Publications

Abstract Based on the coupling effects of contact electrification and electrostatic induction, a triboelectric nanogenerator (TENG) can convert mechanical energy into electric power, which is at the cutting edge of alternative energy technology. Although a considerable number of TENGs with different configurations have been designed, some of them however, which only depend on the electrostatic induction effect have not received enough attention. Here, a non‐contact TENG model consists of copper rings and charged dielectric sphere is presented, which is aimed at exploring the working process of TENGs caused by electrostatic induction. Two classical models, including vertical and horizontal double copper rings models are also proposed. Relevant advanced and accurate models of TENGs have been established through the finite element method. We anticipate that the constructed model and theoretical analysis are helpful for the design of non‐contact model TENGs with complicated geometric construction, and expand their applications in various fields. image

A triboelectric nanogenerator (TENG), which harvests ubiquitous ambient mechanical energy, is a promising power source for distributed energy. Recently reported new generation direct current TENG (DC-TENG) based on the air breakdown effect exhibits unique advantages over conventional modes of TENG devices, such as free-of-rectification and intrinsic switching behavior. However, owing to different working mechanisms and output characteristics, existing theory and power management strategies are not suitable for in-depth understanding and further advancement of air breakdown DC-TENG. Herein, a theoretical study and experimental verification that systematically investigate the physics, output characteristics, and power management strategy of air breakdown DC-TENG is presented. A general simulation model is then proposed and verified through a statistical analysis method. Contrary to previous understanding of a highly conductive breakdown pathway, a huge resistance is observed and causes inevitable energy loss, which is regarded to be caused by corona discharge. Finally, device optimization and power management strategies are discussed, and fundamental guidance is given for the rational design of air breakdown DC-TENG.

Mechanical energy harvesting based on triboelectric effect has been proven to be a simple, cost-effective, and robust method for electricity generation. In this study, we developed a rationally designed triboelectric nanogenerator (TENG) by utilizing the contact electrification between a polytetrafluoroethylene (PTFE) thin film and a layer of TiO2 nanomaterial (nanowire and nanosheet) array. The as-developed TENG was systematically studied and demonstrated as a self-powered nanosensor toward catechin detection. The high sensitivity (detection limit of 5 μM) and selectivity are achieved through a strong interaction between Ti atoms of TiO2 nanomaterial and enediol group of catechin. The output voltage and current density were increased by a factor of 5.0 and 2.9, respectively, when adsorbed with catechin of a saturated concentration, because of the charge transfer from catechin to TiO2. This study demonstrates the possibility of improving the electrical output of TENG through chemical modification.

Abstract Commercial lithium‐ion batteries (LIBs), limited by their insufficient reversible capacity, short cyclability, and high cost, are facing ever‐growing requirements for further increases in power capability, energy density, lifespan, and flexibility. The presence of insulating and electrochemically inactive binders in commercial LIB electrodes causes uneven active material distribution and poor contact of these materials with substrates, reducing battery performance. Thus, nanostructured electrodes with binder‐free designs are developed and have numerous advantages including large surface area, robust adhesion to substrates, high areal/specific capacity, fast electron/ion transfer, and free space for alleviating volume expansion, leading to superior battery performance. Herein, recent progress on different kinds of supporting matrixes including metals, carbonaceous materials, and polymers as well as other substrates for binder‐free nanostructured electrodes in LIBs are summarized systematically. Furthermore, the potential applications of these binder‐free nanostructured electrodes in practical full‐cell‐configuration LIBs, in particular fully flexible/stretchable LIBs, are outlined in detail. Finally, the future opportunities and challenges for such full‐cell LIBs based on binder‐free nanostructured electrodes are discussed.

Harvesting energy from multiple sources available in our personal and daily environments is highly desirable, not only for powering personal electronics, but also for future implantable sensor-transmitter devices for biomedical and healthcare applications. Here we present a hybrid energy scavenging device for potential in vivo applications. The hybrid device consists of a piezoelectric poly(vinylidene fluoride) nanofiber nanogenerator for harvesting mechanical energy, such as from breathing or from the beat of a heart, and a flexible enzymatic biofuel cell for harvesting the biochemical (glucose/O2) energy in biofluid, which are two types of energy available in vivo. The two energy harvesting approaches can work simultaneously or individually, thereby boosting output and lifetime. Using the hybrid device, we demonstrate a "self-powered" nanosystem by powering a ZnO nanowire UV light sensor.

Abstract The rapid development of personal electronics imposes a great challenge on sustainable and maintenance‐free power supplies. The integration of nanogenerators (NG) and electrochromic supercapacitors (SC) offers a promising solution to efficiently convert mechanical energy to stored electrical energy in a predictable and noticeable manner. In this paper, by integrating hybrid NGs and electrochromic micro‐SCs (µ‐SCs) array, the authors demonstrate a smart self‐charging power package capable of indicating the charging state with color change. The electrochromic µ‐SC employs Ag nanowires/NiO as electrode materials, exhibiting high capacitance (3.47 mF cm −2 ) and stable cycling performance (80.7% for 10000 cycles). The hybrid NG can produce a high output voltage of 150 V and an enhanced output current of 20 µA to satisfy the self‐charging requirements. The integrated electrochromic µ‐SCs array is capable of self‐charging to 3 V to light up a LED under human palm impact. The charging states can be estimated according to the color differences with the naked eye during the self‐charging process. Moreover, it is possible to design the planar interdigitated electrodes into different shapes according to user demand. The proposed simple and cost‐effective approaches for smart self‐charging power package may pave the way for future intelligent, independent and continuous operation of daily electronics.

We demonstrate a novel approach for the large-scale, shape-controlled synthesis of one-dimensional (1D) corrugated nanoarrays of Pb(1-x)MnxSe nanocrystals (0.002 ≤ x ≤ 0.008) through an in-situ self-assembly without using either capping polymer or ionic surfactant. The one-step-prepared 1D nanoarrays exhibit a well-defined morphology, single-crystal orientation, and clean surface without amorphous contamination. The average diameter of the 1D nanoarrays can be controlled and varied from <10 to 80 nm by finely tuning the assembly temperature and the growth time. Four growth models were suggested to explain the in-situ self-assembly processes based on the fundamental building blocks of octahedral nanocrystals by sharing {111} facets.

A new type of flexible organic tribotronic transistor memory is proposed, which can be written and erased by externally applied touch actions as an active memory. By further coupling with an organic light-emitting diode (OLED), a visible and wearable touch monitoring system is achieved, in which touch triggering can be memorized and shown as the emission from the OLED.

Recently, piezoelectric and triboelectric energy harvesting devices have been developed to convert mechanical energy into electrical energy. Especially, it is well known that triboelectric nanogenerators have a simple structure and a high output voltage. However, whereas nanostructures improve the output of triboelectric generators, its fabrication process is still complicated and unfavorable in term of the large scale and long-time durability of the device. Here, we demonstrate a hybrid generator which does not use nanostructure but generates much higher output power by a small mechanical force and integrates piezoelectric generator into triboelectric generator, derived from the simultaneous use of piezoelectric and triboelectric mechanisms in one press-and-release cycle. This hybrid generator combines high piezoelectric output current and triboelectric output voltage, which produces peak output voltage of ~370 V, current density of ~12 μA · cm(-2), and average power density of ~4.44 mW · cm(-2). The output power successfully lit up 600 LED bulbs by the application of a 0.2 N mechanical force and it charged a 10 μF capacitor to 10 V in 25 s. Beyond energy harvesting, this work will provide new opportunities for developing a small, built-in power source in self-powered electronics such as mobile electronics.

A comprehensive investigation was carried out on n-type ZnO nanowires for studying the temperature dependence of the piezotronic effect from 77 to 300 K. In general, lowering the temperature results in a largely enhanced piezotronic effect. The experimental results show that the behaviors can be divided into three groups depending on the carrier doping level or conductivity of the ZnO nanowires. For nanowires with a low carrier density (<10(17)/cm(3) at 77 K), the pieozotronic effect is dominant at low temperature for dictating the transport properties of the nanowires; an opposite change of Schottky barrier heights at the two contacts as a function of temperature at a fixed strain was observed for the first time. At a moderate doping (between 10(17)/cm(3) and 10(18)/cm(3) at 77 K), the piezotronic effect is only dominant at one contact, because the screening effect of the carriers to the positive piezoelectric polarization charges at the other end (for n-type semiconductors). For nanowires with a high density of carriers (>10(18)/cm(3) at 77 K), the piezotronic effect almost vanishes. This study not only proves the proposed fundamental mechanism of piezotronic effect, but also provides guidance for fabricating piezotronic devices.