Composite current collector and preparation method thereof, negative plate, battery and power utilization device

Abstract

The invention relates to a composite current collector and a preparation method thereof, a negative plate, a battery and an electric device. The composite current collector comprises a supporting layer and a functional layer arranged on at least one surface of the supporting layer, the functional layer comprises a carbon material layer and a metal layer, and the carbon material layer is located between the supporting layer and the metal layer; wherein the components of the metal layer comprise at least one of transition metal and inner transition metal, and when the metal layer is applied to preparation of the negative plate of the lithium metal battery, the cycle service life of the battery can be prolonged.

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, a negative electrode sheet, a battery and an electric device. BACKGROUND

[0002] In recent years, secondary batteries have been widely used in the fields of smart phones, tablet computers, smart wear, electric tools and electric vehicles. With the wide application of batteries, consumers' demand for the performance of batteries is increasing.

[0003] With the increasing demand, the performance of the secondary battery is getting higher and higher. The theoretical capacity of the traditional lithium ion battery using graphite as the negative active material is limited, which limits the energy density of the lithium ion battery. The lithium metal battery using high-energy-density lithium metal as the negative active material is considered to be one of the important development directions of batteries. However, heterogeneous metal corrosion is prone to occur in the negative electrode sheet of the lithium metal battery, which leads to a decrease in mechanical properties, thereby reducing the cycle performance of the lithium metal battery.

[0004] Therefore, the traditional technology needs to be further improved. SUMMARY

[0005] Therefore, it is necessary to provide a composite current collector, a preparation method thereof, a negative electrode sheet, a battery and an electric device, which aims to improve the cycle life of the battery.

[0006] The present application is achieved by the following technical solutions.

[0007] In a first aspect of the present application, a composite current collector is provided, which comprises a support layer and a functional layer arranged on at least one surface of the support layer; the functional layer comprises a carbon material layer and a metal layer, and the carbon material layer is located between the support layer and the metal layer.

[0008] In some embodiments, the metal layer comprises at least one of a transition metal and an inner transition metal.

[0009] In the above composite current collector, the carbon material layer and the metal layer of a specific component are arranged on the surface of the support layer in sequence, and when applied to prepare the negative electrode sheet of the lithium metal battery, the carbon material layer and the metal layer can play a role in blocking the support layer and the lithium metal. The carbon material layer not only plays a role in blocking corrosion, but also improves the mechanical strength and ductility of the composite current collector. At the same time, the metal layer of a specific component further blocks the corrosion penetration of the lithium metal to the support layer, and also improves the interaction with the lithium metal, thereby achieving the effect of preventing corrosion while further improving the contact stability of the composite current collector and the lithium metal, thereby improving the cycle performance of the battery.

[0010] In some embodiments, the composite current collector satisfies at least one of the following conditions:

[0011] (1) the thickness of the carbon material layer is 100 nm to 5 μm;

[0012] (2) the thickness of the metal layer is 200 nm to 2 μm.

[0013] In some embodiments, the composite current collector satisfies at least one of the following conditions:

[0014] (1) the thickness of the carbon material layer is 500 nm to 2 μm;

[0015] (2) the thickness of the metal layer is 300 nm to 1 μm.

[0016] The carbon material layer is lithium-lean relative to the metal layer, mainly serving to isolate the lithium metal to reduce the probability of heterogeneous metal corrosion, to enhance the mechanical properties of the support layer, to improve the resistance of the composite current collector to volume expansion and material pulling, and to further improve the interaction with the lithium metal while the metal layer of a specific component cooperatively blocks the corrosion and penetration of the lithium metal to the support layer; thus, by adjusting the thicknesses of the two layers, the overall stability of the composite current collector is further improved.

[0017] In some embodiments, the thickness ratio of the carbon material layer to the metal layer is 1:(0.2-2).

[0018] In some embodiments, the thickness ratio of the carbon material layer to the metal layer is 1:(0.85-1.65).

[0019] The thickness ratio of the carbon material layer to the metal layer is further adjusted to achieve better performance synergy and further improve the stability of the composite current collector.

[0020] In some embodiments, the thickness of the functional layer is 300 nm to 6 μm.

[0021] In some embodiments, the thickness of the functional layer is 500 nm to 3 μm.

[0022] In some embodiments, the component of the metal layer includes at least one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, platinum, and gold.

[0023] In some embodiments, the component of the metal layer includes at least one of nickel, titanium, and chromium.

[0024] Further regulate the composition of the metal layer, further improve the overall corrosion resistance stability of the composite current collector; wherein, Ni and Ti and other metals have a larger lattice mismatch with lithium metal, which can increase the interface energy and free energy, and reduce the contact probability of lithium and the base support layer, thereby reducing the probability of corrosion of the support layer.

[0025] In some embodiments, the component of the carbon material layer includes at least one of inorganic carbon and organic carbon.

[0026] Both inorganic carbon and organic carbon have good tensile strength and ductility, and also have good electrical conductivity and thermal conductivity, which can improve the mechanical properties of the composite current collector while playing a role in corrosion prevention.

[0027] It should be noted that organic carbon refers to the carbonized product of carbon-containing organic matter.

[0028] In some embodiments, the component of the support layer includes at least one of copper and its alloy.

[0029] In a second aspect of the present application, a preparation method of a composite current collector is provided, including the following steps:

[0030] forming a carbon material layer and a metal layer on at least one surface of the support layer in sequence;

[0031] wherein, the component of the metal layer includes at least one of transition metal and inner transition metal, and the composite current collector is prepared.

[0032] The step of forming a carbon material layer and a metal layer on at least one surface of the support layer in sequence includes the following steps:

[0033] coating a carbon source solution on at least one surface of the support layer, and performing sintering treatment to form a carbon material layer;

[0034] performing gas phase deposition treatment on the surface of the carbon material layer to form the metal layer.

[0035] The metal layer formed by gas phase deposition treatment is denser, which can better cooperate with the barrier to prevent the corrosion and penetration of lithium metal to the support layer. Further, no holes can be observed under an electron microscope at 5000 times magnification.

[0036] In a third aspect of the present application, a battery is provided, which includes a negative electrode sheet, and the negative electrode sheet includes the composite current collector of the first aspect or the composite current collector prepared by the preparation method of the second aspect.

[0037] In some embodiments, the negative electrode sheet further includes a metal lithium layer, and the metal lithium layer is arranged on the surface of the metal layer in the composite current collector.

[0038] In other words, the battery described above is a lithium metal battery.

[0039] In a fourth aspect of the present application, there is provided an electric device comprising the battery of the third aspect. BRIEF DESCRIPTION OF DRAWINGS

[0040] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a better understanding of the preferred embodiments, and are not to be considered limitations of the present application. Furthermore, in the accompanying drawings, like reference numerals refer to same or similar components throughout the several views. In the drawings:

[0041] Figure 1 is a schematic view of an embodiment of a battery;

[0042] Figure 2 is an exploded view of Figure 1

[0043] Figure 3 is a schematic view of an embodiment of a battery pack;

[0044] Figure 4 is an exploded view of Figure 3

[0045] Figure 5 is a schematic view of an embodiment of an electric device using the battery as a power source;

[0046] Figure 6 is a TEM image of a composite current collector prepared in an example of the present application after cyclic charge-discharge;

[0047] Figure 7 is a TEM image of a composite current collector prepared in a comparative example of the present application after cyclic charge-discharge.

[0048] REFERENCE NUMERALS

[0049] 1. battery pack; 2. upper case; 3. lower case; 4. battery; 41. shell; 42. electrode assembly; 43. cover plate; 5. electric device. DETAILED DESCRIPTION

[0050] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, specific embodiments of the present application are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order not to unnecessarily obscure the present application.

[0051] ​​In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship of two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0052] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0054] In the present application, unless otherwise specified, "room temperature" or "normal temperature" generally refers to 5℃ to 40℃, preferably 20±5℃.

[0055] In summary, the traditional lithium metal battery is prone to heterogeneous metal corrosion, especially in the negative tab lead-out tab part, mainly because two different metals: the current collector copper foil and the metal lithium are in contact in the medium, the corrosion rate of the metal with a more negative potential (such as copper) increases, that is, heterogeneous metal corrosion occurs, a lithium-copper transition layer is formed at the tab, resulting in a decrease in the mechanical strength of the negative electrode, which severely limits the cycle performance of the battery.

[0056] Based on this, after a large number of experimental researches, the technical scheme in the present application is obtained.

[0057] In an embodiment of the present application, a composite current collector is provided, which comprises a support layer and a functional layer arranged on at least one surface of the support layer; the functional layer comprises a carbon material layer and a metal layer, and the carbon material layer is located between the support layer and the metal layer.

[0058] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship of two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0059] In the composite current collector, the carbon material layer and the metal layer of specific components are arranged on the surface of the support layer in sequence, and when applied to the preparation of the negative electrode sheet of the lithium metal battery, the carbon material layer and the metal layer can play a role of blocking the support layer and the lithium metal. The carbon material layer plays a role of blocking corrosion while improving the mechanical strength and ductility of the composite current collector. Meanwhile, the metal layer of specific components further improves the interaction with the lithium metal while further blocking the corrosion and penetration of the lithium metal to the support layer, thereby improving the contact stability of the composite current collector and the lithium metal while preventing corrosion, thereby improving the cycle performance of the battery.

[0060] It can be understood that the support layer has two opposite surfaces in the thickness direction thereof, and the functional layer can be arranged on any one of the two surfaces or on both surfaces.

[0061] In some embodiments, the functional layer is arranged on both surfaces of the support layer.

[0062] In some embodiments, the thickness of the carbon material layer is 100 nm to 5 μm.

[0063] In some embodiments, the thickness of the carbon material layer is 500 nm to 2 μm.

[0064] In some embodiments, the thickness of the metal layer is 200 nm to 2 μm.

[0065] In some embodiments, the thickness of the metal layer is 300 nm to 1 μm.

[0066] Compared with the metal layer, the carbon material layer is lithium-poor and mainly plays a role of isolating the lithium metal to reduce the probability of heterogeneous metal corrosion, enhances the mechanical properties of the support layer, and improves the resistance of the composite current collector to volume expansion and material pulling. The metal layer of specific components further improves the interaction with the lithium metal while cooperating with the lithium metal to block the corrosion and penetration of the lithium metal to the support layer. Therefore, by adjusting the thicknesses of the two layers, the overall stability of the composite current collector is further improved.

[0067] In the range of 100 nm to 5 μm, the values include the minimum value and the maximum value in the range and every value between the minimum value and the maximum value. Specific examples include but are not limited to the following point values in the embodiments: 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm; or a range composed of any two values.

[0068] In the above "200 nm to 2 μm", the values include the minimum and maximum values of the range, and every value between the minimum and maximum values, and specific examples include, but are not limited to, the following point values in the embodiments: 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm; or a range consisting of any two numerical values.

[0069] In some embodiments, the thickness ratio of the carbon material layer and the metal layer is 1:(0.2-2).

[0070] In some embodiments, the thickness ratio of the carbon material layer and the metal layer is 1:(0.85-1.65).

[0071] The thickness ratio of the carbon material layer and the metal layer is further regulated to achieve better performance synergy between the two, further improving the stability of the composite current collector.

[0072] Alternatively, the thickness ratio of the carbon material layer and the metal layer is 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45, 1:1.5, 1:1.55, 1:1.6, 1:1.65, 1:1.7, 1:1.8, 1:1.9, 1:2; or a range consisting of any two numerical values.

[0073] In some embodiments, the thickness of the functional layer is 300 nm to 6 μm.

[0074] In some embodiments, the thickness of the functional layer is 500 nm to 3 μm.

[0075] In the above-mentioned "300 nm to 6 μm", the values include the minimum and maximum values of the range, and every value between the minimum and maximum values, and specific examples include, but are not limited to, the following point values in the embodiments: 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm; or a range composed of any two numerical values.

[0076] It can be understood that the transition metal elements refer to the elements in the d region and the ds region of the periodic table, the elements in the d region include the elements in the groups III B to VII B and VIII of the periodic system, and do not include the lanthanide series and actinide series elements; the elements in the ds region include the elements in the groups IB to IIB of the periodic table. The inner transition metal is at least one of the lanthanide series and actinide series elements.

[0077] In some embodiments, the component of the metal layer includes at least one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, platinum and gold.

[0078] In some embodiments, the component of the metal layer includes at least one of nickel, titanium and chromium.

[0079] The component of the metal layer is further regulated to further improve the corrosion resistance stability of the overall composite current collector; wherein the metals such as Ni, Cr and Ti, especially Ti metal, have a relatively large lattice misfit with lithium metal, the relatively large lattice misfit can improve the interface energy and free energy, and reduce the contact probability of lithium and the base support layer, thereby reducing the probability of corrosion of the support layer.

[0080] In some embodiments, the component of the carbon material layer includes at least one of inorganic carbon and organic carbon.

[0081] Both inorganic carbon and organic carbon have good tensile strength and ductility, and also have good electrical conductivity and thermal conductivity, which can improve the mechanical properties of the composite current collector while playing a role in corrosion prevention.

[0082] The above-mentioned inorganic carbon can use the commonly used inorganic carbon materials of the present application, including but not limited to at least one of mesocarbon microbeads, graphite, carbon nanotubes, carbon fibers, hard carbon and soft carbon. Specifically, it can be selected from at least one of SP, KS-6, acetylene black, vapor grown carbon fiber VGCF, carbon nanotube CNTs and graphene.

[0083] It is to be noted that the organic carbon refers to a carbonization product of carbon-containing organic matter. Further, the carbon-containing organic matter can be a carbon-containing organic matter commonly used in the art, including but not limited to at least one of fructose, glucose, starch and fatty acid.

[0084] In some embodiments, the support layer is a support layer for a negative electrode, and a support layer material for a negative electrode commonly used in the art can be used.

[0085] In some embodiments, the component of the support layer includes at least one of copper and an alloy thereof.

[0086] In some embodiments, the support layer can be a simple metal layer, such as a copper foil or a copper alloy, or a composite support layer including a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer, and the metal layer includes copper and an alloy thereof.

[0087] In some embodiments, the polymer material base material includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0088] Another embodiment of the present application provides a preparation method of a composite current collector, including the following step S10.

[0089] Step S10: sequentially forming a carbon material layer and a metal layer on at least one surface of the support layer.

[0090] In the step S10, the component of the metal layer includes at least one of a transition metal and an inner transition metal, and the composite current collector is prepared.

[0091] The material and thickness range of the carbon material layer and the metal layer are the same as described above, and will not be repeated here.

[0092] In some embodiments, the above preparation method includes the following steps S11-S12.

[0093] Step S11: coating a carbon source solution on at least one surface of the support layer and performing a sintering treatment to form a carbon material layer.

[0094] In some embodiments, the carbon source in the carbon source solution is an organic carbon source, which can be a carbon-containing organic matter commonly used in the art, including but not limited to at least one of fructose, glucose, starch and fatty acid.

[0095] In some embodiments, the solid content of the carbon source solution can be 30%-70%. Further, the solvent in the carbon source solution can be water, ethanol, etc.

[0096] It can be understood that the thickness of the carbon material layer formed can be controlled by controlling the coating amount of the carbon source solution.

[0097] In some embodiments, the sintering process is performed in an inert gas atmosphere.

[0098] In some embodiments, the sintering process is performed at a temperature of 700-1000℃ for 2-6h. The organic carbon source will undergo carbonization reaction during the sintering process to form the organic carbon derived material.

[0099] In some embodiments, before the step of coating, the method further comprises the following steps:

[0100] The support layer is subjected to acid pickling treatment.

[0101] The acid pickling can remove impurities and oxide layer on the surface of the support layer. Further, the acid pickling is performed using a hydrochloric acid solution.

[0102] In some embodiments, after the step of acid pickling, the method further comprises the following steps of sequentially subjecting the acid-pickled support layer to water washing and alcohol washing.

[0103] Further, the alcohol washing is performed using anhydrous ethanol.

[0104] Step S12: performing vapor deposition treatment on the surface of the carbon material layer to form a metal layer.

[0105] The metal layer formed by vapor deposition treatment has high compactness and can better cooperate with the barrier to the corrosion and penetration of lithium metal to the support layer.

[0106] Further, when the metal layer is observed under an electron microscope at a magnification of 5000 times, no holes can be observed.

[0107] It can be understood that when vapor deposition treatment is used, the components of the raw material are the same as those of the metal layer. For example, when the components of the metal layer are nickel, a nickel target is used as the raw material for vapor deposition treatment.

[0108] The vapor deposition treatment can use various types of vapor deposition treatment commonly used in the art, such as physical vapor deposition, including but not limited to: magnetron sputtering, evaporation, ion sputtering, etc. Further, by controlling the preparation parameters during vapor deposition treatment, such as deposition time and temperature, the thickness of the metal layer obtained by deposition can be controlled.

[0109] An embodiment of the present application also provides a battery, which comprises a negative electrode sheet, and the negative electrode sheet comprises the composite current collector or the composite current collector prepared by the method described above.

[0110] In some embodiments, the negative electrode sheet further comprises a metal lithium layer, and the metal lithium layer is arranged on the surface of the metal layer in the composite current collector.

[0111] In other words, the battery described above is a lithium metal battery.

[0112] It can be understood that the metal lithium layer is arranged on the surface of the metal layer of the composite current collector away from the carbon material layer.

[0113] In the negative electrode sheet, the carbon material layer plays a role of corrosion prevention and improves the mechanical strength and ductility of the composite current collector. Meanwhile, the metal layer with specific components further prevents the corrosion penetration of lithium metal to the support layer and improves the interaction with lithium metal, thereby achieving the effects of corrosion prevention and further improving the contact stability of the composite current collector and lithium metal. In particular, the metal layer can prevent heterogeneous metal corrosion from occurring in the tab part of the negative electrode sheet, thereby improving the cycle performance of the battery.

[0114] In some embodiments, the metal lithium layer is in direct contact with the metal layer in the composite current collector.

[0115] In some embodiments, the thickness of the metal layer is 0.5 μm to 2 μm. Optionally, the thickness of the metal layer is 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, or a range formed by any two of the above values.

[0116] It can be understood that the battery further includes a positive electrode sheet, a separator, and an electrolyte. Further, the battery further includes positive and negative electrode tabs which are drawn out from the positive and negative electrode sheets by welding.

[0117] The positive electrode sheet, the separator, and the electrolyte are described as follows, but are not limited to the following.

[0118] The positive electrode sheet includes a current collector and a positive active layer arranged on the surface of the current collector. The components of the positive active layer include a positive active material.

[0119] As an example, the current collector in the positive electrode sheet has two opposite surfaces in the thickness direction of the current collector, and the positive active material layer is arranged on any one or both of the two opposite surfaces of the positive current collector.

[0120] In any embodiment of the present application, the current collector in the positive electrode sheet can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material on a polymer material base material.

[0121] In some embodiments, the metal material includes at least one of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy.

[0122] In some embodiments, the high molecular material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0123] Further, as an example, the lithium ion active material can include at least one of a lithium-containing phosphate of an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material can also be used. These positive electrode active materials can be used alone only one or two or more can be used in combination. Among them, examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2(also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2(also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2), and modified compounds thereof, etc. Examples of the lithium-containing phosphate of the olivine structure can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4(also referred to as LFP)), lithium manganese phosphate (such as LiMnPO4), and lithium manganese iron phosphate.

[0124] In any embodiment of the present application, the lithium ion active material has a molecular formula of LiFe x Mn (1-x) PO4, and x is any number from 0 to 1.

[0125] It can be understood that when x is 0, the lithium ion active material is LiFe x Mn (1-x)PO4 is LiMnPO4 lithium manganese phosphate, when x is 1, LiFePO4 is LiFePO4 lithium iron phosphate (LFP).

[0126] It should be noted that the lithium content in the above-mentioned example positive electrode material refers to the content thereof in the unused state. During use of the battery, repeated charging and discharging will occur, and the Li in the positive electrode active material will change during the charging and discharging process, that is, the molar index of Li in the positive electrode active material in the battery product will not always remain at 1, and will change; further, the change range can be (0-1.2).

[0127] For example, LiFe x Mn (1-x) PO4 can be further represented as Li y Fe x Mn (1-x) PO4, and y is 0-1.1.

[0128] For example, for the ternary material Li y (Ni a Co b Mn c ) 1-d M d O 2-x A x , y is 0.2-1.2, a+b+c=1, 0≤d≤1, 0≤x<2; M is one or more of Zr, Sr, B, Ti, Mg, Sn and Al, and A is one or more of S, N, F, Cl, Br and I.

[0129] The battery will be accompanied by Li deintercalation and consumption during the charging and discharging process, and the molar content of Li is different when the battery is discharged to different states. The above limitation of y includes the molar content of Li under different charging and discharging states of the battery; further, the voltage of the battery is usually between 2-5V.

[0130] Similarly, in the enumeration of the positive electrode material in the present application, the content of oxygen (O) is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual content of O will fluctuate. The content of O can be measured by molar content, but is not limited thereto.

[0131] The weight ratio of the positive electrode active material in the positive electrode active layer based on the total weight of the positive electrode active layer is 80wt%-100wt%.

[0132] In any embodiment of the present application, the components of the positive electrode active layer further include a positive electrode conductive agent and a positive electrode binder.

[0133] The positive electrode conductive agent can be at least one of graphite, carbon nanotube, nanofiber, carbon black, and graphene, which are commonly used in the art. Specifically, it can be at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor grown carbon fiber VGCF, carbon nanotube CNTs, and graphene, and a composite conductive agent thereof.

[0134] The weight ratio of the positive electrode conductive agent in the positive electrode active layer is 0-20 wt% based on the total weight of the positive electrode active layer.

[0135] In any embodiment of the present application, the binder of the positive electrode binder described above can be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS), and fluorine-containing acrylate resin.

[0136] The weight ratio of the positive electrode binder in the positive electrode active layer is 0-30 wt% based on the total weight of the positive electrode active layer.

[0137] In any embodiment of the present application, the positive electrode tab can be prepared by dispersing the components described above for preparing the positive electrode tab in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a current collector, and after drying, cold pressing, etc., the positive electrode tab is obtained. The solid content of the positive electrode slurry is 40-80 wt%, and the viscosity at room temperature is adjusted to 5000-25000 mPa·s. The positive electrode slurry is coated on the surface of the positive electrode current collector, dried, and then cold-pressed by a cold rolling mill to form the positive electrode tab.

[0138] Electrolyte: The electrolyte includes an electrolyte salt and a solvent

[0139] In some embodiments, the electrolyte salt can be selected from commonly used electrolyte salts in the art, such as lithium ion electrolyte salts.

[0140] As an example, lithium ion electrolyte salts include, but are not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bisoxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0141] In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0142] In some embodiments, the concentration of the electrolyte salt in the electrolyte is typically 0.5 mol / L to 15 mol / L.

[0143] In some embodiments, the electrolyte can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, and the like.

[0144] Separator film: The separator film is disposed between the positive electrode sheet and the negative electrode sheet.

[0145] The type of the separator film is not particularly limited in the present application, and any known porous structure separator film having good chemical stability and mechanical stability can be used.

[0146] In some embodiments, the material of the separator film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0147] The thickness of the separator is controlled to be 2 μm to 15 μm; alternatively, the thickness of the separator is controlled to be 2 μm to 13 μm.

[0148] In some embodiments, the above-mentioned battery is a secondary battery; in particular, the above-mentioned battery is a lithium metal battery.

[0149] The shape of the battery of the present application is not particularly limited, and it can be cylindrical, square or any other shape. For example, Figure 1 is a battery 4 in a square structure as an example.

[0150] In some embodiments, with reference to Figure 2 , the housing can include a casing 41 and a cover plate 43. The casing 41 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The casing 41 has an opening communicating with the receiving cavity, and the cover plate 43 can be provided on the opening to close the receiving cavity.

[0151] The positive electrode sheet, the negative electrode sheet and the separator can be formed into an electrode assembly 42 through a winding process or a stacking process. The electrode assembly 42 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 42. The number of electrode assemblies 42 contained in the battery 4 can be one or more, which can be adjusted according to the needs.

[0152] The present application also provides a power consuming device, which includes the above-mentioned battery.

[0153] Further, in the above-mentioned power consuming device, the battery can exist in the form of a battery monomer, or can be further assembled into the form of a battery pack.

[0154] Figure 3 and Figure 4 is a battery pack 1 as an example. The battery pack 1 includes a battery box and one or more batteries 4 arranged in the battery box. The battery box includes an upper casing 2 and a lower casing 3, and the upper casing 2 can be provided on the lower casing 3 to form a closed space for the battery 4.

[0155] The plurality of batteries 4 can be arranged in the battery box in any manner.

[0156] The above-mentioned battery or the battery pack assembled therefrom can be used as a power source of a power consuming device, or as an energy storage unit of a power consuming device.

[0157] The above-mentioned power consuming device can be, but is not limited to, a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0158] Figure 5The power consuming device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the demand of the power consuming device 5 for high power and high energy density of the battery, a battery pack can be used.

[0159] The power consuming device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a battery can be used as a power source.

[0160] The application will be described in detail below with reference to specific embodiments, but the application is not limited to the following embodiments, and it should be understood that the appended claims generalize the scope of the application, and those skilled in the art should realize that certain changes made to the embodiments of the application will be covered by the spirit and scope of the claims of the application.

[0161] The following are specific embodiments.

[0162] Embodiment 1

[0163] (1) Preparation of composite current collector

[0164] S1: Place a copper foil with a thickness of 8 μm in diluted hydrochloric acid (2 mol / L) for cleaning to remove impurities and oxide layers on the surface of the copper foil, then wash repeatedly with deionized water for 3 times, and then wash with anhydrous ethanol for 3 times, and then dry with a hair dryer after washing to obtain a cleaned copper foil;

[0165] Place the dried copper foil directly in a muffle furnace, uniformly coat the two surfaces with a glucose solution for heating treatment, heat to 900℃ at a heating rate of 5℃ / min in an inert gas atmosphere, and keep sintering for 2 h to form a carbon material layer, cool to room temperature after completion, and obtain a pre-prepared current collector.

[0166] S2: Perform deposition treatment on the surface of the carbon material layer of the pre-prepared current collector by magnetic control sputtering: use a nickel target for magnetic control sputtering, sputtering gas pressure is 1.8 Pa, target voltage is 480 V, target current density is 15 mA / cm 2 , deposition rate is 2 m / min, metal layers are formed on both surfaces of the pre-prepared current collector, and a composite current collector is obtained.

[0167] Place the cross section of the composite current collector under SEM (electron microscope), and test the thickness of 3 different regions, take the average value, to test the thickness of the carbon material layer and the metal layer in the composite current collector, wherein the thickness of the carbon material layer and the metal layer on one side of the composite current collector is respectively H1 and H2, and the total thickness of the carbon material layer and the metal layer is T, see Table 1 for details.

[0168] (2) Preparation of the negative electrode sheet: The lithium metal layer with a thickness of 20 μm was prepared on both sides of the composite current collector by calendering:

[0169] First, the lithium metal was calendered onto the release film. Then, the two pieces of release film with lithium metal were placed on the surfaces of the metal layer on both sides of the composite current collector, and were calendered onto the surface of the composite current collector. The release film was gently torn off to obtain the negative electrode sheet. The composite current collector was reserved for 50 mm for tab welding.

[0170] (3) Preparation of the positive electrode sheet

[0171] The positive electrode active material lithium nickel cobalt manganese oxide NCM811, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 94:3:3, and the solvent N-methyl pyrrolidone (NMP) was added. The system was stirred in a vacuum stirrer until it became uniform to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil with a thickness of 12 μm. Drying was performed at 115°C for 15 min, and cold pressing was performed to obtain a positive electrode active layer with a single-sided thickness of 84 μm. The single-sided surface density of the positive electrode active layer was 20 mg / cm 2 , and the compacted density was 2.4 g / cm 3 .

[0172] (4) Preparation of the electrolyte: The organic solvent was a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC, and DEC was 20:20:60. In an argon atmosphere glove box with a water content of <10 ppm, fully dried LiPF6 was dissolved in the organic solvent. After uniform mixing, the electrolyte was obtained, wherein the concentration of LiPF6 was 1 mol / L.

[0173] (5) Separation film: A polyethylene microporous film was used as the porous separation film substrate. Inorganic aluminum oxide powder, polyvinylpyrrolidone, and acetone solvent were mixed in a weight ratio of 3:1.5:5.5 to form a slurry, which was coated on one side of the substrate and dried to obtain the separation film.

[0174] (6) Preparation of the lithium metal battery: The above-mentioned positive electrode sheet, negative electrode sheet, and separation film were wound to obtain a bare cell. After encapsulation, liquid injection, formation, and exhaust processes, the lithium ion battery was prepared.

[0175] (7) Cycle performance test of the lithium metal battery:

[0176] At 25°C, when the constant current charging was performed at a rate of 0.33C to 4.25V, the constant voltage charging was performed. When the current decreased to 0.05C, the charging was stopped. Then, the constant current discharging was performed at a rate of 1C to 2.5V, and the discharging was stopped. At this time, the cycle number was 1.

[0177] The above charge-discharge cycle was repeated until the battery capacity was reduced to 80% of the initial capacity, and the test was stopped at this time, and the cycle number Cy80% of the lithium ion battery at this time was recorded. The test results are shown in Table 1.

[0178] The composite current collector in the negative electrode sheet in the battery after the cycle test was separated out and observed under an electron microscope, and the electron microscope image is shown in FIG. 2. No obvious corrosion marks were observed. Figure 6

[0179] Examples 2-10

[0180] Examples 2-10 are basically the same as Example 1, except that the thickness of the coating glucose solution in the regulation step S1 and / or the time of the magnetron sputtering in the regulation step S2 are regulated, so that the relevant parameters in Table 1 are different from those of Example 1.

[0181] The other step conditions are the same as those of Example 1, and the test results are shown in Table 1.

[0182] Examples 11-12

[0183] Examples 11-12 are basically the same as Example 1, except that the target material used in the magnetron sputtering in step S2 is different from that of Example 1, and the specific parameters are shown in Table 1.

[0184] The other step conditions are the same as those of Example 1, and the test results are shown in Table 1.

[0185] Comparative Example 1

[0186] Comparative Example 1 is basically the same as Example 6, except that in the preparation process of the composite current collector, the step of forming a carbon material layer in step S1 is not performed, and the magnetron sputtering treatment in step S2 is directly performed on the surface of the cleaned copper foil, and the specific parameters are shown in Table 1.

[0187] The other step conditions are the same as those of Example 6, and the test results are shown in Table 1.

[0188] Comparative Example 2

[0189] Comparative Example 2 is basically the same as Example 6, except that in the preparation process of the composite current collector, the magnetron sputtering treatment in step S2 is not performed, and the specific parameters are shown in Table 1.

[0190] The other step conditions are the same as those of Example 6, and the test results are shown in Table 1.

[0191] After the lithium metal battery prepared in Comparative Example 2 was cycled, the composite current collector in the negative electrode sheet was separated out and observed under an electron microscope, and the electron microscope image is shown in FIG. 4. Black spots caused by obvious corrosion were observed. Figure 7

[0192] ​​Comparative Example 3

[0193] Comparative Example 3 is basically the same as Example 6, except that in the preparation process of the negative electrode sheet, the copper foil is directly used to replace the composite current collector, and the specific parameters are shown in Table 1.

[0194] The other step conditions are the same as those in Example 6, and the test results are shown in Table 1.

[0195] Comparative Example 4

[0196] Comparative Example 4 is basically the same as Example 1, except that the preparation steps of the composite current collector are as follows:

[0197] S1: Place the copper foil with a thickness of 8 μm in the diluted hydrochloric acid (2 mol / L) for cleaning to remove the impurities and oxide layer on the surface of the copper foil, and then wash repeatedly with deionized water for 3 times, and then wash with anhydrous ethanol for 3 times, and then dry with a hair dryer after washing.

[0198] The surface of the dried copper foil is subjected to deposition treatment to form a metal layer, and the conditions are the same as those in step S2 in Example 1, to obtain a pre-prepared current collector.

[0199] S2: Place the pre-prepared current collector directly in a muffle furnace, uniformly coat the metal layer surface with a glucose solution, and then perform sintering treatment, and the specific conditions are the same as those in step S1 in Example 1, to form a carbon material layer, and obtain a composite current collector.

[0200] The other step conditions are the same as those in Example 1, and the test results are shown in Table 1.

[0201] The related parameters and performance results of each example and comparative example are shown in Table 1. Among them, the thicknesses of the single-sided carbon material layer and the metal layer in the composite current collector are respectively denoted as H1 and H2, the total thickness of the carbon material layer and the metal layer is denoted as T, and Cy80% is the number of battery cycles.

[0202] Table 1

[0203]

[0204] " / " represents the absence of the structure or parameter.

[0205] From the data in Table 1, it can be seen that in the composite current collector of the present application, the carbon material layer and the metal layer with a specific component are sequentially arranged on the surface of the support layer, which can improve the overall stability of the composite current collector while improving the corrosion of the heterogeneous metal when applied to prepare a lithium metal battery, thereby improving the cycle performance of the battery.

[0206] Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, as long as there is no conflict, any combination of the technical features should be considered within the scope of the present disclosure.

[0207] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A composite current collector, characterized by, The composite current collector comprises a support layer and a functional layer arranged on at least one surface of the support layer; the functional layer comprises a carbon material layer and a metal layer, and the carbon material layer is arranged between the support layer and the metal layer. The metal layer comprises at least one of transition metal and inner transition metal.

2. The composite current collector of claim 1, wherein The composite current collector satisfies at least one of the following conditions: (1) the thickness of the carbon material layer is 100 nm to 5 μm; (2) the thickness of the metal layer is 200 nm to 2 μm.

3. The composite current collector of any one of claims 1-2, wherein, The composite current collector satisfies at least one of the following conditions: (1) the thickness of the carbon material layer is 500 nm to 2 μm; (2) the thickness of the metal layer is 300 nm to 1 μm.

4. The composite current collector of any one of claims 1 to 3, wherein The thickness ratio of the carbon material layer to the metal layer is 1:(0.2-2).

5. The composite current collector of any one of claims 1 to 4, wherein The thickness ratio of the carbon material layer to the metal layer is 1:(0.85-1.65).

6. The composite current collector of any one of claims 1 to 5, wherein, The thickness of the functional layer is 300 nm to 6 μm.

7. The composite current collector of any one of claims 1 to 6, wherein The thickness of the functional layer is 500 nm to 3 μm.

8. The composite current collector of any one of claims 1 to 7, wherein, The metal layer comprises at least one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, platinum and gold.

9. The composite current collector of any one of claims 1 to 8, wherein, The metal layer comprises at least one of nickel, titanium and chromium.

10. The composite current collector of any one of claims 1 to 9, wherein, The carbon material layer comprises at least one of inorganic carbon and organic carbon.

11. The composite current collector of any one of claims 1 to 10, wherein, The support layer comprises at least one of copper and its alloy.

12. A method of making a composite current collector, characterized by, The method comprises the following steps: forming a carbon material layer and a metal layer on at least one surface of a support layer in sequence; The metal layer comprises at least one of transition metal and inner transition metal, and the composite current collector is prepared.

13. The method of making a composite current collector of claim 12, wherein, The step of forming a carbon material layer and a metal layer on at least one surface of a support layer in sequence comprises the following steps: coating a carbon source solution on at least one surface of the support layer, and performing sintering treatment to form a carbon material layer; performing vapor deposition treatment on the surface of the carbon material layer to form the metal layer.

14. A battery, characterized by The battery comprises a negative electrode sheet, and the negative electrode sheet comprises any one of the composite current collector according to any one of claims 1-11, or the composite current collector prepared by the method according to any one of claims 12-13.

15. The battery according to claim 14, wherein the negative electrode sheet further comprises a metal lithium layer arranged on the surface of the metal layer in the composite current collector.

16. An electrical device, comprising: The battery according to any one of claims 14-15. The battery according to any one of claims 14-15.

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