Thermodynamics and Kinetics of the Cathode–Electrolyte Interface in All-Solid-State Li–S Batteries

Abstract

Lithium−sulfur batteries (LSBs) are among the most promising energy storage technologies due to the low cost and high abundance of S. However, the issue of polysulfide shuttling with its corresponding capacity fading is a major impediment to its commercialization. Replacing traditional liquid electrolytes with solidstate electrolytes (SEs) is a potential solution. Here, we present a comprehensive study of the thermodynamics and kinetics of the cathode−electrolyte interface in all-solid-state LSBs using density functional theory based calculations and a machine learning interatomic potential. We find that among the major solid electrolyte chemistries (oxides, sulfides, nitrides, and halides), sulfide SEs are generally predicted to be the most stable against the S 8 cathode, while the other SE chemistries are predicted to be highly electrochemically unstable. If the use of other SE chemistries is desired for other reasons, several binary and ternary sulfides (e.g., LiAlS 2 , Sc 2 S 3 , Y 2 S 3 ) are predicted to be excellent buffer layers. Finally, an accurate moment tensor potential to study the S 8 |β-Li 3 PS 4 interface was developed using an active learning approach. Molecular dynamics (MD) simulations of large interface models (>1000s atoms) revealed that the most stable Li 3 PS 4 (100) surface tends to form interfaces with S 8 with 2D channels and lower activation barriers for Li diffusion. These results provide critical new insights into the cathode−electrolyte interface design for next-generation all-solidstate LSBs.

Visualizing the Chemical Incompatibility of Halide and Sulfide‐Based Electrolytes in Solid‐State Batteries

“…At this stage all these hypotheses are yet highly speculative and require more in‐depth analytical studies. Nevertheless, latest theoretical evaluations of the interfacial stability of halide solid electrolytes with charged S 8 and discharged Li 2 S cathodes suggest a chemical instability of halides in contact with sulfide species, at least in Li 2 S. [ 52 ] The chemical reaction of Li 3 YCl 6 and Li 3 YBr 6 with Li 2 S to LiYS 2 and LiCl/LiBr seems to be thermodynamically favorable as negative formation enthalpies are found, likely driven by the metal sulfide bond formation. Interestingly these chlorides seem to be chemical stable against S 8 , suggesting that the instability stems when sulfide anions are in the vicinity.…”

Transition-Metal Sulfides for High-Performance Lithium Sulfide Cathodes in All-Solid-State Lithium–Sulfur Batteries

“…49 Furthermore, density functional theory calculations indicated the high chemical and electrochemical compatibilities of sulfide SE/Li 2 S and sulfide SE/S 8 interfaces. 50 Given these previous reports, sulfide SEs in composite cathodes may undergo chemical reactions with cathode materials after their electrochemical decomposition; that is, chemical reactions between the cathode materials and redox-active decomposition products occur due to the presence of sulfide SEs at the highly electroactive interface area of carbon. The reduction peak (☆) observed at low potentials (1.1−1.2 V vs In/Li) corresponds to the reduction reaction of cathode materials.…”

Research progress of all-solid-state lithium–sulfur batteries with sulfide solid electrolytes: materials, interfaces, challenges, and prospects

“…17 Compared with oxides and polymers, sulfides have unique merits when applied to ASSLBs. M. L. Chandrappa et al 68 have conducted a comprehensive study on the dynamics and thermodynamics of the sulfur-based electrode/solid electrolyte interface in SSLSBs based on density functional theory (DFT) and machine learning, which shows better compatibility with the sulfur element compared with other SEs. What is more, sulfide SEs have room temperature ionic conductivity comparable to or exceeding that of liquid electrolytes, and a certain degree of flexibility, which gives them better machinability.…”