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Low-cost Prussian blue analogs (PBAs) have attracted great attentions as a group of promising cathodes for sodium-ion batteries (SIBs) due to their tailorable and open frameworks which endue the possibility of ultrahigh Na+ diffusion kinetics. Herein, a unique discharging plateau elevation was firstly determined in the iron hexacyanoferrate. The synergy between the crystal field and ligand field stabilization energy in the OH-coordinated Fe sites lowers the activation energy barrier of low-spin Fe, thus inducing the intercalation pseudocapacitance. Furthermore, we prove that the Na+ storage mechanism of high-spin Fe redox reaction features an ion–diffusion behavior while the low-spin Fe redox reaction shows a pseudocapacitance behavior. Benefitting from the improved ionic diffusivity in intercalation pseudocapacitance, the full cell achieves an outstanding rate performance and long-term cycling stability of over 3000 cycles at 500 mA g−1. It is expected that manipulating Fe redox kinetics of the PBAs through inducing special coordinated groups could be a new pathway towards the design of practical high-voltage SIBs.

Carbonaceous materials are the most promising candidates as the anode for sodium-ion batteries (SIBs), however, they still suffer from low electric conductivity and sluggish sodium ion (Na+) reaction kinetics. Appropriate composition modulation using heteroatoms doping and structure optimization is highly desired. A basic empirical understanding of the structure-capacity relationship is also urgent in tackling the above problems. Herein, multi-functional nitrogen (N) doped carbon micro-rods with enlarged interlayer spacing are synthesized and investigated as the anode in SIBs, showing an ultra-stable capacity of 161.5 mAh g−1 at 2 A g−1 for over 5000 cycles. Experimental investigations and first-principle calculations indicate that the enlarged interlayer spacing can facilitate Na+ intercalation and N doping can guarantee the high electric conductivity and favorable electrochemical active sites. Additionally, pyridinic N is theoretically proved to be more effective to enhance Na+ adsorption than pyrrolic N due to the lower adsorption energy and stronger binding energy with Na+. Full SIBs show a high capacity and cyclability, making the biomass-derived carbon micro-rods to be a promising anode for practical SIBs applications.

Generation of large strains upon Na+ intercalation is one of the prime concerns of the mechanical degradation of Prussian blue (PB) and its analogs. Structural construction from the atomic level is imperative to maintain structural stability and ameliorate the long-term stability of PB. Herein, an inter nickel hexacyanoferrate (NNiFCN) is successfully introduced at the out layer of iron hexacyanoferrate (NFFCN) through ion exchange to improve structural stability through compressive stress locking by forming NNiFCN shell. Furthermore, the kinetics of sodium ion diffusion is enhanced through the built-in electric pathway. The electrochemical performance is therefore significantly improved with a remarkable long-term cycling stability over 3,000 cycles at 500 mA·g−1 in the full sodium-ion batteries (SIBs) with a maximum energy density of 91.94 Wh·g−1, indicating that the core-shell structured NNiFCN/NFFCN could be the low-cost and high-performance cathode for full SIBs in large-scale EES applications.

The surface feature of solid electrolytes fundamentally governs their own physical properties and significantly affects the interaction with the electrode materials. The evaluation of interfacial contact between the electrolyte and the metallic anode is largely relied on the macroscopic contact angle measurement, which is influenced by the intrinsic wettability and the microstructure of the electrolyte. In this work, the surface chemistry of the solid electrolyte is first regulated via facile thermal treatments. Then, scanning probe microscopy (SPM)-based techniques are comprehensively adopted to study the interaction between the electrolyte and metallic anode at the nanoscale. By manipulating the overpotential applied on the SPM tip, the mobile sodium ions at the subsurface of the solid electrolyte can be extracted toward the surface, and the eventual topography of the products is deliberately correlated with the sodium wettability. In this context, the impact of surface treatment on the sodium wettability of the surface layer is systematically evaluated based on the topographic evolution at the nanoscale. Furthermore, the local electrochemical reaction dynamics is revealed by correlating the surface ionic activity and current-voltage (I-V) curves. This work presents a new methodology to effectively evaluate the sodium wettability of the solid electrolyte, and these findings can provide meaningful implications to the surface engineering of ceramic electrolytes for high-performance solid-state batteries.

The development of aqueous dual-ion batteries (DIBs) has been hampered by two omnipresent issues, i.e. limited ESW of electrolyte and unsatisfactory electrode dissolution. In this study, a new DIB concept based on Cl[Formula: see text] and Na[Formula: see text] dual ion shutting with a sodium chloride (NaCl) aqueous electrolyte was reported. The electrochemical stable window (ESW) of the aqueous electrolyte was improved by inducing the urea to stabilize the shared water (H2O) molecule in the solvation sheath around Na[Formula: see text] and Cl[Formula: see text] based on the “water-in-salt” mechanism. Furthermore, an artificial SEI layer was introduced to inhibit the dissolution of Na3V[Formula: see text]Fe[Formula: see text](PO[Formula: see text] (Fe-NVP) cathode, thus ensuring a good cycling stability over 300 cycles of the aqueous DIB with an average discharging voltage of [Formula: see text]0.67 V. These exciting results advance the fundamental understanding of the artificial protective SEI and high-performance “water-in-salt” electrolyte design in developing cheap, stable aqueous DIB systems.

Metal solid-state batteries are regarded as the next-generation energy storage systems with high energy density and high safety. A robust and intimate solid-state interfacial contact between the sodium metal with the solid-state electrolyte (SSE) is vital to achieve good cyclic stability at high current density. However, inorganic SSEs suffer from poor stability when cycling at a current density below 2 mA cm−2. This can be ascribed to the dendrite formation through the SSE due to plating process or void formation during the stripping process. Furthermore, simply direct application of a sodium metal on SSE shows poor interfacial contact and low critical current density. In this review, the recent development of inorganic sodium-ion electrolytes, such as oxide-, sulphide-, and halide-based, are briefly discussed. More particularly, the dendrite formation through the SSE and the loss of solid-solid contact at the sodium/SSE interface are reviewed. Additionally, different engineering approaches to integrate the sodium metal with the solid-state electrolytes and its correlation with the electrochemical performance are discussed. Finally, perspectives in future researches are identified.

Nanomechanical properties are extremely critical to the applications of flexible electric devices and energy harvester; however, the direct mechanical measurement of composite nanofibers is challenging and rarely explored. In this work, we apply an effective method to obtain the elastic modulus distribution of lead zirconium titanate (PZT)-doped polyvinylidene fluoride (PVDF) nanofibers via bimodal amplitude modulated-frequency modulated scanning probe microscopy (AM-FM SPM). All the samples exhibit obvious piezoelectric properties, and the mechanical properties are clearly enhanced through doping of PZT. Compared with pure PVDF nanofibers, the composite nanofibers with PZT doping show higher elastic modulus which indicates superior stability under the same bending condition. The enhancement of mechanical properties in composite nanofibers via filler doping pave a way to the design of stable and flexible sustainable energy harvesters.

The scaling-up issue, mechanical instability, and possible packing capacity loss during pelletization remain as the major obstacles for the application of metal–organic frameworks (MOFs) in practic...

Freeze casting technology has experienced vast development since the early 2000s due to its versatility and simplicity for producing porous materials. A linear relationship between the final porosity and the initial solid material fraction in the suspension was reported by many researchers. However, the linear relationship cannot well describe the freeze casting for various samples. Here, we proposed an artificial neural network (ANN) to analyze the influence of critical parameters on freeze-cast porous materials. After well training the ANN model on experimental data, a porosity value can be predicted from four inputs, which describe the most influential process conditions. Based on the constructed model, two improvements are also successfully added on to infer more information. By involving big data from real experiments, this method effectively summarizes a general rule for diverse materials in one model, which gives a new insight into the freeze casting process. The good convergence and accuracy prove that our ANN model has the potential to be developed for solving more complicated issues of freeze casting. Finally, a user-friendly mini-program based on a well-trained ANN model is also provided to predict the porosity for customized freeze-casting experiments.

Electrostatic energy-storage capacitors, with their ultrahigh storage density and high temperature stability, have been receiving increasing attention of late for their ability to meet the critical requirements of pulsed power devices in low-consumption systems. In such a context, this work reports on the successful production of anti-ferroelectric (AFE) thin films with excellent energy storage performance under a relatively low electric field. In particular, La-doped PbZrO3 thin films were fabricated using a sol-gel method, yielding a recoverable energy storage density of 34.87 J cm−3 with an efficiency of 59.23% at room temperature under the electric field of ~800 kV cm−1. The temperature dependence of the energy storage property was demonstrated from room temperature to 210°C, indicating a stable density variation between 34.87 and 27.98 J cm−3. The films also exhibited excellent anti-fatigue property (endurance of up to 3×109 cycles and the recoverable energy storage density varied from 39.78 to 29.32 J cm−3 combined with an efficiency of 61.03%–44.95% under the test frequencies from 10 to 5000 Hz). All results were obtained using compact films with a high polarization ( P max) of approximately 103.7 μC cm−2 and low remnant polarization ( P r~7 μC cm−2), which was owing to the combination of LaNiO3 buffer layers and vacancies at Pb sites. These results illustrate the great potential of pulsed power devices in low-consumption systems operating in a wide range of temperatures and long-term operations.

NASICON-type Na3V2(PO4)3 (NVP) has been regarded as one of the most promising cathode materials for high-voltage sodium-ion batteries (SIBs) because of its high theoretical energy density and stabl...

To tackle the global restriction on the use of lead-based materials, a feasible strategy of developing a piezoelectric ceramic with a ferroelectric- and relaxor-coexisted hybrid state is proposed in order to reduce the energy barrier as well as to assist polarization rotation. A significantly enhanced piezoelectric coefficient, d33, of 173 pC/N along with a broadened high-temperature stability above 300 °C has been obtained. Further probing via piezoresponse force microscopy unveils the grain boundary-governed domain structures with complicated configurations, suggesting close correlations with the coexistence of ferroelectric and relaxor states. This work demonstrates a recipe for establishing a novel grain-based ferroelectric-relaxor hybrid state with improved piezoelectric performance, which can further be beneficial for realistic applications.

The Garnet-type solid electrolyte Li7La3Zr2O12 (LLZO) showing high ionic conductivity and a wide electrochemical potential window is considered as one of the most promising candidates for solid-sta...

In hunting for safe and cost-effective materials for post-Li-ion energy storage, the design and synthesis of high-performance solid electrolytes (SEs) for all-solid-state batteries are bottlenecks. Many issues associated with chemical stability during processing and storage and use of the SEs in ambient conditions need to be addressed. Now, the effect of water as well as oxyhdryl group (. OH) on NaBi3 O4 Cl2 are investigated by evaluating ionic conductivity. The presence of water and . OH results in an increase in ionic conductivity of NaBi3 O4 Cl2 owing to diffusion of H2 O into NaBi3 O4 Cl2 , partially forming binding . OH through oxygen vacancy repairing. Ab initio calculations reveal that the electrons significantly accumulate around . OH and induce a more negative charge center, which can promote Na+ hopping. This finding is fundamental for understanding the essential role of H2 O in halide-based SEs and provides possible roles in designing water-insensitive SEs through control of defects.

In this study, the underlying physical mechanisms of imprint are addressed in order to obtain a better understanding of the imprint phenomenon of relaxor Pb(Zn1/3Nb2/3)O3-x%PbTiO3 (PZN-x%PT) ferroelectric single crystals. The local domain structure and imprint of Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 (PZN-4.5%PT) single crystals are investigated by using Piezoresponse Force Microscopy (PFM) and Switching Spectroscopy PFM (SS-PFM) techniques, respectively. The results show that the imprint depends on polarization states. It is also found that surface charge accumulation shows no significant effects on the imprint behaviour of the PZN-4.5%PT single crystals. By studying the annealed samples in the oxygen and argon atmospheres respectively, it is found that the alignment of oxygen vacancy related defect dipoles is one of the origins for the occurrence of imprint. This study provides a better understanding of the imprint phenomenon in ferroelectric materials, which is crucial for the enhancement of the reliability and the advancement of ferroelectric relaxors into the application of ferroelectric devices.

Contact mode voltage modulated scanning probe microscopy (SPM) techniques, such as switching spectroscopy piezoresponse force microscopy (SS-PFM), are powerful tools for detecting local electromechanical behaviors. However, interpreting their signals, especially the contact resonance frequency (

Perceiving nanoscale ferroelectric phenomena from real space is of great importance for elucidating underlying ferroelectric physics. During the past decades, nanoscale ferroelectric characterization has mainly relied on the Piezoresponse Force Microscopy (PFM) invented in 1992, however, the fundamental limitations of PFM have made the nanoscale ferroelectric studies encounter significant bottlenecks. In this study, a high-resolution non-contact ferroelectric measurement, named Non-Contact Heterodyne Electrostrain Force Microscopy (NC-HEsFM), is introduced. It is demonstrated that NC-HEsFM can operate on multiple eigenmodes to perform ideal high-resolution ferroelectric domain mapping, standard ferroelectric hysteresis loop measurement, and controllable domain manipulation. By using a quartz tuning fork (QTF) sensor, multi-frequency operation, and heterodyne detection schemes, NC-HEsFM achieves a real non-contact yet non-destructive ferroelectric characterization with negligible electrostatic force effect and hence breaks the fundamental limitations of the conventional PFM. It is believed that NC-HEsFM can be extensively used in various ferroelectric or piezoelectric studies with providing substantially improved characterization performance. Meanwhile, the QTF-based force detection makes NC-HEsFM highly compatible for high-vacuum and low-temperature environments, providing ideal conditions for investigating the intrinsic ferroelectric phenomena with the possibility of achieving an atomically resolved ferroelectric characterization.

Thermoelectric (TE) polymers have unique advantages in converting heat into electricity. But their Seebeck coefficient is lower than that of inorganic TE materials by about one order of magnitude. Here, surface energy filtering is proposed to significantly enhance the Seebeck coefficient of TE polymers. The as-prepared poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, the most popular TE polymer) films from aqueous solution have a low Seebeck coefficient of 15–18 μV K−1 and a power factor of ∼0.008 μW m−1 K−2. Depositing Rhodamine 101, a zwitterion, on PEDOT:PSS films can enhance the Seebeck coefficient to 47.2 μV K−1 and the power factor to 401.2 μW m−1 K−2. The Rhodamine 101 effect on the Seebeck coefficient is consistent with its effect on the work function of PEDOT:PSS. The enhancement in the Seebeck coefficient is ascribed to the dipole moment of Rhodamine 101 and the interfacial dipole moment formed at the surface of the PEDOT:PSS films. This is confirmed by theoretical simulations. We call this mechanism surface energy filtering. Surface energy filtering can increase the mean energy of the transporting carriers and thus the Seebeck coefficient of the PEDOT:PSS films while only slightly affecting the electrical conductivity. It can thus significantly enhance the Seebeck coefficient and the power factor simultaneously.

Carbon nanotubes can affect the self-assembly of amyloid beta peptides (Aβ) related to neurodegenerative diseases. We use molecular dynamics (MD) to investigate the effects of carbon nanotubes (CNT) on the conformational evolution of monomeric Aβ1-42 peptide. The chirality of CNT varies from (10, 10), (15, 15), (20, 20) and (25, 25) that corresponds to declining curvatures. We show that the adhesion of peptide on CNT surface leads to internal structures predisposes to collapse, which might be reasonable methods to impede the initial nucleation and self-assembly. Adsorption induce the loss of the peptides' native structures. Adsorption and subsequent denaturation accompanies by a loss of surface hydration of peptide. When the curvature of CNT decreases, peptide spread almost completely over the CNT surface. Conversely, peptide will wrap around the CNT when the curvature of CNT is high. Peptide adsorption onto CNT also reduces their α-helical content and β-sheet ratio, indicating that the CNT significantly affect the formation of α-helical structures while inducing random coil conformations. The arrangement of peptides on CNT surface relates to the affinity of various amino acids onto CNT. These insights provide useful information for understanding the binding and winding tendency of peptides on carbon nanostructures’ surface.

NASICON-type of solid-state electrolyte, Na3Zr2Si2PO12 (NZSP), is one of the potential solid-state electrolytes for all-solid-state Na battery and Na-air battery. However, in solid-state synthesis, high sintering temperature above 1200 °C and long duration are required, which led to loss of volatile materials and formation of impurities at the grain boundaries. This hampers the total ionic conductivity of NZSP to be in the range of 10-4 S cm-1. Herein, we have reduced both the sintering temperature and time of the NZSP electrolyte by sintering the NZSP powders with different amounts of Na2SiO3 additive, which provides the liquid phase for the sintering process. The addition of 5 wt % Na2SiO3 has shown the highest total ionic conductivity of 1.45 mS cm-1 at room temperature. A systematic study of the effect of Na2SiO3 on the microstructure and electrical properties of the NZSP electrolyte is conducted by the structural study with the help of morphological and chemical observations using X-ray diffraction (XRD), scanning electron microscopy, and using focused ion-beam-time of flight-secondary ion mass spectroscopy. The XRD results revealed that cations from Na2SiO3 diffused into the bulk change the stoichiometry of NZSP, leading to an enlarged bottleneck area and hence lowering activation energy in the bulk, which contributes to the increment of the bulk ion conductivity, as indicated by the electrochemical impedance spectroscopy result. In addition, higher density and better microstructure contribute to improved grain boundary conductivity. More importantly, this study has achieved a highly ionic conductive NZSP only by facile addition of Na2SiO3 into the NZSP powder prior to the sintering stage.

Integrating multiple properties in a single system is crucial for the continuous developments in electronic devices. However, some physical properties are mutually exclusive in nature. Here, we report the coexistence of two seemingly mutually exclusive properties-polarity and two-dimensional conductivity-in ferroelectric Ba$_{0.2}$Sr$_{0.8}$TiO$_3$ thin films at the LaAlO$_3$/Ba$_{0.2}$Sr$_{0.8}$TiO$_3$ interface at room temperature. The polarity of a ~3.2 nm Ba$_{0.2}$Sr$_{0.8}$TiO$_3$ thin film is preserved with a two-dimensional mobile carrier density of ~0.05 electron per unit cell. We show that the electronic reconstruction resulting from the competition between the built-in electric field of LaAlO$_3$ and the polarization of Ba$_{0.2}$Sr$_{0.8}$TiO$_3$ is responsible for this unusual two-dimensional conducting polar phase. The general concept of exploiting mutually exclusive properties at oxide interfaces via electronic reconstruction may be applicable to other strongly-correlated oxide interfaces, thus opening windows to new functional nanoscale materials for applications in novel nanoelectronics., Comment: Main text: 25 pages, 4 figures Supplementary note: 19 pages, 11 figures

Two-dimensional-layered materials (TDLMs) have gained enormous attention because of their open layered structures and high specific capacities in sodium ion batteries (SIBs). However, effectively s...

All-solid-state lithium metal batteries (ASSLiMB) have been considered as one of the most promising next-generation high-energy storage systems that replace liquid organic electrolytes by solid-state electrolytes (SSE). Among many different types of SSE, NASICON-structured Li1+ xAl xGe2- x(PO3)4 (LAGP) shows high a ionic conductivity, high stability against moisture, and wide working electrochemical windows. However, it is unstable when it is in contact with molten Li, hence largely limiting its applications in ASSLiMB. To solve this issue, we have studied reaction processes and mechanisms between LAGP and molten Li, based on which a failure mechanism is hence proposed. With better understanding the failure mechanism, a thin thermosetting Li salt polymer, P(AA- co-MA)Li, layer is coated on the bare LAGP pellet before contacting with molten Li. To further increase the ionic conductivity of P(AA- co-MA)Li, LiCl is added in P(AA- co-MA)Li. A symmetric cell of Li/interface/LAGP/interface/Li is prepared using molten Li-Sn alloy and galvanically cycled at current densities of 15, 30, and 70 μA cm-2 for 100 cycles, showing stable low overpotentials of 0.036, 0.105, and 0.257 V, respectively. These electrochemical results demonstrate that the interface coating of P(AA- co-MA)Li can be an effective method to avoid an interfacial reaction between the LAGP electrolyte and molten Li.

Sodium-metal batteries have strong potential to be utilized as stationary high energy density storage devices. Owing to its high ionic conductivity, low electronic conductivity and relatively easy fabrication, NASICON-structure electrolyte (Na3Zr2Si2PO12) is one of the potential candidates to be considered in the solid-state sodium-metal batteries at room temperature. However, the large interfacial resistance between the solid-state electrolyte and the metallic sodium is known to limit the critical current density (CCD) of the cell. In this study, a simple and cost-effective annealing process is introduced to the electrolyte preparation to improves its interface with metallic sodium. X-ray photoelectron spectroscopy and scanning probe microscopy show that Si forms bonds with the surface functional groups when exposed to the ambient condition. With the removal of surface contamination as well as a partially reduced electrolyte surface, the annealed electrolyte shows an extremely small interfacial resistance of 11 Ω cm2 and a high CCD of 0.9 mA cm−2. This study provides an insight on the electrolyte surface preparation and its significant in a sodium-metal solid-state battery.

The evolution of the domain structures of [001]-oriented relaxor ferroelectric 0.93PbZn1/3Nb2/3O3-0.07PbTiO3 (PZN-7%PT) single crystals as a function of temperature was investigated in situ by using piezoresponse force microscopy (PFM). It was found that the local domain structure of PZN-7%PT single crystals at room temperature is rhombohedral with nanoscale twins. Temperature-dependent domain structures showed that the phase transition process is a collective process and that the sample underwent a sequence of rhombohedral (R) → monoclinic (Mc) → tetragonal (T) → cubic (C) phase transformations when the temperature increased from 25 °C to 170 °C. The results provide direct observation of the phase transition evolution of PZN-7%PT single crystals as a function of temperature, which is of great significance to fully understand the relationships between the domain structure and phase structure of PZN-7%PT single crystals.