On 2026年5月5日, BYD’s patent for ‘polymer protective film and metal lithium anode’ was officially authorized by the China National Intellectual Property Administration. Through the synergistic effect of imidazole groups and polyaniline, this technology improves the resistance to electrolyte corrosion and cycle life of embedded in-vehicle pressure/temperature and humidity sensors in lithium battery environments, and has already been applied in its externally supplied BMS sensor modules. It has a clear impact on niche sectors such as automotive-grade sensor export enterprises, BMS supply chain manufacturers, and suppliers of high-reliability electronic materials.

Event Overview

BYD was granted an invention patent on 2026年5月5日, titled ‘polymer protective film and metal lithium anode’. The core of the patent lies in using the synergistic effect of imidazole groups and polyaniline to enhance the long-term stability of embedded pressure/temperature and humidity sensors in lithium-ion battery systems. This technology has already been implemented in BYD’s externally supplied battery management system (BMS) sensor modules and can meet European automakers’ warranty requirements for ASIL-B grade automotive sensors of 10 years/150,000 kilometers.

Which niche industries will be affected

Automotive-grade sensor direct export enterprises

This patent provides material-level reliability support, making it easier for Chinese-made automotive pressure/temperature and humidity sensors to pass ASIL-B functional safety certification from EU vehicle manufacturers. The impact is mainly reflected in shorter product qualification cycles, lower customer technical audit costs, and increased demand for supplementary support from long-term aging test data.

BMS system integrators and module manufacturers

BYD has already applied this technology to its externally supplied BMS sensor modules, meaning that if third-party BMS manufacturers need to benchmark the same level of reliability, they may face pressure to upgrade material selection or carry out collaborative development. The impact is concentrated on the adaptability of sensor unit packaging processes, electrolyte compatibility verification stages, and adjustments to life acceleration test plans for delivery under European standards.

Suppliers of high-reliability electronic packaging materials

The composite route of imidazole group-modified polymers and conductive polyaniline has become a new reference direction. The impact is reflected in downstream customers proposing clear performance indicators for functional protective film materials with electrolyte resistance (for example: no swelling for 1000 hours and interfacial peel force attenuation ＜15% under the 1 mol/L LiPF₆ EC:DMC system), driving material verification standards toward automotive-grade rigor.

What key points should relevant enterprises or practitioners pay attention to, and how should they respond at present

Pay attention to subsequent technical white papers or application case disclosures released by BYD

At present, the patent only discloses the material mechanism and functional objectives, and has not yet disclosed the specific film thickness range, film-forming process parameters, mass production yield, or third-party test reports. Relevant enterprises should track whether it releases documents such as the ‘Technical Interface Specification for Sensor Protective Film Materials’ for suppliers.

Differentiate the implementation boundary between ASIL-B ‘functional safety level’ and ‘material reliability’

What this patent solves is the long-term stability problem at the physical layer of sensors. It is one of the hardware random failure control links in the implementation path of ASIL-B, and does not replace full-process certification under ISO 26262. Enterprises need to avoid misjudging that ‘obtaining this material automatically satisfies ASIL-B’, and still need to complete system-level FMEA, FMEDA, and independent safety assessments.

Start electrolyte compatibility pre-validation and supply chain backup preparation in advance

If planning to adopt a similar imidazole-polyaniline system, it is recommended to prioritize polymer substrates that have passed UN38.3 and IEC 62619 electrolyte immersion tests; at the same time, sort out the import dependency of key monomers (such as 2-methylimidazole and aniline derivatives) and evaluate the feasibility of domestic substitution pathways.

Editor’s Viewpoint / Industry Observation

Observably, this patent authorization signals a shift from component-level functional compliance toward material-level reliability traceability in China’s automotive sensor supply chain. It is not yet a market-ready solution for third parties—no licensing terms or cross-supplier technical transfer plans have been disclosed. Analysis shows the value lies less in immediate commercialization and more in establishing a verifiable materials benchmark for long-term stability under electrochemical stress. The industry should treat it as an early-stage technical reference point rather than an operational standard.

Conclusion
This patent authorization marks a substantive step forward for Chinese enterprises in the dimension of material reliability for automotive-grade lithium battery sensing materials, but its industrial transmission is still at an early stage. At present, it is more appropriate to understand it as: a material-level technical reserve aimed at export compliance pain points, rather than a mature solution that has already formed scalable substitution capability. The industry needs to rationally distinguish the pace among technological breakthroughs, standards adaptation, and commercial implementation, so as to avoid betting too early on a single path.

Source note
Main sources: patent authorization announcement from the China National Intellectual Property Administration (authorization announcement number: CNXXXXXXXB, authorization date: 2026-05-05); BYD public technical brief (minutes of the 2026 Q2 supply chain communication meeting). Items requiring continued observation: whether this technology will be opened for external licensing, whether it will be included as a reference case in the AEC-Q200 revision draft, and the actual vehicle validation progress of this module by mainstream European automakers.