Lithium ion cell and lithium ion battery

Abstract

The utility model relates to the field of lithium ion batteries, and discloses a lithium ion battery cell and a lithium ion battery. The lithium ion battery cell comprises a naked battery cell and a heat insulation structure layer arranged on the outermost layer of the naked battery cell, the heat insulation structure layer comprises a heat insulation layer, a current collector and an active substance layer, the heat insulation layer and the active substance layer are connected to the two side faces of the current collector respectively, and the active substance layer faces one side of the naked battery cell. According to the utility model, the heat insulation structure layer is arranged on the outermost layer of the naked battery cell, so that heat transfer between the outside and the inside of the battery cell can be reduced on the basis of not influencing a chemical system, and the internal chemical system is prevented from being influenced by environment temperature rise. The pressure of a chemical system is reduced, so that the safety of the lithium battery is improved. Besides, for the lamination structure, the coating of the heat insulation layer on the single surface of the current collector can enable the outermost two layers of pole pieces to be used as the ending of the positive pole pieces, the energy density of the battery cell is improved, and the stress concentration can be reduced when the pole pieces are rolled, so that the processing performance of the process is improved.

Description

Technical Field

[0001] The utility model relates to the field of lithium ion batteries, and in particular to a lithium ion battery cell and a lithium ion battery. Background Art

[0002] Lithium batteries are widely used in 3C, power batteries, energy storage grids and other fields. As people demand high energy density, fast charging and long life, the safety issues of lithium batteries are gradually exposed.

[0003] The most commonly designed lithium battery structures are winding and stacking structures. The outermost layer of the winding is aluminum foil or copper foil coated with active material on one side. The stacking structure is similar, and the outermost two layers are also aluminum foil or copper foil coated with active material on one side.

[0004] There are many safety issues caused by improper use of lithium batteries. For example, long-term use in harsh environments (high temperature environments) can cause the internal diaphragm of the battery to shrink, the positive and negative electrodes to short-circuit, the positive electrode to release oxygen, and the positive and negative electrode materials to react with the electrolyte, generating a large amount of heat, which in turn causes thermal runaway as the temperature rises.

[0005] In power batteries or modules that require multiple cell packs to be assembled, all cells are placed face to face. When charging, it is very easy for heat to accumulate on the large surface of the cell, which can cause thermal failure of the cell. How to effectively isolate the ambient temperature is the most direct and effective means to protect lithium batteries from thermal runaway.

[0006] The improvements that have been made so far are:

[0007] Improvements at the module level: Control the thermal runaway range of the module. In short, when a single cell is thermally abused, the heat diffusion of the failed cell can be blocked so that it does not affect other cells in the module. Thermal abuse is the last link that triggers thermal runaway. The excessive temperature outside the cell causes an exothermic chemical reaction in the internal materials of the cell, which in turn causes failure. The current measure is to isolate or wrap the cell with materials that have thermal insulation or flame retardant effects. Reported thermal insulation materials include aerogel, mica, glass fiber, porous thermal materials, etc. This is an improvement at the module level. The cell will still fail and the fundamental problem has not been solved. The most essential way to solve thermal runaway is to solve failures at the cell level.

[0008] Improvements at the cell level: Researchers have improved the safety of the cell by modifying the positive electrode material, coating the current collector, and adding flame retardant additives to the electrolyte. Application No. 201610220432.2 discloses a pole piece coated with a heat-insulating material between the current collector and the active material material, which can reduce heat transfer between the current collector and the active material layer, but this will increase the resistance of the pole piece membrane, thereby affecting the cycle performance. Application No. 201110460390.7 discloses that by adding phosphazene flame retardant additives to the electrolyte, the battery can capture oxygen free radicals and hydroxyl free radicals under high temperature conditions to achieve a flame retardant effect, but it affects low-temperature discharge.

[0009] It can be seen that the current improvement methods cannot meet the requirements of reducing heat transfer between the outside and the inside of the battery cell and reducing the pressure of the chemical system to improve the safety of lithium batteries without affecting the chemical system.

[0010] In view of this, the present utility model is proposed. Utility Model Content

[0011] The utility model aims to provide a lithium ion battery cell and a lithium ion battery.

[0012] The embodiment of the utility model is achieved as follows:

[0013] In a first aspect, the utility model provides a lithium-ion battery cell, which includes a bare battery cell and a thermal insulation structure layer arranged on the outermost layer of the bare battery cell, the thermal insulation structure layer includes a thermal insulation layer, a current collector and an active material layer, the thermal insulation layer and the active material layer are respectively connected to the two side surfaces of the current collector, and the active material layer faces one side of the bare battery cell.

[0014] In an optional embodiment, the thickness of the thermal insulation layer is 50-1000 μm.

[0015] In an optional embodiment, the thickness of the active material layer is 5-300 μm.

[0016] In an optional embodiment, the thermal insulation layer is made of aerogel.

[0017] In an optional embodiment, the current collector is aluminum foil or copper foil.

[0018] In an optional embodiment, the bare battery cell includes a laminated structure battery cell or a wound structure battery cell.

[0019] In an optional embodiment, the laminated structure battery cell includes a plurality of first positive electrodes, a plurality of first negative electrodes and a continuous membrane layer arranged in a Z shape, the plurality of first positive electrodes and the plurality of first negative electrodes are alternately sandwiched between the continuous membrane layers, and the thermal insulation structure layer is arranged at the bottom and top layers of the laminated structure battery cell.

[0020] In an optional embodiment, the surface of the thermal insulation structure layer is also coated with the continuous film layer of the diaphragm.

[0021] In an optional embodiment, the wound structure battery cell is a strip structure formed by stacking a second positive electrode, a first separator layer, a negative electrode and a second separator layer and winding them, the thermal insulation structure layer is connected to the winding end of the second negative electrode, the current collector in the thermal insulation structure layer is connected to the current collector in the second negative electrode, the active material layer in the thermal insulation structure layer is connected to the active material layer in the inner layer of the second negative electrode, and the thermal insulation layer in the thermal insulation structure layer is connected to the active material layer in the outer layer of the second negative electrode.

[0022] In a second aspect, the utility model provides a lithium-ion battery, which includes a lithium-ion battery cell as described in any one of the aforementioned embodiments.

[0023] The beneficial effects of the embodiments of the utility model are:

[0024] The lithium-ion battery cell provided by the utility model is provided with a heat-insulating structural layer on the outermost layer of the bare battery cell. The introduction of the heat-insulating structural layer can reduce the heat transfer between the outside and the inside of the battery cell without affecting the chemical system. When the external ambient temperature rises, the temperature difference between the inside and the outside of the battery cell is maintained at more than 50°C, ensuring that the internal chemical system is not affected by the increase in ambient temperature. Reduce the pressure of the chemical system to improve the safety of the lithium battery. In addition, for the stacked structure, the coating of the heat-insulating layer on one side of the current collector can make the outermost two layers of pole pieces serve as the positive pole pieces, thereby improving the energy density of the battery cell. In addition, the coating of the heat-insulating layer can reduce the concentration of stress on the pole pieces during rolling, thereby improving the process performance. The lithium-ion battery prepared from the above-mentioned lithium-ion battery cell has good safety and is easy to process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the utility model and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1A schematic diagram of the structure of a lithium-ion battery cell when the bare battery cell provided in an embodiment of the utility model is a laminated structure battery cell;

[0027] Figure 2 A schematic diagram of the structure of the heat insulation structure layer provided in an embodiment of the utility model;

[0028] Figure 3 A schematic diagram of the structure of a lithium-ion battery cell when the bare battery cell provided in an embodiment of the utility model is a wound structure battery cell;

[0029] Figure 4 A schematic diagram of the connection between the heat insulating structure layer and the second negative electrode when the bare battery cell provided in an embodiment of the utility model is a wound structure battery cell.

[0030] Icon: 100-lithium-ion battery cell; 110-bare battery cell; 111-laminated structure battery cell; 1111-first positive electrode; 1112-first negative electrode; 1113-continuous separator layer; 112-wound structure battery cell; 1121-second positive electrode; 1122-first separator layer; 1123-second negative electrode; 1124-second separator layer; 120-thermal insulation structure layer; 121-thermal insulation layer; 122-current collector; 123-active material layer. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Generally, the components of the embodiments of the utility model described and shown in the drawings here can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention to be protected, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0034] In the description of the present utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings, or the orientation or position relationship in which the utility model product is usually placed when in use, which is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0035] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0036] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" 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 a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] Example

[0038] See also Figure 1 and Figure 2 This embodiment proposes a lithium-ion battery cell 100, which includes a bare battery cell 110 and a thermal insulation structure layer 120 arranged on the outermost layer of the bare battery cell 110, the thermal insulation structure layer 120 includes a thermal insulation layer 121, a current collector 122 and an active material layer 123, the thermal insulation layer 121 and the active material layer 123 are respectively connected to the two side surfaces of the current collector 122, and the active material layer 123 faces one side of the bare battery cell 110.

[0039] In this embodiment, the thermal insulation structure layer 120 in this embodiment is formed by connecting the thermal insulation layer 121 to the other side of the aluminum foil or copper foil coated with active material material on one side, wherein the thickness of the thermal insulation layer 121 is 50-1000 μm, and the thickness of the active material layer 123 is 5-300 μm. Among them, the active material layer 123 can be a coating formed by a positive electrode active material, or a coating formed by a negative electrode active material. The specific selection of the active material layer 123 can be determined according to the specific requirements during the preparation of the battery cell. The material of the thermal insulation layer 121 is aerogel. The current collector 122 is made of conventional materials, such as aluminum foil or copper foil.

[0040] When preparing the thermal insulation structure layer 120, if the material of the thermal insulation layer 121 and the material of the active material layer 123 are in liquid state, the material of the thermal insulation layer 121 and the material of the active material layer 123 can be coated on the current collector 122 and dried. If the material of the thermal insulation layer 121 and the material of the active material layer 123 are in sheet form, the material of the thermal insulation layer 121 and the material of the active material layer 123 can be directly connected to the current collector 122 by pressing or bonding. The specific preparation process can be adjusted according to actual conditions.

[0041] The bare cell 110 includes a laminated cell 111 or a wound cell 112. For cells of different structures, this embodiment provides different connection methods of the heat insulation structure layer 120.

[0042] Specifically, see Figure 1 For the laminated structure battery cell 111, the laminated structure battery cell 111 includes a plurality of first positive electrodes 1111, a plurality of first negative electrodes 1112 and a continuous diaphragm layer 1113 arranged in a Z shape, the plurality of first positive electrodes 1111 and the plurality of first negative electrodes 1112 are alternately sandwiched between the continuous diaphragm layers 1113, and the thermal insulation structure layer 120 is arranged at the bottom and top of the laminated structure battery cell 111. Among them, the active material layer 123 faces one side of the laminated structure battery cell 111, providing lithium insertion and removal functions; the thermal insulation layer 121 is the outermost layer of the bare battery cell 110, which plays a role in isolating external heat conduction. The surface of the thermal insulation structure layer 120 (that is, the thermal insulation layer 121) can be coated with the continuous diaphragm layer 1113, or it can be not coated. The specific coating situation can be selected according to the actual situation.

[0043] For example, in a typical embodiment, when the laminated structure battery cell 111 ends with a positive electrode, the top and bottom surfaces of the laminated structure battery cell 111 are both the first positive electrode 1111. The thermal insulation structure layer 120 includes a 200 μm thermal insulation layer 121, a current collector 122, and a 100 μm active material layer 123. The thermal insulation layer 121 and the active material layer 123 are respectively connected to the two side surfaces of the current collector 122. In this embodiment, the material of the active material layer 123 is a cathode active material, and the cathode active material layer 123 faces the side with the anode active material layer 123. The thermal insulation structure layer 120 is arranged at the bottom and top layers of the laminated structure battery cell 111.

[0044] It should be understood that in other embodiments, the laminated structure battery cell 111 may also be finished with a negative electrode, and the specific material selection of the active material layer 123 in the thermal insulation structure layer 120 is determined based on actual conditions.

[0045] See also Figure 3 and Figure 4 For the wound structure battery cell 112, the wound structure battery cell 112 is a strip structure formed by stacking the second positive electrode 1121, the first diaphragm layer 1122, the second negative electrode 1123 and the second diaphragm layer 1124 and winding them, the thermal insulation structure layer 120 is connected to the winding end of the second negative electrode 1123, the current collector 122 in the thermal insulation structure layer 120 is connected to the current collector 122 in the second negative electrode 1123, the active material layer 123 in the thermal insulation structure layer 120 is connected to the active material in the inner layer of the second negative electrode 1123, and the thermal insulation layer 121 in the thermal insulation structure layer 120 is connected to the active material in the outer layer of the second negative electrode 1123.

[0046] For example, in a typical embodiment, when the wound structure battery cell 112 ends with a negative electrode, the thermal insulation structure layer 120 is located at the outermost layer of the winding for termination. In this embodiment, the thermal insulation structure layer 120 includes a 50μm thermal insulation layer 121, a current collector 122, and a 300μm active material layer 123. Specifically, the thermal insulation structure layer 120 is connected to the winding end of the second negative electrode 1123, the current collector 122 in the thermal insulation structure layer 120 is connected to the current collector 122 in the second negative electrode 1123, the active material layer 123 in the thermal insulation structure layer 120 is connected to the active material of the inner layer of the second negative electrode 1123, and the thermal insulation layer 121 in the thermal insulation structure layer 120 is connected to the active material of the outer layer of the second negative electrode 1123.

[0047] It should be understood that, in other embodiments, the wound structure battery cell 112 may also be terminated with a second positive electrode 1121 , and the thermal insulation structure layer 120 is correspondingly connected to the winding end of the second positive electrode 1121 .

[0048] In addition, it should be noted that the positive electrodes in this embodiment are made by coating positive electrode active materials on both sides of the current collector. Similarly, the negative electrodes are made by coating negative electrode active materials on both sides of the current collector.

[0049] In this embodiment, the introduction of the heat insulation structure layer 120 can reduce the heat transfer between the outside and the inside of the battery cell without affecting the chemical system. When the external environment temperature rises, the temperature difference between the inside and the outside of the battery cell is maintained at more than 50°C, ensuring that the internal chemical system is not affected by the increase in ambient temperature. The pressure of the chemical system is reduced to improve the safety of the lithium battery.

[0050] In addition, in the current technical solution, compared with winding, lamination has more prominent process problems due to the existence of single-sided coated pole pieces. When it is rolled, the occurrence of stress concentration will cause the pole piece to curl up and cannot enter the next process-strip die-cutting. In order to improve the energy density, 3C often uses a single-sided positive electrode finishing. Generally, NMP is used to infiltrate the single-sided coated positive electrode material surface after rolling to release stress. The introduction of the NMP coating process increases time and labor costs, and the effect is unstable; power batteries do not have excessive demands for energy density, and are generally negative electrode finishing, and stress is released by hot pressing, or double-sided coating of negative electrode materials is used to balance. Hot pressing requires the introduction of a hot press, which is costly. Double-sided coating of active materials will also increase costs. The lithium-ion battery cell 100 provided in this embodiment, by providing a thermal insulation structure layer 120, can not only reduce the heat transfer between the outside and the inside of the battery cell without affecting the chemical system, but also improve the subsequent processes to a certain extent. The coating of the thermal insulation layer 121 on one side of the current collector 122 can make the outermost two layers of the pole pieces serve as the positive pole pieces, thereby improving the energy density of the battery cell. In addition, the coating of the thermal insulation layer 121 can reduce the stress concentration of the pole pieces during rolling, thereby improving the process performance.

[0051] In summary, the lithium-ion battery cell 100 provided by the utility model is provided with a heat-insulating structural layer 120 on the outermost layer of the bare battery cell 110. The introduction of the heat-insulating structural layer 120 can reduce the heat transfer between the outside and the inside of the battery cell without affecting the chemical system. When the external ambient temperature rises, the temperature difference between the inside and the outside of the battery cell is maintained at more than 50°C, ensuring that the internal chemical system is not affected by the increase in ambient temperature. Reduce the pressure of the chemical system to improve the safety of the lithium battery. In addition, for the laminated structure, the coating of the heat-insulating layer 121 on one side of the current collector 122 can make the outermost two layers of the pole pieces end as positive pole pieces, thereby improving the energy density of the battery cell. In addition, the coating of the heat-insulating layer 121 can reduce the concentration of stress on the pole pieces during rolling, thereby improving the process performance. The lithium-ion battery prepared by the above-mentioned lithium-ion battery cell 100 has good safety and is easy to process.

[0052] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A lithium-ion battery cell, characterized in that: It includes a bare battery core and a heat-insulating structure layer arranged on the outermost layer of the bare battery core, the heat-insulating structure layer includes a heat-insulating layer, a current collector and an active material layer, the heat-insulating layer and the active material layer are respectively connected to the two side surfaces of the current collector, and the active material layer faces one side of the bare battery core.

2. The lithium-ion battery cell according to claim 1, characterized in that: The thickness of the heat insulation layer is 50-1000 μm.

3. The lithium-ion battery cell according to claim 1, characterized in that: The thickness of the active material layer is 5-300 μm.

4. The lithium-ion battery cell according to claim 1, characterized in that: The material of the heat insulation layer is aerogel.

5. The lithium-ion battery cell according to claim 1, characterized in that: The current collector is aluminum foil or copper foil.

6. The lithium-ion battery cell according to any one of claims 1 to 5, characterized in that: The bare battery cell includes a laminated structure battery cell or a wound structure battery cell.

7. The lithium-ion battery cell according to claim 6, characterized in that: The laminated structure battery cell includes a plurality of first positive electrodes, a plurality of first negative electrodes and a continuous diaphragm layer arranged in a Z shape, wherein the plurality of first positive electrodes and the plurality of first negative electrodes are alternately sandwiched between the continuous diaphragm layers, and the thermal insulation structure layer is arranged at the bottom and top layers of the laminated structure battery cell.

8. The lithium-ion battery cell according to claim 7, characterized in that: The surface of the thermal insulation structure layer is also covered with the continuous diaphragm layer.

9. The lithium-ion battery cell according to claim 6, characterized in that: The wound structure battery cell is a strip structure formed by stacking the second positive electrode, the first diaphragm layer, the second negative electrode and the second diaphragm layer and winding them, the thermal insulation structure layer is connected to the winding end of the second negative electrode, the current collector in the thermal insulation structure layer is connected to the current collector in the second negative electrode, the active material layer in the thermal insulation structure layer is connected to the active material in the inner layer of the second negative electrode, and the thermal insulation layer in the thermal insulation structure layer is connected to the active material in the outer layer of the second negative electrode.

10. A lithium ion battery, characterized in that: It comprises a lithium ion battery cell as claimed in any one of claims 1 to 9.

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