Lithium-ion Anode Material Research Articles

Insights into the effect of iron and cobalt doping on the structure of nanosized ZnO.

Here we report an in-depth structural characterization of transition metal-doped zinc oxide nanoparticles that have recently been used as anode materials for Li-ion batteries. Structural refinement of powder X-ray diffraction (XRD) data allowed the determination of small though reproducible changes in the unit cell dimensions of four ZnO samples (wurtzite structure) prepared with different dopants or different synthesis conditions. Moreover, large variations of the full width at half-maximum of the XRD reflections indicate that the crystallinity of the samples decreases in the order ZnO, Zn0.9Co0.1O, Zn0.9Fe0.1O/C, and Zn0.9Fe0.1O (the crystallite sizes as determined by Williamson-Hall plots are 42, 29, 15, and 13 nm, respectively). X-ray absorption spectroscopy data indicate that Co is divalent, whereas Fe is purely trivalent in Zn0.9Fe0.1O and 95% trivalent (Fe(3+)/(Fe(3+) + Fe(2+)) ratio = 0.95) in Zn0.9Fe0.1O/C. The aliovalent substitution of Fe(3+) for Zn(2+) implies the formation of local defects around Fe(3+) such as cationic vacancies or interstitial oxygen for charge balance. The EXAFS (extended X-ray absorption fine structure) data, besides providing local Fe-O and Co-O bond distances, are consistent with a large amount of charge-compensating defects. The Co-doped sample displays similar EXAFS features to those of pure ZnO, suggesting the absence of a large concentration of defects as found in the Fe-doped samples. These results are of substantial importance for understanding and elucidating the modified electrochemical lithiation mechanism by introducing transition metal dopants into the ZnO structure for the application as lithium-ion anode material.

Fe-doped SnO2 nanoparticles as new high capacity anode material for secondary lithium-ion batteries

Herein, Fe-doped tin oxide is presented for the first time as new high-capacity lithium-ion anode material. Pure SnO2, Fe-doped SnO2 (Sn0.9Fe0.1O2, SFO), and carbon-coated SFO (SFO-C) were synthesized and morphologically and electrochemically characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, Brunauer–Emmet–Teller method, and galvanostatic (dis-)charge measurements. Doping SnO2 with Fe results in a substantially enhanced reversible specific capacity and coulombic efficiency. After ten cycles the reversible capacity of SFO-C was about 1519 mAh g−1, i.e., almost twice the specific capacity obtained for pure SnO2 (764 mAh g−1). Moreover, limiting the reversible capacity to 600 mAh g−1 shows the great potential of SFO-C for application in lithium-ion batteries.

Hollow core–shell-structured Si–C composites as high-performance anodes for lithium-ion batteries

Hollow core–shell-structured SiO@void@C composites were synthesized by chemical vapor deposition with acetylene gas, and they could be applied as anode materials for lithium ion (Li-ion) batteries. In addition, this structure was designed to accommodate the volume expansion during lithiation for high-performance Li-ion battery anodes. The structures and morphologies of the synthesized composites were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), from which an egg-like structure was observed due to the deposition of carbon layers on the SiO surface. A void space between the particles and the shell was formed as well. The electrochemical tests of the as-prepared samples indicated that high capacity (1780mAh/g at first cycle) and high Coulombic efficiency (50 cycles with 99.84%) were achieved in this core–shell structured SiO electrode. Therefore, the core–shell SiO/C nanocomposite exhibits better electrochemical performance than pure SiO nanoparticles, indicating that it is a promising material to improve the cyclability and kinetics of nano-anode materials for Li-ion batteries.

Silicon-Graphite Electrode Performance in Lithium Ion Batteries: From Coin Cells to 500 Mah-Pouch Cells

Current lithium ion anode and cathode materials cannot meet the desired gravimetric and volumetric energy demands for hybrid electric vehicles (HEV), plug in hybrid electric vehicles (PHEV) and pure electric vehicles (EV). One way to improve the performance of these systems is to develop a high energy anode material. One system that has shown promise is the incorporation of silicon particles into the anode. Silicon by itself can have capacities up to 3000 mAh/g. While this value is impressive, there are a number of issues that present themselves when trying to use all of that capacity. Argonne National Laboratory has taken up the task to create a silicon-based anode that could be used with the current lithium ion cathode materials to increase the gravimetric and volumetric energy of these systems. The capacity target for this electrode was chosen to be between 600-800 mAh/g (active material). By selecting this value, systems modeling has shown that this anode capacity matched with current cathode materials would produce the most cost effective and energy dense systems. This presentation will first focus on some of the initial development of the anode formulation and processing issues encountered. From there, coin cell data (Figure 1) will be presented on the anode formulation and then the presentation will conclude with xx3450 pouch cell data. Qualitative and quantitative data will be examined for each of the sections. As a final point, the silicon anode formulation has been made into a practical and usable electrode and matched to the Electrode Library which has been created by the Cell Analysis, Modeling, and Prototyping (CAMP) Facility. The silicon based anode, graphite based anodes, and various cathodes are available in the Electrode Library for use in the battery research community. Acknowledgment: Support from Peter Faguy and David Howell of the U.S. Department of Energy’s Office of Vehicle Technologies Program is gratefully acknowledged. This work was performed under the auspices of the U.S. Department of Energy, Office of Vehicle Technologies, under Contract no. DE-AC02-06CH11357 Figure 1

Optimization of the Thermal Treatment of Electrospun Poly(acrylonitrile) for Flexible, Binderless, and Collectorless Lithium-Ion Carbon Nanofibers Anode

The processing of carbon nanofibers prepared by electrospinning poly(acrylonitrile) and subsequent thermal treatment has been optimized for use as a binderless, flexible, and collectorless anode for lithium ion batteries. Previous literature has failed to report, and in some instances account for, all aspects of processing as they relate to specific capacity in a comprehensive and systematic study. Solutions of 12 wt% poly(acrylonitrile) in DMF were used throughout and were electrospun and thermally treated using various approaches. The highest specific capacity obtained after 10 cycles at a current of 100 mA/g was greater than 550 mAh/g and exhibited Coulombic efficiencies of < 98% after the first cycle. This specific capacity is <30% higher than previously reported anodes cycled at half of the reported current (50 mA/g) and almost 200 mAh/g higher than the theoretical capacity of pure graphite (372 mAh/g). Flexible carbon nanofibers prepared by this scalable method have been shown to be a viable binderless and collectorless lithium ion anode material. Applying these concepts to carbon nano-composite anodes previously reported in literature would further enhance their energy and power densities.

Fast Assembly of Si-CNFs Anodes for High-Performance Lithium-Ion Batteries

A hybrid lithium-ion anode material, made of acid-functionalized carbon nanofibers (CNFs) and amino modified Si nanoparticles (SiNPs), was synthesized by fast homogeneous electrophoretic deposition (EPD). Regular distribution of SiNPs in the three dimensional electro-active frameworks with the help of the interactions of surface functional groups can effectively improve the electron transport and restrict volume expansion during Li insertion/extraction. The as-deposited composite film exhibits a stable capacity of 790 mAh g-1 for 100 cycles at a current density of 400 mA g-1. The stability of suspension and weight ratio of Si to CNFs plays the key roles in the electrochemical performance. It provides a possible environmentally friendly and cost-effective preparation method for future high-performance Li-ion battery applications.

KOH etched graphite for fast chargeable lithium-ion batteries

Graphite is the most widely used anode material for lithium ion (Li-ion) batteries, although it has limited power performance at high charging rates (Li-ion input). Alternative materials such as silicon and tin alloys, however, have an even more inferior rate capability. We describe here a multi-channel structure with a graphite surface etched with pores that can greatly increase the number of sites for Li-ion intercalation/de-intercalation and reduce the Li-ion diffusion distance for fast chargeable Li-ion batteries by etching the graphite surface with pores. As a result, the multi-channel structure graphite anode shows better charging and discharging rate capability, cyclability, and higher coulombic efficiency than pristine graphite materials. The multi-channel anode material is proposed for use in fast chargeable Li-ion batteries for electric vehicles and plug-in hybrid vehicles.

Precursor polymers for the carbon coating of Au@ZnO multipods for application as active material in lithium-ion batteries.

The synthesis of statistical and block copolymers based on polyacrylonitrile, as a source for carbonaceous materials, and thiol-containing repeating units as inorganic nanoparticle anchoring groups is reported. These polymers are used to coat Au@ZnO multipod heteroparticles with polymer brushes. IR spectroscopy and transmission electron microscopy prove the successful binding of the polymer onto the inorganic nanostructures. Thermogravimetric analysis is applied to compare the binding ability of the block and statistical copolymers. Subsequently, the polymer coating is transformed into a carbonaceous (partially graphitic) coating by pyrolysis. The obtained carbon coating is characterized by Raman spectroscopy and energy-dispersive X-ray (EDX) spectroscopy. The benefit of the conformal carbon coating of the Au@ZnO multipods regarding its application as lithium-ion anode material is revealed by performing galvanostatic cycling, showing a highly enhanced and stabilized electrochemical performance of the carbon-coated particles (still 831 mAh g(-1) after 150 cycles) with respect to the uncoated ones (only 353 mAh g(-1) after 10 cycles).

Self-improving anodes for lithium-ion batteries: continuous interlamellar spacing expansion induced capacity increase in polydopamine-derived nitrogen-doped carbon tubes during cycling

An interlamellar spacing expansion induced capacity increase during cycling is revealed for polydopamine-derived nitrogen-doped carbon tubes as lithium-ion anode materials.

Scaling up “Nano” Li4Ti5O12 for High-Power Lithium-Ion Anodes Using Large Scale Flame Spray Pyrolysis

Herein, we present the upscaled synthesis of nanoparticulate Li4Ti5O12 (LTO) by means of flame spray pyrolysis (FSP), yielding high phase purity and appropriate morphology for application as high-power lithium-ion anode material. Electrodes based on this optimized LTO nanopowder, carboxymethyl cellulose (CMC) as binder, and copper as current collector revealed excellent rate performance, providing specific capacities of 133, 131, 129, 127, 124, and 115 mAh g−1 when applying C rates of 1C, 2C, 5C, 10C, 20C, and 50C, respectively. Targeting the commercial application of thus synthesized nanoparticles, we optimized also the electrode composition, comparing three different binding agents (CMC, PVdF, and poly(acrylic acid), PAA) and substituting the copper current collector by aluminum. The results of this comparative analysis show, that the combination of nanoparticulate LTO, CMC, and an aluminum current collector appears most suitable toward the realization of environmentally friendly and cost-efficient lithium-ion anodes, presenting very stable cycling performance for more than 1000 cycles at 10C without substantial capacity decay.

Synthesis of quasi-spherical micro-size lithium titanium oxide by an easy sol-gel method

A low-cost and facile method for synthesizing micro-size lithium titanium oxide, micro-size Li4Ti5O12 (MS-LTO), has been proposed in this study. The MS-LTO with a high tap density of 1.38 g cm−3 is prepared from synthesis-grade TiOSO4 through hydrolysis followed by calcination of obtained TiO2 with LiOH · H2O. The parameters of pH, temperature, concentration, etc. are optimized for preparing the precursor H2TiO3. The morphology, size, and structure of H2TiO3, TiO2, and MS-LTO are carefully characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical performances of the as-prepared MS-LTO deliver a reversible capacity of 171 mA · h g−1 at 0.1 C and show a good rate capability by maintaining 47 % of the capacity at 5 C (vs. 0.1 C), as well as remarkable cycling stability without capacity fading after 100 cycles at both 1 and 2 C. This as-prepared MS-LTO shows a potential application in lithium-ion batteries which can be utilized in the next-generation electric vehicles and hybrid electric vehicles. Furthermore, the strategy for synthesizing MS-LTO from production-level TiOSO4 · xH2SO4 · xH2O proposed here provides a facile method for preparing lithium-ion anode materials.

Lithium Alloying Nanoparticles Deposited 3D Carbon Architectures as Anodes for Li-Ion Batteries

Due to the increased demand and interest for mobile electronics, renewable energy production and electronic vehicles, more pressure is being placed on battery technology to deliver higher capacity, longer lasting devices. Researchers have focused on creating advanced materials to increase the energy storage and overall performance of lithium ion batteries. While graphitic carbon is still the commercially preferred material for the negative electrode (anode) of Li-ion batteries, it fails to deliver a high enough capacity (372mAh/g) to meet the increasing energy and performance requirements. With a theoretical gravimetric capacity nearly 3 times greater than graphite (991mAh/g), tin has the potential to replace graphite as the next generation of lithium ion anode material [1]. However, pure Sn anodes suffer from poor cycle performance due to electrical detachment/isolation from the current collector due to particle fracturing. Researches have tried alloying tin with transition metals [2], creating Sn-C composite nanoparticles [3], as well as using both pure SnO2 and SnO2deposited on hard carbon spheres [4,5] as anode materials. A common result of research efforts is usually an increase in capacity but retention of the poor cycle performance. This is due to aggregation of the tin particles which then leads to similar electronic detachment and fracturing characteristics of pure tin. It is believed that improving the mechanical stability of the anode material will, in turn, increase the electrochemical characteristics of the material [6]. Our group has created a material that can facilitate this mechanical stability required for a successful tin-based anode for lithium ion batteries. This is done by using a one-step, solid state process to fabricate porous carbon particles in situ decorated with functional metal nanoparticles. By placing a mixture of powdered carbon and salt precursors in a high temperature furnace and heating these materials to 500-700 oC in an inert Ar atmosphere for an hour, unique metal supported carbon hybrid architectures are achieved. This material is essentially a porous carbon “host” with nanosized metallic “guests”. The carbon matrix helps to mechanically stabilize the tin nanoparticles which are chemically bound to the surface of this matrix. The material demonstrates a surface area of >700m2/g. SEM images of the carbon-tin composite (Figure 1a-b) shows that the naosized Sn is uniformly deposited inside and outside of the supported 3D carbon architectures.The previously mentioned materials were mixed with PVDF binder and carbon black in a ratio of 8:1:1 and coated onto copper foil to make electrodes for testing. Electrochemical tests were performed on the materials against lithium metal in a half-cell configuration using 1M LiPF6 electrolyte in a 1:1 EC:DMC solution and a polypropylene separator. Figure 1 (c) shows the second discharge/charge curves for pure tin nanoparticle coated carbon matrices as well those of the pristine carbon matrix. The pure tin nanoparticles coated carbon has a reversible capacity greater than 500 mAh/g, which shows a vast improvement over the uncoated carbon matrix (~220mAh/g). In addition, the materials synthesized demonstrate stable cycling performance after the first discharge/charge is completed. Additional work will be done to decrease this first cycle inefficiency and to continue to increase the capacity of our new composite materials. A detail analysis of the potentiograms for Sn-carbon composite is demonstrated by their derivatization dQ/dV (Figure 1d), indicating reduction processes and corresponding oxidation processes [7] related to different Li-Sn alloying processes. Figure 1.a-b) Scanning electron micrographs of tin nanoparticles deposited on 3D carbon architecture product at various magnifications, c) Voltage profiles for pristine carbon and Sn-carbon composite cells, and d) dQ/dV plot of Sn-carbon composite cell References I.A. Courtney, J.R. Dahn, J. Electrochem. Soc., 144, 2045 (1997).A. D. Todd, R. E. Mar, J. R. Dahn, J. Electrochem. Soc., 153, A1998 (2006).G. Derrien, J. Housson, S. Panero, B. Scrosati, Adv. Mater., 19, 2336 (2007).V. G. Pol, J. Wen, D. J. Miller and M. M. Thackeray, J. Elec. Soc., 161, A777 (2014). V. G. Pol, J-M. Calderon Moreno, M. M. Thackeray, J. Sol. State Chem., 196, 21 (2012).L. Chu, G. Mingxia, P. Hongge, Y. Liu, M. Yan, J. Alloys and Compounds, 575, 246 (2013).J. Zhu, Z. Lu, S. T. Aruna, D. Aurbach, A. Gedanken, Chem. Mater , 12, 2557 (2000).

Formation of carbon-coated ZnFe2O4 nanowires and their highly reversible lithium storage properties

In this paper, carbon-decorated ZnFe2O4 nanowires, having one-dimensional geometry with diameters of 70–150 nm and lengths of several micrometers, were prepared and used as a highly reversible lithium ion anode material. They can be obtained from calcination of glucose-coated ZnFe2(C2O4)3 nanowires, which were prepared in glucose containing microemulsion solutions. The physicochemical properties of carbon-coated ZnFe2O4 nanowires were investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The carbon-coated ZnFe2O4 nanowires showed a substantially increased discharge capacity of ca. 1285.1 mA h g−1 at the first cycle as compared with non-carbon-coated ZnFe2O4 nanowires (ca. 1024.3 mA h g−1) and ZnFe2O4 nanoparticles (ca. 1148.7 mA h g−1). Moreover, the discharge capacity of the carbon-coated ZnFe2O4 nanowires was maintained with no degradation even after 100 charge/discharge cycles. The high cycling durability, rate capability, and coulombic efficiency suggest that the carbon-coated ZnFe2O4 nanowires prepared here can be promising anode candidates for a highly reversible lithium storage electrode.

Toward Silicon Anodes for Next-Generation Lithium Ion Batteries: A Comparative Performance Study of Various Polymer Binders and Silicon Nanopowders

Silicon is widely regarded as one of the most promising anode materials for lithium ion and next-generation lithium batteries because of its high theoretical specific capacity. However, major issues arise from the large volume changes during alloying with lithium. In recent years, much effort has been spent on preparing nanostructured silicon and optimizing various aspects of material processing with the goal of preserving the electrode integrity upon lithiation/delithiation. The performance of silicon anodes is known to depend on a large number of parameters and, thus, the general definition of a "standard" is virtually impossible. In this work, we conduct a comparative performance study of silicon anode tapes prepared from commercially available materials while using both a well-defined electrode configuration and cycling method. Our results demonstrate that the polymer binder has a profound effect on the cell performance. Furthermore, we show that key parameters such as specific capacity, capacity retention, rate capability, and so forth can be strongly affected by the choice of silicon material, polymer binder and electrolyte system - even the formation of metastable crystalline Li15Si4 is found to depend on the electrode composition and low potential exposure time. Overall, the use of either poly(acrylic acid) with a viscosity-average molecular weight of 450.000 or poly(vinyl alcohol) Selvol 425 in combination with both silicon nanopowder containing a native oxide surface layer of ∼1 nm in diameter and with a monofluoroethylene carbonate-based electrolyte led to improved cycling stability at high loadings.

Functionalized Graphitic Carbon Nitride for Efficient Energy Storage

Using first-principles calculations based on density functional theory, we show that recently synthesized graphitic carbon nitride (g-C4N3 and g-C3N4) can be functionalized with Li atoms for use as materials not only for high-capacity hydrogen storage but also for lithium-ion batteries. The unique properties are due to the high density of Li ions firmly adsorbed over nitrogen triangular holes. The gravimetric and volumetric densities of hydrogen in Li2C3N4 and Li2C4N3 are greater than 10 wt % and 100 g/L, respectively, both exceeding the target set by the U.S. Department of Energy. Similarly, single-layer Li2C3N4 is a good candidate for a lithium-ion anode material with a specific capacity almost twice that of graphite, and bulk LiC4N3 can be used as a cathode material with a specific energy twice that of LiCoO2. The materials have the added advantage that they are stable against clustering of Li and are nontoxic.

Designed synthesis of graphene–TiO2–SnO2 ternary nanocomposites as lithium-ion anode materials

Well-designed graphene–TiO2–SnO2 ternary nanocomposites, in which the nanometer-sized TiO2 and SnO2 nanoparticles formed in situ uniformly anchored on the surface of reduced graphene oxide sheets, are synthesized by a solvothermal method combined with a hydrothermal two-step method. Although the contribution of anatase TiO2 to the total specific capacity of obtained ternary nanocomposites is limited by its low theoretical specific capacity, the small amount of TiO2 nanoparticles can form more clearance space to accommodate the electrode volume change and act as stable barriers to effectively prevent the agglomeration of SnO2 nanoparticles during the charge–discharge process. Additionally, the good combination and synergistic effects among uniformly distributed TiO2 nanoparticles, high-capacity SnO2 and conductive graphene sheets work together to tackle the aggregation of nanoparticles while keeping the overall electrode sturdy and highly active in the lithium storage process. Therefore, when evaluated as anode materials in lithium-ion batteries, the as-synthesized ternary nanocomposites deliver improved cycling performance (537 mA h g−1 at 50 mA g−1 accompanied by coulombic efficiency of 97% after 50 cycles) and good reversible capacities (250 mA h g−1 even at the current density 1000 mA g−1) in the voltage range of 0.01 to 3.00 V. By limiting the voltage window in the range of 0.01 to 1.00 V, which is the optimum voltage range for the alloying–dealloying reaction between lithium and Sn, ternary nanocomposites exhibit a more stable cycling performance (more than 70% of initial reversible capacity being retained).

新規リチウムイオン電池負極材料の開発とその結晶学的評価

新規リチウムイオン電池負極材料の開発とその結晶学的評価

High Performance Lithium-ion Battery Electrode: Silicon Coated on Vertically Aligned Carbon Nanofibers

ABSTRACTThis study reports a high-performance hybrid lithium-ion anode material using coaxially coated silicon shells on vertically aligned carbon nanofiber (VACNF) cores. The robust bush-like highly conductive VACNFs effectively connect high-capacity silicon shells for lithium-ion storage. Such architecture allows the Si shells to freely expand/contract in the radial direction during lithium-ion insertion/extraction. A high specific capacity of 3000-3650 mAh(gSi)-1 was obtained at C/1 rate, comparable to the maximum value of amorphous Si, and ∼89% of the capacity was retained after 100 charge-discharge cycles. The lithium-ion storage capacity remains nearly the same from C/10 to C/0.5 rates. The ability to obtain high capacity at significantly improved power rates while maintaining the extraordinary cycle stability demonstrates the utilization of the unique properties of such hybrid architecture for lithium-ion batteries.

A high-performance lithium-ion battery anode based on the core–shell heterostructure of silicon-coated vertically aligned carbon nanofibers

This study reports a high-performance hybrid lithium-ion anode material using coaxially coated silicon shells on vertically aligned carbon nanofiber (VACNF) cores. The unique “cup-stacking” graphitic microstructure makes VACNFs a good lithium-ion intercalation medium and, more importantly, a robust bush-like conductive core to effectively connect high-capacity silicon shells for lithium-ion storage. The vertical core–shell nanowires remain well separated from each other even after coating with bulk quantities of silicon (equivalent to 1.5 μm thick solid films). This open structure allows the silicon shells to freely expand/contract in the radial direction during lithium-ion insertion/extraction. A high specific capacity of 3000–3650 mA h (gSi)−1, comparable to the maximum value of amorphous silicon, has been achieved. About 89% of the capacity is retained after 100 charge–discharge cycles at the C/1 rate. After long cycling, the electrode material becomes even more stable, showing the invariant lithium-ion storage capacity as the charge–discharge rate is increased by 20 times from C/10 to C/0.5 (or 2C). The ability to obtain high capacity at significantly improved power rates while maintaining the extraordinary cycle stability demonstrates that this novel structure could be a promising anode material for high-performance lithium-ion batteries.

Interconnected nanofibrous titanium dioxide bronze: an emerging lithium ion anode material for high rate performance

Here we report TiO2, in the bronze phase (TiO2-B), with a porous nanostructure designed for rapid lithium storage and charge transfer. A new synthesis method is described that not only facilitates these improvements, but also removes the requirement for an autoclave, which is usually common in the synthesis of this material. Most notably, peak capacities of 235, 148, and 66 mAh g−1 at 0.2 C, 20 C, and 100 C were attained, respectively. These results were achieved with low conductive carbon contents (5%). In addition, recent atomistic reports on TiO2-B were correlated with these results in order to explain how the morphology reported here was leveraged in order to attain high performance. Diffusion coefficients were also calculated for this novel TiO2-B architecture and found to be in good agreement with a previous study performed using NMR.