Composite current collector, method for manufacturing the same, and negative electrode-free battery

Abstract

The present application relates to the technical field of batteries, and 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, a metal layer arranged on at least one side of the porous current collector along the thickness direction, and an insulating layer arranged on the surface of the side of the metal layer away from the porous current collector. The metal layer and the insulating layer have a through-hole structure, the through-hole structure contains an ion-conducting polymer, the metal elements of the metal layer include at least one of copper or nickel, and the insulating layer includes at least one of copper oxide or nickel oxide. The composite current collector can solve the problem of non-uniform lithium deposition in the structure of the negative-electrode-free battery and improve the safety performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a composite current collector, a preparation method thereof and a negative electrode-free battery. BACKGROUND

[0002] In order to improve the energy density of lithium batteries, the weight reduction of the battery cell is one of the feasible solutions. The negative electrode-free structure can greatly reduce the weight of the battery and improve the energy density of the lithium battery because it does not need negative active material. However, the negative electrode-free structure faces a serious problem that, without the lithium intercalation of the negative active material, the lithium ions released from the positive electrode have no place to intercalate. Although the conventional copper foil as the negative electrode can deposit lithium, it faces the risk of uneven lithium deposition, formation of lithium dendrites, contact short circuit of the positive and negative electrodes, and safety problems. In addition, in the high-energy density battery system, the heat generated under the same conditions is larger than that of ordinary batteries due to the large energy density, and therefore the heat generation problem of the high-energy battery is also a major factor affecting its safety performance.

[0003] Based on the above, it is urgent to provide a technical solution that can solve the problems of uneven lithium deposition and poor safety in the negative electrode-free battery. SUMMARY

[0004] Therefore, the present application aims to at least partially solve one of the technical problems in the related art. To this end, the present application provides a composite current collector, a preparation method thereof and a negative electrode-free battery, which can solve the problem of uneven lithium deposition in the negative electrode-free battery structure and also improve the safety performance of the battery.

[0005] To solve the above technical problems, the present application is implemented as follows:

[0006] According to one aspect of the present application, the present application embodiment provides a composite current collector, which comprises a porous current collector;

[0007] a metal layer, which is arranged on at least one side of the porous current collector along the thickness direction;

[0008] an insulating layer, which is arranged on the surface of the metal layer away from the porous current collector;

[0009] wherein the metal layer and the insulating layer have a through-hole structure containing an ion-conducting polymer;

[0010] the metal element of the metal layer comprises at least one of copper or nickel;

[0011] the insulating layer comprises at least one of copper oxide or nickel oxide.

[0012] In some embodiments, the porous current collector comprises at least one of a foamed copper or a foamed nickel.

[0013] In some embodiments, the porosity of the porous current collector is 20% to 60%.

[0014] In some embodiments, the thickness of the porous current collector is 4 μm to 20 μm.

[0015] In some embodiments, the thickness of the metal layer is 1 μm to 2 μm.

[0016] In some embodiments, the thickness of the insulating layer is 50 nm to 200 nm.

[0017] In some embodiments, the pore size of the through-hole structure is 5 μm to 20 μm.

[0018] In some embodiments, the total bottom area of the through-hole structure on one side of the insulating layer is 20% to 40% of the area of the insulating layer.

[0019] In some embodiments, the ion-conducting polymer comprises at least one of polyethylene glycol imine, polyamide-imide, or polyethylene oxide.

[0020] In some embodiments, the through-hole structure further comprises a binder.

[0021] In some embodiments, the mass ratio of the ion-conducting polymer to the binder is (80-90):(10-20).

[0022] According to another aspect of the present application, the embodiments of the present application provide a method for preparing a composite current collector, comprising the following steps:

[0023] depositing a metal on the surface of the porous current collector to form a metal layer;

[0024] coating an oxidizing agent on the surface of the metal layer to oxidize the metal on the surface of the metal layer to form an insulating layer;

[0025] punching a through-hole in the metal layer and the insulating layer, and then filling the through-hole with an ion-conducting polymer slurry to obtain a composite current collector.

[0026] In some embodiments, the method for depositing a metal comprises a plasma sputtering method.

[0027] In some embodiments, the target voltage in the plasma sputtering method 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.

[0028] In some embodiments, the target material comprises copper or nickel; the metal is deposited by the plasma sputtering method in an inert atmosphere, the pressure is 20 Pa to 50 Pa, and the temperature during deposition of the metal is 500 DEG C to 700 DEG C.

[0029] In some embodiments, the oxidizing agent comprises a mixture of hydrogen peroxide and hydrochloric acid.

[0030] In some embodiments, the volume ratio of hydrogen peroxide to hydrochloric acid is (90-110):(2-4).

[0031] In some embodiments, the coating amount of the oxidizing agent is 10 mL / m 2 50 mL / m 2 .

[0032] In some embodiments, the compaction density of the porous current collector is 1.4 g / cm 3 1.6 g / cm 3 .

[0033] In some embodiments, the method for punching a through hole in the metal layer and the insulating layer comprises a laser etching method.

[0034] According to another aspect of the present application, the embodiments of the present application provide a negative electrode-free battery, comprising a current collector, wherein the current collector is the composite current collector described above, or the composite current collector prepared according to the preparation method described above.

[0035] The technical solutions of the present application have at least the following beneficial effects:

[0036] In the embodiments of the present application, the composite current collector provided comprises a porous current collector, wherein the porous structure of the porous current collector can effectively reduce the weight of the current collector, further improve the energy density of the lithium battery, and the porous property is conducive to heat diffusion, reduces the temperature of the battery, and reduces the risk of thermal runaway; and the porous structure of the porous current collector also effectively increases the deposition area of lithium ions, avoids the excessive growth of lithium ion deposition dendrites, and improves the safety of the battery. In addition, the presence of the metal layer can improve the pressure resistance of the porous current collector, provide certain support force for the porous current collector, also compensate for the conductivity of the porous current collector, and provide a more flat platform area for the insulating layer; the insulating layer can avoid the deposition of lithium ions on the surface of the composite current collector, and the phenomenon of lithium dendrite piercing the separator will not occur.

[0037] Further, since the outermost layer of the composite current collector is an insulating layer, lithium ions cannot be deposited in the outermost layer of the composite current collector. The metal layer and the insulating layer of the present application have a through-hole structure, and the through-hole structure further contains an ion-conducting polymer. The ion-conducting polymer preferentially adsorbs lithium ions through physical adsorption characteristics, so that lithium ions can be directionally aggregated and then diffuse into the copper foil through the attraction of electronegativity. Physical adsorption + electronic adsorption can make the lithium deposition in the anode-free battery more uniform, thereby further improving the safety performance of the battery.

[0038] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 A cross-sectional structure schematic diagram of a composite current collector provided by Embodiment 1 of the present application is shown.

[0040] Figure 2 A planar structure schematic diagram of a composite current collector provided by Embodiment 1 of the present application is shown.

[0041] REFERENCE SIGNS

[0042] 1 porous current collector;

[0043] 2 metal layer;

[0044] 3 insulating layer;

[0045] 4 through-hole structure. DETAILED DESCRIPTION

[0046] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments of the present application are only used to illustrate the present application and not to limit the scope of the present application.

[0047] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges or values should be construed to be approximations that allow for significant variation. Various ranges of values that are explicitly delineated in the specification as supplied herein constitute examples of such approximations.

[0048] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0049] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0050] If there is no special indication, all the steps of the present application can be carried out in sequence, or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0051] If there is no special indication, the "includes" and "contains" mentioned in the present application means open, and can also be closed. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0052] The anode-free structure battery has the characteristics of high energy density, but the anode-free structure battery in the prior art still has certain technical defects. For example, Chinese patent CN113013417A discloses an anode-free structure battery, an electronic conductive layer and an ion conductive layer are coated on the outer layer of the traditional anode material. Although this method can accommodate lithium sources from the positive electrode, the patent uses a method of directly soaking the ion coating glue solution with copper foil. The coating layer has no large number of pores, so the deposition rate of lithium ions on the surface of the copper foil is hindered, the efficiency of lithium deposition is low, and in severe cases, it can cause lithium dendrites to pierce the separator and cause short circuits due to the deposition of lithium ions not being timely (high-rate charging). In addition, the ion conductive layer is difficult to prepare, and the mass of the traditional anode metal substrate is large, which affects the energy density of the battery. For example, Chinese patent CN116581361A discloses an anode-free structure battery, which provides a lithium intercalation space and avoids direct reaction with the electrolyte by setting a lithium titanate layer in combination with a solid-state electrolyte. However, the current solid-state electrolyte has the problems of low ion transmission rate and interface contact, which affects the power performance of the battery, and the setting of the lithium titanate layer also brings the problem of weight increase, which is not conducive to the improvement of the energy density of the anode-free battery. For example, Chinese patent CN115863660B discloses a method of etching a copper foil current collector surface to prepare a nano-silver array to induce lithium ion deposition, but this method is difficult to prepare and is not uniform, which can easily cause the separator to be pierced and cause safety problems such as short circuits.

[0053] Therefore, the embodiments of the present application provide a composite current collector, which comprises a porous current collector 1;

[0054] A metal layer 2 is arranged on at least one side of the porous current collector 1 in the thickness direction;

[0055] An insulating layer 3 is arranged on the side surface of the metal layer 2 away from the porous current collector 1;

[0056] The metal layer 2 and the insulating layer 3 have a through-hole structure 4 containing an ion-conducting polymer;

[0057] The metal element of the metal layer 2 includes at least one of copper or nickel;

[0058] The insulating layer 3 includes at least one of copper oxide or nickel oxide.

[0059] The above-mentioned "the metal layer 2 is arranged on at least one side of the porous current collector 1 in the thickness direction" means that the metal layer 2 can be arranged on one surface of the porous current collector 1 in the thickness direction, or can be arranged on both surfaces of the porous current collector 1 in the thickness direction. The "surface" here can be the entire area of the porous current collector 1, or can be a partial area of the porous current collector 1. In the embodiment, the surface can be the entire area of the porous current collector 1, and the present application does not have a special limitation as long as the purpose of the present application can be achieved.

[0060] As an example, the porous current collector 1 has two opposite surfaces in its own thickness direction, and the metal layer 2 is arranged on the two opposite surfaces of the porous current collector 1. Further, the insulating layer 3 is formed on the surface of the metal layer 2 on both sides. It can be understood that the metal layer 2 can also be arranged on any one of the two surfaces of the porous current collector 1.

[0061] In the present application, the composite current collector includes the porous current collector 1, wherein the porous structure of the porous current collector 1 can effectively reduce the weight of the current collector, further improve the energy density of the lithium battery, and the porous property is also beneficial to heat diffusion, reduces the temperature of the battery, and reduces the risk of thermal runaway. In addition, the porous structure of the porous current collector 1 also effectively increases the deposition area of lithium ions, avoids the excessive growth of lithium ion deposition dendrites, and improves the safety of the battery. In addition, the presence of the metal layer 2 can improve the pressure resistance of the porous current collector 1, provide certain support force for the porous current collector 1, make up for the conductivity of the porous current collector 1, and provide a more flat platform area for the insulating layer 3; the insulating layer 3 can avoid the deposition of lithium ions on the surface of the composite current collector, and the phenomenon of lithium dendrite piercing the separator will not occur.

[0062] Further, since the outermost layer of the composite current collector is the insulating layer 3, lithium ions cannot be deposited in the outermost layer of the composite current collector. The metal layer 2 and the insulating layer 3 of the present 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 by physical adsorption characteristics, so that lithium ions can be directionally aggregated, and then diffuse into the copper foil by the attraction of electronegativity. Physical adsorption + electronic adsorption can make the lithium deposition in the anode-free battery more uniform, thereby further improving the safety performance of the battery.

[0063] In some embodiments, the porous current collector 1 includes at least one of foamed copper or foamed nickel. As an example, the porous current collector 1 can be foamed copper.

[0064] In some embodiments, the metal element of the porous current collector 1 and the metal layer 2 is preferably the same, so that the electronegativity of the whole of the porous current collector 1 and the metal layer 2 is the same, and the primary cell effect, i.e. self-discharge and reduced battery performance, will not occur during the charging and discharging of the battery.

[0065] 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., and of course can also be other values within the above range, which are not limited herein.

[0066] In some embodiments, the thickness of the porous current collector 1 is 4 μm to 20 μm. As an example, the thickness of the porous current collector 1 can be 4 μm, 8 μm, 12 μm, 16 μm, 20 μm, etc., and of course can also be other values within the above range, which are not limited herein. The porosity and thickness of the porous current collector 1 are within the above range, so that the structural stability of the copper foil and the balance of lithium ion deposition sites can be achieved. 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 easy to deform, wrinkle, etc. If the porosity is too low, there are fewer lithium ion deposition sites, and the safety performance cannot be guaranteed. If the thickness of the porous current collector is too thick, the weight is larger, and the energy density is lost. If the thickness of the porous current collector is too low, there are fewer total lithium ion deposition sites, which is not conducive to improving the safety performance.

[0067] In some embodiments, the thickness of the metal layer 2 is 1 μm to 2 μm. As an example, the thickness of the metal layer 2 can be 1 μm, 1.5 μm, 2 μm, etc., and of course can also be other values within the above range, which are not limited herein. If the thickness of the metal layer 2 is too small, the support provided is insufficient, the pressure resistance of the composite current collector is not improved enough, and the structural stability of the composite current collector will be significantly reduced. If the thickness of the metal layer 2 is too large, the energy density of the battery will be reduced.

[0068] In some embodiments, the insulating layer 3 has a thickness of 50 nm to 200 nm. For example, the thickness of the insulating layer 3 can be 50 nm, 100 nm, 150 nm, 200 nm, or the like, and can also be other values within the above range, which are not limited herein. 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.

[0069] In some embodiments, the through-hole structure 4 has a pore size of 5 μm to 20 μm. For example, the pore size of the through-hole structure 4 can be 5 μm, 10 μm, 15 μm, 20 μm, or the like, and can also be other values within the above range, which are not limited herein. If the pore size of the through-hole structure 4 is within the above range, the composite current collector will have a certain specific surface area and a relatively 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 will hinder the deposition of lithium ions on the surface of the porous current collector 1, which is prone to cause the rupture of the porous current collector 1 and is not conducive to the deposition of lithium ions; 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 not conducive to the manufacture of the battery and will affect the safety.

[0070] In some embodiments, the total bottom area of the pores of the through-hole structure 4 on the side of the insulating layer accounts for 20% to 40% of the area of the insulating layer. For example, the total bottom area of the pores of the through-hole structure 4 on the side of the insulating layer can account for 20%, 30%, 40%, or the like, of the area of the insulating layer 3, and can also be other values within the above range, which are not limited herein. If the total bottom area of the pores of the through-hole structure 4 on the side of the insulating layer accounts for the area of the insulating layer 3 within the range, the composite copper foil will have sufficient conductivity.

[0071] In some embodiments, the ion-conducting polymer includes at least one of polyethylene glycol imine, polyamide-imide, or polyethylene oxide. For example, the ion-conducting polymer can be polyethylene glycol imine, and can be polyamide-imide.

[0072] In some embodiments, the through-hole structure 4 further contains a binder.

[0073] In some embodiments, the mass ratio of the ion-conducting polymer to the binder is (80-90):(10-20). For example, the mass ratio of the ion-conducting polymer to the binder can be 80:20, 85:15, 90:10, or the like, and can also be a certain ratio within the above range, which is not limited herein.

[0074] In some embodiments, the porous current collector 1 reserves an area for welding the tab, and the area for welding the tab is not provided with the metal layer 2 and the insulating layer 3, which will not affect the production of the lithium ion battery.

[0075] Therefore, based on the above, the composite current collector of the present application comprises a porous current collector 1, wherein the porous structure of the porous current collector 1 can effectively reduce the weight of the current collector, further improve the energy density of the lithium battery, and the porous property is conducive to heat diffusion, reduces the temperature of the battery, and reduces the risk of thermal runaway; and the porous structure of the porous current collector 1 also effectively increases the deposition area of lithium ions, avoids the overgrowth of lithium ion deposition dendrites, and improves the safety of the battery. In addition, the presence of the metal layer 2 can improve the pressure resistance of the porous current collector 1, provide certain support force for the porous current collector 1, also make up for the conductivity of the porous current collector 1, and can provide a more flat platform area for the insulating layer 3; the insulating layer 3 can avoid the deposition of lithium ions on the surface of the composite current collector, and the phenomenon of lithium dendrite piercing the separator will not occur.

[0076] Further, 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 the present application have a through hole structure 4, and the through hole structure 4 also contains an ion-conducting polymer. The ion-conducting polymer will preferentially adsorb lithium ions by physical adsorption characteristics, so that lithium ions can be directionally aggregated, and then diffuse to the inside of the copper foil by the attraction of electronegativity. Physical adsorption + electronic adsorption can make the lithium deposition in the anode-free battery more uniform, thereby further improving the safety performance of the battery.

[0077] [Preparation method of composite current collector]

[0078] Based on the same inventive concept, the present application provides a preparation method of a composite current collector, comprising the following steps:

[0079] depositing metal on the surface of the porous current collector 1 to form a metal layer 2;

[0080] coating an oxidizing agent on the surface of the metal layer 2 to oxidize the metal on the surface of the metal layer 2 to form an insulating layer 3;

[0081] punching through holes in the metal layer 2 and the insulating layer 3, and then filling the through holes with ion-conducting polymer slurry, to obtain a composite current collector.

[0082] It should be understood that all the features and advantages described above for the "composite current collector" also apply to the "preparation method of the composite current collector", which will not be repeated here.

[0083] In some embodiments, the method of depositing metal includes a plasma sputtering method.

[0084] In some embodiments, the target voltage in the plasma sputtering method is 500V-800V, the working voltage is 200V-240V, and the distance between the target and the substrate is controlled to be 20mm-40mm. For example, the target voltage can be 500V, 600V, 700V, 800V, or other values within the above range. For example, the working voltage can be 200V, 220V, 230V, 240V, or other values within the above range. For example, the distance between the target and the substrate can be controlled to be 20mm, 30mm, 40mm, or other values within the above range.

[0085] In some embodiments, the target includes copper or nickel; the deposition of the metal in the plasma sputtering method is carried out in an inert atmosphere, the gas pressure is 20Pa-50Pa, and the temperature during the deposition of the metal is 500℃-700℃. For example, the gas pressure during the deposition of the metal can be 20Pa, 30Pa, 40Pa, 50Pa, or other values within the above range. For example, the temperature during the deposition of the metal can be 500℃, 600℃, 700℃, or other values within the above range. The sputtering time can be controlled, so that the thickness of the metal layer 2 can be controlled.

[0086] In some embodiments, the oxidizing agent includes a mixture of hydrogen peroxide and hydrochloric acid. The volume ratio of hydrogen peroxide to hydrochloric acid is (90-110):(2-4). For example, the volume ratio of hydrogen peroxide to hydrochloric acid can be 90:2, 100:3, 100:4, or other values within the above range.

[0087] In some embodiments, the coating amount of the oxidizing agent is 10mL / m 2 -50mL / m 2 . For example, the coating amount of the oxidizing agent can be 10mL / m 2 , 20mL / m 2 , 30mL / m 2 , 40mL / m 2 , 50mL / m 2 , or other values within the above range.

[0088] In some embodiments, the compacted density of the porous current collector 1 is 1.4g / cm 3 -1.6g / cm 3 . For example, the compacted density of the porous current collector 1 can be 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3and of course can also be a certain ratio within the above range, which is not specifically limited here.

[0089] In some embodiments, the method for punching the through hole in the metal layer 2 and the insulating layer 3 includes a laser etching method. In the laser etching method, the depth of the etching can be controlled by adjusting the power of the laser and the etching time.

[0090] Therefore, based on the above, a preparation method of a composite current collector is provided, which includes depositing a metal layer 2 on a porous current collector 1, coating an oxidizing agent on the metal layer 2 to obtain an oxidation layer, then punching a through hole, and finally filling the through hole with an ion-conducting polymer slurry, thereby obtaining a composite current collector. The current collector has the characteristics of high energy density and high safety, and the preparation process is simple, the application scenarios are wide, and the current collector has good competitiveness in the field of batteries without negative electrodes.

[0091] Based on the same inventive concept, the embodiments of the present application provide a battery without negative electrode, which includes a current collector. The current collector is the composite current collector described above, or is prepared according to the preparation method described above.

[0092] The battery has the characteristics of high energy density and high safety because it contains the composite current collector provided by the embodiments of the present application.

[0093] In some embodiments, the battery described above further includes a positive electrode sheet, an electrolyte, and a separator. That is, the battery includes a positive electrode sheet, a composite current collector, an electrolyte, and a separator.

[0094] In the embodiments, the positive electrode current collector, the conductive agent, the binder, and other materials in the positive electrode active material layer, and the structure of the positive electrode sheet are not limited, and the positive electrode sheet structure and composition known in the art that can be used in secondary batteries can be selected.

[0095] In the embodiments, the specific material or type of the separator is not limited, and the separator known in the art that can be used in secondary batteries can be selected.

[0096] It should be further pointed out that the battery of the present application does not limit the specific material or type of the electrolyte, and the composition and type known in the art that can be used in secondary batteries can be selected, as long as the purpose of the present application can be achieved.

[0097] Since the battery provided by the embodiments of the present application adopts all the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0098] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are for the purpose of explanation only and are not to be understood as limiting the present application. In the embodiments, unless a specific technique or condition is mentioned, the technique or condition described in the literature in the art or according to the product manual is used. The reagents, materials or instruments used are not specified, and are all conventional products that can be obtained commercially.

[0099] Example 1

[0100] A porous copper with a porosity of 40% was selected, and after rolling, a porous current collector with a thickness of 10 μm and a compacted density of 1.5 g / cm 3 was obtained. The plasma sputtering method was used to deposit metal copper on both sides of the porous current collector along the thickness direction of the porous current collector. Copper was used as the target material, the power supply was turned on, the target material voltage was 600 V, the working voltage was 240 V, the distance between the target material and the base film was controlled at 30 mm, the inert gas pressure was 40 Pa, the deposition temperature was 600 ℃, and the copper metal layer thickness was controlled at 1 μm by adjusting the sputtering time; the above steps were repeated on the other side of the porous current collector.

[0101] Hydrogen peroxide and hydrochloric acid were mixed in a volume ratio of 100:3, and then coated on the surface of the deposited metal copper, with a coating amount of 20 mL / m 2 , to obtain a copper oxide insulating layer with a thickness of 100 nm.

[0102] Through the method of laser etching, through holes with a pore size of 10 μm were etched on the copper oxide insulating layer and the copper metal layer, and then the ion-conducting polymer slurry was injected into the etched through holes by a probe, and dried at 60 ℃ 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 is obtained by mixing polyamide-imide and a binder (sodium carboxymethyl cellulose) in a mass ratio of 9:1 in water.

[0103] The cross-sectional structure of the prepared composite current collector is shown in Figure 1 , and the planar structure is shown in Figure 2 . As can be seen from Figure 2 , the porous current collector region is reserved on both sides of the insulating layer, which can be used for welding the tab and will not affect the production of lithium ion batteries.

[0104] Example 2

[0105] The difference between Example 2 and Example 1 is only that the thickness of the porous current collector in Example 2 is 20 μm, and the rest is the same as Example 1.

[0106] Example 3

[0107] The difference between Example 3 and Example 1 is only that the thickness of the copper metal layer in Example 3 is 2 μm, and the rest is the same as Example 1.

[0108] Example 4

[0109] Example 4 is different from Example 1 only in that the porosity of the foamed copper of Example 4 is 60%, and the rest is the same as Example 1.

[0110] Example 5

[0111] Example 5 is different from Example 1 only in that the thickness of the copper oxide insulating layer of Example 5 is 200 nm, and the rest is the same as Example 1.

[0112] Example 6

[0113] Example 6 is different from Example 1 only in that the pore size of the through hole of Example 6 is 20 μm, and the rest is the same as Example 1.

[0114] Example 7

[0115] Example 7 is different from Example 1 only in that the area of the through hole of Example 7 accounts for 40% of the area of the insulating layer, and the rest is the same as Example 1.

[0116] Example 8

[0117] Example 8 is different from Example 1 only in that the foamed copper of Example 8 is replaced by foamed nickel, and the rest is the same as Example 1.

[0118] Comparative Example 1

[0119] Comparative Example 1 is different from Example 1 only in that the thickness of the porous current collector of Comparative Example 1 is 2 μm, and the rest is the same as Example 1.

[0120] Comparative Example 2

[0121] Comparative Example 2 is different from Example 1 only in that the thickness of the copper metal layer of Example Comparative Example 2 is 4 μm, and the rest is the same as Example 1.

[0122] Comparative Example 3

[0123] Comparative Example 3 is different from Example 1 only in that the porosity of the foamed copper of Comparative Example 3 is 80%, and the rest is the same as Example 1.

[0124] Comparative Example 4

[0125] Comparative Example 4 is different from Example 1 only in that the thickness of the copper oxide insulating layer of Comparative Example 4 is 400 nm, and the rest is the same as Example 1.

[0126] Comparative Example 5

[0127] The difference between Comparative Example 5 and Example 1 is only that the pore size of the through hole of Comparative Example 5 is 3 μm, and the rest is the same as Example 1.

[0128] Comparative Example 6

[0129] The difference between Comparative Example 6 and Example 1 is only that the area of the through hole accounts for 10% of the area of the insulating layer, and the rest is the same as Example 1.

[0130] Comparative Example 7

[0131] The difference between Comparative Example 7 and Example 1 is only that Comparative Example 7 does not contain a copper oxide insulating layer, and the rest is the same as Example 1.

[0132] Performance test

[0133] 1. Composite current collector performance test

[0134] (1) Specific surface area test: N2 adsorption method is used for measurement, and the specific surface area of the composite current collector is characterized by the amount of gas adsorption.

[0135] (2) Maximum compaction density test: multiple same samples are prepared, and the thickness change value of the composite current collector under 3.2 T (ton), 3.3 T (ton), 3.4 T (ton), 3.5 T (ton), 3.6 T (ton) pressure is tested. Observe the thickness change, and judge the compaction of the composite current collector by the change of internal pores at different pressures. If there is an adverse situation of internal pore closure at a certain pressure, the pressure can be determined as the maximum pressure resistance, and the compaction density of the composite current collector at this time is the maximum compaction density.

[0136] (3) Conductivity test: four-probe resistance test instrument is used to measure the resistivity of the composite copper foil.

[0137] The test results of the composite current collectors prepared in each example and comparative example are shown in Table 1.

[0138] Table 1

[0139]

[0140] 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, and the thickness of the metal layer also has a positive correlation with the pressure resistance of the composite current collector; the thickness of the insulating layer has an inverse relationship with the conductivity of the composite current collector.

[0141] The greater the porosity of the porous current collector, the more internal pores it has, and the greater the specific surface area of the porous current collector. However, the increase in the number of pores leads to a decrease in the pressure resistance of the porous current collector. The increase in the thickness of the metal layer provides partial support and helps to improve 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 the improvement of the energy density of the battery.

[0142] The thicker the insulating layer, the more adversely it affects the conductivity of the composite current collector, as the insulating layer is not conductive. However, due to the insulating nature of the insulating layer, a relatively thick insulating layer helps to prevent the deposition of lithium ions on the surface of the composite current collector. In addition, increasing the size of the through hole and the area of the through hole relative to the size of the insulating layer can improve the specific surface area of the composite current collector, thereby reducing the resistance of the composite current collector and improving the conductivity. If the size of the through hole and the area of the through hole are too small, it will hinder the deposition of lithium ions on the surface of the porous current collector, and vice versa, which can cause the porous current collector to break and is not conducive to the deposition of lithium ions. In addition, the cost of the composite current collector is closely related to the thickness of the metal layer. The thicker the metal layer, the higher the manufacturing cost, which is not conducive to the cost control of the lithium battery. In addition, the outermost layer of copper oxide is cancelled. Although the conductivity of the foil is improved and the pressure resistance is improved, it is clear that it plays a supporting role. However, attention should be paid to the deposition of lithium ions, which will ultimately affect the safety performance.

[0143] 2. Preparation of the battery

[0144] Preparation of the positive electrode sheet: the positive electrode active material NCM811 (chemical formula LiNi 0.8 Co 0.1 Mn 0.1 O2), the conductive agent is selected as SP and carbon nanotubes, the binder is selected as PVDF5130 (polyvinylidene fluoride), the positive electrode current collector is selected as 13 μm aluminum foil, 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 uniformly coated on the positive electrode current collector, the coating density is 195 g / m 2 , and the positive electrode sheet is obtained after drying and cold pressing, the compaction density is 3.4 g / cm 3 .

[0145] Separator: base film (polypropylene) + ceramic layer + adhesive layer + adhesive layer (9+3+3+3 μm).

[0146] Electrolyte: in an inert gas-filled glove box, 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 to obtain an electrolyte, and the concentration of the lithium salt is 1.2 mol / L.

[0147] 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.

[0148] 3. Perform electrochemical performance testing on the battery.

[0149] (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.

[0150] (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.

[0151] (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.

[0152] Wherein, 1C energy density = 1C discharge capacity * 1C discharge average voltage / total weight of battery.

[0153] (4) 5C rate capacity retention test:

[0154] 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.

[0155] (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.).

[0156] The test results of the examples and comparative examples are shown in Table 2.

[0157] Table 2

[0158]

[0159] As can be seen from the test data in Table 2, the batteries prepared from the composite current collectors of the examples all have excellent electrochemical performance. In Comparative Example 1, the thickness of the porous current collector is too low, and there are not enough pores to accommodate lithium ions from the positive electrode, resulting in plugging of the pores by lithium ions and affecting the cycle performance, rate performance and maximum charge rate of the battery. Although the data of Comparative Example 2 is not much different from that of the examples, the overall advantage is not great considering the manufacturing cost. In Comparative Example 3, the porosity of the porous current collector is too high, resulting in low structural strength of the composite current collector, easy deformation of the structure, plugging of the pores and hindering of lithium ion deposition, which ultimately affects the cycle performance, capacity development and safety performance of the battery. In Comparative Example 4, the thickness of the copper oxide insulating layer is too thick, the internal resistance is increased, the polarization of the battery is increased, and the capacity development and safety performance of the battery are affected. In Comparative Examples 5 and 6, the diameter of the through holes is reduced and the number of the through holes is reduced, which will affect the speed of diffusion of lithium ions into the composite copper foil, easily causing plugging and lithium precipitation, thus affecting the capacity development and safety performance of the lithium battery. In Comparative Example 7, the copper oxide layer is cancelled, and since part of the lithium ions are deposited on the surface, it will cause excessive growth of lithium dendrites, affecting the safety effect, thus affecting the cycle performance, reducing the maximum charge rate and other adverse phenomena.

[0160] The parts of the present application not described in detail are known to those skilled in the art.

[0161] The above describes the basic principles of the present application in combination with specific embodiments, but it should be pointed out that the advantages, advantages, effects and the like mentioned in the present application are only examples and not limitations, and these advantages, advantages, effects and the like cannot be considered as the must-have of each embodiment of the present application. In addition, the above-mentioned specific details are only for the purpose of example and for the purpose of understanding, and are not limited to the above-mentioned specific details to realize the present application.

[0162] It should be noted that the term "and / or" or " / " used herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases of A alone, A and B together, and B alone. The singular form "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural form, unless the context clearly indicates otherwise.

[0163] In the DETAILED DESCRIPTION and in the claims, a list of items connected with the term "at least one of" can mean any combination of the items in the list. For example, if the list contains items A, B, and C, the phrase "at least one of A, B, and C" can mean A alone; B alone; C alone; A and B together; A and C together; B and C together; or A, B, and C together. The item A can include a single element or multiple elements. The item B can include a single element or multiple elements. The item C can include a single element or multiple elements.

[0164] Finally, it should be noted that the above embodiments are merely used to describe but not limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalent ones; and these modifications or replacements 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 application.

Claims

1. A composite current collector, characterized in that, The composite current collector includes 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; The porosity of the porous current collector is 20%~60%, and the thickness of the porous current collector is 4μm~20μm; The thickness of the metal layer is 1μm~2μm; The thickness of the insulating layer is 50nm~200nm; The diameter of the through-hole structure is 5μm~20μm; The total bottom area of ​​the through-hole structure on one side of the insulation layer accounts for 20% to 40% of the area of ​​the insulation layer.

2. The composite current collector according to claim 1, characterized in that, The porous current collector includes at least one of copper foam or nickel foam.

3. The composite current collector according to claim 1, characterized in that, The ion-conducting polymer includes at least one of polyethylene glycol imide, polyamide imide, or polyethylene oxide; And / or, the through-hole structure also contains an adhesive; The mass ratio of the ion-conducting polymer to the binder is (80~90):(10~20).

4. The method for preparing the composite current collector according to any one of claims 1 to 3, characterized in that, Includes 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.

5. The method for preparing the composite current collector according to claim 4, characterized in that, Methods for depositing metals include plasma sputtering; The target voltage in the plasma sputtering method is 500V~800V, the working voltage is 200V~240V, and the distance between the target and the base film is controlled at 20mm~40mm. The target material includes copper or nickel; the plasma sputtering method for depositing metal is carried out in an inert atmosphere with a pressure of 20 Pa to 50 Pa and a temperature of 500 °C to 700 °C.

6. The method for preparing the composite current collector according to claim 4, characterized in that, The oxidizing agent includes a mixture of hydrogen peroxide and hydrochloric acid; The volume ratio of hydrogen peroxide to hydrochloric acid is (90~110):(2~4). And / or, the coating amount of the oxidant is 10 mL / m 2 ~50mL / m 2 .

7. The method for preparing the composite current collector according to claim 4, characterized in that, The compaction density of the porous current collector is 1.4 g / cm³. 3 ~1.6g / cm 3 ; And / or, the method for drilling through holes in the metal layer and insulating layer includes laser etching.

8. A negative electrode-free battery, comprising a current collector, characterized in that, The current collector is the composite current collector according to any one of claims 1 to 3, or the composite current collector prepared by the preparation method according to any one of claims 4 to 7.

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