Greg, I am not aware of any handheld GPS receiver that uses a lithium ion rechargeable battery. Generally, when somebody refers to a lithium battery, they mean a lithium primary battery, and when they refer to a lithium ion battery, they mean a lithium ion rechargeable. Yes, lithium ion rechargeables tend to have a higher voltage, and that makes them incompatible for more normal devices.
One advantage of a lithium primary battery is that it can output huge amounts of instantaneous current. So, that makes them good for things like an emergency radio transmitter. They have a very long shelf life, maybe ten years, so that makes them good for some emergency device that is packaged and stored for a long time before use. They are lighter in weight, which makes them appealing to people here.
If I were using a GPS receiver for an hour or two per day, every day, and if I had a powered up charger for batteries, then the Nickel Metal Hydride rechargeables work good and are very economical.
It's all a matter of compromises.