If using 18650 cells (or other cylindrical metal cased cells) then they are pretty tough, just make sure they can't short out, and use protected cells.
If using pouch cells (or other soft-shell cells) then you need to think about puncture and crush protection, and use protected cells.
NB: Protected cell means a cell which has a protection circuit on it to prevent over discharge (low volt), over charge (high volt) and over discharge current/short circuit, they do not typically protect against over current in the charging direction, only discharging.