Abstract

The demand for lithium-ion batteries (LIBs) with high mass-specific capacities, high rate capabilities and long-term cyclabilities is driving the research and development of LIBs with nickel-rich NMC (LiNixMnyCo1−x−yO2, x geqslant 0.5) cathodes and graphite (LixC6) anodes. Based on this, this review will summarize recently reported and widely recognized studies of the degradation mechanisms of Ni-rich NMC cathodes and graphite anodes. And with a broad collection of proposed mechanisms on both atomic and micrometer scales, this review can supplement previous degradation studies of Ni-rich NMC batteries. In addition, this review will categorize advanced mitigation strategies for both electrodes based on different modifications in which Ni-rich NMC cathode improvement strategies involve dopants, gradient layers, surface coatings, carbon matrixes and advanced synthesis methods, whereas graphite anode improvement strategies involve surface coatings, charge/discharge protocols and electrolyte volume estimations. Electrolyte components that can facilitate the stabilization of anodic solid electrolyte interfaces are also reviewed, and trade-offs between modification techniques as well as controversies are discussed for a deeper understanding of the mitigation strategies of Ni-rich NMC/graphite LIBs. Furthermore, this review will present various physical and electrochemical diagnostic tools that are vital in the elucidation of degradation mechanisms during operation to supplement future degradation studies. Finally, this review will summarize current research focuses and propose future research directions.Graphic The demand for lithium-ion batteries (LIBs) with high mass specific capacities, high rate capabilities and longterm cyclabilities is driving the research and development of LIBs with nickel-rich NMC (LiNixMnyCo1−x−yO2, x ≥ 0.5) cathodes and graphite (LixC6) anodes. Based on this, this review will summarize recently reported and widely recognized studies of the degradation mechanisms of Ni-rich NMC cathodes and graphite anodes. And with a broad collection of proposed mechanisms on both atomic and micrometer scales, this review can supplement previous degradation studies of Ni-rich NMC batteries. In addition, this review will categorize advanced mitigation strategies for both electrodes based on different modifications in which Ni-rich NMC cathode improvement strategies involve dopants, gradient layers, surface coatings, carbon matrixes and advanced synthesis methods, whereas graphite anode improvement strategies involve surface coatings, charge/discharge protocols and electrolyte volume estimations. Electrolyte components that can facilitate the stabilization of anodic solid-electrolyte interfaces (SEIs) are also reviewed and tradeoffs between modification techniques as well as controversies are discussed for a deeper understanding of the mitigation strategies of Ni-rich NMC/graphite LIBs. Furthermore, this review will present various physical and electrochemical diagnostic tools that are vital in the elucidation of degradation mechanisms during operation to supplement future degradation studies. Finally, this review will summarize current research focuses and propose future research directions.

Highlights

  • Due to significant advantages such as high energy densities, high galvanic potentials, wide temperature ranges, no memory effects and long service lifespans, lithium-ion batteries (LIBs) have been widely employed in various applications, including in the fields of communication, aviation and transportation

  • Throughout the operation of Ni-rich NMC-based LIBs, four types of unwanted substances exist on the surface of cathodic particles, including other phases, surface impurities, rocksalt structures and surface films

  • To sum up, aging effects on both micrometer and atomic scales can result in two common outcomes in which the first is the chemical and mechanical damage/loss of active materials and the second is the production of detrimental substances on electrode particle surfaces, including surface films, surface impurities and surface layers

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Summary

Introduction

Due to significant advantages such as high energy densities, high galvanic potentials, wide temperature ranges, no memory effects and long service lifespans, lithium-ion batteries (LIBs) have been widely employed in various applications, including in the fields of communication, aviation and transportation. Controversies in mitigation strategies and trade-offs need to be considered, such as the selection of dopants or coating materials, all of which have yet to be discussed Based on this, these vacancies in the literature will be covered in this review to assist in the further investigation of Ni-rich NMCbased LIBs. Apart from the cathode, graphite—the anode material that has received the most attention in LIBs due to its high mass-specific capacity and economic advantages [26, 31, 32]—can function collaboratively with NMC-based cathodes to provide promising performances in coin cells [20, 33], pouch cells [9, 34], pouch bags [11] and T-cells [35]. This review will provide a summary of the recent advances in Ni-rich NMC-based batteries and can supplement pioneering reviews published previously

Degradation Mechanisms
Ni‐Rich NMC‐Based Cathodes
Surface Degradation During Cell Operation
Impurities and Parasitic Reactions
Other Issues
Graphite Anode
Summary
Electrochemical Techniques
Charge/Discharge Tests
High SOC
15 Low voltage
Cyclic Voltammetry
Electrochemical Impedance Spectroscopy
Crystal Lattice and Particle Morphology
Chemical Analysis
Thermal Stability
Advanced Physical Characterization
Inner Surface
Outer Surface
Advanced Preparation Methods
Synergy of Multiple Mitigation Methods
Testing Protocols
Surface Coating
Electrolyte Volume Adjustment
Electrolyte Additive
Lithium Salt
Solvent
Findings
Summary and Prospective
Full Text
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