Line up circus performers and you’ll see a diverse range of body types that suit their acts—lean and flexible aerialists contrasted by the large, chiselled frames of strongmen. Similarly, lithium-ion batteries come in a spectrum of shapes and sizes uniquely designed to power wearable devices such as smartwatches and smart glasses.
Considering which type of battery works best for these devices is tricky business, said Shengkai Cao, a Research Scientist at A*STAR’s Institute of Materials Research & Engineering (IMRE). Batteries with high energy density electrodes can hold more power but they’re bulky and rigid, which can impact the usability of the wearable device.
“Such electrodes are thick, which can result in poor mechanical flexibility and susceptibility to mechanical fracture or peeling under bending, folding or other deformations,” explained Xiaodong Chen, a Principal Scientist and Science Director at IMRE and President’s Chair Professor in Material Science and Engineering at Nanyang Technological University (NTU), Singapore.
In collaboration with researchers from NTU and Fuzhou University, China, Chen and Cao took on the challenge of creating a novel class of foldable, high energy density lithium-ion batteries. The researchers’ first hurdle was to develop batteries that could balance the trade-off between energy capacity and mechanical flexibility.
To address this, the team turned to a relatively new technology in the field known as mechano-graded electrodes, which required extensive testing to optimise their functionality. “We had to link the mechanical properties with the electrodes’ electrochemical performance,” said Cao, adding that to do this, they deployed a combination of computational and experimental techniques.
Using Finite Element Analysis (a computerised method for predicting how materials respond to physical effects), Cao and colleagues found that their newly developed mechano-graded electrodes had exceptional power density and resilience.
“Most flexible materials gradually degrade at either the anode or cathode due to the highly reductive or oxidative environments over long-term use,” said Chen.
However, the team’s new-and-improved flexible lithium-ion batteries are a big step up—in stress tests, they retained their original electrochemical properties even after being twisted, knotted and folded.
Moreover, it’s easy to manufacture these batteries at commercial scales. “The protocol of fabricating mechano-graded electrodes is compatible with industrial equipment and can easily be scaled up using commercially available chemicals,” remarked Cao.
Moving forward, Chen and Cao aim to boost their innovation’s performance by up to 100-fold in a bid to redefine what’s possible with tomorrow’s wearable electronics.
The A*STAR researchers contributing to this research are from the Institute of Materials Research & Engineering (IMRE).
