Performance Of LiFePO4 Cathode Material Research Articles

Functionalized porous conductive carbon layer improves the low-temperature performance of LiFePO4 cathode material for lithium-ion batteries

Lithium iron phosphate (LiFePO4) has been successfully utilized due to its stable structure, low cost, and higher safety. Nevertheless, the sluggish diffusion kinetics and low electrical conductivity have suppressed the rate capacity and long-term cyclability at lower temperature, causing significant capacity degradation problems. Herein, to address such issues, a well-designed 3D porous structure LFP@NS is synthesized via the sol-gel method combined with a high-temperature calcination route. Furthermore, the nitrogen and sulfur in thiourea can be induced to enter the carbon matrix, resulting in generating more defects and active sites. Simultaneously, N,S co-doped carbon matrix can form successive migration channels for lithium-ion, which can promote the diffusion kinetics and electrical conductivity. The as-prepared LFP@NS-2 sample provides 158.5 mAh g−1 discharge capacity in the room temperature (RT) and 101.3 mAh g−1 (in −20 °C) at 1C, and exhibits remarkable cyclic performance (122.3 mAh g−1 after 2000 circles at 10C in the RT). Furthermore, to investigate the practical application in low temperature, coupled with a graphite (Gr) anode, the LFP@NS-2||Gr full battery releases 100.1mAh g−1 at 1C in −20 °C. Therefore, this work has a far-reaching implication for designing the high-performance LIBs electrode materials for practical application at low temperature.

Enhancing the electrochemical and mechanical performance of LiFePO4 cathode material by ternary doping of Mn, Ti, and N

This study employs a first-principles approach based on density functional theory to analyze the electrochemical and mechanical properties of LiFePO4 system with Mn, Ti, and N ternary doping. Computational findings reveal a formation energy of −1.98 eV, affirming excellent stability. Doping generates impurity bands, reducing the bandgap to 1.21 eV and enhancing conductivity. Doping significantly improves Li-ion diffusion, increasing the coefficient by 6 orders of magnitude and reducing the energy barrier by 0.35 eV. Moreover, Ti doping induces favorable local structural changes and enhances Li-ion diffusion. Mechanical performance calculations indicate improved stability, toughness, and isotropy. Ternary doping raises de-lithiation voltage, optimizing charge–discharge curves without compromising the capacity of LiFePO4, enhancing electrochemical performance.

Indium doping: An effective route to optimize the electrochemical performance of LiFePO4 cathode material

This study aimed to develop In-doped LiFePO4 cathode materials for lithium ion power batteries in electric vehicles that meet the requirements of both fast acceleration and long-term reversible charge-discharge stability. We focused on investigating the role of indium doping in enhancing high-rate capability. Density functional theory (DFT) calculations revealed that successful substitution of In at Fe site exhibits distinct features for both LiFe1-xInxPO4 and Fe1-xInxPO4. The results showed that the presence of In in unlithiated Fe1-xInxPO4 can lower the diffusion energy barrier of lithium ions. On the other hand, the introduction of In in lithiated LiFe1-xInxPO4 creates an impurity energy band at the Fermi energy level, which enhances electron conductivity of the active material. Experimental data demonstrated that with 2% In doping, the 2% In3+-LFP/C electrode delivers 160 mAh g−1 at 0.1C, and 150 mAh g−1 at 1C (with excellent retention rate of 98% after 700 cycles). Additionally, the In-doped electrode provided higher discharge capacity at high-rates (5C and 10C) due to improved electron conductivity and lithium ion diffusion properties. These findings prove that indium doping is an effective approach to reinforcing the electrochemical capabilities of high-rate LiFePO4 cathode material for lithium storage.

Structure and electrochemical performance of LiFePO4 cathode materials modified with carbon coating and metal doping

Structure and electrochemical performance of LiFePO4 cathode materials modified with carbon coating and metal doping

Enhance electrochemical performance of LiFePO4 cathode material by Al-doped Li7La3Zr2O12 and carbon co-coating surface modification

Abstract A composite solid electrolyte based on Al-doped Li7-3xAlxLa3Zr2O12 (LALZO) was synthesized by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were used to characterize Li7La3Zr2O12 (LLZO) precursors with different Al doping concentrations. The results show that LLZO precursor doped with 0.4 mol% Al (LALZO-4) has high stability and good crystallinity. Further, this composite solid electrolyte was co-coated with carbon to optimize the LiFePO4 battery. Electrochemical performance tests show that the LiFePO4/C battery with 5% LALZO-4 precursor (LFP-5) exists in the form of uniformly dispersed spherical particles, and exhibits excellent cycling stability and high rate performance. In addition, the LALZO-4 coating layer can increase the diffusion rate by reducing the charge transfer resistance.

Fluorine doped carbon coating of LiFePO4 as a cathode material for lithium-ion batteries

The present work presents an insightful study on the effect of fluorine doped carbon (FC) modification on the electrochemical performance of LiFePO4 cathode material. To this end, polyvinylidene fluoride is used as fluoride source to synthesize FC, which is designed to coat on LiFePO4 surface with formation of LiFePO4@FC nanocomposites. The microstructure and electrochemical properties of the nanocomposites are systematically examined by various characterization techniques, revealing that FC is tightly attached on surface of LiFePO4 particles forming a three dimensional (3D) conductive network structure. Such favorable structure provides advantages of good grain-to-grain electrical contact, shortening the Li+ diffusion distance between the grain interfaces, and facilitating the rapid transfer of electrons during charge–discharge. The optimal LiFePO4@FC nanocomposites, i.e., with 97.2 wt% of LiFePO4, are verified to show highly desirable electrochemical performance with superior rate capability and excellent cycling performance as the cathode material of lithium-ion batteries.

Optimization of LiFePO4 cathode material based on phosphorus doped graphite network structure for lithium ion batteries

Lithium iron phosphate (LiFePO4) has been recommended as a hopeful cathode material for lithium ion batteries (LIBs) in the future due to its lots of advantages, such as stable operating voltage, excellent cycle performance, controllable cost, and environmental protection. However, pure LiFePO4 (LFP) shows bad reversible capacity and charge/discharge performance at high rate. Many methods including decrease of particle size, optimization of coating carbon, introduction of conductive polymer, and doping of metal or non-metallic element have been developed to improve the electrochemical performance of LFP cathode material. In this study, LFP/C-P composite cathodes were prepared successfully by a facile sol-gel approach that graphite was used to generate a carbon network structure and triphenylphosphine was used to greatly facilitate generation of a network connecting passage. Electrochemical test results show that LFP/C-P composite cathode has achieved a remarkable improvement in capacity and apparent ascension in rate performance. Compared with LFP, LFP/C, and LFP-P cathode, LFP/C-P composite material shows the best electrochemical performance with a discharge capacity of 168.8 mAh g−1 and a remarkable retention rate of 98.8% over 100 cycles at 0.1 C.

Effect of Nanophase Li₃PO₄ and Li₄P₂O7 on the Electrochemical Performance of LiFePO₄ Cathode Materials.

The Li3PO4 modified LiFePO4/C and Li4P2O7 modified LiFePO4/C cathode materials were synthesized by in-situ synthesis method, respectively. Phase compositions and microstructures of the products were characterized by X-ray powder diffraction (XRD), scanning electronic microscope (SEM). Results indicate that Li3PO4 and Li4P2O7 can sufficiently coat on the LiFePO4 surface and does not alter LiFePO4 crystal structure. The electrochemical behavior of cathode materials was analyzed using galvanostatic measurement and cyclic voltammetry (CV). Compared with Li3PO4, the existence of Li4P2O7 can better improve the electrochemical performance of LiFePO4 cathode materials in specific capability and lithium ion diffusion of cathode materials. The charge-discharge specific capacity and apparent lithium ion diffusion coefficient increase with Li4P2O7 content and maximizes around the Li4P2O7 content is 5 wt%. The results indicated that the Li4P2O7 adding enhances the lithium ion diffusion rate of LiFePO4. However, because of the interface fracture between Li4P2O7 and LiFePO4 particles during charging and discharging process, the cycling performance of Li4P2O7 modified LiFePO4/C cathode materials is very poor.

Effect of carbon coating on electrochemical performance of LiFePO4 cathode material for Li-ion battery

Pristine LiFePO4 (LFP) and carbon-coated LiFePO4 (LFP/C) are synthesized by sol-gel process using citric acid as a carbon precursor. LFP/C is prepared with three different stoichiometric ratios of metal ions and citric acid, namely 1:0.5, 1:1, and 1:2. Prepared LFP and LFP/C powder samples are characterized by X-ray diffractometer, field emission scanning electron microscope, transmission electron microscope, and Raman spectrophotometer. Electrochemical performances of pristine and carbon-coated LFP are investigated by charge-discharge and cyclic voltammetry technique. The results show that LFP/C (1:1) with an optimum thickness of 4.2 nm and higher graphitic carbon coating has the highest discharge capacity of 148.2 mA h g−1 at 0.1 C rate and 113.1 mA h g−1 at a high rate of 5 C among all four samples prepared. The sample LFP/C (1:1) shows 96% capacity retention after 300 cycles at 1 C rate. The decrease in discharge capacity (141.4and 105.9 mA h g−1 at 0.1 and 5 C, respectively) is observed for the sample LFP/C (1:2). Whereas, pristine LFP shows the lowest discharge capacity of 111.1 mA h g−1 at 0.1 C and capacity was decreased very fast and work only up to 147 cycles. Moreover, cyclic voltammetry has also revealed the lowest polarization of 0.19 V for LFP/C (1:1) and the highest 0.4 V for pristine LFP.

Improving the Performance of LiFePO4 Cathode Material By: Finding out an Effective Mixing Ratio for Cathode Slurry and Implementing Calendaring Process

The olivine structured lithium iron (II) phosphate (LiFePO4) is a promising cathode material for use in lithium-ion batteries. It has a high operating voltage (~3.4 V vs Li/Li), nontoxic and environmentally benign [1]. Although It has high specific theoretical capacity (~ 170 mAh g− 1), at high ‘C’ rates the discharge capacity decreased exponentially. To get optimum and consistent discharge capacity at different ‘C’ rates, the conductivity has to be improved. Different percentage of PVDF and carbon black were used to prepare slurry mixture of LiFePO4 and then coated on bare aluminum and carbon coated aluminum foil to make the cathode electrodes. Coin cells were made and tested at 1/10 C, 1/5 C, ½ C and 1C rates. Also to compare the effect of binder on cell performance, distinct percentages of water based binder were used. For this experiment each sample cathode electrode were calendared to different densities. A comparison of uncalendered and calendared cathode electrode (with carbon-coated current collector and also non-carbon coated current collector) were made. Before calendaring, material density was 0.8424 gcm-3 at 146 µm thickness of cathode electrode and after calendaring, density increased to 1.59 g/cm-3at 97 µm thickness. Discharge capacity at different “C” rates shows that the calendared electrode provide consistent and better discharge capacity performance than the uncalendered electrode. Electrochemical impedance spectroscopy (EIS) test shows the calendaring of electrode exhibits a large decrease in contact resistance. Reference: [1] Seung-Ah Hong,Su Jin Kim, Kyung Yoon Chung, Myung-Suk Chun, Byung Gwon Lee, Jaehoon Kim, “Continuous synthesis of lithium iron phosphate (LiFePO4) nanoparticles in supercritical water: Effect of mixing tee”, The Journal of Supercritical Fluids, Elsevier, 2013.

Double role of silicon in improving the rate performance of LiFePO4 cathode materials

LiFeP1-xSixO4/(C + yLi2SiO3), (0 ≤ x ≤ 0.04, 0 ≤ y ≤ 2%) composites with a particle size of about 200 nm were synthesized via a simple solid state route. In this work, silicon plays double roles-silicon doping in lattice to enhance the electronic conductance of LiFePO4, meanwhile Li2SiO3 with high Li-ion conductivity and carbon hybrid coating can decrease the interface resistance between LiFePO4 grain and electrolyte. In this work, starch and TEOS were used as carbon source and the silicon source respectively. XRD, SEM, TEM, EIS and galvanostatic charge-discharge test are used to characterize these samples. The effects of the modification on the microstructure and electrochemical performances of LiFePO4 cathodes at 25 °C are systematically investigated. The results show the sample with x = 0.03 and y = 1.0 wt % exhibits excellent rate capacity and cycle performance among the investigated materials. Based on half-cell testing, the best sample achieves a high special discharge capacity of 119 mAh g−1 at 5C rate and a capacity of 94 mAh g−1 at the 10C rate with an excellent cycle life in the usual cycling voltage range 2.5–4.2 V. EIS result demonstrates that the Rct of the samples decrease greatly due to the modification of LiFePO4 via doping and coating.

Effect of silver and carbon double coating on the electrochemical performance of LiFePO4 cathode material for lithium ion batteries

Olivine-type LiFePO4 composite materials for use as the cathode material in lithium-ion batteries were synthesized by using a hydrothermal method and then they were coated with silver and carbon. The phase identification and morphological characterization of four different LFP composites were performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) along with energy dispersive spectroscopy which verified the homogeneous existence of coated silver. The electrochemical performance was studied by conductivity measurements and galvanostatic charge–discharge measurements. The coated LFP sample exhibited an enhanced electronic conductivity of 1.3*10−3 Scm−1 which is six magnitudes higher than that of pure LFP. The results revealed that the first discharge capacity of the LFP@C@Ag electrode was 152 mAhg−1, which is higher than that of the pristine uncoated LFP electrode (122 mAhg−1). The improved capacity of LFP@C@Ag may be attributed to increased electrode conductivity and to the synergistic effect of the double coating on electron and Li+ transport.

Effects of samarium doping on the electrochemical performance of LiFePO4/C cathode material for lithium-ion batteries

Alien atom doping has been adopted to improve the electrochemical performance of LiFePO4 cathode material for rechargeable lithium-ion batteries. In this study, Sm-doped LiFe1−xSmxPO4/C (x=0, 0.02, 0.04, 0.06, 0.08) composites have been synthesized for the first time via a sol–gel method. The structure, morphology and electrochemical behavior of the as-synthesized samples are characterized by X-ray diffraction pattern (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), charge/discharge test and electrochemical impedance spectroscopy (EIS). The results reveal that both the pristine and Sm-doped samples have ordered olivine structure, and the Sm3+ substitution does not affect the structure of LiFePO4/C sample but enhances its discharge capacities especially the rate capability. Among the Sm-doped samples, the LiFe0.94Sm0.06PO4/C composite exhibits the highest capacity and best cycling performance, delivering a discharge capacity of 162.1 mAhg−1 at 0.1C within a voltage range of 2.5–4.2V, which is much higher than that of LiFePO4/C (146.3mAhg−1). At a high rate of 10C, it has a specific discharge capacity of 112.6mAhg−1 and a capacity retention of 96% after 20 cycles. Due to the excellent electrochemical performance, the Sm-doped LiFePO4/C electrodes exhibit great potential applications in rechargeable lithium-ion batteries.

Effect of symbiotic compound Fe2P2O7 on electrochemical performance of LiFePO4/C cathode materials

In order to study the effect of symbiotic compound Fe2P2O7 on electrochemical performance of LiFePO4/C cathode materials, the LiFePO4/Fe2P2O7/C cathode materials were synthesized by in-situ synthesis method. The phase compositions and microstructures of the products were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscope (FESEM). Results indicate that the existence of Fe2P2O7 does not alter LiFePO4 crystal structure and the existence of Fe2P2O7 decreases the particles size of LiFePO4. The electrochemical behavior of cathode materials was analyzed using galvanostatic measurement and cyclic voltammetry (CV). The results show that the existence of Fe2P2O7 improves electrochemical performance of LiFePO4 cathode materials in specific capability and lithium ion diffusion rate. The charge–discharge specific capacity and apparent lithium ion diffusion coefficient increase with Fe2P2O7 content and maximizes around the Fe2P2O7 content is 5 wt%. It has been had further proved that the Fe2P2O7 adding enhances the lithium ion transport to improve the electrochemical performance of LiFePO4 cathode materials. However, excessive Fe2P2O7 will block the electron transfer pathway and affect the electrochemical performances of LiFePO4 directly.

High Electrochemical Performance of LiFePO4 Cathode Material via In-Situ Microwave Exfoliated Graphene Oxide

Compared with thermally exfoliated graphene oxide (TEGO) prepared at high temperature of 800°C and a long time of 12h, microwave exfoliated graphene oxide (MEGO) is successfully synthesized at 800W for 2min benefiting from “inert and instant heating” of microwave irradiation and employed to optimize electrochemical performance of LiFePO4. The as-obtained LiFePO4/MEGO exhibits overwhelming superiorities to LiFePO4/TEGO, particularly in high-rate performance. Although LiFePO4/MEGO delivers the similar specific capacity of 158.1 mAh·g−1 as well as the LiFePO4/TEGO at the rate of 0.1C, the LiFePO4/MEGO performs smaller polarization of 53.3mV resulting in better specific energy of 518.1 Wh·kg−1 and energy efficiency of 89.8%. Even at the high rate of 10C and 20C, the LiFePO4/MEGO delivers excellent specific energy of 300.3 Wh·kg−1 and 229.7 Wh·kg−1 (with corresponding specific capacity of 104.3 mAh·g−1 and 87.3 mAh·g−1 respectively), much better than those of the LiFePO4/TEGO. After 2000 cycles, the LiFePO4/MEGO still performs excellent rate capabilities with 91.2% and 83.8% retention respectively.

Research on Performance and Preparation of LiFePO4

This paper makes use of various synthetic methods and analysis techniques, from material preparation, structure characterization of the electrochemical performance, we systematic study lithium iron phosphate, preparation electrode materials with good performance. This paper mainly aims at the two fatal drawbacks restrict the performance of LiFePO4cathode material, namely, low electron conductivity and lithium ion diffusion rate low, take the material particle, particle deposition on the surface of carbon conductive layer and Mg2+ion doping and other measures to modify it to explore, in order to improve the electrochemical performance of LiFePO4cathode material.

Synthesis and characterization of LiFePO4/C cathode materials by sol-gel method.

The carbon coated LiFePO4 cathode materials (LiFePO4/C) were successfully synthesized by sol-gel method with glucose, citric acid and PEG-4000 as dispersant and carbon source, respectively. The microstructure and grain size of LiFePO4/C composite were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy. The results showed that the carbon source and calcination temperature had important effect on the graphitization degree of carbon; the carbon decomposed by citric acid had higher graphitization degree; with calcination temperature rising, the graphitization degree of carbon increased and the particles size increased. The graphitization degree and grain size were very important for improving the electrochemical performance of LiFePO4 cathode materials, according to the experimental results, the sample LFP-700 (LFP-C) which was synthesized with citric acid as dispersant at 700 degree C had lower polarization and larger discharge capacity.

Research Progress in Improving the Rate Performance of LiFePO4 Cathode Materials

Abstract Olivine lithium iron phosphate (LiFePO4) is considered as a promising cathode material for high power-density lithium ion battery due to its high capacity, long cycle life, environmental friendly, low cost, and safety consideration. The theoretical capacity of LiFePO4 based on one electron reaction is 170 mAh g−1 at the stable voltage plateau of 3.5 V vs. Li/Li+. However, the instinct drawbacks of olivine structure induce a poor rate performance, resulting from the low lithium ion diffusion rate and low electronic conductivity. In this review, we summarize the methods for enhancing the rate performance of LiFePO4 cathode materials, including carbon coating, elements doping, preparation of nanosized materials, porous materials and composites, etc. Meanwhile, the advantages and disadvantages of above methods are also discussed.

Research Progress in Improving the Rate Performance of LiFePO4 Cathode Materials

Olivine lithium iron phosphate (LiFePO4) is considered as a promising cathode material for high power-density lithium ion battery due to its high capacity, long cycle life, environmental friendly, low cost, and safety consideration. The theoretical capacity of LiFePO4 based on one electron reaction is 170 mAh g−1 at the stable voltage plateau of 3.5 V vs. Li/Li+. However, the instinct drawbacks of olivine structure induce a poor rate performance, resulting from the low lithium ion diffusion rate and low electronic conductivity. In this review, we summarize the methods for enhancing the rate performance of LiFePO4 cathode materials, including carbon coating, elements doping, preparation of nanosized materials, porous materials and composites, etc. Meanwhile, the advantages and disadvantages of above methods are also discussed.

Characterization and electrochemical performances of MoO2 modified LiFePO4/C cathode materials synthesized by in situ synthesis method

The MoO2 modified LiFePO4/C cathode materials were synthesized by in situ synthesis method. Phase compositions and microstructures of the products were characterized by X-ray powder diffraction (XRD), SEM, TEM and EDS. Results indicate that MoO2 can sufficiently coat on the LiFePO4 surface and does not alter LiFePO4 crystal structure, the existence of MoO2 decreases the particles size and increases the tap density of cathode materials. The electrochemical behavior of cathode materials was analyzed using galvanostatic measurement, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that the existence of MoO2 improves electrochemical performance of LiFePO4 cathode materials in specific capability and lithium ion diffusion and charge transfer resistance. The initial charge–discharge specific capacity and apparent lithium ion diffusion coefficient increase, the charge transfer resistance decreases with MoO2 content and maximizes around the MoO2 content is 5wt%. It has been had further proved that the MoO2 adding enhances the electronic conductivity and lithium ion transport to improve the electrochemical performance of LiFePO4 cathode materials.