Prediction of superionic state in LiH_(2) at conditions enroute to nuclear fusion

Hydrogen and lithium,along with their compounds,are crucial materials for nuclear fusion research.High-pressure studies have revealed intricate structural transitions in all these materials.However,research on lithium hydrides beyond LiH has mostly focused on the low-temperature regime.Here,we use density functional theory and ab initio molecular dynamics simulations to investigate the behavior of LiH_(2),a hydrogen-rich compound,near its melting point.Our study is particularly relevant to the low-pressure region of the compression pathway of lithium hydrides toward fusion.We discovered a premelting superionic phase transition in LiH_(2)that has significant implications for its mass transportation,elastic properties,and sound velocity.The theoretical boundary for the superionic transition and melting temperature was then determined.In contrast,we also found that the primary compound of lithium hydrides,LiH,does not exhibit a superionic transition.These findings have important implications for optimizing the compression path to achieve the ignition condition in inertial confinement fusion research,especially when lithium tritium-deuteride(LiTD)is used as the fuel.

New Superionic Memory Devices Can Provide Clues to the Human Memory Structure and to Consciousness

Since the work of Penrose and Hameroff the possibility is discussed that the location of human memory and consciousness could be connected with tubulin microtubules. If one would use superionic nano-materials rolled up to microtubules with an electrolyte inside the formed channels mediating fast ionic exchange of protons respectively lithium ions, it seems to be possible to write into such materials whole image arrays (pictures) under the action of the complex electromagnetic spectrum that composes these images. The same material and architecture may be recommended for super-computers. Especially microtubules with a protofilament number of 13 are the most important to note. We connected such microtubules before with Fibonacci nets composed of 13 sub-cells that were helically rolled up to deliver suitable channels. Our recent Fibonacci analysis of Wadsley-Roth shear phases such as niobium tungsten oxide , exhibiting channels for ultra-fast lithium-ion diffusion, suggests to use these materials, besides super-battery main application, in form of nanorods or microtubules as effectively working superionic memory devices for computers that work ultra-fast with the complex effectiveness of human brains. Finally, we pose the question, whether dark matter, ever connected with ultrafast movement of ordinary matter, may be responsible for synchronization between interactions of human brains and consciousness.

IONIC CONDUCTION MECHANISM IN Na_(5+x)YA1_xSi_(4-x)O_(12) SUPERIONIC CONDUCTORS

Na5+xYAlxSi4-xO12 superionic conductors arerhombohedral R3c space group.Their structures arecharacterized by(Alx/4Si1-x/4)O4 tetrahedra linked toform puckered(Al3xSi4-x)4O35 rings parallel to thebasal plane of the hexagonal cell.These rings,separated by parts of sodium oxygen polyhedron,arestacked to form large rigid colums parallel to c axis.The columns are linked by[YO6]octahedra to form athree-dimensional Framework with large channels betweenthe rings.Parts of Na ions located in the cores of thecolumns are movable.In terms of the conductionmechanism,the concentration of conducting Na+ ions wascarried out and compared with the experimental results.It was found that the theoretical values accord withthe experimental results.

Amphoteric covalent organic framework as single Li+superionic conductor in all-solid-state

As a novel class of porous crystalline solids,covalent organic frameworks(COFs)based electrolyte can combine the advantages of both inorganic and polymer electrolytes,leading to such as higher structural stability to inhibit lithium dendrites and better processing facility for improving interfacial contact.However,the ionic components of Li salt tend to be closely associated in the form of ion pairs or even ionic aggregates in the channel of COFs due to strong coulombic interactions,thus resulting in slow ionic diffusion dynamics and low ionic conductivity.Herein,we successfully designed and synthesized a novel single-ion conducting nitrogen hybrid conjugated skeleton(NCS)as all solid electrolyte,whose backbone is consisted with triazine and piperazine rings.A loose bonding between the triazine rings and cations would lower the energy barrier during ions transfer,and electrostatic forces with piperazine rings could“anchor”anions to increase the selectivity during ions transfer.Thus,the NCSelectrolyte exhibits excellent room temperature lithium-ion conductivity up to 1.49 mS·cm−1 and high transference number of 0.84 without employing any solvent,which to the best of our knowledge is one of the highest COF-based electrolytes so far.Moreover,the fabricated all-solid-state lithium metal batteries demonstrate highly attractive properties with quite stable cycling performance over 100 cycles with 82%capacity reservation at 0.5 C.

Stable all-solid-state Li-Te battery with Li_(3)TbBr_(6) superionic conductor

Rare-earth(RE)halide solid electrolytes(HSEs)have been an emerging research area due to their good electrochemical and mechanical properties for all-solid-state lithium batteries(ASSBs).However,only very limited types of HSEs have been reported with high performance.In this work,tens of grams of RE-HSE Li_(3)TbBr_(6)(LTbB)was synthesized by a vacuum evaporationassisted method.The as-prepared LTbB displays a high ionic conductivity of 1.7 mS·cm^(-1),a wide electrochemical window,and good formability.Accordingly,the assembled solid lithium-tellurium(Li-Te)battery based on the LTbB HSE exhibits excellent cycling stability up to 600 cycles,which is superior to most previous reports.The processes and the chemicals during the discharge/charge of Li-Te batteries have been studied by various in situ and ex situ characterizations.Theoretical calculations have demonstrated the dominant conductivity contributions of the direct[octahedral]-[octahedral]([Oct]-[Oct])pathway for Li ion migrations in the electrolyte.The Tb sites guarantee efficient electron transfer while the Li 2s orbitals are not affected during migration,leading to a low activation barrier.Therefore,this successful fabrication and application of LTbB have offered a highly competitive solution for solid electrolytes in ASSBs,indicating the great potential of RE-based HSEs in energy devices.

An end-to-end artificial intelligence platform enables real-time assessment of superionic conductors

Superionic conductors(SCs)exhibiting low ion migration activation energy(Ea)are critical to the performance of electrochemical energy storage devices such as solid-state batteries and fuel cells.However,it is challenging to obtain Ea experimentally and theoretically,and the artificial intelligence(AI)method is expected to bring a breakthrough in predicting Ea.Here,we proposed an AI platform(named AI-IMAE)to predict the Ea of cation and anion conductors,including Li^(+),Na^(+),Ag^(+),Al^(3+),Mg^(2+),Zn^(2+),Cu^((2)+),F^(−),and O^(2−),which is~105 times faster than traditional methods.The proposed AI-IMAE is based on crystal graph neural network models and achieves a holistic average absolute error of 0.19 eV,a median absolute error of 0.09 eV,and a Pearson coefficient of 0.92.Using AI-IMAE,we rapidly discovered 316 promising SCs as solid-state electrolytes and 129 SCs as cathode materials from 144,595 inorganic compounds.AI-IMAE is expected to completely solve the challenge of time-consuming Ea prediction and blaze a new trail for large-scale studies of SCs with excellent performance.As more experimental and high-precision theoretical data become available,AI-IMAE can train custom models and transfer the existing models to new models through transfer learning to constantly meet more demands.

Sodium Superionic Conductors(NASICONs)as Cathode Materials for Sodium‑Ion Batteries

Sodium-ion batteries(SIBs)have developed rapidly owing to the high natural abundance,wide distribution,and low cost of sodium.Among the various materials used in SIBs,sodium superion conductor(NASICON)-based electrode materials with remarkable structural stability and high ionic conductivity are one of the most promising candidates for sodium storage electrodes.Nevertheless,the relatively low electronic conductivity of these materials makes them display poor electrochemical performance,significantly limiting their practical application.In recent years,the strategies of enhancing the inherent conductivity of NASICON-based cathode materials have been extensively studied through coating the active material with a conductive carbon layer,reducing the size of the cathode material,combining the cathode material with various carbon materials,and doping elements in the bulk phase.In this paper,we review the recent progress in the development of NASICON-based cathode materials for SIBs in terms of their synthesis,characterization,functional mechanisms,and performance validation/optimization.The advantages and disadvantages of such SIB cathode materials are analyzed,and the relationship between electrode structures and electrochemical performance as well as the strategies for enhancing their electrical conductivity and structural stability is highlighted.Some technical challenges of NASICON-based cathode materials with respect to SIB performance are analyzed,and several future research directions are also proposed for overcoming the challenges toward practical applications.

RESEARCH ON σ～ω IN AMORPHOUS SUPERIONIC CONDUCTORS

I. INTRODUCTIONIn recent years, people have conducted a lot of experiments and valuable theoretical studies on amorphous superionic conductors. From their results, the σ～ω property of amorphous superionic conductors can generally be concluded as follows:

Molecular dynamics simulation of calcium fluoride——Crystalline, superionic, molten and quenched-amorphous phases

The results from the molecular dynamics simulations on crystalline, superionic, molten and quenched-amorphous states of calcium fluoride system are reported. The Ca++ and F- sublattices are studied by using the method of bond order parameters. The result shows that both Ca++ and F- sublattices can be described with the bond-orientation normal distribution model. In the superionic phase the Ca++ cations keep their original stable fcc frame, but in the F- case random distortion generates from their original simple cubic (sc) structure. The simulation on the molten phase gives three radial distribution functions that are difficult to separate from the experimental X-ray diffraction data. The simulation of quenched-amorphous state shows that a dense random packing of equivalent spheres centered by Ca++ cations occurs in the system simulated. However, the system quenched is not stable enough because the Ca++ cation and F- anions around it do not form themselves into a certain configuration.

First-principles insight into the entanglements between superionic diffusion and Li/Al antisite in Al-doped Li1+xAlxGe2–x(PO4)3(LAGP)

As an ion conductor, the Al-doped Li1+xAlxGe2-x(PO4)3(LAGP) demonstrates the superionic Li diffusion behavior, however,without the convinced verifications. In this context, the density functional theory(DFT) calculations are employed to clarify the structural origin of the fast Li ion migration kinetics in LAGP solid electrolytes. The calculated results show that doping of Al leads to an emerging high-energy 36 f Li site, which plays an important role in promoting the Li diffusion and can largely lower the Li ion diffusion energy barrier. Moreover, the Li/Al antisite defect is investigated firstly, with which the Li ions are excited to occupy a relatively high energy site in LAGP. The obvious local structural distortion by Li/Al antisite results in the coordination change upon Li diffusion(lattice field distortion), which facilitates the Li diffusion significantly and is probably the main reason to account for the superionic diffusion phenomenon. Therefore, the occupation of Li at high-energy sites should be an effective method to establish the fast Li diffusion, which implies a rewarding avenue to build better Li-ion batteries.

NASICON-Structured NaTi2（PO4）3 for Sustainable Energy Storage

Several emerging energy storage technologies and systems have been demonstrated that feature low cost,high rate capability,and durability for potential use in large-scale grid and high-power applications.Owing to its outstanding ion conductivity,ultrafast Na-ion insertion kinetics,excellent structural stability,and large theoretical capacity,the sodium superionic conductor(NASICON)-structured insertion material NaTi2(PO4)3(NTP)has attracted considerable attention as the optimal electrode material for sodium-ion batteries(SIBs)and Na-ion hybrid capacitors(NHCs).On the basis of recent studies,NaTi2(PO4)3 has raised the rate capabilities,cycling stability,and mass loading of rechargeable SIBs and NHCs to commercially acceptable levels.In this comprehensive review,starting with the structures and electrochemical properties of NTP,we present recent progress in the application of NTP to SIBs,including non-aqueous batteries,aqueous batteries,aqueous batteries with desalination,and sodium-ion hybrid capacitors.After a thorough discussion of the unique NASICON structure of NTP,various strategies for improving the performance of NTP electrode have been presented and summarized in detail.Further,the major challenges and perspectives regarding the prospects for the use of NTP-based electrodes in energy storage systems have also been summarized to offer a guideline for further improving the performance of NTP-based electrodes.

Percolation-induced resistivity drop in lutetium dihydride with controllable electrical conductivity over six orders of magnitude

The recent report of near-ambient superconductivity in the nitrogen-doped lutetium hydride has attracted considerable attention.Subsequent follow-up studies confirmed the pressure-induced color changes in both N-free and N-doped LuH_(2) but failed to reproduce superconductivity. It remains a puzzle why the samples in the original report exhibited pronounced resistance anomaly reminiscent of the superconducting transition. Here, we show that percolation of metallic grains with high conductivity through the insulating surfaces in cold-pressed LuH_(2) samples can occasionally produce sharp resistance drops, which even display magnetic field and/or current dependences but stay far from zero resistance. The insulating surface of LuH2grain should be attributed to the modification of hydrogen stoichiometry or the contamination by oxygen/nitrogen, resulting in an increase of resistance by over six orders of magnitude. Such an effect is more significant than that discovered recently in LaH_(3±x), which may indicate that LuH_(2) can be a potential superionic conductor. Our results call for caution in asserting the resistivity drops as superconductivity and invalidate the background subtraction in analyzing the corresponding resistance data.

Enhanced room-temperature Na^(+) ionic conductivity in Na_(4.92)Y_(0.92)Zr_(0.08)Si_(4)O_(12)

Developing cost-effective and reliable solid-state sodium batteries with superior performance is crucial for stationary energy storage.A key component in facilitating their application is a solid-state electrolyte with high conductivity and stability.Herein,we employed aliovalent cation substitution to enhance ionic conductivity while preserving the crystal structure.Optimized substitution of Y^(3+)with Zr^(4+)in Na_(5)YSi_(4)O_(12) introduced Naþion vacancies,resulting in high bulk and total conductivities of up to 6.5 and 3.3 mS cm^(-1),respectively,at room temperature with the composition Na_(4.92)Y_(0.92)Zr_(0.08)Si_(4)O_(12)(NYZS).NYZS shows exceptional electrochemical stability(up to 10 V vs.Naþ/Na),favorable interfacial compatibility with Na,and an excellent critical current density of 2.4 mA cm^(-2).The enhanced conductivity of Naþions in NYZS was elucidated using solid-state nuclear magnetic resonance techniques and theoretical simulations,revealing two migration routes facilitated by the synergistic effect of increased Naþion vacancies and improved chemical environment due to Zr^(4+)substitution.NYZS extends the list of suitable solid-state electrolytes and enables the facile synthesis of stable,low-cost Naþion silicate electrolytes.

Unconventionally anisotropic growth of PbSe nanorods:Controllable fabrication under solution-solid-solid regime over Ag2Se catalysis for broadband photodetection

Broadband optoelectronic devices intrigue enormous interests on account of their promising potential in optical communications,sensors and environmental monitoring.PbSe nanocrystals are promising candidates for the construction of next-generation photodetectors due to their fascinating intrinsic properties and solution-processed compatibility with varied substrates.Here,we report the fabrication of a broadband photodetector on the basis of high-quality solution-processed PbSe nanorods in rock-salt phase grown along unconventionally anisotropic growth direction of<112>zone axis.The rock-salt PbSe nanorods are synthesized in solution phase over the catalysis of Ag2Se with relatively high-temperature body-centered cubic phase via a solution-solid-solid growth regime using oleylamine and oleic acid as solvents and stabilizer surfactants,from which the PbSe nanorods with the unconventionally anisotropic growth direction are controllably grown in size and shape in the synthetic procedure typically with about 17 nm in diameter and 58 nm in length on average.Meanwhile,the PbSe nanorods-based photodetector exhibits a broadband response from 405 to 1,064 nm with a high responsivity of 0.78 A·W^(-1)and a fast response time of 17.5μs.The response time is much faster in comparison with most of the PbSe-based photodetectors with response time in millisecond level.

Tuning crystal structure and redox potential of NASICON-type cathodes for sodium-ion batteries

Sodium superionic conductor(NASICON)-type compounds have been regarded as promising cathodes for sodium-ion batteries(SIBs)due to their favorable ionic conductivity and robust structural stability.However,their high cost and relatively low energy density restrict their further practical application,which can be tailored by widening the operating voltages with earth-abundant elements such as Mn.Here,we propose a rational strategy of infusing Mn element in NASICON frameworks with sufficiently mobile sodium ions that enhances the redox voltage and ionic migration activity.The optimized structure of Na3.5Mn0.5V1.5(PO4)3/C is achieved and investigated systematically to be a durable cathode(76.6%capacity retention over 5,000 cycles at 20 C)for SIBs,which exhibits high reversible capacity(113.1 mAh·g^−1 at 0.5 C)with relatively low volume change(7.6%).Importantly,its high-areal-loading and temperature-resistant sodium ion storage properties are evaluated,and the full-cell configuration is demonstrated.This work indicates that this Na3.5Mn0.5V1.5(PO4)3/C composite could be a promising cathode candidate for SIBs.

Air Stability of Solid‑State Sulfide Batteries and Electrolytes

Sulfides have been widely acknowledged as one of the most promising solid electrolytes(SEs)for all-solid-state batteries(ASSBs)due to their superior ionic conductivity and favourable mechanical properties.However,the extremely poor air stability of sulfide SEs leads to destroyed structure/performance and release of toxic H_(2)S gas,which greatly limits mass-production/practical application of sulfide SEs and ASSBs.This review is designed to serve as an all-inclusive handbook for studying this critical issue.First,the research history and milestone breakthroughs of this field are reviewed,and this is followed by an in-depth elaboration of the theoretical paradigms that have been developed thus far,including the random network theory of glasses,hard and soft acids and bases(HSAB)theory,thermodynamic analysis and kinetics of interfacial reactions.Moreover,the characterization of air stability is reviewed from the perspectives of H2S generation,morphology evolution,mass change,component/structure variations and electrochemical performance.Furthermore,effective strategies for improving the air stabilities of sulfide SEs are highlighted,including H_(2)S absorbents,elemental substitution,design of new materials,surface engineering and sulfide-polymer composite electrolytes.Finally,future research directions are proposed for benign development of air stability for sulfide SEs and ASSBs.

Fast synthesis and improved electrical stability in n-type Ag_(2)Te thermoelectric materials

Cu-and Ag-based superionic conductors are promising thermoelectric materials due to their good electrical properties and intrinsically low thermal conductivity. However, the poor electrical and thermal stability restrict their application. In this work, n-type pure phase Ag_(2) Te compound is synthesized by simply grinding elemental powders at room temperature and compacted by spark plasma sintering. It is found that, because of the migration of Ag+after the phase transition around 425 K, submicron pores are formed inside the samples during the electrical performance measurement, resulting in poor electrical stability and repeatability of Ag_(2) Te samples. However, Pb-doped Ag_(2-x)Pb_(x)Te(x = 0–0.05) specimens exhibit improved electrical stability by the precipitation of the secondary phase Pb Te in the Ag_(2) Te matrix, which is confirmed via cyclic electrical property measurement and microstructure characterization.A maximum z T = 0.72 is obtained at 570 K for x = 0.03 mainly due to the increased power factor.

Ultra-stable carbon-coated sodium vanadium phosphate as cathode material for sodium-ion battery

Based on the excellent sodium ion mobility of sodium superionic conductor structures,Na_(3)V_(2)(PO_(4))_(3)materials have become promising cathode materials in sodium-ion batteries(SIBs).However,inadequate electronic transport of Na_(3)V_(2)(PO_(4))_(3)limits the cycling stability and rate performances in SIBs.In this work,high-performance conductive carbon-coated Na_(3)V_(2)(PO_(4))_(3)materials are obtained via a simple and facile ball-milling assisted solid-state method by utilizing citric acid as carbon sources.The carbon-coated composite electrodes display a high initial specific capacity of 111.6 mAh·g^(-1),and the specific capacity could retention reach 92.83%after 100 cycles at 1C with the high coulombic efficiency(99.95%).More importantly,the capacity of conductive carbon-coated nano-sized Na_(3)V_(2)(PO_(4))_(3)can remain 48.5 mAh·g^(-1) at 10℃after 3000 cycles(initial capacity of 101.2 mAh·g^(-1)).At the same time,high coulombic efficiency(near 100%)has little decay even at a high rate of 20℃during 1000 cycles,demonstrating the excellent cycling stability and remarkable rate performances,and showing potential in largescale productions and applications.

Na_(3)Zr_(2)Si_(2)PO_(12) solid-state electrolyte with glass-like morphology for enhanced dendrite suppression

Rechargeable batteries based on solid-state electrolytes are of great interest and importance for the next-generation energy storage due to their high energy output and improved safety.For building the solid-state batteries,Na_(3)Zr_(2)Si_(2)PO_(12)(NZSP)represents a promising candidate as it features high chemical stability against air exposure and a high Na^(+)conductivity.NZSP pellets were usually calcined at a high temperature,and the high volatility of Na and P elements easily led to the formation of impurity phase.In this work,the effects of calcination temperature and stoichiometry on the phase purity and ionic conductivity of the NZSP electrolyte were studied.At an elevated sintering temperature,the NZSP electrolyte showed a high ionic conductivity owing to decreased porosity,and the highest ionic conductivity at 30℃was observed to be 2.75×10^(-5)S·cm^(-1)with an activation energy of 0.41 eV.For the stoichiometry,the introduction of 5 mol%excessive P results in formation of more Na_(3)PO_(4) and glass-like phase at the grain boundary,which caused the blurred grain boundary and reduced grain barrier,and effectively suppressed Na dendrite growth,then accounted for improved cycling performance of a Na‖Na symmetric cell.Our work provided insights on reasonable design and preparation of NZSP electrolyte towards practical realization of solid-state Na-metal batteries.

Tailoring the LiNbO_(3)coating of Ni-rich cathode materials for stable and high-performance all-solid-state batteries

The research and development of advanced nanocoatings for high-capacity cathode materials is currently a hot topic in the field of solid-state batteries(SSBs).Protective surface coatings prevent direct contact between the cathode material and solid electrolyte,thereby inhibiting detrimental interfacial decomposition reactions.This is particularly important when using lithium thiophosphate superionic solid electrolytes,as these materials exhibit a narrow electrochemical stability window,and therefore,are prone to degradation during battery operation.Herein we show that the cycling performance of LiNbO_(3)-coated Ni-rich LiNi_(x)Co_(y)Mn_(z)O_(2)cathode materials is strongly dependent on the sample history and(coating)synthesis conditions.We demonstrate that post-treatment in a pure oxygen atmosphere at 350℃results in the formation of a surface layer with a unique microstructure,consisting of LiNbO_(3)nanoparticles distributed in a carbonate matrix.If tested at 45℃and C/5 rate in pellet-stack SSB full cells with Li_(4)Ti_(5)O_(12)and Li_(6)PS_(5)Cl as anode material and solid electrolyte,respectively,around 80%of the initial specific discharge capacity is retained after 200 cycles(~160 mAh·g^(−1),~1.7 mAh·cm^(−2)).Our results highlight the importance of tailoring the coating chemistry to the electrode material(s)for practical SSB applications.