CN108169685B - Method for estimating alternating current internal resistance of polymer lithium ion battery - Google Patents

Method for estimating alternating current internal resistance of polymer lithium ion battery Download PDF

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CN108169685B
CN108169685B CN201711373835.1A CN201711373835A CN108169685B CN 108169685 B CN108169685 B CN 108169685B CN 201711373835 A CN201711373835 A CN 201711373835A CN 108169685 B CN108169685 B CN 108169685B
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internal resistance
foil
lithium ion
ion battery
alternating current
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CN108169685A (en
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井婷婷
刘文刚
贾学恒
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Tianjin Juyuan New Energy Technology Co ltd
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Tianjin Lishen Battery JSCL
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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    • G01R31/389—Measuring internal impedance, internal conductance or related variables

Abstract

The invention relates to a method for conjecturing the alternating current internal resistance of a polymer lithium ion battery, wherein the alternating current internal resistance of the polymer lithium ion battery is set as the sum of the internal resistance of a positive electrode foil and a negative electrode foil and the electrochemical internal resistance; establishing an equivalent graph formed by a right-angled triangle A, a parallelogram B and a right-angled triangle C which are connected in sequence for the internal resistance of the foil; the internal resistance of the part A of the right triangle is
Figure DDA0001514248860000011
The right-angled triangles C and A have equal area and equal internal resistance value RC＝RA(ii) a The internal resistance of the parallelogram B part is
Figure DDA0001514248860000012
Internal resistance of the foil is R0＝2*RA+RB(ii) a The electrochemical internal resistance value can be calculated according to Rct constant＝RctS, and correcting the coating quantity M, wherein the electrochemical internal resistance is
Figure DDA0001514248860000013
The calculation formula of the alternating current internal resistance value of the polymer lithium ion battery is represented as R ═ R0 is positive+R0 minus+Rct. Has the advantages that: the calculation method of the invention obtains the internal resistance value close to the measured value, is beneficial to the research of the mechanical performance of the lithium ion battery, and provides more support for the design of the battery.

Description

Method for estimating alternating current internal resistance of polymer lithium ion battery
Technical Field
The invention belongs to the field of electrochemistry, and particularly relates to a method for estimating alternating current internal resistance of a polymer lithium ion battery.
Background
The internal resistance is an important technical index for measuring the performance of the polymer lithium ion battery. The different types of batteries differ in internal resistance. The same type of battery has different internal resistances due to the inconsistency of internal chemical characteristics. The internal resistance of the battery is small and we generally define it in milli-ohm units.
At present, the method for testing the alternating current internal resistance comprises the following steps: the method is characterized in that a constant current of 1000Hz and 50mA is supplied to the battery by utilizing the characteristic that the battery is equivalent to an active resistor, and the resistance value of the battery is accurately measured by carrying out a series of processing such as voltage sampling, rectification filtering and the like. However, in the actual situation, some basic performances of the battery are often required to be evaluated in the early stage of battery manufacturing so as to optimize the design. The method commonly adopted in the engineering application field at present roughly estimates the internal resistance of the battery according to the inverse proportional relation of the internal resistance and the capacity, and has low precision and larger error. It is important to predict the internal resistance of the battery in advance relatively accurately.
Disclosure of Invention
The invention aims to overcome the defects of the technology and provide a method for estimating the alternating internal resistance of a polymer lithium ion battery, aiming at predicting key indexes such as the discharge performance of the battery in advance. The method does not need to test the battery after obtaining the battery entity, and the algorithm is simple, convenient, quick and predictive.
In order to achieve the purpose, the invention adopts the following technical scheme: a method for conjecturing alternating current internal resistance of a polymer lithium ion battery is characterized in that: the method comprises the following specific steps
1) Defining the alternating current internal resistance of the polymer lithium ion battery as the sum of the internal resistance of the positive and negative electrode foils and the electrochemical internal resistance;
2) establishing an equivalent graph of internal resistance of the positive foil and the negative foil: setting a contact point of a lug and a foil as an initial point, dividing an equivalent graph into three parts, wherein the three parts comprise a right-angled triangle A, a parallelogram B and a right-angled triangle C which are sequentially connected to form a rectangular equivalent graph of internal resistance of the positive and negative foils, and the right-angled triangle A and the right-angled triangle C have the same area;
3) integral the internal resistance of right-angled triangle A part according to
Figure BDA0001514248840000025
The internal resistance of the right triangle A part can be expressed as
Figure BDA0001514248840000021
After integration, obtain
Figure BDA0001514248840000022
The internal resistance of the right triangle C part is equal to that of the right triangle A part, RC＝RA；
The internal resistance of the parallelogram B part can be expressed as
Figure BDA0001514248840000023
The internal resistance of the obtained positive and negative electrode foils is expressed as R0＝2*RA+RB；
4) Determination of electrochemical internal resistance, RctIn inverse proportion to S, RctThe product of S is equivalent to a constant, Rct constant＝RctS, further optimizing the coating quantity M to obtain an electrochemical internal resistance expression of
Figure BDA0001514248840000024
In the equivalent diagram, l and w are the length and width of the foil respectively, and d is the diagonal line of the foil;
5) integrating the internal resistances of the steps 3) and 4) to obtain the alternating current internal resistance R ═ R of the polymer lithium ion battery0 is positive+R0 minus+Rct。
Has the advantages that: compared with the prior art, the method has the practical significance that in the initial stage of manufacturing the polymer lithium ion battery, the performance of the battery is evaluated according to the use requirement of the battery at the terminal, and the important parameter internal resistance of the battery is predicted in advance. The method for calculating the alternating internal resistance of the polymer lithium ion battery is simple and efficient, is easy to realize, has small error, is favorable for researching the mechanical performance of the lithium ion battery by obtaining the internal resistance close to an actually measured value, and provides more support for the design of the battery.
Drawings
FIG. 1 is an equivalent schematic diagram of calculating the internal resistance of a foil;
fig. 2 is a graph comparing the calculated internal resistance with the actual value for different models.
Detailed Description
The following detailed description of the preferred embodiments will be made in conjunction with the accompanying drawings.
Referring to the drawings in detail, the embodiment provides a method for estimating the alternating current internal resistance of a polymer lithium ion battery, which comprises the following specific steps:
1) defining the alternating current internal resistance of the polymer lithium ion battery as the sum of the internal resistance of the positive and negative electrode foils and the electrochemical internal resistance;
2) establishing an equivalent graph of internal resistance of the positive foil and the negative foil: setting a contact point of a lug and a foil as an initial point, dividing an equivalent graph into three parts, wherein the three parts comprise a right-angled triangle A, a parallelogram B and a right-angled triangle C which are sequentially connected to form a rectangular equivalent graph of internal resistance of the positive and negative foils, and the right-angled triangle A and the right-angled triangle C have the same area;
3) integral the internal resistance of right-angled triangle A part according to
Figure BDA0001514248840000034
The internal resistance of the right triangle A part can be expressed as
Figure BDA0001514248840000031
After integration, obtain
Figure BDA0001514248840000032
The internal resistance of the right triangle C part is equal to that of the right triangle A part, RC＝RA；
The internal resistance of the parallelogram B part can be expressed as
Figure BDA0001514248840000033
Wherein: theta1-the angle of the foil width w to the diagonal d;
θ2the angle of the foil length l to the diagonal d;
μ -thickness of the foil;
rho-resistivity of the foil;
d-diagonal BD of rectangular foil;
x-is any distance from B as an end point to O, where O is the foot of BD and AE;
e-distance between A and O;
the distance between f-O and E;
the distance between h-B and O.
The internal resistance of the obtained positive and negative electrode foils is expressed as R0＝2*RA+RB；
4) And determining an electrochemical internal resistance value which is equivalent to the internal resistance generated by connecting a plurality of small material particles which are flatly paved on the surface of the foil in parallel. It is characterized in that the larger the area is, the smaller the internal resistance value after parallel connection is, namely RctIs inversely proportional to S, so that R can be expressedctThe product of S is equivalent to a constant, Rct constant＝RctS, further optimizing the coating quantity M to obtain an electrochemical internal resistance expression of
Figure BDA0001514248840000041
In the equivalent diagram, l and w are the length and width of the foil respectively, and d is the diagonal line of the foil;
5) integrating the internal resistance of the step 3) and the step 4) to obtain the alternating current internal resistance R ═ R of the polymer lithium ion battery0 is positive+R0 minus+Rct。
Example 1
1) The basic information of the polymer lithium ion battery cell 1 is as follows: the anode is lithium cobaltate, the cathode is artificial graphite, the volume is 2250mAh, and the external dimensions are 3.7mm in thickness, 66mm in width and 54mm in length respectively. Through preliminary design evaluation, the relevant information of the battery is obtained as shown in table 1:
TABLE 1 cell 1 related design data sheet
Figure BDA0001514248840000042
2) The resistivity of the aluminum foil is found to be
Figure BDA0001514248840000043
The equivalent graph and the estimation method established in the invention are applied to obtain
Figure BDA0001514248840000044
θ1 is just＝arccos(w/d)＝arccos(46.7/757.4)＝1.51；
Figure BDA0001514248840000045
eIs just＝w*sinθ1＝46.7*sin 1.51＝46.61；hIs just＝w*cosθ1＝46.7*cos 1.51＝2.88；fIs just＝h2/e＝2.882/46.61＝0.18。
According to a presumptive formula
Figure BDA0001514248840000046
Figure BDA0001514248840000051
Figure BDA0001514248840000052
By using R of lithium cobaltate system polymer lithium ion battery0Correction is performed to obtain a correction coefficient of 0.25, so R0 is positive＝0.25*(2*RA is just+RB is just)＝11.46Ω。
3) In the same manner as in (2) above, the resistivity of the copper foil was found to be
Figure BDA0001514248840000058
The equivalent graph and the estimation method established in the invention are applied to obtain
Figure BDA0001514248840000053
θ1 is negative＝arccos(w/d)＝arccos(48/760.5)＝1.51；
Figure BDA0001514248840000054
eNegative pole＝w*sinθ1＝48*sin 1.51＝47.9；hNegative pole＝w*cosθ1＝48*cos 1.51＝3.03；fNegative pole＝h2/e＝3.032/47.9＝0.19。
According to a presumption formula to obtain
Figure BDA0001514248840000055
Figure BDA0001514248840000056
Thus R can be obtained0 minus＝0.25*(2*RNegative A+RB negative)＝13.05Ω
4) By collecting and analyzing the internal resistance and related basic data of batteries with different types and different 4.4V systems, lithium cobaltate as the positive electrode and artificial graphite as the negative electrode, R is calculatedct constant. To get closer to the true value, the mean value is taken to get Rct constant＝535824。
For the system and material characteristics, the correction coefficient of the coating amount is selected to be 40mg/cm2. By the formula
Figure BDA0001514248840000057
5) Calculating the alternating current internal resistance of the cell 1 as R ═ R0 is positive+R0 minus+Rct11.46+13.05+16.09 ═ 40.6 Ω, the actual measured internal resistance was 40.2 Ω, with a 1% error.
TABLE 3 comparison table of calculated internal resistance and actually measured internal resistance for different models
Model number capacity/mAh R0 is positive/Ω R0 minus/Ω Rct/Ω Actually measured internal resistance value/omega Calculating internal resistance value/omega Error/%)
Cell 1 2250 11.46 13.05 16.09 40.20 40.60 1.00％
Cell
2 1970 3.61 7.56 17.74 29.00 28.91 -0.31％
Cell
3 1680 9.38 11.21 17.24 41.00 37.84 -7.72％
Cell
4 2470 8.13 10.49 12.89 31.20 31.51 0.99％
Cell
5 2720 6.15 9.02 13.16 27.74 28.32 2.08％
Cell
6 2980 4.47 6.44 9.44 22.00 20.36 -7.47％
Cell
7 3000 5.00 8.32 10.37 25.24 23.69 -6.17％
Cell
8 3040 7.68 10.34 9.50 27.61 27.52 -0.32％
Cell
9 3210 7.10 9.89 10.03 29.00 27.02 -6.82％
Cell
10 3220 7.09 9.86 11.11 27.50 28.06 2.02％
Cell
11 3570 13.71 17.56 9.25 40.10 40.53 1.07％
Cell
12 3855 8.75 11.27 8.93 28.70 28.95 0.87％
Cell
13 3950 14.20 15.79 8.80 36.10 38.79 7.46％
Cell
14 4030 9.54 11.96 7.69 29.30 29.19 -0.37％
Cell
15 4040 9.54 11.96 8.07 29.30 29.57 0.90％
The present invention preferably considers the capacity of polymer lithium ion batteries to be above 1000 mAh. The positive electrode main material of the polymer lithium ion battery comprises, but is not limited to, lithium cobaltate LCO, lithium nickel cobalt manganese NMC, lithium nickel cobalt aluminate NCA, lithium manganese LMO, lithium iron phosphate LFP and the like. The negative electrode main material of the polymer lithium ion battery comprises, but is not limited to, artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, silicon carbon and the like. The diaphragm of the polymer lithium ion battery comprises but is not limited to a common PE diaphragm, a PP diaphragm, a ceramic diaphragm and a ceramic mixed rubber diaphragm. The electrolyte of the polymer lithium ion battery is mixed liquid matched with the main material system.
The above detailed description of the method for estimating the ac internal resistance of the polymer lithium ion battery with reference to the embodiments is illustrative and not restrictive, and several embodiments may be enumerated within the scope of the limitations, so that changes and modifications without departing from the general concept of the present invention shall fall within the protection scope of the present invention.

Claims (3)

1. A method for conjecturing alternating current internal resistance of a polymer lithium ion battery is characterized in that: the method comprises the following specific steps
1) Defining the alternating current internal resistance of the polymer lithium ion battery as the sum of the internal resistance of the positive and negative electrode foils and the electrochemical internal resistance;
2) establishing an equivalent graph of internal resistance of the positive foil and the negative foil: setting a contact point of a lug and a foil as an initial point, dividing an equivalent graph into three parts, wherein the three parts comprise a right-angled triangle A, a parallelogram B and a right-angled triangle C which are sequentially connected to form a rectangular equivalent graph of internal resistance of the positive and negative foils, and the right-angled triangle A and the right-angled triangle C have the same area;
3) integral the internal resistance of right-angled triangle A part according to
Figure FDA0002445843750000011
The internal resistance of the right triangle A part can be expressed as
Figure FDA0002445843750000012
After integration, obtain
Figure FDA0002445843750000013
The internal resistance of the right triangle C part is equal to that of the right triangle A part, RC＝RA；
The internal resistance of the parallelogram B part can be expressed as
Figure FDA0002445843750000014
The internal resistance of the obtained positive and negative electrode foils is expressed as R0＝2*RA+RB；
Wherein: theta1-the angle of the foil width w to the diagonal d;
θ2the angle of the foil length l to the diagonal d;
μ -thickness of the foil;
rho-resistivity of the foil;
d-diagonal BD of rectangular foil;
x-is any distance from B as an end point to O, where O is the foot of BD and AE;
e-distance between A and O;
the distance between f-O and E;
the distance between h-B and O;
s and RctIs in an inversely proportional relationship;
4) determination of electrochemical internal resistance, RctIn inverse proportion to S, RctThe product of S is equivalent to a constant, Rct constant＝RctS, further optimizing the coating quantity M to obtain an electrochemical internal resistance expression of
Figure FDA0002445843750000021
In the equivalent graph, l and w are respectively the length and the width of the foil, d is a diagonal line of the foil, and M is the coating amount;
5) integrating the internal resistances of the steps 3) and 4) to obtain the alternating current internal resistance R ═ R of the polymer lithium ion battery0 is positive+R0 minus+Rct。
2. The method for estimating the alternating current internal resistance of the polymer lithium ion battery according to claim 1, wherein: the correction coefficient of the internal resistance of the right-angled triangle C part and the internal resistance of the right-angled triangle A part is 0.2-0.8.
3. The method for estimating the alternating current internal resistance of the polymer lithium ion battery according to claim 1, wherein: the coating amount correction coefficient of the internal resistance value of the parallelogram B part is 38-42mg/cm2The correction coefficient is in accordance with the range of the coating amount of the material.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN203299350U (en) * 2013-05-08 2013-11-20 山西大学 Battery internal resistance on-line measuring instrument
JP2017059402A (en) * 2015-09-16 2017-03-23 凸版印刷株式会社 Tab sealant heat-resistant insulating structure for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN203299350U (en) * 2013-05-08 2013-11-20 山西大学 Battery internal resistance on-line measuring instrument
JP2017059402A (en) * 2015-09-16 2017-03-23 凸版印刷株式会社 Tab sealant heat-resistant insulating structure for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
再论"测定电池的电动势和内阻"的误差分析;章小萍 等;《课程教学研究》;20160205;第61-63页 *

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