Core/Shell Nanoparticles: Classes, Properties, Synthesis Mechanisms, Characterization, and Applications

Over the past 30 years, significant commercial and academic progress has been made on Li-based battery technologies. From the early Li-metal anode iterations to the current commercial Li-ion batteries (LIBs), the story of the Li-based battery is full of breakthroughs and back tracing steps. This review will discuss the main roles of material science in the development of LIBs. As LIB research progresses and the materials of interest change, different emphases on the different subdisciplines of material science are placed. Early works on LIBs focus more on solid state physics whereas near the end of the 20th century, researchers began to focus more on the morphological aspects (surface coating, porosity, size, and shape) of electrode materials. While it is easy to point out which specific cathode and anode materials are currently good candidates for the next-generation of batteries, it is difficult to explain exactly why those are chosen. In this review, for the reader a complete developmental story of LIB should be clearly drawn, along with an explanation of the reasons responsible for the various technological shifts. The review will end with a statement of caution for the current modern battery research along with a brief discussion on beyond lithium-ion battery chemistries.

30 Years of Lithium-Ion Batteries.

Metal Oxides and Oxysalts as Anode Materials for Li Ion Batteries

The surface and materials science of tin oxide

Despite the imminent commercial introduction of Li-ion batteries in electric drive vehicles and their proposed use as enablers of smart grids based on renewable energy technologies, an intensive quest for new electrode materials that bring about improvements in energy density, cycle life, cost, and safety is still underway. This Progress Report highlights the recent developments and the future prospects of the use of phases that react through conversion reactions as both positive and negative electrode materials in Li-ion batteries. By moving beyond classical intercalation reactions, a variety of low cost compounds with gravimetric specific capacities that are two-to-five times larger than those attained with currently used materials, such as graphite and LiCoO(2), can be achieved. Nonetheless, several factors currently handicap the applicability of electrode materials entailing conversion reactions. These factors, together with the scientific breakthroughs that are necessary to fully assess the practicality of this concept, are reviewed in this report.

Beyond Intercalation-Based Li-Ion Batteries: The State of the Art and Challenges of Electrode Materials Reacting Through Conversion Reactions

Detection of CO and O2 Using Tin Oxide Nanowire Sensors

We show that the rates and extent of oxidation and reduction reactions taking place at the surface of a SnO2 nanowire, configured as a field-effect transistor, can be modified by changing the electron density in the wire with a gate voltage.

Control of Catalytic Reactions at the Surface of a Metal Oxide Nanowire by Manipulating Electron Density Inside It

A general methodology that utilizes confined mesoporous silica as template for preparing highly ordered mesostructured nanowires and nanowire arrays is developed. The prepared Ag, Ni, and Cu2O nanowires, with unprecedented mesostructures of coaxially multilayered helical, and stacked-donut structures, have the unique features of hierarchical organization, modulated surface morphology, high surface area, and chirality. Surface-enhanced Raman spectra from a silver mesostructured-nanowire bundle are presented.

Templated Synthesis of Highly Ordered Mesostructured Nanowires and Nanowire Arrays

Flat arrays (rafts) of aligned silver nanowires were fabricated by electrodepositing silver in the nanopores of highly ordered anodic alumina templates and then releasing the silver nanowires and depositing them on an oxidized, single-crystal silicon surface. SERS spectra were recorded from Rhodamine 6G molecules adsorbed onto the rafts. The SERS spectra showed striking polarization dependence according to the relative disposition of the E-vector with respect to the nanowires' axes. The observations can be adequately described by the classical electromagnetic (EM) response of the strongly interacting metal nanowires to the optical fields when surface plasmon resonances are induced. The discussion relates these observations to the origin of the giant surface enhanced Raman effect with single-molecule detectivity as well as to possible strategies that one might use to construct systems that predictably and repeatedly produce such giant EM fields.

Polarized Surface Enhanced Raman Scattering from Aligned Silver Nanowire Rafts

Tin oxide single nanowires configured as field effect transistors were shown to be operable and tunable alternately as gas sensors or as catalysts under a gaseous atmosphere that simulated realistic ambient conditions. The unusually large surface-to-volume ratio available with nanowires causes adsorption or desorption of donor or acceptor molecules on the nanowire's surface to greatly alter its bulk electron density at relatively small values of the gate voltage. This process can be sensitively monitored as changes in the nanowire's conductivity. The potentially radical change in carrier density can lead to significant changes in the nanowire's sensitivity as a sensor or reciprocally as a catalyst in reactions that involve charge exchange across the nanowire's surface. This leads to the prospect of tuning catalysis or other surface reactions entirely through electronic means.

Youxiang Zhang

Papers

Detection of CO and O2 Using Tin Oxide Nanowire Sensors

Control of Catalytic Reactions at the Surface of a Metal Oxide Nanowire by Manipulating Electron Density Inside It

Templated Synthesis of Highly Ordered Mesostructured Nanowires and Nanowire Arrays

Polarized Surface Enhanced Raman Scattering from Aligned Silver Nanowire Rafts

Electronic control of chemistry and catalysis at the surface of an individual tin oxide nanowire.