Passive RFID does not need a battery. If it was active or semi passive RFID, you would see a battery in there somewhere. The standard door entry type cards that you see and are short range are HF RFID. They are also used for transport ticketing etc. These are based on 13.56Mhz and (sometimes) conform to the MiFare standard which is based on ISO 1443 or ISO15693 standard. They are based on magnetic transfer of data and so are 'near field'.
UHF RFID is up at 900MHz, has longer range, lower size and cost tags. These are used for applications with a range up to 10's of metres (gate openers etc) as well as tagging pallets in supermarkets.
MiFare was designed by Philips (OK, a company that Philips took over). philips is now NXP semiconductors.