Ultrathin Solid Polymer Electrolyte Design for High-Performance Li Metal Batteries: A Perspective of Synthetic Chemistry

Unlocking the Potential of Aqueous Zinc-Ion Batteries: Hybrid SEI Construction through Bifunctional Regulator-Assisted Electrolyte Engineering

Aqueous zinc-ion batteries (AZIBs) represent promising candidates for energy storage devices, because of their inherent high safety and cost efficiency. However, challenges such as uneven zinc ion deposition during electrochemical reduction and anode interface side reactions pose significant obstacles to their advancement and practical deployment. Herein, a medium-concentration aqueous electrolyte combined with a bifunctional regulator (aspartame) is developed to address these issues. Practical validation experiments and theoretical calculations demonstrate that the medium-concentration Zn(OTf)2 aqueous electrolyte containing Aspartame can form a robust hybrid solid electrolyte interface (SEI) containing ZnF2 and ZnS by simultaneously modulating the Zn2+ solvation structure and optimizing the metal-molecule interface, thereby enabling dense Zn deposition. It achieves dendrite-free Zn plating and stripping and excellent Zn reversibility. Significantly, the Zn||V2O5 full cell exhibits an average capacity of 240 mAh g-1 over 8000 cycles at 5 A g-1. This work provides new insight into solvation and interface design for high-performance AZIBs.

Intrinsic Structural and Coordination Chemistry Insights of Li Salts in Rechargeable Lithium Batteries

Lithium batteries, favored for their high energy density and long lifespan, are staples in electric vehicles, portable electronics, and aerospace. A key component, Li salts, aids lithium ion migration and electrode protection, significantly impacting battery performance. Developing an ideal Li salt, balancing stability, solubility, dissociation, solvation, and eco-friendliness, remains challenging. Given the scarcity of relevant reviews, it is endeavored here to present a novel perspective on Li salt chemistry, offering a concise roadmap for future designs and innovations. It is delved into the trends, opportunities, design principles, and evaluation methodologies related to Li salt chemistry, with a particular emphasis on organic anionic compositions. Furthermore, the latest and most representative organic Li salts from their intrinsic structure and coordination chemistry, highlighting their unique features and contributions are organized and presented. Finally, a visionary outlook is articulated for this field, exploring avenues, such as customizing Li salts for specific applications, synthesizing Li salts on demand, and discussing the potential of F-free Li salts alongside with their electrochemical window challenges. Here it is served as a strategic compass, addressing the shortcomings of existing reviews and guiding the design of functionalized Li salts.

In Situ Coordinated MOF-Polymer Composite Electrolyte for Solid-State Lithium Metal Batteries with Exceptional High-Rate Performance

The integration of metal organic frameworks (MOFs) and electrospun polymer fibers offers the potential to achieve uniform dispersion and high loading of fillers, providing a unique perspective for advancing composite solid electrolytes in solid-state lithium metal batteries. In this work, a composite solid electrolyte is fabricated through a combination of electrospinning and chemical immersion, facilitating the in situ nucleation and growth of HKUST-1 on polyacrylonitrile (PAN) electrospun nanofibers. The in situ coordinated HKUST-1 particles not only modify the solvation structure of Li+ and the coordination environment of TFSI-, but also encapsulate PAN fibers to mitigate interfacial side reactions with lithium metal, thereby improving interfacial stability. Consequently, the solid-state electrolyte achieves a high Li ion transference number of 0.77 and an impressive critical current density of 4.5 mA cm-2. The assembled Li||Li symmetric cell exhibits stable operation for over 4000 h at 4.0 mA cm-2, while Li||LFP and Li||NCM811 cells demonstrate exceptional rate capability and cycling stability. This work provides valuable insights into the design and fabrication of MOF/polymer-based composite solid electrolytes.

Multiscale Collaborative Optimization for Composite Solid Electrolyte to Achieve High-Performance Lithium Metal Batteries

Composite solid electrolytes (CSEs) possess significant advantages over individual polymer or inorganic solid electrolytes. However, conventional CSEs suffer from multiple scale issues, including interruptions in ionic transport pathways, incompatibility at heterogeneous interface, and the excessive thickness of electrolytes. Herein, a novel CSE with ultrathin structure (22 µm) based on the strategy of multiscale collaborative optimization (MC-CSE) is designed. This strategy involves continuous, rapid, and homogeneous Li+ transport from macroscale to microscale. i) The bicontinuous structure of MC-CSE is constructed via in situ polymerization of 1,3-dioxolane in a continuous yet porous Li6.4La3Zr1.4Ta0.6O12 (CP-LLZTO) skeleton, which effectively reduces the barrier for Li⁺ transport at macroscale. ii) The continuous interconnected CP-LLZTO and poly 1,3-dioxolane (PDOL) phases within MC-CSE ensures continuous Li+ transport at mesoscale. iii) CP-LLZTO and PDOL synergistic interaction at heterogeneous interface, which facilitates the rapid and homogeneous Li+ transport at microscale. Consequently, the MC-CSE shows both high ionic conductivity and Li⁺ transference number (1.04 mS cm-1 and 0.87). The cells assembled with MC-CSE exhibit outstanding low-temperature (-20 °C) and high-voltage (4.5 V) performance. The strategy of multiscale collaborative optimization provides a promising perspective for the viability of lithium metal batteries at various conditions.

Organic Cationic-Coordinated Perfluoropolymer Electrolytes with Strong Li+-Solvent Interaction for Solid State Li-Metal Batteries

The practical application of solid-state polymer lithium-metal batteries (LMBs) is plagued by the inferior ionic conductivity of the applied polymer electrolytes (PEs), which is caused by the coupling of ion transport with the motion of polymer segments. Here, solvated molecules based on ionic liquid and lithium salt with strong Li+-solvent interaction are inserted into an elaborately engineered perfluoropolymer electrolyte via ionic dipole interaction, extensively facilitating Li+ transport and improving mechanical properties. The intensified formation of solvation structures of contact ion pairs and ionic aggregates, as well as the strong electron-withdrawal properties of the F atoms in perfluoropolymers, give the PE high electrochemical stability and excellent interfacial stability. As a result, Li||Li symmetric cells demonstrate a lifetime of 2500 h and an exceptionally high critical current density above 2.3 mA cm-2, Li||LiFePO4 batteries exhibit consistent cycling for 550 cycles at 10 C, and Li||uncoated LiNi0.8Co0.1Mn0.1O2 cells achieve 1000 cycles at 0.5 C with an average Coulombic efficiency of 98.45 %, one of the best results reported to date based on PEs. Our discovery sheds fresh light on the targeted synergistic regulation of the electro-chemo-mechanical properties of PEs to extend the cycle life of LMBs.

A ternary composite nanofiber-derived thin membrane electrolyte for solid-state Li metal batteries

We develop novel membrane electrolytes comprising h-BN-doped poly(ethylene oxide) modified poly(vinylidene fluoride-co-hexafluoropropylene)-nanofibers (h-BN@PEO/PVH) with high ionic conductivity (3.3 × 10-4 S cm-1) and Li+ transference number (0.74), endowing solid LiFePO4//Li batteries with excellent cyclability over 1000 cycles at 60 °C. Our strategy surmounts the ionic conduction-interface stability trade-off and thin dimension-flexibility conflict.

Block Copoly (Ester-Carbonate) Electrolytes for LiFePO4|Li Batteries with Stable Cycling Performance

To address the challenges posed by the narrow oxidation decomposition potential window and the characteristic of low ionic conductivity at room temperature of solid polymer electrolytes (SPEs), carbon dioxide (CO2), epichlorohydrin (PO), caprolactone (CL), and phthalic anhydride (PA) were employed in synthesizing di-block copolymer PCL-b-PPC and PCL-b-PPCP. The carbonate and ester bonds in PPC and PCL provide high electrochemical stability, while the polyether segments in PPC contribute to the high ion conductivity. To further improve the ion conductivity, we added succinonitrile as a plasticizer to the copolymer and used the copolymer to assemble lithium metal batteries (LMBs) with LiFePO4 as the cathode. The LiFePO4/SPE/Li battery assembled with PCL-b-PPC electrolyte exhibited an initial discharge-specific capacity of 155.5 mAh·g-1 at 0.5 C and 60 °C. After 270 cycles, the discharge-specific capacity was 140.8 mAh·g-1, with a capacity retention of 90.5% and an average coulombic efficiency of 99%, exhibiting excellent electrochemical performance. The study establishes the design strategies of di-block polymer electrolytes and provides a new strategy for the application of LMBs.

Click Chemistry in Lithium-Metal Batteries

Lithium-metal batteries (LMBs) are considered the "holy grail" of the next-generation energy storage systems, and solid-state electrolytes (SSEs) are a kind of critical component assembled in LMBs. However, as one of the most important branches of SSEs, polymer-based electrolytes (PEs) possess several native drawbacks including insufficient ionic conductivity and so on. Click chemistry is a simple, efficient, regioselective, and stereoselective synthesis method, which can be used not only for preparing PEs with outstanding physical and chemical performances, but also for optimizing the stability of solid electrolyte interphase (SEI) layer and elevate the cycling properties of LMBs effectively. Here it is primarily focused on evaluating the merits of click chemistry, summarizing its existing challenges and outlining its increasing role for the designing and fabrication of advanced PEs. The fundamental requirements for reconstructing artificial SEI layer through click chemistry are also summarized, with the aim to offer a thorough comprehension and provide a strategic guidance for exploring the potentials of click chemistry in the field of LMBs.

A Polyzwitterion-Mediated Polymer Electrolyte with High Oxidative Stability for Lithium-Metal Batteries

To achieve high-performance solid-state lithium-metal batteries (SSLMBs), solid electrolytes with high ionic conductivity, high oxidative stability, and high mechanical strength are necessary. However, balancing these characteristics remains dramatically challenging and is still not well addressed. Herein, a simple yet effective design strategy is presented for the development of high-performance polymer electrolytes (PEs) by exploring the synergistic effect between dynamic H-bonded networks and conductive zwitterionic nanochannels. Multiple weak intermolecular interactions along with ample nanochannels lead to high oxidative stability (over 5 V), improved mechanical properties (strain of 1320%), and fast ion transport (ionic conductivity of 10-4 S cm-1 ) of PEs. The amphoteric ionic functional units also effectively regulate the lithium ion distribution and confine the anion transport to achieve uniform lithium ion deposition. As a result, the assembled SSLMBs exhibit excellent capacity retention and long-term cycle stability (average Coulombic efficiency: 99.5%, >1000 cycles with LiFePO4 cathode; initial capacity: 202 mAh g-1 , average Coulombic efficiency: 96%, >230 cycles with LiNi0.8 Co0.1 Mn0.1 O2 cathode). It is exciting to note that the corresponding flexible cells can be cycled stably and can withstand severe deformation. The resulting polyzwitterion-mediated PE therefore offers great promise for the next-generation safe and high-energy-density flexible energy storage devices.

Glass Fiber Reinforced Epoxy-Amine Thermosets and Solvate IL: Towards New Composite Polymer Electrolytes for Lithium Battery Applications

To effectively use (Li) lithium metal anodes, it is becoming increasingly necessary to create membranes with high lithium conductivity, electrochemical and thermal stabilities, as well as adequate mechanical properties. Composite gel polymer electrolytes (CGPE) have emerged as a promising strategy, offering improved ionic conductivity and structural performance compared to polymer electrolytes. In this study, a simple and scalable approach was developed to fabricate a crosslinked polyethylene oxide (PEO)-based membrane, comprising two different glass fiber reinforcements, in terms of morphology and thickness. The incorporation of a solvated ionic liquid into the developed membrane enhances the ionic conductivity and reduces flammability in the resulting CGPE. Galvanostatic cycling experiments demonstrate favorable performance of the composite membrane in symmetric Li cells. Furthermore, the CGPE demonstrated electrochemical stability, enabling the cell to cycle continuously for more than 700 h at a temperature of 40 °C without short circuits. When applied in a half-cell configuration with lithium iron phosphate (LFP) cathodes, the composite membrane enabled cycling at different current densities, achieving a discharge capacity of 144 mAh·g^-1. Overall, the findings obtained in this work highlight the potential of crosslinked PEO-based composite membranes for high-performance Li metal anodes, with enhanced near room temperature conductivity, electrochemical stability, and cycling capability.