Glass Electrolytes with High Ion Conductivity and High Chemical Stability in the System LiI-Li2O-Li2S-P2S5

Abstract

The Li 2 O-Li 2 S-P 2 S 5 glasses, which were prepared by a reaction of the Li 2 S-P 2 S 5 glass and Li 2 O, hardly generated H 2 S gas in air. These glasses showed relatively high ion conductivities about 10 −4 S cm −1 at room temperature. However, these conductivities were lower than those of original sulfide glasses. In this study, an addition of LiI to the Li 2 OLi 2 S-P 2 S 5 glasses was examined in order to improve ion conductivities. The 30LiI·70(0.07Li 2 O·0.68Li 2 S·0.25P 2 S 5 ) glass showed high ion conductivity of 1.3 × 10 −3 S cm −1 at room temperature, and hardly generated H 2 S gas in air. On the other hand, the 30LiI·70(0.07Li 2 O·0.68Li 2 S·0.25P 2 S 5 ) glass was electrochemically stable in the potential range of 0-10 V. Moreover, the all-solid-state C/LiCoO 2 cell using the 30LiI·70(0.07Li 2 O·0.68Li 2 S·0.25P 2 S 5 ) glass as solid electrolytes worked as lithium secondary batteries at room temperature, and exhibited a good cycle performance. Therefore, the 30LiI·70(0.07Li 2 O·0.68Li 2 S·0.25P 2 S 5 ) glass was a suitable electrolyte for all-solidstate cells because the glass had high conductivity, wide electrochemical window and high chemical stability to moisture.

Rock-salt-type lithium metal sulphides as novel positive-electrode materials

“…Li 2 TiS 3 , the glass electrolyte 70(0.75Li 2 S·0.25P 2 S 5 )·30LiI, and acetylene black (AB) were mixed in a weight ratio of 60:30:10 in an agate mortar, and the mixture was used to prepare the positive-electrode material. The glass electrolyte Li 2 S-P 2 S 5 -LiI, which has an ionic conductivity of more than 10 −3  S cm −1 1819, was used as the solid electrolyte. A lithium-indium alloy was used to make the counter electrode.…”

Issues and Challenges for Bulk‐Type All‐Solid‐State Rechargeable Lithium Batteries using Sulfide Solid Electrolytes

“…A reduced H 2 S generation from sulfide SEs exposed to air was achieved using materials with a new composition. For instance, addition of Li 2 O or LiI into Li 2 S ⋅ P 2 S 5 (to give 7Li 2 O ⋅ 68Li 2 S ⋅ 25P 2 S 5 and 30LiI ⋅ 70(0.07Li 2 O ⋅ 0.68Li 2 S ⋅0.25P 2 S 5 )) significantly decreased H 2 S gas generation 32. Addition of FeS and basic metal oxides, such as CaO, to Li 2 S ⋅ P 2 S 5 also suppressed the generation of H 2 S gas 33.…”

“…As for the conventional LIBs using LEs, the layered or spinel Li x MO 2 (M=Co, Ni, Mn) cathode materials are considered as viable candidates for ASLBs because of their highly reversible intercalation‐deintercalation reaction with low dimensional change and high operating potential. To date, many Li x MO 2 materials, including LiCoO 2 ,3a,5a,9,14d,23b,c,32,36,41,42 Li[Ni,Mn,Co]O 2 ,42ae,43 and LiMn 2 O 4 ,42aa have been tested in ASLBs using sulfide SEs. However, the bare Li x MO 2 showed much lower capacity than the theoretical one, a large amount of irreversible reaction during charging, and a high overpotential, shown in Figure 6 42h.…”

“…In the majority of publications regarding the composite electrodes of Li x MO 2 , such as LiCoO 2 , a 30–65 wt % of SEs is included to ensure the creation of facile ionic conduction pathways 3a,5a,9,14d,23b,c,32,36,41–43. Obviously, the very high content of SEs may severely reduce the energy density of ASLBs.…”

Oxide Electrolytes for Lithium Batteries

“…RT conductivities of 10 −3 –10 −2 S/cm has been reported in several sulfide systems, e.g., thio‐LIthium SuperIonic CONductor (thio‐LISICON), Li 2 S‐P 2 S 5 glass‐ceramics, and Li 10±1 MP 2 S 12 (M = Ge, Sn, Si) . The applications of sulfide electrolytes may be largely accelerated once the main problem associated with hygroscopicity is properly tackled . Since we are not going to talk about polymers and sulfides in details in this review, readers who are interested can reach to earlier review articles …”