Lithium Insertion Research Articles

Design and Synthesis of Spherical Multicomponent Aggregates Composed of Core-Shell, Yolk-Shell, and Hollow Nanospheres and Their Lithium-Ion Storage Performances.

Micrometer-sized spherical aggregates of Sn and Co components containing core-shell, yolk-shell, hollow nanospheres are synthesized by applying nanoscale Kirkendall diffusion in the large-scale spray drying process. The Sn2 Co3 -Co3 SnC0.7 -C composite microspheres uniformly dispersed with Sn2 Co3 -Co3 SnC0.7 mixed nanocrystals are formed by the first-step reduction of spray-dried precursor powders at 900 °C. The second-step oxidation process transforms the Sn2 Co3 -Co3 SnC0.7 -C composite into the porous microsphere composed of Sn-Sn2 Co3 @CoSnO3 -Co3 O4 core-shell, Sn-Sn2 Co3 @CoSnO3 -Co3 O4 yolk-shell, and CoSnO3 -Co3 O4 hollow nanospheres at 300, 400, and 500 °C, respectively. The discharge capacity of the microspheres with Sn-Sn2 Co3 @CoSnO3 -Co3 O4 core-shell, Sn-Sn2 Co3 @CoSnO3 -Co3 O4 yolk-shell, and CoSnO3 -Co3 O4 hollow nanospheres for the 200th cycle at a current density of 1 A g-1 is 1265, 987, and 569 mA h g-1 , respectively. The ultrafine primary nanoparticles with a core-shell structure improve the structural stability of the porous-structured microspheres during repeated lithium insertion and desertion processes. The porous Sn-Sn2 Co3 @CoSnO3 -Co3 O4 microspheres with core-shell primary nanoparticles show excellent cycling and rate performances as anode materials for lithium-ion batteries.

Electrochemical characterization of Cr8O21 modified LiNi0.5Co0.2Mn0.3O2 cathode material

A novel modification approach for LiNi0.5Co0.2Mn0.3O2 material was investigated in this work. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) confirmed that the coating/blending structure had been constructed successfully by adding Cr8O21 to parent cathode material LiNi0.5Co0.2Mn0.3O2 via a planetary ball milling method. Charge-discharge tests showed that the irreversible capacity loss decreases from 23.9 to −2.4 mAh/g as the content of Cr8O21 increases from 0 to 7.5 wt% in the composite cathode materials. Such decrease could be attributed to the addition of Cr8O21, which served as lithium insertion oxide to hold the Li+ that could not be inserted back into the LiNi0.5Co0.2Mn0.3O2 during initial cycle. In addition, charge-discharge tests demonstrated the composite cathodes presented improved cycling capability and rate performance compared to the bare NCM523. Electrochemical impedance spectroscopy (EIS) results implied that the increase of capacity retention and rate performance could be mainly attributed to the coating layer, which suppressed the increase in impedance upon cycling by inhibiting the electrolyte/electrode parasitic reaction.

Semi-empirical master curve concept describing the rate capability of lithium insertion electrodes

A simple semi-empirical master curve concept, describing the rate capability of porous insertion electrodes for lithium-ion batteries, is proposed. The model is based on the evaluation of the time constants of lithium diffusion in the liquid electrolyte and the solid active material. This theoretical approach is successfully verified by comprehensive experimental investigations of the rate capability of a large number of porous insertion electrodes with various active materials and design parameters. It turns out, that the rate capability of all investigated electrodes follows a simple master curve governed by the time constant of the rate limiting process. We demonstrate that the master curve concept can be used to determine optimum design criteria meeting specific requirements in terms of maximum gravimetric capacity for a desired rate capability. The model further reveals practical limits of the electrode design, attesting the empirically well-known and inevitable tradeoff between energy and power density.

Improving the elevated-temperature behaviors of LiNi1/3Co1/3Mn1/3O2 by surface modification with Nano-La2O3

The layered LiNi1/3Co1/3Mn1/3O2 as a lithium insertion positive electrode material suffers from severe capacity fading, especially at a high temperature. In order to overcome this problem, nano-La2O3 is directly coated on the surface of layered LiNi1/3Co1/3Mn1/3O2 (LNCM@La2O3) to improve its electrochemical performance. Compared with the pristine one, all the surface modification samples own the better cycling stability than that of the pristine material. Among the surface-modified cathode materials, the 6 wt% surface-modified cathode (LNCM@6 wt % La2O3) has lesser capacity loss than the others. It shows superior performance with higher capacity (206.8 mAh·g−1) and significantly improved cycling stability (maintaining 93.94% of its initial discharge capacity after 100 cycles). In addition, LNCM@6 wt % La2O3 demonstrates dramatically enhanced reversibility and stability even at the elevated temperature due to the optimal nano-La2O3 layer which not only increases the electrical conductivity of the material, but also acts as a medium that prevents the material from degradation during cycling. Thus, we believe that such LNCM@La2O3 composite can be an economical and viable candidate cathode material for Li-ion batteries.

A series of zero-strain lithium insertion materials that undergo a non-topotactic reaction

Lithium titanium oxide spinel, Li[Li1/3Ti5/3]O4 (LTO), is a zero-strain lithium insertion material, which indicates a virtually 0% change in lattice volume (ΔV) during the electrochemical reaction. We have performed systematic structural and electrochemical studies on Li1/2+x/2Fe5/2−3x/2TixO4 (LFTO) with 0 ≤ x ≤ 1.666, where the LFTO formula forms a series of spinel compounds with Fe[Li1/2Fe3/2]O4 and LTO via Li1/2Fe1/2[Li1/2Fe1/2Ti]O4. The LFTO samples with x < 0.875 underwent a typical conversion reaction with large discharge capacities above ∼500 mAh g−1, similar to nano-sized metal oxides. The LFTO samples with 0.875 ≤ x < 1.666 maintained their cubic lattice parameter (ac) during the discharge and charge reactions. Since the Δac and ΔV values were lower than +0.2 and +0.5%, respectively, these LFTO samples are also regarded as zero-strain lithium insertion materials. Surprisingly, ex situ X-ray diffraction measurements revealed a reversible decrease/increase in the intensities of the 111 and 311 diffraction lines, indicating that Fe ions shuttle back and forth between the tetrahedral and octahedral sites of the spinel lattice. This reaction scheme differs from the so-called topotactic reaction, where only Li+ ions are mobile and transition metal ions are immobile. Details of the non-topotactic reaction for LFTO are presented.

A nonlocal species concentration theory for diffusion and phase changes in electrode particles of lithium ion batteries

A nonlocal species concentration theory for diffusion and phase changes is introduced from a nonlocal free energy density. It can be applied, say, to electrode materials of lithium ion batteries. This theory incorporates two second-order partial differential equations involving second-order spatial derivatives of species concentration and an additional variable called nonlocal species concentration. Nonlocal species concentration theory can be interpreted as an extension of the Cahn–Hilliard theory. In principle, nonlocal effects beyond an infinitesimal neighborhood are taken into account. In this theory, the nonlocal free energy density is split into the penalty energy density and the variance energy density. The thickness of the interface between two phases in phase segregated states of a material is controlled by a normalized penalty energy coefficient and a characteristic interface length scale. We implemented the theory in COMSOL Multiphysics\(^{\circledR }\) for a spherically symmetric boundary value problem of lithium insertion into a \(\hbox {Li}_x\hbox {Mn}_2\hbox {O}_4\) cathode material particle of a lithium ion battery. The two above-mentioned material parameters controlling the interface are determined for \(\hbox {Li}_x\hbox {Mn}_2\hbox {O}_4\), and the interface evolution is studied. Comparison to the Cahn–Hilliard theory shows that nonlocal species concentration theory is superior when simulating problems where the dimensions of the microstructure such as phase boundaries are of the same order of magnitude as the problem size. This is typically the case in nanosized particles of phase-separating electrode materials. For example, the nonlocality of nonlocal species concentration theory turns out to make the interface of the local concentration field thinner than in Cahn–Hilliard theory.

Synthesis of Si nanosheets by using Sodium Chloride as template for high-performance lithium-ion battery anode material

Due to the shorter path length and more channels for lithium ion diffusion and insertion, the two-dimensional (2D) Si nanosheets exhibit superior electrochemical performances in the field of electrochemical energy storage and conversion. Recently, various efforts have been focused on how to synthesize 2D Si nanosheets. However, there are many difficulties to achieve the larger area, high purity of 2D Si nanosheets. Herein, we developed a facile and scalable synthesis strategy to fabricate 2D Si nanosheets, utilizing the unique combination of the water-soluble NaCl particles as the sacrificial template and the hydrolyzed tetraethyl orthosilicate as the silica source, and assisting with the magnesium reduction method. Importantly, the obtained Si nanosheets have a larger area up to 10 μm2. Through combining with reduced graphene oxides (rGO), the Si nanosheets@rGO composite electrode exhibits excellent electrochemical performances. It delivers high reversible capacity about 2500 mAh g−1 at the current density of 0.2 A g−1, as well as an excellent rate capability over 900 mAh g−1 at 2 A g−1 even after 200 cycles.

Facile Synthesis of Nitrogen and Halogen Dual‐Doped Porous Graphene as an Advanced Performance Anode for Lithium‐Ion Batteries

AbstractNonmetal‐dual doped graphene has attracted considerable attention as high‐performance anode material for lithium‐ion batteries (LIBs) due to the synergistic effects of heteroatom dopants. Herein, nitrogen and halogen (including Cl, Br, and I) dual‐doped graphene is successfully synthesized by a general wet chemical method and lithium storage performance of N, Cl codoped graphene as anode material for LIBs is investigated in detail. The dual‐doped heteroatoms introduce abundant defects and expand the interlayer spacing of graphene to benefit lithium insertion and extraction. When used as a typical anode material, the N and Cl dual‐doped porous graphene reveals a high specific capacity of 1200 mA h g−1 at 0.1 A g−1 and 1010 mA h g−1 at 1.0 A g−1. The as‐prepared sample exhibits superior cycling performance, whose specific capacity remains 95% at 5.0 A g−1 after 1800 cycles. The excellent performance mainly stems from the synergistic effect of structure modification and heteroatom doping, and the capacitive effects are dictated by kinetical analysis. The synthesized nitrogen and halogen dual‐doped porous graphene is a promising anode material for LIBs.

A Clue to High Rate Capability of Lithium-Ion Batteries Obtained by an Electrochemical Approach Using “Diluted” Electrode

Rate capability of “diluted” electrodes composed of micron-sized particles of an active material, Li[Li0.1Al0.1Mn1.8]O4 (LAMO), and a spectator material, Al2O3, were investigated to determine the rate-limiting step during discharge accompanied with lithium insertion. Capacity retention based on the LAMO-weight specific current density (C-rate) was significantly improved by reducing LAMO contents in the diluted electrodes, whereas no significant difference was found in capacity retention based on area specific current density. These results indicate that the rate-limiting step during discharge is not Li-ion diffusion in the active materials, but the transportation of Li cations and counter anions in the electrodes. Comparison of amounts of Li+ ions inserted to LAMO during charge with that supplied from an electrolyte indicated that rate capability can be improved by increasing the amount of Li ions in the pore of the electrode. The comparison also suggests that transportation of the counter anion causing concentration overvoltage limits the rate capability.

Lithium insertion into silicon electrodes studied by cyclic voltammetry and operando neutron reflectometry.

Operando neutron reflectometry measurements were carried out to study the insertion of lithium into amorphous silicon film electrodes during cyclic voltammetry (CV) experiments at a scan rate of 0.01 mV s-1. The experiments allow mapping of regions where significant amounts of Li are incorporated/released from the electrode and correlation of the results to modifications of characteristic peaks in the CV curve. High volume changes up to 390% accompanied by corresponding modifications of the neutron scattering length density (which is a measure of the average Li fraction present in the electrode) are observed during electrochemical cycling for potentials below 0.3 V (lithiation) and above 0.2 V (delithiation), leading to a hysteretic behaviour. This is attributed to result from mechanical stress as suggested in the literature. Formation and modification of a surface layer associated with the solid electrolyte interphase (SEI) were observed during cycling. Within the first lithiation cycle the SEI grows to 120 Å for potentials below 0.5 V. Afterwards a reversible and stable modification of the SEI between 70 Å (delithiated state) and 120 Å (lithiated state) takes place.

Enhanced electrochemical performance of lithium ion batteries using Sb2S3 nanorods wrapped in graphene nanosheets as anode materials.

Antimony sulfide can be used as a promising anode material for lithium ion batteries due to its high theoretical specific capacity derived from sequential conversion and alloying lithium insertion reactions. However, the volume variation during the lithiation/delithiation process leads to capacity fading and cyclic instability. We report a facile, one-pot hydrothermal strategy to prepare Sb2S3 nanorods wrapped in graphene sheets that are promising anode materials for lithium ion batteries. The graphene sheets serve a dual function: as heterogeneous nucleation centers in the formation process of Sb2S3 nanorods, and as a structural buffer to accommodate the volume variation during the cycling process. The resulting composites exhibit excellent electrochemical performance with a highly reversible specific capacity of ∼910 mA h g-1, cycling at 100 mA g-1, as well as good rate capability and cyclic stability derived from their unique structural features.

Fast and stable lithium-ion storage kinetics of anatase titanium dioxide/carbon onion hybrid electrodes

In this work, we report on nanosized anatase TiO2/carbon onion hybrid materials (nano-TiO2–C) as a rapid and stable lithium insertion host easily synthesized by tailored sol–gel chemistry.

Electrochemical study of two structurally related compounds $$\hbox {FeVMoO}_{7}$$ FeVMoO 7 and $$\hbox {CrVMoO}_{7 }$$ CrVMoO 7 synthesized by sol–gel method

$$\hbox {FeVMoO}_{7}$$ and $$\hbox {CrVMoO}_{7}$$ phases were synthesized by sol–gel method for the first time and used as promising cathode materials for Lithium ion batteries. Effortless and flexible procedure for the preparation of $$\hbox {FeVMoO}_{7}$$ and $$\hbox {CrVMoO}_{7}$$ via a facile sol–gel method was developed. The structure, morphology and the electrochemical properties have been studied by X-ray diffraction (XRD), scanning electronic microscope (SEM) and galvanostatic charge-discharge test measurements. Study of these compounds as electrode materials was motivated by the three-dimensional structure and the redox couples of Fe, V and Mo. The first cycle discharge capacity values for $$\hbox {FeVMoO}_{7}$$ and $$\hbox {CrVMoO}_{7}$$ phases were 284 $$\hbox {mAhg}^{-1}$$ and 264 $$\hbox {mAhg}^{-1}$$ , respectively, in the voltage range of 3.2–1.5 V. The discharge capacity of $$\hbox {FeVMoO}_{7}$$ was 160 $$\hbox {mAhg}^{-1}$$ after 20 cycles. Synopsis FeVMoO $$_{7}$$ and CrVMoO $$_{7}$$ phases have been studied as electrode materials for the first time. Sol–gel method was adopted, for the first time, to synthesize these phases and the phases exhibit good electrochemical behavior. Electrochemical lithium insertion into three dimensional phases of FeVMoO $$_{7}$$ and CrVMoO $$_{7}$$ is feasible and good cycling behavior was observed.

Development of Low Cost and Safe Cathode Material for High Energy Storage Lithium-ion Battery

Spinel LiMn2O4 is a low-cost, eco-friendly, and highly abundant cathode materials for Liion battery, however it has a drastic capacity loss with cycling due to the distortion in crystal structure during discharge. In order to overcome the capacity loss, Mg-doped manganese oxide was synthesised and investigated in order to have a structure with suppressed Jahn- Teller distortion. The distorted Li- Mg-Mn complex has potential merit for lithium ion battery cathode. To fulfil this objective, oxides of Mg and Mn were prepared in different compositions. The synthesized compounds are found to consist of MgMn2O4 as a major phase along with a minor fraction of Mg6MnO8. Lithium insertion was carried out by adding Li2CO3 in appropriate proportion to MgMnO mixture in order to form a single phase LiMgMnO complex. The LiMgMnO complex as a cathode material was successfully demonstrated in a coin cell.

Design of ionic liquid-based hybrid electrolytes with additive for lithium insertion in graphite effectively and their effects on interfacial properties

To address the challenge of the IL-based electrolyte cannot be effectively intercalated in graphite anode, and especially the urgent needs for the compatibility between high performance and high security, the IL-based hybrid electrolyte systems with ethylene carbonate/propylene carbonate (EC/PC) as a co-solvent and vinylene carbonate (VC) as an additive were designed. The high dielectric constant of EC/PC significantly increased the ionic conductivity and lithium ion migration of the electrolyte system. Meanwhile, the presence of VC can form SEI preventing EC and PYR14+ reductive decomposition on the electrode interface, and at the same moment, the SEI promotes effective Li cation insertion into the graphene interlayer. The Li/C half-cells showed high reversible capacity, cycling efficiency, and good cycle stability with the IL-based hybrid electrolyte. It is worth to highlight the better performance, in terms of the excellent thermal stability and high safety. Thus, the IL-based hybrid electrolyte combined with good electrochemical performance holds substantial promise for lithium-ion battery, and should have broad application prospects in the high energy density, especially high-security requirements, of the new lithium-ion battery.

Deconvolution of Cyclic Voltammograms for Blended Lithium Insertion Compounds by using a Model‐Like Blend Electrode

AbstractThe blending of different lithium insertion compounds is a promising attempt to tailor the electrochemical performance of electrodes for lithium‐ion batteries. Remarkable improvements regarding power density and safety issues have been made. However, the understanding of basic interactions between the constituents of the blend is still ongoing. Herein, we separate the current responses from the individual constituents during cyclic voltammetric measurements by using a special experimental setup and a model‐like blended insertion electrode. This approach enables the deconvolution of the cyclic voltammogram of the blend, assignment of redox peaks, identification of kinetic limitations, and observation of internal dynamics, gaining fundamental insights towards the properties of blended insertion electrodes.

Dynamic imaging of metastable reaction pathways in lithiated cobalt oxide electrodes

Understanding how lithium-ion batteries function down to the atomic level during charge and discharge cycling can provide valuable guidance to optimize structure-property relationships and to design and understand new electrode materials. Lithium insertion and reactions with the electrodes during charge and discharge cycling can occur via metastable structures with complex ordering and related non-equilibrium phenomena. Remarkably, these processes remain still poorly understood despite their significance in the operation of lithium battery systems in critical technologies. In this communication, we present the dynamics of lithium insertion into Co3O4 and the evolution of metastable phases as probed by in-situ transmission electron microscopy, in concert with first principles density functional theory calculations. We show that the initial lithium intercalation reaction occurs with the formation of several metastable and intermediate phases, followed by a sequence of conversion reactions that perturb and expand the cubic-close-packed oxygen array, ultimately generating an end-product of finely dispersed cobalt metal clusters within a Li2O matrix. The calculated non-equilibrium lithiation pathways corroborate with the experimental lithiation voltages, and explain the significant hysteresis that occurs during electrochemical cycling. The data provide new insights into the complexity of solid state lithium electrochemistry in metal oxides that are relevant to advancing lithium battery technology.

High and Reversible Lithium Ion Storage in Self‐Exfoliated Triazole‐Triformyl Phloroglucinol‐Based Covalent Organic Nanosheets

AbstractCovalent organic framework (COF) can grow into self‐exfoliated nanosheets. Their graphene/graphite resembling microtexture and nanostructure suits electrochemical applications. Here, covalent organic nanosheets (CON) with nanopores lined with triazole and phloroglucinol units, neither of which binds lithium strongly, and its potential as an anode in Li‐ion battery are presented. Their fibrous texture enables facile amalgamation as a coin‐cell anode, which exhibits exceptionally high specific capacity of ≈720 mA h g−1 (@100 mA g−1). Its capacity is retained even after 1000 cycles. Increasing the current density from 100 mA g−1 to 1 A g−1 causes the specific capacity to drop only by 20%, which is the lowest among all high‐performing anodic COFs. The majority of the lithium insertion follows an ultrafast diffusion‐controlled intercalation (diffusion coefficient, DLi+ = 5.48 × 10−11 cm2 s−1). The absence of strong Li‐framework bonds in the density functional theory (DFT) optimized structure supports this reversible intercalation. The discrete monomer of the CON shows a specific capacity of only 140 mA h g−1 @50 mA g−1 and no sign of lithium intercalation reveals the crucial role played by the polymeric structure of the CON in this intercalation‐assisted conductivity. The potentials mapped using DFT suggest a substantial electronic driving‐force for the lithium intercalation. The findings underscore the potential of the designer CON as anode material for Li‐ion batteries.

TiO2-Based Nanomaterials for the Production of Hydrogen and the Development of Lithium-Ion Batteries.

The photocatalytic activity of different titanium oxide nanowires containing gold (Au@TiO2NWs), and gold-graphene (Au@TiO2NWs-graphene), was evaluated by studying the reaction of hydrogen production by water splitting under UV-vis light. The composites showed high surface areas, with values above 300 m2 per gram, even after the incorporation of gold and graphene on the surface of titanium oxide nanowires. The highest hydrogen production of Au@TiO2NWs was 1436 μmol h-1 g-1, under irradiation at 400 nm, and with a gold loading of 10 wt %. This photocatalytic activity was 11.5 times greater than that shown by the unmodified TiO2NWs. For the Au@TiO2NWs-graphene composites, the highest hydrogen amount obtained was 1689 μmol h-1 g-1, at loadings of 10 and 1 wt % of gold and graphene, respectively. The photocatalytic activity of the gold-graphene compounds was 1.2 times greater than that shown by the titanium oxide catalysts and 13.5 times higher than the bare TiO2NWs. Even at wavelengths greater than 500 nm, the compounds exhibited yields of hydrogen above 1000 μmol h-1 g-1, demonstrating the high catalytic activity of the compounds. In addition, TiO2-based materials are of great interest for energy storage and conversion devices, in particular for rechargeable lithium ion batteries. TiO2 has a significant advantage due to its low volume change (<4%) during the Li ion insertion/desertion process, short paths for fast lithium ion diffusion, and large exposed surface, offering more lithium insertion channels. However, the relatively low theoretical capacity and electrical conductivity of TiO2 greatly hamper its practical application. In this work, free-standing electrodes composed by TiO2NWs and carbon nanotubes, CNT@TiO2NWs, were used as anode materials for Li-ion batteries. As a result, the electronic conductivity and mechanical properties of the composite were greatly improved and a good cycling performance was obtained in these batteries. This research shows the potential of TiO2-based materials for the development of new catalysts for hydrogen production and energy storage systems.

Effects of lithium insertion and deinsertion into V2O5 thin films: Optical, structural, and absorption properties

The lithiated/delithiated vanadium pentoxide films deposited by sol‐gel spin coating on indium tin oxide–coated glass substrates were analyzed by sputter‐induced photon spectroscopy, X‐ray diffraction, and optical absorption techniques. First, it is shown that the crystalline structure of V2O5 after intercalation remains practically unchanged. Particularly, in the optical spectra during 5 keV Kr+ ion bombardment of clean, intercalated, and deintercalated V2O5 films, a series of sharp lines and unexpected continuum radiation were observed and well explained. It is also demonstrated that the intercalation and deintercalation of lithium have strong influences on various characteristics of pentoxide vanadium. The interpretations of the obtained results in the 3 experiments—X‐ray diffraction, sputter‐induced photon spectroscopy, and optical absorption techniques—are coherent and complement each other.