The Shift to Prismatic Battery Form Factor — Reading Samsung SDI and LG Energy Solution’s Patent Standoff

What Is the Issue: What the “1,200 Prismatic Patents” Figure Does Not Say

The prismatic battery patent standoff between Samsung SDI and LG Energy Solution looks like a contest of patent counts, but actual infringement determinations are decided by the elements of individual claims. So rather than the figure “1,200 versus 30–40,” one should look at whether those patents actually limit the prismatic form in their claims and when they expire.

Starting with the industry landscape, at “The Battery Conference,” a side event of “InterBattery 2026” held at COEX in Seoul on March 11, 2026, Samsung SDI research institute head (Vice President) Ju Yong-rak said that the company has more than 1,200 prismatic battery patents registered in the U.S., while other domestic competitors have around 30–40. At the same event he said Samsung SDI would not overlook prismatic-related patent infringement or technology theft. The remark was interpreted as aimed at LG Energy Solution, which had recently declared its entry into the prismatic market. Samsung SDI emphasized that it has been filing prismatic battery patents since 1997.

The source of tension is LG Energy Solution’s response. In March 2026 reports, LG Energy Solution CEO Kim Dong-myung said, in effect, that “we hold enough patents to produce and supply prismatic cells,” putting forward a battery-wide patent portfolio of about 70,000 rather than a portfolio in the single prismatic field. This article answers three questions: which structures of a prismatic cell are the subject of patent competition, how are the claims of an actual Samsung SDI prismatic-family patent structured, and how should late entrants and incumbents read this standoff?

Basic Principle: Pressing Gimbap into a Lunch Box

A prismatic battery is a structure in which an electrode assembly (jelly roll), formed by winding or stacking the cathode, separator and anode, is placed in an angular metal can and sealed with a cap plate on top. The part of the electrode not coated with active material (the uncoated portion) is welded to a current collector plate, which is in turn connected to the terminal of the cap plate. It is more resistant to external impact than a pouch cell and uses space in a pack more efficiently than a cylindrical cell.

By analogy, a prismatic cell looks like gimbap pressed into a square metal lunch box. The gimbap (jelly roll) swells and shrinks slightly with every charge and discharge, and because the box is square, the force is not distributed evenly across the corners and wide faces. That is why can stiffness, the winding or stacking structure of the electrode assembly, and the way the uncoated portion is joined to the current collector plate all become design challenges. Ju Yong-rak’s remark that every process is difficult, from metal forming to welding to stacking high-loading electrodes, is connected to this structural characteristic.

• Can and cap plate: exterior design that withstands swelling stress and maintains sealing
• Electrode assembly: the shape and arrangement of a wound or stacked jelly roll
• Current collection structure: how the uncoated portion is joined to the collector plate, and the welding method

Comparison: The Nature of the Figures Each Company Put Forward

The table below summarizes the patent-related figures of the two companies confirmed in March 2026 reports. Note that even under the same label “patent count,” the counting bases differ.

Item	Samsung SDI	LG Energy Solution
Figure put forward	1,200+ prismatic patents registered in the U.S.	About 70,000 battery patents overall
Counting scope	Single prismatic form factor, U.S. registrations	All fields (reported in some articles as applications)
Comparison figures cited	Domestic competitors 30–40; Chinese and Japanese firms about 600	Not applicable
Start of prismatic filings	1997	Not confirmed in public materials
Solid-state patents (reference)	About 1,000 filed, about 500 registered	Not verified in this article

What this table says: Samsung SDI’s 1,200 is on a “U.S.-registered, prismatic” basis and LG Energy Solution’s roughly 70,000 is on an “all fields” basis, so the two numbers cannot be put on the same scale. This means patent counts alone cannot determine the infringement risk of a specific product.

The difference in counting bases leads to a difference in interpretation. A registration count includes only rights that have passed examination and is therefore a conservative number, but whether it includes rights that have already expired or lapsed for non-payment of annuities cannot be known from the remarks alone. Conversely, an application count can include applications that were rejected or withdrawn, so it can look larger than the rights actually enforceable. Ultimately, both numbers are merely signals at the negotiating table, not indicators that directly show the size of the scope of rights.

Patent Perspective: Do “Prismatic Patents” Actually Claim the Prismatic Form?

To see what Samsung SDI’s prismatic-family portfolio actually looks like, we examine one granted patent that includes a large-format prismatic cell embodiment. US9136538B2 (title: Rechargeable battery having current collection plate with protrusion) is jointly held by Samsung SDI and Robert Bosch GmbH, with a priority date of February 25, 2009, a filing date of September 17, 2013 (a continuation-family application of earlier application US 12/656,983), and a grant date of September 15, 2015. According to Google Patents, its legal status is Active and its anticipated expiration date is May 10, 2030.

Restated, the gist of claim 1 is a rechargeable battery including an electrode assembly made of first and second electrode plates with uncoated portions and a separator between them, and a current collector plate contacting the uncoated portions. The collector plate has a contact portion that protrudes toward the electrode assembly and touches the uncoated portion, and in that contact portion a slit is formed at a predetermined angle with respect to the direction of the electrode assembly. The specification explains that this structure enables laser welding instead of ultrasonic welding, allowing the uncoated portion to be shortened and the active material area to be increased.

Insight: rights classified as “prismatic patents” do not necessarily claim the prismatic form. The specification of US9136538B2 cites a prismatic rechargeable battery with a wound electrode assembly as an embodiment, but the shape of a case or can does not appear at all in claim 1. This has meaning in two directions. First, the “1,200 prismatic patents” tally may include current-collection and welding structure claims that work regardless of form, so reading the prismatic entry barrier at face value from the count could be an overestimate. Second, conversely, such claims may reach non-prismatic cells if the collector-plate structure overlaps, so pouch and cylindrical cell makers cannot exclude them from FTO (freedom-to-operate review) either.

The time axis is also important. The patent term in Korea and the U.S. is, in principle, 20 years from the filing date. Therefore, many of the early prismatic patents filed from around 1997 are likely to have already expired, and even US9136538B2, with a 2009 priority, is scheduled to expire in 2030. The real burden for late entrants is not the entire count but the rights filed over roughly the last ten-plus years relating to stacking of high-loading electrodes, welding and can structure.

Design-around points: The core of claim 1 of US9136538B2 is “a slit formed in the contact portion of the protrusion and arranged at a predetermined angle with respect to the direction of the electrode assembly.” On the literal wording, a flat contact portion without a slit, or a structure that joins the uncoated portion directly to the terminal without a collector plate, may lack this element. CEO Kim Dong-myung’s remark that the company can produce and supply prismatic cells with its own patents is in line with the judgment that non-infringing territory can be secured by varying designs at this level of detailed shape.

Design-around scenario (counterargument): However, if only the shape of the slit is changed while the same function, improved laser weldability, is achieved in the same way, it may become subject to a doctrine-of-equivalents analysis. Also, Samsung SDI can present multiple claims spanning the can, assembly and current collection structure as a bundle rather than a single patent, so even if a late entrant designs around one or two patents, the burden of negotiating against the portfolio as a whole may remain. Ultimately, a non-infringement determination is possible only by comparing product drawings one-to-one with the claims of valid patents.

Limits and Outlook

Some view this standoff as closer to a signaling war aimed at deterring market entry than a fight over the technology itself. According to reports, some in the industry see the dispute as resembling the early phase of the past LG Chem–SK Innovation dispute, while also assessing that because the two companies’ patent structures are complementary, it is uncertain whether it will escalate into full-scale litigation. Amid automakers’ increasing adoption of prismatic cells, coexistence through license negotiations or design-arounds is more likely than litigation.

There is also a counter-scenario. If a late entrant’s prismatic mass production ramps up in earnest and competition for orders from a specific customer intensifies, the possibility cannot be ruled out that warnings at the level of public remarks turn into actual infringement warning letters or litigation. In that case, regardless of the outcome, the litigation period itself could weigh on customers’ supply-chain decisions. And with Chinese companies ramping up patent filings, there is also concern in the industry that competition between domestic companies could weaken their collective ability to respond in the long run.

The strategic alternative is to reclassify the prismatic portfolio not by count but on a grid of “expiration year × structural layer (can, assembly, current collection).” Doing so separates already-expired rights from core rights that remain valid over the next ten years, narrowing the areas where design-arounds or licenses are actually needed.

Practical action: Planning and IP staff reviewing entry into or procurement of prismatic cells should first pick out, among U.S.-registered prismatic-related patents, those scheduled to expire after 2030, and prepare element comparison charts against their own designs for each of can, electrode assembly and current collection structure.

Items requiring verification

• The publication number and claims of the “solid-state/prismatic patent disclosed by Samsung SDI in 2024, designing cathode and anode current collectors with different thicknesses and materials” cited in the original article
• The counting basis of Samsung SDI’s “1,200 U.S.-registered prismatic patents” (classification codes, whether lapsed rights are included)
• The basis of LG Energy Solution’s roughly 70,000 (applications, registrations or holdings) and the size of its prismatic-related rights within that figure
• The exact date and venue of CEO Kim Dong-myung’s remark

Sources

1. Google Patents, US9136538B2 – Rechargeable battery having current collection plate with protrusion (Samsung SDI Co., Ltd., Robert Bosch GmbH)
2. Newspim, “‘1,200 prismatic patents alone’… Samsung SDI says it will not tolerate technology theft” (2026-03-11)
3. Digital Daily, “LGES: ‘Stop copying and pay tuition’ vs Samsung SDI: ‘Domestic rivals have barely 30 patents'” (2026-03-11)
4. Sisa Journal-e, “As solid-state and prismatic competition heats up, Samsung SDI brings out ‘patent management'” (2026-03-21)
5. Newspim, “‘Prismatic is ours?’… LGES draws a line on Samsung SDI’s ‘patent warning'” (2026-03-24)
6. The Korea Financial Newspaper, “LGES vs Samsung SDI showdown: fierce ‘battery patent’ competition” (2026-03-28)

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