Recent Progress on Honeycomb Layered Oxides as a Durable Cathode Material for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are becoming promising candidates for energy storage devices due to the low cost, abundant reserves, and excellent electrochemical performance. As the most important unit, layered cathodes attract much attention, where honeycomb-layered-oxides (HLOs) manifest outstanding structural stability, high redox potential, and long-life electrochemistry. Here, recent progress on HLOs as well as Na₃ Ni₂ SbO₆ and Na₃ Ni₂ BiO₆ as two representative materials are introduced, and the crystal and electronic structure, electrochemical performance, and modification strategies are summarized. The advanced high nickel HLOs are highlighted toward development of state-of-the-art sodium-ion batteries. This review would deepen the understanding of superstructure in layered oxides, as well as structure-property relationship, and inspire more interest in high output voltage, long lifespan sodium-ion batteries.

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.

Li0.93V2.07BO5: a new nano-rod cathode material for lithium ion batteries

The compound Li_0.93V_2.07BO₅ (LVBO) has been successfully designed and used for the first time as a cathode material for lithium ion batteries (LIBs). It belongs to a new family of lithium transition metal borates, namely LiMBO₃ (M = Mn, Fe or Co), which are regarded as good alternatives to phosphates because of their comparably lower molecular weights, which can lead to a larger theoretical specific capacity than those of phosphate-based LiMPO₄. LVBO crystallizes in the space group Pbam with V atom and Li atom occupying the same sites, which makes the structure more stable and brings a disorder effect. Further structure and components of the promising cathode material have been characterized based on the results of X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and inductively coupled plasma mass spectrometry. The synthesized LVBO/C material displays a nanorod morphology with a size of 20-100 nm and shows good electrochemical activity. When used as cathode material in LIBs, LVBO/C delivers an initial discharge specific capacity of 125 mA h g^-1 and exhibits relatively good cycle stability. These results are of great interest for further study of its electrochemical behaviors, which is of significance in exploring new borate cathode materials for LIBs.

A density functional theory study of the carbon-coating effects on lithium iron borate battery electrodes

Density functional theory modelling shows that carbon coatings on a LiFeBO₃ cathode material does not impede the Li transport in a Li-ion battery.

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.

Spherical LiCoBO3 particles prepared via a molten salt method for lithium ion batteries

LiCoBO₃/ketjen black composites were prepared at a moderate temperature of 450 °C by a molten salt method using eutectic mixtures of LiCl and KCl as the reaction medium and ketjen black as a carbon source.

Nanocubic KTi2(PO4)3 electrodes for potassium-ion batteries

Novel nanocubic KTi₂(PO₄)₃ was successfully fabricated via a facile hydrothermal method combined with a subsequent annealing treatment and further evaluated as an electrode material for potassium-ion batteries for the first time.

Electrochemical activity and high ionic conductivity of lithium copper pyroborate Li6CuB4O10

Conductivity of Li₆CuB₄O₁₀ as function of temperature highlighting a reversible structural transition leading to a high ionic conductivity of ∼1.4 mS cm⁻¹ at 500 °C.

Synthesis and electrochemical properties of Li(Fe0.5Co0.5)BO3

A new borate compound LiFe_0.5Co_0.5BO₃ has been successfully synthesized for the first time by a multiple-step process. This compound delivers a very interesting first discharge capacity of 120 mA h g⁻¹ at C/20 rate without in situ carbon coating.

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).

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.