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Wearable strain transducers are poised to transform the field of healthcare owing to the promise of personalized devices capable of real‐time collection of human physiological health indicators. For instance, monitoring patients' progress following injury and/or surgery during physiotherapy is crucial but rarely performed outside clinics. Herein, multifunctional liquid‐free ionic elastomers are designed through the volume effect and the formation of dynamic hydrogen bond networks between polyvinyl alcohol (PVA) and weak acids (phosphoric acid, phytic acid, formic acid, citric acid). An ultra‐stretchable (4600% strain), highly conducting (10 mS cm−1), self‐repairable (77% of initial strain), and adhesive ionic elastomer is obtained at high loadings of phytic acid (4:1 weight to PVA). Moreover, the elastomer displayed durable performances, with intact mechanical properties after a year of storage. The elastomer is used as a transducer to monitor human motions in a device comprising an ESP32‐based development board. The device detected walking and/or running biomechanics and communicated motion‐sensing data (i.e., amplitude, frequency) wirelessly. The reported technology can also be applied to other body parts to monitor recovery after injury and/or surgery and inform practitioners of motion biomechanics remotely and in real time to increase convalescence effectiveness, reduce clinic appointments, and prevent injuries. [ABSTRACT FROM AUTHOR]

The formation of an electric double‐layer (EDL) is an important phenomenon for many research areas, including energy storage technology. Although EDL is well‐known in electrochemistry, most of the studies involve the characterization of liquid electrolyte/electrode interfaces, and only a limited number of studies in solid‐solid contacts, such as solid electrolyte/electrode interface are available. This paper employed electrochemical impedance spectroscopy (EIS) to systematically investigate the influence of experimental factors in the interfacial capacitance arising from the electrode polarization in a lithium disilicate glass/gold electrode interface. It analyzed the influence of a.c. input voltage amplitude, samples' roughness (mechanical and chemomechanical polishing) and thickness, range of applied frequency and temperature, and the number of impedance cycles. In short, it was found that an input voltage range of 15–60 mV is indicated to minimize potential electrochemical processes during electrode polarization, where the data is reproducible from the second measurement cycle onward. Smoother surfaces closely approximated ideal electrode spike behavior, with surface treatment exhibiting influence on interfacial capacitance values. Moreover, as expected, we observed an increase in relative permittivity values with increasing thickness, accompanied by decreased capacitance values. Finally, by employing optimal experimental conditions and analyzing the inflection frequency (finflection${{f}_{inflection}}$) of the ε′$\varepsilon ^{\prime}$ versus log(f$f$) curve, we determined that the ratio between effective charge carriers (ne${{n}_e}$) and the total number of charge carriers (nt${{n}_t}$) nent$\frac{{{{n}_e}}}{{{{n}_t}}}$ falls within the range of 5–12% between 130°C and 280°C. [ABSTRACT FROM AUTHOR]

Garnet-type solid electrolytes stand out as promising Li-ion conductors for the next-generation batteries. It has been demonstrated that the inherent properties of garnets can be tailored by introducing various dopants into their crystal structures. Recently, there has been a growing interest in the concept of high entropy stabilization for materials design. In this study, we synthesized high-entropy garnets denoted as Li6La3Zro.7Tio.3Tao.5Sbo.5Oi2 (LLZTTSO), wherein Ti, Sb, and Ta occupy the Zr site. The formation of the cubic garnet phase in LLZTTSO was confirmed through X-ray diffraction (XRD), and the resulting lattice parameter agreed with predictions made using computational methods. Despite the substantial porosity (relative density 80.6%) attributed to the low sintering temperature, LLZTTSO exhibits a bulk ionic conductivity of 0.099 mS cm-1 at 25°C, and a total ionic conductivity of 0.088 mS cm-1, accompanied by an activation energy of 0.497 eV. Furthermore, LLZTTSO demonstrates a critical current density of 0.275mAcm-2 at 25°C, showcasing its potential even without any interfacial modification. [ABSTRACT FROM AUTHOR]

Inspired by human skin, soft sensors that are capable of sensing various external signals have been an active area of research. However, the vast majority of the developed soft sensors still lag far behind human skin in terms of multimodal sensing capability. Herein, this work reports on a multimodal soft sensor that can decouple thermal and mechanical signals. The sensor is made of poly(ethylene glycol) gel (PEGgel) containing ionic liquid, which is stretchable and transparent and shows decent strain and temperature sensing performances. Importantly, analysis of the ion relaxation dynamics shows that the charge relaxation time and capacitance change of the sensor are independently sensitive to the variations of temperature and mechanical deformation, respectively. By measuring the charge relaxation time and capacitance, the thermal and mechanical signals detected by the PEGgel sensor can be nicely decoupled without signal interference. Such a multimodal soft sensor may serve as a starting point for the development of lifelike soft sensors for high‐tech applications in a variety of fields such as soft robotics, the internet of things, and human–machine interaction. [ABSTRACT FROM AUTHOR]

This study explores multi-component garnet-based materials as solid electrolytes for all-solid-state lithium batteries. Through a combination of computational and experimental approaches, we investigate the thermodynamic and structural properties of lithium lanthanum zirconium oxide garnets doped with various elements. Applying density functional theory, the influence of dopants on the thermodynamic stability of these garnets was studied. Probable atomic configurations and their impact on materials' properties were investigated with the focus on understanding the influence of these configurations on structural stability, phase preference, and ionic conductivity. In addition to the computational study, series of cubic-phase garnet compounds were synthesized and their electrochemical performance was evaluated experimentally. Our findings reveal that the stability of cubic phase in doped Li-garnets is primarily governed by enthalpy, with configurational entropy playing a secondary role. Moreover, we establish that the increased number of doping elements significantly enhances the cubic phase's stability. This in-depth understanding of materials' properties at atomic level establishes the basis for optimizing high-entropy ceramics, contributing significantly to the advancement of solid-state lithium batteries and other applications requiring innovative material solutions. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) have emerged as a promising platform for biosensing, electrophysiology, and neuromorphic devices. However, OECTs are often limited by the stability of the channel materials. Here, we systematically investigate the stability of OECT channels under varied operating voltage ranges. We find that OECT materials can be operated with high stability when the voltage range is reduced. We show that repeated full voltage cycling degrades device performance. The results indicate that to maximize stability, OECTs should either be operated in the saturation regime to maximize current gain (transconductance) or in the subthreshold regime to maximize the on/off ratio. [ABSTRACT FROM AUTHOR]

The need to develop safe solid-state lithium batteries has stimulated intense research efforts for Li+ solid electrolytes. However, the low conductivity limits the development of NASICON LiZr 2 (PO 4) 3 (LZP) electrolyte. Here, the doping effects of Ta on the structure, surface morphologies and electrochemical properties of Li 1- x Zr 2- x Ta x (PO 4) 3 (LZTP, x = 0, 0.01, 0.02, 0.04, 0.06 and 0.08) solid electrolyte were analyzed. LZTP was prepared using a simple solid-state reaction route, followed by sintering at 1200 °C for 12 h. A proper content of Ta5+ substitution for Zr4+ is beneficial to stabilize the high conductive rhombohedral (α) phase of LZP at room temperature. Doping Ta5+ is conducive to unblocking of Li+ at the M1 site and facilitates the occupation of Li+ at the M2 site, thereby expanding the pathway for Li+ conduction. Rietveld refinement data demonstrated that the Zr–O and P–O bond lengths (d Zr-O and d P-O) increased with a decrease in Zr–O–P bond angles (θ Zr-O-P) as x rose. The distortions in the ZrO 6 octahedron may weaken the coulomb attraction in Li+-O2-, resulting in a lower activation energy (E a) and a higher Li+ conductivity. The highest room-temperature conductivity (6.06 × 10−5 S cm−1) was obtained at x = 0.06, which reached 1.5 × 10−4 S cm−1 at 50 °C. The E a was found to decrease from 0.388 eV (x = 0) to 0.306 eV (x = 0.06). In addition, Ta doping resulted in improved connectivity and reduced pore formation, which also contributed to the decrease in resistance. The Raman spectrum demonstrated that some phonon modes of bending vibration in PO 4 were degenerate and external modes became too weak to be observed or even disappeared as Ta content increased. This change in the modes also had an impact on the Li+ conductivity. Overall, the LZTP-0.06 appears to be a promising candidate for the solid electrolyte. [ABSTRACT FROM AUTHOR]

Garnet-type solid electrolytes stand out as promising Li-ion conductors for the next-generation batteries. It has been demonstrated that the inherent properties of garnets can be tailored by introducing various dopants into their crystal structures. Recently, there has been a growing interest in the concept of high entropy stabilization for materials design. In this study, we synthesized high-entropy garnets denoted as Li6La3Zr0.7Ti0.3Ta0.5Sb0.5O12 (LLZTTSO), wherein Ti, Sb, and Ta occupy the Zr site. The formation of the cubic garnet phase in LLZTTSO was confirmed through X-ray diffraction (XRD), and the resulting lattice parameter agreed with predictions made using computational methods. Despite the substantial porosity (relative density 80.6%) attributed to the low sintering temperature, LLZTTSO exhibits a bulk ionic conductivity of 0.099 mS cm−1 at 25°C, and a total ionic conductivity of 0.088 mS cm−1, accompanied by an activation energy of 0.497 eV. Furthermore, LLZTTSO demonstrates a critical current density of 0.275 mA cm−2 at 25°C, showcasing its potential even without any interfacial modification.

This study explores multi-component garnet-based materials as solid electrolytes for all-solid-state lithium batteries. Through a combination of computational and experimental approaches, we investigate the thermodynamic and structural properties of lithium lanthanum zirconium oxide garnets doped with various elements. Applying density functional theory, the influence of dopants on the thermodynamic stability of these garnets was studied. Probable atomic configurations and their impact on materials’ properties were investigated with the focus on understanding the influence of these configurations on structural stability, phase preference, and ionic conductivity. In addition to the computational study, series of cubic-phase garnet compounds were synthesized and their electrochemical performance was evaluated experimentally. Our findings reveal that the stability of cubic phase in doped Li-garnets is primarily governed by enthalpy, with configurational entropy playing a secondary role. Moreover, we establish that the increased number of doping elements significantly enhances the cubic phase’s stability. This in-depth understanding of materials’ properties at atomic level establishes the basis for optimizing high-entropy ceramics, contributing significantly to the advancement of solid-state lithium batteries and other applications requiring innovative material solutions.

Microstructure control of composite electrodes comprising active materials and solid electrolytes is imperative to achieve sufficient ion‐ and electron‐conductive pathways for the development of all‐solid‐state Li ion batteries. Here, we synthesized Li10GeP2S12 solid electrolytes with various particle size distributions by milling and filtering. Impedance spectroscopy revealed that the ionic conductivities in the bulk were hardly changed by the synthetic processes. This enabled us to investigate only the microstructure effects on the electrochemical properties of the composite electrodes. Microscopic and electrochemical tests of the LiCoO2‐Li10GeP2S12 composite cathodes clarified that the size distributions of the Li10GeP2S12 drastically affected the microstructures in the composite cathodes, such as contacts at interfaces and voids between particles. The size distributions also contributed to the appropriate ratio of LiCoO2 to Li10GeP2S12 for superior charge/discharge properties. The (de)intercalation reversibly proceeded in the composite cathode using the filtered Li10GeP2S12 even though the ratio of Li10GeP2S12 decreased from 50 % to 30 % in volume. This study demonstrated the possibility of high‐energy‐density composite cathodes for all‐solid‐state batteries by control of microstructures in composite electrodes. [ABSTRACT FROM AUTHOR]

Low‐grade heat is ubiquitous in the environment and its thermoelectric conversion by the ionic conductors remains a challenge because of the low efficiency and poor sustainability. Here we demonstrate that the thermoelectric performances can be boosted by combining the Soret effect of protons and proton‐coupled electron transfer (PCET) reaction of benzoquinone and hydroquinone in hydrogels. An overall enhancement of thermopower (25.9 mV K−1), power factor (5 mW m−1 K−2), figure of merit (>2.4) and continuity of power output is achieved. Moreover, an energy‐storage function can be achieved by the redox couple, and a retained power output of 27.7 %, or 14 mW m−2 for more than 3 hours is obtained by the re‐balance of PCET reactants in the hydrogel after the removal of the temperature gradient. [ABSTRACT FROM AUTHOR]

Argyrodites, Li6PS5X (X=Cl, Br, I), have piqued the interest of researchers by offering promising lithium ionic conductivity for their application in all-solid-state batteries (ASSBs). However, other than Li6PS5Cl (651Cl) and Li6PS5Br (651Br), Li6PS5I (651I) shows poor ionic conductivity (10−7 S cm−1 at 298 K). Herein, we present Al-doped 651I with I−/S2− site disordering to lower activation energy (Ea) and improve ionic conductivity. They formed argyrodite-type solid solutions with a composition of (Li6−3xAlx)PS5I in 0⩽x⩽0.10, and structural analysis revealed that Al3+ is located at Li sites. Also, the Al-doped samples contained anion I−/S2− site disorders in the crystal structures and smaller lattice parameters than the non-doped samples. Impedance spectroscopy measurements indicated that Al-doping reduced the ionic diffusion barrier, Ea, and increased the ionic conductivity to 10−5 S cm−1; the (Li5.7Al0.1)PS5I had the highest ionic conductivity in the studied system, at 2.6×10−5 S cm−1. In a lab-scale ASSB, with (Li5.7Al0.1)PS5I functioned as a solid electrolyte, demonstrating the characteristics of a pure ionic conductor with negligible electronic conductivity. The evaluated ionic conduction is due to decreased Li+ content and I−/S2− disorder formation. Li-site cation doping enables an in-depth understanding of the structure and provides an additional approach to designing better-performing SEs in the argyrodite system. [ABSTRACT FROM AUTHOR]

Deep eutectic solvent (DES)-based gels, with their biocompatibility, non-volatility, low cost, and electrochemical stability, have attracted widespread interest as novel solid-state ionic conductor for flexible devices. However, fabrication of tough and stretchable DES gels is challenging due to the insufficient understanding of the interactions between polymers and DES. The development of tough DES gels based on hydrogen bonding is attractive but also challenging due to the possible competitive hydrogen bonds between the hydrogen bond-rich choline chloride-based polar DES and polymers. Herein, tough copolymer-supported DES gels with dual-cross-linked dissipative network were fabricated through copolymerization of methacrylic acid and N, N-dimethylacrylamide monomers with good and poor compatibility with DES to promote the formation of stable hydrogen bonds between polymers in the DES. The resulting DES gels were stiff, tough, stretchable, and self-recoverable, with tensile strength, breaking strain, Young's modulus, toughness, and recovery ratio being 2.08 MPa, 792%, 1.76 MPa, 12.88 MJ m−3, and 76%, respectively. The mechanical properties of DES gels could be widely tuned by varying the monomer ratio and solvent structure changes. The carbon-based supercapacitor based on the DES gel shows stable voltage window to 2 V and exhibits the specific capacitance of 93.25 F g−1 at 2 A g−1. An ultratough and stretchable copolymer-supported DES gel ionic conductor with high tensile strength of 2.08 Mpa, high toughness of 12.88 MJ m−3, stretchability of 792%, and excellent recovery properties are facile fabricated for flexible electronics through copolymerization of two monomer pairs of methacrylic acid and N, N-dimethylacrylamide that can form stable hydrogen bonds in the DES environment with a small amount of chemical cross-linker to form a dual-crosslinked dissipative network. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: With the rapid growth of soft electronic and ionotronic devices such as artificial tissues, soft luminescent devices, soft robotics, and human‐machine interfaces, there is a demanding need to accelerate the development of soft ionic conductive materials. To date, the first‐generation ionotronic devices are mainly based on hydrogels or ionogels. However, due to their intrinsic drawbacks, such as freezing or volatilization at extreme temperatures, and the leakage problem under external mechanical forces, the reliability of ionotronic devices under harsh conditions remains a great challenge. The advent of liquid‐free ionic conductive elastomers (ICEs) has the potentials to solve the issues related to the gel‐type soft conductive materials. The free ions shuttling within the ion‐dissolvable polymer network enable liquid‐free ICEs to exhibit unparalleled ionic conductivity and elasticity. Moreover, by tuning the composition and structure of the polymeric network, it is also feasible to integrate other desirable properties, such as self‐healing ability, transparency, biocompatibility, and stimulus responsiveness, into liquid‐free ICE materials. In this review, we summarize the design strategies of recently reported liquid‐free ICEs, and further explore the methods to introduce multifunctionality, which originate from the rational molecular design and/or the synergy with other materials. Moreover, we highlight the representative applications of liquid‐free ICEs in soft ionotronics. It is believed that liquid‐free ICEs might provide a unique material platform for the next‐generation ionotronics. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: With the rapid growth of soft electronic and ionotronic devices such as artificial tissues, soft luminescent devices, soft robotics, and human‐machine interfaces, there is a demanding need to accelerate the development of soft ionic conductive materials. To date, the first‐generation ionotronic devices are mainly based on hydrogels or ionogels. However, due to their intrinsic drawbacks, such as freezing or volatilization at extreme temperatures, and the leakage problem under external mechanical forces, the reliability of ionotronic devices under harsh conditions remains a great challenge. The advent of liquid‐free ionic conductive elastomers (ICEs) has the potentials to solve the issues related to the gel‐type soft conductive materials. The free ions shuttling within the ion‐dissolvable polymer network enable liquid‐free ICEs to exhibit unparalleled ionic conductivity and elasticity. Moreover, by tuning the composition and structure of the polymeric network, it is also feasible to integrate other desirable properties, such as self‐healing ability, transparency, biocompatibility, and stimulus responsiveness, into liquid‐free ICE materials. In this review, we summarize the design strategies of recently reported liquid‐free ICEs, and further explore the methods to introduce multifunctionality, which originate from the rational molecular design and/or the synergy with other materials. Moreover, we highlight the representative applications of liquid‐free ICEs in soft ionotronics. It is believed that liquid‐free ICEs might provide a unique material platform for the next‐generation ionotronics. [ABSTRACT FROM AUTHOR]

Recently, eutectogels have gained significant attention as promising materials for wearable devices. However, developing eutectogels with integrated stretchability, good toughness, self‐healing, and self‐adhesive properties through non‐covalent scaffold assembly is a major challenge. In this study, a fully physically crosslinked double‐network (DN) eutectogel was fabricated by exploiting the high solubility and gelation of gellan gum in a deep eutectic solvent (DES) to form the first physically crosslinked network and combining it with supramolecular poly (2‐hydroxyethyl acrylate‐choline chloride, HEA‐ChCl). The resulting gel showed high stretchability (1835 %), toughness (7.65 MJ m−3), desirable ionic conductivity (0.41 mS cm−1), adhesion, and high transparency. Assembling the gel into strain sensors allows precise monitoring of human motion (finger, wrist, elbow, and knee). The results of this study suggest that gellan gum/poly (ChCl‐HEA) DN eutectogels have significant potential as highly sensitive and reliable strain sensors for wearable technology applications. [ABSTRACT FROM AUTHOR]

The sodium ion–based materials have interesting physical properties which make them suitable for industrial applications. In this paper, we focus our work on sodium ytterbium phosphate NaYbP2O7, prepared by the solid-state method. It is found that NaYbP2O7 crystallizes in the monoclinic system with P121/n1 space group. Impedance analysis shows that this compound exhibits semiconductor behavior and that the conduction mechanism is thermally activated. AC conductivity measurements show that NaYbP2O7 can be a good ionic conductor with an activation energy value up to 0.94eV. The frequency dependence of conductivity is probably caused by the jump of Na ions between octahedral sites of the olive framework. Such properties of NaYbP2O7 make it suitable as an ionic conductor. [ABSTRACT FROM AUTHOR]

The mixed alkali-diphosphate materials are among the widely used commercial materials due to their outstanding physical properties. The Li2Na2P2O7 (LNOP1) and Li3NaP2O7 (LNOP2) compounds have been synthetized by the conventional solid-state method. The structural and morphological analysis, optical properties, electrical and dielectric measurements were taken on the obtained compounds. Their powder X-ray diffraction analysis indicates that they crystallize in the monoclinic system with non-centrosymmetry P12/m1 and P121/m1 space group, respectively. The morphological images show that the two compounds are consisting of irregular block-shaped aggregates. The UV–Vis absorbance spectra show that the cutoff edges for compounds (LNOP1) and (LNOP2) are below 400 nm. The optical gaps of the both compounds are found indirect type with a value of 3.39 eV and 3.42 eV, respectively. The electrical data are investigated using the complex impedance spectroscopy technique in the range of frequency (0.1 Hz–1 MHz) and through large temperature scale (373–673 K). The AC conductivity evolution increases rapidly with appearance of a dispersive behavior, which obeys to Jonscher's law. Furthermore, the complex impedance analysis shows the contribution of only the grains in the conduction mechanism. The complex modulus diagrams confirmed the existence of only the contribution of the grain effect. Finally, the dielectric behavior of both compounds shows a non-Debye relaxation type. [ABSTRACT FROM AUTHOR]

The mixed alkali-diphosphate materials are among the widely used commercial materials due to their outstanding physical properties. The Li2Na2P2O7 (LNOP1) and Li3NaP2O7 (LNOP2) compounds have been synthetized by the conventional solid-state method. The structural and morphological analysis, optical properties, electrical and dielectric measurements were taken on the obtained compounds. Their powder X-ray diffraction analysis indicates that they crystallize in the monoclinic system with non-centrosymmetry P12/m1 and P121/m1 space group, respectively. The morphological images show that the two compounds are consisting of irregular block-shaped aggregates. The UV–Vis absorbance spectra show that the cutoff edges for compounds (LNOP1) and (LNOP2) are below 400 nm. The optical gaps of the both compounds are found indirect type with a value of 3.39 eV and 3.42 eV, respectively. The electrical data are investigated using the complex impedance spectroscopy technique in the range of frequency (0.1 Hz–1 MHz) and through large temperature scale (373–673 K). The AC conductivity evolution increases rapidly with appearance of a dispersive behavior, which obeys to Jonscher's law. Furthermore, the complex impedance analysis shows the contribution of only the grains in the conduction mechanism. The complex modulus diagrams confirmed the existence of only the contribution of the grain effect. Finally, the dielectric behavior of both compounds shows a non-Debye relaxation type. [ABSTRACT FROM AUTHOR]

Additive manufacturing of solid-state batteries is advantageous for improving the power density by increasing the geometric complexity of battery components, such as electrodes and electrolytes. In the present study, bulk three-dimensional Li _1+ _x Al _x Ti _2− _x (PO _4 ) _3 (LATP) electrolyte samples were prepared using the laser powder bed fusion (L-PBF) additive manufacturing method. Li _3 PO _4 (LPO) was added to LATP to compensate for lithium vaporization during processing. Chemical compositions included 0, 1, 3, and 5 wt. % LPO. Resulting ionic conductivity values ranged from 1.4 × 10 ^−6 –6.4 × 10 ^−8 S cm ^−1 , with the highest value for the sample with a chemical composition of 3 wt. % LPO. Microstructural features were carefully measured for each chemical composition and correlated with each other and with ionic conductivity. These features and their corresponding ranges include: porosity (ranging from 5% to 19%), crack density (0.09–0.15 mm mm ^−2 ), concentration of residual LPO (0%–16%), and concentration and Feret diameter of secondary phases, AlPO4 (11%–18%, 0.40–0.61 µ m) and TiO2 (9%–11%, 0.50–0.78). Correlations between the microstructural features and ionic conductivity ranged from −0.88 to 0.99. The strongest negative correlation was between crack density and ionic conductivity (−0.88), confirming the important role that processing defects play in limiting the performance of bulk solid-state electrolytes. The strongest positive correlation was between the concentration of AlPO4 and ionic conductivity (0.99), which is attributed to AlPO4 acting as a sintering aid and the role it plays in reducing the crack density. Our results indicate that additions of LPO can be used to balance competing microstructural features to design bulk three-dimensional LATP samples with improved ionic conductivity. As such, refinement of the chemical composition offers a promising approach to improving the processability and performance of functional ceramics prepared using binderless, laser-based additive manufacturing for solid-state battery applications.

Solid inorganic and polymeric electrolytes have the potential to enable rechargeable batteries with higher energy densities, compared to current lithium-ion technology, which uses liquid electrolyte. Inorganic materials such as ceramics and glasses conduct lithium ions well, but they are brittle, which makes incorporation into a battery difficult. Polymers have the flexibility for facile use in a battery, but their transport properties tend to be inferior to inorganics. Thus, there is growing interest in composite electrolytes with inorganic and organic phases in intimate contact. This article begins with a discussion of ion transport in single-phase electrolytes. A dimensionless number (the Newman number) is presented for quantifying the efficacy of electrolytes. An effective medium framework for predicting transport properties of composite electrolytes containing only one conducting phase is then presented. The opportunities and challenges presented by composite electrolytes containing two conducting phases are addressed. Finally, the importance and status of reaction kinetics at the interfaces between solid electrolytes and electrodes are covered, using a lithium-metal electrode as an example.

Solid-state electrolytes can offer improved lithium-ion battery safety while potentially increasing the energy density by enabling alkali metal anodes. There have been significant research efforts to improve the ionic conductivity of solid-state electrolytes and the electrochemical performance of all-solid-state batteries; however, the root causes of their poor performance - interfacial reaction and subsequent impedance growth - are poorly understood. This is due to the dearth of effective characterization techniques for probing these buried interfaces. In situ and operando methodologies are currently under development for solid-state interfaces, and they offer the potential to describe the dynamic interfacial processes that serve as performance bottlenecks. This article highlights state-of-the-art solid-solid interface probing methodologies, describes practical limitations, and describes a future for dynamic interfacial characterization.

Owing to the advantages of temperature resistance, low cost, and biocompatibility, deep eutectic solvent (DES)‐based ionic conductive gels have attracted increasing research interest for flexible devices in recent years. However, current DES gels are all based on hydrophilic DES, which tend to absorb a large amount of environmental moisture, resulting in gel softening and adversely affecting the durability of the device. In this work, we highlight for the first time that N,N‐dimethylacrylamide monomer, and the obtained polymer can form hydrogen‐bonding networks with hydrophobic DES, methyl trioctyl ammonium chloride/ethyl 4‐hydroxybenzoate (1:2), thereby obtaining a hydrophobic DES‐based gel through photo‐polymerization. The resultant DES gel displays high stretchability (~900%), toughness (341.14 kJ m−3), anti‐fatigue property (recovery after 500 compression cycles), desirable conductivity (0.12 mS cm−1), adhesiveness and high transparency (>90% visible light transmittance). Notably, the hydrophobic DES‐based gel absorbs only 2 wt% water but exhibits significant water‐induced stiffening after exposing in ambient air for 1 week. These properties lead to the successful realization of the DES gels as wearable sensors to precisely monitor human motion. This work may open new avenues for the development of hydrophobic DES‐based gel ionotronics with functional performance. [ABSTRACT FROM AUTHOR]

The lithium thiophosphate group of solid electrolytes (SEs) is considered one of the best lithium-ion conductors that could be compatible with liquid electrolytes. However, the interface stability of lithium thiophosphate SEs against the lithium anode and oxide cathode could be a challenge due to severe degradation over charge-discharge cycles. In this study, we aim to analyze and introduce the addition of halides into lithium thiophosphate SEs with a molar ratio of 3Li 3 PS 4 to 1LiM (M = Cl, Br, I) in order not only to improve ion conductivity but also to increase the interface stability of the SEs. Li 10 P 3 S 12 Br (LPSBr) and Li 10 P 3 S 12 I (LPSI) results in high ionic conductivity at 1.7 and 2.9 mS cm -1 , respectively, at room temperature. Although LPSBr has lower ion conductivity, it shows better electrochemical stability compared to LPSI. By combining the advantages of both LiI and LiBr to form Li 10 P 3 S 12 Br 1- x I x , we have observed improvements not only in high ionic conductivity but also in the interface stability of SEs, which is important for extending the lifetime cycle of all-solid-state lithium batteries (ASSLBs).

Single crystal specimens of apatite‐type compounds Ca5(VO4)3Cl and Ca4.78 (1)Na0.22(PO4)3Cl0.78 were prepared with a flux‐growth technique and their structures were examined with single‐crystal X‐ray diffraction. The anion channel is defined by a face‐sharing array of nearly regular Ca octahedra, which run along c, together with flat O3 trigonal antiprisms that are concentric with the Ca octahedra and highly oblate in [001]. The position of the channel anion in Ca5(VO4)3Cl is split into two at [0, 0, ±0.1691 (6)] with half occupancies. Dynamic disorder among these two positions is suggested from a saddle‐shaped electron density distribution through the Ca regular triangle, i.e. the shared face of the Ca octahedra at z = ¼. The position of Cl− was too close to Ca2+ under bond‐valence consideration. This is due to repulsion on Cl− from the flat O3 trigonal antiprism which is located at z = 0, namely, in between pairs of split Cl site positions. Ca4.78 (1)Na0.22(PO4)3Cl0.78 crystallizes as a disordered hexagonal structure in which the crystallographic pattern is not an intermediate state but a projection of two distinct halves of the monoclinic pattern [doubled in b; Mackie, Elliot & Young (1972). Acta Cryst. B28, 1840–1848] in one hexagonal cell. In spite of quite different environments, the bond‐valence sums for Cl− in these structures are large and similar to each other. The repulsion between O2− and Cl− and a demand for keeping Ca2+ and Cl− apart are balanced at the positions where bond‐valence sums for Cl− are around 1.2. [ABSTRACT FROM AUTHOR]

MgO-doped partially stabilized zirconia (xMgPSZ, with x = 8 or 10 mol%) materials sintered at 1700°C, were characterized with respect to structure, microstructure, thermal expansion and electrical performance. The monoclinic (M) phase content is almost vestigial in 10MgPSZ, unlike in 8MgPSZ. Combined powder XRD and customized thermal expansion data analysis, allowed a separation between M and tetragonal (T) particles, outside or imbedded in cubic grains. Combination of thermal expansion and impedance spectroscopy data provided novel insights on the totally distinct roles of fine and dispersed T or M particles within the PSZ cubic matrix grains. [ABSTRACT FROM AUTHOR]

Lithium metal is regarded as the most promising electrode material for the next generation of energy storage devices. However, low coulombic efficiency and short cycle lifespan caused by the unstable electrode interface have hindered its practical application. Constructing artificial coatings on the anode is one of the most effective approaches for remedying this, but the practical effects are still limited due to their poor regulation of Li+ ions transport and complex construction engineering. Herein, an "inverse concentration gradient" concept is put forward to improve the lithium metal anode, especially at high current density. A Li4Ti5O12 artificial coating layer is fabricated on copper foil by a simple droplet coating method and a concentrated Li+ ions region near the electrode interface in the coating layer is formed in situ after the initial activation process, which alleviates the effects of space charge regions generated by ion depletion on the growth of lithium dendrites. Coupled with high ionic conductivity and "zero strain" characteristics, stable dendrite‐free cycling of lithium metal anodes is achieved even at 5 mA cm−2 in Li/Cu half cell. The unique concentration gradient design provides a new perspective for the interface regulation of advanced lithium metal anodes. [ABSTRACT FROM AUTHOR]

The design and production features of a solid oxide fuel cell greatly impact its microstructure and performance; however, these factors are frequently omitted in related studies. In this work, the influence of the design and formation factors of a solid oxide fuel cell on its performance and long-term stability is studied. The sintering process of multilayer half-cells is studied by heating microscopy and the optimal sintering strategy is identified. We show here the importance of the sintering strategy and suggest an approach for SOFC design that results in a stable in time performance. The electrochemical performance is evaluated by impedance spectroscopy and the distribution of relaxation times (DRT) technique. It is shown that the absence of the barrier layer leads to a decrease in the SOFC performance by 22.5% as-sintered and continues to drop down during the exposure of 850 °C for 400 h. The impregnation of the cathode and anode by Pr(NO3)3 and Ce(NO3)3 improves electrochemical performance by 15% and this increase withstands a heat treatment at least for 215 h without any noticeable degradation. The most stable in time performance of the cell with impregnated electrodes and the barrier layer is 515.3 mW × cm−2 (H2 + 3% H2O used as fuel, air + 3% H2O as oxidizer). [ABSTRACT FROM AUTHOR]

Reactive flash synthesis simplifies the processing of complex ceramics such as alumina doped lithium lanthanum zirconate. Low temperatures and short processing times obviate the loss of lithium while producing dense single-phase ceramics. Here we show the synthesis of non-stoichiometric compositions of this ceramic which increases the ionic conductivity by a factor of more than three. The non-stoichiometry refers to non-equilibrium lithium/lanthanum ratio, and to the addition of boron to produce excess lithium-ion vacancies. The results open the possibility of using non-stoichiometry as a concept, and RFS as the tool, for the discovery of new compositions that enhance lithium-ion conductivity. [ABSTRACT FROM AUTHOR]

Boosting stretchability and electric output is critical for high-performance wearable triboelectric nanogenerators (TENG). Herein, for the first time, a new approach for tuning the composition of surface functional groups through surfactant self-assembly to improve the tribopositivity, where the assembly increases the transferred charge density and the relative permittivity of water polyurethane (WPU). Incorporating bis(trifluoromethanesulfonyl)imide (TFSI - ) and alkali metal ions into a mixture of WPU and the surfactant forms a stretchable film that simultaneously functions as positive tribolayer and electrode, preventing the conventional detachment of tribolayer and electrode in long term usage. Further, the conductivity of the crosslinked film reaches 3.3 × 10 -3 mS cm -1 while the elongation at break reaches 362%. Moreover, the surfactant self-assembly impedes the adverse impact of the fluorine-containing groups on tribopositivity. Consequently, the charge density reaches 155 µC m -2 , being the highest recorded for WPU and stretchable ionic conductor based TENG. This work introduces a novel approach for boosting the output charge density while avoiding the adverse effect of ionic salts in solid conductors through a universal surfactant self-assembly strategy, which can be extended to other materials. Further, the device is used to monitor and harvest the kinetic energy of human body motion., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Developing high specific energy Lithium-ion (Li-ion) batteries is of vital importance to boost the production of efficient electric vehicles able to meet the customers’ expectation related to the electric range of the vehicle. One possible pathway to high specific energy is to increase the operating voltage of the Li-ion cell. Cathode materials enabling operation above 4.2 V are available. The stability of the positive electrode-electrolyte interface is still the main bottleneck to develop high voltage cells.Moreover, important research efforts are devoted to the substitution of graphite anodes with Li metal: this would improve the energy density of the cell dramatically. The use of metallic lithium is prevented by the dendrite growth during charge, with consequent safety problems. To suppress the formation of dendrites solid-state electrolytes are considered the most promising approach.For these reasons the present review summarizes the most recent research efforts in the field of high voltage solid-state electrolytes for high energy density Li-ion cells.

We present a computational approach for identifying the important descriptors of the ionic conductivities of lithium solid electrolytes. Our approach discriminates the factors of both bulk and grain boundary conductivities, which have been rarely reported. The effects of the interrelated structural (e.g. grain size, phase), material (e.g. Li ratio), chemical (e.g. electronegativity, polarizability) and experimental (e.g. sintering temperature, synthesis method) properties on the bulk and grain boundary conductivities are investigated via machine learning. The data are trained using the bulk and grain boundary conductivities of Li solid conductors at room temperature. The important descriptors are elucidated by their feature importance and predictive performances, as determined by a nonlinear XGBoost algorithm: (i) the experimental descriptors of sintering conditions are significant for both bulk and grain boundary, (ii) the material descriptors of Li site occupancy and Li ratio are the prior descriptors for bulk, (iii) the density and unit cell volume are the prior structural descriptors while the polarizability and electronegativity are the prior chemical descriptors for grain boundary, (iv) the grain size provides physical insights such as the thermodynamic condition and should be considered for determining grain boundary conductance in solid polycrystalline ionic conductors.

La2Mo2O9 based Tb-doped compound, La2-xTbxMo2O9 (x=0.1, 0.2, 0.5), was synthesized and characterised by EIS studies. The frequency and temperature dependent dielectric, electric modulus and ac conductivity studies have been done. Different formalisms have been used to understand relaxation mechanism in our compound. The conductivity in these specimens appears to be due to mobility of oxygen ions.

We describe the materials, design, experimental measurements, and simulations of a bio-inspired all-solid tunable optical device: ionic eye. A dielectric elastomer functions as an electroactive material. An ionogel functions as an ionic conductor. Both materials are stretchable and transparent. The ionic eye achieves a ~50% relative change of the focal length, beyond that of the human eye. Our analysis also points out that the ionic eye can respond rapidly (3.6 ms) and be miniaturized in size. This all-solid deformable lens eliminates the risk of leakage of currently used encapsulated fluid lenses and can be integrated into other devices for diverse applications. [ABSTRACT FROM AUTHOR]

Li 2 O-2B 2 O 3 coated Li 4 Ti 5 O 12 anode with protected particle surface and fast ion transfer exhibit desired rate capability and cycling stability for lithium ion batteries. Li 2 O-2B 2 O 3 (LBO) ionic conductor with high conductivity plays an important role in boosting the rate performance and cycling stability of Li 4 Ti 5 O 12 (LTO) anode for lithium-ion batteries by preventing direct exposure of LTO to the electrolyte. Herein, the effect of LBO coating layer on lithium ion (Li+) storage performance is investigated in detail by adjusting the adding amount of LBO precursor dispersion. LTO coated with 2 wt% LBO achieves an optimum performance with a specific capacity of 172.9 mA h g−1 at a current density of 0.1 A g−1, an improved rate capability (specific capacity of 127.9 mA h g−1 is maintained when the current density is 20 times than 0.1 A g−1) and a remarkable cycling stability (capacity retention of 94.2% after 4000 cycles at 2.0 A g−1). These LBO-LTO composites are competitive and promising candidates for electrochemical energy storage and other applications. [ABSTRACT FROM AUTHOR]

Ionic liquid (IL) based gel polymer electrolytes (GPEs) are being investigated extensively at present as substitutes for conventional GPEs based on a polymer, a salt and solvents. The main reason behind this is the drawbacks in usage of solvents. IL based GPEs have been employed for energy storage devices such as batteries and super capacitors due to their interesting mechanical, physical and electrochemical properties. This study focused on synthesis preparation and characterization of an IL based GPE consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-co-HFP), zinc trifluoro metha -nesulfonate (Zn(CF3SO3)2 - ZnTF) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (1E3MITF). Thin film samples were prepared using solvent casting method. The optimized composition was found to be 1 PVdF-co-HFP: 1 1E3MITF: 3 ZnTF (by weight basis). This mechanically stable, thin film has the maximum room temperature conductivity of 7.42×10-3 S cm-1. Conductivity variation with temperature follows Vogel - Tamman - Fulcher (VTF) behavior confirming the relation of conductivity mechanism with the free volume theory. The IL based GPE is a purely an ionic conductor having a considerable anionic contribution. It shows stability up to 2.5 V which is very much convenient from a practical point of view. Oxidation and reduction of Zn takes place at the potentials of 0.5 V and –0.5 V, respectively. In addition, Zn platting and stripping occurs only on the Zn electrodes but not on the stainless steel (SS) electrodes. Impedance measurements taken for the GPE continuously for a long period of time exhibited a satisfactory stability with Zn electrodes.