CN104759397B - Coating method of lithium ion battery positive/negative pole piece and positive/negative pole piece - Google Patents

Abstract

The invention discloses a coating method of a lithium ion battery positive/negative pole piece and the positive/negative pole piece, wherein the coating method comprises the following steps: conveying the anode slurry or the cathode slurry to a coating machine for coating, wherein an oven of the coating machine is divided into a high-temperature front section, a low-temperature middle section and a high-temperature rear section, and the temperature and the circulating air volume of each section are respectively as follows: high-temperature front stage: the temperature of the oven is 125-135 ℃, and the circulating air quantity is 35-50 Hz; low-temperature middle section: the temperature of the oven is 105-125 ℃, is lower than that of the oven at the high-temperature front section, and the circulating air quantity is 30-45 Hz; high-temperature back stage: the temperature of the oven is 125-135 ℃, the temperature of the oven is higher than that of the oven at the low-temperature middle section, and the circulating air quantity is 35-50 Hz. The coating method of the lithium ion battery positive/negative pole piece provided by the invention can reduce the resistivity of the pole piece, improve the conductivity, reduce the internal resistance of the battery, and improve the multiplying power charge-discharge and cycle performance of the battery.

Description

Lithium-ion battery positive/negative electrode sheet coating method and positive/negative electrode sheet

technical field

The invention relates to the field of lithium ion batteries, in particular to a method for coating positive/negative pole pieces of lithium ion batteries and the positive/negative pole pieces.

Background technique

As the application fields of lithium-ion batteries become more and more extensive, the client's requirements for its performance are also getting higher and higher. The basic principle of the traditional coating process is to require the positive and negative electrode slurry to be baked and dried after passing through the oven of the coating machine, and the adhesion of the coating should be qualified. However, there is no systematic research and analysis on the electrical conductivity of the coated electrode. control. If the resistivity of the coated pole piece is too high, it will lead to large internal resistance of the battery, poor charge and discharge rate and poor cycle performance. Therefore, it is obviously necessary to effectively reduce the resistivity of the electrode sheet when coating the positive and negative electrode sheets.

Contents of the invention

In view of the above-mentioned current state of the art, the technical problem to be solved by the present invention is to provide a coating method for the positive/negative pole pieces of lithium-ion batteries, which can effectively reduce the resistivity of the coated pole pieces and improve the positive and negative electrodes of lithium-ion batteries. / Conductivity of the negative pole piece.

In order to solve the above-mentioned technical problems, a kind of coating method of lithium-ion battery positive/negative pole sheet provided by the present invention comprises the following steps:

The positive electrode slurry or the negative electrode slurry is transported to the coater for coating. The oven of the coater is divided into a high-temperature front section, a low-temperature middle section, and a high-temperature rear section arranged in sequence along the conveying direction of the coater. The temperature of each section and The circulating air volumes are as follows:

High-temperature front section: the oven temperature is 125-135°C, and the circulating air volume is 35-50Hz;

Low-temperature middle section: the oven temperature is 105-125°C, which is lower than the oven temperature of the high-temperature front section, and the circulating air volume is 30-45Hz, which is lower than the circulating air volume of the high-temperature front section;

High-temperature post-section: the oven temperature is 125-135°C and higher than that of the low-temperature middle section, and the circulating air volume is 35-50 Hz and larger than that of the low-temperature middle section.

In one of the embodiments, the high-temperature front section is divided into a first section and a second section arranged sequentially along the conveying direction of the coating machine, and the temperature and circulating air volume of each section are as follows:

The first stage: the oven temperature is 125-135°C, and the circulating air volume is 40-50Hz;

The second section: the temperature of the oven is 125-135° C., and the circulating air volume is 35-45 Hz, which is smaller than the circulating air volume of the first section.

In one embodiment, the oven temperature of the first stage is 130° C., and the circulating air volume is 45 Hz; the oven temperature of the second stage is 130° C., and the circulating air volume is 40 Hz.

In one of the embodiments, the low-temperature middle section is divided into the third section, the fourth section, the fifth section and the sixth section arranged sequentially along the conveying direction of the coating machine, and the temperature and circulating air volume of each section are as follows:

The third section: the oven temperature is 115-125°C, and the circulating air volume is 35-45Hz;

The fourth section: the oven temperature is 105-115°C, which is lower than the oven temperature of the third section, and the circulating air volume is 30-40Hz, which is lower than the circulating air volume of the third section;

The fifth section: the oven temperature is 105-115°C, which is lower than the oven temperature of the third section, and the circulating air volume is 30-40Hz, which is lower than the circulating air volume of the third section;

The sixth section: the oven temperature is 105-115°C and lower than the oven temperature of the third section, and the circulating air volume is 30-40Hz and lower than the circulating air volume of the third section.

In one of the embodiments, the oven temperature of the third section is 120°C, and the circulating air volume is 40Hz; the oven temperature of the fourth section is 110°C, and the circulating air volume is 35Hz; the oven temperature of the fifth section is 110°C, the circulating air volume is 35Hz; the temperature of the oven in the sixth section is 110°C, and the circulating air volume is 35Hz.

In one of the embodiments, the high-temperature rear section is divided into the seventh section and the eighth section arranged sequentially along the conveying direction of the coating machine, and the temperature and circulating air volume of each section are as follows:

The seventh section: the temperature of the oven is 120-130°C, and the circulating air volume is 35-45Hz;

The eighth section: the oven temperature is 125-135°C and higher than that of the seventh section, and the circulating air volume is 40-50 Hz and higher than that of the seventh section.

In one embodiment, the oven temperature of the seventh section is 125° C., and the circulating air volume is 40 Hz; the oven temperature of the eighth section is 130° C., and the circulating air volume is 45 Hz.

In one embodiment, the coating speed is 10-20 m/min.

Another technical problem to be solved by the present invention is to provide a lithium-ion battery positive/negative electrode sheet prepared by the above-mentioned coating method for the lithium-ion battery positive/negative electrode sheet.

Compared with the prior art, the coating method of the lithium ion battery positive/negative pole piece provided by the present invention, in the coating process of the lithium ion battery positive and negative pole piece, the oven temperature and the The circulating air volume, compared with the conventional oven temperature and circulating air frequency parameters, can prevent the conductive agent from floating too fast during the drying process of the dressing, reduce the proportion of the conductive agent floating to the surface of the pole piece during the drying process, and reduce The loss of the conductive agent during the drying process of the pole piece dressing ensures that the conductive agent is evenly distributed during the drying process of the pole piece dressing. Finally, the resistivity of the pole piece is reduced, the conductivity is improved, the internal resistance of the battery is reduced, and the battery rate charge-discharge and cycle performance are improved.

The beneficial effects of the additional technical features of the present invention will be described in the specific embodiments of this specification.

Description of drawings

Fig. 1 is a comparison chart of the rate charging performance of the battery of the coating method of the embodiment of the present invention and the battery of the coating method of Comparative Example 4;

Fig. 2 is a comparison chart of the rate discharge performance of the battery with the coating method of the embodiment of the present invention and the battery with the coating method of Comparative Example 4;

Fig. 3 is a comparison chart of the 1C cycle performance of the battery of the coating method of the embodiment of the present invention and the battery group A of the coating method of comparative example 4;

Fig. 4 is a comparison chart of the 1C cycle performance of the battery of the coating method of the embodiment of the present invention and the battery group B of the coating method of comparative example 4;

Fig. 5 is a comparison chart of the 1C cycle performance of the battery of the coating method of the embodiment of the present invention and the battery group C of the coating method of the comparative example 4.

detailed description

The present invention will be described in detail below with reference to the accompanying drawings and examples. It should be noted that, in the case of no conflict, the following embodiments and features in the embodiments can be combined with each other.

The coating method of the positive/negative pole piece of the lithium ion battery in the embodiment of the present invention is mainly to effectively reduce the resistivity of the coated pole piece by adjusting the parameters of the coating machine. The coating method of positive/negative electrode sheet of lithium ion battery comprises the following steps:

The positive electrode slurry or the negative electrode slurry is transported to the coater for coating. The oven of the coater is divided into a high-temperature front section, a low-temperature middle section, and a high-temperature rear section arranged in sequence along the conveying direction of the coater. The temperature of each section and The circulating air volumes are as follows:

High temperature front section: the oven temperature is 125-135°C, and the circulating air volume is 35-50Hz. Further, the high-temperature front section is further divided into the first section and the second section arranged sequentially along the conveying direction of the coating machine, and the temperature and circulating air volume of each section are as follows: The air volume is 40-50Hz; the second section: the temperature of the oven is 125-135°C, the circulating air volume is 35-45Hz, which is smaller than the circulating air volume of the first section. Furthermore, the oven temperature of the first section is 130° C., and the circulating air volume is 45 Hz; the oven temperature of the second section is 130° C., and the circulating air volume is 40 Hz.

Low-temperature middle section: the oven temperature is 105-125°C, which is lower than the oven temperature of the high-temperature front section, and the circulating air volume is 30-45Hz, which is smaller than the high-temperature front-section circulation air volume. Further, the low-temperature middle section is divided into the third section, the fourth section, the fifth section and the sixth section arranged sequentially along the conveying direction of the coating machine, and the temperature and circulating air volume of each section are as follows: The third section: oven temperature 115-125°C, the circulating air volume is 35-45Hz; the fourth stage: the oven temperature is 105-115°C, which is lower than the oven temperature of the third stage, and the circulating air volume is 30-40Hz, which is lower than the third stage The circulating air volume; the fifth section: the oven temperature is 105-115°C, which is lower than the oven temperature of the third section, and the circulating air volume is 30-40Hz, which is less than the circulating air volume of the third section; the sixth section: the oven The temperature is 105-115°C, which is lower than the temperature of the oven in the third section, and the circulating air volume is 30-40 Hz, which is lower than the circulating air volume in the third section. Furthermore, the oven temperature of the third section is 120°C, and the circulating air volume is 40Hz; the oven temperature of the fourth section is 110°C, and the circulating air volume is 35Hz; the oven temperature of the fifth section is 110°C, The circulating air volume is 35Hz; the temperature of the oven in the sixth section is 110°C, and the circulating air volume is 35Hz.

High-temperature post-section: the oven temperature is 125-135°C and higher than that of the low-temperature middle section, and the circulating air volume is 35-50 Hz and larger than that of the low-temperature middle section. Further, the high-temperature rear section is divided into the seventh section and the eighth section arranged sequentially along the conveying direction of the coating machine. The air volume is 35-45Hz; the eighth section: the oven temperature is 125-135°C and higher than that of the seventh section, and the circulating air volume is 40-50Hz and higher than that of the seventh section. Furthermore, the oven temperature of the seventh section is 125° C., and the circulating air volume is 40 Hz; the oven temperature of the eighth section is 130° C., and the circulating air volume is 45 Hz.

In the coating method of the positive/negative electrode sheet of the lithium ion battery provided by the present invention, during the coating process of the positive and negative electrode sheet of the lithium ion battery, the oven temperature and the circulating air volume of the "high-low-high" mode are used, compared with the conventional The parameters of oven temperature and circulating air frequency in this method can prevent the conductive agent from floating too fast during the drying process of the dressing, reduce the proportion of the conductive agent floating to the surface of the pole piece during the drying process of the pole piece dressing, and reduce the speed of the pole piece dressing during the drying process. The loss of conductive agent ensures that the conductive agent is evenly distributed during the drying process of the pole piece dressing. Finally, the resistivity of the pole piece is reduced, the conductivity is improved, the internal resistance of the battery is reduced, and the battery rate charge-discharge and cycle performance are improved.

In order to further reduce the resistivity of the pole piece and improve the conductivity, the coating speed is 10-20 m/min, preferably 15 m/min.

The coating method of the lithium-ion battery positive/negative electrode sheet of the present invention will be described in detail below through specific examples.

Equipment and materials used in each of the following examples are as follows:

1. The coating machine adopts Japanese TORAY coating machine (the length of the oven is 40 meters, divided into eight sections, and the effective coating width is 0.6 meters), steam heating method.

2. The positive electrode slurry used for coating is composed of: oil solvent, lithium iron phosphate, conductive agent and binder, the mass ratio of which is 125:93:3.5:4.5.

3. The negative electrode slurry used for coating consists of: water-based solvent, artificial graphite, conductive agent, binder 1 and binder 2, the mass ratio of which is 190:93:2:2.5:2.5.

4. For the carrier fluid used for coating, aluminum foil with a thickness of 0.020mm and a width of 585mm is used for the positive electrode; copper foil with a thickness of 0.010mm and a width of 585mm is used for the negative electrode.

5. The instrument used to test the surface resistivity of coated pole pieces is a digital display surface resistivity tester.

Embodiment of the invention

The stirred and qualified positive electrode slurry or negative electrode slurry is connected to the coating machine through the conveying system for coating. Coating machine parameter setting (temperature and circulating air setting rule: high-low-high) is shown in Table 1:

Table I:

Comparative Example 1

The stirred and qualified positive electrode slurry or negative electrode slurry is connected to the coating machine through the conveying system for coating. Conventional coating methods, coating machine parameter settings (temperature and circulating air setting law: low-low-high) are shown in Table 2:

Table II:

Comparative Example 2

The stirred and qualified positive electrode slurry or negative electrode slurry is connected to the coating machine through the conveying system for coating. Coating machine parameter setting (temperature and circulating air setting law: low-high-high) see Table 3:

Table three:

Comparative Example 3

The stirred and qualified positive electrode slurry or negative electrode slurry is connected to the coating machine through the conveying system for coating. Conventional coating methods, coating machine parameter settings (temperature and circulating air setting law: high-high-low) are shown in Table 4:

Table four:

Comparative Example 4

The stirred and qualified positive electrode slurry or negative electrode slurry is connected to the coating machine through the conveying system for coating. Coating machine parameter settings (temperature and circulating air setting law: low-high-low) are shown in Table 5:

Table five:

The embodiment of the present invention and comparative examples 1-4 are coated with the positive and negative pole pieces, and the adhesion and resistivity of the pole piece dressing are tested. The test data comparison is shown in Table 6:

Table six:

It can be seen that in the coating process of positive and negative pole pieces of lithium ion batteries, the oven temperature and circulating air frequency parameters using the "high-low-high" mode of the present invention are significantly higher than those using conventional oven temperature and circulating air frequency parameters. Has the following advantages:

(1) It can prevent the conductive agent from floating too fast during the drying process of the dressing, reduce the proportion of the conductive agent floating to the surface of the pole piece during the drying process, and reduce the loss of the conductive agent during the drying process of the pole piece dressing.

(2) Ensure that the conductive agent is evenly distributed during the drying process of the pole piece dressing.

battery production

Positive and negative poles were prepared by using the coating method of the embodiment of the present invention to coat the prepared positive and negative pole pieces and using the coating method of Comparative Example 4 (as can be seen from Table 6, the pole piece resistivity of Comparative Example 4 is the smallest) The pole pieces are made into 22Ah/3.2V-IFP85200235 batteries respectively. The specific production method and process are as follows:

(1) Baking the coated positive and negative coil materials, the baking temperature is 75-100°C, the vacuum degree is less than -0.9Mpa, and the moisture content of the pole piece is controlled within 700ppm.

(2) The baked positive and negative coil material pole pieces are made into small pieces of pole pieces of a certain size.

(3) Vacuum baking of small pole pieces, the pole piece baking temperature is 75-100°C, the vacuum degree is less than -0.9Mpa, and the pole piece moisture is controlled within 700ppm.

(4) Production of batteries: The production environment humidity is within 20% (at 25°C). After the production of the battery is completed, it is quickly circulated downwards, and the process time from the depolarization sheet to the completion of the battery production should not exceed 20 minutes.

(5) Welding lugs

(6) Test short circuit: perform high voltage test on the bare cells after tab welding to eliminate short circuit.

(7) Top-test packaging: Qualified bare cells are put into the pre-punched aluminum-plastic packaging film for local thermal packaging.

(8) Battery baking: After the battery is manufactured, put it in an oven to vacuumize and bake, the vacuum degree is less than -0.9MPa, and the temperature is 75-100°C.

(9) Battery injection: The battery is injected with electrolyte in a special glove box, the humidity in the glove box is less than 1%, and the temperature is 25±2°C. After liquid injection, vacuumize and heat seal.

(10) Standing at high temperature: Put the liquid-filled battery into an oven for baking, and the temperature of the oven is 30-60°C. The baking time is 12-48 hours.

(11) Formation: charge and discharge the battery to fully activate the electrochemical performance of the battery.

(12) Standing at room temperature: put the formed battery in a room temperature of 25°C for 120-240 hours.

(13) Grouping: According to a certain charging and discharging method, the capacitor capacity voltage, internal resistance, etc. are selected and grouped.

Finished battery test analysis

Three batteries made of positive and negative electrodes coated with different coating methods were taken respectively, and the internal resistance, rate and cycle performance of the batteries were tested. The test results are as follows:

Use a probe-type AC internal resistance tester to test the internal resistance of the battery, the data is as follows:

Rate charge performance is shown in Figure 1, rate discharge performance is shown in Figure 2, 1C cycle performance comparison with Group A is shown in Figure 3, 1C cycle performance comparison with Group B is shown in Figure 4, 1C cycle performance comparison with Group C is shown in Figure 4 5.

Analyzed

1. The pole piece coated with the coating method of the present invention is 10% to 30% lower than the pole piece coated with the conventional coating method.

2. The pole piece coated by the coating method of the present invention is about 80% lower than the pole piece coated by the conventional coating method, and the internal resistance of the battery made by the pole piece is about 80%.

3. As shown in Figure 1 and Figure 2: the battery prepared by coating the pole piece with the coating method of the present invention has obvious advantages in rate charge and discharge performance compared with the battery prepared by coating the pole piece with the conventional coating method.

4. As shown in Fig. 3, Fig. 4 and Fig. 5: the battery prepared by using the coating method of the present invention to coat the pole piece is more obvious in terms of cycle performance than the battery made by using the conventional coating method to coat the pole piece. Advantage.

To sum up, it is known that during the coating process of lithium-ion battery positive and negative pole pieces, the oven temperature and circulating air frequency parameters using the "high-low-high" method are significantly higher than those using the conventional oven temperature and circulating air frequency parameters. parameters, which can avoid the floating speed of the conductive agent during the drying process of the dressing too fast, reduce the proportion of the conductive agent floating to the surface of the electrode piece dressing during the drying process, reduce the loss of the conductive agent during the drying process of the electrode dressing, and ensure that the electrode piece The conductive agent is evenly distributed during the drying process of the dressing. Finally, the resistivity of the pole piece is reduced, the conductivity is improved, the internal resistance of the battery is reduced, and the battery rate charge-discharge and cycle performance are improved.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims (7)

1. a kind of coating process of lithium ion battery positive/negative pole piece is it is characterised in that comprise the following steps：

Anode sizing agent or cathode size are delivered to coating machine be coated, the baking oven of described coating machine is divided into along coating machine conveying High temperature leading portion, low temperature stage casing and the high temperature back segment arranged successively in direction, each section of temperature and air circulation are as follows respectively：

High temperature leading portion：Oven temperature is 125～135 DEG C, and air circulation is 35～50Hz；

Low temperature stage casing：Oven temperature be 105～125 DEG C, and less than described high temperature leading portion oven temperature, air circulation be 30～ 45Hz, and the air circulation less than described high temperature leading portion, described low temperature stage casing is divided into arranges successively along coating machine conveying direction 3rd section, the 4th section, the 5th section and the 6th section, each section of temperature and air circulation are as follows respectively：3rd section：Oven temperature is 115～125 DEG C, air circulation is 35～45Hz；4th section：Oven temperature is 105～115 DEG C, and less than described 3rd section Oven temperature, air circulation is 30～40Hz, and the air circulation less than described 3rd section；5th section：Oven temperature be 105～ 115 DEG C, and the oven temperature less than described 3rd section, air circulation is 30～40Hz, and the circulated air less than described 3rd section Amount；6th section：Oven temperature is 105～115 DEG C, and the oven temperature less than described 3rd section, and air circulation is 30～40Hz, And the air circulation less than described 3rd section；

High temperature back segment：Oven temperature be 125～135 DEG C, and more than described low temperature stage casing oven temperature, air circulation be 35～ 50Hz, and the air circulation more than described low temperature stage casing.

2. the coating process of lithium ion battery positive/negative pole piece according to claim 1 is it is characterised in that described high temperature Leading portion is divided into the first paragraph arranged successively along coating machine conveying direction and second segment, and each section of temperature and air circulation are respectively such as Under：

First paragraph：Oven temperature is 125～135 DEG C, and air circulation is 40～50Hz；

Second segment：Oven temperature is 125～135 DEG C, and air circulation is 35～45Hz, and the circulated air less than described first paragraph Amount.

3. the coating process of lithium ion battery positive/negative pole piece according to claim 2 is it is characterised in that described first The oven temperature of section is 130 DEG C, and air circulation is 45Hz；The oven temperature of described second segment is 130 DEG C, and air circulation is 40Hz.

4. the coating process of lithium ion battery positive/negative pole piece according to claim 1 is it is characterised in that the described 3rd The oven temperature of section is 120 DEG C, and air circulation is 40Hz；Described 4th section of oven temperature is 110 DEG C, and air circulation is 35Hz；Described 5th section of oven temperature is 110 DEG C, and air circulation is 35Hz；Described 6th section of oven temperature is 110 DEG C, Air circulation is 35Hz.

5. the coating process of lithium ion battery positive/negative pole piece according to claim 1 is it is characterised in that described high temperature Back segment is divided into the 7th section arranging successively along coating machine conveying direction and the 8th section, and each section of temperature and air circulation are respectively such as Under：

7th section：Oven temperature is 120～130 DEG C, and air circulation is 35～45Hz；

8th section：Oven temperature is 125～135 DEG C, and more than described 7th section of oven temperature, air circulation is 40～ 50Hz, and the air circulation more than described 7th section.

6. the coating process of lithium ion battery positive/negative pole piece according to claim 5 is it is characterised in that the described 7th The oven temperature of section is 125 DEG C, and air circulation is 40Hz；Described 8th section of oven temperature is 130 DEG C, and air circulation is 45Hz.

7. the coating process of lithium ion battery positive/negative pole piece as claimed in any of claims 1 to 6, its feature It is, coating speed is 10～20m/min.