I. Material systemization performance meanings and description specific surface area (m2 / g): refers to the surface area of material unit mass particles. (Test method: calculating the argon volume adsorbed by the material of the unit weight).
Particle size (μm): Description of material particles, refers to the diameter of material particles. D50 describes the average particle diameter of the material. Vain Density (G / CM3): The material is vibrating the mass of the mass of the unit of mechanical vibration.
. In addition, there is also a material itself, an appearance type, discharge capacity, capacity efficiency, impurity content, and the like are also the performance constraints of various materials..
Second, various materials in the electrode and its basic use characteristics 1, conductive agent carbon ink conductive agents, uncomfortable carbon, good conductive properties, strong adsorption, large specific surface area, about 60-100 m2 / g, Its itself has no capacity. Artificial graphite conductive agent, the conductivity is less poor than the carbon ink, but the specific surface area is small, 10-30 mAh / g, which is capacity, about 290 mAh / g, which is better. There is also a natural graphite, depending on its own conductivity, it can also be used as a conductive agent, but also as a negative electrode material due to high capacity.
. And nano-scale carbon fiber, good conductivity, good processing performance, but price is expensive. 2, the electrode material is generally a lithium ion secondary battery, and lithium cobaltate, its own gram capacity 135-150 mAh / g, the compact density is 3.
65-4.00 g / cc, LiCoO2 is a lithium ion battery having a positive electrode has an open circuit voltage height. High than energy (theoretical than energy 1068Wh / kg, theoretical capacity 274mAh / g), long cycle life, fast discharge, but price is expensive.
Negative electrode material: artificial graphite, intermediate phase carbon microsphere, natural graphite modification, etc.. Ordinary artificial graphite: gram capacity 290-310mAh / g, compaction 1.
45-1.55g / cc. Intermediate phase carbon microspheres: gram capacity 310-320mAh / g, compaction 1.
55-1.65g / cc. Natural graphite modification: gram capacity 320-340mAh / g, compact 1.
55-1.65g / cc. 3, the glue is commonly famous for PVDF, the chemical name is polyvinylidene fluoride, and the size of its viscosity is affected by molecular weight, functional group position and processing process.
. In general, regarding the same processing process, the same functional group position, the greater the molecular weight, the higher its viscosity, but with the increase in viscosity, its settlement of the slurry is more pronounced..
CMC and SBR are glue used in aqueous system.. CMC (carboxymethylcellulose): white or micro-yellow powder, itself has bonding properties, but in the aqueous system, its most basic use or dispersion material and SBR.
SBR (butadous-blene-blewell milk): white belt light blue emulsion liquid, polymer compound, mixed with CMC, and its bonding performance is better. Third, the battery performs a good performance to meet several conditions for materials, to make it a good performance, not to reach the following conditions: 1, the material itself structure, the size of the particle size, granules Smoothness of the appearance; the uniform discharge of the active molecules in the electrode; 3, the active molecule and the conductive agent good contact; 4, smoothly conduct the network; 5, and the electrolyte good infiltration degree; 6, for each Good process conditions for material properties. Fourth, stirring method and sequence 1, stir glue PVDF: According to the concentration to be configured, the amount of PVDF dry powder is referred to, put in a dry oven, bake 60-120 min at 70-80 degrees, and then referred to as NMP In the adhesive container, the container is fixed, and the PVDF dry powder is added to the container, and then dissolve while stirring until the PVDF dry powder is added, the container is sealed as possible, stirred 3-4h, until it is completely dissolved, slowly stir Seal for a period of time to remove the bubbles in the rubber or pour their solution into the fixed container.
. This rubber is auspicious, its concentration is generally 12%. CMC: The method step is basically the same, but the solution system is water-based, the solvent is deionized water rather than NMP, and the concentration of the solution is generally 2-3.
5%.. 2, calcouting material to take a material to a vacuum oven for 4 h at 160 degree vacuum oven, and then stir, and then stir, the general steps are as follows: 2.
1 Add a conductive agent SP, and wet it with a sufficient amount NMP, and Stir 10-20min. 2.2 Add other conductive agents to the first step, stir the 10-20 min.
2.3 Adding active products and gum, stirring with a spoon, then stirring it on the stirrer at high speed until it is considered to be more smooth and turned to the agitator for 2 h, and the slurry is required to high speed Thick stir, achieve the purpose of dispersion). 2.
4 Adjust it to solid, slowly stir 30 minutes to remove steam. 2.5 Remove the slurry, filter.
3, stirred material 3.1 Add a conductive agent SP, wet it with a small amount of NMP, stirred for 10-20min. 3.
2 Adding other conductive agents, active products, and CMC and the appropriate amount of H2O, stirred with a spoon, and then stirred at high speed on the stirrer until it is seen that the slurry surface is more smooth, and then fixed to stir Stir on the device 1.2-1.5H (this step requires a high speed thickening to achieve the purpose of dispersion).
3.3 Adding an appropriate amount of H2O to the second step. 3.
4 Adding a sufficient SBR in the upper step, stirring is completely dissolved in SBR, about 30 min. (Requires low temperature and slow speed when adding SBR) 3.5 Add slurry water content 10-15% NMP (containing NMP plus in step 1), slowly stir the bubble, 30 minutes.
3.6 Remove the slurry, filter. V.
Common problems in the experiment, solve the problem and affect 1, the purpose, time and temperature of the bake. Electrode material: to remove moisture, oil and dust, baking conditions generally 160 degrees 4h. Glue: Important deflash, baking conditions generally 70-80 degrees bake 60-120min.
Oxic acid: in addition to moisture and crystalline water, baking conditions generally 70-80 degrees for 30-60 min. 2, principle of use of conductive agents. Conductors are generally mixed, using the extraction method.
3. Effect of conductive agent added to the battery. Conductors have less affected capacity, cycle, platform, high and low temperature discharge properties and high current discharge, safety performance, internal resistance, etc.
. 4, the difference in the order of addition of the ingredients and the advantages and disadvantages. Conductant and adhesive add sequence, oxalic acid add sequence, NMP add sequence in aqueous material, etc.
. 5, glue plus less influence on battery performance. 6.
What is the impact of rapid cooling during ingredients. 7. How to goperate and the addition and amount of oxalic acid in the oily negative configuration and oxalic acid.
There are two purposes of gaseous heating: remove the surface oxide layer of the copper foil and form a corrosive groove on the surface of the copper foil, and the sprinkle of the slurry on the copper foil.. Its usage is generally 2% of PVDF.
8, CMC, SBR Use and Precautions in Waterborne. Both CMC and SBR have adhesive, used in the slurry, where CMC is important at this time, and SBR is important to bonding..
9. How to add NMP and use when the water distribution is negative. Adding NMP in aqueous negative electrode is important to increase the surface tension of the negative foil, making the slurry table more smooth, and to prevent the strapping of the pulp.
However, when feeding, attention should be noted that SBR and NMP are high molecular organics, fast or high temperatures can react in two materials, and jelly-shaped and accompanied by gases.. 10, the relationship between solid, viscosity and gel species.
11. How is the oven temperature when pulling. The pulp is too low to lower the low-sequence powder, the temperature is too high, the polar powder is powdered, or a significant crack, and there is a hike.
12, the density of the puls launched is uneven or large. The slurry surface density is not uniformly divided into several aspects: the front and rear density of the polar sheet is inconsistent, the two side surface density is inconsistent, the polar mixing is unevenly caused the diamonding time to be inconsistent, the material itself is unstable, the mulch surface density is unstable And there is also a large-faced density or small. 13, debugging the roller pressure.
In two ways, one is from the microstructure of the particles, the second is from the appearance of the electrode (gum, flour, wrinkles). 14, during the production process and after the production of the film after the production. The purpose of the pole baking is to remove the moisture, but the temperature and time are controlled, and the polar baking temperature is 130 degrees during the production, and the baked temperature of the film is 90 degrees.
. 15, the storage conditions of the pole. After the film is completed, the pole is stored in a sealing dry environment.