Lithium-ion batteries are composed of positive and negative electrode plates, diaphragm, electrolyte and shell electrode ears and other auxiliary materials. Battery electrode coating can be regarded as a composite material, which is mainly composed of three parts :(1) live matter particles; (2) the component phase of the mixture of conductive agent and binder; (3) Pores need to be filled with electrolyte. The membrane is also porous. On the one hand, it traps electrons, and on the other, the pores need to be filled with electrolyte to allow lithium ions to pass through. Therefore, the electrolyte volume of lithium ion battery mainly needs to fill the pores in the electrode plate and diaphragm, and the pore volume is the electrolyte volume, that is:
Electrolytic liquid volume = positive plate pore volume + negative plate pore volume + diaphragm pore volume
The pore volume of the polar plate and diaphragm is calculated as follows:
Pore volume of polar plate =(length × width × thickness of coating of each polar plate)× number of polar plate × porosity
Pore volume of diaphragm = area of diaphragm × thickness × porosity
Considering that in addition to the cell, there is a space inside the shell that has not been filled (this space can also be calculated according to the battery design), there will also be residual electrolyte, i.e. :
Actual electrolyte volume = all pore volume + residual electrolyte volume
The residual volume of hard shell battery is large, the actual electrolyte consumption is much larger than the theoretical value, the residual space of soft bag battery is general, the amount of residual electrolyte is appropriate, the space utilization rate of cylindrical battery is high, the amount of residual electrolyte is small.
The thickness and porosity of the diaphragm will be provided by the manufacturer, for example, the thickness is 25 microns and the porosity is 49%. The length and width of the diaphragm can be measured according to the cell design or the direct dismantling of the battery, and the diaphragm area can be calculated, so that the amount of electrolyte required by the diaphragm can be calculated.
And the parameters of the pole, according to the actual pole can measure the length, width and thickness of the coating (except foil). The porosity of the polar plate is calculated as follows:
Where, the average coating density and coating compaction density are respectively:
And one of
In practical work experience, the extension rate of copper foil is 0%, and that of aluminum foil is about 1%.
