CN103326027B - A kind of negative electrode of lithium ion battery and lithium ion battery - Google Patents
A kind of negative electrode of lithium ion battery and lithium ion battery Download PDFInfo
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- CN103326027B CN103326027B CN201310208562.0A CN201310208562A CN103326027B CN 103326027 B CN103326027 B CN 103326027B CN 201310208562 A CN201310208562 A CN 201310208562A CN 103326027 B CN103326027 B CN 103326027B
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Abstract
The invention discloses a kind of negative electrode of lithium ion battery, including negative current collector and the negative electrode active material layer for being coated on negative current collector, negative electrode active material layer includes negative electrode active material, conductive agent, polymer viscosifier, water milk type polymer binding agent and water-soluble polymeric binder, water-soluble polymeric binder is polyethyleneimine, and water milk type polymer binding agent and the weight rate of water-soluble polymeric binder are 10：90~90：10.The present invention can significantly improve the cohesive force between negative electrode active material layer and negative current collector and between negative electrode active material layer internal particle, so as to improve structural stability of the negative electrode active material layer in the long-term cyclic process of battery, and reduce the usage amount of the polymeric binder of electrochemicaUy inert, so as to reduce cubical expansivity of the battery in cyclic process, low temperature, multiplying power, cycle performance and the energy density of polymer Li-ion battery are improved.In addition, the invention also discloses a kind of lithium ion battery.
Description
Technical field
The invention belongs to technical field of lithium ion, more particularly to a kind of negative electrode of lithium ion battery and lithium ion battery.
Background technology
Lithium ion battery with its high-energy-density, high working voltage, has had extended cycle life, without note since popularization is commercialized
Recall effect, the big I of green and size shape according to the actual requirements flexible design many advantages, such as be widely used as it is various just
The power supply of formula electronic apparatus is taken, these wide application fields and a variety of actual demands have greatly promoted lithium-ion electric
The development in pond.
With the high speed development of mobile electron electric equipment, it is desirable to provide electricity for the powerful equipment of these frivolous portable functions
The lithium ion battery in source has higher capacity, thus needs exploitation than traditional lithium-ion battery more high working voltage, more high energy
The battery of metric density and more long-life.The lifting of these performances can be related to the material and manufacturing process of lithium ion battery by improving
And realize.At present, positive pole, negative pole, barrier film and electrolysis are all concentrated on regard to substantial amounts of research work in terms of lithium ion battery material
On the critical materials such as liquid.
Performance of lithium ion battery is depended primarily in electrode, electrolyte and other auxiliary materials.Especially, electrode property takes
Certainly in electrode active material, collector and between electrode active material layers and electrode current collecting body and in electrode active material layer
The binding agent of cohesive force is provided between portion's particle.
Binding agent is between negative active core-shell material, between negative active core-shell material and conductive agent, in negative active core-shell material, conduction
Pass through covalent bond or non-covalent bond between agent and metal collector（Model ylid bloom action）Form bonding force is provided and participates in negative pole
Active material surface SEI films are constructed.In terms of negative pole, after between the negative electrode active material layers such as lithium insertion graphite, active material
Volume expand, with periodic discharge and recharge, this circulative expansion with shrink it is reciprocal occur, binding agent is this
Following two main functions are served during periodically：（1）Binding agent provides strong bonding force in cathode pole piece system,
Electronics and lithium ion graceful migration in the electrodes, ensure that the internal resistance of electrode remains at low levels;（2）It is buffered in charge and discharge process
In caused active material Volume Changes so that can also be maintained after expansion and contraction binding agent original bond power and
Electrode interior structure.But the non-covalent bond that binding agent provides in cathode pole piece system（Model ylid bloom action）Active force can be because poly-
Compound binding agent occurs different degrees of Swelling under electrolyte immersion and reduced, when pole piece thickness increases or from expansion
The bigger active material of property（Silicon, silica etc.）When, the loose with coming off of negative electrode active material layer thus can be caused, and then cause
Lithium ion deintercalation difficulty, polarization increase, the analysis lithium in cyclic process, high rate performance variation and cycle life reduction etc. are seriously asked
Topic.
The content of the invention
It is an object of the invention to：For the limitation of current material performance, and provide a kind of negative electrode of lithium ion battery and lithium
Ion battery, the negative electrode of lithium ion battery can significantly improve between negative electrode active material layer and negative current collector and negative electrode active
Cohesive force between material layer internal particle, structural stability of the negative electrode active material layer in the long-term cyclic process of battery is improved,
And the usage amount of the polymeric binder of electrochemicaUy inert is reduced, suppress cubical expansivity of the battery in cyclic process, improve
Low temperature, multiplying power, cycle performance and the energy density of lithium ion battery.
In order to achieve the above object, the present invention provides a kind of negative electrode of lithium ion battery, and the technical scheme is as follows：A kind of lithium
Ion battery negative pole, including negative current collector and the negative electrode active material layer for being coated on the negative current collector, the negative pole are lived
Property material layer includes negative electrode active material, conductive agent, polymer viscosifier, water milk type polymer binding agent and water-soluble polymer
Binding agent, the water-soluble polymeric binder are polyethyleneimine, and the water milk type polymer binding agent and the water
The weight rate of molten type polymeric binder is 10：90~90：10.
Although the chemical formula of polyethyleneimine can be represented with-［ CH2CH2NH ］-, contain one-level, two level, three-level
The chemical constitution of side chain can similarly use.Especially, on its molecular structure, the poly- second of linear polyethyleneimine, branched chain type
Alkene imines and hyperbranched type polyethyleneimine can be used in the present invention.The structure of commercially available polyethylene imines can be aziridine
Polymer carries branched structure, and typically by the acid catalysis ring-opening reaction of aziridine come what is prepared, its polymer is easily
It is dissolved or dispersed in water.Polyethyleneimine can have the molecular weight of 500~1,000,000 g/mol even more highs, but be applicable
In the present invention, preferable typical weight average molecular weight is 5,000~500,000 g/mol.Polyethyleneimine can use sour proton
Change, a kind of polyethyleneimine amine salt is formed in surrounding medium, a kind of production that can partly or entirely dissociate is formed dependent on pH value
Thing, should be in the range of 9~12 suitable for the pH value of the aqueous solution of the concentration of polyethyleneimine 5% of the present invention.
Described water-soluble polymeric binder-polyethyleneimine, due to substantial amounts of polar group be present on its molecular structure
Group, including primary amino radical, secondary amino group and tertiary amino, these polar groups can form coordinate bond between negative current collector copper foil, with
Polar group on negative electrode active material and conductive agent surface（Carboxyl, hydroxyl）Form chemical bond or stronger intermolecular work occurs
Firmly-Van der Waals force（Induction force, dispersion force, hydrogen bond force）, so as between negative electrode active material layer and negative current collector and
Stronger bonding force is provided between negative electrode active material layer internal particle, and the bonding force being consequently formed is not easy in electrolyte
Destroyed under effect and influence bond effect.In addition the very strong polar group of these electron donations helps to increase lithium salts
Dissociation is simultaneously complexed with lithium cation, and polyethyleneimine has relatively low glass transition temperature, its strand
Section has enough compliances, can aid in the conduction for improving lithium ion in electrode interior.
The water milk type polymer binding agent is butadiene-styrene rubber, nitrile rubber, butadiene rubber, chloroprene rubber, three
At least one of first EP rubbers and acrylic rubber, but it is not limited to this.The water milk type polymer binding agent can be with
Be it is any be well known in the art there is viscoelastic binding agent.
The percentage by weight that the water milk type polymer binding agent accounts for the negative electrode active material layer gross weight is 0.5~10
%。
The percentage by weight that the water milk type polymer binding agent accounts for the negative electrode active material layer gross weight is 0.5~3
%。
The polyethyleneimine is the copolymerization of aziridine, the homopolymer of aziridine mixture or aziridine mixture
Thing, the macromolecular structure of the polyethyleneimine include line style, branched chain type and hyperbranched type.
The percentage by weight that the polyethyleneimine accounts for the negative electrode active material layer gross weight is 0.5~10 %.
The percentage by weight that the polyethyleneimine accounts for the negative electrode active material layer gross weight is 0.5~3 %.
In formula of size, if the dosage of binding agent is very few, negative electrode active material layer and bonding for collector can be caused to be deteriorated,
Negative electrode active material layer easily comes off in pole piece and cell fabrication processes.In addition, negative electrode active material layer is also resulted in battery
Structural stability in long-term cyclic process is deteriorated, as cubical expansivity increase of the negative electrode active material layer in cyclic process,
Demoulding etc. caused by the caking property of negative electrode active material layer and negative current collector reduces, these problems can have a strong impact on battery
Cycle life.Conversely, if the dosage of binding agent is excessive（Mass fraction is more than 10%）, binding agent may then coat active material table
Face, cause impedance to increase, influence battery performance.
The weight average molecular weight of the polyethyleneimine is 500~1,000,000 g/mol.
The weight average molecular weight of the polyethyleneimine is 5,000~500,000 g/mol.
The polyethyleneimine macromolecular includes primary amino radical, secondary amino group and tertiary amino, relative to amino total amount, primary amino radical
Molar ratio be more than 20%, the molar ratio of secondary amino group is more than 20%, and the molar ratio of tertiary amino is within 60%.
The pH value of the aqueous solution of the concentration of polyethyleneimine 5% is 9~12.
The negative electrode active material be native graphite, Delanium, graphitized carbon fibre, graphitized intermediate-phase carbon microballon,
At least one of amorphous carbon, silicon, silica, tin oxide and tin alloy compound.
The conductive agent is at least one of conductive black, carbon fiber, CNT and graphene.
The polymer viscosifier be sodium carboxymethylcellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid and
At least one of polyvinyl alcohol.
The percentage by weight that the negative electrode active material accounts for the negative electrode active material layer gross weight is 90~99.5 %.
The present invention also provides a kind of lithium ion battery, including positive pole, negative pole, is interval between the positive pole and the negative pole
Porous polymer barrier film and electrolyte, the negative pole is the above-mentioned negative electrode of lithium ion battery being previously mentioned.
Relative to current lithium ion battery negative material system, negative electrode of lithium ion battery of the invention and described lithium from
Sub- battery has the characteristics that：One, low thermal expansion, due on water-soluble polymeric binder-polyethyleneimine its molecular structure
In the presence of substantial amounts of polar group, so as between negative electrode active material layer and negative current collector and inside negative electrode active material layer
Stronger bonding force is provided between particle, and the bonding force being consequently formed is difficult to be destroyed and influenceed in the presence of electrolyte
Bond effect.In addition, caused activity in charge and discharge process can be buffered in viscoelastic water milk type polymer binding agent
The Volume Changes of material so that the original bond power and electrode interior knot of binding agent can be also maintained after expansion and contraction
Structure.So both combinations maintain Stability Analysis of Structures of the negative electrode active material layer in the long-term cyclic process of battery on the whole
Property, reduce the expansion rate of battery.
Two, Low ESR, high magnification, due to substantial amounts of amine polar group on polyethyleneimine molecular structure be present, these
The very strong polar group of electron donation helps to increase the dissociation of lithium salts and is complexed with lithium cation, and poly- second
Alkene imines has relatively low glass transition temperature, and its molecule segment has enough compliances, can aid in improve lithium from
The sub conduction in electrode interior, the polarization in charge and discharge process is reduced, improves battery efficiency.In addition, the interworking of two kinds of adhesives
Using the overall consumption that can reduce inert binder, reduction impedance can also be equally realized, improves the effect of battery efficiency.
Three, good long circulating characteristic, except the combination of two kinds of adhesives maintains negative electrode active material layer on the whole
Structural stability in the long-term cyclic process of battery, beyond the cyclical stability for improving battery, polyethyleneimine amine molecule knot
A large amount of amidos on structure can also consume electrolyte caused acidic by-products in cyclic process（Such as, hydrofluoric acid etc.）, due to
These accessory substances can have a strong impact on the stability of circulating battery, so equally there is use of polyethyleneimine in terms of this
The stability circulated for a long time beneficial to battery.
Brief description of the drawings
Fig. 1 is the embodiment of the present invention 1 and the rebound curves of battery cathode pole piece thickness in manufacturing process of comparative example 1
Figure.
Fig. 2 is for the battery of the embodiment of the present invention 1 and comparative example 1 in normal temperature environment discharge capacity to discharge current curves
Figure.
Fig. 3 be the embodiment of the present invention 1 and comparative example 1 battery under normal temperature environment battery core thickness rebound rate during loop test
Curve map.
Fig. 4 be the embodiment of the present invention 1 and comparative example 1 battery under normal temperature environment battery core capability retention during loop test
Curve map.
Embodiment
The present invention and its advantage are described in detail with reference to the accompanying drawings and detailed description, but the present invention
Embodiment not limited to this.
Embodiment 1, a kind of negative electrode of lithium ion battery, including negative current collector and the negative electrode active for being coated on negative current collector
Material layer, negative electrode active material layer include negative electrode active material, conductive agent, polymer viscosifier, water milk type polymer binding agent
With water-soluble polymeric binder, water-soluble polymeric binder is polyethyleneimine, and water milk type polymer binding agent and
The weight rate of water-soluble polymeric binder is 10：90~90：10.
The preparation of negative pole：Cathode size formula is based on siccative percentage by weight, by 2% SBR emulsion, 1.5% polyethylene
Imines, 0.5% sodium carboxymethylcellulose, 1% conductive black, the wherein part of 95% negative electrode active material five composition, negative electrode active material
Using Delanium, the weight average molecular weight of polyethyleneimine is about 500 g/mol, and its mass concentration is the pH value of 5% aqueous solution
In the range of 9~12, the substitution value of sodium carboxymethylcellulose in the range of 0.8~1.0, its mass concentration be 1% it is water-soluble
Viscosity of the liquid at 25 DEG C is in the range of 1000~3000mPa.s.In slurry configuration process, solvent is deionized water, and water accounts for
The 60% of total stock quality.
Deionized water and sodium carboxymethylcellulose are added in mixer grinder by formula more than first, molten under vacuo
Solution is complete, obtains aqueous polymer solution, then conductive black is added in the aqueous polymer solution dissolved by formula,
Quick agitation grinding to fineness is less than 5 μm, then adds graphite by formula, scattered to stir, and finally vacuumizes removing gas
Bubble.Required cathode size is obtained with the filtering of 150 mesh stainless steel mesh.
The manufactured slurry is equably coated in the copper foil two sides that thickness is 8 μm, then pole piece is compacted to one with roll squeezer
Determine thickness, cut-parts, soldering polar ear, obtain cathode pole piece.
Preferably, polyethyleneimine is aziridine, the homopolymer of aziridine mixture or aziridine mixture
Copolymer, wherein also including polyethyleneimine, the macromolecular structure of polyethyleneimine includes line style, branched chain type and hyperbranched type.
Polyethyleneimine macromolecular includes primary amino radical, secondary amino group and tertiary amino, and relative to amino total amount, primary amino radical rubs
Your ratio is more than 20%, and the molar ratio of secondary amino group is more than 20%, and the molar ratio of tertiary amino is within 60%.
The preparation of positive pole：Positive pole selects cobalt acid lithium（LiCoO2）For active material, fed intake according to formula and prepare anode sizing agent.
Designed by anode formula, slurry solids composition includes 92% positive active material, 4% Kynoar（PVDF）Binding agent,
And 4% conductive black.Anode sizing agent uses 1-METHYLPYRROLIDONE（NMP）As dispersion solvent, the solids content of slurry is
45%。
1-METHYLPYRROLIDONE and Kynoar are added in mixer grinder by proportioning described above, are sufficiently stirred
Dissolving obtains the polymer solution of Kynoar.Conductive black is added by formula again the Kynoar dissolved to gather
In polymer solution, quick agitation grinding to fineness is less than 5 μm, then adds cobalt acid lithium by formula, scattered to stir, finally
Vacuumize removing bubble.Required anode sizing agent is obtained with the filtering of 150 mesh stainless steel mesh.
The manufactured slurry is equably coated in the aluminium foil two sides that thickness is 12 μm, then pole piece is compacted to one with roll squeezer
Determine thickness, cut-parts, soldering polar ear, obtain anode pole piece.
Polymeric barrier films are from the polyethylene that thickness is 14 μm（PE）Perforated membrane.
The preparation of electrolyte：By ethylene carbonate EC, propene carbonate PC and dimethyl carbonate DMC according to volume ratio 3：3：
4 are configured to mixed solvent, then add lithium salts lithium hexafluoro phosphate（LiPF6）, the concentration for preparing LiPF6 is 1M, is stirred
After obtain electrolyte.
The assembling of battery：Above-mentioned anode pole piece, polymeric barrier films and cathode pole piece are wound into battery core, aluminum-plastic composite membrane
Encapsulation, vacuum state baking inject quantitative electrolyte after removing moisture, battery are melted into and volume test, obtain thick wide long
Respectively 3.6mm, 28mm, 92mm square soft-packaged polymer lithium ion battery.
A kind of lithium ion battery, including positive pole, negative pole, the porous polymer barrier film being interval between positive pole and negative pole
And electrolyte, the negative pole are above-mentioned prepared cathode pole piece.
Embodiment 2, as different from Example 1：The preparation process of the present embodiment negative pole is that cathode size formula presses siccative
Percentage by weight meter, by 2% acrylonitrile-butadiene rubber latex, 1.5% butadiene rubber latex, 2% polyethyleneimine, 0.5% carboxymethyl cellulose
Element, 1% carbon fiber, the part of 93% negative electrode active material five composition, wherein negative electrode active material uses native graphite and graphitized carbon
Fiber, the weight average molecular weight of polyethyleneimine is about 100,000g/mol, its mass concentration be 5% aqueous solution pH value 9~
In the range of 12, the substitution value of carboxymethyl cellulose is in the range of 0.8-1.0, and the aqueous solution that its mass concentration is 1% is at 25 DEG C
Under viscosity in the range of 1000-3000mPa.s.In slurry configuration process, solvent is deionized water, and water accounts for total stock quality
60%.
Deionized water and carboxymethyl cellulose are added in mixer grinder by formula more than first, are dissolved under vacuo
Completely, aqueous polymer solution is obtained, then carbon fiber is added in the aqueous polymer solution dissolved by formula, quickly
Agitation grinding to fineness is less than 5 μm, then adds native graphite and graphitized carbon fibre by formula, scattered to stir, most
After vacuumize removing bubble.Required cathode size is obtained with the filtering of 150 mesh stainless steel mesh.
The manufactured slurry is equably coated in the copper foil two sides that thickness is 8 μm, then pole piece is compacted to one with roll squeezer
Determine thickness, cut-parts, soldering polar ear, obtain cathode pole piece.
It is other same as Example 1, it is not repeated herein.
Embodiment 3, as different from Example 2：The preparation process of the present embodiment negative pole is that cathode size formula presses siccative
Percentage by weight meter, by 2% butadiene rubber latex, 2% polyethyleneimine, 1% hydroxyethyl cellulose, 1% CNT, 94% negative
The part of pole active material five forms, and wherein negative electrode active material uses graphitized intermediate-phase carbon microballon and amorphous carbon, polyethylene
The weight average molecular weight of imines is about 5,000 g/mol, its mass concentration be the pH value of 5% aqueous solution in the range of 9~12,
In the range of 0.8-1.0, viscosity of the aqueous solution at 25 DEG C that its mass concentration is 1% exists the substitution value of hydroxyethyl cellulose
In the range of 1000-3000mPa.s.In slurry configuration process, solvent is deionized water, and water accounts for the 60% of total stock quality.
Deionized water and hydroxyethyl cellulose are added in mixer grinder by formula more than first, are dissolved under vacuo
Completely, aqueous polymer solution is obtained, then CNT is added in the aqueous polymer solution dissolved by formula, soon
Fast agitation grinding to fineness is less than 5 μm, then adds graphitized intermediate-phase carbon microballon and amorphous carbon by formula, disperses stirring
Uniformly, removing bubble is finally vacuumized.Required cathode size is obtained with the filtering of 150 mesh stainless steel mesh.
The manufactured slurry is equably coated in the copper foil two sides that thickness is 8 μm, then pole piece is compacted to one with roll squeezer
Determine thickness, cut-parts, soldering polar ear, obtain cathode pole piece.
It is other same as Example 2, it is not repeated herein.
Embodiment 4, as different from Example 3：The preparation process of the present embodiment negative pole is that cathode size formula presses siccative
Percentage by weight meter, lived by 2% chloroprene rubber emulsion, 2% polyethyleneimine, 1% polyacrylic acid, 1% graphene, 94% negative pole
Property the part of material five composition, wherein negative electrode active material uses amorphous carbon, silicon and silica, the Weight-average molecular of polyethyleneimine
Amount be about 20,000 g/mol, its mass concentration be 5% the aqueous solution pH value in the range of 9~12, the substitution of polyacrylic acid
Spend in the range of 0.8-1.0, model of viscosity of the aqueous solution that its mass concentration is 1% at 25 DEG C in 1000-3000mPa.s
In enclosing.In slurry configuration process, solvent is deionized water, and water accounts for the 60% of total stock quality.
Deionized water and polyacrylic acid are added in mixer grinder by formula more than first, have been dissolved under vacuo
Entirely, aqueous polymer solution is obtained, then graphene is added in the aqueous polymer solution dissolved by formula, is quickly stirred
Mix and be ground to fineness as less than 5 μm, then add amorphous carbon, silicon and silica by formula, it is scattered to stir, finally take out true
Sky removing bubble.Required cathode size is obtained with the filtering of 150 mesh stainless steel mesh.
The manufactured slurry is equably coated in the copper foil two sides that thickness is 8 μm, then pole piece is compacted to one with roll squeezer
Determine thickness, cut-parts, soldering polar ear, obtain cathode pole piece.
It is other same as Example 3, it is not repeated herein.
Embodiment 5, as different from Example 4：The preparation process of the present embodiment negative pole is that cathode size formula presses siccative
Percentage by weight meter, by 1.5% ethylene-propylene-diene monomer latex solution, 1.5% polyethyleneimine, 0.5% polyvinyl alcohol, 1% conductive black,
The part of 95.5% negative electrode active material five forms, and wherein negative electrode active material uses tin oxide, the weight average molecular weight of polyethyleneimine
About 300,000 g/mol, its mass concentration be 5% the aqueous solution pH value in the range of 9~12, the substitution of polyvinyl alcohol
Spend in the range of 0.8-1.0, model of viscosity of the aqueous solution that its mass concentration is 1% at 25 DEG C in 1000-3000mPa.s
In enclosing.In slurry configuration process, solvent is deionized water, and water accounts for the 60% of total stock quality.
Deionized water and polyvinyl alcohol are added in mixer grinder by formula more than first, have been dissolved under vacuo
Entirely, aqueous polymer solution is obtained, then conductive black is added in the aqueous polymer solution dissolved by formula, quickly
Agitation grinding to fineness is less than 5 μm, then adds tin oxide by formula, scattered to stir, and finally vacuumizes removing bubble.
Required cathode size is obtained with the filtering of 150 mesh stainless steel mesh.
The manufactured slurry is equably coated in the copper foil two sides that thickness is 8 μm, then pole piece is compacted to one with roll squeezer
Determine thickness, cut-parts, soldering polar ear, obtain cathode pole piece.
It is other same as Example 4, it is not repeated herein.
Embodiment 6, as different from Example 5：The preparation process of the present embodiment negative pole is that cathode size formula presses siccative
Percentage by weight meter, by 1.5% acrylic rubber emulsion, 1.5% polyethyleneimine, 0.5% sodium carboxymethylcellulose, 1% conduction
Carbon black, the part of 95.5% negative electrode active material five composition, wherein negative electrode active material uses tin alloy compound, polyethyleneimine
Weight average molecular weight be about 1,000,000 g/mol, its mass concentration be the pH value of 5% aqueous solution in the range of 9~12,
The substitution value of sodium carboxymethylcellulose is in the range of 0.8-1.0, viscosity of the aqueous solution at 25 DEG C that its mass concentration is 1%
In the range of 1000-3000mPa.s.In slurry configuration process, solvent is deionized water, and water accounts for the 60% of total stock quality.
Deionized water and sodium carboxymethylcellulose are added in mixer grinder by formula more than first, molten under vacuo
Solution is complete, obtains aqueous polymer solution, then conductive black is added in the aqueous polymer solution dissolved by formula,
Quick agitation grinding to fineness is less than 5 μm, then adds tin alloy compound by formula, scattered to stir, and is finally taken out true
Sky removing bubble.Required cathode size is obtained with the filtering of 150 mesh stainless steel mesh.
The manufactured slurry is equably coated in the copper foil two sides that thickness is 8 μm, then pole piece is compacted to one with roll squeezer
Determine thickness, cut-parts, soldering polar ear, obtain cathode pole piece.
It is other same as Example 5, it is not repeated herein.
Comparative example 1, cathode size formula is based on siccative percentage by weight, by 4% SBR emulsion, 1% carboxymethyl cellulose
Plain sodium, 1% conductive black, the part of 94% negative electrode active material four composition, wherein negative electrode active material uses Delanium, carboxymethyl
The substitution value of sodium cellulosate is in the range of 0.8-1.0, and viscosity of the aqueous solution at 25 DEG C that its mass concentration is 1% is in 1000-
In the range of 3000mPa.s.In slurry configuration process, solvent is deionized water, and water accounts for the 60% of total stock quality.
It is other same as Example 1, it is not repeated herein.
The present invention is tested as follows：(1) the cohesive force test in electrode between active material and adhesive：Take respectively
The cathode pole piece of embodiment 1 to 6 and comparative example 1 after cold pressing, every group of 5 pole pieces, is cut into the test of 20mm × 10cm sizes
Batten, by using the green adhesive tapes of the wide PET of 20mm（Adhesion strength 0.1N/mm）180 are carried out to it on measurer for pulling forceoPeel off
Test, puller system draw speed is 50mm/min.As a result it is recorded in table 1.
(2) the adhesion test in electrode between active material and collector：Take respectively cold pressing after embodiment 1 to 6 and
The cathode pole piece of comparative example 1, every group of 5 pole pieces, the test bars of 20mm × 10cm sizes are cut into, with wide two-sided of 20mm
Glue（Adhesion strength 0.7N/mm）It is adhered on the stainless steel plate of cleaning.180 are carried out to it using measurer for pulling forceoPeel test,
Puller system draw speed is 50mm/min.As a result it is recorded in table 1.
(3) the membrane resistance test of pole piece：Resistance test is carried out to the cathode membrane of embodiment 1 to 6 and comparative example 1,
Acquired results are recorded in table 1.
。
As it can be seen from table 1 negative electrode of lithium ion battery of the present invention employs water-soluble, water milk type polymer binding agent is answered
It is interior between active material and adhesive in electrode after zoarium system compared with single water milk type polymer is as the negative pole of binding agent
Adhesion in poly- power and electrode between active material and collector is significantly improved, and membrane resistance is in relatively low water
It is flat.
(4) pole piece bounce-back test：After being cold-pressed to the cathode membrane of embodiment 1 to 6 and comparative example 1, miking is used
Pole piece thickness, and mark is carried out in measurement position and pole piece, as pole piece original depth.In follow-up battery core manufacturing process
In, successively before pole piece coiling, Battery formation to 3.85V, to be completely charged to several stages such as 4.2V after volume test identical before this
Position measurement negative plate thickness situation of change, calculate the rebound rate of negative plate thickness under different conditions, acquired results are listed in
Fig. 1.
As shown in Figure 1, negative electrode of lithium ion battery of the present invention employs water-soluble, the complex of water milk type polymer binding agent
After system compared with single water milk type polymer is as the negative pole of binding agent, the rebound rate of negative plate thickness has dropped under same stage
It is low.This feature also ensures that battery core thickness may remain within design specification, is more beneficial for battery volume energy density
Stabilization.
(5) battery cryogenic property is tested：Example 1 and the lithium ion battery of comparative example 1 are sample respectively, in 10oC
Under environment, circulated 10 times with 0.7C/0.5C charge-discharge magnification, be finally completely charged to 4.2V, then disassemble battery, observe cathode pole piece
The analysis lithium situation on surface.As a result show：The cathode pole piece surface of embodiment 1 does not find the precipitation of simple substance lithium metal, and contrasts
Example 1 then has the phenomenon that obviously simple substance lithium metal separates out.This phenomenon illustrates the cathode pole piece of embodiment 1 in low-temperature condition
There is down more preferable dynamic performance.
(6) battery discharge multiplying power is tested：Example 1 and the lithium ion battery of comparative example 1 are sample respectively, 25oC
Charged under environment with 0.5C multiplying powers, measure the battery capacity discharged with 0.2C, 0.5C, 1.0C, 2.0C different multiplying successively,
Acquired results are listed in Fig. 2.As seen from Figure 2, the battery high rate performance of embodiment 1 is higher than the forthright again of the battery of comparative example 1
Energy.Polarization of the cathode pole piece of this explanation embodiment 1 in discharge process is smaller, has more preferable dynamic performance.
(7) thickness swelling and cycle performance test during circulating battery：Example 1 and comparative example 1 respectively
Lithium ion battery be sample, carry out circulating battery thickness swelling and cycle performance test：Before circulating battery, using high metric
Thickness of the battery under 3.85V voltage status is tested, is denoted as battery original thickness.Then 25oUnder C environment, with 0.7C/0.5C
Charge-discharge magnification to battery carry out loop test.In cyclic process, battery is measured under first time fully charged state 4.2V voltage,
Thickness after every 50 circulations under battery fully charged state backward, until the 500th circulation, is shown in Fig. 3.Obtain circulating battery mistake simultaneously
Capacity attenuation curve in journey, is shown in Fig. 4.
Cell expansion rate=（4.2V cell thickness/3.85V batteries initial thickness -1）× 100%, as shown in Figure 3：Identical
Under cycle-index, the cell thickness expansion rate of embodiment 1 is significantly less than the battery of comparative example 1.The result shows embodiment 1
Negative pole employ water-soluble, water milk type polymer binding agent compound system latter two binding agent combination preferably maintain it is negative
Structural stability of the pole active material layer in the long-term cyclic process of battery, reduce the expansion rate of battery.Meanwhile as Fig. 4 can
Know：The battery of embodiment 1 still maintains 90% initial capacity after circulating 500 times, hence it is evident that higher than the battery of comparative example 1.
It can be seen that lithium battery of the invention has more preferable long circulation life.
In summary, negative electrode of lithium ion battery of the invention has viscoelastic water milk type polymer using butadiene-styrene rubber class
The interworking system of binding agent and polyethyleneimine amine water-soluble polymeric binder, can significantly improve negative electrode active material layer with
Cohesive force between negative current collector and between negative electrode active material layer internal particle, exist so as to improve negative electrode active material layer
Structural stability in the long-term cyclic process of battery, and the usage amount of the polymeric binder of electrochemicaUy inert is reduced, so as to drop
Cubical expansivity of the low battery in cyclic process, improve low temperature, multiplying power, cycle performance and the energy of polymer Li-ion battery
Density.
The announcement and teaching of book according to the above description, those skilled in the art in the invention can also be to above-mentioned embodiment party
Formula is changed and changed.Therefore, the invention is not limited in above-mentioned embodiment, every those skilled in the art exist
Made any conspicuously improved, replacement or modification belong to protection scope of the present invention on the basis of the present invention.This
Outside, although having used some specific terms in this specification, these terms merely for convenience of description, not to the present invention
Form any restrictions.
Claims (15)
1. a kind of negative electrode of lithium ion battery, including negative current collector and the negative electrode active material for being coated on the negative current collector
Layer, the negative electrode active material layer include negative electrode active material, conductive agent, polymer viscosifier, water milk type polymer binding agent
With water-soluble polymeric binder, it is characterised in that：The water-soluble polymeric binder is polyethyleneimine, and the water
The weight rate of newborn type polymeric binder and the water-soluble polymeric binder is 10：90~90：10；The polyethyleneimine
Amine is the copolymer of aziridine, the homopolymer of aziridine mixture or aziridine mixture, the polyethyleneimine
Macromolecular structure includes branched chain type and hyperbranched type.
2. negative electrode of lithium ion battery according to claim 1, it is characterised in that：The water milk type polymer binding agent is fourth
At least one in benzene rubber, nitrile rubber, butadiene rubber, chloroprene rubber, ethylene propylene diene rubber and acrylic rubber
Kind.
3. negative electrode of lithium ion battery according to claim 2, it is characterised in that：The water milk type polymer binding agent accounts for institute
The percentage by weight for stating negative electrode active material layer gross weight is 0.5~10%.
4. negative electrode of lithium ion battery according to claim 3, it is characterised in that：The water milk type polymer binding agent accounts for institute
The percentage by weight for stating negative electrode active material layer gross weight is 0.5~3%.
5. negative electrode of lithium ion battery according to claim 1, it is characterised in that：The polyethyleneimine accounts for the negative pole and lived
Property material layer gross weight percentage by weight be 0.5~10%.
6. negative electrode of lithium ion battery according to claim 5, it is characterised in that：The polyethyleneimine accounts for the negative pole and lived
Property material layer gross weight percentage by weight be 0.5~3%.
7. negative electrode of lithium ion battery according to claim 1, it is characterised in that：The weight average molecular weight of the polyethyleneimine
For 500~1,000,000g/mol.
8. negative electrode of lithium ion battery according to claim 7, it is characterised in that：The weight average molecular weight of the polyethyleneimine
For 5,000~500,000g/mol.
9. negative electrode of lithium ion battery according to claim 1, it is characterised in that：The polyethyleneimine macromolecular includes
Primary amino radical, secondary amino group and tertiary amino, relative to amino total amount, the molar ratio of primary amino radical is more than 20%, the mol ratio of secondary amino group
Rate is more than 20%, and the molar ratio of tertiary amino is within 60%.
10. negative electrode of lithium ion battery according to claim 1, it is characterised in that：The water of the concentration of polyethyleneimine 5%
The pH value of solution is 9~12.
11. negative electrode of lithium ion battery according to claim 1, it is characterised in that：The negative electrode active material is natural stone
Ink, Delanium, graphitized carbon fibre, graphitized intermediate-phase carbon microballon, amorphous carbon, silicon, silica, tin oxide and tin alloy
At least one of compound.
12. negative electrode of lithium ion battery according to claim 1, it is characterised in that：The conductive agent is conductive black, carbon fibre
At least one of dimension, CNT and graphene.
13. negative electrode of lithium ion battery according to claim 1, it is characterised in that：The polymer viscosifier is carboxymethyl
At least one of sodium cellulosate, hydroxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid and polyvinyl alcohol.
14. negative electrode of lithium ion battery according to claim 11, it is characterised in that：The negative electrode active material accounts for described negative
The percentage by weight of pole active material layer gross weight is 90~99.5%.
15. a kind of lithium ion battery, including positive pole, negative pole, the porous polymerizing being interval between the positive pole and the negative pole
Thing barrier film and electrolyte, it is characterised in that：The negative pole is the lithium ion battery described in any one of claim 1 to 14
Negative pole.
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| CN112201787A (en) * | 2020-09-16 | 2021-01-08 | 深圳大学 | High-capacity negative electrode bonding system, negative electrode and lithium ion battery |
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