Efficient Preparation of Li2FeSiO4/C with High Purity and Excellent Electrochemical Performance in Li-Ion Batteries

One method to enhance the electrochemical performance of carbon-coated Li2FeSiO4 cathode material in lithium-ion batteries is to produce an ideal Li2FeSiO4 precursor with minimal impurities. A novel precursor for Li2FeSiO4 (Li2O·FeCO3·CH3OSiO2H) was synthesized through a methanol solvothermal reaction under stringent conditions (180 °C and 2.7 MPa), achieving a purity level of 93.2%. During synthesis, the new Li2FeSiO4 precursor exhibits unique self-purification properties and maintains a fine morphology after annealing. The resulting carbon-coated Li2FeSiO4 composites demonstrate a Brunauer-Emmett-Teller specific surface area of 102.4 m2/g and approximately 81% mesoporous volume, with 90% of the pore sizes measuring less than 39 nm. As a cathode material for lithium-ion batteries, this carbon-coated Li2FeSiO4 exhibits initial specific capacities of 172.3 mAh/g (charge) and 159.3 mAh/g (discharge). Remarkably, nearly 50% of the theoretical specific capacity remains after 1300 cycles at a rate of 0.1 C. The excellent electrochemical performance of the carbon-coated Li2FeSiO4 materials is demonstrated by their high lithium-ion diffusivity (DLi+) value of 1.26 × 10-11 cm2/s. Additionally, the enormous capacities-controlled diffusion contribution, which accounts for 70% of the total diffusion at a rate of 1C, is noteworthy. This performance can be attributed to the high purity of the carbon-free Li2FeSiO4 composite, which contains 91% Li2FeSiO4, as well as its favorable morphology.

Well-Dispersed Fe Nanoclusters for Effectively Increasing the Initial Coulombic Efficiency of the SiO Anode

An efficient surface modification strategy is proposed to significantly increase the initial Coulombic efficiency (ICE) of SiO anode material. The SiO@Fe material with the Fe nanocluster homogeneously decorating on the SiO surface is successfully prepared by a chemical vapor deposition process. The well-dispersed Fe nanoclusters realize an Ohmic contact with lithium silicates, the commonly regarded irreversible lithiation product, which effectively lowers the electron conduction barriers and promotes the concomitant lithium-ion release of the lithium silicates upon the delithiation process, increasing the ICE of the SiO anode. The prepared SiO@Fe exhibits a much higher ICE of 87.2% compared to 64.4% of pristine SiO, with the largest increment (23%) never reported, except for the prelithiation, and delivers significantly enhanced cycling and rate performance. These findings provide an effective way to convert the "inert" phase to "active" which essentially increases the ICE of the electrode.

Structural and luminescent studies of titanium co-doped SrY2 O4 :Eu phosphors

Herein, europium doped (1 to 11 mol%) and titanium (1 to 5 mol%) co-doped SrY₂ O₄ :Eu phosphors were synthesized via solid-state reaction method. The synthesized samples were characterized via X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and photoluminescence (PL) techniques for structural, morphological, functional group and photoluminescent studies, respectively. XRD patterns confirmed the formation of pure phase SrY₂ O₄ at 1300 °C and structural parameters were further determined by employing Rietveld refinement. FESEM micrographs results revealed that doped and co-doped samples have different morphological features. All the samples were excited at UV excitation and emission spectra consisted of peaks corresponding to the Eu ions. The maximum PL intensity is observed for 9mol% of Eu ions and 3 mol% co-doping of Ti ions. The synthesized phosphors have potential applications in the optoelectronics and display devices.

Excitonic effects in the optical spectra of Li2SiO3 compound

Li2SiO3 compound exhibits unique electronic and optical properties. The state-of-the-art analyses, which based on first-principle calculations, have successfully confirmed the concise physical/chemical picture and the orbital bonding in Li-O and Si-O bonds. Especially, the unusual optical response behavior includes a large red shift of the onset frequency due to the extremely strong excitonic effect, the polarization of optical properties along three-directions, various optical excitations structures and the most prominent plasmon mode in terms of the dielectric functions, energy loss functions, absorption coefficients and reflectance spectra. The close connections of electronic and optical properties can identify a specific orbital hybridization for each distinct excitation channel. The presented theoretical framework will be fully comprehending the diverse phenomena and widen the potential application of other emerging materials.

Raspberry-Like Mesoporous Zn1.07Ga2.34Si0.98O6.56:Cr0.01 Nanocarriers for Enhanced Near-Infrared Afterglow Imaging and Combined Cancer Chemotherapy

Near-infrared (NIR) persistent luminescence (PersL) nanoparticles based on trivalent chromium-doped gallates (ZGO) as nanocarriers show great potential for theranostics, owing to their autofluorescence-free background and deep tissue penetration. However, high drug loading capacity of ZGO nanocarriers remains a big challenge. Herein, raspberry-like mesoporous Zn_1.07Ga_2.34Si_0.98O_6.56:Cr_0.01 (designated as Si-ZGO) is first developed via a unique silica-assisted targeted etching strategy. The composition, morphology, NIR PersL capacities, and drug loading/releasing abilities of Si-ZGO have been explored. These results exhibit that Si-ZGO possess multiple inspiring characteristics including (i) spherical raspberry-like mesoporous morphology with a large cavity (total pore size ∼5.0 nm) and high specific surface area (∼80.653 m²·g^-1), promising excellent drug loading capacity (∼62 wt %); (ii) tunable sizes from 80 to 180 nm and improved aqueous-dispersibility, facilitating cellular uptake and permeation and retention (EPR) effect; (iii) new deep traps related to oxygen vacancies, achieving the brighter NIR PersL. These outstanding merits enable the further nanosystem (DOX-BSA@Si-ZGO) for proof-of-concept theranostics excellent chemotherapy effect, tumor-specific trackable ability, and pronounced NIR afterglow imaging in vivo. This work demonstrates the great potentials of Si-ZGO nanorasperries as a multifunctional theranostics platform, even more it hopefully could inspire other constructions of advanced functional materials.