CN102496714A - Anode active substance, production method thereof, and lithium ion battery employing anode active substance - Google Patents
Anode active substance, production method thereof, and lithium ion battery employing anode active substance Download PDFInfo
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- CN102496714A CN102496714A CN2011104428452A CN201110442845A CN102496714A CN 102496714 A CN102496714 A CN 102496714A CN 2011104428452 A CN2011104428452 A CN 2011104428452A CN 201110442845 A CN201110442845 A CN 201110442845A CN 102496714 A CN102496714 A CN 102496714A
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Abstract
The invention discloses an anode active substance comprising at least one phosphoric acid metal lithium compound and at least one carbon material. The phosphoric acid metal lithium compound has a structural formula of LixMyPO4, wherein M is any transition metal element, x is no smaller than 0 and no larger than 1, and y is no smaller than 0.8 and no larger than 1.2. Also, the invention discloses a production method of the anode active substance and a lithium ion battery employing the anode active substance. According to the invention, with the anode active substance, the diffusion performance of lithium ions can be greatly improved, such that the conductivity of the material can be improved. Therefore, low-resistance improvement can be realized, and negative influences caused by a current carbon cladding method can be avoided. The purity and crystallinity of lithium iron phosphate can be ensured; compaction density and consistency of the material can be improved; and the lithium ion battery employing the anode active substance is provided with good multiplying performance, good low-temperature performance, good high-temperature storing performance, and excellent cyclic performance.
Description
Technical field
The present invention relates to the battery technology field, particularly relate to a kind of positive active material and production method thereof and applied lithium ion battery.
Background technology
At present; Lithium rechargeable battery is current internationally recognized desirable chemical power source; Have voltage height, energy density big, have extended cycle life, numerous advantages such as self discharge is little, memory-less effect, operating temperature range are wide, pollution-free, be widely used in mobile phone, laptop computer, portable power tool, weaponry etc.
Growing along with lithium ion battery has big capacity, the multi-multiplying power charging-discharging lithium ion electrokinetic cell also becomes the emphasis that countries in the world are competitively developed.Lithium-ion-power cell will be mainly used in the power set that electric automobile, battery-operated motor cycle, electric bicycle, stand-by power supply UPS, military equipment, mine lamp, portable weapon, mobile communication equipment etc. require big capacity or high rate charge-discharge.
At present, mainly contain cobalt acid lithium, LiMn2O4, lithium nickelate, ternary material and LiFePO4 as the positive electrode active materials of lithium ion battery.Because LiFePO4 has abundant, the cheap and advantages such as excellent high-temperature cycle performance and security performance in raw material sources, with the LiFePO4 the tool development prospect of lithium ion battery of positive electrode active materials.But, to compare with other positive electrode active materials, LiFePO4 exists electronic conductivity and the low problem of lithium ion diffusion velocity, and in addition, the density of LiFePO4 own is little, causes volume energy density low, also influences the practicability of this material.
Therefore, adopt diverse ways to improve the main direction of studying that conductivity of electrolyte materials is a LiFePO4 at present.The method that is used for improving electrochemical performances of lithium iron phosphate at present mainly contains three kinds, and first method is: the carbon method for coating forms conductive network between particle; Second method is: doped metal ion method, the intrinsic conductivity of raising material; The third method is: improve synthetic method and obtain the product that particle is little and be evenly distributed.
Though above-mentioned three kinds of methods can be improved the chemical property of LiFePO4 to a certain extent, have certain defective.Carbon method for coating for example; Although be an efficient ways aspect the raising iron phosphate powder conductivity, because the introducing of organic lightweight carbon causes density own just relatively little iron phosphate powder jolt ramming and compacted density littler; Apparent specific area (influenced by the lightweight carbon) bigger than normal; Bring difficulty for follow-up battery manufacturing procedure, and in large-scale commercial applications production, the enforcement difficulty of carbon method for coating is very big; Main difficult point is to guarantee the control that the homogeneity that coats and nanoscale coat thickness, and a large amount of LiFePO 4 material evaluation test results show that the carbon covering property determines the stability of batches of materials to a great extent.
In addition, improve the electric conductivity of material through the method for doped with metal elements, it is still indeterminate that this method improves conductivity mechanism at present, has the unsuccessful risk of sneaking into the impurity effect battery performance of mixing.
Therefore, press for a kind of method of developing at present, the negative effect that it can avoid the carbon current method for coating to bring on the one hand; LiFePO4 purity and degree of crystallinity have been guaranteed well; Improve the compacted density and the consistency of material, between the LiFePO4 particle, form conductive network simultaneously, improve the diffusion of lithium ion by a relatively large margin; Thereby improve the electric conductivity of material, realized low resistanceization.
Summary of the invention
In view of this, the purpose of this invention is to provide a kind of positive active material and production method thereof and applied lithium ion battery, this positive active material can let lithium ion in the crystal grain of positive active material, fully spread; Between the LiFePO4 particle, form conductive network; Improve the diffusion of lithium ion by a relatively large margin, thereby improve the electric conductivity of material, realized low resistanceization; The negative effect that simultaneously can also avoid the carbon current method for coating to bring; Guarantee LiFePO4 purity and degree of crystallinity well, improved the compacted density and the consistency of material, therefore; Let and use the lithium ion battery of this positive active material to have good high rate performance, cryogenic property, high-temperature storage performance and superior cycle performance; Can satisfy the long user demand of electronic product, help improving the market application foreground of battery production producer product, be of great practical significance.
For this reason, the invention provides a kind of positive active material, include at least a phosphate metal lithium compound and at least a carbon material;
The structure expression of said phosphate metal lithium compound is Li
xM
yPO
4, wherein, M is any one transition metal, 0≤x≤1,0.8≤y≤1.2.
Wherein, said carbon material comprises at least a in electrically conductive graphite, CNT, carbon nano-fiber, superconduct graphite, acetylene black and the graphene conductive agent.
Wherein, said phosphate metal lithium compound includes LiFePO4 LiFePO
4, lithium manganese phosphate LiMnPO
4, cobalt phosphate lithium LiCoPO
4), LiNiPO LiNiPO
4With iron manganese phosphate for lithium Li (FeMn) PO
4In at least a.
Wherein, said phosphate metal lithium compound is LiFePO4 LiFePO
4
In addition, the present invention also provides a kind of method that is used to produce said positive active material, may further comprise the steps:
The first step: be that Li source compound, transition metal source compound and the P source compound of 1:1:1 mixes at first, join then in the container of mixing and ball milling with mol ratio;
Second step: in the container of mixing and ball milling, add solvent, dispersant and complexing agent simultaneously, in the container of mixing and ball milling, carry out 4 ~ 8 hours ball milling then, under 40 ~ 80 ℃ vacuum, carry out dried then;
The 3rd step: under protective atmosphere, calcine with 550 ~ 650 ℃ temperature then, obtaining grain size is the phosphoric acid transition metal lithium compound of Nano grade;
The 4th step: with resulting grain size is that the transistion metal compound and the granular size of Nano grade is that nano level carbon material mixes, and stirs, and finally obtains needed positive active material.
Wherein, said transition metal source compound is a Fe source compound, and said Fe source compound is ferrous oxalate, ferrous sulfate, frerrous chloride, ferrous acetate, ferrous phosphate or ferrous nitrate.
Wherein, said Li source compound is lithium hydroxide, lithium carbonate, lithium oxalate, lithium acetate or lithium phosphate; Said P source compound is phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate or ferrous phosphate.
Wherein, the container of said mixing and ball milling is corundum ball grinder, agate jar, polyurethane ball grinder, nylon ball grinder or tungsten carbide ball milling jar, and the abrading-ball that the container of said mixing and ball milling has is zirconia ball, corundum ball, agate ball or polyurethane ball.
Wherein, said dried operation is specially: adopt the mode of spraying to carry out drying.
Wherein, said solvent package contains at least a in deionized water, industrial alcohol, absolute ethyl alcohol and the acetone;
Said complexing agent is dimercaprol dimercaptopropanol, Sodium Dimercapto Sulfonate, mercaptoethylmaine, TGA, oxine, acetylacetone,2,4-pentanedione, citric acid, malic acid, tartaric acid, oxalic acid, sulfosalicylic acid, triethanolamine or ethylenediamine tetrapropionic acid;
Said dispersant includes at least a in polyethylene glycol, polyvinyl alcohol, softex kw and the hexadecyltrimethylammonium chloride.
Wherein, said protective atmosphere is hydrogen or argon gas atmosphere.
Wherein, said carbon material comprises at least a in electrically conductive graphite, CNT, carbon nano-fiber, superconduct graphite, acetylene black and the graphene conductive agent.
In addition, the present invention also provides a kind of lithium ion battery that contains said positive active material, includes positive plate, negative plate and barrier film, is injected with electrolyte in the said lithium ion battery;
Said positive plate includes a plus plate current-collecting body, and said plus plate current-collecting body surfaces coated is covered with one deck positive electrode active material layer.
Wherein, said plus plate current-collecting body is an aluminium foil, and said positive electrode active material layer includes said positive active material, binding agent and solvent;
Said binding agent includes polytetrafluoroethylene, gather at least a in inclined to one side tetrafluoroethene, phenolic resins, polyvinyl alcohol and the polyvinylpyrrolidone;
Said solvent package contains N-crassitude ketone solvent.
Wherein, said electrolyte includes electrolytic salt and anhydrous solvent, and said electrolytic salt includes lithium hexafluoro phosphate LiPF
6, lithium perchlorate LiClO
4, hexafluoroarsenate lithium LiAsF
6, LiBF4 LiBF
4At least a with among the di-oxalate lithium borate LiBOB; Said anhydrous solvent includes at least a among ethylene carbonate EC, propene carbonate PC, dimethyl carbonate DMC, methyl ethyl carbonate EMC and the diethyl carbonate DEC.
Visible by above technical scheme provided by the invention, compared with prior art, the invention provides a kind of positive active material and production method thereof and applied lithium ion battery; This positive active material can let lithium ion in the crystal grain of positive active material, fully spread, and between the LiFePO4 particle, forms conductive network, improves the diffusion of lithium ion by a relatively large margin; Thereby improve the electric conductivity of material; Realized low resistanceization, the negative effect that can also avoid the carbon current method for coating to bring has simultaneously guaranteed LiFePO4 purity and degree of crystallinity well; Improve the compacted density and the consistency of material; Therefore, let and use the lithium ion battery of this positive active material to have good high rate performance, cryogenic property, high-temperature storage performance and superior cycle performance, can satisfy the long user demand of electronic product; Help improving the market application foreground of battery production producer product, be of great practical significance.
Description of drawings
Fig. 1 is production method embodiment one to the embodiment three prepared LiFePO that obtains of a kind of positive active material provided by the invention
4X-ray diffraction (XRD) figure of the anodal powder of/CNT;
Fig. 2 is production method embodiment one to the embodiment three prepared pure phase LiFePO that obtains of a kind of positive active material provided by the invention
4Electronic scanning video picture (SEM) figure of anodal powder;
Fig. 3 is production method embodiment one to the embodiment three prepared LiFePO that obtains of a kind of positive active material provided by the invention
4/ CNT blended anode powder SEM figure;
Fig. 4 is production method embodiment one to the embodiment three prepared LiFePO that obtains of a kind of positive active material provided by the invention
4The reduced parameter sketch map of the pure phase specific area between/CNT blended anode powder and the commercialization sample, pure phase conductivity, compound conductivity;
Fig. 5 is the battery charging and discharging indicatrix sketch map of the prepared lithium ion battery of utilization nano composite anode active material provided by the invention;
Fig. 6 is the prepared multiplying power indicatrix sketch map of lithium ion battery under different multiplying electric current C size of utilization nano composite anode active material provided by the invention;
Fig. 7 is the prepared discharge characteristic curve synoptic diagram of lithium ion battery under different temperatures of utilization nano composite anode active material provided by the invention;
Fig. 8 is the cycle specificity curve synoptic diagram of the prepared lithium ion battery of utilization nano composite anode active material provided by the invention.
Embodiment
In order to make those skilled in the art person understand the present invention program better, the present invention is done further detailed description below in conjunction with accompanying drawing and execution mode.
The invention provides a kind of lithium ion battery, it is a non-aqueous secondary batteries, includes positive plate, negative plate and barrier film, is injected with electrolyte in the said lithium ion battery.
In the present invention, the battery of the different shape that said lithium ion battery can be well known to those skilled in the art for example can be the battery of shapes such as circular, square, button and coffee bag.
In the present invention, said negative plate includes a negative current collector, and said negative current collector surfaces coated is covered with one deck negative electrode active material layer (being one deck cathode size coating);
On concrete the realization; Said negative current collector can perhaps contain the conducting polymer of lithium for Copper Foil, metal lithium sheet, aluminum alloy sheet, and said negative electrode active material layer (being the cathode size coating) includes negative electrode active material (being major ingredient), conductive agent, binding agent and solvent.
Wherein, said negative electrode active material (being major ingredient) can be lamellar graphite carbon material or metal oxide; The binding agent of said negative electrode active material of being used to bond can be the normally used binding agent of battery pole piece production field, for example can be for including polytetrafluoroethylene, gathering at least a in inclined to one side tetrafluoroethene, phenolic resins, polyvinyl alcohol and the polyvinylpyrrolidone; Said conductive agent can include at least a in carbon black, CNT, acetylene black, electrically conductive graphite and the Graphene; The solvent of said negative electrode active material includes N-crassitude ketone solvent.
In the present invention, said positive plate includes a plus plate current-collecting body, and said plus plate current-collecting body surfaces coated is covered with one deck positive electrode active material layer (being the anode sizing agent coating);
On concrete the realization, said plus plate current-collecting body can be aluminium foil, and said positive electrode active material layer (being the anode sizing agent coating) includes positive active material (major ingredient), binding agent and solvent.
Wherein, Said positive active material (major ingredient) includes at least a phosphate metal lithium compound and at least a carbon material; Mixed (promptly compound) and formed by phosphate metal lithium compound and carbon material, said positive active material is the nano composite anode active material.
In the present invention, said phosphate metal lithium compound is an olivine structural, and its structure expression is Li
xM
yPO
4, wherein, M is any one transition metal, 0≤x≤1,0.8≤y≤1.2.
On concrete the realization, said phosphate metal lithium compound includes LiFePO4 (LiFePO
4), lithium manganese phosphate (LiMnPO
4), cobalt phosphate lithium (LiCoPO
4), LiNiPO (LiNiPO
4) and iron manganese phosphate for lithium (Li (FeMn) PO
4) at least a.
Need to prove said phosphate metal lithium compound Li
xM
yPO
4The conductivity of powder is greater than 10
-7S/cm (every centimetre of Siemens), and the compacted density of powder is greater than 2.0g/cm
3In addition, phosphate metal lithium compound Li
xM
yPO
4The specific area of powder is greater than 15 m
2/ g.
On concrete the realization, said phosphate metal lithium compound is that size of microcrystal is 50 ~ 100 Nano compound.Said carbon material is preferably the nano carbon material of high conduction, specifically includes at least a in electrically conductive graphite, CNT, carbon nano-fiber, superconduct graphite, acetylene black and the graphene conductive agent.
In the present invention, being used for boning the binding agent of said positive active material can be for including polytetrafluoroethylene, gathering at least a of inclined to one side tetrafluoroethene, phenolic resins, polyvinyl alcohol and polyvinylpyrrolidone; The solvent of said positive active material can include N-crassitude ketone solvent.
Need to prove; Said phosphate metal lithium compound is preferably nano level pure phase lithium iron phosphate; This is because positive active material is the composite material that the nano carbon material by pure phase lithium iron phosphate of nanoscale and high conduction is compounded to form, and the two all belongs to the high-specific surface area material, can be affected with caking property as the metal aluminum foil of plus plate current-collecting body; Therefore; In order to improve battery performance consistency and extending battery life, the present invention handles aluminium foil afterwards as the aluminium foil of plus plate current-collecting body for process, and this foil can be the aluminium foil that contains roughenings such as conductive coating aluminium foil, cloth hole aluminium foil, corona aluminium foil and etching aluminium foil.Here, the conductive coating of said plus plate current-collecting body (aluminium foil) can be the mixture of conductive agent and binding agent, and the said conductive agent of this conductive coating can be deceived or the electrically conductive graphite powder for the high conduction, and said binding agent can be inclined to one side polytetrafluoroethylene or acrylic acid ester.
In the present invention, the barrier film that said lithium ion battery has can for example be polyethylene or polypropylene diaphragm for existing conventional barrier film.
In the present invention, the electrolyte that injects in the said lithium ion battery includes electrolytic salt and anhydrous solvent, and wherein, said electrolytic salt can be for including lithium hexafluoro phosphate (LiPF
6), lithium perchlorate (LiClO
4), hexafluoroarsenate lithium (LiAsF
6), LiBF4 (LiBF
4) and di-oxalate lithium borate (LiBOB) at least a; Said anhydrous solvent can include at least a in ethylene carbonate (EC), propene carbonate (PC), dimethyl carbonate (DMC), methyl ethyl carbonate (EMC) and the diethyl carbonate (DEC).
Lithium ion battery for the invention described above provides specifically prepares through following method:
1, the preparation of negative plate: with negative electrode active material (like graphite), conductive agent (like carbon black S P), Kynoar (PVDF; As binding agent) mix, join solvent N, the N dimethyl is than in the pyrrolidone (NMP); Mixing and stirring then; Obtain having mobile cathode size, cathode size is coated on the negative current collector (like Copper Foil) equably, dry then; Make cathode size on the negative pole currect collecting surface, form one deck negative electrode active material layer (being the cathode size coating) fully, thereby prepare negative plate.In addition, in the present invention, metal lithium sheet can be used as negative electrode active material directly as negative pole.
2, the preparation of positive plate: with positive active material of the present invention (like phosphate metal lithium compound Li
xM
yPO
4Mix the composite material of formation with CNT CNT), Kynoar (PVDF; As binding agent) mix, join solvent N, the N dimethyl is than in the pyrrolidone (NMP); Mixing and stirring then; Obtain having mobile anode sizing agent, anode sizing agent is coated in equably contains on the conductive coating aluminum foil current collector, carry out dried then; Make anode sizing agent on the anode collection surface, form one deck positive electrode active material layer (being the anode sizing agent coating) fully, thereby prepare positive plate.
3, the preparation of lithium ion battery of the present invention: with circular lithium ion battery is example; To process electric core through coiling according to positive plate, negative plate and polyethylene barrier film that above-mentioned technology makes; Cover through going into shell, the weldering end, slot rolling, fluid injection, weldering then, seal, thermal shrinkable sleeve, a plurality of technologies such as soak into, change into, process the lithium ion battery of finished product at last.
In order to prepare the positive active material that has in the lithium ion battery of the present invention; The present invention also provides a kind of method of producing positive active material, and this positive active material is that a kind of phosphate metal lithium compound (for example being LiFePO4) and carbon material mix the composition that (promptly compound) forms.
Wherein, said phosphate metal lithium compound is an olivine structural, and its structure expression is Li
xM
yPO
4, wherein, M is any one transition metal, 0≤x≤1,0.8≤y≤1.2.On concrete the realization, said nanometer phosphate metal lithium compound includes LiFePO
4, LiMnPO
4, LiCoPO
4, LiNiPO
4Or L i (FeMn) PO
4In at least a.
On concrete the realization, said phosphate metal lithium compound is that size of microcrystal is the Nano compound of 50-100.Said carbon material is preferably the nano carbon material of high conduction, specifically comprises at least a in electrically conductive graphite, CNT, carbon nano-fiber, superconduct graphite, acetylene black and the graphene conductive agent.
In addition, a kind of method of producing positive active material that the present invention also provides, be used to produce above-mentioned based lithium-ion battery positive plate the anode collection surface the positive active material that will apply, this method specifically may further comprise the steps:
The first step: be that Li source compound, transition metal source compound (like Fe source compound) and the P source compound of 1:1:1 mixes at first, join then in the container of mixing and ball milling with mol ratio;
Second step: in the container of mixing and ball milling, add solvent, dispersant and complexing agent simultaneously, in the container of mixing and ball milling, carry out 4 ~ 8 hours ball milling then, under 40 ~ 80 ℃ vacuum, carry out dried (for example dry 1 ~ 5 hour) then;
The 3rd step: under protective atmosphere, calcine with 550 ~ 650 ℃ temperature then, obtaining grain size is the phosphoric acid transition metal lithium compound (for example LiFePO4) of Nano grade;
The 4th step: with resulting grain size is that the phosphoric acid transition metal lithium compound (for example LiFePO4) and the granular size of Nano grade is that nano level carbon material mixes, and stirs, and can finally obtain needed positive active material.
In the present invention; Production method through above-mentioned positive active material; The size that finally can obtain crystal grain is the positive active material of 50 ~ 100 nanometers (specifically can be for granular size be that the phosphate metal lithium compound and the carbon material of Nano grade mixes the mixture that forms, for example can be that LiFePO4 and the carbon material of Nano grade mix the mixture that form by granular size).
In the present invention, in the first step, need to prove that the operation purpose of first step is that synthetic to have structure expression be Li
xM
yPO
4Phosphoric acid transition metal lithium compound; Wherein M is any one transition metal; 0≤x≤1,0.8≤y≤1.2, this phosphoric acid transition metal lithium compound are that size of microcrystal is the Nano compound of 50-100; If the transition metal source compound that adds is a Fe source compound, what correspondence was synthetic so will be the LiFePO4 compound.On concrete the realization, said Fe source compound can be ferrous oxalate, ferrous sulfate, frerrous chloride, ferrous acetate, ferrous phosphate or ferrous nitrate.
In the present invention, in the first step, said Li source compound can be lithium hydroxide, lithium carbonate, lithium oxalate, lithium acetate or lithium phosphate.Said P source compound can be phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate or ferrous phosphate.
In the present invention; In the first step; The container of said mixing and ball milling can be non-metallic tank body or the metal can with non-metallic inner liner, and wherein, said nonmetal tank body is preferably corundum ball grinder, agate jar, polyurethane ball grinder, nylon ball grinder or tungsten carbide ball milling jar.For the container of said mixing and ball milling, its abrading-ball that has is preferably the medium spheroid of diameter less than 1mm, and said abrading-ball is preferably zirconia ball, corundum ball, agate ball or polyurethane ball.
In the present invention, in second step, said dried operation is specially: adopt the mode of spraying to carry out drying.
In the present invention, in second step, said solvent can include at least a in deionized water, industrial alcohol, absolute ethyl alcohol and the acetone.
In the present invention; In second step, said complexing agent can be dimercaprol dimercaptopropanol, Sodium Dimercapto Sulfonate, mercaptoethylmaine, TGA, oxine, acetylacetone,2,4-pentanedione, citric acid, malic acid, tartaric acid, oxalic acid, sulfosalicylic acid, triethanolamine or ethylenediamine tetrapropionic acid.
In the present invention, in second step, said dispersant can be for including at least a in polyethylene glycol, polyvinyl alcohol, softex kw and the hexadecyltrimethylammonium chloride.
In the present invention, in the 3rd step, said protective atmosphere can be hydrogen or argon gas atmosphere.
In the present invention, in the 4th step, said carbon material is preferably the granular size nano carbon material of high conduction, specifically comprises at least a in electrically conductive graphite, CNT, carbon nano-fiber, superconduct graphite, acetylene black and the graphene conductive agent.
Method for production positive active material provided by the invention; Basic invention thinking is: the pure phase phosphate metal lithium compound (for example pure phase lithium iron phosphate) of synthesis nano at first mixes itself and high electrical-conductive nanometer carbon material then, thereby forms composite material; Avoided carbon to coat the negative effect that brings so on the one hand; Guaranteed the purity and the degree of crystallinity of phosphate metal lithium compound (for example LiFePO4) well, improved the compacted density and the consistency of material, secondly; Through mixing with high electrical-conductive nanometer carbon material; Can between phosphate metal lithium compound (for example LiFePO4) particle, form conductive network, improve the electric conductivity of material, realize low resistanceization.
In the present invention, through the nano combined iron phosphate lithium positive pole active material that above-mentioned preparation method obtained, the size of its crystal grain is 50 ~ 100 nanometers; Thereby can well bring into play the chemical property of LiFePO4, let lithium ion in the crystal grain of this positive active material, fully spread, between the LiFePO4 particle, form conductive network; Improve the diffusion of lithium ion by a relatively large margin, thereby improve the electric conductivity of material, realized low resistanceization; The negative effect that simultaneously can also avoid the carbon current method for coating to bring; Guarantee LiFePO4 purity and degree of crystallinity well, improved the compacted density and the consistency of material
Below in conjunction with embodiment 1 to embodiment 3, explain that according to a kind of method of producing positive active material provided by the invention producing by structure expression is Li
xM
yPO
4, the compound detailed process that obtains the nano composite anode active material of nano carbon material of nanometer phosphate metal lithium compound and high conduction.Wherein, M is a transition metal, 0≤x≤1,0.8≤y≤1.2, and the size of microcrystal of nanometer phosphate metal lithium compound is 50-100, specifically can be for by phosphate metal lithium compound Li
xM
yPO
4Mix the composite material (being positive active material) of formation with CNT CNT, its synthetic method is following:
At first, be the mixed of 3:1 in molar ratio with lithium hydroxide aqueous solution and phosphoric acid, stirring forms the lithium phosphate suspension of white; Be that ferrous sulfate and the organic additive citric acid of 1:0.002 mixes formed mixed solution and add and splash in the suspension with mol ratio then, stir and also regulate pH value, then this suspension is transferred in the agitated reactor to being about 4.8 sizes; Reaction is 8-12 hour under 230 ℃ temperature; After reaction, obtain the light green color sediment, repeatedly water or ethanol clean then; Pass through 4-8 hour ball milling subsequently; Then carry out dried under 80 ℃ the vacuum, subsequently under protective atmosphere, under 650 ℃ temperature, calcine, thereby sintering obtains nano-grade lithium iron phosphate; At last the CNT (CNT) of the nano-grade lithium iron phosphate that obtains with high conduction mixed, obtain by phosphate metal lithium compound Li
xM
yPO
4Mix the composite material (being positive active material) of formation with CNT CNT.
Embodiment 2
According to preparing positive active material, except calcining heat being become 600 ℃, prepare by phosphate metal lithium compound Li with the same quadrat method of embodiment 1 with embodiment 1 the same method
xM
yPO
4Mix the composite material (being positive active material) of formation with CNT CNT.
According to preparing positive active material, except calcining heat being become 550 ℃, prepare by phosphate metal lithium compound Li with the same quadrat method of embodiment 1 with embodiment 1 the same method
xM
yPO
4Mix the composite material (being positive active material) of formation with CNT CNT.
Positive active material (showing as powder) for embodiment 1 to embodiment 3 is obtained characterizes through testing equipments such as X-ray diffraction (XRD) instrument, scanning electron microscopy SEM, specific area tester and powder conductivity meters.
Fig. 1 is the XRD figure of all embodiment, for the purpose of comparison, has added the conventional LiFePO4 of the LiFePO4 of standard and commercialization at present (appearance provides as a comparison) spectrogram simultaneously.As can beappreciated from fig. 1, except LiFePO4, do not have other dephasign, the present invention has obtained the LiFePO4 of pure phase.
Fig. 2 and Fig. 3 be the pure phase lithium iron phosphate of all embodiment gained with and with the sem photograph of the compound gained material of high conductive carbon nanotube (CNT); As can be seen from the figure; Rising along with sintering temperature; The particle diameter of LiFePO4 primary particle has increase tendency, but at sintering below 650 ℃, the crystal particles controllable size is in the 100nm scope.When this material and CNT compound; Can clearly see that from ESEM Fig. 3 CNT (CNT) plays the conductive network effect between each nano particle; The data that discharge and recharge of lithium ion battery as shown in Figure 5 show that this positive electrode active material material has good invertibity and higher gram capacitance, explain that it is higher powder conductivity that this material has lower impedance.
Fig. 4 is the powder characteristics test data of embodiment 1 to embodiment 4 resulting pure phase lithium iron phosphate (constituent of the positive active material that promptly prepares); As can beappreciated from fig. 4; The pure phase lithium iron phosphate specific area that the present invention synthesizes is bigger than normal; Will exceed more than one times than the commercialization comparison sample, mainly be because the primary particle of the prepared acquisition of the present invention is a nano particle, and existing sample is a micron particles; And the pure phase lithium iron phosphate powder that the present invention prepares continues to mix with CNT CNT, makes the conductivity of powder reach 10
-2S/cm (every centimetre of Siemens) level.In addition, Fig. 6, Fig. 7 and Fig. 8 have shown that further the lithium ion battery (like non-aqueous secondary batteries) for preparing with the present invention has good multiplying power, the gentle cycle characteristics of height.
Therefore, compared with prior art, a kind of positive active material provided by the invention and production method thereof and applied lithium ion battery; This positive active material can let lithium ion in the crystal grain of positive active material, fully spread, and between the LiFePO4 particle, forms conductive network, improves the diffusion of lithium ion by a relatively large margin; Thereby improve the electric conductivity of material; Realized low resistanceization, the negative effect that can also avoid the carbon current method for coating to bring has simultaneously guaranteed LiFePO4 purity and degree of crystallinity well; Improve the compacted density and the consistency of material; Therefore, let and use the lithium ion battery of this positive active material to have good high rate performance, cryogenic property, high-temperature storage performance and superior cycle performance, can satisfy the long user demand of electronic product; Help improving the market application foreground of battery production producer product, be of great practical significance.
The above only is a preferred implementation of the present invention; Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; Can also make some improvement and retouching, these improvement and retouching also should be regarded as protection scope of the present invention.
Claims (15)
1. a positive active material is characterized in that, includes at least a phosphate metal lithium compound and at least a carbon material;
The structure expression of said phosphate metal lithium compound is Li
xM
yPO
4, wherein, M is any one transition metal, 0≤x≤1,0.8≤y≤1.2.
2. positive active material as claimed in claim 1 is characterized in that, said carbon material comprises at least a in electrically conductive graphite, CNT, carbon nano-fiber, superconduct graphite, acetylene black and the graphene conductive agent.
3. positive active material as claimed in claim 1 is characterized in that, said phosphate metal lithium compound includes LiFePO4 LiFePO
4, lithium manganese phosphate LiMnPO
4, cobalt phosphate lithium LiCoPO
4, LiNiPO LiNiPO
4With iron manganese phosphate for lithium Li (FeMn) PO
4In at least a.
4. positive active material as claimed in claim 1 is characterized in that, said phosphate metal lithium compound is LiFePO4 LiFePO
4
5. a method that is used for the said positive active material of production claim 1 is characterized in that, may further comprise the steps:
The first step: be that Li source compound, transition metal source compound and the P source compound of 1:1:1 mixes at first, join then in the container of mixing and ball milling with mol ratio;
Second step: in the container of mixing and ball milling, add solvent, dispersant and complexing agent simultaneously, in the container of mixing and ball milling, carry out 4 ~ 8 hours ball milling then, under 40 ~ 80 ℃ vacuum, carry out dried then;
The 3rd step: under protective atmosphere, calcine with 550 ~ 650 ℃ temperature then, obtaining grain size is the phosphoric acid transition metal lithium compound of Nano grade;
The 4th step: with resulting grain size is that the transistion metal compound and the granular size of Nano grade is that nano level carbon material mixes, and stirs, and finally obtains needed positive active material.
6. method as claimed in claim 5 is characterized in that, said transition metal source compound is a Fe source compound, and said Fe source compound is ferrous oxalate, ferrous sulfate, frerrous chloride, ferrous acetate, ferrous phosphate or ferrous nitrate.
7. method as claimed in claim 5 is characterized in that, said Li source compound is lithium hydroxide, lithium carbonate, lithium oxalate, lithium acetate or lithium phosphate; Said P source compound is phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate or ferrous phosphate.
8. method as claimed in claim 5; It is characterized in that; The container of said mixing and ball milling is corundum ball grinder, agate jar, polyurethane ball grinder, nylon ball grinder or tungsten carbide ball milling jar, and the abrading-ball that the container of said mixing and ball milling has is zirconia ball, corundum ball, agate ball or polyurethane ball.
9. method as claimed in claim 5 is characterized in that, said dried operation is specially: adopt the mode of spraying to carry out drying.
10. method as claimed in claim 5 is characterized in that, said solvent package contains at least a in deionized water, industrial alcohol, absolute ethyl alcohol and the acetone;
Said complexing agent is dimercaprol dimercaptopropanol, Sodium Dimercapto Sulfonate, mercaptoethylmaine, TGA, oxine, acetylacetone,2,4-pentanedione, citric acid, malic acid, tartaric acid, oxalic acid, sulfosalicylic acid, triethanolamine or ethylenediamine tetrapropionic acid;
Said dispersant includes at least a in polyethylene glycol, polyvinyl alcohol, softex kw and the hexadecyltrimethylammonium chloride.
11. method as claimed in claim 5 is characterized in that, said protective atmosphere is hydrogen or argon gas atmosphere.
12. method as claimed in claim 5 is characterized in that, said carbon material comprises at least a in electrically conductive graphite, CNT, carbon nano-fiber, superconduct graphite, acetylene black and the graphene conductive agent.
13. a lithium ion battery that contains the said positive active material of claim 1 is characterized in that, includes positive plate, negative plate and barrier film, is injected with electrolyte in the said lithium ion battery;
Said positive plate includes a plus plate current-collecting body, and said plus plate current-collecting body surfaces coated is covered with one deck positive electrode active material layer.
14. lithium ion battery as claimed in claim 13 is characterized in that, said plus plate current-collecting body is an aluminium foil, and said positive electrode active material layer includes said positive active material, binding agent and solvent;
Said binding agent includes polytetrafluoroethylene, gather at least a in inclined to one side tetrafluoroethene, phenolic resins, polyvinyl alcohol and the polyvinylpyrrolidone;
Said solvent package contains N-crassitude ketone solvent.
15. lithium ion battery as claimed in claim 13 is characterized in that, said electrolyte includes electrolytic salt and anhydrous solvent, and said electrolytic salt includes lithium hexafluoro phosphate LiPF
6, lithium perchlorate LiClO
4, hexafluoroarsenate lithium LiAsF
6, LiBF4 LiBF
4At least a with among the di-oxalate lithium borate LiBOB; Said anhydrous solvent includes at least a among ethylene carbonate EC, propene carbonate PC, dimethyl carbonate DMC, methyl ethyl carbonate EMC and the diethyl carbonate DEC.
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