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The worldwide energy scarcity arising from the massive consumption of nonrenewable energy sources raised a global awareness of the need for cleaner and affordable energy solutions to mitigate climate change and ensure the world sustainable development. The rise of the Internet of Things and the fast growth of the groundbreaking market of wearable electronics boosted a major quest for self-powered technologies merging energy harvesting and energy storage functionalities to meet the demands of a myriad of market segments, such as healthcare, transportation, defense and sports. Thermoelectric devices are a green energy harvesting solution for wearable electronics since they harness the low-grade waste heat from ubiquitous thermal energy sources and convert it into electrical energy. However, these systems generate electrical energy in an intermittent manner, depend on the local heat release availability and require an additional unit to store energy. Flexible and wearable supercapacitors are a safe and eco-friendly energy storage solution to power wearables, offering advantages of security, longer cycle life, higher power density and faster charging over batteries. However, an additional unit that generates energy or that is able to charge the storage device is required. More recently, a new class of all-in-one thermally-chargeable supercapacitors blossomed to meet the requirements of the next generation of autonomous wearable electronics and ensure an endurable energy supply. This self-chargeable hybrid technology combines the functionalities of thermal energy harvesting and supercapacitive energy storage in a single multitasking device. In this Perspective, the advances in the burgeoning field of all-in-one thermally-chargeable supercapacitors for flexible/wearable applications will be critically examined, ranging from their structure and working principle to the rational design of the composing materials and of tailor-made architectures. It will start by introducing the foundations of single flexible/wearable thermoelectric generators and supercapacitors and will evolve into the pioneering venture of fully-integrated thermal energy harvesting/storage systems. It will end by highlighting the current bottlenecks and future pathways for advancing the development of this sophisticated smart technology. [ABSTRACT FROM AUTHOR]

Textile supercapacitors (TESCs) are an emerging energy storage solution to power smart gadgets integrated on clothes. Herein, efficient solid-state TESCs with different active areas (2–8 cm2) were produced based on cotton fabrics coated with industrial grade multi-walled carbon nanotubes (MWCNTs) as electrodes and a safe polyelectrolyte. The textile electrodes were fabricated by an optimized eco-friendly scalable dip-pad-dry process. The lowest electrical resistance (2.62 Ω cm−2) and most uniform coating of the electrodes were achieved using 10 mg mL−1 CNTs dispersion and 8 dip-pad-dry steps. The TESCs exhibited a specific capacitance of 8.01 F g−1 (9.18 F cm−2) and high cyclability (5000 cycles). The energy and power densities were tuned by changing the electrode area: the largest TESC presented the highest energy density of 6.30 Wh kg−1, which was 14× higher than those of other EDLC-type carbon-based TESCs reported in the literature; the smallest TESC presented the highest power density of 2.72 kW kg−1, being 49× higher than the values reported for comparable systems. Finally, a sensor was powered for 47 min by coupling two TESCs in series (14 cm2). This work demonstrated the ability to produce efficient TESCs using industrial grade MWCNTs by processes implemented in the Textile Industry, boosting technological transfer for high-tech applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-functional textile device with energy storage and fluorescence was produced. • A fluorescent redox-active solid-gel electrolyte based on ZnS:Mn was prepared for the first time. • The hybrid textile supercapacitor exhibited enhanced energy storage performance. • Excellent cycling stability (100%) after 8000 charge/discharge cycles. • The device could easily power a sensor for ~12 min when charged during 10 s. The evolution of wearable technologies boosted the development of energy storage textiles that can be charged faster and store energy for longer time. Achieving multifunctionality on textiles is a key milestone towards higher value-added smart products. Herein, we report on the fabrication of a novel dual-functional textile device merging enhanced energy storage performance with optical properties. A redox-active solid-gel electrolyte based on fluorescent manganese(II)-doped zinc(II) sulfide was for the first time used to endow the dual functionality to the device when combined with MWCNT-coated textile electrodes. The textile electrodes were prepared through an eco-sustainable straightforward dip-pad-dry process using a natural cotton fabric substrate. The fluorescent hybrid textile supercapacitor exhibited enhanced energy storage performance relative to the EDLC-type analogue containing the undoped electrolyte, namely 20% higher working voltage (1.64 V), 48% higher energy density (1.63 W h kg−1) and 74% higher power density (641.6 W kg−1). Additionally, it presented excellent cycling stability (100%) after 8000 charge/discharge cycles. The device exhibited intense yellow-orange fluorescence under UV light, while preserving the energy storage functionality. This work demonstrated the versatility of this type of devices for dark environment applications, namely in reflective/safety electronic clothing for nighttime users. [ABSTRACT FROM AUTHOR]

The development of effective dual-function energy harvesting/storage technologies is a milestone demand for the emerging generation of low-consumption autonomous electronics. This work reports the development of a multifunctional thermionic power textile device merging thermal energy harvesting and electrochemical energy storage for application in self-powered systems. An everyday cost-effective non-conductive natural fabric was transformed into an all-solid-state textile-based thermally-chargeable supercapacitor (T-TCSC) via dyeing with multiwalled carbon nanotubes and subsequent assembly with H 3 PO 4 -doped poly(vinyl alcohol) (PVA) solid-gel polyelectrolyte. When subjected to an out-of-plane temperature gradient, the T-TCSC was able to convert the thermal energy into electrical output and store the harvested energy. A Soret coefficient of 1.85 mV K−1 was obtained, which is the highest value achieved so far for TCSCs developed on non-conductive textile substrates reported in literature and ∼10× higher than those of conventional thermoelectric devices. Additionally, a maximum output potential of ∼30 mV was achieved for Δ T = 24.7 K. Concerning the energy storage performance, an energy density of 9.39 μW h cm−2 was obtained at 1.62 mW cm−2 power density. The smart T-TCSC outputs demonstrated its potentialities as a two-in-one self-chargeable textile device that can harvest the thermal energy generated by a temperature gradient, convert it into electrical energy and simultaneously store it. [Display omitted] • Design and assembly of textile-based system merging energy generation and storage. • All-solid-state device produced on natural fabric through scalable dyeing/coating. • Simultaneous thermal-to-electrical energy conversion and supercapacitive storage. • A Soret coefficient S i = 1.85 mV K−1 and maximum V output = 30 mV@Δ T = ∼25 K were reached. • Highest S i reached so far for TCSCs produced on non-conductive textile substrates. [ABSTRACT FROM AUTHOR]