Reversible Li-Ion Conversion Reaction for a TixGe Alloy in a Ti/Ge Multilayer.

Group IV intermetallics electrochemically alloy with Li with stoichiometries as high as Li4.4M (M = Si, Ge, Sn, or Pb). This provides the second highest known specific capacity (after pure lithium metal) for lithium-ion batteries, but the dramatic volume change during cycling greatly limits their use as anodes in Li-ion batteries. We describe an approach to overcome this limitation by constructing electrodes using a Ge/Ti multilayer architecture. In operando X-ray reflectivity and ex situ transmission electron microscopy are used to characterize the heterolayer structure at various lithium stoichiometries along a lithiation/delithiation cycle. The as-deposited multilayer spontaneously forms a one-dimensional TixGe/Ti/TixGe core-shell planar structure embedded in a Ge matrix. The interfacial TixGe alloy is observed to be electrochemically active and exhibits reversible phase separation (i.e., a conversion reaction). Including the germanium components, the overall multilayer structure exhibits a 2.3-fold reversible vertical expansion and contraction and is shown to have improved capacity and capacity retention with respect to a Ge film with equivalent active material thickness.

Metal-metal chalcogenide molecular precursors to binary, ternary, and quaternary metal chalcogenide thin films for electronic devices.

Bulk metals and metal chalcogenides are found to dissolve in primary amine-dithiol solvent mixtures at ambient conditions. Thin-films of CuS, SnS, ZnS, Cu2Sn(S(x),Se(1-x))3, and Cu2ZnSn(S(x)Se(1-x))4 (0 ≤ x ≤ 1) were deposited using the as-dissolved solutions. Cu2ZnSn(S(x)Se(1-x))4 solar cells with efficiencies of 6.84% and 7.02% under AM1.5 illumination were fabricated from two example solution precursors, respectively.

Fabrication based on the Kirkendall effect of Co3O4 porous nanocages with extraordinarily high capacity for lithium storage.

Herein we report a novel facile strategy for the fabrication of Co(3)O(4) porous nanocages based on the Kirkendall effect, which involves the thermal decomposition of Prussian blue analogue (PBA) Co(3)[Co(CN)(6)](2) truncated nanocubes at 400 °C. Owing to the volume loss and release of internally generated CO(2) and N(x) O(y) in the process of interdiffusion, Co(3)O(4) nanocages with porous shells and containing nanoparticles were finally obtained. When evaluated as electrode materials for lithium-ion batteries, the as-prepared Co(3)O(4) porous nanocages displayed superior battery performance. Most importantly, capacities of up to 1465 mA h g(-1) are attained after 50 cycles at a current density of 300 mA g(-1). Moreover, this simple synthetic strategy is potentially competitive for scaling-up industrial production.

Carboxyl and negative charge-functionalized superparamagnetic nanochains with amorphous carbon shell and magnetic core: synthesis and their application in removal of heavy metal ions.

This communication describes carboxyl-functionalized nanochains with amorphous carbon shell (18 nm) and magnetic core using ferrocene as a single reactant under the induction of an external magnetic field (0.40 T), which shows a superparamagnetic behavior and magnetization saturation of 38.6 emu g(-1). Because of mesoporous structure (3.8 nm) and surface negative charge (-35.18 mV), the nanochains can be used as adsorbent for removing the heavy metal ions (90%) from aqueous solution.