Defect Engineering:Can it Mitigate Strong Coulomb Effect of Mg^(2+)in Cathode Materials for Rechargeable Magnesium Batteries?

Rechargeable magnesium batteries(RMBs)have been considered a promising“post lithium-ion battery”system to meet the rapidly increasing demand of the emerging electric vehicle and grid energy storage market.However,the sluggish diffusion kinetics of bivalent Mg^(2+)in the host material,related to the strong Coulomb effect between Mg^(2+)and host anion lattices,hinders their further development toward practical applications.Defect engineering,regarded as an effective strategy to break through the slow migration puzzle,has been validated in various cathode materials for RMBs.In this review,we first thoroughly understand the intrinsic mechanism of Mg^(2+)diffusion in cathode materials,from which the key factors affecting ion diffusion are further presented.Then,the positive effects of purposely introduced defects,including vacancy and doping,and the corresponding strategies for introducing various defects are discussed.The applications of defect engineering in cathode materials for RMBs with advanced electrochemical properties are also summarized.Finally,the existing challenges and future perspectives of defect engineering in cathode materials for the overall high-performance RMBs are described.

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.

Stable multi-electron reaction stimulated by W doping VS_(4)for enhancing magnesium storage performance

Rechargeable magnesium batteries(RMBs)hold promise for offering higher volumetric energy density and safety features,attracting increasing research interest as the next post lithium-ion batteries.Developing high performance cathode material by inducing multi-electron reaction process as well as maintaining structural stability is the key to the development and application of RMBs.Herein,multielectron reaction occurred in VS_(4)by simple W doping strategy.W doping induces valence of partial V as V^(2+)and V^(3+)in VS_(4)structure,and then stimulates electrochemical reaction involving multi-electrons in 0.5%W-V-S.The flower-like microsphere morphology as well as rich S vacancies is also modulated by W doping to neutralize structure change in such multi-electron reaction process.The fabricated 0.5%W-V-S delivers higher specific capacity(149.3 m A h g^(-1)at 50 m A g^(-1),which is 1.6 times higher than that of VS_(4)),superior rate capability(76 mA h g^(-1)at 1000 mA g^(-1)),and stable cycling performance(1500cycles with capacity retention ratio of 93.8%).Besides that,pesudocapaticance-like contribution analysis as well as galvanostatic intermittent titration technique(GITT)further confirms the enhanced Mg^(2+)storage kinetics during such multi-electron involved electrochemical reaction process.Such discovery provides new insights into the designing of multi-electron reaction process in cathode as well as neutralizing structural change during such reaction for realizing superior electrochemical performance in energy storage devices.

A non-nucleophilic electrolyte based on all-inorganic salts with conditioning-free characteristic for rechargeable magnesium batteries

Conditioning-free electrolytes with high reversibility of Mg plating/stripping are of vital importance for the commercialization of the superior rechargeable magnesium batteries(RMBs).In the present work,a non-nucleophilic electrolyte(denoted as MLCH)based on all-inorganic salts of MgCl_(2),LiCl and CrCl_(3) for RMBs is prepared by a straightforward one-step reaction.As a result,the MLCH electrolyte shows the noticeable performance of high ionic conductivity(3.40 mS cm^(−1)),low overpotential(∼46 mV vs Mg/Mg^(2+)),high Coulombic efficiency(∼93%),high anodic stability(SS,∼2.56 V vs Mg/Mg^(2+))and long-term(more than 500 h)cycling stability,especially the conditioning-free characteristic.The main equilibrium species in the MLCH electrolyte are confirmed to be the tetracoordinated anions of[LiCl2(THF)2]−and solvated dimers of[Mg_(2)(μ-Cl)3(THF)6]+.The addition of LiCl can assist the dissolution of MgCl_(2) and activation of the electrode/electrolyte interface,resulting in a superior Mg plating/stripping efficiency.The synergistic effect of LiCl,CrCl_(3),a small amount of HpMS and the absence of polymerization THF enable the conditioning-free characteristic of the MLCH electrolyte.Moreover,the MLCH electrolyte exhibits decent compatibility with the cathodic materials of CuS.The Mg/CuS full cell using the MLCH electrolyte presents a discharge specific capacity of 215 mAh g^(−1)at 0.1 C and the capacity can retain∼72%after 40 cycles.Notably,the MLCH electrolyte has other superiorities such as the broad sources of materials,low-cost and easy-preparation,leading to the potential prospect of commercial application.

Interfacial chemistry of anode/electrolyte interface for rechargeable magnesium batteries

Rechargeable magnesium batteries(RMBs),as a low-cost,high-safety and high-energy storage technology,have attracted tremendous attention in large-scale energy storage applications.However,the key anode/electrolyte interfacial issues,including surface passivation,uneven Mg plating/stripping,and pulverization after cycling still result in a large overpotential,short cycling life,poor power density,and possible safety hazards of cells,severely impeding the commercial development of RMBs.In this review,a concise overview of recently advanced strategies to address these anode/electroyte interfacial issues is systematically classified and summarized.The design of magnesiophilic substrates,construction of artificial SEI layers,and modification of electrolyte are important and effective strategies to improve the uniformity/kinetics of Mg plating/stripping and achieve the stable anode/electrolyte interface.The key opportunities and challenges in this field are advisedly put forward,and the insights into future directions for stabilizing Mg metal anodes and the anode/electrolyte interface are highlighted.This review provides important references fordeveloping the high-performance and high-safety RMBs.

Tailoring Electrode–Electrolyte Interface Using an Electron-Deficient Borate-Based Additive in MgTFSI_(2)-MgCl_(2)/DME Electrolyte for Rechargeable Magnesium Batteries

Rechargeable magnesium metal batteries need an electrolyte that forms a stable and ionically conductive solid electrolyte interphase(SEI)on the anodes.Here,we used molecular dynamic simulation,density functional theory calculation,and X-ray photoelectron spectroscopy analysis to investigate the solvation structures and SEI compositions in electrolytes consisting of dual-salts,magnesium bis(trifluoromethanesulfonyl)imide(MgTFSI_(2)),and MgCl_(2),with different additives in 1,2-dimethoxyethane(DME)solvent.We found that the formed[Mg_(3)(μ-Cl)_(4)(DME)mTFSI_(2)](m=3,5)inner-shell solvation clusters in MgTFSI_(2)-MgCl_(2)/DME electrolyte could easily decompose and form a MgO-and MgF_(2)-rich SEI.Such electron-rich inorganic species in the SEI,especially MgF_(2),turned out to be detrimental for Mg plating/stripping.To reduce the MgF_(2)and MgO contents in SEI,we introduce an electron-deficient tri(2,2,2-trifluoroethyl)borate(TFEB)additive in the electrolyte.Mg//Mg cells using the MgTFSI_(2)-MgCl_(2)/DME-TFEB electrolyte could cycle stably for over 400 h with a small polarization voltage of~150 mV.Even with the presence of 800 ppm H_(2)O,the electrolyte with TFEB additive could still preserve its good electrochemical performance.The optimized electrolyte also enabled stable cycling and high-rate capability for Mg//Mo6S8 and Mg//CuS full cells,showing great potential for future applications.

Development of Magnesium-Insertion Positive Electrode for Rechargeable Magnesium Batteries

Magnesium-based rechargeable batteries might be an interesting future alternative to lithium-based batteries. It is so far well known that Mg2+ ion insertion into ion-transfer hosts proceeds slowly compared with Li+, so it is necessary to realize fast Mg2+ transport in the host in addition to other requirements as practical cathode materials for magnesium batteries. Positive electrode materials based on inorganic transition-metal oxides, sulfides, and borides are the only ones used up to now to insert magnesium ions. In this paper, the available results of research on materials suitable as possible, for secondary magnesium batteries, are reviewed.

Reversible Magnesium Metal Anode Enabled by Cooperative Solvation/Surface Engineering in Carbonate Electrolytes

Magnesium metal anode holds great potentials toward future high energy and safe rechargeable magnesium battery technology due to its divalent redox and dendrite-free nature. Electrolytes based on Lewis acid chemistry enable the reversible Mg plating/stripping,while they fail to match most cathode materials toward highvoltage magnesium batteries. Herein,reversible Mg plating/stripping is achieved in conventional carbonate electrolytes enabled by the cooperative solvation/surface engineering. Strongly electronegative Cl from the MgCl_(2) additive of electrolyte impairs the Mg…O = C interaction to reduce the Mg^(2+) desolvation barrier for accelerated redox kinetics,while the Mg^(2+)-conducting polymer coating on the Mg surface ensures the facile Mg^(2+) migration and the e ective isolation of electrolytes. As a result,reversible plating and stripping of Mg is demonstrated with a low overpotential of 0.7 V up to 2000 cycles. Moreover,benefitting from the wide electrochemical window of carbonate electrolytes,high-voltage(> 2.0 V) rechargeable magnesium batteries are achieved through assembling the electrode couple of Mg metal anode and Prussian blue-based cathodes. The present work provides a cooperative engineering strategy to promote the application of magnesium anode in carbonate electrolytes toward high energy rechargeable batteries.

Porous polymer electrolytes for long-cycle stable quasi-solid-state magnesium batteries

The development of applicable electrolytes is the key point for high-performance rechargeable magnesium batteries(RMBs).The use of liquid electrolyte is prone to safety problems caused by liquid electrolyte leakage.Polymer-based gel electrolytes with high ionic conductivity,great flexibility,easy processing,and high safety have been studied by many scholars in recent years.In this work,a novel porous poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)membrane is prepared by a phase inversion method.By immersing porous PVDF-HFP membranes in MgCl2-AlCl3/TEGDME(Tetraethylene glycol dimethyl ether)electrolytes,porous PVDF-HFP based electrolytes(PPEs)are formed.The PPE exhibits a high ionic conductivity(4.72×10^(-4) S cm-1,25℃),a high liquid electrolyte uptake of 162%,as well as a wide voltage window(3.1 V).The galvanostatic cycling test of Mg//Mg symmetric cell with PPE reveals that the reversible magnesium ion(Mg^(2+))plating/stripping occurs at low overpotentials(~0.13 V).Excellent long cycle stability(65.5 mAh g^(-1) over 1700 cycles)is achieved for the quasisolid-state RMB assembled with MoS2/C cathode and Mg anode.Compared with the liquid electrolyte,the PPE could effectively reduce the side reactions and make Mg^(2+)plating/stripping more uniformly on the Mg electrode side.This strategy herein provides a new route to fabricate high-performance RMB through suitable cathode material and polymer electrolyte with excellent performance.

Low-temperatures synthesis of CuS nanospheres as cathode material for magnesium second batteries

Rechargeable magnesium batteries(RMBs),as one of the most promising candidates for efficient energy storage devices with high energy,power density and high safety,have attracted increasing attention.However,searching for suitable cathode materials with fast diffusion kinetics and exploring their magnesium storage mechanisms remains a great challenge.Cu S submicron spheres,made by a facile low-temperature synthesis strategy,were applied as the high-performance cathode for RMBs in this work,which can deliver a high specific capacity of 396mAh g^(-1)at 20 mA g^(-1) and a remarkable rate capacity of 250 m Ah g^(-1)at 1000 mA g^(-1).The excellent rate performance can be assigned to the nano needle-like particles on the surface of Cu S submicron spheres,which can facilitate the diffusion kinetics of Mg^(2+).Further storage mechanism investigations illustrate that the Cu S cathodes experience a two-step conversion reaction controlled by diffusion during the electrochemical reaction process.This work could make a contribution to the study of the enhancement of diffusion kinetics of Mg2+and the reaction mechanism of RMBs.

The design of Co_(3)S_(4)@MXene heterostructure as sulfur host to promote the electrochemical kinetics for reversible magnesium-sulfur batteries

The rechargeable Mg-S batteries are attractive because of their resource abundances of Mg and S,high volumetric energy density,and less dendrite property of Mg anodes.However,the development is barred by the intrinsic low electronic conductivity of S and the discharge products as well as the lack of understanding the hidden electrochemical kinetics.Here,a Co_(3)S_(4)@MXene heterostructure is proposed as effective sulfur host for reversible Mg-S batteries.XPS results and density functional theory(DFT)calculation confirm that the chemical interaction between the decorated Co_(3)S_(4)nanocrystals host and polysulfide intermediates could well absorb and catalyze the polysulfides conversion,thus improve the electrochemical redox kinetics.Meanwhile,the MXene matrix could promote Mg ion diffusion dynamics greatly.As a result,the developed Mg-S batteries using the Co_(3)S_(4)@MXene-S as the cathode material could demonstrate high sulfur utilization with specific capacity of 1220 mAh g^(-1) and retain a capacity of 528 mAh g^(-1) after 100 cycles,together with a satisfactory rate performance even at 2 C.This work shed light on the advanced cathode design for reversible high energy Mg-S batteries.

Origin of Excellent Charge Storage Properties of Defective Tin Disulphide in Magnesium/Lithium-Ion Hybrid Batteries

Lithium-ion batteries(LIBs)are excellent electrochemical energy sources,albeit with existing challenges,including high costs and safety concerns.Magnesium-ion batteries(MIBs)are one of the potential alternatives.However,the performance of MIBs is poor due to their sluggish solid-state Mg^(2+) diffusion kinetics and severe electrode polarizability.Rechargeable magnesium-ion/lithium-ion(Mg^(2+)/Li^(+))hybrid batteries(MLHBs)with Mg^(2+) and Li+as the charge carriers create a synergy between LIBs and MIBs with significantly improved charge transport kinetics and reliable safety features.However,MLHBs are yet to reach a reasonable electrochemical performance as expected.This work reports a composite electrode material with highly defective two-dimensional(2D)tin sulphide nanosheets(SnS_(x))encapsulated in three-dimensional(3D)holey graphene foams(HGF)(SnS_(x)/HGF),which exhibits a specific capacity as high as 600 mAh g^(−1) at 50 mA g^(−1) and a compelling specific energy density of~330 Wh kg^(−1).The excellent electrochemical performance surpasses previously reported hybrid battery systems based on intercalation-type cathode materials under comparable conditions.The role played by the defects in the SnS_(x)/HGF composite is studied to understand the origin of the observed excellent electrochemical performance.It is found that it is closely related to the defect structure in SnS_(x),which offers percolation pathways for efficient ion transport and increased internal surface area assessable to the charge carriers.The defective sites also absorb structural stress caused by Mg^(2+) and Li+insertion.This work is an important step towards realizing high-capacity cathode materials with fast charge transport kinetics for hybrid batteries.

An efficient Hauser-base electrolyte for rechargeable magnesium batteries

Rechargeable magnesium batteries(RMBs)are considered the promising candidates for post lithium-ion batteries due to the abundant storage,high capacity,and dendrite-rare characteristic of Mg anode.However,the lack of practical electrolytes impedes the development and application of RMBs.Here,through a one-step reaction of LiCl congenital-containing Knochel–Hauser base TMPL(2,2,6,6-tetrame thylpiperidinylmagnesium chloride lithium chloride complex)with Lewis acid AlCl_(3),we successfully synthesized an efficient amino-magnesium halide TMPLA electrolyte.Raman and mass spectroscopy identified that the electrolyte comprises the typical di-nuclear copolymer[Mg_(2)Cl_(3)·6THF]+cation group and[(TMP)2AlCl_(2)]-anion group,further supported by the results of density functional theory calculations(DFT)and the Molecular dynamics(MD)simulations.The TMPLA electrolyte exhibits promising electrochemical performance,including available anodic stability(>2.65 V vs.SS),high ionic conductivity(6.05mS cm^(-1)),and low overpotential(<0.1 V)as well as appropriate Coulombic efficiency(97.3%)for Mg plating/stripping.Both the insertion Mo6S8cathode and conversion Cu S cathode delivered a desirable electrochemical performance with high capacity and good cycling stability based on the TMPLA electrolyte.In particular,when compatible with low cost and easily synthesized Cu S,the Cu S||Mg cell displayed an extremely high discharge capacity of 458.8 mAh g^(-1)for the first cycle and stabilized at 170.2 mAh g^(-1)with high Coulombic efficiency(99.1%)after 50 cycles at 0.05 C.Our work proposes an efficient electrolyte with impressive compatibility with Mg anode and insertion/conversion cathode for practical RMBs and provides a more profound knowledge of the Lewis acid–base reaction mechanisms.

Bi nanoparticles encapsulated in nitrogen-doped carbon as a long-life anode material for magnesium batteries

Bismuth has garnered significant interest as an anode material for magnesium batteries(MBs) because of its high volumetric specific capacity and low working potential. Nonetheless, the limited cycling performance(≤100 cycles) limits the practical application of Bi as anode for MBs. Therefore, the improvement of Bi cycling performance is of great significance to the development of MBs and is also full of challenges. Here, Bi nanoparticles encapsulated in nitrogen-doped carbon with single-atom Bi embedded(Bi@NC) are prepared and reported as an anode material for MBs. Bi@NC demonstrates impressive performance, with a high discharge capacity of 347.5 mAh g^(-1) and good rate capability(206.4 mAh g^(-1)@500 mA g^(-1)) in a fluoride alkyl magnesium salt electrolyte. In addition, Bi@NC exhibits exceptional long-term stability, enduring 400 cycles at 500 mA g^(-1). To the best of our knowledge, among reported Bi and Bi-based compounds for MBs, Bi@NC exhibits the longest cycle life in this work. The magnesium storage mechanism of Bi@NC is deeply studied through X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. This work provides some guidance for further improving the cycling performance of other alloy anodes in MBs.

Mechanisms of electrochemical magnesium(de)alloying of Mg-Sn and Mg-Pb polymorphs

Different polymorphs of Mg-Sn and Mg-Pb intermetallic compounds were prepared by high-energy mechanical alloying and then investigated as active material in magnesium batteries. Beside thermodynamically stable Mg_(2)Sn and Mg_(2)Pb crystallizing in the anti-fluorite structure, other polymorphs Mg_(~2)Sn and Mg_(~2)Pb were prepared by increasing the ball-milling time. The first dealloying process is almost complete only for the cubic polymorphs, then similar capacities are observed during the subsequent alloying and dealloying sequences.Thanks to operando X-ray diffraction, the electrochemical mechanism is revealed and shows that the cubic polymorphs Mg_(2)Sn and Mg_(2)Pb tend to preferentially form during the alloying whatever the pristine intermetallic. Weak traces of Mg_(~2)Sn and Mg_(~2)Pb are observed during the alloying, suggesting that these polymorphs act as a by-product and/or an intermediate phases of the electrochemical process. Finally, the compatibility of cubic Mg_(2)Sn and Mg_(2)Pb with Mg(TFSI)_(2)-based electrolyte is confirmed in full cell vs. a positive electrode based on the Chevrel phase Mo6S8, although limited performance is achieved. This fundamental work provides new insights in the behavior of alloy-type negative electrodes for magnesium-ion batteries.

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.

Hybrid solid electrolyte interphases formed in conventional carbonate electrolyte enable high-voltage and ultra-stable magnesium metal batteries

Magnesium metal batteries are considered as viable alternatives of lithium-ion batteries for their low cost and high capacity of magnesium.Nevertheless,the practical application of magnesium metal batteries is extremely challenging due to a lack of suitable electrolyte that can stabilize magnesium metal anode and high-voltage cathode simultaneously.Herein,we found that in-situ formed lithium/magnesium hybrid electrolyte interphases in conventional LiPF6-containing carbonate-based electrolyte can not only prevent the production of passivation layer on the magnesium metal anode,but also inhibit the oxidation of the electrolyte under high voltage.The symmetric magnesium‖magnesium battery can achieve reversible stripping/plating for 1600 and 600 h at 0.02 and 0.1 mA cm^(-2),respectively.In addition,when coupled with a carbon fiber cathode,the magnesium metal battery exhibited a capacity retention rate of 96.3% for 1000 cycles at a current density of 500 mA g^(-1)and presented a working voltage of ~3.1 V.This research paves a new and promising path to the commercialization process of rechargeable magnesium metal batteries.

Vanadium Oxide/Graphene Nanoplatelet as a Cathode Material for Mg-Ion Battery

The aim of the present work is to introduce a high performance cathode for magnesium-ion batteries. A simple ball mill process is employed to synthesize (V2O5)1-x (Graphene Nanoplatelets (GNP))x nanocomposite, (where x = 0, 5, 10, 15, 20 and 25 wt.% GNP). The synthesized samples are characterized using scanning electron microscope (SEM), X-ray diffraction (XRD) technique, impedance spectroscopy, cyclic voltammetry and charge-discharge test. The maximum conductivity of the investigated samples was found to be 6 × 10-1 S/cm for optimum composite film (25 wt% GNP) at room temperature. Room temperature rechargeable magnesium batteries are constructed from Mg as anode material, (V2O5)1-x(GNP)x as a cathode material and the simple non-aqueous electrolyte based MgNO3·6H2O. Mg/V2O5 cells employing as-prepared electrolyte exhibit initial discharge capacity ~100 mAhg-1 while Mg/(V2O5/GNP (x = 25t.%)) cathode produces a lower initial capacity of ~90 mAhg-1. The high initial discharge capacity of V2O5 can be attributed to the presence of a large (001) interlayer spacing (~11.53 A) for facile Mg+ insertion/extraction.

Activation mechanism of conventional electrolytes with amine solvents:Species evolution and hydride-containing interphase formation

Rechargeable magnesium(Mg)-metal batteries have brought great expect to overcome the safety and energy density concerns of typical lithium-ion batteries.However,interracial passivation of the Mgmetal anode impairs the reversible Mg plating/stripping chemistries,resulting in low Coulombic efficiency and large overpotential.In this work,a facile isobutylamine(IBA)-assisted activation strategy has been proposed and the fundamental mechanism has been unveiled in a specific way of evolving active species and forming MgH_(2)-based solid-electrolyte interphase.After introducing IBA into a typical electrolyte of magnesium bis(trifluoromethanesulfo nyl) imide(Mg(TFSI)_(2)) in diglyme(G2) solvents,electrolyte species of [Mg^(2+)(IBA)5]^(2+) and protonated amine-based cations of [(IBA)H]^(+) have been detected by nuclear magnetic resonance and mass spectra.This not only indicates direct solvation of IBA toward Mg^(2+)but also suggests its ionization,which is central to mitigating the decomposition of G2 and TFSI anions by forming neutrally charged [(IBAH^(+))(TFSI^(-))]~0 and other complex ions.A series of experiments,including cryogenic-electron microscopy,D_(2)O titration-mass spectra,and time of flight secondary ion mass spectrometry results,reveal a thin,non-passivated,and MgH_(2)-containing interphase on the Mg-metal anode.Besides,uniform and dendrite-free Mg electrodeposits have been revealed in composite electrolytes.Benefiting from the activation effects of IBA,the composite electrolyte displays superior electrochemical performance(overpotential is approximately 0.16 V versus 2.00 V for conventional electrolyte;Coulombic efficiency is above 90% versus <10% for conventional electrolyte).This work offers a fresh direction to advanced electrolyte design for next-generation rechargeable batteries.

Electrochemical reactivity of In-Pb solid solution as a negative electrode for rechargeable Mg-ion batteries

A composite In-Pb:carbon was successfully synthetized by a two-step mechanochemical synthesis in order to obtain an adequate particles size and structure to investigate the electrochemical reactivity of the In-Pb solid solution towards Mg.A potential synergetic coupling of electroactive elements In and Pb was examined using electrochemical and ex situ X-ray diffraction analyses.The potential profile of the solid solution indicates the formation of Mg_(2)Pb and Mg In.However,the diffraction study suggests a peculiar electrochemically-driven amorphization of Mg In during the magnesiation,in strong contrast to Mg In crystallization in In-based and In Bi-based electrodes reported in the literature.Combining In and Pb favors the amorphization of Mg In and a high first magnesiation capacity of about 550 m Ah g^(-1),but is thereafter detrimental to the material’s reversibility.These results emphasize the possible influence of electrochemically-driven amorphization and crystallization processes on electrochemical performance of battery materials.