ArticleAchieving High Energy Density through Increasing the Output Voltage: A Highly Reversible 5.3 V Battery A 5.5 V high-voltage electrolyte enables both Li-metal and graphite anodes and 5.3 V LiCoMnO 4 cathodes to achieve a high Coulombic efficiency of >99%, opening new opportunity to develop high-energy Li-ion batteries. The design principle for the high voltage and safe electrolytes will greatly benefit the development of next-generation electrochemical energy storage devices. These findings should therefore be of extensive interest to a broad audience working on energy storage technologies, materials, and electrochemistry in general. HIGHLIGHTSStable 5.5 V electrolytes enable 5.3 V Li-metal battery and 5.2 V Liion battery Investigate the lithiationdelithiation mechanism of 5.3 V LiCoMnO 4 cathodes Reveal the correlation between electrolytes and CEI or SEI on electrodes Chen et al., Chem 5, 896-912 April 11, SUMMARYThe energy density of current Li-ion batteries is limited by the low capacity of intercalation cathode, which leaves relatively little room to further improve because the specific capacities of these cathodes approach the theoretical levels. Increasing the cell output voltage is a possible direction to largely increase the energy density of the batteries. Extensive research has been devoted to exploring >5.0 V cells, but only limited advances have been achieved because of the narrow electrochemical stability window of the electrolytes (<5.0 V). Herein, we report a 5.5 V electrolyte (1 M LiPF 6 in fluoroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, and hydrofluoroether [FEC/FDEC/HFE] with a Li difluoro(oxalate)borate [LiDFOB] additive) that enables 5.3 V LiCoMnO 4 cathodes to provide an energy density of 720 Wh kg À1 for 1,000 cycles and 5.2 V graphitejjLiCoMnO 4 full cells to provide an energy density of 480 Wh kg À1 for 100 cycles. The 5.5 V electrolytes provide a large step toward developing high-energy Li batteries.

This paper presents a novel technique for efficient evaluation of magnetic resonance imaging (MRI)-induced electric fields or induced voltages in the vicinity of implanted metallic leads. The technique is based on the reciprocity theorem in conjunction with the Huygens Principle. This approach allows one to decouple the micro-scale metallic lead simulation/measurement from the macro-level phantom human simulations within the MRI scanners. Consequently, the estimation of MRI-induced heating on an implanted lead, and the induced voltage on the pacemaker device can be greatly simplified. In addition, this method clearly explains the induced lead heating mechanism during MRI procedures. Several numerical examples, as well as measurement results are given to demonstrate the efficiency and accuracy of this method.

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A method of computing the signal-to-noise ratio (SNR) in high-frequency magnetic resonance (MR) imaging systems is presented. The method uses a numerical solution to Maxwell's equations which can capture all relevant electrodynamic effects at high B0-field strengths. Using this method, the intrinsic SNR of both volume and surface coils loaded with the human head is calculated as a function of frequency. It is shown that although the available SNR from any point scales favorably with frequency, phase inhomogeneity over the volume of the head may pose a challenge to achieving improved SNR with traditional imaging techniques at high B0-field strengths.

Conductors with a roughened surface have significant effects on high-speed signal propagation on backplane traces designed for a 10+ Gb/s network. An accurate approach to evaluate these effects, including the signal attenuation and the phase delay, is proposed in this paper. A differential extrapolation roughness measurement technique is first used to extract the dielectric properties of the substrate used for lamination, and then a periodic model is used to calculate an equivalent roughened conductor surface impedance, which is then used to modify the transmission line per-unit-length parameters R and L. The results indicate that the conductor surface roughness increases the conductor loss significantly as well as noticeably increasing the effective dielectric constant. This approach is validated using both a full-wave simulation tool and measurements, and is shown to be able to provide robust results for the attenuation constant within ±0.2 Np/m up to 20 GHz.