Ultrathick battery electrodes are appealing as they reduce the fraction of inactive battery parts such as current collectors and separators. However, thick electrodes are difficult to dry and tend to crack or flake during production. Moreover, the electrochemical performance of thick electrodes is constrained by ion and electron transport as well as fast capacity degradation. Here, we report a thermally induced phase separation (TIPS) process for fabricating thick Li-ion battery electrodes, which incorporates the electrolyte directly in the electrode and alleviates the need to dry the electrode. The proposed TIPS process creates a bicontinuous electrolyte and electrode network with excellent ion and electron transport, respectively, and consequently achieves better rate performance. Using this process, electrodes with areal capacities of more than 30 mAh/cm² are demonstrated. Capacity retentions of 87% are attained over 500 cycles in full cells with 1-mm-thick anodes and cathodes. Finally, we verified the scalability of the TIPS process by coating thick electrodes continuously on a pilot-scale roll-to-roll coating tool. Significance Increasing the thickness of battery electrodes is an attractive approach to reduce the fraction of battery parts that do not store energy, such as current collectors and separators. However, the fabrication of thick electrodes holds challenges of its own such as cracking or flaking during the electrode production and limitations in ion and electron transport. To address the latter, advanced electrode templating techniques have been suggested, but these techniques are not scalable. In this work, ultrathick electrodes are fabricated on a pilot-scale roll-to-roll tool using a thermally induced phase segregation process. This electrode structuring method creates a bicontinuous electrolyte and electrode network with excellent ion and electron transport reducing the charge-transport challenges in thick electrodes.

This review discusses important scientific progress, problems, and prospects of lignin-based materials in the field of rechargeable batteries. Lignin, a component of the secondary cell wall, is considered a promising source of biomass. Compared to cellulose, which is the most extensively studied biomass material, lignin has a competitive price and a variety of functional groups leading to broad utilization such as adhesive, emulsifier, pesticides, polymer composite, carbon precursor, etc. The lignin-based materials can also be applied to various components in rechargeable batteries such as the binder, separator, electrolyte, anode, and cathode. This review describes how lignin-based materials are adopted in these five components with specific examples and explains why lignin is attractive in each case. The electrochemical behaviors including charge–discharge profiles, cyclability, and rate performance are discussed between lignin-based materials and materials without lignin. Finally, current limitations and future prospects are categorized to provide design guidelines for advanced lignin-based materials.

Wearable electronics have been receiving increasing attention for the past few decades. Particularly, fiber-based electronics are considered to be ideal for many applications for their flexibility, lightweight, breathability, and comfortability. Furthermore, fibers and fiber-based textiles can be 3D-molded with ease and potentially integrated with everyday clothes or accessories. These properties are especially desired in the fields of bio-related sensors and energy-storage systems. Wearable sensors utilize a tight interface with human skin and clothes for continuous environmental scanning and non-invasive health monitoring. At the same time, their flexible and lightweight properties allow more convenient and user-friendly experiences to the wearers. Similarly, for the wearable devices to be more accessible, it is crucial to incorporate energy harvesting and storage systems into the device themselves, removing the need to attach an external power source. This review summarizes the recent applications of fibers and fiber-based textiles in mechanical, photonic, and biomedical sensors. Pressure and strain sensors and their implementation as electronic skins will be explored, along with other various fiber sensors capable of imaging objects or monitoring safety and health markers. In addition, we attempt to elucidate recent studies in energy-storing fibers and their implication in self-powered and fully wireless wearable devices.

Recent advancements in implantable bioelectronic devices have increased the demand for biocompatible energy sources with long-term electrochemical and mechanical stability. Here, we present a tough hydrogel-based supercapacitor (THBS) fiber, fabricated via a thermal drawing process (TDP), that enables the integration of all components—electrodes, electrolyte, current collectors, and encapsulation—into a single, unified, and mechanically robust fiber-shaped architecture. Through thermal/mechanical optimization and the incorporation of self-healing properties, THBS fibers exhibit durable, high electrochemical performance under dynamic, high-curvature deformations mimicking in vivo physiological motions. Despite a thickness of only a few hundred microns, they maintain mechanical and electrochemical stability. Long-term functionality was confirmed over five weeks with minimal immune response. In vivo implantation demonstrated successful LED operation in a freely moving mouse, and successful optogenetic stimulation of both central and peripheral nervous systems. These results underscore the promise of THBS fibers as next-generation, fully biocompatible energy storage devices for advanced implantable bioelectronic systems.