The Design Of Porous Carbon Materials With Microstructure And The Research For Their Application In Electrochemical Energy

Fabricating devices for high-performance energy storage has great importance for the advancement of electrical vehicles and renewable energy. Currently, carbon is recognized as the leading electrode material for anodes of commercial lithium-ion batteries(LIBs) and electrochemical supercapacitors due to its low cost, high electrical conductivity, good chemical stability, environmental friendliness and long cycling life. Unfortunately, most common graphitic carbons have relatively low theoretical capacity(372 mA h/g) and poor rate performance, and not meet to the requirement of high energy and power LIBs.As for electrical double layer capacitors(EDLCs), commercially available activated carbons(ACs) offer limited control over specific surface area, conductivity, pore size distribution(PSD) and porosity, suffering from the limitations of commercial supercapacitors(5Wh/kg). Therefore, there is a critical need to develop new and advanced carbon based materials with enhanced characteristics(hierarchical pores, 2D-nanostructures, high speci?c surface area(SBET), heteroatom modification, high electrical conductivity,etc.) through a facile synthesis route for highly efficient energy storage devices. 1. A co-sol-emulsion-gel synthesis of tunable and uniform hollow carbon nanosphereswith interconnected mesoporous forelectrochemical energyWe have synthesized monodispersed hollow polymer-silica and carbon-silica nanocomposites spheres with “interpenetration twins” by using one-step co-sol-emulsion-gel method. As-obtained mesoporous hollow carbon nanospheres(MHCSs) possess features:(i) open interconnected mesoporous shell, endowing high specific surface area(2106-2225 m2/g) and large pore volume(1.95-2.53 cm3/g);(ii) open large mesoporous channels(>5nm);(iii) highly uniform and precisely tuneable particle size(90-240 nm) and shell thickness;(iv) hierarchical nanostructures within-interconnected hollow core/mesoporous shell;(v)high dispersibility in media. The MHCSs remarkable structural characteristics are accommodated by studying their high-rate electrochemical performance. Interesting, the diameter of the uniform MHCSs could be precisely tuned on demand, as an effective electrode materials in supercapacitors, MHCSs with the diameter of ca. 90 nm deliver the shortest time constant(τ0=0.75 s), which are highly beneficial for rate capacitance(180 F/g @ 100 A/g) and cyclic retainability(3% loss after 20000 cycles). The new developed synthesis route leads to unique interconnected mesoporous hollow carbonaceous spheres with open-framework structures, providing a new materials platform in energy storage. This “interpenetration twins” mesostructure design strategy can also be applied to preparation of well-defined interconnected porous hollow spheres materials,e.g.,silica, polymers and a wide range of nanocomposites. Our synthesized polymer, silicon dioxide and carbon spheres are important for various applications including electrode materials, photonics, adsorbents, catalyst loading and multi-drug delivery applications. 2. From Rice Bran to High Energy Density Supercapacitors andLithium ion batteries : ANew Route to Control Porous Structure of 3D Carbon We have reported a new route to produce honeycomb-like 3D porous carbon via carbonization and activation of rice brans precursors. The as-prepared material can be used in advanced EDLCs systems. The rate of activator agent and RB have a signi?cant in?uence on the texture parameters, which make further impact on the different capacitance behavior of these RBC. Activate process at a high weight ratio of KOH/RB(4:1) results in enhanced surface area of RBC and the broadening of the pore size distribution through the formation of additional pores of 0.52–3.85 nm. The increase in mesoporosity facilitates the diffusion rate of electrolyte ions and is bene?cial for electrical conductivity. These superior characteristics could result in high electrochemical performances; RBC-4 s for supercapacitors displaying a speci?c capacitance of 265 Fg-1at large current densities of 10 A g-1in aqueous electrolytes, a stable cycle life over 10 000 cycle, a speci?c energy of 70 Wh kg-1, a speci?c power of 1223 W kg-1 in ionicliquid. The approach developed in this work will open the new avenue for designing and producing a variety of novel materials with great promising applications in highperformance energy storage devices. 3. Hierarchical Porous Nitrogen-Doped Carbon Nanosheets Derived from Silk for Ultrahigh-Capacity Battery Anodes and SupercapacitorsHierarchical porous nitrogen-doped carbon(HPNC) nanosheets(NS) have been prepared via simultaneous activation and graphitization of biomass-derived natural silk. The as-obtained HPNC-NS show favorable features for electrochemical energy storage such as high speci?c surface area(SBET: 2494 m2/g), high volume of hierarchical pores(2.28 cm3/g), nanosheets structures, rich N-doping(4.7 %) and defects. With respect to the multiple synergistic effects of these features, a lithium-ion battery anode and two electrode-based supercapacitors has been prepared. A reversible lithium storage capacity of 1865 mA h/g have been reported, which is the highest for N-doped carbon anode materials to the best of our knowledge. The HPNC-NS supercapacitors electrode in ionic liquid electrolytes exhibit a capacitance of 242 F/g and energy density of 102 W h/kg(48 W h/L), with high cycling life stability(9 % loss after 10000 cycles).Ragone plot for symmetrical HPNC-NS supercapacitorsdepicts that specific energy density is about 90.0 Wh/kg(42.3Wh/L) at power densities of 875 W/kg(~370 s), while the energy density remains as high as 52.5 Wh/kg(24.7 Wh/L)at power densities 8750 W/kg( 22 s).Thus, a high-performance Li-ion battery and supercapacitors were successfully assembled for the same electrode material which was obtained through one-step and facile large-scale synthesis route. It is promising for next generation hybrid energy storage and renewable delivery devices.