Solid-State / Solid-Liquid Electrolyte Li-Ion Battery Innovation & Patent Review

• Company Chapter – Mitsui Kinzoku – Japan

  Version: 2026-09-14, for paid subscribers
• Technology Assessment: Mitsui Kinzoku supplies sulfide electrolyte to cell makers rather than building cells itself, and produces its own lithium sulfide feedstock. The chapter examines how that upstream position shapes process efficiency, why moving from batch consolidation to continuous pressing remains the central scale-up question for a self-supporting electrolyte sheet, and how public statements align with what the patent portfolio reveals about development priorities.
  Product Development Pathway
  (6 R&D Concepts)

  Two-stage reduction route to the lithium sulfide feedstock – a carbon-limited first step finished under a reducing gas, so the raw material every electrolyte grade is fired from is produced in-house at a controlled purity. Self-supporting electrolyte sheet pressed between high-proof-stress metal foils, where the clamping member governs the stiffness the finished sheet reaches and its resistance to lithium penetration. Further concepts address an alternative crystalline phase pursued for higher ionic conductivity, particle size reduction that avoids the surface penalty milling carries, suppression of hazardous gas release to relax the customer's dry-room specification, and a coating holding cathode interface resistance stable in storage.
  Key synergies between R&D concepts: A vertically integrated pathway in which one in-house feedstock sets the ionic conductivity of every downstream grade – powder handling, cathode interface protection and sheet forming advancing together toward a material the customer qualifies rather than develops.
• Document size: ≈4,900 words, 5 images, 1 adjacent Excel file (list of patent families with AI-based summaries)

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