Macroporous nanocomposite polymer electrolyte for lithium-ion batteries

A novel macroporous nanocomposite polymer membrane (NCPM) based on poly(vinylidene difluoride-co-hexafluoropropylene) [P(VDF-HFP)] copolymer was prepared by in situ hydrolysis of Ti(OC₄H₉)₄ using a non-solvent-induced phase separation technique. SEM micrograph shows that the yielding TiO₂ nanoparticles are dispersed uniformly in the polymer matrix and there are a lot of spherical macropores connecting with each other by some smaller pores. DSC results exhibit that the crystallinity of polymer matrix decreases with the incorporation of TiO₂ nanoparticles. The tensile stress of the NCPM is 9.69 MPa and its fracture strain 74.4%. After immersion in 1.0 mol l⁻¹ LiPF₆/ethyl carbonate (EC)–dimethyl carbonate (DMC), the ionic conductivity of the obtained nanocomposite polymer electrolyte (NCPE) is 0.98 × 10⁻³ S cm⁻¹ at 20 °C. Lithium-ion batteries, which use this kind of NCPE as the separator and electrolyte, display good discharging performance at different current densities, presenting promise for its practical application.     

Corrosion of anode current collectors in molten carbonate fuel cells

Corrosion of metallic parts is one of the life-time limiting factors in the molten carbonate fuel cell. In the reducing environment at the anode side of the cell, the corrosion agent is water. As anode current collector, a widely used material is nickel clad on stainless steel since nickel is stable in anode environment, but a cheaper material is desired to reduce the cost of the fuel cell stack. When using the material as current collector one important factor is a low resistance of the oxide layer formed between the electrode and the current collector in order not to decrease the cell efficiency. In this study, some candidates for anode current collectors have been tested in single cell molten carbonate fuel cells and the resistance of the oxide layer has been measured. Afterwards, the current collector was analysed in scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS). The results show that the resistances of the formed oxide layers give a small potential drop compared to that of the cathode current collector.     

Vinylene carbonate and vinylene trithiocarbonate as electrolyte additives for lithium ion battery

Vinylene carbonate (VC) and vinylene trithiocarbonate (VTC) are studied as electrolyte additives in two kinds of electrolytes: (1) propylene carbonate (PC) and diethyl carbonate (DEC) (1:2 by weight) 1 mol dm⁻³ LiPF₆; (2) ethylene carbonate (EC) and DEC (1:2 by weight) 1 mol dm⁻³ LiPF₆. Characterization is performed by cyclic voltammetry, impedance spectroscopy, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and half cell tests. Cyclic life is better in either electrolyte with VC than either electrolyte with/without VTC. SEM shows VC and VTC both form well developed passivation films on the graphite anode, but the films with VTC are thicker than with VC. EIS shows the VTC films have significantly higher charge transfer resistance. The VTC film in PC fails to protect against exfoliation. XPS indicates VTC has different reaction pathways in PC relative to EC. In EC/DEC, VTC forms polymeric C-O-C-like components and sulfide species (C-S-S-C, S and C-S-C). In PC/DEC, VTC does not form polymeric species, instead forming a film mainly containing LiF and Li₂S. It appears that a thinner polymeric film is preferential. The specific data herein are of interest, and the general conclusions may help development of improved additives for enhanced Li-ion battery performance.     

A novel flame retardant and film-forming electrolyte additive for lithium ion batteries

Allyl tris(2,2,2-trifluoroethyl) carbonate (ATFEC) was synthesized as a bi-functional additive of flame retardant and film former in electrolytes for lithium ion batteries (LIBs). The flame retardancy of the additive was characterized with differential scanning calorimetry (DSC) and self-extinguishing time (SET). It is shown that adding 1 vol.% ATFEC in 1 M LiPF₆/propylene carbonate (PC) can effectively enhance the thermal stability of the electrolyte and suppress the co-intercalation of PC into the graphitic anode. Further evaluation indicates that the additive hardly affect the conductivity of electrolyte. These support the feasibility of using ATFEC as an additive on formulating an electrolyte with multiple functions such as film-forming enhancement, high thermal stability and high ionic conductivity.     

Physico-chemical principles of preventing salts crystallization on heat-exchange surfaces

The work discusses physico-chemical grounds of conventional methods for preventing crystallization of salt on heat-exchange surfaces, and dwells upon the role of temperature and supersaturation, as well as the role of the heat-exchange surface as an initiator of calcium carbonate crystallization. The paper provides a brief summary of some methods based on reducing supersaturation of the solution with the salt getting crystallized and on a physical impact upon the solution. Particular consideration is given to a method for preventing calcium carbonate deposits, namely restructurization of the solution as initiated by magneto-hydrodynamic resonance (magnetic treatment). As a criterion for choosing a method of preventing scale formation on the heat-exchange surface, it is suggested that the relative supersaturation with calcium carbonate be taken into consideration. The limitations of and conditions for employment of some methods of preventing scale formation are also presented. The equation of a predictable dependence in increase power consumption by heat-exchange equipment on supersaturation of the solution with calcium carbonate in the surface-adjoining layer is proposed.     

Demonstration of coal gas run molten carbonate fuel cell concept

Integrated gasifier‐molten carbonate fuel cell (IG‐MCFC) offers a clean and efficient route for power generation from coal. A molten carbonate fuel cell (MCFC) was assembled and its performance was tested with simulated coal gas. The output and the stability was found to be comparable to that with conventional feed gas. It was also observed that switching from one type of feed gas to another had only a marginal effect on the cell performance. Copyright © 1999 John Wiley & Sons, Ltd.     

Electrolytic characteristics of asymmetric alkyl carbonates solvents for lithium batteries

Asymmetric alkyl carbonate solvents (ACS) have been used as components of liquid electrolyte systems designed for Li-ion cells. Four ACS were selected: methyl-propyl carbonate (MPC), ethyl-propyl carbonate (EPC), methyl-isopropyl carbonate (MiPC) and ethyl-isopropyl carbonate (EiPC). The common features of all these ACS are a low melting point and a low viscosity, enhancing electrolytes conductivity toward low temperatures. The viscosity and the conductivity (salt: LiPF₆, 1 M) of the ACS and their mixtures with ethylene carbonate (EC, 50% v/v), were studied as a function of the temperature (T). Arrhenius types plots of the logarithm of the conductivity versus 1/T reveals that ACS and ACS/EC mixtures are vitreous at low temperatures. The electrochemical and cycling behaviors of a graphite anode and a LiCoO₂ cathode have been evaluated using coin cells with a Li counter electrode. The charge and discharge capacities have been determined as a function of the cycle number. MiPC which builds an highly stable surface film on the graphite electrode, can be used as a single-solvent electrolyte with only a slight decrease in capacity of the LiCoO₂ cathode. All ACS/EC mixtures exhibit good filming properties at the negative electrode and no capacity loose at the positive electrode. The ability of some of the electrodes–electrolyte systems to undergo increased rates of discharge (C/5 to C/2) has been also evaluated.     

A new lithium salt with dihydroxybenzene and lithium tetrafluoroborate for lithium battery electrolytes

A new unsymmetrical lithium salt containing F⁻, C₆H₄O₂²⁻ [dianion of 1,2-benzenediol], lithium difluoro(1,2-benzene-diolato(2-)-o,o′)borate (LDFBDB) is synthesized and characterized. Its thermal decomposition in nitrogen begins at 170 °C. The cyclic voltammetry study shows that the LDFBDB solution in propylene carbonate (PC) is stable up to 3.7 V versus Li⁺/Li. It is soluble in common organic solvents. The ionic dissociation properties of LDFBDB are examined by conductivity measurements in PC, PC+ ethyl methyl carbonate (EMC), PC + dimethyl ether (DME), PC + ethylene carbonate (EC) + EMC solutions. The conductivity values of the 0.564 mol dm⁻³ LDFBDB electrolyte in PC + DME solution is 3.90 mS cm⁻¹. All these properties of the new lithium salt including the thermal characteristics, electrochemical stabilities, solubilities, ionic dissociation properties are studied and compared with those of its derivatives, lithium difluoro(3-fluoro-1,2-benzene-diolato(2-)-o,o′)borate (FLDFBDB), lithium [3-fluoro-1,2-benzenediolato(2-)-o,o′ oxalato]borate (FLBDOB), and lithium bis(oxalate)borate (LBOB).     

Cyclic CO2 capture performance of carbide slag

The carbonate looping process is a promising technology for CO₂ capture. The decay of sorbents reactivity over multiple cycles is an obstacle for realizing the carbonate looping process. In this work, the reactivity and stability of carbide slag for CO₂ capture have been examined. The results show that carbide slag exhibits superior CO₂ capture performance even at severe calcination temperatures in comparison with limestones, shells, pure CaCO₃, and Ca(OH)₂. X-ray diffraction analysis shows that there is mayenite (Ca₁₂Al₁₄O₃₃) formed in the calcination step for carbide slag, which is the main reason for its high stability in the carbonate looping process.     

Properties of the graphite-lithium anode in N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide as an electrolyte

The ternary [Li⁺][MPPip⁺][NTf₂⁻] ionic liquid, obtained by dissolution of solid lithium bis(trifluoromethanesulfonyl)imide (LiNTf₂) in liquid N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (MPPipNTf₂), was used as an electrolyte, and stable at the lithium or graphite-lithium anodes. The graphite-lithium (C₆Li) anode showed good cyclability and Coulombic efficiency in the presence of a molecular additive (10 wt.% of vinylene carbonate, VC) to the ionic liquid. The electrode showed ca. 90% of its initial discharge capacity after 100 cycles. The addition of ethylene carbonate (EC) does not improve the cyclability of the anode to the same degree as that observed in the case of vinylene carbonate.     

Past and future development of the market for lithium in the World aluminium industry

The use of lithium carbonate in aluminium production has become a very significant end-use for lithium in the 20 years since it was first used for this purpose on a commercial scale. The sparse published information suggests that lithium carbonate will gradually be adopted in more and more plants around the world, and thus that lithium demand for this end-use will continue growing. A recent study of lithium usage in each of the world's aluminium plants shows, however, that there are more complex factors involved in the decision to use lithium carbonate than are commonly thought, that some plants which have adopted lithium carbonate are unlikely to use it indefinitely, and that lithium demand is likely to be cyclical with peaks at times of high aluminium demand. Free World demand for lithium carbonate for aluminium production outside the US is probably about 1000 t in 1977 and is likely to rise to 2500 t in 1980. US demand is much higher, probably 8500 t in 1977.     

Direct carbon fuel cell: Fundamentals and recent developments

The direct carbon fuel cell is a special type of high temperature fuel cell that directly uses solid carbon as anode and fuel. As an electrical power generator for power plants, it has a higher achievable efficiency (80%) than the molten carbonate and solid oxide fuel cells, and has less emissions than conventional coal-burning power plants. More importantly, its solid carbon-rich fuels (e.g. coal, biomass, organic garbage) are readily available and abundant. In this review, some fundamental study results of electrochemical oxidation of carbon in molten salts are summarized. Recent developments in direct carbon fuel cell configurations and performance are also discussed.     

Ammonia and related chemicals as potential indirect hydrogen storage materials

Energy production and combating climate change are among some of the most significant challenges we are facing today. Whilst the introduction of a hydrogen economy has its merits, the associated problems with on-board hydrogen storage are still a barrier to implementation. Ammonia and related chemicals may provide an alternative energy vector. Besides ammonia and metal amine salts, some other ammonia related materials such as hydrazine, ammonia borane, ammonia carbonate and urea also have the potential for use as alternative fuels. These materials conform to many of the US DOE targets for hydrogen storage materials.     

A new lithium salt with 3-fluoro-1,2-benzenediolato and lithium tetrafluoroborate for lithium battery electrolytes

A new unsymmetrical lithium salt containing F⁻, C₆H₃O₂F²⁻ [dianion of 3-fluoro-1,2-benzenediol], lithium difluoro(3-fluoro-1,2-benzene-diolato(2-)-o,o′)borate (FLDFBDB) is synthesized and characterized. The thermal characteristics of it, and its derivatives, lithium bis[3-fluoro-1, 2-benzenediolato(2-)-o,o]borate (FLBBB), and lithium fluoroborate (LiBF₄) are examined by thermogravimetric analysis (TG). The thermal decomposition in air begins at 256 °C, 185 °C, and 162 °C for FLBBB, FLDFBDB and LiBF₄, respectively. The order of the stability toward the oxidation of these organoborates is LiBF₄ > FLDFBDB > FLBBB. The cyclic voltammetry study shows that the FLDFBDB solution in propylene carbonate (PC) is stable up to 3.9 V vs. Li⁺/Li. It is soluble in common organic solvents. Ionic dissociation properties of FLDFBDB and its derivatives are examined by conductivity measurements in PC, PC + ethyl methyl carbonate (EMC), PC + dimethyl ether (DME), PC + ethylene carbonate (EC) + DME, PC + EC + EMC solutions. The conductivity values of the 0.10 mol dm⁻³ FLDFBDB electrolyte in these solutions are higher than those of FLBBB, but lower than those of LiBF₄ electrolytes.     

Conductivity of SDC and (Li/Na)2CO3 composite electrolytes in reducing and oxidising atmospheres

Composite electrolytes made of samarium-doped cerium oxide and a mixture of lithium carbonate and sodium carbonate salts are investigated with respect to their structure, morphology and ionic conductivity. The composite electrolytes are considered promising for use in so called intermediate temperature solid oxide fuel cells (IT-SOFC), operating at 400–600 °C. The electrolytes are tested in both gaseous anode (reducing) and cathode (oxidising) environments and at different humidities and carbon dioxide partial pressures. For the structure and morphology measurements, it was concluded that no changes occur to the materials after usage. From measurements of melting energies, it was concluded that the melting point of the carbonate salt phase decreases with decreasing fraction of carbonate salt and that a partial melting occurs before the bulk melting point of the salt is reached. For all the composites, two regions may be observed for the conductivity, one below the carbonate salt melting point and one above the melting point. The conductivity is higher when electrolytes are tested in anode gas than when tested in cathode gas, at least for electrolytes with less than half the volume fraction consisting of carbonate salt. The higher the content of carbonate salt phase, the higher the conductivity of the composite for the temperature region above the carbonate melting point. Below the melting point, though, the conductivity does not follow this trend. Calculations on activation energies for the conductivity show no trend or value that indicates a certain transport mechanism for ion transport, either when changing between the different composites or between different gas environments.     

A novel high-performance gel polymer electrolyte membrane basing on electrospinning technique for lithium rechargeable batteries

Nonwoven films of composites of thermoplastic polyurethane (TPU) with different proportion of poly(vinylidene fluoride) (PVdF) (80, 50 and 20%, w/w) are prepared by electrospinning 9 wt% polymer solution at room temperature. Then the gel polymer electrolytes (GPEs) are prepared by soaking the electrospun TPU-PVdF blending membranes in 1 M LiClO₄/ethylene carbonate (EC)/propylene carbonate (PC) for 1 h. The gel polymer electrolyte (GPE) shows a maximum ionic conductivity of 3.2 × 10⁻³ S cm⁻¹ at room temperature and electrochemical stability up to 5.0 V versus Li⁺/Li for the 50:50 blend ratio of TPU:PVdF system. At the first cycle, it shows a first charge-discharge capacity of 168.9 mAh g⁻¹ when the gel polymer electrolyte (GPE) is evaluated in a Li/PE/lithium iron phosphate (LiFePO₄) cell at 0.1 C-rate at 25 °C. TPU-PVdF (50:50, w/w) based gel polymer electrolyte is observed much more suitable than the composite films with other ratios for high-performance lithium rechargeable batteries.     

Role of carbonate phase in ceria–carbonate composite for low temperature solid oxide fuel cells: A review

Ceria–salt composites represent one type of promising electrolyte candidates for low temperature solid oxide fuel cells (LT‐SOFCs), in which ceria–carbonate attracts particular attention because of its impressive ionic conductivity and unique hybrid ionic conduction behavior compared with the commonly used single‐phase electrolyte materials. It has been demonstrated that the introduction of carbonate in these new ceria‐based composite materials initiates multi new functionalities over single‐phase oxide, which therefore needs a comprehensive understanding and review focus. In this review, the roles of carbonate in the ceria–carbonate composites and composite electrolyte‐based LT‐SOFCs are analyzed from the aspects of sintering aid, electrolyte densification reagent, electrolyte/electrode interfacial ‘glue’ and sources of super oxygen ionic and proton conduction, as well as the oxygen reduction reaction promoter for the first time. This summary remarks the significance of carbonate in the ceria–carbonate composites for low temperature, 300–600 °C, SOFCs and related highly efficient energy conversion applications. Copyright © 2016 John Wiley & Sons, Ltd.     

A combustion chemistry analysis of carbonate solvents used in Li-ion batteries

Under abusive conditions Li-ion cells can rupture, ejecting electrolyte and other flammable gases. In this paper we consider some of the thermochemical and combustion properties of these gases that determine whether they ignite and how energetically they burn. We find a significant variation among the carbonate solvents in the factors that are important to determining flammability, such as combustion enthalpy and vaporization enthalpy. We also show that flames of carbonate solvents are fundamentally less energetic than those of conventional hydrocarbons. An example of this contrast is given using a recently developed mechanism for dimethyl carbonate (DMC) combustion, where we show that a diffusion flame burning DMC has only half the peak heat release rate of an analogous propane flame. Interestingly, peak temperatures differ by only 25%. We argue that heat release rate is a more useful parameter than temperature when evaluating the likelihood that a flame in one cell will ignite a neighboring cell. Our results suggest that thermochemical and combustion property factors might well be considered when choosing solvent mixtures when flammability is a concern.     

2,2-Dimethoxy-propane as electrolyte additive for lithium-ion batteries

2,2-Dimethoxy-propane (DMP) was studied as an additive in 1 mol dm⁻³ LiPF₆ ethylene carbonate and diethyl carbonate (1:1, w/w) for lithium-ion battery, which was characterized by cyclic voltammetry and half cell tests. Cyclic voltammetry and half cell data show that the use of DMP as an additive to the organic solutions at very low level (ca. 0.005 wt%) offers the advantage of forming fully developed passive films on the graphite anode surface. The electrochemical performance of the additive-containing electrolytes in combination with LiCoO₂ cathode and graphitic anode was also tested in commercial cells 103448. The results reveal that the cyclic life test and storage performance at high temperature (ca. 60 °C) in electrolyte with DMP additive was better than that in an electrolyte without additive. Therefore, DMP can be considered as a desirable additive in electrolyte for lithium-ion batteries operating at high temperature, ca. 60 °C.     

Distributed generation—Molten carbonate fuel cells

High efficiency and ultra-clean molten carbonate fuel cell (MCFC) technology development by FuelCell Energy, with support from the U.S. Department of Energy (DOE), has progressed to commercial power plants for stationary applications such as distributed generation. Lessons learned from this development will also be valuable to DOE for the ongoing Solid State Energy Conversion Alliance (SECA) solid oxide fuel cell (SOFC) development and cost reduction, for fuel cell turbine hybrids, and for hydrogen economy development with FutureGen.