Papers by Keyword: Lithium Iron Phosphate

Abstract: Lithium iron phosphate (LFP) is a commonly used cathode material in lithium-ion batteries, particularly for electric vehicle (EV) battery energy storage systems. To support sustainability and the principles of a circular economy, recycling spent LFP batteries is essential. This study focuses on the direct regeneration of spent LFP cathode material using an aqueous relithiation method conducted at low temperature, followed by post-annealing. The waste precursors and regenerated LFP were fully characterized for its structural, morphological, and compositional properties. Fourier-transform infrared (FTIR) analysis confirmed the presence of additive carbon and electrolyte residues in the spent LFP. XRD analysis revealed that certain components of the LFP structure in the as received spent cathode material decomposed, as evidenced by the presence of impurity peaks due to FePO₄ and P₂O₅, which disappeared after relithiation. The lattice parameter values (a=4.6897 Å and c=10.3211 Å) of the regenerated LFP were also found to be close to the theoretical (a=4.6925 Å and c=10.3253 Å), suggesting successful structure repair after regeneration. SEM indicated that regenerated LFP particles appeared to be more well-dispersed and finer than spent LFP particles. EDS mapping revealed a relatively homogeneous elemental distrbution of the major identified elements. ICP analysis further confirmed the successful restoration of Li content. The composition of the spent cathode, initially Li_0.85FePO₄, transformed to Li_1.03FePO₄ after regeneration, corresponding to an increase in Li content from the as-received 3.75 to 4.53 wt% Li after relithiation.

Abstract: Lithium iron phosphate (LiFePO₄) based material is one of the most prospective candidates as a cathode material in lithium-ion batteries because of its lower cost, safer, and environmental benignity compared to lithium cobalt oxide (LiCoO₂), which is commonly used for lithium-ion batteries manufacturing. However, its low conductivity is the obstacle of this material to solve, so that modification with the addition of silicon (Si) is expected to improve the electrochemical performance. Meanwhile, solid state reaction is considered simple and effective in LiFePO₄ crystal growth process. Therefore, Si-doped LiFePO₄ using solid state reaction in this research aims to study its structure and morphology as well as the effect of adding Si to its conductivity. The synthesis began with mixing LiH₂PO₄, Fe₂O₃, carbon black, and six-mole ratio variation of Si to LiFePO₄ using agate with ethanol: acetone addition then dried in an oven at 80°C and heated at 550°C in a furnace for 6 hours under argon atmosphere and sintering temperature of 870°C for 16 hours with the same condition. The sample of 3% mole ratio performed the highest conductivity of all variations with 3.01 x 10^-6 S.cm^-1, and was identified as Li_0.93Fe_1.07P_0.93O₄Si_0.7 with orthorhombic structure, Pnma space group (Ref. Code: ICSD 98-016-1792) with the highest peak at 2θ = 35.556° from XRD analysis with rectangular-like shape particle.

Abstract: Well-crystallized and nanosized LiFePO₄/C composite have been successfully synthesized by spray-drying under N₂ atmosphere. The morphology, physical and electrochemical properties of the LiFePO₄/C were tested and analyzed. The charge transfer resistances (Rct) and chemical diffusion coefficients of lithium ions (D_Li+) in LiFePO₄/C was systematically tested by EIS. The results show that the lithium ions diffusion coefficients obtained from EIS is 1.58×10^-14 cm²·s^-1. The assembled soft-packed cell with LiFePO₄/C show better rate capability and cycling stability. The average capacity retention of LiFePO₄/C soft-packed cell decreases to 100%, 98.9%, 96.5%, 92.4%, and 90.3% when current rate increases to 0.3, 0.5, 1, 2, and 3C, respectively. The capacity retention after 80 cycles is retained at more than 99%.

Abstract: Synthesis and characterization of LiMn_0.7Fe_0.3PO₄/CNT/C composite used as lithium ion battery cathode has been carried out. The active materials of LiMn_0.7Fe_0.3PO₄ was synthesized via hydrothermal method from the precursors of LiOH, NH₄H₂PO₄, FeSO₄.7H₂O and MnSO₄.7H₂O. The activated carbon was pyrolyzed from coconut shell whereas the carbon nanotube (CNT) was commercially available in the market. The composite was prepared using a ball-mill to mix the components homogeneously. Simultaneous thermal analysis STA was used to determine the formation temperature of LiMn_0.7Fe_0.3PO₄ to which the sintering process was conducted at 700 °C. After sintering, the materials in powder forms were characterized using scanning electron microscope (SEM) to examine the morphology, whereas X-ray diffraction (XRD) was used to identify the phases formed. The performance of the composite as lithium ion battery cathode was characterized using electrochemical impedance spectroscopy (EIS) and battery analyzer. Secondary electron image from SEM showed that the samples have homogeneous particle distribution. Examination result from X-ray diffraction indicated that LiMn_0.7Fe_0.3PO₄ phase has been successfully synthesized with small impurities from a secondary phase. Performance analysis showed that the presence of activated carbon and CNTs in LiMn_0.7Fe_0.3PO₄ to form LiMn_0.7Fe_0.3PO₄/CNTs/C gives significant improvement in the conductivity; however, some more improvement is still needed for the capacity.

Abstract: LiFePO4 is considered as the promising cathode material for a large-scale Li batteries used in electrical vehicles (EVs). However, a practical use of LiFePO4 cathode is limited by its low ionic conductivity, resulting in low battery’s power performance. This work, a facile and practical method to promote ionic conductivity and capacity of LiFePO4 was developed by dispersing LiFePO4 nanoparticles into a porous nitrogen-riched carbon matrix by employing one-pot synthesis approach. The N-containing carbon porous matrix was prepared by utilizing melamine-formaldehyde (MF) resin as the N-containing carbon precursor and Pluronic F127 as the porous template. The pseudo capacitive effect attributed from lone-pair electrons into melamine functional group was expected to support Li ion transport. After carbonization at 600 °C, uniform LiFePO4 nanocomposite clusters with an average size of about 50-300 nm were obtained. The influence of the molar ratio between pluronic F127 and melamine-formaldehyde (i.e. F127:MF molar ratio as 0:1, 0.03:1, 0.3:1) on the LiFePO4 nanocomposite’s morphology and crystalline structure was investigated by using scanning electron microscope and X-ray diffraction technique. The results show that increasing F127 concentrations support more porous structure formation, leading to a higher surface area but does not affect the LiFePO4 nanocrystalline structure. According to the highest surface area, the N-doped carbon coated LiFePO4 composite product obtained from the molar ratio of F127:MF as 0.3:1 exhibited highest discharging specific capacity of 158.1 mAh g-1, at a rate of 0.1 C and also shows high cycle stability.

Abstract: A nanocrystalline LiFePO₄/graphene-carbon nanotubes (LFP-G-CNT) composite has been successfully synthesized by a hydrothermal method followed by heat-treatment. The microstructure and morphology of the LFP-G-CNTs composite were comparatively investigated with LiFePO₄/graphene (LFP-G) and LiFePO₄/carbon nanotubes (LFP-CNT) by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The LFP-G-CNTs nanoparticles were wrapped homogeneously and loosely within a 3D conducting network of graphene-carbon nanotubes. The conducting networks provided highly conductive pathways for electron transfer during the intercalation/deintercalation process, facilitated electron migration throughout the secondary particles, accelerated the penetration of the liquid electrolyte into the LFP-G-CNT composite in all directions and enhanced the diffusion of Li ions. The results indicate that the electrochemical activity of LFP-G-CNT composite may be enhanced significantly. The charge-discharge curves, cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) results demonstrate that LFP-G-CNT composite performes better than LFP-G and LFP-CNT composites. In particular, LFP-G-CNT composite with a low content of graphene and carbon nanotubes exhibites a high initial discharge capacity of 168.4 mAh g⁻¹ at 0.1 C and 103.7 mAh g⁻¹ at 40 C and an excellent cycling stability.

Abstract: LiNi_1/3Co_1/3Mn_1/3O₂ was prepared by high temperature solid-state method under different synthesis temperature. The structure and morphology of LiNi_1/3Co_1/3Mn_1/3O₂ were characterized by Scanning electron microscopy (SEM) and X-ray diffraction (XRD). Electrochemical performance of the cathode material was researched by Land 2001. XRD and SEM results show that the well-crystallized LiNi_1/3Co_1/3Mn_1/3O₂ composite with homogeneous small particles was obtained. And the optimum synthetic temperature was 500°C for 5 hour and 900°C for 20 hour. From charge/discharge test, it can be seen that at 0.1C, 0.2C and 0.5C rate, LiNi_1/3Co_1/3Mn_1/3O₂ has initial discharge capacities of 178.6mAh/g, 172.9mAh/g and 152.7mAh/g, respectively. The discharge capacities of optimum sample remain above 85% after 43 cycles. This study provides the selection of synthetic temperature via solid state methods.

Abstract: In this work, spherical LiFePO₄/C composite had been synthesized by co-precipitation and spray drying method. The structure, morphology and electrochemical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron micrograph (SEM), transmission electron microscope (TEM), constant current charge-discharge tests and electrochemical impedance spectroscopy (EIS) tests. The spherical LiFePO₄/C particles consisted of a number of smaller grains. The results showed that the morphology of LiFePO₄/C particles seriously affected the Li-ion diffusion coefficient and electrochemical properties of lithium ion batteries. Electrochemical tests revealed the spherical LiFePO₄/C composite had excellent Li-ion diffusion coefficient which was calculated to be 1.065×10^-11 cm²/s and discharge capacity of 149 (0.1 C), 139 (0.2 C), 133 (0.5 C), 129 (1 C) and 124 mAhg^-1(2 C). After 50 cycles, the capacity retention rate was still 93.5%.

Abstract: It is well known that the main constraint of electric vehicles (EVs) is the capabilities to supply efficient energy for driving-range that is comparable to petrol fueled vehicles. Moreover, a large number of batteries needed for EV contribute to heavy weight, poor durability and pricy total cost. In view of that, the need to prolong the battery lifetime, and use its full capacity, is of utmost importance. Therefore, an accurate battery model is a challenging first step to the overall problem soving chain. This paper presents a transfer function model prediction with nature-inspired approach for a Lithium iron phosphate battery. An Ant Colony Optimisation technique is used in search for accurate model with robust capability to adapt with different input current based on the New European Driving Cycle (NEDC) range. The model is further validated with autocorrelation and cross-correlation test and it is proven to give an error tolerance between the 95% confidence limit.

Abstract: In this study, a symmetric electrochemical capacitor has been fabricated by adopting the lithiated compound (LiFePO4)-activated carbon (AC) composite as the core electrode materials. The electrochemical performances of the prepared supercapacitor were studied using cyclic voltammetry (CV) in 1.0 M Na2SO3 solution. Experimental results reveal that the maximum specific capacitance of 112.41 F/g is obtained in 40 wt % LiFePO4 loading on AC electrode in comparison to that of pure AC electrode (76.24 F/g) in 1 M Na2SO3. The enhanced capacitive performance of the 40 wt % LiFeO4 –AC composite electrode is believed attributed to the contribution of synergistic effect of electric double layer capacitance (EDLC) on the surface of AC as well as pseudocapacitance via intercalation/extraction of Na+, SO32-and Li+ ions in LiFePO4 lattices. The composite electrodes can sustain a stable capacitive performance at least 1000 cycles with only ~5 % specific capacitance loss after 1000 cycles. Based on the findings above, 40 wt % LiFeO4 –AC composite electrodes which utilise low cost materials and environmental friendly electrolyte is worth being investigated in more details.