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Li1-XNaXFePO4 (X = 0, 0.01 or 0.05) composite cathode materials were synthesized by the simple solvothermal method. SEM images showed that Na doping had little effect on the morphology of particles, which provided a guarantee for its excellent electrochemical performance. Charge/discharge data revealed that an appropriate amount of doped Na could improve electrochemical performance. Li0.99Na0.01FePO4 showed excellent rate capacity and cycle stability, i.e., an extremely high keep in the capacity of 86.7% after 500 cycles at 10C, due to its ac facet morphology, larger lattice parameters in a and c, the enhanced electronic conductivity and Li-ion diffusion processes.

LiFePO4/C cathode material is largely used in Li-ion batteries due to its low toxicity, nonhazardous and high stability features. A facile and simple approach is proposed in LiFePO4/C production using low-cost materials. The effect of carbon addition during the formation of LiFePO4/C was investigated. Based on the XRD and FTIR analyses, olivine-structured LiFePO4/C cathode material was successfully obtained via methanol-based rheological method. The SEM result showed that the material has micron-sized polyhedral shape. The electrochemical performance tests were conducted in an 18,650-type cylindrical battery. The charge–discharge performances were tested at a voltage range of 2.2–3.65 V using charge and discharge rate of 1C. Based on the charge–discharge test, LiFePO4 with 30% carbon addition has the highest specific capacity of 121 mA h/g with excellent cycle and rate performance as a result of successful carbon compositing in LiFePO4 material. This approach is promising to be adapted for mass production of LiFePO4/C.

A Mo-doping LiFe1-xMoxPO4/C cathode material was synthesized via carbothermal reduction route, and the effect of the content of Mo on the structure and electrochemical performance of LiFePO4/C was ...

The synthesis of high purity and crystallinity Fe3(PO4)2·8H2O precursor by polyvinyl pyrrolidone (PVP)–assisted co-precipitation method is reported, and the morphology-controlled tiny and uniform primary particles material has also been obtained. Moreover, the fore-mentioned Fe3(PO4)2∙8H2O was used to synthesize LiFePO4/C via carbothermal reduction. All the materials were systematically characterized by various analytical, spectroscopic, and imaging techniques. Fe3(PO4)2∙8H2O exhibits stronger affinities within primary particles and homogeneity, attributed to PVP, which can greatly improve the properties of LiFePO4/C. The resulting high purity Fe3(PO4)2∙8H2O gave highly crystalline of LiFePO4/C. In addition, LiFePO4/C prepared with PVP demonstrated excellent electrochemical performance of initial discharge capacities at 0.2 C, 0.5 C, 1 C, 2 C, and 5 C are 163.4, 160.9, 155.1, 146.2, and 126.5 mAh g−1, respectively.

In the recent years, LiFePO4 has been widely developed as a cathode for lithium ion batteries because it has high theoretical capacity (170 mAh/g), good stability and is also environmentally friendly. However, the poor electronic conductivity (~10-9 S/cm) and low diffusion coefficient of lithium ion (~10-15-10-14 cm2/s) are limiting its application. Some solutions to overcome this problem are carbon coating and doping metal ions. This study aims to determine the effect of Gd3+ ion doping on the electronic conductivity of LiFePO4/C. The synthesis method was used is carbothermal reduction with Fe2O3, Gd2O3, LiH2PO4 and carbon black reagents. The synthesized LiFe1-xGdxPO4/C was characterized using XRD, SEM-EDS, and four point probes. The results obtained showed that gadolinium ion doping increased the conductivity of LiFePO4/C from 1.8952 x10-6 to 8.69x10-6 Scm-1 using 0.07 mol ion Gd3+.

LiFePO4 (LFP) is one of the cathode materials widely used in lithium ion batteries at present, but its electronic conductivity is still unsatisfactory, which will affect its electrochemical performance. Ga-coated LiFePO4@C (LFP@C) samples were prepared by a hydrothermal method and ultrasonic dispersion technology. Ga has good electrical conductivity and can rapidly conduct electrons within the LFP cathode material under the synergistic effect with C coating, thus improving the dynamic performance of the LFP cathode material. The experimental results show that LFP@C/Ga samples exhibit good electrochemical performance. Compared with the pristine LFP@C, the 1.0 wt % Ga-coated LFP@C cathode exhibits excellent discharge capacity and cycle stability. The former shows a discharge capacity of 152.6 mA h g–1 at 1 C after 100 cycles and a discharge capacity retention rate of 98.77%, while pristine LFP@C shows only a discharge capacity of 114.5 mA h g–1 and a capacity retention rate of 95.84% after 100 cycles at 1 C current density.

A series of LiFePO4/C composites are prepared under the conditions of pH = 3, 5, 7, 8, 9 via biosynthesis method. The X-ray diffraction demonstrates that all of well-crystallized LiFePO4/C ...

Li-ion batteries have drawn increasing attention because of attractive characteristics such as high operating voltage, high particle density, long cycle life, low self-discharge, and not showing a memory effect. LiFePO4/C cathode material was prepared via a sonochemical high-temperature ball milling method using Tween 80 dispersant. The effects of the Tween 80 on the electrochemical properties of LiFePO4/C were investigated. The experimental results showed that the Tween 80 improved the surface area of LiFePO4/C, and the prepared cathode material showed a better electrochemical performance: it delivered discharge capacities of 159.0 mAh g−1 at 0.1 C and 110.4 mAh g−1 at 10 C, which were higher than for Tween 80-free samples. Moreover, the discharge capacity was 119.6 mAh g−1 at a rate of 5.0 C over 100 cycles while the capacity retention was 94.2%.

In this paper, the micro-sized Fe2P2O7/C composites have been successfully prepared by rheological phase method using Fe2O3, H3PO4 and glucose as raw materials. Then, the prepared Fe2P2O7/C is used as a precursor to synthesize LiFePO4/C. The synthesis process of Fe2P2O7/C-dynamic composites is assisted by dynamic calcination. The corresponding LiFePO4/C-dynamic composites exhibit excellent physicochemical performance confirmed by XRD, SEM, TEM, CV, EIS, Elements detection and cyclic tests. The results indicate that the LiFePO4/C-dynamic sample is well-distributed in element level and possesses uniform monodisperse morphology. In addition, it delivers a discharge capacity of 157.1, 146.6, 138.0 and 130.2 mAh g−1 at the rate of 0.2, 1, 2 and 3 C, respectively. Meanwhile, it can retain 99.52% of the initial capacity after 300 cycles at 1 C, exhibiting an excellent cycling stability. The study reveals that the assisting method of dynamic calcination is highly efficient to synthesize Fe2P2O7/C materials with better performance, and eventually, fabricate high performance LiFePO4/C composites for lithium-ion batteries.

LiFePO4/C/reduced graphene oxide (rGO) composites with different morphologies were synthesized, allowing evaluation of the electrochemical performance as a function of the sample morphology. LiFePO4 particles anchored on rGO sheets and rGO sheets wrapping LiFePO4 agglomerations were two of the most pronounced features observed. The structure with LiFePO4 particles anchored on rGO sheets was found to be the most optimal and give rise to both increased capacity and improved rate capability.

Introduction: LiFePO4/C composites were synthesized via physical mixing assisted solvothermal process. Different kinds of carbon materials were investigated including 0D (carbon Ketjen black), 1D (carbon nanotubes) and 2D (graphene) materials. X-rays diffraction patterns of carbon coated LiFePO4 synthesized by solvothermal was indexed to pure crystalline phase without the emergence of second phase. LiFePO4 platelets and rods were in range size of 80-200 nm and dispersed well in carbon matrix. The lithium ion diffusion kinetics was evaluated through the calculated diffusion coefficients to explore the impact of carbon mixing. Methods: In this work, we studied the structure, morphologies and the lithium ion diffusion kinetic of LiFePO4/C composites for Li-ion batteries. Different characterization methods were used including powder X-rays (for crystalline structure); Transmission Electron Microscopy (for particle and morphologies observation) and Cyclic voltammetry (for electrochemical kinetic study). Results: The study indicated LiFePO4/C composites were successfully obtained by mixing process and the electrochemical performance throughout the calculated diffusion coefficient was significantly improved by adding the carbon types. Conclusion: The excellent ion diffusion was obtained for composites LiFePO4/Ketjen black (KB) and LiFePO4/CNT compared to LiFePO4/Graphene. KB could be a potential candidate for large-scale production due to low-cost, stable and high electrochemical performance.

A convenient one-pot method, called high-temperature high-energy mechanical force (HTHEMF), was successfully developed for the preparation of LiFePO4/C composites. Upon the combination of high-temperature with high-energy mechanical force, the whole synthesis process of this method is very simple and only involves two steps, the precursor preparation and the calcination step. The results of XRD, SEM, BET and electrochemical performance tests indicated that after calcination at 600 °C for 9 h, the LiFePO4/C composites have the best properties. The discharge capacity of the composites was 150.3mA h g-1 at 0.1 C. After 30 cycles test, the reversible capacity was 147 mA h g-1 and the retention ratio to the initial capacity was 97.8%. The results indicated that LiFePO4/C composites with good properties can be obtained by one-pot HTHEMF method.

The K-doped Li1-xKxFePO₄ (x = 0, 0.005, 0.01, and 0.02) samples were synthesized successfully via a solid-state method, and the electronic structures of the samples were calculated by the first-principles based on density functional theory. Theoretical calculations show that the bandwidth of Li1-xKxFePO₄ decreases with the increase in K+ doping, which is consistent with the experimental results. It was demonstrated that Li0.995K0.005FePO₄ delivers higher capacity retention with 92.7% after 100 cycles compared with LiFePO₄ (86.3%) at 1 C and shows better high-rate performance with capacities of 151.9, 151.8, 149.2, 128.3, and 84.6 mAh·g-1 at current densities of 0.1 C, 0.2 C, 0.5 C, 1 C, and 3 C; the corresponding values for LiFePO₄ were 153.2, 136.5, 125.9, 111.5, and 66.0 mAh·g-1. Owing to the expanded Li ion diffusion pathway, EIS analysis showed that the lithium ion diffusion coefficient of LiFePO₄ doped with K ion was significantly improved compared to LiFePO₄; the values were 1.934×10-13 and 1.658×10-12 cm²·s-1, respectively. Additionally, Li0.995K0.005FePO₄ showed a lower charge transfer resistance (300.2 Ω compared to 407.1 Ω of LiFePO₄).

In recent years, how to properly recycle increasing spent LiFePO4 batteries is becoming an extremely thorny subject, which is related to not only a severe environmental pollution but also a serious waste of valuable resources. Here, for the first time, a sustainable and smart approach is established for manufacturing LiFePO4/C/FeS composites from spent LiFePO4 powders as novel anode materials for alkaline Ni-Fe secondary battery. The LiFePO4/C/FeS composites are prepared via a facile ball milling method by using spent LiFePO4 and commercial FeS as raw materials. When serving as host anode material for Ni-Fe battery, the LiFePO4/C/FeS (40 wt%) composite exhibits attractive anodic performance in alkaline solution, with a high specific discharge capacity of ～232.9 mAh g−1 (639.1 mAh g−1Fe) at 0.2C, prominent high-rate capabilities (～150.7 mAh g−1 (413.5 mAh g−1Fe) still retains even at a high rate up to 5C) and excellent cyclic stability (with retention of as high as 75.9% of its highest capacity after 300 cycles at 1C). Meaningfully, our study proposes a sustainable and economical approach to produce advanced anodes for alkaline Ni-Fe secondary batteries, simultaneously providing an attractive and facile way to recycle spent LiFePO4 materials in large scale.

Olivine LiFePO4 is challenged by its poor electronic and ionic conductivities for lithium-ion batteries. Polyethylene glycol (PEG) has been applied for LiFePO4 preparation by different research groups, but there is no consensus on the influence of the mean molecular weight of PEG on the structure and electrochemical performances of LiFePO4/C composites. In this work, LiFePO4/C composites were prepared by using micronsized FePO4·2H2O powder as starting material, PEG (mean molecular weight of 200, 400, 4000 or 10000) and citric acid as complex carbon source. The structure and electrochemical performances of LiFePO4/C composites would be decided considerably by the mean molecular weight of PEG, and the sample using PEG200 exhibited the least inter-particle agglomeration, the smallest charge transfer resistance and the highest discharge capacity. A probable growth mechanism is also proposed based on SEM images and electrochemical results: with the assistance of citric acid, PEG molecule with small molecular weight tends to cover one or only a few micron-sized FePO4·2H2O particles, significantly suppress the agglomeration of primary LiFePO4 particles and thus result in uniform particle-size distribution and carbon coating.

V 3+ and F − co-doped LiFePO 4 /C cathode materials are prepared via a facile wet milling-spray drying-carbothermal reduction (WSC) process. The obtained products have bowl-like morphologies with the diameters from 5 to 10 μm, which are composed of numerous nanoparticles smaller than 100 nm integrated by carbon network. The effects of ion doping are studied. V 3+ and F − co-doped LiFePO 4 /C shows improved electrochemical performance, which delivers a discharge capacity of 136 mAh·g −1 (10 C) at 20 °C. At 0 °C, a capacity of 86 mAh·g −1 (10 C) can be obtained, which is 20 mAh·g −1 higher than LiFePO 4 /C. In addition, the V 3+ and F − co-doped LiFePO 4 /C shows excellent cycle performances. The improved performance of V 3+ and F − co-doped LiFePO 4 /C is due to the low charge transfer resistance, enhanced electrical conductivity and the holes on the surface of particles which can provide more ion transport channel.

The sol-gel synthesis and precipitation from dimethyl sulfoxide (DMSO)-water mixture were used to obtain LiFePO4. Sucrose (sucr), citric acid (CA), phthalic acid (phth), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), polyethylene glycol (PEG), polyacrylic acid (PAA) were investigated as carbon precursors. Increasing of the annealing temperature from 600 °» to 800 °» leads to a certain perfection of graphite structure with simultaneous particle size growth. Higher capacities were observed for the materials synthesized at 600 °». The best results for the sol-gel synthesis were obtained when PVDF was used as a source of carbon coating due to the partial fluorination of LiFePO4 (discharge capacity of LiFePO4/ C-PVDF was ~160 and 70 mAh g-1 at 20 mA g-1 and 800 mA g-1 currents, respectively). For nanocrystalline LiFePO4 obtained by precipitation from DMSO-water mixture the best results were obtained when PEG was used as carbon source (discharge capacity LiFePO4/C-PEG was 158 and 77 mAh g-1 at 20 mA g-1 and 800 mA g-1, respectively).

research We synthesized Nb-doped LiFePO4 /C nano composite cathode materials by mechanochemical activation followed by a single step calcination. The starting chemicals of Li2 CO3 , FeC2 O4 .2H2O, NH4 H2 .PO4 and C6 H8 O7 as lithium, iron, phosphate, and carbon sources are mixed in a high energy ball mill (250 rpm, 5h) and calcined at 650 °C and 10 hours. The resultant materials are structurally (XRD, SEM, TEM) and electrochemically characterized and high purity LiFePO4 with high electrochemical performance is obtained. Voltage vs. specific capacity, discharge capacity vs. cycle number in manufactured battery is presented. An initial specific discharge capacity of 153 mAhg?1 and a specific discharge capacity of 128.4 mAhg?1 after the 8th charge/discharge cycling at 1C is recorded. We synthesized Nb-doped LiFePO4 /C nano composite cathode materials by mechanochemical activation followed by a single step calcination. The starting chemicals of Li2 CO3 , FeC2 O4 .2H2O, NH4 H2 .PO4 and C6 H8 O7 as lithium, iron, phosphate, and carbon sources are mixed in a high energy ball mill (250 rpm, 5h) and calcined at 650 °C and 10 hours. The resultant materials are structurally (XRD, SEM, TEM) and electrochemically characterized and high purity LiFePO4 with high electrochemical performance is obtained. Voltage vs. specific capacity, discharge capacity vs. cycle number in manufactured battery is presented. An initial specific discharge capacity of 153 mAhg?1 and a specific discharge capacity of 128.4 mAhg?1 after the 8th charge/discharge cycling at 1C is recorded.

Monodispersed LiFePO4 [001] nanorods have been successfully synthesized via a conventional hydrothermal route with Li2SO4, FeSO4 and KH2PO4 as precursors. Subsequently, in virtue of the good monodispersibility LiFePO4@C core-shell [001] nanorods are facilely prepared by employing a carbon coating process on the obtained monodispersed LiFePO4 [001] nanorods. On the basis of the experimental results, a possible formation mechanism of the monodispersed LiFePO4 [001] nanorods has been proposed. Due to the full carbon coating, size reducing in [010] and the perfect olivine crystal lattice, the LiFePO4@C core-shell [001] nanorods exhibit excellent rate capacity and stable cycle performance.

Owing to high safety, low cost, nontoxicity, and environment-friendly features, LiFePO4 that is served as the lithium ion battery cathode has attracted much attention. In this paper, a novel 3D LiFePO4@C core-shell configuration anchored on carbon cloth is synthesized by a facile impregnation sol-gel approach. Through the binder-free structure, the active materials can be directly combined with the current collector to avoid the falling of active materials and achieve the high-efficiency lithium ion and electron transfer. The traditional slurry-casting technique is applicable for pasting LiFePO4@C powders onto the 2D aluminum foil current collector (LFP-Al). By contrast, LFP-CC exhibits a reversible specific capacity of 140 mAh·g-1 and 93.3 mAh·g-1 at 1C and 10C, respectively. After 500 cycles, no obvious capacity decay can be observed at 10C while keeping the coulombic efficiency above 98%. Because of its excellent capacity, high-rate performance, stable electrochemical performance, and good flexibility, this material has great potentials of developing the next-generation high-rate performance lithium ion battery and preparing the binder-free flexible cathode.

Bicontinuous hierarchical mesoporous LiFePO4/C (BHM-LFP/C) microbelts have been synthesized using a simple dual-solvent electrospinning method for the first time. The use of a dual-solvent is beneficial for the electrospinning synthesis, which increases the salt solubility, as well as decreases the surface tension to improve the spinnability. The sample exhibits a high reversible capacity (153 mA h g−1 at 0.5C), and achieves an excellent high rate cycling performance. The enhanced electrochemical performance can be attributed to the unique microbelts providing bicontinuous electron/ion pathways, and the thoroughly mesoporous structure facilitating electrolyte penetration, especially for hierarchical architectures, which have three-dimensional diffusion channels for Li+. This method can be extended to fabricate other electrospun multi-element oxide cathode materials for advanced lithium-ion batteries.

The effect of particle size and purity of LiFePO4/C material on the low temperature performance of LiFePO4/C material prepared with FePO4·2H2O as precursor are systematically investigated. It is found that reducing particle size of LiFePO4/C material can improve the low temperature performance, and the purity of LiFePO4/C material has more important influence on the low temperature performance. Compared to the high purity LiFePO4/C material, the low purity LiFePO4/C material exhibits poor low temperature performance. At −20 °C under 0.2C, the specific capacity of low purity LiFePO4/C material is 52.4 mAh g−1 lower than that of high purity LiFePO4/C material which is 105.6 mAh g−1. The 18650-1400 mAh cylindrical batteries confirm the opinion. At the operation temperature of 0, −20 and −40 °C under 0.2C, the capacity retentions of low purity LiFePO4/C material are 40.9%, 30.3% and 10.9% much lower than those of high purity LiFePO4/C material which are 81.5%, 70.2% and 46.6% compared with those of at 25 °C, respectively. The studies on the mechanism indicate that low purity LiFePO4/C material contains impurities which could incorporated into LiFePO4 lattice by high-temperature diffusion process and cause the lattice distortion, blocking the Li+ ions diffusion. It have calculated that the DLi value of low purity LiFePO4/C material is 8.28 × 10−15 cm2 s−1 lower two orders than that of high purity LiFePO4/C material which is 2.73 × 10−13 cm2 s−1, leading to the sluggish Li+ ions diffusion kinetics at low temperature. Therefore, the particle size and purity of LiFePO4/C material are the mainly factors influencing the low temperature performance of LiFePO4/C material, of which removing the impurities in the raw materials and improving the purity of the iron source to synthesize FePO4·2H2O material is a deterministic way to improve the low temperature performance of LiFePO4/C material.

A novel process has been demonstrated to recycle LiFePO 4 from spent lithium-ion batteries. The spent LiFePO 4 cathode materials were leached by phosphoric acid (H 3 PO 4 ) solution and followed by subsequent heat treatment to obtain FePO 4 ·2H 2 O hierarchical microflowers. Furthermore, new LiFePO 4 /C sample was prepared via a carbothermal reduction process of calcining the obtained FePO 4 ·2H 2 O precursor with Li 2 CO 3 and glucose in N 2 atmosphere. The re-synthesized LiFePO 4 /C sample inherits the hierarchical microflower structure of the FePO 4 ·2H 2 O precursor, with a diameter of 1–2 μm. Electrochemical test indicates that the re-synthesized LiFePO 4 /C shows excellent electrochemical performance as cathode material for lithium ion batteries. The discharge capacity can reach 159.3 mAh g −1 at 0.1C rate and 86.3 mAh g −1 even at 20C rate, respectively. After 500 cycles at 5C, they still can deliver a discharge capacity of 105 mAh g −1 with a high capacity retention rate of 95.4%. Moreover, the lithium element was also recovered in the form of LiH 2 PO 4 from the filtrate after collecting the FePO 4 ·2H 2 O precipitate. This work provides a promising route for large scale recovery and reuse of spent LiFePO 4 cathode materials of lithium-ion batteries.