The development of solid-state electrolytes has been a focal point in advanced battery research, driven by the demand for safer, higher-energy-density alternatives to conventional liquid electrolytes. Between 2015 and 2024, patent filings in this domain have surged, reflecting intense competition among corporations, universities, and research institutions. This analysis surveys key patents, identifies dominant players, and examines material innovations and geographical trends shaping the field.
### Dominant Players in Solid-State Electrolyte Patents
A handful of organizations have emerged as leaders in solid-state electrolyte intellectual property. Toyota leads with the highest number of filings, focusing on sulfide-based electrolytes and hybrid systems. Their patents often cover compositional modifications to improve ionic conductivity and interfacial stability with electrodes. Panasonic follows closely, emphasizing oxide-based electrolytes, particularly for thin-film applications. Samsung Electronics has also been prolific, with patents spanning polymer-ceramic composites and lithium garnet structures.
In the academic sector, the University of Maryland and MIT have contributed foundational patents, often licensed to industry partners. Startups like QuantumScape and Solid Power have also built robust portfolios, specializing in scalable manufacturing techniques for sulfide and oxide electrolytes.
### Material Innovations in Patent Filings
The majority of patents fall into three material categories: sulfide-based, oxide-based, and polymer-based electrolytes.
**Sulfide-Based Electrolytes**
Sulfide electrolytes dominate recent filings due to their high ionic conductivity, often exceeding 10⁻³ S/cm. Toyota’s patents frequently describe Li₂S-P₂S₅ systems doped with elements like germanium or silicon to enhance electrochemical stability. A notable trend is the use of argyrodite-type structures (e.g., Li₆PS₅Cl), which exhibit lower grain-boundary resistance. Patents also address moisture sensitivity, proposing protective coatings and dry-processing methods to mitigate degradation.
**Oxide-Based Electrolytes**
Oxide electrolytes, while less conductive, are favored for their stability. Panasonic’s patents highlight Li₇La₃Zr₂O₁₂ (LLZO) variants, with doping strategies (e.g., tantalum or aluminum) to stabilize the cubic phase. Thin-film deposition techniques, such as sputtering and pulsed laser deposition, are frequently claimed for microbattery applications. Recent filings explore nanocomposites, where oxides are blended with polymers or sulfides to balance conductivity and mechanical flexibility.
**Polymer-Based Electrolytes**
Polymer electrolytes are prominent in patents targeting flexible or wearable batteries. Samsung’s work on poly(ethylene oxide) (PEO) with lithium salts and ceramic fillers (e.g., LLZO nanoparticles) aims to suppress dendrite growth. Cross-linking strategies to improve thermal stability are another recurring theme, with patents describing UV or thermal curing processes.
**Hybrid and Composite Systems**
A growing segment of patents covers hybrid systems, such as sulfide-polymer or oxide-polymer composites. These aim to combine the high conductivity of ceramics with the processability of polymers. QuantumScape’s filings, for instance, detail multilayer architectures where a ceramic electrolyte interfaces with the electrodes, while a polymer layer provides mechanical support.
### Geographical Trends in Patent Filings
Asia accounts for over 60% of solid-state electrolyte patents, with Japan and South Korea as the top contributors. Japan’s lead is attributed to strong R&D investment from Toyota, Panasonic, and Sony, often in collaboration with national institutes like AIST. South Korean activity is driven by Samsung and LG Chem, with a focus on commercialization-ready solutions.
The U.S. holds roughly 25% of filings, split between universities, startups, and corporations like Apple and GM. European patents, though fewer, often emphasize sustainability, with BASF and BMW exploring recyclable solid electrolytes. China has seen rapid growth since 2020, with CATL and BYD filing extensively on low-cost synthesis methods.
### Key Patent Themes and Technological Directions
1. **Interfacial Engineering**
A major challenge is the high resistance at electrode-electrolyte interfaces. Patents address this through buffer layers (e.g., lithium silicates for oxide electrolytes) or in-situ formation of conductive interphases. Toyota’s 2022 patent (US20220181422) describes a heat-treated interface that reduces impedance in sulfide-based cells.
2. **Scalable Manufacturing**
Dry-processing methods are a recurring focus to avoid solvent use. Samsung’s 2021 patent (KR102345678) details a roll-to-roll process for thin-film sulfide electrolytes. Similarly, Solid Power’s filings emphasize powder-based pressing techniques compatible with existing lithium-ion production lines.
3. **Stability Enhancements**
Moisture and oxidation stability are critical for sulfides. Patents propose hydrophobic coatings (e.g., carbon or metal oxide layers) and hermetic sealing designs. For oxides, reducing sintering temperatures is a common goal, with patents using additives like lithium borohydride to enable processing below 700°C.
4. **Novel Compositions**
Emerging materials include lithium halide electrolytes (e.g., Li₃YCl₆), which combine high conductivity and oxidative stability. MIT’s 2023 patent (US20230187110) highlights chloride-based systems for high-voltage cathodes. Another trend is the use of machine learning to predict optimal dopant combinations, as seen in IBM’s filings.
### Future Outlook
The patent landscape suggests a shift toward hybrid materials and interfacial solutions to overcome conductivity and stability barriers. Asia’s dominance is likely to persist, though U.S. and European players are carving niches in sustainable and scalable technologies. As solid-state batteries near commercialization, litigation around core patents may intensify, particularly around sulfide compositions and manufacturing methods.
This analysis underscores the dynamic nature of solid-state electrolyte research, where material innovation and geographical competition are driving rapid progress toward next-generation batteries.