Cross-Talk-Suppressing Electrolyte Additive Enabling High Voltage Performance of Ni-Rich Layered Oxides in Li-Ion Batteries.

Abstract

Control of electrode-electrolyte interfacial reactivity at high-voltage is a key to successfully obtain high-energy-density lithium-ion batteries. In this study, 2-aminoethyldiphenyl borate (AEDB) is investigated as a multifunctional electrolyte additive in stabilizing surface and bulk of both Ni-rich LiNi0.85 Co0.1 Mn0.05 O2 (NCM851005) and graphite electrodes in a cell operated with elevated upper cutoff voltage of 4.4 V vs. Li+ /Li. The presence of AEDB in a full-cell inhibits structural degradation of both cathode and anode materials, suppressing crack formation, and reduces metal dissolution at the cathode and metal deposition at the anode. As a consequence, the interfacial resistance is significantly reduced. Moreover, this is a case where "the whole is greater than the sum of the parts": the effect of AEDB in half-cells is rather modest, whereas in full-cells its addition results in tremendous performance improvement. The graphite‖NCM851005 full-cell in the presence of AEDB has a capacity retention of 88 % after 100 cycles, even when the upper cutoff voltage is set to 4.35 V, corresponding to 4.4 V vs Li+ /Li, whereas with standard electrolyte under the same conditions it is only 21 %. The study shows a simple and easy approach to using Ni-rich cathodes in an extended voltage window and demonstrates the importance of full-cell testing for electrolyte additive selection.