Substrate for lithium secondary battery, and separator for lithium secondary battery

Disclosed are: a substrate for a lithium secondary battery, which comprises a non-woven fabric containing synthetic resin short fibers and fibrillated Lyocell fibers as essential components; and a separator for a lithium ion secondary battery, which is produced using the substrate. In the substrate and the separator, it is preferred that a synthetic resin that constitutes the synthetic resin short fibers be at least one resin selected from a polyester resin, an acrylic resin and a polyolefin resin or the content of the fibrillated Lyocell fibers is 5 to 80 mass% relative to the mass of the non-woven fabric.