think that this is a promising approach.
Hailiang Wang, Assistant Professor of Chemistry, Yale University. “
The research was supported by the National Science Foundation MRSEC program through Columbia in the Center for Precision Assembly of Superstratic and Superatomic Solids (DMR-1420634).
The study is titled “A Flexible Solid Composite Electrolyte with Vertically Aligned and Connected Ion-Conducting Nanoparticles for Lithium Batteries.” Haowei Zhai, Pengyu Xu, Mingqiang Ning, Qian Cheng, Jyotirmoy Mandal, and Yuan Yang are the authors of this study.