Mitigating evolution of lattice oxygen and stabilizing structure of lithium-rich oxides by fabricating surface oxygen defects

Zhong, Jianjian; Yang, Zhe; Li, Yanying; Li, Jianling; Wang, Xindong; Kang, Feiyu

doi:10.1016/j.electacta.2019.134987

Cited by 29 publications

(12 citation statements)

References 69 publications

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“…It can be clearly observed from Figure 1b that all of the diffraction peaks are consistent with a layered α-NaFeO 2 structure (R3m) with no impure peaks, and the diffraction peaks between 20°and 25°are due to the ordered arrangement of lithium and transition metals in the transition metal layers. 26,27 The two double-diffraction peaks are well separated, which demonstrates the good layered structure of the two samples. The I (003) /I (104) value is related to the degree of cation mixing; the larger the ratio, the weaker the mixing.…”

Section: Resultsmentioning

confidence: 81%

A Simple Dual-Ion Doping Method for Stabilizing Li-Rich Materials and Suppressing Voltage Decay

Yang

Zhong

et al. 2020

ACS Appl. Mater. Interfaces

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A gentle method is used to treat the precursor to induce the doping of SO4 2– and Ni2+. The doped SO4 2– induces the formation of oxygen vacancies and defects, which are beneficial for inhibition of the loss of O2–, stabilization of the structure, and amelioration of voltage decay, and the doped Ni2+ increases the degree of lithium nickel mixing and significantly increases the midvoltage. After modification, the specific discharge capacity reaches 305.20 mAh g–1, with a Coulombic efficiency of 86.20% (the specific discharge capacity and Coulombic efficiency of the original material are only 276.50 mAh g–1 and 77.30%, respectively). In addition, the cycle performance is also significantly improved, and the discharge midvoltage is dramatically increased from 2.74 to 3.00 V after 350 cycles at a large current density of 1C due to the dual-ion synergistic effect. In summary, these results show that the materials exhibit not only a more stable structure but also better electrochemical performance after modification.

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Section: Resultsmentioning

confidence: 81%

A Simple Dual-Ion Doping Method for Stabilizing Li-Rich Materials and Suppressing Voltage Decay

Yang

Zhong

et al. 2020

ACS Appl. Mater. Interfaces

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“…As illustrated in Figure 3a, two peaks can be identified in the O 1s spectrum for all samples, where the lattice-bonded oxygen (around 529 eV) and active oxygen (around 531.5 eV) can be easily identified. 30,53 As shown in Figure 3b, the ratio of lattice oxygen increases and active oxygen decreases as the annealing temperature increases from 300 to 400 °C, which indicates that low-temperature annealing (≤400 °C) could help restore the oxygen lattice frame. In this low-temperature region, the high degree of Li/Ni disorder inherited from hightemperature calcination would be reduced by the thermal annealing promoted lattice ordering according to the Arrhenius relationship.…”

Section: Resultsmentioning

confidence: 89%

“…However, the ratio of active oxygen prominently increases when annealed at high temperatures (>400 °C), which strongly suggest that the breaking of oxygen bonds begins when the temperature is above 400 °C. The increase of active oxygen indicates that more oxygen vacancies are created in the layered lattice, 30 and Ni ions driven by strong migration kinetic at high temperature would easily diffuse into the Li slab.…”

Section: Resultsmentioning

confidence: 99%

“…Extensive works have been devoted to manipulate the Li/Ni disorder and achieve better electrochemical performance . Several approaches have been developed such as building core–shell and concentration-gradient structures, ,− cationic doping, ,− surface modifications, and grain boundary engineering. − Recently, thermodynamically promoting the Li/Ni ordering during the high-temperature synthesis has been successfully demonstrated on the LiNi 0.7 Mn 0.15 Co 0.15 O 2 (NMC71515) cathode, and in situ X-ray diffraction (XRD) has revealed that the calcination at 850 °C can give rise to the lowest cationic disorder and the largest Li slab distance . However, such high temperature would also cause serious O loss from the NMC lattice, which in turn may cause the Ni ions to diffuse back into the Li slab .…”

Section: Introductionmentioning

confidence: 99%

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Tuning the Li/Ni Disorder of the NMC811 Cathode by Thermally Driven Competition between Lattice Ordering and Structure Decomposition

et al. 2020

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Ni-rich layered LiNi x Mn y Co z O2 (NMC) cathodes for lithium-ion batteries are receiving a lot of attention owing to their promising large capacity, whereas the high content of Ni results in several issues including poor thermal stability and serious Li/Ni disorder. Although a little degree of the Li/Ni disorder may be beneficial for the structural stability of NMC cathodes and even migration of Li ions, a high degree of the Li/Ni disorder certainly deteriorates their electrochemical performances. Therefore, tuning the Li/Ni disorder is of great interest in the development of safer NMC cathodes with larger accessible capacity. Post-synthesis annealing is a facile and low-cost way to manipulate lattice defects, yet has not been utilized to optimize the Ni-rich NMC cathodes. In this work, we report that post-synthesis annealing can induce the competition between lattice ordering and structure decomposition. The thermal annealing promoted that lattice ordering would prevail until the decomposition of oxygen lattice. Once the annealing temperature reaches the critical temperature to form oxygen vacancies, Ni ions can easily migrate into the Li slab. The Li/Ni disorder can be facilely tuned through post-synthesis annealing to optimize the electrochemical performances of NMC cathodes.

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“…As shown in Figure 4c−e, the binding energies of Mn 2p 3/2 , Ni 2p 3/2 , and Co 2p 3/2 separately locate at 780.2, 855.0, and 642.2 eV, respectively, suggesting that the elements exist in the form of Mn 4+ , Ni 3+ , and Co 3+ , respectively. 26,27 There is no peak shift in Co, Ni, and Mn ions, suggesting that their valence states in the samples are not changed and the Na + ions may mainly occupy the position of Li + ions in the Li layer. Figure 4f shows the Raman spectroscopy of these three samples.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Morphology Control and Na⁺ Doping toward High-Performance Li-Rich Layered Cathode Materials for Lithium-Ion Batteries

Wang

et al. 2020

ACS Sustainable Chem. Eng.

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The lithium-rich manganese (LRM)-based cathode materials are always subjected to poor rate capacity and terrible voltage fading. Herein, sodium citrate as a chelating agent is introduced to synthesize LRM cathode materials with high structure stability by the solvothermal method to solve the abovementioned issues. Sodium citrate can effectively control the morphology of cathode materials with a small size of primary particles, which can prevent the side reaction between the active materials and electrolyte and benefit Li+ diffusion. Meanwhile, the hydroxyl groups in sodium citrate can alter the crystal growth thermodynamics and thereby induce the formation of the active {010} planes under the solvothermal condition, which facilitates the formation of a good layered structure, so that the electrochemical reaction kinetics and rate performance are facilitated dramatically. Furthermore, benefitting from the doping of Na+, the structure of the cathode material does not collapse during repeated charge–discharge cycles, so that voltage stability is enhanced greatly. Consequently, at a current density of 5 C after cycling 200 times, the reversible capacity of the designed LRM cathode is 166 mA h g–1 with a high capacity retention of 90.1%, and the median voltage remains at 3.21 V with a voltage retention of 91.4%. The median voltage could remain as high as 3.37 V with a very high voltage retention of 94.1% even at 10 C after 200 cycles. This study proposes a novel strategy that utilizes the synergistic modification of morphology design and Na+ doping to increase the lithium storage performance of LRM cathode materials.

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Mitigating evolution of lattice oxygen and stabilizing structure of lithium-rich oxides by fabricating surface oxygen defects

Cited by 29 publications

References 69 publications

A Simple Dual-Ion Doping Method for Stabilizing Li-Rich Materials and Suppressing Voltage Decay

A Simple Dual-Ion Doping Method for Stabilizing Li-Rich Materials and Suppressing Voltage Decay

Tuning the Li/Ni Disorder of the NMC811 Cathode by Thermally Driven Competition between Lattice Ordering and Structure Decomposition

Morphology Control and Na⁺ Doping toward High-Performance Li-Rich Layered Cathode Materials for Lithium-Ion Batteries

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Mitigating evolution of lattice oxygen and stabilizing structure of lithium-rich oxides by fabricating surface oxygen defects

Cited by 29 publications

References 69 publications

A Simple Dual-Ion Doping Method for Stabilizing Li-Rich Materials and Suppressing Voltage Decay

A Simple Dual-Ion Doping Method for Stabilizing Li-Rich Materials and Suppressing Voltage Decay

Tuning the Li/Ni Disorder of the NMC811 Cathode by Thermally Driven Competition between Lattice Ordering and Structure Decomposition

Morphology Control and Na+ Doping toward High-Performance Li-Rich Layered Cathode Materials for Lithium-Ion Batteries

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Product

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Morphology Control and Na⁺ Doping toward High-Performance Li-Rich Layered Cathode Materials for Lithium-Ion Batteries