Chinese automaker BYD has recently filed six additional patents focused on solid-state battery (SSB) technology, building on a previously granted patent for cathode composite structures. All six patents aim to enhance the interface between solid electrolytes and electrodes, addressing challenges in material chemistry, manufacturing processes, and quality control.
Four of the new filings outline innovations in cathode design. One patent proposes incorporating an ion-conducting, electrochemically stable interlayer between halide and sulfide electrolytes to prevent direct contact and unwanted reactions, thereby extending cycle life. Another suggests using a solid-electrolyte buffer layer between the active cathode material and sulfide electrolyte to avoid direct contact and reduce thermal runaway risk, with a limit of 117 J/g for thermal release. A third patent describes a dual-layer composite cathode: an inner layer combining monocrystalline cathode material and solid electrolyte for fracture resistance, and an outer layer pairing polycrystalline material with a different electrolyte composition to boost rate performance. The fourth material innovation involves a tri-component cathode mixing lithium-treated metal oxides and sulfides with solid electrolyte, aiming to lower interfacial resistance, increase specific capacity, and improve cycle stability.
The remaining two patents focus on production readiness. One covers the application of ionic liquid wetting agents in a gradient distribution across the electrode, which BYD says enhances ion transport, solid-solid contact, and longevity. The other establishes a quality-control metric, Re, defining the minimum contact ratio between cathode and electrolyte particles; BYD recommends at least 60% perimeter contact to optimize performance.
Academic studies, including research from the Chinese Academy of Sciences, support the importance of smaller sulfide particles to improve capacity retention—a principle reflected in BYD’s Re metric. According to industry reports, BYD aims to begin small-scale production of dual-electrolyte SSB cells in 2027, with initial trials in camouflaged test vehicles. While solid-state batteries promise higher energy density, enhanced safety, and extended range, experts caution that significant engineering and manufacturing hurdles remain before widespread adoption.
Source: CarNewsChina
