Lithium and sodium aluminum fluoride wide-window solid electrolytes for high-voltage batteries

The fluoride-electrolyte family anchored by Li3AlF6 and its alkali-metal analogs addresses one of the most persistent problems in solid-state battery commercialization: sulfide-based electrolytes decompose at high voltage and react violently with atmospheric moisture, while halide electrolytes are either expensive or oxidatively limited. Fluoride frameworks, by contrast, inherit exceptional chemical stability from the high electronegativity and small ionic radius of fluorine, yielding computed electrochemical stability windows that extend from near 0 V to approximately 5.5 V versus lithium — wide enough to pair with next-generation high-voltage cathodes (NMC811, LNMO, Li-rich layered oxides) without the oxidative decomposition that plagues state-of-the-art sulfide cells. The strategic importance of this filing lies in its timing relative to the solid-state battery industry's forced substitution problem. Thiophosphate electrolytes — the dominant sulfide class in pilot production — face a ceiling: they react with oxide cathodes at the interface, require dry-room manufacturing far beyond what most battery factories can sustain, and their electrochemical windows are genuinely narrower than what emerging 5 V cathode chemistries demand. Halide electrolytes (Li3InCl6, Li3YCl6) have attracted significant investment but bring their own cost and supply-chain constraints. A fluoride framework that is non-sulfide, non-halide, and demonstrably stable across 0-5.5 V creates a distinct third lane — one with defensible intellectual property in a space where the patent landscape is still relatively uncrowded. The portfolio to which this asset belongs — integrated packaging, storage, and PFAS-treatment systems — spans multiple materials classes and application domains. Within that portfolio, the alkali aluminum-fluoride electrolyte family is a lead asset, carrying the broadest compositional claims and the primary commercial upside in the solid-state battery space. The family is honest about its current development stage: the conductivity of undoped Li3AlF6 has been experimentally measured at approximately 5×10⁻⁷ S/cm, which is below the threshold typically required for practical solid-state cells (~10⁻⁴ S/cm). The claim architecture has been deliberately structured around the electrochemical window — the proven, well-supported property — while treating conductivity enhancement through vacancy-creating substitution as the prophetic next step.

Li3AlF6 adopts an octahedral coordination environment in which aluminum is coordinated by six fluorine atoms, forming a rigid, corner-sharing network. This structural motif is what confers its exceptional chemical and electrochemical stability: the Al-F bond is among the most thermodynamically robust in solid-state chemistry, and the fluoride framework resists oxidation because fluorine is already in its most stable oxidation state. The computed electrochemical stability window of approximately 0 to 5.5 V versus lithium places this material class significantly above the practical upper limits of thiophosphate electrolytes (~2.5 V intrinsic window before kinetic passivation) and competitive with or superior to most halide electrolytes. Two independent DFT source calculations underpin this window estimate, both accessed through the materials knowledge graph. The static DFT electrochemical window calculation is the primary computational proof delivered to date. The family extends well beyond the parent Li3AlF6 compound. The claimed composition space includes LiBF4, LiHF2, and their sodium and potassium analogs (NaBF4, Na3AlF6, KBF4, K3AlF6), as well as more complex phases including Na5Al3F14 and NaMgF3. LiBF4 is not a purely prophetic entry: literature reports an ionic conductivity of approximately 1×10⁻³ S/cm in appropriate environments, which the portfolio discloses as corroborating evidence for the broader family's viability. This cross-reference is important because it grounds the family's conductivity potential in prior experimental results from a chemically related member, even as the conductivity of the flagship Li3AlF6 composition remains the principal open validation gate. The experimentally measured conductivity of undoped Li3AlF6 — approximately 5×10⁻⁷ S/cm, obtained in the OBELiX experimental program — is disclosed candidly in the portfolio and was factored into the claim architecture. This value is roughly two to three orders of magnitude below the typical design target for a practical solid-state electrolyte, and represents the primary technical gap that separates the current state of the material from commercial deployment. The identified pathway to closing this gap is vacancy-creation through aliovalent substitution: replacing a fraction of Al³⁺ with lower-valence cations (e.g., Mg²⁺, Zn²⁺) would generate lithium vacancies that act as mobile charge carriers, a strategy with well-established precedent in garnet (Li7La3Zr2O12) and NASICON-family electrolytes. This route is prophetic at the current filing stage — in-house ionic conductivity calculations and targeted doping simulations have been identified as the next computational gate but have not yet been completed. Dynamic stability analysis via multi-potential consensus — which is applied across other materials in this portfolio using MACE, CHGNet, MatterSim, and ORB potentials in parallel — is not applicable here in the same form, because the electrochemical window claim does not depend on phonon stability in the way that a structural candidate for a new thermoelectric or piezoelectric would. The relevant stability assessment is thermodynamic and electrochemical rather than phonon-based, and the DFT evidence for the window is considered sufficient to support the claims as filed. The absence of a multi-MLIP phonon consensus is therefore a deliberate scope decision rather than a gap in the validation methodology.

The addressable market for solid-state electrolytes is commonly estimated in the $1-5 billion range over the next decade, driven primarily by the electric vehicle sector's demand for batteries that offer higher energy density, better thermal safety, and longer cycle life than conventional liquid-electrolyte lithium-ion. This estimate reflects the electrolyte materials and components layer of the value chain — not the full battery market — and should be understood as an early-stage projection subject to significant uncertainty around the pace of solid-state battery commercialization. The primary customers are solid-state battery manufacturers, including Tier 1 automotive battery suppliers, automotive OEMs with captive cell development programs, and emerging pure-play solid-state companies. Licensing or materials supply agreements with any one of these players could be commercially meaningful. The royalty and licensing logic for a composition-of-matter patent covering an electrolyte family is relatively clean: every cell manufactured using a covered compound would constitute a unit of use, and the licensing structure could be applied either per cell, per gram of electrolyte processed, or as a percentage of electrolyte materials revenue. Because the claims are compositional rather than process-based, the IP follows the material regardless of manufacturing method — an advantage over process patents that can be designed around. The $1-5B TAM estimate is an order-of-magnitude estimate; within that range, a royalty rate of even 1-3% on electrolyte material value would represent a significant revenue stream for a licensing program, particularly if the family's claims hold through prosecution and any covered composition achieves broad adoption. The timing dynamic matters here. Solid-state battery pilot lines are being qualified now, and the electrolyte material choices made in 2025-2028 will likely anchor manufacturing infrastructure for a decade. IP that is filed and prosecuted before those design locks happen captures leverage that later-filed art cannot. The non-sulfide, non-halide positioning of the fluoride family also means it does not compete directly with the largest existing IP estates (Solid Power's sulfide portfolio, Toyota's thiophosphate estate, the halide-focused portfolios from LG and Samsung), reducing the likelihood of cross-licensing complications and increasing the probability that a licensee would view this as incremental rather than overlapping protection.

non-sulfide non-halide wide-window fluoride electrolyte; reduced moisture sensitivity

window-only independent claim; conductivity prophetic at the claim

The most natural acquirers or licensees for this asset are solid-state battery developers who are either dissatisfied with sulfide processing constraints or actively searching for alternative electrolyte compositions to diversify their technology portfolio. Tier 1 cell manufacturers with active solid-state programs — including companies with sulfide-first strategies that face moisture-handling cost escalation — would find the fluoride family's processing advantages directly valuable. Automotive OEMs with captive battery development programs (particularly those who have publicly committed to sulfide-free or "dry process" solid-state roadmaps) are a secondary target, as are the handful of pure-play solid-state startups that have not yet locked in an electrolyte chemistry. A licensing structure that provides non-exclusive rights to multiple solid-state developers in exchange for milestone and royalty payments is likely the most capital-efficient path to monetization at this stage, given that the conductivity gap has not yet been closed experimentally. A defensive buyer — a large incumbent battery manufacturer seeking to block a competitor from owning the fluoride electrolyte space — is also a plausible acquirer. The composition-of-matter claims covering the full alkali aluminum fluoride family would, if maintained and enforced, require any commercial user of these compositions to take a license. For a player already investing in halide electrolytes who wants to preserve optionality in the fluoride direction without being blocked out, early acquisition of this asset would be a straightforward defensive investment. Chemical companies with existing fluoride materials manufacturing capabilities (e.g., companies already producing LiBF4 for liquid-electrolyte applications) represent a third category of potential licensee, since they could integrate the solid-state electrolyte use case into existing product lines with relatively low incremental capital expenditure.

The principal technical risk is the conductivity gap. Undoped Li3AlF6 at ~5×10⁻⁷ S/cm is two to three orders of magnitude below what commercial solid-state cells require, and the doping strategy that would close this gap — aliovalent substitution to create lithium vacancies — is prophetic at this stage. There is a meaningful probability that the fluoride framework, even when doped, does not reach the conductivity targets achievable in sulfides or NASICON-type oxides due to intrinsic ion-transport limitations of the rigid, corner-sharing AlF6 network. The roadmap to de-risking this is clear: NEB migration-barrier calculations and experimental synthesis of Mg- or Zn-substituted Li3AlF6 would either validate or falsify the doping hypothesis within 12-18 months of focused effort. The secondary risk is competitive: the solid-state battery IP landscape is moving fast, and a large-scale filer (Toyota, Samsung SDI, QuantumScape) could publish or file on doped fluoride electrolytes before the conductivity-dependent dependent claims are converted from prophetic to supported. The window claim would survive such a disclosure, but the conductivity-specific claims could face prior art challenges. The mitigation is priority date: the family as filed already establishes a priority date for the full compositional scope, including the doped variants, so subsequent publications from third parties after that date do not constitute prior art against the continuation practice. A third, lower-severity risk is that the fluoride processing advantage over sulfides proves less decisive than anticipated if dry-room costs continue to fall as the sulfide battery industry scales — this is a commercial risk rather than a patent risk, and does not affect the validity of the claims.