Operation Mechanism in Hybrid Mg-Li Batteries with TiNb2O7 Allowing Stable High-Rate Cycling

Sebastian Maletti; Oleg Janson; Abraham Herzog-Arbeitman; Ignacio Guillermo Gonzalez Martinez; Ronny Buckan; Johanna Fischer; Anatoliy Senyshyn; Alexander Missyul; Martin Etter; Daria Mikhailova

doi:10.1021/acsami.0c20905

Operation Mechanism in Hybrid Mg-Li Batteries with TiNb₂O₇ Allowing Stable High-Rate Cycling

ACS Appl Mater Interfaces. 2021 Feb 10;13(5):6309-6321. doi: 10.1021/acsami.0c20905. Epub 2021 Feb 2.

Affiliations

¹ Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V., Helmholtzstraße 20, D-01069 Dresden, Germany.
² Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States.
³ Forschungsneutronenquelle Heinz Maier-Leibnitz FRM-II, Technische Universität München, Lichtenbergstr. 1, D-85747 Garching bei München, Germany.
⁴ ALBA Synchrotron Light Source, Carrer de la Llum 2-26, Cerdanyola del Vallès, 08290 Barcelona, Spain.
⁵ Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, D-22607 Hamburg, Germany.

PMID: 33527829
DOI: 10.1021/acsami.0c20905

Abstract

We studied the structural evolution and cycling behavior of TiNb₂O₇ (TNO) as a cathode in a nonaqueous hybrid dual-salt Mg-Li battery. A very high fraction of pseudocapacitive contribution to the overall specific capacity makes the material suitable for ultrafast operation in a hybrid battery, composed of a Mg-metal anode, and a dual-salt APC-LiCl electrolyte with Li and Mg cations. Theoretical calculations show that Li intercalation is predominant over Mg intercalation into the TNO in a dual-salt electrolyte with Mg²⁺ and Li⁺, while experimentally up to 20% Mg cointercalation was observed after battery discharge. In hybrid Mg-Li batteries, TNO shows capacities which are about 40 mA h g^-1 lower than in single-ion Li batteries at current densities of up to 1.2 A g^-1. This is likely due to a partial Mg cointercalation or/and location of Li cations on alternative crystallographic sites in the TNO structure in comparison to the Li-intercalation process in Li batteries. Generally, hybrid Mg-Li cells show a markedly superior applicability for a very prolonged operation (above 1000 cycles) with 100% Coulombic efficiency and a capacity retention higher than 95% in comparison to conventional Li batteries with TNO after being cycled either under a low (7.75 mA g^-1) or high (1.55 A g^-1) current density. The better long-term behavior of the hybrid Mg-Li batteries with TNO is especially pronounced at 60 °C. The reasons for this are an appropriate cathode electrolyte interface containing MgCl₂ species and a superior performance of the Mg anode in APC-LiCl electrolytes with a dendrite-free, fast Mg deposition/stripping. This stable interface stands in contrast to the anode electrolyte interface in Li batteries with a Li anode in conventional carbonate-containing electrolytes, which is prone to dendrite formation, thus leading to a battery shortcut.

Keywords: Li,Mg cointercalation; Wadsley-Roth phase; beyond lithium batteries concept; cathode electrolyte interface; dual-salt batteries; fast Mg deposition/stripping; pseudocapacitive storage.