The effect of synthesis methods on cation mixing degree in cobalt-free, nickel-rich NMA materials

Abstract

Cobalt plays a vital role in conventional cathode active materials (CAM) by stabilizing their crystal structure and prevents Li/Ni cation mixing. However, the cobalt content of cathode materials used in lithium-ion batteries must be reduced or eliminated due to the scarcity of cobalt resources, high price fluctuations, and other factors like its toxicity and some environmental and ethical concerns. To generate superior cathode materials for lithium-ion batteries at a cheaper cost and higher energy density, researchers have identified nickel-rich and cobalt-free cathode materials as their primary targets. This study examines how synthesis methods influence the properties of Ni-rich cathode materials, focusing on cation mixing, a key factor in electrochemical degradation and structural instability of LiNi_0.8Mn_0.15Al_0.05O₂ (NMA). Using solgel and coprecipitation methods, we synthesized cobalt-free, nickel-rich NMA and characterized its crystalline phases through XRD, SEM, Raman, FTIR, ICP, and BET techniques. XRD showed that coprecipitation achieved higher crystallinity with well-defined peaks. SEM revealed that coprecipitation produced uniform particles, whereas solgel yielded irregular shapes with wider size distribution. ICP confirmed that coprecipitation closely matched the theoretical Ni:Mn:Al ratio (0.8:0.15:0.05), and BET analysis indicated a surface area of 1.36 m²/g) of NMA performed via solgel method. These results highlight the superior crystallinity, particle uniformity, and compositional accuracy of coprecipitation, making it more effective for enhancing electrochemical stability and efficiency.