Places where gravimetric density is more important: - Electric vehicles - Aircraft - R/C - Anything that goes into space - Large scale energy storage (good

Places where gravimetric density is more important: - Electric vehicles - Aircraft - R/C - Anything that goes into space - Large scale energy storage (good energy density typically = less lithium used) - Generally: anything that moves Places where both are equally important: - Consumer electronics (you don't want an ultra slim 2lb phone, or a ultra thick featherweight phone) Places where volumetric density is more important: - Batteries in smartcards - Some medical devices - Certain flashlights, IoT devices You'll notice that there are a lot more things where people care more about gravimetric density. Also, the best Li-Ion cells for volumetric density that you can buy are rather inconvenient shapes; a favorite is the 18650, an 18mm diameter by 65mm long cylinder. Yes, the best 18650 technically has much better volumetric density than the iPhone batteries. But if you swapped the iPhone battery with an 18650 you'd have a hilarious looking semi-cylinder protruding from the back.