All-Solid-State Battery Interfacial-Resistance Patents — Why Does Resistance Rise When Solids Meet?

What is in focus: the resistance that arises where solids meet

A leading bottleneck blocking the commercialization of all-solid-state batteries is the resistance at the interface (the boundary where two materials meet) between the solid electrolyte and the electrode. An early attempt to solve this problem through ‘structure’ rather than material composition is KR20130136150A, filed by Hyundai Motor Company on June 4, 2012. This article places that publication side by side with Chery Automobile’s sulfide-coating patent published in 2026 and summarizes the directions in which interfacial-resistance patents have framed their rights.

Start with the industry context. Oxide-based solid electrolytes are a field in which many companies have shown interest. Samsung Electro-Mechanics CEO Jang Duk-hyun was reported to have said at the company’s 2023 shareholders’ meeting that, building on its multilayer ceramic capacitor (MLCC) technology, it holds technology that can produce solid oxides at high temperature, and that it is preparing a small-form-factor all-solid-state battery. The same report said Samsung Electro-Mechanics had filed 14 all-solid-state battery patent applications with the Korean Intellectual Property Office.

The source of tension is interfacial resistance, a wall that companies working with oxide-based materials commonly run into. A liquid electrolyte can seep into the microscopic gaps on an electrode surface, but when solid meets solid, achieving perfectly tight physical contact is difficult. This article answers three questions. Why does resistance grow at a solid-solid interface? What structure did KR20130136150A use to address it, and what is the status of that right today? And how should planning and IP staff read this kind of ‘structural interface patent’?

Basic principle: a pile of gravel touches only at points

Oxide-based solid electrolytes have high material stability and are easy to handle, but the industry consensus is that the interfacial resistance between the electrode material and the solid electrolyte is a major problem. Solid particles lack the fluidity that a liquid has to fill in gaps, so microscopic voids remain at particle-to-particle boundaries, and ion transport is blocked at those points. As charge-discharge cycles repeat, volume changes widen these voids further, creating a vicious cycle in which resistance keeps growing.

By analogy, solid electrolyte powder and electrode particles are like gravel of different sizes poured together. Pieces of gravel touch each other only at a few points, so the channels through which the ‘water’ of lithium ions can flow are narrow and easily broken. A liquid electrolyte is like water filling the spaces between the gravel, so contact area is almost never a problem, but in a solid electrolyte this ‘water’ is absent.

The KR20130136150A specification addresses this problem directly. It states that when a solid high-ion conductor is applied in powder form inside a cell, high interfacial resistance arises between solids, and it divides the locations where resistance arises into two.

• Inside the electrode: the interface between the electrode active material and the solid electrolyte
• Between the electrodes: the interface between the cathode and anode (cathode/separator/anode or cathode/anode)

This patent’s solution is to build a ‘perforated frame’ first instead of pouring gravel. A dense, pore-free layer (the non-porous part) serves as a wall that electrically separates the two electrodes, and electrode active material is filled into the open pores of the porous layer (the porous part) attached to that face, so that the solid electrolyte and active material meet over a wide area.

Comparison: three approaches to interfacial resistance

The table below organizes the two patents covered in the original article and the background art by interfacial approach. The KR20130136150A figures are ranges stated in the publication; for the Chery patent, the original text could not be accessed, so only the reported content is included.

Item	Powder-type solid electrolyte (background art)	KR20130136150A (Hyundai Motor)	CN122348252A (Chery Automobile)
Target electrolyte	Solid high-ion-conductor powder	Oxide- and sulfide-based, etc. (LiSICON, Garnet, LiPON, etc. listed)	Sulfide-based
Interface approach	Particle mixing and pressing	Integrated structure of a non-porous part + porous part bonded to at least one face	Functional coating layer on the electrolyte surface
Key figures	–	Porous-part porosity 20-90%, pore size 0.01-50 μm	No figures in public reports
Porous-part thickness	–	Anode side 10-500 μm, cathode side 10-300 μm (stated in specification)	–
Main problem addressed	High interfacial resistance between solids	Resistance at two interfaces: inside the electrode and between electrodes	Interface degradation during fast charging
Legal status	–	Ceased	Reported as at publication stage (2026-07-08)

What this table says: Hyundai Motor’s 2012 solution increases ‘contact area’ through a porous structure with 20-90% porosity, while Chery Automobile’s 2026 solution coats the sulfide surface to raise ‘the stability of the interface itself.’ Even for the same interface problem, the core elements of the rights split between structural figures and surface composition.

Country-level statistics also help in reading the filing trend. The Korean Intellectual Property Office’s (KIPO) February 2026 analysis of IP5 (Korea, US, Japan, China, Europe) all-solid-state battery patents is as follows.

Office	Cumulative filings (2004-2023)	Average annual growth (%)
Japan	9,881	8.6
China	6,749	33.6
Korea	5,770	18.0
US	4,417	12.3
Europe	2,173	7.8

What this table says: Japan has the most cumulative filings, but China has the highest growth rate at 33.6%. In the same analysis, Toyota (2,337) and LG Energy Solution (2,136) ranked first and second among applicants, and annual filings rose from 331 in 2004 to 3,938 in 2023.

Patent perspective: a ceased publication and a living sibling patent

Bibliographic data: KR20130136150A (title: ‘Solid High-Ion Conductor for Lithium Metal Battery and Lithium Metal Battery Using the Same’) was filed by Hyundai Motor Company, with a filing and priority date of June 4, 2012, and published on December 12, 2013. Google Patents shows its legal status as Ceased, and no granted publication was found. The original article introduced this patent right after Samsung Electro-Mechanics’ remarks on solid-state preparation, but this publication is Hyundai Motor’s application, not Samsung Electro-Mechanics’.

Claim summary (restated): Claim 1 is a solid high-ion conductor for a lithium metal battery consisting of the following elements.

• A non-porous part with a dense, pore-free structure
• One or more porous parts bonded to at least one face of the non-porous part and having multiple open pores
• A porosity of the porous part of 20-90%

The original article described the porous part as bonded to ‘both faces’ of the non-porous part, but the claim language says ‘at least one face.’ The two-sided structure is the embodiment shown in the drawings, and the scope of the right is written to also cover a structure with a porous part on only one face.

Insight: the ‘sibling patent’ filed on the same day is still alive. Hyundai Motor filed a separate application on the same day (June 4, 2012), which was granted on April 8, 2014 as KR101382869B1 (‘Composite Solid High-Ion Conductor for Battery and Lithium-Sulfur Battery Using the Same’). According to Google Patents, this granted patent is Active, with an anticipated expiration of June 4, 2032. Its claim 1 is a structure in which a dense part surrounds the side edges of a porous flat body (porous part) that can be filled with electrode active material, preventing the active material from leaking out above its melting temperature.

In other words, the publication covered in the original article has ceased, but a variant structure of the same idea still stands as a right in Korea. If an FTO (freedom-to-operate) review ends by looking only at the status of a single publication, such sibling applications can be missed.

Design-around points: The ceased KR20130136150A itself is no longer a right against which infringement can be asserted in Korea, so the non-porous/porous laminated structure is close to free-to-practice territory as far as this publication is concerned. Rather, this publication can be used as prior art when challenging the novelty and inventive step of later interface-structure patents. Google Patents lists 8 later documents citing this publication, including LG Energy Solution’s US11264618B2. By contrast, KR101382869B1 requires ‘a dense part surrounding the side edges of the porous part,’ so a design that does not wrap the edges of the porous part with a dense layer may keep a distance from literal infringement.

Design-around scenario (counterargument): However, even if edge sealing is performed by a separate member (e.g., a sealant) rather than a dense part, achieving the same function of preventing active-material leakage in substantially the same way could become subject to a doctrine-of-equivalents analysis. Conversely, from the patentee’s side, KR20130136150A filed on the same day and other prior art on porous/dense composite structures could be used to challenge the validity of KR101382869B1. Ultimately, both design-around potential and the stability of the right can only be judged by comparing the actual cell structure with the claims one to one.

Chery Automobile CN122348252A: The original article said this patent was filed ‘recently’ in 2026, but based on the reports we could confirm, it was reported as published on July 8, 2026. According to the report, it concerns forming a coating layer with functional groups on the surface of a sulfide electrolyte to reduce interface instability and structural degradation during fast charging. Because the original text could not be accessed on Google Patents, the claim language was not verified, and any judgment of its scope is deferred until the original is obtained.

Limits and outlook

The original article stated that global patent filings for core all-solid-state battery technology reached 20,798 as of May 2023, but the primary source for this figure could not be confirmed this time. The verifiable KIPO analysis (February 2026) likewise identifies Toyota as the top applicant. As the view that interfacial resistance is a major bottleneck to commercialization persists, structural-design patents that physically address the interface are likely to grow in share alongside material-composition patents.

There is also a contrary scenario. An integrated structure that fills active material into the pores of a porous part works only when sintering temperature, pore control and the active-material filling process all line up, so at mass-production scale, process costs could offset its advantages. The fact that one of Hyundai Motor’s 2012 structural patents ceased without being granted can also be read as a case showing how easily structural claims can overlap with prior art. In that case, the industry’s center of gravity could shift toward surface coatings and interlayer composition, as in the Chery case.

The strategic alternative is to track interface patents along two axes, ‘structure (porosity, thickness, arrangement)’ and ‘surface chemistry (coatings, interlayers)’, and to manage ceased publications separately as a prior-art pool for each axis. Because ceased publications serve both as grounds for free practice and as weapons for challenging competitors’ patents, this is likely to give more defensive strength than a portfolio that collects only living rights.

Practical action: Planning and IP staff evaluating a solid electrolyte with a porous/dense composite structure should not judge based on KR20130136150A alone; they should first build a table comparing their own structure with the ‘dense part surrounding the side edges’ element of the same applicant’s same-day application (KR101382869B1, expected to expire 2032-06-04).

Items requiring verification

• How KR20130136150A came to cease (whether and when a refusal decision was issued), per KIPO’s prosecution history
• The filing date, original claim language and applicant’s legal entity name for CN122348252A (per the China National Intellectual Property Administration gazette)
• The primary source and counting basis for the original article’s figure of ‘20,798 global filings as of May 2023’
• Whether Samsung Electro-Mechanics’ 14 solid-state battery applications address oxide interface structures

Sources

1. Google Patents, KR20130136150A – Solid High-Ion Conductor for Lithium Metal Battery and Lithium Metal Battery Using the Same (Hyundai Motor Company)
2. Google Patents, KR101382869B1 – Composite Solid High-Ion Conductor for Battery and Lithium-Sulfur Battery Using the Same (Hyundai Motor Company)
3. THE ELEC, Samsung Electro-Mechanics files 14 all-solid-state battery patents (2023-03-20)
4. CarNewsChina, Chasing 600 Wh/kg: Chery files sulfide patent to fix solid state cell degradation (2026-07-08)
5. Paxetv, report on KIPO all-solid-state battery patent trends (2026-02-18)

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