The structure and electrochemical performance of LiFeBO3 as a novel Li-battery cathode material

Active-Site-Specific Structural Engineering Enabled Ultrahigh Rate Performance of the NaLi3Fe3(PO4)2(P2O7) Cathode for Lithium-Ion Batteries

Iron-based mixed-polyanionic cathode Na₄Fe₃(PO₄)₂(P₂O₇) (NFPP) has advantages of environmental benignity, easy synthesis, high theoretical capacity, and remarkable stability. From NFPP, a novel Li-replaced material NaLi₃Fe₃(PO₄)₂(P₂O₇) (NLFPP) is synthesized through active Na-site structural engineering by an electrochemical ion exchange approach. The NLFPP cathode can show high reversible capacities of 103.2 and 90.3 mA h g^-1 at 0.5 and 5C, respectively. It also displays an impressive discharge capacity of 81.5 mA h g^-1 at an ultrahigh rate of 30C. Density functional theory (DFT) calculation demonstrates that the formation energy of NLFPP is the lowest among NLFPP, NFPP, and NaFe₃(PO₄)₂(P₂O₇), indicating that NLFPP is the easiest to form and the conversion from NFPP to NLFPP is thermodynamically favorable. The Li substitution for Na in the NFPP lattice causes an increase in the unit cell parameter c and decreases in a, b, and V, which are revealed by both DFT calculations and in situ X-ray powder diffraction (XRD) analysis. With hard carbon (HC) as the anode, the NLFPP//HC full cell shows a high reversible capacity of 91.1 mA h g^-1 at 2C and retains 82.4% after 200 cycles. The proposed active-site-specific structural tailoring via electrochemical ion exchange will give new insights into the design of high-performance cathodes for lithium-ion batteries.

Titanium-Substituted Tavorite LiFeSO4 F as Cathode Material for Lithium Ion Batteries: First-Principles Calculations and Experimental Study

Titanium-substituted LiTi_x Fe_1-2x SO₄ F (x=0, 0.01, 0.02, 0.03) cathode materials were synthesized by a solvothermal method. X-ray diffraction, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy were used to investigate the effects of Ti substitution on the structure of LiFeSO₄ F, and it was shown that Ti substitutes the Fe(2) site. First-principles calculations and UV-visible spectroscopy demonstrate that Ti substitution reduces the bandgap of LiFeSO₄ F which improves the electronic conductivity from 8.3×10^-12  S cm^-1 to 3.9×10^-11  S cm^-1 . CI-NEB and BV calculations show that the Li diffusion energy barriers along the (100), (010) and (101) directions are decreased after Ti substitution, and the Li diffusion coefficient is increased from 4.99×10^-11  cm²  S^-1 to 1.59×10^-10  cm²  S^-1 . The improved electronic conductivity and ionic diffusivity mean that the Ti-substituted material shows improved electrochemical properties compared to the pristine LiFeSO₄ F.

Ab Initio Study of AMBO3 (A = Li, Na and M = Mn, Fe, Co, Ni) as Cathode Materials for Li-Ion and Na-Ion Batteries

According to the importance of polyanion cathode materials in intercalation batteries, they may play a significant role in energy-storage systems. Here, evaluations of LiMBO₃ and NaMBO₃ (M = Mn, Fe, Co, Ni) as cathode materials of Li-ion and Na-ion batteries, respectively, are performed in the density functional theory (DFT) framework. The structural properties, structural stability after deintercalation, cell voltage, electrical conductivity, and rate capability of the cathodes are assessed. As a result, Li compounds have more structural stability and energy density than Na compounds in the C2/c frame structure. Cell voltage is increased by increasing the atomic number of the transition metal (TM). A noble approach is used to evaluate electrical conductivity and rate capability. M = Fe compounds exhibit the lowest band gaps (BGs), and M = Mn compounds exhibit almost the highest one. The best electrical rate-capable compounds are estimated to be M = Mn ones and the worst are M = Ni ones. As far as cell potential is not the concern, AMnBO₃, ACoBO₃-AFeBO₃, and ANiBO₃ are the best to the worst considered cathode materials.

Spray-Drying Synthesis of LiFeBO3/C Hollow Spheres With Improved Electrochemical and Storage Performances for Li-Ion Batteries

LiFeBO₃/C cathode material with hollow sphere architecture is successfully synthesized by a spray-drying method. SEM and TEM results demonstrate that the micro-sized LiFeBO₃/C hollow spheres consist of LiFeBO₃@C particles and the average size of LiFeBO₃@C particles is around 50–100 nm. The thickness of the amorphous carbon layer which is coated on the surface of LiFeBO₃ nanoparticles is about 2.5 nm. LiFeBO₃@C particles are connected by carbon layers and formed conductive network in the LiFeBO₃/C hollow spheres, leading to improved electrical conductivity. Meanwhile, the hollow structure boosts the Li⁺ diffusion and the carbon layers of LiFeBO₃@C particles protect LiFeBO₃ from moisture corrosion. Consequently, synthesized LiFeBO₃/C sample exhibits good electrochemical properties and storage performance.

Highly active Fe3BO6 as an anode material for sodium-ion batteries

A highly efficient Fe₃BO₆ anode prepared via a solid-state synthesis method is studied for sodium-ion batteries. The Fe₃BO₆ anode shows high capacity and excellent rate capability. The ex situ X-ray diffraction results show that the Na⁺ ion storage mechanism involves conversion based reactions between iron oxides and sodium.

Enhancing the rate performance of spherical LiFeBO3/C via Cr doping

Spherical LiFe_1−xCr_xBO₃/C (x = 0, 0.005, 0.008) has been successfully synthesized by ball-milling and spray-drying assisted high-temperature solid-state reaction.

Mechanical Milling Assisted Synthesis and Electrochemical Performance of High Capacity LiFeBO3 for Lithium Batteries

Borate chemistry offers attractive features for iron based polyanionic compounds. For battery applications, lithium iron borate has been proposed as cathode material because it has the lightest polyanionic framework that offers a high theoretical capacity. Moreover, it shows promising characteristics with an element combination that is favorable in terms of sustainability, toxicity, and costs. However, the system is also associated with a challenging chemistry, which is the major reason for the slow progress in its further development as a battery material. The two major challenges in the synthesis of LiFeBO3 are in obtaining phase purity and high electrochemical activity. Herein, we report a facile and scalable synthesis strategy for highly pure and electrochemically active LiFeBO3 by circumventing stability issues related to Fe(2+) oxidation state by the right choice of the precursor and experimental conditions. Additionally, we carried out a Mössbauer spectroscopic study of electrochemical charged and charged-discharged LiFeBO3 and reported a lithium diffusion coefficient of 5.56 × 10(-14) cm(2) s(-1) for the first time.

Advances in high-capacity Li2MSiO4 (M = Mn, Fe, Co, Ni, …) cathode materials for lithium-ion batteries

This review highlights the high-capacity Li₂MSiO₄ (M = Mn, Fe, Co, Ni, …) cathode materials for lithium-ion batteries.

Relating voltage and thermal safety in Li-ion battery cathodes: a high-throughput computational study

High voltage and high thermal safety are desirable characteristics of cathode materials, but difficult to achieve simultaneously DFT calculations on >1400 Li ion battery cathode materials indicate a complex inverse relationship between voltage and thermal safety.

Thin-film and bulk investigations of LiCoBO₃ as a Li-ion battery cathode

The compound LiCoBO3 is an appealing candidate for next-generation Li-ion batteries based on its high theoretical specific capacity of 215 mAh/g and high expected discharge voltage (more than 4 V vs Li(+)/Li). However, this level of performance has not yet been realized in experimental cells, even with nanosized particles. Reactive magnetron sputtering was therefore used to prepare thin films of LiCoBO3, allowing the influence of the particle thickness on the electrochemical performance to be explicitly tested. Even when ultrathin films (∼15 nm) were prepared, there was a negligible electrochemical response from LiCoBO3. Impedance spectroscopy measurements suggest that the conductivity of LiCoBO3 is many orders of magnitude worse than that of LiFeBO3 and may severely limit the performance. The unusual blue color of LiCoBO3 was investigated by spectroscopic techniques, which allowed the determination of a charge-transfer optical gap of 4.2 eV and the attribution of the visible light absorption peak at 2.2 eV to spin-allowed d → d transitions (assigned as overlapping (4)A2' to (4)A2″ and (4)E″ final states based on ligand-field modeling).

Synthesis, properties and applications of nanoscale nitrides, borides and carbides

Nanoscale nitrides, borides and carbides are a fascinating type of materials, which have aroused tremendous and continuous research interest for decades owing to their special mechanical, electrical, optical, photoelectronic, catalytic properties and widespread uses. In this feature article, recent developments and breakthroughs in the synthesis, properties and applications of nanometre scale nitrides (BN, Si(3)N(4), GaN, noble nitrides), borides (LnB(6), LnB(2), Fe(3)BO(5), LiMBO(3)) and carbides (carbon, SiC, TiC, NbC, WC) were briefly reviewed in sequence of their different dimensions (1D, 2D and 3D). In particular, our latest advances in the "autoclave route" fabrication of nanoscale nitrides, borides, and carbides were highlighted. The challenges, issues and perspectives of the synthetic methodologies and potential applications concerning the above-mentioned materials were also briefly discussed.

Structural modulation in the high capacity battery cathode material LiFeBO3

The crystal structure of the promising Li-ion battery cathode material LiFeBO(3) has been redetermined based on the results of single crystal X-ray diffraction data. A commensurate modulation that doubles the periodicity of the lattice in the a-axis direction is observed. When the structure of LiFeBO(3) is refined in the 4-dimensional superspace group C2/c(α0γ)00, with α = 1/2 and γ = 0 and with lattice parameters of a = 5.1681 Å, b = 8.8687 Å, c = 10.1656 Å, and β = 91.514°, all of the disorder present in the prior C2/c structural model is eliminated and a long-range ordering of 1D chains of corner-shared LiO(4) is revealed to occur as a result of cooperative displacements of Li and O atoms in the c-axis direction. Solid-state hybrid density functional theory calculations find that the modulation stabilizes the LiFeBO(3) structure by 1.2 kJ/mol (12 meV/f.u.), and that the modulation disappears after delithiation to form a structurally related FeBO(3) phase. The band gaps of LiFeBO(3) and FeBO(3) are calculated to be 3.5 and 3.3 eV, respectively. Bond valence sum maps have been used to identify and characterize the important Li conduction pathways, and suggest that the activation energies for Li diffusion will be higher in the modulated structure of LiFeBO(3) than in its unmodulated analogue.