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The fundamental understanding of the relationship between ion transport and segmental dynamics of polymer chains in polymer electrolytes is crucial for achieving high ionic conductivity at room temperature for technological applications in supercapacitors, batteries, etc. In this work, the ion dynamics and relaxation have been studied for gel polymer electrolytes (GPEs) containing P(VdF-HFP) as host polymer, adiponitrile as a plasticizer, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide as ionic liquid, and diphenylamine and copper iodide redox additives as fillers. The crystallization temperature of the ionic liquid and the melting temperature of the plasticizer play important roles in ion dynamics. The highest room-temperature ionic conductivity (3.3 × 10−3 S/cm) was obtained for the GPE filled with dual redox additives. The broadband ac conductivity spectra have been analyzed by using the Universal Power law model coupled with the Poisson–Nernst–Planck (PNP) model. The solid–solid phase transition of the ionic liquid affects the grain and grain boundary regions of the GPEs due to the presence of redox fillers. The temperature dependence of the dielectric spectra of the GPEs containing redox fillers confirms the phase transition at the crystallization temperature. The electric modulus and dielectric spectra have been analyzed by using the Havrilliak–Nigami, Kohlrausch–Williams–Watts, and derivative dielectric constant functions. The scaling of ac conductivity and modulus spectra confirms a common ion conduction and relaxation mechanism for the GPEs. The influence of dual redox additives is clearly observed in the values of ionic conductivity, ion diffusivity, and relaxation time. [ABSTRACT FROM AUTHOR]

Recent experimental results have demonstrated that zwitterionic ionogel comprised of polyzwitterion (polyZI)-supported lithium salt-doped ionic liquid exhibits improved conductivities and lithium transference numbers than the salt-doped base ionic liquid electrolyte (ILE). However, the underlying mechanisms of such observations remain unresolved. In this work, we pursued a systematic investigation to understand the impact of the polyZI content and salt concentration on the structural and dynamic properties of the poly(MPC) ionogel of our model polyZI ionogel, poly(2-methacryloyloxyethyl phosphorylcholine) [poly(MPC)] supported LiTFSI/N-butyl-N-methylpyrrolidinium TFSI base ionic liquid electrolyte. Our structural analyses show strong lithium–ZI interaction consistent with the physical network characteristic observed in the experiments. An increase in polyZI content leads to an increased fraction of Li+ ions coordinated with the polyZI. In contrast, an increase in salt concentration leads to a decreased fraction of Li+ ions coordinated with the polyZI. The diffusivities of the mobile ions in the poly(MPC) ionogel were found to be lower than the base ILE in agreement with experiments at T > 300 K. Analysis of ion transport mechanisms shows that lithium ions within the poly(MPC) ionogel travel via a combination of structural, vehicular diffusion, as well as hopping mechanism. Finally, the conductivity trend crossover between the poly(MPC) ionogel and the base ILE was rationalized via a temperature study that showed that the base ILE ions are influenced more by the variation of temperature when compared to the poly(MPC) ions. [ABSTRACT FROM AUTHOR]

We present a strategic approach for enhancing the ionic conductivity of block copolymer electrolytes. This was achieved by introducing mixed ionic liquids (ILs) with varying molar ratios, wherein the imidazolium cation was paired with either tetrafluoroborate (BF4) anion or bis(trifluoromethylsulfonyl)imide (TFSI) anion. Two polymer matrices, poly(4-styrenesulfonate)-b-polymethylbutylene (SSMB) and poly(4-styrenesulfonyl (trifluoromethanesulfonyl)imide)-b-polymethylbutylene (STMB), were synthesized for this purpose. All the SSMB and STMB containing mixed ILs showed hexagonal cylindrical structures, but the type of tethered acid group significantly influenced the interfacial properties. STMB electrolytes demonstrated enhanced segregation strength, which was attributed to strengthened Coulomb and hydrogen bonding interactions in the ionic domains, where the ILs were uniformly distributed. In contrast, the SSMB electrolytes exhibited increased concentration fluctuations because the BF4 anions were selectively sequestered at the block interfaces. This resulted in the effective confinement of imidazolium TFSI along the ionic domains, thereby preventing ion trapping in dead zones and facilitating rapid ion diffusion. Consequently, the SSMB electrolytes with mixed ILs demonstrated significantly improved ionic conductivities, surpassing the expected values based on the arithmetic average of the conductivities of each IL, whereas the ionic conductivity of the STMB was aligned with the expected average. The methodology explored in this study holds great promise for the development of solid-state polymer electrolytes. [ABSTRACT FROM AUTHOR]

Polymer gel electrolytes (PGE) have seen a renewed interest in their development because they have high ionic conductivities but low electrochemical degradation and flammability. PGEs are formed by mixing a liquid lithium-ion electrolyte with a polymer at a sufficiently large concentration to form a gel. PGEs have been extensively studied, but the direct connection between their microscopic structure and macroscopic properties remains controversial. For example, it is still unknown whether the polymer in the PGE acts as an inert, stabilizing scaffold for the electrolyte or it interacts with the ionic components. Here, a PGE composed of a prototypical lithium-carbonate electrolyte and polyacrylonitrile (PAN) is pursued at both microscopic and macroscopic levels. Specifically, this study focused on describing the microscopic and macroscopic changes in the PGE at different polymer concentrations. The results indicated that the polymer-ion and polymer–polymer interactions are strongly dependent on the concentration of the polymer and the lithium salt. In particular, the polymer interacts with itself at very high PAN concentrations (10% weight) resulting in a viscous gel. However, the conductivity and dynamics of the electrolyte liquid components are significantly less affected by the addition of the polymer. The observations are explained in terms of the PGE structure, which transitions from a polymer solution to a gel, containing a polymer matrix and disperse electrolyte, at low and high PAN concentrations, respectively. The results highlight the critical role that the polymer concentration plays in determining both the macroscopic properties of the system and the molecular structure of the PGE. [ABSTRACT FROM AUTHOR]

Recently, it has been demonstrated that ionic liquids (ILs) with an asymmetric anion render a wider operational temperature range and can be used as a solvent in sodium ion batteries. In the present study, we examine the microscopic structure and dynamics of pure 1-methyl-1-propylpyrrolidinium fluorosulfonyl(trifluoromethylsulfonyl)amide (Pyrr1,3FTA) IL using atomistic molecular dynamics simulations. How the addition of the sodium salt (NaFTA) having the same anion changes the structural landscape and transport properties of the pure IL has also been explored. The simulated x-ray scattering structure functions reveal that the gradual addition of NaFTA salt (up to 1.2 molal) suppresses the charge alternating feature of the pure IL because of the replacement of the Pyrr+ cations with the Na+ ions. The Na+ ions are majorly found near the oxygen atoms of the anions, but the probability of finding the Na+ ions near these atoms slightly decreases with increasing salt concentration. As expected, the Na+ ions stay away from the Pyrr+ cations. However, the probability of finding the anions around anions increases with increasing salt concentration. The simulated self-diffusion coefficients of the ions in the pure IL reveal slightly faster diffusion of the Pyrr+ cations as compared to the FTA− anions. Interestingly, in the salt solution, despite having smaller size, the diffusion of the Na+ ions is found to be lesser than the Pyrr+ cations and the FTA− anions. The analysis of the ionic conductivity and transport numbers reveals that the fractional contribution of the FTA− anion to the overall conductivity remains nearly constant with increasing salt concentration, but the contribution of Pyrr+ cation decreases and Na+ ion increases. [ABSTRACT FROM AUTHOR]

Chemically compatible additives were utilized to increase the ionic conductivity of polyethylene melts. When subjected to unconfined electrospinning, a predictable and significant decrease in the resultant fiber diameter with enhanced melt conductivity was observed. This generalized approach was confirmed for viscous melts, varying in conductivity over five orders of magnitude and viscosity 5×, from multiple commercial polyethylene formulations with various additives. These experimental results are connected to theory for the relevant length scales of capillary length, jet spacing, and jet radius. In particular, jet radius scales as conductivity to the −1/4 power. Fitting experimental fiber radius vs ionic conductivity data results in a similar power law exponent (−0.29). This trend, occurring at orders of magnitude higher viscosity and six orders of magnitude lower conductivity, is similar to results from needle-based, solution phase electrospinning, suggesting the generality of the effect. The connection between larger length scales, such as the distance between jets and the thickness of the film at the plate edge, and fluid properties (surface tension, viscosity, and conductivity) is also discussed. [ABSTRACT FROM AUTHOR]

Owing to the inherent properties combining high ionic conductivity and electrochemical stability, the lithium triborates (LBOs) have emerged as a promising solid-state electrolyte for next-generation batteries. Specific fundamental details of the ionic conduction mechanism and related physicochemical properties remain to be understood. In this study, using the first-principles density functional theory calculations, we present a systematic computational investigation on LBOs in the respect of electronic structures, mechanical and thermodynamic properties, Li-ion transport, and interfacial (with Li metal) behaviors. Our results show that LBO is a thermodynamically and mechanically stable insulator with an indirect wide bandgap of 6.4 eV. Notably, LBOs could behave as a fast Li-ion conductor with a low migration energy barrier (15 meV) and are characterized by a zig–zag Li+-diffusion path along the c direction. We found that the interface between Li metal and LBO is both physically and chemically stable with no new phase formed while exhibiting a metallic character due to the charge transfer from a Li metal. Our study highlights the intriguing promise of LBOs as solid-state electrolytes for high-energy cells. [ABSTRACT FROM AUTHOR]

We present here a gel polymer electrolyte, where the Li+-ion transport is completely decoupled from the polymer host solvation and dynamics. A free-standing gel polymer electrolyte with a high volume content (nearly 60%) of xM LiTFSI in G4 (tetraglyme) (x = 1–7; Li+:G4 = 0.2–1.5) liquid electrolyte confined inside the PAN (polyacrylonitrile)-PEGMEMA [poly (ethylene glycol) methyl ether methacrylate oligomer] based polymer matrix is synthesized using a one-pot free radical polymerization process. For LiTFSI concentrations, x = 1–7 (Li+:G4 = 0.2–1.5), Raman and vibrational spectroscopies reveal that like in the liquid electrolyte, the designed gel polymer electrolytes (GPEs) also show direct coordination of Li+-ions with the tetraglyme leading to the formation of [Li(G4)]+. Coupled with the spectroscopic studies, impedance and nuclear magnetic resonance investigations also show that the ion transport is independent of the polymer segmental motion and is governed by the solvated species {[Li(G4)]+}, very similar to the scenario in ionic liquids. As a result, the magnitude of ionic conductivity and activation energies of the gel polymer electrolyte are very similar to that of the liquid electrolyte. The Li+-ion transport number for the GPE varied from 0.44 (x = 1) to 0.5 (x = 7) with the maximum being 0.52 at x = 5. [ABSTRACT FROM AUTHOR]

Through first-principles calculations, we successfully identified a two-dimensional layered nitridosilicate-MnSi2N4 in hexagonal structure, as a novel anode for lithium (Li) and sodium (Na) ion batteries. Phonon and molecular dynamics simulations manifest the favorable dynamic stability of MnSi2N4. The predicted material exhibits metallic behavior with high Young's modulus of 457 GPa and aqueous insolubility. MnSi2N4 possesses low diffusion barrier for Li (0.32 eV) and Na (0.19 eV), as well as high storage capacity as an anode for Li (320 mAh g−1) and Na (160 mAh g−1) ion batteries, respectively. These properties, including excellent electronic conductivity, low diffusion barrier, and high storage capacity, enable MnSi2N4 a promising anode for Li and Na ion batteries. [ABSTRACT FROM AUTHOR]

Na superionic conductor-type Na1+xZr2SixP3-xO12 (0 ≤ x ≤ 3, NZSPO) is considered as one of the most promising solid electrolytes for solid-state sodium batteries, while its relatively low ionic conductivity of 10−4 S cm−1 requires improvement for application. In this study, a synergetic strategy is applied to improve the ionic conductivity of NZSPO, i.e., by combining bulk doping and grain-boundary engineering. Hf4+ is selected as the substitution for Zr4+ to stabilize the highly conducting rhombohedral phase. La2O3 is added as a sintering aid to promote the ion transport along the grain boundaries with Na3La(PO4)2 formed therein. The optimized Na3Zr1.8Hf0.2Si2PO12-Na3La(PO4)2 (NZHSPO-NLPO) ceramic electrolytes show a high relative density of 98.8% and the superior ionic conductivity of 1.66 × 10−3 S cm−1 at 30 °C. The Na symmetric batteries display the stable plating/stripping cycling over 500 h at 0.1 mA cm−2 and 0.05 mAh cm−2. With ionic liquid as a wetting agent at cathode sides and PEO as an intermediate layer at anode sides, the NZHSPO-NLPO-based Na batteries with Na3V2(PO4)3 cathodes exhibit the discharge capacity of 109.9 mAh g−1 and capacity retention of 92.7% at 0.1 and 30 °C for 50 cycles. It is proved that the simultaneous optimization of bulk and grain boundaries is powerful for increasing the ionic conductivity of ceramic solid electrolytes. [ABSTRACT FROM AUTHOR]

A solid-state electrolyte with high ionic conductivity and improved safety is a strong competitor in the race for the development of next-generation solid-state lithium batteries, which have stepped into the limelight of materials research. Li1.5Al0.5Ge1.5(PO4)3 (LAGP) with satisfied ionic conductivity (∼10−4 S cm−1) at room temperature, high stability in the ambient atmosphere, and a facile sintering nature shows a promising potential for applications in solid-state lithium batteries. However, the current synthesis methods like solid-state strategy and liquid phase route all require harsh conditions, such as long thermal treatments, expensive raw materials, and complex operation. In this study, we propose a co-precipitation method for synthesizing the LAGP solid electrolyte with low-cost and nontoxic GeO2 as the germanium source. Process optimization in the pH value and water bath temperature was employed as a strategy to eliminate the remnants of GeO2, and the pure LAGP phase is acquired. Moreover, the co-precipitation method can also reduce the sintering temperature of LAGP to 750 °C so that uniform nano-LAGP grains (∼150 nm) can be obtained. During the subsequent processing, denser LAGP pellets are fabricated and exhibit a high ionic conductivity of 5.87 × 10−4 S cm−1 at 30 °C; the Li/Li symmetrical batteries periodically cycle at room temperature for above 310 h with a constant current density of 0.05 mA cm−2. [ABSTRACT FROM AUTHOR]

Exploring solid electrolytes with promising electrical properties and desirable compatibility toward electrodes for safe and high-energy sodium metal batteries remains a challenge. In this work, these issues are addressed via an in situ hybrid strategy, viz., highly conductive and thermally stable 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide is immobilized in nanoscale silica skeletons to form ionogel via a non-hydrolytic sol-gel route, followed by hybridizing with polymeric poly(ethylene oxide) and inorganic conductor Na3Zr2Si2PO12. Such hybrid design yields the required solid electrolyte, which shows not only a stable electrochemical stability window of 5.4 V vs Na/Na+ but also an extremely high ionic conductivity of 1.5 × 10−3 S cm−1 at 25 °C, which is demonstrated with the interacted and monolithic structure of the electrolyte by SEM, XRD, thermogravimetric (TG), and XPS. Moreover, the capabilities of suppressing sodium metal dendrite growth and enabling high-voltage cathode Mg-doped P2-type Na0.67Ni0.33Mn0.67O2 are verified. This work demonstrates the potential to explore the required solid electrolytes by hybridizing an in situ ionogel, a polymer, and an inorganic conductor for safe and high-energy solid-state sodium metal batteries. [ABSTRACT FROM AUTHOR]