The further development of lithium-ion batteries is often desired to obtain higher capacities by charging to higher potentials. However, such a high potential (> 4.3 V) will inevitably result in capacity loss of the LiMn 2 O 4 cathode material over numerous cycles. In this work, degradation mechanisms of LiMn 2 O 4 electrode cycled at different charge cut-off potentials (4.4, 4.5, 4.6, 4.7, and 4.8 V vs. Li/Li + , respectively) have been investigated. It is found that the capacity degraded seriously after aging cycles at the cut-off potentials (< 4.6 V), especially at 4.4 V. Remarkably, a thicker cathode-electrolyte interface (CEI) film on the cathode surface can be observed when the potential reached 4.7 and 4.8 V. Thus, two degradation mechanisms are proposed, which are also verified by the calculation of the diffusion coefficient of Li + ions (D Li + ). This work demonstrates the relationship between the capacity fade and cut-off potentials and provides a useful guidance for other cathode materials with high-voltage operation.

Degradation mechanism of LiMn 2 O 4 cathode at high cut-off voltage of 4.8V has been investigated. Electrochemical tests of the cathode show that the rapid capacity loss due to the oxidation of electrolyte and the generation of oxygen species under high voltage operation leads to the increase of electrode resistance. In addition, a thick layer is found on the cathode surface from scanning electron microscope. The thickness of the layer increases with the increment of charge potentials.

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