Positive plate, winding battery cell and battery

Abstract

The utility model discloses a positive plate, a winding battery cell and a battery, the positive plate is used for mutually laminating with a diaphragm and a negative plate and winding to form the winding battery cell, and the positive plate comprises a current collector, a positive electrode and a negative electrode, the active material layer is coated on the surface of the current collector, one surface, deviating from the current collector, of the active material layer is sunken to form a groove, and the groove is positioned at the corner position of the winding cell after the positive plate is wound; and the filling part is arranged in the groove in a filling manner. The positive plate disclosed by the utility model can effectively improve lithium precipitation at the corner position of the wound battery cell and improve the reliability and the safety of the battery.

Description

Technical Field

[0001] This utility model relates to the field of lithium battery technology, and in particular to a positive electrode sheet, a wound cell, and a battery. Background Technology

[0002] Lithium batteries are batteries that contain lithium (including metallic lithium, lithium alloys, lithium ions, and lithium polymers) in their electrochemical system and are widely used in digital products and other fields.

[0003] The mainstream types of lithium batteries on the market include stacked cells and wound cells. Stacked cells are formed by stacking positive and negative electrodes and separators in sequence, which has advantages such as regular structure and low internal resistance. Wound cells, on the other hand, are formed by winding positive and negative electrodes and separators in sequence, which has certain advantages in terms of production efficiency and cost control, and therefore occupies a considerable share of the market.

[0004] However, wound battery cells face several pressing issues in practical applications. The defects at the corners are particularly prominent. During the winding process, the CB value (the margin by which the negative electrode capacity exceeds the positive electrode capacity under the same conditions and at the same stage) at the corners is lower than the CB value in the flat areas of the cell. This makes lithium plating highly likely at the corners during cycling. As lithium plating intensifies, side reactions occur, ultimately leading to severe deformation of the battery sides and failure. In severe cases, lithium-ion dendrites can pierce the separator, causing a short circuit and fire. Utility Model Content

[0005] The main purpose of this invention is to propose a positive electrode sheet that aims to solve, to some extent, the technical problem of lithium deposition at the corner positions of existing wound battery cells.

[0006] To achieve the above objectives, this utility model proposes a positive electrode sheet for being stacked and wound with a separator and a negative electrode sheet to form a wound battery cell, wherein the positive electrode sheet comprises:

[0007] current collector;

[0008] An active material layer is coated on the surface of the current collector. The side of the active material layer facing away from the current collector has a recessed groove. The groove is located at the corner of the wound cell after the positive electrode sheet is wound.

[0009] A filling portion is provided in the groove.

[0010] In some embodiments, the positive electrode further includes:

[0011] A base coating is applied between the current collector and the active material layer, wherein the coating area of ​​the base coating on the current collector covers the projected area of ​​the groove on the current collector.

[0012] In some embodiments, the undercoat layer is a ceramic layer or a lithium salt layer.

[0013] In some embodiments, the filler is viscous, and the filler is a mixture of ceramic and adhesive; and / or,

[0014] The porosity of the filling portion is greater than that of the active material layer.

[0015] In some embodiments, the number of grooves is multiple, and the multiple grooves are divided into multiple groove groups, wherein the grooves in the groove groups are arranged in an array;

[0016] Multiple groove groups are spaced apart along the length of the active material layer, and each groove group is located at a corner of the wound cell after the positive electrode sheet is wound.

[0017] In some embodiments, the spacing between the groove group and the edge of the active material layer along the width direction of the active material layer ranges from 3 mm to 5 mm; and / or,

[0018] The spacing between any two adjacent grooves in the groove group is in the range of 0.5mm to 1.5mm.

[0019] In some embodiments, the ratio of the depth of the groove to the thickness of the active material layer ranges from 20% to 40%.

[0020] In some embodiments, the filling portion protrudes from the side of the active material layer opposite to the current collector.

[0021] In some embodiments, the protrusion height of the filling portion is 1 μm to 3 μm.

[0022] In some embodiments, the porosity of the filling portion is greater than the porosity of the active material layer.

[0023] This utility model also proposes a wound battery cell, which includes a negative electrode, a separator, and a positive electrode as described above, wherein the positive electrode, separator, and negative electrode are stacked and wound together to form the wound battery cell.

[0024] The present invention also proposes a battery comprising a housing and a wound cell as described above, wherein the wound cell is disposed in the housing.

[0025] In the positive electrode of this invention, a groove is provided on the active material layer and the groove is filled with a filler portion. After the positive electrode is combined with the separator and negative electrode to form a wound cell, the groove is located at the corner of the wound cell. Furthermore, since the groove is filled with a filler portion, the positive electrode capacity at the corner is reduced, thereby increasing the CB value at the corner. This can effectively improve lithium plating at the corner of the wound cell and enhance the reliability and safety of the battery. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the positive electrode sheet in one embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the positive electrode sheet in another embodiment of the present invention;

[0028] Figure 3 for Figure 1 Enlarged view of point A in the middle; Attached image description:

[0030] label name label name 100 Positive electrode film 110 current collector 120 Active material layer 121 groove 130 Filling part 140 Primer

[0031] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0032] The solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0033] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0034] It should also be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component present. When a component is described as "connected to" another component, it can be directly connected to the other component or there may be an intervening component present.

[0035] Furthermore, the use of terms such as "first" and "second" in this utility model is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.

[0036] In the battery manufacturing industry, wound cells are widely used due to their compact structure and high energy density. However, during the production and use of wound cells, lithium plating is prone to occur at the corners of the cells. Lithium plating not only reduces battery capacity and performance but also causes safety issues, seriously affecting battery reliability and safety. Currently, conventional positive electrode sheets, when wound with separators and negative electrode sheets to form wound cells, exhibit poor contact between the electrodes and cannot effectively solve the problem of lithium plating at the corners, requiring urgent improvement.

[0037] This utility model embodiment provides a positive electrode 100 for being stacked and wound with a separator and a negative electrode to form a wound battery cell, wherein, with reference to Figure 1 and Figure 2 The positive electrode 100 includes:

[0038] Current collector 110;

[0039] An active material layer 120 is coated on the surface of the current collector 110. A groove 121 is formed on the side of the active material layer 120 away from the current collector 110. The groove 121 is located at the corner of the wound cell after the positive electrode sheet 100 is wound.

[0040] The filling part 130 is filled in the groove 121.

[0041] The current collector 110 can be made of aluminum foil, which has good conductivity, ductility, and corrosion resistance, enabling it to collect and transmit current while providing support for the active material layer 120. The active material layer 120 can consist of two layers, coated on opposite surfaces of the current collector 110. The active material layer 120 comprises a positive electrode active material, a binder, and a conductive agent. The positive electrode active material can be lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, ternary materials, etc., selected according to actual needs. During charging and discharging, the positive electrode active material undergoes a redox reaction, enabling the insertion and extraction of lithium ions. The binder bonds the positive electrode active material and the conductive agent together, ensuring their firm adhesion to the current collector 110. The conductive agent improves the electronic conductivity of the electrode, ensuring the smooth progress of the electrochemical reaction.

[0042] A groove 121 is formed on the active material layer 120. The side of the active material layer 120 facing the current collector 110 is bonded to the current collector 110, while the groove 121 is located on the side of the active material layer 120 away from the current collector 110. The groove 121 can be formed by laser cleaning of the surface of the active material layer 120 or by rolling the surface of the active material layer 120 with a roller with raised dots. Furthermore, a filler portion 130 is filled within the groove 121. The filler portion 130 can be flush with the surface of the active material layer 120 or protrude from the surface of the active material layer 120. The filler portion 130 has a certain degree of adhesion and can be a gel.

[0043] After the positive electrode 100, the separator, and the negative electrode are stacked and wound together to form a wound battery cell, the wound battery cell has a straight position and a corner position. The groove 121 is located at the corner position of the wound battery cell, and the filling part 130 filled in the groove 121 is located at the corner position.

[0044] In the positive electrode 100 of this embodiment, a groove 121 is provided on the active material layer 120 and a filling portion 130 is filled in the groove 121. After the positive electrode 100 is combined with the separator and the negative electrode to form a wound cell, the groove 121 is located at the corner of the wound cell. Furthermore, since the filling portion 130 is provided in the groove 121, the positive electrode capacity at the corner is reduced, thereby increasing the CB value at the corner. This can effectively improve lithium plating at the corner of the wound cell and enhance the reliability and safety of the battery.

[0045] In some embodiments, the positive electrode 100 further includes:

[0046] The base coating 140 is applied between the current collector 110 and the active material layer 120, and the coating area of ​​the base coating 140 on the current collector 110 covers the projected area of ​​the groove 121 on the current collector 110.

[0047] The base coating 140 can be square, with a certain length and width. The projected area of ​​the groove 121 on the current collector 110 is within the coating area of ​​the base coating 140 on the current collector 110. The thickness of the base coating 140 ranges from 2μm to 4μm and can be set according to actual needs. Furthermore, the material of the base coating 140 can be set according to actual needs and is not limited here. The function of the base coating 140 is to occupy volume space within the active material layer 120, reducing the content of active material, thereby further reducing the positive electrode content at the corner position, increasing the CB value at the corner position, and improving lithium plating at the corner position of the wound cell.

[0048] In some embodiments, the undercoat 140 is a ceramic layer or a lithium salt layer. Wherein, the undercoat 140 is made of ceramic, which can increase electrode impedance, reduce the number of lithium ion insertions and extractions, and further prevent lithium plating at corners. Alternatively, the undercoat 140 is made of lithium salt, which can be a low-specific-capacity lithium salt, such as lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium titanate, etc. Lithium salt can increase the ion migration rate of the electrolyte, thereby improving the charge and discharge efficiency of the battery.

[0049] In some embodiments, the filler portion 130 is adhesive and is a mixed filler made of ceramic and adhesive. Due to its adhesiveness, the filler portion 130 can bond with the separator and negative electrode at corner positions, thereby achieving good contact between the electrodes and improving corner lithium plating. The filler portion 130 can be a mixed filler made of ceramic and adhesive. The adhesive in the filler portion 130 can be PVDF adhesive, i.e., polyvinylidene fluoride adhesive, which has good weather resistance, high temperature resistance, chemical corrosion resistance, electrical insulation properties, and excellent adhesiveness, thus giving the filler portion 130 good adhesion. Other adhesives can also be used, and this embodiment does not limit this. The filler portion 130 also includes ceramic, which can be at least one of oxide ceramics, carbide ceramics, nitride ceramics, and glass ceramics, such as alumina, zirconium oxide, silicon carbide, silicon nitride, etc. The ceramic can increase electrode impedance, reduce the number of lithium ion insertions and extractions, and further prevent corner lithium plating.

[0050] In some embodiments, the porosity of the filling portion 130 is greater than that of the active material layer 120. The filling portion 130 has pores that can accommodate and allow electrolyte to pass through. The higher porosity of the filling portion 130 compared to the active material layer 120 means it has a higher porosity, allowing it to hold a sufficient amount of electrolyte and preventing the electrolyte from being squeezed out at corners due to electrode expansion during cycling, thus helping to further improve corner lithium deposition.

[0051] In some embodiments, the filler 130 is viscous and is a mixed filler made of ceramic and adhesive. At the same time, the porosity of the filler 130 is greater than that of the active material layer 120. The corresponding effect can be found in the foregoing embodiments, and will not be described in detail here.

[0052] In some embodiments, refer to Figure 1 and Figure 2 The number of grooves 121 is multiple, and the multiple grooves 121 are divided into multiple groove groups, and the grooves 121 in the groove group are arranged in an array.

[0053] Multiple groove groups are spaced apart along the length of the active material layer 120, and each groove group is located at a corner of the wound cell after the positive electrode sheet 100 is wound.

[0054] On the active material layer 120 of the positive electrode 100, multiple grooves 121 are provided and divided into multiple groove groups. For each groove group, the grooves 121 included are arranged in an array. For example, a groove group has ten grooves 121, arranged in five rows and two columns. Along the length direction of the active material layer 120, two grooves 121 are spaced apart; and along the width direction of the active material layer 120, five grooves 121 are sequentially spaced apart. This is merely exemplary and not limiting. Each groove 121 is correspondingly filled with a filling portion 130.

[0055] Along the length of the active material layer 120 (i.e., the length of the positive electrode 100), multiple groove groups are arranged sequentially at intervals. The number of groove groups on the positive electrode 100 can be set according to the number of turns of the wound cell, while the spacing between the groove groups can be set according to the size of the wound cell, ensuring that after the positive electrode 100 is wound with the separator and negative electrode to form a wound cell, each groove group is located at a corner of the wound cell.

[0056] In this embodiment, the multiple grooves 121 are divided into multiple groove groups, each groove group corresponds to a corner position of the wound cell, and the grooves 121 in the groove group are arranged in an array. This structural design improves the distribution uniformity of the grooves 121 and the filling portion 130, making the effect of enhancing electrode contact and improving corner lithium plating more uniform and stable, which helps to comprehensively improve the performance of the battery.

[0057] Correspondingly, in some embodiments, there are multiple base coating layers 140, which are spaced apart along the length of the active material layer 120, and each base coating layer 140 is located at a corner of the wound cell after the positive electrode sheet 100 is wound. Optionally, the coating area of ​​each base coating layer 140 on the current collector 110 covers the projected area of ​​a groove group on the current collector 110.

[0058] In some embodiments, refer to Figure 1 and Figure 3The spacing M between the groove group and the edge of the active material layer 120 along the width direction of the active material layer 120 is in the range of 3mm to 5mm. Specifically, the spacing M between the groove group and the edge of the active material layer 120 along the width direction of the active material layer 120 (that is, the width direction of the positive electrode 100) can be set in the range of 3mm to 5mm. For example, the spacing M between the groove group and the edge of the active material layer 120 along the width direction of the active material layer 120 can be set to 3mm, 4mm or 5mm. Optionally, the spacing M between the groove group along the width direction of the active material layer 120 and the edge of the active material layer 120 can be set based on the degree of lithium plating prevention requirements of the battery cell. For example, when the degree of lithium plating prevention requirements is low, the spacing M between the groove group along the width direction of the active material layer 120 and the edge of the active material layer 120 can be set to 5 mm; when the degree of lithium plating prevention requirements is moderate, the spacing M between the groove group along the width direction of the active material layer 120 and the edge of the active material layer 120 can be set to 4 mm; when the degree of lithium plating prevention requirements is high, the spacing M between the groove group along the width direction of the active material layer 120 and the edge of the active material layer 120 can be set to 3 mm. Of course, this is only an example and is not limiting. The spacing M between the groove group along the width direction of the active material layer 120 and the edge of the active material layer 120 can also be set based on other factors.

[0059] In some embodiments, refer to Figure 1 and Figure 3 The spacing N between any two adjacent grooves 121 in the groove group ranges from 0.5mm to 1.5mm. Specifically, the spacing N between any two adjacent grooves 121 in the groove group can be set within the range of 0.5mm to 1.5mm; for example, the spacing N between two adjacent grooves 121 in the groove group can be set to 0.5mm, 1mm, or 1.5mm. Optionally, the spacing N between two adjacent grooves 121 in the groove group can be set based on the degree of lithium plating prevention requirements of the battery cell. For example, when the degree of lithium plating prevention requirements is low, the spacing N between two adjacent grooves 121 in the groove group can be set to 1.5mm to make the grooves 121 more widely distributed; when the degree of lithium plating prevention requirements is moderate, the spacing N between two adjacent grooves 121 in the groove group can be set to 1mm; when the degree of lithium plating prevention requirements is high, the spacing N between two adjacent grooves 121 in the groove group can be set to 0.5mm. Of course, this is merely an example and not a limitation. The spacing N between two adjacent grooves 121 in the groove group can also be set based on other factors.

[0060] In some embodiments, the distance M between the groove group and the edge of the active material layer 120 along the width direction of the active material layer 120 ranges from 3mm to 5mm, and at the same time, the distance N between any two adjacent grooves 121 in the groove group ranges from 0.5mm to 1.5mm, which corresponds to having the same effect as the aforementioned embodiments.

[0061] In some embodiments, the ratio of the depth of the groove 121 to the thickness of the active material layer 120 ranges from 20% to 40%. Specifically, the ratio of the depth of the groove 121 to the thickness of the active material layer 120 can be set within the range of 20% to 40%, for example, it can be set to 20%, 30%, or 40%. Taking a thickness of 50 μm for the active material layer 120 as an example, the depth of the groove 121 can be set from 10 μm to 20 μm. Optionally, the ratio of the depth of the groove 121 to the thickness of the active material layer 120 can be set based on the degree of requirement for preventing lithium plating at the corner of the battery cell. For example, when the degree of requirement for preventing lithium plating at the corner of the battery cell is low, the ratio of the depth of the groove 121 to the thickness of the active material layer 120 can be set to 20%; when the degree of requirement for preventing lithium plating at the corner of the battery cell is medium, the ratio of the depth of the groove 121 to the thickness of the active material layer 120 can be set to 30%; and when the degree of requirement for preventing lithium plating at the corner of the battery cell is high, the ratio of the depth of the groove 121 to the thickness of the active material layer 120 can be set to 40%. Of course, this is only an example and not a limitation. The ratio of the depth of the groove 121 to the thickness of the active material layer 120 can also be set based on other factors. In addition, by controlling the ratio of the depth of the groove 121 to the thickness of the active material layer 120 to be within the range of 20% to 40%, the groove 121 can be prevented from being too deep in the active material layer 120, so as to ensure the structural strength of the active material layer 120 and reduce the risk of breakage and separation of the active material layer 120.

[0062] In some embodiments, refer to Figure 2 The filling portion 130 protrudes from the side of the active material layer 120 opposite to the current collector 110. Specifically, the thickness of the filling portion 130 is greater than the depth of the groove 121, and when the filling portion 130 fills the groove 121 of the active material layer 120, it protrudes from the surface of the active material layer 120. After the positive electrode 100 is combined with the separator and negative electrode to form a wound cell, the protruding filling portion 130 contacts the separator and negative electrode at the corner, creating a gap between the positive and negative electrode at the corner. This gap can effectively store electrolyte, helping to improve the local electrolyte retention at the corner. Sufficient electrolyte ensures smooth ion transport in this area, further reducing the probability of lithium plating and improving the overall performance and stability of the battery.

[0063] In some embodiments, the protrusion height of the filling portion 130 is 1 μm to 3 μm. The protrusion height of the filling portion 130 can be set between 1 μm and 3 μm, for example, it can be 1 μm, 2 μm, or 3 μm. Optionally, the protrusion height of the filling portion 130 can be set based on the degree of lithium plating prevention requirements of the battery cell. For example, when the degree of lithium plating prevention requirements is low, the protrusion height of the filling portion 130 can be set to 1 μm; when the degree of lithium plating prevention requirements is moderate, the protrusion height of the filling portion 130 can be set to 2 μm; and when the degree of lithium plating prevention requirements is high, the protrusion height of the filling portion 130 can be set to 3 μm. Of course, this is only exemplary and not limiting; it can also be set based on other factors.

[0064] This utility model embodiment also proposes a wound battery cell, which includes a negative electrode sheet, a separator, and a positive electrode sheet 100 as described in the foregoing embodiments. The positive electrode sheet 100, the separator, and the negative electrode sheet are stacked and wound together to form the wound battery cell. The specific structure of the positive electrode sheet 100 is as described in the above embodiments. Since this wound battery cell adopts all the technical solutions of all the above embodiments, it has at least all the technical effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0065] This utility model embodiment also proposes a battery, which includes a casing and a wound battery cell as described in the foregoing embodiments, wherein the wound battery cell is disposed in the casing. The specific structure of the wound battery cell is the same as described in the foregoing embodiments. Since this battery adopts all the technical solutions of all the foregoing embodiments, it has at least all the technical effects brought about by the technical solutions of the foregoing embodiments, and will not be described in detail here. The battery can be a lithium battery.

[0066] The above description is only a part or preferred embodiment of this utility model. Neither the text nor the drawings should limit the scope of protection of this utility model. All equivalent structural transformations made using the content of this utility model specification and drawings under the overall concept of this utility model, or direct / indirect applications in other related technical fields, are included within the scope of protection of this utility model.

Claims

1. A positive electrode sheet, used for being stacked and wound with a separator and a negative electrode sheet to form a wound battery cell, characterized in that, The positive electrode sheet comprises: a current collector; an active material layer coated on a surface of the current collector, a side of the active material layer away from the current collector being recessed to form a groove, the groove being located at a corner position of the wound battery cell after the positive electrode sheet is wound; a filling part filled in the groove.

2. The positive electrode sheet according to claim 1, characterized by The positive electrode sheet further comprises: a primer layer coated between the current collector and the active material layer, a coated area of the primer layer on the current collector covering a projected area of the groove on the current collector.

3. The positive electrode sheet according to claim 2, characterized by The primer layer is a ceramic layer or a lithium salt layer.

4. The positive electrode sheet according to claim 1, characterized by The filling part has viscosity, the filling part is a mixed filler made of ceramic and glue solution; and / or, The porosity of the filling part is greater than the porosity of the active material layer.

5. The positive electrode sheet according to claim 1, characterized by The number of the grooves is multiple, the multiple grooves are divided into multiple groove groups, and the grooves in the groove groups are arranged in an array. The multiple groove groups are arranged at intervals along the length direction of the active material layer, and each groove group corresponds to a corner position of the wound battery cell after the positive electrode sheet is wound.

6. The positive electrode sheet according to claim 5, wherein a spacing between the groove group and an edge of the active material layer along the width direction of the active material layer is in a range of 3mm to 5mm; and / or a spacing between any two adjacent grooves in the groove group is in a range of 0.5mm to 1.5mm.

7. The positive electrode sheet according to claim 1, characterized by A ratio of the depth of the groove to the thickness of the active material layer is in a range of 20% to 40%.

8. The positive electrode sheet according to claim 1, characterized by The filling part is protruded from a side of the active material layer away from the current collector.

9. The positive electrode sheet according to claim 6, characterized by The protruding height of the filling part is 1μm to 3μm.

10. A wound cell core, characterized by, The wound battery cell comprises a negative electrode sheet, a separator, and the positive electrode sheet according to any one of claims 1 to 9, the positive electrode sheet, the separator, and the negative electrode sheet being stacked and wound to form the wound battery cell.

11. A battery, characterized by The battery comprises a housing and the wound battery cell according to claim 10, the wound battery cell being arranged in the housing.

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