镀钴泡沫镍基板界面机理研究

研究了泡沫镍镀钴镍电极的初期化成行为,发现在电池端电压0.2V附近出现一个充电电压平台,1.0V附近出现第二个充电电压平台,而纯泡沫镍做基板的镍电极无此现象.循环伏安和XRD测试验证了两个电压平台对应的反应是Co氧化为Co(OH)2和Co(OH)2氧化为CoOOH反应.EPMA线扫描显示,镍电极化成后基板表面钴元素呈梯度分布.结果表明,泡沫镍表面的金属钴通过电化学溶解沉淀机理,在基板附近生成梯度分布的CoOOH.     

纳米级氢氧化镍和钴对镍电极性能的影响

通过充放电曲线和交流阻抗谱的测定探讨了纳米级氢氧化镍和氢氧化镍表面包复CoOOH以及镍箔上电镀钴层对氢氧化镍粉末压制的镍电极性能的影响。结果表明．纳米级氢氧化镍有较快的活化能力，CoOOH包Ni(OH)2则有较高的放电容量，而比例适当的纳米复合镍电极才有更好的电化学性能。氢氧化镍表面包复CoOOH可改善镍电极的充放电性能；镍箔上镀钴可大大降低电极过程的电荷转移电阻；钴含量大于3％后．虽然活化速度有所下降，但是大电流充放电时，镍电极活性物的利用率更高，放电容量更大。纳米级Ni(OH)2含量大于30%后，镍电极的活化速度不仅未能加快，反而略有减慢，而且容量也降低。     

“HOT” Alkaline Hydrolysis of Amorphous MOF Microspheres to Produce Ultrastable Bimetal Hydroxide Electrode with Boosted Cycling Stability

Nickel/cobalt hydroxide is a promising battery‐type electrode material for supercapacitors. However, its low cycle stability hinders further applications. Herein, Ni_0.7Co_0.3(OH)₂ core–shell microspheres exhibiting extreme‐prolonged cycling life are successfully synthesized, employing Ni‐Co‐metal–organic framework (MOF) as the precursor/template and a specific hydrolysis strategy. The Ni‐Co‐MOF and KOH aqueous solution are separated and heated to 120 °C before mixing, rather than mixing before heating. Through this hydrolysis strategy, no MOF residual exists in the product, contributing to close stacking of the hydroxide nanoflakes to generate Ni_0.7Co_0.3(OH)₂ microspheres with a robust core–shell structure. The electrode material exhibits high specific capacity (945 C g^?1 at 0.5 A g^?1) and unprecedented cycling performance (100% after 10 000 cycles). The fabricated asymmetric supercapacitor delivers an energy density of 40.14 Wh kg^?1 at a power density of 400.56 W kg^?1 and excellent cycling stability (100% after 20 000 cycles). As far as is known, it is the best cycling performance for pure Ni/Co(OH)₂.     

Effects of single electrodes of Ni(OH)2 and activated carbon on electrochemical performance of Ni(OH)2–activated carbon asymmetric supercapacitor

Nickel hydroxide consisting of loosely packed nanospheres was synthesized as positive electrode material for an asymmetric capacitor based on Ni(OH)₂ and activated carbon (AC). Two series of supercapacitors were fabricated to investigate the effects of the single electrodes of Ni(OH)₂ and AC on the electrochemical performance of asymmetric Ni(OH)₂–AC capacitor. Parameters including cell voltage window, specific capacitance and cyclic stability were assessed. In one series of supercapacitors, mass of Ni(OH)₂ was excessive while mass of AC was varied, the AC electrode thus constrained both the capacitance and the upper limit of cell voltage. Deficiency of AC resulted in lower specific capacitance and narrower cell voltage window but benefited to cyclic stability. In the other series of supercapacitors, the mass of AC was excessive whereas the mass of Ni(OH)₂ was changeable in each cell, Ni(OH)₂ electrode thus dominated both the capacitance and the lower limit of cell voltage. As a consequence, deficiency of Ni(OH)₂ led to higher specific capacity and wider cell voltage window as well as lower cyclic stability. These results can contribute to improving understanding of and optimizing performance of asymmetric Ni(OH)₂–AC capacitor.     

镍氢电池掺钴镍正极的研究进展

对镍氢电池的镍正极覆钴改性的研究进展进行了综述,系统归纳了添加剂Co、CoO、Co(OH)2、CoOOH对电池镍正极性能的改善及覆钴工艺的研究进展,并对覆钴工艺的前景提出了新的展望.     

Synthesis,characterization, and electrochemical properties of Ni(OH)<Subscript>2</Subscript>/ultra-stable Y zeolite composite

A novel composite of Ni(OH)₂/ultra-stable Y zeolite materials was synthesized by an improved chemical precipitation method, which used the ultra-stable Y zeolite as the template. The Ni(OH)₂/ultra-stable Y zeolite composite and its microstructure were characterized by X-ray diffraction measurements and transmission electron microscopy. Electrochemical studies were carried out using cyclic voltammetry, chronopotentiometry technology and ac impedance spectroscopy, respectively. The result shows that the loose-packed whisker Ni(OH)₂ phase has profound impacts on electrode performance at very high power output. A maximum discharge capacity of 185.6 mA-h/g (1670 F/g), or 371 mA-h/g (3340 F/g) after correcting for weight percent of nickel hydroxide phase at the current density of 625 mA/g could be achieved in a half-cell setup configuration for the Ni(OH)₂/ultra-stable Y zeolite electrode, suggesting its potential application in electrode material for secondary batteries and electrochemical capacitors. Furthermore, the effect of NH₄Cl concentration on the electrochemical properties characteristics has also been systemically explored.     

Study on medium-temperature chemical heat storage using mixed hydroxides

It was demonstrated that chemical heat storage materials mixed with metal hydroxides were capable of storing heat at medium temperatures of approximately 200–300 °C. The performances of the developed materials were demonstrated in a thermo-balance and packed bed reactor. The mixed hydroxides can increase the operation heat storage temperature by changing the composition of mixed metal oxides in the material. Mg_αNi_1?α(OH)₂, which is a mixed hydroxide of magnesium hydroxide, Mg(OH)₂, and nickel hydroxide, Ni(OH)₂, is a candidate heat storage material. The mixed hydroxide was dehydrated, that is, it was capable of storing heats at 200–300 °C, at which pure Mg(OH)₂ could not be dehydrated and could not store heat. The heat output performance of the material was examined in a packed bed reactor. It was shown that the mixed hydroxide material was potentially useful for chemically storing medium-temperature heat such as waste heats emitted from internal combustion engines, solar energy system and high-temperature processes.     

An improvement on redox reversibility of cobalt oxyhydroxide in nickel hydroxide electrodes

In this paper, two kinds of cobalt oxyhydroxide conductive networks were introduced into nickel hydroxide electrodes by different methods—electrochemically-oxidized (EO) or chemically oxidized (CO) CoOOH on the surface of nickel hydroxide particles. The redox behaviors of them were studied by using cyclic voltammetry (CV) and X-ray diffraction (XRD) measurements. It shows that because CoOOH(CO) has better redox reversibility than CoOOH(EO), the structure of the former can be kept when nickel hydroxide electrodes are subjected to a negative potential. Thus, 98.5% capacity retention is demonstrated on nickel/metal-hydride (Ni–MH) batteries with CoOOH(CO) after being imposed over-discharge state storage; on the contrary, only 81.4% capacity retention is found on the batteries with CoOOH(EO).     

磺化酞菁钴对Ni-MH电池性能的影响

研究磺化酞菁钴作为负极添加剂时Ni-MH电池容量、放电电压、电极的循环伏安特性和循环性能,并将其与酞菁钴比较.实验数据显示,当磺化酞菁钴添加量为3%时, Ni-MH-MH电池的放电中值电压较高,以1C倍率充放电循环300次时,容量仍保持在75%以上.     

Series of Halogen Engineered Ni(OH)2 Nanosheet for Pseudocapacitive Energy Storage with High Energy Density

Ni(OH)₂ nanosheet, acting as a potential active material for supercapacitors, commonly suffers from sluggish reaction kinetics and low intrinsic conductivity, which results in suboptimal energy density and long cycle life. Herein, a convenient electrochemical halogen functionalization strategy is applied for the preparation of mono/bihalogen engineered Ni(OH)₂ electrode materials. The theoretical calculations and experimental results found that thanks to the extraordinarily high electronegativity, optimal reversibility, electronic conductivity, and reaction kinetics could be achieved through F functionalization  . However, benefiting from the largest ionic radius, I Ni(OH)₂ contributes the best specific capacity and morphology transformation, which is a new finding that distinguishes it from previous reports in the literature. The exploration of the interaction effect of halogens (F, I Ni(OH)₂, F, Br Ni(OH)₂, and Cl, I Ni(OH)₂) manifests that F, I Ni(OH)₂ delivers a higher specific capacity of 200.6 mAh g⁻¹ and an excellent rate capability of 58.2% due to the weaker electrostatic repulsion, abundant defect structure, and large layer spacing. Moreover, the F, I Ni(OH)₂//FeOOH@NrGO device achieves a high energy density of 97.4 Wh kg⁻¹ and an extremely high power density of 32426.7 W kg⁻¹, as well as good cycling stability. This work develops a pioneering tactic for designing energy storage materials to meet various demands.     

A Universal Converse Voltage Process for Triggering Transition Metal Hybrids In Situ Phase Restruction toward Ultrahigh‐Rate Supercapacitors

Defect engineering holds great promise for precise configuration of electrode materials for dramatically enhanced performance in the field of energy storage, but the high energy/large time cost and lack of control involved in this process represent a serious limit to its use. In response, a low‐energy‐cost and ultrafast universal converse voltage process is developed to effectively activate the capacitive performance of transition metal compounds integrated on carbon fiber paper, including Co‐, Ni‐, Mn‐, Fe‐, and Cr‐based hybrids. As a representative example, this process triggers a phase conversion from cobalt hydroxide to electric‐field‐activated CoOOH (EA‐CoOOH), leading to the formation of molecular structure with abundant defects, lattice disorders, and connecting holes, responsible for an enhanced performance within 10 min at room temperature. Moreover, the retained Co²⁺ in EA‐CoOOH results in increased activity, confirmed by density functional theory calculations. Consequently, these EA‐CoOOH hybrids deliver a capacitance value of 832 F g^?1 at a current density of 1 A g^?1 and exhibit a retention rate up to 78% (649 F g^?1) at a super‐large current density of 200 A g^?1. This technology paves a way for ultrafast configuration/modulation of defects on advanced materials toward application in the fields of energy and catalysis.     

Quinary icosahedral quasicrystalline Ti–V–Ni–Mn–Cr alloy: A novel anode material for Ni-MH rechargeable batteries

The substitution of manganese and chromium for 6 at.% nickel in Ti_1.6V_0.4Ni leads the rapid quenching synthesis of quinary icosahedral phase (i-phase) evidenced by the observations of 2-, 3- and 5-fold symmetries. As negative electrode in Ni-MH battery, the quinary Ti–V–Ni–Mn–Cr i-phase can deliver a maximum discharge capacity of 278 mAh g^?1 at 30 mA g^?1, larger than that of Ti_1.6V_0.4Ni master alloy anode owing to Mn and/or Cr doping. After a preliminary test of 30 consecutive cycles the cycling capacity retention rate (CR%) is 80%. The strong chemisorption of hydrogen shown in cyclic voltammetric (CV) response indicates that the electrocatalytic activity improvement for the i-phase negative electrode is highly demanded.     

Self‐Stacked Reduced Graphene Oxide Nanosheets Coated with Cobalt–Nickel Hydroxide by One‐Step Electrochemical Deposition toward Flexible Electrochromic Supercapacitors

The implementation of an optical function into supercapacitors is an innovative approach to make energy storage devices smarter and to meet the requirements of smart electronics. Here, it is reported for the first time that nickel–cobalt hydroxide on reduced graphene oxide can be utilized for flexible electrochromic supercapacitors. A new and straightforward one‐step electrochemical deposition process is introduced that is capable of simultaneously reducing GO and depositing amorphous Co_(1−x)Ni _x (OH)₂ on the rGO. It is shown that the rGO nanosheets are homogeneously coated with metal hydroxide and are vertically stacked. No high temperature processes are used so that flexible polymer‐based substrates can be coated. The synthesized self‐stacked rGO–Co_(1−x)Ni _x (OH)₂ nanosheet material exhibits pseudocapacitive charge storage behavior with excellent rate capability, high Columbic efficiency, and nondiffusion limited behavior. It is shown that the electrochemical behavior of the Ni(OH)₂ can be modulated, by simultaneously depositing nickel and cobalt hydroxide, into broad oxidization and reduction bands. Further, the material exhibits electrochromic property and can switch between a bleached and transparent state. Literature comparison reveals that the performance characteristics of the rGO–Co_(1−x)Ni _x (OH)₂ nanosheet material, in terms of gravimetric capacitance, areal capacitance, and long‐term cycling stability, are among the highest reported values of supercapacitors with electrochromic property.     

A study on the effect of nanosized tin oxide on the electrochemical performance of nanosized nickel hydroxide in alkali solution

The nickel hydroxide nanopowders mixed with SnO₂ nanoparticles as an additive in different proportions were prepared and characterised by X-ray diffraction (XRD), transmission electron microscope (TEM) and electrochemical measurement by cyclic voltammetry. XRD examination suggests that the composite Ni(OH)₂/SnO₂ has both the phases of α-Ni(OH)₂ and β-Ni(OH)₂ with SnO₂ nanoparticles. TEM images show the nanostructures of nickel hydroxide, SnO₂ and dispersion of SnO₂ nanoparticles on nickel hydroxide particles in the composite. The electrochemical studies revealed that the composite electrode has better redox reversibility and specific capacitance values compared to the pure Ni(OH)₂, α-Ni(OH)₂ and usual β-Ni(OH)₂ electrodes and it can be applied as a promising positive active material for alkaline rechargeable batteries.     

Multilayer super-short carbon nanotube/nickel hydroxide nanoflakes for enhanced supercapacitor properties

Multilayer super-short carbon nanotubes (SSCNTs) could be synthesized by tailoring the raw multiwalled carbon nanotubes with a simple ultrasonic oxidation-cut method. Nanostructured layered nickel hydroxide and SSCNTs have been successfully assembled to form Ni(OH)₂/SSCNTs composite by electrostatic force. Compared with pure Ni(OH)₂ (665 F g^?1), the Ni(OH)₂/SSCNTs composite exhibits the much better electrochemical performance with a specific capacitance of 1887 F g^?1 at 1 A g^?1, and demonstrates a good rate capability and excellent long-term cyclic stability (92 % capacity retention after 3000 cycles). It is the reason that the SSCNTs can form a conductive network onto the surface of Ni(OH)₂ nanoflakes, and their excellent electric conductivity is advantaged to the charge transport on the electrode in discharge process and charge process. Therefore, the greatly enhanced capacitive performance of Ni(OH)₂/SSCNTs can be attributed to a synergetic effect of Ni(OH)₂ and SSCNTs.     

Plasmon-promoted oxygen evolution catalysis with Ag nanocrystals loaded α-Co(OH)2 nanosheets

Exploration of low-cost and high efficiency oxygen evolution reaction (OER) electrocatalysts is very important for the large-scale industrial application of alkaline water splitting driven by electricity. The present promising cobalt-based catalysts still leave room to meet the activity requirement. Here, a composite catalyst of α-Co(OH)₂/Ag was synthesized by a simple photochemical deposition route, which was designed to improve the electrocatalytic activity for OER. Moreover, a photoinduced surface plasmon on Ag particles was found to further enhance the catalytic performance under low power of laser irradiation. Loading of silver nanocrystals on α-Co(OH)₂ nanosheets can decrease the overpotential towards OER for 10 mA cm^?2 from 320 to 288 mV, this value can be further decreased of 45 mV under 1000 mW of laser irradiation with a wavelength of 532 nm. The derivation of the catalyst during the OER process was examined, which indicates the structural transformation from α-Co(OH)₂ to CoOOH. The photoinduced surface plasmon modulates the electronic structure of cobalt sites, facilitates the formation of active cobalt species, and induces the enhancement of catalytic activity. These findings may give some hints for plasmon-induced electrocatalysis and the design of advanced electrocatalysts.     

Tetrahedral Bonding Structure (Ni3-Se) Induced by Lattice-Distortion of Ni to Achieve High Catalytic Activity in Na–Se Battery

Fabrication of transition-metal catalytic materials is regarded as a promising strategy for developing high-performance sodium–selenium (Na–Se) batteries. However, more systematic explorations are further demanded to find out how their bonding interactions and electronic structures can affect the Na storage process. This study finds that lattice-distorted nickel (Ni) structure can form different bonding structures with Na₂Se₄, providing high activity to catalyze the electrochemical reactions in Na–Se batteries. Using this Ni structure to prepare electrode (Se@NiSe₂/Ni/CTs) can realize rapid charge transfer and high cycle stability of the battery. The electrode exhibits high storage performance of Na⁺; i.e., 345 mAh g⁻¹ at 1 C after 400 cycles, and 286.4 mAh g⁻¹ at 10 C in rate performance test. Further results reveal the existence of a regulated electronic structure with upshifts of the d-band center in the distorted Ni structure. This regulation changes the interaction between Ni and Na₂Se₄ to form a Ni₃–Se tetrahedral bonding structure. This bonding structure can provide higher adsorption energy of Ni to Na₂Se₄ to facilitate the redox reaction of Na₂Se₄ during the electrochemical process. This study can inspire the design of bonding structure with high performance in conversion-reaction-based batteries.     

A low temperature route to prepare LaFeO3 and LaCoO3

A combination of digestion and further low temperature calcination to crystallize the product was employed to prepare LaFeO₃ (LF) and LaCoO₃ (LC) powders. Freshly co-precipitated lanthanum and ferric (or cobalt) hydroxide gels by sodium hydroxide were allowed to react at 100 °C under refluxing and stirring conditions for 4-6 h. These oven dried powders were heated at 450 °C to form crystalline LF (or LC) powders. The phase contents and lattice parameters were investigated by X-ray diffraction (XRD). Transmission electron microscope (TEM) investigations were carried out to examine the morphology and average particle size of these powders.     

Synthesis and characterizations of nano-sized Ni(OH)2 and Ni(OH)2/poly(vinyl alcohol) nano composite

Nano-sized Ni(OH)₂ was synthesized by a co-precipitation method. Peaks between 500 and 750 cm⁻¹ in Fourier transform infrared spectroscopy (FTIR) confirmed the presence of metal hydroxide stretching. Thermo gravimetric analysis inferred that 69 wt% residue remained above 750 °C. High-resolution transmission electron microscopy analysis of Ni(OH)₂ revealed its size ranged from 80 to 110 nm with smooth morphology. Scanning electron microscopy inferred that pure Ni(OH)₂ has nano rod-like morphology and higher weight percentage of aniline-intercalated Ni(OH)₂ has agglomerated structure. UV–Vis spectrum detected the presence of Ni²⁺ ions at 210 nm and the existence of amino group in the basal spacing of Ni(OH)₂ was not clearly appeared in the spectrum. Photoluminescence (PL) inferred that aniline-intercalated Ni(OH)₂ showed higher PL intensity than the pristine poly(vinyl alcohol) its and nano composite.     

Exploration of Advanced Electrode Materials for Approaching High‐Performance Nickel‐Based Superbatteries

The surging interest in high performance, low‐cost, and safe energy storage devices has spurred tremendous research efforts in the development of advanced electrode active materials. Herein, the in situ growth of zinc–iron layered double hydroxide (Zn–Fe LDH) on graphene aerogel (GA) substrates through a facile, one‐pot hydrothermal method is reported. The strong interaction and efficient electronic coupling between LDH and graphene substantially improve interfacial charge transport properties of the resulting nanocomposite and provide more available redox active sites for faradaic reactions. An LDH–GA||Ni(OH)₂ device is also fabricated that results in greatly enhanced specific capacity (187 mAh g^?1 at 0.1 A g^?1), outstanding specific energy (147 Wh kg^?1), excellent specific power (16.7 kW kg^?1), along with 88% capacity retention after >10 000 cycles. This approach is further extended to Ni–MH and Ni–Cd batteries to demonstrate the feasibility of compositing with graphene for boosting the energy storage performance of other well‐known Ni‐based batteries. In contrast to conventional Ni‐based batteries, the nearly flat voltage plateau followed by a sloping potential profile of the integrated supercapacitor–battery enables it to be discharged down to 0 V without being damaged. These findings provide new prospects for the design of high‐performance and affordable superbatteries based on earth‐abundant elements.