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, far away from a first current collector, of an active substance layer of a pole piece is sunken inwards to form a groove, and the end part of the groove in the extension direction is communicated with the edge of the pole piece so as to be communicated with the containing cavity; the surface roughness of the surface, away from the first current collector, of the active material layer is R, the median particle size of the active material in the active material layer is Dv50, and the depth of the groove at the position with the width Dv50 is D1, the sum of the depth D1 of the # imgabs0 # groove at the position with the width being the median particle size Dv50 of the active material and the surface roughness R of the surface, away from the first current collector, of the active material layer is larger than or equal to half of the median particle size Dv50 of the active material, so that active material particles falling into the groove are not prone to protruding out of the surface, away from the first current collector, of the active material layer to make contact with the isolating membrane. And the possibility that the isolating membrane is punctured is reduced, so that the battery cell has good reliability.

Description

Technical Field

[0001] The present application relates to the field of batteries, and particularly to an electrode core 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 be used continuously. 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] With the development of science and technology and industrial technology, batteries have gradually become a bottleneck for electronic devices and electric devices. How to improve the cycle life and reliability of secondary batteries has always attracted the attention of those skilled in the art. Summary of the Invention

[0004] The present application provides an electrode core and an electrical device using the same. The electrode core has a long cycle life and good reliability at the same time.

[0005] In a first aspect, the present application provides an electrode core, which includes a housing and an electrode assembly. The housing forms a cavity filled with electrolyte; the electrode assembly is disposed in the cavity and includes stacked electrode plates and a separator for isolating adjacent electrode plates. The electrode plate 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 at least one of the first surfaces is provided with an active material layer. A groove is formed by inward depression on the surface of the active material layer away from the first current collector, and the end of the groove in the extending direction communicates with the edge of the electrode plate to communicate with the cavity; the surface roughness of the surface of the active material layer away from the first current collector is R, the median particle size of the active material in the active material layer is Dv50, and the depth of the groove at the width of Dv50 is D1.

[0006] In the above structure, since the groove in the active material layer communicates with the edge of the electrode plate and then with the cavity, and the sum of the depth D1 of the groove at the width of the median particle size Dv50 of the active material and the surface roughness R of the surface of the active material layer away from the first current collector is greater than or equal to half of the median particle size Dv50 of the active material, the electrolyte in the cavity can flow into the electrode assembly through the groove. While infiltrating the inside of the electrode assembly, the active material particles falling into the groove are not likely to protrude from the surface of the active material layer away from the first current collector and contact the separator, reducing the possibility of the separator being pierced. Thus, the electrode assembly in the electrode core is well infiltrated, has a long cycle life, and good reliability at the same time.

[0007] For the battery cell provided by some embodiments of the present application, along the orientation of the groove opening, the width of the groove shows an increasing trend. This not only ensures that even if particles or debris fall into the groove, there is still an electrolyte channel at the bottom of the groove, making the groove not easily blocked, but also enables the particles or debris falling into the groove to easily escape from the opening of the groove.

[0008] For the battery cell provided by some embodiments of the present application, the median particle size of the active material in the active material layer is Dv50, and 4μm ≤ Dv50 ≤ 25μm. This not only makes it difficult for the active material particles in the active material layer to block the groove due to too small a particle size, but also makes it difficult for the active material particles in the active material layer to protrude from the groove due to too large a particle size, reducing the possibility of the active material particles contacting and piercing the separator.

[0009] For the battery cell provided by some embodiments of the present application, 5μm ≤ Dv50 ≤ 20μm. This makes it difficult for the active material particles in the active material layer to block the groove due to too small a particle size, and at the same time, it is not easy to protrude from the groove, reducing the possibility of the active material particles contacting and piercing the separator.

[0010] For the battery cell provided by some embodiments of the present application, the surface roughness of the surface of the active material layer away from the first current collector is R, and 0.8μm ≤ R ≤ 8μm. This not only makes it difficult for the surface roughness R of the active material layer to damage the separator due to being too large, but also makes the surface roughness R of the active material layer not too small to reduce the surface area of the surface of the active material layer away from the first current collector, enabling the active material layer to have sufficient contact area with the electrolyte.

[0011] For the battery cell provided by some embodiments of the present application, 1μm ≤ R ≤ 6μm. This makes the surface roughness R of the active material layer within a suitable range, such that the surface of the active material layer is not easily damaged to the separator and also has sufficient contact area with the electrolyte.

[0012] For the battery cell provided by some embodiments of the present application, the groove extends in the first direction, and the first direction is perpendicular to the thickness direction; along the first direction, the length of the groove is A, and the length of the electrode sheet is B. This enables the groove to guide the electrolyte to the central position of the electrode sheet in the first direction, so that the central position of the electrode sheet can be replenished with electrolyte in a timely manner.

[0013] According to the battery cell provided by some embodiments of the present application, the active material layer includes two end faces oppositely arranged along a first direction, and the groove connects the two end faces, and the first direction is perpendicular to the thickness direction. By making the groove connect the two end faces, the groove can guide the electrolyte from the two opposite end faces into the electrode assembly, so that the electrolyte can be replenished into the electrode assembly more timely, and the possibility of the lack of electrolyte inside the electrode assembly can be reduced.

[0014] According to the battery cell provided by some embodiments of the present application, there are multiple grooves, and at least two grooves intersect, so that at least two grooves can guide the electrolyte to a preset area at the same time, which is beneficial to improving the speed of replenishing the electrolyte to the preset area.

[0015] According to the battery cell provided by some embodiments of the present application, there are multiple grooves, and the multiple grooves are arranged at intervals, and the extending directions of at least two grooves intersect, and the extending directions of at least two grooves are not parallel, so that the multiple grooves can be adaptively arranged according to the demand degree of the electrolyte inside the electrode assembly.

[0016] According to the battery cell provided by some embodiments of the present application, the groove extends along the first direction, and multiple grooves are arranged at intervals along the second direction, and the second direction, the thickness direction and the first direction are perpendicular to each other. By arranging the multiple grooves at equal intervals along the second direction, the multiple grooves are evenly distributed on the active material layer, so that the improvement of the wettability of the groove to the electrode assembly is uniform, and the electrolyte inside the electrode assembly can be replenished more evenly.

[0017] According to the battery cell provided by some embodiments of the present application, the multiple grooves are arranged at equal intervals along the second direction, and the interval between two adjacent grooves in the second direction is H, and 100 μm ≤ H ≤ 5000 μm. This not only enables the multiple grooves to have sufficient density to guide the electrolyte into the electrode assembly, so that the inside of the electrode assembly is well wetted, but also makes the grooves on the active material layer not easily reduce the structural strength due to excessive density.

[0018] According to the battery cell provided by some embodiments of the present application, 400 μm ≤ H ≤ 2500 μm, which enables the inside of the electrode assembly to be well wetted and at the same time makes the grooves on the active material layer not easily reduce the structural strength due to excessive density.

[0019] According to 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. This not only enables the groove to have sufficient width in the second direction so that the groove has sufficient cross-sectional area, but also makes the groove not easily affect the structural strength of the active material layer due to too large an opening.

[0020] For the battery cell provided by some embodiments of the present application, 50μm ≤ J ≤ 200μm, such that while the groove has a sufficient cross-sectional area, it is not easily affected by an overly large opening, which may impact the structural strength of the active material layer.

[0021] 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. Such that the groove is not easily affected by an overly deep depth, which may impact the structural strength of the active material layer.

[0022] For the battery cell provided by some embodiments of the present application, along the thickness direction, the depth of the groove is K, 4μm ≤ K ≤ 45μm. This not only enables the groove to have a sufficient depth to guide the electrolyte to flow into the electrode assembly but also ensures that the depth of the groove is not overly deep, which may damage the structure of the active material layer and lead to an overly low structural strength of the active material layer.

[0023] For the battery cell provided by some embodiments of the present application, 5μm ≤ K ≤ 40μm, such that while the groove has a sufficient depth to guide the electrolyte to flow into the electrode assembly, it is not easily damaged the structure of the active material layer.

[0024] For the battery cell provided by some embodiments of the present application, the groove is formed by laser grooving or chemical etching.

[0025] For the battery cell provided by some embodiments of the present application, the cross-sectional shape of the groove is one of a triangle, a trapezoid, a semi-circle, and a rectangle.

[0026] For the battery cell provided by some embodiments of the present application, the electrode sheet is a negative electrode sheet, which not only enables the electrolyte to infiltrate into the electrode assembly along the negative electrode sheet but also increases the active ion insertion sites on the negative electrode sheet, facilitating the diffusion of active ions and reducing the problem of ion precipitation.

[0027] In a second aspect, some embodiments of the present application provide an electrical device, which includes the battery cell provided by any of the above technical solutions, and the battery cell is used to provide electrical energy.

[0028] The technical solutions provided by the embodiments of the present disclosure at least bring the following beneficial effects:

[0029] The present application provides an electric core, which includes a housing and an electrode assembly. The housing forms a cavity filled with an electrolyte, and the electrode assembly is disposed in the cavity. The electrode assembly includes stacked electrode plates and a separator for isolating adjacent electrode plates. The electrode plate 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. A groove is formed by inward depression on the surface of the active material layer away from the first current collector. The end of the groove in the extending direction communicates with the edge of the electrode plate to communicate with the cavity; the surface roughness of the surface of the active material layer away from the first current collector is R, the median particle size of the active material in the active material layer is Dv50, and the depth of the groove at a width of Dv50 is D1. Since the groove in the active material layer communicates with the edge of the electrode plate and thus with the cavity, when the active material particles enter the position where the width of the groove is Dv50, the height by which the active material particles in the groove exceed this position is the radius, that is, half of the particle size Dv50. Additionally, the surface of the active material layer is not smooth and has a certain roughness. Therefore, half of the particle size Dv50 needs to be less than or equal to the sum of D1 and the roughness R, so that the electrolyte in the cavity can flow into the electrode assembly through the groove. While infiltrating the inside of the electrode assembly, the active material particles falling into the groove are not likely to protrude from the surface of the active material layer away from the first current collector and contact the separator, reducing the possibility of the separator being punctured. This enables the electrode assembly in the electric core to be well infiltrated, have a long cycle life, and also have good reliability. Description of the Drawings

[0030] The features, advantages, and technical effects of the exemplary embodiments of the present application will be described below with reference to the drawings.

[0031] Figure 1 Schematic exploded view of the electric core provided by an embodiment of the present application;

[0032] Figure 2 Cross-sectional view of the electrode assembly provided by an embodiment of the present application;

[0033] Figure 3 Cross-sectional view of the electrode assembly provided by another embodiment of the present application;

[0034] Figure 4 Cross-sectional view of the electrode plate provided by an embodiment of the present application;

[0035] Figure 5 For Figure 4 Enlarged view at F in

[0036] Figure 6 Top view of the electrode plate provided by the first embodiment of the present application;

[0037] Figure 7The top view of the electrode sheet provided by the second embodiment of the present application;

[0038] Figure 8 The top view of the electrode sheet provided by the third embodiment of the present application;

[0039] Figure 9 The top view of the electrode sheet provided by the fourth embodiment of the present application.

[0040] In the figure:

[0041] 1. Housing; 2. Cavity; 3. Electrode assembly; 31. Electrode sheet; 311. First current collector; 3111. First surface; 312. Active material layer; 3121. End face; 313. Groove; 32. Separator; 33. Positive electrode sheet; 34. Negative electrode sheet; X. Thickness direction; Y. First direction; Z. Second direction.

[0042] In the drawings, the drawings are not necessarily drawn to actual scale. Detailed implementation manners

[0043] 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. Obviously, the described embodiments are some, but not all, of the embodiments of the present application.

[0044] 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 plants, but also widely applied to electric transportation means such as electric bicycles, electric motorcycles, and electric vehicles, as well as multiple fields such as military equipment and aerospace.

[0045] The battery cells mentioned in the embodiments of the present application can be secondary batteries or primary batteries. A secondary battery refers to a battery that can be activated by charging after discharging so as to be used continuously.

[0046] 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.

[0047] The battery cells generally include an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of the battery cell, active ions (such as lithium ions) are embedded 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 at the same time allow the active ions to pass through.

[0048] In some embodiments, the electrode assembly is a wound structure or a stacked structure. Optionally, the electrode assembly is a cylindrical wound structure.

[0049] 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.

[0050] 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.

[0051] The electrolyte plays a very important role during 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 internal 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 capacity 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.

[0052] 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 stacked electrode plates and a separator for isolating adjacent electrode plates. The electrode plate includes a first current collector and an active material layer. The first current collector includes two first surfaces oppositely arranged in the thickness direction, and at least one of the first surfaces is provided with an active material layer. The surface of the active material layer away from the first current collector is recessed inward to form a groove, and the end of the groove in the extending direction communicates with the edge of the electrode plate to communicate with the cavity; the surface roughness of the surface of the active material layer away from the first current collector is R, the median particle size of the active material in the active material layer is Dv50, and the depth of the groove at a width of Dv50 is D1. Since the groove in the active material layer communicates with the edge of the electrode plate and thus with the cavity, when the active material particles enter the position where the width of the groove is Dv50, the height of the active material particles in the groove exceeding this position is the radius, that is, half of the particle size Dv50. Since the surface of the active material layer is not smooth and has a certain roughness, half of the particle size Dv50 needs to be less than or equal to the sum of D1 and the roughness R, so that the electrolyte in the cavity can flow into the electrode assembly through the groove. While infiltrating the inside of the electrode assembly, the active material particles falling in the groove are not likely to protrude from the surface of the active material layer away from the first current collector and contact the separator, reducing the possibility of the separator being pierced. This enables the electrode assembly in the battery cell to be well infiltrated, have a long cycle life, and at the same time have good reliability.

[0053] The technical solutions of the battery cell and the electrical device provided by the present application will be further described below through specific embodiments.

[0054] 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. Referring to Figure 2 and Figure 3 , the electrode assembly 3 includes stacked electrode plates 31 and a separator 32 that isolates adjacent electrode plates 31. Referring to Figure 4 , the electrode plate 31 includes a first current collector 311 and an active material layer 312. The first current collector 311 includes two first surfaces 3111 oppositely disposed along the thickness direction X, and at least one first surface 3111 is provided with an active material layer 312. A groove 313 is formed by inward depression on the surface of the active material layer 312 away from the first current collector 311. The end of the groove 313 in the extending direction communicates with the edge of the electrode plate 31 to communicate with the cavity 2; Referring to Figure 5 , the surface roughness of the surface of the active material layer 312 away from the first current collector 311 is R, the median particle size of the active material in the active material layer 312 is Dv50, and the depth of the groove 313 at a width of Dv50 is D1.

[0055] The housing 1 can be a wall structure disposed on the outer periphery of 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, and the housing 1 can protect the components in the cavity 2.

[0056] The electrolyte is a liquid that conducts active ions between the positive electrode plate 33 and the negative electrode plate 34 in the electrode assembly 3. By infiltrating the positive electrode plate 33 and the negative electrode plate 34 in the electrode assembly 3, the active ions can be conducted between the positive electrode plate 33 and the negative electrode plate 34.

[0057] The electrode assembly 3 is an important structure in the battery cell. It is disposed 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.

[0058] The electrode assembly 3 includes stacked positive electrode plates 33 and negative electrode plates 34. In the wound electrode assembly 3, the stacked positive electrode plates 33 and negative electrode plates 34 are wound into a wound structure.

[0059] In the electrode assembly 3 in a laminated structure, a plurality of positive electrode plates 33 and a plurality of negative electrode plates 34 are provided respectively, and the plurality of positive electrode plates 33 and the plurality of negative electrode plates 34 are alternately laminated. Exemplarily, a plurality of positive electrode plates 33 can be provided, and the negative electrode plate 34 can be folded to form a plurality of folded segments arranged in a stacked manner, and a positive electrode plate 33 is clamped between adjacent folded segments. As an example, both the positive electrode plate 33 and the negative electrode plate 34 are folded to form a plurality of folded segments arranged in a stacked manner.

[0060] Exemplarily, the shape of the electrode assembly 3 can be cylindrical, flat, or multi-prismatic, etc.

[0061] The electrode plate 31 includes the positive electrode plate 33 and the negative electrode plate 34 in the foregoing technical solution. The positive electrode plate 33 and the negative electrode plate 34 are laminated, and a separator 32 is provided between the positive electrode plate 33 and the negative electrode plate 34. The separator 32 insulates and isolates the adjacent positive electrode plate 33 and negative electrode plate 34, which can prevent the short circuit between the positive electrode plate 33 and the negative electrode plate 34, and at the same time allows active ions to pass through.

[0062] Those skilled in the art can choose to provide a groove 313 on the positive electrode plate 33 according to the actual situation, or provide a groove 313 on the negative electrode plate 34, or provide grooves 313 on both the positive electrode plate 33 and the negative electrode plate 34.

[0063] The first current collector 311 can be the matrix structure in the electrode plate 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 relatively spaced apart 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.

[0064] The active material layer 312 can be a layered structure formed by the active material, and it 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 first surface 3111 of the first current collector 311, or it can also mean that the active material layers 312 are provided on both first surfaces 3111 of the first current collector 311.

[0065] The groove 313 may be a groove 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 concave 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 electrode tab 31 to communicate with the cavity 2, which may mean that the end of the groove 313 in the extending direction communicates with the edge of the electrode tab 31. Since the edge of the 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 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. The electrolyte in the cavity 2 can supplement the interior of the electrode assembly 3, enabling the electrolyte to better infiltrate and timely supplement the interior of the electrode assembly 3, which is beneficial to extending the cycle life of the battery cell.

[0066] 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.

[0067] In the stacked electrode assembly 3, the end of the groove 313 in the extending direction communicates with the edge of the electrode tab 31, 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.

[0068] By setting the surface roughness of the surface of the active material layer 312 away from the first current collector 311 as R, setting the median particle size of the active material in the active material layer 312 as Dv50, and setting the depth of the groove 313 at the width of Dv50 as D1, the relationship among the three is set as such that the sum of the depth D1 of the groove 313 at the width of the median particle size Dv50 of the active material and the surface roughness R of the surface of the active material layer 312 away from the first current collector 311 is greater than or equal to half of the median particle size Dv50 of the active material. Since the groove in the active material layer communicates with the edge of the electrode tab and thus with the cavity, when the active material particles enter the position where the width of the groove is Dv50, the height of the active material particles in the groove exceeding this position is the radius, that is, half of the particle size Dv50. Since the surface of the active material layer is not smooth and has a certain roughness, half of the particle size Dv50 needs to be less than or equal to the sum of D1 and the roughness R, so that the active material particles falling into the groove 313 are not easily protruded from the surface of the active material layer 312 away from the first current collector 311 to contact the separator 32, reducing the possibility of the separator 32 being pierced.

[0069] Exemplarily, the surface roughness R of the surface of the active material layer away from the first current collector can be obtained by measuring the surface of the active material layer away from the first current collector according to the national standard GB / T 3505-2000. The specific measurement method can refer to the national standard for the surface of the active material layer away from the first current collector, which will not be elaborated here.

[0070] Since the grooves in the active material layer communicate with the edge of the electrode tab and the cavity, when the active material particles enter the position where the width of the groove is Dv50, the height of the active material particles in the groove exceeding this position is the radius, that is, half of the particle size Dv50. Since the surface of the active material layer is not smooth and has a certain roughness, half of the particle size Dv50 needs to be less than or equal to the sum of D1 and the roughness R, so that the electrolyte in the cavity 2 can flow into the electrode assembly 3 through the groove 313. While infiltrating the inside of the electrode assembly 3, the active material particles falling into the groove 313 are not easily protruded from the surface of the active material layer 312 away from the first current collector 311 to contact the separator 32, reducing the possibility of the separator 32 being pierced, so that the electrode assembly 3 in the battery cell is well infiltrated, has a long cycle life, and also has good reliability.

[0071] In some embodiments, along the orientation of the opening of the groove 313, the width of the groove 313 shows an increasing trend.

[0072] Along the orientation of the opening of the groove 313, the width of the groove 313 shows an increasing trend, which can mean that along the orientation of the opening of the groove 313, the width of the groove 313 continuously increases, so 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; it can also mean that along the orientation of the opening of the groove 313, the width of the groove 313 increases step by step, and the width of the groove 313 is larger at the position closer to the opening of the groove 313.

[0073] By setting the width of the groove 313 to show an increasing trend along the orientation of the opening of the groove 313, not only does the bottom of the groove 313 still have a channel for the electrolyte even if particles or debris fall into the groove 313, and the groove 313 is 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.

[0074] In some embodiments, the median particle size of the active material in the active material layer 312 is Dv50, and 4μm ≤ Dv50 ≤ 25μm.

[0075] By setting the range of the median particle size Dv50 of the active material in the active material layer 312 to be 4 μm ≤ Dv50 ≤ 25 μm, not only are the active material particles in the active material layer 312 less likely to block the groove 313 in the groove 313 due to too small a particle size, but also the active material particles in the active material layer 312 are less likely to protrude from the groove 313 due to too large a particle size, reducing the possibility that the active material particles contact and pierce the separator film 32.

[0076] In some embodiments, 5 μm ≤ Dv50 ≤ 20 μm.

[0077] By setting the range of the median particle size Dv50 of the active material in the active material layer 312 to be 5 μm ≤ Dv50 ≤ 20 μm, not only are the active material particles in the active material layer 312 less likely to block the groove 313 in the groove 313 due to too small a particle size, but also the active material particles in the active material layer 312 are less likely to protrude from the groove 313 due to too large a particle size, reducing the possibility that the active material particles contact and pierce the separator film 32.

[0078] Preferably, the range of the median particle size Dv50 of the active material in the active material layer 312 is set to 8 μm ≤ Dv50 ≤ 15 μm. The median particle size Dv50 of the active material in the active material layer 312 can be set to 8 μm, 10 μm, 12 μm, or 15 μm, so that the active material particles in the active material layer 312 are neither likely to block the groove 313 in the groove 313 due to too small a particle size nor likely to protrude from the groove 313 due to too large a particle size, reducing the possibility that the active material particles contact and pierce the separator film 32.

[0079] In some embodiments, the surface roughness of the surface of the active material layer 312 away from the first current collector 311 is R, and 0.8 μm ≤ R ≤ 8 μm.

[0080] By setting the range of the surface roughness R of the surface of the active material layer 312 away from the first current collector 311 to be 0.8 μm ≤ R ≤ 8 μm, not only is the surface roughness R of the active material layer 312 less likely to damage the separator film 32 due to being too large, but also the surface roughness R of the active material layer 312 is not too small to reduce the surface area of the surface of the active material layer 312 away from the first current collector 311, enabling the active material layer 312 to have sufficient contact area with the electrolyte.

[0081] In some embodiments, 1 μm ≤ R ≤ 6 μm.

[0082] By setting the surface roughness R of the surface of the active material layer 312 away from the surface of the first current collector 311 within the range of 1 μm ≤ R ≤ 6 μm, the surface roughness R of the active material layer 312 is within a suitable range, such that the surface of the active material layer 312 is not easily damaged to the separator 32 and also has a sufficient contact area with the electrolyte. Exemplarily, the surface roughness R of the surface of the active material layer 312 away from the first current collector 311 can be set to 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or 6 μm.

[0083] In some embodiments, referring to Figure 6 , the groove 313 extends in 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 groove 313 is A, and the length of the electrode tab 31 is B.

[0084] 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 in the first direction Y, the groove 313 can be arranged in a plane direction perpendicular to the thickness direction X.

[0085] By setting the length of the groove 313 in the first direction Y to A, setting the length of the electrode tab 31 in the first direction Y to B, and setting the relationship between the length A of the groove 313 in the first direction Y and the length B of the electrode tab 31 in the first direction Y to such that the length of the groove 313 in the first direction Y is greater than or equal to half of the length of the electrode tab 31 in the first direction Y, the groove 313 can guide the electrolyte to the central position of the electrode tab 31 in the first direction Y, enabling the central position of the electrode tab 31 to be replenished with electrolyte in a timely manner.

[0086] In some embodiments, referring to Figure 7 , 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, and the first direction Y is perpendicular to the thickness direction X.

[0087] As in the foregoing solution, the first direction Y can be a direction perpendicular to the thickness direction X of the first current collector 311. The end faces 3121 can 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.

[0088] By enabling the groove 313 to 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, enabling the electrolyte to be replenished into the interior of the electrode assembly 3 more timely and reducing the possibility of the lack of electrolyte in the interior of the electrode assembly 3.

[0089] In some embodiments, referring to Figure 8 , a plurality of grooves 313 are provided, and at least two grooves 313 intersect.

[0090] Providing a plurality of grooves 313 may mean that a plurality of grooves 313 are formed on the active material layer 312, which can better guide the electrolyte into the electrode assembly 3, so that the electrolyte inside the electrode assembly 3 can be replenished more timely.

[0091] 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, which can enable at least two grooves 313 to guide the electrolyte to a preset area simultaneously, facilitating the improvement of the speed of replenishing the electrolyte in the preset area.

[0092] Exemplarily, in the electrode assembly 3 having a stacked structure, a plurality of grooves 313 may be arranged radially, and the radially arranged plurality of grooves 313 guide the electrolyte into the electrode assembly 3.

[0093] In some embodiments, referring to Figure 9 , a plurality of grooves 313 are provided, and the plurality of grooves 313 are arranged at intervals, and the extending directions of at least two grooves 313 intersect.

[0094] As in the foregoing technical solution, the plurality of grooves 313 formed on the active material layer 312 can better guide the electrolyte into the electrode assembly 3, so that the electrolyte inside the electrode assembly 3 can be replenished more timely.

[0095] 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.

[0096] In some embodiments, the groove 313 extends along the first direction Y, and a plurality of grooves 313 are arranged at intervals along the second direction Z, and the second direction Z, the thickness direction X, and the first direction Y are perpendicular to each other.

[0097] By arranging a plurality of grooves 313 at equal intervals along the second direction Z, the plurality of grooves 313 are uniformly distributed on the active material layer 312, so that the improvement of the wettability of the groove 313 to the electrode assembly 3 is uniform, and the electrolyte inside the electrode assembly 3 can be replenished more uniformly.

[0098] By setting the range of the interval H between two adjacent grooves 313 in the second direction Z to be 100 μm ≤ H ≤ 2500 μm, not only can a sufficient density of the multiple grooves 313 be achieved to guide the electrolyte into the electrode assembly 3, enabling good wetting inside the electrode assembly 3, but also the grooves 313 on the active material layer 312 are not likely to have their structural strength reduced due to excessive density.

[0099] In some embodiments, 400 μm ≤ H ≤ 2500 μm.

[0100] By setting the range of the interval H between two adjacent grooves 313 in the second direction Z to be 400 μm ≤ H ≤ 2500 μm, not only can a sufficient density of the multiple grooves 313 be achieved to guide the electrolyte into the electrode assembly 3, enabling good wetting inside the electrode assembly 3, but also the grooves 313 on the active material layer 312 are not likely to have their structural strength reduced due to excessive density.

[0101] Preferably, the range of the interval H between two adjacent grooves 313 in the second direction Z is set to 500 μm ≤ H ≤ 2000 μm. Exemplarily, the interval between two adjacent grooves 313 in the second direction Z can be set to 500 μm, 1000 μm, 1500 μm, or 2000 μm, so that a sufficient density of the multiple grooves 313 can be achieved to guide the electrolyte into the electrode assembly 3, enabling good wetting inside the electrode assembly 3 while also ensuring that the active material layer 312 has sufficient structural strength.

[0102] In some embodiments, the width of the opening of the groove 313 in the second direction Z is J, and 40 μm ≤ J ≤ 250 μm.

[0103] By setting the width of the opening of the groove 313 in the second direction Z to be J and setting the range of this width J to be 40 μm ≤ J ≤ 250 μm, not only can the groove 313 have a sufficient width in the second direction Z to ensure that the groove 313 has 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.

[0104] In some embodiments, 50 μm ≤ J ≤ 200 μm.

[0105] By setting the range of the width J of the opening of the groove 313 in the second direction Z to be 50 μm ≤ J ≤ 200 μm, not only can the groove 313 have a sufficient width in the second direction Z to ensure that the groove 313 has 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.

[0106] Preferably, the width J of the opening of the groove 313 in the second direction Z is set in the range of 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.

[0107] 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.

[0108] The depth of the groove 313 along the thickness direction X may refer to the depth of the groove 313, and the thickness of the active material layer 312 along 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 being too deep.

[0109] In some embodiments, along the thickness direction X, the depth of the groove 313 is K, and 4 μm ≤ K ≤ 45 μm.

[0110] By setting the depth of the groove 313 along 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 being too deep, resulting in too low structural strength of the active material layer 312.

[0111] In some embodiments, 5 μm ≤ K ≤ 40 μm.

[0112] By setting the range of the depth K of the groove 313 along 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 being too deep, resulting in too low structural strength of the active material layer 312. Preferably, the range of the depth K of the groove 313 along the thickness direction X can be set to 8 μm ≤ K ≤ 25 μm. Exemplarily, the depth of the groove 313 along the thickness direction X can be set to 8 μm, 12 μm, 16 μm, 20 μm, or 25 μm, so that the groove 313 has sufficient depth to guide the electrolyte to flow into the electrode assembly 3 while the depth of the groove 313 is not likely to damage the structural strength of the active material layer 312 due to being too deep.

[0113] In some embodiments, the groove 313 is formed by laser grooving or chemical etching.

[0114] The groove 313 is formed by laser grooving, which may mean that the groove 313 is formed by using a laser to process on the surface of the active material layer 312 away from the first current collector 311. The groove 313 is formed by chemical etching, which may mean that the groove 313 is formed by etching the surface of the active material layer 312 away from the first current collector 311 with a chemical reagent.

[0115] In some embodiments, the cross-sectional shape of the groove 313 is one of a triangle, a trapezoid, a semi-circle, and a rectangle.

[0116] The cross-section of the groove 313 may refer to a cross-section perpendicular to the extension 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 shapes of all the grooves 313 among multiple grooves 313 are triangles, trapezoids, semi-circles, or rectangles; it may also 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.

[0117] In some embodiments, the electrode tab 31 is a negative electrode tab 34.

[0118] By setting the 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 upward along the negative electrode tab 34 into the electrode assembly 3, 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 is beneficial to reducing the problem of ion precipitation.

[0119] The beneficial effects of the battery cell provided by the specific embodiments of the present application are further described below through comparative experiments.

[0120] A fiber laser is used to form multiple grooves that are parallel and equally spaced on the active material layer of the negative electrode tab, and the surface roughness R of the surface of the active material layer away from the first current collector is 3 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 an aluminum-plastic material, electrolyte is injected, and after processes such as encapsulation and formation, the battery cell provided by the embodiments of the present application is manufactured.

[0121] The battery cell without grooves made by the same process method is used as the battery cell for the comparative example.

[0122] The self-discharge test is performed on the battery cell, and the passing rate of the self-discharge test of the battery cell is used as a standard for measuring whether the separator is punctured and whether it has good reliability.

[0123] The self-discharge rate test is a characterization method that can characterize the internal short circuit situation of the battery cell. When the active material particles pierce the separator, it will cause an internal short circuit of the battery cell and the self-discharge rate will increase.

[0124] The self-discharge rate test process of the battery cell is as follows:

[0125] Step 1: Charge the battery cell at a rate of 0.2C to 3.9V;

[0126] Step 2: After standing for 2 hours, measure its initial voltage V0;

[0127] Step 3: Let the battery cell stand at 25°C for 72 hours and measure the voltage V1 after standing.

[0128] Then, the self-discharge rate of the battery cell is |V1 - V0| / 72 mV / h. If the self-discharge rate of the battery cell is less than or equal to 0.04 mV / h, it means that the battery cell passes the self-discharge rate test.

[0129] In each example and comparative example of this application, 200 battery cells were prepared for self-discharge testing. Among them, the differences in the negative electrode plates in each comparative example and example and the results of the passing rate of the self-discharge rate test are as follows:

[0130] Table 1

[0131]

[0132] The cycle performance and cycle interface of the battery cells in the above comparative examples and examples were evaluated. The specific method is as follows:

[0133] The cycle performance of the battery cell is evaluated by the capacity retention rate. The calculation method of the capacity retention rate is to cycle charge and discharge the battery cells in the comparative examples and examples 500 times using the same charging process at an ambient temperature of 25°C, and then divide the discharge capacity of the battery cell after 500 times of cycle charge and discharge by the discharge capacity at the first time to obtain the capacity retention rate.

[0134] The charging process of the battery cell is as follows:

[0135] Step 1: Charge the battery cell at a constant current of 2C to 4.5V;

[0136] Step 2: Charge the battery cell at a constant voltage of 4.5V to 0.05C;

[0137] Step 3: Let the battery cell stand for 5 minutes;

[0138] Step 4: Discharge the battery cell at a constant current of 0.5C to 3.0V;

[0139] Step 5: Let the battery cell stand for 5 minutes;

[0140] Step 6: Repeat the above Steps 1 to 5 for 500 times.

[0141] The evaluation of the cycling interface of the battery cell is carried out by observing 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 intermittent dot-shaped purple spots, lithium deposition, or lithium deposition on the purple spots appear on the negative electrode plate, it is determined that there is slight lithium deposition; if large-area continuous purple spots, lithium deposition, or lithium deposition on the purple spots appear on the main body of the negative electrode plate, and the abnormal area accounts for less than 50%, it is determined that there is lithium deposition; if large-area continuous purple spots, lithium deposition, or lithium deposition on the purple spots appear on the main body of the negative electrode plate, and the abnormal area accounts for more than or equal to 50%, it is determined that there is severe lithium deposition.

[0142] The cycling performance and cycling interface of the battery cells in the comparative examples and the examples are as follows:

[0143] Table 2

[0144]

[0145] As can be seen from Table 1 and Table 2, when the electrode plate compaction is relatively high, the electrolyte replenishment ability of the unslotted electrode assemblies in Comparative Examples 1-2 is poor, the wettability of the electrode assemblies 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, it can be seen from Comparative Examples 3-4 that after forming grooves on the negative electrode plate, the wettability of the electrode assembly is improved, and both the capacity retention rate and the cycling interface are significantly improved. However, the sum of the depth D1 at the width of Dv50 of the groove and the surface roughness R of the surface of the active material layer away from the first current collector is less than half of the median particle size Dv50 of the active material, and there is a possibility that the active material particles contact the separator, reducing the passing rate of the self-discharge rate test of the battery cell. Comparing Comparative Examples 3-4 with Examples 1-2,

[0146] it can be seen that when the sum of the depth D1 at the width of Dv50 of the groove and the surface roughness R of the surface of the active material layer away from the first current collector is greater than or equal to half of the median particle size Dv50 of the active material, the possibility of contact between the active material particles and the separator is reduced, and the passing rate of the self-discharge rate test of the battery cell is significantly improved. Comparing Examples 1-2 with Examples 3-4, it can be seen that as the sum of the depth D1 at the width of Dv50 of the groove and the surface roughness R of the surface of the active material layer away from the first current collector increases, the possibility of contact between the active material particles and the separator is further reduced, and the passing rate of the self-discharge rate test of the battery cell can be further improved.

[0147] 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.

[0148] Although the present application has been described with reference to the preferred embodiments, various improvements can be made to it and components therein can be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, 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 arranged in the cavity, the electrode assembly includes stacked pole pieces and an isolation film isolating adjacent pole pieces, the pole piece includes a first current collector and an active material layer, the first current collector includes two first surfaces arranged opposite to each other in the thickness direction, at least one of the first surfaces is provided with the active material layer, the surface of the active material layer away from the first current collector is recessed inward to form a groove, and the end of the groove in the extension direction is connected to the edge of the pole piece to communicate with the cavity; the surface roughness of the active material layer away from the first current collector is R, the median particle size of the active material in the active material layer is Dv50, and the depth of the groove at the width of Dv50 is D1, 2. The battery cell according to claim 1, characterized in that: Along the direction of the groove opening, the width of the groove increases.

3. The battery cell according to claim 1, characterized in that: The median particle size of the active material in the active material layer is Dv50, 4 μm≤Dv50≤25 μm.

4. The battery cell according to claim 1, characterized in that: 5μm≤Dv50≤20μm.

5. The battery cell according to claim 1, characterized in that: 0.8μm≤R≤8μm.

6. The battery cell according to claim 1, characterized in that: 1μm≤R≤6μm.

7. 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 groove is A, and the length of the pole piece is B, 8. The battery cell according to claim 1, characterized in that: The active material layer includes two end surfaces arranged opposite to each other along a first direction, the groove connects the two end surfaces, and the first direction is perpendicular to the thickness direction.

9. 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.

10. 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.

11. The battery cell according to claim 10, characterized in that: The groove extends along a first direction, and a plurality of the grooves are arranged at intervals along a second direction, and the second direction, the thickness direction and the first direction are perpendicular to each other.

12. The battery cell according to claim 11, characterized in that: The plurality of grooves are arranged at equal intervals along the second direction, and an interval between two adjacent grooves in the second direction is H, where 100 μm≤H≤5000 μm.

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

14. The battery cell according to claim 11, 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: Along the thickness direction, the depth of the groove is K, the thickness of the active material layer is M, 17. 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.

18. The battery cell according to claim 17, characterized in that: 5μm≤K≤40μm.

19. The battery cell according to claim 1, characterized in that: The groove is formed by laser engraving or chemical etching.

20. The battery cell according to claim 1, characterized in that: The cross-sectional shape of the groove is one of a triangle, a trapezoid, a semicircle, and a rectangle.

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

22. An electrical device, characterized in that: The invention comprises a battery cell as described in any one of claims 1 to 21, wherein the battery cell is used to provide electrical energy.

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