Battery structure

Abstract

The utility model belongs to the technical field of batteries, and particularly relates to a battery structure which comprises a first battery cell, a partition plate and a second battery cell which are stacked in sequence, the rated capacity of the first battery cell is the same as that of the second battery cell, and pole piece structures of the first battery cell and the second battery cell are respectively composed of a single positive pole piece and a single negative pole piece. The tab structures of the first battery cell and the second battery cell are respectively composed of a pair of single-layer tabs with opposite polarities, and the first battery cell and the second battery cell are connected in series or in parallel. According to the utility model, the battery cell structure is divided into two small battery cells with the same capacity, so that the temperature rise of the battery structure can be effectively reduced, and the safety of the battery structure can be improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of batteries, and particularly relates to a battery structure. Background Art

[0002] Lithium-ion batteries are widely used in power fields such as electric vehicles and consumer fields such as mobile phones, watches, tablets, and laptops because of their advantages of high specific energy, strong endurance, long cycle life, wide working range, short charging time, and large current discharge. With the gradual development of lithium-ion batteries towards fast charging and high energy density fields, the temperature rise problem brought by the battery core has gradually become the focus of attention. In the existing technology, there are no effective improvement measures in the industry at present. At the same time, the current technical capabilities cannot make major breakthroughs, so the improvement of temperature rise is very limited. It can be seen that the overheated temperature in the battery will seriously affect the battery performance and shorten the battery life. Therefore, how to make the battery structure have sufficient safety has become an important difficulty in the battery structure design. For this reason, it is urgent to propose a new technical solution to solve the above problems. Content of the Utility Model

[0003] The purpose of the utility model is to provide a battery structure aiming at the deficiencies of the existing technology, which can effectively reduce the temperature rise of the battery structure and improve the safety of the battery structure.

[0004] In order to achieve the above purpose, the utility model adopts the following technical scheme:

[0005] A battery structure includes a first battery core, a separator, and a second battery core stacked in sequence. The rated capacities of the first battery core and the second battery core are the same. The electrode structure of the first battery core and the second battery core is composed of single positive and negative electrode sheets, and the tab structure of the first battery core and the second battery core is composed of a pair of single-layer tabs with opposite polarities. The first battery core and the second battery core are connected in series or in parallel.

[0006] As an improvement of the battery structure of the utility model, the first battery core and the second battery core are connected in parallel by internal connection of two tabs, or the first battery core and the second battery core are connected in series by one of the internal series connection structures of three tabs or four tabs.

[0007] As an improvement of the battery structure of the utility model, there are tabs on both sides of the central axis in the width direction of the battery structure, and the tabs of the first battery core and the tabs of the second battery core are symmetrically distributed or staggeredly distributed along the width direction of the battery structure.

[0008] As an improvement to the battery structure of the present utility model, the first tab of the first battery cell and the first tab of the second battery cell are both located on one side of the central axis, and the second tab of the first battery cell and the second tab of the second battery cell are both located on the other side of the central axis.

[0009] As an improvement to the battery structure of the present utility model, the first tab and the second tab of the first battery cell are symmetrically distributed along the central axis, and the first tab and the second tab of the second battery cell are symmetrically distributed along the central axis.

[0010] As an improvement to the battery structure of the present utility model, the two tabs of the first battery cell are located on one side of the central axis, and the two tabs of the second battery cell are located on the other side of the central axis.

[0011] As an improvement to the battery structure of the present utility model, at least one of the first battery cell and the second battery cell is a wound battery cell.

[0012] As an improvement to the battery structure of the present utility model, the first battery cell and the second battery cell are formed by dividing a finished battery cell, and the rated capacity of both the first battery cell and the second battery cell is half of the rated capacity of the finished battery cell.

[0013] As an improvement to the battery structure of the present utility model, the internal resistance of each of the first battery cell and the second battery cell is less than twice the internal resistance of the finished battery cell.

[0014] As an improvement to the battery structure of the present utility model, the tab thickness and tab width of both the first battery cell and the second battery cell are less than the tab thickness and tab width of the finished battery cell, and the separator thickness of both the first battery cell and the second battery cell is less than the separator thickness of the finished battery cell.

[0015] As an improvement to the battery structure of the present utility model, the thickness of the separator is 20 μm to 40 μm.

[0016] As an improvement to the battery structure of the present utility model, the first battery cell, the separator, and the second battery cell are all installed in a packaging film, and the first battery cell, the separator, and the second battery cell are all fixed to the inner wall of the packaging film.

[0017] As an improvement to the battery structure of the present utility model, both the first battery cell and the second battery cell are lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries.

[0018] The beneficial effects of the present utility model are as follows: 1) The present utility model includes a first battery cell, a separator, and a second battery cell stacked in sequence. The rated capacities of the first battery cell and the second battery cell are the same. The electrode structure of both the first battery cell and the second battery cell is composed of single positive and negative electrode sheets, and the tab structure of both the first battery cell and the second battery cell is composed of a pair of single-layer tabs with opposite polarities. When the first battery cell and the second battery cell are connected in parallel with two tabs inside, the current of each battery cell is effectively reduced to control the heat generated during charge and discharge, ensuring the working temperature of the battery cell and avoiding the influence of long-term operation of the battery cell in a high-temperature environment on its performance and lifespan. When the first battery cell and the second battery cell are connected in series, the heat of each single battery cell is effectively reduced, thus effectively controlling the working temperature of the battery cell; 2) By splitting one battery cell into two battery cells in the present utility model, at the same charging current, the current distributed to the two battery cells is only 1 / 2 of the original. According to the formula Q = I 2 Rt, it can be known that the heat generated by a single battery cell can become 1 / 4 of the original, thereby effectively reducing the heat generated by the battery; 3) Moreover, after splitting into two battery cells, since the capacities of the two battery cells are only half of the original, the heat generation caused by battery failure is easier to control, and at the same time, the safety performance of the battery cell is effectively improved. Description of the Drawings

[0019] Figure 1 It is one of the schematic structural diagrams of Embodiment 1 of the present utility model.

[0020] Figure 2 It is the second schematic structural diagram of Embodiment 1 of the present utility model.

[0021] Figure 3 It is one of the schematic structural diagrams of Embodiment 2 of the present utility model.

[0022] Figure 4 It is the second schematic structural diagram of Embodiment 2 of the present utility model.

[0023] Figure 5 It is the assembly schematic diagram of the present utility model.

[0024] Wherein: 1. First battery cell; 2. Second battery cell; 3. Separator; 4. First tab; 5. Second tab; 6. Packaging film; 61. First encapsulation film; 62. Second encapsulation film; T. Width direction of the battery structure. Detailed Embodiments

[0025] As certain terms are used in the specification and claims to refer to specific components, those skilled in the art should understand that manufacturers may use different names to refer to the same component. The specification and claims do not use the difference in names as a way to distinguish components, but rather use the difference in the functions of components as the criterion for distinction. As the term "comprising" mentioned throughout the specification and claims is an open-ended term, it should be interpreted as "comprising but not limited to". In the utility model, unless otherwise clearly specified and limited, terms such as "installed", "connected", "joined", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0026] According to Q = I 2 Rt formula, it can be known that the temperature rise is related to three parameters: charging current, internal resistance, and time. However, due to the fast charging requirement, the time parameter is basically a constant; therefore, the direction of the prior art is to reduce the overall internal resistance of the battery cell to achieve the method of reducing the temperature rise. However, the inventor found that: 1) At present, the internal resistance of the battery cell is already very small, and the reduction range is very limited, so the improvement of reducing the temperature rise is very limited; 2) Since the existing products have a large demand for capacity, this will cause the length of the electrode tabs of the subsequent battery cells to become longer and longer, and the internal resistance control will become more and more difficult. Only controlling the temperature rise by the internal resistance has little effect; 3) At the same time, the reduction of the impedance will lead to the need to re-develop the corresponding system, which causes the original system to be unable to be directly used, and the development difficulty and time are greatly increased, increasing the R & D cost. Therefore, the present application optimizes the heat generation situation of the battery through a structure that more effectively reduces the battery temperature rise.

[0027] The following combines the attached Figures 1 to 5 drawings and specific embodiments to further elaborate on the present utility model in detail, but it does not limit the present utility model.

[0028] Embodiment 1

[0029] A battery structure, see Figures 1 to 2 , including a first battery cell 1, a separator 3, and a second battery cell 2 stacked in sequence. The first battery cell 1 and the second battery cell 2 have the same rated capacity. The electrode tab structures of the first battery cell 1 and the second battery cell 2 are both composed of single positive and negative electrode tabs. The tab structures of the first battery cell 1 and the second battery cell 2 are both composed of a pair of single-layer tabs with opposite polarities, and moreover, the tabs are connected to the electrode tabs with the same polarity. The first battery cell 1 and the second battery cell 2 are connected in parallel by the two tabs inside to complete the external connection.

[0030] Specifically, this solution aims at the formula Q = I2 Improve the current I in Rt. When two battery cells are connected in parallel for current sharing, the temperature rise can be effectively reduced. Therefore, in this embodiment, one battery cell is split into two small battery cells and then the two small battery cells are connected in parallel. At the same charging current, the current distributed to the two small battery cells is only 1 / 2 of the original. According to the formula Q = I 2 Rt, the heat generation of a single small battery cell can become 1 / 4 of the original.

[0031] Moreover, when designing the structure of the battery, a finished battery cell can be selected first, and then the first battery cell 1 and the second battery cell 2 are formed by splitting the finished battery cell. It should be noted that the rated capacities of the first battery cell 1 and the second battery cell 2 are both half of the rated capacity of the finished battery cell to ensure battery cell matching. When the first battery cell 1 and the second battery cell 2 are combined into a new battery cell, the energy density of the integrated battery is lossless, and the internal resistances of the first battery cell 1 and the second battery cell 2 are respectively less than 2 times the internal resistance of the finished battery cell.

[0032] In addition, under the same current condition, the single-cell DC impedances of the first battery cell 1 and the second battery cell 2 can be no greater than 1.34 - 2 times the DC impedance of the finished battery cell.

[0033] For example: For a battery with a single finished battery cell of model 416386, the rated capacity of this finished battery cell is 4381.5 Ah, and the internal resistance of this finished battery cell is 14.3 Ω. After splitting this finished battery cell into the first battery cell 1 and the second battery cell 2 with the same rated capacity, the total internal resistance of the first battery cell 1 and the second battery cell 2 will increase by 8.39% compared to the internal resistance of the previous finished battery cell, that is, the total internal resistance is about 1.09 times the internal resistance of the finished battery cell, and the total DC impedance of the first battery cell 1 and the second battery cell 2 will increase by 33.33% compared to the DC impedance of the previous finished battery cell.

[0034] Among them, Q 1 = I 2 R = (I / 2)2(1.08R + 1.08R) = 0.54I 2 R, Q 2 = I 2 R = (I / 2)2(1.33R + 1.33R) = 0.66I 2R, that is, the combined heat generation of the new battery cell formed by combining the first battery cell 1 and the second battery cell 2 is 54%-66% of the original. Therefore, the heat generation of the combined new battery cell is reduced by at least ≥34%. According to the above data, after the pole piece is cut in half, the internal resistance does not increase by 1 time. At the same time, according to the experimental data, the total internal resistance only increases by about 8%, and the total DC resistance only increases by about 33%. At the same time, the heat dissipation of the battery cell also changes from the 2 surfaces of the original single battery cell to the 4 surfaces of the two battery cells for heat dissipation, which can increase the heat dissipation area and make the surface temperature of the battery cell lower. It can be seen that after being split into two battery cells, because the capacities of the two battery cells are only half of the original, the heat generation during failure is easier to control, and at the same time, the safety performance of the battery cell is also effectively improved.

[0035] In addition, due to the reduced capacity and halved current, the tab thickness and width of the first battery cell 1 and the second battery cell 2 can be thinned, thereby thinning the tab position thickness at the head of the battery cell. At the same time, a smaller slot design for the tab slot can narrow the width of the tab slot due to the narrowing of the tab to reduce capacity loss; and because the battery cell capacity is halved and the safety performance is improved, the thickness design of the separator can also be thinned, which can reduce the battery cell thickness and improve the energy density of the battery.

[0036] Specifically, the tab thicknesses of the first battery cell 1 and the second battery cell 2 are both smaller than the tab thickness of the finished battery cell, the tab widths of the first battery cell 1 and the second battery cell 2 are both smaller than the tab width of the finished battery cell, and the separator thicknesses of the first battery cell 1 and the second battery cell 2 are both smaller than the separator thickness of the finished battery cell.

[0037] In addition, since the pole piece lengths of the first battery cell 1 and the second battery cell 2 can be half of the pole piece length of the original single finished battery cell, the overall polarization of the combined new battery cell is smaller. The electrochemical window after the parallel connection of the first battery cell 1 and the second battery cell 2 can be adjusted to be the same as the electrochemical window of the original single finished battery cell by increasing the areal density and using a compaction method, so as to further improve the energy density of the battery cell. Among them, after the battery cell capacity becomes smaller, the electrochemical window and safety performance are significantly improved; at the same time, according to the actual needs of the battery cell, the excess performance can be converted into energy density.

[0038] Preferably, there are tabs on both sides of the central axis in the width direction T of the battery structure, and the tabs of the first battery cell 1 and the tabs of the second battery cell 2 are symmetrically distributed along the width direction T of the battery structure.

[0039] Preferably, the first tab 4 of the first battery cell 1 and the first tab 4 of the second battery cell 2 are both located on one side of the central axis, and the two first tabs 4 are welded and connected in parallel. The second tab 5 of the first battery cell 1 and the second tab 5 of the second battery cell 2 are both located on the other side of the central axis, and the two second tabs 5 are welded and connected in parallel. The first tab 4 is the positive tab, and the second tab 5 is the negative tab.

[0040] Preferably, the thickness of the separator 3 can be 20 μm - 25 μm, 25 μm - 30 μm, 30 μm - 35 μm, or 35 μm - 40 μm. Moreover, the thinner the thickness of the separator 3 separating the two battery cells, the better. Since the separator 3 between the first battery cell 1 and the second battery cell 2 does not participate in the pit punching, and this separator 3 is only located inside the battery and has no contact with the outside world, the separator 3 can be formed by simply bonding a CPP film and the upper and lower layers of aluminum-plastic films together with an adhesive. The separator 3 can adopt a single-layer film with a thickness of about 30 μm to effectively reduce the capacity loss.

[0041] Preferably, the first battery cell 1, the separator 3, and the second battery cell 2 are all installed inside the packaging film 6, and the first battery cell 1, the separator 3, and the second battery cell 2 are all fixed to the inner wall of the packaging film 6. Among them, at least part of the first battery cell 1, the separator 3, and the second battery cell 2 can be bonded to the inner wall of the packaging film 6 with an adhesive, and the left and right sides of the separator 3 can also be fusion-sealed with the inner wall of the packaging film 6 under suitable high-temperature conditions.

[0042] Specifically, referring to Figure 5 , the packaging film 6 can be heat-sealed from a first packaging film 61 and a second packaging film 62. Both the first packaging film 61 and the second packaging film 62 are aluminum-plastic films. The positions of each battery cell can be defined by these two aluminum-plastic films. The contact surfaces between each aluminum-plastic film and the battery cell can be bonded and fixed with a solid adhesive or a liquid adhesive. Moreover, the pit depths of the first packaging film 61 and the second packaging film 62 are the same, but the lengths of the air bags of the first packaging film 61 and the second packaging film 62 are designed differently, and the two air bags can be staggered. This is mainly to effectively monitor the liquid injection and liquid retention during the subsequent sample preparation process, ensure the quality and performance of each battery cell. In addition, after the battery is encapsulated, the first packaging film 61 and the second packaging film 62 can be adjusted to a structure with basically the same size. The battery structure after the battery is encapsulated is composed of two independent small battery cells spliced together, and the two small battery cells are connected externally and used as one battery cell.

[0043] Preferably, at least one of the first battery cell 1 and the second battery cell 2 is a wound battery cell. Since both the first battery cell 1 and the second battery cell 2 are composed of a single positive and negative electrode sheet and a single-layer tab, that is, the structures of both the first battery cell 1 and the second battery cell 2 are neither a stacked structure with more than two electrode sheets stacked nor a multi-tab battery cell structure. Both the first battery cell 1 and the second battery cell 2 can be formed by stacking a positive electrode sheet connected to the first tab 4, a separator, and a negative electrode sheet connected to the second tab 5 and then winding them.

[0044] Example 2

[0045] Different from Example 1, referring to Figures 3 to 4On both sides of the central axis in the width direction T of the battery structure, there are pole ears, and the pole ears of the first battery cell 1 and the pole ears of the second battery cell 2 are staggered along the width direction T of the battery structure.

[0046] Preferably, the first pole ears 4 of the first battery cell 1 and the first pole ears 4 of the second battery cell 2 are both located on one side of the central axis, and the second pole ears 5 of the first battery cell 1 and the second pole ears 5 of the second battery cell 2 are both located on the other side of the central axis.

[0047] In this embodiment, since it is considered that if the adhesive tape and the pole ears in the thickness direction of the battery structure overlap, it will affect the integration space of the battery, so in this embodiment, the pole ear lead-out positions of the two battery cells are different, so that the pole ears of the two battery cells connected in parallel do not overlap, that is, the positions of the adhesive tapes of the different pole ears in the thickness direction of the battery structure in Embodiment 1 are adjusted at the same time, so that the like-polarity pole ears of the two battery cells are staggered.

[0048] The other structures of this embodiment are the same as those of Embodiment 1 and will not be described in detail here.

[0049] Embodiment 3

[0050] Different from Embodiments 1-2, on both sides of the central axis in the width direction T of the battery structure of this embodiment, there are pole ears, and the pole ears of the first battery cell 1 and the pole ears of the second battery cell 2 are staggered along the width direction T of the battery structure. Moreover, the two pole ears of the first battery cell 1 are located on one side of the central axis, and the two pole ears of the second battery cell 2 are located on the other side of the central axis. Although the pole ears are staggered, the first battery cell 1 and the second battery cell 2 can also be connected in parallel for current sharing.

[0051] The other structures of this embodiment are the same as those of Embodiments 1-2 and will not be described in detail here.

[0052] Embodiment 4

[0053] Different from Embodiments 1-3, the first battery cell 1 and the second battery cell 2 are connected in series by adopting one of a three-pole-ear internal series structure and a four-pole-ear internal series structure to complete the external connection. By splitting the large battery cell structure into two small battery cells with the same capacity, through structural regulation, the heat of a single battery cell is reduced, which can effectively reduce the temperature rise of the battery structure and improve the safety of the battery structure. At the same time, the series connection and parallel connection of the two small battery cells can obtain approximate or even the same experimental data, which effectively verifies the feasibility of this solution.

[0054] Generally speaking, the way to reduce the temperature rise of the battery cell in the prior art is that the structure of the battery cell remains unchanged, that is, the battery cell is still a single battery cell. The main way to reduce the temperature of this single battery cell is to reduce the internal resistance of the battery cell system. However, at present, the internal resistance of the battery cell is in the range of 10-20 mΩ, and the DC impedance is in the range of 30-50 mΩ. At present, its impedance is already very small, and the reduction range is very limited, so the reduction of the temperature rise is also very limited.

[0055] Compared with the prior art, 1) the present utility model adjusts the temperature rise by changing the structure, and the combined heat generation of the two small battery cells can be reduced by about 34%, that is, the present utility model significantly improves the temperature rise; 2) at the same time, the present utility model only changes the structure, so that the original developed and mature system can be directly substituted and used, and the R & D difficulty and time will be greatly reduced, and the R & D cost will be effectively reduced; 3) under the same charge and discharge power, the present utility model controls the heat generation by reducing the current through shunting to ensure the working temperature of the battery cell, thereby ensuring the performance and life of the battery cell; 4) the two battery cells after splitting of the present utility model are significantly improved in terms of polarization and safety, and the excess performance can be converted into energy density according to the actual project requirements in the future; therefore, this application optimizes and controls the heat generation situation of the battery through a structure that more effectively reduces the battery temperature rise, and effectively improves the safety of the battery structure.

[0056] According to the disclosure and teachings of the above specification, those skilled in the art of the present utility model can also make changes and modifications to the above embodiments. Therefore, the utility model is not limited to the above specific embodiments, and any obvious improvements, substitutions or variations made by those skilled in the art on the basis of the present utility model belong to the protection scope of the present utility model. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present utility model.

Claims

1. A battery structure, characterized in that: include: A first battery cell (1), a separator (3), and a second battery cell (2) stacked in sequence; The first battery cell (1) and the second battery cell (2) have the same rated capacity; The electrode structure of the first battery cell (1) and the second battery cell (2) are both composed of a single positive and negative electrode; The tab structures of the first battery cell (1) and the second battery cell (2) are both composed of a pair of single-layer tabs with opposite polarities; The first battery cell (1) and the second battery cell (2) are connected in series or in parallel.

2. The battery structure according to claim 1, characterized in that: Both sides of the central axis in the width direction of the battery structure are provided with pole lugs, and the pole lugs of the first battery cell (1) and the pole lugs of the second battery cell (2) are symmetrically distributed or staggered along the width direction of the battery structure.

3. The battery structure according to claim 2, characterized in that: The first pole lug of the first battery cell (1) and the first pole lug of the second battery cell (2) are both located on one side of the central axis, and the second pole lug of the first battery cell (1) and the second pole lug of the second battery cell (2) are both located on the other side of the central axis.

4. The battery structure according to claim 2, characterized in that: The two pole lugs of the first battery cell (1) are located on one side of the central axis, and the two pole lugs of the second battery cell (2) are located on the other side of the central axis.

5. The battery structure according to any one of claims 1 to 4, characterized in that: At least one of the first battery cell (1) and the second battery cell (2) is a wound battery cell.

6. The battery structure according to any one of claims 1 to 4, characterized in that: The first battery cell (1) and the second battery cell (2) are obtained by dividing finished battery cells, and the rated capacity of the first battery cell (1) and the second battery cell (2) are both half of the rated capacity of the finished battery cell.

7. The battery structure according to claim 6, characterized in that: The internal resistance of each of the first battery cell (1) and the second battery cell (2) is less than twice the internal resistance of the finished battery cell.

8. The battery structure according to claim 6, characterized in that: The tab thickness and tab width of the first battery cell (1) and the second battery cell (2) are both smaller than the tab thickness and tab width of the finished battery cell, and the diaphragm thickness of the first battery cell (1) and the second battery cell (2) are both smaller than the diaphragm thickness of the finished battery cell.

9. The battery structure according to any one of claims 1 to 4, characterized in that: The thickness of the separator (3) is 20 μm to 40 μm.

10. The battery structure according to any one of claims 1 to 4, characterized in that: The first battery cell (1), the partition (3) and the second battery cell (2) are all installed in a packaging film (6), and the first battery cell (1), the partition (3) and the second battery cell (2) are all fixed to the inner wall of the packaging film (6).

Images