To state the conclusion first, the biggest obstacle for all-solid-state batteries using a sulfide-based solid electrolyte is that they “age quickly at high temperature.” CATL (Contemporary Amperex Technology Co Ltd) solved this problem with a cathode-side coating in international application WO2026045268A1, published in March 2026, while U.S. automaker-affiliated battery company Rivian (Rivian IP Holdings LLC) solved it with an anode-side interface layer in US12424625B2, granted in September 2025. Same problem, different electrode, different chemistry. This article places the claim scope of both patents side by side and examines how much freedom a latecomer has to design around them.
The all-solid-state battery industry competes over “which year we reach mass production,” but what actually blocks mass production is not a flashy new material but an inconspicuous interface — the surface where the electrode and the solid electrolyte meet. A liquid electrolyte fills the contours of the electrode surface like a liquid, but two solids find it hard to achieve perfect physical contact, and at high temperature they also chemically erode each other. These two recently published patents are worth comparing precisely because they approach this interface problem from opposite directions.
① What’s the Story
CATL published international patent application WO2026045268A1 on March 5, 2026. Its title is “Positive electrode sheet, solid-state battery cell, battery device, electric device, and positive electrode active material and preparation method therefor,” its application number is PCT/CN2025/086307, and its priority date is August 30, 2024 (based on Chinese patent application 202411214822.X). A direct check of the original text on Google Patents shows its current legal status is ‘Pending (under examination),’ with an expected expiration date listed as February 28, 2027.
Around the same time, in the United States, it is confirmed that Rivian’s subsidiary Rivian IP Holdings holds US12424625B2. Its title is “Stable lithium metal sulfide coatings for solid-state batteries,” its application number is US17/744,998, its priority date is May 16, 2022, and its grant date is September 23, 2025. Based on the original text on Google Patents, its legal status is ‘Active,’ and its expected expiration date is confirmed as December 25, 2043. For both patents, the applicant, priority date, and legal status were directly cross-checked against the original text on Google Patents.
② Basic Principle
Let’s compare the surface where the solid electrolyte and the electrode meet to noise passing between apartment walls. Just as thinly applying soundproofing material across an entire wall reduces noise (a side reaction), coating the electrode surface with a very thin “buffer coating layer” reduces the area where the electrode and the solid electrolyte make direct contact and trigger a chemical reaction. The CATL patent applies this buffer to the surface of the cathode (nickel-cobalt-manganese-based oxide, etc.), while the Rivian patent applies it to the surface of the anode (lithium metal, etc.).
Source: reconstructed by the editorial team from the claims of WO2026045268A1 and US12424625B2
CATL’s method is a bit more elaborate. When the cathode surface is coated with a fluorine-containing lithium salt (of the lithium difluoro(oxalato)borate family commonly used in the secondary battery industry, among others), this coating material decomposes ahead of the sulfide solid electrolyte during charging, forming a lithium fluoride (LiF) film. This film acts as a “shield” that suppresses decomposition of the sulfide electrolyte, and the patent’s core effect is that capacity does not fade easily and the crystal structure remains stable even at high temperature. Rivian’s method takes an approach that secures stability by directly forming an interface layer made of lithium metal sulfide between the anode and the solid electrolyte, and it is structurally different in that the coating is positioned at the anode-electrolyte interface rather than on the cathode.
③ Comparison
| Category | CATL (WO2026045268A1) | Rivian (US12424625B2) |
|---|---|---|
| Application location | Cathode (positive electrode) surface | Anode (negative electrode)-solid electrolyte interface |
| Core material | Fluorine-based lithium salt coating → forms a LiF protective film | Lithium metal sulfide interface layer |
| Target electrolyte | Sulfide-based solid electrolyte | Solid electrolytes in general (cells with a lithium metal anode) |
| Claimed effect | Reduced high-temperature capacity fade rate, improved high-temperature cycle performance | Secures interface stability (suppresses side reactions between the electrolyte and the anode) |
| Filing/priority date | 2024-08-30 | 2022-05-16 |
| Publication/grant date | Published 2026-03-05 (PCT) | Granted 2025-09-23 |
| Legal status (per Google Patents) | Pending | Active, expires 2043-12-25 |
Source: compiled by the editorial team from WO2026045268A1 and US12424625B2 (Google Patents public records)
What This Table Tells Us: Both patents address the same problem — “stabilizing the solid electrolyte interface” — but the electrodes they apply to are exact opposites, and while the Rivian patent was filed earlier and is already granted and in force, the CATL patent is still at the examination stage. Since the claim scope is clearly divided by electrode location and coating material, the likelihood of the two patents colliding appears low based on the claim structures confirmed so far.
④ Patent Perspective
Looking at the claim structure of the CATL patent, its core elements are the combination of a positive electrode active material (a transition-metal-oxide-based substrate material), a fluorine-based lithium salt coating material covering part or all of its surface, and a sulfide solid electrolyte material. Numerical limitations — the coating material’s mass ratio (0.1 to 3% relative to the active material), coating coverage (90 to 100% of the substrate surface), and active material particle size (3 to 10µm) — are included in the detailed working examples, giving the impression that the claim scope has been designed quite specifically. This type of numerically limited claim has the characteristic that determining infringement requires a precise analysis of the actual product’s coating thickness or composition ratio.
The Rivian patent, by contrast, centers its claims on a configuration that applies a lithium metal sulfide to the interface layer between the anode and the solid electrolyte, and since it is a granted patent remaining in force until 2043, any company developing or selling lithium-metal-anode-based all-solid-state cells in the U.S. market should check it for possible infringement.
Design-Around Scenario (Counterargument): Since the claims of the two patents are clearly distinguished by electrode location and coating chemistry, the following design-around approaches could be considered. First, a cell design that applies an interface coating only to the cathode and performs no separate treatment at the anode-electrolyte interface may not satisfy the elements of the Rivian claim (a lithium metal sulfide layer at the anode-electrolyte interface). Second, conversely, applying the lithium metal sulfide interface layer only to the anode side while using a cathode coating material other than a fluorine-based lithium salt (for example, an oxide-based coating) may leave room to fall outside part of the CATL claim’s elements (the fluorine-based lithium salt coating).
That said, this is only an interpretation based on the currently published claim language, and a final Freedom to Operate (FTO) determination would require a comprehensive review that also considers the possibility that the claim scope is amended during actual examination or that the doctrine of equivalents is applied, as well as the possibility that each company holds separate follow-on applications beyond these two patents.
⑤ Limitations and Outlook
An optimistic outlook could emerge in which, if the CATL patent is eventually granted, it secures a strong claim scope in the field of cathode coatings. But an opposing scenario also exists. This patent is still at the PCT international phase, and the possibility that its claim scope will be narrowed, or that some claims will be rejected, cannot be ruled out depending on whether it enters national phase in individual countries such as Korea, the United States, and Europe, and depending on each country’s examination standards. In fact, it is not uncommon for composition claims with extensive numerical limitations to have their scope narrowed during examination on the grounds that the working examples provide insufficient support.
As a strategic alternative, for a domestic cell or materials company, a portfolio strategy of diversifying the cathode coating material into substances other than fluorine-based lithium salts (for example, phosphate-based or borate-based compounds) appears to be a valid approach. This is a design-around that steps outside the specific claim language while also offering the dual benefit of broadening one’s own patent portfolio.
Reader Action: IP personnel are advised to monitor, on a quarterly basis via KIPRIS, whether WO2026045268A1 enters the Korean national phase, and to set up a process for cross-checking with your in-house materials team whether your own cathode coating process falls within the claim’s numerical limitations (coating mass ratio of 0.1 to 3%, coating coverage of 90 to 100%, etc.).
This content was written after directly reviewing the original patent publication text as published on Google Patents, and it has been restated in text form without reproducing the original patent text verbatim. Whether the patents will be granted, the final determination of claim scope, and any judgment of infringement or non-infringement are all analyses at the level of possibility and do not constitute definitive legal advice. Specific matters require separate review.