Challenges and Strategies to Advance High‐Energy Nickel‐Rich Layered Lithium Transition Metal Oxide Cathodes for Harsh Operation

Abstract

Nickel-rich layered lithium transition metal oxides (LiNi 1−x−y Co x Mn y O 2 and LiNi 1−x−y Co x Al y O 2 , x + y ≤ 0.2) are the most attractive cathode materials for the next generation lithium-ion batteries for automotive application. However, they suffer from structural/interfacial instability during repeated charge/discharge, resulting in severe performance degradation and serious safety concerns. This work provides a comprehensive review about challenges and strategies to advance nickel-rich layered cathodes specifically for harsh (high-voltage, hightemperature, and fast charging) operations. Firstly, the degradation pathways of nickel-rich cathodes including surface/interface degradation, undesired cathode-electrolytes parasitic reactions, gas evolution, inter/intragranular cracking, and electrical/ionic isolation are discussed. Then, recent achievements in stabilizing the structure/interface of nickel-rich cathodes via surface coating, cation/anion doping, composition tailoring, morphology engineering, and electrolytes optimization are summarized. Moreover, challenges and strategies to improve the performance of Ni-rich cathodes at the electrode level are discussed. Outlook and perspectives to promote the practical application of nickel-rich layered cathodes toward automotive application are provided as well.

Cross‐Talk‐Suppressing Electrolyte Additive Enabling High Voltage Performance of Ni‐Rich Layered Oxides in Li‐Ion Batteries

“…Compared with commercialized cathode materials, such as LiCoO 2 (145 mAh g À 1 ) and spinel-LiMn 2 O 4 (120 mAh g À 1 ), the Ni-rich layered oxides (LiNi x Mn y Co z O 2 ; x � 0.6, x + y + z = 1, Ni-rich NCMs) have a higher practical specific capacity of around 180 mAh g À 1 with the same upper cutoff potential of 4.2 V vs. Li + /Li at C/10. [4][5][6][7][8] Even more of the specific capacity can be extracted from Ni-rich NCM cathodes by expanding the voltage window of the cells to cutoff potential above 4.2 V vs. Li + /Li, despite a small 0.1 V difference in upper cutoff voltage. [9][10][11][12][13] However, both limited anodic stability of the standard electrolytes above 4.2 V vs. Li + /Li and instability of Nirich NCM cathode materials in a highly-charged state make high-voltage performance difficult to achieve.…”

Calendar Aging of Li-Ion Cells—Experimental Investigation and Empirical Correlation

“…It also revealed a complex dependency on the NMC composition with respect to the stability of the materials to a temperature rise and increased cut-off voltage. An increase in the nickel content to enhance energy density reduces the stability and raises the degradation rate, which can be counteracted by an increase in the manganese content within the composition [18][19][20][21].…”

Unusual Surface Texture, Dimensions and Morphology Variations of Chiral and Single Crystals**

“…Crystallization processes are also known to produce hierarchical superstructures by the alignment of small crystallites. Such crystals have a multidomain morphology and are expected to be polycrystalline [11–14] …”

“…Therefore, the predesign and control of crystal morphology,u niformity and monodispersity is still at remendous challenge.C rystal-lization processes are also known to produce hierarchical superstructures by the alignment of small crystallites.S uch crystals have amultidomain morphology and are expected to be polycrystalline. [11][12][13][14] Many naturally occurring crystals have shapes which do not correlate with their crystallographic symmetry.B iomineralization can afford materials with superior properties, complex morphologies and hierarchical order. [15][16][17][18] Most of these natural materials are based on single crystals of calcium carbonate.T he existence of specific and complex morphologies is ad irect result of the evolutionary approach of nature and needed to fulfill various tasks.For example,coccoliths are composed of calcium carbonate which is known to be brittle.…”