Anode-free lithium metal battery porous copper current collector and its slm additive manufacturing method and application

Abstract

The application discloses an SLM additive manufacturing method of a porous copper current collector of an anode-free lithium metal battery, which comprises the following steps: copper powder composite modification, mixing spherical copper powder with nano-carbon powder and then heat treatment, so that a nano-carbon layer is coated on the surface of the copper powder; gradient porosity digital modeling, designing a double-region porous structure model with different porosities and pore diameters along the thickness direction; SLM partition forming, realizing porosity regulation by adjusting the laser energy density of different regions; post-processing and lithiumophilic modification, stress relief annealing of the porous copper green body, and deposition of a Cu3P lithiumophilic coating on the surface of the porous copper green body by using an electroplating method. The porous copper current collector prepared by the method has a gradient porosity structure, the region close to the positive electrode side of the battery is used for inhibiting lithium dendrite penetration, and the region close to the negative electrode side of the battery is used for buffering the volume expansion in the lithium deposition process, so that the cycle stability and safety of the lithium metal battery can be significantly improved.

Description

Technical Field

[0001] This invention relates to the field of anode-free lithium metal battery technology, and more specifically, to a porous copper current collector for anode-free lithium metal batteries, its SLM additive manufacturing method, and its application. Background Technology

[0002] With the increasing demand for high-energy-density batteries from electric vehicles and portable electronic devices, lithium metal batteries are considered one of the most promising next-generation battery technologies due to their advantages such as high theoretical specific capacity (3860 mAh / g) and low electrode potential (-3.04V vs. SHE). However, lithium metal batteries are prone to lithium dendrite formation during charging and discharging, leading to problems such as short battery cycle life and poor safety, which seriously restricts their commercial application.

[0003] Porous copper current collectors, used as negative electrode current collectors in lithium metal batteries, have attracted widespread attention due to their advantages such as providing lithium deposition space, reducing local current density, and suppressing lithium dendrite growth through their three-dimensional porous structure. Currently, the main methods for preparing porous copper current collectors include dealloying, powder metallurgy, and electrochemical deposition. CN107293754B discloses a method for etching porous copper current collectors with different pore sizes using Cu-X alloy sheets as substrates via electrochemical methods. This method can effectively provide deposition space for lithium metal and limit lithium dendrite growth. CN116344836A proposes a method for preparing bidirectional through-hole structure current collectors using copper powder and binders. This method can achieve porous metal current collectors with a lithium affinity gradient. CN120072954A discloses a method for preparing a uniformly distributed through-hole array structure on copper foil using nanosecond laser processing and stacking it with copper foam to form a composite structure current collector. This structure has a larger specific surface area, can change the current density distribution, and induce uniform lithium deposition. CN114628686A proposes a method for preparing porous copper micro-hollow spheres using zinc microspheres or zinc oxide microspheres as self-sacrificing templates. The current collector prepared by this method can accommodate lithium metal in the pores of the porous copper micro-hollow spheres, effectively suppressing lithium dendrite growth. CN113564524B discloses a method for preparing a three-dimensional porous copper framework using powder sintering, followed by depositing a uniform carbon film on its surface using arc discharge plasma physical vapor deposition. This method can improve the mechanical strength of the material and enhance the battery's capacity retention, lifespan, and cycle stability. Chinese patent application CN202210489786 discloses a selective laser melting (SLM) method for forming porous foamed copper, achieving a porous structure by adjusting parameters such as laser power and scanning speed. International patent application WO-2023055585-A1 discloses a multilayer current collector for anode-free lithium metal batteries. However, these methods are not specifically optimized for the high reflectivity and thermal conductivity of copper, making it difficult to guarantee the forming quality. Furthermore, they do not consider the special requirements of anode-free lithium metal batteries for the lithium affinity of the current collector, making them unsuitable for direct application in anode-free lithium metal batteries. Some also do not involve SLM additive manufacturing processes, hindering the customization of complex pore structures.

[0004] In recent years, selective laser melting (SLM) additive manufacturing technology has shown great potential in the field of porous metal material preparation due to its ability to precisely manufacture complex three-dimensional structures. However, existing SLM techniques for preparing porous copper current collectors still face several challenges: copper has high laser reflectivity (near-infrared laser reflectivity >90%) and high thermal conductivity, resulting in low laser energy absorption efficiency and poor molten pool stability during SLM forming, easily leading to defects such as spheroidization, incomplete fusion, and cracks; furthermore, existing SLM-prepared porous copper current collectors generally suffer from insufficient lithiophilicity, affecting the uniform deposition of lithium; the pore structure of porous copper current collectors is difficult to match the lithium deposition requirements of anode-free lithium metal batteries, making them unsuitable for anode-free lithium metal battery applications. In addition, traditional preparation methods also have their limitations: dealloying methods suffer from poor structural uniformity and difficulty in achieving complex topological structure designs; powder metallurgy methods produce porous structures with poor pore connectivity; and electrochemical deposition methods are complex, with the template removal process easily leading to structural collapse. Therefore, there is an urgent need to develop a method for preparing porous copper current collectors that can precisely control the pore structure, improve lithium affinity, and adapt to the application requirements of anode-free lithium metal batteries. Summary of the Invention

[0005] One of the technical problems to be solved by the present invention is to provide a SLM additive manufacturing method for porous copper current collectors in anode-free lithium metal batteries, so as to solve the problems that pure copper powder has many SLM forming defects due to high laser reflectivity, and conventional porous copper current collectors lack matching gradient pore structure and lithiophilic surface modification, thus failing to effectively suppress lithium dendrite growth and buffer volume expansion.

[0006] To overcome the shortcomings of the prior art, this invention provides an SLM additive manufacturing method for a porous copper current collector in anode-free lithium metal batteries, comprising the following steps: S1: Copper powder composite modification: Select gas-atomized spherical copper powder, mix it with nano carbon powder at a mass ratio of 100:(1–5), and keep it at 300–400℃ for 1–2 h in an inert gas atmosphere to make the nano carbon layer coat the surface of the copper powder, thereby obtaining modified copper powder to improve the laser absorption rate. S2: Gradient Porosity Digital Modeling: Design a porous structure model, which is divided into two regions along the thickness direction: a low porosity region near the positive electrode of the battery, with a porosity of 15%–60% and a pore size of 10–50 μm; and a high porosity region near the negative electrode of the battery, with a porosity of 60%–70% and a pore size of 20–150 μm, wherein the pore size of the region near the negative electrode of the battery is larger than that of the region near the positive electrode of the battery. S3: SLM partition molding: Modified copper powder is added to the SLM equipment, and partition scanning molding is performed according to the porous structure model. Porosity is controlled by adjusting the laser energy density of different regions to obtain a porous copper billet. S4: Post-processing and lithophile modification: The porous copper green billet is subjected to stress relief annealing, and then Cu3P lithophile coating is deposited in the internal pores and surface of the porous copper by electroplating to obtain the finished porous copper current collector.

[0007] Compared with existing technologies, the SLM additive manufacturing method for porous copper current collectors in anode-free lithium metal batteries of the present invention has the following advantages: The present invention improves the existing technology by directly using high-reflectivity pure copper powder to form homogeneous random pores without surface modification of the current collector, and uses nano-carbon coated modified copper powder. Combined with partitioned variable parameter SLM process, a gradient pore structure from dense to sparse is achieved, and a Cu3P lithiophilic coating is constructed in situ on the skeleton surface. The nano-carbon layer, as an excellent photothermal absorber, can increase the absorption rate of copper to near-infrared laser to more than 30%, improve the stability of the molten pool, and overcome physical metallurgical defects such as spheroidization and lack of fusion. At the same time, the Cu3P layer generated by electroplating greatly reduces the nucleation energy barrier of lithium on the copper surface (the overpotential drops to about 50 mV), which plays a role in chemically induced uniform deposition. High-precision SLM molding quality is the foundation for the complex framework to exert its physical function. The small pores on the positive electrode side form a robust physical barrier to inhibit lithium dendrite penetration, while the large pores on the negative electrode side provide sufficient volume expansion buffer space for the lithium deposition process. On this gradient physical structure, the chemical induction effect of the Cu3P coating is superimposed, realizing the dual role of macroscopic physical buffering and microscopic chemical guidance. Through the above synergistic design, the problems of current collector structure collapse and poor electrochemical stability in the background technology are solved, the growth of dead lithium and dendrites is inhibited, the cycle stability and safety of anode-free lithium metal batteries are improved, and the stringent requirements of next-generation high-energy batteries are met.

[0008] In one possible implementation, in step S1, the spherical copper powder has a particle size of 15–53 μm, a sphericity ≥95%, and the modified copper powder after coating has an absorption rate of ≥30% for near-infrared laser.

[0009] Compared with existing technologies, the above-mentioned technical solution can significantly improve the uniformity of powder spreading and melting efficiency. This embodiment ensures the fluidity of powder during the spreading process through the high sphericity and specific particle size distribution, reducing the gaps in the powder spreading. The nano-carbon layer, through its excellent photothermal conversion effect, breaks through the high reflectivity barrier of pure copper to infrared laser, increasing the laser absorption rate from less than 10% to more than 30%, further forming a stable molten pool dynamic behavior, suppressing the spheroidization and splashing phenomena commonly seen in SLM processing, ensuring the forming accuracy and density of the complex porous skeleton, and laying a solid micromaterial foundation for subsequent gradient control.

[0010] In one possible implementation, in step S2, the porosity of the low-porosity region is 10–40 μm, which is used to suppress lithium dendrite penetration; and the porosity of the high-porosity region is 35–150 μm, which is used to buffer the volume expansion during the lithium deposition process.

[0011] Compared with existing technologies, the above-mentioned technical solution enables more precise adaptation of the current collector to the extreme working environment of anode-free lithium metal batteries. This implementation not only utilizes the gradient difference between porosity and pore size, but also performs rigorous critical optimization on the physical boundaries of functional zones: the upper limit of the pore size in the small pore region near the positive electrode is strictly controlled within 40 μm, further increasing the critical threshold of the physical confinement of this region, greatly increasing the tortuosity of lithium dendrite growth, effectively blocking the sharp dendrites that abnormally protrude under high-rate charge and discharge, and completely eliminating the risk of them piercing the microporous membrane; and the lower limit of the pore size in the large pore region near the negative electrode is raised to 35 μm. Above μm, while ensuring three-dimensional connectivity, it reserves more ample absolute physical space for deposited metallic lithium, preventing premature pore blockage caused by excessive local lithium expansion during deep charge / discharge or large-capacity deposition, thus maintaining efficient electrolyte wetting during long cycles. Building upon the advantages of the gradient porous structure, it further maximizes the deformation resistance and cycle life of anode-free batteries, solving the problems of current collector microstructure collapse, pore failure, and battery short circuits under high current and long-cycle conditions, thereby extending the battery's service life.

[0012] In one possible implementation, in step S3, the ambient oxygen content of the partition scanning molding environment is ≤50ppm, and the substrate preheating temperature is 200–300℃; the parameter logic of the partition scanning molding is as follows: In the low porosity region, the scanning interval is 80–110 μm and the laser power is 300–400 W. In the high porosity region, the scanning spacing is 120–150 μm and the laser power is 200–300 W.

[0013] Compared with existing technologies, the above-mentioned technical solution can control the overlap rate and instantaneous temperature field of the molten pool by spatially differentiating the laser energy input: in the low porosity region, high energy density is used to achieve full melting and dense packing, while in the high porosity region, low energy density combined with large spacing induces the formation of controlled unfused pores; at the same time, the extremely low oxygen content and substrate preheating effectively reduce the oxidation tendency of copper and the internal stress during the forming process, thereby achieving consistency between model parameters and actual structure, ensuring that the porous copper current collector has both high specific surface area and excellent mechanical strength and electrical conductivity, and avoiding structural distortion caused by internal stress.

[0014] In one possible implementation, the partitioned scanning molding is a layered powder spreading molding, with each layer of powder spreading having a thickness of 20–50 μm, a laser scanning speed of 500–1500 mm / s, and the laser scanning paths of adjacent layers being perpendicular to each other.

[0015] Compared with existing technologies, the above-mentioned technical solution can significantly improve the three-dimensional structural stability and isotropy of porous copper skeleton. The present invention ensures that the laser energy can completely penetrate the current powder layer and form a good metallurgical bond with the previous layer by matching the powder thickness of 20–50 μm and the scanning speed of 500–1500 mm / s, thus avoiding interlayer non-fusion. The linear scanning strategy of rotating the scanning direction of adjacent layers by 90° effectively interrupts the continuous growth of columnar crystals along a single heat flow direction and homogenizes the anisotropic thermal stress generated during rapid cooling.

[0016] In one possible implementation, in step S4, the stress relief annealing is performed under argon protection at a temperature of 400–600°C for a holding time of 1–2 h.

[0017] Compared with existing technologies, the above-mentioned technical solution can significantly improve the comprehensive mechanical properties of the current collector and prevent high-temperature oxidation. The SLM additive manufacturing process is accompanied by extremely high temperature gradients and rapid solidification, which inevitably introduces a large amount of residual thermal stress into the porous copper. This embodiment promotes the diffusion of atoms and dislocation rearrangement in the copper matrix by holding the copper in a specific temperature range of 400–600℃, effectively eliminating residual stress and refining the grains. The argon atmosphere isolates oxygen and protects the porous copper with high specific surface area from oxidation at high temperatures. This significantly improves the flexibility and conductivity continuity of the porous copper current collector, enabling it to perfectly adapt to the repeated and drastic volume changes during the lithium metal deposition / stripping process without brittle fracture failure.

[0018] In one possible implementation, in step S4, the specific process of the electroplating method is as follows: using a 0.1–0.5 mol / L NaH2PO2 solution as the electroplating solution, at a concentration of 5–15 mA / cm²... 2 Electroplating was performed at a current density of 5–15 min, followed by heat treatment at 300 °C for 10–20 min in an argon atmosphere to allow the generated Cu3P to form a strong bond with the copper substrate.

[0019] Compared with existing technologies, the above technical solution utilizes a specific concentration of 0.1–0.5 mol / L NaH₂PO₂ solution and a concentration of 5–15 mA / cm². 2The mild electroplating conditions with a lower current density allow for precise control of the growth rate of the crystal nuclei, enabling phosphides to not only deposit on the outer surface of the current collector but also to penetrate deep into the three-dimensional interconnected pores for conformal coating. The subsequent 300℃ argon heat treatment promotes elemental interdiffusion at the interface between the coating and the porous copper substrate, forming a strong chemical bond and metallurgical bond. Ultimately, a uniform and highly adhesive Cu3P lithiophilic coating is formed on the porous copper surface, significantly reducing the lithium nucleation overpotential (from ~200 mV to ~50 mV).

[0020] Another technical problem to be solved by the present invention is to provide a porous copper current collector for anode-free lithium metal batteries, so as to solve the problem that the porous copper current collector in the prior art has a uniform pore structure and lacks lithium affinity, which leads to the inability to effectively buffer the volume change of lithium deposition / stripping during the cycling process of anode-free lithium metal batteries, and is prone to local polarization and severe lithium dendrite growth, which eventually punctures the separator and causes battery failure.

[0021] To overcome the shortcomings of the prior art, the present invention provides an anode-free lithium metal battery porous copper current collector, which is prepared by the method described above. The porous copper current collector includes a porous copper substrate and a Cu3P lithiophilic layer coated on the surface of the porous copper substrate.

[0022] This invention provides a porous copper current collector for anode-free lithium metal batteries. It replaces the existing single pure copper framework with uniform pores and unmodified surfaces with a composite current collector featuring a three-dimensional interconnected gradient pore structure and an in-situ conformal Cu3P lithiophilic coating on both inner and outer surfaces. The three-dimensional interconnected gradient pores achieve a synergistic effect of blocking and buffering in physical space, while the Cu3P lithiophilic coating on the surface provides highly active lithiophilic induction sites electrochemically. Utilizing this dual mechanism of physical confinement and chemical induction, the lithium nucleation overpotential is significantly reduced, inducing uniform lithium deposition. During deposition, lithium ions preferentially nucleate uniformly and grow layer by layer within the large pores with ample buffer space, while the small pores near the positive electrode form a robust physical barrier to inhibit lithium dendrite penetration. This solves the problems of short circuits and poor cycle stability caused by current collectors in the prior art, improving the safety and energy density of anode-free lithium metal batteries.

[0023] In one possible implementation, the porous copper current collector has a thickness of 50–550 μm and a lithium nucleation overpotential ≤55 mV.

[0024] The present invention also provides an application of the porous copper current collector in an anode-free lithium metal battery. When assembling the battery, the low porosity region of the porous copper current collector is arranged towards the positive electrode side of the battery, and the high porosity region is arranged towards the negative electrode side of the battery substrate.

[0025] Compared with existing technologies, the battery using this invention can maximize the physical confinement and volume buffering advantages of the gradient pore structure. During charge-discharge cycles, lithium ions are extracted from the positive electrode and deposited on the negative electrode side. By arranging the low porosity (small pore size) region towards the positive electrode side, its dense physical framework can effectively block and interrupt the vertical growth path of lithium dendrites. At the same time, by arranging the high porosity (large pore size) region towards the negative electrode side, the deposited metallic lithium can be mainly guided and stored in the ample pores of this region. This allows the huge volume changes during lithium deposition / stripping to be perfectly absorbed and buffered by the large pores at the bottom, without causing macroscopic deformation or even breakage of the entire current collector framework. This fundamentally prevents the risk of structural collapse and dendrite piercing the separator caused by volume expansion, ensuring the structural integrity of the battery during long-term cycling. Thus, it achieves extremely high capacity retention and excellent safety performance of the anode-free lithium metal battery under long-term cycling. Attached Figure Description

[0026] Figure 1 Microscopic images of the surface morphology of the low-porosity region of the porous copper current collector prepared in an embodiment of the present invention; Figure 2 Microscopic images of the surface morphology of the high-porosity region of the porous copper current collector prepared in an embodiment of the present invention. Detailed Implementation

[0027] First, those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0028] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0029] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0030] This invention provides an SLM additive manufacturing method for a porous copper current collector in an anode-free lithium metal battery, comprising the following steps: S1: Copper powder composite modification: Select gas-atomized spherical copper powder, mix it with nano carbon powder at a mass ratio of 100:(1–5), and keep it at 300–400℃ for 1–2 h in an inert gas atmosphere to make the nano carbon layer coat the surface of the copper powder, thereby obtaining modified copper powder to improve the laser absorption rate. S2: Gradient Porosity Digital Modeling: Design a porous structure model, which is divided into two regions along the thickness direction: a low porosity region near the positive electrode of the battery, with a porosity of 15%–60% and a pore size of 10–50 μm; and a high porosity region near the negative electrode of the battery, with a porosity of 60%–70% and a pore size of 20–150 μm, wherein the pore size of the region near the negative electrode of the battery is larger than that of the region near the positive electrode of the battery. S3: SLM partition molding: Modified copper powder is added to the SLM equipment, and partition scanning molding is performed according to the porous structure model. Porosity is controlled by adjusting the laser energy density of different regions to obtain a porous copper billet. S4: Post-processing and lithophile modification: The porous copper green billet is subjected to stress relief annealing, and then Cu3P lithophile coating is deposited in the internal pores and surface of the porous copper by electroplating to obtain the finished porous copper current collector.

[0031] In one possible implementation, in step S1, the spherical copper powder has a particle size of 15–53 μm, a sphericity ≥95%, and the modified copper powder after coating has an absorption rate of ≥30% for near-infrared laser.

[0032] In one possible implementation, in step S2, the porosity of the low-porosity region is 10–40 μm, which is used to suppress lithium dendrite penetration; and the porosity of the high-porosity region is 35–150 μm, which is used to buffer the volume expansion during the lithium deposition process.

[0033] In one possible implementation, in step S3, the ambient oxygen content of the partition scanning molding environment is ≤50ppm, and the substrate preheating temperature is 200–300℃; the parameter logic of the partition scanning molding is as follows: In the low porosity region, the scanning interval is 80–110 μm and the laser power is 300–400 W. In the high porosity region, the scanning spacing is 120–150 μm and the laser power is 200–300 W.

[0034] In one possible implementation, the partitioned scanning molding is a layered powder spreading molding, with each layer of powder spreading having a thickness of 20–50 μm, a laser scanning speed of 500–1500 mm / s, and the laser scanning paths of adjacent layers being perpendicular to each other.

[0035] In one possible implementation, in step S4, the stress relief annealing is performed under argon protection at a temperature of 400–600°C for a holding time of 1–2 h.

[0036] In one possible implementation, in step S4, the specific process of the electroplating method is as follows: using a 0.1–0.5 mol / L NaH2PO2 solution as the electroplating solution, at a concentration of 5–15 mA / cm²... 2 Electroplating was performed at a current density of 5–15 min, followed by heat treatment at 300 °C for 10–20 min in an argon atmosphere to allow the generated Cu3P to form a strong bond with the copper substrate.

[0037] The present invention provides a porous copper current collector for anode-free lithium metal batteries, which is prepared by the method described above. The porous copper current collector includes a porous copper substrate and a Cu3P lithiophilic layer coated on the surface of the porous copper substrate.

[0038] In one possible implementation, the porous copper current collector has a thickness of 50–550 μm and a lithium nucleation overpotential ≤55 mV.

[0039] The present invention also provides an application of the porous copper current collector in an anode-free lithium metal battery. When assembling the battery, the low porosity region of the porous copper current collector is arranged towards the positive electrode side of the battery, and the high porosity region is arranged towards the negative electrode side of the battery substrate.

[0040] The following are embodiments and comparative examples incorporating specific data to further illustrate the above-described technical solutions of the present invention: Example 1 This embodiment provides a porous copper current collector for anodeless lithium metal batteries and its SLM additive manufacturing method. The preparation method specifically includes the following steps: S1: Copper powder composite modification: Gas-atomized spherical copper powder was selected, with a particle size range of 15–38 μm, sphericity of 96%, and loose packing density of 4.8 g / cm³. 3 The etched copper powder and nano carbon powder were mixed at a mass ratio of 100:3 and kept at 350℃ for 1.5 h under an argon atmosphere to obtain modified copper powder with a nano carbon layer on the surface.

[0041] S2: Gradient Porosity Digital Modeling: Design a porous structure model with an overall thickness of 500 μm; the region near the positive electrode of the battery is designed with a porosity of 55% and a pore size of 15 μm; the region near the negative electrode of the battery is designed with a porosity of 65% and a pore size of 35 μm.

[0042] S3: SLM Partition Molding: Modified copper powder is added to the powder hopper of the SLM equipment. An oxygen-free copper substrate is selected and preheated to 250°C. High-purity argon gas is introduced into the molding cavity to ensure that the oxygen content is ≤30 ppm. Partition scanning molding is performed according to the model: for low porosity areas, a laser power of 350 W, a scanning speed of 800 mm / s, a scanning interval of 100 μm, and a powder thickness of 30 μm are used; for high porosity areas, a laser power of 250 W, a scanning speed of 1200 mm / s, a scanning interval of 130 μm, and a powder thickness of 30 μm are used. A linear scanning strategy is adopted, with each layer rotating 90° in the scanning direction to complete the layer molding and obtain a porous copper blank.

[0043] S4: Post-treatment and lithophile modification: After removing unmelted powder, the porous copper billet was placed in an argon atmosphere annealing furnace, held at 500℃ for 1.5 h, and cooled with the furnace; subsequently, a Cu3P lithophile coating was deposited by electroplating with a 0.3 mol / L NaH2PO2 solution and an electroplating current density of 10 mA / cm². 2 The electroplating time is 10 min, and after electroplating, it is kept at 300℃ for 15 min in an argon atmosphere.

[0044] The porous copper current collector prepared by the above method has a thickness of 500 μm and includes a porous copper substrate and a Cu3P lithiophilic layer uniformly covering the internal pores and surface of the porous copper substrate; it has a three-dimensionally interconnected gradient pore structure along the thickness direction, wherein the region near the positive electrode side of the battery (e.g.) Figure 1 (As shown) The porosity is 55% and the pore size is 15 μm; the region near the negative electrode side of the battery (such as...) Figure 2 (As shown) The porosity is 65% and the pore size is 35 μm.

[0045] Performance test results: Laser absorption rate increased to 35%, forming defect rate ≤5%; lithium nucleation overpotential decreased to 48mV; when applied to anode-free lithium metal batteries, capacity retention rate was ≥85% after 200 cycles at 1C rate.

[0046] Example 2 This embodiment provides a porous copper current collector for anodeless lithium metal batteries and its SLM additive manufacturing method. The preparation method specifically includes the following steps: S1: Copper powder composite modification: Gas-atomized spherical copper powder was selected, with a particle size range of 38–53 μm, sphericity of 95%, and loose packing density of 4.5 g / cm³. 3 Copper powder and nano-carbon powder were mixed at a mass ratio of 100:1 and kept at 300℃ for 2 h under an argon atmosphere to obtain modified copper powder.

[0047] S2: Gradient Porosity Digital Modeling: Design a porous structure model with an overall thickness of 500 μm; the region near the positive electrode of the battery is designed with a porosity of 50% and a pore size of 10 μm; the region near the negative electrode of the battery is designed with a porosity of 70% and a pore size of 50 μm.

[0048] S3: SLM partitioning: Use oxygen-free copper substrate and preheat to 200℃, oxygen content in the forming cavity ≤50 ppm; low porosity area uses laser power 400 W, scanning speed 500 mm / s, scanning spacing 80 μm, powder thickness 20 μm; high porosity area uses laser power 200 W, scanning speed 1500 mm / s, scanning spacing 150 μm, powder thickness 20 μm; rotate 90° in the scanning direction of each layer to obtain porous copper blank.

[0049] S4: Post-treatment and lithophile modification: The porous copper billet was placed in an argon atmosphere annealing furnace and held at 400℃ for 2 h before being cooled in the furnace; subsequently, a Cu3P lithophile coating was deposited by electroplating in a 0.1 mol / L NaH2PO2 solution at a current density of 5 mA / cm². 2 Electroplating time 15 min, heat treatment at 300℃ for 20 min.

[0050] The current collector structure obtained: A porous copper current collector was obtained by the above method. The porous copper current collector has a thickness of 500 μm and includes a porous copper substrate and a Cu3P lithiophilic layer coated on its surface. It is divided into two regions along the thickness direction. The region near the positive electrode of the battery has a porosity of 50% and a pore size of 10 μm. The region near the negative electrode of the battery has a porosity of 70% and a pore size of 50 μm.

[0051] Performance test results: molding defect rate ≤8%, lithium nucleation overpotential reduced to 52 mV; applied to anode-free lithium metal batteries, capacity retention ≥82% after 200 cycles at 1 C rate.

[0052] Example 3 This embodiment provides a porous copper current collector for anodeless lithium metal batteries and its SLM additive manufacturing method. The preparation method specifically includes the following steps: S1: Copper powder composite modification: Gas-atomized spherical copper powder was selected, with a particle size range of 15–53 μm, sphericity of 97%, and loose packing density of 5.0 g / cm³. 3 Copper powder and nano-carbon powder were mixed at a mass ratio of 100:5 and kept at 400℃ for 1 h under an argon atmosphere to obtain modified copper powder.

[0053] S2: Gradient Porosity Digital Modeling: Design a porous structure model with an overall thickness of 500 μm; the region near the positive electrode of the battery is designed with a porosity of 30% and a pore size of 20 μm; the region near the negative electrode of the battery is designed with a porosity of 60% and a pore size of 80 μm.

[0054] S3: SLM zone forming: Select oxygen-free copper substrate and preheat to 300℃, oxygen content ≤20 ppm; use laser power of 380 W, scanning speed of 800 mm / s, scanning spacing of 90 μm, and powder thickness of 50 μm in low porosity area; use laser power of 300 W, scanning speed of 1000 mm / s, scanning spacing of 120 μm, and powder thickness of 50 μm in high porosity area to obtain porous copper blank.

[0055] S4: Post-treatment and lithophilic modification: Placed in an annealing furnace at 600℃ for 1 h and cooled with the furnace; Cu3P lithophilic coating was deposited by electroplating in a 0.5 mol / L NaH2PO2 solution at a current density of 15 mA / cm². 2 Electroplating time: 5 min; heat treatment at 300℃ for 10 min.

[0056] The current collector structure obtained: A porous copper current collector was obtained by the above method. The porous copper current collector has a thickness of 500 μm and includes a porous copper substrate and a Cu3P lithiophilic layer coated on its surface. The porosity of the region near the positive electrode of the battery is 30% and the pore size is 20 μm. The porosity of the region near the negative electrode of the battery is 60% and the pore size is 80 μm.

[0057] Performance test results: molding defect rate ≤3%, lithium nucleation overpotential reduced to 45 mV; applied to anode-free lithium metal batteries, capacity retention ≥88% after 200 cycles at 1 C rate.

[0058] Example 4 This embodiment provides a porous copper current collector for anodeless lithium metal batteries and its SLM additive manufacturing method. The preparation method specifically includes the following steps: S1: Copper powder composite modification: Gas-atomized spherical copper powder with a particle size range of 20–45 μm and a sphericity of 96% was selected; copper powder and nano carbon powder were mixed at a mass ratio of 100:2 and kept at 380℃ for 1.5 h under an argon atmosphere to obtain modified copper powder.

[0059] S2: Gradient Porosity Digital Modeling: Design a porous structure model with an overall thickness of 550 μm; the region near the positive electrode of the battery is designed with a porosity of 15% and a pore size of 10 μm; the region near the negative electrode of the battery is designed with a porosity of 65% and a pore size of 150 μm.

[0060] S3: SLM zone molding: an oxygen-free copper substrate is selected and preheated to 280℃, with an oxygen content ≤20 ppm in the molding cavity; the low porosity region uses the highest densification parameters: laser power 400 W, scanning speed 500 mm / s, scanning spacing 80 μm, and powder thickness 20 μm; the high porosity region uses laser power 250 W, scanning speed 1200 mm / s, scanning spacing 140 μm, and powder thickness 20 μm; a porous copper green blank is obtained.

[0061] S4: Post-treatment and lithophilic modification: The green billet was placed in an argon atmosphere annealing furnace and held at 550℃ for 1.5 h before being cooled in the furnace; a Cu3P lithophilic coating was deposited using a 0.2 mol / L NaH2PO2 solution at a current density of 8 mA / cm². 2 Electroplating time 12 min, heat treatment at 300℃ for 15 min.

[0062] The current collector structure obtained: A porous copper current collector was obtained by the above method. The porous copper current collector has a thickness of 550 μm and includes a porous copper substrate and a Cu3P lithiophilic layer coated on its surface. The region near the positive electrode of the battery exhibits a highly dense porous state with a porosity of 15% and a pore size of 10 μm. The region near the negative electrode of the battery has a porosity of 65% and a pore size of 150 μm.

[0063] Performance test results: Although the extremely low porosity of the positive electrode side enhances the physical barrier ability, the small specific surface area leads to a higher local real current density, and the lithium nucleation overpotential rises to 54 mV; when applied to anode-free lithium metal batteries, the capacity retention rate is 81% after 200 cycles at 1C rate.

[0064] Examples 1-4 further demonstrate that the additive manufacturing method and the porous copper current collector proposed in this invention can achieve precise adaptation to the harsh working environment of anode-free lithium metal batteries and obtain excellent comprehensive electrochemical performance. The data performance of each example fully confirms the scientific nature of the multi-dimensional synergistic mechanism of this invention: In this invention, the pre-modification of nano-carbon composites effectively breaks the physical barrier of high infrared laser reflectivity of pure copper powder, laying the material foundation for high-quality SLM molding of complex topological structures; the three-dimensional interconnected gradient pores constructed by digital layered regulation achieve a balance between blocking and buffering in physical space; the low porosity and small pore size region on the positive electrode side specially designed in this invention constructs a robust physical confinement barrier, delaying and blocking the penetration of lithium dendrites, while the high porosity and large pore size region on the negative electrode side utilizes its ample internal voids to completely absorb and alleviate the huge volume expansion stress caused by repeated deposition and stripping of metallic lithium; at the same time, the Cu3P lithiophilic layer in situ conformally coated on the inner and outer surfaces plays a strong electrochemical induction role, significantly reducing the lithium nucleation overpotential and guiding the uniform nucleation of lithium ions. The deep coupling between the aforementioned macroscopic physical structure gradient and the microscopic chemical in-situ induced by the above-mentioned deep coupling endows the porous copper skeleton in the structure with extremely high mechanical stability, overcomes the industry problem that existing anode-free batteries are prone to short circuit failure due to dendrite piercing the separator and the collapse of the current collector skeleton, improves the battery's long cycle life and safety performance, and has extremely high commercial application prospects.

[0065] In the description of the embodiments of the present invention, it should be noted that the terms "inner" and "outer" and other terms indicating the direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention.

[0066] In the description of this invention, the references to "one embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0067] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for SLM additive manufacturing of a porous copper current collector for anode-free lithium metal batteries, characterized in that, Includes the following steps: S1: Copper powder composite modification: Select gas-atomized spherical copper powder, mix it with nano carbon powder at a mass ratio of 100:(1–5), and keep it at 300–400℃ for 1–2 h in an inert gas atmosphere to make the nano carbon layer coat the surface of the copper powder, thereby obtaining modified copper powder to improve the laser absorption rate. S2: Gradient Porosity Digital Modeling: Design a porous structure model, which is divided into two regions along the thickness direction: a low porosity region near the positive electrode of the battery, with a porosity of 15%–60% and a pore size of 10–50 μm; and a high porosity region near the negative electrode of the battery, with a porosity of 60%–70% and a pore size of 20–150 μm, wherein the pore size of the region near the negative electrode of the battery is larger than that of the region near the positive electrode of the battery. S3: SLM partition molding: Modified copper powder is added to the SLM equipment, and partition scanning molding is performed according to the porous structure model. Porosity is controlled by adjusting the laser energy density of different regions to obtain a porous copper billet. S4: Post-processing and lithophile modification: The porous copper green billet is subjected to stress relief annealing, and then Cu3P lithophile coating is deposited in the internal pores and surface of the porous copper by electroplating to obtain the finished porous copper current collector.

2. The method according to claim 1, characterized in that: In step S1, the spherical copper powder has a particle size of 15–53 μm, a sphericity of ≥95%, and the modified copper powder after coating has an absorption rate of ≥30% for near-infrared laser.

3. The method according to claim 1, characterized in that: In step S2, the porosity of the low-porosity region is 10–40 μm, which is used to suppress lithium dendrite penetration; the porosity of the high-porosity region is 35–150 μm, which is used to buffer the volume expansion during lithium deposition.

4. The method according to claim 1, characterized in that: In step S3, the ambient oxygen content of the partition scanning molding environment is ≤50 ppm, the substrate preheating temperature is 200–300℃, and the parameter logic of the partition scanning molding is as follows: In the low porosity region, the scanning interval is 80–110 μm and the laser power is 300–400 W. In the high porosity region, the scanning spacing is 120–150 μm and the laser power is 200–300 W.

5. The method according to claim 4, characterized in that: The partitioned scanning molding is a layered powder spreading molding, with each layer of powder spreading having a thickness of 20–50 μm, a laser scanning speed of 500–1500 mm / s, and the laser scanning paths of adjacent layers being perpendicular to each other.

6. The method according to claim 1, characterized in that: In step S4, the stress relief annealing is carried out under argon protection at a temperature of 400–600℃ for 1–2 hours.

7. The method according to claim 1, characterized in that: In step S4, the specific process of the electroplating method is as follows: using a 0.1–0.5 mol / L NaH2PO2 solution as the electroplating solution, at a concentration of 5–15 mA / cm²... 2 Electroplating was performed at a current density of 5–15 min, followed by heat treatment at 300 °C for 10–20 min in an argon atmosphere to allow the generated Cu3P to form a strong bond with the copper substrate.

8. A porous copper current collector for anode-free lithium metal batteries, characterized in that, It is prepared by the method according to any one of claims 1-7, wherein the porous copper current collector includes a porous copper substrate and a Cu3P lithiophilic layer coated on the surface of the porous copper substrate.

9. The porous copper current collector for anode-free lithium metal batteries according to claim 8, characterized in that: The thickness of the porous copper current collector is 50–550 μm, and its lithium nucleation overpotential is ≤55 mV.

10. The application of the porous copper current collector for anode-free lithium metal batteries according to any one of claims 8-9 in anode-free lithium metal batteries, characterized in that: When assembling the battery, the low porosity region of the porous copper current collector is arranged towards the positive electrode side of the battery, and the high porosity region is arranged towards the negative electrode side of the battery substrate.

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