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Lithium bisoxalatodifluorophosphate (LiBODFP) is a promising multifunctional lithium salt-type electrolyte additive used to enhance the performance of 5 V LiNi0.5Mn1.5O4 (LNMO)-based lithium-ion batteries (LIBs). Compared to cells without the additive, the cycling retention of the LNMO/Li half cells with 1.0% LiBODFP was improved from 77.6% to 93.7% at a 1C rate after 300 cycles. The capacity retention of the high voltage LNMO/graphite full cells with LiBODFP reached 82% at a 0.5C rate after 100 cycles, which was much higher than that of the cells without the additive (50%). It is shown that the LiBODFP can be preferentially oxidized and reduced to form robust interface films with low resistance and high conductivity on the surfaces of LNMO cathodes and graphite anodes, respectively. The LiBODFP-derived interface film can protect the cathode and anode materials, alleviate the decomposition of the electrolyte, and prevent the dissolution of metal ions from the LNMO cathode and their deposition on the graphite surface. This work provides an effective strategy for developing a functional electrolyte that matches the requirement of LNMO-based batteries with a high-voltage window and enhanced performance. [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]

An electrochemical sensor based on a polyfurfural-electrochemically reduced graphene oxide modified glassy carbon electrode has been developed for the sensitive and rapid determination of nitrofurazone. The morphologies and properties of the sensor were characterized by electrochemical impedance spectroscopy, scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry (DPV). In pH 7.0 Britton–Robinson buffer solution, the as-prepared polyfurfural-electrochemically reduced graphene oxide modified glassy carbon electrode shows excellent electrocatalytic performance for the electrochemical reduction of nitrofurazone, and the reduction peak current is about 9.45, 1.31, and 1.25 times higher than that of the bare glassy carbon electrode, polyfurfural modified glassy carbon electrode, and electrochemically reduced graphene oxide modified glassy carbon electrode, respectively. The DPV determination of nitrofurazone indicates that the linear range and detection limit of nitrofurazone are 1–50 and 0.25 µmol/dm3, respectively. In addition, this sensor exhibits high selectivity, reproducibility, stability, and also was successfully used to directly determine nitrofurazone in the commercial antibacterial lotion with comparative sensitivity to high-performance liquid chromatography, showing its promising application prospects. [ABSTRACT FROM AUTHOR]

The adsorptive removal of Ni2+ and Cd2+ at concentrations of approximately 50 mg L−1 in wastewater is investigated using an agricultural adsorbent, longan hull, and the adsorptive mechanism is characterized. The maximum adsorption capacity of approximately 4.19 mg g−1 Cd2+ was obtained under the optimized conditions of room temperature, pH 5.0, and a solid-to-liquid ratio of 1:30 in approximately 15 min. For Ni2+, the maximum adsorption capacity of approximately 3.96 mg g−1 was obtained at pH 4.7 in approximately 20 min. The adsorption kinetics for both metal ions on the longan hull can be described by a pseudo second-order rate model and are well fitted to the Langmuir adsorption isotherm. The adsorption mechanism of the longan hull to Ni2+ and Cd2+ ions is shown to be a monolayer adsorption of metal ions onto the absorbent surface. Thereinto, the longan hull adsorbent contains N–H, C–H, C=O, and C=C functional groups that can form ligands when loaded with Ni2+ and Cd2+, which reduces the fluorescence of the dried longan hull material. [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]