What Is the Story: A Piece of a Korean Cell Maker’s Foundational Sulfide Technology
U.S. patent US11955601B2, jointly held by Samsung SDI and the Sejong University Industry-Academia Cooperation Foundation, covers an argyrodite-type (Li-P-S-halogen) sulfide solid electrolyte and its manufacturing method, and the scope of its independent claim is fenced by two boundaries: “numerical ranges in a composition formula” and “X-ray diffraction (XRD) impurity peak ratios.” Design-around potential for this patent is therefore likely to be decided not by the type of halogen but by the ratios of lithium, sulfur, and halogen and by phase purity.
Looking at the industry landscape, in the race for all-solid-state batteries (batteries that use a solid electrolyte instead of a liquid one), the trend of “oxide first, sulfide delayed” has recently been discussed as something like an industry consensus. The reason is that sulfide electrolytes have high ionic conductivity but are sensitive to moisture and make interfacial stability hard to secure.
The tension is that, amid this, how much foundational sulfide-electrolyte technology Korean cell makers have actually secured is not well known. This patent is part of that answer. This article answers two questions. What exactly does this patent claim? And where should those preparing similar compositions look for infringement risk and design-around room?
Basic Principle: The Lithium Pathways Halogens Widen
The argyrodite-type structure raises ionic conductivity by substituting halogens (Cl, Br, etc.) into a Li-P-S framework. The known core principle is that halogen substitution widens the lithium-ion migration pathways within the crystal structure.
Source: reconstructed by the editorial team from claims 12-14 and the specification of US11955601B2
By analogy, the crystal structure is an “underground tunnel network” through which lithium ions travel. Halogen substitution is construction work that widens parts of the tunnels to speed up traffic, and impurity phases are “debris” piled up in the middle of the tunnels. Even with good construction, leftover debris slows traffic. That this patent puts XRD impurity peaks into the claim alongside composition means it made the amount of this debris a requirement of the right.
The specification explains this relationship directly. Impurity phases may be observed near diffraction angles (2θ) of 17.5-18.5°, 26.5-27.5°, and 29°, and as impurity phases increase, ionic conductivity decreases. The specification states that the condition of both peak ratios in the claim being 0.06 or less indicates a high-purity state with few impurity phases.
- Composition axis: in LiaP1SbXc, 4.7<a<5.3, 4.4≤b≤4.5, 0.7<c<1.5
- Purity axis: XRD peak ratios I(29.0)/I(30.0) ≤ 0.06 and I(27.1)/I(30.0) ≤ 0.06
- Process axis: mixing sulfur, phosphorus, and halogen precursors, then heat-treating at 350°C or higher (dependent process claims)
However, the weaknesses common to sulfide electrolytes, moisture sensitivity and high-voltage interfacial stability, are not fully resolved by this patent’s compositional improvement alone.
Besides ionic conductivity, another property the specification emphasizes is mechanical. The specification states that the Young’s modulus (the degree to which a material resists deformation) of this electrolyte may be 80 GPa or higher, for example 80-95 GPa, and explains that a higher Young’s modulus allows a denser solid electrolyte layer to be made with the same pressure. Because the density of the electrolyte layer in an all-solid-state cell is tied to reducing gaps between particles and connecting ion pathways, the fact that this patent describes conductivity and mechanical properties together reads as a design with the cell manufacturing process in mind.
Comparison: Bibliographic Data and Example Ionic Conductivities
First, the bibliographic data. The four items in the original table are kept, and bibliographic values confirmed on Google Patents are added.
| Item | Description |
|---|---|
| Patent number | US11955601B2 |
| Applicant | Samsung SDI, Sejong University Industry-Academia Cooperation Foundation |
| Electrolyte family | Argyrodite-type sulfide (Li-P-S-halogen) |
| Core claim | High-ionic-conductivity composition (composition formula + XRD peak ratios) and manufacturing method |
| Priority | KR10-2020-0110596 (2020-08-31) |
| U.S. application / publication | US17/412,589 (2021-08-26) / US20220069343A1 (2022-03-03) |
| Grant / legal status | Granted 2024-04-09 / Active, anticipated expiration 2042-01-15 |
Source: compiled by the editorial team from Google Patents US11955601B2
What this table says: The fact that a major Korean conglomerate co-filed with Sejong University shows that the foundational technology is being built up from the academia-industry collaboration stage onward. With an anticipated expiration of January 15, 2042, this right overlaps with the whole period in which commercialization of sulfide all-solid-state batteries is being discussed. Patent registration, however, does not in itself mean mass-production readiness.
Next are the ionic conductivities at 25°C reported in Table 2 of the specification. Some comparative examples are included to show how the values change inside and outside the claimed composition boundary.
| Item | Composition | Ionic conductivity (mS/cm, 25°C) | Claim 1 composition range |
|---|---|---|---|
| Example 1 | Li5.04PS4.46Cl1.13 | 4.46 | Inside |
| Example 2 | Li5.28PS4.47Cl1.34 | 3.87 | Inside |
| Example 3 | Li5.20PS4.44Cl1.32 | 2.56 | Inside |
| Example 4 | Li5.20PS4.46Cl1.29 | 2.30 | Inside |
| Comparative Example 1 | Li4.54PS4.21Cl1.11 | 0.36 | Outside (a, b) |
| Comparative Example 3 | Li5.33PS4.5Cl1.34 | 1.867 | Outside (a) |
| Comparative Example 5 | Li5.38PS4.52Cl1.34 | 1.562 | Outside (a, b) |
Source: compiled by the editorial team from Table 2 of the US11955601B2 specification (range assessment by the editorial team)
What this table says: All four examples are 2 mS/cm or higher (2.30-4.46 mS/cm), while the comparative examples stay at 0.36-1.867 mS/cm. In particular, Comparative Example 3 has a lithium index a of 5.33, just above the claimed upper limit (less than 5.3), suggesting that the claim boundary was drawn at exactly such a “point where performance drops off.”
Patent Perspective: Two Fences and the Gaps Between Them
Gist of the claims (paraphrased): Independent claim 1 claims a sulfide solid electrolyte represented by the formula LiaP1SbXc (X being one of F, Cl, Br, or I) that has an argyrodite-type crystal structure and whose XRD peak intensity ratios at 29.0°/30.0° and 27.1°/30.0° are each 0.06 or less. The dependent claims narrow the scope with a Li/S atomic ratio of 1.13 or higher (claim 4), a narrow Li-P-S-Cl composition range (claim 5), four specific compositions (claim 6), a Young’s modulus of 80 GPa or higher (claim 7), and ionic conductivity of 2 mS/cm or higher (claim 8). Claims 9-11 cover an all-solid secondary battery using this electrolyte, and claims 12-14 cover a manufacturing method of precursor mixing, mechanical milling, and heat treatment at 350°C or higher (including vacuum at 500-650°C for 5 hours or longer).
Source: reconstructed by the editorial team from the claims of US11955601B2
Filing trend: This patent was filed in the U.S. on August 26, 2021 claiming priority from a Korean application filed August 31, 2020 (KR10-2020-0110596), published on March 3, 2022, and granted on April 9, 2024. The specification explains that this composition can reduce the use of expensive lithium sulfide raw material and lower manufacturing cost. Reading this explanation together with the composition range (a of about 5), it can be interpreted as a design targeting a region with a lower lithium index than Li6PS5Cl, the composition often cited as representative (and used by the specification as an XRD reference).
Design-around points: The original article held that “changing the type and ratio of halogen leaves room for design-around,” but because claim 1 covers X as any of F, Cl, Br, or I, changing the halogen type alone makes avoidance difficult. Design-around room lies in two places. First, placing even one of the composition indices a, b, or c outside the claimed range. For example, a stoichiometric composition with a lithium index close to 6 falls outside the a<5.3 requirement. Second, even with a composition inside the range, if an XRD peak ratio exceeds 0.06, the literal requirement is not met.
Design-around scenario (counterargument): The second route, however, means deliberately leaving impurity phases, so as the specification and Table 2 show, it is likely to require accepting lower ionic conductivity. In addition, parameter limitations such as peak ratios can vary with measurement equipment and conditions, so the measurement method itself may become an issue in an infringement dispute. If a composition just outside the boundary (for example, near a=5.3) delivers the same performance, there may be room for an equivalents argument, but how the range of equivalents is recognized for numerically limited inventions is decided case by case. Registration and litigation outcomes cannot be determined now, and this remains a judgment at the level of possibility.
Limits and Outlook
If the oxide-first consensus holds for the next two to three years, commercialization of sulfide electrolytes is expected to hinge on resolving interfacial resistance and pressure requirements. Conversely, if the interface problem is solved sooner than expected, those holding foundational argyrodite patents could be the first to take the high ground.
There is also a clear counter-scenario to the optimistic outlook. Argyrodite composition patents are likely being filed on similar frameworks by many companies and research institutes, so the bargaining power of any single composition patent may be limited. When rights are drawn with a narrow composition range and purity parameters, as in this patent, competitors can more easily sidestep them with adjacent compositions.
A strategic alternative is to evaluate composition patents not as standalone assets but as a “composition-process-cell structure” bundle. This patent also claims an all-solid battery structure (claims 9-11) and a manufacturing method (claims 12-14) in addition to the electrolyte composition, so one can assess whether a competitor that sidesteps the composition may meet the patent again in process or cell structure.
Practical action: Planning and IP staff reviewing sulfide electrolytes should tabulate the a, b, and c indices and XRD peak ratios of their candidate compositions against the ranges in claims 1, 5, and 6 of US11955601B2, and record their roadmap’s sulfide adoption timing alongside this patent’s anticipated expiration date (2042-01-15).
This article is a commentary on technology and patent trends, not legal advice, and determining the scope of rights of any individual patent requires confirmation by a patent attorney or lawyer.
Items requiring verification
- Primary sources supporting the industry consensus of “oxide first, sulfide delayed”
- Whether the Korean priority application KR20220028942A has been granted, and its claim scope
- Whether applications in this family exist in other jurisdictions (Europe, Japan, China)
Sources
- Google Patents, US11955601B2 – Sulfide solid electrolyte for all-solid secondary battery, method of preparing same, and all-solid secondary battery including the same