Battery cell structure and battery

Abstract

The utility model provides a battery cell structure and a battery. The battery cell structure comprises a battery roll core and a flexible rubber mat, and the flexible rubber mat is wound on the outer side of the battery roll core. The flexible rubber mat is further provided with a first thickness section and a second thickness section, and the thickness of the first thickness section is smaller than that of the second thickness section. The first thickness section is specifically wound on the outer side of the battery roll core, and when the battery roll core expands in the radial direction in the charging and discharging process, the first thickness section in direct contact with the battery roll core firstly bears the pressure. And the first thickness section can effectively resist the radial expansion of the battery roll core, so that the risk of foil cracking of the battery pole piece is reduced. The second thickness section is wound on the outer side of the first thickness section, and is used for adjusting the pressure borne by the battery roll core in the battery and adjusting the pressure to the optimal apparent ratio. And the second thickness section plays a role in adjusting the pressure borne by the battery roll core in the battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and more particularly relates to a battery cell structure and a battery. BACKGROUND

[0002] With the rapid development of the new energy industry, the requirements for the cycle life and energy density of batteries are also increasing. With the increase in the cycle number of the battery, the expansion thereof is also more serious. With the increase in the energy density of the battery, the compaction density and surface density of the pole piece are also increased. However, due to the stress change of the material itself and the expansion of the material caused by the electrochemical reaction, the expansion force of the battery is also increased, which can easily lead to problems such as lithium precipitation of the pole piece and pole piece crack foil. CONTENT OF THE UTILITY MODEL

[0003] The purpose of the embodiment of the application is to provide a battery cell structure and a battery to solve the technical problem of the pole piece crack foil in the prior art.

[0004] To achieve the above-mentioned purpose, the technical scheme adopted by the application is:

[0005] A battery cell structure is provided, comprising:

[0006] a battery roll core;

[0007] a flexible rubber pad, which is arranged outside the battery roll core; the flexible rubber pad has a first thickness section and a second thickness section, the thickness of the first thickness section is smaller than that of the second thickness section, the first thickness section is arranged outside the battery roll core, and the second thickness section is arranged outside the first thickness section.

[0008] As a further improvement of the above technical scheme:

[0009] Optionally, the thickness of the first thickness section is 0.2 mm, and the thickness of the second thickness section is 0.7 mm.

[0010] Optionally, the length of the first thickness section accounts for one-third of the total length of the flexible rubber pad, and the length of the second thickness section accounts for two-thirds of the total length of the flexible rubber pad.

[0011] Optionally, the flexible rubber pad is a silica gel flexible rubber pad.

[0012] The application further provides a battery comprising the above-mentioned battery cell structure.

[0013] As a further improvement of the above technical scheme:

[0014] Optionally, the battery comprises a shell having a containing cavity, the battery cell structure is arranged in the containing cavity, and the outer side of the flexible rubber pad is in contact with the shell.

[0015] The electric cell structure and the battery provided by the application have the following advantages:

[0016] The electric cell structure provided by the application comprises a battery roll cell and a flexible rubber pad. The flexible rubber pad is arranged on the outer side of the battery roll cell. The flexible and compressible property of the flexible rubber pad makes the pressure on the battery roll cell in the radial direction be distributed more evenly. On this basis, the flexible rubber pad further comprises a first thickness section and a second thickness section, wherein the thickness of the first thickness section is smaller than the thickness of the second thickness section. The first thickness section is specifically arranged on the outer side of the battery roll cell. When the battery roll cell expands in the radial direction during the charging and discharging process, the first thickness section in direct contact with the battery roll cell will first bear this pressure. By virtue of its flexible and compressible property, the first thickness section can effectively resist the radial expansion of the battery roll cell, thereby reducing the risk of foil cracking of the battery pole piece. The second thickness section is arranged on the outer side of the first thickness section, and the second thickness section is used to adjust the pressure on the battery roll cell in the battery and adjust the pressure to an optimal loose packing ratio. The second thickness section plays a role in adjusting the pressure on the battery roll cell in the battery. By adjusting the thickness of the second thickness section, it can be ensured that the pressure of the battery roll cell in the battery is adjusted to an optimal loose packing ratio, thereby solving the problem of lithium precipitation of the pole piece and further improving the overall performance and stability of the battery.

[0017] The battery provided by the application comprises the above-mentioned electric cell structure, and therefore, the battery also has the advantages of the above-mentioned electric cell structure. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, without creative labor, other drawings can also be obtained from these drawings.

[0019] Figure 1 The partial cross-sectional structure schematic diagram of the battery provided by the application is shown in the figure.

[0020] In the figure, various reference signs:

[0021] 1, battery roll cell; 2, flexible rubber pad; 3, shell. DETAILED DESCRIPTION

[0022] The embodiments of the application will be described in detail below, and the examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the application, and cannot be understood as a limitation of the application.

[0023] In the description of the utility model, it is necessary to understand that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like is the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the utility model and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the utility model.

[0024] In addition, the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the utility model, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0025] In the utility model, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between two elements. For ordinary skilled persons in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0026] In the utility model, unless otherwise specifically defined and limited, the "upper" or "lower" of the first feature in the second feature can include the direct contact of the first and second features, or the indirect contact of the first and second features through another feature between them. Moreover, the "upper", "upper" and "upper" of the first feature in the second feature include the vertical direction of the first feature above and obliquely above the second feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The "below", "below" and "below" of the first feature in the second feature include the vertical direction of the first feature below and obliquely below the second feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0027] In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of ordinary skilled persons in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the scope of the utility model disclosed.

[0028] In the subsequent description, suffixes such as "circuit", "component", "assembly" or "unit" are used only for the convenience of the description of the present application, and do not have a specific meaning in itself. Therefore, they can be used mixedly.

[0029] The present application will be further described in detail below with the specific embodiments in conjunction with the drawings.

[0030] The cylindrical lithium ion battery is mainly composed of a positive electrode, a negative electrode, an electrolyte, a separator and a steel shell. The positive electrode material of the ternary lithium ion battery is generally lithium nickel cobalt manganese oxide. The lithium nickel cobalt manganese oxide has stable crystal structure, and the volume of the crystal lattice is almost zero affected by the lithium ion deintercalation in the charging and discharging process. In addition, the electrolyte and the separator have a small proportion in the battery, and are compressible in itself, so the influence of the lithium ion deintercalation on the negative electrode graphite is mainly considered.

[0031] The negative electrode material graphite has a layered atomic structure, and its electrochemical equation is:

[0032] 6C+xLi++xe - =Li x C6.

[0033] In an ideal state, during charging, lithium ions are deintercalated from the positive electrode and uniformly embedded into the negative electrode graphite; and during discharging, lithium ions are deintercalated from the negative electrode graphite, pass through the separator and are embedded into the positive electrode. In the process of deintercalation of lithium ions, the internal structure of the original layered graphite is not affected, and the gap in the graphite is elastic, so although the lithium ion battery expands and shrinks every cycle, its volume remains unchanged in theory.

[0034] However, in actual situation, when the lithium ions in the positive electrode material are deintercalated and then pass through the separator during charging, they are not uniformly embedded into the negative electrode graphite, and the transport channel of the lithium ions is changing all the time; during discharging, the lithium ions are deintercalated from the negative electrode graphite and then pass through the separator and enter the positive electrode material. At this time, the position of the lithium ions deintercalated in the graphite is different from the position embedded during charging, and the amount of lithium ions embedded and deintercalated is also not equal. In addition, in actual situation, the gap in the layered graphite is not completely elastic. When the lithium ions are embedded into the negative electrode graphite, the original force balance between the graphite layers is destroyed, the repulsive force between the atoms is increased, and thus the graphite expands; when the lithium ions are deintercalated from the negative electrode graphite, the graphite shrinks. Practical experience shows that the total expansion amount of the negative electrode graphite is more than the total shrinkage amount, and finally leads to the fact that the plastic deformation of the negative electrode material is iteratively increased with each charging and discharging cycle.

[0035] The expansion of the negative graphite is superimposed to cause the increase of the diameter of the battery roll core. If the pressure in the radial direction of the battery is uneven, the material on the negative plate will extend to the position where the constraint is weaker, and force the copper foil coated with negative material to extend to the position where the constraint is weaker. The greater the pressure applied (i.e. the loose packing ratio), the more the copper foil is drawn. After two or three hundred charge and discharge cycles, the copper foil is drawn beyond the tensile fatigue strength, thereby causing the negative plate to break.

[0036] To solve the problem of battery plate foil cracking, as shown in Figure 1 The present application provides a battery structure, which specifically comprises a battery roll core 1 and a flexible rubber pad 2.

[0037] The battery roll core 1 is rolled from positive material, negative material, separator, etc. Since the battery roll core 1 can use the existing roll core, its structure and manufacturing process will not be described in detail.

[0038] The key to solving the above problem is to wrap the flexible rubber pad 2 on the outside of the battery roll core 1. The flexible and compressible properties of the flexible rubber pad 2 enable the pressure on the battery roll core 1 in the radial direction to be more evenly distributed. On this basis, the flexible rubber pad 2 also has a first thickness section and a second thickness section, wherein the thickness of the first thickness section is less than the thickness of the second thickness section. The first thickness section is specifically wrapped on the outside of the battery roll core 1. When the battery roll core 1 expands radially during the charge and discharge process, the first thickness section in direct contact with the battery roll core 1 will first bear this pressure. By virtue of its flexible and compressible properties, the first thickness section can effectively resist the radial expansion of the battery roll core 1, thereby reducing the risk of battery plate foil cracking.

[0039] The second thickness section is wrapped on the outside of the first thickness section, and the second thickness section is used to adjust the pressure (i.e. the loose packing ratio) on the battery roll core 1 inside the battery, and adjust the pressure to the optimal loose packing ratio.

[0040] The second thickness section plays a role in adjusting the pressure (i.e. the loose packing ratio) on the battery roll core 1 inside the battery. By adjusting the thickness of the second thickness section, it can be ensured that the pressure of the battery roll core 1 inside the battery is adjusted to the optimal loose packing ratio, thereby solving the problem of lithium precipitation on the plate and further improving the overall performance and stability of the battery.

[0041] In one specific embodiment of the present application, the thickness of the first thickness section is specifically 0.2mm, and the thickness of the second thickness section is specifically 0.7mm, which is most suitable for 21700 type lithium ion batteries.

[0042] In one specific embodiment of the present application, the length of the first thickness section accounts for one third of the total length of the flexible rubber pad 2, and the length of the second thickness section accounts for two thirds of the total length of the flexible rubber pad 2. This length distribution is most suitable for a 21700 model lithium ion battery. For other models of lithium ion batteries, the length distribution of the first thickness section and the second thickness section can be adjusted according to the actual situation according to the different circumference of the winding core.

[0043] In one specific embodiment of the present application, the flexible rubber pad 2 is a silica gel flexible rubber pad. The silica gel flexible rubber pad has good elasticity and deformation recovery ability, and can maintain appropriate softness and good adhesion to the surface of the battery winding core 1 when the pressure changes and the temperature fluctuates.

[0044] The present application also provides a battery comprising the above-mentioned cell structure in the embodiments, and therefore the battery also has the advantages of the cell structure in the above-mentioned embodiments.

[0045] In one specific embodiment of the present application, the battery comprises a shell 3 having a receiving cavity. The cell structure is arranged in the receiving cavity, and the outer side of the flexible rubber pad 2 is in contact with the shell 3, which supports the flexible rubber pad 2.

[0046] The following uses a ternary polymer lithium ion battery with a model number of 21700 to experimentally demonstrate the cell structure of the present application. The capacity of the battery is 5Ah-3C, and the winding process is used, and the separator is a PE film.

[0047] The batteries for experimental testing are divided into four groups, and each group has five batteries. Three groups (labeled as Group 1, Group 2, and Group 3) of batteries are subjected to charge-discharge cycles at a loose packing ratio of 94.0%, 96.0%, and 98.0%, respectively. The other group (i.e., Group 4) of batteries has the cell structure with the flexible rubber pad 2 of the present application and is subjected to charge-discharge cycles at a loose packing ratio of 96.0% (including the flexible rubber pad 2).

[0048] The charge-discharge cycles are performed using a laboratory cycle cabinet. A complete charge-discharge cycle is as follows: in the charging process, first, charge at a constant current of 5A until the voltage reaches 4.2V, then charge at a constant voltage, maintain the voltage at 4.2V, and stop charging when the current decreases to 0.1A. After resting for 10 minutes, discharge at a constant current of 15A until the battery voltage drops to 2.5V, then rest for 45 minutes. This continuous charge-discharge cycle is repeated for 300 experiments.

[0049] After the batteries are disassembled:

[0050] The battery poles of Group 1 have not been broken at all;

[0051] The battery poles of Group 2 have not been broken, but there is a tendency for the tail of the pole to break;

[0052] The tail of the battery pole piece of the 3rd group was almost completely broken. It is known that reducing the pressure is effective in preventing the pole piece from breaking.

[0053] The battery pole piece of the 4th group also did not break completely. It is verified that increasing the flexible rubber pad 2 is effective in preventing the pole piece from breaking.

[0054] It is also found that the surface of the negative pole piece of the 1st group generates a large amount of lithium precipitation, and the lithium precipitation range almost covers the entire negative pole piece; the negative pole pieces of the 2nd, 3rd and 4th groups generate local lithium precipitation, among which the negative pole pieces of the 3rd and 4th groups have a small amount of lithium precipitation, and the negative pole piece of the 2nd group has a large area of lithium precipitation. This shows that appropriately increasing the loose packing ratio can inhibit the occurrence of lithium precipitation.

[0055] At the same time, different loose packing ratios have different effects on the life of the battery. The residual capacity of the four groups of batteries when the charge and discharge times reach 100 and 300 times is shown in Table 1:

[0056] Table 1 Residual capacity of batteries in each experimental group / mAh (design capacity 5000mAh)

[0057] Group 100 weeks 300 weeks Capacity retention rate / % 1 (94% loose packing ratio) 4000 2000 40 2 (96% loose packing ratio) 4500 3500 70 3 (98% loose packing ratio) 1000 0 0 4 (96% loose packing ratio*) 4900 4500 90

[0058] Note: * indicates containing flexible rubber pad 2.

[0059] From the analysis of the data in the table, when the loose packing ratio is 96%, the capacity retention rate is the highest. Too small (94%) or too large (98%) loose packing ratio has an adverse effect on the residual capacity of the battery. The battery with too small loose packing ratio shows a large capacity gap at 300 cycles and maintains a very low capacity, so too small loose packing ratio is not suitable. The two groups of batteries with a loose packing ratio of 96% also have a certain difference in capacity. The 4th group of batteries with increased flexible rubber pad 2 has a significantly higher average residual capacity.

[0060] Therefore, preventing the pole piece from breaking cannot be simply solved by reducing the loose packing ratio of the battery, and the requirement of battery life should also be considered. A higher service life pressure should be applied in the battery.

[0061] From the above comparative experiments, it is known that the pressure with a loose packing ratio of about 96%, combined with the flexible rubber pad 2, not only prevents the battery pole piece from breaking, but also has a relatively better cycle life.

[0062] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A battery cell structure, characterized in that, include: Battery core (1); A flexible pad (2) is wound around the outside of the battery core (1); the flexible pad (2) has a first thickness segment and a second thickness segment, the thickness of the first thickness segment is less than that of the second thickness segment, the first thickness segment is wound around the outside of the battery core (1), and the second thickness segment is wound around the outside of the first thickness segment.

2. The cell structure as described in claim 1, characterized in that, The thickness of the first thickness segment is 0.2 mm, and the thickness of the second thickness segment is 0.7 mm.

3. The cell structure as described in claim 1, characterized in that, The length of the first thickness segment accounts for one-third of the total length of the flexible pad (2), and the length of the second thickness segment accounts for two-thirds of the total length of the flexible pad (2).

4. The cell structure as described in claim 1, characterized in that, The flexible pad (2) is a silicone flexible pad.

5. A battery, characterized in that, Includes the cell structure as described in any one of claims 1 to 4.

6. The battery as described in claim 5, characterized in that, It includes a housing (3) with a cavity, the battery cell structure is disposed in the cavity, and the outer side of the flexible pad (2) is in contact with the housing (3).

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