Aluminum and Gallium Substitution into 0.5Li 2 MnO 3 ·0.5Li(Ni 0.375 Mn 0.375 Co 0.25 )O 2 Layered Composite and the Voltage Fade Effect

Abstract

Lithium- and manganese- rich layered composite cathodes in the general form (Li2MnO3 center dot LiMO2; M = transition metals), suffer from voltage profile suppression during cycling in Li- ion cells leading to overall gradual energy losses in the system. The suppression in cathode voltage which is called ` voltage fade' is a general phenomenon for these class of materials which needs to be understood and mitigated for enabling this chemistry in advanced Li- ion cells. Synthetic manipulation of the composition in 0.5Li(2)MnO(3)center dot 0.5LiNi(0.375)Mn(0.375)Co(0.25)O(2) (= Li1.2Ni0.15Mn0.55Co0.1O2 in layered notation) cathode material via aluminum and gallium substitution (max. 10%) via sol- gel reaction was completed and the voltage fade percentage was measured following a prescribed electrochemical testing protocol. While the specific capacities (similar to 250 mAh/g) are unaffected by the Al and Ga substitution (up to 5%), similar to 3 to 4% of the impedance- corrected average voltage is still lost (first 25 cycles) which is comparable to what the pristine material experiences. This result suggests that the path of structural change that occurs in the material during Li cycling is unaltered by synthetic manipulation of octahedral and/or tetrahedral sites though the use of Al and Ga non- redox active cations. (C) The Author(s) 2014. Published by ECS. All rights reserved.