Screening method for lithium iron phosphate battery cell

Abstract

The invention discloses a screening method for a lithium iron phosphate battery cell. The screening method comprises the following steps: measuring the open-circuit voltage and Ohmic internal resistance of cells and rejecting cells with open-circuit voltage lower than 2 V or Ohmic internal resistance beyond a range from mu+sigma to mu-sigma; measuring the charge and discharge capacity, median potential and constant-voltage-section charge capacity and time of cells under at least two different rates, and rejecting cells with discharge capacity 60% lower than nominal capacity, constant-voltage-section charge capacity accounting for more than 5% of the total charge capacity or charge and discharge coulombic efficiency of lower than 95%; measuring the charge and discharge direct-current internal resistance of cells at different discharge depth; measuring the positive pole temperature difference, negative pole temperature difference and shell temperature difference of cells from time point when charging begins to time point when charging ends; and classifying the cells by using a cluster analysis method. The method provided by the invention can screen out cells with good security and excellent consistency, which facilitates subsequent assembling of a battery pack and is beneficial for improving the use security and energy utilization rate of the battery pack.

Description

technical field [0001] The invention relates to a screening method for batteries, in particular to a screening method for lithium iron phosphate single batteries. Background technique [0002] With the current increase in the production of hybrid and pure electric vehicles year by year, the production capacity of power lithium batteries, which are the core components, is also expanding rapidly. As the battery is used, its performance gradually decreases, including battery safety performance and electrical performance. When it cannot meet the needs of the vehicle, the battery must be replaced. At present, it is generally believed that when the battery capacity decays to less than 80% of the initial capacity, the battery must be replaced. However, since the replacement battery still has a relatively high energy density, if the replacement battery is directly disassembled and recycled, it will be a waste of energy. The great waste will also cause great pollution to the environ...

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Problems solved by technology

[0004] The technical problem to be solved by the present invention is to overcome that in the prior art, when the consistency screening of the lithium iron phosphate single battery is carried out, due to the lack of measurement parameters of the battery, the current state of the battery cannot be well explained, resulting in the consistency of the battery. In order to solve the defect of deviation during the performance screening, a screening method for lithium iron phosphate single battery is provided

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