Secondary atomization pore-forming method for lithium ion battery

Abstract

The invention discloses a secondary atomization pore-forming method for a lithium ion battery. The secondary atomization pore-forming method includes the steps: S1 preparing pore-forming agent solution according to normal-temperature saturation concentration serving as a standard; S2 adding a spray tank and a rapid oven to the tail of a coater, and filling the inside of the spray tank with atomization pore-forming agent solution; S3 uniformly coating a current collector base material with prepared positive electrode slurry and negative electrode slurry, and enabling the dried base material topass the spray tank and the oven; S4 winding baked electrode slices into roll materials and rolling the roll materials by a roller press according to normal processes; S5 enabling the rolled electrodeslices to pass a nitrogen atmosphere oven set according to pore-forming agent decomposition or boiling point temperature. High compaction of the electrode slices can be kept, the energy density of the battery can be improved, the uniformity of the battery electrode slices can be also improved, performances such as a rate performance, a cycle performance and a low-temperature performance can be ensured, surface layers of the electrode slices are provided with a large number of pores, the proportion of closed pores and shrink pores can be greatly reduced, and the effective porosity of the electrode slices is increased.

Description

technical field [0001] The invention relates to the technical field of lithium-ion batteries, in particular to a secondary atomization pore-forming method for lithium-ion batteries. Background technique [0002] Lithium-ion batteries have the advantages of high energy density, long service life and high voltage, not only in portable electronic devices, such as mobile phones, mobile power supplies, digital cameras and notebooks, and other consumer markets have developed rapidly, but also in electric vehicles, electric bicycles And emerging markets such as power markets such as power tools and energy storage markets have also been widely used. [0003] In these emerging market areas, especially in automotive power applications, whether it is market demand or national policy guidance, higher requirements are placed on the capacity density of power batteries. Therefore, various enterprises and research institutes increase the energy density by replacing the positive and negativ...

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Problems solved by technology

What CN104157827A patent adopts is to add liquid pore-forming agent in the slurry to form more pores when coating and baking, but this will increase the thickness of the pole piece. In the subsequent rolling process, these holes produced will also The phenomenon of closed cells and shrinkage occurs, and the ratio of shrinkage and closed cells is larger than that of normal pole pieces, because what the pole piece lacks is not the overall pores, but the pores on the surface, so this pore-making method actually obtains more closed cells. , the difference between inner and outer pores is larger

The CN103515607A patent mentions that by adding a solid pore-forming agent and configuring it into a slurry, after the pole piece is rolled, the pore-forming agent is decomposed at a high temperature to produce more pores. This method can improve the pole piece porosity to a certain extent. , but there are also positions where the inner layer does not need to make holes, and more holes are created, resulting in an increase in the thickness of the pole piece, reducing the energy density of the battery, and failing to achieve the desired result of the density.

The CN106848148A patent proposes that the pore-forming agent is sprayed when the pole piece is not dry after coating, and is baked in the oven of the coating machine, so that the pore-forming agent is dispersed to the surface layer of the pole piece slurry, and after drying, a pore-forming agent is formed on the surface layer of the pole piece. There are many holes, and they are heated and decomposed to form holes after rolling. However, there is also an obvious problem with this solution, that is, although the pore-forming agent is inside the surface pole piece, the hole-making will also cause the thickness of the pole piece to rebound, although for closed holes It is good to re-open the holes, but it is not helpful for the compression of small holes. Others generated will be directly discharged through these small holes. Some of the generated pores still need to be communicated with the outside world through the reduced holes, which has a certain effect on reducing surface polarization. effect, but it still cannot solve the problem of increasing the really useful porosity while keeping the pole piece under high compaction

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