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Rechargeable Mg ion batteries (MIBs) have aroused great interests, and using alloy-type anodes and conventional electrolytes offers an effective way to develop high energy density Mg battery systems. However, the dealloying-induced nanoporosity evolution of alloy-type anodes during the charging process has received less attention. Herein, using a magnetron-sputtered Mg3Bi2 film as an example, we investigate its electrochemical dealloying and associated structural evolution in an all-phenyl-complex electrolyte by in-situ and ex-situ characterizations. The microstructures and length scales of nanoporous Bi can be facilely regulated by changing electrochemical parameters, and there exists a good linear correlation between the surface diffusivity of Bi and the applied current density/potential scan rate on a logarithm scale. More importantly, the self-supporting nanoporous Bi electrodes deliver satisfactory Mg storage performance and alloy-type anodes show good compatibility with conventional electrolytes. Furthermore, the charging-induced dealloying in MIBs is a general strategy to fabricate nanoporous less noble metals like Sn, Pb, In, Cu, Zn and Al, which shows advantages over chemical dealloying in aqueous solutions. Our findings highlight the significance of nanoporosity evolution of alloy-type anodes during dealloying, and open opportunities for the fabrication of nanoporous reactive metals.

Solid electrolytes with high Mg-ion conductivity are required to develop solid-state Mg-ion batteries. The migration energies of the Mg2+ ions of 5,576 Mg compounds tabulated from the inorganic crystal structure database (ICSD) were evaluated via high-throughput calculations. Among the computational results, we focused on the Mg2+ ion diffusion in Mg0.6Al1.2 Si1.8O6, as this material showed a relatively low migration energy for Mg2+ and was composed solely of ubiquitous elements. Furthermore, first-principles molecular dynamics calculations confirmed a single-phase Mg2+ ion conductor. The bulk material with a single Mg0.6Al1.2Si1.8O6 phase was successfully prepared using the sol-gel method. The relative density of the sample was 81%. AC impedance measurements indicated an electrical conductivity of 1.6 × 10−6 Scm−1 at 500°C. The activation energy was 1.32 eV, which is comparable to that of monoclinic-type Mg0.5Zr2(PO4)3.

Rechargeable Mg ion batteries (MIBs) have aroused great interests, and using alloy-type anodes and conventional electrolytes offers an effective way to develop high energy density Mg battery systems. However, the dealloying-induced nanoporosity evolution of alloy-type anodes during the charging process has received less attention. Herein, using a magnetron-sputtered Mg 3 Bi 2 film as an example, we investigate its electrochemical dealloying and associated structural evolution in an all-phenyl-complex electrolyte by in-situ and ex-situ characterizations. The microstructures and length scales of nanoporous Bi can be facilely regulated by changing electrochemical parameters, and there exists a good linear correlation between the surface diffusivity of Bi and the applied current density/potential scan rate on a logarithm scale. More importantly, the self-supporting nanoporous Bi electrodes deliver satisfactory Mg storage performance and alloy-type anodes show good compatibility with conventional electrolytes. Furthermore, the charging-induced dealloying in MIBs is a general strategy to fabricate nanoporous less noble metals like Sn, Pb, In, Cu, Zn and Al, which shows advantages over chemical dealloying in aqueous solutions. Our findings highlight the significance of nanoporosity evolution of alloy-type anodes during dealloying, and open opportunities for the fabrication of nanoporous reactive metals. [ABSTRACT FROM AUTHOR]

Solid electrolytes with high Mg-ion conductivity are required to develop solid-state Mg-ion batteries. The migration energies of the Mg2+ ions of 5,576 Mg compounds tabulated from the inorganic crystal structure database (ICSD) were evaluated via high-throughput calculations. Among the computational results, we focused on the Mg2+ ion diffusion in Mg0.6Al1.2 Si1.8O6, as this material showed a relatively low migration energy for Mg2+ and was composed solely of ubiquitous elements. Furthermore, first-principles molecular dynamics calculations confirmed a single-phase Mg2+ ion conductor. The bulk material with a single Mg0.6Al1.2Si1.8O6 phase was successfully prepared using the sol-gel method. The relative density of the sample was 81%. AC impedance measurements indicated an electrical conductivity of 1.6 × 10−6 Scm−1 at 500°C. The activation energy was 1.32 eV, which is comparable to that of monoclinic-type Mg0.5Zr2(PO4)3. [ABSTRACT FROM AUTHOR]

Solid electrolytes with high Mg-ion conductivity are required to develop solid-state Mg-ion batteries. The migration energies of the Mg2+ ions of 5,576 Mg compounds tabulated from the inorganic crystal structure database (ICSD) were evaluated via high-throughput calculations. Among the computational results, we focused on the Mg2+ ion diffusion in Mg0.6Al1.2 Si1.8O6, as this material showed a relatively low migration energy for Mg2+ and was composed solely of ubiquitous elements. Furthermore, first-principles molecular dynamics calculations confirmed a single-phase Mg2+ ion conductor. The bulk material with a single Mg0.6Al1.2Si1.8O6 phase was successfully prepared using the sol-gel method. The relative density of the sample was 81%. AC impedance measurements indicated an electrical conductivity of 1.6 × 10−6 Scm−1 at 500°C. The activation energy was 1.32 eV, which is comparable to that of monoclinic-type Mg0.5Zr2(PO4)3. [ABSTRACT FROM AUTHOR]

The recently proposed hybrid Mg-Li ion battery technology delivers good reaction kinetics and excellent safety features because it integrates the advantages of the Mg metal anode and the Li + ion intercalation/conversion electrodes. The inexpensive and resource-abundant FeS is a suitable candidate as a cathode material due to its medium redox potential and high theoretical capacity; however, a conventional FeS cathode suffers from low electronic conductivity, low coulombic efficiency and poor cycling performance. Here, in this work, to overcome these drawbacks, a free-standing membrane electrode with FeS nanoparticles embedded in carbon nanofibers was designed and prepared via a facile electrospinning method. Additionally, because of the absence of inactive materials, such as the current collector and binder, the energy density was enhanced compared with that in the conventional batteries. The hybrid Mg-Li ion battery fabricated in this study can deliver a maximum energy density of ∼300 Wh kg −1 , which is superior to that of most conventional Mg ion batteries. An outstanding cyclic performance for up to 800 cycles with high coulombic efficiencies above 97% was demonstrated, and a specific capacity above 200 mAh g −1 was retained with a current density of 257 mA g −1 . [ABSTRACT FROM AUTHOR]

In this work, the electrochemical properties of micron In–Sn–Bi alloy electrodes for rechargeable magnesium batteries (RMBs) are evaluated. Compared with the low stability pure Bi anode, In–Sn–Bi alloy anodes show high reversible specific capacity and high cycle stability. Among the studied alloys, In 10 Sn 10 Bi 80 electrode shows high reversible specific capacity up to 260 mAh g−1, good rate performance and excellent cycle stability (capacity retention above 98% after 80 cycles). The synergistic effects coming from the multi-phase structure have been clarified. The multi-phase structure resists the volume change and structural collapse and then guarantee the good cycle stability compared with that of pure Bi. Additionally, benefited by the fast kinetics of magnesiation/de-magnesiation of the dispersed Bi-rich phase, the reversibility of magnesiation/de-magnesiation of In and Sn are also realized. The multi-phase & fine-substructure design of the electrode materials is promising for the application in RMBs. [Display omitted] • Ternary In–Sn–Bi anodes were synthesized by simple mechanical ball milling method. • Bi-rich fine-substructure designed alloy provides good diffusion kinetics of Mg2+. • Multi-phase structure resists volume change and delivers excellent cycle stability. • In 10 Sn 10 Bi 80 delivers capacity >250mAh g−1 with retention >98% after 80 cycles. [ABSTRACT FROM AUTHOR]

• The interlayer spacing of V 2 O 5 was adjusted through the intercalation of PEDOT. • V 2 O 5 interacts with PEDOT with the phase transition from Quinoid to Benzoid. • A reversible and fast Mg2+ ion storage of V 2 O 5 /PEDOT was achieved. • The enlarged interlayer and water activation improved the kinetic performances. • Bilayer structured V 2 O 5 /PEDOT achieved the high rate and cycling performances. Magnesium ion batteries (MIBs) are attracting attention as promising alternatives to next-generation energy storage systems owing to their high safety, high volumetric capacity, low reduction potential, abundant raw materials, and economic efficiency. However, developing highly reversible and kinetically fast MIB cathode materials is very challenging owing to the sluggish Mg2+ ion diffusion and low reversible capacity typical of bivalent magnesium ions, as well as the strong electrostatic interactions with the host cathode material. Herein, we designed a charge transfer interaction of a bilayered V 2 O 5 /PEDOT (VOP) complex with involving the phase transition of PEDOT from a quinoid to a benzoid structure which could be realized because of reversible and fast Mg2+ ion storage through an enlarged interlayer spacing of 19.02Å. Furthermore, the effect of water activation on the enhancement of the kinetics was confirmed by conducting electrochemical and in-situ/ex-situ characterizations. Consequently, the as-designed VOP electrodes delivered a high specific capacity of 339.7 mAh/g at 100 mA g−1, high-rate capacity of 256.3 mAh/g at 500 mA g−1, and long-term cyclic stability with a 0.065 % decay rate and high capacity of 172.5 mAh/g after 500 cycles. [ABSTRACT FROM AUTHOR]

Hybrid Mg/Li-ions batteries (MLIBs), combining the fast kinetics of Li and the advantages of magnesium ion batteries (MIBs), are regarded as one of the most prospective electrochemical energy storage systems. Nevertheless, the electrochemical properties of batteries are generally limited by the diffusion kinetics of highly-polarized divalent Mg ions in the cathode materials. Herein, rutile-type molybdenum dioxide (R-MoO 2) was synthesized by the hydrothermal treatment and subsequent thermal treatment and used as the cathode materials in MIBs and MLIBs. The initial discharge capacities of R-MoO 2 cathodes in MIBs and MLIBs are 50 and 253 mAh·g −1 at the current density of 50 mA·g −1, respectively. The specific capacities are 17 and 111 mAh·g −1 after 100 cycles. The R-MoO 2 cathode possesses good Coulombic efficiency and rate capability in MLIBs. Compared with MIBs, the electrochemical performances of MLIBs were greatly enhanced. The energy storage mechanisms were investigated by the experiments results and density functional theory (DFT) calculations. Moreover, the discharge-charge mechanisms were also explored by ex-situ characterizations. The diffusion/migration of Mg2+ and Mg storage abilities are improved by introducing the Li+, promoting electrochemical performances. The energy storage mechanisms are Mg2+ intercalation in MIBs and Mg2+/Li+ co-intercalation in MLIBs. This work further investigates the energy storage mechanism of MLIBs and provides the theoretical groundwork for the follow-up development of high-performance cathode materials. [ABSTRACT FROM AUTHOR]

Rechargeable ion batteries based on the intercalation of multivalent ions are attractive due to their high energy density and structural stability. Surface of cathode materials plays an important role for the electrochemical performance of the rechargeable ion batteries. In this work we calculated surface energies of (001), (110) and (111) facets with different terminations in spinel MgMn 2 O 4 and MgNi 0.5 Mn 1.5 O 4 cathodes. Results showed clearly that atomic reconstruction occurred due to surface relaxation. The surface energies for the (001), (110) and (111) surfaces of the MgNi 0.5 Mn 1.5 O 4 were 0.08, 0.13 and 0.11 J/m 2 , respectively, whereas those of the Ni-doped MgMn 2 O 4 showed less dependence on the surface structures. [ABSTRACT FROM AUTHOR]

Abstract: Magnesium has been inserted electrochemically into manganese oxide octahedral molecular sieves (OMS-5 MnO2) at room temperature. Discharge/charge profiles show that a large amount of Mg, i.e., 0.37Mg/Mn can be inserted electrochemically using 1M Mg(ClO4)2/AN electrolyte when OMS-5 is prepared in presence of acetylene black. X-ray diffraction analysis and discharge/charge profiles verify that a solid state solution reaction takes place upon Mg insertion into the host lattice with concurrent reduction of Mn4+ to Mn2+. However, upon each reduction of Mn by Mg insertion and resultant dissolution into electrolyte, decrease in the active compound occurs consequently. A low intrinsic electronic conductivity of OMS-5 was suggested to play a vital role in Mg insertion into the host. [Copyright &y& Elsevier]

[Display omitted] • The three new phases of M 2 B (M = Sc, Ti, and V) of MBenes are proved stable. • M 2 B has high specific capacity and low open-circuit voltage for Mg ion batteries. • The M 2 B undergoes a slight change in lattice constant when metal ion adsorption. Rechargeable magnesium ion batteries (MIBs) have attracted great interests as a prospective candidate for next generation large-scale energy storage systems owing to the low cost and high abundance of Mg resources. However, MIBs have been restricted by the lack of suitable electrode materials for a long term. Therefore, three new phases of two-dimensional transition metal borides (MBenes) including Sc 2 B, Ti 2 B and V 2 B are explored as electrode candidates for MIBs. All the three M 2 B (M = Sc, Ti, and V) with ground states of ferromagnetic configurations are proved dynamically and thermally stable by using phonon dispersions and molecular dynamics simulations. The results show that all M 2 B phases have ultra-high specific capacity of 3192.813 mA h/g, 3018.414 mA h/g and 2853.953 mA h/g for Mg on Sc 2 B, Ti 2 B and V 2 B, respectively. In addition, the M 2 B monolayer only undergoes a small change in lattice constant with adsorption of single layer or multilayer ions. This work not only reports three new phases of M 2 B with layered structure but also further provides useful information of MBenes as promising electrode candidates for high-performance metal ion batteries. [ABSTRACT FROM AUTHOR]

Solid electrolytes with high Mg-ion conductivity are required to develop solid-state Mg-ion batteries. The migration energies of the Mg 2+ ions of 5,576 Mg compounds tabulated from the inorganic crystal structure database (ICSD) were evaluated via high-throughput calculations. Among the computational results, we focused on the Mg 2+ ion diffusion in Mg 0.6 Al 1.2  Si 1.8 O 6 , as this material showed a relatively low migration energy for Mg 2+ and was composed solely of ubiquitous elements. Furthermore, first-principles molecular dynamics calculations confirmed a single-phase Mg 2+ ion conductor. The bulk material with a single Mg 0.6 Al 1.2 Si 1.8 O 6 phase was successfully prepared using the sol-gel method. The relative density of the sample was 81%. AC impedance measurements indicated an electrical conductivity of 1.6 × 10 -6 Scm -1 at 500°C. The activation energy was 1.32 eV, which is comparable to that of monoclinic-type Mg 0.5 Zr 2 (PO 4 ) 3 ., (© 2020 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)