Fine-tuning of particle size and morphology has been shown to result in differential material performance in the area of secondary lithium-ion batteries. For instance, reduction of particle size to the nanoregime typically leads to better transport of electrochemically active species by increasing the amount of reaction sites as a result of higher electrode surface area. The spinel-phase oxide LiNi0.5Mn1.5O4 (LNMO), was prepared using a sol-gel based template synthesis to yield nanowire morphology without any additional binders or electronic conducting agents. Therefore, proper experimentation of the nanosize effect can be achieved in this study. The spinel phase LMNO is a high energy electrode material currently being explored for use in lithium-ion batteries, with a specific capacity of 146 mAh/g and high-voltage plateau at ∼4.7 V (vs Li/Li(+)). However, research has shown that extensive electrolyte decomposition and the formation of a surface passivation layer results when LMNO is implemented as a cathode in electrochemical cells. As a result of the high surface area associated with nanosized particles, manganese ion dissolution results in capacity fading over prolonged cycling. In order to prevent these detrimental effects without compromising electrochemical performance, various coating methods have been explored. In this work, TiO2 and Al2O3 thin films were deposited using atomic layer deposition (ALD) on the surface of LNMO particles. This resulted in effective surface protection by prevention of electrolyte side reactions and a sharp reduction in resistance at the electrode/electrolyte interface region.

Fatty acid analysis is essential to a broad range of applications including those associated with the nascent algal biofuel and algal bioproduct industries. Current fatty acid profiling methods require lengthy, sequential extraction and transesterification steps necessitating significant quantities of analyte. We report the development of a rapid, microscale, single-step, in situ protocol for GC–MS lipid analysis that requires only 250 μg dry mass per sample. We furthermore demonstrate the broad applications of this technique by profiling the fatty acids of several algal species, small aquatic organisms, insects and terrestrial plant material. When combined with fluorescent techniques utilizing the BODIPY dye family and flow cytometry, this micro-assay serves as a powerful tool for analyzing fatty acids in laboratory and field collected samples, for high-throughput screening, and for crop assessment. Additionally, the high sensitivity of the technique allows for population analyses across a wide variety of taxa.

Magnesium-ion batteries (MIBs) have twofold volumetric energy density than that of lithium without the dendritic deposition morphology associated with Li, which makes MIBs attractive options. We investigate the feasibility of using anatase-phase TiO 2 as an electrode material for MIBs. Electrochemical, microscopic, and spectroscopic analyses are performed in order to probe Mg-ion insertion as well as determine the limitation of TiO 2 as a viable electrode material.

The advent of lithium-ion electrochemical has ushered in a new era of high energy density rechargeable batteries, with applications ranging from portable electronics to electric vehicles.1 However, several challenges have stymied the implementation of lithium-ion batteries that approach the thermodynamic capacity and energy density limit. This is largely associated with the use of a lithium-metal anode, which under extensive cycling conditions and current densities promotes the formation of dendritic lithium deposits. Lithium dendrites result in the formation of electrochemically “dead” lithium, resulting in poor cycling efficiency.2 In addition, dendritic lithium has been implicated in the cell shorting and thermal runaway. To mitigate such problems, alternative energy storage systems have been heavily pursued recently, with efforts largely focused on the development of sodium-ion and magnesium-ion electrochemical cells.3 The implementation of a magnesium metal anode is highly advantageous to lithium, as the volumetric capacity is nearly double (3833 mAh/mL vs. 2062 mAh/mL, respectively) and the deposition morphology is described as non-dendritic.2 As such, considerable attention has been focused the development of magnesium electrochemical cells utilizing a magnesium metal anode, high capacity cathode, and suitable electrolyte. One of the leading cathode materials is the Chevrel-phase Mo6S8, introduced in 2000 with an experimentally determined specific capacity of 105 mAh/g.4 Recently, Sheha described an anatase TiO2/ reduced graphene oxide (rGO) composite cathode material was used in a magnesium-ion electrochemical cell utilizing a Mg metal anode and polyvinyl alcohol/ MgBr2/ tetraglyme/ H2O electrolyte. This cathode was shown to maintain cyclability to fifty cycles. Following this report and the plethora of publications concerning the insertion electrochemistry of anatase-phase titanium dioxide, we decided to investigate the feasibility of TiO2/ carbon black/ poly tetrafluoroethylene (PTFE) as an electrode for magnesium-ion batteries.  Herein, we report a study concerning the electrochemistry of Mg/TiO2 cells as well as a full characterization using spectroscopic and microscopic techniques. Figure 1 shows the voltage profiles of the TiO2/Mg coin cell with the All Phenyl Complex (APC) electrolyte between 0.05 and 2.2 V at a current density of 5 μA/ mg. During the first discharge, TiO2exhibits a well-defined plateau at approximately 0.5 V. The first discharge capacity is ~80 mAh/g. The material experiences a large polarization where the charge plateau increases to 1.2 V. The corresponding irreversible capacity in the first cycle is 20  mAh/g, which may arise from the poor conductivity of the electrode as well as the electrolyte side reactions. The close capacity between the discharge and charge process from the second cycle manifests excellent reversibility of the electrode. Figure 1 shows discharge and charge capacities with respect to cycle number at the same current density over 50 cycles. The capacity of the electrode remains at a quite considerable value after 50 cycles, which demonstrates relatively promising cycling stability.  Following electrochemical galvanostatic/ potentiostatic charge/ discharge experiments, TiO2 electrodes were carefully removed from electrochemical cells and examined for magnesium insertion mechanism. Following a careful transfer step to mitigate any exposure to oxygen, the TiO2 electrodes were examined using scanning electron microscopy (Phillips XL30) with an equipped energy dispersive X-ray detector (EDX), synchrotron X-ray diffraction, and ultraviolet-visible spectroscopy. Both the spectroscopic and microscopic characterization confirm that a Mg:Ti ratio of ~0.1:1 is able to reversibly shuttle between the working and counter electrodes in this battery system.  Acknowledgement The authors acknowledge the support by the seed funding from Sustainable Power and Energy Center under the Frontier of Innovation Award by Vice Chancellor of Research at UC San Diego. References (1) Whittingham, M. S. Chem. Rev. 2004, 104, 4271 – 4301. (2) Muldoon, J.; Bucur, C. B.; Gregory, T. Chem. Rev. 2014, 114, 11683 – 11720. (3) Dahbi, M.; Yabuuchi, N.; Kubota, K.; Tokiwa, K.; Komaba, S. Phys. Chem. Chem. Phys. 2014, 16, 15007 – 15028. (4) Aurbach, D.; Weissman, I.; Goffer, Y.; Levi, E. Chem. Record 2003, 3, 61 – 73. Figure 1