Unlike some batteries, like the AA battery, both the anode and the cathode are situated on the top plate, which is often made of sturdy plastic. The cathode is the positive electrode, through which current flows when the battery is connected. This is the smaller, stubby cylindrical connector. The cathode is often, but not always, marked with a "+" sign beside or near the cathode.
The anode is the negative electrode through which current flows when the battery is connected. This is the larger, stubby cylindrical connector, sometimes with slits or a "pie-crust" or otherwise hexagonal edge. The anode is often, but not always, marked with a "-" sign beside or near the anode. Because of natural chemical reactions, the zinc anode corrodes more slowly in alkaline batteries than acid batteries.
The metal jacket of a 9-volt battery is crimped, or gathered, around the exterior of the battery. It is the part that carries the company logo. Often, there will be printed information about the battery type, the code number, country of origin and safety advice. The metal jacket keeps all the internal components together and helps to resist breakage, leakage and bulging.
Inside some 9-volt batteries are 6 x 1.5 volt cells very similar to AAAA-type "batteries," being cylindrical and containing the same chemicals, depending on the battery type. In other 9-volt batteries, there are 6 x 1.5-volt "cakes" reminiscent of voltaic piles. In both cases, the 6 x 1.5-volt cells are connected in series and work together to deliver the 9 volts. 9 volts is an average rating and the true voltage lies in a range which, in some cases, is as wide as 5.4 to 9.9 volts.