The rule, and the date it started
The Civil Aviation Administration of China issued an urgent notice prohibiting passengers from carrying power banks without CCC markings, with unclear CCC markings, or from recalled models or batches on domestic flights, starting 28 June 2025.
CAAC Bans Passengers from Carrying Power Banks Without CCC Markings or from Recalled Models on Domestic Flights (Civil Aviation Administration of China, page dated 2025-07-09, read 2026-07-25)