Instability of electrolytes toward both highly reactive Li-metal anode and highvoltage cathodes has greatly impeded the development of Li-metal batteries. The authors designed an ether-based localized high-concentration electrolyte that can form stable interphases on both the Li anode and the Ni-rich NMC811 cathode to inhibit the undesired side reactions. This electrolyte enables a significantly enhanced battery performance under stringent practical conditions with a thin Limetal anode or Li-free anode, a high-loading cathode, and lean electrolyte.

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Porous carbon nanofiber (CNF)-supported tin-antimony (SnSb) alloys are synthesized and applied as a sodium-ion battery anode. The chemistry and morphology of the solid electrolyte interphase (SEI) film and its correlation with the electrode performance are studied. The addition of fluoroethylene carbonate (FEC) in the electrolyte significantly reduces electrolyte decomposition and creates a very thin and uniform SEI layer on the cycled electrode surface, which an promote the kinetics of Na-ion migration/transportation, leading to excellent electrochemical performance.

Nano-structured vanadium oxide (V 2 O 5 ) is fabricated via a facile thermal-decomposition of vanadium precursor, vanadyl oxalate, which is produced by reacting micro-sized V 2 O 5 with oxalic acid. The V 2 O 5 nanoparticles produced by this method exhibit much better electrochemical performance than commercial micro-sized V 2 O 5 . The optimized-nanorod electrodes give the best specific discharge capacities of 270 mAh g À1 at C/2 (147 mA g À1 ) coupled with good cycle stability with only 0.32% fading per cycle. Even at a high rate of 4C (1176 mA g À1 ), the nanorod electrode still delivers 198 mAh g À1 . These results suggest that the well-separated V 2 O 5 nanorod is a good cathode material for high-rate lithium battery applications.

Recently we have reported structural transformation features of SnO(2) upon initial charging using a configuration that leads to the sequential lithiation of SnO(2) nanowire from one end to the other (Huang et al. Science2010, 330, 1515). A key question to be addressed is the lithiation behavior of the nanowire when it is fully soaked into the electrolyte (Chiang Science2010, 330, 1485). This Letter documents the structural characteristics of SnO(2) upon initial charging based on a battery assembled with a single nanowire anode, which is fully soaked (immersed) into an ionic liquid based electrolyte using in situ transmission electron microscopy. It has been observed that following the initial charging the nanowire retained a wire shape, although highly distorted. The originally straight wire is characterized by a zigzag structure following the phase transformation, indicating that during the phase transformation of SnO(2) + Li ↔ Li(x)Sn + Li(y)O, the nanowire was subjected to severe deformation, as similarly observed for the case when the SnO(2) was charged sequentially from one end to the other. Transmission electron microscopy imaging revealed that the Li(x)Sn phase possesses a spherical morphology and is embedded into the amorphous Li(y)O matrix, indicating a simultaneous partitioning and coarsening of Li(x)Sn through Sn and Li diffusion in the amorphous matrix accompanied the phase transformation. The presently observed composite configuration gives detailed information on the structural change and how this change takes place on nanometer scale.