All-solid-state batteries with inorganic solid electrolytes are recognized as an ultimate goal of rechargeable batteries because of their high safety, versatile geometry and good cycle life. Compared to thin-film batteries, increasing the reversible capacity of bulk-type all-solid-state batteries using electrode active material particles is difficult because contact areas at solid–solid interfaces between the electrode and electrolyte particles are limited. Sulfide solid electrolytes have several advantages of high conductivity, wide electrochemical window, and appropriate mechanical properties such as formability, processability, and elastic modulus. Sulfide electrolyte with Li7P3S11 crystal has the highest Li+ ion conductivity of 1.7 × 10-2 S cm-1 at 25 °C. It is far beyond the Li+ ion conductivity of conventional organic liquid electrolytes. The Na+ ion conductivity of 7.4 × 10-4 S cm-1 is achieved for Na3.06P0.94Si0.06S4 with cubic structure. Moreover, formation of favorable solid–solid interfaces between electrode and electrolyte is important for realizing solid-state batteries. Sulfide electrolytes have better formability than oxide electrolytes. Consequently, a dense electrolyte separator and closely attached interfaces with active material particles are achieved via “room-temperature sintering” of sulfides merely by cold pressing without heat treatment. Elastic moduli for sulfide electrolytes are smaller than that of oxide electrolytes, and Na2S-P2S5 glass electrolytes have smaller Young’s modulus than Li2S-P2S5 electrolytes. Cross-sectional SEM observations for a positive electrode layer reveal that sulfide electrolyte coating on active material particles increases interface areas even with a minimum volume of electrolyte, indicating that the energy density of bulk-type solid-state batteries is enhanced. Both surface coating of electrode particles and preparation of nanocomposite are effective for increasing the reversible capacity of the batteries. Our approaches to form solid–solid interfaces are demonstrated.

/pdf/development-of-sulfide-solid-electrolytes-and-interface-2cjir8j3g8.pdf

Development of Sulfide Solid Electrolytes and Interface Formation Processes for Bulk-Type All-Solid-State Li and Na Batteries

Biocorrosion behavior of biodegradable nanocomposite fibers coated layer-by-layer on AM50 magnesium implant.

The carbonation behavior and decarbonation annealing of a protective (Mg,Ca)O layer for flat panel plasma discharge devices were investigated. Compared with a conventional MgO protective layer, the (Mg,Ca)O protective layer showed both high and low discharge voltages. Quantitative X-ray photoelectron spectroscopy analyses indicated that the high discharge voltages were caused by Ca carbonation. The progression of Ca carbonation was enhanced by exposure to air containing H2O but not by exposure to dry air. In addition, once (Mg,Ca)O is carbonated, it is impossible to decarbonate Ca by annealing in air at the temperature applied during the production process. We propose the use of annealing in vacuum as an effective method to promote the decarbonation of Ca and maintain a low discharge voltage for plasma discharge devices with (Mg,Ca)O protective layers.

/pdf/annealing-process-for-recovery-of-carbonated-mg-ca-o-45hwxkudpu.pdf

Annealing process for recovery of carbonated (Mg,Ca)O protective layer for plasma discharge device

We have been applying a low discharge voltage (Ca, Mg)O protective layer to plasma display panels to reduce their power consumption However, (Ca, Mg)O is highly reactive with CO2, and the resulting carbonate formation during high-temperature panel sealing in air impairs the low discharge voltage characteristic We investigated the mechanism of the carbonation reaction that occurs on a (Ca, Mg)O surface during annealing in air at 450°C and found that the CO2 diffuses through the formed CaCO3 layer and that a (Ca, Mg)O + CO2  CaCO3 + MgO reaction then occurs This carbonation reaction evidently stops when the growing MgO finally forms a layer at all boundaries between the CaCO3 and (Ca, Mg)O regions

Carbonation reaction of (Ca, Mg)O protective layer on plasma display panel

The lifespan of plasma discharge devices is strongly influenced by the deterioration characteristics of MgO protective layer deposited on the dielectric covering the electrode. In order to attain both lower driving voltage and higher luminous efficiency in these devices, different complex metal oxides protective layers have been extensively studied as alternatives to MgO. However, the interaction between energetic ions and fast neutral atoms with the protective layer can produce serious damages to it and their nearby components. In this paper, we study the ion beam bombardment for several protective layers by low-energy noble gas with various ion incidence angles by using the Monte Carlo simulation. On the basis of the binary collision approximation using SRIM-2013, different parameters are discussed for instance backscattering yield, retained dose, sputtering yield, number of vacancies, and ion range of MgO, (Mg,Ca)O, (Mg,Sr)O, (Mg,Ba)O and (Mg,Ca,Sr)O. From our results, the retained dose, sputtering yield and number of vacancies of complex metal oxide protective layers are lower than that of MgO. Moreover, the backscattering yield increases by increasing the incident angles and it is highest for complex metal oxide protective layers.

Monte Carlo simulations of MgO and complex oxide protective thin layers bombarded with noble-gas ion in plasma discharge devices

The thickness of the CaCO3 layer formed on the surface of the CaMgO protective layer during a high-temperature process in air was reduced by optimizing the concentration of MgO in the CaMgO protective layer. The discharge voltage of the panel with Ca0.3Mg0.7O protective layer stabilized at low values (Vf=163V, Vs min=112V) within 40hours of aging. This duration was remarkably short for a high-γ protective layer under the air annealing process. These voltages were considerably lower those of MgO (Vf=241V, Vs min=142V).

Improvement of Chemical Stability of a CaMgO Protective Layer

We have been applying a low discharge voltage (Ca, Mg)O protective layer to plasma display panels (PDPs) to reduce their power consumption. However, (Ca, Mg)O is highly reactive with CO2, and the resulting carbonate formation during high-temperature panel sealing in air impairs the low discharge voltage characteristic. We investigated the mechanism of the carbonation reaction that occurs on a (Ca, Mg)O surface during annealing in air at 450°C and found that the CO2 diffuses through the formed CaCO3 layer and that a (Ca, Mg)O + CO2 r CaCO3 + MgO reaction then occurs. This carbonation reaction evidently stops when the growing MgO finally forms a layer at all boundaries between the CaCO3 and (Ca, Mg)O regions.

Daisuke Kato

Papers

Carbonation reaction of (Ca, Mg)O protective layer on plasma display panel

Improvement of Chemical Stability of a CaMgO Protective Layer

13.1: Invited Paper: Carbonation Reaction of (Ca, Mg)O Protective Layer on PDP