Enhancing the stability of lithium ion cathode active materials to over-insertion of lithium can improve overdischarge tolerance in cells that have excess reversible lithium compared to the stoichiometric cathode capacity. In the present work, a solution deposited coating of AlPO4 on LiCoO2, known to stabilize overcharge, is applied to test its effect on the overdischarge (or over-insertion) tolerance of LiCoO2. Cathode testing versus lithium metal is performed with constant current charge to 140 mAh/gLiCoO(2), constant current discharge to 3.0 V vs. Li/Li+ and 7 mAh/gLiCoO(2) lithium over-insertion at fixed resistive load. Results show that the AlPO4 coating maintains >99% of the discharge energy (compared to 96% for the as-received LiCoO2) after 10 cycles. X-ray diffraction analysis of the relative intensity of {003} peak of the R (3) over barM space group indicates that after repeated lithium over-insertion, the AlPO4 coating suppresses irreversible cation exchange between Li and Co ions in the octahedral layers of LiCoO2. Thus, AlPO4 surface coatings can prevent crystal structure changes detrimental to charge/discharge performance in LiCoO2 caused by over-insertion of lithium ions. (C) The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.