Thermally Aged Li–Mn–O Cathode with Stabilized Hybrid Cation and Anion Redox

Li, Sa; Sun, Xin; Liu, Yang; Liu, Guang; Xue, Weimin; Waluyo, Iradwikanari; Zhi, Zhang; Zhu, Yunguang; Dong, Yanhao; Huang, Yunhui; Li, Ju

doi:10.1021/acs.nanolett.0c04920

Cited by 6 publications

(3 citation statements)

References 39 publications

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“…Interestingly, even though the Li:TM ratio in CD-LNMO is situated between LLO and LNMO, the electrochemical behavior of CD-LNMO (Fig. 2a) was different from that of the LLO/LNMO composites in previous reports [37][38][39][40][41][42][43][44] . After the electrochemical removal of Li ions during the initial charging process, CD-LNMO showed two discharge plateaus at ~4.6 V and ~2.7 V, which are associated with the insertion of Li ions into tetrahedral sites and octahedral sites in the spineltype structure, respectively 45 .…”

Section: Resultsmentioning

confidence: 61%

A medium-entropy transition metal oxide cathode for high-capacity lithium metal batteries

et al. 2022

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The limited capacity of the positive electrode active material in non-aqueous rechargeable lithium-based batteries acts as a stumbling block for developing high-energy storage devices. Although lithium transition metal oxides are high-capacity electrochemical active materials, the structural instability at high cell voltages (e.g., >4.3 V) detrimentally affects the battery performance. Here, to circumvent this issue, we propose a Li1.46Ni0.32Mn1.2O4-x (0 < x < 4) material capable of forming a medium-entropy state spinel phase with partial cation disordering after initial delithiation. Via physicochemical measurements and theoretical calculations, we demonstrate the structural disorder in delithiated Li1.46Ni0.32Mn1.2O4-x, the direct shuttling of Li ions from octahedral sites to the spinel structure and the charge-compensation Mn3+/Mn4+ cationic redox mechanism after the initial delithiation. When tested in a coin cell configuration in combination with a Li metal anode and a LiPF6-based non-aqueous electrolyte, the Li1.46Ni0.32Mn1.2O4-x-based positive electrode enables a discharge capacity of 314.1 mA h g−1 at 100 mA g−1 with an average cell discharge voltage of about 3.2 V at 25 ± 5 °C, which results in a calculated initial specific energy of 999.3 Wh kg−1 (based on mass of positive electrode’s active material).

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Section: Resultsmentioning

confidence: 61%

A medium-entropy transition metal oxide cathode for high-capacity lithium metal batteries

et al. 2022

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“…Li et al developed a scalable three-phase Li 4 Mn 5 O 12 -LiMn 2 O 4 -Li 2 MnO 3 nanocomposite structure using a two-step heat treatment to promote the leaching of high-activity oxygen near the surface before electrochemical cycling. High-temperature in situ XRD provided an in-depth understanding of the reaction mechanism and the formation of nanocomposite structures, confirming that Li 2 MnO 3 -type ordering started at 400 °C and stabilized after 2 h at 600 °C [179]. Chen et al reported hetero-structured spinel/layered oxide (Li 1.15 Ni 0.20 Mn 0.87 O 2 ) nanofibers as superior cathode materials.…”

Section: Oxygen Releasementioning

confidence: 91%

Understanding anion-redox reactions in cathode materials of lithium-ion batteries through in situ characterization techniques: a review

et al. 2022

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As the demand for rechargeable lithium-ion batteries (LIBs) with higher energy density increases, the interest in lithium-rich oxide (LRO) with extraordinarily high capacities is surging. The capacity of LRO cathodes exceeds that of conventional layered oxides. This has been attributed to the redox contribution from both cations and anions, either sequentially or simultaneously. However, LROs with notable anion redox suffer from capacity loss and voltage decay during cycling. Therefore, a fundamental understanding of their electrochemical behaviors and related structural evolution is a prerequisite for the successful development of high-capacity LRO cathodes with anion redox activity. However, there is still controversy over their electrochemical behavior and principles of operation. In addition, complicated redox mechanisms and the lack of sufficient analytical tools render the basic study difficult. In this review, we aim to introduce theoretical insights into the anion redox mechanism and in situ analytical instruments that can be used to prove the mechanism and behavior of cathodes with anion redox activity. We summarized the anion redox phenomenon, suggested mechanisms, and discussed the history of development for anion redox in cathode materials of LIBs. Finally, we review the recent progress in identification of reaction mechanisms in LROs and validation of engineering strategies to improve cathode performance based on anion redox through various analytical tools, particularly, in situ characterization techniques. Because unexpected phenomena may occur during cycling, it is crucial to study the kinetic properties of materials in situ under operating conditions, especially for this newly investigated anion redox phenomenon. This review provides a comprehensive perspective on the future direction of studies on materials with anion redox activity.

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“…71−73 Apparently, this analysis also holds for LRNCM, which accounts for the long, flat voltage plateau at ∼4.5 V (vs Li + /Li, contributing to ∼200 mAh/g capacity in Li 1.2 Mn 0.48 Ni 0.16 Co 0.16 O 2 when charged to 4.8 V) in the first charge half-cycle beyond the accessible TM redox couples (Ni 3+/2+ , Ni 4+/3+ , and Co 4+/3+ , contributing to ∼120 mAh/g capacity in Li 1.2 Mn 0.48 Ni 0.16 Co 0.16 O 2 ). Similar local structure analysis of O has been extended to interpret the oxygen redox activity in Li-excess cation-disordered rocksalt cathodes 74−76 and Li-rich spinel cathodes 77 as well as other functional oxides, 78 the oxygen instability at surface and interfaces, and the functioning of protective cathode coating. 79 The flatness of the voltage plateau is interesting to note, as no similar shapes have been identified for TM redox couples in layered cathodes, including NCM, NCA, LiCoO 2 , and LRNCM.…”

Section: Electronic Structure Perspectivementioning

confidence: 99%

Oxide Cathodes: Functions, Instabilities, Self Healing, and Degradation Mitigations

Dong

2022

Chem. Rev.

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Recent progress in high-energy-density oxide cathodes for lithium-ion batteries has pushed the limits of lithium usage and accessible redox couples. It often invokes hybrid anion-and cation-redox (HACR), with exotic valence states such as oxidized oxygen ions under high voltages. Electrochemical cycling under such extreme conditions over an extended period can trigger various forms of chemical, electrochemical, mechanical, and microstructural degradations, which shorten the battery life and cause safety issues. Mitigation strategies require an in-depth understanding of the underlying mechanisms. Here we offer a systematic overview of the functions, instabilities, and peculiar materials behaviors of the oxide cathodes. We note unusual anion and cation mobilities caused by high-voltage charging and exotic valences. It explains the extensive lattice reconstructions at room temperature in both good (plasticity and self-healing) and bad (phase change, corrosion, and damage) senses, with intriguing electrochemomechanical coupling. The insights are critical to the understanding of the unusual self-healing phenomena in ceramics (e.g., grain boundary sliding and lattice microcrack healing) and to novel cathode designs and degradation mitigations (e.g., suppressing stress-corrosion cracking and constructing reactively wetted cathode coating). Such mixed ionic-electronic conducting, electrochemically active oxides can be thought of as almost "metalized" if at voltages far from the open-circuit voltage, thus differing significantly from the highly insulating ionic materials in electronic transport and mechanical behaviors. These characteristics should be better understood and exploited for high-performance energy storage, electrocatalysis, and other emerging applications.

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Thermally Aged Li–Mn–O Cathode with Stabilized Hybrid Cation and Anion Redox

Cited by 6 publications

References 39 publications

A medium-entropy transition metal oxide cathode for high-capacity lithium metal batteries

A medium-entropy transition metal oxide cathode for high-capacity lithium metal batteries

Understanding anion-redox reactions in cathode materials of lithium-ion batteries through in situ characterization techniques: a review

Oxide Cathodes: Functions, Instabilities, Self Healing, and Degradation Mitigations

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