Surface engineering of nickel-rich materials can efficiently prevent the materials from adsorbing water and CO2 in the atmosphere to restrain the formation of the insulating Li2CO3 on the surface of ...the materials. Herein, we report a facile approach to preserve the surface state of LiNi0·82Co0·15Al0·03O2 via surface self-assembly of hydride terminated polydimethylsiloxane. The hydride terminated polydimethylsiloxane can be tightly linked to the hydroxyl groups on the surface of LiNi0·82Co0·15Al0·03O2 through hydrogen bonding likely as a monolayer, endowing the surface of the material with strong hydrophobicity. Consequently, the LiNi0·82Co0·15Al0·03O2 material modified with the siloxane polymer after stored for 14 days exhibits electrochemical performance similar to that of the fresh pristine counterpart, whereas the stored pristine sample shows severely deteriorated performance due to the formation of the thick Li2CO3 layer insulating to lithium ion transportation at the electrode/electrolyte interface. Furthermore, the similarity in the initial discharge capacity, cyclability and rate capability of the fresh pristine and siloxane polymer-modified samples demonstrates that differing from coating of most inorganic materials, the modified layer is favorable to the lithium ion transportation, probably due to rich oxygens in the backbone of the siloxane polymer.
•Modification of siloxane polymer could preserve original surface state of NCA.•Storage capability of NCA can be greatly improved by modification of siloxane polymer.•The siloxane polymer possesses good compatibility with NCA and electrolyte.•Monolayer modification of siloxane polymer could be achieved by self-assembly.
A complete and ordered layered structure on the surface of LiNi0.815Co0.15Al0.035O2 (NCA) has been achieved via a facile surface-oxidation method with Na2S2O8. The field-emission transmission ...electron microscopy images clearly show that preoxidation of the hydroxide precursor can eliminate the crystal defects and convert Ni(OH)2 into layered β-NiOOH, which leads to a highly ordered crystalline NCA, with its (006) planes perpendicular to the surface in the sintering process. X-ray photoelectron spectroscopy and Raman shift results demonstrate that the contents of Ni2+ and Co2+ ions are reduced with preoxidization on the surface of the hydroxide precursor. The level of Li+/Ni2+ disordering in the modified NCA determined by the peak intensity ratio I (003)/I (104) in X-ray diffraction patterns decreases. Thanks to the complete and ordered layered structure on the surface of secondary particles, lithium ions can easily intercalate/extract in the discharging–charging process, leading to greatly improved electrochemical properties.
•Crystallinity of CoAl3 HT-like compounds increases with coprecipitation temperature.•After calcination CoAl3HTlcs with larger crystallites form low crystalline spinels.•The surface of Co3O4 or ...Co2AlO4spinels is enriched in aluminum.•CoAl3 spinel is the most efficient catalyst in toluene combustion with T50=257°C.•Catalytic activity results from the high lattice/adsorbed, electrophilic oxygen ratio.
Hydrotalcite-like compounds (HTlcs) containing cobalt and aluminum (intended Co/Al molar ratio=3.0) were coprecipitated at 30, 50 and 70°C. Their crystallinity, which was confirmed by powder X-ray diffraction, increased with the precipitation temperature. Furthermore, HTlcs with various cobalt contents were prepared at 70°C. Thermogravimetric analysis showed that HTlcs were transformed into stable oxides at 550°C. The decrease in the crystallite size of the formed spinels with the increase in the precipitation temperature was observed. Low temperature sorption of nitrogen revealed meso-macroporous nature of the oxides with extended interparticle porosity. Aluminum segregated on the samples surface, which contained various amounts of lattice and adsorbed/electrophilic oxygen as detected by X-ray electron spectroscopy. The high ratio of lattice to adsorbed/electrophilic oxygen found for the sample with Co/Al=3:1 caused that it turned out to be the most efficient catalyst in the total oxidation of toluene (50% conversion at 257°C).
Ni-rich cathode materials always suffer from surface lithium residues mainly caused by the reduction of Ni3+ to Ni2+ when exposing to moisture, and severe side reactions between organic electrolyte ...and highly active Ni4+ when fully charged. An appropriate amount of NH4H2PO4 is firstly coated on the hydroxide precursor Ni0.815Co0.15Al0.035(OH)2 before mixing with Li2CO3. The NH4H2PO4 can react with the lithium residues and form a uniform Li3PO4 coating layer. X-ray diffraction, scanning electron microscopy, field emission transmission electron microscopy and element mapping are employed to investigate the Li3PO4 coating layer. Electrochemical measurements results show that the cycle stability of the synthesized LiNi0.815Co0.15Al0.035O2 both at room temperature and 55 °C has been significantly improved. Its thermal stability has also been greatly enhanced.
•NH4H2PO4 can remove lithium residues and form a uniform Li3PO4 coating layer.•Porous Li3PO4 coating layer suppresses side reactions.•The thermal stability of Ni-rich cathode materials can be significantly enhanced.
Amorphous CoO/Al2O3/C hybrids were synthesized using a simple pyrolysis method at various temperatures and reagent ratios. At 500 °C, CoO localized from homogenous distribution to quantum dots ...(∼10 nm) on the Al2O3/C matrix. X-ray photoelectron spectroscopy results suggested that the feed nitrate ions doped the hybrids with pyridinic (398.8 eV) and pyrrolic (400.55 eV) N, which ameliorated the electrochemical performance of the hybrids. The optimum pyrolysis temperature to obtain a reversible capacity of 0.45 Ah g−1 at the 1000th cycle at a current density of 1 A g−1 was 500 °C. However, owing to the polarization electrode, the specific capacity decreased by 54 % after increasing the material mass loading (0.5–3 mg cm−2), which resulted in a maximum areal capacity of 0.78 mAh cm−2. After regulating the C content in the hybrid, the loss in reversible capacity was only 29 % for an eight-fold gain in the mass-loading (0.4–3.2 mg cm−2) and the areal capacity was up to 1.13 mAh cm−2. The specific capacity of the optimized electrode was 0.52 Ah g−1 at the 1000th cycle. In addition, it only lost 28 % of its capacity along with a ten-fold increase in current density (0.2–2 A g−1). In a full cell test involving a LiNi0.8Mn0.1Co0.1O2-based cathode and a CoO/Al2O3/C-based anode, 91 % of the maximum theoretical specific capacity was obtained, whereas the capacity retention at the 100th cycle was 97 %. Electrochemical impedance spectra suggested that small resistances (<38 Ω) and high Li+ diffusivity (5.5–6.8 × 10−11 cm2 s−1) supported the fast-charging properties of the hybrid.
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•Pyrolysis temperature affects CoO/Al2O3/C hybrid's cyclability via CoO's distribution.•Increasing C content in the hybrid improves electrode's polarization.•Current density, capacity balance, and electrolyte affects a full-cell's performance.
The temperature-dependent behaviors of five nickel-containing positive electrodes (NCA, NMC811, NMC622, NMC532, and NMC111) in lithium-ion batteries are investigated using an electrochemical protocol ...involving rate studies, mild aging (∼100 cycles), and hybrid pulse power characterization (HPPC). Tests are conducted using coin-cells with graphite negative electrodes at −20 °C, 0 °C, 20 °C, and 40 °C. Three techniques are compared for determining the area-specific impedance (ASI): i) fits to the rate study average voltages, ii) fitting to the entire voltage curves using a regularization scheme, and iii) HPPC. When fit to an Arrhenius-type equation, all methods yield similar apparent activation energies (±2 kJ/mol) for the impedance, which range from −20 to −31 kJ/mol for the electrodes. Impedance growth increases with temperature but remains at less than 0.2% per cycle for most electrodes and temperatures. NCA and NMC811 are the exceptions, which yield 0.5% and 1.5% increases in ASI per cycle, respectively, at 40 °C. For cells with the same electrodes, the capacities are similar at 20 and 40 °C but reduce at lower temperatures, with up to a 52% reduction at −20 °C and 2C. The fade in energy of the cells during C/3 cycling is attributed to decreasing capacity as opposed to increasing ASI.
•Studied effects of temperature on nickel-manganese-cobalt oxide cathode performance.•Three methods for determining impedance produce the same temperature dependence.•Arrhenius equations describe the temperature-dependent area-specific impedance.•Curve fitting with regularization is useful for determining impedance in batteries.•Energy change and impedance growth depend on temperature and cathode type.
Since the clock of antimicrobial resistance was set, modern medicine has shed light on a new cornerstone in technology to overcome the worldwide dread of the post-antimicrobial era. Research ...organizations are exploring the use of nanotechnology to modify metallic crystals from macro to nanoscale size, demonstrating significant interest in the field of antimicrobials. Herein, the antimicrobial activities of aluminum oxide (Al2O3), cobalt aluminum oxide (CoAl2O4), and aluminum doped zinc oxide (Zn0.9Al0.1O) nanoparticles were examined against some nosocomial pathogens. The study confirmed the formation and characterization of Al2O3, CoAl2O4, and Zn0.9Al0.1O nanoparticles using various techniques, revealing the generation of pure nanoscale nanoparticles. With inhibition zones ranging from 9 to 14 mm and minimum inhibitory concentrations varying from 4 mg/mL to 16 mg/mL, the produced nanoparticles showed strong antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. Meanwhile, the bactericidal concentrations ranged from 8 mg/mL to 40 mg/mL. In culture, Zn0.9Al0.1O NPs demonstrated a unique ability to inhibit the development of nosocomial infections with high bactericidal activity (8 mg/mL). Transmission electron microscope images revealed changes in cell shape, bacterial cell wall morphology, cytoplasmic membrane, and protoplasm due to the introduction of tested nanoparticles. These results pave the way for the use of these easily bacterial wall-piercing nanoparticles in combination with potent antibiotics to overcome the majority of bacterial strains' resistance.
•Cobalt or zinc-casing aluminum oxide nanoparticles synthesis and characterization.•Nanoparticles sized 4–32 nm were studied.•Nanoparticles as antimicrobials against nosocomial infections.•Deformed cell wall and cytoplasm were related to nanoparticles toxicity.
A commercial lithium-ion battery with LiNi0.8Co0.15Al0.05O2 (NCA) cathode has been studied in situ using high-intensity and high-resolution neutron diffraction. Structure and phase composition of the ...battery electrodes have been probed during charge-discharge in different cycling modes. The dependence of the anode composition on the charge rate has been determined quantitatively. Different kinetics of Li (de)intercalation in the graphite anode during charge/discharge process have been observed. Phase separation of the cathode material has not been detected in whole voltage range. Non-linear dependencies of the unit cell parameters, atomic and layer spacing on the lithium content in the cathode have been observed. Measured dependencies of interatomic spacing and interlayer spacing, and unit cell parameters of the cathode structure on the lithium content could be qualitatively explained by several factors, such as variations of oxidation state of cation in oxygen octahedra, Coulomb repulsion of oxygen layers, changes of average effective charge of oxygen layers and van der Waals interactions between MeO2-layers at high level of the NCA delithiation.
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•A commercial battery with NCA cathode studied in situ using TOF neutron diffraction.•Different kinetics of Li (de)intercalation in graphite during cycling are observed.•NCA retains a single-phase structure in the whole voltage range of cycling.•The explanation of the c-parameter unusual behavior of NCA unit cell is given.
In this study, a Si-graphene composite, which is composed of nano Si particles and nano-sized multi-layer graphene particles, and micro-sized multi-layer graphene plate conductor, was used as the ...anode for Li-ion battery. The Si-graphene electrode showed the high capacity and stable cyclability at charge/discharge rate of C/2 in half cell tests. Nickel cobalt aluminum material (NCA) was used as a cathode in the full cell to evaluate the practicality of the new Si-graphene material. Although the Si-graphene anode has more capacity than the NCA cathode in this designed full cell, the Si-graphene anode had a greater effect on the full-cell performance due to its large initial irreversible capacity loss and continuous SEI formation during cycling. When fluoro-ethylene carbonate was added to the electrolyte, the cyclability of the full cell was much improved due to less SEI formation, which was confirmed by the decreases in the 1st irreversible capacity loss, overpotential for the 1st lithiation, and the resistance of the SEI.
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