CN102195032B - Preparation method of lithium ion battery pole piece - Google Patents

Abstract

The invention discloses a preparation method of a lithium ion battery pole piece, which comprises the following steps: adding the carbon nano tube conductive agent powder into a solvent and a surfactant to be uniformly dispersed to obtain improved uniformly dispersed carbon nano tube slurry; and preparing pole piece slurry by using the carbon nanotube slurry, and preparing the lithium ion battery pole piece by using the obtained pole piece slurry. Compared with the prior art, the surface dispersing agent is utilized to effectively disperse the carbon nano tube in the battery anode/cathode material, so that the excellent performance of the carbon nano tube conductive agent is fully exerted, and the following electrochemical performances of the lithium ion battery are greatly improved: 1) the internal resistance of the battery is reduced, the rate capability and the energy density of the battery are improved, and particularly the high-rate charge-discharge performance is obviously improved; 2) the high and low temperature performance of the battery is improved, and the application field of the lithium ion battery is widened; 3) the cycle service life of the battery is prolonged; 4) the safety performance of the battery is improved.

Description

Lithium-ion battery pole piece preparation method

technical field

The invention relates to a preparation method of a lithium-ion battery pole piece, in particular to an application method of a carbon nanotube conductive agent in preparing a lithium-ion battery pole piece.

Background technique

Due to the advantages of high energy density, high operating voltage, wide application temperature range, and long cycle life, lithium-ion batteries are widely used as power sources for various mobile devices, even in aviation, aerospace, navigation, automobiles, medical equipment and other fields. Gradually replace other traditional batteries.

For a battery, a large internal resistance affects its energy output. During use, the internal voltage of the battery itself is high, which will lead to a decrease in the output voltage platform, so the battery capacity is low. This low capacity is not only related to the structure of the battery, the combination of positive and negative electrode materials, and the electrolyte system, but also to the amount, type and process of conductive carbon added to the positive and negative electrode materials. In addition, during the discharge process, the energy consumed by the battery itself is converted into heat energy, and a large internal resistance has a great impact on battery output, battery life and safety. After research, the parts where the internal resistance of the battery is generated include the positive electrode sheet, the negative electrode sheet, the separator, the outer packaging, etc., and the positive electrode sheet has a low electrical conductivity of the material itself, and its resistance accounts for 80-90% of the internal resistance.

In addition, the current application fields of batteries, especially lithium-ion batteries, are expanding. As far as their use is concerned, they are gradually entering some high-temperature and low-temperature places, which requires batteries to exhibit better electrochemical performance under harsh conditions. . Studies have shown that the high and low temperature performance of lithium-ion batteries has a great relationship with the electrolyte, positive electrode materials, and negative electrode materials. Especially in low temperature environments, the conductivity of positive electrode materials has a great impact on battery performance.

Furthermore, another shortcoming of the current lithium-ion battery is its short service life. Generally, it cannot be charged and discharged normally after 3 to 5 years of use. This lack of function is mainly due to the loss of a part of the active materials in the battery system. The ability of lithium ions causes lithium ions to not shuttle back and forth between the positive and negative electrodes normally. Experiments have shown that the service life of the battery can be extended by improving the conductivity of the positive and negative materials and the structure of the conductive agent.

Based on the above analysis, it can be seen that the conductivity of positive and negative electrode materials is the key to overcome the above defects. Accordingly, the inventors believe that a carbon nanotube conductive agent with a certain aspect ratio and excellent electrical conductivity is an ideal choice for solving the above problems.

Carbon nanotubes were discovered by Japanese scientist Iijima Sumio in 1991 (Helical microtubules of graphitic carbon", SIijima, Narure. Vol.354, P56 (1991)), because of their excellent mechanical, thermal and electrical properties, they have attracted the attention of scientific and technological workers. , there are many reports about its preparation, characterization and application performance, and there are corresponding documents in the application of lithium-ion batteries and batteries. As a positive electrode conductive agent for lithium-ion batteries", Wang Guoping, 2004 China Nanotechnology Application Symposium, P302 (2004)), however, the internal resistance of the above-mentioned lithium-ion batteries is still relatively large, so that the charge and discharge performance is not good.

Contents of the invention

The object of the present invention is to provide a method for preparing a lithium-ion battery pole piece to prepare a lithium-ion battery pole piece with strong electrical conductivity.

In order to achieve the above invention, the inventors of the present application have found through long-term painstaking research that the reason why carbon nanotubes with excellent electrical conductivity are not effective as conductive materials in battery pole pieces is that the dispersion is not good, because compared to other common conductive carbons In other words, carbon nanotubes have a linear structure with a smaller diameter and shorter length, and are more likely to agglomerate when dispersed. Therefore, the dispersion of carbon nanotubes is an important issue for their application in batteries. For this reason, a method of adding carbon nanotube powder into solvent and surfactant for pre-dispersion and preparing slurry was proposed to solve the problem of difficult dispersion of nano-conductive carbon.

The invention provides a preparation method of a lithium ion battery pole piece, the steps of which are: adding carbon nanotube powder into a solvent and a surfactant to disperse evenly to obtain a carbon nanotube slurry; preparing the pole piece slurry with the carbon nanotube slurry material, and prepare lithium-ion battery pole pieces with the obtained pole piece slurry.

Since the finer the carbon nanotubes, the larger the specific surface area and the higher the oil absorption value, more binders are needed. On the other hand, the particle size of the current positive and negative active materials is between several μm and 20 μm, so In order to achieve better dispersion and conductivity, as an improvement of the lithium ion battery pole piece preparation method of the present invention, the carbon nanotubes are single-walled, double-walled or multi-walled carbon nanotubes with a diameter of 2-20nm, The length is 0.2-20 μm.

As an improvement to the method for preparing lithium-ion battery pole pieces of the present invention, the weight content of carbon nanotubes in the carbon nanotube slurry is 2-13.8%.

As an improvement of the method for preparing lithium-ion battery pole pieces of the present invention, the surfactant is a surfactant with stable properties within the electrochemical working voltage range of the lithium-ion battery, and is a dispersant, defoamer, wetting agent, One or more of leveling agents.

As an improvement to the preparation method of lithium-ion battery pole pieces of the present invention, the carbon nanotube slurry includes water-based slurry and oil-based slurry: in the water-based slurry, the dispersant is polyoxyethylene ether block copolymer , polyamine salts, alcohols, etc., such as AFE1080, PE100; in oil-based slurry, the dispersant is polysiloxane and its modified products, polyamine salts, organic solvents (high molecular weight alkanes, esters, Ketones, etc.), polypyrrolidone (PVP), etc., such as Texaphor963, PVP.

As an improvement to the preparation method of the lithium-ion battery pole piece of the present invention, the defoamer is polysiloxane or its modified products, such as 8034, 8034A, E8, E2.

As an improvement to the preparation method of the lithium-ion battery pole piece of the present invention, the wetting agent is polyoxyethylene alkylphenol ether, such as 436 and 478.

As an improvement to the preparation method of the lithium-ion battery pole piece of the present invention, the leveling agent is a polysilane solvent (ester, alcohol, etc.), such as 878, 876.

As an improvement of the preparation method of the lithium ion battery pole piece of the present invention, the pole piece is a positive pole piece or a negative pole piece, and the positive electrode active material used in the positive pole piece is lithium cobaltate, lithium nickelate, lithium nickel cobalt multi-element material, One or more of lithium iron phosphate and lithium manganese phosphate; the negative electrode active material used in the negative plate is one or more of graphite, lithium titanate, silicon-carbon alloy, and silicon-tin alloy.

The carbon nanotube conductive agent has different additions to different active materials, and the addition amount of the carbon nanotubes is: when the negative electrode active material is graphite, the carbon nanotubes 0.1-3.0%; when the negative electrode active material is lithium titanate, carbon nanotubes are 0.5-5.0%; when the positive electrode active material is lithium cobaltate, carbon nanotubes are 0.2-5.0%; when the positive electrode active material is lithium nickelate , carbon nanotubes are 0.2-6.0%; when the positive electrode active material is lithium nickel cobalt multi-component material, carbon nanotubes are 1.0-6.0%; when the positive electrode active material is lithium iron phosphate, carbon nanotubes are 1.0-6.0%; positive electrode activity When the material is lithium manganese phosphate, the content of carbon nanotubes is 1.0-7.0%.

The solvent is one or more of deionized water, alcohols (such as ethanol, ethylene glycol, isopropanol) or ketones (such as acetone, cyclohexanone, N-methylpyrrolidone, etc.).

The metal impurity content of the catalyst introduced during the preparation of carbon nanotubes, especially the content of metal impurities such as iron and nickel, is required to be less than 1% by dry weight.

The water-based slurry includes an aqueous solvent, a surfactant and a carbon nanotube conductive agent, and the aqueous solvent is at least one of deionized water and isopropanol; the oil-based slurry includes an oily solvent, a surfactant and a carbon nanotube conductive agent, the oily solvent is one or more of N-methylpyrrolidone (NMP), cyclohexanone, acetone, and isopropanol.

The battery is a square battery or a cylindrical battery.

Compared with the prior art, the present invention uses a surface dispersant to effectively disperse the carbon nanotubes in the positive and negative electrode materials of the battery, so that the excellent performance of the carbon nanotubes can be fully utilized, and the following electrochemical performance of the lithium-ion battery is greatly improved : 1) The internal resistance of the battery is reduced, the battery rate performance and energy density are improved, especially the high rate charge and discharge performance is significantly improved; 2) The high and low temperature performance of the battery is improved, and the application field of lithium-ion batteries is broadened; 3) The cycle life of the battery is prolonged; 4) The safety performance of the battery is improved.

Description of drawings

The present invention and its beneficial technical effects will be described in detail below in conjunction with the accompanying drawings and specific embodiments, wherein:

Fig. 1 and Fig. 2 are the SEM images of positive/negative electrode sheets prepared in various examples and comparative examples.

detailed description

The carbon nanotube conductive agent used in the present invention is a kind of good conductive material that can be added and applied to the positive electrode and negative electrode of the battery. On the one hand, it is used as a conductive material to improve the electronic conductivity in the pole piece. A class of linear components with excellent thermal conductivity can improve the internal heat dissipation of the battery, thereby improving the performance of the battery in an all-round way. The carbon nanotubes used in the present invention have a diameter of 2-20 nm and a length of 0.2-20 μm, and can be single-walled, double-walled or multi-walled carbon nanotubes.

The following will describe step by step the preparation process of the lithium-ion battery using the carbon nanotube conductive agent in the positive and negative electrodes.

Reagents and suppliers used in this instruction manual are as shown in Table 1 (Table 1 is just to illustrate the source and composition of the various reagents adopted in the test of the present invention, and does not mean that the reagents provided by other similar reagents or other suppliers cannot be used. realize the present invention).

Reagents used in the embodiment of table 1 and details of suppliers

Material serial number Reagent name supplier 1 Carbon nano conductive agent Dongguan New Energy Technology Co., Ltd. 2 graphite Dongguan New Energy Technology Co., Ltd. 3 Lithium cobaltate Dongguan New Energy Technology Co., Ltd. 4 lithium nickel cobalt manganese Dongguan New Energy Technology Co., Ltd. 5 Lithium iron phosphate Dongguan New Energy Technology Co., Ltd. 6 lithium manganese phosphate Dongguan New Energy Technology Co., Ltd. 7 Silicon alloy material Dongguan New Energy Technology Co., Ltd.

8 Super "p" Li Temeco 9 Polyvinylidene fluoride Solvay Chemical Co., Ltd. 10 SBR Latex Dongguan New Energy Technology Co., Ltd. 3 --> 11 Surfactant Corning Chemical Co., Ltd. 12 N-Methylpyrrolidone (NMP) Dongguan New Energy Technology Co., Ltd. 13 PVDF-HEP (PVDF) Solvay Polymers 14 electrolyte Dongguan New Energy Technology Co., Ltd. 15 Sodium carboxymethyl cellulose Dongguan New Energy Technology Co., Ltd.

1. Preparation of carbon nanotube slurry

The carbon nanotube slurry can be made into an oil-based slurry or a water-based slurry, and the preparation process will be described respectively below.

①The preparation process of oil-based slurry in the prior art is generally as follows: Weigh 95-98 parts by weight of NMP and other solvents in a dispersion container, then add 2-5 parts by weight of carbon nanotube conductive agent to stir, mix and disperse evenly, and use Or do not use a sand mill and a three-roller for grinding. Hereinafter, the slurry prepared here is referred to as the prior art carbon nanotube oil-based slurry.

② The preparation process of the oil-based slurry of the present invention is as follows: Weigh 85-95 parts by weight of solvent in a dispersion container, and then add 0.2-1.0 parts by weight of dispersant, 0.05-0.2 parts by weight of defoamer, 0.1- 1.0 parts by weight of wetting agent, 0.1 to 1.0 parts by weight of leveling agent, after all surfactants are fully dispersed and uniform, add 2.0 to 13.8 parts by weight of carbon nanotube conductive agent to the solution while stirring, the addition is complete and After the slurry is uniformly dispersed, the slurry is pumped into a sand mill or a three-roll mill to grind to a suitable particle size. The slurry prepared hereafter is referred to as the carbon nanotube oil-based slurry of the present invention.

Table 2 is a list of components of several specific examples of carbon nanotube oil-based slurries.

Table 2, carbon nanotube oil-based slurry embodiment component list (parts by weight)

③The preparation process of water-based slurry in the prior art is generally: weigh 95-98 parts by weight of deionized water in a dispersion container, then add 2-5 parts by weight of carbon nanotube conductive agent to disperse and stir evenly, and then use or Do not use a sand mill or three-roll mill for grinding. Hereinafter, the slurry prepared here is referred to as the prior art carbon nanotube aqueous slurry.

④ The preparation process of the water-based slurry of the present invention is: weigh 90-95 parts by weight of the water-based solvent in a dispersion container, and then add 0.1-1.0 parts by weight of a dispersant, 0.1-1.0 parts by weight of an antifoaming agent, and 0.3- 1.0 parts by weight of wetting agent, 0.2 to 1.0 parts by weight of leveling agent, after the surfactant is fully dispersed and uniform, add 3.3 to 9.2 parts by weight of carbon nanotube conductive agent to the solution while stirring. After the slurry is fully dispersed and uniform, the slurry is pumped into a sand mill or a three-roll mill to grind to a suitable particle size. The slurry prepared here is referred to as the carbon nanotube water-based slurry of the present invention hereinafter.

Table 3 is a list of components of several specific examples of carbon nanotube water-based slurry.

Table 3, carbon nanotube aqueous slurry embodiment component table (weight parts)

2. Preparation of cathode slurry

The preparation process of the positive electrode slurry is as follows: weigh 5-60 parts by weight of the solvent in a dispersion container, then weigh 0.7-3.9 parts by weight of the adhesive to disperse evenly in the solvent, and then add 1.8-66.5 parts by weight of carbon nano Tube slurry, continue stirring to disperse evenly, then add 11.1-73.3 parts of active material, stir and disperse evenly, and finally prepare a positive electrode slurry sample with a viscosity of 2000-10000 mPas. The charging mode and dispersion process of the comparative examples are the same as those of the inventive examples. Table 4 shows the component list of the positive electrode slurry prepared by using the carbon nanotube slurry prepared in Examples 1-1 to 1-6.

Table 4. Example component list and performance index of positive electrode slurry

3. Preparation of negative electrode slurry

The negative electrode slurry adopts two kinds of carbon nanotube slurry of oil system and water system due to different materials:

① The preparation process of the water-based negative electrode slurry is: weigh 5.8-48.4 parts by weight of deionized water in a dispersion container, then add 1.0-40.0 parts by weight of carbon nanotube water-based slurry and disperse evenly, then add 34.8-60.9 parts by weight 2.3-4.2 parts by weight of an adhesive such as styrene-butadiene rubber is added to further disperse uniformly, and finally a negative electrode slurry of 1500-4000 mPas is prepared.

② The preparation process of the oil-based negative electrode slurry is: first weigh 5.8-48.8 parts of the solvent in the dispersion container, then weigh 2.3-4.8 parts of the adhesive to fully dissolve in the container, and then add 3.3-40.0 parts by weight of carbon The nanotube slurry is fully dispersed in the above slurry, and 34.8-60.9 parts by weight of effective active substances are added to continue to disperse evenly, and finally a qualified negative electrode slurry with a viscosity of 2000-5000 mPas is prepared for use.

Table 5 shows the components of the negative electrode slurry prepared using the carbon nanotube slurry prepared in Examples 1-1 to 1-12.

Table 5. Example components and slurry performance indicators of negative electrode slurry

4. Battery preparation

Coat the above-mentioned qualified positive and negative electrode pastes on a coating machine with qualified positive and negative electrode sheets according to the requirements of the designed Model (such as 383450 square battery, 423482 square battery, 18650 cylindrical battery, etc.).

According to the designed Model, the above-mentioned comparative samples and the qualified positive/negative pole pieces of the invention application examples were rolled and assembled into batteries, and filled with electrolytes for chemical film formation, aged to obtain lithium-ion batteries, and the electrochemical performance of the batteries was tested. EIS evaluates the performance of electrode sheet resistance.

5. Beneficial effect experiment

The above-mentioned batteries were stored at high temperature, and the safety performance of the batteries was tested according to the UL1642 standard.

According to the UL1642 standard, the high and low temperature performance of the battery is tested, and the electrochemical performance of the battery is evaluated.

1. Dispersion effect evaluation one

One of the difficulties in the application of carbon nanotubes is the dispersion problem, especially in water-based slurries. Even if the slurries are well dispersed and pass the inspection, they will still agglomerate together during storage. In order to detect the dispersion effect of the present invention, SEM detection is carried out on the pole pieces made by using the slurry of all the above embodiments before rolling, and the electron microscope photos shown in Figure 1 and Figure 2 are obtained. It can be seen that the carbon nanometers of the comparison group system The dispersion of the tubes is not good, and there are obvious coarse particles of carbon nanotubes, and the particles are distributed in isolation, indicating that there is a big problem in the dispersion of carbon nanotubes. In the pole piece after the improvement and process treatment of the present invention, the carbon nanotubes are evenly distributed on the surface of the active material, and they are connected to each other to form a network, which solves the problem of difficult dispersion of carbon nanotubes, and no matter in water The base system is still well dispersed in the solvent-based system, which is conducive to the performance of the conductive carbon material.

2. Dispersion effect evaluation II

The pole pieces prepared by coating the slurry of Examples 2-1 to 2-20 and Examples 3-1 to 3-14 are rolled into pole pieces of different densities according to different active materials, and then the prepared Electrochemical impedance spectroscopy (EIS) was used to measure the resistance of the diaphragm with a contact area of 10 mm ² at a frequency of 1000 Hz to 1 Hz, and the results shown in Table 6 were obtained.

The sheet resistance measurement result that all embodiments of table 6 make

Example pole piece Density (g/cm3) Current (μA) 1000Hz Imp(mΩ) Remark Example 2-1 positive electrode 3.90 13.677 32505.6 Comparative sample Example 2-2 positive electrode 3.90 -25.389 45758.9 Comparative sample Example 2-3 positive electrode 3.90 -27.275 2928.8 Invention application example Example 2-4 positive electrode 3.90 3.1693 2942.0 Invention application example Example 2-5 positive electrode 3.30 3.1893 19708.8 Comparative sample Example 2-6 positive electrode 3.30 243.85 14853.0 Comparative sample Example 2-7 positive electrode 3.30 -18.465 6058.0 Invention application example Example 2-8 positive electrode 3.30 -10.523 6817.5 Invention application example Example 2-9 positive electrode 3.00 53.201 14853.0 Comparative sample Example 2-10 positive electrode 3.00 -15.565 13058.0 Comparative sample Example 2-11 positive electrode 3.00 -12.535 1817.5 Invention application example Example 2-12 positive electrode 3.00 24.213 2025.5 Invention application example Example 2-13 positive electrode 2.20 -10.523 31986 Comparative sample Example 2-14 positive electrode 2.20 -33.254 31868 Comparative sample Example 2-15 positive electrode 2.20 -23.586 9111 Invention application example Example 2-16 positive electrode 2.20 -35.546 9565 Invention application example Example 2-17 positive electrode 2.00 -10.523 184270 Comparative sample Example 2-18 positive electrode 2.00 -15.368 181160 Comparative sample Example 2-19 positive electrode 2.00 22.306 7927 Invention application example Example 2-20 positive electrode 2.00 57.568 7969 Invention application example Example 3-1 negative electrode 1.60 0.1342 6827 Comparative sample Example 3-2 negative electrode 1.60 0.1869 6210 Comparative sample Example 3-3 negative electrode 1.60 1.2342 4613 Invention application example Example 3-4 negative electrode 1.60 1.8612 2042 Invention application example 8 --> Example 3-5 negative electrode 1.60 0.7642 3566 Comparative sample

Example 3-6 negative electrode 1.60 0.4375 2693 Embodiment of the invention Example 3-7 negative electrode 1.80 0.1316 14566.3 Comparative sample Example 3-8 negative electrode 1.80 -16.423 13338.5 Comparative sample Example 3-9 negative electrode 1.80 -16.258 8128.3 Invention application example Example 3-10 negative electrode 1.80 -8.762 8377.2 Invention application example Example 3-11 negative electrode 1.40 -8.586 14566.9 Comparative sample Example 3-12 negative electrode 1.40 3.7523 17289.3 Comparative sample Example 3-13 negative electrode 1.40 3.1569 8059 Invention application example Example 3-14 negative electrode 1.40 3.5823 11657 Invention application example

As can be seen from Table 6, under the same coating weight and the same compaction density, for the pole piece prepared by the same active material, the pole piece using the dispersion method of the present invention to pre-disperse the carbon nanotubes is due to the conductive The materials and active materials are evenly dispersed, and the carbon nanotubes are well distributed in three-dimensional directions, so the corresponding sheet resistance is significantly reduced, which is conducive to improving the electrochemical performance of the battery.

3. The impact on the high rate discharge performance of the battery

The pole pieces of each embodiment were assembled into batteries with different structures according to the comparison group and the improved group, and the prepared batteries were chemically aged and aged, and the rate performance was tested, and the results shown in Table 7 were obtained. performance data.

Table 7, the discharge performance of the batteries made in each embodiment at different rates

It can be seen from Table 7 that the rate performance of the battery, especially the high rate discharge performance, has been significantly improved due to the carbon nanotubes being more uniformly dispersed in the cell using the dispersion method of the present invention to pre-disperse the carbon nanotubes. The advantage is that high-performance lithium-ion batteries can be prepared to meet the requirements of high-power power sources such as electric energy storage stations, electric tools, electric vehicles, etc.; The tube can achieve the use effect that a larger amount of conductive carbon can achieve, thereby improving the overall energy density of the battery.

4. The impact on the high and low temperature performance of the battery

Table 8. The battery high and low temperature test results made in each embodiment

It can be seen from Table 8 that compared with the normal group, the low-temperature and high-temperature performance of the battery has been improved to varying degrees after the carbon nanotubes are pre-dispersed by the dispersion method of the present invention. This may be due to the addition of carbon nanotubes to the pole pieces. In the end, because carbon nanotubes have more stable electronic conductivity compared with normal conductive carbon at high and low temperatures, the electrical and thermal conductivity of the pole piece in the three-dimensional direction is improved, which broadens the range of lithium-ion batteries. The scope of application, in some fields where lithium-ion batteries cannot be used under special conditions, can also be used to play a more stable performance by using batteries with carbon nanotubes, so lithium-ion batteries can be applied in these new fields.

5. Effect on battery cycle performance

Table 9. Cycle performance test results at room temperature

Example Battery type cycle rate Cycles Capacity retention Embodiment 2-1 (comparison group) 383450 0.7C/0.5C 338 64% Embodiment 2-3 (invention application group) 383450 0.7C/0.5C 746 88% Embodiment 2-5 (contrast group) 454261 0.5C/0.5C 817 87% Embodiment 2-8 (invention application group) 454261 0.5C/0.5C 1445 66% Embodiment 3-1 (comparison group) 374270 0.7C/0.5C 620 63% Embodiment 3-3 (invention application group) 374270 0.7C/0.5C 5000 93%

Table 10. Cyclic performance test results at 45 degrees

Example Battery type cycle rate Cycles Capacity retention Embodiment 2-1 (comparison group) 383450 0.7C/0.5C 500 72% Embodiment 2-3 (invention application group) 383450 0.7C/0.5C 500 74% Embodiment 2-5 (contrast group) 454261 0.5C/0.5C 539 89% Embodiment 2-8 (invention application group) 454261 0.5C/0.5C 600 76% Embodiment 3-1 (comparison group) 374270 0.7C/0.5C 799 82% Embodiment 3-3 (invention application group) 374270 0.7C/0.5C 732 93% Embodiment 3-7 (comparison group) 454261 0.5C/0.5C 400 82% Embodiment 3-8 (invention application group) 454261 0.5C/0.5C 2200 89%

Table 11. Cyclic performance test results at 60 degrees

Example Battery type cycle rate Cycles Capacity retention Embodiment 2-1 (comparison group) 383450 0.7C/0.5C 652 68% Embodiment 2-3 (invention application group) 383450 0.7C/0.5C 720 70% Embodiment 2-5 (contrast group) 454261 0.5C/0.5C 255 78% Embodiment 2-8 (invention application group) 454261 0.5C/0.5C 550 70% Embodiment 3-1 (comparison group) 374270 0.7C/0.5C 912 79% Embodiment 3-4 (invention application group) 374270 0.7C/0.5C 1700 78%

Embodiment 3-11 (comparison group) 18650 0.5C/0.5C 400 59% Embodiment 3-13 (invention application group) 18650 0.5C/0.5C 6830 85%

Table 9 to Table 11 have listed the cycle performance test results of the batteries of each embodiment at normal temperature, 45 degrees and 60 degrees. Compared with the comparative sample, the battery using the dispersion method of the present invention to pre-disperse the carbon nanotubes can be recycled. The service life has been qualitatively improved: the cycle life of ordinary lithium-cobalt batteries can reach more than 1,000 times, and the battery of lithium iron phosphate system can reach more than 6,000 times. According to the standard of 300 cycles, which is equivalent to more than 5 years of ordinary batteries, this Such batteries have been used for 15 to 20 years, and their electrochemical performance is still very good, which can save natural resources and reduce environmental pollution. At the same time, lithium-ion batteries can be used in new fields such as permanent power stations and vehicle batteries.

6. Impact on battery safety performance

According to the UL1642 standard, safety tests were carried out on the batteries prepared in each embodiment, and the results are shown in Table 13.

Table 12, the electrochemical safety performance of each embodiment battery

It can be seen from Table 12 that compared with the batteries of the normal comparison group, the batteries using the dispersion method of the present invention to pre-disperse the carbon nanotubes have the same safety performance, and the performance of some items is better than that of the normal group. This may be due to In the case of abuse, there is a rapid heat release inside the battery, and the linear structure and good thermal conductivity of the carbon nanoconductive agent can timely conduct away the heat locally generated in the battery, thus avoiding worse situations such as explosion, Extreme situations such as fire and gas leakage occur.

According to the disclosure and teaching of the above specification, those skilled in the art to which the present invention pertains can also make appropriate changes and modifications to the above embodiment. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (7)

1. a lithium-ion battery pole piece preparation method, is characterized in that, comprises the following steps: The carbon nanotube conductive agent powder is added to a solvent and a surfactant to disperse evenly to obtain a uniform and stable dispersed carbon nanotube slurry; the carbon nanotubes in the carbon nanotube conductive agent powder have a length of 0.2-20 μm, Single-walled, double-walled or multi-walled carbon nanotubes with a diameter of 2-20nm; the surfactant is a surfactant with stable properties within the electrochemical working voltage range of lithium-ion batteries, which includes a dispersant and also includes a defoaming agent agent, wetting agent and leveling agent; the carbon nanotube slurry is divided into water-based slurry and oil-based slurry; when preparing water-based slurry, the dispersant is polyoxyethylene ether block copolymer, alcohol One; when preparing the oil-based slurry, the dispersant is one or more of polysiloxane and its modified products, organic solvents, and polypyrrolidone; The carbon nanotube slurry is used to prepare the pole piece slurry, and the obtained pole piece slurry is used to prepare the lithium ion battery pole piece. 2. The method for preparing lithium-ion battery pole pieces according to claim 1, characterized in that: in the prepared carbon nanotube slurry, the weight content of carbon nanotubes is 2%-13.8%. 3. The lithium-ion battery pole piece preparation method according to claim 1, characterized in that: the defoamer is polysiloxane or a modified product thereof; the wetting agent is polyoxyethylene alkylphenol ether ; The leveling agent is a polysilane solvent. 4. The lithium-ion battery pole piece preparation method according to claim 1, characterized in that: when preparing the water-based slurry, the solvent is at least one of deionized water and isopropanol; when preparing the oil-based slurry, the solvent One or more of N-methylpyrrolidone, cyclohexanone, acetone, and isopropanol. 5. The lithium ion battery pole piece preparation method according to claim 4, characterized in that: the carbon nanotube oil-based slurry is used to prepare positive pole pieces or negative pole pieces; the carbon nanotube water-based slurry is used for the preparation of negative electrodes. 6. lithium ion battery pole piece preparation method according to claim 1 is characterized in that: described carbon nanotube has different additions to different active materials, by the solid part weight of the prepared pole piece slurry, The amount of carbon nanotubes added is: when the negative active material is graphite, the carbon nanotubes are 0.1-3.0%; when the negative active material is lithium titanate, the carbon nanotubes are 0.5-5.0%; when the positive active material is lithium cobaltate , carbon nanotubes are 0.2-5.0%; when the positive electrode active material is lithium nickelate, the carbon nanotubes are 0.2-6.0%; When the material is lithium iron phosphate, the content of carbon nanotubes is 1.0-6.0%; when the positive electrode active material is lithium manganese phosphate, the content of carbon nanotubes is 1.0-7.0%. 7. The method for preparing lithium-ion battery pole pieces according to claim 1, characterized in that: in the carbon nanotube powder, the content of metal impurities is less than 1% by dry weight.