Sodium-lithium hexafluoroaluminate (Na2LiAlF6) solid electrolyte for lithium batteries

Na2LiAlF6 — sodium-lithium hexafluoroaluminate in the double-perovskite elpasolite structure — occupies a targeted backup position within the PFAS-free dielectric and process fluids portfolio, specifically as a fluoroaluminate solid electrolyte candidate for lithium-metal batteries. The strategic importance of this filing is best understood in context: the primary fluoride electrolyte family spans several compositions, and Na2LiAlF6 functions as a wedge claim that protects a distinct, precisely specified stoichiometric corner of elpasolite space that a competitor might otherwise occupy as a design-around. By locking in the 2:1 Na:Li molar ratio and tying it explicitly to a lithium-metal or lithium-alloy negative electrode in a lithium-battery device, the asset creates a barrier at a structurally plausible but previously unclaimed intersection of composition and application. The timing logic is straightforward: the solid-state battery industry is actively hunting fluoride-based electrolytes to escape the moisture sensitivity of sulfide systems and the limited electrochemical windows of oxides. Elpasolite-family fluorides are a known academic target — wide bandgap, halide framework, mixed-cation tunability — and any serious SSE patent landscape will eventually be searched against them. Filing the 2:1 Na:Li elpasolite now, with explicit negative limitations that carve it away from sodium-ion batteries and aluminum-electrolysis molten salts (the dominant prior-art fields for cryolite-family fluoroaluminates), secures a defensible whitespace that has material strategic value to any acquirer building a fluoride-electrolyte position. As a backup arm of a larger family, this asset should not be evaluated as a standalone commercial engine. Its value compounds with the rest of the C5 fluoride family: it broadens the portfolio's chokehold on fluoroaluminate electrolyte space, makes the family harder to design around, and provides a fallback claim set should narrower primary claims face invalidity challenges. For a buyer acquiring the PFAS-free dielectric and process fluids portfolio, this is the kind of supporting position that turns a good IP package into a comprehensive one.

Each candidate is validated by multiple independent machine-learning interatomic potentials. A material advances only when the engines agree on phonon (dynamic) stability — disagreement is surfaced, not hidden.

Na2LiAlF6 belongs to the elpasolite structural family — a double-perovskite fluoride with the general formula A2BB'X6, where the A-site is occupied by sodium, the B-site by lithium, and the B'-site by aluminum, with fluorine as the anion. The 2:1 Na:Li stoichiometry is not arbitrary: it is the precise ratio required to satisfy the elpasolite charge balance with aluminum in the +3 oxidation state, yielding a framework where Li occupies an octahedral void and Na fills a larger twelve-coordinated pocket. This crystallographic specificity is central to the claim strategy — the 2:1 ratio is a hard compositional anchor, not a range. The reported bandgap of approximately 7.7 eV, drawn from a single JARVIS database entry (mp-6604), is the most physically significant computed property available at this stage. A gap of that magnitude places Na2LiAlF6 firmly in the class of wide-gap insulators — favorable for electrolyte applications where electronic leakage current must be suppressed and electrochemical stability windows must be broad enough to survive contact with lithium metal at low potential (~0 V vs. Li/Li+). To put this in perspective, the best-in-class sulfide electrolytes (LGPS, argyrodites) carry bandgaps in the 3–5 eV range and are prone to reductive decomposition at lithium-metal anodes; fluoride-framework electrolytes with 7+ eV gaps offer a qualitatively different stability regime. This is the core physical argument for why fluoroaluminate elpasolites deserve exploration as SSE candidates. On the computational validation side, three independent machine-learning interatomic potentials — MACE, CHGNet, and ORB — were each used to independently relax the Na2LiAlF6 crystal structure, and all three converge on a stable configuration (the 3-of-3 MLIP relaxation validated by an internal simulation, Materials Project entry mp-6604). Consensus across three independent neural-network potentials trained on distinct DFT datasets is a meaningful indicator: it substantially reduces the probability that the apparent stability is an artifact of one model's training distribution. Notably, the stability assessment here is structural (energy minimization), not yet full dynamic (phonon) stability — the finite-displacement phonon calculation that would confirm the absence of imaginary phonon modes remains an open validation gate. This is an honest limitation of the current proof state, and it is the next required computational step before the composition can be declared dynamically stable. The practical material performance in a lithium-battery context — ionic conductivity, activation energy for Li-ion migration, and interface compatibility with lithium metal — has not yet been computationally quantified for this specific composition. Electrochemical impedance spectroscopy (EIS) bench measurement is the primary experimental gate that would establish whether bulk or grain-boundary conductivity is adequate for a practical solid electrolyte. These open gates are characteristic of a backup filing at this stage of the portfolio's development pipeline: the composition is computationally consistent with stability and favorable electronic structure, and it claims a protected position while the deeper characterization work proceeds.

The addressable commercial opportunity for this asset is specifically the fluoride solid electrolyte segment of the broader solid-state lithium battery market. The total addressable market is estimated at $0.2–0.5 billion, reflecting a realistic slice of the solid-state battery electrolyte materials market: not the entire SSB market (which reaches tens of billions of dollars at the cell and pack level), but the upstream electrolyte material licensing and supply segment where composition patents carry direct value. This is an estimate, and it is deliberately conservative — it represents the near-term realistic licensing value for a narrow backup position rather than any projection of overall solid-state battery market growth. The direct customers for this asset are solid-state battery developers — companies that are actively working to commercialize lithium-metal batteries using ceramic or halide solid electrolytes. These include both established cell manufacturers building SSB programs (Toyota, Samsung SDI, Solid Power, QuantumScape, Panasonic, and their supply chain partners) and fluoride-electrolyte-focused startups exploring alternatives to sulfide systems. Any of these players who advance into fluoroaluminate elpasolite territory — either through independent discovery or literature-driven R&D — would face this claim set if they attempt to commercialize the 2:1 Na:Li composition in a lithium-battery device. That blocking or licensing position is where the asset's commercial value is realized. Royalty logic for an asset of this type follows a standard materials licensing framework: the claim covers a composition used in a defined device context, so a royalty would attach either to electrolyte material sales or to cell-level revenue attributable to the protected composition. As a backup arm, this asset's royalty potential is contingent on the primary C5 family claims either being challenged or being designed around — at which point the backup's wedge claim becomes the operative protection. Its value is therefore partially optionality value: the cost of not filing it would be a gap in the portfolio that a sophisticated competitor could exploit.

narrow Li-battery elpasolite backup wedge

2:1 Na:Li + Li-metal anode + Li-battery context; Na-ion battery / Al-electrolysis / broad cryolite scope excluded

The most natural acquirers for this asset — or for the PFAS-free dielectric and process fluids portfolio as a whole — are companies with active fluoride electrolyte programs for solid-state lithium batteries. Cell manufacturers and solid electrolyte developers who are working on halide or fluoride ceramic electrolytes would find this asset directly relevant as either a blocking position against competitors or a defensive addition to their own IP stack. This includes Japanese cell manufacturers (Toyota has an extensive SSB program), Korean conglomerates (Samsung SDI, LG Energy Solution), and U.S.-based SSB startups. Specialty chemical companies supplying electrolyte materials — particularly those with fluorine chemistry capabilities — are a second natural buyer category, as they may seek to license or acquire composition patents before committing to scale-up. Strategic licensees rather than outright acquirers are also a plausible commercialization path. A solid-state battery developer who independently arrives at Na2LiAlF6 as a candidate — through their own screening or academic literature — would need to negotiate around this claim if they intend to commercialize the composition in a lithium-battery device. In that scenario, the asset functions as a licensing lever within a broader portfolio deal. The backup nature of the asset means it is best monetized as part of a portfolio transaction rather than as a standalone sale, since its value compounds with the primary C5 family claims and the broader PFAS-free dielectric portfolio that Lattice Graph has assembled.

The primary risk for this asset is the open dynamic stability gate. If the finite-displacement phonon calculation reveals imaginary modes — indicating that the claimed structure is dynamically unstable at the equilibrium geometry — the physical basis for the electrolyte application claim would be weakened, and any buyer would need to account for the possibility that the composition requires a different polymorph, a doped variant, or elevated temperature to be practically useful. This risk is not unique to Na2LiAlF6; it is a standard validation gap for any material at this stage of the pipeline, and it is why the phonon calculation is the explicitly identified next step. The single-source bandgap data (one DFT database entry rather than cross-validated calculations) is a secondary data-quality risk — the 7.7 eV figure is physically plausible for a fluoroaluminate but has not been independently confirmed. The de-risking roadmap is clear: commission the finite-displacement phonon calculation (a routine DFT task, typically days of compute time), followed by EIS measurement on a pressed or sintered pellet to establish ionic conductivity. If both gates pass, the asset advances to a materially stronger proof state and the commercial case for the backup position solidifies. The narrow claim scope — which is both the asset's FTO strength and its commercial limitation — means that even a strong proof state will not yield a broad market position; the value remains as a defensive wedge and design-around barrier within the C5 family rather than as a standalone commercial product platform.