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Acid and peroxide values are important indicators to evaluate the hydrolysis or oxidation level of vegetable oil. In order to achieve rapid determination of these parameters by Raman spectroscopy, rapeseed and soybean oil were analyzed, and a competitive adaptive reweighted sampling-back propagation neural network (CARS-BPNN) method was developed. First, the Raman spectrum was preprocessed to reduce noise using moving window smoothing. Next, competitive adaptive reweighted sampling (CARS), successive projections algorithm (SPA), and uninformative variable elimination (UVE) was applied to extract the Raman characteristic information that indicated the acid and peroxide values. Based on the extracted characteristic information, back propagation neural network (BPNN), partial least squares regression (PLSR), and support vector machine (SVM) prediction models were established and compared. The results showed that the best accuracy was obtained using CARS-BPNN. For rapeseed oil, the coefficients of determination (R2) of acid value and peroxide value were 0.9207 and 0.9772. The root mean square error (RMSE) values were 0.0909 and 0.0022, respectively. For soybean oil, the coefficients of determination (R2) of acid and peroxide values were 0.9381 and 0.9716. The RMSE values were 0.1250 and 0.0027, respectively. A good correlation coefficient and a small RMSE value were obtained. The results indicate that Raman spectroscopy combined with CARS-BPNN accurately evaluated the acid and peroxide values, which provides a reference for the optimization of the Raman spectrum and creates a new approach for the evaluation of vegetable oil quality. [ABSTRACT FROM AUTHOR]

Cathodes are critical components of rechargeable batteries. Conventionally, the search for cathode materials relies on experimental trial-and-error and a traversing of existing computational/experimental databases. While these methods have led to the discovery of several commercially viable cathode materials, the chemical space explored so far is limited and many phases will have been overlooked, in particular, those that are metastable. We describe a computational framework for battery cathode exploration based on ab initio random structure searching (AIRSS), an approach that samples local minima on the potential energy surface to identify new crystal structures. We show that by delimiting the search space using a number of constraints, including chemically aware minimum interatomic separations, cell volumes, and space group symmetries, AIRSS can efficiently predict both thermodynamically stable and metastable cathode materials. Specifically, we investigate LiCoO2, LiFePO4, and LixCuyFz to demonstrate the efficiency of the method by rediscovering the known crystal structures of these cathode materials. The effect of parameters, such as minimum separations and symmetries, on the efficiency of the sampling is discussed in detail. The adaptation of the minimum interatomic distances on a species-pair basis, from low-energy optimized structures to efficiently capture the local coordination environment of atoms, is explored. A family of novel cathode materials based on the transition-metal oxalates is proposed. They demonstrate superb energy density, oxygen-redox stability, and lithium diffusion properties. This article serves both as an introduction to the computational framework and as a guide to battery cathode material discovery using AIRSS. [ABSTRACT FROM AUTHOR]

The discovery of 250-kelvin superconducting lanthanum polyhydride under high pressure marked a significant advance toward the realization of a room‐temperature superconductor. X-ray diffraction (XRD) studies reveal a nonstoichiometric LaH9.6 or LaH10±δ polyhydride responsible for the superconductivity, which in the literature is commonly treated as LaH10 without accounting for stoichiometric defects. Here, we discover significant nuclear quantum effects (NQE) in this polyhydride, and demonstrate that a minor amount of stoichiometric defects will cause quantum proton diffusion in the otherwise rigid lanthanum lattice in the ground state. The diffusion coefficient reaches ~10−7 cm2/s in LaH9.63 at 150 gigapascals and 240 kelvin, approaching the upper bound value of interstitial hydrides at comparable temperatures. A puzzling phenomenon observed in previous experiments, the positive pressure dependence of the superconducting critical temperature Tc below 150 gigapascals, is explained by a modulation of the electronic structure due to a premature distortion of the hydrogen lattice in this quantum fluxional structure upon decompression, and resulting changes of the electron-phonon coupling. This finding suggests the coexistence of the quantum proton fluxion and hydrogen-induced superconductivity in this lanthanum polyhydride, and leads to an understanding of the structural nature and superconductivity of nonstoichiomectric hydrogen-rich materials. The role of stoichiometric defects in the superconducting polyhydride LaH10±δ has received little attention so far. Here, the authors use molecular-dynamics simulations to show that a small amount of stoichiometric defects will cause quantum proton diffusion in the otherwise rigid lanthanum lattice. [ABSTRACT FROM AUTHOR]

The development of rechargeable Ca metal batteries (RCMBs) is hindered by the Ca2+ passivating solid electrolyte interphases (SEIs). The cation solvation structure dictated by electrolyte chemistry plays a critical role in the SEIs properties. While a relatively weak cation‐solvent binding is preferred in Li metal anodes to promote anion‐derived SEIs, we demonstrate an enhanced Ca deposition/stripping reversibility under a strong cation‐solvent interaction, which is materialized in strongly‐solvating solvent and highly‐dissociated salt combinations. Such electrolyte formulations benefit the formation of solvent‐occupied solvation structure and minimize the anion reduction, resulting in organic‐rich/CaF2‐poor SEIs for reversible Ca metal anodes. Furthermore, RCMBs paired with an organic cathode using the optimized electrolytes are demonstrated as a proof‐of‐concept. Our work reveals the paradigm shift in SEIs design for Ca metal anodes, opening up new opportunities for emerging RCMBs. [ABSTRACT FROM AUTHOR]

The development of rechargeable Ca metal batteries (RCMBs) is hindered by the Ca2+ passivating solid electrolyte interphases (SEIs). The cation solvation structure dictated by electrolyte chemistry plays a critical role in the SEIs properties. While a relatively weak cation‐solvent binding is preferred in Li metal anodes to promote anion‐derived SEIs, we demonstrate an enhanced Ca deposition/stripping reversibility under a strong cation‐solvent interaction, which is materialized in strongly‐solvating solvent and highly‐dissociated salt combinations. Such electrolyte formulations benefit the formation of solvent‐occupied solvation structure and minimize the anion reduction, resulting in organic‐rich/CaF2‐poor SEIs for reversible Ca metal anodes. Furthermore, RCMBs paired with an organic cathode using the optimized electrolytes are demonstrated as a proof‐of‐concept. Our work reveals the paradigm shift in SEIs design for Ca metal anodes, opening up new opportunities for emerging RCMBs. [ABSTRACT FROM AUTHOR]

SiO–based materials are promising alloys and conversion‐type anode materials for lithium‐ion batteries and are recently found to be excellent dendrite‐proof layers for lithium‐metal batteries. However, only a small fraction of the Li–Si–O compositional space has been reported, significantly impeding the understanding of the phase transition mechanisms and the rational design of these materials both as anodes and as protection layers for lithium‐metal anodes. Herein, we identify three new thermodynamically stable phases within the Li–Si–O ternary system (Li2SiO5, Li4SiO6, and Li4SiO8) in addition to the existing records via first‐principle calculations. The electronic structure simulation shows that Li2SiO5 and Li4SiO8 phases are metallic in nature, ensuring high electronic conductivity required as electrodes. Moduli calculations demonstrate that the mechanical strength of Li–Si–O phases is much higher than that of lithium metal. The diffusion barriers of interstitial Li range from 0.1 to 0.6 eV and the interstitial Li hopping serves as the dominating diffusion mechanism in the Li–Si–O ternary systems compared with vacancy diffusion. These findings provide a new strategy for future discovery of improved alloying anodes for lithium‐ion batteries and offer important insight towards the understanding of the phase transformation mechanism of alloy‐type protection layers on lithium‐metal anodes. [ABSTRACT FROM AUTHOR]

Metallic Zn is a preferred anode material for rechargeable aqueous batteries towards a smart grid and renewable energy storage. Understanding how the metal nucleates and grows at the aqueous Zn anode is a critical and challenging step to achieve full reversibility of Zn battery chemistry, especially under fast‐charging conditions. Here, by combining in situ optical imaging and theoretical modeling, we uncover the critical parameters governing the electrodeposition stability of the metallic Zn electrode, that is, the competition among crystallographic thermodynamics, kinetics, and Zn2+‐ion diffusion. Moreover, steady‐state Zn metal plating/stripping with Coulombic efficiency above 99 % is achieved at 10–100 mA cm−2 in a reasonably high concentration (3 M) ZnSO4 electrolyte. Significantly, a long‐term cycling‐stable Zn metal electrode is realized with a depth of discharge of 66.7 % under 50 mA cm−2 in both Zn||Zn symmetrical cells and MnO2||Zn full cells. [ABSTRACT FROM AUTHOR]

Metallic Zn is a preferred anode material for rechargeable aqueous batteries towards a smart grid and renewable energy storage. Understanding how the metal nucleates and grows at the aqueous Zn anode is a critical and challenging step to achieve full reversibility of Zn battery chemistry, especially under fast‐charging conditions. Here, by combining in situ optical imaging and theoretical modeling, we uncover the critical parameters governing the electrodeposition stability of the metallic Zn electrode, that is, the competition among crystallographic thermodynamics, kinetics, and Zn2+‐ion diffusion. Moreover, steady‐state Zn metal plating/stripping with Coulombic efficiency above 99 % is achieved at 10–100 mA cm−2 in a reasonably high concentration (3 M) ZnSO4 electrolyte. Significantly, a long‐term cycling‐stable Zn metal electrode is realized with a depth of discharge of 66.7 % under 50 mA cm−2 in both Zn||Zn symmetrical cells and MnO2||Zn full cells. [ABSTRACT FROM AUTHOR]

The choice of cathode material in Li-ion batteries underpins their overall performance. Discovering new cathode materials is a slow process, and all major commercial cathode materials are still based on those identified in the 1990s. Discovery of materials using high-throughput calculations has attracted great research interest; however, reliance on databases of existing materials begs the question of whether these approaches are applicable for finding truly novel materials. In this work, we demonstrate that ab initio random structure searching (AIRSS), a first-principles structure prediction method that does not rely on any pre-existing data, can locate low energy structures of complex cathode materials efficiently based only on chemical composition. We use AIRSS to explore three Fe-containing polyanion compounds as low-cost cathodes. Using known quaternary LiFePO4 and quinary LiFeSO4F cathodes as examples, we easily reproduce the known polymorphs, in addition to predicting other, hitherto unknown, low energy polymorphs and even finding a new polymorph of LiFeSO4F that is more stable than the known ones. We then explore the phase space for Fe-containing fluoroxalates, predicting a range of redox-active phases that are yet to be experimentally synthesized, demonstrating the suitability of AIRSS as a tool for accelerating the discovery of novel cathode materials. [ABSTRACT FROM AUTHOR]

The electrochemical thermodynamic and kinetic characteristics of rechargeable batteries are critically influenced by the ordering of mobile ions in electrodes or solid electrolytes. However, because of the experimental difficulty of capturing the lighter migration ion coupled with the theoretical limitation of searching for ordered phases in a constrained cell, predicting stable ordered phases involving cell transformations or at extremely dilute concentrations remains challenging. Here, a group-subgroup transformation method based on lattice transformation and Wyckoff-position splitting is employed to predict the ordered ground states. We reproduce the previously reported Li0.75CoO2, Li0.8333CoO2, and Li0.8571CoO2 phases and report a new Li0.875CoO2 ground state. Taking the advantage of Wyckoff-position splitting in reducing the number of configurations, we identify the stablest Li0.0625C6 dilute phase in Li-ion intercalated graphite. We also resolve the Li/La/vacancy ordering in Li3xLa2/3−xTiO3 (0 < x < 0.167), which explains the observed Li-ion diffusion anisotropy. These findings provide important insight towards understanding the rechargeable battery chemistry. [ABSTRACT FROM AUTHOR]

Dendrite penetration in ceramic lithium conductors severely constrains the development of solid‐state batteries (SSBs) while its nanoscale origin remains unelucidated. An in situ nanoscopic electrochemical characterization technique is developed based on conductive‐atomic force microscopy (c‐AFM) to reveal the local dendrite growth kinetics. Using Li7La3Zr2O12 (LLZO) as a model system, significant local inhomogeneity is observed with a hundredfold decrease in the dendrite triggering bias at grain boundaries compared with that at grain interiors. The origin of the local weakening is assigned to the nanoscale variation of elastic modulus and lithium flux detouring. An ionic‐conductive polymeric homogenizing layer is designed which achieves a high critical current density of 1.8 mA cm–2 and a low interfacial resistance of 14 Ω cm2. Practical SSBs based on LiFePO4 cathodes can be stably cycled over 300 times. Beyond this, highly reversible electrochemical dendrite healing in LLZO is discovered using the c‐AFM electrode, based on which a model memristor with a high on/off ratio of ≈105 is demonstrated for >200 cycles. This work not only provides a novel tool to investigate and design interfaces in SSBs but also offers opportunities for solid electrolytes beyond energy applications. [ABSTRACT FROM AUTHOR]

Low-cost and high-safety aqueous Zn ion batteries have been considered as promising alternatives to Li-ion batteries, provided that a stable Zn metal anode could be developed. Dendrite growth and low coulombic efficiency (CE) are the primary two issues afflicting the design of advanced Zn metal anodes. Inspired by complexing agents in the electroplating industry, acetonitrile (AN) is proposed as an electrolyte additive to guide the smooth growth of Zn. The enhanced intermolecular interactions between Zn2+ and mixed H2O/AN solvents lead to the supersaturating of adatoms on the current collector, as revealed by the complementary theoretical and experimental studies. Consequently, homogeneous nucleation and smooth growth of Zn are enabled for achieving exceptional stability up to 1000 cycles with an excellent CE of 99.64% on average. Application-wise, the incorporation of a complexing agent into the electrolyte is fully compatible with the cathode while maintaining the non-flammable nature for safe operation. The solvation chemistry regulation strategy provides a promising route to stabilize Zn metal anodes. [ABSTRACT FROM AUTHOR]

Abstract: Solid‐state batteries hold great promise because of their safety and high projected energy density. However, the sizeable interfacial resistance between the electrodes and the electrolyte of such batteries is a significant bottleneck in the development of this technology. In this work, we develop a Li6.4La3Zr1.4Ta0.6O12 (LLZTO) and polyvinylidene fluoride (PVDF) solid‐state composite membrane characterized by high conductivity, tensile strength, and flexibility as well as low impedance if interfacially modified by a minute amount of liquid electrolyte. A solid‐state lithium‐ion battery using this electrolyte with LiFePO4 and Li as electrodes delivers excellent rate capability and cycling stability at room temperature. In particular, the battery shows an initial discharge capacity of 155 mAh g−1 and, after 100 cycles at 1C, of 145 mAh g−1. Even at 4C, the discharge capacity is 96 mAh g−1. Our study suggests that the interfacially modified LLZTO‐PVDF membrane is a promising electrolyte for solid‐state lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: 2D layer‐structured materials are considered a promising candidate as a coupling material in lithium sulfur batteries (LSBs) due to their high surface‐volume ratio and abundant active binding sites, which can efficiently mitigate shuttling of soluble polysulfides. Herein, an electrochemical Li intercalation and exfoliation strategy is used to prepare 2D Sb2S3 nanosheets (SSNSs), which are incorporated onto a separator in LSBs as a new 2D coupling material for the first time. The cells containing a rationally designed separator which is coated with an SSNS/carbon nanotube (CNT) coupling layer deliver a much improved specific capacity with a remarkable 0.05% decay rate for over 200 cycles at a current density of 2 C. The capability of the SSNSs to entrap polysulfides through their favorable interfacial functionality and the high electrical conductivity of the CNT network facilitates recycling of active materials. The first‐principle calculations verify the important roles of SSNSs, which demonstrate ideal binding strengths (1.33–2.14 eV) to entrap Li2Sx as well as a low‐energy barrier (189 meV) for Li diffusion. These findings offer new insights into discovering novel coupling layers for high‐performance LSBs and shed new light on the application of 2D layer‐structured materials in energy storage systems. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are considered promising low-cost alternatives to prevailing lithium-ion batteries (LIBs). The inherently sluggish kinetics of their anode materials, however, poses a great challenge to the SIBs' rate capabilities. This work reports the synthesis of novel MoS2/Carbon (MoS2/C) microspheres with three-dimensional (3D) architecture as an anode for SIBs using a facile hydrothermal strategy. The MoS2/C electrode delivers a reversible capacity of 498 mA h g−1 at 100 mA g−1, which stabilizes at 450 mA h g−1 after 100 cycles. Even at 4 A g−1, the electrode maintains a high reversible capacity above 310 mA h g−1 after 600 cycles, demonstrating its superior rate capability and long-term cyclic stability. Quantitative kinetics analysis reveals a pseudocapacitance-dominated Na+ storage mechanism, especially at high current densities. Furthermore, density functional theory (DFT) calculations show that the Na transport rates are faster through the MoS2/C heterointerface, due to a low diffusion energy barrier, than along the MoS2/MoS2 bilayers. [ABSTRACT FROM AUTHOR]

Abstract: SnS2 nanoplatelet electrodes can offer an exceptionally high pseudocapacitance in an organic Na+ ion electrolyte system, but their underlying mechanisms are still largely unexplored, hindering the practical applications of pseudocapacitive SnS2 anodes in Na‐ion batteries (SIBs) and Na hybrid capacitors (SHCs). Herein, SnS2 nanoplatelets are grown directly on SnO2/C composites to synthesize SnS2/graphene‐carbon nanotube aerogel (SnS2/GCA) by pressurized sulfidation where the original morphology of carbon framework is preserved. The composite electrode possessing a large surface area delivers a remarkable specific capacity of 600.3 mA h g−1 at 0.2 A g−1 and 304.8 mA h g−1 at an ultrahigh current density of 10 A g−1 in SIBs. SHCs comprising a SnS2/GCA composite anode and an activated carbon cathode present exceptional energy densities of 108.3 and 26.9 W h kg−1 at power densities of 130 and 6053 W kg−1, respectively. The in situ transmission electron microscopy and the density functional theory calculations reveal that the excellent pseudocapacitance originates from the combination of Na adsorption on the surface/Sn edge of SnS2 nanoplatelets and ultrafast Na+ ion intercalation into the SnS2 layers. [ABSTRACT FROM AUTHOR]

It was recently discovered that Li2FeChO (Ch = S, Se, Te) anti-perovskites exhibit an outstanding rate capability and a good discharge capacity as Li-ion battery cathodes. In this work, we use density functional theory calculations to study the origin of the electrochemical characteristics of anti-perovskite cathodes using Li2FeSO as a model material. We evaluate the phase stability, ion-transport, and structural stability of this material and, interestingly, found that Li2FeSO is meta-stable at 0 K. The experimentally observed anti-perovskite phase likely originates from either entropy stabilization or sluggish decomposition kinetics. When delithiated, the stability of the material worsens. Additionally, over-delithiation may lead to irreversible structural change. The good rate capability of Li2FeSO is attributed to the high Li conductivity, where the low Li ion diffusion barrier (∼0.32 eV) rivals those of state-of-art superionic Li conductors. In the search for materials with a voltage higher than that of Li2FeSO, we screen Co, Cr, Cu, Mn, Mo, Ni, and V substitutions into the Fe site of Li2FeSO. While Cu and Ni substitutions may offer higher average voltages, the corresponding materials are less stable than Li2FeSO. [ABSTRACT FROM AUTHOR]

Carbon-coated van der Waals stacked Sb2S3 nanorods (SSNR/C) are synthesized by facile hydrothermal growth as anodes for sodium ion batteries (SIBs). The sodiation kinetics and phase evolution behavior of the SSNR/C anode during the first and subsequent cycles are unraveled by coupling in situ transmission electron microscopy analysis with first-principles calculations. During the first sodiation process, Na+ ions intercalate into the Sb2S3 crystals with an ultrafast speed of 146 nm s−1. The resulting amorphous Na xSb2S3 intermediate phases undergo sequential conversion and alloying reactions to form crystalline Na2S, Na3Sb, and minor metallic Sb. Upon desodiation, Na+ ions extract from the nanocrystalline phases to leave behind the fully desodiated Sb2S3 in an amorphous state. Such unique phase evolution behavior gives rise to superb electrochemical performance and leads to an unexpectedly small volume expansion of ≈54%. The first-principles calculations reveal distinctive phase evolution arising from the synergy between the extremely low Na+ ion diffusion barrier of 190 meV and the sharply increased electronic conductivity upon the formation of amorphous Na xSb2S3 intermediate phases. These findings highlight an anomalous Na+ ion storage mechanism and shed new light on the development of high performance SIB anodes based on van der Waals crystals. [ABSTRACT FROM AUTHOR]

Recently reported superionic Na closo-borates have drawn considerable attention due to their potential as solid-state electrolytes for Na ion batteries. However, a fundamental understanding of the ion transport mechanism in these materials is still missing. We studied Na conduction in Na2B10H10, a model material, using first-principles calculations. We found that the superior Na diffusivity is closely linked to the behavior of the large B10H102− anionic groups. The reorientations and disorder of these groups facilitate the Na+ hopping to the octahedral (Oh) sites, which link the tetrahedral (Td) sites to form a connected diffusion network. We also found that, in spite of the frequent Na hopping events, the diffusional paths are often blocked, thereby hindering Na transport. Such a mechanism suggests that the Na conductivity can be improved by introducing extrinsic vacancies. By simulating Na-deficient systems, we found that at high temperatures, even a minimal amount of additional Na vacancies significantly increases the ionic diffusivity. [ABSTRACT FROM AUTHOR]

Lithium-rich anti-perovskites (LiRAPs) are a promising family of solid electrolytes, which exhibit ionic conductivities above 10−3 S cm−1 at room temperature, among the highest reported values to date. In this work, we investigate the defect chemistry and the associated lithium transport in Li3OCl, a prototypical LiRAP, using ab initio density functional theory (DFT) calculations and classical molecular dynamics (MD) simulations. We studied three types of charge neutral defect pairs, namely the LiCl Schottky pair, the Li2O Schottky pair, and the Li interstitial with a substitutional defect of O on the Cl site. Among them the LiCl Schottky pair has the lowest binding energy and is the most energetically favorable for diffusion as computed by DFT. This is confirmed by classical MD simulations, where the computed Li ion diffusion coefficients for LiCl Schottky systems are significantly higher than those for the other two defects considered and the activation energy in LiCl deficient Li3OCl is comparable to experimental values. The high conductivities and low activation energies of LiCl Schottky systems are explained by the low energy pathways of Li between the Cl vacancies. We propose that Li vacancy hopping is the main diffusion mechanism in highly conductive Li3OCl. [ABSTRACT FROM AUTHOR]

Solid-State Batteries: Modulating Nanoinhomogeneity at Electrode-Solid Electrolyte Interfaces for Dendrite-Proof Solid-State Batteries and Long-Life Memristors (Adv. Keywords: conductive-atomic force microscope; critical current density; lithium filament; memristor; solid-state batteries EN conductive-atomic force microscope critical current density lithium filament memristor solid-state batteries 1 1 1 04/29/21 20210428 NES 210428 In article number 2003811, Ziheng Lu, Chunlei Yang, Wenjie Li and co-workers develop a high-resolution in-situ electrochemical characterization technique to reveal the nanoscale kinetics of lithium dendrites in solid-state batteries. Conductive-atomic force microscope, critical current density, lithium filament, memristor, solid-state batteries. [Extracted from the article]

A facile and scalable approach is reported to stabilize the lithium‐metal anode by regulating the Li nucleation and deposition kinetics with laser‐induced graphene (LIG). By processing polyimide (PI) films on copper foils with a laser, a 3D‐hierarchical composite material is constructed, consisting of a highly conductive copper substrate, a pillared array of flexible PI, and most importantly, porous LIG on the walls of the PI pillars. The high number of defects and heteroatoms present in LIG significantly lowers the Li nucleation barrier compared to the copper foil. An overpotential‐free Li nucleation process is identified at current densities lower than 0.2 mA cm−2. Theoretical computations reveal that the defects serve as nucleation centers during the heterogeneous nucleation of lithium. By adopting such composites, ultrastable lithium‐metal anodes are obtained with high Coulombic efficiencies of ≈99%. Full lithium‐metal cells based on LiFePO4 cathodes with a material loading of ≈15 mg cm−2 and a negative/positive ratio of 5/1 could be cycled over 250 times with a capacity loss of less than 10%. The current work highlights the importance of nucleation kinetics on the stability of metallic anodes and demonstrates a practical method toward long lasting Li‐metal batteries. [ABSTRACT FROM AUTHOR]

Solid Electrolytes: A New Lithium-Ion Conductor LiTaSiO5: Theoretical Prediction, Materials Synthesis, and Ionic Conductivity (Adv. Funct. In article number 1904232, Francesco Ciucci, Wei Kong Pang, Xin Guo, and co-workers design and synthesize a novel lithium-ion conductor LiTaSiO SB 5 sb , in which additional lithium ions are introduced into lattice sites of high energy through Zr-doping, thereby favoring the concerted motion of lithium ions and lowering the energy barrier for the ion transport. Concerted ion migration, ionic conductivity, LiTaSiO5, solid electrolytes. [Extracted from the article]

Owing to the nonleakage and incombustibility, solid electrolytes are crucial for solving the safety issues of rechargeable lithium batteries. In this work, a new class of solid electrolyte, acceptor‐doped LiTaSiO5, is designed and synthesized based on the concerted migration mechanism. When Zr4+ is doped to the Ta5+ sites in LiTaSiO5, the high‐energy lattice sites are partly occupied by the introduced lithium ions, and the lithium ions at those sites interact with the lithium ions placed in the low‐energy sites, thereby favoring the concerted motion of lithium ions and lowering the energy barrier for ion transport. Therefore, the concerted migration of lithium ions occurs in Zr‐doped LiTaSiO5, and a 3D lithium‐ion diffusion network is established with quasi‐1D chains connected through interchain channels. The lithium‐ion occupation, as revealed by ab initio calculations, is validated by neutron powder diffraction. Zr‐doped LiTaSiO5 electrolytes are successfully synthesized; Li1.1Ta0.9Zr0.1SiO5 shows a conductivity of 2.97 × 10−5 S cm−1 at 25 °C, about two orders of magnitude higher than that of LiTaSiO5, and it increases to 3.11 × 10−4 S cm−1 at 100 °C. This work demonstrates the power of theory in designing new materials. [ABSTRACT FROM AUTHOR]

Understanding Li diffusion in solid conductors is essential for the next generation Li batteries. Here we show that density-based clustering of the trajectories computed using molecular dynamics simulations helps elucidate the Li diffusion mechanism within the Li7La3Zr2O12 (LLZO) crystal lattice. This unsupervised learning method recognizes lattice sites, is able to give the site type, and can identify Li hopping events. Results show that, while the cubic LLZO has a much higher hopping rate compared to its tetragonal counterpart, most of the Li hops in the cubic LLZO do not contribute to the diffusivity due to the dominance of back-and-forth type jumps. The hopping analysis and local Li configuration statistics give evidence that Li diffusivity in cubic LLZO is limited by the low vacancy concentration. The hopping statistics also shows uncorrelated Poisson-like diffusion for Li in the cubic LLZO, and correlated diffusion for Li in the tetragonal LLZO in the temporal scale. Further analysis of the spatio-temporal correlation using site-to-site mutual information confirms the weak site dependence of Li diffusion in the cubic LLZO as the origin for the uncorrelated diffusion. This work puts forward a perspective on combining machine learning and information theory to interpret results of molecular dynamics simulations. [ABSTRACT FROM AUTHOR]