Lithium-supplementing current collector and preparation method and application thereof

Abstract

The invention belongs to the technical field of battery manufacturing, and relates to a lithium-supplementing current collector and a preparation method and application thereof.The lithium-supplementing current collector comprises a base film, a first metal layer and a second metal layer, the first metal layer and the second metal layer are arranged on the surface of at least one side of the base film in a stacked mode, and the first metal layer is located between the base film and the second metal layer; and the second metal layer is a lithium-containing alloy layer. The preparation method comprises the following steps: (1) arranging a first metal layer on the surface of at least one side of a base film; and (2) depositing a lithium-containing alloy layer on the surface of the first metal layer as a second metal layer to obtain the lithium-supplementing current collector. The lithium-containing alloy layer is prepared in the current collector, so that accurate lithium supplementation of the negative electrode is realized, safety, economy and stability are considered, and large-scale mass production is facilitated.

Description

A lithium-supplemented current collector, its preparation method and application Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, and relates to a lithium replenishing current collector, and more particularly to a lithium replenishing current collector, its preparation method and application. Background Technology

[0002] Lithium-ion batteries, as crucial energy components for new energy vehicles, energy storage systems, and portable electronic devices, have seen their energy density, cycle life, and safety performance become key factors restricting the upgrading of related industries. During the charge-discharge cycle of lithium-ion batteries, lithium loss in the first week is a common technical problem. The formation of a solid electrolyte interphase (SEI) film due to electrolyte decomposition and side reactions on the surface of active materials consume a large amount of lithium ions, leading to a decrease in the battery's coulombic efficiency in the first week. Furthermore, the continuous growth of the SEI film and lithium dendrite shedding in subsequent cycles exacerbate lithium loss, ultimately causing rapid capacity decay and severely impacting battery lifespan. Therefore, lithium replenishment technology is considered a key breakthrough for improving the overall performance of lithium-ion batteries.

[0003] Currently, the lithium replenishment technologies used in the industry are mainly divided into two routes: exogenous pre-lithiation and endogenous lithium enrichment. The exogenous pre-lithiation route achieves lithium replenishment by introducing an additional lithium source into the battery system. Among these, negative electrode lithium replenishment technology is the most widely used, including lithium foil rolling and lamination, lithium powder slurry coating, and lithiation reagent mixing. While lithium foil rolling can directly provide a large amount of lithium source, the lithium foil itself is soft and highly ductile, easily causing wrinkles when bonded to the negative electrode active material layer, leading to uneven interface contact. Lithium powder slurry coating faces the challenge of the extremely high chemical activity of lithium powder, which readily reacts violently with oxygen and moisture in the air, not only reducing lithium replenishment efficiency but also posing serious safety hazards. Therefore, production must be completed in an inert atmosphere environment, significantly increasing manufacturing costs. Positive electrode exogenous lithium replenishment mostly relies on lithium-rich additives or electrochemical pre-lithiation. The former requires precise control of the additive dosage and dispersion uniformity; excessive addition will lead to a decrease in the stability of the positive electrode structure. The latter requires additional pre-lithiation process steps, extending the production cycle and making large-scale mass production difficult.

[0004] In contrast, the endogenous lithium-rich route uses materials containing an excess of lithium as electrode active materials, typically represented by lithium metal anodes and lithium-silicon alloy anodes. Lithium metal anodes have a theoretical specific capacity as high as 3860 mAh / g and sufficient lithium content, but their volume expansion rate exceeds 300% during cycling, which easily leads to problems such as lithium dendrite growth, pulverization and shedding. This not only damages the integrity of the electrode structure but also easily punctures the separator, causing short circuits, posing significant safety risks. Although lithium-silicon alloys combine high capacity and a certain lithium storage capacity, they also suffer from defects such as severe volume expansion, high interfacial impedance, and poor cycling stability.

[0005] It is evident that while existing lithium replenishment technologies have alleviated lithium loss in the first week to some extent, there are still many problems that need to be solved, which seriously restrict the industrialization and performance improvement of lithium-ion battery lithium replenishment technology. There is an urgent need to develop a new lithium replenishment technology solution that takes into account safety, economy, stability and precise lithium replenishment capabilities. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a lithium replenishment current collector, its preparation method and application, to overcome the defects of the existing lithium replenishment technology, while taking into account safety, economy, stability and accurate lithium replenishment capability.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a lithium current collector, comprising a base film and a first metal layer and a second metal layer stacked on at least one side surface of the base film, wherein the first metal layer is located between the base film and the second metal layer, and the second metal layer is a lithium-containing alloy layer.

[0008] This invention incorporates a lithium alloy layer in the current collector, which acts as a "lithium reservoir" to enable precise lithium replenishment to the negative electrode, providing a stable electronic pathway. Furthermore, after cycling, the current collector transforms into a porous structure, reserving an expansion buffer for the active material layer to accommodate changes in lithium metal volume, effectively balancing safety, economy, stability, and precise lithium replenishment capabilities.

[0009] Preferably, the second metal layer further includes copper, and the mass of copper accounts for 20% to 50% of the total mass of the second metal layer.

[0010] Preferably, the source of lithium in the second metal layer includes pure metallic lithium or lithium compounds, and the lithium compounds include at least one of Li5FeO4, Li2O2, Li3N, Li6CoO4, Li2NiO2, Li2CuO2, Li2MoO3 or Li2CO3.

[0011] Preferably, the crystallinity of lithium in the second metal layer is 30% to 60%.

[0012] Preferably, the lithium grains in the second metal layer have a particle size of 10-50 nm, and more preferably 30-50 nm.

[0013] Preferably, the base film is made of at least one of polypropylene, polyethylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyimide, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, or polyamide.

[0014] Preferably, the thickness of the base film is 1~10μm.

[0015] Preferably, the material of the first metal layer includes at least one of titanium, silver, aluminum alloy, aluminum, nickel alloy, nickel, copper alloy, or copper.

[0016] Preferably, the thickness of the first metal layer is 0.8μm-2μm.

[0017] Preferably, the material of the second metal layer further includes at least one of titanium, silver, aluminum alloy, aluminum, nickel alloy, nickel, copper alloy, or copper.

[0018] Preferably, the thickness of the second metal layer is 0.2μm-15μm.

[0019] In a second aspect, the present invention provides a method for preparing a lithium-replenishing current collector as described in the first aspect, comprising the following steps: (1) providing a first metal layer on at least one side surface of a base film; (2) depositing a lithium-containing alloy layer on the surface of the first metal layer as a second metal layer to obtain a lithium-replenishing current collector.

[0020] Preferably, the lithium current collector is further subjected to heat treatment and cold treatment.

[0021] The heat treatment temperature is 0.65T~0.75T, and the cold treatment temperature is -0.2T~-0.1T, where T refers to the melting point of lithium metal.

[0022] Preferably, the temperature difference between the heat treatment and the cold treatment is 0.85T~0.9T.

[0023] Preferably, in step (2), the deposition method of the second metal layer is magnetron sputtering, the target material is a lithium alloy target material, the target power is 7~20kW, the gas source is high-purity argon, the gas source flow rate is 80~100mL / min, the gas pressure in the chamber during sputtering is 0.06~0.10Pa, and the cooling temperature of the main roller is -40℃ to -15℃.

[0024] Preferably, the method of setting the first metal layer in step (1) includes magnetron sputtering, and the target material used is selected from at least one of titanium target, silver target, aluminum alloy target, aluminum target, nickel alloy target, nickel target, copper alloy target or copper target.

[0025] Thirdly, the present invention provides an electrode containing at least the lithium current collector as described in the first aspect.

[0026] Fourthly, the present invention provides a battery comprising at least a lithium current collector as described in the first aspect, or an electrode as described in the third aspect.

[0027] Compared with the prior art, the present invention has the following beneficial effects: The present invention sets a lithium alloy layer in the current collector, which serves as a "lithium reservoir" to achieve precise lithium replenishment to the negative electrode, providing a stable electronic pathway. After cycling, the current collector transforms into a porous structure, reserving an expansion buffer for the active material layer, adapting to changes in the volume of lithium metal, and effectively balancing safety, economy, stability and precise lithium replenishment capability. Detailed Implementation

[0028] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0029] One embodiment of the present invention provides a lithium current collector, including a base film and a first metal layer and a second metal layer stacked on at least one side surface of the base film, wherein the first metal layer is located between the base film and the second metal layer, and the second metal layer is a lithium-containing alloy layer.

[0030] This invention incorporates a lithium alloy layer in the current collector, which acts as a "lithium reservoir" to enable precise lithium replenishment to the negative electrode, providing a stable electronic pathway. Furthermore, after cycling, the current collector transforms into a porous structure, reserving an expansion buffer for the active material layer to accommodate changes in lithium metal volume, effectively balancing safety, economy, stability, and precise lithium replenishment capabilities.

[0031] In some embodiments, the second metal layer further includes copper, the mass of which accounts for 20% to 50% of the total mass of the second metal layer. For example, it can be 20%, 25%, 30%, 35%, 40%, 45%, or 50%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] The present invention limits the copper content in the second metal layer to the above-mentioned range, which can form a metal skeleton structure and suppress the growth of lithium grains, exerting a mechanical constraint on lithium. By suppressing the abnormal growth of lithium grains, the uniformity of lithium grains is improved. This not only reduces the stress of the second metal layer, but also reduces the probability of crack formation, thereby avoiding the pulverization of the second metal layer during cycling.

[0033] In some embodiments, the lithium source in the second metal layer includes pure metallic lithium or lithium compounds, and the lithium compounds include at least one of Li5FeO4, Li2O2, Li3N, Li6CoO4, Li2NiO2, Li2CuO2, Li2MoO3 or Li2CO3.

[0034] When pure metallic lithium is preferred as the lithium source for the second metal layer, the lithium replenishment effect is better and the efficiency is faster. If lithium compounds are used, the stringent environmental requirements of the production process can be reduced, and a flexible balance between lithium replenishment performance and production feasibility can be achieved.

[0035] In some embodiments, the crystallinity of lithium in the second metal layer is 30% to 60%, for example, it can be 30%, 35%, 40%, 45%, 50%, 55% or 60%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] This invention can limit the crystallinity of lithium in the second metal layer to the above-mentioned range by adjusting the temperature and time of heat treatment, thereby achieving micro-control of SEI film growth. It utilizes amorphous lithium to generate a thin and dense uniform SEI film, and utilizes crystalline lithium to generate a thick and mechanically strong SEI film, ultimately effectively improving the cycle performance and rate performance of the battery, while increasing the thermal runaway trigger temperature of the battery.

[0037] In some embodiments, the particle size of lithium crystals in the second metal layer is 10~50nm, for example, it can be 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm, preferably 30~50nm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0038] The aforementioned particle size range ensures that the lithium crystals are small and uniform, further reducing the orientation disorder at the copper-lithium interface, lowering residual stress, and preventing cracking and pulverization of the alloy layer. The small particle size also increases the specific surface area, resulting in more uniform lithium release. This can accurately compensate for lithium loss during battery cycling, balance grain stability and lithium activity, ensure mechanical support, enhance adhesion to the active material layer, and balance lithium replenishment efficiency and structural reliability.

[0039] In some embodiments, the second metal layer has a carbon coating on the surface away from the first metal layer, which effectively prevents the lithium in the metal layer from reacting with oxygen, nitrogen and other gases in the air, thereby reducing the risk of lithium reactivity.

[0040] In some embodiments, the thickness of the carbon coating layer is 0.5~2μm, for example, it can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm or 2μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0041] In some embodiments, the base film is made of at least one of polypropylene, polyethylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyimide, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, or polyamide.

[0042] In some embodiments, the thickness of the base film is 1 to 10 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0043] In some embodiments, the material of the first metal layer includes at least one of titanium, silver, aluminum alloy, aluminum, nickel alloy, nickel, copper alloy, or copper.

[0044] In some embodiments, the thickness of the first metal layer is 0.8 μm-2 μm, for example, it can be 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm or 2 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0045] In some embodiments, the material of the second metal layer further includes at least one of titanium, silver, aluminum alloy, aluminum, nickel alloy, nickel, copper alloy, or copper.

[0046] In some embodiments, the thickness of the second metal layer is 0.2μm-15μm, for example, it can be 0.2μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm or 15μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0047] One embodiment of the present invention also provides a method for preparing the lithium replenishing current collector described in any of the above embodiments, comprising the following steps: (1) providing a first metal layer on at least one side surface of a base film; (2) depositing a lithium-containing alloy layer on the surface of the first metal layer as a second metal layer to obtain the lithium replenishing current collector.

[0048] In some embodiments, the lithium current collector is also subjected to heat treatment and cold treatment.

[0049] The heat treatment temperature is 0.65T to 0.75T, for example, 0.65T, 0.66T, 0.67T, 0.68T, 0.69T, 0.7T, 0.71T, 0.72T, 0.73T, 0.74T, or 0.75T. The cold treatment temperature is -0.2T to -0.1T, for example, -0.2T, -0.19T, -0.18T, -0.17T, -0.16T, -0.15T, -0.14T, -0.13T, -0.12T, -0.11T, or -0.1T. T refers to the melting point of lithium metal, but is not limited to the listed values; other unlisted values ​​within this range also apply.

[0050] In some embodiments, the temperature difference between the heat treatment and the cold treatment is 0.85T to 0.9T, for example, it can be 0.85T, 0.86T, 0.87T, 0.88T, 0.89T or 0.9T, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] This invention limits the heat treatment temperature to the above-mentioned range, enabling simultaneous heat treatment of copper and lithium. This not only improves crystallinity and grain size by increasing the grain boundary mobility of lithium, but also facilitates stress release and density improvement due to atomic rearrangement.

[0052] In addition, heat treatment within the above temperature range can reduce the dislocation density of copper, prevent excessive copper growth, and enable deep diffusion between copper and lithium. The resulting nanoscale interface phase significantly enhances interlayer bonding and prevents the formation of brittle metal alloy layers.

[0053] Furthermore, the present invention performs cold treatment after heat treatment, which is beneficial to the preservation of the product's microstructure and the full release of residual stress.

[0054] In some embodiments, the deposition method of the second metal layer in step (2) is magnetron sputtering, the target material is a lithium alloy target, the target power is 7~20kW, for example, it can be 7kW, 8kW, 9kW, 10kW, 11kW, 12kW, 13kW, 14kW, 15kW, 16kW, 17kW, 18kW, 19kW or 20kW, the gas source is high-purity argon, and the gas source flow rate is 80~100mL / min, for example, it can be 80mL / min or 85mL / min. Sputtering rates of 90 mL / min, 95 mL / min, or 100 mL / min are used. The chamber pressure during sputtering is 0.06~0.10 Pa, for example, 0.06 Pa, 0.07 Pa, 0.08 Pa, 0.09 Pa, or 0.10 Pa. The main roller cooling temperature is -40℃ to -15℃, for example, -40℃, -35℃, -30℃, -25℃, -20℃, or -15℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] This invention employs magnetron sputtering to deposit a second metal layer. During magnetron sputtering, lithium readily nucleates and grows in defective regions on the surface of the first metal layer, significantly improving the surface smoothness of the current collector. This dynamic lithium replenishment mechanism adapts to lithium loss during long-cycle operation. Combined with interface optimization and improved structural stability, it significantly improves battery cycle performance, reduces capacity decay in later stages, and ultimately effectively balances safety, economy, stability, and precise lithium replenishment capability.

[0056] In some embodiments, the method of setting the first metal layer in step (1) includes magnetron sputtering, and the target material used is selected from at least one of titanium target, silver target, aluminum alloy target, aluminum target, nickel alloy target, nickel target, copper alloy target or copper target.

[0057] One embodiment of the present invention also provides an electrode sheet containing at least the lithium replenishing current collector described in any of the above embodiments.

[0058] One embodiment of the present invention also provides a battery containing at least the lithium replenishing current collector described in any of the above embodiments, or the electrode sheet described in any of the above embodiments.

[0059] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0060] Example 1 This example provides a lithium-filled current collector, electrode, lithium-ion battery and its preparation method, specifically including the following steps: (1) Preparation of lithium-filled current collector: ① Place a PET base film with a thickness of 4.5 μm in a magnetron sputtering device, and sputter copper layers as the first metal layers on both sides of the film. The magnetron sputtering conditions are: copper target (purity 99.99%) as the target material, target power of 10kW, argon gas as the gas source, gas flow rate of 80mL / min, gas pressure in the chamber during sputtering of 0.08Pa, cooling temperature of the main roller of -10℃, and sputtering thickness of 1.5 μm. m; ② A copper-lithium alloy layer (Cu content of 33wt%) is magnetron sputtered on the surface of the first metal layer as the second metal layer. The magnetron sputtering conditions are as follows: copper-lithium target is used as the target material, target power is 9kW, high-purity argon (purity 99.99%) is used as the gas source, gas flow rate is 90mL / min, gas pressure in the chamber during sputtering is 0.08Pa, main roller cooling temperature is -20℃, and sputtering thickness is 8μm; ③ The obtained lithium replenishing current collector is first heat-treated at 128℃ for 5min, and then cold-treated at -30℃ for 5min to obtain the treated lithium replenishing current collector.

[0061] (2) Preparation of negative electrode sheet: The lithium replenishing current collector obtained in step (1) is used as the negative electrode current collector. Graphite, conductive carbon black Super P, carbon nanotubes and CMC are mixed in a mass ratio of 96:3:0.6:0.4 to prepare a negative electrode slurry. The negative electrode slurry is coated on the surface of the active material coating area of ​​the negative electrode current collector and dried to form a negative electrode active material layer.

[0062] (3) Preparation of positive electrode sheet: A composite aluminum current collector is used as the positive electrode current collector. NCM622, conductive carbon Super P, carbon nanotubes and polyvinylidene fluoride are mixed in a mass ratio of 96:1.8:0.5:1.7 to prepare a positive electrode slurry. The positive electrode slurry is coated on the surface of the active material coating area of ​​the positive electrode current collector and dried to form a positive electrode active material layer.

[0063] (4) Assemble lithium-ion batteries: Stack the above positive electrode, PP separator and negative electrode in sequence to prepare bare cells; place the bare cells in the outer packaging shell of lithium batteries, dry them and inject electrolyte, and obtain lithium-ion batteries through vacuum sealing, standing, formation and shaping processes.

[0064] Example 2 This example provides a lithium-filled current collector, electrode, lithium-ion battery and its preparation method. Except for adjusting the Cu content in the copper-lithium target to make the Cu content in the copper-lithium alloy layer 21%, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0065] Example 3 This example provides a lithium-filled current collector, electrode, lithium-ion battery and its preparation method. Except for adjusting the Cu content in the copper-lithium target to make the Cu content in the copper-lithium alloy layer 48%, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0066] Example 4 This example provides a lithium-filled current collector, electrode, lithium-ion battery and its preparation method. Except for adjusting the Cu content in the copper-lithium target to make the Cu content in the copper-lithium alloy layer 9%, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0067] Example 5 This example provides a lithium replenishing current collector, an electrode, a lithium-ion battery, and a method for preparing the same. Except that the obtained lithium replenishing current collector is first heat-treated at 120°C for 3 minutes and then cold-treated at -30°C for 5 minutes, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0068] Example 6 This example provides a lithium replenishing current collector, an electrode, a lithium-ion battery, and a method for preparing the same. Except that the obtained lithium replenishing current collector is first heat-treated at 135°C for 8 minutes and then cold-treated at -30°C for 5 minutes, the other steps and conditions are the same as in Example 1, so they will not be described again here.

[0069] Example 7 This example provides a lithium replenishing current collector, an electrode, a lithium-ion battery, and a method for preparing the same. Except that the obtained lithium replenishing current collector is first heat-treated at 140°C for 10 minutes and then cold-treated at -30°C for 5 minutes, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0070] Example 8 This example provides a lithium replenishing current collector, an electrode, a lithium-ion battery, and a method for preparing the same. Except that the obtained lithium replenishing current collector is first heat-treated at 60°C for 1 min and then cold-treated at -30°C for 5 min, the other steps and conditions are the same as in Example 1, so they will not be described again here.

[0071] Example 9 This example provides a lithium replenishing current collector, an electrode, a lithium-ion battery, and a method for preparing the same. Except that the obtained lithium replenishing current collector is first heat-treated at 128°C for 5 minutes and then cold-treated at -38°C for 5 minutes, the other steps and conditions are the same as in Example 1, so they will not be described again here.

[0072] Example 10 This example provides a lithium replenishing current collector, an electrode, a lithium-ion battery, and a method for preparing the same. Except that the obtained lithium replenishing current collector is first heat-treated at 128°C for 5 minutes and then cold-treated at -10°C for 5 minutes, the other steps and conditions are the same as in Example 1, so they will not be described again here.

[0073] Comparative Example 1 provides a current collector, an electrode, a lithium-ion battery, and a method for preparing the same. Except for not magnetron sputtering a copper-lithium alloy layer as a second metal layer on the surface of the first metal layer, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0074] The lithium current collectors obtained in Examples 1-10 were used to test the lithium crystallinity of their copper-lithium alloy layers by X-ray diffraction and to test the particle size of lithium grains by scanning electron microscopy. The relevant test results are shown in Table 1 below.

[0075] Table 1 Performance test: (1) First efficiency: At 25°C, the battery was charged to 4.2V with constant current and constant voltage (CC-CV) at 0.5C (cutoff current 0.05C), and the first charging capacity was recorded; then it was left to stand for 5~10 minutes, and then discharged to 2.8V with constant current at 0.5C, and the first discharge capacity was recorded. The first coulombic efficiency (first efficiency) η = (first discharge capacity / first charging capacity) × 100% was calculated.

[0076] (2) Cycle performance: At 25°C, the battery is first discharged at a constant current of 0.5C to 2.8V (considered as the initial capacity being zero), and then left to rest for 30 minutes; then charged at a constant current and constant voltage of 0.5C to 4.2V (cutoff current 0.05C), and left to rest for 30 minutes; then discharged at a constant current of 0.5C to 2.8V, and left to rest for 30 minutes. This process is defined as one complete charge-discharge cycle. The above charge-discharge steps are then repeated until the battery's discharge capacity decays to 80% of the initial discharge capacity. The number of cycles experienced at this point is the battery's cycle life (maximum number of cycles).

[0077] (3) Discharge capacity retention rate: The battery was charged at room temperature of 25°C with a current of 1cA. After charging to 4.2V, constant voltage charging was performed. When the current dropped to 500mA, the charging was terminated. Then, the battery was discharged to 2.75V with a current of 7cA, and the discharge capacity retention rate was recorded.

[0078] (4) Tensile strength: Take a lithium current collector sample and use an MTS Criterion 42 tensile testing machine to measure the tensile strength of the sample; Parameter settings: The clamp spacing on the tensile testing machine is 100 mm, the test speed is 225 mm / min, and the tensile strength when the sample begins to crack is obtained.

[0079] (5) Number of holes: The finished product is placed in a surface quality detection system (micro-visual charge-coupled device CCD) to scan the surface. Then the light signal is converted into an electrical signal and sent to a computer to count the number of holes on the surface of the finished product per unit area.

[0080] (6) Adhesion: After disassembling the battery after the cycle test, 10 samples with a size of 120mm×50mm were randomly selected from different positions of the negative electrode as test samples. The cut test samples were attached to the steel plate with 3M double-sided tape and rolled back and forth twice with a 2kg pressure roller. Then, 3M transparent tape with a size of 220mm×12.7mm was attached to the self-supporting film or negative electrode active coating and rolled back and forth twice with a 2kg pressure roller. The peel force between the self-supporting film or negative electrode active coating and the current collector was tested using a horizontal peel tester. The final result is expressed as peel strength (N / m).

[0081] (7) Residual stress: The residual stress of the current collectors provided in the above embodiments and comparative examples was tested using a μ-360s X-ray residual stress tester.

[0082] The test results of the current collectors and lithium-ion batteries obtained in Examples 1-10 and Comparative Example 1 are shown in Table 2 below.

[0083] Table 2 The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A lithium-filled current collector, characterized in that, The lithium current collector includes a base film and a first metal layer and a second metal layer stacked on at least one side of the base film, wherein the first metal layer is located between the base film and the second metal layer, and the second metal layer is a lithium-containing alloy layer.

2. The lithium replenishing current collector according to claim 1, characterized in that, The second metal layer also includes copper, and the mass of copper accounts for 20% to 50% of the total mass of the second metal layer.

3. The lithium replenishing current collector according to claim 1 or 2, characterized in that, The lithium source in the second metal layer includes pure metallic lithium or lithium compounds, and the lithium compounds include at least one of Li5FeO4, Li2O2, Li3N, Li6CoO4, Li2NiO2, Li2CuO2, Li2MoO3 or Li2CO3; and / or, the crystallinity of lithium in the second metal layer is 30% to 60%; and / or, the particle size of lithium grains in the second metal layer is 10 to 50 nm, preferably 30 to 50 nm.

4. The lithium replenishing current collector according to claim 1 or 2, characterized in that, The base film is made of at least one of polypropylene, polyethylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyimide, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, or polyamide; and / or the thickness of the base film is 1~10 μm.

5. The lithium replenishing current collector according to claim 1 or 2, characterized in that, The material of the first metal layer includes at least one of titanium, silver, aluminum alloy, aluminum, nickel alloy, nickel, copper alloy or copper; and / or, the thickness of the first metal layer is 0.8μm-2μm; and / or, the material of the second metal layer further includes at least one of titanium, silver, aluminum alloy, aluminum, nickel alloy, nickel, copper alloy or copper; and / or, the thickness of the second metal layer is 0.2μm-15μm.

6. A method for preparing a lithium-supplemented current collector as described in any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: (1) setting a first metal layer on at least one side of the base film; (2) depositing a lithium-containing alloy layer on the surface of the first metal layer as a second metal layer to obtain a lithium-supplemented current collector.

7. The method for preparing the lithium current collector according to claim 6, characterized in that, The lithium current collector also undergoes heat treatment and cold treatment; wherein the temperature of the heat treatment is 0.65T~0.75T, the temperature of the cold treatment is -0.2T~-0.1T, and T refers to the melting point of lithium metal; preferably, the temperature difference between the heat treatment and the cold treatment is 0.85T~0.9T.

8. The method for preparing the lithium-supplemented current collector according to claim 6 or 7, characterized in that, Step (2) The deposition method of the second metal layer is magnetron sputtering, the target material is lithium alloy target material, the target power is 7~20kW, the gas source is high-purity argon gas, the gas source flow rate is 80~100mL / min, the gas pressure in the chamber during sputtering is 0.06~0.10Pa, and the cooling temperature of the main roller is -40℃ to -15℃; and / or, Step (1) The setting method of the first metal layer includes magnetron sputtering, and the target material used is selected from at least one of titanium target, silver target, aluminum alloy target, aluminum target, nickel alloy target, nickel target, copper alloy target or copper target.

9. An electrode sheet, characterized in that, The electrode contains at least the lithium replenishing current collector as described in any one of claims 1 to 5.

10. A battery, characterized in that, The battery contains at least the lithium replenishing current collector as described in any one of claims 1 to 5, or the electrode as described in claim 9.

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