2001 ford focus

I don't understand what the battery may have to do with it, but keys jamming in the ignition lock is a known defect in early production Focus. It happened to me. It requires a dealer or qualified locksmith to fix, since the new lock must be set to the old key. Fortunately it's not too expensive (maybe $200 U.S.).

The replacement locks seem to be better quality than the original ones, but for safety, it's a good idea to squirt lock lubricant (not regular oil) into the key slot once or twice a year.