Secondary battery and electric device
By designing stepped walls and fillers in the secondary battery casing to support the electrodes, the problem of insufficient support for the electrodes at the stepped positions is solved, which improves the interface yield and energy density after formation and reduces the risk of lithium plating.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NINGDE AMPEREX TECHNOLOGY LTD
- Filing Date
- 2024-12-03
- Publication Date
- 2026-06-11
AI Technical Summary
In the formation process of irregularly shaped secondary batteries, the electrodes lack support at the step positions, resulting in low interface yield and high risk of lithium plating.
Design a secondary battery casing structure including stepped walls and fillers. The fillers provide support for the electrode assembly, ensuring consistent pressure on the electrodes during the formation process and improving the adhesion between the positive electrode and the separator, as well as between the negative electrode and the separator.
It improves the interface yield of electrode components after formation, reduces the possibility of lithium plating in secondary batteries during long cycles, makes full use of the internal space of the casing, and improves energy density.
Smart Images
Figure CN2024136457_11062026_PF_FP_ABST
Abstract
Description
Secondary batteries and electrical equipment Technical Field
[0001] This application relates to the field of energy storage technology, and in particular to a secondary battery and electrical equipment. Background Technology
[0002] Currently, to adapt to different application scenarios, secondary batteries are processed into different shapes, resulting in irregularly shaped secondary batteries. The casing of irregularly shaped secondary batteries has different depths in different areas, forming steps in the transition regions at different depths. The electrodes lack support at these step locations. During the secondary battery formation process, the portion of the electrode corresponding to the step region is not sufficiently compressed, resulting in low interface yield and a high risk of lithium plating after formation. Summary of the Invention
[0003] In view of the above situation, it is necessary to provide a secondary battery to improve the pressure uniformity of the electrode assembly during the formation process, thereby improving the interface yield of the electrode assembly after formation.
[0004] A first aspect of this application provides a secondary battery, which includes a casing, an electrode assembly, and a first filler. The casing includes a first wall, a second wall, a third wall, a fourth wall, and a surrounding wall. The first and second walls are disposed opposite each other along a first direction, and the first and third walls are disposed opposite each other along the first direction. The third wall is located on the side of the second wall along a second direction. The fourth wall connects the second and third walls. The surrounding wall connects the first, second, third, and fourth walls and, together with the first, second, third, and fourth walls, encloses a first space. Along the first direction, the distance between the first and second walls is less than the distance between the first and third walls. The electrode assembly is housed in the first space and includes a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate includes a first positive electrode plate and a second positive electrode plate. Along the second direction, the length of the first positive electrode plate is greater than the length of the second positive electrode plate. The negative electrode plate includes a first negative electrode plate and a second negative electrode plate. Along the second direction, the length of the first negative electrode plate is greater than the length of the second negative electrode plate. A first portion of an electrode assembly is formed by alternately stacking multiple first positive electrode sheets, multiple separators, and multiple first negative electrode sheets along a first direction. A second portion of the electrode assembly is formed by alternately stacking multiple second positive electrode sheets, multiple separators, and multiple second negative electrode sheets along the first direction. The first and second portions are stacked along the first direction, with the second portion located on the side of the first portion facing the third wall. The projection of the second portion along the first direction lies within the area of the third wall. The thickness of the second portion along the first direction is H1, and the distance between the second and third walls along the first direction is H2, where H1 > H2. A first gap is formed between the first portion and the second wall. The first direction is the thickness direction of the positive electrode sheet, and the second direction is perpendicular to the first direction. A first filler is housed in a first space, with at least a portion of the first filler located in the first gap.
[0005] In this secondary battery, the second, third, and fourth walls together form a stepped structure to adapt to the requirements of the application scenario. The shape of the electrode assembly adapts to the shape of the casing, which helps to make full use of the internal space of the casing and improve the energy density of the secondary battery. Furthermore, by setting the first filler, support can be provided for the first part of the electrode assembly to improve the pressure resistance of the first part during the formation process, thereby improving the pressure uniformity of the electrode assembly during the formation process. In this way, on the one hand, the adhesion between the positive electrode and the separator, and between the negative electrode and the separator, is improved, and on the other hand, the interface yield of the electrode assembly after formation is improved, reducing the possibility of lithium plating in the secondary battery during long-term cycling.
[0006] In one optional embodiment of this application, the first filler is separated from the second portion. This helps to reduce the possibility of the first filler compressing the second portion, thereby maintaining the stacked state of the positive electrode, separator, and negative electrode in the second portion.
[0007] In one optional embodiment of this application, the thickness of the first filler along the first direction is H3, where 0.1(H1-H2)≤H3≤(H1-H2). Setting H3≥0.1(H1-H2) prevents the thickness of the first filler from being too small, which is beneficial for improving the support effect of the first filler on the first part, improving the quality of the SEI film formed in the first part of the electrode assembly during the formation process, and reducing the possibility of lithium plating in the secondary battery during long cycles. Setting H3≤(H1-H2) prevents the thickness of the first filler from being too large, which is beneficial for saving material costs while taking into account the quality of film formation.
[0008] In an optional embodiment of this application, 0.7(H1-H2)≤H3≤(H1-H2). Setting H3≥0.7(H1-H2) is beneficial to further improve the supporting effect of the first filler on the first part, improve the quality of the SEI film formed in the first part of the electrode assembly during the formation process, and reduce the possibility of lithium plating in the secondary battery during long-term cycling.
[0009] In an optional embodiment of this application, the projection of the second wall along the first direction is separate from the projection of the third wall along the first direction. The first portion has a first end, which is the end of the first portion facing away from the second portion along the second direction. The distance from the first end along the second direction to the third wall is W1, and the distance from the second wall along the second direction to the third wall is W2. The length of the first filler is W, where W1-W2≤W≤W1. Setting W≥W1-W2, the first filler extends above the fourth wall along the first direction, providing support for the first portion corresponding to the housing step position, improving the quality of the SEI film formed in the formation process of the first portion of the electrode assembly, and reducing the possibility of lithium plating in the secondary battery during long cycles. Setting W≤W1 prevents the width of the first filler from becoming too large, which helps save material costs.
[0010] In one optional embodiment of this application, the length of the electrode assembly along the third direction is L1, and the length of the first filler along the third direction is L. The third direction is perpendicular to the first and second directions, and 0.9L1≤L≤L1. Setting L≥0.9L1 prevents the dimension of the first filler along the third direction from being too small, which is beneficial to further increase the dimension of the portion of the electrode assembly supported by the first filler along the third direction, thereby improving the supporting effect of the first filler on the electrode assembly. Setting L≤L1 prevents the dimension of the first filler along the third direction from being too large, which is beneficial to reduce the possibility of the first filler encroaching on the internal space of the housing.
[0011] In an optional embodiment of this application, the second portion is separate from the fourth wall, and the secondary battery includes a second filler. Along a first direction, the second filler is located between the first portion and the third wall; along a second direction, the second filler is located between the fourth wall and the second portion.
[0012] In one optional embodiment of this application, the first filler is a hot-melt pressure-sensitive adhesive or an expanding adhesive. By providing a second filler, support can be provided for the electrode assembly at the step of the housing, thereby increasing the pressure resistance of the electrode assembly during the formation process, improving the interface yield after formation, and reducing the possibility of lithium plating in the secondary battery during long cycles.
[0013] In one optional embodiment of this application, the dimension of the first positive electrode along the second direction is D1, and the dimension of the second positive electrode is D2, where 0.1D1≤D2≤0.9D1.
[0014] In one optional embodiment of this application, the dimension of the first negative electrode sheet along the second direction is D3, and the dimension of the second negative electrode sheet is D4, where 0.1D3≤D4≤0.9D3.
[0015] A second aspect of the embodiments of this application provides an electrical device that includes a secondary battery as described in any of the foregoing embodiments. Attached Figure Description
[0016] Figure 1 is a schematic diagram of the structure of a secondary battery in one embodiment of this application.
[0017] Figure 2 is a schematic diagram of the cross-sectional structure at point II-II in Figure 1.
[0018] Figure 3 is a partial structural schematic diagram of the secondary battery in one embodiment of this application.
[0019] Figure 4 is a cross-sectional structural diagram of a secondary battery in one embodiment of this application.
[0020] Figure 5 is a schematic diagram of the structure of an electrical device in one embodiment of this application.
[0021] Explanation of main component symbols
[0022] Secondary battery 100
[0023] Casing 10
[0024] First Wall 11
[0025] Second Wall 12
[0026] Third Wall 13
[0027] Fourth Wall 14
[0028] Wall 15
[0029] First Space 16
[0030] First gap 16a
[0031] Electrode assembly 20
[0032] Part 1 201
[0033] First end 201a
[0034] Part Two 202
[0035] Positive electrode 21
[0036] Positive current collector 21a
[0037] Positive electrode active material layer 21b
[0038] First positive electrode plate 211
[0039] Second positive electrode plate 212
[0040] Negative electrode 22
[0041] Negative current collector 22a
[0042] Negative electrode active material layer 22b
[0043] First negative electrode 221
[0044] Second negative electrode 222
[0045] Separator 23
[0046] First filler 30
[0047] Second filler 40
[0048] 1000 electrical appliances
[0049] First direction X
[0050] Second direction Y
[0051] Third direction Z
[0052] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation
[0053] 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.
[0054] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.
[0055] 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.
[0056] 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.
[0057] In the description of the embodiments of this application, the term "perpendicular" is used to describe the ideal state between two components. In actual production or use, two components may exist in a state that is approximately perpendicular. The two components described as "perpendicular" may not be absolutely straight lines or planes, but may be approximately straight lines or planes. From a macroscopic perspective, if the overall extension direction is a straight line or plane, the component can be considered as a "straight line" or "plane".
[0058] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. Where there is no conflict, the various embodiments in this application can be combined with each other.
[0059] It should be noted that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative examples and should not constitute any limitation on this application.
[0060] Embodiments of this application provide a secondary battery, which includes a casing, an electrode assembly, and a first filler. The casing includes a first wall, a second wall, a third wall, a fourth wall, and a surrounding wall. The first and second walls are disposed opposite each other along a first direction, and the first and third walls are disposed opposite each other along the first direction. The third wall is located on the side of the second wall along a second direction. The fourth wall connects the second and third walls. The surrounding wall connects the first, second, third, and fourth walls and, together with the first, second, third, and fourth walls, encloses a first space. Along the first direction, the distance between the first and second walls is less than the distance between the first and third walls. The electrode assembly is housed in the first space and includes a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate includes a first positive electrode plate and a second positive electrode plate. Along the second direction, the length of the first positive electrode plate is greater than the length of the second positive electrode plate. The negative electrode plate includes a first negative electrode plate and a second negative electrode plate. Along the second direction, the length of the first negative electrode plate is greater than the length of the second negative electrode plate. A first portion of an electrode assembly is formed by alternately stacking multiple first positive electrode sheets, multiple separators, and multiple first negative electrode sheets along a first direction. A second portion of the electrode assembly is formed by alternately stacking multiple second positive electrode sheets, multiple separators, and multiple second negative electrode sheets along the first direction. The first and second portions are stacked along the first direction, with the second portion located on the side of the first portion facing the third wall. The projection of the second portion along the first direction lies within the area of the third wall. The thickness of the second portion along the first direction is H1, and the distance between the second and third walls along the first direction is H2, where H1 > H2. A first gap is formed between the first portion and the second wall. The first direction is the thickness direction of the positive electrode sheet, and the second direction is perpendicular to the first direction. A first filler is housed in a first space, with at least a portion of the first filler located in the first gap.
[0061] In this secondary battery, the second, third, and fourth walls together form a stepped structure to adapt to the requirements of the application scenario. The shape of the electrode assembly adapts to the shape of the casing, which helps to make full use of the internal space of the casing and improve the energy density of the secondary battery. Furthermore, by setting the first filler, support can be provided for the first part of the electrode assembly to improve the pressure resistance of the first part during the formation process, thereby improving the pressure uniformity of the electrode assembly during the formation process. In this way, on the one hand, the adhesion between the positive electrode and the separator, and between the negative electrode and the separator, is improved, and on the other hand, the interface yield of the electrode assembly after formation is improved, reducing the possibility of lithium plating in the secondary battery during long-term cycling.
[0062] The embodiments of this application will be further described below with reference to the accompanying drawings. For ease of explanation, in the following text, the thickness direction of the positive electrode sheet of the secondary battery is taken as the first direction X, and the first direction X, the second direction Y, and the third direction Z are perpendicular to each other.
[0063] As shown in Figures 1 and 2, an embodiment of this application provides a secondary battery 100, which includes a housing 10 and an electrode assembly 20. The housing 10 has a first space 16, and the electrode assembly 20 is housed in the first space 16.
[0064] In some embodiments, the housing 10 is a rigid outer shell, such as a plastic shell, or a metal shell including at least one of steel alloy, aluminum alloy, and copper alloy.
[0065] In some embodiments, as shown in FIG2, the electrode assembly 20 includes a positive electrode 21, a negative electrode 22, and a separator 23.
[0066] In some embodiments, as shown in FIG2, the positive electrode 21 includes a positive current collector 21a and a positive active material layer 21b, wherein the positive active material layer 21b is disposed on at least one surface of the positive current collector 21a along the thickness direction of the positive electrode 21.
[0067] In some embodiments, the positive current collector 21a is a metal layer. As an example, the positive current collector 21a may be a metal layer including at least one of aluminum, nickel, tantalum, and titanium, such as aluminum foil.
[0068] In some embodiments, the positive electrode active material includes 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.
[0069] In some embodiments, as shown in FIG2, the negative electrode 22 includes a negative electrode current collector 22a and a negative electrode active material layer 22b, wherein the negative electrode active material layer 22b is disposed on at least one surface of the negative electrode current collector 22a along the thickness direction of the negative electrode 22.
[0070] In some embodiments, the negative electrode current collector 22a is a metal layer. The negative electrode current collector 22a may be a metal layer including at least one of copper, nickel, tantalum, and titanium, such as copper foil.
[0071] In some embodiments, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen materials, and silicon-carbon materials.
[0072] In some embodiments, the separator 23 is an insulating film material such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film.
[0073] In some embodiments, the secondary battery 100 further includes an electrolyte contained in a first space 16.
[0074] In some embodiments, the electrolyte comprises an electrolyte salt. The electrolyte salt comprises at least one of an organic lithium salt or an inorganic lithium salt.
[0075] In some embodiments, the electrolyte salt includes 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).
[0076] In some embodiments, as shown in Figures 1 and 2, the housing 10 includes a first wall 11, a second wall 12, a third wall 13, a fourth wall 14, and a surrounding wall 15. The first wall 11 and the second wall 12 are arranged opposite each other along a first direction X, and the first wall 11 and the third wall 13 are also arranged opposite each other along the first direction X. The third wall 13 is located on the side of the second wall 12 along a second direction Y. The fourth wall 14 connects the second wall 12 and the third wall 13. The surrounding wall 15 connects the first wall 11, the second wall 12, the third wall 13, and the fourth wall 14, and together with the first wall 11, the second wall 12, the third wall 13, and the fourth wall 14, it encloses a first space 16. Along the first direction X, the distance between the first wall 11 and the second wall 12 is less than the distance between the first wall 11 and the third wall 13. Thus, the second wall 12, the third wall 13, and the fourth wall 14 together form a stepped structure to adapt to the needs of the application scenario.
[0077] In some embodiments, as shown in Figures 1 and 2, the positive electrode 21 includes a first positive electrode 211 and a second positive electrode 212. Along the second direction Y, the size of the first positive electrode 211 is larger than the size of the second positive electrode 212. The negative electrode 22 includes a first negative electrode 221 and a second negative electrode 222. Along the second direction Y, the size of the first negative electrode 221 is larger than the size of the second negative electrode 222. A plurality of first positive electrode 211, a plurality of separators 23, and a plurality of first negative electrode 221 are alternately stacked along the first direction X to form a first portion 201 of the electrode assembly 20; a plurality of second positive electrode 212, a plurality of separators 23, and a plurality of second negative electrode 222 are alternately stacked along the first direction X to form a second portion 202 of the electrode assembly 20. The first portion 201 and the second portion 202 are stacked along the first direction X, and the second portion 202 is located on the side of the first portion 201 facing the third wall 13, and the projection of the second portion 202 along the first direction X is within the range of the third wall 13. Thus, the shape of the electrode assembly 20 is adapted to the shape of the housing 10, which helps to make full use of the internal space of the housing 10 and improve the energy density of the secondary battery 100.
[0078] Figure 3 shows a schematic diagram of the secondary battery 100 when viewed along the first direction X after omitting the second wall 12, the third wall 13 and the fourth wall 14.
[0079] In some embodiments, as shown in FIG3, the first positive electrode 211 has a dimension of D1 along the second direction Y, and the second positive electrode 212 has a dimension of D2, where 0.1D1≤D2≤0.9D1.
[0080] In some embodiments, as shown in FIG3, the first negative electrode 221 has a dimension of D3 along the second direction Y, and the second negative electrode 222 has a dimension of D4, where 0.1D3≤D4≤0.9D3.
[0081] In some embodiments, as shown in FIG2, the thickness of the second portion 202 along the first direction X is H1, the distance between the second wall 12 and the third wall 13 along the first direction X is H2, H1 > H2, and a first gap 16a is formed between the first portion 201 and the second wall 12. The secondary battery 100 also includes a first filler 30, the first portion 201 is received in the first space 16, and at least a portion of the first filler 30 is located in the first gap 16a.
[0082] It should be noted that the distance H2 between the second wall 12 and the third wall 13 along the first direction X is the distance between the surface of the second wall 12 located inside the housing 10 and the surface of the third wall 13 located inside the housing 10. When measuring the thickness H1 of the second part 202 along the first direction X, the second part 202 can be removed from the electrode assembly 20, and the distance between the surfaces of the electrode plates at both ends of the second part 202 along the first direction X can be measured using a micrometer. When measuring the distance between the second wall 12 and the third wall 13, the distance between the first wall 11 and the third wall 13 along the first direction X can be measured using a micrometer, and then the distance between the first wall 11 and the second wall 12 along the first direction X can be measured. Subtracting the two measurements yields the distance between the second wall 12 and the third wall 13 along the first direction X.
[0083] In this secondary battery 100, by providing the first filler 30, support can be provided for the first portion 201 of the electrode assembly 20, thereby increasing the pressure resistance of the first portion 201 during the formation process and improving the pressure uniformity of the electrode assembly 20 during the formation process. This, on the one hand, improves the adhesion between the positive electrode 21 and the separator 23, and between the negative electrode 22 and the separator 23; on the other hand, it improves the interface yield of the electrode assembly 20 after formation and reduces the possibility of lithium plating in the secondary battery 100 during long-term cycling.
[0084] In some embodiments, as shown in FIG2, the first filler 30 is separated from the second portion 202. This helps to reduce the possibility that the first filler 30 may compress the second portion 202, so as to maintain the stacked state of the positive electrode 21, the separator 23 and the negative electrode 22 in the second portion 202.
[0085] In some embodiments, as shown in FIG2, the thickness of the first filler 30 along the first direction X is H3, 0.1(H1-H2)≤H3≤(H1-H2). Setting H3≥0.1(H1-H2) prevents the thickness of the first filler 30 from being too small, which is beneficial to improving the support effect of the first filler 30 on the first part 201, improving the quality of the SEI film formed by the first part 201 of the electrode assembly 20 in the formation process, and reducing the possibility of lithium plating in the secondary battery 100 during long-term cycling. Setting H3≤(H1-H2) prevents the thickness of the first filler 30 from being too large, which is beneficial to saving material costs while taking into account the quality of film formation.
[0086] In some embodiments, 0.7(H1-H2)≤H3≤(H1-H2). Setting H3≥0.7(H1-H2) is beneficial to further improve the support effect of the first filler 30 on the first part 201, improve the quality of the SEI film formed in the first part 201 of the electrode assembly 20 during the formation process, and reduce the possibility of lithium plating in the secondary battery 100 during long-term cycling.
[0087] In some embodiments, as shown in FIG2, the projection of the second wall 12 along the first direction X is separate from the projection of the third wall 13 along the first direction X. The first portion 201 has a first end 201a, which is the end of the first portion 201 along the second direction Y that is away from the second portion 202. The distance from the first end 201a along the second direction Y to the third wall 13 is W1, the distance from the second wall 12 along the second direction Y to the third wall 13 is W2, and the length of the first filler 30 is W, where W1-W2≤W≤W1. Setting W≥W1-W2, the first filler 30 extends above the fourth wall 14 along the first direction X, which can provide support for the first portion 201 corresponding to the step position of the housing 10, improve the quality of the SEI film formed by the first portion 201 of the electrode assembly 20 in the formation process, and reduce the possibility of lithium plating in the secondary battery 100 during long cycles. Setting W≤W1, the width of the first filler 30 is not too large, which helps to save material costs.
[0088] In some embodiments, as shown in FIG3, the length of the electrode assembly 20 along the third direction Z is L1, and the length of the first filler 30 along the third direction Z is L, where 0.9L1≤L≤L1. Setting L≥0.9L1 prevents the dimension of the first filler 30 along the third direction Z from being too small, which is beneficial to further increase the dimension of the portion of the electrode assembly 20 supported by the first filler 30 along the third direction Z, thereby improving the support effect of the first filler 30 on the electrode assembly 20. Setting L≤L1 prevents the dimension of the first filler 30 along the third direction Z from being too large, which is beneficial to reduce the possibility of the first filler 30 encroaching on the internal space of the housing 10.
[0089] In some embodiments, the first filler 30 is a hot melt pressure-sensitive adhesive or an expanding adhesive.
[0090] In some embodiments, the hot-melt pressure-sensitive adhesive includes a first adhesive layer, a first substrate layer, and a second adhesive layer. The first adhesive layer bonds the housing 10 to the first substrate layer, and the second adhesive layer bonds the electrode assembly 20 to the first substrate layer. Thus, the first filler 30 provides support for the electrode assembly 20 while also bonding the electrode assembly 20 to the housing 10, thereby improving the stability of the electrode assembly 20 within the housing 10.
[0091] In some embodiments, the material of the first adhesive layer includes styrene-isoprene-styrene block copolymer; the material of the first substrate layer includes at least one of polyethylene terephthalate, polyimide, or polypropylene; and the material of the second adhesive layer includes at least one of polymethyl methacrylate (PMMA, commonly known as acrylic), polypropylene (PP), polyethylene (PE), or polyamide.
[0092] In some embodiments, the expanding adhesive is a liquid-absorbing expanding adhesive or a heat-expanding adhesive.
[0093] In some embodiments, the liquid-absorbing and expanding adhesive includes a liquid-absorbing and expanding material that expands after absorbing liquid, thereby providing support for the electrode assembly 20.
[0094] In some embodiments, the liquid-absorbing and swelling adhesive includes a second substrate layer and a third adhesive layer disposed on the second substrate layer. The liquid-absorbing and swelling material can be added to the second substrate layer or to the third adhesive layer. Of course, the liquid-absorbing and swelling material can also be added to both the second substrate layer and the third adhesive layer.
[0095] In some embodiments, the liquid-absorbing and swelling material includes at least one of polycaprolactam, sodium polyacrylate, and lithium polyacrylate. Polymer materials such as polycaprolactam, sodium polyacrylate, and lithium polyacrylate utilize the polyanionic properties within their crystal structures to absorb small-molecule solvents into the crystal structure. By adding the aforementioned polymer material to the liquid-absorbing and swelling adhesive paper, when electrolyte is injected, small-molecule solvents such as ethylene carbonate (EC) can be absorbed by the polymer material. The polymer expands in volume after absorbing the liquid, thus filling the gap between the electrode assembly 20 and the housing 10.
[0096] In some embodiments, the heat-expanding adhesive includes a heat-expanding material that expands when heated, thereby providing support for the electrode assembly 20.
[0097] In some embodiments, the heat-expanding adhesive paper includes a third substrate layer and a fourth adhesive layer disposed on the third substrate layer. The heat-expanding material can be added to the third substrate layer or to the fourth adhesive layer. Of course, the heat-expanding material can also be added to both the third substrate layer and the fourth adhesive layer.
[0098] In some embodiments, the thermal expansion material may be at least one of polycaprolactam, ethylene-ethyl acrylate, and cellulose acetate.
[0099] In some embodiments, as shown in FIG4, the second portion 202 is separate from the fourth wall 14, and the secondary battery 100 includes a second filler 40; along the first direction X, the second filler 40 is located between the first portion 201 and the third wall 13, and along the second direction Y, the second filler 40 is located between the fourth wall 14 and the second portion 202. By providing the second filler 40, support can be provided for the electrode assembly 20 at the step of the housing 10, thereby improving the pressure resistance of the electrode assembly 20 during the formation process, improving the interface yield after formation, and reducing the possibility of lithium plating in the secondary battery 100 during long-term cycling.
[0100] In some embodiments, the second filler 40 is a hot melt pressure-sensitive adhesive or an expanding adhesive.
[0101] As shown in Figure 5, an embodiment of this application also provides an electrical device 1000, including a secondary battery 100 as described in any of the foregoing embodiments.
[0102] In some embodiments, the electrical device 1000 includes, but is not limited to, mobile phones, laptops, electric toys, power tools, and electronic cigarettes.
[0103] To verify the effect of the technical solution provided in the embodiments of this application on the pressure resistance of the secondary battery 100 during the formation process, the inventors conducted an experimental investigation. The experiment included one set of comparative examples and 10 sets of specific examples, each set of comparative examples and each set of specific examples including 10 secondary batteries 100.
[0104] The preparation process of the secondary battery 100 in Example 1 includes the following steps:
[0105] (1) Preparation of positive electrode 21: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), CNTs (carbon nanotubes), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:0.5:0.5:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode active material with a solid content of 75 wt%, which was then stirred evenly for later use. A 10 μm thick aluminum foil was used as the positive electrode current collector 21a. The above active material was uniformly coated on one surface of the positive electrode current collector 21a along its thickness direction using a slit coater, and then dried at 90°C to obtain a positive electrode 21 with a single-sided coating of positive electrode active material. At this time, the thickness of the positive electrode active material layer 21b along the thickness direction of the positive electrode current collector 21a was 50 μm. The coating process is then repeated on the other surface of the positive current collector 21a along its thickness direction to obtain a positive electrode sheet 21 coated with a positive active material layer 21b on both sides. The coated positive electrode sheet 21 is then cold-pressed, resulting in a positive active material layer 21b thickness of 35 μm. The area of the positive current collector 21a not covered by the positive active material layer 21b is the empty foil area, which is cut to obtain the positive electrode tab. Multiple positive electrode sheets 21 are fabricated through the aforementioned steps, a portion of which is the first positive electrode sheet 211, and the remainder is the second positive electrode sheet 212. Two of the first positive electrode sheets 211 have a positive active material layer 21b coated only on one side of the positive current collector 21a, while the rest have a positive active material layer 21b coated on both sides of the positive current collector 21a; two of the second positive electrode sheets 212 have a positive active material layer 21b coated only on one side of the positive current collector 21a, while the rest have a positive active material layer 21b coated on both sides of the positive current collector 21a.
[0106] (2) Preparation of negative electrode 22: Artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), and CMC (sodium carboxymethyl cellulose) were mixed in a weight ratio of 97:0.5:1.3:1.2. Deionized water was added as a solvent to prepare a negative electrode active material with a weight percentage of 50 wt%, and the mixture was stirred evenly for later use. A copper foil with a thickness of 10 μm was used as the negative electrode current collector 22a. The above negative electrode active material was uniformly coated onto one surface of the negative electrode current collector 22a along its thickness direction using a slot coater, and then dried at 110°C to obtain a negative electrode 22 with a single-sided coating of negative electrode active material layer 22b. At this time, the thickness of the negative electrode active material layer 22b along the thickness direction of the negative electrode current collector 22a was 55 μm. The above steps were then repeated on the other surface of the negative electrode current collector 22a along its thickness direction to obtain a negative electrode 22 with negative electrode active material layers 22b coated on both sides. The coated negative electrode sheet 22 is then cold-pressed, resulting in a negative electrode active material layer 22b thickness of 45 μm. The area of the negative electrode current collector 22a not covered by the negative electrode active material layer 22b is the empty foil area, which is then cut to obtain the negative electrode tab. Multiple negative electrode sheets 22 are fabricated through the aforementioned steps, some of which are first negative electrode sheets 221, and the remainder are second negative electrode sheets 222. Two of the first negative electrode sheets 221 have the negative electrode active material layer 22b coated only on one side of the negative electrode current collector 22a, while the rest have the negative electrode active material layer 22b coated on both sides of the negative electrode current collector 22a. Similarly, two of the second negative electrode sheets 222 have the negative electrode active material layer 22b coated only on one side of the negative electrode current collector 22a, while the rest have the negative electrode active material layer 22b coated on both sides of the negative electrode current collector 22a. The dimensions of the first negative electrode 221 in the second direction Y and the third direction Z are both larger than those of the first positive electrode 211, and the dimensions of the second negative electrode 222 in the second direction Y and the third direction Z are both larger than those of the second positive electrode 212.
[0107] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.
[0108] (4) Preparation of the isolation membrane 23: A 7 μm thick polyethylene porous polymer film was used as the isolation membrane 23.
[0109] (5) Fabrication of electrode assembly 20: A first part 201 of electrode assembly 20 is obtained by alternately stacking a first positive electrode 211, a separator 23, and a first negative electrode 221 along a first direction X. The two outermost electrodes of the first part 201 along the first direction X are both first positive electrode 211 with a positive active material layer 21b only on one side of the positive current collector 21a. A second part 202 of electrode assembly 20 is obtained by alternately stacking a second positive electrode 212, a separator 23, and a second negative electrode 222 along the first direction X. The two outermost electrodes of the second part 202 along the first direction X are both second positive electrode 212 with a positive active material layer 21b only on one side of the positive current collector 21a. The first part 201 and the second part 202 are stacked along the first direction X and separated by the separator 23. After the first part 201 and the second part 202 overlap, one edge of the first negative electrode 221 along the second direction Y and one edge of the second negative electrode 222 along the second direction Y are aligned with each other in the first direction Z (ignoring manufacturing errors). Since the size of the first negative electrode 221 in the second direction Y is larger than that of the first positive electrode 211, the size of the first part 201 in the second direction Y is determined by the size of the first negative electrode 221; since the size of the second negative electrode 222 in the second direction Y is larger than that of the second positive electrode 212, the size of the second part 202 in the second direction Y is determined by the second negative electrode 222.
[0110] (6) Assembly of secondary battery 100: Take a first filler 30, put the first filler 30 and electrode assembly 20 into the steel shell 10, cover the surface of electrode assembly 20 facing the first wall 11 with pressure-sensitive test paper, and after the processes of injecting electrolyte, encapsulation, standing, hot pressing formation, and shaping, secondary battery 100 is obtained.
[0111] The preparation process of the secondary battery 100 in Comparative Example 1 is basically the same as that in Example 1. The difference is that the secondary battery 100 in Comparative Example 1 does not have a first filler 30.
[0112] The preparation process of the secondary battery 100 in Examples 2-10 is basically the same as that in Example 1. The difference is that the size of the first filler 30 of the secondary battery 100 in Examples 2-10 is different from that in Example 1.
[0113] After the secondary batteries 100 in Comparative Example 1 and Examples 2-10 were prepared, they were pressurized to a pressure of 1.7 MPa. The area of the electrode assembly 20 facing the first wall 11 under this pressure, where the pressure exceeded 1.2 MPa, was observed. Specifically, after pressurization, the secondary battery 100 was disassembled, and the area of the color-developing region of the pressure-sensitive test paper was observed. The ratio of the color-developing region area to the area of the corresponding first part 201 of the pressure-sensitive test paper extending beyond the second part 202 was calculated, and the average percentage of the color-developing region of the pressure-sensitive test paper of the 10 secondary batteries 100 in the same group was calculated. The area of the corresponding first part 201 of the pressure-sensitive test paper extending beyond the second part 202 was calculated by multiplying the dimension of the first negative electrode 221 extending beyond the second negative electrode 222 along the second direction Y by the dimension of the first negative electrode 221 along the third direction Z to obtain the area value.
[0114] In comparative examples and Examples 1-10, the secondary battery 100 has the following dimensions: H1 = 2.98 mm; H2 = 2.25 mm; 0.05(H1-H2) = 0.037 mm; 0.1(H1-H2) = 0.073 mm; 0.7(H1-H2) = 0.51 mm; H1-H2 = 0.73 mm; W1 = 13.11 mm; W2 = 0.77 mm; W1-W2 = 12.34 mm; L1 = 73.65 mm; 0.9L1 = 66.29 mm.
[0115] After the experiment, the results were recorded in Table 1.
[0116] Table 1
[0117] Note: In the table, " / " indicates that the data is not present.
[0118] As shown in Table 1, the average area ratio of the color-developing region of the pressure-sensitive test paper in the secondary batteries 100 of Examples 1-10 is significantly higher than that in Comparative Example 1 due to the inclusion of the first filler 30. Therefore, in the embodiments of this application, by incorporating the first filler 30 in the secondary battery 100, support can be provided for the first part 201 of the electrode assembly 20, improving the pressure uniformity of the electrode assembly 20 during the formation process. This, in turn, helps to improve the interface yield of the electrode assembly 20 after formation and reduces the possibility of lithium plating in the secondary battery 100 during long-term cycling.
[0119] In Examples 2-4, the secondary battery 100 satisfies 0.1(H1-H2)≤H3≤(H1-H2). Compared to Example 1, the average area ratio of the color-developing region of the pressure-sensitive region in Examples 2-4 is higher than that in Example 1. It is evident that setting H3≥0.1(H1-H2) prevents the thickness of the first filler 30 from being too small, which is beneficial for improving the support effect of the first filler 30 on the first part 201, improving the quality of the SEI film formed in the first part 201 of the electrode assembly 20 during the formation process, and reducing the possibility of lithium plating in the secondary battery 100 during long-term cycling. Furthermore, setting H3≤(H1-H2) prevents the thickness of the first filler 30 from being too large, which is beneficial for saving material costs while ensuring film quality.
[0120] In Examples 3 and 4, the secondary battery 100 satisfies 0.7(H1-H2)≤H3≤(H1-H2). Compared to Example 2, the average area ratio of the color-developing region of the pressure-sensitive region in the secondary battery 100 is further increased. It is evident that setting H3≥0.7(H1-H2) is beneficial for further improving the support effect of the first filler 30 on the first part 201, improving the quality of the SEI film formed in the first part 201 of the electrode assembly 20 during the formation process, and reducing the possibility of lithium plating in the secondary battery 100 during long-term cycling.
[0121] In Examples 4 and 6-7, the secondary battery 100 satisfies W1-W2≤W≤W1. Compared to Example 5, the average area ratio of the color-developing region of the pressure-sensitive region in the secondary battery 100 of Examples 4 and 6-7 is higher. Compared to Example 8, there is no significant difference in the average area ratio of the color-developing region of the pressure-sensitive region in the secondary battery 100 of Examples 4 and 6-7. It can be seen that by setting W≥W1-W2, the first filler 30 extends above the fourth wall 14 along the first direction X, providing support for the first portion 201 corresponding to the step position of the housing 10, improving the quality of the SEI film formed in the first portion 201 of the electrode assembly 20 during the formation process, and reducing the possibility of lithium plating in the secondary battery 100 during long-term cycling. By setting W≤W1, the width of the first filler 30 is not too large, which helps to save material costs.
[0122] In Examples 4 and 10-11, the secondary battery 100 satisfies 0.9L1≤L≤L1. Compared to Example 9, the average area ratio of the color-developing region of the pressure-sensitive region in Examples 4 and 10-11 of the secondary battery 100 is higher. It is evident that setting L≥0.9L1 prevents the dimension of the first filler 30 along the third direction ZZ from becoming too small, which is beneficial for further increasing the dimension of the portion of the electrode assembly 20 supported by the first filler 30 along the third direction Z, thereby improving the supporting effect of the first filler 30 on the electrode assembly 20. Furthermore, setting L≤L1 prevents the dimension of the first filler 30 along the third direction Z from becoming too large, which helps reduce the possibility of the first filler 30 encroaching on the internal space of the housing 10.
[0123] 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 (100), characterized in that, include: The housing (10) includes a first wall (11), a second wall (12), a third wall (13), a fourth wall (14), and a surrounding wall (15). The first wall (11) and the second wall (12) are arranged opposite each other along a first direction (X), and the first wall (11) and the third wall (13) are arranged opposite each other along the first direction (X). The third wall (13) is located on the side of the second wall (12) along a second direction (Y). The fourth wall (14) connects the second wall (12) and the surrounding wall (15). The third wall (13) and the enclosure wall (15) connect the first wall (11), the second wall (12), the third wall (13) and the fourth wall (14), and together with the first wall (11), the second wall (12), the third wall (13) and the fourth wall (14) enclose the first space (16); along the first direction (X), the distance between the first wall (11) and the second wall (12) is less than the distance between the first wall (11) and the third wall (13); An electrode assembly (20) is housed in the first space (16). The electrode assembly (20) includes a positive electrode (21), a negative electrode (22), and a separator (23). The positive electrode (21) includes a first positive electrode (211) and a second positive electrode (212). Along the second direction (Y), the length of the first positive electrode (211) is greater than the length of the second positive electrode (212). The negative electrode (22) includes a first negative electrode (221) and a second negative electrode (222). Along the second direction (Y), the length of the first negative electrode (221) is greater than the length of the second negative electrode (222). A plurality of first positive electrodes (211), a plurality of separators (23), and a plurality of first negative electrodes (221) are alternately stacked along the first direction (X) to form a first part (201) of the electrode assembly (20). A plurality of second positive electrodes (212), a plurality of separators (23), and a plurality of separators (23) are also stacked. The second negative electrode (222) is alternately stacked along the first direction (X) to form the second part (202) of the electrode assembly (20). The first part (201) and the second part (202) are stacked along the first direction (X). The second part (202) is located on the side of the first part (201) facing the third wall (13). The projection of the second part (202) along the first direction (X) is located within the range of the third wall (13). The thickness of the second part (202) along the first direction (X) is H1. The distance between the second wall (12) and the third wall (13) along the first direction (X) is H2, where H1 > H2. A first gap (16a) is formed between the first part (201) and the second wall (12). The first direction (X) is the thickness direction of the positive electrode (21). The second direction (Y) is perpendicular to the first direction (X). A first filler (30) is housed in the first space (16), with at least a portion of the first filler (30) located in the first gap (16a).
2. The secondary battery (100) as described in claim 1, characterized in that, The first filler (30) is separate from the second part (202).
3. The secondary battery (100) as described in any one of claims 1-2, characterized in that, The thickness of the first filler (30) along the first direction (X) is H3, 0.1(H1-H2)≤H3≤(H1-H2).
4. The secondary battery (100) as described in claim 3, characterized in that, 0.7(H1-H2)≤H3≤(H1-H2).
5. The secondary battery (100) as described in any one of claims 1-4, characterized in that, The projection of the second wall (12) along the first direction (X) is separate from the projection of the third wall (13) along the first direction (X); The first part (201) has a first end (201a), which is the end of the first part (201) away from the second part (202) along the second direction (Y). The distance from the first end (201a) along the second direction (Y) to the third wall (13) is W1, the distance from the second wall (12) along the second direction (Y) to the third wall (13) is W2, and the length of the first filler (30) is W, where W1-W2≤W≤W1.
6. The secondary battery (100) as described in any one of claims 1-5, characterized in that, The length of the electrode assembly (20) along the third direction (Z) is L1, and the length of the first filler (30) along the third direction (Z) is L. The third direction (Z) is perpendicular to the first direction (X) and the second direction (Y), and 0.9L1≤L≤L1.
7. The secondary battery (100) as described in claim 1, characterized in that, The second part (202) is separate from the fourth wall (14), and the secondary battery (100) includes a second filler (40); Along the first direction (X), the second filler (40) is located between the first portion (201) and the third wall (13), and along the second direction (Y), the second filler (40) is located between the fourth wall (14) and the second portion (202).
8. The secondary battery (100) as described in claim 1, characterized in that, The first filler (30) is a hot melt pressure-sensitive adhesive or an expanding adhesive.
9. The secondary battery (100) as described in any one of claims 1-8, characterized in that, The first positive electrode (211) has a dimension D1 along the second direction (Y), and the second positive electrode (212) has a dimension D2, where 0.1D1≤D2≤0.9D1; and / or The first negative electrode (221) has a dimension of D3 along the second direction (Y), and the second negative electrode (222) has a dimension of D4, where 0.1D3≤D4≤0.9D3.
10. An electrical appliance (1000), characterized in that, Includes the secondary battery (100) as described in any one of claims 1 to 9.