Negative Electrode For Lithium-ion Batteries Research Articles

Nanostructured Lithium-Aluminum Alloy Electrodes for Lithium-Ion Batteries

Electrodeposited aluminum films and template-synthesized aluminum nanorods are examined as negative electrodes for lithium-ion batteries. The lithium-aluminum alloying reaction is observed electrochemically with cyclic voltammetry and galvanostatic cycling in lithium half-cells. The electrodeposition reaction is shown to have high faradaic efficiency, and electrodeposited aluminum films reach theoretical capacity for the formation of LiAl (1 Ah/g). The performance of electrodeposited aluminum films is dependent on film thickness, with thicker films exhibiting better cycling behavior. The same trend is shown for electron-beam deposited aluminum films, suggesting that aluminum film thickness is the major determinant in electrochemical performance regardless of deposition technique. Synthesis of aluminum nanorod arrays on stainless steel substrates is demonstrated using electrodeposition into anodic aluminum oxide templates followed by template dissolution. Unlike nanostructures of other lithium-alloying materials, the electrochemical performance of these aluminum nanorod arrays is worse than that of bulk aluminum.

The influence of the local current density on the electrochemical exfoliation of graphite in lithium-ion battery negative electrodes

The local current density related to the exfoliation process of graphite negative electrodes in mixed ethylene carbonate/propylene carbonate electrolytes was controlled by a variation of the current applied to lithium half-cells containing either single type graphite electrodes or electrodes consisting of mixtures of an exfoliating and a non-exfoliating graphite. The partial local current density attributed to graphite passivation and its distribution within the volume of the electrode was found to be a key parameter to explain differences in the exfoliation behaviour observed for graphite electrodes. The local current density is related with a local overpotential which may suppress one of several possible electrochemical processes. In a negative electrode consisting of a mixture of a non-exfoliating and an exfoliating graphite component, the exfoliation of the exfoliation-sensitive graphite component can be completely suppressed when increasing the partial local current density attributed to the graphite exfoliation process above a certain threshold, by either decreasing the amount of exfoliating graphite particles in the electrode or by increasing the total current density, i.e., the specific current. The consideration of the local current density distribution for the electrochemical processes throughout the electrode leads to a more general concept for the graphite passivation behaviour during the first lithium insertion in lithium-ion batteries.

Preparation and electrochemical properties of nano-sized SnF 2 as negative electrode for lithium-ion batteries

Nanocrystalline SnF 2 was prepared via recrystallization of commercially available tin (II) fluoride. The electrochemical performance of tin fluoride as anode material for Li-ion batteries was investigated. The cyclic voltammetry of the obtained material showed occurrence of SnF 2 decomposition at first and a typical reversible alloying/de-alloying process at low potentials. Furthermore, it was found that the synthesized material delivered a high reversible capacity of 1016 mAh g − 1 and a capacity retention of 54.8% after 30 cycles when the electrode was cycled at a current of 100 mA g − 1 .

Graphite materials prepared by HTT of unburned carbon from coal combustion fly ashes: Performance as anodes in lithium-ion batteries

The behaviour as the potential negative electrode in lithium-ion batteries of graphite-like materials that were prepared by high temperature treatment of unburned carbon concentrates from coal combustion fly ashes was investigated by galvanostatic cycling. Emphasis was placed on the relation between the structural/morphological and electrochemical characteristics of the materials. In addition, since good electrode capacity retention on cycling is an important requirement for the manufacturing of the lithium-ion batteries, the reversible capacity provided by the materials prepared on prolonged cycling (50 cycles) was studied and the results were compared with those of petroleum-based graphite which is commercialized as anodic material for lithium-ion batteries. The graphite-like materials prepared lead to battery reversible capacities up to ∼310mAhg−1 after 50 cycles, these values were similar to those of the reference graphite. Moreover, they showed a remarkable stable capacity along cycling and low irreversible capacity. Apparently, both the high degree of crystallinity and the irregular particle shape with no flakes appear to contribute to the good anodic performance in lithium-ion batteries of these materials, thus making feasible their utilization to this end.

Electrodeposited porous-microspheres Li–Si films as negative electrodes in lithium-ion batteries

A porous-microspheres Li–Si film (PMLSF) is prepared by multi-step constant current (MSCC) electrodeposition on Cu foil. Its structure and morphology are characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM). As negative electrodes of lithium-ion batteries, the PMLSF electrode delivers the first gravimetric and geometric charge capacities of 2805.7 mA h g −1 and 621.9 μA h cm −2 at the current density of 25.5 μA cm −2, and its initial coulombic efficiency is as high as 98.2%. When the PMLSF electrode is cycled in VC-containing electrolyte, the superior cycling performance can be obtained. After 50 cycles, 96.0% of its initial capacity is retained at the current density of 50.0 μA cm −2. Electrochemical impedance spectra (EIS) research confirms the positive effect of VC additive on the behavior of the PMLSF electrode.

Self-discharge behavior of polyacenic semiconductor and graphite negative electrodes for lithium-ion batteries

Variations in open-circuit potential (OCP) of artificial graphite and polyacenic semiconductor (PAS) negative electrodes have been investigated as a function of the storage time in alkylcarbonate-based electrolyte solutions after their cathodic charging (electrochemical lithiation) to discuss self-discharge phenomena of these negative electrodes for lithium ion batteries. The OCP of the graphite showed a plateau at ca. 90 mV vs. Li/Li + for a long period (>8 × 10 5 s), which suggested the retention of a stage structure of lithiated graphite during the storage. The lithiated PAS electrode gave gradual changes in OCP during the storage in the carbonate-based electrolyte solutions, suggesting continuous loss of Li species in the electrode. Variations in the interfacial resistance determined by an ac method, corresponding to the changes in the structure and properties at the electrode/electrolyte interface, also showed different features for the lithiated graphite and PAS electrodes. The mechanisms of self-discharging for these carbonaceous electrodes are discussed from the results of the influences of temperature and additives on the OCP variations.

Atomistic mechanisms of lithium insertion in amorphous silicon

Understanding the lithium–silicon alloying behavior is essential for achieving maximum charge capacity in the negative electrodes of lithium-ion batteries. Our atomistic simulations show that in amorphous silicon with a disordered network structure, inserted lithium atoms can find equilibrium positions in the interstices of big rings. Alternatively, lithium is incorporated into the network by the destruction and reformation of smaller rings. These atomic-level mechanisms are characterized by using the network topology measure of ring statistics, which are correlated to the lithiation responses of silicon electrodes. The results reveal the influence of lithium concentrations on the electro-chemical–mechanical behavior of silicon. Implications on the reversibility and dynamics of the lithiation process are discussed.

Carboxymethylcellulose and carboxymethylcellulose-formate as binders in MgH2–carbon composites negative electrode for lithium-ion batteries

Influence of carboxymethylcellulose sodium salt (CMC) and carboxymethylcellulose-formate (CMC-f) binders on the cyclability of a MgH2–33.3% CMC type binder–33.3%Ct,x electrodes has been investigated for the first time. These electrodes show a large reversible capacity of 1800–1900mAhg−1 at an average voltage of 0.5V vs. Li+/Li° which is suitable for the negative electrode in lithium-ion batteries. Moreover, addition of CMC or CMC-f binder with Ct,x carbon leads to an improved capacity retention with 240mAhg−1 and 542mAhg−1, respectively, compare to 174mAhg−1 for MgH2–18%Ct,x after 40 cycles.

A new form of manganese carbonate for the negative electrode of lithium-ion batteries

A reverse micelles method is used in the synthesis of manganese carbonate. The use of cetyl-trimethylammonium bromide surfactant and hexanol cosurfactant allows the preparation of a new monodispersed form of MnCO3. Particles with a regular shape and ca. 200nm edges are observed by electron microscopy. The electrochemical reaction with lithium of the manganese carbonate leads to the formation of the manganese metal and lithium carbonate as the main side product, which yields higher capacity than graphite and good capacity retention. Submicron MnCO3 could replace other more toxic and expensive anodes used in recent commercial Li-ion products.

Alkali Chloride Coating for Graphite Electrode of Lithium-Ion Batteries

Battery performance of a graphite electrode for negative electrodes of lithium-ion batteries was successfully enhanced by pretreatment of graphite powders with lithium, sodium, and potassium chloride aqueous solutions. In the process of the pretreatment, graphite powders were simply dispersed in the aqueous solutions and dried to coat the graphite powder with alkali chloride solid after filtration. When the optimum concentrations of each chloride, LiCl, NaCl, and KCl, were adopted for the pretreatment, the irreversible electroreduction capacity at the initial cycle was reduced by the chloride coating which was capable of modifying the solid electrolyte interphase formed on the graphite electrode surface, furthermore, the reversible capacity at a relatively high rate was improved by the coating from ≊ during successive cycles in a ethylene carbonate:diethyl carbonate electrolyte solution. The origins of the improvement were discussed from surface and electrochemical analyses.

SnCo nanowire array as negative electrode for lithium-ion batteries

Amorphous SnCo alloy nanowires (NWs) grown inside the channels of polycarbonate membranes by potentiostatic codeposition of the two metals (SnCo- PM) were tested vs. Li by repeated galvanostatic cycles in ethylene carbonate-dimethylcarbonate – LiPF 6 for use as negative electrode in lithium ion batteries. These SnCo electrodes delivered an almost constant capacity value, near to the theoretical for an atomic ratio Li/Sn of 4.4 over more than 35 lithiation–delithiation cycles at 1 C. SEM images of fresh and cycled electrodes showed that nanowires remain partially intact after repeated lithiation–delithiation cycles; indeed, several wires expanded and became porous. Results of amorphous SnCo nanowires grown inside anodic alumina membranes (SnCo- AM) are also reported. The comparison of the two types of NW electrodes demonstrates that the morphology of the SnCo- PM is more suitable than that of the SnCo- AM for electrode stability over cycling. Optimization of NW technology should thus be a promising route to enhancing the mechanical strength and durability of tin-based electrodes.

Carbothermal synthesis of Sn-based composites as negative electrode for lithium-ion batteries

The composite [Sn–BPO 4/ xC] to be used as negative electrode material for the storage of electrochemical energy was obtained by dispersing electroactive tin species onto a BPO 4 buffer matrix by carbothermal reduction of a mixture of SnO 2 and nanosized BPO 4. This composite material was thoroughly characterized by X-ray diffraction, Scanning Electron Microscopy, 119Sn Mössbauer spectroscopy and Raman spectroscopy. The electrochemical tests of this new material highlight its very interesting electrochemical properties, i.e., a discharge capacity of 850 mAh g −1 for the first cycle and reversible capacity around 585 mAh g −1 at C/5 rate. These electrochemical performances are attributed to the very high dispersion and stabilisation of tin metal particles onto the BPO 4 matrix. The irreversible capacity observed for the first charge/discharge cycle is due the reduction of interfacial Sn II species and to the passivation of the anode surface by liquid electrolyte decomposition (formation of the SEI layer).

Comparative study of NiSb 2 and FeSb 2 as negative electrodes for Li-ion batteries

Crystalline FeSb 2 powder prepared by ceramic route is examined as negative electrodes for lithium-ion batteries. The complete reaction mechanism of FeSb 2 is investigated by 121Sb and 57Fe Mössbauer spectroscopy as well as magnetic measurements and the results are correlated with a previous in situ XRD characterization. On the first discharge the reaction with Li proceeds through a biphasic process transforming FeSb 2 into a new Li xFe ySb 2 phase, and this ternary phase is then converted into fcc Li 3Sb and metallic Fe nanoparticles. The combination of Mössbauer spectroscopy and magnetic analyses leads i) to a better understanding of the FeSb 2 → ternary phase reaction and concomitantly allowed ii) to specify the stoichiometry of the new ternary phase. On charge, the extrusion of lithium includes the back conversion of the Li 3Sb/Fe mixture into both Li 4Fe 0.5Sb 2 and metallic Sb, which are the main active species for the following cycles, responsible for the poor cycling life of the FeSb 2 electrode. The nature of these resulting products is quite different from that previously observed for the isotype NiSb 2 electrode which is characterized by a highly reversible mechanism.

Carbothermal Synthesis of Sn-Based Composites as Negative Electrode for Lithium-Ion Batteries

not Available.

Computational Study on the Solubility of Lithium Salts Formed on Lithium Ion Battery Negative Electrode in Organic Solvents

The solubility of lithium salts, found in solid-electrolyte interface (SEI) films on the anode surface in lithium ion battery cells, has been examined in organic solvents through atomistic computer simulations. The salts included lithium oxide (Li2O), lithium carbonate (Li2CO3), lithium oxalate ([LiCO2]2), lithium fluoride (LiF), lithium hydroxide (LiOH), lithium methoxide (LiOCH3), lithium methyl carbonate (LiOCO2CH3), lithium ethyl carbonate (LiOCO2C2H5), and dilithium ethylene glycol dicarbonate (([CH2OCO2Li]2: LiEDC). The organic solvents were dimethyl carbonate (DMC) and ethylene carbonate (EC). The atomic charges in the force field have been fitted to the electrostatic potential obtained from density functional theory calculations for each salt. The heat of dissolution in DMC for the salts calculated from computer simulations ranged from exothermic heats for the organic salts in general to endothermic heats for the inorganic salts in the order of LiEDC < LiOCO2CH3 < LiOH < LiOCO2C2H5 < LiOCH3 < LiF ...

Cycling parameters of MAG graphite as anode material for lithium-ion batteries

Integrated analysis of the cycling parameters (reversible specific capacity, Coulomb efficiency, irreversible loss of cycle capacity, accumulated irreversible capacity, and retention of reversible capacity) of synthetic graphite of MAG brand as an active material for the negative electrode of lithium-ion batteries was made.

Lithium polyacrylate as a binder for tin–cobalt–carbon negative electrodes in lithium-ion batteries

A lithium polyacrylate (Li-PAA) binder has been developed by 3M Company that is useful with electrodes comprising alloy anode materials. This binder was used to prepare electrodes made with Sn 30Co 30C 40 material prepared by mechanical attrition. The electrochemical performance of electrodes using Li-PAA binder was characterized and compared to those using sodium carboxymethyl cellulose (CMC) and polyvinylidene fluoride (PVDF) binders. The Sn 30Co 30C 40 electrodes using Li-PAA and CMC binders show much smaller irreversible capacity than the ones using PVDF binder. Poor capacity retention is observed when PVDF binder is used. By contrast, the electrodes using Li-PAA binder show excellent capacity retention for Sn 30Co 30C 40 materials and a specific capacity of 450 mAh/g is achieved for at least 100 cycles. The results suggest that Li-PAA is a promising binder for electrodes made from large-volume change alloy materials.

Tin-based materials as negative electrodes for Li-ion batteries: Combinatorial approaches and mechanical methods

Graphite has been used as the negative electrode in lithium-ion batteries for more than a decade. To attain higher energy density batteries, silicon and tin, which can alloy reversibly with lithium, have been considered as a replacement for graphite. However, the volume expansion of these metal elements upon lithiation can result in poor capacity retention. Alloying the active metal element with an inactive material can limit the overall volume expansion and improve cycle life. This paper presents a summary of tin-based materials as negative electrodes. After reviewing attempts to improve and understand the electrochemical behaviour of metallic tin and its oxides, the focus turns to alloys of tin with a transition metal (TM) and, optionally, carbon. To do so, a combinatorial sputtering technique was used to simultaneously prepare many different compositions of Sn-TM-based materials. The structural and electrochemical results of these samples are presented and they show that cobalt is the preferred TM to give optimal performance. Finally, a comparison of a Sn–Co–C negative electrode material prepared by a rapid quenching method (sputtering) with a material prepared by an economical milling method (mechanical attrition) is presented and discussed. Copyright © 2010 John Wiley & Sons, Ltd.

Graphite‐Grafted Silicon Nanocomposite as a Negative Electrode for Lithium‐Ion Batteries

Graphite‐Grafted Silicon Nanocomposite as a Negative Electrode for Lithium‐Ion Batteries

Influence of alkali ion doping on the electrochemical performances of tin-based composite materials

In this paper, we report an investigation of three tin-based composite materials as negative electrodes for lithium-ion batteries. Theses composites were synthesized by solid state reaction from dispersion of micrometric tin into BPO 4, Li-doped BPO 4 (LiBPO) and Na-substituted BPO 4 (NaBPO) matrix, respectively. We have investigated more particularly the influence of the two alkaline ions (Li +, Na +) introduced into the matrix on electrochemical performances. The morphology of powders was observed by SEM and the composition studied by EDX analysis. The conductivity measurements showed that the modified BPO 4 matrixes (Li or Na) exhibit improved conductivity ( σ RT = 2 × 10 −11 S cm −1 for NaBPO). A focus of our interest was to relate the nature and structural composition of the composite interface between active tin and inactive matrix to the irreversible capacity in this type of composite materials. The electrochemical analysis shows a decrease of the irreversible capacity for the composite based on modified matrixes (around 150 and 190 mAh g −1 for SnNaBPO and SnLiBPO, respectively) with respect to the reference composite SnBPO (245 mAh g −1).