Zijie Tang

An Intrinsically Stretchable and Compressible Supercapacitor Containing a Polyacrylamide Hydrogel Electrolyte

Stretchability and compressibility of supercapacitors is an essential element of modern electronics, such as flexible, wearable devices. Widely used polyvinyl alcohol-based electrolytes are neither very stretchable nor compressible, which fundamentally limits the realization of supercapacitors with high stretchability and compressibility. A new electrolyte that is intrinsically super-stretchable and compressible is presented. Vinyl hybrid silica nanoparticle cross-linkers were introduced into polyacrylamide hydrogel backbones to promote dynamic cross-linking of the polymer networks. These cross-linkers serve as stress buffers to dissipate energy when strain is applied, providing a solution to the intrinsically low stretchability and compressibility shortcomings of conventional supercapacitors. The newly developed supercapacitor and electrolyte can be stretched up to an unprecedented 1000 % strain with enhanced performance, and compressed to 50 % strain with good retention of the initial performance.

An extremely safe and wearable solid-state zinc ion battery based on a hierarchical structured polymer electrolyte

Flexible and safe batteries, coupled with high performance and low cost, constitute a radical advance in portable and wearable electronics, especially considering the fact that these flexible devices are likely to experience more mechanical impacts and potential damage than well-protected rigid batteries. However, flexible lithium ion batteries (LIBs) are vastly limited by their intrinsic safety and cost issues. Here we introduce an extremely safe and wearable solid-state zinc ion battery (ZIB) comprising a novel gelatin and PAM based hierarchical polymer electrolyte (HPE) and an α-MnO2 nanorod/carbon nanotube (CNT) cathode. Benefiting from the well-designed electrolyte and electrodes, the flexible solid-state ZIB delivers a high areal energy density and power density (6.18 mW h cm−2 and 148.2 mW cm−2, respectively), high specific capacity (306 mA h g−1) and excellent cycling stability (97% capacity retention after 1000 cycles at 2772 mA g−1). More importantly, the solid-state ZIB offers a high wearability and an extreme safety performance over conventional flexible LIBs, and performs very well under various severe conditions, such as being greatly cut, bent, hammered, punctured, sewed, washed in water or even put on fire. In addition, flexible ZIBs were integrated in series to power a commercial smart watch, a wearable pulse sensor, and a smart insole, which has been achieved to the best of our knowledge for the first time. These results demonstrate the promising potential of ZIBs in many practical wearable applications and offer a new platform for flexible and wearable energy storage technologies.

Fabrication of Boron Nitride Nanosheets by Exfoliation.

Nanomaterials with layered structures, with their intriguing properties, are of great research interest nowadays. As one of the primary two-dimensional nanomaterials, the hexagonal boron nitride nanosheet (BNNS, also called white graphene), which is an analogue of graphene, possesses various attractive properties, such as high intrinsic thermal conductivity, excellent chemical and thermal stability, and electrical insulation properties. After being discovered, it has been one of the most intensively studied two-dimensional non-carbon nanomaterials and has been applied in a wide range of applications. To support the exploration of applications of BNNSs, exfoliation, as one of the most promising approaches to realize large-scale production of BNNSs, has been intensively investigated. In this review, methods to yield BNNSs by exfoliation will be summarized and compared with other potential fabrication methods of BNNSs. In addition, the future prospects of the exfoliation of h-BN will also be discussed.

Component Matters: Paving the Roadmap toward Enhanced Electrocatalytic Performance of Graphitic C3N4-Based Catalysts via Atomic Tuning

Atomically precise understanding of componential influences is crucial for looking into the reaction mechanism and controlled synthesis of efficient electrocatalysts. Herein, by means of comprehensive experimental and theoretical studies, we carefully examine the effects of component dopants on the catalytic performance of graphitic C3N4 (g-C3N4)-based electrocatalysts. The g-C3N4 monoliths with three types of dopant elements (B, P, and S) embedded in different sites (either C or N) of the C-N skeleton are rationally designed and synthesized. The kinetics, intrinsic activity, charge-transfer process, and intermediate adsorption/desorption free energy of the selected catalysts in oxygen reduction reaction and hydrogen evolution reaction are investigated both experimentally and theoretically. We demonstrate that the component aspect within the g-C3N4 motifs has distinct and substantial effects on the corresponding electroactivities, and proper component element engineering can be a viable yet efficient protocol to render the metal-free composites as competent catalysts rivaling the metallic counterparts. We hope that this study may shed light on the empirical trial-and-error exploration in design and development of g-C3N4-based materials as well as other metal-free catalysts for energy-related electrocatalytic reactions.

Mn3O4 nanoparticles on layer-structured Ti3C2 MXene towards the oxygen reduction reaction and zinc–air batteries

Non-precious metal catalysts, such as manganese oxide (Mn3O4), with efficient activity and superior stability are highly required. However, poor conductivity, dissolution, and high cohesion significantly limit the performance of Mn3O4 nanoparticles as an electrode material. Herein, Mn3O4 nanoparticles supported on layered Ti3C2 MXene (Mn3O4/MXene) nanocomposite with superb oxygen reduction reaction performance have been reported for the first time. The as-prepared Mn3O4/MXene nanocomposite display favorable electrochemical activity in oxygen reduction reaction with a dominant four-electron oxygen reduction pathway and an onset potential at 0.89 V (same as that of Pt/C) in an alkaline solution. Layered MXenes exhibit metal conductivity as well as hydrophilicity, which would greatly improve the chemical properties of the nano-sized particles by inhibiting aggregation and increasing the electron transfer speed. Furthermore, Mn3O4/MXene exhibits higher stability than Mn3O4/acetylene black owing to the highly stable Mn3O4/MXene hybrid structure. The as-prepared Zn–air battery based on the Mn3O4/MXene air-cathode exhibits a high open potential (1.37 V), superb power density (150 mW cm−2), and excellent stability (no obvious potential change in 100 hours). The prepared low-cost Mn3O4/MXene nanocomposite with superior oxygen reduction reaction performance can be a promising candidate as an oxygen reduction reaction catalyst and for use in zinc–air batteries and other energy storage devices.

Waterproof and Tailorable Elastic Rechargeable Yarn Zinc Ion Batteries by a Cross-Linked Polyacrylamide Electrolyte

Emerging research toward next-generation flexible and wearable electronics has stimulated the efforts to build highly wearable, durable, and deformable energy devices with excellent electrochemical performances. Here, we develop a high-performance, waterproof, tailorable, and stretchable yarn zinc ion battery (ZIB) using double-helix yarn electrodes and a cross-linked polyacrylamide (PAM) electrolyte. Due to the high ionic conductivity of the PAM electrolyte and helix structured electrodes, the yarn ZIB delivers a high specific capacity and volumetric energy density (302.1 mAh g-1 and 53.8 mWh cm-3, respectively) as well as excellent cycling stability (98.5% capacity retention after 500 cycles). More importantly, the quasi-solid-state yarn ZIB also demonstrates superior knittability, good stretchability (up to 300% strain), and superior waterproof capability (high capacity retention of 96.5% after 12 h underwater operation). In addition, the long yarn ZIB can be tailored into short ones, and each part still functions well. Owing to its weavable and tailorable nature, a 1.1 m long yarn ZIB was cut into eight parts and woven into a textile that was used to power a long flexible belt embedded with 100 LEDs and a 100 cm2 flexible electroluminescent panel.

Flexible Dual-Mode Tactile Sensor Derived from Three-Dimensional Porous Carbon Architecture

Detecting and monitoring varieties of human activities is one of the most essential functions and design purposes of different kinds of wearable sensors. Apart from excellent sensitivity and durability, limited by the materials, most of the sensors reported in the literature are capable of detecting signals only on the basis of a sole mechanism. In this work, a dual-mode flexible sensor derived from a high-temperature-pyrolysized 3D carbon sponge (C-Sponge) was proposed as a peculiar sensor material that is able to detect human activities based on fundamentally different mechanisms, by either the triboelectric effect or the piezoresistive effect. The sensor generated an average open circuit voltage up to ∼2 V and short circuit current up to ∼70 nA when being used as self-powered triboelectric sensor, which was sufficiently sensitive for detecting finger touching and plantar pressure distribution of human feet. On the other hand, by incorporating MWCNT into the 3D structure, the sensor at piezoresistive mode exhibited a sensitivity improvement of nearly 20-fold, from less than 40% to more than 800%, and a durability improvement of more than 22-fold (240 000 cycles) compared with those of original C-Sponge fabricated at 1000 °C (10 800 cycles). All the experimental results indicated that the proposed flexible dual-mode sensor is potentially applicable as wearable sensors for human activity monitoring.

Construction of a hierarchical 3D Co/N-carbon electrocatalyst for efficient oxygen reduction and overall water splitting

Exploration of a highly efficient and multifunctional electrocatalytic material is crucial for renewable energy technologies. Herein, by studying a multidimensional and multifunctional Co/N–C catalyst, we have demonstrated that two categories of preferential characteristics, i.e. activity distinctions between different reactions and feature distinctions between component and structure aspects, for electrocatalysts are not mutually exclusive, but can be well-addressed simultaneously. This rationally designed and cost-effective hybrid catalyst synergically integrates the features, including ample active species, prompt mass transport, excellent conductivity, and structural stability in both acidic and alkaline electrolytes, for an efficient and versatile electrocatalyst. The thus-obtained multidimensional catalyst delivers excellent activities in oxygen reduction and overall water-splitting reactions in conjunction with a good durability, which then enables a prominent performance in a rechargeable Zn–air battery and also demonstrates feasibility in a self-powered water-splitting unit. This study opens up new avenues for the rational design and easy fabrication of multidimensional catalysts with desired performances for various renewable energy applications.

Toward Enhancing Wearability and Fashion of Wearable Supercapacitor with Modified Polyurethane Artificial Leather Electrolyte

Inspired by the sophisticated artificial leather garment industry and toward enhancing wearability of energy storage devices, we demonstrate a polyurethane artificial leather supercapacitor with large sheet electrodes embedded in the leather layer simultaneously working as a polyelectrolyte. This design totally reserves textiles underneath and thus addresses the well-known challenge of wearing comfortability. It provides a revolutionary configuration of wearable supercapacitors: the artificial leather on garment is also a supercapacitor. Unlike the polyvinyl alcohol-based acidic electrolytes, which are widely used, sodium chloride is used to modify the intrinsically fluorescent polyurethane leather for ionic transportation, which has no harm to human. The fluorescent leather supercapacitor is easily transferrable from any arbitrary substrates to form various patterns, enabling multifunctionalities of practical wearability, fashion, and energy storage.

Light-permeable, photoluminescent microbatteries embedded in the color filter of a screen

The battery and the screen are the two components occupying the largest volume in many electronic devices. Integrating them together will eventually engender a great reduction of device size. The current study demonstrates a promising strategy towards ultimate-compact electronic devices. Herein, a photoluminescent microbattery with reasonable light-permeability and hazing ability is developed. This aqueous Zn–MnOx/polypyrrole based microbattery features a flat architecture with interdigitated electrodes and utilizes a photoluminescent gelatin based electrolyte by embedding colloidal CdTe quantum dots. Furthermore, borax is introduced into the electrolyte as an additive, which effectively prevents luminescence quenching of the quantum dots and simultaneously enhances the electrochemical performance of the microbattery. A high device energy density of 21 mW h cm−3 is obtained. One step further, a three-primary-color (red–green–blue, RGB) photoluminescent microbattery array is assembled, endowing the battery with the function of a color filter and realizing a battery-in-screen configuration.