Process suggestions when LA is used in LFP（for reference only）
Notes：
The electrode composition of lithium-ion battery (formula) is determined by the final requirements of battery performance, the specific operation process is closely related to the physical and chemical properties of the electrode materials that are used, the composition of slurry, the condition of the equipment and the thickness of the electrode etc. So this information has no practical guiding significance and can only be used as a reference document, the example listed in this paper is only used to evaluate the performance of the binder, but not the production instance.
LA aqueous binder has excellent mechanical stability, there’s no demulsification while stirring it for as long as less than 10h under the linear velocity of 18m/s; the appropriate range of PH is 4 to 10, it is applicable to both ordinary and high viscosity slurry preparation process.
The thermal decomposition temperature of LA is no less than 220℃.
1 formula
Hangzhou Jinma：
LFP（P3）：SP：KS-6：LA132（S）=93.5 or 93：1.5：2：3 or 3.5
ALEEES：
Rate type: LFP（M121）：SP：KS-6：LA132=91 or 90：4：2：3 or 4
Capacity type: LFP（M121）：SP：KS-6：LA132=93 or 92：3：1：3 or 4
2 Preparation of electrode slurry
2.1 Dispersion of binder
First, add water (distilled water, deionized water or pure water) to the agitate tank, make the solid content of slurry is about 70%, then add LA that is needed, turn on stirring, revolution of 10-20 r/min, rotation of 5-10r/min, stirring for 15-20min.
2.2 Dispersion of SP
Add conductive agent to the prepared binder dispersion, turn on stirring, revolution of 10-20 r/min, stirring for 3-5min,then turn on rotation of 10-20 r/min, stirring for 10-20 min, after the conductive agent is fully wetted, rising the stirring paddle, scrape the drier which stick to the agitate tank wall, bottom and stirring paddle to the tank; after repeating the above process for 1-2 times, dispersing conductive agent under high-speed, revolution of 30-45 r/min, rotation of 25-35 r/min, stirring for 1.0-2.0 h.
2.3 Dispersion of LFP
Add LFP in batches (according to the amount of powder and the condition of equipment, it can be divided into 2-6 batches to ensure each addition of dry powder can be fully wetted) to the dispersion of binder and conductive agent which has been initially dispersed, after each feeding, turn on stirring, revolution of 15-20 r/min for 3-5min to wet the powder, then turn on the rotation of 15-20 r/min, stirring for 10-20min; rising the stirring paddle, scrape the drier which stick to the agitate tank wall, bottom and stirring paddle to the tank; and then continue stirring for 10-20min, feeding again, repeat the operation; KS-6 can be added in as LFP if necessary.
2.4 Disperse under high-speed
Turn on the revolution to 40-45 r/min and the rotation to 35-40 r/min, stirring under high-speed for about 2.5-4h to ensure that the slurry mixing uniformity, vacuumizing in the whole process or after stirring for 1.5-2h (vacuum degree is about -0.09Mpa).
2.5 Viscosity test
The viscosity of slurry must be controlled within 2000-6000(cps,25℃) (different materials and coating thickness need different viscosity); if the viscosity is to high, fill a moderate amount of water to adjust it, to avoid re-introducing bubbles into the slurry, vacuumizing first and then turn on stirring after adding water.
2.6 Sieving and discharging
The slurry can be coated after it through 100-150 mesh screen.
2.7 Precautions
a、Prevent the mixing of other impurities;
b、Prevent the splash of slurry. The feeding amount must subjected to the optimal design of agitator, the amount is too high or too low is not conducive to the stirring and the dispersion of slurry;
c、The concentration of slurry (solid content) should be adjusted from high to low gradually to avoid unnecessary waste caused by the slurry concentration which is too low;
d、During the stirring process, stop the machine for 3-5 times and scrape the tank wall and bottom, ensure uniform dispersion;
e、To avoid precipitation or decreasing the uniformity, the slurry is not suitable for long time placing, if it needs to place for a long time, stirring the slurry evenly again before coating; to avoid bringing bubbles into the slurry, vacuumizing first and then turn on stirring;
f、The stirring time is related to the condition of equipment and the surface properties of the material etc.
2.8 Instructions
The slurry is suitable for high viscosity stirring;
The purpose of compositing the slurry is to disperse various of materials evenly. The way to achieve this goal can be adjusted according to the characteristics of the material and the condition of equipment.
3 Coating（Example）
3.1 Ratio：
3.2 The solid content of slurry：≥55%.
3.3 The viscosity of slurry is 3000~5500(cps,25℃) for reference；the fluidity of the slurry is good; the surface of the coating is uniform and exquisite without cracks, the electrode does not drop powder after slitting.
3.4 The capacity ratio of the positive and negative should be greater than 1.10 to avoid the evolution of lithium.
3.5 Coating parameters
3.6 Precautions
a、The raw material may not need to be dried beforehand, remove water if accurate weight of the raw material needs to be calculated;
b、To better stabilize the viscosity of the slurry while coating, the temperature difference of slurry and the environment should less than 5℃;
c、Cling film can be used to seal the hopper to avoid the formation of drier due to the rapid evaporation of water in the coater hopper (especially when the humidity of the coating environment is lower than 50% RH );
d、Due to the big difference of boiling point between water (100℃) and NMP (203℃), the coating process of organic solvent system is not suitable for water system, in principle, the coating temperature of water system is lower than organic solvent system;
e、Control the temperature and the temperature distribution of the oven, the tape speed, avoid coating cracking caused by drying too fast, and influence the bonding strength between the coating and the current collector;
f、The electrode made by water system has a relatively high water content during preparation (between 0.5% and 2%), but the removal of water only need to be carried for once before electrolyte injection, so compare to organic solvent system , it needs more time to remove water, the number of exchanging dry gas may also need to increase, however, the combination form of binder and water is adsorption, so the water is easy to be removed (the water content of lithium-ion battery is lower than 100ppm);
g、The electrode based on aqueous binder is brittle, it is suitable for lamination process, for winding process, it is advised to adopt intermittent coating method in the first 1-4 fold.