High Power Anode Material Research Articles

Electrochemical Performances Ti4Ti5O12/Si Composite Anodes for Li-Ion Batteries

LTO /Si anode material for lithium-ion batteries were successfully synthesized by two-step hydrothermal method and ball milling synthesis , using tetrabutyl titanate, lithium acetate,silicone powder. In this work, LTO/Si composites with different weight ratios (50%,70%) were prepared and tested as anodes of Li-Ion Batteries.The electrochemical properties of the electrodes were investigated using by cyclic voltammetry , charge-discharge galvanostatic and impedance spectroscopy .Both the anodic and cathodic peaks from LTO and silicon were seen in the composites.LTO/SI Composites with higher Si contents (LTO =30 %et Si = 70%) have higher specific capacity .the results confirme that This material can be used as a high-power anode material in lithium-ion batteries.

Combinatorial Screening of Nb1-x-YTixWyOz Materials for Li-Ion Battery Anodes

While much attention in recent years has been given to high performance Li-ion batteries for electrical vehicles, other applications require properties that demand a different set of material considerations such as long lifetimes and extremely high safety and reliability. Anodes for such batteries must be carefully selected to properly achieve these goals. The most commonly industrially utilized anode material, graphite, is not ideal for such applications due to particle fracture and Li dendrite growth at high rates. The current state of the art for high power anode materials is Li4Ti5O12 (LTO) where energy density is sacrificed (theoretical capacity of about 170 mAh/g) in order to operate at potentials where the electrolytes are highly stable.Nb-based oxides have been of interest recently in this regard, with materials such as Nb2TiO7 being considered as industrially relevant for applications where LTO currently dominates. To date in the literature, only 3 compositions have been considered.[1-2] Herein, a wide array of Nb based materials are explored for use as anodes by way of high-throughput experimentation. Over 128 different compositions in the Nb-Ti-W-O pseudoternary space are prepared and characterized with both X-ray diffraction and cyclic voltammetry. Of note, this system features a number of promising solid-solutions that extend well into the ternary system. These compositions derive from crystal structures that are found on both the Nb2O5-WO3 and Nb2O5-TiO2 pseudobinaries, but wide substitutions of the third metal are found to be feasible. This dramatically increases the candidate list for potential anodes. Importantly, the electrochemical performance varies dramatically across the solid solutions. Some ternary compositions feature high discharge capacities of up to 300 mAh/g and high reversibility with 98% capacity retention after 10 cycles. It should be noted that the pseudobinaries have been previously studied in our group with a far lower capacity retention than those found here for some pseudoternary compositions. The rate performance is also found to be outstanding.The improved specific capacity at a comparable potential as LTO makes Nb-W-Ti-O materials highly promising for applications where high rates and safety are paramount. Results presented here will guide further exploration of the rich chemistry available for Nb-based anodes.

Intrinsic Defects and Their Role in the Phase Transition of Na-Ion Anode Na2Ti3O7.

The development of high-power anode materials for Na-ion batteries is one of the primary obstacles due to the growing demands for their use in the smart grid. Despite the appealingly low cost and non-toxicity, Na2Ti3O7 suffers from low electrical conductivity and poor structural stability, which restricts its use in high-power applications. Viable approaches for overcoming these drawbacks reported to date are aliovalent doping and hydrogenation/hydrothermal treatments, both of which are closely intertwined with native defects. There is still a lack of knowledge, however, of the intrinsic defect chemistry of Na2Ti3O7, which impairs the rational design of high-power titanate anodes. Here, we report hybrid density functional theory calculations of the native defect chemistry of Na2Ti3O7. The defect calculations show that the insulating properties of Na2Ti3O7 arise from the Na and O Schottky disorder that act as major charge compensators. Under high-temperature hydrogenation treatment, these Schottky pairs of Na and O vacancies become dominant defects in Na2Ti3O7, triggering the spontaneous partial phase transition to Na2Ti6O13 and improving the electrical conductivity of the composite anode. Our findings provide an explanation on the interplay between intrinsic defects, structural phase transitions, and electrical conductivity, which can aid understanding of the properties of composite materials obtained from phase transitions.

CuCo2S4: Versatile anode for high capacity and high rate for lithium and sodium ion battery application

In an attempt to exploit ternary metal sulfides as high energy and high power anode material for lithium and sodium ion batteries, in-house prepared CuCo2S4 (CCS) nanoparticles, obtained through template free one pot solvothermal synthesis has been deployed. Herein, particle size of CCS obtained below 50 nm helps to address two main challenges such as capacity fading and inferior rate capability behavior. Further, we demonstrate the composite of CCS consisting of multi-walled carbon nanotube (MWCNT) in the form of CCS/MWCNT as potential anode for LIBs and SIBs. While pristine CCS delivers a specific capacity of 934 mA h g−1 at 50 mA g−1 even after 50 cycles, the CCS/MWCNT anode exhibits an appealing capacity of 1300 mA h g−1 for 200 cycles at 500 mA g−1 and 1700 mA h g−1 at 100 mA g−1 for 50 cycles in LIBs. Similarly, CCS/MWCNT anode exhibits 181 mA h g−1 and 236 mA h g−1 at 5 and 1 A g−1 respectively upto 500 cycles in SIBs with 90 and 95% capacity retention, which is noteworthy. CCS/MWCNT anode tolerates up to 20 A g−1 current density and delivers a capacity of 87 mA h g−1, thus qualifying itself as the versatile anode for application in LIBs and SIBs.

α-VPO4: A Novel Many Monovalent Ion Intercalation Anode Material for Metal-Ion Batteries.

In this paper, we report on a novel α-VPO4 phosphate adopting the α-CrPO4 type structure as a promising anode material for rechargeable metal-ion batteries. Obtained by heat treatment of a structurally related hydrothermally prepared KTiOPO4-type NH4VOPO4 precursor under reducing conditions, the α-VPO4 material appears stable in a wide temperature range and possesses an interesting "sponged" needle-like particle morphology. The electrochemical performance of α-VPO4 as the anode material was examined in Li-, Na-, and K-based cells. The carbon-coated α-VPO4/C composite exhibits 185, 110, and 37 mA h/g specific capacities respectively at the first discharge and around 120, 80, and 30 mA h/g at consecutive cycles at a C/10 rate. The considerable capacity drop after the first cycle in Li and Na cells is presumably due to irreversible alkali ion consumption taking place upon alkali-ion de/insertion. The EDX analysis of the recovered electrodes revealed an uptake of ∼23% of Na after the first discharge with significant cell parameter alteration validated by operando XRD measurements. In contrast to the known β-VPO4 anode materials, both Li and Na de/insertion into the new α-VPO4 proceed via an intercalation mechanism with the parent structural framework preserved but not via a conversion mechanism. The dimensionality of alkali-ion migration pathways and diffusion energy barriers was analyzed by the BVEL approach. Na-ion diffusion coefficients measured by the potentiostatic intermittent titration technique are in the range of (0.3-1.0)·10-10 cm2/s, anticipating α-VPO4 as a prospective high-power anode material for Na-ion batteries.

High capacity monoclinic Nb2O5 and semiconducting NbO2 composite as high-power anode material for Li-Ion batteries

Niobium pentoxide, Nb2O5, is an intercalation-type material with a high theoretical capacity of ∼404 mAh g−1 for Li-ion batteries. However, electrochemical properties of Nb2O5 largely depend on its various polymorphs with different crystal structures, and their low electrical conductivity acts as the main obstacle. Here, we report high-temperature calcined monoclinic Nb2O5 and semiconducting NbO2 composite as a high-power anode material. Monoclinic Nb2O5 itself as a main active material shows a high capacity of ∼280 mAh g−1, and NbO2 with a small band gap of ∼0.5 eV not only improves electrical conductivity but also gives a capacity of ∼110 mAh g−1. To have a synergic effect of these two materials, the Nb2O5/NbO2 composite is prepared via simple post-calcination of as-prepared Nb2O5 under a reduction atmosphere. It shows a discharge capacity of ∼214 mAh g−1 at 0.05 C, a high initial Coulombic efficiency of 94.7%, a superior rate capability of ∼40 mAh g−1 at 100 C, and a robust cycle performance of 81% retention over 900 cycles.

Porosity Controlled TiNb2O7 Nanotubes As High Power Anode Materials for Li-Ion Batteries

Porosity of transition metal oxides makes their unique physicochemical properties for using energy storage. However, synthesizing active materials by a simple method is still hard to develop without sacrificial templates. In this regard, we report a synthesis of hollow TiNb2O7 nanotubes through dual nozzle electrospinning as a high power anode material for LIBs. The porosity of hollow TiNb2O7 nanotube was controlled by molar ratios of acetic acid to Ti/Nb alkoxide precursors and degree of Ti/Nb metal hydroxides formation in electrospun fibers. The TiNb2O7 nanotubes have the average diameter of 260 nm and a surface area in the range of 52–151 m2g-1. Moreover, the porous nanotubes consist of micropores below 2 nm and mesopores in the range of 5–60 nm in their walls that are connected to the inner hole with a diameter of 150 nm. Particularly, the unique structure of the nanotubes shows a high discharge capacity of 294 mAh g-1, stable cycle performance of 86% capacity retention over 700 cycles, and superior rate capability of 230 mAh g-1 at high 50C. Our strategy confirmed a facile synthesis of porous TiNb2O7 nanotubes without templates and the potential to use of high power anode material for LIBs.

Facile fabrication of porous Ti2Nb10O29 microspheres for high-rate lithium storage applications

Ti2Nb10O29 (TNO) microspheres are fabricated combining a solvothermal method with a subsequent heat-treatment. Structural and morphological properties of the as-prepared material have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption/desorption. The electrochemical performance is evaluated by performing cyclic voltammograms and galvanostatic discharge/charge tests. The electrochemical characterization demonstrates that the as-prepared TNO microspheres exhibit a good electrochemical performance with a discharge capacity of 185 mAh g−1 after 200 cycles and a capacity retention of 94% at 10 C. Furthermore, since TNO may react with Li at a voltage above 1.0 V vs. Li+/Li, TNO microspheres could be the promising high-power anode materials for 2 V vs. Li+/Li lithium-ion batteries applications.

Hybrid Supercapacitors: High‐Performance Sodium‐Ion Hybrid Supercapacitor Based on Nb2O5@Carbon Core–Shell Nanoparticles and Reduced Graphene Oxide Nanocomposites (Adv. Funct. Mater. 21/2016)

High-power anode materials are essential for development of high-performance sodium-ion battery–supercapacitor hybrid systems (sodium-ion hybrid supercapacitors, Na-HSCs). On page 3711, J. Lee and co-workers report the synthesis of Nb2O5@carbon core–shell nanoparticles and reduced graphene oxide nanocomposites (Nb2O5@C/rGO), and their application to Na-HSCs as anode materials. The Na-HSCs using Nb2O5@C/rGO anode materials deliver high energy and power densities with stable cycle life.

Advanced Mesoporous Spinel Li4Ti5O12/rGO Composites with Increased Surface Lithium Storage Capability for High-Power Lithium-Ion Batteries.

Spinel Li4Ti5O12 (LTO) and reduced graphene oxide (rGO) are attractive anode materials for lithium-ion batteries (LIBs) because of their unique electrochemical properties. Herein, we report a facile one-step hydrothermal method in preparation of a nanocomposite anode consisting of well-dispersed mesoporous LTO particles onto rGO. An important reaction step involves glucose as a novel linker agent and reducing agent during the synthesis. It was found to prevent the aggregation of LTO particles, and to yield mesoporous structures in nanocomposites. Moreover, GO is reduced to rGO by the hydroxyl groups on glucose during the hydrothermal process. When compared to previously reported LTO/graphene electrodes, the newly prepared LTO/rGO nanocomposite has mesoporous characteristics and provides additional surface lithium storage capability, superior to traditional LTO-based materials for LIBs. These unique properties lead to markedly improved electrochemical performance. In particular, the nanocomposite anode delivers an ultrahigh reversible capacity of 193 mA h g(-1) at 0.5 C and superior rate performance capable of retaining a capacity of 168 mA h g(-1) at 30 C between 1.0 and 2.5 V. Therefore, the newly prepared mesoporous LTO/rGO nanocomposite with increased surface lithium storage capability will provide a new opportunity to develop high-power anode materials for LIBs.

Atomic investigation on reversible lithium storage in amorphous silicon oxycarbide as a high power anode material

The formation of LixO and LiySi makes a major contribution to the capacity of amorphous SiCO.

Effect of Co Incorporation of Ordered Mesoporous Sn-Based Alloy Materials for Li-Storage

Sn-based intermetallic compound is general concept introducing second metal element to accommodate the inevitable internal strain caused by electrochemically induced volume change between tin and lithium-tin alloy during lithiation and delithiation processes. Particularly Co-Sn intermetallic compounds as an alternative anode material have been widely investigated during last decade due to the high capacity, cycle stability, and high rate performance. To the best of our knowledge, porous nanostructured intermetallic compound has not been investigated as anode for Li-ion battery because of the synthetic difficulty of controlling metal nucleation and sintering. Ordered mesoporous CoSn intermetallic (CoxSny) with various Co/Sn ratio is successfully synthesized through nano-replication technique as stable and high power anode materials for lithium ion battery. Especially, this is the first result for the synthesis of ordered mesoporous CoSn intermetallic through the direct template method. The electrochemical results show that mesoporous CoxSny exhibits much better capacity than non-porous CoSn. Reversible capacity, coulombic efficiency, and cycle stability of mesoporous CoxSny materials are dependent on their structures and compositions. Especially, 30 atomic % Co contained ordered mesoporous Co0.3Sn0.7 shows 83% capacity retention after 50 cycle, which means Co atoms effectively accommodate the volume strain associates with the lithiation–delithiation processes. The rate performance of mesoporous Co0.3Sn0.7 is significantly improved, which was deeply related to the kinetic behavior such as low charge transfer resistance, large diffusion coefficient (small Warburg factor) and low internal resistance. Sustainable ordered pore structure even after 50 cycle was also observed with TEM, which means Co atoms play a buffer role effectively to accommodate the volume strain associated with the lithiation–delithiation processes.

Facile Synthesis of Nb2O5@Carbon Core-Shell Nanocrystals with Controlled Crystalline Structure for High-Power Anodes in Hybrid Supercapacitors.

Hybrid supercapacitors (battery-supercapacitor hybrid devices, HSCs) deliver high energy within seconds (excellent rate capability) with stable cyclability. One of the key limitations in developing high-performance HSCs is imbalance in power capability between the sluggish Faradaic lithium-intercalation anode and rapid non-Faradaic capacitive cathode. To solve this problem, we synthesize Nb2O5@carbon core-shell nanocyrstals (Nb2O5@C NCs) as high-power anode materials with controlled crystalline phases (orthorhombic (T) and pseudohexagonal (TT)) via a facile one-pot synthesis method based on a water-in-oil microemulsion system. The synthesis of ideal T-Nb2O5 for fast Li(+) diffusion is simply achieved by controlling the microemulsion parameter (e.g., pH control). The T-Nb2O5@C NCs shows a reversible specific capacity of ∼180 mA h g(-1) at 0.05 A g(-1) (1.1-3.0 V vs Li/Li(+)) with rapid rate capability compared to that of TT-Nb2O5@C and carbon shell-free Nb2O5 NCs, mainly due to synergistic effects of (i) the structural merit of T-Nb2O5 and (ii) the conductive carbon shell for high electron mobility. The highest energy (∼63 W h kg(-1)) and power (16 528 W kg(-1) achieved at ∼5 W h kg(-1)) densities within the voltage range of 1.0-3.5 V of the HSC using T-Nb2O5@C anode and MSP-20 cathode are remarkable.

Porous TiNb2O7 nanofibers decorated with conductive Ti1−xNbxN bumps as a high power anode material for Li-ion batteries

Porous TiNb2O7 nanofibers with metal nitride bumps show ultra-fast rate capability even at 100 C.

Hydrogenated TiO2 Nanotubes as High-Power Anode Materials for Lithium-Ion Batteries

Titanium oxide (TiO2) has received much attention as the most promising alternative to the conventional graphite anode of Li-ion batteries for high energy and power. The performance of TiO2 anode for Li-ion batteries depends strongly on the crystalline phase, the morphology, and the porosity of the structure. The nanostructured TiO2 materials, such as nanoparticles, nanorods, nanowires, and nanotubes have been studied to improve the performance of TiO2 anode. Recently, it was reported that the hydrogenated TiO2, called a ‘black TiO2’ nanostructures are more attractive for photovoltaics, photocatalysis, and supercapacitors owing to their narrower bandgap (less than typical 3 eV value) and relatively high electrical conductivity. The smooth and well-ordered TiO2 nanotubes were synthesized on a Ti disk successfully by anodization in a non-aqueous solution containing fluoride ions. The as-prepared TiO2 nanotubes were annealed to obtain crystalline anatase (A-TiO2 NTs) and hydrogenated TiO2 nanotubes (H-TiO2 NTs) at 450 °C for 2 h in air and hydrogen atmosphere, and then their electrochemical performances were investigated as alternative anode materials for Li-ion batteries.The initial discharge capacity of the H-TiO2 NTs (0.117 mAh cm-2) was superior to that of the A-TiO2 NTs (0.110 mAh cm-2) and the discharge capacities of the H-TiO2 NTs and A-TiO2 NTs maintained nearly 72 and 44 % at a current density of 10 mA cm-2. In addition, the H-TiO2 NTs (89 %) exhibited much higher the capacity retention than the A-TiO2 NTs (70 %) at the current density of 1 mA cm-2 (~10 C-rate) after 300 cycles, as shown in Figure 1. The H-TiO2 NTs presented smaller the crystallite size and charge transfer resistance (Rc) compared with the A-TiO2 NTs and the oxygen vacancies were formed in the H-TiO2 NTs during hydrogenation, which was proved by the presence of Ti3+ from the XPS analysis. These results indicate that the insertion and extraction of Li+ through the H-TiO2 NTs were preferable to those through the A-TiO2 NTs, which were probably attributed to the short diffusion length for Li+, innumerable reaction sites, and relatively high electrical conductivity. Therefore, the H-TiO2 NTs exhibited vastly superior the rate capability and capacity retention property during cycling to the A-TiO2 NTs at high current density as anode materials for Li-ion batteries.

Nanostructured Anatase TiO2 - from Lithium- to Sodium-Ion Anodes

Lithium-ion batteries are nowadays the energy storage device of choice for portable electronic devices due to their superior energy and power density. Consequently, they are considered also as most promising power source for large-scale applications as, for instance, electric vehicles [1–3]. However, for such applications further improvement of the existing technology is required in terms of energy, power, and particularly safety. Beside Li4Ti5O12, which is already used in commercial cells, anatase TiO2 – particularly in its nanostructured form - is seriously considered as alternative anode material to replace graphite due to its enhanced safety and rate capability [4,5].Remarkably, anatase TiO2 was recently demonstrated to be highly promising as high power anode material for sodium-ion batteries [6,7], which are considered as low-cost alternative for lithium-ion batteries. These batteries are especially interesting for stationary energy storage applications in order to balance the energy supply provided by renewables, for which size and weight are less important, while cost are of major importance.Herein we will report our latest results on the utilization of nanostructured anatase TiO2 for lithium- and sodium-ion batteries, including the importance of carbonaceous coatings and percolating networks, and highlight the major differences regarding the lithium- and sodium-ion storage mechanism.

Preparation and characterization of anode materials using expanded graphite/pitch composite for high-power Li-ion secondary batteries

Expanded graphite was prepared by the intercalation of natural graphite using ammonium peroxodisulfate as an oxidizing agent and a high purity of sulfuric acid as an intercalate. The amounts of oxidizing agent and intercalate were changed to determine the preparation conditions of expanded graphite as the anode material for high-power Li-ion batteries. The expanded graphite was tested as the anode material and further composited with the different amounts of petroleum pitch to improve the electrochemical properties. Although the expanded graphite anode showed the improved electrochemical properties such as initial reversible capacities of around 400 mAh/g and a charge capacity at 5 C-rate of 83 mAh/g as compared with those for the natural graphite anode of 378 and 19.4 mAh/g, respectively, it still had some weak points for a high-power anode material such as low initial efficiency and potential plateaus with the stage characteristic. The anode composites with high performance could be obtained by compositing the expanded graphite and the petroleum pitch at the ratio of 1:2, showing an improved initial efficiency of 78 % and decreased potential plateaus with 389 mAh/g of the initial reversible capacity.

Comparative study of Na2Li2Ti6O14 prepared by different methods as advanced anode material for lithium-ion batteries

In this paper, Na2Li2Ti6O14 anode materials are synthesized by solid-state reaction and sol–gel method, respectively. Sol–gel formed Na2Li2Ti6O14 shows smaller particle size (0.05–0.1μm) than that (0.2–0.4μm) of samples prepared by solid-state reaction. Electrochemical results show that all the four samples have similar reduction peak at 1.20V and oxidation peak at 1.35V with average working potential of 1.28V. Among all the as-obtained compounds, Na2Li2Ti6O14 synthesized by sol–gel method at 700°C shows the highest initial charge specific capacity of 106.6mAhg−1. After 40cycles, the reversible charge capacity can be maintained at 114.7mAhg−1. Moreover, this sample shows excellent rate properties with a high reversible charge capacity of 110mAhg−1 at 160mAg−1. The improved electrochemical performance is attributed to the proper particle size, high specific surface area and decreased electrochemical resistances. Therefore, Na2Li2Ti6O14 prepared from sol to gel technique will be a promising high-power anode material for rechargeable lithium-ion batteries.

Hydrogen treated, cap-opened Si nanotubes array anode for high power lithium ion battery

Silicon is a promising anode material for lithium ion batteries due to its low discharge potential and high theoretical capacity. However, rapid capacity fading caused by large volume change during cycling and poor rate capability came from low lithium ion diffusivity limit its practical use. Here, we report a novel approach to provide higher accessibility of lithium ions to the Si surface and shorter lithium ion diffusion length in Si nanotube structures. Its tubular geometry and large surface area enable effective accommodation of large volume change and large lithium ion flux at the interface between Si and electrolyte, respectively. Hydrogen treated, cap-opened Si nanotubes electrode shows excellent rate capability. The proposed electrode geometry provides a significant new insight into designing high power anode materials for the advanced lithium ion batteries.

Carbon coating of Li4Ti5O12 using amphiphilic carbonaceous material for improvement of lithium-ion battery performance

Carbon coating of fine particles of Li4Ti5O12 synthesized under hydrothermal condition is carried out by amphiphilic carbonaceous material (ACM) in aqueous solution, followed by carbonization at 800°C for 2h. The particles prepared are comprised of highly-crystalline spinel-type Li4Ti5O12 with the size in the range of 100–400nm without any agglomeration, of which surface is uniformly covered by a thin carbon layer. Their electrochemical performance as an anode in lithium-ion batteries is evaluated. The initial discharge capacity of carbon-coated Li4Ti5O12 at 20C rate is 137mAhg−1 and remains as high as 125mAhg−1 after 100 cycles (91% retention), exhibiting good rate and cyclic performance. Carbon coating by using ACM as carbon precursor gives the Li4Ti5O12 particles an enhanced performance as an anode in lithium-ion batteries, owing to the improvement in electrical conductivity, polarization and ability of dispersion. This non-organic coating process may present a new economic, facile, and green pathway for the preparation of carbon-coated Li4Ti5O12 as a high power anode material in lithium-ion batteries.