Secondary battery, manufacturing method for secondary battery, and electrical apparatus
By placing ceramic and resin fillers in the grooves of the active material layer of the secondary battery, the safety hazard of lithium dendrites piercing the separator is solved, thereby improving safety and energy density.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NINGDE AMPEREX TECHNOLOGY LTD
- Filing Date
- 2025-06-25
- Publication Date
- 2026-05-21
Smart Images
Figure CN2025103413_21052026_PF_FP_ABST
Abstract
Description
Secondary batteries, methods for manufacturing secondary batteries, and electrical devices using secondary batteries. Technical Field
[0001] This application relates to the field of energy storage technology, and in particular to a secondary battery, a method for manufacturing the secondary battery, and an electrical device for using it. Background Technology
[0002] In secondary battery design, energy density can be increased by increasing the weight of the active material coating on the electrode. However, with the increased weight of the active material coating on the electrode, the electrolyte does not easily wet the electrode, thus requiring pores to be drilled in the active material layer to improve the electrolyte's wetting effect on the electrode. Summary of the Invention
[0003] The grooves formed by drilling holes in the active material layer have long lithium-ion transport paths and high local current densities, making it easy for lithium dendrites to form. Moreover, the lithium dendrites in the grooves are not hindered by the separator, and they grow in a free state, which can easily puncture the separator and cause safety hazards.
[0004] In view of this, it is necessary to provide a secondary battery, a method for manufacturing a secondary battery, and an electrical device for using it, which can help reduce the risk of the separator being punctured by lithium dendrites.
[0005] An embodiment of the first aspect of this application provides a secondary battery, including an electrode assembly. The electrode assembly includes a first electrode, a second electrode, and a separator. The first electrode includes a first current collector and a first active material layer, the first active material layer being disposed on at least one surface of the first current collector along its thickness direction. The second electrode includes a second current collector and a second active material layer, the second active material layer being disposed on at least one surface of the second current collector along its thickness direction. The separator is disposed between the first and second active material layers. The first active material layer has a groove, the groove including an opening and a wall. Along the thickness direction of the first electrode, the opening faces the separator, and the other side of the separator facing the opening corresponds to the second active material layer. The first electrode also includes a filler, the filler including a filling portion located in the groove, the filling portion covering at least a portion of the groove wall.
[0006] In the above embodiments, when lithium dendrites precipitate in the groove, the filler located in the groove can separate the lithium dendrites precipitated in the groove from the separator, and restrict the growth of the lithium dendrites in the groove towards the separator, so that the lithium dendrites are less likely to puncture the separator. When the lithium dendrites precipitated on the first active material layer come into contact with the filler, the filler can also apply pressure to the lithium dendrites, so that the lithium dendrites are less likely to generate sharp free growth ends, thereby reducing the risk of lithium dendrites puncturing the separator and improving the safety of secondary battery applications.
[0007] In one or more of the above embodiments, the filler material includes at least one of ceramic material and resin material.
[0008] In the above embodiments, the ceramic and resin materials provide support, inhibiting lithium dendrite growth; furthermore, their large porosity allows lithium ions to pass through, reducing the impact on lithium ion transport. The ceramic and resin materials also provide insulation, balancing electrolyte wetting with the safety performance of the secondary battery.
[0009] In one or more of the above embodiments, the ceramic material is selected from at least one of alumina, boehmite, titanium dioxide, magnesium oxide, calcium oxide, and zirconium oxide.
[0010] In one or more of the above embodiments, the resin material is selected from at least one of polyimide, polytetrafluoroethylene, and polyvinyl butyral.
[0011] In one or more of the above embodiments, the filler material also includes an adhesive.
[0012] In the above embodiments, the binder can improve the adhesion between the filler and the active material layer, which is beneficial for the filler to solidify in the groove, and thus more beneficial for suppressing the growth of lithium dendrites in the groove.
[0013] In one or more of the above embodiments, the internal space volume of the groove is V1, the volume of the filling part is V2, and the thickness of the first active material layer at the position where the groove is not provided is h, satisfying: 0.6V1≤V2≤V1.
[0014] In the above embodiments, V2 ≥ 0.6V1 ensures that the filling portion within the groove has a certain volume, thereby inhibiting the growth of lithium dendrites. V2 ≤ V1 prevents the filling portion from protruding beyond the groove, thus reducing the thickness of the secondary battery and minimizing its energy density. When V2 = V1, the filling portion fills the groove, improving the smoothness of the first active material layer surface. Simultaneously, the entire groove is filled with the filling portion, which covers the entire groove wall, ensuring that all parts of the groove wall are supported by the filling portion. Compared to grooves where the filling portion is not fully filled, this provides better inhibition of lithium dendrites.
[0015] In one or more of the above embodiments, 0.9V1≤V2≤V1.
[0016] In the above embodiments, V2≥0.9V1, which makes the filling part have a larger volume, thereby making the area of the groove wall covered by the filling part larger, and the suppression effect on lithium dendrite growth in the groove more obvious.
[0017] In one or more of the above embodiments, the filler is entirely disposed within the groove.
[0018] In the above embodiments, no filler is provided at the location where the groove is not provided in the first active material layer, so that the electrode thickness is not easily increased while suppressing the growth of lithium dendrites, and thus the energy density of the secondary battery is not easily reduced.
[0019] In one or more of the above embodiments, the filler further includes a coating portion disposed on the area of the first active material layer facing the diaphragm where no groove is provided.
[0020] In the above embodiments, the coating can protect the electrode, improve the mechanical strength of the first electrode, and facilitate the storage of more electrolyte, which is more conducive to the transport of lithium ions; and can also play a certain role in inhibiting the growth of lithium dendrites on the side of the first active material layer facing the separator where no groove is provided.
[0021] In one or more of the above embodiments, the coating portion and the filling portion are integrally formed.
[0022] In the above embodiments, the integrally formed coating portion and filling portion can reduce the separation between the coating portion and the filling portion, thereby reducing lithium deposition in the gap between the coating portion and the filling portion, and further improving the effect of suppressing lithium dendrite growth.
[0023] In one or more of the above embodiments, the thickness of the coating portion along the thickness direction of the first electrode is h1, satisfying 0.5um≤h1≤2um.
[0024] In the above embodiments, when h1≥0.5um, the requirements for improving the mechanical strength of the first electrode, enhancing the electrolyte storage of the first electrode, and suppressing lithium dendrite growth can be met; when h1≤2um, it is not easy to make the cell too thick and reduce the energy density.
[0025] In one or more of the above embodiments, along the thickness direction of the first electrode, the thickness of the first active material layer at the location where no groove is provided is H1, and the depth of the groove is H2, satisfying: H1 / 4≤H2≤H1 / 2.
[0026] In the above embodiments, when H2≥H1 / 4, the groove has a certain depth, which facilitates the electrolyte to wet the first active material layer through the groove, thereby providing transport power for lithium ions and promoting the insertion of lithium ions into the first active material layer, thus reducing lithium plating; when H2≤H1 / 2, the first active material layer at the groove is not too thin, thereby providing sufficient space for lithium ion insertion and reducing lithium plating.
[0027] The second aspect of this application also provides a method for manufacturing a secondary battery, used to manufacture the secondary battery in any of the above embodiments, comprising the following steps:
[0028] Fill: Set filler in the groove;
[0029] Stacking: The separator and the second electrode are stacked sequentially on the first electrode along the thickness direction of the first electrode, with the separator located between the first active material layer and the second electrode.
[0030] In the above embodiments, by providing a filler in the groove of the first active material layer, the filler can block the extension and growth of lithium dendrites in the groove, thereby inhibiting lithium plating in the groove, making the separator less likely to be punctured by freely growing lithium dendrites, and improving the safety performance of the electrode assembly.
[0031] In one or more of the above embodiments, the filling step includes:
[0032] Coating: Applying the filler slurry to the side of the first active material layer facing the diaphragm;
[0033] Leveling: The coated filler slurry flows into the groove.
[0034] In the above embodiments, by coating first and then leveling, the filler slurry can flow into multiple grooves of the first active material layer simultaneously, which helps to improve the efficiency of setting fillers into the grooves.
[0035] In one or more of the above embodiments, the filling step further includes:
[0036] Curing: Curing the filler slurry into a filler.
[0037] An embodiment of the third aspect of this application also provides an electrical device, including a secondary battery as described in any of the above embodiments.
[0038] In the above embodiments, by providing fillers on the first active material layer of the secondary battery, the growth of lithium dendrites is suppressed, the risk of the separator being punctured is reduced, and the service life of the secondary battery and the service life of the electrical device are improved. Attached Figure Description
[0039] Figure 1 is a schematic diagram of a secondary battery in one embodiment of this application.
[0040] Figure 2 is an enlarged view of part II in Figure 1.
[0041] Figure 3 is a partial cross-sectional view of the first electrode in one embodiment of this application.
[0042] Figure 4 is a partial schematic diagram of the first active material layer of the first electrode in one embodiment of this application.
[0043] Figure 5 is a partial top view of the first electrode in one embodiment of this application.
[0044] Figure 6 is a partial side view of the first electrode in another embodiment of this application.
[0045] Figure 7 is a partial cross-sectional view of the first active material layer and the filler in one embodiment of this application.
[0046] Figure 8 is a schematic diagram of an electrical device in one embodiment of this application.
[0047] Key Component Symbols: Electrical Device 1000, Secondary Battery 100, Electrode Assembly 10, First Electrode 11, First Current Collector 111, First Surface 111a, Second Surface 111b, First Active Material Layer 112, Groove 1121, Groove Opening 1121a, Groove Wall 1121b, Filler 113, Filling Section 1131, Coating Section 1132, First Tab 114, Second Electrode 12, Second Current Collector 121, Third Surface 121a, Fourth Surface 121b, Second Active Material Layer 122, Second Tab 123, Separator 13, First Separator 13a, Second Separator 13b, Housing 20, Main Body of the Device200 First direction X Second direction Y
[0048] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation
[0049] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.
[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
[0051] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.
[0052] In secondary battery design, energy density can be increased by increasing the weight of the active material coating on the electrodes. However, with the increased weight of the active material coating, the electrolyte does not easily wet the electrodes, thus requiring pores to be drilled in the active material layer to improve the electrolyte's wetting effect on the electrodes.
[0053] The grooves formed by drilling holes in the active material layer have long lithium-ion transport paths and high local current densities, making it easy for lithium dendrites to form. Moreover, the lithium dendrites in the grooves are not hindered by the separator, and they grow in a free state, which can easily puncture the separator and cause safety hazards.
[0054] Embodiments of this application provide a secondary battery, including an electrode assembly. The electrode assembly includes a first electrode, a second electrode, and a separator. The first electrode includes a first current collector and a first active material layer, the first active material layer being disposed on at least one surface of the first current collector along its thickness direction. The second electrode includes a second current collector and a second active material layer, the second active material layer being disposed on at least one surface of the second current collector along its thickness direction. The separator is disposed between the first and second active material layers. The first active material layer has a groove, the groove including an opening and a wall. Along the thickness direction of the first electrode, the opening faces the separator, and the other side of the separator facing the opening corresponds to the second active material layer. The first electrode also includes a filler, the filler including a filling portion located in the groove, the filling portion covering at least a portion of the groove wall.
[0055] In the above embodiments, when lithium dendrites precipitate in the groove, the filler located in the groove can separate the lithium dendrites precipitated in the groove from the separator, and restrict the growth of the lithium dendrites in the groove towards the separator, so that the lithium dendrites are less likely to puncture the separator. When the lithium dendrites precipitated on the first active material layer come into contact with the filler, the filler can also apply pressure to the lithium dendrites, so that the lithium dendrites are less likely to generate sharp free growth ends, thereby reducing the risk of lithium dendrites puncturing the separator and improving the safety of secondary battery applications.
[0056] The embodiments of this application will be further described below with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.
[0057] As shown in Figure 1, a first embodiment of this application provides a secondary battery 100, including an electrode assembly 10 and a housing 20, with the electrode assembly 10 housed within the housing 20. The electrode assembly 10 includes a first electrode 11, a second electrode 12, and a separator 13, with the separator 13 disposed between the first electrode 11 and the second electrode 12, and the separator 13 serving to isolate the first electrode 11 and the second electrode 12.
[0058] In some embodiments, the housing 20 is a flexible packaging bag, such as an aluminum-plastic film. In other embodiments, the housing 20 is a rigid outer shell, such as a plastic shell, or a metal shell including at least one of steel alloys, aluminum alloys, and copper alloys.
[0059] In some embodiments, an electrolyte (not shown) is injected into the housing 20, and the electrolyte components include solvents, electrolyte salts, and additives.
[0060] In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.
[0061] In some embodiments, the electrolyte salt includes, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium hexafluorocesium oxide (LiCsF6), lithium perchlorate (LiClO4), or lithium trifluoromethanesulfonate (LiCF3SO3).
[0062] In some embodiments, the first electrode 11 and the second electrode 12 have different polarities. For example, the first electrode 11 is an anode electrode, and the second electrode 12 is a cathode electrode.
[0063] Please refer to Figure 1. In some embodiments, the first electrode 11, the diaphragm 13, and the second electrode 12 are stacked and wound together to form a wound structure.
[0064] In some embodiments, the secondary battery 100 includes a plurality of first electrodes 11, a plurality of separators 13 and a plurality of second electrodes 12, wherein any adjacent first electrode 11 and any adjacent second electrode 12 are separated by a separator 13.
[0065] Referring to Figures 1 and 2, in some embodiments, the first electrode 11 includes a first current collector 111 and a first active material layer 112, the first active material layer 112 being disposed on at least one surface of the first current collector 111 along its thickness direction. The second electrode 12 includes a second current collector 121 and a second active material layer 122, the second active material layer 122 being disposed on at least one surface of the second current collector 121 along its thickness direction. A separator 13 is disposed between the first active material layer 112 and the second active material layer 122. The thickness direction of the first current collector 111 and the thickness direction of the second current collector 121 form a first direction X.
[0066] Referring to Figures 2 and 3, in some embodiments, along the thickness direction of the first electrode 11, the first current collector 111 has a first surface 111a and a second surface 111b disposed opposite to each other. The thickness direction of the first electrode 11 is consistent with the thickness direction of the first current collector 111, and the thickness direction of the first electrode 11 is a first direction X. At least one of the first surface 111a and the second surface 111b is provided with a first active material layer 112, for example, both the first surface 111a and the second surface 111b are provided with a first active material layer 112.
[0067] Referring to Figure 2, in some embodiments, along the thickness direction of the second electrode 12, the second current collector 121 has a third surface 121a and a fourth surface 121b disposed opposite to each other, and the thickness direction of the second electrode 12 is consistent with the thickness direction of the second current collector 121. At least one of the third surface 121a and the fourth surface 121b is provided with a second active material layer 122, for example, both the third surface 121a and the fourth surface 121b are provided with a second active material layer 122.
[0068] Referring to Figure 1, in some embodiments, for the wound electrode assembly 10, the first electrode 11 further includes a first tab 114, which is welded to the first current collector 111; the second electrode 12 further includes a second tab 123, which is welded to the second current collector 121.
[0069] In some embodiments, for the stacked electrode assembly 10, the first electrode 11 further includes a first tab 114, which is integrally disposed with the first current collector 111; the second electrode 12 further includes a second tab 123, which is integrally disposed with the second current collector 121.
[0070] In some embodiments, the first tab 114 and the second tab 123 are located on the same side or opposite side of the electrode assembly 10.
[0071] Taking the first electrode 11 as the anode electrode and the second electrode 12 as the cathode electrode as an example, the first current collector 111 and the second current collector 121 can be metal layers. The first current collector 111 can be a metal layer including at least one of copper, nickel, tantalum, titanium, etc., such as copper foil. The second current collector 121 can be a metal layer including at least one of aluminum, nickel, tantalum, titanium, etc., such as aluminum foil.
[0072] Taking the first electrode 11 as the anode electrode and the second electrode 12 as the cathode electrode as an example, the first active material layer 112 is anode-polarized and includes an anode active material, which may include at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen materials, and silicon-carbon materials. The second active material layer 122 is cathode-polarized and includes a cathode active material, which may include at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide.
[0073] Referring to Figures 2 to 4, in some embodiments, the first active material layer 112 is provided with a groove 1121, which includes a groove opening 1121a and a groove wall 1121b. Along the thickness direction of the first electrode 11, the groove opening 1121a faces the diaphragm 13, and the other side of the diaphragm 13 facing the groove opening 1121a corresponds to the second active material layer 122. The first electrode 11 also includes a filler 113, which includes a filling portion 1131 located in the groove 1121 and covering at least a portion of the groove wall 1121b. Understandably, the groove wall 1121b is a wall surface that encloses and forms the internal space of the groove 1121, and includes a sidewall and a bottom. The filling portion 1131 covers at least a portion of the sidewall and the bottom.
[0074] In related secondary battery designs, energy density can be increased by increasing the coating weight of the active material layer on the electrode. However, with the increase in the weight of the coated active material layer, the thickness of the active material layer increases accordingly, reducing the overall kinetic performance of the electrode assembly 10 and making it difficult for the electrolyte to wet the electrode. Therefore, it is necessary to use laser drilling technology to set grooves 1121 on the active material layer to improve the electrolyte wetting effect in the thickness direction of the electrode. After setting grooves 1121 on the active material layer, the coating weight of the electrode can be increased, improving the energy density compared to the original coating weight. However, setting grooves 1121 may result in insufficient coating weight of active material at the location of the grooves 1121 on the electrode, leading to a long lithium-ion transport path within the grooves 1121, high local current density, and easier deposition of dendritic lithium. The lithium dendrites grow in a free state and are prone to piercing the separator 13.
[0075] The pores of the filler 113 allow the electrolyte to pass through, so that the electrolyte wets the first active material layer 112 in the groove 1121. When lithium dendrites are deposited in the groove 1121, the filler 113 located in the groove 1121 can separate the lithium dendrites deposited in the groove 1121 from the separator 13, and restrict the lithium dendrites in the groove 1121 from growing towards the separator 13, so that the lithium dendrites are less likely to pierce the separator 13.
[0076] When the lithium dendrites deposited on the first active material layer 112 come into contact with the filler 113, the filler 113 can also apply pressure to the lithium dendrites so that the lithium dendrites are less likely to generate free growth ends, thereby reducing the risk of lithium dendrites piercing the separator 13 and improving the safety of the secondary battery 100 application.
[0077] Referring to Figures 3 and 5, in some embodiments, a plurality of grooves 1121 are provided on the first active material layer 112, and the plurality of grooves 1121 are distributed in an array. For example, the plurality of grooves 1121 are distributed in a rectangular array.
[0078] Referring to Figures 3 and 5, in some embodiments, the groove 1121 extends along the width direction of the first electrode 11, which is the second direction Y shown in the figures. Viewed from the side view of the first active material layer 112, the groove 1121 has a generally semi-circular outline; viewed from the top view of the first active material layer 112, the groove 1121 has a rectangular outline, and multiple grooves 1121 are arranged sequentially along the length direction of the first active material layer 112.
[0079] Along the thickness direction of the first electrode 11, the thickness of the first active material layer 112 at the position where the groove 1121 is not provided is H1, and the depth of the groove 1121 is H2, satisfying: H1 / 4≤H2≤H1 / 2.
[0080] When H2≥H1 / 4, the groove 1121 has a certain depth, which facilitates the electrolyte to wet the first active material layer 112 through the groove 1121, thereby providing the transport power for lithium ions and promoting the insertion of lithium ions into the first active material layer 112, thus reducing lithium plating; when H2≤H1 / 2, the first active material layer 112 at the groove 1121 is not too thin, thus providing sufficient space for lithium ion insertion and reducing lithium plating.
[0081] Referring to Figure 5, in some embodiments, the distance between adjacent grooves 1121 is L, satisfying 0.8mm ≤ L ≤ 2.0mm. As an example, L can be, but is not limited to, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, or 2.0mm, or other values included in the above range.
[0082] Please refer to Figures 3, 4, and 6. In some embodiments, the internal space volume of the groove 1121 is V1, and the volume of the filling portion 1131 is V2, satisfying: 0.6V1≤V2≤V1. As an example, V2 can be, but is not limited to, 0.6V1, 0.65V1, 0.7V1, 0.75V1, 0.8V1, 0.85V1, 0.9V1, 0.95V1, or V1, or other values within the range of V2 described above.
[0083] V2≥0.6V1 ensures that the filling portion 1131 within the groove 1121 has a certain volume, thereby inhibiting the growth of lithium dendrites. V2≤V1 prevents the filling portion 1131 from protruding beyond the groove 1121, thus reducing the thickness of the secondary battery 100 and minimizing its energy density.
[0084] In some embodiments, 0.9V1≤V2≤V1 and V2≥0.9V1 result in a larger volume for the filling portion 1131, thereby increasing the area of the trench wall 1121b covered by the filling portion 1131 and making the suppression effect of the filling portion 1131 on lithium dendrite growth more significant.
[0085] Referring to Figure 3, in some embodiments, V2 = V1, and the filling portion 1131 covers the entire groove wall 1121b. This allows the filling portion 1131 at the location of the groove 1121 to fill the groove 1121 flat, improving the smoothness of the surface of the first active material layer 112. The entire groove 1121 is filled with the filler 113, and the filling portion 1131 covers the entire groove wall 1121b, so that each position of the groove wall 1121b can be supported by the filling portion 1131. Compared with the groove 1121 where the filling portion 1131 is not fully filled, the suppression effect on lithium dendrites is better.
[0086] It should be noted that during the manufacturing process, when the filler 113 is coated onto the groove 1121 in the form of a filler slurry, the groove 1121 is gradually filled by the fluidity of the slurry. For a single groove 1121, when the volume of the coated slurry is less than the volume of the groove 1121, the slurry first flows gradually along the sidewall of the groove 1121, and when it flows to the bottom of the groove 1121, it gradually fills the entire groove 1121. As shown in Figure 3, the filling portion 1131 fills the entire groove 1121; as shown in Figure 6, the filling portion 1131 does not fill the entire groove 1121. It can be understood that compared to the state where the filling portion 1131 does not fill the entire groove 1121, when the filling portion 1131 fills the entire groove 1121, the possibility of forming a gap between the filling portion 1131 and the groove wall 1121b of the groove 1121 is smaller, resulting in a better effect of suppressing lithium plating.
[0087] Referring to Figure 3, in some embodiments, the filler 113 is entirely disposed within the groove 1121. The filler 113 is not disposed at the locations of the first active material layer 112 where the groove 1121 is not located. This suppresses lithium dendrite growth while minimizing the increase in the thickness of the first electrode 11, thus minimizing the reduction in the energy density of the secondary battery 100.
[0088] Referring to Figure 7, in some embodiments, the filler 113 further includes a coating portion 1132, which is disposed in the area of the first active material layer 112 facing the diaphragm 13 where the groove 1121 is not provided.
[0089] The coating 1132 can protect the first electrode 11, improve the mechanical strength of the first electrode 11, and facilitate the storage of more electrolyte and the transport of lithium ions; it can also inhibit the growth of lithium dendrites on the side of the first active material layer 112 facing the separator 13 where the groove 1121 is not provided.
[0090] In some embodiments, the coating portion 1132 and the filling portion 1131 are integrally disposed. The integrally disposed coating portion 1132 and filling portion 1131 can reduce the occurrence of separation between the coating portion 1132 and the filling portion 1131, thereby reducing the occurrence of lithium deposition in the gaps between the coating portion 1132 and the filling portion 1131, and further improving the effect of suppressing lithium dendrite growth.
[0091] Referring to Figure 7, in some embodiments, the thickness of the coating portion 1132 along the thickness direction of the first electrode 11 is h1, satisfying 0.5um≤h1≤2um. When h1≥0.5um, it can meet the requirements of improving the mechanical strength of the first electrode 11, enhancing the electrolyte storage of the first electrode 11, and suppressing lithium dendrite growth; when h1≤2um, it is not easy to make the cell too thick and reduce the energy density.
[0092] As an example, h1 can be, but is not limited to, 0.5um, 0.6um, 0.7um, 0.8um, 0.9um, 1.0um, 1.1um, 1.2um, 1.3um, 1.4um, 1.5um, 1.6um, 1.7um, 1.8um, 1.9um, or 2.0um, or other values other than those mentioned above that satisfy the range of h1.
[0093] In some embodiments, the material of filler 113 includes at least one of ceramic material and resin material.
[0094] On the one hand, ceramic and resin materials provide rigid support. When lithium dendrites extend and come into contact with these materials, the ceramic or resin material blocks their growth, thus inhibiting further growth. On the other hand, ceramic and resin materials have large pores, allowing lithium ions to pass through and reducing the impact on lithium ion transport. Furthermore, ceramic and resin materials also possess insulating properties, balancing electrolyte wetting effectiveness with the safety performance of the secondary battery.
[0095] In some embodiments, the ceramic material is selected from at least one of alumina, boehmite, titanium dioxide, magnesium oxide, calcium oxide, and zirconium oxide.
[0096] In some embodiments, the resin material is selected from at least one of polyimide (PI), polytetrafluoroethylene (PTFE), and polyvinyl butyral (PVB).
[0097] In some embodiments, the filler 113 is made of ceramic material, binder, solvent, and additives. The ceramic material includes ceramic particles, which provide rigid support and exhibit excellent thermal stability and dimensional integrity, thus maintaining support at high temperatures while ensuring lithium-ion transport in the electrolyte. The binder improves the adhesion between the filler 113 and the first active material layer 112, facilitating the curing of the filler 1131 within the groove 1121. This prevents the filler 1131 from easily detaching from the groove 1121, further inhibiting the growth of lithium dendrites within the groove 1121.
[0098] As an example, the adhesive is selected from at least one of polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) (aqueous), and polyvinylidene fluoride (PVDF), wherein polyvinylidene fluoride can increase the adhesion between the coating portion 1132 on the surface of the first electrode 11 and the diaphragm 13 and improve conductivity; the solvent can be an aqueous solvent or an oil-based solvent, the aqueous solvent including water, ethanol, glycerol and other polar organic solvents, and the oil-based solvent including acetone, N-methylpyrrolidone (NMP) and other non-polar solvents.
[0099] Referring to Figures 1 and 2, in some embodiments, two diaphragms 13 are provided, namely a first diaphragm 13a and a second diaphragm 13b. The first diaphragm 13a, the first electrode 11, the second diaphragm 13b, and the second electrode 12 are stacked sequentially to form a wound structure.
[0100] In some embodiments, the diaphragm 13 includes a base membrane, which is an insulating membrane material such as a polyethylene membrane, a polypropylene membrane, a polyester membrane, or a polyimide membrane.
[0101] The embodiments in this application also provide a method for manufacturing a secondary battery 100, including the following steps:
[0102] Filling: Filler 113 is provided in groove 1121;
[0103] Stacking: The diaphragm 13 and the second electrode 12 are stacked sequentially on the first electrode 11 along the thickness direction of the first electrode 11, with the diaphragm 13 located between the first active material layer 112 and the second electrode 12.
[0104] By providing a filler 113 in the groove 1121 of the first active material layer 112, the filler 113 can block the extension and growth of lithium dendrites in the groove 1121, thereby inhibiting lithium deposition in the groove 1121, making the separator 13 less likely to be punctured by freely growing lithium dendrites, and improving the safety performance of the electrode assembly 10.
[0105] In some embodiments, the filling step includes:
[0106] Coating: The filler slurry is coated onto the side of the first active material layer 112 facing the diaphragm 13;
[0107] Leveling: The coated filler slurry flows into the groove 1121.
[0108] By coating first and then leveling, the filler slurry can flow into multiple grooves 1121 of the first active material layer 112 simultaneously, which helps to improve the efficiency of placing the filler 113 into the grooves 1121.
[0109] In some embodiments, the filler slurry can be applied by a slit extrusion coating method, a spraying method, or a gravure coating method. The slit extrusion coating method is a process in which the filler slurry is extruded from a nozzle and applied onto the first active material layer 112 under pressure. The coating thickness is controlled by the nozzle slit width and a metering pump. Compared to spraying and gravure coating methods, slit extrusion coating provides more uniform coating, easier control of the coating amount, less risk of excessive coating thickness, and higher coating speed.
[0110] In some embodiments, the filler slurry is made to flow into the groove 1121 by vibrating the first electrode 11, so as to accelerate the flow speed of the filler slurry, improve the molding efficiency of the filler 113, and improve the flatness of the filler slurry in the groove 1121.
[0111] In some embodiments, the coated filler slurry flows entirely into the groove 1121 to form the filler portion 1131.
[0112] In other embodiments, a portion of the coated filler slurry flows into the groove 1121 to form a filler portion 1131, while another portion is located in the area of the first active material layer 112 where the groove 1121 is not provided to form a coating portion 1132. The thickness of the coating portion 1132 is adjusted by setting the weight of the filler slurry coated per unit area.
[0113] In some embodiments, the filler slurry is a slurry of ceramic material or a slurry of resin material.
[0114] In some embodiments, the filling step further includes:
[0115] Curing: Curing the filler slurry into filler 113.
[0116] As an example, the curing method can be thermal curing. For example, the first electrode 11 after being filled with filler slurry can be placed in a vacuum oven for drying to improve the curing efficiency of filler 113.
[0117] In some embodiments, the stacking step includes: stacking a plurality of second electrodes 12, a plurality of diaphragms 13 and a plurality of first electrodes 11 along the thickness direction of the first electrodes 11, wherein a diaphragm 13 is disposed between each first electrode 11 and a second electrode 12.
[0118] Please refer to Figure 8. An embodiment of this application also provides an electrical device 1000, which includes the secondary battery 100 in any of the above embodiments.
[0119] By providing a filler 113 on the first active material layer 112 of the secondary battery 100, the generation of lithium dendrites is suppressed, thereby improving the service life of the secondary battery 100 and the service life of the electrical device 1000.
[0120] In some embodiments, the electrical device 1000 may be a mobile phone, laptop computer, tablet computer, drone, power tool, electric toy, game console, video recorder, portable recorder, radio, or smartwatch, etc., which will not be listed here.
[0121] Referring to Figure 8, in some embodiments, the power device 1000 further includes a device body 200, and a secondary battery 100 is installed in the device body 200. Since the power device 1000 adopts the technical solution of the secondary battery 100 in any of the above embodiments, it has at least the beneficial effects brought about by the technical solution of any of the above embodiments of the secondary battery 100, which will not be described in detail here.
[0122] To verify the effect of filler 113 on the performance of secondary battery 100, the inventors conducted the following experiment:
[0123] The experiment includes one set of comparative examples and 16 sets of embodiments. The anode plate of the secondary battery 100 used in the comparative examples does not have a filling part 1131. The anode plate of the secondary battery 100 used in the embodiments has a filling part 1131. The configuration of the coating part 1132 in each embodiment is shown in Table 1 below. The secondary batteries 100 in different sets of embodiments differ only in the parameters listed in Table 1 below, and are the same in all other aspects.
[0124] The specific implementation of the secondary battery 100 in the embodiments and comparative examples will be described below.
[0125] The assembly process of the secondary battery 100 in the comparative example is as follows:
[0126] 1. Preparation of the cathode electrode:
[0127] The cathode active material is lithium cobalt oxide, the cathode conductive agent is acetylene black, and the cathode binder is polyvinylidene fluoride (PVDF, with a weight-average molecular weight of 5 × 10⁻⁶). 5The cathode slurry was mixed at a mass ratio of 94:3:3, with N-methylpyrrolidone (NMP) added as a solvent, and stirred under vacuum until a homogeneous cathode slurry with a solid content of 75 wt% was obtained. An 8 μm thick aluminum foil was selected as the cathode current collector, and expanding foam was adhered to a predetermined position on one surface of the aluminum foil along its thickness direction. The cathode slurry was then uniformly coated onto one surface of the aluminum foil along its thickness direction and dried at 110°C to obtain a cathode electrode with a single-sided coating of cathode active material (80 μm thick). The above steps were then repeated on the other surface of the aluminum foil along its thickness direction to obtain a cathode electrode with a double-sided coating of cathode active material. The previously adhered expanding foam was then removed, creating an empty aluminum foil area for welding the cathode tabs.
[0128] 2. Preparation of the anode sheet
[0129] Anode active materials graphite powder, silicon powder, conductive agent conductive carbon black (Super P), and binder styrene-butadiene rubber (SBR) were mixed in a weight ratio of 67.5:30:1:1.5. Deionized water was then added as a solvent to prepare an anode slurry with a solid content of 50 wt%, and the mixture was stirred thoroughly. A 5 μm thick copper foil was selected as the anode current collector. The anode slurry was uniformly coated onto one surface of the copper foil along its thickness direction and dried at 90°C to obtain a single-sided anode electrode. This completes the single-sided coating of the anode electrode. The above steps were then repeated on the other surface of the anode electrode along its thickness direction to obtain a double-sided coated anode active material layer. Next, grooves 1121 with a width of 85 μm and a depth of 10 μm were laser-etched into the double-sided anode active material layer, with a distance L of 1.3 mm between adjacent grooves 1121. Then, empty copper foil areas for welding anode tabs were laser-etched at predetermined positions on the anode electrode.
[0130] 3. Preparation of diaphragm 13
[0131] A polyethylene (PE) film with a thickness of 8 μm was used as the separator 13.
[0132] 4. Electrolyte preparation
[0133] In a dry argon atmosphere, ethylene carbonate, methyl ethyl carbonate and diethyl carbonate are mixed in a mass ratio of 30:50:20 to obtain an organic solution. Then, lithium hexafluorophosphate is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.
[0134] 5. Preparation of secondary battery 100
[0135] Al tabs are welded onto a pre-designed empty aluminum foil area for welding cathode tabs using ultrasonic welding to obtain a cathode electrode with welded cathode tabs; Ni tabs are welded onto a pre-designed empty copper foil area for welding anode tabs using ultrasonic welding to obtain an anode electrode with welded anode tabs. The prepared diaphragm 13, the cathode electrode with welded cathode tabs, the diaphragm 13, and the anode electrode with welded anode tabs are stacked in sequence and wound to obtain an electrode assembly 10. The electrode assembly 10 is placed in an aluminum-plastic film packaging bag, with both the cathode tabs and anode tabs extending from the top seal edge of the packaging bag. After dehydration at 80°C, electrolyte is injected and the bag is sealed.
[0136] The secondary battery 100 used in Comparative Example 1 and Examples 1 to 16 has a length of 78.35 mm, a width of 68.62 mm, and a thickness of 5.15 mm. The width of the anode electrode is 73.95 mm, and the length direction of the secondary battery 100 is consistent with the width direction of the anode and cathode electrodes. The groove 1121 etched on the anode electrode has a length of 73.95 mm, and the length direction of the groove 1121 is consistent with the width direction of the anode electrode. The packaging bag occupies a dimension of 4.4 mm in the length direction of the secondary battery 100.
[0137] The anode plates used in Examples 1 to 16, in addition to the steps described above, also include the filling step in the manufacturing method of the secondary battery 100 described above. The filler slurry is made of alumina material. In Examples 1 to 3 and Examples 12 to 16, only the filling part 1131 is formed through the filling step. In Examples 4 to 11, the filling part 1131 and the coating part 1132 are formed through the filling step. For details, please refer to the previous text. It will not be repeated here.
[0138] After the secondary batteries 100 in Comparative Example 1 and Examples 1-16 were prepared, the secondary batteries 100 in the group were subjected to the following tests.
[0139] The testing method is as follows:
[0140] (1) The secondary battery 100 was cyclically tested according to the following procedure: the secondary battery 100 was charged to the limit voltage of 4.26V with a maximum constant current (CC) of 2.8C, the secondary battery 100 was charged to the limit voltage of 4.3V with a maximum constant current (CC) of 2.5C, the secondary battery 100 was charged to the limit voltage of 4.45V with a maximum constant current (CC) of 2.0C, and then charged under a constant voltage condition (CV) of 4.45V until the current decreased to 1.2C, the secondary battery 100 was charged to the limit voltage of 4.5V with a maximum constant current (CC) of 1.2C, and then charged under a constant voltage condition (CV) of 4.5V until the current decreased to 1.0C, the secondary battery 100 was charged to the limit voltage of 4.515V with a maximum constant current (CC) of 1.0C, and then charged under a constant voltage condition (CV) of 4.515V until the current decreased to 0.025C.
[0141] Secondary battery 100 was charged in stages, allowed to rest for 5 minutes, then discharged at 0.7C to 3.0V, and allowed to rest for 5 minutes. This constituted one cycle. After 700 cycles at 25℃, secondary battery 100 was discharged at 0.7C to 3.0V, and then disassembled. A rectangular anode plate with a laser-etched groove 1121, 85µm wide and 1cm long, was selected as test sample 1. The lithium metal signal peak on the fully discharged anode plate of test sample 1 was detected using DSC (differential scanning calorimetry), i.e., the DSC peak intensity within the groove. The amount of lithium deposition could be calculated from the signal peak intensity. Under full discharge conditions, the lithium metal in the anode plate was irreversible lithium.
[0142] (2) Test method for lithium deposition area of the coating: The secondary battery 100 is discharged to 3V at 0.2C. The secondary battery 100 is disassembled, and a rectangular electrode with a width of 1.3mm and a length of 1cm at the same lithium deposition location is taken as the test sample 2. The signal peak of metallic lithium on the fully discharged anode electrode of the test sample 2 is detected by DSC (differential scanning calorimetry), that is, the DSC peak intensity of the coating. The amount of lithium deposition can be calculated from the signal peak intensity. Under full discharge conditions, the metallic lithium in the anode electrode is irreversible lithium.
[0143] (3) Test method for volumetric energy density: Place the secondary battery 100 in a constant temperature chamber at 25℃ and let it stand for 30 minutes to allow the secondary battery 100 to reach a constant temperature. Charge the secondary battery 100 at a constant current of 0.2C until the voltage reaches the full charge voltage, then charge it at a constant voltage of the full charge voltage until the current is 0.025C, and discharge it at 0.2C until the voltage is 3.0V. Record the discharge energy.
[0144] Volumetric energy density = discharge capacity × plateau voltage / (length of secondary battery 100 × width of secondary battery 100 × thickness of secondary battery 100). The capacity is 6500mAh, and the plateau voltage is 3.82V.
[0145] The test samples taken in Comparative Example 1 and Examples 1 to 16 were taken at the same location in different secondary batteries 100.
[0146] (4) Measurement method of volume V1 of a single groove 1121: The volume of the sample 1 to be tested is measured using an optical profilometer.
[0147] Sample preparation: First, ensure that the sample surface is clean and free of dust, grease and other impurities.
[0148] Instrument calibration: Before measurement, the optical profilometer needs to be calibrated to ensure the accuracy and repeatability of the measurement. Calibration typically includes zero-point calibration, system calibration, and standard sample calibration.
[0149] Setting parameters: Set the measurement parameters.
[0150] Sample positioning: Place the sample on the instrument's measuring stage and use a microscope or camera to position it, ensuring that the measurement area is accurate.
[0151] Data Acquisition: Upon starting the measurement program, the instrument automatically scans the sample surface and acquires surface morphology data. In white light interferometry, the instrument records interference fringes when light of different wavelengths is reflected from the sample surface; in confocal microscopy, the instrument obtains depth information of the sample surface by scanning point by point using the confocal principle.
[0152] Data Processing: After measurement, the acquired data is processed using the accompanying software to generate a three-dimensional image or two-dimensional contour map of the sample surface. The volume V1 of groove 1121 is calculated by multiplying the depth integral in the width direction by the length of groove 1121 using the software analysis.
[0153] (5) Sampling method for the sample to be tested:
[0154] Sample preparation: First, the sample is fixed onto a microscope slide. The sample is then fixed with liquid nitrogen to maintain its structural stability.
[0155] Positioning: Place the glass slide under the microscope of the laser micro-cutting system and observe the sample using a high-powered microscope to determine the area to be cut. The system is equipped with a high-resolution camera for precise positioning.
[0156] Setting parameters: Based on the sample cutting requirements, set parameters such as laser power, frequency, and scanning speed. These parameters need to be adjusted according to the sample thickness, hardness, and required cutting precision.
[0157] Cutting: Once the laser micro-cutting system is activated, the laser beam will precisely cut the sample along a preset path. Laser cutting can achieve micron-level precision.
[0158] Sample collection: After cutting, sample fragments fall into a collection container placed pre-positioned below the cutting area. The collection container is typically a microplate or a specially designed collection membrane to ensure that the cut sample is not lost.
[0159] The sampling method for the test sample is applicable to the test sample 1 in (1), the test sample 2 in (2), and the sampling when measuring the volume V1 of a single groove 1121 in (4).
[0160] After the experiment, the experimental data were compiled and obtained as shown in Table 1 below:
[0161] Table 1 Note: " / " indicates that there is no data for this experiment.
[0162] The method for measuring the volume of a single groove in Table 1 is as described in (4) above. The relationship between the volume of a single groove and the groove volume of the sample 1 to be tested is: the volume of a single groove V1 = the groove volume of the sample 1 to be tested × the length of a single groove / 1cm.
[0163] In Examples 4 to 11, the "volume energy density" is the volume energy density calculated compared to Example 3 with the addition of 10 coating layers 1132. Each turn of the wound anode sheet includes two folds, and one coating layer 1132 refers to the coating layer 1132 on one of the folds of the anode sheet on a layer of anodic active material.
[0164] By comparing the comparative examples with any one of Examples 1-16, it can be seen that the degree of lithium plating in the groove 1121 without the filling part 1131 is higher than the degree of lithium plating in the groove 1121 with the filling part 1131.
[0165] In Examples 2 to 15, V2 satisfies: 0.6V1≤V2≤V1. As can be seen from Examples 2 to 15, under these conditions, as V2 increases, that is, as the filling portion 1131 within the groove 1121 increases, the DSC peak intensity within the groove gradually decreases, and the lithium plating situation gradually improves. Compared to Example 1, when V2 is too small, the suppression of lithium plating is poor and insufficient to meet the required lithium plating effect; compared to Example 16, when V2 > V1, that is, when the filling portion 1131 protrudes from the groove 1121, although the degree of lithium plating can be improved, it leads to an increase in cell thickness, thereby reducing the energy density of the secondary battery 100.
[0166] In Examples 5 to 10, h1 satisfies: 0.5µm ≤ h1 ≤ 2µm. As can be seen from Examples 5 to 10, under these conditions, as the thickness h1 of the coating portion 1132 increases, the degree of lithium plating in the region without the groove 1121 on the anode active material layer improves, but the volumetric energy density of the secondary battery 100 increases. Compared to Example 4 where the coating portion 1132 is not provided, providing the coating portion 1132 is more beneficial for reducing lithium plating. Compared to Example 11, it can be seen that when h1 is greater than 2µm, the volumetric energy density of the secondary battery 100 is lower, significantly affecting its energy storage capacity. Therefore, satisfying 1.5µm ≤ h1 ≤ 2µm allows for reduced lithium plating without significantly impacting the volumetric energy density of the secondary battery 100.
[0167] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of this application.
Claims
1. A secondary battery, comprising an electrode assembly, characterized in that, The electrode assembly includes a first electrode, a second electrode, and a separator. The first electrode includes a first current collector and a first active material layer, the first active material layer being disposed on at least one surface of the first current collector along its thickness direction. The second electrode includes a second current collector and a second active material layer, the second active material layer being disposed on at least one surface of the second current collector along its thickness direction. The separator is disposed between the first active material layer and the second active material layer. The first active material layer has a groove, the groove including an opening and a wall. Along the thickness direction of the first electrode, the opening faces the separator, and the other side of the separator facing the opening corresponds to the second active material layer. The first electrode also includes a filler, the filler including a filling portion located in the groove, the filling portion covering at least a portion of the groove wall.
2. The secondary battery as described in claim 1, characterized in that, The filler material includes at least one of ceramic materials and resin materials.
3. The secondary battery as described in claim 2, characterized in that, The ceramic material is selected from at least one of alumina, boehmite, titanium dioxide, magnesium oxide, calcium oxide, and zirconium oxide.
4. The secondary battery as described in claim 2, characterized in that, The resin material is selected from at least one of polyimide, polytetrafluoroethylene, and polyvinyl butyral.
5. The secondary battery as described in claim 2, characterized in that, The filler material also includes an adhesive.
6. The secondary battery as described in claim 1, characterized in that, The internal space volume of the groove is V1, and the volume of the filling part is V2, satisfying: 0.6V1≤V2≤V1.
7. The secondary battery as described in claim 6, characterized in that, 0.9V1≤V2≤V1.
8. The secondary battery as described in any one of claims 1 to 7, characterized in that, The filler is entirely disposed within the groove.
9. The secondary battery as described in any one of claims 1 to 7, characterized in that, The filler also includes a coating portion, which is disposed in the area on the side of the first active material layer facing the diaphragm where the groove is not provided.
10. The secondary battery as described in claim 9, characterized in that, The coating portion and the filling portion are integrally formed.
11. The secondary battery as described in claim 9, characterized in that, Along the thickness direction of the first electrode, the thickness of the coating portion is h1, which satisfies 0.5um≤h1≤2um.
12. The secondary battery as described in claim 1, characterized in that, Along the thickness direction of the first electrode, the thickness of the first active material layer at the location where the groove is not formed is H1, and the depth of the groove is H2, satisfying: H1 / 4≤H2≤H1 / 2.
13. The secondary battery as described in claim 1, characterized in that, The first electrode is the anode electrode.
14. A method for manufacturing a secondary battery, used to manufacture a secondary battery as described in any one of claims 1 to 13, characterized in that, Includes the following steps: Filling: The filler is provided in the groove; Stacking: The separator and the second electrode are stacked sequentially on the first electrode along the thickness direction of the first electrode, with the separator located between the first active material layer and the second electrode.
15. The method for manufacturing a secondary battery as described in claim 14, characterized in that, The filling step includes: Coating: Applying the filler slurry to the side of the first active material layer facing the diaphragm; Leveling: The coated filler slurry flows into the groove.
16. The method for manufacturing a secondary battery as described in claim 15, characterized in that, The filling step further includes: Curing: Curing the filler slurry into the filler.
17. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 1 to 13.