Formation of Pillar-Ions in the Li Layer Decreasing the Li/Ni Disorder and Improving the Structural Stability of Cation-Doped Ni-Rich LiNi0.8Co0.1Mn0.1O2: A First-Principles Verification

Rajkamal, Anand; Kim, Hern

doi:10.1021/acsaem.1c02837

Cited by 20 publications

(16 citation statements)

References 78 publications

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“…The decreasing of the a parameter may indicate increased structural stability due to stronger metal–oxygen bonds, while a mild increase in the c parameter supports other findings and has been shown to increase rate performance . The Al may also form pillar ions, as supported by calculations . The impact of increased Li content in the precursor solution was also explored.…”

Section: Resultssupporting

confidence: 64%

“…29 The Al may also form pillar ions, as supported by calculations. 30 The impact of increased Li content in the precursor solution was also explored. Increasing Li content from 10% excess to 20% and 30% increased the a parameter and decreased the c parameter, bringing the Ni-rich compositions more in line with those of the literature, as shown in Table 1.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

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Combinatorial Investigation of the Impact of Systematic Al Substitution into LiNi_1–x–yMn_xCo_yO₂ Materials

Hebert

David

McCalla

2023

ACS Appl. Energy Mater.

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State-of-the-art Li-ion batteries in long-range electric vehicles increasingly rely on LiNi 1−x−y Mn x Co y O 2 (NMC) cathodes with a trend toward higher Ni content. While high-Ni compositions can increase capacity, they also decrease the material's stability and therefore battery lifetime. Though aluminum has been substituted into a few NMC compositions, to date, no systematic study has been performed. In this study, the impact of different levels of Al substitution was explored across the full range of NMC compositions by preparing a total of 320 materials with varying aluminum content from 0 to 15%. Both Xray diffraction (XRD) and cyclic voltammetry were performed on all samples. The single-phase layered oxide region is quite large when no Al is present and decreases slightly in size as aluminum content increases. The nickel-rich region (1 − x − y > 0.8) was entirely single phase for 0 and 5% Al levels, while at higher Al content small amounts of Li−Al−O phases were found as contaminants detrimental to the electrochemistry, indicating an optimal Al level in high-Ni materials. Key battery metrics including discharge capacity, average voltage, and diffusion coefficients were obtained for all materials and correlated to structural changes seen in the XRD. It was found that Al suppressed the detrimental hexagonal phase transitions at high voltage (∼4.3 V) in Ni-rich compositions. Increased Al content also improved the diffusion coefficients in the Ni-rich materials. Overall, this study provides the first generalized view of the effects of Al substitution on NMC cathode materials. This work can serve as a base for further exploration into Al substitution on less-studied NMC compositions.

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Section: Resultssupporting

confidence: 64%

Section: ■ Experimental Methodsmentioning

confidence: 99%

Combinatorial Investigation of the Impact of Systematic Al Substitution into LiNi_1–x–yMn_xCo_yO₂ Materials

Hebert

David

McCalla

2023

ACS Appl. Energy Mater.

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“…Consequently, the parasitic reaction that forms NiO-like rocksalt impurity phases, with oxygen release, occurs throughout the particle due to microcracks, accelerating cathode degradation. [5][6][7][8][9][10] Various methods of overcoming these problems have been proposed, including doping, [11][12][13][14][15][16][17][18][19][20][21][22][23] coating, [24,25] and concentration gradient design [14,26,27] in the cathode. Among these methods, doping is the most widely applied due to its simplicity and effectiveness.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, Mg 2+ , Al 3+ , Zr 4+ , and Ti 4+ increase the thermodynamic barrier for unfavorable migration of Ni 2+ ions from the transition metal (TM) site to the lithium site. [11][12][13][15][16][17] Additionally, these elements strengthen the bond to oxygen, which improves the structural stability and suppresses oxygen loss accompanied by a layered-to-rocksalt phase transition. [15][16][17] In general, stabilizing the structure of cathodes by doping has been mostly conducted with those conventional dopants with oxidation states lower than 4+.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Doping with High‐Valence Elements for Developing Ni‐Rich Cathode Materials

Park

Kim

et al. 2023

Advanced Energy Materials

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Introducing additional elements into Ni‐rich cathodes is an essential strategy for addressing the instability of the cathode material. Conventionally, this doping strategy considers only the incorporation of additional elements into the bulk structure of the cathode in terms of fortifying the crystal structure. However, high‐valence elements such as Nb5+, Ta5+, and Mo6+ are likely to be insoluble in the crystal structure, resulting in accumulation along the interparticle boundaries. Herein, a new mechanism for doping high‐valence elements into Ni‐rich cathodes and their effects on the morphology and crystal structure are investigated by calcining LiNiO2 (LNO) and X‐doped LNO cathodes (X = Al, Nb, Ta, and Mo) at various temperatures. Operando X‐ray diffraction analysis reveals that the temperature at which the content of Li‐X‐O compounds declines is higher for the dopants with high oxidation states, reinforcing segregation at the grain boundary and widening the calcination temperature range. Thus, the highly aligned microstructure and high crystallinity of the LNO cathode are maintained over a wide calcination temperature range after doping with high‐valence elements, enhancing the electrochemical performance. As next‐generation dopants, high‐valence elements can fortify not only the crystal structure, but also the microstructure, to maximize the electrochemical performance of Ni‐rich cathodes.

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“…or incorporation of “inactive” dopants (say, Mg 2+ , Al 3+ , Zn 2+ , Na + , etc.) in the T M /Li-layer, or both. − …”

Section: Introductionmentioning

confidence: 99%

Understanding the Effects of Tetrahedral Site Occupancy by the Zn Dopant in Li-NMCs toward High-Voltage Compositional–Structural–Mechanical Stability via Operando and 3D Atom Probe Tomography Studies

Sharma

Pandey

Jangid

et al. 2023

ACS Appl. Mater. Interfaces

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Ni-containing “layered”/cation-ordered LiTMO2s (TM = transition metal) suffer from Ni-migration to the Li-layer at the unit cell level, concomitant transformation to a spinel/rock salt structure, hindrance toward Li-transport, and, thus, fading in Li-storage capacity during electrochemical cycling (i.e., repeated delithiation/lithiation), especially upon deep delithiation (i.e., going to high states-of-charge). Against this backdrop, our previously reported work [ACS Appl. Mater. Interfaces 2021, 13, 25836–25849] revealed a new concept toward blocking the Ni-migration pathway by placing Zn2+ (which lacks octahedral site preference) in the tetrahedral site of the Li-layer, which, otherwise, serves as an intermediate site for the Ni-migration to the Li-layer. This, nearly completely, suppressed the Ni-migration, despite being deep delithiated up to a potential of 4.7 V (vs Li/Li+) and, thus, resulted in significant improvement in the high-voltage cyclic stability. In this regard, by way of conducting operando synchrotron X-ray diffraction, operando stress measurements, and 3D atom probe tomography, the present work throws deeper insights into the effects of such Zn-doping toward enhancing the structural–mechanical–compositional integrity of Li-NMCs upon being subjected to deep delithiation. These studies, as reported here, have provided direct lines of evidence toward notable suppression of the variations of lattice parameters of Li-NMCs, including complete prevention of the detrimental “c-axis collapse” at high states-of-charges and concomitant slower-cum-lower electrode stress development, in the presence of the Zn-dopant. Furthermore, the Zn-dopant has been found to also prevent the formation of Ni-enriched regions at the nanoscaled levels in Li-NMCs (i.e., Li/Ni-segregation or “structural densification”) even upon being subjected to 100 charge/discharge cycles involving deep delithiation (i.e., up to 4.7 V). Such detailed insights based on direct/real-time lines of evidence, which reveal important correlations between the suppression of Ni-migration and high-voltage compositional–structural–mechanical stability, hold immense significance toward the development of high capacity and stable “layered” Li-TM-oxide based cathode materials for the next-generation Li-ion batteries.

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Formation of Pillar-Ions in the Li Layer Decreasing the Li/Ni Disorder and Improving the Structural Stability of Cation-Doped Ni-Rich LiNi_0.8Co_0.1Mn_0.1O₂: A First-Principles Verification

Cited by 20 publications

References 78 publications

Combinatorial Investigation of the Impact of Systematic Al Substitution into LiNi_1–x–yMn_xCo_yO₂ Materials

Combinatorial Investigation of the Impact of Systematic Al Substitution into LiNi_1–x–yMn_xCo_yO₂ Materials

Mechanism of Doping with High‐Valence Elements for Developing Ni‐Rich Cathode Materials

Understanding the Effects of Tetrahedral Site Occupancy by the Zn Dopant in Li-NMCs toward High-Voltage Compositional–Structural–Mechanical Stability via Operando and 3D Atom Probe Tomography Studies

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Formation of Pillar-Ions in the Li Layer Decreasing the Li/Ni Disorder and Improving the Structural Stability of Cation-Doped Ni-Rich LiNi0.8Co0.1Mn0.1O2: A First-Principles Verification

Cited by 20 publications

References 78 publications

Combinatorial Investigation of the Impact of Systematic Al Substitution into LiNi1–x–yMnxCoyO2 Materials

Combinatorial Investigation of the Impact of Systematic Al Substitution into LiNi1–x–yMnxCoyO2 Materials

Mechanism of Doping with High‐Valence Elements for Developing Ni‐Rich Cathode Materials

Understanding the Effects of Tetrahedral Site Occupancy by the Zn Dopant in Li-NMCs toward High-Voltage Compositional–Structural–Mechanical Stability via Operando and 3D Atom Probe Tomography Studies

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Formation of Pillar-Ions in the Li Layer Decreasing the Li/Ni Disorder and Improving the Structural Stability of Cation-Doped Ni-Rich LiNi_0.8Co_0.1Mn_0.1O₂: A First-Principles Verification

Combinatorial Investigation of the Impact of Systematic Al Substitution into LiNi_1–x–yMn_xCo_yO₂ Materials

Combinatorial Investigation of the Impact of Systematic Al Substitution into LiNi_1–x–yMn_xCo_yO₂ Materials