Abstract: A pressure relief device is disclosed, such as may be used with a battery. According to one embodiment, the pressure relief device may include a pressure-retaining membrane—which may be a polymer or flexible graphite membrane—supported by a support strip. In response to a predetermined pressure on the pressure-retaining membrane, the support strip may be caused to deform, allowing the pressure-retaining membrane to open. The pressure-retaining membrane may include one or more lines of weakness to define an opening area and/or to determine the pressure conditions under which the membrane may open. One or more stress-applying devices or piercing mechanisms may be provided to cause the membrane to open.