Composite current collector, preparation method thereof and cathode-free battery

Abstract

The invention relates to the technical field of batteries, in particular to a composite current collector, a preparation method thereof and a negative-electrode-free battery. The composite current collector comprises a porous current collector; the metal layer is arranged on at least one side of the porous current collector along the thickness direction; the insulating layer is arranged on the surface of one side, far away from the porous current collector, of the metal layer; wherein the metal layer and the insulating layer have a through hole structure, and the through hole structure contains a conductive ion polymer; the metal element of the metal layer comprises at least one of copper or nickel; the insulating layer comprises at least one of copper oxide or nickel oxide. The composite current collector can solve the problem of non-uniform lithium deposition in a negative-electrode-free battery structure, and can improve the safety performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a composite current collector, its preparation method, and a negative electrode-free battery. Background Technology

[0002] To improve the energy density of lithium-ion batteries, reducing cell weight is currently one feasible solution. Anode-less structures, because they eliminate the need for negative electrode active materials, significantly reduce battery weight and thus increase energy density. However, anode-less structures face a serious problem: without the lithium intercalation of negative electrode active materials, lithium ions extracted from the positive electrode have nowhere to intercalate. While conventional copper foil can deposit lithium as a negative electrode, it faces the risk of uneven lithium deposition, forming lithium dendrites that can puncture the separator, causing short circuits between the positive and negative electrodes and posing a safety hazard. Furthermore, in high-energy-density battery systems, due to the higher energy density, the heat generated under the same conditions is greater than in ordinary batteries; therefore, heat generation in high-energy batteries is also a major factor affecting their safety performance.

[0003] Based on the above, there is an urgent need to provide a technical solution that can solve the problems of uneven lithium deposition and poor safety in negative electrode batteries. Summary of the Invention

[0004] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides a composite current collector, a method for preparing the same, and a negative electrode-free battery. This composite current collector can solve the problem of uneven lithium deposition in a negative electrode-free battery structure and can also improve the safety performance of the battery.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows: According to one aspect of this application, an embodiment of this application provides a composite current collector, the composite current collector comprising a porous current collector; A metal layer is disposed on at least one side of the porous current collector along its thickness direction; An insulating layer is disposed on the surface of the metal layer away from the porous current collector; The metal layer and the insulating layer have a through-hole structure, and the through-hole structure contains an ion-conducting polymer. The metallic element of the metal layer includes at least one of copper or nickel; The insulating layer includes at least one of copper oxide or nickel oxide.

[0006] In some of these embodiments, the porous current collector comprises at least one of copper foam or nickel foam.

[0007] In some embodiments, the porosity of the porous current collector is 20% to 60%.

[0008] In some embodiments, the thickness of the porous current collector is 4 μm to 20 μm.

[0009] In some of these embodiments, the thickness of the metal layer is 1 μm to 2 μm.

[0010] In some of these embodiments, the thickness of the insulating layer is 50 nm to 200 nm.

[0011] In some of these embodiments, the diameter of the through-hole structure is 5 μm to 20 μm.

[0012] In some of these embodiments, the total bottom area of ​​the through-hole structure on one side of the insulating layer accounts for 20% to 40% of the area of ​​the insulating layer.

[0013] In some embodiments, the ion-conducting polymer includes at least one of polyethylene glycol imide, polyamide imide, or polyethylene oxide.

[0014] In some embodiments, the through-hole structure also contains an adhesive.

[0015] In some of these embodiments, the mass ratio of the ion-conducting polymer to the binder is (80~90):(10~20).

[0016] According to another aspect of this application, embodiments of this application provide a method for preparing a composite current collector, comprising the following steps: Metal is deposited on the surface of a porous current collector to form a metal layer; An oxidant is coated on the surface of the metal layer to oxidize the metal on the surface of the metal layer and form an insulating layer; By drilling through holes in the metal layer and the insulating layer, and then filling the through holes with an ion-conducting polymer slurry, a composite current collector is obtained.

[0017] In some of these embodiments, the method for depositing metal includes plasma sputtering.

[0018] In some embodiments, the target voltage in the plasma sputtering method is 500V~800V, the operating voltage is 200V~240V, and the distance between the target and the substrate is controlled between 20mm~40mm.

[0019] In some embodiments, the target material includes copper or nickel; the plasma sputtering deposition of metal is carried out in an inert atmosphere at a pressure of 20 Pa to 50 Pa and a temperature of 500 °C to 700 °C.

[0020] In some embodiments, the oxidant comprises a mixture of hydrogen peroxide and hydrochloric acid.

[0021] In some of these embodiments, the volume ratio of hydrogen peroxide to hydrochloric acid is (90~110):(2~4).

[0022] In some embodiments, the coating amount of the oxidant is 10 mL / m 2 ~50mL / m 2 .

[0023] In some embodiments, the compaction density of the porous current collector is 1.4 g / cm³. 3 ~1.6g / cm 3 .

[0024] In some embodiments, the method for drilling through-holes in the metal layer and insulating layer includes laser etching.

[0025] According to another aspect of this application, an embodiment of this application provides a negative electrode-free battery, including a current collector, wherein the current collector is the aforementioned composite current collector, or a composite current collector prepared according to the aforementioned preparation method.

[0026] Implementing the technical solution of the present invention has at least the following beneficial effects: In this embodiment, the provided composite current collector includes a porous current collector. The porous structure of the porous current collector effectively reduces its weight, further improving the energy density of the lithium battery. Furthermore, the porous nature facilitates heat dissipation, lowering the battery temperature and reducing the risk of thermal runaway. The porous structure also effectively increases the deposition area of ​​lithium ions, preventing excessive dendrite growth and improving battery safety. In addition, the presence of a metal layer enhances the compressive strength of the porous current collector, providing support and compensating for its conductivity. It also provides a smoother platform area for the insulating layer. The insulating layer prevents lithium ions from depositing on the surface of the composite current collector, avoiding lithium dendrite piercing the separator.

[0027] Furthermore, since the outermost layer of the composite current collector is an insulating layer, lithium ions cannot be deposited on the outermost layer of the composite current collector. The metal layer and insulating layer of this application have a through-pore structure, and the through-pore structure also contains an ion-conducting polymer. The ion-conducting polymer preferentially adsorbs lithium ions through physical adsorption properties, allowing lithium ions to aggregate in a directional manner. Then, they diffuse into the interior of the copper foil through electronegativity attraction. Physical adsorption + electronic adsorption can make lithium deposition in the negative electrode-free battery more uniform, thereby further improving the battery's safety performance.

[0028] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] Figure 1 The figure shown is a cross-sectional structural diagram of the composite current collector provided in Embodiment 1 of the present invention.

[0030] Figure 2 The figure shown is a schematic diagram of the planar structure of the composite current collector provided in Embodiment 1 of the present invention.

[0031] Explanation of reference numerals in the attached figures: 1Porous current collector; 2 metal layers; 3. Insulation layer; 4. Through-hole structure. Detailed Implementation

[0032] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0033] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0034] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0035] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0036] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0038] Electrodeless batteries have the advantage of high energy density, but existing electrodeless batteries still have certain technical drawbacks. For example, Chinese patent CN113013417A discloses an electrodeless battery that coats an electronically conductive layer and an ionically conductive layer on the outer layer of a traditional negative electrode material. Although this method can accommodate lithium sources extracted from the positive electrode, the patent uses a method of directly immersing copper foil in an ion-coating adhesive. This coating lacks a large number of pores, thus hindering the deposition rate of lithium ions on the copper foil surface. The deposition efficiency is low, and in severe cases, lithium ions may not be deposited in time (during high-rate charging) and may deposit on the coating surface, causing lithium dendrites to pierce the separator and trigger a short circuit. Furthermore, the ion-conductive layer is difficult to prepare, and the traditional negative electrode metal substrate has a large mass, affecting the energy density of the battery. For example, Chinese patent CN116581361A discloses a negative electrode-free battery structure. This structure combines a lithium titanate layer with a solid electrolyte to provide lithium intercalation space and avoid direct reaction with the electrolyte. However, current solid electrolytes suffer from low ion transport rates and interfacial contact issues, affecting battery power performance. Furthermore, the lithium titanate layer also increases weight, hindering the improvement of energy density in negative electrode-free batteries. Another example is Chinese patent CN115863660B, which discloses a method for preparing a silver nanoarray by etching the surface of a copper foil current collector to induce lithium ion deposition. However, this method is difficult to implement and produces uneven results, easily leading to membrane penetration and short circuits, among other safety issues.

[0039] In view of this, embodiments of this application provide a composite current collector, which includes a porous current collector 1; Metal layer 2 is disposed on at least one side of the porous current collector 1 along the thickness direction; Insulating layer 3 is disposed on the surface of metal layer 2 away from porous current collector 1; Among them, the metal layer 2 and the insulating layer 3 have a through-hole structure 4, and the through-hole structure 4 contains an ion-conducting polymer. The metallic element of metal layer 2 includes at least one of copper or nickel; The insulating layer 3 includes at least one of copper oxide or nickel oxide.

[0040] The phrase "metal layer 2 is disposed on at least one side of the porous current collector 1 along the thickness direction" means that the metal layer 2 can be disposed on one surface of the porous current collector 1 along the thickness direction, or it can be disposed on two surfaces of the porous current collector 1 along the thickness direction. Here, "surface" can be the entire area of ​​the porous current collector 1 or a part of the porous current collector 1. As in this embodiment, the surface can be the entire area of ​​the porous current collector 1. This application does not have any particular limitation in this regard, as long as the purpose of this application can be achieved.

[0041] As an example, the porous current collector 1 has two surfaces opposite each other in its thickness direction, and a metal layer 2 is disposed on the two opposite surfaces of the porous current collector 1. Furthermore, an insulating layer 3 is formed on both surfaces of the metal layer 2. It is understood that the metal layer 2 can also be disposed on either of the two surfaces of the porous current collector 1.

[0042] In this application, the composite current collector includes a porous current collector 1. The porous structure of the porous current collector 1 can effectively reduce the weight of the current collector, further improving the energy density of the lithium battery. In addition, the porous characteristics are conducive to heat dissipation, reducing the battery temperature and the risk of thermal runaway. Furthermore, the porous structure of the porous current collector 1 also effectively increases the deposition area of ​​lithium ions, avoiding excessive growth of lithium ion dendrites and improving battery safety. In addition, the presence of the metal layer 2 can improve the compressive strength of the porous current collector 1, provide a certain support for the porous current collector 1, compensate for the conductivity of the porous current collector 1, and provide a flatter platform area for the insulating layer 3. The insulating layer 3 can prevent lithium ions from depositing on the surface of the composite current collector, and prevent lithium dendrites from piercing the separator.

[0043] Furthermore, since the outermost layer of the composite current collector is the insulating layer 3, lithium ions cannot be deposited on the outermost layer of the composite current collector. The metal layer 2 and the insulating layer 3 of this application have a through-hole structure 4, and the through-hole structure 4 also contains an ion-conducting polymer. The ion-conducting polymer preferentially adsorbs lithium ions through its physical adsorption properties, allowing the lithium ions to aggregate directionally. Then, through electronegativity attraction, they diffuse into the copper foil. This combination of physical adsorption and electronic adsorption makes lithium deposition in the electrodeless battery more uniform, thereby further improving the battery's safety performance.

[0044] In some embodiments, the porous current collector 1 comprises at least one of copper foam or nickel foam. As an example, the porous current collector 1 may be copper foam.

[0045] In some embodiments, the porous current collector 1 and the metal layer 2 preferably contain the same metal element, so that the porous current collector 1 and the metal layer 2 have the same overall electronegativity, and will not cause the galvanic cell effect during battery charging and discharging, i.e., generate self-discharge and reduce battery performance.

[0046] In some embodiments, the porosity of the porous current collector 1 is 20% to 60%. As an example, the porosity of the porous current collector 1 can be 20%, 40%, 60%, etc., or other values ​​within the above range, which are not limited here.

[0047] In some embodiments, the thickness of the porous current collector 1 is 4μm to 20μm. As an example, the thickness of the porous current collector 1 can be 4μm, 8μm, 12μm, 16μm, 20μm, etc., or other values ​​within the above range, which are not limited here. The porosity and thickness of the porous current collector 1 are within the above range. If the porosity of the porous current collector is within this range, a balance can be achieved between the structural stability of the copper foil and the lithium-ion deposition sites. If the porosity is too high, i.e., there are too many internal pores, the structural strength of the copper foil is weak, and it is prone to deformation, wrinkles, and other defects. If the porosity is too low, there are fewer lithium-ion deposition sites, and safety performance cannot be guaranteed. If the thickness of the porous current collector is too thick, the weight is greater, and the energy density loss is greater. If the thickness is too low, the total number of lithium-ion deposition sites is less, which is not conducive to improving safety performance.

[0048] In some embodiments, the thickness of metal layer 2 is 1 μm to 2 μm. As an example, the thickness of metal layer 2 can be 1 μm, 1.5 μm, 2 μm, etc., or other values ​​within the above range, and is not limited here. If the thickness of metal layer 2 is too small, the supporting force provided will be insufficient, the voltage resistance of the composite current collector will not be adequately improved, and the structural stability of the composite current collector will be significantly reduced; if the thickness of metal layer 2 is too large, the energy density of the battery will be reduced.

[0049] In some embodiments, the thickness of the insulating layer 3 is 50 nm to 200 nm. As an example, the thickness of the insulating layer 3 can be 50 nm, 100 nm, 150 nm, 200 nm, etc., or other values ​​within the above range, which are not limited here. If the thickness of the insulating layer 3 is too large, it will affect the overall conductivity of the composite current collector; if the thickness of the insulating layer 3 is too small, it will be difficult to prevent lithium ions from depositing on the surface of the composite current collector.

[0050] In some embodiments, the pore size of the through-hole structure 4 is 5μm to 20μm. As an example, the pore size of the through-hole structure 4 can be 5μm, 10μm, 15μm, 20μm, etc., or other values ​​within the above range, which are not limited here. A pore size within the above range allows the composite current collector to have a certain specific surface area and a low resistance value, thereby improving the conductivity of the composite current collector. If the pore size of the through-hole structure 4 is too small, it hinders the deposition of lithium ions onto the surface of the porous current collector 1, easily causing the porous current collector 1 to crack, which is detrimental to lithium ion deposition. If the pore size of the through-hole structure 4 is too large, the copper foil will be prone to cracking under stress, which is detrimental to battery manufacturing and also affects safety.

[0051] In some embodiments, the total bottom area of ​​the through-hole structure 4 on the insulating layer side accounts for 20% to 40% of the area of ​​the insulating layer. As an example, the total bottom area of ​​the through-hole structure 4 on the insulating layer side can be 20%, 30%, 40%, etc., of the area of ​​the insulating layer 3, or other values ​​within the above range, which are not limited here. When the total bottom area of ​​the through-hole structure 4 on the insulating layer side is within this range, the composite copper foil can have sufficient conductivity.

[0052] In some embodiments, the ion-conducting polymer includes at least one of polyethylene glycol imide, polyamide imide, or polyethylene oxide. As an example, the ion-conducting polymer may be polyethylene glycol imide or polyamide imide.

[0053] In some embodiments, the through-hole structure 4 also contains an adhesive.

[0054] In some embodiments, the mass ratio of the ion-conducting polymer to the binder is (80~90):(10~20). As an example, the mass ratio of the ion-conducting polymer to the binder can be 80:20, 85:15, 90:10, etc., or any ratio within the above range, and is not specifically limited here.

[0055] In some embodiments, the porous current collector 1 has a reserved area for welding tabs. The area for welding tabs is not provided with a metal layer 2 and an insulating layer 3, so as not to affect the production of lithium-ion batteries.

[0056] Therefore, based on the above, the composite current collector of the present invention includes a porous current collector 1. The porous structure of the porous current collector 1 can effectively reduce the weight of the current collector, further improving the energy density of the lithium battery. Furthermore, the porous nature facilitates heat dissipation, reducing the battery temperature and lowering the risk of thermal runaway. Moreover, the porous structure of the porous current collector 1 effectively increases the deposition area of ​​lithium ions, preventing excessive growth of lithium ion dendrites and improving battery safety. In addition, the presence of the metal layer 2 can enhance the compressive strength of the porous current collector 1, providing it with a certain supporting force. It can also compensate for the conductivity of the porous current collector 1 and provide a smoother platform area for the insulating layer 3. The insulating layer 3 can prevent lithium ions from depositing on the surface of the composite current collector, preventing lithium dendrites from piercing the separator.

[0057] Furthermore, since the outermost layer of the composite current collector is the insulating layer 3, lithium ions cannot be deposited on the outermost layer of the composite current collector. The metal layer 2 and the insulating layer 3 of this application have a through-hole structure 4, and the through-hole structure 4 also contains an ion-conducting polymer. The ion-conducting polymer preferentially adsorbs lithium ions through its physical adsorption properties, allowing the lithium ions to aggregate directionally. Then, through electronegativity attraction, they diffuse into the copper foil. This combination of physical adsorption and electronic adsorption makes lithium deposition in the electrodeless battery more uniform, thereby further improving the battery's safety performance.

[0058] [Preparation Method of Composite Current Collector] Based on the same inventive concept, this application provides a method for preparing a composite current collector, comprising the following steps: Metal is deposited on the surface of porous current collector 1 to form metal layer 2; An oxidant is coated on the surface of the metal layer 2 to oxidize the metal on the surface of the metal layer 2, forming an insulating layer 3; Through holes are drilled in the metal layer 2 and the insulating layer 3, and then the through holes are filled with ion-conducting polymer slurry to obtain a composite current collector.

[0059] It should be understood that all the features and advantages described above regarding the "composite current collector" also apply to the "preparation method of the composite current collector," and will not be repeated here.

[0060] In some embodiments, the method for depositing metal includes plasma sputtering.

[0061] In some embodiments, the target voltage in plasma sputtering is 500V~800V, the operating voltage is 200V~240V, and the distance between the target and the substrate is controlled between 20mm~40mm. As an example, the target voltage can be 500V, 600V, 700V, 800V, etc., or other values ​​within the above range, which are not limited here. As an example, the operating voltage can be 200V, 220V, 230V, 240V, etc., or other values ​​within the above range, which are not limited here. As an example, the distance between the target and the substrate can be controlled between 20mm, 30mm, 40mm, etc., or other values ​​within the above range, which are not limited here.

[0062] In some embodiments, the target material includes copper or nickel; the plasma sputtering deposition of metal is performed under an inert atmosphere with a pressure of 20 Pa to 50 Pa and a deposition temperature of 500°C to 700°C. As an example, the deposition pressure can be 20 Pa, 30 Pa, 40 Pa, 50 Pa, etc., or other values ​​within the above range, and is not limited herein. As an example, the deposition temperature can be 500°C, 600°C, 700°C, etc., or other values ​​within the above range, and is not limited herein. The sputtering time can be adjusted, thereby controlling the thickness of the metal layer 2.

[0063] In some embodiments, the oxidant includes a mixture of hydrogen peroxide and hydrochloric acid. The volume ratio of hydrogen peroxide to hydrochloric acid is (90~110):(2~4). As an example, the volume ratio of hydrogen peroxide to hydrochloric acid can be 90:2, 100:3, 100:4, etc., or any ratio within the above range, and is not specifically limited here.

[0064] In some embodiments, the coating amount of oxidant is 10 mL / m 2 ~50mL / m 2 As an example, the coating amount of oxidant can be 10 mL / m. 2 20mL / m 2 30mL / m 2 40mL / m 2 50mL / m 2 "etc." can also be any ratio within the above range, without being specifically limited here.

[0065] In some embodiments, the compaction density of the porous current collector 1 is 1.4 g / cm³. 3 ~1.6g / cm 3 As an example, the compaction density of the porous current collector 1 can be 1.4 g / cm³. 3 1.5g / cm 3 1.6g / cm 3"etc." can also be any ratio within the above range, without being specifically limited here.

[0066] In some embodiments, the method for creating through-holes between the metal layer 2 and the insulating layer 3 includes laser etching. When using laser etching to create through-holes, the etching depth can be controlled by adjusting the laser power and the etching time.

[0067] Therefore, based on the above, a method for preparing a composite current collector is provided. This involves depositing a metal layer 2 on a porous current collector 1, then coating the metal layer 2 with an oxidant to obtain an oxide layer, then drilling through-holes, and finally filling the through-holes with an ion-conducting polymer slurry to obtain the composite current collector. This current collector features high energy density and high safety, and its preparation process is simple and its application scenarios are wide-ranging, giving it a strong competitive advantage in the field of electrodeless batteries.

[0068] Based on the same inventive concept, this application provides a negative electrode-free battery, including a current collector, which is the aforementioned composite current collector or a composite current collector prepared according to the aforementioned preparation method.

[0069] Because this battery contains the composite current collector provided in the embodiments of this application, it has the characteristics of high energy density and high safety.

[0070] In some embodiments, the battery further includes a positive electrode, an electrolyte, and a separator. That is, the battery includes a positive electrode, a composite current collector, an electrolyte, and a separator.

[0071] In this embodiment, the materials and structures of the positive electrode current collector, the conductive agent and the binder in the positive electrode active material layer are not limited, and the positive electrode structure and composition known in the art that can be used in secondary batteries can be selected.

[0072] In this embodiment, the specific material or type of the separator is not limited, and any separator known in the art that can be used in secondary batteries can be selected.

[0073] It should also be noted that the battery in this application does not limit the specific material or type of electrolyte. Any components and types known in the art that can be used in secondary batteries can be selected, as long as the purpose of this application can be achieved.

[0074] Since the battery provided in this embodiment of the invention adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0075] The following describes the implementation methods of this application. The implementation methods described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the implementation methods, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents, materials, or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0076] Example 1 Copper foam with a porosity of 40% was selected and rolled to obtain a thickness of 10 μm and a compaction density of 1.5 g / cm³. 3 A porous current collector was constructed. Copper was deposited on both sides of the porous current collector along its thickness direction using plasma sputtering. Copper was used as the target material. The power supply was connected with a target voltage of 600V and a working voltage of 240V. The distance between the target and the substrate was controlled at 30mm, the inert gas pressure was 40Pa, and the deposition temperature was 600℃. The copper metal layer thickness was controlled to 1µm by adjusting the sputtering time. The above steps were repeated on the other side of the porous current collector.

[0077] Hydrogen peroxide and hydrochloric acid were mixed at a volume ratio of 100:3, and then coated onto the deposited copper surface, with the coating amount controlled at 20 mL / m. 2 A copper oxide insulating layer with a thickness of 100 nm was obtained.

[0078] Through-holes with a diameter of 10 μm were etched into the copper oxide insulating layer and the copper metal layer using laser etching. Then, an ion-conducting polymer slurry was injected into the etched through-holes using a probe, and the slurry was dried at 60°C to obtain a composite current collector. The area of ​​the through-holes accounts for 30% of the area of ​​the insulating layer. The ion-conducting polymer slurry was obtained by mixing polyamide-imide and a binder (sodium carboxymethyl cellulose) in water at a mass ratio of 9:1.

[0079] A schematic diagram of the cross-sectional structure of the prepared composite current collector is shown below. Figure 1 See the schematic diagram of the planar structure. Figure 2 Among them, by Figure 2 As can be seen, porous current collector areas are reserved on both sides of the insulating layer, which can be used to weld the tabs without affecting the production of lithium-ion batteries.

[0080] Example 2 The only difference between Example 2 and Example 1 is that the thickness of the porous current collector in Example 2 is 20 μm, and all other aspects are the same as in Example 1.

[0081] Example 3 The only difference between Example 3 and Example 1 is that the thickness of the copper metal layer in Example 3 is 2 μm, and all other aspects are the same as in Example 1.

[0082] Example 4 The only difference between Example 4 and Example 1 is that the porosity of the copper foam in Example 4 is 60%, while the rest are the same as in Example 1.

[0083] Example 5 The only difference between Example 5 and Example 1 is that the thickness of the copper oxide insulating layer in Example 5 is 200 nm, while the rest is the same as in Example 1.

[0084] Example 6 The only difference between Example 6 and Example 1 is that the diameter of the through hole in Example 6 is 20 μm, while the rest are the same as in Example 1.

[0085] Example 7 The only difference between Example 7 and Example 1 is that the area of ​​the through hole in Example 7 accounts for 40% of the area of ​​the insulating layer, while the rest is the same as in Example 1.

[0086] Example 8 The only difference between Example 8 and Example 1 is that in Example 8, copper foam is replaced with nickel foam; otherwise, they are the same as in Example 1.

[0087] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the thickness of the porous current collector in Comparative Example 1 is 2 μm, while the rest are the same as in Example 1.

[0088] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the thickness of the copper metal layer in Comparative Example 2 is 4 μm, while the rest are the same as in Example 1.

[0089] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the porosity of the copper foam in Comparative Example 3 is 80%, while the rest are the same as in Example 1.

[0090] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that the thickness of the copper oxide insulating layer in Comparative Example 4 is 400 nm, while the rest are the same as in Example 1.

[0091] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that the diameter of the through hole in Comparative Example 5 is 3 μm, while the rest are the same as in Example 1.

[0092] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that the area of ​​the through hole in Comparative Example 6 accounts for 10% of the area of ​​the insulating layer, while the rest is the same as in Example 1.

[0093] Comparative Example 7 The only difference between Comparative Example 7 and Example 1 is that Comparative Example 7 does not contain a copper oxide insulating layer; otherwise, they are the same as Example 1.

[0094] Performance testing 1. Composite current collector performance test (1) Specific surface area test: The N2 adsorption method was used to measure the specific surface area of ​​the composite current collector by the amount of gas adsorbed.

[0095] (2) Maximum compaction density test: Prepare multiple identical samples and test the thickness change of the composite current collector under pressures of 3.2 T, 3.3 T, 3.4 T, 3.5 T, and 3.6 T. Observe the thickness change and judge the compaction condition of the composite current collector by the change of internal pores under different pressures. If poor pore closure occurs under a certain pressure, the pressure can be determined as the maximum pressure resistance pressure, and the compaction density of the composite current collector at this time is the maximum compaction density.

[0096] (3) Conductivity test: The resistivity of the composite copper foil was measured using a four-probe resistance tester.

[0097] The test results of the composite current collectors prepared in each embodiment and comparative example are shown in Table 1.

[0098] Table 1 As can be seen from the test results in Table 1, the porosity and thickness of the porous current collector directly affect the pressure resistance and specific surface area of ​​the composite current collector. The thickness of the metal layer is also positively correlated with the pressure resistance of the composite current collector. The thickness of the insulating layer is inversely proportional to the conductivity of the composite current collector.

[0099] The higher the porosity of a porous current collector, the more internal pores there are, and the larger the specific surface area of ​​the porous current collector becomes. However, the increased number of pores leads to a decrease in the pressure resistance of the porous current collector. Increasing the thickness of the metal layer provides some support and is beneficial to improving the pressure resistance of the composite current collector. However, if the metal layer is too thick, the weight will increase too much, which is not conducive to improving the energy density of the battery.

[0100] A thicker insulating layer, while non-conductive, negatively impacts the conductivity of the composite current collector. However, its insulating properties also help prevent lithium ion deposition on the outer surface. Furthermore, increasing the aperture size and the area of ​​the through-hole relative to the insulating layer area increases the specific surface area of ​​the composite current collector, thus reducing its resistance and improving conductivity. Conversely, excessively low values ​​hinder lithium ion deposition on the porous current collector surface, while excessively high values ​​can cause it to crack, hindering deposition. Additionally, the cost of the composite current collector is highly dependent on the thickness of the metal layer; a thicker metal layer increases manufacturing costs, hindering cost control in lithium batteries. While removing copper oxide from the outermost layer improves the foil's conductivity and withstand voltage, indicating a support function, lithium ion deposition should be carefully monitored to ensure safety.

[0101] 2. Battery manufacturing Preparation of the positive electrode: The positive electrode active material NCM811 (chemical formula LiNi) is used. 0.8 Co 0.1 Mn 0.1 The active material (O2), conductive agent (SP), and carbon nanotubes are used. PVDF5130 (polyvinylidene fluoride) is used for bonding. 13μm aluminum foil is used as the positive electrode current collector. The positive electrode active material, SP, carbon nanotubes, and binder are mixed in a ratio of 97:1.5:0.5:1. NMP is added and stirred to form a uniform and stable positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector with a coating density of 195 g / m². 2 After drying and cold pressing, a positive electrode sheet is obtained with a compacted density of 3.4 g / cm³. 3 .

[0102] Separator membrane: base membrane (polypropylene) + ceramic layer + adhesive layer + adhesive layer (9+3+3+3μm).

[0103] Electrolyte: In a glove box filled with inert gas, ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate are mixed in a mass ratio of 1:1:1 to obtain an organic solvent. Then, lithium salt LiPF6 is dissolved in the organic solvent with a concentration of 1.2 mol / L to obtain the electrolyte.

[0104] Battery assembly: The positive electrode, separator, and negative electrode are arranged in sequence and assembled using a stacking method. Electrolyte is injected into the dry cell and immersed for 24 hours. Formation is then carried out at 45°C. The formation process involves charging to 3.4V at 0.05C, followed by charging to 3.75V at 0.2C. Cell fabrication is completed after 24 hours of aging at room temperature.

[0105] 3. Perform electrochemical performance testing on the battery. (1) DC internal resistance ACR test: The battery is charged and discharged according to the standard 0.5C / 1C charging and discharging system. The battery is charged to 4.25V with constant current and constant voltage at the standard 0.5C current, and left to stand for 30 minutes. Then it is discharged with constant current at 1C current for 30 minutes and left to stand for 60 minutes. The DC internal resistance of the battery is tested using a DC internal resistance meter.

[0106] (2) Capacity retention test after 500 cycles at 1C: At 25°C, the battery is charged to 4.25V at a constant current and constant voltage of 0.5C, left to stand for 30 minutes, and then discharged to 2.5V at a constant current of 1C, left to stand for 30 minutes. This is one complete charge and discharge cycle. 500 cycles are performed in sequence.

[0107] (3) 1C energy density test: At 25°C, the battery was charged to 4.25V with constant current and constant voltage at a standard 0.5C current, left to stand for 30 minutes, and then discharged to 2.5V with constant current at 1C current. The discharge capacity and average discharge voltage were recorded.

[0108] Wherein, 1C energy density = 1C discharge capacity * 1C discharge average voltage / total weight of battery.

[0109] (4) 5C rate capacity retention test: The battery is charged and discharged according to the 0.5C / 5C charging and discharging regime. The battery is charged to 4.25V at a constant current and constant voltage of 0.5C, left to stand for 30 minutes, and then discharged to 2.5V at a constant current of 5C. The 5C capacity retention rate = 5C discharge capacity / 1C discharge capacity. (5) Maximum charging rate test: The charging and discharging test is carried out according to the standard test procedure of 0.5C / XC. The cell is charged to 4.25V with constant current and constant voltage at the standard 0.5C current, and left to stand for 30 minutes. Then it is discharged to 2.5V with constant current at XC current, and left to stand for 30 minutes until the battery experiences thermal runaway. The rate at which thermal runaway occurs is the maximum safe rate of the negative electrode-less current collector battery, which indirectly reflects the safety performance of the negative electrode-less current collector structure. Where X is an integer (such as 1, 2, 3, etc.).

[0110] The test results of each embodiment and comparative example are shown in Table 2.

[0111] Table 2 As can be seen from the test data in Table 2, the batteries prepared with the composite current collectors in the examples all exhibit superior electrochemical performance. In Comparative Example 1, the porous current collector thickness is too low, resulting in insufficient pores to accommodate lithium ions from the positive electrode, leading to lithium ion blockage and deposition, which affects battery cycle life, rate performance, and maximum charging rate. While Comparative Example 2's data is similar to the examples, its overall advantage is not significant considering manufacturing costs. In Comparative Example 3, the high porosity of the porous current collector results in low structural strength of the composite current collector, making it prone to deformation and causing blockage, hindering lithium ion deposition and ultimately affecting battery cycle life, capacity utilization, and safety performance. In Comparative Example 4, the excessively thick copper oxide insulating layer increases internal resistance, leading to increased battery polarization and affecting overall battery capacity and safety performance. In Comparative Examples 5 and 6, the reduced diameter and number of through-holes both affect the diffusion rate of lithium ions into the composite copper foil, easily causing blockage and lithium deposition, thus impacting the battery's capacity and safety performance. In Comparative Example 7, the copper oxide layer was removed. Since some lithium ions were deposited on the surface, excessive growth of lithium dendrites would occur, affecting the safety performance. As a result, the cycle life would be affected, and the maximum charging rate would be reduced, among other adverse phenomena.

[0112] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0113] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0114] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "described," and "the" used in the embodiments of the invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0115] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite current collector, characterized by, The composite current collector comprises a porous current collector; a metal layer disposed on at least one side of the porous current collector along the thickness direction; an insulating layer disposed on the surface of the metal layer away from the porous current collector; wherein the metal layer and the insulating layer have a through-hole structure containing an ion-conducting polymer therein; the metal element of the metal layer comprises at least one of copper or nickel; the insulating layer comprises at least one of copper oxide or nickel oxide.

2. The composite current collector of claim 1, wherein the porous current collector comprises at least one of foamed copper or foamed nickel; and / or, the porosity of the porous current collector is 20% to 60%; and / or, the thickness of the porous current collector is 4 μm to 20 μm.

3. The composite current collector of claim 1, wherein the thickness of the metal layer is 1 μm to 2 μm; and / or, the thickness of the insulating layer is 50 nm to 200 nm.

4. The composite current collector of claim 1, wherein the pore size of the through-hole structure is 5 μm to 20 μm; and / or, the total bottom area of the through-hole structure on one side of the insulating layer accounts for 20% to 40% of the area of the insulating layer.

5. The composite current collector of claim 1, wherein the ion-conducting polymer comprises at least one of polyethylene glycol imine, polyamide-imide or polyethylene oxide; and / or, the through-hole structure further contains a binder; the mass ratio of the ion-conducting polymer to the binder is (80-90):(10-20).

6. The method of making a composite current collector of any one of claims 1 to 5, wherein, comprising the following steps: depositing a metal on the surface of the porous current collector to form a metal layer; coating an oxidizing agent on the surface of the metal layer to oxidize the metal on the surface of the metal layer and form an insulating layer; punching through-holes in the metal layer and the insulating layer, and then filling the through-holes with ion-conducting polymer slurry to obtain the composite current collector.

7. The method of making a composite current collector of claim 6, wherein, The method of depositing the metal comprises a plasma sputtering method; in the plasma sputtering method, the target voltage is 500 V to 800 V, the working voltage is 200 V to 240 V, and the distance between the target and the substrate is controlled to be 20 mm to 40 mm; the target comprises copper or nickel; the plasma sputtering method is carried out in an inert atmosphere, the gas pressure is 20 Pa to 50 Pa, and the temperature during deposition of the metal is 500 ℃ to 700 ℃.

8. The method of making a composite current collector of claim 6, wherein, the oxidizing agent comprises a mixture of hydrogen peroxide and hydrochloric acid; the volume ratio of the hydrogen peroxide to the hydrochloric acid is (90-110):(2-4); and / or the coating amount of the oxidizing agent is 10 mL / m 2 50 mL / m 2 .

9. The method of making a composite current collector of claim 6, wherein, The compacted density of the porous current collector is 1.4 g / cm 3 1.6 g / cm 3 ; and / or, the method of punching through-holes in the metal layer and the insulating layer comprises a laser etching method.

10. A negative electrode-free battery comprising a current collector, characterized by, The current collector is the composite current collector of any one of claims 1-5, or is prepared by the preparation method of any one of claims 6-9.

Images