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Abstract: Carbon-coated LiMn0.4Fe0.6PO4 (LMFP) was synthesized by sol–gel technique using citric acid as foaming agent and carbon precursor. To evaluate the effect of synthetic conditions on the electrochemical properties of LMFP for use as cathode active material, the carbon-coated olivines were synthesized by a two-step thermal treatment at different temperatures. The composites were characterized by elemental analysis, XRD, SEM, TEM, Raman microprobe spectroscopy and their electrochemical properties were also studied. The composite that shows the better electrochemical performance has more porous structure, lower D/G band ratio in Raman spectra, and charge and discharge capacities of same 155mAhg−1 with higher material utilization of 97% at 0.1C-rate (0.05mAcm−2). The material exhibiting the better performance was also incorporated in a polymer electrolyte hosted in an electrospun P(VdF-HFP) membrane. The lithium polymer battery composed of LiMn0.4Fe0.6PO4 cathode and polymer electrolyte showed a good cycling performance with the initial discharge capacity of 146mAhg−1. [Copyright &y& Elsevier]

Abstract: Composite membranes of poly(vinylidene fluoride-co-hexafluoropropylene) {P(VdF-HFP)} and different composition of silica have been prepared by electrospinning polymer solution containing in situ generated silica. These membranes are made up of fibers of 1–2μm diameters. These fibers are stacked in layers to produce fully interconnected pores that results in high porosity. Polymer electrolytes were prepared by immobilizing 1M LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC) in the membranes. The composite membranes exhibit a high electrolyte uptake of 550–600%. The optimum electrochemical properties have been observed for the polymer electrolyte containing 6% in situ silica to show ionic conductivity of 8.06mScm−1 at 20°C, electrolyte retention ratio of 0.85, anodic stability up to 4.6V versus Li/Li+, and a good compatibility with lithium metal resulting in low interfacial resistance. A first cycle specific capacity of 170mAhg−1 was obtained when the polymer electrolyte was evaluated in a Li/lithium iron phosphate (LiFePO4) cell at 0.1C-rate at 25°C, corresponding to 100% utilization of the cathode material. The properties of composite membrane prepared with in situ silica were observed to be comparatively better than the one prepared by direct addition of silica. [Copyright &y& Elsevier]

Abstract: Ni3S2 powder has been fabricated by mechanical alloying Ni and S powders and the electrochemical properties of Na/Ni3S2 cells fabricated from Na anodes and Ni3S2 cathodes and 1 M sodium trifluoromethanesulfonate in tetraethyleneglycol dimethylether liquid electrolyte have been investigated. Upon discharging, the Ni3S2 cathode transformed to amorphous Na2S, Ni and residual unconverted Ni3S2. On charging, the pristine structure of Ni3S2 is fully recovered. The reversibility of this anode/cathode pair has been demonstrated and the discharge capacity loss of Na/Ni3S2 cells has been investigated over 100 cycles. From TEM, EDS, XRD, and EIS results, the degradation mechanism appears to be the formation of nano-particles of Ni3S2 and Na2S which become detached from the bulk cathode material causing the continuous increase in the interfacial resistance. Furthermore, many small cracks in Ni3S2 cathode material are caused during repeated cycling and this is an additional phenomenon that leads to further degradation of the discharge capacity during cycling. [Copyright &y& Elsevier]

Abstract: Prepared by the deposition of a solid electrode and electrolyte, all-solid-state batteries are a promising next generation battery system. Aerosol deposition (AD) offers many advantages compared to the conventional thin film deposition methods, including the deposition of a crystallized thin film with no heat treatment and a fast deposition rate. In this study, a LiFePO4/C composite thin film is directly fabricated using a LiFePO4/C composite raw powder. SEM and EDS results show the successful deposition of a LiFePO4/C composite thin film on a stainless steel substrate and X-ray diffraction patterns reveal that the as-deposited thin film has a crystalline structure, corresponding to the olivine phase, without any heat treatment. In a CV test, oxidation and reduction peaks appear at 3.51 and 3.36 V, corresponding closely to the peaks of bulk olivine LiFePO4. Furthermore, the profiles of the charge and discharge curves are similar to those of the bulk electrode and the discharge capacity is 31.1 μAh cm−2 μm−1 in the first cycle. After 20 cycles of 10.65 and 106.5 μA cm−2 μm−1, the capacity is recovered to 30.7 μAh cm−2 μm−1. Aerosol deposition can potentially be used in the fabrication of all-solid-state batteries. [Copyright &y& Elsevier]

Abstract: Carbon-coated LiMn0.4Fe0.6PO4 composites (LiMn0.4Fe0.6PO4/C) were synthesized for use as cathode materials in lithium batteries. The composites were synthesized by a mechanical activation process that consists of high-energy ball milling for 10h, followed by thermal treatment at different temperatures. The structure, particle size and surface morphology of these cathode active materials were investigated by inductively coupled plasma (ICP) analysis, energy dispersive spectrometry (EDS), high-resolution Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). The firing temperature was observed to affect morphology, particle size, elemental distribution, structure of the residual carbon, and consequently the electrochemical properties of the composites. LiMn0.4Fe0.6PO4/C synthesized at 600°C possessed the most desirable properties and it exhibited the best performance when used as cathode in lithium batteries at room temperature. The cell, comprising cathode of this composite, exhibited the initial discharge capacities of 144.5mAhg−1 (85.0% of theoretical capacity) and 122.0mAh g−1 (71.8%), respectively, at 0.1 and 1 C-rates. The cathode showed good cycle stability without substantial capacity fade up to 50 cycles. [Copyright &y& Elsevier]

Abstract: Carbon-coated sulfur cathodes were prepared by sputtering method and electrochemical properties of lithium/sulfur cells were investigated. As a result of charge/discharge test, sulfur cathode having carbon layer of 180Å showed the highest capacity of 1178mAhg−1 at first discharge. Moreover, discharge capacity showed about 500mAhg−1 until 50th cycle, which is two times larger than that of no-coated sulfur cathode. This capacity increase could be considered due to the decrease of polysulfides dissolution and the enhancement of electrical contact by surface carbon layer. The changes of sulfur cathode during discharge process were investigated by SEM observation, XRD and DSC measurements. From these results, a discharge reaction mechanism of lithium/carbon-coated sulfur cell was suggested. [Copyright &y& Elsevier]

Abstract: The discharge properties of a Na/Ni3S2 cell using 1M NaCF3SO3 in tetra(ethylene glycol)dimethyl ether liquid electrolyte were investigated at room temperature. The products were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Electrochemical properties of Na/Ni3S2 cells were also presented by cyclic voltammetry and the galvanostatic current method. Na/Ni3S2 cells have an initial discharge capacity of 420mAhg−1 with a plateau potential at 0.94V versus Na/Na+. After the first discharge, Ni3S2 and Na react at room temperature and then form sodium sulfide (Na2S) and nickel. Sodium ion can be partially deintercalated from Na2S charge reaction. The discharge process can be explained as follows: Ni3S2 +4Na↔3Ni+2Na2S. [Copyright &y& Elsevier]

Abstract: Pure, nano-sized LiFePO4 and carbon-coated LiFePO4 (LiFePO4/C) positive electrode (cathode) materials are synthesized by a mechanical activation process that consists of high-energy ball milling and firing steps. The influence of the processing parameters such as firing temperature, firing time and ball-milling time on the structure, particle size, morphology and electrochemical performance of the active material is investigated. An increase in firing temperature causes a pronounced growth in particle size, especially above 600°C. A firing time longer than 10h at 600°C results in particle agglomeration; whereas, a ball milling time longer than 15h does not further reduce the particle size. The electrochemical properties also vary considerably depending on these parameters and the highest initial discharge capacity is obtained with a LiFePO4/C sample prepared by ball milling for 15h and firing for 10h at 600°C. Comparison of the cyclic voltammograms of LiFePO4 and LiFePO4/C shows enhanced reaction kinetics and reversibility for the carbon-coated sample. Good cycle performance is exhibited by LiFePO4/C in lithium batteries cycled at room temperature. At the high current density of 2C, an initial discharge capacity of 125mAhg−1 (73.5% of theoretical capacity) is obtained with a low capacity fading of 0.18% per cycle over 55 cycles. [Copyright &y& Elsevier]