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Magnesium (Mg) batteries hold promise as a large-scale energy storage solution, but their progress has been hindered by the lack of high-performance cathodes. Here, we address this challenge by unlocking the reversible four-electron Te0/Te4+ conversion in elemental Te, enabling the demonstration of superior Mg//Te dual-ion batteries. Specifically, the classic magnesium aluminum chloride complex (MACC) electrolyte is tailored by introducing Mg bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2), which initiates the Te0/Te4+ conversion with two distinct charge-storage steps. Te cathode undergoes Te/TeCl4 conversion involving Cl– as charge carriers, during which a tellurium subchloride phase is presented as an intermediate. Significantly, the Te cathode achieves a high specific capacity of 543 mAh gTe–1 and an outstanding energy density of 850 Wh kgTe–1, outperforming most of the previously reported cathodes. Our electrolyte analysis indicates that the addition of Mg(TFSI)2 reduces the overall ion-molecule interaction and mitigates the strength of ion-solvent aggregation within the MACC electrolyte, which implies the facilized Cl– dissociation from the electrolyte. Besides, Mg(TFSI)2 is verified as an essential buffer to mitigate the corrosion and passivation of Mg anodes caused by the consumption of the electrolyte MgCl2 in Mg//Te dual-ion cells. These findings provide crucial insights into the development of advanced Mg-based dual-ion batteries.

Reference: Ahiud Morag, Xingyuan Chu, Maciej Marczewski, Jonas Kunigkeit, Christof Neumann, Davood Sabaghi, Grażyna Zofia Żukowska, Jingwei Du, Xiaodong Li, Andrey Turchanin, Eike Brunner, Xinliang Feng,* Minghao Yu* Angew. Chem. Int. Ed. 2024, e202401818

Acknowledgements: This work was financially supported by European Union’s Horizon Europe research and innovation programme (ERC Starting Grant, BattSkin, 101116722), European Union’s Horizon 2020 research and innovation programme (LIGHT-CAP 101017821), German Research Foundation (DFG) within the Cluster of Excellence, CRC 1415 (Grant No. 417590517), and the European Fonds for Regional Development (Europäischer Fonds für Regionale Entwicklung; EFRE-OP 2014-2020; Project No. 2021 FGI 0035, NanoLabXPS) as part of the REACT-EU program. The authors also acknowledge the use of the facilities in the Dresden Center for Nanoanalysis (DCN) at Technische Universität Dresden, the GWK support for providing computing time through the Center for Information Services and High-Performance Computing (ZIH) at TU Dresden. We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at PETRA III, and we would like to thank Edmund Welter and Dr. Andre L. C Conceição for assistance in using beamlines P65 and P62, respectively. WAXS experiments were also performed at BL11 beamline at ALBA Synchrotron with the collaboration of Dr. Cristián Huck Iriart. We acknowledge the European Synchrotron Radiation Facility (ESRF) for the provision of synchrotron radiation facilities, and we would like to thank Dr. Cesare Atzorifor's assistance and support in using beamline BM23.