Lithium Diffusion Research Articles

Multiscale modification of graphdiyne-based electrodes and diffusion kinetics analysis of lithium ions

The diffusion of lithium ions is highly related to the chemical structure, packing mode, and pore size distribution of the electrode materials. In this paper, a multiscale modification strategy is performed to investigate the correlation between the chemical structure and diffusion kinetics of lithium ions in graphdiyne (GDY) based electrodes. Various electrochemical tests show consistent results that hydrogen-substituted GDY has the fastest lithium-ion diffusion rate, and the doping of Cl and F atoms with large atomic radii leads to slower lithium-ion diffusion in the system. The functional groups (H, Cl, F) introduced in the GDY-based electrodes not only regulate the pore size of the materials but also modulate the binding energy with lithium ions. chlorine-substituted GDY shows a higher diffusion coefficient than that of fluorine-substituted GDY for proper affinity to lithium. In addition, the specific surface area and the pore size distribution also collectively contribute to the differences in lithium-ion diffusion. Finally, the lithium storage mechanism of substituted GDY electrodes is explored. Our strategy sheds some light on the design and fabrication of anode materials for lithium-ion batteries.

Achieving CoAl2O4@Li1.2Ni0.13Co0.13Mn0.54O2 with Long Cyclic and High-Rate Performance via Citric Acid Combustion Method

Lithium-rich manganese-based cathode materials (LNCM) have high specific capacities and operating voltages. However, they also have intractable deficiencies such as low capacity retention and unsatisfactory rate capability. Herein, CoAl2O4 with spinel structure and chemically stable is adopted to decorate the surface of LNCM to modify the cyclic and high-rate performance of final product. 3CoAl2O4@LNCM synthesized by self combustion of citric acid shows the best electrochemical properties such as lower voltage drop (4.7 mV per cycle) and higher capacity retention of 81.33% (1 C) after 100 cycles, which is exceed to bare LNCM (7.7 mV per cycle, 47.65%). Besides, the charge transfer resistance R ct of the modified sample is lower, and its lithium ion diffusion coefficient D Li + is higher. Consequently, 3CoAl2O4@LNCM is able to demonstrate high rate performance, whereby a capacity retention of 65.84% (5 C) is achieved after 100 cycles. The improved electrochemical properties of 3CoAl2O4@LNCM because of the 3D diffusion channel of CoAl2O4 benefits lithium ion diffusion; and the chemical stability of CoAl2O4 enhances the corrosion resistance of LNCM bulk to the electrolyte. As such, this results in the suppression of TM ion dissolution, and the enhancement of cyclic stability and initial coulomb efficiency.

Spherical Graphite Anodes: Influence of Particle Size Distribution and Multilayer Structuring in Lithium-Ion Battery Cells

Current research focuses on lithium-ion battery cells with a high energy density and efficient fast-charging capabilities. However, transport limitations, and, therefore, the uniform diffusion of lithium-ions across the electrode layers, remain a challenge and could lead to reduced cell performance. One approach to overcome these transport challenges is the use of subsequently produced two-layer anodes with the particle size variation of spherical graphite (x50 = 18 µm; x50 = 11 µm). Thereby, a defined pore network is created, which reduces the ionic resistance and ensuring improved fast charging capabilities. The analysis focuses on the evaluation of electrode properties and the electrochemical performance. By examining the pore size distribution of the anodes, it has been found that during the manufacturing of the two-layer anodes, carbon black and binder particles are transported into the existing microstructure of the lower layer, resulting in localized densification between the anode layers. This could also be supported by color measurements. This effect also extends to electrochemical investigations, with electrochemical impedance spectroscopy showing significantly lower ionic resistances in all two-layer anodes. Reduced ionic resistance and tortuosity near the separator due to absorption effects enhance the ion diffusion and have a direct impact on anode performance. Cell ageing analysis showed a significant capacity decrease of almost 15 mAh g −1 in the single-layer references only, in contrast to the stability of the two-layer anodes. This could also be attributed to the reduced ionic resistance and active counteraction of binder migration. In conclusion, this study highlights how subsequently produced two-layer anodes significantly shape the electrode properties and cell performance of lithium-ion batteries.

Improved electrochemical properties of Lu-doped LiNi0.5Mn1.5O4 cathode materials for 5 V lithium-ion batteries

LiNi0.5Mn1.5O4 (LNMO) is considered as a promising cathode material for the next-generation high-energy–density lithium-ion batteries. However, the application of LNMO is hindered by its severe Mn dissolution and capacity decay at high voltages. To address this issue, a novel LiNi0.5-x/2Mn1.5-x/2LuxO4 (x = 0, 0.005, 0.02, 0.04) material was successfully prepared using a solid-state method to investigate the effects of phase structures and morphologies induced by Lu3+ doping on the electrochemical properties of the LNMO. When compared to the pristine LNMO material, the LNMO doped with Lu3+ exhibited a significant increase in lattice parameters, resulting in a larger lithium-ion diffusion channel. Furthermore, the truncated octahedral structure enhanced the contact area with the electrolyte, leading to a substantial decrease in Mn3+ concentration. It's noteworthy that the LiNi0.49Mn1.49Lu0.02O4 (LNMO-Lu0.02) sample exhibits the most favorable electrochemical properties. After 200 charge–discharge cycles at a current density of 1 C, the LNMO-Lu0.02 sample demonstrates a discharge capacity of 129.54 mAh/g with a capacity retention rate of 97.46 %. Even at a high current density of 20 C, it maintains a discharge capacity of 107.19 mAh/g, which is much better than the pristine sample. The results indicate a significant improvement in the electrochemical properties and structural stability of Lu-doped LNMO cathode materials.

Structure-defined viologen-polyoxometalate modified separator dominating endurable Li-S batteries by a synergistic adsorption-electrocatalysis mechanism

The crystalline materials can provide atomically accurate model for comprehending the structure-property-function relationships, which would be an innovative strategy to address the inherent issues in Li-S batteries. Herein, we synthesize a new crystalline compound of (HAV)[PMo12O40]·6H2O (marked as {AV-PMo12}) using Keggin-type H3PMo12O40·3H2O (PMo12) and aminopropyl viologen (AV) as precursors, which are connected by intermolecular hydrogen bonding and electrostatic attraction. When {AV-PMo12} is utilized as a modified material for separator, PMo12captures lithium polysulfides (LiPSs) by forming Li–O bonds and AV interacts with polysulfides via electrostatic attraction. More significantly, based on the precise and stable structure of {AV-PMo12}, this work innovatively utilizes in-situ Raman spectra and ex-situ XPS to intuitively reveal the catalytic mechanism of {AV-PMo12}. Specifically, {AV-PMo12} possesses bidirectional catalytic activity during charge-discharge cycles, accompanied by the stable conversion between reduced and oxidized states of PMo12. AV preferentially captures electrons and transfers them to PMo12 through hydrogen bond, which improves electron-obtaining ability of PMo12, thus promoting the catalytic activity of PMo12 for LiPSs conversion. PMo12 facilitates the desolvation process of Li+, which accelerates high-flux lithium ion diffusion and achieves uniform lithium deposition. As expected, Li-S cell using {AV-PMo12} modified separator achieves decent reversibility of 469 mAh g−1 at 2.0C after 1000 cycles and the degradation rate is only 0.034 % per cycle at 5.0C upon 1000 cycles. Meanwhile, it achieves a high capacity of 550 mAh g−1 after 200 cycles at 0.2C under a sulfur loading of 5.1 mg cm−2 with a low electrolyte/sulfur ratio of 5 μL mg−1. This work offers a comprehensive analysis of catalytic mechanism of viologen-polyoxometalate based functional material at the molecular level to boost the high-performance Li-S batteries.

Boosting the cycle stability of nickel-rich ternary materials at high voltage by coating mixed conductor Li7.5La3Zr1.5Co0.5O12

Ni-rich NCM materials have the high electrochemical capacities and low costs. However, the disadvantage of poor cycle performance severely limits their large-scale use. In this work, the nanoscale ion-electron mix-conductor Li7.5La3Zr1.5Co0.5O12 was prepared by ball milling and used to directly mix LiNi0.83Co0.11Mn0.06O2. After annealing, a mixed conductive protective layer could be formed on the surface of the NCM. The coating layer can protect the structural integrity of the NCM particles during cycling. At a current density of 1C between 2.8 and 4.5 V, the modified sample exhibited a capacity of 196 mAh g−1, and the capacity retention rate was as high as 85.7 % after 200 cycles, which was a significant improvement of 23.8 % over the pristine sample. The lithium-ion diffusion coefficient is enhanced and the charge transfer resistance is reduced by the mixed conductor cladding. The modified material shows an excellent rate performance. The specific capacity at 5C was 181 mAh g−1. The proposed modification method is simple in process and suitable for large-scale applications. The method has reference significance for the modification of other cathode materials.

Li‐Rich Organosulfur Cathode with Boosted Kinetics for High‐Energy Lithium‐Sulfur Batteries

Organosulfur materials containing sulfur–sulfur bonds are an emerging class of high‐capacity cathodes for lithium storage. However, it remains a great challenge to achieve rapid conversion reaction kinetics at practical testing conditions of high cathode mass loading and low electrolyte utilization. In this study, a Li‐rich pyrolyzed polyacrylonitrile/selenium disulfide (pPAN/Se2S3) composite cathode is synthesized by deep lithiation to address the above challenges. The Li‐rich molecular structure significantly boosts the lithium storage kinetics by accelerating lithium diffusivity and improving electronic conductivity. Even under practical test conditions requiring a lean electrolyte (Electrolyte/sulfur ratio of 4.1 μL mg−1) and high loading (7 mg cm−2 of pPAN/Se2S3), DL‐pPAN/Se2S3 exhibits a specific capacity of 558 mAh g−1, maintaining 484 mAh g−1 at the 100th cycle with an average Coulombic efficiency of near 100%. Moreover, it provides (electro)chemically stable Li resources to offset Li consumption over charge–discharge cycles. As a result the as‐fabricated anode‐free cell shows a superior cycling stability with 90% retention of the initial capacity over 45 cycles. This study provides a novel approach for fabricating high‐energy and stable Li–SPAN cells.

A Two-dimensional Metal-Organic Framework as Promising Cathode for Advanced Lithium Storage.

Anthraquinone electrode materials are promising candidates for lithium-ion batteries (LIBs) due to the abundance of anthraquinone and the high theoretical capacity, and good reversibility of the anthraquinone electrodes. However, the active anthraquinone materials are soluble in organic electrolytes, resulting in a sharp decay of capacity during the charge and discharge processes. Herein, we report on a two-dimensional calcium anthraquinone 2,3-dicarboxy metal-organic framework (2D CaAQDC MOF) fabricated using a simple hydrothermal method. The 2D CaAQDC MOF not only effectively inhibits the dissolution of active electrode substances into the electrolyte, but also promotes the diffusion of lithium ion into the pores of the MOF. When used as a cathode for the LIBs, the resulting CaAQDC electrode delivers a high specific capacity of ~100 mAh g-1 at a current density of 50 mA g-1 after 200 cycles, demonstrating its good cycle stability. Even at a high current density of 200 mA g-1 , the CaAQDC electrode exhibits a specific capacity of ~60 mAh g-1 . The fabricated 2D coordination polymers effectively restrains the dissolution of anthraquinone into the organic electrolyte and enhances the structural stability, which greatly improves the electrochemical performance of anthraquinone. These research results offer a rational molecular design strategy to address the dissolution of this and other active organic electrode materials.

Investigation and optimisation of a lithium-drift silicon detector using Si–Li structure and bidirectional diffusion and drift techniques

Abstract The research relevance is predefined by the continuous development and improvement of radiation analysis methods and the need for more efficient and accurate detectors for various applications. This research may improve the sensitivity and resolution of Si(Li) detectors, which is important for scientific and industrial research as well as radiation safety monitoring. The research aims to analyse and improve the performance of a Si(Li) lithium-drift silicon detector. The methods used include an analytical method, classification method, functional method, statistical method, synthesis method and others. The results of the two-sided observation of lithium diffusion in silicon monocrystals provided valuable information about the characteristics of the process and its dependence on the method of silicon production. A large-diameter detector detection mode was found to be important for optimising the production of such detectors. The diffusion process in monocrystalline silicon produced by the shadowless zone melting method is relatively fast. This means that lithium ions penetrate the material rapidly and spread evenly throughout its volume. This fast diffusion process can be useful for detectors that need to respond quickly to incoming signals. It was found that in monocrystalline silicon produced by the Czochralski method, there is a delayed penetration of lithium ions.

Interfacial polymerization achieved integration of pore size adjustment, electrostatic repulsion and physical adsorption into one to inhibit polysulfide shuttle for enhanced lithium–sulfur battery

The application of lithium-sulfur battery is seriously hindered by the shuttle of dissolved polysulfide between sulfur cathode and lithium anode, by which is not selectively inhibited by the conventional separator. Developing functional separator is considered as a preferred solution for this issue, but it is always challenged by the tedious preparation process. Herein, interfacial polymerization (IP) is employed to modify the surface property of ZrO2 nanoparticles embedded polyetherimide (PZ) based separator, and the integration of pore size adjustment, electrostatic repulsion and physical adsorption into one is facilely achieved to effectively inhibit the polysulfide shuttle. Consequently, the optimized PZ separator presents a high lithium-ion transference number (0.55) and diffusion coefficient (2.16 × 10−8 cm s−1). Compared with the pristine one, the electrochemical performance of the assembled lithium-sulfur battery is obviously enhanced, and an initial discharge specific capacity of 1242 mAh g−1 and a capacity retention of 68 % after 200 cycles are obtained.

Compositionally complex ball-in-ball type metal oxide anode via laser-induced fast fabrication for binder-free high-capacity Li-ion batteries

This study focuses on addressing the limited cycleability challenge of conversion-type anodes in rechargeable lithium-ion batteries (LIBs) by utilizing new high entropy materials with innovative fabrication techniques. This is the inaugural exploration of first-row transition metals (Fe, Co, Ni, Mn, Cr) composed in an entropically stabilized glycerate form (HEG) as an efficient LIB anode with a high reversible capacity exceeding 500 mAh/g (0.1 A/g) over 270 cycles. Further, we demonstrate an innovative rapid conversion of the HEG to a spinel phase high entropy oxide (HEO) via a CO2 laser treatment and demonstrate the fabrication of a binder-free anode comprising laser-induced reduced graphene oxide (rGO) and HEO ((Fe0.45Co0.14Ni0.2Cr0.13Mn0.08)3O4) composites. The composite (HEO@rGO) showed a high specific capacity of ~794 mAh/g (0.1 A/g) after 100 cycles and a specific capacity of ~530 mAh/g (0.5 A/g) after 200 cycles. These results surpass the performance of many previous reports on high entropy materials. The charge storage mechanism demonstrated the persistence of the spinel structure within HEO, accompanied by a partial transformation towards a rock salt configuration. The undulating nature of the cycling stability profile was found to be linked with a variation in charge transfer resistance and lithium diffusion with cycling.

Lithium-copolymerized polyimide cathodes for stable and fast lithium-ion storage

Organic materials as cathodes have attracted a lot of attention for lithium-ion batteries due to their structural designability and high theoretical capacity. However, most organic polymer cathode materials, such as π-conjugated polymers, have slow diffusion of lithium ions due to closely packed structures, resulting in inferior properties. Herein, we have synthesized lithium modified polyimides by condensation polymerization between 3,4,9,10-perylenetetracarboxylic acid dianhydride and 1,2-ethylenediamine in the presence of N-(2-aminoethyl)glycine lithium salt. The lithium-copolymerized polyimides exhibit lamellar structure and have increased specific surface area and therefore lead to enhanced lithium-ion diffusion coefficient and electronic conductivity. Lithium metal half cells employing lithium modified polyimide cathodes have a high discharge capacity of 138.3 mAh g−1 at a current density of 30 mA g−1 and good cycling stability with 71 % capacity retention at a current density of 1000 mA g−1 after 5000 cycles, which are much better than those employing general polyimides.

Sulphur-template method for facile manufacturing porous silicon electrodes with enhanced electrochemical performance

Sulphur (S)-template method based on conventional slurry-casting method has been developed to produce porous silicon (Si) electrodes. The facile fabrication technology is suitable for current production line and expected to be widely applied to various electrode materials under large volume change during operation. Specifically, S particles as template agent are mixed with active material Si, carbon conductor and binder forming uniform slurry. After casting and drying, the electrodes are immersed in carbon disulfide solution to remove S particles rapidly, generating pores in-situ at the original position of S particles. Electrochemical analysis shows that the pores inside electrodes are able to shorten lithium ion diffusion paths, reduce normal expansion rate and decrease formation of cracks in the Si electrode (2 mgSi/cm2), demonstrating a reversible capacity of 951 mAh/g at 0.5 A/g after 100 cycles (with a capacity retention of 99.5%) and a capacity of ∼826 mAh/g at 2 A/g.

Theoretical calculations of the performance of Li7NbO6 and its doped Phases as solid electrolytes.

Materials with Hexagonal Close Packed (HCP) anionic configuration contain promising lithium-ion conductors. In the HCP anionic structure, when the non-lithium cations occupy the octahedral sites (the important diffusion channels for lithium ions), it is not known whether the nature of fast lithium-ion diffusion will be retained. This work systematically studied the lithium-ion diffusion properties of Li7NbO6 as well as its doped phases on the basis of first-principles calculations. The calculation results show that the lithium-ion conductivity of Li7NbO6 is 0.008 mS cm-1 at room temperature, while the doped phase Li55Nb7WO48 with W6+ doping at the Nb sites possesses a higher lithium-ion conductivity of 0.28 mS cm-1 at room temperature and an activation energy of 0.34 eV. The lithium-ion diffusion mechanism in Li7NbO6 and its doped phase involves concerted migration; besides, they are poor conductors of electrons regardless of whether doping is applied. In addition, W6+ doping increases the reduction limit of the electrochemical window due to its strong oxidizing property; therefore, an artificial SEI film needs to be applied to reduce interfacial decomposition. The discovery and characterization of the new fast lithium-ion conductor Li55Nb7WO48 provide theoretical guidance for the development of new solid electrolytes.

Graphite-Si@TiO2 Core-Shell Nanoparticles as Composite Anode for Li-ion Batteries: Electrochemical Response

This study focuses on optimizing composite anode through varying Si@TiO2 core–shell nanoparticles (core is silicon and shell is titania) percentages in graphite. Material characterization reveals the morphological transformation of graphite and silicon nanoparticles into composite anodes. Electrochemical tests, including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy, provide essential insights into the electrochemical behavior of these composites. In the cycling tests, graphite with 5% core–shell (GrCS5), graphite with 10% core–shell (GrCS10), and graphite with 15% core–shell (GrCS15) show initial discharge capacities of 568 mAh g−1, 675 mAh g−1, and 716 mAh g−1, retaining 76%, 75%, and 72% after 100 cycles, respectively. Conversely, the graphite with 10% bare silicon (GrSi10) composite, commencing with 728 mAh g−1, exhibits rapid degradation, retaining 54% after 100 cycles. Moreover, the EIS analysis reveals higher values of ohmic, SEI, and charge transfer resistances in GrSi10 compared to other composite anodes after 100 cycles. The examination of the lithium diffusion coefficient indicates that GrCS5 demonstrates superior lithium diffusion kinetics, displaying the highest coefficient among all composite anodes. The research objective is to identify the optimal composite anode composition through quadrant analysis, considering specific capacity and lithium diffusivity after 100 cycles. In conclusion, integrating Si@TiO2 core–shell nanoparticles in graphite anodes improves their performance, with GrCS10 demonstrating notable effectiveness.

Exploring lithium ion interactions in graphite electrodes through non-equilibrium molecular dynamics and density functional theory.

In molecular dynamics (MD) simulations, selecting an appropriate potential function is a crucial element for accurately simulating the kinetic properties of lithium ion intercalation, storage, and diffusion in graphite systems. This work employed a combination of non-equilibrium molecular dynamics (NEMD) and density-functional theory (DFT) for simulation and analysis. The findings indicate that the AIREBO potential function precisely describes the motion of ordered lithium ions between graphite layers, consistent with the models proposed by Rüdorff and Hofmann (R-H) and Daumas and Hérold (D-H). Conversely, for the folded structure within the graphite layer, the Tersoff potential function provides a more suitable description, consistent with the localized-domains model. Further analysis reveals that with increasing Li-ion concentration, the voltage, Young's modulus, and ultimate tensile strength of the LixC6 system exhibit a decreasing trend. Notably, the diffusion coefficient of lithium ions within the graphite layer varies widely, ranging from 10-6 cm2 s-1 to 10-16 cm2 s-1. In summary, this work is anticipated to provide further insights into the mechanism of lithium ion intercalation and diffusion kinetics in graphite electrodes. It also serves as a valuable theoretical framework for guiding the design and optimization of high-performance lithium-ion batteries.

Enhancement of multilayer lithium storage in a β12-borophene/graphene heterostructure with built-in dipoles.

The combination of borophene with a supporting metallic layer is beneficial in stabilizing its structure and promoting its application in energy storage. Here, through first-principles calculations, we screen a β12-borophene/graphene (β12-B/G) heterostructure with superior structural integrity, strong interlayer binding, and high thermodynamic stability among different B/G heterostructures. Besides, it is noteworthy that β12-B/G has been recently synthesized, further opening the possibility of expanding its use in energy storage. Then the selected target is systematically investigated as an anode material for lithium-ion batteries (LIBs). Compared with each monolayer component, multiple lithium-ion adsorption is achieved in the β12-B/G heterostructure, resulting in an ultra-high theoretical specific capacity of 2267 mA h g-1. In addition, a lower diffusion energy barrier indicates faster electron transport and lithium-ion diffusion in the β12-B/G heterostructure. Notably, the multilayer lithium adsorption avoids the formation of dendritic deposits, as evidenced by complete ionization of the cationic layers. Moreover, the disparity in the work functions of the individual layers gives rise to a built-in dipole in β12-B/G, further enhancing the multilayer lithium storage and ion migration. All these results suggest that the construction of borophene-based heterostructures with built-in dipoles is a feasible way to design high-performance LIB anode materials.

Charge–discharge mechanism, lithium-ion diffusion in Al, Ca, and Cu doped lithium metatitanate based anodes for Li-ion batteries: first principles study

Understanding the charge–discharge mechanism at the atomic-scale and the evolution of electrochemical properties for lithiated/de-lithiated compounds is a key challenge in lithium ion batteries (LIBs).

A redox-active organic cage as a cathode material with improved electrochemical performance.

Organic cages offer numerous opportunities for creating novel materials suitable for a wide range of applications. Among these, energy-related applications are beginning to attract attention. We report here the synthesis of a [3 + 6] trigonal prismatic cage constituted by three redox-active dibenzotetraazahexacene subunits. Cathodes formulated with the organic cage show enhanced performance compared to those formulated with the individual subunits, showing improvements in terms of electrochemical stability, lithium-ion diffusivity, and cathode capacity.

Thermal behaviors during lithium diffusion in Li0.4WO3 bronze studied by elastic and quasi-elastic neutron scattering.

Polycrystalline Li0.4WO3 bronze has been synthesized by solid state reaction carried out in a silica tube at 10-7 MPa and 973 K. The sample is characterized by temperature-dependent neutron elastic and quasielastic scatterings. The room-temperature neutron powder data Rietveld refinement confirmed the space group Im3̄ along with lithium occupancy found predominantly at the 6b crystallographic site. Upon increasing temperature above 300 K lithium at 6b site decreases and at 2a site increases, suggesting Li+ cation diffusion between these two sites demonstrated by quasielastic neutron scattering as well. The lattice thermal expansion anomaly is observed between 380 K and 450 K, which is explained in terms of lithium dynamic disorder (non-equilibrium) as complemented by elastic and quasielastic neutron scatterings. DFT calculations with different lithium distributions at two different crystallographic sites guide to understand the lattice expansion anomaly. The lattice thermal expansion is modeled using Grüneisen first-order approximation, where the Debye-Einstein-Anharmonicity approach provides the temperature-dependent vibrational energy. The DFT-calculated phonon density of states and bulk modulus help extract the characteristic Debye and Einstein frequencies.