All-Solid-State Battery Pressure-Structure Patents — The Dilemma of a Battery That Only Works Under Pressure

① What is in the spotlight

An all-solid-state battery works without a liquid electrolyte, but in exchange it must be “pressed” so its solid particles stay in contact, and this pressing is needed twice. Once during manufacturing, to densify the layers, and once during use, to maintain contact. The patent landscape is moving in two directions: preventing the edge short circuits that are a side effect of the first pressing, and reducing the size of the second.

Start with the industry context. A perspective published in Nature Energy in August 2025 summarized that stack pressure (pressure applied along the direction in which the cell is stacked) is essential for ensuring solid-solid interfacial contact in batteries, and that the required pressure spans multiple orders of magnitude depending on the chemistry. In other words, there is still no agreed answer to the question of “how hard to press.”

That is where the tension comes from. The harder the cell is pressed to improve contact, the easier it becomes for electrode edges to crack or detach, and detached fragments become a cause of internal short circuits linking the cathode and anode. This article answers three questions: why is pressing needed, how have patents solved the edge problem that pressing creates, and where are the paths to avoid or go beyond that scope of rights?

② Basic principle

A liquid electrolyte fills the gaps between particles on its own, like water. A solid electrolyte cannot. The analogy is building a castle from dry sand: if the grains have few points of contact, the bridges that ions cross are broken. That is why manufacturing includes a pressing step that squeezes electrode and solid electrolyte together to enlarge the contact area between particles.

The problem is that pressing does not give equally good results across the whole cell. The center becomes dense, but the edges, which have no lateral support, are instead prone to crumbling and detaching. Fragments of active material that break off can become a path bridging the cathode and anode across the thin electrolyte layer. This is the dilemma: pressing intended to improve contact simultaneously creates a new defect pathway.

Pressing during use is a separate challenge. During charge and discharge the electrodes repeatedly swell and shrink, so a constant stack pressure must be applied from outside the cell to maintain contact. A 2020 study by Doux et al. in Advanced Energy Materials reported, in room-temperature all-solid-state lithium-metal cells, stable operation at 5 MPa stack pressure: more than 1,000 hours in a lithium symmetric cell and more than 200 cycles in full cells at room temperature. The researchers interpreted this as suggesting the possibility of using lithium-metal anodes at “reasonable stack pressures.”

• Manufacturing pressure: up to the hundreds-of-MPa range; the purpose is densification and interface formation.
• Operating pressure: levels of a few MPa are being studied; the purpose is maintaining contact during use.
• Common side effect: edge damage and the resulting risk of internal short circuits.

③ Comparison

Gathering the pressure figures in public documents into one table makes the difference between “manufacturing” and “operation” pressure clear. Units are aligned to MPa, and conversions are the editorial team’s calculations.

Document	Stage	Pressure condition	Reported result / limitation
KR20160060171A background (Hyundai Motor)	Manufacturing (coin cell)	350 MPa	Discharge capacity 1,000 mAh/g (sulfur basis); states that applying it to large cells of 100×100 mm² or more is unreasonable
US20260088331A1 specification (Solid Power)	Manufacturing (pouch cell, WIP)	20k-60k psi (about 138-414 MPa), fluid up to 90°C	Points out edge pinching and short-circuit risk when pressed without protection
KR102529492B1 claim 1 (Hyundai Motor, Kia)	Manufacturing (edge insulating layer)	3-5 ton/m² (as literally written)	States fundamental prevention of edge short circuits as its effect
Doux et al., Adv. Energy Mater. 2020	Operation (stack pressure)	5 MPa	Lithium symmetric cell over 1,000 h; full cell over 200 cycles (room temperature)

What this table says: Manufacturing pressures are in the hundreds of MPa, such as 138-414 MPa and 350 MPa, whereas operating-pressure research sits around 5 MPa. Because the two differ by orders of magnitude, patent analysis should also separate “manufacturing pressure” from “operating pressure.”

Methods for preventing edge short circuits have also changed over time. The table below places the prior art cited in the KR20190056666A specification side by side with an external-jig approach published later.

Approach	Document	Key means	Limitation or feature noted
Insulator insertion	JP2015-125893	Insert an insulator at the electrode edge	The edge may detach during pressing and destroy the insulator itself
Taped pouch	JP2015-76272	A pouch containing tape holds detached fragments	High likelihood of shorts due to gaps between pouch and edge
Pressure-plastic polymer coating	KR20190056666A (KR102529492B1)	Coat edges, seal in pouch, press to form an insulating layer	The pressing step itself completes the insulating layer
External frame jig	US20260088331A1	Rigid perimeter + flexible interior frame blocks force on the cell end	Solved in the process jig, not inside the cell

What this table says: Solutions moved from “adding a part that withstands pressing” to “using pressing to form an insulating layer,” and then to “controlling the direction of pressure itself.” This can be read as a sign that the arena of rights competition is widening from in-cell materials to process jigs.

④ Patent perspective

Bibliographic data. KR20190056666A, “Method for manufacturing an all-solid battery and all-solid battery manufactured thereby,” was filed by Hyundai Motor Company and Kia on November 17, 2017 and published on May 27, 2019. It was later granted as KR102529492B1 on May 4, 2023; according to Google Patents its legal status is Active, with an anticipated expiration of November 17, 2037.

Gist of the claims. In substance, claim 1 is a manufacturing method that “includes forming a cathode layer, an anode layer and an electrolyte layer, and forming an insulating layer of pressure-plastic polymer at the edges, wherein the insulating layer is formed by sealing a cell whose edges are coated with pressure-plastic polymer material in a pouch and pressing it at 3-5 ton/m².” The specification describes this pressing as cold isostatic pressing, in which liquid pressure is applied uniformly in all directions at low temperature, and gives examples of the polymer as mixtures of two or more of polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC) and others. Claims 13 onward also cover the battery itself made by this method.

Filing history. The same applicant’s KR20160060171A (filed November 17, 2014; published May 30, 2016) recorded, in its background, the 350 MPa pressed coin-cell example and the limits of large-area application. However, according to Google Patents this application was rejected/ceased and never granted, so it should be read only as evidence of the technology trajectory, not as a right. The 2017 filing can be seen as the next step after the recognition that “high pressure is difficult at large area,” an improvement that brings pressing itself into the process as an element.

Design-around points. Claim 1 requires all four elements (pressure-plastic polymer, edge coating, pouch sealing, pressing at 3-5 ton/m²), so literally lacking any one of them may reduce the risk of infringement.

• Design-around scenario: move edge protection from an in-cell coating to an external frame jig, or form the insulating layer under conditions outside the numerical range.
• Counterargument: if conditions just outside the numerical range produce the same effect, infringement under the doctrine of equivalents may be disputed. And because the external-jig approach has its own application, such as US20260088331A1, one must also check the possibility of falling into another scope of rights while avoiding one.

⑤ Limits and outlook

Pressing equipment adds volume and weight to cells and modules, so it fundamentally conflicts with designs that prioritize energy density. That is why the patent landscape is gradually shifting from “how hard to press” toward “materials and structures that maintain contact at lower pressure.” The optimistic outlook is that a solid-electrolyte composition capable of pressure-free or low-pressure operation emerges and becomes a turning point for commercialization.

There is also a counter-scenario. Even if operating pressure falls to a few MPa, manufacturing pressure may remain in the hundreds of MPa. In that case edge short circuits do not disappear, and manufacturing-process and jig patents may become even more important. The strategic alternative is to manage the IP portfolio along two axes: “operating-pressure reduction (materials)” and “control of manufacturing-pressure side effects (process and jigs).”

One more interpretation from this article. Converting the “3-5 ton/m²” of claim 1 literally gives about 0.03-0.05 MPa, orders of magnitude different from the manufacturing pressures (hundreds of MPa) in the same table. In a claim with a numerical limitation, the boundary of the range becomes the baseline for design-around, so the actual condition the unit denotes needs to be confirmed against the working examples in the specification.

Practical action: IP staff planning an all-solid-state cell process should map their pressing conditions (pressure, temperature, sealing) against the four elements of claim 1 of KR102529492B1, confirm the interpretation of the “3-5 ton/m²” range from the specification’s working examples, and then add it to the FTO review list.

Items requiring verification

• The actual pressing condition denoted by the “3-5 ton/m²” unit in claim 1 of KR102529492B1 (comparison with working-example values)
• Current legal status and applicants of JP2015-125893 and JP2015-76272
• Published figures for operating stack pressure actually applied to large-format automotive all-solid-state cells

Sources

1. Google Patents, KR20190056666A / KR102529492B1 – Method for manufacturing an all-solid battery and all-solid battery manufactured thereby (Hyundai Motor Company, Kia)
2. Google Patents, KR20160060171A – A cathode for all-solid-state battery, its manufacturing process, and all-solid-state battery comprising the same (Hyundai Motor Company)
3. Google Patents, US20260088331A1 – Flexible frame for use in applying high pressure in the manufacture of a solid-state battery cell (Solid Power Operating Inc)
4. Doux et al., “Stack Pressure Considerations for Room-Temperature All-Solid-State Lithium Metal Batteries,” Advanced Energy Materials, 2020
5. Li, Q. et al., “The critical importance of stack pressure in batteries,” Nature Energy, 2025