Analysis of the technological transformation of 2025 button cell battery separators

With the increase in the density demand of lithium batteries and the further improvement of the quality of 2025 button cell battery separators, dry film making will gradually be replaced by wet process.

Separators are one of the important components of lithium-ion batteries. They are usually also called battery separators, separator paper, ion separation membranes, etc., and are in the upstream part of the new energy vehicle industry chain. According to different production processes, they are generally divided into dry separators and wet separators. The dry process can be divided into dry single-pull separators and dry double-pull separators, or dry single-layer separators and dry multi-layer separators.

The main raw material of the separator is polyolefin resin. According to different processes, dry separators generally use PP as raw material, and sometimes dry multi-layer separators also use PP and PE multi-layer co-extrusion. Wet separators generally use ultra-high molecular weight polyethylene (UHMWPE) as the separator body, paraffin oil as a pore-forming agent, and dichloromethane as an extractant.

As the main body of the diaphragm, paraffin oil is used as a pore-forming agent, and dichloromethane is used as an extractant.

2025 button cell battery diaphragm is a key inner component in lithium batteries, which can affect key performances such as capacity, cycle performance, and charge and discharge current density of lithium batteries. A diaphragm with excellent performance needs to isolate the positive and negative electrodes to prevent short circuits while allowing the conduction of lithium ions. It also needs to have high-temperature self-closing properties to block current and prevent explosion when overcharged or the temperature is too high. In addition, it must have the characteristics of high strength, fire resistance, good resistance, and non-toxicity.

Generally speaking, according to the main functions of the diaphragm, the diaphragm has high performance requirements in terms of safety and passability:

1. Provide safety protection for the battery. It has good insulation to prevent short circuits caused by contact between the positive and negative electrodes or puncture by burrs, particles, and dendrites. Therefore, the diaphragm needs to have a certain tensile and puncture strength, not easy to tear, and basically maintain dimensional stability under sudden high temperature conditions, and will not melt and shrink, resulting in large-area short circuits and thermal runaway of the battery.

2. Provide lithium batteries with microporous channels to realize charging and discharging functions and rate performance. Therefore, the diaphragm must have a high porosity and the pore characteristics restrict the migration of lithium ions in the battery, which is reflected in the parameter of conductivity.

For power batteries used in new energy vehicles, since the vehicle has high requirements for battery safety and energy density, the diaphragms used in power batteries generally require the following points:

1. Higher safety, including thermal stability, electrochemical stability, puncture resistance and short circuit resistance;

2. Better consistency, including thickness, pore size and pore size distribution;

3. Ideal porosity and pore structure;

4. Stronger liquid absorption capacity and smaller resistance;

5. Higher energy density will require a larger electrochemical stability window, that is, high voltage resistance (0-5V) is also a future trend.

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