Considerable attention has been paid to electrochemical energy storage devices with both high energy and high power densities, because of their potential use in powering electric vehicles and portable electronic devices. Rechargeable lithium-based batteries are amongst the most promising candidates in terms of energy density, [1][2][3][4] whilst the achievement of high power density is hindered by kinetic problems of the electrode materials. For achieving a high rate capability of lithium batteries, rapid ionic and electronic diffusion is necessary. Extensive research work has focused on enhancing mixed conduction by doping the electrode materials with foreign atoms [4][5][6] or by admixing electronically conductive phases (electronic wiring through carbon, Ag, conducting polymers, etc.). [6][7][8][9][10][11][12][13][14][15][16][17] The wiring technique has been applied widely to micro-and submicro-sized particles (typically > 50 nm), but not to the 10 nm range, and has been most systemically studied by Jamnik et al. [14] A successful example of this is the well-known carbon-coating technique used in the synthesis of the LiFePO 4 electrode material. [9][10][11][12][13][14][15] However, the rate performance enhancement of such electrode materials is still limited, as availability or percolation of the electronically conducting phase and/or the electrolyte become insufficient at very high rates. Two recently reported optimization procedures intended for high rate performance may be mentioned in this context: 1) the use of nano-architectured electrodes consisting of the electrochemical plating of Fe 3 O 4 onto Cu nanorods acting as a current collector; [16] 2) the use of porous TiO 2 thin films.[17] Both designs lead to enhanced power performance but are naturally not meant for achieving high energy demands. In this communication, we propose and realize optimized nanostructure designs of electrode materials for high power and high energy lithium batteries: effectively highly Li-permeable materials are obtained by introducing a hierarchical, self-similar mixed conducting 3D network. The nanoscopic network structure is composed of a dense net of metalized mesopores that allow both Li + and e -to migrate.This network, with a mesh size of about 10 nm, is superimposed by a similar net on the microscale, formed by the composite of the mesoporous particles and the conductive admixture. The power of this concept is demonstrated by the synthesis of a mesoporous TiO 2 :RuO 2 nanocomposite, which shows a superior high rate capability when used as the anode material for lithium batteries. The general scheme of the optimized nanostructure design of electrode materials, which is still simple to fabricate, is shown in Figure 1. We introduce an efficient mixed conducting 3D nano-network with a mesh size of only a few nanometers, and with channel widths of comparable size. In this way the insertion kinetics in the electroactive material (here TiO 2 ) indeed becomes negligible, and the insertion rate of Li is enhanced to such a degre...

Nanoporous materials have attracted great technological interest during the past two decades, essentially due to their wide range of applications: they are used as catalysts, molecular sieves, separators and gas sensors as well as for electronic and electrochemical devices. Most syntheses of nanoporous materials reported so far have focused on template-assisted bottom-up processes, including soft templating (chelating agents, surfactants, block copolymers and so on) and hard templating (porous alumina, carbon nanotubes and nanoporous materials) methods. Here, we exploit a mechanism implicitly occurring in lithium batteries at deep discharge to develop it into a room-temperature template-free method of wide applicability in the synthesis of not only transition metals but also metal oxides with large surface area and pronounced nanoporosity associated with unprecedented properties. The power of this top-down method is demonstrated by the synthesis of nanoporous Pt and RuO2, both exhibiting superior performance: the Pt prepared shows outstanding properties when used as an electrocatalyst for methanol oxidation, and the RuO2, when used as a supercapacitor electrode material, exhibits a distinctly better performance than that previously reported for non-hydrated RuO2 (refs 19,20).

The sintering of ceria solid solutions, such as Ce 0.9 Gd 0.1 O 1.95 (CGO10), is strongly promoted by the addition of 1 cat% of cobalt oxide, lowering the maximum sintering temperature by 200 • C and triplicating the maximum densification rate. This change in sintering behavior results from cobalt ion segregated at the grain boundaries. An average cobalt ion boundary coverage is at maximum 3.0 ± 1.9 at/nm 2 and is shown to depend on the cooling rate. Coverage by segregated gadolinium is also found and amounts to 13.2 ± 11.4 at/nm 2 for a slowly cooled sample. From cobalt excess measured at the boundary, an estimated concentration of only 0.06 cat% of cobalt oxide is necessary to promote the sintering effect. The remaining amount of cobalt oxide is found in triple points and as particles in clusters. It is expected that the amount of cobalt oxide necessary for fast densification can be reduced with a doping process that distributes the additives more homogeneously.

This paper describes the synthesis of intermetallic Pt/Bi and Pt/Pb nanoparticles (NPs) using waterin-oil (w/o) microemulsions (μe) as template. For that purpose, w/o-microemulsions containing H 2 PtCl 6 þ Pb(NO 3 ) 2 and H 2 PtCl 6 þBi(NO) 3 , respectively, were mixed either with a w/o-microemulsion containing the reducing agent (NaBH 4 ) or with solid NaBH 4 . A variation of the amount of reducing agent led to different particle compositions and sizes, while different ratios of the two metal salts only affected the composition but not the size of the resulting NPs. The size and structure of the microemulsion droplets were studied via small angle X-ray scattering (SAXS), and the intermetallic NPs were characterized by high resolution transmission electron microscopy (HRTEM) in combination with energy dispersive X-ray spectroscopy (EDX) and selected area electron diffraction (SAED). The results revealed that it is indeed possible to synthesis Pt/Pb and Pt/Bi intermetallic nanoparticles of ∼3-8 nm in diameter at low temperatures.

For the synthesis of Pt nanoparticles we used water-in-oil droplet microemulsions as templates. The focus was on the correlation between the size of the microemulsion droplets and that of the resulting Pt particles. To study this correlation in a systematic way, all particles were synthesized at the water emulsification failure boundaries where the microemulsion droplets are spherical and where their size can easily be tuned by the amount of added water. The metallic particles were synthesized by mixing two microemulsions one of which contains the metal salt H(2)PtCl(6) and the other the reducing agent NaBH(4). The size and structure of the microemulsion droplets was studied via small-angle X-ray scattering, while the Pt particles were characterized by high-resolution transmission electron microscopy in combination with energy-dispersive X-ray spectroscopy and selected area electron diffraction. The clear correlation between droplet and particle size was further supported by accompanying Monte Carlo simulations.