High-Energy Cathode Materials (Li2MnO3–LiMO2) for Lithium-Ion Batteries

Yu, Haijun; Zhou, Haoshen

doi:10.1021/jz400032v

Cited by 583 publications

(457 citation statements)

References 80 publications

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“…Mn‐based Li‐rich layered oxides Li 1+ x Mn 1− x − y M y O 2 ( x > 0 and M = transition metal) offer high capacities of >250 mA h g −1 , but are faced with a fundamental challenge of working voltage decline during electrochemical cycling due to a layered to spinel‐like phase transformation, which leads to severe decrease in energy density during operation 1, 2, 3, 4. To overcome this problem, many studies have focused on stabilizing the structure with various efforts, such as surface modifications and transition‐metal‐ion substitutions,2, 5, 6, 7, 8 but none of the efforts could completely eliminate the phase transition.…”

Section: Introductionmentioning

confidence: 99%

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High‐Performance Heterostructured Cathodes for Lithium‐Ion Batteries with a Ni‐Rich Layered Oxide Core and a Li‐Rich Layered Oxide Shell

et al. 2016

Advanced Science

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The Ni‐rich layered oxides with a Ni content of >0.5 are drawing much attention recently to increase the energy density of lithium‐ion batteries. However, the Ni‐rich layered oxides suffer from aggressive reaction of the cathode surface with the organic electrolyte at the higher operating voltages, resulting in consequent impedance rise and capacity fade. To overcome this difficulty, we present here a heterostructure composed of a Ni‐rich LiNi0.7Co0.15Mn0.15O2 core and a Li‐rich Li1.2− xNi0.2Mn0.6O2 shell, incorporating the advantageous features of the structural stability of the core and chemical stability of the shell. With a unique chemical treatment for the activation of the Li2MnO3 phase of the shell, a high capacity is realized with the Li‐rich shell material. Aberration‐corrected scanning transmission electron microscopy (STEM) provides direct evidence for the formation of surface Li‐rich shell layer. As a result, the heterostructure exhibits a high capacity retention of 98% and a discharge‐voltage retention of 97% during 100 cycles with a discharge capacity of 190 mA h g−1 (at 2.0–4.5 V under C/3 rate, 1C = 200 mA g−1).

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Section: Introductionmentioning

confidence: 99%

“…Figure 1 a shows the practical capacities of various cathode materials for lithium‐ion batteries along with the charge cutoff voltages 3, 9. Each cathode material has a trade‐off relationship between its capacity and cyclability 10.…”

Section: Introductionmentioning

confidence: 99%

High‐Performance Heterostructured Cathodes for Lithium‐Ion Batteries with a Ni‐Rich Layered Oxide Core and a Li‐Rich Layered Oxide Shell

et al. 2016

Advanced Science

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“…Practical implementation of some of these materials is thwarted by their high first-cycle coulombic inefficiencies [17][18][19][20] , capacity fading 18,21 and voltage instability [20][21][22] , especially during high-voltage operation. Specifically, high-voltage charge capacities achieved in lithiumrich/manganese-rich layered cathodes are directly associated with various irreversible electrochemical processes including oxygen loss and concomitant lithium ion removal 23 and electrode/electrolyte reactions 24 .…”

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confidence: 99%

Surface reconstruction and chemical evolution of stoichiometric layered cathode materials for lithium-ion batteries

et al. 2014

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The present study sheds light on the long-standing challenges associated with high-voltage operation of LiNi x Mn x Co 1 À 2x O 2 cathode materials for lithium-ion batteries. Using correlated ensemble-averaged high-throughput X-ray absorption spectroscopy and spatially resolved electron microscopy and spectroscopy, here we report structural reconstruction (formation of a surface reduced layer, R 3m to Fm 3m transition) and chemical evolution (formation of a surface reaction layer) at the surface of LiNi x Mn x Co 1 À 2x O 2 particles. These are primarily responsible for the prevailing capacity fading and impedance buildup under high-voltage cycling conditions, as well as the first-cycle coulombic inefficiency. It was found that the surface reconstruction exhibits a strong anisotropic characteristic, which predominantly occurs along lithium diffusion channels. Furthermore, the surface reaction layer is composed of lithium fluoride embedded in a complex organic matrix. This work sets a refined example for the study of surface reconstruction and chemical evolution in battery materials using combined diagnostic tools at complementary length scales. C hemical evolution and structural transformations at the surface of a material directly influence characteristics relevant to a wide range of prominent applications including heterogeneous catalysis 1-3 and energy storage 4,5 . Structural and/or chemical rearrangements at surfaces determine the way a material interacts with its surrounding environment, thus controlling the functionalities of the material [6][7][8][9][10] . Specifically, the surfaces of lithium-ion battery electrodes evolve simultaneously with charge-discharge cycling (that is, in situ surface reconstruction and formation of a surface reaction layer (SRL)) that can lead to deterioration of performance 4,5,11 . An improved understanding of in situ surface reconstruction phenomena imparts knowledge not only for understanding degradation mechanisms for battery electrodes but also to provide insights into the surface functionalization for enhanced cyclability 12,13 .The investigation of in situ surface reconstruction of layered cathode materials, such as stoichiometric LiNi x Mn x Co 1 À 2x O 2 (that is, NMC), lithium-rich Li(Li y Ni x À y Mn x Co 1 À 2x )O 2 , lithium-rich/ manganese-rich (composite layered-layered) xLi 2 MnO 3 Á (1 À x) LiMO 2 (M ¼ Mn, Ni, Co, and so on) materials, is technologically significant as they represent a group of materials with the potential to improve energy densities and reduce costs for plug-in hybrid electric vehicles and electric vehicles [14][15][16][17] . Practical implementation of some of these materials is thwarted by their high first-cycle coulombic inefficiencies [17][18][19][20] , capacity fading 18,21 and voltage instability [20][21][22] , especially during high-voltage operation. Specifically, high-voltage charge capacities achieved in lithiumrich/manganese-rich layered cathodes are directly associated with various irreversible electrochemical processes including o...

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“…[17][18][19][20][21][22] During first charge, they exhibit an initial sloping region corresponding to the oxidation of transitionmetal (TM) ions, and a subsequent plateau region assigned to an irreversible loss of oxygen from the lattice. 23,24 The oxygen loss would induce the migration of TM ions from the surface to the bulk, leading to elimination of TM and Li vacancies in the bulk and formation of a spinel-defect phase on the surface.…”

Section: -14mentioning

confidence: 99%

Sensitivity and Intricacy of Cationic Substitutions on the First Charge/Discharge Cycle of Lithium-Rich Layered Oxide Cathodes

Xiang¹,

Knight²,

Li³

et al. 2015

J. Electrochem. Soc.

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]O 2 also first increases because Ni 3+ can be fully oxidized to Ni 4+ before the oxygen loss begins while Co 3+ can be oxidized only to around Co 3.6+ and then decreases due to suppressed oxygen loss caused by the decrease in metal-oxygen covalence. Also, the Ni substitution raises the average discharge potential as Ni 3+ ions will be reduced to Ni 2+ before the Mn 4+ ions are reduced to Mn 3+ . The study demonstrates the sensitivity and intricacies associated with the nature of the cations in lithium-rich layered oxide cathodes. Since the successful commercialization of lithium-ion batteries by Sony in 1991, much attention has been focused on improving their electrochemical performance and safety by investigating new cathode materials, 1-5 anode materials, 6-10 and electrolyte additives. 11-14Currently, lithium-ion batteries are widely utilized as a power source for portable electronic devices, such as mobile phones and laptop computers. They are also being intensively pursued for large-scale applications in electric vehicles and grid storage of renewable energies, such as wind and solar. 15,16 However, further improvement in energy density and cycle life as well as cost reduction are critical for utilizing the lithium-ion technology for these large-scale applications.Lithium-rich layered oxides xLi 2 MnO 3 -(1-x)LiMO 2 (LLOs, M = Co, Ni, Mn, et al.) are of great interest as promising cathodes for high energy lithium-ion batteries due to their high capacities of ∼ 250 mAh g −1 and low cost. [17][18][19][20][21][22] During first charge, they exhibit an initial sloping region corresponding to the oxidation of transitionmetal (TM) ions, and a subsequent plateau region assigned to an irreversible loss of oxygen from the lattice. 23,24 The oxygen loss would induce the migration of TM ions from the surface to the bulk, leading to elimination of TM and Li vacancies in the bulk and formation of a spinel-defect phase on the surface. During first discharge, Li ions insert into the remaining Li vacancies and induce reduction of the TM ions. To compensate for the oxygen loss and Li vacancy reduction, some Mn 4+ ions are reduced to Mn 3+ , producing a high discharge capacity. After the first cycle, reversible oxidation/reductions of the TM ions, including Mn, occur in subsequent charge/discharge cycles, without further oxygen loss. Obviously, the oxygen loss in the first cycle is special and plays an important role in determining the electrochemical performance of LLOs.While previous studies have shown that factors such as the metaloxygen bond strength and dimerization can affect the degree of oxygen loss, 25,26 Wang et al. concluded that the metal-oxygen bond covalence and its subsequent effect on electron localization is the primary influence on the oxygen loss process. 27 For instance, Ti substitution dramatically reduces the oxygen loss and reversible capacity due to the decrease in metal-oxygen bond covalence caused by a large separation between the Ti 3+/4+

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High-Energy Cathode Materials (Li₂MnO₃–LiMO₂) for Lithium-Ion Batteries

Cited by 583 publications

References 80 publications

High‐Performance Heterostructured Cathodes for Lithium‐Ion Batteries with a Ni‐Rich Layered Oxide Core and a Li‐Rich Layered Oxide Shell

High‐Performance Heterostructured Cathodes for Lithium‐Ion Batteries with a Ni‐Rich Layered Oxide Core and a Li‐Rich Layered Oxide Shell

Surface reconstruction and chemical evolution of stoichiometric layered cathode materials for lithium-ion batteries

Sensitivity and Intricacy of Cationic Substitutions on the First Charge/Discharge Cycle of Lithium-Rich Layered Oxide Cathodes

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