China had encountered inflation of its own after printing the world's first paper money in the 12th century, so they switched back to coins. Initially, Chinese coins were made out of copper or bronze, but their economy was so big, they were the leading producer of consumer goods until the 19th century, that they ran out. So they went to silver. Now, China didn't have a lot of silver itself, but Japan did, so they traded manufactured goods for it, but soon even that wasn't enough. This was mostly because in the 16th century, China changed its tax structure. Taxes, man! They're at the center of human history.