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Issue 46, 2014
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Electrochemistry and structure of the cobalt-free Li1+xMO2 (M = Li, Ni, Mn, Fe) composite cathode

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Abstract

The development of cathode materials with high capacity and cycle stability is essential to emerging electric-vehicle technologies, however, of serious environmental concern is that materials with these properties developed so far contain the toxic and expensive Co. We report here the Li-rich, Co-free Li1+xMO2 (M = Li, Ni, Mn, Fe) composite cathode material, prepared via a template-free, one-step wet-chemical method followed by conventional annealing in an oxygen atmosphere. The cathode has an unprecedented level of cation mixing, where the electrochemically-active component contains four elements at the transition-metal (3a) site and 20% Ni at the active Li site (3b). We find Ni2+/Ni3+/Ni4+ to be the active redox-center of the cathode with lithiation/delithiation occurring via a solid-solution reaction where the lattice responds approximately linearly with cycling, differing to that observed for iso-structural commercial cathodes with a lower level of cation mixing. The composite cathode has ∼75% active material and delivers an initial discharge-capacity of ∼103 mA h g−1 with a reasonable capacity retention of ∼84.4% after 100 cycles. Notably, the electrochemically-active component possesses a capacity of ∼139 mA h g−1, approaching that of the commercialized LiCoO2 and Li(Ni1/3Mn1/3Co1/3)O2 materials. Importantly, our operando neutron powder-diffraction results suggest excellent structural stability of this active component, which exhibits ∼80% less change in its stacking-axis than for LiCoO2 with approximately the same capacity, a characteristic that may be exploited to enhance significantly the capacity retention of this and similar materials.

Graphical abstract: Electrochemistry and structure of the cobalt-free Li1+xMO2 (M = Li, Ni, Mn, Fe) composite cathode

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Publication details

The article was received on 01 Jul 2014, accepted on 13 Oct 2014 and first published on 16 Oct 2014


Article type: Paper
DOI: 10.1039/C4CP02864C
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Citation: Phys. Chem. Chem. Phys., 2014,16, 25377-25385

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    Electrochemistry and structure of the cobalt-free Li1+xMO2 (M = Li, Ni, Mn, Fe) composite cathode

    W. K. Pang, S. Kalluri, V. K. Peterson, S. X. Dou and Z. Guo, Phys. Chem. Chem. Phys., 2014, 16, 25377
    DOI: 10.1039/C4CP02864C

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