Dongyan Yu’s research while affiliated with Xiamen University and other places

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Publications (5)


DOD‐dependent electrochemical performance distinctions between NCM and LRLO. (a) Discharge profiles of NCM half‐cells after 100 cycles at 115 mA/g within the voltage ranges of 3.6–4.3 V (LDOD) and 2.7–4.3 V (HDOD). Insert: Corresponding capacity retention. (b) Discharge profiles of LRLO half‐cells after 100 cycles at 115 mA/g within the voltage ranges of 3.3–4.5 V (LDOD) and 2.7–4.5 V (HDOD). Insert: capacity retention. (c) Discharge profiles of LRLO||Gr pouch‐type full‐cells after 100 cycles at 115 mA/g within the voltage ranges of 3.0–4.43 V (LDOD) and 2.5–4.43 V (HDOD). Insert: Corresponding capacity retention and the pouch‐type full‐cell photograph (Reproduced with permission). (d) The available capacity decay schematic illustrations of NCM and LRLO cathodes under HDOD and LDOD long‐term cycling. Insert: HDOD and LDOD cycling models. (e) Models of ideal cycling step (HDOD) and practical cycling scene (LDOD).
Cationic/anionic charge compensation mechanism of LRLO at different potentials. (a) Evolution of normalized XANES spectra of Ni K‐edge and Mn K‐edge of LRLO during the initial discharge process. Insert: Half‐height changes in XANES at the Ni and Mn K‐edge. (b) O K‐edge sXAS spectra of LRLO during the initial discharge process. Difference spectra are shown inset for clarity. (c) Voltage profiles and corresponding dQ/dV curves in Li half‐cells as the charge window is opened stepwise from 2.5 to 4.5 V. The dQ/dV curves for the 30th cycle within the voltage ranges of 3.3–4.5 V (LDOD) and the 31th cycle within the voltage ranges of 2.7–4.5 V (HDOD) are on the right side.
The charge compensation mechanism of LRLO for HDOD and LDOD cycling. (a) The dQ/dV curves of HDOD (2.7–4.5 V) and LDOD (3.3–4.5 V) cycling from 5th to 50th cycles at a current of 115 mA/g and the 51th cycle at a current of 23 mA/g within the voltage ranges of 2.0–4.5 V (extend cycle). The dQ/dV curves of the 51th cycle discharge state are presented. (b) the O K‐edge absorption spectra and corresponding differential spectra after 50 cycles charge states (4.5 V, green area) and discharge states (yellow area) at HDOD (2.7 V) and LDOD (3.3 V) cycling. (c) Evolution of normalized XANES spectra of Ni K‐edge during the initial discharge process and the 1st and 50th discharge states under HDOD (2.7 V) and LDOD (3.3 V) cycling. (d) The models of reversible redox capacity changes for O and Ni during long cycles of HDOD and LDOD cycling.
Structural evolution of LRLO cathode cycled under different DODs. (a) A schematic model illustrating coordination changes induced by the in‐plane migration of Mn within the TM layer. Green, blue, and red spheres denote Mn‐Mn3, Mn‐Mn4, and Mn‐Mn5 configurations, respectively. The red arrows depict in‐plane migration of TM. (b) The EXAFS spectra of Mn and the intensity variations of Mn‐TM for the 1st and 100th cycles under different DODs. Insert: Mn‐TM coordination and the locally enlarged image of LDOD cycling. (c) High‐resolution RIXS spectra recorded at an excitation energy of 531 eV for LRLO in the OCV, charged (4.5 V, 1st), and discharged states of the same 3.3 V of HDOD and LDOD cycling after 50 cycles. Insert: locally enlarged image of 0.125–2 eV. (d) The formation and evolution schematic illustrations of clusters and the out‐of‐plane migration pathways of TM during different DODs. Colour‐coding in insets is the same as the other structural Figures: green, Li; red, O; blue, TM. The black arrow signifies the electrostatic repulsion between TM at Li sites and TM within the TM layer.
Mechanistic evolution of cathode structure under different DODs cycling. (a) Ex situ sXRD patterns and refined results of HDOD and LDOD cycling after 100 cycles. Insets present the peak intensity ratio of (003)/(104) and the refined values of Li/Ni. Upper left inset: schematic of 003 and 104 crystal face. (b) GITT potential curve and chemical diffusion coefficient [log(DLi+)] of HDOD and LDOD cycling after 10 cycles. (c) TEM images for HDOD and (d) LDOD cycling after 100 cycles; the IFFT images represent surface (R1) and bulk (R2) regions also listed in the Figure.

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Depth‐of‐Discharge Dependent Capacity Decay Induced by the Accumulation of Oxidized Lattice Oxygen in Li‐Rich Layered Oxide Cathode
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  • Publisher preview available

December 2024

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52 Reads

Kang Zhang

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Yilong Chen

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Yuanlong Zhu

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[...]

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Shi‐Gang Sun

More and more basic practical application scenarios have been gradually ignored/disregarded, in fundamental research on rechargeable batteries, e.g. assessing cycle life under various depths‐of‐discharge (DODs). Herein, although benefit from the additional energy density introduced by anionic redox, we critically revealed that lithium‐rich layered oxide (LRLO) cathodes present anomalously poor capacity retention at low‐DOD cycling, which is essentially different from typical layered cathodes (e.g. NCM), and pose a formidable impediment to the practical application of LRLO. We systemically demonstrated that DOD‐dependent capacity decay is induced by the anionic redox and accumulation of oxidized lattice oxygen (Oⁿ⁻). Upon low‐DOD cycling, the accumulation of Oⁿ⁻ and the persistent presence of vacancies in the transition metal (TM) layer intensified the in‐plane migration of TM, exacerbating the expansion of vacancy clusters, which further facilitated detrimental out‐of‐plane TM migration. As a result, the aggravated structural degradation of LRLO at low‐DOD impeded reversible Li⁺ intercalation, resulting in rapid capacity decay. Furthermore, prolonged accumulation of Oⁿ⁻ persistently corroded the electrode‐electrolyte interface, especially negative for pouch‐type full‐cells with the shuttle effect. Once the “double‐edged sword” effect of anionic redox being elucidated under practical condition, corresponding modification strategies/routes would become distinct for accelerating the practical application of LRLO.

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Depth‐of‐Discharge Dependent Capacity Decay Induced by the Accumulation of Oxidized Lattice Oxygen in Li‐Rich Layered Oxide Cathode

November 2024

·

25 Reads

Angewandte Chemie

More and more basic practical application scenarios have been gradually ignored/disregarded, in fundamental research on rechargeable batteries, e.g. assessing cycle life under various depths‐of‐discharge (DODs). Herein, although benefit from the additional energy density introduced by anionic redox, we critically revealed that lithium‐rich layered oxide (LRLO) cathodes present anomalously poor capacity retention at low‐DOD cycling, which is essentially different from typical layered cathodes (e.g. NCM), and pose a formidable impediment to the practical application of LRLO. We systemically demonstrated that DOD‐dependent capacity decay is induced by the anionic redox and accumulation of oxidized lattice oxygen (On‐). Upon low‐DOD cycling, the accumulation of On‐ and the persistent presence of vacancies in the transition metal (TM) layer intensified the in‐plane migration of TM, exacerbating the expansion of vacancy clusters, which further facilitated detrimental out‐of‐plane TM migration. As a result, the aggravated structural degradation of LRLO at low‐DOD impeded reversible Li+ intercalation, resulting in rapid capacity decay. Furthermore, prolonged accumulation of On‐ persistently corroded the electrode‐electrolyte interface, especially negative for pouch‐type full‐cells with the shuttle effect. Once the “double‐edged sword” effect of anionic redox being elucidated under practical condition, corresponding modification strategies/routes would become distinct for accelerating the practical application of LRLO.