Researchers have developed a new method of freezing lithium batteries that could make them safer and increase their shelf life. The technique could also make batteries more flexible, raising the possibility they could be used in the bendy smartphones of the future.
Known as 'ice-templating', or freeze-casting, the technique is used to control the structure of the solid electrolyte for the lithium batteries used in portable electronics such as phones, tablets and cameras. Lithium batteries are also used in electric vehicles and for grid-level energy storage.
Commercial lithium batteries currently use liquid electrolyte, which as the recent exploding Samsung Galaxy Note 7 saga highlighted, is highly flammable.
As a safer alternative, researchers at Columbia University explored the idea of using solid, rather than liquid, electrolyte in order to make safer, solid-state lithium batteries as part of a study published in the journal Nano Letters.
"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," said Columbia professor Yuan Yang.
The researchers used ice-templating to fabricate vertically aligned structures of ceramic solid electrolytes, for high conductivity. The aqueous solution was then cooled with ceramic particles before ice was allowed to grow and push away, and concentrate, the ceramic particles. A vacuum converted the solid ice into a gas, leaving the vertically aligned structure and this structure was combined with a polymer to give extra support and flexibility to the electrolyte.
Previous studies have used either randomly dispersed ceramic particles in polymer electrolyte or fibre-like ceramic electrolytes that were not vertically aligned.
"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," explained 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 optimise ion conduction for next-generation rechargeable batteries."
The researchers now intend to construct a prototype of a full lithium battery using the new freezing technique. The technology could eventually lead to safer smartphones with less flammable batteries, and could also be used to power bendable gadgets.
This article was originally published by WIRED UK
