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1.
Insertion/extraction of lithium ions into/from Bi 2Se 3 crystals was investigated by means of cyclic voltammetry. The process of insertion is reflected in the appearance of two bands on voltammograms at ∼1.7 and ∼1.5 V, corresponding to the insertion of Li + ions into octahedral and tetrahedral sites of the van der Waals gap of these layered crystals. The process of extraction of Li + ions from the gap results in the appearance of four bands on the voltammograms. The bands 1 and 2 at ∼2.1 and ∼2.3 V correspond to the extraction of a part of Li + guest ions from the octahedral and tetrahedrals sites and this extraction has a character of a reversible intercalation/deintercalation process. A part of Li + ions is bound firmly in the crystal due to the formation of negatively charged clusters of the (LiBiSe 2.Bi 3Se 4−) type. A further extraction of Li + ions from the van der Waals gap is associated with the presence of bands 3 and 4 placed at ∼2.5 and ∼2.7 V on the voltammograms as their extraction needs higher voltage due to the influence of negative charges localized on these clusters. 相似文献
2.
A Na 3V 2(PO 4) 3 sample coated uniformly with a layer of 6 nm carbon has been successfully synthesized by a one-step solid state reaction. This material shows two flat voltage plateaus at 3.4 V vs. Na +/Na and 1.63 V vs. Na +/Na in a nonaqueous sodium cell. When the Na 3V 2(PO 4) 3/C sample is tested as a cathode in a voltage range of 2.7-3.8 V vs. Na +/Na, its initial charge and discharge capacities are 98.6 and 93 mAh/g. The capacity retention of 99% can be achieved after 10 cycles. The electrode shows good cycle performance and moderate rate performance. When it is tested as an anode in a voltage range of 1.0-3.0 V vs. Na +/Na, the initial reversible capacity is 66.3 mAh/g and the capacity of 59 mAh/g can be maintained after 50 cycles. These preliminary results indicate that Na 3V 2(PO 4) 3/C is a new promising material for sodium ion batteries. 相似文献
3.
Copper phosphide (CuP 2) and lithium copper phosphide (Li 1.75-Cu 1.25P 2) were synthesized by high-energy ballmilling at room temperature. The electrochemical reactions between lithium and these samples have been studied. The first lithium insertion into the CuP 2 phase till 0.0 V vs. Li leads to copper reduction and the formation of lithium phosphide (Li 3P), corresponding to a long voltage plateau. The subsequent lithium extraction until 1.3 V vs. Li presents three voltage plateaus related to the formation of new phases such as Li 2CuP, giving a reversible capacity about 810 mAh/g and faradic yield about 61%. It means that both copper and phosphorus face a change of the oxidation state for the electrochemical insertion and extraction. Lithium copper phosphide exhibits a similar reaction process. However, it provides a reversible capacity of 750 mAh/g and faradic yield of 100% at the first cycle. 相似文献
4.
The new ramsdellite series LiTi 2−yV yO 4 (0≤ y≤1) has been prepared by conventional solid state chemistry techniques and was characterized by X-ray powder diffraction and electron diffraction. To our knowledge, this is the first report on ramsdellites containing vanadium. The magnetic behaviour of these ramsdellites is strongly influenced by its vanadium content. In this sense, LiTi 2O 4 ( y=0) exhibits metallic-like temperature independent paramagnetism, but d electrons tend to localize with increasing V content. LiTiVO 4, though also paramagnetic, follows then the Curie-Weiss law. The crossover from delocalized to localized electrons is observed between compositions y=0.6 and 0.8. For y≥0.8 the magnetic results evidence an isovalent substitution mechanism of trivalent Ti by V. The electrochemical lithium intercalation and deintercalation chemistry of LiTi 2−yV yO 4 is grouped into two different operating voltage regions. Reversible lithium deintercalation of vanadium-substituted ramsdellite titanates LiTi 2−yV yO 4 in the high voltage range 2-3 V vs. Li occurs in two main steps, one at about 2 V and the other at about 3 V. The 3 V process capacity increases with the vanadium content, while the 2 V capacity decreases at the same time. The vanadium to titanium substitution rate in LiTi 2O 4 was found to be beneficial to the specific energy in as much as a 50% increase (1 V) of the working voltage is observed. On the other hand, reversible lithium intercalation in vanadium-substituted ramsdellite titanates LiTi 2−yV yO 4 in the low voltage range 1-2 V vs. Li occurs in one main single step, in which the capacity is not affected by the vanadium content, although vanadium-doping produces an improved capacity retention with an excellent cycling behaviour observed for y≤0.6. 相似文献
5.
The effects of nitrogen on the electrochemical properties of silicon-nitrogen (Si 1−xN x) thin films were examined in terms of their initial capacities and cycling properties. In particular, Si 0.76N 0.24 thin films showed negligible initial capacity but an abrupt capacity increase to ∼2300 mA h/g after ∼650 cycles. The capacity of pure Si thin films was deteriorated to ∼20% of the initial level after 200 cycles between 0.02 and 1.2 V at 0.5 C (1 C=4200 mA/g), whereas the Si 0.76N 0.24 thin films exhibited excellent cycle-life performance after ∼650 cycles. In addition, the Si 0.76N 0.24 thin films at 50 °C showed an abrupt capacity increase at an earlier stage of only ∼30 cycles. The abnormal electrochemical behaviors in the Si 0.76N 0.24 thin films were demonstrated to be correlated with the formation of Li 3N and Si 3N 4. 相似文献
6.
Electrochemical lithium insertion studies on WNb 12O 33 synthesized by solid state reaction (SSR) are carried out in the voltage range 1.0-3.2 V. During first discharge 15.6 Li are inserted with a specific capacity of 221 mAh/g. WNb 12O 33 is also synthesized by sol-gel (SG) technique with a view to enhance the rate capability and cycling properties. The SSR and SG samples are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and galvanostatic cycling. Electrochemical cycling performance of SG samples is superior to that of the SSR sample at high ‘C’ rates. The sample synthesized by SG method exhibits high specific capacity of 142 mAh/g after 20 cycles at 20C rate. 相似文献
7.
A new type of three-dimensional (3D) oxy-phosphate materials are explored for the application of Li and Na batteries. The molybdenum tungsten oxy phosphate, MoWO3(PO4)2, was synthesized by solid-state method and evaluated for Li/Na insertion/de-insertion electrode material for the first time. The cell at charged state (vs. Li+/Li) showed a discharge capacity of 786 mAh g−1 within the voltage window of 0.3 V with amorphization of crystalline MoWO3(PO4)2 as observed from ex-situ powder XRD analysis. The structural integrity was revealed in this material, even with nearly more than 5 Li+ ions into the lattice, leading to the discharge capacity of 250 mAh g−1. The reversible charge/discharge behavior with insertion/de-insertion of 2.4 Li+ ions in the voltage range of 1.65 − 3.5 V resulted in 110 and 95 mAh g−1 at C/10 and C/5 rates, respectively. On the other hand, poor cycling performance was noticed for Na ion insertion and desertion, with a discharge capacity of 250 mAh/g within the voltage range of 0.3 − 3.5 V (vs. Na+/Na). 相似文献
8.
Antimony nitride thin film has been successfully fabricated by magnetron sputtering method and its electrochemistry with lithium was investigated for the first time. The reversible discharge capacity of Sb 3N/Li cells cycled between 0.3 V and 3.0 V was found above 600 mAh/g. By using transmission electron microscopy and selected area electron diffraction measurements, the conversion reaction of Sb 3N into Li 3Sb and Li 3N was revealed during the lithium electrochemical reaction of Sb 3N thin film electrode. The high reversible capacity and the good cycleability made Sb 3N one of promising anode materials for future rechargeable lithium batteries. 相似文献
9.
To find new cathode materials for future applications in lithium-ion batteries, lithium transition metal fluorides represent an interesting class of materials. In principle the Li intercalation voltage can be increased by replacing oxygen in the cathode host structure with the more electronegative fluorine. A facile pyrolytic sol–gel process with trifluoroacetic acid as fluorine source was established to synthesize monoclinic Li 3FeF 6 using nontoxic chemicals. The acicular Li 3FeF 6 powder was characterized with X-ray diffraction and a detailed structure model was calculated by Rietveld analysis. For the preparation of cathode films to cycle versus lithium monoclinic Li 3FeF 6 was ball milled with carbon and binder down to nanoscale. After 100 cycles galvanostatic cycling (C/20) 47 % fully reversible capacity of the initial capacity (129 mAh/g) could be retained. To the best of our knowledge the results presented in this work include the first rate performance test for monoclinic Li 3FeF 6 up to 1 C maintaining a capacity of 71 mAh/g. The redox reaction involving Fe 3+/Fe 2+ during Li insertion/extraction was confirmed by post-mortem XPS and cyclic voltammetry. 相似文献
10.
Using LiI as the reducing agent, the compound O2-Li (2/3)+x(Ni 1/3Mn 2/3)O 2, x∼1/3 (O2(Li+ x)) has been prepared from the O2-Li 2/3(Ni 1/3Mn 2/3)O 2 (O2(Li)). Cyclic voltammetry and voltage-capacity profiles of the O2(Li+ x) phase are qualitatively different from that of O2(Li) phase. The first extraction capacity of O2(Li+ x) at C/10 rate is 190 mAh/g corresponding to the removal of 2/3 mole of Li from the compound. At C/5 rate it delivers a reversible capacity of 158 mAh/g at 25 °C and 184 mAh/g at 50 °C (vs Li metal; voltage window 2.5–4.6 V). In Li-ion cells, with MCMB anode and O2(Li+ x) as cathode, a discharge capacity of 140 mAh/g was obtained at C/5 rate in the voltage window 2.5–4.5 V (25 °C). The charge–discharge cycling performance and the cyclic voltammograms reveal that O2(Li) and O2(Li+ x) do not convert to the spinel structure. 相似文献
11.
A new vanado-molybdate LiMg 3VMo 2O 12 has been synthesized, the crystal structure determined an ionic conductivity measured. The solid solution Li 2−zMg 2+zV zMo 3−zO 12 was investigated and the structures of the z=0.5 and 1.0 compositions were refined by Rietveld analysis of powder X-ray (XRD) and powder neutron diffraction (ND) data. The structures were refined in the orthorhombic space group Pnma with a∼5.10, b∼10.4 and c∼17.6 Å, and are isostructural with the previously reported double molybdates Li 2M2(MoO 4) 3 ( M=M 2+, z=0). The structures comprise of two unique (Li/Mg)O 6 octahedra, (Li/Mg)O 6 trigonal prisms and two unique (Mo/V)O 4 tetrahedra. A well-defined 1:3 ratio of Li +:Mg 2+ is observed in octahedral chains for LiMg 3VMo 2O 12. Li + preferentially occupies trigonal prisms and Mg 2+ favours octahedral sheets. Excess V 5+ adjacent to the octahedral sheets may indicate short-range order. Ionic conductivity measured by impedance spectroscopy (IS) and differential scanning calorimetry (DSC) measurements show the presence of a phase transition, at 500-600 °C, depending on x. A decrease in activation energy for Li + ion conductivity occurs at the phase transition and the high temperature structure is a good Li + ion conductor, with σ=1×10 −3-4×10 −2 S cm −1 and Ea=0.6 to 0.8 eV. 相似文献
12.
Lithium iron phospho-olivine cathode material with optimized lithium amount for lithium-ion batteries was successfully prepared from low cost Fe 2O 3 as raw materials by thermal reduction method. The as-obtained material showed a reversible discharge capacity of 153.8 mAh g –1 in the voltage window of 2.0–4.2 V at half-cell level. The pouch-typed cells with prepared Li 1.05FePO 4 were assembled to investigate electrochemical performance at level of full-cell. The results show that the assembled pouch-typed full-cells present better rate capability and cycle life. The low-cost approach reported here firstly sheds light on application of mass production of olivinestructured LiFePO 4 at level of full-cell. 相似文献
13.
The transport properties and lithium insertion mechanism into the first mixed valence silver-copper oxide AgCuO 2 and the B-site mixed magnetic delafossite AgCu 0.5Mn 0.5O 2 were investigated by means of four probes DC measurements combined with thermopower measurements and in situ XRD investigations. AgCuO 2 and AgCu 0.5Mn 0.5O 2 display p-type conductivity with Seebeck coefficient of Q=+2.46 and +78.83 μV/K and conductivity values of σ=3.2×10 −1 and 1.8×10 −4 S/cm, respectively. The high conductivity together with the low Seebeck coefficient of AgCuO 2 is explained as a result of the mixed valence state between Ag and Cu sites. The electrochemically assisted lithium insertion into AgCuO 2 shows a solid solution domain between x=0 and 0.8Li + followed by a plateau nearby 1.7 V (vs. Li +/Li) entailing the reduction of silver to silver metal accordingly to a displacement reaction. During the solid solution, a rapid structure amorphization was observed. The delafossite AgCu 0.5Mn 0.5O 2 also exhibits Li +/Ag + displacement reaction in a comparable potential range than AgCuO 2; however, with a prior narrow solid solution domain and a less rapid amorphization process. AgCuO 2 and AgCu 0.5Mn 0.5O 2 provide a discharge gravimetric capacity of 265 and 230 mA h/g above 1.5 V (vs. Li +/Li), respectively, with no evidence of a new defined phases. 相似文献
14.
Electrochemical behavior and stability of spinel Li 4Ti 5O 12 are investigated in a broad voltage window (0.0–5.0 V vs. Li/Li +). The voltage profile of the Li 4Ti 5O 12 electrode shows a plateau region at 1.55 V and two sloped regions below 1.55 V when the electrode is cycled between 0.0 and
2.0 V. It is found that Li 4Ti 5O 12 maintains high lithium storage characteristic with the increase of the current density. Moreover, Li 4Ti 5O 12 shows excellent rate performance in 0.0–2.0 V and good cyclic performances in 0.0–4.0 and 1.0–5.0 V. Besides, the crystal
structure is kept when it is cycled between 0.0 and 5.0 V. 相似文献
15.
Copolymer, poly(acrylonitrile- co-methyl methacrylate) (P(AN- co-MMA)), was synthesized by solution polymerization with different mole ratios of monomers, acrylonitrile (AN) and methyl methacrylate (MMA). Polyethylene (PE) supported copolymer and gel polymer electrolyte (GPE) were prepared with this copolymer and their performances were characterized with FTIR, TGA, SEM, and electrochemical methods. It is found that the GPE using the PE-supported copolymer with AN to MMA = 4:1 (mole) exhibits an ionic conductivity of 2.06 × 10 −3 S cm −1 at room temperature. The copolymer is stable up to 270 °C. The PE-supported copolymer shows a cross-linked porous structure and has 150 wt% of electrolyte uptake. The GPE is compatible with anode and cathode of lithium ion battery at high voltage and its electrochemical window is 5.5 V (vs. Li/Li +). With the application of the PE-supported GPE in lithium ion battery, the battery shows its good rate and initial discharge capacity and cyclic stability. 相似文献
16.
Effect of surface fluorination and conductive additives on the charge/discharge behavior of lithium titanate (Li 4/3Ti 5/3O 4) has been investigated using F 2 gas and vapor grown carbon fiber (VGCF). Surface fluorination of Li 4/3Ti 5/3O 4 was made using F 2 gas (3 × 10 4 Pa) at 25-150 °C for 2 min. Charge capacities of Li 4/3Ti 5/3O 4 samples fluorinated at 70 °C and 100 °C were larger than those for original sample at high current densities of 300 and 600 mA/g. Optimum fluorination temperatures of Li 4/3Ti 5/3O 4 were 70 °C and 100 °C. Fibrous VGCF with a large surface area (17.7 m 2/g) increased the utilization of available capacity of Li 4/3Ti 5/3O 4 probably because it provided the better electrical contact than acetylene black (AB) between Li 4/3Ti 5/3O 4 particles and nickel current collector. 相似文献
17.
Polycrystalline samples of La 18Li 8Rh 4MO 39 ( M=Ti, Mn, Ru) have been prepared by a solid-state method and studied by neutron powder diffraction. They are isostructural with La 18Li 8Rh 5O 39 and adopt the cubic space group with a ∼12.22 Å. Their structure consists of a La-O framework containing intersecting channels that run along 〈111〉. These channels are occupied by chains made up of alternating, face-sharing trigonal-prismatic and octahedral coordination polyhedra; there are two crystallographically distinct types of octahedral site. The prisms are occupied by Li and the transition metals are disordered over the two octahedral sites. 相似文献
18.
The magnetic, thermoelectric, and structural properties of Li xNa yCoO 2, prepared by intercalation and deintercalation chemistry from the thermodynamically stable phase Li 0.41Na 0.31CoO 2, which has an alternating Li/Na sequence along the c-axis, are reported. For the high Li-Na content phases Li 0.41Na 0.31CoO 2 and Li 0.40Na 0.43CoO 2, a sudden increase in susceptibility is seen below 50 K, whereas for Li 0.21Na 0.14CoO 2 an antiferromagnetic-like transition is seen at 10 K, in spite of a change from dominantly antiferromagnetic to dominantly ferromagnetic interactions with decreasing alkali content. The Curie constant decreases linearly with decreasing alkali content, at the same time the temperature-independent contribution to the susceptibility increases, indicating that as the Co becomes more oxidized the electronic states become more delocalized. Consistent with this observation, the low alkali containing phases have metallic-like resistivities. The 300 K thermopowers fall between 30 μV/K ( x+ y=0.31) and 150 μV/K ( x+ y=0.83). 相似文献
19.
The pure Cr 2O 3 coated Li 4Ti 5O 12 microspheres were prepared by a facile and cheap solutionbased method with basic chromium(III) nitrate solution (pH=11.9). And their Li-storage properties were investigated as anode materials for lithium rechargeable batteries. The pure Cr 2O 3 works as an adhesive interface to strengthen the connections between Li 4Ti 5O 12 particles, providing more electric conduction channels, and reduce the inter-particle resistance. Moreover, LixCr 2O 3, formed by the lithiation of Cr 2O 3, can further stabilize Li 7Ti 5O 12 with high electric conductivity on the surface of particles. While in the acid chromium solution (pH=3.2) modification, besides Cr 2O 3, Li 2CrO 4 and TiO 2 phases were also found in the final product. Li 2CrO 4 is toxic and the presence of TiO 2 is not welcome to improve the electrochemical performance of Li 4Ti 5O 12 microspheres. The reversible capacity of 1% Cr 2O 3-coated sample with the basic chromium solution modification was 180 mAh/g at 0.1 C, and 134 mAh/g at 10 C. Moreover, it was even as high as 127 mAh/g at 5 C after 600 cycles. At-20℃, its reversible specific capacity was still as high as 118 mAh/g. 相似文献
20.
The lithiation mechanism of the spinel LiCuVO 4 was studied by X-ray diffraction, XPS, and electrochemical measurements using the lithium cell with the spinel cathode. The lithiation proceeded by the following steps: (1) in the multiphasic reaction for x < 1.5 in Li 1+xCuVO 4, the LiCuVO 4 spinel transforms to a new phase, Li 2.5Cu 0.5VO 4, and Cu metal; (2) in the monophasic electrochemical displacement reaction for 1.5 < x < 2.0, the copper ions extrude from Li 2.5Cu 0.5VO 4 with lithium intercalation, which forms Li 3VO 4 and Cu metal; (3) in the intercalation reaction for 2.0 < x < 5.0, lithium ions intercalate into Li 3VO 4 with several reaction steps. The new phase, Li 2.5Cu 0.5VO 4, lithiated reversibly with the electrochemical displacement between copper and lithium ions. 相似文献
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