Multilayer NiO@Co3O4 hollow spheres are modified by graphene quantum dots and exhibit superior performances for lithium-ion batteries and supercapacitors.

No abstract

weight, ultrathinness, high flexibility, and comfortable characteristics, wearable electronics that can realize the detection and quantification of electric signals produced by physiological activities and human motions have attracted worldwide research attention. [1][2][3] These wearable electronics integrated with sensing elements can conformally be attached to clothes, skin, or organs, enabling new human motion detection, different disease recognition and personal healthcare management. From this respect, people are working on the "Internet of Medical Things (IoMTs)," which connects numerous wearable sensors to a communication network center to enable regular or real-time communication between doctors and patients. [4,5] As pressure changes can show deteriorated behavior of specific disease area, different wearable health sensors have considered pressure monitoring. [6] However, the traditionally designed electrogram system is usually attached to the human body, in which the electrodes are connected to the skin or organs through the clips, tapes, or puncture needles. The cumbersome design often leads to the incompatible contact between electrodes and the human body and results in signal distortion or high noise. In addition, these electrodes must be connected to external power sources, rigid circuit boards, and communication components to record electrical signals from the human body. Except for electrograms, wearable pressure sensing systems with the lightweight, ultrathin, and flexible features that detects changes in physical stimuli and converts biomechanical stimuli into recorded signals, which are in conformal contact with skin or organs, can be intended in human motion monitoring and individual medical care. [7,8] Most of physical stimuli are generally produced through the normal activities and physical contact by human body, such as pulse, blood pressure, and skin strain, all of which are important health indicators of the human body. [9,10] Herein, wearable pressure sensing can contribute to low-cost wearable noninvasive solutions to record continuous human body signal of electrophysiological activity.Harvesting energy from human mechanical sources like motion-generated pressure and strains has attracted extensive attention to develop self-powered wearable devices, [11,12] Highly sensitive flexible pressure sensors are extensively investigated for various applications, such as electronic skin, human physiological monitoring, and artificial intelligence. However, traditional fabrication technologies are hard to realize the large-area and mass production of wearable sensing devices. Current trend of miniaturization, systematization, and multifunction has raised the problems of total energy consumption, frequent charging, and reduced usage time. These issues have hindered the progress of wearable sensing electronics. In the light of nanomaterial design, mass production, and facile manufacturing, electrospun piezoelectric pressure sensors offer the best properties of self-powering, breathability, stretcha...

Yolk-shell NiO microspheres are modified by two types of functionalized graphene quantum dots (denoted as NiO/GQDs) via a facile solvothermal treatment. The modification of GQDs on the surface of NiO greatly boosts the stability of the NiO/GQD electrode during long-term cycling. Specifically, the NiO with carboxyl-functionalized GQDs (NiO/GQDsCOOH) exhibits better performances than NiO with amino-functionalized GQDs (NiO/GQDsNH ). It delivers a capacity of ≈1081 mAh g (NiO contribution: ≈1182 mAh g ) after 250 cycles at 0.1 A g . In comparison, NiO/GQDsNH electrode holds ≈834 mAh g of capacity, while the bald NiO exhibits an obvious decline in capacity with ≈396 mAh g retained after cycling. Except for the yolk-shell and mesoporous merits, the superior performances of the NiO/GQD electrode are mainly ascribed to the assistance of GQDs. The GQD modification can support as a buffer alleviating the volume change, improve the electronic conductivity, and act as a reservoir for electrolytes to facilitate the transportation of Li . Moreover, the enrichment of carboxyl/amino groups on GQDs can further donate more active sites for the diffusion of Li and facilitate the electrochemical redox kinetics of the electrode, thus together leading to the superior lithium storage performance.

Hierarchical “tube-on-fiber” carbon/mixed-metal selenide nanostructures (Co–Zn–Se@CNTs–CNFs) are constructed and exhibit high performance for hybrid supercapacitors.