Li-ion CR2 / 15270 voltage and charging circuitry
I thought Li-ion and Lipo batteries were always 3.7v,


Actually the most common Li-ion are 3.6V. The charlatan vendors on eBay and Amazon like to incorrectly use 3.7V.  You can find the Panasonic NCR18650 cells on eBay and Amazon as 3.7V.  Yet the Panasonic NCR18650 datasheet says 3.6v.

There are various Li-ion chemistries. The more expensive Li-manganese, used in power tools, is 3.7V.  Most Li-ion are Li-cobalt or Lithium Nickel Manganese.  

The 3.2V Li-phosphate is becoming more popular especially as an automotive Lead Acid replacement.  The expensive Li-titanate are 2.4V.

See the "Nominal Voltage" row of the various Li-ion batteries:  Summary Table of Lithium-based Batteries  




  Does it require a different charger circuit than normal 3.7v
  li-ion/lipo batteries?


You cannot use a charger on a CR2.

The CR2 lithium (Lithium/Iron Disulfide, Li/MnO2) is a primary battery, not rechargeable.  Lithium AA batteries have a nominal 1.5V.  The CR2 is a dual cell, Li/MnO2 battery

LINK: Lithium (CR2) Datasheet