Enabling Stable High‐Rate Cycling of Energy Dense Lithium‐Ion Batteries (LiFePO 4 || Graphite) Based on Thick Electrodes by Employing Ester‐Based Electrolytes

Increasing the thickness of the electrodes offers the benefit of increasing the energy density while reducing the costs of the lithium‐ion battery (LIB) cells. However, with conventional carbonate‐based electrolytes, thick electrode‐based LIB cells can only deliver reasonable performance up to a certain critical C‐rate. At higher C‐rates, their power density and cyclic stability are greatly compromised owing to inferior Li + mass transport and elongation of Li + diffusion pathways within the porous structure of the thick electrode. To counter this challenge and extend the rate capability of the thick electrode‐based LIB, this study investigated the use of ester‐based electrolytes with enhanced Li + mass transport properties. Compared to a conventional carbonate‐based electrolyte, methyl acetate (MA)‐based electrolytes with a small quantity of sacrificial additive can improve the rate performance and enable long‐term cycling of thick electrode (5.4 mAh cm −2 ) LiFePO 4 || graphite cells at high C‐rate by reducing Li + mass transport induced polarization, improving charge transfer kinetics, and suppressing lithium metal deposition (plating) on graphite during charging.