Effects of carbon coating on the electrochemical properties of sulfur cathode for lithium/sulfur cell

Carbon-coated sulfur cathodes were prepared by sputtering method and electrochemical properties of lithium/sulfur cells were investigated. As a result of charge/discharge test, sulfur cathode having carbon layer of 180 Å showed the highest capacity of 1178 mA hg⁻¹ at first discharge. Moreover, discharge capacity showed about 500 mA hg⁻¹ until 50th cycle, which is two times larger than that of no-coated sulfur cathode. This capacity increase could be considered due to the decrease of polysulfides dissolution and the enhancement of electrical contact by surface carbon layer. The changes of sulfur cathode during discharge process were investigated by SEM observation, XRD and DSC measurements. From these results, a discharge reaction mechanism of lithium/carbon-coated sulfur cell was suggested.     

Galvanostatic cycling of vanadium oxide (V6O13) in a nonaqueous secondary lithium cell

The galvanostatic cycling of Li(Al)-V₆O₁₃ cells in 1M LiAsF₆/propylene carbonate (PC)-acetonitrile (AN) and 1M LiAsF₆/PC electrolytes is reported. The discharge capacity and voltage of the Li(Al)-V₆O₁₃ cell were shown to be consistently higher than those of the corresponding Li(Al)-TiS₂ cell. Discharge rates of 1.2, 2.5, 5.0 and 10.0 mA cm^?2 with active material utilisations of 20 – 60% were obtained from the Li(Al)-V₆O₁₃ cell. The addition of fresh PC-AN electrolyte resulted in an improvement in cell capacity, but did not stop capacity decline on cycling. Cycle life of Li(Al)-V₆O₁₃ cells was normally less than 50 cycles. It was also found that exposure of the V₆O₁₃ electrode to moist air reduced the OCV and the discharge capacity of the cell. Short circuiting and complete discharge of the cell resulted in lower capacity and this may have been due to some degree of irreversible reduction of the V₆O₁₃.     

Optimization of the vanadium oxide (V6O13) electrode in a nonaqueous secondary lithium cell

The V₆O₁₃ electrode was tested in a nonaqueous lithium cell using 1M LiAsF₆ in propylene carbonate- acetonitrile mixture as the electrolyte. It was shown that incorporation of acetylene black in the V₆O₁₃ electrodes improved cell performance in terms of active material utilisation. Also, cells using hydrophilic microporous polypropylene separators, e.g., Celgard 5511 and 3501, displayed less resistive losses enabling larger charge/discharge rates to be used. Voltage changes in the cell were shown to be controlled almost entirely by the V₆O₁₃ electrode. Analysis of the exhausted V₆O₁₃ electrodes showed that they contained at least 4 moles of lithium per mole of V₆O₁₃.     

Rechargeable lithium sulfide electrode for a polymer tin/sulfur lithium-ion battery

In this work we investigate the electrochemical behavior of a new type of carbon-lithium sulfide composite electrode. Results based on cyclic voltammetry, charge (lithium removal)-discharge (lithium acceptance) demonstrate that this electrode has a good performance in terms of reversibility, cycle life and coulombic efficiency. XRD analysis performed in situ in a lithium cell shows that lithium sulfide can be converted into sulfur during charge and re-converted back into sulfide during the following discharge process. We also show that this electrochemical process can be efficiently carried out in polymer electrolyte lithium cells and thus, that the Li₂S-C composite can be successfully used as cathode for the development of novel types of rechargeable lithium-ion sulfur batteries where the reactive and unsafe lithium metal anode is replaced by a reliable, high capacity tin-carbon composite and the unstable organic electrolyte solution is replaced by a composite gel polymer membrane that is safe, highly conductive and able to control dendrite growth across the cell. This new Sn-C/Li₂S polymer battery operates with a capacity of 600 mAh g⁻¹ and with an average voltage of 2 V, this leading to a value of energy density amounting to 1200 Wh kg⁻¹.     

Design of a safe cylindrical lithium/thionyl chloride cell

Cell design criteria have been established which can result in a safe lithium/thionyl chloride cell. A cell vent, a low area internal anode design, cel     

Rechargeable lithium/sulfur battery with liquid electrolytes containing toluene as additive

The effect of incorporating varying amounts (in the range 2.5–10 vol%) of toluene additive in 1 M LiCF₃SO₃ in tetra(ethylene glycol) dimethyl ether (TEGDME) liquid electrolyte on the electrochemical performance of Li/S cell at room temperature was studied. Cyclic voltammetry measurements showed the same active voltage range for the electrolytes with and without toluene, consisting of an oxidation peak at 2.5 V and a pair of reduction peaks at 2.35 and 1.9 V. Electrolytes with toluene have higher redox currents resulting from increased ion mobility and ionic conductivity. Toluene addition enhanced initial discharge capacity; a maximum of 750 mAh g⁻¹ (45% of the theoretical specific capacity of sulfur) was obtained with 5% of toluene, which was 1.8 times that of the cell without toluene. The electrolyte with 5% toluene exhibited a stable cycle performance with the highest discharge capacity and charge–discharge efficiency. AC impedance analyses of Li/S cells with the electrolytes showed that toluene addition resulted in a lower initial interfacial resistance and a fast stabilization of electrode/electrolyte interfaces in the cell. Addition of toluene in low amounts is thus an effective means to enhance the electrochemical performance of 1 M LiCF₃SO₃ in TEGDME electrolyte in Li/S cells at room temperature.     

Polysulfide rubber-based sulfur-rich composites as cathode material for high energy lithium/sulfur batteries

Novel sulfur-rich polymer composites were prepared from the commercial polysulfide rubber through facile vulcanization methods and were firstly used as cathode material for lithium/sulfur batteries. The sulfur enriched in the composites includes three parts, the first part was inserted into the main chains of the polysulfide rubber, the second part formed insoluble polysulfide (-S_n-)through self-polymerization and the third part was trapped inside the network of the above two polymer chains. The obtained sulfur-rich polymer composites have high sulfur content over 80%. Compared with the pure sulfur electrode, the composites showed better cycle stability and coulomb efficiency.     

Preparation of iron sulfides and the study of their electrochemical characteristics for use in a nonaqueous—lithium battery

A variety of iron sulfides was prepared by changing both the mixing ratio of iron to sulfur and the reaction heating temperatures. Samples were then subjected to chemical and X-ray diffraction analyses to check their composition. These iron sulfides were polarized in a nonaqueous electrolyte. As a result, the sample prepared with a S/Fe ratio of 1.1/1 and heated at 800 °C showed the highest electrochemical capacity and had the molecular formula FeS. A button-type, nonaqueous electrolyte—lithium battery using the FeS as the cathode material was constructed and evaluated. The energy density of the battery was calculated to be 0.448 W h/cm³ and 0.137 W h/g.     

Behavior of a sodium-sulfur cell with a dynamic sulfur electrode

A sodium-sulfur cell was constructed with sodium polysulfide circulating in a narrow annulus around a β-alumina tube. The absence of carbon mat in the electrode reduced the current collector surface area appreciably, localized the electrochemical reactions, and ultimately led to film formation on the electrode. The results are consistent with existing models and interpretations of sulfur electrode behavior. Film formation on the electrode is responsible for the rather poor electrical characteristics of the cell.     

Capacity fade analysis of a lithium ion cell

A physics-based single particle model was used to simulate the life cycling data of a lithium ion cell. The simulation indicates that there are probably three stages of capacity fade in a lithium ion cell used at low rates. In the first stage, lithium ions are lost to a film formation reaction (e.g. SEI formation) and, consequently, the cathode becomes less intercalated during cycling. In the second stage, the loss of active cathode material outpaces the loss of lithium ions and the cathode gradually becomes more intercalated at the end of discharge. The anode is the limiting electrode in stages one and two and the change in the anode voltage causes the cell to reach end of discharge voltage. In the third stage, the limiting electrode shifts from the anode to the cathode, and the anode becomes increasingly less discharged at the end of discharge. Thus, more and more “cyclable” lithium ions are left inside the anode, which causes additional capacity fade.     

Optimal charge rates for a lithium ion cell

The optimum charge rate for a lithium ion cell at each cycle is determined to maximize the useful life of the cell without using optimization algorithms. In previous work, we showed that by applying a dynamic optimization routine the number of cycles can be increased by approximately 29.4% with respect to the case with one optimal charge current [7]. The dynamic optimization results indicated that the optimum charge rates are the minimum currents at which the constraints for the useful life are satisfied. This is due to the minimum charge rate resulting in minimum side reaction rate and capacity fade. Useful cell life is defined as the number of cycles before the end of discharge voltage (EODV) drops below 3.0 V or the cell discharge capacity becomes less than 20% of the original discharge capacity. The new approach presented in this work is able to find the optimal charge rates in a few minutes while the previous optimization algorithm takes at least one day, and improves the useful cell life by approximately 41.6% with respect to using only one optimal charge current.     

Analysis of internal short-circuit in a lithium ion cell

An electrochemical thermal model was developed to study the internal short-circuit behavior of a lithium ion cell. The model was used to understand several experimental observations: several short-circuit scenarios possible in a lithium ion cell were simulated and the power generated from each case was calculated. Influence of parameters like the SOC and initial temperature of the cell was studied.Experiments were carried out to verify the predictions made using the model. Some pointers are provided towards design of a safer cell.     

Performance of lithium alloy/lithium and calcium/ lithium anodes in thionyl chloride cells

A laminar composite anode construction comprising an inner metal completely surrounded by Li foil was studied as a means of obtaining an end-of-life in     

固态锂硫电池电解质及其界面问题研究进展

固态锂硫(Li-S)电池通过固态电解质代替传统液态电解液体系,有望同时解决液态Li-S电池多硫化物的穿梭效应、锂金属与液态电解液的副反应、安全性能差等关键科学问题,发挥其高稳定性、高能量密度的优势.然而,固态Li-S电池在固态电解质和电极/电解质界面问题上面临着巨大挑战,本文详细介绍了硫化物固态电解质和聚合物基体电解质...     

Solid polymer electrolytes with sulfur based ionic liquid for lithium batteries

The electrochemical properties of a solid hybrid polymer electrolyte for lithium batteries based upon tri-ethyl sulfonium bis(trifluorosulfonyl) imide (S₂TFSI), lithium TFSI, and poly(ethylene oxide) (PEO) is presented. We have synthesized homogenous freestanding films that possess low temperature ionic conductivity and wide electrochemical stability. The hybrid electrolyte has demonstrated ionic conductivity of 0.117 mS cm⁻¹ at 0 °C, and 1.20 mS cm⁻¹ at 25 °C. At slightly elevated temperature ionic conductivity is on the order of 10 mS cm⁻¹. The hybrid electrolyte has demonstrated reversible stability against metallic lithium at the anodic interface and >4.5 V vs. Li/Li⁺ at the cathodic interface.     

Expansion and shrinkage of the sulfur composite electrode in rechargeable lithium batteries

The expansion and shrinkage characteristics of sulfur composite cathode electrode in rechargeable lithium batteries have been investigated. It was found that the sulfur composites electrodes expanded when discharging and shrank when charging again. The thickness change of the electrode was measured to be about 22%. The thickness of lithium metal anodes was also changed when lithium deposition and dissolution, while the sulfur composites electrodes expanded and shrank conversely. The investigation showed that the thickness changes of lithium anode and sulfur composite cathode could be compensated with each other to keep the total thickness of the cell not to change so much.     

Investigation of discharge reaction mechanism of lithium|liquid electrolyte|sulfur battery

The influence of current density on the discharge reaction of Li–S batteries is investigated by discharge tests (first discharge curve), differential scanning calorimetry (DSC), X-ray diffraction (XRD) (discharge products), and scanning electron microscopy (the surface morphology of sulfur electrodes). The first discharge capacity and the plateau potential both decrease with increasing current density. When the current density is increased from 100 to 1600 mA g⁻¹ S, the discharge capacity decreases from 1178 to 217 mAh g⁻¹ S.     

The lithium—sulfur dioxide primary battery — its characteristics,performance and applications

The lithium—sulfur dioxide battery is a new primary battery system with many advantages over conventional batteries. It has an energy density up to 330 W h/kg (150 W h/lb.), two to four times greater than zinc batteries, and can perform to temperatures as low as ?54 °C (?65 °F). The battery can withstand high temperature storage 71 °C (160 °F) for long periods of time and its shelf life is projected to be 5 – 10 years at 21 °C (70 °F). The chemistry, construction and detailed performance characteristics of the battery are presented. The Li/SO₂ system provides an all-purpose, all-climate primary battery that is capable of filling a wide variety of military, industrial and consumer applications. A number of these applications are discussed. With increasing production and cost reduction, the Li/SO₂ battery will be cost-competitive and will receive wide acceptability and use.     

The polyaniline/lithium battery

Polyaniline (PAn), synthesized by electro-polymerization, has exhibited good reversibility in an LiClO₄/propylene carbonate electrolyte. The reversible specific capacity reaches 120 A h kg⁻¹. PAn appears to be a candidate positive electrode for a secondary lithium battery because of its reversibility, high-rate discharge performance, and low self-discharge. The compatibility of the electrolyte between PAn and lithium electrodes is an important problem to be solved.