Lithium battery ingredients knowledge and technical information

First, the composition of the electrode:

1, positive composition:

a. Lithium cobaltate: positive active material, lithium ion source, lithium source for batteries.

b. Conductive agent: The conductivity of the positive electrode sheet is increased to compensate for the electronic conduction of the positive electrode active material, the electrolyte absorption amount of the positive electrode sheet is increased, the reaction interface is increased, and polarization is reduced.

c, PVDF adhesive: Lithium cobaltate, conductive agent and aluminum foil or aluminum mesh bonded together.

d, positive lead: made of aluminum foil or aluminum tape.

2, the anode composition:

a. Graphite: Anode active materials, constitute the main material of the negative reaction; mainly divided into natural graphite and artificial, graphite two categories.

b. Conductive agent: The conductivity of the negative electrode sheet is increased to compensate for the electronic conduction of the negative electrode active material.

Improve reaction depth and utilization. Prevent dendrite production. Using the liquid-absorbing ability of the conductive material, the reaction interface is increased and polarization is reduced. (According to the graphite particle size distribution, choose to add or not).

c. Additives: reduce irreversible reactions, increase adhesion, increase slurry viscosity, and prevent slurry from sedimentation.

d. Water* Adhesives: Adheres graphite, conductive agents, additives, and copper or copper mesh.

e, negative lead: Made of copper foil or nickel tape.

Second, lithium battery ingredients purpose:

The dosing process actually mixes the various components in the slurry at a standard ratio and modulates them into a slurry so as to facilitate uniform coating and ensure the uniformity of the pole piece. The ingredients generally include five processes, namely: pretreatment, blending, soaking, dispersing, and flocculation of the raw materials.

Third, lithium battery ingredients principle:

(A), the principle of positive ingredients 1, raw material physical and chemical * energy.

(1) Lithium cobaltate: non-polar * material, irregular shape, particle size D50 is generally 6-8μm, water content ≤ 0.2%, usually alkali *, PH value of about 10-11.

Lithium manganate: non-polar * material, irregular shape, particle size D50 is generally 5-7μm, water content ≤ 0.2%, usually weak base *, PH value of about 8.

(2) Conductive: non-polar * substances, grape chain, moisture content of 3-6%, oil absorption value ~ 300, particle size is generally 2-5μm; mainly common carbon black, superconductive carbon black, graphite milk, etc. For high volume applications, superconducting carbon black and graphite latex are generally chosen; usually medium.

(3) PVDF adhesives: non-polar* materials, chains, molecular weights ranging from 300,000 to 3,000,000; molecular weight decreases after water absorption, and viscosity* deteriorates.

(4) NMP: Poor pole * liquid, used to dissolve/swell PVDF and also used to dilute the slurry.

2. Pretreatment of raw materials (1) Lithium cobaltate: Dehydration. It is usually baked at 120oC atmospheric pressure for about 2 hours.

(2) Conductive agent: Dehydration. It is usually baked at 200oC atmospheric pressure for about 2 hours.

(3) Adhesive: Dehydration. Normally baked at 120-140oC under normal pressure for about 2 hours, the baking temperature is determined by the size of the molecular weight.

(4) NMP: Dehydration. Use dry molecular sieves for dehydration or use special reclaiming facilities for direct use.

3, the mixing of raw materials:

(1) Dissolution of the binder (at standard concentration) and heat treatment.

(2) Lithium cobaltate and conductive agent ball milling: The powder is initially mixed, lithium cobaltate and a conductive agent are bonded together to improve agglomeration and conduction. After being formulated into a slurry, it will not be separately distributed in the binder. The ball milling time is generally about 2 hours; in order to avoid mixing impurities, agate balls are usually used as ball milling mesons.

4, dry powder dispersion, soaking:

(1) Principle: The solid powder is placed in the air. As time passes, some air will be adsorbed on the surface of the solid. After the liquid binder is added, the liquid and gas begin to compete for the solid surface; if the solid and gas adsorbability Than the liquid with strong adsorption, the liquid can not soak the solid; if the solid and liquid adsorption force than the gas adsorption force, the liquid can wet the solid, the gas extrusion. When the wetting angle is ≤ 90 degrees, the solid wets. When the wetting angle is > 90 degrees, the solid does not wet. All members of the positive electrode material can be wetted by the binder solution, so the positive electrode powder is relatively easy to disperse.

(2) The effect of the dispersion method on dispersion:

A, standing method (long time, poor effect, but does not damage the original structure of the material);

B. Stirring method; rotation or rotation plus revolution (short time, good effect, but may damage the structure of individual materials).

1. Effect of stirring paddle on dispersion speed. The stirring paddle generally includes a serpentine shape, a butterfly shape, a spherical shape, a paddle shape, a gear shape, and the like. Generally serpentine, butterfly, and paddle type paddles are used to deal with the initial stage of materials or ingredients that are difficult to disperse; spheres and gears are used to disperse difficult states with good results.

2. The effect of stirring speed on the dispersion speed. In general, the higher the stirring speed, the faster the dispersion speed, but the greater the damage to the material's own structure and equipment.

3, the concentration of the dispersion speed. Under normal circumstances, the smaller the slurry concentration, the faster the dispersion speed, but too thin will lead to material waste and slurry precipitation.

4, the concentration of the bond strength. The greater the concentration, the greater the flexural strength and the greater the bond strength; the lower the concentration, the lower the bond strength.

5, the degree of vacuum on the dispersion speed. The high vacuum is beneficial to the material gap and the surface of the gas discharge, reduce the difficulty of liquid adsorption; the difficulty of the material in the case of complete weightlessness or gravity reduction will be greatly reduced.

6, the temperature on the dispersion speed. At a suitable temperature, the slurry flows well and is easily dispersed. Too hot slurry is easily crusted, and the flow of too cold slurry will be greatly reduced.

5, dilution. The slurry is adjusted to a suitable concentration for easy coating.

(B), negative electrode ingredients principle (roughly the same with the positive electrode ingredients principle)

1, the physical and chemical * energy.

(1) Graphite: non-polar * substances, easily contaminated by non-polar * substances, easily dispersed in non-polar * substances; not easy to absorb water, but also difficult to disperse in water. Contaminated graphite is easily re-agglomerated after being dispersed in water. The general particle size D50 is about 20 μm. The particles have various shapes and irregularities, mainly spherical, flaky, and fibrous.

(2) Water * Adhesive (SBR): small molecular chain * chain emulsion, easily soluble in water and extremely solvent.

(3) Precipitating agent (CMC): Polymer compound, soluble in water and extremely solvent.

(4) Isopropanol: A weak polar material, which can reduce the viscosity of the binder solution after it is added, improve the compatibility of the graphite and the binder solution, has a strong defoaming effect, and is easy to catalyze an adhesive network. Chain, improve bond strength.

Ethanol: Poor polar material, can reduce the polarity of the binder solution after adding, improve the compatibility of the graphite and binder solution; has a strong defoaming effect; easy to catalyze the adhesive line * cross link, improve the bond strength (The effect of isopropyl alcohol and ethanol is essentially the same. In mass production, you can consider the cost factor and then choose which one to add.)

(5) Deionized water (or distilled water): Diluent, added as appropriate, changes the flow of the slurry.

2. Pretreatment of raw materials:

(1) Graphite:

A. Mixing to homogenize raw materials and increase consistency.

B. Baking at 300-400°C under normal pressure to remove surface oil and improve the compatibility with the water adhesive. The corners of the graphite surface are rounded. (Some materials maintain the surface characteristics and do not allow baking, otherwise the performance is reduced).

(2) Water adhesive: Properly diluted to increase dispersion capacity.

3, blending, soaking and dispersing:

(1) Graphite and binder solutions are very different and do not easily disperse.

(2) The graphite can be initially wetted with an aqueous alcohol solution and then mixed with a binder solution.

(3) The stirring concentration should be properly reduced to increase the dispersion.

(4) The dispersion process is to reduce the distance between the polar material and the non-polar material and increase the potential energy or surface energy. Therefore, for the endothermic reaction, the overall temperature during stirring decreases. If the conditions permit, the stirring temperature should be increased appropriately to make the endotherm easy, increase the flow*, and reduce the difficulty of dispersion.

(5) The stirring process, such as adding vacuum degassing process, eliminates gas and promotes solid-liquid adsorption.

(6) Dispersion principle, dispersion method and related content of positive electrode ingredients,

It is discussed in details in (a) and (4) and will not be explained in detail here.

4, dilution. The slurry is adjusted to a suitable concentration for easy coating.

Fourth, lithium battery ingredients note:

1. Prevent mixing with other impurities;

2, to prevent the slurry splash;

3, slurry concentration (solids content) should be gradually adjusted from high to low, so as not to increase the trouble;

4, in the mixing process should pay attention to scraping and scraping the bottom to ensure that the dispersion;

5, the slurry should not be put on hold for a long time, so as not to precipitate or reduce it evenly;

6. The material to be baked must be sealed and cooled before it can be added to avoid changes in the quality of the component materials;

7. The length of the mixing time is mainly based on the equipment energy and the amount of material added; the use of the mixing paddle is replaced by the slurry dispersion difficulty, and the speed can be adjusted from slow to fast to avoid damage to the equipment.

8. Before the material is discharged, the slurry is sieved to remove large particles to prevent breakage when coated;

9, to strengthen the training of ingredients to ensure that they master professional knowledge, so as not to cause a disaster; 10, the key ingredient is to spread evenly, master the center, and other methods can be adjusted.

V. General:

With the increasingly transparent battery process, lithium-ion battery manufacturers are increasingly classifying ingredients as core secrets, because the selection of materials, processing to a reasonable match contains too much effort of the technical staff, the same material, and some manufacturers use It is particularly smooth, and some manufacturers have troubles; some manufacturers use mid-range materials to make high-end batteries, and some manufacturers use the best materials to make them look terrible. If there is any deficiency in the above information, we It will be corrected in time.