High reversible capacity and rate capability of ZnCo2O4/graphene nanocomposite anode for high performance lithium ion batteries

A facile and straightforward method was adopted to synthesize ZnCo₂O₄/graphene nanocomposite anode. In the first step, pure ZnCo₂O₄ nanoparticles were synthesized using urea-assisted auto-combustion synthesis followed by annealing at a low temperature of 400 °C. In the second step, in order to synthesize ZnCo₂O₄/graphene nanocomposite, the obtained pure ZnCo₂O₄ nanoparticles were milled with 10 wt% reduced graphene nanosheets using high energy spex mill for 30 s. The ZnCo₂O₄ nanoparticles, with particle sizes of 25–50 nm, were uniformly dispersed and anchored on the reduced graphene nanosheets. Compared with pure ZnCo₂O₄ nanoparticles anode, significant improvements in the electrochemical performance of the nanocomposite anode were obtained. The resulting nanocomposite delivered a reversible capacity of 1124.8 mAh g⁻¹ at 0.1 C after 90 cycles with 98% Coulombic efficiency and high rate capability of 515.9 mAh g⁻¹ at 4.5 C, thus exhibiting one of the best lithium storage properties among the reported ZnCo₂O₄ anodes. The significant enhancement of the electrochemical performance of the nanocomposite anode could be credited to the strong synergy between ZnCo₂O₄ and graphene nanosheets, which maintain excellent electronic contact and accommodate the large volume changes during the lithiation/delithiation process.     

Preparing graphene oxide–copper composite material from spent lithium ion batteries and catalytic performance analysis

The wide use of lithium ion batteries (LIBs) has created much waste, which has become a global issue. It is vital to recycle waste LIBs considering their environmental risks and resource characteristics. Anode graphite from spent LIBs still possess a complete layer structure and contain some oxygen-containing groups between layers, which can be reused to prepare high value-added products. Given the intrinsic defect structure of anode graphite, copper foils in LIB anode electrodes, and excellent properties of graphene, graphene oxide–copper composite material was prepared in this work. Anode graphite was firstly purified to remove organic impurities by calcination and remove lithium. Purified graphite was used to prepare graphene oxide–copper composite material after oxidation to graphite oxide, ultrasonic exfoliation to graphene oxide (GO), and Cu²⁺ adsorption. Compared with natural graphite, preparing graphite oxide using anode graphite consumed 40% less concentrated H₂SO₄ and 28.6% less KMnO₄. Cu²⁺ was well adsorbed by 1.0 mg L^?1 stable GO suspension at pH 5.3 for 120 min. Graphene oxide–copper composite material could be successfully obtained after 6 h absorption, 3 h bonding between GO and Cu²⁺ with 3/100 of GO/CuSO₄ mass ratio. Compared to CuO, graphene oxide–copper composite material had better catalytic photodegradation performance on methylene blue, and the electric field further improved the photodegradation efficiency of the composite material.     

Electrochemical performance of Co–Al layered double hydroxide nanosheets mixed with multiwall carbon nanotubes

Regular hexagonal Co–Al layered double hydroxides (Co–Al LDH) were synthesized by urea-induced homogeneous precipitation. This material proved to be nanosheets by scanning electron microscopy and X-ray diffraction measurements. The electrochemical capacitive behavior of the nanosheets in 1 M KOH solution were evaluated by constant current charge/discharge and cyclic voltammetric measurements, showing a large specific capacitance of 192 F·g⁻¹ even at the high current density of 2 A·g⁻¹. When multiwall carbon nanotubes (MWNTs) were mixed with the Co–Al LDH, it was found that the specific capacitance and long-life performance of all composite electrodes at high current density are superior to pure LDH electrode. When the added MWNTs content is 10 wt%, the specific capacitance increases to 342.4 F·g⁻¹ and remains at a value of 304 F·g⁻¹ until the 400th cycle at 2 A·g⁻¹, showing that this is a promising electrode material for supercapacitors working at heavy load. According to the electrochemical impedance spectra, MWNTs greatly increase the electronic conductivity between MWNTs and the surface of Co–Al LDH, which consequently facilitates the access of ions in the electrolyte and electrons to the electrode/electrolyte interface.     

Electropolymerized composite film of polypyrrole and functionalized multi-walled carbon nanotubes: effect of functionalization time on capacitive performance

The composite film of polypyrrole and functionalized multi-walled carbon nanotubes (PPy/F-MWNTs) was prepared by electropolymerization. MWNTs were functionalized by sonicating with a concentrated solution of H₂SO₄/HNO₃ (3/1, volume ratio) in a water bath for different times. The carbon nanotubes (CNTs) are cut into smaller portions with more functional groups introduced on their surface when the sonicating time (nominated as functionalization time hereafter) is increased. However, the specific capacitance of the composite film reaches a maximum of 240 F g⁻¹ at the scanning rate of 10 mV s⁻¹ when MWNTs are functionalized for 24 h, which is about 205 F g⁻¹, 225 F g⁻¹ and 232 F g⁻¹, respectively, when MWNTs are functionalized for 6 h, 12 h and 48 h. At a current load of 1.0 A g⁻¹, PPy/F-MWNT composite film functionalized for 24 h (PPy/F-MWNTs (24 h)) retains 93.49% of its initial capacitance after 1,000 cycles of galvanostatic charge/discharge, and the discharge efficiency is higher than 98.15% during cycling. High specific capacitance, good rate performance, fast charge/discharge ability and long cycling life are ascribed to the synergistic effect of the two components to form a porous composite film as well as the easy accessibility of counter ions into the film. Therefore, PPy/F-MWNT (24 h) composite film is a kind of promising electrode material for supercapacitors. The mechanism of underfunctionalization and overfunctionalization of carbon nanotubes is also discussed.     

Properties of LiNiO2 cathode and graphite anode in N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide

Electrochemical properties of LiNiO₂|Li and LiNiO₂|graphite cells were analysed in ionic liquid electrolyte [Li⁺][MePrPyrr⁺][NTf₂^-] (based on N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulphonyl)imide, [MePrPyrr⁺][NTf₂^-]) using impedance spectroscopy and galvanostatic techniques. The ionic liquid is incapable of protective solid electrolyte interface (SEI) formation on metallic lithium or lithiated graphite. However, after addition of VC, the protective coating is formed, facilitating a proper work of the Li-ion cell. Scanning electron microscopy images of pristine electrodes and those taken after electrochemical cycling showed changes which may be interpreted as a result of SEI formation. The charging/discharging capacity of the LiNiO₂ cathode is between 195 and 170 mAh g⁻¹, depending on the rate. The charging/discharging efficiency of the graphite anode drops after 50 cycles from an initial value of ca. 360 mAh g⁻¹ to stabilise at 340 mAh g⁻¹. The replacement of a classical electrolyte in molecular liquids (cyclic carbonates) with an electrolyte based on the MePrPyrrNTf₂ ionic liquid highly increases in the cathode/electrolyte non-flammability.     

Sandwich-like mesoporous graphene@magnetite@carbon nanosheets for high-rate lithium ion batteries

Sandwich-like mesoporous GS@Fe₃O₄@C nanosheets with a 2D nanoarchitecture have been successfully synthesized by one-step solvothermal treatment. Such type of 2D nanoarchitecture is made up of a number of Fe₃O₄ nanoparticles uniformly grown on a graphene sheet and an even amorphous carbon layer covering on their surface. The Li-cycling properties of GS@Fe₃O₄@C nanosheets have been evaluated by galvanostatic discharge-charge cycling and impedance spectroscopy. Results indicate that the GS@Fe₃O₄@C nanosheets with about 5 wt % of graphene content provides a very high discharge capacity of 913.2 mAh g⁻¹ at a current densities of 200 mA g⁻¹ after 100 cycles and reveals a stable discharge capacity of 483.2 mAh g⁻¹ at a rate of 1600 mA g⁻¹.     

Structural and electrochemical behavior of Mn–V oxide synthesized by a novel precipitation method

Manganese–vanadium oxide had been synthesized by a novel simple precipitation technique. Scanning electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller, thermogravimetric analysis/differential scanning calorimetry, and X-ray photoelectron spectroscopy were used to characterize Mn–V binary oxide and δ-MnO₂. Electrochemical capacitive behavior of the synthesized Mn–V binary oxide and δ-MnO₂ was investigated by cyclic voltammetry, galvanostic charge–discharge curve, and electrochemical impedance spectroscope methods. The results showed that, by introducing V into δ-MnO₂, the specific surface area of the mixed oxide increased due to a formation of small grain size. The specific capacitance increased from 166 F g⁻¹ estimated for MnO₂ to 251 F g⁻¹ for Mn–V binary oxide, and the applied potential window extended to −0.2–1.0 V (vs. saturated calomel electrode). Through analysis, it is suggested that the capacitance performance of Mn–V binary oxide materials may be improved by changing the following three factors: (1) small grain and particle size and large activity surface area, (2) appropriate amount of lattice water, and (3) chemical state on the surface of MnO₂ material.     

Tin oxide-titanium oxide/graphene composited as anode materials for lithium-ion batteries

A tin oxide-titanium oxide/graphene (SnO₂-TiO₂/G) ternary nanocomposite as high-performance anode for Li-ion batteries was prepared via a simple reflux method. The graphite oxide (GO) was reduced to graphene nanosheet, and the SnO₂-TiO₂ nanocomposites were evenly distributed on the graphene matrix in the SnO₂-TiO₂/G nanocomposite. The as-prepared SnO₂-TiO₂/G nanocomposites were employed as anode materials for lithium-ion batteries, showing an outstanding performance with high reversible capacity and long cycle life. The composite delivered a superior initial discharge capacity of 1,594.6 mAh g^?1 and a reversible specific capacity of 1,500.3 mAh g^?1 at a current density of 100 mA g^?1. After 100 cycles, the reversible discharge capacity was still maintained at 1,177.4 mAh g^?1 at a current density of 100 mA g^?1 with a high retained rate of reversible capacity of 73.8 %. The addition of small amount of TiO₂ nanoparticles improved the cycling stability and specific capacity of SnO₂-TiO₂/G nanocomposite, obviously. The results demonstrate that the SnO₂-TiO₂/G nanocomposite is a promising alternative anode material for practical Li-ion batteries.     

On the pseudocapacitive behavior of nanostructured molybdenum oxide

Nanostructured molybdenum oxide having a particle size in the range of 30–80 nm was prepared by potentiodynamic electrodeposition method, and the effects of H₂SO₄ concentration on its capacitive behavior were studied by cyclic voltammetry, galvanostatic discharge, and electrochemical impedance spectroscopy. Poor to fair capacitive behaviors were witnessed depending on the electrolyte concentration and conditions of charge/discharge. Increasing acid concentration to 0.02 M had favorable effect, while beyond that, the effect was detrimental. Capacitance around 600 F g⁻¹ was recorded in the potential range of 0 to −0.55 V vs. Ag/AgCl.     

Study of capacitive properties in supercapacitor for copolymer of aniline with m-phenylenediamine

The copolymers were synthesized with different molar ratios of m-phenylenediamine to aniline (R for short) by a chemical oxidation method. The products were first used as electrochemical activity materials of the supercapacitor. Capacitive behaviors of the prepared copolymers in 1 mol·L⁻¹ H₂SO₄ electrolyte were examined by electrochemical impedance spectroscopy, cyclic voltammeter, and galvanostatic charge/discharge. The relationship of molar ratios with capacitive property of the prepared products was investigated too. The results showed that the product with R of 2:98 displayed better electrochemical properties than that of the other products. Compared with the synthesized polymer in the absence of m-phenylenediamine, the polymerized copolymer with R of 2:98 exhibited the initial specific capacitance value of 475 F·g⁻¹, which increased by nearly 10.1% than that of the former at a current density of 200 mA·g⁻¹ in 1 mol·L⁻¹ H₂SO₄ electrolyte in the potential range of −0.3 to 0.7 V. The discharge specific capacitance value of the copolymer remained 300 F·g⁻¹ after 1,000 cycles, exhibiting a good cycling performance and the structure stability.     

Fe3O4/Graphene Composite Anode Material for Fast-Charging Li-Ion Batteries

Composite anode material based on Fe₃O₄ and reduced graphene oxide is prepared by base-catalysed co-precipitation and sonochemical dispersion. Structural and morphological characterizations demonstrate an effective and homogeneous embedding of Fe₃O₄ nanoparticles in the carbonaceous matrix. Electrochemical characterization highlights specific capacities higher than 1000 mAh g⁻¹ at 1C, while a capacity of 980 mAhg⁻¹ is retained at 4C, with outstanding cycling stability. These results demonstrate a synergistic effect by nanosize morphology of Fe₃O₄ and inter-particle conductivity of graphene nanosheets, which also contribute to enhancing the mechanical and cycling stability of the electrode. The outstanding capacity delivered at high rates suggests a possible application of the anode material for high-power systems.     

氮掺杂碳层包覆金属钴颗粒与氮掺杂石墨烯纳米复合材料作为高容量锂离子电池负极材料

合成了一种石墨烯基纳米复合材料即：由氮掺杂碳层包覆的金属钴纳米颗粒,充分分散于氮掺杂的石墨烯表面。这种纳米复合材料进一步提高了石墨烯的导电性,增加了石墨烯的储锂容量。该材料被用作锂离子电池负极材料,在性能测试中展现了良好的循环性能,在以100 mA·g^-1的电流密度循环200圈后,放电容量高达950.1 mAh·g^-1,库伦效率约为98%。     

In-situ Grown SnO2 Nanospheres on Reduced GO Nanosheets as Advanced Anodes for Lithium-ion Batteries

Nanostructured tin dioxide (SnO₂) has emerged as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity (1494 mA h g⁻¹) and excellent stability. Unfortunately, the rapid capacity fading and poor electrical conductivity of bulk SnO₂ material restrict its practical application. Here, SnO₂ nanospheres/reduced graphene oxide nanosheets (SRG) are fabricated through in-situ growth of carbon-coated SnO₂ using template-based approach. The nanosheet structure with the external layer of about several nanometers thickness can not only accommodate the volume change of Sn lattice during cycling but also enhance the electrical conductivity effectively. Benefited from such design, the SRG composites could deliver an initial discharge capacity of 1212.3 mA h g⁻¹ at 0.1 A g⁻¹, outstanding cycling performance of 1335.6 mA h g⁻¹ after 500 cycles at 1 A g⁻¹, and superior rate capability of 502.1 mA h g⁻¹ at 5 A g⁻¹ after 10 cycles. Finally, it is believed that this method could provide a versatile and effective process to prepare other metal-oxide/reduced graphene oxide (rGO) 2D nanocomposites.     

石墨烯/钴镍双金属氢氧化物复合材料的制备及电化学性能研究

采用微波辐射与高温裂解相结合的二步还原法制备石墨烯。二步还原使氧化石墨被充分还原和剥离,所得到的石墨烯有较好的传导性,其比表面达675.4 m2.g-1。以此石墨烯为原料,水热法合成出石墨烯/钴镍双金属氢氧化物复合材料,并考察了复合材料作为超级电容电极材料的电化学性能。研究发现,褶皱的石墨烯纳米片均匀分散在钴镍双金属氢氧化物中,这改善了钴镍双金属氢氧化物的传导性和结构稳定性。在0.25 A.g-1电流密度下,复合材料的比电容量是800.2 F.g-1。当电流密度增加至10 A.g-1,比电容量为386.5 F.g-1,恒电流充-放电500次后比电容量仍能保持99%以上,这些呈示该复合材料具有优良的电化学性能。     

氮掺杂碳层包覆金属钴颗粒与氮掺杂石墨烯纳米复合材料作为高容量锂离子电池负极材料

合成了一种石墨烯基纳米复合材料即：由氮掺杂碳层包覆的金属钴纳米颗粒,充分分散于氮掺杂的石墨烯表面。这种纳米复合材料进一步提高了石墨烯的导电性,增加了石墨烯的储锂容量。该材料被用作锂离子电池负极材料,在性能测试中展现了良好的循环性能,在以100 mA·g^-1的电流密度循环200圈后,放电容量高达950.1 mAh·g^-1,库伦效率约为98%。     

Preparation and characterization of silicon monoxide/graphite/carbon nanotubes composite as anode for lithium-ion batteries

Silicon monoxide/graphite/multi-walled carbon nanotubes (SiO/G/CNTs) material was prepared by ball milling followed by chemical vapor deposition method and characterized by X-ray diffraction, scanning electron microscopy (SEM), galvanostatic charge–discharge, and AC impedance spectroscopy, respectively. The results revealed that SiO/G/CNTs exhibited an initial specific discharge capacity of 790 mAh g⁻¹ with a columbic efficiency of 65%. After 100 cycles, a high reversible capacity of 495 mAh g⁻¹ is still retained. The improved electrochemical properties were due to beneficial SEI by the SEM and EIS results.     

Structural and electrochemical characterization of LiFePO4/C prepared by a sol–gel route with long- and short-chain carbon sources

A fast and convenient sol–gel route was developed to synthesize LiFePO₄/C composite cathode material, and the sol–gel process can be finished in less than an hour. Polyethyleneglycol (PEG), d-fructose, 1-hexadecanol, and cinnamic acid were firstly introduced to non-aqueous sol–gel system as structure modifiers and carbon sources. The samples were characterized by X-ray powder diffraction, field emission scanning electron microscopy, and elemental analysis measurements. Electrochemical performances of LiFePO₄/C composite cathode materials were characterized by galvanostatic charge/discharge and AC impedance measurements. The material obtained using compound additives of PEG and d-fructose presented good electrochemical performance with a specific capacity of 157.7 mAh g⁻¹ at discharge rate 0.2 C, and the discharge capacity remained about 153.6 mAh g⁻¹ after 50 cycles. The results indicated that the improved electrochemical performance originated mainly from the microporous network structure, well crystalline particles, and the increased electronic conductivity by proper carbon coating (3.11%).     

Improved disordered carbon as high performance anode material for lithium ion battery

A sulfur-substituted disordered carbon is explored as anode material for lithium-ion battery. Its physical and electrochemical properties are characterized by a variety of techniques such as powder X-ray diffraction, element analysis, Fourier transform infrared spectrum, scanning electron microscopy, and typical electrochemical tests. Electrochemical tests show the activated carbon displays a first cycle discharge capacity of 1,216 mAh·g⁻¹. It also has a remarkable cycling stability with an average capacity fade of 0.92% per cycle from 11th to 100th cycle in the range of 0.01–3.00 V versus metallic lithium at a current density of 100 mA·g⁻¹. After 100 cycles, the electrode still maintained a capacity of 420 mAh·g⁻¹.     

Electrochemical performance of LiVPO<Subscript>4</Subscript>F/C composite cathode prepared through amorphous vanadium phosphorus oxide intermediate

LiVPO₄F/C composites with better electrochemical performance were prepared by calcination of LiF and amorphous vanadium phosphorus oxide (VPO) intermediate synthesized by a sol–gel method using H₃PO₄, V₂O₅ and citric acid as raw materials. The properties of LiVPO₄F/C composites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The analysis of XRD patterns and Fourier transform infrared spectra (FTIR) reveal that VPO intermediate prepared by sol–gel method is amorphous and VPO₄ may exist in VPO intermediate. The compositions of LiVPO₄F/C composites are related to the calcination temperature for preparation of amorphous VPO/C intermediate and LiVPO₄F/C composite prepared by VPO/C synthesized at 700°C consists of a single crystal phase of LiVPO₄F. The electrochemical tests show that LiVPO₄F/C composite prepared by VPO/C synthesized at 700°C exhibits higher discharge capacity and excellent cycle performance. This LiVPO₄F/C composite displays discharge capacity of 133 mAh g⁻¹ at 0.5 C (78 mA g⁻¹) and remains capacity retention of 96.8% after 30 cycles, even at a high rate of 5 C, the composite exhibits high discharge capacity of 115 mAh g⁻¹ and capacity retention of 97% after 100 cycles.     

Anode performance of Mn-doped ceria–ScSZ for solid oxide fuel cell

The 70 wt.% Mn-doped CeO₂ (MDC)-30 wt.% Scandia-stabilized zirconia (ScSZ) composites are evaluated as anode materials for solid oxide fuel cells (SOFCs) in terms of chemical compatibility, thermal expansion coefficient, electrical conductivity, and fuel cell performance in H₂ and CH₄. The conductivity of MDC10 (10 mol.% Mn-doping), MDC20, and CeO₂ are 4.12, 2.70, and 1.94 S cm⁻¹ in H₂ at 900 °C. With 10 mol.% Mn-doping, the fuel cells performances improve from 166 to 318 mW cm⁻² in H₂ at 900 °C. The cell with MDC10–ScSZ anode exhibits a better performance than the one with MDC20–ScSZ in CH₄, the maximum power density increases from 179 to 262 mW cm⁻². Electrochemical impedance spectra indicate that the Mn doping into CeO₂ can reduce the ohmic and polarization resistance, thus leading to a higher performance. The results demonstrate the potential ability of MDC10–ScSZ composite to be used as SOFCs anode.