Why Dry Processing Is Becoming Non-Negotiable for Solid-State Batteries

Dry electrode manufacturing is a solvent-free production method in which electrode and electrolyte powders are mechanically processed into a self-supporting film without any liquid carrier — and for solid-state batteries using sulfide electrolytes, it is not merely advantageous but increasingly essential. The reason is chemical incompatibility: N-methylpyrrolidone (NMP), the standard solvent in conventional wet-process electrode coating, chemically degrades sulfide-based solid electrolytes, causing electrolyte decomposition and elevated boundary-layer resistance that directly impairs cell performance.

Beyond chemical compatibility, dry processing eliminates the need for costly solvent recovery infrastructure and enables thicker, denser electrodes that deliver higher energy density. These combined advantages explain why the patent dataset — spanning more than 50 filings across US, WO, EP, CN, JP, IN, and BR jurisdictions from 2012 to 2026 — shows accelerating activity from both battery specialists and automotive OEMs. According to WIPO, solid-state battery patents have grown substantially in recent years, with dry-process methods representing one of the fastest-moving sub-domains.

The overarching motivation across all patent filings is therefore twofold: eliminating NMP and other hazardous solvents that damage sulfide electrolytes, and achieving higher energy density through the thicker, denser electrode structures that dry processing makes possible. Three dominant technical clusters have emerged: fibrillizable binder-based dry film formation, slurry-based co-coating processes that minimise interlayer mixing, and advanced compaction and assembly techniques including warm isostatic pressing, high-line-force calendering, and roll-to-roll continuous processing.

Fibrillization, Calendering, and the Core Dry Process Mechanism

The defining step of dry electrode manufacturing is binder fibrillization under mechanical shear — a process that transforms a powdered binder such as polytetrafluoroethylene (PTFE) into a three-dimensional fibrous network that holds electrode and electrolyte powders together without any solvent. The powder mixture, in which the dry electrolyte powder constitutes 80–97% of the total weight with a fibrillizable binder as the minority component, is subjected to controlled shear force through jet milling, kneading, or high-shear mixing. The fibrillized mixture is then pressed by calendering rolls into a free-standing film, which is laminated onto a current collector to yield the electrode.

LICAP Technologies has established the foundational IP position on this specific architecture, with a core US patent (2023) replicated through PCT, Japanese (2024 and 2026), and Chinese (2024, jointly with Lirong Technology) counterpart filings. The breadth of this filing strategy — covering the same core claims across seven jurisdictions — signals LICAP’s intent to control the dominant dry-process stack architecture globally.

A critical sub-process within fibrillization is monitoring the degree of binder microfibrillization, which LG Energy Solution’s 2024 CN patent addresses by tracking crystallinity of the binder resin to enable feedback control over kneading and pulverisation conditions. Without adequate crystallinity monitoring, particle agglomeration can block process flow channels and compromise roll-to-roll scalability. The same assignee’s system patent adds that the dry electrode film’s edge geometry — prone to irregular, jagged profiles due to the anisotropic nature of the calendered dry mixture — must be actively controlled throughout continuous processing to prevent film cracking and width variation between production batches.

An alternative dry-process variant disclosed by the Tianmu Lake Institute of Advanced Energy Storage Technologies (CN, 2021) avoids the PTFE fibrillization step entirely by using in-situ polymerization. Electrode active materials, unsaturated-bond small-molecule monomers, a conductive agent, and an initiator are mixed and coated onto a current collector, then polymerized at a set temperature to build the 3D network structure. This approach introduces temperature sensitivity and initiator chemistry as new process variables in place of the mechanical shear parameters that govern PTFE fibrillization.

Interface Resistance: The Central Engineering Obstacle

Interface resistance between electrode and solid electrolyte is universally identified across the patent dataset as the central obstacle distinguishing solid-state batteries from liquid-electrolyte cells — and dry processing, despite solving the solvent-compatibility problem, introduces its own interface challenges. Two canonical failure modes have been documented: in the dry-mix-then-press route, the absence of a binder prevents sustained electrode-electrolyte contact; in the wet-mix-then-dry route, solvent evaporation generates pores that elevate resistance.

“Residual porosity from PTFE binder expansion during dry processing leaves inter-particle voids that increase impedance — a problem that simple solvent injection cannot solve in dense, low-porosity electrodes because the liquid cannot penetrate the compressed structure.”

For purely dry-process solid-state electrodes, the pore and void management problem is acute. Beijing Welion New Energy Technology (EP, 2024) directly addresses the residual porosity intrinsic to PTFE-fibrillization-based dry electrodes: the PTFE binder expands during processing, leaving pores that increase impedance and reduce face-to-face contact. Their proposed solution is a eutectic electrolyte incorporated into the dry electrode formulation — upon heating to the eutectic phase-transition temperature, this material liquefies and wicks into inter-particle voids, then solidifies at room temperature to fill them, providing ionic conductivity pathways through previously resistive gaps. The Chinese counterpart filing (Zhongke Chaoneng, CN, 2024) reinforces this approach and explicitly notes that simple solvent injection into dense, low-porosity electrodes is inadequate because the liquid cannot penetrate the compressed structure.

LG Energy Solution has provided the clearest quantitative benchmark for interfacial quality: their 2025 US patent specifies that surface resistance of the negative electrode in contact with the solid electrolyte layer must be 3 mΩ/cm² or less in a properly manufactured unit cell. The related EP filing (2024) identifies sulfide-based electrolytes as particularly problematic due to higher ionic and electronic resistance between electrodes compared with liquid-electrolyte cells, motivating further assembly optimisation. These resistance targets are consistent with the performance thresholds discussed in research published by Nature on solid electrolyte interface engineering.

Hyundai Motor’s approach to interface management in co-coating (US, 2026) is process-parametric: the electrode slurry must be partially dried to 20–50% dryness before the electrolyte slurry is coated over it, and the viscosity ratio of the solid electrolyte slurry to the electrode slurry must fall between 0.2 and 1.0. Too high a ratio causes the electrolyte slurry to sink into the electrode layer and disrupt the N/P ratio; too low a ratio leaves the interface uneven. Drying both layers together at 60–120°C then yields a uniform interface. This “wet-on-partially-dry” technique is a direct response to delamination and N/P ratio drift problems documented in related Kia filings (CN, 2026).

At the atomic level, Jiyi Technology (CN, 2024) proposes atomic layer etching followed by atomic layer deposition of alumina (Al₂O₃) and silicon oxynitride or silicon nitride protective layers between the solid electrolyte layer and the cathode. This reduces short-circuit probability and extends battery life, demonstrating that the interface problem ultimately requires materials engineering solutions complementary to the mechanical process controls. This class of surface engineering is consistent with thin-film deposition research standards documented by IEEE in solid-state device fabrication.

Roll-to-Roll Scalability, Edge Control, and Assembly Challenges

Translating laboratory-scale dry electrode films into high-volume production requires solving three interconnected engineering problems: controlling film edge geometry across continuous processing, achieving reliable adhesion between the dry film and the current collector, and assembling multi-layer stacks without introducing short circuits or compaction non-uniformities. Each of these has attracted independent patent filings, reflecting the maturity gap between the core fibrillization process and the manufacturing systems needed to deploy it at scale.

Edge Geometry and Width Control

LG Energy Solution’s 2023 US and EP patents on dry electrode edge insulation identify the inherently irregular edge geometry of calendered dry film as a persistent yield risk: an additional wet-coating step for the insulating layer is sometimes required, partially negating the benefits of the dry approach. The companion 2024 CN system patent adds that active width-control throughout continuous processing is necessary to prevent film cracking and width variation between production batches. Samsung SDI (EP, 2024) addresses a related problem — intermittent patterning of the film on the metal current collector — by controlling the film supply speed: a primary speed for deposition and a reduced third speed for non-deposition intervals.

Current Collector Adhesion

Dry electrode films lack the wetting-driven adhesion of slurry coatings, making bonding to the current collector a distinct engineering challenge. Samsung SDI’s 2025 CN filings propose two independent solutions: one eliminates the separate primer coating layer by using a bond-enhancement structure; the other introduces deliberate surface topography — protrusions and recesses — on the current collector surface, exploiting mechanical interlocking to replace chemical adhesion. Samsung SDI’s 2025 EP device patent further addresses inhomogeneous packing density by introducing a dispersing rod within a guide chute to actively adjust particle size distribution of the electrode powder before it reaches the rolling nip, preventing thickness variation in the rolled sheet.

Stack Assembly and Compaction

Ford Global Technologies (CN, 2025) addresses contact resistance at the electrode-electrolyte separator boundary through a double-sided positive electrode assembly positioned between two single-sided negative electrode assemblies, with a single high-line-pressure roll-to-roll calendering step compressing the three-layer A-B-A stack simultaneously. This replaces multiple sequential laminations and reduces process complexity. LG Energy Solution’s warm isostatic pressing (WIP) strategy (BR, 2025) takes a different architectural approach: applying WIP to individual unit cells — mono-cells or bi-cells — before stacking, preventing edge short circuits that occur when multiple uncompacted layers are stacked and pressed together. According to OECD technology readiness assessments, process-level innovations in battery stack assembly are among the most commercially critical barriers to solid-state battery scale-up.

Volkswagen’s two CN filings (2023 and 2024) represent a decoupled architecture: the 2023 patent applies roll-to-roll slurry coating of ceramic solid electrolyte precursor followed by high-energy surface-emitter sintering to form the dense ceramic separator layer, bypassing dry-film calendering for the electrolyte component entirely. The 2024 process apparatus patent then separates film formation from densification into two independent stages, allowing independent optimisation of each. Even in dry-process cells, residual moisture management remains a concern: Hyundai Motor’s 2026 JP patent on vacuum drying of unit cell stacks demonstrates that residual moisture in solid electrolytes degrades electrochemical performance even after solvent-free processing, requiring dedicated vacuum drying as a post-assembly step.

Patent Landscape: Who Is Leading and Where Innovation Is Heading

LG Energy Solution and LG Chem dominate the dataset quantitatively, with at least 10 distinct filings spanning EP, US, JP, IN, BR, and CN jurisdictions. Their portfolio covers dry electrode edge insulation, binder fibrillization control and monitoring, all-solid-state battery assembly using WIP, interface surface resistance quantification, and electrode slurry concentration control — a system-level approach that addresses the full manufacturing chain rather than individual process steps. LICAP Technologies, by contrast, is the focused specialist in pure dry-process electrode and electrolyte film manufacture, with its core US patent (2023) and PCT, JP, and CN counterparts establishing foundational claims on fibrillizable-binder-based dry electrolyte film formation.

Samsung SDI has filed aggressively on manufacturing equipment and film structure — particle dispersion control (EP, 2025), intermittent film deposition (EP, 2024), current-collector adhesion (CN, 2025), and multi-active-material dry electrode composition (EP, 2025). Hyundai Motor and Kia focus on electrode-electrolyte co-coating and assembly process control, with recent filings on partial-drying co-coating viscosity ratios (US, 2026), vacuum drying of unit cell stacks (JP, 2026), and dry-process self-supporting electrode films (CN, 2025). Volkswagen and Ford represent the OEM-tier entrants, each contributing process equipment and cell assembly innovations. Beijing Welion New Energy Technology and Zhongke Chaoneng represent Chinese independent innovators targeting the residual porosity problem through eutectic electrolyte gap-filling — an approach distinct from the Western mainstream.

The trend within the dataset is clear: filings from 2020 to 2023 predominantly define the core processes, while 2024 to 2026 filings shift toward equipment design, process control systems, and scalability — with growing attention to quantified interfacial resistance targets, roll-to-roll edge quality, and moisture management. This trajectory is consistent with the technology maturation patterns tracked by EPO in its annual patent index for energy storage technologies, where process control and manufacturing system patents typically follow foundational process patents by two to four years. The PatSnap IP Intelligence platform provides real-time tracking of these filing trends across all major jurisdictions, enabling R&D teams to monitor competitive positioning as the landscape continues to evolve rapidly.

For R&D teams and IP professionals monitoring this space, the PatSnap Insights blog provides ongoing analysis of emerging patent clusters in battery technology. The shift toward process control and equipment patents in 2024–2026 suggests that the competitive battleground is moving from “can we make a dry electrode?” to “can we make it consistently, at scale, with quantified interfacial performance?”