Effect of lithium boron oxide glass coating on the electrochemical performance of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript>

The effect of the lithium boron oxide glass coating on the electrochemical performance of LiNi_1/3Co_1/3Mn_1/3O₂ has been investigated via solution method. The morphology, structure, and electrochemical properties of the bare and coated LiNi_1/3Co_1/3Mn_1/3O₂ are characterized by scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, and charge–discharge tests. The results showed that the lattice structure of LiNi_1/3Co_1/3Mn_1/3O₂ is not changed after coating. The coating sample shows good high-rate discharge performance (148 mAh g⁻¹ at 5.0 C rate) and cycling stability even at high temperature (with the capacities retention about 99% and 87% at room and elevated temperature after 50 cycles). The Li⁺ diffusion coefficient is also largely improved, while the charge transfer resistance, side reactions within cell, and the erosion of Hydrofluoric Acid all reduced. Consequently, the good electrochemical performances are obtained.     

Synthesis of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> nanoparticles by modified Pechini method and their enhanced rate capability

Layered LiNi_1/3Co_1/3Mn_1/3O₂ nanoparticles were prepared by modified Pechini method and used as cathode materials for Li-ion batteries. The pyrolytic behaviors of the foamed precursors were analyzed by use of simultaneous thermogravimetric and differential thermal analysis (TG-DTA). Structure, morphology and electrochemical performance characterization of the samples were investigated by X-ray diffraction (XRD), field emission scanning electron macroscopy(SEM), Brunauer-Emmett-Teller (BET) specific surface area and charge–discharge tests. The results showed that the samples prepared by modified Pechini method caclined at 900 °C for 10 h were indexed to pure LiNi_1/3Co_1/3Mn_1/3O₂ with well hexagonal structure. The particle size was in a range of 100–300 nm. The specific surface area was larger than that of the as-obtained sample by Pechini method. Initial discharge capacity of 163.8 mAh/g in the range 2.8–4.4 V (vs. Li/Li⁺) and at 0.1C for LiNi_1/3Co_1/3Mn_1/3O₂ prepared by modified Pechini method was obtained, higher than that of the sample prepared by Pechini method (143.5 mAh/g). Moreover, the comparison of electrochemical results at different current rates indicated that the sample prepared by modified Pechini method exhibited improved rate capability.     

Towards high-performance cathode materials for lithium-ion batteries: Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-coated LiNi<Subscript>0.8</Subscript>Co<Subscript>0.15</Subscript>Zn<Subscript>0.05</Subscript>O<Subscript>2</Subscript>

Zn-doped LiNi_0.8Co_0.2O₂ exhibits impressive electrochemical performance but suffers limited cycling stability due to the relative large size of irregular and bare particle which is prepared by conventional solid-state method usually requiring high calcination temperature and prolonged calcination time. Here, submicron LiNi_0.8Co_0.15Zn_0.05O₂ as cathode material for lithium-ion batteries is synthesized by a facile sol-gel method, which followed by coating Al₂O₃ layer of about 15 nm to enhance its electrochemistry performance. The as-prepared Al₂O₃-coated LiNi_0.8Co_0.15Zn_0.05O₂ cathode delivers a highly reversible capacity of 182 mA h g^?1 and 94% capacity retention after 100 cycles at a current rate of 0.5 C, which is much superior to that of bare LiNi_0.8Co_0.15Zn_0.05O₂ cathode. The enhanced electrochemistry performance can be attributed to the Al₂O₃-coated protective layer, which prevents the direct contact between the LiNi_0.8Co_0.15Zn_0.05O₂ and electrolyte. The escalating trend of Li-ion diffusion coefficient estimated form electrochemical impedance spectroscopic (EIS) also indicate the enhanced structural stability of Al₂O₃-coated LiNi_0.8Co_0.15Zn_0.05O₂, which rationally illuminates the protection mechanism of the Al₂O₃-coated layer.     

BiFeO<Subscript>3</Subscript>-coated spinel LiNi<Subscript>0.5</Subscript>Mn<Subscript>1.5</Subscript>O<Subscript>4</Subscript> with improved electrochemical performance as cathode materials for lithium-ion batteries

Spinel LiNi_0.5Mn_1.5O₄ cathode material is a promising candidate for next-generation rechargeable lithium-ion batteries. In this work, BiFeO₃-coated LiNi_0.5Mn_1.5O₄ materials were prepared via a wet chemical method and the structure, morphology, and electrochemical performance of the materials were studied. The coating of BiFeO₃ has no significant impact on the crystal structure of LiNi_0.5Mn_1.5O₄. All BiFeO₃-coated LiNi_0.5Mn_1.5O₄ materials exhibit cubic spinel structure with space group of Fd3m. Thin BiFeO₃ layers were successfully coated on the surface of LiNi_0.5Mn_1.5O₄ particles. The coating of 1.0 wt% BiFeO₃ on the surface of LiNi_0.5Mn_1.5O₄ exhibits a considerable enhancement in specific capacity, cyclic stability, and rate performance. The initial discharge capacity of 118.5 mAh g^?1 is obtained for 1.0 wt% BiFeO₃-coated LiNi_0.5Mn_1.5O₄ with very high capacity retention of 89.11% at 0.1 C after 100 cycles. Meanwhile, 1.0 wt% BiFeO₃-coated LiNi_0.5Mn_1.5O₄ electrode shows excellent rate performance with discharge capacities of 117.5, 110.2, 85.8, and 74.8 mAh g^?1 at 1, 2, 5, and 10 C, respectively, which is higher than that of LiNi_0.5Mn_1.5O₄ (97.3, 90, 77.5, and 60.9 mAh g^?1, respectively). The surface coating of BiFeO₃ effectively decreases charge transfer resistance and inhibits side reactions between active materials and electrolyte and thus induces the improved electrochemical performance of LiNi_0.5Mn_1.5O₄ materials.     

Understanding the accumulated cycle capacity fade caused by the secondary particle fracture of LiNi<Subscript>1-x-y</Subscript>Co<Subscript>x</Subscript>Mn<Subscript>y</Subscript>O<Subscript>2</Subscript> cathode for lithium ion batteries

Effect of secondary particle fracture on the accumulated cycle capacity fade of LiNi_1-x-yCo_xMn_yO₂ cathode is difficult to evaluate since performance degradation of electrode material is always caused by several factors simultaneously. Herein, LiNi_0.5Co_0.2Mn_0.3O₂ single particles (Sin-P) are prepared and introduced as a reference to understand the accumulated cycle capacity fade caused by the secondary particle fracture of LiNi_0.5Co_0.2Mn_0.3O₂ secondary particles (Sec-P). Sec-P exhibited accumulated cycle capacity fade compared to Sin-P when cycled at high rate, high voltage, and high temperature. The accumulated cycle capacity fade was mainly caused by the secondary particle fracture of Sec-P, which was confirmed by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM) analysis. Further, XPS and electrochemical impedance spectroscopy (EIS) analysis indicated that the surface property changes and resistance rise were responsible for the accumulated cycle capacity fade. The study provides a novel way to analyze the accumulated cycle capacity fade caused by the secondary particle fracture and is helpful for understanding the performance degradation mechanism of electrode material.     

A study on carbon-coated LiNi1/3Mn1/3Co1/3O2 cathode material for lithium secondary batteries

The surface of LiNi_1/3Mn_1/3Co_1/3O₂ was coated with amorphous carbon to enhance the conductivity of the material. Electrochemical studies were performed by assembling 2032 coin cells with lithium metal as an anode. When carbon was coated on the surface, the LiNi_1/3Mn_1/3Co_1/3O₂ cathode material showed an improved rate capability, thermal stability, and cycle performance.     

Influence of Li source on tap density and high rate cycling performance of spherical Li[Ni<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>]O<Subscript>2</Subscript> for advanced lithium-ion batteries

Spherical Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode materials with different microstructure have been prepared by a continuous carbonate co-precipitation method using LiOH⋅H₂O, Li₂CO₃, CH₃COOLi⋅2H₂O and LiNO₃ as lithium source. The effects of Li source on the physical and electrochemical properties of Li[Ni_1/3Co_1/3Mn_1/3]O₂ are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. The results show that the morphology, tap density and high rate cycling performance of Li[Ni_1/3Co_1/3Mn_1/3]O₂ spherical particles are strongly affected by Li source. Among the four Li sources used in this study, LiOH⋅H₂O is beneficial to enhance the tap density of Li[Ni_1/3Co_1/3Mn_1/3]O₂, and the tap density of as-prepared sample reaches 2.32 g cm⁻³. Meanwhile, Li₂CO₃ is preferable when preparing the Li[Ni_1/3Co_1/3Mn_1/3]O₂ with high rate cycling performance, upon extended cycling at 1 and 5C rates, 97.5% and 92% of the initial discharge capacity can be maintained after 100 cycles.     

Synthesis and surface treatment of LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion batteries

In order to shorten process time and possibly reduce synthesis cost of LiNi_1/3Co_1/3Mn_1/3O₂, the cathode material was prepared by solution combustion and microwave synthesis routes with reduced duration of calcination. The products were also surface-modified with Al₂O₃ by a mechano-thermal coating process to enhance cyclability. The structure and morphology of the bare and the surface-modified LiNi_1/3Co_1/3Mn_1/3O₂ samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, and differential scanning calorimetry techniques. At a 0.1-C rate and between 4.6 and 2.5 V, the products delivered a first-cycle discharge capacity of as much as 195 mA h/g. Surface modification of LiNi_1/3Co_1/3Mn_1/3O₂ with alumina resulted in improved cyclability.     

Mechanism of the Enhanced Electrochemical Properties of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> Cathode Materials by a Pre-Sintering Process

α-NaFeO₂ layered LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials were synthesized by mechanical milling accompanied by the solid phase sintering. The sample exhibited a good crystallinity and layered structure while sintered at 900°C, which can be further improved by adding a pre-sintering process at 500°C before high temperature sintering. The sample with a pre-sintering process presents an average particle size about 0.6 μm, and a hexagonal crystalline structure. The optimally fabricated sample showed a first charge capacity of 210.2 mA h/g, discharge capacity of 171.2 mA h/g with a current rate of 0.2 C within the voltage range of 2.7~4.5 V. With increasing the current rate to 1 C, the charge–discharge capacity faded quickly during the cycling process, which can be partially recovered while operated at a low current rate. However, the capacity fading at a current rate of 2 C was largely irreversible. The evolution of the surface chemical states was evaluated using X-ray photoelectron spectroscopy on the charged and discharged samples to understand the high rate capacity fading.     

Effect of the preparation method of the cathode material LiNi<Subscript>0.33</Subscript>Mn<Subscript>0.33</Subscript>Co<Subscript>0.33</Subscript>O<Subscript>2</Subscript> on the electrochemical characteristics of a lithium ion cell

Complex metal oxides with the composition LiNi_0.33Mn_0.33Co_0.33O₂ prepared by various methods: sol–gel method, solid-phase method, and thermal destruction of metal-containing compounds in oil were studied. The results of elemental analysis, TGA/DSC, powder X-ray diffraction, SEM, TEM, as well as the results of electrochemical testing of the cathodes based on the obtained materials are presented. The complex metal oxides LiNi_0.33Mn_0.33Co_0.33O₂ prepared by sol–gel processes and thermal destruction of metal-containing compounds in oil consist of primary nanosized crystallites with an average size of 90 nm covered by a nanometer carbon layer, which improves the electrochemical characteristics of lithium ion batteries.     

Improvement of electrochemical properties of LiNi1/3Mn1/3Co1/3O2 by coating with La0.4Ca0.6CoO3

In this paper, La_0.4Ca_0.6CoO₃-coated LiNi_1/3Mn_1/3Co_1/3O₂ is successfully prepared by the sol–gel method associated with microwave pyrolysis method. The structure and electrochemical properties of the La_0.4Ca_0.6CoO₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ are investigated by using X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and charge/discharge tests. XRD analyses show that the La_0.4Ca_0.6CoO₃ coating does not change the structure of LiNi_1/3Co_1/3Mn_1/3O₂. The electrochemical performance studies demonstrate that 2 wt.% La_0.4Ca_0.6CoO₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ powders exhibit the best electrochemical properties, with an initial discharge capacity of 156.9 mAh g^–1 and capacity retention of 98.9 % after 50 cycles when cycled at a current density of 0.2 C between 2.75 and 4.3 V. La_0.4Ca_0.6CoO₃ coating can improve the rate performance because of the enhancement of the surface electronic/ionic transportation by the coating layer. EIS results suggest that the coating La_0.4Ca_0.6CoO₃ plays an important role in suppressing the increase of cell impedance with cycling especially for the increase of charge-transfer resistance.     

Effects of Mg,Al Co-doping into Mn site on electrochemical performance of LiNi<Subscript>0.5</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.3</Subscript>O<Subscript>2</Subscript>

In order to study the influence of multiple ions doping into single-site on the structure and electrochemical properties of Ni-rich layered-structure cathode material LiNi_0.5Co_0.2Mn_0.3O₂, the coprecipitation of hydroxides was applied to synthesize Mg, Al co-doped cathode material LiNi_0.5Co_0.2Mn_0.3–x Mg_1/2x Al_1/2x O₂ (x = 0.00, 0.01, 0.02, 0.04) in this paper. Morphology and structure, kinetic parameter, impedance and electrochemical performance of the material were respectively characterized by SEM, XRD, CV, EIS and galvanostatic charge/discharge test. The results of comprehensive analysis showed that the properties of material were improved obviously when the amount of doping was 0.02. At this amount of doping, the corresponding material has smaller cation mixing, higher hexagonal ordering of layered-structure, larger Li⁺ ion diffusion coefficients which are 2.444 × 10^–10 and 4.186 × 10^–10 cm² s^–1 for Li+ intercalation and deintercalation respectively, smaller impedance which is 33.93 Ω, higher specific capacity of first-discharge which is 168.01 mA h g^–1 and higher capacity retention rate which is up to 95.06% after 20 cycles at 0.5 C (100 mA g^–1).     

Li4Mn5O12包覆对三元正极材料结构和性能的影响

LiNi(1/3)Mn(1/3)Co(1/3)O2具有很高的理论比容量,但是三元正极材料在高电压下长循环时,其表面结构发生较大的衰退,导致电池的循环性能和倍率性能变差。本文采用耐高电压且结构稳定的富锂尖晶石Li4Mn5O(12)包覆LiNi(1/3)Mn(1/3)Co(1/3)O2可以有效改善材料的电化学性能。通过XRD、SEM、XPS和TEM等手段对包覆后的材料进行分析,证实了在LiNi(1/3)Mn(1/3)Co(1/3)O2的表面形成了10nm厚的均匀Li4Mn5O(12)的包覆层;在循环100圈后,包覆后的LiNi(1/3)Mn(1/3)Co(1/3)O2仍具有179.5m Ah/g的放电比容量和88.6%容量保持率,明显高于未包覆的LiNi(1/3)Mn(1/3)Co(1/3)O2的78.3%容量保持率。因此,利用富锂尖晶石Li4Mn5O(12)包覆LiNi(1/3)Mn(1/3)Co(1/3)O2为实现更高能量密度的锂离子电池提供了新的途径。     

Co-precipitation spray-drying synthesis and electrochemical performance of stabilized LiNi<Subscript>0.5</Subscript>Mn<Subscript>1.5</Subscript>O<Subscript>4</Subscript> cathode materials

In this paper, the LiNi_0.5Mn_1.5O₄ cathode materials of lithium-ion batteries are synthesized by a co-precipitation spray-drying and calcining process. The use of a spray-drying process to form particles, followed by a calcination treatment at the optimized temperature of 750 °C to produce spherical LiNi_0.5Mn_1.5O₄ particles with a cubic crystal structure, a specific surface area of 60.1 m² g^?1, a tap density of 1.15 g mL^?1, and a specific capacity of 132.9 mAh g^?1 at 0.1 C. The carbon nanofragment (CNF) additives, introduced into the spheres during the co-precipitation spray-drying period, greatly enhance the rate performance and cycling stability of LiNi_0.5Mn_1.5O₄. The sample with 1.0 wt.% CNF calcined at 750 °C exhibits a maximum capacity of 131.7 mAh g^?1 at 0.5 C and a capacity retention of 98.9% after 100 cycles. In addition, compared to the LiNi_0.5Mn_1.5O₄ material without CNF, the LiNi_0.5Mn_1.5O₄ with CNF demonstrates a high-rate capacity retention that increases from 69.1% to 95.2% after 100 cycles at 10 C, indicating an excellent rate capability. The usage of CNF and the synthetic method provide a promising choice for the synthesis of a stabilized LiNi_0.5Mn_1.5O₄ cathode material.

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Graphical Abstract Micro/nanostructured LiNi_0.5Mn_0.5O₄ cathode materials with enhanced electrochemical performances for high voltage lithium-ion batteries are synthesized by a co-precipitation spray-drying and calcining routine and using carbon nanofragments (CNFs) as additive.

     

Al,B, and F doped LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> as cathode material of lithium-ion batteries

A series of the mixed transition metal compounds, Li[(Ni_1/3Co_1/3Mn_1/3)_1–x-y Al _x B _y ]O_2-z F _z (x = 0, 0.02, y = 0, 0.02, z = 0, 0.02), were synthesized via coprecipitation followed by a high-temperature heat-treatment. XRD patterns revealed that this material has a typical α-NaFeO₂ type layered structure with R3^- m space group. Rietveld refinement explained that cation mixing within the Li(Ni_1/3Co_1/3Mn_1/3)O₂ could be absolutely diminished by Al-doping. Al, B and F doped compounds showed both improved physical and electrochemical properties, high tap-density, and delivered a reversible capacity of 190 mAh/g with excellent capacity retention even when the electrodes were cycled between 3.0 and 4.7 V.     

Surface modification of LiNi0.8Co0.1Mn0.1O2 with conducting polypyrrole

A facile method for the surface modification of high-voltage and high-temperature LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials is demonstrated. In order to prepare polypyrrole (PPy) coating LiNi_0.8Co_0.1Mn_0.1O₂ material, the facile chemical polymerization method uses Fe(III) tosylate as oxidant and ethanol as solvent to avoid the side reaction with solvent. TEM depicts that LiNi_0.8Co_0.1Mn_0.1O₂ serves as hard template and the nanoscale PPy layer grows along the surface of LiNi_0.8Co_0.1Mn_0.1O₂ during the synthesis process. Because of flocculent and nanofiber coating layer, much improved rate performance, high temperature cycling, as well as high voltage performance are obtained. Cyclic voltammetry (CV) and electrochemical impedance spectroscopic (EIS) results demonstrate that the PPy coating layer effectively alleviates the side reactions between liquid electrolytes and LiNi_0.8Co_0.1Mn_0.1O₂ surface that are highly unstable at high temperature and high charge voltage.     

Effects of Nb substitution on structure and electrochemical properties of LiNi<Subscript>0.7</Subscript>Mn<Subscript>0.3</Subscript>O<Subscript>2</Subscript> cathode materials

Nb-doped cathode materials with the formula Li(Ni_0.7Mn_0.3)_1?xNb_xO₂ (x?=?0, 0.01, 0.02, 0.03, 0.04) have been prepared successfully by calcining the mixtures of LiOH·H₂O, Nb₂O₅, and Ni_0.7Mn_0.3(OH)₂ precursor formed through a simple continuous co-precipitation method. The effects of Nb substitution on the crystal structure and electrochemical properties of LiNi_0.7Mn_0.3O₂ were studied systematically by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and various electrochemical measurements. The results show that the lattice parameters of the Nb substitution LiNi_0.7Mn_0.3O₂ samples are slightly larger than that of pure LiNi_0.7Mn_0.3O₂, and the basic α-NaFeO₂ layered structure does not change with the Nb doping. What’s more, better morphology, lower resistance, and good cycle stability were obtained after Nb substitution. In addition, CV test exhibits that Nb doping results in lower electrode polarization and XPS results indicate that the valence of Mn kept constant but the component of Ni³⁺ decreased after doping. All the results indicate that Nb doping in LiNi_0.7Mn_0.3O₂ is a promising method to improve the properties of Ni-rich lithium-ion batteries positive-electrode materials.     

Effects of complexants on [Ni1/3Co1/3Mn1/3]CO3 morphology and electrochemical performance of LiNi1/3Co1/3Mn1/3O2

LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials for the application of lithium ion batteries were synthesized by carbonate co-precipitation routine using different ammonium salt as a complexant. The structures and morphologies of the precursor [Ni_1/3Co_1/3Mn_1/3]CO₃ and LiNi_1/3Co_1/3Mn_1/3O₂ were investigated through X-ray diffraction, scanning electron microscope, and transmission electron microscopy. The electrochemical properties of LiNi_1/3Co_1/3Mn_1/3O₂ were examined using charge/discharge cycling and cyclic voltammogram tests. The results revealed that the microscopic structures, particle size distribution, and the morphology properties of the precursor and electrochemical performance of LiNi_1/3Co_1/3Mn_1/3O₂ were primarily dependent on the complexant. Among all as-prepared LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials, the sample prepared from Na₂CO₃–NH₄HCO₃ routine using NH₄HCO₃ as the complexant showed the smallest irreversible capacity of 19.5 mAh g⁻¹ and highest discharge capacity of 178.4 mAh g⁻¹ at the first cycle as well as stable cycling performance (98.7% of the initial capacity was retained after 50 cycles) at 0.1 C (20 mA g⁻¹) in the voltage range of 2.5–4.4 V vs. Li⁺/Li. Moreover, it delivered high discharge capacity of over 135 mAh g⁻¹ at 5 C (1,000 mA g⁻¹).     

Supercapacitive performance of homogeneous Co<Subscript>3</Subscript>O<Subscript>4</Subscript>/TiO<Subscript>2</Subscript> nanotube arrays enhanced by carbon layer and oxygen vacancies

Self-supported and binder-free electrodes based on homogeneous Co₃O₄/TiO₂ nanotube arrays enhanced by carbon layer and oxygen vacancies (Co₃O₄/co-modified TiO₂ nanotube arrays (m-TNAs)) are prepared via a simple and cost-effective method in this paper. The highly ordered TNAs offer direct pathways for electron and ion transport and can be used as 3D substrate for the decoration of electroactive materials without any binders. Then, by a facile one-step calcination process, the electrochemical performance of the as-obtained carbon layer and oxygen vacancy m-TNAs is approximately 83 times higher than that of pristine TNAs. In addition, Co₃O₄ nanoparticles are uniformly deposited onto the m-TNAs by a universal chemical bath deposition (CBD) process to further improve the supercapacitive performance. Due to the synergistic effect of m-TNAs and Co₃O₄ nanoparticles, a maximum specific capacitance of 662.7 F g^?1 can be achieved, which is much higher than that of Co₃O₄ decorated on pristine TNAs (Co₃O₄/TNAs; 166.2 F g^?1). Furthermore, the specific capacitance retains 86.0 % of the initial capacitance after 4000 cycles under a high current density of 10 A g^?1, revealing the excellent long-term electrochemical cycling stability of Co₃O₄/m-TNAs. Thus, this kind of heterostructured Co₃O₄/m-TNAs could be considered as promising candidates for high-performance supercapacitor electrodes.     

High effective electrocatalytic oxidation of cyclohexanol on stable Fe-Mn/Mn<Subscript>2</Subscript>O<Subscript>3</Subscript> membrane electrode

A new composite electrode material with iron-manganic oxide coating (Fe-Mn/Mn₂O₃) was prepared, and its catalytic performance for oxidizing cyclohexanol was investigated in this work. The new electrode material, based on iron substrate covered with electrolytic manganese, was obtained by further coating the manganese surface with 50 % manganese nitrate solution and then conducting program thermal decomposition treatment. X-ray diffraction (XRD) was used to determine the surface crystal phase compositions, which were Mn and Mn₂O₃. The catalytic results showed an excellent electrocatalytic performance on the oxidation of cyclohexanol, and the main products were cyclohexanone and hexanedioic acid. According to our experiment results and the literature reports, the existence of mixed valent Mn^III and Mn^IV played a key role in the electrocatalytic oxidation process. A probable process was proposed: the Mn^IV seized the hydrogen from cyclohexanol, the resulting cyclohexaneoxy radical was oxidized into cyclohexanone, and then the absorbed cyclohexanone was further oxidized into hexanedioic acid.