Behold lithium battery technology, a USB charger, and a buck voltage converter mashed into an AA alkaline package:
Those are two of a quartet bought from a randomly named Amazon seller to appease my ancient venerable classic Sony DSC-H5’s need for more voltage than new and freshly charged NiMH AA cells can provide for more than a few tens of minutes.
The label claims 1500 mA·h, not the 1120 mA·h I measured:
My numbers would be higher with a load less than 500 mA. I doubt the 2.5 A maximum current rating.
The claim of 2.25 W·h is rather optimistic:
Back of the envelope: 2.25 W·h at 1.5 V equals 1.5 A·h, all right. If you squint carefully, though, the output voltages run around 1.4 V, some of which is surely IR drop in my battery holder & test wiring, but it still knocks nearly 10% off the wattage and doesn’t seem to add to the runtime.
The camera’s battery charge indicator will obviously show Full right up until it shuts off, but I’ve always carried a spare pair of cells in my pocket anyway.
Recharging them with a USB meter in series required 425 to 600 mA·h at about 4.8 V, so about 2.5 W·h.
Enlarging the instructions from the back of the box, should they become useful:
Nowhere does the package mention the “brand name”, manufacturer, specifications, or much of anything substantial. I suppose anybody selling white-label products appreciates this level of detail.
The Smell of Molten Projects in the Morning 
It took me a surprisingly long time to realize “Fuvaly Bucked” was not meant as a spoonerism.
You can expect delicate wording should their (unknown) self-discharge rate combine unfavorably with their (tiny) capacity …