High Energy Density and Ecofriendly Lithium-Ion Smart Battery

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Recent advances in wearable devices boosted demand of batteries with high energy density and excellent robustness towards mechanical stresses. We address this challenge by eliminating electrochemically inactive metal current collectors, binders and additives from Li-ion battery architecture by using self-standing electrodes, and thereby approaching the ceiling of gravimetric energy density imposed by Li-storage material. This novel solution-free flexible electrode fabrication technology is based on in-situ mixing of as-grown pristine single-wall carbon nanotubes with aerosolized active materials in ratios that provide electrical conductivity higher than percolation value, adequate mechanical robustness under stretching ( ≤15%), bending (d≥2mm) and twisting (θ>180^o) cycles. Moreover, the resultant SWNT scaffold in composite electrodes operates as an intrinsic piezoresistive strain sensor (Gauge Factor ~6.2) that enables in situ/operando self-monitoring of battery structural health. The technology eliminates the use of toxic solutions and binders from production line, and thereby allows easy recycling of the constituent materials. Moreover, it promotes the ecofriendly circular economy for batteries, which is vital in anticipation of about two million metric tons of annual battery waste generated globally by industries. As an example, I will present a wristband-shape flexible battery that powers a commercial smartwatch (3.7V, 250mAh) that operates as a heart rate monitoring sensor.