A battery cell, a method for manufacturing the same, a battery device, and a power-using device

Abstract

The application provides a battery monomer, a preparation method thereof, a battery device and a power utilization device, and belongs to the technical field of batteries. The battery monomer comprises an electrode tab, the electrode tab comprises a current collector and a film layer, the current collector is provided with a plurality of through holes, the film layer comprises at least two sub-film layers, and the Dv50 particle size of the active material in the at least two sub-film layers changes in a gradient along the thickness direction of the film layer. The battery monomer of the application is provided with a plurality of through holes on the current collector, in the process of drying the electrode tab, the solvent can volatilize out through the plurality of through holes of the current collector, a capillary force difference is formed between the sub-film layer close to the current collector and the sub-film layer away from the current collector, the capillary force difference promotes the movement of at least part of the solvent in the sub-film layer away from the current collector in the direction of the current collector, thereby improving the problem of binder floating caused by the electrode tab in the drying process, and further improving the fast-charging performance of the battery monomer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery monomer, a preparation method thereof, a battery device and a power utilization device. BACKGROUND

[0002] In recent years, with the application range of lithium ion batteries becoming more and more extensive, lithium ion batteries are widely used in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Since lithium ion batteries have achieved great development, higher requirements have been put forward for their performance.

[0003] During the drying process of the electrode tab, the solvent in the slurry is easy to carry the binder during the volatilization process, thereby causing the binder to float up, so that the binder is unevenly distributed in the film layer, and the final electrode tab presents a state of surface enrichment of the binder and less binder in the lower layer. The binder floating up not only affects the production efficiency, but also causes problems such as blockage of electron and ion transmission, local stress concentration and deterioration of adhesion, thereby seriously restricting the fast charging performance of the battery. SUMMARY

[0004] The present application is made in view of the above-mentioned problems, and aims to provide a battery monomer, a preparation method thereof, a battery device and a power utilization device, which can improve the problem of electrode tab binder floating up, thereby improving the fast charging performance of the battery monomer.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a battery monomer, which comprises an electrode tab, the electrode tab comprising a current collector and a film layer provided on one surface of the current collector, the current collector being provided with a plurality of through holes, the film layer comprising an active material, the active material being a positive electrode active material or a negative electrode active material, the film layer comprising at least two sub-film layers, along the thickness direction of the film layer, the Dv50 particle size of the active material in the at least two sub-film layers changes in a gradient manner, and the Dv50 particle size of the active material in the sub-film layer close to the current collector is smaller than the Dv50 particle size of the active material in the sub-film layer away from the current collector, the ratio of the area density of any two adjacent sub-film layers in the at least two sub-film layers is 5:1~1:5; the binder floating amount ratio of the film layer is 0.1%~40%, and the binder floating amount ratio=(surface layer binder content-bottom layer binder content) / bottom layer binder content.

[0006] Therefore, the battery cell of the present application can reduce the migration of the bottom binder to the surface layer by the capillary force difference and changing the solvent evaporation direction, thereby being beneficial to improve the problem of binder floating caused by the drying process of the electrode sheet, so that the binder floating amount of the film layer accounts for the above range, and the fast charging performance of the battery cell is improved.

[0007] In any embodiment, the ratio of the Dv50 particle diameter of the active material in the sub-film layer far from the current collector to the sub-film layer close to the current collector is greater than 1 and less than or equal to 30. By making the ratio of the Dv50 particle diameter of the active material in the sub-film layer far from the current collector to the sub-film layer close to the current collector in the above range, the capillary force difference is formed between the sub-film layer close to the current collector and the sub-film layer far from the current collector, thereby promoting the movement of at least part of the solvent in the sub-film layer far from the current collector to the direction of the current collector.

[0008] In any embodiment, the diameter of the through hole is 5-50 μm. By making the diameter of the through hole of the current collector in the above range, at least part of the solvent in the film layer can volatilize through the plurality of through holes of the current collector during the drying process of the electrode sheet, and the precipitation of the active material and the binder in the film layer is avoided.

[0009] In any embodiment, the surface area of the through hole accounts for 15-60% of the surface area of the current collector. By making the surface area of the through hole account for the surface area of the current collector in the above range, at least part of the solvent in the film layer can volatilize through the plurality of through holes of the current collector during the drying process of the electrode sheet, and the strength of the current collector can be maintained.

[0010] In any embodiment, the film layer includes a first film layer and a second film layer, the first film layer is bonded to the current collector, the second film layer is bonded to the first film layer, the ratio of the Dv50 particle size of the active material in the second film layer to the Dv50 particle size of the active material in the first film layer is greater than 1 and less than or equal to 30, and the ratio of the areal density of the second film layer to the areal density of the first film layer is 5:1 to 1:5. By dividing the film layer into the first film layer and the second film layer, the difference in the Dv50 particle size of the active material in the first film layer and the second film layer in the thickness direction thereof forms capillaries of different sizes, so that a capillary force difference is formed between the first film layer and the second film layer, which promotes the movement of at least part of the solvent in the film layer away from the current collector to the direction of the current collector.

[0011] In any embodiment, the hole wall of the through hole is provided with a hydrophilic layer. By providing the hole wall of the through hole of the current collector with the hydrophilic layer, the hydrophilic layer has hydrogen bonding to water molecules, thereby accelerating the capillary action on the solvent in the film layer, so that at least part of the water solvent in the film layer moves in the direction of the current collector, and this part of the water solvent is finally also volatilized through the plurality of through holes of the current collector.

[0012] In any embodiment, the material of the hydrophilic layer includes at least one of an oxygen group modified carbon material, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate, and aluminum oxide. By using the above-mentioned material to make the hydrophilic layer, the capillary action on the solvent in the film layer can be accelerated, so that at least part of the water solvent in the film layer moves in the direction of the current collector, and this part of the water solvent is finally also volatilized through the plurality of through holes of the current collector.

[0013] In any embodiment, the thickness of the hydrophilic layer is 1 nm to 300 nm. By making the thickness of the hydrophilic layer in the above-mentioned range, it is beneficial to accelerate the capillary action on the solvent in the film layer, and it will not affect the volatilization of the solvent in the film layer through the plurality of through holes of the current collector.

[0014] In any embodiment, at least one of the inner wall and the outer wall of the current collector is provided with a hydrophilic layer. By providing at least one of the inner wall and the outer wall of the current collector with the hydrophilic layer, the hydrophilic layer has hydrogen bonding to water molecules, thereby accelerating the capillary action on the solvent in the film layer, so that at least part of the water solvent in the film layer moves in the direction of the current collector, and in particular when the outer wall of the current collector is provided with the hydrophilic layer, at least part of the water solvent in the film layer can directly move to the side of the current collector where no film layer is provided.

[0015] In any embodiment, the hole wall of the through hole is further provided with a linear conductive carbon, and the linear conductive carbon extends to the middle part of the through hole. By providing the hole wall of the through hole of the current collector with the linear conductive carbon extending to the middle part of the through hole, the linear conductive carbon can anchor the binder and prevent the binder in the film layer from being precipitated through the through hole.

[0016] In any embodiment, the length of the linear conductive carbon is 0.5 μm to 10 μm. By making the length of the linear conductive carbon in the above range, the linear conductive carbon can anchor the binder and prevent the binder in the film layer from being precipitated through the through holes, and will not damage the hydrophilic layer on the inner wall of the through holes of the current collector because it is too long.

[0017] In any embodiment, the linear conductive carbon comprises at least one of carbon nanotubes and carbon fibers.

[0018] In any embodiment, the inner wall of the current collector is provided with at least one of porous conductive carbon and linear conductive carbon. By providing the inner wall of the current collector with at least one of porous conductive carbon and linear conductive carbon, the porous conductive carbon and the linear conductive carbon have a large area, which can provide more bonding sites for the film layer, improve the adhesion of the film layer to the current collector, and improve the conductivity of the interface between the film layer and the current collector. In addition, when the inner wall of the current collector is provided with porous conductive carbon, the porous structure can provide a siphon effect to promote the movement of at least part of the solvent in the film layer away from the current collector in the direction of the current collector.

[0019] The second aspect of the present application provides a method for preparing a battery cell, which comprises: providing at least two layers of slurry on one surface of a current collector provided with a plurality of through holes, the at least two layers of slurry comprising an active material, the active material being a positive electrode active material or a negative electrode active material, the Dv50 particle size of the active material in the at least two layers of slurry changing in a gradient along the thickness direction of the current collector, the Dv50 particle size of the active material in the slurry close to the current collector being smaller than the Dv50 particle size of the active material in the slurry away from the current collector, and the ratio of the area density of any two adjacent layers of slurry being 5:1 to 1:5, and then heating the current collector on one side by at least one of magnetic induction, infrared and hot air until the solvent in the slurry is volatilized through the plurality of through holes.

[0020] Therefore, the preparation method of the battery cell of the application can heat the side of the current collector by using magnetic induction, infrared, hot air and the like during the drying process of the electrode tab, the solvent in the slurry close to the current collector can first absorb heat and then volatilize through the multiple through holes of the current collector, and when the mass ratio of the area density of any two adjacent layers of slurry is in the above range, the difference in the Dv50 particle size of the active material in the slurry in the thickness direction will form capillaries of different sizes, so that a capillary force difference is formed between the slurry close to the current collector and the slurry away from the current collector, which will promote the movement of at least part of the solvent in the slurry away from the current collector in the direction of the current collector, and this part of the solvent will also volatilize through the multiple through holes of the current collector. The application can reduce the migration of the binder in the bottom layer to the surface layer by the capillary force difference and changing the evaporation direction of the solvent, thereby improving the problem of binder floating caused by the drying process of the electrode tab, and further improving the fast charging performance of the battery cell.

[0021] The third aspect of the application provides a battery device, which comprises the battery cell in the above-mentioned embodiments or the battery cell prepared according to the preparation method of the battery cell in the above-mentioned embodiments.

[0022] The fourth aspect of the application provides a power utilization device, which comprises the battery cell in the above-mentioned embodiments or the battery device in the above-mentioned embodiments, and the battery cell or the battery device is used to provide electric energy. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of the first electrode tab of the application.

[0024] Figure 2 is a schematic diagram of the second electrode tab of the application.

[0025] Figure 3 is a schematic diagram of the third electrode tab of the application.

[0026] Figure 4 is a schematic diagram of the fourth electrode tab of the application.

[0027] Figure 5 is a schematic diagram of the battery cell of an embodiment of the application.

[0028] Figure 6 is Figure 5 is an exploded view of the battery cell of an embodiment of the application.

[0029] Figure 7 is a schematic diagram of the battery module of an embodiment of the application.

[0030] Figure 8 is a schematic diagram of the battery pack of an embodiment of the application.

[0031] Figure 9 is Figure 8 exploded view of a battery pack according to an embodiment of the present application.

[0032] Figure 10 is a schematic view of an electric device using a battery cell according to an embodiment of the present application as a power source.

[0033] BRIEF DESCRIPTION OF DRAWINGS

[0034] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 case; 52 electrode assembly; 53 cover plate; 54 current collector; 541 through hole; 542 first film layer; 543 second film layer; 544 hydrophilic layer; 545 linear conductive carbon. DETAILED DESCRIPTION

[0035] Hereinafter, a battery cell, a method of manufacturing the same, a battery device, and an electric device according to an embodiment of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there can be cases where unnecessary detailed descriptions are omitted. For example, there can be cases where detailed descriptions of matters well known in the art, repetitive descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0036] The ranges disclosed herein are defined by their lower and upper limits. Ranges created by the upper and lower limits are inclusive of the endpoints. Ranges created by the upper and lower limits are also inclusive of the endpoints. Ranges created by the upper and lower limits are also inclusive of the endpoints. Any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, all sub-ranges having a minimum value of equal to or greater than 1 and a maximum value of equal to or less than 10, so long as the sub-range is otherwise within the range. In other words, a range of "1 to 10" means "between 1 and 10" including 1 and 10. The same applies to ranges having endpoints of "to" (open-ended) rather than "from and to" (closed). Also, the terms "first", "second", "third", etc. do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. In addition, the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise. Stated differently, the use of the singular includes the plural unless it would be clear that the singular is meant unless explicitly identified as "one", "only one", or "exactly one". All numerical ranges are inclusive of their endpoints.

[0037] If not particularly specified, all the embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0038] If not particularly specified, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0039] If not particularly specified, all the steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0040] The preparation process of the electrode tab of the battery device is an important process affecting the performance of the battery. The microstructure of the electrode tab, such as the floating of the binder, will directly affect the transmission of electrons and ions in the electrode tab. At present, in the preparation process of the electrode tab of the battery device, the following wet coating process is usually adopted: preparation of active material slurry → coating → drying → rolling. During the drying process of the electrode tab, especially near the transition point (the junction of the upper layer of the electrode tab which has been dried and the lower layer which has not been dried), the solvent in the upper layer of the active material layer is first volatilized, and the solvent in the lower layer quickly rises. The solvent in the slurry is easy to carry the binder in the rising process, thereby causing the floating of the binder, making the binder unevenly distributed in the film layer, and the final electrode tab showing a state of surface enrichment of the binder and less binder in the lower layer.

[0041] The floating of the binder during the drying process of the electrode tab will cause the surface layer of the electrode tab to be rich in binder, and the surface layer of the electrode tab is easy to be densified after cold pressing. On the one hand, the densified surface layer of the electrode tab will cause the electrolyte to be difficult to infiltrate, which seriously affects the production efficiency of the battery device; on the other hand, the low porosity of the surface layer of the electrode tab will cause the ion and electron to be difficult to shuttle in the electrode tab, local stress concentration and deterioration of the adhesion, etc., thereby seriously restricting the fast charging performance of the battery.

[0042] Based on this, the present application proposes a battery monomer and a preparation method thereof, a battery device and a power utilization device. The present application and optional embodiments will be described in more detail below.

[0043] The application provides a battery monomer, which comprises an electrode tab, the electrode tab comprises a current collector and a film layer arranged on one surface of the current collector, the current collector is provided with a plurality of through holes, the film layer comprises active material, the active material is positive active material or negative active material, the film layer comprises at least two sub-film layers, the Dv50 particle size of the active material in the at least two sub-film layers changes in a gradient along the thickness direction of the film layer, and the Dv50 particle size of the active material in the sub-film layer close to the current collector is smaller than the Dv50 particle size of the active material in the sub-film layer far from the current collector, and the ratio of the area density of any two adjacent sub-film layers in the at least two sub-film layers is 5:1-1:5.

[0044] The adhesive floating amount ratio of the film layer is 0.1%-40%, and the adhesive floating amount ratio=(surface layer adhesive content-bottom layer adhesive content) / bottom layer adhesive content.

[0045] The electrode tab comprises a negative electrode tab or a positive electrode tab, and the punched current collector of the application is suitable for the negative electrode tab and the positive electrode tab.

[0046] The through hole is a pore structure penetrating through the current collector, and the application does not limit the cross-sectional shape of the through hole, for example, the cross-sectional shape of the through hole can be circular, rectangular, rhombic or triangular.

[0047] The at least two sub-film layers of the film layer refer to a plurality of sub-film layers arranged in sequence along the thickness direction of the film layer, and the application does not limit the number of sub-film layers, for example, the number can be two, three, four or five.

[0048] The Dv50 particle size of the active material in the at least two sub-film layers changes in a gradient, that is, the Dv50 particle size of the active material in the plurality of sub-film layers changes in a gradient along the thickness direction of the film layer, and the Dv50 particle size in each sub-film layer can also change in a gradient or be uniformly distributed.

[0049] For example, when the sub-film layer is two layers, i.e., a first layer sub-film layer and a second layer sub-film layer, the first layer sub-film layer is combined with the current collector, the second layer sub-film layer is combined with the first layer sub-film layer, and the Dv50 particle size of the active material in the first layer sub-film layer is smaller than the Dv50 particle size of the active material in the second layer sub-film layer.

[0050] When the sub-film layer is three layers, i.e., a first layer sub-film layer, a second layer sub-film layer and a third layer sub-film layer, the first layer sub-film layer is combined with the current collector, the second layer sub-film layer is combined with the first layer sub-film layer, and the third layer sub-film layer is combined with the second layer sub-film layer, the Dv50 particle size of the active material in the first layer sub-film layer is smaller than the Dv50 particle size of the active material in the second layer sub-film layer, and the Dv50 particle size of the active material in the second layer sub-film layer is smaller than the Dv50 particle size of the active material in the third layer sub-film layer.

[0051] When the sub-film layers are four layers, which are the first layer sub-film layer, the second layer sub-film layer, the third layer sub-film layer and the fourth layer sub-film layer, the first layer sub-film layer is combined with the current collector, the second layer sub-film layer is combined with the first layer sub-film layer, the third layer sub-film layer is combined with the second layer sub-film layer, the fourth layer sub-film layer is combined with the third layer sub-film layer, the Dv50 particle size of the active material in the first layer sub-film layer is smaller than the Dv50 particle size of the active material in the second layer sub-film layer, and the Dv50 particle size of the active material in the second layer sub-film layer is smaller than the Dv50 particle size of the active material in the third layer sub-film layer, and the Dv50 particle size of the active material in the third layer sub-film layer is smaller than the Dv50 particle size of the active material in the fourth layer sub-film layer.

[0052] The Dv50 particle size of the active material in different sub-film layers can be measured by dissolving the scraped powder in water and then using a laser, or by sampling and ion polishing the cross section and then using a scanning electron microscope (SEM) to obtain statistics.

[0053] The ratio of the area density of any two adjacent sub-film layers in the at least two sub-film layers refers to the mass contained per unit area of any two adjacent sub-film layers in the at least two sub-film layers.

[0054] The area density of the sub-film layer can be measured by the following method: taking a regular size electrode tab, weighing it, the mass is m1, measuring its length and width, and calculating its area, which is S1; scraping different sub-film layers on the electrode tab to obtain the mass of different sub-film layers, and the area density of different sub-film layers = the mass of different sub-film layers / S1.

[0055] As an example, the ratio of the area density of any two adjacent sub-film layers in the at least two sub-film layers can be 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4 or 1:5.

[0056] The surface binder content refers to the mass percentage of the binder in the surface layer (far from the current collector) of the film layer with a thickness of 10 μm to 30 μm.

[0057] The bottom binder content refers to the mass percentage of the binder in the bottom layer (close to the current collector) of the film layer with a thickness of 10 μm to 30 μm.

[0058] As an example, the binder floating amount percentage of the film layer can be 0.1%, 0.5%, 1%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40%.

[0059] Optionally, the binder floating amount percentage of the film layer is 0.1% to 30%.

[0060] Optionally, the binder floating amount percentage of the film layer is 0.1% to 20%.

[0061] Optionally, the binder floating amount of the film layer accounts for 0.1% to 10%.

[0062] Optionally, the binder floating amount of the film layer accounts for 5% to 10%.

[0063] The binder floating amount of the film layer can be measured by the following method: using a surface and interface cutting analysis system (SAICAS) or manually scraping powder to obtain 20 μm-thick film layer powder from the surface layer and the bottom layer of the film layer, respectively, and testing the surface layer binder content and the bottom layer binder content by thermogravimetric analysis (TG), and the binder floating amount accounts for = (surface layer binder content-bottom layer binder content) / bottom layer binder content.

[0064] The battery cell of the present application can reduce the migration of the bottom layer binder to the surface layer by opening multiple through holes in the current collector, heating the side of the current collector using magnetic induction, infrared, hot air, etc. during the drying process of the electrode plate, and the solvent in the sub-film layer close to the current collector can first absorb heat and then volatilize through the multiple through holes of the current collector. When the specific surface density ratio of any two adjacent sub-film layers in the at least two sub-film layers is in the above range, the difference in the Dv50 particle size of the active material in different sub-film layers in the thickness direction will form capillaries of different sizes, so that a capillary force difference is formed between the sub-film layer close to the current collector and the sub-film layer far from the current collector. The capillary force difference will promote the movement of at least part of the solvent in the sub-film layer far from the current collector in the direction of the current collector, and this part of the solvent will also volatilize through the multiple through holes of the current collector. The present application can reduce the migration of the bottom layer binder to the surface layer by the capillary force difference and changing the solvent evaporation direction, thereby improving the problem of binder floating caused by the drying process of the electrode plate, so that the binder floating amount of the film layer accounts for in the above range, and the fast charging performance of the battery cell is improved.

[0065] In some embodiments, the ratio of the Dv50 particle size of the active material in the sub-film layer far from the current collector to the sub-film layer close to the current collector is greater than 1 and less than or equal to 30.

[0066] For example, the ratio of the Dv50 particle size of the active material in the sub-film layer far from the current collector to the sub-film layer close to the current collector can be 1.1, 1.5, 2, 5, 10, 15, 20, 25, or 30.

[0067] It should be noted that the Dv50 particle size ratio of the active material in the different adjacent two sub-film layers can be the same or different. For example, when the film layer includes three sub-film layers, i.e., a first layer sub-film layer, a second layer sub-film layer and a third layer sub-film layer, the first layer sub-film layer is combined with the current collector, the second layer sub-film layer is combined with the first layer sub-film layer, and the third layer sub-film layer is combined with the second layer sub-film layer, the Dv50 particle size ratio of the active material in the first layer sub-film layer and the second layer sub-film layer is 1.5, the Dv50 particle size ratio of the active material in the first layer sub-film layer and the second layer sub-film layer is 1.5, and the Dv50 particle size ratio of the active material in the second layer sub-film layer and the third layer sub-film layer is 5.

[0068] The present application forms a capillary force difference between the sub-film layer close to the current collector and the sub-film layer far from the current collector by making the Dv50 particle size ratio of the active material in the sub-film layer far from the current collector and the sub-film layer close to the current collector in the above range, thereby promoting the movement of at least part of the solvent in the sub-film layer far from the current collector to the direction of the current collector.

[0069] In some embodiments, the diameter of the through hole is 5 μm to 50 μm.

[0070] For example, the diameter of the through hole can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm.

[0071] The diameter of the through hole of the current collector can be directly observed by scanning electron microscopy (SEM) to measure the surface morphology of the through hole.

[0072] The present application makes the diameter of the through hole of the current collector in the above range, so that at least part of the solvent in the film layer can volatilize through the multiple through holes of the current collector during drying of the electrode tab, and the active material and the binder in the film layer are not precipitated.

[0073] In some embodiments, the surface area ratio of the through hole area to the surface area of the current collector is 15% to 60%.

[0074] For example, the surface area ratio of the through hole area to the surface area of the current collector can be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%.

[0075] The surface area ratio of the through hole area of the current collector to the surface area of the current collector = the through hole area of the current collector / the surface area of the current collector * 100%.

[0076] The application can make at least part of the solvent in the membrane layer volatilize through the plurality of through holes of the current collector while maintaining the strength of the current collector by making the ratio of the through hole area of the current collector to the surface area of the current collector in the above range during drying of the electrode tab.

[0077] In some embodiments, the membrane layer includes a first membrane layer and a second membrane layer, the first membrane layer is combined with the current collector, and the second membrane layer is combined with the first membrane layer. The ratio of the Dv50 particle size of the active material in the second membrane layer to the Dv50 particle size of the active material in the first membrane layer is greater than 1 and less than or equal to 30. The ratio of the area density of the second membrane layer to the area density of the first membrane layer is 5:1 to 1:5.

[0078] The first membrane layer is a membrane layer structure containing active material close to the current collector.

[0079] Optionally, the mass percentage of the active material in the first membrane layer is 90wt% to 99wt%.

[0080] The second membrane layer is a membrane layer structure containing active material away from the current collector.

[0081] Optionally, the mass percentage of the active material in the second membrane layer is 90wt% to 99wt%.

[0082] Optionally, the thickness ratio of the first membrane layer to the second membrane layer is 0.2 to 8.

[0083] The application divides the membrane layer into a first membrane layer and a second membrane layer. The difference in the Dv50 particle size of the active material in the first membrane layer and the second membrane layer in the thickness direction thereof forms capillaries of different sizes, so that a capillary force difference is formed between the first membrane layer and the second membrane layer, which promotes the movement of at least part of the solvent in the membrane layer away from the current collector in the direction of the current collector.

[0084] In some embodiments, the hole wall of the through hole is provided with a hydrophilic layer.

[0085] The hydrophilic layer is a layered structure with strong water molecule affinity.

[0086] The application provides the hydrophilic layer on the hole wall of the through hole of the current collector. The hydrophilic layer has hydrogen bonding effect on water molecules, thereby accelerating the siphoning of the solvent in the membrane layer, so that at least part of the water solvent in the membrane layer moves in the direction of the current collector, and finally volatilizes through the plurality of through holes of the current collector.

[0087] In some embodiments, the material of the hydrophilic layer includes at least one of an oxygen-containing group modified carbon material, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS), and aluminum oxide. PEDOT:PSS

[0088] ​The oxygen-containing group modified carbon material refers to a composite carbon material which significantly improves the hydrophilicity of the carbon material by introducing polar groups such as hydroxyl groups, carboxyl groups, and epoxy groups on the surface of the carbon material, while retaining the high electrical conductivity and mechanical strength of the carbon material. The oxygen-containing group modified carbon material includes graphene oxide, oxidized carbon nanotubes, and oxidized carbon black.

[0089] Poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) is a composite composed of a substituted polythiophene and a polyanion compound, and has a conductivity of 1000 S / cm, and has both hydrophilicity and conductivity.

[0090] The surface of aluminum oxide contains 4-6 hydroxyl groups per square nanometer, can form a hydrogen bond network with water molecules, and can spontaneously adsorb water molecules in an exposed state to form a water film, and is a good material for a hydrophilic layer.

[0091] The hydrophilic layer made of the above material can accelerate the siphoning of the solvent in the film layer, so that at least part of the water solvent in the film layer moves towards the current collector, and this part of the water solvent is finally volatilized through the multiple through holes of the current collector.

[0092] In some embodiments, the thickness of the hydrophilic layer is 1 nm-300 nm.

[0093] For example, the thickness of the hydrophilic layer can be 1 nm, 2 nm, 5 nm, 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, or 300 nm.

[0094] Alternatively, the thickness of the hydrophilic layer is 5-300 nm.

[0095] The present application has the advantages of accelerating the siphoning of the solvent in the film layer by the hydrophilic layer, and not affecting the volatilization of the solvent in the film layer through the multiple through holes of the current collector.

[0096] In some embodiments, at least one of the inner wall and the outer wall of the current collector is provided with a hydrophilic layer.

[0097] The inner wall of the current collector refers to the side of the current collector used to combine the film layer.

[0098] The outer wall of the current collector refers to the side of the current collector that does not combine the film layer, and the outer wall and the inner wall of the current collector are oppositely arranged.

[0099] Alternatively, the material of the hydrophilic layer on at least one of the inner wall and the outer wall of the current collector includes at least one of an oxygen-containing group modified carbon material, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate, and aluminum oxide.

[0100] Optionally, the thickness of the hydrophilic layer on at least one of the inner wall and the outer wall of the current collector is 1 nm to 300 nm.

[0101] Optionally, the thickness of the hydrophilic layer on at least one of the inner wall and the outer wall of the current collector is 5 nm to 300 nm.

[0102] The present application can accelerate the siphon effect of the solvent in the membrane layer by arranging the hydrophilic layer on at least one of the inner wall and the outer wall of the current collector, and the hydrogen bond of the hydrophilic layer to water molecules, so that at least part of the water solvent in the membrane layer moves towards the current collector. In particular, when the outer wall of the current collector is provided with a hydrophilic layer, at least part of the water solvent in the membrane layer can directly move to the side of the current collector without the membrane layer.

[0103] It should be noted that the arrangement position of the hydrophilic layer includes the following cases:

[0104] The first case is that the hydrophilic layer is arranged only on the hole wall of the through hole of the current collector; the second case is that the hydrophilic layer is arranged only on the inner wall of the current collector; the third case is that the hydrophilic layer is arranged only on the outer wall of the current collector; the fourth case is that the hydrophilic layer is arranged on the hole wall of the through hole of the current collector and the inner wall of the current collector; the fifth case is that the hydrophilic layer is arranged on the hole wall of the through hole of the current collector and the outer wall of the current collector; the sixth case is that the hydrophilic layer is arranged on the inner wall and the outer wall of the current collector; and the seventh case is that the hydrophilic layer is arranged on the hole wall of the through hole of the current collector, the inner wall and the outer wall of the current collector.

[0105] In some embodiments, the hole wall of the through hole is further provided with linear conductive carbon extending to the middle part of the through hole.

[0106] The linear conductive carbon refers to a carbon-based material in the form of a line or a fiber, which can construct an efficient conductive network through its high aspect ratio.

[0107] Optionally, the aspect ratio of the linear conductive carbon is ≥100.

[0108] The present application can anchor the binder and prevent the binder in the membrane layer from being precipitated through the through hole by arranging the linear conductive carbon extending to the middle part of the through hole on the hole wall of the through hole of the current collector.

[0109] In some embodiments, the length of the linear conductive carbon is 0.5 μm to 10 μm.

[0110] For example, the length of the linear conductive carbon can be 0.5 μm, 1 μm, 2 μm, 5 μm, 8 μm or 10 μm.

[0111] The present application can anchor the binder and prevent the binder in the membrane layer from being precipitated through the through hole by arranging the linear conductive carbon extending to the middle part of the through hole on the hole wall of the through hole of the current collector.

[0112] In some embodiments, the linear conductive carbon comprises at least one of carbon nanotubes and carbon fibers.

[0113] As an example, the linear conductive carbon can be carbon nanotubes or carbon fibers, or can be a mixture of carbon nanotubes and carbon fibers.

[0114] In some embodiments, the inner wall of the current collector is provided with at least one of the porous conductive carbon and the linear conductive carbon.

[0115] As an example, the inner wall of the current collector can be provided with only the porous conductive carbon or only the linear conductive carbon, or provided with both the porous conductive carbon and the linear conductive carbon.

[0116] Optionally, the linear conductive carbon has an aspect ratio ≥ 100.

[0117] Optionally, the linear conductive carbon has a length of 0.5 μm to 10 μm.

[0118] Optionally, the linear conductive carbon comprises at least one of carbon nanotubes and carbon fibers.

[0119] Optionally, the porous conductive carbon has a specific surface area of 500 m2 / g to 1500 m2 / g.

[0120] Optionally, the porous conductive carbon comprises Ordered Mesoporous Carbon (OMC).

[0121] The present application provides at least one of the porous conductive carbon and the linear conductive carbon on the inner wall of the current collector, which has a large area and can provide more bonding sites for the film layer, thereby improving the adhesion of the film layer to the current collector and the conductivity of the interface between the film layer and the current collector. In addition, when the inner wall of the current collector is provided with the porous conductive carbon, the porous structure can provide a siphon effect to promote the movement of at least part of the solvent in the film layer away from the current collector to the direction of the current collector.

[0122] It should be noted that the setting positions of the porous conductive carbon and the linear conductive carbon include the following cases:

[0123] First, only the linear conductive carbon is provided on the hole wall of the current collector; second, at least one of the porous conductive carbon and the linear conductive carbon is provided on the inner wall of the current collector; and third, the linear conductive carbon is provided on the hole wall of the current collector, and at least one of the porous conductive carbon and the linear conductive carbon is provided on the inner wall of the current collector.

[0124] The application also provides a preparation method of a battery monomer, which comprises: arranging at least two layers of slurries on one surface of a current collector provided with a plurality of through holes, the at least two layers of slurries comprising active materials, the active materials being positive or negative active materials, the Dv50 particle size of the active materials in the at least two layers of slurries changing in a gradient along the thickness direction of the current collector, the Dv50 particle size of the active materials in the slurry close to the current collector being smaller than the Dv50 particle size of the active materials in the slurry far from the current collector, and the ratio of the area densities of any two adjacent layers of slurries being 5:1-1:5, and then heating the current collector on one side thereof by at least one of magnetic induction, infrared and hot air until the solvent in the slurry volatilizes through the plurality of through holes.

[0125] The preparation method of the battery monomer of the application can heat one side of the current collector by magnetic induction, infrared, hot air and the like during the drying process of the electrode sheet, the solvent in the slurry close to the current collector can first absorb heat and then volatilize through the plurality of through holes of the current collector, and when the ratio of the area densities of any two adjacent layers of slurries is in the above range, the difference in the Dv50 particle size of the active materials in the slurry in the thickness direction thereof can form capillary tubes of different sizes, so that a capillary force difference is formed between the slurry close to the current collector and the slurry far from the current collector, the capillary force difference can promote the movement of at least part of the solvent in the slurry far from the current collector to the direction of the current collector, and this part of the solvent also volatilizes through the plurality of through holes of the current collector. The application can reduce the migration of the bottom binder to the surface layer by the capillary force difference and the change of the solvent evaporation direction, thereby being beneficial to improving the problem of binder floating caused by the drying process of the electrode sheet, and further improving the fast-charging performance of the battery monomer.

[0126] Please refer to Figure 1 The first electrode sheet provided by the embodiment of the application comprises a current collector 54 and a film layer arranged on one surface of the current collector 54, the current collector 54 is provided with a plurality of through holes 541, the film layer comprises active materials, the film layer comprises a first film layer 542 and a second film layer 543, the first film layer 542 is combined with the current collector 54, the second film layer 543 is combined with the first film layer 542, the ratio of the Dv50 particle size of the active materials in the second film layer 543 to the Dv50 particle size of the active materials in the first film layer 542 is greater than 1 and less than or equal to 30, and the hole wall of the through hole 541 is provided with a hydrophilic layer 544 and linear conductive carbon 545.

[0127] Please refer to Figure 2The second electrode tab provided by the embodiment of the application includes a current collector 54 and a film layer arranged on one surface of the current collector 54. The current collector 54 is provided with a plurality of through holes 541. The film layer includes an active material. The film layer includes a first film layer 542 and a second film layer 543. The first film layer 542 is combined with the current collector 54. The second film layer 543 is combined with the first film layer 542. The ratio of the Dv50 particle size of the active material in the second film layer 543 to the Dv50 particle size of the active material in the first film layer 542 is greater than 1 and less than or equal to 30. The hole wall of the through hole 541 is provided with a hydrophilic layer 544 and linear conductive carbon 545. The inner wall of the current collector 54 is provided with the hydrophilic layer 544 and the linear conductive carbon 545.

[0128] Referring to Figure 3 The third electrode tab provided by the embodiment of the application includes a current collector 54 and a film layer arranged on one surface of the current collector 54. The current collector 54 is provided with a plurality of through holes 541. The film layer includes an active material. The film layer includes a first film layer 542 and a second film layer 543. The first film layer 542 is combined with the current collector 54. The second film layer 543 is combined with the first film layer 542. The ratio of the Dv50 particle size of the active material in the second film layer 543 to the Dv50 particle size of the active material in the first film layer 542 is greater than 1 and less than or equal to 30. The hole wall of the through hole 541 is provided with a hydrophilic layer 544.

[0129] Referring to Figure 4 The fourth electrode tab provided by the embodiment of the application includes a current collector 54 and a film layer arranged on one surface of the current collector 54. The current collector 54 is provided with a plurality of through holes 541. The film layer includes an active material. The film layer includes a first film layer 542 and a second film layer 543. The first film layer 542 is combined with the current collector 54. The second film layer 543 is combined with the first film layer 542. The ratio of the Dv50 particle size of the active material in the second film layer 543 to the Dv50 particle size of the active material in the first film layer 542 is greater than 1 and less than or equal to 30. The hole wall of the through hole 541 and the inner wall of the current collector 54 are both provided with a hydrophilic layer 544.

[0130] In addition, one battery cell and a preparation method thereof, a secondary battery and an electric device provided by the application are described below with reference to the accompanying drawings.

[0131] [Battery cell]

[0132] The battery cell provided by the application is not particularly limited, for example, the battery cell can be a lithium ion battery or the like.

[0133] Generally, the battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During charging and discharging of the battery, active ions are intercalated and deintercalated between the positive electrode sheet and the negative electrode sheet. The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet and functions to prevent short circuiting between the positive and negative electrodes while allowing ions to pass through.

[0134] The electrolyte is not particularly limited in the present application and can be selected as desired. For example, the electrolyte can be selected from at least one of a solid-state electrolyte and a liquid electrolyte (i.e., electrolyte solution).

[0135] [Positive electrode sheet]

[0136] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material.

[0137] As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0138] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0139] In some embodiments, when the battery cell is a lithium ion battery, the positive electrode active material can be a positive electrode active material for a lithium ion battery known in the art. As an example, the positive electrode active material can include at least one of a lithium-containing phosphate having an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material for a battery can also be used. These positive electrode active materials can be used alone or in combination of two or more. Examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3Mn 1 / 3O2(also can be referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(also can be referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be referred to as NCM 811 ), lithium nickel cobalt aluminum oxides (such as LiNi 0.8 Co 0.15 Al 0.05 O2), and modified compounds thereof. Examples of olivine-structured lithium-containing phosphates can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also can be referred to as LFP), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon.

[0140] In some embodiments, to further increase the energy density of the battery cell, the cathode active material for the lithium ion battery can include one or more of lithium transition metal oxides of the general formula Li a Ni b Co c M d O e A f , and modified compounds thereof. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.

[0141] In some embodiments, as an example, the cathode active material for the lithium ion battery can include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523 LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 LiNi 0.85 Co 0.15 Al 0.05 O2, LiFePO4, and LiMnPO4.

[0142] In the present application, the modified compound of each of the above positive electrode active materials can be a doping modification and / or a surface coating modification to the positive electrode active material.

[0143] As an optional technical manner of the present application, the polyanionic compound can be Li 1+x Mn 1-y A y P 1-z R z O4; wherein, x is an arbitrary value in the range of -0.100~0.100, y is an arbitrary value in the range of 0.001~0.500, z is an arbitrary value in the range of 0.001~0.100, A includes one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and R includes one or more elements of B, S, Si, and N.

[0144] As an optional technical manner of the present application, the polyanionic compound can be Li a A e Mn 1-f B f P 1-g C g O 4-n D n , wherein A includes one or more elements of Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes one or more elements of B, S, Si, and N; D includes one or more elements of S, F, Cl, and Br; a is selected from the range of 0.9 to 1.1, e is selected from the range of 0.001 to 0.1, f is selected from the range of 0.001 to 0.5, g is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, and the second positive electrode active material is electrically neutral.

[0145] The battery will be accompanied by Li deintercalation and consumption during charging and discharging process, and the molar content of Li is different when the battery is discharged to different states. In the enumeration of the positive electrode material in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode material is applied to the battery system, the molar content of Li will change after charging and discharging cycle.

[0146] In the enumeration of the positive electrode material in this application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will appear to float.

[0147] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer formed on at least part of the surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material. The positive electrode active material can use the positive electrode active material known in the art for sodium ion batteries. As an example, the positive electrode active material can include at least one of the following materials: polyanion compound, sodium transition metal oxide, prussian blue compound, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination with two or more.

[0148] As an optional technical manner of the present application, the polyanion compound can be Na 4+x R 3-y P 4-m O 15 / C; wherein 0 < x < 0.5, 0 < y < 0.5, 0 < m < 0.2, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W and Pb.

[0149] As an optional technical manner of the present application, the polyanion compound can be Na x-a A a V y-b M b (PO4) 2-2c (DO4) 2c F z-d Q dwherein A represents an alkali metal element doped to substitute Na, M represents a metal element to substitute V, D represents a doping element to substitute P, Q represents a doping element to substitute F, D includes at least one of Si and S, and Q includes at least one of Cl and O; 3.5≤x≤4.5, 0≤a≤0.15x, 0.8≤y≤1.1, 0≤b≤0.3y, 0≤c≤0.15, 0.8≤z≤1.1, 0≤d≤0.2z. Optionally, A includes at least one of K and Li; and M includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu and Co.

[0150] As an optional technical solution of the present application, the polyanionic compound can be a compound having a sodium ion, a transition metal ion and a tetrahedral (YO4) n- anion unit. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; and n represents the valence of (YO4) n- .

[0151] The polyanionic compound can also be a compound having a sodium ion, a transition metal ion, a tetrahedral (YO4) n- anion unit and a halogen anion. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; n represents the valence of (YO4) n- ; and the halogen can be at least one of F, Cl and Br.

[0152] The polyanionic compound can also be a compound having a sodium ion, a tetrahedral (YO4) n- anion unit, a polyhedral unit (ZO y ) m+ and an optional halogen anion. Y can be at least one of P, S and Si, n represents the valence of V; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents the valence of (ZO y ) m+ .

[0153] The polyanionic compound can be, for example, NaFePO4, Na3V2(PO4)3, NaM’PO4F (M’ is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F.3-2y at least one of (0≤y≤1).

[0154] As an optional technical solution of the present application, the transition metal in the sodium transition metal oxide can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. The sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0

[0155] As an optional technical solution of the present application, the Prussian blue compound can be a kind of compound having sodium ions, transition metal ions and cyanide ions (CN - )6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0

[0156] In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylic ester resin.

[0157] In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0158] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (for example, N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after processes such as drying, cold pressing and the like, obtaining the positive electrode tab.

[0159] [Negative electrode tab]

[0160] In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.

[0161] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is provided on either one or both of the two opposite surfaces of the negative electrode current collector.

[0162] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0163] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material can be a negative electrode active material known in the art for use in a battery. As an example, the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0164] In some embodiments, the negative electrode film layer can further optionally include a binder. The binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0165] In some embodiments, the negative electrode film layer can further optionally include a conductive agent. The conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0166] In some embodiments, the negative electrode film layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0167] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after drying, cold pressing, and the like, a negative electrode sheet can be obtained.

[0168] In other embodiments, the current collector of the negative electrode sheet can generally include a current collector body and a primer layer, which can be provided on at least one side of the current collector body, and the primer layer can be substantially free of the negative electrode active material and can include a small amount of carbon material, but the carbon material forms a coating layer with a thickness that is too thin to function as the negative electrode active material. In this embodiment, the negative electrode sheet can be an electrode sheet without a negative electrode active material layer. For the negative electrode sheet without a negative electrode active material layer, when the current collector of the negative electrode sheet does not include a primer layer, the film layer can be provided on the surface of at least one side of the current collector; when the current collector of the negative electrode sheet includes a primer layer, the film layer can be provided on the surface of the side of the primer layer away from the current collector.

[0169] In some embodiments, the film layer can further include a binder for fixing the additive to the negative electrode sheet. The type of the binder is not particularly limited, and can be selected as desired by those skilled in the art.

[0170] [Electrolyte]

[0171] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not particularly limited in the present application, and can be selected as desired. For example, the electrolyte can be in a liquid state, a gel state, or a full solid state.

[0172] In some embodiments, the electrolyte can be an electrolyte solution. The electrolyte solution can include an electrolyte salt and a solvent.

[0173] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro oxalate borate, lithium di oxalate borate, lithium difluoro di-oxalate phosphate, and lithium tetrafluoro oxalate phosphate.

[0174] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0175] In some embodiments, the electrolyte solution can further optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature or low-temperature performance of the battery, and the like.

[0176] [Separator]

[0177] In some embodiments, a separator is further included in the battery cell. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0178] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0179] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a stacking process.

[0180] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte solution described above.

[0181] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, and the like. The outer package of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, and the like can be listed.

[0182] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape. For example, Figure 5 is a square structure battery cell 5 as an example.

[0183] In some embodiments, referring to Figure 6 , the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte solution is impregnated in the electrode assembly 52. The number of the electrode assembly 52 contained in the battery cell 5 can be one or more, and a person skilled in the art can select according to the specific actual needs.

[0184] In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0185] Figure 7 The battery module 4 is an example. Referring to FIG. 1, the battery module 4 includes a plurality of battery cells 5 and a housing 6. Figure 7 In the battery module 4, the plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0186] Optionally, the battery module 4 can further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0187] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0188] Figure 8 And Figure 9 The battery pack 1 is an example. Referring to FIG. 2, the battery pack 1 includes a plurality of battery modules 4 and a battery box. Figure 8 Figure 9 In the battery pack 1, the battery box and the plurality of battery modules 4 arranged in the battery box can be included. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be arranged on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0189] In addition, the present application also provides a power utilization device, which includes at least one of the battery cell, the battery module, or the battery pack provided by the present application. The battery cell, the battery module, or the battery pack can be used as a power source of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0190] As the power utilization device, the battery cell, the battery module, or the battery pack can be selected according to the use requirements thereof.

[0191] Figure 10 ​The device is a use electric device as an example. The use electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the use electric device on the battery monomer, a battery pack or a battery module can be used.

[0192] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a battery monomer can be used as a power supply.

[0193] Embodiments

[0194] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not indicated by the manufacturer, it is a conventional product that can be obtained by purchase.

[0195] The related parameters of the negative electrode film layer and the negative electrode current collector of Examples 1-20 and Comparative Examples 1-5 are shown in Tables 1-2 below.

[0196] Table 1 Related parameters of the negative electrode film layer of Examples 1-20 and Comparative Examples 1-5

[0197]

[0198] Table 2 Related parameters of the negative electrode current collector of Examples 1-20 and Comparative Examples 1-5

[0199]

[0200] The material of the hydrophilic layer of the negative electrode current collector through hole wall, inner wall and outer wall is poly (3, 4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT:PSS) PEDOT:PSS , the length of the carbon nanotube is 13 μm, and the specific surface area of the ordered mesoporous carbon is 980 m 2 / g.

[0201] The Dv50 particle size of the negative electrode active material in the first film layer and the second film layer is measured by laser after the powder is dissolved in water.

[0202] The area densities of the first film layer and the second film layer can be measured by the following method: taking a negative electrode tab with a regular size, weighing it, and recording the mass as m1; measuring the length and width thereof, and calculating the area thereof, which is recorded as S1; scraping off the second film layer from the negative electrode tab, weighing the negative electrode tab from which the second film layer is scraped off, and recording the mass as m2, the mass of the second film layer being m1-m2; continuing to scrape off the first film layer, weighing the negative electrode current collector, and recording the mass as m3, the mass of the first film layer being m2-m3, the area density of the first film layer being (m2-m3) / S1, and the area density of the second film layer being (m1-m2) / S1.

[0203] The pore diameter of the negative electrode current collector through hole is obtained by scanning electron microscope observation and calculation; the through hole area of the current collector accounts for the surface area of the current collector = through hole area of the current collector / surface area of the current collector * 100%.

[0204] The thickness of the hydrophilic layer of the negative electrode current collector through hole wall, inner wall and outer wall is obtained by SEM cross-section.

[0205] The preparation method of the battery cell of the embodiments 1-20 and the comparative example 5 of the present application comprises the following steps:

[0206] S1, preparing a positive electrode tab

[0207] The ternary NCM, conductive carbon SP and polyvinylidene fluoride are mixed in a mass ratio of 97:2:1, then a solvent N-methyl pyrrolidone is added, and after being fully stirred and mixed uniformly, a positive electrode slurry is prepared; the positive electrode slurry is coated on both sides of the positive electrode current collector aluminum foil in a single-sided weight of ~15 mg / cm 2 , and then dried, cold-pressed and cut to obtain a positive electrode tab.

[0208] S2, preparing a negative electrode tab

[0209] The first negative electrode active material, conductive carbon SP, butadiene rubber, carboxymethyl cellulose and solvent water are uniformly mixed in a mass ratio of 97:1:1:1:100 to prepare a first negative electrode slurry, and the second negative electrode active material, conductive carbon SP, butadiene rubber, carboxymethyl cellulose and solvent water are uniformly mixed in a mass ratio of 97:1:1:1:100 to prepare a second negative electrode slurry, the first negative electrode active material and the second negative electrode active material are both graphite, the first negative electrode slurry is coated on one side of the negative electrode current collector copper foil, the negative electrode current collector is provided with through holes, the second negative electrode slurry is coated on the surface of the first negative electrode slurry, and the negative electrode current collector is heated on one side by infrared, so that the solvent in the negative electrode slurry volatilizes through the through holes, and then cold-pressed and cut to obtain a negative electrode tab.

[0210] S3, preparing a separator

[0211] A polyethylene film with a thickness of 10 pm is used as the separator film.

[0212] S4, preparing an electrolyte

[0213] In an argon atmosphere glove box with a water content of <10 ppm, ethylene carbonate, diethyl carbonate, and dimethyl carbonate are mixed in a volume ratio of 1:1:1, and LiPF6 is dissolved in the above solution to obtain an electrolyte. In the electrolyte, the concentration of LiPF6 is 1 mol / L.

[0214] S5, assembling

[0215] The above positive electrode sheet, separator, and negative electrode sheet are stacked in order to obtain a stacked cell; the cell is placed in an outer package, the above-prepared electrolyte is added, and after processes such as packaging, standing, formation, and aging, a battery monomer is obtained.

[0216] The battery monomer preparation method of the present application Comparative Examples 1-2 includes the following steps:

[0217] S1, preparing a positive electrode sheet

[0218] After the ternary NCM, conductive carbon SP, and polyvinylidene fluoride are mixed in a mass ratio of 97:2:1, a solvent N-methylpyrrolidone is added, and after being fully stirred and mixed uniformly, a positive electrode slurry is prepared; the positive electrode slurry is coated on both sides of the positive electrode current collector aluminum foil at a single-sided weight of ~15 mg / cm 2 After drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0219] S2, preparing a negative electrode sheet

[0220] The negative electrode active material, conductive carbon SP, butadiene rubber, carboxymethyl cellulose, and solvent water are uniformly mixed in a mass ratio of 97:1:1:1:100 to prepare a negative electrode slurry, the negative electrode slurry is coated on one side of the negative electrode current collector copper foil, and the negative electrode current collector is heated on the side of the negative electrode slurry by infrared until the solvent in the negative electrode slurry volatilizes, and then cold pressing and slitting are performed to obtain a negative electrode sheet.

[0221] S3, preparing a separator film

[0222] A polyethylene film with a thickness of 10 pm is used as the separator film.

[0223] S4, preparing an electrolyte

[0224] In an argon atmosphere glove box with a water content of <10 ppm, ethylene carbonate, diethyl carbonate, and dimethyl carbonate are mixed in a volume ratio of 1:1:1, and LiPF6 is dissolved in the above solution to obtain an electrolyte. In the electrolyte, the concentration of LiPF6 is 1 mol / L.

[0225] S5, Assembling

[0226] Stacking the above positive electrode sheet, the separator, and the negative electrode sheet in order to obtain a stacked cell; placing the cell into an outer package, adding the above prepared electrolyte, and obtaining a battery monomer after processes such as packaging, standing, formation, and aging.

[0227] The preparation method of the battery monomer of the application comparative examples 3-4 includes the following steps:

[0228] S1, Preparing a positive electrode sheet

[0229] The ternary NCM, conductive carbon SP, and polyvinylidene fluoride are mixed in a mass ratio of 97:2:1, then added to the solvent N-methylpyrrolidone, and fully stirred and mixed uniformly to prepare a positive electrode slurry; the positive electrode slurry is coated on both sides of the positive electrode current collector aluminum foil according to a single-sided weight of 15 mg / cm 2 The battery monomer is obtained after drying, cold pressing, and slitting.

[0230] S2, Preparing a negative electrode sheet

[0231] The first negative electrode active material, conductive carbon SP, butadiene rubber, carboxymethyl cellulose, and solvent water are uniformly mixed in a mass ratio of 97:1:1:1:100 to prepare a first negative electrode slurry, and the second negative electrode active material, conductive carbon SP, butadiene rubber, carboxymethyl cellulose, and solvent water are uniformly mixed in a mass ratio of 97:1:1:1:100 to prepare a second negative electrode slurry, both the first negative electrode active material and the second negative electrode active material are graphite, the first negative electrode slurry is coated on one side of the negative electrode current collector copper foil, and then the second negative electrode slurry is coated on the surface of the first negative electrode slurry, the negative electrode current collector is heated by infrared on the side of the negative electrode slurry until the solvent in the negative electrode slurry volatilizes, and then cold pressing and slitting are performed to obtain a negative electrode sheet.

[0232] S3, Preparing a separator

[0233] A polyethylene film with a thickness of 10 μm is used as the separator.

[0234] S4, Preparing an electrolyte

[0235] In an argon atmosphere glove box with a water content of <10 ppm, ethylene carbonate, diethyl carbonate, and dimethyl carbonate are mixed in a volume ratio of 1:1:1, and LiPF6 is dissolved in the above solution to obtain an electrolyte. In the electrolyte, the concentration of LiPF6 is 1 mol / L.

[0236] S5, Assembling

[0237] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence to obtain a laminated cell; the cell is placed in an outer package, the electrolyte prepared above is added, and after processes such as packaging, standing, formation, and aging, a battery monomer is obtained.

[0238] In addition, the binder floating ratio of the negative electrode sheet, the adhesion of the negative electrode sheet after cold pressing, and the fast charging performance of the battery monomer of Examples 1-20 and Comparative Examples 1-5 were measured, and the results are shown in Table 3.

[0239] The test method is as follows:

[0240] 1. Binder floating ratio of negative electrode sheet

[0241] The powders of the surface layer and the bottom layer of the negative electrode film layer each having a thickness of 20 μm were obtained using a surface and interface cutting analysis system (SAICAS) or manual powder scraping, the binder content of the surface layer and the binder content of the bottom layer were tested by thermogravimetric analysis (TG), and the binder floating ratio = (binder content of surface layer - binder content of bottom layer) / binder content of bottom layer.

[0242] 2. Adhesion of negative electrode sheet after cold pressing

[0243] The long strip sample was adhered to the patch using double-sided tape, a portion was torn, and the tensile curve was measured using a tensile testing machine, in which the lower grip clamp gripped the iron sheet below the torn portion, and the upper grip clamp gripped the electrode sheet of the torn portion, to obtain the cohesive force.

[0244] 3. Fast charging performance of battery monomer

[0245] The charge-discharge rate refers to the current value required by the battery to discharge its rated capacity within a specified time, expressed in C. 3C indicates that the charging or discharging is completed in 1 / 3 h, and 1 / 3C indicates that the charging or discharging is completed in 3 h. When testing the charge-discharge rate performance of the battery, the current sizes of 1 / 3C and 3C were set, and the capacity retention rate under 3C charging rate = 3C charging capacity / (1 / 3C charging capacity).

[0246] Table 3. Binder floating ratio of negative electrode sheet, adhesion of negative electrode sheet after cold pressing, and fast charging performance of battery monomer of Examples 1-20 and Comparative Examples 1-5

[0247]

[0248] As can be seen from Examples 1, 6-20, when the Dv50 particle size of the first negative electrode active material is 4.52 μm, the areal density of the first film layer is 77.54 mg / 1540.25 mm 2 , the Dv50 particle size of the second negative electrode active material is 16.27 μm, and the areal density of the second film layer is 67.46 mg / 1540.25 mm 2When the binder floats to the negative electrode sheet, the proportion is 5.2%~37.6%, the adhesion strength of the electrode sheet after cold pressing is 10.7N / m~18.4N / m, and the capacity retention rate of the battery cell at 3C charging rate is 93.76%~97.37%. Furthermore, when the through-hole wall of the negative electrode current collector has a hydrophilic layer and carbon nanotubes, the inner wall of the negative electrode current collector has no hydrophilic layer and carbon nanotubes, and the outer wall of the negative electrode current collector has no hydrophilic layer (Example 15), the proportion of binder floats to the negative electrode sheet is the lowest, and the adhesion strength of the electrode sheet after cold pressing and the capacity retention rate of the battery cell at 3C charging rate are the highest. When the through-hole wall of the negative electrode current collector has no hydrophilic layer and carbon nanotubes, the inner wall of the negative electrode current collector has no hydrophilic layer and carbon nanotubes, and the outer wall of the negative electrode current collector has no hydrophilic layer (Example 20), the proportion of binder floats to the negative electrode sheet is the highest, and the adhesion strength of the electrode sheet after cold pressing and the capacity retention rate of the battery cell at 3C charging rate are the lowest.

[0249] Comparing Examples 1-3, it can be seen that the particle size of the first negative electrode active material Dv50 in Examples 1-3 is 1.3μm~11.2μm, the particle size of the second negative electrode active material Dv50 is 12.32μm~39μm, and the particle size ratio of the active material Dv50 in the second film layer and the first film layer is 1.1~30. As the particle size ratio of the active material Dv50 in the second film layer and the first film layer increases, the proportion of binder floating on the negative electrode sheet first decreases and then increases, the adhesion of the electrode sheet after cold pressing first increases and then decreases, and the capacity retention of the battery cell at the 3C charging rate first increases and then decreases. When the particle size of the first negative electrode active material Dv50 is 4.52μm and the particle size of the second negative electrode active material Dv50 is 16.27μm (Example 1), the proportion of binder floating on the negative electrode sheet is the lowest, and the adhesion of the electrode sheet after cold pressing and the capacity retention rate of the battery cell at the 3C charging rate are the highest.

[0250] As can be seen from the comparison of Examples 1 and 4-5, the areal density of the first film layer in Examples 1 and 4-5 is 24.17 mg / 1540.25 mm. 2 ~116mg / 1540.25mm 2 The areal density of the second film layer is 29 mg / 1540.25 mm. 2 ~120.83mg / 1540.25mm 2 The ratio of the areal density of the second film layer to that of the first film layer is 0.2~5. As the ratio of the areal density of the second film layer to that of the first film layer increases, the proportion of the binder floating on the negative electrode sheet first decreases and then increases; the adhesion force of the electrode sheet after cold pressing first increases and then decreases; and the capacity of the battery cell at the 3C charging rate first increases and then decreases. Furthermore, when the areal density of the first film layer is 77.54 mg / 1540.25 mm², this ratio is particularly significant. 2 The areal density of the second film layer is 67.46 mg / 1540.25 mm. 2The binder floating amount of the negative electrode tab is the lowest, the adhesion of the tab after cold pressing is the highest, and the capacity retention rate of the battery cell at 3C charging rate is the highest.

[0251] As can be seen from the comparison of Comparative Examples 1-4 and Example 1, the negative electrode current collectors of Comparative Examples 1-4 all have no through holes, the negative electrode film layers of Comparative Examples 1-2 only have one layer, the negative electrode film layers of Comparative Examples 3-4 include the first film layer and the second film layer, and the negative electrode current collectors are heated and dried by infrared on the side of the negative electrode slurry. The binder floating amount of the negative electrode tab of Comparative Examples 1-4 is 42.5%-48.9%, the adhesion of the tab after cold pressing is 8.8 N / m-9.8 N / m, and the capacity retention rate of the battery cell at 3C charging rate is 92.41%-92.89%, all of which are worse than those of Example 1. This shows that by opening holes in the negative electrode current collector and heating the negative electrode current collector by infrared on the side of the negative electrode current collector, the migration of the binder from the bottom layer to the surface layer can be reduced, thereby improving the problem of binder floating caused by the drying process of the negative electrode tab, and further improving the fast-charging performance of the battery cell.

[0252] As can be seen from the comparison of Comparative Example 5 and Example 1, the negative electrode current collector of Comparative Example 5 is provided with through holes, the negative electrode film layer includes the first film layer and the second film layer, and the negative electrode current collector is heated by infrared on the side of the negative electrode current collector. The Dv50 particle size ratio of the active material in the second film layer to the first film layer is 0.28. The binder floating amount of the negative electrode tab of Comparative Example 5 is 46.6%, the adhesion of the tab after cold pressing is 9.2 N / m, and the capacity retention rate of the battery cell at 3C charging rate is 92.63%, all of which are worse than those of Example 1. This shows that by making the Dv50 particle size of the negative electrode active material in the film layer close to the negative electrode current collector smaller than that of the negative electrode active material in the film layer away from the negative electrode current collector, a capillary force difference can be formed between the film layer close to the negative electrode current collector and the film layer away from the negative electrode current collector. The capillary force difference will promote the movement of at least part of the solvent in the film layer away from the negative electrode current collector to the direction of the negative electrode current collector, and this part of the solvent will eventually volatilize out through the multiple through holes of the negative electrode current collector.

[0253] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having substantially the same technical idea and playing the same role and effect within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications of the embodiments that can be thought of by those skilled in the art, and other ways constructed by combining part of the constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized by, The battery cell comprises an electrode tab, the electrode tab comprises a current collector and a film layer arranged on one surface of the current collector, the current collector is provided with a plurality of through holes, the film layer comprises an active material, the active material is a positive active material or a negative active material, the film layer comprises at least two sub-film layers, along the thickness direction of the film layer, the Dv50 particle size of the active material in the at least two sub-film layers changes in a gradient manner, and the Dv50 particle size of the active material in the sub-film layer close to the current collector is smaller than the Dv50 particle size of the active material in the sub-film layer far from the current collector, and the ratio of the area density of any two adjacent sub-film layers in the at least two sub-film layers is 5:1-1:5; The binder floating amount of the film layer accounts for 0.1%-40%, and the binder floating amount ratio=(surface layer binder content-bottom layer binder content) / bottom layer binder content; The diameter of the through hole is 5-50 microns; At least one of the hole wall of the through hole and the inner wall and the outer wall of the current collector is provided with a hydrophilic layer; The hole wall of the through hole is provided with linear conductive carbon, the linear conductive carbon extends to the middle part of the through hole, and / or the inner wall of the current collector is provided with at least one of porous conductive carbon and linear conductive carbon.

2. The battery cell of claim 1, wherein, The ratio of the Dv50 particle size of the active material in the sub-film layer far from the current collector to the sub-film layer close to the current collector is greater than 1 and less than or equal to 30.

3. The battery cell of claim 1, wherein, The through hole area accounts for 15%-60% of the surface area of the current collector.

4. The battery cell of claim 1, wherein, The film layer comprises a first film layer and a second film layer, the first film layer is combined with the current collector, the second film layer is combined with the first film layer, the ratio of the Dv50 particle size of the active material in the second film layer to the Dv50 particle size of the active material in the first film layer is greater than 1 and less than or equal to 30, and the ratio of the area density of the second film layer to the area density of the first film layer is 5:1-1:

5.

5. The battery cell of claim 1, wherein, The material of the hydrophilic layer comprises at least one of an oxygen group modified carbon material, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate and aluminum oxide.

6. The battery cell of claim 1, wherein, The thickness of the hydrophilic layer is 1-300 nm.

7. The battery cell of claim 1, wherein, The length of the linear conductive carbon is 0.5-10 microns.

8. The battery cell of claim 1, wherein, The linear conductive carbon comprises at least one of carbon nanotubes and carbon fibers.

9. A method of producing a battery cell, characterized by, The preparation method of the battery cell comprises the following steps: arranging at least two layers of slurry on one surface of a current collector provided with a plurality of through holes, the at least two layers of slurry comprising an active material, the active material being a positive active material or a negative active material, along the thickness direction of the current collector, the Dv50 particle size of the active material in the at least two layers of slurry changes in a gradient manner, and the Dv50 particle size of the active material in the slurry close to the current collector is smaller than the Dv50 particle size of the active material in the slurry far from the current collector, the ratio of the area density of any two adjacent layers of slurry in the at least two layers of slurry is 5:1-1:5, then heating the current collector on one side of the current collector by at least one of magnetic induction, infrared and hot air, until the solvent in the slurry volatilizes through the plurality of through holes. The diameter of the through hole is 5-50 μm; At least one of the hole wall of the through hole, the inner wall and the outer wall of the current collector is provided with a hydrophilic layer; The hole wall of the through hole is provided with linear conductive carbon extending to the middle part of the through hole, and / or the inner wall of the current collector is provided with at least one of porous conductive carbon and linear conductive carbon.

10. A battery device characterized by comprising: The battery device comprises the battery cell of any one of claims 1-8 or the battery cell prepared according to the preparation method of the battery cell of claim 9.

11. An electrical device, characterized by The power utilization device comprises the battery cell of any one of claims 1-8 or the battery device of claim 10, and the battery cell or the battery device is used to provide electric energy.

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