Processes on the Thermodynamic Properties of Lithium Borates

1 Introduction Lithium and its compounds as national strategic resources are extensively used in national defense,industrial and agricultural production.As we know,the salt lakes in the western of China are famous for its high

Transformation Process and Mechanism of Lithium Borates

Amounts of lithium-containing salt lake brine resources are widely distributed in the four provinces named Qinghai,Tibet,Inner Mongolia and Xinjiang province,especially the salt lakes in Qinghai-Tibet Plateau are abundant of

Synthesis, Structure and Thermodynamic Property of a New Lithium Borate： Li4[B8O13（OH）2]·3H2O

A new hydrated lithium borate, Li4[B8O13（OH）2]·3H2O, has been hydrothermally synthesized and characterized by single crystal X-ray diffraction, FT-IR spectroscopy, simultaneous TGA-DTA and chemical analysis. It crystal- lizes in the triclinic, space group P]-, a=8.4578（5） A, b=8.7877（5） A, c= 10.8058（7） A, a=87.740（3）°, β= 71.819（3）°, γ=61.569（3）°, Z=2, V=665.26（7） A3, Dc=2.043 g/cm3. Its crystal structure features polyborate ani- onic layers with the larger odd 13-membered boron rings constructed by [B8O13（OH）2]4- FBBs. Through designing the thermochemical cycle, the standard molar enthalpy of formation of this borate was determined to be -（7953.8 ± 6.6） kJ·mol-1 by using a heat conduction microcalorimeter.

Synthesis of lithium difluoro(oxalate)borate(LiODFB), phase diagram and ions coordination of LiODFB in dimethyl carbonate

A new two-step synthetic method was successfully developed to simplify the recrystallization process of lithium difluoro(oxalate)borate(LiODFB).Meanwhile,the purity of LiODFB as-prepared was determined by NMR,ICP-AES and Karl Fisher measurements,respectively.The as-prepared LiODFB presents a high purity up to 99.95%.Its metal ions and water contents are under good control as well.Besides,its structure information and thermal properties were confirmed by FTIR,Raman and DSC-TGA analyses,respectively.LiODFB exerts fine thermostability and hypo-water-sensitivity and its structure information agrees well with previous literature.Furthermore,a combination of phase diagram and Raman spectroscopy were utilized to study the thermal phase behavior and ions coordination of LiODFB-DMC binary system to optimize the synthesis and recrystallization process.Although there are three types of molecular interaction forms(CIPs,AGG-IIa,AGG-IIIb)in LiODFB-DMC binary system,LiODFB can only be isolated as large single crystal solvate as LiODFB·(DMC)3/2 by slowly cooling subjected to the nucleation kinetics.Therefore,the fundamental information of our work is helpful in accelerating the application of LiODFB in Li-ion secondary batteries.

Electrochemical response of Nd^3＋ ions containing lithium borate glasses

The present investigation was to understand the electrical properties of 27.5 Li2O-（72.5–x） B2O（3-x）Nd2O3 with x=0.5, 1, 1.5 and 2 glasses. We analyzed the impedance data for a wide frequency range to get inside the conduction phenomenon. The conductivity of the glasses decreased due to the decrease in the mobility of mobile Li~＋ ions. This decrease was due to polymerization of glass network caused by the Nd^3＋ ions. Modulus formalism confirmed that the Li~＋ ions overcame the same barrier no matter whether it took part in the conduction process or relaxation process. Scaling of the electrochemical data showed that conduction process in the ion conducting glasses was composition dependent and not the temperature dependent.

Crystal Structure of Lithium Yttrium Borate LiY_6O_5(BO_3)_3

Single crystals of LiY6O5（BO3）3 were obtained by the flux method and its structure was determined by a four-circle automatic diffractometer with a MoKα radiation. It crystallizes in monoclinic, space group P21/n with a = 8.330（3）, b = 15.444（4）, c = 8.780（3）°A,β = 91.85（3）°, V = 1129.0（6）°A^3, Z = 4, Mr= 796.83, F（000） = 1456, μ = 30.567 mm^-1, Dc= 4.688 g/cm^3, the final R = 0.0722 and wR = 0.1304. It exhibits a three-dimensional fiamework of yttrium-oxygen polyhedra interconnected by common edges and corners. B and Li atoms are located in the planes and cavities formed by oxygen atoms, respectively.

The Fluorescence of Pr3+ in Zinc Lithium Bismuth Borate Glasses with Large Stimulated Emission Cross Section

Glass sample of Zinc Lithium Bismuth Borate (25-x) Bi2O3:20Li2O:20ZnO:35B2O3:xPr6O11, (where x = 1, 1.5 and 2 mol%) has been prepared by melt-quenching technique. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction. The absorption spectra of three Pr3+ doped zinc lithium bismuth borate glasses have been recorded at room temperature. The observed optical spectra are discussed in terms of energy states and the intensity of the transitions. The various interaction parameters like Slater-Condon, Lande, bonding and Racah parameters have been computed. Judd-Ofelt intensity parameters and laser parameters have also been calculated. The stimulated emission cross section (σp) for the transition (3P0 → 3F2) is found to be in the range 3.12 - 10.43 * 10-20 cm2. The σp values are comparatively large suggesting the possible utilization of these materials in laser applications.

Structure characterization and electrochemical properties of new lithium salt LiODFB for electrolyte of lithium ion batteries

Lithium difluoro(axalato)borate (LiODFB) was synthesized in dimethyl carbonate (DMC) solvent and purified by the method of solventing-out crystallization. The structure characterization of the purified LiODFB was performed by Fourier transform infrared (FTIR) spectrometry and nuclear magnetic resonance (NMR) spectrometry. The electrochemical properties of the cells using 1 mol/L LiPF6 and 1 mol/L LiODFB in ethylene carbonate (EC)/DMC were investigated, respectively. The results indicate that LiODFB can be reduced at about 1.5 V and form a robust protective solid electrolyte interface (SEI) film on the graphite surface in the first cycle. The graphite/LiNi1/3Mn1/3Co1/3O2 cells with LiODFB-based electrolyte have very good capacity retention at 55 ℃, and show very good rate capability at 0.5C and 1C charge/discharge rate. Therefore, as a new salt, LiODFB is a most promising alternative lithium salt to replace LiPF6 for lithium ion battery electrolytes in the future.

Mechanism of aluminum corrosion in LiFSI-based electrolyte at elevated temperatures

Lithium bis(fluorosulfonyl)imide(LiFSI) is a promising replacement for lithium hexafluorosphate due to its excellent properties. A solution to the corrosion of aluminum(Al) current collectors by LiFSI at elevated temperatures is essential. The mechanisms of Al corrosion in LiFSI-based electrolyte at 45 ℃ were studied with density functional theory calculations and spectroscopic investigations. It is found that the irregular, loose and unprotected AlF3 materials caused by the dissolution of co-generated Al(FSI)3 can exacerbate Al corrosion with the increase of temperature. Lithium bis(oxalate)borate(LiBOB) can effectively inhibit the Al corrosion with a robust and protective interphase;this can be attributed to the interfacial interactions between the Al foil and electrolyte. Boron-containing compounds promote the change from AlF3 to LiF, which further reinforces interfacial stability. This work allows the design of an interface to Al foil using LiFSI salt in lithium-ion batteries.

Forecasting conductivities of LiBOB-EC/DEC electrolytes by the mass triangle model

Conductivities of lithium bis（oxalato）borate （LiBOB）-ethyl carbonate （EC）/diethyl carbonaten （DEC） electrolytes at 25℃ and 50℃ were studied. The electrolyte component with the highest conductivity at each temperature was obtained through changing the concentration of LiBOB and the ratio of EC/DEC. The mass triangle model was applied to calculate the conductivity of Li- BOB-EC/DEC ternary system at 25℃ and 50℃. The results show that the calculated and experimental results have reached a good agreement. Therefore, it is expected that the experimental work can be vastly reduced by introducing the mass triangle model.

Multi-scale boron penetration toward stabilizing nickel-rich cathode

Nickel-rich layered oxides LiNi_(x)Co_(y)Mn_(1-x-y)O_(2)(x≥0.8)have been recognized as the preferred cathode materials to develop lithium-ion batteries with high energy density(>300 Wh kg^(−1)).However,the poor cycling stability and rate capability stemming from intergranular cracks and sluggish kinetics hinder their commercialization.To address such issues,a multi-scale boron penetration strategy is designed and applied on the polycrystalline LiNi_(0.83)Co_(0.11)Mn_(0.06)O_(2)particles that are pre-treated with pore construction.The lithium-ion conductive lithium borate in grain gaps functions as the grain binder that can bear the strain/stress from anisotropic contraction/expansion,and provides more pathways for lithium-ion diffusion.As a result,the intergranular cracks are ameliorated and the lithium-ion diffusion kinetics is improved.Moreover,the coating layer separates the sensitive cathode surface and electrolyte,helping to suppress the parasitic reactions and related gas evolution.In addition,the enhanced structural stability is acquired by strong B-O bonds with trace boron doping.As a result,the boron-modified sample with an optimized boron content of 0.5%(B5-NCM)exhibits a higher initial discharge capacity of 205.5 mAh g^(−1)at 0.1C(1C=200 mA g^(−1))and improved capacity retention of 81.7%after 100 cycles at 1C.Furthermore,the rate performance is distinctly enhanced by high lithium-ion conductive LBO(175.6 mAh g^(−1)for B5-NCM and 154.6 mAh g^(−1)for B0-NCM at 5C)

Boron nitride nanotube growth via boron oxide assisted chemical vapor transport-deposition process using LiNO3 as a promoter

High-purity straight and discrete multiwalled boron nitride nanotubes （BNNTs） were grown via a boron oxide vapor reaction with ammonia using LiNO3 as a promoter. Only a trace amount of boron oxide was detected as an impurity in the BNNTs by energy-dispersive X-ray （EDX） and Raman spectroscopies. Boron oxide vapor was generated from a mixture of B, FeO, and MgO powders heated to 1,150 ℃, and it was transported to the reaction zone by flowing ammonia. Lithium nitrate was applied to the upper side of a BN bar from a water solution. The bar was placed along a temperature gradient zone in a horizontal tubular furnace. BNNTs with average diameters of 30-50 nm were mostly observed in a temperature range of 1,280-1,320 ℃. At higher temperatures, curled polycrystalline BN fibers appeared. Above 1,320 ℃, the number of BNNTs drastically decreased, whereas the quantity and diameter of the fibers increased. The mechanism of BNNT and fiber growth is proposed and discussed.