CN114626002A - Python-based quick judgment method for micro cold welding and micro fracture of inner tab of laminated lithium ion battery - Google Patents
Python-based quick judgment method for micro cold welding and micro fracture of inner tab of laminated lithium ion battery Download PDFInfo
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- CN114626002A CN114626002A CN202110856879.XA CN202110856879A CN114626002A CN 114626002 A CN114626002 A CN 114626002A CN 202110856879 A CN202110856879 A CN 202110856879A CN 114626002 A CN114626002 A CN 114626002A
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Abstract
The invention discloses a Python-based quick judgment method for micro-insufficient welding and micro-fracture of an inner tab of a laminated lithium ion battery, which solves a multivariate linear equation of a charging or discharging curve by Python, establishes a regular equation set of a least square method and solves to obtain a curve equation; comparing a battery charging or discharging curve with a curve equation, setting an offset judgment value, calculating an offset value through a matrix, and sequentially calculating, wherein the value larger than the offset is used for judging whether micro insufficient soldering and micro fracture of the tab inside the laminated battery are screened out; the laminated lithium ion battery is easy to identify and judge the micro insufficient welding and micro fracture of the inner tab, and is quick and not easy to omit.
Description
Technical Field
The invention relates to the technical field of energy, in particular to a Python-based quick judgment method for micro cold welding and micro fracture of an inner tab of a laminated lithium ion battery.
Background
The laminated lithium ion battery is mainly characterized in that positive and negative pole pieces are respectively cut into single pieces, diaphragms are overlapped in a Z shape, the positive and negative pole pieces are sequentially and alternately stacked, the middle of each pole piece is separated by the diaphragm, each positive and negative pole piece is respectively provided with a pole lug, and the pole lugs on the positive and negative pole pieces are respectively stacked together and welded together through ultrasonic waves. Compared with a winding type lithium ion battery, the laminated lithium ion battery has the advantages of higher energy density, low internal resistance, long cycle life, good rate capability, small battery deformation and expansion and the like under the same chemical system, and is widely applied to the fields of mobile communication, energy storage, power supply and the like. However, the phenomena of tab insufficient welding, missing welding, tab or single tab fracture, single micro fracture and the like easily occur in the manufacturing processes such as lamination welding, tab bending assembly, battery assembly and the like and internal stress change and the like under working conditions, so that the internal resistance of the battery is increased, the capacity is attenuated, and even the safety performance is influenced.
The laminated battery tab rosin joint, missing welding, tab or single tab fracture, single micro fracture and the like are generally identified by an alternating current internal resistance method, a direct current internal resistance method, a capacity method, a charging and discharging curve abnormal point observation method and the like, but only obvious abnormality can be identified. And the alternating current internal resistance, the direct current internal resistance, the capacity, the charging and discharging curve and the like of the laminated lithium ion battery with the internal tab slightly cold-welded and slightly broken have no obvious abnormality, and are difficult to identify, judge and omit easily.
Disclosure of Invention
Therefore, the invention mainly solves the problems of difficult identification, judgment and easy omission of micro insufficient welding and micro fracture of the inner tab of the conventional laminated lithium ion battery.
In order to achieve the above object, the embodiments of the present invention provide the following technical solutions:
a Python-based quick judgment method for micro cold welding and micro fracture of an inner tab of a laminated lithium ion battery is characterized by comprising the following steps:
s1, charging or discharging the laminated lithium ion battery, and recording charging or discharging data to obtain a charging or discharging curve;
s2, establishing a charging or discharging curve equation;
s3, solving the unknown quantity in the equation by using a python function, and calculating a fitting curve;
s4, comparing the charging or discharging curve in the S1 with the fitting curve, and screening out deviated data points;
and S5, judging whether the laminated lithium ion battery has micro insufficient solder and micro fracture of the tab according to the deviation data points.
Preferably, the discharge process in S1 is constant current discharge, and the recorded data is voltage-discharge capacity. The data can be conveniently read.
Preferably, in the S2, the independent variable of the curve equation is discharge capacity, the dependent variable is voltage, and the formula is as follows:
y＝a0+a1*x+a2*x^2+…am*x^m
. The fitting effect is good.
Preferably, the solving of the unknowns in S3 includes changing a curve equation into a regular equation system based on a least square method, where the formula is:
Preferably, the procedure in S3 includes generating a coefficient matrix a, calculating the coefficient of each equation, calculating each coefficient of the current equation, calculating the right-hand vector b of the equation set, and generating plotted points of the fitted curve. And the calculation is convenient.
Preferably, the python function in S3 includes a linear-solve (a, b) function in the numpy packet, and the linear-solve (a, b) function solves a linear equation system in a matrix manner, where the parameter a is a coefficient matrix and the parameter b is a value of the ordinate. The calculation is convenient, and the accuracy is high.
Preferably, when the program is written in S4, the set value offset is equal to or less than 2 mV. The values are closer.
Preferably, the programming in S4 includes calculating a matrix, sequentially calculating offset values of the deviations, and subtracting the fitted curve voltage from the discharge voltage to obtain the deviation values, where the deviation values are greater than the set values. And the calculation is simple.
The embodiment of the invention has the following advantages:
based on the simple structure, the simplicity, the readability and the expandability of Python language compared with C + + or Java codes, various curves can be fitted, and the multivariate linear equation of various curves can be solved; in addition, the micro-insufficient welding and micro-fracture of the laminated battery inner electrode lug can be rapidly identified through compiling program batch processing data.
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In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
The structures, ratios, sizes, and the like shown in the specification are only used for matching with the contents disclosed in the specification, so that those skilled in the art can understand and read the invention, and do not limit the limit conditions of the invention, so that the invention has no technical essence, and any structural modification, ratio relationship change or size adjustment should still fall within the scope of the technical contents disclosed in the invention without affecting the efficacy and the achievable purpose of the invention.
Fig. 1 is a graph comparing an actual voltage-capacity curve with a fitted curve according to a first embodiment of the present invention.
FIG. 2 is a graph comparing an actual voltage-capacity curve with a fitted curve according to a second embodiment of the present invention.
Detailed Description
While embodiments of the present invention will be described with reference to particular embodiments, those skilled in the art will readily appreciate that the present invention has additional advantages and benefits that may be realized from the teachings herein, and that the embodiments described are only a few, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, a first embodiment of the present invention provides a Python-based method for quickly determining micro cold solder joint and micro fracture of an inner tab of a laminated lithium ion battery, including the following steps:
(1) discharging a 45Ah laminated lithium ion battery of an NCM/C system with a battery state of 100% SOC to 2.7V at a constant current of 1C, and recording voltage-capacity data during discharging;
(2) establishing a charge or discharge curve equation, wherein the equation of the curve is as follows:
y＝a0+a1*x+a2*x^2+…am*x^m
solving a multivariate linear equation y and unknowns a0, a1 and a2.. am thereof by using a linear.
(3) And (3) programming a program based on Python language, setting the voltage value offset to be less than or equal to 2mV, comparing the discharge curve in the step (1) with a multivariate linear equation, and automatically screening out deviated data points through a matrix calculation and sequence calculation running program.
In another embodiment, the method comprises the following steps:
(1) discharging a 45Ah laminated lithium ion battery of an NCM/C system with a battery state of 100% SOC to 2.7V at a constant current of 1C, and recording voltage-capacity data during discharging;
(2) establishing a charge or discharge curve equation (same as the first embodiment);
(3) based on the program written in Python language in the embodiment, the voltage value offset is set to be less than or equal to 2mV, and the program in the first embodiment is operated by using the discharge curve in the step (1) and the linear equation with multiple elements.
The program operation result is the data deviation point without abnormal value in the second embodiment, such as the data deviation point without abnormal voltage in the discharge curve and fitting in the second embodiment shown in fig. 2.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (7)
1. A Python-based quick judgment method for micro cold welding and micro fracture of an inner tab of a laminated lithium ion battery is characterized by comprising the following steps:
s1, charging or discharging the laminated lithium ion battery, and recording charging or discharging data to obtain a charging or discharging curve;
s2, establishing a charging or discharging curve equation;
s3, solving the unknown quantity in the equation by using a python function, and calculating a fitting curve;
s4, comparing the charging or discharging curve in the S1 with the fitting curve, and screening out deviated data points;
and S5, judging whether the laminated lithium ion battery has micro insufficient solder and micro fracture of the tab according to the deviation data points.
2. The Python-based method for rapidly judging micro cold welding and micro fracture of inner tab of a laminated lithium ion battery according to claim 1, wherein the discharge process in S1 is constant current discharge, and the recorded data is voltage-discharge capacity.
3. The Python-based method for rapidly judging micro-insufficient-soldering and micro-fracture of an inner tab of a laminated lithium ion battery according to claim 1, wherein the curve equation in S2 is as follows:
y＝a0+a1*x+a2*x^2+…am*x^m
in the formula, the independent variable is the discharge capacity, and the dependent variable is the voltage.
4. The method of claim 1, wherein the solving for the unknowns in S3 includes changing a curve equation into a least-squares-based regular equation system, wherein the equation is as follows:
5. the Python-based rapid judgment method for micro-cold-joint and micro-fracture of inner tab of laminated lithium ion battery according to claim 1, wherein the Python function in S3 comprises a linear.
6. The Python-based method for rapidly judging the micro cold welding and micro fracture of the inner tab of the laminated lithium ion battery according to claim 1 or 2, wherein the set value offset is less than or equal to 2 mV.
7. The Python-based method for rapidly determining micro cold joint and micro fracture of inner tab of laminated lithium ion battery according to claim 1, wherein the programming in S4 comprises matrix calculation, sequential calculation of offset values, and subtraction of fitted curve voltage by discharge voltage to obtain offset values, and points where the offset values are greater than a set value are offset data points.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112363069A (en) * | 2020-09-18 | 2021-02-12 | 万向一二三股份公司 | Lithium ion battery tab fracture detection method |
| CN115808635A (en) * | 2023-02-07 | 2023-03-17 | 四川新能源汽车创新中心有限公司 | Power battery and detection method for tearing defects of pole lugs of power battery pack |
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2021
- 2021-07-28 CN CN202110856879.XA patent/CN114626002A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112363069A (en) * | 2020-09-18 | 2021-02-12 | 万向一二三股份公司 | Lithium ion battery tab fracture detection method |
| CN112363069B (en) * | 2020-09-18 | 2023-07-07 | 万向一二三股份公司 | Method for detecting breakage of tab of lithium ion battery |
| CN115808635A (en) * | 2023-02-07 | 2023-03-17 | 四川新能源汽车创新中心有限公司 | Power battery and detection method for tearing defects of pole lugs of power battery pack |
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