A Facile Strategy for Constructing High-Performance Polymer Electrolytes via Anion Modification and Click Chemistry for Rechargeable Magnesium Batteries.

Polymer electrolytes play a crucial role in advancing rechargeable magnesium batteries (RMBs) owing to their exceptional characteristics, including high flexibility, superior interface compatibility, broad electrochemical stability window, and enhanced safety features. Despite these advantages, research in this domain remains nascent, plagued by single preparation approaches and challenges associated with the compatibility between polymer electrolytes and Mg metal anode. In this study, we present a novel synthesis strategy to fabricate a glycerol α,α'-diallyl ether-3,6-dioxa-1,8-octanedithiol-based polymer electrolyte supported by glass fiber substrate (GDT@GF) through anion modification and thiol-ene click chemistry polymerization. The developed route exhibits novelty and high efficiency, leading to the production of GDT@GF membranes featuring exceptional mechanical properties, heightened ionic conductivity, elevated Mg2+ transference number, and commendable compatibility with Mg anode. The assembled modified Mo6S8||GDT@GF||Mg cells exhibit outstanding performance across a wide temperature range and address critical safety concerns, showcasing the potential for applications under extreme conditions. Our innovative preparation strategy offers a promising avenue for the advancement of polymer electrolytes in high-performance rechargeable magnesium batteries, while also opens up possibilities for future large-scale applications and the development of flexible electronic devices.

In Situ Integration of a Flame Retardant Quasisolid Gel Polymer Electrolyte with a Si-Based Anode for High-Energy Li-Ion Batteries.

Silicon (Si) stands out as a promising high-capacity anode material for high-energy Li-ion batteries. However, a drastic volume change of Si during cycling leads to the electrode structure collapse and interfacial stability degradation. Herein, a multifunctional quasisolid gel polymer electrolyte (QSGPE) is designed, which is synthesized through the in situ polymerization of methylene bis(acrylamide) with silica-nanoresin composed of nanosilica and a trifunctional cross-linker in cells, leading to the creation of a "breathing" three-dimensional elastic Li-ion conducting framework that seamlessly integrates an electrode, a binder, and an electrolyte. The silicon particles within the anode are encapsulated by buffering the QSGPE after cross-linking polymerization, which synergistically interacts with the existing PAA binder to reinforce the electrode structure and stabilize the interface. In addition, the formation of the LiF- and Li3N-rich SEI layer further improves the interfacial property. The QSGPE demonstrates a wide electrochemical window until 5.5 V, good flame retardancy, high ionic conductivity (1.13 × 10-3 S cm-1), and a Li+ transference number of 0.649. The advanced QSGPE and cell design endow both nano- and submicrosized silicon (smSi) anodes with high initial Coulombic efficiencies over 88.0% and impressive cycling stability up to 600 cycles at 1 A g-1. Furthermore, the NCM811//Si cell achieves capacity retention of ca. 82% after 100 cycles at 0.5 A g-1. This work provides an effective strategy for extending the cycling life of the Si anode and constructing an integrated cell structure by in situ polymerization of the quasisolid gel polymer electrolyte.

Interphase Engineering via Solvent Molecule Chemistry for Stable Lithium Metal Batteries.

Lithium metal battery has been regarded as promising next-generation battery system aiming for higher energy density. However, the lithium metal anode suffers severe side-reaction and dendrite issues. Its electrochemical performance is significantly dependant on the electrolyte components and solvation structure. Herein, a series of fluorinated ethers are synthesized with weak-solvation ability owing to the duple steric effect derived from the designed longer carbon chain and methine group. The electrolyte solvation structure rich in AGGs (97.96 %) enables remarkable CE of 99.71 % (25 °C) as well as high CE of 98.56 % even at -20 °C. Moreover, the lithium-sulfur battery exhibits excellent performance in a wide temperature range (-20 to 50 °C) ascribed to the modified interphase rich in LiF/LiO2. Furthermore, the pouch cell delivers superior energy density of 344.4 Wh kg-1 and maintains 80 % capacity retention after 50 cycles. The novel solvent design via molecule chemistry provides alternative strategy to adjust solvation structure and thus favors high-energy density lithium metal batteries.

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 , 243 Wh kg-1 at 5 A g-1 ) as well as excellent cycling stability after 600 cycles and rate capability (138 mAh g-1 , 81 Wh kg-1 at 10 A g-1 ).

Toward High-Performance Mg-S Batteries via a Copper Phosphide Modified Separator.

Magnesium-sulfur (Mg-S) batteries are emerging as a promising alternative to lithium-ion batteries, due to their high energy density and low cost. Unfortunately, current Mg-S batteries typically suffer from the shuttle effect that originates from the dissolution of magnesium polysulfide intermediates, leading to several issues such as rapid capacity fading, large overcharge, severe self-discharge, and potential safety concern. To address these issues, here we harness a copper phosphide (Cu3P) modified separator to realize the adsorption of magnesium polysulfides and catalyzation of the conversion reaction of S and Mg2+ toward stable cycling of Mg-S cells. The bifunctional layer with Cu3P confined in a carbon matrix is coated on a commercial polypropylene membrane to form a porous membrane with high electrolyte wettability and good thermal stability. Density functional theory (DFT) calculations, polysulfide permeability tests, and post-mortem analysis reveal that the catalytic layer can adsorb polysulfides, effectively restraining the shuttle effect and facilitating the reversibility of the Mg-S cells. As a result, the Mg-S cells can achieve a high specific capacity, fast rates (449 mAh g-1 at 0.1 C and 249 mAh g-1 at 1.0 C), and a long cycle life (up to 500 cycles at 0.5 C) and operate even at elevated temperatures.

Insights into the stability of magnesium borate salts for rechargeable magnesium batteries from AIMD simulations.

We present AIMD simulations for the stability of boron-center salts, Mg[B(Ohfip)4]2 and Mg[B(Otfe)4]2, compared to Mg(TFSI)2, and provide a visible reaction process at the atomic level. -CF3 groups have a positive effect on the electrochemical performance, and C atoms do not easily fall off from the anion groups to form a SEI in Mg[B(Ohfip)4]2, which will help to find high-performance magnesium electrolytes.

Ti3C2 MXene with pillared structure for hybrid magnesium-lithium batteries cathode material with long cycle life and high rate capability.

Cationic surfactants (CS) pillared Ti3C2 composites (Ti3C2/CS) were prepared by a facile electrostatic assembly method, which have large interlayer spacing and slight N-doping. In hybrid magnesium-lithium batteries (HMLBs), the Ti3C2/CS composites exhibit excellent performance by utilizing both Li+ and Mg2+ as charge carriers. Among these composites, the Ti3C2/CTAB (CTC) electrode displays a reversible capacity of 115.9 and 60 mAh g-1 in APC/LiCl (APCL) and APC electrolytes at 0.1 A g-1, and it also exhibits excellent high rate performance and ultralong cycle performance. It is verified that CS is vital to significantly improve the diffusion kinetics of Mg2+ on the electrode surface. The CS can act as the conductive "bridge" which connects different Ti3C2 layers and the interlayer pillar which expands the interlayer distance. In addition, the N element in CS is effective in neutralizing electronegativity and enhancing electrical conductivity for the CTC electrode. The electrode design strategy can adapt to the synthesis of cathode materials with high rate capability in HMLBs.

SnSe2 /FeSe2 Nanocubes Capsulated in Nitrogen-Doped Carbon Realizing Stable Sodium-Ion Storage at Ultrahigh Rate.

Metal selenides have attracted increasing attention recently as anodes for sodium-ion batteries (SIBs) because of their large capacities, high electric conductivity, as well as environmental benignity. However, the application of metal selenides is hindered by the huge volume variation, which causes electrode structure devastation and the consequent degrading cycling stability and rate capability. To overcome the aforementioned obstacles, herein, SnSe2 /FeSe2 nanocubes capsulated in nitrogen-doped carbon (SFS@NC) are fabricated via a facile co-precipitation method, followed by poly-dopamine wrapping and one-step selenization/carbonization procedure. The most remarkable feature of SFS@NC is the ultra-stability under high current density while delivering a large capacity. The synergistic effect of dual selenide components and core-shell architecture mitigates the volume effect, alleviates the agglomeration of nanoparticles, and further improves the electric conductivity. The as-prepared SFS@NC nanocubes present a high capacity of 408.1 mAh g-1 after 1200 cycles at 6 A g-1 , corresponding to an 85.3% retention, and can achieve a capacity of 345.0 mAh g-1 at an extremely high current density of 20 A g-1 . The outstanding performance of SFS@NC may provide a hint to future material structure design strategy, and promote further developments and applications of SIBs.

A Novel Filler for Gel Polymer Electrolyte with a High Lithium-Ion Transference Number toward Stable Cycling for Lithium-Metal Anodes in Lithium-Sulfur Batteries.

Although the lithium metal is considered as the most promising anode for high energy density batteries, uncontrolled lithium dendrite growth and continuous side reactions with electrolyte hinder its practical applications for rechargeable batteries. Herein, we prepared a gel polymer electrolyte by synthesizing a novel 250 nm filler (KMgF3), which is greatly beneficial to the formation of a uniformly deposited lithium-metal anode. This is due to the regulation effect of KMgF3 that double the lithium-ion transference number up to 0.63 and adjust the solid electrolyte interphase layer full of dense LiF and flexible polycarbonates, which greatly reduces the side reactions on the lithium-metal surface and inhibits the growth of lithium dendrites. Consequently, the composite gel polymer electrolyte guarantees a stable long cycle performance of more than 1400 h with 1 mA h cm-2 for symmetric cells. Moreover, the composite gel polymer electrolyte demonstrates high compatibility and great promise for rechargeable lithium-sulfur (Li-S) batteries.

Iron Phosphide Confined in Carbon Nanofibers as a Free-Standing Flexible Anode for High-Performance Lithium-Ion Batteries.

Iron phosphide with high specific capacity has emerged as an appealing candidate for next-generation lithium-ion battery anodes. However, iron phosphide could undergo conversion reactions and generally suffer from a rapid capacity degradation upon cycling due to its structure pulverization. Chemomechanical breakdown of iron phosphide due to its rigidity has been a challenge to fully realizing its electrochemical performance. To address this challenge, we report here on an enticing opportunity: a flexible, free-standing iron phosphide anode with Fe2P nanoparticles confined in carbon nanofibers may overcome existing challenges. For the synthesis, we introduce a facile electrospinning strategy that enables in situ formation of Fe2P within a carbon matrix. Such a carbon matrix can effectively minimize the structure change of Fe2P particles and protect them from pulverization, allowing the electrodes to retain a free-standing structure after long-term cycling. The produced electrodes showed excellent electrochemical performance in lithium-ion half and full cells, as well as in flexible pouch cells. These results demonstrate the successful development of iron phosphide materials toward high capacity, light weight, and flexible energy storage.

A Chlorine-Free Electrolyte Based on Non-nucleophilic Magnesium Bis(diisopropyl)amide and Ionic Liquid for Rechargeable Magnesium Batteries.

The electrolyte based on magnesium bis(diisopropyl)amide (MBA), a low-cost and non-nucleophilic organic magnesium salt, is proposed to be an admirable alternative for rechargeable magnesium batteries but suffers from limited ionic conductivity and an inferior electrochemical window in the commonly used ether solvents. In this work, the 1-butyl-1-methylpiperidinium bis(trifluoromethyl sulfonyl)imide (PP14TFSI) ionic liquid as the cosolvent of tetrahydrofuran (THF) in chlorine-free MBA-based electrolytes has been first demonstrated to remarkably improve the ionic conductivity and broaden the oxidative stable potential (2.2 V vs Mg/Mg2+) on stainless steel. Reversible Mg electrochemical plating/stripping with a low overpotential below 200 mV and ca. 90% Coulombic efficiency are obtained. The current density of Mg plating/stripping is increased 238 times after the addition of PP14TFSI, where the mechanism of competitive coordination of TFSI- making an easier Mg plating/stripping is proposed theoretically. The MBA-2AlF3 electrolyte with a ratio-optimized THF/PP14TFSI cosolvent exhibits good compatibility with the Mo6S8 cathode. Furthermore, the Se@pPAN|Mg full cell exhibits an initial capacity of 447.8 mAh g-1 and as low as ∼0.66% capacity decay per cycle for more than 70 cycles at 0.2 C with the synergy of LiTFSI additives. The facile modification strategy of ionic liquid in the MBA-based electrolyte sheds inspiring light on exploring non-nucleophilic and chlorine-free electrolytes for practical rechargeable magnesium batteries.

Coupling-Agent-Coordinated Uniform Polymer Coating on LiNi0.6Co0.2Mn0.2O2 for Improved Electrochemical Performance at Elevated Temperatures.

The high-voltage Ni-rich LiNixCoyMnzO2 cathode materials attract attention due to their high capacity and relatively low cost. However, the undesired instability originating from side reactions with liquid electrolytes at elevated temperatures still hinders their practical application. This research aims to build a stable interface between cathode and electrolyte. We use the coupling agent KH570 to induce vinyl ethylene carbonate (VEC) monomers to in situ polymerize on the surface of LiNi0.6Co0.2Mn0.2O2 (NCM622) to form a uniform, ultrathin (∼12 nm), and highly ion-conductive poly(vinyl ethylene carbonate) (PVEC) solid polymer electrolyte layer. The modified cathode material exhibits significant improvement in rate performance and cycling stability up to 4.5 V at elevated temperatures. Scanning electron microscopy and X-ray diffraction techniques prove that the flexible polymer coating layer effectively suppresses the mechanical degradation and crystal structure changes during cycling.

A high-performance rechargeable Mg2+/Li+ hybrid battery using CNT@TiO2 nanocables as the cathode.

Porous CNT@TiO2 nanocables are prepared via an impregnation method combined with calcination, which not only display the illusive capacity of 233.5 mAh g-1 but also possess outstanding rate performance (144.9 mAh g-1 at 500 mA g-1). Compared with TiO2 nanoparticles and nanotubes, CNT@TiO2 exhibits the excellent electrochemical performance on account of the unique coaxial nanocable feature (short ion diffusion path, large contact surface area, supernal conductivity, and favorable structure stability), which simultaneously overcomes the aggregation of TiO2 particles and the collapse of TiO2 nanotubes. Importantly, there are no significant changes in the morphology and phase after long cycling, meaning that CNT@TiO2 has a highly structural stability and reversibility. Therefore, CNT@TiO2 can be applied as a promising cathode material for Mg2+/Li+ hybrid batteries.

High Molecular Weight Polyacrylonitrile Precursor for S@pPAN Composite Cathode Materials with High Specific Capacity for Rechargeable Lithium Batteries.

Sulfurized pyrolyzed poly(acrylonitrile) (S@pPAN) demonstrates high sulfur utilization, no polysulfide dissolution, no self-discharge, and extremely stable cycling. Its precursor, PAN, directly determines the performances of cathode materials, including the sulfur content and its utilization for S@pPAN composite materials. Adopting PAN with the molecular weight approaching 550,000 as the precursor, the sulfur content in S@pPAN approaches 55 wt %, and its reversible specific capacity was 901 mAh g-1(composite) at 50 °C with sulfur utilization over 98%. Moreover, it enabled stable cycling and excellent high rate capability with a specific capacity of 645 mAh g-1 at 5 C. These significantly enhanced electrochemical properties are mainly due to the high molecular weight of the PAN precursor, which provides more space to accommodate amorphous sulfur, along with improved interfacial resistance of S@pPAN.

MLi2Ti6O14 (M = Sr, Ba, and Pb): new cathode materials for magnesium-lithium hybrid batteries.

Magnesium-lithium hybrid batteries (MLHBs) are playing an increasingly important role in energy storage systems owing to their abundant raw materials and favorable safety characteristics. Consequently, MLi2Ti6O14 (M = Sr, Ba, and Pb) compounds have been synthesized via a sol-gel method, followed by calcination. For the first time, as cathodes for MLHBs, MLi2Ti6O14 (M = Sr, Ba, and Pb) showed good electrochemical properties. For example, at 50 mA g-1, the specific capacities of MLi2Ti6O14 (M = Sr, Ba, and Pb) after 300 cycles are 75.6, 68.2 and 76.3 mA h g-1, respectively. In addition, MLi2Ti6O14 (M = Sr, Ba, and Pb) also possess outstanding rate performances. Importantly, the ion storage mechanism of MLi2Ti6O14 (M = Sr, Ba, and Pb) compounds in MLHBs was studied with PbLi2Ti6O14 as the representative. These results reveal that MLi2Ti6O14 (M = Sr, Ba, and Pb) have good electrochemical reversibility, and can be used as cathodes for MLHBs.

Highly Reversible Lithium-Metal Anode and Lithium-Sulfur Batteries Enabled by an Intrinsic Safe Electrolyte.

Rechargeable lithium-metal batteries have gained significant attention as potential candidates of energy storage systems; however, severe safety issues including flammable electrolyte and dendritic lithium formation hinder their further practical application. In this work, we develop a novel intrinsic flame-retardant electrolyte, which enables a stable and dendrite-free cycling with lithium plating/stripping Coulombic efficiency of up to 99.1% over 500 cycles. Raman spectra indicate that no free molecular solvent exists, and X-ray photoelectron spectroscopy reveals the LiF-rich interphase on the Li-metal anode. When coupled with sulfurized pyrolyzed poly(acrylonitrile) cathode, it shows a benign electrochemical reversibility with the areal capacity of up to 3.41 mAh cm-2 after 70 cycles. To further check its compatibility with sulfur cathode, a higher sulfur content (51.6%) is examined with the areal capacity of 3.92 mAh cm-2 and sulfur utilization of 81.7%. This work provides an alternative for safe and high-performance Li-S batteries via a novel electrolyte strategy.

A new class of electrolytes based on magnesium bis(diisopropyl)amide for magnesium-sulfur batteries.

We present a new class of electrolytes, which has relatively high anodic stability on stainless steel (2.65 V, vs. Mg RE), low over-potential for Mg plating/stripping and close to 100% coulombic efficiency, for Mg-S batteries prepared by a facile in situ reaction of commercial magnesium bis(diisopropyl)amide (MBA) with AlCl3, The resulting Mg-S battery shows a highly stable discharge capacity of approximately 540 mA h g-1 for 30 cycles and one well-defined voltage plateau of about 1.1 V vs. Mg.

High Active Magnesium Trifluoromethanesulfonate-Based Electrolytes for Magnesium-Sulfur Batteries.

The shortage of high-performance and easily prepared electrolyte has hindered the progress of rechargeable magnesium-sulfur (Mg-S) batteries. In this paper, we develop a new electrolyte based on Mg(CF3SO3)2-AlCl3 dissolved in tetrahydrofuran and tetraglyme mixed solvents. Mg(SO3CF3)2 as an Mg2+ source is nonnucleophilic, easy to handle, and much cheaper than Mg(TFSI)2 (TFSI = bis(trifluoromethanesulfonyl)imide). After modification with anthracene (π stabilizing agent) as a coordinating ligand to stabilize the Mg2+ ions and MgCl2 to improve the interface properties by accelerating the reaction of Mg(CF3SO3)2 with AlCl3, the electrolyte exhibits a low overpotential for overall Mg deposition and dissolution, moderate anodic stability (3.25 V on Pt, 2.5 V on SS, 2.0 V on Cu, and 1.85 V on Al, respectively), and a suitable ionic conductivity (1.88 mS cm-1). More importantly, this electrolyte modulated by Li-salt additives exhibits good compatibility with S cathode and can be applicable for Mg-S batteries. The rational formulation of the new electrolyte could provide a new avenue for simply prepared Mg electrolytes of Mg-S and rechargeable magnesium batteries.

Highly Reversible and Rechargeable Safe Zn Batteries Based on a Triethyl Phosphate Electrolyte.

Zinc metal is an attractive anode material for next-generation batteries. However, dendrite growth and limited Coulombic efficiency (CE) during cycling are the major roadblocks towards the widespread commercialization of batteries employing Zn anodes. In this work we report the novel adoption of triethyl phosphate (TEP) as a solvent and co-solvent with aqueous electrolytes to obtain a highly stable and dendrite-free Zn anode. Stable Zn plating/stripping for over 3000 h was obtained, accompanied by a CE of 99.68 %. SEM images of the Zn anodes revealed highly porous interconnected dendrite-free Zn deposits. The electrolyte displayed good compatibility with both Zn anodes and potassium copper hexacyanoferrate (KCuHCf) cathodes for Zn ion batteries (ZIBs). The full cell showed a long cycling stability and high rate capability. The present work is a contribution towards cost-effective and safe battery systems.

An Intrinsic Flame-Retardant Organic Electrolyte for Safe Lithium-Sulfur Batteries.

Safety concerns pose a significant challenge for the large-scale employment of lithium-sulfur batteries. Extremely flammable conventional electrolytes and dendritic lithium deposition cause severe safety issues. Now, an intrinsic flame-retardant (IFR) electrolyte is presented consisting of 1.1 m lithium bis(fluorosulfonyl)imide in a solvent mixture of flame-retardant triethyl phosphate and high flashpoint solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl (1:3, v/v) for safe lithium-sulfur (Li-S) batteries. This electrolyte exhibits favorable flame-retardant properties and high reversibility of the lithium metal anode (Coulombic efficiency >99 %). This IFR electrolyte enables stable lithium plating/stripping behavior with micro-sized and dense-packing lithium deposition at high temperatures. When coupled with a sulfurized pyrolyzed poly(acrylonitrile) cathode, Li-S batteries deliver a high composite capacity (840.1 mAh g-1 ) and high sulfur utilization of 95.6 %.