Data‐Driven Materials Exploration for Li‐Ion Conductive Ceramics by Exhaustive and Informatics‐Aided Computations

Interest in all‐solid‐state Li‐ion batteries (LIBs) using non‐flammable Li‐conducting ceramics as solid electrolytes has increased, as safe and robust batteries are urgently desired as power sources for (hybrid) electric vehicles. However, the low Li‐ion conductivities of ceramics have hindered all‐solid‐state LIB commercialization; many researchers have attempted to develop fast Li‐ion conductors. We introduce two efficient high‐throughput computational approaches for materials exploration: (i) exhaustive search and (ii) informatics‐aided prediction. For demonstration, ～400 Li‐ and Zn‐containing oxide (Li?Zn?X?O) compounds of varied crystal structures are extracted from Materials Project datasets. We calculate the migration energies for Li‐ion conduction and the phase stabilities (decomposition energies) of these materials by simulation and apply Bayesian optimization to determine the material with the highest ionic conductivity. The results show much greater efficiency than a random search algorithm.     

Lithium Chlorides and Bromides as Promising Solid‐State Chemistries for Fast Ion Conductors with Good Electrochemical Stability

Enabling all‐solid‐state Li‐ion batteries requires solid electrolytes with high Li ionic conductivity and good electrochemical stability. Following recent experimental reports of Li₃YCl₆ and Li₃YBr₆ as promising new solid electrolytes, we used first principles computation to investigate the Li‐ion diffusion, electrochemical stability, and interface stability of chloride and bromide materials and elucidated the origin of their high ionic conductivities and good electrochemical stabilities. Chloride and bromide chemistries intrinsically exhibit low migration energy barriers, wide electrochemical windows, and are not constrained to previous design principles for sulfide and oxide Li‐ion conductors, allowing for much greater freedom in structure, chemistry, composition, and Li sublattice for developing fast Li‐ion conductors. Our study highlights chloride and bromide chemistries as a promising new research direction for solid electrolytes with high ionic conductivity and good stability.     

The Significance of Ion Conduction in a Hybrid Organic–Inorganic Lead‐Iodide‐Based Perovskite Photosensitizer

The success of perovskite solar cells has sparked enormous excitement in the photovoltaic community not only because of unexpectedly high efficiencies but also because of the future potential ascribed to such crystalline absorber materials. Far from being exhaustively studied in terms of solid‐state properties, these materials surprised by anomalies such as a huge apparent low‐frequency dielectric constant and pronounced hysteretic current–voltage behavior. Here we show that methylammonium (but also formamidinium) iodoplumbates are mixed conductors with a large fraction of ion conduction because of iodine ions. In particular, we measure and model the stoichiometric polarization caused by the mixed conduction and demonstrate that the above anomalies can be explained by the build‐up of stoichiometric gradients as a consequence of ion blocking interfaces. These findings provide insight into electrical charge transport in the hybrid organic–inorganic lead halide solar cells as well as into new possibilities of improving the photovoltaic performance by controlling the ionic disorder.     

Fluorine‐Doped Antiperovskite Electrolyte for All‐Solid‐State Lithium‐Ion Batteries

A fluorine‐doped antiperovskite Li‐ion conductor Li₂(OH)X (X=Cl, Br) is shown to be a promising candidate for a solid electrolyte in an all‐solid‐state Li‐ion rechargeable battery. Substitution of F^? for OH^? transforms orthorhombic Li₂OHCl to a room‐temperature cubic phase, which shows electrochemical stability to 9 V versus Li⁺/Li and two orders of magnitude higher Li‐ion conductivity than that of orthorhombic Li₂OHCl. An all‐solid‐state Li/LiFePO₄ with F‐doped Li₂OHCl as the solid electrolyte showed good cyclability and a high coulombic efficiency over 40 charge/discharge cycles.     

Reducing the Charge Carrier Transport Barrier in Functionally Layer‐Graded Electrodes

Lithium‐ion batteries (LIBs) are primary energy storage devices to power consumer electronics and electric vehicles, but their capacity is dramatically decreased at ultrahigh charging/discharging rates. This mainly originates from a high Li‐ion/electron transport barrier within a traditional electrode, resulting in reaction polarization issues. To address this limitation, a functionally layer‐graded electrode was designed and fabricated to decrease the charge carrier transport barrier within the electrode. As a proof‐of‐concept, functionally layer‐graded electrodes composing of TiO₂(B) and reduced graphene oxide (RGO) exhibit a remarkable capacity of 128 mAh g⁻¹ at a high charging/discharging rate of 20 C (6.7 A g⁻¹), which is much higher than that of a traditionally homogeneous electrode (74 mAh g⁻¹) with the same composition. This is evidenced by the improvement of effective Li ion diffusivity as well as electronic conductivity in the functionally layer‐graded electrodes.     

High Uptake and Fast Transportation of LiPF6 in a Porous Aromatic Framework for Solid‐State Li‐Ion Batteries

Solid‐state Li‐ion batteries (SSLIBs) have recently attracted substantial attention from scientists for the advantages of better safety performance. However, there are still several key challenges in SSLIBs that need to be addressed, such as low energy density, poor thermal stability or cycle stability, and large interface resistance. This contribution introduces a novel SSLIB with a porous aromatic framework (PAF‐1) accommodating LiPF₆ that was used as the solid‐state electrolyte (SSE) replacing the liquid electrolyte and diaphragm of traditional Li‐ion batteries. The charge, discharge capacity, rate performance and cycle stability of the SSLIB were remarkably enhanced.     

Self‐Stabilized and Strongly Adhesive Supramolecular Polymer Protective Layer Enables Ultrahigh‐Rate and Large‐Capacity Lithium‐Metal Anode

Constructing a solid electrolyte interface (SEI) is a highly effective approach to overcome the poor reversibility of lithium (Li) metal anodes. Herein, an adhesive and self‐healable supramolecular copolymer, comprising of pendant poly(ethylene oxide) (PEO) segments and ureido‐pyrimidinone (UPy) quadruple‐hydrogen‐bonding moieties, is developed as a protection layer of Li anode by a simple drop‐coating. The protection performance of in‐situ‐formed LiPEO–UPy SEI layer is significantly enhanced owing to the strong binding and improved stability arising from a spontaneous reaction between UPy groups and Li metal. An ultrathin (approximately 70 nm) LiPEO–UPy layer can contribute to stable and dendrite‐free cycling at a high areal capacity of 10 mAh cm^?2 at 5 mA cm^?2 for 1000 h. This coating together with the promising electrochemical performance offers a new strategy for the development of dendrite‐free metal anodes.     

Ion‐Specific Self‐Assembly of Low‐Dimension Aggregate Structures of Conjugated Polymer at Two‐Phase Interface

A novel and facile approach to manipulate the morphology of Cu²⁺‐ion‐specific assembly of conjugated polymer by coordinative interaction at an oil–water two‐phase interface is present. The application of increasing importance is the use of π‐conjugated polymers as receptors, exploiting their ability to selectively form complexes, which can obviously change the optical properties in solution and induce the formation of varied solid nano/microstructures. By this method, microtubes are formed through self‐rolling of a strained ionic bilayer film at the oil/water interface.     

Lithium Ion Pathway within Li7La3Zr2O12‐Polyethylene Oxide Composite Electrolytes

Polymer–ceramic composite electrolytes are emerging as a promising solution to deliver high ionic conductivity, optimal mechanical properties, and good safety for developing high‐performance all‐solid‐state rechargeable batteries. Composite electrolytes have been prepared with cubic‐phase Li₇La₃Zr₂O₁₂ (LLZO) garnet and polyethylene oxide (PEO) and employed in symmetric lithium battery cells. By combining selective isotope labeling and high‐resolution solid‐state Li NMR, we are able to track Li ion pathways within LLZO‐PEO composite electrolytes by monitoring the replacement of ⁷Li in the composite electrolyte by ⁶Li from the ⁶Li metal electrodes during battery cycling. We have provided the first experimental evidence to show that Li ions favor the pathway through the LLZO ceramic phase instead of the PEO‐LLZO interface or PEO. This approach can be widely applied to study ion pathways in ionic conductors and to provide useful insights for developing composite materials for energy storage and harvesting.     

Solid‐State Electrolyte Anchored with a Carboxylated Azo Compound for All‐Solid‐State Lithium Batteries

Organic electrode materials are promising for green and sustainable lithium‐ion batteries. However, the high solubility of organic materials in the liquid electrolyte results in the shuttle reaction and fast capacity decay. Herein, azo compounds are firstly applied in all‐solid‐state lithium batteries (ASSLB) to suppress the dissolution challenge. Due to the high compatibility of azobenzene (AB) based compounds to Li₃PS₄ (LPS) solid electrolyte, the LPS solid electrolyte is used to prevent the dissolution and shuttle reaction of AB. To maintain the low interface resistance during the large volume change upon cycling, a carboxylate group is added into AB to provide 4‐(phenylazo) benzoic acid lithium salt (PBALS), which could bond with LPS solid electrolyte via the ionic bonding between oxygen in PBALS and lithium ion in LPS. The ionic bonding between the active material and solid electrolyte stabilizes the contact interface and enables the stable cycle life of PBALS in ASSLB.     

Li-KCl熔融界面上离子扩散的分子动力学研究

采用分子动力学(MD)方法研究了熔融Li(电极)-KCl(电解质)界面上离子的扩散行为。熔融界面上离子的扩散动力学通过离子质心的均方位移(MSD)和速度自相关函数(VACF)进行研究,扩散系数由MSD(t)函数线性区间的斜率和VACF(t)函数积分得到。模拟结果表明,在熔融的Li-KCl界面上,Li+离子在浓度梯度的驱动下穿过界面发生定向迁移,导致双电层的形成和外电路上电流的输出。Li+离子的扩散系数比K+和Cl-离子的大7～8倍,说明在界面上Li+离子是主要的载荷子,热电池的电荷传输机制主要与Li+离子的扩散运动有关。由Nernst-Einstein公式对电导率进行估算,由扩散到KCl层中的Li+离子产生的电导率约为0.4 S.cm-2,对应的电流密度估算值为3.27×105A.cm-2。     

Is there a ‘matrix suppression effect’ under fast‐atom bombardment liquid secondary ion mass spectrometry of ionic surfactants in glycerol?

Some features of a ‘matrix suppression effect’ caused by ionic surface‐active compounds under fast‐atom bombardment (FAB) liquid secondary ion mass spectrometry (LSIMS) are being revised. It is shown that abundant transfer of the glycerol matrix molecules to the gas phase does occur under FAB‐LSIMS of ionic surfactants, contrary to popular belief. This process can be obscure because of the dependence of the charge state of the glycerol‐containing cluster ions on the type of ionic surfactant. It is revealed that, while glycerol matrix signals are really completely suppressed in the positive ion mass spectra of cationic surfactants (decamethoxinum, aethonium), abundant deprotonated glycerol and glycerol‐anion clusters are recorded in the negative ion mode. In the case of an anionic surfactant (sodium dodecyl sulfate), on the contrary, glycerol is completely suppressed in the negative ion mode, but is present in the protonated and cationized forms in the positive ion mass spectra. It is suggested that such patterns of positive and negative ion FAB‐LSIMS spectra of ionic surfactants solutions reflect the structure and composition of the electric double layer formed at the vacuum‐liquid interface by organic cations or anions and their counterions. Processes leading to the formation of the glycerol‐containing ions preferentially of positive or negative charge are discussed. The most obvious of them is efficient binding of glycerol to inorganic counterions of the salts Cl^? or Na⁺, which is confirmed by data from quantum chemical calculations. The high content of the counterions and relatively small content of glycerol in the sputtered zone may be responsible for the charge‐selective suppression of neat glycerol clusters of opposite charge to the counterions. In the case of a mixture of cationic and anionic surfactants the substitution of inorganic counterions by organic ones was observed. The dependence of the exchange rate in the surface layer is not a linear function of the bulk solution concentration, and an effect of abrupt recharging of the surface can be registered. No both positively or negatively charged pure glycerol and glycerol‐inorganic counterion clusters are recorded for the mixture. Correlations between the mass spectrometric observations and some phenomena of surface and colloid chemistry and physics are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

In Situ Construction of an Ultra‐Stable Conductive Composite Interface for High‐Voltage All‐Solid‐State Lithium Metal Batteries

The garnet electrolyte presents poor wettability with Li metal, resulting in an extremely large interfacial impedance and drastic growth of Li dendrites. Herein, a novel ultra‐stable conductive composite interface (CCI) consisting of Li_ySn alloy and Li₃N is constructed in situ between Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) pellet and Li metal by a conversion reaction of SnN_x with Li metal at 300 °C. The Li_ySn alloy as a continuous and robust bridge between LLZTO and Li metal can effectively reduce the LLZTO/Li interfacial resistance from 4468.0 Ω to 164.8 Ω. Meanwhile, the Li₃N as a fast Li‐ion channel can efficiently transfer Li ions and give their uniform distribution at the LLZTO/Li interface. Therefore, the Li/LLZTO@CCI/Li symmetric battery stably cycles for 1200 h without short circuit, and the all‐solid‐state high‐voltage Li/LLZTO@CCI/LiNi_0.5Co_0.2Mn_0.3O₂ battery achieves a specific capacity of 161.4 mAh g^?1 at 0.25 C with a capacity retention rate of 92.6 % and coulombic efficiency of 100.0 % after 200 cycles at 25 °C.     

Description of the Effects of Non‐ion‐exchange Extraction and Intra‐membrane Interactions on the Ion‐selective Electrodes Response within the Interface Equilibria‐triggered Model

The recently proposed interface equilibria‐triggered dynamic diffusion model of the boundary potential has proven its high predictive efficiency for quantification of the ion exchange and co‐extraction effects at the interface, as well as of the trans‐membrane transfer effect, on the electrode response. It is applicable for both ion exchanger‐based and neutral carrier‐based electrodes. In this communication, the adaptability of this model to more complex cases, when non‐ion‐exchange extraction processes at the interface (partition of organic acids’ and bases’ molecular forms and extraction of ionic associates) are coupled with protolytic equilibria in the aqueous phase and with self‐solvation process in the membrane phase, is demonstrated. By the example of electrodes reversible to ions of highly lipophilic physiologically active bases and acids (amiodarone, verapamil, vinpocetine, salicylic acid), it is shown that the peculiarities of their functioning, such as a very strong pH effect on the potential of cation‐selective electrodes, non‐monotonic pH dependence of the potential and super‐Nernstian response slope in certain pH region for a salicylate‐selective electrode, are well described within the model.     

Structure of the electrical double layer on the aqueous solution side of the polarized interface between water and a room-temperature ionic liquid, tetrahexylammonium bis(trifluoromethylsulfonyl)imide

The structure of the electrical double layer on the aqueous solution side has been studied by measuring electrocapillary curves at the polarized interface between a room-temperature ionic liquid (RTIL), tetrahexylammonium bis(trifluoromethylsulfonyl)imide, and water (W) at different concentrations of LiCl. Thermodynamic analysis of the electrocapillary curves indicates that Li+ ions negatively adsorb at the point of zero charge. The adsorption of Li+ and Cl- ions in the polarized potential window of about 200 mV can be explained by the Gouy's double layer model, and the specific adsorption of Li+ and Cl- ions at the RTIL|W interface is negligible within the polarized potential window.     

A 3D Nanostructured Hydrogel‐Framework‐Derived High‐Performance Composite Polymer Lithium‐Ion Electrolyte

Solid‐state electrolytes have emerged as a promising alternative to existing liquid electrolytes for next generation Li‐ion batteries for better safety and stability. Of various types of solid electrolytes, composite polymer electrolytes exhibit acceptable Li‐ion conductivity due to the interaction between nanofillers and polymer. Nevertheless, the agglomeration of nanofillers at high concentration has been a major obstacle for improving Li‐ion conductivity. In this study, we designed a three‐dimensional (3D) nanostructured hydrogel‐derived Li_0.35La_0.55TiO₃ (LLTO) framework, which was used as a 3D nanofiller for high‐performance composite polymer Li‐ion electrolyte. The systematic percolation study revealed that the pre‐percolating structure of LLTO framework improved Li‐ion conductivity to 8.8×10^?5 S cm^?1 at room temperature.     

Mass Distribution and Diffusion of [1‐Butyl‐3‐methylimidazolium][Y] Ionic Liquids Adsorbed on the Graphite Surface at 300–800 K

The structure and diffusion behavior of 1‐butyl‐3‐methylimidazolium ([bmim]⁺) ionic liquids with [Cl]^?, [PF₆]^?, and [Tf₂N]^? counterions near a hydrophobic graphite surface are investigated by molecular dynamics simulation over the temperature range of 300–800 K. Near the graphite surface the structure of the ionic liquid differs from that in the bulk and it forms a well‐ordered region extending over 30 Å from the surface. The bottom layer of the ionic liquid is stable over the investigated temperature range due to the inherent slow dynamics of the ionic liquid and the strong Coulombic interactions between cation and anion. In the bottom layer, diffusion is strongly anisotropic and predominantly occurs along the graphite surface. Diffusion perpendicular to the interface (interfacial mass transfer rate k_t) is very slow due to strong ion–substrate interaction. The diffusion behaviors of the three ionic liquids in the two directions all follow an Arrhenius relation, and the activation barrier increases with decreasing anion size. Such an Arrhenius relation is applied to surface‐adsorbed ionic liquids for the first time. The ion size and the surface electrical charge density of the anions are the major factors determining the diffusion behavior of the ionic liquid adjacent to the graphite surface.     

Microphase separation and ion‐conduction mechanisms in polypropylene oxide/lithium perchlorate (LiClO4) complexes

Broadband dielectric spectroscopy was used to examine ion‐conduction mechanisms in polypropylene oxide (PPO) with a molecular weight of 4000 complexed with LiClO₄. Two distinct conduction mechanisms were proposed with respect to high and low salt concentration regions. In a concentrated regime (Li/O >10%), the segmental motion of PPO molecules is significantly slowed down by enhanced cation coordination that results in a marked decrease in molar conductivity. We found a linear relationship between the ionic diffusion coefficient and the relaxation frequency of slowed segmental motion over broad temperature and salt‐concentration ranges. The use of a random walk scheme revealed that ions hop around at the same rate as slowed segmental motion for a monomer length. In a dilute regime (Li/O <0.1%), ions are temporarily localized in a limited domain. The direct current conductivity is achieved by structural renewal that releases ions from such localization and provides a diffusional character. At intermediate salt concentrations, microphase separation into ion‐depleted and ion‐rich regions was evidenced by the coexistence of fast and slow segmental processes. The molar conductivity revealed a maximum at Li/O = 3%. Its decrease at higher salt concentrations was attributed to the slowing down of segmental motion, and that at lower salt concentrations was attributed to localization of ionic motion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 613–622, 2002; DOI 10.1002/polb.10123     

Formation of Nanostructured MnO/Co/Solid–Electrolyte Interphase Ternary Composites as a Durable Anode Material for Lithium‐Ion Batteries

Nanoporous MnO frameworks with highly dispersed Co nanoparticles were produced from MnCO₃ precursors prepared in a gel matrix. The MnO frameworks that contain 20 mol % Co exhibited excellent cycle performance as an anode material for Li‐ion batteries. The solid–electrolyte interphase (SEI) formed in the frameworks through the electrochemical reaction mediates the active materials, such as MnO, Mn, and Li₂O, during the conversion reaction in the charge–discharge cycle. The Co nanoparticles and SEI provide the electron and Li‐ion conductive networks, respectively. The ternary nanocomposites of the MnO framework, metallic Co nanoparticles, and embedded SEI are categorized as durable anode materials for Li‐ion batteries.