Green's theorem and potentials in a volume conductor.
Boundary value problem for potentials in volume conductor based on Green theorem
ELECTROCARDIOGRAPHY↗
SEARCH · Engineering Papers
Results for “conductors”
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On bioelectric potentials in an inhomogeneous volume conductor.
Quasi-static potential distribution in inhomogeneous volume conductor analyzed using Green theorem
GREEN THEOREM↗
Ion Pair Uptake in Ion Gel Devices Based on Organic Mixed Ionic–Electronic Conductors
Abstract In organic mixed ionic–electronic conductors (OMIECs), it is critical to understand the motion of ions in the electrolyte and OMIEC. Generally, the focus is on the movement of net charge during gating, and the motion of neutral anion–cation pairs is seldom considered. Uptake of mobile ion pairs by the semiconductor before electrochemical gating (passive uptake) can be advantageous as this can improve device speed, and both ions can participate in charge compensation during gating. Here, such passive ion pair uptake in high‐speed solid‐state devices is demonstrated using an ion gel electrolyte. This is compared to a polymerized ionic liquid (PIL) electrolyte to understand how ion pair uptake affects device characteristics. Using X‐ray photoelectron spectroscopy, the passive uptake of ion pairs from the ion gel into the OMIEC is detected, whereas no uptake is observed with a PIL electrolyte. This is corroborated by X‐ray scattering, which reveals morphological changes to the OMIEC from the uptake of ion pairs. With in situ Raman, a reorganization of both anions and cations is then observed during gating. Finally, the speed and retention of OMIEC‐based neuromorphic devices are tuned by controlling the freedom of charge motion in the electrolyte.
Quill, Tyler J.↗
Photoluminescence Probes Ion Insertion into Amorphous and Crystalline Regions of Organic Mixed Conductors
Abstract Organic mixed ionic‐electronic conductors (OMIECs) have emerged as promising materials for a wide range of next‐generation technologies, including bioelectronics and neuromorphic computing. The performance of these materials depends on the transport of ions through the polycrystalline polymer matrix as well as how the distribution of ions and polarons in crystalline and amorphous regions impacts electronic transport. However, it is often challenging to distinguish whether ions enter crystalline or amorphous regions. In this work, steady‐state and time‐resolved photoluminescence (PL) spectroelectrochemistry is used to probe initial ion insertion in crystalline and amorphous regions of the OMIEC material poly(3‐[2‐[2‐(2‐methoxyethoxy)ethoxy]ethyl]thiophene ‐2,5‐diyl) (P3MEEET) as a function of applied voltage. It is found that PL spectroelectrochemistry reports on the initial stages of electrochemical doping through the quenching of PL emission. By distinguishing between amorphous and crystalline contributions to the PL spectrum, ion insertion in crystalline and amorphous regions as a function of voltage is tracked. It is found that PL spectroelectrochemistry is much more sensitive to the initial injection of ions than complementary methods, highlighting its potential as a sensitive tool for interrogating ion injection in OMIECs.
Collins, Garrett W.↗
Charge Carrier Induced Structural Ordering And Disordering in Organic Mixed Ionic Electronic Conductors
Operational stability underpins the successful application of organic mixed ionic-electronic conductors (OMIECs) in a wide range of fields, including biosensing, neuromorphic computing, and wearable electronics. Here in this work, both the operation and stability of a p-type OMIEC material of various molecular weights are investigated. Electrochemical transistor measurements reveal that device operation is very stable for at least 300 charging/discharging cycles independent of molecular weight, provided the charge density is kept below the threshold where strong charge–charge interactions become likely. When electrochemically charged to higher charge densities, an increase in device hysteresis and a decrease in conductivity due to a drop in the hole mobility arising from long-range microstructural disruptions are observed. By employing operando X-ray scattering techniques, two regimes of polaron-induced structural changes are found: 1) polaron-induced structural ordering at low carrier densities, and 2) irreversible structural disordering that disrupts charge transport at high carrier densities, where charge–charge interactions are significant. These operando measurements also reveal that the transfer curve hysteresis at high carrier densities is accompanied by an analogous structural hysteresis, providing a microstructural basis for such instabilities. This work provides a mechanistic understanding of the structural dynamics and material instabilities of OMIEC materials during device operation.
36 MATERIALS SCIENCE↗
Coherent-Precipitation-Stabilized Phase Formation in Over-Stoichiometric Rocksalt-Type Li Superionic Conductors
Rationalizing synthetic pathways is crucial for material design and property optimization, especially for polymorphic and metastable phases. Over-stoichiometric rocksalt (ORX) compounds, characterized by their face-sharing configurations, are a promising group of materials with unique properties; however, their development is significantly hindered by challenges in synthesizability. Here, taking the recently identified Li superionic conductor, over-stoichiometric rocksalt Li–In–Sn–O (o-LISO) material as a prototypical ORX compound, the mechanisms of phase formation are systematically investigated. It is revealed that the spinel-like phase with unconventional stoichiometry forms as coherent precipitate from the high-temperature-stabilized cation-disordered rocksalt phase upon fast cooling. This process prevents direct phase decomposition and kinetically locks the system in a metastable state with the desired face-sharing Li configurations. This insight enables us to enhance the ionic conductivity of o-LISO to be >1 mS cm -1 at room temperature through low-temperature post-annealing. This work offers insights into the synthesis of ORX materials and highlights important opportunities in this new class of materials.
36 MATERIALS SCIENCE↗
A Polymer-Assisted Spinodal Decomposition Strategy toward Interconnected Porous Sodium Super Ionic Conductor-Structured Polyanion-Type Materials and Their Application as a High-Power Sodium-Ion Battery Cathode
A general polymer-assisted spinodal decomposition strategy is used to prepare hierarchically porous sodium super ionic conductor (NASICON)-structured polyanion-type materials (e.g., Na 3 V 2 (PO 4 ) 3 , Li 3 V 2 (PO 4 ) 3 , K 3 V 2 (PO 4 ) 3 , Na 4 MnV(PO 4 ) 3 , and Na 2 TiV(PO 4 ) 3 ) in a tetrahydrofuran/ethanol/H 2 O synthesis system. Depending on the boiling point of solvents, the selective evaporation of the solvents induces both macrophase separation via spinodal decomposition and mesophase separation via self-assembly of inorganic precursors and amphiphilic block copolymers, leading to the formation of hierarchically porous structures. We find that the resulting hierarchically porous Na 3 V 2 (PO 4 ) 3 possessing large specific surface area (≈77 m 2 g -1 ) and pore volume (≈0.272 cm 3 g -1 ) shows a high specific capacity of 117.6 mAh g -1 at 0.1 C achieving the theoretical value and a long cycling life with 77% capacity retention over 1000 cycles at 5 C. This method presented here can open a facile avenue to synthesize other hierarchically porous polyanion-type materials.
36 MATERIALS SCIENCE↗
A New Sodium Thioborate Fast Ion Conductor: Na 3 B 5 S 9
Abstract We report a new sodium fast‐ion conductor, Na 3 B 5 S 9 , that exhibits a high Na ion total conductivity of 0.80 mS cm −1 (sintered pellet; cold‐pressed pellet=0.21 mS cm −1 ). The structure consists of corner‐sharing B 10 S 20 supertetrahedral clusters, which create a framework that supports 3D Na ion diffusion channels. The Na ions are well‐distributed in the channels and form a disordered sublattice spanning five Na crystallographic sites. The combination of structural elucidation via single crystal X‐ray diffraction and powder synchrotron X‐ray diffraction at variable temperatures, solid‐state nuclear magnetic resonance spectra and ab initio molecular dynamics simulations reveal high Na‐ion mobility (predicted conductivity: 0.96 mS cm −1 ) and the nature of the 3D diffusion pathways. Notably, the Na ion sublattice orders at low temperatures, resulting in isolated Na polyhedra and thus much lower ionic conductivity. This highlights the importance of a disordered Na ion sublattice—and existence of well‐connected Na ion migration pathways formed via face‐sharing polyhedra—in dictating Na ion diffusion.
Zhou, Laidong↗
Small‐Molecule Mixed Ionic‐Electronic Conductors for Efficient N‐Type Electrochemical Transistors: Structure‐Function Correlations
Abstract The fundamental challenge in electron‐transporting organic mixed ionic‐electronic conductors (OMIECs) is simultaneous optimization of electron and ion transport. Beginning from Y6‐type/U‐shaped non‐fullerene solar cell acceptors, we systematically synthesize and characterize molecular structures that address the aforementioned challenge, progressively introducing increasing numbers of oligoethyleneglycol (OEG; g) sidechains from 1 g to 3 g, affording OMIECs 1gY, 2gY, and 3gY, respectively. The crystal structure of 1gY preserves key structural features of the Y n series: a U‐shaped/planar core, close π–π molecular stacking, and interlocked acceptor groups. Versus inactive Y6 and Y11, all of the new glycolated compounds exhibit mixed ion‐electron transport in both conventional organic electrochemical transistor (cOECT) and vertical OECT (vOECT) architectures. Notably, 3gY with the highest OEG density achieves a high transconductance of 16.5 mS, an on/off current ratio of ~10 6 , and a turn‐on/off response time of 94.7/5.7 ms in vOECTs. Systematic optoelectronic, electrochemical, architectural, and crystallographic analysis explains the superior 3gY‐based OECT performance in terms of denser n gY OEG content, increased crystallite dimensions with decreased long‐range crystalline order, and enhanced film hydrophilicity which facilitates ion transport and efficient redox processes. Finally, we demonstrate an efficient small‐molecule‐based complementary inverter using 3gY vOECTs, showcasing the bioelectronic applicability of these new small‐molecule OMIECs.
Cho, Yongjoon↗
A New Sodium Thioborate Fast Ion Conductor: Na 3 B 5 S 9
Abstract We report a new sodium fast‐ion conductor, Na 3 B 5 S 9 , that exhibits a high Na ion total conductivity of 0.80 mS cm −1 (sintered pellet; cold‐pressed pellet=0.21 mS cm −1 ). The structure consists of corner‐sharing B 10 S 20 supertetrahedral clusters, which create a framework that supports 3D Na ion diffusion channels. The Na ions are well‐distributed in the channels and form a disordered sublattice spanning five Na crystallographic sites. The combination of structural elucidation via single crystal X‐ray diffraction and powder synchrotron X‐ray diffraction at variable temperatures, solid‐state nuclear magnetic resonance spectra and ab initio molecular dynamics simulations reveal high Na‐ion mobility (predicted conductivity: 0.96 mS cm −1 ) and the nature of the 3D diffusion pathways. Notably, the Na ion sublattice orders at low temperatures, resulting in isolated Na polyhedra and thus much lower ionic conductivity. This highlights the importance of a disordered Na ion sublattice—and existence of well‐connected Na ion migration pathways formed via face‐sharing polyhedra—in dictating Na ion diffusion.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Small‐Molecule Mixed Ionic‐Electronic Conductors for Efficient N‐Type Electrochemical Transistors: Structure‐Function Correlations
Abstract The fundamental challenge in electron‐transporting organic mixed ionic‐electronic conductors (OMIECs) is simultaneous optimization of electron and ion transport. Beginning from Y6‐type/U‐shaped non‐fullerene solar cell acceptors, we systematically synthesize and characterize molecular structures that address the aforementioned challenge, progressively introducing increasing numbers of oligoethyleneglycol (OEG; g) sidechains from 1 g to 3 g, affording OMIECs 1gY, 2gY, and 3gY, respectively. The crystal structure of 1gY preserves key structural features of the Y n series: a U‐shaped/planar core, close π–π molecular stacking, and interlocked acceptor groups. Versus inactive Y6 and Y11, all of the new glycolated compounds exhibit mixed ion‐electron transport in both conventional organic electrochemical transistor (cOECT) and vertical OECT (vOECT) architectures. Notably, 3gY with the highest OEG density achieves a high transconductance of 16.5 mS, an on/off current ratio of ~10 6 , and a turn‐on/off response time of 94.7/5.7 ms in vOECTs. Systematic optoelectronic, electrochemical, architectural, and crystallographic analysis explains the superior 3gY‐based OECT performance in terms of denser n gY OEG content, increased crystallite dimensions with decreased long‐range crystalline order, and enhanced film hydrophilicity which facilitates ion transport and efficient redox processes. Finally, we demonstrate an efficient small‐molecule‐based complementary inverter using 3gY vOECTs, showcasing the bioelectronic applicability of these new small‐molecule OMIECs.
Cho, Yongjoon↗
Probing Interfacial Reaction Pathways in Atomic Layer Deposition on Sulfide Superionic Conductors
Sulfide superionic conductors (e.g., argyrodite Li 6 PS 5 Cl, LPSCl) are extremely promising for all solid-state batteries, but poor atmospheric stability and high interfacial reactivity limit widespread adoption. Coating LPSCl powders with ultrathin coatings using atomic layer deposition (ALD) mitigates these problems, protecting against atmospheric degradation and reducing reactivity with Li metal, yielding more stable cycling. Despite significant promise, the ALD mechanism is unknown, hampering the development of new coating chemistries. In this study, we elucidate the mechanism for Al 2 O 3 ALD on LPSCl using trimethyl aluminum (TMA) and H 2 O by combining in situ Fourier transform infrared spectroscopy, ex situ solid-state magic angle spinning nuclear magnetic resonance, UV Raman spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations. We determine that ALD Al 2 O 3 nucleates promptly via TMA reaction with native —OH, —SH, and PS 3 -OH groups to form transient C–Al–O(S) species that are rapidly hydrolyzed during the subsequent H 2 O exposure. This reversible transformation maintains surface nucleophilicity and prevents sulfide decomposition. The resulting layer-by-layer growth leads to highly conformal Al 2 O 3 coatings on LPSCl that are readily scalable to ≥ 50 g quantities using a rotating drum fixture. This detailed understanding of ALD surface reactions provides critical insights guiding the selection of future ALD chemistries with improved performance.
atomic layer deposition↗
Ion transport in composites of binary electrolyte and single ion conductor—A chronoamperometry study
Composite electrolytes for lithium batteries typically combine materials with very different mechanical properties and ionic transport mechanisms and the degree to which these two phases affect each other is not well understood. In this work we used numerical simulations and experiments to investigate the transport in composite electrolytes consisting of polyethylene oxide (PEO) with Lithium bis-triuoromethanesulfonimide (LiTFSI) and Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) lithium ion conducting glass-ceramic particles. In particular we are interested in how the introduction of a single ion conductor (SIC) changes the salt concentration gradients in the polymer electrolyte (PE) under applied potential. To study this, we performed numerical simulations and chronoamperometry experiments in electrolytes with different arrangements of the SIC and PE phases, i.e. layers and particulate composites. The results show that the particulate composites have the highest concentration gradients and take the longest time to reach steady state current. Furthermore, the high concentration gradient can be exacerbated by a high SIC/PE interfacial resistance. Finally, the best arrangement appears to have a layer of SIC impenetrable to anions in the polymer phase within the electrolyte membrane.
25 ENERGY STORAGE↗
Designing transparent conductors using forbidden optical transitions
Many semiconductors present weak or forbidden transitions at their fundamental band gaps, inducing a widened region of transparency. This occurs in high-performing n-type transparent conductors (TCs) such as Sn-doped In 2 O 3 (ITO); however, thus far, the presence of forbidden transitions has been neglected in the search for new p-type TCs. To address this, we first compute high-throughput absorption spectra across ~18, 000 semiconductors, showing that over half exhibit forbidden or weak optical transitions at their band edges. Next, we demonstrate that compounds with highly localized band-edge states are more likely to present forbidden transitions. Lastly, we search this set for p-type and n-type TCs with forbidden transitions and, by performing defect calculations, propose unexplored TC candidates such as ambipolar BeSiP 2 , p-type wurtzite BAs, and n-type Ba 2 InGaO 5 , among others. In conclusion, we share our dataset and recommend that future screenings for optical properties consider the impact of forbidden transitions.
36 MATERIALS SCIENCE↗
Insights into the Rich Polymorphism of the Na + Ion Conductor Na 3 PS 4 from the Perspective of Variable-Temperature Diffraction and Spectroscopy
Solid electrolytes are crucial for next-generation solid-state batteries, and Na 3 PS 4 is one of the most promising Na + conductors for such applications, despite outstanding questions regarding its structural polymorphs. In this contribution, we present a detailed investigation of the evolution in structure and dynamics of Na 3 PS 4 over a wide temperature range 30 < T T < 500 °C, which we attribute to dynamic local tetragonal distortions. The first-order phase transition to the mesophasic high-temperature polymorph (γ, Fddd ) is associated with a sharp volume increase and the onset of liquid-like dynamics for sodium-cations (translational) and thiophosphate-polyanions (rotational) evident by inelastic neutron and Raman spectroscopies, as well as pair-distribution function and molecular dynamics analyses. Overall, these results shed light on the rich polymorphism of Na 3 PS 4 and are relevant for a range host of high-performance materials deriving from the Na 3 PS 4 structural archetype.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Li-Rich and Halide-Deficient Argyrodite Fast Ion Conductors
Here, we report on a new family of halide-deficient and Li-rich argyrodite fast-ion conductors, Li 6+x PS 5+x (Cl/Br/I) 1–x (0 ≤ x ≤ 0.85). Exploration of the influence of aliovalent anion substitution in Li 6 PS 5 X (X = Cl, Br, I)–using a combination of high-resolution powder neutron diffraction and electrochemical impedance spectroscopy–reveals that aliovalent anion substitution induces higher Li-ion concentration and Li site disorder, and creates S 2– /I – anion site disorder on the 4a site. In the series Li 6+x PS 5+x I 1–x (0 ≤ x ≤ 0.4), the resulting conductivity for Li 6.4 PS 5.4 I 0.6 (0.13 mS·cm –1 ) represents almost a 100-fold increase over that of the parent phase, Li 6 PS 5 I (0.0033 mS·cm –1 ), and establishes one of the first fast-ion conducting argyrodite thiophosphate iodides. For Cl-argyrodites, the ionic conductivity decreases a little with lower halide-content but ionic conductivity for the Br-argyrodites is almost unchanged. Overall, all Cl/Br-argyrodites Li 6 +xPS 5+x (Cl/Br) 1–x (0 ≤ x ≤ 0.75) with a low halide content exhibit surprisingly high ionic conductivities > 1 mS·cm –1 despite a very low degree of sulfur/halogen anion site disorder. Our findings highlight the importance of attaining a disordered Li-ion sublattice and sulfur/halogen anion site disorder (anionic charge homogeneity) in argyrodites, where Li ions occupy high energy sites and activate concerted ion migration that drives the ionic conductivity.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Resonant X-ray Diffraction Reveals the Location of Counterions in Doped Organic Mixed Ionic Conductors
Organic mixed ionic–electronic conductors (OMIECs) have the potential to enable diverse new technologies, ranging from novel in situ biosensors to flexible energy storage devices and neuromorphic computing platforms. However, their complex behavior in functional films involving electrolyte-induced swelling, ion ingress, and electrochemical doping inhibits rational material design. Of critical importance is an understanding of the specific location of the ions in the volumetrically doped material, yet this information is not readily available. Here, in this report, we present the use of grazing- incidence resonant X-ray diffraction (RXRD, also known as anomalous diffraction) at S and Cl K-edges to determine the structure of a doped, prototypical, semicrystalline polymer OMIEC based on oligo(ethylene glycol) substitution of regioregular polythiophene. The RXRD measurement provides two key insights. Quantitative analysis of the RXRD allows the determination of the position of the ion relative to the polymer backbone in the crystalline regions. We find that the anion is relatively distant from the backbone, nearer to the lamella mid-plane naively in conflict with expected Coulombic attraction between the ion and the doped polymer polaron. Comparison of RXRD to Cl – fluorescence (total Cl – ) allows determination of the relative order of doping between the crystalline and amorphous regions. We find preferential doping of the crystalline regions. Both insights, the preferential doping of crystals at low potential and the specific location of the counterion with respect to the polymer backbone, are critical to developing a microscopic understanding of transport in OMIECs.
36 MATERIALS SCIENCE↗
Synthetic Accessibility and Sodium Ion Conductivity of the Na8–x A x P2O9 (NAP) High-Temperature Sodium Superionic Conductor Framework
Advancement of solid-state electrolytes (SSEs) for all solid-state batteries typically focuses on modification of a known structural framework to improve conductivity, e.g., cation substitution for an immobile ion or varying the concentration of the mobile ions. Novel frameworks can be disruptive by enabling fast ion conduction aided by different structure and diffusion mechanisms, thereby unlocking optimal conductors with different properties. Herein, we perform a high-throughput survey of a structural framework for sodium ion conduction, Na8–x A x P2O9 (NAP), to understand the family’s thermodynamic stability, synthesizability, and ionic conduction. We show that the parent phase Na4TiP2O9 (NTP) undergoes a structural distortion (with accompanying conductivity transition) due to unstable phonons arising from pseudo-Jahn–Teller mode in the 1D titanium chains. Screening compounds in which Ti is substituted by other metals computationally reveal a number of candidates that are predicted to be low in formation energy and have high predicted ionic conductivities. High-throughput experimental and subsequent methodology optimization trials deliver one new compound, Na4SnP2O9 (NSP). X-ray diffraction (XRD), microscopy, and spectroscopy characterization indicate that the room-temperature structure of NSP is similar to the high-temperature, orthorhombic NTP phase but with some small unresolved structural differences. These uncharacterized structural details are speculated to limit the ion conductivity. Temperature-dependent XRD and electrochemical impedance spectroscopy indicate multiple coupled conductivity–structure transitions at a high temperature. We demonstrate the challenges with synthesis development and a priori identification of promising SSE phases as a major bottleneck in new (energy) materials development.
Chemical reactions↗