High‐Nickel NMA: A Cobalt‐Free Alternative to NMC and NCA Cathodes for Lithium‐Ion Batteries

Abstract

High-nickel LiNi_1- _x _- _y Mn_x Co_y O₂ (NMC) and LiNi_1- _x _- _y Co_x Al_y O₂ (NCA) are the cathode materials of choice for next-generation high-energy lithium-ion batteries. Both NMC and NCA contain cobalt, an expensive and scarce metal generally believed to be essential for their electrochemical performance. Herein, a high-Ni LiNi_1- _x _- _y Mn_x Al_y O₂ (NMA) cathode of desirable electrochemical properties is demonstrated benchmarked against NMC, NCA, and Al-Mg-codoped NMC (NMCAM) of identical Ni content (89 mol%) synthesized in-house. Despite a slightly lower specific capacity, high-Ni NMA operates at a higher voltage by ≈40 mV and shows no compromise in rate capability relative to NMC and NCA. In pouch cells paired with graphite, high-Ni NMA outperforms both NMC and NCA and only slightly trails NMCAM and a commercial cathode after 1000 deep cycles. Further, the superior thermal stability of NMA to NMC, NCA, and NMCAM is shown using differential scanning calorimetry. Considering the flexibility in compositional tuning and immediate synthesis scalability of high-Ni NMA very similar to NCA and NMC, this study opens a new space for cathode material development for next-generation high-energy, cobalt-free Li-ion batteries.