Enabling Multi-Chemisorption Sites on Carbon Nanofibers Cathodes by an In-situ Exfoliation Strategy for High-Performance Zn–Ion Hybrid Capacitors

Carbon nanofibers films are typical flexible electrode in the field of energy storage,but their application in Zinc-ion hybrid capacitors(ZIHCs)is limited by the low energy density due to the lack of active adsorption sites.In this work,an in-situ exfoliation strategy is reported to modulate the chemisorption sites of carbon nanofibers by high pyridine/pyrrole nitrogen doping and carbonyl functionalization.The experimental results and theoretical calculations indicate that the highly electronegative pyridine/pyrrole nitrogen dopants can not only greatly reduce the binding energy between carbonyl group and Z n2+by inducing charge delocalization of the carbonyl group,but also promote the adsorption of Zn2+by bonding with the carbonyl group to form N–Zn–O bond.Benefit from the multiple highly active chemisorption sites generated by the synergy between carbonyl groups and pyridine/pyrrole nitrogen atoms,the resulting carbon nanofibers film cathode displays a high energy density,an ultralong-term lifespan,and excellent capacity reservation under commercial mass loading(14.45 mg cm-2).Particularly,the cathodes can also operate stably in flexible or quasi-solid devices,indicating its application potential in flexible electronic products.This work established a universal method to solve the bottleneck problem of insufficient active adsorption sites of carbon-based ZIHCs.Imoproved should be changed into Improved.

Research of Supercritical CO2 Fluid Refined Natural Borneol

In this study, with borneol fragments in the crystallized mother liquor of natural borneol used as the raw materials, supercritical carbon dioxide method is adopted for refining to get high purity borneol. The result of the experiment shows that the yield and purity are excellent with an extraction pressure of 11 MPa, an extracting temperature of 40°C, a carbon dioxide flow rate of 25 L·h-1 and an extraction time of 20 minutes. After detected by gas chromatography, the purity of the crystallization products could reach 96%.

Design of Flexible Films Based on Kinked Carbon Nanofibers for High Rate and Stable Potassium-Ion Storage

With the emergence of wearable electronics,flexible energy storage materials have been extensively studied in recent years.However,most studies focus on improving the electrochemical properties,ignoring the flexible mechanism and structure design for flexible electrode materials with high rate capacities and long-time stability.In this study,porous,kinked,and entangled network structures are designed for highly flexible fiber films.Based on theoretical analysis and finite element simulation,the bending degree of the porous structure(30%porosity)increased by 192%at the micro-level.An appropriate increase in kinking degree at the meso-level and contact points in entanglement network at the macro-level are beneficial for the flexibility of fiber films.Therefore,a porous and entangled network of sulfur-/nitrogen-co-doped kinked carbon nanofibers(S/N-KCNFs)is synthesized.The nanofiber films synthesized from melamine as nitrogen sources and segmented vulcanization exhibited a porous,kinked,and entangled network structure,and the stretching degree increased several times.The flexible S/N-KCNFs anode delivered a higher rate performance of 270 mAh g−1 at a current density of 2000 mA g−1 and a higher capacity retention rate of 93.3%after 2000 cycles.Moreover,the foldable pouch cell assembled by potassium-ion hybrid supercapacitor operated safely at large-angle bending and showed long-time stability of 88%capacity retention after 4000 cycles.This study provides a new idea and strategy for the flexible structure design of high-performance potassium-ion storage materials.

Designing g-C_(3)N_(4)/N-Rich Carbon Fiber Composites for High-Performance Potassium-Ion Hybrid Capacitors

Potassium-based energy storage devices(PEDS)are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte.although carbon materials show great potential for potassium-ion storage,poor rate performance,and unsatisfactory cycle lifespan in existing carbon-based PIBs anode,it also cannot match the dynamics and stability of the capacitor cathode.Nitrogen doping has been proven to be a effective modification strategy to improve the electrochemical performance of carbon materials.Hence,we prepare carbon nanofibers and g-C_(3)N_(4)composites with high nitrogen contents(19.78 at%);moreover,the sum of pyrrolic N and pyridinic N is up to 59.51%.It achieves high discharge capacity(391 m Ah g^(-1)at0.05 A g^(-1)),rate capacity(141 m Ah g^(-1)at 2 A g^(-1)),and long cycling performance(201 m Ah g^(-1)at 1 A g^(-1)over 3000 cycles)when as an anode for PIBs.Furthermore,it can deliver promising discharge capacity of132 m Ah g^(-1)at 0℃.Moreover,as battery anode for potassium-ion hybrid capacitors(PIHC)device with an active carbon cathode,it delivers energy/power density(62 and 2102 W kg^(-1))as well as high reversible capacity(106 m Ah g^(-1)at 1 A g^(-1)).

具有异质结构的多功能氧化石墨烯改性纳米纤维膜(ZnS-CoS@GO@CNFs)用于长期稳定的钾离子储存

过渡金属硫化物作为钾离子电池的高理论容量阳极,由于其电导率低、循环过程体积膨胀大,导致其倍率性能和循环稳定性较差.本文采用氧化石墨烯(GO)来控制纳米颗粒在纤维中的粒径和分布,以提高复合纤维的导电性和拉伸变形.此外,由异质结构和氧化石墨烯组成的三维导电碳网络(ZnS-CoS@GO@CNFs)可以加速钾离子储存的动力学并稳定钾离子储存.作为钾离子电池的阳极材料,该复合材料在3 A g^(−1)下具有210 mA h g^(−1)的优异倍率性能.在2 A g^(−1)的大电流下经历2800次循环后仍表现出171 mA h g^(−1)的容量,容量保持率为97.7%.此外,当纳米纤维膜用作自支撑阳极时,仍然可以保持稳定的容量输出(在0.1 A g^(−1)下100次循环后容量为302 mA h g^(−1)).由钾离子混合电容器组装的可折叠袋状电池在多角度重复弯曲和最终恢复的情况下仍然可以安全地工作,并且可以提供大的能量密度(134 W h kg^(−1))和功率密度(5815 W kg^(−1)).优异的电化学性能进一步揭示了多功能氧化石墨烯复合纤维膜的应用前景.

碳纤维中可控修饰FeV_(2)S_(4)及其高容量长寿命储钠研究

拥有高比容量的金属硫化物作为负极材料在钠离子电池(SIBs)领域备受关注.FeV_(2)S_(4)作为一种典型的金属硫化物,由于体积变化大,存在容量衰减快、稳定性差的问题.本文利用氧化石墨烯(GO)实现了对FeV_(2)S_(4)纳米粒子尺寸和分布的调控,使其更好地包裹在碳纳米纤维(CNFs)中,从而制备了FeV_(2)S_(4)@GO@CNF.FeV_(2)S_(4)@GO@CNF负极与表面拥有更多粒子的FeV_(2)S_(4)@CNF负极相比具有更优异的Na+存储性能.FeV_(2)S_(4)@GO@CNF用于钠离子电池负极时,200次循环(0.1 A g^(−1))后容量仍然可保持在411 mA h g^(−1),500次循环(1 A g^(−1))后可保持在227 mA h g^(−1).此外,在0℃下,经过150次循环(0.1 A g^(−1))后,仍可以输出170.2 mA h g−1的容量.以FeV_(2)S_(4)@GO@CNF作为负极,Na_(3)V_(2)(PO4)3/C作为正极的全电池在0.5 A g^(−1)下循环100次后,其容量达到164 mA h g^(−1).FeV_(2)S_(4)@GO@CNF表现出高比容量和稳定性,这是由于GO控制了FeV_(2)S_(4)的颗粒大小及其在CNFs中的分布,从而提高了FeV_(2)S_(4)@GO@CNF的稳定性.本研究为纳米CNF复合材料的制备提供了新思路.

使用NiS2作为硫源和前驱体合成Ni3S2@S纳米管用于高性能钠离子半/全电池（英文）

由于结构的多样性和丰富的自然储量,硫化镍是钠离子电池极具潜力的负极材料.然而,大体积膨胀和差的循环性能阻碍了它们的应用.引入中空结构和杂原子掺杂碳层是解决这些问题的有效方法.本文通过新颖的模板法制备了氮、硫共掺杂碳层包覆的Ni3S2纳米管(Ni3S2@NSCs).在退火过程中, NiS2既作为形成Ni3S2的前体又作为S掺杂的硫源.在S掺杂过程中没有使用额外的硫源,这表明合成过程具有原子经济性.作为钠离子半电池的阳极, Ni3S2@NSCs在0.1 A g^-1的电流密度下循环100次后表现出481 mA h g^-1的高放电容量,具有98.6%的优异容量保持率.此外,即使在5 A g^-1的高电流密度下,它们仍保持318 m A h g^-1的优异倍率性能.由Ni3S2@NSC阳极和Na3V2(PO4)3(NVP@C)阴极组装的钠离子全电池也具有优异的容量和循环稳定性.这些特征可归因于N, S共掺杂碳涂覆的中空结构.此结构可使电极和电解质之间充分接触,增强表面离子存储性能(电容效应),并改善电极材料的结构稳定性.

石墨烯调控FeSe纳米颗粒嵌入碳纳米纤维用于高性能钾离子电池

硒化亚铁因其资源丰富、环境友好、低毒等优点而备受关注.然而,与许多过渡金属硒化物类似,FeSe在充放电过程中存在电导率低、体积膨胀大等缺陷.因此,我们通过在静电纺丝前驱体中加入氧化石墨烯作为添加剂,合成了一种氧化石墨烯调控的FeSe纳米颗粒嵌入到碳纳米纤维中的复合材料.作为钾离子电池(KIB)的负极,该复合材料在0.2 A g^(-1)的电流密度下400次循环后可保持409 mA h g^(-1)高容量,容量保持率接近100%.即使在2 A g^(-1)的电流密度下,1700次循环后容量仍能保持在200 mA h g^(-1),容量保持率约为80.9%.研究发现,氧化石墨烯的引入可以减小FeSe纳米颗粒的直径,使得大部分纳米颗粒被包裹在碳纤维中,从而减轻了复合材料的体积膨胀,提高了复合材料的稳定性.此外,由石墨烯和碳纤维组成的基体可诱导高钾离子扩散动力学,改善材料的导电性并且增强赝电容性能,这赋予了复合材料优异的循环和倍率性能.利用氧化石墨烯来调控碳纤维复合材料的微观结构和提高其导电性的策略可能为碳纤维在其他能源设备中的应用和发展提供新的启发.