Planar and 3D deposition of Li<inf>4</inf>Ti<inf>5</inf>O<inf>12</inf> thin film electrodes by MOCVD

Li4Ti5O12 is well known to be a safe and efficient anode material for Li-ion batteries. A metal-organic chemical vapor deposition process has been developed for the synthesis of Li4Ti5O12 thin film anodes on planar and 3D substrates. The influences of various deposition parameters, including precursor flow rates and post-annealing temperatures, have been investigated by material and electrochemical analyses. Li4Ti5O12 thin films deposited at the optimized process parameters showed a high crystallinity and high electrochemical activity. A reversible storage capacity of 151 mAh/g was achieved at a current of 0.5 C, corresponding to 86.3% of the theoretical specific capacity of Li4Ti5O12. Up to almost 600 cycles, the electrodes showed no significant capacity loss. Furthermore, the deposited thin film anodes also showed excellent rate performance. Compared to the storage capacity at 0.5 C, 93% of the capacity was maintained at 10 C. Thin films were also deposited on highly structured substrates to investigate the uniformity and electrochemical performance. With the same footprint area, the 3D Li4Ti5O12 film anode showed a 2.5 times higher storage capacity than planar electrode

Carbon-coated core-shell Li<inf>2</inf>S@C nanocomposites as high performance cathode materials for lithium-sulfur batteries

Li2S has made the concept of Li-S batteries much more promising due to the relatively high storage capacity, the possibility of using Li-free anodes and the increase of microstructural stability. However, similar to S, Li2S also suffers from an insulating nature and polysulfide dissolution problem. The results presented here show a facile and cost-effective approach by using a plasma sparking and chemical sulfurization process to synthesize core-shell Li2S@C nanocomposites. The nanocomposites show a significantly reduced particle size and well-developed core-shell architecture, effectively shortening the Li-ion diffusion distance, enhancing the electronic conductivity and suppressing the dissolution losses of polysulfides. As a result, a much improved rate and cycling performance has been achieved. The method presented in this study offers good opportunities for scaling up the production of high performance cathode materials in a simple and low-cost way to be applied in future generation Li-S batteries

Planar and 3D deposition of Li\u3csub\u3e4\u3c/sub\u3eTi\u3csub\u3e5\u3c/sub\u3eO\u3csub\u3e12\u3c/sub\u3e thin film electrodes by MOCVD

\u3cp\u3eLi\u3csub\u3e4\u3c/sub\u3eTi\u3csub\u3e5\u3c/sub\u3eO\u3csub\u3e12\u3c/sub\u3e is well known to be a safe and efficient anode material for Li-ion batteries. A metal-organic chemical vapor deposition process has been developed for the synthesis of Li\u3csub\u3e4\u3c/sub\u3eTi\u3csub\u3e5\u3c/sub\u3eO\u3csub\u3e12\u3c/sub\u3e thin film anodes on planar and 3D substrates. The influences of various deposition parameters, including precursor flow rates and post-annealing temperatures, have been investigated by material and electrochemical analyses. Li\u3csub\u3e4\u3c/sub\u3eTi\u3csub\u3e5\u3c/sub\u3eO\u3csub\u3e12\u3c/sub\u3e thin films deposited at the optimized process parameters showed a high crystallinity and high electrochemical activity. A reversible storage capacity of 151 mAh/g was achieved at a current of 0.5 C, corresponding to 86.3% of the theoretical specific capacity of Li\u3csub\u3e4\u3c/sub\u3eTi\u3csub\u3e5\u3c/sub\u3eO\u3csub\u3e12\u3c/sub\u3e. Up to almost 600 cycles, the electrodes showed no significant capacity loss. Furthermore, the deposited thin film anodes also showed excellent rate performance. Compared to the storage capacity at 0.5 C, 93% of the capacity was maintained at 10 C. Thin films were also deposited on highly structured substrates to investigate the uniformity and electrochemical performance. With the same footprint area, the 3D Li\u3csub\u3e4\u3c/sub\u3eTi\u3csub\u3e5\u3c/sub\u3eO\u3csub\u3e12\u3c/sub\u3e film anode showed a 2.5 times higher storage capacity than planar electrode.\u3c/p\u3

Investigation of the Li-ion conduction behavior in the Li10GeP2S12 solid electrolyte by two-dimensional T1-spin alignment echo correlation NMR.

Li10GeP2S12 (LGPS) is the fastest known Li-ion conductor to date due to the formation of one-dimensional channels with a very high Li mobility. A knowledge-based optimization of such materials for use, for example, as solid electrolyte in all-solid-state batteries requires, however, a more comprehensive understanding of Li ion conduction that considers mobility in all three dimensions, mobility between crystallites and different phases, as well as their distributions within the material. The spin alignment echo (SAE) nuclear magnetic resonance (NMR) technique is suitable to directly probe slow Li ion hops with correlation times down to about 10-5 s, but distinction between hopping time constants and relaxation processes may be ambiguous. This contribution presents the correlation of the 7Li spin lattice relaxation (SLR) time constants (T1) with the SAE decay time constant τc to distinguish between hopping time constants and signal decay limited by relaxation in the τc distribution. A pulse sequence was employed with two independently varied mixing times. The obtained multidimensional time domain data was processed with an algorithm for discrete Laplace inversion that does not use a non-negativity constraint to deliver 2D SLR-SAE correlation maps. Using the full echo transient, it was also possible to estimate the NMR spectrum of the Li ions responsible for each point in the correlation map. The signal components were assigned to different environments in the LGPS structure

Hetero- and homogeneous three-dimensional hierarchical tungsten oxide nanostructures by hot-wire chemical vapor deposition

We present the synthesis of three-dimensional tungsten oxide (WO3 − x) nanostructures, called nanocacti, using hot-wire chemical vapor deposition. The growth of the nanocacti is controlled through a succession of oxidation, reduction and re-oxidation processes. By using only a resistively heated W filament, a flow of ambient air and hydrogen at subatmospheric pressure, and a substrate heated to about 700 °C, branched nanostructures are deposited. We report three varieties of simple synthesis approaches to obtain hierarchical homo- and heterogeneous nanocacti. Furthermore, by using catalyst nanoparticles site-selection for the growth is demonstrated. The atomic, morphological and crystallographic compositions of the nanocacti are determined using a combination of electron microscopy techniques, energy-dispersive X-ray spectroscopy and electron diffraction

Investigation of the Li-ion conduction behavior in the Li\u3csub\u3e10\u3c/sub\u3eGeP\u3csub\u3e2\u3c/sub\u3eS\u3csub\u3e12\u3c/sub\u3e solid electrolyte by two-dimensional T\u3csub\u3e1\u3c/sub\u3e-spin alignment echo correlation NMR

\u3cp\u3eLi\u3csub\u3e10\u3c/sub\u3eGeP\u3csub\u3e2\u3c/sub\u3eS\u3csub\u3e12\u3c/sub\u3e (LGPS) is the fastest known Li-ion conductor to date due to the formation of one-dimensional channels with a very high Li mobility. A knowledge-based optimization of such materials for use, for example, as solid electrolyte in all-solid-state batteries requires, however, a more comprehensive understanding of Li ion conduction that considers mobility in all three dimensions, mobility between crystallites and different phases, as well as their distributions within the material. The spin alignment echo (SAE) nuclear magnetic resonance (NMR) technique is suitable to directly probe slow Li ion hops with correlation times down to about 10\u3csup\u3e−5\u3c/sup\u3e s, but distinction between hopping time constants and relaxation processes may be ambiguous. This contribution presents the correlation of the \u3csup\u3e7\u3c/sup\u3eLi spin lattice relaxation (SLR) time constants (T\u3csub\u3e1\u3c/sub\u3e) with the SAE decay time constant τ\u3csub\u3ec\u3c/sub\u3e to distinguish between hopping time constants and signal decay limited by relaxation in the τ\u3csub\u3ec\u3c/sub\u3e distribution. A pulse sequence was employed with two independently varied mixing times. The obtained multidimensional time domain data was processed with an algorithm for discrete Laplace inversion that does not use a non-negativity constraint to deliver 2D SLR–SAE correlation maps. Using the full echo transient, it was also possible to estimate the NMR spectrum of the Li ions responsible for each point in the correlation map. The signal components were assigned to different environments in the LGPS structure.\u3c/p\u3