Li–Ti Cation Mixing Enhanced Structural and Performance Stability of Li‐Rich Layered Oxide

Liu, Shuai; Liu, Zepeng; Shen, Xi; Wang, Xuelong; Liao, Shu-Hsien; Yu, Richeng; Wang, Zhaoxiang; Hu, Zhiwei; Chen, Chien‐Te; Yu, Xiqian; Yang, Xiao‐Qing; Chen, Liquan

doi:10.1002/aenm.201901530

Cited by 79 publications

(61 citation statements)

References 45 publications

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“…Note that the pre‐edge peaks integral intensity in the O K‐edge spectra is mainly attributed to the TM–O hybridization degree in the TMO 6 crystal field, that is, the TM–O covalency. [ 18 ] Stronger covalency introduces a larger population of O 2p electrons in the molecular antibonding orbitals, resulting in more intense pre‐edge peaks. Hence, these results demonstrate that Ta substitution reduces the TM–O covalency (i.e., more ionic features in TM–O covalent bonds) and Ta concentration gradually decreases from the surface to the bulk in NCAT1, thus leading to the TM–O covalency variations.…”

Section: Resultsmentioning

confidence: 99%

Structure and Charge Regulation Strategy Enabling Superior Cyclability for Ni‐Rich Layered Cathode Materials

Huang

Wang

et al. 2021

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Ni‐rich layered oxides are significantly promising cathode materials for commercial high‐energy‐density lithium‐ion batteries. However, their major bottlenecks limiting their widespread applications are capacity fading and safety concerns caused by their inherently unstable crystal structure and highly reactive surface. Herein, surface structure and bulk charge regulation are concurrently achieved by introducing high‐valence Ta5+ ions in Ni‐rich cathodes, which exhibit superior electrochemical properties and thermal stability, especially a remarkable cyclic stability with a capacity retention of 80% for up to 768 cycles at a 1C rate versus Li/Li+. Due to the partial Ta enrichment on surface, the regulated surface enables high reversibility of Li+ insertion/extraction by preventing surface Ni reduction in deep charging. Moreover, bulk charge regulation that boosts charge density and its localization on oxygen remarkably suppresses microcracks and oxygen loss, which in turn prevents the fragmentation of the regulated surface and structural degradation associated with oxygen skeleton. This study highlights the significance of an integrated optimization strategy for Ni‐rich cathodes and, as a case study, provides a novel and deep insights into the underlying mechanisms of high‐valence ions substitution of Ni‐rich layered cathodes.

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Section: Resultsmentioning

confidence: 99%

Structure and Charge Regulation Strategy Enabling Superior Cyclability for Ni‐Rich Layered Cathode Materials

Huang

Wang

et al. 2021

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“…According to the doping site, cation doping can be further divided into doping-substitution on the TM layer (Mg 2+ , [125] Al 3+ , [101,126] La 3+ , [127] Zr 4+ , [128] Nb 5+ , [129] etc.) and doping substitution on the Li layer (Na + , [88b,110,130] K + , [131] Ti 3+ , [132] etc.). Anion doping can be simply divided into lowvalence anion doping (F − , [133] Cl − , [134] S 2− , [135] etc.)…”

Section: Dopingmentioning

confidence: 99%

Section: Dopingmentioning

confidence: 99%

“…Generally, Ti 4+ ion doping occupies the TM layer; however, Liu et al [132] designed an LRM cathode material with the chemical formula Li 1.2 Ti 0.26 Ni 0.18 Co 0.18 Mn 0.18 O 2 (LTR), using a modified Pechini method, in which some of the Ti 4+ ions occupy the Li layers, as shown in Figure 12c,d. The native Li-Ti (LT) cation mixing structure enhanced the tolerance for structural distortion and inhibited the migration of the TM ions in the TMO 2 slabs during (de)lithiation.…”

Section: Dopingmentioning

confidence: 99%

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Challenges and Recent Advances in High Capacity Li‐Rich Cathode Materials for High Energy Density Lithium‐Ion Batteries

et al. 2021

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mismatch between the cathode and anode materials (the cathode capacity is nearly an order of magnitude smaller than the anode capacity) has seriously hindered the development of LIBs. [2] Li-rich cathode materials have been regarded as one of the most promising candidates for next-generation cathode materials for rechargeable LIBs owing to their prominent specific capacity. For instance, in Li-rich Mn-based (LRM) cathode materials with the chemical formula xLi 2 MnO 3 ⋅(1 -x)LiTMO 2 (TM = Ni, Mn, Co, etc.), when x = 0.5, in the form of Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O 2 , the theoretical capacity of the LRM cathode reaches over 250 mA h g −1 for 1 Li + extraction, and ≈378 mA h g −1 for 1.2 Li + extraction. [3] Furthermore, LRM cathodes reduce the use of expensive Co and have the advantages of low cost, environmental friendliness, and high thermal stability. However, LRM cathode materials have inherent issues, such as low initial Coulombic efficiency (ICE), poor rate capacity, and serious voltage fading, which inhibit their further practical applications. [4] These issues need to be immediately addressed to eliminate range and safety anxiety in the electric consumption market. The development of state-of-the-art characterization techniques has brought new understandings of the origins of these problems. [5] In this case, considerable progress has been made in the evolution of LRM cathode structures and its various reaction mechanisms during long-time cycles, the electrochemical activity of anions, and other aspects. In addition, significant advances have also been made in the novel modification methods for promoting the electrochemical performances of LRM cathode materials as well as other branches of Li-rich cathode materials. Herein, we present a comprehensive review of the recent challenges and prospects in high-capacity Li-rich cathode materials. This paper aims to offer a global and critical perspective on Lirich cathode materials for LIBs, as shown in Figure 1, including an in-depth evaluation of degradation mechanisms, the prevailing modification methods and development trends, application, and future opportunities for LRM electrode materials in full-cells and future solid-state batteries. We intend to provide perspectives on the practical development and application of Li-rich cathode materials have attracted increasing attention because of their high reversible discharge capacity (>250 mA h g −1 ), which originates from transition metal (TM) ion redox reactions and unconventional oxygen anion redox reactions. However, many issues need to be addressed before their practical applications, such as their low kinetic properties and inefficient voltage fading. The development of cutting-edge technologies has led to cognitive advances in theory and offer potential solutions to these problems. Herein, a recent in-depth understanding of the mechanisms and the frontier electrochemical research progress of Li-rich cathodes are reviewed. In addition, recent advances associated with various strategies to promot...

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“…Instead of doping Co sites,d oping Li sites in LCO could stabilize the bulk structure and adjust the surface structure. [11] Herein, we demonstrate aMg-pillared LCO (LMCO) that has an excellent cycling stability at ahigh charge voltage of 4.6 V. We intentionally substitute at Octa-3a site in the Li-slab by using Mg 2+ with ah igher Pauling electronegativity (1.35) as "pillar" to prevent slab sliding at highly delithiated state. Thus,the adverse phase transition from O3 to H1-H3, M2, can be eased in LMCO when charged to 4.6 V. Furthermore,t he Mg occupancyofthe Li site on the surface of LMCO can lead to an in situ generation of aL i-Mg mixing structure.T he resulted Li-Mg mixing structure is beneficial for the suppression of the cathode-electrolyte interphase overgrowth and phase transformation in the close-to-surface region, thereby resulting in an enhanced interface stability.Density functional theory (DFT) calculations confirmed that Li ions diffusion and oxygen stability are greatly enhanced in LMCO than that of pristine LCO.A saresult, LMCO shows excellent rate capability (138 mAh g À1 at 4C)a nd cycling stability (84 % capacity retention over 100 cycles), which is much better than pristine LCO (nearly 0mAh g À1 at 4C and 14 %c apacity retention over 100 cycles).…”

Section: Introductionmentioning

confidence: 99%

Mg‐Pillared LiCoO₂: Towards Stable Cycling at 4.6 V

Huang

Zhu

et al. 2021

Angewandte Chemie

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LiCoO2 is used as a cathode material for lithium‐ion batteries, however, cationic/anodic‐redox‐induced unstable phase transitions, oxygen escape, and side reactions with electrolytes always occur when charging LiCoO2 to voltages higher than 4.35 V, resulting in severe capacity fade. Reported here is Mg‐pillared LiCoO2. Dopant Mg ions, serving as pillars in the Li‐slab of LiCoO2, prevent slab sliding in a delithiated state, thereby suppressing unfavorable phase transitions. Moreover, the resulting Li‐Mg mixing structure at the surface of Mg‐pillared LiCoO2 is beneficial for eliminating the cathode‐electrolyte interphase overgrowth and phase transformation in the close‐to‐surface region. Mg‐pillared LiCoO2 exhibits a high capacity of 204 mAh g−1 at 0.2 C and an enhanced capacity retention of 84 % at 1.0 C over 100 cycles within the voltage window of 3.0–4.6 V. In contrast, pristine LiCoO2 has a capacity retention of 14 % within the same voltage window.

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Li–Ti Cation Mixing Enhanced Structural and Performance Stability of Li‐Rich Layered Oxide

Cited by 79 publications

References 45 publications

Structure and Charge Regulation Strategy Enabling Superior Cyclability for Ni‐Rich Layered Cathode Materials

Structure and Charge Regulation Strategy Enabling Superior Cyclability for Ni‐Rich Layered Cathode Materials

Challenges and Recent Advances in High Capacity Li‐Rich Cathode Materials for High Energy Density Lithium‐Ion Batteries

Mg‐Pillared LiCoO₂: Towards Stable Cycling at 4.6 V

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Li–Ti Cation Mixing Enhanced Structural and Performance Stability of Li‐Rich Layered Oxide

Cited by 79 publications

References 45 publications

Structure and Charge Regulation Strategy Enabling Superior Cyclability for Ni‐Rich Layered Cathode Materials

Structure and Charge Regulation Strategy Enabling Superior Cyclability for Ni‐Rich Layered Cathode Materials

Challenges and Recent Advances in High Capacity Li‐Rich Cathode Materials for High Energy Density Lithium‐Ion Batteries

Mg‐Pillared LiCoO2: Towards Stable Cycling at 4.6 V

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Mg‐Pillared LiCoO₂: Towards Stable Cycling at 4.6 V