Ion Path Research Articles

Detection, Analysis, and Behavior of Soft-Shorts in Solid-State Batteries

Lithium metal batteries face numerous challenges before being employed in practical energy storage systems. Chief among these is the suppression of lithium dendrites, which lead to cell shorting and thermal runaway. In the field of solid-state batteries, there is often talk of “soft-shorts”, where small lithium dendrites form, short, then disappear. However, there is no clear consensus on the definition of soft-shorts, how they behave, and what their presence means for solid electrolyte development. Here, we use composite polymer electrolytes as exemplary solid electrolytes to detect, analyze, and thoroughly describe the varied behavior of soft-shorts. We define soft-shorts and show quantitatively that both ionic and electronic current flow simultaneously in a soft-shorted cell. The amount of each current depends on dendrite size, which dictates the resistance to the electronic pathway as well as Joule heating of the thin metal filaments. This heating leads to the “burning out” of the dendrites, which is responsible for the rapid un-shorting of soft-shorted cells. We use computational modeling to quantify the dendrite properties and explain how this leads to the observed transient behavior. More persistent soft-shorts are analyzed with temperature-dependent, quantitative electrochemical impedance fitting, where it is shown that parallel ionic and electronic current paths present impedance data that can be misinterpreted without rigorous analysis. The advantages and disadvantages of several soft-short characterization techniques are discussed. In the end, we show that soft-shorts are diverse in nature and thus require diverse tools and keen eyes from researchers to avoid the over-selling of flawed materials for lithium metal batteries.

Femtosecond-Laser Microstructuring Improves Solid-State Electrolyte/Cathode Ionic Transport

All-solid-state batteries (ASSBs) provide the opportunity for substantially enhanced gravimetric and volumetric energy and power density and improved safety. However, these gains will not be realized without first overcoming substantial challenges, notably, the high interfacial resistance between electrodes and the solid-state electrolyte (SSE) which requires high stack pressures, on the order of 10,000 psi, to achieve high performance metrics.[1,2]. Already there is a large and growing body of research demonstrating the advantages of laser structuring of Li-ion battery materials for enhanced kinetics and shorter diffusion pathways [3,4]. This work extends these advantages to ASSBs through lowering the catholyte-SSE interfacial impedance by increasing its surface area and providing less torturous paths for ion diffusion.The work presented here uses a near-IR (1030 nm) femtosecond laser (pulse duration approx. 250 fs) to ablate microstructures into the surface of a slurry-cast LiNi0.8Mn0.1Co0.1O2 (NMC811):Li6PS5Cl catholyte. Micrometer-sized channel structures were ablated at various depths and pitch spacings to assess the effect of patterning on cell performance. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) measurements were acquired on both pristine and patterned samples to ensure that the femtosecond laser pulses do not cause any residual compositional or phase changes, respectively. Critically, low interfacial resistance will require that an SSE layer be applied to the patterned catholyte such that the microstructure is preserved while maintaining intimate contact between the catholyte and SSE layer. SSE layers were both slurry cast and pellet-pressed onto both pristine and patterned electrodes. Cross-sectional SEM was used to investigate the degree of interfacial contact, and relate interface quality to parameters such as SSE application technique (e.g., pellet pressing vs. slurry casting) and slurry properties (i.e., viscosity). The improvement to interfacial ionic conductivity is assessed using electrochemical impedance spectroscopy (EIS). The effect of stack pressure is analyzed in order to assess the degree to which laser patterning can alleviate stack pressure requirements in ASSBs.

Advancing osmotic power generation using bioinspired MXene-based membrane via maze breaking

The osmotic energy generated by the salinity gradient between seawater and river water is a potential blue energy that can be harnessed to alleviate the current energy crisis but without causing environmental pollution. Two dimensional (2D) MXene nano sheets can be horizontally assembled into laminar membranes to create nanochannels enabling the ionic selective transport and thus to capture the osmotic energy. However, the ions have to transport through the maze-like tortuous laminar channels sourced from the interspaces between two neighboring nanosheets, which lead to super-high transport resistance and low power density, hindering their wide applications. Enlightened by the water and mineral ions transport in trees, here, a bioinspired MXene-based membrane with aligned and ordered vertical channels is developed for efficient osmotic power generation from salinity gradient. The peak power density of the electrical devices composed of such maze-breaking membranes could be achieved up to 372 W m−2, which is at least one order of magnitude higher than conventionally horizontal membranes reported in the literature. The high-power generation efficiency was attributed to the shortened ionic transport path (by breaking the maze). Moreover, the membrane possesses a high antifouling performance as well as long-term stability, possibly due to the strong combination of MXene and GO via the hydrogen bonds and cross-linking in preparation. This work reports a new and high-performance MXene-based membrane not only for osmotic energy conversion but also for other practical separations.

ZIF-8 derived ZnFe2O4 nanoparticles as a high-performance anode material for lithium-ion batteries

ZnFe2O4 nanoparticles and ZnO/ZnFe2O4 composites were prepared by simple calcination of Fe2O3/ZIF-8. The bimetallic ZnFe2O4 not only inherit the high lithium storage capacity of Fe2O3, but also exhibit higher conductivity than that of single Fe or Zn oxides. The effect of Fe2O3 content in the raw materials on the structure and electrochemical performance of the product was discussed. Appropriate amount of Fe2O3 helps to obtain ZnFe2O4 nanoparticles with small size and porous structure, which can shorten the diffusion path of lithium ions, increase the contact area between the electrode material and electrolyte, thus improving the performance of the material. After 200 cycles at a current density of 300 mA g−1, the specific capacity can reach 1223.2 mAh/g. When the current density is increased to 2 A/g, the discharge specific capacity is retained at 809.4 mAh/g after 500 cycles.

Rationally Designed ZnTe@C Nanowires with Superior Zinc Storage Performance for Aqueous Zn Batteries.

Te-based materials with excellent electrical conductivity and ultra-high volume specific capacity have attracted much attention for the cost-efficient aqueous Zn batteries. However, the construction of functional structures with mild volume expansion and suppressed shuttle effects, enabling an expanded lifespan, is still a challenge for conversion-type materials. Herein, the carbon-coated zinc telluride nanowires (ZnTe@C NWs) are rationally designed as a high-performance cathode material for aqueous Zn batteries. The carbon-coated1Dnanostructure could not only provide optimized transmission path for electrons and ions, but also help to maintain structure integrity upon volume variation and suppress intermediates dissolution, endowing the ZnTe@C NWs with improved cycling stability and reaction kinetics. Consequently, a reversible six-electron reaction mechanism of ZnTe@C NWs based on Te2- /Te4+ conversion with excellent output capacity (586 mAh g-1 at 0.1 A g-1 ) and lifespan (>250 mAh g-1 retained for 400 cycles at 1 A g-1 ) is eventually achieved.

3D Nanocellulose Matrix Enhancing the Lithiation Dynamics of FePS3 Anode

Abstract2D layered FePS3 is an anode material with high energy density for lithium‐ion batteries. Here, a simple and effective vacuum filtration method is used to successfully synthesize nanocellulose (NC) and FePS3 into a FePS3‐NC electrode with a 3D network structure. Based on the detailed structural characterization, electrochemical testing, and density functional theory, the relationship between NC and FePS3 materials in the lithium storage process is established from the perspective of lithium ions dynamics. The results display that NC can effectively decrease the adsorption energy of FePS3 materials, promote the construction of a 3D network structure, and form flexible FePS3‐NC electrodes. In addition, the migration path of lithium ions in the FePS3‐NC system is more inclined to the Y‐axis, and the migration barrier is also significantly reduced from 0.7714 to 0.4245 eV, which significantly improves the migration speed of lithium ions and the battery capacity. Therefore, the results of this study are conducive to further understand the dynamic mechanism of NC promoting rapid lithium storage in FePS3 materials and can provide good guidance for the study of flexible electrodes.

Synergistic Effect of Zn–Co Bimetallic Selenide Composites for Lithium–Sulfur Battery

Compared with monometallic selenides, heterogeneous bimetallic selenides have rich phase boundaries and superior electrical conductivity. ZnSe/CoSe2 composites were prepared by introducing Zn metal and using ZIF-8/67 as the precursor through the synergistic effect between Zn and Co after selenification. The electrocatalytic conversion of polysulfide is accelerated by ZnSe through chemical adsorption and the catalytic effect. The conductive CoSe2 surface provides a rapid diffusion path for lithium ions, accelerating the conversion of the polysulfide. On the basis of their individual strengths, ZnSe and CoSe2 can jointly promote the smooth adsorptive–diffuse–catalytic conversion process of polysulfide and induce the growth of lithium sulfide around its heterogeneous interface, thus enhancing the electrochemical performance of the lithium–sulfur battery cathode materials. The ZnSe/CoSe2–S electrode, at the optimal Zn-to-Co ratio of 1:1, has a 790.06 mAh g−1 initial specific capacity at 0.2 C and excellent cycling stability at 1 C. After 300 cycles, the final capacity is 300.85 mAh g−1, and the capacity retention rate reaches 82.71%.

Al Implantation in Sic; Where Will the Ions Come to Rest?

In all implantations into crystalline targets, quite a few ions find a path along a crystal channel or plane, so called channeling, and these ions travel deep into the crystal. This paper treats aluminum (Al) implantation in 4H-SiC and show how the crystal lattice will guide incoming ions deep into the target and modify the final dopant distribution. 4H-SiC samples have been implanted with 100 keV Al-ions, in a “random” direction using the wafer miscut angle of 4°, as well as with the impact beam aligned anti-parallel to the [0001] direction. Aluminium concentration versus depth profiles has been recorded by secondary ion mass spectrometry (SIMS). To track the most probable ion paths during stopping process, SIIMPL, a Monte Carlo simulation code based on the binary collision approximation (MC-BCA) has been used. In addition, the remaining ion energy has been extracted from SIIMPL at various depth along the ion path. Our results show that, independent of the used impact angle, some ions will be steered by crystal planes predominantly into the direction and also along the six directions. The energy loss is smaller along these low index axes. Therefore, at a depth of 1.2 μm, some Al ions along a path may still have kinetic energy, more than 40% of the original 100 keV, and continues to move deep into the SiC sample. The mean projected range of 100 keV ions in 4H-SiC is about 120 nm.

Competition between Hydration Shell and Ordered Water Chain Induces Thickness-Dependent Desalination Performance in Carbon Nanotube Membrane

Exploring new reverse osmosis (RO) membranes that break the permeability-selectivity trade-off rule is the ultimate goal in seawater desalination. Both nanoporous monolayer graphene (NPG) and carbon nanotube (CNT) channels have been proposed to be promising candidates for this purpose. From the perspective of membrane thickness, both NPG and CNT can be classified into the same category, as NPG is equivalent to the thinnest CNT. While NPG has the advantage of a high water flux rate and CNT is excellent at salt rejection performance, a transition is expected in practical devices when the channel thickness increases from NPG to infinite-sized CNTs. By employing molecular dynamics (MD) simulations, we find that as the thickness of CNT increases, the water flux diminishes but the ion rejection rate increases. These transitions lead to optimal desalination performance around the cross-over size. Further molecular analysis reveals that this thickness effect originates from the formation of two hydration shells and their competition with the ordered water chain structure. With the increase in CNT thickness, the competition-dominated ion path through CNT is further narrowed. Once above this cross-over size, the highly confined ion path remains unchanged. Thus, the number of reduced water molecules also tends to stabilize, which explains the saturation of the salt rejection rate with the increasing CNT thickness. Our results offer insights into the molecular mechanisms of the thickness-dependent desalination performance in a one-dimensional nanochannel, which can provide useful guidance for the future design and optimization of new desalination membranes.

Oxidation behavior of the CVD-Al2O3 coatings on tungsten substrate at 1000 °C

In this paper, TiN/TiCN/Al2O3 coating, as a classic coating system for cemented carbide tools, was prepared by chemical vapor deposition (CVD) on pure tungsten substrate for improved oxidation resistance. It is found that the oxidation weight gain per unit surface area of the coated sample is 7.45 mg/cm2 after 5 h oxidation at 1000 °C, significantly lower than that of 218.44 mg/cm2 in uncoated specimen. Due to the difference of thermal expansion coefficient, a network of microcracks were formed within the top Al2O3 layer during fabrication process. These microcracks provide a diffusion path for titanium ions and oxygen ions in the initial oxidation stage (0−1h), which produces TiO2 at cracking regions. As oxidation time prolongs (1–5 h), the oxidation of nitride layer beneath the microcracking region creates short-circuit oxygen diffusion paths towards the metal substrate. The generation of volcanic-like WO3 breaks the graded structure of CVD coating and expands the channel between oxygen and substrate. Nevertheless, the weight gain is still limited at this stage as the main area of Al2O3 coating is dense and protective. Finally, the oxidation kinetics accelerate at 5–10 h when coating failure occurs and severe breakaway oxidation appears in tungsten.

Synergetic effect of ternary MnVMo-oxide electrode by hydrothermal method for high-performance asymmetric supercapacitor

The binder-free deposition facilitates fast electron transfer and smoothens the diffusion path of electrolyte ions into the matrix of electrode material. Herein, the ternary metal oxides, such as manganese vanadium molybdenum oxide (MnVMo-oxide) is directly deposited on nickel foam by a single-step hydrothermal method. X-ray diffraction study confirms formation of MnVMo-oxide phase. The X-ray photoelectron spectroscopy confirms the Mn, V, and Mo are in the +2 (and +3), +5, and +6 oxidation states. Deposition time variation results, change in nanostructures from nanoparticle-assembled sheets to rectangular nanosheets, also the size of micro rods. The porous microrods formed with uneven quasi-rectangular shaped nanosheets of MnVMo-oxide exhibit high areal capacitance of 814.5 mFcm−2 (as compared to other electrodes) measured in 1 M KOH electrolyte at 3 mAcm−2 current density. The enhanced capacitance of the MnVMo-8 electrode is due to the dominance of the diffusion process over the capacitive-controlled contribution and high diffusion coefficient. The fabricated asymmetric supercapacitor device MnVMo-oxide//activated carbon shows good areal capacitance of 40 mFcm−2 with 0.025 mWhcm−2 energy at 1.5 mWcm−2 power density measured at 2 mAcm−2 current density, and cyclic stability of about 71.45 % (Coulombic efficiency of 98 %) quantified up to ∼9000 consecutive cycles.

The XQR-30 metal absorber catalogue: 778 absorption systems spanning 2 ≲ z ≲ 6.5

ABSTRACT Intervening metal absorption lines in the spectra of z ≳ 6 quasars are fundamental probes of the ionization state and chemical composition of circumgalactic and intergalactic gas near the end of the reionization epoch. Large absorber samples are required to robustly measure typical absorber properties and to refine models of the synthesis, transport, and ionization of metals in the early Universe. The Ultimate XSHOOTER legacy survey of quasars at z ∼ 5.8–6.6 (XQR-30) has obtained high signal-to-noise spectra of 30 luminous quasars, nearly quadrupling the existing sample of 12 high quality z ∼ 6 quasar spectra. We use this unprecedented sample to construct a catalogue of 778 systems showing absorption in one or more of Mg ii (360 systems), Fe ii (184), C ii (46), C iv (479), Si iv (127), and N v (13) which span 2 ≲ z ≲ 6.5. This catalogue significantly expands on existing samples of z ≳ 5 absorbers, especially for C iv and Si iv which are important probes of the ionizing photon background at high redshift. The sample is 50 per cent (90 per cent) complete for rest-frame equivalent widths W ≳ 0.03 Å (0.09 Å). We publicly release the absorber catalogue along with completeness statistics and a python script to compute the absorption search path for different ions and redshift ranges. This data set is a key legacy resource for studies of enriched gas from the era of galaxy assembly to cosmic noon, and paves the way for even higher redshift studies with JWST and 30 m-class telescopes.

Control of the ion flux and energy distribution of dual-frequency capacitive RF plasmas by the variation of the driving voltages

Due to its advantages of spatial uniformity and ion energy control, a dual-frequency (DF) capacitive-coupled plasma is widely used in semiconductor etching and deposition processes. In low-pressure discharges, the mean free path of ions is longer than the sheath width, and the ion energy distribution function is sensitive to the driving voltage waveform. In this respect, it is necessary to use a particle-in-cell (PIC) simulation to observe ion movement according to the time-varying electric field in the sheath. This study uses a two-dimensional PIC simulation parallelized with a graphics processing unit to monitor the ion energy distribution and flux according to the DF voltage waveform. We suggested a method to control the ion energy through a phase-resolved ion energy distribution in the region, where the ion transit time is longer than the high-frequency period and shorter than the low-frequency period.

Advanced Composite Solid Electrolytes for Lithium Batteries: Filler Dimensional Design and Ion Path Optimization.

Composite solid electrolytes are considered to be the crucial components of all-solid-state lithium batteries, which are viewed as the next-generation energy storage devices for high energy density and long working life. Numerous studies have shown that fillers in composite solid electrolytes can effectively improve the ion-transport behavior, the essence of which lies in the optimization of the ion-transport path in the electrolyte. The performance is closely related to the structure of the fillers and the interaction between fillers and other electrolyte components including polymer matrices and lithium salts. In this review, the dimensional design of fillers in advanced composite solid electrolytes involving 0D-2D nanofillers, and 3D continuous frameworks are focused on. The ion-transport mechanism and the interaction between fillers and other electrolyte components are highlighted. In addition, sandwich-structured composite solid electrolytes with fillers are also discussed. Strategies for the design of composite solid electrolytes with high room temperature ionic conductivity are summarized, aiming to assist target-oriented research for high-performance composite solid electrolytes.

Effect of the thermalization of secondary electron energies on plasma formation during the irradiation of heavy ions

This study aims at understanding the effect of the thermalization of secondary electrons produced by incident heavy-ion impact ionization on plasma formation. The motions of the secondary electrons were simulated using pseudo-initial secondary electron energy distribution functions. These simulations allowed us to estimate the times when thermalization occurred and the probabilities of secondary electrons escaping the electric field created near the incident ion path according to the initial secondary electron energy distribution functions. The probabilities and thermalization processes were found to be almost independent of these functions which indicated that the secondary electrons were thermalized before the plasma was formed.

Defect and interface engineering of MXene-tagged N,F-doped carbon-CoSe2 heterostructure for superior hydrogen evolution reactions and supercapacitors

Defect and interface engineering on heterostructured electrode materials is an effective approach to improve the electrochemical performance of supercapacitors and water-splitting. Herein, we have prepared MXene nanosheets-tagged hetero atom-doped graphitic carbons wrapped CoSe2 (MXe-F,N-gCW-CoSe2) polyhedral heterostructure electrode material, and further investigated kinetic and thermodynamic factors that affect on defect and interface engineering to facilitate efficient electron and ionic path and promote the electrochemical active sites. The composites exhibit excellent hydrogen evolution reaction (HER) performances of the Tafel slope of 84.2 mV dec−1 and 94.5 mV dec−1 in 1 M KOH and 0.5 M H2SO4, respectively. It also shows a high specific capacity of 403.4C g−1 at 1 A g−1 and the thus-assembled MXe-F,N-gCW-CoSe2//AC hybrid supercapacitor revealed an energy density of 44.2 Wh kg−1 at a power density of 851.3 W kg−1 with superior stability of ∼94% after 10,000 cycles.

Ultrathin NiO/Ni3S2 Heterostructure as Electrocatalyst for Accelerated Polysulfide Conversion in Lithium–Sulfur Batteries

The practical application of Lithium–Sulfur batteries largely depends on highly efficient utilization and conversion of sulfur under the realistic condition of high‐sulfur content and low electrolyte/sulfur ratio. Rational design of heterostructure electrocatalysts with abundant active sites and strong interfacial electronic interactions is a promising but still challenging strategy for preventing shuttling of polysulfides in lithium–sulfur batteries. Herein, ultrathin nonlayered NiO/Ni3S2 heterostructure nanosheets are developed through topochemical transformation of layered Ni(OH)2 templates to improve the utilization of sulfur and facilitate stable cycling of batteries. As a multifunction catalyst, NiO/Ni3S2 not only enhances the adsorption of polysulfides and shorten the transport path of Li ions and electrons but also promotes the Li2S formation and transformation, which are verified by both in‐situ Raman spectroscopy and electrochemical investigations. Thus, the cell with NiO/Ni3S2 as electrocatalyst delivers an area capacity of 4.8 mAh cm−2 under the high sulfur loading (6 mg cm−2) and low electrolyte/sulfur ratio (4.3 μL mg−1). The strategy can be extended to 2D Ni foil, demonstrating its prospects in the construction of electrodes with high gravimetric/volumetric energy densities. The designed electrocatalyst of ultrathin nonlayered heterostructure will shed light on achieving high energy density lithium–sulfur batteries.

Nitrogen doped porous carbon with high rate performance for lithium ion storage

Amorphous carbon has been studied in anode electrode materials of lithium ion batteries (LIBs) due to its rich resources and adjustable structure. However, due to its low conductivity, it shows poor rate performance. In this work, amorphous nitrogen doped porous carbon (NDPC) was synthesized by salt template method using ionic liquid (C10H15N5) as sources of carbon and nitrogen. The structure characterization shows that there is an interaction between the introduction of nitrogen atoms and porous structure: nitrogen doping can promote charge transfer, and porous carbon structure can reduce the diffusion path of lithium ions. Therefore, the NDPC shows excellent lithium ion diffusion ability and good electronic conductivity. When NDPC is applied to the anode material of LIBs, it shows a superior lithium ion storage performance of 412 mA h g−1 after 200 cycles at a current density of 1860 mA g−1. The study provides favorable conditions for the development of carbon anode materials with in situ heteroatom doping and porous structure.

Enhanced Coloration Time of Electrochromic Device Using Integrated WO3@PEO Electrodes for Wearable Devices

Electrochromic technologies that exhibit low power consumption have been spotlighted recently. In particular, with the recent increase in demand for paper-like panel displays, faster coloration time has been focused on in researching electrochromic devices. Tungsten trioxide (WO3) has been widely used as an electrochromic material that exhibits excellent electrochromic performance with high thermal and mechanical stability. However, in a solid film-type WO3 layer, the coloration time was long due to its limited surface area and long diffusion paths of lithium ions (Li-ions). In this study, we attempted to fabricate a fibrous structure of WO3@poly(ethylene oxide) (PEO) composites through electrospinning. The fibrous and porous layer showed a faster coloration time due to a short Li-ion diffusion path. Additionally, PEO in fibers supports Li-ions being quickly transported into the WO3 particles through their high ionic conductivity. The optimized WO3@PEO fibrous structure showed 61.3 cm2/C of high coloration efficiency, 1.6s fast coloration time, and good cycle stability. Lastly, the electrochromic device was successfully fabricated on fabric using gel electrolytes and a conductive knitted fabric as a substrate and showed a comparable color change through a voltage change from -2.5 V to 1.5 V.

Synthesis and characterization of nickel doped LSM as possible cathode materials for LT-SOFC application

Doping lanthanum strontium manganite with Ni2+ at Mn site for 10–30 mol% was investigated as cathode material for LT-SOFC application. Nanopowders were prepared using a simple solution combustion technique and only after calcination at 1200 °C phase purity was obtained. While TEM analysis confirmed particle size around 30 nm, the DLS study showed average most probable size as 13 nm. The SEM-EDAX analysis revealed porous nanopowder of all the studied compositions. It also confirmed composition of the cathode material. In symmetric cell configuration, using lanthanum gallate as electrolyte, oxygen reduction reaction (ORR) and hence polarization resistance (RP) was studied in detail in the temperature range 500–800 °C. The composition La0.7Sr0.3Mn0.8Ni0.2O3 (LSMN7382) showed lowest RP value of 0.117–0.039 Ω-cm2 in the temperature range 500–800 °C. In contrast, La0.7Sr0.3MnO3 (LSM731) showed much higher RP value. Among the cathodes with Sr2+doping variation in La site, 30 mol% showed the best performance. The electrical conductivity of ∼80% dense electrolyte pellets were studied and highest conductivity of 70 S/cm at 800 °C was observed for LSMN7382 among the all compositions. Generation of hole takes place due to the charge compensation in Mn3+ to Mn4+ conversion while doping Sr2+ as well as Ni2+. At 30 mol% Ni2+ doping (LSMN7373), the decrease of conductivity may be attributed to the secondary phase formation. A detailed electrical circuit analysis of the impedance spectrum indicates that charge transfer polarization resistance is the key to control the interface performance. Such high ORR performance by nickel doping can be explained due to Mn4+ converted to Mn3+ at high temperature and thus creating oxygen vacancy to enhance ORR ionic path on the cathode surface.