In the field of lithium batteries, tap density and compaction density are two crucial parameters, which are directly related to the energy density, performance and final application effect of the battery. This article will provide an in-depth analysis of these two concepts from various aspects, such as definition, influencing factors, testing methods, and practical applications.

In the field of lithium batteries, tap density and compaction density are two crucial parameters, which are directly related to the energy density, performance and final application effect of the battery. This article will provide an in-depth analysis of these two concepts from various aspects, such as definition, influencing factors, testing methods, and practical applications.

Ⅰ. Definition analysis

1. Tapping density

Tapping density refers to the mass of the powder in the container measured per unit volume after tapping under specified conditions, and the unit is g/cm³. This parameter is determined by a special tapping density instrument and reflects the maximum density that can be achieved by the substance during vibration or compaction. For lithium batteries, tap density mainly refers to the quality of the active material per unit volume, which directly affects the energy density and endurance of the battery.

2. Compaction density

Compaction density is an important concept in the design process of lithium-ion batteries, and its calculation formula is: compaction density = areal density / (thickness of the pole piece after rolling - current collector thickness), and the unit is also g/cm³. The compaction density is divided into Anode Density and Cathode Density, which have a significant impact on the electrochemical performance and cycle life of the battery.

Ⅱ. What are the effects of tap density and compaction density in the field of battery materials?

Effect of tap density

1. Capacity and energy density:

The increase in tap density can significantly increase the mass of the cathode or anode material in the battery, thereby increasing the total capacity and energy density of the battery at the same volume. This is because the tap density reflects the quality of the active material per unit volume, and a higher tap density means that more active material can be encapsulated in the battery.

2. Cycle life:

The higher tap density helps to reduce the deformation and flaking of the material during charging and discharging, thereby extending the cycle life of the battery. The tightly packed structure can reduce the voids and defects between the materials, reduce the stress changes caused by the expansion and contraction of the materials, and improve the stability of the battery.

3. Security:

The increase in tap density can also improve the safety of the battery. Tightly packed materials can reduce voids and defects inside the battery, reducing the risk of internal short circuits and overheating. In addition, the internal structure of a battery with a high tap density is also more stable when subjected to external shocks, which helps to prevent battery breakage and leakage.

4. Conveying, mixing and flow process:

Tap density also plays an important role in the transport, mixing, and flow of battery materials. Powders with high tapped density may increase pipeline resistance, reduce conveying efficiency, and increase energy consumption and equipment wear when conveying. However, in the mixing process, it is easier to achieve uniform mixing with powders with similar tapping density.

which improves the mixing efficiency.

1. Electrochemical performance:

The compacted density directly affects the pore structure and ion transport path of the electrode material. The moderate compaction density can provide a good pore structure, ensure sufficient wetting of the electrolyte and rapid ion transport, and optimize the kinetic performance of the electrochemical reaction. At the same time, the high compaction density can also improve the conductivity of the electrode, reduce the internal resistance, and enhance the power performance of the battery.

2. Cycle stability:

The compacted density also affects the cyclic stability of the battery. Excessive compaction density may cause structural damage to the material during charging and discharging, which can affect the cycle life of the battery. Therefore, it is necessary to find the optimal compaction density balance point in the battery design process to ensure the performance of the battery while extending its cycle life.

3. Processability:

The compaction density is also closely related to the processing performance of the battery. In coating, tableting, etc., the right compaction density helps to achieve uniform distribution and tight packing of materials, improving production efficiency and product quality. At the same time, the appropriate compaction density can also reduce the waste and loss of the material during processing.

4. Energy density and rate performance:

Compaction density is one of the important factors affecting the energy density and rate performance of batteries. Within the allowable compaction range of the material, increasing the compaction density can increase the active material content per unit volume, thereby increasing the energy density of the battery. At the same time, the appropriate compaction density can also optimize the pore structure of the electrode, improve the ion diffusion rate and the rate performance of the battery.

Ⅲ. Test Methods

1. Test of tap density

The tap density test is usually performed with a tap density tester (e.g. FT-100A). During the test, the graduated cylinder filled with powder vibrates vertically up and down with the motor driving the mechanical vibrating device, and the vibration stops vibrating after the number of vibrations reaches the set value, and the volume of the graduated cylinder is read out, so as to calculate the tapped density.

2. Test of compaction density

The test of compaction density involves the preparation and measurement of electrodes. The slurry is first applied to the current collector through a coating process and then rolled to form electrode sheets. By measuring the areal density of the electrode sheet and the thickness after rolling, combined with the thickness of the current collector, the compaction density can be calculated.

Ⅳ. practical application

1. Application of tap density

As an important indicator to measure the degree of filling of active materials in the battery, the tap density has a direct impact on the energy density and endurance of the battery. A high tap density means that more active material can be accommodated in the same volume, thus increasing the energy density of the battery. Therefore, in the R&D and production process of lithium batteries, the pursuit of high tap density is an important goal.

2. Application of compaction density

Compaction density has a significant impact on the electrochemical performance and cycle life of lithium-ion batteries. The moderate compaction density can provide a good pore structure, ensure sufficient wetting of the electrolyte and rapid ion transport, and optimize the kinetic performance of the electrochemical reaction. At the same time, the high compaction density can also improve the conductivity of the electrode, reduce the internal resistance, and improve the power performance of the battery. However, excessive compaction density can also lead to increased mechanical stress on the material, increasing the risk of cracking and failure of the material. Therefore, it is necessary to find the optimal balance of compaction density during the battery design process.

V. Conclusions

In summary, tap density and compaction density are two crucial parameters in the field of lithium batteries. They are not only related to the energy density and performance of batteries, but also directly affect the application effect and market demand of batteries. Therefore, in the R&D and production process of lithium batteries, it is necessary to attach great importance to the testing and optimization of these two parameters to promote the continuous progress and development of lithium battery technology.