Effect of molecular structure of nitrile additives on the cyclability of LiNi_0.9Co_0.05Mn_0.04Al_0.01O₂||SiO_x/Gr pouch cell

Nitriles are effective electrolyte additives commonly used in lithium-ion batteries (LIBs). However, the concept of molecular-level screening and design for electrolyte modification has not yet been fully explored. In this article, we examine adiponitrile (ADN) and 1,3,6-Hexanetri carbonitrile (HTCN) as examples of nitrile additives to better understand how nitrile molecular structure impacts the surface modification of Ni-rich materials. The LiNi_0.9Co_0.05Mn_0.04Al_0.01O₂||SiO_x/graphite pouch cell with tridentate ligand-carrying HTCN improved cycling performance, achieving 88.97 % capacity retention after 300 cycles. In contrast, the pouch cell with bidentate ligand-carrying ADN experiences capacity rollover failure after just 250 cycles. This enhanced performance is attributed to the tri-ligand molecular configuration of HTCN, which allows for more cyanide-anchored transition metal (TM) ions to be presented at the same content of the cyanide group. This work offers original and in-depth insights into the mechanisms underlying cyanide-anchored TM ions of Ni-rich layered cathodes. It emphasizes the importance of optimizing the molecular conformation of nitrile additives for enhancing the performance of Ni-rich cathodes.