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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).

Halide solid electrolytes (SEs) have been highlighted for their high-voltage stability. Among the halide SEs, the ionic conductivity has been improved by aliovalent metal substitutions or choosing a ccp-like anion-arranged monoclinic structure ( C 2/ m ) over hcp- or bcc-like anion-arranged structures. Here, we present a new approach, hard-base substitution, and its underlying mechanism to increase the ionic conductivity of halide SEs. The oxygen substitution to Li 2 ZrCl 6 (trigonal, hcp) increased the ionic conductivity from 0.33 to 1.3 mS cm -1 at Li 3.1 ZrCl 4.9 O 1.1 (monoclinic, ccp), while the sulfur and fluorine substitutions were not effective. A systematic comparison study revealed that the energetic stabilization of interstitial sites for Li migration plays a key role in improving the ionic conductivity, and the ccp-like anion sublattice is not sufficient to achieve high ionic conductivity. We further examined the feasibility of the oxyhalide SE for practical and all-solid-state battery applications.

β ″ -Al 2 O 3 has been proven as a fast ionic conductor in solid batteries due to its unique structure. In this work, β ″ -Al 2 O 3 was further modified by LiAlO 2 and employed as the electrolyte material for low-temperature solid oxide fuel cells and electrolyzers, i.e., proton-conducting ceramic fuel cells and electrolysis cells, named as PCFC and PCEC, respectively. At 550 °C, thanks to this superior electrolyte with a remarkable conductivity of 0.161 S·cm -1 , the PCFC reached a high power density up to 1029 mW·cm -2 , and the PCEC demonstrated a significant current density of 1.49 A·cm -2 at a low operation voltage of 2.0 V. It has been found that the introduction of the LiAlO 2 phase into β ″ -Al 2 O 3 reduces the total impedance, while it increases the oxygen vacancy concentration and thus promotes the proton transport process with the reduced activation energy. This work provides a new approach for exploring two-dimensional materials with high-ionic conductivity that can be applied for solid oxide fuel cells and water electrolyzers and more wider power-to-X devices such as electrosynthesis for green ammonia production.

Multifunctional flexible sensors are the development trend of wearable electronic devices in the future. As the core of flexible sensors, the key is to construct a stable multifunctional integrated conductive elastomer. Here, ionic conductive elastomers (ICEs) with self-wrinkling microstructures are designed and prepared by in situ phase separation induced by a one-step polymerization reaction. The ICEs are composed of ionic liquids as ionic conductors doped into liquid crystal elastomers. The doped ionic liquids cluster into small droplets and in situ induce the formation of wrinkle structures on the upper surface of the films. The prepared ICEs exhibit mechanochromism, conductivity, large tensile strain, low hysteresis, high cycle stability, and sensitivity during the tension-release process, which achieve dual-mode outputs of optical and electrical signals for information transmission and sensors.

Recently, flexible wearable and implantable electronic devices have attracted enormous interest in biomedical applications. However, current bioelectronic systems have not solved the problem of mechanical mismatch of tissue-electrode interfaces. Therefore, the biomimetic hydrogel with tissue-like mechanical properties is highly desirable for flexible electronic devices. Herein, we propose a strategy to fabricate a biomimetic hydrogel with strain-stiffening property via regional chain entanglements. The strain-stiffening property of the biomimetic hydrogel is realized by embedding highly swollen poly(acrylate sodium) microgels to act as the microregions of dense entanglement in the soft polyacrylamide matrix. In addition, poly(acrylate sodium) microgels can release Na + ions, endowing hydrogel with electrical signals to serve as strain sensors for detecting different human movements. The resultant sensors own a low Young's modulus (22.61-112.45 kPa), high nominal tensile strength (0.99 MPa), and high sensitivity with a gauge factor up to 6.77 at strain of 300%. Based on its simple manufacture process, well mechanical matching suitability, and high sensitivity, the as-prepared sensor might have great potential for a wide range of large-scale applications such as wearable and implantable electronic devices.

A solid-state electrolyte (SSE) is the core component for fabricating solid-state batteries competitive with the currently commercial Li-ion batteries. In the present study, a LiBH 4 ·1/2NH 3 -MgO nanocomposite has been developed as a fast Li-ion conductor. The conductive properties depend strongly on the size of MgO nanopowders. By adding MgO nanoparticles, the first-order transition at 55 °C observed in the crystalline LiBH 4 ·1/2NH 3 is suppressed due to the conversion of LiBH 4 ·1/2NH 3 into the amorphous state. When the size of MgO decreases from 163.6 to 13.9 nm, the MgO amount required for the phase-transition suppression of LiBH 4 ·1/2NH 3 decreases linearly from 92 to 75 wt %, accompanied by a significant enhancement of ionic conductivity. The optimized nanocomposite with 75 wt % MgO of size 13.9 nm exhibits a pronouncedly high conductivity of 4.0 × 10 -3 S cm -1 at room temperature, which is 20 times higher than that of the crystalline LiBH 4 ·1/2NH 3 . Furthermore, a smaller size MgO contributes to a higher electrochemical stability window (ESW) owing to the stronger interfacial interaction via B-O bonds, i.e. , an ESW of 4.0 V is achieved with the addition of 75 wt % MgO of size 13.9 nm.

Interfacial engineering is an efficient approach to improve the ionic conductivity of solid-state electrolytes. In the present study, we report the enhancement of in situ formed nanocrystalline Li 2 O on the thermal stability and electrochemical properties of amide lithium borohydride, LiBH 4 · x NH 3 ( x = 0.67-0.8). LiBH 4 · x NH 3 -Li 2 O composites with different amounts of Li 2 O are prepared by a one-step synthesis process by ball milling the mixture of LiBH 4 , LiNH 2 , and LiOH in molar ratios of 1: n : n ( n = 1, 2, 3, 4). Owing to the strong interfacial effect with nanocrystalline Li 2 O, LiBH 4 · x NH 3 is converted to the amorphous state in the presence of 78 wt % Li 2 O at n = 4. Consequently, the ionic conductivity of LiBH 4 · x NH 3 at 20 °C is improved by orders of magnitude up to 5.4 × 10 -4 S cm -1 , the NH 3 desorption temperature is increased by more than 20 °C, and the electrochemical window is widened from 0.5 to 3.8 V.

A freestanding ion membrane with high ionic conductivity, electrochemical compatibility, satisfactory strength, and safety is a goal pursued for advanced energy storage. Geminal dicationic ionic liquids (GDILs) are expected to be designed and synthesized as a basic building block for the target ionic conductors. Herein, we fabricated a GDIL-based flexible ion conductive material, which appears and behaves as a freestanding film, an ion membrane actually, denoted as iMembrane. The iMembrane presented high thermal stability, broad electrochemical stability, and capable ionic conductivity. Stable lithium-ion intercalation/de-intercalation can be achieved at the iMembrane/graphite interface without co-intercalation of imidazole rings, which is attributed to the specific anion-derived solid electrolyte interphase. Moreover, iMembrane is well compatible with the lithium metal anode and LiFePO 4 cathode. The soft-packed batteries assembled with iMembrane were punctured with a nail without any fire or smoke. Hence, as an ionic membrane in nonprotonic, iMembrane is promising to enhance safety and energy density of lithium batteries.

Polar H 2 O molecules generally act as trapping sites and suppress the electron mobility of n-type organic semiconductors, making chemical design of H 2 O-tolerant and responsive n-type semiconductors an important step toward multifunctional electron-ion coupling devices. The introduction of effective electrostatic interactions between potassium ions (K + ) and carboxylate (-COO - ) anions into the electron-transporting naphthalenediimide π-framework enables the design of high-performance H 2 O-tolerant n-type semiconductors with a reversible H 2 O adsorption-desorption ability, where the electron mobility and K + ionic conductivity were coupled with the reversible H 2 O sorption behavior. The reversible H 2 O adsorption into the crystals enhanced the electron mobility from 0.04 to 0.28 cm 2 V -1 s -1 , whereas the K + ionic conductivity decreased from 3.4 × 10 -5 to 4.7 × 10 -7 S cm -1 . Because this reversible electron-ion conducting switch is responsive to H 2 O sorption behavior, it is a strong candidate for H 2 O gating carrier transport systems.

Ionic conductors are normally prepared from water-based materials in the solid form and feature a combination of intrinsic transparency and stretchability. The sensitivity toward humidity inevitably leads to dehydration or deliquescence issues, which will limit the long-term use of ionic conductors. Here, a novel ionic conductor based on natural bacterial cellulose (BC) and polymerizable deep eutectic solvents (PDESs) is developed for addressing the abovementioned drawbacks. The superstrong three-dimensional nanofiber network and strong interfacial interaction endow the BC-PDES ionic conductor with significantly enhanced mechanical properties (tensile strength of 8 × 10 5 Pa and compressive strength of 6.68 × 10 6 Pa). Furthermore, compared to deliquescent PDESs, BC-PDES composites showed obvious mechanical stability, which maintain good mechanical properties even when exposed to high humidity for 120 days. These materials were demonstrated to possess multiple sensitivity to external stimulus, such as strain, pressure, bend, and temperature. Thus, they can easily serve as supersensitive sensors to recognize physical activity of humans such as limb movements, throat vibrations, and handwriting. Moreover, the BC-PDES ionic conductors can be used in flexible, patterned electroluminescent devices. This work provides an efficient strategy for making cellulose-based sustainable and functional ionic conductors which have broad application in artificial flexible electronics and other products.

An aqueous solution approach has been utilized to prepare nanolaminates of TiO 2 and ionically conductive Li 2 O-Al 2 O 3 (LiAlO). This new approach utilizes low curing temperatures, resulting in fully oxidized films as demonstrated by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The layered structures have been characterized by scanning electron microscopy, X-ray diffraction, and X-ray reflectivity. Incorporation of sufficiently thick (13 and 27 nm) ion blocking TiO 2 layers into nanolaminate structures with LiAlO layers resulted in an increase in breakdown voltage by more than a factor of two, relative to LiAlO. Nanolaminate structures also preserve the large double layer capacitance of the ionically conductive layer. Increased breakdown strength coupled with large capacitances results in a doubling of ultimate charge storage capacity, illustrating how nanolaminates can be used to improve properties relevant for energy/charge storage applications.

Recent progress in the printing of soft materials has made it possible to fabricate soft stretchable devices for a range of engineering applications. These devices tend to be heterogeneous systems, and their reliability depends to a large extent on the integrity of the interfaces between the various materials in the system. Previous studies on the printing of hydrogels have highlighted the need to investigate the adhesion between extrusion printable dielectric elastomers and hydrogels. Here we consider polydimethylsiloxane (PDMS) and a polyacrylamide hydrogel that contains lithium chloride and a nonionic rheological modifier. We show that the adhesion between oxygen plasma-treated PDMS and the hydrogel increases with time to reach a stable value of 15 J m -2 after ∼6 days. During that time, the contact angle of water on the PDMS interface remains constant at ∼30°, suggesting that hydrophobic recovery of plasma-treated PDMS is suppressed by the presence of the hydrogel. It is further observed that a thin viscous layer develops at the interface between PDMS and hydrogel, which results in energy dissipation upon debonding and which allows full recovery of the adhesion after debonding and rejoining. This viscous layer develops only in the presence of the rheological modifier in the hydrogel and the hydrophilic surface treatment of the PDMS.

The coupling between ionic degrees of freedom and ferroelectricity has received renewed attention in recent years, given that surface electrochemical processes have been shown to be intrinsically linked to ferroelectric phase stability in ultrathin ferroelectric films. However, the coupling between bulk ionic transport and local polarization switching has received less attention, as typically the bulk ionic mobilities are low for common ferroelectrics at room temperature. Here, we use the coupled band-excitation method in conjunction with site-correlated time-of-flight secondary ion mass spectrometry, to determine the coupling between ferroelectric switching and ionic motion in single crystal KTiOPO 4 . The local scanning probe measurements indicate a substantial softening, as determined by resonant frequency changes, during reversal of polarization along one direction. These changes are correlated with the mass spectrometry measurements, showing a polarization-dependent accumulation of K ions at the polar surfaces, thus corroborating their role in the screening process. These studies shed light on the interplay between ionic dynamics and bulk ferroelectric switching and have implications for studies on domain wall conductivity, chemical switching, and bulk and surface-screening phenomena.

Stretchable strain sensors have promising applications in health monitoring and human motion detection. However, only a few of the strain sensors reported to date have exhibited a multiscale strain range and a high gauge factor simultaneously. As such, most strain sensors cannot be used in applications that require both high sensitivity and a multiscale strain range. In this work, we develop a wearable multifunctional strain sensor using graphene and a new ionic conductor as the sensing material and Ecoflex as the encapsulant. In the ionic conductor, KCl and glycerol are used as the electrolyte and solvent, respectively. This deformable ionic conductor connects cracked graphene sheets electronically, enabling the strain sensor to be stretched to 300% of its original length with a moderate gauge factor of 25.2. The sensor can respond to various mechanical deformations including stretching, bending, and pressing. When attached to human body, the sensor can monitor large-scale strains (>50%) for joint movement and small-scale strains (<10%) for facial expressions and pulses. When stretched, the sensor also shows good sensitivity in static temperature sensing. Therefore, this multifunctional stretchable sensor has good prospect of applications in human motion detection and health monitoring.

Inorganic solid electrolytes (SEs) possess substantial safety and electrochemical stability, which make them as key components of safe rechargeable solid-state Li batteries with high energy density. However, complicated integrally molding process and poor wettability between SEs and active materials are the most challenging barriers for the application of SEs. In this regard, we explore composite SEs of the active ceramic Li 1+x Al x Ge 2-x (PO 4 ) 3 (LAGP) as the main medium for ion conduction and the polymer P(VDF-HFP) as a matrix. Meanwhile, for the first time, we choice high chemical, thermal, and electrochemical stability of ionic liquid swelled in polymer, which significantly ameliorate the interface in the cell. In addition, a reduced crystallinity degree of the polymer in the electrolyte can also be achieved. All of these lead to good ionic conductivity of the composite electrolyte (LPELCE), at the same time, good compatibility with the lithium electrode. Especially, high mechanical strength and stable solid electrolyte interphase which suppressed the growth of lithium dendrites and high thermal safety stability can also be observed. For further illustration, the solid-state lithium battery of LiFePO 4 /LPELCE/Li shows relatively satisfactory performance, indicating the promising potentials of using this type of electrolyte to develop high safety and high energy density solid-state lithium batteries.

The emergence of stretchable electronics and its potential integration with textiles have highlighted a challenge: Textiles are wearable and washable, but electronic devices are not. Many stretchable conductors have been developed to enable wearable active textiles, but little has been done to make them washable. Here we demonstrate a new class of stretchable conductors that can endure wearing and washing conditions commonly associated with textiles. Such a conductor consists of a hydrogel, a dissolved hygroscopic salt, and a butyl rubber coating. The hygroscopic salt enables ionic conduction and matches the relative humidity of the hydrogel to the average ambient relative humidity. The butyl rubber coating prevents the loss and gain of water due to the daily fluctuation of ambient relative humidity. We develop the chemistry of dip-coating the butyl rubber onto the hydrogel, using silanes to achieve both the cross-link of the butyl rubber and the adhesion between the butyl rubber and the hydrogel. We test the endurance of the conductor by soaking it in detergent while stretching it cyclically and by machine-washing it. The loss of water and salt is minimal. It is hoped that these conductors open applications in healthcare, entertainment, and fashion.

Ionic conductor of Li 2 SiO 3 (LSO) was used as an effective modifier to fabricate surface-modified Li 4 Ti 5 O 12 (LTO) via simply mixing followed by sintering at 750 °C in air. The electrochemical performance of LTO was enhanced by merely adjusting the mass ratio of LTO/LSO, and the LTO/LSO composite with 0.51 wt % LSO exhibited outstanding rate capabilities (achieving reversible capacities of 163.8, 157.6, 153.1, 147.0, and 137.9 mAh g -1 at 100, 200, 400, 800, and 1600 mA g -1 , respectively) and remarkable long-term cycling stability (120.2 mAh g -1 after 2700 cycles with a capacity fading rate of only 0.0074% per cycle even at 500 mA g -1 ). Combining structural characterization with electrochemical analysis, the LSO coating coupled with the slight doping effect adjacent to the LTO surface contributes to the enhancement of both electronic and ionic conductivities of LTO.

The selection and optimization of coating material/approach for electrode materials have been under intensive pursuit to address the high-voltage induced degradation of lithium ion batteries. Herein, we demonstrate an efficient way to enhance the high-voltage electrochemical performance of LiCoO 2 cathode by postcoating of its composite electrode with Li 4 Ti 5 O 12 (LTO) via magnetron sputtering. With a nanoscale (∼25 nm) LTO coating, the reversible capacity of LiCoO 2 after 60 cycles is significantly increased by 40% (to 170 mAh g -1 ) at room temperature and by 118% (to 139 mAh g -1 ) at 55 °C. Meanwhile, the electrode's rate capability is also greatly improved, which should be associated with the high Li + diffusivity of the LTO surface layer, while the bulk electronic conductivity of the electrode is unaffected. At 12 C, the capacity of the coated electrode reaches 113 mAh g -1 , being 70% larger than that of the uncoated one. The surface interaction between LTO and LiCoO 2 is supposed to reduce the space-charge layer at the LiCoO 2 -electrolyte interface, which makes the Li + diffusion much easier as evidenced by the largely enhanced diffusion coefficient of the coated electrode (an order of magnitude improvement). In addition, the LTO coating layer, which is electrochemically and structurally stable in the applied potential range, plays the role of a passivation layer or an artificial and friendly solid electrolyte interface (SEI) layer on the electrode surface. Such protection is able to impede propagation of the in situ formed irreversible SEI and thus guarantee a high initial columbic efficiency and superior cycling stability at high voltage.