Summary of the invention
The technical problem that the present invention solves is to provide a kind of secondary cell collector; Coating modified through collection liquid surface being carried out Graphene; Reduced the contact resistance between collector and active material, improved cohesive force between the two, the final comprehensive lifting that realizes battery performance.
The invention discloses a kind of collector, comprise the collector foil, said collector foil has the coating of graphitiferous alkene and binding agent on the one side at least.
The invention also discloses a kind of preparation method of collector, comprising:
Graphene and binding agent are disperseed in solvent, form slurry; Said slurry coating at least one surface of collector foil, is formed the coating that contains Graphene and binding agent; Carry out drying then.
Preferably, the mass ratio of said Graphene and binding agent is (1~49): 1.
Preferably, the number of plies of said Graphene is an individual layer or between 1~30 layer; Carbon content>the 95wt% of said Graphene, the body conductance>100S/cm of said Graphene.
Preferably, the method for said dispersion be stirring, high speed shear, emulsification and ultrasonic in one or more.
Preferably, said solvent is water, water and ethanol mixed solvent or N-methyl pyrrolidone.
Preferably, also comprise after the said step that Graphene and binding agent are disperseed in solvent: deaeration is handled and is sieved.
Preferably, said solid content of slurry is 0.2~20wt%, and the viscosity of said slurry is 50~5000mPas.
Preferably, the thickness of said coating is 0.005~10 micron.
Preferably, said coating is 30%~100% in the coverage rate on collector foil surface.
Preferably, said coating also comprises one or more in graphite, carbon black, acetylene black, CNT, the carbon fiber.
The invention provides a kind of preparation method of collector, compared with prior art, the collection liquid surface of preparing according to method provided by the invention has the coating of graphitiferous alkene and binding agent.The graphene conductive performance is very excellent in the coating, and its conductivity can reach 10
6S/cm can strengthen the conductivity between collector and the active material, reduces the internal resistance of battery; Simultaneously because exclusive two-dimentional laminar structured of Graphene; Make Graphene form even, fine and close coating on collector foil surface; Improved Graphene greatly in collector foil surface contact area; Increase active material and contact, can reduce the interface resistance between collector and the active material effectively, the reduction internal resistance with conduction between the collector; Be tiled between the Graphene lamella of collection liquid surface and and the collector foil between contact area big; Interaction force is strong; Difficult drop-off, adhesion strength is strong, and the disengaging between active material and collector can not take place in charging and discharging process; Help reducing internal resistance, thereby improve the performance of battery comprehensively.
Embodiment
In order further to understand the present invention, below in conjunction with embodiment the preferred embodiment of the invention is described, describe just to further specifying feature and advantage of the present invention but should be appreciated that these, rather than to the restriction of claim of the present invention.
The embodiment of the invention discloses a kind of secondary cell collector, comprise the collector foil, said collector foil has the coating of graphitiferous alkene and binding agent on the one side at least.Said collector foil is preferably Copper Foil or aluminium foil.
As preferred version, the content of Graphene is 50wt%~98wt% in the said coating.The effect of binding agent in coating be make Graphene can firm attachment on collector, be unlikely in use to come off.Binding agent is originally as insulator, and addition can influence the conductivity of Graphene coating.Therefore, the addition of binding agent is preferably 2wt%~50wt%, too much can cause the collector too high in resistance, and I haven't seen you for ages excessively influences the adhesion strength of Graphene coating.Said binding agent is preferably one or more in sodium carboxymethylcellulose, Kynoar, polytetrafluoroethylene, butadiene-styrene rubber and the LA series binding agent.
The present invention also provides a kind of preparation method of secondary cell collector, comprising: Graphene and binding agent are disperseed in solvent, form slurry; Said slurry coating at least one surface of collector foil, is formed the coating that contains Graphene and binding agent; Carry out drying then.
In order to make coating have good electrical conductivity, as preferred version, the mass ratio of above-mentioned Graphene and binding agent is (1~49): 1; The number of plies of said Graphene is preferably between individual layer or 1~30 layer, is sp in the layer
2Carbon atom six sides of hydridization are tightly packed, the coating carbon material that interlayer combines with the π key; Carbon content>the 95wt% of Graphene, bulk conductivity>100S/cm.Said binding agent is preferably one or more in sodium carboxymethylcellulose, Kynoar, polytetrafluoroethylene, butadiene-styrene rubber and the LA series binding agent.
In the preparation method of collector, the method for above-mentioned dispersion is preferably stirring, high speed shear, emulsification, in ultrasonic one or more.In order to make in the coating Graphene and binding agent more tiny evenly, as preferred version, also comprise after the above-mentioned step that Graphene and binding agent are disperseed in solvent: deaeration is handled and is sieved, thereby guarantees the coating of formation even compact on the collector foil.According to the present invention, above-mentioned slurry can apply through coating process, and said coating process is preferably coating machine coating, casting, dip coating or printing.Continuous or discrete application pattern can be preferably adopted in said coating.The temperature of above-mentioned drying is preferably 30~200 ℃.As preferred version, said drying can be right after coating process carries out synchronously, also can be dry in the lump after coating finishes.
In the preparation method, said solvent is preferably water, water and ethanol mixed solvent or n-formyl sarcolysine base pyrrolidones, and the mass ratio of water and ethanol is preferably (20~400) in said water and the alcohol mixed solvent: 1, more preferably (50~300): 1.Said solid content of slurry is preferably 0.2~20wt%; The viscosity of said slurry is preferably 50~5000mPas; 500~1000mPas more preferably; The viscosity of slurry too little or too big city influence the coating or the printing performance of slurry, the uniformity of coating and continuity are affected, even can't be coated with or print.In order to make coating have better conductivity, the present invention also can add other electric conducting materials in solvent, is preferably in graphite, carbon black, acetylene black, CNT, the carbon fiber one or more.
According to the present invention, coating is as the non-active material in the electrode, and itself can reduce the energy density of battery along with the increase of coating layer thickness on the contrary for the not contribution of capacity of battery, and therefore, in theory, coating is to get over Bao Yuehao.But, might adverse effect be arranged to its performance along with the coating attenuate.For the material with carbon element of routine, the scope of conductive coating is usually at one micron to tens microns.And for Graphene, because the distinguished two-dimensional structure of Graphene even its thickness has only tens to the hundreds of nanometer, can both play good effect, the thickness of coating of the present invention is preferably 0.005~10 micron, more preferably 0.1~5 micron.Coating is preferably 30%~100% in the coverage rate on collector foil surface.
The present invention has prepared the secondary cell collector, and at least one mask of the collector foil of preparation has the coating of graphitiferous alkene and binding agent, because the electric conductivity of Graphene is excellent; Greatly strengthened the conductivity between collector and active material, the exclusive two-dimensional structure of Graphene makes Graphene can form the coating of even compact on collector foil surface simultaneously; Having increased collector contacts with conduction between active material; Reduced interface resistance, and be tiled between the Graphene lamella on collector foil surface and and the collector foil between contact area big, interaction force is strong; Difficult drop-off, adhesion strength is strong.Therefore can improve the performance of battery effectively through the coating that has Graphene in collector foil surface applied.
In order further to understand the present invention, below in conjunction with embodiment the preparation method of collector provided by the invention is described in detail, protection scope of the present invention is not limited by the following examples.
Embodiment 1
Taking by weighing the 2g sodium carboxymethylcellulose joins in the 1000g deionized water; The employing mixer mixes, and then adding 40g Graphene slurry mixes graphitiferous alkene 8g in the Graphene slurry; Add the 2000g deionized water and regulate slurry viscosity; Viscosity Control is 800mPas, adds 30g ethanol at last and carries out low speed vacuum stirring deaeration processing, crosses 150 eye mesh screens and obtains slurry; This slurry is coated on aluminium foil surface uniformly through the transfer type coating machine, and in air dry oven, dries, obtaining the single face coating layer thickness is the graphene conductive coating of 500 nanometers.
Adopting the peeling strength test machine to record peel strength above-mentioned prepared collector is 0.5N, and adopting the resistivity of four probe method test pole piece is 4.553E
-6Ohm.cm.
Fig. 1 is the structural representation of the collector of embodiment 1 preparation, and this sketch map comprises tinsel 1 and be overlying on said tinsel 1 coating surfaces 2 that coating comprises Graphene and binding agent.
Collection liquid surface to present embodiment preparation scans, and Fig. 2 is the sem photograph of graphene conductive coating, as can be seen from the figure, and the densification that on the collector foil, is evenly distributed of graphene conductive coating.
Embodiment 2
Taking by weighing the 1.5g sodium carboxymethylcellulose joins in the 1000g deionized water; The employing mixer mixes, and then adds 30g Graphene slurry and 0.5g conductive carbon black (Super P) mixes, and contains the 8g Graphene in the Graphene slurry; Add the 2000g deionized water and regulate slurry viscosity; Viscosity Control is 600mPas, adds 30g ethanol at last and carries out low speed vacuum stirring deaeration processing, crosses 150 eye mesh screens and obtains slurry; This slurry is coated on aluminium foil surface uniformly through the transfer type coating machine, and in air dry oven, dries, obtaining the single face coating layer thickness is the graphene conductive coating of 200 nanometers.
Adopting the peeling strength test machine to record peel strength above-mentioned prepared collector is 0.5N, and adopting the resistivity of four probe method test pole piece is 4.761E
-6Ohm.cm.
Embodiment 3
Take by weighing the 8g graphene powder and join in the 500g n-formyl sarcolysine base pyrrolidones and to soak 8 hours, ultrasonic dispersion 10 minutes, supersonic frequency is 15KHz; Taking by weighing the 2g Kynoar joins in the 1000g n-formyl sarcolysine base pyrrolidones; The employing mixer mixes; And then the Graphene slurry mixes after adding the ultrasonic dispersion of 508g; Add 1500g n-formyl sarcolysine base pyrrolidones then and regulate slurry viscosity, viscosity Control is 1000mPas, crosses 150 eye mesh screens and obtains slurry; This slurry is coated on aluminium foil surface uniformly through the transfer type coating machine, and in air dry oven, dries, obtaining the single face coating layer thickness is the graphene conductive coating of 200 nanometers.
Adopting the peeling strength test machine to record peel strength above-mentioned prepared collector is 0.25N, and adopting the resistivity of four probe method test pole piece is 5.653E
-6Ohm.cm.
Embodiment 4
Take by weighing the 8g graphene powder and join in the 500g n-formyl sarcolysine base pyrrolidones and to soak 8 hours, ultrasonic then dispersion 10 minutes, supersonic frequency is 15KHz; Taking by weighing the 1.5g Kynoar adds in the 1000g n-formyl sarcolysine base pyrrolidones; The employing mixer mixes; Add 0.5g SP and mix, and then the 508g Graphene slurry that adds after the ultrasonic dispersion mixes adding 1500g n-formyl sarcolysine base pyrrolidones adjusting slurry viscosity; Viscosity Control is 1000mPas, crosses 150 eye mesh screens and obtains slurry; This slurry is coated on aluminium foil surface uniformly through the transfer type coating machine, and in air dry oven, dries, obtaining the single face coating layer thickness is the graphene conductive coating of 500 nanometers.
Adopting the peeling strength test machine to record peel strength above-mentioned prepared collector is 0.25N, and adopting the resistivity of four probe method test pole piece is 5.362E
-6Ohm.cm.
Embodiment 5
Taking by weighing 53.3g LA133 (solid content is 15%) joins in the 1100g deionized water; The employing mixer mixes, and then adds 40g Graphene slurry and mix, and contains the 8g Graphene in the Graphene slurry; Add the 1900g deionized water and regulate slurry viscosity; Viscosity Control is 800mPas, adds 30g ethanol at last and carries out low speed vacuum stirring deaeration processing, crosses 150 eye mesh screens and obtains slurry; This slurry is coated on aluminium foil surface uniformly through the transfer type coating machine, and in air dry oven, dries, obtaining the single face coating layer thickness is the graphene conductive coating of 100 nanometers.
Adopting the peeling strength test machine to record peel strength above-mentioned prepared collector is 0.6N, and adopting the resistivity of four probe method test pole piece is 4.453E
-6Ohm.cm.
Embodiment 6
Taking by weighing the 2g sodium carboxymethylcellulose joins in the 1000g deionized water; The employing mixer mixes, and then adds 40g Graphene slurry and mix, and contains the 8g Graphene in the Graphene slurry; Add the 2000g deionized water and regulate slurry viscosity; Viscosity Control is 800mPas, adds 30g ethanol at last and carries out low speed vacuum stirring deaeration processing, crosses 150 eye mesh screens and obtains slurry; This slurry is coated on copper foil surface uniformly through the transfer type coating machine, and in air dry oven, dries, obtaining the single face coating layer thickness is the graphene conductive coating of 200 nanometers.
Adopting the peeling strength test machine to record peel strength above-mentioned prepared collector is 0.5N, and adopting the resistivity of four probe method test pole piece is 1.353E
-6Ohm.cm.
Embodiment 7
Taking by weighing the 2g sodium carboxymethylcellulose joins in the 1000g deionized water; The employing mixer mixes, and then adds 40g Graphene slurry and mix, and contains the Graphene of 8g in the Graphene slurry; Add the 2000g deionized water and regulate slurry viscosity; Viscosity Control is 200mPas, adds 30g ethanol at last and carries out low speed vacuum stirring deaeration processing, crosses 150 eye mesh screens and obtains slurry; This slurry is coated on aluminium foil surface uniformly through screen process press, and in air dry oven, dries, obtaining the single face coating layer thickness is 200 nanometers, and is the graphene conductive coating of discontinuous gridding, and the Graphene coating is 50% in the coverage rate of aluminium foil surface.
Adopting the peeling strength test machine to record peel strength above-mentioned prepared collector is 0.5N, and adopting the resistivity of four probe method test pole piece is 3.632E
-6Ohm.cm.
Embodiment 8
Taking by weighing the 2g sodium carboxymethylcellulose joins in the 1000g deionized water; The employing mixer mixes, and then adds 40g Graphene slurry and mix, and contains the 8g Graphene in the Graphene slurry; Add the 2000g deionized water and regulate slurry viscosity; Viscosity Control is 200mPas, adds 30g ethanol at last and carries out low speed vacuum stirring deaeration processing, crosses 150 eye mesh screens and obtains slurry; This slurry is coated on aluminium foil surface uniformly through extrusion coater, and in air dry oven, dries, obtaining the single face coating layer thickness is the graphene conductive coating of 100 nanometers.
Adopting the peeling strength test machine to record peel strength above-mentioned prepared collector is 0.5N, and adopting the resistivity of four probe method test pole piece is 4.372E
-6Ohm.cm.
Comparative example 1
The tinsel that employing is buied from market is as collector, and tinsel is an aluminium foil.
Adopt the collector of embodiment 1 to prepare 18650 column type power lithium-ion batteries, be numbered: battery 1; Adopt the collector of Comparative Examples 1 to prepare lithium ion battery simultaneously, be numbered: battery 2.Test the ac impedance spectroscopy of above-mentioned two kinds of battery high magnifications front and back; Test result is as shown in Figure 3; Fig. 3 is the AC impedance spectrogram of battery 1 and battery 2 high magnifications test front and back, and the ■ curve is the AC impedance spectral curve before the test of battery 2 high magnifications among Fig. 3, ● curve is the AC impedance spectral curve after the test of battery 2 high magnifications; ▲ curve is the AC impedance spectral curve before the test of battery 1 high magnification; The ★ curve is the AC impedance spectral curve after the test of battery 1 high magnification, and as can beappreciated from fig. 3, the internal resistance of battery 1 will be lower than the internal resistance of battery 2.
The internal resistance of battery 1 and battery 2 is tested; Test result is as shown in Figure 4, and Fig. 4 is battery 1 and the internal resistance variation diagram of battery 2 in different phase, and the ■ curve is the internal resistance change curve of battery 2 among Fig. 4; ▲ curve is the internal resistance change curve of battery 1; As can beappreciated from fig. 4, the internal resistance of battery 1 reduces by 10%~50% than the internal resistance of battery 2, and the internal resistance of battery 1 changes more steady.
Voltage when battery 1 and battery 2 are discharged under the 5C multiplying power is tested; Test result is as shown in Figure 5; Fig. 5 is battery 1 and the discharge curve of battery 2 under the 5C multiplying power, and curve a is the discharge curve of battery 1 under the 5C multiplying power, and curve b is the discharge curve of battery 2 under the 5C multiplying power; As can beappreciated from fig. 5, battery 1 improves 0.1~0.2V than pressing in the discharge of battery 2 under the 5C multiplying power.
The surface temperature variation that battery 1 and battery 2 discharge under the 5C multiplying power is tested; Test result is as shown in Figure 6; Fig. 6 is battery 1 a battery surface variations in temperature when discharging under the 5C multiplying power with battery 2, and curve a is the surface temperature change curve that battery 2 discharges under the 5C multiplying power among Fig. 6, and curve b is the surface temperature change curve that battery 1 discharges under the 5C multiplying power; Surface temperature when as can beappreciated from fig. 6, battery 1 discharges under the 5C multiplying power than battery 2 fully reduces more than 20 ℃.
Battery 1 and battery 2 are tested-20 ℃ of following discharge capacities; Test result is as shown in Figure 7; Fig. 7 is battery 1 and the discharge curve of battery 2 in the time of-20 ℃, and curve a is the discharge curve of battery 1 in the time of-20 ℃ among Fig. 7, and curve b is the discharge curve of battery 2 in the time of-20 ℃.As can be seen from Figure 7, battery 1 promotes more than 20% than battery 2-20 ℃ of following discharge capacities.
Can know from above test result, adopt in the battery use of collector preparation of the present invention, for the battery that adopts conventional collector preparation; Internal resistance stability better; Reduced internal resistance, strengthened cyclical stability, the performance of battery is improved.
The explanation of above embodiment just is used for helping to understand method of the present invention and core concept thereof.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 carry out some improvement and modification to the present invention, these improvement and modification also fall in the protection range of claim of the present invention.
To the above-mentioned explanation of the disclosed embodiments, make this area professional and technical personnel can realize or use the present invention.Multiple modification to these embodiment will be conspicuous concerning those skilled in the art, and defined General Principle can realize under the situation that does not break away from the spirit or scope of the present invention in other embodiments among this paper.Therefore, the present invention will can not be restricted to these embodiment shown in this paper, but will meet and principle disclosed herein and features of novelty the wideest corresponding to scope.