Sulfide solid electrolytes represent a critical advancement in solid-state battery technology due to their high ionic conductivity and favorable mechanical properties. The patent landscape in this field reveals significant innovation in material compositions, synthesis techniques, and application-specific formulations. This analysis examines key patents that have shaped the development of sulfide-based electrolytes, focusing on material-level intellectual property.

The earliest foundational patents in sulfide electrolytes focused on binary and ternary systems. One notable patent disclosed a lithium thiophosphate composition with ionic conductivity exceeding 1×10⁻³ S/cm at room temperature. The claims specified a molar ratio of Li₂S to P₂S₅ between 70:30 and 80:20, with the optimal composition demonstrating maximum conductivity at 75:25. This work established the basis for subsequent modifications through doping and substitution.

Several patents have addressed the challenge of electrochemical stability by introducing halogen substitutions. A significant innovation involved the partial replacement of sulfur with iodine in the Li₂S-P₂S₅ system, resulting in improved oxidative stability up to 3.5 V versus Li/Li⁺. The patent claims specified that replacing 5-10 mol% of sulfur with iodine maintained high ionic conductivity while enhancing stability. Another approach combined bromine and chlorine substitutions to create a gradient halogen distribution within the electrolyte particles.

Germanium-doped systems have been extensively patented as an alternative to phosphorus-based electrolytes. One patent detailed a Li₄GeS₄-Li₃PS₄ composite with Ge:S ratios between 1:4 and 1:5, demonstrating both high conductivity and improved moisture resistance. The synthesis method involved a two-step mechanochemical process followed by annealing at 250-300°C. The patent specifically claimed the formation of a glass-ceramic phase with nanocrystalline domains embedded in an amorphous matrix.

The patent literature reveals multiple approaches to synthesis methods. Conventional solid-state reaction patents typically claim specific temperature profiles and mixing procedures. One patent described a room-temperature mechanochemical synthesis using high-energy ball milling for 10-20 hours under argon atmosphere, with particle size control achieved through milling speed adjustments between 300-500 rpm. Another approach patented a solution-based synthesis using organic solvents to create precursor mixtures, followed by solvent removal and thermal treatment.

Several patents have focused on improving the mechanical properties of sulfide electrolytes. One innovation disclosed a composite electrolyte containing 5-15 wt% polymer binder to enhance flexibility while maintaining ionic conductivity above 1×10⁻⁴ S/cm. The patent specified the use of specific polyether-based polymers with ethylene oxide content exceeding 70%. Another approach patented the incorporation of nano-sized ceramic fillers, with claims covering particle sizes between 10-50 nm and loading levels of 1-5 vol%.

Moisture stability has been a major focus area in recent patents. One significant development involved the surface passivation of sulfide particles through controlled oxidation. The patent described forming a 2-5 nm thick lithium oxysulfide layer that reduced moisture sensitivity while maintaining bulk conductivity. Another approach patented the use of moisture scavenging additives, specifically lithium nitride compounds dispersed at 0.1-1 wt% concentration within the electrolyte matrix.

Recent patents have explored novel compositions beyond traditional systems. One filing disclosed a lithium rare earth sulfide electrolyte with general formula Li₃MX₆, where M represents a rare earth element and X is sulfur or selenium. The patent demonstrated ionic conductivity values above 5×10⁻³ S/cm for certain compositions. Another innovation patented a dual-anion system combining sulfide with borohydride groups, claiming improved reduction stability compared to pure sulfide electrolytes.

Several patents have addressed the interface stability between sulfide electrolytes and electrode materials. One approach patented a gradient composition electrolyte with varying lithium content across its thickness, designed to match the chemical potential of both anode and cathode materials. Another patent disclosed a surface-treated electrolyte where particles were coated with a thin lithium-conducting polymer layer to reduce interfacial resistance.

The patent landscape shows increasing attention to scalable production methods. One recent patent described a continuous synthesis process using twin-screw extrusion, claiming production rates exceeding 1 kg/hr while maintaining consistent material properties. The process parameters included temperature zones between 100-200°C and screw rotation speeds of 50-100 rpm. Another patent focused on particle size control through classified milling, with claims covering the production of particles with D50 between 1-5 micrometers.

Safety-related innovations have also been prominent in sulfide electrolyte patents. One approach patented the incorporation of thermal shutdown additives that would form insulating layers above 150°C. The patent specified the use of low-melting-point lithium compounds that would decompose endothermically during thermal runaway. Another safety-focused patent disclosed an electrolyte composition containing flame-retardant sulfur-phosphorus compounds that would release flame-quenching gases when heated.

The evolution of sulfide electrolyte patents shows a clear trend toward multicomponent systems. Later patents frequently claim compositions with three or more major components, often including doping elements at precise concentrations. One example patented a quaternary system containing lithium, phosphorus, silicon, and germanium sulfides with carefully controlled stoichiometry to optimize both ionic conduction and mechanical properties.

Processing patents have increasingly focused on reducing energy consumption during production. One innovation disclosed a low-temperature synthesis route using lithium hydride as a starting material, claiming energy savings of 30-40% compared to conventional methods. The patent specified reaction temperatures below 200°C and the use of catalytic additives to promote complete conversion. Another energy-efficient approach patented a microwave-assisted synthesis method that reduced processing times from hours to minutes.

Recent filings indicate growing interest in sulfide electrolytes for specific applications. One patent focused on high-pressure applications, claiming a composition with exceptional densification behavior suitable for stack pressures above 10 MPa. Another application-specific patent disclosed an electrolyte formulation optimized for operation below -20°C, demonstrating maintained conductivity at low temperatures through careful control of amorphous phase content.

The analysis of sulfide solid electrolyte patents reveals several key trends in intellectual property development. Early patents focused on establishing basic compositions with high ionic conductivity, while later innovations addressed secondary challenges such as stability, processability, and interfacial compatibility. The field has evolved from simple binary systems to complex multicomponent formulations with precisely controlled microstructures. Recent patents demonstrate increasing sophistication in addressing multiple performance parameters simultaneously through compositional engineering and advanced processing methods. The continued development of sulfide electrolyte technology through these patented innovations suggests ongoing progress toward practical solid-state battery applications.