Battery cell structure with high safety and high energy density and battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a high-safety and high-energy-density battery cell structure and a battery, the battery cell structure comprises positive pole pieces and negative pole pieces which are alternately laminated, and the battery cell structure further comprises a first diaphragm and a second diaphragm, the head part of the first diaphragm and the head part of the second diaphragm are perpendicular to each other and are in direct contact and overlap or are in spacer overlap, the first diaphragm and the second diaphragm are wrapped between the positive pole piece and the negative pole piece in a Z-shaped crossed folding manner, and a single diaphragm layer or a double diaphragm layer is formed between the positive pole piece and the negative pole piece. According to the invention, the safety of the lithium ion battery cell can be greatly improved, especially the hot box trafficability of the lithium ion battery is improved, the lithium ion battery has a significant advantage of improving the high-temperature thermal stability of the lithium ion battery, and the potential safety hazard of short circuit caused by electrical abuse and mechanical abuse can be eradicated in advance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a battery cell structure and a battery with high safety and high energy density. Background Art

[0002] With the continuous development of technology, the performance of mobile devices such as mobile phones, cameras, and laptop batteries has also undergone earth-shaking changes, and at the same time, the requirements for lithium-ion batteries are getting higher and higher. For example, the functions of these mobile devices are becoming more and more complex, and higher requirements are also put forward for the high-rate discharge performance of the battery. In addition, with the continuous improvement of people's environmental protection awareness, electric vehicles are increasingly favored by people because of their pollution-free characteristics, and the development of electric vehicles themselves depends to a large extent on the development of the power source, that is, the battery. Therefore, the development of electric vehicle batteries is crucial.

[0003] A lithium-ion battery generally consists of a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and a casing. The safety problems of the battery cell caused by the increase in the energy density of the lithium-ion battery have gradually attracted wide attention, especially the safety problems in aspects such as electricity, mechanics, and thermal runaway. To improve the safety performance of the lithium-ion battery, it can start from the battery cell material and the battery cell structure design. Most of the existing technologies improve the safety performance of the lithium-ion battery based on the improvement of single materials or the change of the battery cell structure, and rarely consider the matching between the battery cell material and the battery cell structure. It is difficult to effectively improve the safety performance of the lithium-ion battery in all aspects by changing single materials or structures.

[0004] In the two-way matching of the battery cell material and the battery cell structure, the separator is the most important link. As a barrier to isolate the direct contact between the positive and negative electrode materials, the separator seriously affects the safety performance of the lithium-ion battery. With the trend of the separator becoming thinner, the impact of reducing the thickness of the separator on the safety performance of the battery cell becomes more prominent, especially the thermal box passability and internal short-circuit problems of the lithium-ion battery. Since the base film of the lithium-ion battery separator is a polymer material, its thermal stability is poor, and it shrinks and deforms severely when heated. The surface ceramic coating of the conventional separator has an effect of improving thermal stability, especially the dimensional stability of the separator in a thermal shock environment. However, in the actual application process of the battery cell, the improvement of the thermal stability of the separator by the ceramic coating is limited. The current heat shock limit of most battery cells can only reach 130°C, and it is difficult to pass a higher heat shock temperature. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a battery cell structure and a battery with high safety and high energy density, and at least solve the problems of poor high-temperature thermal stability and internal short circuit existing in the existing lithium-ion batteries.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] In a first aspect, the present invention provides an electrode structure of a battery cell with high safety and high energy density, which includes a positive electrode sheet and a negative electrode sheet arranged in an alternating laminated manner. The battery cell structure further includes a first separator and a second separator. The heads of the first separator and the second separator are perpendicular to each other and directly contact and overlap or overlap with a spacer. The first separator and the second separator are folded and wrapped in a Z-shaped cross pattern between the positive electrode sheet and the negative electrode sheet, and form a single separator layer or a double separator layer between the positive electrode sheet and the negative electrode sheet.

[0008] In combination with the first aspect, in some embodiments, the heads of the first separator and the second separator directly contact and overlap. The upper and lower surfaces of the positive electrode sheet are both coated with the first separator, and the upper and lower surfaces of the negative electrode sheet are both coated with the second separator. A double separator layer composed of the first separator and the second separator is formed between the positive electrode sheet and the negative electrode sheet; the second separator is a separator layer with a heat dissipation carbon layer on one side surface obtained by coating a carbon paste on one side surface of the first separator and drying.

[0009] In combination with the first aspect, in some embodiments, the surface of the second separator with the heat dissipation carbon layer faces the positive electrode sheet and is isolated from the positive electrode sheet by the first separator.

[0010] In combination with the first aspect, in some embodiments, the carbon material is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, conductive carbon black, graphene, and graphene oxide; the thickener is any one of carboxymethyl cellulose, sodium carboxymethyl cellulose, and lithium carboxymethyl cellulose; the binder is any one of styrene-butadiene rubber, polyacrylate, and polytetrafluoroethylene.

[0011] In combination with the first aspect, in some embodiments, the structural materials of the first separator and the second separator are the same, and the first separator and the second separator are both coated on the positive electrode sheet and the negative electrode sheet.

[0012] In combination with the first aspect, in some embodiments, the lower surface of the negative electrode sheet is coated with the first separator, and the upper surface is coated with the second separator. The lower surface of the positive electrode sheet is also coated with the first separator, and the upper surface is also coated with the second separator. A double-layer separator layer composed of the second separator and the first separator is formed between the positive electrode sheet and the negative electrode sheet.

[0013] In combination with the first aspect, in some embodiments, the lower surface of the negative electrode sheet is coated with the first separator, and the upper surface is coated with the second separator. The lower surface of the positive electrode sheet is coated with the second separator, and the upper surface is coated with the first separator. A single separator formed by the second separator or the first separator is provided between the positive electrode sheet and the negative electrode sheet.

[0014] In combination with the first aspect, in some embodiments, the first separator is one of a polyethylene separator, a polypropylene separator, and a polyethylene-polypropylene hybrid separator; or a polyethylene separator with a ceramic coating on its surface, or a polypropylene separator with a ceramic coating on its surface, or a polyethylene-polypropylene hybrid separator with a ceramic coating on its surface.

[0015] In combination with the first aspect, in some embodiments, the battery cell structure uses the metal current collector of the positive electrode tab as the positive electrode ear, and the metal current collector of the negative electrode tab as the negative electrode ear; or the positive electrode ear and the negative electrode ear in the battery cell structure are respectively welded on opposite sides of the cell and are parallel to each other, and the extending directions of the positive electrode ear and the negative electrode ear are opposite.

[0016] The above ear welding position design is beneficial to reducing the excessive heat concentration at the ear position caused by the conventional ear welding method, can effectively disperse the heat concentration distribution phenomenon on the entire cell, can accelerate the heat diffusion, and avoid the risk of thermal runaway caused by heat concentration. And the earless design using the metal current collector as the ear is beneficial to improving the rate performance of the lithium-ion battery.

[0017] For the battery cell structure of the present invention, on the one hand, the first separator and the second separator folded in a Z-shaped cross pattern cover both the upper and lower surfaces and partial side edges of the positive electrode tab and the negative electrode tab. When subjected to a high-temperature thermal shock test, it can avoid the short-circuit risk caused by the contact between the positive and negative electrode tabs due to the thermal shrinkage of the separator, greatly improving the safety of the lithium-ion battery, especially improving the thermal box passability of the lithium-ion battery, and having a significant advantage in improving the high-temperature thermal stability of the lithium-ion battery. On the other hand, by using the second separator with a heat-dissipating carbon layer on one side surface, the coated heat-dissipating carbon layer can avoid the attenuation of the electrical performance of the cell caused by the thickening of the separator, especially the rate performance of the cell, and the heat-dissipating carbon layer has an excellent safety alarm function. If an internal short circuit is caused by lithium dendrites or the like, the negative electrode first has a voltage response with the heat-dissipating carbon layer on the second separator, thus avoiding further electrical connection between the positive and negative electrodes, and thus can prevent in advance the short-circuit safety hazards caused by electrical abuse and mechanical abuse.

[0018] For the battery cell structure of the present invention, the earless position design using the metal current collector as the ear or the ear position design with opposite extending directions and parallel to each other is beneficial to reducing the excessive heat concentration at the ear position caused by the conventional ear welding method, can effectively disperse the heat concentration distribution phenomenon on the entire cell, can accelerate the heat diffusion, and avoid the risk of thermal runaway caused by heat concentration. And the earless design is beneficial to improving the rate performance of the lithium-ion battery.

[0019] In the second aspect, the present invention also provides a battery, and the battery includes the above battery cell structure.

[0020] It can be understood that for the beneficial effects of the above second aspect, reference can be made to the relevant descriptions of the above first aspect, which will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the battery cell for Embodiment 1 Figure 1 ;

[0022] Figure 2 Schematic diagram of the partial lamination sequence of the battery cell structure for Embodiment 1;

[0023] Figure 3 Schematic diagram of the tab welding position design for Embodiment 1;

[0024] Figure 4 Schematic diagram of the structure of the battery cell for Embodiment 7 Figure 1 ;

[0025] Figure 5 Schematic diagram of the partial lamination sequence of the battery cell structure for Embodiment 7;

[0026] Figure 6 Schematic diagram of the structure of the battery cell for Embodiment 8 Figure 1 ;

[0027] Figure 7 Schematic diagram of the partial lamination sequence of the battery cell structure for Embodiment 8;

[0028] Positive electrode tab 11, negative electrode tab 12, first separator 21, second separator 22, positive electrode ear 31, negative electrode ear 32, heat dissipation carbon layer 4. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] In the following embodiments, those not specified in specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. For raw materials, equipment or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0031] To improve the thermal box passability of lithium-ion batteries and prevent safety risks caused by internal short circuits, the present invention designs a winding and laminating technique for a first separator that is a conventional separator and a second separator with a heat-dissipating carbon layer. The two separators are wound and laminated in a "Z" shape along the horizontal and vertical directions, combining high thermal stability and fast heat dissipation performance. The heat-dissipating carbon layer can play a warning role for the risk of internal short circuits and effectively delay the occurrence of battery thermal runaway and internal short circuits.

[0032] The battery cell structure of the present invention includes a positive electrode plate and a negative electrode plate that are alternately laminated. The battery cell structure also includes a first separator and a second separator. The head of the first separator and the head of the second separator are perpendicular to each other and directly contact and overlap or overlap with a spacer. The first separator and the second separator are folded in a "Z" shape and cross-wrapped between the positive electrode plate and the negative electrode plate, and form a single separator layer or a double separator layer between the positive electrode plate and the negative electrode plate.

[0033] Among them, the side of the second separator with the heat-dissipating carbon layer faces the positive electrode plate. The first separator is one of a polyethylene separator, a polypropylene separator, and a polyethylene-polypropylene hybrid separator; or a polyethylene separator with a ceramic coating on the surface, or a polypropylene separator with a ceramic coating on the surface, or a polyethylene-polypropylene hybrid separator with a ceramic coating on the surface. The carbon-coated slurry includes 60-80 parts by mass of a carbon-containing solution, 10-25 parts by mass of a thickener, and 1-10 parts by mass of a binder. The carbon material content in the carbon-containing solution is 2-50 parts by mass. Specifically, the carbon material is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, conductive carbon black, graphene, and graphene oxide; the thickener is any one of carboxymethyl cellulose, sodium carboxymethyl cellulose, and lithium carboxymethyl cellulose; the binder is any one of styrene-butadiene rubber, polyacrylate, and polytetrafluoroethylene.

[0034] Among them, the thickness of the first separator ≤ 10 μm, and the thickness of the heat-dissipating carbon layer ≤ 3 μm.

[0035] Regarding the design of the tab, the battery cell structure of the present invention uses the metal current collector of the positive electrode plate as the positive tab and the metal current collector of the negative electrode plate as the negative tab; or the positive tab and the negative tab in the cell structure are respectively welded on opposite sides of the cell and are parallel to each other, and the extending directions of the positive tab and the negative tab are opposite. The design of the above tab welding positions is beneficial to reducing the excessive heat concentration at the tab position caused by the conventional tab welding method, can effectively disperse the heat concentration distribution phenomenon on the entire cell, accelerate the heat diffusion, and avoid the thermal runaway risk caused by heat concentration. And the design without tabs is beneficial to improving the rate performance of lithium-ion batteries.

[0036] The direct contact and overlap of the first separator and the second separator means that the second separator is directly stacked on the first separator. The overlap of the first separator and the second separator with spacer means that after stacking the positive electrode sheet or the negative electrode sheet between the first separator and the second separator, they overlap. In the present invention, the description is mainly made by placing the negative electrode sheet.

[0037] Through the following embodiments in combination Figure 1-7 The high-safety and high-energy-density battery cell structure and battery of the present invention are described as follows:

[0038] Embodiment 1

[0039] Please refer to Figure 1-3 , the high-energy-density safety battery cell of this embodiment includes alternately stacked positive electrode sheets 11 and negative electrode sheets 12 separated by separators. The separators include a first separator 21 and a second separator 22. The heads of the first separator 21 and the second separator 22 are in direct contact and perpendicular to each other. Here, the head refers to the starting end of the winding and folding of the first separator 21 and the second separator 22. The first separator 21 and the second separator 22 are folded and cross-wrapped in a Z shape between the positive electrode sheet 11 and the negative electrode sheet 12. Specifically, the first separator 21 is folded and wrapped on the upper and lower surfaces of the positive electrode sheet 11, and the second separator 22 is folded and wrapped on the upper and lower surfaces of the negative electrode sheet 12. Between the positive electrode sheet 11 and the negative electrode sheet 12 is a double separator layer composed of the first separator 21 and the second separator 22.

[0040] The second separator 22 includes a base film and a heat-dissipating carbon layer 44 coated on one side surface of the base film. The side of the second separator 22 with the heat-dissipating carbon layer 4 faces the positive electrode sheet 11 and is isolated from the positive electrode sheet 11 by the first separator 21. The base film in the second separator 22 is the same as the first separator 21 in terms of material and structural composition. Specifically, the first separator 21 of this embodiment is a polyethylene separator. The carbon-coated slurry for preparing the heat-dissipating carbon layer 4 includes 70 parts by mass of a carbon-containing solution, 22 parts by mass of lithium carboxymethylcellulose, and 8 parts by mass of styrene-butadiene rubber. The content of graphene oxide in the carbon-containing solution is 10 parts by mass. The thickness of the first separator 21 in this embodiment is ≤10 μm, and the thickness of the heat-dissipating carbon layer 4 is ≤3 μm.

[0041] Please refer to Figure 3 , in this embodiment, the positive electrode tab 31 and the negative electrode tab 32 in the battery cell are respectively welded on opposite sides of the battery cell and are parallel to each other. The extending directions of the positive electrode tab 31 and the negative electrode tab 32 are opposite, which is beneficial to improving or avoiding the problem of excessive heat generation caused by the too-close positions of the positive electrode tab 31 and the negative electrode tab 32.

[0042] The manufacturing method of the high-energy-density safety battery cell of this embodiment is as follows:

[0043] Clamp one end of the first separator 21 with a fixture to fix the first separator 21. Place the second separator 22 perpendicularly to the first separator 21 on the first separator 21, and use the fixture to clamp and fix the second separator 22. Then stack the negative electrode plate 12, fold the second separator 22 along the edge of the negative electrode plate 12 so that the second separator 22 covers the negative electrode plate 12. Next, fold the first separator 21 along the edge of the second separator 22 and the negative electrode plate 12 so that the first separator 21 covers the second separator 22. Then stack the positive electrode plate 11, and fold the first separator 21 along the edge of the positive electrode plate 11 so that the first separator 21 covers the positive electrode plate 11. Then fold the second separator 22 along the edge of the first separator 21 and the positive electrode plate 11 so that it covers the first separator 21. The subsequent winding and stacking sequence is repeated in the above manner until the entire battery cell winding is completed.

[0044] Please refer to Figure 2 , obtained according to the above manufacturing method. Along the winding direction of the separator of the battery cell, from bottom to top are the first separator 21, the second separator 22, the negative electrode plate 12, the second separator 22, the first separator 21, the positive electrode plate 11, the first separator 21, the second separator 22, the negative electrode plate 12, the second separator 22, the first separator 21. For the battery cell wound and stacked in this order, at the end of the winding, from inside to outside are the positive electrode plate 11, the first separator 21, the second separator 22, the negative electrode plate 12, the first separator 21.

[0045] Example 2

[0046] The difference between the high-energy density battery cell structure of this example and that of Example 1 is that this example adopts a design without pole ears. The metal current collector of the positive electrode plate 11 is used as the positive pole ear 31, and the metal current collector of the negative electrode plate 12 is used as the negative pole ear 32. When directly manufacturing the positive electrode plate 11 and the negative electrode plate 12 of the battery cell, reserve a part of the metal current collector in the uncoated area to serve as the pole ear, and connect the inside and outside to complete the conversion between electrical energy and chemical energy. During encapsulation, press and weld the reserved metal current collectors, so as to achieve connection between the positive electrode plates 11 and connection between the negative electrode plates 12.

[0047] The design without pole ear positions using the metal current collector as the pole ear adopted in this example is beneficial to reducing the excessive heat concentration at the pole ear positions caused by the conventional pole ear welding method, can effectively disperse the heat concentration distribution phenomenon on the entire battery cell, can accelerate the heat diffusion, avoid the risk of thermal runaway caused by heat concentration, and the design without pole ears is beneficial to improving the rate performance of the lithium-ion battery.

[0048] Example 3

[0049] The difference between the battery cell structure of this embodiment and that of Embodiment 1 is that the first separator 21 of this embodiment is a polypropylene separator with a ceramic coating on its surface. The carbon coating slurry for preparing the heat dissipation carbon layer 4 includes 60 parts by mass of a carbon-containing solution, 10 parts by mass of lithium carboxymethyl cellulose, and 1 part by mass of styrene-butadiene rubber. The content of graphene oxide in the carbon-containing solution is 50 parts by mass. The rest of the structural designs are the same as those of Embodiment 1.

[0050] Embodiment 4

[0051] The difference between the battery cell structure of this embodiment and that of Embodiment 1 is that the first separator 21 of this embodiment is a polypropylene separator with a ceramic coating on its surface. The carbon coating slurry for preparing the heat dissipation carbon layer 4 includes 80 parts by mass of a carbon-containing solution, 25 parts by mass of lithium carboxymethyl cellulose, and 10 parts by mass of styrene-butadiene rubber. The content of graphene oxide in the carbon-containing solution is 1 part by mass. The rest of the structural designs are the same as those of Embodiment 1.

[0052] Embodiment 5

[0053] The difference between the battery cell structure of this embodiment and that of Embodiment 1 is that the first separator 21 of this embodiment is a polyethylene-polypropylene mixed separator with a mass ratio of 1:1. The carbon coating slurry for preparing the heat dissipation carbon layer 4 includes 70 parts by mass of a carbon-containing solution, 22 parts by mass of sodium carboxymethyl cellulose, and 8 parts by mass of polytetrafluoroethylene. The content of multi-walled carbon nanotubes in the carbon-containing solution is 10 parts by mass. The rest of the structural designs are the same as those of Embodiment 1.

[0054] Embodiment 6

[0055] The difference between the battery cell structure of this embodiment and that of Embodiment 1 is that the first separator 21 of this embodiment is a polyethylene-polypropylene mixed separator with a mass ratio of 1:1 and a ceramic coating on its surface. The carbon coating slurry for preparing the heat dissipation carbon layer 4 includes 70 parts by mass of a carbon-containing solution, 22 parts by mass of carboxymethyl cellulose, and 8 parts by mass of polyacrylate. The content of conductive carbon black in the carbon-containing solution is 10 parts by mass. The rest of the structural designs are the same as those of Embodiment 1.

[0056] Embodiment 7

[0057] Please refer to Figure 4 and Figure 5, The battery cell structure of this embodiment includes alternately stacked positive electrode plates 11 and negative electrode plates 12, and also includes a first separator 21 and a second separator 22. The head of the first separator 21 and the head of the second separator 22 are perpendicular to each other, and a negative electrode plate 12 is provided between the head of the first separator 21 and the head of the second separator 22. The first separator 21 and the second separator 22 are folded in a Z-shaped cross to wrap between the positive electrode plate 11 and the negative electrode plate 12, and a double-layer separator composed of the second separator 22 and the first separator 21 is folded between the negative electrode plate 12 and the positive electrode plate 11. The first separator 21 is folded and wrapped on the lower surface of the positive electrode plate 11, and the second separator 22 is folded and wrapped on the upper surface; the first separator 21 is also folded and wrapped on the lower surface of the negative electrode plate 12, and the second separator 22 is also folded and wrapped on the upper surface.

[0058] In this embodiment, the first separator 21 and the second separator 22 are the same separator, that is, the materials, shapes, structures, etc. are exactly the same. The base film of the separator can be one or a mixture of two of PE and PP diaphragms, and the thickness of the separator ≦ 15um.

[0059] In this embodiment, one or both sides of the first separator 21 are provided with a ceramic coating, and an adhesive layer is provided on the outside of the ceramic coating. The adhesive layer can be any one of PMMA or PVDF. Since the first separator 21 and the second separator 22 are the same, the structure of the second separator 22 will not be described in detail here.

[0060] Please refer to Figure 4 , In this embodiment, the positive electrode tab 31 and the negative electrode tab 32 in the cell structure are respectively welded on opposite sides of the cell and are parallel to each other. The extending directions of the positive electrode tab 31 and the negative electrode tab 32 are opposite, which is beneficial to improving or avoiding the problem of excessive heat generation caused by the too-close positions of the positive electrode tab 31 and the negative electrode tab 32.

[0061] The manufacturing method of the high energy density cell structure of this embodiment is as follows:

[0062] Please refer to Figure 4, clamp one end of the first separator 21 with a fixture to fix the first separator 21, then stack the negative electrode plate 12, then stack the second separator 22 on the negative electrode plate 12, and use the fixture to fix one end of the second separator 22. Then fold the first separator 21 along the edge of the second separator 22 so that the first separator 21 covers the second separator 22. Then stack the positive electrode plate 11. Subsequently, fold the second separator 22 along the edge of the positive electrode plate 11 so that it covers the upper side of the positive electrode plate 11. Then fold the first separator 21 along the edge of the second separator 22 again so that it covers above the second separator 22, and then stack the negative electrode plate 12. The subsequent stacking order is repeated in the above manner until the entire battery cell is wound up. After winding is completed, first attach the termination tape at the top of the battery cell to complete the shaping and fixing of the battery cell, then remove the bottom separator fixing device, and complete the bottom gluing.

[0063] Please refer to Figure 5 , obtained according to the above manufacturing method. Along the winding direction of the separator of the battery cell, from bottom to top are the first separator 21, the negative electrode plate 12, the second separator 22, the first separator 21, the positive electrode plate 11, and the second separator 22. The battery cell wound and stacked in this order has, from the inside to the outside at the end of winding, the first separator 21, the negative electrode plate 12, the second separator 22, and the first separator 21. For each pair of adjacent sides of each positive electrode plate 11 and negative electrode plate 12 in the obtained battery cell structure, the first separator 21 and the second separator 22 are correspondingly coated.

[0064] Example 8

[0065] Please refer to Figure 6 and Figure 7 , the battery cell structure of this embodiment includes the positive electrode plates 11 and negative electrode plates 12 stacked alternately, and also includes the first separator 21 and the second separator 22. The heads of the first separator 21 and the second separator 22 are perpendicular to each other, and a negative electrode plate 12 is provided between the heads of the first separator 21 and the second separator 22. Here, the head refers to the starting end of the winding and folding of the first separator 21 and the second separator 22. The first separator 21 and the second separator 22 are folded in a Z-shaped cross to wrap between the positive electrode plates 11 and negative electrode plates 12, and a single-layer separator formed by the second separator 22 or the first separator 21 is folded between the negative electrode plate 12 and the positive electrode plate 11. The second separator 22 is folded and coated on the lower surface of the positive electrode plate 11, and the first separator 21 is folded and coated on the upper surface; the first separator 21 is folded and coated on the lower surface of the negative electrode plate 12, and the second separator 22 is folded and coated on the upper surface.

[0066] In this embodiment, the first separator 21 and the second separator 22 are the same separator, that is, the materials, shapes, structures, etc. are exactly the same. The base film of the separator can be one or a mixture of two of PE and PP diaphragms, and the thickness of the separator ≦ 15um.

[0067] In this embodiment, one side or both sides of the first separator 21 are provided with a ceramic coating, and an adhesive layer is provided on the outer side of the ceramic coating. The adhesive layer can be any one of PMMA or PVDF. Since the first separator 21 and the second separator 22 are the same, the structure of the second separator 22 will not be described herein again.

[0068] Please refer to Figure 6 , in this embodiment, the positive electrode tab 31 and the negative electrode tab 32 in the battery cell structure are respectively welded to opposite sides of the battery cell and are parallel to each other. The extending directions of the positive electrode tab 31 and the negative electrode tab 32 are opposite, which is beneficial to improving or avoiding the problem of excessive heat generation caused by the too-close positions of the positive electrode tab 31 and the negative electrode tab 32.

[0069] The manufacturing method of the high energy density battery cell structure of this embodiment is as follows:

[0070] Please refer to Figure 6 , clamp one end of the first separator 21 with a fixture to fix the first separator 21, then stack the negative electrode plate 12, then stack the second separator 22 on the negative electrode plate 12, and use the fixture to fix one end of the second separator 22, then stack the positive electrode plate 11, then fold the first separator 21 along the edge of the positive electrode plate so that it covers the positive electrode plate 11, then stack the negative electrode plate, and then fold the second separator 22 along the edge of the negative electrode plate 12 so that it covers the negative electrode plate, and then stack the positive electrode plate. The subsequent separator winding method is repeated in the above manner until the entire battery cell is wound.

[0071] Please refer to Figure 7 , obtained according to the above manufacturing method, along the winding direction of the separator of the battery cell, from bottom to top are the first separator 21, the negative electrode plate 12, the second separator 22, the positive electrode plate 11, the first separator 21, the negative electrode plate 12, the second separator 22, the positive electrode plate 11. For the battery cell wound and stacked in this order, from inside to outside at the end of the winding are the positive electrode plate 11, the first separator 21, the negative electrode plate 12, the second separator 22. For each pair of adjacent sides of each positive electrode plate 11 and negative electrode plate 12 in the obtained battery cell structure, the first separator 21 and the second separator 22 are correspondingly covered.

[0072] Comparative Example 1

[0073] The difference between the battery cell structure of this embodiment and that of Embodiment 1 is that in this embodiment, the first separator 21, the negative electrode plate 12, the second separator 22, the positive electrode plate 11, and the second separator 22 are sheared into single sheets during lamination, and then laminated according to the winding and lamination sequence of Embodiment 1, that is, Z-shaped cross winding is not used.

[0074] Comparative Example 2

[0075] The difference between the battery cell structure of this embodiment and that of Embodiment 1 is that in this embodiment, the first separator 21 is cut into pieces and stacked between the positive and negative electrode plates, and there is no second separator 22 in this embodiment.

[0076] The above Embodiments 1-8 and Comparative Examples 1-2 were subjected to a thermal shock test at 150 °C, and the test results are shown in Table 1.

[0077] Table 1 Thermal shock test results at 150 °C

[0078]

[0079] The data in Table 1 show that the cell structure with the first separator 21 and the second separator 22 having a zigzag cross-fold has excellent heat dissipation performance, and the heat dissipation performance is greatly improved compared with the cell structure of single-piece stacking and the cell structure of single-piece stacking without the second separator 22; the rate of change of resistance in the cell structure with the first separator 21 and the second separator 22 having a zigzag cross-fold is also greatly improved in the high-temperature thermal shock test experiment.

[0080] The battery cell structures of the above Embodiments 1-8 can all be used as cells in lithium-ion batteries. Therefore, the battery cell structures of the above Embodiments 1-8 can be installed as cells in lithium-ion batteries.

[0081] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention. The technologies, shapes, and structures not described in detail in the present invention are all well-known technologies.

Claims

1. A battery cell structure with high safety and high energy density, comprising a positive electrode plate and a negative electrode plate arranged in an alternating laminated manner, characterized in that, The battery cell structure further includes a first separator and a second separator. The heads of the first separator and the second separator are perpendicular to each other and directly contact and overlap or overlap with a spacer. The first separator and the second separator are folded and wrapped in a Z-shape between the positive electrode plate and the negative electrode plate, and form a single separator layer or a double separator layer between the positive electrode plate and the negative electrode plate.

2. The structure of an electric cell with high safety and high energy density according to claim 1, wherein The heads of the first separator and the second separator directly contact and overlap. The upper and lower surfaces of the positive electrode plate are both wrapped with the first separator, and the upper and lower surfaces of the negative electrode plate are both wrapped with the second separator. A double separator layer composed of the first separator and the second separator is formed between the positive electrode plate and the negative electrode plate. The second separator is a separator layer with a heat-dissipating carbon layer on one side surface obtained by coating a carbon paste on one side surface of the first separator and drying.

3. The structure of an electrochemical cell with high safety and high energy density according to claim 2, characterized in that, The side of the second separator with the heat-dissipating carbon layer faces the positive electrode plate and is isolated from the positive electrode plate by the first separator.

4. A cell structure with high safety and high energy density according to claim 3, characterized in that, The carbon paste includes 60-80 parts by mass of a carbon-containing solution, 10-25 parts by mass of a thickener, and 1-10 parts by mass of a binder. The carbon material content in the carbon-containing solution is 2-50 parts by mass. The carbon material is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, conductive carbon black, graphene, and graphene oxide; the thickener is any one of carboxymethyl cellulose, sodium carboxymethyl cellulose, and lithium carboxymethyl cellulose; the binder is any one of styrene-butadiene rubber, polyacrylate, and polytetrafluoroethylene.

5. A high-safety and high-energy-density battery cell structure according to claim 1, characterized in that, The structural materials of the first separator and the second separator are the same, and the first separator and the second separator are both wrapped on the positive electrode plate and the negative electrode plate.

6. The core structure with high safety and high energy density according to claim 5, characterized in that The lower surface of the negative electrode plate is wrapped with the first separator, and the upper surface is wrapped with the second separator. The lower surface of the positive electrode plate is also wrapped with the first separator, and the upper surface is also wrapped with the second separator. A double separator layer composed of the second separator and the first separator is formed between the positive electrode plate and the negative electrode plate.

7. A high-safety and high-energy-density battery cell structure according to claim 5, characterized in that, The lower surface of the negative electrode plate is wrapped with the first separator, and the upper surface is wrapped with the second separator. The lower surface of the positive electrode plate is wrapped with the second separator, and the upper surface is wrapped with the first separator. A single separator formed by the second separator or the first separator is provided between the positive electrode plate and the negative electrode plate.

8. A high-safety and high-energy-density battery cell structure according to claim 1, characterized in that, The first separator is one of a polyethylene separator, a polypropylene separator, and a polyethylene-polypropylene hybrid separator. Or a polyethylene separator with a ceramic coating on the surface, or a polypropylene separator with a ceramic coating on the surface, or a polyethylene-polypropylene hybrid separator with a ceramic coating on the surface.

9. A high-safety and high-energy-density battery cell structure according to claim 1, characterized in that, The battery cell structure uses the metal current collector of the positive electrode plate as the positive electrode tab and the metal current collector of the negative electrode plate as the negative electrode tab. Or the positive electrode tab and the negative electrode tab in the cell structure are respectively welded on opposite sides of the cell and are parallel to each other, and the extending directions of the positive electrode tab and the negative electrode tab are opposite.

10. A battery, characterized in that, The battery includes the battery cell structure according to any one of claims 1-9.

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