We studied the photoresponse of a membrane electrode of stoichiometric LiCo
O2 used in lithium ion batteries. The electrode LiCoO2 in contact with dime
thyl carbonate, propylene carbonate and LiClO4 presents the behavior of a p
-semiconductor /electrolyte junction. The deinsertion of lithium of the LiC
oO2 suppresses the photoresponse at 3.9 V versus the lithium potential. The
reappearance of the photoresponse after re-intercalation suggests that the
alterations in the electronic structure of the LixCoO2 electrode probed by
the photoelectrochemical experiments during deinsertion are reversible unt
il x = 0.5. The direct band gap energy of the LiCoO2 stoichiometry is 2.5 e
V before and after lithium reinsertion. The experiments showed also that a
small photo-intercalation current is observed in this cathodic material. (C
) 2001 Elsevier Science B.V. All rights reserved.