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Lithiation mechanism in high-entropy oxides as anode materials for Li-ion batteries: an operando XAS study

DOI: 10.1021/acsami.0c13161 DOI Help

Authors: P. Ghigna (University of Pavia) , L. Airoldi (University of Pavia) , M. Fracchia (University of Pavia) , D. Callegari (University of Pavia) , U. Anselmi-Tamburini (University of Pavia) , P. D’angelo (University of Rome La Sapienza) , N. Pianta (University of Milano) , R. Ruffo (University of Milano) , G. Cibin (Diamond Light Source) , Danilo Oliveira De Souza (Elettra-Sincrotrone Trieste) , E. Quartarone (University of Pavia)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Applied Materials & Interfaces

State: Published (Approved)
Published: October 2020
Diamond Proposal Number(s): 17198

Abstract: High-entropy oxides based on transition metals, such as Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O (TM-HEO), have recently drawn special attention as potential anodes in lithium-ion batteries due to high specific capacity and cycling reversibility. However, the lithiation/delithiation mechanism of such systems is still controversial and not clearly addressed. Here, we report on an operando XAS investigation into TM-HEO-based anodes for lithium-ion cells during the first lithiation/delithiation cycle. This material showed a high specific capacity exceeding 600 mAh g–1 at 0.1 C and Coulombic efficiency very close to unity. The combination of functional and advanced spectroscopic studies revealed complex charging mechanisms, developing through the reduction of transition-metal (TM) cations, which triggers the conversion reaction below 1.0 V. The conversion is irreversible and incomplete, leading to the final collapse of the HEO rock-salt structure. Other redox processes are therefore discussed and called to account for the observed cycling behavior of the TM-HEO-based anode. Despite the irreversible phenomena, the HEO cubic structure remains intact for ∼60% of lithiation capacity, so proving the beneficial role of the configuration entropy in enhancing the stability of the HEO rock-salt structure during the redox phenomena.

Journal Keywords: high-entropy oxides; anodes; lithium-ion batteries; operando XAS; lithiation mechanism

Diamond Keywords: Batteries; Lithium-ion

Subject Areas: Materials, Chemistry, Energy

Instruments: B18-Core EXAFS

Other Facilities: XAFS at Elettra

Added On: 02/11/2020 08:56

Discipline Tags:

Energy Storage Energy Physical Chemistry Energy Materials Chemistry Materials Science

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS)