Well, it can just use some ultra thin, rechargeable micro-capacitors, and the electronics can possibly be shielded. We're already working on thin, flexible batteries IRL anyways. Though this is supposed to be a moderate to high end piece of equipment, I suggest against making it overcomplicated by adding on more features. Though it would be cool to simply have the card open the door for you, we have to admit that just disabling the electronics so we can card it the old fashioned way is more fun. My own opinion, is that this tool is a 'burn' type of tool, one that's used because it's quick and fast, but destroys to get entry. A more complex ones should be used to covertly enter without leaving behind clues, but that's my own opinion, which does not have to be taken.
As we last left off, a different material is needed - I actually suggest an advanced polymer, since the metal alloys aren't as flexible, something that's necessary when carding a door to unlock it. The thing has to swedge in there, and if the armor grade alloy is thin enough to do that, then it'd risk cutting the user.