CN114976449B

CN114976449B - Long-life battery module and application thereof

Info

Publication number: CN114976449B
Application number: CN202111215064.XA
Authority: CN
Inventors: 暴旭; 马华; 刘峰; 卫晓燕; 陈卓
Original assignee: Tianjin EV Energies Co Ltd
Current assignee: Tianjin EV Energies Co Ltd
Priority date: 2021-10-19
Filing date: 2021-10-19
Publication date: 2023-07-07
Anticipated expiration: 2041-10-19
Also published as: CN114976449A

Abstract

The invention provides a long-life battery module and application thereof, wherein the module comprises at least three cells connected in series and/or in parallel, and each cell comprises an outer-layer cell and an inner-layer cell; the capacity of the outer layer battery core is larger than that of the inner layer battery core. The invention prolongs the service life of the module, reduces the use cost of the module, increases extra capacity on the outer layer of the module, and can ensure the service life of the inner layer of the module.

Description

Long-life battery module and application thereof

Technical Field

The invention relates to the field of power batteries, in particular to a long-life battery module and application thereof.

Background

Electric vehicles in the market are powered by a battery system, wherein the battery system is formed by connecting a plurality of modules in series, and one module is formed by a plurality of battery cores. During operation of the vehicle, each cell will have a capacity fade whose rate of decay determines the life of the module. At the same time, the attenuation of the cells is affected by a number of circumstances. The decay lifetime of a module is determined by the lowest capacity cell in the module, which is typically the "barrel effect". It is often the case that the decay rates of the cells in the module are not the same, and that cells in certain particular locations often decay much faster than other cells, resulting in other cells not reaching the end of life, but the module has been at the end of life.

Various studies have been made by those skilled in the art to improve the life of the module.

CN211530140U discloses a battery module and a battery pack. The size of the thermal barrier part is gradually reduced from the end part of the battery module to the middle part of the battery module along the arrangement direction of the battery cells, so that the temperature consistency of the battery cells at different positions is ensured, the purpose of uniform temperature is achieved, and the service life is effectively prolonged. The purpose of prolonging the service life is achieved by ensuring the same temperature of each battery cell, but the disclosed invention can not achieve good improvement effect on shortening of the service life of the module caused by capacity attenuation of the module by a temperature control method.

CN109920969a discloses a long-life energy storage module battery, an energy storage system and a battery cell monomer, which are configured to realize liquid injection by a certain structure, so as to improve the service life of the module, but the method has high cost, and the liquid injection is carried out again in the later period, so that the operation is troublesome and is not suitable for disposable modules.

CN108777329a discloses a lithium battery matching method, by means of capacity mathematical sequencing and matching, capacity difference between each string of single battery cells and between battery modules is greatly reduced, single battery cell matching utilization rate is improved, error is reduced, cost is reduced, and meanwhile overall performance of the battery modules and the battery system is ensured, so that stability and service life of the battery system are improved. The battery module and the battery system are integrally unified by sorting and assembling the capacities, so that the stability and the service life of the battery system are improved. However, the calculation method is complex and the sequencing is troublesome.

How to simply and effectively relatively prolong the service life of the module is an important research direction in the field.

Disclosure of Invention

The invention aims to provide a long-life battery module, which can lead the inner and outer battery cells to be at the same attenuation level when the service life of the module reaches the end through the specific design of the capacity of the battery cells, so that the module has longer service life.

In order to achieve the aim of the invention, the invention adopts the following technical scheme:

it is an object of the present invention to provide a battery module comprising at least three cells connected in series and/or in parallel, the cells comprising an outer cell and an inner cell.

The capacity of the outer layer battery core is larger than that of the inner layer battery core.

In the invention, because the cell capacity in the module is assembled according to the cell with the approximate capacity, but because the cell is positioned at different positions in the module, the use temperature and the use binding force of the cell are different, and therefore, the attenuation rates of the cells at different positions are different. Generally, the decay rate of the outermost cells of the module is fastest, and when the outermost cells reach the end life, the module life is also terminated, but the remaining cells are still not reaching the end life, and can continue to be used, which certainly wastes the middle cell. Therefore, the module consists of n cells connected in series and parallel, and when the service life of the module is terminated by the specific design of the capacity of the cells, the inner and outer cells can be at an attenuation level, so that the service life of the module is relatively prolonged.

As a preferred technical solution of the present invention, the capacity of the outer layer cell-the capacity of the inner layer cell=m.

The m calculating method comprises the following steps:

the average initial capacity of the inner layer battery core is A1, the initial capacity of the outer layer battery core is A2, the average residual capacity of the inner layer battery core after charge and discharge cycles is B1, the residual capacity of the outer layer battery core is B2, and m= (A2-B2) - (A1-B1).

As a preferable technical scheme of the invention, the A2 is the initial capacity of the battery cell with the largest capacity difference before and after the charge and discharge cycle in the outer layer battery cell.

Preferably, B2 is the remaining capacity of the cell with the largest difference in capacity between before and after the charge and discharge cycles in the outer cell.

As a preferable technical scheme of the invention, the inner-layer battery cells are all battery cells except the outer-layer battery cells.

As a preferable technical scheme of the invention, the charging in the charging and discharging cycle is constant-current constant-voltage charging.

Preferably, the discharge in the charge-discharge cycle is constant-current constant-voltage discharge.

In a preferred embodiment of the present invention, the charging current in the charging and discharging cycle is 0.05 to 100C, wherein the charging current may be 0.05C, 1C, 5C, 10C, 15C, 20C, 25C, 30C, 35C, 40C, 45C, 50C, 55C, 60C, 65C, 70C, 75C, 80C, 85C, 90C, 95C, 100C, etc., but not limited to the recited values, and other non-recited values within the range of values are equally applicable.

Preferably, the discharge current in the charge-discharge cycle is 0.05 to 100C, wherein the charge current may be 0.05C, 1C, 5C, 10C, 15C, 20C, 25C, 30C, 35C, 40C, 45C, 50C, 55C, 60C, 65C, 70C, 75C, 80C, 85C, 90C, 95C, 100C, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.

In a preferred embodiment of the present invention, the charging voltage in the charging and discharging cycle is 2 to 500V, wherein the voltage may be 2C, 10C, 20C, 35C, 40C, 50C, 60C, 70C, 80C, 90C, 100C, 150C, 200C, 250C, 300C, 350C, 400C, 450C, 500C, or the like, but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.

Preferably, the discharge voltage in the charge-discharge cycle is 16.5 to 25.8V, wherein the voltage may be 16.5V, 17V, 17.5V, 18V, 18.5V, 19V, 19.5V, 20V, 20.5V, 21V, 21.5V, 22V, 22.5V, 23V, 23.5V, 24V, 24.5V, 25V, 25.5V or 25.8V, but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.

In a preferred embodiment of the present invention, the off condition of the charge-discharge cycle is that the capacity of the outer layer cell is reduced by 80 to 85%, and the capacity may be 80%, 80.5%, 81%, 81.5%, 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, or the like, but is not limited to the above-mentioned values, and other non-mentioned values within the above-mentioned value range are similarly applicable, and more preferably 80 to 82%.

As a preferable technical scheme of the invention, the battery cell comprises any one of a soft package battery cell, a plastic shell battery cell or an aluminum shell battery cell.

A second object of the present invention is to provide an application of the battery module according to the first aspect, wherein the module is applied to the field of power batteries.

The module is applied to lithium ion batteries, lead-acid batteries, sodium ion batteries, lithium sulfur batteries and the like, and relates to a device for storing energy by using electrochemistry.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a long-life battery module, which has long service life and low use cost.

Drawings

FIG. 1 is a schematic cross-sectional view of the module in examples 1-3 of the present invention.

FIG. 2 is a graph showing capacity calibration corresponding to the data of Table 1 in example 1 of the present invention.

Fig. 3 is a capacity map corresponding to table 2 data in example 1 of the present invention.

FIG. 4 is a graph showing capacity calibration corresponding to the data of Table 1 in example 2 of the present invention.

Fig. 5 is a capacity map corresponding to table 2 data in example 2 of the present invention.

FIG. 6 is a graph showing capacity calibration corresponding to the data of Table 1 in example 3 of the present invention.

Fig. 7 is a capacity map corresponding to the data of table 2 in example 3 of the present invention.

Detailed Description

The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.

Example 1

The embodiment provides a preparation method of a battery module, which comprises the following steps:

(1) For a VDA model 355 module, the size is 355×151×108mm, the module is composed of 12 cells in 2-6 strings, the capacity of 1 cell is 50Ah, and the size is 306×103×11.4mm. The cross-sectional structure is shown in figure 1.

(2) The module was stopped when the capacity was 80% of the initial capacity at cycling to 1600 weeks (constant current charge 100A to 25.8V, rest 30 minutes, constant current discharge 100A to 16.5V). Each cell is then removed for individual capacity calibration. The capacities of the different locations are shown in fig. 2. (A represents the initial capacity and B represents the capacity of the cell when the module decays to 80%).

(3) A cell was designed and fabricated with a capacity value of 52.46Ah. When the module is assembled, high-capacity cells (the design value is 52.46 Ah) are placed at the outermost positions #1 and #12, and the cells with the original design value of 50Ah are placed at the positions #2 to #10, so that the module is assembled.

(4) The module was stopped when the capacity was 80% of the initial capacity at cycling to 2133 weeks (constant current charge 100A to 25.8V, rest 30 minutes, constant current discharge 100A to 16.5V). As the capacity-rich margin of the outermost side of the module is more, the module compensates more attenuation of the outermost side, fully utilizes the service life of each battery cell and prolongs the service life of the module. The capacities of the different locations are shown in fig. 3. (A represents the initial capacity and B represents the capacity of the cell when the module decays to 80%)

Example 2

(2) The module was stopped when the capacity was 80% of the initial capacity at cycling to 2000 weeks (constant current charge 74A to 25.8V, resting for 30 minutes, constant current discharge 74A to 16.5V). Each cell is then removed for individual capacity calibration.

(3) A cell was designed and fabricated with a capacity value of 38.9Ah. When the module is assembled, high-capacity cells (with a design value of 38.9 Ah) are placed at the outermost positions #1 and #12, and cells with an original design value of 50Ah are placed at the positions #2 to #10, so that the module is assembled.

(4) The module was stopped when the capacity was 80% of the initial capacity at 2400 weeks (constant current charge 74A to 25.8V, rest 30 minutes, constant current discharge 74A to 16.5V) cycle. As the capacity-rich margin of the outermost side of the module is more, the module compensates more attenuation of the outermost side, fully utilizes the service life of each battery cell and prolongs the service life of the module. The comparison results are shown in fig. 4 and 5.

Example 3

(1) For a VDA model 355 module, the size is 355×151×108mm, the module is composed of 12 cells in 2-6 strings, the capacity of 1 cell is 78Ah, and the size is 306×103×11.4mm. The cross-sectional structure is shown in figure 1.

(2) The module was stopped when the capacity was 80% of the initial capacity at cycling to 1500 weeks (constant current charge 156A to 25.8V, resting for 30 minutes, constant current discharge 156A to 16.5V). Each cell is then removed for individual capacity calibration.

(3) A cell was designed and fabricated with a capacity value of 80.3Ah. When the module is assembled, high-capacity cells (with a design value of 80.3 Ah) are placed at the outermost positions #1 and #12, and cells with an original design value of 50Ah are placed at the positions #2 to #10, so that the module is assembled.

(4) The module was stopped when the capacity was 80% of the initial capacity at cycling to 1800 weeks (constant current charge 156A to 25.8V, rest 30 minutes, constant current discharge 156A to 16.5V). As the capacity-rich margin of the outermost side of the module is more, the module compensates more attenuation of the outermost side, fully utilizes the service life of each battery cell and prolongs the service life of the module. The comparison results are shown in fig. 6 and 7.

The capacity calibration was performed for each cell in step (2) of examples 1-3, the capacities at different positions of which are shown in table 1, and the values of m were calculated using the formulas m= (A2-B2) - (A1-B1), respectively, and then the module described in step (3) was involved, and the capacity calibration was performed for each cell in step (4), the capacities at different positions of which are shown in table 2. Wherein A represents initial capacity and B represents capacity of the battery cell after attenuation of the module.

TABLE 1

TABLE 2

Compared with the prior art, the invention prolongs the service life of the module, reduces the use cost of the module, increases extra capacity on the outer layer of the module, and can ensure the service life of the inner layer of the battery core to be fully exerted.

The applicant declares that the above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that are easily conceivable within the technical scope of the present invention disclosed by the present invention fall within the scope of the present invention and the disclosure.

Claims

1. A battery module, characterized in that the module comprises at least three cells connected in series and/or parallel, wherein the cells comprise an outer layer cell and an inner layer cell; the battery cores in the module are arranged in a stacked mode;

the capacity of the outer layer battery core is larger than that of the inner layer battery core;

the capacity of the outer layer cell-the capacity of the inner layer cell = m;

the m calculating method comprises the following steps:

the average initial capacity of the inner layer battery core is A1, the initial capacity of the outer layer battery core is A2, the average residual capacity of the inner layer battery core after charge and discharge cycles is B1, the residual capacity of the outer layer battery core is B2, and m= (A2-B2) - (A1-B1);

a2 is the initial capacity of the cell with the largest capacity difference before and after charge and discharge cycles in the outer cell;

b2 is the residual capacity of the battery cell with the largest capacity difference before and after charge and discharge cycles in the outer battery cell; the inner layer battery cells are all battery cells except the outer layer battery cells.

2. The battery module according to claim 1, wherein the charge in the charge-discharge cycle is constant-current constant-voltage charge.

3. The battery module according to claim 1, wherein the discharge in the charge-discharge cycle is constant-current constant-voltage discharge.

4. The battery module according to claim 1, wherein the charge current in the charge-discharge cycle is 0.05-100 ℃.

5. The battery module according to claim 1, wherein the discharge current in the charge-discharge cycle is 0.05 to 100 ℃.

6. The battery module according to claim 1, wherein the charge voltage in the charge-discharge cycle is 2 to 500v.

7. The battery module according to claim 1, wherein the discharge voltage in the charge-discharge cycle is 16.5 to 25.8v.

8. The battery module according to claim 1, wherein the cutoff condition of the charge-discharge cycle is that the capacity fade of the outer layer cell is 80 to 85%.

9. The battery module of claim 8, wherein the cutoff condition of the charge-discharge cycle is a capacity fade of 80-82% for the outer cells.

10. The battery module of claim 1, wherein the cells comprise any one of soft pack cells, plastic case cells, or aluminum case cells.

11. Use of a battery module according to any one of claims 1-10, wherein the module is used in the field of power batteries.