Aluminum current collectors for cathodes in 61 life-tested lithium-ion batteries were microscopically examined for evidence of corrosion. In addition, galvanostatic anodic polarization tests were conducted in LiPF 6-containing battery electrolytes on samples of bare aluminum, of aluminum coated with a LiFePO 4 cathode, and of aluminum affixed with polyethylene crevices. The results indicate that aluminum current collectors are susceptible to corrosion, which most likely occurs as underdeposit corrosion at pores in the cathode.