Solar power Circuit?

I want to power a RF transmitter with a rechargeable Polymer Lithium Ion Battery. I will use a small solar panel to recharge the battery.
Do I need a special charging circuit or will just a diode work. I will stay below the max voltage of the battery. Suggestions wanted.

Thanks
Rico Bravo

For lithium (LiIon or LiPo) batteries, you must use a special charging circuit. Overcharging them can cause them to catch fire.

Ran