Dianpeng Qi

Unravelling the Correlation between the Aspect Ratio of Nanotubular Structures and Their Electrochemical Performance To Achieve High-Rate and Long-Life Lithium-Ion Batteries†

The fundamental understanding of the relationship between the nanostructure of an electrode and its electrochemical performance is crucial for achieving high-performance lithium-ion batteries (LIBs). In this work, the relationship between the nanotubular aspect ratio and electrochemical performance of LIBs is elucidated for the first time. The stirring hydrothermal method was used to control the aspect ratio of viscous titanate nanotubes, which were used to fabricate additive-free TiO2 -based electrode materials. We found that the battery performance at high charging/discharging rates is dramatically boosted when the aspect ratio is increased, due to the optimization of electronic/ionic transport properties within the electrode materials. The proof-of-concept LIBs comprising nanotubes with an aspect ratio of 265 can retain more than 86 % of their initial capacity over 6000 cycles at a high rate of 30 C. Such devices with supercapacitor-like rate performance and battery-like capacity herald a new paradigm for energy storage systems.

Suspended Wavy Graphene Microribbons for Highly Stretchable Microsupercapacitors

Highly stretchable microsupercapacitors with stable electrochemical performance are fabricated. Their excellent stretchable and electrochemical performance relies on the suspended wavy structures of graphene microribbons. This avoids the detachment and cracks of the electrode materials. In addition, it ensures the electrode fingers keep a relatively constant distance so the stability of the microsupercapacitors can be enhanced.

Ambient fabrication of large-area graphene films via a synchronous reduction and assembly strategy

A synchronous reduction and assembly strategy is designed to fabricate large-area graphene films and patterns with tunable transmittance and conductivity. Through an oxidation-reduction reaction between the metal substrate and graphene oxide, graphene oxide is reduced to chemically converted graphene and is organized into highly ordered films in situ. This work will form the precedent for industrial-scale production of graphene materials for future applications in electronics and optoelectronics.

Simple approach to wafer-scale self-cleaning antireflective silicon surfaces.

A simple approach to wafer-scale self-cleaning antireflective hierarchical silicon structures is demonstrated. By employing the KOH etching and silver catalytic etching, pyramidal hierarchical structures were generated on the crystalline silicon wafer, which exhibit strong antireflection and superhydrophobic properties after fluorination. Furthermore, a flexible superhydrophobic substrate was fabricated by transferring the hierarchical Si structure to the NOA 63 film with UV-assisted imprint lithography. This method is of potential application in optical, optoelectronic, and wettability control devices.

Programmable photo-electrochemical hydrogen evolution based on multi-segmented CdS-Au nanorod arrays.

Programmable photocatalysts for hydrogen evolution have been fabricated based on multi-segmented CdS-Au nanorod arrays, which exhibited high-efficiency and programmability in hydrogen evolution as the photoanodes in the photoelectrochemical cell. Multiple different components each possess unique physical and chemical properties that provide these cascade nanostructures with multiformity, programmability, and adaptability. These advantages allow these nanostructures as promising candidates for high efficient harvesting and conversion of solar energy.

Thickness‐Gradient Films for High Gauge Factor Stretchable Strain Sensors

High-gauge-factor stretchable strain sensors are developed by utilizing a new strategy of thickness-gradient films with high durability, and high uniaxial/isotropic stretchability based on the self-pinning effect of SWCNTs. The monitoring of detailed damping vibration modes driven by weak sound based on such sensors is demonstrated, making a solid step toward real applications.

Biomimetic Antireflective Si Nanopillar Arrays

The Fresnel reflection of incident light comes from the large refractive index discontinuity at the interface of two media. The high reflective index of Si results in the reflection of up to 40% of the incident light, which severely limits the performance of Si based optical and optoelectronic devices, such as solar cells, displays, and light sensors. Thin film coatings with intermediate or gradient refractive indices are commonly utilized to suppress undesired Fresnel reflection. However, the stability problems induced by adhesiveness and thermal mismatch are often associated with such approaches. Since the corneas of nocturnal-moth eyes were found to have antireflective properties, surface-relief arrays with dimension smaller than the wavelength of incident light have been considered an alternative to thin-film coatings, which are more stable and durable than surface coatings since only one material is involved. In the last decade, increasing effort has been devoted to the fabrication of such surface antireflection structures. Many different structures, such as nanorods and nanopillars, gratings, porous structures, and nanotubes have been created in order to suppress surface reflection. The basic purpose of this technique is to introduce a refractive index gradient between air and a substrate material by creating a structured layer. Reflection can be substantially suppressed for a wide spectral bandwidth and over a large field of view. Due to the applications of Si in modern optical and optoelectronic industry, a variety of techniques for producing subwavelength ‘‘moth eye’’ structures on Si have been proposed, such as electron-beam lithography, laser interference lithography, and nanoimprint lithography. However, these

Conductive Inks Based on a Lithium Titanate Nanotube Gel for High‐Rate Lithium‐Ion Batteries with Customized Configuration

Solution-processable inks based on lithium titanate with a conductive network architecture, toward high-rate lithium-ion batteries (LIBs) with a customized configuration are developed. The inks, with tunable viscosity, are compatible for on-demand coating techniques. The lithium titanate electrode derived from these inks exhibits excellent high-rate capacity (≈124 mA h g(-1) at 90 C, 15.7 A g(-1) ) after 1000 cycles.

Design of Architectures and Materials in In‐Plane Micro‐supercapacitors: Current Status and Future Challenges

The rapid development of integrated electronics and the boom in miniaturized and portable devices have increased the demand for miniaturized and on-chip energy storage units. Currently thin-film batteries or microsized batteries are commercially available for miniaturized devices. However, they still suffer from several limitations, such as short lifetime, low power density, and complex architecture, which limit their integration. Supercapacitors can surmount all these limitations. Particularly for micro-supercapacitors with planar architectures, due to their unique design of the in-plane electrode finger arrays, they possess the merits of easy fabrication and integration into on-chip miniaturized electronics. Here, the focus is on the different strategies to design electrode finger arrays and the material engineering of in-plane micro-supercapacitors. It is expected that the advances in micro-supercapacitors with in-plane architectures will offer new opportunities for the miniaturization and integration of energy-storage units for portable devices and on-chip electronics.

High-Performance Photothermal Conversion of Narrow-Bandgap Ti2O3 Nanoparticles

Ti2 O3 nanoparticles with high performance of photothermal conversion are demonstrated for the first time. Benefiting from the nanosize and narrow-bandgap features, the Ti2 O3 nanoparticles possess strong light absorption and nearly 100% internal solar-thermal conversion efficiency. Furthermore, Ti2 O3 -nanoparticle-based thin film shows potential use in seawater desalination and purification.