What is the effect of the ternary material of the lithium battery on the overvoltage of the pole piece?

There are two reasons for the over-voltage of the ternary material pole piece. One is that the battery manufacturer tries to over-press the pole piece in order to pursue the high energy density of the battery; the other is that the process control of the material manufacturer is not strict, so that different batches of ternary materials are made. The compaction density is inconsistent, and the battery manufacturer does not analyze the specific conditions of the material, and the pole piece is over-pressed when the pole piece is prepared according to the conventional process parameters.

Extreme pressure on the pole piece can cause problems such as reduced battery capacity, worsening of the cycle, and increased internal resistance. First, the extreme pressure of the pole piece will cause the spherical ternary material to be broken in a large area. The newly produced surface has many small particles that are separated from the secondary ball. They either fall from the pole piece because they are not in contact with PVDF, or because there is no contact. To the conductive agent, the conductive properties of the pole piece are locally deteriorated.

The generation of the new surface also increases the specific surface area, the contact surface with the electrolyte increases, and the side reaction increases, thereby causing a decrease in battery performance, such as battery swelling, cycle decay, and the like. Over-pressure will also cause deformation of the aluminum foil, the chip is easy to break, and the internal resistance of the battery increases.

In addition, in the over-pressure pole piece, the degree of extrusion between the material particles is too large, resulting in a low porosity of the pole piece, and the amount of electrolyte absorbed by the pole piece is also lowered, and the electrolyte is difficult to penetrate into the inside of the pole piece, and the direct consequence That is, the specific capacity of the material is degraded. A battery with poor liquid retention ability has a large polarization during the cycle, a rapid decay, and an obvious increase in internal resistance.

Whether the pole piece is over-pressed can be judged by observing whether the pole piece is a chip, whether it is broken by an electron microscope, whether the material is broken, and the porosity of the pole piece is estimated. The porosity of the pole piece is an important indicator for judging the amount of liquid absorption and the rate of liquid absorption of the pole piece, which has a direct impact on the performance of the battery.

The pole piece porosity refers to the percentage of the inner-hole limit volume after the roll pressing. Too low a porosity of the pole piece will reduce the amount of electrolyte to the rate of infiltration of the pole piece, affecting the performance of the battery. Too high will reduce the energy density of the battery and waste effective space. Therefore, the compaction density cannot be excessively increased in order to pursue energy density.

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