Preparation and coating method of lithium ion battery pole piece coating slurry

Abstract

The invention provides a lithium ion battery pole piece coating slurry preparation and coating method, and belongs to the field of lithium batteries. The preparation method comprises the following steps: firstly preparing a three-dimensional porous pole piece substrate, then preparing uniformly dispersed slurry, finally obtaining a coating which is good in combination, uniform in thickness and excellent in cycle performance through multiple times of adsorption-drying, and completing slurry coating of the pole piece. The invention overcomes the problems of poor uniformity and combinability of slurry preparation and coating and poor battery performance in the existing pole piece coating, and can be used for slurry coating treatment of high-performance lithium ion battery pole pieces.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of coating slurry preparation and coating method, especially a kind of lithium ion battery pole piece coating slurry preparation and coating method, belong to lithium battery, new material, new energy, advanced manufacturing, surface engineering field. BACKGROUND

[0002] Lithium ion battery has the advantages of high energy density, high working voltage, wide working temperature range, etc. With the rapid development of new energy vehicles, energy storage, consumer electronics and other industries, lithium ion batteries are developing rapidly. The pole piece of lithium ion battery is the core of the battery, and the preparation of the slurry for the surface coating of the battery pole piece and the process control directly affect the battery performance.

[0003] CN119361711A discloses a lithium battery positive electrode slurry composite additive and its use method, comprising the following mass fraction of raw materials: 15%-30% hexamethylcyclotrisiloxane, 15%-30% oleic acid, 5%-15% polyoxyethylene alkyl phenol ether and 25%-65% N-methyl pyrrolidone; the present application can improve the dispersion effect in the process of positive electrode material homogenization, realize the dispersion of agglomerated particles, and effectively avoid the secondary agglomeration in the homogenization process; shorten the homogenization time, improve the homogenization efficiency and improve the equipment productivity; enhance the bonding ability of the slurry, improve the peeling strength between the slurry and the current collector, and avoid electrode defects. CN119314995A discloses a lithium iron phosphate battery positive electrode slurry, a lithium iron phosphate battery electrode, a lithium iron phosphate battery and a manufacturing method thereof. The slurry comprises the following components by weight: 95-97 parts of active lithium iron phosphate material; 0.1-1 parts of rare earth oxide; 1-2 parts of acetylene black; 0.5-2 parts of conductive agent; 1-5 parts of binder; 2-3 parts of positive electrode organic additive; and 30-40 parts of positive electrode solvent. The present application has the advantages of good slurry stability, high positive electrode slurry active material content and significantly improved battery electrochemical performance. CN119386797A discloses a positive electrode slurry, a preparation method and application thereof. The positive electrode active material particles used for preliminary slurry preparation are first subjected to particle size classification, and the fine particle active material and fine strip-shaped conductive agent particles are preferentially and uniformly dispersed, i.e. under the condition that the binder is fully dissolved, the fine particle positive electrode active material preferentially forms adhesion with the fibrous and tubular conductive agents, the fibrous and tubular conductive agents and the positive electrode active material particles form a better conductive network without changing the original substances and their proportions, avoid the agglomeration of fine strip-shaped conductive agents, and improve the electrical conductivity of the positive electrode sheet.

[0004] However, the uniformity of the slurry used for pole piece coating in the current lithium ion battery pole piece manufacturing, the adhesion of the slurry after coating, the energy density and cycle performance of the battery still need to be improved. SUMMARY

[0005] The present application aims to provide a lithium ion battery pole piece coating slurry preparation and coating method to meet the requirements of improving the pole piece slurry coating and battery performance. The present application proposes to first prepare a three-dimensional porous pole piece substrate, then prepare a uniformly dispersed slurry, and then complete the slurry coating of the pole piece through multiple adsorption-drying to obtain a coating with good combination, uniform thickness and excellent cycle performance.

[0006] The lithium ion battery pole piece coating slurry preparation and coating method of the present application comprises the following steps in sequence: (1) Three-dimensional porous pole piece substrate preparation: weigh the raw materials according to the percentage by weight, wherein TiH2 accounts for 0.5-1%, stearic acid accounts for 1-2%, SBS rubber solution accounts for 6-12%, and the rest is Al powder with D90≦75μm; mix the weighed TiH2, stearic acid and Al powder in a three-dimensional mixer for 30-60min; then add the weighed SBS rubber solution, stir, dry and sieve to form a uniform pressing mixture; press into a battery pole piece green body under 150-300MPa; sinter the green body in an atmosphere sintering furnace at 660-680℃ for 60-120min, first raise the temperature to 250℃ during the sintering process, then fill in argon and control the relationship between the gas pressure P and the temperature T as P=0.8+(1-7)×10 -4 T MPa to balance the densification process and the process of SBS, stearic acid and TiH2 forming pores through high temperature decomposition, thereby preparing a three-dimensional porous pole piece substrate with a porosity of 45-60% and an average pore size≦100μm; (2) Pole piece coating slurry preparation: weigh the raw materials according to the percentage by weight, wherein carbon black accounts for 2-3%, active substance accounts for 45-50%, PVDF accounts for 2-3%, sodium dodecylbenzenesulfonate accounts for 0.5-1%, Tween 80 accounts for 0.5-1%, and the rest is NMP solvent; take 25% of the total amount of NMP solvent and mix it with carbon black, sodium dodecylbenzenesulfonate and Tween 80, ultrasonic dispersion treatment for 20-40min to make the Zeta potential of the solution 25-35mv, and obtain a well-dispersed carbon black mixture; add PVDF to the remaining NMP solvent, magnetically stir at 30-50℃ for 30-60min to form a PVDF solution; finally mix the carbon black mixture, PVDF solution and active substance in a planetary ball mill for 6-10h to prepare a uniformly dispersed pole piece coating slurry; (3) The pole piece slurry coating: the three-dimensional porous pole piece substrate is immersed into the pole piece coating slurry for adsorption-drying treatment, first kept for 5-10 min at normal temperature in a vacuum drying box, so that the pole piece coating slurry is adsorbed into the pores of the three-dimensional porous pole piece substrate, and then dried for 3-5 min at 80-90 DEG C in another vacuum drying box; the adsorption-drying process is repeated for 5-10 times, the slurry fills the inside of the three-dimensional porous electrode and forms a uniform, well-bonded and excellent cycle performance coating on the surface of the pole piece, the thickness deviation of the pole piece surface coating is ≦5 μm, the peeling strength is 15-22 N / m, and the capacity retention rate after 100 cycles at 0.1 C rate is 80%-90%, that is, the pole piece slurry coating is completed.

[0007] Further, in the preparation and coating method of the lithium ion battery pole piece coating slurry of the present application, each step is as follows: (1) In the preparation of the three-dimensional porous pole piece substrate, the rotating speed of the three-dimensional mixer is 15-20 r / min; the drying temperature after the SBS rubber solution is added is 80-90 DEG C, and then sieved through a 60-mesh sieve; the initial vacuum degree during sintering is 1x10 -2 ~8x10 -2 Pa, and the furnace is cooled down after the sintering holding is completed; (2) In the preparation of the electrode coating slurry, the active material is one of lithium iron phosphate or ternary lithium nickel cobalt manganese oxide; the ultrasonic frequency and power during the ultrasonic dispersion treatment are 40 kHz and 100 W respectively; the rotating speed of the planetary ball mill is 250-400 r / min; (3) In the pole piece slurry coating, the vacuum degree during the adsorption and drying process is 80-100 kPa.

[0008] The advantages of the present application are as follows: (1) the three-dimensional porous pole piece substrate has high and uniform porosity, which can relieve the volume expansion caused by lithium ion insertion and extraction, reduce the stress and cracking risk of the electrode, and has high stability; (2) the three-dimensional porous pole piece substrate can increase the active material loading, provide more diffusion channels, and improve the battery capacity and performance; (3) in the present application, the electrostatic stabilization and steric hindrance effect are utilized to make the carbon black and the active material uniformly dispersed, so as to form a stable conductive network, avoiding the reduction of lithium battery life or even safety hazards caused by local overcharge or insufficient charge; (4) the pole piece prepared by the immersion coating has high active material content, and the connection between the coating and the pole piece has a porous network effect, and has good bonding force. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 The preparation and coating method of the lithium ion battery pole piece coating slurry of the present application is shown in the schematic diagram. DETAILED DESCRIPTION

[0010] Example 1: the preparation and coating of the lithium ion battery pole piece coating slurry are carried out according to the following steps.

[0011] (1) Three-dimensional porous electrode substrate preparation: the raw materials are weighed according to the percentage by weight, wherein TiH2 accounts for 0.5%, stearic acid accounts for 1%, SBS rubber solution accounts for 8%, and the rest is Al powder with D90=75μm; the weighed TiH2, stearic acid and Al powder are mixed in a three-dimensional mixer for 35 min, and the rotation speed of the three-dimensional mixer is 15r / min; then the already weighed SBS rubber solution is added, and after stirring, 8℃ drying and 60 mesh sieving, a uniform pressing mixture is formed; the green body is pressed into a battery electrode under 180MPa; the green body is sintered in an atmospheric sintering furnace at 660℃ for 65 min, and the initial vacuum degree during sintering is 2×10 -2 Pa, and during the sintering process, the temperature is first raised to 250℃, then argon is filled, and the relationship between the gas pressure P and the temperature T is controlled as P=0.8+(1~7)×10 -4 T MPa to balance the densification process and the process of SBS, stearic acid and TiH2 forming pores through high temperature decomposition, and the sintering is cooled down in the furnace after the sintering holding, thereby preparing a three-dimensional porous electrode substrate with a porosity of 46% and an average pore size of 93μm; (2) Preparation of electrode coating slurry: the raw materials are weighed according to the percentage by weight, wherein carbon black accounts for 2%, active material lithium iron phosphate accounts for 46%, PVDF accounts for 2%, sodium dodecyl benzene sulfonate accounts for 0.6%, Tween 80 accounts for 0.5%, and the rest is NMP solvent; 25% of the total amount of NMP solvent is mixed with carbon black, sodium dodecyl benzene sulfonate and Tween 80, and ultrasonic dispersion treatment is carried out for 25 min, the ultrasonic frequency and power during ultrasonic dispersion treatment are 40 kHz and 100 W respectively, the Zeta potential of the solution is 27mv, and a well-dispersed carbon black mixture is obtained; PVDF is added to the remaining NMP solvent, and magnetic stirring is carried out at 30℃ for 335 min to form a PVDF solution; finally, the carbon black mixture, the PVDF solution and the active material are mixed and ball milled in a planetary ball mill for 6h, and the rotation speed of the planetary ball mill is 250r / min; a uniformly dispersed electrode coating slurry is prepared; (3) Electrode slurry coating: the three-dimensional porous electrode substrate is immersed in the electrode coating slurry for adsorption-drying treatment, first kept in a vacuum drying box at room temperature for 5 min to make the electrode coating slurry adsorbed into the pores of the three-dimensional porous electrode substrate, and then dried in another vacuum drying box at 80℃ for 3 min; the adsorption-drying process is repeated 5 times, and the vacuum degree during the adsorption and drying process is 80kPa; the slurry fills the inside of the three-dimensional porous electrode and forms a uniform, well-bonded and excellent cycle performance coating on the surface of the electrode, the thickness deviation of the electrode surface coating is 4.6μm, the peeling strength is 16N / m, and the capacity retention rate after 100 cycles at 0.1C rate is 82%, i.e. the electrode slurry coating is completed.

[0012] Example 2: The preparation and coating of the lithium ion battery electrode coating slurry were carried out according to the following steps.

[0013] (1) Preparation of three-dimensional porous electrode substrate: the raw materials were weighed according to the percentage by weight, wherein TiH2 accounted for 0.9%, stearic acid accounted for 1.5%, SBS rubber solution accounted for 10%, and the rest was Al powder with D90=70μm; the weighed TiH2, stearic acid and Al powder were mixed in a three-dimensional mixer for 50min, and the rotation speed of the three-dimensional mixer was 20r / min; then the weighed SBS rubber solution was added, and after stirring, drying at 85℃ and sieving through a 60 mesh sieve, a uniform pressing mixture was formed; the green body was pressed into a battery electrode under 280MPa; the green body was sintered in an atmospheric sintering furnace at 680℃ for 100min, and the initial vacuum degree during sintering was 6×10 -2 Pa, and during sintering, the temperature was first raised to 250℃, then argon was filled and the relationship between gas pressure P and temperature T was controlled as P=0.8+(1~7)×10 -4 T MPa to balance the densification process and the process of SBS, stearic acid and TiH2 decomposing at high temperature to form pores, and the sintering was cooled in the furnace after holding, thereby preparing a three-dimensional porous electrode substrate with a porosity of 56% and an average pore size of 86μm; (2) Preparation of electrode coating slurry: the raw materials were weighed according to the percentage by weight, wherein carbon black accounted for 3%, active material was ternary nickel-cobalt-manganese lithium accounted for 48%, PVDF accounted for 2.5%, sodium dodecylbenzenesulfonate accounted for 1%, Tween 80 accounted for 0.8%, and the rest was NMP solvent; 25% of the total amount of NMP solvent was mixed with carbon black, sodium dodecylbenzenesulfonate and Tween 80, and ultrasonic dispersion treatment was carried out for 40min, the ultrasonic frequency and power during ultrasonic dispersion treatment were 40kHz and 100W respectively, the Zeta potential of the solution was 32mv, and a well-dispersed carbon black mixture was obtained; PVDF was added to the remaining NMP solvent, and magnetic stirring was carried out at 40℃ for 60min to form a PVDF solution; finally, the carbon black mixture, PVDF solution and active material were mixed in a planetary ball mill for 8h, and the rotation speed of the planetary ball mill was 350r / min; a uniformly dispersed electrode coating slurry was prepared; (3) The pole piece slurry coating: the three-dimensional porous pole piece substrate is immersed into the pole piece coating slurry for adsorption-drying treatment, first kept for 10 min at normal temperature in a vacuum drying box, so that the pole piece coating slurry is adsorbed into the pores of the three-dimensional porous pole piece substrate, and then dried for 5 min at 90 DEG C in another vacuum drying box; the adsorption-drying process is repeated for 10 times, and the vacuum degree of the adsorption and drying process is 90 kPa; the slurry fills the inside of the three-dimensional porous electrode and forms a uniform, well-bonded and excellent cycle performance coating on the surface of the electrode, the pole piece surface coating thickness deviation is 4.1 um, the peeling strength is 21 N / m, and the capacity retention rate after 100 cycles at 0.1 C rate is 87%, that is, the pole piece slurry coating is completed.

Claims

1. A method for preparing and coating a lithium-ion battery electrode coating slurry, characterized in that... The steps are as follows: (1) Preparation of three-dimensional porous electrode substrate: Weigh the raw materials according to the weight percentage, of which TiH2 accounts for 0.5~1%, stearic acid 1~2%, SBS rubber solution 6~12%, and the remainder is Al powder with D90≦75μm; mix the weighed TiH2, stearic acid and Al powder in a three-dimensional mixer for 30~60min; then add the weighed SBS rubber solution, and after stirring, drying and sieving, form a uniform pressing mixture; press into battery electrode green blanks at 150~300MPa; sinter the green blanks in an atmosphere sintering furnace at 660~680℃ for 60~120min, during the sintering process, first raise the temperature to 250℃, then fill with argon gas and control the relationship between the gas pressure P and the temperature T as P=0.8+(1~7)×10 -4 T MPa balances the densification process and the process of SBS, stearic acid and TiH2 decomposing at high temperature to form pores, thereby preparing a three-dimensional porous electrode substrate with a porosity of 45~60% and an average pore size of ≤100μm; (2) Preparation of electrode coating slurry: Weigh the raw materials according to the weight percentage, of which carbon black accounts for 2-3%, active material accounts for 45-50%, PVDF accounts for 2-3%, sodium dodecylbenzenesulfonate accounts for 0.5-1%, Tween 80 accounts for 0.5-1%, and the remainder is NMP solvent; take 25% of the total amount of NMP solvent and mix it with carbon black, sodium dodecylbenzenesulfonate and Tween 80, and perform ultrasonic dispersion treatment for 20-40 min to make the solution Zeta potential 25-35 mV to obtain a well dispersed carbon black mixture; add PVDF to the remaining NMP solvent and stir magnetically at 30-50℃ for 30-60 min to form a PVDF solution; finally mix the carbon black mixture, PVDF solution and active material, and ball mill in a planetary ball mill for 6-10 h to prepare a uniformly dispersed electrode coating slurry; (3) Electrode slurry coating: The three-dimensional porous electrode substrate is immersed in the electrode coating slurry for adsorption-drying treatment. First, it is kept at room temperature in a vacuum drying oven for 5~10 min to allow the electrode coating slurry to be adsorbed into the pores of the three-dimensional porous electrode substrate. Then, it is dried in another vacuum drying oven at 80~90℃ for 3~5 min. This adsorption-drying process is repeated 5~10 times. The slurry fills the interior of the three-dimensional porous electrode and forms a uniform, well-bonded coating with excellent cycling performance on its surface. The coating thickness deviation on the electrode surface is ≦5μm, the peel strength is 15~22N / m, and the capacity retention rate after 100 cycles at 0.1C is 80%~90%, which means the electrode slurry coating is completed.

2. The method for preparing and coating lithium-ion battery electrode coating slurry according to claim 1, further characterized in that: (1) When preparing the three-dimensional porous electrode substrate, the rotation speed of the three-dimensional mixer is 15~20 r / min; the drying temperature after adding SBS rubber solution is 80~90℃, and then it is sieved through a 60-mesh sieve; the initial vacuum degree during sintering is 1×10 -2 ~8×10 -2 Pa, cooled with the furnace after sintering and heat preservation; (2) When preparing the electrode coating slurry, the active material is either lithium iron phosphate or ternary lithium nickel cobalt manganese oxide; the ultrasonic frequency and power during ultrasonic dispersion treatment are 40 kHz and 100 W, respectively; the planetary ball mill speed is 250~400 r / min. (3) When coating the electrode slurry, the vacuum degree of both the adsorption and drying processes is 80~100kPa.

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