Lithium metal negative electrode and preparation method therefor, and solid-state battery

Abstract

The present application provides a lithium metal negative electrode and a preparation method therefor, and a solid-state battery. The lithium metal negative electrode comprises: a lithium layer and porous metal layers bonded to the surfaces of both sides of the lithium layer, wherein the porous metal layers are metal layers provided with a plurality of through holes in a penetrating manner. The porous metal layers comprise a metal having an electrode potential higher than that of lithium; the porous metal layers are used to connect tabs; and the hole diameter of the through holes is greater than or equal to 100 μm.

Description

Lithium metal anode, preparation method thereof and solid-state battery

[0001] The present application claims priority to the Chinese patent application No. 202411276929.7, filed on September 12, 2024, to the Chinese Patent Office, the whole content of the above application being incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of batteries, in particular to a lithium metal anode, a preparation method of the lithium metal anode, and a solid-state battery. BACKGROUND

[0003] With the wide application of electric vehicles, portable devices and wearable devices, the demand for high energy density batteries is increasing. Lithium metal anode is considered to be a better choice to realize high energy density battery system due to its low electrochemical potential and high theoretical specific capacity. TECHNICAL PROBLEM

[0004] However, the host-free lithium metal anode usually has a large volume expansion during charging, which is caused by the disordered deposition of lithium metal. The volume expansion of the lithium metal anode exacerbates the uncontrollable growth of lithium dendrites and the rupture of the solid electrolyte interphase (SEI), thereby leading to rapid capacity decline and exacerbating the potential short circuit risk. TECHNICAL SOLUTION

[0005] The present application provides a lithium metal anode. The lithium metal anode comprises: a lithium layer and a porous metal layer combined on both sides of the surface of the lithium layer, the porous metal layer being a metal layer provided with a plurality of through holes, the porous metal layer comprising a metal with an electrode potential higher than that of lithium, the porous metal layer being used to connect a tab, and the aperture of the through hole being greater than or equal to 100 μm.

[0006] The present application also provides a preparation method of the lithium metal anode. The preparation method of the lithium metal anode comprises:

[0007] providing a lithium foil and a porous metal foil, the porous metal foil being a metal foil provided with a plurality of through holes, the metal foil comprising a metal with an electrode potential higher than that of lithium, the porous metal foil being used to connect a tab, and the aperture of the through hole being greater than or equal to 100 μm;

[0008] alternately laying the lithium foil and the porous metal foil together and making the lithium foil located between two adjacent porous metal foils to obtain a multi-layer structure;

[0009] roll-pressing the multi-layer structure to obtain the lithium metal anode.

[0010] The application further provides a solid-state battery. The solid-state battery comprises a positive electrode, a negative electrode and a solid-state electrolyte film, the positive electrode and the negative electrode are arranged on two sides of the solid-state electrolyte film, and the negative electrode is the lithium metal negative electrode or the lithium metal negative electrode prepared by the preparation method. Advantages

[0011] The lithium metal negative electrode provided by the application can locally protect the lithium layer during discharging by sandwiching the lithium layer between two porous metal layers, thereby improving the stability of the lithium metal negative electrode; meanwhile, the through holes on the porous metal layer can provide growth space for lithium metal deposition during charging, thereby relieving the volume expansion rate of the lithium metal negative electrode.

[0012] The preparation method of the lithium metal negative electrode provided by the application is simple and easy to implement, and the obtained lithium metal negative electrode can locally protect the lithium foil during discharging by sandwiching the lithium foil between two porous metal foils, thereby improving the stability of the lithium metal negative electrode; meanwhile, the through holes on the porous metal foil can provide growth space for lithium metal deposition during charging, thereby relieving the volume expansion rate of the lithium metal negative electrode.

[0013] The lithium metal negative electrode used in the solid-state battery provided by the application has better anti-expansion property, thereby improving the cycle stability of the solid-state battery. BRIEF DESCRIPTION OF DRAWINGS

[0014] FIG. 1 is a schematic diagram of the front structure of the lithium metal negative electrode provided by the embodiment of the application;

[0015] FIG. 2 is a schematic diagram of the top structure of the porous metal layer in the lithium metal negative electrode provided by the embodiment of the application;

[0016] FIG. 3 is a flowchart of the preparation method of the lithium metal negative electrode provided by the embodiment of the application;

[0017] FIG. 4 is a schematic diagram of the exploded structure of the solid-state battery provided by the embodiment of the application.

[0018] Reference signs:

[0019] 10, lithium metal negative electrode; 1, lithium layer; 2, porous metal layer; 201, through hole; 21, main part; 22, extension; 100, solid-state battery; 20, positive electrode; 20a, positive electrode current collector; 20b, positive electrode active material layer; 30, solid-state electrolyte film; 40, shell. Embodiments of the application

[0020] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of the present application.

[0021] In addition, it should be understood that the specific implementation described herein is only used to illustrate and explain the present application, and is not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, and specifically refer to the direction of the drawing surface in the drawings; and "inner" and "outer" refer to the outline of the device.

[0022] The terms "first", "second", "third", etc. are only used for descriptive purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0023] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection or can communicate with each other; can be directly connected, can also be indirectly connected through an intermediate medium, can be the communication or interaction relationship between two elements. 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.

[0024] The terms "including", "containing" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or equipment. Without more limitation, the element defined by the sentence "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0025] In the description of the embodiments of the present application, the words "example" or "for example" or similar words are used to represent examples, illustrations, or descriptions. Any embodiment or design scheme described as "example" or "for example" in the embodiments of the present application is not interpreted as more preferred or having more advantages than another embodiment or design scheme. The use of "example" or "for example" or similar words is intended to present a relative concept in a clear manner.

[0026] In order to facilitate the understanding of the scheme of the present application, the spline curves and arrows used in the reference signs in the drawings are described here: the components indicated by the spline curves without arrows are solid components, i.e. components with solid structures; the components indicated by the spline curves with arrows are virtual components, i.e. components without solid structures.

[0027] In a first aspect, the embodiments of the present application provide a lithium metal negative electrode, comprising: a lithium layer and a porous metal layer combined on both sides of the surface of the lithium layer, the porous metal layer being a metal layer provided with a plurality of through holes, the porous metal layer containing a metal with an electrode potential higher than that of lithium, the porous metal layer being used to connect a tab, and the pore size of the through hole being greater than or equal to 100 μm.

[0028] The lithium metal negative electrode provided by the embodiments of the present application can locally protect the lithium layer during discharge by sandwiching the lithium layer between two porous metal layers, thereby improving the stability of the lithium metal negative electrode; at the same time, the through holes on the porous metal layer can provide growth space for lithium metal deposition during charging, thereby relieving the volume expansion rate of the lithium metal negative electrode.

[0029] Specifically, referring to FIG. 1 and FIG. 2, the lithium metal negative electrode 10 provided by the embodiments of the present application can be applied in a lithium battery. Optionally, the lithium battery is a solid-state battery. The solid-state battery here includes but is not limited to at least one of a polymer solid-state battery, an oxide solid-state battery and a sulfide solid-state battery.

[0030] In detail, the lithium metal negative electrode 10 includes a lithium layer 1 and a porous metal layer 2.

[0031] The lithium layer 1 refers to a layered structure containing lithium metal. Herein, the lithium layer 1 can contain only lithium, or can contain lithium and other metals, for example, the lithium layer 1 contains a lithium alloy. Along the thickness direction of the lithium layer 1, the lithium layer 1 has two opposite side surfaces, namely a first side surface and a second side surface. A porous metal layer 2 is arranged on the two side surfaces of the lithium layer 1, and the porous metal layer 2 is connected together with the lithium layer 1, i.e. the porous metal layer 2 is combined together with the lithium layer 1. In other words, the porous metal layer 2 is combined together with the lithium layer 1 only under the action of gravity, i.e. the porous metal layer 2 and the lithium layer 1 will not be separated. As an example, the porous metal layer 2 is physically combined together with the lithium layer 1. It can be understood that the number of layers of the porous metal layer 2 is greater than the number of layers of the lithium layer 1. Specifically, the porous metal layer 2 is arranged on the first side surface of the lithium layer 1, and the porous metal layer 2 is also arranged on the second side surface of the lithium layer 1, i.e. the lithium layer 1 is sandwiched between the two porous metal layers 2, thereby forming a sandwich structure of "porous metal layer-lithium layer-porous metal layer". The shape of the lithium layer 1 and the porous metal layer 2 can be square, circular or long strip-shaped, which is not limited herein.

[0032] In detail, the porous metal layer 2 refers to a metal layer through which a plurality of through holes 201 are arranged, i.e. the porous metal layer 2 has a plurality of through holes 201. That is, the porous metal layer 2 is a metal layer with through holes. Specifically, the through holes 201 are arranged through the metal layer along the thickness direction, so that the through holes 201 serve as transmission channels, and lithium ions can move from one side of the porous metal layer 2 to the corresponding lithium layer 1 through the through holes 201. The plurality of through holes 201 are distributed at intervals on the porous metal layer 2, which can be equidistant distribution or non-equidistant distribution. In addition, the diameters of the through holes 201 on the porous metal layer 2 can be equal or unequal.

[0033] In composition, the porous metal layer 2 comprises a high electrode potential metal. Here, the high electrode potential metal refers to a metal with an electrode potential higher than that of lithium metal. Optionally, the high electrode potential metal has a standard electrode potential at least 1 V greater than that of lithium metal. Optionally, the difference between the standard electrode potential of the high electrode potential metal and that of lithium metal is 1 V, 2 V, 3 V, 4 V, 5 V, or 6 V. When the lithium metal anode 10 is applied to a battery, during discharge of the battery, because the electrode potential of the metal in the porous metal layer 2 is higher than that of lithium metal, it can be ensured that lithium metal will be preferentially oxidized to form lithium ions, thereby improving the structural stability of the porous metal layer 2, and the structural stability of the porous metal layer 2 is a prerequisite for the stability of the through hole 201. As an example, the high electrode potential metal is copper, aluminum, titanium, tantalum, or nickel. The porous metal layer 2 is used to connect the tab, for example, the porous metal layer 2 is used to be welded with the tab, thereby realizing connection with the external circuit. It can be understood that in the lithium metal anode 10, the porous metal layer 2 acts as a current collector, and the porous metal layer 2 is located on both sides of the lithium layer 1 and is used to converge current, which facilitates shortening the path of electron transfer in the lithium metal anode 10 and improves the rate performance of the battery. In addition, by using the porous metal layer 2 as a current collector, it is not necessary to additionally provide a separate current collector, which is conducive to improving the energy density of the battery.

[0034] During discharge of the battery, part of the lithium metal in the lithium layer 1 can also be oxidized to form lithium ions, thereby supplementing lithium ions to the battery system. In the embodiments of the present application, the through hole 201 is at least a large hole, and the pore size of the through hole 201 should not be too small. Specifically, the pore size of the through hole 201 is greater than or equal to 100 μm. By increasing the pore size of the through hole 201, it is beneficial to ensure that the lithium metal anode 10 has good resistance to swelling. Generally, the part of the lithium metal exposed on the lithium layer 1 corresponding to the through hole 201 will be oxidized to form lithium ions, while the part of the lithium metal on the lithium layer 1 offset from the through hole 201 and covered by the porous metal layer 2 is more likely to be retained. This part of the lithium metal can continue to support the porous metal layer 2, improve the structural stability of the lithium metal anode 10, and reduce the risk of rupture of the solid electrolyte interphase (SEI) on the lithium metal anode 10.

[0035] In the embodiments of the present application, the lithium metal negative electrode 10 is provided with the porous metal layer 2 on both sides of the lithium layer 1, and the lithium layer 1 is clamped between the two porous metal layers 2, that is, for the lithium metal negative electrode 10, the porous metal layer 2 is the outer layer, and the lithium layer 1 is the core layer. When the lithium metal negative electrode 10 is applied to a battery, the lithium layer 1 will undergo volume change due to redox reaction during the charging and discharging process of the battery. The porous metal layer 2 as the outer layer can locally protect the lithium layer 1 as the inner layer during the discharging process of the battery, thereby improving the stability of the lithium metal negative electrode 10. In addition, the porous metal layer 2 has the through hole 201, and when lithium ions are reduced to form lithium metal and deposited on the lithium metal negative electrode 10 in disorder during the charging process of the battery, the through hole 201 can provide a growth space for the deposition of lithium metal, thereby relieving the volume expansion rate of the lithium metal negative electrode 10.

[0036] In addition, since lithium metal is relatively soft, and the porous metal layer 2 is arranged on both sides of the lithium layer 1, the porous metal layer 2 can also protect the lithium layer 1 during the preparation of the lithium metal negative electrode 10, thereby reducing the probability of mechanical damage to the lithium layer 1.

[0037] In addition, the porous metal layer 2 as the outer layer of the lithium metal negative electrode 10, when the lithium metal negative electrode 10 is applied to a battery, for example, to a solid-state battery, the porous metal layer 2 is used to contact the solid-state electrolyte film in the solid-state battery. The porous metal layer 2 has a relatively stable structure, which can promote the stability of the electrode interface.

[0038] In the embodiments of the present application, the number of layers of the lithium layer 1 can be single layer or multiple layers. In some embodiments, the number of layers of the lithium layer 1 is multiple layers, and the number of layers of the porous metal layer 2 is one more than the number of layers of the lithium layer 1, and one layer of the lithium layer 1 is arranged between two adjacent layers of the porous metal layer 2. For example, the number of layers of the lithium layer 1 is two layers, and the number of layers of the porous metal layer 2 is three layers. The lithium layer 1 and the porous metal layer 2 are arranged together in the order of “porous metal layer-lithium layer-porous metal layer-lithium layer-porous metal layer”. In some embodiments, the lithium metal negative electrode 10 only includes a single layer of lithium layer 1 and a porous metal layer 2 arranged on both sides of the lithium layer 1, that is, the number of layers of the lithium layer 1 is one layer, and the number of layers of the porous metal layer 2 is two layers.

[0039] The porous metal layer 2 can contain only one high electrode potential metal, i.e., the porous metal layer 2 is a metal element layer; or the porous metal layer 2 can contain multiple high electrode potential metals, i.e., the porous metal layer 2 is an alloy layer. In some embodiments, the porous metal layer 2 contains at least one of copper, aluminum, titanium, tantalum, and nickel. The standard electrode potentials of the above-mentioned metals are all greater than the standard electrode potential of lithium, and they also have good electrical conductivity, plasticity, hardness, and strength, which are conducive to ensuring that the lithium metal anode 10 has good electrical conductivity and mechanical strength, and the lithium metal anode 10 is easy to manufacture. As an example, the porous metal layer 2 is a copper layer, an aluminum layer, a titanium layer, a tantalum layer, or a nickel layer.

[0040] For ease of distinction, the porous metal layer 2 located on the first side surface of the lithium layer 1 is referred to as a first porous metal layer, and the porous metal layer 2 located on the second side surface of the lithium layer 1 is referred to as a second porous metal layer. The first porous metal layer and the second porous metal layer can be the same or different. The first porous metal layer and the second porous metal layer being the same means that the first porous metal layer and the second porous metal layer are identical. The first porous metal layer and the second porous metal layer being different means that the first porous metal layer and the second porous metal layer differ at least in one aspect, including but not limited to material, pore size, thickness, etc. As an example, the first porous metal layer and the second porous metal layer differ in material, e.g., the first porous metal layer is a porous copper layer and the second porous metal layer is a porous nickel layer. As an example, the pore sizes of the through holes in the first porous metal layer and the second porous metal layer are different, e.g., the pore size of the through hole 201 in the first porous metal layer is 100 pm and the pore size of the through hole 201 in the second porous metal layer is 200 pm. Alternatively, the first porous metal layer and the second porous metal layer are the same, which facilitates reducing the manufacturing cost of the lithium metal anode 10.

[0041] In some embodiments, the through hole 201 is a straight hole. Compared with a curved hole, a straight hole can effectively shorten the path of lithium ions in the lithium metal anode 10, and the through hole 201 serves as a growth space for lithium metal during charging. Therefore, by setting the through hole 201 as a straight hole, the risk of local blockage of the through hole 201 can be effectively reduced, thereby accommodating more lithium metal and effectively relieving the volume expansion rate of the lithium metal anode 10. In addition, compared with a curved hole, a straight hole is easier to manufacture, which facilitates reducing the manufacturing difficulty of the lithium metal anode 10 and controlling the cost.

[0042] In some embodiments, the through hole 201 is a punched hole. The punched hole refers to a hole formed by a punching process. In the preparation of the through hole 201, a punching machine can be used to punch a metal substrate of high electrode potential to obtain the through hole 201.

[0043] In some embodiments, the through holes 201 are laser etching holes. Laser etching holes, also known as laser engraved holes, are holes formed by burning away part of a material using the light energy of a laser beam. In making the through holes 201, a laser device can be used to emit a laser beam to burn through a local area of the high electrode potential metal base material.

[0044] In some embodiments, the porous metal layer 2 is a porous metal foil and the lithium layer 1 is a lithium foil, and the porous metal foil and the lithium foil are physically combined together. By using the porous metal foil and the lithium foil to be physically combined together to form the lithium metal anode 10, the manufacturing difficulty is low, which is conducive to reducing the production cost of the lithium metal anode 10.

[0045] During the charging process of the battery, the lithium metal deposited on the lithium metal anode 10 mainly comes from the reduction of lithium ions from the positive electrode. In theory, when the positive electrode is the same, the charging current is the same, and the charging time is the same, the amount of lithium metal deposited on the lithium metal anode 10 should be the same. The porous metal layer 2 has through holes 201, and the lithium metal grows in the through holes 201. The total volume V1 of the through holes on the porous metal layer 2 represents the accommodation capacity of the lithium metal of the porous metal layer 2. The larger V1 is, the larger the amount of lithium metal that the porous metal layer 2 can accommodate is, and the smaller the volume expansion of the lithium metal anode 10 is, and vice versa. The total volume V1 of the through holes refers to the sum of the volumes of all the through holes 201 on the porous metal layer 2.

[0046] In some embodiments, the volume ratio of the through holes 201 in the porous metal layer 2 is P. Here, the volume ratio of the through holes 201 in the porous metal layer 2 refers to the percentage of the total volume V1 of all the through holes 201 in the porous metal layer 2 to the total volume of the porous metal layer 2 without the through holes 201. Generally, the larger V1 is, the larger P is, which means that the volume expansion resistance of the lithium metal anode 10 is higher. Specifically, 1%≤P≤55%. As an example, P is 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 55%.

[0047] The pore size and the pitch of the plurality of through holes 201 distributed on the porous metal layer 2 will affect the total volume V1 of the through holes on the porous metal layer 2, and further affect the expansion size of the lithium metal anode 10. Here, the pore size refers to the diameter of the hole, and the pitch refers to the minimum distance value between the boundaries of two holes. In a unit volume, the smaller the pore size and the larger the pitch of the through holes 201 on the porous metal layer 2, the smaller the total volume V1 of the through holes, and the larger the volume expansion of the lithium metal anode 10. If the pore size of the through holes 201 on the porous metal layer 2 is larger and the pitch is smaller in a unit area, the total volume V1 of the through holes is larger, and the volume expansion of the lithium metal anode 10 is smaller. However, the larger and more the through holes 201 on the porous metal layer 2, the better the performance of the lithium metal anode 10, because the larger and more the through holes 201, the mechanical strength of the porous metal layer 2 will decrease, and the coverage of the lithium layer 1 by the porous metal layer 2 will decrease, so that not only the contact area between the porous metal layer 2 and the solid electrolyte membrane is small, but also the deformation resistance of the porous metal layer 2 decreases, and the stability of the lithium metal anode 10 decreases, which is not conducive to maintaining the stability of the electrode interface, that is, the interface stability of the lithium metal anode 10 decreases.

[0048] In some embodiments, the pitch of the through holes 201 is greater than or equal to 200 μm. During the discharge process of the battery, the lithium metal corresponding to the through holes 201 in the lithium layer 1 is easily oxidized to form lithium ions, and the lithium metal itself is relatively soft. If the pitch of the through holes 201 is too small, the remaining lithium metal will be deformed and locally collapsed due to the decrease in strength, which will affect the structural stability of the lithium metal anode 10, and further affect the stability of the electrode interface. Therefore, increasing the pitch of the through holes 201 is beneficial to improving the structural stability of the lithium metal anode 10, and further improving the interface stability of the lithium metal anode 10.

[0049] In some embodiments, the pore size of the through holes 201 is 100 μm to 1000 μm, and the pitch of the through holes 201 is 200 μm to 800 μm. Within this range, the porous metal layer 2 can have both better lithium metal accommodation capacity and mechanical strength, thereby improving the anti-expansion property and the interface stability of the lithium metal anode 10. For example, the pore size of the through holes 201 is 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm; and the pitch of the through holes 201 is 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 600 μm, 700 μm, or 800 μm. In addition, controlling the pore size and the pitch of the through holes 201 within the above range is also beneficial to reducing the difficulty of manufacturing the porous metal layer 2 and reducing the production cost of the lithium metal anode 10. It is found in actual production process that reducing the pore size and the pitch of the through holes 201 will reduce the production efficiency.

[0050] In some embodiments, the plurality of through holes 201 on the porous metal layer 2 are equidistantly distributed, and the diameters of the through holes 201 are equal, so as to improve the uniformity of the distribution of the through holes on the porous metal layer 2, improve the uniformity of the properties of the porous metal layer 2, and reduce the risk of local expansion or collapse of the lithium metal negative electrode 10.

[0051] In addition, the total volume V1 of the through holes on the porous metal layer 2 is also affected by the thickness of the porous metal layer 2. Since the through holes 201 are arranged through the thickness direction of the porous metal layer 2, the thickness of the porous metal layer 2 determines the depth of the through holes 201, and further affects the volume of the through holes 201. The greater the thickness of the porous metal layer 2, the greater the total volume V1 of the through holes, and the stronger the accommodation capacity of lithium metal. In addition, the greater the thickness of the porous metal layer 2, the stronger the mechanical strength of the porous metal layer 2, and the better the structural stability of the porous metal layer 2. However, the porous metal layer 2 usually contributes less to the capacity of the battery, and the thickness of the porous metal layer 2 is too thick, which will affect the specific capacity of the battery. In some embodiments, the thickness of the porous metal layer 2 is 2 μm to 12 μm. For example, the thickness of the porous metal layer 2 is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm or 12 μm.

[0052] The lithium metal negative electrode 10 includes the lithium layer 1. When the lithium metal negative electrode 10 is applied to a battery, the lithium layer 1 can supplement lithium for the battery system to a certain extent. However, the lithium layer 1 should not be too thin, otherwise it will affect the stability of the lithium metal negative electrode 10 during discharging. In addition, the lithium layer 1 should not be too thick, otherwise it will cause the specific capacity of the battery to decrease. In some embodiments, the thickness of the lithium layer 1 is 10 μm to 100 μm. For example, the thickness of the lithium layer 1 is 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0053] In some embodiments, the porous metal layer 2 is arranged on both sides of the lithium layer 1, that is, the porous metal layer 2 covers both sides of the lithium layer 1. That is, the area of the single side surface of the porous metal layer 2 is greater than or equal to the area of the single side surface of the lithium layer 1. By arranging the lithium layer 1 between the porous metal layers 2, the risk of local expansion of the lithium metal negative electrode 10 can be reduced. Alternatively, the area of the single side surface of the porous metal layer 2 is greater than the area of the single side surface of the lithium layer 1, that is, the porous metal layer 2 partially protrudes from the lithium layer 1, so as to facilitate the connection of the porous metal layer 2 to the tab.

[0054] In some embodiments, the porous metal layer 2 has a main portion 21 and an extension portion 22, which are integrally arranged, and can be welded together or integrally formed. The main portion 21 covers the side surface of the lithium layer 1, i.e., the main portion 21 is in a laminated relationship with the lithium layer 1, and the area of the single side surface of the main portion 21 is equal to that of the lithium layer 1. The extension portion 22 is the part of the porous metal layer 2 extending out of the lithium layer 1. That is, the projection of the main portion 21 overlaps that of the lithium layer 1, and the projection of the extension portion 22 is in a misaligned relationship with that of the lithium layer 1 along the thickness direction of the lithium metal anode 10. At least the main portion 21 is provided with a through hole 201, and the extension portion 22 can or can not be provided with a through hole 201. The extension portion 22 of the porous metal layer 2 is used for connecting the tab, for example, by welding. Optionally, the width W of the extension portion 22 extending out of the lithium layer 1 is 5-25 mm. For example, W is 5 mm, 10 mm, 15 mm, 20 mm or 25 mm. By setting the width W of the extension portion 22 extending out of the lithium layer 1 to 5-25 mm, the size of the extension portion 22 is limited, which can not only ensure that the extension portion 22 can be effectively connected with the tab, but also prevent the extension portion 22 from being too large and affecting the energy density of the battery.

[0055] In some embodiments, the extension portions 22 of the porous metal layers 2 combined on the two side surfaces of the lithium layer 1 are welded together. That is, during the preparation of the lithium metal anode 10, the extension portions 22 of the plurality of porous metal layers 2 are first connected together, and then the connected extension portions 22 are connected with the tab during the preparation of the battery, which reduces the difficulty of connecting the lithium metal anode 10 with the tab.

[0056] In a second aspect, the embodiments of the present application further provide a preparation method of a lithium metal anode, which comprises:

[0057] providing a lithium foil and a porous metal foil, the porous metal foil being a metal foil provided with a plurality of through holes, the porous metal foil containing a metal having an electrode potential higher than that of lithium, and the porous metal foil being used for connecting a tab;

[0058] arranging the lithium foil and the porous metal foil alternately and allowing the lithium foil to be located between two adjacent porous metal foils to obtain a multi-layer structure;

[0059] performing a rolling treatment on the multi-layer structure to obtain a lithium metal anode.

[0060] The preparation method of the lithium metal negative electrode is simple, easy to implement, and the obtained lithium metal negative electrode has the following advantages: the lithium foil is clamped between two porous metal foils, the porous metal foils can protect the lithium foil during discharging, and the stability of the lithium metal negative electrode is improved; meanwhile, the through holes on the porous metal foils can provide growth space for lithium metal deposition during charging, and the volume expansion rate of the lithium metal negative electrode is relieved.

[0061] Specifically, referring to FIG. 3, the preparation method of the lithium metal negative electrode comprises the following steps:

[0062] S01, providing a lithium foil and a porous metal foil, the porous metal foil is a metal foil provided with a plurality of through holes, the porous metal foil contains a metal with an electrode potential higher than that of lithium, the porous metal foil is used for connecting a tab, and the pore diameter of the through hole is greater than or equal to 100 μm.

[0063] The lithium foil refers to a metal foil containing lithium. Here, the lithium foil can contain only lithium, or can contain lithium and other metals, for example, the lithium foil is a lithium alloy foil. The thickness of the foil is usually less than 0.1 mm. Along the thickness direction of the lithium foil, the lithium foil has two opposite side surfaces. In some embodiments, the thickness of the lithium foil is 10 μm to 100 μm. Because the lithium foil is too thin, on the one hand, it will increase the difficulty of preparation of the lithium foil, and on the other hand, the mechanical strength of the lithium foil will decrease, and it is very easy to deform and break, which reduces the yield of the lithium metal negative electrode. For example, if the lithium foil is too thin, it is very easy to stick to the pressure roller of the rolling equipment during rolling. However, the lithium foil should not be too thick, because too thick lithium foil will not only aggravate the expansion of the lithium metal negative electrode, but also cause the specific capacity of the battery to decrease. As an example, the thickness of the lithium foil is 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm. Moreover, too thin lithium foil will also affect the stability of the lithium metal negative electrode during discharging.

[0064] Specifically, the porous metal foil is a metal foil provided with a plurality of through holes, that is, the porous metal foil has a plurality of through holes. That is, the porous metal foil is a metal foil with through holes. Specifically, the through hole is provided through the metal foil along the thickness direction of the metal foil, so that the through hole serves as a transmission channel, and lithium ions can move from one side of the porous metal foil to the other side of the porous metal foil through the through hole. The plurality of through holes are distributed at intervals on the porous metal foil, which can be equidistant distribution or non-equidistant distribution. In addition, the pore diameters of the through holes on the porous metal foil can be equal or not equal. Here, the through hole is at least a large hole, and the pore diameter of the through hole should not be too small. Specifically, the pore diameter of the through hole is greater than or equal to 100 μm. By increasing the pore diameter of the through hole, it is beneficial to ensure that the lithium metal negative electrode has good anti-expansion property.

[0065] In composition, the porous metal foil comprises a high electrode potential metal. The high electrode potential metal herein refers to a metal having an electrode potential higher than that of lithium metal. Optionally, the high electrode potential metal has a standard electrode potential at least 1 V greater than that of lithium metal. Optionally, the difference between the standard electrode potential of the high electrode potential metal and that of lithium metal is 1 V, 2 V, 3 V, 4 V, 5 V, or 6 V. As an example, the high electrode potential metal is one of copper, aluminum, titanium, tantalum, and nickel. The porous metal foil can comprise only one kind of high electrode potential metal, i.e., the porous metal foil is a single metal foil; or the porous metal foil can comprise multiple kinds of high electrode potential metal, i.e., the porous metal foil is an alloy foil. In some embodiments, the porous metal foil comprises at least one of copper, aluminum, titanium, tantalum, and nickel. The standard electrode potentials of the above-mentioned metals are all greater than that of lithium, and the above-mentioned metals also have good electrical conductivity, plasticity, hardness, and strength, which are conducive to ensuring the electrical conductivity and mechanical strength of the porous metal foil, while reducing the manufacturing difficulty of the porous metal foil. As an example, the porous metal foil is a copper foil, an aluminum foil, a titanium foil, a tantalum foil, or a nickel foil.

[0066] The shape of the lithium foil and the porous metal foil can be square, circular, or long strip-shaped, which is not limited herein.

[0067] The porous metal foil is used to connect the tab, thereby realizing connection with an external circuit. It can be understood that the porous metal foil serves as a current collector to converge current in the lithium metal negative electrode, which facilitates shortening the path of electron transfer in the lithium metal negative electrode and improving the rate performance of the battery.

[0068] During charging of the battery, the lithium metal deposited on the lithium metal negative electrode mainly comes from lithium ions of the positive electrode being reduced. In theory, when the positive electrode is the same, the charging current is the same, and the charging time is the same, the amount of lithium metal deposited on the lithium metal negative electrode should be the same. The porous metal foil has through holes, and lithium metal grows in the through holes. The total volume V2 of the through holes on the porous metal foil represents the accommodation capacity of the porous metal foil for lithium metal. The greater V2 is, the greater the amount of lithium metal that can be accommodated by the porous metal foil, and the smaller the volume expansion of the lithium metal negative electrode, and vice versa. The total volume V2 of the through holes refers to the sum of the volumes of all the through holes on the porous metal foil.

[0069] In some embodiments, the volume ratio of the through holes in the porous metal foil is P. The volume ratio of the through holes in the porous metal foil herein refers to the percentage of the total volume V2 of all the through holes in the porous metal foil to the total volume of the porous metal foil assuming that the porous metal foil has no through holes. Generally, the greater V2 is, the greater P is, which means that the anti-volume expansion capacity of the lithium metal negative electrode is higher. Specifically, 1%≤P≤55%. As an example, P is 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 55%.

[0070] Generally, the pore size and the pitch of the plurality of through-holes distributed on the porous metal foil affect the total volume V2 of the through-holes on the porous metal foil, and further affect the expansion size of the lithium metal negative electrode. Here, the pore size refers to the diameter of the hole, and the pitch refers to the minimum distance value between the boundaries of two holes. In a unit volume, the smaller the pore size of the through-holes on the porous metal foil, and the larger the pitch, the smaller the total volume V2 of the through-holes, and the larger the volume expansion of the lithium metal negative electrode. If the larger the pore size of the through-holes on the porous metal foil in a unit area, and the smaller the pitch, the larger the total volume V2 of the through-holes, and the smaller the volume expansion of the lithium metal negative electrode. However, the larger and more the through-holes on the porous metal foil, the better the performance of the lithium metal negative electrode, because the larger and more the through-holes on the porous metal foil, the mechanical strength of the porous metal foil will decrease, and the coverage of the lithium foil by the porous metal foil will decrease, so that not only the contact area between the porous metal foil and the solid electrolyte membrane becomes small, but also the deformation resistance of the porous metal foil decreases, and the stability of the lithium metal negative electrode decreases, which is not conducive to maintaining the stability of the electrode interface, that is, the interface stability of the lithium metal negative electrode decreases.

[0071] In some embodiments, the pitch of the through-holes is greater than or equal to 200 pm. By increasing the pitch of the through-holes, the stability of the lithium metal negative electrode is improved, and further the interface stability of the lithium metal negative electrode is improved.

[0072] In some embodiments, the pore size of the through-holes is 100 pm to 1000 pm, and the pitch of the through-holes is 200 pm to 800 pm. In this range, the porous metal foil can have both better lithium metal accommodation capacity and mechanical strength, thereby improving the anti-expansion property and the interface stability of the lithium metal negative electrode. As an example, the pore size of the through-holes is 100 pm, 200 pm, 300 pm, 400 pm, 500 pm, 600 pm, 700 pm, 800 pm, 900 pm, or 1000 pm; and the pitch of the through-holes is 200 pm, 250 pm, 300 pm, 350 pm, 400 pm, 450 pm, 500 pm, 600 pm, 700 pm, or 800 pm.

[0073] In some embodiments, the plurality of through-holes on the porous metal foil are distributed at equal intervals, and the pore size of each through-hole is equal, thereby improving the uniformity of the distribution of the holes on the porous metal foil, improving the uniformity of the properties of the porous metal foil, and reducing the risk of local expansion or collapse of the lithium metal negative electrode.

[0074] In some embodiments, the thickness of the porous metal foil is 2-12 μm. The total volume of the through holes on the porous metal foil V2 is also affected by the thickness of the porous metal foil. Since the through holes are arranged through the thickness of the porous metal foil, the thickness of the porous metal foil determines the depth of the through holes, and thus affects the volume of the through holes. The greater the thickness of the porous metal foil, the greater the total volume of the through holes V2, and the stronger the capacity of the porous metal foil to accommodate lithium metal. Meanwhile, the greater the thickness of the porous metal foil, the stronger the mechanical strength of the porous metal foil, and the better the structural stability of the porous metal foil. However, the porous metal foil usually contributes less to the capacity of the battery, and an excessively thick porous metal foil can affect the specific capacity of the battery. In addition, an excessively thin porous metal foil can increase the difficulty of manufacturing the porous metal foil. For example, the thickness of the porous metal foil is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or 12 μm.

[0075] In some embodiments, the method for preparing the porous metal foil comprises: providing a metal foil, and punching through holes on the metal foil. The metal foil refers to a foil containing a high electrode potential metal. The metal foil usually does not have holes. The metal foil is punched by a punch press to obtain the through holes, and the metal foil is formed into a porous metal foil. The through holes prepared by punching are punch holes, which are generally straight holes.

[0076] In some embodiments, the method for preparing the porous metal foil comprises: providing a metal foil, and laser etching through holes on the metal foil. The metal foil is formed into a porous metal foil by emitting laser to etch away part of the metal foil to obtain the through holes. The through holes prepared by laser etching are laser etching holes, which are also straight holes.

[0077] Specifically, referring to FIG. 3, the method for preparing the lithium metal negative electrode further comprises:

[0078] S02, the lithium foil and the porous metal foil are alternately laid together, and the lithium foil is located between two adjacent porous metal foils to obtain a multi-layer structure.

[0079] In the preparation of the multi-layer structure, the number of layers of the porous metal foil is usually greater than the number of layers of the lithium foil. The lithium foil and the porous metal foil are alternately laid, and the lithium foil is located between two porous metal foils. That is, the outer layer of the multi-layer structure is always the porous metal foil, and the lithium foil mainly serves as the core layer of the multi-layer structure.

[0080] For example, the specific preparation process of the multi-layer structure can comprise: laying a porous metal foil, then laying a lithium foil on one side surface of the porous metal foil, and then laying another porous metal foil on the other side surface of the lithium foil, thereby obtaining a sandwich multi-layer structure in the form of “porous metal foil-lithium foil-porous metal foil”.

[0081] Of course, in some embodiments, more layers of porous metal foil and lithium foil can be superimposedly laid, so that the multi-layer structure is more complex and diverse. For example, on a laid porous metal foil, two layers of lithium foil and two layers of porous metal foil are continuously alternately laid, so that a five-layer structure in the form of "porous metal foil-lithium foil-porous metal foil-lithium foil-porous metal foil" is obtained.

[0082] In some embodiments, the surface area of the porous metal foil is greater than or equal to the surface area of the lithium foil. In the process of making the multi-layer structure, the porous metal foil covers one side surface of the lithium foil completely. Alternatively, the surface area of the porous metal foil is greater than the surface area of the lithium foil, and in the process of making the multi-layer structure, the porous metal foil covers the lithium foil on one side and extends out of the lithium foil on the other side, and usually this part can be used to connect the tab. Alternatively, the width of the part of the porous metal foil extending out of the lithium foil is 5mm-25mm, for example, it can be 5mm, 10mm, 15mm, 20mm or 25mm. By limiting the width of the part of the porous metal foil extending out of the lithium foil, on the one hand, it can ensure that the porous metal foil can be effectively connected with the tab, and on the other hand, it can prevent the part of the porous metal foil extending out of the lithium foil from being too large and causing a volume burden, affecting the energy density of the battery.

[0083] Specifically, referring to FIG. 3, the preparation method of the lithium metal negative electrode further comprises:

[0084] S03, performing a rolling treatment on the multi-layer structure to obtain a lithium metal negative electrode.

[0085] The rolling treatment refers to placing the multi-layer structure in a rolling machine and rolling the multi-layer structure by using a pressure roller.

[0086] In some embodiments, the rolling pressure of the rolling treatment is 5T-20T. By controlling the pressure in the rolling treatment process within the above range, the lithium foil and the porous metal foil can be effectively combined together, and the structure of the lithium foil and the porous metal foil changes little. As an example, the rolling pressure in the rolling treatment process is 5T, 6T, 7T, 8T, 9T, 10T, 11T, 12T, 13T, 14T, 15T, 18T or 20T.

[0087] In some embodiments, the speed of the rolling treatment is 8m / min-12m / min. Here, the speed refers to the speed of the material being rolled during the rolling treatment. Alternatively, the speed is 8m / min, 9m / min, 10m / min, 11m / min or 12m / min.

[0088] In some embodiments, the preparation method of the lithium metal negative electrode provided by the embodiments of the present application is used to prepare the lithium metal negative electrode 10 provided by the first aspect of the embodiments of the present application, so that the lithium foil is formed into the lithium layer 1, the porous metal foil is formed into the porous metal layer 2, and the through hole is formed into the through hole 201.

[0089] The preparation method of the lithium metal negative electrode provided by the embodiments of the present application is simple and easy to implement, and the lithium metal negative electrode obtained by clamping the lithium foil between the two layers of porous metal foils can locally protect the lithium foil during discharge, thereby improving the stability of the lithium metal negative electrode. Meanwhile, the through hole on the porous metal foil can provide a growth space for lithium metal deposition during charging, thereby relieving the volume expansion rate of the lithium metal negative electrode.

[0090] In addition, since the lithium metal itself is soft, the embodiments of the present application protect the lithium foil by clamping the lithium foil between the two layers of porous metal foils, and the porous metal foil as the outermost layer of the multi-layer structure can effectively reduce the occurrence of the phenomenon of the lithium foil sticking to the roller during the rolling process, thereby improving the production yield of the lithium metal negative electrode.

[0091] Third aspect, please refer to FIG. 4, the embodiments of the present application also provide a solid-state battery 100, including a positive electrode 20, a negative electrode and a solid-state electrolyte film 30, the positive electrode 20 and the negative electrode are arranged on both sides of the solid-state electrolyte film 30, and the negative electrode is the lithium metal negative electrode 10 provided by the first aspect or the lithium metal negative electrode prepared by the preparation method provided by the second aspect.

[0092] The lithium metal negative electrode used by the solid-state battery 100 provided by the embodiments of the present application has better anti-expansion property, so that the cycle stability of the solid-state battery 100 is improved.

[0093] In some embodiments, the positive electrode 20 includes a positive electrode current collector 20a and a positive electrode active material layer 20b, and the positive electrode active material layer 20b is arranged on the positive electrode current collector 20a. Optionally, the positive electrode active material layer 20b contains a positive electrode active material, a solid-state electrolyte, a conductive agent and a binder. Exemplarily, the positive electrode active material includes but is not limited to at least one of lithium cobaltate (LiCoO2), lithium manganate (LiMn2O4), lithium iron phosphate (LiFePO4), lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA); the solid-state electrolyte includes but is not limited to at least one of a polymer electrolyte, an oxide electrolyte, a sulfide electrolyte and a halide electrolyte; the conductive agent includes but is not limited to at least one of carbon black, graphene and carbon nanotube; and the binder includes but is not limited to polyvinylidene fluoride (PVDF).

[0094] In some embodiments, the solid-state electrolyte film 30 contains at least one of a polymer electrolyte, an oxide electrolyte, a sulfide electrolyte and a halide electrolyte.

[0095] In some embodiments, the solid-state battery 100 further comprises a housing 40, and the positive electrode 20, the negative electrode and the solid-state electrolyte film 30 are located in the housing 40. Optionally, the housing 40 is a soft housing, and the obtained solid-state battery 100 is a soft package battery. Exemplarily, the housing 40 is an aluminum plastic film.

[0096] The specific embodiments are described in detail below.

[0097] Example 1

[0098] A lithium strip with a thickness of 34 μm and a porous copper foil with a thickness of 6 μm (pore diameter 100 μm, pore distance 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34 μm lithium strip at a composite speed of 10 m / min, and no strip breaking phenomenon occurred, obtaining a lithium metal negative electrode with a sandwich structure of porous copper foil-lithium strip-porous copper foil. The pores on the porous copper foil are distributed at equal size and equal interval, and the volume ratio of the through holes in the porous metal foil is P, and P is 5%.

[0099] Example 2

[0100] A lithium strip with a thickness of 34 μm and a porous copper foil with a thickness of 6 μm (pore diameter 200 μm, pore distance 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34 μm lithium strip at a composite speed of 10 m / min, and no strip breaking phenomenon occurred, obtaining a lithium metal negative electrode with a sandwich structure of porous copper foil-lithium strip-porous copper foil. The pores on the porous copper foil are distributed at equal size and equal interval, and P is 13%.

[0101] Example 3

[0102] A lithium strip with a thickness of 34 μm and a porous copper foil with a thickness of 6 μm (pore diameter 480 μm, pore distance 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34 μm lithium strip at a composite speed of 10 m / min, and no strip breaking phenomenon occurred, obtaining a lithium metal negative electrode with a sandwich structure of porous copper foil-lithium strip-porous copper foil. The pores on the porous copper foil are distributed at equal size and equal interval, and P is 30%.

[0103] Example 4

[0104] A lithium strip with a thickness of 34 μm and a porous copper foil with a thickness of 6 μm (pore diameter 500 μm, pore distance 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34 μm lithium strip at a composite speed of 10 m / min, and no strip breaking phenomenon occurred, obtaining a lithium metal negative electrode with a sandwich structure of porous copper foil-lithium strip-porous copper foil. The pores on the porous copper foil are distributed at equal size and equal interval, and P is 31%.

[0105] Example 5

[0106] A 34-μm-thick lithium ribbon and a 10-μm-thick porous copper foil (pore diameter 100 μm, pore distance 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34-μm-thick lithium ribbon at a composite speed of 10 m / min, without occurrence of ribbon breakage, to obtain a lithium metal negative electrode with a sandwich structure of porous copper foil-lithium ribbon-porous copper foil. The pores on the porous copper foil were distributed at equal size and equal interval, and P was 5%.

[0107] Example 6

[0108] A 34-μm-thick lithium ribbon and a 10-μm-thick porous copper foil (pore diameter 200 μm, pore distance 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34-μm-thick lithium ribbon at a composite speed of 10 m / min, without occurrence of ribbon breakage, to obtain a lithium metal negative electrode with a sandwich structure of porous copper foil-lithium ribbon-porous copper foil. The pores on the porous copper foil were distributed at equal size and equal interval, and P was 13%.

[0109] Example 7

[0110] A 34-μm-thick lithium ribbon and a 10-μm-thick porous copper foil (pore diameter 480 μm, pore distance 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34-μm-thick lithium ribbon at a composite speed of 10 m / min, without occurrence of ribbon breakage, to obtain a lithium metal negative electrode with a sandwich structure of porous copper foil-lithium ribbon-porous copper foil. The pores on the porous copper foil were distributed at equal size and equal interval, and P was 30%.

[0111] Example 8

[0112] A 34-μm-thick lithium ribbon and a 10-μm-thick porous copper foil (pore diameter 500 μm, pore distance 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34-μm-thick lithium ribbon at a composite speed of 10 m / min, without occurrence of ribbon breakage, to obtain a lithium metal negative electrode with a sandwich structure of porous copper foil-lithium ribbon-porous copper foil. The pores on the porous copper foil were distributed at equal size and equal interval, and P was 31%.

[0113] Example 9

[0114] A 20-μm-thick lithium ribbon and a 6-μm-thick porous copper foil (pore diameter 100 μm, pore distance 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 20-μm-thick lithium ribbon at a composite speed of 10 m / min, without occurrence of ribbon breakage, to obtain a lithium metal negative electrode with a sandwich structure of porous copper foil-lithium ribbon-porous copper foil. The pores on the porous copper foil were distributed at equal size and equal interval, and P was 5%.

[0115] Example 10

[0116] A 20 μm thick lithium ribbon was selected, and a 6 μm thick porous copper foil (pore diameter 200 μm, pore distance 300 μm) was roll-composited on both sides of the 20 μm lithium ribbon at a composite speed of 10 m / min, without occurrence of belt breakage, to obtain a lithium metal negative electrode of a porous copper foil-lithium ribbon-porous copper foil sandwich structure. The pores on the porous copper foil were of equal size and equal pitch, and P was 13%.

[0117] Example 11

[0118] A 20 μm thick lithium ribbon was selected, and a 6 μm thick porous copper foil (pore diameter 480 μm, pore distance 300 μm) was roll-composited on both sides of the 20 μm lithium ribbon at a composite speed of 10 m / min, without occurrence of belt breakage, to obtain a lithium metal negative electrode of a porous copper foil-lithium ribbon-porous copper foil sandwich structure. The pores on the porous copper foil were of equal size and equal pitch, and P was 30%.

[0119] Example 12

[0120] A 20 μm thick lithium ribbon was selected, and a 6 μm thick porous copper foil (pore diameter 500 μm, pore distance 300 μm) was roll-composited on both sides of the 20 μm lithium ribbon at a composite speed of 10 m / min, without occurrence of belt breakage, to obtain a lithium metal negative electrode of a porous copper foil-lithium ribbon-porous copper foil sandwich structure. The pores on the porous copper foil were of equal size and equal pitch, and P was 31%.

[0121] Example 13

[0122] A 50 μm thick lithium ribbon was selected, and a 6 μm thick porous copper foil (pore diameter 100 μm, pore distance 300 μm) was roll-composited on both sides of the 50 μm lithium ribbon at a composite speed of 10 m / min, without occurrence of belt breakage, to obtain a lithium metal negative electrode of a porous copper foil-lithium ribbon-porous copper foil sandwich structure. The pores on the porous copper foil were of equal size and equal pitch, and P was 5%.

[0123] Example 14

[0124] A 50 μm thick lithium ribbon was selected, and a 6 μm thick porous copper foil (pore diameter 200 μm, pore distance 300 μm) was roll-composited on both sides of the 50 μm lithium ribbon at a composite speed of 10 m / min, without occurrence of belt breakage, to obtain a lithium metal negative electrode of a porous copper foil-lithium ribbon-porous copper foil sandwich structure. The pores on the porous copper foil were of equal size and equal pitch, and P was 13%.

[0125] Example 15

[0126] A 50-μm-thick lithium ribbon and a 6-μm-thick porous copper foil (pore diameter 480 μm, pore pitch 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 50-μm-thick lithium ribbon at a composite speed of 10 m / min, without occurrence of belt breakage, to obtain a lithium metal negative electrode of a porous copper foil-lithium ribbon-porous copper foil sandwich structure. The pores on the porous copper foil were of equal size and equal pitch, and P was 30%.

[0127] Example 16

[0128] A 50-μm-thick lithium ribbon and a 6-μm-thick porous copper foil (pore diameter 500 μm, pore pitch 300 μm) were selected, and the porous copper foil was roll-composited on both sides of the 50-μm-thick lithium ribbon at a composite speed of 10 m / min, without occurrence of belt breakage, to obtain a lithium metal negative electrode of a porous copper foil-lithium ribbon-porous copper foil sandwich structure. The pores on the porous copper foil were of equal size and equal pitch, and P was 31%.

[0129] Example 17

[0130] A 34-μm-thick lithium ribbon and a 6-μm-thick porous copper foil (pore diameter 480 μm, pore pitch 200 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34-μm-thick lithium ribbon at a composite speed of 10 m / min, without occurrence of belt breakage, to obtain a lithium metal negative electrode of a porous copper foil-lithium ribbon-porous copper foil sandwich structure. The pores on the porous copper foil were of equal size and equal pitch, and P was 39%.

[0131] Example 18

[0132] A 34-μm-thick lithium ribbon and a 6-μm-thick porous copper foil (pore diameter 480 μm, pore pitch 600 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34-μm-thick lithium ribbon at a composite speed of 10 m / min, without occurrence of belt breakage, to obtain a lithium metal negative electrode of a porous copper foil-lithium ribbon-porous copper foil sandwich structure. The pores on the porous copper foil were of equal size and equal pitch, and P was 16%.

[0133] Example 19

[0134] A 34-μm-thick lithium ribbon and a 6-μm-thick porous copper foil (pore diameter 480 μm, pore pitch 800 μm) were selected, and the porous copper foil was roll-composited on both sides of the 34-μm-thick lithium ribbon at a composite speed of 10 m / min, without occurrence of belt breakage, to obtain a lithium metal negative electrode of a porous copper foil-lithium ribbon-porous copper foil sandwich structure. The pores on the porous copper foil were of equal size and equal pitch, and P was 11%.

[0135] Comparative Example 1

[0136] Select 20 pm thickness lithium strip, 6 pm thickness copper foil (non-porous), roll composite 20 pm lithium strip on both sides of 6 pm copper foil, composite speed 5 m / min, 5 times of belt breaking phenomenon, get lithium strip-copper foil-lithium strip sandwich structure of lithium metal negative electrode.

[0137] Comparative Example 2

[0138] Select 34 pm thickness lithium strip, 6 pm thickness copper foil (non-porous), roll composite 34 pm lithium strip on both sides of 6 pm copper foil, composite speed 5 m / min, 5 times of belt breaking phenomenon, get lithium strip-copper foil-lithium strip sandwich structure of lithium metal negative electrode.

[0139] Table 1 is the parameter characteristics of lithium strip and metal foil in each of the above examples and comparative examples.

[0140] Table 1

[0141] The lithium metal negative electrode samples provided by the above examples and comparative examples are tested as follows:

[0142] 1. Calculate the yield rate: the yield rate is the actual output qualified meters / theoretical output meters, and the results are recorded in Table 2.

[0143] 2. Calculate the battery full charge negative electrode expansion rate:

[0144] 2.1, prepare a solid-state battery according to the following steps

[0145] (1) Prepare the positive electrode sheet:

[0146] The positive electrode active material lithium nickel manganese cobalt oxide, the conductive agent carbon black and carbon nanotube, and the binder polyvinylidene fluoride are mixed according to the weight ratio of 95:2:3, N-methyl pyrrolidone is added as a solvent, and a slurry with a solid content of 70% is prepared and stirred uniformly; the slurry is uniformly coated on the positive electrode current collector aluminum foil, and dried to obtain the positive electrode sheet.

[0147] (2) Prepare the negative electrode sheet:

[0148] The negative electrode sheet is the lithium metal negative electrode provided by the above examples and comparative examples.

[0149] (3) Prepare the solid-state electrolyte film:

[0150] The amount of drug was calculated according to the stoichiometric ratio. LiOH H2O, La2O3, ZrO2, Ga2O3, Al2O3 were configured in the ratio of 6.1:3:2:0.15, and then loaded into a polyethylene ball mill tank filled with zirconia balls. Isopropyl alcohol was added to about 2 / 3 of the inner wall of the ball mill tank. After uniform ball milling for 12 hours, the slurry was poured into a glass container and placed in an oven at 70°C for about 8 hours. After drying the sample, it was ground into powder in a mortar, then transferred to an alumina crucible and placed in a muffle furnace for pre-sintering. The pre-sintering method was to increase the temperature to 900°C at a rate of 2°C / min, and then keep the temperature at 900°C for 8 hours. Then, the temperature was decreased to 500°C at a rate of 2°C / min, and finally the sample was cooled to room temperature with the furnace, thereby removing the impurity water and obtaining a precursor with a certain crystal structure. After sintering, the crucible was cooled to room temperature, the powder was transferred to a ball mill tank, and isopropyl alcohol was added for secondary ball milling. The ball milling time was 10 hours. After ball milling, the slurry was poured into a glass container and placed in an oven at 70°C until dry. Since the LLZO powder is fluffy, it does not need to be granulated, so the dried sample is only ground into a uniform fine powder in a mortar for tabletting. About 0.3g of the mother powder particles was weighed on a balance and placed in a tabletting die. A tablet press was used to press the particles into a circular tablet blank with a diameter of 10mm and a thickness of about 1.0mm at a pressure of 10MPa. The sample disc was placed in a muffle furnace for sintering, with the upper and lower surfaces covered with mother powder. The temperature was increased at a rate of 2°C / min to 1100°C and sintered for 12 hours.

[0151] (4) Battery assembly

[0152] The positive electrode sheet, solid-state electrolyte film, and negative electrode sheet were prepared into a 3Ah soft package battery cell through the processes of lamination, compounding, packaging, formation, and capacity test.

[0153] 2.2, Test process

[0154] The prepared 3Ah battery cell was fully charged with a constant current of 300mA and a cutoff voltage of 4.25V. Subsequently, the fully charged battery cell was disassembled in an inert gas and low humidity environment. The thickness of the negative electrode sheet in the fully charged state was tested using a micrometer. The upper, middle, and lower points of the negative electrode sheet were tested, and the average value was taken as the thickness of the negative electrode sheet. The thickness increment of the negative electrode sheet after full charging was calculated by subtracting the production thickness of the lithium metal negative electrode from the tested thickness of the negative electrode sheet. The thickness increment of the negative electrode sheet after full charging was compared with the production thickness of the lithium metal negative electrode. The full charging expansion rate = thickness increment of the negative electrode sheet after full charging / production thickness. The results are shown in Table 2.

[0155] Table 2

[0156] Analysis in combination with Table 1 and Table 2 shows that:

[0157] Comparing Examples 1 to 18 with Comparative Examples 1 to 2, it is found that the lithium metal negative electrode with the porous copper foil-lithium ribbon-porous copper foil sandwich structure is superior to the lithium metal negative electrode with the lithium ribbon-copper foil-lithium ribbon sandwich structure in terms of yield and battery full-charged negative electrode expansion rate, because in the lithium metal negative electrode with the porous copper foil-lithium ribbon-porous copper foil sandwich structure, the porous copper foil protects the lithium ribbon, reducing the occurrence of lithium ribbon breakage caused by sticking to the roller, thereby significantly improving the product yield; in addition, the porous copper foil clamps the lithium ribbon, the porous copper foil can protect the lithium ribbon, and the porous copper foil has a large number of through holes, which can provide growth space for the lithium metal deposited on the lithium metal negative electrode during battery charging, thereby relieving the expansion of the lithium metal negative electrode.

[0158] Comparing Examples 1 to 4, Examples 5 to 8, Examples 9 to 12, and Examples 13 to 16 as four groups respectively, it can be seen from the comparison of the examples within each group that: under the condition that the thickness of the porous copper foil is the same and the pitch is the same, as the pore diameter of the porous copper foil increases, P increases, and the expansion rate of the lithium metal negative electrode decreases. This is because after the pore diameter increases, the volume of the hole increases, and then the accommodation capacity of the porous copper foil for the deposited lithium metal is enhanced, thereby improving the anti-expansion property of the lithium metal negative electrode.

[0159] Comparing Example 1 with Example 5, Example 2 with Example 6, Example 3 with Example 7, and Example 4 with Example 8, it can be seen that: under the condition that P, the pitch, and the pore diameter of the porous copper foil are the same, as the thickness of the porous copper foil increases, the expansion rate of the lithium metal negative electrode decreases. This is because after the thickness of the porous copper foil increases, the volume of the hole increases, and then the accommodation capacity of the porous copper foil for the deposited lithium metal is enhanced, and the mechanical strength of the porous copper foil is also improved, i.e., the mechanical strength of the lithium metal negative electrode is improved, and the anti-expansion property of the lithium metal negative electrode is improved by the dual effects.

[0160] Comparing Example 13 with Example 1 and Example 9, Example 14 with Example 2 and Example 10, Example 15 with Example 3 and Example 11, and Example 16 with Example 4 and Example 12, it can be seen that: under the condition that the porous copper foil is the same, as the thickness of the lithium ribbon decreases, the expansion rate increases instead. This is because the porous copper foil is the same, and under the same positive electrode and the same charging condition, the thickness increment of the negative electrode sheet after full charging is the same, but as the thickness of the lithium ribbon decreases, the production thickness of the lithium metal negative electrode decreases, thereby causing the expansion rate to appear to increase instead.

[0161] It can be seen from the comparison of Example 17, Example 3, Example 18 and Example 19 that, under the condition that the lithium ribbon is the same, the thickness of the porous copper foil is the same, and the pore diameter on the porous copper foil is the same, as the pore distance on the porous copper foil increases, the P decreases, and the expansion rate of the lithium metal negative electrode increases, because after the pore distance increases, the number of pores on the porous copper foil decreases, so that the accommodation capacity of the porous copper foil for the deposited metal lithium decreases, and the expansion rate of the lithium metal negative electrode increases.

[0162] The above has carried out the detailed introduction to the embodiment of the application, the principle and implementation mode of the application are described in this paper by applying specific examples, the above embodiment is only used to help understanding the method of the application and its core idea; at the same time, for those skilled in the art, according to the idea of the application, the specific implementation mode and application range will be changed, and the above is not understood as the limitation of the application.

Claims

1. A lithium metal anode, comprising: A lithium layer and a porous metal layer combined with side surfaces of the lithium layer, the porous metal layer being a metal layer provided with a plurality of through holes, the porous metal layer comprising a metal having an electrode potential higher than that of lithium, the porous metal layer being used for connecting a tab, and the through holes having a pore diameter greater than or equal to 100 μm.

2. The lithium metal anode of claim 1, wherein, The through holes are straight holes; and / or, the through holes are punched holes or laser etched holes.

3. The lithium metal anode of claim 1, wherein, The through holes are equally spaced on the porous metal layer.

4. The lithium metal anode of claim 1, wherein, The through holes have a pore diameter of 100 μm to 1000 μm.

5. The lithium metal anode of claim 1, wherein, The through holes have a pitch greater than or equal to 200 μm.

6. The lithium metal anode of claim 5, wherein, The through holes have a pitch of 200 μm to 800 μm.

7. The lithium metal anode of claim 1, wherein, The volume fraction of the through holes in the porous metal layer is P, and 1%≤P≤55%.

8. The lithium metal anode of claim 1, wherein, The thickness of the porous metal layer is 2 μm to 12 μm; and / or, the thickness of the lithium layer is 10 μm to 100 μm.

9. The lithium metal anode of claim 1, wherein, The porous metal layer comprises at least one of copper, aluminum, titanium, tantalum and nickel.

10. The lithium metal anode of any one of claims 1-5, wherein, The porous metal layer has a main part and an extension part, the main part covering the side surface of the lithium layer, and the through holes being provided on at least the main part, and the extension part extending out of the lithium layer and being used for connecting a tab.

11. The lithium metal anode of claim 10, wherein, The width of the extension part extending out of the lithium layer is 5 mm to 25 mm.

12. A preparation method of a lithium metal negative electrode, comprising: providing a lithium foil and a porous metal foil, the porous metal foil being a metal foil provided with a plurality of through holes, the metal foil comprising a metal having an electrode potential higher than that of lithium, the porous metal foil being used for connecting a tab, and the through holes having a pore diameter greater than or equal to 100 μm; alternately laying the lithium foil and the porous metal foil together and making the lithium foil located between two adjacent porous metal foils to obtain a multi-layer structure; performing a rolling treatment on the multi-layer structure to obtain a lithium metal negative electrode.

13. The method of producing a lithium metal anode according to claim 12, wherein, The preparation method of the porous metal foil comprises: providing a metal foil, and preparing through holes on the metal foil by punching or laser etching to obtain a porous metal foil.

14. The method of producing a lithium metal anode according to claim 12, wherein, The rolling pressure of the rolling treatment is 5T to 20T, and / or the speed of the rolling treatment is 8 m / min to 12 m / min.

15. The method of producing a lithium metal anode according to claim 12, wherein, The through holes have a pore diameter of 100 μm to 1000 μm.

16. The method of producing a lithium metal anode according to claim 12, wherein, The through holes have a pitch greater than or equal to 200 μm.

17. The method of producing a lithium metal anode according to claim 16, wherein, The through holes have a pitch of 200 μm to 800 μm.

18. The method of producing a lithium metal anode according to claim 12, wherein, The volume fraction of the through holes in the porous metal foil is P, and 1%≤P≤55%.

19. The method of producing a lithium metal anode according to claim 12, wherein, The thickness of the porous metal foil is 2 μm to 12 μm; and / or, the thickness of the lithium foil is 10 μm to 100 μm.

20. A solid-state battery comprising a positive electrode, a negative electrode and a solid-state electrolyte film, the positive electrode and the negative electrode being arranged on two sides of the solid-state electrolyte film, the negative electrode being a lithium metal negative electrode according to any one of claims 1 to 11 or prepared by the preparation method according to any one of claims 12 to 19.

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