Correlating Structural Changes and Gas Evolution during the Thermal Decomposition of Charged LixNi0.8Co0.15Al0.05O2 Cathode Materials

Bak, Seong‐Min; Nam, Kyung‐Wan; Chang, Wonyoung; Yu, Xiqian; Hu, Enyuan; Hwang, Sooyeon; Stach, Eric A.; Kim, Kwang Bum; Chung, Kyung Yoon; Yang, Xiao Qing

doi:10.1021/cm303096e

Cited by 334 publications

(276 citation statements)

References 47 publications

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“…In other words, the NMC structure is thermodynamically unstable at high degrees of delithiation, and only retains its oxygen and its layered bulk structure due to the kinetically hindered oxygen diffusion. This hypothesis is supported by the literature, where it is reported that layered NMC 21,25,27,70,71 and NCA 22,25,26,70 structures in the charged state (low lithium content) are not stable at high temperatures (> 170…”

Section: Discussionsupporting

confidence: 75%

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Oxygen Release and Its Effect on the Cycling Stability of LiNi_xMn_yCo_zO₂(NMC) Cathode Materials for Li-Ion Batteries

Jung

Metzger

Maglia

et al. 2017

J. Electrochem. Soc.

959

1,278

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Layered LiNi x Mn y Co z O 2 (NMC) is a widely used class of cathode materials with LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC111) being the most common representative. However, Ni-rich NMCs are more and more in the focus of current research due to their higher specific capacity and energy. In this work we will compare LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC111), LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622), and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) with respect to their cycling stability in NMC-graphite full-cells at different end-of-charge potentials. It will be shown that stable cycling is possible up to 4.4 V for NMC111 and NMC622 and only up to 4.0 V for NMC811. At higher potentials, significant capacity fading was observed, which was traced back to an increase in the polarization of the NMC electrode, contrary to the nearly constant polarization of the graphite electrode. Furthermore, we show that the increase in the polarization occurs when the NMC materials are cycled up to a high-voltage feature in the dq/dV plot, which occurs at ∼4.7 V vs. Li/Li + for NMC111 and NMC622 and at ∼4.3 V vs. Li/Li + for NMC811. For the latter material, this feature corresponds to the H2 → H3 phase transition. Contrary to the common understanding that the electrochemical oxidation of carbonate electrolytes causes the CO 2 and CO evolution at potentials above 4.7 V vs. Li/Li + , we believe that the observed CO 2 and CO are mainly due to the chemical reaction of reactive lattice oxygen with the electrolyte. This hypothesis is based on gas analysis using On-line Electrochemical Mass Spectrometry (OEMS), by which we prove that all three materials release oxygen from the particle surface and that the oxygen evolution coincides with the onset of CO 2 and CO evolution. Interestingly, the onsets of oxygen evolution for the different NMCs correlate well with the high-voltage redox feature at ∼4.7 V vs. Li/Li + for NMC111 and NMC622 as well as at ∼4.3 V vs. Li/Li + for NMC811. To support this hypothesis, we show that no CO 2 or CO is evolved for the LiNi 0.43 Mn 1.57 O 4 (LNMO) spinel up to 5 V vs. Li/Li + , consistent with the absence of oxygen release. Lastly, we demonstrate by the use of 13 C labeled conductive carbon that it is the electrolyte rather than the conductive carbon which is oxidized by the released lattice oxygen. Taking these findings into consideration, a mechanism is proposed for the reaction of released lattice oxygen with ethylene carbonate yielding CO 2 , CO, and Li-Ion batteries have recently been used as power supply for electric vehicles (EVs). In order to penetrate the mass market, a significant reduction in costs and further performance improvements have to be achieved to realize a longer driving range of EVs.1 The latter highly depends on the choice of the cathode active material, for which several potential materials exist, 2 of which layered lithium nickel manganese cobalt oxide (LiNi x Mn y Co z O 2 , NMC) is one of the most promising class of cathode materials.3 This is due to the high specific capacity and good stability of the lay...

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Section: Discussionsupporting

confidence: 75%

“…5) and a layered to rock-salt (Eq. 6) transformation using, in analogy to the literature, 21,22,36,83 the following general equations with M = (Ni, Mn, Co):…”

Section: Discussionmentioning

confidence: 99%

Oxygen Release and Its Effect on the Cycling Stability of LiNi_xMn_yCo_zO₂(NMC) Cathode Materials for Li-Ion Batteries

Jung

Metzger

Maglia

et al. 2017

J. Electrochem. Soc.

959

1,278

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“…[42][43][44][45] Hwang and coworkers studied the correlation between the gas evolution and phase transition in highly delithiated nickel-rich cathode by conducting combined in situ time resolved-X-ray diffractometer with mass spectroscopy (MS). [46] The points that phase transition occurs (from layered structure to spinel structure and from spinel structure to rock salt structure) precisely coincided with the oxygen gas release peaks. Furthermore, at temperature over 320 °C, the carbon dioxide was formed.…”

Section: Phase Transitionmentioning

confidence: 74%

Prospect and Reality of Ni‐Rich Cathode for Commercialization

Kim

Lee

Cha

et al. 2017

Advanced Energy Materials

644

582

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practical candidate for the wide application of the LIBs with respect to the reversible capacity, rate capability, and capital cost. [4][5][6][7] In terms of nickel contents, the nickel-rich cathodes with nickel content above 80% have advantages in gravimetric capacity, allowing high gravimetric energy density, compared with the nickel content less than 80%. Currently, the nickel-rich cathodes with the amount of nickel less than 60% are fully commercialized. However, the nickel-rich cathodes with nickel content of ≥80% still have many difficulties in the commercialization with respect to powder properties and electrode fabrication process.The unstable powder properties originate from residual lithium compounds such as LiOH and Li 2 CO 3 that formed by the spontaneous reduction of sensitive trivalent nickel ions during the synthesis process and storage in air. [8][9][10][11] The Li 2 CO 3 significantly promotes the gas evolution and increase the moisture of the cathode powder, which strongly related to the safety issue. [12][13][14] Furthermore, the LiOH on the cathode increases the powder pH value, causing the gelation of the slurry during the electrode fabrication process. The nickel-rich cathode with nickel content of ≤60% have acceptable amount of residual lithium compounds for the practical use. By contrast, the cathode with amount of nickel of ≥80% should be treated by additional process to reduce the residual lithium compounds ( Table 1). Furthermore, other powder properties, such as powder pH and moisture, should be carefully controlled when nickel contents were exceeded of ≥80%. Thus, for the practical application of these cathode materials, most battery companies have adapted the washing process, in which the cathode power was stirred in purified water for 20-40 min. [15,16] The washing process could greatly reduce the residual lithium compounds and powder pH value. [15] However, the washing process not only increases process time and capital cost but also make the nickel-rich cathode more chemically sensitive than nonwashed cathodes. [16] More seriously, the water washing deteriorates the thermal stability of the nickel-rich cathodes, indicating that the washing process should be substituted by other methods for the battery safety.Another important factor for the commercialization of the nickel-rich cathodes is the electrode density directly related to the energy density. In general, the nickel-rich cathodesThe layered nickel-rich cathode materials are considered as promising cathode materials for lithium-ion batteries (LIBs) due to their high reversible capacity and low cost. However, several significant challenges, such as the unstable powder properties and limited electrode density, hindered the practical application of the nickel-rich cathode materials with the nickel content over 80%. Herein, important stability issues and in-depth understanding of the nickel-rich cathode materials on the basis of the industrial electrode fabrication condition for the commercialization of the nickel-rich cathode m...

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“…10 Such chemically driven spinel and/or rocksalt formation have been shown and intensively characterized for the thermally induced transformation of partially delithiated NCMs. 52,53 The general chemical reaction for spinel formation is given in Equation 3. Since rocksalt structures could not be observed by HRTEM measurements (see Figure 7 and Figure 8), the surface layer thickness is estimated only assuming the formation of a spinel surface layer.…”

Section: Discussionmentioning

confidence: 99%

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li₂MnO₃Content

Teufl

Strehle

Müller³

et al. 2018

J. Electrochem. Soc.

157

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In this study, we will show how the oxygen release depends on the Li 2 MnO 3 content of the material and how it affects the actual voltage fading of the material. Thus, we compared overlithiated NCMs (x Li 2 MnO 3 • (1-x) LiMeO 2 ; Me = Ni, Co, Mn) with x = 0.33, 0.42 and 0.50, focusing on oxygen release and electrochemical performance. We could show that the oxygen release differs vastly for the materials, while voltage fading is similar, which leads to the conclusion that the oxygen release is a chemical material degradation, occurring at the surface, while voltage fading is a bulk issue of these materials. We could prove this hypothesis by HRTEM, showing a surface layer, which is dependent on the amount of oxygen released in the first cycles and leads to an increase of the charge-transfer resistance of these materials. Furthermore, we could quantitatively deconvolute capacity contributions from bulk and surface regions by dQ/dV analysis and correlate them to the oxygen loss. As a last step, we compared the gassing to the base NCM (LiMeO 2 , Me = Ni, Co, Mn), showing that surface degradation follows a similar reaction pathway and can be easily To face future issues, as global warming, air pollution, as well as the consumption of fossil fuels, an alternative is required to cover the future demand of energy and mobility in an environmentally friendly and sustainable way. In this context, lithium-ion batteries are viable options for large scale energy storage and for electric vehicles, as they have been used to power consumer electronics for many years. 1,2Since graphite is an excellent anode material at potentials of ≈0.1 V vs. Li + /Li with a roughly 2-fold higher specific capacity of about 360 mAh/g compared to currently used cathode active materials (CAMs), many efforts have been undertaken to increase the specific capacity and energy density of CAMs. As first practical cathode active material Lithium-Cobalt-Oxide (LCO) was investigated by Goodenough et al. in the 1980s, exhibiting a specific capacity of about 140 mAh/g and having a layered structure composed of lithium and transition metal layers.3 As these layered structures showed good structural stability during lithium extraction and insertion, and therefore good capacity retention, many attempts have been undertaken to further develop alternative layered structures which would offer higher capacity. One promising attempt that led to the currently used Lithium-NickelCobalt-Manganese-Oxides (NCMs) is to change the occupancy of the transition metal layer by not using exclusively cobalt, but also introducing nickel and manganese into the transition metal layer; hereby it was found that nickel shows a high redox activity, while manganese helps to stabilize the structure during lithium extraction.4-6 By using different transition metals and metal compositions, a playground has been created that allows to tune the properties of the material: while initially a Ni:Co:Mn ratio of 1:1:1 was used (also referred to as NCM-111), trends nowadays favor the so-called Ni...

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Correlating Structural Changes and Gas Evolution during the Thermal Decomposition of Charged Li_xNi_0.8Co_0.15Al_0.05O₂ Cathode Materials

Cited by 334 publications

References 47 publications

Oxygen Release and Its Effect on the Cycling Stability of LiNi_xMn_yCo_zO₂(NMC) Cathode Materials for Li-Ion Batteries

Oxygen Release and Its Effect on the Cycling Stability of LiNi_xMn_yCo_zO₂(NMC) Cathode Materials for Li-Ion Batteries

Prospect and Reality of Ni‐Rich Cathode for Commercialization

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li₂MnO₃Content

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Correlating Structural Changes and Gas Evolution during the Thermal Decomposition of Charged LixNi0.8Co0.15Al0.05O2 Cathode Materials

Cited by 334 publications

References 47 publications

Oxygen Release and Its Effect on the Cycling Stability of LiNixMnyCozO2(NMC) Cathode Materials for Li-Ion Batteries

Oxygen Release and Its Effect on the Cycling Stability of LiNixMnyCozO2(NMC) Cathode Materials for Li-Ion Batteries

Prospect and Reality of Ni‐Rich Cathode for Commercialization

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li2MnO3Content

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Correlating Structural Changes and Gas Evolution during the Thermal Decomposition of Charged Li_xNi_0.8Co_0.15Al_0.05O₂ Cathode Materials

Oxygen Release and Its Effect on the Cycling Stability of LiNi_xMn_yCo_zO₂(NMC) Cathode Materials for Li-Ion Batteries

Oxygen Release and Its Effect on the Cycling Stability of LiNi_xMn_yCo_zO₂(NMC) Cathode Materials for Li-Ion Batteries

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li₂MnO₃Content