Battery cell and electric device

Abstract

The invention discloses a battery cell and a power utilization device, the battery cell comprises a shell and an electrode assembly, the shell forms a containing cavity filled with electrolyte, the electrode assembly is arranged in the containing cavity, the surface of an active substance layer of the electrode assembly is recessed inwards to form a groove, and the groove extends to the edge of a pole piece; the thickness of the active material layer is M, and the thickness of the isolating membrane in the thickness direction is C; the isolating membrane is laminated with the first pole piece along the thickness direction, and the porosity of the isolating membrane is F; the interval between every two adjacent grooves in the second direction is H, the sectional area of each groove in the section perpendicular to the extending direction is G, and 0.03 M * H < = (G + (0.1 C * F * H)). Through reasonable arrangement of the isolating membrane and the groove, the isolating membrane and the groove can transmit sufficient electrolyte to the active substance layer to infiltrate the interior of the electrode assembly and meet the requirement of the electrode assembly for electrolyte consumption, so that the electrolyte in the electrode assembly can be supplemented in time in the circulation process, and the cycle life of the battery cell can be prolonged.

Description

Technical Field

[0001] This application relates to the field of batteries, and particularly to a battery cell and an electrical device using the same. Background Art

[0002] A rechargeable battery, which can also be called a secondary battery, refers to a battery that can be activated by charging after discharging so as to continue to be used. Rechargeable batteries are widely used in electronic devices such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and electric tools, etc.

[0003] As the requirement for the energy density of battery cells by people is getting higher and higher, it has become a trend to increase the energy density by thinning the separator of the battery cell. However, with the thinning of the separator, not only does the electrolyte transmission channel on the separator decrease, but also the mechanical strength and adhesive strength of the separator both decrease. At present, although there is a technical solution of setting an adhesive layer to increase the adhesive strength, the adhesive layer will block the pores of the separator, further reducing the electrolyte transmission channel and affecting the cycle life of the battery cell. Summary of the Invention

[0004] This application provides a battery cell and an electrical device using the same, and the battery cell has a long cycle life.

[0005] In a first aspect, this application provides a battery cell, which includes a housing and an electrode assembly. The housing forms a cavity filled with an electrolyte; the electrode assembly is disposed in the cavity and includes a first electrode tab and a separator. The first electrode tab includes a first current collector and an active material layer. The first current collector includes two first surfaces oppositely disposed in the thickness direction, and an active material layer is provided on at least one of the first surfaces. The thickness of the active material layer is M. A groove is formed by the surface of the active material layer away from the first current collector indenting inward, and the groove extends to the edge of the first electrode tab; in the thickness direction, the thickness of the separator is C; the separator is stacked with the first electrode tab in the thickness direction, and the porosity of the separator is F; there are a plurality of grooves, and the plurality of grooves are equally spaced in a second direction, the second direction is perpendicular to the extending direction of the groove, the interval between two adjacent grooves in the second direction is H, and the cross-sectional area of the groove in the cross-section perpendicular to the extending direction is G, and 0.03M×H≤(G+(0.1C×F×H)).

[0006] In the above structure, since a groove is formed by the surface of the active material layer away from the first current collector indenting inward, and the groove extends to the edge of the first electrode tab and communicates with the cavity, the electrolyte in the cavity can fully flow into the electrode assembly through the groove, infiltrate the inside of the electrode assembly and meet the consumption of the electrolyte by the electrode assembly, which is beneficial to timely supplement the electrolyte inside the electrode assembly during the cycle process and is beneficial to extending the cycle life of this battery cell.

[0007] It is defined that 0.03M×H ≤ (G + (0.1C×F×H)), which means that the pore volume of the grooves and the pore volume in the separator need to be greater than the product of 0.03 and the active material layer, and can meet the requirement of rapid infiltration of the electrolyte into the active material.

[0008] For the battery cell provided by some embodiments of the present application, the grooves extend in a first direction, and the first direction is perpendicular to the thickness direction; along the first direction, the length of the first electrode is B, and the length of the groove is A.

[0009] For the battery cell provided by some embodiments of the present application, the active material layer includes two end faces oppositely arranged along the first direction, and the grooves communicate the two end faces.

[0010] For the battery cell provided by some embodiments of the present application, the thickness of the separator is C, and 2.5μm ≤ C ≤ 15μm.

[0011] For the battery cell provided by some embodiments of the present application, 3.5μm ≤ C ≤ 13μm.

[0012] For the battery cell provided by some embodiments of the present application, the separator includes a base film, and an adhesive layer is provided on the surface of the base film in the thickness direction, and the adhesive layer is adhered to the first electrode; along the thickness direction, the thickness of the base film is D, and the thickness of the adhesive layer is E, 2.25μm ≤ D ≤ 11μm, 0.25μm ≤ E ≤ 4μm.

[0013] For the battery cell provided by some embodiments of the present application, 3μm ≤ D ≤ 10μm.

[0014] 0.5μm ≤ E ≤ 3μm.

[0015] For the battery cell provided by some embodiments of the present application, 15% ≤ F ≤ 90%.

[0016] For the battery cell provided by some embodiments of the present application, 20% ≤ F ≤ 80%.

[0017] For the battery cell provided by some embodiments of the present application, 30% ≤ F ≤ 50%.

[0018] For the battery cell provided by some embodiments of the present application, multiple grooves all extend in the first direction, and the second direction, the thickness direction and the first direction are perpendicular to each other.

[0019] For the battery cell provided by some embodiments of the present application, 100μm ≤ H ≤ 5000μm.

[0020] For the battery cell provided by some embodiments of the present application, 400μm ≤ H ≤ 2500μm.

[0021] For the battery cell provided by some embodiments of the present application, the width of the opening of the groove in the second direction is J, and 40 μm ≤ J ≤ 250 μm.

[0022] For the battery cell provided by some embodiments of the present application, 50 μm ≤ J ≤ 200 μm.

[0023] For the battery cell provided by some embodiments of the present application, a plurality of grooves are provided, the plurality of grooves are arranged at intervals, and the extending directions of at least two grooves intersect.

[0024] For the battery cell provided by some embodiments of the present application, a plurality of grooves are provided, and at least two grooves intersect.

[0025] For the battery cell provided by some embodiments of the present application, along the thickness direction, the depth of the groove is K, and the thickness of the active material layer is M.

[0026] For the battery cell provided by some embodiments of the present application, along the thickness direction, the depth of the groove is K, and 4 μm ≤ K ≤ 45 μm.

[0027] For the battery cell provided by some embodiments of the present application, 5 μm ≤ K ≤ 40 μm.

[0028] For the battery cell provided by some embodiments of the present application, in the thickness direction, along the orientation of the opening of the groove, the width of the groove shows an increasing trend.

[0029] For the battery cell provided by some embodiments of the present application, in the cross-section perpendicular to the extending direction of the groove, the cross-sectional shape of the groove is one of a triangle, a trapezoid, a semi-circle, and a rectangle.

[0030] For the battery cell provided by some embodiments of the present application, the groove is formed by laser grooving or chemical etching.

[0031] For the battery cell provided by some embodiments of the present application, the first electrode sheet is a negative electrode sheet.

[0032] In a second aspect, some embodiments of the present application provide an electrical device, and the electrical device includes the battery cell provided by any of the above technical solutions, and the battery cell is used to provide electrical energy.

[0033] The technical solutions provided by the embodiments of the present disclosure at least bring the following beneficial effects:

[0034] The present application provides an electric core, which includes a housing and an electrode assembly. The housing forms a cavity filled with electrolyte, and the electrode assembly is disposed in the cavity. The electrode assembly includes a first electrode tab and a separator. The first electrode tab includes a first current collector and an active material layer. The first current collector includes two first surfaces disposed opposite to each other in the thickness direction. The active material layer is provided on at least one of the first surfaces, and the thickness of the active material layer is M. The surface of the active material layer away from the first current collector is recessed inward to form a groove, and the groove extends to the edge of the first electrode tab in the extending direction. In the thickness direction, the thickness of the separator is C. The separator is laminated with the first electrode tab in the thickness direction, and the porosity of the separator is F. There are multiple grooves, and the multiple grooves are equally spaced in a second direction perpendicular to the extending direction. The interval between two adjacent grooves in the second direction is H, and the cross-sectional area of the groove in the cross-section perpendicular to the extending direction is G, and 0.03M×H≤(G+(0.1C×F×H)). In the above structure, since the surface of the active material layer away from the first current collector is recessed inward to form a groove, and the groove extends to the edge of the first electrode tab and communicates with the cavity, the electrolyte in the cavity can fully flow into the electrode assembly through the groove. By setting the sum of the equivalent size of the pores of the separator in the thickness direction multiplied by the resistance coefficient and the equivalent depth of the groove in the thickness direction to be greater than or equal to 0.03M, the separator and the groove can transport sufficient electrolyte to the active material layer to infiltrate the inside of the electrode assembly and meet the consumption of the electrolyte by the electrode assembly, which is beneficial to timely supplement the electrolyte inside the electrode assembly during the cycle and is beneficial to extending the cycle life of the electric core. Description of the Drawings

[0035] The features, advantages, and technical effects of the exemplary embodiments of the present application will be described below with reference to the drawings.

[0036] Figure 1 Schematic structural diagram of the electric core provided by an embodiment of the present application;

[0037] Figure 2 Cross-sectional view of the first electrode tab provided by an embodiment of the present application;

[0038] Figure 3 Top view of the first electrode tab provided by an embodiment of the present application;

[0039] Figure 4 Top view of the first electrode tab provided by another embodiment of the present application;

[0040] Figure 5 Cross-sectional view of the electrode assembly provided by an embodiment of the present application;

[0041] Figure 6 Cross-sectional view of the electrode assembly provided by another embodiment of the present application;

[0042] Figure 7 A cross-sectional view of the separator provided by an embodiment of the present application;

[0043] Figure 8 A top view of the first electrode tab provided by another embodiment of the present application;

[0044] Figure 9 A top view of the first electrode tab provided by still another embodiment of the present application.

[0045] In the figure:

[0046] 1. Housing; 2. Cavity; 3. Electrode assembly; 31. First electrode tab; 311. First current collector; 3111. First surface; 312. Active material layer; 3121. End face; 313. Groove; 32. Separator; 321. Base film; 322. Adhesive layer; 33. Positive electrode tab; 34. Negative electrode tab; X. Thickness direction; Y. First direction; Z. Second direction.

[0047] In the accompanying drawings, the drawings are not necessarily drawn to actual scale. Detailed implementation manners

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some but not all of the embodiments of the present application.

[0049] Currently, from the perspective of the development of the market situation, the application of batteries is becoming more and more extensive. Batteries are not only applied to energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, but also widely used in electric transportation means such as electric bicycles, electric motorcycles, and electric vehicles, as well as in multiple fields such as military equipment and aerospace.

[0050] The battery cells mentioned in the embodiments of the present application can be secondary batteries or primary batteries. A secondary battery is a battery that can be reused by activating the active materials through charging after discharging.

[0051] The battery cells can be lithium-ion battery cells, sodium-ion battery cells, sodium-lithium-ion battery cells, lithium-metal battery cells, sodium-metal battery cells, lithium-sulfur battery cells, magnesium-ion battery cells, nickel-metal hydride battery cells, nickel-cadmium battery cells, lead-acid battery cells, etc.

[0052] The battery cells generally include an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are inserted and extracted back and forth between the positive electrode and the negative electrode. The separator is disposed between the positive electrode and the negative electrode, which can prevent the short circuit between the positive and negative electrodes and allow the active ions to pass through at the same time.

[0053] In some embodiments, the electrode assembly is of a wound structure or a stacked structure. Optionally, the electrode assembly is a cylindrical wound structure.

[0054] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as the electrode assembly and the electrolyte. The housing can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell), etc.

[0055] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, or a battery cell of other shapes. The prismatic battery cell includes a square shell battery cell, a blade-shaped battery cell, a multi-prismatic battery cell, and the multi-prismatic battery cell is, for example, a hexagonal prism battery cell, etc.

[0056] The electrolyte plays a very important role in the operation of the battery cell. During the cyclic use of the battery cell, the electrolyte is continuously consumed. Since there is a gap between the electrode assembly and the housing in the battery cell, the area of the electrode assembly close to the outside can contact the electrolyte in the gap, and the infiltrated electrolyte is relatively sufficient. However, after the electrolyte is consumed, the inner area of the electrode assembly far from the outside needs the surrounding electrolyte to be transported to the inside of the electrode assembly for replenishment. If the transport ability of the electrolyte is insufficient, it will cause a lack of liquid inside the battery cell, ultimately leading to a rapid decay of the battery cell capacity and a serious shortening of the cycle life.

[0057] Based on the above considerations, in order to improve the cycle life of the battery cell, the present application provides a battery cell, which includes a housing and an electrode assembly. The housing forms a cavity filled with electrolyte, and the electrode assembly is disposed in the cavity. The electrode assembly includes a first electrode tab and a separator. The first electrode tab includes a first current collector and an active material layer. The first current collector includes two first surfaces oppositely disposed in the thickness direction, and an active material layer is provided on at least one of the first surfaces. The thickness of the active material layer is M. The surface of the active material layer far from the first current collector is recessed inward to form a groove, and the groove extends to the edge of the first electrode tab; in the thickness direction, the thickness of the separator is C; the separator is stacked with the first electrode tab in the thickness direction, and the porosity of the separator is F; there are a plurality of grooves, and the plurality of grooves are equally spaced in a second direction perpendicular to the extending direction. The interval between two adjacent grooves in the second direction is H, and the cross-sectional area of the groove in a cross-section perpendicular to the extending direction is G. In the above structure, since the surface of the active material layer far from the first current collector is recessed inward to form a groove, and the groove extends to the edge of the first electrode tab and communicates with the cavity, the electrolyte in the cavity can fully flow into the electrode assembly through the groove. By setting the sum of the equivalent size of the pores of the separator in the thickness direction multiplied by the resistance coefficient 0.1 and the equivalent depth of the groove in the thickness direction to be greater than or equal to 0.03M, the separator and the groove can transport sufficient electrolyte to the active material layer to infiltrate the inside of the electrode assembly and meet the consumption of the electrolyte by the electrode assembly, which is beneficial to timely replenish the electrolyte inside the electrode assembly during the cycle, and is beneficial to extending the cycle life of the battery cell.

[0058] The meanings of the various components of the formula are explained as follows:

[0059] Assume that W is the width of the electrode tab, and H can refer to the distance from the middle of the first groove to the middle of the second groove; G refers to the cross-sectional area of the grooves in the area from the middle of the first groove to the middle of the second groove, and G×W is the volume of the grooves in this unit area; 0.1C×F×H is the cross-sectional area of the pores in all the separator films in this unit area. Since the pores in the separator film are irregular, a resistance coefficient of 0.1 needs to be multiplied, and 0.1C×F×W×H is the volume of the pores in this unit area; M×H is the cross-sectional area of the active material layer in this area, M×H×W is the volume of the active material layer, and 0.03 is an empirical coefficient. When the volume of the active material layer is M×H×W, the volume ratio of the pores needs to be above 0.03. At this time, the requirement for the electrolyte to quickly infiltrate the active material can be met. Therefore, the formula 0.03M×H×W ≤ (G + (0.1C×F×H))×W is obtained. Finally, we get: 0.03M×H ≤ (G + (0.1C×F×H)).

[0060] In the above structure, since the surface of the active material layer away from the first current collector is recessed inward to form grooves, and the grooves extend to the edge of the first electrode tab and communicate with the cavity, the electrolyte in the cavity can flow into the electrode assembly fully through the grooves. By defining 0.03M×H ≤ (G + (0.1C×F×H)), the separator film and the grooves can transport sufficient electrolyte to the active material layer to infiltrate the inside of the electrode assembly and meet the consumption of the electrolyte by the electrode assembly, which is beneficial to timely supplement the electrolyte inside the electrode assembly during the cycling process and is beneficial to extending the cycle life of the battery cell.

[0061] The technical solutions of the battery cell and the electrical device provided by the present application will be further described below through specific embodiments.

[0062] Some embodiments of the present application provide a battery cell, as Figure 1 shown. The battery cell includes a housing 1 and an electrode assembly 3. The housing 1 forms a cavity 2, and the cavity 2 is filled with an electrolyte; the electrode assembly 3 is disposed in the cavity 2, and the electrode assembly 3 includes a first electrode tab 31 and a separator film 32. Refer to Figure 2, the first electrode tab 31 includes a first current collector 311 and an active material layer 312. The first current collector 311 includes two first surfaces 3111 oppositely arranged along the thickness direction X. The active material layer 312 is provided on at least one of the first surfaces 3111. The thickness of the active material layer 312 is M. The surface of the active material layer 312 away from the first current collector 311 is recessed inward to form a groove 313. The groove 313 extends to the edge of the first electrode tab 31 in the extending direction; along the thickness direction X, the thickness of the separator 32 is C; the separator 32 is laminated with the first electrode tab 31 along the thickness direction X, and the porosity of the separator 32 is F; there are multiple grooves 313, and the multiple grooves 313 are arranged at equal intervals along a second direction Z perpendicular to the extending direction. The interval between two adjacent grooves 313 in the second direction Z is H, and the cross-sectional area of the groove 313 in the cross-section perpendicular to the extending direction is G,

[0063] The housing 1 can be a wall structure arranged on the outer periphery in the battery cell, which can form a cavity 2 for accommodating other components of the battery cell such as the electrode assembly 3 and the electrolyte. The housing 1 can protect the components in the cavity 2.

[0064] The electrolyte is a liquid that conducts active ions between the positive electrode tab 33 and the negative electrode tab 34 in the electrode assembly 3. By infiltrating the positive electrode tab 33 and the negative electrode tab 34 in the electrode assembly 3, the active ions can be conducted between the positive electrode tab 33 and the negative electrode tab 34.

[0065] The electrode assembly 3 is an important structure in the battery cell. It is arranged in the cavity 2 and infiltrated by the electrolyte, and can undergo an electrochemical reaction with the electrolyte. The electrode assembly 3 can be a wound structure, a stacked structure, or a mixed structure of winding and stacking.

[0066] The electrode assembly 3 includes a positive electrode tab 33 and a negative electrode tab 34 arranged in a stacked manner. In the wound electrode assembly 3, the stacked positive electrode tab 33 and negative electrode tab 34 are wound into a wound structure.

[0067] In the stacked electrode assembly 3, there are multiple positive electrode tabs 33 and multiple negative electrode tabs 34 respectively. The multiple positive electrode tabs 33 and the multiple negative electrode tabs 34 are alternately arranged in a stacked manner. Exemplarily, multiple positive electrode tabs 33 can be provided, and the negative electrode tab 34 can be folded to form multiple folded segments arranged in a stacked manner. One positive electrode tab 33 is clamped between adjacent folded segments. As an example, both the positive electrode tab 33 and the negative electrode tab 34 are folded to form multiple folded segments arranged in a stacked manner.

[0068] Exemplarily, the shape of the electrode assembly 3 can be cylindrical, flat, or multi-prismatic, etc.

[0069] The first electrode tab 31 can be the positive electrode tab 33 in the foregoing technical solution, or the negative electrode tab 34 in the foregoing technical solution. Those skilled in the art can set the positive electrode tab 33 or the negative electrode tab 34 as the first electrode tab 31 according to the actual situation.

[0070] The first current collector 311 can be the matrix structure in the first electrode tab 31. It can be used as a load-bearing structure for carrying the active material and can conduct and collect the current generated by the active material. The first current collector 311 can be a metal foil, such as copper foil and aluminum foil, or a composite current collector formed by a polymer material base layer and a metal layer. The first surface 3111 can be two surfaces of the first current collector 311 that are spaced apart relative to each other in the thickness direction X. The first surface 3111 can be used to set the active material layer 312 so that the active material layer 312 can be carried on the first current collector 311.

[0071] The active material layer 312 can be a layered structure formed by the active material, which is provided on the first surface 3111 of the first current collector 311. The active material layer 312 is provided on at least one first surface 3111, which can mean that the active material layer 312 is provided on one of the first surfaces 3111 of the first current collector 311, or that the active material layer 312 is provided on both of the first surfaces 3111 of the first current collector 311.

[0072] The groove 313 can be a groove-like structure provided on the active material layer 312. By making the surface of the active material layer 312 away from the first current collector 311 recess inward, a groove 313 is formed on the active material layer 312. The end of the groove 313 in the extending direction communicates with the edge of the first electrode tab 31 to communicate with the cavity 2, which can mean that the end of the groove 313 in the extending direction communicates with the edge of the first electrode tab 31. Since the edge of the first electrode tab 31 is directly exposed to the cavity 2 and immersed in the electrolyte, the end of the groove 313 communicating with the edge of the first electrode tab 31 communicates with the gap between the electrode assembly 3 and the housing 1, so that the electrolyte in the gap can enter the groove 313 from the end of the groove 313 in the extending direction and flow along the groove 313 into the interior of the electrode assembly 3, and the electrolyte in the cavity 2 can supplement the interior of the electrode assembly 3, so that the electrolyte can better infiltrate the interior of the electrode assembly 3.

[0073] In the wound electrode assembly 3, the end of the groove 313 in the extending direction communicates with the edge in the direction perpendicular to the winding direction, so that the groove 313 is not easily blocked by the wound components in the electrode assembly 3, and the end of the groove 313 in the extending direction can communicate with the gap between the electrode assembly 3 and the housing 1.

[0074] In the electrode assembly 3 in a laminated structure, the groove 313 extends to the edge of the first electrode sheet 31 in the extending direction, so that the end of the groove 313 in the extending direction can communicate with the gap between the electrode assembly 3 and the housing 1.

[0075] The dimension of the active material layer 312 in the thickness direction X may refer to the thickness of the active material layer 312 in the thickness direction X. By forming a plurality of grooves 313 on the surface of the active material layer 312 away from the first surface 3111, the plurality of grooves 313 can better guide the electrolyte into the electrode assembly 3, so that the electrolyte inside the electrode assembly 3 can be replenished more in time. By arranging the plurality of grooves 313 at equal intervals in the second direction Z, the interval between any two adjacent grooves 313 in the second direction Z is equal, so that the plurality of grooves 313 are evenly distributed on the active material layer 312, so that the improvement of the wettability of the electrode assembly 3 by the grooves 313 is uniform, and the electrolyte inside the electrode assembly 3 can be replenished more evenly.

[0076] The cross section of the groove 313 may refer to the cross section perpendicular to the extending direction of the groove 313. The interval between two adjacent grooves 313 in the second direction Z may refer to the distance between the central axes of two adjacent grooves 313 in the second direction Z.

[0077] The separator 32 may be a member disposed between the positive electrode sheet 33 and the negative electrode sheet 34. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and extracted back and forth between the positive electrode sheet 33 and the negative electrode sheet 34.

[0078] The separator 32 is laminated with the first electrode sheet 31 in the thickness direction X, so that the separator 32 can be disposed between the positive electrode sheet 33 and the negative electrode sheet 34, which can prevent the positive electrode sheet 33 and the negative electrode sheet 34 from short-circuiting, and at the same time allow active ions to pass through.

[0079] The porosity may refer to the percentage of the pore volume in the separator 32 to the total volume in the separator 32. The pores in the separator 32 are used to form channels for active ions to pass through.

[0080] Since the thicker the thickness M of the active material layer 312 in the thickness direction X is, the greater the ability of the groove 313 and the separator 32 to transport the electrolyte is required to replenish the electrolyte into the electrode assembly 3 to meet the wetting requirements inside the electrode assembly 3.

[0081] Since the transport of the electrolyte inside the electrode assembly 3 occurs in the pores of the separator 32 and the grooves 313, the ability of the electrolyte to flow into the interior of the electrode assembly 3 is determined by the equivalent size of the pores of the separator 32 in the thickness direction X and the equivalent depth of the grooves 313 in the thickness direction X. The equivalent size of the pores of the separator 32 in the thickness direction X refers to the thickness when the space occupied by the pores in the separator 32 is laid flat on the separator 32. The equivalent depth of the grooves 313 in the thickness direction X refers to the thickness when the space occupied by the grooves 313 in the active material layer 312 is laid flat on the active material layer 312. The larger the equivalent size of the pores of the separator 32 in the thickness direction X, the larger the space of the pores in the separator 32 that can pass the electrolyte, and the better the electrolyte can flow through the pores of the separator 32 into the interior of the electrode assembly 3 to infiltrate the active material layer 312. The larger the equivalent depth of the grooves 313 in the thickness direction X, the larger the space of the grooves 313 in the active material layer 312 that can pass the electrolyte, and the better the electrolyte can flow through the grooves 313 of the active material layer 312 into the interior of the electrode assembly 3 to infiltrate the active material layer 312.

[0082] Since the pores in the separator 32 are tortuous, the resistance to the flow of the electrolyte when flowing through the pores of the separator 32 is large. When using the thickness when the space occupied by the pores in the separator 32 is laid flat on the separator 32 to measure the ability of the electrolyte to flow into the interior of the electrode assembly 3, it is necessary to multiply by the resistance coefficient when the electrolyte flows through the tortuous pores. Therefore, the ability of the pores of the separator 32 to pass the electrolyte is measured by multiplying the equivalent size of the pores of the separator 32 in the thickness direction X by the resistance coefficient.

[0083] Therefore, the relationship among the thickness M of the active material layer 312 in the thickness direction X, the interval H between two adjacent grooves 313 in the second direction Z, the porosity F of the separator 32, and the cross-sectional area G of the grooves 313 is set as

[0084] Assume that W is the width of the electrode tab, H can refer to the distance from the middle of the first groove to the middle of the second groove; G refers to the cross-sectional area of the groove 313 within the region from the middle of the first groove 313 to the middle of the second groove 313, and GG×W is the volume of the groove 313 within this unit region; 0.1C×F×H is the cross-sectional area of the pores in all the separator films 32 within this unit region. Since the pores in the separator film 32 are irregular, a resistance coefficient of 0.1 needs to be multiplied, and 0.1C×F×W×H is the volume of the pores within this unit region; M×H is the cross-sectional area of the active material layer 312 within this region, M×H×W is the volume of the active material layer 312, and 0.03 is an empirical coefficient. When the volume of the active material layer 312 is M×H×W, the volume ratio of the pores needs to be above 0.03. At this time, the requirement for the electrolyte to quickly infiltrate the active material can be met. Therefore, the formula 0.03M×H×W ≤ (G + (0.1C×F×H))×W is obtained. Finally, it is obtained that: 0.03M×H ≤ (G + (0.1C×F×H)). In the above structure, since the surface of the active material layer 312 far from the first current collector 311 is recessed inward to form the groove 313, and the end of the groove 313 in the extending direction communicates with the cavity 2, the electrolyte in the cavity 2 can flow into the electrode assembly 3 through the groove 313 to infiltrate the inside of the electrode assembly 3, which is beneficial to timely supplement the electrolyte inside the electrode assembly 3 during the cycle and is beneficial to extending the cycle life of the battery cell.

[0085] In some embodiments, referring to Figure 3 , the groove 313 extends along the first direction Y, and the first direction Y is perpendicular to the thickness direction X; along the first direction Y, the length of the first electrode tab is B, and the length of the groove 313 is A.

[0086] The first direction Y can be a direction perpendicular to the thickness direction X of the first current collector 311. By extending the groove 313 along the first direction Y, the groove 313 can be arranged in a plane direction perpendicular to the thickness direction X.

[0087] By setting the length of the groove 313 along the first direction Y as A, the length of the first electrode tab 31 along the first direction Y as B, and setting the relationship between the length A of the groove 313 along the first direction Y and the length B of the first electrode tab 31 along the first direction Y as such that the length of the groove 313 along the first direction Y is greater than or equal to half of the length of the first electrode tab 31 along the first direction Y, so that the groove 313 can at least guide the electrolyte to the central position of the first electrode tab 31 in the first direction Y, enabling the central position of the first electrode tab 31 to be timely supplemented with electrolyte.

[0088] In some embodiments, referring to Figure 4, the active material layer 312 includes two end faces 3121 oppositely arranged along the first direction Y, and the groove 313 connects the two end faces 3121.

[0089] As described in the foregoing solution, the first direction Y may be a direction perpendicular to the thickness direction X of the first current collector 311. The end faces 3121 may be two surfaces of the active material layer 312 oppositely arranged in the first direction Y, and the material in the active material layer 312 is arranged between the two oppositely arranged end faces 3121.

[0090] By making the groove 313 connect the two end faces 3121, the groove 313 can guide the electrolyte from the two opposite end faces 3121 into the electrode assembly 3, so that the electrolyte can be replenished into the electrode assembly 3 more timely, and the possibility of the lack of electrolyte inside the electrode assembly 3 can be reduced.

[0091] In some embodiments, referring to Figure 5 and Figure 6 , 2.5μm ≤ C ≤ 15μm.

[0092] By setting the range of the thickness C of the separator 32 in the thickness direction X to 2.5μm ≤ C ≤ 15μm, not only does the separator 32 have sufficient thickness to provide sufficient active ion channels, but also the thickness of the separator 32 is not too thick to occupy too much space, which is beneficial to improving the energy density of the battery cell.

[0093] In some embodiments, 3.5μm ≤ C ≤ 13μm.

[0094] By setting the range of the thickness C of the separator 32 in the thickness direction X to 3.5μm ≤ C ≤ 13μm, not only does the separator 32 have sufficient thickness to provide sufficient active ion channels, but also the thickness of the separator 32 is not too thick to occupy too much space, which is beneficial to improving the energy density of the battery cell. Preferably, the range of the thickness C of the separator 32 in the thickness direction X can be set to 4.5μm ≤ C ≤ 7.5μm, and the thickness of the separator 32 in the thickness direction X can be set to 4.5μm, 5.5μm, 6.5μm or 7.5μm, so that the separator 32 has sufficient thickness to provide sufficient active ion channels and maintain the structural strength, and also the thickness of the separator 32 is not too thick to occupy too much space, which is beneficial to improving the energy density of the battery cell.

[0095] In some embodiments, referring to Figure 7 , the separator 32 includes a base film 321, and an adhesive layer 322 is provided on the surface of the base film 321 in the thickness direction X. The adhesive layer 322 is bonded to the first electrode sheet 31. Along the thickness direction X, the thickness of the base film 321 is D, and the thickness of the adhesive layer 322 is E, 2.25μm ≤ D ≤ 11μm, 0.25μm ≤ E ≤ 4μm.

[0096] The adhesive layer 322 can be a structural layer provided on the separator film 32 for bonding the separator film 32 to the first pole piece 31. It can be formed of a material with adhesive properties, enabling the base film 321 to be bonded to other components through the adhesive layer 322.

[0097] By setting the thickness of the base film 321 in the thickness direction X to D and setting the thickness range to 2.25 μm ≤ D ≤ 11 μm, not only does the base film 321 in the separator film 32 have sufficient thickness to form sufficient active ion channels, but also the thickness of the base film 321 is not too thick to occupy excessive space, which is beneficial to improving the energy density of the battery cell.

[0098] By setting the thickness of the adhesive layer 322 in the thickness direction X to E and setting the thickness range to 0.25 μm ≤ E ≤ 4 μm, not only does the adhesive layer 322 have sufficient thickness to provide sufficient adhesive force to bond the separator film 32 to the first pole piece 31, but also the thickness of the adhesive layer 322 is not too thick to cause waste.

[0099] In some embodiments, 3 μm ≤ D ≤ 10 μm, 0.5 μm ≤ E ≤ 3 μm.

[0100] By setting the range of the thickness D of the base film 321 in the thickness direction X to 3 μm ≤ D ≤ 10 μm, not only does the base film 321 in the separator film 32 have sufficient thickness to form sufficient active ion channels, but also the thickness of the base film 321 is not too thick to occupy excessive space, which is beneficial to improving the energy density of the battery cell.

[0101] Preferably, the range of the thickness D of the base film 321 in the thickness direction X can be set to 4 μm ≤ D ≤ 6 μm. Exemplarily, the thickness of the base film 321 in the thickness direction X can be set to 4 μm, 5 μm, or 6 μm. Not only does the base film 321 in the separator film 32 have sufficient thickness to form sufficient active ion channels, but also the thickness of the base film 321 is not too thick to occupy excessive space, which is beneficial to improving the energy density of the battery cell.

[0102] By setting the range of the thickness E of the adhesive layer 322 in the thickness direction X to 0.5 μm ≤ E ≤ 3 μm, not only does the adhesive layer 322 have sufficient thickness to provide sufficient adhesive force to bond the separator film 32 to the first pole piece 31, but also the thickness of the adhesive layer 322 is not too thick to cause waste.

[0103] Preferably, the thickness E of the adhesive layer 322 in the thickness direction X can be set in the range of 0.5 μm ≤ E ≤ 1.5 μm. Exemplarily, the thickness of the adhesive layer 322 in the thickness direction X can be set to 0.5 μm, 1 μm, or 1.5 μm. This not only enables the adhesive layer 322 to have sufficient thickness to provide sufficient adhesive force to bond the separator 32 to the first electrode tab 31, but also ensures that the thickness of the adhesive layer 322 is not too thick to cause waste.

[0104] In some embodiments, 15% ≤ F ≤ 90%.

[0105] By setting the porosity of the separator 32 to F and the range of the porosity F of the separator 32 to 15% ≤ F ≤ 90%, not only can the separator 32 provide sufficient channels for active ions to pass through, enabling the separator 32 to have good active ion permeability, but also the separator 32 will not have too low a structural strength due to too large a porosity, which is beneficial to reducing the possibility of damage to the separator 32.

[0106] In some embodiments, 20% ≤ F ≤ 80%.

[0107] By setting the range of the porosity of the separator 32 to 20% ≤ F ≤ 80%, not only can the separator 32 provide sufficient channels for active ions to pass through, enabling the separator 32 to have good active ion permeability, but also the separator 32 will not have too low a structural strength due to too large a porosity, which is beneficial to reducing the possibility of damage to the separator 32.

[0108] Preferably, the range of the porosity of the separator 32 is set to 30% ≤ F ≤ 50%. Exemplarily, the porosity of the separator 32 can be set to 30%, 40%, 50%. This not only enables the separator 32 to provide sufficient channels for active ions to pass through, enabling the separator 32 to have good active ion permeability, but also the separator 32 will not have too low a structural strength due to too large a porosity, which is beneficial to reducing the possibility of damage to the separator 32.

[0109] In some embodiments, referring to Figure 4 , a plurality of grooves 313 all extend along the first direction Y, and the second direction Z, the thickness direction X, and the first direction Y are perpendicular to each other.

[0110] By making a plurality of grooves 313 all extend along the first direction Y, the guiding directions of the plurality of grooves 313 for the electrolyte are the same, and it is possible to supplement a large amount of electrolyte to a specific area inside the electrode assembly 3 in a timely manner, especially in an area where the electrolyte is likely to be in short supply.

[0111] The second direction Z can be a direction perpendicular to both the first direction Y and the thickness direction X. By arranging a plurality of grooves 313 at intervals in the second direction Z, the plurality of grooves 313 can be conveniently arranged in parallel on a surface perpendicular to the thickness direction X.

[0112] In some embodiments, 100μm ≤ H ≤ 5000μm.

[0113] By setting the range of the interval H between two adjacent grooves 313 in the second direction Z to 100μm ≤ H ≤ 5000μm, not only does it enable the plurality of grooves 313 to have sufficient density to guide the electrolyte into the electrode assembly 3, ensuring good wetting inside the electrode assembly 3, but also makes the grooves 313 on the active material layer 312 less likely to reduce the structural strength due to excessive density.

[0114] In some embodiments, 400μm ≤ H ≤ 2500μm.

[0115] By setting the range of the interval H between two adjacent grooves 313 in the second direction Z to 400μm ≤ H ≤ 2500μm, not only does it enable the plurality of grooves 313 to have sufficient density to guide the electrolyte into the electrode assembly 3, ensuring good wetting inside the electrode assembly 3, but also makes the grooves 313 on the active material layer 312 less likely to reduce the structural strength due to excessive density.

[0116] Preferably, the range of the interval H between two adjacent grooves 313 in the second direction Z is set to 500μm ≤ H ≤ 2000μm. Exemplarily, the interval between two adjacent grooves 313 in the second direction Z can be set to 500μm, 1000μm, 1500μm or 2000μm, enabling the plurality of grooves 313 to have sufficient density to guide the electrolyte into the electrode assembly 3, ensuring good wetting inside the electrode assembly 3 while also enabling the active material layer 312 to have sufficient structural strength.

[0117] In some embodiments, the width of the opening of the groove 313 in the second direction Z is J, and 40μm ≤ J ≤ 250μm.

[0118] By setting the width of the opening of the groove 313 in the second direction Z to J and setting the range of this width J to 40μm ≤ J ≤ 250μm, not only does the groove 313 have sufficient width in the second direction Z to have a sufficient cross-sectional area, but also makes the groove 313 less likely to affect the structural strength of the active material layer 312 due to an overly large opening.

[0119] In some embodiments, 50μm ≤ J ≤ 200μm.

[0120] By setting the range of the width J of the opening of the groove 313 in the second direction Z to 50 μm ≤ J ≤ 200 μm, not only does the groove 313 have a sufficient width in the second direction Z to have a sufficient cross-sectional area, but also the groove 313 is not likely to affect the structural strength of the active material layer 312 due to an overly large opening.

[0121] Preferably, the range of the width J of the opening of the groove 313 in the second direction Z is set to 60 μm ≤ J ≤ 150 μm. Exemplarily, the spacing between two adjacent grooves 313 in the second direction Z can be set to 60 μm, 90 μm, 120 μm, or 150 μm, so that the groove 313 has a sufficient cross-sectional area while the active material layer 312 has sufficient structural strength.

[0122] In some embodiments, referring to Figure 8 , a plurality of grooves 313 are provided, and the plurality of grooves 313 are spaced apart, and the extending directions of at least two grooves 313 intersect.

[0123] As in the foregoing technical solution, the plurality of grooves 313 formed on the active material layer 312 can better guide the electrolyte to the inside of the electrode assembly 3, so that the electrolyte inside the electrode assembly 3 can be replenished more timely.

[0124] The intersecting arrangement of the extending directions of at least two grooves 313 may mean that the extending directions of at least two grooves 313 are not parallel, so that the plurality of grooves 313 can be adaptively arranged according to the demand degree of the electrolyte inside the electrode assembly 3.

[0125] In some embodiments, referring to Figure 9 , a plurality of grooves 313 are provided, and at least two grooves 313 intersect.

[0126] The intersecting arrangement of at least two grooves 313 may mean that at least two of the plurality of grooves 313 communicate with each other, and can enable at least two grooves 313 to guide the electrolyte to a preset area simultaneously, which is beneficial to improving the speed of replenishing the electrolyte to the preset area.

[0127] Exemplarily, in the electrode assembly 3 having a stacked structure, the plurality of grooves 313 can be arranged radially, and the plurality of radially arranged grooves 313 guide the electrolyte to the inside of the electrode assembly 3.

[0128] In some embodiments, along the thickness direction X, the depth of the groove 313 is K, and the thickness of the active material layer 312 is M.

[0129] The depth of the groove 313 in the thickness direction X may refer to the depth of the groove 313, and the thickness of the active material layer 312 in the thickness direction X may refer to the thickness of the active material layer 312. By setting the relationship between the depth K of the groove 313 and the thickness M of the active material layer 312 as the groove 313 is not likely to affect the structural strength of the active material layer 312 due to excessive depth.

[0130] In some embodiments, in the thickness direction X, the depth of the groove 313 is K, and 4 μm ≤ K ≤ 45 μm.

[0131] By setting the depth of the groove 313 in the thickness direction X as K and setting the range of K as 4 μm ≤ K ≤ 45 μm, not only does the groove 313 have sufficient depth to guide the electrolyte to flow into the electrode assembly 3, but also the depth of the groove 313 is not likely to damage the structure of the active material layer 312 due to excessive depth, resulting in too low structural strength of the active material layer 312.

[0132] In some embodiments, 5 μm ≤ K ≤ 40 μm.

[0133] By setting the range of the depth K of the groove 313 in the thickness direction X as 5 μm ≤ K ≤ 40 μm, not only does the groove 313 have sufficient depth to guide the electrolyte to flow into the electrode assembly 3, but also the depth of the groove 313 is not likely to damage the structure of the active material layer 312 due to excessive depth, resulting in too low structural strength of the active material layer 312. Preferably, the range of the dimension K of the groove 313 in the thickness direction X can be set as 8 μm ≤ K ≤ 25 μm. Exemplarily, the dimension of the groove 313 in the thickness direction X can be set as 8 μm, 12 μm, 16 μm, 20 μm or 25 μm, so that while the groove 313 has sufficient depth to guide the electrolyte to flow into the electrode assembly 3, the depth of the groove 313 is not likely to damage the structural strength of the active material layer 312 due to excessive depth.

[0134] In some embodiments, in the thickness direction X, along the orientation of the opening of the groove 313, the width of the groove 313 shows an increasing trend.

[0135] In the thickness direction X, along the orientation of the opening of the groove 313, the width of the groove 313 showing an increasing trend may mean that along the orientation of the opening of the groove 313 in the thickness direction X, the width of the groove 313 continuously increases, such that the side wall of the groove 313 is continuously inclined and the width of the groove 313 is larger at the position closer to the opening of the groove 313; or it may mean that along the orientation of the opening of the groove 313 in the thickness direction X, the width of the groove 313 increases in a stepped manner and the width of the groove 313 is larger at the position closer to the opening of the groove 313.

[0136] By setting the width of the groove 313 to increase along the orientation of the opening of the groove 313 in the thickness direction X, not only can the bottom of the groove 313 still have an electrolyte channel even if particles or debris fall into the groove 313, making the groove 313 not easily blocked, but also the particles or debris falling into the groove 313 can be more easily removed from the opening of the groove 313.

[0137] In some embodiments, in a cross-section perpendicular to the extending direction of the groove, the cross-sectional shape of the groove 313 is one of a triangle, a trapezoid, a semi-circle, and a rectangle.

[0138] The cross-section of the groove 313 may refer to a cross-section perpendicular to the extending direction of the groove 313. The cross-sectional shape of the groove 313 being one of a triangle, a trapezoid, a semi-circle, and a rectangle may mean that the cross-sectional shape of each groove 313 among multiple grooves 313 is a triangle, a trapezoid, a semi-circle, or a rectangle; or it may mean that among multiple grooves 313, the cross-sectional shapes of the grooves 313 are diverse, and each groove 313 among the multiple grooves 313 can be one of a triangle, a trapezoid, a semi-circle, and a rectangle. Those skilled in the art can select the cross-sectional shape of the groove 313 according to the actual situation.

[0139] In some embodiments, the groove 313 is formed by laser grooving or chemical etching.

[0140] The groove 313 being formed by laser grooving may mean that the groove 313 is formed by processing with a laser on the surface of the active material layer 312 away from the first current collector 311. The groove 313 being formed by chemical etching may mean that the groove 313 is formed by corroding the surface of the active material layer 312 away from the first current collector 311 with a chemical reagent.

[0141] In some embodiments, the first electrode tab 31 is a negative electrode tab 34.

[0142] By setting the first electrode tab 31 as the negative electrode tab 34, such that the groove 313 is disposed on the active material layer 312 of the negative electrode tab 34, not only can the electrolyte infiltrate into the electrode assembly 3 along the negative electrode tab 34, but also the active ion embedding sites on the negative electrode tab 34 can be increased, which is beneficial to the diffusion of active ions and beneficial to reducing the problem of ion precipitation.

[0143] Measurement of the groove depth K, groove width J, groove pitch H, and cross-sectional area G of the groove:

[0144] Use a laser confocal microscope with the model number VK-1050 to photograph the groove area and obtain the optical and depth information of the electrode within the microscope's field of view. At a magnification of 20 times, scan the surface of the electrode using the laser confocal mode. After the scanning is completed, process the acquired measurement data in the data analysis software associated with the instrument. Use the "datum plane setting" function in "processing images" to set the datum plane for the measurement data. Then, select the "smoothing" function, choose a size of "5×5" and a type of "simple average" to smooth the graph. After the processing is completed, use the "profile measurement" function to measure the groove parameters.

[0145] Groove depth K and groove width J: As Figure 8 shown, the depth difference between the deepest part of the groove and the datum plane is the groove depth, and the distance between the intersection points of the two sides of the groove and the datum plane is the groove width. Along the same groove, measure once every 10 μm, for a total of 20 measurements. Calculate the average values of the depth and width for the 20 measurements, and record the groove depth K and width J.

[0146] Groove pitch H: For adjacent grooves (when observing along the length direction of the electrode, if the overlapping part of two adjacent grooves is more than 50% of their respective lengths, they are adjacent grooves), in the vertical direction of the groove, the distance between the midpoints of the widths of the two grooves is the groove pitch. Along the selected groove, measure once every 10 μm, for a total of 20 measurements. Calculate the average value, denoted as the groove pitch H.

[0147] Groove area G: Use a laser confocal microscope with the model number VK-1050 to photograph the groove area and obtain the optical and depth information of the electrode within the microscope's field of view. At a magnification of 20 times, scan the surface of the electrode using the laser confocal mode. After the scanning is completed, obtain the depth data relative to the reference line for each pixel width. Within the above-mentioned groove width range, integrate the depth (h i) for each pixel width (w0), which is the cross-sectional area G of the groove:

[0148] G = ∑i h i × w0.

[0149] Test method for the porosity of the separator:

[0150] Adopt the gas displacement method, and the test instrument is a true density tester (AccuPyc II1340). Cut the separator into the rated size, with a length of A0, a width of B0, and a thickness of C0. Calculate the space volume V0 of the separator = A0 * B0 * C0. Place the separator in the true density meter and measure the true volume as V1.

[0151] The porosity of the separator = (V0 - V1) / V1 * 100%.

[0152] The beneficial effects of the battery cells provided in the specific embodiments of the present application will be further described below through comparative experiments.

[0153] A fiber laser is used to form a plurality of grooves arranged in parallel and at equal intervals on the active material layer of the negative electrode tab. The thickness M of the active material layer is 40 μm. After laminating the negative electrode tab, the separator, and the positive electrode tab to form an electrode assembly, it is installed in a housing made of aluminum-plastic material, electrolyte is injected, and after processes such as encapsulation and formation, the battery cells provided in the embodiments of the present application are manufactured.

[0154] The battery cells without grooves manufactured using the same process method are used as the battery cells for the comparative examples.

[0155] The differences between the negative electrode tabs in each comparative example and embodiment are as follows:

[0156] Table 1

[0157]

[0158] Note: That is, 0.03M * H ≤ (G + (0.1C * F * H)).

[0159] The cycle performance and cycle interface of the battery cells in the above comparative examples and embodiments are evaluated. The specific method is as follows:

[0160] The cycle performance of the battery cells is evaluated through the capacity retention rate. The calculation method of the capacity retention rate is to charge and discharge the battery cells in the comparative examples and embodiments 500 times using the same charging process at an ambient temperature of 25°C, and then divide the discharge capacity of the battery cells after 500 times of charge and discharge by the discharge capacity at the first time to obtain the capacity retention rate.

[0161] The charging process of the battery cells is as follows:

[0162] Step 1: Charge the battery cell at a constant current of 2C to 4.5V;

[0163] Step 2: Charge the battery cell at a constant voltage of 4.5V to 0.05C;

[0164] Step 3: Let the battery cell stand for 5 minutes;

[0165] Step 4: Discharge the battery cell at a constant current of 0.5C to 3.0V;

[0166] Step 5: Let the battery cell stand for 5 minutes;

[0167] Step 6: Repeat the above steps 1 to 5 five hundred times.

[0168] The evaluation of the cycling interface of the battery cell is carried out by evaluating the lithium deposition situation on the negative electrode plate. The battery cell that has undergone 500 charge-discharge cycles is disassembled, and the interface of the negative electrode plate is observed and compared. In order to describe the lithium deposition situation on the cycling interface, the interface situation is now classified. Through the naked eye observation of the operator, if the surface of the negative electrode plate is golden yellow and there are no abnormal phenomena, it is determined that there is no lithium deposition; if there are intermittent dot-shaped purple spots, lithium deposition, or lithium deposition on the purple spots on the negative electrode plate, it is determined that there is slight lithium deposition; if there are large-area continuous purple spots, lithium deposition, or lithium deposition on the purple spots on the main body of the negative electrode plate, and the abnormal area ratio is less than 50%, it is determined that there is lithium deposition; if there are large-area continuous purple spots, lithium deposition, or lithium deposition on the purple spots on the main body of the negative electrode plate, and the abnormal area ratio is greater than or equal to 50%, it is determined that there is severe lithium deposition.

[0169] The cycling performance and cycling interface of the battery cells in the comparative examples and examples are as follows:

[0170] Table 2

[0171]

[0172] As can be seen from Table 1 and Table 2, when the compaction of the electrode plate is relatively high, the electrolyte replenishment ability of the unslotted electrode assembly 3 in Comparative Examples 1-2 is poor, the wettability of the electrode assembly 3 is poor, and severe lithium deposition occurs in the later stage of cycling, and at the same time, the capacity retention rate is significantly reduced; compared with Comparative Examples 1-2, in Comparative Examples 3-4, it can be seen that after forming the groove 313 by slotting the negative electrode plate 34, the wettability of the electrode assembly 3 is improved, and both the capacity retention rate and the cycling interface are significantly improved, but the sum of the equivalent size of the pores of the separator 32 in the thickness direction X multiplied by the resistance coefficient and the equivalent depth of the groove 313 in the thickness direction X is not in the optimal range, and the electrolyte replenishment ability is not improved enough. Compared with Comparative Examples 3-4, in Examples 1-2, it can be seen that after forming the groove 313 by slotting the negative electrode plate 34, the sum of the equivalent size of the pores of the separator 32 in the thickness direction X multiplied by the resistance coefficient and the equivalent depth of the groove 313 in the thickness direction X is in the optimal range, so the capacity retention rate and the cycling interface are further improved compared with Comparative Examples 3-4. By comparing Comparative Example 2, Comparative Example 4, Example 2, and Example 3, it can be seen that as the sum of the equivalent size of the pores of the separator 32 in the thickness direction X multiplied by the resistance coefficient and the equivalent depth of the groove 313 in the thickness direction X increases, the capacity retention rate of the battery cell is continuously improved.

[0173] Some embodiments of the present application also provide an electrical device, which includes the battery cell provided by the above technical solution, and the battery cell is used to provide electrical energy. Since the electrical device includes the battery cell provided by the above technical solution, the electrical device has a long service life.

[0174] Although the present application has been described with reference to the preferred embodiments, various modifications can be made thereto without departing from the scope of the present application, and components thereof can be replaced with equivalents. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any manner. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that: include: A shell, forming a cavity, wherein the cavity is filled with an electrolyte; An electrode assembly is disposed in the cavity, the electrode assembly comprising a first pole piece and a separator, the first pole piece comprising a first current collector and an active material layer, the first current collector comprising two first surfaces arranged opposite to each other in a thickness direction, at least one of the first surfaces is provided with the active material layer, the thickness of the active material layer is M, the surface of the active material layer away from the first current collector is inwardly recessed to form a groove, and the groove extends to the edge of the first pole piece; Along the thickness direction, the thickness of the isolation membrane is C; the isolation membrane is stacked with the first pole piece along the thickness direction, and the porosity of the isolation membrane is F; there are multiple grooves, and the multiple grooves are arranged at equal intervals along the second direction, the second direction is perpendicular to the extension direction of the grooves, the interval between two adjacent grooves in the second direction is H, and the cross-sectional area of ​​the groove in the cross section perpendicular to the extension direction is G, 0.03M×H≤(G+(0.1C×F×H)).

2. The battery cell according to claim 1, characterized in that: The groove extends along a first direction, and the first direction is perpendicular to the thickness direction; along the first direction, the length of the first pole piece is B, and the length of the groove is A.

3. The battery cell according to claim 2, characterized in that: The active material layer includes two end surfaces arranged opposite to each other along the first direction, and the groove connects the two end surfaces.

4. The battery cell according to claim 1, characterized in that: 2.5μm≤C≤15μm.

5. The battery cell according to claim 4, characterized in that: 3.5μm≤C≤13μm.

6. The battery cell according to claim 4, characterized in that: The isolation film includes a base film, and the base film is provided with an adhesive layer on the surface in the thickness direction, and the adhesive layer is bonded to the first pole piece; along the thickness direction, the thickness of the base film is D, the thickness of the adhesive layer is E, 2.25μm≤D≤11μm, 0.25μm≤E≤4μm.

7. The battery cell according to claim 6, characterized in that: 3μm≤D≤10μm, 0.5μm≤E≤3μm.

8. The battery cell according to claim 1, characterized in that: 15％≤F≤90％。 9. The battery cell according to claim 8, characterized in that: 20％≤F≤80％。 10. The battery cell according to claim 9, characterized in that: 30％≤F≤50％。 11. The battery cell according to claim 1, characterized in that: The plurality of grooves extend along a first direction, and the second direction, the thickness direction and the first direction are perpendicular to each other.

12. The battery cell according to claim 1, characterized in that: 100μm≤H≤5000μm.

13. The battery cell according to claim 12, characterized in that: 400μm≤H≤2500μm.

14. The battery cell according to claim 10, characterized in that: The width of the opening of the groove in the second direction is J, and 40 μm≤J≤250 μm.

15. The battery cell according to claim 14, characterized in that: 50μm≤J≤200μm.

16. The battery cell according to claim 1, characterized in that: There are a plurality of grooves, the grooves are arranged at intervals, and the extension directions of at least two of the grooves intersect.

17. The battery cell according to claim 1, characterized in that: There are a plurality of grooves, and at least two of the grooves are intersectingly arranged.

18. The battery cell according to claim 1, characterized in that: Along the thickness direction, the depth of the groove is K, the thickness of the active material layer is M, 19. The battery cell according to claim 1, characterized in that: Along the thickness direction, the depth of the groove is K, 4 μm≤K≤45 μm.

20. The battery cell according to claim 19, characterized in that: 5μm≤K≤40μm.

21. The battery cell according to claim 1, characterized in that: In the thickness direction, along the direction of the groove opening, the width of the groove tends to increase.

22. The battery cell according to claim 1, characterized in that: In a cross section perpendicular to an extending direction of the groove, a cross-sectional shape of the groove is one of a triangle, a trapezoid, a semicircle, and a rectangle.

23. The battery cell according to claim 1, characterized in that: The grooves are formed by laser engraving or chemical etching.

24. The battery cell according to claim 1, characterized in that: The first pole piece is a negative pole piece.

25. An electrical device, characterized in that: The invention comprises a battery cell as described in any one of claims 1 to 24, wherein the battery cell is used to provide electrical energy.

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