Operation Mechanism in Hybrid Mg-Li Batteries with TiNb 2 O 7 Allowing Stable High-Rate Cycling

• Published in: ACS applied materials & interfaces 2021-02, Vol.13 (5), p.6309-6321
• Main Authors: Maletti, Sebastian, Janson, Oleg, Herzog-Arbeitman, Abraham, Gonzalez Martinez, Ignacio Guillermo, Buckan, Ronny, Fischer, Johanna, Senyshyn, Anatoliy, Missyul, Alexander, Etter, Martin, Mikhailova, Daria
• Format: Article
• Language: English
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.0c20905

We studied the structural evolution and cycling behavior of TiNb O (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 Mg 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 lower than in single-ion Li batteries at current densities of up to 1.2 A g . 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 ) or high (1.55 A g ) 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 MgCl 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.