With the rapid development of flexible wearable electronics, a piezoresistive sensor with low detection limit and wide strain sensing range turns out to be a great challenge for its application in this field. Here, a cracked cellulose nanofibril/ silver nanowire (CA) layer-coated polyurethane (PU) sponge was acquired through a simple dip-coating process followed by precompression treatment. The electrical conductivity and mechanical property of the conductive CA@PU sponge could be effectively tuned through changing the dip-coating number. As a piezoresistive sensor, the sponge exhibited the capability of detecting both small and large motions over a wide compression strain range of 0−80%. Based on the "crack effect", the sensor possessed a detection limit as low as 0.2% and the gauge factor [GF, GF = (ΔR/R 0 )/ε, where ΔR, R 0 , and ε represent the instantaneous resistance change, original resistance, and strain applied, respectively] was as high as 26.07 in the strain range of 0−0.6%. Moreover, the "contact effect" enabled the sensor to be applicable for larger strain, and the GF decreased first and then became stable with increasing compression strain. In addition, frequency-and strain-dependent sensing performances were observed, demonstrating that the sensor can respond reliably to different applied frequencies and strains. Furthermore, the sensor displayed exceptional stability, repeatability, and durability over 500 cycles. Finally, the sensor could be applicable for the detection of various human bodily motions, such as phonation, stamping, knee bending, and wrist bending. Most importantly, the sponge also exhibited great potential for the fabrication of artificial electronic skin. Herein, the conductive CA@PU sponge will undoubtedly promote the development of high-performance flexible wearable electronics.

Sodium‐ion batteries (SIBs) have gained tremendous interest for grid scale energy storage system and power energy batteries. However, the current researches of anode for SIBs still face the critical issues of low areal capacity, limited cycle life, and low initial coulombic efficiency for practical application perspective. To solve this issue, a kind of hierarchical 3D carbon‐networks/Fe7S8/graphene (CFG) is designed and synthesized as freestanding anode, which is constructed with Fe7S8 microparticles well‐welded on 3D‐crosslinked carbon‐networks and embedded in highly conductive graphene film, via a facile and scalable synthetic method. The as‐prepared freestanding electrode CFG represents high areal capacity (2.12 mAh cm−2 at 0.25 mA cm−2) and excellent cycle stability of 5000 cycles (0.0095% capacity decay per cycle). The assembled all‐flexible sodium‐ion battery delivers remarkable performance (high areal capacity of 1.42 mAh cm−2 at 0.3 mA cm−2 and superior energy density of 144 Wh kg−1), which are very close to the requirement of practical application. This work not only enlightens the material design and electrode engineering, but also provides a new kind of freestanding high energy density anode with great potential application prospective for SIBs.

Flexible strain sensors have attracted tremendous interest due to their potential application as intelligent wearable sensing devices. Among them, crack-based flexible strain sensors have been studied extensively owing to their ultrahigh sensitivity. Nevertheless, the detection range of a crack-based sensor is quite narrow, limiting its application. In this work, a stretchable strain sensor based on a designed crack structure was fabricated by spray-coating carbon nanotube (CNT) ink onto an electrospun thermoplastic polyurethane (TPU) fibrous mat and prestretching treatment to overcome the trade-off relationship. Our sensor exhibited combined features of high sensitivity in a greatly widened workable sensing range [a gauge factor of 428.5 within 100% strain, 9268.8 for a strain of 100–220%, and larger than 83982.8 for a strain of 220–300%], a fast response time (about 70 ms), superior durability (>10 000 stretching–releasing cycles), and excellent response toward bending. The microstructural evolution of CNT branches extending from two edges of the cracks and the excellent stretchability of TPU fibrous mats are mainly related to the remarkable sensing properties. Our sensor is then assembled to detect various human motions and physical vibrational signals, demonstrating its potential applications in intelligent devices, electronic skins, and wearable healthcare monitors.

A novel method to adjust the composition of a material while maintaining its morphology was described in this study. Nickel sulfide, the material investigated in this work, was found to be useful as a high surface area electrode material for supercapacitor applications. First, a nest-like Ni 3 S 2 @NiS composite electrode with 1D nanorod as structural unit was synthesized by simultaneously using Ni foam as template and Ni as a source through a one-step in situ growth method. Co and Se ions, which respectively acted as beneficial cation and anion, were successfully introduced into the nest-like Ni 3 S 2 @NiS material, resulting in the formation of Ni 3 S 2 @Co 9 S 8 and NiS@NiSe 2 composite electrodes with structures similar to those of the parent materials. The material structure was virtually retained and single-crystal-to-single-crystal transformation was achieved in the process. Introducing the cation and anion into the same type of material while maintaining topology could be important for the field of material synthesis and preparation of supercapacitor electrodes. Moreover, the electrochemical properties of these three materials were studied by cyclic voltammetry measurements and galvanostatic charge−discharge tests. The results indicated that the rate performance was improved significantly by ion exchange. In particular, the derived electrode with Se still showed superior oxidation and reduction ability at high scan rate of 10000 mV s −1 . In addition, the second charge−discharge specific capacity also increased from 516 F g −1 to 925 F g −1 and 1412 F g −1 at the current density of 0.5 A g −1 and by Co and Se exchange, respectively. This work contributes to the knowledge on electrode materials for supercapacitors and can provide good reference for the fabrication of desired materials.