Anode Material For Lithium-ion Cells Research Articles

Nanostructured Silicon as Potential Anode Material for Li-Ion Batteries.

Commercial micrometer silicon (Si) powder was investigated as a potential anode material for lithium ion (Li-ion) batteries. The characterization of this powder showed the mean particle size of approx.75.2 nm, BET surface area of 10.6 m2/g and average pore size of 0.56 nm. Its band gap was estimated to 1.35 eV as determined using UV-Vis diffuse reflectance spectra. In order to increase the surface area and porosity which is important for Li-ion batteries, the starting Si powder was ball-milled and threatened by metal-assisted chemical etching. The mechanochemical treatment resulted in decrease of the particle size from 75 nm to 29 nm, an increase of the BET surface area and average pore size to 16.7 m2/g and 1.26 nm, respectively, and broadening of the X-ray powder diffraction (XRD) lines. The XRD patterns of silver metal-assisted chemical etching (MACE) sample showed strong and narrow diffraction lines typical for powder silicon and low-intensity diffraction lines typical for silver. The metal-assisted chemical etching of starting Si material resulted in a decrease of surface area to 7.3 m2/g and an increase of the average pore size to 3.44 nm. These three materials were used as the anode material in lithium-ion cells, and their electrochemical properties were investigated by cyclic voltammetry and galvanostatic charge-discharge cycles. The enhanced electrochemical performance of the sample prepared by MACE is attributed to increase in pore size, which are large enough for easy lithiation. These are the positive aspects of the application of MACE in the development of an anode material for Li-ion batteries.

Sn/Al 2 O 3 /C/CNT composite prepared by wet milling as anode material for lithium-ion cells

Abstract Sn/Al2O3/C/CNT (SAC/CNT) composite was synthesized by a simple wet milling route. The physico-chemical, structural and morphological properties of the material were studied. The electrochemical performance of the composite as an anode material in Li-ion cells was evaluated by Cyclic Voltammetry (CV), charge–discharge cycling and electrochemical impedance measurements. The SAC/CNT material delivered an initial specific capacity of 835 mAh g−1 with the coulombic efficiency of ∼77% along with good charge–discharge cycle performance retaining ∼88% of the initial capacity after 35 cycles. A comparison of the results with those for Sn/C (SC) and Sn/Al2O3/C (SAC) showed that the SAC/CNT composite exhibited better overall performance compared to the other two materials. The enhanced performance of SAC/CNT is attributed to the combined effect of the buffer action provided by Al2O3 accommodating volume changes of the electrode during cycling and the reduced charge transfer resistance of the electrode resulting from the inclusion of conductive CNTs.

Electrochemical Characterization of Silicon Nanocrystals Embedded in Alloy Matrix As Anode Materials for Lithium-Ion Cells

Silicon has been regarded as one of the most promising anode materials to increase the energy density of lithium-ion batteries by replacing graphite materials due to its high theoretical capacity.1 However, the practical application of silicon materials in lithium-ion batteries is hampered by the large volume changes that occur during repeated cycling, which result in the cracking of the electrode, loss of electrical contact, unstable solid electrolyte interphase (SEI) formation, and eventually rapid capacity fading upon cycling.2,3 The promising approach to overcome the above problems is the utilization of active-inactive alloy systems, where the electrochemical reaction occurs in the active phase and the inactive phases help to improve electronic conductivity and act as a volume buffer. In the present work, we synthesized silicon alloys composed of silicon nanoparticles embedded in Cu-Al-Fe matrix phases. The matrix phases have a mechanical property to endure the stress generated by the volume expansion of Si during cycling in addition to high electrical conductivity for fast electron transfer to silicon. This strategy resulted in enhanced cycling performance in terms of discharge capacity, capacity retention and rate capability. These superior performances could be attributed to its unique structure with silicon particle embedded by alloy matrix, which could effectively accommodate the large volume change during cycling and provide continuous electronic pathway in the electrode. Detailed characterization of the silicon alloy materials along with their electrochemical performance as anode in lithium-ion cells will be presented.

Promising anode material for lithium-ion cells based on cobalt oxide synthesized by microwave heating

High-performance anode material for lithium-ion cell based on cobalt oxide was synthesized through a combination of sol-gel route and subsequent microwave heating. The influence of microwave irradiation temperature of the precursor on the characteristics of the active materials formed was studied. The physicochemical, structural, and morphological properties of the materials were studied in addition to the electrochemical performance by cyclic voltammetry and charge-discharge cycling vs. Li+/Li. Microwave heating at 350 °C resulted in the formation of Co3O4, whereas at 450 and 550 °C, a mixture of Co3O4, CoO, and Co was formed. Co3O4 synthesized at 350 °C possessed porous morphology with high specific surface area and exhibited superior electrochemical performance with initial specific capacity of 982 mAh g−1 and coulombic efficiency of ~75% along with good cycle performance retaining ~87% of initial capacity after 60 cycles.

Anodic Materials for Lithium-ion Batteries: TiO2-rGO Composites for High Power Applications

Titanium dioxide/reduced graphene oxide (TiO2-rGO) composites were synthesized at different loadings of carbonaceous phase, characterized and used as anode materials in Lithium-ion cells, focusing not only on the high rate capability but also on the simplicity and low cost of the electrode production. It was therefore chosen to use commercial TiO2, GO was synthesized from graphite, adsorbed onto TiO2 and reduced to rGO following a chemical, a photocatalytic and an in situ photocatalytic procedure. The synthesized materials were in-depth characterized with a multi-technique approach and the electrochemical performances were correlated i) to an effective reduction of the GO oxidized moieties and ii) to the maintenance of the 2D geometry of the final graphenic structure observed. TiO2-rGO obtained with the first two procedures showed good cycle stability, high capacity and impressive rate capability particularly at 10% GO loading. The photocatalytic reduction applied in situ on preassembled electrodes showed similarly good results reaching the goal of a further simplification of the anode production.

Improved Cyclability of Silicon/Porous-Carbon Composite with Ag Nanoparticles for Lithium-Ion Battery Anodes

A Silicon/Porous-Carbon (Si/Porous-C) composite with Ag nanoparticles was prepared by the co-assembly of polyvinylidene fluoride (PVdF), nano-SiO2 (~20 nm), AgNO3 and Si nanoparticles (~ 50 nm) followed by a carbonizing process and subsequent removal of SiO2 template. The Si/Porous-C and Ag/Si/Porous-C composite were characterized by scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD). Ag nanoparticles remained even after heat treatment at high temperature and hydrofluoric acid etching. The Ag/Si/Porous-C composite electrode exhibited good electrochemical performances with a reversible capacity of 1,470 mAh/g as an anode material in lithium-ion cells, showing a stable capacity of 1,150 mAh/g after 100 cycles at a rate of 500 mA/g per hour. Cycling performances of the Si/Porous-C and Ag/Si/Porous-C composite electrodes were determined at various rates as shown in figure. The Ag/Si/Porous-C composite electrode showed better rate capability and recovery as the rates decreased, while the capacity of the Si/Porous-C composite electrode faded drastically as the rates increased. Figure 1

Lithium titanate as anode material for lithium-ion cells: a review

Lithium titanate (Li4Ti5O12) has emerged as a promising anode material for lithium-ion (Li-ion) batteries. The use of lithium titanate can improve the rate capability, cyclability, and safety features of Li-ion cells. This literature review deals with the features of Li4Ti5O12, different methods for the synthesis of Li4Ti5O12, theoretical studies on Li4Ti5O12, recent advances in this area, and application in Li-ion batteries. A few commercial Li-ion cells which use lithium titanate anode are also highlighted.

Designing Si/porous-C composite with buffering voids as high capacity anode for lithium-ion batteries

A novel Si/porous-C composite with buffering voids was prepared by the co-assembly of phenol-formaldehyde resin, SiO2 and Si nanoparticles, followed by a carbonizing process and subsequent removal of SiO2 template. Si nanoparticle was coated with a layer of porous carbon shell with rationally designed void in between which provides the accommodating space for the volume change of Si over cycling. The as-prepared composite electrode exhibited good electrochemical performances as an anode material in lithium-ion cells, showing a stable reversible capacity of 980 mAh g−1 over 80 cycles with small capacity fade of 0.17%/cycle and high rate capability (721mAhg−1 at 2000mAg−1).

Mesoporous Tin Phosphate as Anode Material for Lithium-Ion Cells

Mesoporous SnP2O7was synthesized via a surfactant templating method where an anionic surfactant, sodium dodecyl sulfate was used. X-ray diffraction (XRD) analysis indicates presence of mesostructure when the precursors were calcined at 200, 300 and 400 °C. Cyclic voltammetry tests carried out within 0-2.0 V (vs. Li/Li+) indicated that irreversible reduction of tin phosphate to form lithium phosphate phases and metallic tin occurred around 1.10 V and 0.69 V whereas the reversible alloying and de-alloying reaction involving lithium with tin occurred at 0.19 V and 0.52 V, respectively. Galvanostatic charge-discharge cycling tests carried out within 0-1.2V (vs. Li/Li+) showed that the mesoporous tin phosphate calcined at 400 °C exhibited a reversible discharge capacity of 738 mAh/g in the second cycle and upon reaching the tenth cycle, it retained a discharge capacity of 461 mAh/g. The relatively high capacity obtained for this anode was attributed to the mesoporous framework which provided larger surface area for reaction with lithium and minimized effect of volume changes experienced by the anode during repeated charging and discharging cycling.

Nanostructured Sn–Ti–C composite anodes for lithium ion batteries

Nanostructured Sn–Ti–C composites have been synthesized by a facile, inexpensive high energy mechanical milling process and investigated as an anode material for lithium-ion cells. Characterization data collected with X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) reveal an uniform dispersion of Sn nanoparticles within the conductive, amorphous (or poorly crystalline) TiC + C matrix. Among the three Sn–Ti–C compositions investigated, the Sn 11Ti 31C 58 composite exhibits the best electrochemical performance, with a capacity of ∼370 mAh/g and excellent capacity retention over 300 cycles studied. It also exhibits excellent cycle life with LiMn 2O 4 spinel cathode, suggesting a tolerance of the Sn–Ti–C anodes toward poisoning by the manganese leached out from the spinel cathode. The superior electrochemical performance of Sn 11Ti 31C 58 composite is attributed to a homogeneous distribution of the electrochemically active amorphous Sn, suppression of Sn grain growth, and the mechanical buffering effect provided by the conductive TiC + C matrix toward the volume expansion-contraction occurring during cycling.

Performance of Lithium Ion Cell Anode Graphites Under Various Cycling Conditions

Graphites MCMB-2810 and OMAC-15 (made by Osaka Gas Inc.), and SNG12 (Hydro Quebec, Inc.) were evaluated in lithium half-cells as anode materials for lithium-ion cells intended for use in hybrid electric vehicles. Though the reversible capacity obtained for SNG was slightly higher than that of OMAC or MCMB, its 1st cycle efficiency was considerably lower. Voltage vs capacity plots of cycling data show that the discharge and charge limits shift to higher capacity values due to continuation of anode side reactions. Varying the cycle charge and discharge limits was found to have an insignificant effect on fractional capacity shift per cycle.

Electrochemical performance of α-Fe 2O 3 nanorods as anode material for lithium-ion cells

α-Fe 2O 3 nanorods were synthesized by a facile hydrothermal method. The as-prepared α-Fe 2O 3 nanorods have a high quality crystalline nanostructure with diameters in the range of 60–80 nm and lengths extending from 300 to 500 nm. The crystal structure of the α-Fe 2O 3 nanorods was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The α-Fe 2O 3 nanorod anodes exhibit a stable specific capacity of 800 mAh/g. This indicates significantly improved electrochemical performance in lithium-ion cells, compared to that of commercial microcrystalline α-Fe 2O 3 powders.

Electrochemical performances of Si-coated MCMB as anode material in lithium-ion cells

Crystalline silicon has been deposited onto the surface of mesocarbon microbeads (MCMB) particles by chemical vapor deposition (CVD) using silane as the precursor gas. The microstructure of the Si-coated MCMB was characterized by Raman spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) analysis. It was found that the Si coated on the surface of MCMB particles exists in the crystalline state, and Si-coated MCMB exhibits increased reversible capacity compared to pristine MCMB without sacrificing its cycling behavior. As a result, Si-coated MCMB emerges as a promising anode material for secondary lithium-ion batteries.

The influence of graphite surface modification on the exfoliation during electrochemical lithium insertion

Lithium-ion cells have good performance in terms of high voltage, high specific energy, and long cycle life. Graphitic carbons are the first-choice anode materials in lithium-ion cells for the reasons of performance and cost. It is now well known that, in lithium-ion cells the carbon surface is always covered by a protective thin solid film called the Solid Electrolyte Interphase (SEI). The SEI formation mechanism is rather complex and not yet completely understood. Lithium ions are consumed for the formation of this protective film. This decreases the maximum possible charge and energy density of the battery. Thus, losses have to be minimized.

Si/C Composites for High Capacity Lithium Storage Materials

Thermal pyrolysis of polyvinyl chloride dispersed with nanosized silicon and fine graphite particles at 900°C produces a novel Si/C composite for lithium storage material. Incorporated silicon provides major capacity for lithium insertion, while the introduction of graphite component suppresses the initial irreversibility and hysteresis between charge and discharge caused by pyrolyzed carbon. The first cycle efficiency of the composite is about 85%. The large reversible capacity of ca. 700 mAh/g and good cyclability indicates that such Si/C composite may be a useful alternative to conventional graphite-based anode materials for lithium-ion cells.

Phase separation and amorphisation in lithium inserted Cu–In–Sn sulfospinels: experimental and theoretical approach

119 Sn Mössbauer spectroscopy, X-ray diffraction (XRD) and electrochemical experiments were carried out to characterise the reaction mechanism of lithium with spinel phases Cu x In y Sn z S 4. The electrochemical investigations have shown interesting reversible capacities for these materials, and their possible use as anode materials in lithium-ion cells. This analysis reveals a multi-phase mechanism linked to the reduction of the cations involving a spinel to rocksalt transformation followed by a structural breakdown. Density functional calculations by the linearised augmented plane wave (LAPW) method give a good interpretation of experimental results for crystalline phases.

Tin and tin-based intermetallics as new anode materials for lithium-ion cells

The galvanostatic cycling behaviour of Sn/SnSb composite electrodes has been studied in 1 mol l −1 LiClO 4/propylene carbonate (PC), 1 mol l −1 LiPF 6/ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1), and 1 mol l −1 LiClO 4/PC saturated with trans-decalin ( t-Dec). Capacities between 500 and 600 mA h g −1 (with respect to the mass of active material) were obtained. Reasons for the irreversible capacities are given and film formation on lithium storage metals and alloys is discussed. The observed coulombic efficiencies were slightly higher for the EC-containing electrolyte than for the PC-based one. Alternatively, improved efficiencies and stand-time behaviour were obtained when the PC electrolyte was saturated with t-Dec, which acts as a surfactant.

Electrochemical and 119Sn Mössbauer study of sulfospinels as anode materials for lithium-ion batteries

119Sn Mössbauer spectroscopy, X-ray diffraction and electrochemical experiments were carried out to characterize the reaction mechanism of lithium with spinel phases of the Cu 2S–In 2S 3–SnS 2 system. This analysis reveals an irreversible part of the mechanism linked to the reduction of the cations involving a spinel to rocksalt transformation followed by a structural breakdown, and a reversible part linked to the formation of lithium-metal alloys. The electrochemical investigation has shown interesting reversible capacities for these materials, and their possible use as anode materials in lithium-ion cells.

99/01266 Commercial cokes and graphites as anode materials for lithium-ion cells : Derwin, D. J. et al. Mater. Res. Soc. Symp. Proc., 1998, 496, 575–580

99/01266 Commercial cokes and graphites as anode materials for lithium-ion cells : Derwin, D. J. et al. Mater. Res. Soc. Symp. Proc., 1998, 496, 575–580

Improved Carbon Anode Materials for Lithium-Ion Cells

ABSTRACTSeveral carbon materials have been studied for suitability as anode materials in lithium-ion cells. Carbons that have been included in this evaluation are three grades of commercially available mesophase carbon microbeads (MCMB) 6–28, 10–28 and 25–28, two specially prepared mesophase fibers (Amoco), a foreign mesophase fiber and KS-15 graphite (Lonza). Differences in cycling behavior between the three types of MCMB material are shown. Data of full lithium-ion cells demonstrate the effect that the choice of carbon material has on the cell discharge voltage and capacity. Lithium reference electrode experiments in full cells (3.0–4.0Ah capacity), elucidate the dynamics under several charge/discharge regimes and provide a comparison between the performance of carbon fiber and graphite anode materials. These test results indicate that the fibers can be charged at significantly higher rates than graphite without showing polarization at the anode. Full and half cell data also demonstrates the high coulombic efficiencies of the mesophase materials and first cycle efficiencies as compared to graphite. A comparison of two mesophase materials with different textures in full cells under strenuous cycling conditions shows significant differences in capacity retention. SEM photos of fibers showing the different textures are also presented.