Consistency screening method for high-rate lithium titanate unit cells

A single battery and screening method technology, applied in sorting and other directions, can solve the problems of unsuitable industrialization promotion and application, low screening efficiency, cumbersome calculation process, etc., to simplify the battery internal resistance test method, save equipment and electricity costs, The effect of an efficient screening process

Inactive Publication Date: 2020-02-21
RISESUN MENGGULI NEW ENERGY SCIENCE & TECHNOLOGY CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Battery consistency screening needs to comprehensively consider multiple parameters such as the discharge capacity, platform voltage, open circuit voltage, battery internal resistance, and self-discharge of the single battery. However, there are few parameter settings in the existing screening methods, and the screening results are accurate and precise. low
In addition, for the testing of specific parameters such as self-discharge and polarization internal resistance, the existing methods (for example, the commonly used HPPC method for measuring polarization internal resistance) take a long time, consume a lot of energy, are more complicated to operate, and require a large current Pulse charging and discharging equipment, so it is not suitable for industrial application
For example, the Chinese patent application with application number 201710818877.5 discharges the battery to 1.3-1.8V (about 46-64% SOC ) within the range of high temperature, and the battery with excessive self-discharge is screened out by testing the open circuit voltage difference before and after the storage, but the screening time used by the application is still relatively long in the selected voltage range, about 1-2 days, and the application The method does not take into account the difference in the polarization int

Method used

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  • Consistency screening method for high-rate lithium titanate unit cells
  • Consistency screening method for high-rate lithium titanate unit cells
  • Consistency screening method for high-rate lithium titanate unit cells

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0026] Take a battery with a rated capacity of 25Ah, a positive electrode made of a ternary material, and a negative electrode made of lithium titanate as an example. In this embodiment, 11 batteries are selected to form a 24V 11-string battery pack.

[0027] Step 1: Put the pre-charged battery on the test cabinet, charge it to 2.8V with 1C constant current and constant voltage, cut off the constant voltage charging current to 0.05C A, charge and discharge 3 times, record the discharge capacity D and constant voltage charging time CV -T; Charge the battery to 10% SOC (CC-CV charge to 2.365V, constant voltage cut-off current 0.05CA), measure the open circuit voltage OCV1 after 1 hour at room temperature;

[0028] Step 2: Put the above battery in a constant temperature box at 55°C for 10 hours, take out the battery and cool it to room temperature, measure the open circuit voltage OCV2 of the battery, the static internal resistance Rh at a frequency of 1 kHz, and the single point...

Embodiment 2

[0031] Also taking a 25Ah ternary / lithium titanate battery as an example, 20 batteries are randomly tested in this embodiment.

[0032] The test process is the same as that of Example 1, except that the charging SOC in the first step in Example 1 is adjusted to 20% soc, and the battery is placed in a 55° C. incubator for 12 hours.

[0033] Table 3 is the detailed screening parameters of all 20 batteries in Example 2. Among them, although the battery capacity, constant voltage charging time, high-frequency AC internal resistance, OCV1 and OCV2 of 8#, 13# and 17# have little difference with other batteries, the low-frequency AC internal resistance exceeds the screening of 0-25% range, so these three batteries are judged to be unqualified batteries. Among the remaining qualified batteries, 11 batteries (respectively 1~3#, 9~12#, 14#, 18~20#) were randomly selected to form 11 strings of battery packs. Discharge performance under current, the results are shown in image 3 .

[...

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Abstract

The invention relates to a consistency screening method for high-rate lithium titanate unit cells. The screened lithium titanate cells have high consistency under a high-current discharge working condition. The method comprises the following steps of adjusting the cells to a specific charge state and storing the cells at elevated temperature for a short time so as to quickly screen out the cells with large self-discharge; and then carrying out a specific single-point high-frequency and low-frequency alternating-current impedance test on the cells stored at the elevated temperature so as to directly reflect the ohmic internal resistance and the polarization internal resistance of the cells. According to the method, self-discharge and dynamic internal resistance of the cells are rapidly andaccurately evaluated while the parameters of conventional discharge capacity, open-circuit voltage, constant voltage time, static internal resistance and the like are taken into consideration, and thescreening result is more comprehensive, accurate and effective; and according to the scheme, the consistency screening of the cells can be completed within one day, the screening cycle of the cells can be greatly shortened, the operation is simple and convenient, the energy consumption is low, and the method is suitable for large-scale batch application of an automatic production line.

Description

technical field [0001] The invention belongs to the technical field of battery detection, and relates to a consistency screening method for a lithium titanate single battery with a large rate. Background technique [0002] Lithium titanate battery's unique high safety, excellent high-current charge and discharge performance, long life and low temperature characteristics have become the preferred choice for fast-charge lithium-ion power batteries, rail transit vehicle lithium batteries and start-stop system power supplies. In practical applications, lithium titanate batteries need to be used in the form of series-parallel battery packs, and the charging and discharging conditions can reach about 10C. This series-parallel mode has extremely strict requirements on the consistency between single batteries. Therefore, the lithium titanate battery with high consistency screened out quickly, efficiently and accurately will help to improve the service life, safety and energy efficie...

Claims

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Application Information

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IPC IPC(8): B07C5/344
CPCB07C5/344
Inventor 高雅陈啸天钱丽吴可
Owner RISESUN MENGGULI NEW ENERGY SCIENCE & TECHNOLOGY CO LTD
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