Answer:
The electrochemical reaction of the battery must be reversible.
Step-by-step explanation:
An electrochemical cell is device in which chemical reactions produce electricity. There are two main types of electrochemical cells:
Primary cells: In primary cells, the chemical reaction through which electric current is generated is irreversible and hence cannot be re-charged.
Secondary cells: are those in which chemical reactions through which electricity is generated is reversible. Hence they can be re-charged.