Battery top cover detection method

Abstract

The invention belongs to the field of battery detection, and particularly relates to a battery top cover detection method, and compared with the prior art, the battery top cover detection method pre-judges the edge voltage quality trend of a battery monomer finished product after the battery monomer finished product is offline through battery monomer part level process welding measurement and calculation. The poor side voltage of the single battery can be found in advance before assembly, the material and capacity waste caused by a battery top cover is reduced at the battery end, and the overall poor grouping is avoided at the module end.

Description

Technical Field

[0001] The present application relates to the technical field of battery detection, and in particular to a battery top cover detection method. Background Art

[0002] Lithium-ion batteries have a risk of failure due to leakage during daily storage and use. The external manifestations are corrosion of the aluminum shell and leakage of the battery core. This phenomenon will lead to a decrease in the insulation performance of the battery, a decrease in the cycle life, and even safety hazards such as short circuits. From an electrochemical analysis, the corrosive product is a white powder of lithium-aluminum alloy cations, indicating that the lithium ions have been partially deintercalated between the aluminum molecules in the shell. When the positive electrode and the aluminum shell have the same potential, lithium ion transfer will not occur. When the aluminum shell potential is reduced due to internal or external reasons, which is usually called an increase in the edge voltage, the negative electrode and the aluminum shell will have electrical contact, which will cause the lithium ions to swim to the aluminum shell with a higher potential, causing a lithium-aluminum composite reaction and further oxidation over time.

[0003] The edge voltage screening of battery cells can greatly reduce the risk of leakage after grouping. The current production process is to measure and screen the cells after they are batched off the production line before batch production of the modules in the later stage (such as Fig. 9 As shown), the module is welded and the voltage of the battery cell side is re-measured after welding to remove unqualified products. This is a passive detection method after the battery product is offline and it is a defect magnification detection method. Summary of the invention

[0004] The embodiment of the present application provides a battery top cover detection method for solving the problem that the existing battery cell side voltage screening is passive and causes defect magnification detection after the battery product is offline.

[0005] To achieve the above object, the present application provides a battery top cover detection method, comprising the following steps:

[0006] Detect the temperature T of the conductive plastic between the top cover and the positive pole in the battery top cover during busbar welding 焊接 , compared with the injection temperature T in the PPS physical property table of conductive plastic 注塑 ;

[0007] Detect the positive resistance R of the battery top cover 正 , according to the formula V 边 =(R 正 / (R 负 +R 正 ))×3.2Calculate the side voltage V 边 , where 43MΩ≦R 负 ≦67MΩ; the calculated edge voltage V 边 With the set value V 设 Compare;

[0008] If T 焊接 >T 注塑 or V 边 >V 设 , then the battery top covers of this batch are unqualified and will not be used in the production of subsequent battery cells;

[0009] If T 焊接 ≦T 注塑 And V 边 ≦V 设 When the test result is , the battery top covers of this batch are qualified and can be used to participate in the production of subsequent single cells.

[0010] Optionally, the temperature T of the conductive plastic between the top cover sheet and the positive electrode column in the battery top cover during busbar welding is detected. 焊接 The following steps are involved:

[0011] Punch holes in the conductive plastic in the battery cover;

[0012] Insert the temperature sensor into the hole on the conductive plastic, and connect the temperature sensor to the data collector through a temperature sensing line;

[0013] The busbar is laser welded on the positive pole of the battery top cover to simulate the welding of multiple single cells. The highest temperature collected by the temperature sensor during the welding process is recorded as T 焊接 .

[0014] Optionally, when punching the conductive plastic in the battery top cover, at least two holes are punched along the circumference of the conductive plastic, and the at least two holes are located on different sides of the conductive plastic.

[0015] Optionally, after punching the conductive plastic in the battery top cover, the following steps are also included:

[0016] Measure the depth of the hole in the conductive plastic to ensure that the hole penetrates the thickness of the conductive plastic to below the positive terminal welding area.

[0017] Optionally, when punching holes in the conductive plastic in the battery top cover, the battery top cover is first fixed with a clamp, and then the conductive plastic is punched.

[0018] Optionally, the temperature sensor is inserted into the hole on the conductive plastic, and the space between the temperature sensor and the hole on the conductive plastic is filled with thermal conductive silicone.

[0019] The battery top cover detection method provided by the present application has the following beneficial effects: compared with the prior art, the battery top cover detection method of the present application predicts the quality trend of the side voltage of the battery cell finished product after it is offline through a battery cell component-level process welding measurement and calculation. It can detect the side voltage of the battery cell before assembly, reduce the waste of materials and production capacity caused by the battery top cover at the battery end, and avoid overall group defects at the module end. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] in:

[0022] Figure 1 is a flow chart of a battery top cover detection method according to an embodiment of the present application;

[0023] Figure 2 In a battery top cover detection method shown in an embodiment of the present application, the temperature T of the conductive plastic between the top cover sheet and the positive electrode column in the battery top cover is detected during busbar welding. 焊接 Schematic diagram of the process;

[0024] Figure 3-Figure 7 In a battery top cover detection method shown in an embodiment of the present application, the temperature T of the conductive plastic between the top cover sheet and the positive electrode column in the battery top cover is detected during busbar welding. 焊接 The process flow diagram is as follows: Figure 3 To punch holes in the battery cover; Figure 4 Drilling holes along the circumference of the conductive plastic; Figure 5 To measure the hole depth; Figure 6 For fixing the temperature sensor in the hole; Figure 7 To simulate group process welding;

[0025] Figure 8 In the battery top cover detection method shown in one embodiment of the present application, the positive electrode resistance R of the battery top cover is detected. 正 Schematic diagram of

[0026] Fig. 9 This is a schematic diagram of the measurement of the traditional single cell side voltage. DETAILED DESCRIPTION

[0027] In order to facilitate the understanding of the present application, the present application will be described more comprehensively with reference to the relevant drawings below. The preferred embodiments of the present application are provided in the drawings. However, the present application can be implemented in many other different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0028] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0029] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In the description of the present application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0031] As described in the background technology, the edge voltage screening of battery cells can greatly reduce the risk of leakage after grouping. The current production process is a passive detection after the battery products are offline, and it is a defect-amplifying detection method that cannot predict and discover problems in advance, and is prone to batch abnormal events after the arrival of new batches of materials.

[0032] In order to solve the above problems, the embodiments of the present application provide a battery cover detection method, such as Figure 1 As shown, the battery top cover detection method includes the following steps:

[0033] Detect the temperature T of the conductive plastic between the top cover and the positive pole in the battery top cover during busbar welding 焊接 , compared with the injection temperature T in the PPS physical property table of conductive plastic 注塑 ;

[0034] Detect the positive resistance R of the battery top cover 正 (like Figure 8 As shown), according to the formula V边 =(R 正 / (R 负 +R 正 ))×3.2Calculate the side voltage V 边 , where 43MΩ≦R 负 ≦67MΩ, 1MΩ=1000000Ω, R 负 The specific value is determined according to the negative electrode material; the calculated edge voltage V 边 With the set value V 设 Compare;

[0035] If T 焊接 >T 注塑 or V 边 >V 设 , then the battery top covers of this batch are unqualified and will not be used in the production of subsequent battery cells;

[0036] If T 焊接 ≦T 注塑 And V 边 ≦V 设 When the test result is , the battery top covers of this batch are qualified and can be used to participate in the production of subsequent single cells.

[0037] It should be noted that in single cells, the secondary design, i.e. the positive electrode and the aluminum shell are integrated, has been widely used. At the same time, in order to avoid the risk of ignition or even short circuit caused by the contact between the negative electrode post and the aluminum shell during transportation or operation, conductive plastic is usually added between the top cover sheet and the positive electrode post of the battery in the battery top cover of the lithium-ion battery to increase the conduction resistance between the aluminum shell and the positive electrode.

[0038] Different conductive plastic materials (PPS material, 60% glass mineral filled natural color high temperature resistant fireproof PPS composite material) have different injection temperatures. 焊接 With T 注塑 By comparing the resistance after welding and combining it with Ohm's law of battery, the predicted edge voltage of various battery top covers can be identified in advance.

[0039] The edge voltage calculation principle is that the positive electrode and the shell of the single battery are designed to be connected to each other. Under normal circumstances, when the resistance between the positive electrode and the shell is 10000Ω≥R≥20Ω, the edge voltage is less than the process setting value of 0.01mv; when the conductive plastic on the top cover of the single battery causes the positive electrode resistance to increase due to material reasons or welding factors, the edge voltage will be greater than the process setting value of 0.01mv.

[0040] In the embodiment of the present application, the battery top cover detection method predicts the edge voltage quality trend of the battery cell finished product after it is offline through a battery cell component-level process welding measurement and calculation. It can detect the poor edge voltage of the battery cell in advance before assembly, reduce the waste of materials and production capacity caused by the battery top cover at the battery end, and avoid overall poor grouping at the module end.

[0041] In one embodiment, in combination Figure 2 and Figure 3-Figure 7 As shown, the temperature T of the conductive plastic between the top cover sheet and the positive electrode column in the battery top cover is detected during the busbar welding. 焊接 The following steps are involved:

[0042] Punch holes in the conductive plastic in the battery cover;

[0043] Insert the temperature sensor into the hole on the conductive plastic, and connect the temperature sensor to the data collector through a temperature sensing line;

[0044] The busbar is laser welded on the positive pole of the battery top cover to simulate the welding of multiple single cells. The highest temperature collected by the temperature sensor during the welding process is recorded as T 焊接 .

[0045] Through the above steps, the temperature T of the conductive plastic inside the positive electrode near the positive electrode during welding can be measured more accurately. 焊接 .

[0046] In a specific embodiment, Figure 3-Figure 4 As shown, when punching the conductive plastic in the battery top cover, at least two holes are punched along the circumference of the conductive plastic, and at least two holes are located on different sides of the conductive plastic (adjacent sides, not on the same side). Exemplarily, one hole is punched on each of the three sides of the conductive plastic. This arrangement further improves the comprehensiveness and reliability of temperature detection.

[0047] In a further specific embodiment, Figure 5 As shown, after punching the conductive plastic in the battery top cover, the following steps are also included:

[0048] Measure the depth of the hole in the conductive plastic to ensure that the hole penetrates the thickness of the conductive plastic to below the positive terminal welding area.

[0049] When multiple battery cells are welded in groups to form a battery pack, the busbar is welded to the positive electrode post in the battery top cover, ensuring that the hole depth on the conductive plastic penetrates the thickness of the conductive plastic to the positive electrode post can more accurately judge the temperature of the conductive plastic during welding.

[0050] In one embodiment, when punching holes in the conductive plastic in the battery top cover, the battery top cover is fixed with a clamp, and a drill is used to manually punch holes in the conductive plastic.

[0051] The holes between the temperature sensor and the conductive plastic are filled with thermally conductive silicone to ensure reliable contact between the sensor and the conductive plastic, thereby ensuring the reliability of the collected values.

[0052] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A battery top cover detection method, It is characterized in that The following steps are involved: Detect the temperature T of the conductive plastic between the top cover and the positive pole in the battery top cover during busbar welding 焊接 , compared with the injection temperature T in the PPS physical property table of conductive plastic 注塑 ; Detect the positive resistance R of the battery top cover 正 , according to the formula V 边 =(R 正 / (R 负 +R 正 ))×3.2Calculate the side voltage V 边 , where 43MΩ≦R 负 ≦67MΩ; the calculated edge voltage V 边 With the set value V 设 Compare; If T 焊接 >T 注塑 or V 边 >V 设 , then the battery top covers of this batch are unqualified and will not be used in the production of subsequent battery cells; If T 焊接 ≦T 注塑 And V 边 ≦V 设 When the test result is , the battery top covers of this batch are qualified and can be used to participate in the production of subsequent single cells.

2. The battery top cover detection method according to claim 1, It is characterized in that Detect the temperature T of the conductive plastic between the top cover and the positive pole in the battery top cover during busbar welding 焊接 The following steps are involved: Punch holes in the conductive plastic in the battery cover; Insert the temperature sensor into the hole on the conductive plastic, and connect the temperature sensor to the data collector through a temperature sensing line; The busbar is laser welded on the positive pole of the battery top cover to simulate the welding of multiple single cells. The highest temperature collected by the temperature sensor during the welding process is recorded as T 焊接 .

3. The battery top cover detection method according to claim 2, It is characterized in that When punching the conductive plastic in the battery top cover, at least two holes are punched along the circumference of the conductive plastic, and the at least two holes are located on different sides of the conductive plastic.

4. The battery top cover detection method according to claim 2 or 3, It is characterized in that After punching the conductive plastic in the battery cover, the following steps are also included: Measure the depth of the hole in the conductive plastic to ensure that the hole penetrates the thickness of the conductive plastic to below the positive terminal welding area.

5. The battery top cover detection method according to claim 2, It is characterized in that When punching holes in the conductive plastic in the battery top cover, the battery top cover is first fixed by a clamp, and then the conductive plastic is punched.

6. The battery top cover detection method according to claim 2, It is characterized in that The temperature sensor is inserted into the hole on the conductive plastic, and the space between the temperature sensor and the hole on the conductive plastic is filled with thermal conductive silicone.

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