Chemical and structural evolutions of Li–Mn-rich layered electrodes at different current densities

He, Xin; Wu, Jue; Zhu, Zhuoying; Li, Ning; Zhou, Dong; Hou, Xu; Wang, Jun; Zhang, Haowei; Bresser, Dominic; Fu, Yanbao; Crafton, Matthew J.; McCloskey, Bryan D.; Chen, Yan; An, Ke; Liu, Haodong; Jain, Anubhav; Li, Jie; Yang, Wanli; Yang, Yong; Winter, Martin; Kostecki, Robert

doi:10.1039/d2ee01229d

Cited by 13 publications

(17 citation statements)

References 52 publications

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“…[ 19 ] The energy of removing one Li + per cell from the Li layer is lower than that from the TM layer. [ 21 ] And the Li ions in the Li layer are preferentially extracted during charging. [ 22 ] Therefore, the lowest oxygen vacancy formation energy and the generation of OO dimers can be achieved in the high delithiation state for O 2 release in the first charge process of P‐LR as shown in Figure 4c.…”

Section: Resultsmentioning

confidence: 99%

Regulating the Unhybridized O 2p Orbitals of High‐Performance Li‐Rich Mn‐Based Layered Oxide Cathode by Gd‐Doping Induced Bulk Oxygen Vacancies

Wan

Zhang

et al. 2023

Adv Funct Materials

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Li-rich Mn-based layered oxides (LRLOs) with ultrahigh specific capacities are promising cathode materials for high energy density lithium-ion batteries. Nevertheless, severe irreversible oxygen release, structure degradation, capacity and voltage attenuation hinder their commercialization due to the uncontrollable oxygen redox chemistry originated from unhybridized O 2p orbitals. Herein, a strategy to generate bulk oxygen vacancies is proposed. And bulk oxygen vacancies are constructed by lowering the formation energy of oxygen vacancies in LRLOs via Gd-doping. The energy level and the amount of unhybridized O 2p states are reduced to partly inhibit the oxygen redox activity. Surprisingly, the oxygen redox is not fully activated in the first cycle and is further activated in the second cycle. Moreover, the reduced oxygen redox activity significantly suppresses the oxygen release, lattice volume change, layered-to-spinel phase transition. As a result, the amount of oxygen gas release is reduced from 98.80 to ≈0 nmol mg −1 in the first cycle. Superior cycle stability of 90.4% capacity retention after 300 cycles and small voltage decay of only 1.013 mV per cycle are achieved. This study provides a valuable bulk oxygen vacancies strategy to regulate the unhybridized O 2p orbitals for designing high-performance Li-rich Mn-based layered oxide cathode materials.

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Section: Resultsmentioning

confidence: 99%

Regulating the Unhybridized O 2p Orbitals of High‐Performance Li‐Rich Mn‐Based Layered Oxide Cathode by Gd‐Doping Induced Bulk Oxygen Vacancies

Wan

Zhang

et al. 2023

Adv Funct Materials

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“…In the outermost part, the rock‐salt phase even shows slightly different lattice orientations, which can be attributed to the heavy disorganization of the local structure during cycling. [ 20 ] While on the SC‐NCM90, a single‐phase layered structure in the bulk is observed, only with a thin layer of rock‐salt phase on the surface and a cation mixed transition layer between the rock‐salt phase and layered phase (Figure 6d–f). In addition, as shown in Figure 6g and Figure S15, Supporting Information, compared with the cycled SC‐NCM90, two groups of XRD peaks from NCM90‐SS (750 °C‐8 h) at (006) and (012), (108), and (110) merge into broad peaks with reduced intensities, indicating a heavier Li/Ni disorder after cycling, consistent with the HR‐TEM images.…”

Section: Resultsmentioning

confidence: 99%

Pulse High Temperature Sintering to Prepare Single‐Crystal High Nickel Oxide Cathodes with Enhanced Electrochemical Performance

Huang

Zhang

Tian

et al. 2022

Advanced Energy Materials

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is still the most popular cathode material in the LIBs for 3C products, mainly owing to its extraordinarily high tap density, [2] since there is a stricter requirement on the volumetric energy density. To reduce the amount of high-cost Co, part of Co was substituted by Ni and Mn with the generation of Li(Ni x Co y Mn z )O 2 (NCM, x + y + z = 1), which not only improves the structural and thermal stability but also allows more reversible extraction-intercalation of Li + and so endows more capacity, making it currently the dominant cathode materials in the market of power batteries of EVs. [3] Currently, compared with internal combustion engine vehicles, the main concerns for the popularization of EVs are the higher price, lower continue voyage course, and heavier safety risk, mainly resulting from the LIBs.For NCM cathodes, the capacities increase gradually with the increment of Ni contents; for instance, from Li(Ni 0.5 Co 0.2 Mn 0.3 )O 2 (NCM523) to Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 (NCM811), the capacity rises from 165 to 200 mAh g −1 , around 20% promotion. [4] However, with the increment of capacity, more Li + will reversibly intercalate into and extract from the NCM layered structure, resulting in larger volumetric change, more intergranular microcracks, and heavier interfacial reactions. [5] In addition, with the increase of Ni content, more superficial Ni 4+ ions lead to heavier catalytic oxidation of electrolytes, causing more serious capacity fading and safety risks. [6] To reduce the intergranular microcracks

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“…To analyze the variation in electronic states upon cycling, XAS measurements under bulk-sensitive IPFY and surface-sensitive TEY modes were conducted. , Absorption peaks at 640.3 and 642.0 eV emerge in the Mn L 2,3 -edge IPFY XAS spectrum after the first charge (Figure a), indicating the reduction of a fraction of Mn 4+ to Mn 3+ in the bulk . The Mn K-edge XANES spectrum also confirms the partial reduction of Mn (Figure S5).…”

Section: Resultsmentioning

confidence: 87%

High-Voltage Electrochemical Properties of Lithium-Rich Spinel Oxides

et al. 2023

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Conventional cathode materials of lithium-ion batteries deliver moderate specific capacity based on the redox reaction of transition metals; using additional oxygen redox reactions in lithium-rich oxides is a strategy to increase their energy density. However, a delithiated layered structure is prone to the irreversible migration of transition metals to lithium-ion layers during oxygen redox reactions, which results in performance degradation. Thus, exploring alternative oxygen redox host frameworks is required to develop high-capacity and durable cathode materials. Herein, we investigated the oxygen redox activity of lithium-rich spinel oxides. First-principles calculations predict that nonbonding O 2p orbitals exist just below the Fermi level of lithium-rich spinel oxides and undergo oxidation through delithiation. Electrochemical measurements demonstrate that delithiation occurs at 5.0 V vs Li/Li + during the first charge, but this high-voltage capacity fades rapidly upon cycling. X-ray absorption/emission spectroscopy, high-resolution transmission electron microscopy, and X-ray diffraction indicate that the oxidized oxide ions are highly unstable to form O 2 molecules accompanied by a reduction of Mn 4+ .

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Chemical and structural evolutions of Li–Mn-rich layered electrodes at different current densities

Abstract: Although the two active redox centers in Li-rich cathodes, including the anionic and cationic contributions, can enable Li-ion batteries to achieve outstanding specific energy, their behaviors at different current densities...

Cited by 13 publications

References 52 publications

Regulating the Unhybridized O 2p Orbitals of High‐Performance Li‐Rich Mn‐Based Layered Oxide Cathode by Gd‐Doping Induced Bulk Oxygen Vacancies

Regulating the Unhybridized O 2p Orbitals of High‐Performance Li‐Rich Mn‐Based Layered Oxide Cathode by Gd‐Doping Induced Bulk Oxygen Vacancies

Pulse High Temperature Sintering to Prepare Single‐Crystal High Nickel Oxide Cathodes with Enhanced Electrochemical Performance

High-Voltage Electrochemical Properties of Lithium-Rich Spinel Oxides

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