Reversible S0/MgSx Redox Chemistry in a MgTFSI2/MgCl2/DME Electrolyte for Rechargeable Mg/S Batteries

The redox chemistry of magnesium and its application in rechargeable Mg batteries has received increasing attention owing to the unique benefits of Mg metal electrodes, namely high reversibility without dendrite formation, low reduction potentials, and high specific capacities. The Mg/S couple is of particular interest owing to its high energy density and low cost. Previous reports have confirmed the feasibility of a rechargeable Mg/S battery; however, only limited cycling stability was achieved, and the complicated procedure for the preparation of the electrolytes has significantly compromised the benefits of Mg/S chemistry and hindered the development of Mg/S batteries. Herein, we report the development of the first rechargeable Mg/S battery with a MgTFSI₂/MgCl₂/DME electrolyte (DME=1,2‐dimethoxyethane, TFSI=bis(trifluoromethanesulfonyl)imide) and realize the best cycling stability among all reported Mg/S batteries by suppressing polysulfide dissolution. Mechanistic studies show that the battery works via S⁰/MgS_x redox processes and that the large voltage hysteresis is mainly due to the Mg anode overpotential.     

Superhalogens as Building Blocks of Halogen‐Free Electrolytes in Lithium‐Ion Batteries

Most electrolytes currently used in Li‐ion batteries contain halogens, which are toxic. In the search for halogen‐free electrolytes, we studied the electronic structure of the current electrolytes using first‐principles theory. The results showed that all current electrolytes are based on superhalogens, i.e., the vertical electron detachment energies of the moieties that make up the negative ions are larger than those of any halogen atom. Realizing that several superhalogens exist that do not contain a single halogen atom, we studied their potential as effective electrolytes by calculating not only the energy needed to remove a Li⁺ ion but also their affinity towards H₂O. Several halogen‐free electrolytes are identified among which Li(CB₁₁H₁₂) is shown to have the greatest potential.     

A Stable,Non‐Corrosive Perfluorinated Pinacolatoborate Mg Electrolyte for Rechargeable Mg Batteries

Mg batteries are a promising energy storage system because of the physicochemical merits of Mg as an anode material. However, the lack of electrochemically and chemically stable Mg electrolytes impedes the development of Mg batteries. In this study, a newly designed chloride‐free Mg perfluorinated pinacolatoborate, Mg[B(O₂C₂(CF₃)₄)₂]₂ (abbreviated as Mg‐FPB ), was synthesized by a convenient method from commercially available reagents and fully characterized. The Mg‐FPB electrolyte delivered outstanding electrochemical performance, specifically, 95 % Coulombic efficiency and 197 mV overpotential, enabling reversible Mg deposition, and an anodic stability of up to 4.0 V vs. Mg. The Mg‐FPB electrolyte was applied to assemble a high voltage, rechargeable Mg/MnO₂ battery with a discharge capacity of 150 mAh g^?1.     

A Stable,Non‐Corrosive Perfluorinated Pinacolatoborate Mg Electrolyte for Rechargeable Mg Batteries

Mg batteries are a promising energy storage system because of the physicochemical merits of Mg as an anode material. However, the lack of electrochemically and chemically stable Mg electrolytes impedes the development of Mg batteries. In this study, a newly designed chloride‐free Mg perfluorinated pinacolatoborate, Mg[B(O₂C₂(CF₃)₄)₂]₂ (abbreviated as Mg‐FPB ), was synthesized by a convenient method from commercially available reagents and fully characterized. The Mg‐FPB electrolyte delivered outstanding electrochemical performance, specifically, 95 % Coulombic efficiency and 197 mV overpotential, enabling reversible Mg deposition, and an anodic stability of up to 4.0 V vs. Mg. The Mg‐FPB electrolyte was applied to assemble a high voltage, rechargeable Mg/MnO₂ battery with a discharge capacity of 150 mAh g^?1.     

Stability of B12(CN)122−: Implications for Lithium and Magnesium Ion Batteries

Multiply charged negative ions are seldom stable in the gas phase. Electrostatic repulsion leads either to autodetachment of electrons or fragmentation of the parent ion. With a binding energy of the second electron at 0.9 eV, B₁₂H₁₂^2? is a classic example of a stable dianion. It is shown here that ligand substitution can lead to unusually stable multiply charged anions. For example, dodecacyanododecaborate, B₁₂(CN)₁₂^2?, created by substituting H by CN is found to be highly stable with the second electron bound by 5.3 eV, which is six times larger than that in the B₁₂H₁₂^2?. Equally important is the observation that CB₁₁(CN)₁₂^2?, which contains one electron more than needed to satisfy the Wade‐Mingos rule, is also stable with its second electron bound by 1.1 eV, while CB₁₁H₁₂^2? is unstable. The ability to stabilize multiply charged anions in the gas phase by ligand manipulation opens a new door for multiply charged species with potential applications as halogen‐free electrolytes in ion batteries.     

Difunctionalized {closo‐1‐CB11} Clusters: 1‐ and 2‐Amino‐12‐ethynylcarba‐closo‐dodecaborates

Carba‐closo‐dodecaborate anions with two functional groups have been synthesized via a simple two‐step procedure starting from monoamino‐functionalized {closo‐1‐CB₁₁} clusters. Iodination at the antipodal boron atom provided access to [1‐H₂N‐12‐I‐closo‐1‐CB₁₁H₁₀]^? ( 1 a ) and [2‐H₂N‐12‐I‐closo‐1‐CB₁₁H₁₀]^? ( 2 a ), which have been transformed into the anions [1‐H₂N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀]^? (R=H ( 1 b ), Ph ( 1 c ), Et₃Si ( 1 d )) and [2‐H₂N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀]^? (R=H ( 2 b ), Ph ( 2 c ), Et₃Si ( 2 d )) by microwave‐assisted Kumada‐type cross‐coupling reactions. The syntheses of the inner salts 1‐Me₃N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀ (R=H ( 1 e ), Et₃Si ( 1 f )) and 2‐Me₃N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀ (R=H ( 2 e ), Et₃Si ( 2 f )) are the first examples for a further derivatization of the new anions. All {closo‐1‐CB₁₁} clusters have been characterized by multinuclear NMR and vibrational spectroscopy as well as by mass spectrometry. The crystal structures of Cs 1 a , [Et₄N] 2 a , K 1 b , [Et₄N] 1 c , [Et₄N] 2 c , 1 e , and [Et₄N][1‐H₂N‐2‐F‐12‐I‐closo‐1‐CB₁₁H₉]?0.5 H₂O ([Et₄N ]4 a ?0.5 H₂O) have been determined. Experimental spectroscopic data and especially spectroscopic data and bond properties derived from DFT calculations provide some information on the importance of inductive and resonance‐type effects for the transfer of electronic effects through the {closo‐1‐CB₁₁} cage.     

A 3D Analogue of Phenyllithium: Solution‐Phase,Solid‐State,and Computational Study of the Lithiacarborane [Li−CB11H11]−

The lithiacarborane [Li?CB₁₁H₁₁]^? plays a central role in carborane chemistry, as it is a key intermediate to achieve the selective functionalization of the monocarba‐closo‐dodecaborate [CB₁₁H₁₂]^? for applications in various fields. Also, it is an organometallic species of fundamental interest because it represents a 3D analogue of phenyllithium featuring an exo C?Li bond in addition to the delocalized negative endo charge of the spherical cluster. For the first time, the elusive and highly reactive endo/exo formal dianion [CB₁₁H₁₁]^2? has been isolated as its lithiate as well as zincate in pure form and fully characterized. DFT calculations corroborate the experimental findings and underscore the remarkably high reactivity of the lithiacarborane. Subsequent derivatizations demonstrate the relevance of its initial clean formation.     

A 3D Analogue of Phenyllithium: Solution‐Phase,Solid‐State,and Computational Study of the Lithiacarborane [Li−CB11H11]−

The lithiacarborane [Li?CB₁₁H₁₁]^? plays a central role in carborane chemistry, as it is a key intermediate to achieve the selective functionalization of the monocarba‐closo‐dodecaborate [CB₁₁H₁₂]^? for applications in various fields. Also, it is an organometallic species of fundamental interest because it represents a 3D analogue of phenyllithium featuring an exo C?Li bond in addition to the delocalized negative endo charge of the spherical cluster. For the first time, the elusive and highly reactive endo/exo formal dianion [CB₁₁H₁₁]^2? has been isolated as its lithiate as well as zincate in pure form and fully characterized. DFT calculations corroborate the experimental findings and underscore the remarkably high reactivity of the lithiacarborane. Subsequent derivatizations demonstrate the relevance of its initial clean formation.     

苯硫酚盐基溶液的可充镁电池电解液

将4-甲基苯硫酚、4-异丙基苯硫酚和4-甲氧基苯硫酚(RSH)分别与格氏试剂C₂H₅MgCl/THF(四氢呋喃)反应制得的苯硫酚氯化镁(RSMgCl)(分别标记为MBMC、IPBMC和MOBMC)/THF和进一步与Lewis 酸AlCl₃反应制得的(RSMgCl)_n-AlCl₃/THF(n=1,1.5,2)苯硫酚盐基溶液用作可充镁电池电解液,采用循环伏安和恒电流充放电测试研究了电解液的镁沉积-溶出性能和氧化分解电位. 结果表明,苯硫酚上的基团种类和RSMgCl与AlCl₃的比例对其电化学性能有影响. 其中,0.5 mol·L^-1(IPBMC)_1.5-AlCl₃/THF 溶液具有最佳的电化学性能,其氧化分解电位适宜(2.4 V(vs Mg/Mg²⁺)),镁沉积-溶出循环效率稳定,过电位低,电导率较高(2.48 mS·cm^-1),与正极材料Mo₆S₈兼容性良好,且具有一定的空气稳定性,配制方便,有希望应用于实际的可充镁电池体系中.     

Lithium Ion Pathway within Li7La3Zr2O12‐Polyethylene Oxide Composite Electrolytes

Polymer–ceramic composite electrolytes are emerging as a promising solution to deliver high ionic conductivity, optimal mechanical properties, and good safety for developing high‐performance all‐solid‐state rechargeable batteries. Composite electrolytes have been prepared with cubic‐phase Li₇La₃Zr₂O₁₂ (LLZO) garnet and polyethylene oxide (PEO) and employed in symmetric lithium battery cells. By combining selective isotope labeling and high‐resolution solid‐state Li NMR, we are able to track Li ion pathways within LLZO‐PEO composite electrolytes by monitoring the replacement of ⁷Li in the composite electrolyte by ⁶Li from the ⁶Li metal electrodes during battery cycling. We have provided the first experimental evidence to show that Li ions favor the pathway through the LLZO ceramic phase instead of the PEO‐LLZO interface or PEO. This approach can be widely applied to study ion pathways in ionic conductors and to provide useful insights for developing composite materials for energy storage and harvesting.     

Li7P3S11电解质的合成、传导及应用

固态电解质是固态电池中的关键材料,开发具有高离子电导率、高化学/电化学稳定性、电极兼容性良好的固态电解质正成为研究热点。硫化物固态电解质相较其它固态电解质具有更高的离子电导率和良好的机械加工性能等优势,是最有前景实现实用化的固态电解质之一。在众多硫化物固态电解质中,Li₇P₃S₁₁因其高的离子电导率和较低的原料成本而极具研究意义。本文首先介绍了Li₇P₃S₁₁电解质的结构、Li⁺传导机理及合成路径;其次,针对该电解质的电导率提高、空气/水稳定性提升、固固界面稳定性及电解质自身稳定性改善等问题,综述了目前常用的改性策略研究;再次,总结了基于Li₇P₃S₁₁电解质的全固态锂离子电池和全固态锂硫电池的构筑;最后,本文分析了Li₇P₃S₁₁电解质的研究和应用面临的挑战,并指出该电解质未来发展的趋势。     

Synthesis and Characterization of 2‐Mono‐ and 1,2‐Diaminocarba‐closo‐dodecaborates M[1‐R‐2‐H2N‐closo‐CB11H10] (R=H,Ph, H2N,CyHN)

The first primary 2‐aminocarba‐closo‐dodecaborates [1‐R‐2‐H₂N‐closo‐CB₁₁H₁₀]^? (R=H ( 1 ), Ph ( 2 )) have been synthesized by insertion reactions of (Me₃Si)₂NBCl₂ into the trianions [7‐R‐7‐nido‐CB₁₀H₁₀]^3?. The difunctionalized species [1,2‐(H₂N)₂‐closo‐CB₁₁H₁₀] ( 3 ) and 1‐CyHN‐2‐H₃N‐closo‐CB₁₁H₁₀ (H‐ 4 ) have been prepared analogously from (Me₃Si)₂NBCl₂ and 7‐H₃N‐7‐nido‐CB₁₀H₁₂. In addition, the preparation of [Et₄N][1‐H₂N‐2‐Ph‐closo‐CB₁₁H₁₀] ([Et₄N]‐ 5 ) starting from PhBCl₂ and 7‐H₃N‐7‐nido‐CB₁₀H₁₂ is described. Methylation of the [1‐Ph‐2‐H₂N‐closo‐CB₁₁H₁₀]^? ion ( 2 ) to produce 1‐Ph‐2‐Me₃N‐closo‐CB₁₁H₁₀ ( 6 ) is reported. The crystal structures of [Et₄N]‐ 2 , [Et₄N]‐ 5 , and 6 were determined and the geometric parameters were compared to theoretical values derived from DFT and ab initio calculations. All new compounds were studied by NMR, IR, and Raman spectroscopy, MALDI mass spectrometry, and elemental analysis. The discussion of the experimental NMR chemical shifts and of selected vibrational band positions is supported by theoretical data. The thermal properties were investigated by differential scanning calorimetry (DSC). The pK_a values of 2‐H₃N‐closo‐CB₁₁H₁₁ (H‐ 1 ), 1‐H₃N‐closo‐CB₁₁H₁₀ (H‐ 7 ), and 1,2‐(H₃N)₂‐closo‐CB₁₁H₁₀ (H₂‐ 3 ) were determined by potentiometric titration and by NMR studies. The experimental results are compared to theoretical data (DFT and ab initio). The basicities of the aminocarba‐closo‐dodecaborates agree well with the spectroscopic and structural properties.     

Understanding High‐Rate K+‐Solvent Co‐Intercalation in Natural Graphite for Potassium‐Ion Batteries

Graphite shows great potential as an anode material for rechargeable metal‐ion batteries because of its high abundance and low cost. However, the electrochemical performance of graphite anode materials for rechargeable potassium‐ion batteries needs to be further improved. Reported herein is a natural graphite with superior rate performance and cycling stability obtained through a unique K⁺‐solvent co‐intercalation mechanism in a 1 m KCF₃SO₃ diethylene glycol dimethyl ether electrolyte. The co‐intercalation mechanism was demonstrated by ex situ Fourier transform infrared spectroscopy and in situ X‐ray diffraction. Moreover, the structure of the [K‐solvent]⁺ complexes intercalated with the graphite and the conditions for reversible K⁺‐solvent co‐intercalation into graphite are proposed based on the experimental results and first‐principles calculations. This work provides important insights into the design of natural graphite for high‐performance rechargeable potassium‐ion batteries.     

Synthesis and Structure of (N,)C,N‐chelated Organoantimony(III) and Bismuth(III) Cations and Isolation of Their Adducts with Ag[CB11H12]

The treatment of N,C,N‐chelated antimony(III) and bismuth(III) chlorides [C₆H₃‐2,6‐(CH=NR)₂]MCl₂ [R = tBu and M = Sb ( 1 ) or Bi ( 2 ); R = Dmp and M = Sb ( 3 ) or Bi ( 4 )] (Dmp = 2,6‐Me₂C₆H₃) with one molar equivalent of Ag[CB₁₁H₁₂] led to a smooth formation of corresponding ionic pairs {[C₆H₃‐2,6‐(CH=NR)₂]MCl}⁺[CB₁₁H₁₂]^– [R = tBu and M = Sb ( 7 ) or Bi ( 8 ), R = Dmp and M = Sb ( 9 ) or Bi ( 10 )]. Similarly, the reaction of C,N‐chelated analogues [C₆H₂‐2‐(CH=NDip)‐4,6‐(tBu)₂]MCl₂ [M = Sb ( 5 ) or Bi ( 6 ), Dip = 2′,6′‐iPr₂C₆H₃] gave compounds {[C₆H₂‐2‐(CH=NDip)‐4,6‐(tBu)₂]MCl}⁺[CB₁₁H₁₂]^– [M = Sb ( 11 ) or Bi ( 12 )]. All compounds 7 – 12 were characterized with ¹H, ¹¹B and ¹³C{¹H} NMR spectroscopy, ESI‐mass spectrometry, IR spectroscopy, and molecular structures of 7 – 9 and 12 were determined by the help of single‐crystal X‐ray diffraction analysis. In contrast, all attempts to cleave also the second M–Cl bond in 7 – 12 using another molar equivalent Ag[CB₁₁H₁₂] remained unsuccessful. Nevertheless, the reaction between 7 (or 8 ) and Ag[CB₁₁H₁₂] produced unprecedented adducts of both reagents namely {[C₆H₃‐2,6‐(CH=NtBu)₂]SbCl}₂²⁺[Ag₂(CB₁₁H₁₂)₄]^2– ( 13 ) and {[C₆H₃‐2,6‐(CH=NtBu)₂]BiCl}⁺[Ag(CB₁₁H₁₂)₂]^– ( 14 ) in a reproducible manner. The molecular structures of these sparingly soluble compounds were determined by single‐crystal X‐ray diffraction analysis.     

The Stabilization Effect of CO2 in Lithium–Oxygen/CO2 Batteries

The lithium (Li)–air battery has an ultrahigh theoretical specific energy, however, even in pure oxygen (O₂), the vulnerability of conventional organic electrolytes and carbon cathodes towards reaction intermediates, especially O₂^?, and corrosive oxidation and crack/pulverization of Li metal anode lead to poor cycling stability of the Li‐air battery. Even worse, the water and/or CO₂ in air bring parasitic reactions and safety issues. Therefore, applying such systems in open‐air environment is challenging. Herein, contrary to previous assertions, we have found that CO₂ can improve the stability of both anode and electrolyte, and a high‐performance rechargeable Li–O₂/CO₂ battery is developed. The CO₂ not only facilitates the in situ formation of a passivated protective Li₂CO₃ film on the Li anode, but also restrains side reactions involving electrolyte and cathode by capturing O₂^?. Moreover, the Pd/CNT catalyst in the cathode can extend the battery lifespan by effectively tuning the product morphology and catalyzing the decomposition of Li₂CO₃. The Li–O₂/CO₂ battery achieves a full discharge capacity of 6628 mAh g^?1 and a long life of 715 cycles, which is even better than those of pure Li–O₂ batteries.     

Influence of Electrolyte on the Electrode/Electrolyte Interface Formation on InSb Electrode in Mg-Ion Batteries

Achieving the full potential of magnesium-ion batteries (MIBs) is still a challenge due to the lack of adequate electrodes or electrolytes. Grignard-based electrolytes show excellent Mg plating/stripping, but their incompatibility with oxide cathodes restricts their use. Conventional electrolytes like bis(trifluoromethanesulfonyl)imide ((Mg(TFSI)₂) solutions are incompatible with Mg metal, which hinders their application in high-energy Mg batteries. In this regard, alloys can be game changers. The insertion/extraction of Mg²⁺ in alloys is possible in conventional electrolytes, suggesting the absence of a passivation layer or the formation of a conductive surface layer. Yet, the role and influence of this layer on the alloys performance have been studied only scarcely. To evaluate the reactivity of alloys, we studied InSb as a model material. Ex situ X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy were used to investigate the surface behavior of InSb in both Grignard and conventional Mg(TFSI)₂/DME electrolytes. For the Grignard electrolyte, we discovered an intrinsic instability of both solvent and salt against InSb. XPS showed the formation of a thick surface layer consisting of hydrocarbon species and degradation products from the solvent (THF) and salt (C₂H₅MgCl−(C₂H₅)₂AlCl). On the contrary, this study highlighted the stability of InSb in Mg(TFSI)₂ electrolyte.     

Synthesis,Crystal Structure,and Electrochemical Properties of a Simple Magnesium Electrolyte for Magnesium/Sulfur Batteries

Most simple magnesium salts tend to passivate the Mg metal surface too quickly to function as electrolytes for Mg batteries. In the present work, an electroactive salt [Mg(THF)₆][AlCl₄]₂ was synthesized and structurally characterized. The Mg electrolyte based on this simple mononuclear salt showed a high Mg cycling efficiency, good anodic stability (2.5 V vs. Mg), and high ionic conductivity (8.5 mS cm^?1). Magnesium/sulfur cells employing the as‐prepared electrolyte exhibited good cycling performance over 20 cycles in the range of 0.3–2.6 V, thus indicating an electrochemically reversible conversion of S to MgS without severe passivation of the Mg metal electrode surface.     

Synthesis,Crystal Structure,and Electrochemical Properties of a Simple Magnesium Electrolyte for Magnesium/Sulfur Batteries

Most simple magnesium salts tend to passivate the Mg metal surface too quickly to function as electrolytes for Mg batteries. In the present work, an electroactive salt [Mg(THF)₆][AlCl₄]₂ was synthesized and structurally characterized. The Mg electrolyte based on this simple mononuclear salt showed a high Mg cycling efficiency, good anodic stability (2.5 V vs. Mg), and high ionic conductivity (8.5 mS cm⁻¹). Magnesium/sulfur cells employing the as‐prepared electrolyte exhibited good cycling performance over 20 cycles in the range of 0.3–2.6 V, thus indicating an electrochemically reversible conversion of S to MgS without severe passivation of the Mg metal electrode surface.     

Vacancy‐Controlled Na+ Superion Conduction in Na11Sn2PS12

Highly conductive solid electrolytes are crucial to the development of efficient all‐solid‐state batteries. Meanwhile, the ion conductivities of lithium solid electrolytes match those of liquid electrolytes used in commercial Li⁺ ion batteries. However, concerns about the future availability and the price of lithium made Na⁺ ion conductors come into the spotlight in recent years. Here we present the superionic conductor Na₁₁Sn₂PS₁₂, which possesses a room temperature Na⁺ conductivity close to 4 mS cm^?1, thus the highest value known to date for sulfide‐based solids. Structure determination based on synchrotron X‐ray powder diffraction data proves the existence of Na⁺ vacancies. As confirmed by bond valence site energy calculations, the vacancies interconnect ion migration pathways in a 3D manner, hence enabling high Na⁺ conductivity. The results indicate that sodium electrolytes are about to equal the performance of their lithium counterparts.     

Functionalization of closo‐Borates via Iodonium Zwitterions

A simple method for the functionalization of closo‐borates [closo‐B₁₀H₁₀]^2? ( 1 ), [closo‐1‐CB₉H₁₀]^? ( 2 ), [closo‐B₁₂H₁₂]^2? ( 3 ), [closo‐1‐CB₁₁H₁₂]^? ( 4 ), and [3,3′‐Co(1,2‐C₂B₉H₁₁)₂]^? ( 5 ) is described. Treatment of the anions and their derivatives with ArI(OAc)₂ gave aryliodonium zwitterions, which were sufficiently stable for chromatographic purification. The reactions of these zwitterions with nucleophiles provided facile access to pyridinium, sulfonium, thiol, carbonitrile, acetoxy, and amino derivatives. The synthetic results are augmented by mechanistic considerations.