Lithium metal is considered to be the most promising anode for next-generation batteries due to its high energy density of 3840 mAh g(-1). However, the extreme reactivity of the Li surface can induce parasitic reactions with solvents, contamination, and shuttled active species in the electrolyte, reducing the performance of batteries employing Li metal anodes. One promising solution to this issue is application of thin chemical protection layers to the Li metal surface. Using a custom-made ultrahigh vacuum integrated deposition and characterization system, we demonstrate atomic layer deposition (ALD) of protection layers directly on Li metal with exquisite thickness control. We demonstrate as a proof-of-concept that a 14 nm thick ALD Al2O3 layer can protect the Li surface from corrosion due to atmosphere, sulfur, and electrolyte exposure. Using Li-S battery cells as a test system, we demonstrate an improved capacity retention using ALD-protected anodes over cells assembled with bare Li metal anodes for up to 100 cycles.

One-dimensional (1D) nanostructured materials have been intensively investigated as building components in electrochemical energy storage 1 and solar energy conversion 2 devices because they provide short diffusion path lengths to ions and excitons, leading to high charge/discharge rates 1 and high solar energy conversion efficiency. 2 More recently, coaxial nanowires have attracted greater attention in this field due to their added synergic properties (e.g., high conductivity) 3a or functionalities (e.g., core/shell p-n junction) 3b,c arising from the combination of different materials. 3 Various materials such as semiconductor/semiconductor, metal/ metal oxide, and metal oxide/metal oxide, have been employed as core/shell in coaxial nanowires. 3 However, there have been few studies on the coaxial nanowires with transition metal oxide and conductive polymer, although both of them are important electroactive materials used in electrochemical energy storage. 4 The combination of these two materials at 1D nanostructures may exhibit excellent electrical, electrochemical, and mechanical properties for electrochemical energy storage. To date, only a few reports have been published on the synthesis of metal oxide/ conductive polymer with core/shell structures. 5 In all of these reports, a stepwise synthetic approach was adopted: metal oxide nanoparticles, 5a nanostrands, 5b or nanotubes 5c were first synthesized and subsequently coated chemically by conductive polymers as shells.In this paper, we introduce a simple one-step method to synthesize MnO 2 /poly(3,4-ethylenedioxythiophene) (PEDOT) coaxial nanowires by coelectrodeposition in a porous alumina template. 6 MnO 2 is one of the most popular electrochemical energy storage materials because of its high energy density, low cost, environmental friendliness, and natural abundance, 7 but it has poor conductivity. 4c PEDOT has merits of excellent conductivity, high stability, and mechanical flexibility, 8 but it provides low electrochemical energy density. Electrodeposition is used here because it is a simple yet versatile method in controlling structures and their composition by tuning applied potentials and electrolyte ingredients. 9 In this report, MnO 2 /PEDOT coaxial nanowires are found to be promising electrochemical energy storage materials. The core MnO 2 provides high energy storage capacity, while the highly conductive, porous, and flexible PEDOT shell facilitates the electron transport and ion diffusion into the core MnO 2 and protects it from structurally significant collapsing and breaking. These combined properties enable the coaxial nanowires to have very high specific capacitances at high current densities.Scheme 1 illustrates the growth of MnO 2 /PEDOT coaxial nanowires. Under a constant potential (typically 0.75 V vs Ag/ AgCl), Mn 2+ (10 mM manganese acetate) is converted to its higher oxidization state, which can readily undergo hydrolysis to yield MnO 2 . 7 Simultaneously, EDOT monomer (80 mM) is electropolymerized into PEDOT in the pores of t...

Tube-shaped nanostructures (nanotubes) have a number of attributes that make them potentially useful for biomedical applications such as drug delivery/detoxification and enzyme immobilization. Template synthesis provides a route for preparing monodisperse nanotubes of nearly any size and composed of nearly any material. We show here that template-synthesized silica nanotubes can be biochemically functionalized such that they act as biocatalysts and highly selective nano-phase extraction agents for bioseparations. For example, nanotubes containing an enantioselective antibody selectively extract the enantiomer of a drug molecule that binds to the antibody, relative to the enantiomer that has no specific interaction with the antibody. Nanotubes containing the enzyme glucose oxidase function as nanophase bioreactors to catalyze the oxidation of glucose.

Synthetic bio-nanotube membranes were developed and used to separate two enantiomers of a chiral drug. These membranes are based on alumina films that have cylindrical pores with monodisperse nanoscopic diameters (for example, 20 nanometers). Silica nanotubes were chemically synthesized within the pores of these films, and an antibody that selectively binds one of the enantiomers of the drug was attached to the inner walls of the silica nanotubes. These membranes selectively transport the enantiomer that specifically binds to the antibody, relative to the enantiomer that has lower affinity for the antibody. The solvent dimethyl sulfoxide was used to tune the antibody binding affinity. The enantiomeric selectivity coefficient increases as the inside diameter of the silica nanotubes decreases.