We demonstrate that extensive electrochemical shock-electrochemical cycling induced fracture-occurs due to coherency stresses arising from first order cubic-to-cubic phase transformations in the spinels LiMn2O4 and LiMn1.5Ni0.5O4. Electrochemical shock occurs despite the isotropy of the shape changes in these materials. This electrochemical shock mechanism is strongly sensitive to particle size; for LiMn2O4 and LiMn1.5Ni0.5O4, fracture can be averted with particle sizes smaller than similar to 1 mu m. As a further critical test of the proposed mechanism, iron-doping was used to induce continuous solid solubility of lithiuni in LiMn1.5Ni0.5O4, and shown to virtually avert electrochemical shock, while having minimal impact on the electrode potential and capacity. (C) The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: [email protected]. All rights reserved.