Aqueous Magnesium Ion Battery Research Articles

Valence Engineering Boosts Kinetics and Storage Capacity of Layered Double Hydroxides for Aqueous Magnesium‐Ion Batteries

AbstractThe kinetics and storage‐capacity of NiCoMg‐ternary layered double hydroxide (NiCoMg‐LDH) are successfully boosted by valence engineering. As the cathode for aqueous magnesium‐ion batteries (AMIBs), the assembled NiCoMg‐LDH//active carbon (AC) delivers a high specific discharge capacity (121.0 mAh·g−1 at 0.2 A·g−1), long‐term cycling stability (85% capacity retention after 2000 cycles at 1.0 A·g−1) and an excellent performance at −30 °C. Moreover, NiCoMg‐LDH//perylenediimide (PTCDI) is assembled, achieving a high specific discharge capacity and long‐term cycling stability. X‐ray absorption spectra (XAS)/X‐ray photoelectron spectroscopy (XPS) analyses and Density functional theory (DFT) calculations disclose that the electrons are redistributed due to the 3d orbital overlap of Co/Ni atoms in NiCoMg‐LDH, which obviously reduces the valence states of Co/Ni atoms, enhances Mg─O bond strength and degree of hybridization of Co/Ni 3d and O 2p orbitals. Hence, the electronic conductivity is significantly enhanced and the electrostatic repulsion between Mg2+ and host layers is greatly reduced, giving rise to the improved diffusion kinetics and storage‐capacity of Mg2+. Furthermore, in situ Raman/X‐ray diffraction (XRD) and ex situ XPS reveal corresponding energy‐storage mechanism. This paper not only demonstrates the feasibility of LDHs as cathode for AMIBs, but also offers a new modification method of valence engineering for high‐performance electrode materials.

High cycling stability of MnO2 cathode for aqueous Mg-ion batteries enabled by Fe doping

MnO2 has been widely investigated as a promising cathode material for aqueous magnesium-ion batteries, which, however, suffers from the severe capacity fading during charge/discharge cycling. In present work, we report that the doping of Fe in α-MnO2 enlarges the lattice and alleviates the Jahn–Teller distortions and thus accelerates the Mg2+ diffusion and strengthens the structural stability. Consequently, the capacity retention remarkably increases from 44.3 % to 85.2 % after 1000 cycles by Fe doping. Furthermore, it is found for the first time that Fe doping enables the co-insertion of H+ and Mg2+ in the tunnels of α-MnO2, which improves remarkably the specific capacity from 131.9 to 205.9 mA h g−1 at 0.1 A g−1.

High-rate aqueous magnesium ion battery enabled by Li/Mg hybrid superconcentrated electrolyte

Rechargeable aqueous magnesium ion batteries (AMIBs) are considered a promising energy storage system due to the relatively high energy density, excellent rate performance and reversibility, and absence of dendrite formation during cycling. However, the high surface charge density of Mg2+ ions results in slow diffusion kinetics, and high voltage leads to excessive electrolyte decomposition at the electrode/aqueous electrolyte interface, thereby limiting the development of high-energy–density MIBs. In this work, we extend the electrochemical stability window of the aqueous electrolyte to 2.1 V by using a hybrid ion superconcentrated electrolyte at concentrations not achievable with Mg2+ electrolytes alone. The AMIB with a water-in-salt (WIS) electrolyte delivers discharge capacities of up to 200.6 and 84.4 mAh g−1, and energy densities of 170.1 and 68.1 Wh Kg−1 at 0.5 and 20 A g−1, respectively, representing excellent rate performance, while retaining 85 % of the specific capacity after 2000 cycles. Additionally, we explore the corresponding electrochemical reaction mechanism, revealing the synergistic effect of Mg2+ and Li+ ions in the charge/discharge process, which supports the excellent electrochemical performance of AMIB.

Elektrohemijske karakteristike kompozita V2O5/rGO kao elektrodnog materijala za Mg-jonske baterije sa vodenim elektrolitom

Herein, the composite of vanadium pentoxide and graphene oxide (V2O5/GO) was synthesized by the solgel method. The synthesized composite V2O5/GO was characterized by X-Ray diffraction analysis and Raman spectroscopy. After in situ reduction of GO, the electrochemical characteristics of V2O5/rGO were analyzed by cyclic voltammetry in Mg(NO3)2 aqueous solutions. The V2O5/rGO composite showed following intercalation capacities: initially 139.1 mA h g-1 and 101.8 mA h g-1 after the 10th cycle, which along with easy, fast and low-cost synthesis, make this composite a potentially good electrode material for application in secondary aqueous magnesium-ion batteries.

Improvements in the Electrochemical Performance of Sodium Manganese Oxides by Ti Doping for Aqueous Mg-Ion Batteries.

In recent times, the research on cathode materials for aqueous rechargeable magnesium ion battery has gained significant attention. The focus is on enhancing high-rate performance and cycle stability, which has become the primary research goal. Manganese oxide and its derived Na-Mn-O system have been considered as one of the most promising electrode materials due to its low cost, non-toxicity and stable spatial structure. This work uses hydrothermal method to prepare titanium gradient doped nano sodium manganese oxides, and uses freeze-drying technology to prepare magnesium ion battery cathode materials with high tap density. At the initial current density of 50 mA g-1 , the NMTO-5 material exhibits a high reversible capacity of 231.0 mAh g-1 , even at a current density of 1000 mA g-1 , there is still 122.1 mAh g-1 . It is worth noting that after 180 cycles of charging and discharging at a gradually increasing current density such as 50-1000 mA g-1 , it can still return to the original level after returning to 50 mA g-1 . Excellent electrochemical performance and capacity stability show that NMTO-5 material is a promising electrode material.

H+/Mg2+ dual ions insertion mechanism in vanadium oxide nanosheet anode for aqueous magnesium-ion batteries

Aqueous magnesium-ion batteries (AMIB) are attracting rising interest owing to high safety, low cost and high energy density in energy storage. Yet, it is difficult in finding high-performance anode materials, which thus hinders realization of its advantages. Herein, an ultra-thin VOx nanosheet with abundant lattice defects and large interlayer distance was obtained via an electrodeposition method, which exhibits excellent electrochemical performance as a binder-free anode for Mg2+ storage, such as a high specific capacity of 402 mAh g−1 at the current density of 0.13 Ag−1 and excellent cycling stability with 89.5 % capacity retention after 500 cycles at 4 A g−1 in 4.5 M MgCl2 aqueous electrolyte. Spectroscopy analysis indicates that VOx experiences a dual ions (H+, Mg2+) co-intercalation reaction with part of phase transition for charge storage during the discharge process. This work not only provides a charge storage mechanism of VOx in an AMIB system but also highlights a high-performance electrode material for AMIBs.

Boosting Magnesium Ion Storage Behavior via Heteroelement Doping in a Porous Tunnel Framework Cathode for Aqueous Mg-Ion Batteries.

To relieve the overwhelming pressure on fossil energy, aqueous magnesium ion batteries attracted tremendous attention owing to their low cost and high safety. However, the cathode materials are apt to occur lattice distortion because of the electrostatic interaction between magnesium ions and crystal. The 2×2 manganese octahedral molecular sieve with potassium ions and water located in the tunnels (K-OMS-2), utilized as a cathode material for chargeable magnesium ions batteries, is exposed to irreversible Mg2+ intercalation/deintercalation due to lattice distortion, which heavily damages the electrochemical properties and declines the capacity. Herein, we carry out an ion doping strategy to overcome the above issues, leading to an enhanced Mg Mg2+ storage behavior. The Nb or V cation is successfully doped into K-OMS-2 by a facile reflux method under room temperature. The specific surface area is enlarged by the addition of cations, which promise a large electrode-electrolyte contact area. The Nb and V doped K-OMS-2 present a capacity of 252.6 and 265.9 mAh/g at 20 mA/g, respectively. This work demonstrates an ion doping approach toward exploiting the stable and high-capacity Mg-ion battery cathode and provides potential cathode materials for a large-scale aqueous Mg-ion-based energy storage system.

High-Energy Aqueous Magnesium Ion Batteries with Capacity-Compensation Evolved from Dynamic Copper Ion Redox.

The low specific capacity and low voltage plateau are significant challenges in the advancement of practical magnesium ion batteries (MIBs). Here, a superior aqueous electrolyte combining with a copper foam interlayer between anode and separator is proposed to address these drawbacks. Notably, with the dynamic redox of copper ions, the weakened solvation of Mg2+ cations in the electrolyte and the enhanced electronic conductivity of anode, which may offer effective capacity-compensation to the 3,4,9,10-perylenetetracarboxylic diimide (PTCDI)-Mg conversion reactions during the long-term cycles. As a result, the unique MIBs using expanded graphite cathode coupled with PTCDI anode demonstrate exceptional performance with an ultra-high capacity (205 mAh g-1 , 243Wh kg-1 at 5 A g-1 ) as well as excellent cycling stability after 600 cycles and rate capability (138 mAh g-1 , 81Wh kg-1 at 10 A g-1 ).

Studying δ-MnO2/reduced graphene oxide composite cathode in a low-temperature and high-voltage-tolerant hybrid electrolyte for aqueous Mg-ion batteries

Optimization of the aqueous electrolyte concentration is a significant issue in the development of high-performance aqueous rechargeable magnesium ion batteries (MIBs). In this study, a novel magnesium ion-based hybrid electrolyte composed of 2 M magnesium sulfate (MgSO4)/2 M acetate (MgOAc) was designed, and its corresponding physiochemical properties were systemically investigated by simply tuning their molar ratios. Additionally, a δ-MnO2/reduced graphene oxide (rGO) composite cathode material was successfully synthesized and delivered a high specific capacity and excellent rate capability in the optimized hybrid electrolyte. The as-fabricated device based on the δ-MnO2/rGO composite cathode exhibited a high operating voltage of up to 2 V and delivered a maximum energy density of 29.8 Wh kg−1 at the power density of 823 W kg−1. More importantly, the device showed impressive discharge capacity and excellent cycling stability even at the low temperature of −20 °C. In view of the outstanding electrochemical properties of the δ-MnO2/rGO composite cathode in an optimized hybrid electrolyte of MgSO4/MgOAc, it could be regarded as a novel prototype for low-cost aqueous MIBs.

Manganese valence state regulated beta‑manganese dioxide porous nanoflowers as high-performance cathodes at large current densities for aqueous magnesium ions battery capacitor

Aqueous magnesium ion battery capacitor (AMIBC) is a promising sustainable clean and safe energy storage system to replace lithium-ion batteries, due to its similar electrochemical characteristics to lithium, low cost and safety. In this work, beta‑manganese dioxide (β-MnO2) porous nanoflowers with Mn valence modulation are demonstrated to be a promising cathode material for AMIBC. Due to the promotion of Faradic reaction by Mn3+ introduction and the high capacitive absorption from its high specific surface area, sample with 16 % Mn3+/Mn can exhibit a high specific capacity of 260 mAh g−1 at 0.2 A g−1 in 1 M MgSO4 electrolytes with greatly improved rate and cycle performance at large current densities. As assembled with active carbon (AC), β-MnO2//AC AMIBC shows a high energy density of 60.8 W h kg−1 at 180 W kg−1 with a cycling stability of 74.1 % after 3500 cycles at 2 A g−1.

An aqueous magnesium-ion battery working at −50 °C enabled by modulating electrolyte structure

The earth-abundant magnesium resource and aqueous electrolyte make aqueous magnesium-ion batteries (AMIBs) a promising post-lithium-ion battery technology to synchronously address cost and safety concerns. Nonetheless, the freeze issue of aqueous electrolytes is curbing the development of AMIBs working at low-temperature conditions. Here, we report an MgCl2 solution having a great low-temperature property via anion and concentration adjustment, which roots in the variation of the pristine hydrogen bond reticulation. Consequently, a 4 M MgCl2 aqueous electrolyte endows a low freezing point (−62 °C) as well as ultra-high ionic conductivity (2.77 mS/cm at −50 °C). By using 4 M MgCl2 as an electrolyte, the MnO2//VO2 battery is capable of working in a wide temperature range from +25 to −50 °C, achieving a high discharge capacity of 97.9 mAh/g (0.1 A/g) and a high cycling capability of 1000 cycles (∼90 % capacity retention at −20 °C). Furthermore, MgCl2 can be well compatible with polyacrylamide into an outstanding hydrogel electrolyte (in terms of mechanical property, anti-freeze performance, and high ionic conductivity) for a flexible quasi-solid-state MIBs application. The assembled flexible device attains appealing electrochemical properties across a broad temperature region, while the constructed pouch cell demonstrates superior flexibility and reliable safety. Our current exploration depicts an expeditious but productive paradigm for devising the high-performing AMIBs for low-temperature energy storage sectors.

Emerging rechargeable aqueous magnesium ion battery

Recently, aqueous rechargeable batteries have played an essential role in developing renewable energy due to the merits of low cost, high security, and high energy density. Among various aqueous-based batteries, aqueous magnesium ion batteries (AMIBs) have rich reserves and high theoretical specific capacity (3833 mAh cm −3 ). However, for future industrialization, AMIBs still face many scientific issues to be solved, such as the slow diffusion of magnesium ions in the material structure, the desolvation penalty at electrode-electrolyte interfaces, the cost of water-in-salt electrolyte, the low voltage of traditional aqueous electrolyte, etc. And yet a comprehensive summary of the components of AMIBs is lacking in the research community. This review mainly introduces the exploration and development of AMIB systems and related components. We conduct an in-depth study of the cathode materials appropriate for magnesium ion batteries from their crystal structures, focusing primarily on layered structures, spinel structures, tunnel structures, and three-dimensional framework structures. We also investigate the anode materials, ranging from inorganic materials to organic materials, as well as the electrolyte materials (from the traditional electrolyte to water-in-salt electrolyte). Finally, some perspectives on ensuing optimization design for future research efforts in the AMIBs field are summarized.

Mg-intercalation engineering of MnO2 electrode for high-performance aqueous magnesium-ion batteries

Mg-intercalation engineering of MnO2 electrode for high-performance aqueous magnesium-ion batteries

Simply Prepared Magnesium Vanadium Oxides as Cathode Materials for Rechargeable Aqueous Magnesium Ion Batteries.

Vanadium-oxide-based materials exist with various vanadium oxidation states having rich chemistry and ability to form layered structures. These properties make them suitable for different applications, including energy conversion and storage. Magnesium vanadium oxide materials obtained using simple preparation route were studied as potential cathodes for rechargeable aqueous magnesium ion batteries. Structural characterization of the synthesized materials was performed using XRD and vibrational spectroscopy techniques (FTIR and Raman spectroscopy). Electrochemical behavior of the materials, observed by cyclic voltammetry, was further explained by BVS calculations. Sluggish Mg2+ ion kinetics in MgV2O6 was shown as a result of poor electronic and ionic wiring. Complex redox behavior of the studied materials is dependent on phase composition and metal ion inserted/deinserted into/from the material. Among the studied magnesium vanadium oxides, the multiphase oxide systems exhibited better Mg2+ insertion/deinsertion performances than the single-phase ones. Carbon addition was found to be an effective dual strategy for enhancing the charge storage behavior of MgV2O6.

Porous Spinel Magnesium Manganese Oxide/Multiwalled Carbon Nanotubes Composite Synthesized by Electrochemical Conversion as High-Performance Cathode for Aqueous Magnesium Ion Battery

Aqueous magnesium ion batteries (AMIBs) have attracted great interest due to the low manufacture cost and eco-friendliness, but the lack of suitable cathodes with good electrochemical performance obstructs their development. Here, a composite of spinel magnesium manganese oxide (MgMn2O4) and multiwalled carbon nanotubes (MWCNTs) with a porous structure is synthesized by electrochemical conversion method and used as the cathode for the AMIB, which improves the inherent low conductivity for MgMn2O4 and enhanced its specific capacity. The electrochemical conversion method helps preserve the surface integrity and structure stability of the electrode, and the MWCNTs network provides the pathway of Mg ion migration among the MgMn2O4 particles. The obtained MgMn2O4/MWCNTs displays a discharge capacity of 322.3 mAh g−1 at 50 mA g−1, and the capacity retention is 81.8% after 2000 iterations at 1000 mA g−1. Further, the MgMn2O4/MWCNTs//VO2 system is assembled, which displays a capacity retention rate of near 100%. The electrochemical mechanism of Mg ion insertion/extraction is investigated though the ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. This paper extends synthesis method of the high performance cathode material for AIMB system.

Water-induced 3D MgMn2O4 assisted by unique nanofluidic effect for energy-dense and durable aqueous magnesium-ion batteries

Aqueous magnesium (Mg)-ion batteries (AMIBs) are gaining considerable amount of attention for large-scale energy storage applications due to their safety, abundance and low cost. Herein we propose a 3D flower-like MgMn2O4 (s-MMO) that tackles main bottlenecks (sluggish electrochemical kinetics) of AMIBs cathode and conduct in-depth research on charge–discharge behaviors in aqueous electrolyte for the first time. With this design, a unique nanofluidic effect with strong confinement of molecules and ions has been achieved by constructing abundant nanofluidic channels, which can fundamentally address the sluggish Mg2+ ion diffusion. It is further elucidated that water molecules enter and remain within MgMn2O4 lattice, presenting a crystalline-to-amorphous phase transformation of lattice during water activation process. These induced water molecules expand the interplanar spacing (64.1%) and screen the electrostatic interactions between Mg2+ and host framework, which contribute to the significant increase of specific capacity, enhanced electrochemical kinetics and stability of s-MMO electrode. As a proof of this concept, the as-fabricated s-MMO based cell exhibits a high specific capacity up to 194.0 mAh g−1 at 0.1 A g−1 and maintains capacity retention of 80.9% even after 5 000 cycles at 1.0 A g−1. Here, we have demonstrated a novel water-induced 3D flower-like MgMn2O4 assisted by nanofluidic effect, achieving ultrahigh energy density of 481.4 Wh kg−1 and unprecedentedly durable cycling life (over 16 000 cycles).

Exploration of hydrated lithium manganese oxide with a nanoribbon structure as cathodes in aqueous lithium ion and magnesium ion batteries

Aqueous lithium/magnesium ion battery was assembled with Li0.21MnO2·H2O (LMO) as the cathode and VO2 as the anode.

An Aqueous Magnesium-Ion Battery Working at -50 °C Enabled by Modulating Electrolyte Structure

An Aqueous Magnesium-Ion Battery Working at -50 °C Enabled by Modulating Electrolyte Structure

Is proton a charge carrier for δ-MnO2 cathode in aqueous rechargeable magnesium-ion batteries?

Manganese dioxide (MnO2) is considered as a potential cathode material for aqueous magnesium-ion batteries. However, the charge/discharge mechanism of MnO2 in aqueous electrolyte is still unclear. In present study, highly porous δ-MnO2 is investigated, which delivers a high capacity of 252.1 mAh g−1 at 0.05 A g−1 and excellent rate capability, i.e., 109.7 mAh g−1 at 1 A g−1, but a low-capacity retention of 54.4% after 800 cycles at 1 A g−1. The two-step discharging process, namely a consequent H+ and Mg2+ insertion reaction, is verified, by comparing the electrochemical performance of δ-MnO2 in 1 M MgCl2 and 1 M MnCl2 aqueous electrolyte and analyzing detailedly the Mg content and the bonding state of Mn at different charge/discharge state. Furthermore, partial irreversibility of Mg2+ ion insertion/extraction is observed, which may be one of the major reasons leading to capacity decay.

Non-layer-transformed Mn3O4 cathode unlocks optimal aqueous magnesium-ion storage via synergizing amorphous ion channels and grain refinement

Aqueous rechargeable magnesium ion batteries (ARMBs) have obtained more attention due to the two-electrons transfer nature, low cost and safety. However, the scarcity of cathode materials seriously hinders the development of ARMBs because of the unfavorable strong interaction between Mg2+ and cathode material. Herein, we choose a pre-treated spinel Mn3O4 cathode for aqueous Mg2+ storage. The pre-treatment in Na2SO4 solution induces the grain refinement decorated with tortuous amorphous ion diffusion channels, facilitating the production of electrochemical reaction active sites and the diffusion of Mg2+, respectively, which achieve a (sub-)surface pseudocapacitance reaction between Mn (II) and Mn (III). As a result, the pre-treated Mn3O4 cathode exhibits a package of optimal performances, i.e., a capacity of 98.9 mAh g−1 and a high capacity retention rate of 99.4% after 2000 cycles. To the best of our knowledge, our work not only provides a new reaction mechanism of spinel Mn3O4 in aqueous batteries system, but also affords a high cycle stability electrode material for rechargeable Mg2+ energy storage.