CN115775868A

CN115775868A - Battery pole piece and preparation method and application thereof

Info

Publication number: CN115775868A
Application number: CN202310092329.4A
Authority: CN
Inventors: 祁原深; 谢红波; 王伟毅
Original assignee: Guangdong Israel Institute Of Technology
Current assignee: Guangdong Israel Institute Of Technology
Priority date: 2023-02-10
Filing date: 2023-02-10
Publication date: 2023-03-10
Anticipated expiration: 2043-02-10
Also published as: CN115775868B

Abstract

The invention discloses a battery pole piece and a preparation method and application thereof, and relates to the technical field of lithium ion batteries. The preparation method of the battery pole piece comprises the following steps: (1) Uniformly mixing an active substance, a conductive agent, an adhesive and a solvent to obtain mixed slurry; (2) Coating the mixed slurry on a substrate, drying, rolling and cutting to obtain a pole piece A; (3) And carrying out constant current electrifying treatment on the pole piece A to obtain the battery pole piece. According to the invention, through electrifying the pole piece, the defects generated during rolling are compensated, the contact mode among active material particles is changed, and the conductivity and the capacity of the pole piece are improved.

Description

Battery pole piece and preparation method and application thereof

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a battery pole piece and a preparation method and application thereof.

Background

In order to increase the conductivity of the battery electrode plate, the prior art mostly increases the proportion of the conductive agent in the slurry formula when the battery electrode slurry is prepared, so as to achieve the purposes of increasing the conductivity and improving the battery power. And after the slurry is prepared, coating the slurry on a current collector metal foil, rolling, and finally slitting and flaking.

In the slurry preparation process, the proportion of the conductive agent is increased, the conductivity of the pole piece can be improved, but the conductive agent occupies the space of the active substance, so that the energy density of the battery is reduced, and in some fields, high power and high energy density are required, such as the fields of new energy automobiles and the like. Increasing the proportion of the conductive agent does not satisfy the above requirements.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a battery pole piece, a preparation method and application thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a battery pole piece comprises the following steps:

(1) Uniformly mixing an active substance, a conductive agent, an adhesive and a solvent to obtain mixed slurry;

(2) Coating the mixed slurry on a substrate, drying and rolling to obtain a pole piece A;

(3) And carrying out constant current electrifying treatment on the pole piece A to obtain the battery pole piece.

The purpose of rolling is to enhance the bonding strength of the active substance and the foil, compress the volume of the battery core, improve the material density of the battery pole piece and the energy density of the battery core, and reduce the porosity among the active substance, the conductive agent and the binder in the pole piece; but the rolling process can cause some microcracks on the pole piece, introduce crystal defects and reduce the performance of the pole piece in service. According to the invention, through constant current electrifying treatment on the pole piece, active ingredient particles can be sintered, and the electronic conduction mode among the particles is changed from original point contact to surface contact, so that the resistance value is reduced, and the conductivity is improved. By adopting the method, the dependence on the conductive agent can be greatly reduced, and the conductivity of the pole piece is improved under the condition of not sacrificing energy density.

Preferably, in step (3), the conditions of the constant current energization processing are as follows: the current density is 50 to 3000A/mm ² The time is 0.0001 to 0.2s; further preferably, the conditions of the constant current energization processing are as follows: the current density is 500 to 2000A/mm ² The time is 0.001 to 0.1s. The pole piece is heated when the current density is too high or the electrifying time is too long, the physical and chemical properties of the active substances are influenced, and the electrical property of the pole piece is reduced; the defects generated in the rolling process cannot be repaired due to too low current density or too short electrifying time, and the contact mode among the active component particles can be changed. The conductivity of the pole piece can be obviously improved by carrying out the electrifying treatment under the conditions.

The invention also discloses the positive plate prepared by the method, the active substance is lithium iron phosphate, the conductive agent is at least one of conductive carbon black, a carbon nano tube and graphene, the adhesive is polyvinylidene fluoride (PVDF), and the solvent is N-methylpyrrolidone (NMP); the mass ratio of the active substance to the conductive agent to the adhesive to the solvent is (94 to 95): (0.3 to 1.5): (4 to 6): (48 to 52).

Preferably, the conductive agent is a compound of graphene and a carbon nanotube, and the mass ratio of the graphene to the carbon nanotube is (1 to 3): 1. when the ratio of graphene to carbon nanotubes in the conductive agent meets the above-mentioned limit, the conductivity and capacity of the electrode sheet can be greatly improved by the above-mentioned electrification treatment.

Preferably, the substrate is an aluminum foil with the thickness of 10 to 12 mu m, and the coating surface density of the mixed slurry on the substrate is 200 to 400g/m ² The compacted density after rolling is 2 to 2.2g/m ² . Further preferably, the coating surface density of the mixed slurry on the substrate is 250 to 350g/m ² . When the size, the coating surface density and the compaction density of the pole piece meet the conditions, the defects generated by rolling can be quickly repaired by electrifying treatment, and the conductivity of the pole piece is improved.

Meanwhile, the invention also disclosesThe negative plate prepared by the method is provided, the active substance is graphite, the conductive agent is conductive carbon black, the adhesive is a compound of carboxymethyl cellulose (CMC) and styrene butadiene latex (SBR), and the solvent is water; the mass ratio of the active substance to the conductive agent to the adhesive to the solvent is (95 to 96): (0.5 to 1.5): (2.5 to 4.5): (95 to 97). The substrate of the negative plate is a copper foil with the thickness of 6-8 mu m, and the coating surface density of the mixed slurry on the substrate is 120-180g/m ² The compacted density after rolling is from 1.3 to 1.5g/m ² 。

In addition, the invention also discloses a battery, and the positive plate and/or the negative plate of the battery are/is prepared by adopting the method.

Compared with the prior art, the invention has the beneficial effects that: according to the invention, the pole piece is subjected to constant-current electrifying treatment, and the treatment conditions are selected, so that the defects generated in the rolling process can be compensated, the contact mode among active substance particles is changed, and the conductivity of the pole piece is improved. In addition, the components of the pole piece are selected, and the pole piece is processed under the preparation conditions, so that the capacity and the conductivity of the pole piece are greatly improved. The battery prepared by the pole piece has good electrical property.

Drawings

FIG. 1 is a surface topography of the positive plate described in example 1 after the positive plate has been subjected to an electrical treatment;

fig. 2 is a surface topography diagram of the positive electrode sheet described in example 1 before the electrification treatment.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments.

Examples 1 to 11

In the embodiment of the preparation method of the battery pole piece, the processing method in the embodiments 1 to 11 comprises the following steps:

(1) Uniformly mixing lithium iron phosphate (delustered nano), carbon nanotubes, PVDF and NMP in a mass ratio of 94;

(2) Coating the mixed slurryOn a 12 μm aluminum foil, the coating surface density was 300g/m ² Drying at 120 deg.C, rolling, and compacting at density of 2.1g/m ² Cutting into pole pieces of 58mm x 690mm to obtain a positive pole piece A;

(3) And (3) respectively clamping the positive electrode and the negative electrode of the power supply at two ends of the positive electrode plate A, and electrifying the positive electrode plate A to obtain the battery electrode plate, wherein the treatment conditions are shown in Table 1.

TABLE 1 electrification treating conditions Table

Item	Current density (A/mm 2)	Time(s)
			Example 1	50	0.01
Example 2	100	0.01
			Example 3	500	0.01
Example 4	1000	0.01
			Example 5	2000	0.01
Example 6	3000	0.01
			Example 7	1000	0.001
Example 8	1000	0.1
			Example 9	1000	0.0001
Example 10	1000	0.2
			Example 11	1000	0.5

Examples 12 to 20

In the examples of the method for manufacturing a battery pole piece of the present invention, the differences between the methods for manufacturing the battery pole piece of examples 12 to 20 and example 4 are only that the components of the mixed slurry are different, and are specifically shown in table 2.

TABLE 2 ingredient Table of the Mixed slurry (parts by weight)

Item	Lithium iron phosphate	Carbon nanotube	Graphene	Conductive carbon black	PVDF	NMP
							Example 12	94		1	5	50
Example 13	94			1	5	50
							Example 14	94	0.5	0.5	5	50
Example 15	94	0.25	0.75		5	50
							Example 16	94	0.4	0.6	5	50
Example 17	94	0.1	0.9		5	50
							Example 18	94	0.6	0.4	5	50
Example 19	94.5		0.3		4	48
							Example 20	95		1.5	6	52

Examples 21 to 24

In the examples of the preparation method of the battery pole piece, the difference between the examples 21 to 24 and the example 4 is only that the coating amount of the mixed slurry on the aluminum foil is different, and the density of the coating surface is respectively 200g/m ² 、250g/m ² 、350g/m ² 、400g/m ² 。

Example 25

In the embodiment of the preparation method of the battery pole piece, the preparation method comprises the following steps:

(1) Uniformly mixing graphite (Shenzhenbei), conductive carbon black, CMC, SBR and water in a mass ratio of 95.5;

(2) The mixed slurry was coated on a copper foil of 8 μm with a coating surface density of 150g/m ² Drying at 120 deg.C, rolling, and compacting at density of 1.4g/m ² Cutting into pole pieces of 58mm to 700mm to obtain a negative pole piece A;

(3) Respectively clamping the positive and negative electrodes of a power supply at two ends of the negative plate APerforming electrification treatment at a current density of 1000A/mm ² The energization time was 0.01s.

Comparative example 1

A method for manufacturing a battery pole piece, which is different from example 4 only in that the pole piece is not subjected to energization treatment.

Comparative example 2

A method of manufacturing a battery electrode sheet, which differs from example 25 only in that the electrode sheet is not subjected to an energization treatment.

The performance of the pole pieces of the examples and the comparative examples was tested with a conductivity tester, and the test results are shown in table 3.

TABLE 3 Performance test results Table

Item	Conductivity (S/m)
		Example 1	55
Example 2	58
		Example 3	73
Example 4	75
		Example 5	75
Example 6	57
		Example 7	75
Example 8	75
		Example 9	61
Example 10	60
		Example 11	59
Example 12	74
		Example 13	53
Example 14	75
		Example 15	76
Example 16	76
		Example 17	58
Example 18	59
		Example 19	58
Example 20	60
		Example 21	54
Example 22	75
		Example 23	74
Example 24	54
		Example 25	120
Comparative example 1	35
		Comparative example 2	100

The 1C discharge capacity and the 20C discharge capacity of examples 1 to 24 and comparative example 1 were measured. The positive plates prepared in examples 1 to 24 and comparative example 1 were respectively wound with a graphite negative electrode and a PP separator, placed in a battery case, injected with an electrolyte, sealed, baked for 24 hours, and charged at a small rate of 0.05C for 20 hours, to obtain batteries to be tested (the graphite negative electrode, the PP separator, and the electrolyte used in each group of batteries are all the same material). The test results are shown in table 4.

Table 4 table of performance test results

Item	1C discharge Capacity (mAh)	20C discharge capacity (mAh)
			Example 1	1000	800
Example 2	1020	805
			Example 3	1050	830
Example 4	1080	831
			Example 5	1080	829
Example 6	1009	809
			Example 7	1080	831
Example 8	1080	830
			Example 9	1010	807
Example 10	1008	810
			Example 11	1009	811
Example 12	1010	810
			Example 13	1008	807
Example 14	1080	830
			Example 15	1081	831
Example 16	1080	831
			Example 17	1011	810
Example 18	1009	809
			Example 19	1008	808
Example 20	995	810
			Example 21	1001	801
Example 22	1060	835
			Example 23	1065	837
Example 24	990	787
			Comparative example 1	950	750

As can be seen from tables 3 to 4, the electrical property of the electrode sheet after being electrified is obviously superior to that of the electrode sheet without being electrified.

In addition, the test results of comparative examples 1 to 9 show that the performances of examples 3 to 5 and examples 7 to 8 are obviously better than those of examples 1 to 2, 6 and 9, and the results show that the conditions of the electrification treatment preferably have the current density of 500 to 2000A/mm ² The time is 0.001 to 0.1s.

The test results of comparative examples 12 to 18 show that when the conductive agent used for preparing the positive electrode sheet is a carbon nanotube or graphene, the mass ratio of the conductive agent to the graphene is 1: (1 to 3), the electrical properties of the positive electrode sheet are significantly better.

The test results of comparative examples 21 to 24 show that the coating surface density also has great influence on the performance, and when the coating surface density of the positive plate is 250 to 350g/m ² And the prepared battery has higher discharge capacity.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a battery pole piece is characterized by comprising the following steps:

(2) Coating the mixed slurry on a substrate, drying, rolling and cutting to obtain a pole piece A;

(3) Carrying out constant current electrifying treatment on the pole piece A to obtain the battery pole piece;

the conditions of the constant current electrifying treatment are as follows: the current density is 50 to 3000A/mm ² The time is 0.0001 to 0.2s.

2. The production method according to claim 1, wherein in the step (3), the conditions of the constant-current energization treatment are: the current density is 500 to 2000A/mm ² Time 0.001-time0.1s。

3. A positive plate is prepared by the method of any one of claims 1 to 2, wherein the active material is lithium iron phosphate, the conductive agent is at least one of conductive carbon black, a carbon nanotube and graphene, the adhesive is polyvinylidene fluoride, and the solvent is N-methylpyrrolidone; the mass ratio of the active substance to the conductive agent to the adhesive to the solvent is (94 to 95): (0.3 to 1.5): (4 to 6): (48 to 52).

4. The positive electrode sheet according to claim 3, wherein the conductive agent is a compound of graphene and a carbon nanotube, and the mass ratio of the graphene to the carbon nanotube is (1 to 3): 1.

5. the positive electrode sheet according to claim 3, wherein the substrate is an aluminum foil of 10 to 12 μm, and the density of the coated surface of the mixed slurry on the substrate is 200 to 400g/m ² The compacted density after rolling is 2 to 2.2g/m ² 。

6. The negative plate is characterized by being prepared by the method of any one of claims 1 to 2, wherein the active substance is graphite, the conductive agent is conductive carbon black, the binder is a compound of carboxymethyl cellulose and styrene-butadiene latex, and the solvent is water; the mass ratio of the active substance to the conductive agent to the adhesive to the solvent is (95 to 96): (0.5 to 1.5): (2.5 to 4.5): (95 to 97).

7. The negative electrode sheet according to claim 6, wherein the substrate is a copper foil of 6 to 8 μm, and the density of the coating surface of the mixed slurry on the substrate is 120 to 180g/m ² The compacted density after rolling is 1.3 to 1.5g/m ² 。

8. A battery, characterized in that at least one of the positive plate and the negative plate of the battery is prepared by the method of any one of claims 1 to 2.