A lithium-ion battery self-discharge detection and assembly process

Abstract

The invention relates to a lithium-ion battery self-discharge detection and assembly process. The steps are as follows: form the lithium battery that has been filled with electrolyte solution and activated, the charging cut-off voltage is V1, and record the battery capacity C1 after formation; After formation, the battery is subjected to high-temperature aging, the aging temperature is 40-80°C, and the aging time is 3-7 days; the high-temperature-aged battery is reverse-charged, the charging cut-off voltage is V2, the battery capacity C2 is recorded, and the ratio of C2 / C1 is calculated. Ratio K, select the battery with larger self-discharge through the K value and classify the rest of the batteries, and divide the batteries with K between 0 and R into N grades according to the K value; the graded batteries are exported according to the grade library. The batteries with large self-discharge can be quickly and effectively selected, and the batteries are divided into different levels during the detection, which saves the grading process of the module assembly section.

Description

technical field [0001] The invention relates to the screening and matching of lithium ion batteries, in particular to a process for self-discharge detection and matching of lithium ion batteries. Background technique [0002] Lithium batteries are more and more widely used in mobile phones, power tools and other products. Due to the low voltage and capacity of lithium batteries, multiple lithium batteries must be connected in series when applied to tools to meet the requirements of these tools. This requires high consistency of these series-connected single cells. [0003] In the lithium battery production process, there are currently two ways to screen batteries: 1. The battery is charged to a half-electric state, and then selected after being stored for a period of time, that is, the selection in the range of flat voltage, but the voltage and capacity of the battery in this range do not change. Obviously, it is difficult to pick out, and the storage time required is long...

AI Technical Summary

Problems solved by technology

[0003] In the production process of lithium batteries, there are currently two ways to screen batteries: 1. The battery is charged to a half-electric state, and it is selected after storage for a period of time. Obviously, it is difficult to pick out, and the storage time required is long; 2. After the battery is divided and discharged (discharged to 2.0 or 2.5V), after a period of storage, the rebound voltage is detected and selected. This method has a short storage time. The process time can be shortened, but this method has high requirements for product processing consistency. Due to the inconsistent polarization state during the battery discharge process, some batteries cannot judge self-discharge by rebound voltage.

[0004] Patent 2018100737887 discloses a self-discharge detection method for nickel-cobalt-manganese-manganese-oxide batteries. In this invention, the nickel-cobalt-manganese-oxide lithium batteries are first charged and discharged after pretreatment, and then placed in different temperature environments for a period of time. , test the open circuit voltage V1 and V2, calculate the value of W=V1-V2, and select the battery with large self-discharge by judging the W value. This method eliminates electrode polarization through pretreatment, and minimizes polarization and system instability factors. The impact on the voltage pair, but this method has high requirements for product processing consistency. Due to the inconsistent polarization state during the battery discharge process, some batteries cannot judge self-discharge through the rebound voltage.

[0005] Patent 2017111901166 discloses a battery self-discharge detection method and lithium battery sorting method. The invention discharges the battery to be tested to 0% state of charge to form the first empty battery; Shelving at a temperature for a first preset time period to form a second empty battery to obtain a first voltage; shelving the second empty battery at a second preset temperature for a second preset time period to form a third empty battery, Obtain the second voltage; calculate the self-discharge rate of the battery to be tested according to the first voltage, the second voltage and the second preset time period. The measurement steps are simple and the measurement cost is low, but it needs to be shelved twice, and the selection time is too long. long

[0006] Patent 201110388882X discloses a self-discharge detection method for lithium iron phosphate batteries. In this invention, the battery is fully charged and placed in a uniform magnetic field with a magnetic field strength of 0.01-1.3T. After being placed for 1-15 days, take it out from the strong magnetic field, and test the self-discharge rate of the shelved battery after degaussing. According to the measured self-discharge rate data, the battery with abnormal self-discharge properties can be selected, but the required detection time is too long