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A series of pore-controllable polyamine (PAI) layer-coated polyolefin (PE) separators (PAI-PE-1, PAI-PE-2, and PAI-PE-3) are prepared by using a phase-transfer and gravure-printing method and used to improve the safety of pouch lithium-ion batteries (LIBs) based on a PAI "guest-host transition" and PE "pore on-off" cooperative strategy. And the safety mechanism for the LIBs using PAI-PE-1, PAI-PE-2, and PAI-PE-3 separators with pore sizes of approximately 0.02, 0.17, and 0.85 μm is discussed. In the overcharge, nail, and hot box tests, the LIBs with PAI-PE separators all meet safety requirements, while the LIBs with PE separators exhibit either fire or smoke issues. The LIBs with PAI-PE-1 separators have the lowest temperature of 102 °C and the highest residual voltage of 3.97 V in the nail and hot box tests, respectively, and the LIBs with PAI-PE-3 separators have the lowest temperature of 129 °C in the overcharge test. The mechanism for the enhanced safety of LIBs with PAI-PE separators is ascribed to a PAI "guest-host transition" and PE "pore on-off" cooperative process. These results indicate that this pore-controllable PAI-PE separator has promising prospects in the application of LIBs with enhanced safety requirements. [ABSTRACT FROM AUTHOR]

The iodine-doped bismuth oxychloride (I-doped BiOCl) microspheres are synthesized as the visible light photocatalysts for the photocatalytic removal of three toxic hydroxyl-contained intermediates of parabens. With the aid of the unique heating mode of microwave method, the I-doped BiOCl photocatalysts with tunable iodine contents and dispersed energy bands, instead of a mixture of BiOI and BiOCl or solid solution, are synthesized under the controllable conditions. Due to the stretched architectures, high specific surface area, and effective separation of photogenerated carriers, they exhibit high activity to the photocatalytic degradation of methyl 2,4-dihydroxybenzoate (MDB), methyl 3,4-dihydroxybenzoate (MDHB), and ethyl 2,4-dihydroxybenzoate (EDB). As a typical result, it is indicated that though MDB as the most difficult intermediate of parabens to be degraded, a 91.2% removal ratio can still be achieved over the I-doped BiOCl with an energy band of 2.79 eV within 60 min. In addition, it is also confirmed that these photocatalysts remain stable throughout the photocatalytic reaction and can be reused, and more importantly, the photogenerated h+ and •O2− are the key reactive species, while •OH plays a negligible role in the photocatalytic reaction. Resorcinol was identified as the main photodegraded intermediate. These results demonstrate that this photocatalytic system not only exhibit a high efficiency but also avoid the consequent secondary pollutions due to the no formation of complex hydroxyl derivatives. [ABSTRACT FROM AUTHOR]

With the expanding applications, concerns about the charging safety of lithium-ion batteries (LIBs) have become more significant. In this paper, the constant-current (CC) overcharge electrode process of pouch LiCoO2/graphite batteries are analyzed at 0.25 C, and then, a self-protection mechanism for decreasing the overcharge risk of batteries is evaluated. As for the batteries passing the safety test, their typical overcharge behaviors show the battery voltage and temperature begin to dramatically increase to about 5.2 V and 65 °C from about 155% state of charge (SOC) and then decrease slowly after a short fluctuating period. The element analysis of two electrodes and separator reveals that besides the well-known metal lithium, cobalt precipitation pierces the separator and subsequently forms an internal micro-short circuit at about 155% SOC to consume the charge energy and subsequently avoid the overcharge explosion and ignition. As a conclusion, a self-protection mechanism based on an internal micro-short circuit model, which is closely related with the deposited electric lithium and cobalt and the separator porosity, is proposed and experimentally verified. These results offer an idea and method to decrease the CC overcharge risk of LIBs and can advance the safe application of LIBs. [ABSTRACT FROM AUTHOR]

In this paper, the LiNi0.5Mn1.5O4 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 LiNi0.5Mn1.5O4 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 LiNi0.5Mn1.5O4. 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 LiNi0.5Mn1.5O4 material without CNF, the LiNi0.5Mn1.5O4 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 LiNi0.5Mn1.5O4 cathode material.Micro/nanostructured LiNi0.5Mn0.5O4 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. [ABSTRACT FROM AUTHOR]

The leaching characteristics of hazardous materials from Ni-Cd batteries immersed in four typical water samples, i.e., water with NaCl, river water, tap water, and deionized water, were investigated to evaluate the potential environmental harm of spent Ni-Cd batteries in the water surroundings. It is shown that four water surroundings all could leach hazardous materials from the Ni-Cd batteries. The water with NaCl concentration of 66.7 mg L−1 had the highest leaching ability, the hazardous materials were leached after only approximately 50 days (average time, with a standard deviation of 4.1), while less than 100 days were needed in the others. An electrochemical corrosion is considered to be the main leaching mechanism leading to battery breakage, while the dissolution-deposition process and the powder route result in the leakage and transference of nickel and cadmium materials from the electrodes. The anions, i.e., SO42− and Cl−, and dissolved oxygen in water were demonstrated to be the vital factors that influence the leaching processes. Thus, it is proposed that spent Ni-Cd batteries must be treated properly to avoid potential danger to the environment. [ABSTRACT FROM AUTHOR]

A glassy carbon electrode was modified with carbon nanofragments and bismuth oxide, and the resulting electrode (CNF-Bi/GCE) was applied to the voltammetric determination of catechol (CC) in the presence of a large excess (>100-fold) of hydroquinone (HQ). The CNF-Bi was synthesized by anchoring bismuth oxide on CNFs in a hydrothermal and calcining process. Compared to CNF-modified GCE and bare GCE, the CNF-Bi/GCE exhibits enhanced electrocatalytic activity with respect to the redox reaction of CC (at 0.28 V vs. SCE) and HQ (at 0.15 V). Differential pulse voltammetry was applied to quantify traces of CC in the presence of excess HQ. The calibration plot is linear in the 3 to 20 μmol L concentration range, with a 0.2 μmol L detection limit (at a signal-to-noise ratio of 3). These results indicate the CNF-Bi/GCE is a promising sensor for analyzing trace isomers of dihydroxybenzene. In addition, it is also applicable to the determination of ascorbic acid, dopamine, resorcin, and rutin. [ABSTRACT FROM AUTHOR]

The preparation of polyethylene-supported poly(vinylidene fluoride)/cellulose acetate butyrate/nano-SiO particle (PVDF-CAB-SiO/PE) blended gel polymer electrolytes (GPEs) is reported here. The electrolyte uptake, mechanical properties, thermal stability, and electrochemical performance of these electrolytes are characterized to evaluate their potential application in lithium-ion batteries (LIBs). The results indicate that the particle size of SiO can be adjusted by the tetraethyl orthosilicate (TEOS) concentration and affects the physicochemical properties of the membrane. By doping 5 wt.% SiO (500 nm) into the PVdF-CAB blended polymer, the porosity of the membrane increases from 40 to 42.3 %, the mechanical strength from 117.3 to 138.7 MPa, the electrolyte uptake from 149 to 195 %, the oxidation decomposition potential from 4.7 to 5.2 V, and the ionic conductivity of the corresponding GPE is improved from 1.16 to 2.98 mS cm at ambient temperature. The PVDF-CAB-SiO/PE-based GPE and the two electrodes are suitably compatible, and the thermal stability is higher than that of the polyethylene (PE) membrane. The LIBs with the as-prepared GPE also exhibit enhanced discharge capacity and cycle stability, indicating the promising application of these GPEs in LIBs. [ABSTRACT FROM AUTHOR]

Vinyl ethylene carbonate (VEC) is investigated as an electrolyte additive to improve the electrochemical performance of LiNiMnCoO/graphite lithium-ion battery at higher voltage operation (3.0-4.5 V) than the conventional voltage (3.0-4.25 V). In the voltage range of 3.0-4.5 V, it is shown that the performances of the cells with VEC-containing electrolyte are greatly improved than the cells without additive. With 2.0 wt.% VEC addition in the electrolyte, the capacity retention of the cell is increased from 62.5 to 74.5 % after 300 cycles. The effects of VEC on the cell performance are investigated by cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), x-ray powder diffraction (XRD), energy dispersive x-ray spectrometry (EDS), scanning electron microscopy (SEM), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR). The results show that the films electrochemically formed on both anode and cathode, derived from the in situ decomposition of VEC at the initial charge-discharge cycles, are the main reasons for the improved cell performance. [ABSTRACT FROM AUTHOR]

We report on a method for electrochemical enantioselective recognition of tryptophan (Trp) enantiomers. It is based on competitive host-guest interaction between a deoxy-(2-aminoethylamino)-β-cyclodextrin (CD) bound to graphene nanosheets and the Cu(II) complexes of the Trp enantiomers via a ligand exchange mechanism. Chiral recognition was investigated via cyclic voltammetry and electrochemical impedance spectroscopy. The results reveal that the CD bound to graphene displays a stronger interaction with the Cu(II) complex of L-Trp than to that of D-Trp. The method was applied to the determination of the ratio of Trp enantiomers in mixtures. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We have developed a stable and sensitive nonenzymatic glucose sensor by modifying a glassy carbon electrode (GCE) with a composite incorporating nickel(II) oxides and reduced graphene. The oxides were generated by directly electrodepositing nickel on the GCE with a graphene modifier using a multi-potential pulse process, and then oxidizing nickel to nickel(II) oxides by potential cycling. In comparison to the conventional nickel(II) oxides-modified GCE, this new nickel(II) oxides-graphene modified GCE (NiO-GR/GCE) has an about 1.5 times larger current response toward the nonenzymatic oxidation of glucose in alkaline media. The response to glucose is linear in the 20 μM to 4.5 mM concentration range. The limit of detection is 5 μM (at a S/N of 3), and the response time is very short (<3 s). Other beneficial features include selectivity, reproducibility and stability. A comparison was performed on the determination of glucose in commercial red wines by high-performance liquid chromatography (HPLC) and revealed the promising aspects of this sensor with respect to the determination of glucose in real samples. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]