China's Ministry of Industry and Information Technology (MIIT) released on March 28, 2025 the updated Safety Requirements for Power Batteries Used in Electric Vehicles (GB38031-2025). Unlike the previous standard, which emphasized "no fire or explosion within five minutes after thermal runaway to ensure passenger escape time," the new version prioritizes "monitoring + proactive prevention."
Specifically, it mandates that battery cells must issue an alarm within five minutes of thermal runaway, and remain fire and explosion-free for two hours, while maintaining the monitoring point temperatures below 60°C.
To achieve these goals, the standard also imposes stringent testing requirements, including:
- Fast-charge cycle safety tests (SOC range: 20%–80%; charging time: 15 minutes);
- Bottom impact tests (impact energy: 150J);
- Thermal runaway trigger methods (e.g., nail penetration, external/internal heating); etc.
The industry has made technological breakthroughs across cell-level protection, battery-pack-level safeguards, and state monitoring to meet the "no fire/no explosion" mandate. Below is an analysis of current technologies and applications.
Composite Aluminum Foil Enhances Cell-Level Safety
Composite aluminum foil (aluminum coated with high-temperature polymers like PI, PET, or ceramic materials such as alumina) is widely adopted to improve cell safety. Its core functions include:
- Suppressing internal short circuits by reducing lithium dendrite growth. Smooth composite surfaces minimize surface burrs, lowering dendrite formation. Data from leading battery makers show a 40% reduction in dendrite length after 500 cycles at 1C rate.
- Delaying thermal runaway. PI-coated foil exhibits higher toughness than pure aluminum, delaying voltage drop by 2–3 seconds during nail penetration tests and reducing peak thermal runaway temperatures by over 50°C.
- Ceramic coatings (melting point >400°C) slow heat propagation. In 150°C hot-box tests, composite foil delays thermal runaway by 15 minutes compared to traditional foil.
- Anti-corrosion. Ceramic layers mitigate electrolyte reactions, reducing gas generation and swelling. Capacity retention improves from 75% to 85% after 2,000 cycles.
Despite these advantages, challenges lay ahead. First, the costs are 30% higher due to precision coating processes (e.g., sputtering). Major players like CATL (Qilin battery) and BYD (blade battery) have achieved mass production, but uniformity control remains technically demanding. To achieve this, the production process requires the adoption of certain semiconductor techniques, such as sputtering coating.
Aerogel for Pack-Level Safety: Effective but Costly
To prevent thermal runaway propagation between cells, aerogel is deployed as an ultra-low thermal conductivity barrier (0.02 W/m·K, 20% of traditional mica). The key advantages include:
- 0.5mm thickness suffices for insulation, aiding lightweight design.
- Chemically inert, avoiding reactions with electrolytes.
GAC's Aion batteries use aerogel meshes, limiting adjacent cell temperature rise to 60°C during thermal events. GM applies it between modules, preventing flames for 50 minutes.
Currently, the use of aerogel incurs approximately 30% higher costs compared to conventional processes, making it predominantly adopted in premium battery systems. Building upon this technology, domestic automakers and battery manufacturers have developed integrated solutions combining aerogel with phase-change materials and liquid cooling plates to achieve dual functionality in thermal insulation and heat dissipation. A notable example is Dongfeng's Voyah "Amber Battery," which exemplifies this advanced thermal management approach.
BMS Monitoring: Heavy Reliance on Imported Chips
The monitoring function is primarily performed by the Battery Management System (BMS), with the State of Charge (SOC) serving as its core monitored parameter, from which other physical quantities can be derived. The BMS relies heavily on key semiconductor components, including Analog Front-End (AFE) chips, Microcontroller Units (MCUs), and Analog-to-Digital Converters (ADCs), which collectively handle data acquisition, processing, and signal conversion.
Notably, the localization rate for mission-critical MCUs remains below 5%. This low adoption stems from three key barriers:
- Technical Challenges: Automotive-grade MCUs must comply with stringent AEC-Q100 reliability certification and ISO 26262 functional safety standards (ASIL-D being the highest level). Domestic manufacturers face bottlenecks in high-temperature stability (e.g., 150°C operation) and analog-digital signal interference mitigation in integrated interfaces. Developing such MCUs requires at least 18 months of R&D with substantial capital investment, posing prohibitive risks for SMEs.
- Cost Disadvantage: At comparable performance tiers, domestic MCUs are typically 10%–30% more expensive than foreign alternatives (e.g., Infineon, STMicroelectronics), dampening automakers' incentive to switch.
- Trust Deficit: Given near-zero fault tolerance requirements in safety-critical applications like battery lifespan management, automakers exhibit strong preference for globally proven MCU brands due to perceived reliability gaps in domestic offerings.
Current Industry Status:
As of now, over 80% of enterprises have established the necessary technical capabilities. However, due to cost constraints, these advancements are primarily implemented in high-end EVs. Consequently, when the updated national standard takes effect on July 1, 2026, some battery manufacturers failing to meet compliance requirements risk being excluded from the market.
Consumer Considerations:
For consumers planning to purchase a vehicle in 2025, long-term safety benefits may influence their decision-making. While subsidies incentivize EV purchases this year, opting for a 2026 model could offer enhanced safety features aligned with the stricter standards.
