Abstract
Currently, the application of high voltage cathode is hindered by its instability of electrode/electrolyte interphase. Continuous electrolyte oxidation and products accumulation lead to the increase of electrode polarization, and the degeneration of cycle life, rate capability and low temperature performance. Such interfacial challenge is even more serious for Ni-rich cathode materials, because the high nickel state generated during charging would further aggravate these side reactions. Lithium tetraborate (Li2TB), a novel electrolyte film-forming additive is proposed in this work to conduct a high stability and low impedance interphase on the Ni-rich cathode surface. After 300 cycles, the capacity retention of LiNi0.6Co0.2Mn0.2O2 (NCM622)/Li half-cell with 2 wt% Li2TB increases from 50% to 76%. After 150 cycles at low temperature, the capacity retention with Li2TB achieves 99%, compared with 47% for the one without additive. Moreover, the capability of Li2TB additive on enhancing the interphasial stability of NCM622 cathode has been further verified in 2 Ah-grade NCM622/graphite pouch cell. Finally, the mechanism of additive is proposed by combining theoretical calculation and experimental results.
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