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Both the cycling performance of LiFePO4 cells prepared with Li or MCMB anodes, and 1 M LiPF6 in EC/DEC electrolytes with/without adding tris(pentafluorophenyl) borane (TPFPB) are used to ascertain the effects of the TPFPB additive. It is found that the cycling performance of the LiFePO4/MCMB cell is improved significantly by the TPFPB additive at 60°C, though the influence of the additive on the cycling performance of LiFePO4/MCMB cell at 25°C and LiFePO4/Li at 25 and 60°C are indistinct. The results of soak study, FTIR, and XPS analyzes for the electrodes obtained from cycled LiFePO4/Li and LiFePO4/MCMB cells reveal that the improvement on cycling performance of the LiFePO4/MCMB cell at 60°C can be mainly attributed to the reduction of LiF content in SEI layer and the layer growth rate by adding TPFPB to enhance re-dissolution of lithium salts.

Neutron diffraction is an alternative tool to study the structural changes of a commercial lithium ion cell in operando due to its high penetration, low interaction with matter, and sensitive to low atomic number elements. High resolution neutron diffractometer (Echidna at ANSTO) and high intensity neutron powder diffractometer (Wombat at ANSTO) were used in this study to investigate the structures of a fresh and storage aged commercial 18650 cells (comprised with LiNi0.5Mn0.3Co0.2O2 (NMC)/Li1.1Mn1.9O4 (LMO) composite cathode and graphite anode) and their structural changes upon charge/discharge cycling. It was found that the storage capacity fade increases significantly with increasing storage temperature after 6 months storage. The capacity fades of the cells stored at 0, 25, 50, 75, and 100% DOD are 9.9, 17.5, 7.5, 3.6, and 0.7 %, respectively, after stored at 60oC for 6 months. Figure 1 shows the typical high resolution NPD pattern and its refinement of a fresh cell, while Table 1 lists the results of Rietveld refinement for the NPD patterns of the fresh and aged cells at their the fully discharged and charged states after been stored at 0, 25, and 50 %DOD at 60oC for 6 months. It can be found that the aged cells manifest similar lattice parameters of LMO and NMC at their fully charged state as those of fresh cell, respectively. However, the aged cells show smaller lattice parameter of LMO than that of fresh one and the value decreases with decreasing DOD of storage. That suggests the cell stored at 0% DOD has the most severe structure change in LMO among the samples stored at 60oC for 6 months. From the in-situ 2D ND patterns of the fresh and aged cells collected every 5 minutes with Wombat upon cycling at 215 mA within 2.75 and 4.2 V, shown in Fig. 2, the variation in lattice parameters of LMO and NMC can be determined. The values of the parameters at their charged and discharged states obtained from sequential Rietveld refinement are similar as those shown in Table 1. From the intensity changes of LMO 222 plane after storage for 6 months, it can be found that the sample stored at 0% DOD shows higher LMO loss than other stored samples, which can also be revealed from the abrupt change in lattice parameter of the sample at 4.06 V upon charge/discharge cycling, while linear change in parameter are observed in case of other samples. Aged sample stored at 25% DOD shows lower intensity of LiC6 001 plane manifests the sample has higher lithium loss of inventory (LLI) than others, which can also be revealed from the changes after storage in lattice parameters of NMC at discharged state, shown in Table 1, and intensity of NMC 003 plane at discharged state shown in Fig. 2. These are in consistent with the results obtained from ICA study for the charge/discharge curves and post-mortem studies. The results suggest that the capacity losses of the samples stored at 0 and 25% DOD can be attributed to loss of LMO and LLI, whereas samples stored at depth of discharge higher than 50% DOD can be caused by loss of LLI only. Figure 1

High-voltage spinel LiNi0.5Mn1.5O4 (LNMO) were synthesized by a spray pyrolysis method followed by heat treatment at 900oC for 8 hours then post annealing at 700oC for varies duration (0-96 hours) under air atmosphere. The crystalline structure and morphology of the prepared samples are studied with X-ray diffraction (XRD), neutron powder diffraction (NPD), Raman spectroscopy, scanning electron microscope (SEM), and high-resolution transmission microscope (HR-TEM). The electrochemical properties of the prepared materials had also been investigated by the studies of cyclic voltammetry (CV) and the capacity retention with coin-type cells by use of battery testing system. The results show all of the prepared samples have similar morphology and average particle size, but crystalize into mixtures of ordered P4332 and disordered Fd-3 m phases with various fractions. It can be found from Table 1 that the phase fraction of ordered phase obtained from the Rietveld refinement of NPD patterns increases with increasing duration of post annealing at 700oC. Fig. 1 manifests the results of cycling performance of the coin cells comprised with the prepared samples at 0.1 and 1.0 C rates, respectively. Samples containing the higher phase fraction of disordered phase exhibits the lower capacity fade than those dominated with ordered phase. It may be attributed to the ordered phase dominated sample experienced more complex phase change than the disordered phase dominant sample, which had been revealed from the in-situ NPD studies. Figure 1

The capacity and power loss are usually observed when lithium ion batteries were cycled or stored, however, the degradation mechanisms and their correlation with cell performance fade are not only dependent on the cell chemistry but also on the cell design and manufacture technique. The capacity loss diagnosis and the lifetime prediction for LIBs are still critical issues for large format applications. Commercial 18650 lithium ion cells containing a composite cathode of LiNi0.5Mn0.3Co0.2 (NMC) and LiMn2O4 (LMO) and graphite anode with a nominal capacity of 2.15 Ah were used in this study. Although the aging behavior of the battery comprised with LiNi1/3Mn1/3Co1/3O2/LiMn2O4 composite cathode and graphite anode cycled between 4.2 and 2.8V had been studied with an incremental capacity technique and suggested that there are two stages of capacity fade with first stage mainly caused by the loss of inventory (LLI) and further suffered from loss of active material (LAM) in positive electrode in the second stage [1, 2]. The results of capacity retention study within the voltag e range between 4.2 and 2.75V by following the manufacturer’s suggestion and charging the cells with CC-CV mode with 0.5C rate (cut-off at 0.04C) and discharging at 0.5, 1.0, and 2.0C rates, respectively, shown in Fig.1 (a), manifest that the cells cycled at higher discharge rate exhibit longer cycle life than that cycled at 0.5C. It is contrary to the generally accepted notion that high C-rate will accelerate cell aging. However, the expected tendency can be observed when cells were cycled between 4.2 and 3.0V (Fig. 1 (b)). From the results incremental capacity analysis (ICA) for the charge/discharge curves of the cells discharged at 1.0C rate with lower cut-off voltage of 2.75 and 3.0V, respectively, the redox peaks at around 3.53V, those relates with the amount of active graphite, decreases abruptly after 300th cycle where the accelerated capacity fade occurs for cell cycled between 4.2 and 2.75V.That suggests the accelerated capacity loss can be caused by loss of anode material instead of cathode material in additional to the continued loss of lithium inventory that can be observed from the shifting of the peak at around 3.53V to higher voltage and lowering of the peak at about 3.69V (Fig. 2). In order to understand the non-linear capacity fade when cells were cycled between 4.2 and 2.75V, post-mortem studies with XRD, SEM, ICP, and capacity retention for the electrodes obtained from fresh, 200 cycled, and aged cells will be performed for comparison with those of the cells cycled within 4.2 and 3.0V to support the results obtained from ICA. Reference [1] M. Dubarry, C. Truchot, M. Cugnet, B.Y. Liaw, K. Gering, S. Sazhin, D. Jamison, C. Michelbacher, Journal of Power Sources, 196 (2011) 10328-10335. [2] M. Dubarry, C. Truchot, B.Y. Liaw, K. Gering, S. Sazhin, D. Jamison, C. Michelbacher, Journal of Power Sources, 196 (2011) 10336-10343. Figure 1

In this study, the capacities and electrochemical impedances at various states of charge (SOC) are measured after the screened commercial 18650 lithium ion cells assembled with composite cathode of layered mixed oxide (NMC) and spinel lithium manganite (LMO) and graphite anode were stored at various states of depth-of-discharge (DOD) at various temperatures for various durations. The results manifest that the capacity fading is strongly affected by the storage temperature and becomes prominent at temperatures higher than 45oC. Incremental capacity analyses (ICA) for the charge/discharge curves before and after storage were performed for the qualitative mechanism study. It demonstrates that the capacity fade of the cell stored at 60oC and 0% DOD can be attributed to the loss of active materials, and the loss of graphite anode is higher than that of composite cathode. The capacity fade of the cell stored at 60oC and 25% DOD can be caused by the lithium inventory loss, the loss of NMC, and the loss due to the morphology change of LMO. Cell stored at 50% DOD manifests similar fading behavior as that of the cell stored at 0% DOD, however, the ICA plots demonstrate that the capacity loss of the cell comes from losses of lithium inventory and NMC caused by the dissolution of transition metals with additional losses of LMO and graphite anode occur after 10 months of accumulated storage. For cell stored at 75% DOD, most the capacity loss can be due to the loss of NMC with minor contribution of lithium inventory loss, while cell stored at 100% DOD shows almost no change after storage for 12 accumulated months. These results revealed from the ICA study are consistent with those determined from the post mortem study of the electrodes obtained from cells before and after storage.

LiNi0.5Mn1.5O4 powders were prepared via a spraying-dry method followed by heating at temperatures between 600 and 1000oC for 8 hours in air with oven cooling. In order to eliminate the particle size effects, 900oC samples were annealed at 700oC under air for various durations. The crystalline structure of the prepared samples were investigated from their high resolution neutron powder diffraction data collected with Echidna at ANSTO and refined with Rietica Ver. 1.77. The results of Rietveld refinement for the NPD patterns manifest that the 700oC prepared sample contains 85% of ordered P4332 and 15% of disordered Fd m phases whereas the powders prepared at temperatures higher than 800oC prevailed with disordered Fd m phase (72`75%) with amount of rock-salt LixNi1-xO increases from 1 to 4% with heating temperature. For the annealed samples, the molar fraction of the ordered phase increases with increasing duration of annealing and converts completely into ordered phase after annealing for 60 hours. It suggests that the phase conversion and LixNi1-xO evolution/dissolution are reversible [1]. From the results of capacity retention study of the cells comprised with the prepared powders, it was found that sample prepared at 900oC with oven cooling exhibits the most promising performance among the prepared powders. These results are different from those reported by Fang et al. [2], however, they are similar to those reported previously that the disordered phase has better electrochemical properties than the ordered phase [3-5]. Though various reasons had been suggested [3, 6-7], the effects of crystalline structure on the cycling performance of high voltage spinel are still not clear. In this study, the effects are hope to reveal from the results of dissolution study for transition metals upon storage and cycling, linear sweep voltammetry for electrolyte oxidation on high voltage spinel, cyclic voltammetry for Li+ ion diffusivity, and the phase evolution detected by high resolution TEM for the fresh and cycled electrodes and in-situ NPD study. Reference: [1] L. Cai, Z. Liu, K. An, and C. Liang, J. Mater. Chem. A, 1,6908 (2013). [2] H. Fang, Z. Wang, B. Zhang, X. Li and G. Li, Electrochem. Commun., 9, 1077 (2007). [3] J. H. Kim, S. T. Myung, C. S. Yoon, S. G. Kang and Y. K. Sun, Chem. Mater., 16, 906 (2004). [4] A. Bhaskar, N. N. Bramnik, A. Senyshyn, H. Fuess and H. Ehrenberg, J. Electrochem. Soc., 157, A689 (2010). [5] K. Takahashi, M. Saitoh, M. Sano, M. Fujita and K. Kifune, J. Electrochem. Soc., 151, A173 (2004). [6] M. Kunduraci, J. F. Al-Sharab and G. G. Amatucci, Chem. Mater., 18, 3585 (2006). [7] X. H. Ma, B. Kang and G. Ceder, J. Electrochem. Soc., 157, (2010).

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Nanosized zinc gallate phosphors were prepared via the citric gel route and their luminous properties were characterized by photoluminescence in this study. From the results of X-ray diffraction studies, it was found that a spinel phase of formed after the dry gel had been heat-treated at 470°C for 1 h and well-crystallized spinel phosphors with an average particle size of 35 nm were obtained after the dry gel had been heat-treated at 700°C for 5 h. The photoluminescence studies manifested that the shapes and the wavelengths of maximum intensity of the absorption and emission spectra were independent of the heat-treatment temperature in the range between 600 and 1000°C. Instead of the normally observed bell-shaped spectrum, peak-shaped emission spectra were observed when these nanosized phosphors were excited with UV light of wavelength of 254 nm. The peak-shaped emissions with maximum intensity at a wavelength of 470 nm correspond to the self-activated luminescence of © 2004 The Electrochemical Society. All rights reserved.