Ruiqing Liu

Morphology-dependent performance of CuO anodes via facile and controllable synthesis for lithium-ion batteries.

Nanostructured CuO anode materials with controllable morphologies have been successfully synthesized via a facile and environmentally friendly approach in the absence of any toxic surfactants or templates. In particular, leaf-like CuO, oatmeal-like CuO, and hollow-spherical CuO were obtained by changing the ligand agents. The structures and electrochemical performance of these as-prepared CuO were fully characterized by various techniques, and the properties were found to be strongly dependent on morphology. As anode materials for lithium-ion batteries, the leaf-like CuO and oatmeal-like CuO electrodes exhibit relatively high reversible capacities, whereas hollow-spherical CuO shows enhanced reversible capacity after initial degradation. Furthermore, an excellent high rate capability was obtained for the leaf-like CuO and hollow-spherical CuO electrodes. These results may provide valuable insights for the development of nanostructured anodes for next-generation high-performance lithium-ion batteries.

Graphene/Fe2O3/SnO2 Ternary Nanocomposites as a High-Performance Anode for Lithium Ion Batteries

We report an rGO/Fe2O3/SnO2 ternary nanocomposite synthesized via homogeneous precipitation of Fe2O3 nanoparticles onto graphene oxide (GO) followed by reduction of GO with SnCl2. The reduction mechanism of GO with SnCl2 and the effects of reduction temperature and time were examined. Accompanying the reduction of GO, particles of SnO2 were deposited on the GO surface. In the graphene nanocomposite, Fe2O3 nanoparticles with a size of ∼20 nm were uniformly dispersed surrounded by SnO2 nanoparticles, as demonstrated by transmission electron microscopy analysis. Due to the different lithium insertion/extraction potentials, the major role of SnO2 nanoparticles is to prevent aggregation of Fe2O3 during the cycling. Graphene can serve as a matrix for Li+ and electron transport and is capable of relieving the stress that would otherwise accumulate in the Fe2O3 nanoparticles during Li uptake/release. In turn, the dispersion of nanoparticles on graphene can mitigate the restacking of graphene sheets. As a result, the electrochemical performance of rGO/Fe2O3/SnO2 ternary nanocomposite as an anode in Li ion batteries is significantly improved, showing high initial discharge and charge capacities of 1179 and 746 mAhg(-1), respectively. Importantly, nearly 100% discharge-charge efficiency is maintained during the subsequent 100 cycles with a specific capacity above 700 mAhg(-1).

Copper Mesh Templated by Breath-Figure Polymer Films as Flexible Transparent Electrodes for Organic Photovoltaic Devices

UNLABELLED Metal mesh is a significant candidate of flexible transparent electrodes to substitute the current state-of-the-art material indium tin oxide (ITO) for future flexible electronics. However, there remains a challenge to fabricate metal mesh with order patterns by a bottom-up approach. In this work, high-quality Cu mesh transparent electrodes with ordered pore arrays are prepared by using breath-figure polymer films as template. The optimal Cu mesh films present a sheet resistance of 28.7 Ω·sq(-1) at a transparency of 83.5%. The work function of Cu mesh electrode is tuned from 4.6 to 5.1 eV by Ag deposition and the following short-time UV-ozone treatment, matching well with the PEDOT PSS (5.2 eV) hole extraction layer. The modified Cu mesh electrodes show remarkable potential as a substitute of ITO/PET in the flexible OPV and OLED devices. The OPV cells constructed on our Cu mesh electrodes present a similar power conversion efficiency of 2.04% as those on ITO/PET electrodes. The flexible OLED prototype devices can achieve a brightness of 10 000 cd at an operation voltage of 8 V.

Self-propelled manganese oxide-based catalytic micromotors for drug delivery

A manganese oxide-based catalytic tubular micromotor (PEDOT/MnO2) is described that displays effective autonomous motion in hydrogen peroxide with high speed (318.80 µm s−1) and can operate in very low levels of fuel, down to 0.4%. The polymer bilayer micromotor also exhibits efficient locomotion in different biological media including bovine serum albumin and bovine serum. Moreover, the micromotor is applied to deliver a chemotherapeutic anticancer drug, camptothecin, using electrostatic interactions, offering considerable potential for diverse clinical and biomedical applications such as drug delivery for theranostic microsystems.

Towards free-standing MoS2 nanosheet electrocatalysts supported and enhanced by N-doped CNT–graphene foam for hydrogen evolution reaction

Large-scale free-standing porous carbon-based catalyst supports are critically needed for the hydrogen evolution reaction (HER) in view of their practical application. In this work, MoS2 nanosheets were uniformly deposited onto N-doped carbon nanotube–graphene (N-CNT–G) hybrids, forming a three-dimensional (3D) free-standing architecture. The designed 3D hybrid materials exposed the MoS2 nanosheet catalyst on the one-dimensional CNTs and there was facilitated ion transportation because of the porous graphene foam, and these 3D hybrid materials were used as electrocatalysts for HER directly without any transferring process. Moreover, N doping decreased the overpotential to 0.08 V, which increased the stability and promoted the catalytic activity, providing a facile route to design advanced high-performance HER catalysts towards a free-standing configuration.

Hierarchical dispersed multi-phase nickel cobalt oxide mesoporous thorn microspheres as superior rate anode materials for lithium ion batteries

Hierarchical nickel cobalt oxide (NCO) microspheres comprised of nanoscale mesoporous thorn arrays are developed as superior rate high capacity anodes in this work, i.e. 1063.3 and 860 mA h g−1 at 180 and 4500 mA g−1, respectively. Stoichiometric urea serves as a self-template to favor the self-assembly of well-organized NiCo(OH)2CO3 thorn microsphere precursors under an optimized hydrothermal reaction. The dispersed multi-phase hybrid crystal structure and the favorable specific surface area obtained during the controlled pyrolysis of NiCo(OH)2CO3 microspheres markedly promote the cyclic stability of the single phase Ni1.5Co1.5O4.

High rate Li-ion storage properties of MOF-carbonized derivatives coated on MnO nanowires

Recently, metal–organic framework (MOF) derived porous carbon-based composites have become one of the most advanced electrode materials for high performance energy storage systems. In this work, zeolitic imidazolate framework (ZIF) types of MOF strung by MnO2 NWs, forming an interesting structure like Chinese candied hawthorn fruit on a stick, are used as precursors to prepare C/Co-coated MnO nanowires (C/Co-MnO NWs). It is interesting and exciting to observe that the simultaneously formed carbon coating derived from the ZIFs significantly promotes the cyclic and rate performances of manganese oxide because of the synergistic effect of the highly conductive uniform carbon coating and the high capacity contribution from the MnO NWs. The obtained C/Co-MnO NWs could deliver 848.4 and 718 mA h g−1 at 500 and 5000 mA g−1 after 40 charge/discharge cycles, respectively, which is superior to other reported MOF-derived nanostructured materials, and makes it a very promising candidate anode material for future high-power lithium ion batteries.

Industrially weavable metal/cotton yarn air electrodes for highly flexible and stable wire-shaped Li–O2 batteries

Li–O2 batteries feature extremely high energy density, making their wire-shaped devices a promising candidate for wearable energy-storage application. However, it is a major challenge to explore industrially feasible electrodes for this type of linear batteries. Herein, for the first time, we have demonstrated an effective strategy to fabricate a feasible electrode on a large scale by dyeing industrially weavable and highly conductive metal/cotton yarns with the active material ink, RuO2-coated nitrogen-doped carbon nanotube (CNT). The obtained wire-shaped Li–O2 battery exhibits a high discharge capacity of 1981 mA h gcarbon−1 at a current density of 320 mA gcarbon−1 and could stably work beyond 100 cycles (more than 600 hours) without obvious degradation, even under bending conditions. The new freestanding type electrode will represent a critical step towards the production and practical application of flexible Li–O2 batteries.

Flexible all-solid-state micro-supercapacitor based on Ni fiber electrode coated with MnO 2 and reduced graphene oxide via electrochemical deposition

Flexible and micro-sized energy conversion/ storage components are extremely demanding in portable and multifunctional electronic devices, especially those small, flexible, roll-up and even wearable ones. Here in this paper, a two-step electrochemical deposition method has been developed to coat Ni fibers with reduced graphene oxide and MnO2 subsequently, giving rise to Ni@reduced-graphene-oxide@MnO2 sheath-core flexible electrode with a high areal specific capacitance of 119.4 mF cm−2 at a current density of 0.5 mA cm−2 in 1 mol L−1 Na2SO4 electrolyte. Using polyvinyl alcohol (PVA)- LiCl as a solid state electrolyte, two Ni@reduced-grapheneoxide@ MnO2 flexible electrodes were assembled into a freestanding, lightweight, symmetrical fiber-shaped micro-supercapacitor device with a maximum areal capacitance of 26.9 mF cm−2. A high power density of 0.1W cm−3 could be obtained when the energy density was as high as 0.27 mW h cm−3. Moreover, the resulting micro-supercapacitor device also demonstrated good flexibility and high cyclic stability. The present work provides a simple, facile and low-cost method for the fabrication of flexible, lightweight and wearable energy conversion/storage micro-devices with a high-performance.摘要便携式及多功能电子设备的不断进步要求为其提供动力能量的存储与转换器件向尺寸小、柔性、能够卷曲甚至可穿戴方向发展. 本文采用两步电化学沉积法依次将还原氧化石墨烯(rGO)和MnO2沉积到镍纤维上得到Ni@rGO@MnO2壳核结构的柔性电极. 该电极在 1 mol L−1 Na2SO4 电解液中电流密度为0.5 mA cm−2时面积比电容为119.4 mF cm−2. 以PVA-LiCl为固态电解液, 将两根Ni@rGO@MnO2电 极组装成自支撑、质轻、对称的纤维状微型超级电容器, 最大面积比电容为26.9 mF cm−2, 能量密度高达0.1 W cm−3 (0.27 mW h cm−3). 此 外, 该微型超级电容器还展现了良好的柔性和循环性能. 这项研究工作主要提供了一种简单、易操作、低成本的制备柔性、质轻、可穿 戴的高性能能量存储设备的方法.

Bimetal-organic-framework derived CoTiO 3 mesoporous micro-prisms anode for superior stable power sodium ion batteries

Durability, rate capability, capacity and tap density are paramount performance metrics for promising anode materials, especially for sodium ion batteries. Herein, a carbon free mesoporous CoTiO3 micro-prism with a high tap density (1.8 g cm−3) is newly developed by using a novel Co-Ti-bimetal organic framework (BMOF) as precursor. It is also interesting to find that the Co-Ti-BMOF derived carbon-free mesoporous CoTiO3 micro-prisms deliver a superior stable and more powerful Na+ storage than other similar reported titania, titanate and their carbon composites. Its achieved capacity retention ratio for 2,000 cycles is up to 90.1% at 5 A g−1.摘要负极材料的循环、 倍率、 容量和堆积密度是评价钠离子电池性能的关键指标. 为此本工作开发了一种新型的钴-钛双金属-有机框架结构材料并以其作为前躯体衍生制备了具有1.8 g cm−3高堆积密度的无碳介孔钛酸钴微米棱柱状材料. 作为钠离子电池负极材料该种材料展示了超高稳定性同时拥有比其他类似的钛氧化物、 钛酸盐及其碳基复合材料更优异的倍率性能, 其在5 A g−1的电流密度下循环2000圈后容量保持率高达90.1%.