Electrode Composite LiFePO₄@Carbon: Structure and Electrochemical Performances

Abstract

This work aimed at preparing the electrode composite LiFePO4@carbon by hydrothermal and the calcination process was conducted at 600, 700, and 800°C. The structure and morphology were determined by X-ray diffraction (XRD), SEM, Raman spectroscopy, X-ray photon spectroscopy (XPS), and thermal analysis. The XRD refinement’s results point out the orthorhombic structure without impurity phase and the high crystalline of synthesized olivines. The results of Raman spectroscopy and XPS confirmed the pure olivine phase as well as the successful carbon coating on the surface of olivines’ powders. Moreover, the calcinated temperature affected the morphology as well as the electrochemical performance of synthesized olivines. The electrochemical measurements were conducted by cyclic voltammetry and galvanostatic cycling test. The diffusion coefficients were calculated from cyclic voltammetry curves and reached 1.09 × 10−12 cm2/s for LFP600, 2.28 × 10−11 cm2/s for LFP700, and 3.27 × 10−12 cm2/s LFP800. The cycling test at rate C/10 exhibited an excellent cyclability with discharge capacity of 145 mAh/g for LFP600, 170 mAh/g for LFP700, and 160 mAh/g for LFP800.

Lithium Iron Phosphate/Carbon (LFP/C) Composite Using Nanocellulose as a Reducing Agent and Carbon Source

“…The C 1s spectrum (Figure 8A) shows the same signals identified in the cathode (below) as in the cycled coin cell (above), but with greater intensity-mainly because the cycled cathode was dried inside the glove box, so it might contain remains of the used electrolyte (LiPF 6 , in EC/DMC solvents) that contain C-C, C-O, and C=O bonds, which would influence the intensities observed in the cathode after cycling. The same tendency can be observed in the high-resolution O 1s spectrum (Figure 8B), with the C-O functional groups; the peak near 531 eV can be attributed to the phosphate group in the LFP material [51]. On the other hand, the appearance of a second signal in the F 1s spectrum (Figure 8C) when the coin cell is cycled indicates the presence of LiF ionic bonds [52] formed for the reduction of anions in carbonate electrolytes [53] (e.g., the LiPF 6 electrolyte in the EC/DMC solvent that may have remained once the cell was opened to characterise the cathode).…”

Structure and Electrochemical Behavior of Minor Mn-Doped Olivine LiMnxFe1−xPO4

“…e TEM images were coherent to SEM images. e Raman spectra of two Mn-doped olivines in Figure 5 show two fingerprint signals of carbon in the high-frequency region at 1385 cm − 1 (D-band) and 1583 cm − 1 (G-band) that confirm the composites between Mn-doped olivine and carbon LiMn x Fe 1− x PO 4 @C [14][15][16][17].…”

“…where A is the surface area of the cathode (0.785 cm 2 ); C is the concentration of Li + ions in the material (cm 3 /mol); and n is the number of transferred electron (n � 1). Figure 7(c) shows a linear proportion between i pc and v were obtained between 10 − 14 − 10 − 13 cm 2 /s [15,19,20]. erefore, partial Mn substitution in the olivine structure benefits the ionic conductivity through the soar of D Li , compared with the original olivine phase.…”

Synthesis of LiFePO4/C as the positive material for LiFePO4/GRAPHITE Lithium‒Ion batteries

“…Để cải thiện các nhược điểm trên, vật liệu LFP đã được nghiên cứu tổng hợp ở kích thước nano, phủ carbon lên bề mặt hạt vật liệu và pha tạp thêm các kim loại như Ni, Mn, Co… Vật liệu LFP phủ carbon (LFP/C) được xem là một hướng hiệu quả để khắc phục các nhược điểm của vật liệu này vì giúp ngăn chặn sự hình thành tạp chất Fe 3+ , giảm kích thước hạt, tăng độ dẫn điện electron, khả năng khuếch tán ion Li + , từ đó cải thiện dung lượng riêng và độ bền phóng sạc của vật liệu LFP 2 . Một số nguồn tiền chất hữu cơ được sử dụng để tạo lớp phủ carbon cho LFP đã được nghiên cứu như sucrose, glucose, carboxylic acid, adipic acid, tinh bột, ethylene glycol, polythiophene và polyacene [4][5][6][7][8][9][10][11] . Mỗi tiền chất có khả năng tạo lớp phủ carbon khác nhau, ảnh hưởng đến tính chất điện hóa của vật liệu LFP [12][13][14] .…”