Last Updated on 09/03/2025 by Bonnen Battery
Key Materials for Solid-State Batteries: A Comprehensive Analysis of Solid-State Electrolytes
The global solid-state battery industry is accelerating rapidly, with technological pathways becoming increasingly defined. According to major manufacturers’ mass production plans, small-scale production is expected to advance to 2026–2027, while large-scale adoption is anticipated post-2030. Solid-state batteries are regarded as the most promising next-generation battery technology, prompting intensified investments from global battery manufacturers, automakers, and upstream/downstream material and equipment suppliers.
1. Overview of Solid-State Electrolytes
Solid-state electrolytes ⇱ are the critical variable in solid-state batteries. These batteries replace the liquid electrolyte in traditional lithium-ion batteries partially or entirely with solid-state electrolytes. Based on electrolyte content, batteries are categorized into four types:
- Liquid (25wt% electrolyte),
- Semi-solid-state (5–10wt% electrolyte),
- Quasi-solid-state (<5wt% electrolyte),
- All-solid-state (0wt% electrolyte).
Semi-solid-state batteries use a hybrid solid-liquid electrolyte (5–10wt% liquid), while quasi-solid-state batteries contain <5wt% liquid. All-solid-state batteries eliminate liquid electrolytes entirely. Due to unresolved interfacial challenges, all-solid-state batteries face technical barriers to mass production, making semi-solid-state variants the current focus for industrialization. Semi-solid-state systems reduce liquid electrolyte content while incorporating solid electrolytes to enhance safety. However, their reliance on residual liquid electrolyte means they are not a direct stepping stone to all-solid-state batteries but rather an exploratory phase to advance solid electrolyte industrialization.
Semi-solid-state batteries remain rooted in liquid lithium-ion systems, utilizing oxide, sulfide, polymer, and other electrolytes, with oxides dominating the market. In contrast, all-solid-state batteries are expected to adopt sulfide electrolytes, characterized by complete liquid electrolyte removal and reliance on solid electrolytes for lithium-ion conduction.
2. Oxide Solid-State Electrolytes
Oxide solid-state electrolytes ⇱ exhibit moderate ionic conductivity and typically retain ~5% liquid electrolyte. Examples include:
- LLZO (Li₇La₃Zr₂O₁₂): Density = 5.07 g/cm³,
- LLTO (Li₀.₃₃La₀.₅₅TiO₃): Density = 5.01 g/cm³,
- LAGP (Li₁.₅Al₀.₅Ge₁.₅(PO₄)₃): Density = 3.56 g/cm³,
- LATP (Li₁.₃Al₀.₃Ti₁.₇(PO₄)₃): Density = 2.93 g/cm³.
LLZO (Lithium Lanthanum Zirconium Oxide)
LLZO is among the most attractive solid-state electrolytes, featuring cubic or tetragonal crystal structures, with cubic phases delivering superior ionic conductivity. Aluminum doping enhances room-temperature conductivity. However, its reliance on rare metals (e.g., zirconium, lanthanum) raises material costs.
- Qingtao Energy has mastered LLZO/LLTO production and developed composite electrolyte membranes via high-speed dispersion and tape-casting. Its 10GWh solid-state battery project and collaboration with SAIC have yielded batteries for new EV models.
- LanGu New Energy supplies LATP/LLZO/LLTO in kilogram-to-ton quantities to Weilan New Energy and others.
- Shanghai Xiba achieves LLZO ton-scale production, supplying BYD’s blade solid-state battery project.
- Ganfeng Lithium focuses on oxide thick-film technology, inventing a flexible inorganic-polymer composite electrolyte. Its 0.3GWh hybrid solid-liquid production line powers Dongfeng’s E70 model.
- Tiamen Advanced delivers LATP/LLZO/LLTO powders/slurries to Weilan New Energy.
- Sanxiang New Materials and Oriental Zirconium (global leader with >50% market share) supply zirconium oxide for LLZO, targeting 10,000-ton nano-zirconium capacity by 2025.
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| Comparison | Liquid-State | Semi-Solid-State | All-Solid-State |
| Cathode | NCM/LFP | High-nickel/Ultra-high-nickel NCM | High-nickel NCM, Li-rich Mn-based, S/air |
| Anode | Graphite (Si-doped) | Si-based/Li metal | Li metal |
| Separator | Wet/dry-processed | Wet-processed + coated (large pores) | Not required |
| Electrolyte | Liquid (20-10 wt%) | Liquid (10-1 wt%) + LiTFSI-enhanced | Solid-state electrolyte |
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| Iteration | Type | Electrolyte | Separator | Anode | Cathode |
| Gen 1 | Semi-Solid-State | Partially replaced with solid-state | Retained (conventional) | Graphite/Si-C (with pre-lithiation) | NCM |
| Gen 2 | All-Solid-State | Fully replaced with solid-state | Removed (retained in designs) | Graphite/Si-C (with pre-lithiation) | NCM |
| Gen 3 | All-Solid-State | Fully replaced with solid-state | Removed (retained in designs) | Lithium metal | NCM |
| Gen 4 | All-Solid-State | Fully replaced with solid-state | Removed (retained in designs) | Lithium metal | Sulfides/LiNi₀.₅Mn₁.₅O₄/Li-rich Mn-based |
LLTO (Lithium Lanthanum Titanium Oxide)
This perovskite-type electrolyte offers high ionic conductivity (~10⁻⁴–10⁻³ S/cm at room temperature) but suffers from poor lithium metal wettability, dendrite growth risks, and instability with commercial cathodes like LiFePO₄. LLTO is integral to Weilan New Energy and SVOLT’s electrolyte systems.
LAGP (Lithium Aluminum Germanium Phosphate)
LAGP combines high ionic conductivity and chemical stability. Key players include Deeptek (260 Wh/kg oxide-based batteries) and Narada Power (350 Wh/kg all-solid-state batteries passing safety tests).
LATP (Lithium Aluminum Titanium Phosphate)
LATP, a composite of lithium aluminum titanium phosphate and polymer, has a raw material cost of ~¥20,000/ton, with current prices at ¥100,000–300,000/ton. Notable players:
- Jinlongyu: Validated 10kg-level LATP production, with 10-ton annual capacity.
- Putailai: Completed LATP pilot trials, producing high-density, high-conductivity electrolyte sheets.
- MGL: Certified LATP materials with leading solid-state battery firms.
Others include Kunlun New Materials, XTC New Energy, Pride New Energy, and Ruide New Materials.
Commercial Progress: Ganfeng Lithium, Tiamen Advanced, Qingtao Energy, Betray, and Putailai have achieved oxide electrolyte commercialization. Sinocera and Ronbay Technology have also developed oxide electrolytes compatible with high-nickel cathodes. Battery firms like BYD, Weilan New Energy, and Tailan New Energy are advancing oxide-based batteries with energy densities of 300–500 Wh/kg. Overall, China leads in oxide electrolyte commercialization.
3. Sulfide Solid-State Electrolytes
Sulfides are the mainstream path for all-solid-state batteries, offering high ionic conductivity and low density. For example, the Li₇P₃S₇.₅O₃.₅ (LPSO) electrolyte developed by Prof. Ma Cheng’s team at USTC has a density of 1.70 g/cm³.
Composition and Challenges
Sulfide electrolytes ⇱ primarily consist of lithium and sulfur, supplemented with phosphorus, silicon, germanium, or halides. Key challenges include high costs, poor interfacial stability, and air sensitivity.
- Binary systems (Li₂S-P₂S₅): Players include Xingfa Group and Yuegui Co.
- Ternary systems (e.g., Li₂S-P₂S₅-GeS₂): Yunnan Germanium supplies GeCl₄ for synthesis.
Cost Reduction Strategies
Efforts focus on lowering Li₂S costs and substituting Li₂O for Li₂S. TrendForce estimates sulfide-based cell BOM costs at ¥1–2/Wh initially, potentially dropping to ~¥1/Wh by 2030 at 10GWh+ scales.
Production Methods
- Carbothermal reduction (solid-phase): Adopted by Ronbay Technology and Enjie Co.
- Gas-phase synthesis: Leveraged by XTC New Energy for high-purity Li₂S.
Global Players
Chinese firms (CATL, Enpower, SVOLT, Gotion High-Tech), Japanese automakers (Toyota, Panasonic), Korean firms (Samsung SDI, SK On), and U.S.-based Solid Power are driving sulfide-based all-solid-state battery development.
4. Conclusion
Solid-state batteries hold strategic significance in global competition. With accelerating industrialization, battery manufacturers and automakers are scaling investments, creating opportunities across the supply chain. Oxide electrolytes are advancing rapidly in China, while sulfides remain the long-term focus for all-solid-state systems. Cost reduction, interfacial optimization, and material innovation will dictate the pace of commercialization.
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