CN101315993A - Manufacturing method of laminated lithium ion battery - Google Patents

Abstract

The invention relates to a manufacturing method of a laminated lithium ion battery. The lithium ion battery comprises a positive electrode layer and a negative electrode layer prepared from an aqueous or non-aqueous binding material, and a microporous separator interposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer and the negative electrode layer or the separator comprises a polymer coating layer after special treatment. And then assembling the positive electrode layer, the negative electrode layer and the separator in a lamination way, and enabling the positive electrode layer and the negative electrode layer to form firm bonding with the separator under certain pressure and temperature so as to form a good interface layer and guarantee the performance of the lithium ion battery.

Description

A kind of manufacturing method of laminated lithium ion battery

Technical field:

The invention relates to a manufacturing method of a lithium ion battery, in particular to a manufacturing method of a laminated lithium ion battery.

Background technique:

At present, there are two methods of preparing lithium-ion batteries in actual production: lamination type and winding type.

The main process of the lamination process is as follows: using acetone as a solvent, the plasticizer, non-aqueous binder (PVDF-HFP copolymer), conductive additives and electrode materials are stirred to form an electrode mixture, and then coated on the polyester film (Mylar) substrate, acetone volatilizes to obtain the electrode mixture layer containing plasticizer, and then it is separated from the polyester film (Mylar) substrate, and the electrode mixture layer containing plasticizer and the current collector ( Aluminum foil (mesh) or copper foil (mesh)) are composited to obtain positive and negative electrode sheets, and then the positive and negative electrode sheets containing plasticizer and the microporous separator containing plasticizer are composited by hot rolling to obtain a Battery cells (Bi-cell), the obtained battery cells are extracted by organic solvents (such as methanol, etc.), and after a series of drying to obtain battery cells without plasticizers, different numbers of batteries are used according to capacity requirements The monomers are connected in parallel to form a bare cell, the bare cell is packaged in an aluminum foil bag, and the electrolyte is injected after vacuum drying. Lithium-ion batteries can be obtained by discharging and activating. The main advantage of this process is that the alignment of the pole pieces between the positive and negative electrodes is relatively good, and more importantly: the interface formed between the positive and negative electrode pole pieces and the separator is relatively good, which is beneficial to ensure the electrochemical performance of the ion battery . But the disadvantages of this method are: firstly, the solvents such as acetone and methanol used in the process are flammable and explosive substances, which have certain safety hazards, and the substances are not easy to recycle; secondly, the process is to contain plasticized The electrode mixture of the agent is coated on the polyester film, and then the electrode tab is formed by hot rolling, and the prepared electrode sheet needs to be extracted from the plasticizer. These processes result in low process efficiency. Increased processing costs; Finally, due to structural and material reasons, lithium-ion batteries prepared by this process are difficult to pass safety performance tests such as nail penetration and impact when the capacity reaches a certain value.

The main process of the winding process is as follows: using deionized water or N-methylpyrrolidone (NMP) as a solvent, mixing water-based or non-aqueous binder materials, conductive additives and electrode materials together to form an electrode mixture, the electrode mixture is directly Coated on the current collector (aluminum foil or copper foil), both positive and negative electrodes are coated on both sides. After drying and compacting, the positive and negative electrode pieces are formed, and then the positive and negative electrode pieces and the separator are wound by winding to obtain a bare cell, and the subsequent process flow is similar to the lamination type. The main advantage of the winding process is that it is safe to use, and it uses recyclable deionized water or N-methylpyrrolidone (NMP) as a solvent, which can reduce product manufacturing costs. In addition, the roll-to-roll manufacturing process directly coats the electrode mixture on the current collector, which does not contain plasticizers and thus does not require extraction, making the entire process highly efficient and low in cost. However, the main disadvantage of this process is that the interface formed between the positive and negative electrode sheets and the separator is contact rather than adhesive, which makes the interface performance much lower than that of the laminated process, which is not conducive to lithium ionization. The performance of ion batteries.

Invention content:

The technical problem to be solved by the present invention is to provide a method for manufacturing laminated lithium-ion batteries by combining the two current manufacturing processes. The method proposed by the present invention maintains the respective advantages of the two current manufacturing processes to the greatest extent, and removes their disadvantages, that is, the positive and negative electrode pieces and the separator form a strong bond, thereby forming a good interface layer, and simplifying production at the same time Process, improve production efficiency, thereby reducing product manufacturing costs.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical scheme: a layer of polymer coating is coated on the surface of the polyolefin separator, and the separator and the positive and negative pole pieces are bonded under hot pressing through the polymer coating. Strong adhesion is generated between them, so that the interface formed between the positive and negative electrodes and the separator is better, so as to ensure the electrochemical performance of the ion battery. The technical solution includes the following steps: A, mixing water-based or non-aqueous binding materials (such as PVDF homopolymer), conductive additives and electrode materials in a solvent to form an electrode mixture; B, directly coating the electrode mixture on the current collector After drying and compacting, the positive and negative electrode pieces are formed; C. Prepare a separator, and the surface of the separator has a polymer coating; D. Alternately stack the prepared positive and negative electrode pieces with the separator, and heat roll , so that the positive and negative electrodes and the separator form a firm bond to obtain a battery cell; E. Connect different numbers of battery cells in parallel to form a battery cell, pack the battery cell with an aluminum foil bag, and inject it into the electrolytic cell after vacuum drying After the electrolyte, the positive and negative pole pieces and the separator are fully soaked and wetted, the lithium-ion battery is obtained by charging and discharging activation.

In the above technical scheme, there are two ways to coat the electrode mixture: one is to coat the positive electrode on one side, and the negative electrode is coated on both sides; the other is to coat the positive electrode on both sides, and the negative electrode is coated on both sides. The sheet is coated on one side.

The separator is a polyolefin separator modified by polymer coating. The polymer used is at least one selected from the following material groups: polyvinylidene fluoride homopolymer, polyvinylidene fluoride hexafluoropropylene copolymer, polyacrylonitrile, polyacrylonitrile copolymer, polystyrene oxide or polystyrene oxide copolymer.

The water-based binder includes styrene-butadiene rubber and its derivatives, polytetrafluoroethylene and its derivatives, and polyacrylic acid and its derivatives; the non-aqueous binder includes polyvinylidene fluoride homopolymer, and its derivatives.

The temperature for hot pressing the positive and negative electrode pieces and the separator is 80-140° C., and the pressure is 30-100 kgf.

Certainly, the present invention also can adopt another kind of similar technical scheme, promptly does not coat one deck polymer coating on the surface of separator, but coats one deck polymer coating on positive and negative electrode sheet, it can also be Strong adhesion between the separator and the positive and negative pole pieces is generated under hot pressing. The specific method includes A. mixing water-based or non-aqueous binder materials, conductive additives and electrode materials in a solvent to form an electrode mixture; B. directly coating the electrode mixture on the current collector, drying and compacting to form positive and negative electrode sheets , and coat a layer of polymer coating on the surface of the positive and negative electrode pieces; C, prepare the separator; D, alternately superimpose the prepared positive and negative electrode pieces and the separator, and through hot rolling, pass the positive and negative The polymer coating on the surface of the electrode sheet makes the positive and negative electrode sheets and the separator firmly bonded to form a battery cell; E. Connect different numbers of battery cells in parallel to form a cell, and use an aluminum foil bag for the cell Encapsulation, vacuum drying, injection of electrolyte, after the electrolyte, positive and negative pole pieces and separators are fully soaked and wetted, and then activated by several times of charging and discharging, a lithium-ion battery can be obtained.

This technical solution is similar to the above-mentioned technical solution, and the difference is that this technical solution coats the polymer coating on the surface of the positive and negative electrode pieces. That is, according to whether the positive and negative electrodes are treated or not, it is determined whether the corresponding separator is modified by polymer coating. If the positive and negative electrode pieces do not undergo polymer surface treatment, the separator needs to be modified with polymer coating; if the positive and negative electrode pieces are treated with polymer surface, it is not necessary to carry out polymer coating on the separator modified.

The surface of the positive and negative electrode pieces is coated with a layer of polymer coating, which is at least one selected from the following material groups: polyvinylidene fluoride hexafluoride and propylene copolymer, polyacrylonitrile, polyacrylonitrile copolymer compounds, polystyrene oxide or polystyrene oxide copolymers.

The present invention adopts the above two technical solutions, not only makes the positive and negative electrode layers and the separator form a strong bond, thereby forming a good interface layer to ensure the performance of the lithium ion battery. At the same time, adopting the manufacturing method of the present invention can simplify the production process, improve the production efficiency, and thereby reduce the manufacturing cost of the product.

Description of drawings:

Fig. 1 is a schematic diagram of a stack of battery cells in Example 1 of the present invention;

Fig. 2 is a schematic diagram of stacked battery cells in Example 2 of the present invention;

Detailed ways:

In the present invention, water-based or non-aqueous binding materials, conductive additives and electrode materials are mixed together to form an electrode mixture, and the electrode mixture is directly coated on the current collector, dried and compacted to form positive and negative electrode sheets, and there are two coating methods : One is single-sided coating for positive electrode pieces and double-sided coating for negative electrode pieces; the other is double-sided coating for positive electrode pieces and single-side coating for negative electrode pieces. The positive and negative electrode sheets formed after drying and compacting can be directly used in the preparation of lithium-ion batteries without any treatment; the positive and negative electrode sheets can also be treated to make the surface contain a polymer coating before being used in lithium-ion batteries. preparation. According to whether the positive and negative electrodes are treated or not, it is determined whether the corresponding separator is modified by polymer coating. If the positive and negative electrode pieces are not treated with surface polymers, polymer coating modification on the separator is required; if the positive and negative electrode pieces are treated with surface polymers, no polymer coating modification on the separator is required sex.

When the electrode pole pieces and separators are stacked and assembled, there are two assembly methods: one is two single-sided coated positive electrode pieces 1, one double-sided coated negative electrode piece 2 and two separators 3, See Figure 1. The other is a positive electrode sheet 1 coated on both sides, two negative electrode sheets 2 coated on one side and two separators 3, as shown in FIG. 2 .

The assembled battery cell is hot-rolled at a certain temperature and pressure to form a strong bond between the positive and negative electrode layers and the separator to form a battery cell with a good interface. Then, according to the capacity requirements of the lithium-ion battery, different numbers of The battery cells are connected in parallel to form a bare cell, the bare cell is packaged in an aluminum foil bag, and the electrolyte is injected after vacuum drying. Lithium-ion batteries can be obtained by sub-charge discharge activation.

The polymer used in the present invention can be polyvinylidene fluoride homopolymer PVdF, polyvinylidene fluoride hexafluoropropylene copolymer PVdF/HFP, polyacrylonitrile, polyacrylonitrile copolymer, polystyrene oxide or Polystyrene oxide copolymer, etc. The polymer is used as an adhesive and coated on the surface of the positive and negative electrode sheets or on the surface of the separator. Under heating conditions, the polymer forms a good interface between the positive and negative electrode pieces and the separator under pressure.

The water-based binder used in the present invention includes: styrene-butadiene rubber and its derivatives, polytetrafluoroethylene and its derivatives, polyacrylic acid and its derivatives. Non-aqueous binders include: polyvinylidene fluoride homopolymers, copolymers and their derivatives.

The temperature for hot pressing the positive and negative electrode pieces and the separator is 80-140° C., and the pressure is 30-100 kgf.

The following are specific embodiments of the present invention:

Example 1

See Figure 1, the preparation of positive electrode piece 1: add polyvinylidene fluoride (PVDF): conductive carbon: LiCoO ₂ =1% to 5%: 1% to 5%: 90% to 98% of the electrode mixture and add N-formazine in sequence Among the base pyrrolidone (NMP), after fully stirring evenly, prepare a slurry with a solid content of 30% to 70%, and directly coat the electrode mixture slurry on the aluminum foil 11, with a weight of 18mg/cm ² to 26mg/cm ² , the coating method is single-sided coating, and then dried and compacted into a positive electrode sheet 1 with a certain thickness according to a density of 2.8g/cm ³ -4.0g/cm ³ . The positive electrode sheet 1 includes an aluminum foil 11 as a current collector and a positive electrode layer 12 coated on the current collector, and the porosity of the positive electrode sheet 1 is controlled at 10% to 30%.

Negative electrode pole piece 2 preparation: carboxymethylcellulose (CMC): styrene-butadiene rubber (SBR): conductive carbon: graphite=1%～3%: 1%～4%: 1%～3%: 90%～ Add 97% of the electrode mixture into deionized water (H ₂ O) sequentially, and after fully stirring evenly, prepare a slurry with a solid content of 30% to 70%, and directly coat the electrode mixture slurry on the copper foil 21 to form The negative electrode layer 22 has a weight of 7 mg/cm ² to 15 mg/cm ² , the coating method is double-sided coating, and then dried and compacted into a negative electrode layer of a certain thickness with a density of 1.3 g/cm ³ to 1.8 g/cm ³ . Electrode pad 2.

The negative electrode sheet 2 includes a copper foil 21 as a current collector and a negative electrode layer 22 coated on the current collector. The porosity of the negative electrode sheet 1 is controlled at 10% to 30%.

Separator 3 treatment: the microporous polyolefin separator 31 is treated with a polymer matrix to form a 2um-8um polymer treatment layer 32.

Cut the positive and negative electrode pole pieces 1, 2 and separator 3 into appropriate sizes according to the required requirements, and then coat the positive electrode pole piece 1 on two sides, one negative electrode pole piece 2 on both sides and two pieces The structure of the separator 3 is assembled into a battery cell, and then it is hot-rolled at a temperature of 80-140°C and a pressure of 30-100kgf, so that the positive and negative electrode layers 12, 22 and the separator 3 form a firm bond, forming A battery cell with a good interface 4, and then according to the lithium-ion battery capacity requirements, different numbers of battery cells are connected in parallel to form a bare cell, the bare cell is packaged in an aluminum foil foil bag, and the electrolyte is injected after vacuum drying. After fully infiltrating and wetting the positive and negative electrode sheets and separators with the liquid, and then activated by several times of charging and discharging, a lithium-ion battery can be obtained.

Example 2

See Fig. 2, the preparation of positive electrode sheet 1: the same as in Example 1, but the coating method is double-sided coating.

Preparation of the negative electrode pole piece 2: the same as in Example 1, but the coating method is single-side coating.

Separator treatment: with embodiment 1.

Cut the positive and negative electrode sheets 1, 2 and separator 3 into appropriate sizes according to the required requirements, and then apply one piece of double-sided coated positive electrode piece 1, two pieces of single-sided coated negative electrode piece 2 and two pieces The structure of the separator 3 is assembled into a battery cell, and then it is hot-rolled at a temperature of 80-140°C and a pressure of 30-100kgf, so that the positive and negative electrode layers 11, 21 and the separator 3 form a firm bond, forming A battery cell with a good interface 5, and then according to the capacity requirements of the lithium-ion battery, connect different numbers of battery cells in parallel to form a bare cell, pack the bare cell with an aluminum foil bag, and inject electrolyte after vacuum drying. After fully infiltrating and wetting the positive and negative electrode sheets and separators with the liquid, and then activated by several times of charging and discharging, a lithium-ion battery can be obtained.

The above-mentioned embodiment is to coat one layer of polymer coating on the surface of separator, certainly, according to the technical scheme of the present invention, also can coat one deck of polymer coating on positive and negative electrode sheet, and it can also be in heat Press down to produce stronger adhesion between the separator and the positive and negative pole pieces. For specific implementation manners, reference may be made to the descriptions of the foregoing embodiments, and details will not be repeated here.

Of course, the above descriptions are only examples of the present invention, and are not intended to limit the implementation scope of the present invention. All equivalent changes or modifications made according to the structure, features and principles described in the scope of the patent application of the present invention should be included in Within the protection scope of the patent of this application.

Claims (10)

1, a kind of manufacture method of stack type lithium ion battery, this method comprises following steps:

A, water-based or non-aqueous binding material, conductive additive and electrode material are mixed in the solvent, form electrode mixture;

B, electrode mixture directly is coated on the collector forms the positive and negative electrode pole piece after the drying compacting;

C, preparation dividing plate, the surface of this dividing plate has polymer coating;

D, with the alternately stack of positive and negative electrode pole piece and dividing plate of preparation, and, make positive and negative electrode pole piece and dividing plate form firm bonding through the hot-rolling pressure, obtain battery cell;

E, the battery cell of different numbers is together in parallel forms an electric core,, inject electrolyte after the vacuumize electric core encapsulation, treat electrolyte and both positive and negative polarity pole piece and dividing plate fully soak into wetting after, activate by impulse electricity again and obtain lithium ion battery.

2, the manufacture method of a kind of stack type lithium ion battery according to claim 1 is characterized in that: the mode of electrode mixture coating has two kinds among the described step B: a kind of is the coating of positive electrode pole piece single face, negative electrode pole piece double spread; Another kind is a positive electrode pole piece double spread, the coating of negative electrode pole piece single face.

3, the manufacture method of a kind of stack type lithium ion battery according to claim 1 and 2 is characterized in that: described dividing plate is the polyolefin separator through polymer coating layer modification; The polymer that is adopted is at least and is selected from a kind of in the following material group: polyvinylidene fluoride homopolymers, polyvinylidene fluoride hexafluoropropylene copolymer, polyacrylonitrile, polyacrylonitrile copolymer, polystyrene oxide or polystyrene oxide copolymer.

4, the manufacture method of a kind of stack type lithium ion battery according to claim 3 is characterized in that: described aqueous binders comprises butadiene-styrene rubber and derivative, polytetrafluoroethylene and derivative thereof and polyacrylic acid and derivative thereof; Described non-aqueous binding agent comprises polyvinylidene fluoride homopolymer, copolymer and derivative thereof.

5, the manufacture method of a kind of stack type lithium ion battery according to claim 3 is characterized in that: the temperature that positive and negative electrode pole piece and dividing plate carry out hot pressing is 80～140 ℃, and pressure is 30～100kgf.

6, a kind of manufacture method of stack type lithium ion battery, this method comprises following steps:

A, water-based or non-aqueous binding material, conductive additive and electrode material are mixed in the solvent, form electrode mixture;

B, electrode mixture directly is coated on the collector forms the positive and negative electrode pole piece after the drying compacting, and in the surface coated one layer of polymeric coating of positive and negative electrode pole piece;

C, preparation dividing plate;

D, with the alternately stack of positive and negative electrode pole piece and dividing plate of preparation, and through the hot-rolling pressure, the polymer coating by positive and negative electrode pole piece surface makes positive and negative electrode pole piece and dividing plate form firm bonding, obtains battery cell;

E, the battery cell of different numbers is together in parallel forms an electric core,, inject electrolyte after the vacuumize electric core encapsulation, treat electrolyte and both positive and negative polarity pole piece and dividing plate fully soak into wetting after, activate by impulse electricity again and obtain lithium ion battery.

7, the manufacture method of a kind of stack type lithium ion battery according to claim 6 is characterized in that: the mode of electrode mixture coating has two kinds among the described step B: a kind of is the coating of positive electrode pole piece single face, negative electrode pole piece double spread; Another kind is a positive electrode pole piece double spread, the coating of negative electrode pole piece single face.

8, according to the manufacture method of claim 6 or 7 described a kind of stack type lithium ion batteries, it is characterized in that: the surface coated one layer of polymeric coating of described positive and negative electrode pole piece is at least and is selected from a kind of in the following material group: polyvinylidene fluoride hexafluoropropylene copolymer, polyacrylonitrile, polyacrylonitrile copolymer, polystyrene oxide or polystyrene oxide copolymer.

9, the manufacture method of a kind of stack type lithium ion battery according to claim 8 is characterized in that: described aqueous binders comprises butadiene-styrene rubber and derivative, polytetrafluoroethylene and derivative thereof and polyacrylic acid and derivative thereof; Described non-aqueous binding agent comprises polyvinylidene fluoride homopolymer, copolymer and derivative thereof.

10, the manufacture method of a kind of stack type lithium ion battery according to claim 9 is characterized in that: the temperature that positive and negative electrode pole piece and dividing plate carry out hot pressing is 80～140 ℃, and pressure is 30～100kgf.