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Electrolyte engineering is a highly promising strategy in lithium-sulfur batteries to increase the sulfur utilization and maintain a stable interface at the lithium metal anode for long-term cycling. Whereas high donor electrolytes can increase the solubility of polysulfides to promote the sulfur utilization and therefore operate under lean electrolyte conditions, their poor thermodynamic stability toward lithium metal anode causes uncontrolled decomposition at its interface and impair the cycle life severely. Here, we introduce a dual functional high donor electrolyte, 3-fluoropyridine (3-FPN), to simultaneously achieve high polysulfide solubility up to 1.5 M and compatibility with lithium metal. These features result in a high specific capacity of 1087.9 mAh g(sulfur)(-1) and robust cycling under a lean electrolyte condition of 7 mu Lelectrolyte mgsulfur-1in the absence of LiNO3. Remarkably, 3-FPN preserves stable cyclability even at a high areal sulfur loading of 8 mgsulfur cm-2, which opens a new avenue in advancing the electrolytes for lithium-sulfur batteries toward their high volumetric energy density and long cycle life.

Sulfide‐based all‐solid‐state batteries (ASSBs) have been featured as promising alternatives to the current lithium‐ion batteries (LIBs) mainly owing to their superior safety. Nevertheless, a solution‐based scalable manufacturing scheme has not yet been established because of the incompatible polarity of the binder, solvent, and sulfide electrolyte during slurry preparation. This dilemma is overcome by subjecting the acrylate (co)polymeric binders to protection−deprotection chemistry. Protection by the tert‐butyl group allows for homogeneous dispersion of the binder in the slurry based on a relatively less polar solvent, with subsequent heat‐treatment during the drying process to cleave the tert‐butyl group. This exposes the polar carboxylic acid groups, which are then able to engage in hydrogen bonding with the active cathode material, high‐nickel layered oxide. Deprotection strengthens the electrode adhesion such that the strength equals that of commercial LIB electrodes, and the key electrochemical performance parameters are improved markedly in both half‐cell and full‐cell settings. The present study highlights the potential of sulfide‐based ASSBs for scalable manufacturing and also provides insights that protection−deprotection chemistry can generally be used for various battery cells that suffer from polarity incompatibility among multiple electrode components.

Organosulfur polymers have emerged as promising electrode materials for lithium– sulfur (Li–S) batteries, mainly because of their ability to incorporate and stabilize high sulfur content. The low ionic and electronic conductivity of these polymers, however, limit their cycling performance at high active mass loadings. Moreover, Li–polysulfide (Li–PS) shuttling, a fatal phenomenon in the cyclability of Li–S batteries, can be mitigated via the entrapment of Li–PS by utilizing various supramolecular interactions. Herein, we report a new approach that incorporates one-dimensional charged polypyrrole into a two-dimensional covalent triazine framework (cPpy-S-CTF) synthesized in the presence of elemental sulfur. The cPpy-S-CTF enabled sulfur loadings up to 83 wt %, thanks to the perfluoroaryl-elemental sulfur SNAr chemistry. Notably, the addition of charged polypyrrole, cPpy, triggered a 3D nanochannel formation in the cPpy-S-CTF with high-affinity anchoring sites toward Li–PS, while achieving decent ionic and electronic conductivity. The cPpy-S-CTF showed a remarkable electrochemical performance with a specific capacity of 1203.4 mA h g–1 at 0.05 C, an initial Coulombic efficiency of 94.1%, and a capacity retention of 86.8% after 500 cycles. These results point to the fact that the incorporation of charged conducting polymers could be a universal strategy to boost the electrochemical performance of organosulfur polymers in Li–S batteries.

A new strategy for the synthesis of a covalent triazine framework (CTF‐1) was introduced based on the cyclotrimerization reaction of 1,4‐dicyanobenzene using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) under ionothermal conditions. LiTFSI not only served as a catalyst, but also facilitated the in situ generation and homogeneous distribution of LiF particles across the framework. The hierarchical structure resulting upon integration of CTF‐LiF onto an airlaid‐paper (AP) offered unique features for lithium metal anodes, such as lithiophilicity from CTF, interface stabilization from LiF, and sufficient lithium storage space from AP. Based on this synergistic effect, the AP‐CTF‐LiF anode exhibited stable cycling performance even at a current density of 10 mA cm−2

Despite their unparalleled theoretical capacity, lithium‐metal anodes suffer from well‐ known indiscriminate dendrite growth and parasitic surface reactions. Conductive scaffolds with lithium uptake capacity are recently highlighted as promising lithium hosts, and carbon nanotubes (CNTs) are an ideal candidate for this purpose because of their capability of percolating a conductive network. However, CNT networks are prone to rupture easily due to a large tensile stress generated during lithium uptake– release cycles. Herein, CNT networks integrated with a polyrotaxane‐incorporated poly(acrylic acid) (PRPAA) binder via supramolecular interactions are reported, in which the ring‐sliding motion of the polyrotaxanes endows extraordinary stretchability and elasticity to the entire binder network. In comparison to a control sample with inelastic binder (i.e., poly(vinyl alcohol)), the CNT network with PRPAA binder can endure a large stress during repeated lithium uptake–release cycles, thereby enhancing the mechanical integrity of the corresponding electrode over battery cycling. As a result, the PRPAA‐incorporated CNT network exhibits substantially improved cyclability in lithium–copper asymmetric cells and full cells paired with olivine‐LiFePO4, indicating that high elasticity enabled by mechanically interlocked molecules such as polyrotaxanes can be a useful concept in advancing lithium‐metal batteries.

Bistable [2]rotaxanes are a unique class of supramolecules that have two constitutional isomers. Upon sandwiched between two electrodes, these two isomeric states show different conducting states, thus behaving as molecular switches. In this thesis, I describe how the bistable [2]rotaxanes have been investigated to ensure that the switching characteristics in solid-state devices are those of the bistable [2]rotaxanes and not those of extraneous elements. In addition, integration of these molecules onto ultradense nanowire arrays to constitute a memory circuit is presented. The bistable [2]rotaxanes have been examined in various environments to study kinetics and ground-state thermodynamics between both isomeric states. In the kinetic study, as molecules are embedded in more viscous environments (solution→polymer gel→solid-state device), a key step in switching cycle slows down significantly, thus reflecting the environments where the molecules are surrounded. In thermodynamic study, one of the major units in the molecular structure was modified and then equilibrium population ratio between both isomeric states was monitored at various temperatures. In both solution and solid-state devices, the population ratio of the modified [2]rotaxane was more sensitive to temperature. This result is very critical in that the properties of devices can be tailored by manipulating the structure of molecular components. The bistable [2]rotaxanes were integrated into crossbar nanowire arrays to constitute a memory circuit. Ultra-dense nanowire arrays used as electrodes are generated by superlattice nanowire pattern transfer (SNAP) method. Due to extremely narrow pitch (~33 nm) of the SNAP nanowire arrays, the device sets a remarkable record in memory density (~1011 Bits/cm2). Although the circuits were found to have large numbers of defects, those defects were identified through electronic testing and the working bits were configured to form a f

Lithium ion batteries are encountering ever-growing demand for further increases in energy density. Li-rich layered oxides are considered a feasible solution to meet this demand because their specific capacities often surpass 200 mAh g^<−1> due to the additional lithium occupation in the transition metal layers. However, this lithium arrangement, in turn, triggers cation mixing with the transition metals, causing phase transitions during cycling and loss of reversible capacity. Here we report a Li-rich layered surface bearing a consistent framework with the host, in which nickel is regularly arranged between the transition metal layers. This surface structure mitigates unwanted phase transitions, improving the cycling stability. This surface modification enables a reversible capacity of 218.3 mAh g^<−1> at 1C (250 mA g^<−1>) with improved cycle retention (94.1% after 100 cycles). The present surface design can be applied to various battery electrodes that suffer from structural degradations propagating from the surface., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/15369

The effects of surface treatment combining corona discharge and hydrogen peroxide (H2O2) on the electrochemical performance of carbon felt electrodes for vanadium redox flow batteries (VRFBs) have been thoroughly investigated. A high concentration of oxygen functional groups has been successfully introduced onto the surface of the carbon felt electrodes by a specially designed surface treatment, which is mainly responsible for improving the energy efficiency of VRFBs. In addition, the wettability of the carbon felt electrodes also can be significantly improved. The energy efficiency of the VRFB cell employing the surface modified carbon felt electrodes is improved by 7% at high current density (148 mA cm−2). Such improvement is attributed to the faster charge transfer and better wettability allowed by surface-active oxygen functional groups. Moreover, this method is much more competitive than other surface treatments in terms of processing time, production costs, and electrochemical performance.

We describe our research into building integrated molecular electronics circuitry for a diverse set of functions, and with a focus on the fundamental scientific issues that surround this project. In particular, we discuss experiments aimed at understanding the function of bistable [2]rotaxane molecular electronic switches by correlating the switching kinetics and ground state thermodynamic properties of those switches in various environments, ranging from the solution phase to a Langmuir monolayer of the switching molecules sandwiched between two electrodes. We discuss various devices, low bit-density memory circuits, and ultra-high density memory circuits that utilize the electrochemical switching characteristics of these molecules in conjunction with novel patterning methods. We also discuss interconnect schemes that are capable of bridging the micrometre to submicrometre length scales of conventional patterning approaches to the near-molecular length scales of the ultra-dense memory circuits. Finally, we discuss some of the challenges associated with fabricated ultra-dense molecular electronic integrated circuits.