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

• Published in: Advanced functional materials 2019-07, Vol.29 (30), p.n/a
• Main Authors: Lee, Seon Hwa, Hwang, Jang‐Yeon, Park, Seong‐Jin, Park, Geon‐Tae, Sun, Yang‐Kook
• Format: Article
• Language: English
• Subjects: Additives; Anode effect; Batteries; Battery cycles; bi‐functional additives; Cathodes; Concentration gradient; Electrolytes; Energy storage; fast charging; Flux density; high‐energy density; lithium‐metal batteries; Materials science; Nickel; Ni‐rich NCM cathodes; Organic chemistry; Organic compounds; Rechargeable batteries
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201902496

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 Ni‐rich 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. The addition of adiponitrile in the electrolyte plays an important role in stabilizing both the Li‐metal anode/electrolyte and Ni‐rich NCM cathode/electrolyte interfaces; moreover, it subsequently suppresses the undesired electrolyte decomposition. Upon using 1 wt% adiponitrile‐containing electrolyte, Li/Ni‐rich NCM batteries can survive at a practical operating condition during long‐term cycling over 830 cycles.