Current collector, method for manufacturing the same, electrode sheet, secondary battery, and electric device

Abstract

The embodiment of the present application provides a kind of current collector, including porous three-dimensional skeleton and lithiumophilic substance, lithiumophilic substance is distributed in the hole of porous three-dimensional skeleton, current collector includes first side, and the second side away from first side, first side is used to be towards separator, in the direction from first side to second side, porous three-dimensional skeleton includes first part and second part, the thickness of lithiumophilic substance in the hole of first part is less than the thickness of lithiumophilic substance in the hole of second part.The present application also provides the preparation method of the above-mentioned current collector, anode sheet, secondary battery and electric device.The thickness of lithiumophilic substance of the current collector provided in the present application increases along the thickness direction of porous three-dimensional skeleton, which can induce lithium metal to preferentially deposit inside porous three-dimensional skeleton, make full use of the porosity of three-dimensional current collector, and limit the volume expansion of deposited lithium.

Description

[0001] This application claims priority to PCT international patent application No. PCT / CN2023 / 082336 filed on March 17, 2023, entitled “Current Collector and Preparation Method thereof, Electrode Sheet, Secondary Battery and Electrical Device”, which is incorporated herein by reference in its entirety. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a current collector and a preparation method thereof, an electrode sheet, a secondary battery, and an electrical device. Background Art

[0003] Secondary batteries can enhance the battery's endurance, significantly improve the economic benefits of power storage, and promote the upgrade and transformation of consumer electronic products, which is of great significance to human life. In order to improve the performance of secondary batteries, especially lithium metal batteries, existing current collectors generally use metal skeletons. However, the metal skeleton has insufficient lithium-affinity sites and a large lithium nucleation overpotential. Currently, lithium metal adopts a localized nucleation mode on the current collector surface and tends to deposit preferentially on the surface, resulting in loose lithium deposition on the current collector surface. The pores inside the current collector cannot be utilized, and the volume expansion and dendrite growth are serious during the secondary battery cycle. Dendrites may even directly pierce the isolation membrane and cause short circuits.

[0004] Therefore, how to propose a current collector and its preparation method, anode sheet, secondary battery and electrical device to reduce the lithium nucleation overpotential, increase lithium active sites, and at the same time improve the diffusion ability of lithium atoms on the current collector surface, inhibit lithium dendrites and volume expansion during the secondary battery cycle, and improve the secondary battery cycle performance and safety is a problem that needs to be solved urgently. Summary of the Invention

[0005] In view of the above problems, the present application provides a current collector and a preparation method thereof, an anode sheet, a secondary battery and an electrical device to solve the above technical problems existing in secondary batteries.

[0006] In a first aspect, the present application provides a current collector comprising a porous three-dimensional skeleton and a lithium-philic substance, wherein the lithium-philic substance is distributed in the pores of the porous three-dimensional skeleton, and the mass proportion of the lithium-philic substance in the current collector is smaller on the side close to the isolation membrane than on the side close to the electrode.

[0007] In the technical solution of the embodiment of the present application, by placing the lithium-philic substance in the pores of the porous three-dimensional skeleton, the nucleation overpotential of lithium on the surface of the porous three-dimensional skeleton can be reduced, the active sites can be increased, and the diffusion ability of lithium atoms on the surface of the porous three-dimensional skeleton can be improved, thereby avoiding the local nucleation and deposition of lithium metal, inhibiting the formation of dendrites, and improving the cycle performance and safety of the secondary battery. Moreover, the mass proportion of the lithium-philic substance in the current collector is smaller on the side close to the isolation membrane than on the side close to the electrode. The lithium-philic substance increases gradually from the isolation membrane side to the electrode side, which can induce lithium metal to preferentially deposit inside the porous three-dimensional skeleton, making full use of the pores of the three-dimensional current collector, limiting the infinite volume expansion of the deposited lithium, and further improving the safety of the secondary battery.

[0008] In some embodiments, the lithium-philic substance is distributed in the pores of the porous three-dimensional skeleton, the current collector includes a first side and a second side facing away from the first side, the first side is used to face the isolation membrane, and along the direction from the first side to the second side, the porous three-dimensional skeleton includes a first part and a second part, the first lithium-philic substance layer is arranged in the pores of the three-dimensional skeleton of the first part, and the second lithium-philic substance layer is arranged in the pores of the three-dimensional skeleton of the second part, and the thickness of the first lithium-philic substance layer is less than the thickness of the second lithium-philic substance layer.

[0009] In the technical solution of the embodiment of the present application, the thickness of the first lithium-philic material layer in the first part of the pores is less than the thickness of the second lithium-philic material layer in the second part of the pores. The gradual increase in the thickness of the lithium-philic material in the current collector from the isolation membrane side to the electrode side can induce lithium metal to preferentially deposit inside the porous three-dimensional skeleton, fully utilize the pores of the three-dimensional current collector, limit the infinite volume expansion of deposited lithium, and further improve the safety of the secondary battery.

[0010] In some embodiments, the thickness of the second lithiophilic material layer is greater than or equal to 50 nm and less than or equal to 1 μm, preferably 50-60 nm.

[0011] If the thickness of the second lithium-philic material layer is too small, the lithium-philic effect is not obvious and the formation of lithium dendrites cannot be improved; if the thickness of the second lithium-philic material layer is too large, it is not conducive to alleviating the volume expansion of the secondary battery and increases the cost of the secondary battery.

[0012] In the technical solution of the embodiment of the present application, the thickness of the second lithium-philic material layer is controlled to be greater than or equal to 50 nm and less than or equal to 1 μm, preferably 50-60 nm, which can give full play to the lithium-philic effect, alleviate the growth of lithium dendrites, at least partially avoid battery short circuit, alleviate the volume expansion of the secondary battery, and improve the cycle performance and safety performance of the secondary battery.

[0013] In some embodiments, the thickness of the first lithiophilic material layer is greater than 0 nm and less than 1 μm, preferably 8-12 nm.

[0014] In the technical solution of the embodiment of the present application, the thickness of the first lithium-philic material layer in the pores of the first part is set to be greater than 0 nm and less than 1 μm, preferably 8-12 nm, so that the thickness of the lithium-philic material increases gradually from the first part to the second part. When the current collector is in use, the first part is close to the isolation membrane and the second part is far away from the isolation membrane. When the electrolyte is infiltrated, lithium metal can be induced to preferentially deposit inside the porous three-dimensional skeleton, making full use of the pores of the three-dimensional current collector, limiting the infinite volume expansion of the deposited lithium, and further improving the battery safety performance.

[0015] In some embodiments, the thickness of the first lithiophilic material layer is d1, the thickness of the second lithiophilic material layer is d2, and the range of d1 is greater than 0 and less than or equal to d2*50%.

[0016] In the technical solution of the embodiment of the present application, by controlling the percentage of the thickness of the first lithium-philic material layer in the pores of the first part and the thickness of the second lithium-philic material layer in the pores of the second part, the thickness of the lithium-philic material increases gradually from the first part to the second part. When the current collector is in use, the first part is close to the isolation membrane and the second part is far away from the isolation membrane. When the electrolyte is infiltrated, lithium metal can be induced to preferentially deposit inside the porous three-dimensional skeleton, making full use of the pores of the three-dimensional current collector, limiting the infinite volume expansion of the deposited lithium, and further improving the battery safety performance.

[0017] In some embodiments, along a direction from the first side to the second side, a height of the first portion is h1, a height of the current collector is h, and a range of h1 is greater than 5 μm and less than or equal to h*50%.

[0018] If the height of the first section is too small, the gradient variation of the thickness of the lithiophilic substance throughout the porous three-dimensional framework is not obvious. If the height of the first section is too large, the concentration of the lithiophilic substance throughout the porous three-dimensional framework is too low, affecting the lithiophilic effect. This application simultaneously ensures the lithiophilic effect and the gradient variation of the thickness of the lithiophilic substance in the porous three-dimensional framework by controlling the range of h1 to be greater than 5 μm and less than or equal to h*50%.

[0019] In some embodiments, the lithiophilic substance includes at least one of a metal capable of forming an alloy with lithium, a metal alloy capable of forming an alloy with lithium, a metal capable of forming a solid solution with lithium, a metal alloy capable of forming a solid solution with lithium, silicon (Si), a carbon-based material, or an oxide.

[0020] In the technical solutions of the embodiments of the present application, metals, metal alloys, silicon (Si), carbon-based materials, or oxide-based lithiophilic substances have good lithiophilic effects, can effectively induce lithium deposition in the pores of the porous three-dimensional skeleton, and can effectively increase the active sites for lithium deposition, reduce the nucleation overpotential of lithium, reduce localized lithium nucleation, reduce the formation of lithium dendrites, and improve the safety performance of the secondary battery. In addition, the good conductivity of metals and carbon-based materials helps to reduce the impedance of the secondary battery and improve the initial coulombic efficiency of the secondary battery.

[0021] In some embodiments, the metal includes at least one of Sn, Mg, Zn, Bi, Pb, Au, Ag, Al, In, and Ga; the metal alloy includes at least two of Sn, Mg, Zn, Bi, Pb, Au, Ag, Al, In, and Ga; the carbon-based material includes at least one of graphite, graphene, graphyne, and hard carbon; and the oxide includes at least one of Cu2O, CuO, ZnO, MgO, and graphene oxide.

[0022] In the technical solutions of the embodiments of the present application, the above-mentioned substances have relatively good lithium affinity, can well induce lithium deposition in the pores of the porous three-dimensional skeleton, and can effectively increase the active sites for lithium deposition, reduce the nucleation overpotential of lithium, reduce local nucleation of lithium, reduce the formation of lithium dendrites, and improve the safety performance of secondary batteries.

[0023] Moreover, Sn, Mg, Zn, Bi, Pb, Au, Ag, Al, In, Ga and graphite, graphene, graphyne, and hard carbon have good conductivity, which helps to reduce the impedance of secondary batteries and improve the first coulombic efficiency of secondary batteries. At the same time, the cost is low, thereby reducing the cost of secondary batteries.

[0024] In some embodiments, the metal includes at least one of Sn, Mg, and Zn, and the metal alloy includes at least two of Sn, Mg, and Zn.

[0025] In the technical solution of the embodiment of the present application, since the metals Sn, Mg, and Zn have a stable structure and are not prone to collapse, the structural stability of the secondary battery is increased.

[0026] In some embodiments, the loading amount of the lithium-philic substance in the pores of the porous three-dimensional framework is greater than or equal to 0.3 g / m 2 And less than or equal to 60g / m 2 .

[0027] If the loading amount of the lithiophilic substance is too small, the lithiophilic substance cannot cover the pore surface of the porous three-dimensional skeleton, and the lithiophilic effect is not obvious. If the loading amount of the lithiophilic substance is too large, the cost is increased. In the technical solution of the embodiment of the present application, by controlling the loading amount of the lithiophilic substance in the pores of the porous three-dimensional skeleton to be greater than or equal to 0.3 g / m 2And less than or equal to 60g / m 2 The lithium-philic substance covers the pore surface of the porous three-dimensional skeleton, and the lithium-philic effect is obvious.

[0028] In some embodiments, the porous three-dimensional framework comprises a porous three-dimensional metallic framework.

[0029] In the technical solution of the embodiment of the present application, the metal skeleton is relatively stable to corrosive liquids such as nitric acid and hydrochloric acid, and the metal has good conductivity, high surface smoothness, and is easy to clean, which can reduce the difficulty of the process.

[0030] In some embodiments, the material of the porous three-dimensional metal framework includes at least one of Cu, Ni, Ti, Mg, and Al.

[0031] In the technical solution of the embodiments of this application, the metals Cu, Ni, Ti, Mg, and Al are stable to corrosive solutions such as nitric acid and hydrochloric acid, ensuring that they will not be corroded during the etching process of lithium-philic substances. Furthermore, Cu, Ni, Ti, Mg, and Al are relatively low in cost, which can reduce the production cost of secondary batteries.

[0032] In some embodiments, the porous three-dimensional framework has a porosity of 60% to 90%.

[0033] If the porosity of the porous three-dimensional skeleton is too small, for example, the porosity is less than 60%, the electrolyte infiltration is difficult, and the lithium ions cannot be induced to deposit in the pores within the porous three-dimensional skeleton; if the porosity of the porous three-dimensional skeleton is too large, for example, the porosity is greater than 90%, the rib area is insufficient, the electrochemical active area is reduced, and the lithium ions cannot be induced to deposit in the pores within the porous three-dimensional skeleton.

[0034] In the technical solution of the embodiment of the present application, the porosity of the porous three-dimensional skeleton is controlled to 60% to 90%, which can not only ensure good infiltration of the electrolyte, but also make the electrochemical active area sufficient, thereby inducing lithium ions to deposit into the pores in the porous three-dimensional skeleton.

[0035] In a second aspect, the present application provides a method for preparing the current collector according to any of the above embodiments, comprising:

[0036] Providing a porous three-dimensional skeleton, the porous three-dimensional skeleton comprising a first side and a second side facing away from the first side, wherein the first side is used to face the isolation membrane;

[0037] A lithiophilic substance is formed on the porous three-dimensional skeleton. From the first side to the second side, the obtained lithiophilic porous three-dimensional skeleton includes a first portion and a second portion. The thickness of the first lithiophilic substance layer in the pores of the first portion is less than the thickness of the second lithiophilic substance layer in the pores of the second portion.

[0038] In the technical solution of the embodiment of the present application, by forming a lithium-philic substance in the inner pores of the porous three-dimensional skeleton, the lithium nucleation overpotential can be reduced, the lithium active sites can be increased, and the diffusion ability of lithium atoms on the surface of the current collector skeleton can be improved, thereby inhibiting the growth of lithium dendrites and improving the cycle performance and safety performance of the secondary battery. In addition, the preparation method can realize the thickness gradient design of the lithium-philic substance layer in the current collector from the side of the separator to the side of the electrode, which can induce lithium metal to preferentially deposit in the pores within the porous three-dimensional skeleton, fully utilizing the pores of the three-dimensional current collector, limiting the unlimited volume expansion of lithium metal, and further improving the safety performance of the secondary battery.

[0039] In some embodiments, a method for preparing a current collector includes:

[0040] The first part of the lithiophilic porous three-dimensional skeleton is immersed in a corrosive solution so that the thickness of the first lithiophilic material layer in the first part of the pores is less than the thickness of the second lithiophilic material layer in the second part of the pores, thereby obtaining a current collector containing a lithiophilic material.

[0041] In the technical solution of the embodiment of the present application, the preparation method can achieve a thickness gradient design of the lithium-philic material layer in the current collector from the isolation membrane side to the electrode side by corroding the lithium-philic material in the first part of the porous three-dimensional skeleton, which can induce lithium metal to preferentially deposit in the pores in the porous three-dimensional skeleton, make full use of the three-dimensional current collector pores, limit the infinite volume expansion of lithium metal, and further improve the safety performance of the secondary battery.

[0042] In some embodiments, the etching solution includes at least one of nitric acid or hydrochloric acid.

[0043] In the technical solution of the embodiments of this application, both nitric acid and hydrochloric acid corrode only the lithium-philic substances and do not corrode the porous three-dimensional framework of Cu, Ni, Ti, Mg, and Al. By immersing the first portion of the porous three-dimensional framework in nitric acid or hydrochloric acid, a thickness gradient design of the lithium-philic substance layer within the current collector can be achieved from the separator side to the electrode side. Furthermore, nitric acid or hydrochloric acid has low environmental pollution and is relatively low in cost, thereby reducing the production cost of the current collector.

[0044] In some embodiments, the first portion of the porous three-dimensional framework is immersed in the etching solution for 1-60 minutes.

[0045] If the first portion of the porous three-dimensional framework is immersed in the etching solution for too short a time, the lithium-philic material in the pores of the first portion is not fully corroded, resulting in a weak thickness gradient between the first lithium-philic material layer and the second lithium-philic material layer in the pores of the second portion. Conversely, if the immersion time is too long, the thickness of the first lithium-philic material layer in the pores of the first portion is too small, or even fails to completely cover the surface of the pores of the first portion, resulting in a weak lithium-philic effect. In the technical solution of the embodiment of the present application, the first portion of the porous three-dimensional framework is controlled to be immersed in the etching solution for 1-60 minutes, ensuring that the lithium-philic material forms a thickness gradient in the current collector from the separator side to the electrode side, thereby making the lithium-philic effect more significant.

[0046] In a third aspect, the present application provides an electrode sheet, comprising the current collector as described above or the current collector prepared by the method for preparing the current collector as described above.

[0047] In a fourth aspect, the present application provides a secondary battery comprising an anode sheet, a cathode sheet and an isolation membrane, wherein the isolation membrane is arranged between the anode sheet and the cathode sheet, the anode sheet is the electrode sheet as described above, the first part of the current collector in the anode sheet is close to the isolation membrane, and the second part is away from the isolation membrane.

[0048] In a fifth aspect, the present application provides an electrical device comprising the secondary battery as described above.

[0049] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0051] Figure 1 This is a schematic structural diagram of an electrical device according to some embodiments of the present application;

[0052] Figure 2 Schematic diagram of the exploded structure of batteries according to some embodiments of the present application;

[0053] Figure 3 This is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0054] Figure 4Schematic diagram of the thickness d1 of the first lithiophilic material layer, the thickness d2 of the second lithiophilic material layer, and the ratio of the height h1 of the first portion to the height h of the current collector in some embodiments of the present application;

[0055] Figure 5 Schematic cross-section of the current collector prepared in Example 1.

[0056] In the drawings, the drawings are not drawn to scale.

[0057] Marking description: electrical device 1000;

[0058] Battery 100, controller 200, motor 300;

[0059] Box body 10, first part 11, second part 12;

[0060] Battery cell 20, end cap 21, electrode terminal 21a, housing 22, battery cell assembly 23, tab 23a, functional component 24;

[0061] Current collector 40 , porous three-dimensional skeleton 402 , and lithium-philic substance 404 . DETAILED DESCRIPTION

[0062] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0064] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0065] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0066] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0067] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0068] Currently, market developments indicate that power batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As power battery applications continue to expand, market demand is also growing.

[0069] Secondary batteries can enhance the battery's endurance, significantly improve the economic benefits of power storage, and promote the upgrade and transformation of consumer electronic products, which is of great significance to human life. In order to improve the performance of secondary batteries, especially lithium metal batteries, existing current collectors generally use metal skeletons. However, the metal skeleton has insufficient lithium-affinity sites and a large lithium nucleation overpotential. Currently, lithium metal adopts a localized nucleation mode on the current collector surface and tends to deposit preferentially on the surface, resulting in loose lithium deposition on the current collector surface and unusable pores inside the current collector. This leads to severe volume expansion of the secondary battery during the cycle, rapid growth of dendrites, and even dendrites directly piercing the isolation membrane, causing safety risks such as short circuits.

[0070] In order to solve the above technical problems existing in secondary batteries, it is found that research can be conducted from the current collector.

[0071] The present invention designs a current collector and its preparation method, electrode sheet, secondary battery and power-consuming device. By depositing a lithium-philic substance in the pores of a porous three-dimensional skeleton and increasing the thickness of the lithium-philic substance in the pores from the separator side to the electrode side, the nucleation overpotential of lithium on the surface of the porous three-dimensional skeleton can be reduced, the active sites can be increased, and the diffusion capacity of lithium atoms on the surface of the porous three-dimensional skeleton can be improved, thereby avoiding the localized nucleation and deposition of lithium metal, inhibiting the formation of dendrites, and improving the cycle performance and safety of the secondary battery. Moreover, the increasing thickness gradient of the lithium-philic substance from the separator side to the electrode side can induce the preferential deposition of lithium metal inside the porous three-dimensional skeleton, fully utilizing the pores of the three-dimensional current collector, limiting the unlimited volume expansion of the deposited lithium, and further improving the safety of the secondary battery.

[0072] Based on the above considerations, in order to solve the problems of severe dendrite growth and volume expansion of secondary batteries, the inventors conducted in-depth research and designed a current collector, including a porous three-dimensional skeleton and a lithium-philic substance. The lithium-philic substance is distributed in the pores of the porous three-dimensional skeleton, and the mass proportion of the lithium-philic substance in the current collector is smaller on the side close to the isolation membrane than on the side close to the electrode.

[0073] By placing the lithiophilic substance within the pores of the porous three-dimensional skeleton, the nucleation overpotential of lithium on the surface of the porous three-dimensional skeleton can be reduced, the active sites can be increased, and the diffusion capacity of lithium atoms on the surface of the porous three-dimensional skeleton can be improved, thereby avoiding the localized nucleation and deposition of lithium metal, inhibiting the formation of dendrites, and improving the cycle performance and safety of the secondary battery. Moreover, the mass proportion of the lithiophilic substance in the current collector is smaller on the side close to the separator than on the side close to the electrode. The lithiophilic substance increases gradually from the separator side to the electrode side, which can induce the preferential deposition of lithium metal inside the porous three-dimensional skeleton, fully utilizing the pores of the three-dimensional current collector, limiting the unlimited volume expansion of the deposited lithium, and further improving the safety of the secondary battery.

[0074] The current collector disclosed in the embodiments of the present application can be applied to battery cells, which can be used in electrical devices that use batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical devices can be, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0075] For the convenience of description, the following embodiments are described by taking an electric device 1000 according to an embodiment of the present application as a vehicle as an example.

[0076] Please refer to Figure 1 , Figure 1A schematic structural diagram of an electric device 1000 provided for some embodiments of the present application. The electric device 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the electric device 1000. The battery 100 may be provided at the bottom, head or tail of the electric device 1000. The battery 100 may be used to power the electric device 1000. For example, the battery 100 may serve as an operating power source for the electric device 1000. The electric device 1000 may further include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, to meet the power requirements of the electric device 1000 during startup, navigation and driving.

[0077] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the electrical device 1000, but also serve as a driving power source for the electrical device 1000, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1000.

[0078] Please refer to Figure 2 , Figure 2 This is a schematic diagram of the exploded structure of a battery 100 provided in some embodiments of the present application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 is used to provide a storage space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 can include a first portion 11 and a second portion 12, which overlap each other and together define a storage space for the battery cell 20. The second portion 12 can be a hollow structure with one end open. The first portion 11 can be a plate-like structure, with the first portion 11 overlapping the open side of the second portion 12, so that the first portion 11 and the second portion 12 together define a storage space. The first portion 11 and the second portion 12 can also be hollow structures with one end open, with the open side of the first portion 11 overlapping the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0079] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 20 may be housed within the housing 10. Alternatively, the battery 100 may be constructed by first connecting multiple battery cells 20 in series, in parallel, or in a hybrid connection to form a battery module, which is then connected in series, in parallel, or in a hybrid connection to form a complete battery module, and then housed within the housing 10. The battery 100 may also include other structures, such as a busbar assembly for electrically connecting the multiple battery cells 20.

[0080] Each battery cell 20 may be a secondary battery, such as a lithium-sulfur battery, a lithium-ion battery, or a lithium metal battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0081] Please refer to Figure 3 , Figure 3 The following is a schematic diagram of the decomposition structure of a battery cell 20 provided in some embodiments of the present application. A battery cell 20 is the smallest unit that makes up a battery. Figure 3 The battery cell 20 includes an end cover 21 , a shell 22 , a battery cell assembly 23 and other functional components 24 .

[0082] The end cap 21 is a component that covers the opening of the housing 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the housing 22 to match the housing 22. The end cap 21 can be made of a material with a certain hardness and strength (such as an aluminum alloy). In this way, the end cap 21 is less likely to deform when squeezed or collided, allowing the battery cell 20 to have higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminals 21a can be used to electrically connect to the battery cell assembly 23 for outputting or inputting electrical energy into or out of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for relieving internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The end cap 21 can also be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application are not particularly limited in this regard. In some embodiments, an insulating member may be provided inside the end cap 21 to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be made of plastic, rubber, or the like.

[0083] The housing 22 is a component that cooperates with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can be used to accommodate the battery cell assembly 23, electrolyte, and other components. The housing 22 and end cap 21 can be separate components. An opening can be provided in the housing 22, and the end cap 21 is placed over the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and housing 22 can be integrated. Specifically, the end cap 21 and housing 22 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 22 needs to be enclosed, the end cap 21 is placed over the housing 22. The housing 22 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined based on the specific shape and size of the battery cell assembly 23. The housing 22 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any specific limitations on this.

[0084] The battery cell assembly 23 is a component in the battery cell 100 where electrochemical reactions occur. One or more battery cell assemblies 23 may be contained in the shell 22. The battery cell assembly 23 is mainly formed by winding or stacking cathode sheets and anode sheets, and a separator is usually provided between the cathode sheets and the anode sheets. The parts of the cathode sheets and the anode sheets with active substances constitute the main body of the battery cell assembly, and the parts of the cathode sheets and the anode sheets without active substances each constitute a tab 23a. The cathode tab and the anode tab may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the cathode active substance and the anode active substance react with the electrolyte, and the tab 23a connects the electrode terminals to form a current loop.

[0085] According to some embodiments of the present application, the present application provides a current collector comprising a porous three-dimensional skeleton and a lithium-philic substance, wherein the lithium-philic substance is distributed in the pores of the porous three-dimensional skeleton, and the mass proportion of the lithium-philic substance in the current collector is smaller on the side close to the isolation membrane than on the side close to the electrode.

[0086] The porous three-dimensional framework includes a plurality of pores evenly distributed within the framework. The size and shape of the pores can be selected based on actual needs, and the sizes and shapes of the pores can be the same or different. By way of example, the pores include, but are not limited to, micropores.

[0087] The mass proportion of the lithium-philic substance in the current collector close to the isolation membrane side refers to the proportion of the mass of the lithium-philic substance in the pores of the current collector close to the isolation membrane side to the mass of the lithium-philic substance in the entire pores of the current collector. The mass proportion of the lithium-philic substance in the current collector close to the electrode side refers to the proportion of the mass of the lithium-philic substance in the pores of the current collector close to the electrode side to the mass of the lithium-philic substance in the entire pores of the current collector.

[0088] By placing the lithiophilic substance within the pores of the porous three-dimensional skeleton, the nucleation overpotential of lithium on the surface of the porous three-dimensional skeleton can be reduced, the active sites can be increased, and the diffusion capacity of lithium atoms on the surface of the porous three-dimensional skeleton can be improved, thereby avoiding the localized nucleation and deposition of lithium metal, inhibiting the formation of dendrites, and improving the cycle performance and safety of the secondary battery. Moreover, the mass proportion of the lithiophilic substance in the current collector is smaller on the side close to the separator than on the side close to the electrode. The lithiophilic substance increases gradually from the separator side to the electrode side, which can induce the preferential deposition of lithium metal inside the porous three-dimensional skeleton, fully utilizing the pores of the three-dimensional current collector, limiting the unlimited volume expansion of the deposited lithium, and further improving the safety of the secondary battery.

[0089] According to some embodiments of the present application, the lithium-philic substance is distributed in the pores of the porous three-dimensional skeleton, the current collector includes a first side, and a second side facing away from the first side, the first side is used to face the isolation membrane, and along the direction from the first side to the second side, the porous three-dimensional skeleton includes a first part and a second part, and the first lithium-philic substance layer is arranged in the pores of the three-dimensional skeleton of the first part, and the second lithium-philic substance layer is arranged in the pores of the three-dimensional skeleton of the second part, and the thickness of the first lithium-philic substance layer is less than the thickness of the second lithium-philic substance layer.

[0090] The porous three-dimensional framework includes a first portion and a second portion along the direction from the first side to the second side. For example, in some embodiments, the porous three-dimensional framework may also include a first portion, a second portion, a third portion, a fourth portion, and so on along the direction from the first side to the second side, as long as the thickness of the lithium-philic material layer increases gradually along the direction from the first side to the second side.

[0091] The thickness of the first lithium-philic material layer in the first part of the pores is less than the thickness of the second lithium-philic material layer in the second part of the pores. The gradual increase in the thickness of the lithium-philic material in the current collector from the isolation membrane side to the electrode side can induce lithium metal to preferentially deposit inside the porous three-dimensional skeleton, fully utilize the pores of the three-dimensional current collector, limit the infinite volume expansion of deposited lithium, and further improve the safety of secondary batteries.

[0092] According to some embodiments of the present application, the thickness of the second lithiophilic material layer is greater than or equal to 50 nm and less than or equal to 1 μm, preferably 50-60 nm.

[0093] As an example, the thickness of the second lithium-philic material layer can be 55nm, 75nm, 100nm, 300nm, 450nm, 650nm, 900nm, 990nm, etc., or it can be 55nm-75nm, 75-100nm, 100-300nm, 300-450nm, 450-650nm, 650-900nm, 900nm-990nm, etc.

[0094] If the thickness of the second lithiophilic material layer is too small, the lithiophilic effect is not significant and the formation of lithium dendrites cannot be improved. If the thickness of the second lithiophilic material layer is too large, it is not conducive to alleviating the volume expansion of the battery and increases the battery cost. Therefore, controlling the thickness of the second lithiophilic material layer to be greater than or equal to 50 nm and less than or equal to 1 μm, preferably 50-60 nm, can fully exert the lithiophilic effect, alleviate the growth of lithium dendrites, at least partially prevent short circuits, alleviate the volume expansion of the secondary battery, and improve the cycle performance and safety of the secondary battery.

[0095] According to some embodiments of the present application, the thickness of the first lithium-philic material layer is greater than 0 nm and less than 1 μm, preferably 8-12 nm.

[0096] As an example, the thickness of the first lithium-philic material layer can be 0.1 nm, 0.6 nm, 5 nm, 50 nm, 100 nm, 300 nm, 450 nm, 650 nm, 900 nm, etc., and can also be 0.1-0.6 nm, 0.6-5 nm, 5-50 nm, 50-100 nm, 100-300 nm, 300-450 nm, 450-650 nm, 650-900 nm, etc.

[0097] In the present application, the thickness of the first lithium-philic material layer is set to be greater than 0 nm and less than 1 μm, preferably 8-12 nm, so that the lithium-philic material increases gradually from the first part to the second part. When the current collector is in use, the first part is close to the isolation membrane and the second part is far away from the isolation membrane. When the electrolyte is infiltrated, lithium metal can be induced to preferentially deposit inside the porous three-dimensional skeleton, making full use of the pores of the three-dimensional current collector, limiting the infinite volume expansion of the deposited lithium, and further improving the battery safety performance.

[0098] See also Figure 4 According to some embodiments of the present application, the thickness of the first lithium-philic material layer is d1, the thickness of the second lithium-philic material layer is d2, and the range of d1 is greater than 0 and less than or equal to d2*50%.

[0099] By controlling the thickness percentage of the first lithium-philic material layer in the pores of the first part and the thickness percentage of the second lithium-philic material layer in the pores of the second part, the lithium-philic material increases gradually from the first part to the second part. When the current collector is in use, the first part is close to the isolation membrane and the second part is far away from the isolation membrane. When the electrolyte is infiltrated, lithium metal can be induced to preferentially deposit inside the porous three-dimensional skeleton, making full use of the pores of the three-dimensional current collector, limiting the infinite volume expansion of the deposited lithium, and further improving the battery safety performance.

[0100] According to some embodiments of the present application, along the direction from the first side to the second side, the height of the first portion is h1, the height of the current collector is h, and the range of h1 is greater than 5 μm and less than or equal to h*50%.

[0101] If the height of the first section is too small, the gradient variation of the thickness of the lithiophilic substance throughout the porous three-dimensional framework is not obvious. If the height of the first section is too large, the concentration of the lithiophilic substance throughout the porous three-dimensional framework is too low, affecting the lithiophilic effect. This application simultaneously ensures the lithiophilic effect and the gradient variation of the thickness of the lithiophilic substance in the porous three-dimensional framework by controlling the range of h1 to be greater than 5 μm and less than or equal to h*50%.

[0102] According to some embodiments of the present application, the lithium-philic substance includes at least one of a metal capable of forming an alloy with lithium, a metal alloy capable of forming an alloy with lithium, a metal capable of forming a solid solution with lithium, a metal alloy capable of forming a solid solution with lithium, silicon (Si), a carbon-based material or an oxide.

[0103] The aforementioned lithiophilic substances exhibit a strong lithiophilic effect, effectively inducing lithium deposition within the pores of the porous three-dimensional framework. Furthermore, they can effectively increase the number of active sites for lithium deposition, lower the overpotential for lithium nucleation, reduce localized lithium nucleation, and reduce the formation of lithium dendrites, thereby improving the safety performance of secondary batteries. Furthermore, the good electrical conductivity of metal and carbon-based materials helps reduce the impedance of secondary batteries and improve their initial coulombic efficiency.

[0104] According to some embodiments of the present application, the metal includes at least one of Sn, Mg, Zn, Bi, Pb, Au, Ag, Al, In, and Ga; the metal alloy includes at least two of Sn, Mg, Zn, Bi, Pb, Au, Ag, Al, In, and Ga; the carbon-based material includes at least one of graphite, graphene, graphyne, and hard carbon; and the oxide includes at least one of Cu2O, CuO, ZnO, MgO, and graphene oxide.

[0105] The above substances all have good lithium affinity and can well induce lithium deposition in the pores of the porous three-dimensional skeleton. They can also effectively increase the active sites for lithium deposition, reduce the nucleation overpotential of lithium, reduce local nucleation of lithium, reduce the formation of lithium dendrites, and improve the safety performance of secondary batteries.

[0106] Moreover, Sn, Mg, Zn, Bi, Pb, Au, Ag, Al, In, Ga and graphite, graphene, graphyne, and hard carbon have good conductivity, which helps to reduce the impedance of secondary batteries and improve the first coulombic efficiency of secondary batteries. At the same time, the cost is low, thereby reducing the cost of secondary batteries.

[0107] According to some preferred embodiments of the present application, the metal includes at least one of Sn, Mg, and Zn, and the metal alloy includes at least two of Sn, Mg, and Zn.

[0108] Since metal Sn, Mg, and Zn have stable structures and are not prone to collapse, they increase the structural stability of the secondary battery.

[0109] According to some embodiments of the present application, the loading amount of the lithium-philic substance in the pores of the porous three-dimensional skeleton is greater than or equal to 0.3 g / m 2 And less than or equal to 60g / m 2 .

[0110] If the loading amount of the lithiophilic substance is too small, the lithiophilic substance cannot cover the pore surface of the porous three-dimensional skeleton, and the lithiophilic effect is not obvious. If the loading amount of the lithiophilic substance is too large, the cost is increased. In the technical solution of the embodiment of the present application, by controlling the loading amount of the lithiophilic substance in the pores of the porous three-dimensional skeleton to be greater than or equal to 0.3 g / m 2 And less than or equal to 60g / m 2 The lithium-philic substance covers the pore surface of the porous three-dimensional skeleton, and the lithium-philic effect is obvious.

[0111] In some preferred embodiments, the loading amount of the lithium-philic substance in the pores of the porous three-dimensional skeleton is greater than or equal to 0.5 g / m 2 .

[0112] According to some embodiments of the present application, the porous three-dimensional framework includes a porous three-dimensional metal framework.

[0113] The metal skeleton is relatively stable to corrosive liquids such as nitric acid and hydrochloric acid. In addition, the metal has good conductivity, high surface smoothness, and is easy to clean, which can reduce the difficulty of the process.

[0114] The material of the porous three-dimensional metal skeleton can be a metal current collector material well known to those skilled in the art. According to some embodiments of the present application, the material of the porous three-dimensional metal skeleton includes at least one of Cu, Ni, Ti, Mg, and Al.

[0115] Metals like Cu, Ni, Ti, Mg, and Al are stable to corrosive solutions like nitric acid and hydrochloric acid, ensuring they are not corroded by lithium-philic materials. Furthermore, Cu, Ni, Ti, Mg, and Al are relatively low-cost, reducing the manufacturing cost of secondary batteries.

[0116] According to some embodiments of the present application, the porosity of the porous three-dimensional skeleton is 60% to 90%.

[0117] As an example, the porosity of the porous three-dimensional skeleton can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc., or it can be 60%-65%, 65%-70%, 70%-75%, 75%-80%, 80%-85%, 85%-90%, etc. It can be reasonably set according to needs to meet the porosity range of 60% to 90%.

[0118] If the porosity of the porous 3D skeleton is too low, for example, a porosity of less than 60%, electrolyte infiltration is difficult, and lithium ions cannot be induced to deposit in the pores of the porous 3D skeleton. If the porosity of the porous 3D skeleton is too high, for example, a porosity of more than 90%, the rib area is insufficient, reducing the electrochemically active area and also failing to induce lithium ion deposition in the pores of the porous 3D skeleton. Therefore, when the porosity of the porous 3D skeleton is between 60% and 90%, it can ensure good electrolyte infiltration and sufficient electrochemically active area, thereby inducing lithium ion deposition in the pores of the porous 3D skeleton.

[0119] According to some embodiments of the present application, the present application provides a method for preparing the above-mentioned current collector, comprising:

[0120] Providing a porous three-dimensional skeleton, the porous three-dimensional skeleton comprising a first side and a second side facing away from the first side, wherein the first side is used to face the isolation membrane;

[0121] A lithiophilic substance is formed on the porous three-dimensional skeleton. From the first side to the second side, the obtained lithiophilic porous three-dimensional skeleton includes a first portion and a second portion. The thickness of the first lithiophilic substance layer in the pores of the first portion is less than the thickness of the second lithiophilic substance layer in the pores of the second portion.

[0122] By forming a lithium-philic substance within the pores of the porous three-dimensional skeleton, the lithium nucleation overpotential can be reduced, lithium active sites can be increased, and the diffusion capacity of lithium atoms on the surface of the current collector skeleton can be improved, thereby inhibiting the growth of lithium dendrites and improving the cycle performance and safety of the secondary battery. In addition, this preparation method can achieve a thickness gradient design of the lithium-philic substance layer within the current collector from the separator side to the electrode side, which can induce lithium metal to preferentially deposit in the pores within the porous three-dimensional skeleton, fully utilizing the three-dimensional current collector pores, limiting the unlimited volume expansion of lithium metal, and further improving the safety performance of the secondary battery.

[0123] According to some embodiments of the present application, a method for preparing a current collector includes:

[0124] The first part of the lithiophilic porous three-dimensional skeleton is immersed in a corrosive solution so that the thickness of the first lithiophilic material layer in the first part of the pores is smaller than the thickness of the second lithiophilic material layer in the second part of the pores, thereby obtaining a current collector containing the lithiophilic material.

[0125] This preparation method, by corroding the lithium-philic material in the first part of the porous three-dimensional framework, can achieve a thickness gradient design of the lithium-philic material within the current collector from the separator side to the electrode side. This can induce lithium metal to preferentially deposit in the pores within the porous three-dimensional framework, fully utilizing the pores of the three-dimensional current collector, limiting the unlimited volume expansion of lithium metal, and further improving the safety performance of the secondary battery. In addition, the method has a simple operation process.

[0126] Methods for depositing the lithiophilic material layer in the pores of the porous three-dimensional skeleton include, but are not limited to, physical vapor deposition (PVD), atomic layer deposition (ALD), electroplating, or vacuum evaporation.

[0127] According to some embodiments of the present invention, the etching solution includes at least one of nitric acid and hydrochloric acid.

[0128] Both nitric acid and hydrochloric acid corrode only lithiophilic substances, without corroding porous three-dimensional metal frameworks such as Cu, Ni, Ti, Mg, and Al. By immersing the first portion of the porous three-dimensional metal framework in nitric acid or hydrochloric acid, a thickness gradient design of the lithiophilic substance within the current collector can be achieved. Furthermore, nitric acid or hydrochloric acid poses less environmental pollution and is relatively low cost, thereby reducing the production cost of the current collector. Of course, the corrosive liquid is not limited to nitric acid and hydrochloric acid; other corrosive liquids that corrode lithiophilic substances but do not corrode the porous three-dimensional framework can also be used.

[0129] The immersion time of the first part of the porous three-dimensional skeleton in the etching solution can be designed according to actual conditions. According to some preferred embodiments of the present application, the first part of the porous three-dimensional skeleton is placed in the etching solution and immersed for 1-60 minutes.

[0130] If the first portion of the porous three-dimensional framework is immersed in the etching solution for too short a time, the lithium-philic substance in the pores of the first portion is not fully corroded, resulting in a weak thickness gradient between the first lithium-philic substance layer and the second lithium-philic substance layer in the pores of the second portion. Conversely, if the immersion time is too long, the thickness of the first lithium-philic substance layer in the pores of the first portion is too small, or even fails to completely cover the surface of the pores of the first portion, resulting in a less pronounced lithium-philic effect. In the technical solution of the embodiment of the present application, the first portion of the porous three-dimensional framework is controlled to be immersed in the etching solution for 1-60 minutes, ensuring that the lithium-philic substance forms a thickness gradient in the current collector from the separator side to the electrode side, thereby making the lithium-philic effect more pronounced.

[0131] According to some more preferred embodiments of the present application, the first portion of the porous three-dimensional framework is immersed in the etching solution for 5-20 minutes.

[0132] After the first part of the lithiophilic porous three-dimensional skeleton is immersed in the etching solution, the etching solution on the sample can be further cleaned using, but not limited to, anhydrous ethanol. Specifically, the corroded sample can be immersed in anhydrous ethanol or other cleaning solution for about 5 minutes.

[0133] After cleaning the sample, it can be dried in an oven or by natural drying.

[0134] Other technical features of the preparation method of the current collector are exactly the same as those of the current collector introduced above, and will not be elaborated here.

[0135] According to some embodiments of the present application, the present application provides an electrode sheet, including the current collector as described above or the current collector prepared by the preparation method of the current collector as described above.

[0136] According to some embodiments of the present application, the present application provides a secondary battery, including an anode sheet, a cathode sheet and a separator. The separator is disposed between the anode sheet and the cathode sheet. The anode sheet is the electrode sheet as described above. A first part of the current collector in the anode sheet is close to the separator, and a second part is far from the separator.

[0137] The thickness of the lithiumophilic substance in the current collector increases along the direction from the separator to the current collector. The secondary battery can be the battery 100 or the battery cell 20 as described above.

[0138] The secondary battery includes a cathode sheet, an anode sheet, an electrolyte and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the cathode sheet and the anode sheet. The electrolyte plays a role in conducting ions between the cathode sheet and the anode sheet. The separator is disposed between the cathode sheet and the anode sheet, mainly playing a role in preventing the positive anode from short-circuiting, and at the same time allowing ions to pass through.

[0139] The cathode sheet includes a cathode current collector and a cathode film disposed on the cathode current collector. For example, the cathode current collector has two surfaces opposite to each other in its own thickness direction, and the cathode film layer can be disposed on any one or both of the two opposite surfaces of the cathode current collector.

[0140] The cathode film includes a cathode active material. The specific type of the cathode active material is not specifically limited and can be selected according to requirements. Preferably, the cathode active material includes lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium iron phosphate (LiFePO4), lithium cobalt phosphate (LiCoPO4), lithium manganese phosphate (LiMnPO4), lithium nickel phosphate (LiNiPO4), lithium manganate (LiMnO2), binary material LiNi x A (1-x) O2 (A is selected from one of Co and Mn, 0 < x < 1), ternary material LiNi m B n C (1-m-n) O2 (B and C are each independently selected from at least one of Co, Al, and Mn, and B and C are different, 0 < m < 1, 0 < n < 1), one or several of its doping and / or coating modification materials.

[0141] The cathode film optionally includes a binder. The specific type of the binder is not specifically limited and can be selected according to requirements.

[0142] As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0143] The cathode membrane may optionally include a conductive agent. The specific type of the conductive agent is not subject to specific restrictions and can be selected according to needs.

[0144] As an example, the conductive agent may include one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0145] In some embodiments, the cathode membrane may further include an ion conductor polymer, a lithium salt, and a plasticizer. The ion conductor polymer may be selected from one or more of polyethylene oxide, polyethylene terephthalate, polyimide, polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polypropylene carbonate, polyvinyl chloride, vinylidene fluoride, 2-acrylamido-2-methylpropanesulfonic acid, trimethylolpropane triacrylate, hyperbranched polyacrylate, and methyl methacrylate copolymer. The lithium salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium trifluoromethanesulfonate (LiCF3SO3). The plasticizer can be selected from one or more of polyethylene glycol diglycidyl ether (PEGDE), polyethylene glycol diacrylate (PEGDA), polyethylene glycol amine (PEGNH2), succinonitrile (SN), triethyl phosphate (TEP), fluoroethylene carbonate (TEP), dimethyl ether (DME), diethyl carbonate (DEC), ethylene carbonate (EC), and phthalates.

[0146] The anode sheet includes the current collector described above. In some embodiments, the anode sheet further includes an anode film layer disposed on the surface of the current collector, wherein the anode film layer includes an anode active material. The anode active material includes, but is not limited to, graphite, mesocarbon microbeads, soft carbon / hard carbon, amorphous carbon, lithium titanate, silicon-carbon alloy, and the like.

[0147] In some embodiments, the anode film layer may further include a binder. As an example, the binder includes but is not limited to styrene-butadiene rubber (SBR).

[0148] In some embodiments, the anode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0149] In some embodiments, the anode film layer may further include additives such as a thickener. For example, the thickener may be, but is not limited to, sodium carboxymethyl cellulose (CMC).

[0150] It can be understood that in some embodiments, the secondary battery may also be a negative electrode-free secondary battery. In this case, the anode sheet does not include an anode active material, and the anode sheet serves as the current collector.

[0151] The electrolyte may be at least one of a liquid electrolyte (ie, an electrolyte solution) and a solid electrolyte.

[0152] In some optional embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0153] In some embodiments, the electrolyte salt can be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0154] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC) and butylene carbonate (BC).

[0155] In some preferred embodiments, the electrolyte comprises a solid electrolyte. The solid electrolyte is typically provided between the anode and cathode electrodes in the form of a solid electrolyte membrane. The solid electrolyte membrane may be selected from one or more of an inorganic solid electrolyte membrane, a solid polymer electrolyte membrane, and an inorganic-organic composite solid electrolyte membrane. The use of a solid electrolyte membrane facilitates reducing the thickness of the battery and, compared to liquid electrolytes, eliminates the risk of leakage. In these embodiments, the secondary battery is an all-solid-state battery or a semi-solid-state battery.

[0156] According to some embodiments of the present application, the present application provides an electrical device, including a secondary battery provided by any of the above solutions, and the secondary battery is used to provide electrical energy to the electrical device.

[0157] The power-consuming device may be any of the aforementioned devices or systems using secondary batteries.

[0158] The preparation process and test data are introduced as follows:

[0159] Example 1:

[0160] Preparation of current collector:

[0161] Step (S1): plating a 0.05 μm thick lithiophilic material Sn in the holes of a 150 μm thick copper foam to obtain a lithiophilic copper foam, wherein the copper foam includes a first side and a second side facing away from the first side, wherein the first side is used to face the isolation membrane, and along the direction from the first side to the second side, the copper foam includes a first portion and a second portion;

[0162] Step (S2): placing the first portion of the lithiophilic copper foam obtained in step (S1) in a culture dish containing a 6 mol / L nitric acid etching solution and immersing it for 1 minute, wherein the etching solution has a height of 5 μm, so that the thickness of the first lithiophilic material layer in the first portion of the pores is less than the thickness of the second lithiophilic material layer in the second portion of the pores, thereby obtaining a first sample;

[0163] Step (S3): taking out the first sample in step (S2), soaking it in anhydrous ethanol for 5 minutes to obtain a second sample; and

[0164] Step (S4): placing the second sample obtained in step (S3) in an oven at 60° C. and drying for 10 minutes to obtain a gradient lithium-philic three-dimensional current collector.

[0165] See also Figure 5 , which is a schematic cross-sectional view of the current collector 40 prepared in Example 1. The current collector 40 includes a porous three-dimensional skeleton 402. The thickness of the lithium-philic material 404 is gradiently distributed within the current collector 40. The thickness of the first lithium-philic material layer close to the separator side (first portion) is less than the thickness of the second lithium-philic material layer away from the separator side (second portion).

[0166] 3D current collector / Li half-cell assembly and discharge performance testing:

[0167] A button-type half-cell was assembled. The positive electrode of the battery used the gradient lithium-philic three-dimensional current collector obtained in Example 1, the negative electrode used a lithium sheet, the electrolyte used 1M LiFSI dissolved in DME, and the isolation membrane used a 12μm PE film.

[0168] Discharge conditions: The button half-cell was discharged at a constant current density of 1 mA / cm at room temperature. 2 , continue discharging until a short circuit signal appears, that is, the battery voltage jumps to 0V.

[0169] Record the time from the start of discharge to short circuit.

[0170] LFP / 3D current collector full battery assembly and cycle performance testing:

[0171] Button-type full battery assembly: The positive electrode of the full battery uses lithium iron phosphate, wherein the mass ratio of lithium iron phosphate: conductive carbon black: PVDF binder is 8:1:1, the negative electrode uses the gradient lithium-philic three-dimensional current collector obtained in Example 1, the electrolyte uses 1M LiFSI dissolved in DME, and the isolation membrane uses a 12μm PE film.

[0172] Charging conditions: Full cells were charged at room temperature using constant current-constant voltage (CC-CV) mode. First, charge at a fixed rate of 0.2C in constant current mode until the voltage reached 3.65V. Then, switch to constant voltage mode with a cutoff current of 0.05C to fully charge the cell.

[0173] Discharge conditions: Discharge in constant current mode at a discharge rate of 0.5C to 2V and cycle 200 times.

[0174] The number of cycles at which the discharge capacity retention rate reached 50% was recorded.

[0175] Example 2:

[0176] The only difference between Example 2-3 and Example 1 is that the thickness of the lithiophilic material Sn is different, and other conditions are the same, as shown in Table 1.

[0177] Example 4:

[0178] The only difference between Example 4 and Example 2 is that different etching solutions are used. Other conditions are the same, as shown in Table 1.

[0179] Example 5-7:

[0180] The only difference between Examples 5-7 and Example 2 is that the immersion time of the lithiophilic copper foam in the etching solution is different, and other conditions are the same, as shown in Table 1.

[0181] Examples 8-10:

[0182] The only difference between Examples 8-10 and Example 5 is that the height in the etching solution is different, and other conditions are the same, as shown in Table 1.

[0183] Examples 11-14:

[0184] The only difference between Examples 11-14 and Example 9 is that the lithiophilic substances are different, and other conditions are the same, as shown in Table 1.

[0185] Comparative Example 1:

[0186] The current collector is blank copper foam without any deposition of lithiophilic substances.

[0187] Comparative Examples 2-6:

[0188] Different lithiophilic substances are used respectively, and the lithiophilic substances are not subjected to gradient treatment.

[0189] Thickness test of the three-dimensional current collector lithium-philic layer, where the lithium-philic layer can be the first lithium-philic material layer or the second lithium-philic material layer:

[0190] The three-dimensional cross-section of the current collector was observed using a scanning electron microscope to measure the thickness of the lithium-philic layer from the surface to the interior.

[0191] Sample preparation: A 5 mm × 5 mm × 0.12 mm three-dimensional current collector sample was fixed on a 5 mm × 4 mm silicon wafer support layer. The three-dimensional current collector cross section was bombarded using an ion beam polisher (model: Leica EM TIC 3X). The ion gun was perpendicular to the three-dimensional current collector cross section, and the polishing efficiency was 2 h / mm. A complete, flat truncated observation surface was obtained to obtain a cross-sectional sample.

[0192] Observation: The cross-sectional sample prepared above was placed in the sample chamber of a scanning electron microscope (model: Phenom ProX) and the vacuum chamber was evacuated. The electron beam switch was turned on and the acceleration voltage was 10-20 kV. The upper surface of the three-dimensional current collector was selected and observed at a longitudinal depth of 50 μm and 120 μm respectively. Three points were taken at each depth to obtain the average thickness of the lithium-philic layer.

[0193] 3D current collector / Li half-cell assembly and discharge performance testing:

[0194] Assemble button-type half-cells. The positive electrodes of the batteries use the three-dimensional current collectors obtained in Examples 1-14 and Comparative Examples 1-6, respectively. The negative electrodes use lithium sheets. The electrolyte uses 1M LiFSI dissolved in DME. The separator uses a 12 μm PE film.

[0195] Discharge conditions: The button half-cell was discharged at a constant current density of 1 mA / cm at room temperature. 2 , continue discharging until a short circuit signal appears, that is, the battery voltage jumps to 0V.

[0196] Record the time from the start of discharge to short circuit.

[0197] LFP / 3D current collector full battery assembly and cycle performance testing:

[0198] Button-type full-cell assembly: The positive electrode of the full-cell uses lithium iron phosphate, wherein the mass ratio of lithium iron phosphate: conductive carbon black: PVDF binder is 8:1:1, the negative electrode uses the three-dimensional current collector obtained in Examples 1-14 and Comparative Examples 1-6, respectively, the electrolyte uses 1M LiFSI dissolved in DME, and the isolation membrane uses a 12μm PE film.

[0199] Charging conditions: Full cells were charged at room temperature using constant current-constant voltage (CC-CV) mode. First, charge at a fixed rate of 0.2C in constant current mode until the voltage reached 3.65V. Then, switch to constant voltage mode with a cutoff current of 0.05C to fully charge the cell.

[0200] Discharge conditions: Discharge in constant current mode at a discharge rate of 0.5C to 2V and cycle 200 times.

[0201] The number of cycles at which the discharge capacity retention rate reached 50% was recorded.

[0202] Table 1: Current collector parameters and battery performance parameters of various embodiments and comparative examples

[0203]

[0204] The results of Examples 1-12 compared with Comparative Example 1 in Table 1 show that the gradient lithium-philic foam copper current collector has a longer short-circuit time of the half-cell and a longer number of cycles of maintaining 50% capacity of the full battery compared with the blank foam copper current collector, indicating that the gradient lithium-philic current collector of the present application achieves half-cell short-circuit suppression and improves the cycle performance of the full battery.

[0205] The results of Examples 1-10 compared with Comparative Example 2, Example 11 compared with Comparative Example 3, and Example 12 compared with Comparative Example 4 in Table 1 show that the copper foam containing lithium-philic substances must be gradient treated to significantly suppress short circuits and improve the full battery cycle performance.

[0206] The results of Examples 1-3 in Table 1 show that compared with the second lithium-philic material layer having a thickness of 0.05 μm and 1 μm, the lithium-philic material has the best lithium-philic effect when the thickness of the second lithium-philic material layer is 0.5 μm, and both the half-cell short-circuit performance and the cycle performance of the full battery are improved.

[0207] Comparison of the results of Example 2 and Example 4 in Table 1 shows that nitric acid is more effective as a corrosive solution than hydrochloric acid and has a more significant effect on improving the electrochemical performance of the battery.

[0208] Comparison of the results of Example 2 and Examples 5-7 shows that when the immersion time of the lithiophilic copper foam in the etching solution is 10 minutes, the half-cell short-circuit suppression performance and the full-cell cycle performance are best.

[0209] Comparison of the results of Examples 8-10 shows that the best effect is achieved when the height of the etching solution in the container is 30 μm, that is, the half-cell short-circuit performance and the full-cell cycle performance are best suppressed when the etching thickness of the lithiated copper foam is 30 μm.

[0210] Comparison of the results of Example 9, Example 11, and Example 12 shows that when the lithiophilic material is Sn, the half-cell short-circuit performance and the cycle performance of the full battery are best suppressed, indicating that the gradient lithiophilic improvement effect of Sn is better than that of Zn and Mg.

[0211] Comparison of the results of Example 13 with those of Comparative Example 5 shows that when the lithiophilic substance is carbon-based graphite, designing a graphite thickness gradient can significantly improve the electrochemical performance of the battery.

[0212] Comparison of the results of Example 14 and Comparative Example 6 shows that when the lithiophilic substance is CuO oxide, designing the CuO thickness gradient can significantly improve the electrochemical performance of the battery.

[0213] Based on the test results in Table 1, it can be concluded that Example 9 is the optimal embodiment. The porous three-dimensional skeleton is a copper foam with a thickness of 150 μm, the lithium-philic substance is Sn, the initial thickness of the lithium-philic substance (the thickness of the second lithium-philic substance layer in the second part of the copper foam) is 0.5 μm, the immersion time of the first part of the copper foam in nitric acid is 10 min, and the height of the nitric acid etching solution is 30 μm. The thickness of the first lithium-philic substance layer is 0.01 μm, the mass proportion of the lithium-philic substance Sn in the first part of the current collector (close to the isolation membrane side) is 0.5%, and the mass proportion of the lithium-philic substance Sn in the second part of the current collector (close to the electrode side) is 99.5%.

[0214] By comparing the above embodiments with the comparative examples, it can be seen that by placing the lithium-philic substance in the pores of the porous three-dimensional skeleton, the nucleation overpotential of lithium on the surface of the porous three-dimensional skeleton can be reduced, the active sites can be increased, and the diffusion ability of lithium atoms on the surface of the porous three-dimensional skeleton can be improved, thereby avoiding the local nucleation and deposition of lithium metal, inhibiting the formation of dendrites, and improving the cycle performance and safety of the secondary battery. Moreover, along the direction from the isolation membrane side to the electrode side, the mass proportion of the lithium-philic substance in the current collector is smaller on the side close to the isolation membrane than on the side close to the electrode, and the increasing thickness gradient of the lithium-philic substance layer can induce lithium metal to preferentially deposit inside the porous three-dimensional skeleton, making full use of the pores of the three-dimensional current collector, limiting the infinite volume expansion of the deposited lithium, and further improving the safety of the secondary battery.

[0215] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A current collector, characterized in that: The present invention comprises a porous three-dimensional skeleton and a lithium-philic substance, wherein the lithium-philic substance is distributed in the pores of the porous three-dimensional skeleton, and the mass proportion of the lithium-philic substance in the current collector is smaller on the side close to the separator than on the side close to the electrode; The lithium-philic substance is distributed in the pores of the porous three-dimensional skeleton, the current collector includes a first side and a second side away from the first side, the first side is used to face the isolation membrane, and along the direction from the first side to the second side, the porous three-dimensional skeleton includes a first part and a second part, the first lithium-philic substance layer is provided in the pores of the three-dimensional skeleton of the first part, and the second lithium-philic substance layer is provided in the pores of the three-dimensional skeleton of the second part, and the thickness of the first lithium-philic substance layer is less than the thickness of the second lithium-philic substance layer; The thickness of the first lithiophilic material layer is d1, the thickness of the second lithiophilic material layer is d2, and the range of d1 is greater than 0 and less than or equal to d2*50%.

2. The current collector according to claim 1, characterized in that The thickness of the second lithium-philic material layer is greater than or equal to 50 nm and less than or equal to 1 μm.

3. The current collector according to claim 2, wherein The thickness of the second lithium-philic material layer is 50-60 nm.

4. The current collector according to claim 1, characterized in that The thickness of the first lithium-philic material layer is greater than 0 nm and less than 1 μm.

5. The current collector according to claim 4, wherein The thickness of the first lithium-philic material layer is 8-12 nm.

6. The current collector according to claim 1, characterized in that Along a direction from the first side to the second side, a height of the first portion is h1, a height of the current collector is h, and a range of h1 is greater than 5 μm and less than or equal to h*50%.

7. The current collector according to any one of claims 1 to 6, characterized in that The lithiophilic substance includes at least one of a metal capable of forming an alloy with lithium, a metal alloy capable of forming an alloy with lithium, a metal capable of forming a solid solution with lithium, a metal alloy capable of forming a solid solution with lithium, silicon (Si), a carbon-based material, or an oxide.

8. The current collector according to claim 7, characterized in that: The metal includes at least one of Sn, Mg, Zn, Bi, Pb, Au, Ag, Al, In, and Ga; the metal alloy includes at least two of Sn, Mg, Zn, Bi, Pb, Au, Ag, Al, In, and Ga; the carbon-based material includes at least one of graphite, graphene, graphyne, and hard carbon; and the oxide includes at least one of Cu2O, CuO, ZnO, and MgO.

9. The current collector according to claim 8, characterized in that: The metal includes at least one of Sn, Mg, and Zn, and the metal alloy includes at least two of Sn, Mg, and Zn.

10. The current collector according to any one of claims 1 to 6, wherein The loading amount of the lithium-philic substance in the pores of the porous three-dimensional skeleton is greater than or equal to 0.3 g / m 2 and less than or equal to 60 g / m 2 .

11. The current collector according to any one of claims 1 to 6, characterized in that: The porous three-dimensional framework comprises a porous three-dimensional metal framework.

12. The current collector according to claim 11, characterized in that: The material of the porous three-dimensional metal skeleton includes at least one of Cu, Ni, Ti, Mg, and Al.

13. The current collector according to any one of claims 1 to 6, characterized in that The porosity of the porous three-dimensional skeleton is 60% to 90%.

14. A method for preparing the current collector according to any one of claims 1 to 13, characterized in that: include: Providing a porous three-dimensional skeleton, the porous three-dimensional skeleton comprising a first side and a second side facing away from the first side, wherein the first side is configured to face the isolation membrane; forming a lithium-philic substance on the porous three-dimensional skeleton, wherein the lithium-philic substance is distributed in the pores of the porous three-dimensional skeleton, and along the direction from the first side to the second side, the porous three-dimensional skeleton includes a first portion and a second portion, wherein a first lithium-philic substance layer is disposed in the pores of the three-dimensional skeleton of the first portion, and a second lithium-philic substance layer is disposed in the pores of the three-dimensional skeleton of the second portion, and a thickness of the first lithium-philic substance layer is less than a thickness of the second lithium-philic substance layer; The thickness of the first lithiophilic material layer is d1, the thickness of the second lithiophilic material layer is d2, and the range of d1 is greater than 0 and less than or equal to d2*50%.

15. The method for preparing the current collector according to claim 14, characterized in that: The method comprises: The first part of the porous three-dimensional skeleton is immersed in a corrosive solution so that the thickness of the first lithium-philic material layer in the first part of the pores is smaller than the thickness of the second lithium-philic material layer in the second part of the pores, thereby obtaining a current collector containing lithium-philic material.

16. The method for preparing a current collector according to claim 15, characterized in that: The etching solution includes at least one of nitric acid or hydrochloric acid.

17. The method for preparing a current collector according to claim 15 or 16, characterized in that: The first part of the porous three-dimensional framework is placed in the etching solution and immersed for 1-60 minutes.

18. An electrode sheet, characterized in that: A current collector comprising the current collector according to any one of claims 1 to 13 or a current collector prepared by the method for preparing the current collector according to any one of claims 14 to 17.

19. A secondary battery, characterized in that: It includes an anode sheet, a cathode sheet and an isolation membrane, the isolation membrane is arranged between the anode sheet and the cathode sheet, the anode sheet is the electrode sheet as claimed in claim 18, the first part of the current collector in the anode sheet is close to the isolation membrane, and the second part is far away from the isolation membrane.

20. An electrical device, characterized in that: Comprising the secondary battery as claimed in claim 19.

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