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The first main challenge is ‘encapsulation’ – the materials in which the battery components are housed – according to the team at North Carolina State University (NC State). Oxygen and moisture exposure accelerate lithium-ion batteries’ degradation and lower their effectiveness, so the outer casings of the batteries must be able to keep those elements out – but they also need to be flexible enough to act like fabric, so they can be woven into clothing.
The team evaluated five strategies, ranging from early methods such as sheathing batteries in polymer tubes to “promising” new technology such as liquid metal encapsulation. “Each method showed strengths but also lacked in one or more critical areas,” an NC State announcement said. “Even the liquid metal, which was both highly water-resistant and flexible, was found to be so complicated and costly that it is still not yet a viable option.”
Mengli Wei, graduate student in the Wilson College of Textiles and lead author of the study, said that solving this problem was the most pressing issue facing fibre battery researchers, and that solutions could be found in the packaging industry.
The second problem is mathematical modelling, which scientists use to predict the output of woollen batteries based on an array of different parameters. Models could improve predictions about the relationship between battery chemistry and the maximum effective length of wool batteries.
Previous studies found that as fibre length increases, so does the output of the battery, but those gains in efficiency and output eventually fall off. Wei Gao, an associate professor at the Wilson College of Textiles and corresponding author of the study, said that existing models struggle to accurately predict those outcomes.
“If the model is accurate, we can plug in different device parameters, and it can predict the optimal battery length,” Gao said. “That way we would be able to provide better guidance when making fibre batteries for practical applications, such as their incorporation in textile fabrics and garments.”
The paper was published in Small.
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