Method for improving consistency of terminal voltage of lithium-ion battery module and battery structure

Abstract

The present invention belongs to the technical field of lithium-ion batteries and relates to a method for improving the voltage consistency at the end of a lithium-ion battery module. The steps of the method for improving the voltage consistency at the end of a lithium-ion battery module are as follows: performing constant-power charge and discharge on n single cells; screening each single cell according to the voltage in the last second of constant-power discharge; dividing multiple single cells into multiple groups; not adding an aerogel layer on the end plate side of one of the battery modules, and respectively adding aerogel layers with different thicknesses on the end plate sides of the other groups of battery modules; respectively recording the end voltages of each battery module, and the thickness of the aerogel layer of the group of battery modules with the smallest end voltage difference is the optimal aerogel layer thickness L. The method for improving the voltage consistency at the end of a lithium-ion battery module and the battery structure for improving the voltage consistency at the end of a lithium-ion battery module according to the present invention can conveniently and reliably realize the grouping and pairing combination of battery modules, and improve the performance and service life of battery modules.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries. More specifically, it relates to a method for improving the consistency of the terminal voltage of a lithium-ion battery module, and the present invention also relates to a battery structure for improving the consistency of the terminal voltage of a lithium-ion battery module. Background Art

[0002] Currently, in devices such as new energy vehicles and energy storage of green energy where lithium batteries are used as power sources, most of them are combined batteries. These power sources are composed of several, dozens, or even hundreds of single cells connected in series and parallel. In a combined battery, its service life mainly depends on the single cell with the worst performance, and the single cell with poor performance will affect other single cells. Therefore, it is necessary to match each single cell so that parameters such as the capacity, internal resistance, voltage, and K value of each single cell in the combined battery tend to be consistent, thereby ensuring the conversion efficiency and service life of the module's capacity. In the prior art, when lithium-ion batteries are paired and combined during actual production, most of them use methods of simultaneously pairing capacity, internal resistance, and voltage for grouping. These methods are time-consuming and laborious, and the efficiency is extremely low. Therefore, the prior art processes cannot effectively solve the problem. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for improving the consistency of the terminal voltage of a lithium-ion battery module, which has simple steps, can effectively solve the problem of inconsistent terminal voltage caused by the difference between the temperature of the end plate side and the temperature of the single cell, and can conveniently and reliably realize the grouping and pairing combination of the battery module, thereby improving the performance and service life of the battery module.

[0004] To solve the above-mentioned technical problem, the technical solution adopted by the present invention is as follows:

[0005] The present invention is a method for improving the consistency of the terminal voltage of a lithium-ion battery module. The steps of the method for improving the consistency of the terminal voltage of a lithium-ion battery module are as follows:

[0006] S1. Perform constant-power charge and discharge on n single cells; screen each single cell according to the voltage in the last second of constant-power discharge.

[0007] S2. Divide multiple single cells into multiple groups according to the proximity range of the voltage in the last second of constant-power discharge of each single cell. Multiple single cells in each group form a battery module.

[0008] S3. Do not add an aerogel layer to the end plate side of one of the battery modules, and add aerogel layers with different thicknesses to the end plate sides of the other groups of battery modules respectively.

[0009] S4. Place multiple groups of battery modules under normal temperature conditions for T hours; then use the same equipment to perform constant-power charge and discharge on the four groups of batteries respectively;

[0010] S5. Record the terminal voltages of each battery module respectively, and screen out the group of battery modules with the smallest terminal voltage difference among the multiple groups of battery modules with the aerogel layer added. The thickness of the aerogel layer of the group of battery modules with the smallest terminal voltage difference is the optimal aerogel layer thickness L.

[0011] When performing constant-power charge and discharge on n single cells, charge the n single cells to 3.6V - 3.8V at normal temperature respectively, perform rest after charging respectively, and then discharge the n single cells to 3.0V - 3.3V at normal temperature respectively.

[0012] According to the voltage proximity range of the last second of constant-power discharge of each single cell, when dividing multiple single cells into multiple groups, the △V between multiple single cells in each group is less than or equal to 5mV.

[0013] When dividing multiple single cells into multiple groups, divide them into Group A, Group B, Group C, and Group D to form four groups of battery modules.

[0014] When placing multiple groups of battery modules under normal temperature conditions for T hours, the T is 1h - 2h.

[0015] Add aerogel layers with different thicknesses to the end plate sides of multiple battery modules. The three battery modules in Group B, Group C, and Group D are respectively added with three different thicknesses of aerogel layers L1, L2, and L3 on the end plate sides, and the battery modules in Group A are not added with aerogel layers.

[0016] Place the four groups of battery modules under normal temperature conditions for T hours; use the same equipment to perform constant-power charge and discharge on the four groups of battery modules respectively; record the terminal voltages of the four battery modules respectively.

[0017] Select the group with the smallest terminal voltage difference from the three groups of battery modules in Group B, Group C, and Group D. The thickness of the aerogel layer of this group of battery modules is the optimal aerogel layer thickness L.

[0018] The present invention also relates to a battery structure for improving the terminal voltage consistency of lithium-ion battery modules, which has simple steps, can effectively solve the problem of inconsistent terminal voltages caused by the difference between the temperature of the end plate side and the temperature of the single cells, and can conveniently and reliably realize the grouping and pairing combination of battery modules, thereby improving the performance and service life of battery modules. Multiple single cells are connected in series to form a battery module. End plate Ⅰ is arranged at one end of the battery module, end plate insulating cover Ⅰ is arranged inside end plate Ⅰ, aerogel layer Ⅰ is arranged between end plate insulating cover Ⅰ and the battery module, end plate Ⅱ is arranged at the other end of the battery module, end plate insulating cover Ⅱ is arranged inside end plate Ⅱ, and aerogel layer Ⅱ is arranged between end plate insulating cover Ⅱ and the battery module.

[0019] Multiple single cells are fixed to form a battery module by steel hoops and binding straps, and multiple single cells are connected in series by connection bars to form a battery module.

[0020] Adopting the technical solution of the present invention, the working principle and beneficial effects are as follows:

[0021] The method for improving the consistency of the terminal voltage of a lithium-ion battery module according to the present invention adds a layer of aerogel layer between the end plate insulating cover of the battery module and the single cell close to the end plate insulating cover. The aerogel makes the temperature diffusion at both ends of the module not too fast, so as to ensure that the temperature of the single cell on the end plate side and the lithium battery at other positions remains at the same level. And the method of the present invention, by detecting and grouping single cells respectively, then forming multiple modules, and then through a special process, finds the optimal thickness L of the aerogel layer. The method for improving the consistency of the terminal voltage of a lithium-ion battery module and the battery structure for improving the consistency of the terminal voltage of a lithium-ion battery module according to the present invention have simple steps, can effectively solve the problem of inconsistent terminal voltage caused by the different temperatures of the end plate side and the single cell, and can conveniently and reliably realize the grouping and pairing combination of the battery module, improving the performance and service life of the battery module. Description of the Drawings

[0022] The following briefly describes the content expressed by each drawing in this specification and the marks in the drawings:

[0023] Figure 1 It is a schematic structural diagram of the battery structure described in the present invention;

[0024] The marks in the drawings are respectively: 1, top cover plate; 2, end plate I; 3, end plate insulating cover I; 4, gel layer I; 5, end plate II; 6, steel hoop; 7, binding strap; 8, connection bar; 9, end plate insulating cover II; 10, aerogel layer II; 11, single cell; 12, battery module. Detailed Embodiments

[0025] The following, with reference to the drawings, through the description of the embodiments, further details are given on the specific embodiments of the present invention, such as the shapes, structures of the various components involved, the mutual positions and connection relationships between the various parts, the functions of the various parts, and the working principles, etc.:

[0026] As shown in the attached Figure 1 figure, the present invention is a method for improving the consistency of the terminal voltage of a lithium-ion battery module, and the steps of the method for improving the consistency of the terminal voltage of a lithium-ion battery module are as follows:

[0027] S1. Perform constant-power charge and discharge on n single cells; screen each single cell according to the voltage in the last second of constant-power discharge; S2. Divide multiple single cells into multiple groups according to the proximity range of the voltage in the last second of constant-power discharge of each single cell, and multiple single cells in each group form a battery module; S3. Do not add an aerogel layer on the end plate side of one of the battery modules, and add aerogel layers with different thicknesses on the end plate sides of the other groups of battery modules respectively; S4. Place multiple groups of battery modules at room temperature for T hours; then perform constant-power charge and discharge on the four groups of batteries respectively using the same equipment; S5. Record the terminal voltage of each battery module respectively, and screen out the battery module with the smallest terminal voltage difference among the multiple groups of battery modules with aerogel layers added. The thickness of the aerogel layer of the group of battery modules with the smallest terminal voltage difference is the optimal aerogel layer thickness L. The above steps propose a brand-new technical solution for the deficiencies in the prior art. In the field of lithium-ion batteries, the assembly of lithium battery modules often greatly reduces the efficiency of converting single cells into modules due to inconsistencies in battery capacity, internal resistance, voltage, K value, etc. In actual production, through research and verification, it is found that the terminal voltage difference of single cells can better improve the module consistency. At the same time, some cathode materials are extremely sensitive to temperature. The different positions of single cells in the module will cause inconsistent surface temperatures of the cells, thus affecting the voltage difference consistency of the module. The present invention provides a simple device to solve the problem of excessive terminal voltage difference caused by the temperature sensitivity of battery modules. In actual production, it is found that it is more convenient and effective to use the terminal voltage of battery discharge as the screening condition. However, since the temperature diffuses faster at both ends of the battery, the temperature at the side end of the battery is lower than the surface temperature of the battery, and the voltage will be inconsistent due to the influence of temperature, resulting in an M-shaped voltage difference problem in the module. Therefore, it is necessary to eliminate the inconsistency of the voltage difference caused by the temperature difference. In the method of the present invention, an aerogel layer is added between the end plate insulating cover of the battery module and the single cell close to the end plate insulating cover. The aerogel makes the temperature diffusion at both ends of the module not too fast, thus ensuring that the temperature of the single cell on the end plate side is kept at the same level as that of the elevator cells in other positions. And the method of the present invention, by detecting and grouping single cells respectively, then forming multiple modules, and through a special process, finds the optimal aerogel layer thickness L. The method for improving the terminal voltage consistency of lithium-ion battery modules described in the present invention has simple steps, can effectively solve the problem of inconsistent terminal voltage caused by different temperatures between the end plate side and the single cell, and is convenient and reliable to realize the grouping and pairing combination of battery modules, improving the performance and service life of battery modules.

[0028] When performing constant-power charge and discharge on n single cells, the n single cells are respectively charged to 3.6V - 3.8V at room temperature, left to stand after charging, and then the n single cells are respectively discharged to 3.0V - 3.3V at room temperature. In the above steps, when charging the n single cells at room temperature respectively, the optimal charging voltage is 3.65V. When discharging the n single cells at room temperature respectively, the optimal discharging voltage is 3.0V. In this way, the effect of the improvement method is enhanced.

[0029] When dividing multiple single cells into multiple groups according to the voltage proximity range in the last second of constant-power discharge of each single cell, the ΔV between multiple single cells in each group is less than or equal to 5mV. In the above steps, different single cells (cells) are grouped according to the above parameters.

[0030] As a specific embodiment, when dividing multiple single cells into multiple groups, they are divided into Group A, Group B, Group C, and Group D to form four battery modules. When placing the multiple battery modules under room temperature conditions for T hours, the T is 1h - 2h. Aerogel layers with different thicknesses are respectively added to the end plate sides of the multiple battery modules. Three battery modules in Group B, Group C, and Group D are respectively added with three different thicknesses of aerogel layers L1, L2, and L3 on the end plate side, and the battery module in Group A is not added with an aerogel layer. Place the four battery modules under room temperature conditions for T hours; perform constant-power charge and discharge on the four battery modules respectively with the same equipment; record the terminal voltages of the four battery modules respectively. Select the group with the smallest terminal voltage difference from the three battery modules in Group B, Group C, and Group D, and the thickness of the aerogel layer of this group of battery modules is the optimal aerogel layer thickness L. In this way, through the operations and verifications of different groups, it is convenient to obtain the optimal aerogel layer thickness L.

[0031] The present invention also relates to a battery structure for improving the consistency of the terminal voltage of a lithium-ion battery module, which has simple steps, can effectively solve the problem of inconsistent terminal voltages caused by the difference between the temperature on the end plate side and the temperature of the single cell, is convenient and reliable for grouping and pairing combination of battery modules, and improves the performance and service life of the battery module. Multiple single cells 11 are connected in series to form a battery module 12. One end of the battery module 12 is provided with an end plate Ⅰ2, an end plate insulation cover Ⅰ3 is arranged inside the end plate Ⅰ2, an aerogel layer Ⅰ4 is arranged between the end plate insulation cover Ⅰ3 and the battery module, the other end of the battery module 12 is provided with an end plate Ⅱ5, an end plate insulation cover Ⅱ9 is arranged inside the end plate Ⅱ5, and an aerogel layer Ⅱ10 is arranged between the end plate insulation cover Ⅱ9 and the battery module 12. The multiple single cells 11 are fixed to form the battery module 12 through steel hoops 6 and binding straps 7, and the multiple single cells 11 are connected in series through connection bars 8 to form the battery module 12. In this way, a battery module with reliable performance is formed.

[0032] For the battery module of the present invention, according to specific parameters, a specific operation embodiment is as follows:

[0033] S1. Perform constant - power charge - discharge on N single - cell batteries (cells).

[0034] S2. Screen the batteries in S1 according to the voltage in the last second of constant - power discharge, and group them with ΔV≤5mV.

[0035] S3. Select n single - cell batteries that meet the conditions and assemble them into four battery modules, namely Group A, Group B, Group C, and Group D. Each battery module includes m batteries.

[0036] S4. Add three different - thickness aerogel layers, L1, L2, and L3, to the end - plate sides of the three battery modules in Group B, Group C, and Group D respectively. Do not add an aerogel layer to Group A.

[0037] S5. Place the four groups of battery modules at room temperature for T hours.

[0038] S6. Use the same device to perform constant - power charge - discharge on the four groups of battery modules.

[0039] S7. Record the terminal voltages of the four groups of battery modules.

[0040] S8. Select the group with the smallest terminal voltage difference among Group B, Group C, and Group D. The thickness of the aerogel layer of the group of battery modules with the smallest terminal voltage difference is the optimal aerogel layer thickness L.

[0041] Further, in the above step S1, the single - cell battery is a 280Ah square aluminum - shell battery, and N = 300.

[0042] Further, in the above step S3, n = 56 and m = 14.

[0043] Further, in the above step S4, L1 = 1.5mm, L2 = 1mm, and L3 = 0.5mm.

[0044] Further, in the above step S5, T = 2h.

[0045] Further, in the above step S6, the constant - power charge - discharge is 0.5P, and the cut - off voltages for constant - power charge - discharge are 3.65V and 2.5V respectively.

[0046] Further, in the above step S8, 1mm aerogel is the optimal thickness for the module.

[0047] The method for improving the consistency of the terminal voltage of a lithium-ion battery module according to the present invention adds a layer of aerogel layer between the end plate insulating cover of the battery module and the single battery close to the end plate insulating cover. The aerogel makes the temperature diffusion at both ends of the module not too fast, thus ensuring that the temperature of the single battery on the end plate side is kept at the same level as that of the elevator batteries at other positions. And the method of the present invention detects and groups the single batteries respectively, then forms multiple modules, and then finds the optimal thickness L of the aerogel layer through a special process. The method for improving the consistency of the terminal voltage of a lithium-ion battery module and the battery structure for improving the consistency of the terminal voltage of a lithium-ion battery module according to the present invention have simple steps, can effectively solve the problem of inconsistent terminal voltage caused by the difference between the temperature on the end plate side and the temperature of the single battery, and can conveniently and reliably realize the grouping and pairing combination of the battery modules, improving the performance and service life of the battery modules.

[0048] The present invention has been described exemplarily above in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above-mentioned manner. As long as various improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for improving the voltage consistency at the end of a lithium-ion battery module, the lithium-ion battery module comprising: Multiple single cells (11) are connected in series to form a battery module (12). One end of the battery module (12) is provided with an end plate I (2). An end plate insulating cover I (3) is arranged inside the end plate I (2). An aerogel layer I (4) is arranged between the end plate insulating cover I (3) and the battery module. The other end of the battery module (12) is provided with an end plate II (5). An end plate insulating cover II (9) is arranged inside the end plate II (5). An aerogel layer II (10) is arranged between the end plate insulating cover II (9) and the battery module (12). Multiple single cells (11) are fixed to form a battery module (12) through steel hoops (6) and strapping tapes (7). Multiple single cells (11) are connected in series through connection bars (8) to form a battery module (12). It is characterized in that the steps of the method for improving the end voltage consistency of a lithium-ion battery module are as follows: S1. Constant power charge and discharge are carried out on n single cells, including: charging n single cells to 3.6V - 3.8V at normal temperature respectively, carrying out rest after charging respectively, and then discharging n single cells to 3.0V - 3.3V at normal temperature respectively; each single cell is screened according to the voltage in the last second of constant power discharge. S2. According to the voltage range of each single cell in the last second of constant power discharge, multiple single cells are divided into multiple groups, and multiple single cells in each group form a battery module. S3. An aerogel layer is not added to the end plate side of one of the battery modules, and aerogel layers with different thicknesses are respectively added to the end plate sides of other groups of battery modules. S4. Multiple groups of battery modules are respectively placed under normal temperature conditions for T hours; then the four groups of batteries are respectively subjected to constant power charge and discharge with the same equipment. S5. The end voltages of each battery module are respectively recorded, and the group of battery modules with the smallest end voltage difference among the multiple groups of battery modules with aerogel layers added is screened out, and the thickness of the aerogel layer of the group of battery modules with the smallest end voltage difference is the optimal aerogel layer thickness L.

2. The method for improving the consistency of the terminal voltage of a lithium-ion battery module according to claim 1, wherein: When multiple single cells are divided into multiple groups according to the voltage range of each single cell in the last second of constant power discharge, the △V between multiple single cells in each group is less than or equal to 5mV.

3. The method for improving the voltage consistency at the end of a lithium-ion battery module according to claim 2, wherein: When multiple single cells are divided into multiple groups, they are divided into group A, group B, group C, and group D to form four groups of battery modules.

4. The method for improving the consistency of the terminal voltage of a lithium-ion battery module according to claim 3, characterized in that: When multiple groups of battery modules are respectively placed under normal temperature conditions for T hours, the T is 1 - 2.

5. The method for improving the voltage consistency at the end of a lithium-ion battery module according to claim 4, characterized in that: Aerogel layers with different thicknesses are respectively added to the end plate sides of multiple battery modules. Aerogel layers with three different thicknesses L1, L2, and L3 are respectively added to the end plate sides of the three battery modules in group B, group C, and group D, and no aerogel layer is added to the battery module in group A.

6. The method for improving the consistency of the terminal voltage of a lithium-ion battery module according to claim 5, characterized in that: Four groups of battery modules are respectively placed under normal temperature conditions for T hours; the four groups of battery modules are respectively subjected to constant power charge and discharge with the same equipment; the end voltages of the four battery modules are respectively recorded.

7. The method for improving the consistency of the terminal voltage of a lithium-ion battery module according to claim 6, characterized in that: Select the group with the smallest end voltage difference from the three groups of battery modules in group B, group C, and group D, and the thickness of the aerogel layer of this group of battery modules is the optimal aerogel layer thickness L.

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