A battery cell, a battery, and an electrical device

Abstract

Embodiments of the present application provide a battery cell, a battery, and an electrical device, relating to the technical field of lithium batteries. The anode active material layer of the anode electrode sheet in the battery cell of the embodiments of the present application includes a first end region, a middle region, and a second end region arranged along a first direction. The anode active material layer contains graphite and a high-expansion active material. Based on the mass of the middle region, the graphite content in the middle region is Q1%, and the high-expansion active material content is W1%. Based on the mass of the first end region, the graphite content in the first end region is Q2%, and the high-expansion active material content is W2%. Based on the mass of the second end region, the graphite content in the second end region is Q3%, and the high-expansion active material content is W3%. W1 > W2, and W1 > W3, Q1 < Q2, and Q1 < Q3. The battery cell, battery, and electrical device of the embodiments of the present application can improve the capacity retention rate of the battery.

Description

Technical Field

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

[0002] At present, lithium batteries are developing towards high power and high energy density. However, there is a problem that the heat inside the battery cell cannot be effectively dissipated, which in turn leads to a rapid decline in the battery capacity. Summary of the Invention

[0003] This application is made in view of the above problems, and its purpose is to provide a battery cell, a battery, and an electrical device that can improve the capacity retention rate of the battery.

[0004] To achieve the above purpose, a first aspect of this application provides a battery cell, including an electrode assembly. The electrode assembly includes a cathode electrode sheet and an anode electrode sheet. The electrode assembly has two ends arranged along a first direction. The anode electrode sheet includes an anode current collector and an anode active material layer attached to the surface of the anode current collector. The anode active material layer includes a first end region, a middle region, and a second end region arranged along the first direction. The anode active material layer contains graphite and a high-expansion active material. The high-expansion active material includes at least one of a silicon-based material, a tin-based material, and a metal oxide.

[0005] Among them, based on the mass of the middle region, the graphite content in the middle region is Q1%, and the high-expansion active material content is W1%. Based on the mass of the first end region, the graphite content in the first end region is Q2%, and the high-expansion active material content is W2%. Based on the mass of the second end region, the graphite content in the second end region is Q3%, and the high-expansion active material content is W3%. W1 > W2, and W1 > W3, Q1 < Q2, and Q1 < Q3.

[0006] Thus, in this application, by arranging a higher content of high-expansion active material and a lower content of graphite in the middle region of the anode active material layer compared to the two end regions (the first end region and the second end region), during charging, since the volume expansion rate of the high-expansion active material is greater than that of graphite, the thickness expansion rate of the middle region of the anode active material layer in the thickness direction is greater than that of the two end regions in the thickness direction, making the thickness of the middle region of the anode electrode sheet after charging greater than that of the two end regions; during discharging, due to the heat in the middle of the battery, the reaction rate of the middle region is faster than that of the two end regions, and the shrinkage rate of the middle region is greater than that of the two end regions, enabling the thickness of the anode active material layer and the anode electrode sheet after discharging to recover to be nearly uniform, reducing the gap between the middle region of the anode electrode sheet and the adjacent separator and cathode electrode sheet, thereby reducing lithium plating and improving the capacity retention rate of the battery.

[0007] In any embodiment, the two end portions of the electrode assembly are respectively the first end and the second end, and the middle region of the anode active material layer is the region at a distance of 1 / 4 to 1 / 2 from the first end and at a distance of 1 / 4 to 1 / 2 from the second end. This design matches the usage condition where the heat of the battery is concentrated at the position 1 / 4 to 1 / 2 away from the end, enabling the thickness of the anode electrode sheet after charge and discharge to recover to be nearly uniform.

[0008] In any embodiment, W1 > W2 > W3 and Q1 < Q2 < Q3. By arranging more high-expansion active material and less graphite in the first end region compared to the second end region, the thickness expansion rate of the first end region of the anode active material layer during charging is greater than that of the second end region, so as to match the usage condition where the heat and reaction rate at one end of the anode active material layer during discharging are higher than those at the other end, thereby improving the capacity retention rate of the battery.

[0009] In any embodiment, in the anode active material layer, the middle region contains the high-expansion active material, and the first end region and the second end region contain the graphite.

[0010] In any embodiment, the mass ratio of the graphite in the anode active material layer is 93% - 97%, and the mass ratio of the high-expansion active material is 0.3% - 1.5%. By using a certain amount of graphite and high-expansion active material in combination, the anode active material has a suitable thickness expansion rate during charging and maintains a high battery activity.

[0011] In any embodiment, in the anode active material layer, the position where the content of the highly swelling active material is the largest and the content of the graphite is the smallest in the middle region is defined as the peak line. In the directions from the peak line to both ends respectively, the content of the highly swelling active material decreases, and the content of the graphite increases. By setting the thickness expansion rate of the anode active material layer during charging to decrease from the peak line to both ends, the thickness of the anode active material layer after charging decreases from the peak line to both ends. Then, by using the situation that the shrinkage rate of the anode active material layer during discharging decreases from the middle peak line to both ends, the thickness of the anode active material layer and the anode electrode can be restored to be nearly uniform.

[0012] In any embodiment, in the anode active material layer, the peak line is at a distance of 1 / 3 to 1 / 2 from one of the two ends. This design matches the situation where the heat of the battery is concentrated at the position 1 / 3 to 1 / 2 from the end, so that the thickness of the anode electrode can be restored to be nearly uniform after charge and discharge.

[0013] In any embodiment, the anode active material layer includes a first active material layer and a second active material layer stacked in sequence on the anode current collector. In the directions from the peak line to both ends respectively, the thickness of the first active material layer or the second active material layer increases, and the thickness of the other layer decreases. And the content of the highly swelling active material in the layer with decreasing thickness is greater than the content of the highly swelling active material in the layer with increasing thickness, and the content of the graphite in the layer with decreasing thickness is less than the content of the graphite in the layer with increasing thickness. By setting the first active material layer and the second active material layer with gradually changing thickness from the peak line to both ends, the thickness of the anode active material layer itself is made uniform; moreover, by using different contents of graphite and highly swelling active material in the first active material layer and the second active material layer, the thickness expansion rate of the anode active material layer as a whole during charging decreases from the peak line to both ends respectively. After discharging, the thickness of the anode active material layer and the anode electrode can be restored to be nearly uniform.

[0014] In any embodiment, in the directions from the peak line to both ends respectively, the thickness of the first active material layer increases, the thickness of the second active material layer decreases, and the content of the highly swelling active material in the second active material layer is greater than the content of the highly swelling active material in the first active material layer, and the content of the graphite in the second active material layer is less than the content of the graphite in the first active material layer.

[0015] In any embodiment, the thickness of one end of the first active material layer is H D , the thickness of the same end of the second active material layer is 0, the thickness of the other end of the first active material layer is H1, the thickness of the same end of the second active material layer is H2, and H1 + H2 = H DThis setting causes the position with the maximum thickness expansion rate of the anode active material layer during charging to deviate from the center line of the anode electrode sheet, so as to match the situation where the heat concentration position of the anode active material layer deviates from the center line, enabling the thickness of the anode electrode sheet to recover to be nearly uniform.

[0016] In any implementation, the first active material layer contains graphite, and the second active material layer contains graphite and a highly expandable active material.

[0017] In any implementation, the silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys; the tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys; the metal oxide can be selected from at least one of tungsten oxide, vanadium oxide, iron oxide, ferrous oxide, cobalt oxide, cobalt sesquioxide, stannous oxide, stannic oxide, manganese monoxide, manganese dioxide, manganese sesquioxide, manganese tetroxide, antimony trioxide, antimony pentoxide, molybdenum trioxide, and molybdenum dioxide.

[0018] The second aspect of the present application also provides a battery, including the battery cell of the first aspect.

[0019] The third aspect of the present application also provides an electrical device, including the battery of the second aspect, and the battery is used to provide electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of a battery cell of an embodiment of the present application.

[0021] Figure 2 is Figure 1 a exploded view of the battery cell of an embodiment of the present application shown in

[0022] Figure 3 is for Figure 1 a schematic diagram of the electrode assembly in the battery cell of

[0023] Figure 4 is a schematic diagram of charge and discharge of a lower high-rebound battery cell in double-layer coating of the electrode assembly.

[0024] Figure 5 is a cross-sectional schematic diagram of the anode electrode sheet of Embodiment 1 of the present application.

[0025] Figure 6 is for Figure 5 the cross-sectional schematic diagram of the anode electrode sheet of after full charge.

[0026] Figure 7 is for Figure 6 the cross-sectional schematic diagram of the anode electrode sheet of after full discharge.

[0027] Figure 8Schematic cross-sectional view of the anode plate of Embodiment 2 of the present application.

[0028] Figure 9 Schematic cross-sectional view of the anode plate of Embodiment 3 of the present application.

[0029] Figure 10 Schematic cross-sectional view of the anode plate of Embodiment 4 of the present application.

[0030] Figure 11 Schematic cross-sectional view of the anode plate of Embodiment 5 of the present application.

[0031] Figure 12 Schematic diagram of the manufacturing process of the anode plate of Embodiment 1 of the present application.

[0032] Figure 13 For Figure 14 Schematic diagram of the positions of the extrusion heads of the first coater and the second coater in

[0033] Figure 14 For Figure 13 Schematic diagram of the structure of the first extrusion head in

[0034] Figure 15 For Figure 13 Schematic diagram of the structure of the second extrusion head in

[0035] Figure 16 Schematic diagram of a battery module according to an embodiment of the present application.

[0036] Figure 17 Schematic diagram of a battery pack according to an embodiment of the present application.

[0037] Figure 18 Is Figure 17 Exploded view of the battery pack according to an embodiment of the present application shown in

[0038] Figure 19 Schematic diagram of an electrical device using a battery cell as a power source according to an embodiment of the present application.

[0039] Explanation of reference numerals:

[0040] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly; 511 Anode current collector; 512 First active material layer; 513 Second active material layer; 514 Middle active material layer; 515 End active material layer Detailed implementation manners

[0041] Hereinafter, embodiments of the battery cell, battery, and electrical device of the present application will be specifically described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there are cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0042] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" represents that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0044] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0045] If there is no special instruction, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0046] At present, lithium batteries are continuously developing towards high power and high energy density. However, the greater the power and energy density of lithium batteries, the greater the temperature difference at different positions. Considering the temperature distribution characteristics during the high-power use of lithium batteries, the temperature in the middle of the battery cell is usually the highest because heat cannot be effectively dissipated, which leads to the highest reaction rate and the fastest performance degradation in the middle; while in the upper part of the battery cell, due to the presence of the tab, a large current will be received and more heat will be generated. However, there is an empty structure at this part and it is located at the edge, so the heat dissipation is better and the temperature is relatively low, and the performance degradation is relatively the smallest; although there is no empty structure at the lower part of the battery cell, it is located at the edge, and the temperature and performance degradation are between the upper and middle parts.

[0047] Under the condition of small-rate charging and high-power discharging of ordinary battery cells, since the middle part is under high-temperature conditions, the reaction rate increases, and the stored electric energy will be preferentially released. The battery cell will be misjudged as over-discharged, resulting in the thinning of the middle part of the anode electrode sheet and an increase in the gap between the anode and the cathode. When recharging, lithium metal will be easily deposited, increasing the battery cell loss and accelerating the attenuation. After multiple cycles, the capacity loss is relatively large.

[0048] If the thickness difference between the middle part and the two ends (upper part and lower part) of the anode electrode sheet after discharging can be reduced, the attenuation of the middle part of the battery cell during recharging can be reduced, thereby improving the capacity retention ability of the battery cell and further extending the service life of the battery cell.

[0049] Based on this, the embodiments of the present application propose a battery cell, a battery and an electrical device. The following will describe the present application and optional embodiments in more detail.

[0050] Please refer to Figures 1 to 7 , in the first aspect of the embodiments of the present application, a battery cell is provided, including an electrode assembly. The electrode assembly includes a cathode electrode sheet and an anode electrode sheet. The electrode assembly has two ends (corresponding to the upper part and the lower part in Figure 3 respectively) arranged along a first direction. The anode electrode sheet includes an anode current collector and an anode active material layer attached to the surface of the anode current collector. The anode active material layer includes a first end region, a middle region and a second end region arranged along the first direction. The anode active material layer contains graphite and a high-expansion active material. The high-expansion active material includes at least one of a silicon-based material, a tin-based material, and a metal oxide;

[0051] Among them, based on the mass of the middle region, the graphite content in the middle region is Q1%, and the high-expansion active material content is W1%. Based on the mass of the first end region, the graphite content in the first end region is Q2%, and the high-expansion active material content is W2%. Based on the mass of the second end region, the graphite content in the second end region is Q3%, and the high-expansion active material content is W3%. W1 > W2 and W1 > W3, Q1 < Q2 and Q1 < Q3.

[0052] In the embodiments of the present application, the content refers to the mass ratio, that is, the mass ratio of active materials such as graphite and high-expansion active materials in the anode active material layer. The content of each active material in the anode active material layer can be detected by means such as EDS, ICP, and XRD.

[0053] In some embodiments of the present application, the total content of active materials in different regions of the anode active material layer is the same. Exemplarily, the total content of graphite and high-expansion active materials in any region is the same. In other embodiments, the total content of active materials in different regions of the anode active material layer can also be different. Exemplarily, the total content of graphite and high-expansion active materials in any region is different.

[0054] In the anode active material layer of the present application, the content of the high-expansion active material in the middle region is higher than that in the two end regions, and the content of graphite in the middle region is lower than that in the two end regions. By setting a larger amount of high-expansion active material and a smaller amount of graphite in the middle region of the anode active material layer, and a smaller amount of high-expansion active material and a larger amount of graphite in the two end regions, the thickness expansion rate of the middle region of the anode active material layer and the anode electrode during charging is greater than that of the two end regions; after the anode electrode is assembled into a battery and the middle of the anode electrode corresponds to the middle of the battery, the thickness of the middle of the anode electrode after charging is greater than that of the two ends; during discharge, due to the heat in the middle of the battery, the reaction rate of the middle region is faster than that of the two end regions, and the shrinkage rate of the middle region is greater than that of the two end regions, which can make the thickness of the anode electrode after discharge recover to be close to uniform, thereby reducing lithium plating and improving the capacity retention rate of the battery.

[0055] In the embodiments of the present application, the thickness expansion rate refers to the thickness change rate of different positions (middle region, first end region, second end region) of the anode active material layer when the battery cell is charged. Since the thickness expansion rate of the anode electrode is positively correlated with the thickness expansion rate of the anode active material layer, therefore, by designing the content difference of graphite and high-expansion active materials in different regions of the anode active material layer, the thickness expansion rate difference of different regions during charging can be made to control the thickness difference of different regions of the anode active material layer and the anode electrode after charging.

[0056] The embodiments of the present application do not have specific limitations on the types of battery cells. For example, the battery cell can be a lithium-ion battery or the like.

[0057] The present application does not have specific limitations on the shape of the battery cell, and it can be cylindrical, square or any other shape. For example, Figure 1 is a battery cell 5 with a square structure as an example.

[0058] In some embodiments, please refer to Figure 2 , the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The cathode electrode sheet, the anode electrode sheet and the separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0059] Please refer to Figure 3 in combination. In the embodiments of the present application, the electrode assembly is a structure made of a cathode electrode sheet, an anode electrode sheet and a separator through a winding process or a stacking process, and the separator is arranged between the cathode electrode sheet and the anode electrode sheet. The two end positions (upper part, lower part) of the electrode assembly are the two end regions (the first end region, the second end region) of the anode electrode sheet, and the middle part of the electrode assembly is the middle region of the anode electrode sheet. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the cathode electrode sheet and the anode electrode sheet. The electrolyte plays a role in conducting ions between the cathode electrode sheet and the anode electrode sheet. The separator is arranged between the cathode electrode sheet and the anode electrode sheet, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0060] Please refer to Figure 3 in combination. In some embodiments, the electrode assembly includes electrode tabs, and the electrode tabs include a positive electrode tab and a negative electrode tab arranged at the second end.

[0061] Figure 4It is a schematic diagram of the charge and discharge process of an electrode assembly. In the figure, the anode active material layer of the anode electrode sheet and the cathode active material layer of the cathode electrode sheet are both film layers with uniform thickness, and the two are separated by a separator. Looking at the process of the first charge + discharge, in the embodiment of the present application, by arranging a larger amount of highly swelling active material and a smaller amount of graphite in the middle region of the anode active material layer, and a smaller amount of highly swelling active material and a larger amount of graphite in the two end regions, the thickness expansion rate of the middle region of the anode active material layer and the anode electrode sheet during charging is greater than that of the two end regions. That is, during the charging process, the middle region of the anode electrode sheet is more likely to expand compared to the two end regions; after full charge, the thickness of the middle region of the anode electrode sheet is greater than that of the two end regions; during the discharge process, since the heat in the middle of the battery is not easily dissipated, correspondingly, the reaction rate of the middle region of the anode electrode sheet is faster and the shrinkage rate is faster than that of the two end regions; after full discharge, the thickness of the anode electrode sheet can be restored to be nearly uniform, reducing the gaps between the anode, the separator, and the cathode electrode sheet, thereby reducing problems such as lithium deposition and performance degradation, and improving the capacity retention rate. Especially for the working condition of small-rate charging and high-power discharging of the battery cell, the above design can promote the upper, middle, and lower parts to approach consistency in reaction temperature and performance degradation, effectively improving the cycle performance and service life of the battery cell.

[0062] In some embodiments, the two opposite end portions of the electrode assembly are the first end and the second end respectively, and the middle region of the anode active material layer is the region at a distance of 1 / 4 to 1 / 2 from the first end and at a distance of 1 / 4 to 1 / 2 from the second end. Correspondingly, the region where the middle region extends towards the first end is the first end region (corresponding to the lower part of the electrode assembly), and the region where the middle region extends towards the second end is the second end region (corresponding to the upper part of the electrode assembly).

[0063] For the convenience of description, it is defined that the surface (coating surface) of the anode electrode sheet has two directions: the length direction (coating direction) and the width direction perpendicular to the length direction. Usually, the anode electrode sheet is assembled into an electrode assembly in a stacked or wound manner. The two ends of the anode electrode sheet along the width direction (the first direction) correspond to the two ends (the upper part and the lower part) of the electrode assembly, and the middle of the anode electrode sheet along the width direction corresponds to the middle of the electrode assembly.

[0064] In some embodiments, the middle region contains highly swelling active material, and the first end region and the second end region contain graphite. Exemplarily, the active material in the middle region is highly swelling active material (Q1 = 0), and the active materials in the first end region and the second end region are graphite (W2 = W3 = 0), so that the thickness expansion rate of the first end region is equal to that of the second end region, and it can also achieve that the thickness expansion rate of the middle region is greater than that of the first end region and greater than that of the second end region, thereby improving the capacity retention rate of the battery.

[0065] In some embodiments, the mass ratio of graphite in the anode active material layer is 93% to 97%, and the mass ratio of the highly expandable active material is 0.3% to 1.5%.

[0066] In some embodiments, in the anode active material layer, the position with the largest content of the highly expandable active material and the smallest content of graphite in the middle region is defined as the peak line. In the directions from the peak line to both ends respectively, the content of the highly expandable active material decreases, and the content of graphite increases. Specifically, in the direction from the peak line to the first end, the content of the highly expandable active material decreases, and the content of graphite increases. In the direction from the peak line to the second end, the content of the highly expandable active material decreases, and the content of graphite increases.

[0067] In the embodiments of the present application, the peak line can be considered as the position with the largest thickness expansion rate of the anode active material layer during charging, and it can be regarded as a dividing line. Taking this dividing line as the boundary, the thickness expansion rates towards both ends gradually decrease.

[0068] In some embodiments, in the anode active material layer, the peak line is at a distance of 1 / 3 to 1 / 2 from one of the two ends.

[0069] In the embodiments of the present application, the peak line is located at any position within the region at a distance of 1 / 3 to ½ from the first end and at a distance of 1 / 3 to ½ from the second end. As an embodiment, the peak line is located at any position within the region at a distance of 1 / 3 to 1 / 2 from the first end to match the situation where the temperature at the lower part of the battery is higher than that at the upper part in the actual working condition, so that the thickness of the anode electrode can be restored to be uniform.

[0070] In some embodiments of the present application, in order to arrange more highly expandable active material and less graphite in the middle region of the anode active material layer than in the two end regions, the anode active material layer with this feature can be constructed by the method of layer-by-layer coating in the thickness direction, or can also be constructed by the method of coating in sub-regions on the surface of the electrode.

[0071] The following shows some embodiments of layer-by-layer construction of the anode active material layer.

[0072] Please refer to Figure 5, in some embodiments, the anode active material layer includes a first active material layer 512 and a second active material layer 513 stacked in sequence on the anode current collector 511. In the direction from the peak line to both ends, the thickness of the first active material layer 512 or the second active material layer 513 increases, and the thickness of the other layer decreases. Moreover, the content of the high-expansion active material in the layer with decreasing thickness is greater than that in the layer with increasing thickness, and the content of graphite in the layer with decreasing thickness is less than that in the layer with increasing thickness. Specifically, the thickness of the first active material layer 512 increases, the thickness of the second active material layer 513 decreases, and the content of the high-expansion active material in the second active material layer 513 is greater than that in the first active material layer 512, and the content of graphite in the second active material layer 513 is less than that in the first active material layer 512; or, the thickness of the first active material layer 512 decreases, the thickness of the second active material layer 513 increases, and the content of the high-expansion active material in the first active material layer 512 is greater than that in the second active material layer 513, and the content of graphite in the first active material layer 512 is less than that in the second active material layer 513.

[0073] In other embodiments, the thicknesses of the first active material layer 512 and the second active material layer 513 do not necessarily need to change uniformly, as long as it is ensured that the middle region of the anode active material layer has a higher content of high-expansion active material and a lower content of graphite than the two end regions.

[0074] In the embodiments of the present application, unless otherwise specified, the thickness of the anode active material layer (the first active material layer 512 and the second active material layer 513) generally refers to the thickness before the first charge. After charge and discharge cycles, this thickness may change.

[0075] As an embodiment, in the direction from the peak line to both ends, the thickness of the first active material layer 512 increases, the thickness of the second active material layer 513 decreases, and the content of the high-expansion active material in the second active material layer 513 is greater than that in the first active material layer 512, and the content of graphite in the second active material layer 513 is less than that in the first active material layer 512.

[0076] Figure 5 In [the description], the end portion of the anode current collector 511 of the anode tab is the negative electrode tab, and this end portion (the second end region) of the anode tab corresponds to the upper part of the electrode assembly adjacent to the second end.

[0077] In some embodiments, the thickness of one end of the first active material layer 512 is H D, the thickness of one end of the second active material layer 513 is 0, the thickness of the other end of the first active material layer 512 is H1, the thickness of the same end of the second active material layer 513 is H2, and H1 + H2 = H D , H D is the thickness of the anode active material layer on one side of the anode tab. Among them, the thickness of the second active material layer 513 at the peak line is Hz, and the thickness decreases towards both ends respectively. The thickness of the first active material layer 512 at the peak line increases towards both ends respectively, making the thickness of the anode active material layer uniform (the thickness is H D ).

[0078] Please refer to Figure 6 , after the above anode tab is fully charged, the thickness of the anode active material layer changes, and the thickness in the middle significantly increases. The increase rate of the thickness Hz of the second active material layer 513 at the peak line is relatively the largest, and the thickness of the anode active material layer at the peak line is the largest.

[0079] Please refer to Figure 7 , after the above anode tab is fully discharged, the thickness of the anode active material layer changes again, and the thickness returns to be nearly uniform (the thickness is close to Figure 5 the uniform state before the first charge as shown). The thickness of the middle region bulges slightly compared with the two end regions, which can reduce the gaps between the middle of the anode tab and the adjacent separator and cathode tab.

[0080] In some other embodiments, the anode active material layer includes a first active material layer 512 and a second active material layer 513 stacked in sequence on the anode current collector 511. The second active material layer 513 is embedded in the middle of the first active material layer 512. The second active material layer 513 is only distributed in the middle region of the anode tab. The two end regions of the first active material layer 512 are distributed to both ends of the anode tab. The content of the highly swelling active material in the second active material layer 513 is greater than the content of the highly swelling active material in the first active material layer 512, and the content of graphite in the second active material layer 513 is less than the content of graphite in the first active material layer 512.

[0081] As an implementation manner, please refer to Figure 8 , the thickness of the second active material layer 513 decreases from the peak line towards the direction close to both ends respectively, and the thickness decreases to 0 and no longer changes at the positions close to both ends. The thickness of the second active material layer 513 at the peak line is Hz; the thickness of the first active material layer 512 increases from the peak line towards the direction close to both ends respectively, and the thickness increases to H D and no longer changes, that is, the thickness of both ends of the first active material layer 512 is H D (the thickness of the anode active material layer).

[0082] As an implementation, please refer to Figure 9 , the second active material layer 513 is located in the middle region and extends along both end regions, and its thickness is uniformly Hz. The first active material layer 512 is located in the middle region and all end regions, and the thickness near both ends is H D (thickness of the anode active material layer).

[0083] In some other embodiments, please refer to Figure 10 , the anode active material layer includes a first active material layer 512 and a second active material layer 513 that are sequentially stacked on the anode current collector 511. The first active material layer 512 is only distributed in the two end regions near the anode tab. The thickness of the first active material layer 512 is H1. The second active material layer 513 is distributed in the middle region and the end regions. The thickness of the middle region is H D , and the thickness of the two end regions near both ends is H2, and H1 + H2 = H D .

[0084] In some embodiments, the first active material layer 512 contains graphite, and the second active material layer 513 contains graphite and a high-expansion active material.

[0085] In some embodiments, the high-expansion active material includes at least one of a silicon-based material, a tin-based material, and a metal oxide;

[0086] The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys; the tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys; the metal oxide can be selected from at least one of tungsten oxide, vanadium oxide, iron oxide, ferrous oxide, cobalt oxide, cobalt sesquioxide, stannous oxide, stannic oxide, manganese monoxide, manganese dioxide, manganese sesquioxide, manganese tetroxide, antimony trioxide, antimony pentoxide, molybdenum trioxide, and molybdenum dioxide.

[0087] In addition, some embodiments of constructing the anode active material layer by sub-regions are also shown below.

[0088] In some embodiments, please refer to Figure 11 , the anode active material layer includes a middle active material layer 514 distributed on the middle region of the surface of the anode current collector 511 and an end active material layer 515 distributed on the two end regions of the surface of the anode current collector 511. The content of the high-expansion active material in the middle active material layer 514 is greater than the content of the high-expansion active material in the end active material layer 515, and the content of graphite in the middle active material layer 514 is less than the content of graphite in the end active material layer 515. The middle active material layer 514 can be rectangular, circular or other shapes, and the present application does not limit this.

[0089] In addition, the battery cell and the electrical device of the present application will be described in detail below with appropriate reference to the accompanying drawings.

[0090] [Anode current collector]

[0091] The anode current collector is also known as the negative electrode current collector. The anode current collector includes an anode current collector body and an anode active material layer attached to the surface of the anode current collector body.

[0092] In some embodiments, the anode current collector includes an anode current collector body and an anode active material layer provided on at least one surface of the anode current collector body. As an example, the anode current collector has two surfaces opposite to each other in its own thickness direction, and the anode active material layer is provided on either one or both of the two opposite surfaces of the anode current collector body.

[0093] In some embodiments, the anode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0094] In some other embodiments, the current collector of the anode current collector generally can include a current collector body and a bottom coating. The bottom coating can be provided on at least one side of the current collector body. The bottom coating basically does not contain negative electrode active material and may include a small amount of carbon material, but the carbon material forms a thin coating thickness and cannot play the role of negative electrode active material.

[0095] In some embodiments, the anode active material layer may also optionally include a binder. The binder can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0096] In some embodiments, the anode active material layer may also optionally include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0097] In some embodiments, the anode active material layer may also optionally include other additives, such as a thickening agent (such as sodium carboxymethyl cellulose (CMC-Na), etc.).

[0098] In some embodiments, the composition of the anode active material layer includes, by mass percentage, 93% - 97% graphite, 0.3% - 1.5% highly expandable active material, 0.5% - 2% binder, 1% - 3% plasticizer, and 0.2% - 1% conductive agent.

[0099] [Cathode electrode sheet]

[0100] The cathode electrode sheet is also known as the cathode electrode plate. The cathode electrode sheet includes a cathode current collector and a cathode active material layer provided on at least one surface of the cathode current collector. The cathode active material layer includes a positive electrode active material.

[0101] As an example, the cathode current collector has two surfaces opposite to each other in its own thickness direction, and the cathode active material layer is provided on either or both of the two opposite surfaces of the cathode current collector.

[0102] In some embodiments, the cathode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0103] In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material can be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material can include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides can include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 )、lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) and at least one of its modified compounds, etc. Examples of olivine-structured lithium phosphate may include but are not limited to lithium iron phosphate (such as LiFePO4 (which can also be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), composite materials of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of composite materials of lithium manganese iron phosphate and carbon.

[0104] In some embodiments, in order to further improve the energy density of the battery cell, the cathode active material for the lithium-ion battery may include one or more of lithium transition metal oxides with the general formula Li a Ni b Co c M d O e A f and their modified compounds. 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.

[0105] In some embodiments, by way of example, the cathode active material for the lithium-ion battery may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi0.85 Co 0.15 Al 0.05 One or more of O2, LiFePO4, and LiMnPO4.

[0106] In this application, the modified compounds of the above positive electrode active materials can be doping modification and / or surface coating modification of the positive electrode active materials.

[0107] As an optional technical solution of this application, the polyanionic compound can be Li 1+x Mn 1-y A y P 1-z R z O4; where x is any value within the range of -0.10 to 0.10, y is any value within the range of 0.001 to 0.50, z is any value within the range of 0.001 to 0.10, A includes one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and R includes one or more elements of B, S, Si, and N;

[0108] As an optional technical solution of this application, the polyanionic compound can be Li a A e Mn 1-f B f P 1-g C g O 4-n D n , where A includes one or more elements of Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes one or more elements of B, S, Si, and N; D includes one or more elements of S, F, Cl, and Br; a is selected from the range of 0.9 to 1.1, e is selected from the range of 0.001 to 0.1, f is selected from the range of 0.001 to 0.5, g is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, and the second positive electrode active material is electrically neutral.

[0109] During the charge and discharge process of the battery, the insertion and extraction and consumption of Li will occur, and the molar content of Li is different when the battery is discharged to different states. In the listing of the positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode material is applied to the battery system, after charge and discharge cycles, the molar content of Li will change.

[0110] In the enumeration of the cathode material in this application, the molar content of O is only the theoretical value. Oxygen release from the lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0111] As an optional technical solution of this application, the polyanionic compound can be Na 4+x R 3-y P 4-m O 15 / C; where 0 < x < 0.5, 0 < y ≤ 0.5, 0 < m ≤ 0.2, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0112] As an optional technical solution of this application, the polyanionic compound can be Na x-a A a V y-b M b (PO4) 2-2c (DO4) 2c F z-d Q d , where the A element represents an alkali metal element that dopes and replaces the Na element, the M element represents a metal element that replaces the V element, the D element represents a doping element that replaces the P element, the Q element represents a doping element that replaces the F element, the D element includes at least one of Si and S, and the Q element includes at least one of Cl and O; 3.5 ≤ x ≤ 4.5, 0 ≤ a ≤ 0.15x, 0.8 ≤ y ≤ 1.1, 0 ≤ b ≤ 0.3y, 0 ≤ c ≤ 0.15, 0.8 ≤ z ≤ 1.1, 0 ≤ d ≤ 0.2z. Optionally, the A element includes at least one of K and Li; the M element includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu, and Co.

[0113] The cathode electrode includes a cathode current collector and a cathode active material layer formed on at least a part of the surface of the cathode current collector. The cathode active material layer includes a cathode active substance, and the cathode active substance can include at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as cathode active materials for sodium ion batteries can also be used.

[0114] As an optional technical solution of this application, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, Na xMO₂, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1.

[0115] As an optional technical solution of this application, the polyanionic compound can be a type of compound having sodium ions, transition metal ions, and tetrahedral (YO₄) n- anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents the valence state of (YO₄) n- .

[0116] The polyanionic compound can also be a type of compound having sodium ions, transition metal ions, tetrahedral (YO₄) n- anionic units and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents the valence state of (YO₄) n- ; the halogen can be at least one of F, Cl, and Br.

[0117] The polyanionic compound can also be a type of compound having sodium ions, tetrahedral (YO₄) n- anionic units, polyhedral units (ZO y ) m+ and optionally halogen anions. Y can be at least one of P, S, and Si, n represents the valence state of V; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents the valence state of (ZO y ) m+ ; the halogen can be at least one of F, Cl, and Br.

[0118] The polyanionic compound is, for example, at least one of NaFePO₄, Na₃V₂(PO₄)₃, NaM’PO₄F (M’ is one or more of V, Fe, Mn, and Ni), and Na₃(VO y )₂(PO₄)₂F 3-2y (0 ≤ y ≤ 1).

[0119] The Prussian blue compound can be a type of compound having sodium ions, transition metal ions, and cyanide ions (CN - ). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound is, for example, Na a Me b Me’ c(CN)6, where Me and Me’ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0120] In some embodiments, the cathode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0121] In some embodiments, the cathode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0122] In some embodiments, the cathode electrode sheet can be prepared by the following method: dispersing the components for preparing the cathode electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the cathode current collector, and after processes such as drying and cold pressing, the cathode electrode sheet can be obtained.

[0123] [Electrolyte]

[0124] The electrolyte plays a role in conducting ions between the cathode electrode sheet and the anode electrode sheet. There is no specific limitation on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0125] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0126] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluorooxalate phosphate.

[0127] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0128] In some embodiments, the electrolyte may further optionally include additives. For example, the additives may include anode film-forming additives, cathode film-forming additives, and may also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0129] [Separator film]

[0130] In some embodiments, the battery cell further includes a separator film. The present application does not particularly limit the type of the separator film, and any well-known porous structure separator film with good chemical stability and mechanical stability can be selected.

[0131] In some embodiments, the material of the separator film may be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film may be a single-layer thin film or a multi-layer composite thin film, without particular limitation. When the separator film is a multi-layer composite thin film, the materials of each layer may be the same or different, without particular limitation.

[0132] In some embodiments, the cathode electrode sheet, the anode electrode sheet, and the separator film can be made into an electrode assembly by a winding process or a stacking process.

[0133] In some embodiments, the battery cell may include an outer package. The outer package can be used to encapsulate the above electrode assembly and electrolyte.

[0134] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0135] The embodiment of the present application also provides a preparation method of the battery cell of the foregoing embodiment. The active material slurry corresponding to the anode active material layer is coated on the surface of the anode current collector, and then dried and compacted to obtain the anode electrode sheet; the anode electrode sheet is used to assemble the battery cell.

[0136] In some embodiments, the coating method is as follows: during the parallel running of the anode current collector, the first active material slurry corresponding to the first active material layer is coated first, and then the second active material slurry corresponding to the second active material layer is coated; the coating thickness of the first active material slurry increases from the peak line to both ends respectively, and the coating thickness of the second active material slurry decreases from the peak line to both ends respectively.

[0137] Please refer to Figure 12 , as an embodiment, the preparation process of the anode electrode sheet includes the following steps:

[0138] (1) The anode current collector unwinds and runs, and the running speed needs to be controlled during this process;

[0139] (2) Pass through the first coater, and coat the first active material slurry corresponding to the first active material layer on one side of the anode current collector. The coating weight, etc. need to be controlled during this process;

[0140] (3) Pass through the second coater, and coat the second active material slurry corresponding to the second active material layer on one side of the anode current collector again. The coating weight, etc. need to be controlled during this process;

[0141] (4) Pass through the oven to dry the solvent in the active material slurry. The drying temperature and time need to be controlled during this process;

[0142] (5) The anode current collector continues to run, and successively passes through another first coater and another second coater to coat the active material slurry on the other side of the anode current collector, and then passes through the oven to dry the solvent in the active material slurry;

[0143] (6) Pass through the cold pressing roller for compaction. The pressure of the pressing roller needs to be controlled during this process to obtain the anode plate. The cross-sectional structure of the anode plate along the direction perpendicular to the running direction (length direction) is as Figure 5 shown.

[0144] In the above process, the arrangement of the first extrusion head of the first coater and the second extrusion head of the second coater is as Figure 13 shown. On one side of the anode current collector, first coat the slurry corresponding to the first active material layer through the first extrusion head of the first coater, and then coat the slurry corresponding to the second active material layer through the second extrusion head of the second coater. For the implementation where the thickness of the first active material layer increases from the peak line to both ends respectively, and the thickness of the second active material layer decreases from the peak line to both ends respectively, when looking from one end of the anode plate, only the first active material layer or the superimposed first active material layer and second active material layer may be seen.

[0145] During the coating process, extrusion heads with different structures need to be properly matched to coat the active material layers with corresponding structures. In some embodiments, the shape of the coating head is the same as the cross-sectional shape of the active material layer. Please refer to Figure 14 , the first extrusion head includes a first upper die and a first lower die. The shape of the extrusion outlet between the first upper die and the first lower die is the same as the cross-sectional shape of the first active material layer, and the thickness increases from the peak line in the middle to both ends respectively. Please refer to Figure 15 , the second extrusion head includes a second upper die and a second lower die. The shape of the extrusion outlet between the second upper die and the second lower die is the same as the cross-sectional shape of the second active material layer, and the thickness decreases from the peak line in the middle to both ends respectively. In order to control the shape of the active material layer, it is necessary to adjust the viscosity of the slurry used for coating so that the coating shape is the same as the shape of the active material layer after coating and before drying.

[0146] In other embodiments, it is also possible to first synchronously coat the first active material slurry on both sides of the anode current collector, and then synchronously coat the second active material slurry on both sides of the anode current collector; it is also possible to first dry through an oven after coating each layer of the active material slurry, and then coat another layer of the active material slurry and dry through the oven.

[0147] As an implementation manner, the preparation method of the battery cell includes the following steps:

[0148] Wind the prepared anode electrode sheet through a winding process to form a bare battery core;

[0149] Install the bare battery core into a housing to form a battery core;

[0150] Test various performances of the battery core.

[0151] The second aspect of the implementation manner of the present application provides a battery, including the battery cell of the foregoing embodiment or the battery cell obtained by the preparation method of the battery cell according to the foregoing embodiment.

[0152] In some implementation manners, the battery cells can be assembled into a battery module. The number of battery cells included in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0153] Figure 16 This is the battery module 4 as an example. Refer to Figure 16 , in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. Further, the multiple battery cells 5 can be fixed by fasteners.

[0154] Optionally, the battery module 4 can further include a housing with a receiving space, and multiple battery cells 5 are received in the receiving space.

[0155] In some implementation manners, the above battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0156] Figure 17 and Figure 18 This is the battery pack 1 as an example. Refer to Figure 17 and Figure 18 , in the battery pack 1, it can include a battery box and multiple battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for receiving the battery modules 4. The multiple battery modules 4 can be arranged in the battery box in any manner.

[0157] In addition, the present application also provides an electrical device, which includes the battery provided by the present application, specifically including at least one of battery cells, battery modules, or battery packs. The battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0158] As the electrical device, battery cells, battery modules, or battery packs can be selected according to its usage requirements.

[0159] Figure 19 is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the battery, a battery pack or a battery module can be adopted.

[0160] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thin and light, and battery cells can be used as the power source.

[0161] Embodiment

[0162] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0163] Embodiment 1

[0164] S1. Prepare the anode electrode

[0165] Take graphite, binder styrene-butadiene rubber, plasticizer sodium carboxymethyl cellulose, conductive agent carbon black, and high-expansion active material in a certain mass ratio, and mix them evenly with deionized water to form a first slurry for preparing the first active material layer. In this embodiment, the mass ratio (corresponding content) of graphite, binder, plasticizer, conductive agent, and high-expansion active material is 96.5%: 1%: 2%: 0.5%: 0, the content of graphite is 96.5%, and the content of high-expansion active material is 0.

[0166] Take graphite, binder styrene-butadiene rubber, plasticizer sodium carboxymethyl cellulose, conductive agent carbon black and highly expandable active material in a certain mass ratio, and mix them evenly with deionized water to form a second slurry for preparing the second active material layer. In this embodiment, the mass ratio of graphite, binder, plasticizer, conductive agent and highly expandable active material is 95.5%: 1%: 2%: 0.5%: 1%. Among them, the content of graphite is 95.5%, and the content of highly expandable active material is 1%. The highly expandable active material is elemental silicon.

[0167] In all embodiments of this experiment, the total mass ratio of graphite and highly expandable active material in the slurry remains unchanged, both being 96.5%.

[0168] According to Figure 12 the preparation process, prepare the anode electrode sheet. The anode current collector is a 7-μm copper foil. Use the first extrusion head and the second extrusion head to coat the first slurry and the second slurry on the anode current collector, fully dry and then cold press to form the first active material layer and the second active material layer respectively. After die-cutting and slitting, the anode electrode sheet is obtained. The upper thickness and the lower thickness of the first active material layer and the second active material layer respectively refer to the thicknesses of the two side surfaces in the coating direction. The thickness of the side surface where the anode current collector extends is the upper thickness, which is adjacent to the second end region, and the thickness of the other side surface is the lower thickness, which is adjacent to the first end region. The middle thickness of the first active material layer and the second active material layer refers to the thickness at the thickness peak line (corresponding to the position with the maximum thickness and the minimum thickness), which is located within the middle region. Control the coating morphology of the first slurry and the second slurry through the first extrusion head and the second extrusion head to control the thicknesses of different regions of the first active material layer and the second active material layer (including the upper thickness, the middle thickness and the lower thickness), so as to control the content of highly expandable active material and the content of graphite in different regions of the anode active layer (the middle region, the first end region, and the second end region).

[0169] S2. Prepare the cathode electrode sheet

[0170] Take the positive electrode active material ternary material, binder polyvinylidene fluoride, conductive agent acetylene black and plasticizer sodium carboxymethyl cellulose in a mass ratio of 93%: 3%: 3%: 1%, dissolve them in the solvent N-methylpyrrolidone (NMP) to make a positive electrode slurry. Then evenly coat the positive electrode slurry on a 13-μm aluminum foil, fully dry, cold press, die-cut and slit to obtain the cathode electrode sheet.

[0171] S3. Prepare the electrolyte

[0172] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), mix the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) evenly according to a volume ratio of 3:7, add 1 mol / L LiPF6 lithium salt and dissolve it in the organic solvent, and stir evenly to obtain the electrolyte.

[0173] S4. Assembly

[0174] Stack the cathode electrode sheet, separator, and anode electrode sheet in sequence, with the separator placed between the positive and negative electrode sheets to play an isolation role. Then wind them to obtain a bare battery cell, weld the electrode tabs to the bare battery cell, place the bare battery cell into an aluminum shell, bake it at 80°C to remove water, then inject electrolyte and seal it to obtain a non-charged battery. The non-charged battery then undergoes processes such as standing, formation, shaping, and capacity testing in sequence to obtain battery monomers.

[0175] The relevant parameters of the anode electrode sheets of Examples 1-10 and Comparative Examples 1-2 are shown in Table 1 below.

[0176] Table 1: Anode Parameter Results of Examples 1-10 and Comparative Examples 1-2

[0177]

[0178] Test the temperature distribution of the upper, middle, and lower parts of the battery monomers of Examples 1-10 and Comparative Examples 1-2, as well as the 200cls capacity retention rate. The results are shown in Table 2.

[0179] The test method is as follows: Under the connection of a charge and discharge machine, the battery monomers are continuously cycled at a charging current of 1C and a discharging current of 0.5C. At the same time, temperature sensors are pasted on the aluminum shells of the upper part (corresponding to the second end region of the anode electrode sheet), middle part (corresponding to the middle region of the anode electrode sheet), and lower part (corresponding to the first end region of the anode electrode sheet) of the battery monomers to sense temperature changes, record them at the same time, and calculate the battery monomer consistency based on the highest temperature (generally, the temperature is the highest at the end of charging). At the same time, the energy that each battery monomer can release in each cycle is used as the capacity of the battery monomer at this time to calculate the capacity retention rate of the battery monomer after 200cls of cycling.

[0180] Table 2: Test Results of Battery Monomer Parameters of Examples 1-10 and Comparative Examples 1-2

[0181]

[0182]

[0183] According to the above results, it can be seen that in the middle region of the anode active material layer of Examples 1-8, more high-expansion active materials are provided and less graphite is provided compared to the two end regions (the first end region and the second end region), which can make the temperatures of the middle, upper, and lower parts tend to be consistent. Compared with the situation where the graphite and high-expansion active material contents in different regions of the anode active material layer of Comparative Examples 1-2 are the same, it can improve the capacity retention rate of the battery.

[0184] Compared with Comparative Example 2, Examples 1 to 3 and Examples 4 to 6 can promote the temperatures in different regions to approach consistency and improve the capacity retention rate of the battery by adjusting the contents of the highly swelling active material and graphite in different regions of the anode active material layer.

[0185] According to Examples 1 to 3 and Examples 4 to 6, by adjusting the coating shapes of the first active material layer and the second active material layer, the contents of the highly swelling active material and graphite in different regions of the anode active material layer can be adjusted, which will affect the capacity retention rate of the battery.

[0186] According to Example 1 and Example 7, on the basis that the contents of the highly swelling active material and graphite in different regions of the anode active material layer change according to a certain rule (the content of the highly swelling active material in the middle region is higher and the content of graphite is lower than that in the two end regions), by changing the coating order of the first active material layer and the second active material layer, the capacity retention rates of the batteries are roughly equivalent.

[0187] According to Example 1 and Example 8, on the basis that the contents of the highly swelling active material and graphite in different regions of the anode active material layer change according to a certain rule, by selecting different highly swelling active materials, the capacity retention rates of the batteries are roughly equivalent.

[0188] According to Examples 4 to 6 and Example 9, when the peak line of the anode active material layer is at a distance of 1 / 3 to 1 / 2 from the first end, the capacity retention rate of the battery can be improved.

[0189] Compared with Comparative Example 1, Example 10 can improve the capacity retention rate of the battery by adding a small amount of highly swelling active material to the anode active material layer.

[0190] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same structure and the same function and effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope not departing from the gist of this application, various modifications that can be thought of by those skilled in the art to the embodiments and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of this application.

Claims

1. A battery cell, characterized in that: An electrode assembly comprising a cathode electrode sheet and an anode electrode sheet, the electrode assembly having two ends arranged along a first direction, the anode electrode sheet comprising an anode current collector and an anode active material layer attached to a surface of the anode current collector, the anode active material layer comprising a first end region, a middle region, and a second end region arranged along the first direction, the anode active material layer comprising graphite and a high-expansion active material, the high-expansion active material comprising at least one of a silicon-based material, a tin-based material, and a metal oxide; Among them, based on the mass of the middle region, the graphite content in the middle region is Q1%, and the high-expansion active material content is W1%; based on the mass of the first end region, the graphite content in the first end region is Q2%, and the high-expansion active material content is W2%; based on the mass of the second end region, the graphite content in the second end region is Q3%, and the high-expansion active material content is W3%, W1>W2, and W1>W3, Q1<Q2, and Q1<Q3.

2. The battery cell according to claim 1, wherein The two ends of the electrode assembly are respectively a first end and a second end, and the middle region of the anode active material layer is a region 1 / 4 to 1 / 2 away from the first end and 1 / 4 to 1 / 2 away from the second end.

3. The battery cell according to claim 1, wherein W1>W2>W3, Q1<Q2<Q3.

4. The battery cell according to claim 1, wherein: In the anode active material layer, the middle region contains the high-expansion active material, and the first end region and the second end region contain the graphite.

5. The battery cell according to claim 1, wherein: The graphite in the anode active material layer accounts for 93% to 97% by mass, and the high-expansion active material accounts for 0.3% to 1.5% by mass.

6. The battery cell according to claim 1, wherein: In the anode active material layer, the position in the middle region where the high-expansion active material content is the largest and the graphite content is the smallest is defined as a peak line. From the peak line to both ends, the content of the high-expansion active material decreases and the content of the graphite increases.

7. The battery cell according to claim 6, wherein: In the anode active material layer, the peak line is 1 / 3 to 1 / 2 away from one of the two ends.

8. The battery cell according to claim 6, wherein: The anode active material layer includes a first active material layer and a second active material layer stacked in sequence on the anode current collector. From the peak line to the two ends, the thickness of the first active material layer or the second active material layer increases, and the thickness of the other layer decreases, and the content of the high-expansion active material in the layer with decreasing thickness is greater than the content of the high-expansion active material in the layer with increasing thickness, and the content of the graphite in the layer with decreasing thickness is less than the content of the graphite in the layer with increasing thickness.

9. The battery cell according to claim 8, wherein: From the peak line toward both ends, the thickness of the first active material layer increases, the thickness of the second active material layer decreases, and the content of the high-expansion active material in the second active material layer is greater than the content of the high-expansion active material in the first active material layer, and the content of the graphite in the second active material layer is less than the content of the graphite in the first active material layer.

10. The battery cell according to claim 9, wherein The thickness of one end of the first active material layer is H D The thickness of the second active material layer at the same end is 0, the thickness of the first active material layer at the other end is H1, and the thickness of the second active material layer at the same end is H2, H1+H2=H D .

11. The battery cell according to claim 9, wherein: The first active material layer includes graphite, and the second active material layer includes graphite and a high-expansion active material.

12. The battery cell according to claim 1, wherein The silicon-based material can be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites and silicon alloys; the tin-based material can be selected from at least one of elemental tin, tin oxides and tin alloys; the metal oxide can be selected from at least one of tungsten oxide, vanadium oxide, iron oxide, ferrous oxide, cobalt oxide, cobalt trioxide, tin monoxide, tin dioxide, manganese monoxide, manganese dioxide, manganese trioxide, manganese tetraoxide, antimony trioxide, antimony pentoxide, molybdenum trioxide and molybdenum dioxide.

13. A battery, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 12.

14. An electrical device, characterized in that: The battery of claim 13 is provided for providing electrical energy.

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