Comparative Study of Ni-Rich Layered Cathodes for Rechargeable Lithium Batteries: Li[Ni0.85Co0.11Al0.04]O2 and Li[Ni0.84Co0.06Mn0.09Al0.01]O2 with Two-Step Full Concentration Gradients

Abstract

Compositionally graded Li[Ni0.84Co0.06Mn0.09Al0.01]O2 (TSFCG-Al) with two-step concentration gradients was prepared as a high-capacity cathode for Li batteries. The concentration gradients were introduced within a single particle to maximize the Ni fraction; this increased the discharge capacity while ensuring cyclic stability with a Mn-enriched surface layer. The concentration gradients also produced a unique morphology, in which rod-shaped primary particles were radially aligned in a spoke-like pattern. The fundamental electrochemical performance of TSFCG-Al is compared against that of commercial Li[Ni0.85Co0.11Al0.04]O2 (NCA). The TSFCG-Al cathode exhibits a higher discharge capacity and better cycling stability than the NCA cathode, even when they are charged to 4.5 V. Structural analysis of the cycled TSFCG-Al and NCA cathodes shows that the TSFCG-Al keeps its original structural integrity, while the NCA particles undergo serious particle degradation due to the accumulation of strain in the grain boundaries upon cycling.