All-Solid-State Battery Sulfide Electrolyte Patents — Who Got There First?

What Is at Issue: The Center of Gravity in Sulfide Electrolyte Patents Is Moving from “Composition” to “Additives”

The race to stake out sulfide-based all-solid-state patents is shifting away from finding new base compositions and toward what, and how much, to add to already-known sulfide electrolytes to shore up their weaknesses. The two patents examined here — Samsung SDI’s KR102893044B1 (published as KR20230036851A) and POSCO JK Solid Solution’s KR102918440B1 (published as KR20250018801A) — both claim configurations that add a set amount of non-conductive inorganic particles or dopants to a sulfide electrolyte.

Looking first at the industry context, it was reported that at InterBattery 2026 on March 11, 2026, Samsung SDI Research Institute head Joo Yong-rak stated that the company holds about 1,100 U.S. all-solid-state patents. At the same event the company presented a schedule of completing product development and verification by the end of 2026 and entering mass production in 2027. Samsung SDI has been developing all-solid-state batteries since 2008 in collaboration with Samsung Electronics’ SAIT (Samsung Advanced Institute of Technology) and SRJ (its Japan research institute), and explained in 2021 that it chose sulfides for their productivity because polymers are easy to make but lack durability and oxides are hard to make large.

The statistics point the same way. According to reports on a February 2026 announcement by the Korean Intellectual Property Office, IP5 (Korea, US, China, Japan, Europe) all-solid-state battery patent filings grew from 331 in 2004 to 3,938 in 2023, an average annual increase of 13.9%, and Samsung SDI (51.7%) and LG Energy Solution (50.8%) ranked first and second in average annual filing growth over the most recent three years (2021–2023). The tension is the moisture sensitivity of sulfides. This article answers two questions: with what configurations do patents guard against the weaknesses of sulfide electrolytes, and does that claim scope target cell makers or material suppliers?

Basic Principle: An Electrolyte Like Soft Clay — but Weak Against Water

Sulfide-based solid electrolytes use lithium, phosphorus, and sulfur as their basic framework, with halogen elements such as chlorine or bromine added to form an argyrodite-type crystal structure (a structure type named after a mineral with that crystal structure). This structure offers high ionic conductivity and enough ductility to make good contact with electrodes, but its weakness is that it releases toxic hydrogen sulfide (H₂S) gas when it reacts with moisture.

Fig. 1. A concept diagram of how sulfide solid electrolyte patents branch into four directions: ionic conductivity, moisture stability, crack suppression, and manufacturing environment.
Source: reconstructed by the editorial team from the specifications of KR102893044B1 and KR102918440B1 and the original article's classification

By analogy, a sulfide electrolyte is a soft clay that can be shaped by hand, while an oxide electrolyte is closer to hard ceramic. Clay is easy to press tightly between electrode particles, but it changes properties when it absorbs moisture and cracks when pressed repeatedly. Patents therefore split into mixing a reinforcement like sand into the clay so it cracks less (structural design), or adding moisture-resistant components to the clay itself (dopants).

The patent trend generally falls into three directions.

Composition optimization: adjusting the base composition and halogen ratio to raise ionic conductivity
Dopant addition: small added components that improve stability against air and moisture
Structural design: suppressing cracks and interfacial resistance caused by volume changes during cycling and pressing

Comparison: Claimed Configurations and Example Figures of the Two Patents

First, the logic behind Samsung SDI’s choice of electrolyte family is summarized below. These are qualitative company explanations, not quantitative figures.

Electrolyte family	Ease of manufacture	Weakness (company explanation)	Samsung SDI choice
Polymer	Easy to make	Lacks durability	Not adopted
Oxide	Hard to scale up	Low productivity	Not adopted
Sulfide	Good productivity	Releases H₂S on reaction with moisture	Adopted (developed since 2008)

Fig. 2. Samsung SDI’s stated logic for choosing among solid electrolyte families
Source: compiled by the editorial team from Samsung SDI’s explanation in a Dailian report of 2021-05-25 (the H₂S weakness follows the principle section of this article)

What this table says: Samsung SDI chose sulfides for productivity and, in return, took on the problem of moisture sensitivity. The two patents below address that very problem at different layers.

Item	KR102893044B1 (Samsung SDI)	KR102918440B1 (POSCO JK Solid Solution)
Claimed subject	All-solid-state secondary battery (cell)	Argyrodite sulfide solid electrolyte (material)
Core configuration	Sulfide electrolyte layer + lithium-non-conductive metal oxide particles	Li₂S-P₂S₅-LiX doped with SnS₂ and Cu₃(PO₄)₂
Numerical limits	Average particle size 50 nm–5 μm, content 1–10 wt%	SnS₂ 1–15 wt%, Cu₃(PO₄)₂ 0.1–10 wt%
Example ionic conductivity	–	5.28–6.09 mS/cm
Moisture stability (decomposition time in deionized water)	–	Examples 12–14.5 min vs. comparative 1–4 min
Decrease rate after 24 h in dry room	–	Examples 16.86% and 12.64% vs. undoped 35.25%
Filing date / grant date	2021-09-08 / 2025-11-27	2023-07-31 / 2026-01-27

Fig. 3. Claimed configurations and specification example figures of the two sulfide electrolyte patents compared
Source: compiled by the editorial team from the claims and specifications of KR102893044B1, KR20230036851A, KR102918440B1, and KR20250018801A

What this table says: The doping patent states in its examples that the 24-hour dry-room decrease rate was lowered from 35.25% to 12.64–16.86%. These are the applicant’s example values, however, not third-party replication data.

Patent Perspective: Claims Aimed at Cells, Claims Aimed at Materials

Bibliographic data (Samsung SDI): KR20230036851A (“All-Solid-State Secondary Battery and Method of Manufacturing the Same”) was filed on September 8, 2021, published on March 15, 2023, and granted as KR102893044B1 on November 27, 2025. Per Google Patents, its status is Active with an anticipated expiry of September 8, 2041, and family members US20240429436A1 and WO2023038392A1 are listed.

Claim summary (restated): In an all-solid-state secondary battery consisting of a cathode layer, an anode layer, and a solid electrolyte layer between them, the solid electrolyte layer contains a sulfide-based solid electrolyte and inorganic particles with an average particle size of 50 nm to 5 μm. The published claim limits the inorganic particles to metal oxides that are non-conductive to lithium ions, at 1–10 wt% of the entire solid electrolyte layer. The granted claim further specifies the metal oxides — MgO, SiO₂, Al₂O₃, TiO₂, ZrO₂, ZnO, and others — as a Markush group (a format that lists candidate substances to choose from). The specification points to the problem in conventional composite electrolytes that use lithium-ion-conductive oxide particles as spacers: ionic conductivity drops sharply.

Fig. 4. A map of the claim 1 elements of KR102893044B1 and the design-around potential of each.
Source: reconstructed by the editorial team from the claims of KR102893044B1

Bibliographic data (POSCO JK Solid Solution): KR20250018801A (“Argyrodite Sulfide-Based Solid Electrolyte for Secondary Batteries and Preparation Method Thereof”) was filed on July 31, 2023, published on February 7, 2025, and granted as KR102918440B1 on January 27, 2026 (Active, anticipated expiry July 31, 2043). Published claim 1 covers a Li₂S-P₂S₅-LiX (X being one or more of Cl, F, Br, I) argyrodite electrolyte doped with SnS₂ and Cu₃(PO₄)₂, while the formula Li₇₋ₓ₊ᵧCu₃ₐP₁₊₂ₐSnᵦS₆₋ₓ₊₂ᵦO₈ₐXₓ₊ᵧ and the ranges of x, y, a, and b were in claim 5 at the publication stage. Granted claim 1 combines this formula (0.5≤x≤2, etc.) with the dopant contents, narrowing its scope.

Insight: even “sulfide patents” aim at different targets. Because the Samsung SDI patent is a cell claim, infringement risk arises at the stage of assembling a cell with an electrolyte layer mixed with non-conductive oxide particles. Conversely, because the doping patent claims the electrolyte material itself, material suppliers who synthesize and sell the powder become direct subjects of review. And because a composition claimed by formula does not ask what raw materials it was synthesized from, merely changing the dopant precursors is unlikely to avoid it. A cell maker’s FTO (freedom-to-operate) review will likely need to cover not only its own process but also the composition analysis sheets of the electrolyte powder it purchases.

Design-around points: The Samsung SDI claim has a three-fold limitation: particle size of 50 nm–5 μm, content of 1–10 wt%, and the listed metal oxides. Falling outside any one of them may leave room to avoid literal infringement. The doping patent requires both SnS₂ and Cu₃(PO₄)₂, so a design using only one, or falling outside the content ranges, could be a design-around option.

Design-around scenario (counterargument): However, switching to lithium-ion-conductive oxides as a workaround brings back the drop in ionic conductivity that the specification itself points out. In other words, the more one avoids, the more performance suffers, so in practice a license or data near the particle-size and content boundaries may be the realistic response. Near numerical boundaries, the judgment may also vary depending on measurement methods (particle-size distribution basis, content calculation basis).

Limitations and Outlook

Sulfide-based electrolytes lead in ionic conductivity, but the fundamental constraint of moisture sensitivity remains. Looking at the patent trend, the center of gravity is shifting away from the composition itself toward “additives and structures that suppress toxic gas generation even when exposed to humidity.” With Samsung SDI having announced mass production for 2027, patents on moisture management during cell assembly are likely to increase alongside.

There is also a counter-scenario. Ranking first and second in filing growth shows “speed,” not “accumulated scale.” According to the same report, the top cumulative filer was Toyota (2,337 filings), while Samsung SDI had 706. The rise of additive patents may also signal that rights to base compositions have already been staked out, in which case latecomers may find it hard to avoid FTO burdens with overseas prior rights holders at the base-composition layer.

A strategic alternative is to map rights across four layers: “base composition,” “additives and dopants,” “cell structure,” and “manufacturing environment (moisture control).” The additive layer is relatively easy to design around, whereas the manufacturing-environment layer is a common bottleneck every company will hit at mass production, so preemptive filings there may carry greater value.

Practical action: Planning and IP staff who procure or develop sulfide electrolytes should add to the supplied powder’s composition sheet the presence and content of Sn and Cu doping, and the particle size and content of non-conductive oxide particles in the electrolyte layer, and compare them with the claim scope of KR102918440B1 and KR102893044B1.

Items requiring verification

The official wording for “No. 1 in Korea” in the original’s statement that Samsung SDI holds some 1,100 U.S.-registered all-solid-state patents, the most in Korea
The exact release date of the Korean Intellectual Property Office announcement on all-solid-state battery patent trends (reports differ between 2026-02-18 and 19) and the share of filings by electrolyte family
The prosecution history of US20240429436A1 (the US family member of KR102893044B1) and differences in its claims
Whether the KR102918440B1 examples include measured hydrogen sulfide generation data

Sources

Google Patents, KR20230036851A and KR102893044B1 bibliographic data and claims
Google Patents, KR20250018801A and KR102918440B1 bibliographic data, claims, and specification
Hankyung Business, report on Samsung SDI’s InterBattery 2026 presentation (2026-03-11)
Money Today, report on KIPO all-solid-state battery patent filing trends (2026-02-19)
Electronic Times, report on KIPO all-solid-state battery filing growth (2026-02)
Dailian, report on Samsung SDI all-solid-state battery development (2021-05-25)