Battery Cable Problem

I successfully replaced by original battery on my 1999 Accord. However, the positive cable is corroded and makes poor contact. The cable lug, that goes around the battery terminal, is partially deteriorated (about a quarter inch square is missing near the bottom of the lug) but the lug stills goes completely around the terminal. The nut and bolt on the lug is seized up and I cannot loosen them without destroying the lug. For now the lug fits snuggly on the terminal but today it got loosened and the car would not start.

Should I replace the battery cable? Replace the lug? Somehow secure the existing lug?

Any suggestions, comments most welcomed.