Cross-alkali solid-state battery cell with sodium sulfide anode and lithium halide cathode electrolytes

The solid-state battery field is converging on a practical architecture challenge: sulfide electrolytes offer the ionic conductivity and mechanical compliance needed at the anode, while halide electrolytes offer the oxidative stability and compatibility needed at the cathode — but pairing them in a single cell without chemical cross-contamination has become the defining engineering problem. The halide-sulfide trilayer concept, in which a nanometer-scale barrier separates the two electrolyte layers, is rapidly maturing as a genus. What this asset addresses is the next speciation: what happens when the two electrolyte layers are drawn from different alkali systems — specifically a sodium thiophosphate anode-side layer paired with a lithium halide cathode-side layer — rather than from a single lithium-centric material set? That cross-alkali pairing is the specific novel ground this patent family occupies. The rationale is not arbitrary. Sodium thiophosphate materials (principally Na3PS4 and its derivatives) are independently compelling as anode-side electrolytes: they are less expensive than lithium analogues, mechanically softer in ways that can accommodate anode volume change, and synthesizable without the lithium cost premium that is squeezing cell economics. Lithium halides at the cathode side are simultaneously gaining ground as the oxidatively stable partner to lithium-rich oxide cathodes. Pairing these two chemically orthogonal electrolyte systems through a discrete barrier — chosen from a set of lithium-conducting oxides and oxynitrides — creates a cell stack that is compositionally distinct from any prior-art lithium-only barriered trilayer. That compositional distinction is also the freedom-to-operate position: the cross-alkali embodiment is not anticipated by the crowding lithium-only genus, even as that genus advances toward prior-art saturation through 2025-2026. The commercial context matters here. The addressable market for all-solid-state battery components and integrator licensing sits in the $5-10 billion range as automotive and consumer electronics manufacturers accelerate qualification timelines for ASSB cells. A patent family that can credibly claim a distinguishable sub-architecture — one that enables sodium sulfide anode electrolytes, a cost-reducing substitution, while retaining the halide cathode-side advantages — sits at a natural licensing inflection as integrators seek design freedom from the lithium-only trilayer patents that the large cell manufacturers and their suppliers are accumulating.

This is a system-level architecture asset rather than a single-composition materials discovery. The cell stack reads, from cathode to anode: a lithium halide electrolyte layer (nominally 5-50 micrometers thick) serving the cathode side, a mandatory inter-electrolyte barrier layer (5-200 nanometers thick) composed of one or more lithium-conducting oxide or oxynitride materials drawn from a set that includes Li3PO4, LiNbO3, LiTaO3, and LiPON, followed by a sodium thiophosphate sulfide electrolyte layer (30-150 micrometers thick) on the anode side, and a lithium, lithium alloy, or intercalation anode as the final element. The cell therefore deliberately mixes alkali systems — sodium chemistry on the anode side, lithium chemistry on the cathode side — separated by a structurally and chemically distinct barrier layer that must conduct lithium ions (for cell operation) while arresting the halide-sulfide chemical interaction that would otherwise degrade both electrolyte layers at their mutual interface. The barrier layer candidates share a key property: they are known lithium-ion conductors with substantially greater chemical stability than a direct halide-sulfide contact. Li3PO4 in particular is a well-characterized lithium-ion conductor with low electronic conductivity and documented compatibility with sulfide electrolytes in coatings and interfacial engineering contexts. LiNbO3 and LiTaO3 are used in related roles as protective coatings for lithium cathode particles, precisely because of their resistance to oxidative and reductive degradation. LiPON, the amorphous lithium phosphorus oxynitride, is one of the most widely studied solid electrolyte thin-film materials and has been deployed industrially in thin-film batteries for decades. The selection set is therefore grounded in established interfacial materials chemistry, even though the specific cross-alkali barriered geometry is novel. The 5-200 nm thickness window is practically significant: thin enough that the barrier does not contribute meaningfully to total cell ionic resistance (which scales with inverse thickness), but thick enough to arrest diffusive mixing between the sulfide and halide layers over the thermal and cycling history of a practical cell. The sodium-thiophosphate anode-side electrolyte is the distinguishing compositional choice. Na3PS4 and substituted or doped variants (for example, Na3PS4 with halide or oxygen substitution, or glassy phases) form a sub-family of sodium thiophosphate materials that have been shown in the academic literature to reach room-temperature ionic conductivities of roughly 0.1-1 mS/cm, placing them in the same practical range as early lithium thiophosphate electrolytes before optimization. Their mechanical properties — in particular a tendency to sinter under moderate pressure without the brittle cracking that affects oxide electrolytes — make them physically compatible with the kind of stack pressing used in solid-state cell assembly. The economic argument for the sodium variant is straightforward: sodium is orders of magnitude more abundant than lithium and the raw-material cost differential at the electrolyte layer level is potentially meaningful at scale. From a computational perspective, this asset is characterized as a system-level architecture claim rather than a single-crystal composition, and the simulation work reflects that: the primary computational contribution is a barrier-candidate ground-state survey (designated Y-3-pre), which screens the candidate barrier materials for structural stability and lithium-transport properties using ground-state energy calculations. This is a targeted, early-stage computational study appropriate to the asset type. The deeper validation gates — interfacial stability calculations of the barrier candidates against both parent electrolyte layers (halide and sulfide), and demonstration of cross-alkali cell cycling in hardware — remain open. This is an honest characterization of the asset's current maturity: the architecture is claimed and the barrier set is computationally surveyed, but the full interfacial thermodynamic and electrochemical validation against physical cells has not yet been completed.

The total addressable market for all-solid-state battery technology, spanning electrolyte materials, cell stack manufacturing, and component licensing, is broadly estimated at $5-10 billion in annual revenue by the late 2020s, with projections anchored to the automotive qualification timelines of Toyota, Samsung SDI, QuantumScape, Solid Power, and a number of tier-1 Asian cell manufacturers. These figures represent estimates based on analyst consensus and technology roadmap announcements rather than realized revenue; the market is still in pre-commercial to early-commercial qualification for most formats. The sub-segment directly relevant to this asset — halide-sulfide composite cell architectures for pouch or cylindrical solid-state automotive cells — is embedded within that broader number but is not separately published at this time. The customers for a licensing or sale of this asset are solid-state battery integrators: companies that are building or qualifying all-solid-state cells at the pilot or early-production stage and need design freedom around the emerging halide-sulfide trilayer genre. The economic logic for licensing follows naturally from the crowding dynamic: as the lithium-only barriered trilayer space fills with patents from established players (cell manufacturers and their electrolyte suppliers), integrators working toward sodium-thiophosphate anode electrolytes — for cost reasons or supply-chain diversification reasons — will need freedom to operate against a cross-alkali configuration. A patent covering the cross-alkali barriered architecture specifically fills that gap and could support either an exclusivity license to a single integrator willing to commit to sodium-side electrolyte development, or a non-exclusive royalty stream across multiple integrators developing cost-optimized ASSB chemistries. Royalty benchmarks in solid-state battery materials and architecture patents have been reported in the range of 1-3% of cell revenue for foundational architecture claims, which at even modest cell volumes represents a material stream as the market approaches commercial scale.

cross-alkali barriered architecture distinguishes the lithium-only barriered genus

cross-alkali (Na-sulfide anode + Li-halide cathode) separated by discrete barrier

The natural first-call buyers for this asset are solid-state battery integrators that are actively developing halide-sulfide composite cell architectures and have either an existing sodium electrolyte materials program or an economic motivation to reduce lithium electrolyte content at the anode side. Automotive-adjacent ASSB developers (companies building cells for EV qualification) are the highest-value prospective licensees, particularly those that are constrained by lithium-only trilayer IP from established cell manufacturers and need design freedom around a sodium-side alternative. A single exclusivity deal with an integrator willing to fund the open validation gates (interfacial stability calculations and physical cell cycling) would be the highest-value transaction structure. A secondary buyer class is electrolyte materials suppliers — companies producing lithium halide or sodium thiophosphate electrolyte powders or layers who want a position in the architecture-level IP as a complement to their materials-level IP. For such a buyer, this asset functions defensively: owning the system claim covering the cross-alkali architecture protects the supplier's integration path with customers even if individual composition claims are contested. Strategic acquirers in the broader battery IP aggregation space (patent holding companies with solid-state battery portfolios) represent a third class, though the narrow FTO carve-out means the asset's value in an aggregation context depends on the acquirer's ability to combine it with adjacent sodium electrolyte composition claims to build a broader blocking position.

The principal risk is timing. The halide-sulfide genus is crowding rapidly through 2025-2026, and while the cross-alkali sub-space is currently unclaimed by the major lithium-only trilayer filers, independent academic and corporate work on sodium thiophosphate electrolytes is active. A large cell manufacturer or electrolyte supplier with a sodium-side development program could file a covering claim on the cross-alkali barriered architecture before this family reaches grant, which would compress or eliminate the whitespace. The prosecution timeline matters enormously here, and the asset's commercial value is highest if the patent family is actively prosecuted and claims are established before the crowding window closes. There is also the inherent risk of a narrow FTO position: a buyer who wants broad design freedom in the halide-sulfide space, rather than specifically in the cross-alkali sub-architecture, will find this asset insufficient on its own. The de-risking roadmap has two parallel tracks. On the technical side, completing the interfacial stability calculations for the barrier-halide and barrier-sulfide interfaces would transform the asset from a computationally surveyed architecture into a thermodynamically validated cell design, meaningfully increasing confidence in the practical operability of the stack and the defensibility of the enablement disclosure. Simultaneously, obtaining even proof-of-concept cross-alkali cell cycling data — initial charge-discharge curves showing that a sodium thiophosphate anode-side electrolyte can function in a lithium cell context with the barrier in place — would be the single most value-accretive technical milestone available. Either track reduces acquirer risk substantially; completing both would position this asset as a technically substantiated, prosecution-hardened position in a space that is otherwise filling up with untested architecture filings.