Chinese automaker and battery producer BYD has submitted a patent application for a composite solid electrolyte membrane intended for use in sulfide-based solid-state batteries, according to a filing published by the country’s intellectual property office. The patent covers the membrane’s structure and preparation method, as well as its integration into solid-state cells, battery packs and related electrical devices.
The disclosed design combines multiple inorganic solid electrolyte particles of differing sizes with a polymer electrolyte fiber network coating. In this configuration, the polymer matrix—containing a lithium salt—encapsulates portions of the inorganic particles in a fibrous network. BYD states that this arrangement is intended to enhance both ionic conductivity and mechanical strength in the electrolyte membrane.
The patent documents do not provide specific performance metrics such as energy density, charging rates, cycle life, or cost targets. They also omit details on lithium-metal anode integration, vehicle-level packaging or pressure management systems commonly associated with sulfide all-solid-state cells.
In April 2026, BYD’s chief scientist noted that the company’s solid-state battery program had reached a “critical breakthrough stage,” while emphasizing that commercialization remained challenged by engineering complexity, cost control and production yields. Key technical hurdles include stabilizing solid–solid interfaces and suppressing lithium dendrite growth. The company has previously indicated plans to pilot solid-state cells around 2027 and to advance third-generation sodium-ion batteries capable of 10,000 charge cycles.
BYD’s filing follows similar moves by other Chinese battery makers. In March, one manufacturer unveiled a 60-ampere-hour sulfide solid-state prototype exceeding 450 watt-hours per kilogram, while another reported a 60-ampere-hour cell at 400 Wh/kg with vehicle tests slated for 2027. Several firms have also disclosed sulfide-based solid-state patents and pilot production targets in the 2027 timeframe, and some are conducting small-batch validation of automotive-grade cells above 60 Ah.
Meanwhile, data tracking battery installations in Chinese electric vehicles shows BYD’s deployment volume for lithium iron phosphate cells reached 10.49 gigawatt-hours in April 2026, securing a 16.8% share of the market. The company’s installation mix remained exclusively LFP during the period.
Source: CarNewsChina: https://carnewschina.com/2026/05/25/byd-files-new-sulfide-solid-state-battery-patent-as-china-targets-2027-pilot-production/
