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Solid polymer electrolytes based on plastic crystals are promising for solid‐state sodium metal (Na0) batteries, yet their practicality has been hindered by the notorious Na0‐electrolyte interface instability issue, the underlying cause of which remains poorly understood. Here, by leveraging a model plasticized polymer electrolyte based on conventional succinonitrile plastic crystals, we uncover its failure origin in Na0 batteries is associated with the formation of a thick and non‐uniform solid electrolyte interphase (SEI) and whiskery Na0 nucleation/growth. Furthermore, we design a new additive‐embedded plasticized polymer electrolyte to manipulate the Na0 deposition and SEI formulation. For the first time, we demonstrate that introducing fluoroethylene carbonate (FEC) additive into the succinonitrile‐plasticized polymer electrolyte can effectively protect Na0 against interfacial corrosion by facilitating the growth of dome‐like Na0 with thin, amorphous, and fluorine‐rich SEIs, thus enabling significantly improved performances of Na//Na symmetric cells (1,800 h at 0.5 mA cm−2) and Na//Na3V2(PO4)3 full cells (93.0 % capacity retention after 1,200 cycles at 1 C rate in coin cells and 93.1 % capacity retention after 250 cycles at C/3 in pouch cells at room temperature). Our work provides valuable insights into the interfacial failure of plasticized polymer electrolytes and offers a promising solution to resolving the interfacial instability issue. [ABSTRACT FROM AUTHOR]

Single Li+ ion conducting polyelectrolytes (SICs), which feature covalently tethered counter‐anions along their backbone, have the potential to mitigate dendrite formation by reducing concentration polarization and preventing salt depletion. However, due to their low ionic conductivity and complicated synthetic procedure, the successful validation of these claimed advantages in lithium metal (Li0) anode batteries remains limited. In this study, we fabricated a SIC electrolyte using a single‐step UV polymerization approach. The resulting electrolyte exhibited a high Li+ transference number (t+) of 0.85 and demonstrated good Li+ conductivity (6.3×10−5 S/cm at room temperature), which is comparable to that of a benchmark dual ion conductor (DIC, 9.1×10−5 S/cm). Benefitting from the high transference number of SIC, it displayed a three‐fold higher critical current density (2.4 mA/cm2) compared to DIC (0.8 mA/cm2) by successfully suppressing concentration polarization‐induced short‐circuiting. Additionally, the t+ significantly influenced the deposition behavior of Li0, with SIC yielding a uniform, compact, and mosaic‐like morphology, while the low t+ DIC resulted in a porous morphology with Li0 whiskers. Using the SIC electrolyte, Li0||LiFePO4 cells exhibited stable operation for 4500 cycles with 70.5 % capacity retention at 22 °C. [ABSTRACT FROM AUTHOR]

Solid polymer electrolyte (SPE) may provide a path for next generation high‐performance, hazard‐free lithium ion batteries. However, the low lithium ion transference number (tLi+) and electrolyte conductivity limit device performance. In this study, a diblock copolymer with a polycarbonate first block and poly(sulfonated styrene) second block has been synthesized and characterized for conductivity and shows improved tLi+. The low dissociation of lithium salts from the tethered sulfonate anion was overcome by incorporating plasticizers. The diblock SPE material had room temperature conductivity of up to 1.95 ⋅ 10−6 S/cm, and lithium transference number of up to 0.83 with the tethered sulfonate anion. [ABSTRACT FROM AUTHOR]

Anion exchange membranes (AEMs) are employed as the gas separator and hydroxide ion conductor between the anode and the cathode of alkaline polyelectrolyte fuel cell (APEFC). Highly conductive and stable AEMs are urgently needed in order to achieve satisfactory fuel cell performance. Nevertheless, the low hydroxide conductivity remains major challenge that limits the development and application of APEFC. In order to improve the hydroxide conductivity of AEMs, highly ordered ion conducting channels must be constructed within the membrane matrix. In this study, an AEM with particular polymer structure was designed to achieve fine ion conducting channels by facilitating the hydrophilic-hydrophobic phase separation. Concretely, the side chain of this polyelectrolyte contains two quaternary ammonium groups and terminates with one long hydrophobic tail. Ascribing to the enhanced nano-phase separation ability, inter-connected ion conducting channels were observed by AFM as well as SAXS. A high hydroxide conductivity of 47 mS/cm at 25 °C and 85 mS/cm at 80 °C was achieved. In addition, when applied in an APEFC system, the synthesized AEM showed an outstanding peak power density of 369.3 mW/cm 2 . Good alkaline tolerance, lowered water uptake and swelling ratio were also observed attributing to its carefully designed polymer structure. [ABSTRACT FROM AUTHOR]

High conductivity, solid polymer electrolytes (sPE) are an enabling technology for safe, high energy-density lithium ion batteries. Unfortunately, polymer architectures with high ion conductivity are usually associated with poor mechanical properties. In this study, a difunctional block copolymer (DFBCP) which addresses the need has been synthesized and demonstrated. The first block, P(DBEA-co-MA), has tethered double bonds and can form a dense, crosslinked network upon UV irradiation to provide mechanical strength. The second block is a pendant type polyethylene glycol (PEG) moiety with low crystallization to provide ion solvation. The PEG moiety is confined on one side of the polymer and has high segmental motion, resulting in an adequate ionic conductivity, 0.6 mS/cm. The amorphous nature of PEG second block also ensures low interfacial resistance, <80 Ω∙cm2, and mechanical adaptability to electrode volumetric changes. The combined advantages of high conductivity, low interfacial resistance and good mechanical stability enable full cell durability, >1000 cycles at 2C in a Li–LiFePO 4 battery. Image 1 • Difunctional block copolymer was synthesized as solid polymer electrolyte. • Comb-shaped second block conductivity (0.6 mS/cm). • Crosslinked first block enabled dendrite free lithium plating. • Solid state cell showed stable cycling for 1000 cycles. [ABSTRACT FROM AUTHOR]

Alkaline polyelectrolyte fuel cell now receives growing attention as a promising candidate to serve as the next generation energy-generating device by enabling the use of non-precious metal catalysts (silver, cobalt, nickel et al.). However, the development and application of alkaline polyelectrolyte fuel cell is still blocked by the poor hydroxide conductivity of anion exchange membranes. In order to solve this problem, we demonstrate a methodology for the preparation of highly OH− conductive anion exchange polyelectrolytes with good alkaline tolerance and excellent dimensional stability. Polymer backbones were grafted with flexible aliphatic chains containing two or three quaternized ammonium groups. The highly flexible and hydrophilic multi-functionalized side chains prefer to aggregate together to facilitate the formation of well-defined hydrophilic-hydrophobic microphase separation, which is crucial for the superior OH− conductivity of 69 mS/cm at room temperature. Besides, the as-prepared AEMs also exhibit excellent alkaline tolerance as well as improved dimensional stability due to their carefully designed polymer architecture, which provide new directions to pursue high performance AEMs and are promising to serve as a candidate for fuel cell technology. [ABSTRACT FROM AUTHOR]