Battery monomer, battery and electric device

Abstract

The embodiment of the invention provides a battery monomer, a battery and a power utilization device, and relates to the technical field of lithium batteries, an anode active material layer of an anode plate in the battery monomer comprises a first end part region, a middle region and a second end part region which are arranged along a first direction, the anode active material layer comprises graphite and a high-expansion active material, based on the mass of the middle region, the graphite content in the middle region is Q1%, 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%, 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 Q2%, and the high-expansion active material content in the second end region is W2%. In the second end region, the graphite content is Q3%, the high-expansion active material content is W3%, W1 > W2, W1 > W3, Q1 < Q2, and Q1 < Q3. According to the battery monomer, the battery and the power utilization device provided by the embodiment of the invention, the capacity retention ratio of the battery can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a battery cell, a battery and an electrical device. Background Art

[0002] At present, lithium batteries are continuously developing towards high power and high energy density, but at the same time there is a problem that the heat inside the battery cell cannot be effectively dissipated, which leads to rapid capacity decay of the battery. Summary of the invention

[0003] The present application is made in view of the above-mentioned problems, and its object is to provide a battery cell, a battery, and an electric device that can improve the capacity retention rate of the battery.

[0004] In order to achieve the above-mentioned object, the first aspect of the present application provides a battery cell, comprising an electrode assembly, the 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 the 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;

[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] Therefore, the present application arranges 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 the volume expansion rate of graphite, the thickness expansion rate of the middle region of the anode active material layer in the thickness direction is greater than the thickness expansion rate of the two end regions, so that the thickness of the middle region of the anode pole piece after charging is greater than the thickness of the two end regions; during discharging, due to the effect of 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, so that the thickness of the anode active material layer and the anode pole piece after discharge can be restored to nearly uniform, reducing the gap between the middle region of the anode pole piece and the adjacent isolation membrane and cathode pole piece, thereby reducing lithium plating and improving the capacity retention rate of the battery.

[0007] In any embodiment, the two ends 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 1 / 4 to 1 / 2 away from the first end and 1 / 4 to 1 / 2 away from the second end. This design matches the use of the battery where the heat is concentrated at the position 1 / 4 to 1 / 2 away from the end, so that the thickness of the anode plate after charge and discharge can be restored to a nearly uniform state.

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

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

[0010] In any embodiment, the mass proportion of the graphite in the anode active material layer is 93% to 97%, and the mass proportion of the high expansion active material is 0.3% to 1.5%. By using a certain amount of graphite and high expansion active material together, 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 in the middle region where the content of the high-expansion active material is the largest and the content of the graphite is the smallest is defined as a peak line, and the content of the high-expansion active material decreases and the content of the graphite increases in the direction from the peak line to both ends. By setting the thickness expansion rate of the anode active material layer to decrease from the peak line to both ends during charging, the thickness of the anode active material layer after charging decreases from the peak line to both ends, and then using the shrinkage rate of the anode active material layer to decrease from the middle peak line to both ends during discharge, the thickness of the anode active material layer and the anode electrode sheet can be restored to a nearly uniform state.

[0012] In any embodiment, in the anode active material layer, the peak line is 1 / 3 to 1 / 2 away from one of the two ends. This design matches the use of the battery where the heat is concentrated at a position 1 / 3 to 1 / 2 away from the end, so that the thickness of the anode plate can be restored to a nearly uniform thickness 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 sequentially stacked on the anode current collector, and in the direction from the peak line to both 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. By setting the first active material layer and the second active material layer whose thickness gradually changes from the peak line to both ends, the thickness of the anode active material layer itself is made uniform; and by using the different contents of graphite and high-expansion 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, and after discharge, the thickness of the anode active material layer and the anode electrode sheet can be restored to be nearly uniform.

[0014] In any embodiment, 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.

[0015] In any embodiment, 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 DThis setting makes the position where the thickness expansion rate of the anode active material layer is the largest during charging deviate from the center line of the anode pole piece to match the use situation where the heat concentration position of the anode active material layer deviates from the center line, so that the thickness of the anode pole piece can be restored to be nearly uniform.

[0016] In any embodiment, the first active material layer comprises graphite, and the second active material layer comprises graphite and a high expansion active material.

[0017] In any embodiment, 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.

[0018] A second aspect of the present application further provides a battery, comprising the battery cell of the first aspect.

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

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

[0021] Figure 2 yes Figure 1 An exploded view of a battery cell according to an embodiment of the present application is shown.

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

[0023] Figure 4 Schematic diagram of charging and discharging of a double-layer coated middle and lower high-rebound battery cell of the electrode assembly.

[0024] Figure 5 It is a cross-sectional schematic diagram of the anode electrode sheet according to the first embodiment of the present application.

[0025] Figure 6 for Figure 5 Schematic diagram of the cross section of the anode plate after full charge.

[0026] Figure 7 for Figure 6 Schematic diagram of the cross section of the anode plate after full discharge.

[0027] Figure 8It is a cross-sectional schematic diagram of the anode electrode sheet of the second embodiment of the present application.

[0028] Fig. 9 This is a schematic cross-sectional view of the anode electrode sheet according to the third embodiment of the present application.

[0029] Fig.10 It is a cross-sectional schematic diagram of the anode electrode sheet of the fourth embodiment of the present application.

[0030] Fig.11 This is a schematic cross-sectional view of the anode electrode sheet of the fifth embodiment of the present application.

[0031] Fig.12 Schematic diagram of the manufacturing process of the anode electrode according to the first embodiment of the present application.

[0032] Fig.13 for Fig.14 Schematic diagram of the position of the extrusion heads of the first coater and the second coater.

[0033] Fig.14 for Fig.13 Schematic diagram of the structure of the first extrusion head.

[0034] Fig.15 for Fig.13 Schematic diagram of the structure of the second extrusion head.

[0035] Fig.16 is a schematic diagram of a battery module according to an embodiment of the present application.

[0036] Fig.17 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0037] Fig.18 yes Fig.17 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0038] Fig.19 It is a schematic diagram of an electrical device using a battery cell according to an embodiment of the present application as a power source.

[0039] Description of reference numerals:

[0040] 1 battery pack; 2 upper box; 3 lower box; 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 DESCRIPTION

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

[0042] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0044] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

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

[0046] At present, lithium batteries are developing towards high power and high energy density, but the greater the power and energy density of lithium batteries, the greater the temperature difference at different positions. Combined with the temperature distribution characteristics of lithium batteries during high-power use, the temperature in the middle of the battery cell is usually the highest because the heat cannot be effectively dissipated, which leads to the highest reaction rate and the fastest performance decay in the middle; the upper part of the battery cell will receive a large current due to the presence of the pole ear, and the heat generated will also be relatively large, but this part has a spare structure and is at the edge, so the heat dissipation is better, so the temperature is relatively low and the performance decay is relatively minimal; although there is no spare structure in the lower part of the battery cell, it is at the edge, and the temperature and performance decay are between the upper and middle parts.

[0047] When ordinary batteries are charged at a low rate and discharged at a high power, the middle part of the battery is at a high temperature, which accelerates the reaction rate and causes the stored energy to be released first. The battery cell will be mistakenly considered to be over-discharged, causing the middle part of the anode electrode to become thinner and the gap between the anode and the cathode to increase. Lithium is easily deposited during recharging, increasing battery cell loss and accelerating attenuation. After multiple cycles, the capacity loss is large.

[0048] If the thickness difference between the middle and the two ends (upper and lower parts) of the anode electrode after discharge 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 improving 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 present application and optional embodiments are described in more detail below.

[0050] Please see Figure 1 to Figure 7 In a first aspect, a battery cell is provided in an embodiment of the present application, including an electrode assembly, the electrode assembly including a cathode electrode sheet and an anode electrode sheet, the electrode assembly having two ends arranged along a first direction (corresponding to Figure 3 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 a first direction, the anode active material layer includes graphite and a high expansion active material, and 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, content refers to the mass percentage, that is, the mass percentage of active materials such as graphite and high expansion active material in the anode active material layer. The content of each active material in the anode active material layer can be detected by EDS, ICP, XRD and the like.

[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, and illustratively, 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 may also be different, and illustratively, 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 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 arranging more high-expansion active material and less graphite in the middle region of the anode active material layer and arranging less high-expansion active material and more graphite in the two end regions, the thickness expansion rate of the anode active material layer and the anode electrode sheet in the middle region during charging is greater than the thickness expansion rate of the two end regions; after the anode electrode sheets are assembled into a battery and the middle of the anode electrode sheets corresponds to the middle of the battery, the thickness of the middle of the anode electrode sheet after charging is greater than that of the two end regions; during discharge, due to the effect of 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, so that the thickness of the anode electrode sheet after discharge can be restored to nearly uniform, thereby reducing lithium plating and improving the capacity retention rate of the battery.

[0055] In the embodiment 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 pole piece is positively correlated with the thickness expansion rate of the anode active material layer, the thickness expansion rate of different regions during charging can be different by designing the difference in the content of graphite and high expansion active material in different regions of the anode active material layer, so as to control the thickness difference of different regions of the anode active material layer and the anode pole piece after charging.

[0056] The embodiments of the present application have no particular limitation on the type of battery cells. For example, the battery cells may be lithium-ion batteries, etc.

[0057] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0058] In some embodiments, see Figure 2 , the outer package may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to 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 isolation membrane can form an electrode assembly 52 through a winding process or a lamination 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 contained 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 an embodiment 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 lamination process, and the separator is arranged between the cathode electrode sheet and the anode electrode sheet. The two end positions (upper part and lower part) of the electrode assembly are the two end regions (first end region and 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 battery charging and discharging process, active ions are embedded and removed back and forth between the cathode electrode sheet and the anode electrode sheet. The electrolyte plays the role of 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, which mainly plays the role of preventing the positive and negative electrodes from short-circuiting, and at the same time allows ions to pass through.

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

[0061] Figure 4The schematic diagram of the charging and discharging process of the electrode assembly, in which the anode active material layer of the anode plate and the cathode active material layer of the cathode plate are both film layers with uniform thickness, and the two are separated by a separator. In the process of the first charge + discharge, the embodiment of the present application sets a larger amount of high-expansion active material and a smaller amount of graphite in the middle area of ​​the anode active material layer, and sets a smaller amount of high-expansion active material and a larger amount of graphite in the two end areas, so that the thickness expansion rate of the anode active material layer and the anode plate in the middle area during charging is greater than the thickness expansion rate of the two end areas, that is, during the charging process, the middle area of ​​the anode plate is easier to expand than the two end areas; after full charging, the thickness of the middle area of ​​the anode plate is larger than that of the two end areas; during the discharge process, since the heat in the middle of the battery is not easy to dissipate, the reaction rate and shrinkage rate of the middle area of ​​the anode plate are faster than those of the two end areas; after full discharge, the thickness of the anode plate can be restored to nearly uniform, reducing the gap between the anode and the separator and the cathode plate, thereby reducing problems such as lithium precipitation and performance attenuation, and improving the capacity retention rate. Especially for the battery cells under low-rate charging and high-power discharging conditions, the above design can promote the upper, middle and lower parts to be close to the same reaction temperature and performance attenuation, effectively improving the cycle performance and service life of the battery cells.

[0062] In some embodiments, the two opposite ends 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 1 / 4 to 1 / 2 away from the first end and 1 / 4 to 1 / 2 away from the second end. Accordingly, the region extending from the middle region to the first end is the first end region (corresponding to the lower part of the electrode assembly), and the region extending from the middle region to the second end is the second end region (corresponding to the upper part of the electrode assembly).

[0063] For ease of explanation, the surface (coating surface) of the anode electrode sheet is defined as having two directions: the length direction (coating direction) and the width direction perpendicular to the length direction. Generally, the anode electrode sheets are assembled into an electrode assembly in the form of lamination or winding, and the two ends of the anode electrode sheet along the width direction (first direction) correspond to the two ends (upper and lower parts) of the electrode assembly, and the middle part of the anode electrode sheet along the width direction corresponds to the middle part of the electrode assembly.

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

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

[0066] In some embodiments, in the anode active material layer, the position in the middle region where the high-swelling active material content is the largest and the graphite content is the smallest is defined as a peak line, and the content of the high-swelling active material decreases and the content of the graphite increases in the direction from the peak line to both ends. Specifically, in the direction from the peak line to the first end, the content of the high-swelling active material decreases and the content of the graphite increases, and in the direction from the peak line to the second end, the content of the high-swelling active material decreases and the content of the graphite increases.

[0067] In the embodiment of the present application, the peak line can be considered as the position where the thickness expansion rate of the anode active material layer is the largest during charging, which can be regarded as a dividing line. With the dividing line as the boundary, the thickness expansion rate gradually decreases towards both ends.

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

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

[0070] In some embodiments of the present application, in order to provide the middle region of the anode active material layer with more high-expansion active material and less graphite relative to the two end regions, the anode active material layer with this feature can be constructed by layered coating along the thickness direction, or by regional coating on the surface of the pole piece.

[0071] Some examples of layered construction of the anode active material layer are shown below.

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

[0073] In other embodiments, the thickness of the first active material layer 512 and the second active material layer 513 may not need to vary uniformly, as long as 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, and the thickness may change after charge and discharge cycles.

[0075] As an embodiment, from the peak line toward 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 high-expansion active material in the second active material layer 513 is greater than the content of high-expansion 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.

[0076] Figure 5 In the embodiment, the end of the anode current collector 511 of the anode electrode sheet extending out is the negative electrode ear, and this end of the anode electrode sheet (the second end region) corresponds to the upper portion 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 the second active material layer 513 at the same end is 0, the thickness of the first active material layer 512 at the other end is H1, and the thickness of the second active material layer 513 at the same end is H2, H1+H2=H D , H D That is, the thickness of the anode active material layer on one side of the anode electrode sheet, wherein the thickness of the second active material layer 513 at the peak line is Hz, and the thickness decreases towards both ends, and the thickness of the first active material layer 512 at the peak line increases towards both ends, so that the thickness of the anode active material layer is uniform (thickness is H D ).

[0078] Please see Figure 6 After the anode electrode is fully charged, the thickness of the anode active material layer changes, the thickness in the middle portion increases significantly, the thickness increase rate 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 see Figure 7 After the anode electrode is fully charged, the thickness of the anode active material layer changes again, and the thickness returns to a nearly uniform thickness (thickness close to Figure 5 The thickness of the middle area is slightly higher than that of the two end areas, which can reduce the gap between the middle of the anode electrode and the adjacent isolation membrane and cathode electrode.

[0080] In 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 area of ​​the anode electrode sheet, and the two end areas of the first active material layer 512 are distributed to the two ends of the anode electrode sheet, the content of high-expansion active material in the second active material layer 513 is greater than the content of high-expansion 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 method, see Figure 8 , the thickness of the second active material layer 513 decreases from the peak line toward the two ends, and its thickness decreases to 0 near the two ends and does not change. 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 toward the two ends, and its thickness increases to H near the two ends. D and no longer changes, that is, the thickness of both ends of the first active material layer 512 is H D (Thickness of the anode active material layer).

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

[0083] In some other embodiments, see Fig.10 The anode active material layer includes a first active material layer 512 and a second active material layer 513 sequentially stacked on the anode current collector 511. The first active material layer 512 is only distributed in the two end regions adjacent to the two ends of the anode electrode sheet. 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 two end regions. The thickness of the middle region is H D The thickness of the two end areas adjacent to the two ends is H2, H1+H2=H D .

[0084] In some embodiments, the first active material layer 512 includes graphite, and the second active material layer 513 includes 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 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.

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

[0088] In some embodiments, see Fig.11 The anode active material layer includes a middle active material layer 514 distributed in the middle area of ​​the surface of the anode current collector 511 and end active material layers 515 distributed in the two end areas of the surface of the anode current collector 511. The content of high-swelling active material in the middle active material layer 514 is greater than the content of high-swelling 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 or circular, and the present application does not limit this.

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

[0090] [Anode Plate]

[0091] The anode electrode sheet is also called the negative electrode sheet, and the anode electrode sheet includes an anode current collector and an anode active material layer attached to the surface of the anode current collector.

[0092] In some embodiments, the anode electrode sheet includes an anode current collector and an anode active material layer disposed on at least one surface of the anode current collector. 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 disposed on any one or both of the two opposite surfaces of the anode current collector.

[0093] In some embodiments, the anode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may 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 may be formed by forming a metal material (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 other embodiments, the current collector of the anode electrode sheet may generally include a current collector body and a primer layer. The primer layer may be disposed on at least one side of the current collector body. The primer layer substantially does not contain negative electrode active materials and may include a small amount of carbon material. However, the coating formed by the carbon material is thin and cannot function as a negative electrode active material.

[0095] In some embodiments, the anode active material layer may further include a binder. The binder may 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 further include a conductive agent, which may 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 further include other auxiliary agents, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

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

[0099] [Cathode Plate]

[0100] The cathode plate is also called a cathode plate, and the cathode plate includes a cathode current collector and a cathode active material layer disposed on at least one surface of the cathode current collector, and 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 thickness direction, and the cathode active material layer is disposed on any one or both of the two opposite surfaces of the cathode current collector.

[0102] In some embodiments, the cathode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (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 may adopt a positive electrode active material for lithium-ion batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may 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 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to 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-containing phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon.

[0104] In some embodiments, in order to further improve the energy density of the battery cell, the positive electrode active material for a lithium-ion battery may include a lithium transition metal oxide represented by the general formula Li a Ni b Co c M d O e A f and one or more of its 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 positive electrode active material for a 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 the present application, the modified compounds of the above-mentioned positive electrode active materials may be the ones subjected to doping modification and / or surface coating modification of the positive electrode active materials.

[0107] As an optional technical method of the present application, the polyanionic compound can be Li 1+x Mn 1-y A y P 1-z R z O4; wherein x is any value in the range of -0.100 to 0.100, y is any value in the range of 0.001 to 0.500, z is any value in the range of 0.001 to 0.100, A includes one or more elements selected from 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 selected from B, S, Si and N;

[0108] As an optional technical method of the present application, the polyanionic compound can be Li a A e Mn 1-f B f P 1-g C g O 4-n D n , wherein A includes one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements selected from the group consisting of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes one or more elements selected from the group consisting of B, S, Si, and N; D includes one or more elements selected from the group consisting 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] The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after charge and discharge cycles.

[0110] In the enumeration of the cathode material in this application, the molar content of O is only the theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen to change, 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 positive electrode active material, and the positive electrode active material 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 the positive electrode active material of a sodium ion battery 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, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0 <x≤1。

[0115] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with 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 (YO4) n- valence state.

[0116] Polyanionic compounds can also be those with sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds of anion 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 (YO4) n- valence state; the halogen may be at least one of F, Cl and Br.

[0117] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedral unit (ZO y ) m+ and an optional halogen anion. Y can be at least one of P, S and Si, n represents the valence 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, m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl and Br.

[0118] Polyanionic compounds include NaFePO4, Na3V2(PO4)3, NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

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

[0120] In some embodiments, the cathode active material layer may also 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 fluorine-containing acrylate resin.

[0121] In some embodiments, the cathode active material layer may further 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 in the following manner: the above-mentioned components for preparing the cathode electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the cathode current collector, and after drying, cold pressing and other processes, the cathode electrode sheet can be obtained.

[0123] [Electrolytes]

[0124] The electrolyte plays a role in conducting ions between the cathode electrode and the anode electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0125] In some embodiments, the electrolyte is an electrolyte solution, which 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[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, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0128] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0129] [Isolation film]

[0130] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

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

[0132] In some embodiments, the cathode electrode sheet, the anode electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0133] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

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

[0135] The present application also provides a method for preparing the battery cell of the aforementioned embodiment, coating the surface of the anode current collector with an active material slurry corresponding to the anode active material layer, and then drying and compacting the slurry to obtain an anode pole piece; and assembling the anode pole piece into a battery cell.

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

[0137] Please see Fig.12 As an embodiment, the preparation process of the anode electrode sheet includes the following steps:

[0138] (1) The anode current collector is unwound and the tape speed needs to be controlled during this process;

[0139] (2) Using a first coating machine, coating one side of the anode current collector with a first active material slurry corresponding to the first active material layer. This process requires controlling the coating weight, etc.;

[0140] (3) After the second coating machine, the second active material slurry corresponding to the second active material layer is coated on one side of the anode current collector. The coating weight, etc., needs to be controlled in this process;

[0141] (4) drying the solvent in the active material slurry in an oven, and the drying temperature and time must be controlled in this process;

[0142] (5) The anode current collector continues to be conveyed, and passes through another first coating machine and another second coating machine in sequence, and the active material slurry is coated on the other side of the anode current collector, and then passes through an oven to dry the solvent in the active material slurry;

[0143] (6) After being compacted by a cold roller, the roller pressure needs to be controlled in this process to obtain an anode electrode sheet. The cross-sectional structure of the anode electrode sheet along the direction perpendicular to the belt running direction (length direction) is as follows: 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 follows: Fig.13 As shown, on one side of the anode current collector, the slurry corresponding to the first active material layer is first coated by the first extrusion head of the first coater, and then the slurry corresponding to the second active material layer is coated by the second extrusion head of the second coater. For the implementation in which 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, from one end of the anode electrode sheet, only the first active material layer or the superimposed first and second active material layers may be seen.

[0145] The coating process requires the use of extrusion heads of different structures to achieve the coating of the active material layer of the corresponding structure. In some embodiments, the shape of the coating head is the same as the cross-sectional shape of the active material layer. Fig.14 The first extrusion head includes a first upper die and a first lower die. The shape of the extrusion port between the first upper die and the first lower die is the same as the cross-sectional shape of the first active material layer. The thickness increases from the peak line in the middle to both ends. Fig.15 The second extrusion head includes a second upper die and a second lower die. The shape of the extrusion port between the second upper die and the second lower die is the same as the cross-sectional shape of the second active material layer. The thickness decreases from the peak line in the middle to both ends. 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 shape of the coating is the same as that of the active material layer after coating and before drying.

[0146] In other embodiments, the first active material slurry may be simultaneously coated on both sides of the anode current collector, and then the second active material slurry may be simultaneously coated on both sides of the anode current collector; and each layer of active material slurry may be coated and then dried in an oven, and then another layer of active material slurry may be coated and then dried in an oven.

[0147] As an embodiment, the method for preparing a battery cell includes the following steps:

[0148] The anode electrode sheet prepared above is subjected to a winding process to become a bare battery cell;

[0149] The bare battery cell is placed into the housing to form a battery cell;

[0150] Test the performance of the battery.

[0151] A second aspect of the embodiments of the present application provides a battery, comprising the battery cell of the aforementioned embodiment or a battery cell manufactured according to the method for manufacturing the battery cell of the aforementioned embodiment.

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

[0153] Fig.16 4 is an example of a battery module. Fig.16 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0154] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0155] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0156] Fig.17 and Fig.18 1 is a battery pack 1 as an example. Fig.17 and Fig.18 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed 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 accommodating the battery modules 4. The plurality of 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 in the present application, specifically including at least one of a battery cell, a battery module, or a battery pack. The battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may 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 and satellites, energy storage systems, etc., but are not limited thereto.

[0158] As an electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

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

[0160] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and a battery cell may be used as a power source.

[0161] Example

[0162] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0163] Example 1

[0164] S1. Preparation of anode electrode

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

[0166] Graphite, binder styrene butadiene rubber, plasticizer sodium hydroxymethyl cellulose, conductive agent carbon black and high-swelling active material are taken in a certain mass ratio and mixed with deionized water to form a second slurry for preparing a second active material layer. In this embodiment, the mass ratio of graphite, binder, plasticizer, conductive agent and high-swelling active material is 95.5%: 1%: 2%: 0.5%: 1%, wherein the content of graphite is 95.5%, the content of high-swelling active material is 1%, and the high-swelling active material is single-substance silicon.

[0167] In all the examples of this test, the total mass proportion of graphite and high expansion active material in the slurry remained unchanged, which was 96.5%.

[0168] according to Fig.12 The anode electrode sheet is prepared by the preparation process, the anode current collector is a copper foil of 7 μm, the first slurry and the second slurry are coated on the anode current collector by the first extrusion head and the second extrusion head, and the first active material layer and the second active material layer are formed by cold pressing after sufficient drying, and the anode electrode sheet is obtained after die cutting and slitting. The upper thickness and the lower thickness of the first active material layer and the second active material layer refer to the thickness of the two sides in the coating direction, respectively. The thickness of one side of the anode current collector extending out is the upper thickness, which is adjacent to the second end region, and the thickness of the other side 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 maximum thickness position and the minimum thickness position), which is located in the middle region. The coating morphology of the first slurry and the second slurry is controlled by the first extrusion head and the second extrusion head to control the thickness 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), thereby controlling the content of high expansion 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. Preparation of cathode electrode

[0170] The positive electrode active material ternary material, binder polyvinylidene fluoride, conductive agent acetylene black and plasticizer sodium hydroxymethyl cellulose are taken in a mass ratio of 93%:3%:3%:1% and dissolved in a solvent N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The positive electrode slurry is then evenly coated on a 13μm aluminum foil, and after sufficient drying, cold pressing, die cutting, and slitting are performed to obtain a cathode electrode sheet.

[0171] S3. Preparation of electrolyte

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

[0173] S4. Assembly

[0174] The cathode electrode sheet, the separator, and the anode electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare cell, the tabs are welded to the bare cell, and the bare cell is placed in an aluminum shell and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery. The uncharged battery then goes through the processes of static, formation, shaping, capacity testing, etc. in sequence to obtain a battery cell.

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

[0176] Table 1: Anode parameter results of Examples 1 to 10 and Comparative Examples 1 to 2

[0177]

[0178] The temperature distributions at the top, middle and bottom of the battery cells of Examples 1 to 10 and Comparative Examples 1 to 2 and the 200 cls capacity retention rates were tested. The results are shown in Table 2.

[0179] The test method is: the battery cell is connected to the charger and discharger and continuously cycles at a current of 1C charging and 0.5C discharging. At the same time, temperature sensors are attached to the aluminum shells of the upper part (corresponding to the second end area of ​​the anode electrode), the middle part (corresponding to the middle area of ​​the anode electrode), and the lower part (corresponding to the first end area of ​​the anode electrode) of the battery cell to sense and record the temperature changes. The consistency of the battery cell is calculated based on the highest temperature (generally the temperature is highest at the end of charging). At the same time, the energy that can be released by the battery cell in each cycle is taken as the capacity of the battery cell at this time, so as to calculate the capacity retention rate of the battery cell after 200cls of circulation.

[0180] Table 2: Battery cell parameter test results of Examples 1 to 10 and Comparative Examples 1 to 2

[0181]

[0182]

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

[0184] Compared with Comparative Example 2, Examples 1 to 3 and Examples 4 to 6 can promote the temperature of different regions to be close to each other and improve the capacity retention rate of the battery by adjusting the content of high expansion 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 content of high expansion active material and the content of 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 high-expansion active material content and graphite content in different areas of the anode active material layer change according to a certain rule (the content of high-expansion active material in the middle area is higher than that in the two end areas, and the content of graphite is lower), the coating order of the first active material layer and the second active material layer is changed, and the capacity retention rate of the battery is roughly the same.

[0187] According to Example 1 and Example 8, different high-expansion active materials are selected on the basis that the high-expansion active material content and graphite content in different regions of the anode active material layer change according to a certain rule, and the capacity retention rate of the battery is roughly the same.

[0188] According to Examples 4 to 6 and Example 9, the peak line of the anode active material layer is 1 / 3 to 1 / 2 away from the first end, which can improve the capacity retention rate of the battery.

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

[0190] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: An electrode assembly is provided, wherein the electrode assembly comprises a cathode electrode sheet and an anode electrode sheet, wherein the electrode assembly has two ends arranged along a first direction, wherein the anode electrode sheet comprises an anode current collector and an anode active material layer attached to a surface of the anode current collector, wherein the anode active material layer comprises a first end region, a middle region, and a second end region arranged along the first direction, wherein the anode active material layer comprises graphite and a high-expansion active material, wherein the high-expansion active material comprises 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, characterized in that: 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, characterized in that: W1>W2>W3, Q1<Q2<Q3.

4. The battery cell according to claim 1, characterized in that: 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, characterized in that: The mass proportion of the graphite in the anode active material layer is 93% to 97%, and the mass proportion of the high expansion active material is 0.3% to 1.5%.

6. The battery cell according to claim 1, characterized in that: 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, characterized in that: 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, characterized in that: The anode active material layer includes a first active material layer and a second active material layer sequentially stacked on the anode current collector, and in the direction from the peak line to both 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites and silicon alloys; the tin-based material may be selected from at least one of elemental tin, tin oxides and tin alloys; the metal oxide may 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: Comprising a battery as claimed in claim 13, the battery is used to provide electrical energy.

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