Ion Transport Barriers Research Articles

Low-Solvent-Coordination Solvation Structure for Lithium-Metal Batteries via Electric Dipole-Dipole Interaction.

Unveiling inherent interactions among solvents, Li+ ions, and anions are crucial in dictating solvation-desolvation kinetics at the electrode/electrolyte interface. Developing an electrolyte with a low ion-transport barrier and minimal solvent coordination in its interfacial solvation structure is essential for forming an anion-derived solid-electrolyte interface, a key component for high-performance Li-metal batteries. In this study, we harness electric dipole-dipole synergistic interactions to formulate an electrolyte with significantly reduced interfacial solvent coordination. Operando characterization and theoretical analysis reveal that 2-fluoropyridine (FPy) with high dipole preferentially adsorbs onto the Li metal surface. The adsorbed FPy molecule squeezes succinonitrile in the primary solvation sheath through steric hindrance, leading to the formation of an inorganic-rich interphase. Consequently, the introduction of FPy enhances the reversible capacity of the LiCoO2||Li cell, which maintains a capacity of 143 mAh g-1 after 500 cycles at a 1C rate. Moreover, the cycle life of LiCoO2 batteries with a limited supply of lithium extends from 120 cycles to over 200 cycles. These findings offer a strategy that can be applied broadly to design interfacial solvation structures for various metal-ion/metal-based batteries.

Light-Powered Directional Ion Transport via PFN-Br/MoS2 Heterogeneous Membranes: Band Alignment and Activation Energy Barrier Engineering.

Biological photoresponsive ion transport systems consistently attract researchers' attention owing to their remarkable functions of harvesting energy from nature and participating in visual perception systems. Designing and constructing artificial light-driven ion transport devices to mimic biological counterparts remains a challenge owing to fabrication limitations in nanoconfined spaces. Herein, a typical conjugated polyelectrolyte (PFN-Br) was assembled onto a laminated MoS2M using simple solution-processing vacuum filtration, resulting in a heterogeneous three- and two-dimensional nanoporous membrane. The designed band alignment between PFN-Br and MoS2 enables effective directional ion transport under irradiation in an equilibrium solution, even against a 30-fold concentration gradient. The staggered energy structure of PFN-Br and MoS2 enhances charge separation and establishes a photogenerated potential as the driving force for ion transport. Additionally, the activation energy barrier for ion transport across the heterogeneous membrane decreased by 60% after light irradiation, considerably improving ion transport flux. The easy fabrication and high performance of the membrane in light-powered ion transport provide promising approaches for designing nanofluidic devices with possible applications in energy conversion, light-enhanced biosensing, and photoresponsive ionic devices.

Synergistic effects and electrocatalytic insight of single-phase hexagonal structure as low-temperature solid oxide fuel cell cathode

Enhancing the electrocatalytic activity of the electrode materials, specifically oxygen reduction reaction (ORR), at lower operating temperatures (<600 °C) is the prime rank to realize the commercialization of solid oxide fuel cells (SOFCs) research. Herein, a new hexagonal structure-based cathode material was developed with the co-doping of Gd2O3 and Cr2O3 of parent SrFe12O19 oxide, respectively. At 550‒475 °C, Sr0.90Gd0.10Fe11.90Cr0.10O19 (SFO-10) cathode sample leading to the large peak power density (PPD) of 395 mW/cm2, has appropriate surface oxygen defects (Oβ) up to 17%, as verified by X-ray photoelectron microscopy (XPS). Theoretical calculations reveal that the co-doping of Gd and Cr oxides creates lattice disorder at the hexagonal lattice, which decreases the energy barrier for ion transport and enhances the electrocatalytic characteristics of ORR. Consequently, the SFO-10 cathode shows a favorable ORR activity with the least lower polarization resistance (ASR) at 550 °C with gadolinium-doped ceria (GDC) electrolyte. This work provides a self-assembled single-phase hexagonal cathode to accelerate the low-temperature hindrance of SOFC technology.

Strategy to improve synaptic behavior of ion-actuated synaptic transistors—the use of ion blocking layer to improve state retention

Synaptic transistors (STs) with a gate/electrolyte/channel stack, where mobile ions are electrically driven across the solid electrolyte, have been considered as analog weight elements for neuromorphic computing. The current (ID) between the source and drain in the ST is analogously updated by gate voltage (VG) pulses, enabling high pattern recognition accuracy in neuromorphic systems; however, the governing physical mechanisms of the ST are not fully understood yet. Our previous physics-based simulation study showed that ion movement in the electrolyte, rather than the electrochemical reactions that occur in the channel, plays an important role in switching. In this study, we experimentally explore the properties of the HfOx electrolyte and show that by tuning the density of oxygen vacancies, it can assume the dual role of electrolyte and channel. We demonstrate analog synaptic behavior using a novel ST with a two-layer stack of CuOx/HfOx, where the CuOx is the gate and Cu ion reservoir, and the HfOx is the electrolyte and channel. To improve state retention and linearity, we introduce a Cu ion transport barrier in the form of a dense and stoichiometric Al2O3 layer. The CuOx/Al2O3/HfOx exhibits excellent state retention and improved potentiation and depression response. Energy dispersive spectroscopy mapping following potentiation confirms the role of the Al2O3 layer in confining the Cu ions in the HfOx layer. We also show that a two-step programming scheme can further enhance synaptic response and demonstrate high recognition accuracy on the Fashion-MNIST dataset in simulation.

A Fast Na‐Ion Conduction Polymer Electrolyte via Triangular Synergy Strategy for Quasi‐Solid‐State Batteries

AbstractPolymer electrolytes provide a visible pathway for the construction of high‐safety quasi‐solid‐state batteries due to their high interface compatibility and processability. Nevertheless, sluggish ion transfer at room temperature seriously limits their applications. Herein, a triangular synergy strategy is proposed to accelerate Na‐ion conduction via the cooperation of polymer‐salt, ionic liquid, and electron‐rich additive. Especially, PVDF‐HFP and NaTFSI salt acted as the framework to stably accommodate all the ingredients. An ionic liquid (Emim+‐FSI−) softened the polymer chains through a weakening molecule force and offered additional liquid pathways for ion transport. Physicochemical characterizations and theoretical calculations demonstrated that electron‐rich Nerolin with π‐cation interaction facilitated the dissociation of NaTFSI and effectively restrained the competitive migration of large cations from EmimFSI, thus lowering the energy barrier for ion transport. The strategy resulted in a thin F‐rich interphase dominated by NaTFSI salt's decomposition, enabling rapid Na+ transmission across the interface. These combined effects resulted in a polymer electrolyte with high ionic conductivity (1.37×10−3 S cm−1) and tNa+ (0.79) at 25 °C. The assembled cells delivered reliable rate capability and stability (200 cycles, 99.2 %, 0.5 C) with a good safety performance.

A Fast Na-Ion Conduction Polymer Electrolyte via Triangular Synergy Strategy for Quasi-Solid-State Batteries.

Polymer electrolytes provide a visible pathway for the construction of high-safety quasi-solid-state batteries due to their high interface compatibility and processability. Nevertheless, sluggish ion transfer at room temperature seriously limits their applications. Herein, a triangular synergy strategy is proposed to accelerate Na-ion conduction via the cooperation of polymer-salt, ionic liquid, and electron-rich additive. Especially, PVDF-HFP and NaTFSI salt acted as the framework to stably accommodate all the ingredients. An ionic liquid (Emim+ -FSI- ) softened the polymer chains through a weakening molecule force and offered additional liquid pathways for ion transport. Physicochemical characterizations and theoretical calculations demonstrated that electron-rich Nerolin with π-cation interaction facilitated the dissociation of NaTFSI and effectively restrained the competitive migration of large cations from EmimFSI, thus lowering the energy barrier for ion transport. The strategy resulted in a thin F-rich interphase dominated by NaTFSI salt's decomposition, enabling rapid Na+ transmission across the interface. These combined effects resulted in a polymer electrolyte with high ionic conductivity (1.37×10-3 S cm-1 ) and tNa+ (0.79) at 25 °C. The assembled cells delivered reliable rate capability and stability (200 cycles, 99.2 %, 0.5 C) with a good safety performance.

Hydrogel electrolyte membrane with regulated pore effect to stabilize zinc anode in aqueous zinc-ion batteries

The unregulated dendrite growth and deleterious derivative reactions at Zn anodes lie in the path of research and industrialization of aqueous Zn-ion batteries (AZBs). The pore of the separator is a natural sieve for ion diffusion, but the high energy barrier for transmembrane transport can cause the “bridging” effect of ion congestion at the pore entrance, and induce the incubation of dendrites instead. In this work, a continuous, stable and fast ion transport channel is constructed by in-situ guided cross-linking of zinc alginate (ZA) hydrogels through the porous membrane to conquer the negative pore effect. The homogeneity and continuity of the channel structure, as well as the high ionic conductivity and zincophilicity of the ZA, can homogenize the electric field and reduce the energy barrier for ion transport. In battery systems, the physical ion shunting effect of a homogeneous pore structure, combined with the chemical/electrochemical effects of ZA guiding the diffusion of Zn2+ and binding free water, combat zinc dendrites and interfacial side reactions. The novel electrolyte membrane enables a highly reversible Zn plating/stripping to stabilize the Zn anode. This work provides illuminating insights into the regulation and application of pore effects in porous electrolyte membranes in metal-based batteries.

Voltage Controlled Ab-Initio Simulations of Metal-Insulator Interfaces Immersed in Electrolyte for Corrosion and Battery Applications Via the Quantum Continuum Approximation (QCA)

While Density Functional Theory (DFT) has been an invaluable tool for exploring atomic interaction of defects and interfaces, it has been difficult to include information about the voltage of the larger electrochemical system into these calculations. This is because the electric field at any given simulation region is dependent on the broader interface, which is usually 10s of nm long. Fully simulating this interface with DFT is computationally prohibitive, and most studies simulate smaller portions. This reduction eliminates the information about the surrounding electric field, however, and thus the interaction with the global potential is unaccounted for. In this talk, we introduce the Quantum Continuum Approximation (QCA) as a methodology for including interface voltage information into limited-size DFT calculations by self-consistently coupling DFT calculations of defect/interface regions to Poisson-Boltzmann descriptions of the surrounding insulating and electrolyte regions. By reducing the number of atoms needed to incorporate voltage information into DFT calculations by an order of magnitude, QCA makes the voltage-dependent first-principles study of full electrochemical interfaces viable. We demonstrate this methodology to examine Cl- ion insertion into aluminum/aluminum oxide interfaces as a function of voltage. We find good agreement between the voltage threshold for stability predicted by QCA and those found experimentally. We then demonstrate QCA as a tool for measuring Li+ ion transport barriers through different solid-electrolyte interface (SEI) regions in battery chemistry as a function of voltage. Our work demonstrates the ability to attach a potentiostat to DFT calculations of interfaces relevant to simulations of electrochemical applications at reasonable computational cost. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525

Understanding the Energetics of Ion Intercalation in Lithium-Ion Batteries

Researchers around the world are working to increase the energy efficiency and the energy density of lithium-ion batteries. However, the mechanism and the factors influencing the charge transfer (CT) kinetics at the electrode-electrolyte interface remain poorly understood. Recently, Fraggedakis et al. [1] proposed the theory of coupled ion-electron transfer (CIET) to explain the process of charge transfer at the electrode-electrolyte interfaces. In this work, we provide deep atomistic understanding of the interfacial CT mechanism, the underlying microscopic steps, and the factors influencing the CT rates in a Li-ion battery. In addition, we connect our computational results with the experimental measurements and Marcus-like theories of charge transfer (viz. CIET [1]).Using state-of-the-art computational techniques, such as metadynamics and molecular dynamics simulations, we model the electrode-electrolyte interface and compute the free energy profiles of Li-ion adsorption at the interface, subsequent ion-desolvation, and intercalation into the cathode. Specifically, we study the adsorption of Li+ ion on LixCoO2 surface for different (i) electrolytes, (ii) Li+ concentrations in electrolyte, (iii) salt compositions, and (iv) temperatures to uncover the trends governing charge transfer kinetics. Using the obtained free energy profiles of Li+ desolvation and intercalation at the solid-liquid interface, we provide estimation of the adsorption and desolvation energy at the interface and identify the key energy barrier which acts as the roadblock for ion transfer in Li-ion batteries. Based on this identified key kinetic barrier, we then propose strategies to tune the energy barrier for ion transport. In addition, we identify important thermo-physical observations that can explain the existing experimental trends. For instance, we find that increasing the salt concentration in the electrolyte increases the accessible solvation states to Li+ ion, thereby changing the energy barrier for the Li+ ion to intercalate into the electrode, and thus leading to higher currents. Moreover, we find that changing the salt from LiPF6 to LiClO4 further modifies the energy landscape of Li+ ion, leading to increased measured experimental kinetics as well. This work builds an understanding of the influence of various effects, such as salt concentration and electrolyte composition, on the Li+ transport properties at interfacial regions. Our computational framework can also provide descriptors to enhance the performance and stability of lithium-ion batteries.

A Review of Nb2CTx MXene: Synthesis, Properties and Applications

Nb2CTx is an important member of MXene family. It has attracted widespread attention because of its abundant functional groups, high hydrophilicity, high electrical conductivity as well as low ion transport barrier, showing great potential in various applications. In order to utilize the advantages of Nb2CTx MXene, the progress of preparation, properties and applications are reviewed in this work. This work focuses on different methods of Nb2CTx preparation and applications in electrochemical energy storage (supercapacitors and secondary batteries), electrocatalytic hydrogen evolution, photocatalytic hydrogen evolution, sensors, etc. Additionally, the main problems of self-stacking and prospect of Nb2CTx MXene are discussed.

Deep eutectic solvent assisted synthesis of molybdenum nitride entrapped graphene aerogel heterostructure with enhanced electrochemical behavior for ronidazole drug detection

In the wake of the ascendancy of pharmaceutics to the forefront of modern-era medicine, antibiotic usage has seen an exponential increase. However, as an inevitable corollary of its misuse, the deleterious aftereffects of antibiotic pollution have emerged globally as a pressing health concern. Ronidazole (RND), a popular veterinary antibiotic and growth promoter, is ill-famed for its carcinogenic, genotoxic, and mutagenic properties. A recurring challenge that curtails the quantitative monitoring of RND is the lack of sensing devices with pronounced detection characteristics. Owing to the unparalleled wealth of synergistic features, nanocomposite architectures featuring transition metal nitrides and graphene aerogels have garnered tremendous attention among the scientific community. In this study, we propose a molybdenum nitride entrapped graphene aerogel (MoN@GA) nanocomposite synthesized via a deep eutectic solvent (DES) assisted procedure. The choline chloride–urea DES system allows for a more energy-efficient production of MoN and adorns the role of a multifunctional agent and acts simultaneously as a solvent, reducing agent, and nitridation agent. The prepared MoN@GA nanocomposite is utilized as the working electrode for the electrochemical detection of RND. The superior active surface area and conductivity of GA-anchored MoN can efficiently overcome the kinetic barrier for ion transport. The optimized MoN@GA glassy carbon electrode (GCE) showed a wide response range of 0.001–918.44 μM with a detection limit of 1.3 nM and high sensitivity of 78.65 μA μM−1 cm−2 toward RND. Furthermore, the developed sensor is unaffected by the presence of other similar interferons. Under optimal conditions, a proof-of-concept amperometric analysis of RND was performed using a MoN@GA modified electrochemical system, and an acceptable recovery value of ±97.4–99.93% was obtained.

Ultra-microporous anion conductive membranes for crossover-free pH-neutral aqueous organic flow batteries

Aqueous organic redox flow battery (AORFB) operating in pH-neutral solutions is an attractive electrochemical energy storage device because of its decoupled energy and power, high safety, low corrosivity, and potentially low cost. However, it remains largely unclear how to develop high-performing AORFB membranes that enable fast ion transport while impeding electrolyte cross-contamination. Here we report a series of anion conductive membranes derived from Tröger's Base polymers with intrinsic microporosity as promising contender membranes for pH-neutral AORFBs. The quantity of sub-nanometer-sized pores in these membranes is regulated by tuning chain rigidity, while a similar pore size distribution is retained. We discover that membrane conductivity is determined by the quantity of pores, whereas the energy barrier for ion transport is related to the pore size distribution. Contrasting conventional knowledge, crossover-free operation of pH-neutral AORFB can be accomplished by implementing microporous polymer membranes that enable fast ion conduction but are moderately selective to redox-active electrolytes. The pH-neutral AORFB exhibits a low capacity fade rate of 0.002% per cycle (0.02% per hour) during 500 consecutive charge/discharge cycles at 40 mA cm−2 while maintaining an energy efficiency of up to 80% and a coulombic efficiency of ∼100%. These results demonstrate that ultra-microporous membranes possess great potential for AORFB applications.

Novel preparation of lithium‐ion battery wet‐processed separator based on the synergistic effect of porous skeleton nano‐Al2O3in situ blending and synchro‐draw

AbstractRoutine lithium‐ion battery separators with uneven micropores and poor electrolyte affinity raise ion transport barriers and become the battery‐performance‐limiting factors. A wet‐processed separator with homogeneous porous structure and porous skeleton nano‐Al2O3 in situ blending is readily prepared by thermally induced phase separation of paraffin, nano‐Al2O3 and ultra‐high molecular weight polyethylene (UHMWPE) in this work. SEM, ImageJ statistical analysis, porosity and Gurley calculation show that a separator that has undergone asynchronous drawing exhibits ample sturdy fibrils, heterogeneous pore size dispersion, poor permeability and strong anisotropy. However, UHMWPE deforms much more uniformly under a synchro‐draw, which distinctly lessens coarse fibrils, centralizes porous construction after stretching and brings better isotropy for the separator. Additionally, nano‐Al2O3 scattered in the cast film further weakens the heterogeneity of micropores stemming from the uneven thermally induced phase separation. Wettability tests and thermal diagnoses also show that nano‐Al2O3 on the porous skeleton strengthens the thermal stability and electrolyte affinity of the separator. Consequently, batteries containing nano‐Al2O3 composite separators show much higher electrochemical stability, ionic conductivity and Li+ transport number because of the synergistic effect of the even microvoids and nano‐Al2O3 on the porous skeleton, which expedites Li+ transport and endows superior lithium‐ion battery performance. © 2022 Society of Industrial Chemistry.

MAX-phase Derived Tin Diselenide for 2D/2D Heterostructures with Ultralow Surface/Interface Transport Barriers toward Li-/Na-ions Storage.

2D tin diselenide and its derived 2D heterostructures have delivered promising potentials in various applications ranging from electronics to energy storage devices. The major challenges associated with large-scale fabrication of SnSe2 crystals, however, have hindered its engineering applications. Herein, a tin-extraction synthetic method is proposed for producing large-size SnSe2 bulk crystals. In a typical synthesis, a Sn-containing MAX phase (V2 SnC) and a Se source are heat-treated under a reducing atmosphere, by which Sn is extracted from the V2 SnC phase as a rectified Sn source to form SnSe2 crystals in the cold zone. After the following liquid exfoliation, the obtained 2D SnSe2 nanosheets have a lateral size of a few centimeters and an atomic thickness. Furthermore, by coupling with 2D graphene to form 2D/2D SnSe2 /graphene heterostructured electrodes, as validated by theoretical calculation and experimental studies, the superior Li-/Na-ion storage performance with ultralow surface/interface ion transport barriers are achieved for rechargeable Li-/Na-ion batteries. This innovative synthetic strategy opens a new avenue for the large-scale synthesis of selenides and offers more options into the practical application of emerging 2D/2D heterostructure for electrochemical energy storage.

Oxygen vacancies Nb2O5-x: Ultrastable lithium storage anode materials for advanced rechargeable batteries

Optimizing the charge and ion transport of Nb2O5 composite is great significance for developing high-performance fast charge lithium-ion batteries. We designed Nb2O5 with oxygen vacancies through a simple and cost-effective hydrothermal and high-temperature calcination treatments. Oxygen vacancies can not only improve the electronic conductivity of the composite, but also effectively provide more active sites and reduce the ion transport barrier, which improved electrochemical reaction kinetics of the Nb2O5 composite. Consequently, the synthesized Nb2O5-x microflowers delivered a specific capacity of 191.2 mA h g−1 at 1C (a retention of 94% over 200 cycles) and outstanding rate capability (103.3 mA h g−1 at 50C) for lithium storage. Significantly, this work may also broaden the pathways for designing other electrode materials with oxygen vacancies for battery systems.

Effect of Nb5+ doping on the microstructure and conductivity of Li1.125Ta0.875Zr0.125SiO5 electrolyte

The microstructure and electrochemical properties of Li1.125Ta0.875-xNbxZr0.125SiO5 (x = 0, 0.0625, 0.1875, 0.25, 0.5) ceramics prepared via the solid-phase reaction method were studied. The results reveal that the conductivity of the ceramic specimens at 25 °C increases and then decreases as the Nb increases from 0 to 0.5 mol. 0.1875 mol of Nb doping facilitates the fusion and connection between grains, reduces the number of grain boundaries, leads to densification of the ceramics, decreases the total resistance, and thus increases the conductivity. Moreover, the small structural distortion caused of the discrepancy in ionic radii of Ta5+ and Nb5+ creates more space to accommodate Li ions and promotes the diffusion of Li+, reducing the energy potential barrier for ion transport. The best performing Li1.125Ta0.6875Nb0.1875Zr0.125SiO5 has a conductivity of 3.521 × 10-5 S/cm at 25 °C, with an order of magnitude greater than that of the original sample Li1.125Ta0.875Zr0.125SiO5, reaching 2.288 × 10-4 S/cm at 150 °C and has a minimum activation energy: 0.225 eV. The prepared Li1.125Ta0.6875Nb0.1875Zr0.125SiO5 ceramic is a new type of fast Li-ion conductor with potential for application in all-solid-state batteries.

Oxygen defected T-Nb2O5-x confined in necklace-like N-doped carbon fibers for Li+/Na+ capacitor

Optimizing the transmission dynamics and stability of orthorhombic (T-) Nb 2 O 5 is the development direction of hybrid supercapacitors. In this work, Necklace-like T-Nb 2 O 5-x @NC assembled by Yolk-Shell nanosphere is applied for self-supporting anode of the Li + /Na + capacitor. Each Yolk-Shell T-Nb 2 O 5-x @NC unit effectively alleviates the volume effect of Nb 2 O 5 during Li + /Na + embedding repeatedly, thus achieving good structural stability. In addition, oxygen vacancy optimizes the transmission barrier of Li + /Na + and its conductivity. T-Nb 2 O 5-x @NC units are stringed along the carbon fibers, which are further interconnected to form integrated 3D conductive network for excellent electron conductivity. As a result, T-Nb 2 O 5-x @NC-7, as the optimal sample, has high specific capacity (up to 208.3 mAh g −1 at 0.1 A g −1 in Li half-cell) and long cycle life (92.3% after 2000 cycles in Li capacitor). Also, it exhibits superior electrochemical performance in Na energy storage (84.2% after 2000 cycles). • Yolk-shell structure greatly relieved the volume expansion effect. • Oxygen vacancy reduces the ion transport barrier. • The independent unmatched electrons generated optimize its conductivity. • Carbon interconnected network improves electron conductivity.

Ion Selectivity and Permeation Mechanism in a Cyclodextrin-Based Channel.

Synthetic ion channels are a promising technology in the medical and materials sciences because of their ability to conduct ions. Channels based on cyclodextrin, a cyclic oligomer of glucose, are of particular interest because of their nontoxicity and biocompatibility. Using molecular dynamics-based free energy calculations, this study identifies cyclodextrin channel types that are best suited to serve as synthetic ion channels. Free energy profiles show that the connectivity in the channel determines whether the channel is cation-selective or anion-selective. Furthermore, the energy barrier for ion transport is governed by the number of glucose molecules making up the cyclodextrin units of the channel. A detailed mechanism is proposed for ion transport through these channels. Findings from this study will aid in designing cyclodextrin-based channels that could be either cation-selective or anion-selective, by modifying the linkages of the channel or the number of glucose molecules in the cyclodextrin rings.

(Invited) Entropy-Enhanced Ion Transport in Solid Electrolytes

Long-range ion transport is composed of microscopic steps of ion migration, which is governed by local structures and interactions of the charge carriers with their surroundings. Therefore, understanding the local environments of conducting ions and their impact on ion dynamics and transport pathways are critical to design of high-performance solid electrolytes. We have synthesized and studied a variety of Li superionic conductors. Systematic solid-state nuclear magnetic resonance (NMR) investigations, complemented by pair distribution analysis (PDF) and DFT/MD simulations, have revealed that entropies in structures, compositions, and Li-coordination play a key role in determining ion hoping frequencies, jumping distance, transport pathways, and activation barriers. Via maximizing these entropies, “liquid-like” Li-sublattice is produced with a flattened energy landscape yielding extremely low activation barrier for ion transport. A few such examples will be discussed, including glass, ceramic, and glass-ceramic composites.

Enhanced Cycling and Rate Capability by Epitaxially Matched Conductive Cubic TiO Coating on LiCoO2 Cathode Films.

Layered lithium transition-metal oxides, such as LiCoO2 and its doped and lithium-rich analogues, have become the most attractive cathode material for current lithium-ion batteries due to their excellent power and energy densities. However, parasitic reactions at the cathode–electrolyte interface, such as metal-ion dissolution and electrolyte degradation, instigate major safety and performance issues. Although metal oxide coatings can enhance the chemical and structural stability, their insulating nature and lattice mismatch with the adjacent cathode material can act as a physical barrier for ion transport, which increases the charge-transfer resistance across the interface and impedes cell performance at high rates. Here, epitaxial engineering is applied to stabilize a cubic (100)-oriented TiO layer on top of single (104)-oriented LiCoO2 thin films to study the effect of a conductive coating on the electrochemical performance. Lattice matching between the (104) LiCoO2 surface facets and the (100) TiO plane enables the formation of the titanium mono-oxide phase, which dramatically enhances the cycling stability as well as the rate capability of LiCoO2. This cubic TiO coating enhances the preservation of the phase and structural stability across the (104) LiCoO2 surface. The results suggest a more stable Co3+ oxidation state, which not only limits the cobalt-ion dissolution into the electrolyte but also suppresses the catalytic degradation of the liquid electrolyte. Furthermore, the high c-rate performance combined with high Columbic efficiency indicates that interstitial sites in the cubic TiO lattice offer facile pathways for fast lithium-ion transport.