Mixture Of LiBH4 Research Articles

Li-Ion Conductivity Enhancement of LiBH4·xNH3 with In Situ Formed Li2O Nanoparticles.

Interfacial engineering is an efficient approach to improve the ionic conductivity of solid-state electrolytes. In the present study, we report the enhancement of in situ formed nanocrystalline Li2O on the thermal stability and electrochemical properties of amide lithium borohydride, LiBH4·xNH3 (x = 0.67-0.8). LiBH4·xNH3-Li2O composites with different amounts of Li2O are prepared by a one-step synthesis process by ball milling the mixture of LiBH4, LiNH2, and LiOH in molar ratios of 1:n:n (n = 1, 2, 3, 4). Owing to the strong interfacial effect with nanocrystalline Li2O, LiBH4·xNH3 is converted to the amorphous state in the presence of 78 wt % Li2O at n = 4. Consequently, the ionic conductivity of LiBH4·xNH3 at 20 °C is improved by orders of magnitude up to 5.4 × 10-4 S cm-1, the NH3 desorption temperature is increased by more than 20 °C, and the electrochemical window is widened from 0.5 to 3.8 V.

Solid-state hydrogen desorption of 2 MgH2 + LiBH4 nano-mixture: A kinetics mechanism study

The dehydrogenation reaction pathway and rate-limiting step of a nano-LiBH4 + nano-MgH2 mixture with a 0.5:1 molar ratio, which has been shown to have the ability to reversibly release and absorb ∼5.7 wt% H2 at 265 °C, have been investigated in detail. The study reveals that the solid-state dehydrogenation kinetics of the MgH2 + 0.5 LiBH4 mixture at 265 °C is nucleation-and-growth controlled. The rate-limiting step for dehydrogenation via the two parallel reaction pathways has been identified through examination of the elementary reactions as the nucleation and growth of reaction products LiH and MgB2. The interfacial area between MgH2 and LiBH4 plays a critical role in the nucleation and growth of LiH and MgB2, and thus influence the dehydrogenation kinetics and H2 storage capacity of the MgH2 + 0.5 LiBH4 mixture. X-ray diffraction, SEM analysis and specific surface area measurements reveal that the evolution of the powder characteristics before and after isothermal hydrogen uptake/release cycles is consistent with the kinetics observation and analysis. This study indicates that to further improve the dehydrogenation kinetics of the MgH2 + LiBH4 mixture, the nucleation and growth rates of LiH and/or MgB2 should be enhanced in the future, while the interfacial area between MgH2 and LiBH4 should be increased and maintained to be as large as possible during hydrogen uptake/release cycles.

A quasielastic and inelastic neutron scattering study of the alkaline and alkaline-earth borohydrides LiBH4 and Mg(BH4)2 and the mixture LiBH4 + Mg(BH4)2.

Quasielastic neutron scattering was used to investigate the low energy transfer dynamics of the complex borohydrides Mg(BH4)2 in the α- and β-modifications, LiBH4 in the low and high temperature crystal structure, and an 1 : 1 molar mixture of LiBH4 + α-Mg(BH4)2. All investigated compounds show a rich dynamic behaviour below an energy range of ΔE = 10 meV with the superposition of rotational dynamics of the constituent [BH4]- anions and low lying lattice modes. For Mg(BH4)2, the rotational diffusion of the [BH4] units was found to be much more activated in the metastable β-polymorph compared to the α-phase, and the low lying lattice modes are even softer in the former crystal structure. In Mg(BH4)2, the structural phase transition is mainly governed by the lattice dynamics, while alkaline LiBH4 exhibits a transition of the [BH4] rotations around the phase transition temperature. Ball milled LiBH4 + α-Mg(BH4)2 remains a physical mixture of the parent compounds and each component retains its characteristic dynamic signature up to the melting temperature.

Enhanced hydrogen storage properties of 2LiBH4-LiAlH4 nanoconfined in resorcinol formaldehyde carbon aerogel

Resorcinol formaldehyde carbon aerogel (RFC)was synthesized in this paper to be used as a scaffold for nanoconfining 2LiBH4-LiAlH4composite. LiBH4 and LiAlH4 were nanoconfined into the pores of the prepared resorcinol formaldehyde carbon aerogel by a two-step melt-infiltration process. The microstructure evolution was investigated by XRD, FTIR analysis, and BET measurements. The hydrogen storage properties were studied by TPD, TG/DSC/MS measurements. The experimental results show that LiBH4 and LiAlH4 are well dispersed in the scaffold after the melt infiltration process. The nano-confined 2LiBH4-LiAlH4 composite (denoted as 2LiBH4-LiAlH4/RFC) shows a two-step dehydrogenation process. The onset dehydrogenation temperatures for the two steps are 100 °C and 280 °C, respectively, which are 70 °C and 170 °C lower than that of the milled 2LiBH4-LiAlH4 mixture. The formation of AlB2 during the second dehydrogenation step alters the reaction pathway of LiBH4. The kinetic properties of the composite are greatly enhanced compared to the physical mixture of LiBH4 and LiAlH4. The nanoconfinement and the formation of AlB2 have a combined effect on the improvement of hydrogen storage properties for nanoconfined 2LiBH4-LiAlH4/RFC. It could be rehydrogenated at 350 °C and 5 MPa H2. A reversible hydrogen storage capacity of 5.7 wt.% is achieved.

Development of complex hydride-based all-solid-state lithium ion battery applying low melting point electrolyte

Abstract A thermally durable all-solid-state lithium ion battery composed of a complex hydride, oxide electrolytes, and LiNi1/3Mn1/3Co1/3O2 active material is developed. This battery exhibits a discharge capacity of 56 mAh g−1, and the tenth capacity retention ratio is 29% at 150 °C owing to the large contact resistance between the electrolyte layer and the composite positive electrode layer. This large contact resistance is reduced by introducing an adhesive layer comprised of a mixture of LiBH4 and LiNH2 that is easily melted by thermal treatment and fills the voids and pores at the interface between the two layers. As a result, repeated charge-discharge cycles are successfully demonstrated at 150 °C with a high discharge capacity and discharge capacity retention ratio. The first discharge capacity is enhanced to 114 mAh g−1 and the capacity retention ratio at the tenth cycle is improved to 71%. These results demonstrate that using an adhesive layer is an effective measure to reduce the contact resistance and thereby enhance the performance of the battery.

Boric acid-destabilized lithium borohydride with a 5.6 wt% dehydrogenation capacity at moderate temperatures.

Boric acid effectively promotes the dehydrogenation of lithium borohydride due to the interactions between protonic and hydridic hydrogen. The simple mixture of LiBH4-(4/3)B(OH)3 can release 5.6 wt% hydrogen below 180 °C with only a trace amount of water, thus constituting a highly attractive single-use hydrogen storage material.

Synthesis Approach Influence on Morphology and Conductivity in (LiBH4)1-X(LiNH2)x

The aim of this work is understanding the relationship between Lithium diffusion in grain boundary and conductivity of LiBH4-LiNH2 ionic conductors. For the combinations of LiNH2 with other compounds in phase diagram, it seems that grain boundary area and grain size play an important role in conductivity. Studied material is combination of (LiBH4)1-x(LiNH2)x, where x=0.50 (Li2BH4NH2) and 0.75 (Li4BH4(NH2)3) synthesized by different methods (QU-quenching and BM-ball milling), so that they will have different grain sizes. Theoretically, QU has greatest grain size so lowest grain boundary and BM has lowest grain size with largest grain boundary. SEM and TEM characterization measurements are perform in order to have some overview conclusions about grain size as well as XRD patterns to calculate grain size by Bragg's law. HP DSC experiments have been perofrmed in order to understand the evolution of phases, and the released heat. Data can help in entropy calculations, which later can be used to obtain the Gibbs free energy values. System will be investigated by the electrochemical study (voltammogram measurements with different scan rates) for each sample to have information about diffusion of Li+. Furthermore, conductivity measurements of the materials will be executed for comparison. One of the key challenges toward high-power Li-ion batteries is to develop cheap, easy-to-prepare materials that combine high volumetric and gravimetric energy density with high power densities and a long cycle life. This requires electrode materials with large tap densities, which generally compromises the charge transport and hence the power density. In this work morphology - the surface properties, grain size and compaction of material will be studied. On the other hand, conductivity considering proper pressure usage and thermal cycling will be also introduced. Main motivation for this system selection was work of Orimo et al. They have reported the lithium fast-ion conductions in Li2(BH4)(NH2) and Li4(BH4)(NH2)3 consisting of (BH4)- and (NH2)- anions and now we would like to analyze it in context of microstructure. Mixtures of LiBH4 and LiNH2 from commercially available powders were handled in an inert atmosphere in glovebox. Ball milled samples were kept inside the O-ring sealed, hardened steel ball mill jars. Samples were milled at Laboratoire de Cristallographie in Geneva with a Fritsch Pulverisette 7. Another approach is using oven, where after heating at 190°C for 3h for composition 1:1 and 110°C for composition 1:3, the samples were quenched through immersing the reaction tube in cold water with presence of ice and finally re-ground under argon to improve crystallinity. Samples have been characterized by XRD, TEM, SEM, DSC as well as through electrochemical study and conductivity measurements. Quneching and ball milling is serving different purities of desired phase. Attached pictures is presenting differences in heat transfer of each approach as well as images after scanning electron microscopy. It is well established that ion diffusion along the grain boundaries can be orders of magnitude faster than bulk diffusion through the grains. Figure 1

ChemInform Abstract: Phase Behavior in the LiBH4—LiBr System and Structure of the Anion‐Stabilized Fast Ionic, High Temperature Phase.

AbstractPolycrystalline samples of Li(BH4)1‐xBrx are prepared from appropriate mixtures of LiBH4 and LiBr by both intermittent ball milling (24 h, 2 min breaks) alone and ball milling (4 h) followed by annealing (573 K, 5‐24 h).

Synthesis, crystal structure, thermal stability, and luminescent properties of lithium trimesate coordination polymer

A metal-organic coordination polymer of the formula [Li3(btc)(H2O)] (1a) (H3btc is the trimesic acid, C6H3(COOH)3) was obtained upon heating a mixture of LiBH4 and H3btc in ethanol. The structure was established by single crystal X-ray diffraction study. The studies by TGA show that polymer 1a loses the coordinated water at T ≥ 250 °C, whereas the metal-organic framework of lithium trimesate disintegrates only above 500 °C. The luminescence spectra showed a considerable (5-fold) increase in luminescence intensity and a bathochromic shift upon dehydration of 1a.

ChemInform Abstract: Synthesis of a Bimetallic Dodecaborate LiNaB12H12 with Outstanding Superionic Conductivity.

AbstractThe title compound is synthesized from a mixture of LiBH4, NaBH4, and B10H14 in a molar ratio of 1:1:1 (673 K, 10 h) and characterized by powder XRD, Raman spectroscopy, and 11B MAS NMR spectroscopy.

ChemInform Abstract: Construction of Two‐Dimensional MoS2/CdS p‐n Nanohybrids for Highly Efficient Photocatalytic Hydrogen Evolution.

AbstractTwo‐Dimensional MoS2/CdS nanohybrids with a sandwich‐like p‐n junction heterostructure, large specific surface area, and decreased band gap are solvothermally prepared from a DMSO suspension of well‐dispersed MoS2 nanosheets (obtained from a mixture of LiBH4 and bulk MoS2 in the molar ratio of 2.5:1 at 350 °C for 3 d) and Cd(OAc)2 (ultrasound, autoclave, 220 °C, 18 h).

Dust cloud combustion characterization of a mixture of LiBH4 destabilized with MgH2 for reversible H2 storage in mobile applications

This study discusses results of an experimental program to determine dust cloud combustion characteristics of 2LiBH4 + MgH2 binary system in air. The determined parameters of hydrided and partially-dehydrided states of this system include: maximum deflagration pressure rise (PMAX), maximum rate of pressure rise (dP/dt)MAX, minimum ignition temperature (TC), minimum explosible concentration (MEC), minimum ignition energy (MIE), and explosion severity index (KSt). Impact of dust particle size on the measured parameters is evaluated for the partially-dehydrided state. For dust of same mean particle size, results show the hydrided state to be more explosible in air compared to its partially-dehydrided state. Moreover, MIE of the partially-dehydrided mixture is identified in the test with lowest ignition delay time (IDT) and highest dust cloud concentration (DC). Taguchi's mixed-levels design of experiments (DoE) methodology is employed to calculate dust's MIE response surface as a function of DC and IDT. The one-at-a-time effect and interaction effect between DC and IDT on dust MIE are determined. The core insights of this contribution are useful for quantifying risks in mobile and stationary H2 storage applications, informing H2 safety standards, and augmenting property databases of H2 storage materials.

A Revisit to the Hydrogen Desorption/Absorption Behaviors of LiAlH4/LiBH4: Effects of Catalysts

The hydrogen desorption/absorption behaviors of LiAlH4/LiBH4 with a focus on the effects of catalysts, namely TiCl3, TiO2, VCl3, and ZrCl4, were investigated using a thermal-volumetric apparatus. The hydrogen desorption was performed from room temperature to 300 °C with a heating rate of 2 °C min−1. The LiAlH4–LiBH4 mixture with a molar ratio of 2:1 decomposed between 100 and 220 °C, and the hydrogen desorption capacity reached up to 6.6 wt %. Doping 1 mol % of a catalyst to the mixture resulted in the two-step decomposition and a decrease in the hydrogen desorption temperature. All the doped samples provided lower amountz of desorbed hydrogen than that obtained from the undoped one. No hydrogen absorption was observed under 8.5 MPa of hydrogen pressure and 300 °C for 6 h. Despite the fact each of the catalysts may affect the hydrogen storage behaviors of the mixture differently, none resulted in a change in the sample reversibility.

Dehydrogenation Kinetics and Modeling Studies of 2LiBH4 + MgH2 Enhanced by NbF5 Catalyst

Although LiBH4–MgH2 composite shows excellent hydrogen storage capacity, it still has the problem of sluggish kinetics. To improve the hydrogen desorption kinetics, mixtures of LiBH4–MgH2 (2:1) wer...

Nanoconfined mixed Li and Mg borohydrides as materials for solid state hydrogen storage

Several mixtures of LiBH4 and Mg(BH4)2 borohydrides in different stoichiometric ratios (1:0, 2:1, 1:1, 1:2, 0:1), prepared by high energy ball milling, have been investigated with X-ray powder diffraction and thermal programmed desorption (TPD) volumetric analysis to test the dehydrogenation kinetics in correlation with the physical mixture composition. Afterwards mixed and unmixed borohydrides were dispersed on high specific surface area ball milled graphite by means of the solvent infiltration technique. BET and statistical thickness methods were used to characterize the support surface properties, and SEM micrographs gave a better understanding of the preparation techniques. It has been observed by TPD volumetric measurements that the confinement of the reactive borohydrides on the nanoporous supports leads to a lower dehydrogenation temperature compared to unsupported borohydrides. Moreover, a further decrease of the dehydrogenation temperature has been observed by increasing the specific surface area of the support and the pores volume and by using the prepared mixtures instead of pure materials. The dehydrogenation process seems to be favoured by the heterogeneous nucleation on the graphite surface of decomposition products or intermediate phases from melted liquid borohydrides.

A Novel Li–Ca–B–H Complex Borohydride: Its Synthesis and Hydrogen Storage Properties

The synthesis and hydrogen-storage properties of the mixed alkali metal and alkaline-earth metal borohydride are systematically investigated. It is found that mechanical milling a mixture of LiBH4 and CaCl2 with molar ratio of 3:1 in tetrahydrofuran (THF) forms a new LiBH4·Ca(BH4)2·2THF compound. Thermal analysis indicates that the decomposition process of the new compound involves four steps: (1) LiBH4·Ca(BH4)2·2THF decomposes first into high temperature phase of LiBH4, CaB6, and an intermediate phase Ca–B–H–Cl hydride and synchronously releases a large number of H2 and THF gas together with less B2H6; (2) the eutectic melting of LiBH4 and Ca–B–H–Cl hydride; (3) Ca–B–H–Cl hydride decomposes into CaHCl, CaB6, and a little H2; (4) LiBH4 reacts with CaHCl, generating H2, CaH2, CaB6, LiH, and LiCl. The first dehydrogenation step starts at ca. 70 °C, which is much lower than that of the pristine LiBH4 and Ca(BH4)2. According to Kissenger’s equation, the activation energies of the different dehydrogenation ste...

Superior Destabilization Effects of MnF2 over MnCl2 in the Decomposition of LiBH4

A 3LiBH4/MnF2 composite was prepared by mechanically milling a mixture of LiBH4 and MnF2. The decomposition properties of the 3LiBH4/MnF2 composite were investigated and compared with those of the 3LiBH4/MnCl2 composite. Differing from the case for the 3LiBH4/MnCl2 composite where only cation substitution occurs, both the cation substitution of Mn2+ for Li+ and the anion substitution of F– for H– occur in the 3LiBH4/MnF2 composite. Moreover, compared to the 3LiBH4/MnCl2 composite, the 3LiBH4/MnF2 composite has a lower decomposition temperature, a higher purity of evolved hydrogen, and faster decomposition kinetics. These results suggest that MnF2 has superior destabilization effects over MnCl2 in the decomposition of LiBH4, which can be attributed to the reduced stability of B–H bonds by partial anion substitution of the F– for the H–.

Promotional Effect of Aluminum on MgH<SUB>2</SUB>+LiBH<SUB>4</SUB> Hydrogen Storage Materials

The effect of Al addition on the reversibility of a MgH2+2LiBH4 hydrogen storage mixture was examined in order to improve the mixture’s requirement for a hydrogen atmosphere even in dehydrogenation. The experiments using high pressure differential scanning calorimetry and X-ray powder diffraction confirmed that a MgH2+Al+4LiBH4 mixture can reversibly dehydrogenate and rehydrogenate below 773 K under mild conditions of 0.1 MPa H2 for dehydrogenation and 4.0 MPa H2 for rehydrogenation. Moreover, thermogravimetry tests revealed that this mixture starts hydrogen desorption at about 530 K, which is 80 K lower than the corresponding temperature for the MgH2+2LiBH4 mixture, and desorbs 9.5 mass% of hydrogen below 773 K. Thus, the addition of Al improves not only the reversibility of the reaction but also dehydrogenation kinetics. The hydrogen desorption of the mixture occurs by three steps, which includes the formation of Mg-Al alloys by the reaction of MgH2 and metallic Al followed by the formation of Mg1−xAlxB2 by the reaction of the Mg-Al alloys and LiBH4. Al in this mixture suppresses the formation of metallic Mg and accelerates the formation of Mg1−xAlxB2 from B produced by dehydrogenation of LiBH4. Mg1−xAlxB2 is derived from partial substitution of Al for Mg in MgB2, which contributes to reversible hydrogenation and dehydrogenation of MgH2+2LiBH4.

LiMn(BH<sub>4</sub>)<sub>3</sub>/2LiCl Composite Synthesized by Reactive Ball-Milling and Its Dehydrogenation Properties

以LiBH4和MnCl2为初始原料,采用反应球磨法制备了LiMn(BH4)3/2LiCl复合物,并系统地研究了该复合物的脱氢性能及含钛催化剂的掺杂对其脱氢性能的影响.结果表明:LiMn(BH4)3/2LiCl复合物是由非晶态的LiMn(BH4)3和晶态的LiCl组成,在135-190℃分解,分解反应的活化能为114.0 kJ·mol-1;LiMn(BH4)3/2LiCl复合物分解失重约7.0%(w).组分分析表明除H2外,释放的气体中还含有4.0%(摩尔分数,x)的B2H6.B2H6的生成是该复合物失重超过其理论储氢容量6.3%(w(的原因;进一步研究发现,含钛催化剂(TiF3、TiC、TiN和TiO2)中,仅TiF3能够催化LiMn(BH4)3/2LiCl复合物的分解反应,使其起始分解温度和分解反应活化能分别降低至125℃和104.0 kJ·mol-1.这主要归因于TiF3中的Ti原子取代了LiMn(BH4)3中的部分Li原子,并在局域形成了易于分解的Ti(BH4)3.

LiSc(BH4)4 as a Hydrogen Storage Material: Multinuclear High-Resolution Solid-State NMR and First-Principles Density Functional Theory Studies

A lithium salt of anionic scandium tetraborohydride complex, LiSc(BH4)4, was studied both experimentally and theoretically as a potential hydrogen storage medium. Ball milling mixtures of LiBH4 and ScCl3 produced LiCl and a unique crystalline hydride, which has been unequivocally identified via multinuclear solid-state nuclear magnetic resonance (NMR) to be LiSc(BH4)4. Under the present reaction conditions, there was no evidence for the formation of binary Sc(BH4)3. These observations are in agreement with our first-principles calculations of the relative stabilities of these phases. A tetragonal structure in space group I4̅ (#82) is predicted to be the lowest energy state for LiSc(BH4)4, which does not correspond to structures obtained to date on the crystalline ternary borohydride phases made by ball milling. Perhaps reaction conditions are resulting in formation of other polymorphs, which should be investigated in future studies via neutron scattering on deuterides. Hydrogen desorption while heating these Li−Sc−B−H materials up to 400 °C yielded only amorphous phases (besides the virtually unchanged LiCl) that were determined by NMR to be primarily ScB2 and [B12H12]−2 anion containing (e.g., Li2B12H12) along with residual LiBH4. Reaction of a desorbed LiSc(BH4)4 + 4LiCl mixture (from 4LiBH4/ScCl3 sample) with hydrogen gas at ∼70 bar resulted only in an increase in the contents of Li2B12H12 and LiBH4. Full reversibility to reform the LiSc(BH4)4 was not found. Overall, the Li−Sc−B−H system is not a favorable candidate for hydrogen storage applications.