CN101364643B - Boron containing lithium iron phosphate/carbon composite material and preparation thereof - Google Patents

Boron containing lithium iron phosphate/carbon composite material and preparation thereof Download PDF

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Publication number
CN101364643B
CN101364643B CN2008101200921A CN200810120092A CN101364643B CN 101364643 B CN101364643 B CN 101364643B CN 2008101200921 A CN2008101200921 A CN 2008101200921A CN 200810120092 A CN200810120092 A CN 200810120092A CN 101364643 B CN101364643 B CN 101364643B
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carbon composite
composite material
boracic
iron phosphate
lithium
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CN101364643A (en
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龚金保
余爱水
戴康泉
王伯良
王叶滔
陆越兴
卢宇驰
萧张兴
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Hangzhou Golden Horse Energy Technology Co ltd
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HANGZHOU SNSO BATTERY CO Ltd
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    • 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
    • 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

Abstract

The invention relates to an anode material for secondary lithium batteries, in particular to a lithium iron phosphate/carbon composite material containing boron, and the preparation method thereof, and mainly solves the technical problems of lower bonding strength of coating the carbon layer and the lithium iron phosphate surface, relatively low product tap density, rapid growth of the grain size,non-uniform and non-centralized distribution, and poor uniformity in the electrical property of lithium iron phosphate and the product quality, etc., in the prior art. The chemical formula of the lithium iron phosphate/carbon composite material is Li1-xMxFe1-yNyP1-zSizO4.XiB2O3/C or Li1-xMxFe1-yNyP1-zSizO4.ZetaLiBO2/C. The preparation method comprises the following steps: adding a boric acid ester surface active agent or/and a fluxing agent to a ball milling tank filled with a solvent; stirring uniformly; further adding iron-source compounds, lithium-source compounds, phosphorus-source compounds and carbon-coated carbon source respectively and mixing; evaporating the solvent to dryness and sintering the obtained solid powder under the protection of inert gases; cooling and taking out; andpulverizing, grading and obtaining the finished product.

Description

Lithium iron phosphate/carbon composite material of a kind of boracic and preparation method thereof
Technical field
The present invention relates to a kind of positive pole material of secondary lithium battery, especially relate to lithium iron phosphate/carbon composite material of a kind of boracic and preparation method thereof.
Background technology
Since the beginning of the nineties in last century Sony company at first since releasing lithium ion battery on the market, lithium ion battery just becomes the first-selected power supply of miniaturized electronics such as mobile communication, notebook computer and photograph (shooting) machine with the advantages such as cyclical stability of its high working voltage (lithium metal is more than 3 volts relatively), high-energy-density, low self-discharge rate, memory-less effect and excellence.The range of application of lithium ion battery has expanded big capacity, the high-power power supply of electric tool, mine lamp, electric bicycle, electric automobile, hybrid electric vehicle, satellite and weaponry etc. at present, has very huge market prospects.Big capacity, high power lithium ion cell key in application are to develop inexpensive, environmental protection, high security, have the excellent high magnification characteristic and the electrode material of cyclical stability.People such as U.S. John B.Goodenough in 1997 reported based on the phosphate radical polyanionic have olivine structural LiFePO 4 material (1, A.K.Padhi, K.S.Nanjundaswamy, and J.B.Goodenough, Journal of the Electrochemical Society, Vol.144 (4), 1188 (1997); 2, US Patent No.5,910,382), this materials theory discharge capacity 170mAh/g, about 3.4 volts of discharge voltage (lithium metal relatively), outstanding advantage is that fail safe and cyclical stability are better than all known anode material for lithium-ion batteries at present, and inexpensive, pollution-free, is well suited for doing the positive electrode of big capacity and high power lithium ion cell.But also exist the low distinct disadvantage of electronics and ionic conductivity (only to have an appointment 10 under the room temperature -10Scm -1Referring to: C.Delacourt, L.Laffond, R.Bouchet, C.Wurm, J-B.Leriche, M.Morcrette, J-M.Tarascon, C.Masquelier, Journal of the Electrochemical Society, Vol.152 (5) (2005) A913), so they are at that time with 0.05mA/cm 2The low current density discharge, capacity can only reach about 110mAh/g.For overcoming above shortcoming, electronics and ionic conductivity that they find to adopt charcoal coating, iron position doping high volence metal ion and can effectively improve LiFePO4 with methods such as the alternative phosphate radicals of other tetrahedron anionicsite, thereby make discharge capacity and multiplying power property increase substantially (1, N.Ravet, J.B.Goodenough, S.Besner, M.Simoneau, P.Hovington, M.Armand, in:Proceedings ofthe 196th ECS Meeting, Honolulu, October 1999; 2, US Patent No.5,910,382, US PatentNo.6085015, US Patent No.6391493B1, US Patent No.6514640B1).
The discoveries such as Yet-Ming Chiang of Massachusetts Institute Technology in 2002 can improve electronic conductivity maximum at the above metal ion of lithium position doping+divalent and reach eight orders of magnitude, thereby increased substantially LiFePO4 the rate charge-discharge characteristic (1, Sung-Yoon Chung, Jason T.Bloking andYet-Ming Chiang, Nature Materials, 2002No.1 pp:123-128; 2, Yet-MingChiang, Sung-Yoon, Jason T.Bloking, Anna M.Andersson, US Patent ApplicationNo.2004/0005265A1, Jan.8,2004).They think, can cause lithium position or iron position to produce the cation room at lithium position doping high volence metal ion, make the same Fe that has different valence state in mutually 3+/ Fe 2+Ion forms the p-N-type semiconductor N.For improving the diffusion velocity of lithium ion in the LiFePO4 granule interior, they make nanoscale with lithium position doped iron phosphate lithium particle, electronics, ionic conductivity are increased substantially, the high magnification characteristic of LiFePO 4 material be achieved (1, Yet-Ming Chiang, Anthony E.Pullen, Nonglak Meethong, US 2007/0292747A1; 2, US Patent No.7338734).
There is experiment test to prove, the electrons/ions conductance that improves LiFePO4 is no more than an order of magnitude by mixing, and surperficial charcoal coats the effect that improves electronic conductivity and wants much remarkable (C.Wang, J.Hong, " Ionic/Electronic Conducting Characteristics of LiFePO4 Cathode Materials-The Determining Factors for High Rate Performance ", Electrochemical and Solid-State Letters, 10 (3) A65-A69 (2007).Therefore, surface coating raw material of wood-charcoal material is to improve LiFePO4 electron conduction method commonly used at present.And a large amount of experimental results show that arranged: the effect of macromolecule pyrolytic carbon coated LiFePO 4 for lithium ion batteries is better than acetylene black class raw material of wood-charcoal material, and preparation temperature is also lower; Contain SP in the macromolecule pyrolytic carbon 2The carbon composition of hydridization is higher, and is more favourable to the raising of LiFePO4 electrical property, selects ferrocene and ferric nitrate etc. to help improving SP in the pyrolytic carbon as catalyst 2The content of hydridization carbon composition, reduce H/C atomic ratio in the pyrolytic carbon, thereby increase substantially the electron conduction that coats the raw material of wood-charcoal material and LiFePO4 electrical property (1, N.Ravet, M.Gauthier, K.Zaghib, J.B.Goodenough, A.Mauger, F.Gendron, andC.M.Julien, Chemistry of Materials 19 (2007) 2595-2602; 2, Marca M.Doeff, JamesD.Wilcox, Robert Kostecki, Grace Lau, Journal of Power Sources 163 (2006) 180-184; 3, James D.Wilcox, Marca M.Doeff, Marek Marcinek, and Robert Kostecki, Journalof the Ellectrochemical Society, Vol.154 (5) (2007) A389-A395.).Add the little amount of catalyst vanadium oxide in raw material, also can promote the reduction of carbon containing matters such as LiFePO4 surface macromolecule, generation free charcoal and raising coat SP in the charcoal layer 2The content of hydridization carbon composition promotes FeP, Fe simultaneously 2P, Fe 3P etc. have the generation of high electron conduction material, thereby increase substantially the electrical property (USPatent No.7282301B2) of LiFePO4.
Above technology has been laid theoretical foundation for the electronics and the ionic conductivity that improve LiFePO4, but needs to break through many other technological difficulties in actual fabrication LiFePO4 process.These technological difficulties mainly comprise: 1, raw material ultra-fine grinding, evenly disperse and hybrid technology, this is to guarantee that preparation has the precondition of the pure phase LiFePO4 of excellent electrical.With existing anode material for lithium-ion batteries LiCoO 2, Li (Mn xNi yCo 1-x-y) O 2(0＜x, y＜1) and a spar LiMn 2O 4Deng comparing, the electrons/ions conductance of LiFePO4 is much lower, its primary particle particle diameter must be reduced to and could guarantee good electrical properties (US Patent No.814764B2) below the 3.1 μ m.Therefore, the raw material particle size that is used to prepare LiFePO4 must be enough tiny, and this gives the raw material ultra-fine grinding, evenly disperse and hybrid technology has been brought new difficulty; 2, because LiFePO4 primary particle particle diameter is tiny, the surface coats carbon content can not be too high, otherwise can significantly reduce the tap density and the transmission speed of lithium ion between electrolyte and LiFePO4 granular boundary of material; The surface carbon content can not be too low, otherwise be difficult to reach the purpose of the electronic conductivity that significantly improves LiFePO 4 material.And do not match owing to coat between charcoal and the LiFePO4 structure, realize having of the even coating of the coating charcoal of high electronic conductivity, and guarantee that coating charcoal layer and LiFePO4 surface have enough difficulty such as bond strength very big on the LiFePO4 surface.If coat charcoal layer and LiFePO4 surface enough bond strengths are arranged, can effectively suppress the reunion between the conduction charcoal in the anode pole piece in the battery charge and discharge process on the one hand, this is one of a lot of battery electrical property failure reasons (Marie Kerlau, Marek Marcinek, Robert Kostecki, " Diagnostic Evaluation of Detrimental Phenomena in 13C-labeledComposite cathodes for Li-ion batteries ", Abstract #14 in International Meetingon Lithium Battery 2006 (France)); When also helping on the other hand entering the crushing and classification operation after material at high temperature burns till, avoid the LiFePO4 surface is coated the destruction of charcoal layer as far as possible; 3, raw-material selection can influence material sintering temperature and product purity mutually, also can influence the complexity that industrialization realizes; 4, particle size after raw material are pulverized and distribution thereof are directly connected to the reactivity between them, and therefore screen suitable sintering processing, sintering temperature and time so as to obtain the appropriate particle size size and product that distribution, crystal structure integrated degree reach unanimity most important to the combination property that improves LiFePO4; 5, because the LiFePO4 particle diameter is tiny, and the ordinary circumstance lower surface is coated with the lower raw material of wood-charcoal material of density, causes the jolt ramming of product or compacted density on the low side, influences the making quality of battery pole piece, thereby has influence on the performance of battery.
Summary of the invention
The purpose of this invention is to provide lithium iron phosphate/carbon composite material of a kind of boracic and preparation method thereof, it mainly is to solve the ultra-fine grinding of existing in prior technology raw material, evenly dispersion and hybrid technology are comparatively difficult, the bond strength that coats charcoal layer and LiFePO4 surface is not high enough, the crushing and classification operation can damage the coating charcoal layer on LiFePO4 surface, the product tap density is on the low side, higher particle diameter fast growth that causes of sintering temperature and skewness are concentrated, LiFePO4 crystal structure integrated degree is difficult to reach unanimity, the technical problem that LiFePO4 electrical property and product quality consistency are relatively poor etc.
Above-mentioned technical problem of the present invention is mainly solved by following technical proposals:
The lithium iron phosphate/carbon composite material of a kind of boracic of the present invention is characterized in that chemical formula is: Li 1-xM xFe 1-yN yP 1-zSi zO 4ξ B 2O 3/ C or Li 1-xM xFe 1-yN yP 1-zSi zO 4ζ LiBO 2/ C, bulk phase-doped metallic element M in the lithium position are at least a among Mg, Ca, Zn, Al, Cr, V, Ti, Zr and the Nb, 0≤x≤0.1; Bulk phase-doped metallic element N in the iron position is at least a among Li, Cu, Mg, Ca, Mn, Ni, Co, Zn, Al, Cr, V, Ti, Zr and the Nb, 0≤y≤0.1; Element silicon is bulk phase-doped at phosphate potential, 0≤z≤0.5; 0.006≤ξ≤0.25,0.01≤ζ≤0.5; B 2O 3Or LiBO 2Be present in the surface of LiFePO4 with amorphous state, and mix mutually with conduction raw material of wood-charcoal material, the weight ratio that the raw material of wood-charcoal material accounts for the lithium iron phosphate/carbon composite material of boracic is 0.1～10%.
LiFePO4 can be not mix or bulk phase-doped LiFePO4, and doping position can be at least a position in lithium position, iron position, the phosphate potential.Be coated with amorphous B on the surface of LiFePO 4 material 2O 3Or LiBO 2, and they and Li 1-xM xFe 1-yN yP 1-zSi zO 4Mol ratio ξ or ζ be respectively 0.006≤ξ≤0.25 or 0.01≤ζ≤0.5, be preferably 0.03≤ξ≤0.15 or 0.05≤ζ≤0.3.At amorphous B 2O 3Or LiBO 2In be mixed with conduction raw material of wood-charcoal material, and the weight ratio that the raw material of wood-charcoal material accounts for the lithium iron phosphate/carbon composite material of boracic is 0.1～10%, is preferably 0.5～5%.
The preparation method of the lithium iron phosphate/carbon composite material of a kind of boracic of the present invention is characterized in that:
A. in the ball grinder of solvent is housed, add boric acid fat surfactant or/and flux, 0.05～5% of boric acid fat surfactant comprise solid raw material gross mass, stir, the Fe source compound, Li source compound, P source compound and the charcoal that add stoichiometric proportion more respectively coat the charcoal source and carry out a ball milling mixing;
B. after the solvent evaporated; the pressed powder heat treated under the protection of inert gas that obtains is carried out sintering; treat to take out after temperature is reduced to room temperature; through pulverizing, obtain after the classification lithium iron phosphate/carbon composite material of boracic, wherein coating the weight ratio that charcoal accounts for the boracic lithium iron phosphate/carbon composite material is 0.1～10%.
Solvent among the step a is the mixed solvent of organic solvent, water or organic solvent and water, is preferably organic solvent.0.05～5% of boric acid fat surfactant comprise solid raw material gross mass is preferably 0.5～2.5%.In described addition scope, boric acid fat surfactant can effectively prevent the reunion between the particle in the liquid phase mechanical milling process, with the added-time is not compared, the beneficial effect that adding boric acid fat surfactant brings in the ball milling slurry comprises: 1, raw-material average grain diameter can be ground forr a short time under identical ball milling condition, raw material disperse, mix more evenly, for the tiny lithium iron phosphate/carbon composite material of preparation particle diameter also and enhance product performance and the quality uniformity consistency is created necessary condition; 2, under the raw material ball milling situation identical to particle diameter, solids content can improve in the slurry, improves grinding efficiency, energy savings; 3, owing to raw-material average grain diameter under identical ball milling condition can be ground forr a short time, obtain the dry powder that particle diameter is littler, reactivity is higher after drying, thereby the temperature of preparation lithium iron phosphate/carbon composite material can be lower, the time can be shorter; 3, the catabolite of boric acid fat surfactant under the high temperature inert atmosphere protection is B 2O 3With gases such as volatility alkane, residual B 2O 3Can be used as the composition of flux, to reducing the lithium iron phosphate/carbon composite material preparation temperature, it is useful improving tap density.
As preferably, described step b is by step b ' replacement:
B '. after the solvent evaporated; the pressed powder heat treated under the protection of inert gas that obtains is carried out first sintering; treat to take out after temperature is reduced to room temperature; put into ball grinder once more; do not adding or adding boric acid fat surfactant or/and carry out secondary ball milling under the flux situation; after the solvent evaporated pressed powder heat treated under inert atmosphere protection that obtains is carried out the sintering second time; obtain the lithium iron phosphate/carbon composite material of boracic through crushing and classification; wherein coating the weight ratio that charcoal accounts for the boracic lithium iron phosphate/carbon composite material is 0.1～10%, is preferably 0.5～5%.
As preferably, described boric acid fat surfactant is at least a in the two fat of boric acid monoester, boric acid, boric acid three fat, four-coordination volution boric acid fat and their derivative, its addition accounts for 0.05～5% of solid raw material gross mass, is preferably 0.5～2.5%.Boric acid fat surfactant is nonionic space bit resistance type macromolecule boric acid fat surfactant more preferably.
Described flux is at least a in boron compound, the alkali metal fluoride; Described boron compound is preferably B 2O 3, H 3BO 3, LiBO 2Or pyrolysis can form B 2O 3, H 3BO 3, LiBO 2Boron-containing compound; Alkali metal fluoride is preferably lithium fluoride.The use amount of flux depends on the particle diameter and the specific area of the boracic lithium iron phosphate/carbon composite material of preparing, and particle diameter is littler, and specific area is higher, and use amount is higher.Wherein, the addition of boron compound flux is its last decomposition or product B that obtains through high-temperature process 2O 3Or LiBO 2Be respectively 0.006≤ξ≤0.25 or 0.01≤ζ≤0.5 with the mol ratio ξ or the ζ of LiFePO4, be preferably 0.03≤ξ≤0.15 or 0.05≤ζ≤0.3; The addition of alkali metal fluoride is 0.015～0.5: 1 by the mol ratio of itself and LiFePO4, is preferably 0.07～0.3.Compare when not adding flux, adding the beneficial effect that flux brings in raw material of the present invention has: 1, reduce the material sintering temperature, the control rate of crystalline growth is prepared the tiny boracic LiFePO4 carbon composite of particle diameter at a lower temperature; 2, reduce the material porosity, each several part is heated evenly degree when improving the raw material high temperature sintering, effectively avoids dephasign to generate; 3, improve tap density, improve the processability of anode pole piece; 4, improve LiFePO4 and the bond strength that coats the charcoal interlayer, avoid or reduce follow-up crushing and classification operation the LiFePO4 surface is coated the destruction of charcoal layer, improve the electrical property of LiFePO4.
As preferably, when the Fe source compound that adds stoichiometric proportion, Li source compound, P source compound, charcoal coating charcoal source, also added doping element compound simultaneously among the described step a.Doping element compound promptly is the compound that contains metallic element, element silicon.
As preferably, described Fe source compound is at least a in ferrous oxide, di-iron trioxide, tri-iron tetroxide, ferrous oxalate, ferric oxalate or ferrous phosphate, the ferric phosphate; Described Li source compound is at least a in lithium carbonate, lithium hydroxide, lithium acetate, lithium phosphate and the lithium dihydrogen phosphate; Described P source compound is at least a in phosphoric acid, lithium phosphate, lithium dihydrogen phosphate, diammonium hydrogen phosphate, the phosphoric acid dihydro amine; Charcoal coats at least a in the mixture that the charcoal source is macromolecular compound or macromolecular compound and CNT (carbon nano-tube), acetylene black, carbon black class conductive additive.
As preferably, the inert gas among described step b and the b ' is at least a in nitrogen, argon gas, the ammonia, or nitrogen, argon gas, ammonia and volume account at least a in the mist that the hydrogen below 15% forms.
As preferably, the temperature of sintering is 550～850 ℃ among the described step b, and sintering time is 1～30 hour.
As preferably, the temperature of the first sintering among the described step b ' is 300～550 ℃, and the temperature of sintering is 550～850 ℃ for the second time, for the first time with the second time sintering time be respectively 1～30 hour.
The present invention have the raw material ultra-fine grinding, evenly disperse and hybrid technology comparatively simple, efficient; The bond strength that coats charcoal layer and LiFePO4 surface is higher, the crushing and classification operation not can or less coating charcoal layer to the LiFePO4 surface damage; Characteristics such as the particle diameter of LiFePO4 carbon composite is tiny, tap density is higher, combination property is better.
Embodiment
Below by embodiment, technical scheme of the present invention is described in further detail.
Embodiment 1: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
LiFePO 4·3.769×10 -2B 2O 3/C
Its preparation methods steps is:
A. in the ball grinder that the 820g absolute ethyl alcohol is housed, add 3.540g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.5 mole of Li more respectively 2CO 336.945g, 1.0 moles of FeC 2O 42H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, the B of 19.500g glucose and 2.624g 2O 3, mix; Add the 5mm zirconia balls in mixed pressed powder, the mass ratio of pressed powder and zirconia balls was 1: 8, with 300 rev/mins speed stirring ball-millings 7 hours;
B '. behind the evaporate to dryness ethanol, be 92: 8 high pure nitrogen in volume ratio with the pressed powder that produces among the step a: the mixed gas protected of hydrogen carries out sintering in 400 ℃ of heat treated down, the heat treated program is: rose to 400 ℃ from room temperature in 3 hours, reduce to room temperature 400 ℃ of maintenances after 4 hours, then pressed powder is put into the 420g absolute ethyl alcohol, add the 5mm zirconia balls again and carried out secondary ball milling 2 hours with 300 rev/mins speed, the mass ratio of pressed powder and zirconia balls is 1: 8; After the solvent evaporated; in volume ratio 92: 8 high pure nitrogen: carry out sintering in 620 ℃ of heat treated under the protection of hydrogen; the heat treated program is: rose to 620 ℃ from room temperature in 4 hours; kept 5 hours at 620 ℃; reduced to room temperature in 2 hours; treat that temperature reduces to take out after the room temperature and ground 300 mesh sieves, obtain the lithium iron phosphate/carbon composite material of boracic.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain B 2O 33.769 * 10 -2Mole, i.e. ξ=3.769 * 10 -2
Adopt HCS-140 type high frequency infrared ray carbon sulphur analyser to record that carbon content is 3.02% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.22g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.632 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 4.16 μ m.
The boracic lithium iron phosphate/carbon composite material that obtains and N-methyl pyrrolidone (NMP) solution, the acetylene black of Kynoar (PVDF) are mixed and made into slurry, evenly be coated on the Al paper tinsel collector and dry, the about 100 microns positive plate of thickness is made in roll extrusion, LiFePO4: the mass ratio of conduction charcoal: PVDF is 86: 6: 8, and the charcoal that wherein conducts electricity comprises that boracic LiFePO4 surface coats the acetylene black of charcoal and adding.Be the positive pole of the disk of 20mm from wherein taking out diameter then as button-shaped 2430 type batteries, metal lithium sheet with thickness 1mm is a negative pole, Celgard2400 is a barrier film, electrolyte is 1M LiPF6+EC/DMC (volume ratio 1: 1), be assembled into behind the half-cell after 2-4.2V (lithium metal relatively) is with 0.2C (30mA/g) constant current impulse electricity 10 times, it is stable that charge/discharge capacity reaches substantially, with the discharge capacity of the 10th circulation time as the discharge capacity under the 0.2C.During discharge capacity, earlier battery is charged to 4.2V with 0.2C under the test 0.2C above multiplying power, tests the discharge capacity under this multiplying power condition then, all specific discharge capacity data all with the Mass Calculation of LiFePO4 surface coating charcoal and boride flux interior.
Embodiment 2: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
LiFePO 4·0.070LiBO 2/C
Its preparation methods steps is:
A. in the ball grinder that the 820g absolute ethyl alcohol is housed, add 3.583g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.535 mole of Li more respectively 2CO 339.531g, 1.0 moles of FeC 2O 42H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose and 0.070 mole of H 3BO 34.327g, mix;
All the other steps are with embodiment 1.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain LiBO 20.070 mole, i.e. ζ=0.070.The average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.638 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 4.21 μ m, HCS-140 type high frequency infrared ray carbon sulphur analyser records that carbon content is 2.97% in the boracic LiFePO4 carbon composite, and the tap density that adopts PF-300B tap density tester to record this material is 1.25g/cm 3
Embodiment 3: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
LiFePO 4·0.25B 2O 3/C
Its preparation methods steps is:
A. in the ball grinder that the 820g absolute ethyl alcohol is housed, add 3.688g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.5 mole of Li more respectively 2CO 336.945g, 1.0 moles of FeC 2O 42H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, the B of 19.500g glucose and 17.405g 2O 3, mix;
All the other steps are with embodiment 1.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain B 2O 30.25 mole, i.e. ξ=0.25.
Adopt HCS-140 type high frequency infrared ray carbon sulphur analyser to record that carbon content is 2.92% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.47g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.637 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 4.69 μ m.
Embodiment 4: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
LiFePO 4·0.5LiBO 2/C
Its preparation methods steps is:
A. in the ball grinder that the 933g absolute ethyl alcohol is housed, add 1.799g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.75 mole of Li more respectively 2CO 355.418g, 1.0 moles of FeC 2O 42H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, 22.700g glucose and 0.5 mole of H 3BO 330.905g, mix;
All the other steps are with embodiment 1.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain LiBO 20.5 mole, i.e. ζ=0.5.The average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.631 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 4.62 μ m, HCS-140 type high frequency infrared ray carbon sulphur analyser records that carbon content is 3.25% in the boracic LiFePO4 carbon composite, and the tap density that adopts PF-300B tap density tester to record this material is 1.41g/cm 3
Embodiment 5: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
LiFePO 4·3.769×10 -2B 2O 3/C
Its preparation methods steps is:
A. in the ball grinder that the 933g absolute ethyl alcohol is housed, add 1.792g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.5 mole of Li more respectively 2CO 336.945g, 1.0 moles of FeC 2O 4.2H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, the glucose of 65.965g and the B of 2.624g 2O 3, mix;
All the other steps are with embodiment 1.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain B 2O 33.769 * 10 -2Mole, i.e. ξ=3.769 * 10 -2
The average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.641 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 3.61 μ m, HCS-140 type high frequency infrared ray carbon sulphur analyser records that carbon content is 9.96% in the boracic LiFePO4 carbon composite, and the tap density that adopts PF-300B tap density tester to record this material is 0.90g/cm 3
Embodiment 6: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
LiFePO 4·0.006B 2O 3/C
Its preparation methods steps is:
A. in the ball grinder that the 820g absolute ethyl alcohol is housed, add 3.496g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.4 mole of Li more respectively 2CO 329.556g, 0.2 mole of LiF 5.188g, 1.0 moles of FeC 2O 42H 2O179.900g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose and B 2O 30.418g mix;
All the other steps are with embodiment 1.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain B 2O 30.006 mole, i.e. ξ=0.006.Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 3.10% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.31g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.629 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 3.75 μ m.
Embodiment 7: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
LiFePO 4·0.006B 2O 3/C
Its preparation methods steps is:
A. in the ball grinder that the 820g absolute ethyl alcohol is housed, add 3.463g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.25 mole of Li more respectively 2CO 318.473g, 0.5 mole of LiF 12.971g, 1.0 moles of FeC 2O 42H 2O179.900g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose and B 2O 30.418g, mix;
All the other steps are with embodiment 1.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain B 2O 30.006 mole, i.e. ξ=0.006.Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 3.06% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.34g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.620 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 3.81 μ m.
Embodiment 8: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
Li 0.98Zr 0.005FePO 4·3.016×10 -2B 2O 3/C
Its preparation methods steps is:
A. in the ball grinder that the 818g absolute ethyl alcohol is housed, add 3.543g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.49 mole of Li more respectively 2CO 336.206g, 1.0 moles of FeC 2O 42H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose and 0.005 mole of ZrOCl 28H 2O 1.611g and 2.100g B 2O 3, mix; Add the 5mm zirconia balls in mixed pressed powder, the mass ratio of pressed powder and zirconia balls was 1: 8, with 300 rev/mins speed stirring ball-millings 7 hours;
B '. behind the evaporate to dryness ethanol, be 92: 8 high pure nitrogen in volume ratio with the pressed powder that produces among the step a: the mixed gas protected of hydrogen carries out sintering in 400 ℃ of heat treated down, the heat treated program is: rose to 400 ℃ from room temperature in 3 hours, reduce to room temperature 400 ℃ of maintenances after 4 hours, then pressed powder is put into the 420g absolute ethyl alcohol, add the 5mm zirconia balls again and carried out secondary ball milling 2 hours with 300 rev/mins speed, the mass ratio of pressed powder and zirconia balls is 1: 8; After the solvent evaporated; in volume ratio 92: 8 high pure nitrogen: carry out sintering in 620 ℃ of heat treated under the protection of hydrogen; the heat treated program is: rose to 620 ℃ from room temperature in 4 hours; kept 5 hours at 620 ℃; reduced to room temperature in 2 hours; treat that temperature reduces to take out after the room temperature and ground 300 mesh sieves, obtain the Li of boracic 0.98Zr 0.005FePO 4/ carbon composite.
All the other steps are with embodiment 1.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain B 2O 33.016 * 10 -2Mole, i.e. ξ=3.016 * 10 -2Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 2.99% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.20g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.631 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 3.90 μ m.
Embodiment 9: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
Li 0.98Zr 0.005FePO 4·0.070LiBO 2/C
Its preparation methods steps is:
A. in the ball grinder that the 818g absolute ethyl alcohol is housed, add 3.557g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.49 mole of Li more respectively 2CO 336.206g, 1.0 moles of FeC 2O 42H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose, 0.005 mole of ZrOCl 28H 2O 1.611g and 3.483gLiBO 2, mix;
All the other steps are with embodiment 8.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain LiBO 20.070 mole, i.e. ζ=0.07.Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 2.95% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.25g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.623 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 3.94 μ m.
Embodiment 10: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
Li 0.98Zr 0.005FePO 4·0.006B 2O 3/C
Its preparation methods steps is:
A. in the ball grinder that the 818g absolute ethyl alcohol is housed, add 3.504g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.39 mole of Li more respectively 2CO 328.817g, 0.2 mole of LiF 5.188g, 1.0 moles of FeC 2O 42H 2O179.900g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose, 0.005 mole of ZrOCl 28H 2O 1.611g and 0.418g B 2O 3,, mix;
All the other steps are with embodiment 8.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain B 2O 30.006 mole, i.e. ξ=0.006.Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 2.92% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.27g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.639 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 3.68 μ m.
Embodiment 11: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
Li 0.99Fe 0.995Zr 0.005PO 4·4.453×10 -2B 2O 3/C
Its preparation methods steps is:
A. in the ball grinder that the 818g absolute ethyl alcohol is housed, add 3.548g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.495 mole of Li more respectively 2CO 336.576g, 0.995 mole of FeC 2O 42H 2O 179.000g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose, 0.005 mole of ZrOCl 28H 2O 1.611g and 3.100gB 2O 3,, mix;
All the other steps are with embodiment 8.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain B 2O 34.453 * 10 -2Mole, i.e. ξ=4.453 * 10 -2Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 3.11% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.20g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.619 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 3.83 μ m.
Embodiment 12: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
Li 0.99Fe 0.995Zr 0.005PO 4·0.070LiBO 2/C
Its preparation methods steps is:
A. in the ball grinder that the 818g absolute ethyl alcohol is housed, add 3.552g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.495 mole of Li more respectively 2CO 336.576g, 0.995 mole of FeC 2O 42H 2O 179.000g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose, 0.005 mole of ZrOCl 28H 2O 1.611g and 3.483gLiBO 2, mix;
All the other steps are with embodiment 8.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain LiBO 20.07 mole, i.e. ζ=0.07.Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 3.00% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.23g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.617 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 3.90 μ m.
Embodiment 13: the lithium iron phosphate/carbon composite material of a kind of boracic of this example, and its molecular formula is:
Li 0.99Fe 0.995Zr 0.005PO 4·0.006B 2O 3/C
Its preparation methods steps is:
A. in the ball grinder that the 818g absolute ethyl alcohol is housed, add 3.499g nonionic macromolecule boric acid fat surfactant PBE (counterpoise relative molecular weight Mw=28400), stir, add 0.395 mole of Li more respectively 2CO 329.187g, 0.2 mole of LiF 5.188g, 0.995 mole of FeC 2O 42H 2O179.000g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose, 0.005 mole of ZrOCl 28H 2O 1.611g and 0.418g B 2O 3,, mix;
All the other steps are with embodiment 8.
Calculate in the boracic LiFePO4 carbon composite that makes by stoichiometric proportion and to contain B 2O 30.006 mole, i.e. ξ=0.006.Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 2.91% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.24g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.630 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 3.62 μ m.
The lithium iron phosphate/carbon composite material of the non-not boracic of the present invention of comparing embodiment 1 ' preparation
A. in the ball grinder that the 820g absolute ethyl alcohol is housed, add 0.5 mole of Li respectively 2CO 336.945g, 1.0 moles of FeC 2O 42H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, mix with 19.500g glucose;
B. add the 5mm zirconia balls in mixed pressed powder, the mass ratio of pressed powder and zirconia balls was 1: 8, with 300 rev/mins speed stirring ball-millings 7 hours;
C. behind the evaporate to dryness ethanol, be 92: 8 high pure nitrogen in volume ratio with the pressed powder that produces among the step b: the mixed gas protected of hydrogen carries out sintering in 400 ℃ of heat treated down, the heat treated program is: rose to 400 ℃ from room temperature in 3 hours, reduce to room temperature 400 ℃ of maintenances after 4 hours, then pressed powder is put into the 420g absolute ethyl alcohol, add the 5mm zirconia balls again and carried out secondary ball milling 2 hours with 300 rev/mins speed, the mass ratio of pressed powder and zirconia balls is 1: 8;
D. after the solvent evaporated; in volume ratio 92: 8 high pure nitrogen: carry out sintering in 700 ℃ of heat treated under the protection of hydrogen; the heat treated program is: rose to 700 ℃ from room temperature in 4 hours; kept 5 hours at 700 ℃; reduced to room temperature in 2 hours; treat that temperature reduces to take out after the room temperature and ground 300 mesh sieves, obtain the lithium iron phosphate/carbon composite material of boracic.
Adopt HCS-140 type high frequency infrared ray carbon sulphur analyser to record that carbon content is 2.96% in the boracic lithium iron phosphate/carbon composite material, the tap density that adopts PF-300B tap density tester to record this material is 1.08g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.865 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 4.66 μ m.The lithium iron phosphate/carbon composite material of the non-not boracic of the present invention of comparing embodiment 2 ' preparation
A. in the ball grinder that the 820g absolute ethyl alcohol is housed, add 0.5 mole of Li respectively 2CO 336.945g, 1.0 moles of FeC 2O 42H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, mix with 19.500g glucose;
All the other steps are with embodiment 1.
Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 3.10% in the lithium iron phosphate/carbon composite material of boracic not, the tap density that adopts PF-300B tap density tester to record this material is 1.02g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.879 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 4.41 μ m.
The lithium iron phosphate/carbon composite material of the non-not boracic of the present invention of comparing embodiment 3 ' preparation
A. in the ball grinder that the 820g absolute ethyl alcohol is housed, add 0.5 mole of Li respectively 2CO 336.945g, 1.0 moles of FeC 2O 42H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, mix with 65.965g glucose;
All the other steps are with embodiment 1.
Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 9.98% in the lithium iron phosphate/carbon composite material of boracic not, the tap density that adopts PF-300B tap density tester to record this material is 0.79g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.871 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 4.35 μ m.
The Li of the non-not boracic of the present invention of comparing embodiment 4 ' preparation 0.98Zr 0.005FePO 4/ carbon composite
A. in the ball grinder that the 818g absolute ethyl alcohol is housed, add 0.49 mole of Li respectively 2CO 336.206g, 1.0 moles of FeC 2O 42H 2O 179.900g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose and 0.005 mole of ZrOCl 28H 2O 1.611g mixes;
All the other steps are with embodiment 1.
Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 3.14% in the lithium iron phosphate/carbon composite material of boracic not, the tap density that adopts PF-300B tap density tester to record this material is 1.00g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.859 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 4.39 μ m.
The Li of the non-not boracic of the present invention of comparing embodiment 5 ' preparation 0.99Fe 0.995Zr 0.005PO 4/ carbon composite
A. in the ball grinder that the 818g absolute ethyl alcohol is housed, add 0.495 mole of Li respectively 2CO 336.576g, 0.995 mole of FeC 2O 42H 2O 179.000g, 1.0 moles of NH 4H 2PO 4115.000g, 19.500g glucose, 0.005 mole of ZrOCl 28H 2O 1.611g mixes;
All the other steps are with embodiment 1.
Record with HCS-140 type high frequency infrared ray carbon sulphur analyser that carbon content is 3.16% in the lithium iron phosphate/carbon composite material of boracic not, the tap density that adopts PF-300B tap density tester to record this material is 0.98g/cm 3, the average grain diameter that laser particle size analyzer records solid particle in 7 hours disposed slurries of step b ball milling is 0.863 μ m, the average grain diameter of the boracic LiFePO4 carbon composite that steps d makes is 4.33 μ m.
Table 1 has been listed in each embodiment and the comparing embodiment, the average grain diameter of raw material ball milling after 7 hours and the average grain diameter of the composite products that makes of high temperature sintering.As can be seen, substantially maintain about 30% at the slurry solid content, the boric acid fat surfactant comprise solid raw material mass percent of adding all is under 1.00% the situation, and the average grain diameter of particle changes little behind the ball milling, between 0.61 μ m-0.65 μ m, average out to 0.630 μ m.Do not add boric acid fat surfactant in the comparing embodiment, the average grain diameter of particle is also relatively more consistent behind the ball milling, but the average grain diameter ratio increases obviously when adding surfactant, reach 0.867 μ m, increase approximately 37.7%, illustrate that the adding of boric acid fat surfactant has significantly improved the liquid phase grinding efficiency.Contrast embodiments of the invention and non-comparing embodiment of the present invention, behind adding boric acid fat surfactant and the flux, the average grain diameter of the product that identical sintering temperature and time make is also fashionable tiny than not adding.
Table 1 boric acid fat surfactant is to the influence of material particle size
Embodiment Slurry solid content (wt%) The ball milling time (h) The ancient solid material percentage by weight (wt%) of boric acid fat Average grain diameter behind the ball milling 7h (μ m) Composite material average grain diameter (μ m)
1 30.6 7 1.00 0.632 4.16
2 30.31 7 1.00 0.638 4.21
3 30.92 7 1.00 0.637 4.69
4 30.30 7 1.00 0.631 4.62
5 29.99 7 1.00 0.641 3.61
Embodiment Slurry solid content (wt%) The ball milling time (h) The ancient solid material percentage by weight (wt%) of boric acid fat Average grain diameter behind the ball milling 7h (μ m) Composite material average grain diameter (μ m)
6 29.80 7 1.00 0.629 3.75
7 29.60 7 1.00 0.620 3.81
8 30.13 7 1.00 0.631 3.90
9 30.21 7 1.00 0.623 3.94
10 29.90 7 1.00 0.639 3.68
11 30.16 7 1.00 0.619 3.83
12 30.18 7 1.00 0.617 3.90
13 29.87 7 1.00 0.630 3.62
1’ 0 7 0 0.865 5.76
2’ 0 7 0 0.879 5.15
3’ 0 7 0 0.871 4.72
4’ 0 7 0 0.859 5.39
5’ 0 7 0 0.863 5.33
Table 2 has been listed the situations such as preparation condition, tap density and average grain diameter of boracic lithium iron phosphate/carbon composite material in the various embodiments of the present invention, and for ease of contrast, the corresponding situation of non-each comparing embodiment of the present invention is also listed in the lump.Comparative example 1～7 and comparing embodiment 1 '～3 ' be as can be seen: 1) account for composite material and be all about 3% material for coating charcoal, even low 80 ℃ of preparation temperature, the tap density of composite material of the present invention increases by 11.11% at least, the highest increase is about 36.11%, and the increase of tap density is at least 17.64% under the uniform temp.Carbon content is all about 10% composite material (embodiment 5 and comparing embodiment 3 '), and the tap density of composite material of the present invention increases about 13.92%; 2) under preparation temperature, carbon content and the essentially identical situation of flux content, more than the general 1 μ m less than normal of the average grain diameter of composite material of the present invention.To lithium position or iron position doped iron phosphate lithium (Li 0.98Zr 0.005FePO 4And Li 0.99Fe 0.995Zr 0.005PO 4), the variation tendency of tap density and average grain diameter situation when not mixing is similar.Therefore, the boracic LiFePO4 carbon composite that adopts the present invention to prepare has the advantages that tap density is higher, particle diameter is tiny.The interpolation of agglutinant is described, is of value to and prepares tiny, the fine and close lithium iron phosphate/carbon composite material particle of particle diameter at a lower temperature.
Table 2 preparation temperature and agglutinant are to the influence of lithium iron phosphate/carbon composite material tap density
Embodiment The LiFePO4 molecular formula Sintering temperature (℃) Charcoal accounts for composite material percentage by weight (%) Boron compound flux type and and LiFePO4 mol ratio Lithium fluoride and LiFePO4 mol ratio Tap density (g/cm 3) Composite material average grain diameter (μ m)
1 LiFePO 4 620℃ 3.02 B 2O 3，ξ＝3.769*10 -2 0 1.22 4.16
2 LiFePO 4 620℃ 2.97 H 3BO 3，ζ＝0.07 0 1.25 4.21
3 LiFePO 4 620℃ 2.92 B 2O 3，ξ＝0.25 0 1.47 4.69
4 LiFePO 4 620℃ 3.25 H 3BO 3，ζ＝0.5 0 1.41 4.62
5 LiFePO 4 620℃ 9.96 B 2O 3，ξ＝3.769*10 -2 0 0.90 3.61
6 LiFePO 4 620℃ 3.10 B 2O 3，ξ＝0.006 0.20 1.31 3.75
7 LiFePO 4 620℃ 3.06 B 2O 3，ξ＝0.006 0.50 1.34 3.81
Embodiment The LiFePO4 molecular formula Sintering temperature (℃) Charcoal accounts for composite material percentage by weight (%) Boron compound flux type and and LiFePO4 mol ratio Lithium fluoride and LiFePO4 mol ratio Tap density (g/cm 3) Composite material average grain diameter (μ m)
8 Li 0.98Zr 0.005FePO 4 620℃ 2.99 B 2O 3，ξ＝3.016*10 -2 0 1.20 3.90
9 Li 0.98Zr 0.005FePO 4 620℃ 2.95 LiBO 2，ζ＝0.07 0 1.25 3.94
10 Li 0.98Zr 0.005FePO 4 620℃ 2.92 B 2O 3，ξ＝0.006 0.20 1.27 3.68
11 Li 0.99Fe 0.995Zr 0.005PO 4 620℃ 3.11 B 2O 3，ξ＝4.453*10 -2 0 1.20 3.83
12 Li 0.99Fe 0.995Zr 0.005PO 4 620℃ 3.00 LiBO 2，ζ＝0.07 0 1.23 3.90
13 Li 0.99Fe 0.995Zr 0.005PO 4 620℃ 2.91 B 2O 3，ξ＝0.006 0.20 1.24 3.62
1’ LiFePO 4 700℃ 2.96 0 0 1.08 5.76
Embodiment The LiFePO4 molecular formula Sintering temperature (℃) Charcoal accounts for composite material percentage by weight (%) Boron compound flux type and and LiFePO4 mol ratio Lithium fluoride and LiFePO4 mol ratio Tap density (g/cm 3) Composite material average grain diameter (μ m)
2’ LiFePO 4 620℃ 3.10 0 0 1.02 5.15
3’ LiFePO 4 620℃ 10.00 0 0 0.79 4.72
4’ Li 0.98Zr 0.005FePO 4 620℃ 3.14 0 0 1.00 5.39
5’ Li 0.99Fe 0.995Zr 0.005PO 4 620℃ 3.16 0 0 0.98 5.33
The lithium iron phosphate/carbon composite material and the metal lithium sheet of the boracic of each embodiment and comparing embodiment preparation are formed 2430 type button batteries, and rate charge-discharge the results are shown in Table 3.Can see, to mix, lithium position or iron position doped iron phosphate lithium, coating under the suitable situation of carbon content, composite material of the present invention in the discharge capacity of different multiplying generally than non-composite material discharge capacity height of the present invention, this is because the composite material granular average grain diameter is tiny on the one hand, has quickened lithium ion diffusion velocity therein; Be because " bonding " effect of flux increases the bond strength on raw material of wood-charcoal material and LiFePO4 surface on the other hand, thereby increased the electronic conductivity of composite material.Therefore, composite material of the present invention has that preparation temperature is low, the particle average grain diameter is tiny, advantage such as tap density height, rate charge-discharge characteristic are good.
Discharge capacity under the different charge-discharge magnifications of button-shaped 2430 half-cells of table 3
Embodiment C d/mAh/g (0.2C) C d/mAh/g (1.0C) C d/mAh/g (3.0C) C d/mAh/g (5.0C) C d/mAh/g (8.0C)
1 160 135 119 102 98
2 149 132 112 100 94
3 145 129 108 96 89
4 142 124 102 93 85
5 158 149 138 127 120
6 152 139 123 118 109
7 149 138 121 115 105
8 150 133 118 101 98
9 147 133 115 96 90
10 152 141 125 107 102
11 154 143 133 120 113
12 157 145 130 119 110
13 157 146 136 124 117
1′ 155 114 95 86 77
2′ 150 119 100 91 80
Embodiment C d/mAh/g (0.2C) C d/mAh/g (1.0C) C d/mAh/g (3.0C) C d/mAh/g (5.0C) C d/mAh/g (8.0C)
3′ 153 134 113 105 97
4′ 145 126 105 92 81
5′ 151 129 109 96 84

Claims (9)

1. the preparation method of the lithium iron phosphate/carbon composite material of a boracic is characterized in that:
A. in the ball grinder of solvent is housed, add boric acid fat surfactant and flux, 0.05～5% of boric acid fat surfactant comprise solid raw material gross mass, stir, the Fe source compound, Li source compound, P source compound and the charcoal that add stoichiometric proportion more respectively coat the charcoal source and carry out a ball milling mixing;
B. after the solvent evaporated; the pressed powder heat treated under the protection of inert gas that obtains is carried out sintering; treat to take out after temperature is reduced to room temperature; through pulverizing, obtain after the classification lithium iron phosphate/carbon composite material of boracic, wherein coating the weight ratio that charcoal accounts for the boracic lithium iron phosphate/carbon composite material is 0.1～10%.
2. the preparation method of the lithium iron phosphate/carbon composite material of a kind of boracic according to claim 1 is characterized in that described step b is by step b ' replacement:
B '. after the solvent evaporated; the pressed powder heat treated under the protection of inert gas that obtains is carried out first sintering; treat to take out after temperature is reduced to room temperature; put into ball grinder once more; do not adding or adding boric acid fat surfactant or/and carry out secondary ball milling under the flux situation; after the solvent evaporated pressed powder heat treated under inert atmosphere protection that obtains is carried out the sintering second time; obtain the lithium iron phosphate/carbon composite material of boracic through crushing and classification, wherein coating the weight ratio that charcoal accounts for the boracic lithium iron phosphate/carbon composite material is 0.1～10%.
3. the preparation method of the lithium iron phosphate/carbon composite material of a kind of boracic according to claim 1 is characterized in that the boric acid fat surfactant that adds among the described step a is at least a in the two fat of boric acid monoester, boric acid, boric acid three fat, four-coordination volution boric acid fat and their derivative.
4. the preparation method of the lithium iron phosphate/carbon composite material of a kind of boracic according to claim 1 and 2 is characterized in that described flux is at least a in boron compound, the alkali metal fluoride; Described boron compound is B 2O 3, H 3BO 3, LiBO 2Or pyrolysis can form B 2O 3, H 3BO 3, LiBO 2Boron-containing compound; Alkali metal fluoride is a lithium fluoride.
5. the preparation method of the lithium iron phosphate/carbon composite material of a kind of boracic according to claim 1, it is characterized in that among the described step a at the Fe source compound that adds stoichiometric proportion, Li source compound, P source compound, when charcoal coats the charcoal source, also added doping element compound simultaneously.
6. the preparation method of the lithium iron phosphate/carbon composite material of a kind of boracic according to claim 1 is characterized in that described Fe source compound is at least a in ferrous oxide, di-iron trioxide, tri-iron tetroxide, ferrous oxalate, ferric oxalate or ferrous phosphate, the ferric phosphate; Described Li source compound is at least a in lithium carbonate, lithium hydroxide, lithium acetate, lithium phosphate and the lithium dihydrogen phosphate; Described P source compound is at least a in phosphoric acid, lithium phosphate, lithium dihydrogen phosphate, diammonium hydrogen phosphate, the phosphoric acid dihydro amine; Charcoal coats at least a in the mixture that the charcoal source is macromolecular compound or macromolecular compound and CNT (carbon nano-tube), acetylene black, carbon black class conductive additive.
7. the preparation method of the lithium iron phosphate/carbon composite material of a kind of boracic according to claim 1 and 2, it is characterized in that described inert gas is at least a in nitrogen, argon gas, the ammonia, or nitrogen, argon gas, ammonia and volume account at least a in the mist that the hydrogen below 15% forms.
8. the preparation method of the lithium iron phosphate/carbon composite material of a kind of boracic according to claim 1, the temperature that it is characterized in that sintering among the described step b is 550～850 ℃, sintering time is 1～30 hour.
9. the preparation method of the lithium iron phosphate/carbon composite material of a kind of boracic according to claim 2, the temperature that it is characterized in that the middle first sintering of described step b ' is 300～550 ℃, for the second time the temperature of sintering is 550～850 ℃, for the first time with the second time sintering time be respectively 1～30 hour.
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