High-efficiently doping nitrogen in kapok fiber-derived hard carbon used as anode materials for boosting rate performance of sodium-ion batteries

The engineering of plant-based precursor for nitrogen doping has become one of the most promising strategies to enhance rate capability of hard carbon materials for sodium-ion batteries;however,the poor rate performance is mainly caused by lack of pyridine nitrogen,which often tends to escape because of high temperature in preparation process of hard carbon.In this paper,a high-rate kapok fiber-derived hard carbon is fabricated by cross-linking carboxyl group in 2,6-pyridinedicarboxylic acid with the exposed hydroxyl group on alkalized kapok with assistance of zinc chloride.Specially,a high nitrogen doping content of 4.24%is achieved,most of which are pyridine nitrogen;this is crucial for improving the defect sites and electronic conductivity of hard carbon.The optimized carbon with feature of high nitrogen content,abundant functional groups,degree of disorder,and large layer spacing exhibits high capacity of 401.7 mAh g^(−1)at a current density of 0.05 A g^(−1),and more importantly,good rate performance,for example,even at the current density of 2 A g^(−1),a specific capacity of 159.5 mAh g^(−1)can be obtained.These findings make plant-based hard carbon a promising candidate for commercial application of sodium-ion batteries,achieving high-rate performance with the enhanced pre-cross-linking interaction between plant precursors and dopants to optimize aromatization process by auxiliary pyrolysis.

Oxidation Modification of Polyacrylonitrile-Based Carbon Fiber and Its Electro-Chemical Performance as Marine Electrode for Electric Field Test

A novel sensor for ocean electric field testing has been fabricated by polyacrylonitrile-based on carbon fibers with electro-chemical oxidation.The surface profile characteristics of the carbon fibers were characterized by scanning electron microscope,Fourier transform infrared spectra and contact angle.Cyclic voltammetry and Tafel curves have been used to study its electro-chemical performances.Two identical electrodes in sea water as the electric field sensor will swiftly respond to applied electric field which causes positive and negative ions to move in opposite direction,resulting in a electric potential difference(ΔE).Test result indicates that the offset potential is typically below 1 m V with a drift of 60-170μVd^-1.Typical self noise level is 1.07 nV√Hz^(1/2)@1 Hz.The electric field response indicates that the modified electrode pair shows better response to AC sine signal of amplitude and frequency(5 mV and 1 mHz)respectively than its blank.The electric field response model of the modified electrodes is creatively presented according to its electric double layer capacitance and Faraday pseudo-capacitance.Many advantages of the carbon fiber electric field electrode will make it have potential application prospect.

Deciphering the lithium storage chemistry in flexible carbon fiber-based self-supportive electrodes

Flexible carbon fiber cloth(CFC)is an important scaffold and/or current collector for active materials in the development of flexible self-supportive electrode materials(SSEMs),especially in lithium-ion batteries.However,during the intercalation of Li ions into the matrix of CFC(below 0.5 V vs.Li/Li+),the incompatibility in the capacity of the CFC,when used directly as an anode material or as a current collector for active materials,leads to difficulty in the estimation of its actual contribution.To address this issue,we prepared Ni_(5)P_(4)nanosheets on CFC(denoted CFC@Ni_(5)P_(4))and investigated the contribution of CFC in the CFC@Ni_(5)P_(4)by comparing to the powder Ni_(5)P_(4)nanosheets traditionally coated on a copper foil(CuF)(denoted P-Ni_(5)P_(4)).At a current density of 0.4 mA cm^(−2),the as-prepared CFC@Ni_(5)P_(4)showed an areal capacity of 7.38 mAh cm^(−2),which is significantly higher than that of the PNi_(5)P_(4)electrode.More importantly,theoretical studies revealed that the CFC has a high Li adsorption energy that contributes to the low Li-ion diffusion energy barrier of the Ni_(5)P_(4)due to the strong interaction between the CFC and Ni_(5)P_(4),leading to the superior Li-ion storage performance of the CFC@Ni_(5)P_(4)over the pristine Ni_(5)P_(4)sample.This present work unveils the underlying mechanism leading to the achievement of high performance in SSEMs.

The Study of Electrochemical Behavior of Dopamine at Nano-gold Modified Carbon Fiber Electrode

The electrochemical behaviors (cyclic voltammetry, CV and different pulse voltammetry, DPV) of dopamine (DA) were studied in this paper. The result indicated that the oxidation of dopamine was controlled by diffusion and adsorption simultaneously at nano-gold (NG) modified carbon fiber electrode (CFE). This modified electrode can separate the peak potentials of dopamine and ascorbic acid (AA). The peak current of DA in DPV curve was found to be linearly proportional to the concentration of DA at range of 2.0?0-6～1.5?0-5mol/L and 1.0?0-5～5.0?0-4mol/L, respectively.

Examining the Effects of Common Laboratory Methods on the Sensitivity of Carbon Fiber Electrodes in Amperometric Recordings of Dopamine

Carbon fiber microelectrodes (CFEs) are useful when combined with electrochemical techniques for measuring changes in neurotransmitter concentrations. We addressed conflicting details regarding the use of CFEs. Experimental groups consisted of CFEs at different ages (1 week, 1 month, or 2 months), cleaned in solvents (isopropanol or xylene), and exposed to in vitro use (flow cell calibrations) or in vivo use (in brain tissue). In order to determine if any of these factors affect CFE sensitivity, the present study utilized fixed potential amperometry and a flow injection system to calibrate CFEs for the measurement of dopamine. The sensitivity index (nA/μM per 100 μm of exposed carbon fiber) was not affected by the age of CFEs or pre-cleaning with xylene or isopropanol. CFE sensitivity of the in vitro exposure group also did not differ from untreated CFEs, indicating the calibration process did not alter sensitivity. However, in vivo use in brain tissue did reduce sensitivity. This effect was negated and sensitivity restored by cleaning CFEs in isopropanol or xylene following in vivo brain recordings. Given that variations in CFE sensitivity can skew results, our findings can help standardize CFE use and explain discrepancies between researchers.

A Method of Using a Carbon Fiber Spiral-Contact Electrode to Achieve Atmospheric Pressure Glow Discharge in Air

During discharge, appropriately changing the development paths of electron avalanches and increasing the number of initial electrons can effectively inhibit the formation of filamentary discharge. Based on the aforementioned phenomenon, we propose a method of using microdischarge electrodes to produce a macroscopic discharge phenomenon. In the form of an asymmetric structure composed of a carbon fiber electrode, an electrode structure of carbon fiber spiral-contact type is designed to achieve an atmospheric pressure glow discharge in air, which is characterized by low discharge voltage, low energy consumption, good diffusion and less ozone generation.

Boosting Capacitive Deionization Performance of Commercial Carbon Fibers Cloth via Structural Regulation Based on Catalytic-Etching Effect

Monolithic carbon electrodes with robust mechanical integrity and porous architecture are highly desired for capacitive deionization but remain challenging.Owing to the excellent mechanical strength and electroconductivity,commercial carbon fibers cloth demonstrates great potential as high-performance electrodes for ions storage.Despite this,its direct application on capacitive deionization is rarely reported in terms of limited pore structure and natural hydrophobicity.Herein,a powerful metal-organic framework-engaged structural regulation strategy is developed to boost the desalination properties of carbon fibers.The obtained porous carbon fibers features hierarchical porous structure and hydrophilic surface providing abundant ions-accessible sites,and continuous graphitized carbon core ensuring rapid electrons transport.The catalytic-etching mechanism involving oxidation of Co and subsequent carbonthermal reduction is proposed and highly relies on annealing temperature and holding time.When directly evaluated as a current collector-free capacitive deionization electrode,the porous carbon fibers demonstrates much superior desalination capability than pristine carbon fibers,and remarkable cyclic stability up to 20 h with negligible degeneration.Particularly,the PCF-1000 showcases the highest areal salt adsorption capacity of 0.037 mg cm^(−2) among carbon microfibers.Moreover,monolithic porous carbon fibers-carbon nanotubes with increased active sites and good structural integrity by in-situ growth of carbon nanotubes are further fabricated to enhance the desalination performance(0.051 mg cm^(−2)).This work demonstrates the great potential of carbon fibers in constructing high-efficient and robust monolithic electrode for capacitive deionization.

All-carbon positive electrodes for stable aluminium batteries

For addressing the critical problems in current collectors in the aluminium batteries,a variety of carbonbased current collectors,including carbon fiber textiles and three-dimensional(3D)biomass-derivative carbon(BDC)networks,are employed for serving as lightweight non-metal current collectors.The results indicate that all the carbon-based current collectors have electrochemical stability in the acidic electrolyte environments.In the assembled aluminium batteries with all-carbon positive electrodes,thermal annealing process on the carbon-based current collectors has substantially promoted the entire electrochemical energy storage performance.Additionally,both the structure configuration and chemical components of the current collectors have also great impact on the rate capability and cycling stability,implying that the 3D BDC networks are more favorable to offer promoted energy storage capability.Implication of the results from suggests that the carbon-based current collectors and all-carbon positive electrodes are able to deliver more advantages in energy storage behaviors in comparison with the traditional positive electrodes with metal Mo current collectors.Such novel strategy promises a new route for fabricating highperformance positive electrodes for stable advanced aluminium batteries.

DNA Nano-netting Intertexture on Carbon Electrodes

Native calf thymus double stranded DNA (ct-dsDNA) is successfully immobilized from solution onto carbon substrates by covalent linkages under an optimized deposition potential of 1 .8±0.3 V vs. 50 mmol/L NaCl-Ag/AgCl. The long chain DNA fabricates a layer of well conductive nano-netting intertexture, which is stable in pH 14 alkaline solution and in boiling water. The ct-dsDNA modified carbon fiber disk electrode shows two to three orders of magnitude enlarged electrode effective surface area and similarly enlarged voltammetric responses to Co(phen)33+ and dopamine. Thermal dissociated single stranded ct-DNA can also lead to similar result. This modified electrode will find wide applications in the fields of DNA-based electrochemical biosensors.

Structural energy storage composites based on modified carbon fiber electrode with metal-organic frame enhancing layered double hydroxide

Structural energy storage composites present advantages in simultaneously achieving structural strength and electrochemical properties.Adoption of carbon fiber electrodes and resin structural electrolytes in energy storage composite poses challenges in maintaining good mechanical and electrochemical properties at reasonable cost and effort.Here,we report a simple method to fabricate structural supercapacitor using carbon fiber electrodes(modified by Ni-layered double hydroxide(Ni-LDH)and in-situ growth of Co-metal-organic framework(Co-MOF)in a two-step process denoted as Co-MOF/Ni-LDH@CF)and bicontinuous-phase epoxy resin-based structural electrolyte.Co-MOF/Ni-LDH@CF as electrode material exhibits improved specific capacity(42.45 F·g^(-1))and cycle performance(93.3%capacity retention after 1000 cycles)in a three-electrode system.The bicontinuous-phase epoxy resin-based structural electrolyte exhibits an ionic conductivity of 3.27×10^(-4) S·cm^(-1).The fabricated Co-MOF/Ni-LDH@CF/SPE-50 structural supercapacitor has an energy density of 3.21 Wh·kg^(-1) at a power density of 42.25 W·kg^(-1),whilst maintaining tensile strength and modulus of 334.6 MPa and 25.2 GPa.These results show practical potential of employing modified commercial carbon fiber electrodes and epoxy resin-based structural electrolytes in structural energy storage applications.

Integrated Co3O4/carbon fiber paper for high-performance anode of dual-ion battery

In dual-ion batteries (DIBs), energy storage is achieved by intercalation/de-intercalation of both cations and anions. Due to the mismatch between ion diameter and layer space of active materials, however, volume expansion and exfoliation always occur for electrode materials. Herein, an integrated electrode Co3O4/carbon fiber paper (CFP) is prepared as the anode of DIB. As the Co3O4 nanosheets grow on CFP substrate vertically, it promotes the immersion of electrolyte and shortens the pathway for ionic transport. Besides, the strong interaction between Co3O4 and CFP substrate reduces the possibility of sheet exfoliation. An integrated-electrode-based DIB is therefore packaged using Co3O4/CFP as anode and graphite as cathode. As a result, a high energy density of 72 Wh/kg is achieved at a power density of 150 W/kg. The design of integrated electrode provides a new route for the development of high-performance DIBs.

All Binder-Free Electrodes for High-Performance Wearable Aqueous Rechargeable Sodium-Ion Batteries

Extensive efforts have recently been devoted to the construction of aqueous rechargeable sodium-ion batteries(ARSIBs)for large-scale energy-storage applications due to their desired properties of abundant sodium resources and inherently safer aqueous electrolytes.However,it is still a significant challenge to develop highly flexible ARSIBs ascribing to the lack of flexible electrode materials.In this work,nanocube-like KNiFe(CN)6(KNHCF)and rugby balllike NaTi2(PO4)3(NTP)are grown on carbon nanotube fibers via simple and mild methods as the flexible binder-free cathode(KNHCF@CNTF)and anode(NTP@CNTF),respectively.Taking advantage of their high conductivity,fast charge transport paths,and large accessible surface area,the as-fabricated binder-free electrodes display admirable electrochemical performance.Inspired by the remarkable flexibility of the binder-free electrodes and the synergy of KNHCF@CNTF and NTP@CNTF,a high-performance quasi-solid-state fiber-shaped ARSIB(FARSIB)is successfully assembled for the first time.Significantly,the as-assembled FARSIB possesses a high capacity of 34.21 mAh cm?3 and impressive energy density of 39.32 mWh cm?3.More encouragingly,our FARSIB delivers superior mechanical flexibility with only 5.7%of initial capacity loss after bending at 90°for over 3000 cycles.Thus,this work opens up an avenue to design ultraflexible ARSIBs based on all binder-free electrodes for powering wearable and portable electronics.

基于纳米金修饰碳纤维微电极的电化学法测定黄芩素

利用柠檬酸三钠还原氯金酸的方法制得小粒径的纳米金颗粒(AuNPs),采用电化学沉积法将其修饰在碳纤维电极(CFME)表面,基于电化学法构建了一种灵敏度高、抗干扰性良好的测定黄芩素的微型电化学传感器.采用透射电镜、紫外分光光度法、扫描电镜等对电极及修饰材料进行表征,运用差分脉冲法、循环伏安法、电化学阻抗谱法考查了黄芩素在电极修饰前后的电化学性质,并优化了扫速、缓冲液pH、电沉积时间等实验条件.实验结果表明,AuNPs对黄芩素具有显著的电催化性能,AuNPs/CFME对黄芩素表现出良好的电化学响应,最佳修饰时间为10 min.黄芩素浓度在0.05~10μmol/L时,其氧化峰电流与浓度呈良好的线性关系,线性方程为I_(p)(nA)=0.4409C(μmol/L)+0.7066,R^(2)=0.998.该方法响应速度快、稳定性较好,可用于黄芩素的定量检测.

无机酸掺杂聚苯胺/碳纤维复合海洋电场传感器电极

碳纤维电极具有成本低、化学稳定性好、性能可调控等优点,可用于开发高性能海洋电场传感器.利用电化学原位聚合法制备盐酸、硫酸、磷酸掺杂的聚苯胺/碳纤维(PANI/CF)复合电场电极,提高其电化学性能与电场响应性能.结果表明:碳纤维表面生成致密的导电聚苯胺膜,并在循环伏安测试中出现特征氧化还原峰;电化学阻抗分析显示PANI/CF复合电极低频(0.01 Hz)阻抗值至少降低为空白电极的1/118,利于对水下微弱电场信号进行响应.在电场响应性能测试中,盐酸掺杂PANI/CF复合电极电位漂移量最低达1.77 mV/d;能够较好地响应1 mV/10 mHz的低频率低强度电场信号;误差线性度最小值为0.111%,在同类电极中具有最好响应灵敏度.该新型复合电场电极制备方法简单、成本低廉,有助开发新一代低成本、高性能海洋电场传感器.

One dimensional pea-shaped NiSe_(2) nanoparticles encapsulated in N-doped graphitic carbon fibers to boost redox reversibility in sodium-ion batteries

In recent years,sodium-ion batteries(SIBs)have emerged as a promising technology for energy storage systems(ESSs)because of the abundance and affordability of sodium.Recently,metal selenides have been studied as promising high-performance conversion-type anode materials in SIBs.Among them,nickel se-lenide(NiSe_(2))has received considerable attention due to its high theoretical capacity of 495 mAh g^(-1)and conductivity.However,it still suffers from poor cycling stability because of the low electrochemical reactivity,large volume expansion,and structural instability during cycles.To address these challenges,NiSe_(2)nanoparticles encapsulated in N-doped graphitic carbon fibers(NiSe_(2)@NGCF)were synthesized by using ZIF-8 as a template.NiSe_(2)@NGCF showed a high discharge capacity of 558.3 mAh g^(-1)with a fading rate of 0.14%per cycle after 200 cycles at 0.5 A g^(-1)in 0.01-3.0 V.At a very high current density of 5 A g^(-1),the capacity still displayed excellent long-term cycle life with a discharge capacity of 406.1 mAh g^(-1)with a fading rate of 0.016%per cycle after 3000 cycles.The mechanism of the excellent electrochem-ical performance of NiSe_(2)@NGCF was thoroughly investigated by ex-situ XRD,TEM,and SEM analyses.Furthermore,NiSe_(2)@NGCF//Na_(3)V_(2)(PO_(4))_(3)full-cell also delivered an excellent reversible capacity of 378.7 mAh g^(−1)at 0.1 A g^(−1)after 50 cycles,demonstrating its potential for practical application in SIBs.

静电纺丝碳纳米纤维电极液流电池研究进展

液流电池因其具有安全、循环寿命长、环境友好和扩容性强等优势,成为目前最有前途的大规模储能技术之一。电极作为液流电池的关键材料,其性能对电池性能有着重大影响。综述了静电纺丝碳纳米纤维电极在液流电池中的研究进展,介绍了静电纺丝碳纳米纤维的制备原理以及关键制备参数的影响,详细阐述了电纺碳纳米纤维电极结构和化学性质的调控方法及其对电池性能的影响,包括纤维微观结构的调控、杂原子掺杂和催化改性等;指出电极反应活性面积和化学性质影响的电化学活性与传质性能之间的协同是电极调控的关键,通过对纤维进行造孔或新型结构设计可以调控纤维的微观结构和表面性质,杂原子掺杂和引入催化剂可以提高电极的活性面积和亲水性,以促进电极的电化学活性;提出了电纺碳纳米纤维电极从实验室制备到规模化发展存在的问题及未来发展方向。

杂原子掺杂木质素基碳纤维的制备及其在超级电容器中的应用

木质素由于具有高含碳量、低成本和生物可再生的特点成为研究低成本超级电容器电极材料的优良碳前驱体原料.为了实现木质素的高值化利用并且获得高性能的超级电容器,研究具有优良孔隙结构、兼具双电层电容和赝电容储能方式的木质素碳纤维是当前需要解决的问题.本研究通过采用H_(2)SO_(4)/HNO_(3)的混酸化学氧化、简单水热处理木质素碳纤维实现杂原子掺杂,以研究不同处理方法对其比表面积和孔隙结构的影响.结果表明,未经任何处理的木质素碳纤维样品(LCF)的比表面积为317.4 m^(2)·g^(-1),比电容为6.2 F·g^(-1).采用H_(2)SO_(4)/HNO_(3)的混酸化学氧化处理的碳纤维样品(S,N-LCF)获得了更多的微孔,其比表面积达到611.6 m^(2)·g^(-1),比电容为23.0 F·g^(-1)(0.5 A·g^(-1));水热条件下,镍钴锰硫杂原子掺杂的样品(HLCF)由于杂原子的掺杂改善了其电极材料的电化学性能,使其比电容增加至15.4 F·g^(-1)(0.5 A·g^(-1));使用两种方法连续处理的样品S,N-HLCF_(2)因适宜的孔隙结构和杂原子掺杂增加的赝电容,使其比电容增加至46.8 F·g^(-1)(0.5 A·g^(-1)).

超级电容器用碳纤维纸基电极制备

为解决商用碳纤维纸成本高、脆性大的问题,提出了一种柔性超级电容器用碳纤维纸的批量制备方法。利用分散剂CMC-Na对短切碳纤维进行超声分散,使其在水体系中均匀分散。添加PE/PET复合纤维不仅提高了CFP的抗张强度,而且巩固了在碳纤维结构基础上形成的电极网络结构。使用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和拉曼光谱对碳纤维纸基电极(CFP-X)的形貌和结构进行表征,测试了CFP-X电极的力学性能、导电性能和电化学性能。结果表明:CFP-3电极具有优异的抗张强度和柔韧性,电化学性能优异,同时成本低。这项研究为低成本、大规模生产纸质柔性超级电容器提供了有价值的见解。

碳纤维织物基MoS_(2)柔性电极的制备及其电化学性能

为了扩大二硫化钼(MoS_(2))较小的层间距尺寸,提高其在水系锌离子电池正极材料的存储性能,以高导电性碳纤维织物基MoS_(2)为柔性负载基底,使用碳酸氢铵和碳酸氢钠2种物相调节剂对MoS_(2)的合成过程进行调控,获得不同层间嵌入结构的MoS_(2)材料(MoS_(2)-NH4+和MoS_(2)-Na^(+)),并探究了嵌入离子类型对层间结构及锌离子存储特性的影响。测试结果表明:在反应中碳酸氢铵释放的NH_(4)^(+)离子(扩层尺寸0.39 nm)相比于碳酸氢钠释放的Na^(+)离子(扩层尺寸0.12 nm)具有更好的扩层效果。在电流密度为500 mA·g^(-1)下,MoS_(2)-NH4+电极循环300次后容量保持率高达97.39%,并且在后续柔性纤维状电池应用中表现出良好的工作特性。提出的具有高性能的MoS_(2)基柔性电极材料的制备方法,为锌离子电池柔性电极材料的结构优化设计开拓了新的思路。

复合材料结构超级电容器碳纤维电极的制备与改性方法

高性能的碳纤维电极可以应用于更多的电化学装置,拓宽超级电容器的应用范围。通过优化制备和改性工艺,可以降低碳纤维电极的生产成本,从而降低超级电容器的整体成本,使其更具市场竞争力。通过分析复合材料结构超级电容器工作原理,基于氧化处理、电极涂覆和化学气相沉积等手段,探讨了复合材料结构超级电容器碳纤维电极的制备工艺,并提出相应的改进方法。通过分析碳纳米管(CNTs)、石墨烯和金属纳米颗粒等改性材料对碳纤维电极性能的影响,并通过测试对比,证实了复合改性材料对于提升碳纤维电极性能具有显著效果。通过测试分析,以期为未来超级电容器和其他电化学装置的开发提供一定参考。