BYD published a new patent for a composite solid electrolyte membrane in May 2026. Image rendered by CNC Understand China EV’s Market Real-time notifications when critical EV data is released All important data in one place 2,000,000+ data points Become a member BYD has filed a new patent for a composite solid electrolyte membrane used in solid-state batteries, adding to a broader wave of sulfide solid-state battery development across China’s battery industry, reported by Sina. According to patent filing CN121983643A published by China’s National Intellectual Property Administration, the patent covers a “composite solid electrolyte membrane and its preparation method, solid-state battery, battery pack and electrical device.” BYD solid-state battery patent The patent describes a composite electrolyte structure comprising multiple inorganic solid electrolyte particles combined with a polymer electrolyte fibre network coating. The inorganic electrolyte section includes both smaller and larger particles. The polymer electrolyte comprises a polymer matrix and a lithium salt, with the material wrapped around portions of the inorganic electrolyte surface in a fibre network. The filing states the structure is intended to improve ionic conductivity and mechanical strength of the electrolyte membrane. The document does not disclose energy density figures, charging performance, cycle life data, manufacturing cost targets, or commercialisation timing. The patent also does not discuss lithium-metal anodes, vehicle-level integration, or pack-pressure management systems commonly associated with sulfide all-solid-state battery architectures. BYD chief scientist outlines bottlenecks In April 2026, BYD chief scientist Lian Yubo said the company’s all-solid-state battery development had entered a “critical breakthrough stage,” while commercialisation remained constrained by engineering complexity, cost control, and production yield challenges. Lian identified solid-solid interfacial stability and lithium dendrite suppression as core technical bottlenecks. He also stated the industry should focus on full-chain system development rather than only optimising individual battery cells. Earlier disclosures from BYD referenced a pilot-scale deployment around 2027, alongside the development of third-generation sodium-ion batteries targeting 10,000 charging cycles. China’s solid-state battery competition BYD’s latest filing comes as multiple Chinese battery makers move toward larger-capacity solid-state prototypes and pilot lines. In March, CALB presented a 60 Ah all-solid-state battery prototype with energy density exceeding 450 Wh/kg. Chery also disclosed the development of a 60 Ah all-solid-state battery with an energy density of 400 Wh/kg and vehicle integration testing planned for 2027. CATL has also disclosed sulfide-based solid-state battery patents and pilot production targets around 2027. GAC previously stated its automotive-grade solid-state cells above 60 Ah had entered small-batch production for validation testing. Battery Installation Volume for EVs BYD’s EV battery installation volume in China. Credit: China EV DataTracker Battery installation volumes According to China EV DataTracker data, battery installation data for 2025 and 2026 showed that BYD remained concentrated in LFP battery deployments during the period. BYD battery installation volume reached 10.49 GWh in April 2026 with a 16.8% market share, compared with 12.84 GWh and 22.5% share in May 2025. The reported installation mix during the listed months consisted entirely of LFP batteries.