Understanding the Degradation Mechanisms of LiNi0.5Co0.2Mn0.3O2 Cathode Material in Lithium Ion Batteries

Jung, Sung‐Kyun; Gwon, Hyeokjo; Hong, Jihyun; Park, Kyu‐Young; Seo, Dong‐Hwa; Kim, Haegyeom; Hyun, Jinho; Yang, Wonyoung; Kang, Kisuk

doi:10.1002/aenm.201300787

Cited by 967 publications

(801 citation statements)

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“…Though no significant bulk structural change was observed from XRD, some structural changes may have occurred on the surface, which contribute to the irreversible capacity loss and impedance growth. 16,43 In particular, Ni 4+ is known to be highly reactive with the electrolyte, which leads to surface reconstruction and the buildup of surface reaction layers. In addition, formation and growth of cracks in the cathode particles degrade their ionic and electronic connectivity and further lead to a sluggish, incomplete reaction.…”

Section: Resultsmentioning

confidence: 99%

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Mao

Wood

David

et al. 2018

J. Electrochem. Soc.

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Most lithium-ion batteries still rely on intercalation-type graphite materials for anodes, so it is important to consider their role in full cells for applications in electric vehicles. Here, we systematically evaluate the chemical and physical properties of six commerciallyavailable natural and synthetic graphites to establish which factors have the greatest impact on the cycling stability of full cells with nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Electrochemical data and post-mortem characterization explain the origin of capacity fade. The NMC811 cathode shows large irreversible capacity loss and impedance growth, accounting for much of full cell degradation. However, six graphite anodes demonstrate significant differences with respect to structural change, surface area, impedance growth, and SEI chemistry, which impact overall capacity retention. We found long cycle life correlated most strongly with stable graphite crystallite size. In addition, graphites with lower surface area generally had higher coulombic efficiencies during formation cycles, which led to more stable long-term cycling. The best graphite screened here enables a capacity retention around 90% in full pouch cells over extensive long-term cycling compared to only 82% for cells with the lowest performing graphite. The results show that optimal graphite selection improves cycling stability of high energy lithium-ion cells. With the booming demands for electric vehicles and electronic devices, high energy density lithium-ion batteries with long cycle life are highly desired. Despite the recent progress in Si 1 and Li metal 2 as future anode materials, graphite still remains the active material of choice for the negative electrode. 3,4 Lithium ions can be intercalated into graphite sheets at various stages like Li x C 12 and Li x C 6 , providing a high specific capacity of 372 mAh/g (∼2.5 times higher than LiCoO 2 ) and high volumetric capacity (similar to LiCoO 2 ) corresponding to LiC 6 . 5,6 In addition to its low cost and non-toxicity, graphite has a lowest average voltage (150 mV vs. Li/Li + ) and the flat voltage profile, rendering a high overall cell voltage. 7 Graphite also displays a very low voltage hysteresis, which in turn results in high energy efficiency. 8 For applications in lithium-ion batteries, many properties of the graphite powders must be optimized including crystallinity, particle size, morphology, and surface chemistry. However, most research effort has been placed on the development and characterization of high performance cathodes, while the impact of the graphite anode on full cell performance has been largely unexplored.Compared to widely used battery cathodes such as LiCoO 2 (140 mAh/g), LiFePO 4 (160 mAh/g), LiNi 1/3 Mn 1/3 Co 1/3 O 2 (160 mAh/g), and LiNi 0.5 Mn 0.3 Co 0.2 O 2 (175 mAh/g), 9-11 nickel-rich LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) is delivers a higher specific capacity (180-220 mAh/g), which increases the battery life on a single charge. 12,13 The high capacity arises because Ni is the main red...

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Section: Resultsmentioning

confidence: 99%

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Mao

Wood

David

et al. 2018

J. Electrochem. Soc.

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“…The passivation layer forms during the rst charge, 12 and during exposure to electrolytic solution, 10,12 and accumulates during extended charging-discharging cycles. 10,11 The passivation layer inhibits lithium diffusion kinetics and increases the overall cell impedance, leading to the loss of practical capacity at moderate discharge rates. However, it has been shown that the lost capacity can mostly be recovered when a much slower charging rate is adopted.…”

Section: 8mentioning

confidence: 99%

“…The reliability of NMC materials at high voltages is strongly governed by the structural and chemical stability at the particle surfaces. [10][11][12] The particle surfaces usually undergo undesirable structural and chemical evolution (surface passivation) under harsh cycling conditions, such as high-voltage cycling. One of the major passivation mechanisms is surface reconstruction through the reduction of transition metals to form rock-salt and/or spinel phases.…”

Section: 8mentioning

confidence: 99%

Influence of synthesis conditions on the surface passivation and electrochemical behavior of layered cathode materials

et al. 2014

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Understanding the relationship between materials synthesis and electrochemical behaviors should provide valuable knowledge to further the advancement of lithium-ion batteries. In this work, layered cathode materials {e.g., LiNi 0.4 Mn 0.4 Co 0.18 Ti 0.02 O 2 (NMCs)} were prepared under three different annealing conditions, i.e., 900 C for 6 hours, 8 hours, and 12 hours, respectively. The resulting materials exhibit equivalent crystal structures and morphologies yet likely different surface chemical environments. These materials show distinctively different resistances against the surface passivation/ reconstruction (reduction of the transition metals in the layered structure to form rock-salt and/or spinel phases) during electrochemical cycling (2.0-4.7 V vs. Li + /Li). In general, the materials annealed for longer durations exhibited lower tendencies to form the surface passivation layer. Furthermore, the surface passivation became less severe when the electrode materials were cycled under mild conditions, such as slow constant current charging-discharging as opposed to cyclic voltammetry. The present study correlates the synthetic conditions with the surface instability and the electrochemical performance in cathode materials, and provides new insights into improving synthetic protocols for battery materials.

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“…17 This leads to cell impedance rise and an effective loss of capacity. In addition, rock salt or mixed rock salt/spinel phases on particle surfaces have been detected under various cycling or storage conditions for NMC-442, 18 LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC-532), 19 and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC-811). 20 In the study of NMC-532, it was found that surface reconstruction to a rock salt phase dominates when high voltage (4.8 V) cutoffs are used due to oxygen loss under the highly oxidizing conditions, while spinel forms under milder cycling conditions.…”

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confidence: 99%

Depth-Dependent Redox Behavior of LiNi_0.6Mn_0.2Co_0.2O₂

Tian

Nordlund

Xin

et al. 2018

J. Electrochem. Soc.

144

125

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Nickel-rich layered materials are emerging as cathodes of choice for next-generation high energy density lithium ion batteries intended for electric vehicles. This is because of their higher practical capacities compared to compositions with lower Ni content, as well as the potential for lower raw materials cost. The higher practical capacity of these materials comes at the expense of shorter cycle life, however, due to undesirable structure and chemical transformations, especially at particle surfaces. To understand these changes more fully, the charge compensation mechanism and bulk and surface structural changes of LiNi 0.6 Mn 0.2 Co 0.2 O 2 were probed using synchrotron techniques and electron energy loss spectroscopy in this study. In the bulk, both the crystal and electronic structure changes are reversible upon cycling to high voltages, whereas particle surfaces undergo significant reduction and structural reconstruction. While Ni is the major contributor to charge compensation, Co and O (through transition metal-oxygen hybridization) are also redox active. An important finding from depth-dependent transition metal L-edge and O K-edge X-ray spectroscopy is that oxygen redox activity exhibits depth-dependent characteristics. This likely drives the structural and chemical transformations observed at particle surfaces in Ni-rich materials. The need for lithium-ion batteries with higher energy density and lower cost than currently available, particularly for transport applications, has led to intensified interest in Ni-rich NMC (LiNi x Mn y Co z O 2 ; x+y+z≈1, where x>y) cathode materials.1-5 These materials deliver higher practical capacities in a typically used voltage range than NMCs with lower Ni content (e.g., LiNi 1/3 Mn 1/3 Co 1/3 O 2 or NMC-333), and most formulations contain less of the expensive Co component, reducing raw material costs. The increase in practical capacity roughly scales with the Ni content, but comes at the expense of cycle life and thermal stability at high states-of-charge (SOC). 6 To circumvent these problems, several different strategies have been utilized to improve cycling, particularly to higher potentials. These include partial substitution with Ti 7-9 or Zr, 10 engineering the micro-or nano-structure to reduce surface Ni content using metal segregation, 11 surface pillared structures, 12 and concentration gradients, 13 coating particle surfaces, 14 and development of electrolyte additives. 15,16 While all of these approaches have resulted in improvements, further understanding of the factors that lead to capacity fading is clearly needed in order to meet the stringent performance requirements of traction applications.The formation of a resistive cathode/electrolyte interphase (CEI), such as an electrolyte decomposition layer, has been observed during cycling of LiNi 0. 20 In the study of NMC-532, it was found that surface reconstruction to a rock salt phase dominates when high voltage (4.8 V) cutoffs are used due to oxygen loss under the highly oxidizing conditions, while ...

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Understanding the Degradation Mechanisms of LiNi_0.5Co_0.2Mn_0.3O₂ Cathode Material in Lithium Ion Batteries

Abstract: Figure 4. HR-TEM images and FFTs after 50 cycles under 3.0-4.8 V conditions. a) Lattice image of the surface region where (b-e) correspond to the FFTs of Regions 1-4, respectively. (11-1) c is the diffraction spot of the rock salt phase of the metal monoxide.

Cited by 967 publications

References 35 publications

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Influence of synthesis conditions on the surface passivation and electrochemical behavior of layered cathode materials

Depth-Dependent Redox Behavior of LiNi_0.6Mn_0.2Co_0.2O₂

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Understanding the Degradation Mechanisms of LiNi0.5Co0.2Mn0.3O2 Cathode Material in Lithium Ion Batteries

Abstract: Figure 4. HR-TEM images and FFTs after 50 cycles under 3.0-4.8 V conditions. a) Lattice image of the surface region where (b-e) correspond to the FFTs of Regions 1-4, respectively. (11-1) c is the diffraction spot of the rock salt phase of the metal monoxide.

Cited by 967 publications

References 35 publications

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Influence of synthesis conditions on the surface passivation and electrochemical behavior of layered cathode materials

Depth-Dependent Redox Behavior of LiNi0.6Mn0.2Co0.2O2

Contact Info

Product

Resources

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Understanding the Degradation Mechanisms of LiNi_0.5Co_0.2Mn_0.3O₂ Cathode Material in Lithium Ion Batteries

Depth-Dependent Redox Behavior of LiNi_0.6Mn_0.2Co_0.2O₂