The metal which is actually oxidized/reduced in a lithium ion battery is: a. cobalt b. lithium c. manganese d. zinc

b. Lithium

Explanation:

Lithium-ion batteries (LIB) is a rechargeable battery. It was first proposed by M stanley  Whittingham in 1970s. These kind of batteries are commonly used in electrical vehicles and portable electronics. It also have military , naval and aerospace applications.

In LIB, the lithium ions move from the negatively charged electrode to the positively charged electrode during the discharge process and move in the reverse direction when the during the charging process. The battery uses an intercalated lithium compound is used to form anode and graphite is used to form cathode.

Thus, Lithium is oxidized/reduced in a lithium ion battery.