TW201349641A - Electrode assembly and its fabrication method - Google Patents

Abstract

The present invention relates to an electrode assembly and its fabrication method. The electrode assembly includes an anode, a cathode, a separator interposed between the cathode and the anode, and an adhesive applied to stick the electrodes to the separator. The adhesive includes a high-viscosity solvent, and further optionally includes a low-viscosity solvent, if necessary. The adhesive for sticking the electrodes to the separator during the process of fabricating electrode assembly could simplify the process of fabricating electrode assembly because the electrodes and separator were stacked or rolled without using a stacking or winding machine, thereby the manufacturing costs could be reduced.

Description

Electrode group and manufacturing method thereof

The invention relates to an electrode group and a preparation method thereof, in particular to an electrode group with simple preparation method and low production cost and a preparation method thereof.

In recent years, due to the development of mobile device related technologies and the increasing demand, such as portable computers, portable telephones and video cameras, etc., secondary batteries suitable for power supply of portable electrical appliances are gradually inclined to high capacitance. Mini-, lightweight and ultra-thin requirements. With the research and development of secondary lithium batteries, among the secondary battery types, secondary lithium batteries have the advantages of high voltage, long life and high energy density, so in the secondary battery type, the secondary lithium battery The research and development of Chi has reached productization and sales.

The secondary battery is a structure having an electrode group including an anode, a cathode, and a separator interposed between the electrodes, and the electrode group is packaged in a battery can. The electrode group can be divided into a winding type and a stacked type. The winding type is formed by coating an electrode active material on both sides of a long-plate type current collecting foil to form a negative electrode and a positive electrode, and inserting a separator film between the negative electrode and the positive electrode, and stacking the electrode active material. The two sides of the current collecting foil of a predetermined size are arranged to form a plurality of negative electrodes and a positive electrode, and the separator is interposed between the positive electrode and the negative electrode and stacked in layers.

In the case of manufacturing the electrode group required for the secondary battery, taking the stacked electrode group as an example, since the electrode group stack has a direct relationship with the battery capacity, it is usually required to be combined with an automated stacker so that the positive electrode 1 and the negative electrode 3 can Appropriate The separators 2 are staggered and stacked neatly as shown in FIG. However, stacking the electrode sets using the stacker is still inevitable, and the electrode group may be unevenly arranged, resulting in poor battery capacity consistency, and in addition, in the case of increasing demand for high-power, miniaturized batteries, stacking is used. Machine-made electrode sets will increase manufacturing difficulties, resulting in increased cost and difficulty of the process.

Therefore, it is necessary to simplify the manufacturing process of the electrode group, thereby reducing the manufacturing cost and difficulty, reducing the defects formed by the uneven arrangement of the electrode groups, and further providing a simple stacking electrode to facilitate the close stacking of the electrodes.

SUMMARY OF THE INVENTION The main object of the present invention is to provide a bonding adhesive for manufacturing an electrode assembly which can simplify the inconvenience of the prior art electrode assembly manufacturing process and reduce the manufacturing cost thereof.

Another object of the present invention is to provide an electrode assembly manufacturing process in combination with the above-mentioned adhesive, which can simplify the inconvenience of the conventional electrode assembly manufacturing process and reduce the manufacturing cost thereof.

In order to achieve the above object, the present invention is to laminate the positive electrode and the negative electrode to the separator by using a bonding glue, respectively, thereby eliminating the need to stack or wind the electrode and the separator in a stacker or a winder. And a process wherein the adhesive comprises a high viscosity solvent, and more optionally a low viscosity solvent.

Accordingly, the present invention provides an electrode assembly including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a spacer a bonding glue between the positive electrode and the separator and between the negative electrode and the separator. Wherein, the bonding glue can be used for bonding the positive electrode and the negative electrode to the separator. More specifically, the positive electrode and the negative electrode may be respectively attached to opposite sides of the separator.

In the present invention, the high viscosity solvent may be any cyclic carbonate compound, lactone compound or a combination thereof having a viscosity higher than 1 cP and not causing deterioration of battery performance, and the low viscosity solvent may be any viscosity lower than 1 cP. A chain diether compound, a cyclic diether compound, an epoxy compound, a chain ester compound, a chain carbonate compound, or a combination thereof. For example, the high viscosity solvent may be selected from the group consisting of C _3-20 cyclic carbonate compounds, C _4-20 lactone compounds, and combinations thereof, and the low viscosity solvent may be any viscosity less than 1 cP. a chain diether compound, a cyclic diether compound, an epoxy compound, a chain ester compound, a chain acid ester compound or a combination thereof, for example, the low viscosity solvent may be selected from a C _3-10 chain a diether compound, a C _3-10 cyclic diether compound, a C _4-10 epoxy compound, a C _2-10 chain ester compound, a C _3-10 chain acid ester compound, and a combination thereof Group of.

For example, the high viscosity solvent of the present invention may be a cyclic carbonate compound having the structure shown in the following Chemical Formula 1, a lactone compound having the structure shown in the following Chemical Formula 2, or a combination thereof:

Wherein R ₁ is a C ₁ -C ₆ alkyl group, n is an integer from 1 to 3, m is an integer from 0 to 8, and p is an integer from 0 to 10.

The low-viscosity solvent of the present invention may be a chain-shaped diether compound having the structure shown in the following Chemical Formula 3, a cyclic diether compound having the structure shown in the following Chemical Formula 4, or an epoxy compound having the structure shown in the following Chemical Formula 5, A chain ester compound having a structure represented by the following Chemical Formula 6, a chain carbonate compound having a structure represented by the following Chemical Formula 7 or a combination thereof:

Wherein R ₂ , R ₃ , R ₄ , R ₅ , R ₇ , R ₈ and R ₉ are each independently C ₁ -C ₆ alkyl, R ₆ is hydrogen or C ₁ -C ₆ alkyl, and r is 1 to An integer of 6 wherein p is an integer from 0 to 10, y is an integer from 0 to 12, s and t are each an integer from 1 to 3, and s+t is an integer from 2 to 4.

In addition, the viscosity of the high viscosity solvent of the present invention is preferably in the range of 1.5 cP to 4.0 cP to facilitate application of the adhesive to the material. For example, the viscosity of the high viscosity solvent in the embodiment of the present invention ranges from about 1.7 cP to 3.2 cP. The viscosity of the low viscosity solvent of the present invention is preferably from 0.3 cP to 0.8 cP. For example, the viscosity of the low viscosity solvent in the embodiment of the present invention ranges from about 0.33 cP to 0.75 cP. More specifically, the high viscosity solvent used in the examples of the present invention includes ethylene carbonate (EC), propylene carbonate (PC), butanediol carbonate (BC) and γ-butyrolactone (GBL), and is low. Viscosity solvents include diethyl carbonate (DEC), ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), 1,3-dioxolane (DOL), 4-methyl -1,3-dioxolane (4MeDOL), methyl formate (MF), methyl acetate (MA), methyl propionate (MP), dimethyl carbonate (DMC) or ethyl methyl carbonate (EMC) ), but the invention is not particularly limited thereto.

In the present invention, the volume ratio of the high viscosity solvent to the low viscosity solvent may be from 1:1 to 1:0.01.

The positive electrode and the negative electrode of the present invention are not particularly limited, and may be any of the conventionally known positive electrode and negative electrode which are suitable for use in an electrochemical device such as a secondary battery. Here, the electrodes (ie, the positive electrode and the negative electrode) may include an electrode substrate (such as a metal piece) and an electrode coating, wherein the electrode coating is applied to the electrode substrate, and the electrode coating may include an electrode. Active material, and optionally including an appropriate amount of adhesive (such as polyvinylidene fluoride). Further, the separator of the present invention is also not particularly limited, and it may be any separator (e.g., a polypropylene film) which is suitably used in an electrochemical device. Furthermore, the present invention further provides a method of fabricating the above electrode assembly, comprising: bonding a positive electrode and a negative electrode to a separator separately using a bonding glue. More specifically, the positive electrode and the negative electrode can be respectively bonded to the separator by a roll hot pressing method. Accordingly, the adhesive having the plasticizing property of the present invention can be brought into close contact with the separator by rolling hot pressing.

In addition, the method of fabricating the electrode assembly of the present invention may further comprise a drying step to reduce the water content in the positive electrode and the negative electrode. For example, this drying step can be carried out by vacuum heating.

In the above method, in the case of manufacturing a stacked electrode group, the positive electrode, the negative electrode and the separator may be first cut into a desired size, and then coated on the positive electrode and the negative electrode by a bonding glue, and subjected to hot pressing by rolling. The method is such that the positive electrode, the separator and the negative electrode can be smoothly laminated to form a single electrode group. According to the method, a single electrode group can be assembled into a battery, and according to the amount of the battery to be manufactured, a glue can be applied between each single electrode group and a separator can be interposed, and then a plurality of electrodes are stacked. The group and the conductive handles reserved for the electrode sheets on the plurality of electrode groups are welded to each other, and the plurality of electrode pole pieces and the isolation film are not required to be stacked through the stacker.

The stacked electrode assembly and the battery manufacturing method thereof are only for specifically describing the advantages of the present invention. The method for fabricating the electrode assembly and the battery of the present invention is not limited to the above exemplary methods, and is not limited to the fabrication of the stacked electrode group, any conventional electrode group. The structure (such as a wound electrode group, etc.) can use the bonding technique of the present invention, that is, in addition to the present invention, the conventional stacking machine stack is replaced by a bonding technique. In addition to the technology, other related art techniques for fabricating electrode sets and batteries can be applied to the present invention.

Accordingly, the electrode group produced by the bonding glue and the method of manufacturing the electrode group by rolling hot pressing has the characteristics of being easier to operate than the conventional electrode group manufacturing method, such as the electrode group The close bonding of the glue does not cause the subsequent processing of the pole piece and the isolation film to be dislocated due to the inadvertent movement of the electrode group, which may cause subsequent processing to be difficult, and even cause the battery capacity of the manufactured battery to decrease. Further, when the electrode group is conventionally produced by using a stacker, the electrode and the separator are not closely adhered to each other, and there is still a gap therebetween, which is disadvantageous in pursuit of thinning. In addition, the battery manufacturing technology needs to be stacked in a special drying plant or drying chamber and electrolyte perfusion to avoid the moisture contained in the fabricated battery, and the reaction with the components in the battery causes the quality of the battery product to decrease. However, after the pole piece of the present invention is dried, it is closely adhered to the separator by rolling and hot pressing through the bonding glue, and this step only needs to be carried out in an ordinary factory. When the electrolyte is subsequently poured in the drying room, the whole process can be exempted from being carried out in the drying chamber, and the low moisture content of the battery can be achieved. Further, since the electrode group is easy to operate, it can be used in an inert gas such as a glove box. Electrolyte perfusion and battery encapsulation in the environment can result in better battery quality and lower maintenance costs in the drying chamber.

As described above, since the adhesive used in the present invention can be compatible with the electrolyte used in general batteries, the present invention can prevent the electrolyte from being impregnated and filled into the electrode group due to the adhesive. The problem of the battery forming defective products. Accordingly, the present invention further provides an electrochemical device (eg, A secondary battery) comprising an electrode group and an electrolyte, wherein the electrolyte is used to form an ion channel between the positive electrode and the negative electrode.

In the present invention, the term "viscosity" generally means the viscosity value measured at 25 °C. However, the viscosity of the EC of the present invention is the viscosity value measured at 40 ° C, and the viscosity of the other solvent of the present invention is the viscosity value measured at 25 ° C.

In the present invention, the term "cyclic carbonate compound" means a saturated or unsaturated cyclic hydrocarbon compound containing a carbonate group (-OC(O)O-) in a ring structure, such as: EC, PC, BC, etc.; the term "lactone compound" means a saturated or unsaturated cyclic hydrocarbon (also referred to as a cyclic ester compound) containing an ester group (-C(O)O-) in the ring structure, Such as: GBL; "chain double ether compound" refers to a saturated or unsaturated linear or branched hydrocarbon containing two ether groups in the chain structure, such as: DEC; "cyclic diether compound" The term is a saturated or unsaturated cyclic hydrocarbon containing two ether groups in the ring structure, such as: DOL, 4MeDOL; the term "epoxy compound" means a saturated or unsaturated ring containing an oxygen atom in the ring structure. Hydrocarbons (also known as cyclic ethers) such as THF, 2MeTHF; the term "chain esters" refers to saturated or unsaturated straight or branched chains containing ester groups in the chain structure. Hydrocarbons such as MF, MA, MP, etc. The term "chain carbonate compound" means a saturated or unsaturated linear or branched hydrocarbon group containing a carbonate group in a chain structure, such as DEC, DMC, EMC, etc.; Refers to a saturated straight or branched hydrocarbon group such as: -CH ₃ or -CH(CH ₃ ) ₂ .

Unless otherwise specified, cyclic carbonate compounds, lactone compounds, chain diether compounds, cyclic diether compounds, epoxy compounds, chain ester compounds, and chains are described herein. The carbonate compound may be a substituted or unsubstituted compound in which a substituent may be substituted on any carbon atom of the ring structure or chain structure, for example, a substituent such as an alkyl group, an alkenyl group or an alkynyl group may be substituted. Any carbon atom on the ring structure.

The embodiments of the present invention are described below by way of specific specific examples, and those skilled in the art can readily appreciate the other advantages and advantages of the present invention. The present invention may be embodied or applied in various other specific embodiments. The various details of the present invention can be applied to various aspects and applications, and various modifications and changes can be made without departing from the spirit of the invention.

The electrode fabrication method of the present invention in the embodiment 1-2 is a conventional method in the technical field, and is only described in detail for the related embodiments of the present invention.

Example 1

80-95% of MnO ₂ , acetylene black 3-15% and adhesive polyvinylidene fluoride (PVDF) 3-10% dissolved in N-methyl-2-pyrrolidone (NMP) to form a positive active material slurry Then, the slurry was applied to an aluminum foil having a length of 50 m, a width of 15 cm, and a thickness of 20 μm, and dried at 120 ° C for 4 hours, and finally slit and rolled to form a desired positive electrode plate.

Example 2

90% of the interphase carbon microspheres (MCMB) and 10% of the adhesive PVDF were dissolved in NMP to form a negative active material slurry, and then the slurry was applied to a copper foil having a length of 50 m, a width of 15 cm, and a thickness of 20 μm. And drying at 120 ° C for 4 hours, and finally striping and rolling to form the desired negative electrode plate.

Example 3

The desired solvent was prepared by mixing EC and DEC in a volume ratio of 1:1, and then 152 g of LiPF _{6 was} dissolved in 1 L of the above mixed solvent to prepare 1 M LiPF ₆ as an electrolyte in the perfusion cell.

Example 4

The adhesive gel a was prepared by mixing EC and PC in a 1:1 volume ratio. Next, as shown in FIG. 2, the positive electrode tab 1 and the negative electrode tab 3 prepared in the above Examples 1 and 2 were respectively wetted with the adhesive 4 prepared in the present embodiment, and then the separator 2 was interposed. Between the positive electrode 1 and the negative electrode 3 which are wetted by the bonding glue, the electrode electrode piece and the separator 2 are closely adhered by rolling hot pressing to form a sandwich structure of the positive electrode/separator/negative electrode as shown in FIG. Among them, the separator is a polypropylene (PP) film having a high mechanical property and a thickness of 20 μm.

Example 5

The preparation method of the fifth embodiment of the present invention is substantially the same as that described in the fourth embodiment, except that the bonding glue b used in the embodiment is mixed with an EC:PC:DEC of 0.8:1:0.2 (volume ratio). be made of.

Example 6

The preparation method of the sixth embodiment of the present invention is substantially the same as that described in the fourth embodiment except that the adhesive glue c-n described in the following Tables 1-3 is used instead of the adhesive gel a. In Table 1-3, except that the EC viscosity is 1.9 cP at 40 ° C; the remaining solvent has a PC viscosity of 2.5 cP at 25 ° C; BC viscosity is 3.2 cP; GBL viscosity is 1.7 cP; DOL viscosity is 0.59 cP; 4 MeDOL viscosity 0.6cP; THF viscosity is 0.46cP; 2MeTHF viscosity is 0.47cP; MA viscosity is 0.3cP; MP viscosity is 0.43cP; MF viscosity is 0.33cP; DEC viscosity is 0.75cP; EMC viscosity is 0.65cP; and DME viscosity is 0.46cP.

Comparative example 1

The electrode pad and the separator used in this comparative example are the same as those in the above embodiment, except that the comparative example uses the stacker method to sequentially stack the electrode pad and the separator without using a bonding paste.

Test case

The electrode groups prepared in the above-mentioned Embodiment 4, Example 5 and Comparative Example 1 are respectively used to form a stacked battery, wherein the electrolyte composition used is as described in Embodiment 3, and the electrode group is stacked with a single electrode group and the battery is The discharge rates were all 0.05 C, and the battery discharge test was performed at a normal temperature of 25 °C. The test results are shown in Fig. 4. The horizontal axis of Fig. 4 is the discharge capacity per unit weight, the unit is mAh/g, the battery capacity is about 14 mAh; the vertical axis is the battery voltage, and the unit is V. In the battery, the capacitance is related to the number of electrode stacks of the battery. Therefore, it can be found from FIG. 4 that the battery of Comparative Example 1 and Embodiments 4 and 5 under the same number of electrode stacks and the same electrolyte. The operating voltage values of the batteries are similar, and it is shown that the battery produced by the bonding glue of the present invention and the battery manufacturing method thereof does not impair the performance of the battery.

The above-mentioned embodiments are merely examples for convenience of description, and the scope of the claims is intended to be limited to the above embodiments.

1‧‧‧ positive

2‧‧‧Separator

3‧‧‧negative

4‧‧‧Finishing glue

Fig. 1 is a conventional method of fabricating a stacked electrode assembly.

2 is a schematic view of a rolling hot pressing device for fabricating an electrode assembly in accordance with a preferred embodiment of the present invention.

3 is a schematic view showing a sandwich structure of a positive electrode/separator/negative electrode according to a preferred embodiment of the present invention.

4 is a comparison result of a battery discharge test prepared by the electrode groups of Examples 4 and 5 of the present invention and Comparative Example 1.

1‧‧‧ positive

2‧‧‧Separator

3‧‧‧negative

4‧‧‧Finishing glue

Claims (14)

An electrode assembly comprising: a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and a bonding glue disposed between the positive electrode and the separator and the negative electrode and the separator The positive electrode and the negative electrode are respectively attached to the separator, wherein the adhesive comprises a high viscosity solvent having a viscosity higher than 1 cP, which is selected from the group consisting of a cyclic carbonate compound, a lactone compound, and A group of its combination. The electrode assembly of claim 1, wherein the adhesive further comprises a low viscosity solvent having a viscosity lower than 1 cP, which is selected from the group consisting of a chain diether compound, a cyclic diether compound, and an epoxy resin. A group consisting of a compound, a chain ester compound, a chain carbonate compound, and a combination thereof. The electrode group according to claim 1, wherein the cyclic carbonate compound has a structure represented by the following Chemical Formula 1, and the lactone compound has a structure represented by the following Chemical Formula 2: Wherein R ₁ is a C ₁ -C ₆ alkyl group, n is an integer from 1 to 3, m is an integer from 0 to 8, and p is an integer from 0 to 10. The electrode group according to claim 2, wherein the chain-shaped diether compound has a structure represented by the following chemical formula 3, and the cyclic diether compound has a structure represented by the following chemical formula 4, the epoxy group The compound has a structure represented by the following Chemical Formula 5, and the chain ester compound has a structure represented by the following Chemical Formula 6, and the chain carbonate compound has a structure represented by the following Chemical Formula 7: Wherein R ₂ , R ₃ , R ₄ , R ₅ , R ₇ , R ₈ and R ₉ are each independently C ₁ -C ₆ alkyl, R ₆ is hydrogen or C ₁ -C ₆ alkyl, and r is 1 to An integer of 6 wherein p is an integer from 0 to 10, y is an integer from 0 to 12, s and t are each an integer from 1 to 3, and s+t is an integer from 2 to 4. The electrode group according to claim 1, wherein the high viscosity solvent has a viscosity ranging from 1.5 cP to 4.0 cP. The electrode assembly of claim 2, wherein the low viscosity solvent has a viscosity ranging from 0.3 cP to 0.8 cP. The electrode assembly of claim 2, wherein the volume ratio of the high viscosity solvent to the low viscosity solvent is 1:1 to 1:0.01. A method for manufacturing an electrode assembly, comprising: (A) providing a positive electrode, a negative electrode, and a separator; and (B) using a bonding glue, the positive electrode and the negative electrode are respectively attached to the separator, wherein the sticker The gel comprises a high viscosity solvent having a viscosity higher than 1 cP selected from the group consisting of cyclic carbonate compounds, lactone compounds, and combinations thereof. The method for preparing an electrode assembly according to claim 8, wherein the adhesive further comprises a low viscosity solvent having a viscosity lower than 1 cP, which is selected from the group consisting of a chain diether compound, a cyclic diether compound, A group consisting of an epoxy compound, a chain ester compound, a chain carbonate compound, and a combination thereof. The electrode group manufacturing method according to claim 8, wherein the step (B) is performed by bonding a positive electrode and the negative electrode to the separator by a hot press method. The production method according to the eighth aspect of the invention, wherein the cyclic carbonate compound has a structure represented by the following Chemical Formula 1, and the lactone compound has a structure represented by the following Chemical Formula 2: Wherein, Rl is C ₁ -C ₆ alkyl, n is an integer of from 1 to 3, m is an integer of 0-8, and p is an integer of 0 to 10. The production method according to claim 9, wherein the chain-shaped diether compound has a structure represented by the following Chemical Formula 3, and the cyclic diether compound has a structure represented by the following Chemical Formula 4, the epoxy The compound has a structure represented by the following Chemical Formula 5, and the chain ester compound has a structure represented by the following Chemical Formula 6, and the chain carbonate compound has a structure represented by the following Chemical Formula 7: Wherein R ₂ , R ₃ , R ₄ , R ₅ , R ₇ , R ₈ and R ₉ are each independently C ₁ -C ₆ alkyl, R ₆ is hydrogen or C ₁ -C ₆ alkyl, and r is 1 to An integer of 6 wherein p is an integer from 0 to 10, y is an integer from 0 to 12, s and t are each an integer from 1 to 3, and s+t is an integer from 2 to 4. The manufacturing method according to claim 8, wherein the high viscosity solvent has a viscosity ranging from 1.5 cP to 4.0 cP. The manufacturing method according to claim 9, wherein the low viscosity solvent has a viscosity ranging from 0.3 cP to 0.8 cP. The production method according to claim 9, wherein the volume ratio of the high viscosity solvent to the low viscosity solvent is 1:1 to 1:0.01.