Effect of safety valve types on the gas venting behavior and thermal runaway hazard severity of large-format prismatic lithium iron phosphate batteries

The safety valve is an important component to ensure the safe operation of lithium-ion batteries(LIBs).However,the effect of safety valve type on the thermal runaway(TR)and gas venting behavior of LIBs,as well as the TR hazard severity of LIBs,are not known.In this paper,the TR and gas venting behavior of three 100 A h lithium iron phosphate(LFP)batteries with different safety valves are investigated under overheating.Compared to previous studies,the main contribution of this work is in studying and evaluating the effect of gas venting behavior and TR hazard severity of LFP batteries with three safety valve types.Two significant results are obtained:(Ⅰ)the safety valve type dominates over gas venting pressure of battery during safety venting,the maximum gas venting pressure of LFP batteries with a round safety valve is 3320 Pa,which is one order of magnitude higher than other batteries with oval or cavity safety valve;(Ⅱ)the LFP battery with oval safety valve has the lowest TR hazard as shown by the TR hazard assessment model based on gray-fuzzy analytic hierarchy process.This study reveals the effect of safety valve type on TR and gas venting,providing a clear direction for the safety valve design.

Study on Preparation of Cathode Material of Lithium Iron Phosphate Battery by Self-Craning Thermal Method

The cathode material of carbon-coated lithium iron phosphate(LiFePO4/C)lithium-ion battery was synthesized by a self-winding thermal method.The material was characterized by X-ray diffraction(XRD)and scanning electron microscope(SEM).The electrochemical properties of LiFePO4/C materials were measured by the constant current charge-discharge method and cyclic voltammetry.The results showed that the LiFePO4/C material prepared by the self-propagating heat method has a typical olivine crystal structure,and the product had fine grains and good electrochemical properties.The optimal sintering temperature is 700℃,the sintering time is 24 h,the particle size of the lithium iron phosphate material is about 300 nm,and the maximum discharge capacity is 121 mAh/g at 0.1 C rate.

Process for recycle of spent lithium iron phosphate battery via a selective leaching-precipitation method

Applying spent lithium iron phosphate battery as raw material,valuable metals in spent lithium ion battery were effectively recovered through separation of active material,selective leaching,and stepwise chemical precipitation.Using stoichiometric Na2S2O8 as an oxidant and adding low-concentration H2SO4 as a leaching agent was proposed.This route was totally different from the conventional methods of dissolving all of the elements into solution by using excess mineral acid.When experiments were done under optimal conditions(Na2S2O8-to-Li molar ratio 0.45,0.30 mol/L H2SO4,60℃,1.5 h),leaching efficiencies of 97.53% for Li^+,1.39%for Fe^3+,and 2.58% for PO4^3−were recorded.FePO4 was then recovered by a precipitation method from the leachate while maintaining the pH at 2.0.The mother liquor was concentrated and maintained at a temperature of approximately 100℃,and then a saturated sodium carbonate solution was added to precipitate Li2CO3.The lithium recovery yield was close to 80%.

Phosphorus release from phosphate rock and iron phosphate by low-molecular-weight organic acids

Low-molecular-weight(LMW) organic acids widely exist in soils, particularly in the rhizosphere. A series of batch experiments were carried out to investigate the phosphorus release from rock phosphate and iron phosphate by low-molecular-weight organic acids. Results showed that citric acid had the highest capacity to solubilize P from both rock and iron phosphate. P solubilization from rock phosphate and iron phosphate resulted in net proton consumption. P release from rock phosphate was positively correlated with the p K _a values. P release from iron phosphate was positively correlated with Fe-organic acid stability constants except for aromatic acids, but was not correlated with p K _a. Increase in the concentrations of organic acids enhanced P solubilization from both rock and iron phosphate almost linearly. Addition of phenolic compounds further increased the P release from iron phosphate. Initial solution pH had much more substantial effect on P release from rock phosphate than from iron phosphate.

AN IRREVERSIBILITY PHENOMENA IN ELECTRICAL CONDUCTIVITY OF THE MELTS IN SODIUM IRON PHOSPHATE SYSTEM

Theelectricalresistivityofsodium iron phosphate melts wasinvestigated asa functionoftem peratureand composition. Irreversibility was found in thetemperature dependent electricalresistivityinthe melts withlow Na2 Ocontentduringtheheating andcoolingcycle. Theirre versibility wasreduced withincreasing Na2 Ocontent. Theelectricalresistivity tendedto de creaseslightly withtime. Theelectricalconduction ofthe meltscontainingsimulatedindustry waste wassimilartothatofthe melts withsimilarsodacontent. Thetemperature dependent electricalresistivity and activation energy ofthese melts was discussed using the Motttheory and wascorrelatedtothe Fe(II) contentinthe melts

Hydrometallurgical recovery of lithium carbonate and iron phosphate from blended cathode materials of spent lithium-ion battery

The recycling of cathode materials from spent lithium-ion battery has attracted extensive attention,but few research have focused on spent blended cathode materials.In reality,the blended materials of lithium iron phosphate and ternary are widely used in electric vehicles,so it is critical to design an effective recycling technique.In this study,an efficient method for recovering Li and Fe from the blended cathode materials of spent LiFePO_(4)and LiNi_(x)Co_(y)Mn_(1-x-y)O_(2)batteries is proposed.First,87%A1 was removed by alkali leaching.Then,91.65%Li,72.08%Ni,64.6%Co and 71.66%Mn were further separated by selective leaching with H_(2)SO_(4)and H_(2)O_(2).Li,Ni,Co and Mn in solution were recovered in the form of Li_(2)CO_(3)and hydroxide respectively.Subsequently,98.38%Fe was leached from the residue by two stage process,and it is recovered as FePO_(4)·2H_(2)O with a purity of 99.5%by precipitation.Fe and P were present in FePO_(4)·2H_(2)O in amounts of 28.34%and 15.98%,respectively.Additionally,the drift and control of various components were discussed,and cost-benefit analysis was used to assess the feasibility of potential application.

Highly selective and green recovery of lithium ions from lithium iron phosphate powders with ozone

Since lithium iron phosphate cathode material does not contain high-value metals other than lithium,it is therefore necessary to strike a balance between recovery efficiency and economic benefits in the recycling of waste lithium iron phosphate cathode materials.Here,we describe a selective recovery process that can achieve economically efficient recovery and an acceptable lithium leaching yield.Adjusting the acid concentration and amount of oxidant enables selective recovery of lithium ions.Iron is retained in the leaching residue as iron phosphate,which is easy to recycle.The effects of factors such as acid concentration,acid dosage,amount of oxidant,and reaction temperature on the leaching of lithium and iron are comprehensively explored,and the mechanism of selective leaching is clarified.This process greatly reduces the cost of processing equipment and chemicals.This increases the potential industrial use of this process and enables the green and efficient recycling of waste lithium iron phosphate cathode materials in the future.

Recursive calibration for a lithium iron phosphate battery for electric vehicles using extended Kalman filtering

In this paper,an efficient model structure composed of a second-order resistance-capacitance network and a simply analytical open circuit voltage versus state of charge(SOC) map is applied to characterize the voltage behavior of a lithium iron phosphate battery for electric vehicles(EVs).As a result,the overpotentials of the battery can be depicted using a second-order circuit network and the model parameterization can be realized under any battery loading profile,without a special characterization experiment.In order to ensure good robustness,extended Kalman filtering is adopted to recursively implement the calibration process.The linearization involved in the calibration algorithm is realized through recurrent derivatives in a recursive form.Validation results show that the recursively calibrated battery model can accurately delineate the battery voltage behavior under two different transient power operating conditions.A comparison with a first-order model indicates that the recursively calibrated second-order model has a comparable accuracy in a major part of the battery SOC range and a better performance when the SOC is relatively low.

Ambient synthesis, characterization, and electrochemical activity of LiFePO4 nanomaterials derived from iron phosphate intermediates

LiFePO4 materials have become increasingly popular as a cathode material due to the many benefits they possess including thermal stability, durability, low cost, and long life span. Nevertheless, to broaden the general appeal of this material for practical electrochemical applications, it would be useful to develop a relatively mild, reasonably simple synthesis method of this cathode material. Herein, we describe a generalizable, 2-step methodology of sustainably synthesizing LiFePO4 by incorporating a template-based, ambient, surfactantless, seedless, U-tube protocol in order to generate size and morphologically tailored, crystalline, phase-pure nanowires. The purity, composition, crystallinity, and intrinsic quality of these wires were systematically assessed using transmission electron microscopy （TEM）, high-resolution TEM （HRTEM）, scanning electron microscopy （SEM）, X-ray diffraction （XRD）, selected area electron diffraction （SAED）, energy dispersive analysis of X-rays （EDAX）, and high-resolution synchrotron XRD. From these techniques, we were able to determine that there is an absence of any obvious defects present in our wires, supporting the viability of our synthetic approach. Electrochemical analysis was also employed to assess their electrochemical activity. Although our nanowires do not contain any noticeable impurities, we attribute their less than optimal electrochemical rigor to differences in the chemical bonding between our LiFePO4 nanowires and their bulk-like counterparts. Specifically, we demonstrate for the first time experimentally that the Fe-O3 chemical bond plays an important role in determining the overall conductivity of the material, an assertion which is further supported by recent ＂first-principles＂ calculations. Nonetheless, our ambient, solution-based synthesis technique is capable of generating highly crystalline and phase-pure energy-storage-relevant nanowires that can be tailored so as to fabricate different sized materials of reproducible, reliable morphology.

Contribntion of Iron Phosphate in Calcareous Paddy Soils to Phosphorus Nntrition of Rice Plant

A study was carried out on contribution of iron pbosphate to phosphorus nutrition of rice plant nnderwaterlogged and moist conditions, respectively, by use of synthetic Fe￣(32) PO_4 . nH_2O, tagging directly the ironphophate in calcareous paddy soils.Results showed that under waterlogged condition, similar to iron phosphate in acidic paddy soils, that incalcareous paddy soils was an important source of phosphorus to rice plant, and the amount of phosphorusoriginated from it generally constituted 30-65% of the total phosphorus absorbed by rice plant.

Hydrothermal Synthesis and Properties of Open-Framework Mixed-valence Iron Phosphates IIIII21.543FeFe(PO) with Three-dimensional Structure

The open-framework iron phosphate IIIII21.543FeFe(PO) was hydrothermally synthesized and characterized by elemental analysis, IR, EPR, XPS and single crystal X-ray diffraction analysis. The title compound crystallized in the triclinic, space group P1with a=0.64724(4) nm, b=0.79651(6) nm, c=0.94229(5) nm, =104.447(2)? =108.919(4)? =101.741(4)? V=0.42302(5) nm3, Z=1 and R1 (wR2)=0.0307 (0.0793). Crystal data were collected on a Rigaku R-AXIS RAPID IP diffractometer with Mo K?(=0.071073 nm) at 293(2) K in the range of 2.43埃迹?7.46? The structure of 1 consists of 19 non-hydrogen atoms including three and a half crystallographically in-dependent Fe and three P atoms. Fe(1) connects its symmetrical Fe(1A) through bridging oxygen forming a dimer and the dimers are connected by Fe(4) forming an infinite staircase-like chain. Fe(2) and Fe(3) connect the infinite chains into a layer with bridging oxygen. Layers are interconnected via Fe(4) forming the six-membered and eight-membered channel systems.

Theoretical model of lithium iron phosphate power battery under high-rate discharging for electromagnetic launch

Due to the large error of the traditional battery theoretical model during large-rate discharge for electromagnetic launch,the Shepherd derivative model considering the factors of the pulse cycle condition,temperature,and life is proposed by the Naval University of Engineering.The discharge rate of traditional lithium-ion batteries does not exceed 10C,while that for electromagnetic launch reaches 60C.The continuous pulse cycle condition of ultra-large discharging rate causes many unique electrochemical reactions inside the cells.The traditional model cannot accurately describe the discharge characteristics of the battery.The accurate battery theoretical model is an important basis for system efficiency calculation,precise discharge control,and remaining capacity prediction.To this purpose,an experimental platform for electromagnetic launch is built,and discharge characteristics of the battery under different rate,temperature,and life decay are measured.Through the experimental test and analysis,the reason that the traditional model cannot accurately characterize the large-rate discharge process is analyzed.And a novel battery theoretical model is designed with the help of genetic algorithm,which is integrated with the electromagnetic launch topology.Numerical simulation is compared with the experimental results,which verifies the modeling accuracy for the large-rate discharge.On this basis,a variety of discharge conditions are applied to test the applicability of the model,resulting in better results.Finally,with the continuous cycle-pulse condition in the electromagnetic launch system,the stability and accuracy of the model are confirmed.

A New Non-centrosymmetric Microporous Fluorinated Iron Phosphate： Structural Elucidation, Spectroscopic Study and Hirshfeld Surface Analysis

The crystal structure of a new non-centrosymmetric microporous fluorinated iron phosphate, （H30）2[Fe4（H2O）2F4（PO4）2（HPO4）2]（H2O）, was determined by single crystal X-ray diffraction analysis and the result reveals that it belongs to the orthorhombic system with four molecules in the unit cell（space group P212121）. Thus, the complex was characterized by powder X-ray diffraction, spectroscopic techniques（Fourier transform infrared and Fourier transform Raman） and 19F MAS NMR. The elemental analysis of the sample was also carried out. The chiral inorganic sheets, which stacked along [100] showed the presence of FeF2O4 as well as FeF2O3H2O octahedra, PO4 besides HPO4 tetrahedra, hydronium ions（H3O＋） and isolated water molecules. Hirshfeld surface analysis, especially dnom surface and fingerprint plots, were used for decoding the intermolecular interactions in the crystal network and the contribution of component units for the construction of the 3D architecture. From the Hirshfeld surfaces and 2D fingerprint analysis, it was found that the subtle interactions, such as H...H associating the third intense interaction of all intercontacts, provide extra stabilization in addition to the presence of the strong hydrogen bonds mentioned above.

Effects of different iron sources on the performance of LiFePO_4/C composite cathode materials

Olivine LiFePO4/C composite cathode materials were synthesized by a solid state method in N2 ＋ 5vol% H2 atmosphere. The effects of different iron sources, including Fe（OH）3 and FeC2O4·2H2O, on the performance of as-synthesized cathode materials were investigated and the causes were also analyzed. The crystal structure, the morphology, and the electrochemical performance of the prepared samples were characterized by X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, laser particle-size distribution measurement, and other electrochemical techniques. The results demonstrate that the LiFePO4/C materials obtained from Fe（OH）3 at 800℃ and FeC2O4·2H2O at 700℃ have the similar electrochemical performances. The initial discharge capacities of LiFePO4/C synthesized from Fe（OH）3 and FeC2O4·2H2O are 134.5 mAh.g^-1 and 137.4 mAh.g^-1 at the C/5 rate, respectively. How- ever, the tap density of the LiFePO4/C materials obtained from Fe（OH）3 are higher, which is significant for the improvement of the capacity of the battery.

Preparation of Novel Scorzalite Imitated Phosphate Pigments

Novel phosphate pigments imitated with Scorzalite,FeAl2(PO4)2(OH)2,were prepared from iron and aluminum nitrate solutions,ascorbic acid,and phosphoric acid with pH adjustments(pH 5,7,9).The obtained precipitates were heated at 300,500,and 700°C for 1 h.The precipitates and their thermal products were estimated with X-ray diffraction(XRD),Infrared(IR)spectra,ultraviolet-visible(UV-Vis)reflectance spectra,and L*a*b*color space.The precipitated sample was not clearly colored,but it turned orange to red when heated.Samples prepared at low pH showed higher whiteness than samples prepared at high pH.The theoretical amount of ascorbic acid was sufficient to completely reduce iron during the adjustment.This study showed the possibility of novel inorganic phosphate red pigment.

Perspective on cycling stability of lithium-iron manganese phosphate for lithium-ion batteries

Lithium-iron manganese phosphates(LiFex Mn_(1-x)PO_(4),0.1<x<0.9)have the merits of high safety and high working voltage.However,they also face the challenges of insufficient conductivity and poor cycling stability.Some progress has been achieved to solve these problems.Herein,we firstly summarized the influence of different electrolyte systems on the electrochemical performance of LiFexMn_(1-x)PO_(4),and then discussed the effect of element doping,lastly studied the influences of conductive layer coating and morphology control on the cycling stability.Finally,the prospects and challenges of developing high-cycling LiFexMn_(1-x)PO_(4) were proposed.

Thermodynamics analysis of LiFePO_4 pecipitation from Li-Fe(Ⅱ)-P-H_2O system at 298 K

Thermodynamics of the precipitation from Li-Fe（II）-P-H2O system at 298 K was investigated.The results demonstrate that LiFePO4 can be formed at room temperature under pH value of 0-11.3,and the impurities Li3PO4 and Fe（OH）2 will be yielded at pH value above 11.3 and 12.9,respectively.The optimum pH value for LiFePO4 precipitation is 8-10.5.Considering the low rate of phase transformation kinetics,metastable Li-Fe（II）-P-H2O system was also studied.The results indicate that equimolar ratio of co-precipitation precursor Fe3（PO4）2.8H2O and Li3PO4 cannot be obtained at the initial molar ratio 1：1：1 and 1：1：3 of Li：Fe：P.In contrast,equimolar ratio of the co-precipitation precursor can be yielded by adjusting the pH value to 7-9.2,matching the molar ratio 3：1：1 of Li：Fe：P,meaning that Li＋-excess is one of the essential conditions for LiFePO4 preparation by co-precipitation method.

Synthesis and Electrochemical Property of Flowerlike LiFePO4 by Poly（ethylene glycol）-assisted Hydrothermal Process

Flowerlike LiFePO4 particles self-assembled by plate-like crystals with about 200 nm thickness were prepared by the poly（ethylene glycol）-assisted hydrothermal synthesis. Poly（ethylene glycol） in the hydrothermal system played an important role in reducing the thickness of the plate-like LiFePO4 crystals as a co-solvent and forming the flower- like structure as a soft template. The flowerlike LiFePO4 exhibits high discharge capacity of 140 mAh/g and shows quite good cycling performance in the lithium-ion batteries. Con- sidering that the conductive carbon in the obtained LiFePO4 is negligible, the excellent cell performance suggests that the flowerlike LiFePO4 is a promising cathode material for the lithium-ion batteries.

LiFePO_4 doped with magnesium prepared by hydrothermal reaction in glucose solution

Lithium iron phosphate （LiFePO4） doped with magnesium was hydrothermally synthesized from commercial LiOH, FeSO4, H3PO4 and MgSO4 with glucose as carbon precursor in aqueous solution. The samples were characterized by X-ray powder diffraction, scanning electron microscopy and constant charge-discharge cycling. The results show that the synthesized powders have been in situ coated with carbon precursor produced from caramel reaction of glucose. At ambient temperature （28±2℃）, the electrochemical performances of LiFePO4 prepared exhibit the high discharge capacity of 135 mAh g^-1 at 5C and good capacity retention of 98% over 90 cycles. The excellent electrochemical performances should be correlated with the intimate contact between carbon and LiFePO4 primary and secondary particles, resulting from the in situ formation of carbon precursor/carbon, leading to the increase in conductivity of LiFePO4.

Electrochemical performances of LiFePO_4/C composites prepared by molten salt method

LiFePO4/C composites were synthesized by a molten salt (MS) method using the mixture of LiCl,LiOH and NaCl.The prepared LiFePO4/C composites are characterized by X-ray diffractometry (XRD),field emission scanning electron microscopy (FESEM) and charge-discharge test.XRD patterns indicate that LiFePO4 prepared in the temperature range of 550-700 ℃ crystallizes well in an olivine-type structure.Through FESEM images,the sphere-like and homogeneous particles of 0.2 μm can be observed.The charge-discharge test shows that the materials prepared at 600 ℃ for 12 h have good electrochemical performance.At the rates of 0.2C (34 mA/g) and 0.5C,the discharge capacities are 144.6 and 122.3 mA·h/g,respectively,together with good cycle performances.