All mics will need power, either from a battery or from the camera they are attached to. As the 5DII doesn't supply power via the mic jack then you will have to use a mic that has its own power supply like a Rode Video mic, Rode Stereo mic, Sennheiser mke 400 etc...
If you want to use a higher grade of mic like a Rode NTG1 or similar then you will need a power source as these only run from phantom power. You can get an adapter made by Beachtec that will allow you to adjust audio levels and supply phantom power to the mic but they are expensive, especially if you buy the one made especially for the 5DII.
Any more questions just ask.