I'd recommend against using Schottky diodes for isolation of a lithium primary cell. It's important to minimize reverse leakage current, which tends to "charge" the cell, which is a no-no. Usually a small-signal silicon diode is used, and sometimes a special
low-leakage one. It depends on the particular cell type and size. There may be specifications on primary Li cells regarding how much reverse current they can safely absorb, but it's best to make it as tiny as possible.