Is there a left luggage in any of the train stations in Xian?

Hi,

My original trip is to visit Beijing and Shanghai. However, a friend suggested that I drop by Xian to visit the Terracotta Warriors' site, and I am very much interested to do so. My plan is take the sleeper train from Beijing to Xian, leave my luggage in any secured facility, visit the museum, and take the sleep train to Shanghai?

Is there such a facility? A secured one? If there is, how much would it cost me? Will need to leave that for 8-10 hours.

When I was in Seoul, several of their train stations have lockers that are available for tourists.

Thank you so much.