Synthesis Of Nanoparticles Via Microreactor Method And Research On Their Electrochemical Performance

The preparation of energy-storage materials plays an important role in the field of energy research.However,traditional preparation strategies for energy-storage materials involve multi-step synthetic,time-consuming processes and cannot produce products in massive,hindering their practical application.Herein,we take full of the advantages of the confined impingement jet mixer in turbulence and laminar flow to design and prepare three types of energy-storage materials.The effects of micro-mixing on morphology,micro-structure,and electrochemical performance of materials are explored:1.This work demonstrates scalable and continuous flow production of sulfur nanoparticles?SNPs?using a confined impingement jet mixer?CIJ?.Sizes and morphology of SNPs can be easily controlled by varying micro-mixing degree.Using high feed speed equal to 110 mL/min,spherical composites containing SNPs covered with polyvinylpyrrolidone?S@PVP?with uniform morphology and average diameter?400 nm?were obtained.These composites were tested as active cathode materials for Li-S batteries.Cathodes containing S@PVP composites exhibited high initial capacity equal to 1030.7 mA h/g.After 50 cycles at C/10,capacity was807.7 mA h/g.Such excellent capacity and capacity retention were attributed to small size and homogeneous dispersion of SNPs as well as conducting PVP layer,which provided effective multidimensional electron and ion transport pathways.PVP layer also mitigated problem associated with volume expansion typically occurring during battery cycling.Simplicity and scalability of the method proposed in this work give it a very strong potential for large-scale continuous fabrication of SNPs for Li-S rechargeable batteries.2.NiAl Layered Double Hydroxide?NiAl-LDH?with tunable interlayer space is first in situ synthesized using a confined impinging jets microreactor?CIJ?.It is found that CIJ allows simultaneous guests?water molecules and carbonate?intercalation and in situ growth of NiAl-LDH by imposing a proper micro-mixing scale in a space-confined mixing chamber.The final interlayer spacing of NiAl-LDH can be easily regulated from 0.9 to 3.6 by tuning the Reynolds number flows range 4.8*10³ to 6.7*10².Supercapacitor has been chosen as a model reaction to investigate the electrochemical activity of NiAl-LDHs.Results demonstrate that higher interlayer space increases the electrochemical activity and enhances supercapacitor performances due to improvement in space accessibility of NiAl-LDHs during faradaic redox reaction.NiAl-LDH with the interlayer space up to 3.6 nm presents fairly good performance as supercapacitor electrode material in terms of specific capacitance(1285.2 F·g^-1 at 1 A·g^-1)and stability?capacitance retention rates over 80%after 5000 cycles?.This work develops a rapid and continuous flow methodology for one-pot,in situ formation of NiAl-LDH with controlled interlayer spacing via microreactor technology.3.Ni_xCo_1-x-x oxides nanoparticles have been successfully synthesized via a facile and scalable CIJ followed by a simple post annealing process.The process involves the synthesis of the bimetallic?Ni,Co?hydroxide in a space-confined microreactor?CIJ?and subsequent followed by a post-annealing process for transformation to Ni_xCo_1-x oxides.It was found that the composition,micro-structure and electrochemical behavior of porous Ni_xCo_1-x-x oxides can be readily manipulated by simply varying the Ni/Co molar ratio in CIJ.As the molar ratio of the Ni/Co decreasing,the composition of Ni_xCo_1-x oxide was gradually changed from monometallic oxide?NiO?to bimetallic?Ni,Co?oxide and finally to monometallic oxide?Co?.When the molar ratio of Ni/Co was appropriate in CIJ?Ni/Co=3:1?,the corresponding Ni_x Co_1-x oxide?NiCo₂O₄?as electrode shows a large specific capacitance of 840 F·g^-1 at 1 A·g^-1 and83%of rate retention after 10000 cycles can be retained at a high current density of 5 A·g^-1.The superior electrochemical behavior should be attributed to their unique porous architecture,facilitating the electron and ion transport,as well as bimetallic oxide?Ni,Co?shows higher electrical conductivity in redox reactions.To further assess its practical application,an asymmetric supercapacitor based on the NiCo₂O₄ electrode as a positive electrode was fabricated and the asymmetric device delivers a prominent energy density of 41 W h?kg^-1 at a power density of 142 W?kg^-1,which holds great promise for potential applications in energy storage.