Electrodeposition of three-dimensional Ni(OH)<Subscript>2</Subscript> nanoflakes on partially crystallized activated carbon for high-performance supercapacitors

Three-dimensional Ni(OH)₂ nanoflakes were prepared via a facile and cost-effective electrodeposition method using commercial activated carbon (AC) as substrate. Nitric acid treatment (NT) and partial crystallization (PC) by metal nickel catalysis were applied for AC. The effects of the oxygen-containing functional groups and the degree of crystallization on the electrochemical performance of the electrode were investigated. The resulting Ni(OH)₂/PC–NT–AC/nickel foam electrode exhibits distinct performance with a specific capacitance of 2971 F/g (scaled to the mass of active Ni(OH)₂) at a current density of 6 A/g. A high capacitance of 1919 F/g was still achieved even at 40 A/g, which is much higher than Ni(OH)₂/AC/nickel foam electrode and Ni(OH)₂/NT–AC/nickel foam electrode. The excellent performance of Ni(OH)₂/PC–NT–AC/nickel foam electrode can be attributed to the presence of large surface area and highly conductive PC–NT–AC network on nickel foam. This study presents an effective method to improve the dispersion and rate capability of Ni(OH)₂ nanostructure electrodes.     

Hybrid nanonet/nanoflake NiCo2O4 electrodes with an ultrahigh surface area for supercapacitors

An integrated electrode consisting of hybrid nanonet/nanoflake NiCo₂O₄ grown on stainless steel mesh substrates exhibits a high specific capacitance while maintaining high-rate capability and good cycling stability. The specific capacitance reaches a maximum of 911 F g^?1 at a current density of 10 A g^?1, which can still retain 864 F g^?1 (94.8 % retention) after 10,000 cycles. These much-improved electrochemical performances are attributed to the unique architecture of NiCo₂O₄ electrode. The interconnected nanonet NiCo₂O₄ with an ultrahigh surface area significantly facilitates the rapid ion/electron transport and guarantees good mechanical adhesion, while the ultrathin nanoflakes further extend the active sites for fast redox reactions for efficient energy storage. Figure

Hybrid nanonet/nanoflake NiCo₂O₄ grown on stainless steel mesh exhibits superior capacitive performance and long-life stability as an integrated electrode for high-performance supercapacitors.     

The rods-like manganese dioxide films grown on nickel foam for electrochemical capacitor applications

MnO₂ films grown on nickel foam (NF) with a desirable 3D structure are investigated as electrochemical pseudocapacitor materials for potential energy storage applications. The prepared MnO₂ films are characterized by X-ray diffraction, FT-IR and scanning electron microscopy. Results indicate that the products are typical hexagonal ?-MnO₂ with a uniform nanorod structure. The electrochemical measurements showed that the MnO₂ films with rods-like morphology have excellent electrochemical performances and its specific capacitance value as single electrode is up to 664 F g^?1 at a discharge current density of 5.5 A g^?1, which is higher than that of most reported corresponding materials. The specific capacitance retention ratio is 76.7% at the current density range from 5.5 to 30 A g^?1. Furthermore, we found that the deposition conditions such as deposition potential and deposition mass have a pronounced effect on their electrochemical activities.     

Synthesis of tungsten disulfide (WS2) nanoflakes for lithium ion battery application

A novel method (a rheological phase reaction) was used to synthesize WS₂ nanoflakes by adding oxalic acid as a reducing reagent. High resolution electron microscopy observations revealed that the as-prepared WS₂ nanoflakes had started to curve and that WS₂ nanotubes were partly formed. The lithium intercalation/deintercalation behavior of as-prepared WS₂ electrode was also investigated. It was found that the WS₂ nanoflake electrode exhibited higher specific capacity with very good cycling stability compared to WS₂ nanotube or nanoparticle electrodes. The reasons for the improved electrochemical performance of the nanoflake electrodes are also discussed.     

Preparation of hexagonal nanoporous nickel hydroxide film and its application for electrochemical capacitor

Nanoporous nickel hydroxide film has been successfully electrodeposited on titanium substrate from nickel nitrate dissolved in the aqueous domains of the hexagonal lyotropic liquid crystalline phase of Brij 56. Low-angle X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM) studies show that the film has a regular nanostructure consisting of a hexagonal array of cylindrical pores with a repeat center-to-center spacing of about 7 nm. Preliminary electrochemical studies are carried out using cyclic voltammetry (CV) and chronopotentiometry technology. A maximum specific capacitance of 578 F g⁻¹ could be achieved for the nanoporous Ni(OH)₂ film electrode, suggesting its potential application in electrochemical capacitors.     

A Novel V<Subscript>2</Subscript>AlC Electrode Material for Supercapacitors

A novel V₂AlC electrode material for supercapacitors was investigated in this study. The structure and surface morphology were examined using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The formation of irregularly shaped V₂AlC with different particle size distribution was confirmed by XRD and FESEM. The electrochemical measurements were performed by cyclic voltammetry (CV), galvanostatic charge discharge and electrochemical impedance spectroscopy (EIS). V₂AlC electrode exhibited 27.6 F g^–1 of specific capacitance at the current density of 0.5 A g^–1. The specific capacitance of V₂AlC electrode remained 93.8% of the first cycle after 2000 cycles. V₂AlC has great potential for application in supercapacitors.     

Hierarchical porous nanofibers of carbon@nickel oxide nanoparticles derived from polymer/block copolymer system

The triblock copolymer (PAA-b-PAN-b-PAA) is prepared by reversible addition-fragmentation chain-transfer polymerization, and then blended with polymer (PAN) and metal hydroxide (Ni(OH)₂) as a precursor for heat-treatment. A composite material of hierarchical porous nanofibers and nickel oxide nanoparticles (HPCF@NiO) is prepared by electrospinning combined with high-temperature carbonization. The effects of the ratio of PAA and PAA-b-PAN-b-PAA on the internal structure of nanofibers and their electrochemical properties as positive electrode materials are investigated. The experimental results show that when the ratio of PAA to PAA-b-PAN-b-PAA is 1.3 to 0.4, it has good pore structure and excellent electrochemical performance. At the current density of 1 A/g, the specific capacitance is 188.7 F/g and the potential window is −1 V to 0.37 V. The asymmetric supercapacitor assembled with activated carbon as the negative electrode materials has a specific capacitance of 21.2 F/g in 2 mol/L KOH and a capacitance retention of 85.7% after 12,500 cycles at different current density.     

Hybrid Hydrogels of Porous Graphene and Nickel Hydroxide as Advanced Supercapacitor Materials

Graphene‐based hydrogels can be used as supercapacitor electrodes because of their excellent conductivity, their large surface area and their high compatibility with electrolytes. Nevertheless, the large aspect ratio of graphene sheets limits the kinetics of processes occurring in the electrode of supercapacitors. In this study, we have introduced in‐plane and out‐of‐plane pores into a graphene–nickel hydroxide (Ni(OH)₂) hybrid hydrogel, which facilitates charge and ion transport in the electrode. Due to its optimised chemistry and architecture, the hybrid electrode demonstrates excellent electrochemical properties with a combination of high charge storage capacitance, fast rate capability and stable cycling performance. Remarkably, the Ni(OH)₂ in the hybrid contributes a capacitance as high as 3138.5 F g^?1, which is comparable to its theoretical capacitance, suggesting that such structure facilitates effectively charge‐transfer reactions in electrodes. This work provides a facile pathway for tailoring the porosity of graphene‐based materials for improved performances. Moreover, this work has also furthered our understanding in the effect of pore and hydrogel structures on the electrochemical properties of materials.     

Effect of surfactant on the morphology and capacitive performance of porous NiCo2O4

A promising nickel cobaltite oxide (NiCo₂O₄) composite electrode material was successfully synthesized by a sol-gel method and followed by a simple sintering process. The microstructure and surface morphology of NiCo₂O₄ modified by hexadecyltrimethylammonium bromide (CTAB) and polyvinyl alcohol were physically characterized by powder X-ray diffraction and scanning electron microscopy. Meanwhile, electrochemical performance was widely investigated in 2 M KOH aqueous electrolyte using cyclic voltammetry, galvanostatic charge-discharge test, and electrochemical impedance spectroscopy. The results show that evident porous microstructure was successfully fabricated by CTAB. The NiCo₂O₄ controlled by CTAB exhibited highly specific capacitance of 1,440 F?g^?1 at a current density of 5 mA?cm^?2. Remarkably, it still displays desirable cycle retention of 94.1 % over 1,000 cycle numbers at a current density of 20 mA?cm^?2. The excellent electrochemical performance suggests its potential application in electrode material for electrochemical capacitors.     

Electrodeposited Ni(OH)<Subscript>2</Subscript> nanostructures on electro-etched carbon fiber paper for highly stable supercapacitors

Herein, we introduce a facile, inexpensive and fast, and additive-/template-free method to fabricate highly stable nickel hydroxide nanofibers for supercapacitor applications. Ni(OH)₂ nanofibers were electrodeposited on electro-etched carbon fiber paper by a potential step method (Ni(OH)₂-ECFs) and characterized using scanning electron microscopy and X-ray diffraction analysis. Electrochemical performance of Ni(OH)₂-ECF was studied in symmetric two-electrode assembly by cyclic voltammetry, galvanostatic charge–discharge method, and electrochemical impedance spectroscopy. A specific capacitance of 277.5 F g^?1 was achieved for the symmetric supercapacitor based on two identical Ni(OH)₂-ECFs. Our findings demonstrate high-rate capability with excellent stability (approximately 100 % capacitance retention) for Ni(OH)₂-ECF supercapacitor, originated from the intimate contact between Ni(OH)₂ and ECF. Our studies suggest the Ni(OH)₂-ECF electrode as an excellent material for supercapacitor applications.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体,水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂）,制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM）,透射电镜（TEM）,X射线衍射（XRD）,热重分析（TGA）对其结构进行表征;采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面,形成多层次结构,并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构;MnO₂纳米片具有典型的K-Birnessite 型晶体结构;复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1;随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极,活性炭（AC）为负极,1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器,发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V,容量可达86F·g^-1,且表现出良好的电容特性和大电流放电性能.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.