Abstract: The spent secondary battery contains a lot of valued metals, suchas Ni, Co and rare earths, so its recycling and reuse are most important to reduce the production cost and possible environmental pollution. A reduction and alkali dissolution method isused, by which Co is dissolved into the concentrated alkali solution after the addition of reducing agent, NaBH₄. The results show that the lowest Co content reaches 1.84% when the 11.0 mol/L KOH solution isused.In addition, the dissolved Co in alkali solution, can be regenerated by the air oxidization and reduction into Co(OH)₂ as the conducting agent for the Ni-M(H) positive electrodes.