Improving the performance of LiNi0.5Mn1.5O4 cathode based high-voltage lithium-ion batteries via manipulating the electrolyte solution with trimesic and terephthalic acids

The sustainable electrochemical behavior of Li-metal/ion batteries heavily relies on the modulation of solid-electrolyte interphases (SEI) formed on their electrodes. In this study, we introduced trimesic acid (TMA) and terephthalic acid (TPA) into a conventional liquid electrolyte solution (LP57) comprised of 1.0 M LiPF₆ in EC/EMC (3:7) to create suspension electrolyte systems. These solutions were tested in high-voltage Li and Li-ion cells comprising Li metal or graphite anodes (respectively) and LiNi_0.5Mn_1.5O₄ (LNMO spinel) cathodes. The electrolyte solutions’ modifications tested herein resulted in forming a LiF-rich interphase on the negative electrodes, which improved the Li-plating and stripping process, lowered voltage hysteresis, and reduced electrolyte solutions decomposition during prolonged electrochemical processes. We tested the suspension electrolyte systems in comparison to LP57 in Li│LNMO and Gr│LNMO cells at 30 °C and established significant improvements in the electrochemical performance, including long-term cycling, rate capability and capacity retention, average voltage, hysteresis, and evolution of the direct current internal resistance (DCIR) of cells containing the modified suspension solutions compared to the reference cells. The LNMO cathodes in Li-cells comprising the suspension electrolyte systems displayed remarkable structural, morphological, and thermal stability during prolonged cycling, delivering 98 % and 92 % capacity retention after 400 cycles in LP57 + TMA and LP57 + TPA, respectively, compared to only 38 % in the cells containing the conventional LP57 solution.