CN109830680A - A kind of LiFePO4Hydrothermal synthesis method - Google Patents

A kind of LiFePO4Hydrothermal synthesis method Download PDF

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CN109830680A
CN109830680A CN201711184557.5A CN201711184557A CN109830680A CN 109830680 A CN109830680 A CN 109830680A CN 201711184557 A CN201711184557 A CN 201711184557A CN 109830680 A CN109830680 A CN 109830680A
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lifepo
hydrothermal synthesis
source
synthesis method
lithium
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王晓辉
杨金星
李昭进
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Institute of Metal Research of CAS
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/84—Recycling of batteries or fuel cells

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Abstract

The present invention relates to field of lithium ion battery material, specially a kind of LiFePO4Hydrothermal synthesis method, solve hydrothermal synthesis LiFePO4In the process, lithium source cannot make full use of, thus the problem of increasing cost of material.The present invention uses Lithium hydroxide monohydrate, phosphoric acid and ferrous sulfate heptahydrate for raw material, matches according to a certain percentage, under stirring, using microwave heating, synthesizes the nano-sheet LiFePO with high rate charge-discharge performance in water4Positive electrode, and by the lithium source recycling and reusing of unreacted 2/3rds, as Material synthesis nano-sheet LiFePO4Positive electrode, to substantially reduce cost of material.Using the method for microwave agitating and heating, mixed liquor can be made to be rapidly achieved reaction temperature, improve the degree of supersaturation of solution, make the nano-sheet LiFePO of synthesis4Uniformly suspended dispersed in the solution, to make that more raw materials can be put into unit volume, higher yield can be obtained, industrialized production is more suitable for.

Description

A kind of LiFePO4Hydrothermal synthesis method
Technical field
The present invention relates to field of lithium ion battery material, specially a kind of LiFePO4Hydrothermal synthesis method.
Background technique
Today's society, with the continuous enhancing of environmental consciousness, people start to pay attention to developing renewable and clean energy resource, to alleviate The energy crisis and ecological environmental pollution problem got worse.Green Chemistry power supply, can be very as a kind of novel energy-conserving technology The storage of these renewable and clean energy resources, conversion and utilization are realized well.Also, national governments are to fulfil " Paris agreement ", Numerous and confused formulate bans fuel vehicle timetable, and cumulative year after year trend is presented in the yield and sales volume of new-energy automobile, and battery is system The about key factor of its cruising ability.Currently, positive electrode mainly has LiFePO4、LiCoO2、LiMn2O4And ternary material LiNi1-x-yCoxAlyO2、LiNi1-x-yCoxMnyO2Deng, compared with other positive electrodes, LiFePO4Positive electrode has cost The many advantages such as low, safe and environment-friendly are the positive electrodes of middle large capacity, middle high power lithium ion cell first choice.Therefore, LiFePO4Positive electrode is attracted extensive attention in field of lithium ion battery.
Currently, synthesis LiFePO4Method mainly have high-temperature solid phase reaction method, carbon thermal reduction synthetic method, microwave process for synthesizing, Sol-gel synthesis method and hydrothermal synthesis method etc..In numerous synthetic methods, hydrothermal synthesis method, which can directly obtain to be free of, appoints The LiFePO of what impurity phase4, the crystal form and particle size of product are easily controllable, and source of iron is cheap.But prepared by hydro-thermal method LiFePO4, every generation 1mol LiFePO4, will result in 2mol lithium source and waste, there are a large amount of SO in mother liquor4 2 ﹣、Fe2 ﹢Etc. miscellaneous Matter, direct emission not only pollute environment and also result in lithium resource significant wastage, and in order to obtain lesser particle size, generally Hydro-thermal method needs longer soaking time, although and utilizing organic solvent available nano-scale in a short time LiFePO4Particle, but lithium source can not almost recycle, and this greatly increases cost of material.And what most of hydro-thermal methods synthesized LiFePO4Yield is not high, therefore synthesizes LiFePO using hydro-thermal method4The difficulty of industrialized production is larger.
Chinese invention patent (publication number CN102897803A) is introduced a kind of liquid phase method and prepared to be produced in LiFePO 4 method The recoverying and utilizing method of breeder mother's liquid, this method include preparing seasoning liquid, LiCl slurries, LiCl solution, LiCl refined liquid etc..The party Method recycles LITHIUM BATTERY LiCl, generates certain economic benefit using the lithium salts resource in mother liquor.But this method process is very numerous It is trivial, Li to be added into mother liquor2SO4、CaCl2、CaO、Li2O、Ca(OH)2, the raw materials such as LiOH, by repeatedly adjust pH value and Evaporative crystallization, complex process, lithium source cost recovery are higher.
Chinese invention patent (publication number CN101830484A) is introduced a kind of from liquid phase method preparation LiFePO4Material is discarded Hydrogen-oxygen is added in the waste filtrate that liquid phase method prepares LiFePO4 technique in the method that lithium hydroxide is recycled in filtrate, this method Change potassium or sodium hydroxide, sediment washing, drying are obtained a hydronium(ion) lithia crude product by heated concentration, filtering, then will Barium hydroxide octahydrate is added in it after dissolving, agitated, filtering, heating concentration obtain after sediment washing, drying and other steps To a hydronium(ion) lithia product.This method is using the lithium source discarded in the partially recycled preparation process of two-step method, to a certain extent Reduction prepares the cost of LiFePO 4 material, but obtains a hydronium(ion) lithia using method of purification, and complex process, process is very Cumbersome, lithium source cost recovery is higher, and this method is independently of LiFePO4Except preparation process.
Chinese invention patent (publication number CN102751548A) introduces one kind and recycles preparation from LiFePO4 old and useless battery The method of LiFePO4, this method peel off battery case after disassembling the waste lithium iron phosphate battery of recycling, then impregnate, pass through Ultrasound and the alternate method of mechanical stirring obtain mixed liquor after separating pole piece with positive and negative anodes powder, and mixed liquor obtains after ball milling Slurry is baked to, calcines, obtains salvage material, after being added to it source of iron, phosphorus source and carbon source etc. using high-energy ball milling, It handles to obtain LiFePO4 product using microwave sintering or solid-phase sintering under protective atmosphere.Although this method is kept away to a certain extent Exempt from the waste of lithium source, but its removal process is cumbersome, needs to be added organic solvent, long-time ball milling, high-temperature calcination etc., energy consumption Greatly, cost recovery is high.
Most of document liquid phase methods prepare nano-scale LiFePO4 and all use organic solvent, but the excessive lithium source in filtrate It can not effectively recycle, not only cause lithium source waste to be also unfavorable for discharging of waste liquid, to pollute environment.Chinese invention patent is (open Number CN105060266A) although preparing nano-scale LiFePO4 using hydro-thermal method, it needs small in 150~170 DEG C of heat preservations 2 When, energy consumption is big, and the sample prepared is 90~100nm thick, although recycling obtains sulphur after mother liquid evaporation is concentrated the patent Sour lithium, avoids lithium source from wasting to a certain extent, but be concentrated by evaporation consumption the energy it is big, be unfavorable for industrialized production, and do not refer to by The lithium sulfate later use problem of recycling.
Summary of the invention
The purpose of the present invention is to provide a kind of LiFePO4Hydrothermal synthesis method, solve hydrothermal synthesis LiFePO4Process In, sample particle size is big, and lithium source waste is thus the problem of increasing cost of material.
The technical scheme is that；
A kind of LiFePO4Hydrothermal synthesis method, synthesis step are as follows:
1) hydrothermal synthesis: lithium source, phosphorus source, source of iron and antioxidant are added in aqueous solvent under stirring, are mixed It closes uniformly, lithium source, phosphorus source, source of iron and antioxidant molar ratio are (2.2~3.8): (0.3~1.8): (0.8~1.2): Mixed solution is heated 5~180 minutes at 120~220 DEG C, after suspension is separated by solid-liquid separation, obtains ash by (0.001~0.01) White depositions LiFePO4And mother liquor；
2) enough Ba (OH) is added into mother liquor2, after it is sufficiently reacted, remove sediment, that is, LiOH aqueous solution；With Recycling LiOH aqueous solution is lithium source, is recycled in step 1) and continues with.
The LiFePO4Hydrothermal synthesis method, aqueous solvent is defined as water or containing a small amount of ion or organic solvent Aqueous solution.
The LiFePO4Hydrothermal synthesis method, aqueous solvent use deionized water or distilled water.
The LiFePO4Hydrothermal synthesis method, lithium source is Lithium hydroxide monohydrate, and source of iron is ferrous sulfate heptahydrate, phosphorus Source is phosphoric acid, and antioxidant is ascorbic acid.
The LiFePO4Hydrothermal synthesis method, phosphoric acid concentration 85wt%.
The LiFePO4Hydrothermal synthesis method, solution is always under stirring in reaction process.
The LiFePO4Hydrothermal synthesis method, heating means are microwave heating, and heating temperature is 140~200 DEG C, Heating time is 5~60 minutes.
The LiFePO4Hydrothermal synthesis method, solid-liquid separating method be filter or centrifugation.
The LiFePO4Hydrothermal synthesis method, remove mother liquor in impurity materials be Ba (OH)2·8H2O, dosage are (0.2~0.6) g/mL mother liquor.
Design philosophy of the invention is:
The present invention uses Lithium hydroxide monohydrate, phosphoric acid and ferrous sulfate heptahydrate for raw material, matches according to a certain percentage, Under stirring, using microwave heating, the nano-sheet LiFePO with high rate charge-discharge performance is synthesized in pure water4Just Pole material, and by the lithium source recycling and reusing of unreacted 2/3rds, continue to synthesize nano-sheet LiFePO4Positive electrode, To substantially reduce cost of material, it is more suitable for industrialized production.The present invention can be in lower temperature, synthesize in the extremely short time Provide the LiFePO of excellent chemical property4Positive electrode solves hydro-thermal so that it is long to substantially reduce hydro-thermal reaction synthesis cycle Method synthesizes LiFePO4Positive electrode particle size is bigger than normal, the low problem of charging and discharging capacity under the conditions of high magnification, will be excessive Lithium source recycling and reusing, can be greatly reduced cost of material.
The invention has the advantages and beneficial effects that:
1, the present invention can recycle excessive lithium source from mother liquor, LiOH solution be generated, and using it as lithium source, with phosphorus After mixing, microwave heating prepares nano-sheet LiFePO under stirring for source, source of iron and antioxidant4, thus significantly Reduce cost of material.
2, the solvent that the present invention uses is deionized water or distilled water, to more easily efficiently return lithium source from mother liquor It receives.
3, the present invention can synthesize pure phase, nano-sheet under lower synthesis temperature, shorter generated time LiFePO4。
4, the nano-sheet LiFePO that the present invention synthesizes4It can be evenly dispersed in solution, so that reaction kettle (polytetrafluoro Ethylene) in can put into more raw materials, therefore LiFePO in unit volume4Yield be greatly improved.
5, the nano-sheet LiFePO that the present invention synthesizes4With excellent big multiplying power chemical property, including charge and discharge ratio Capacity height, good cycle.
6, it in the present invention, is heated using microwave agitating mode, the degree of supersaturation of solute can be improved, to prepare nanometer Sheet LiFePO4。
Detailed description of the invention
Fig. 1 is the solvent for being 1:1 by spent glycol and deionized water volume ratio, using LiOHH in comparative example 12O And H3PO4Neutralization reaction generates Li3PO4For lithium source, FeSO4·7H2O is the LiFePO that source of iron obtains4Stereoscan photograph.
Fig. 2 is the solvent for being 1:1 by spent glycol and deionized water volume ratio, using LiOHH in comparative example 12O And H3PO4Neutralization reaction generates Li3PO4For lithium source, FeSO4·7H2O is the LiFePO that source of iron obtains4Different multiplying charge and discharge Curve.
Fig. 3 is in comparative example 2, by being solvent with pure ethylene glycol, using LiOHH2O and H3PO4Neutralization reaction generates Li3PO4For lithium source, FeSO4·7H2O is the laminar LiFePO that source of iron obtains4Stereoscan photograph.
Fig. 4 is in comparative example 2, by being solvent with pure ethylene glycol, using LiOHH2O and H3PO4Neutralization reaction generates Li3PO4For lithium source, FeSO4·7H2O is the laminar LiFePO that source of iron obtains4Different multiplying charging and discharging curve.
Fig. 5 is in embodiment 1, and hydro-thermal method prepares LiFePO4And recycling lithium source, and lithium source is recycled into process signal Figure.
Fig. 6 is, by being solvent with pure deionized water, to be synthesized using microwave agitating and heating final in embodiment 1 LiFePO4Suspension.
Fig. 7 be embodiment 1 in, by being solvent with pure deionized water, the nanometer sheet synthesized using microwave agitating and heating Shape LiFePO4Scanning electron microscopic picture.
Fig. 8 be embodiment 1 in, by being solvent with pure deionized water, the nanometer sheet synthesized using microwave agitating and heating Shape LiFePO4Transmission picture.
Fig. 9 is to prepare LiFePO in embodiment 14Yield and document in using solvent heat, hydrothermal method prepare LiFePO4 Yield comparison figure.
Figure 10 be embodiment 1 in, by being solvent with pure deionized water, the nanometer sheet synthesized using microwave agitating and heating Shape LiFePO4LiFePO after carbon coating4/ C-scan electron microscopic picture.
Figure 11 be embodiment 1 in, by being solvent with pure deionized water, the nanometer sheet synthesized using microwave agitating and heating Shape LiFePO4By the infrared curve before and after carbon coating.
The LiFePO that Figure 12 is comparative example 1,1 three kinds of comparative example 2, embodiment methods synthesize4Specific surface area relationship.
Figure 13 be embodiment 1 in, by being solvent with pure deionized water, the nanometer sheet synthesized using microwave agitating and heating Shape LiFePO4Different multiplying charging and discharging curve.
Figure 14 be embodiment 1 in, by being solvent with pure deionized water, the nanometer sheet synthesized using microwave agitating and heating Shape LiFePO4Different multiplying cycle performance curve.
Figure 15 is the stereoscan photograph that BaSO4 is generated in embodiment 1.
Figure 16 is the EDS energy spectrum diagram that BaSO4 is generated in embodiment 1.
Figure 17 is that LiOH clear solution is recycled in embodiment 1.
Figure 18 be in embodiment 1 using recycling LiOH be raw material, prepare LiFePO4Stereoscan photograph.
Figure 19 be in embodiment 1 using recycling LiOH be raw material, prepare LiFePO4XRD spectrum and standard card compare.
Figure 20 is to change the reaction time in embodiment 2, and heat preservation prepares LiFePO after five minutes4Stereoscan photograph.
Figure 21 is to change the reaction time in embodiment 3, and heat preservation prepared LiFePO after 15 minutes4Stereoscan photograph.
Figure 22 is to change lithium source in embodiment 4, uses lithium phosphate for raw material, heat preservation prepared LiFePO after 30 minutes4Sweep Retouch electromicroscopic photograph.
Specific embodiment
In the specific implementation process, LiFePO of the present invention4Hydrothermal synthesis method, the specific steps are as follows:
(1)LiFePO4Synthesis: under stirring, Lithium hydroxide monohydrate is added in deionized water or distilled water, H is added dropwise later3PO4Solution adds FeSO4·7H2O and antioxidants ascorbic acid (LiOHH2O、H3PO4、FeSO4· 7H2O and antioxidants ascorbic acid molar ratio are (2.5~3.5): (0.5~1.5): (0.8~1.2): (0.001~ 0.01)), by mixed solution under stirring microwave heating to 140~200 DEG C hydro-thermal reaction 5~60 minutes, preparation LiFePO4, then carry out being separated by solid-liquid separation acquisition pale precipitation object LiFePO4And mother liquor.
(2) by disposing mother liquor, (mother liquor main component is Li2SO4), it is added Ba (OH)2·8H2O (additional amount be (0.2~ 0.6) g/mL mother liquor), remove the Fe in mother liquor2 ﹢And SO4 2 ﹣Impurity, obtained after being separated by solid-liquid separation clarification LiOH aqueous solution, then to LiOH sample is added in it, is configured to such as preceding solution concentration.Take a certain amount of LiOH aqueous solution as lithium source, according to above-mentioned Step synthesizes LiFePO4Sample.
In the following, being further elaborated on by comparing example and embodiment.
Comparative example 1
The solution that solvent is ethylene glycol, deionized water volume ratio is 1:1, solvent-thermal method prepare the LiFePO of sheet4.Lithium The lithium phosphate that source is obtained using Lithium hydroxide monohydrate and phosphoric acid neutralization reaction, source of iron use ferrous sulfate heptahydrate, and antioxidant is adopted Use ascorbic acid.
The preparation method comprises the following steps: taking 13.38g Lithium hydroxide monohydrate to be added to 50mL using polytetrafluoroethyltank tank as reaction kettle and being in In ethylene glycol, deionized water mixed liquor under stirring, phosphoric acid (concentration 85wt%) 7.6mL is then added and seven water sulfuric acid are sub- Iron 29.2g and ascorbic acid 0.4g.It is to be mixed uniformly after, be transferred quickly in microwave heating work station, stirring shape It is heated to 180 DEG C of hydro-thermal reactions 0.5 hour within state lower 5 minutes, obtains sheet LiFePO4Particle.Mother liquor is collected after separation of solid and liquid The Ba (OH) of 30~60g is added in (about 80mL)2·8H2O sample, after sufficiently reacting with mother liquor, there are also a large amount of insoluble Ba (OH)2 Sample.After suspension is separated by solid-liquid separation, remove unreacted Ba (OH)2Sample, according to sediment quality, the lithium source rate of recovery is only Between 20% to 30%.
Fig. 1 is the obtained LiFePO in the case where ethylene glycol, deionized water are solvent condition by microwave heating4Scanning Photo, the LiFePO obtained as seen from Figure 14Particle size is very uneven.Fig. 2 it is found that under 0.1C charge-discharge magnification, The prepared LiFePO in the case where ethylene glycol, deionized water are solvent condition4First discharge specific capacity reaches 152mAh g-1, Under 2C charge-discharge magnification, specific discharge capacity is 116mAh g-1.It can be seen that being closed using deionized water and ethylene glycol mixed solvent At the LiFePO gone out4Particle size is uneven, and chemical property is poor.
Comparative example 2
The difference is that, solvent uses pure ethylene glycol with comparative example 1, prepares the LiFePO of sheet4。
Fig. 3 is the sheet LiFePO for using ethylene glycol to prepare for solvent4Photo, it can be seen that when with pure ethylene glycol system Standby LiFePO out4Partial size is reduced compared with ethylene glycol, water mixed liquid (comparative example 1), and the uniformity of particle size improves.
Mother liquor is collected into (about 80mL) after separation of solid and liquid, the Ba (OH) of 30~60g is added2·8H2O sample, it is abundant with mother liquor After reaction, Ba (OH)2Sample is practically insoluble in mother liquor, and the lithium source rate of recovery is almost 0.
Under 0.1C charge-discharge magnification, the prepared LiFePO in ethylene glycol4First discharge specific capacity is 160mAh g-1, under 2C charge-discharge magnification, specific discharge capacity is 124mAh g-1(Fig. 4).It can be seen that using pure ethylene glycol for solvent conjunction At the LiFePO gone out4Chemical property increases, but since partial size is still bigger, so that it discharges under the conditions of big multiplying power Specific capacity is lower.
Embodiment 1
In the present embodiment, by hydro-thermal method using pure deionized water as reaction dissolvent, is prepared and received and paid out using microwave agitating and heating Rice sheet LiFePO4.In the present embodiment, lithium source is neutralized using Lithium hydroxide monohydrate and phosphoric acid, and lithium phosphate is generated in reaction kettle, Source of iron uses ferrous sulfate heptahydrate, and antioxidant uses ascorbic acid.
Fig. 5 is LiFePO4Preparation and lithium source recovery process schematic diagram, method particularly includes: with polytetrafluoroethyltank tank be reaction Kettle takes 13.38g Lithium hydroxide monohydrate to be added to 50mL and is in the deionized water under stirring, and 7.6mL phosphoric acid is then added (concentration 85wt%), 29.2g ferrous sulfate heptahydrate and 0.4g ascorbic acid.It is to be mixed uniformly after, be transferred quickly to micro- In Wave heating work station, it is heated to 180 DEG C of hydro-thermal reactions 0.5 hour within 5 minutes under stirring, obtains nano-sheet LiFePO4。
Fig. 6 show the LiFePO of the preparation of embodiment 14.It is different from comparative example 1 and comparative example 2, use pure deionized water for The available nano-sheet LiFePO of solvent4(Fig. 7).The LiFePO prepared4Nanometer leaf length be 50~200nm (Fig. 8). LiFePO is prepared using solvent heat hydro-thermal method with most of document reports4It compares, the present invention prepares LiFePO4Yield significantly mention High (Fig. 9).The nano-sheet LiFePO after carbon coating is handled4Pattern do not change (Figure 10).Figure 11 infared spectrum shows, Fe is characterized before and after carbon coatingLiThe characteristic peak of antistructure defect concentration is respectively 973cm-1And 970cm-1, close to zero defect concentration Characteristic peak (957cm-1).The nano-sheet LiFePO obtained in this way4Specific surface area reach 23.9m2g-1, higher than comparing The value (Figure 12) of example 1 and comparative example 2.This nano-sheet LiFePO4Putting under the charge-discharge magnification of 0.1C, 2C, 5C and 10C Electric specific capacity respectively reaches 166.6mAh g-1、144.7mAh g-1、133.0mAh g-1And 120.0mAhg-1(Figure 13).With with second Two pure and mild deionized waters are that solvent compares (comparative example 1), are that anode material for lithium-ion batteries can be improved in solvent with pure deionized water LiFePO4High magnification chemical property.Also, it still has good smoothly cycle performance (figure under different multiplying 14)。
Mother liquor is collected into (about 80mL), the Ba (OH) of 30~60g is added2·8H2O sample removes the impurity in mother liquor, obtains (Figure 15) is precipitated to yellow-white, predominantly BaSO4(Figure 16).According to the amount of substance precipitated, the lithium source rate of recovery reaches 90% More than.After turbid solution filtering, clear yellow solution, as LiOH solution (Figure 17) are obtained.
The LiOH solution for taking 50mL to recycle, 7.8mL H3PO4、29.2g FeSO4·7H2O and 0.4g ascorbic acid is stirring It is added sequentially in solution under state, after mixing evenly, keeps the temperature 30 minutes for 80 DEG C in a water bath, subsequent microwave heating is to 180 DEG C And keep the temperature 30 minutes.The pale precipitation object i.e. LiFePO of nano-sheet obtained after solution is filtered4(Figure 18).By XRD Analysis, gained sample and standard PDF card compare, and obtained pale precipitation object is the LiFePO of pure phase4(Figure 19).
Embodiment 2
Difference from Example 1 is that the reaction time used by testing is different, equally prepares nano-sheet LiFePO4.In the present embodiment, lithium source is sequentially added in reaction kettle using Lithium hydroxide monohydrate and phosphoric acid, is neutralized in a kettle Reaction generates lithium phosphate, and source of iron uses ferrous sulfate heptahydrate, and antioxidant uses ascorbic acid.
Solution used is pure deionized water.Hydrothermal condition are as follows: 180 DEG C of temperature, the time 5 minutes.
Lithium source is recycled from mother liquor with embodiment 1, for the lithium source rate of recovery 90% or so, the product of acquisition is nano-sheet LiFePO4(Figure 20), the specific discharge capacity under the conditions of high power charging-discharging of 2C reach 138.2mAh g-1。
Embodiment 3
Difference from Example 1 is that the reaction time used by testing is different, equally prepares nano-sheet LiFePO4.In the present embodiment, lithium source is sequentially added in reaction kettle using Lithium hydroxide monohydrate and phosphoric acid, is neutralized in a kettle Reaction generates lithium phosphate, and source of iron uses ferrous sulfate heptahydrate, and antioxidant uses ascorbic acid.
Solution used is pure deionized water, hydrothermal condition are as follows: 180 DEG C of temperature, the time 15 minutes.
Lithium source is recycled from mother liquor with embodiment 1, for the lithium source rate of recovery 90% or so, the product of acquisition is nano-sheet LiFePO4(Figure 21), the specific discharge capacity under the conditions of high power charging-discharging of 2C reach 139.5mAh g-1。
Embodiment 4
Difference from Example 1 is that lithium source used by testing is different, equally prepares nano-sheet LiFePO4.In the present embodiment, lithium source uses lithium phosphate, and source of iron uses ferrous sulfate heptahydrate, and antioxidant uses ascorbic acid.
Solvent for use is pure deionized water, hydrothermal condition are as follows: 180 DEG C of temperature, the time 30 minutes.
Lithium source is recycled from mother liquor with embodiment 1, for the lithium source rate of recovery 90% or so, the product of acquisition is nano-sheet LiFePO4(Figure 22), the specific discharge capacity under the conditions of high power charging-discharging of 2C are only 128mAh g-1。
Embodiment the result shows that, the present invention uses pure deionized water or distilled water for solvent, can be in wider time model Nano-sheet LiFePO is prepared in enclosing4, and the lithium source rate of recovery is 90% or more, can be with without further by sample cleanup It is directly raw material using it, continues to prepare LiFePO4, to greatly simplify technique.The LiFePO of this nano-sheet4Have compared with High high rate charge-discharge specific capacity and high rate performance and stable cycle performance.In lower reaction temperature and shorter Synthesize high yield in the case of reaction time and there is excellent chemical property anode material for lithium-ion batteries LiFePO4, substantially Degree ground reduces the pressure-resistant performance requirement to hydrothermal reaction kettle and greatly shortens manufacturing cycle, synthesized LiFePO out4Nothing is appointed The presence of what impurity phase.Also, pass through the LiFePO synthesized using deionized water as solvent4It can uniformly be dispersed in suspension within molten In liquid, so that more raw materials can be put into unit volume, higher yield is obtained.And by prepared by this method The no matter big multiplying power of material or small multiplying power have excellent chemical property.

Claims (9)

1. a kind of LiFePO4Hydrothermal synthesis method, which is characterized in that synthesis step are as follows:
1) hydrothermal synthesis: lithium source, phosphorus source, source of iron and antioxidant are added in aqueous solvent under stirring, and mixing is equal Even, lithium source, phosphorus source, source of iron and antioxidant molar ratio are (2.2~3.8): (0.3~1.8): (0.8~1.2): (0.001 ~0.01) mixed solution is heated 5~180 minutes at 120~220 DEG C, after suspension is separated by solid-liquid separation, it is heavy to obtain canescence Starch LiFePO4And mother liquor；
2) enough Ba (OH) is added into mother liquor2, after it is sufficiently reacted, remove sediment, that is, LiOH aqueous solution；With recycling LiOH aqueous solution is lithium source, is recycled in step 1) and continues with.
2. LiFePO described in accordance with the claim 14Hydrothermal synthesis method, which is characterized in that aqueous solvent is defined as water or contains There is the aqueous solution of a small amount of ion or organic solvent.
3. LiFePO according to claim 24Hydrothermal synthesis method, which is characterized in that aqueous solvent use deionized water Or distilled water.
4. LiFePO described in accordance with the claim 14Hydrothermal synthesis method, which is characterized in that lithium source is Lithium hydroxide monohydrate, Source of iron is ferrous sulfate heptahydrate, and phosphorus source is phosphoric acid, and antioxidant is ascorbic acid.
5. LiFePO described in accordance with the claim 14Hydrothermal synthesis method, which is characterized in that phosphoric acid concentration 85wt%.
6. LiFePO described in accordance with the claim 14Hydrothermal synthesis method, which is characterized in that solution exists always in reaction process Under stirring.
7. LiFePO described in accordance with the claim 14Hydrothermal synthesis method, which is characterized in that heating means are microwave heating, Heating temperature is 140~200 DEG C, and heating time is 5~60 minutes.
8. LiFePO described in accordance with the claim 14Hydrothermal synthesis method, which is characterized in that solid-liquid separating method be filter or Centrifugation.
9. LiFePO described in accordance with the claim 14Hydrothermal synthesis method, which is characterized in that removal mother liquor in impurity materials For Ba (OH)2·8H2O, dosage are (0.2~0.6) g/mL mother liquor.
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CN110894066A (en) * 2019-12-31 2020-03-20 瓮福（集团）有限责任公司 Method for preparing sheet iron phosphate from titanium dioxide slag
CN112125292A (en) * 2020-08-14 2020-12-25 中国科学院金属研究所 Hydrothermal synthesis method of lithium manganese iron phosphate
CN115028153A (en) * 2022-04-18 2022-09-09 福州华复新能源科技有限公司 Low-cost equimolar lithium resource-saving hydrothermal method for producing lithium iron phosphate

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