Cathode Material For Magnesium-ion Batteries Research Articles

Nanostructured Design Cathode Materials for Magnesium-Ion Batteries.

Energy is undeniably one of the most fundamental requirements of the current generation. Solar and wind energy are sustainable and renewable energy sources; however, their unpredictability points to the development of energy storage systems (ESSs). There has been a substantial increase in the use of batteries, particularly lithium-ion batteries (LIBs), as ESSs. However, low rate capability and degradation due to electric load in long-range electric vehicles are pushing LIBs to their limits. As alternative ESSs, magnesium-ion batteries (MIBs) possess promising properties and advantages. Cathode materials play a crucial role in MIBs. In this regard, a variety of cathode materials, including Mn-based, Se-based, vanadium- and vanadium oxide-based, S-based, and Mg2+-containing cathodes, have been investigated by experimental and theoretical techniques. Results reveal that the discharge capacity, capacity retention, and cycle life of cathode materials need improvement. Nevertheless, maintaining the long-term stability of the electrode-electrolyte interface during high-voltage operation continues to be a hurdle in the execution of MIBs, despite the continuous research in this field. The current Review mainly focuses on the most recent nanostructured-design cathode materials in an attempt to draw attention to MIBs and promote the investigation of suitable cathode materials for this promising energy storage device.

Hierarchical FeS2 cathode with suppressed shuttle effect for high performance magnesium-ion batteries

2D transition metal sulfides (such as FeS2) are promising cathode materials for magnesium-ion batteries due to their high capacity, low cost, and abundance. However, unexpected side effects of the electrochemical process result in poor cycling performance, which hamper their widespread use. Herein, we demonstrate the shuttle effects of metal sulfide cathodes in magnesium-ion batteries for the first time and propose a strategy of phase engineering to retard such side effects, improving the magnesium storage performance of the FeS2 cathode. We also show the correlation between structure evolution of FeS2 and electrochemical performance using cryogenic transmission electron microscopy, time-of-flight secondary ion mass spectrometry and X-ray diffraction. The stress caused by the magnesiation-induced expansion of FeS2 is shown to be alleviated in porous hierarchical spheres, which has been verified by finite element simulations. This boosts the electrochemical performance of FeS2, with a respectable capacity of 556 mAh g−1 maintained after 80 cycles at 25 mA g−1. Our results can guide the use of other metal sulfides in magnesium-ion batteries.

Self-assembled vanadium oxide nanoflowers as a high-efficiency cathode material for magnesium-ion batteries

Magnesium-ion batteries (MIBs) are expected to be an alternative energy storage system for lithium-ion batteries in the future due to their high theoretical capacity and high safety. However, the current MIB cathode materials suffer from structural instability and poor cycle performance during Mg ions intercalation/deintercalation, which limit the further development of MIBs. Therefore, exploring high-performance cathode materials has become the focus of current MIB research. Currently, vanadium oxides are considered as a promising class of advanced MIB cathode materials. Among them, V5O12·6H2O has high theoretical capacity and stable crystal structure, making it a potential cathode material for MIBs. Herein, we employ a facile one-step solvothermal method for the controllable synthesis of V5O12·6H2O nanoflowers formed by self-assembly of nanosheets, and investigate them as a cathode material for MIBs for the first time. The structural water contained in the interlayer of V5O12·6H2O can improve the stability of the crystal structure and create more active sites for Mg2+ storage. In addition, the unique nanoflower morphology can enhance the contact between the electrode material and the electrolyte, thereby improving the diffusion kinetics of Mg2+. The synthesized V5O12·6H2O nanoflowers exhibit encouraging electrochemical properties, including high specific capacity (234.3 mAh g−1 at 10 mA g−1), satisfactory rate performance (53.2 mAh g−1 at a high current density of 500 mA g−1), and excellent cycling stability (0.017% capacity loss per cycle during 1500 cycles). Our findings highlight an efficient approach to exploit high-performance cathode materials for MIBs with excellent structural stability and cycling capability.

Implanting CuS Quantum Dots into Carbon Nanorods for Efficient Magnesium-Ion Batteries.

Magnesium-ion batteries (MIBs) are emerging as potential next-generation energy storage systems due to high security and high theoretical energy density. Nevertheless, the development of MIBs is limited by the lack of cathode materials with high specific capacity and cyclic stability. Currently, transition metal sulfides are considered as a promising class of cathode materials for advanced MIBs. Herein, a template-based strategy is proposed to successfully fabricate metal-organic framework-derived in-situ porous carbon nanorod-encapsulated CuS quantum dots (CuS-QD@C nanorods) via a two-step method of sulfurization and cation exchange. CuS quantum dots have abundant electrochemically active sites, which facilitate the contact between the electrode and the electrolyte. In addition, the tight combination of CuS quantum dots and porous carbon nanorods increases the electronic conductivity while accelerating the transport speed of ions and electrons. With these architectural and compositional advantages, when used as a cathode material for MIBs, the CuS-QD@C nanorods exhibit remarkable performance in magnesium storage, including a high reversible capacity of 323.7 mAh g-1 at 100mA g-1 after 100 cycles, excellent long-term cycling stability (98.5 mAh g-1 after 1000 cycles at 1.0 A g-1 ), and satisfying rate performance (111.8mA g-1 at 1.0 A g-1 ).

First principle study of benzoquinone based microporous conjugated polymers as cathode materials for high-performance magnesium ion batteries

Rechargeable magnesium-ion batteries (MIBs) can fulfill large-scale energy storage needs due to the abundance of Mg but technical challenges due to complexity of its chemistry results uncertainties about their commercialization. We for the first report benzoquinone-based microporous conjugated polymer (BQMCP) as cathode material for MIBs using density functional theory. It is dynamically and thermodynamically stable with a strong affinity for Mg-ions. The Mg ions strongly attaches to the CO group (redox-active sites) than π-bonds of BQMCP. The binding energy demonstrates that the interaction of the 2 Mg-ion system (BE = −47.32 kcal.mol−1) is stronger than the mono-Mg ion system (BE = −39.57 kcal.mol−1). The attachment of first Mg2+ to the BQMCP facilitate the attachment of another Mg ion. The BQMCP shows higher positive redox potential, which decreases with the increase of Mg atoms with the high storage capacity of twelve Mg ions/ BQMCP unit at redox-active sites without any structure distortion. Mg ions successfully entraps in bulk porous stacked BQMCP layers with higher negative binding energy values. The results demonstrates that the BQMCP is a promising cathode material for magnesium ion batteries in future.

Core-Shell-Structured Carbon Nanotube@VS4 Nanonecklaces as a High-Performance Cathode Material for Magnesium-Ion Batteries.

As a typical layered transition metal chalcogenide, VS4 is considered as a promising cathode material for advanced magnesium-ion batteries. However, the poor electronic conductivity and severe polarization effect restrict its practical applications. Herein, we report a betaine-assisted solvothermal strategy to coat VS4 nanoblocks on the surface of carbon nanotubes (CNTs), obtaining unique core-shell-structured CNT@VS4 nanonecklaces. As a result of the morphology-controlling effect of betaine, VS4 exhibits an unusual nanoblock morphology, which renders abundant active sites and promotes the contact between the electrode and electrolyte. CNTs serve as a highly conductive skeleton, combining with the VS4 nanoblocks and ensuring their uniform distribution. As a benefit from the synergistic effect of abundant active sites and electron-conductive highways, the as-synthesized CNT@VS4 nanonecklaces manifest remarkable performance for magnesium storage, including a large reversible capacity of 170 mAh g-1 at 0.1 A g-1, outstanding cycle stability (76.3 mAh g-1 after 800 cycles at 0.5 A g-1), and superior rate performance (77.2 mAh g-1 at 2 A g-1).

Mechanisms of Water-Stimulated Mg2+ Intercalation in Vanadium Oxide: Toward the Development of Hydrated Vanadium Oxide Cathodes for Mg Batteries

As lithium-ion batteries approach their theoretical limits for energy density, magnesium-ion batteries are emerging as a promising next-generation energy storage technology. However, progress in magnesium-ion battery research has been stymied by a lack of available high capacity cathode materials that can reversibly insert magnesium ions. Vanadium Oxide (V2O5) has emerged as one of the more promising candidate cathode materials, owing to its high theoretical capacity, facile synthesis methods, and relatively high operating voltage. This review focuses on the outlook of hydrated V2O5 structures as a high capacity cathode material for magnesium-ion batteries. In general, V2O5 structures exhibit poor experimental capacity for magnesium-ion insertion due to sluggish magnesium-ion insertion kinetics and poor electronic conductivity. However, several decades ago, it was discovered that the addition of water to organic electrolytes significantly improves magnesium-ion insertion into V2O5. This review clarifies the various mechanisms that have been used to explain this observation, from charge shielding to proton insertion, and offers an alternative explanation that examines the possible role of structural hydroxyl groups on the V2O5 surface. While the mechanism still needs to be further studied, this discovery fueled new research into V2O5 electrodes that incorporate water directly as a structural element. The most promising of these hydrated V2O5 materials, many of which incorporate conductive additives, nanostructured architectures, and thin film morphologies, are discussed. Ultimately, however, these hydrated V2O5 structures still face a significant barrier to potential applications in magnesium-ion batteries. During full cell electrochemical cycling, these hydrated structures tend to leach water into the electrolyte and passivate the surface of the magnesium anode, leading to poor cycle life and low capacity retention. Recently, some promising strides have been made to remedy this problem, including the use of artificial solid electrolyte interphase layers as an anode protection scheme, but a call to action for more anode protection strategies that are compatible with trace water and magnesium metal is required.

Water-Pillared Sodium Vanadium Bronze Nanowires for Enhanced Rechargeable Magnesium Ion Storage.

Owing to the advantages of high safety, low cost, high theoretical volumetric capacities, and environmental friendliness, magnesium-ion batteries (MIBs) have more feasibility for large-scale energy storage compared to lithium-ion batteries. However, lack of suitable cathode materials due to sluggish kinetics of magnesium ion is one of the biggest challenges. Herein, water-pillared sodium vanadium bronze nanowires (Na2 V6 O16 ·1.63H2 O) are reported as cathode material for MIBs, which display high performance in magnesium storage. The hydrated sodium ions provide excellent structural stability. The charge shielding effect of lattice water enables fast Mg2+ diffusion. It exhibits high specific capacity of 175 mAh g-1 , long cycle life (450 cycles), and high coulombic efficiency (≈100%). At high current density of 200 mA g-1 , the capacity retention is up to 71% even after 450 cycles (compared to the highest capacity), demonstrating excellent long-term cycling performance. The nature of charge storage kinetics is explored. Furthermore, a highly reversible structure change during the electrochemical process is proved by comprehensive electrochemical analysis. The remarkable electrochemical performance makes Na2 V6 O16 ·1.63H2 O a promising cathode material for low-cost and safe MIBs.

Fast and stable Mg2+ intercalation in a high voltage NaV2O2(PO4)2F/rGO cathode material for magnesium-ion batteries

Sluggish kinetics of Mg2+ intercalation and low working potential seriously hinder the development of high-energy-density magnesium-ion batteries (MIBs). Hence developing cathode materials with fast Mg2+ diffusion and high working voltage is a key to overcome the obstacles in MIBs. Herein, a tetragonal NaV2O2(PO4)2F/reduced graphene oxide (rGO) is proposed as an effective Mg2+ host for the first time. It exhibits the highest average discharge voltage (3.3 V vs. Mg2+/Mg), fast diffusion kinetics of Mg2+ with the average diffusivity of 2.99×10−10 cm2 s−1, and ultralong cycling stability (up to 9500 cycles). The Mg2+ storage mechanism ofNaV2O2(PO4)2F/rGO is demonstrated as a single-phase (de)intercalation reaction by in situ X-ray diffraction (XRD) technology. Density functional theory (DFT) computations further reveal that Mg2+ ions tend to migrate along the a direction. X-ray absorption near edge structure (XANES) demonstrates a decrease in the average valence of vanadium, and the local coordination environment around vanadium site is highly conserved after magnesiation. Moreover, the assembled NaV2O2(PO4)2F//Mg0.79NaTi2(PO4)3 Mg-ion full cell exhibits high power and energy densities, which indicates thatNaV2O2(PO4)2F/rGO owns potential for practical applications. This work achieves a breakthrough in the working voltage of cathode materials for MIBs and provides a new opportunity for high-energy-density MIBs.

Experimental Investigation and First-Principles Calculations of a Ni3Se4 Cathode Material for Mg-Ion Batteries.

Magnesium ion batteries (MIBs) have attracted increasing attention due to their advantages of abundant reserves, low price, and high volumetric capacity. However, the large Coulombic interactions of Mg2+ with the cathode framework seriously hinder the rate capability and cycle stability of the battery cell. For this reason, finding a suitable cathode material has become a main task in MIB research. In this study, Ni3Se4 was first proposed as a new cathode material for MIBs. First-principles calculations showed that Ni3Se4 could accommodate up to 1 mol of Mg2+, but the migration energy barrier was as high as 1.35 eV. Accordingly, nanosized Ni3Se4 was prepared by a hydrothermal method to achieve satisfying electrochemical performance. The prepared Ni3Se4 material showed a discharge capacity of 99.8 mA·h·g-1 at 50 mA·g-1 current density with a capacity retention of 75% after 100 cycles. Combined with first-principles calculations and spectroscopic studies, it was demonstrated that the material underwent a solid-solution structural change during Mg2+ insertion, with all charge transfer taking place on the Ni cations.

Dual Effect of Structure and Hydration on Magnesium-Ion Insertion into Electrodeposited V2O5 Thin Films

In recent years there has been some discrepancy about whether crystalline or amorphous V2O5 is the superior cathode material for magnesium-ion batteries, with many publications suggesting that amorphous V2O5 more readily stores magnesium ions. In this work, we report the systematic investigation of magnesium ion storage in crystalline and amorphous V2O5 electrodeposited thin films. Our results indicate that the electrochemical performance of V2O5 thin films is primarily impacted by the presence of adsorbed water. This study finds that the adsorbed water left over from aqueous electrodeposition is mostly responsible for the observed improved performance of amorphous V2O5 thin films, thereby indicating that the drying conditions, rather than the crystal structure, play a direct role in enhancing the electrochemical performance. We propose an explanation for this observation in that the amorphous thin film has much larger water content, leading to increased interlayer spacing within the disordered structure and possible charge shielding for magnesium-ion storage. Ultimately, this study demonstrates the importance of considering the effect of adsorbed water, especially when comparing the electrochemical performance of amorphous and crystalline V2O5 synthesized from wet electrodeposition techniques.

Surface modification of tin oxide through reduced graphene oxide as a highly efficient cathode material for magnesium-ion batteries

Among post-lithium ion technologies, magnesium-ion batteries (MIBs) are receiving great concern in recent years. However, MIBs are mainly restrained by the lack of cathode materials, which may accommodate the fast diffusion kinetics of Mg2+ ions. To overcome this problem, herein we attempt to synthesize a reduced graphene oxide (rGO) encapsulated tin oxide (SnO2) nanoparticles composites through an electrostatic-interaction-induced-self-assembly approach at low temperature. The surface modification of SnO2 via carbonaceous coating enhanced the electrical conductivity of final composites. The SnO2-rGO composites with different weight ratios of rGO and SnO2 are employed as cathode material in magnesium-ion batteries. Experimental results show that MIB exhibits a maximum specific capacity of 222 mAhg−1 at the current density of 20 mAg−1 with a good cycle life (capacity retention of 90%). Unlike Li-ion batteries, no SnO2 nanoparticles expansion is observed during electrochemical cycling in all-phenyl-complex (APC) magnesium electrolytes, which ultimately improves the capacity retention. Furthermore, ex-situ x-ray diffraction and scanning electron microscopy (SEM) studies are used to understand the magnesiation/de-magnesiation mechanisms. At the end, SnO2-rGO composites are tested for Mg2+/Li+ hybrid ion batteries and results reveal a specific capacity of 350 mAhg−1 at the current density of 20 mAg−1. However, hybrid ion battery exhibited sharp decay in capacity owing to volume expansion of SnO2 based cathodes. This work will provide a new insight for synthesis of electrode materials for energy storage devices.

Vanadium Oxide Pillared by Interlayer Mg2+ Ions and Water as Ultralong-Life Cathodes for Magnesium-Ion Batteries

Summary Magnesium-ion batteries (MIBs) show great potential for large-scale energy storage because of the advantages of low cost and safety, but their application is severely hindered by the difficulty in finding desirable electrode materials. Herein, we develop a bilayer-structured vanadium oxide (Mg0.3V2O5·1.1H2O) with synergistic effect of Mg2+ ions and lattice water as the cathode material for MIBs. The pre-intercalated Mg2+ ions provide high electronic conductivity and excellent structural stability. The lattice water enables fast Mg2+ ions mobility because of its charge shielding effect. As a result, the Mg0.3V2O5·1.1H2O exhibits excellent rate performance and an unprecedented cycling life with capacity retention of 80.0% after 10,000 cycles. In addition, the Mg0.3V2O5·1.1H2O exhibits good electrochemical performance in full MIBs. This scalable Mg2+ host material is a promising candidate as a cathode for MIBs, and its high performance is expected to meet the requirements for large-scale storage applications.

Preparation of MgCo2O4/graphite composites as cathode materials for magnesium-ion batteries

Magnesium-ion batteries are fabricated with MgCo2O4/graphite composites as the cathode material. MgCo2O4 nanoparticles are prepared using a co-precipitation method. A three-dimensional mixing process is utilized to mechanically decorate MgCo2O4 nanoparticles on graphite particles. The MgCo2O4 spinel crystals of size ranging from 20 to 70 nm on micrometer-sized graphite chunks are analyzed by using X-ray diffraction and scanning electron microscopy. The electrochemical properties of the as-prepared composites are well characterized by cyclic voltammetry, charge and discharge cycling, and electrochemical impedance spectroscopy (EIS). Surprisingly, the MgCo2O4/graphite composite with a relatively low proportion of MgCo2O4, compared with the other as-prepared composites, achieves the highest specific capacity of 180 mAh g−1 at a C rate of 0.05 C. EIS results suggest that the electrical conductivity of the composite material is an increasing function of the graphite proportion. The superior performance of the MgCo2O4/graphite composite could be ascribed to the decoration of nanosized MgCo2O4 particles as well as to the increased conductivity provided by graphite.

Molecular-Scale Insights of Aluminum-Ion Intercalation into Chevrel Phase Mo6S8

Rechargeable aluminum batteries are a promising alternative to lithium-ion batteries due to the high volumetric energy density (8040 mAh/cm3), high abundance in the earth’s crust, and low cost of aluminum metal. However, aluminum ion intercalation into crystalline electrode materials is challenging, as the high coulombic charge of trivalent aluminum ions significantly increases the activation energy of diffusion compared to monovalent ions. Chevrel phase Mo6S8 is one of the most well-studied and successful cathode materials for magnesium-ion batteries, partly due to the facile transport of divalent magnesium ions within its crystal structure. Reversible intercalation of aluminum ions within chevrel phase has been reported, though the intercalation mechanism is not well understood at a molecular level. Here, we report enhanced understanding of aluminum-ion intercalation in chevrel using a combination of spectroscopic, diffraction, and imaging techniques. Ex situ solid-state 27Al MAS NMR measurements were performed as a function of state-of-charge to observe changes in the environments and populations of aluminum ions within the host crystal structure, revealing both intercalated ions and additional aluminum species associated with surface layers and/or decomposition products. In situ diffraction methods were performed to observe changes in the crystal structure during the cycling process, while transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were conducted to characterize surface structures and compositions. Variable-temperature electrochemical measurements including cyclic voltammetry (CV), galvanostatic cycling, and electrochemical impedance spectroscopy (EIS) were performed to study the effects of temperature on the diffusion of Al3+ ions, electrochemical performance, and capacity retention. In combination, the results yield molecular-level insights into the aluminum-ion intercalation mechanism in the chevrel phase as well as changes of surface compositions and structures upon cycling in the ionic liquid electrolyte. Figure 1

Ammonium Vanadium Bronze (NH4V4O10) as a High-Capacity Cathode Material for Nonaqueous Magnesium-Ion Batteries

Magnesium-ion batteries (MIBs) offer improved safety, lower cost, and higher energy capacity. However, lack of cathode materials with considerable capacities in conventional nonaqueous electrolyte at ambient temperature is one of the great challenges for their practical applications. Here, we present high magnesium-ion storage performance and evidence for the electrochemical magnesiation of ammonium vanadium bronze NH4V4O10 as a cathode material for MIBs. NH4V4O10 was synthesized via a conventional hydrothermal reaction. It shows reversible magnesiation with an initial discharge capacity of 174.8 mAh g–1 and the average discharge voltage of ∼2.31 V (vs Mg/Mg2+) using 0.5 M Mg(ClO4)2 in acetonitrile as the electrolyte. Cyclic voltammetry, galvanostatic, discharge–charge, FTIR, XPS, powder XRD, and elemental analyses unequivocally show evidence for the reversible magnesiation of the material and suggest that keeping the ammonium ions in the interlayer space of NH4V4O10 could be crucial for the structural st...