It is common wisdom that '\' is the path separator on Windows and '/' is the separator on unixlike operating systems. It is also common wisdom that you should always use the native path separator in your programs to minimise errors.
The first one of these is flat out wrong and the second one can be questioned.
On Windows both '\' and '/' work as directory separators. You can even mix them within one path. The end result is that '/' is the truly universal directory separator, it works everywhere (except maybe classic Mac OS, which is irrelevant).
So the question then is whether you should use '\' or '/' when dealing with paths on Windows. I highly recommend always using '/'. The reason for this is a bit unexpected but makes perfect sense once you get it.
The difference between these two characters is that '\' is a quoting character whereas '/' is not. You probably have to pass your path strings through many systems (bat files, persist to disk, files, sql, etc) using libraries and frameworks outside your control. They will most likely have bugs in the way they handle quotes. You may need to quote your quote chars to get them to work. You might need to quote them differently in different parts of your program. Quoting issues are the types of bugs that strike you at random, usually in production and are really difficult to hunt down.
So always use '/' if possible. It will survive any serialisation/deserialisation combination without problems since '/' is not a special character.