Bimetallic-organic coordination polymers to prepare N-doped hierarchical porous carbon for high performance supercapacitors

Single metal-organic coordination polymers have limited functions as precursors for porous carbon electrode materials.The construction of bimetallic organic coordination polymers can effectively utilize the advantages of each single metal-organic coordination polymer to improve the performance of the derived carbon materials.Herein,High performance nitrogen-doped porous carbon(BC_(Fe–Ni))have been produced by directly carbonizing bimetallic organic coordination polymers formed by 4,4'-bipyridine(BPD)reaction with Fe Cl_3and NiCl_2.The BC_(Fe–Ni) exhibits high nitrogen content(12.66 at%),large specific surface area(1049.51 m~2g~(-1))and hierarchical porous structure,which contributes to an excellent gravimetric specific gravity of 320.5 Fg~(-1)and 108%of specific capacitance retention after 10000 cycles.The BC_(Fe–Ni)assembled symmetrical supercapacitor shows an energy density of 18.3 Wh kg~(-1)at a power density of 350 W kg~(-1).It is expected that the as-prepared N-doped porous carbon derived from bimetallic-organic coordination polymer is a promising electrode material for high performance energy storage devices.     

Mangosteen peel-derived activated carbon for supercapacitors

This work reports the effects of activation temperatures on the porous development and electrochemical performance of activated carbons. Herein, activated carbons were prepared from the biowaste of mangosteen peel by using KOH activation at temperatures of 400, 600, and 800 ?°C. The results demonstrate that the specific surface area increases with increasing the activation temperatures in which the well-developed porous structure after KOH activation at 800 ?°C provides the highest specific surface area of 1039 ?m² ?g^?1. At 600 ?°C, the activated carbon delivers the highest specific capacitance value of 182 ?F ?g^?1 ?at a current density of 0.5 ?A ?g^?1 in 3 ?M KOH aqueous electrolyte. This is correlated well with its high micropore fractions (99%). Moreover, it was found that the activation temperature changes the major contribution of oxygen-containing functional group on surface of activated carbon, which is beneficial for the enhancement of the specific capacitance value of activated carbon at the temperature of 600 ?°C. This work suggests that the activation temperature is a key to optimizing the electrochemical performance of activated carbons. Overall, our activated carbons can be considered as a strong candidate for use as electrode materials in supercapacitors.     

Rational design of MnS nanoparticles anchored on N,S-codoped carbon matrix as anode for lithium-ion batteries

The manganese sulfide (MnS) has attracted more attention as anode material on energy storage and conversion field, owing to its high theoretical capacity (616 ​mA ​h ​g⁻¹) and good electrochemical activity. However, low electronic conductivity and large volume expansion during charge-discharge processes have limited its further application. In order to address above mentioned problems, the composites, MnS nanoparticles embedded in N,S-codoped porous carbon skeleton (named as MnS/N,S–C composites), herein have been prepared successfully using metal organic framework (Mn-NTA) as template. The porous carbon skeleton not only can enhance electrode conductivity, but also relieve volume expansion during charge-discharge processes. Thus, the rational design towards electrode architectures has endowed MnS/N,S–C nanocomposites with superior electrochemical performance, which delivers the specific capacities of 676.7 ​mA ​h ​g⁻¹ at the current density of 100 ​mA ​g⁻¹.     

Cobalt coordination modified double-schiff-base with low solubility as a long-cycle life anode for sodium-ion batteries

Sodium-ion batteries (SIBs) have been recently considered as an intriguing candidate for next-generation battery systems with their advantages in large-scale energy storage applications. However, the design of electrode materials of SIBs still suffers from severe volume expansion and low capacity caused by the larger ion radius, high re-dox potential and heavy atom weight of Na. Organic electrode materials with structural flexibility have attracted great attention recently for their potential in alleviating volume expansion. However, most organic electrode materials suffer from dissolution in electrolytes and consequent capacity fading during the long-term cycling process. In this work, a method coordinating with Co²⁺ was applied to solve the shuttle effect of H₄salphdc (N, N’-phenylene-bis-(salicylideneimine) dicarboxylic acid). By virtue of the Co²⁺ coordination, the Co(H₂salphdc) electrode delivered a desirable discharge capacity of 123 mAh g^?1 after 1500 cycles at the current density of 200 ?mA ?g^?1, while the H₄salphdc electrode exhibited severe capacity fading. Such excellent electrochemical performance can be credited to the Co²⁺ coordination repressing the electrode dissolution and improving the structure stability.     

Rational construction of NiCo_2O_4@Fe_2O_3 core-shell nanowire arrays for high-performance supercapacitors

Fe_2O_3 electrode materials exhibit excellent electrochemical performance in electrochemical energy storage system. However, its poor electrical conductivity limits its future practical application. The binder-free Ni Co_2O_4@Fe_2O_3 composites was reasonably designed and fabricated on carbon fiber paper with NiCo_2 O_4 nanowires as conductive scaffold in the present investigation. The three-dimensional nanostructure of the porous Fe_2O_3 nanorods coated the Ni Co2 O4 nanowire arrays showed the fascinating electrochemical performance, including high specific capacitance of 262 m F/cm2 at a current density of 1 m A/cm2, and remarkable cycle stability with～74.2% capacitance retention after 4000 cycles. The excellent pseudocapacitance performance of NiCo_2O_4@Fe_2O_3 composite materials is due to synergistic effect between NiCo_2O_4 and Fe_2O_3. The results of the present work show that NiCo_2O_4@Fe_2O_3 core-shell composite electrode is expected to exhibit excellent performance in the field of supercapacitors.     

Electrochemical performance of MCMB/(AC+LiFePO4) lithium-ion capacitors

Lithium-ion capacitors(LICs) were fabricated using mesocarbon microbeads(MCMB) as a negative electrode and a mixture of activated carbon(AC) and LiFePO4 as a positive electrode(abbreviated as LAC).The phase structure and morphology of LAC samples were characterized by X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM).The electrochemical performance of the LICs was studied using cyclic voltammetry,charge-discharge rate measurements,and cycle performance testing.A LIC with 30 wt% LiFePO4 was found to have the best electrochemical performance with a specific energy density of 69.02 W h kg-1 remaining at 4 C rate after 100 cycles.Compared with an AC-only positive electrode system,the ratio of practical capacity to theoretical calculated capacity of the LICs was enhanced from 42.22% to 56.59%.It was proved that adding LiFePO4 to AC electrodes not only increased the capacity of the positive electrode,but also improved the electrochemical performances of the whole LICs via Li+ pre-doping.     

泡沫镍上原位生长CoMn2O4多级空心纳米球作为超级电容器电极材料的电化学性能研究

采用水热法结合空气气氛中的热处理过程,在泡沫镍（NF）表面生长了锰酸钴（CoMn₂O₄）多级空心纳米球,通过X射线衍射仪（XRD）、场发射扫描电镜（FE-SEM）和X射线光电子能谱（XPS）等测试手段对纳米球进行了表征.在三电极电化学测量系统中,0.1Co²⁺-250电极材料在5 mA·cm^-2时的面积比电容高达6 184 mF·cm^-2.以0.1Co²⁺-250为正极,商用活性炭（AC）为负极组装而成的混合超级电容器,在1.6 mW·cm^-2时的最大能量密度为0.112 mWh·cm^-2.即使在功率密度为16 mW·cm^-2时,能量密度仍达到0.064 mWh·cm^-2.在2 mA·cm^-2的电流密度下,经过10 000次充放电循环后,电容保持了初始值的93%.因其优越的电化学性能和低成本的便捷合成方法,CoMn₂O₄多级空心纳米球作为电极材料具有重要的应用前景.     

RGO/NiCo_2O_4复合电极材料制备及电化学性能研究

采用层-层自组装法制备了前驱体RGO/Ni-Co@Ni-foam(泡沫镍负载石墨烯/镍-钴金属化合物),并在高温下煅烧得到RGO/NiCo_2O_4@Ni-foam复合电极材料。运用X射线衍射仪、扫描电子显微镜以及能谱仪对多孔RGO/NiCo_2O_4@Ni-foam复合材料进行结构表征,并通过循环伏安、恒流充放电等测试方法考察了其作为电极材料的电化学性能。结果表明,制备的多孔RGO/NiCo_2O_4@Ni-foam复合电极材料的比电容在电流密度为0.5A/g时可达到444F/g,并且在经过1 000次循环实验后,比电容仍有342F/g。这表明多孔RGO/NiCo_2O_4@Ni-foam复合材料在超级电容器领域具有广阔的应用前景。     

Flexible free-standing polyaniline/poly(vinyl alcohol) composite electrode with good capacitance performance and shape memory behavior

The increasing demand for portable and flexible energy storage devices drives the development of flexible electrodes and electrolytes. The aim of this work is to fabricate the flexible free-standing polyaniline/poly (vinyl alcohol) (PANI/PVA) composite electrode with good capacitance performance and shape memory behavior. The electrodes were fabricated by chemical oxidation polymerization of aniline in porous PVA (P-PVA) films. The morphology, electrochemical and mechanical properties of PANI/P-PVA electrodes were studied by scanning electron microscope, cyclic voltammetry, galvanostatic charge-discharge, and tensile test etc. The results revealed that the flexible PANI/P-PVA-1 electrode had good specific capacitance of 173.86 ​mF ​cm⁻² at 1 ​mA ​cm⁻², with the capacitance retention of 70.16% after 4000 charge-discharge cycles. Besides, it had excellent heat-induced shape memory effect. The fixed shape could completely recover to its original shape within 10 ​s at 80 ​°C, which is above the glass transition temperature (75.89 ​°C) of PANI/P-PVA-1. The comparatively tensile strength (2.86 ​MPa) and high elongation at break (315.72%) indicated its outstanding flexibility. Up to 200 times folding had no effect on the electrochemical properties. The free-standing polymer electrodes with excellent comprehensive performance provide potential applications in flexible energy-storage devices, electronic encapsulation and high stretchable electric devices etc.     

多孔Ti3C2Tx/SnSe复合材料的制备及其储钾性能

采用原位氧化-刻蚀法和水热合成法制备了多孔MXene复合材料(Ti₃C₂T_x/SnSe),并对所制备的材料进行了结构表征与电化学性能测试. 结果表明:在0.05 A/g的电流密度下,多孔Ti₃C₂T_x/SnSe电极具有381.9 mA ·h/g的储钾容量,而相同情况下SnSe电极的比容量仅为119.2 mA ·h/g. 在1 A/g的电流密度下,多孔Ti₃C₂T_x /SnSe电极的初始可逆比容量为118.5 mA ·h/g,循环500次的比容量仍保持在35.4 mA ·h/g. 多孔Ti₃C₂T_x/SnSe电极材料优异的电化学性能得益于多孔Ti₃C₂T_x材料的高导电性,它不仅缓解了SnSe的体积膨胀,而且为离子的转移提供了良好的通路.     

Preparation of mesoporous MgO-templated carbons from phenolic resin and their applications for electric double-layer capacitors

Mesoporous carbons were synthesized using thermoplastic phenolic resin (PF) as carbonaceous precursor and magnesium citrate as template precursor. Pore structure was determined as ink-bottle-like geometry through TEM, N2 adsorption analysis combined with TG curves. The porous carbons prepared were then applied as electrode material for electric double-layer capacitors. The capacitor performance was examined in 30 wt% KOH aqueous solution by cyclic voltammetry and galvanostatic charge/discharge measurements. The carbon prepared with MgO/PF mass ratio of 8/2 had a BET surface area of 1920 m² g^?1 and exhibited a capacitance of 220 F g^?1 at a current density of 50 mA g^?1. Besides, the carbon with the ratio of 4/6 had the optimize proportion of mesopores, which ensures its good rate performance that up to 98.3%, expressed as the ratio of the capacitance measured at 1000 mA g^?1 against that at 50 mA g^?1.     

Enhanced low-humidity performance of proton-exchange membrane fuel cell by introducing hydrophilic CNTs in membrane electrode assembly

Hydrophilic carbon nanotubes (HCNTs) were introduced into the membrane electrode assembly (MEA) to improve its low-humidity performance. The effects of types, placement, loading, and relative humidity on the MEA performance were investigated. It has been found that the MEA with 20 ?wt% HCNTs loading both in anode and cathode achieved the best self-humidifying performance. Its current density reached 1550 ?mA ?cm^?2 at 0.6 ?V, with a maximum power density of 953 ?mW/cm² at 70 ?°C, 30 psi and 30% relative humidity conditions. Besides, the stability test shows that its current density at 0.6 ?V only decreased by 6.4% after 44 ?h performance test, while the performance of blank MEA without HCNTs decreased by 45% within 6 ?h testing period. This extraordinary performance under low humidity condition is ascribed to that the HCNTs contained in the MEA improve the water management and mass transportation by functioning as a dispersant and hydrophilic agent.     

微纳结构硅在锂离子电池中的研究现状

近年来,随着人们对能量需求的日益增大,已商业化应用的石墨电极已经很难满足高性能电子产品对高能量密度的需求,因此发展高能量密度的锂离子电池显得尤为重要。在已研究的先进材料中,硅已被证明存在巨大的储能潜力,其理论比容量（约4 200 mA·h·g^-1）远高于已商业化应用的石墨类电极材料。对锂离子电池中硅电极材料的微纳结构、制备方法、电化学性能及相关机理进行了总结,目的是研究不同结构的硅电极材料对电池性能的影响,以找到性能较为优异的硅电极结构。结果表明,在已被研究的硅基复合材料中,核壳结构和多壁纳米管结构硅电极材料在电化学性能方面均体现出了明显的优势。最后简要分析了硅基电极材料发展中存在的问题,并对其研究前景进行了展望。     

超级电容器电极材料的结构设计

超级电容器由于具有功率密度大和循环寿命长的优势受到了广泛的关注.电极材料是超级电容器的核心部分,是发展高性能超级电容器的关键要素.电极材料的组成、晶体结构、微纳结构形态等对其电化学性能具有重大影响.赝电容电极材料的性能与晶体内部的孔道结构密切相关,具有大孔道的电极材料其比容量明显高于只含有小孔道的电极材料.合理调控电极材料微纳结构形态如设计多孔结构、中空结构有利于增大电极的电化学活性表面,进而获得更多的电荷存储量,是提高储能性能的有效途径之一.将赝电容电极材料与导电基体复合生长可以提高材料整体的电导率,进而提高材料的比容量与倍率性能.通过对超级电容器电极材料结构的合理设计进而实现其储能性能的提高已经成为电化学储能领域的研究热点,对于推动超级电容器的发展具有重要意义.     

Gas-Liquid Interfacial Plasma engineering under dilute nitric acid to improve hydrophilicity and OER performance of nickel foam

The world has been moving rapidly to find new eco-friendly energy sources. Water electrolysis consists of two reactions of Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER), whereas the OER is considered the rate-limiting step. The most commercialized electrode for OER in the alkaline electrolyte is Ni foam, but its original surface is hydrophobic. It is possible to accelerate the adsorption and desorption process of reactants and products during OER by adding hydrophilic functional groups such as –OH on the surface of Ni foam. In this study, a novel Gas-Liquid Interfacial Plasma (GLIP) engineering at room temperature was successfully applied to modify the Ni foam surface dilute (1 ?M) HNO₃ solution. At a current density of 400 ?mA ?cm^?2, GLIP-treated Ni foam electrodes at 1 ?M HNO₃ concentrations showed OER overpotentials of 458 ?mV. Among all, GLIP with 1 ?M HNO₃ treatment of 30 ?min showed 129 ?mV less overpotential than the nickel foam before treatment. In summary, GLIP can be justified as an environmentally friendly and efficient surface treatment to improve the wettability and OER performance of Ni-based electrodes in water electrolysis.     

Nanostructure designing and hybridizing of high-capacity silicon-based anode for lithium-ion batteries

Lithium-ion batteries have long been used in electronic products and electric vehicles, but their energy density is slowly failing to keep up with demand. Because of its extraordinarily high theoretical specific capacity, silicon is regarded as the most potential next-generation anode material for practical lithium-ion batteries. However, its unavoidable volume expansion issue can cause electrode deformation and loss of electrical contact during cycling,resulting in significant performance reduc...     

Lithium-ion full cell with high energy density using nickel-rich LiNi0.8Co0.1Mn0.1O2 cathode and SiO-C composite anode

A high-energy-density Li-ion battery with excellent rate capability and long cycle life was fabricated with a Ni-rich layered LiNi_0.8Mn_0.1Co_0.1O₂ cathode and SiO-C composite anode. The LiNi_0.8Mn_0.1Co_0.1O₂ and SiO-C exhibited excellent electrochemical performance in both half and full cells. Specifically, when integrated into a full cell configuration, a high energy density (280 Wh·kg-1) with excellent rate capability and long cycle life was attained. At 0.5C, the full cell retained 80% of its initial capacity after 200 charge/discharge cycles, and 60% after 600 cycles, indicating robust structural tolerance for the repeated insertion/extraction of Li+ ions. The rate performance showed that, at high rate of 1C and 2C, 96.8% and 93% of the initial capacity were retained, respectively. The results demonstrate strong potential for the development of high energy density Li-ion batteries for practical applications.     

Electrochemical characterization of MnO2 as the cathode material for a high voltage hybrid capacitor

Manganese dioxide (MnO₂) was prepared using the ultrasonic method. Its electrochemical performance was evaluated as the cathode material for a high voltage hybrid capacitor. And the specific capacitance of the MnO₂ electrode reached 240 F·g-1. The new hybrid capacitor was constructed, combining A1/Al₂O₃ as the anode and MnO₂ as the cathode with electrolyte for the aluminum electrolytic capacitor to solve the problem of low working voltage of a supercapacitor unit. The results showed that the hybrid capacitor had a high energy density and the ability of quick charging and discharging according to the electrochemical performance test. The capacitance was 84.4 μF, and the volume and mass energy densities were greatly improved compared to those of the traditional aluminum electrolytic capacitor of 47 μF. The analysis of electrochemical impedance spectroscopy (EIS) showed that the hybrid capacitor had good impedance characteristics.     

Preparation and electrochemical properties of carbon-coated LiFePO4 hollow nanofibers

Carbon-coated LiFePO₄ hollow nanofibers as cathode materials for Li-ion batteries were obtained by coaxial electrospinning. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller specific surface area analysis, galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) were employed to investigate the crystalline structure, morphology, and electrochemical performance of the as-prepared hollow nanofibers. The results indicate that the carbon-coated LiFePO₄ hollow nanofibers have good long-term cycling performance and good rate capability: at a current density of 0.2C (1.0C = 170 mA·g-1) in the voltage range of 2.5–4.2 V, the cathode materials achieve an initial discharge specific capacity of 153.16 mAh·g-1 with a first charge–discharge coulombic efficiency of more than 97%, as well as a high capacity retention of 99% after 10 cycles; moreover, the materials can retain a specific capacity of 135.68 mAh·g-1, even at 2C.     

Flexible micro-supercapacitors fabricated from MnO2 nanosheet/graphene composites with black phosphorus additive

Supercapacitors are widely used for powering flexible/wearable electronics owing to their excellent charge storage capabilities. In this study, MnO₂ nanosheets were grown on the surface of graphene using a simple water bath method to prepare graphene/MnO₂ composites for fabricating supercapacitors. In addition, two-dimensional black phosphorus was introduced as an additive into the electronic ink based on the as-prepared graphene/MnO₂ composites. The characterization and electrochemical analyses results showed that adding black phosphorus considerably improved the capacitive performance of the material, yielding a high specific capacitance of 241.5 ?F ?g^-1 at 0.1 ?A ?g^-1 and an impressive rate capability improvement from 52.5% to 80.3%. Then the micro-supercapacitor having an area-specific capacitance of 20.15 ?mF ?cm^-2 at a scanning rate of 2 ?mV ?s^-1 was utilized to demonstrate the practical applicability of this material. To further evaluate the practical applicability of this micro-supercapacitor, the micro-supercapacitor was integrated with a flexible thin-film pressure sensor on paper and cloth through screen printing.