Feasibility of Using Li<sub>2</sub>MoO<sub>3</sub> in Constructing Li-Rich High Energy Density Cathode Materials

Ma, Jun; Zhou, Yong‐Ning; Gao, Yurui; Yu, Xiqian; Kong, Qingyu; Gu, Lin; Wang, Zhaoxiang; Yang, Xiao‐Qing; Chen, Liquan

doi:10.1021/cm501025r

Cited by 107 publications

(101 citation statements)

References 44 publications

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“…They also provide valuable guidance for the research and development of new electrodes for other rechargeable battery systems, such as sodium and magnesium ion batteries. The detailed synthesis was reported in our recent publications 25 . Cathode specimens were prepared by slurrying the active material with 10 wt % carbon black and 10 wt % poly-vinylidene fluoride in N-methylpyrrolidone solvent, and then coating the mixture on Al foil.…”

Section: Resultsmentioning

confidence: 99%

Tuning charge–discharge induced unit cell breathing in layer-structured cathode materials for lithium-ion batteries

et al. 2014

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For LiMO 2 (M ¼ Co, Ni, Mn) cathode materials, lattice parameters, a(b), contract during charge. Here we report such changes in opposite directions for lithium molybdenum trioxide (Li 2 MoO 3 ). A 'unit cell breathing' mechanism is proposed based on crystal and electronic structural changes of transition metal oxides during charge-discharge. Metal-metal bonding is used to explain such 'abnormal' behaviour and a generalized hypothesis is developed. The expansion of the metal-metal bond becomes the controlling factor for a(b) evolution during charge, in contrast to the shrinking metal-oxygen bond as controlling factor in 'normal' materials. The cation mixing caused by migration of molybdenum ions at higher oxidation state provides the benefits of reducing the c expansion range in the early stage of charging and suppressing the structure collapse at high voltage charge. These results may open a new strategy for designing layered cathode materials for high energy density lithium-ion batteries.

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Section: Resultsmentioning

confidence: 99%

Tuning charge–discharge induced unit cell breathing in layer-structured cathode materials for lithium-ion batteries

et al. 2014

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“…Before 3.8 V, it shows that there are three phase transitions during the fi rst charge. On further oxidation to about 4.25 V plateau, which is considered as the activation process of Li 2 RuO 3 , [ 9,[11][12][13] a solid solution reaction with very small lattice change occurs. During next discharge and second charge, we can observe that two-phase change happen at certain voltage (about 3.3 V for discharge and 3.8 V for charge).…”

Section: Introductionmentioning

confidence: 99%

Understanding the Stability for Li‐Rich Layered Oxide Li₂RuO₃ Cathode

Shao

Yan

et al. 2016

Adv Funct Materials

132

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wileyonlinelibrary.comcathode materials with well-ordered structures where most of doping metal atoms exist in the transition-metal sublattice. However, the conventional layered oxide cathode after modifi cation can only deliver a practical capacity of less than 200 mAh g −1 .In recent years, lithium-rich layered oxides based on Li 2 MO 3 (M = Mn, Ru etc.) with layered structure are considered as promising cathodes for Li-ion batteries due to their higher capacity of more than 220 mAh g −1 and higher stability at high voltage as compared with the conventional LiMO 2 layered oxides, provoking worldwide attentions. [8][9][10][11][12][13][14] The common feature accounting for the high capacities of these lithium-rich layered oxides is the two redox processes involving both of cation and anion. [ 10,13,15,16 ] Despite the same process of partly charge compensation by oxygen during deep charging/discharging process, the lithiumrich layered oxides can deliver much higher reversible capacity than that of conventional cathode materials. To the best of our knowledge, such difference on the structural stability between the conventional and lithium-rich layered oxides has attracted limited attention. It is of high importance that there must be some unknown mechanism leading to the stability difference since the geometric and electronic structure between these two kinds of layered materials are similar, except for the superlattice structure. In present work, we elucidate why lithium-rich layered oxides Li 2 RuO 3 exhibit high capacities without undergoing a structural collapse for a certain number of cycles by tracking the electronic and geometric structural changes induced in Li 2 RuO 3 during charging/discharging. Backed up with the density functional theory (DFT) calculations and a series of in situ experiments, we unravel that the presence of the lithium atoms in the transition metal layer could make the lithium-rich structure fl exible, facilitating the formation of O 2 2− -like species, which favors the structural integrity and providing high capacity. Results and DiscussionWe chose Li 2 RuO 3 as the model lithium-rich compound because it contains a single metal, making it convenient to track the electronic and geometric structural changes during charging/discharging process without interference. In addition,

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Section: Llcs Containing Heavy Atomsmentioning

confidence: 99%

“…101,107 Despite the small contribution of oxygen to the expected redox reaction, its electrochemical profile severely changes after the first charge process (Figure 20a). 107 Ma et al revealed that the structure of Li 2 MoO 3 underwent a significant transformation upon cycling, even for the first cycle. As shown in Figures 20a and 20b, many Mo cations migrate from the TM to Li layers during the first charge process, forming a disordered O1 structure followed by partial recovery during the first discharge process.…”

Section: Llcs Containing Heavy Atomsmentioning

confidence: 99%

“…As shown in Figures 20a and 20b, many Mo cations migrate from the TM to Li layers during the first charge process, forming a disordered O1 structure followed by partial recovery during the first discharge process. 101,107 This massive Mo migration is attributed the site energy of oxidized Mo 6+ being lower at the distorted MoO 6 octahedra or MoO 4 tetrahedra than at the undistorted MoO 6 octahedra; thus, the energy barrier for the Mo migration from Mo oct to Li oct through Mo tet becomes facile at a higher oxidation state of Mo. The severe cation migration induces a wide deviation of the Li chemical potential, which results in the sloppy electrochemical profiles for the subsequent cycling.…”

Section: Llcs Containing Heavy Atomsmentioning

confidence: 99%

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Review—Lithium-Excess Layered Cathodes for Lithium Rechargeable Batteries

Hong

Gwon

Jung

et al. 2015

J. Electrochem. Soc.

156

122

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The exceptionally high gravimetric capacity of lithium-excess layered cathodes (LLCs) has generated interest in their use in lithiumion batteries (LIBs) for high-capacity applications. Their unique electrochemical and structural properties are responsible for this high capacity, which exceeds the theoretical redox capability of transition metal oxides and have been intensively investigated. However, various fundamental and practical challenges must be overcome before LLCs can be successfully commercialized. The structure of pristine LLCs, which varies with the composition and type of transition metal species used, remains unclear. In addition, the structure continuously changes during electrochemical cycling, which further complicates its understanding. In this review, we discuss the current understanding of LLCs, including their pristine structures, redox chemistries, and structural evolution during cycling, and suggest future research directions to address the critical issues.There has been a recent upsurge of interest in overcoming the current energy density limitation of lithium-ion batteries (LIBs) to address the pressing demand from the electric vehicle and large-scale energy storage system industries. 1-3 As one of the key components of LIBs that govern their performance, cathode materials that are capable of delivering a high energy density have been extensively sought after. 4-16 Although some currently used cathode materials possess a high theoretical capacity (C th ), i.e., LiCoO 2 (LCO, C th = 274 mAh g −1 ), LiNi 0.33 Co 0.33 Mn 0.33 O 2 (NCM, C th = 278 mAh g −1 ), LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA, C th = 279 mAh g −1 ), LiMn 2 O 4 (LMO, C th = 148 mAh g −1 ), and LiFePO 4 (LFP, C th = 170 mAh g −1 ), the practically usable capacity remains at 100-180 mAh g −1 , as shown in Figure 1, which is insufficient for future applications. As an alternative high-energy cathode, lithium-excess layered cathodes (LLCs) have been intensively studied in recent years. 6-10 Whereas the aforementioned cathode materials, LCO, NCM, NCA, and LFP, have a lithium-to-transition metal (TM) ratio of unity, LLCs have a lithiumto-TM ratio exceeding 1, indicating the possible utilization of more than one Li in the chemical formula unit, which would substantially increase C th . However, the utilization of the excess Li requires an additional redox active center in the material, and most M 4+ /M 5+ (M = Mn, Fe, Co, or Ni) redox reactions occur at a high potential beyond the electrochemical stability window of electrolytes; thus, the "lithium-excess" strategies did not appear suitable for achieving high capacity. Nevertheless, most reported LLCs exhibit exceptionally high reversible capacities exceeding 250 mAh g −1 , which far surpass the C th values calculated based on the redox capabilities of the TM ions.This unique property of LLCs and their consequent high capacities have attracted significant attention from the community, and extensive investigations have been conducted accordingly. These investigations primarily focused ...

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Feasibility of Using Li₂MoO₃ in Constructing Li-Rich High Energy Density Cathode Materials

Cited by 107 publications

References 44 publications

Tuning charge–discharge induced unit cell breathing in layer-structured cathode materials for lithium-ion batteries

Tuning charge–discharge induced unit cell breathing in layer-structured cathode materials for lithium-ion batteries

Understanding the Stability for Li‐Rich Layered Oxide Li₂RuO₃ Cathode

Review—Lithium-Excess Layered Cathodes for Lithium Rechargeable Batteries

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Feasibility of Using Li2MoO3 in Constructing Li-Rich High Energy Density Cathode Materials

Cited by 107 publications

References 44 publications

Tuning charge–discharge induced unit cell breathing in layer-structured cathode materials for lithium-ion batteries

Tuning charge–discharge induced unit cell breathing in layer-structured cathode materials for lithium-ion batteries

Understanding the Stability for Li‐Rich Layered Oxide Li2RuO3 Cathode

Review—Lithium-Excess Layered Cathodes for Lithium Rechargeable Batteries

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Feasibility of Using Li₂MoO₃ in Constructing Li-Rich High Energy Density Cathode Materials

Understanding the Stability for Li‐Rich Layered Oxide Li₂RuO₃ Cathode