Exploiting cationic vacancies for increased energy densities in dual-ion batteries

Abstract

Dual-ion Li-Mg batteries offer a potential route to cells that combine desirable properties of both single-ion species. To maximize the energy density of a dual-ion battery, we propose a strategy for achieving simultaneous intercalation of both ionic species, by chemically modifying the intercalation host material to produce a second, complementary, class of insertion sites. We show that donor-doping of anatase TiO 2 to form large numbers of cationic vacancies allows the complementary insertion of Li + and Mg 2+ in a dual-ion cell with a net increase in cell energy density, due to a combination of an increased reversible capacity, an increased operating voltage, and a reduced polarization. By tuning the lithium concentration in the electrolyte, we achieve full utilization of the Ti 4+ /Ti 3+ redox couple with excellent cyclability and rate capability. We conclude that native interstitial sites preferentially accommodate Li + ions, while Mg 2+ ions occupy single-vacancy sites. We also predict a narrow range of electrochemical conditions where adjacent vacancy pairs preferentially accommodate one ion of each species, i.e., a [Li Ti +Mg Ti ] configuration. These results demonstrate the implementation of additional host sites such as cationic sites as an effective approach to increase the energy density in dual-ion batteries.

Synthesis and Performance Optimization of Manganese‐based Cathode Materials for Zinc‐Ion Batteries

“…Cation vacancy could weak the electrostatic interaction between the ions and the host lattice and then promote the insertion of ions into the host, which have been applied in various ion batteries. [130][131][132][133] In the field of ZIBs, Mn vacancy is the most common cation vacancies in manganese-based cathode materials. Zhu et al prepared a Mn 0.61 & 0.39 O (& refers to Mn defect) cathode with Mn defects (Figure 19a) and analyzed the influence of Mn vacancy through DFT calculations.…”

“…Cation vacancy could weak the electrostatic interaction between the ions and the host lattice and then promote the insertion of ions into the host, which have been applied in various ion batteries [130–133] . In the field of ZIBs, Mn vacancy is the most common cation vacancies in manganese‐based cathode materials.…”

Rationalizing the Anion Storage in Cathodes for Optimum Dual-Ion Batteries: State of the Art and the Prospect

“…To achieve an optimal match between the anode and cathode in a DIB configuration, more efforts have been made via modifications of the anode, such as designing an integrated anode or flexible interface − , preparing high-working-potential , and high-capacity − anode materials. However, the capacity and stability of DIBs are still restricted by the incompatible capacity between the anode and cathode.…”

Effect of the Niobium Doping Concentration on the Charge Storage Mechanism of Mesoporous Anatase Beads as an Anode for High-Rate Li-Ion Batteries

“…The 3D hierarchical porous structure of the microbeads needs to be combined with an increased electronic conductivity of the semiconducting TiO 2 without affecting the Ti 4+ available reduction sites. 9,10 This can be achieved by introducing Nb 5+ ions into the TiO 2 lattice through a donortype doping process. 11−14 The ionic radius of Nb 5+ is only 5.8% larger than that of Ti 4+ (0.64 Å vs 0.605 Å), and Nb 5+ can thus easily substitute Ti 4+ in the lattice of TiO 2 in a wide range of concentrations.…”

“…Herein, we aim at overcoming the low electronic conductivity, the low ion diffusivity, and the capacity fading of anatase by introducing pentavalent niobium ion doping and directly using our microbeads as anodes for fast rechargeable Li-ion batteries. The 3D hierarchical porous structure of the microbeads needs to be combined with an increased electronic conductivity of the semiconducting TiO 2 without affecting the Ti 4+ available reduction sites. , This can be achieved by introducing Nb 5+ ions into the TiO 2 lattice through a donor-type doping process. − The ionic radius of Nb 5+ is only 5.8% larger than that of Ti 4+ (0.64 Å vs 0.605 Å), and Nb 5+ can thus easily substitute Ti 4+ in the lattice of TiO 2 in a wide range of concentrations. Moreover, the solvo-thermal synthesis process used in this work allows the insertion of Nb 5+ into the anatase lattice without undesirable phase transitions, in contrast to previously reported preparation routes …”