Peichao Zou

An Ultralong, Highly Oriented Nickel-Nanowire-Array Electrode Scaffold for High-Performance Compressible Pseudocapacitors

Ultralong, highly oriented Ni nanowire arrays are used as the electrode scaffold to support metal-oxide- and conductive-polymer-based electrode materials with a high mass loading; the as-obtained asymmetric supercapacitor can be compressed by fourfold and exhibits superior energy and power densities with ultrahigh cycle stability.

Shape-Tailorable Graphene-Based Ultra-High-Rate Supercapacitor for Wearable Electronics

With the bloom of wearable electronics, it is becoming necessary to develop energy storage units, e.g., supercapacitors that can be arbitrarily tailored at the device level. Although gel electrolytes have been applied in supercapacitors for decades, no report has studied the shape-tailorable capability of a supercapacitor, for instance, where the device still works after being cut. Here we report a tailorable gel-based supercapacitor with symmetric electrodes prepared by combining electrochemically reduced graphene oxide deposited on a nickel nanocone array current collector with a unique packaging method. This supercapacitor with good flexibility and consistency showed excellent rate performance, cycling stability, and mechanical properties. As a demonstration, these tailorable supercapacitors connected in series can be used to drive small gadgets, e.g., a light-emitting diode (LED) and a minimotor propeller. As simple as it is (electrochemical deposition, stencil printing, etc.), this technique can be used in wearable electronics and miniaturized device applications that require arbitrarily shaped energy storage units.

A reduced graphene oxide/mixed-valence manganese oxide composite electrode for tailorable and surface mountable supercapacitors with high capacitance and super-long life

Developing supercapacitor electrodes with an ultra-long cycle life and a high specific capacitance is critical to the future energy storage devices. Herein, we report a scalable synthesis technology of mixed-valence manganese oxide nanoparticles anchored to reduced graphene oxide (rGO/MnOx) as the high-performance supercapacitor electrodes. First, 2-dimensional (2D) δ-MnO2 nanosheets are formed on a graphene oxide (GO) template, which is then in situ reduced by hydrazine vapour to mixed-valence manganese oxide nanoparticles evenly distributed on a rGO conductive network. The obtained rGO/MnOx electrode material exhibits a high specific capacitance of 202 F g−1 (mass loading of 2 mg cm−2), a large areal specific capacitance of 2.5 F cm−2 (mass loading of up to 19 mg cm−2), and a super-long-life stability of 106% capacitance retention after 115 000 charge/discharge cycles. By using an ionic liquid electrolyte and an activated carbon anode, asymmetric supercapacitors (AScs) are also constructed and can be packaged into a high performance miniaturized energy storage component in either a tailorable or surface mountable configuration. Our ASc shows superior performance characteristics, with typical figures of merit including maximum energy densities of 47.9 W h kg−1 at 270 W kg−1 and 19.1 W h kg−1 at the maximum power density of 20.8 kW kg−1. The capacitance retention of the ASc is 96% after 80 000 charge/discharge cycles, which is the most excellent stability performance in an ionic liquid electrolyte as compared with the recently reported pseudo-supercapacitors. This technology may find vast applications in future miniaturized portable and wearable electronics.

Flexible copper wires through galvanic replacement of zinc paste: a highly cost-effective technology for wiring flexible printed circuits

Conventional electronic circuit wiring methods involve subtractive processes such as etching the copper foils, and thus are inefficient and cause serious environmental problems. Printed electronics technology is expected to be more environmentally benign and have lower cost, due to its additive characteristics. In this paper, we present a simple and efficient strategy to fabricate high performance copper metal fine circuits by a galvanic replacement deposition method. Zinc nanoparticles filled epoxy resin paste is printed onto the substrate film as the seed layer; with a subsequent simple galvanic replacement reaction between Zn and Cu2+, we can obtain a conductive Cu layer that can be further thickened by electroplating. The as-prepared circuits show bulk Cu conductivity, excellent flexibility, adhesion strength and pattern resolution. By adjusting the processing parameters, this technology is suitable for various practical applications, such as flexible circuit boards, RFID tags, touch panels, membrane switches, and photovoltaics, making it a promising solution for low-cost and environmentally friendly fabrication for flexible electronic devices.

Directing lateral growth of lithium dendrites in micro-compartmented anode arrays for safe lithium metal batteries

Uncontrolled growth of lithium dendrites during cycling has remained a challenging issue for lithium metal batteries. Thus far, various approaches have been proposed to delay or suppress dendrite growth, yet little attention has been paid to the solutions that can make batteries keep working when lithium dendrites are already extensively present. Here we develop an industry-adoptable technology to laterally direct the growth of lithium dendrites, where all dendrites are retained inside the compartmented copper current collector in a given limited cycling capacity. This featured electrode layout renders superior cycling stability (e.g., smoothly running for over 150 cycles at 0.5 mA cm−2). Numerical simulations indicate that reduced dendritic stress and damage to the separator are achieved when the battery is abusively running over the ceiling capacity to generate protrusions. This study may contribute to a deeper comprehension of metal dendrites and provide a significant step towards ultimate safe batteries.The formation of lithium dendrites remains a great challenge to lithium metal batteries. Here the authors show an anode design to laterally direct the dendrite growth inside the compartments, providing a feasible post-mortem solution to batteries with lithium dendrites already present.

MoO3@Ni nanowire array hierarchical anode for high capacity and superior longevity all-metal-oxide asymmetric supercapacitors

In this communication, a general technology for improving the electrochemical performances of metal oxide based electrode materials has been demonstrated via in situ growth of the electrode materials on Ni nanowire array (NNA) current collector films, which can attain a loading level up to ∼25 mg cm−2. The NNA@MoO3 electrode delivered a high areal capacity ∼477 mF cm−2 and superior longevity (∼5% capacitance loss after 20 000 cycles). Moreover, crystalline VO2 was electro-deposited on NNA as the cathode, which was assembled with the NNA@MoO3 anode into an all-metal oxide-based asymmetric supercapacitor (AAS). The AAS can deliver an open circuit voltage of 1.6 V in an aqueous electrolyte and a high energy density (2.19 mW h cm−3) at the power density of 8.2 mW cm−3. This work provides an example of a flexible AAS device featuring a high areal capacity (307 mF cm−2) and excellent cyclability (116% retention after 20 000 cycles) simultaneously purely involved with metal oxide electrodes.

Vapor-Phase Polymerized Poly(3,4-Ethylenedioxythiophene) on a Nickel Nanowire Array Film: Aqueous Symmetrical Pseudocapacitors with Superior Performance

Three-dimensional (3D) nanometal scaffolds have gained considerable attention recently because of their promising application in high-performance supercapacitors compared with plain metal foils. Here, a highly oriented nickel (Ni) nanowire array (NNA) film was prepared via a simple magnetic-field-driven aqueous solution deposition process and then used as the electrode scaffold for the vapor-phase polymerization of 3,4-ethylenedioxythiophene (EDOT). Benefiting from the unique 3D open porous structure of the NNA that provided a highly conductive and oriented backbone for facile electron transfer and fast ion diffusion, the as-obtained poly(3,4-ethylenedioxythiophene) (PEDOT) exhibited an ultra-long cycle life (95.7% retention of specific capacitance after 20 000 charge/discharge cycles at 5 A/g) and superior capacitive performance. Furthermore, two electrodes were fabricated into an aqueous symmetric supercapacitor, which delivered a high energy density (30.38 Wh/kg at 529.49 W/kg) and superior long-term cycle ability (13.8% loss of capacity after 20 000 cycles). Based on these results, the vapor-phase polymerization of EDOT on metal nanowire array current collectors has great potential for use in supercapacitors with enhanced performance.

Ultrahigh power graphene based supercapacitor

Supercapacitor as a type of new energy storage device has important applications in the development of smart electronics and vehicles, which can provide a high current density to drive the devices. Recently, although graphene has been considered as a very promising electrode material for supercapacitors, the poor control of the dispersion of graphene and the limited way of electrode preparation process severely hinder its power performance. Here, we report a supercapacitor technology with ultrahigh power combining the electrochemically reduced graphene oxide deposited on nickel nanocone array with printed ethylene vinyl acetate cofferdams. The supercapacitor showed excellent rate performance, ultrahigh power density (1230 mWh/cm3) and high ionic mobility, especially when compared to those with separator. In light of the simple process (electrochemical-deposition and stencil printing, etc.), this technology can meet the demand of applications with high power density and inspire the development of other energy storages to achieve better performance.

Hierarchical nickel nanowire@NiCo2S4 nanowhisker composite arrays with a test-tube-brush-like structure for high-performance supercapacitors

Well-ordered, hierarchical and nanostructured composite electrodes have gained tremendous research attention for energy storage applications, because of their highly efficient electron and ion transport channels and abundant electrochemically active sites. However, it still remains a great challenge to prepare such architectures on a large scale with high active material mass loadings for making better use of the whole electrode area. Herein, needle-like NiCo2S4 nanowhiskers are radially grown on a uniform nickel nanowire array (NNA), forming a unique densely packed test-tube-brush-like nanostructure. Since these NiCo2S4 nanowhiskers are intrinsically highly electrically conductive, the hierarchical electrode structure can drastically elevate the charge transport ability in the whole electrode region; additionally, it can greatly help to release stresses at micro- and nano-scales, leading to robust mechanical flexibility and superior energy storage capability. Experimental results show that this composite array electrode exhibits an ultrahigh specific capacitance of 1523 F g−1 at a mass loading of 4.03 mg cm−2 at a current density of 1 A g−1, and a rate capability of 61.8% from 1 to 40 A g−1, together with a superior cycle stability with 92.4% capacitance retention after 20 000 cycles at a current density as high as 10 A g−1. An asymmetric supercapacitor consisting of a NNA@NiCo2S4 (NNANCS) cathode and activated carbon (AC) anode delivers a maximum energy density of 47.29 W h kg−1 at a power density of 793.5 W kg−1 and still delivers an energy density of 29.50 W h kg−1 at a maximum power density of 27.64 kW kg−1. This work may inspire new ideas for constructing high-performance electrodes for energy storage.

Scalable synthesis of mono-dispersed nickel nanoparticles and their application as thermal conductive fillers

With the rapid development of the electronic industry, it is critical for electronic packaging industry to develop superior materials with high thermal conductivity and lower cost, so as to dissipate heat from the central components. Metallic materials are compelling in thermal conductivity application over decades. However, it is still a great challenge to synthetize metal nanomaterials which have specific structure. Here we report a one-step method to synthesis mono-dispersed nickel nanoparticles with durian structure in a large scale. These nickel nanoparticles can be prepared by mixing the nickel salts, reducing agents, coupling agents and nucleating agent in aqueous solution. The morphology of the nanoparticles can be well controlled by adjusting the reaction parameters. The average size of these nanoparticles is about 100 nm and extremely uniform. These nickel nanoparticles possess uniform cone-shape surface structure, which can provide excellent interconnection ability among themselves. Results show that, the thermal conductivity of the sample which nickel filler content of about 80 wt% embedded in a thermosetting-type insulating polymer resin reached 0.49 W·m−1·K−1. Due to the unique durian-like morphology, facile and efficiency synthetic method, and prominent thermal conductivity, the nickel nanoparticles can be widely used in some relatively low-end and large-scale applications of heat conductivity, such as high-power electrical heat sink, LED plastic shell, wireless signal base station.