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Practical high‐voltage lithium metal batteries hold promise for high energy density applications, but face stability challenges in electrolytes for both 4 V‐class cathodes and lithium anode. To address this, we delve into the positive impacts of two crucial moieties in electrolyte chemistry: fluorine atom (‐F) and cyano group (‐CN) on the electrochemical performance of polyether electrolytes and lithium metal batteries. Cyano‐bearing polyether electrolytes possess strong solvation, accelerating Li+ desolvation with minimal SEI impact. Fluorinated polyether electrolytes possess weak solvation, and stabilize the lithium anode via preferential decomposition of F‐segment, exhibiting nearly 6000‐h stable cycling of lithium symmetric cell. Furthermore, the electron‐withdrawing properties of ‐F and ‐CN groups significantly bolster the high‐voltage tolerance of copolymer electrolyte, extending its operational range up to 5 V. This advancement enables the development of 4 V‐class lithium metal batteries compatible with various cathodes, including 4.45 V LiCoO2, 4.5 V LiNi0.8Co0.1Mn0.1O2, and 4.2 V LiNi0.5Co0.2Mn0.3O2. These findings provide insights into design principles centered around polymer components for high‐performance polymer electrolytes. [ABSTRACT FROM AUTHOR]

High ionic conductivity, outstanding mechanical stability, and a wide electrochemical window are the keys to the application of solid-state lithium metal batteries (LMBs). Due to their regular channels for ion transport and tailored functional groups, covalent organic frameworks (COFs) have been applied to solid electrolytes to improve their performance. Herein, we report a flexible polyethylene oxide-COF-LZU1 (abbreviated as PEO-COF) electrolyte membrane with a high lithium ion transference number and satisfactory mechanical strength, allowing for dendrite-free and long-time cycling for LMBs. Benefiting from the interaction between bis(triflfluoromethanesulonyl)imide anions (TFSI−) and aldehyde groups in COF-LZU1, the Li+ transference number of the PEO-5% COF-LZU1 electrolyte reached up to 0.43, much higher than that of neat PEO electrolyte (0.18). Orderly channels are conducive to the homogenous Li-+ deposition, thereby inhibiting the lithium dendrites. The assembled LiFePO4|PEO-5% COF-LZU1/Li cells delivered a discharge specific capacity of 146 mAh g−1 and displayed a capacity retention of 80% after 200 cycles at 0.1 C (60 °C). The Li/Li symmetrical cells of the PEO-5% COF-LZU1 electrolyte presented a longer working stability at different current densities compared to that of the PEO electrolyte. Therefore, the enhanced comprehensive performance of the solid electrolyte shows potential application prospects for use in LMBs. [ABSTRACT FROM AUTHOR]

Solid‐state electrolytes are key to achieving high energy density, safety, and stability for lithium‐ion batteries. In this Review, core indicators of solid polymer electrolytes are discussed in detail including ionic conductivity, interface compatibility, mechanical integrity, and cycling stability. Besides, we also summarize how above properties can be improved by design strategies of functional monomers, groups, and assembly of batteries. Structures and properties of polymers are investigated here to provide a basis for all‐solid‐state electrolyte design strategies of multi‐component polymers. In addition, adjustment strategies of quasi‐solid‐state polymer electrolytes such as adding functional additives and carrying out structural design are also investigated, aiming at solving problems caused by simply adding liquids or small molecular plasticizer. We hope that fresh and established researchers can achieve a general perspective of solid polymer electrolytes via this Review and spur more extensive interests for exploration of high‐performance lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Solid‐state lithium metal batteries (SSLMBs) are highly desirable for energy storage because of the urgent need for higher energy density and safer batteries. However, it remains a critical challenge for stable cycling of SSLMBs at low temperature. Here, a highly viscoelastic polyether‐b‐amide (PEO‐b‐PA) based composite solid‐state electrolyte is proposed through a one‐pot melt processing without solvent to address this key process. By adjusting the molar ratio of PEO‐b‐PA to lithium bis(trifluoromethanesulphonyl)imide (ethylene oxide:Li = 6:1) and adding 20 wt.% succinonitrile, fast Li+ transport channel is conducted within the homogeneous polymer electrolyte, which enables its application at ultra‐low temperature (−20 to 25 °C). The composite solid‐state electrolyte utilizes dynamic hydrogen‐bonding domains and ion‐conducting domains to achieve a low interfacial charge transfer resistance (<600 Ω) at −20 °C and high ionic conductivity (25 °C, 3.7 × 10−4 S cm−1). As a result, the LiFePO4|Li battery based on composite electrolyte exhibits outstanding electrochemical performance with 81.5% capacity retention after 1200 cycles at −20 °C and high discharge specific capacities of 141.1 mAh g−1 with high loading (16.1 mg cm−2) at 25 °C. Moreover, the solid‐state SNCM811|Li cell achieves excellent safety performance under nail penetration test, showing great promise for practical application. [ABSTRACT FROM AUTHOR]

Here, we describe the synthesis of a CO2-based polycarbonate with pendent alkene groups and its functionalization by grafting methoxypolyethylene glycol in view of its application possibility in gel polymer electrolyte lithium-ion batteries. The gel polymer electrolyte is prepared by an in-situ thiol-ene click reaction between polycarbonate with pendent alkene groups and thiolated methoxypolyethylene glycol in liquid lithium hexafluorophosphate electrolyte and exhibits conductivity as remarkably high as 2.0 × 10 − 2 S cm − 1 at ambient temperature. To the best of our knowledge, this gel polymer electrolyte possesses the highest conductivity in all relevant literatures. A free-standing composite gel polymer electrolyte membrane is obtained by incorporating the gel polymer electrolyte with electrospun polyvinylidene fluoride as a skeleton. The as-prepared composite membrane is used to assemble a prototype lithium iron phosphate cell and evaluated accordingly. The battery delivers a good reversible charge-discharge capacity close to 140 mAh g-1 at 1 C rate and 25°C with only 0.022% per cycle decay after 200 cycles. This work provides an interesting molecular design for polycarbonate application in gel electrolyte lithium-ion batteries. [ABSTRACT FROM AUTHOR]

High‐nickel cathode materials is known to have high specific capacity but poor stability and safety due to nickel diffusion. While Al‐doped high‐nickel cathode (NCMA) particles exhibit enhanced stability, their durability under high‐charge cut‐off voltages remains uncertain. Herein, a polymer electrolyte with semi‐interpenetrating network (SIPN) structure is designed for high‐voltage lithium‐metal battery application. The matrix of the polymer electrolyte is composed of a CO2‐derived thermoplastic polyurethane (TPU) and an in situ polymerized polyacrylonitrile (PAN), where the PAN provides strength and the TPU offers excellent high‐voltage resistance and abundant ion‐complexing sites. With the assistance of additives, the PAN‐TPU‐based electrolyte performs excellent flame retardancy, wide electrochemical stability window (>5.1 V) and can lead to stable organic–inorganic hybrid cathode‐electrolyte interface during cycling. The Li‖PAN‐TPU/TEP‐E‖Li cell lasts over 3400 h at 0.2 mA cm−2. With the construction of well‐connected ion pathway by incorporating of the TPU as binder for cathode and in situ forming the PAN‐TPU‐based electrolyte. The NCMA@TPU‖PAN‐TPU/triethyl phosphate‐based electrolyte (TEP‐E)‖Li cell shows outstanding performances, which maintains a capacity of 186 mAh g−1 at a 4.3 V charging cut‐off voltage, retaining 82% capacity after 300 cycles at 0.5 C. Even at a 4.5 V cut‐off voltage, it retains 78% capacity after 200 cycles at 0.5 C. [ABSTRACT FROM AUTHOR]

Nanobrick wall hybrid coating with super oxygen barrier properties were fabricated on polyethylene terephthalate (PET) film using a quadlayer (QL) assembly of polyelectrolytes and nanoplateles. A quadlayer assembly consists of three repeat units of polyacrylic acid (PAA), poly (dimethyl diallyl ammonium chloride) (PDDA) and layered α-zirconium phosphate (α-ZrP). PDDA with positive charges can assemble alternatively with both α-ZrP and PAA with negative charges to form nanobrick wall architectures on the surface of PET film via the electrostatic interaction. The lamellar structure of α-ZrP platelets and the dense QL assembly coating can greatly reduce the oxygen transmission rate (OTR) of PET film. Compared to pristine PET film, the OTR of PET (QL)19 is reduced from 57 to 0.87 cc/m2/day. Moreover, even with 19 QLs coating, PET (QL)19 composite film is still with an optical transparency higher than 90% and a haze lower than 10%. Therefore, the transparent PET (QL)n composite films with super oxygen barrier properties show great potential application in food packaging and flexible electronic packaging. [ABSTRACT FROM AUTHOR]

The mechanically hard phase and ionically conductive phase endow suitably designed block copolymer electrolytes (BCPEs) with the "Janus" property, thus providing the opportunity to decouple the trade-off between mechanical strength and ionic conductivity by controlling the phase-separated structures. The conductivity of BCPEs is predominantly determined by the molecular structure of block copolymers and the type and concentration of additives, while the manipulation of phase-separated structures helps strengthen their mechanical support and ion transport. This review article presents an overview of BCPEs and focuses on the "molecular structure-phase structure-property" relationship. Ideally, BCPE membranes should have high-throughput and aligned ion transport channels perpendicular to electrodes. First, given the desired attributes of polymer electrolytes, i.e., high ionic conductivity, high strength, low thickness, and high limiting current density, we summarize the research status and optimization strategies for BCPEs. Second, we present a summary of methods that control the phase behavior of BCPEs based on the phase separation mechanism. Third, BCPEs are classified into dual-ion conductor and single-ion conductor, whose advantages and disadvantages are analyzed. Furthermore, we propose a design rationale for high-performance quasi-solid-state BCPEs. We elaborate polymerization methods for the regulation of molecular and phase structure. These aspects are believed to collectively contribute to BCPE membranes with both high ion-conductivity and high mechanical strength, further boosting the development of safe and high-energy solid-state lithium metal batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Phosphoric acid (PA)-doped polymer electrolyte membranes are the most promising materials for high-temperature proton exchange membranes (HT-PEMs). However, their development is subject to the compromise between proton conductivity and phosphoric acid (PA) doping level. Here, an ether-free QPAF-4 membrane (a copolymer containing perfluoroalkylene and fluorenyl groups with pendant ammonium groups) is directly doped with phosphoric acid and studied as HT-PEMs. Due to the intrinsic micro-phase separation structure of QPAF-4 matrix and strong interaction of quaternary ammonium (QA)-PA, the PA-doped membranes possess high proton conductivity and eminent PA retention at comparatively low PA doping level, respectively. The QPAF-4 membrane with 150% PA uptake (QPAF-4-150%PA) offers a proton conductivity of 52 mS cm−1 at 160 °C. As expected, the single cell with QPAF-4-150%PA membrane shows the maximum peak power density of 683 mW cm−2 at 160 °C under anhydrous condition. Meanwhile, the single cell exhibits excellent durability over a period of 60 h with only a slight reduction in voltage of 3.1%. These results indicate that the as-prepared PA-doped quaternized polymer with micro-phase separation structure seems to offer a promising way to develop performing and long-life HT-PEMs with low PA doping levels. [Display omitted] • The PA-doped QPAF-4 membrane has continuous H+ transport channels. • The QPAF-4 membrane achieves high proton conductivity at low PA doping level. • The PA-doped QPAF-4 membrane owns eminent PA retention. • Single cell possesses high peak power density and excellent durability. [ABSTRACT FROM AUTHOR]

Proton exchange membranes (PEMs) have received immense attentions for their core roles in high temperature proton exchange membrane fuel cells (HT-PEMFCs). For a high-performance polymer electrolyte, stable mechanical property and high proton conductivity on the order of 10−2 S cm−1 at low humidity (or anhydrous conditions) and high temperature are ultimately necessary. With emphasis on this practical principle, phosphoric acid doped polybenzimidazoles (PBIs) have become one of the hottest materials in the field of proton conducting membrane that exhibit high proton conductivity with values closing to 10−2 S cm−1. In addition to PBI, non-PBI based proton conducting polymers that exhibit satisfactory conductivity and intrinsic mechanical stability are also exciting research in HT-PEMs. This review summarizes the recent progresses in the HT-PEMs, and addresses the challenges and promising directions for further development of HT-PEMs. • Influences of structure for membrane on single cell performance are analyzed. • Four categories of high temperature proton exchange membranes are summarized. • Advantages and drawbacks for proton exchange membranes are contrasted. • Suggestions of future development for proton exchange membranes are discussed. [ABSTRACT FROM AUTHOR]