BEIJING, May 29 (Reuters) - China may invest about 6 billion yuan ($827.87 million) in an "unprecedented" government-led project to encourage research and development in all-solid-state batteries, the official China Daily reported on Wednesday.

Among the six companies that might receive government basic research and development support are CATL, BYD , FAW, SAIC and Geely , the report said.

Solid-state batteries enable improved safety, a longer lifespan and faster charging compared with conventional lithium-ion batteries that use flammable liquid electrolytes, but constraints in raw material availability, intricate manufacturing processes and resultant high costs are mass adoption roadblocks. ($1 = 7.2475 Chinese yuan renminbi) (Reporting by Qiaoyi Li, Ethan Wang and Liz Lee; Editing by Christian Schmollinger)