CN103311500A - Lithium-ion battery negative pole piece and production method - Google Patents

Abstract

The invention discloses a lithium-ion battery negative pole piece and a production method. The negative pole piece comprises a first coating which is coated with an active substance, a second coating which is arranged on the surface of the first coating, and a third coating which is arranged on the surface of the second coating, wherein the second coating is a ceramic diaphragm coating, and the thickness of the second coating is 10 to 25 microns; the third coating is a porous polyvinylidene fluoride (PVDF) coating, and the thickness of the third coating is 2 to 6 microns. The lithium-ion battery negative pole piece solves the problems that the ceramic material directly coated on the pole piece drops off easily, high in brittleness and poor in binding property, the lithium dendritic crystal can be avoided in over-charging and over-discharging, the negative pole piece can be prevented from being separated from stripping caused by inflation in the charging-discharging process, so that the safety performance of the lithium battery can be improved.

Description

Negative pole piece of lithium ion battery and manufacturing method thereof

technical field

The invention relates to the technical field of lithium-ion batteries, in particular to a lithium-ion battery negative pole piece and a manufacturing method.

Background technique

At present, the energy crisis has become the most serious problem in the 21st century, and it has become an inevitable development trend that non-renewable fossil energy will be replaced by green energy. Lithium-ion batteries have the advantages of high energy density, long cycle life, and environmental protection. They have occupied an important position in the energy storage device market and are used in a variety of portable mobile devices, such as mobile phones, cameras, and notebook computers. Gradually applied to electric bicycles (E-bike), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), pure electric vehicles (EV) and other large electric equipment.

With the continuous expansion of the application field of lithium-ion batteries, more and more attention has been paid to the safety performance of lithium-ion batteries. Among the factors affecting the safety performance of lithium-ion batteries, as a separator to prevent positive and negative contact and avoid internal short circuit of the battery is a key component. At present, the main separators used in lithium-ion batteries are: PE (polyethylene), PP (propylene), PP-PE-PP (polypropylene-polyethylene-polypropylene), ceramic separators, etc. PE, PP, PP-PE-PP and other polyolefin microporous polymer membranes have poor liquid absorption and liquid retention properties, too small temperature range from closed cells to ruptured membranes, easy to shrink at high temperatures, poor safety, and are not conducive to high-current charging and discharging. The production method of the ceramic diaphragm is to coat the inorganic ceramic oxide coating on the surface of the high temperature resistant cloth, which can ensure that the inorganic ceramic coating can still separate the positive and negative electrodes and prevent the internal short circuit when the organic high temperature resistant cloth is melted, but the cost Too high, more easily broken, poor air permeability. Related patents have proposed to apply an insulating coating on the surface of the positive/negative electrode sheet, in which doped inorganic particles are used as the skeleton, which improves the extrusion resistance of the separator, prevents the shrinkage of the separator at high temperature, and improves the performance of the lithium-ion battery. safety performance. However, if the ceramic layer is directly coated on the pole piece, the particles are easily lost, the brittleness is increased, and the gas permeability is deteriorated. Therefore, due to the consideration of the safety performance of lithium-ion batteries, it is necessary to propose a high-safety, high-reliability, and low-cost diaphragm manufacturing method to overcome the shortcomings of the prior art.

Contents of the invention

The purpose of the present invention is to provide a lithium-ion battery negative pole piece and its production method, which can solve the problems of easy falling off, high brittleness and weak adhesion when the ceramic material is directly coated on the pole piece, and avoid lithium ion battery during overcharging and overdischarging. The formation of dendrites can effectively prevent the expansion and defilming of the negative electrode sheet during charging and discharging, thereby improving the safety performance of the lithium battery.

The object of the present invention is achieved through the following technical solutions, a lithium ion battery negative electrode sheet, the negative electrode sheet includes a first coating coated with an active material, a second coating disposed on the surface of the first coating layer, and a third coating disposed on the surface of the second coating, wherein:

The second coating is a ceramic diaphragm coating with a thickness of 10-25 μm; the third coating is a porous polyvinylidene fluoride PVDF coating with a thickness of 2-6 μm.

The ceramic powder contained in the ceramic diaphragm coating is one or more of oxides, nitrides, and carbides of aluminum Al, titanium Ti, barium Ba, and silicon Si;

The binder contained in the ceramic diaphragm coating is one or more of styrene-butadiene rubber SBR, polyacrylic acid PAA, polyacrylonitrile PAN, and sodium hydroxymethyl cellulose CMC;

The organic solvent contained in the ceramic diaphragm coating is one of N-dimethylpyrrolidone NMP, dimethylformamide DMF or dimethylacetamide DMAC.

The material contained in the porous polyvinylidene fluoride PVDF coating is one of polyvinylidene fluoride PVDF, polyvinylidene fluoride-hexafluoropropylene PVDF-HFP or polyacrylonitrile PAN.

A method for making a negative pole piece of a lithium ion battery, the method comprising:

Mixing the negative electrode active material, binder, and conductive agent in a certain proportion, stirring at a high speed to obtain a slurry, coating the slurry on the current collector of the negative electrode of the lithium ion battery, and forming the first active material coating after drying;

At 40-60°C, mix a certain amount of ceramic powder, binder and organic solvent, wherein the ceramic powder accounts for 10-50wt% of the mixed solution, stir to form a uniform slurry, and spray the obtained slurry on on the surface of the first active material coating, and bake at 70-110°C for 5-60min to form a second coating;

Dissolve a certain amount of polyvinylidene fluoride PVDF-based copolymer material in acetone at 40-60°C, add 1-5wt% water, wherein the PVDF-based copolymer material accounts for 5-15wt% of the mixed solution, and stir A uniform slurry is formed, and the obtained slurry is sprayed on the surface of the second coating, and baked at 60-100° C. until dry to form a third coating.

The current collector of the negative electrode of the lithium ion battery is copper foil with a thickness of 8-12 μm;

The negative electrode active material adopts one or more of natural graphite, artificial graphite, silicon alloy, silicon-carbon composite material, and lithium titanate;

The binder is one or more of sodium hydroxymethyl cellulose CMC, butyl propylene rubber SBR, polyvinylidene fluoride PVDF, polytetrafluoroethylene PTFE;

The conductive agent is one or both of super conductive carbon black, conductive graphite, acetylene black, carbon nanotubes, and graphene.

The ceramic powder is one or more of oxides, nitrides, and carbides of aluminum Al, titanium Ti, barium Ba, and silicon Si;

The binder is one or more of styrene-butadiene rubber SBR, polyacrylic acid PAA, polyacrylonitrile PAN, sodium hydroxymethyl cellulose CMC;

The organic solvent is one of NMP, dimethylformamide DMF or dimethylacetamide DMAC.

The polyvinylidene fluoride PVDF-based copolymer material is one of polyvinylidene fluoride PVDF, polyvinylidene fluoride-hexafluoropropylene PVDF-HFP or polyacrylonitrile PAN.

The thickness of the second coating is 10-25 μm; the thickness of the third coating is 2-6 μm.

A lithium ion battery, the lithium ion battery comprises a positive pole piece, a negative pole piece according to claims 1-3, a diaphragm spaced between the positive and negative pole pieces, an electrolyte and a battery case.

It can be seen from the above-mentioned technical solution provided by the present invention that the negative electrode sheet includes a first coating coated with an active material, a second coating disposed on the surface of the first coating, and a coating disposed on the second coating. The third coating on the coating surface, wherein: the second coating is a ceramic diaphragm coating with a thickness of 10-25 μm; the third coating is a porous polyvinylidene fluoride PVDF coating with a thickness of 2- 6 μm. Compared with the prior art, the negative pole piece proposed by the present invention combines the advantages of the strong thermal stability of the ceramic layer and the high adhesion of the PVDF layer, effectively reducing the interface impedance, and the porous PVDF layer plays a role in slowing down the charging and discharging process of the pole piece. The effect of volume expansion can effectively prevent the ceramic particles from falling off on the pole piece, and ensure the high gram specific capacity of the negative pole piece while ensuring its safety performance.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings on the premise of not paying creative work.

Fig. 1 provides the structural representation of lithium-ion battery negative pole piece for the embodiment of the present invention;

FIG. 2 is a schematic flowchart of a method for manufacturing a lithium-ion battery negative electrode sheet provided by an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The embodiment of the present invention will be described in further detail below in conjunction with the accompanying drawings. As shown in FIG. The first coating 1, the second coating 2 arranged on the surface of the first coating, and the third coating 3 arranged on the surface of the second coating, wherein:

The second coating 2 is a ceramic diaphragm coating with a thickness of 10-25 μm; the third coating 3 is a porous polyvinylidene fluoride PVDF coating with a thickness of 2-6 μm.

In a specific implementation, the ceramic powder contained in the ceramic diaphragm coating is one or more of oxides, nitrides, and carbides of aluminum Al, titanium Ti, barium Ba, and silicon Si;

The binder contained in the ceramic diaphragm coating is one or more of styrene-butadiene rubber SBR, polyacrylic acid PAA, polyacrylonitrile PAN, and sodium hydroxymethyl cellulose CMC;

The organic solvent contained in the ceramic diaphragm coating is one of N-dimethylpyrrolidone NMP, dimethylformamide DMF or dimethylacetamide DMAC.

The material contained in the porous polyvinylidene fluoride PVDF coating is one of polyvinylidene fluoride PVDF, polyvinylidene fluoride-hexafluoropropylene PVDF-HFP or polyacrylonitrile PAN.

In addition, the present invention also provides a method for manufacturing a lithium-ion battery negative pole piece, as shown in FIG. 2 , which is a schematic flow chart of the production method for a lithium-ion battery negative pole piece provided by an embodiment of the present invention. The production method includes:

Step 21: Mix the negative electrode active material, binder, and conductive agent in a certain proportion to make a slurry, and coat it on the current collector of the negative electrode of the lithium ion battery to form a first active material coating.

In this step, specifically, the negative electrode active material, the binder, and the conductive agent are mixed in a certain proportion, stirred at a high speed to obtain a slurry, and the slurry is coated on the current collector of the negative electrode of the lithium ion battery, and dried to form the first An active material coating.

In a specific implementation, the current collector of the negative electrode of the lithium-ion battery is a copper foil with a thickness of 8-12 μm; the negative electrode active material is one or more of natural graphite, artificial graphite, silicon alloy, silicon-carbon composite material, and lithium titanate; The binder is one or more of hydroxymethylcellulose sodium CMC, butylpropylene rubber SBR, polyvinylidene fluoride PVDF, polytetrafluoroethylene PTFE; the conductive agent is super conductive carbon black, conductive graphite, acetylene black, One or both of carbon nanotubes and graphene.

Step 22: Mix a certain amount of ceramic powder, binder and organic solvent to make a slurry, and spray it on the surface of the first active material coating to form a second coating.

In this step, a certain amount of ceramic powder, binder and organic solvent can be mixed at 40-60°C, wherein the ceramic powder accounts for 10-50 wt% of the mixed solution, stirred to form a uniform slurry, and the The obtained slurry is sprayed on the surface of the first active material coating, and baked at 70-110° C. for 5-60 minutes to form a second coating, where the thickness of the second coating is 10-25 μm.

In a specific implementation, the ceramic powder is one or more of oxides, nitrides, and carbides of aluminum Al, titanium Ti, barium Ba, and silicon Si; the binder is styrene-butadiene rubber SBR, polyacrylic acid One or more of PAA, polyacrylonitrile PAN, sodium hydroxymethylcellulose CMC; the organic solvent is NMP in N-dimethylpyrrolidone NMP, dimethylformamide DMF or dimethylacetamide DMAC A sort of.

Step 23: dissolving a certain amount of polyvinylidene fluoride PVDF-based copolymer material in acetone to make a slurry, and spraying it on the surface of the second coating layer to form a third coating layer.

In this step, a certain amount of polyvinylidene fluoride PVDF-based copolymer material can be dissolved in acetone at 40-60 ° C, and 1-5 wt% of water is added, wherein the PVDF-based copolymer material accounts for the mixed solution. 5-15 wt%, stirring to form a uniform slurry, spraying the resulting slurry on the surface of the second coating, and baking at 60-100°C until dry to form a third coating, the third coating The thickness of the layer is 2-6 μm.

In a specific implementation, the polyvinylidene fluoride PVDF-based copolymer material is one of polyvinylidene fluoride PVDF, polyvinylidene fluoride-hexafluoropropylene PVDF-HFP or polyacrylonitrile PAN. Among them, the PVDF system material has high dielectric strength, excellent heat resistance, good mechanical properties, and strong electronic stretching functional group (-C-F), which is an ideal diaphragm material.

Based on the above-mentioned lithium ion battery negative pole piece and the manufacturing method, the embodiment of the present invention also provides a lithium ion battery, the lithium ion battery includes a positive pole piece, and a negative pole piece made by the method described in the above embodiment, a spacer The diaphragm between the positive and negative pole pieces, the electrolyte and the battery case.

The above-mentioned positive electrode sheet includes a current collector and a positive electrode active slurry coated on the current collector. The positive electrode active slurry includes a positive electrode active material, a conductive agent, and a binder. The current collector is aluminum foil with a thickness of 14-20 μm; the positive active material is lithium cobaltate (LiCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium nickelate (LiNiO ₂ ), lithium iron phosphate (LiFePO ₄ ), manganese Cobalt binary (Mn-Co), nickel-manganese binary (Mn-Ni), nickel-cobalt binary (Ni-Co) or nickel-manganese-cobalt ternary material (LiNi _{1-x- y} Co _x Mn _y O ₂ ) Any one or more materials; the conductive agent is a mixture of one or two of super conductive carbon black, conductive graphite, acetylene black and carbon nanotubes; the binder is polyvinylidene fluoride (PVDF), polytetrafluoroethylene One of vinyl fluoride (PTFE).

The diaphragm spaced between the positive and negative electrodes is one of PE (polyethylene), PP (propylene), and PP-PE-PP (polypropylene-polyethylene-polypropylene).

The electrolyte is lithium hexafluorophosphate (LiPF ₆ ) or lithium tetrafluoroborate (LiBF ₄ ) and ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and dicarbonate Composition of two or more substances in ethyl ester (DEC) organic solution.

The battery casing is aluminum-plastic film, plastic casing, plastic and metal composite casing, metal casing or metal alloy casing.

The specific manufacturing method of the lithium-ion battery is as follows: the positive and negative electrodes are rolled, cut, spot-welded, wound with 25 μm PP-PE-PP composite separator in sequence, wrapped with aluminum-plastic film and heat-sealed at the edge, and then Subsequent treatments such as baking, liquid injection, chemical formation, pumping and sealing, etc., make a soft-packed lithium-ion battery.

Further, the electrochemical performance and safety performance test can be carried out to the above-mentioned prepared lithium-ion battery, specifically:

(1) Cycling performance test: 300 cycles of charging and discharging with a current of 0.5C, and the capacity retention rate is above 80%;

(2) Thermal shock test: After the battery is fully charged, put it in an oven. The battery will rise to 130°C±2°C at a rate of 5±2°C/min at room temperature and keep at this temperature for 30 minutes. The battery will not catch fire. not explode;

(3) Puncture test: After the sample battery is fully charged, after standing for 1 hour, use a steel needle with a diameter of 2.5-3.5 mm to penetrate the center of the large surface of the battery cell and keep it for more than 2 hours. The battery will not catch fire or explode;

(4) Overcharge test: overcharge test with 3C/4.8V, no fire or explosion;

(5) Heavy object impact test: After the battery is fully charged, put it on hold for 1 hour, place the battery cell on the impact table, drop a 9.1Kg weight freely from a height of 610mm, and impact the battery fixed in the fixture. The battery deforms, but No fire, no explosion;

(6) Normal temperature short circuit test: After the battery is fully charged, at 20±5°C, connect the battery connected to the thermoelectric cell directly with a wire whose total resistance of the external circuit does not exceed 50mΩ, until the open circuit voltage of the battery is not greater than 0.1V, At the same time, the test was terminated when the surface temperature of the battery returned to not higher than the ambient temperature by 10°C. The battery does not smoke, explode, or catch fire, and the surface temperature does not exceed 150°C.

It can be seen that the advantages of adopting the above scheme are:

(1) The present invention combines the strong thermal stability of the ceramic layer and the high cohesion of the PVDF layer to solve the problems that the ceramic material is directly coated on the pole piece and is easy to fall off, has high brittleness and weak cohesion. The safety performance of the lithium-ion battery made of the negative pole piece is greatly enhanced;

(2), the preparation method of the negative plate of the present invention is simple, the process is simple, and it is easy to produce on a large scale;

(3) The lithium-ion battery made by using the negative electrode sheet of the present invention has good cycle stability and thermal stability, the charge-discharge cycle at 0.5C current is 300 cycles, and the capacity retention rate is above 80%. It can pass the high-temperature storage test at 60℃×7 days, the high-temperature capacity test at 55℃×2h, as well as the 3C/20V overcharge test, thermal shock test (keep at 130℃ for 30 minutes without fire), short circuit, acupuncture, and heavy impact and other safety performance testing.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field can easily conceive of changes or changes within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (9)

1. a lithium ion battery negative electrode is characterized in that, described cathode pole piece comprises the first coating that scribbles active material, is arranged at the second coating of described the first coating surface, and the 3rd coating that is arranged at described the second coating surface, wherein:

Described the second coating is the ceramic diaphragm coating, and thickness is 10-25 μ m; Described the 3rd coating is porous Kynoar PVDF type coating, and thickness is 2-6 μ m.

2. described lithium ion battery negative electrode according to claim 1 is characterized in that, the ceramic powders that described ceramic diaphragm coating comprises is one or more in the oxide, nitride, carbide of aluminium Al, titanium Ti, barium Ba, silicon Si;

The adhesive that described ceramic diaphragm coating comprises is one or more among styrene butadiene rubber sbr, polyacrylic acid PAA, polyacrylonitrile (PAN), the sodium cellulose glycolate CMC;

The organic solvent that described ceramic diaphragm coating comprises is a kind of among N-dimethyl pyrrolidone NMP, dimethyl formamide DMF or the dimethylacetylamide DMAC.

3. described lithium ion battery negative electrode according to claim 1 is characterized in that, the material that described porous Kynoar PVDF type coating comprises is a kind of in Kynoar PVDF, Kynoar-hexafluoropropylene PVDF-HFP or the polyacrylonitrile (PAN).

4. the manufacture method of a lithium ion battery negative electrode is characterized in that, described manufacture method comprises:

Negative active core-shell material, binding agent, conductive agent are mixed by a certain percentage, and high-speed stirred obtains slurry, described slurry is coated on the collector of lithium ion battery negative, dry rear first coating layer of active substance that forms;

Under 40-60 ℃, a certain amount of ceramic powders, adhesive and organic solvent are mixed, wherein said ceramic powders accounts for the 10-50wt% of mixed solution, stir and form uniform sizing material, resulting pulp spraying is coated on described the first coating layer of active substance surface, and at 70-110 ℃ of baking 5-60min, form the second coating;

Under 40-60 ℃, a certain amount of Kynoar PVDF base co-polymer material is dissolved in the acetone, add 1-5wt% water, wherein said PVDF base co-polymer material accounts for the 5-15wt% of mixed solution, stir and form uniform sizing material, resulting pulp spraying is coated on described the second coating surface, and is baked to drying at 60-100 ℃, form the 3rd coating.

5. the manufacture method of lithium ion battery negative electrode as claimed in claim 4 is characterized in that,

The collector of described lithium ion battery negative is the Copper Foil of thickness 8-12 μ m;

Described negative active core-shell material adopts one or more in native graphite, Delanium, silicon alloy, Si-C composite material, the lithium titanate;

Described binding agent is one or more in sodium cellulose glycolate CMC, fourth the third rubber SBR, Kynoar PVDF, the polytetrafluoroethylene PTFE;

Described conductive agent is one or both in super conductive black, electrically conductive graphite, acetylene black, carbon nano-tube, the Graphene.

6. the manufacture method of lithium ion battery negative electrode as claimed in claim 4 is characterized in that,

Described ceramic powders is one or more in the oxide, nitride, carbide of aluminium Al, titanium Ti, barium Ba, silicon Si;

Described adhesive is one or more among styrene butadiene rubber sbr, polyacrylic acid PAA, polyacrylonitrile (PAN), the sodium cellulose glycolate CMC;

Described organic solvent is a kind of among N-dimethyl pyrrolidone NMP, dimethyl formamide DMF or the dimethylacetylamide DMAC.

7. the manufacture method of lithium ion battery negative electrode as claimed in claim 4 is characterized in that,

Described Kynoar PVDF base co-polymer material is a kind of in Kynoar PVDF, Kynoar-hexafluoropropylene PVDF-HFP or the polyacrylonitrile (PAN).

8. the manufacture method of lithium ion battery negative electrode as claimed in claim 4 is characterized in that,

The thickness of described the second coating is 10-25 μ m; The thickness of described the 3rd coating is 2-6 μ m.

9. a lithium ion battery is characterized in that, described lithium ion battery comprises anode pole piece, such as the described cathode pole piece of claim 1-3, be interval in barrier film, electrolyte and battery case between the both positive and negative polarity pole piece.

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