阅读说明：本技术 定量确定电芯平整度的方法 (Method for quantitatively determining flatness of battery core ) 是由 暴旭 任正鑫 郑彦俊 马华 刘峰 王驰伟 于 2020-12-14 设计创作，主要内容包括：本发明提供了定量确定电芯平整度的方法,属于锂离子电池的电芯平整度测量技术领域,包括以下步骤,S1、将待测量的电芯放在测量工具的测试台上,启动测量工具；S2、测量工具的测量端与电芯接触并挤压电芯,最小压力为20Kgf,在最小压力下得到第一个电芯厚度值f(1),逐渐增大测量工具的压力进行多次测量,单次压力增大30Kgf,根据公式K(n)＝1-f(n)/f(n-1)求得厚度变化率K(n),根据公式G(n)＝K(n)-K(n-1)求得厚度变化率的变化量G(n)；S3、将第一次测得的电芯厚度值f(1)减去厚度变化率的变化量G(n)第一次为负值时测量出的电芯厚度值得到平整度数值。本发明操作简单,测量结果准确,在满足低成本的测量条件下实现定量确定电芯的平整度,能够更好的帮助工程技术人员研究软包电池的装配特性。(The invention provides a method for quantitatively determining the flatness of a battery cell, which belongs to the technical field of measuring the flatness of the battery cell of a lithium ion battery, and comprises the following steps of S1, placing the battery cell to be measured on a test board of a measuring tool, and starting the measuring tool; s2, enabling a measuring end of a measuring tool to be in contact with the battery cell and press the battery cell, enabling the minimum pressure to be 20Kgf, obtaining a first battery cell thickness value f (1) under the minimum pressure, gradually increasing the pressure of the measuring tool to measure for multiple times, increasing the pressure by 30Kgf for a single time, obtaining a thickness change rate K (n) according to a formula K (n) ═ 1-f (n) (/ n) (1), and obtaining a change amount G (n) of the thickness change rate according to a formula G (n) ═ K (n) — K (n) (1); s3, subtracting the variation G (n) of the thickness change rate from the first measured battery cell thickness value f (1) to obtain a flatness value when the first time is a negative value. The method is simple to operate, has accurate measurement results, realizes quantitative determination of the flatness of the battery cell under the condition of meeting the measurement condition of low cost, and can better help engineering technicians to research the assembly characteristics of the soft package battery.)

1. The method for quantitatively determining the flatness of the battery core is characterized by comprising the following steps: comprises the following steps of (a) carrying out,

s1, placing the battery cell to be measured on a test board of the measuring tool, and starting the measuring tool;

s2, enabling a measuring end of a measuring tool to be in contact with the battery cell and press the battery cell, enabling the minimum pressure to be 20Kgf, obtaining a first battery cell thickness value f (1) under the minimum pressure, gradually increasing the pressure of the measuring tool to measure for multiple times, increasing the pressure for a single time by 30Kgf, enabling the battery cell thickness value measured for the nth time to be f (n), obtaining a thickness change rate K (n) according to a formula K (n) ═ 1-f (n)/f (n-1), and obtaining a change quantity G (n) of the thickness change rate according to a formula G (n) ═ K (n) — K (n-1);

s3, subtracting the variation G (n) of the thickness change rate from the first measured battery cell thickness value f (1) to obtain a flatness value when the first time is a negative value.

2. The method of quantitatively determining cell flatness of claim 1, wherein: the number of measurements n is not less than 5.

3. The method of quantitatively determining cell flatness of claim 1, wherein: confirm through the test that can satisfy the minimum liquid volume of annotating of electric core normal use, the electric core when making minimum liquid volume of annotating, then the single increases 5g and annotates the liquid volume and make a plurality of electric cores respectively, puts a plurality of electric cores of making respectively on measuring tool and measures, obtains a plurality of roughness numerical values.

4. The method of quantitatively determining cell flatness of claim 1, wherein: confirm through the test that can satisfy the minimum of electric core normal use and dash the hole degree of depth, produce the electric core when the minimum is dashed the hole degree of depth, then the single increases 0.5mm and dashes the hole degree of depth and make a plurality of electric cores respectively, puts a plurality of electric cores of making respectively on measuring tool and measures, obtains a plurality of roughness numerical values.

5. The method of quantitatively determining cell flatness of claim 1, wherein: the measurement tool measures the cell thickness value f (n), and simultaneously measures the pressure value f (n) and the pressure value p (n).

6. The method of quantitatively determining cell flatness of claim 1, wherein: the measuring tool is a flat panel thickness gauge model PPG-1015 or PPG 500.

7. The method of quantitatively determining cell flatness of claim 1, wherein: the measuring area of the measuring tool is larger than the area of the battery core, the measuring tool controls the equipment mechanism through a servo control or an air cylinder, the precision value of the thickness measured by the measuring tool is smaller than 0.001mm, and the measuring range of the pressure intensity measured by the measuring tool is between 0 and 1.0 Mpa.

Technical Field

The invention belongs to the technical field of cell flatness measurement of lithium ion batteries, and relates to a method for quantitatively determining cell flatness.

Background

In the prior art, the method for measuring the flatness of the soft package battery cell mainly adopts a visual observation method or a laser scanning method. The visual observation method is commonly called visual observation method, namely the surface state of the battery cell is observed by utilizing visible light, and the visual observation method is a rough and non-quantitative observation method, and the difference of the flatness of the battery cell cannot be quantitatively given although the visual observation is rapid; the laser scanning method is to scan the whole contour of the battery cell by using optical equipment to manufacture a 3D model, and then calculate the difference value between the whole thickness value and the thickness value of the cross section, although quantitative measurement can be carried out, the equipment is expensive and has limited application.

Disclosure of Invention

The invention aims to solve the problem of quantitatively determining the flatness of the battery core, belongs to the technical field of measuring the flatness of the battery core of a lithium ion battery, is simple to operate, has accurate measuring results, realizes quantitatively determining the flatness of the battery core under the condition of meeting the measuring conditions of low cost, and can better help engineering technicians to research the assembly characteristics of the soft package battery.

In order to solve the technical problems, the invention adopts the technical scheme that: a method for quantitatively determining the flatness of a battery core belongs to the technical field of measuring the flatness of the battery core of a lithium ion battery and comprises the following steps,

s1, placing the battery cell to be measured on a test board of the measuring tool, and starting the measuring tool;

s2, enabling a measuring end of a measuring tool to be in contact with the battery cell and press the battery cell, enabling the minimum pressure to be 20Kgf, obtaining a first battery cell thickness value f (1) under the minimum pressure, gradually increasing the pressure of the measuring tool to measure for multiple times, increasing the pressure for a single time by 30Kgf, enabling the battery cell thickness value measured for the nth time to be f (n), obtaining a thickness change rate K (n) according to a formula K (n) ═ 1-f (n)/f (n-1), and obtaining a change quantity G (n) of the thickness change rate according to a formula G (n) ═ K (n) — K (n-1);

s3, subtracting the variation G (n) of the thickness change rate from the first measured battery cell thickness value f (1) to obtain a flatness value when the first time is a negative value.

Further, the number of measurements n is not less than 5.

Further, confirm through the test that can satisfy the minimum notes liquid volume of electric core normal use, electric core when making minimum notes liquid volume, then the single increases 5g and annotates the liquid volume and make a plurality of electric cores respectively, puts a plurality of electric cores of making respectively on measuring tool and measures, obtains a plurality of roughness numerical values.

Further, confirm through the test that can satisfy electric core normal use's minimum dashes the hole degree of depth, produce the electric core when minimum dashing the hole degree of depth, then the single increases 0.5mm and dashes the hole degree of depth and make a plurality of electric cores respectively, puts a plurality of electric cores of making respectively on measuring tool and measures, obtains a plurality of roughness numerical values.

Further, the measurement tool measures the cell thickness value f (n), and simultaneously measures the pressure value f (n) and the pressure value p (n).

Further, the measuring tool is a flat panel thickness gauge of type PPG-1015 or PPG 500.

Furthermore, the measuring area of the measuring tool is larger than the area of the battery core, the measuring tool controls the equipment mechanism through a servo control or an air cylinder, the precision value of the thickness measured by the measuring tool is smaller than 0.001mm, and the measuring range of the pressure intensity measured by the measuring tool is between 0 and 1.0 Mpa.

Compared with the prior art, the invention has the advantages and positive effects as follows:

1. the method is simple to operate, has accurate measurement results, realizes quantitative determination of the flatness of the battery cell under the condition of meeting the measurement condition of low cost, and can better help engineering technicians to research the assembly characteristics of the soft package battery.

2. The invention determines the minimum liquid injection amount which can meet the normal use of the battery cell through testing, the battery cell with the minimum liquid injection amount is manufactured, then 5g of liquid injection amount is increased once and a plurality of battery cells are manufactured respectively, the manufactured battery cells are placed on a measuring tool respectively for measurement to obtain a plurality of flatness values, the contrast analysis of a plurality of groups of measured data leads the result to be more convincing, the influence degree of the liquid injection amount on the flatness of the battery cell can be analyzed, on the premise that the battery cell can be normally used, the smaller battery cell flatness indicates that the volume energy density of the battery cell is higher, and the minimum flatness value corresponds to the optimal liquid injection amount.

3. The invention determines the minimum pit punching depth which can meet the normal use of the battery cell through testing, the battery cell with the minimum pit punching depth is manufactured, then the pit punching depth of 0.5mm is increased once and a plurality of battery cells are manufactured respectively, the manufactured battery cells are placed on a measuring tool respectively for measurement, a plurality of flatness values are obtained, the result is more convincing through the contrast analysis of a plurality of groups of measurement data, the influence degree of the pit punching depth on the flatness of the battery cell can be analyzed, the pit punching depth is smaller, the flatness value of the battery cell is favorably reduced, and the energy density of the battery cell is indirectly improved.

4. The measuring tool of the invention can simultaneously measure the pressure value F (n) and the pressure value P (n) while measuring the thickness value f (n) of the battery cell, the pressure is used as an independent variable, the measured thickness is used as an output variable, the change rule of the change curve of the output variable is detected to determine the flatness of the battery cell, the thickness change curve under different pressures is measured, the change speed is observed, the flatness can be represented, and the measured data is precise and convincing.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic diagram of a cell of the method of quantitatively determining cell flatness of the present invention;

fig. 2 is a schematic diagram of pit punching in the method for quantitatively determining cell flatness according to the present invention;

FIG. 3 is a graph of cell thickness curves at different pressures for different charge volumes for the method of quantitatively determining cell flatness of the present invention;

fig. 4 is a graph of cell thickness curves at different pressures for different punch depths for the method of quantitatively determining cell flatness of the present invention;

FIG. 5 shows measured data of the method for quantitatively determining cell flatness according to the present invention at a pour amount of 140g and a pit depth of 5.5 mm;

FIG. 6 shows measured data of the method for quantitatively determining cell flatness according to the present invention at a liquid injection amount of 145g and a pit depth of 5.5 mm;

FIG. 7 shows measured data of the method for quantitatively determining the flatness of a battery cell according to the invention, wherein the measured data comprise a liquid injection amount of 150g and a pit depth of 5.5 mm;

FIG. 8 shows measured data of the method for quantitatively determining cell flatness according to the present invention at a liquid injection amount of 140g and a pit depth of 6 mm;

FIG. 9 shows measured data of the method for quantitatively determining cell flatness according to the present invention at a pour amount of 140g and a pit depth of 6.5 mm.

Reference numerals:

1. and (5) punching pits.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

The following detailed description of specific embodiments of the invention refers to the accompanying drawings.

As shown in fig. 1 to 9, the present invention is a method for quantitatively determining cell flatness, which belongs to the technical field of cell flatness measurement of lithium ion batteries, and comprises the following steps,

s1, placing the battery cell to be measured on a test board of the measuring tool, and starting the measuring tool; s2, enabling a measuring end of a measuring tool to be in contact with the battery cell and press the battery cell, enabling the minimum pressure to be 20Kgf, obtaining a first battery cell thickness value f (1) under the minimum pressure, gradually increasing the pressure of the measuring tool to measure for multiple times, increasing the pressure for a single time by 30Kgf, enabling the battery cell thickness value measured for the nth time to be f (n), obtaining a thickness change rate K (n) according to a formula K (n) ═ 1-f (n)/f (n-1), and obtaining a change quantity G (n) of the thickness change rate according to a formula G (n) ═ K (n) — K (n-1); s3, when the variation G (n) of the thickness change rate is a negative value for the first time, the thickness is considered to be a sign that the thickness tends to be stable, then the cell is pressed by using a larger pressure, the cell is compressed and changed and can not reflect the real cell thickness, the cell thickness value measured when the variation G (n) of the thickness change rate is subtracted from the cell thickness value f (1) measured for the first time to obtain a flatness value, the flatness reflects the uneven degree of the surface of the soft-package cell, the smaller cell flatness value means a smaller thickness, the volume energy density of the cell is higher, and the volume energy density is the ratio of the cell energy to the cell volume.

Preferably, the number of measurements n is not less than 5.

Preferably, confirm through the test and to satisfy electric core normal use's minimum notes liquid volume, electric core when making minimum notes liquid volume, then the single increases 5g and annotates the liquid volume and make a plurality of electric cores respectively, put a plurality of electric cores of making respectively on measuring tool and measure, obtain a plurality of roughness numerical values, multiunit measured data contrastive analysis makes the result more convincing, can analyze out the influence degree of annotating the liquid volume to electric core roughness, under the prerequisite that satisfies electric core and can normally use, the volume energy density of less electric core roughness explanation electric core is higher, minimum roughness numerical value corresponds optimum notes liquid volume.

Preferably, confirm through the test that can satisfy the minimum of electric core normal use and dash the hole degree of depth, produce the electric core when the minimum is dashed the hole degree of depth, then the single increases 0.5mm and dashes the hole degree of depth and make a plurality of electric cores respectively, put a plurality of electric cores of making respectively on measuring tool and measure, obtain a plurality of roughness numerical values, multiunit measured data contrastive analysis makes the result more convincing, can analyze out and dash the influence degree of hole degree of depth to electric core roughness, the less hole degree of depth that dashes, be favorable to reducing the roughness numerical value of electric core, indirect improvement the energy density of electric core.

Preferably, the measuring tool measures the cell thickness value f (n), simultaneously measures a pressure value f (n) and a pressure value p (n), the pressure is used as an independent variable, the measured thickness is used as an output variable, a change rule of a change curve of the output variable is detected to determine the flatness of the cell, the method can be used as the principle of the method for evaluating the flatness of the battery cell because the unevenness of the battery cell is caused by that the shell of the soft package battery cell is made of soft material and is not made of high-hardness material, therefore, the problem of unevenness can occur, when a pressure is applied to the soft material, the soft material is deformed, the deformation amount is limited, the limit is that when the soft material is flattened, therefore, the thickness change curve under different pressures is measured, the change speed is observed, the flatness can be characterized, and the measured data is rigorous and convincing.

Preferably, the measurement tool is a flat panel thickness gauge of the type PPG-1015 or PPG 500.

Preferably, the measurement area of the measurement tool is larger than the area of the battery core, the measurement requirement of the thickness can be met, the measurement tool controls the equipment mechanism through a servo control or an air cylinder, the precision value of the measurement tool for measuring the thickness is smaller than 0.001mm, the range of the measurement tool for measuring the pressure intensity is between 0 and 1.0Mpa, and the accuracy of experimental data is ensured.

In the actual working process, 29 layers of positive pole pieces with the thickness of 130um, 30 layers of negative pole pieces with the thickness of 190um, a barrier film with the thickness of 16um, electrolyte, a positive pole lug, a negative pole lug and an aluminum plastic film with the pit depth of 5.5mm are manufactured into a finished product battery cell through the procedures of lamination, assembly, formation and the like, the finished product battery cell has three parts in total, 140g of electrolyte, 145g of electrolyte and 150g of electrolyte are respectively injected into the finished product battery cell, the battery cell state is adjusted to 50% SOC, the three finished product battery cells are respectively measured by using a measuring tool to obtain data in figures 5, 6 and 7, then curves in figure 3 are drawn, the index number corresponds to the measured times, then the flatness value when the injection quantity is 140g is 0.464mm, the flatness value when the injection quantity is 145g is 0.58mm, the flatness value when the injection quantity is 150g is 0.662mm, the thicknesses of the three battery cells are all the same, but the injection quantities are different, some electrolyte cannot be absorbed by the interior of the battery cell and exists between the position between the aluminum plastic film and the battery cell and the pole piece, so that the thickness of the battery cell is inconsistent and the flatness of the battery cell is inconsistent, the better flatness of the battery cell means smaller thickness, the volume energy density of the battery cell is higher, through the analysis, the circulation test of the battery cell is combined, the liquid injection amount of the battery cell is determined to be 140g, the battery cell circulation in the state can be ensured, and the volume energy density is improved by 0.6%;

29 layers of positive pole pieces with the thickness of 130um, 30 layers of negative pole pieces with the thickness of 190um, 16um isolating films, 140g of electrolyte, positive pole tabs, negative pole tabs and aluminum plastic films are manufactured into finished product battery cores through the procedures of lamination, assembly, formation and the like, the finished product battery cores are three in total, the aluminum plastic films with the pit punching depths of 5.5mm, 6mm and 6.5mm are respectively used, the battery core electrical state is adjusted to 50% SOC, the three finished product battery cores are respectively measured by using measuring tools to obtain data in figures 5, 8 and 9, then curves in figure 4 are drawn, index numbers correspond to the measuring times, then the flatness value with the pit punching depth of 5.5mm is 0.464mm, the flatness value with the pit punching depth of 6mm is 0.579mm, the flatness value with the pit punching depth of 6.5mm is 0.5mm, and the drawing amount of the core package of the soft package battery aluminum plastic film and the binding degree of the soft package battery are determined by the pit punching depth, and then the flatness and the thickness of the battery cell are influenced, the smaller pit punching depth can be seen, the flatness value of the battery cell is favorably reduced, the energy density of the battery cell is indirectly improved, and the influence of the pit punching depth on the flatness of the battery cell can be quantitatively analyzed, so that the energy density of the battery cell is improved.

While one embodiment of the present invention has been described in detail, the description is only a preferred embodiment of the present invention and should not be taken as limiting the scope of the invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.