Ultrasonic Spray Coating Solid Electrolyte — PatSnap Eureka
Ultrasonic Spray Coating for Uniform Solid Electrolyte Thin Films in Bipolar Battery Stacks
USC applies 30–130 kHz acoustic energy to produce conformal, pinhole-free electrolyte layers with material utilization exceeding 90% — enabling the sequential multi-layer deposition that bipolar stack architectures demand.
How Ultrasonic Spray Coating Achieves Uniform Solid Electrolyte Films
Ultrasonic spray coating (USC) applies high-frequency acoustic energy — typically 30–130 kHz — to a liquid precursor feed, atomizing it into a fine, low-velocity aerosol of narrowly distributed droplet sizes. Unlike pneumatic spray, which relies on high-pressure gas jets that can induce turbulence and uneven deposition, USC produces a nearly laminar, low-momentum spray that settles uniformly onto a substrate. This mechanism is directly leveraged in solid electrolyte deposition for batteries, as formalized in a Chinese patent from Zhejiang Fengli New Energy Technology, which describes controlling ultrasonic atomization frequency at 30–130 kHz, carrier gas flow at 1–5 L/min, and liquid feed rate at 1–10 mL/min to deposit composite solid electrolyte slurries onto electrode substrates.
The low carrier gas pressure — only kilopascal-level flow — is a defining advantage of USC compared to air-atomized spraying. This near-splatter-free condition prevents material back-spray and produces coatings that are thinner, more uniform, and more controllable, with nozzle-to-substrate distances optimized at 20–50 mm. The resulting films have inorganic solid electrolyte particle sizes of 0.5–10 μm dispersed in organic polymer matrices, with solid content maintained at 15–20 wt% to balance flowability and coating density. The ability to combine inorganic (e.g., LLZO, LLTO) and organic polymer electrolyte components into a single-pass conformal coating is particularly relevant to bipolar stack designs, where each repeating unit requires an independently deposited, continuous electrolyte layer to prevent cross-talk between adjacent cells.
Surface tension management is the primary obstacle to smooth film formation via USC. Research from Jilin University showed that introducing a low-surface-tension diluent (methanol) into formulations enabled smooth, phase-separated films — a finding directly transferable to ionic-conductor slurry formulations for solid electrolytes. The principle applies whether the target film is an organic emitter or a lithium-conducting ceramic-polymer composite: the droplet-substrate interaction must be controlled to avoid dewetting, crater formation, or agglomeration. For deeper analysis of USC patent filings, PatSnap's analytics platform provides landscape mapping across all relevant assignees.
Ultrasonic vibration also plays a secondary role at the electrode-electrolyte interface beyond deposition. Research from Wuhan University of Technology demonstrated that applying high-frequency ultrasonic vibration to a pre-formed polymer electrolyte/cathode interface reduces interfacial resistance by 96.2%, by locally melting the electrolyte and generating intimate contact. This suggests that USC-deposited films can be further consolidated post-deposition using in-line ultrasonic annealing steps, opening a pathway to sintering-free bipolar cell fabrication. For life sciences and advanced materials applications, see also PatSnap's materials science solutions.
USC Process Parameters and Competing Method Benchmarks
Key quantitative findings from patent and literature analysis across 50+ documents, visualised from verified data in the PatSnap Eureka dataset.
USC Parameter Window for Solid Electrolyte Deposition
Key process parameter ranges from the Zhejiang Fengli patent for USC of composite solid electrolyte slurries onto electrode substrates, yielding >90% material utilisation.
Deposition Method Landscape in Dataset
Distribution of dominant technical approaches across 50+ patent documents and research publications in the dataset, showing USC as an emerging high-precision subset of wet-chemical methods.
Oxford All-Spray-Deposited Three-Layer Cell: Key Separator and Electrolyte Properties
Properties of the spray-deposited Al₂O₃-based separator and polymeric ionic liquid electrolyte enabling the first all-spray-deposited LiFePO₄/Al₂O₃/Li₄Ti₅O₁₂ full cell (Oxford, 2022) — a direct analogue of bipolar stack sequential layer deposition.
Conformal Coverage on Complex Electrode Geometries
A critical requirement for bipolar battery stacks is that the solid electrolyte layer must conformally coat electrode surfaces — including rough, porous, or topographically complex geometries — without pinholes or discontinuities that would cause internal short circuits.
3D Micro-Pillar Conformal Deposition of LLT Electrolyte
Ultrasonic spray deposition of precursor solutions achieved conformal coatings of tungsten oxide (WO₃) negative electrodes and amorphous lithium lanthanum titanium oxide (LLT) solid electrolyte on micro-scale silicon template structures. Both materials produced fully covering coatings on these 3D substrates. Electrochemical half-cells fabricated by coating WO₃ with LLT demonstrated functional electron-blocking behaviour — a key requirement for solid electrolytes in series-stacked cells. The work explicitly confirmed that ultrasonic spray deposition could reach all surfaces of micro-pillar geometries, demonstrating coverage that sputtering cannot achieve on re-entrant structures.
Functional electron-blocking confirmedSequential Spray-Printed All-Organic Solid-State Battery
A polymeric ionic liquid solid-state electrolyte (σ_Li: ~10⁻⁴ S cm⁻¹) was spray-printed as a second functional layer infiltrating through a porous spray-printed electrode, with additional electrode and electrolyte layers deposited sequentially to form a symmetric all-organic battery. This sequential, spray-based layer-by-layer approach directly mirrors the architecture required in bipolar stacks, where each cathode/electrolyte/anode unit must be deposited in sequence with precise interlayer adhesion. See PatSnap customer case studies for real-world deployment examples.
σ_Li ~10⁻⁴ S cm⁻¹ achievedFirst All-Spray-Deposited Three-Layer Full Cell
A spray-deposited Al₂O₃-based separator (50 nm particles, 5–22 μm thick, ~58% porosity) enabled a sequentially deposited LiFePO₄/Al₂O₃/Li₄Ti₅O₁₂ full cell with competitive rate performance — the first reported all-spray-deposited three-layer cell assembly. This represents the most direct experimental analogue to bipolar stack fabrication via USC methods. The PatSnap analytics platform tracks all sequential deposition patent filings from Oxford and competing groups.
First all-spray 3-layer full cellUSC Functional Separator: Nitride/Oxide Coatings for Dendrite Suppression
A patent from China Electronics Technology Group Corporation 18th Research Institute formalizes USC for battery separator fabrication: spray liquid containing nitride or oxide coating material, binder, and dispersant is deposited on separator surfaces using USC at nozzle heights of 100–200 mm, nozzle travel speeds of 50–100 mm/s, liquid flow rates of 0.5–2 mL/min, and ultrasonic power of 1–4 W. The resulting functional coating improves mechanical strength, thermal stability, and regulates lithium ion deposition at the negative electrode — directly relevant to suppressing dendrite penetration across bipolar electrolyte films. The EPO and CNIPA both show growing filing activity in this area.
0.5–2 mL/min · 1–4 W USC powerCompeting Deposition Techniques vs Ultrasonic Spray Coating
Understanding why USC is specifically advantageous requires benchmarking it against the competing methods that dominate the broader field. Data drawn from 50+ patent documents and peer-reviewed publications.
| Method | Vacuum Required | 3D Conformal | Throughput | Temp. Budget | Key Limitation for Bipolar Stacks |
|---|---|---|---|---|---|
| Ultrasonic Spray (USC) | No | Yes — micro-pillar confirmed | High (roll-to-roll compatible) | Room temp / mild heating | Surface tension management required; slurry formulation sensitivity |
| PVD / Magnetron Sputtering | Yes — expensive | No — line-of-sight only | Low — inherently slow | Moderate | Cannot coat 3D/rough electrodes; vacuum infrastructure cost; low throughput |
| Electrostatic Spray (ESD) | No | Partial | Medium | Low–moderate | High electric fields; ESD risk near sulfide electrolytes; cone-jet sensitivity to solvent conductivity |
| Curtain Coating (ETH Zurich) | No | No — planar only | >80 m/min web speed | Low | Cannot accommodate textured or 3D electrode geometries; films below 15 μm only on flat substrates |
| Thermal Spray | No | Partial | High | High thermal budget | High temperatures incompatible with sulfide or polymer electrolytes |
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Key Players and Innovation Trends in USC for Solid-State Batteries
Analysis of the 50+ document dataset reveals several dominant entities shaping this technical domain, with a notable trend toward USC process development aligned with bipolar-specific requirements.
Applied Materials, Inc.
Holds the highest patent volume in the dataset, with at least four distinct filings across US, WO, and CN jurisdictions on ceramic coating on battery separators. Their layer-by-layer nano/micro-particle coating approach is methodologically adjacent to USC, establishing a foundational IP position on controlled-thickness, uniform ceramic films for lithium-ion battery cells.
Forschungszentrum Jülich
Contributes both the definitive PVD review and the landmark 3D ultrasonic spray deposition study, positioning it as a bridging institution between vacuum-based and wet-chemical spray techniques for solid-state batteries. Their 2017 work on WO₃/LLT micro-pillar conformal coatings remains the most direct evidence for USC's 3D coverage capability.
University of Oxford (Materials)
The leading academic contributor on sequential spray deposition of integrated battery multilayers, with two significant publications demonstrating full-cell assembly via spray methods — including the first all-spray-deposited three-layer LiFePO₄/Al₂O₃/Li₄Ti₅O₁₂ cell reported in 2022. Their work provides the most direct experimental precedent for bipolar stack USC fabrication.
Zhejiang Fengli & China Electronics Technology Group
Represent emerging Chinese patent activity specifically on USC of solid electrolytes and separator functional coatings — reflecting strong domestic R&D investment. The Zhejiang Fengli patent formalizes the 30–130 kHz / 1–10 mL/min parameter window with >90% utilisation, while China Electronics Technology Group Corp. 18th Research Institute addresses dendrite suppression via USC-coated functional separators.
Why USC Is the Enabling Technology for Bipolar Stack Solid Electrolyte Deposition
The convergence of evidence from patent filings and peer-reviewed literature identifies ultrasonic spray coating as uniquely suited to the manufacturing demands of bipolar battery stacks. Its advantages are not incremental — they are categorical: USC is the only wet-chemical method demonstrated to achieve conformal coverage on 3D micro-pillar electrode geometries, as confirmed by Forschungszentrum Jülich's 2017 work on LLT electrolyte deposition.
The process operates at room temperature, requires no vacuum infrastructure, and achieves material utilisation exceeding 90% — a critical cost advantage for the multi-layer, multi-unit architectures inherent to bipolar stacks. Sequential layer-by-layer spray deposition has been experimentally demonstrated at the full-cell level by University of Oxford (2022), providing a direct fabrication precedent. The PatSnap platform enables R&D teams to track all emerging filings in this space.
Post-deposition ultrasonic vibration — reducing interfacial resistance by 96.2% — provides a complementary consolidation step that eliminates the need for high-temperature sintering, preserving the integrity of polymer and sulfide electrolyte components. Surface tension control via low-surface-tension diluents is the critical formulation variable that must be addressed in translating USC from laboratory demonstration to production-scale bipolar stack manufacturing. For enterprise-grade IP monitoring and competitive intelligence, see PatSnap's trust centre.
- USC at 30–130 kHz yields >90% slurry utilisation — critical for cost-sensitive bipolar manufacturing
- Conformal 3D coverage confirmed on micro-pillar geometries — impossible with PVD/sputtering
- First all-spray three-layer full cell demonstrated (Oxford, 2022) — direct bipolar stack analogue
- Post-deposition ultrasonic vibration reduces interfacial resistance by 96.2%
- Room temperature processing — compatible with sulfide and polymer electrolytes
- USC-coated functional separators suppress dendrite penetration in tightly stacked configurations
Ultrasonic Spray Coating for Solid Electrolyte Deposition — Key Questions Answered
Ultrasonic spray coating applies high-frequency acoustic energy typically in the range of 30–130 kHz to atomize liquid precursor feeds into a fine, low-velocity aerosol of narrowly distributed droplet sizes. This frequency window avoids over-spraying, achieves precise droplet distribution, and yields slurry utilization rates exceeding 90%.
PVD and magnetron sputtering are fundamentally line-of-sight processes that cannot easily coat complex 3D or rough electrode surfaces, require expensive vacuum infrastructure, and have inherently slow deposition rates — making them poorly suited to the high-throughput, roll-to-roll manufacturing demanded by bipolar stack fabrication at scale. USC operates at room temperature or mild heating, requires no vacuum, and generates droplets with sufficient kinetic energy to wet complex surfaces without damaging thermally or chemically sensitive electrolyte materials.
Surface tension control is the critical process variable governing film uniformity in USC. Low-surface-tension diluents are required to suppress dewetting and crater formation. Research from Jilin University showed that introducing a low-surface-tension diluent (methanol) into PEDOT:PSS formulations enabled smooth, phase-separated films — principles directly applicable to ionic conductor slurry formulations.
Research from Wuhan University of Technology demonstrated that applying high-frequency ultrasonic vibration to a pre-formed polymer electrolyte/cathode interface reduces interfacial resistance by 96.2%, by locally melting the electrolyte and generating intimate contact. This suggests that USC-deposited films can be further consolidated post-deposition using in-line ultrasonic annealing steps, opening a pathway to sintering-free bipolar cell fabrication.
Yes. The University of Oxford demonstrated the first reported all-spray-deposited three-layer cell assembly: a spray-deposited Al₂O₃-based separator (50 nm particles, 5–22 μm thick, ~58% porosity) enabled a sequentially deposited LiFePO₄/Al₂O₃/Li₄Ti₅O₁₂ full cell with competitive rate performance, as published in 2022.
The Zhejiang Fengli patent describes inorganic solid electrolyte particle sizes of 0.5–10 μm dispersed in organic polymer matrices, with solid content maintained at 15–20 wt% to balance flowability and coating density. The ability to combine inorganic (e.g., LLZO, LLTO) and organic polymer electrolyte components into a single-pass conformal coating is particularly relevant to bipolar stack designs.
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References
- Wet-Chemical Synthesis of 3D Stacked Thin Film Metal-Oxides for All-Solid-State Li-Ion Batteries — Forschungszentrum Jülich, 2017
- Method for Preparing a Positive or Negative Electrode Sheet for a Solid-State Battery — Zhejiang Fengli New Energy Technology, 2020
- Ultrasonic Spray Coating to Optimize Performance of Bio-Electrochemical Systems — Politecnico di Torino, 2023
- Ultrasonic Spray Coating Polymer and Small Molecular Organic Film for Organic Light-Emitting Devices — Jilin University, 2016
- Promotion of Interface Fusion of Solid Polymer Electrolyte and Cathode by Ultrasonic Vibration — Wuhan University of Technology, 2022
- Sequential Deposition of Integrated Cathode–Inorganic Separator–Anode Multilayers for High Performance Li-Ion Batteries — University of Oxford, 2022
- Single-Step Spray Printing of Symmetric All-Organic Solid-State Batteries Based on Porous Textile Dye Electrodes — University of Oxford, 2019
- Lithium Battery Separator with a Functional Coating on the Surface and Method for Preparation — China Electronics Technology Group Corp. 18th Research Institute, 2025
- Physical Vapor Deposition in Solid-State Battery Development: From Materials to Devices — Forschungszentrum Jülich, 2021
- Sputter-Deposited Amorphous Li₃PO₄ Solid Electrolyte Films — National Institute for Materials Science (NIMS), 2022
- Ultra-High Throughput Manufacturing Method for Composite Solid-State Electrolytes — ETH Zurich, 2021
- Method for Producing Lithium Secondary Battery Thick Film by Electrostatic Slurry Spraying — Industry-University Cooperation Foundation Hanyang University, 2022
- Electrostatic Spray Deposition of YSZ Thin Films with Different Microstructures — 2005
- Ceramic Coating on Battery Separators — Applied Materials, Inc., 2015
- Direct Thermal Spray Synthesis of Li-Ion Battery Components — The Regents of the University of Michigan, 2011
- Thermal Spray Synthesis of Supercapacitor and Battery Components — Mridangam Research Intellectual Property Trust, 2014
- Thin Film Deposition Techniques in Surface Engineering Strategies for Advanced Lithium-Ion Batteries — Shanghai Advanced Research Institute, Chinese Academy of Sciences, 2023
- WIPO — World Intellectual Property Organization
- EPO — European Patent Office
- Forschungszentrum Jülich
- University of Oxford
- Jilin University
All data and statistics on this page are sourced from the references above and from PatSnap's proprietary innovation intelligence platform.
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