In this study, I examine the global and Chinese patent landscapes of sulfide solid electrolyte cells and construct a quantitative model to identify their core patents. The sulfide solid electrolyte cell is widely regarded as a leading candidate for next-generation power batteries because of its high ionic conductivity and intrinsic safety. However, the rapid growth of patent applications has produced a large volume of heterogeneous data, in which defensive filings often obscure truly foundational inventions. From the perspective of library and information science and competitive intelligence, I combine patentometrics with multi-attribute decision-making to reveal technological trajectories, competitive positions, and core patent assets in the field of sulfide solid electrolyte cells.
My research is guided by three questions. First, how has the global and Chinese patent landscape of sulfide solid electrolyte cells evolved in terms of application trends, legal status, technology flows, and innovation actors? Second, how can a robust evaluation model be built to identify core patents in this highly cross-disciplinary domain? Third, what strategic implications can be drawn for latecomer firms and policy makers seeking to overcome existing patent barriers in sulfide solid electrolyte cell commercialization?
To answer these questions, I use the incoPat global patent database and retrieve patent records up to the end of 2025. After manual and automatic denoising, I obtain 12,996 patent records related to sulfide solid electrolyte cells, including 12,898 invention applications and 98 utility models. From this corpus, I extract 4,407 valid invention patents for core patent identification. I then build a three-dimensional indicator system covering technology, law, and market value, and I apply a combined weighting strategy based on the entropy method and the CRITIC method. Finally, I use the TOPSIS model to rank patents and identify the core set. The results show that 13 patents can be regarded as core patents in the sulfide solid electrolyte cell field.
Data Sources and Processing
I use the incoPat platform as the primary data source because it integrates patent data from more than 173 countries, organizations, and regions and provides rich bibliographic, legal, and citation fields. The retrieval strategy follows three stages: initial retrieval, comprehensive retrieval, and supplementary retrieval. In the initial stage, I identify core keywords, relevant IPC classes, and key applicants. In the comprehensive stage, I expand keywords and classification codes using truncation and logical operators. In the supplementary stage, I focus on major applicants and add related family and citation records. After retrieval, I merge application numbers, remove irrelevant records, and standardize applicant names.
The final dataset contains 12,996 records. The recall rate is 87.25%, and the precision rate is 90.56%, which meets the basic requirements for patent analysis. For the core patent identification model, I keep only valid invention patents, resulting in 4,407 samples. This filtering step removes withdrawn, expired, and fee-related invalid patents, ensuring that the evaluation focuses on legally stable and commercially relevant patents in the sulfide solid electrolyte cell domain.
| Stage | Action | Result |
|---|---|---|
| Initial retrieval | Core keywords, IPC classes, key applicants | Preliminary patent set |
| Comprehensive retrieval | Expanded keywords and classification codes | Broad coverage of sulfide solid electrolyte cell patents |
| Supplementary retrieval | Major applicants, families, citations | Improved completeness |
| Denoising and standardization | Automatic and manual cleaning, applicant name merging | 12,996 final records |
| Validity filtering | Remove invalid, withdrawn, and expired patents | 4,407 valid invention patents |
Global Patent Landscape of Sulfide Solid Electrolyte Cells
The global patent landscape of sulfide solid electrolyte cells has passed through three main phases. From 1981 to 2010, annual applications remained very low, reflecting a period of basic scientific exploration. From 2011 to 2016, the discovery of ultra-high ionic conductivity in sulfide systems triggered a wave of patenting. Since 2017, applications have grown exponentially, reaching a peak of more than 1,400 filings in 2023. This growth indicates that sulfide solid electrolyte cells have moved from laboratory validation to industrialization-oriented competition.
In terms of legal status, the global dataset shows 5,007 invalid patents (38%), 4,407 valid patents (34%), and 3,582 pending patents (28%). Among invalid patents, 1,891 are expired, 926 are inactive due to unpaid fees, and 1,109 are abandoned or withdrawn. The high number of expired patents indicates that early foundational technologies in sulfide solid electrolyte cells are already in the public domain. At the same time, the large number of valid patents confirms that major players have built dense legal fences around current materials and manufacturing processes. The pending patents are concentrated in recent years and are likely to cover scale-up production and system integration.
| Legal Status | Number | Share | Interpretation |
|---|---|---|---|
| Invalid | 5,007 | 38% | Expired, unpaid, abandoned, or withdrawn |
| Valid | 4,407 | 34% | Active legal rights, mainly held by leading firms |
| Pending | 3,582 | 28% | Under examination, concentrated in recent years |
Technology flow analysis reveals a highly asymmetric global structure. Japan is the main technology exporter in sulfide solid electrolyte cells. It holds 2,283 domestic patents and has filed 635 patents in the United States, 526 in China, and 334 in South Korea. In contrast, China has 3,608 domestic patents but only 45 in the United States, 15 in Japan, and 13 in South Korea. This pattern indicates that China’s patent portfolio is highly domestic and lacks international spillover, while Japan has built a global defensive network around sulfide solid electrolyte cells.
From the perspective of target markets, the United States receives large inflows from Japan, South Korea, and Germany. Germany also attracts significant Japanese filings, reflecting the strategic importance of the European automotive supply chain. The global technology flow matrix therefore shows that sulfide solid electrolyte cell innovation is concentrated in a few countries, with Japan occupying a central hub position.
The IPC composition of global patents shows that H01M10/0562 (solid electrolyte materials) is the dominant class, followed by H01M4/36 (composite electrode materials), H01M4/58 (inorganic active materials for positive electrodes), and H01M4/62 (conductive agents and binders). This distribution indicates that material development remains the primary battleground, while electrode-electrolyte interface engineering and manufacturing processes are becoming increasingly important for sulfide solid electrolyte cell commercialization.
| IPC Class | Meaning | Global Patent Count |
|---|---|---|
| H01M10/0562 | Solid electrolyte materials | 2,715 |
| H01M4/36 | Composite electrode materials | 1,143 |
| H01M4/58 | Inorganic active materials for positive electrodes | 566 |
| H01M4/62 | Conductive agents and binders | 418 |
| H01B13/00 | Manufacture of conductors | 282 |
| H01M10/056 | Battery electrolytes in general | 273 |
| H01B1/06 | Solid ionic conductors | 250 |
Global innovation actors are highly concentrated. A leading Japanese automaker holds 1,076 patent applications, far ahead of a major Japanese materials company with 454 and a Korean conglomerate with 388. Other prominent actors include a Japanese mining company with 271, a Japanese electronics group with 332, and a Korean battery maker with 214. Chinese actors are represented by a Chinese academy of sciences with 112, a Chinese university with 95, a Chinese startup with 95, and a major Chinese battery manufacturer with 93. This distribution shows that Japanese firms dominate the entire supply chain of sulfide solid electrolyte cells, while Chinese actors are still stronger in academic research than in industrial commercialization.
| Rank | Applicant Group | Patent Count | Country/Region |
|---|---|---|---|
| 1 | Japanese automaker | 1,076 | Japan |
| 2 | Japanese materials company | 454 | Japan |
| 3 | Korean conglomerate | 388 | South Korea |
| 4 | Japanese electronics group | 332 | Japan |
| 5 | Japanese mining company | 271 | Japan |
| 6 | Korean battery maker | 214 | South Korea |
| 7 | Chinese academy | 112 | China |
| 8 | Chinese university | 95 | China |
| 9 | Chinese startup | 95 | China |
| 10 | Chinese battery manufacturer | 93 | China |
Chinese Patent Landscape of Sulfide Solid Electrolyte Cells
In China, the development of sulfide solid electrolyte cells started later but has accelerated rapidly. From 1993 to 2010, annual applications remained below 20. From 2011 to 2015, policy support and academic interest pushed applications above 80 per year. From 2016 to 2020, applications entered the hundreds, although 2020 saw a temporary decline. From 2021 to 2025, applications grew exponentially, reaching 630 in 2024. The apparent drop in 2025 is partly due to the 18-month publication lag for invention patents and the delayed publication of utility models.
| Period | Characteristics | Approximate Annual Applications |
|---|---|---|
| 1993–2010 | Basic theory period | < 20 |
| 2011–2015 | Policy-guided start | 20–83 |
| 2016–2020 | Industrial acceleration | 100–300 |
| 2021–2025 | Explosive sprint | > 500 (peak 630 in 2024) |
The legal status of Chinese patents in sulfide solid electrolyte cells shows a strong screening effect. There are 1,356 pending patents (37.58%), 1,305 valid patents (36%), and 947 invalid patents. Among the pending patents, 1,291 are in substantive examination, indicating a large pipeline of future rights. Among invalid patents, 460 were rejected and 257 were withdrawn, together accounting for 75.71% of invalid cases. Only 216 patents lapsed due to unpaid fees, which is a relatively low share. This low lapse rate suggests that applicants maintain high confidence in the commercial prospects of sulfide solid electrolyte cells.
| Legal Status | Number | Share | Key Feature |
|---|---|---|---|
| Pending | 1,356 | 37.58% | 1,291 in substantive examination |
| Valid | 1,305 | 36.00% | Granted and maintained |
| Invalid | 947 | 26.42% | Rejection and withdrawal dominate |
China’s IPC composition differs from the global pattern. H01M10/0562 (895 patents) and H01M4/36 (808 patents) are almost equal, showing that Chinese innovators treat electrolyte materials and electrode-electrolyte interface engineering as an integrated problem. H01M4/58 (227 patents) appears frequently, indicating a strong interest in sulfide-based lithium-sulfur systems. H01M10/058 and H01M10/42 also appear, reflecting a shift toward cell structure, manufacturing, and safety management. This triangular structure of interface synergy, high-energy systems, and process support is a distinctive feature of China’s sulfide solid electrolyte cell patent portfolio.
| IPC Class | Meaning | Chinese Patent Count |
|---|---|---|
| H01M10/0562 | Solid electrolyte materials | 895 |
| H01M4/36 | Composite active materials | 808 |
| H01M4/58 | Non-oxide active materials | 227 |
| H01M4/62 | Conductive agents and binders | 169 |
| H01M10/056 | Battery electrolytes in general | 158 |
| H01M10/058 | Cell structure and manufacturing | 95 |
| H01M10/0525 | Rocking-chair lithium batteries | 80 |
| H01M10/42 | Battery management and safety | 72 |
Regionally, China’s sulfide solid electrolyte cell patents are concentrated in a few innovation clusters. Shanghai ranks first with 298 patents, followed by Beijing with 277, Shenzhen with 269, Changsha with 172, Ningbo with 154, Hangzhou with 132, Wuhan with 125, Changzhou with 122, and Nanjing with 104. The Yangtze River Delta cluster, including Shanghai, Ningbo, Hangzhou, Changzhou, and Nanjing, accounts for a large share of filings. Beijing relies on top universities and research institutes, while Shenzhen is driven by battery and electronics firms. Changsha benefits from materials science and metallurgy, and Wuhan leverages its automotive base.
| Rank | City/Province | Patent Count | Innovation Driver |
|---|---|---|---|
| 1 | Shanghai | 298 | Research and manufacturing integration |
| 2 | Beijing | 277 | Academic and basic research |
| 3 | Shenzhen | 269 | Industrial application and system integration |
| 4 | Changsha | 172 | Materials science and metallurgy |
| 5 | Ningbo | 154 | Chemical and battery manufacturing |
| 6 | Hangzhou | 132 | Private R&D and digitalization |
| 7 | Wuhan | 125 | Automotive industry transformation |
| 8 | Changzhou | 122 | Battery supply chain |
| 9 | Nanjing | 104 | University-industry collaboration |
China’s applicant structure is markedly different from that of Japan and South Korea. Enterprises hold 1,761 patents (48.81%), while universities hold 1,412 and research institutes hold 346, together accounting for 48.73%. Individuals hold 81, and government agencies hold 8. This near parity between enterprises and academic institutions indicates that sulfide solid electrolyte cells in China are still in a transition from basic research to industrial application. Leading enterprises file patents with broader claims, while universities and institutes hold many foundational materials patents.
| Applicant Type | Patent Count | Share | Interpretation |
|---|---|---|---|
| Enterprise | 1,761 | 48.81% | Industrial application and process integration |
| University | 1,412 | 39.13% | Basic research and materials discovery |
| Research institute | 346 | 9.60% | Applied research and national projects |
| Individual | 81 | 2.24% | Limited due to high entry barriers |
| Government agency | 8 | 0.22% | Minor direct filing |
The top Chinese applicants include a Chinese academy with 102 patents, a startup with 95, a university with 95, and a major battery manufacturer with 93. The activity levels vary widely. Some emerging firms show 100% activity within the last five years, indicating a saturation R&D strategy. In contrast, long-established institutes have lower recent activity but hold highly cited foundational patents. Average claim counts are highest for the major battery manufacturer (16 claims), followed by an automotive firm (14.90) and an energy company (14.62), showing a strong focus on legal fencing. Average citations are highest for a leading university (4.68) and a materials institute (4.11), confirming that academic institutions hold many foundational sulfide solid electrolyte cell patents.
| Rank | Applicant Type | Patents (20 years) | Active Rate | Avg. Claims | Avg. Citations |
|---|---|---|---|---|---|
| 1 | Chinese academy | 102 | 36.27% | 9.94 | 3.01 |
| 2 | Chinese startup | 95 | 97.89% | 8.93 | 1.15 |
| 3 | Chinese university | 95 | 43.16% | 9.40 | 1.94 |
| 4 | Battery manufacturer | 93 | 58.06% | 16.00 | 0.36 |
| 5 | Energy company | 61 | 75.41% | 14.62 | 1.69 |
| 6 | Power battery firm | 51 | 84.31% | 10.46 | 0.98 |
| 7 | Materials institute | 49 | 40.82% | 8.59 | 4.11 |
| 8 | Comprehensive university | 38 | 42.11% | 8.04 | 3.78 |
Patent operations in China remain underdeveloped. Technology transfers were rare before 2010 and became more frequent after 2017, peaking at 51 transfers in 2021. Licensing, however, is extremely low. In most years, licensing counts are zero, with a maximum of only five in 2021. Pledge activities started later, with a peak of 12 in 2021 and 11 in 2024. This pattern suggests a “possession over sharing” strategy, where firms prefer to hold patents internally or transfer ownership rather than license to potential competitors. For sulfide solid electrolyte cells, the lack of licensing indicates that a mature patent operation ecosystem has not yet formed.
Core Patent Identification Model
To identify core patents in sulfide solid electrolyte cells, I construct an evaluation system with three first-level dimensions: technology value, legal value, and market value. The technology dimension includes citation received, citation made, IPC count, and inventor count. The legal dimension includes claim count and simple family size. The market dimension includes transfer/license count and family country count. This system reflects the multi-dimensional nature of core patents and avoids the bias of single-indicator screening.
| First-Level Dimension | Second-Level Indicator | Code | Description |
|---|---|---|---|
| Technology value | Citations received | X11 | Number of times cited by later patents |
| Technology value | Citations made | X12 | Number of references to prior patents |
| Technology value | IPC count | X13 | Breadth of technical coverage |
| Technology value | Inventor count | X14 | R&D human resource input |
| Legal value | Claim count | X21 | Scope of legal protection |
| Legal value | Simple family size | X22 | Density of legal protection |
| Market value | Transfer/license count | X31 | Commercial implementation |
| Market value | Family country count | X32 | Global market coverage |
I standardize all indicators using min-max normalization because all eight indicators are positively correlated with patent value. The formula is:
$$x’_{ij} = \frac{x_{ij} – \min(x_{ij})}{\max(x_{ij}) – \min(x_{ij})}$$
For the entropy method, I calculate the proportion of each patent in each indicator, then compute the entropy value and the divergence factor. The entropy value is:
$$e_j = -\frac{1}{\ln m} \sum_{i=1}^{m} p_{ij} \ln p_{ij}$$
where
$$p_{ij} = \frac{x’_{ij}}{\sum_{i=1}^{m} x’_{ij}}$$
The entropy weight is:
$$w_j^{E} = \frac{1 – e_j}{\sum_{j=1}^{n} (1 – e_j)}$$
For the CRITIC method, I calculate the standard deviation and the conflict intensity of each indicator. The standard deviation is:
$$\sigma_j = \sqrt{\frac{\sum_{i=1}^{m}(x’_{ij} – \bar{x}_j)^2}{m-1}}$$
The information quantity is:
$$C_j = \sigma_j \sum_{k=1}^{n} (1 – r_{jk})$$
where \(r_{jk}\) is the correlation coefficient between indicator \(j\) and indicator \(k\). The CRITIC weight is:
$$w_j^{C} = \frac{C_j}{\sum_{j=1}^{n} C_j}$$
I combine the two objective weights using equal linear weighting:
$$w_j = 0.5 w_j^{E} + 0.5 w_j^{C}$$
The combined weights are then used in the TOPSIS model. I construct the weighted decision matrix:
$$Q = (q_{ij})_{m \times n}, \quad q_{ij} = w_j x’_{ij}$$
The positive ideal solution and negative ideal solution are:
$$K^+ = \left\{ \max_i q_{ij} \right\}, \quad K^- = \left\{ \min_i q_{ij} \right\}$$
The Euclidean distances to the ideal solutions are:
$$E_i^+ = \sqrt{\sum_{j=1}^{n}(q_{ij} – K_j^+)^2}, \quad E_i^- = \sqrt{\sum_{j=1}^{n}(q_{ij} – K_j^-)^2}$$
The relative closeness is:
$$S_i = \frac{E_i^-}{E_i^+ + E_i^-}$$
I define core patents as those with a value greater than 0.9 of the maximum value:
$$0.9 S_{\max} < S_i \le S_{\max}$$
Patents with values between 0.4 and 0.9 of the maximum are considered key patents, while those below 0.4 are ordinary patents. This classification allows me to separate core patents from the broader population of sulfide solid electrolyte cell patents.
Empirical Results and Core Patent Analysis
After cleaning, I obtain 4,407 valid invention patents for sulfide solid electrolyte cells. The descriptive statistics show wide variation across indicators. Citations received range from 0 to 135, with a mean of 3.358. Citations made range from 0 to 355, with a mean of 20.982. IPC count ranges from 1 to 29, with a mean of 6.418. Inventor count ranges from 1 to 29, with a mean of 4.947. Claim count ranges from 1 to 117, with a mean of 14.923. Simple family size ranges from 1 to 72, with a mean of 11.177. Transfer/license count ranges from 0 to 13, with a mean of 0.923. Family country count ranges from 1 to 17, with a mean of 4.671.
| Indicator | Minimum | Maximum | Mean | Std. Dev. |
|---|---|---|---|---|
| Citations received | 0 | 135 | 3.358 | 9.906 |
| Citations made | 0 | 355 | 20.982 | 51.232 |
| IPC count | 1 | 29 | 6.418 | 4.269 |
| Inventor count | 1 | 29 | 4.947 | 3.070 |
| Claim count | 1 | 117 | 14.923 | 12.342 |
| Simple family size | 1 | 72 | 11.177 | 13.317 |
| Transfer/license count | 0 | 13 | 0.923 | 1.386 |
| Family country count | 1 | 17 | 4.671 | 4.230 |
The weight results show that the entropy method assigns the highest weights to citations received (31.42%) and citations made (23.53%), reflecting the highly skewed distribution of citation data in sulfide solid electrolyte cells. The CRITIC method assigns the highest weight to citations made (50.59%), followed by simple family size (13.63%) and claim count (12.29%). The combined weights place citations made first (37.06%), citations received second (20.53%), and simple family size third (11.66%). This combined weighting balances dispersion and conflict, avoiding the distortion that can occur with a single objective method.
| Indicator | Entropy Weight | CRITIC Weight | Combined Weight |
|---|---|---|---|
| Citations received | 31.42% | 9.64% | 20.53% |
| Citations made | 23.53% | 50.59% | 37.06% |
| IPC count | 3.59% | 4.34% | 3.97% |
| Inventor count | 3.22% | 3.54% | 3.38% |
| Claim count | 4.94% | 12.29% | 8.62% |
| Simple family size | 9.68% | 13.63% | 11.66% |
| Transfer/license count | 16.71% | 1.44% | 9.08% |
| Family country count | 6.91% | 4.53% | 5.72% |
The patent value distribution is positively skewed. Most patents fall between 0.1 and 0.3. Only 13 patents exceed 0.9, and these are identified as core patents. Another 541 patents fall between 0.4 and 0.9 and are classified as key patents. The remaining 3,853 patents are ordinary patents. This distribution confirms that core patents in sulfide solid electrolyte cells are extremely rare and that the field is dominated by incremental and defensive filings.
| Value Interval | Number of Patents | Classification |
|---|---|---|
| (0, 0.1] | — | Ordinary |
| (0.1, 0.2] | 1,763 | Ordinary |
| (0.2, 0.3] | 1,158 | Ordinary |
| (0.4, 0.9] | 541 | Key |
| (0.9, 1] | 13 | Core |
The 13 core patents are held by a small group of multinational firms. Their publication numbers, applicants, countries, and main IPC classes are summarized below. I have anonymized individual inventor names to comply with privacy requirements, but the corporate applicants are shown because they are essential to understanding the competitive landscape of sulfide solid electrolyte cells.
| Rank | Publication Number | Application Year | Publication Year | Applicant | Country | Main IPC |
|---|---|---|---|---|---|---|
| 1 | US8617748B2 | 2007 | 2013 | Seeo | United States | H01M4/02 |
| 2 | US12294050B2 | 2021 | 2025 | Polyplastics | United States | H01M10/0562 |
| 3 | US12294051B2 | 2022 | 2025 | Polyplastics | United States | H01M10/0525 |
| 4 | US12482857B2 | 2024 | 2025 | Polyplastics | United States | H01M10/0562 |
| 5 | US12374717B2 | 2024 | 2025 | Polyplastics | United States | H01M10/0562 |
| 6 | US12237511B2 | 2024 | 2025 | Polyplastics | United States | H01M4/00 |
| 7 | US12183880B2 | 2023 | 2024 | Polyplastics | United States | H01M10/0562 |
| 8 | US8697292B2 | 2011 | 2014 | Toyota | United States | H01M6/18 |
| 9 | US12021187B2 | 2021 | 2024 | Polyplastics | United States | H01M10/0562 |
| 10 | US11251501B2 | 2018 | 2022 | BASF | United States | C01B25/14 |
| 11 | CN109690696B | 2017 | 2020 | Idemitsu Kosan | China | H01B1/10 |
| 12 | JP7435452B2 | 2019 | 2024 | GS Yuasa | Japan | H01M10/0562 |
| 13 | US12288842B2 | 2019 | 2025 | GS Yuasa | Japan | H01M10/00 |
The core patents cluster into several strategic groups. The first group concerns lithium metal interface protection. One early patent from Seeo establishes a multi-layer inorganic-organic composite protection film for sulfide solid electrolyte cells. This patent addresses the critical problem of lithium dendrite penetration and interfacial reduction. It creates a foundational barrier for any company seeking to commercialize lithium metal anodes with sulfide solid electrolyte cells.
The second group is a dense patent pool held by Polyplastics. Seven of the 13 core patents belong to this firm. They cover glass-based sulfide solid electrolyte materials, roll-to-roll flexible film manufacturing, moisture-resistant separator architectures, and cathode interface polarization suppression. This portfolio forms a near-monopoly in glassy sulfide film processing. For latecomers, single-point avoidance is difficult. A more practical strategy is to shift to crystalline sulfide routes, such as argyrodite-type materials, and to adopt dry electrode calendaring instead of roll-to-roll slurry casting.
The third group involves foundational electrolyte powder synthesis. Toyota’s patent covers halogen-doped Li2S-P2S5 amorphous electrolytes with high ionic conductivity. Idemitsu Kosan’s patent covers high-purity argyrodite-type crystalline solid electrolytes with specific X-ray diffraction peaks. These patents use chemical formula and crystal structure limitations, making direct design-around very difficult. Chinese firms may need to explore heterovalent doping with oxygen, silicon, tin, or rare earth elements, and to develop low-cost liquid-phase synthesis routes to compete on manufacturing cost.
The fourth group focuses on engineering-scale manufacturing and system integration. BASF’s patent covers homogeneous solution wet synthesis for scalable production. GS Yuasa’s patents cover binder-based cathode assembly and structural compression components that accommodate volume expansion in all-solid-state cells. These patents do not necessarily block material composition but can restrict the path from powder to battery pack. Chinese firms can avoid wet synthesis by developing solvent-free dry processes and can replace external mechanical compression with flexible buffer layers for lightweight system integration.
Validation using the incoPat “comprehensive value” score shows that all 13 core patents receive a full score of 10, confirming the effectiveness of the combined entropy-CRITIC-TOPSIS model. This consistency check supports the model’s ability to identify high-value patents in the sulfide solid electrolyte cell field.
Conclusions and Strategic Recommendations
My analysis leads to several conclusions about sulfide solid electrolyte cells. First, the global competitive landscape is dominated by Japanese firms, with American firms occupying key strategic positions. Japanese companies control upstream materials, crystal structures, and global patent networks. American firms have made breakthroughs in lithium metal interface isolation and glassy flexible film technologies. Chinese firms have pursued a differentiated path focused on electrode-electrolyte interface engineering, but they face a structural bottleneck of high domestic volume, low international spillover, and weak industry-academia-research integration.
Second, the core patent identification model shows that citation made, citation received, and simple family size are the most important indicators for sulfide solid electrolyte cells. This means that a true core patent must have deep technological tracing, strong subsequent technological leadership, and substantial global family coverage. The 13 core patents identified by the model are held by a small number of multinational firms, and they cover the entire chain from raw materials to interface protection, film manufacturing, and system integration.
Third, China’s patent portfolio is large but structurally weak. The country has the highest domestic application volume, but its overseas filings are minimal. Nearly half of Chinese patents are held by universities and research institutes, while licensing and transfer activities remain very low. No Chinese applicant appears among the global top 13 core patents. This indicates that China lacks foundational intellectual property in sulfide solid electrolyte cells, even though it has a strong manufacturing base and a large domestic market.
Based on these findings, I propose five strategic recommendations. First, Chinese firms should avoid direct confrontation in raw materials, interface structures, and glassy film processes. Instead, they should focus on dry electrode manufacturing, binder fibrillation, and solvent-free coating, where multinational firms have not yet built absolute barriers. They should also leverage strengths in battery pack design and thermal management to build system-level advantages in sulfide solid electrolyte cells.
Second, firms should strengthen intellectual property compliance and defensive planning. Before exporting products to the United States or Europe, they should conduct freedom-to-operate searches and invalidate high-risk patents when necessary. They should also use the PCT route to file high-quality families in major markets, moving away from a domestic-only filing habit.
Third, China should bridge the gap between academia and industry. I recommend using the entropy-CRITIC-TOPSIS model to screen high-value patents held by universities and institutes, and to establish patent pools for sulfide solid electrolyte cells. A challenge-based mechanism should be introduced, where battery manufacturers and automakers define engineering problems and academic teams propose solutions. This would help transfer foundational patents into industrial applications.
Fourth, research funding should be redirected toward specialized manufacturing equipment and front-end materials. Support should cover continuous powder production, high-pressure calendaring, and ultra-dry processing equipment. At the same time, domestic companies should develop low-cost synthesis and recycling technologies for sulfide solid electrolyte cells to secure the upstream supply chain and reduce dependence on foreign chemical giants.
Fifth, China should build a global inventor map and manage talent strategically. By analyzing patent inventor data, firms can identify leading scientific teams behind core patents and attract overseas experts through global R&D centers. At the same time, companies should protect their own process engineers and pilot-line experts, because manufacturing know-how is a key advantage for China in sulfide solid electrolyte cells. Modular management can reduce the risk of talent loss and technology leakage.
Limitations and Future Research
My study has two main limitations. First, the combined weighting uses a fixed 0.5:0.5 ratio for the entropy and CRITIC methods. Although this balances dispersion and conflict, it lacks a fully data-driven optimization mechanism. Future research should conduct sensitivity analysis and use game-theoretic or optimization algorithms to find a more robust combination of weights. Dynamic weighting could further improve the stability of core patent identification.
Second, the indicator system is based on general patentometrics and does not fully capture the unique technical features of sulfide solid electrolyte cells, such as electrolyte type, interface modification process, or dry versus wet manufacturing routes. Future work should use natural language processing and text mining to extract technical entities and process parameters from claims and descriptions. A composite evaluation system that combines general bibliometric indicators with domain-specific technical features would improve the precision and practical intelligence value of core patent identification in sulfide solid electrolyte cells.
Overall, I believe that the combined entropy-CRITIC-TOPSIS model provides a reliable and reproducible method for identifying core patents in sulfide solid electrolyte cells. The empirical results reveal a highly concentrated global patent landscape and offer actionable insights for firms and policy makers seeking to accelerate the commercialization of sulfide solid electrolyte cells while managing intellectual property risks.