Why One Foundational Technology Becomes 800 Patents — LG Chem’s SRS Separator and Patent Portfolio Strategy

What Is at Issue: The Structure Behind the Number of Patents

Several hundred patents often do not mean several hundred inventions; they are frequently the result of dividing one foundational technology into units of detailed implementation, such as particles, composition, thickness, placement and assembly method, and filing on them layer upon layer. SRS® (Safety Reinforced Separator), which LG Chem developed in 2004, and its follow-up patent KR101750239B1 (publication number KR20160054219A) are a case that shows this structure. This article explains how one foundational technology grows into a patent portfolio, and how that number should be read.

Start with the industry context. Patent counts are often used as weapons in public statements in the battery industry. At “The Battery Conference,” a side event of InterBattery 2026 held at COEX in Seoul on March 11, 2026, Ju Yong-rak, head of Samsung SDI’s research institute (Vice President), was reported as saying that the company “will not overlook patent infringement or technology theft related to prismatic batteries,” and as claiming that it holds more than 1,200 prismatic battery patents registered in the U.S., while domestic competitors hold around 30 to 40. At the same event, Kim Je-young, CTO of LG Energy Solution, was reported as saying that latecomers “must legitimately pay tuition and use the technology.” LG Energy Solution was reported as stating that, as of May 2026, its global patents exceeded 100,000 on a filing basis and about 59,000 on a registration basis.

The tension comes from a past case. In April 2019, LG Chem filed a complaint against SK Innovation with the U.S. International Trade Commission (ITC) for trade secret misappropriation, and on February 10, 2021 the ITC ruled in LG’s favor, issuing a 10-year import ban on SK products. On April 11, 2021, the two companies settled for 1 trillion won in cash and 1 trillion won in royalties, 2 trillion won in total, withdrew all domestic and overseas lawsuits and agreed not to bring further suits for 10 years. This article answers three questions: what SRS solves, how a foundational technology is split into hundreds of patents, and how the number called a patent count should be evaluated.

Basic Principle: A Heat-Resistant Coating on Plastic Wrap

A separator is a thin porous film placed between the cathode and anode that keeps the two electrodes from touching directly while letting only lithium ions pass. Commonly used polyolefin separators tend to shrink when heated, like plastic wrap. If the separator shrinks and the cathode and anode touch, an internal short circuit occurs, which can lead to heat generation and fire.

SRS is a separator whose film surface is coated with ceramic particles and a polymer binder to raise its thermal and mechanical strength. By analogy, it dresses plastic wrap that shrinks easily in a thin ceramic garment so that it holds its shape even under heat. According to a March 2015 report, LG Chem explained that this technology prevents internal short circuits and thereby improves the safety of lithium-ion batteries. The original article stated that ordinary separators shrink at around 100°C while SRS keeps its shape even at 200°C; the primary source for these figures could not be confirmed, so they are left as an item requiring verification below.

KR101750239B1 is a follow-up patent that subdivides this principle one step further. The problem it targets is the edge of the separator. The end portion of the separator that protrudes beyond the electrodes (the surplus portion) tends to shrink first at high temperature. The patent proposes a structure that prevents this shrinkage by applying a coating layer thicker than the separator to the surplus portion.

• Foundational concept: coat the separator with ceramic particles plus binder (SRS, developed in 2004)
• Follow-up detailed implementation: add a thick coating layer only to the surplus portion of the separator extending beyond the electrodes (KR101750239B1, filed 2014)

Comparison: Ordinary Separators vs. SRS, and the Timeline of SRS Patents

Item	Ordinary separator	SRS (ceramic-coated)
Surface composition	Porous polymer film	Ceramic particles + polymer binder coated on the film surface
Heat-resistance limit (as stated in original)	about 100°C	about 200°C
Number of coating layers (as stated in original)	2 layers (ordinary ceramic coating)	3 layers
Suitability for high-nickel batteries	Limited	Suitable

What this table says: Per the original’s stated values, the heat-resistance limit of SRS is about twice that of an ordinary separator (100°C→200°C). The higher the energy density, as in high-nickel batteries, the more this margin becomes a key variable in safety design.

Date	Event	Meaning in the portfolio
2004	LG Chem develops SRS® technology	Foundational concept secured
2007	Korean patent registered	Rights secured in home country
2010-2014	Registered in the U.S. (2010), China (2012), Europe and Japan (2014)	Family expanded into key markets
2014-11-06	KR20160054219A filed (surplus-portion coating)	Follow-up filing at the detailed-implementation level
2014 / March 2015	License agreements with Ube Maxell of Japan and Senior of China	Royalties received as a fixed share of product sales
2017-06-23	KR101750239B1 registered	Expected to remain in force until 2034

What this table says: There is a 10-year gap between the registration of the foundational concept (2007) and the registration of the detailed-implementation follow-up patent (2017). The term of the portfolio as a whole is extended by that gap.

Patent Perspective: How One Foundational Technology Splits into Hundreds of Patents

Bibliographic data: KR20160054219A is titled “Electrode assembly with SRS coated separator,” and the applicant is LG Chem. The inventors are Seo Jung-min, Kim Dong-myung, Yun Hyung-gu and Jung Yi-hyun. The priority and filing date is November 6, 2014, the publication date is May 16, 2016, and it was registered as KR101750239B1 on June 23, 2017. The rights were transferred to LG Energy Solution in 2021; according to Google Patents, the legal status is Active and the expected expiry date is November 6, 2034. The original article introduced this patent as an “LG Chem SRS patent,” but the current right holder is LG Energy Solution.

Gist of the claims (restated): Claim 1 claims an electrode assembly in which a separator lies between the cathode and anode, the separator extends wider than the cathode and anode on both sides in the width direction to form surplus portions, and a coating layer thicker than the separator is formed on one or both sides of these surplus portions. The dependent claims narrow this with numbers.

• Surplus width: 5-12% of the separator width
• Coating width: 50-90% of the surplus width
• Coating thickness: 30-99% of the anode thickness
• Coating composition and method: inorganic particles + binder polymer, wet or dry coating
• Assembly type: wound, stacked or folded

This structure is the substance of the “portfolio strategy” the original article described. If coating location (surplus portion), thickness ratio, width ratio, composition and assembly type are each stacked as claim units on top of the foundational concept (ceramic-coated separator), then even if a competitor tries to avoid the foundational concept, it becomes more likely to be caught by a detailed implementation at the periphery. Based on this technology, LG Chem was reported to have signed license agreements with Ube Maxell of Japan in 2014 and Senior of China in March 2015, receiving a fixed share of related product sales as royalties.

Insight: the real effect of a portfolio is not its “count” but the “extension of its term.” The foundational patents filed right after the 2004 development may already have expired, or be close to expiring, based on a term of 20 years from filing. In contrast, KR101750239B1, filed in 2014, is expected to remain in force until 2034. Even when the foundational concept passes into the public domain, the right holder keeps its negotiating power as long as the detailed implementations needed for actual mass production are tied up in follow-up patents. So when evaluating a patent count, one should first look at the distribution of “when each patent expires” rather than the number.

Avoidance points: The key limitation of claim 1 is that “the coating layer on the surplus portion is thicker than the separator.” A structure that designs the surplus-portion coating to be no thicker than the separator, or that applies only a uniform full-surface coating with no separate coating on the surplus portion, may lack this element. Placing the design outside the numerical ranges of the dependent claims (5-12%, 50-90%, 30-99%) can keep a distance from those dependent claims.

Design-around scenario (counterargument): However, even if the coating thickness is matched to roughly that of the separator, it could become subject to a doctrine-of-equivalents analysis if it achieves the same function, preventing shrinkage of the surplus portion, in the same way. Conversely, from the right holder’s side, claim 1 is a broad claim that stands on “a surplus coating thicker than the separator” alone, with no numerical limitation, so it may become the subject of a validity dispute if prior art on reinforcing separator edges is presented. Both the possibility of avoidance and the stability of the right can only be judged by comparing individual designs and prior-art documents one-to-one.

Limits and Outlook

Holding many patents does not lead directly to litigation. As the original article noted, there is also a cautious view that the current sparring between LG Energy Solution and Samsung SDI is closer to a strategic message aimed at claiming technological leadership than to a full legal dispute. However, as in the LG-SK case, if key personnel moves or signs of technology leakage are confirmed, the possibility that public warnings escalate into litigation remains.

The optimistic outlook is that the side with more patents gains the upper hand in negotiations and licensing. There is a counter-scenario as well. Because detailed-implementation patents are numerous, each individual claim is narrow, and a competitor may find room to steer around them by changing numerical ranges or placement only slightly. In that case, numbers like “1,200 vs. 30 to 40” overstate the size of the rights that can actually be enforced. Also, figures mentioned in the original such as “about 800 SRS-related patents” or “up to six times more” are each company’s own counts and may differ from third-party databases.

The strategic alternative is to evaluate a competitor’s portfolio not by count but by a “map of core claims.” Picking out the independent claims that actually overlap one’s own products and arranging them with their expiry dates often reduces hundreds of numbers to a handful of real risks.

Practical action: IP staff working on separator coating design should first check whether the coating thickness on the separator surplus portion of their electrode assembly exceeds the separator thickness, and if so, prepare a table comparing it with claim 1 and the dependent-claim numerical ranges of KR101750239B1, and also check whether foreign family members exist.

Items requiring verification

• The primary source and counting basis of the figure “about 800 SRS-related patents worldwide”
• The primary source of the heat-resistance limits (ordinary separator about 100°C, SRS about 200°C) and the coating-layer comparison (2 layers / 3 layers)
• The speaker, date and counting basis of LG Energy Solution’s statement of “up to six times more next-generation battery patents than competitors”
• The specific numbers and expiry dates of the foundational SRS patents filed around 2004
• The filing and registration status of foreign family members of KR101750239B1

Sources

1. Google Patents, KR20160054219A – Electrode assembly with SRS coated separator (LG Chem)
2. Google Patents, KR101750239B1 – Electrode assembly with SRS coated separator
3. Hankook Ilbo, LG Chem exports battery separator patent technology to China (2015-03-08)
4. Etoday, Samsung SDI “will not overlook prismatic battery patent infringement or technology theft” [InterBattery 2026] (2026-03-11)
5. Aju Business Daily, Unexpected exchange between LG Energy Solution and Samsung SDI at a battery event (2026-03-12)
6. Financial News, LG Energy Solution surpasses 100,000 global patents (2026-06-21)
7. Seoul Shinmun, LG and SK “settle battery dispute for 2 trillion won”… all domestic and overseas lawsuits withdrawn (2021-04-11)

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