Winding type energy storage assembly, preparation method thereof and energy storage device

Abstract

The invention provides a winding type energy storage assembly, a preparation method thereof and an energy storage device. The winding type energy storage assembly comprises a winding core main body, a first lead-out tab and a second lead-out tab, the roll core main body is formed by laminating and winding a layer of composite current collector and a layer of diaphragm; the composite current collector comprises a base material layer which is provided with a first end face and a second end face which are oppositely arranged; the first end face is provided with a first conductive layer and a first blank area, and the first conductive layer is provided with a positive electrode active layer; the second end face is provided with a second conductive layer and a second blank area, and the second conductive layer is provided with a negative active layer; orthographic projections of the first blank area and the second blank area on the base material layer are positioned at two ends of the base material layer; the first lead-out tab is connected with a partial area, opposite to the second blank area, of the first conductive layer, and the second lead-out tab is connected with a partial area, opposite to the first blank area, of the second conductive layer. The energy density of the assembly and the safety of the energy storage device are improved.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, and relates to a wound energy storage component, its preparation method and energy storage device. Background Technology

[0002] Currently, in the niche market of medium-to-high voltage and small-to-medium capacity batteries, bipolar internal series structure batteries use solid electrolytes to achieve internal series connection, thereby increasing the battery voltage and giving it certain advantages over traditional electrodes, thus attracting widespread attention. CN114824154A discloses a bipolar battery, its preparation method, and applications, with a single-cell voltage reaching 6V, or even 9V. CN117613193A discloses a negative electrode-free sodium-ion bipolar solid-state battery structure, with a single-cell voltage reaching 6~12V. CN114094170A proposes a "folded" bipolar sodium-ion battery structure, with a single-cell voltage reaching 9V.

[0003] However, existing bipolar internal series structures have significant drawbacks. For example, preventing short circuits requires complex sealing processes to seal the edges of each electrode. While increasing voltage, the bipolar internal series structure does not improve capacity; capacity increases require increasing the surface area of ​​the active material, significantly increasing the size and weight of a single battery. In some cases, external parallel connection may be necessary to meet capacity requirements.

[0004] Therefore, how to make good use of bipolar electrodes to improve the energy density of energy storage components has become a key concern. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a wound energy storage module, its preparation method, and energy storage device. The composite current collector adopts a misaligned structure. By setting a positive electrode active layer and a negative electrode active layer on both sides of the composite current collector, and drawing out electrode tabs in the misaligned area, a bipolar electrode structure is formed, which effectively improves the energy density of the module.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a wound energy storage module, the wound energy storage module comprising a core body, a first lead-out tab, and a second lead-out tab; the core body is formed by winding a composite current collector layer and a separator layer stacked together; the composite current collector extends along a first direction, the composite current collector comprising a substrate layer, the substrate layer having a first end face and a second end face disposed opposite to each other; the first end face is provided with a first conductive layer and a first blank area, the first conductive layer being provided with a positive electrode active layer; the second end face is provided with a second conductive layer and a second blank area, the second conductive layer being provided with a negative electrode active layer; the orthogonal projections of the first blank area and the second blank area onto the substrate layer are respectively located at both ends of the substrate layer along the first direction; the first lead-out tab is located on the first end face and connects to a portion of the first conductive layer opposite to the second blank area, the second lead-out tab is located on the second end face and connects to a portion of the second conductive layer opposite to the first blank area.

[0008] As a preferred embodiment of the present invention, the orthogonal projections of the positive electrode active layer and the negative electrode active layer onto the substrate layer are not connected to the orthogonal projections of the first blank area onto the substrate layer, and are also not connected to the orthogonal projections of the second blank area onto the substrate layer.

[0009] As a preferred embodiment of the present invention, the distance between the first lead-out tab and the positive electrode active layer is ≥1mm, and the distance between the orthographic projection of the positive electrode active layer on the substrate layer and the second lead-out tab is ≥1mm.

[0010] The distance between the second lead-out tab and the negative electrode active layer is ≥1mm, and the distance between the orthogonal projection of the negative electrode active layer on the substrate layer and the first lead-out tab is ≥1mm.

[0011] In this invention, the edges of both the positive and negative active layers maintain a safe distance from the tabs on both sides, ensuring high welding strength even during internal short circuits and effectively preventing internal short circuits.

[0012] In a preferred embodiment of the present invention, in a first direction, the length of the positive electrode active layer is less than the length of the first conductive layer, and the length of the negative electrode active layer is less than the length of the second conductive layer.

[0013] In one embodiment of the present invention, the orthogonal projection of the negative electrode active layer on the substrate layer covers the orthogonal projection of the positive electrode active layer on the substrate layer.

[0014] As a preferred embodiment of the present invention, the linear lengths of the first blank area and the second blank area in the first direction are each ≥5mm.

[0015] As one embodiment of the present invention, the thickness of the substrate layer is 2~12μm, for example, it can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm or 12μm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0016] The thickness of both the first conductive layer and the second conductive layer is 0.1~3.0μm, for example, it can be 0.1μm, 0.2μm, 0.5μm, 0.6μm, 0.8μm, 1.0μm, 1.2μm, 1.5μm, 1.8μm, 2.0μm, 2.2μm, 2.5μm, 2.8μm or 3.0μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] As a preferred embodiment of the present invention, the innermost ring of the core body is formed by winding the diaphragm, or by simultaneously winding the composite current collector and the diaphragm, and the negative electrode active layer in the core body is close to the winding center.

[0018] The core body is formed by the diaphragm winding itself for at least one turn before the winding ends.

[0019] After the composite current collector is wound, the diaphragm is wound at least one more turn so that the outermost ring of the core body is wrapped with the diaphragm, preventing the core from directly contacting the outer shell and causing a short circuit.

[0020] As a preferred embodiment of the present invention, the outer surface of the core body is further covered with a negative electrode protective layer, the negative electrode protective layer comprising a metal foil layer and a negative electrode active coating disposed on at least one side surface of the metal foil layer, the negative electrode active coating being close to the core body.

[0021] The present invention coats the outer layer of the core body with a negative electrode active coating, which is beneficial to the performance of the positive electrode material and can also effectively eliminate safety hazards.

[0022] In a second aspect, the present invention provides a method for preparing the wound energy storage module described in the first aspect. The method includes: coating a first conductive paste and a second conductive paste onto a portion of a first end face and a second end face of a substrate layer, respectively, to form a first conductive layer and a first blank area on the first end face, and a second conductive layer and a second blank area on the second end face, such that the orthogonal projections of the first blank area and the second blank area onto the substrate layer are respectively located at both ends of the substrate layer along a first direction, thereby obtaining a composite current collector; coating a positive electrode active paste onto the surface of the first conductive layer to form a positive electrode active layer, and coating a negative electrode active paste onto the surface of the second conductive layer to form a negative electrode active layer; providing a first lead and a second lead, placing the first lead on the first end face and welding it to a portion of the first conductive layer opposite to the second blank area, placing the second lead on the second end face and welding it to a portion of the second conductive layer opposite to the first blank area; providing a separator, and then layering it with the composite current collector and winding it to obtain a wound energy storage module.

[0023] As a preferred embodiment of the present invention, during the winding process, the negative electrode active layer is placed on the inner side and the positive electrode active layer is placed on the outer side for winding.

[0024] It should be noted that, in this invention, the inner side refers to the side of the composite current collector facing the winding center, while the outer side refers to the other side of the composite current collector opposite to the inner side.

[0025] Thirdly, the present invention provides an energy storage device, the energy storage device comprising a housing, wherein a wound energy storage component is disposed within the housing, the wound energy storage component being the wound energy storage component described in the first aspect, and the housing is further filled with an electrolyte or electrolyte solution.

[0026] The energy storage device of the present invention adopts a double-ended tab core structure formed by winding a composite current collector and a diaphragm, which reduces the amount of material used, achieves lightweighting, reduces the risk of internal short circuits, and also improves energy density.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The present invention provides a wound energy storage module, the preparation method of which and the energy storage device adopt a composite current collector with a staggered structure, a positive active layer and a negative active layer are coated on both sides of the current collector, and tabs are led out in the staggered area to form a bipolar structure with double-ended tabs. The current collector is wound with a separator to obtain the energy storage module, which reduces the amount of material used, achieves lightweighting, and increases the energy density of the energy storage module by 5% to 10%. At the same time, it avoids the internal short circuit problem caused by direct contact between the positive and negative current collectors of traditional battery cells, thus improving the overall safety. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the core body provided in a specific embodiment of the present invention.

[0030] Figure 2 A front view of a composite current collector provided for a specific embodiment of the present invention.

[0031] Figure 3 A bottom view of a composite current collector provided for a specific embodiment of the present invention.

[0032] Figure 4 This is a front view of a composite current collector coated with a positive electrode active layer and a negative electrode active layer, provided as a specific embodiment of the present invention.

[0033] Figure 5 This is a schematic diagram showing the connection between the composite current collector and the first lead-out electrode in a specific embodiment of the present invention.

[0034] Figure 6 This is a schematic diagram showing the connection between the composite current collector and the second lead-out electrode in a specific embodiment of the present invention.

[0035] Wherein, 10-composite current collector; 101-substrate layer; 102-first conductive layer; 103-second conductive layer; 104-first blank area; 105-second blank area; 201-positive electrode active layer; 202-negative electrode active layer; 30-separator; 40-first lead-out electrode; 50-second lead-out electrode. Detailed Implementation

[0036] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" or "several" means two or more.

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0038] In one specific embodiment, the present invention provides a wound energy storage component, such as... Figure 1 As shown, it includes a core body, a first lead-out tab 40, and a second lead-out tab 50. The core body is formed by layering and winding a composite current collector 10 and a diaphragm 30. Figures 2-6 As shown, the composite current collector 10 extends along a first direction and includes a substrate layer 101. The substrate layer 101 has a first end face and a second end face disposed opposite to each other. The first end face is provided with a first conductive layer 102 and a first blank area 104. A positive electrode active layer 201 is provided on the first conductive layer 102. The second end face is provided with a second conductive layer 103 and a second blank area 105. A negative electrode active layer 202 is provided on the second conductive layer 103. The orthogonal projections of the first blank area 104 and the second blank area 105 onto the substrate layer 101 are respectively located at both ends of the substrate layer 101 along the first direction. The first lead-out tab 40 is located on the first end face and connects to a portion of the first conductive layer 102 opposite to the second blank area 105. The second lead-out tab 50 is located on the second end face and connects to a portion of the second conductive layer 103 opposite to the first blank area 104.

[0039] The composite current collector 10 has a staggered "sandwich" structure, such as Figure 2 and Figure 3 As shown, with the substrate layer 101 as the center, the first conductive layer 102 and the second conductive layer 103 do not completely cover the end face of the substrate layer 101. Instead, they leave blank areas at their respective ends, ensuring that the first blank area 104 and the second blank area 105 are located diagonally opposite to the composite current collector 10. This results in one end of the composite current collector 10 having a structure of "first conductive layer 102 - substrate layer 101 - second blank area 105" perpendicular to the first direction, and the other end having a structure of "first blank area 104 - substrate layer 101 - second conductive layer 103" perpendicular to the first direction. The linear lengths of the first blank area 104 and the second blank area 105 in the first direction are each ≥5mm and ≤1 / 10 of the length of the composite current collector in the first direction.

[0040] The substrate layer 101 is made of a polymer substrate, including but not limited to at least one of polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), biaxially oriented polypropylene (BOPP), or polyethylene naphthalate (PEN). The thickness of the substrate layer 101 is 2~12 μm. Both the first conductive layer 102 and the second conductive layer 103 are made of aluminum film with a thickness of 0.1~3.0 μm. The first conductive layer 102 and the second conductive layer 103 are fabricated by physical vapor deposition or chemical vapor deposition, including but not limited to magnetron sputtering, vacuum evaporation, electroplating, etc.

[0041] like Figure 4 , Figure 5 and Figure 6 As shown, the orthographic projections of the positive electrode active layer 201 and the negative electrode active layer 202 onto the substrate layer 101 are not connected to the orthographic projection of the first blank area 104 onto the substrate layer 101, nor are they connected to the orthographic projection of the second blank area 105 onto the substrate layer 101. That is, one end of each of the positive electrode active layer 201 and the negative electrode active layer 202 is kept at a certain distance from the boundary line of the first blank area 104, and the other end is kept at a certain distance from the boundary line of the second blank area 105.

[0042] In the first direction, such as Figure 5 As shown, the linear length of the first conductive layer 102 covered by the first lead-out tab 40 is smaller than the linear length of the second blank area 105, and at the same time... Figure 6 As shown, the linear length of the second conductive layer 103 covered by the second lead tab 50 is less than the linear length of the first blank area 104, thereby avoiding the problem of direct contact between the positive electrode active layer or the negative electrode active layer when soldering the first lead tab 40 and the second lead tab 50, which would cause an internal short circuit. Figure 5 The gray area on the first blank area 104 shown in the image is the solder mark of the second lead tab 50. Figure 6 The gray area on the second blank area 105 shown in the image is the solder mark of the first lead tab 40.

[0043] Specifically, the distance d between the first lead-out tab 40 and the positive electrode active layer 201 is ≥1mm, and the distance d between the orthographic projection of the positive electrode active layer 201 on the substrate layer 101 and the second lead-out tab 50 is ≥1mm. The distance d between the second lead-out tab 50 and the negative electrode active layer 202 is ≥1mm, and the distance d between the orthographic projection of the negative electrode active layer 202 on the substrate layer 101 and the first lead-out tab 40 is ≥1mm.

[0044] In some implementations, such as Figure 4 As shown, in the first direction, the length of the positive electrode active layer 201 is less than the length of the first conductive layer 102, and neither end of the positive electrode active layer 201 is flush with the end of the first conductive layer 102; in the first direction, the length of the negative electrode active layer 202 is less than the length of the second conductive layer 103, and neither end of the negative electrode active layer 202 is flush with the end of the second conductive layer 103.

[0045] Furthermore, the orthogonal projection of the negative electrode active layer 202 onto the substrate layer 101 overlaps the orthogonal projection of the positive electrode active layer 201 onto the substrate layer 101. That is, in the first direction, the linear length of the negative electrode active layer 202 is greater than the linear length of the positive electrode active layer 201.

[0046] In some embodiments, the innermost loop of the core body is formed by winding the diaphragm 30, or by simultaneously winding the composite current collector 10 and the diaphragm 30. The negative electrode active layer 202 is wound close to the winding center in the core body. At least one loop of the core body before the end of winding is formed by the diaphragm 30 winding itself. That is, when winding begins, the diaphragm 30 is unwound first to form the innermost loop, then the composite current collector 10 is unwound, and subsequently the diaphragm 30 and the composite current collector 10 are simultaneously wound to form the core body, or the diaphragm 30 and the composite current collector 10 are unwound simultaneously to form the innermost loop together, and then synchronous unwound continues. Before the end of winding, the diaphragm 30 is wound at least one more loop than the composite current collector 10 to wrap around the outer layer of the core body, avoiding short circuit problems caused by direct contact between the electrode and the casing during subsequent energy storage device fabrication.

[0047] In some embodiments, the outer surface of the core body is further covered with a negative electrode protective layer, the negative electrode protective layer comprising a metal foil layer and a negative electrode active coating disposed on at least one side surface of the metal foil layer, the negative electrode active coating being close to the core body.

[0048] The diaphragm 30 includes, but is not limited to, polyethylene, polypropylene, polyimide, and ceramic-coated diaphragms 30, etc.

[0049] In another specific embodiment, the present invention provides a method for preparing a wound energy storage module as described in a specific embodiment, the method comprising the following steps.

[0050] Step 1: Coat a portion of the first end face and the second end face of the substrate layer 101 with a first conductive paste and a second conductive paste, respectively, to form a first conductive layer 102 and a first blank area 104 on the first end face, and a second conductive layer 103 and a second blank area 105 on the second end face, such that the orthographic projections of the first blank area 104 and the second blank area 105 on the substrate layer 101 are located at both ends of the substrate layer 101 along the first direction, thus obtaining a composite current collector 10.

[0051] The substrate layer 101 is made of at least one of polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), biaxially oriented polypropylene (BOPP), or polyethylene naphthalate (PEN), and is prepared using a commonly used extrusion method in the art. Both the first and second conductive pastes are made of aluminum and are coated onto the surface of the substrate layer 101 using physical vapor deposition or chemical vapor deposition. During the coating process, the first and second conductive pastes do not completely cover the end faces of the substrate layer 101, leaving a space with a length ≥ 5 mm, resulting in a first blank area 104 and a second blank area 105.

[0052] Step 2: Apply the positive electrode active slurry to the surface of the first conductive layer 102 to form the positive electrode active layer 201, and apply the negative electrode active slurry to the surface of the second conductive layer 103 to form the negative electrode active layer 202.

[0053] The positive electrode active slurry comprises a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder in a mass ratio of (80~96):(2~10):(2~10). The positive electrode active material is a layered material and, depending on the classification of different energy storage components, can be a lithium-ion positive electrode material, a sodium-ion positive electrode material, a potassium-ion positive electrode material, or activated carbon. For lithium battery energy storage components, the positive electrode active material includes, but is not limited to, lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), and LiNi... 0.5 Mn 1.5 O4, lithium iron phosphate (LiFePO4), lithium manganese iron phosphate (LiFe) 1-x Mn x At least one of the following: PO4. For sodium battery energy storage components, the positive electrode active material includes, but is not limited to, transition metal oxides (NaxMO2, where M is selected from at least one of Fe, Mn, Ni, Co, Ti, and Cu), polyanionic compounds, Prussian blue / white compounds (Na... x Ma[Mb(CN)6]·zH2O, where Ma / Mb is selected from at least one of Fe, Mn, and Ni. For potassium-ion battery energy storage components, the positive electrode active material includes, but is not limited to, K. x At least one of MnO2, KVPO4F, K3V2(PO4)3, and Prussian blue analogues. For electric double-layer capacitors, the positive electrode active material can be activated carbon. The positive electrode conductive agent includes at least one of conductive carbon black, carbon nanotubes, conductive graphite, and graphene. The positive electrode binder includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, and acrylic acid.

[0054] The negative electrode active slurry comprises a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder in a mass ratio of (80~98):(1~10):(1~10). Depending on the classification of different energy storage components, different materials are selected for the negative electrode active material. For lithium-ion battery energy storage components, the negative electrode active material includes lithium titanate and / or niobium titanate. For sodium-ion battery energy storage components, the negative electrode active material can be hard carbon. For potassium-ion battery energy storage components, the negative electrode active material can be hard carbon or other carbon-based materials. For electric double-layer capacitors, the negative electrode active material is activated carbon. The negative electrode conductive agent includes at least one of conductive carbon black, carbon nanotubes, conductive graphite, and graphene. The negative electrode binder is at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, and acrylic acid.

[0055] This invention involves mixing and dissolving a positive electrode active material and a positive electrode conductive agent in a desired ratio in a positive electrode binder, and then stirring and dispersing them to form a first conductive slurry. A negative electrode active material and a negative electrode conductive agent are then mixed and dissolved in a desired ratio in a negative electrode binder, and stirred and dispersed to form a second conductive slurry. The first and second conductive slurries are then extruded and coated onto the first and second end faces of a substrate layer 101, respectively. After drying, they are rolled and slit to form a bipolar electrode.

[0056] In some embodiments, the coating areas of the positive and negative active slurries are centered, such that the length of the positive active layer 201 is less than the length of the first conductive layer 102, and neither end of the positive active layer 201 is flush with the ends of the first conductive layer 102. In the first direction, the length of the negative active layer 202 is less than the length of the second conductive layer 103, and neither end of the negative active layer 202 is flush with the ends of the second conductive layer 103. Simultaneously, the orthographic projections of both the positive and negative active layers 201 onto the substrate layer 101 are not connected to the orthographic projection of the first blank area 104 onto the substrate layer 101, nor are they connected to the orthographic projection of the second blank area 105 onto the substrate layer 101. Further, the coating area of ​​the negative active slurry is greater than the coating area of ​​the positive active slurry, such that the orthographic projection of the negative active layer 202 onto the substrate layer 101 overlaps the orthographic projection of the positive active layer 201 onto the substrate layer 101.

[0057] Step 3: Provide a first lead-out tab 40 and a second lead-out tab 50. Place the first lead-out tab 40 on the first end face and solder it to a portion of the first conductive layer 102 opposite to the second blank area 105. Place the second lead-out tab 50 on the second end face and solder it to a portion of the second conductive layer 103 opposite to the first blank area 104.

[0058] The first lead-out tab 40 and the second lead-out tab 50 can be made of aluminum tabs, and the welding method is at least one of ultrasonic welding, spot welding and laser welding.

[0059] To ensure the lead-out tabs are centered in the winding structure, their positions are fixed at the edge of the composite current collector 10, and the winding needles of the winding machine are kept close to this edge during winding. During the welding process, the first conductive layer 102 of the composite current collector 10 is placed upwards, and the first lead-out tab 40 is placed in the edge region of the first conductive layer 102, such that the distance between the lead-out position of the first lead-out tab 40 and the positive electrode active layer 201 is ≥1mm, and the distance between the orthographic projection of the positive electrode active layer 201 onto the substrate layer 101 and the lead-out position of the second lead-out tab 50 is ≥1mm. Subsequently, the second conductive layer 103 of the composite current collector 10 is placed upwards, and the second lead-out tab 50 is placed in the edge region of the second conductive layer 103, such that the distance between the lead-out position of the second lead-out tab 50 and the negative electrode active layer 202 is ≥1mm, and the distance between the orthographic projection of the negative electrode active layer 202 onto the substrate layer 101 and the lead-out position of the first lead-out tab 40 is ≥1mm. The width of the lead-out tab does not exceed the radius of the winding machine needle. The lead-out tab can be used directly as the tab of a sodium ion energy storage device, or further converted into the tab of an energy storage component, forming a double-ended tab bipolar electrode structure.

[0060] Step 4: Provide a diaphragm 30, stack it with the composite current collector 10, and then wind it to obtain a wound energy storage module.

[0061] In this invention, a separator 30 and a composite current collector 10 are stacked and wound together, with the negative electrode active layer 202 placed on the inside and the positive electrode active layer 201 placed on the outside.

[0062] When the winding begins, the diaphragm 30 is unwound first to form the innermost ring, and then the composite current collector 10 is unwound. Subsequently, the diaphragm 30 and the composite current collector 10 are wound synchronously to form the core body, or the diaphragm 30 and the composite current collector 10 are unwound simultaneously to form the innermost ring and then continue to be unwound synchronously.

[0063] Before the winding ends, the diaphragm 30 is wound at least one more turn than the composite current collector 10 to wrap around the outer layer of the core body.

[0064] In some embodiments, after the winding of the core body is completed, a negative electrode protective layer is wound around its outer surface to form a coating layer. The negative electrode protective layer includes a metal foil layer, and a negative electrode active coating is disposed on one or both surfaces of the metal foil layer. The negative electrode active coating is wound close to the core body.

[0065] In another specific embodiment, the present invention provides an energy storage device, which includes a housing, wherein a wound energy storage component is disposed within the housing, the wound energy storage component being the wound energy storage component described in a specific embodiment, and the housing is further filled with an electrolyte or electrolyte solution.

[0066] The energy storage device described in this invention includes, but is not limited to, lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, and double-layer capacitors. This invention utilizes a liquid electrolyte filling the casing to form an internal parallel structure, or a solid electrolyte filling to form an internal series structure. This allows for capacity and voltage adjustment within a single cell structure as needed. Furthermore, it employs a dual-tab bipolar electrode structure with a composite current collector 10 as the electrode, thereby improving the safety of the energy storage device while achieving a lightweight design.

[0067] Specifically, the electrolyte includes, but is not limited to, liquid electrolytes using LiPF6, NaPF6, KPF6, or TEABF4 as solutes. The electrolyte itself includes, but is not limited to, solid electrolytes such as polymers, oxides, or sulfides.

[0068] Example 1

[0069] This embodiment provides a method for preparing a sodium-ion battery, which specifically includes the following steps:

[0070] (1) A composite current collector 10 is provided, which includes a substrate layer 101. The substrate layer 101 has a first end face and a second end face opposite to each other. A first conductive layer 102 and a first blank area 104 are provided on the first end face. A second conductive layer 103 and a second blank area 105 are provided on the second end face. The orthographic projections of the first blank area 104 and the second blank area 105 on the substrate layer 101 are located at both ends of the substrate layer 101 along the length direction of the composite current collector 10. The length of the first blank area 104 and the second blank area 105 is 5 mm. The substrate layer 101 is made of polyethylene terephthalate with a thickness of 5 μm. The first conductive layer 102 and the second conductive layer 103 are both made of aluminum with a thickness of 0.5 μm.

[0071] (2) Sodium ion layered metal oxide and conductive carbon black are dissolved in polyvinylidene fluoride and stirred and dispersed evenly at a ratio of 94:3:3 to obtain a positive electrode active slurry. Hard carbon and conductive carbon black are dissolved in styrene-butadiene rubber and stirred and dispersed evenly at a ratio of 96:2:2 to obtain a negative electrode active slurry.

[0072] (3) The positive electrode active slurry and the negative electrode active slurry are respectively extruded and coated onto the first conductive layer 102 and the second conductive layer 103 of the composite current collector 10 with a staggered structure to obtain the positive electrode active layer 201 and the negative electrode active layer 202. After drying, they are rolled and slit to form a bipolar electrode. The length of the positive electrode active layer 201 is less than the length of the first conductive layer 102, and the length of the negative electrode active layer 202 is less than the length of the second conductive layer 103. The positive electrode active layer 201 and the negative electrode active layer 202 are centrally located, and the orthogonal projection of the negative electrode active layer 202 onto the substrate layer 101 covers the orthogonal projection of the positive electrode active layer 201 onto the substrate layer 101.

[0073] (4) Provide a first lead-out tab 40 and a second lead-out tab 50, both of which are aluminum tabs. With the first conductive layer 102 facing upward, weld the first lead-out tab 40 to a portion of the first conductive layer 102 corresponding to the second blank area 105, and the distance between the welding position of the first lead-out tab 40 and one end of the orthogonal projection of the negative electrode active layer 202 on the substrate layer 101 is ≥1mm, i.e., leave a safe distance. Then, with the second conductive layer 103 facing upward, weld the second lead-out tab 50 to a portion of the second conductive layer 103 corresponding to the first blank area 104, and the distance between the welding position of the second lead-out tab 50 and the other end of the orthogonal projection of the negative electrode active layer 202 on the substrate layer 101 is ≥1mm, i.e., leave a safe distance, to obtain a double-ended tab bipolar electrode.

[0074] (5) After stacking a layer of double-ended bipolar electrode and a layer of diaphragm 30, feed the sheet with the negative active layer 202 facing inward and the positive active layer 201 facing outward. Simultaneously feed the diaphragm 30 and the double-ended bipolar electrode into the winding machine for winding. After the double-ended bipolar electrode is fed, the diaphragm 30 wraps around the outer layer of the core body by at least one turn. Then, a negative protective layer is coated on the outer surface of the core body, which includes an aluminum foil layer and a negative active coating on both sides of the aluminum foil layer. The negative active coating is close to the core body, and the material of the negative active coating is the same as that of the negative active layer 202.

[0075] (6) Insert the bipolar electrode with double tabs into the housing, weld the first lead tab 40 and the second lead tab 50 to the housing respectively to complete the housing and encapsulation, and then inject sodium ion electrolyte NaPF6 into the housing to obtain a double-tab wound sodium ion battery.

[0076] Example 2

[0077] This embodiment provides a method for preparing a sodium-ion battery. The difference from Embodiment 1 is that the mass ratio of sodium ion layered metal oxide, activated carbon, conductive carbon black and polyvinylidene fluoride in the positive electrode active slurry for preparing the positive electrode active layer 201 is 45:45:5:5. The remaining steps are the same as in Embodiment 1.

[0078] Example 3

[0079] This embodiment provides a method for preparing a lithium-ion battery, which specifically includes the following steps:

[0080] (1) A composite current collector 10 is provided, which includes a substrate layer 101. The substrate layer 101 has a first end face and a second end face opposite to each other. A first conductive layer 102 and a first blank area 104 are provided on the first end face. A second conductive layer 103 and a second blank area 105 are provided on the second end face. The orthographic projections of the first blank area 104 and the second blank area 105 on the substrate layer 101 are located at both ends of the substrate layer 101 along the length direction of the composite current collector 10. The lengths of the first blank area 104 and the second blank area 105 are both 6 mm. The substrate layer 101 is made of polyethylene terephthalate with a thickness of 8 μm. The first conductive layer 102 and the second conductive layer 103 are both made of aluminum with a thickness of 0.4 μm.

[0081] (2) Lithium nickel cobalt manganese oxide and conductive carbon black are dissolved in polyvinylidene fluoride and stirred and dispersed evenly at a ratio of 90:5:5 to obtain a positive electrode active slurry. Lithium titanate and conductive carbon black are dissolved in polyvinylidene fluoride and stirred and dispersed evenly at a ratio of 92:4:2 to obtain a negative electrode active slurry.

[0082] (3) The positive electrode active slurry and the negative electrode active slurry are respectively extruded and coated onto the first conductive layer 102 and the second conductive layer 103 of the composite current collector 10 with a staggered structure to obtain the positive electrode active layer 201 and the negative electrode active layer 202. After drying, they are rolled and slit to form a bipolar electrode. The length of the positive electrode active layer 201 is less than the length of the first conductive layer 102, and the length of the negative electrode active layer 202 is less than the length of the second conductive layer 103. The positive electrode active layer 201 and the negative electrode active layer 202 are centrally located, and the orthogonal projection of the negative electrode active layer 202 onto the substrate layer 101 covers the orthogonal projection of the positive electrode active layer 201 onto the substrate layer 101.

[0083] (4) Provide a first lead-out tab 40 and a second lead-out tab 50, both of which are aluminum tabs. With the first conductive layer 102 facing upward, weld the first lead-out tab 40 to a portion of the first conductive layer 102 corresponding to the second blank area 105, and the distance between the welding position of the first lead-out tab 40 and one end of the orthogonal projection of the negative electrode active layer 202 on the substrate layer 101 is ≥1mm, i.e., leave a safe distance. Then, with the second conductive layer 103 facing upward, weld the second lead-out tab 50 to a portion of the second conductive layer 103 corresponding to the first blank area 104, and the distance between the welding position of the second lead-out tab 50 and the other end of the orthogonal projection of the negative electrode active layer 202 on the substrate layer 101 is ≥1mm, i.e., leave a safe distance, to obtain a double-ended tab bipolar electrode.

[0084] (5) After stacking a layer of double-ended bipolar electrode and a layer of diaphragm 30, feed the sheet with the negative active layer 202 facing inward and the positive active layer 201 facing outward. Simultaneously feed the diaphragm 30 and the double-ended bipolar electrode into the winding machine for winding. After the double-ended bipolar electrode is fed, the diaphragm 30 wraps around the outer layer of the core body by at least one turn. Then, a negative protective layer is coated on the outer surface of the core body, which includes an aluminum foil layer and a negative active coating on both sides of the aluminum foil layer. The negative active coating is close to the core body, and the material of the negative active coating is the same as that of the negative active layer 202.

[0085] (6) Install the bipolar electrode with double tabs into the housing, weld the first lead tab 40 and the second lead tab 50 to the housing respectively to complete the housing and encapsulation, and then inject sodium ion electrolyte LiPF6 into the housing to obtain a double-tab wound sodium ion battery.

[0086] Example 4

[0087] This embodiment provides a method for preparing a sodium-ion battery. The difference between this embodiment and Embodiment 1 is that no safety distance is provided, but the rest of the structure and steps are the same as in Embodiment 1.

[0088] Comparative Example 1

[0089] This comparative example provides a sodium-ion battery and its preparation method. The core body uses conventional aluminum foil as the positive electrode current collector, with positive active layers formed on both sides of the current collector. The materials used are the same as in Example 1. Simultaneously, copper foil is used as the negative electrode current collector, with negative active layers formed on both sides of the current collector. The materials used are the same as in Example 1. The positive electrode is ultrasonically welded onto the current collector to form a positive electrode tab, and the negative electrode is ultrasonically welded onto the current collector to form a negative electrode tab. The core body is obtained by stacking the positive electrode sheet, separator, and negative electrode sheet in that order and then winding them. The length of the positive electrode sheet, the two separators, and the negative electrode sheet is half the length of the composite current collector in Example 1.

[0090] Comparative Example 2

[0091] This comparative example provides a sodium-ion battery and its preparation method. The core body uses conventional aluminum foil as the positive electrode current collector, with positive active layers formed on both sides of the current collector. The materials used are the same as in Example 2. Simultaneously, copper foil is used as the negative electrode current collector, with negative active layers formed on both sides of the current collector. The materials used are the same as in Example 2. The positive electrode is ultrasonically welded onto the current collector to form a positive electrode tab, and the negative electrode is ultrasonically welded onto the current collector to form a negative electrode tab. The core body is obtained by stacking the positive electrode sheet, separator, and negative electrode sheet in that order and then winding them. The lengths of the positive electrode sheet, the two separators, and the negative electrode sheet are half the length of the composite current collector in Example 2.

[0092] Comparative Example 3

[0093] This comparative example provides a lithium-ion battery and its preparation method. The core body uses conventional aluminum foil as the positive electrode current collector, with positive active layers formed on both sides of the current collector. The materials used are the same as in Example 3. Simultaneously, copper foil is used as the negative electrode current collector, with negative active layers formed on both sides of the current collector. The materials used are the same as in Example 3. The positive electrode is ultrasonically welded onto the current collector to form a positive electrode tab, and the negative electrode is ultrasonically welded onto the current collector to form a negative electrode tab. The core body is obtained by stacking the positive electrode sheet, separator, and negative electrode sheet in that order and then winding them. The lengths of the positive electrode sheet, the two separators, and the negative electrode sheet are half the length of the composite current collector in Example 3.

[0094] The present invention tested the energy density of the batteries in Examples 1-4 and Comparative Examples 1-3, and the results are shown in Table 1. The test conditions for battery energy density were: 25°C environment and 1C discharge current.

[0095] Table 1

[0096]

[0097] As can be seen from Table 1, the present invention uses a bipolar core with double-ended tabs formed by winding a separator and a composite current collector with a staggered structure. Compared with the conventional core formed by winding positive electrode, negative electrode and two separators, the energy density of the battery is increased by more than 5% to 10%. In addition, when welding the tabs, the present invention leaves a safe distance between the welding position and the negative electrode active layer, avoiding the risk of internal short circuit and improving the battery's service life and safety.

[0098] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A wound energy storage module, characterized in that, The wound energy storage component includes a core body, a first lead-out tab, and a second lead-out tab; The core body is formed by stacking and winding a composite current collector layer and a diaphragm layer; the composite current collector extends along a first direction and includes a substrate layer, the substrate layer having a first end face and a second end face disposed opposite to each other; The first end face is provided with a first conductive layer and a first blank area, and a positive electrode active layer is provided on the first conductive layer; the second end face is provided with a second conductive layer and a second blank area, and a negative electrode active layer is provided on the second conductive layer; the orthogonal projections of the first blank area and the second blank area on the substrate layer are respectively located at both ends of the substrate layer along a first direction; The first lead is located on the first end face and is connected to a portion of the first conductive layer opposite to the second blank area. The second lead is located on the second end face and is connected to a portion of the second conductive layer opposite to the first blank area.

2. The wound energy storage module according to claim 1, characterized in that, The orthographic projections of the positive electrode active layer and the negative electrode active layer onto the substrate layer are not connected to the orthographic projections of the first blank area onto the substrate layer, and are also not connected to the orthographic projections of the second blank area onto the substrate layer.

3. The wound energy storage module according to claim 1 or 2, characterized in that, The distance between the first lead-out tab and the positive electrode active layer is ≥1mm, and the distance between the orthographic projection of the positive electrode active layer on the substrate layer and the second lead-out tab is ≥1mm; The distance between the second lead-out tab and the negative electrode active layer is ≥1mm, and the distance between the orthogonal projection of the negative electrode active layer on the substrate layer and the first lead-out tab is ≥1mm.

4. The wound energy storage module according to claim 1 or 2, characterized in that, In a first direction, the length of the positive electrode active layer is less than the length of the first conductive layer, and the length of the negative electrode active layer is less than the length of the second conductive layer; Preferably, the orthogonal projection of the negative electrode active layer on the substrate layer overlaps the orthogonal projection of the positive electrode active layer on the substrate layer.

5. The wound energy storage module according to any one of claims 1-4, characterized in that, The linear lengths of the first blank area and the second blank area in the first direction are each ≥5mm. Preferably, the thickness of the substrate layer is 2~12μm, and the thickness of both the first conductive layer and the second conductive layer is 0.1~3.0μm.

6. The wound energy storage module according to any one of claims 1-5, characterized in that, The innermost ring of the core body is formed by winding the diaphragm, or by simultaneously winding the composite current collector and the diaphragm, and the negative electrode active layer in the core body is close to the winding center; The core body is formed by the diaphragm winding itself for at least one turn before the winding ends.

7. The wound energy storage module according to claim 6, characterized in that, The outer surface of the core body is also covered with a negative electrode protective layer, which includes a metal foil layer and a negative electrode active coating disposed on at least one side of the metal foil layer, the negative electrode active coating being close to the core body.

8. A method for preparing a wound energy storage module according to any one of claims 1-7, characterized in that, The preparation method includes: A first conductive paste and a second conductive paste are respectively coated on a portion of the first end face and the second end face of the substrate layer to form a first conductive layer and a first blank area on the first end face, and a second conductive layer and a second blank area on the second end face, such that the orthographic projections of the first blank area and the second blank area on the substrate layer are located at both ends of the substrate layer along a first direction, thus obtaining a composite current collector. A positive electrode active slurry is coated on the surface of the first conductive layer to form a positive electrode active layer, and a negative electrode active slurry is coated on the surface of the second conductive layer to form a negative electrode active layer. A first lead-out electrode and a second lead-out electrode are provided. The first lead-out electrode is placed on the first end face and soldered to a portion of the first conductive layer opposite to the second blank area. The second lead-out electrode is placed on the second end face and soldered to a portion of the second conductive layer opposite to the first blank area. A diaphragm is provided, which is then laminated with a composite current collector and wound to obtain a wound energy storage module.

9. The preparation method according to claim 8, characterized in that, During the winding process, the negative electrode active layer is placed on the inside and the positive electrode active layer is placed on the outside for winding.

10. An energy storage device, characterized in that, The energy storage device includes a housing, and a wound energy storage component is disposed inside the housing. The wound energy storage component is the wound energy storage component according to any one of claims 1-7. The housing is also filled with an electrolyte or electrolyte solution.

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