FePO4 Cathode Research Articles

The art of Lithiation Revisited: Solvent-free room temperature reaction

The lithiation reaction holds immense significance across various branches of chemistry, particularly in the realm of electrochemical energy storage. Here, we report a new method that enables a solvent-free process at room temperature, exhibiting remarkably swift reaction kinetics. Through this process, the chemical integration of Li+ into charged materials based on transition metals is achieved using lithium iodide, LiI. An evident application of this method lies in advancing the direct recycling of cathode materials reclaimed from spent batteries. Notably, the process facilitates the efficient and direct recycling of spent Li(1-x)FePO4 cathode material, sourced from a commercial LIB, without the need for any solvents or heat treatments. The regenerated material exhibits a fully reversible capacity of approximately 168 mAh/g against Li metal, even under high current density conditions, with a consistently stable coulombic efficiency surpassing 99 % over 45 cycles. This regenerative approach holds the potential for seamless extension to other LIB cathode materials, including but not limited to LMFP, LMO, LCO and NMC.

Lithium recovery from brine by PEG-modified porous LiFePO4/FePO4 electrode system

Lithium recovery from high Mg/Li brine through the electrochemical intercalation /de-intercalation technology has attracted great attention due to its good selectivity. To obtain higher equipment capacity, the LiFePO4/FePO4 electrodes with higher coating density are applied for lithium extraction. Unfortunately, it also brings a problem of slow diffusion of Li+ within the electrode, which limits the intercalation rate of lithium. To solve the problem of Li+ diffusion, a PEG-modified porous LiFePO4 electrode was prepared for lithium recovery. After modification, a “microcracks-microporosity” composite structure appears on the electrode, and the agglomeration of electrode materials reduces due to the dispersing effect of PEG. Therefore, the diffusion resistance of Li+ within the electrode decreases, and the electrode polarization reduces. Using the PEG-modified porous LiFePO4/FePO4 system to recover lithium, the Li+ intercalation rate reaches 4.45 g(Li)·m−2·h−1, while that of unmodified electrode is only 2.10 g(Li)·m−2·h−1. Besides, the intercalation of Na+ was significantly reduced from 0.28 to 0.07 of Na/Fe ratio in FePO4 cathode, which means better selectivity and circularity. Therefore, the application of PEG-modified porous electrode systems can efficiently recover lithium from brines.

Synthesis of highly dispersed FePO4 cathode material for rechargeable lithium battery

Synthesis of highly dispersed FePO4 cathode material for rechargeable lithium battery

A Yolk-Shell-Structured FePO4 Cathode for High-Rate and Long-Cycling Sodium-Ion Batteries.

Amorphous iron phosphate (FePO4 ) has attracted enormous attention as a promising cathode material for sodium-ion batteries (SIBs) because of its high theoretical specific capacity and superior electrochemical reversibility. Nevertheless, the low rate performance and rapid capacity decline seriously hamper its implementation in SIBs. Herein, we demonstrate a sagacious multi-step templating approach to skillfully craft amorphous FePO4 yolk-shell nanospheres with mesoporous nanoyolks supported inside the robust porous outer nanoshells. Their unique architecture and large surface area enable these amorphous FePO4 yolk-shell nanospheres to manifest remarkable sodium storage properties with high reversible capacity, outstanding rate performance, and ultralong cycle life.

Optimizing Calcium Electrolytes by Solvent Manipulation for Calcium Batteries

AbstractCalcium is a highly attractive metal anode because of its high earth abundance and low reduction potential. However, the lack of calcium electrolytes for reversible calcium deposition significantly hampers the development of Ca rechargeable batteries. Herein, the calcium deposition/stripping behaviors of a calcium salt electrolyte, Ca[B(hfip)4]2 ([B(hfip)4]−=tetrakis(hexafluoroisopropyloxy)borate) were systematically studied using different working electrodes (GC, Pt, Cu, and Al) and different solvents including tetrahydrofuran (THF), dimethoxyethane (DME), and diglyme (DGM). It was found that the Ca[B(hfip)4]2/DGM electrolyte demonstrated the highest reversibility and stability in cyclic voltammetry and symmetric Ca/Ca half‐cell studies. The Ca[B(hfip)4]2/DGM electrolyte was further employed to demonstrate a 3.4 V Ca battery using a FePO4 cathode with a discharge capacity of 120 Ah/mg.

Spectroscopic and Electrochemical Properties of Lithium-Rich LiFePO4 Cathode Synthesized by Solid-State Reaction

Lithium iron phosphate (LixFePO4) is synthesized by a solid-state reaction method. The structural, electrical and electrochemical properties are studied in detail. It is found that the increment of lithium concentration (up to x = 1.05) does not affect the structure of LiFePO4 but improves its electrical conductivity as well as electrochemical performance. Surface morphological studies exhibited the formation of rod-like nanoparticles with small size. Electric and dielectric properties are also investigated over a frequency range of 1 Hz–1 MHz at different temperatures. The conductivity increased with increasing temperature, which follows the Arrhenius relation with the activation energy of about 0.31 eV. And the electrochemical tests found that the Li1.05FePO4 cathode possessed improved discharge capacity with better cycling performance.

One-Dimensional Peptide Nanostructure Templated Growth of Iron Phosphate Nanostructures for Lithium-Ion Battery Cathodes

Template-directed synthesis of nanomaterials can provide benefits such as small crystalline size, high surface area, large surface-to-volume ratio, and structural stability. These properties are important for shorter distance in ion/electron movement and better electrode surface/electrolyte contact for energy storage applications. Here nanostructured FePO4 cathode materials were synthesized by using peptide nanostructures as a template inspired by biomineralization process. The amorphous, high surface area FePO4 nanostructures were utilized as a cathode for lithium-ion batteries. Discharge capacity of 155 mAh/g was achieved at C/20 current rate. The superior properties of biotemplated and nanostructured amorphous FePO4 are shown compared to template-free crystalline FePO4.

Investigating Olivine Cathode for Rechargeable Magnesium Battery with Theoretical and Experiment Approach

Lithium ion batteries (LIBs) are quickly becoming the mainstream power sources for environmentally friendly vehicles such as hybrid vehicles (HV), plug-in hybrid vehicles (PHV) and electric vehicles (EV) due to their high energy density. On the other hand, a battery system with even higher energy density is required for the long-range PHV and EV applications, and therefore, post lithium ion batteries (PLIB) such as Li-sulfur batteries and Li-air batteries have been getting more attention in recent years. Rechargeable magnesium batteries are also a candidate for the PLIB thank to the natural abundance of magnesium and the absence of dendrite formation when magnesium metal is used as the anode. In addition, the magnesium batteries are expected to have high energy density because of its divalent nature. However, there is not much progress on the development of novel cathodes since an innovation of Chevrel phase materials such as MgxMo6S8. The difficulty lies in the strong polarization character of the small and divalent Mg2+ and consequently the intercalation and diffusion of Mg2+ ions is somewhat difficult and complicated. Because of the so-called “diagonal relationship” in the periodic table stating the chemical similarity between lithium and magnesium, significant amount of efforts have been attempted to use compounds analogous to classical Li-ion battery cathode as Mg-intercalation hosts. As olivine LiFePO4 is one of the commercialized Li-ion battery cathode, it is of great interest to examine the performance of olivine compounds as Mg battery cathode. In this work, a comprehensive study about the performance of olivine FePO4 as Mg battery cathode is performed. With a combined theoretical and experimental approach we show that the intercalation of magnesium does not occur in the electrochemical operations. On the contrary to the common belief that the intercalation of magnesium is critically determined by the mobility of Mg2+ ions in the lattice, we demonstrate that the failure of FePO4 cathode is due to the formation of amorphous layer in the electrochemical process that passivates the active particle, similar to the phenomenon that we reported before for α-MnO2 cathode. Our research provides new insight for the magnesiation mechanism of a classical cathode and elucidate several directions towards future rechargeable Mg battery.

Enhancement of electrochemical behavior of nanostructured LiFePO4/Carbon cathode material with excess Li

We have synthesized carbon coated LiFePO4 (C-LiFePO4) and C-Li1.05FePO4 with 5 mol% excess Li via sol–gel method using oleic acid as a source of carbon for enhancing electronic conductivity and reducing the average particle size. Although the phase purity of the crystalline samples was confirmed by x-ray diffraction (XRD), the 57Fe Mössbauer spectroscopy analyses show the presence of ferric impurity phases in both stoichiometric and non-stoichiometric C-LiFePO4 samples. Transmission electron microscopy measurements show nanosized C-LiFePO4 particles uniformly covered with carbon, with average particle size reduced from ∼100 nm to ∼50 nm when excess lithium is used. Electrochemical measurements indicate a lower charge transfer resistance and better electrochemical performance for C-Li1.05FePO4 compared to that of C-LiFePO4. The aim of this work is to systematically analyze the nature of impurities formed during synthesis of LiFePO4 cathode material, and their impact on electrochemical performance. The correlation between the morphology, charge transfer resistance, diffusion coefficient and electrochemical performance of C-LiFePO4 and C- Li1.05FePO4 cathode materials are discussed.

High-throughput ab initio screening of binary solid solutions in olivine phosphates for Li-ion battery cathodes

A promising approach to improving the performance of iron-phosphate FePO4 cathode materials for Li-ion batteries is to partly or fully substitute Fe with other metals. Here, we use high-throughput density-functional theory (DFT) calculations to investigate binary mixtures of metal atoms M and M′ in (Li)MyM′1−yPO4 olivine phosphates. We determine the formation energy for various stoichiometries of different binary combinations of metals for the cases of full lithiation and delithiation. Systematic screening of all combinations of Fe and Mn with elements of the 3d transition-metal (TM) series allows us to identify trends with average band filling and atomic size. We also included compounds that verify the observed relations or that were discussed as cathode materials, particularly Ni–Co, V–Cu and V–Ni, as well as combinations with 4d TMs (Fe–Zr, Fe–Mo, Fe–Ag) and with Mg (Fe–Mg and Ni–Mg). Based on our DFT calculations for each compound, we estimate the volume change during intercalation, the intercalation voltage, the energy density and the thermal stability with respect to reaction with oxygen. Our calculations indicate that the energy density of the binary TM phosphates increases with average band filling while the thermal stability of the compounds decreases.

High-Density Li<sub>0.95</sub>Na<sub>0.05</sub>FePO<sub>4</sub> Cathode Material Synthesized by Co-Precipitation and Microwave Heating

The high-density Li0.95Na0.05FePO4 cathode material was synthesized through microwave heating, using a spherical sample prepared by co-precipitation method as precursor. The morphology, structure, electrochemical performance and the tap density of the materials were characterized by scanning electron microscope (SEM), x-ray diffraction (XRD), cyclic voltammetry (CV), constant current charge-discharge experiment and the tap density measurement. The results indicated that the samples have rules spherical or similar spherical morphology and simple pure olive-type phase. The Na doped Li0.95Na0.05FePO4 material showed excellent performance with a tap density of 1.63g/cm3. At room temperature, its initial discharge capacities reached 164.2 mAh/g, 151.5mAh/g, 130.5mAh/g at 0.2C, 1C, 2C current rates, respectively.

Synthesis and Electrochemical Performances of Nanoparticle FePO<sub>4</sub> and Ce-Doped FePO<sub>4</sub> Cathode Materials for Lithium Ion Batteries by Microemulsion Method

nanosized FePO4 and Fe1-xCexPO4 (x=0.02, 0.04, 0.08) cathode materials were synthesized by microemulsion method. The samples were prepared via a microemulsion system in a H2O/cyclohexane/Triton x-100/n-butyl alcohol at different temperatures (30 , 45 , 50 , 60 ) and then sintered at 380 and 460 for 3 h. The thermal stability, structure and morphology were investigated by means of TG/DCS, X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and the electrochemical properties were characterized by cyclic voltammetry (CV) and galvanostatic charge and discharge tests. Results show that synthesis temperature has a great influence on the performances of FePO4, and the sample synthesized at 45 shows the best performances with a diameter of about 20 nm and a high discharge initial specific capacity of 142mAh/g and retaining 123mAh/g after 20 cycles at 0.1 C. The Ce-doped FePO4, Fe1-xCexPO4 (x=0.02, 0.04, 0.08), can effectively improve the electrochemical properties of FePO4 cathode materials. The Fe0.96Ce0.04PO4 exhibits an initial discharge capacity of 158.2mAh/g and retains 152mAh/g after 20 cycles at 0.1 C. Hence, Fe0.96Ce0.04PO4 is a promising candidate for cathode materials of lithium ion batteries.

A novel conversion of converter sludge into amorphous multi-doped FePO4 cathode material for lithium ion batteries

A multi-doped FePO4 was synthesized using converter sludge as raw material for lithium ion battery cathodes. The processes included sulfolysis of the sludge to leach target ions into the filtrate, reacting the filtrate with phosphoric acid to prepare a precursor, and roasting the precursor to obtain the single-phase multi-doped FePO4. The results indicated that the obtained product delivers an enhanced capacity of 130 mA h g−1 at 0.1 C owing to the doping effect of the multiple metal ions derived from the converter sludge.

In situ analysis of LiFePO4 batteries: Signal extraction by multivariate analysis

The electrochemical reaction behavior of a commercial Li-ion battery (LiFePO4-based cathode, graphite-based anode) has been measured via in situ neutron diffraction. A multivariate analysis was successfully applied to the neutron diffraction data set facilitating in the determination of Li bearing phases participating in the electrochemical reaction in both the anode and cathode as a function of state-of-charge (SOC). The analysis resulted in quantified phase fraction values for LiFePO4 and FePO4 cathode compounds as well as the identification of staging behavior of Li6, Li12, Li24, and graphite phases in the anode. An additional Li-graphite phase has also been tentatively identified during electrochemical cycling as LiC48 at conditions of ∼5% to 15% SOC.

Synthesis of Mesoporous FePO4 Cathode Material for Its Application in Rechargeable Lithium-Ion Batteries

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Electrochemical Impedance Spectroscopy of Meso-structured FePO4 Cathode Materials for Rechargeable Lithium Batteries

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Electrochemical and magnetic characterization of LiFePO4 and Li0.95Mg0.05FePO4 cathode materials

A series of lithium iron phosphates was synthesized via the sol–gel route. Iron phosphides, which are electronic conductors, were formed when sintered at 850°C. Magnetic susceptibility measurements on the samples show antiferromagnetic behaviour with TN=50±2 K for LiFePO4 and Li0.95Mg0.05PO4 sintered at temperatures below 850°C. The LiFePO4 and Li0.95Mg0.05FePO4 cathodes show a stable electrochemical capacity in the range of 150–160 mA h/g on cycling. The cyclability deteriorates with increasing sample sintering temperature due to the increased crystal size and impurities.