Production process of lithium battery ternary cathode material

The main technology of ternary cathode materials lies in the production and production process of ternary precursors. With ternary material precursors, it is much more convenient to make ternary cathode materials, and the only steps required are calcination to obtain That’s it. So today we will talk about the main technologies and means of ternary cathode materials.

Preparation technology of ternary material precursors

1. The role of ammonia concentration in ternary precursors

If we want to prepare M(OH)2 with regular shape, we need to control the rate of the precipitation reaction, which is very closely related to the ternary precursor. We can use NH3 to complex with Ni2+, CO2+ and Mn2+ to adjust the concentration of metal ions in the reaction system, so that you can control the nucleation rate and crystal growth rate. Thus, the generation rate of the ternary material precursor is controlled.

During the co-precipitation process, the pH value was controlled at 11, and different NH4OH concentrations were selected. It can be found that with the increase of NH3+ concentration, there is no significant difference in the XRD patterns, but there are significant differences in the density and morphology of the vibrations.

The NH4OH concentrations from left to right are 0.12mol·1-1, 0.24mol·l-1 and 0.36mol·l-1, respectively

With the increase of the total ammonia concentration, the particle size of the precipitates increased significantly, the surface of spherical particles became smoother, the sphericity and density gradually increased, and the dispersion among the particles was good. The solubility of nickel and cobalt in the system increased significantly, the supersaturation of the co-precipitation system decreased sharply, the nucleation rate of crystals decreased greatly, the growth rate of crystals increased rapidly, and the particle size of the precipitates gradually increased.

2. The role of pH in ternary precursors

In multi-component co-precipitation systems, pH control is very important. Due to the continuous addition of the alkali-ammonia mixture and the complexation reaction, the pH value is difficult to control in the production process of the ternary cathode material precursor. In addition, manganese hydroxide is easily formed containing Mn. When the temperature is higher than 60 °C and the pH value increases Within a certain range, manganese hydroxide precipitates while preferentially oxidizing manganese. Certain manganese oxides are also readily formed in the presence of alkali and oxygen. At this time, the importance of PH value is fully realized in the ternary material.

The researchers found that in the range of 8, when the pH of the control system was 11, the precipitates had a single morphology, good sphericity, narrow particle size distribution, and high vibrational density, which were beneficial to improve the electrochemical performance of anode materials. performance.

3. The role of mixing ratio in ternary precursors

Increasing the stirring speed can increase the vibrational density of the sediment. Intense stirring enables rapid dispersion of nickel, cobalt, manganese and hydroxide ions in the reactor and avoids massive nucleation caused by excessive local supersaturation of the system during feeding.

An increase in agitation rate can also accelerate the mass transfer of reactive ions in the system.

In addition, it can accelerate the dissolution of small particles and then recrystallize on the surface of large particles, resulting in a narrow particle size distribution of the precipitate, a single morphology, and a corresponding increase in the vibrational density.

However, when the stirring intensity reaches a certain extreme value, the crystal growth changes from diffusion-controlled to surface-controlled. At this time, the stirring speed continued to increase, and the crystal growth rate remained basically unchanged.

4. The role of reaction time in ternary precursors

The reaction time affects the particle size and morphology of the coprecipitated product, and these factors directly affect the bulk density of the product. Accumulation time concentration is required for the formation of precipitated crystals. When the reaction time is relatively short and the particles are small, the precipitated particles are poorly crystalline (possibly in colloidal form), or they are small spherical and have a broad particle size distribution. The particle size of different particles varies greatly, and the crystal density is relatively poor.

However, when the reaction time is too long, the particle size distribution of the precipitated particles begins to broaden. Therefore, if the reaction time is increased again, the morphology of the product will not be greatly improved, while for the particle size distribution, it will develop into a bad trend.

5. The role of reaction temperature in ternary precursors

Under other conditions of the same treatment body, the densities of the precursors prepared at different reaction temperatures were different, and the density increased with the increase of temperature. However, the bulk density of the ternary material precursor will tend to decrease after the maximum value occurs at a certain temperature.

The reason for this phenomenon is that with the increase of temperature, the supersaturation of the solution generally decreases, and the grain formation rate increases, but the effect is not obvious, and the grain growth rate increases greatly. However, if the temperature is too high, the kinetic energy of the reactants increases too fast, which is not conducive to the formation of stable nuclei.

Preparation technology of ternary cathode material

sol-gel technique

The sol-gel method is an advanced soft chemistry method for the synthesis of ultrafine particles. Widely used in synthetic ceramic powders, coatings, films, fibers and other products. The method is to uniformly mix low viscosity precursors to make a uniform sol, gel formation, drying, and then sintering or calcining after the gelation or gelation process.

Compared with the traditional high-temperature solid-phase reaction method, the sol-gel method has the following advantages:

The raw material components can be uniformly mixed at the atomic level. The product has good chemical uniformity and high purity. As shown in FIG. 2, the heat treatment temperature can be significantly reduced, and the heat treatment time can be significantly shortened. Suitable for thin nanopowder film synthesis; by controlling the sol-gel process parameters, the structure of the material can be precisely tailored. Furthermore, the sol-gel technique requires a simple process and easy control. However, the synthesis cycle is longer and industrial production is more difficult.

co-precipitation technology

Co-precipitation generally involves mixing chemical feedstocks in solution and adding an appropriate precipitant to the solution so that all components in a solution that are homogeneously mixed can co-precipitate in a stoichiometric ratio. Alternatively, the intermediate product is first precipitated in solution, and then the ternary cathode material precursor is calcined for the purpose of decomposing to produce a fine powder product.

Traditional solid-phase synthesis techniques make it difficult to achieve molecular or atomic linear stoichiometric mixing of materials, and co-precipitation is usually used to solve this problem, so as to achieve the purpose of producing high-quality materials while reducing production costs.

According to the latest preparation method of Shanshan lithium energy cathode material, we need to pay attention to:

1. The ternary cathode material must be carried out in a protective atmosphere during the co-precipitation process to prevent the oxidation of divalent metal ions. Nitrogen is relatively economical and applicable!

2. The main purpose of the stirring speed is to make the PH body more uniform and help to form the ball; the speed needs to be adjusted by itself. 100ml is a very small amount, easy to mix well. The rotation speed of the ternary cathode material can be adjusted according to its appearance and the speed of adding ammonia droplets during the preparation process.

3. Lithium power supply is not required for power supply in the pre-drive system. Lithium carbonate is better than lithium hydroxide in the later calcination process. In addition, lithium hydroxide is more corrosive and has higher requirements on the reactor. Often, manufacturers are reluctant to use lithium hydroxide. Because the price of lithium hydroxide is relatively high when making ternary materials.

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