Enhanced electrochemical performance of Li-ion batteries with nanoporous titania as negative electrodes

Nanoporous anatase TiO2(np-TiO2) electrodes have been developed via the anodization of titanium foils in fluoride containing electrolytes,and its application in rechargeable lithium-ion batteries(LIBs) was investigated. Four different types of np-TiO2 electrodes with different pore diameters of 14.7±8.2 nm, 12.8±6.8 nm, 11.0±5.5, and 26.7±13.6 nm were fabricated for evaluating the effect of nanoporous characteristics on the LIB performance. The discharge capacity of the four battery types 1, 2, 3, and 4 were 132.7 m Ah g-1, 316.7 m Ah g-1, 154.3 m Ah g-1,and 228.4 m Ah g-1, respectively. In addition, these electrodes 1, 2, 3, and 4 exhibited reversible capacity of 106.9 m Ah g-1after 295 th,180.9 m Ahg-1 after 220 th, 126.1 m Ah g-1after 150 th, and 206.7 m Ahg-1after 85 th cycle at a rate of 1 C, respectively. It was noted that the cyclic life of the batteries had an inverse relationship, and the capacity had a proportional relationship to the pore diameter. The enhanced electrochemical performance of the nanoporous electrodes can be attributed to the improved conductivity and the enhanced kinetics of lithium insertion/extraction at electrode/electrolyte interfaces because of the large specific surface area of np-TiO2 electrodes.     

Importance of nanostructure for high capacity negative electrode materials for Li-ion batteries

Sn–Co–C alloys are currently used as negative electrode materials for Li-ion batteries. A comparison between sputter deposited and mechanically alloyed Sn–Co–C materials has revealed a difference in the achieved specific capacity of materials prepared by the two methods. Only the sputtered materials reached the expected capacity even though both types of materials showed similar X-ray diffraction patterns. The structure of these materials has been described as being grains of amorphous CoSn embedded in a carbon matrix. Here, the sizes of the CoSn grains were determined using small angle neutron scattering measurements on various Sn₃₀Co₃₀C₄₀ samples. Small grain sizes, on the order of 10 Å, were obtained for the sputtered samples while grain sizes between 55 and 100 Å were obtained for samples with the same composition but prepared by mechanical alloying methods. The inability of the mechanically prepared materials to achieve their theoretical capacity may be due to the larger size of the CoSn grains.     

Goethite nanorods as anode electrode materials for rechargeable Li-ion batteries

Although various transition metal oxides have been reported to act as low potential Li insertion hosts, the oxyhydroxides have remained unexplored to date. We show here that the hydroxide ions present in transition metal oxyhydroxides do not interfere with the lithium uptake and extraction, permitting very good reversibility of the reduction/oxidation reactions. Goethite (α-FeOOH) nanocrystals can uptake and extract large amount of Li via the conversion reaction mechanism, providing a reversible capacity of 500 mA h g⁻¹ at an average potential of 0.85 V vs. Li/Li⁺. The mechanism was examined using a combination of X-ray diffraction, electron microscopy, and the corresponding selected area electron diffractions (SAEDs). The α-FeOOH is reduced into nanoparticles of metallic Fe⁰ embedded in an amorphous matrix of Li₂O and LiOH in the first discharge; the subsequent cyclings are redox reactions between metallic Fe⁰ and Fe₂O₃ clusters.     

Full structural and electrochemical characterization of Li2Ti6O13 as anode for Li-ion batteries

A detailed structural and electrochemical study of the ion exchanged Li(2)Ti(6)O(13) titanate as a new anode for Li-ion batteries is presented. Subtle structural differences between the parent Na(2)Ti(6)O(13), where Na is in an eightfold coordinated site, and the Li-derivative, where Li is fourfold coordinated, determine important differences in the electrochemical behaviour. While the Li insertion in Na(2)Ti(6)O(13) proceeds reversibly the reaction of lithium with Li(2)Ti(6)O(13) is accompanied by an irreversible phase transformation after the first discharge. Interestingly, this new phase undergoes reversible Li insertion reaction developing a capacity of 170 mAh g(-1) at an average voltage of 1.7 V vs. Li(+)/Li. Compared with other titanates this result is promising to develop a new anode material for lithium ion rechargeable batteries. Neutron powder diffraction revealed that Na in Na(2)Ti(6)O(13) and Li in Li(2)Ti(6)O(13) obtained by Na/Li ion exchange at 325 °C occupy different tunnel sites within the basically same (Ti(6)O(13))(2-) framework. On the other hand, electrochemical performance of Li(2)Ti(6)O(13) itself and the phase released after the first full discharge is strongly affected by the synthesis temperature. For example, heating Li(2)Ti(6)O(13) at 350 °C produces a drastic decrease of the reversible capacity of the phase obtained after full discharge, from 170 mAh g(-1) to ca. 90 mAh g(-1). This latter value has been reported for Li(2)Ti(6)O(13) prepared by ion exchange at higher temperature.     

Nickel metal-organic framework nanoparticles as electrode materials for Li-ion batteries and supercapacitors

Journal of Solid State Electrochemistry - Nickel-based metal-organic framework ([Ni(4,4′-bpy)(tfbdc)(H2O)2], Ni-MOF) nanoparticles with the size of 45–250 nm were synthesized...     

LiCoO_2 electrode/electrolyte interface of Li-ion batteries investigated by electrochemical impedance spectroscopy

The storage behavior and the first delithiation of LiCoO2 electrode in 1 mol/L LiPF6-EC:DMC:DEC elec- trolyte were investigated by electrochemical impedance spectroscopy (EIS). It has found that, along with the increase of storage time, the thickness of SEI film increases, and some organic carbonate lithium compounds are formed due to spontaneous reactions occurring between the LiCoO2 electrode and the electrolyte. When electrode potential is changed from 3.8 to 3.95 V, the reversible breakdown of the resistive SEI film occurs, which is attributed to the reversible dissolution of the SEI film component. With the increase of electrode potential, the thickness of SEI film increases rapidly above 4.2 V, due to overcharge reactions. The inductive loop observed in impedance spectra of the LiCoO2 electrode in Li/LiCoO2 cells is attributed to the formation of a Li1-xCoO2/LiCoO2 concentration cell. Moreover, it has been demonstrated that the lithium-ion insertion-deinsertion in LiCoO2 hosts can be well described by both Langmuir and Frumkin insertion isotherms, and the symmetry factor of charge transfer has been evaluated at 0.5.     

PVDF-HFP composite polymer electrolyte with excellent electrochemical properties for Li-ion batteries

Poly (vinylidene fluoride-co-hexafluoropropylene)-based composite polymer electrolyte (CPE) was prepared by phase inversion technique. In this work, we first applied a novel surface-modified sub-micro-sized alumina, PC-401, as ceramic filler. Various electrochemical methods were applied to investigate the electrochemical properties of the polymer electrolytes. We found that the CPE with 10 wt.% PC-401 has excellent electrochemical properties, including the ionic conductivity as high as 0.89 mS cm⁻¹ and the Li-ion transference number of 0.46. Polymer Li-ion batteries using LiFePO₄ as cathode active material exhibited excellent cycling and high-temperature performances. PC-401 shows a promising applicability in the preparation of polymer electrolyte with high electrochemical properties.     

Synthesis and electrochemical properties of high-voltage LiNi0.5Mn1.5O4 electrode material for Li-ion batteries by the polymer-pyrolysis method

A submicron LiNi_0.5Mn_1.5O₄ cathode was synthesized via the pyrolysis of polyacrylate salts as precursor polymerized by reaction of the metal salts with acrylate acid. The structure and morphology of the resulting compound was characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results reveal that the prepared LiNi_0.5Mn_1.5O₄ cathode material has a pure cubic spinel structure and submicron-sized morphology even if calcined at 900 °C and quenched to room temperature. The LiNi_0.5Mn_1.5O₄ electrodes exhibited promising high-rate characteristics and delivered stable discharge capacity (90 mAh/g) with excellent retention capacity at the current density of 50 mA/g between 3.5 and 4.9 V. The capacity of the LiNi_0.5Mn_1.5O₄ electrodes remains stable even after 30 cycles at low or high current density. This polymer-pyrolysis method is simple and particularly suitable for preparation of the spinel LiNi_0.5Mn_1.5O₄ cathode material compared to the conventional synthesis techniques.     

Facile synthesis and long cycle life of SnSb as negative electrode material for Na-ion batteries

We report significant electrochemical performances promoting SnSb as one of the most promising negative electrode material for rechargeable batteries. Appropriately formulated with the carboxymethyl cellulose binder and cycled in fluoroethylene carbonate containing electrolyte, it could sustain a reversible capacity largely exceeding 525 mAh g^− 1 over more than 125 cycles at a rate of C/2 (55 mA/g), with a satisfactory coulombic efficiency of more than 97%. To our knowledge, this is actually the longest cycle life ever reported for an electrode material vs. sodium.     

Model Ge microstructures as anodes for Li-ion batteries

We examine the properties of microstructured Ge electrodes for Li-ion battery applications. Model-microfabricated single-crystalline Ge electrode structures are used to investigate the effects of Cu coating and partial discharging on cycle life. Results show that the Ge microstructures insert Li more isotropically than do comparable ones comprised of Si. A model Ge microbar electrode with a Cu coating is capable of 95 % coulombic efficiency after 40 cycles when the amount of charge is limited. The microstructured Ge electrode is found to exhibit poor performance at higher delithiation rates (above C/5) relative to microstructured Si electrodes. These results provide an understanding of the effects of electrochemical processes on model-microstructured Ge electrodes which may ultimately aid in the development of advanced anodes for Li-ion batteries.     

Amorphous silicon thin films as a high capacity anodes for Li-ion batteries in ionic liquid electrolytes

High lithiation capacity at low red-ox potentials in combination with good safety characteristics makes amorphous Si as a very promising anode material for rechargeable Li batteries.Thin film silicon electrodes were prepared by DC magnetron sputtering of silicon on stainless steel substrates. Their behavior as Li insertion/extraction electrodes was studied by voltammetry and chronopotentiometry at room temperature in the ionic liquid (IL) 1-methyl-1-propylpiperidinium bis(trifluoromethylsuphonil)imide containing 1 M Li bis(trifluoromethylsuphonil)imide. Li/Si cells containing this electrolyte showed good performance with a stable Si electrodes capacity of about 3000 mA h g⁻¹ and a relatively low irreversible capacity. Preliminary results on cycling Si–LiCoO₂ cells using this IL electrolyte are also presented.     

Electrochemical reactivity of In-Pb solid solution as a negative electrode for rechargeable Mg-ion batteries

A composite In-Pb:carbon was successfully synthetized by a two-step mechanochemical synthesis in order to obtain an adequate particles size and structure to investigate the electrochemical reactivity of the In-Pb solid solution towards Mg.A potential synergetic coupling of electroactive elements In and Pb was examined using electrochemical and ex situ X-ray diffraction analyses.The potential profile of the solid solution indicates the formation of Mg₂Pb and Mg In.However,the diffraction study suggests a peculiar electrochemically-driven amorphization of Mg In during the magnesiation,in strong contrast to Mg In crystallization in In-based and In Bi-based electrodes reported in the literature.Combining In and Pb favors the amorphization of Mg In and a high first magnesiation capacity of about 550 m Ah g^-1,but is thereafter detrimental to the material’s reversibility.These results emphasize the possible influence of electrochemically-driven amorphization and crystallization processes on electrochemical performance of battery materials.     

Practical anodes for Li-ion batteries comprising metallurgical silicon particles and multiwall carbon nanotubes

Journal of Solid State Electrochemistry - Silicon is considered to be a very attractive anode material for next-generation lithium-ion batteries due to its high theoretical capacity...     

Sn-0.4BPO4 composite as a promising negative electrode for rechargeable lithium batteries

The structural and textural properties of a Sn-0.4BPO₄ composite material synthesized by ex situ dispersion of β-Sn in a BPO₄ matrix were investigated by using several complementary techniques to study the global order (XRD, TGA-DSC, SEM-XEDS) and the local order (FT-IR, ¹¹⁹Sn Mössbauer spectroscopy and X-ray absorption spectroscopy). The results reveal that the composite material consists of three main components: an electrochemically active species “Sn”, an inactive matrix “BPO₄”, and an amorphous Sn(II) borophosphate which acts as a link between the two former and which improves the cohesion of the composite. The electrochemical performances of the composite material were tested in Swagelok-type cells with metallic Li as counter-electrode. It shows a high reversible capacity of about 500 mAh g^?1 at a C/20 rate, and a very good stability under cycling even at very fast rates of C or C/1.3.     

High performance silicon nanoparticle anode in fluoroethylene carbonate-based electrolyte for Li-ion batteries

Electrodes composed of silicon nanoparticles (SiNP) were prepared by slurry casting and then electrochemically tested in a fluoroethylene carbonate (FEC)-based electrolyte. The capacity retention after cycling was significantly improved compared to electrodes cycled in a traditional ethylene carbonate (EC)-based electrolyte.     

An ionic liquid-type carbon paste electrode for electrochemical investigation and determination of calcium dobesilate

An ionic liquid-type carbon paste electrode (IL-CPE) had been fabricated by replacing non-conductive organic binders with a conductive room temperature ionic liquid, 1-pentyl-3-methylimidazolium hexafluorophosphate (PMIMPF₆). The electrochemical responses of calcium dobesilate were investigated at the IL-CPE and the traditional carbon paste electrode (T-CPE) in 0.05 mol L⁻¹ H₂SO₄, respectively. The results showed the superiority of IL-CPE to T-CPE in terms of provision of higher sensitivity, faster electron transfer and better reversibility. A novel method for determination of calcium dobesilate was proposed. The oxidation peak current was rectilinear with calcium dobesilate concentration in the range of 8.0 × 10⁻⁷ to 1.0 × 10⁻⁴ mol L⁻¹, with a detection limit of 4.0 × 10⁻⁷ mol L⁻¹(S/N = 3) by differential pulse voltammetry. The proposed method was applied to directly determine calcium dobesilate in capsule and urine samples.