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Typically 10 Ohms according to http://data.energizer.com/pdfs/lithiumcoin_appman.pdf. I'd say that was still too low, and an additional 40 Ohms at least would perhaps be advised. But granted I was not aware that Lithium cells had such high IR.
Note that LED are not light bulbs and require a series resistor to drive them correctly. Without that, the LED may not last long and the battery certainly won't, and it will be unnecessarily bright. For a typical red LED, a minimum 50Ohm series resistor would be required for a 3V supply. See http://www.resistorguide.com/resistor-for-led/. If you use an AA 1.2V rechargable or a 1.5V regular cell, then you may not need a resistor if the battery voltage is less than the LED forward voltage. If you don't know the LED specs, best use a series resistor in any case. Since you need not run it at max brightness, a larger resistor will nor hurt - say 100Ohm to be safe.