CN114203966A

CN114203966A - Preparation method of lithium battery pole piece, pole piece and battery

Info

Publication number: CN114203966A
Application number: CN202111268799.9A
Authority: CN
Inventors: 梁德声; 王守军; 刘新华; 吴凤梅
Original assignee: SHENZHEN EPT BATTERY CO Ltd
Current assignee: SHENZHEN EPT BATTERY CO Ltd
Priority date: 2021-10-29
Filing date: 2021-10-29
Publication date: 2022-03-18

Abstract

The embodiment of the application provides a preparation method of a lithium battery pole piece, the pole piece and a battery, wherein the preparation method comprises the steps of obtaining a conductive substrate of the pole piece; preparing a first slurry and a second slurry for coating on the conductive substrate, wherein the particle size of the first slurry is smaller than the particle size of the second slurry; the method comprises the steps of firstly coating first slurry on the surface of a conductive substrate, drying the first slurry, and then coating second slurry on the surface of the first slurry.

Description

Preparation method of lithium battery pole piece, pole piece and battery

Technical Field

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

Background

In the prior art, the pole pieces of the lithium ion battery are coated with the sizing agents, and the granularity of the sizing agents is not specially set, so that the sizing agents with small granularity of the whole battery are possibly far away from the surface of the conductive substrate, the adhesive force with the substrate is reduced, and the conductive performance is reduced; or the large-particle size slurry is arranged on the inner layer of the conductive substrate, so that the consumption of active materials of the SEI film is increased under high temperature, and the loss of the capacity of the positive electrode under high temperature is increased.

Disclosure of Invention

The invention aims to provide a preparation method of a lithium battery pole piece, the pole piece and a battery, which are used for solving or partially solving the technical problems in the prior art.

In order to achieve the above purpose, the embodiments of the present application provide the following technical solutions:

the preparation method of the lithium battery pole piece provided by the embodiment of the application comprises the following steps,

obtaining a conductive matrix of the pole piece;

preparing a first slurry and a second slurry for coating on the conductive substrate, wherein the particle size of the first slurry is smaller than the particle size of the second slurry;

the method comprises the steps of firstly coating first slurry on the surface of a conductive substrate, drying the first slurry, and then coating second slurry on the surface of the first slurry.

Compared with the prior art, according to the preparation method of the lithium battery pole piece, the first slurry with small granularity is coated on the surface of the conductive substrate, the second slurry with large granularity is coated on the surface of the first slurry, and the first slurry with small granularity is favorable for ensuring the low-temperature performance of the lithium battery, enhancing the adhesive force with the conductive substrate and enhancing the conductive performance; the large-particle-size second slurry is beneficial to ensuring the high-temperature performance of the lithium ion battery, and the small-particle-size second slurry reduces the dissolution of consumed active materials of an SEI film at high temperature and reduces the loss of the capacity of the anode at high temperature.

In a second aspect, an embodiment of the present application further provides a pole piece, which is prepared by the method for preparing a lithium battery pole piece provided in the first aspect.

In a second aspect, an embodiment of the present application further provides a battery, where the pole piece is described in the second aspect of the battery.

Compared with the prior art, the beneficial effects of the pole piece and the battery provided by the second aspect and the third aspect of the embodiment of the present application are the same as the beneficial effects of the method for preparing the lithium battery pole piece provided by the embodiment of the first aspect of the embodiment of the present application, and are not repeated herein.

Drawings

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic flow chart of a method for manufacturing a lithium battery pole piece according to an embodiment of the present application;

FIG. 2 is a graph showing a comparison of discharge efficiencies at different temperatures of batteries manufactured in examples and comparative examples of the present application;

FIG. 3 is a graph showing the comparison of the expansion ratios of the batteries prepared in examples and comparative examples;

fig. 4 is a comparative diagram illustrating capacity recovery of batteries manufactured in examples and comparative examples of the present application.

Detailed Description

In order to make the technical solutions of the embodiments of the present invention better understood, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of the embodiments of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the embodiments of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein.

The drawings are for illustrative purposes only and are presented in the form of illustrations rather than physical illustrations and are not to be construed as limiting the invention; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The following will further explain the specific implementation and the implementation effect of the technical solution of the present invention by combining the comparative example and the embodiment of the present invention.

As shown in fig. 1, an embodiment of the present application provides a method for preparing a lithium battery pole piece, including the following steps:

step S01, obtaining a conductive matrix of the pole piece;

it should be noted that, if the electrode plate to be prepared is a positive electrode plate, the conductive substrate is an aluminum foil, and if the electrode plate to be prepared is a negative electrode plate, the conductive substrate is a copper foil.

Step S02, preparing a first slurry and a second slurry for coating on the conductive substrate, wherein the particle size of the first slurry is smaller than the particle size of the second slurry;

the conductive substrate is coated with a first slurry having a small particle size, and then coated with a second slurry having a large particle size, wherein the first slurry has a particle size D50 of 4-8 μm and the second slurry has a particle size D50 of 20-30 μm.

If the pole piece is a positive pole piece, the first sizing agent and the second sizing agent for preparing the electrode comprise,

adding a first conductive agent into an N-methyl pyrrolidone solution containing polyvinylidene fluoride, stirring, adding a ternary positive electrode material with the particle size D50 of 4-8 mu m, and stirring to prepare a first slurry of a positive electrode sheet;

adding a third conductive agent into an N-methyl pyrrolidone solution containing polyvinylidene fluoride, stirring, adding a ternary positive electrode material with the particle size D50 of 20-30 mu m, and stirring to prepare a second slurry of the positive electrode plate; wherein the first conductive agent and the third conductive agent are both superconducting carbon black and/or carbon nano tubes, and the particle size D50 of the ternary cathode material is 4-6 μm.

If the pole piece is a negative pole piece, the first slurry and the second slurry for preparing the electrode comprise,

adding the second conductive agent into the aqueous solution containing sodium carboxymethylcellulose, stirring, adding N-methyl pyrrolidone, stirring, adding a graphite material with the particle size D50 of 4-8 mu m, and stirring to prepare the first slurry of the negative plate.

And adding a fourth conductive agent into an N-methyl pyrrolidone solution containing polyvinylidene fluoride, stirring, adding a graphite material with the particle size D50 of 20-30 mu m, and stirring to prepare a second slurry of the negative plate, wherein the second conductive agent and the fourth conductive agent are both superconducting carbon black, and the particle size D50 of the graphite material is 20-30 mu m.

Step S03, first coating the first slurry on the surface of the conductive substrate, drying the first slurry, and then coating the second slurry on the surface of the first slurry.

If the pole piece is a positive pole piece, the first slurry accounts for 60-85% of the total slurry, and the second slurry accounts for 15-40% of the total slurry; if the pole piece is a negative pole piece, the first slurry accounts for 20-50% of the total slurry, and the second slurry accounts for 50-80% of the total slurry.

In the following examples, polyvinylidene fluoride is abbreviated as PVDF, N-methylpyrrolidone is abbreviated as NMP, and sodium carboxymethylcellulose is abbreviated as CMC

Comparative example 1 preparation of high-temperature ternary lithium ion battery

Adding conductive agents such as superconducting carbon black, carbon nano tubes and the like into a solution of N-methylpyrrolidone (NMP) containing polyvinylidene fluoride (PVDF) for stirring, adding a ternary cathode material with the granularity D50 of 20 mu m for stirring to prepare slurry, coating the slurry on an aluminum foil with the granularity of 12 mu m, and drying, splitting, spot-welding to prepare a cathode plate;

adding a superconducting carbon black conductive agent into a water solution containing sodium carboxymethylcellulose (CMC), stirring, adding N-methyl pyrrolidone (NMP), stirring, adding a graphite material with the D50 value of 20 mu m, stirring to prepare a slurry, coating the slurry on a copper foil with the thickness of 10 mu m, drying, slitting, spot welding to prepare a negative plate;

and winding the positive plate, the negative plate and the diaphragm to obtain an electrode group, and filling the electrode group into a shell, and carrying out liquid injection, sealing and formation to obtain the high-temperature ternary lithium ion battery.

Comparative example 2 preparation of low-temperature ternary lithium ion battery

Adding conductive agents such as superconducting carbon black, carbon nano tubes and the like into an N-methyl pyrrolidone (NMP) solution containing polyvinylidene fluoride (PVDF), stirring, adding a ternary positive electrode material with the D50 value of 8 mu m, stirring to prepare slurry, coating the slurry on an aluminum foil with the thickness of 12 mu m, drying, slitting, spot welding and preparing a positive plate;

adding a superconducting carbon black conductive agent into a water solution containing sodium carboxymethylcellulose (CMC), stirring, adding N-methyl pyrrolidone (NMP), stirring, adding a graphite material with the D50 value of 8 mu m, stirring to prepare a slurry, coating the slurry on a copper foil with the thickness of 10 mu m, drying, slitting, spot welding to prepare a negative plate;

and winding the positive plate, the negative plate and the diaphragm to obtain an electrode group, and filling the electrode group into a shell, and carrying out liquid injection, sealing and formation to obtain the low-temperature ternary lithium ion battery.

Example 1 preparation of wide temperature lithium ion battery of the present application

The preparation method of the positive plate comprises the following steps:

adding conductive agents such as superconducting carbon black, carbon nano tubes and the like into an N-methyl pyrrolidone (NMP) solution containing polyvinylidene fluoride (PVDF), stirring, adding a ternary anode material with the D50 of 5 mu m, and stirring to prepare a first slurry of the anode plate;

adding conductive agents such as superconducting carbon black, carbon nano tubes and the like into an N-methyl pyrrolidone (NMP) solution containing polyvinylidene fluoride (PVDF), stirring, adding a ternary anode material with the D50 of 25 mu m, and stirring to prepare a second slurry of the anode plate;

the first slurry was coated on a 12 μm aluminum foil and dried, the first sizing amount accounting for 65% of the total sizing amount. Coating the second sizing agent on the dried pole piece, wherein the sizing amount of the second time is 35%, and drying, splitting, spot welding to obtain a positive pole piece;

the preparation method of the negative plate comprises the following steps:

adding a superconducting carbon black conductive agent into a sodium carboxymethylcellulose (CMC) -containing aqueous solution, stirring, adding N-methyl pyrrolidone (NMP), stirring, adding a graphite material with the D50 of 6 mu m, and stirring to prepare a first slurry of the negative plate;

adding the superconducting carbon black conductive agent into an N-methyl pyrrolidone (NMP) solution containing sodium carboxymethylcellulose (CMC) and stirring, adding a graphite material with the D50 of 25 mu m and stirring to prepare a second slurry of the negative plate;

coating the first slurry of the negative pole piece on a copper foil with the thickness of 10 mu m, and drying to obtain the pole piece, wherein the first powder loading accounts for 40% of the total powder loading. And coating the slurry 2 on the dried pole piece, wherein the secondary powder coating amount is 60%, and drying, slitting, spot welding to obtain the negative pole piece.

And winding the positive plate, the negative plate and the diaphragm to obtain a plate group, assembling the plate group into a shell, and performing liquid injection, sealing and formation to obtain the wide-temperature ternary lithium ion battery.

The batteries prepared in comparative example 1, comparative example 2 and example 1 were subjected to the following performance test;

1. discharge efficiency at different temperatures:

fully charging the battery at 20 +/-5 ℃ with a current of 0.5 ℃, and then discharging at an ambient temperature of 20 +/-5 ℃ with a current of 0.5 ℃ to obtain a capacity C0;

the battery was fully charged at 20 ± 5 ℃ with a current of 0.5C and then discharged at different ambient temperatures with a current of 0.5C to obtain a capacity C1.

C0/C1 100% is the discharge efficiency at that temperature;

TABLE 1

-30℃

-20℃

0℃

20℃

60℃

80℃

Comparative example 1

34.3％

63.5％

93.7％

100.0％

100.9％

101.3％

Comparative example 2

76.3％

88.3％

97.5％

100.0％

78.6％

67.3％

Example 1

77.9％

89.4％

98.4％

100.0％

101.4％

101.1％

As can be seen from fig. 2 and table 1, the discharge efficiency of example 1 in the range of-30 ℃ to 80 ℃ is from 77.9% to 101.1%, the discharge efficiency of comparative example 1 in the range of-30 ℃ to 80 ℃ is from 34.3% to 101.3%, the discharge efficiency of comparative example 2 in the range of-30 ℃ to 80 ℃ is from 76.3% to 67.3%, and the discharge efficiency of the battery prepared in example 1 is not less than the discharge efficiency of comparative example 1 and comparative example 2 at each temperature point.

2. 3 days expansion at 85 ℃ (soft pack lithium ion battery only):

the cell thickness T1 was tested after fully charging the cell at 20 ± 5 ℃ with a current charge of 0.5C, and then stored at ambient temperature of 85 ± 2 ℃ for three days at a test cell thickness T2 with an expansion rate of (T2-T1)/T1 x 100%.

TABLE 2

As can be seen from fig. 3 and table 2, the 1#, 2# and 3# batteries prepared by comparative example 1, comparative example 2 and example 1, respectively, were subjected to the expansion rate test, and it is seen that the expansion rates of the 1# batteries prepared by comparative example 1, comparative example 2 and example 1, respectively, were 1.8%, 7.6% and 1.7% obtained by the expansion rate test when they were stored at an ambient temperature of 85 ± 2 ℃ for three days, and it can be concluded that the expansion rate of the battery prepared by example 1 was the smallest; the expansion rates of the batteries # 2 prepared in comparative example 1, comparative example 2 and example 1, respectively, after the expansion rate test of the three-day storage test at the ambient temperature of 85 ± 2 ℃ were 1.3%, 9.8% and 1.2%, and the minimum expansion rate of the battery prepared in example 1 could be obtained; the expansion rates of the 3# batteries respectively prepared by comparative example 1, comparative example 2 and example, which were subjected to the expansion rate test stored at an ambient temperature of 85 ± 2 ℃ for three days, were 1.6%, 7.7% and 1.4%, and it was found that the expansion rate of the battery prepared in example 1 was the smallest.

3. Capacity recovery of battery after temperature shock

The cell prepared by example 1 was tested in a temperature shock box according to GB T2423.22-2012, predicting a shelf time T of 20min, a temperature shock maximum temperature Tmax of +80 ℃, a temperature shock minimum temperature Tmin of-30 ℃, a total duration: 300 cycles are more than or equal to 200 h; the capacity before temperature shock is C1, the battery capacity after temperature shock is C2, and the expansion rate is (C2-C1)/C1 x 100%.

TABLE 3

	1#	2#	3#
				Comparative example 1	61.6％	58.5％	57.9％
Comparative example 2	43.5％	57.7％	51.3％
				Example 1	93.4％	95.7％	92.8％

As can be seen from fig. 4 and table 3, the capacity recovery rates of the batteries # 1, # 2 and # 3 prepared by comparative example 1, comparative example 2 and example 1, respectively, after the temperature shock were obtained, and the capacity recovery rates of the batteries # 1, comparative example 2 and example 1, respectively, after the temperature shock were obtained were 61.6%, 43.5% and 93.4%, respectively, and it was found that the capacity recovery rate of the battery prepared in example 1 was the highest; the capacity recovery rates obtained by the capacity recovery of the batteries after the temperature shock of the batteries of comparative example 1, comparative example 2 and # 1 prepared in example were 58.5%, 57.7% and 95.7%, respectively, and it was found that the capacity recovery rate of the battery prepared in example 1 was the highest; the capacity recovery rates obtained by the capacity recovery of the batteries of comparative example 1, comparative example 2 and example # 1 after the temperature shock were 57.9%, 51.3% and 92.8%, respectively, and it was found that the capacity recovery rate of the battery of example 1 was the highest.

Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims

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

obtaining a conductive matrix of the pole piece;

2. The method of claim 1, wherein the step of forming the lithium battery electrode sheet comprises the steps of,

the particle size of the first slurry D50 is 4-8 μm, and the particle size of the second slurry D50 is 20-30 μm.

3. The method of claim 1, wherein preparing the first slurry for the electrode comprises,

4. The method of claim 3, wherein preparing the second slurry for the electrode comprises,

adding a third conductive agent into an N-methyl pyrrolidone solution containing polyvinylidene fluoride, stirring, adding a ternary positive electrode material with the particle size D50 of 20-30 mu m, and stirring to prepare a second slurry of the positive electrode plate;

and adding the fourth conductive agent into an N-methyl pyrrolidone solution containing polyvinylidene fluoride, stirring, adding a graphite material with the particle size D50 of 20-30 mu m, and stirring to prepare a second slurry of the negative plate.

5. The method for preparing a lithium battery pole piece as claimed in claim 3 or 4,

the particle size D50 of the ternary anode material is 4-6 μm, and the particle size D50 of the graphite material is 20-30 μm.

6. The method of claim 1, wherein the step of forming the lithium battery electrode sheet comprises the steps of,

if the pole piece is a positive pole piece, the first slurry accounts for 60-85% of the total slurry, and the second slurry accounts for 15-40% of the total slurry;

if the pole piece is a negative pole piece, the first slurry accounts for 20-50% of the total slurry, and the second slurry accounts for 50-80% of the total slurry.

7. The method according to claim 5, wherein the step of preparing the lithium battery electrode plate,

if the pole piece is a positive pole piece, the first sizing agent accounts for 65% of the total sizing agent, and the second sizing agent accounts for 35% of the total sizing agent;

if the pole piece is a negative pole piece, the first slurry accounts for 40% of the total slurry, and the second slurry accounts for 60% of the total slurry.

8. The method of claim 1, wherein the conductive substrate of the positive plate is aluminum foil and the conductive substrate of the negative plate is copper foil.

9. A pole piece prepared by the method of manufacturing a lithium battery pole piece of claims 1 to 8.

10. A battery comprising a pole piece according to claim 9.