RECHARGEABLE BATTERY 26650- PIKCELL 3.7V 5000 MAH

That looks like a high-capacity lithium-ion cell! Specifically, you have a 26650 Lithium Rechargeable Battery. These are the "big brothers" to the common 18650 batteries you might find in laptop packs or vapes; they are thicker and pack a significantly punchier runtime.
​Here is a breakdown of what those markings actually mean:
​Spec Breakdown
​3.7V: This is the nominal voltage. When fully charged, it will actually sit around 4.2V, and you should stop using it (recharge it) once it hits about 3.0V.
​ICR: This refers to the chemistry, typically Lithium Cobalt Oxide. These provide high energy density but require careful handling (never overcharge or short them!)