The development of lithium–sulfur (Li–S) batteries is hindered by the disadvantages of shuttling of polysulfides and the sluggish redox kinetics of the conversion of sulfur species during discharge and charge. Herein, the crystallinities of a titanium nitride (TiN) film on copper-embedded carbon nanofibers (Cu-CNFs) are regulated and the nanofibers are used as interlayers to resolve the aforementioned crucial issues. A low-crystalline TiN-coated Cu-CNF (L-TiN-Cu-CNF) interlayer is compared with its highly crystalline counterpart (H-TiN-Cu-CNFs). It is demonstrated that the L-TiN coating not only strengthens the chemical adsorption toward polysulfides but also greatly accelerates the electrochemical conversion of polysulfides. Due to robust carbon frameworks and enhanced kinetics, impressive high-rate performance at 2 C (913 mAh g ⁻¹ based on sulfur) as well as remarkable cyclic stability up to 300 cycles (626 mAh g ⁻¹) with capacity retention of 46.5% is realized for L-TiN-Cu-CNF interlayer-configured Li–S batteries. Even under high loading (3.8 mg cm ⁻²) of sulfur and relatively lean electrolyte (10 μL electrolyte per milligram sulfur) conditions, the Li–S battery equipped with L-TiN-Cu-CNF interlayers delivers a high capacity of 1144 mAh g ⁻¹ with cathodic capacity of 4.25 mAh cm ⁻² at 0.1 C, providing a potential pathway toward the design of multifunctional interlayers for highly efficient Li–S batteries.

Flexible piezocapacitive sensors utilizing nanomaterial-polymer composite-based nanofibrous membranes offer an attractive alternative to more traditional piezoelectric and piezoresistive wearable sensors owing to their ultralow powered nature, fast response, low hysteresis, and insensitivity to temperature change. In this work, we propose a facile method of fabricating electrospun graphene-dispersed PVAc nanofibrous membrane-based piezocapacitive sensors for applications in IoT-enabled wearables and human physiological function monitoring. A series of electrical and material characterization experiments were conducted on both the pristine and graphene-dispersed PVAc nanofibers to understand the effect of graphene addition on nanofiber morphology, dielectric response, and pressure sensing performance. Dynamic uniaxial pressure sensing performance evaluation tests were conducted on the pristine and graphene-loaded PVAc nanofibrous membrane-based sensors for understanding the effect of two-dimensional (2D) nanofiller addition on pressure sensing performance. A marked increase in the dielectric constant and pressure sensing performance was observed for graphene-loaded spin coated membrane and nanofiber webs respectively, and subsequently the micro dipole formation model was invoked to explain the nanofiller-induced dielectric constant enhancement. The robustness and reliability of the sensor have been underscored by conducting accelerated lifetime assessment experiments entailing at least 3000 cycles of periodic tactile force loading. A series of tests involving human physiological parameter monitoring were conducted to underscore the applicability of the proposed sensor for IoT-enabled personalized health care, soft robotics, and next-generation prosthetic devices. Finally, the easy degradability of the sensing elements is demonstrated to emphasize their suitability for transient electronics applications.

In this work, we report a class of fabric-like flexible and wearable capacitive sensors utilizing electrospun polyvinyl acetate (PV Ac)-graphene nanofibers for human motion monitoring applications. The sensor reported in this work features flexible PV Ac-graphene thin film sandwiched between two layers of conductive fabric and fully encapsulated in transparent adhesive films. The fabricated pressure sensor demonstrates two linear regimes with sensitivity figures of 0.0136 kPa-1 (pressure < 75 kPa) and 0.0063 kPa-1 (pressure > 75 kPa), respectively. The realized pressure sensor is flexible and apparel integrable, and the facile fabrication method will enable reliable and repeatable performance over roll-to-roll manufacturing suitable for mass production.

Self-powered wearable devices are gaining increasing attention to fulfil the sensing and energy harvesting needs for the next-generation wearable systems and body sensor networks. Here, we developed a wearable, flexible and lightweight nanofiber-based triboelectric nanogenearator (NF-TENG) for body motion energy harvesting. Polyvinylidene difluoride (PVDF) and nylon were electrospun into nanofiber films to form the two triboelectric materials. Under a load force of 10 N, the NF-TENG could generate an output voltage of 140 V, current of 0.5 μA and transferred charges of 50 nC. Preliminary body energy harvesting applications of the proposed NF-TENG were demonstrated, wherein the NF-TENG was able to generate an output voltage of 8 V and 10 V during typing and elbow bending, respectively.