Negative Electrode For Li-ion Batteries Research Articles

A comparison of sputtered and mechanically milled Cu6Sn5 + C materials for Li-ion battery negative electrodes

Sn27Cu33C40 produced by mechanical milling is compared with Sn27Cu31C42 and Sn26Cu31C43 produced by magnetron sputtering for use as anode materials in Li-ion batteries. The sputtered samples were found to be amorphous/nanostructured and had a greater degree of atomic intermixing in comparison to the milled sample, which was more crystalline. Samples were incorporated as electrodes in Li-half cells and had a capacity of about 400 mAh g−1. Significant capacity loss was observed beginning near the 50th cycle for the mechanically milled sample, while little capacity loss was observed for the sputtered samples after 100 cycles. Despite its good cycling performance, amorphous Cu6Sn5 + C was found to crystallize as Li is cycled, resulting in the aggregation of Cu6Sn5 grains. Structural changes during lithiation and delithiation as well as the evolution of the electrochemistry are compared and contrasted for the two materials.

3D morphological evolution of Li-ion battery negative electrode LiVO2 during oxidation using X-ray nano-tomography

Lithium vanadium oxide (LiVO211More precisely, it is “Li1+xV1−xO2 (x>0)”. But “LiVO2” is used throughout the text for brevity [1].) holds the potential promise to replace graphite as an anode material in commercial Li-ion batteries as it doubles the volumetric energy density compared to graphite but can still operate at low voltage (~0.1V vs. Li/Li+). Its degradation mechanism was investigated using a synchrotron X-ray nano-tomography technique to image the LiVO2 in three dimensions (3D). In particular an oxidation effect is discussed by a direct visualization and quantification of the 3D microstructure of the LiVO2 before and after being exposed to the air, which results in the oxidation of the LiVO2. After being exposed to air, an oxidation layer with thickness ~120–240nm was observed at the interface of the LiVO2 particles and the binders/pores. While the total volume of LiVO2 remains relatively constant before and after oxidation, the particle size reduces, which is consistent with crack growth possibly due to the local exothermal oxidation reactions, accompanied by phase transition at an elevated temperature. The findings confirm the air-sensitivity of LiVO2 observed indirectly in the literature.

Synthesis, characterization and electrochemical performance of Sn3F3PO4 anode material for lithium-ion batteries

Tin fluorophosphate (Sn3F3PO4) powder was synthesized via a microemulsion route. Physical properties of the synthesized material were investigated by means of X-ray powder diffractometry (XRD) and field emission scanning electron microscopy (FE-SEM). The investigation showed that the synthesized powder was crystalline Sn3F3PO4 with needle-like morphology with a thickness of 300–500nm and length of 5–10μm. The electrochemical performance of the synthesized powder as a negative electrode for Li-ion batteries was studied. The results showed that the synthesized Sm3F3PO4 possessed an initial discharge capacity of 1370mAhg−1 and charge capacity of 968mAhg−1 in a potential range of 0.005–3V. In addition, the material showed capacity retention of 70.8% after 30 cycles at a constant current density of 100mAg−1.

Nanosilicon Electrodes for Lithium-Ion Batteries: Interfacial Mechanisms Studied by Hard and Soft X-ray Photoelectron Spectroscopy

Largely based on its very high rechargeable capacity, silicon appears as an ideal candidate for the next generation of negative electrodes for Li-ion batteries. However, a crucial problem with sili ...

A Combinatorial Study of the Sn-Si-C System for Li-Ion Battery Applications

In the present work three pseudobinary libraries of the Sn-Si-C system were produced using combinatorial methods. X-ray diffraction was used to study the structure of these libraries and Mossbauer spectroscopy was employed to probe the atomic environment. Cyclic voltammetry measurements were performed using a multichannel pseudopotentiostat to study the behavior of these materials as negative electrodes for Li-ion batteries. These three libraries were compared in terms of the phases formed, amorphous vs. crystalline structure, the reversible capacity as a function of composition and the capacity retention. The addition of carbon to Sn-Si inhibits the aggregation of Sn into regions of relatively pure tin. This minimization of free tin has the effect of improving cycleability by reducing the adverse effects of volume expansion, by eliminating two-phase coexistence regions during delithiation and lithiation.

Characterization of Carbonaceous Active Materials Used for the Negative Electrode of Li-Ion Batteries and Capacitors

During the course of investigating carbonaceous materials for the active materials of Li-ion batteries (LIB) or supercapacitors (SPC) we have found interesting properties and behaviors of the carbon in contact with an electrolyte containing Li+. In this article the author would like to exhibit these attractive matters. Especially use of carbon fiber (CF) attracted our attention since we can use a single fiber as the working electrode, which enables us to measure not only the conductivity change but also the volume change during Li insertion/extraction. Determination of the lithium diffusion coefficient in carbon could be performed with ease. Surprisingly propylene carbonate showed no decomposition during cathodic polarization of graphite in propylene carbonate electrolyte when we use a single graphitzed fiber. On the other hand, by the use of rounded graphite particle we suggested presence of holes on the graphene layer. We proved that homogeneous distribution of conductivity over the surface of coated electrode is the key factor to keep long cycle life.

High Concentration Dinitrile, 3-Alkoxypropionitrile, and Linear Carbonate Electrolytes Enabled by Vinylene and Monofluoroethylene Carbonate Additives

Li-ion batteries intended to operate over extremes in temperature or at cell voltages approaching 5 V exceed the fundamental capabilities of the electrolytes presently available. The most promising solvents that do meet the fundamental requirements exhibit exceptional instability at the low potentials found with negative electrodes of Li-ion batteries today. Herein, nitrile and linear carbonate electrolytes were stabilized with only the use of a small percentage of additives to enable formulations that may be of use for low temperature and high voltage operating conditions, respectively. In this work, the electrochemical characteristics of Li-ion cells were explored for a variety of electrolytes, with promising performance identified in systems composed predominantly of ethyl methyl carbonate (EMC), 3-methoxypropionitrile (3MPN), or adiponitrile (ADN). Vinylene carbonate (VC) and monofluoroethylene carbonate (FEC) were added in low concentrations (≤5 vol%) to stabilize the interface of the carbon negative electrode and the electrolyte, with FEC proving to be effective across all electrolytes examined herein. The fluoride decomposition products of FEC contributing to the SEI have been identified for the first time without the presence of lithium hexafluorophosphate (LiPF6) in the electrolyte, thereby leading to a clearer explanation of its exceptional protective effect within the SEI.

One-step electrochemical preparation of graphene-based heterostructures for Li storage

We report a facile method to prepare nanoarchitectured metal oxides/graphene hybrids as both positive and negative electrodes for Li-ion batteries. The metal oxides/graphene hybrids were synthesized by deposition of metal oxides and exfoliation of graphene sheets in a one-step electrochemical process. The hybrid electrodes showed high specific capacities with excellent cycling stability. For example, the Fe2O3/graphene anode was able to deliver a discharge capacity of up to 894 mA h g−1 during the 50th cycle at 0.3 C. Co3O4/graphene depicted a discharge capacity of 880 mA h g−1 during the 40th cycle at 0.3 C. The V2O5/graphene cathode delivered a discharge capacity of 208 mA h g−1 during the 100th cycle at 6.8 C.

Comparative Study of Sodium Polyacrylate and Poly(vinylidene fluoride) as Binders for High Capacity Si–Graphite Composite Negative Electrodes in Li-Ion Batteries

To study the effect of different polymer binders on electrochemical performance of the Si composite electrode in rechargeable lithium-ion batteries, sodium polyacrylate (PAANa), sodium carboxymethyl cellulose (CMCNa), and poly(vinylidene fluoride) (PVdF) are utilized as the polymer binders for the preparation of composite electrodes consisting of powdery silicon, graphite, and Ketjen black. The electrodes are examined by cross-sectional observation using a scanning electron microscope after a focused ion beam process, X-ray photoelectron spectroscopy, micro Raman spectroscopy, X-ray diffraction, and a peel test. We report that electrode performance of the Si composites depends on a selection of binders, and PAANa binder remarkably improves the electrochemical lithiation and delithiation performance of the Si–graphite composite electrode compared to that of conventional binders of PVdF and CMCNa. When the electrode is prepared with 30 wt % PAANa binder, the higher initial efficiency is obtained with much improved cyclability. Furthermore, the specific capacity of the electrode reaches 1000 mAh g–1 and exceeds 800 mAh g–1 of reversible capacity during the 30 continuous cycling test. The PAANa polymer binder increases the mechanical strength and adhesive strength as composite electrodes. Furthermore, the polymer layer reduces the electrolyte decomposition at the Si particles and suppresses the capacity deterioration by volume change and pulverization due to Si–Li alloying, compared with PVdF, leading to the better electrochemical reversibility.

On the synthesis conditions for tailoring lithium composition in ramsdellite phases: Application for Li-ion batteries

TiO2 with the ramsdelitte-type (R) structure has a potential use as negative electrode for Li-ion battery due to its high theoretical capacity (335mAhg−1), a weak irreversible loss during the first cycle and a low polarization. However due to its metastability, TiO2 (R) has been rarely reported. In the present work we report on the carbothermal synthesis of some LixTiO2 delithiated R phases (0<x<0.57), from TiO2 to Li2Ti3O7, with ramsdellite-type structure. The variation of the synthesis parameters such as wt% of carbonaceous additive and reductive gas flow has conducted to the formation of poor lithiated LixTiO2 phases and Li2TiO3 as additional phase. Their ratio was found to be strongly dependent on the amount of carbonaceous precursor. These new LixTiO2(R)/Li2TiO3 composites (with (0≤x≤0.57)) were characterized by chemical analysis, X-ray diffraction and thermogravimetric analysis and finally by electrochemical tests. High capacities as well as good cycleability have been reached.

Design of Hierarchical Porous Carbonaceous Foams from a Dual-Template Approach and Their Use as Electrochemical Capacitor and Li Ion Battery Negative Electrodes

Porous carbon foams were prepared by pyrolysis of phenolic resin from a dual-template approach using silica monoliths as hard templates and triblock copolymers as soft templating agents. Macroporosity of 50-80% arose from the Si(HIPE) hard template (the acronym HIPE refers to the high internal phase emulsion process), while the soft template generated micro- or mesoporosity, according to the operating procedure. The final materials exhibited a Brunauer-Emmett- Teller specific surface area of 600-900 m2 3 g-1. Their performances as electrodes for electrochemical capacitors or Li ion battery negative electrodes were investigated. The mesoporous foams gave the best capacitance, up to 20 F 3 g-1. In battery configuration, the microporous foams delivered an irreversible capacity of 500-600 mA 3 h 3 g-1 during the first discharge. Upon charging, partial extraction of Li gave reversible capacities of 125-150 mA 3 h 3 g-1.

Mössbauer spectroscopy: analysis and predictions for Li-ion batteries

Due to their high storage capacity Sn-based materials are of considerable interest as negative electrode for Li-ion batteries. However the strong volume change occurring during the alloy formation strongly limits the electrochemical performances (cycle and time life). Analysis by Mossbauer spectroscopy using model compounds (Sn, Sn-Li and transition metal-Sn alloys) shows that the volume expansion is related to the structural change from a Sn based network to a Li based network. Two types of materials are proposed here to overcome this problem: tin dispersion in an electrochemically inactive oxide matrix with buffer role to absorb volume changes or tin alloying with an inactive transition metal to minimize the volume expansion. The use of Mossbauer spectroscopy (in situ operando mode) allows a dynamic approach which is essential to understand the fundamental causes of ageing on cycling and to define then the key issues to be solved for material’s application.

The Mixing Mechanism during Lithiation of Si Negative Electrode in Li-Ion Batteries: An Ab Initio Molecular Dynamics Study

In order to realize Si as a negative electrode material in commercial Li-ion batteries, it is important to understand the mixing mechanism of Li and Si, and stress evolution during lithiation in Si negative electrode of Li-ion batteries. Available experiments mainly provide the diffusivity of Li in Si as an averaged property, neglecting information regarding diffusivity of Si. However, if Si can diffuse as fast as Li, the stress generated during Li diffusion can be reduced. We, therefore, studied the diffusivity of Li as well as Si atoms in the Si-anode of Li-ion battery using an ab initio molecular dynamics-based methodology. The electrochemical insertion of Li into crystalline Si prompts a crystalline-to-amorphous phase transition. We considered this situation and thus examined the diffusion kinetics of Li and Si atoms in both crystalline and amorphous Si. We find that Li diffuses faster in amorphous Si as compared to crystalline Si, while Si remains relatively immobile in both cases and generates stresses during lithiation. To further understand the mixing mechanism and to relate the structure with electrochemical mixing, we analyzed the evolution of the structure during lithiation and studied the mechanism of breaking of Si-Si network by Li. We find that Li atoms break the Si rings and chains and create ephemeral structures such as stars and boomerangs, which eventually transform to Si-Si dumbbells and isolated Si atoms in the LiSi phase. Our results are found to be in agreement with the available experimental data and provide insights into the mixing mechanism of Li and Si in Si negative electrode of Li-ion batteries.

Composite lithium battery anodes based on carbon@Co 3O 4 nanostructures: Synthesis and characterization

We report on the formation of carbon/Co 3O 4 (C@Co 3O 4) composite nanospheres using a hydrothermal approach, followed by application of a thin coating of monosaccharide-derived carbon veneered on the surface of Co 3O 4 by high temperature calcination. When evaluated as the negative electrode for Li-ion batteries (LIBs), the C@Co 3O 4 structures exhibit attractive energy storage capacity and improved cycle life, over more than 100 repeated discharge/charge cycles. We hypothesize that the improved electrochemical performance of the composite electrodes originates from the enhanced structural stability of the active Co 3O 4 particles, imparted by the carbon coating. Consistent with this hypothesis, post mortem analysis performed on pristine Co 3O 4 and composite C@Co 3O 4 anodes subjected to prolonged cycling indicate that surface cracking, particle breakage, and primary particle fusion evident in the pristine Co 3O 4 material are substantially reduced in anodes comprised of C@Co 3O 4.

Highly Improved Rate Capability for a Lithium-Ion Battery Nano-Li4Ti5O12 Negative Electrode via Carbon-Coated Mesoporous Uniform Pores with a Simple Self-Assembly Method

A mesostructured spinel Li4Ti5O12 (LTO)-carbon nanocomposite (denoted as Meso-LTO-C) with large (>15 nm) and uniform pores is simply synthesized via block copolymer self-assembly. Exceptionally high rate capability is then demonstrated for Li-ion battery (LIB) negative electrodes. Polyisoprene-block-poly(ethylene oxide) (PI-b-PEO) with a sp2-hybridized carbon-containing hydrophobic block is employed as a structure-directing agent. Then the assembled composite material is crystallized at 700 °C enabling conversion to the spinel LTO structure without loss of structural integrity. Part of the PI is converted to a conductive carbon that coats the pores of the Meso-LTO-C. The in situ pyrolyzed carbon not only maintains the porous mesostructure as the LTO is crystallized, but also improves the electronic conductivity. A Meso-LTO-C/Li cell then cycles stably at 10 C-rate, corresponding to only 6 min for complete charge and discharge, with a reversible capacity of 115 mA h g−1 with 90% capacity retention after 500 cycles. In sharp contrast, a Bulk-LTO/Li cell exhibits only 69 mA h g−1 at 10 C-rate. Electrochemical impedance spectroscopy (EIS) with symmetric LTO/LTO cells prepared from Bulk-LTO and Meso-LTO-C cycled in different potential ranges reveals the factors contributing to the vast difference between the rate-capabilities. The carbon-coated mesoporous structure enables highly improved electronic conductivity and significantly reduced charge transfer resistance, and a much smaller overall resistance is observed compared to Bulk-LTO. Also, the solid electrolyte interphase (SEI)-free surface due to the limited voltage window (>1 V versus Li/Li+) contributes to dramatically reduced resistance.

Direct synthesis and coating of advanced nanocomposite negative electrodes for Li-ion batteries via electrospraying

A direct approach for the synthesis and coating of advanced nanocomposite negative electrodes via a single-step process at low temperature is presented. Metal-oxide/PVdF nanocomposites are obtained in one step by electrospray pyrolysis of precursor solutions containing dissolved metal salts together with polyvinylidene fluoride (PVdF) as binder. In this way, small oxide nanoparticles are generated and dispersed in situ in the binder creating nanocomposite structures, while being coated at once as thin electrode layers on stainless steel coin cell cans. The intimate contact between the nanoparticles and the binder favours enhanced adhesion of the materials in the overall electrode structure and adequate electrochemical performances are obtained without any conductive additive. Three nanocomposite oxide/PVdF materials (i.e. SnO 2, CoO and Fe 2O 3) are reported here as preliminary examples of negative electrodes. The results show that this approach is suitable, not only for the fabrication of nanocomposite electrodes for Li-ion batteries, but also for other novel applications.

Tin-Based composite Materials Fabricated by Anodic Oxidation for the Negative Electrode of Li-Ion Batteries

We report an easy, inexpensive and environmentally clean route for fabricating tin-based composite materials with complex texture using anodic oxidation of bulk tin foils in an electrolyte bath based on polyethylenglycol and oxalic acid in the trans-passive region. Electron microscopy data reveal micrometric particles with a complex texture at the nano scale, which is preserved after annealing at 350°C. The characterization by X-ray diffraction and 119Sn Mössbauer spectroscopy showed that the materials consisted of mixtures of tin and tin oxides with amorphous and crystalline structures. Their potential application as negative electrodes for Li-battery in terms of capacity and cycle life is evaluated in lithium test cells. The capacity fade due to volume changes during Li alloying and de-alloying can be averted for these Sn-based composite nanostructures. The materials containing a mixture of SnIV and Sn0 are particularly attractive for batteries demanding low capacity fading.

Production of Si-O-C Nano Composites by Plasma Spray for Negative Electrode of Li-Ion Batteries

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Anatase TiO2 Nanorods as High Capacity Negative Electrodes for Li-ion Batteries

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Hydrides as Negative Electrode for Li-Ion Batteries: New Opportunities for Metal Hydrides and Li-Ion Technologies from Micrometrics to Nanometric Size Range

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