Zero-strain Insertion Material Research Articles

Operando X-ray Diffraction and Double-Edge X-ray Absorption Spectroscopy Studies on a Perfect Zero-Strain Material.

"Zero-strain" insertion materials are essential for high-performance Li-ion batteries, but the experimental determination of changes in their local structures remains challenging. In this study, we successfully visualized the reaction scheme of a perfect zero-strain material, (Li0.75Zn0.25)[Li0.417Ti1.583]O4 with a spinel framework, using operando X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The operando XRD/XAS technique, which provided a series of XRD, Ti K-edge XAS, and Zn K-edge XAS data, can be employed owing to a recently developed tapered undulator and monochromator system. Although previous ex situ XRD measurements indicated the immutable cubic lattice parameter (ac) during the discharge process, these studies unveiled drastic structural variations occurring on the atomic scale between the charge and discharge reactions, such as differences in the ac, bond distances, and occupancies of the Zn2+ ions. This dynamic information obtained under operating conditions could be useful not only for understanding the zero-strain reaction scheme but also for designing advanced zero-strain insertion materials with enhanced energy density.

Li2Ni0.2Co1.8O4 having a spinel framework as a zero-strain positive electrode material for lithium-ion batteries

A zero-strain insertion material of Li2Ni0.2Co1.8O4 having a spinel framework was synthesized and showed very small dimensional change during charge–discharge reaction with large volumetric capacity.

LiY(MoO4)2 nanotubes: Novel zero-strain anode for electrochemical energy storage

In this work, a novel zero-strain anode, LiY(MoO4)2 nanotubes, is firstly prepared by a simple electrospinning technique, which exhibits outstanding rate performance and stable cycling performance. After 580 cycles, the capacity retention of LiY(MoO4)2 nanotubes is up to 94%, while that of LiY(MoO4)2 bulks is only 30%. The enhancement can be attributed to the hollow structure of nanotubes. More importantly, in situ X-ray diffraction (XRD) technique is used for the first time to explore the mechanism of Li ion insertion/extraction for LiY(MoO4)2 nanotubes. It can be concluded that Li ions initially occupy vacant 8c sites for energy storage through tunnels built by Mo-O tetrahedra. With repeated lithiation, the Y(Li)O8 polyhedra are gradually distorted. The distortion of Y(Li)O8 polyhedra not only relieves the volume expansion caused by lithiation, but also induces the 8d site to be opened to allow more Li ions to be embedded. Moreover, in situ XRD and ex situ transmission electron microscopy (TEM) studies demonstrate that LiY(MoO4)2 nanotubes have outstanding structural stability with the maximum volume expansion of LiY(MoO4)2 nanotubes of only 0.53%, suggesting that LiY(MoO4)2 nanotubes, like Li4Ti5O12, are zero-strain insertion materials. All of these advantages suggest that LiY(MoO4)2 nanotubes are possible anode material for LIBs.

Pseudo zero-strain insertion materials for Li-ion batteries: cross-sectional observations of LiNi1/2Co1/2O2, LiNi1/3Co1/3Mn1/3O2, and LiNi0.8Co0.15Al0.05O2

Constructing robust interfaces between a positive (or negative) electrode and a solid electrolyte is essential for realizing more practical all-solid-state lithium-ion batteries (ALIBs). For the negative electrode, a zero-strain insertion material exists, Li[Li1/3Ti5/3]O4, which indicates a virtually 0% change in lattice volume (ΔV). In contrast, for the positive electrode, no zero-strain insertion material is currently available. In this paper, we observed cross-sections of charged Li x Ni1/2Co1/2O2 (NC11), Li x Ni1/3Co1/3Mn1/3O2 (NCM111), and Li x Ni0.8Co0.15Al0.05O2 (NCA) samples to clarify whether these positive electrode materials are applicable for ALIBs. Hardly any fractures were observed between primary particles in the NC11 and NCM111 samples, while fractures were observed in the NCA sample. This difference was due to the pseudo zero-strain character of the NC11 and NCM111 samples, which have ΔV values of approximately 0%, although their lattice parameters vary with x. Therefore, the ability of NC11 and NCM111 to maintain ionic and electronic contacts with a solid electrolyte makes them ideal positive electrode materials for ALIBs.

LiCrTiO4 Nanowires with the (111) Peak Evolution during Cycling for High-Performance Lithium Ion Battery Anodes

LiCrTiO4 is a lithium insertion material which is isostructural with Li4Ti5O12. By modified its morphology, LiCrTiO4 nanowires exhibit a high charge capacity of 154.6 mAh g-1 at 100 mA g-1, and this value can be maintained at 121.0 mAh g-1 even at a high current density of 700 mA g-1. Furthermore, the cycling performance shows that LiCrTiO4 nanowires can also deliver a reversible capacity of 120.0 mAh g-1 with 95.6 % capacity retention of the first cycle after 550 cycles. The excellent electrochemical properties are revalidated by the cyclic voltammetry and electrochemical impedance spectroscopy measurements. The most interesting feature in this work is the relationship between the periodic variation of the (111) peak intensities and the migration of lithium ions during cycling. It proves that LiCrTiO4 nanowires are zero-strain insertion material which can be a promising anode material for lithium ion batteries.

Black Li4Ti5O12 Anode Materials for High-Rate Li-Ion Batteries

Li4Ti5O12 (LTO) with a spinel structure has received much attention as the most promising alternative to the conventional graphite anode material of Li-ion batteries for hybrid electric vehicle, electric vehicle, and large-scale energy storage applications, due primarily to its advantageous material properties, such as enhanced safety, good capacity retention during cycling, and high power density. Also, LTO is a zero-strain insertion material, which has excellent Li+ insertion/extraction reversibility with no volume change. In spite of these advantages, LTO presents a relatively poor rate capability due to its low electrical conductivity and Li+ diffusion coefficient. Recently, the nanostructured LTO materials coated with carbon-based materials have been extensively studied in the hope of achieving further improvement in the rate capability due to both good electrical conductivity and short Li+ diffusion length. However, these nanomaterials present relatively low volumetric energy density and difficulty in the electrode coating process, and also high production cost. Therefore, it is very important to develop a novel method to achieve simultaneously the enhanced electrical conductivity and volumetric energy density of LTO material. In this work, we suggest a facile method to achieve the improved electrochemical performance of LTO anode material composed of the micro-sized primary particles for high-power Li-ion batteries. The electrochemical performances of the micro-sized LTO particles, including the rate capability and cycling stability were significantly improved by hydrogenation. The hydrogenated LTO (denoted as H-LTO) particles were obtained by thermal annealing of the P-LTO (denoted as P-LTO) particles at 800 °C for 2~7 h in hydrogen atmosphere. Thermal annealing was performed in a quartz tube furnace filled with ultrahigh purity hydrogen gas. The H-LTO particles exhibited vastly superior the rate capability and capacity retention property during cycling to the P-LTO particles at high current density, since the insertion and extraction of Li+ through the H-LTO particles were preferable to those through the P-LTO particles, which were probably attributed to the short diffusion length for Li+, innumerable reaction sites, and relatively high electrical conductivity.

Improved Electrochemical Performance of Hydrogenated Li4Ti5O12 As Anode Materials for High-Power Li-Ion Batteries

Li4Ti5O12 (LTO) with a spinel structure has received much attention as the most promising alternative to the conventional graphite anode material of Li-ion batteries for hybrid electric vehicle, electric vehicle, and large-scale energy storage applications, due primarily to its advantageous material properties, such as enhanced safety, good capacity retention during cycling, and high power density. Also, LTO is a zero-strain insertion material, which has excellent Li+ insertion/extraction reversibility with no volume change. In spite of these advantages, LTO presents a relatively poor rate capability due to its low electrical conductivity and Li+ diffusion coefficient. Recently, the nanostructured LTO materials coated with carbon-based materials have been extensively studied in the hope of achieving further improvement in the rate capability due to both good electrical conductivity and short Li+ diffusion length. However, these nanomaterials present relatively low volumetric energy density and difficulty in the electrode coating process, and also high production cost. Therefore, it is very important to develop a novel method to achieve simultaneously the enhanced electrical conductivity and volumetric energy density of LTO material. In this work, we suggest a facile method to achieve the improved electrochemical performance of LTO anode material composed of the micro-sized primary particles for high-power Li-ion batteries. The electrochemical performances of the micro-sized LTO particles, including the rate capability and cycling stability were significantly improved by hydrogenation. The hydrogenated LTO (denoted as H-LTO) particles were obtained by thermal annealing of the P-LTO (denoted as P-LTO) particles at 800 °C for 2~7 h in hydrogen atmosphere. Thermal annealing was performed in a quartz tube furnace filled with ultrahigh purity hydrogen gas. The H-LTO particles exhibited vastly superior the rate capability and capacity retention property during cycling to the P-LTO particles at high current density, since the insertion and extraction of Li+ through the H-LTO particles were preferable to those through the P-LTO particles, which were probably attributed to the short diffusion length for Li+, innumerable reaction sites, and relatively high electrical conductivity.

Impedance measurements on lithium-ion battery consisting of Li[Li 1/3Ti 5/3]O 4 and LiCo 1/2Ni 1/2O 2

A 2-V lithium-ion battery consisting of Li[Li 1/3Ti 5/3]O 4 (zero-strain insertion material) and LiCo 1/2Ni 1/2O 2 was constructed, and accelerated cycle tests were performed for 50,000 cycles in order to examine whether or not high-rate charge and discharge were possible for the lithium-ion battery. Mode of accelerated cycle tests consisted of quick charge at 2.5 V and discharge at 1.7 V, respectively, for 25.6 s, which corresponded to about 10% change in capacity determined for the fresh cell. Maximum charge and discharge currents were, respectively, 3.4 and 4.2 A g −1 based on LiCo 1/2Ni 1/2O 2 weight. Capacity failure was not observed even after 50,000 cycles; specifically 90% of initial capacity was observed when the cell was cycled at 0.17 mA cm −2 in voltages of 1.0–2.7 V. However, power fade was observed during the accelerated cycle tests for both input and output. Impedance spectra as a function of depth-of-discharge (DOD) were measured before and after the cycle tests. After the 50,000 cycle tests, internal resistance observed at 0.1 Hz increased twice, while that at 1 kHz increased about 10% for 50% of DOD. From these results, an application of impedance measurements to basic researches on lithium insertion materials for high-power and long-life lithium-ion batteries was discussed.

Electrochemistry and local structure of nano-sized Li 4/3Me 5/3O 4 (Me [dbnd]Mn, Ti) spinels

We report the structural and electrochemical characteristics of Li 4/3Me 5/3O 4 (Me Ti, Mn) spinel materials exhibiting nanostructured morphology. We have applied Raman and FTIR spectroscopy to study the local structure. Vibrational features are in good concordance with the factor group analysis (O h 7 symmetry). The zero-strain insertion material Li 4/3Ti 5/3O 4 delivers 150 mAh/g while Li 4/3Mn 5/3O 4 inserts 2.8 Li/mole of oxide leading to a specific capacity of 158 mAh/g.

Three-volt lithium-ion battery with Li[Ni 1/2Mn 3/2]O 4 and the zero-strain insertion material of Li[Li 1/3Ti 5/3]O 4

A 3 V lithium-ion cell with Li[Ni 1/2Mn 3/2]O 4 ( Fd 3 ̄ m ; a=8.17 Å) and the zero-strain insertion material of Li[Li 1/3Ti 5/3]O 4 ( Fd 3 ̄ m ; a=8.36 Å) was examined with an emphasis on rate-capability and cycle life. This cell showed a quite flat operating voltage of 3.2 V with excellent cycleability. Accelerated cycle tests indicated that 83% of the initial capacity was delivered and stored even after 1100 cycles. Although the calculated energy density of a Li[Li 1/3Ti 5/3]O 4/Li[Ni 1/2Mn 3/2]O 4 cell was about 250 Wh kg −1 or 1000 Wh dm −3 based on the active material weight or volume, the 3 V lithium-ion battery exhibited positive characteristic features, such as flatness in operating voltage, high rate capability, and cycle life.

Electrochemical study of Li4Ti5O12 as negative electrode for Li-ion polymer rechargeable batteries

Abstract Li4Ti5O12 a zero-strain insertion material was prepared by conventional method and by high energy ball milling (HEBM) of precursor to form nanocrystalline phases. The electrochemical performance of solid-state negative electrode was carried out using a solvent-free solid polymer electrolyte at 60°C and 80°C. A Li4Ti5O12 vs. lithium cell discharged at C/12 delivered 155 mA h g−1 for the conventional method and 157 mA h g−1 for the method using high ball energy milling, corresponding respectively to 97% and 96% first-cycle coulombic efficiency. The chemical diffusion coefficient of Li4Ti5O12 spinel-type compound is about 2×10−8 cm2 s−1. This is one order of magnitude higher than that of carbonaceous negative electrodes. Li4Ti5O12, which is a zero-strain insertion material, offers advantage for the SPE cell including safety, long life, and reliability.