Jian Zhu

NiMoO4 nanowires supported on Ni foam as novel advanced electrodes for supercapacitors

NiMoO4 nanowires (NWs) supported on Ni foam were fabricated via a template-free hydrothermal route, and could be directly used as integrated electrodes for electrochemical capacitors (ECs). Such unique integrated architectures exhibited remarkable electrochemical performance with high capacitance, excellent rate capability and desirable cycle life at high rates.

Atomic-Scale Control of Silicon Expansion Space as Ultrastable Battery Anodes

Development of electrode materials with high capability and long cycle life are central issues for lithium-ion batteries (LIBs). Here, we report an architecture of three-dimensional (3D) flexible silicon and graphene/carbon nanofibers (FSiGCNFs) with atomic-scale control of the expansion space as the binder-free anode for flexible LIBs. The FSiGCNFs with Si nanoparticles surrounded by accurate and controllable void spaces ensure excellent mechanical strength and afford sufficient space to overcome the damage caused by the volume expansion of Si nanoparticles during charge and discharge processes. This 3D porous structure possessing built-in void space between the Si and graphene/carbon matrix not only limits most solid-electrolyte interphase formation to the outer surface, instead of on the surface of individual NPs, and increases its stability but also achieves highly efficient channels for the fast transport of both electrons and lithium ions during cycling, thus offering outstanding electrochemical performance (2002 mAh g(-1) at a current density of 700 mA g(-1) over 1050 cycles corresponding to 3840 mAh g(-1) for silicon alone and 582 mAh g(-1) at the highest current density of 28u202f000 mA g(-1)).

Bacteria Absorption-Based Mn2P2O7-Carbon@Reduced Graphene Oxides for High-Performance Lithium-Ion Battery Anodes.

The development of freestanding flexible electrodes with high capacity and long cycle-life is a central issue for lithium-ion batteries (LIBs). Here, we use bacteria absorption of metallic Mn(2+) ions to in situ synthesize natural micro-yolk-shell-structure Mn2P2O7-carbon, followed by the use of vacuum filtration to obtain Mn2P2O7-carbon@reduced graphene oxides (RGO) papers for LIBs anodes. The Mn2P2O7 particles are completely encapsulated within the carbon film, which was obtained by carbonizing the bacterial wall. The resulting carbon microstructure reduces the electrode-electrolyte contact area, yielding high Coulombic efficiency. In addition, the yolk-shell structure with its internal void spaces is ideal for sustaining volume expansion of Mn2P2O7 during charge/discharge processes, and the carbon shells act as an ideal barrier, limiting most solid-electrolyte interphase formation on the surface of the carbon films (instead of forming on individual particles). Notably, the RGO films have high conductivity and robust mechanical flexibility. As a result of our combined strategies delineated in this article, our binder-free flexible anodes exhibit high capacities, long cycle-life, and excellent rate performance.

A hyperaccumulation pathway to three-dimensional hierarchical porous nanocomposites for highly robust high-power electrodes

Natural plants consist of a hierarchical architecture featuring an intricate network of highly interconnected struts and channels that not only ensure extraordinary structural stability, but also allow efficient transport of nutrients and electrolytes throughout the entire plants. Here we show that a hyperaccumulation effect can allow efficient enrichment of selected metal ions (for example, Sn2+, Mn2+) in the halophytic plants, which can then be converted into three-dimensional carbon/metal oxide (3DC/MOx) nanocomposites with both the composition and structure hierarchy. The nanocomposites retain the 3D hierarchical porous network structure, with ultrafine MOx nanoparticles uniformly distributed in multi-layers of carbon derived from the cell wall, cytomembrane and tonoplast. It can simultaneously ensure efficient electron and ion transport and help withstand the mechanical stress during the repeated electrochemical cycles, enabling the active material to combine high specific capacities typical of batteries and the cycling stability of supercapacitors.

Large-scale production of silicon nanoparticles@graphene embedded in nanotubes as ultra-robust battery anodes

The nanosized silicon for lithium-ion batteries (LIBs) is mainly limited by cracking and pulverization caused by the large volume change during deep cycles. Here, we demonstrated a commercial viability (scalable synthesis) of Si nanoparticles@graphene encapsulated in titanium dioxide nanotubes (Si@G@TiO2NTs) or carbon nanotubes (Si@G@CNTs) for the next generation of high-energy battery anodes. The nanotubes can not only provide strong protection and sufficient void space to buffer the huge volume expansion of Si nanoparticles during the charge/discharge process, but also enforce a most solid-electrolyte interphase to form on the outer surface of the nanotube instead of on individual Si nanoparticles, leading to ultrahigh coulombic efficiency and excellent cycling stability. The obtained Si@G@TiO2NT and Si@G@CNT electrodes showed a high reversible capacity of 1919.2 mA h g−1 (1.02 mA h cm−2) after 800 cycles and 2242.2 mA h g−1 (1.19 mA h cm−2) after 1000 cycles (>1 year) at the constant current density of 500 mA g−1, respectively. Furthermore, both Si@G@TiO2NT and Si@G@CNT electrodes presented superior average coulombic efficiency more than 99.9% during the whole cycling process.

Humidity sensors based on graphene/SnOx/CF nanocomposites

In this study, we investigated the nanocomposites composed of graphene, SnOx and carbon fibers (CFs) for humidity sensing applications. The composites were obtained by an electrospinning method followed by addition of graphene. SnOx/CFs uniformly dispersed into graphene nanosheets. SnOx and graphene were proved to be promising sensing materials. The amorphous carbon fibers could supply more channels for transportation of protons or electrons. Therefore, the composites exhibited high humidity sensing performance. The resistance of the sensor increases two times with decreasing relative humidity from 55% to 30%. The sensitivity to humidity increased by almost 100% after adding graphene to SnOx/CF nanocomposites. The response and recovery times were 8 s and 6 s at 30% RH, respectively. The results demonstrated that rational design of nanocomposites with graphene could be a favorable strategy to improve humidity sensing properties.

RuO2@Co3O4 heterogeneous nanofibers: a high-performance electrode material for supercapacitors

Novel RuO2@Co3O4 heterogeneous nanofibers (HNFs) were synthesized by a simple electrospinning method, followed by calcination. The possible mechanism of formation of RuO2@Co3O4 HNFs is presented. The synergy between RuO2 and Co3O4 and the unique feature of heterostructure allow the composite to exhibit a high reversible capacity of 1103.6 F g−1 at a current density of 10 A g−1 and a high-rate capability of 500.0 F g−1 at a current density of 100 A g−1. Moreover, excellent cycling performance was observed, where the capacities could be maintained at 93.0%, 91.8%, and 88.0% after 1000, 2000 and 5000 cycles, respectively, at a current density of 10 A g−1. This study therefore confirms that the as-prepared RuO2@Co3O4 HNFs can serve as advanced supercapacitor (SCs) materials. It is highly anticipated that this simple method of electrospinning can be extended to preparing other new types of heterostructural materials that could be used in the field of electrochemical energy storage.