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Li metal is regarded as the "Holy Grail" in the next generation of anode materials due to its high theoretical capacity and low redox potential. However, sluggish Li ions interfacial transport kinetics and uncontrollable Li dendrites growth limit practical application of the energy storage system in high‐power device. Herein, separators are modified by the addition of a coating, which spontaneously grafts onto the Li anode interface for in situ lithiation. The resultant alloy possessing of strong electron‐donating property promotes the decomposition of lithium bistrifluoromethane sulfonimide in the electrolyte to form a LiF‐rich alloy‐doped solid electrolyte interface (SEI) layer. High ionic alloy solid solution diffusivity and electric field dispersion modulation accelerate Li ions transport and uniform stripping/plating, resulting in a high‐power dendrite‐free Li metal anode interface. Surprisingly, the formulated SEI layer achieves an ultra‐long cycle life of over 8000 h (20,000 cycles) for symmetric cells at a current density of 10 mA cm−2. It also ensures that the NCM(811)//PP@Au//Li full cell at ultra‐high currents (40 C) completes the charging/discharging process in only 68 s to provide high capacity of 151 mAh g−1. The results confirm that this scalable strategy has great development potential in realizing high power dendrite‐free Li metal anode. [ABSTRACT FROM AUTHOR]

Crystalline diphosphonium iodides [MeR2P‐spacer‐R2Me]I with phenylene (1, 2), naphthalene (3, 4), biphenyl (5) and anthracene (6) as aromatic spacers, are photoemissive under ambient conditions. The emission colors (λem values from 550 to 880 nm) and intensities (Φem reaching 0.75) are defined by the composition and substitution geometry of the central conjugated chromophore motif, and the anion‐π interactions. Time‐resolved and variable‐temperature luminescence studies suggest phosphorescence for all the titled compounds, which demonstrate observed lifetimes of 0.46–92.23 μs at 297 K. Radiative rate constants kr as high as 2.8×105 s−1 deduced for salts 1–3 were assigned to strong spin‐orbit coupling enhanced by an external heavy atom effect arising from the anion‐π charge‐transfer character of the triplet excited state. These rates of anomalously fast metal‐free phosphorescence are comparable to those of transition metal complexes and organic luminophores that utilize triplet excitons via a thermally activated delayed fluorescence mechanism, making such ionic luminophores a new paradigm for the design of photofunctional and responsive molecular materials. [ABSTRACT FROM AUTHOR]

Ionic organic crystals containing organic planar π‐conjugated units has become one of the hot spots as nonlinear optical (NLO) materials. However, although this type of ionic organic NLO crystals commonly have remarkable second harmonic generation (SHG) responses, they also suffer from overlarge birefringences and relatively small band gaps that be hardly beyond 6.2 eV. Herein, a flexible π‐conjugated [C3H(CH3)O4]2− unit was theoretically revealed, showing great potential for designing NLO crystals with balanced optical properties. Accordingly, through the reasonable NLO‐favourable layered design, a new ionic organic material, NH4[LiC3H(CH3)O4], was successfully obtained. As expected, it achieves not only a large SHG effect (4×KDP), but also a suitable birefringence (0.06@546 nm) and an ultrawide band gap (>6.5 eV). This study provides a new flexible π‐conjugated NLO‐active unit, contributing to design more ionic organic NLO materials with excellent balanced optical properties. [ABSTRACT FROM AUTHOR]

Among ferroelectric crystals based on small molecules, plastic/ferroelectric crystals are currently receiving particular attention because they can be used as bulk polycrystals. Herein, we show that an ionic molecular ferroelectric crystal, guanidinium tetrafluoroborate, exhibits significant malleability and multiaxial ferroelectricity despite the absence of a plastic crystal phase. Powder samples of this crystal can be processed into transparent bulk crystalline plates either by press‐forming or by melt‐growing. The plates show high ferroelectric performance and related properties, demonstrating the largest hitherto reported spontaneous polarization for bulk polycrystals of small‐molecule‐based ferroelectrics. Owing to the ready availability of large‐scale materials and processability into various bulk crystalline forms, this ferroelectric crystal represents a highly promising functional material that will boost research on diverse applications as bulk crystals. [ABSTRACT FROM AUTHOR]

Under cold pressure sp1/sp2‐to‐sp3 hybridization transformation has been exclusively observed in covalent or molecular crystals overwhelmingly above ≈10 GPa, and the approaches to lower the transition pressure are limited on external heat‐treatment and/or catalyzers. Herein we demonstrate that, by internal‐lattice stress‐transfer from ionic to covalent groups, the transformation can be significantly prompted, as shown in a crystal of LiBO2 under 2.85 GPa for the first case in ionic crystals. This unprecedentedly low transformation pressure is ascribed to the enhanced localized stress on covalent B−O frames transferred from ionic Li−O bonds in LiBO2, and accordingly the corresponding structural feature is summarized. This work provides an internal structural regulation strategy for pressure‐reduction of the s‐p orbital hybridization transformation and extends the sp1/sp2‐to‐sp3 transformation landscape from molecular and covalent compounds to ionic systems. [ABSTRACT FROM AUTHOR]

Der so genannte SCILL‐Katalysator (englisch: solid catalyst with ionic liquid layer) beschreibt ein neues, äußerst erfolgreiches Konzept im Bereich der heterogenen Katalyse. Hierbei besteht die Grundidee darin, die Selektivität eines Katalysators durch die Beladung mit ionischen Flüssigkeiten drastisch zu erhöhen. In dieser Arbeit zeigen wir, dass das Konzept auf die Elektrokatalyse übertragbar ist und zur selektiven Umsetzung von organischen Verbindungen genutzt werden kann. Bei der hier untersuchten Elektrooxidation von 2,3‐Butandiol können zwei Produkte entstehen. Das einfach oxidierte Acetoin und das zweifach oxidierte Diacetyl. Durch die Zugabe einer ionischen Flüssigkeit (1‐Ethyl‐3‐methyl‐imidazolium‐trifluormethansulfonat, [C2C1Im][OTf]) kann die Selektivität des Katalysators zu Gunsten der Acetoinbildung drastisch erhöht werden. Der zugrundeliegende Mechanismus wurde dabei spektroskopisch in situ untersucht: Die Adsorption des Anions der ionischen Flüssigkeit verhindert die Wasseraktivierung. Dies unterbindet den zweiten Oxidationsschritt vom Acetoin zum Diacetyl und erhöht damit die Selektivität. Unsere Studie zeigt das große Potential elektrochemischer SCILL‐Katalysatoren für die selektive Umsetzung von organischen Verbindungen. [ABSTRACT FROM AUTHOR]

Recent development of most organic long persistent luminescence (OLPL) systems employed binary or tertiary doping. However, the design strategies towards OLPL materials with hour‐long afterglow duration are still quite limited. Here, we propose a novel OLPL system through melt‐casting method with 0.1 mol % of CuI complexes: 2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl BINAP‐CuX (X=Cl, Br and I) doped into the triphenylphosphine (TPP) host. The charge separation was initiated prior to excitation through host coordination with CuI complexes, resulting in semi‐free halogen ions and in situ generated CuI cations, which forms TPP + BINAP‐CuX ionic pairs and subsequently ionic solids. The OLPL lifetime can be readily modulated by different halogen atoms and the afterglow can last up to more than 3 hours perceivable to human eyes. This is a rare example of OLPL initiated through host‐guest coordination that could potentially expand the definition of OLPL systems and design strategies. [ABSTRACT FROM AUTHOR]

Emerging machine learning (ML) methods are widely applied in chemistry and materials science studies and have led to a focus on data‐driven research. This Minireview summarizes the application of ML to rechargeable batteries, from the microscale to the macroscale. Specifically, ML offers a strategy to explore new functionals for density functional theory calculations and new potentials for molecular dynamics simulations, which are expected to significantly enhance the challenging descriptions of interfaces and amorphous structures. ML also possesses a great potential to mine and unveil valuable information from both experimental and theoretical datasets. A quantitative "structure–function" correlation can thus be established, which can be used to predict the ionic conductivity of solids as well as the battery lifespan. ML also exhibits great advantages in strategy optimization, such as fast‐charge procedures. The future combination of multiscale simulations, experiments, and ML is also discussed and the role of humans in data‐driven research is highlighted. [ABSTRACT FROM AUTHOR]

In this study, we developed a superstrong and reversible adhesive, which can possess a high bonding strength in the "adhesive" state and detach with the application of heating. An ionic crystal (IC) gel, in which an IC was immobilized within a soft‐polymer matrix, were synthesized via in situ photo‐crosslinking of a precursor solution composed of N, N‐dimethyl acrylamide (DMAA) and a melted IC. The obtained IC gel is homogenous and transparent at melt point. When cooled to the phase transition temperature of the IC, the gel turns into the adhesive with the adhesion strength of 5.82 MPa (on glasses), due to the excellent wetting of melted gel and a thin layer of crystalline IC with high cohesive strength formed on the substrates. The synergistic effects between IC, polymer networks and substrates were investigated by solid state 1H NMR and molecular dynamics simulation. Such an adhesive layer is reversable and can be detached by heating and subsequent re‐adhesion via cooling. This study proposed the new design of removable adhesives, which can be used in dynamic and complex environments. [ABSTRACT FROM AUTHOR]

Although organic ionic crystals represent an attractive class of active materials for rechargeable batteries owing to their high capacity and low solubility in electrolytes, they generally suffer from limited electronic conductivity and moderate voltage. Furthermore, the charge storage mechanism and structural evolution during the redox processes are still not clearly understood. Here we describe ethyl viologen iodide (EVI2) and ethyl viologen diperchlorate (EV(ClO4)2) as cathode materials of lithium batteries which crystallize in a monoclinic system with alternating organic EV2+ layers and inorganic I−/ClO4− layers. The EVI2 electrode exhibits a high initial discharge plateau of 3.7 V (vs. Li+/Li) because of its anion storage ability. When I− is replaced by ClO4−, the obtained EV(ClO4)2 electrode displays excellent rate performance with a theoretical capacity of 78 % even at 5 C owing to the good electron conductivity of ClO4− layers. EVI2 and EV(ClO4)2 also show excellent cycling stability (capacity retention >96 % after 200 cycles). [ABSTRACT FROM AUTHOR]

Aminocyclopropenium ions have raised much attention as organocatalysts and redox active polymers. However, the self‐assembly of amphiphilic aminocyclopropenium ions remains challenging. The first deltic ionic liquid crystals based on aminocyclopropenium ions have been developed. Differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction provided insight into the unique self‐assembly and nanosegregation of these liquid crystals. While the combination of small headgroups with linear p‐alkoxyphenyl units led to bilayer‐type smectic mesophases, wedge‐shaped units resulted in columnar mesophases. Upon increasing the size and polyphilicity of the aminocyclopropenium headgroup, a lamellar phase was formed. [ABSTRACT FROM AUTHOR]

The Pauling rules have been used for decades to rationalise the crystal structures of ionic compounds. Despite their importance, there has been no statistical assessment of the performances of these five empirical rules so far. Here, we rigorously and automatically test all five Pauling rules for a large data set of around 5000 known oxides. We discuss each Pauling rule separately, stressing their limits and range of application in terms of chemistries and structures. We conclude that only 13 % of the oxides simultaneously satisfy the last four rules, indicating a much lower predictive power than expected. [ABSTRACT FROM AUTHOR]

Water, considered as a universal solvent to dissolve salts, has been extensively studied as liquid electrolyte in electrochemical devices. The water/ice phase transition at around 0 °C presents a common phenomenon in nature, however, the chemical and electrochemical behaviors of ice have rarely been studied. Herein, we discovered that the ice phase provides efficient ionic transport channels and therefore can be applied as generalized solid‐state ionic conductor. Solid state ionic conducting ices (ICIs) of Li+, Na+, Mg2+, Al3+, K+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+, frozen from corresponding sulphate solutions, exhibit ionic conductivities ranging from ≈10−7 S cm−1 (Zn2+) to ≈10−3 S cm−1 (Li+) at temperatures spanning from −20 °C to −5 °C. The discovery of ICIs opens new insight to design and fabrication of solid‐state electrolytes that are simple, inexpensive, and versatile. [ABSTRACT FROM AUTHOR]

Abstract: A new type of materials, organic salts in the crystal state, have ultralong organic phosphorescence (UOP) under ambient conditions. The change of cations (NH4+, Na+, or K+) in these phosphors gives access to tunable UOP colors ranging from sky blue to yellow green, along with ultralong emission lifetimes of over 504 ms. Single‐crystal analysis reveals that unique ionic bonding can promote an ordered arrangement of organic salts in crystal state, which then can facilitate molecular aggregation for UOP generation. Additionally, reversible ultralong phosphorescence can be realized through the alternative employment of fuming gases (ammonia and hydrogen chloride), demonstrating its potential as a candidate for visual ammonic or hydrogen chloride gas sensing. The results provide an environmental responsible and practicable synthetic approach to expanding the scope of ultralong organic phosphorescent materials as well as their applications. [ABSTRACT FROM AUTHOR]

Since the first prediction by Frenkel, many follow-up studies have been carried out to show the presence of subsurface space-charge layers having the opposite sign to that of the excess charge at the surface, producing overall neutrality in ionic crystals. However, no precise experimental evidence demonstrating how the aliovalent solutes segregate in the space-charge region beneath the surface has been provided over the past several decades. By utilizing atomic-scale imaging and chemical probing in a perovskite oxide, the origin of the surface excess charge at the topmost surface and the position of segregated dopants in the space-charge region is precisely determined. The impact of the space-charge contribution to the dopant distribution near the surface in oxide crystals is explored. [ABSTRACT FROM AUTHOR]

Cation adsorption and exchange has been an important topic in both basic and applied chemistry relevant to materials synthesis and chemical conversion, as well as purification and separation. Selective Cs+ uptake from aqueous solutions is especially important because Cs+ is expensive and is contained in radioactive wastes. However, the reported adsorbents incorporate Rb+ as well as Cs+, and an adsorbent with high selectivity toward Cs+ has not yet been reported. Highly selective uptake of Cs+ by an ionic crystal (etpyH)2[Cr3O(OOCH)6(etpy)3]2[α-SiMo12O40]⋅3 H2O (etpy =4-ethylpyridine) is described. The compound incorporated up to 3.8 mol(Cs+) mol(s)−1 (where s=solid) by cation-exchange with etpyH+ and reduction of silicododecamolybdate with ascorbic acid. The amount of Cs+ uptake was comparable to that of Prussian blue, which is widely recognized as a good Cs+ adsorbent. Moreover, other alkali-metal and alkaline-earth-metal cations were almost completely excluded (<0.2 mol mol(s)−1). [ABSTRACT FROM AUTHOR]

The first cycloparaphenylene (CPP)-based ionic donor-acceptor supramolecule Li+@C60⊂[10]CPP⋅X− has been synthesized. X-ray crystallography not only confirmed the molecular structure of Li+@C60⊂[10]CPP⋅X− but also uncovered the formation of a unique ionic crystal. The strong charge-transfer interaction between [10]CPP and Li+@C60, which was confirmed by electrochemical measurement and spectroscopic analyses, caused significant delocalization of the positive charge across the entire complex. [ABSTRACT FROM AUTHOR]

Ionic crystals (ICs) of the azobenzene derivatives show photoinduced IC-ionic liquid (IL) phase transition (photoliquefaction) upon UV-irradiation, and the resulting cis-azobenzene ILs are reversibly photocrystallized by illumination with visible light. The photoliquefaction of ICs is accompanied by a significant increase in ionic conductivity at ambient temperature. The photoliquefaction also brings the azobenzene ICs further significance as photon energy storage materials. The cis-IL shows thermally induced crystallization to the trans-IC phase. This transition is accompanied by exothermic peaks with a total ΔH of 97.1 kJmol-1, which is almost double the conformational energy stored in cisazobenzene chromophores. Thus, the integration of photoresponsive ILs and self-assembly pushes the limit of solar thermal batteries. [ABSTRACT FROM AUTHOR]