Preparations and Electrochemical Properties of BC/CoNi2S4@PPy Flexible Composites for Supercapacitors

本文采用溶剂热、原位聚合和真空抽滤相结合的方法制备了用于超级电容器的细菌纤维素/镍钴硫化物/聚吡咯(BC/CoNi2S4@PPy)柔性电极材料,通过X射线衍射、场发射扫描电镜、红外光谱、氮气吸脱附、拉伸强度和接触角表征了材料的形貌结构、组成、机械性能和亲水性,并采用循环伏安法和恒电流充放电测试了复合材料的电化学性能。结果表明,表面含氧官能团丰富的BC纤维网络结构对氧化还原活性物质CoNi2S4的生长和导电聚合物PPy的分布具有引导作用,CoNi2S4均匀分布在BC网络中,且PPy均匀包覆在BC纤维和CoNi2S4纳米球表面构成具有丰富孔隙结构的三维导电网络,使得该复合材料具有较好的机械性(抗拉强度达28.0±0.1 MPa)、亲水性(对6 mol·L-1 KOH的瞬间接触角为43.6°)及良好的导电性。该电极材料在1 A·g-1下比电容高达2670 F·g-1,充放电循环10000次后比电容的保持率为82.73%,且经1000次反复弯曲后电化学性能保持不变。此外,将其与活性炭组成的非对称超级电容器,在1 A·g-1下比电容为1428 F·g-1,最高能量密度和功率密度分别达49.8 Wh·kg-1和741.8 W·kg-1。Flexible supercapacitor is one of the most promising energy storage devices for portable and wearable electronic products due to its advantages of high power density, fast charging and long cycle life. Therefore, self-supporting flexible electrode materials with high performance have attained more and more attention both in academia and in industry recently. In this work, using bacterial cellulose (BC) as a flexible substrate, the bacterial cellulose/nickel-cobalt sulfide@polypyrrole (BC/CoNi2S4@PPy) flexible composites with three-dimensional porous network and good conductivity were prepared by a combined solvothermal-in-situ polymerization-vacuum filtration method. The samples were characterized by X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectrometry, N2 physisorption, tensile strength and contact angle measurements. Their electrochemical performances were tested by cyclic voltammetry, galvanostatic charge/discharge testing and electrochemical impedance spectroscopy. The results show that the three-dimensional porous network of BC fibers with rich oxygen-containing surface groups play a guiding role in the growth of the redox active material CoNi2S4 and the distribution of conductive polymer PPy, resulting in uniformly distributed CoNi2S4 nanospheres in the network of BC fibers, both coated evenly with a layer of conductive PPy. The resulting BC/CoNi2S4@PPy composites, a three-dimensional conductive network with high porosity, displayed good mechanical property (tensile strength up to 28.0±0.1 MPa), hydrophilicity (the instantaneous contact angle in 6 mol·L-1 KOH is 43.6°), as well as excellent electrochemical performance. The specific capacitance of the flexible BC/CoNi2S4@PPy was 2670 F·g-1 at 1 A·g-1 in a three-electrode system, and retained 82.7% after 10000 charge and discharge cycles. In addition, the electrochemical performance remained unchanged after 1000 times of repeated bending. In an asymmetric supercapacitor composed of BC/CoNi2S4@PPy and activated carbon, the area specific capacitance was 1428 F·g-1 at 1 A·g-1. The asymmetric supercapacitor achieved the maximum energy density of 49.8 Wh·kg-1 and power density of 741.8 W·kg-1.国家重点基础研究发展计划项目(2014CB239702);国家自然科学基金项目(21676082)通讯作者:周静红E-mail:[email protected]:Jing-HongZhouE-mail:[email protected]华东理工大学化工学院,上海 200237School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, Chin

Simulating fluid within elastic pipe(弹性管道约束下的流体仿真)

Research on simulating the interaction of fluids in elastic pipes is a significant topic in the field of physical simulation. In this paper, we adopt position based dynamics to achieve high controllability and real-time performance. A hybrid approach is employed, using particles to simulate fluids, allowing for a more flexible representation of continuously flowing fluids while using triangular meshes to model pipes, enabling the establishment of overall elastic constraints. This approach comprehensively considers collisions within the pipe, ensuring the non-penetrative interaction between fluids and pipes, resulting in a realistic and closely coupled simulation. Additionally, elastic constraints are introduced to endow the pipe with specific elastic properties, and GPU parallel computing is utilized to accelerate the simulation. Experimental results indicate that the proposed approach is suitable for simulating particle-based fluids and triangular mesh-based pipes, providing an effective solution for simulating fluid flow within elastic pipes.(模拟流体和弹性管道之间的交互是物理仿真领域的重要研究方向。基于位置动力学方法进行了模拟，得到了高可控性和实时性结果。采用混合模型，其中，粒子模型用于流体建模，灵活模拟流动的流体；三角形网格模型用于管道建模，建立管道的弹性约束。全面考虑流体在管道内的碰撞情况，确保无穿透，实现流体与管道的紧密交互仿真。引入弹性管道约束，赋予管道一定的弹性特性，并利用GPU进行并行计算提升仿真速度。实验结果表明，所提算法适用于基于粒子的流体与基于三角形网格的管道的仿真，为弹性管道的流体仿真提供了有效的解决方案。