05-acs-low-body-ratio

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Lithium-rich layered oxide materials x Li2MnO3 · (1 -x )LiMO2 (M = Mn, Ni, Co, Fe, Cr, etc.) have attracted much attention for the use of cathode materials in lithiumion batteries in recent years. However, there are many issues still unclear (the structure and reaction mechanism are ambiguous until now), and numerous scienti fi c challenges (low initial Coulombic e ffi ciency, poor rate capability, and voltage degradation during cycling) of these materials that must be overcome to realize their utilization in commercial lithium-ion batteries. This Perspective focuses on the challenges and prospects associated with the current researching results of these lithium-rich layered cathode materials. Speci fi cally, their average/local structures, reaction mechanisms, and electrochemical properties are discussed.

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• p1 front_summary coverage=0.0: s the problems of fossil energy exhaustion, global warming, and environment pollution plague modern society, sustainable energies have gradually become a world- wide topic. There have also been increasing demands for wind or solar power stations and low-emissi
• p1 front_summary coverage=0.0: Owing to the key roles of cathode materials on energy density and the cost of current lithium-ion batteries, several alternative cathode materials, such as LiCoO2, Li- Ni0.8Co0.15Al0.05O2, LiNi0.33Co0.33Mn0.33O2, spinel LiMn2O4, olive LiFePO4, and so on, have
• p1 front_summary coverage=0.014: notations are equal to the same material and have been used extensively in the published literature. For example, the 0.5Li2MnO3·0.5LiMn0.42Ni0.42Co0.16O2 material can also be described as Li[Li0.2Mn0.567Ni0.166Co0.067]O2.13−15 In this Perspective, we will foc
• p1 front_summary coverage=0.02: Among the reported cathode materials so far, the lithium-rich layered oxide materials (LLOs) have attracted much attention in recent years because their capacities can be larger than 280 mAhg−1 with 3.6 V or larger operating voltages when these materials are c
• p2 scientific_body coverage=0.047: inspired by Hunter’s discovery that acid treatment of the spinel LiMn2O4 yielded λ-MnO2 with a Mn2O4 spinel framework, Thackeray et al. synthesized the layered lithium−manganese oxide compound Li2−xMnO3−x/2 (0 < x < 2) with a cubic-close- packed oxygen anion a
• p3 scientific_body coverage=0.039: ion batteries can be designed with different contents of LiMO2 (M = Mn, Ni, Co, Fe, Cr, etc.) and Li2MnO3 components, realizing the variational electrochemical performances (re- chargeable capacity, rate performance, and cycle stability) of lithium ion batterie
• p3 scientific_body coverage=0.0: Li2MnO3 structure (space group: C2/m) viewed from their [100] crystallographic direction, respectively. As the Li2MnO3 structure can be reformulated with Li[Li1/3Mn2/3]O2, the monoclinic Li2MnO3 structure is very similar to the rhombohedral LiMO2 structure, an
• p4 scientific_body coverage=0.0: monoclinic Li2MnO3 (space group C2/m) structures are chosen. The phase fractions of the rhombohedral and monoclinic components are 43% and 57%, respectively, and very close to the composition of the studied 0.5Li2MnO3·0.5LiMn0.42Ni0.42Co0.16O2 material.13
• p4 scientific_body coverage=0.011: worth noting that the X-ray diffraction techniques (XRD or SXRD) can only provide key information on the average crystal structure. As a matter of fact, the large difference between the atomic number, size, and tendency for like or unlike atom clusters of the el
• p4 scientific_body coverage=0.0: By the high-resolution transmission electron microscopy (HRTEM) technique combined with electron energy-loss spectroscopy (EELS) technique, Wen, Abraham, Tabuchi et al. find that the locally monoclinic (Li2MnO3-like) regions are existed in the parent rhombohedr
• p4 scientific_body coverage=0.008: Thus, the local structure studies on these LLOs are very important to investigate their actual structure. Jarvis et al. carefully investigated the Li[Li0.2Ni0.2Mn0.6]O2 material with a diffraction scanning transmission electron microscopy (D- STEM) technique, a
• p4 scientific_body coverage=0.0: Although there is much two-phase evidence of these LLOs by average and local structure studies, on the other hand, some researchers think that these LLOs are homogeneous solid solutions between the two components Li2MnO3 and LiMO2 (M = Co, Ni, Mn, Fe, Cr), bec
• p5 scientific_body coverage=0.0: domains with Li2MnO3-like components most probably exist inside these LLOs, increased with the lithium and manganese content (in proportion to x in the xLi2MnO3·(1−x)LiCoO2 equation) increasing, which is described by the simulated figure in Figure 4.29
• p5 scientific_body coverage=0.0: The reaction mechanisms of these LLOs are very complicated, and have been extensively researched and discussed in the past decade.6,11,12,25,35,40,42,48−55 However, these reaction mechanisms proposed are still being debated, and most of them cannot explain all
• p5 scientific_body coverage=0.0: these LLOs during lithium extraction and insertion processes can be well explained. For the 0.5Li2MnO3·0.5LiMn0.42Ni0.42Co0.16O2 electrode material, the reaction pathways and phase composition changes during the first charge region below 4.4 V with different cur
• p6 scientific_body coverage=0.0: long voltage plateaus in Figure 5 b, more lithium ions can be extracted from the Li2MnO3 component together with the loss of oxygen and structure rearrangement, and there is probably a new phase (MnO2) formed. The oxygen accompanied with lithium ions extractio
• p6 scientific_body coverage=0.0: gas quantity in Figure 6a is associated with the voltage increasing, and the large amount of oxygen gas is emitted above 4.5 V, corresponding to the charge plateau of these LLOs. Through first-principles calculations, the oxygen 2p electron clouds change signifi
• p6 scientific_body coverage=0.0: During the first discharge process, lithium ions will insert into the Mn0.42Ni0.42Co0.16O2 and newly formed MnO2 components, respectively, while the unactivated Li2MnO3 component still exist in these “composite” layered materials. Our previous and Yabuuchi’s re
• p7 scientific_body coverage=0.0: charge/discharge currents, is 272, 224, and 184 mAh/g, respectively (Figure 5c). It is obvious that all of the discharge capacity except for the value with small current density (≤5 mA/g) can be explained by the proposed reaction mechanism. On the basis of sur
• p7 scientific_body coverage=0.0: presenting a serious trade-offin lithium-ion battery design. At present, most of the initial Coulombic efficiencies of these LLOs in the published literature are smaller than 80% at room temperature, and the main reason is due to the irreversible reaction resulti
• p7 scientific_body coverage=0.0: and ruthenium substitution14 for manganese on these LLOs have been conducted. The experiment results of ruthenium substitution for manganese (Figure 8) show that all of the initial columbic efficiency increased with the ruthenium content increasing, and the high
• p7 scientific_body coverage=0.06: Nevertheless, with the temperature increased to 55 and 85 °C, the rechargeable charge/discharge capacity of the Li/ Li[Li1/5Ni1/5Mn3/5]O2 can reach 300 mAh/g (Figure 7a), and even 350 mAh/g (Figure 7b), which are much larger than the theoretical capacity if we
• p8 scientific_body coverage=0.006: reduction peaks shifting to the lower voltage region (Figure 9d), indicating that the structures of these LLOs are not stable during long cycling. Observing Figure 9b,d, we found that there are obvious swellings on the oxidation curves of dQ/dV between 3.0 and
• p8 scientific_body coverage=0.0: 151st cycle). The increased capacity in Stage I is obvious and corresponds to the new redox peaks (Ox3/Re3) increasing after the first cycle (Figure 9b). This indicates that the content of activated manganese increases step by step during Stage I. Consequently,
• p10 scientific_body coverage=0.01: components and interfaces (between electrode and electrolyte) are very consistent with the two-phase models proposed and confirmed in Figure 2. Therefore, the electrochemical kinetics of the lithium ion extraction and insertion reactions in these LLOs is mainly
• p10 scientific_body coverage=0.033: Through surface modification with insulating materials (Al2O3 and AlPO4), Manthiram et al. also found that the rate capability of these LLOs can be improved, which may be contributed to the lower charge-transfer resistance with small activation energy compared
• p10 scientific_body coverage=0.0: contributed by the weakened structure damage and little structure arrangement after electrochemical cycling of these materials with this pretreatment method. In order to reveal the kinetically controlled charge and discharge processes of these cathode material
• p11 scientific_body coverage=0.003: (1) Tarascon, J. M.; Armand, M. Issues and Challenges Facing Rechargeable Lithium Batteries. Nature 2001, 414, 359−367. (2) Armand, M.; Tarascon, J. M. Building Better Batteries. Nature 2008, 451, 652−657. (3) Goodenough, J. B.; Kim, Y. Challenges for Recharge
• p12 scientific_body coverage=0.002: (14) Yu, H. J.; Zhou, H. S. Initial Coulombic Efficiency Improvement of the Li1.2Mn0.567Ni0.166Co0.067O2 Lithium-Rich Material by Ruthe- nium Substitution for Manganese. J. Mater. Chem. 2012, 22, 15507− 15510. (15) Yu, H. J.; Wang, Y. R.; Asakura, D.; Hosono,
• p12 scientific_body coverage=0.001: (31) Bareno, J.; Lei, C. H.; Wen, J. G.; Kang, S. H.; Petrov, I.; Abraham, D. P. Local Structure of Layered Oxide Electrode Materials for Lithium-Ion Batteries. Adv. Mater. 2010, 22, 1122−1127. (32) Gu, M.; Belharouak, I.; Genc, A.; Wang, Z. G.; Wang, D. P.; A
• p13 scientific_body coverage=0.006: (66) Tabuchi, M.; Nakashima, A.; Ado, K.; Sakaebe, H.; Kobayashi, H.; Kageyama, H.; Tatsumi, K.; Kobayashi, Y.; Seki, S.; Yamanaka, A. The Effects of Preparation Condition and Dopant on the Electro- chemical Property for Fe-Substituted Li2MnO3. J. Power Source
• p13 scientific_body coverage=0.0: (49) Lu, Z. H.; Beaulieu, L. Y.; Donaberger, R. A.; Thomas, C. L.; Dahn, J. R. Synthesis, Structure, and Electrochemical Behavior of Li[NixLi1/3−2x/3Mn2/3−x/3]O2. J. Electrochem. Soc. 2002, 149, A778− A791. (50) Yabuuchi, N.; Yoshii, K.; Myung, S. T.; Nakai, I