Has there ever been a DAP using button cell？

[Tomoe Hotaru]

I would like to get one

 

[RayDunzl]

Unlikely..

If you mean these:

Button cell - Wikipedia

en.wikipedia.org

 

[Tomoe Hotaru]

Unlikely..

If you mean these:

Button cell - Wikipedia

en.wikipedia.org

Yes，I want to buy a protable player using these

 

[DVDdoug]

I assume the problem is that headphones (or Bluetooth transmission) require a fair amount of energy.

 

[solderdude]

That and button cells are designed to provide a low voltage for a long time but with very low current capability and are not really suited for 'dynamic' load currents.
So... you find them as backup batteries, in watches, flat remotes and toys.

 

[Killingbeans]

They are also not rechargeable. A small LiPo makes way more sense.

 

[voodooless]

Why is the shape of the battery an important criterium for buying a DAP?

 

[staticV3]

There are DAPs that are powered by a single AAA battery:

Could that be an acceptable compromise?

 

[somebodyelse]

They are also not rechargeable. A small LiPo makes way more sense.

Some are, some aren't. There are Lithium Ion rechargeable ones in a lot of the same sizes as the non-rechargeable ones. See LIR2032 and LIR2450 for examples. I don't know of any players using them though, and I agree about the small LiPo.