Abstract
The structural and electrochemical properties of Li0.99Ni0.46Mn1.56O4 (Fd m, disordered spinel) cathode material were studied and compared with stoichiometric LiNi0.5Mn1.5O4 (P4332, ordered spinel). First cycle discharge capacity of Li0.99Ni0.46Mn1.56O4 was similar to that of LiNi0.5Mn1.5O4 at C/3 and 1C rate, but cycling performance of Li0.99Ni0.46Mn1.56O4 was better than that of LiNi0.5Mn1.5O4 especially at high rate of 1C. This can be explained by performing synchrotron based in-situ XRD and results of GITT measurements. It is considered that faster lithium ion diffusion in the Li0.99Ni0.46Mn1.56O4 cathode results in the improvement of the rate capability. To study structural changes during cycling, synchrotron in-situ XRD patterns of both the samples were recorded at C/ 3 and 1C rate. Compared to stoichiometric LiNi0.5Mn1.5O4, disordered Li0.99Ni0.46Mn1.56O4 spinel sample has pseudo one phase behavior and one step phase transition between two cubic phases. So, LiNi0.5Mn1.5O4 would experience a much greater strain and stress, originating from the two phase transitions between three cubic phases and suffer from capacity loss during cycling especially at high rate.
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