The Role of Porosity-Graded Electrode in Mitigating Performance Degradation of High Voltage Lithium-Ion Battery

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LiNi0.5Mn1.5O4 (LNMO) is one of the most potential candidates as cathode material for lithium-ion batteries (LIBs) due to the high operating voltage (4.7 V vs. Li) and high specific energy (650Wh·kg-1). However, severe accelerated performance degradations as well as electrolyte decomposition, especially at the interface between electrode and electrolyte, hinder the implementation of the LNMO. The degradations can cause capacity fade and reduce the battery life time. In this work, porosity-graded electrodes are designed to mitigate the LNMO degradation. The LNMO was synthetized by solid-state reaction. X-ray powder diffraction (XRD) experiment was applied to confirm the crystal structure of the LNMO. Scanning electron microscope (SEM) experiment was used to observe the porosities and confirm the elements in the electrode. A double-layered electrode with different porosities was fabricated in this experiment. The increase in porosity can improve the conductivity and diffusivity of lithium-ions through the electrode. In addition, solid electrolyte interphase (SEI) growth is location dependent due to its growth related to the electron current flow and Li+ diffusion. Therefore, SEI formation can be varied and controlled when the porosity is different inside the electrode. The testing results showed, comparing with single layer electrode, the porosity-graded electrode reduced the capacity fade about 8.285% for full cell and 5.290% for half-cell.