I wanted to say that the material that was used to store documents were made of animals' bones and skins in Shang Dynasty. This is my sentence: "Bamboo strips books were invented as a replacement for the materials that stored documents for which they were made by animals’ bones and skins". Thank you very much, guys,
Let's start with how I'd write the sentence (which is but one of many ways):
Bamboo-strip books were invented to replace materials that traditionally stored information: animal bones and skin.
Working with your original sentence, you could say:
Bamboo-strip books were invented as a replacement for the materials that stored documents, which were animal bone and skin.
You're not setting off a clause as much as you are using a pronoun. "Which" being a pronoun referring to "materials."
"For which" is inappropriate here because it is used to set off a clause. Using an example from the above linked reference, "it was a crisis for which he was totally unprepared." The clause "he was totally unprepared," can stand alone. Your oringinal sentence could have had the clause, "they were made [using] animal bones and skin," but to keep this clause (which may have used "for which...") would require a very complicated sentence.