Stability of aluminum substrates in lithium-ion battery electrolytes

The stability of aluminum positive electrode substrates in rechargeable lithium-ion batteries was investigated in solutions of lithium imide salt in ethylene carbonate-propylene carbonate-dimethyl carbonate (20:20:60 vol.%) using the technique of controlled potential coulometry. It was found that the protective surface film formed on aluminum in these solutions breaks down at potentials above 3.5 V during the charging of lithium-ion cells resulting in the corrosion of aluminum substrates and the premature failure of these cells. It was also found that the use of lithium tetrafluoroborate as an electrolyte additive prevents the breakdown of the protective film on aluminum substrates and prevents their corrosion at potentials above 3.5 V. In contrast to the lithium imide solutions, the aluminum substrates were found to be quite stable in lithium methide electrolyte solutions and did not undergo any significant corrosion at potentials up to about 4.25 V vs. the lithium reference electrode. (C) 1998 Elsevier Science S.A.