The ornamental design for an energystoragedevice, as shown and described.
FIG. 1 is a perspective view of an energy storage device showing an embodiment of the new design;
FIG. 2 is a front view of an embodiment of the energy storage device;
FIG. 3 is a rear view of an embodiment of the energy storage device;
FIG. 4 is a top view of an embodiment of the energy storage device;
FIG. 5 is a side view of an embodiment of the energy storage device (in embodiments, the left side and right side are the same); and,
FIG. 6 is a bottom view of an embodiment of the energy storage device.
The broken lines depict portions of the energy storage device that form no part of the claimed design.
The energy storage device is shown with a symbolic break in its length. The appearance of any portion of the article between the break lines forms no part of the claimed design.