A negative electrode current collector and negative electrode sheet capable of safe lithium replenishment and a lithium replenishment battery

Abstract

This invention discloses a negative electrode current collector, comprising a basic foil material; multiple vertically penetrating through-holes are uniformly distributed at equal intervals on the basic foil material; each through-hole contains a lithium replenishment filler; the lithium replenishment filler includes lithium metal powder; the lithium replenishment filler is a multi-layered lithium replenishment filler; the multi-layered lithium replenishment filler includes at least one layer of lithium metal powder. This invention also discloses a negative electrode sheet and a lithium replenishment-type battery. This invention is scientifically designed, effectively improving the energy density of the battery cell, ensuring the safety of the lithium replenishment process, and allowing for controlled and gradual lithium replenishment, thus possessing significant practical value.

Description

Technical Field

[0001] This invention relates to the field of current collectors and lithium replenishment technology in batteries, and in particular to a negative electrode current collector and negative electrode sheet capable of safe lithium replenishment and a lithium replenishment type battery. Background Technology

[0002] Lithium supplementation is an ideal and practical technology for improving energy density and cycle life, and it is currently being widely researched and applied by various manufacturers in the industry.

[0003] While lithium replenishment technology plays a significant role, it also faces enormous risks and technological challenges, as follows:

[0004] 1. How to minimize the probability of safety issues arising from lithium replenishment of the negative electrode; it should be noted that, since lithium metal is an active metal, the negative electrode is more prone to chemical reactions due to changes in moisture in the environment after lithium replenishment, which may lead to fire.

[0005] 2. The rapid reaction caused by lithium replenishment can lead to structural defects inside the battery cell;

[0006] 3. Traditional lithium battery replenishment will waste the internal space of the battery cell, such as reducing the casing ratio and failing to significantly improve the energy density. Summary of the Invention

[0007] The purpose of this invention is to address the technical deficiencies of existing technologies by providing a negative electrode current collector, a negative electrode sheet, and a lithium-replenishing battery that can safely replenish lithium.

[0008] Therefore, the present invention provides a negative electrode current collector, which includes a negative electrode current collector basic foil material;

[0009] On the negative electrode current collector basic foil, there are multiple vertical through holes evenly distributed at equal intervals;

[0010] Each through-hole is filled with lithium-filling material;

[0011] The lithium replenishing filler includes metallic lithium powder;

[0012] The lithium replenishing filler is a multi-layered lithium replenishing filler;

[0013] The multilayer lithium filler includes at least one layer of metallic lithium powder.

[0014] Preferably, the multilayer lithium replenishing filler is a three-layer lithium replenishing filler;

[0015] The three-layer lithium filler includes a first filler material layer, a lithium metal powder layer and a second filler material layer arranged from top to bottom.

[0016] The lithium metal powder layer is located between the first filler layer and the second filler layer, and the upper and lower sides of the lithium metal powder layer are in contact with the bottom surface of the first filler layer and the top surface of the second filler layer, respectively.

[0017] Preferably, the upper and lower sides of the lithium metal powder layer are pressed into contact with the bottom surface of the first filler layer and the top surface of the second filler layer, respectively.

[0018] Preferably, the filling materials in the first filling material layer and the second filling material layer are exactly the same.

[0019] Preferably, the volume of the lithium metal powder layer in each through-hole accounts for 70% to 90% of the volume of the through-hole cavity;

[0020] The sum of the volumes of the first and second filling material layers within each through-hole accounts for 10% to 30% of the volume of the through-hole cavity.

[0021] Preferably, the three layers—the first filler layer, the lithium metal powder layer, and the second filler layer—are physically stacked and there is no binder between them.

[0022] In addition, the present invention also provides a negative electrode sheet, including the negative electrode current collector as described above;

[0023] The negative electrode current collector has a layer of negative electrode active material covering the upper and lower surfaces of the basic foil material.

[0024] Preferably, the negative electrode active material layer includes the negative electrode main material, binder, conductive agent and dispersant;

[0025] The negative electrode active material layer includes 93% to 98% negative electrode main material by mass, 0.5% to 3% binder by mass, 0.2% to 2% conductive agent by mass, and 0.4% to 2.5% dispersant by mass.

[0026] Among them, the main material of the negative electrode is lithium storage active material;

[0027] Lithium storage active materials specifically include at least one of natural graphite, artificial graphite, soft carbon, hard carbon, and silicon;

[0028] The adhesive specifically includes at least one of styrene-butadiene rubber, polyacrylate, polyacrylonitrile, and polyvinylidene fluoride;

[0029] Conductive agents, including at least one of carbon nanotubes, spherical carbon black and graphene;

[0030] The dispersant is a cellulose derivative.

[0031] In addition, the present invention also provides a lithium-filled battery, including the negative electrode as described above.

[0032] As can be seen from the technical solutions provided by the present invention above, compared with the prior art, the present invention provides a negative electrode current collector and negative electrode sheet capable of safe lithium replenishment and a lithium replenishment battery. Its design is scientific, which can effectively improve the energy density of the battery cell, ensure the safety of the lithium replenishment process, and can slow down and control the lithium replenishment process, which has significant practical significance.

[0033] Compared with the prior art, the technical solution of the present invention is safer in two ways. The lithium replenishing agent is filled in the current collector, which avoids the side reactions and risks caused by direct contact with air in subsequent production. In addition, the porous current collector and the hidden lithium replenishment can improve the energy density of the battery cell to a certain extent. It can also achieve the effect of slow release and controllable lithium replenishment by controlling external conditions, and can also replenish film-forming additives. Attached Figure Description

[0034] Figure 1 A schematic diagram of the structure of a negative electrode current collector provided by the present invention;

[0035] Figure 2 This is a schematic diagram of the structure of a negative electrode sheet provided by the present invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] See Figure 1 The present invention provides a negative electrode current collector, comprising a negative electrode current collector basic foil 2;

[0038] On the negative electrode current collector basic foil 2, there are multiple vertical through holes 3 evenly distributed at equal intervals;

[0039] Each through hole 3 is filled with lithium replenishing material;

[0040] The lithium replenishing filler includes lithium metal powder.

[0041] In this invention, specifically, the lithium replenishing filler is a multi-layered lithium replenishing filler;

[0042] The multilayer lithium filler includes at least one layer of metallic lithium powder.

[0043] In specific implementation, the lithium replenishment filler with a multi-layer structure is preferably a three-layer structure.

[0044] The three-layer lithium filler includes a first filler layer 5, a lithium metal powder layer 4, and a second filler layer 6 arranged from top to bottom.

[0045] The lithium metal powder layer 4 is located between the first filler layer 5 and the second filler layer 6, and the upper and lower sides of the lithium metal powder layer 4 are in contact with the bottom surface of the first filler layer 5 and the top surface of the second filler layer 6, respectively.

[0046] In practice, the upper and lower sides of the lithium metal powder layer 4 are pressed and contacted with the bottom surface of the first filling material layer 5 and the top surface of the second filling material layer 6, respectively.

[0047] In specific implementation, the substances filled in the first filling material layer 5 and the second filling material layer 6 are solid electrolyte additives (specifically, solid additives from the electrolyte of the lithium-ion battery to be assembled with the negative electrode sheet, which can dissolve in the electrolyte). These substances are solid target substances that can slowly dissolve in the electrolyte. Target substances are, for example, additives in the electrolyte, such as lithium hexafluorophosphate, carbonate additives, etc.

[0048] It should be noted that the filling materials in the first filling material layer 5 and the second filling material layer 6 are exactly the same.

[0049] In specific implementation, the additive includes at least one of vinylene carbonate, vinyl sulfate, and N,N-dimethylacrylamide (DMAA). It should be noted that such substances are solid in the absence of electrolyte. When electrolyte is subsequently added to the battery, the electrolyte can slowly dissolve the solid, making it part of the liquid electrolyte, and at the same time, it will release the added metallic lithium.

[0050] It should be noted that the first filling material layer 5, the lithium metal powder layer 4, and the second filling material layer 6 together form a three-layer structure. The first filling material layer 5 and the second filling material layer 6 are located on the outermost surface of the through hole 3, occupying the outer two layers of the structure, while the lithium metal powder layer 4 is the inner central layer material.

[0051] In specific implementation, the volume of the lithium metal powder layer 4 in each through hole 3 accounts for 70% to 90% of the volume of the cavity inside the through hole 3;

[0052] The sum of the volumes of the first filling material layer 5 and the second filling material layer 6 within each through hole 3 accounts for 10% to 30% of the volume of the cavity within the through hole 3.

[0053] In terms of specific implementation, it should be noted that the three layers of material, namely the first filling material layer 5, the lithium metal powder layer 4, and the second filling material layer 6, are physically stacked and there is no adhesive between them.

[0054] In this invention, specifically, the basic foil material 2 of the negative electrode current collector is a copper foil or a composite copper foil; both copper foil and composite copper foil are conventional copper foils, and will not be described in detail here.

[0055] In specific implementation, when the basic foil material 2 of the negative electrode current collector is copper foil, the thickness of the copper foil is 2 to 30 μm, and the diameter of the through hole on the copper foil is 3 to 100 μm;

[0056] It should be noted that when the negative electrode current collector base foil 2 is copper foil, the copper foil has a through-hole porous structure, and the pores are filled with two substances, which together form a three-layer structure.

[0057] It should be noted that the multiple through holes 3 are arranged in an array and are evenly distributed on the copper foil.

[0058] Based on the negative electrode current collector provided by the present invention, see [link to related information]. Figure 2 The present invention also discloses a negative electrode sheet, including the negative electrode current collector described above;

[0059] The negative electrode current collector has a negative electrode active material layer 1 covering the upper and lower surfaces of the negative electrode current collector basic foil 2.

[0060] It should be noted that the negative electrode active material layer 1 adheres to the surface of the negative electrode current collector basic foil 2 by means of the binder inside it.

[0061] The negative electrode active material layer 1 includes the negative electrode main material, binder, conductive agent and dispersant;

[0062] The negative electrode active material layer includes 93% to 98% negative electrode main material by mass, 0.5% to 3% binder by mass, 0.2% to 2% conductive agent by mass, and 0.4% to 2.5% dispersant by mass.

[0063] Among them, the main material of the negative electrode is lithium storage active material;

[0064] Lithium storage active materials specifically include at least one (i.e., one or more) of natural graphite, artificial graphite, soft carbon, hard carbon and silicon;

[0065] The adhesive can be a styrene-butadiene rubber-based adhesive, a polyvinylidene fluoride-based adhesive, etc., specifically including at least one (i.e., one or more) of styrene-butadiene rubber, polyacrylate, polyacrylonitrile and polyvinylidene fluoride.

[0066] Conductive agents include at least one (i.e., one or more) of carbon nanotubes, spherical carbon black and graphene, and may also be any substance that can conduct electricity.

[0067] Dispersants can be cellulose derivatives (cellulose-based substances), such as carboxymethylated derivatives, like sodium carboxycellulose. Common dispersants include sodium cellulose and similar substances.

[0068] It should be noted that, in summary, the present invention provides a negative electrode current collector and a negative electrode sheet, wherein the negative electrode current collector has a through-hole porous structure, and there is a three-layer lithium replenishment filler in the through-hole. The surface layer of the negative electrode current collector is covered with a main material layer (i.e., the negative electrode active material layer). The main material layer is mainly used to provide a lithium ion receiving site for charging and discharging. The negative electrode current collector and the main material layer together constitute the negative electrode sheet.

[0069] Based on the negative electrode sheet provided by the present invention, the present invention also provides a lithium-filled battery, including the aforementioned negative electrode sheet.

[0070] Based on the above technical solutions, compared with the prior art, the technical solutions of the present invention have the following beneficial technical effects:

[0071] 1. This invention designs a concealed lithium replenishment structure, hiding metallic lithium within the foil material, thus avoiding the safety risks associated with lithium powder contacting the controlled environment. It should be noted that, because lithium metal is highly reactive, the negative electrode is relatively prone to chemical reactions due to changes in moisture in the environment after lithium replenishment, potentially leading to a fire.

[0072] 2. The through-hole filler on the negative electrode current collector of the present invention can replenish the film-forming agent in the electrolyte. Furthermore, by controlling the temperature (the solid can melt when the temperature rises - recognized by industry professionals), the dissolution rate of solid additives (such as vinylene carbonate VC) in the electrolyte can be controlled, which can control the release rate of lithium metal powder to a certain extent, thus playing a role in slow and controllable lithium replenishment.

[0073] 3. The through-type current collector designed in this invention can reduce the weight of the battery cell. At the same time, by accommodating metallic lithium powder in the copper foil that serves as the current collector, the volume occupied by the copper foil can be reduced. Both of these factors work together to improve the energy density of the battery cell.

[0074] It should be noted that the lithium metal powder occupies a volume of copper foil inside the copper foil, which is equivalent to reducing the amount of copper foil used, thus increasing the energy density.

[0075] 4. The through-hole design also enables uniform distribution of electrolyte and lithium intercalation between the two active material layers of the electrode.

[0076] It should be noted that, because the battery electrode is a current collector coated with active material on both sides, the lithium distribution on both sides of the current collector may be uneven without through holes (affected by structural differences, etc.). With the design scheme of this invention, when through holes are provided, the lithium in the active material on both sides may diffuse freely, resulting in a uniform distribution of lithium on both sides. Similarly, with through holes, the electrolyte on both sides of the current collector can diffuse, enhancing the uniformity of electrolyte distribution.

[0077] To better understand the technical solution of the present invention, the following specific embodiments will be used to illustrate the technical solution of the present invention.

[0078] Example 1.

[0079] In Example 1, the present invention provides a negative electrode current collector, comprising a basic foil material for the negative electrode current collector;

[0080] The base foil for the negative electrode current collector is copper foil or composite copper foil. The copper foil is 6µm thick, and the diameter of the through holes on the base foil is 20µm. Multiple through holes are arranged in an array, with a center-to-center spacing of 5mm, and are evenly distributed on the base foil.

[0081] The filling material inside the through hole is two substances: substance 1 is lithium powder, which is used to form a lithium metal powder layer 4 by filling; substance 2 is vinylene carbonate, which is used to form a first filling material layer 5 and a second filling material layer 6 by filling twice.

[0082] One layer of material 1 and two layers of material 2 together form a three-layer structure. The two layers of material 2 are located on the outermost surface of the through hole, occupying the outer two layers of the structure, while the one layer of material 1 is the inner central layer. The two layers of material 2 occupy 20% of the volume of the through hole on the outermost sides, while the one layer of material 1 occupies 80% of the volume of the through hole.

[0083] The specific processing steps for the three-layer structure are as follows:

[0084] First, cover the bottom surface of the negative electrode current collector base foil with a protective film (e.g., polypropylene PP film). Then, fill the lower part of the through-hole cavity of the negative electrode current collector base foil with a single layer of material 2, which accounts for 10% of the volume of the through-hole (the bottom opening of the through-hole is sealed by the protective film, and during operation, the negative electrode current collector base foil is placed horizontally on the top surface of a horizontal support platform), and compact it with a pressure of 10MPa (compaction can be done using an existing roller press, the specific brand is not limited), to ensure that material 2 does not scatter.

[0085] Then, lithium metal powder, accounting for 80% of the volume of the through hole, is filled into the middle of the through hole and compacted with a pressure of 10MPa to form a lithium metal powder layer, so that substance 1 and substance 2 act together under pressure.

[0086] Finally, a single layer of material 2, accounting for 10% of the volume of the through hole, is continued to fill the through hole, covering the top of the lithium metal powder layer, and compacted using a pressure of 10 MPa.

[0087] Therefore, the present invention can form a physical stacking structure without binders by filling the middle of the through hole with three layers of material.

[0088] Through the above operations, a porous lithium-filled copper foil is formed, which is the negative electrode current collector of the present invention.

[0089] In practice, after the porous lithium-filling copper foil is manufactured, a protective film is applied to both sides of the foil. The protective film is made of PP (polypropylene) and is 10µm thick. This protective film serves to protect the foil during the actual production process.

[0090] In order to prepare the negative electrode sheet, the protective film must be removed before coating the negative electrode current collector with the negative electrode active material layer.

[0091] In Example 1, the negative electrode active material layer of the negative electrode sheet includes lithium storage active material, binder, dispersant and conductive agent;

[0092] The negative electrode active material includes natural graphite and artificial graphite, etc., with an added mass ratio of 96%.

[0093] The conductive agent is spherical carbon black, and the mass ratio of its addition is 1%.

[0094] The adhesive is styrene-butadiene rubber, and the addition ratio is 1.5% by mass.

[0095] The dispersant is carboxycellulose, and the mass ratio of sodium added is 1.5%.

[0096] The above substances are mixed evenly in a planetary homogenizer using NMP as a solvent to obtain a negative electrode active material slurry. Then, the negative electrode active material slurry is sprayed onto the upper and lower surfaces of the negative electrode current collector base foil (e.g., copper foil) by spraying (i.e., a layer of negative electrode active material is sprayed onto the upper and lower surfaces respectively) to form the negative electrode sheet of the present invention.

[0097] After testing, the negative electrode current collector and negative electrode sheet of Example 1 can improve energy density compared with the existing negative electrode current collector and negative electrode sheet without lithium replenishment and through holes (i.e., the negative electrode current collector and negative electrode sheet of the comparative example). For the present invention, by replenishing lithium at the negative electrode, active lithium can be replenished on the one hand, and cycle life and storage performance can be improved on the other hand. Furthermore, the current collector can indirectly improve energy density and balance the electrolyte and lithium ions, as described above.

[0098] It should be noted that the comparative electrode current collector has no through holes and no lithium replenishment. The active material coating is the same as that in the example, and the active material coating includes the same components, various proportions and materials. The only difference is that the specific current collector foil material is different from the design of Example 1 of this invention.

[0099] Example 2.

[0100] In Example 2, the present invention provides a negative electrode current collector, comprising a basic foil material for a negative electrode current collector;

[0101] The base foil for the negative electrode current collector is copper foil or composite copper foil. The copper foil is 8µm thick, and the diameter of the through holes on the base foil is 10µm. Multiple through holes are arranged in an array, with a center-to-center spacing of 10mm between each hole, and are evenly distributed on the base foil.

[0102] The through-hole is filled with two substances: substance 1 is lithium powder, which is used to form a lithium metal powder layer 4 through filling; substance 2 is vinylene carbonate, which is used to form a first filling material layer 5 and a second filling material layer 6 through two filling processes.

[0103] One layer of material 1 and two layers of material 2 together form a three-layer structure. The two layers of material 2 are located on the outermost surface of the through hole, occupying the outer two layers of the structure, while the one layer of material 1 is the inner central layer. The two layers of material 2 occupy 30% of the volume of the through hole on the outermost sides, while the one layer of material 1 occupies 70% of the volume of the through hole.

[0104] The specific processing steps for the three-layer structure are as follows:

[0105] First, cover the bottom surface of the negative electrode current collector basic foil with a protective film (such as polypropylene PP film). Then, fill the lower part of the through hole cavity of the negative electrode current collector basic foil with a single layer of material 2, which accounts for 15% of the volume of the through hole, and compact it with a pressure of 10MPa to ensure that material 2 will not fall off.

[0106] Then, lithium metal powder, accounting for 80% of the volume of the through hole, is filled into the middle of the through hole and compacted with a pressure of 10 MPa to form a lithium metal powder layer, so that substance 1 and substance 2 act together under pressure.

[0107] Finally, material 2, accounting for 15% of the volume of the through hole, is filled into the through hole, covering the top of the lithium metal powder layer, and compacted using a pressure of 10 MPa.

[0108] Therefore, the present invention can form a physical stacking structure without binders by filling the middle of the through hole with three layers of material.

[0109] Through the above operations, a porous lithium-filled copper foil is formed, which is the negative electrode current collector of the present invention.

[0110] In practice, after the porous lithium-filling copper foil is manufactured, a protective film is applied to both sides of the porous lithium-filling copper foil. The protective film is made of PP (polypropylene) material and has a thickness of 10um. This protective film serves to protect the foil and fillers during the actual production process.

[0111] In order to prepare the negative electrode sheet, the protective film must be removed before coating the negative electrode current collector with the negative electrode active material layer.

[0112] In Example 2, the negative electrode active material layer of the negative electrode sheet includes lithium storage active material, binder, dispersant and conductive agent;

[0113] The negative electrode active material includes natural graphite, artificial graphite, etc., and the added mass ratio is 96%.

[0114] The conductive agent is spherical carbon black, and the mass ratio of its addition is 1%.

[0115] The adhesive is styrene-butadiene rubber, and the addition ratio is 1.5% by mass.

[0116] The dispersant is sodium carboxycellulose, and the mass ratio of the dispersant added is 1.5%.

[0117] The above substances are mixed evenly in a planetary homogenizer using NMP as a solvent to obtain a negative electrode active material slurry. Then, the negative electrode active material slurry is sprayed onto the upper and lower surfaces of the negative electrode current collector base foil (e.g., copper foil) by spraying (i.e., a layer of negative electrode active material is sprayed onto the upper and lower surfaces respectively) to form the negative electrode sheet of the present invention.

[0118] After testing, the negative electrode current collector and negative electrode sheet of Example 2 can improve energy density compared with the existing negative electrode current collector and negative electrode sheet without lithium replenishment and through holes (i.e., the negative electrode current collector and negative electrode sheet of the comparative example). For the present invention, by replenishing lithium at the negative electrode, active lithium can be replenished on the one hand, and cycle life and storage performance can be improved on the other hand. Furthermore, the current collector can indirectly improve energy density and balance the electrolyte and lithium ions, as described above.

[0119] It should be noted that the current collector in the comparative example has no through holes and no lithium replenishment. The active material coating is the same as that in the example, and the active material coating includes the same components, various proportions and materials. The only difference is that the specific current collector foil is different from the design of Example 2 of this invention.

[0120] It should be noted that, for this invention, the main reason for the safety risks associated with lithium replenishment of the negative electrode is the direct leakage of metallic lithium, which can lead to heat generation and water absorption reactions. The main solution of this invention is a concealed approach, where the lithium replenishing material is hidden inside a copper foil, with an active material layer covering the copper foil. This prevents the metallic lithium from contacting the air, reducing the probability of safety incidents. Therefore, this invention can effectively reduce the probability of safety problems arising from lithium replenishment of the negative electrode.

[0121] Without the method described in this invention, lithium metal powder is evenly distributed on the surface of the negative electrode active material (on both sides), resulting in an uneven surface of the negative electrode (caused by strip-shaped lithium adsorption). Gaps are formed between the positive and negative electrodes, and these gaps may lead to lithium plating during the lithium insertion / extraction reaction, thus affecting battery performance. Existing technologies, due to the rapid reaction caused by lithium replenishment, can lead to structural defects within the cell.

[0122] The reason why traditional lithium-ion battery replacement methods waste internal space in the battery cell, such as reducing the battery pack integration ratio and failing to significantly improve energy density, is that the lithium-ion battery pack, attached to the surface of the negative electrode active material, has a certain thickness. When assembled into a battery, the metallic lithium occupies some space, leading to a decrease in the battery pack integration ratio. However, by using the technical solution of this invention, which hides the metallic lithium inside the current collector, this situation is avoided.

[0123] In summary, compared with the prior art, the negative electrode current collector, negative electrode sheet and lithium-replenishing battery provided by the present invention are scientifically designed, can effectively improve the energy density of the battery cell, ensure the safety of the lithium replenishment process, and can slow down and control the lithium replenishment process, which has significant practical significance.

[0124] It should be noted that the reason why this invention can effectively improve the energy density of the battery cell is because: firstly, lithium metal replenishment can supplement active lithium ions, increasing the available lithium ions; secondly, lithium metal does not occupy the space on the surface of the negative electrode, meaning that compared with non-hidden lithium replenishment, it does not affect the in-cell ratio, thus relatively increasing the in-cell ratio. More active material can be accommodated per unit volume of battery. Furthermore, the hidden lithium replenishment in the current collector of this invention reduces the weight of the current collector, and consequently increases the energy density.

[0125] It should be noted that the safety of the lithium replenishment process can be guaranteed in this invention because: firstly, the metallic lithium is not exposed on the surface of the negative electrode active material, reducing the safety issues caused by the environment during the preparation of the electrode sheet; secondly, the upper and lower protective layers filling the pores can further protect the metallic lithium from reacting with air during long-term storage, and will not cause the metallic lithium to react with the active material during the electrode sheet storage process (before it is made into a battery) (if it reacts in advance, it will lead to inconsistent battery capacity).

[0126] It should be noted that the reason why this invention can achieve slow-release control of lithium replenishment is because: firstly, slow release is mainly achieved by the slow dissolution of the substances on top of the lithium metal after the battery is filled with electrolyte, thus slowly releasing the lithium metal; secondly, slow release is achieved through the slow action of the lithium metal itself; and thirdly, slow release ensures the slow replenishment of lithium metal, meaning that during long-cycle operation, for every certain amount of lithium consumed, a certain amount of lithium metal will be replenished. This ensures a longer cycle life.

[0127] Compared with the prior art, the technical solution of the present invention is safer in two ways. The lithium replenishing agent is filled in the current collector, which avoids the side reactions and risks caused by direct contact with air in subsequent production. In addition, the porous current collector and the hidden lithium replenishment can improve the energy density of the battery cell to a certain extent. It can also achieve the effect of slow release and controllable lithium replenishment by controlling external conditions, and can also replenish film-forming additives.

[0128] It should be noted that the external conditions here refer to temperature or pressure. For example, the reaction rate increases when the temperature rises, and slows down when the temperature falls. Increased pressure, or stronger compression, can also make the reaction faster.

[0129] In this invention, the film-forming additive is the filler inside the through-hole, excluding metallic lithium (i.e., the filler in the first filler layer 5 and the second filler layer 6). Its main component is the additive component in the electrolyte. After the filler dissolves into the electrolyte, it replenishes the additives already consumed in the electrolyte. The long cycle life of the battery is largely related to the film-forming additive.

[0130] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A negative electrode current collector, characterized in that, Including the basic foil material for negative electrode current collector (2); On the negative electrode current collector basic foil (2), there are multiple vertical through holes (3) evenly distributed at equal intervals. Each through hole (3) is provided with lithium filler; The lithium replenishing filler includes metallic lithium powder; The lithium replenishing filler is a multi-layered lithium replenishing filler; The multi-layered lithium filler is a three-layered lithium filler. The three-layer lithium filler includes a first filler layer (5), a lithium metal powder layer (4), and a second filler layer (6) arranged sequentially from top to bottom. The lithium metal powder layer (4) is located between the first filler layer (5) and the second filler layer (6), and the upper and lower sides of the lithium metal powder layer (4) are in contact with the bottom surface of the first filler layer (5) and the top surface of the second filler layer (6), respectively. The substances filled in the first filling material layer (5) and the second filling material layer (6) are solid electrolyte additives, including at least one of vinylene carbonate, vinyl sulfate and N,N-dimethylacrylamide (DMAA). The solid electrolyte additives are solid in the absence of electrolyte. When the battery is subsequently filled with electrolyte, the electrolyte can slowly dissolve the solid, making it part of the liquid electrolyte, and at the same time, it will release the replenished metallic lithium.

2. The negative electrode current collector as described in claim 1, characterized in that, The upper and lower sides of the lithium metal powder layer (4) are pressed and contacted with the bottom surface of the first filling material layer (5) and the top surface of the second filling material layer (6), respectively.

3. The negative electrode current collector as described in claim 1, characterized in that, The filling materials in the first filling material layer (5) and the second filling material layer (6) are exactly the same.

4. The negative electrode current collector as described in claim 1, characterized in that, The volume of the lithium metal powder layer (4) in each through hole (3) accounts for 70% to 90% of the volume of the cavity inside the through hole (3); The sum of the volumes of the first filling material layer (5) and the second filling material layer (6) in each through hole (3) accounts for 10% to 30% of the volume of the cavity inside the through hole (3).

5. The negative electrode current collector as described in claim 1, characterized in that, The first filler layer (5), the lithium metal powder layer (4), and the second filler layer (6) are physically stacked and there is no adhesive between them.

6. A negative electrode sheet, characterized in that, Includes the negative electrode current collector as described in any one of claims 1 to 5; The negative electrode current collector has a negative electrode active material layer (1) covering the upper and lower surfaces of the negative electrode current collector basic foil (2).

7. The negative electrode sheet as described in claim 6, characterized in that, The negative electrode active material layer (1) includes the negative electrode main material, binder, conductive agent and dispersant; The negative electrode active material layer includes 93% to 98% negative electrode main material by mass, 0.5% to 3% binder by mass, 0.2% to 2% conductive agent by mass, and 0.4% to 2.5% dispersant by mass. Among them, the main material of the negative electrode is lithium storage active material; The adhesive includes at least one of styrene-butadiene rubber, polyacrylate, polyacrylonitrile, and polyvinylidene fluoride; Conductive agents, including at least one of carbon nanotubes and graphene; The dispersant is a cellulose derivative.

8. The negative electrode sheet according to claim 7, characterized in that, Lithium storage active materials include at least one of soft carbon, hard carbon, and silicon.

9. The negative electrode sheet according to claim 7, characterized in that, Lithium storage active materials include at least one of natural graphite and artificial graphite.

10. A lithium-ion battery, characterized in that, Includes the negative electrode sheet as described in any one of claims 6-9.

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