China's BYD advances solid-state battery development with new patent
BYD has filed a new patent for a composite solid electrolyte membrane used in solid-state batteries, adding to a wider wave of sulfide solid-state battery development across China’s battery industry, according to Sina, News.Az reports, citing CNC.
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.”
The patent describes a composite electrolyte structure made up of multiple inorganic solid electrolyte particles combined with a polymer electrolyte fibre network coating.
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The inorganic electrolyte section includes both smaller and larger particles. The polymer electrolyte consists of a polymer matrix and a lithium salt, with the material wrapped around parts of the inorganic electrolyte surface in a fibre network structure.
The filing states that this design is intended to improve the ionic conductivity and mechanical strength of the electrolyte membrane.
However, the document does not provide details on energy density, charging performance, cycle life, manufacturing cost targets, or commercialisation timelines.
It also does not address lithium-metal anodes, vehicle integration, or pack-pressure management systems commonly linked to sulfide all-solid-state battery designs.
In April 2026, BYD chief scientist Lian Yubo said the company’s all-solid-state battery development had entered a “critical breakthrough stage,” although commercialisation remained limited by engineering complexity, cost control, and production yield challenges.
Lian identified solid-solid interfacial stability and lithium dendrite suppression as key technical bottlenecks.
He also noted that the industry should focus on full-chain system development rather than only optimising individual cells.
Earlier statements from BYD indicated a pilot-scale deployment target around 2027, alongside development of third-generation sodium-ion batteries aimed at 10,000 charging cycles.
BYD’s latest filing comes as multiple Chinese battery manufacturers move toward larger-capacity solid-state prototypes and pilot production lines.
In March, CALB presented a 60 Ah all-solid-state battery prototype with energy density exceeding 450 Wh/kg. Chery also announced development of a similar 60 Ah cell with 400 Wh/kg energy density 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 that its automotive-grade solid-state cells above 60 Ah had entered small-batch production for validation testing.
According to China EV DataTracker, battery installation data for 2025 and 2026 showed BYD remained largely focused on LFP battery deployments during this period.
BYD’s battery installation volume reached 10.49 GWh in April 2026 with a 16.8% market share, compared with 12.84 GWh and a 22.5% share in May 2025.
The reported installation mix during these months consisted entirely of LFP batteries.
By Nijat Babayev
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