Battery

Abstract

The present invention provides a battery, comprising a battery cell and an insulating film coated on the circumferential side of the battery cell, wherein the battery cell comprises a positive electrode sheet and a negative electrode sheet, and the two ends of the insulating film respectively form a starting end and a tail end, and on the circumferential side of the battery cell, the tail end of the insulating film is arranged beyond the starting end, so that an overlapping area is formed between the starting end and the tail end, wherein the product of the size of the overlapping area along the circumference of the battery cell, the elastic modulus of the insulating film, and the cohesive force of the negative electrode sheet is in the range of 0.1 to 2000. By adjusting the product value of the elastic modulus of the insulating film and the cohesive force of the negative electrode sheet, the binding force applied by the insulating film to the battery cell can be adapted to the cohesive force of the electrode sheet, thereby preventing the cylindrical battery cell from excessively expanding during the charging and discharging process.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy batteries, and in particular to a battery. Background Art

[0002] The battery pack is a key component of new energy vehicles. The batteries in the battery pack are in various forms, such as cylindrical batteries, square batteries, blade batteries, etc. For cylindrical batteries, the internal battery cells are formed by stacking the pole pieces and the diaphragm and then winding them. The winding is relatively tight, especially the inner part of the core. Therefore, during the charging and discharging process of the cylindrical battery, the pole pieces have a tendency to rebound outward, and will cause the battery cells to expand. Large expansion of the battery cells will increase the internal resistance of the cylindrical battery, resulting in energy loss of the cylindrical battery during the charging and discharging process, resulting in poor cycling performance of the cylindrical battery. Summary of the invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defects of cylindrical batteries in the prior art that the pole pieces have a tendency to rebound during the charge and discharge process, which leads to serious expansion of the battery cell and increased internal resistance, thereby providing a battery.

[0004] In order to solve the above problems, the present invention provides a battery, comprising a battery cell and an insulating film coated on the circumferential side of the battery cell, the battery cell comprising a positive electrode sheet and a negative electrode sheet, the two ends of the insulating film respectively form a starting end and a tail end, and on the circumferential side of the battery cell, the position of the tail end of the insulating film is set beyond the starting end to form an overlapping area between the starting end and the tail end, wherein the product of the size of the overlapping area along the circumference of the battery cell, the elastic modulus of the insulating film and the cohesive force of the negative electrode sheet is in the range of 0.1 to 2000.

[0005] The present invention has the following advantages:

[0006] By using the technical solution of the present invention, the insulating film is coated on the outside of the battery cell, and the starting end and the tail end have an overlapping area, so the insulating film can generate a binding force on the battery cell. The above scheme uses the size of the overlapping area of ​​the insulating film to tighten the battery cell by comprehensively adjusting the relationship between the overlapping area along the axial size of the battery cell, the elastic modulus of the insulating film, and the cohesive force of the negative electrode sheet, so as to avoid the battery cell from expanding during the charging and discharging process, which leads to an increase in the battery impedance. At the same time, it is also necessary to avoid the overlapping size of the overlapping area of ​​the insulating film being too large, which leads to a large reverse force of the insulating film on the battery cell, indentations on the pole piece, and an increased risk of lithium precipitation; in addition, it may cause the pole piece to drop. Further, when the cohesive force of the negative electrode sheet is small, the expansion of the pole piece increases during the charging and discharging process of the battery cell, so the size of the overlapping area needs to be appropriately increased to restrain the battery cell and avoid the situation where the battery cell expands too much and causes an increase in the internal resistance of the battery. In addition, the size of the overlapping area cannot be too large, which will cause the overlapping area of ​​the insulating film to generate stress on the pole piece in the reverse direction, indentations on the pole piece, and an increased risk of lithium precipitation; in addition, the risk of pole piece dropping is increased. Furthermore, by increasing the elastic modulus of the insulating film, the confinement effect on the battery cell is enhanced, and the size of the overlapping area can be avoided to be too large. In addition, the elastic modulus of the insulating film cannot be too large, which will cause the insulating film to exert a greater force on the pole piece in the opposite direction. Therefore, the technical solution of the present invention solves the defect of the cylindrical battery in the prior art that the pole piece has a rebound tendency during the charging and discharging process, causing the battery cell to expand severely and the internal resistance to increase. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0008] Figure 1 A schematic diagram of the structure of a battery of the present invention is shown;

[0009] Figure 2 Shows Figure 1 A schematic diagram of the structure of the battery cell in the battery;

[0010] Figure 3 Shows Figure 2 Schematic diagram showing that the edge of the insulating film of the medium cell does not exceed the edge of the positive electrode sheet;

[0011] Figure 4 Shows Figure 2 Schematic diagram showing that the edge of the insulating film of the medium cell is located between the edge of the positive electrode sheet and the edge of the negative electrode sheet;

[0012] Figure 5 Shows Figure 2Schematic diagram showing that the edge of the insulating film of the medium cell is located between the edge of the negative electrode sheet and the edge of the separator;

[0013] Figure 6 Shows Figure 2 Schematic diagram of the edge of the insulating film of the battery cell exceeding the edge of the diaphragm.

[0014] Description of reference numerals:

[0015] 10. Battery cell; 11. Positive electrode sheet; 12. Negative electrode sheet; 13. Positive electrode ear; 14. Negative electrode ear; 15. Diaphragm; 20. Insulating film; 21. Starting end; 22. Ending end; 30. Shell; S. Overlapping area. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0017] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0018] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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.

[0019] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0020] like Figure 1 and Figure 2As shown, an embodiment of a battery according to the present application includes a battery cell 10 and an insulating film 20 coated on the circumferential side of the battery cell 10. The battery cell 10 includes a positive electrode sheet 11 and a negative electrode sheet 12, and the two ends of the insulating film 20 form a starting end 21 and a tail end 22, respectively. On the circumferential side of the battery cell 10, the position of the tail end 22 of the insulating film 20 is set beyond the starting end 21, so that an overlapping area S is formed between the starting end 21 and the tail end 22, and further, the product of the size L of the overlapping area S along the circumference of the battery cell, the elastic modulus M of the insulating film 20 and the cohesive force F of the negative electrode sheet 12 is in the range of 0.1 to 2000.

[0021] That is, the value of L*M*F is in the range of 0.1 to 2000.

[0022] Using the technical solution of this embodiment, the insulating film 20 is coated on the outside of the battery cell 10, and there is an overlapping area S between the starting end 21 and the tail end 22, so the insulating film 20 can generate a binding force on the battery cell 10. The technical solution of this embodiment comprehensively adjusts the relationship between the overlapping area S along the axial dimension L of the battery cell 10, the elastic modulus M of the insulating film 20, and the cohesive force F of the negative electrode sheet 12, and uses the size L of the overlapping area S of the insulating film 20 to tighten the battery cell 10, so as to avoid the battery cell 10 from expanding during the charging and discharging process, which leads to an increase in the battery impedance. At the same time, it is also necessary to avoid the overlapping size L of the overlapping area S of the insulating film 20 being too large, which leads to a large reverse force of the insulating film 20 on the battery cell 10, indentations on the electrode sheet, and an increased risk of lithium precipitation. In addition, the electrode sheet may fall off. Furthermore, when the cohesive force of the negative electrode sheet 12 is small, the electrode sheet expands more during the charging and discharging process of the battery cell 10, so the size L of the overlapping area S needs to be appropriately increased to restrain the battery cell 10 and avoid the situation where the battery cell 10 expands too much and causes an increase in the internal resistance of the battery. In addition, the size L of the overlapping area S cannot be too large, which will cause the overlapping area S of the insulating film 20 to generate stress on the pole piece in the reverse direction. The pole piece may be indented, and the risk of lithium deposition increases. In addition, the risk of pole piece falling off may increase. Furthermore, by increasing the elastic modulus M of the insulating film 20, the confinement effect on the battery cell 10 is improved, and the size of the overlapping area S can be avoided from being too large. In addition, the elastic modulus M of the insulating film 20 cannot be too large, which will cause the insulating film 20 to exert a greater force on the pole piece in the reverse direction. Therefore, the technical solution of this embodiment solves the defect of the cylindrical battery in the prior art that the pole piece has a rebound tendency during the charging and discharging process, which causes the battery cell to expand severely and the internal resistance to increase.

[0023] It is worth noting that the battery cell 10 includes a positive electrode sheet 11, a negative electrode sheet 12 and a separator 15, and the separator 15 is arranged between the positive electrode sheet 11 and the negative electrode sheet 12. The positive electrode sheet 11, the negative electrode sheet 12 and the separator 15 are wound or laminated to form the battery cell 10. The positive electrode sheet 11 includes a positive electrode collector and a positive electrode active material layer, and the negative electrode sheet 12 includes a negative electrode collector and a negative electrode active material layer. The material of the positive electrode collector is not limited, as long as it has conductivity and does not cause adverse chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. can be used. Further, the negative electrode collector can be made of copper, stainless steel, nickel, titanium, etc. In a specific embodiment, the positive electrode collector can be made of aluminum, and the negative electrode collector can be made of copper.

[0024] Furthermore, the battery shell may be a steel shell, an aluminum shell, etc.; wherein the steel shell may be stainless steel, nickel-plated steel, etc.; and the aluminum shell may be an aluminum alloy, an aluminum-manganese alloy, etc.

[0025] Furthermore, the battery also includes an electrolyte, and the electrolyte of the present invention can be any electrolyte suitable for electrochemical energy storage devices in the art. The electrolyte includes an electrolyte and a solvent, and the electrolyte can generally include a lithium salt.

[0026] Specifically, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP). The concentration of the electrolyte in the electrolyte may be 0.5 to 5 mol / L.

[0027] Specifically, the solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0028] Furthermore, if Figure 2 As shown, the battery cell 10 of the cylindrical battery is cylindrical, and the battery cell 10 is formed by stacking the positive electrode sheet 11, the separator 15 and the negative electrode sheet 12 in sequence and then winding them. In order to keep the shape of the battery cell 10 and insulate it from other structures, the outer surface of the battery cell 10 in the circumferential direction after winding is covered with an insulating film 20. The material of the insulating film can be PP, PE, PET, PI, etc.

[0029] like Figure 2 As shown, along the circumference of the battery cell 10 , the insulating film 20 has a starting end 21 and an ending end 22 , wherein the starting end 21 refers to the end where the insulating film 20 begins to be attached to the battery cell 10 , and the ending end 22 refers to the end where the insulating film 20 ends.

[0030] like Figure 2 As shown, when attaching the insulating film 20, first attach the starting end 21 to the battery cell 10, then wrap the insulating film around the battery cell 10; then extend the insulating film 20 beyond the starting end 21 for a certain distance; finally, cut the insulating film 20 (or process the insulating film 20 to have a predetermined size) to form the tail end 22, and attach it to the insulating film. Figure 2 It can be seen that since the end end 22 passes over the start end 21, there is an overlap area S between the end end 22 and the start end 21 ( Figure 2 Due to the existence of the overlapping area S, the insulating film 20 as a whole provides a binding force to the battery cell 10.

[0031] Furthermore, when the cohesive force F of the negative electrode sheet 12 is greater, the rebound of the electrode sheet is smaller, so the elastic modulus of the insulating film 20 can be appropriately reduced.

[0032] Furthermore, when the cohesive force F of the negative electrode sheet 12 is smaller, the rebound of the electrode sheet is greater, so the elastic modulus M of the insulating film 20 should be appropriately increased to prevent the battery cell 10 from excessive expansion.

[0033] In this embodiment, by comprehensively adjusting the relationship between the length of the overlapping area S, the elastic modulus M of the insulating film 20, and the cohesive force F of the negative electrode sheet 12, the size of the overlapping area S of the insulating film 20 is used to tighten the battery cell 10 to prevent the battery cell 10 from expanding during the charging and discharging process, which leads to an increase in battery impedance. At the same time, the overlapping area S of the insulating film 20 is prevented from causing indentations on the electrode sheet, which increases the risk of lithium deposition and may increase the risk of electrode sheet dropout.

[0034] Furthermore, when the cohesive force of the negative electrode sheet 12 is smaller, the expansion of the electrode sheet increases during the charge and discharge process of the battery cell 10, so the dimension L is appropriately increased to restrain the battery cell 10 and prevent the battery cell 10 from expanding too much, which leads to an increase in the internal resistance of the battery. However, the dimension L cannot be too large. If the dimension L is too large, the overlapping area S of the insulating film 20 will generate stress on the electrode sheet in the reverse direction, and the electrode sheet may be indented, increasing the risk of the electrode sheet falling off.

[0035] Furthermore, by increasing the elastic modulus M of the insulating film 20, the confinement effect on the battery cell 10 is increased, and the need for an excessively large size L can also be avoided. However, the elastic modulus M of the insulating film 20 cannot be too large, as an excessively large elastic modulus M will also cause a greater force acting in the opposite direction on the pole piece. Therefore, it is necessary to comprehensively control the relationship between the pole piece cohesion F, the size L of the overlapping area S, and the elastic modulus M of the insulating film 20 (that is, the product value of the three).

[0036] Therefore, in the embodiment, the value of L*M*F is in the range of 0.1 to 2000.

[0037] Optionally, the value of L*M*F may be any value among 0.1, 0.5, 1, 100, 500, 1000, 2000, etc., or a value between any two values.

[0038] More preferably, the value of L*M*F is in the range of 1 to 600.

[0039] Optionally, the value of L*M*F may be any value of 1, 5, 10, 50, 100, 500 or 600, etc., or a value between any two values.

[0040] Specifically, by further controlling L*M*F within the range of 1 to 600, the battery can have a smaller internal resistance DCR and the risk of electrode falling off can be further reduced.

[0041] Furthermore, the unit of the cohesive force F of the negative electrode sheet 12 is N / m, the unit of the elastic modulus of the insulating film 20 is GPa, and the unit of the size L of the overlapping area S is mm.

[0042] The following describes a method for manufacturing the battery of this embodiment.

[0043] 1. Preparation of positive electrode sheet 11

[0044] The positive electrode active material LiNi x Co y Mn zO2 (where x+y+z=1) or lithium iron phosphate, conductive agent acetylene black and binder PVDF are mixed in a mass ratio of 96:2:2, and solvent NMP is added. The system is stirred in a vacuum mixer until the system is uniform to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying, and then cold pressed and cut to obtain a positive electrode sheet 11.

[0045] Table 1 shows the LiNi content of the positive electrode active materials in the eighteen samples of this application. x Co y Mn z O2 is specifically selected, as well as the content of silicon in the negative electrode active material, wherein the eighteen samples include sixteen embodiments and two comparative examples.

[0046]

[0047] Taking the first embodiment as an example, x=0.9, y=0.05, z=0.05, and therefore x+y+z=1.

[0048] Taking Example 9 as an example, x=0.6, y=0.3, z=0.1, so x+y+z=1.

[0049] 2. Preparation of negative electrode sheet 12

[0050] The negative electrode active material artificial graphite, or a mixture of artificial graphite and silicon-based material in a mass ratio of 1.25% to 20%. The conductive agent (SP) and the binder (SBR and / or PAA) are mixed in a certain mass ratio, and deionized water is added as a solvent, and stirred under the action of a vacuum mixer until the system is uniform to obtain a negative electrode slurry. The negative electrode slurry is evenly coated on both surfaces of the negative electrode current collector copper foil (according to the requirements of each embodiment and comparative example in Table 2), dried at room temperature, and then transferred to an oven for further drying, and then cold pressed and cut to obtain a negative electrode sheet 12.

[0051]

[0052] Furthermore, the mass ratio of the conductive agent, the binder SBR and the binder PAA is in the range of: (92%-96%): (0%-4%): (2%-4%).

[0053] It should be noted that the cohesive force of the negative electrode sheet 12 can be adjusted by the components and ratio of the binder. Table 2 shows the cohesive force of the negative electrode sheet 12 under different components and ratios of SBR and PAA in the binder of the negative electrode sheet 12.

[0054] Taking Example 1 as an example, in the negative electrode active material, the mass ratio of SBR is 1.8%, the mass ratio of PAA is 1.2%, and thus the mass ratio of the binder in the negative electrode active material is 3%.

[0055] Taking Example 9 as an example, in the negative electrode active material, the mass ratio of SBR is 3%, so the mass ratio of the binder in the negative electrode active material is 3% (ie, excluding PAA).

[0056] Taking Example 10 as an example, in the negative electrode active material, the mass ratio of PAA is 3%, so the mass ratio of the binder in the negative electrode active material is 3% (ie, excluding SBR).

[0057] It should be noted that the method for adjusting the cohesive force F of the negative electrode sheet 12 is not limited in the present application. For example, the cohesive force F of the negative electrode sheet 12 can be adjusted by the formulation of the binder.

[0058] 3. Preparation of electrolyte

[0059] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, FEC is added according to the embodiment and the comparative example, and then the fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0060] 4. Preparation of diaphragm 15

[0061] In this embodiment, a polyethylene film is selected as the separator, and the polyethylene film is cut to form the separator 15 .

[0062] 5. Preparation of lithium-ion batteries

[0063] The positive electrode sheet 11, the separator 15, and the negative electrode sheet 12 are stacked in order, so that the separator 15 is between the positive electrode sheet 11 and the negative electrode sheet 12 to play an isolating role, and then wound to obtain a bare battery cell 10;

[0064] The battery cell 10 coated with the insulating film 20 is placed in an outer packaging shell (shell 30), and after drying, the electrolyte is injected, and vacuum packaging, standing, and forming are performed: according to the forming process, shaping and other processes of the embodiment and comparative example, a lithium-ion battery is obtained.

[0065] In addition, the test method of the cohesive force F of the negative electrode sheet 12 is not limited in the present application. Here, illustratively, the cohesive force F of the negative electrode sheet 12 can be tested by the following method: First, the cohesive force F of the negative electrode sheet 12 involved in this embodiment refers to the bonding force between the negative electrode active particles in the negative electrode active coating, and the steps of obtaining the cohesive force F include:

[0066] 1. Take a standard steel plate (50mmx125mm) as the rigidity test base plate, wipe the surface of the steel plate with dust-free paper dipped in alcohol, and stick one side of a 50mmx125mm 3M double-sided tape on the steel plate to ensure that it is smooth and wrinkle-free;

[0067] 2. Cut the negative electrode sheet 12 with the active coating into 50 mm x 125 mm samples to be tested;

[0068] 3. Paste the electrode to be tested on the other side of the double-sided tape, and then paste another layer of double-sided tape on the surface of the electrode. Ensure that the contact is flat and wrinkle-free during the pasting process;

[0069] 4. After rolling with the roller, use the universal testing machine to clamp the steel plate at one end and the 3M tape at the other end. Set the tensile machine stroke to 100mm, and do the pulling test at a speed of 300mm / min. Set the tensile machine stroke to 100mm, and record that when the curve in the tensile machine software diagram is flat and the displacement is greater than 80mm, the machine stops and reads the average tensile force of the flat part of the curve, which is the cohesive force.

[0070] Further, the present application does not limit the test method of the elastic modulus M of the insulating film 20. Here, for example, the elastic modulus M of the insulating film 20 can be tested by a static tensile test method in accordance with the national standard GB22315-2008. The test method includes:

[0071] Fix the sample on the tensile machine, apply gradually increasing tensile force, and measure the deformation of the sample;

[0072] The elastic modulus is calculated based on the stress-strain relationship.

[0073] In addition, the present application does not limit the method for adjusting the elastic modulus M of the insulating film 20. For example, the elastic modulus M of the insulating film 20 can be adjusted by changing the material of the insulating film 20 and by selecting the insulating film 20 obtained under different process conditions.

[0074] Further, illustratively, the method for testing the size L of the overlapping area S in this embodiment may include:

[0075] A soft ruler can be used to measure along the circumferential direction of the battery cell 10 to obtain the distance between the starting end 21 and the ending end 22. Alternatively, a flexible body such as a line can be used to first obtain a marking line of equal length between the starting end 21 and the ending end 22, and then a ruler can be used to measure the length of the marking line to obtain the distance between the ending end 22 and the starting end 21.

[0076] Table 3 shows the battery internal resistance (DCR, in mΩ) and the electrode conditions under different values ​​of the elastic modulus M of the insulating film 20, the cohesive force F of the negative electrode sheet 12, and the size L of the overlapping area S in the above-mentioned 16 embodiments and two comparative examples. The following first describes in detail the considerations for the values ​​of the elastic modulus M of the insulating film 20, the cohesive force F of the negative electrode sheet 12, and the size L of the overlapping area S under different conditions.

[0077]

[0078] Optionally, the cohesive force F of the negative electrode sheet 12 is in the range of 1.5 N / m to 40 N / m.

[0079] For example, the value of the cohesive force F of the negative electrode sheet 12 may be any value among 1.5 N / m, 5 N / m, 10 N / m, 20 N / m, 30 N / m or 40 N / m, or a value between any two values.

[0080] Furthermore, the cohesive force F of the negative electrode sheet 12 reflects the bonding force between the particles of the negative electrode active material. Under the appropriate cohesive force, the negative electrode sheet 12 has good structural stability, which can reduce the rebound of the electrode sheet of the battery cell 10 during the charge and discharge process, thereby reducing the internal resistance of the battery. By controlling the size of the cohesive force F of the negative electrode sheet 12 to be between 1.5N / m-40N / m, it is avoided that the cohesive force is too small, and the rebound of the electrode sheet cannot be fully suppressed, causing serious expansion of the battery cell and increased internal resistance; at the same time, it is also avoided that the cohesive force is too large, and the required binder content increases. If the binder content is too large, it will affect the transmission of lithium ions and electrons, causing the internal resistance DCR of the battery to increase.

[0081] Preferably, the cohesive force F of the negative electrode sheet 12 is in the range of 6 N / m to 20 N / m.

[0082] By further controlling the cohesive force of the negative electrode sheet 12 within the preferred range of 6-20 N / m, the rebound of the electrode sheet and the increase in the internal resistance of the battery can be further reduced.

[0083] For example, the value of the cohesive force F of the negative electrode sheet 12 can be any value among 6 N / m, 8 N / m, 10 N / m, 15 N / m, 20 N / m, etc., or a value between any two values.

[0084] More preferably, the cohesive force F of the negative electrode sheet 12 is in the range of 6 N / m to 18 N / m.

[0085] For example, the value of the cohesive force F of the negative electrode sheet 12 can be any value among 6 N / m, 8 N / m, 10 N / m, 12 N / m, 15 N / m or 18 N / m, or a value between any two values.

[0086] Optionally, the product of the dimension L of the overlapping area along the circumference of the battery cell and the elastic modulus M of the insulating film 20 is in the range of 0.05 to 60. For example, the value of the product of the dimension L of the overlapping area along the circumference of the battery cell and the elastic modulus M of the insulating film 20 can be selected as any value of 0.05, 1, 5, 10, 20, 50 or 60, or a value between any two values.

[0087] Furthermore, the product of the overlapping dimension L and the elastic modulus M of the insulating film 20 is controlled within an appropriate range, and the relationship between the two can be further taken into account. When the overlapping dimension L is relatively large, the value of the elastic modulus M can be appropriately reduced to avoid excessive reverse force of the insulating film 20 on the battery cell 10, which increases the risk of pole piece falling off; when the overlapping dimension L is relatively small, the value of the elastic modulus M can be appropriately increased to avoid weak binding effect on the battery cell 10 and increased expansion of the battery cell 10 due to the overlapping dimension L being too small; by controlling the product of the overlapping dimension L and the elastic modulus M of the insulating film 20 between 0.05 and 60, it is avoided that the product of the two is too large, resulting in excessive overlapping dimension L and / or excessive elastic modulus M, indentation of the pole piece, increased risk of lithium deposition on the pole piece, and may also increase the risk of pole piece falling off; it is also avoided that the overlapping dimension L and / or the elastic modulus M are too small, resulting in weak binding effect on the battery cell, and the battery cell still has a large expansion, which increases the internal resistance of the battery.

[0088] Further, a dimension L of the overlapping area S along the circumferential direction of the battery is in the range of 0.15 mm to 20 mm.

[0089] Specifically, by controlling the overlapping area size L of the insulating film 20 in the circumferential direction of the battery within an appropriate range, better restraint of the battery cell 10 can be achieved. At the same time, the overlapping area size L is too large, which will not cause a large reverse force on the battery cell 10, indentations on the pole pieces, and easy material falling off. Moreover, an excessively large overlapping area size L will also affect the heat dissipation performance of the battery cell 10 and cause the expansion of the battery cell 10 to intensify. Furthermore, the overlapping area S size L is too small, which will not cause a weak restraint effect on the battery cell 10, thereby avoiding the situation where the battery cell 10 still has a large expansion.

[0090] For example, the size L of the overlapping area S can be selected as any value among 0.15 mm, 0.2 mm, 0.5 mm, 1 mm, 10 mm or 20 mm, etc., or a value between any two values.

[0091] Preferably, a dimension L of the overlapping region S along the axial direction of the battery is in the range of 0.5 mm to 10 mm.

[0092] For example, the size L of the overlapping area S can be selected as any value among 0.5 mm, 0.6 mm, 1 mm, 5 mm, 7 mm or 10 mm, etc., or a value between any two values.

[0093] Further, the elastic modulus M of the insulating film 20 is in the range of 0.1 GPa to 5 GPa. The elastic modulus of the insulating film 20 can be adjusted by selecting insulating films of different materials or insulating films prepared under different process conditions. The insulating film 20 can be obtained by conventional purchase.

[0094] Specifically, by controlling the elastic modulus M of the insulating film within an appropriate range, better restraint on the battery cell 10 can be achieved. At the same time, when the battery cell 10 expands, the insulating film 20 will not expand along with the battery cell 10 due to the elastic modulus M being too small, and will not be unable to inhibit the expansion of the battery cell 10. Nor will the elastic modulus M be too large, causing the insulating film to exert a large reverse force on the battery cell 10 when the battery cell 10 expands, resulting in indentations on the pole piece. In addition, the risk of pole piece falling off may increase.

[0095] For example, the elastic modulus M of the insulating film 20 can be selected as any value among 0.1 GPa, 0.5 GPa, 1 GPa, 2 GPa, 3 GPa or 5 GPa, or a value between any two values.

[0096] Preferably, the elastic modulus M of the insulating film 20 is in the range of 0.2 GPa to 4 GPa.

[0097] For example, the elastic modulus M of the insulating film 20 may be selected as 0.1 GPa, 0.5 GPa, 1 GPa, 2 GPa, 3 GPa, 5 GPa, or the like.

[0098] like Figure 2 As shown, in the technical solution of this embodiment, the battery cell 10 further includes a battery cell body, a positive electrode tab 13 and a negative electrode tab 14. Along the direction of the battery cell body, the positive electrode tab 13 and the negative electrode tab 14 are both led out from one end of the battery cell 10, and the product of the dimension L of the overlapping area S along the circumference of the battery cell 10 and the elastic modulus M of the insulating film 20 is in the range of 0.1 to 40.

[0099] In this embodiment, the positive electrode tab 13 and the negative electrode tab 14 are both Figure 2 The lead is drawn from above the battery cell 10 shown in FIG.

[0100] In this embodiment, since the positive electrode tab 13 and the negative electrode tab 14 are led out on the same side of the battery cell 10, the current transmission path is short and the battery impedance is small. However, since the positive electrode tab 13 and the negative electrode tab 14 are led out on the same side of the battery cell 10, the heat generated on one side of the battery cell 10 (the side where the tabs are led out) is large, resulting in an increased expansion degree of the battery cell 10. The product of the dimension L of the overlapping area S along the circumference of the battery cell 10 and the elastic modulus M of the insulating film 20 needs to be appropriately increased.

[0101] Optionally, when the positive electrode tab 13 and the negative electrode tab 14 are both led out from the same side of the battery cell 10, the product of the dimension L of the overlapping area S along the circumference of the battery cell 10 and the elastic modulus M of the insulating film 20 can be selected as any value among 0.1, 1, 5, 10, 20, 30, 40, etc. or a value between any two values. Figure 3 As shown, in the production of the battery, in order to ensure that the negative electrode sheet 12 has sufficient lithium insertion positions, a "negative-covered-positive" lamination mode is usually adopted, that is, the negative electrode sheet 12 should cover the positive electrode sheet 11. At the same time, the separator 15 covers the positive electrode sheet 11 and the negative electrode sheet 12, thereby ensuring that the two are completely isolated and preventing the edges of the positive electrode sheet 11 and the negative electrode sheet 12 from contacting and causing a short circuit.

[0102] Figure 3 In the figure, the uppermost horizontal line represents the edge of one axial end of the battery cell 10 , and this edge is also the edge of the diaphragm 15 .

[0103] Various configurations of the edge of the insulating film 20 along the axial direction of the battery cell 10 in this embodiment are described below.

[0104] Setting method 1:

[0105] like Figure 3 As shown, in the axial direction of the battery cell 10, the distance from the edge of the insulating film 20 to the end of the battery cell 10 is greater than the distance from the edge of the positive electrode sheet 11 to the end of the battery cell 10, that is, the edge of the insulating film 20 does not exceed the edge of the positive electrode sheet 11. The dimension L of the overlapping area S along the circumferential direction of the battery cell 10 is in the range of 0.6 mm to 15 mm.

[0106] exist Figure 3 In the arrangement shown, the edge of the insulating film 20 does not exceed the edge of the positive electrode sheet 11. Therefore, the edge of the insulating film 20 does not exceed the edge of the negative electrode sheet 12 and the separator 15.

[0107] Specifically, since the tabs (positive tabs 13 and / or negative tabs 14) are led out from the ends of the battery cell 10, the end positions of the battery cell 10 generate a large amount of heat. In order to prevent the heat generated by the tabs from damaging the insulating film 20, the edge of the insulating film 20 is set to be lower than the edge of the positive electrode sheet 11. However, since the edge height of the insulating film 20 is relatively small, the top of the battery cell 10 is not covered, and the heat generated by the top tabs is relatively large, and the heat can be transferred from the top to the bottom. Therefore, in this embodiment, the size L of the overlapping area S should be appropriately increased to restrain the battery cell 10 to avoid the problem of increased impedance caused by excessive expansion of the battery cell 10.

[0108] Optionally, when the distance from the edge of the insulating film 20 to the end of the battery cell 10 is greater than the distance from the edge of the positive electrode sheet 11 to the end of the battery cell 10, the value of the dimension L of the overlapping area S along the circumference of the battery cell 10 can be selected as any value among 0.6mm, 0.8mm, 1mm, 5mm, 10mm or 15mm, or a value between any two values.

[0109] Setting method 2:

[0110] like Figure 4 As shown, the negative electrode sheet 12 covers the positive electrode sheet 11, and along the axial direction of the battery cell 10, the edge of the insulating film 20 is between the edge of the negative electrode sheet 12 and the edge of the positive electrode sheet 11, and the dimension L of the overlapping area S along the circumference of the battery cell 10 is in the range of 0.4 mm to 13 mm.

[0111] exist Figure 4 In the configuration shown, the edge of the insulating film 20 exceeds the edge of the positive electrode sheet 11 but does not exceed the edge of the negative electrode sheet 12 , that is, the edge of the insulating film 20 is located between the edge of the positive electrode sheet 11 and the edge of the negative electrode sheet 12 .

[0112] Specifically, since the insulating film 20 covers the positive electrode sheet 11, the expansion of the positive electrode sheet 11 is restrained. Therefore, the size L of the overlapping area S can be limited on the basis of the range of the above-mentioned setting mode 1, that is, the size of the overlapping area S is appropriately reduced. However, since there is still a part of the negative electrode sheet 12 that is not restrained, the size L of the overlapping area S cannot be too small.

[0113] Optionally, when the edge of the insulating film 20 is between the edge of the negative electrode sheet 12 and the edge of the positive electrode sheet 11, the circumferential dimension L of the overlapping area S along the battery cell 10 can be selected as any value among 0.4mm, 0.6mm, 1mm, 5mm, 10mm or 13mm, or a value between any two values.

[0114] Setting method three:

[0115] like Figure 5 As shown, along the axial direction of the battery cell 10 , the edge of the insulating film 20 is between the edge of the negative electrode sheet 12 and the edge of the separator 15 , and the dimension L of the overlapping area S along the circumference of the battery cell is in the range of 0.2 mm to 12 mm.

[0116] exist Figure 5 In the arrangement shown, the edge of the insulating film 20 exceeds the edge of the negative electrode sheet 12 but does not exceed the edge of the separator 15 , that is, the edge of the insulating film 20 is located between the edge of the negative electrode sheet 12 and the edge of the separator 15 .

[0117] Specifically, since the insulating film 20 covers the negative electrode sheet 12 , the insulating film 20 can better confine the battery cell 10 in the axial direction of the battery cell 10 , so the size L of the overlapping area S can be further appropriately reduced compared with the above-mentioned second setting method.

[0118] Optionally, when the edge of the insulating film 20 is between the edge of the negative electrode sheet 12 and the edge of the separator 15, the dimension L of the overlapping area S along the circumference of the battery cell can be selected as any value among 0.2mm, 0.5mm, 1mm, 5mm10mm or 12mm, or a value between any two values.

[0119] Setting method 4:

[0120] like Figure 6 As shown, along the axial direction of the battery cell 10, the edge of the insulating film 20 is flush with the edge of the diaphragm 15, or the edge of the insulating film 20 exceeds the edge of the diaphragm 15, and the edge of the insulating film is folded to the end face of the battery cell. At this time, the size of the overlapping area S along the circumference of the battery cell 10 is in the range of 0.5 mm to 10 mm.

[0121] exist Figure 6 In the arrangement shown, along the axial direction of the battery cell 10, the edge of the insulating film 20 can be flush with the edge of the diaphragm 15, that is, the insulating film 20 completely covers the positive electrode sheet 11, the negative electrode sheet 12 and the diaphragm 15. Further, the edge of the insulating film 20 can also be processed to exceed the edge of the diaphragm 15, and when processing the battery cell, the portion of the edge of the insulating film 20 that exceeds the diaphragm 15 is bent inward and attached to the end face of the battery cell 10. This arrangement can also achieve the effect that the insulating film 20 completely covers the positive electrode sheet 11, the negative electrode sheet 12 and the diaphragm 15.

[0122] Specifically, those skilled in the art can understand that the diaphragm 15 itself has pores, and the pores can be used to transfer heat gas. In the fourth setting, the edge of the insulating film 20 is set beyond the edge of the diaphragm 15, that is, the insulating film 20 also covers the diaphragm 15. This setting is not conducive to heat dissipation from the gap of the diaphragm 15. The inability of gas to escape will increase the expansion of the battery cell 10, so the size L of the overlapping area S needs to be appropriately increased.

[0123] Optionally, the edge of the insulating film 20 is flush with the edge of the diaphragm 15, or the edge of the insulating film 20 exceeds the edge of the diaphragm 15, and when the edge of the insulating film is folded over to the end face of the battery cell 10, the dimension L of the overlapping area S along the circumference of the battery cell 10 can be selected as any value among 0.5mm, 1mm, 3mm, 5mm or 10mm, or a value between any two values.

[0124] like Figure 1 and Figure 2As shown, in the technical solution of this embodiment, the battery further includes a shell 30, and the outer contour of the shell 30 is cylindrical. The product of the dimension L of the overlapping area S along the circumference of the battery cell and the elastic modulus M of the insulating film 20 is in the range of 0.1 to 38.

[0125] Specifically, when the shell 30 is a cylindrical shell, since the shape of the battery cell 10 is also cylindrical, there is a small gap between the outer surface of the battery cell 10 and the inner surface of the shell 30. The gap between the cylindrical battery cell 10 and the cylindrical shell 30 is small, and it is more necessary to limit the expansion of the battery cell 10. The product of the dimension L of the overlapping area S along the circumference of the battery cell and the elastic modulus M of the insulating film 20 needs to be appropriately increased.

[0126] Optionally, when the outer contour of the shell 30 is cylindrical, the product of the dimension L of the overlapping area S along the circumference of the battery cell and the elastic modulus M of the insulating film 20 can be selected as any value of 0.1, 0.5, 1, 5, 10, 20, 30 or 38, or a value between any two values. In some embodiments not shown, the outer contour of the shell 30 can also be a hexagonal prism. In this embodiment, the product of the dimension L of the overlapping area S along the circumference of the battery cell and the elastic modulus M of the insulating film 20 is in the range of 0.08 to 30.

[0127] Specifically, when the shell 50 is hexagonal, the battery cell 10 is cylindrical, so the space between the shell 50 and the battery cell 10 is relatively large (especially at the intersection of the prisms), allowing the expansion space of the battery cell 10 to increase, so the product of the dimension L of the overlapping area S along the circumference of the battery cell and the elastic modulus M of the insulating film 20 can be appropriately reduced.

[0128] Optionally, when the outer contour of the shell 30 can also be a hexagonal prism, the product of the dimension L of the overlapping area S along the circumference of the battery cell and the elastic modulus M of the insulating film 20 can be selected as any value of 0.08, 0.1, 0.5, 1, 5, 10, 20 or 30, or a value between any two values. In the technical solution of this embodiment, the ratio of the dimension L of the overlapping area S along the circumference of the battery cell to the diameter of the battery cell 10 is in the range of 0.006 to 0.4.

[0129] Specifically, the larger the diameter of the battery cell 10 is, the greater the expansion of the battery cell 10 during charging and discharging. In particular, as the diameter of the battery cell 10 increases, the force on the inner battery cell 10 increases, causing the expansion to intensify, and the size L of the overlapping portion S needs to be appropriately increased.

[0130] In contrast, when the battery cell 10 is smaller, the size L of the overlapping portion S can be appropriately reduced.

[0131] Optionally, the relationship between the dimension L of the overlapping area S along the circumference of the battery cell and the diameter of the battery cell 10 can be selected as any value among 0.006, 0.01, 0.05, 0.1, 0.2 or 0.4, etc., or a value between any two values.

[0132] Furthermore, the negative electrode sheet 12 in this embodiment includes graphite, and the cohesive force F of the negative electrode sheet 12 is in the range of 1.5 N / m to 20 N / m.

[0133] Optionally, the cohesive force F of the negative electrode sheet 12 can be selected as any value among 1.5 N / m, 5 N / m, 10 N / m, 15 N / m or 20 N / m, or a value between any two values.

[0134] Further, the negative electrode sheet 12 includes a silicon-based material, and a cohesive force F of the negative electrode sheet 12 is in a range of 2.5 N / m to 30 N / m.

[0135] Specifically, when the negative electrode sheet 12 includes too much silicon-based material, the expansion of the silicon-containing negative electrode sheet 12 will be greater. In order to avoid excessive expansion of the electrode sheet, the cohesive force of the silicon-based system needs to be greater.

[0136] Optionally, when the negative electrode sheet 12 includes a silicon-based material, the cohesive force F of the negative electrode sheet 12 can be selected as any value among 2.5 N / m, 5 N / m, 10 N / m, 20 N / m, 25 N / m, 30 N / m, etc., or a value between any two values.

[0137] Furthermore, the positive electrode sheet 11 includes a positive electrode active material, which includes a nickel-cobalt-manganese ternary material. The molar content of the nickel element is greater than or equal to 0.7 based on the total molar amount of transition metal elements other than lithium in the positive electrode active material, and the dimension L of the overlapping area S along the circumference of the battery cell is in the range of 0.3 mm to 20 mm.

[0138] Specifically, the greater the nickel content in the positive electrode sheet 11 , the greater the heat generated and the greater the expansion during the battery charging and discharging process, so the size L of the overlapping area S needs to be larger.

[0139] Optionally, based on the total molar amount of transition metal elements other than lithium in the positive electrode active material, the molar content of nickel element can be selected as 0.7, 0.8, 0.9, etc., and the size L of the overlapping area S along the circumference of the battery cell 10 can be selected as 0.3mm, 0.5mm, 1mm, 5mm, 10mm or 20mm, etc.

[0140] The following, in combination with Tables 1 to 3, introduces the test results of the battery internal resistance (DCR, unit: mΩ) and the electrode condition, i.e., the battery performance, under different values ​​of the elastic modulus M of the insulating film 20, the cohesive force F of the negative electrode sheet 12, and the size L of the overlapping area S in sixteen embodiments and two comparative examples.

[0141] In combination with Examples 1 to 16, as well as Comparative Examples 1 and 2, it can be seen that when the product of the elastic modulus M of the battery insulating film 20, the cohesive force F of the negative electrode sheet 12, and the size L of the overlapping area S (the value of L*M*F) is in the range of 0.1-2000, the battery has a lower internal resistance DCR, and therefore the battery performance of the examples is better than that of the comparative examples.

[0142] In comparative example 1, when the cohesive force F of the negative electrode sheet 12 is too small, when the overlapping size L and the elastic modulus M of the overlapping area S are also relatively small (that is, the value of L*M*F is too small, less than 0.1), the insulating film 20 cannot fully confine the battery cell 10, causing the battery cell to expand more and the battery internal resistance DCR to increase significantly (reaching a peak value of 5).

[0143] In the second comparative example, when the cohesive force F of the negative electrode sheet 12 is too large, the overlapping dimension L of the overlapping area S, and the elastic modulus M of the insulating film 20 is too large (that is, the value of L*M*F is too large, greater than 2000), although the battery cell 10 can be well imprisoned, the large elastic modulus M and overlapping dimension L cause a large reverse force on the electrode sheet, resulting in a severe indentation on the electrode sheet, and a high risk of subsequent lithium deposition on the electrode sheet. (Indentation refers to a pit on the electrode sheet in the corresponding area).

[0144] In the batteries of Examples 1 to 5, the elastic modulus M of the insulating film 20, the cohesive force F of the negative electrode sheet 12, and the size L of the overlapping area S, the three parameters and the product of the three parameters are all within the preferred range (the cohesive force F of the negative electrode sheet 12 of Examples 1 to 4 is within the more preferred range), so the internal resistance DCR of the battery remains at a low level, and the electrode sheet does not have an indentation, or the size of the indentation is controlled within 10μm. When there is no indentation on the electrode sheet, and the difference in thickness between the indentation position and other areas of the electrode sheet is controlled within 10μm, it is collectively referred to as "no"

[0145] In Examples 6 and 7, the three parameters of the elastic modulus M of the insulating film 20, the cohesive force F of the negative electrode sheet 12, and the size L of the overlapping area S are within the preferred range, but the value of L*M*F is not within the preferred range. Therefore, the internal resistance DCR of the battery is slightly increased compared with Examples 1 to 5, but is still at a relatively low level. In addition, in Example 7, the size L of the overlapping area S and the elastic modulus M of the insulating film 20 are slightly larger, resulting in a slight indentation at the position of the electrode sheet corresponding to the overlapping area of ​​the insulating film.

[0146] In the eighth to twelfth embodiments, at least some of the three parameters of the elastic modulus M of the insulating film 20, the cohesive force F of the negative electrode sheet 12, and the size L of the overlapping area S are not within the preferred range, but the value of L*M*F is within the preferred range. Therefore, the internal resistance DCR of the battery is slightly increased compared with the first to fifth embodiments.

[0147] In combination with Example 14, it can be seen that although the cohesive force F of the negative electrode sheet 12, the size of the overlapping area S and the elastic modulus M of the insulating film 20 satisfy the formula range, since the cohesive force F of the negative electrode sheet 12 is relatively large and the size L of the overlapping area S is also relatively large, the battery DCR is large and moderate indentation occurs on the electrode sheet.

[0148] It can be seen from the ninth embodiment and the twelfth embodiment that when the battery is a silicon-doped system, when the cohesive force F of the negative electrode sheet 12 is lower than 2.5 N / m, the battery internal resistance DCR performance is slightly poor.

[0149] It can be seen from the fifteenth embodiment that when the nickel content of the positive electrode sheet 11 is relatively high, the overlapping size L of the overlapping area S is too small, which will result in slightly poor internal resistance DCR performance of the battery.

[0150] Among them, for the pole piece, the specific explanation is as follows:

[0151] "No": means that there is no indentation on the electrode, or the difference between the thickness of the indentation position and the rest of the thickness is less than 10μm; "Slight indentation" means that the difference between the thickness of the indentation area of ​​the electrode and the thickness of the rest of the electrode is greater than 10μm and less than or equal to 30μm; "Moderate indentation" means that the difference between the thickness of the indentation area and the thickness of the rest of the electrode is greater than 30μm and less than or equal to 50μm; "Severe indentation" means that the difference between the thickness of the indentation area of ​​the electrode and the thickness of the rest of the electrode is greater than 50μm. Further, the following introduces the test methods of the parameters and battery performance in Table 3.

[0152] 1. Test method for cohesive force F of negative electrode sheet 12:

[0153] 1. Take the empty negative electrode sheet and soak it in dimethyl carbonate (DMC) solution at room temperature for 4 hours. After soaking, dry it;

[0154] 2. Take a standard steel plate (50mmx125mm) as the rigidity test base plate, wipe the surface of the steel plate with dust-free paper dipped in alcohol, and stick one side of a 50mmx125mm 3M double-sided tape on the steel plate to ensure that it is smooth and wrinkle-free;

[0155] 3. Cut the negative electrode sheet 12 with the active coating into 50 mm x 125 mm samples to be tested;

[0156] 4. Paste the electrode to be tested on the other side of the double-sided tape, and then paste another layer of double-sided tape on the surface of the electrode. During the pasting process, ensure that the contact is flat and there are no wrinkles;

[0157] 5. After rolling with the roller, use the universal testing machine to clamp the steel plate at one end and the 3M tape at the other end. Set the tensile machine stroke to 100mm, and do the pulling test at a speed of 300mm / min. Set the tensile machine stroke to 100mm. Record the curve in the tensile machine software diagram. When the displacement is greater than 80mm, the machine stops and reads the average tensile force of the flat part of the curve, which is the cohesive force.

[0158] 2. Elastic modulus test:

[0159] 1. Take out the empty battery cell and separate the insulating film from the battery cell;

[0160] 2. Fix the sample on the tensile machine, apply gradually increasing tensile force, and measure the deformation of the sample;

[0161] 3. Calculate the elastic modulus based on the stress-strain relationship.

[0162] 3. Battery internal resistance DCR test:

[0163] 1. Place the battery in a 25°C incubator until thermal equilibrium is reached;

[0164] 2. Charge at a constant current of 1 / 3C to the upper limit voltage (LiFePO4 upper limit voltage is 3.65V, LiNixCoyMnzO2 upper limit voltage is 4.25V), charge at a constant voltage until the current is less than 0.05C, perform more than 3 steps, and record the battery capacity C1;

[0165] 3. Let stand for 5 minutes;

[0166] 4. Charge the battery to 80% SOC at a 1 / 3C discharge rate;

[0167] 5. Discharge at a current rate of 1C for 18S, record the battery voltage U2 before discharge termination, the current I, and the battery voltage U1 after the battery voltage stabilizes. Calculate the DC internal resistance R1 according to the formula R1=(U2-U1) / I. This R1 is the 25℃ 1C discharge DCR.

[0168] In the technical solution of the present application, the insulating film 20 is coated on the outside of the battery cell 10, and there is an overlapping area S between the starting end 21 and the tail end 22, so the insulating film 20 can generate a binding force on the battery cell 10. The technical solution of this embodiment uses the size L of the overlapping area S of the insulating film 20 to tighten the battery cell 10 by comprehensively adjusting the relationship between the axial dimension L of the overlapping area S along the battery cell 10, the elastic modulus M of the insulating film 20, and the cohesive force F of the negative electrode sheet 12, so as to avoid the battery cell 10 from expanding during the charging and discharging process, which leads to an increase in the battery impedance. At the same time, it is also necessary to avoid the overlapping size L of the overlapping area S of the insulating film 20 being too large, which leads to a large reverse force of the insulating film 20 on the battery cell 10, indentations on the electrode sheet, and an increased risk of lithium precipitation. In addition, the electrode sheet may fall off. Furthermore, when the cohesive force of the negative electrode sheet 12 is small, the electrode sheet expands more during the charging and discharging process of the battery cell 10, so the size L of the overlapping area S needs to be appropriately increased to restrain the battery cell 10 and avoid the situation where the battery cell 10 expands too much and causes an increase in the internal resistance of the battery. In addition, the size L of the overlapping area S cannot be too large, which will cause the overlapping area S of the insulating film 20 to generate stress on the pole piece in the reverse direction. The pole piece may be indented, and the risk of lithium deposition increases. In addition, the risk of pole piece falling off may increase. Furthermore, by increasing the elastic modulus M of the insulating film 20, the confinement effect on the battery cell 10 is improved, and the size of the overlapping area S can be avoided from being too large. In addition, the elastic modulus M of the insulating film 20 cannot be too large, which will cause the insulating film 20 to exert a greater force on the pole piece in the reverse direction. Therefore, the technical solution of this embodiment solves the defect of the cylindrical battery in the prior art that the pole piece has a rebound tendency during the charging and discharging process, which causes the battery cell to expand severely and the internal resistance to increase.

[0169] It is worth noting that the battery cell 10 includes a positive electrode sheet 11, a negative electrode sheet 12 and a separator 15, and the separator 15 is arranged between the positive electrode sheet 11 and the negative electrode sheet 12. The positive electrode sheet 11, the negative electrode sheet 12 and the separator 15 are wound or laminated to form the battery cell 10. The positive electrode sheet 11 includes a positive electrode collector and a positive electrode active material layer, and the negative electrode sheet 12 includes a negative electrode collector and a negative electrode active material layer. The material of the positive electrode collector is not limited, as long as it has conductivity and does not cause adverse chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. can be used. Further, the negative electrode collector can be made of copper, stainless steel, nickel, titanium, etc. In a specific embodiment, the positive electrode collector can be made of aluminum, and the negative electrode collector can be made of copper.

[0170] Furthermore, the battery shell may be a steel shell, an aluminum shell, etc.; wherein the steel shell may be stainless steel, nickel-plated steel, etc.; and the aluminum shell may be an aluminum alloy, an aluminum-manganese alloy, etc.

[0171] Furthermore, the battery also includes an electrolyte, and the electrolyte of the present invention can be any electrolyte suitable for electrochemical energy storage devices in the art. The electrolyte includes an electrolyte and a solvent, and the electrolyte can generally include a lithium salt.

[0172] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A battery, characterized in that: The invention comprises a shell, a battery cell (10), and an insulating film (20) coated on the circumferential side surface of the battery cell (10); the battery cell (10) is cylindrical, the battery cell (10) comprises a positive electrode sheet (11) and a negative electrode sheet (12); two ends of the insulating film (20) respectively form a starting end (21) and a tail end (22); on the circumferential side surface of the battery cell (10), the tail end (22) of the insulating film (20) is arranged to be positioned beyond the starting end (21) so that an overlapping area (S) is formed between the starting end (21) and the tail end (22); The product of the dimension (L) of the overlapping area (S) along the circumference of the battery cell (10), the elastic modulus (M) of the insulating film (20) and the cohesive force (F) of the negative electrode sheet (12) is in the range of 0.1 to 2000; The unit of the dimension (L) of the overlapping area (S) along the circumference of the battery cell is mm; the unit of the elastic modulus (M) of the insulating film (20) is GPa; the unit of the cohesive force (F) of the negative electrode sheet (12) is N / m. The cohesive force (F) of the negative electrode sheet (12) is in the range of 1.5 N / m to 40 N / m; The elastic modulus (M) of the insulating film (20) is in the range of 0.1 GPa to 5 GPa; The dimension (L) of the overlapping area (S) along the circumference of the battery is in the range of 0.15 mm to 20 mm.

2. The battery according to claim 1, characterized in that The product of the dimension (L) of the overlapping area (S) along the circumference of the battery cell, the elastic modulus (M) of the insulating film (20) and the cohesive force (F) of the negative electrode sheet (12) is in the range of 1 to 600.

3. The battery according to claim 1, characterized in that The product of a dimension (L) of the overlapping region along the circumference of the battery core (10) and an elastic modulus (M) of the insulating film (20) is in the range of 0.05 to 60.

4. The battery according to claim 1, characterized in that The battery cell (10) comprises a battery cell body, a positive electrode tab (13) and a negative electrode tab (14); along the axial direction of the battery cell (10), the positive electrode tab (13) and the negative electrode tab (14) are respectively led out from two ends of the battery cell body; and the product of a dimension (L) of the overlapping region (S) along the circumference of the battery cell (10) and an elastic modulus (M) of the insulating film (20) is in the range of 0.08 to 35.

5. The battery according to claim 1, characterized in that The battery cell (10) further comprises a battery cell body, a positive electrode tab (13) and a negative electrode tab (14); in the axial direction of the battery cell (10), the positive electrode tab (13) and the negative electrode tab (14) are both led out from the same end of the battery cell body, and the product of the dimension (L) of the overlapping area (S) along the circumference of the battery cell (10) and the elastic modulus (M) of the insulating film (20) is in the range of 0.1 to 40.

6. The battery according to any one of claims 1 to 5, characterized in that In the axial direction of the battery cell (10), the distance from the edge of the insulating film (20) to the end of the battery cell (10) is greater than the distance from the edge of the positive electrode sheet (11) to the end of the battery cell (10), and the dimension (L) of the overlapping area (S) along the circumference of the battery cell (10) is in the range of 0.6 mm to 15 mm.

7. The battery according to any one of claims 1 to 5, characterized in that In the axial direction of the battery cell (10), the edge of the negative electrode sheet (12) is arranged beyond the edge of the positive electrode sheet (11), the edge of the insulating film (20) is between the edge of the negative electrode sheet (12) and the edge of the positive electrode sheet (11), and the dimension (L) of the overlapping area (S) along the circumference of the battery cell (10) is in the range of 0.4 mm to 13 mm.

8. The battery according to any one of claims 1 to 5, characterized in that The battery cell (10) further comprises a diaphragm (15), wherein in the axial direction of the battery cell (10), the edge of the diaphragm (15) exceeds the edge of the negative electrode sheet (12) and the edge of the positive electrode sheet (11), the edge of the insulating film (20) is between the edge of the negative electrode sheet (12) and the edge of the diaphragm (15), and the dimension (L) of the overlapping area (S) along the circumference of the battery cell is in the range of 0.2 mm to 12 mm.

9. The battery according to any one of claims 1 to 5, characterized in that The battery cell (10) further comprises a diaphragm (15), wherein in the axial direction of the battery cell (10), the edge of the diaphragm (15) exceeds the edge of the negative electrode sheet (12) and the edge of the positive electrode sheet (11), and the edge of the insulating film (20) is flush with the edge of the diaphragm (15); or, the edge of the insulating film (20) exceeds the edge of the diaphragm (15), and the edge of the insulating film is folded onto the end face of the battery cell (10), and the dimension (L) of the overlapping area (S) along the circumference of the battery cell (10) is in the range of 0.5 mm to 10 mm.

10. The battery according to any one of claims 1 to 5, characterized in that The battery further comprises a shell (30), the outer contour of the shell (30) is a hexagonal prism, and the product of the dimension (L) of the overlapping area (S) along the circumference of the battery cell and the elastic modulus (M) of the insulating film (20) is in the range of 0.08 to 30.

11. The battery according to any one of claims 1 to 5, characterized in that The battery further comprises a shell (30), the outer contour of the shell (30) is cylindrical, and the product of the dimension (L) of the overlapping area (S) along the circumference of the battery core and the elastic modulus (M) of the insulating film (20) is in the range of 0.1 to 38.

12. The battery according to any one of claims 1 to 5, characterized in that The ratio of the dimension (L) of the overlapping area (S) along the circumference of the battery core to the diameter of the battery core (10) is in the range of 0.006 to 0.

4.

13. The battery according to any one of claims 1 to 5, characterized in that The negative electrode sheet (12) comprises graphite, and the cohesive force (F) of the negative electrode sheet (12) is in the range of 1.5 N / m to 20 N / m.

14. The battery according to any one of claims 1 to 5, characterized in that The negative electrode sheet (12) comprises a silicon-based material, and the cohesive force (F) of the negative electrode sheet (12) is in the range of 2.5 N / m to 30 N / m.

15. The battery according to any one of claims 1 to 5, characterized in that The positive electrode sheet (11) comprises a positive electrode active material, wherein the positive electrode active material comprises a nickel-cobalt-manganese ternary material, wherein the molar content of the nickel element accounts for greater than or equal to 0.7 of the total molar amount of transition metal elements other than lithium in the positive electrode active material, and the dimension (L) of the overlapping region (S) along the circumference of the battery cell is in the range of 0.3 mm to 20 mm.

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