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CN100416897C - Negative electrode of lithium ion secondary cell and lithium ion secondary cell comprising the same - Google Patents

Negative electrode of lithium ion secondary cell and lithium ion secondary cell comprising the same Download PDF

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CN100416897C
CN100416897C CNB2005100022088A CN200510002208A CN100416897C CN 100416897 C CN100416897 C CN 100416897C CN B2005100022088 A CNB2005100022088 A CN B2005100022088A CN 200510002208 A CN200510002208 A CN 200510002208A CN 100416897 C CN100416897 C CN 100416897C
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graphite
negative pole
weight
flakey
native graphite
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CN1808745A (en
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肖峰
孙华军
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BYD Co Ltd
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    • Y02E60/10Energy storage using batteries

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Abstract

The present invention relates to active substances of a negative pole for a lithium ion secondary battery, the negative pole containing the active substances and the lithium ion secondary battery comprising the negative pole, wherein the active substances of the negative pole comprise mixed graphite composed of squamous natural graphite, spherical natural graphite and squamous synthetic graphite. The weight of the squamous natural graphite accounts for 35 to 70 weight percent of the total weight of the mixed graphite, the weight of the spherical natural graphite accounts for 5 to 45 weight percent of the total weight of the mixed graphite, and the weight of the squamous synthetic graphite accounts for 5 to 30 weight percent of the total weight of the mixed graphite. The density of a negative electrode using the active substances of the negative pole reaches 1.55 to 1.60 g/cm<3>, and a lithium ion battery using the active substances of the negative pole has advantages of high reversible capacity and good cycle life.

Description

A kind of negative pole of lithium rechargeable battery and comprise the lithium rechargeable battery of this negative pole
[technical field]
The present invention relates to a kind of negative pole of lithium rechargeable battery and comprise the lithium rechargeable battery of this negative electrode.
[background technology]
In recent years, the portability of consumer electronic device, the positive develop rapidly of wireless penetration, therefore urgent small-sized, in light weight, lithium rechargeable battery of wishing exploitation as above-mentioned electronic equipment driving power with high-energy-density.
The anodal general composite oxides that use lithium cobalt oxygen, lithium nickel oxygen, lithium manganese oxygen etc. to contain lithium of lithium rechargeable battery.
In the prior art, the various material with carbon elements of the general use of the negative pole of lithium rechargeable battery, this material with carbon element comprises the graphite of crystalline state and amorphous state, particularly crystalline state.Negative pole uses the reason of graphite to be advantages such as its initial irreversible capacity with the density height of the battery capacity height of Unit Weight, negative electrode, negative pole is little.
Graphite mainly is divided into native graphite and Delanium.Native graphite has types such as amorphous graphite, flaky graphite, and wherein amorphous graphite purity is low, irreversible specific capacity height, and opposite flaky graphite purity is higher, and reversible capacity can reach 300~350mah/g, and first charge-discharge efficiency is greater than 90%.The spheroidal particle that aftertreatment obtains through physics is arranged again in the native graphite, be called spherical native graphite.
Flakey native graphite and spherical native graphite are easy to compression, have higher packed density.But the mixture layer density when calendering that with the native graphite is negative pole also can only be pressed onto 1.50-1.55g/cm 3About, this is because the too high meeting of density of calendering causes the fragmentation of negative electrode active material particle and defeated and dispersed, causes peeling off of particle, thereby reduces the cycle performance of battery.
The purity of Delanium has certain relation with different processing technologys, generally all be difficult to compression by the flakey Delanium that easy graphitized carbon is carried out obtain after the graphitization processing, the density of anode mixture layer is lower, but the fragmentation and the defeated and dispersed degree of negative pole particle in the charge and discharge cycles process that with the flakey Delanium is active material is less, the degree that expands in the charge and discharge cycles process simultaneously and shrink is also less, adds the cycle performance that this graphite can effectively improve whole negative electrode active material.
Because the theoretical capacity of graphite is 372mah/g, so the raising that requires along with battery capacity needs to solve the problem of the high capacity of material itself.Turn to target with high-energy-density more, the technology of studying the density by improving anode mixture layer realizes.As the bulk density of mixture layer is brought up to 1.6g/cm 3About or higher.In the operation with calendering anode mixture layers such as rolling processes of reality, occur the problem in the manufacturing easily, can't reach the thickness of regulation; Perhaps reached the thickness of regulation but the defective on the various performances but appears in prepared battery, as: the irreversible capacity height, cycle performance is poor.
Day disclosure special permission communique 2000-195518 discloses a kind of negative pole that is made of the mixture of carbon fiber and carbonaceous material, but adopts this negative material to reach 1.4g/cm in bulk density 3The irreversible capacity of negative pole increases when above.
CN1472832A discloses a kind of negative pole of being made up of spherical native graphite and graphitized carbon fibre.But because the shape of particle difference of graphite and carbon fiber is too big, there is the sufficient inadequately risk of mixing in both, cause irreversible capacity to increase and high rate capability decline.
On the other hand, the specific area of negative pole graphite particle is relevant with the initial stage irreversible capacity of negative pole, if the specific area of particle is big, the initial stage can consume too much lithium ion when forming the SEI film, and irreversible capacity will increase.Therefore, require to weigh, wish that specific area is as far as possible little from the high capacity of battery.
[summary of the invention]
Problem for the high capacity that solves negative material itself, the inventor considers by dissimilar graphite is mixed mixing, reach the bulk density that promptly can improve negative pole, the while can guarantee the reversible capacity of battery again and the purpose of better cycle performance is arranged.
Therefore, the object of the present invention is to provide a kind of negative electrode and the lithium rechargeable battery that comprises this negative electrode that contains the lithium rechargeable battery of the negative electrode active material that mixes by three kinds of different graphite, this negative electrode has higher packed density, and this lithium ion battery has higher reversible capacity and cycle life preferably.
According to the present invention, a kind of negative pole of lithium rechargeable battery is provided, this negative pole comprises negative pole matrix and the cathode coating material that is coated on this matrix, described cathode coating material comprises negative electrode active material and binding agent, it is characterized in that described negative electrode active material comprises by the flakey native graphite, the admixed graphite that spherical native graphite and flakey Delanium are formed, wherein the flakey native graphite accounts for the 35-70 weight % of admixed graphite total weight, spherical native graphite accounts for the 5-45 weight % of admixed graphite total weight, and the flakey Delanium accounts for the 5-30 weight % of admixed graphite total weight.
The average grain diameter D of described flakey native graphite 50Be preferably 10-30 μ m, the BET specific area is at 3m 2Below/the g.
The average grain diameter D of described spherical native graphite 50Be preferably 5-20 μ m, the BET specific area is at 8m 2Below/the g.This spherical native graphite can form by known commercial run manufacturing, for example, is that raw material is prepared according to Japanese kokai publication hei 11-263612 disclosed method with the flakey native graphite.In the present invention, preferably, globular graphite is to be dissolved in the tarvia by the particle with the flakey native graphite, and oven dry is with the granulation of mechanical dispersion mode, particle is collided mutually, carry out the shape control (spheroidization) of particle, under 1000-1500 ℃ high temperature, carry out graphitization then, cooling, and, obtain the spherical native graphite that can use in the present invention to its air classification that carries out intensity.Described flakey native graphite and spherical native graphite have essentially identical X-ray diffraction (XRD) data, as shown in Figures 2 and 3.
The particle circularity is used in the particle image projecting in the plane, and the ratio l/L that has the perimeter L of girth l that quite justifies of the same area and particle projection image with particle projection image represents.
Because employed spherical native graphite has the circularity of particle preferably more than 0.8 among the present invention, has the smaller particle size that D50 is 5-20 μ m, can guarantee that spherical native graphite is particle-filled in the hole of flakey native graphite and the formation of flakey Delanium, thereby improve the density of anode mixture layer.
Described flakey Delanium has no particular limits, and can adopt the flakey Delanium of prepared in various methods of the prior art, its average grain diameter D 50Be preferably 10-35 μ m, the BET specific area is preferably at 3m 2Below/the g, its XRD data as shown in Figure 4.
By Fig. 2-4 as can be known, the interplanar distance d of (002) face in flakey native graphite and the spherical native graphite XRD data 002Between 0.3354-0.3360; The interplanar distance d of (002) face in the XRD data of flakey Delanium 002Between 0.3354-0.3370.From the XRD data of three kinds of graphite, can find, except d 002Outside the characteristic peak, there is difference clearly at 2 θ angles between the 40-50 degree, flakey native graphite and spherical native graphite belong to the native graphite scope, tangible 4 characteristic peaks are arranged between the 40-50 degree, and the flakey Delanium show as 2 obvious characteristics peaks between the 40-50 degree.
Above-mentioned, D 50Be by being particle diameter with transverse axis a, longitudinal axis b is that the particle size distribution of the volume reference represented of the a-b coordinate system of population is tried to achieve.In above-mentioned particle size distribution, begin the accumulative total volume from the little particle diameter of a value, a value that the accumulative total volume reaches 50% o'clock correspondence of integral body is particle diameter D 50
Described negative pole matrix has no particular limits, and can adopt in the prior art conventional negative pole matrix, for example aluminium pool, Copper Foil etc., wherein preferred Copper Foil.
Described binding agent has no particular limits, can adopt all types of binding agents that are used for lithium ion battery negative in the prior art, for example can contain one of them or its mixture of the gluey adhesive, polytetrafluoroethylene (PTFE) class etc. of butadiene unit for butadiene-styrene rubber (SBR) class, styrene butadiene rubber latex class etc.The addition of adhesive is generally determined by the bonding strength between anode mixture layer and the matrix, but because the binding agent of described rubber particle mostly is insulator, if excessively add, can cause the heavy-current discharge performance of battery to descend, therefore be preferably below the 10 weight %, for example can be 1~10 weight % of admixed graphite total weight.
In order further to improve between the described negative electrode active material and adhesive property between negative electrode active material and the negative pole matrix and stability, also contain tackifier in the negative pole of the present invention, described tackifier can for, for example, one of them of carboxymethyl cellulose (CMC), hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), hydroxypropyl cellulose (HPC), carboxymethyl hydroxyethyl cellulose cellulose-based materials such as (CMHEC) or its mixture.The content of these tackifier is preferably 1~10 weight % of admixed graphite total weight.
The negative pole of lithium rechargeable battery provided by the present invention can be prepared by existing known method, for example, with described native graphite, spherical native graphite, flakey Delanium, binding agent and tackifier by a certain percentage water make cathode size, this cathode size is coated on the two sides of negative current collectors such as Copper Foil equably, and dry back roll-in also is cut into the size of respective specified size.
The present invention also provides a kind of lithium rechargeable battery, it is characterized in that containing foregoing negative pole.
Specifically, lithium rechargeable battery provided by the invention comprises positive pole, negative pole, electrolyte and barrier film, wherein said negative pole is made up of negative pole matrix and the cathode coating material that is coated on this matrix, described cathode coating material comprises negative electrode active material and bonding agent, it is characterized in that described negative electrode active material is by the flakey native graphite, the admixed graphite that spherical native graphite and flakey Delanium are formed, wherein the flakey native graphite accounts for the 35-70 weight % of admixed graphite total weight, spherical native graphite accounts for the 5-45 weight % of admixed graphite total weight, and the flakey Delanium accounts for the 5-30 weight % of admixed graphite total weight.
In lithium rechargeable battery provided by the invention, described negative pole and all material thereof such as front define, and are not described in detail in this.
In lithium rechargeable battery provided by the invention, described positive pole, electrolyte and barrier film have no particular limits, and can use all types of positive poles, electrolyte and the barrier film that can use in lithium rechargeable battery.Those of ordinary skill in the art can be according to the instruction of prior art, can select and prepare the described positive pole of lithium rechargeable battery of the present invention easily, and described electrolyte and barrier film, and make lithium rechargeable battery of the present invention by described positive pole, negative pole, electrolyte and barrier film.
For example, described positive pole comprises anodal matrix and the anodal coating material that is coated on this matrix, and described anodal coating material comprises positive active material and binding agent, and described positive active material can use the composite oxides of lithium, as LiCoO 2, LiNiO 2, LiMn 2O 4Deng.
For example, described electrolyte is generally nonaqueous electrolytic solution, and it is made up of nonaqueous solvents and the electrolyte that is dissolved in this nonaqueous solvents.Described nonaqueous solvents has no particular limits, and can use known up to now all available nonaqueous solventss, for example preferably uses the mixed solvent of chain acid esters and ring-type acid esters; Described chain acid esters can be selected from dimethyl carbonate, diethyl carbonate, ethyl propyl carbonic acid ester, diphenyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dimethoxy-ethane, diethoxyethane with and fluorine-containing, sulfur-bearing and contain one of them or its mixture of the chain organosilane ester of unsaturated bond; Described ring-type acid esters can be selected from ethylene carbonate, propene carbonate, vinylene carbonate, gamma-butyrolacton, sultone with and fluorine-containing, sulfur-bearing or contain one of them or its mixture of the ring-type organosilane ester of unsaturated bond.Described electrolyte has no particular limits equally, can use all types of lithium electrolytes that are generally used for nonaqueous electrolytic solution secondary battery, for example, it can be a kind of or its mixture that is selected from the lithium salts of lithium perchlorate, chlorine lithium aluminate, lithium hexafluoro phosphate, LiBF4, lithium halide, fluorocarbon based fluorine oxygen lithium phosphate or fluorocarbon based sulfonic acid lithium.
Described barrier film can for, for example, be the barrier film of material with polypropylene, polyethylene (PP/PE).
Usually three kinds of graphite materials involved in the present invention are the private negative electrode active material of doing of coverlet all, wherein the capacity of native graphite is higher, the negative electrode made from this graphite has higher packed density, and the reversible capacity of graphite is higher, but the relatively poor phenomenon of cycle life can appear in the lithium ion battery with this graphite preparation, and the expansion of graphite is bigger.The lithium ion battery that opposite a lot of lepidiod Delaniums are prepared from have preferably cycle life and graphite expansion less, but capacity is less relatively, and the packed density of the negative electrode made from this graphite is lower.The present invention mixes these three kinds of graphite with different pluses and minuses just by a certain percentage, can give play to the advantage of every kind of graphite, remedies the shortcoming that other two kinds of graphite exist, thereby reaches purpose of the present invention.
In the negative electrode active material of the present invention, the ratio of flakey Delanium preferably is not higher than 30 weight %, otherwise the anode mixture layer of higher density can not be provided; Be not less than 5 weight % simultaneously, otherwise the lithium secondary battery of better cycle life can not be provided.The ratio of spherical native graphite preferably is not higher than 45 weight %, otherwise too much globular graphite can't be filled in the hole that flaky graphite forms, and can influence peeling off of pole piece calendering back particle, causes cycle performance to descend; Be not less than 5 weight % simultaneously, otherwise hole is too many between the anode mixture layer particle, influences mixture layer density.
Use graphite to compare as the lithium rechargeable battery of negative pole with other, the advantage that the present invention gives prominence to is:
Big in the bulk density of negative material, expand less in, also have higher reversible capacity; And, use the lithium ion battery of this negative electrode active material still to have cycle life preferably.
[description of drawings]
Fig. 1 is a curve chart, shows the charge and discharge cycles of the secondary lithium battery that embodiment and Comparative Examples make and the relation between the discharge capacity;
Fig. 2 is the XRD figure of native graphite;
Fig. 3 is the XRD figure of spherical native graphite;
Fig. 4 is the XRD figure of flakey Delanium;
Fig. 5 is scanning electron microscopy (SEM) photo of native graphite;
Fig. 6 is the SEM photo of spherical native graphite;
Fig. 7 is the SEM photo of flakey Delanium.
[embodiment]
Below in conjunction with embodiment, reach performance evaluation to corresponding lithium ion battery, the present invention will be further explained and explanation.
In each embodiment and Comparative Examples, employed globular graphite is that the particle with the flakey native graphite is dissolved in the tarvia, oven dry, with the granulation of mechanical dispersion mode, particle is collided mutually, carry out the shape control (spheroidization) of particle, under 1000-1500 ℃ high temperature, carry out graphitization then, cool off, and its air classification that carries out intensity is made.
[embodiment 1]
The preparation of spherical native graphite: flakey native graphite (Chinese Qingdao product graphite powder) 200 grams are dissolved in the 20 gram tarvias, 200 ℃ of oven dry down, with the granulation of mechanical dispersion mode, then 1200 ℃ roasting temperature 5 hours, cooling, obtain spherical native graphite, recording its average grain diameter is 10 μ m, and the BET specific area is 8m 2/ g, the particle circularity is 0.86, its XRD figure as shown in Figure 3, the SEM photo is as shown in Figure 6.
The preparation of negative electrode active material: (commercial goods, trade names are SODIIF DAG84, and its average grain diameter is 15 μ m, and the BET specific area is 2.82m with the flakey native graphite 2/ g, its XRD figure as shown in Figure 2, the SEM photo is as shown in Figure 5), the spherical native graphite of above-mentioned preparation, (its average grain diameter is 16 μ m to the flakey Delanium for Changsha starlight company commodity, the fine powder of 325 orders, and the BET specific area is 2.1m 2/ g, its XRD figure as shown in Figure 4, its SEM photo is as shown in Figure 7) mode of mixing by ball milling with 65: 5: 30 ratio of weight ratio fully mixes the back and carry out vacuumize under 200 ℃, the gained admixed graphite is as negative electrode active material.
The preparation of adhesive solution: with water, as butadiene-styrene rubber (SBR) latex (the Nantong Shen Hua chemical company commodity of binding agent, the trade mark is TAIPOL1500E) and as carboxymethyl cellulose (Jiangmen quantum Gao Ke company commodity of tackifier, model is CMC1500) with water: SBR: CMC=125: 4: 2 weight ratio mixes, and makes adhesive solution.
The preparation of negative pole: above-mentioned negative electrode active material (admixed graphite) and the weight ratio of above-mentioned adhesive solution with 100: 130 are mixed, make cathode size; This cathode size evenly is coated in two (the coating gross thickness is 200 μ m) of the thick copper of 10 μ m pool collector, with it 125 ℃ of dryings 1 hour, then at 1.0Kgf/cm 3Pressure under be rolled into the thick negative plate of 125 μ m.
Anodal preparation: (Atuofeina Corp 761#PVDF) is dissolved in the 1350 gram N-N-methyl-2-2-pyrrolidone N-solvents and makes adhesive solution, adds 2895 gram LiCoO then in gained solution with 90 gram polyvinylidene fluoride 2(FMC Corp.'s commodity) fully mix and make anode sizing agent.This anode sizing agent is uniformly applied on the thick aluminium foil of 20 μ m,, obtains the thick positive plate of about 125 μ m after the calendering through 125 ℃ of dryings 1 hour.
The preparation of battery: the polypropylene diaphragm that above-mentioned positive and negative plate and 20 μ m are thick is wound into rectangular lithium ion battery electricity core, in the battery case of packing into and weld, and subsequently will be by LiPF 6Be dissolved in the concentration of 1mol/l that formed electrolyte is injected in the battery case in the mixed solvent of EC/DMC (vinyl carbonate/diethyl carbonate)=1: 1,453450A type lithium rechargeable battery is made in sealing, be that thickness is 4.5mm, width is 34mm, highly be the square lithium ion secondary battery of 50mm, the design capacity of this battery is 750mAh.
[embodiment 2]
Preparing spherical native graphite according to the same procedure with embodiment 1, is 15 μ m but the condition of control granulation makes the average grain diameter of the spherical native graphite of gained, and the BET specific area is 5m 2/ g, the particle circularity is 0.90.
The preparation of negative electrode active material: (average grain diameter is 20 μ m, and the BET specific area is 2.82m with the flakey native graphite 2/ g), the spherical native graphite of above-mentioned preparation, (average grain diameter is 25 μ m to the flakey Delanium, and the BET specific area is 3m 2/ the mode of g) mixing by ball milling with 70: 15: 15 ratio of weight ratio fully mixes the back and carry out vacuumize under 200 ℃, and the gained admixed graphite is as negative electrode active material.
The preparation of adhesive solution: with water, (company's commodity are liked to be rich in Shanghai three as the polytetrafluoroethylene of binding agent, model is PTFE F301B) and as hydroxypropyl methylcellulose (Jiangmen quantum Gao Ke company commodity of tackifier, model is HPMC1500) with water: PTFE: HPMC=120: 3.5: 1.5 weight ratio mixes, and makes adhesive solution.
The preparation of negative pole: above-mentioned negative electrode active material (admixed graphite) and the weight ratio of above-mentioned adhesive solution with 100: 125 are mixed, make cathode size; This cathode size evenly is coated in two (the coating gross thickness is 200 μ m) of the thick copper of 10 μ m pool collector, with it 125 ℃ of dryings 1 hour, then at 1.0Kgf/cm 3Pressure under be rolled into the thick negative plate of 125 μ m.
Use above-mentioned negative plate, prepare secondary lithium battery according to same procedure with embodiment 1.
[embodiment 3]
Select to prepare negative plate and secondary lithium battery with embodiment 1 identical three kinds of graphite and identical method, the weight ratio of different is flakey native graphite, spherical native graphite and flakey Delanium is 50: 45: 5.
[embodiment 4]
Select to prepare negative plate and secondary lithium battery with embodiment 1 identical three kinds of graphite and identical method, the weight ratio of different is flakey native graphite, spherical native graphite and flakey Delanium is 35: 45: 20.
[Comparative Examples 1]
Prepare negative plate and secondary lithium battery according to the method identical with embodiment 1, different is only uses flakey native graphite among the independent embodiment 1 to replace admixed graphite among the embodiment 1.
[Comparative Examples 2]
Prepare negative plate and secondary lithium battery according to the method identical with embodiment 1, different is only uses spherical native graphite among the independent embodiment 1 to replace admixed graphite among the embodiment 1.
[Comparative Examples 3]
Prepare negative plate and secondary lithium battery according to the method identical with embodiment 1, different is only uses flakey Delanium among the independent embodiment 1 to replace admixed graphite among the embodiment 1.
[battery performance test]
1. anode mixture layer density
Anode mixture layer density is calculated by following mode:
The weight of supposing the anode mixture layer of given size is W, and the mixture layer thickness that advanced after rolling process is rolled is H1, and the thickness of collector is H2, and the pole piece size is long to be L1, and wide is L2, then the density p 1=W/{ of mixture layer (H1-h1) * L1*L2}
Certain expansion can take place in negative pole after lithium secondary battery advanced first charge-discharge, the lithium secondary battery that makes is dissected the negative plate that battery obtains needs in the glove box that is being full of argon gas under the voltage 3.0V after finishing first charge-discharge, and survey its thickness H2, mixture layer density p 2=W/{ (H2-h1) the * L1*L2} after then expanding
Data from table 1 all reach higher packed density according to the anode mixture layer in the embodiments of the invention as can be seen, and the density after expanding is all greater than the density on expansion of the graphite in the Comparative Examples.
Table 1
Figure C20051000220800131
2. negative electrode active material initial stage reversible capacity
The battery that embodiment 1-4 and Comparative Examples 1-3 are made is under 25 ℃, and with the current value of 0.1C (75mA), initial charge is to voltage 4.2V.Then, being discharged to voltage with the current value of 0.2C (150mA) is 3.8V, and the current value with 0.1C (75mA) is discharged to 3.0V again.The initial stage reversible capacity of negative electrode active material can obtain according to following account form (weight of supposing the anode mixture layer of given size is W, negative electrode active material in the mixture layer: binding agent: tackifier=1: x: y):
Initial stage reversible capacity=(above-mentioned total discharge capacity)/{ W * [1/ (1+x+y)] }
Its result is as shown in table 2.
Table 2
Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Comparative Examples 1 Comparative Examples 2 Comparative Examples 3
The reversible capacity of battery (mAh/g) 335 337 340 335 338 340 290
3. battery cycle life
The lithium secondary battery of the embodiment 1-4 that measured the initial stage reversible capacity and comparative example 1-3 is carried out 50 charge and discharge cycles of following mode.The capacity C that compares 50 circulation times 50Capacity C with first circulation Mi, the capacity of trying to achieve gets conservation rate (C 50/ C Mi) its result as shown in Figure 1.
● charging: constant-current constant-voltage mode 1C (700mA) charging control voltage 4.2V
● placed 10 minutes the charging back
● discharge: decide electric current 1C (700mA), discharge is by voltage 3.0V
● placed 10 minutes the discharge back
As can be seen from the above results:
1) negative electrode of embodiment 1, embodiment 2, embodiment 3 and embodiment 4 all has a higher packed density and expands less;
2) battery of each embodiment all has higher reversible capacity and cycle life preferably.
Though the reversible capacity of four embodiment batteries wants high unlike the reversible capacity of Comparative Examples 2, or it is lower slightly, and four embodiment compare with Comparative Examples 1, the reversible capacity value that has also is lower than the reversible capacity value of Comparative Examples 1, but embodiment compares ratio 1 and Comparative Examples 2, shows cycle life preferably.Though Comparative Examples 3 shows best cycle life, its reversible capacity is too low.

Claims (7)

1. the negative pole of a lithium rechargeable battery, this negative pole comprises negative pole matrix and the cathode coating material that is coated on this matrix, described cathode coating material comprises negative electrode active material and binding agent, it is characterized in that described negative electrode active material comprises the admixed graphite of being made up of flakey native graphite, spherical native graphite and flakey Delanium, wherein the flakey native graphite accounts for the 5-45 weight % that the 35-70 weight % of admixed graphite total weight, spherical native graphite account for the admixed graphite total weight, and the flakey Delanium accounts for the 5-30 weight % of admixed graphite total weight.
2. the negative pole of lithium rechargeable battery according to claim 1, the average grain diameter D of wherein said flakey native graphite 50Be 10-30 μ m, the specific area of using BET method mensuration is at 3m 2Below/the g; The average grain diameter D of described spherical native graphite 50Be 5-20 μ m, the specific area of using BET method mensuration is at 8m 2Below/the g, the particle circularity is 0.8~1; The average grain diameter D of described flakey Delanium 50Be 10-35 μ m, the specific area of using BET method mensuration is at 3m 2Below/the g.
3. the negative pole of lithium rechargeable battery according to claim 1, wherein said binding agent are one of them or its mixture that is selected from butadiene-styrene rubber, polytetrafluoroethylene.
4. according to the negative pole of claim 1 or 3 described lithium rechargeable batteries, the content of wherein said binding agent is 1~10 weight % of admixed graphite total weight.
5. the negative pole of lithium rechargeable battery according to claim 1 also contains tackifier in the wherein said negative pole.
6. the negative pole of lithium rechargeable battery according to claim 5, wherein said tackifier are one of them or its mixture that is selected from carboxymethyl cellulose, hydroxypropyl methylcellulose, methylcellulose, hydroxypropyl cellulose, carboxymethyl hydroxyethyl cellulose, and the content of these tackifier is 1~10 weight % of admixed graphite total weight.
7. a lithium rechargeable battery is characterized in that it comprises any described negative pole in the claim 1~6.
CNB2005100022088A 2005-01-17 2005-01-17 Negative electrode of lithium ion secondary cell and lithium ion secondary cell comprising the same Expired - Fee Related CN100416897C (en)

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