An energy storage apparatus, whereby the energy storage apparatus is a single battery, comprising a battery end cover assembly, the battery end cover assembly comprising: an end cover of a rectangle; terminal assemblies, the terminal assemblies being connected to the end cover; and a pressure relief mechanism, the pressure relief mechanism being disposed on the end cover, and the pressure relief mechanism and the terminal assemblies being distributed at intervals in the length direction of the end cover; wherein the area of a figure formed by an outer contour of the end cover is a first area S1, the area of a projection of the pressure relief mechanism on the end cover is a second area S2, and the second area S2 accounts for 0.5% to 5% of the first area S1; the size of the pressure relief mechanism in the length direction of the end cover is b1, and b1 accounts for 5% to 12% of the length b0 of the end cover; and the size of the pressure relief mechanism in the width direction of the end cover is e1, and e1 accounts for 15% to 25% of the width e0 of the end cover; wherein the pressure relief mechanism comprises an anti-explosion valve, and the anti-explosion valve comprises a preset opening area; the anti-explosion valve is provided with a notch groove, and the notch groove is located in the preset opening area; the minimum thickness of the anti-explosion valve on the position of the notch groove is a first thickness n1, the thickness of the anti-explosion valve on the position of the preset opening area is a second thickness n2, and the first thickness n1 accounts for 15% to 25% of the second thickness n2; the tensile strength of the anti-explosion valve is 90-130 N/mm 2; an area of the preset opening area is at least a half of the second area S2 and not more than 95% of the second area S2; and a ratio (a/S2) of a capacity a of the energy storage apparatus to the second area is at least equal to 1.8, wherein the unit of the capacity a is ampere-hour, and the unit of the second area S2 is mm 2. an end cover of a rectangle; terminal assemblies, the terminal assemblies being connected to the end cover; and a pressure relief mechanism, the pressure relief mechanism being disposed on the end cover, and the pressure relief mechanism and the terminal assemblies being distributed at intervals in the length direction of the end cover; wherein the area of a figure formed by an outer contour of the end cover is a first area S1, the area of a projection of the pressure relief mechanism on the end cover is a second area S2, and the second area S2 accounts for 0.5% to 5% of the first area S1; the size of the pressure relief mechanism in the length direction of the end cover is b1, and b1 accounts for 5% to 12% of the length b0 of the end cover; and the size of the pressure relief mechanism in the width direction of the end cover is e1, and e1 accounts for 15% to 25% of the width e0 of the end cover; wherein the pressure relief mechanism comprises an anti-explosion valve, and the anti-explosion valve comprises a preset opening area; the anti-explosion valve is provided with a notch groove, and the notch groove is located in the preset opening area; the minimum thickness of the anti-explosion valve on the position of the notch groove is a first thickness n1, the thickness of the anti-explosion valve on the position of the preset opening area is a second thickness n2, and the first thickness n1 accounts for 15% to 25% of the second thickness n2; the tensile strength of the anti-explosion valve is 90-130 N/mm 2; an area of the preset opening area is at least a half of the second area S2 and not more than 95% of the second area S2; and a ratio (a/S2) of a capacity a of the energy storage apparatus to the second area is at least equal to 1.8, wherein the unit of the capacity a is ampere-hour, and the unit of the second area S2 is mm 2.