Microstructural analyses of all-solid-state Li–S batteries using LiBH4-based solid electrolyte for prolonged cycle performance

Complex hydride materials have been widely investigated as potential solid electrolytes because they have good compatibility with the lithium metal anodes used in all-solid-state batteries. However, the development of all-solid-state batteries utilizing complex hydrides has been difficult as these cells tend to have short cycle lives. This study investigated the capacity fading mechanism of all-solid-state lithium–sulfur(Li–S) batteries using Li4(BH4)3I solid electrolytes by analyzing the cathode microstructure. Crosssectional scanning electron microscopy observations after 100 discharge–charge cycles revealed crack formation in the Li4(BH4)3I electrolyte and an increased cathode thickness. Raman spectroscopy indicated that decomposition of the Li4(BH4)3I solid electrolyte occurred at a constant rate during the cycling tests.To combat these effects, the cycle life of Li–S batteries was improved by increasing the amount of solid electrolyte in the cathode.

Lithium ion conductivity of complex hydrides incorporating multiple closo–type complex anions

We report the lithium ionic conductivities of closo –type complex hydrides synthesized from various molar ratios of lithium borohydride(LiBH4) and decaborane(B10H14) as starting materials. The prepared closo –type complex hydrides comprised [B12H12]^2-, [B11H11]^2-, and [B10H10]^2- complex anions. In addition, increasing the LiBH4 content in the starting materials increased the amounts of [B11H11]^2- and [B10H10]^2-, leading to an improved ion conductivity of the prepared sample. The present study offers useful insights into strategies for controlling the complex anion composition in emerging solid electrolytes of closo-type complex hydrides at the molecular level, and improving their ionic conductivities.

Room temperature operation of all-solid-state battery using a closo-type complex hydride solid electrolyte and a LiCoO_(2) cathode by interfacial modification

We report on an all-solid-state battery that employs a closo-type complex hydride solid electrolyte and a LiCoO2 cathode.Interfacial modification between the solid electrolyte and cathode with a LiNbO3 buffer layer enables reversible charge-discharge cycling with a cell voltage of 3.9V (vs.Li^+/Li) at room temperature.Electrochemical analyses clarify that the given modification effectively suppresses side reactions at the cathode/solid electrolyte interface.The interfacial resistance is lowered by ca.10 times with a 5 nm thick LiNbO3 buffer layer compared to that without a buffer layer,so that a discharge capacity of 109 mAh g^-1 is achieved.These results suggest that interfacial modification can be a viable approach to the development of high-voltage all-solid-state batteries using closo-type complex hydride solid electrolytes and oxide cathodes.

Influence of morphology of hollow silica-alumina composite spheres on their activity for hydrolytic dehydrogenation of ammonia borane

Hollow silica-alumina composite spheres were prepared by a polystyrene(PS)template method using various amounts of PS suspension.Homogeneous hollow spheres prepared using 40 g were found to be with a diameter of about 300 nm in scanning electron microscopy,and transmission electron microscopy demonstrated their hollow sphere morphology.From the nitrogen adsorption isotherm results,the homogeneous hollow spheres prepared using 40 g of the PS suspension were found to be an ordered pore structure.The activities of the hollow spheres prepared using various amounts of the PS suspension for hydrolytic dehydrogenation of ammonia borane were compared.The results showed that 10,7,and 6 mL of hydrogen were evolved from the aqueous ammonia borane solution in about 40 min in the presence of the hollow spheres prepared using 40,80,and 120 g of PS suspension,respectively.The homogeneous hollow spheres with an ordered pore structure showed the highest activity among all the hollow spheres.The amount of acid sites and the coordination number of aluminum active species were characterized using neutralization titration and solid-state ^(27)Al magic angle spinning nuclear magnetic resonance spectroscopy.The homogeneous hollow spheres with an ordered pore structure had high amount of acid sites and 4-coordinated aluminum species.The relative proportion of 4-coordinated aluminum species was related to the dispersion of aluminum species.These results indicate that the homogeneous hollow spheres with an ordered pore structure showed the high activity because of high amount of acid sites induced by the highly dispersed aluminum species.