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 cm3).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.

Multidimensional defects tailoring local electron and Mg^(2+) diffusion channels for boosting magnesium storage performance of WO_(3)/MoO_(2)

Defect engineering presents great promise in addressing lower specific capacity,sluggish diffusion kinetics and poor cycling life issues in energy storage devices.Herein,multidimensional(0D/2D/3D) structural defects are constructed in WO_(3)/MoO_(2) simultaneously via competing for and sharing with O atoms during simple hydrothermal process.OD and 2D defects tailor local electron,activating more sites and generating built-in electric fields to yield ion reservoir,meanwhile,3D defect owning lower anisotropic property tailors Mg^(2+) diffusion channels to fully exploit Mg^(2+) adsorbed sites induced by OD and 2D defects,enhance the kinetics and maintain structural stability.Benefitted from synergistic effect of 0D/2D/3D structural defects,the designed WO_(3)/MoO_(2) shows the higher specific capacity(112.8 mA h g^(-1) at 50 mA g^(-1) with average attenuation rate per cycle of 0.068%),superior rate capability and excellent cycling stability(specific capacity retention of 80% after 1500 cycles at 1000 mA g^(-1)).This strategy provides design ideas of introducing multidimensional structural defects for tailoring local electron and microstructure to improve energy storage property.

Highly cycle-stable VOPO_(4)-based cathodes for magnesium ion batteries:Insight into the role of interlayer engineering in batteries performance

It is the sluggish ion migration kinetics that seriously affects the practical performance of the magnesium ion batteries.Even though an electrode material design using rational interlayer engineering method could effectively solve this issue,the optimal interlayer distance remains undetermined.Herein,various VOPO_(4)-based electrodes with expanded interlayer spacing were fabricated and the relationship between interlayer structure and battery performance was revealed.Electrochemical analysis combined with computations unveils the existence of an optimal interlayer structure,as inadequate expansion failed to fully utilization of the material performance,while excessive expansion degraded the electrode stability.Among them,the electrode with triethylene glycol(TEG)intercalation exhibited optimized performance,maintaining excellent cycling stability(191.3 mAh·g^(−1)after 800 cycles).Density functional theory(DFT)demonstrated the effectiveness and limitations to lowering the migration energy barrier by expanding the interlayer engineering.In addition,systematic mechanism research revealed the Mg^(2+)storage process:The stepwise shuttling of Mg^(2+)along the directions that lie in(001)plane triggers two pairs of redox processes,namely V^(5+)/V^(4+)and V^(4+)/V^(3+).This study,regulation of layer spacing to achieve the best integrated performance of electrodes,could deepen the understanding of interlayer engineering and guide the design of advanced multivalent-ion batteries.

Flexible three-dimensional-networked iron vanadate nanosheet arrays/carbon cloths as high-performance cathodes for magnesium ion batteries

Owing to their safety and low cost,magnesium ion batteries(MIBs)have attracted much attention in recent years.However,the sluggish diffusion dynamics of magnesium ions hampers the search for appropriate cathode materials with excellent electrochemical performance.Herein,we design and synthesize a novel flexible three-dimensional-networked composite of iron vanadate nanosheet arrays/carbon cloths(3 D FeVO/CC)as a binder-free cathode for MIBs.Relative to bare FeVO nanosheets,the 3 D binder-free electrode with designed architecture enables a full range of electrochemical potential,including a high specific capacity of270 mA h g^(-1) and an increased life span(over 5000 cycles).Such achievable high-density energy originates from the synergistic optimization of electron and ion kinetics,while the durability benefits from the robust structure that prevents degradation in cycling.The single-phase reaction mechanism of FeVO in the magnesium ion storage process is also explored by in-situ X-ray diffraction and Raman technologies.Moreover,a flexible MIB pouch cell(3 D FeVO/CCIMgNaTi_(3)O_(7)) is assembled and exhibits practical application potential.This work verifies that 3 D FeVO/CC is a potential candidate cathode material that can satisfy the requirements of highperformance MIBs.It also opens a new avenue to improve the electrochemical performance of cathode materials for MIBs.

Crystal reconstruction of V_(2)O_(3)/carbon heterointerfaces via anodic hydration for ultrafast and reversible Mg-ion battery cathodes

Magnesium-ion batteries(MIBs)have promising applications because of their high theoretical capacity and the natural abundance of magnesium Mg.However,the kinetic performance and cyclic stability of cathode materials are limited by the strong interactions between Mg ions and the crystal lattice.Here,we demonstrate the unique Mg^(2+)-ion storage mechanism of a hierarchical accordion-like vanadium oxide/carbon heterointerface(V_(2)O_(3)@C),where the V_(2)O_(3) crystalline structure is reconstructed into a MgV_(3)O_(7)·H_(2)O phase through an anodic hydration reaction upon first cycle,for the improved kinetic and cyclic performances.As verified by in situ/ex situ spectroscopic and electrochemical analyses,the fast charge transfer kinetics of the V_(2)O_(3)@C cathode were due to the crystal-reconstruction and chemically coupled heterointerface.The V_(2)O_(3)@C demonstrated an ultrahigh rate capacity of 130.4 mAh g^(-1)at 50000 mA g^(-1)and 1000 cycles,achieving a Coulombic efficiency of 99.6%.The high capacity of 381.0 mA h g^(-1)can be attributed to the reversible Mg^(2+)-ion intercalation mechanism observed in the MgV_(3)O_(7)·H_(2)O phase using a 0.3 M Mg(TFSI)2/ACN(H_(2)O)electrolyte.Additionally,within the voltage range of 2.25 V versus Mg/Mg^(2+),the V_(2)O_(3)@C exhibited a capacity of 245.1 mAh g^(-1)when evaluated with magnesium metal in a 0.3 M Mg(TFSI)^(2+)0.25 M MgCl_(2)/DME electrolyte.These research findings have important implications for understanding the relationship between the Mg-ion storage mechanism and reconstructed crystal phase of vanadium oxides as well as the heterointerface reconstruction for the rational design of MIB cathode materials.