Solid-State vs. Semi-Solid Batteries: Key Differences

In the rapidly advancing world of battery technology, terms like "solid-state" and "semi-solid" are often used interchangeably, leading to confusion. However, recent industry efforts have aimed to clarify these distinctions, emphasizing critical differences in composition, safety, and commercial viability .

Core Differences in Electrolyte Composition
The primary distinction lies in the electrolyte. Solid-state batteries use 100% solid electrolytes, eliminating liquid components entirely. In contrast, semi-solid batteries (now termed "solid-liquid hybrid batteries" under new standards) retain 5–10% liquid electrolyte . This hybrid approach mitigates risks like leakage and thermal runaway while maintaining ion conductivity .

Safety and Performance Trade-Offs
Solid-state batteries excel in safety, as solid electrolytes are non-flammable and resistant to high temperatures—critical for electric vehicles (EVs). Semi-solid batteries offer a middle ground, raising thermal runaway thresholds from 80°C in liquid batteries to 93°C, providing crucial extra minutes for safety systems to activate .

Commercial Readiness and Cost
Semi-solid batteries are already powering EVs like the Nio ET7 and IM L6, with energy densities of 300–360 Wh/kg . Solid-state batteries, though promising densities over 500 Wh/kg, remain confined to labs due to high costs (up to 5 times that of liquid batteries) and manufacturing challenges .

Regulatory Clarity and Future Outlook
To curb misleading marketing, China’s automotive authorities are standardizing classifications, grouping batteries into solid-state, solid-liquid hybrid, and liquid categories . While solid-state batteries are projected to see small-scale adoption by 2030, semi-solid variants will dominate as the pragmatic near-term solution .

Conclusion
Understanding these differences is vital for consumers and industry stakeholders. Semi-solid batteries deliver incremental advancements today, while solid-state technology represents a transformative—yet distant—future for energy storage.