Sulfide Solid Electrolytes for Lithium Battery Applications

Abstract

The use of solid electrolytes is a promising direction to improve the energy density of lithium‐ion batteries. However, the low ionic conductivity of many solid electrolytes currently hinders the performance of solid‐state batteries. Sulfide solid electrolytes can be processed in a number of forms (glass, glass‐ceramic, and crystalline) and have a wide range of available chemistries. Crystalline sulfide materials demonstrate ionic conductivity on par with those of liquid electrolytes through the utilization of near ideal conduction pathways. Low‐temperature processing is also possible for these materials due to their favorable mechanical properties. The main drawback of sulfide solid electrolytes remains their electrochemical stability, but this can be addressed through compositional tuning or the use of artificial solid electrolyte interphase (SEI). Implementation of sulfide solid electrolytes, with proper treatment for stability, can lead to substantial improvements in solid‐state battery performance leading to significant advancement in electric vehicle technology.

Boosting Solid‐State Diffusivity and Conductivity in Lithium Superionic Argyrodites by Halide Substitution

“…Developing high performance cells is—amongst many other factors—dependent on the implementation of SSEs that possess high ionic conductivities at room temperature, the ability to form good interfaces and which present scalable synthetic routes to their realisation . Although a number of sulfide, oxide, and phosphate fast ion‐conducting solids are now known, many exhibit drawbacks such as poor mechanical properties, and difficulty in their processing. For example, garnets based on Li 7 La 3 Zr 2 O 12 are popular owing to their chemical stability and high conductivity, but they have the detriment of very low ductility and high‐cost precursors.…”

Boosting Solid‐State Diffusivity and Conductivity in Lithium Superionic Argyrodites by Halide Substitution

“…All-solid-state Li-ion batteries eliminate the flammable liquid organic electrolyte in Li-ion batteries by implementing as olid-state electrolyte (SSE), hence potentially increasing safety and also volumetric energy density by allowing more efficient packaging.D eveloping high performance cells isamongst many other factors-dependent on the implementation of SSEs that possess high ionic conductivities at room temperature,t he ability to form good interfaces and which present scalable synthetic routes to their realisation. [1] Although an umber of sulfide,o xide,a nd phosphate fast ion-conducting solids are now known, [2][3][4] many exhibit drawbacks such as poor mechanical properties,a nd difficulty in their processing. Forexample,garnets based on Li 7 La 3 Zr 2 O 12 are popular owing to their chemical stability and high conductivity, [5,6] but they have the detriment of very low ductility and high-cost precursors.Sulfide-based materials,on the other hand, exhibit the highest ductility of all the above candidates,w hich is important to optimise solid-solid interfaces.…”

A Lithium Oxythioborosilicate Solid Electrolyte Glass with Superionic Conductivity

“…Nonannealed glassy Li 2 S‐P 2 S 5 and Li 2 S‐P 2 S 5 ‐LiI exhibit conductivities of 2.8 × 10 −4 and 5.6 × 10 −4 S cm −1 , respectively, while 10 −3 S cm −1 is generally considered a benchmark for practical thick‐electrode cells . While sulfide glasses exhibit favorable mechanical properties and enable easy low‐temperature processability, they suffer from moisture stability . Oxysulfide glasses have been explored as a middle‐ground to provide an acceptable compromise, but to date, only very limited amounts of oxygen have been incorporated in the glasses—for example, as lithium ortho‐oxosalts (e.g., 4–5 mole % Li 4 SiO 4 , Li 3 PO 4 )—without incurring a penalty in conductivity.…”

“…Oxysulfide glasses have been explored as a middle‐ground to provide an acceptable compromise, but to date, only very limited amounts of oxygen have been incorporated in the glasses—for example, as lithium ortho‐oxosalts (e.g., 4–5 mole % Li 4 SiO 4 , Li 3 PO 4 )—without incurring a penalty in conductivity. Typically, amorphous glasses contain Li 2 S in addition to a network glass former and modifier such as P 2 S 5 , SiS 2 , or GeS 2 , and lithium halide salts (e.g., LiX–X = Cl, Br, I) to increase the lithium concentration. B 2 S 3 is also a glass former that was explored 20–30 years ago, but has since received little attention.…”