Li2 CO Research Articles

Impact of anode catalyst layer porosity on the performance of a direct formic acid fuel cell

Direct formic acid fuel cells (DFAFCs) have attracted much attention in the last few years for portable electronic devices, due to their potential of being high efficiency power sources. They have the potential to replace the state-of-the-art batteries in cell phones, PDAs, and laptop computers if their power density and durability can be improved. In the present investigation, the influence of increased anode catalyst layer porosity on DFAFC power density performance is studied. Lithium carbonate (Li 2CO 3) was used as a pore-former in this study because of its facile and complete removal after catalyst layer fabrication. The anode catalyst layers presented herein contained unsupported Pt/Ru catalyst and Li 2CO 3 (in the range of 0–50 wt%) bound with proton conducting ionomer. Higher DFAFC performance is obtained because of the increased porosity within the anode catalyst layer through enhanced reactant and product mass transport. The maximum power density of DFAFC increased by 25% when pore-former was added to the anode catalyst ink. The formic acid onset potential for the anode catalyst layer with 17.5 wt% pore-former was reduced by 30 mV. A constant phase element based equivalent-circuit model was used to investigate anode impedance spectra. Fitted values for the anode impedance spectra confirm the improvement in performance due to an increase in formic acid concentration inside the anode catalyst layer pores along with efficient transport of reactants and products.

Novel self-catalyzed sol–gel synthesis of high-rate cathode Li 3V 2(PO 4) 3/C for lithium ion batteries

A novel sol–gel method for synthesizing high-rate Li 3V 2(PO 4) 3/C cathode material has been developed via a self-catalyzed reaction between the raw materials of Li 2CO 3, V 2O 5 and NH 4H 2PO 4. X-ray diffraction, scanning electron microscopy and field emission transmission electron microscopy were used to define the crystal structure and morphology of the composite. Electrochemical measurements indicate that the obtained Li 3V 2(PO 4) 3/C composite presents a specific discharge capacity of 129.97 mAh g − 1 at 1 C rate while maintaining 115.35 mAh g − 1 (88.75%) at 10 C rate, without significant capacity fading after 200 cycles. The results demonstrate that the Li 3V 2(PO 4) 3/C material prepared via the novel sol–gel method has great potential to be used in high-power lithium ion batteries.

Well-ordered spherical LiNi xCo (1−2 x) Mn xO 2 cathode materials synthesized from cobolt concentration-gradient precursors

Spherical Ni x Co (1−2 x) Mn x (OH) 2 ( x = 0.333, 0.4, 0.416, 0.45) precursors with Co concentration-gradient were prepared by co-precipitation from sulfate solutions using NaOH and NH 4OH as precipitation and complexing agents. Then, well-ordered spherical LiNi x Co (1−2 x) Mn x O 2 was synthesized by sintering the mixture of as-prepared precursor and Li 2CO 3 at 950 °C for 16 h in air. EDXS results indicated that the concentration of cobalt decreased gradually inside out of the spherical precursor particle, and it was uniform in spherical LiNi x Co (1−2 x) Mn x O 2 particle obtained by sintering with Li 2CO 3. According to Rietveld refinement of XRD patterns, the LiNi x Co (1−2 x) Mn x O 2 synthesized from Co gradient precursor showed lower degree of cation disorder than that prepared from conventional precursor. The well-ordered LiNi x Co (1−2 x) Mn x O 2 from Co gradient precursor delivered much better high-rate capability than conventional one. The decrease of cation disorder of LiNi x Co (1−2 x) Mn x O 2 is attributed to the cobalt-rich in core of the precursor particles. Both abundant Co 3+ and Li + can restrain cation mixing effectively. Since Li + needs long time to reach core during calcining, cobalt-rich in core of the precursor particle is very important for restraining cation mixing. Concentration-gradient precursor is helpful to prepare well-ordered LiNi x Co (1−2 x) Mn x O 2 with good high-rate capability, and the total content of expensive and toxic cobalt does not need to be increased.

Low-temperature sintered Zn 2SiO 4–CaTiO 3 ceramics with near-zero temperature coefficient of resonant frequency

The microwave dielectric properties and the microstructures of (1 − x)Zn 2SiO 4 − xCaTiO 3 composite ceramics with Li 2CO 3–H 3BO 3 additives prepared by solid-state reaction method have been investigated. The crystalline phases were studied systematically by using the X-ray diffraction (XRD), microstructures by the scanning electron microscopy (SEM) and composition analysis by energy-dispersive spectroscopy (EDS). The τ f of (1 − x)Zn 2SiO 4 − xCaTiO 3 was found to be dependent on phase constitution, which is related to the amount of CaTiO 3. When x = 0.05, the τ f of (1 − x)Zn 2SiO 4 − xCaTiO 3 was near 0 ppm/°C. The microwave dielectric properties of 0.95Zn 2SiO 4–0.05CaTiO 3 ceramics samples with Li 2CO 3–H 3BO 3 additives sintered at 900–1000 °C were characterized, and the results indicated that the permittivity and Q × f were associated with the amount of Li 2CO 3–H 3BO 3 and the sintering temperature. The sintering temperature of ceramics was effectively reduced to 950 °C from about 1250 °C and the temperature coefficient of resonant frequency ( τ f ) was modified to −4.5 ppm/°C with good Q × f. The addition of 4.0 wt% Li 2CO 3–H 3BO 3 in 0.95Zn 2SiO 4–0.05CaTiO 3 ceramics sintered at 950 °C showed excellent dielectric properties of ɛ r = 7.1, Q × f = 26,300 GHz ( f = 7.1 GHz) and τ f = −4.5 ppm/°C. Moreover, this material has a chemical compatibility with silver, making it a very promising candidate material for LTCC applications.

Effects of TiO 2 crystal structure on the performance of Li 4Ti 5O 12 anode material

Li 4Ti 5O 12 anode material is synthesized using TiO 2 with different crystal structure as titanium source by solid-state method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical test methods are applied to characterize the effects of TiO 2 crystal structure on the structure, morphology and electrochemical performance of Li 4Ti 5O 12. Results show that the reaction of TiO 2 with Li 2CO 3 is an exothermic behavior. The reactivity of TiO 2 with Li 2CO 3 gradually decreases and the particles size of Li 4Ti 5O 12 increases with the TiO 2 crystal structure changing from amorphous to rutile. The TiO 2 crystal structure has a slight influence on the reversibility of Li 4Ti 5O 12, while the specific capacities of Li 4Ti 5O 12 at different current densities decreases obviously with the TiO 2 crystal structure changing from amorphous to rutile and the sample using amorphous TiO 2 as titanium sources shows highest specific capacity. The capacity retentions of all Li 4Ti 5O 12 samples are above 97% after 50 cycles and these materials show good cycle performance. The TiO 2 crystal structure has not large effects on the cycling performance of Li 4Ti 5O 12 material.

Environmental impacts of a transition toward e-mobility: the present and future role of lithium carbonate production

Whether the environmental benefits of emerging technologies are outweighed by the environmental impacts of producing and using scarce technology metals remains an open question. We present a three-level approach to assess how increasing environmental impacts on the resource provision level affect the overall impacts on the product level and on the service level, at an early stage of technology implementation. The approach is described based on a case example: we evaluate the environmental impacts of different supply options for lithium carbonate (Li 2CO 3) – required for the production of Li-ion batteries – and their influence on the environmental impacts associated with an electric vehicle (EV). We applied the methodology of Life Cycle Assessment (LCA) and considered the production of Li 2CO 3 from three different deposit types: natural brines (currently dominant), ores (less common) and seawater (hypothetical future option). For each of the three supply options, we established an inventory dataset for both favorable and unfavorable processing conditions. The inventory datasets were combined with those used in a recently published LCA, which compared the environmental impacts of an EV with those of an internal combustion engine vehicle (ICEV). The results of this study indicate that the environmental impacts of Li 2CO 3 production as a percentage of the total transportation impacts caused by an EV are currently negligible. Only if seawater was used under unfavorable processing conditions, these impacts could outweigh the environmental benefits of EV over an ICEV; however, the uncertainty is high due to the limited data availability regarding future lithium production processes. The break-even point for the environmental impacts of 1 km driven with an EV and with an ICEV would be reached only if the impacts per kilogram of Li 2CO 3 were increased by about two orders of magnitude (more than 200 times higher for the impact assessment method Cumulative Energy Demand, about 450 times higher for Global Warming Potential and about 100 times higher for ecoindicator 99).

Processing of a Zimbabwean petalite to obtain lithium carbonate

Processing of petalite concentrate from the Bikita deposits in Zimbabwe for production of high-purity Li 2CO 3 has been studied. XRF and ICP-OES analysis showed that the concentrate consists of oxides of Li, Si, and Al as major components, with an average Li 2O content of 4.10%. XRD examination confirmed that the sample is a petalite. Processing of the petalite involves roasting the pre-heated concentrate with concentrated H 2SO 4 followed by water leaching of the resulting Li 2SO 4, solution purification and precipitation of Li 2CO 3. The effects of roasting temperature, stirring speed, solid to liquid ratio, leaching temperature and time on the lithium dissolution are reported. The dissolution rates are significantly influenced by roasting temperature and stirring speed. Water-washed lithium carbonate with a purity of 99.21% (metal basis) was produced. Synthesised and commercial Li 2CO 3 samples were characterised and compared using X-ray diffraction (XRD) and thermogravimetric analysis (TGA).

Synthesis and electrochemical performance of Li 4Ti 5O 12/C composite by a starch sol assisted method

Li 4Ti 5O 12/C composite anode materials were synthesized by a simple starch sol assisted method using TiO 2-anatase and Li 2CO 3 as raw materials and soluble starch as carbon source. The influences of calcination temperature and starch amounts on the microstructure and electrochemical performance were systematically investigated. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and constant-current charge/discharge cycling tests. The results showed that the Li 4Ti 5O 12/C composite with 10 wt.% starch synthesized at 800 °C for 6 h had homogeneous particle size distribution with an average particle size of 200–300 nm and exhibited the optimal electrochemical performance with specific discharge capacities of 168.5, 160.8, 155.1 and 141.8 mAh g − 1 at 0.2 °C, 1 °C, 2 °C and 5 °C rates, respectively, and satisfactory cycling stability. It could be attributed to the homogeneous ultrafine particles and in situ carbon coating, which enhanced the electronic conductivity and diffusion of lithium ions in the electrode.

Extraction of lithium from micaceous waste from china clay production

The granites of South-West England are a potential source of lithium which is generally found within the mica mineral, zinnwaldite. It is mainly found in the central and western end of the St. Austell granite. When kaolin extraction occurs in these areas a mica-rich waste product is produced which is currently disposed of in tailings storage facilities. In this study a tailings sample containing 0.84% Li 2O was upgraded by a combination of froth flotation, using dodecylamine as the collector, and wet high intensity magnetic separation (WHIMS) to 2.07% Li 2O. The concentrate was then roasted with various additives, including limestone, gypsum and sodium sulphate, over a range of temperatures. The resulting products were then pulverised before being leached with water at 85 °C. Analysis of these products by XRD revealed that the water-soluble sulphates, KLiSO 4 and Li 2KNa(SO 4) 2, were produced under specific conditions. A maximum lithium extraction of approximately 84% was obtained using gypsum at 1050 °C. Sodium sulphate produced a superior lithium extraction of up to 97% at 850 °C. In all cases iron extraction was very low. Preliminary tests on the leach solution obtained by using sodium sulphate as an additive have shown that a Li 2CO 3 product with a purity of >90% could be produced by precipitation with sodium carbonate although more work is required to reach the industrial target of >99%.

Novel red perovskite phosphor Ca 2AlNbO 6:Eu 3+ for white light-emitting diode application

Eu 3+-doped perovskite phosphors of Ca 2AlNbO 6 were synthesized from a solid state reaction. A small amount of the Li 2CO 3 flux was found to greatly shorten calcination time and reduce reaction temperature. The structural and optical properties of the samples were systematically investigated. The excitation spectra of Ca 2AlNbO 6:Eu 3+ reveal two excitation bands at 398 ( 7F 0→ 5L 6) and 466 nm ( 7F 0→ 5D 2), which match well with the two popular emissions from near-UV and blue LED chips. Under blue light excitation, the red emission of Ca 2AlNbO 6:0.05Eu 3+ is twice more intense than that of (Y 0.95Eu 0.05) 2O 3. The chromaticity coordinates of (Ca 0.95Eu 0.05) 2AlNbO 6 ( x=0.654, y=0.346) are close to the standard values ( x=0.670, y=0.330) of National Television Standard Committee (NTSC). The optical properties suggest that Ca 2AlNbO 6:Eu 3+ is an efficient red-emitting phosphor for light-emitting diode applications.

Low-temperature sintering and dielectric properties of high-permittivity microwave (Ca, Nd)TiO 3 ceramics

The effect of H 3BO 3–CuO–Li 2CO 3 combined additives on the sintering temperature, microstructure and microwave dielectric properties of (Ca 0.61Nd 0.26) (Ti 0.98Sn 0.02)O 3 (CNTS) ceramics was investigated. The H 3BO 3–CuO–Li 2CO 3 combined additives lowered the sintering temperature of CNTS ceramics effectively from 1300 to 950 °C. This may be due to the interim liquid-phase of Li 2O–CuO–B 2O 3, which were formed in the sintering process. (Li 0.5Nd 0.5)TiO 3 (LNT) demonstrated an effective compensation in τ f value of the low-fired CNTS ceramics. The 0.4CNTS–0.6LNT ceramics with 5 wt% (H 3BO 3–CuO)–0.5 wt% Li 2CO 3 sintered at 900 °C for 2 h shows excellent dielectric properties: ɛ r = 90.6, Q × f = 3400 GHz, and τ f = 9 ppm/°C. Also, the LTCC material is compatible with Ag electrode.

Effects of the starting materials and mechanochemical activation on the properties of solid-state reacted Li 4Ti 5O 12 for lithium ion batteries

Li 4Ti 5O 12 was synthesized by a solid-state reaction between Li 2CO 3 and TiO 2 for applications in lithium ion batteries. The effects of the TiO 2 phase and mechanochemical activation on the Li 4Ti 5O 12 particles as well as the corresponding electrochemical properties were investigated. Rutile TiO 2 was more desirable in acquiring high purity Li 4Ti 5O 12 than anatase due to the anatase to rutile phase transformation, which was found to be more rigid in the solid-state reaction than the intact rutile phase. Mechanochemical activation of the starting materials was effective in decreasing the reaction temperature and particle size as well as increasing the Li 4Ti 5O 12 content. The specific capacity depended significantly on the Li 4Ti 5O 12 content, whereas the rate capability improved with decreasing particle size due to the enhanced contact area and reduced diffusion path. Overall, a 200 nm-sized Li 4Ti 5O 12 powder with a specific capacity of 165 mAh/g could be synthesized by optimizing the milling method and starting materials.

Reaction mechanisms for the limited reversibility of Li–O 2 chemistry in organic carbonate electrolytes

The Li–O 2 chemistry in nonaqueous liquid carbonate electrolytes and the underlying reason for its limited reversibility was systematically investigated. X-ray diffraction data showed that regardless of discharge depth lithium alkylcarbonates (lithium propylenedicarbonate (LPDC), or lithium ethylenedicarbonate (LEDC), with other related derivatives) and lithium carbonate (Li 2CO 3) are constantly the main discharge products, while lithium peroxide (Li 2O 2) or lithium oxide (Li 2O) is hardly detected. These lithium alkylcarbonates are generated from the reductive decomposition of the corresponding carbonate solvents initiated by the attack of superoxide radical anions. More significantly, in situ gas chromatography/mass spectroscopy analysis revealed that Li 2CO 3 and Li 2O cannot be oxidized even when charged to 4.6 V vs. Li/Li +, while LPDC, LEDC and Li 2O 2 are readily oxidized, with CO 2 and CO released from LPDC and LEDC and O 2 evolved from Li 2O 2. Therefore, the apparent reversibility of Li–O 2 chemistry in an organic carbonate-based electrolyte is actually an unsustainable process that consists of (1) the formation of lithium alkylcarbonates through the reductive decomposition of carbonate solvents during discharging and (2) the subsequent oxidation of these same alkylcarbonates during charging. Therefore, a stable electrolyte that does not lead to an irreversible by-product formation during discharging and charging is necessary for truly rechargeable Li–O 2 batteries.

Lithium transport within the solid electrolyte interphase

A LiClO 4 SEI film grown on copper was examined with time-of-flight secondary ion mass spectrometry. The SEI porosity profile and Li + transport processes within the SEI were studied with isotopically labeled 6LiBF 4 electrolyte. An ~ 5 nm porous region, into which electrolytes can easily diffuse, was observed at the electrolyte/SEI interface. Below the porous region, a densely packed layer of Li 2O and/or Li 2CO 3 prevents electrolyte diffusion, but Li + transports through this region via ion exchange.

Flux growth and characterization of Ti- and Ni-doped enstatite single crystals

Single crystals of Ti- and Ni-doped enstatite MgSiO 3 were grown by the slow-cooling flux growth method. Acidic oxides such as V 2O 5, MoO 3 and lithium carbonate Li 2CO 3 were used as fluxes. The starting mixture was first held at 950 °C and then slowly cooled to 600 °C at a rate of 1.8 °C/h. Both Ti- and Ni-doped crystals were characterized and studied by stereo and polarized optical microscopy, powder crystal X-ray diffraction and scanning electron microscopy with energy-dispersive spectrometry. Some crystals were further characterized by single-crystal X-ray diffraction, Fourier transform infrared and cathodoluminescence. Doped enstatite consists mainly of aggregations of single crystals, and other phases were also detected in variable amounts in all the runs. Transparent Ti-doped enstatite (1.5–0.2 mm in length) and green Ni-doped enstatite (0.6–0.2 mm in length) single crystals were euhedral in form and not homogeneous in width. The effects of growth parameters on yield and size of crystals are also discussed.

Catalytic effect of alkali carbonates on CO 2 gasification of Pingshuo coal

Na 2CO 3, Li 2CO 3, and K 2CO 3 were used as additives to Pingshuo (PS) coal that was subsequently gasified under a CO 2 stream. The catalytic gasification of coal samples by CO 2 in the presence single or mixed alkali carbonates was investigated by thermogravimetric analysis. The experimental results indicate that the catalytic effect of Li 2CO 3 is significantly larger than that of Na 2CO 3 or K 2CO 3. The catalytic effect of the mixed, bi-metal carbonate containing Li 2CO 3 and Na 2CO 3, or Li 2CO 3, and K 2CO 3, is related to the composition of the catalyst and the proportion of the two components. The bi-metal carbonates having a mole ratio of 9:1 (Li:X) has the largest catalytic effect for PS coal gasification. A synergistic effect between Li and K, or Na, carbonate appears at temperatures greater than 1300 K. An un-reacted shrinking core model is suitable for kinetic analysis of catalytic gasification of coal samples in the presence of alkali carbonates. It is inappropriate, however, to evaluate the catalytic effect only by the activation energy obtained from the kinetic calculations.

Effects of Li 2CO 3 on the sintering behavior and piezoelectric properties of Bi 2O 3-excess (Bi 0.5Na 0.5) 0.94Ba 0.06TiO 3 ceramics

(Bi 0.5Na 0.5) 0.94Ba 0.06TiO 3 ceramics doped with Li 2CO 3 and Bi 2O 3 as sintering aids were manufactured, and their micro structural, dielectric and piezoelectric properties were investigated. All specimens could be well sintered at a low-temperature of 1080 °C. The bulk density of the specimens doped with a small amount of Li 2CO 3 was enhanced. The dielectric and piezoelectric properties of ceramics were investigated with different amounts of Li 2CO 3 substitutions. High electrical properties of d 33 = 167 pC/N, k p = 0.34, P r = 40 μC/cm 2 and E c = 38 kV/cm were obtained from the specimen containing 0.1 mol% of Li 2CO 3 sintered at 1080 °C.

Fe valence determination and Li elemental distribution in lithiated FeO 0.7F 1.3/C nanocomposite battery materials by electron energy loss spectroscopy (EELS)

Electron energy loss spectroscopy (EELS) is a powerful technique for studying Li-ion battery materials because the valence state of the transition metal in the electrode and charge transfer during lithiation and delithiation processes can be analyzed by measuring the relative intensity of the transition metal L 3 and L 2 lines. In addition, the Li distribution in the electrode material can be mapped with nanometer scale resolution. Results obtained for FeO 0.7F 1.3/C nanocomposite positive electrodes are presented. The Fe average valence state as a function of lithiation (discharge) has been measured by EELS and results are compared with average Fe valence obtained from electrochemical data. For the FeO 0.7F 1.3/C electrode discharged to 1.5 V, phase decomposition is observed and valence mapping with sub-nanometer resolution was obtained by STEM/EELS analysis. For the lowest discharge voltage of 0.8 V, a surface electrolyte inter-phase (SEI) layer is observed and STEM/EELS results are compared with the Li–K edges obtained for various Li standard compounds (LiF, Li 2CO 3 and Li 2O).

Molten salt synthesis of Li 1 + x (Ni 0.5Mn 0.5) 1 − xO 2 as cathode material for Li-ion batteries

Li 1 + x (Ni 0.5Mn 0.5) 1 − x O 2 cathode material for Li-ion batteries has been prepared by a molten salt method using Li 2CO 3 salt. The influences of synthetic temperature and time have been intensively investigated. It is easy to obtain materials with a hexagonal α-NaFeO 2 structure except broad peaks between 20° and 25°. Nickel in Li 1 + x (Ni 0.5Mn 0.5) 1 − x O 2 is oxidized to a trivalent state while manganese maintained a tetravalent state. It is found that the discharge capacities of all samples increase with cycling. The sample prepared at 850 °C for 5 h has a discharge capacity of 130 mAh g − 1 between 2.5 and 4.5 V versus V Li+/Li at a specific current of 0.13 mA cm − 2 after 50 cycles at 25 °C.

XPS, XRD and SEM characterization of a thin ceria layer deposited onto graphite electrode for application in lithium-ion batteries

Thin ceria layer deposited by electro-precipitation onto graphite was synthesised and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electro-precipitated ceria has a cubic structure with nanocrystallites of about 6 nm. The SEM analyses shows that the ceria layer reflects the morphology of the graphite electrode, exhibits small cracks usually found on the electro-precipitated films but covers almost completely the surface of the graphite. The ceria layer is composed of 75% Ce(IV) and 25% Ce(III) oxides as indicated by the XPS analyses. Cyclic voltammetry and galvanostatic charge–discharge tests in ethylene carbonate/dimethyl carbonate (1/1) (wt/wt) in the presence of 1 M LiPF 6 show that reversible lithium insertion and deinsertion occurs in the graphite/ceria electrode and that the ceria layer on the graphite electrode prevents from the loss of capacity during the first four cycles. The reduction of the electrolyte occurs at about 0.7 V vs Li/Li + on both electrodes but XPS and SEM analyses show that the SEI layer is thin and not as homogenous on the graphite as on the graphite/ceria electrode. The composition of the SEI layer on the graphite/ceria electrode, mainly composed of Li 2CO 3, ROCO 2Li, R–CH 2OLi and LiF, is different than those obtained on the graphite.