Structural and electrochemical characterization of Fe–Si/C composite anodes for Li-ion batteries synthesized by mechanical alloying

A Fe–Si (FeSi₂ + Si)/C composite was prepared by mechanical ball milling and investigated as a new inserting anode for use in Li-ion batteries. The composite so prepared has a sandwich structure with the alloy particles as middle cores and the graphite layer as outer shells. The charge-discharge measurements revealed that the Fe–Si/C composite not only had a quite high initial capacity of approximately 680 mAh g⁻¹, but also exhibited greatly improved capacity retention with a reversible capacity of approximately 500 mAh g⁻¹ after 15 cycles in comparison with pure Si and Fe–Si alloy. Based on XRD, XPS, SEM, Raman and EIS analysis of the composite electrode in different lithiated states, the mechanism for improved cycleability is found to be due to the effective buffering of the volumetric changes of the Fe–Si particles by the graphite shell.     

Electrochemical properties of anatase TiO2 nanotubes as an anode material for lithium-ion batteries

Titanium oxides with a one-dimensional nanostructure are of great significance in electrochemical lithium insertion due to their high specific surface area and pore volume. In this paper, anatase TiO₂ nanotubes with diameters of about 10 nm and lengths of 200–400 nm were synthesized by a hydrothermal process. The phase structure and morphology were analyzed by X-ray diffraction, Raman scattering, and transmission electron microscopy. The electrochemical properties were investigated by constant current discharge–charge and cyclic voltammetry. There is a potential plateau at 1.73 and 1.88 V in the process of Li insertion and extraction, and the initial Li insertion/extraction capacity is 290 and 238 mAh g⁻¹ at 36 mA g⁻¹, respectively. The Li insertion capacity at the potential plateau of 1.73 V in the first cycle is about 150 mAh g⁻¹. In the 20th cycle, the reversible capacity still remains at about 200 mAh g⁻¹, and the coulombic efficiency is approximately 98%, exhibiting excellent cycling stability. The discharging capacity is about 168 mAh g⁻¹ in the 30th cycle at 210 mA g⁻¹, demonstrating a good high-rate performance. Anatase TiO₂ nanotubes might be a promising negative material for lithium-ion batteries.     

Electrochemical performance of Sn film reinforced by Cu nanowire

Sn/Cu nanowire composite film was electrodeposited on copper foil substrates and used as an anode material for lithium-ion batteries. The structure of the obtained composite film anode was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical performance was evaluated by cyclic voltammetry, galvanostatic cycling and impedance spectroscopy. It was found that the Sn/Cu nanowire composite film anode showed a better cycle stability than Sn film anode, whereas the Sn/CNT composite film anode indicated poor capacity retention. It could be deduced that copper nanowire reinforced the Sn film anode due to the better wetting property of Sn on the surface of copper and reduced the loss of electric contact among tin particles in the Sn/Cu nanowire composite film anode.     

Electrodeposition of Sn-Cu alloy anodes for lithium batteries

Electrodeposition and heat-treatment was attempted to directly obtain a Sn-Cu alloy anode with fine grain of crystals for lithium ion batteries. The preparation of Sn-Cu alloy anode started with pulsed electrochemically depositing tin on the substrate of copper foil collector, and a protection coating layer of copper was plated on the surface of deposited Sn. An alloy of tin and copper was formed when heated. The energy dispersive spectroscope (EDS) and X-ray diffraction (XRD) analysis showed the copper and tin were partially alloyed to form Cu₆Sn₅ and Cu₃Sn after annealing. The SEM analysis showed the uncoated electrode is cracked after a cycle and the copper coated electrode was not cracked after 50 cycles. The Cu-coated electrode presented the first cycle coulomb efficiency reaching 95% and good cycleability.     

Removal of metal ions in aqueous solutions by organic polymers: use of a polydiphenylamine resin

Adsorption of Ni(II), Cu(II), Zn(II), Pb(II) and Cd(II) ions on a polydiphenylamine resin prepared at a strongly oxidizing controlled potential of 3.2 V (vs. ECS) was studied in aqueous solutions. The optimum sorption conditions were determined. The optimum pH for the removal of metal ions was between 4 and 6 for Ni(II), 6 for Cu(II) and Pb(II) and 5 for Zn(II) and Cd(II). The total sorption capacity of the resin was 57.3 mg g⁻¹ for Ni(II), 23 mg g⁻¹ for Cu(II), 36.9 mg g⁻¹ for Zn(II), 19 mg g⁻¹ for Pb(II) and 24.5 mg g⁻¹ for Cd(II). The sorption capacity was compared with other conventional chelating polymers. The sorption kinetics was fairly rapid, as apparent from the loading half time (t_1/2) values, indicating a better accessibility of the chelating sites. The study of the selectivity of the metal ions in the binary solutions shows that the resin presents a higher affinity for the ions of nickel (II).     

Effect of structural and electrochemical properties of different Cr-doped contents of Li[Ni1/3Mn1/3Co1/3]O2

Layered Li[Ni_(1−x)/3Mn_(1−x)/3Co_(1−x)/3Cr_x]O₂ materials with x = 0, 0.01, 0.02, 0.03, 0.05 are prepared by a solid-state pyrolysis method. The oxide compounds were calcined with various Cr-doped contents, which result in greater difference in morphological (shape, particle size and specific surface area) and the electrochemical (first charge profile, reversible capacity and rate capability) differences. The Li[Ni_(1−x)/3Mn_(1−x)/3Co_(1−x)/3Cr_x]O₂ powders were characterized by means of X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammetry, and SEM. XRD experiment revealed that the Li[Ni_(1−x)/3Mn_(1−x)/3Co_(1−x)/3Cr_x]O₂ (x = 0, 0.01, 0.02, 0.03, 0.05) were crystallized to well layered -NaFeO₂ structure. The first specific discharge capacity and coulombic efficiency of the electrode of Cr-doped materials were higher than that of pristine material. When x = 0.02, the sample showed the highest first discharge capacity of 241.9 mAh g⁻¹ at a current density of 30 mA g⁻¹ in the voltage range 2.3–4.6 V, and the Cr-doped samples exhibited higher discharge capacity and better cycleability under medium and high current densities at room temperature.     

Rapid discharge performance of composite electrode of hydrated sodium manganese oxide and acetylene black

Hydrated sodium manganese oxide was synthesized by reducing permanganate ion using ethanol by a sol–gel method. By including acetylene black in the synthetic reaction, we obtained composite materials in which sodium manganese oxide hydrate particles were small and mixed well with the acetylene black. We evaluated those composites as a lithium battery cathode and found that they showed 170 mA h g⁻¹ under 5 mA g⁻¹ and 117 mA h g⁻¹ under 5 A g⁻¹ on the basis of composite weight. This rapid discharge performance was probably caused by the favorable contact condition of the composite constituents.     

Comparative studies of chloride and chloride/citrate based electrolytes for zinc–polyaniline batteries

Electrochemical behavior of zinc and thin polyaniline (PANI) polymerized from 0.1 M HCl to 0.1 M aniline on graphite electrode, in 0.2 M ZnCl₂ and 0.50 M NH₄Cl (chloride electrolyte) and with addition of 0.33 M Na-citrate (chloride/citrate electrolyte) were investigated. In the chloride/citrate comparing with chloride containing electrolyte zinc electrode shows negative shift of the open circuit potential of 130 mV, decreases of exchange current density for more than order of magnitude and increase of cathodic Tafel slope, due to the zinc ions complexation. In citrate/chloride electrolyte zinc dendrite formation were suppressed. In the range of investigated charge/discharge current densities of 0.25–1 mA cm⁻², initially obtained specific capacity was in the range of 140–85 mAh g⁻¹, respectively. In cycling regime specific capacity and columbic efficiency were affected with anodic potential limits. For anodic potential limits of 0.32 V (SCE) citrate/chloride electrolyte shows better characteristic than chloride electrolyte, due to the influence of citrate ions on negative shift of doping reaction. Increasing anodic potential limit to 0.5 V (SCE), leads to faster decrease of specific capacity in citrate/chloride than in chloride electrolyte, which was. explained by higher hydrophilic effect of citrate anions.     

In situ electrical resistance and X‐ray tomography study of copper–tin polymer composites during thermal annealing

In situ electrical conductivity and X‐ray tomography experiments are conducted on a conductive polymer composite containing polyvinylidene fluoride (PVDF) copolymer, copper (Cu), and tin (Sn) during thermal annealing. During annealing, the electrical resistivity drops by an order of magnitude, while X‐ray tomography, electron microscopy, and spectroscopy results show increasingly homogeneous dispersion of Sn in the conductive filler network, accompanied by the formation of Cu–Sn intermetallic around Cu and Sn particles. This study provides detailed insight into the morphological origins of the beneficial effect of thermal annealing on the electrical properties of conductive composites containing low melting metal fillers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45399.     

Kombucha SCOBY-based carbon and graphene oxide wrapped sulfur/polyacrylonitrile as a high-capacity cathode in lithium-sulfur batteries

Hierarchically-porous carbon nano sheets were prepared as a conductive additive for sulfur/polyacrylonitrile (S/PAN) composite cathodes using a simple heat treatment. In this study, kombucha (that was derived from symbiotic culture of bacteria and yeast) carbon (KC) and graphene oxide (GO) were used as a carbon host matrix. These rational-designed S/PAN/KC/GO hybrid composites greatly suppress the diffusion of polysulfides by providing strong physical and chemical adsorption. The cathode delivered an initial discharge capacity of 1652 mAh·g⁻¹ at a 0.1 C rate and a 100^th cycle capacity of 1193 mAh·g⁻¹. The nano sheets with embedded hierarchical pores create a conductive network that provide effective electron transfer and fast electrochemical kinetics. Further, the nitrogen component of PAN can raise the affinity/interaction of the carbon host with lithium polysulfides, supporting the cyclic performance. The results exploit the cumulative contribution of both the conductive carbon matrix and PAN in the enhanced performance of the positive electrode.     

A novel method for the preparation of submicron-sized LiNi0.8Co0.2O2 cathode material

A novel method has been employed to synthesize layered LiNi_0.8Co_0.2O₂ cathode material by calcination of Ni–Co hydroxide–carbonate precursor prepared by a route involving separate nucleation and aging steps (SNAS) together with LiOH under air atmosphere. Thermogravimetry (TG) and differential thermal analysis (DTA) combined with on-line evolved gas mass spectrometry (EGMS) analysis were employed to study the reaction process. The synthesized material was characterized by means of X-ray diffraction (XRD), laser particle size distribution analysis, field emission scanning electron microscope (FE-SEM) and galvanostatic charge/discharge cycling. The synthesized LiNi_0.8Co_0.2O₂ presents a narrow distribution of submicron-sized particles and exhibits a good electrochemical property with initial discharge specific capacity of 194.8 mAh g⁻¹ in the voltage range 2.75–4.5 V (versus Li/Li⁺). The novel method for the preparation of submicron-sized LiNi_0.8Co_0.2O₂ material has the particular advantage of simple synthesis process and low synthesis cost.     

Highly thiocyanate-selective membrane electrodes based on the N,N′-bis-(benzaldehyde)-glycine copper(II) complex as a neutral carrier

Some novel PVC membrane electrodes based on N,N′-bis-(benzaldehyde)-glycine metallic complexes of Cu(II), Ni(II), Zn(II) and Co(II) as neutral carriers are described. The results showed that the electrode based on the N,N′-bis-(benzaldehyde)-glycine copper(II) complex [Cu(II)-BBAG] had a near-Nernstian response to the thiocyanate ion ranging from 1.0×10⁻¹ to 9.0×10⁻⁷ M in a phosphate buffer solution of pH 4.0 with a detection limit of 7.0×10⁻⁷ M and a slope of −57.6 mV/decade at 25°C. The electrode displays an anti-Hofmeister selectivity sequence in the following order: SCN⁻>ClO⁻₄>Sal⁻>I⁻>Br⁻>NO⁻₂>NO⁻₃>SO²⁻₃>SO²⁻₄>Cl⁻>H₂PO The response mechanism is discussed in view of both AC impedance and UV spectroscopy techniques. The [Cu(II)-BBAG]-based electrode was successfully applied to the determination of the thiocyanate ion in wastewater and human saliva.     

Facile preparation of flexible multifunction current collector loaded with SiO2 nanotubes@N-doped carbon for lithium-ion batteries

Although SiO₂ as an anode for lithium-ion batteries has an attractive high theoretical capacity (1965 mAh g⁻¹), violent volume changes and poor electrical conductivity during alloying reaction limit its lithium storage performance. Here, we report a SNTs@NC composite anode loaded on flexible CNTs conducting paper (CP). The conductive network of CP promotes the rapid migration of Li ions and electrons, and the multi-dimensional skeleton formed by CNTs and SNTs@NC is conducive to the steady deposition of Li-ions. The excellent flexibility effectively defuses the impact of internal stress on the pole plate structure, showing a longer service life and better cycling stability compared with the traditional copper foil. The composite anode has the advantages of simple preparation, low cost and little environmental pollution, and as an innovative collector, CP effectively eliminates the influence of the volume effect of the anode on the electrochemical performance. This work may provide a novel way for the commercial development of SiO₂ anode or the preparation of flexible self-supporting electrode.     

化学镀制备锡-锌-镍合金锂离子电池阳极材料

应用经过改进的化学镀工艺,即:采用硼氢化钠、次磷酸钠同时作为还原剂,结合锡的碱性歧化反应,分别在铜箔及泡沫铜上制备Sn-Zn-Ni三元合金镀层。用X射线衍射仪（XRD）、扫描电子显微镜（SEM）、X射线能量衍射谱（EDS）分析镀层的结构与组成。结果表明:镀层中含有锡、锌、镍三种元素;优化沉积条件,镀层中锌的质量分数可达25%。采用三维多孔泡沫铜为基体,制备化学镀层并对其进行水热葡萄糖碳包覆处理。作为锂离子电池阳极材料,充放电循环10周,放电容量仍可保持在400 mA·h·g^-1以上。     

Synthesis of nano Sb-encapsulated pyrolytic polyacrylonitrile composite for anode material in lithium secondary batteries

A novel process was proposed to synthesize nano Sb-encapsulated pyrolytic polyacrylonitrile composite for anode material in lithium secondary batteries. The preparation started with the dissolution of SbCl₃ and polyacrylonitrile (PAN) in dimethylformamide (DMF) solution, followed by the addition of KBH₄ to reduce Sb³⁺ in the solution. The Sb composite was obtained by pyrolysis of the Sb/PAN mixture that precipitated out when the DMF solution was added by plentiful water. The TEM analysis showed that about 100-200 nm Sb particles were embedded by the pyrolyzed PAN, which provided a conductive matrix to relieve the morphological change of Sb during electrochemical cycling. As-prepared composite presented good cycleability for lithium storage. The proposed process paves an effective way to prepare high performance alloy based composite anode materials for high performance lithium-ion batteries.     

Conductive fibers based on poly(ethylene terephthalate)–polyaniline composites manufactured by electrochemical polymerization

A novel method of manufacturing composite conductive fibers was developed through electrochemical polymerization with an apparatus consisting of insulating fibers, cotton fabrics as electrolytic solution holders, an electrolytic solution, and planer electrodes. By this method, poly(ethylene terephthalate) (PET) fibers coated with polyaniline (PAN) were prepared readily and yielded PET–PAN composite conductive fibers (PPCFs). The content of PAN in PPCFs increased with an increase in both the aniline concentration in the electrolytic solution and the polymerization voltage, although it did not depend on the load applied to the electrodes. Observations of the PPCF surface by scanning electron microscopy confirmed that the formation processes of PPCFs could be divided into three steps: (1) fine (nanometer‐size) granular PAN was generated from the anode and adsorbed onto the PET fiber surface, (2) the size of the granular PAN increased up to about 90 nm in a short time, and (3) the granular PAN was linked together to form networks. The conductivity of PPCFs increased with an increasing content of PAN networks. The surface resistance of the PPCF fabric was about 3 × 10⁵ Ω/□ at a PAN content of approximately 2 wt %. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1073–1078, 2003     

Water-tolerant catalysis of a silica composite of a sulfonic acid resin, Aciplex

A silica composite of a perfluorocarbonsulfonic acid resin, Aciplex, has been used as a solid acid catalyst for a variety of reactions concerning water. The Aciplex–SiO₂ composite containing 20 wt% Aciplex has a surface area of 1.3 m² g⁻¹ and possesses an ion-exchanged capacity of 0.46 meq. g⁻¹ after pretreatment at 423 K, which is higher than that of 13 wt% Nafion–SiO₂ (0.12 meq. g⁻¹). The acid strengths estimated from an initial heat of adsorption of NH₃ were similar for these polymer resin composites. It was found that the Aciplex–SiO₂ was more active than typical solid acids such as Cs_2.5H_0.5PW₁₂O₄₀, H-ZSM-5, and SO₄²⁻/ZrO₂ for hydrolysis of ethyl acetate in excess water and esterification of acrylic acid with 1-butanol, while it was less active than Cs_2.5H_0.5PW₁₂O₄₀ for N-alkylation of acrylonitrile with 1-adamantanol and solid–solid hydrolysis of 2-naphthyl acetate. The Aciplex–SiO₂ was superior in activity to Nafion–SiO₂ for all the above reactions and in thermal stability. These results indicate that Aciplex–SiO₂ is a promising solid acid catalyst for reactions involving liquid phase water.     

Hard carbon/lithium composite anode materials for Li-ion batteries

Hard carbon/lithium composite anode electrode is prepared to reduce the initial irreversible capacity of hard carbon, which hinders practical application of hard carbon in lithium ion batteries, by introducing lithium into hard carbon. Lithium foil effectively compensates the irreversible capacity of hard carbon in the first cycle. A full cell using LiCoO₂ cathode and the composite anode shows much higher initial coulombic efficiency than that of a cell using LiCoO₂ cathode and hard carbon anode. This paves the way to reduce the large initial irreversible capacity of hard carbon. Besides that, this composite anode enables conductive polymer/sulfur composite cathode to be used in Li-ion batteries with non-lithiated anode materials.     

Synthesis of confinement structure of Sn/C-C (MWCNTs) composite anode materials for lithium ion battery by carbothermal reduction

A composite anode material was prepared with confined tin into multiwall carbon nanotube by carbothermal reduction. The morphology and structure of Sn/C (nature graphite) and Sn/C-C (nature graphite + multiwall carbon nanotube) were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was revealed that the additive of MWCNT was a crucial factor to improve Sn /C composite anodes for cyclability and reversible capacity. Volume changes and morphological changes in Sn can be reduced by encasing MWCNT in a carbonaceous material that has sufficient flexibility to act as a buffer. Electrochemical performance test shows that the charge capacity of the Sn/C-C (NG + MWCNT) electrode in the fiftieth cycle was 400 mAh/g, which was higher than that of the Sn/C (NG) electrode. After 50 cycles, the retention of the Sn/C-C electrode and the Sn/C electrode was 80% and 63%, respectively.     

Selective Pd(II) and Pt(IV) sorption using novel polymers containing azamacrocycle functional groups

The synthesis of a new coordinating polymer containing nitrogen atoms by the copolymerization of a 15-membered triolefinic azamacrocycle, 9, named (E,E,E)-1-[(4-methylphenyl)sulfonyl]-6-[(2-trimethylsilylethyl)sulfonyl]-11-[(4-vinylphenyl)sulfonyl)]-1,6,11-triazacyclopentadeca-3,8,13-triene, with styrene is achieved. The novel polymeric material is characterized by means of elemental analysis, IR, ¹³C-CP MAS, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. We also report the study of palladium and platinum sorption from acidic solutions. A capacity of 0.36 mmol g⁻¹ of polymer for Pd(II) and 0.28 mmol g⁻¹ of polymer for Pt(IV) is determined by the batch-mode. The functionalised polymer presents a high selectivity towards precious metals over base metals such us Cu(II) and Ni(II).