Nickel-Rich Cathode Yarn for Wearable Lithium-Ion Batteries

Wearable fiber-based lithium-ion batteries (LiBs) made with textile-like functional electrode materials are key to realizing smart energy options for powering wearable electronics. However, the process of attenuating the existing functional materials commonly used in planar and solid-state batteries to functional fiber or yarn electrodes tends to deteriorate the material performance when assembled into textile-based electrodes. In this work, we focus on understanding and enabling layered Ni-rich cathode material into a wearable cathode yarn. Layered Ni-rich cathode materials typically contain a higher proportion of Ni compared to other metals like Co and Mn, with a Li[Ni 1−x M x ]O 2 (M = transition metal element, such as Mn, Al, Co, and so on) typical structure. They are increasingly gaining popularity in the research and development of LiBs as they offer several advantages, including higher energy density, improved cycle life, and reduced cost compared to many commercial cathode materials. Our fabricated flexible Ni-rich cathode yarn with an overall diameter of ~ 360 µm and a coating thickness of ~ 80 µm exhibited textile properties with promising mechanical strength and the ability to conform to any shape. When tested in a half-cell arrangement with Li metal as the counter electrode, the Ni-rich cathode yarn electrode showed stable cyclic performance with a discharge areal capacity of ~ 3 mAh/cm 2 and an average coulombic efficiency of 99.5% at a 0.2 mA/cm 2 current density. Overall, the results show that Ni-rich cathode materials, despite their layered structure, are integrateable into usable wearable textile LiBs. Graphical Abstract