Adiponitrile (C6H8N2): A New Bi-Functional Additive for High-Performance Li-Metal Batteries

Abstract

Rechargeable batteries with a Li metal anode and Ni-rich Li[NixCoyMn1−x−y]O2 cathode (Li/Ni-rich NCM battery) have been emerging as promising energy storage devices because of their high-energy density. However, Li/Ni-rich NCM batteries have been plagued by the issue of the thermodynamic instability of the Li metal anode and aggressive surface chemistry of the Ni-rich cathode against electrolyte solution. In this study, a bi-functional additive, adiponitrile (C6H8N2), is proposed which can effectively stabilize both the Li metal anode and Nirich NCM cathode interfaces. In the Li/Ni-rich NCM battery, the addition of 1 wt% adiponitrile in 0.8 m LiTFSI + 0.2 M LiDFOB + 0.05 M LiPF6 dissolved in EMC/FEC = 3:1 electrolyte helps to produce a conductive and robust Li anode/ electrolyte interface, while strong coordination between Ni4+ on the delithiated Ni-rich cathode and nitrile group in adiponitrile reduces parasitic reactions between the electrolyte and Ni-rich cathode surface. Therefore, upon using 1 wt% adiponitrile, the Li/full concentration gradient Li[Ni0.73Co0.10Mn0.15Al0.02] O2 battery achieves an unprecedented cycle retention of 75% over 830 cycles under high-capacity loading of 1.8 mAh cm−2 and fast charge–discharge time of 2 h. This work marks an important step in the development of high-performance Li/Ni-rich NCM batteries with efficient electrolyte additives.