An electrochemical cell comprising a cathode material contacted to a perforated current collector having a portion left uncovered and an anode material contacted to an anode current collector is described. A separator sheet segregating the anode from direct contact with the cathode is folded back upon itself along a crease with an upper portion at least partially sealed to a lower portion along an aligned peripheral edge to form an envelope. A first envelope portion houses the cathode having the uncovered portion of the cathode current collector spaced from the crease and a second envelope portion houses the anode. The first envelope portion is sealed to the second envelope portion through the uncovered perforations of the cathode current collector to lock the anode aligned with the cathode. The anode and cathode are then wound into a jellyroll electrode assembly housed in a cylindrical casing and activated with an electrolyte.