Stable battery operation of a bulk-type all-solid-state lithium-sulfur battery was demonstrated by using a LiBH4 electrolyte. The electrochemical activity of insulating elemental sulfur as the positive electrode was enhanced by the mutual dispersion of elemental sulfur and carbon in the composite powders. Subsequently, a tight interface between the sulfur-carbon composite and the LiBH4 powders was manifested only by cold-pressing owing to the highly deformable nature of the LiBH4 electrolyte. The high reducing ability of LiBH4 allows using the use of a Li negative electrode that enhances the energy density. The results demonstrate the interface modification of insulating sulfur and the architecture of an all-solid-state Li-S battery configuration with high energy density.

No abstract

We have operated a 4V-class bulk-type, all-solid-state LiCoO 2 /Li battery at room temperature. The battery consisted of a Li 4 (BH 4 ) 3 I complex hydride electrolyte as the electrolyte layer, and a 80Li 2 S 20P 2 S 5 sul de glass as an electrolyte in the positive electrode layer. The assembled battery exhibited a 92 mAh g −1 initial discharge capacity at 298 K and 0.1 C. The discharge capacity for the 20 th cycle remained as high as 83 mAh g −1 , corresponding to a capacity retention ratio of nearly 90%.

Silicon sulfide (SiS2) was synthesized from Si, SiC, Si3N4, and a eutectic Al-Si liquid. An Ar-CS2 gas mixture, after bubbling through liquid CS2, was passed over pulverized Si, SiC, Si3N4, or a eutectic Al-Si alloy liquid. White, needle-shaped SiS2 was precipitated as a single phase on the colder downstream surface when Si powder in a SiO2 liner was heated over 1273 K. This deposition mechanism involves a reaction between Si and CS2 to form SiS2, with the vaporization of SiS(g) and deposition as SiS2(s) from SiS(g) and S2(g). Quartz was unaffected by the reaction gases. Notably, Si, SiC, Si3N4, and the eutectic Al-Si liquid were found to be suitable sources for SiS2 synthesis, although this was suppressed owing to Al2S3 formation on the latter.

We have operated a 4 V class bulk type, all solid state LiCoO 2 /Li battery at room temperature. The composition consisted of a Li 4 (BH 4 ) 3 I complex hydride electrolyte for the electrolyte layer, and a 80Li 2 S 20P 2 S 5 sulfide glass for an electrolyte in the positive electrode layer. The battery assembled exhibited a 92 mAh･g -1 initial discharge capacity at 298 K and 0.1 C. The discharge capacity for the 20 th cycle remained as high as 83 mAh･g -1 , corresponding to a capacity retention ratio of nearly 90.