Li₃Y(PS₄)₂ and Li₅PS₄Cl₂: New Lithium Superionic Conductors Predicted from Silver Thiophosphates using Efficiently Tiered Ab Initio Molecular Dynamics Simulations

We report two novel, earth-abundant lithium superionic conductors, Li₃Y­(PS₄)₂ and Li₅PS₄Cl₂, that are predicted to satisfy the necessary combination of good phase stability, high Li⁺ conductivity, wide band gap and good electrochemical stability for solid electrolyte applications in all-solid-state rechargeable lithium-ion batteries. These candidates were identified from a high-throughput first-principles screening of the Li–P–S ternary and Li–M–P–S (where M is a non-redox-active element) quaternary chemical spaces, including candidates obtained by replacing Ag with Li in the Ag–P–S and Ag–M–P–S chemical spaces. An efficient tiered screening strategy was developed that combines topological analysis with <i>ab initio</i> molecular dynamics simulations to exclude rapidly candidates unlikely to satisfy the stringent conductivity requirements of lithium superionic conductors. In particular, we find Li₃Y­(PS₄)₂ to be an extremely promising candidate exhibiting a room-temperature Li⁺ conductivity of 2.16 mS/cm, which can be increased multifold to 7.14 and 5.25 mS/cm via aliovalent doping with Ca²⁺ and Zr⁴⁺, respectively. More critically, we show that the phase and electrochemical stability of Li₃Y­(PS₄)₂ is expected to be better than current state-of-the-art lithium superionic conductors

Data-Driven First-Principles Methods for the Study and Design of Alkali Superionic Conductors

We present a detailed exposition of how first-principles methods can be used to guide alkali superionic conductor (ASIC) study and design. Using the argyrodite Li₆PS₅Cl as a case study, we demonstrate how modern information technology (IT) infrastructure and software tools can facilitate the assessment of alkali superionic conductors in terms of various critical properties of interest such as phase and electrochemical stability and ionic conductivity. The emphasis is on well-documented, reproducible analysis code that can be readily generalized to other material systems and design problems. For our chosen Li₆PS₅Cl case study material, we show that Li excess is crucial to enhancing its conductivity by increasing the occupancy of interstitial sites that promote long-range Li⁺ diffusion between cage-like frameworks. The predicted room-temperature conductivities and activation barriers are in reasonably good agreement with experimental values

Role of Na⁺ Interstitials and Dopants in Enhancing the Na⁺ Conductivity of the Cubic Na₃PS₄ Superionic Conductor

In this work, we performed a first-principles investigation of the phase stability, dopant formation energy and Na⁺ conductivity of pristine and doped cubic Na₃PS₄ (c-Na₃PS₄). We show that pristine c-Na₃PS₄ is an extremely poor Na ionic conductor, and the introduction of Na⁺ excess is the key to achieving reasonable Na⁺ conductivities. We studied the effect of aliovalent doping of M⁴⁺ for P⁵⁺ in c-Na₃PS₄, yielding Na_3+<i>x</i>M_<i>x</i>P_1–<i>x</i>S₄ (M = Si, Ge, and Sn with <i>x</i> = 0.0625; M = Si with <i>x</i> = 0.125). The formation energies in all the doped structures with dopant concentration of <i>x</i> = 0.0625 are found to be relatively low. Using <i>ab initio</i> molecular dynamics simulations, we predict that 6.25% Si-doped c-Na₃PS₄ has a Na⁺ conductivity of 1.66 mS/cm, in excellent agreement with previous experimental results. Remarkably, we find that Sn⁴⁺ doping at the same concentration yields a much higher predicted Na⁺ conductivity of 10.7 mS/cm, though with a higher dopant formation energy. A higher Si⁴⁺ doping concentration of <i>x</i> = 0.125 also yields a significant increase in Na⁺ conductivity with an even higher dopant formation energy. Finally, topological and van Hove correlation function analyses suggest that the channel volume and correlation in Na⁺ motions may play important roles in enhancing Na⁺ conductivity in this structure

Table_1_Altered Interoceptive Processing in Generalized Anxiety Disorder—A Heartbeat-Evoked Potential Research.pdf

Generalized anxiety disorder (GAD) is one of the most common anxiety disorders. The brain’s dysfunctional processing of interoceptive information is increasingly recognized as an important component of anxiety disorders. However, the neural mechanisms remain insufficiently understood. In the present study, patients with GAD and healthy control participants underwent an eyes-closed (EC) resting state (interoception) and eyes-open (EO) resting state (exteroception) without paying conscious attention to heartbeat. Electrocardiography (ECG) and electroencephalography (EEG) signals were recorded at the same time. The results show that in healthy controls, the heartbeat-evoked brain potential (HEP) was modulated by the conditions, with a significantly higher amplitude under EC than EO, while this was not the case in GAD patients. Further analysis revealed that the dysfunction of HEP modulation in GAD patients may be attributed to excessive interoceptive processing under EO, with a marginally higher HEP in GAD than in the healthy controls. Finally, the right prefrontal HEP amplitude during EC condition was significantly correlated with the severity of the patients’ anxiety symptoms. Our results suggest that altered cortical processing of interoceptive signals may play an important role in the pathophysiology of generalized anxiety disorder.</p

New Insights into the Interphase between the Na Metal Anode and Sulfide Solid-State Electrolytes: A Joint Experimental and Computational Study

In this work, we investigated the interface between the sodium anode and the sulfide-based solid electrolytes Na₃SbS₄ (NAS), Na₃PS₄ (NPS), and Cl-doped NPS (NPSC) in all-solid-state-batteries (ASSBs). Even though these electrolytes have demonstrated high ionic conductivities in the range of 1 mS cm^–1 at ambient temperatures, sulfide sold-state electrolytes (SSEs) are known to be unstable with Na metal, though the exact reaction mechanism and kinetics of the reaction remain unclear. We demonstrate that the primary cause of capacity fade and cell failure is a chemical reaction spurred on by electrochemical cycling that takes place at the interface between the Na anode and the SSEs. To investigate the properties of the Na-solid electrolyte interphase (SSEI) and its effect on cell performance, the SSEI was predicted computationally to be composed of Na₂S and Na₃Sb for NAS and identified experimentally via X-ray photoelectron spectroscopy (XPS). These two compounds give the SSEI mixed ionic- and electronic-conducting properties, which promotes continued SSEI growth, which increases the cell impedance at the expense of cell performance and cycle life. The SSEI for NPS was similarly found to be comprised of Na₂S and Na₃P, but XPS analysis of Cl-doped NPS (NPSC) showed the presence of an additional compound at the SSEI, NaCl, which was found to mitigate the decomposition of NPS. The methodologies presented in this work can be used to predict and optimize the electrochemical behavior of an all-solid-state cell. Such joint computational and experimental efforts can inform strategies for engineering a stable electrolyte and SSEI to avoid such reactions. Through this work, we call for more emphasis on SSE compatibility with both anodes and cathodes, essential for improving the electrochemical properties, longevity, and practicality of Na-based ASSBs

Elucidating the Limit of Li Insertion into the Spinel Li₄Ti₅O₁₂

In this work, we show that the well-known lithium-ion anode material, Li4Ti5O12, exhibits exceptionally high initial capacity of 310 mAh g–1 when it is discharged to 0.01 V. It maintains a reversible capacity of 230 mAh g–1, far exceeding the “theoretical” capacity of 175 mAh g–1 when this anode is lithiated to the composition Li7Ti5O12. Neutron diffraction analyses identify that additional Li reversibly enters into the Li7Ti5O12 to form Li8Ti5O12. density functional theory (DFT) calculations reveal the average potentials of the Li4Ti5O12 to Li7Ti5O12 step and the Li7Ti5O12 to Li8Ti5O12 step are 1.57 and 0.19 V, respectively, which are in excellent agreement with experimental results. Transmission electron microscopy (TEM) studies confirm that the irreversible capacity of Li4Ti5O12 during its first cycle originates from the formation of a solid electrolyte interface (SEI) layer. This work clarifies the fundamental lithiation mechanism of the Li4Ti5O12, when lithiated to 0.01 V vs Li

Elucidating the Limit of Li Insertion into the Spinel Li₄Ti₅O₁₂

In this work, we show that the well-known lithium-ion anode material, Li4Ti5O12, exhibits exceptionally high initial capacity of 310 mAh g–1 when it is discharged to 0.01 V. It maintains a reversible capacity of 230 mAh g–1, far exceeding the “theoretical” capacity of 175 mAh g–1 when this anode is lithiated to the composition Li7Ti5O12. Neutron diffraction analyses identify that additional Li reversibly enters into the Li7Ti5O12 to form Li8Ti5O12. density functional theory (DFT) calculations reveal the average potentials of the Li4Ti5O12 to Li7Ti5O12 step and the Li7Ti5O12 to Li8Ti5O12 step are 1.57 and 0.19 V, respectively, which are in excellent agreement with experimental results. Transmission electron microscopy (TEM) studies confirm that the irreversible capacity of Li4Ti5O12 during its first cycle originates from the formation of a solid electrolyte interface (SEI) layer. This work clarifies the fundamental lithiation mechanism of the Li4Ti5O12, when lithiated to 0.01 V vs Li

Elucidating the Limit of Li Insertion into the Spinel Li₄Ti₅O₁₂

In this work, we show that the well-known lithium-ion anode material, Li4Ti5O12, exhibits exceptionally high initial capacity of 310 mAh g–1 when it is discharged to 0.01 V. It maintains a reversible capacity of 230 mAh g–1, far exceeding the “theoretical” capacity of 175 mAh g–1 when this anode is lithiated to the composition Li7Ti5O12. Neutron diffraction analyses identify that additional Li reversibly enters into the Li7Ti5O12 to form Li8Ti5O12. density functional theory (DFT) calculations reveal the average potentials of the Li4Ti5O12 to Li7Ti5O12 step and the Li7Ti5O12 to Li8Ti5O12 step are 1.57 and 0.19 V, respectively, which are in excellent agreement with experimental results. Transmission electron microscopy (TEM) studies confirm that the irreversible capacity of Li4Ti5O12 during its first cycle originates from the formation of a solid electrolyte interface (SEI) layer. This work clarifies the fundamental lithiation mechanism of the Li4Ti5O12, when lithiated to 0.01 V vs Li

Elucidating the Limit of Li Insertion into the Spinel Li₄Ti₅O₁₂

In this work, we show that the well-known lithium-ion anode material, Li4Ti5O12, exhibits exceptionally high initial capacity of 310 mAh g–1 when it is discharged to 0.01 V. It maintains a reversible capacity of 230 mAh g–1, far exceeding the “theoretical” capacity of 175 mAh g–1 when this anode is lithiated to the composition Li7Ti5O12. Neutron diffraction analyses identify that additional Li reversibly enters into the Li7Ti5O12 to form Li8Ti5O12. density functional theory (DFT) calculations reveal the average potentials of the Li4Ti5O12 to Li7Ti5O12 step and the Li7Ti5O12 to Li8Ti5O12 step are 1.57 and 0.19 V, respectively, which are in excellent agreement with experimental results. Transmission electron microscopy (TEM) studies confirm that the irreversible capacity of Li4Ti5O12 during its first cycle originates from the formation of a solid electrolyte interface (SEI) layer. This work clarifies the fundamental lithiation mechanism of the Li4Ti5O12, when lithiated to 0.01 V vs Li