Current collector and preparation method and application thereof

Abstract

The invention relates to the field of batteries, in particular to a current collector and a preparation method and application thereof. The current collector comprises a groove current collector substrate, wherein at least one surface of the groove current collector substrate is provided with a regularly arranged groove array; the lithium-loving nano-particles are fixed in the grooves in an in-situ deposition manner; and the composite carbon layer is laminated and attached to the surface of the groove current collector substrate provided with the groove array. According to the current collector, through the collaborative design of the groove current collector, the lithium-loving nano particles and the composite carbon layer, the battery performance is comprehensively improved: the groove structure and the composite carbon layer jointly inhibit the growth of lithium dendrites and the agglomeration of active substances, effectively accommodate the volume change and ensure the interface stability; meanwhile, the lithium-loving nano-particles guide lithium to be uniformly deposited, and the rigid carbon cloth framework provides excellent mechanical strength, so that the current collector can still keep a complete structure when bearing high pressure in the battery, and the cycle life and the safety of the negative-electrode-free battery are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more specifically, to a current collector, its preparation method, and its application. Background Technology

[0002] With the increasing demand for high-energy-density energy storage devices, electrodeless lithium metal batteries have attracted much attention due to their ability to significantly improve battery energy density and simplify manufacturing processes. However, the core challenge facing this system is that lithium metal undergoes significant volume changes during deposition / stripping and is prone to forming lithium dendrites, leading to rapid performance degradation and even internal short circuits.

[0003] To address these challenges, existing technologies have proposed various solutions involving the introduction of lithium-friendly metals or three-dimensional structures on the negative electrode current collector side, but all of these solutions have significant drawbacks: The first type of technical solution employs composite three-dimensional current collectors, such as in-situ formation of silver-modified copper nanowires and carbon nanomaterials within polymer foam. However, the metal particles in this type of structure are prone to migration and aggregation during cycling, forming large-sized particles, which increases the risk of dendrites piercing the separator. Simultaneously, the mechanical strength of the three-dimensional carbon-based framework is typically insufficient, making it susceptible to structural collapse under battery testing pressure and cycling volume changes, thus accelerating battery performance degradation.

[0004] The second type of technical solution focuses on constructing three-dimensional porous metal / lithophile metal composite gradient current collectors to increase specific surface area and reduce lithium deposition overpotential. However, these porous structures made of stacked nanowires are difficult to prepare on a large scale, and their porosity will decrease significantly under the high pressure required by solid-state battery systems, failing to effectively alleviate the volume expansion of the battery.

[0005] The third type of technical solution increases the contact area and conductivity by coating the current collector surface with conductive layers such as carbon nanotubes. However, the combination of pure carbon materials and solid current collectors makes it difficult to effectively control the local current density, the interfacial lithium affinity is still poor, and it is impossible to effectively suppress the volume change of the battery during cycling, resulting in insufficient structural stability.

[0006] In summary, the current technical challenges in the industry are as follows: while simply introducing a carbon layer and lithiophilic metal onto the current collector can optimize lithium deposition and suppress dendrite formation to some extent, it cannot solve the problem of significant volume expansion. Furthermore, while employing a high-porosity three-dimensional porous structure can accommodate volume changes, its mechanical strength deteriorates significantly under high pressure (especially in solid-state batteries), leading to decreased porosity and structural failure. Therefore, developing a current collector structure that combines excellent mechanical strength, effective volume expansion management, and durable lithiophilic interface stability is crucial for driving the development of electrodeless lithium metal batteries, especially electrodeless all-solid-state batteries.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] To suppress the migration, agglomeration, and dendrite growth of lithium-loving metal particles during cycling, alleviate the volume expansion stress caused by lithium deposition / stripping, and prevent functional structure failure, improve the bonding strength between lithium metal and the current collector interface, and reduce the accumulation of "dead lithium", this invention provides a current collector, its preparation method, and its application.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: One aspect of the present invention relates to a current collector comprising: A grooved current collector substrate, wherein at least one surface is provided with a regularly arranged array of grooves; Lithophilic nanoparticles, wherein the lithophilic nanoparticles are fixed in the groove by in-situ deposition; And a composite carbon layer, wherein the composite carbon layer is laminated and bonded to the surface of the groove current collector substrate having the groove array.

[0010] The aforementioned current collector, through the synergistic design of "grooved current collector - lithium-affinity nanoparticles - composite carbon layer", comprehensively improves battery performance: the groove structure and composite carbon layer jointly suppress lithium dendrite growth and active material aggregation, and effectively accommodate volume changes to ensure interface stability; at the same time, the lithium-affinity nanoparticles guide uniform lithium deposition, while the rigid carbon cloth skeleton provides excellent mechanical strength, enabling the current collector to maintain structural integrity even when subjected to high internal pressure of the battery, thereby significantly improving the cycle life and safety of the negative electrodeless battery.

[0011] Another aspect of the present invention relates to a method for preparing the aforementioned current collector, comprising the following steps: A grooved current collector matrix is ​​obtained by forming a regularly arranged array of grooves on the surface of a metal substrate. Lithophilic nanoparticles are deposited within the groove; Conductive carbon material and binder are coated onto porous carbon cloth to form a composite carbon layer; The composite carbon layer is combined with the surface of a grooved current collector substrate on which the lithium-loving nanoparticles are deposited.

[0012] This preparation method is simple and easy to implement: a regular groove array can be precisely and efficiently fabricated through laser etching; firmly bonded and uniformly distributed lithium-loving nanoparticles are formed in situ within the grooves using electrodeposition, sputtering, evaporation, spin coating, vapor deposition, or atomic layer deposition (ALD); and a functional interface layer with both high strength and high conductivity is successfully constructed by combining a conductive paste with porous carbon cloth and then roll-pressing it. This method has clear steps, good compatibility with traditional battery processes, and provides a reliable pathway for the large-scale manufacturing of high-performance electrodeless batteries.

[0013] Another aspect of the invention relates to a negative electrode-free lithium metal battery, comprising the aforementioned current collector.

[0014] The three-dimensional grooved current collector composite carbon layer structure provided by this invention brings the following significant benefits to negative electrode-free lithium metal batteries: 1. Effectively inhibits the aggregation of active substances. The groove structure reduces the migration activation energy of lithium-loving metal particles such as silver through its steric hindrance effect, thereby significantly inhibiting their migration and aggregation during cycling and making the particle size distribution more concentrated after cycling.

[0015] The rigid carbon cloth skeleton in the composite carbon layer and the carbon paste filling the pores together provide physical constraints and a highly conductive network, which not only improves the surface diffusion coefficient of silver particles, but also enhances the contact between the current collector and the electrolyte interface, thus jointly promoting the uniform deposition of lithium and the stable dispersion of silver particles.

[0016] 2. Significantly enhances the current collector structure The locally grooved metal foil current collector used in this structure has higher mechanical rigidity compared to traditional high-porosity three-dimensional structures. It is less prone to deformation and porosity decay in high-pressure battery environments, while maintaining excellent tensile strength and facilitating mechanized winding processing.

[0017] Composite carbon layers (carbon cloth and carbon paste) have a higher Young's modulus than single carbon cloth, can withstand greater mechanical stress, and ensure the long-term stability of the structure while protecting the interface and preventing lithium dendrite piercing.

[0018] 3. Optimize the electrode-electrolyte interface The introduction of porous carbon layers and binders greatly increases the contact area and adhesion between the current collector and the electrolyte, ensuring that the interface contact remains good during repeated expansion and contraction of the battery.

[0019] The concave structure on the current collector provides a buffer space for volume changes, further suppressing the overall expansion and contraction stress of the battery.

[0020] In summary, this invention ensures the intrinsic strength and processability of the structure by retaining the metal foil substrate; it provides space for accommodating lithium metal and suppressing volume expansion by constructing a groove array on its surface; it guides the uniform deposition of lithium by introducing lithium-affinity nanoparticles within the grooves and suppresses their aggregation by utilizing the spatial confinement effect; finally, it solves the problems of poor affinity and uneven conductivity at the metal current collector interface by laminating a conductive carbon layer containing a binder on the surface. The synergistic effect of the above components collectively achieves a significant improvement in battery cycle stability. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the current collector structure provided in an embodiment of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0024] One aspect of the present invention relates to a current collector, such as Figure 1 As shown, it includes: A grooved current collector substrate, wherein at least one surface is provided with a regularly arranged array of grooves; Lithophilic nanoparticles, wherein the lithophilic nanoparticles are fixed in the groove by in-situ deposition; And a composite carbon layer, wherein the composite carbon layer is laminated and bonded to the surface of the groove current collector substrate having the groove array.

[0025] This invention improves the overall performance of the battery through the following three synergistic mechanisms: I. Aggregation Inhibition: The groove structure reduces the migration activation energy of silver particles through the steric hindrance effect. After multiple cycles, the standard deviation of particle size distribution decreases, which significantly inhibits particle aggregation.

[0026] Rigid carbon cloth, which combines carbon particles and binder to fill pores, provides physical constraint and high conductivity, improves the surface diffusion coefficient of silver particles, enhances the interfacial contact between the porous current collector and the electrolyte, and promotes uniform lithium deposition and dispersed silver distribution.

[0027] II. Structural Reinforcement: Some porous current collectors are more rigid than three-dimensional porous structures and will not deform under high pressure, thus reducing the porosity of the structure. They also have good tensile strength, making them easy to process into rolls by machinery.

[0028] The composite carbon layer (carbon cloth + carbon paste) has a higher Young's modulus than the simple carbon cloth, can withstand higher mechanical stress, and can protect the interface to inhibit dendrite penetration.

[0029] III. Interface Optimization: The introduction of porous carbon layers and binders increases the contact area and adhesion at the interface, ensuring good contact throughout the battery's expansion and contraction. Simultaneously, the concave pores in the current collector further suppress battery expansion and contraction.

[0030] In summary, retaining the metal foil current collector provides structural strength and processability, while creating pores within it to accommodate lithium metal suppresses battery volume expansion. Furthermore, introducing lithium-affinity metal particles into the pores promotes uniform lithium deposition within the pits, and the spatial effect of the pores inhibits the continuous aggregation of lithium-affinity metals during cycling. Due to the poor interfacial affinity between the metal foil current collector and the electrolyte, and the uneven conductivity distribution after pore creation, adding a conductive layer containing a binder to the surface improves interfacial affinity and conductivity, synergistically enhancing battery cycle stability.

[0031] Furthermore, the composite carbon layer comprises: porous carbon cloth and conductive carbon material and binder distributed on the porous carbon cloth.

[0032] This invention does not specifically limit the type of adhesive; any conventional adhesive in the art can be used to implement this invention.

[0033] Furthermore, the porosity of the porous carbon cloth is 4% to 80% (for example, it can be any one of 4%, 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80% or any range between two), and the pore size is 1 to 10 μm (for example, it can be any one of 1 μm, 3 μm, 5 μm, 7 μm, 9 μm or 10 μm or any range between two).

[0034] Furthermore, the conductive carbon material includes, but is not limited to, carbon nanotubes and / or graphene.

[0035] Furthermore, the thickness of the composite carbon layer is 3~20μm, including but not limited to a point value of any one of 3μm, 5μm, 10μm, 15μm or 20μm or a range between any two.

[0036] Furthermore, the groove array includes: an axisymmetric regular polygon array or a circular array.

[0037] Furthermore, the groove array includes a hexagonal honeycomb array.

[0038] Furthermore, the depth of the groove is 0.8~1.2μm (for example, it can be any one of 0.8μm, 1.0μm or 1.2μm or a range between any two), and the diameter of the inscribed circle of the groove is 4.5~5.5μm (for example, it can be any one of 4.5μm, 4.7μm, 4.9μm, 5.1μm, 5.3μm or 5.5μm or a range between any two).

[0039] Furthermore, the particle size of the lithium-loving nanoparticles is 10~100nm, including but not limited to the point value of any one of 10nm, 20nm, 40nm, 50nm, 70nm, 80nm, 90nm or 100nm or the range between any two.

[0040] Furthermore, the material of the lithium-loving nanoparticles includes at least one of magnesium, zinc, indium, silicon, silver, aluminum, or tin.

[0041] During battery assembly, the composite carbon layer and the grooved current collector are placed sequentially on the negative electrode side, with the composite carbon layer in contact with the electrolyte layer. The stacking process can be simplified by premixing the two layers through roll forming.

[0042] Another aspect of the present invention relates to a method for preparing the aforementioned current collector, comprising the following steps: A grooved current collector matrix is ​​obtained by forming a regularly arranged array of grooves on the surface of a metal substrate. Lithophilic nanoparticles are deposited within the groove; Conductive carbon material and binder are coated onto porous carbon cloth to form a composite carbon layer; The composite carbon layer is combined with the surface of a grooved current collector substrate on which the lithium-loving nanoparticles are deposited.

[0043] The aforementioned preparation method is simple and easy to implement: Regular groove arrays can be precisely and efficiently fabricated through laser etching; electrodeposition, sputtering, evaporation, spin coating, vapor deposition, or atomic layer deposition (ALD) can all form firmly bonded and uniformly distributed lithium-loving nanoparticles in situ within the grooves; by combining conductive paste with porous carbon cloth and roll-pressing the composite, a functional interface layer with both high strength and high conductivity is successfully constructed. This method has clear steps, good compatibility with traditional battery processes, and provides a reliable pathway for the large-scale manufacturing of high-performance electrodeless batteries.

[0044] Furthermore, the metal substrate includes, but is not limited to, at least one of: copper foil, carbon-coated copper foil, aluminum foil, or stainless steel foil.

[0045] This invention does not specifically limit the method for forming a regularly arranged array of grooves on the surface of a metal substrate; conventional methods in the art can be used to implement this invention. In some specific embodiments, laser etching can be used to prepare the groove array.

[0046] This invention does not specifically limit the deposition method of lithium-loving nanoparticles; conventional deposition methods in the art can be used to implement this invention.

[0047] Another aspect of the invention relates to a negative electrode-free lithium metal battery, comprising the aforementioned current collector.

[0048] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0049] Example 1 Preparation steps: Copper foil pretreatment: 10μm thick copper foil is ultrasonically cleaned in 1% dilute sulfuric acid and laser etched to form a hexagonal groove array with a depth of 1μm and a side length of 5μm. Silver particle deposition: Pulsed electrodeposition method was used (peak current density 5 mA / cm²). 2 (with a duty cycle of 30%), silver particles with a diameter of 25 nm are generated in the groove; Composite carbon layer: Carbon nanotubes (20nm in diameter) and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 9:1 to form a slurry, which was then coated on the two surfaces of a porous carbon cloth with a porosity of 60% to obtain a composite carbon layer with a thickness of 5μm. The composite carbon layer is pre-composite with a concave copper foil with deposited silver particles by roll pressing to form a functional three-dimensional porous current collector.

[0050] Example 2 The only difference from Example 1 is that In particles are deposited in the groove.

[0051] Example 3 The only difference from Example 1 is that the porosity of the porous carbon cloth is 80%.

[0052] Example 4 The only difference from Example 1 is that the thickness of the composite carbon layer is 20 μm.

[0053] Comparative Example 1 Bright copper foil.

[0054] Comparative Example 2 The only difference from Example 1 is that the copper foil was not pretreated.

[0055] Comparative Example 3 The only difference from Example 1 is that no silver particles were deposited in the groove.

[0056] Comparative Example 4 The only difference from Example 1 is that there is no composite carbon layer.

[0057] Battery assembly method Using Li6PS5Cl as the solid electrolyte, the solid electrolyte sheet and the aforementioned functional three-dimensional porous current collector are placed in a mold battery in a glove box. A ternary composite positive electrode material is added to the other side of the electrolyte, and the battery is pressed under a pressure of 300 MPa to obtain a negative electrode-free all-solid-state battery. This method can also be used in liquid negative electrode-free batteries. The functional three-dimensional porous current collector serves as the negative electrode, and a separator and positive electrode sheet are added. After adding electrolyte, the battery is encapsulated to obtain a negative electrode-free liquid battery.

[0058] This three-dimensional porous current collector can also be used as a current collector base film. By covering its surface with negative electrode materials such as graphite, silicon, and lithium metal, it can promote the interfacial contact of the negative electrode, suppress volume expansion, and reduce the total weight of the negative electrode.

[0059] Battery testing methods The positive electrode capacity is 2mAh. The test pressure for assembling coin cells in a liquid battery or mold cells in a solid-state battery is 25MPa. The charge / discharge voltage window is 2.5-4.25V. The cells are first charged and discharged at 0.1C for 2 cycles, then charged and discharged at 1C for 100 cycles. The coulombic efficiency of the first 0.1C cycle and the capacity retention rate after 100 1C cycles are recorded, as shown in Table 1. A solid-state mold testing device with a pressure sensor is used to test and calculate the battery expansion rate.

[0060] Table 1. Cycle performance of the mold battery after 100 cycles

[0061] As shown in Table 1, the use of the functional three-dimensional porous current collector prepared in this application can significantly improve the cycle performance of the battery. This is attributed to the combined effects of the uniform regulation of lithium deposition by the lithium-loving metal, the suppression of volume change and lithium-loving metal agglomeration by the artificial pores, the improvement of interfacial contact and optimization of interfacial electronic conduction by the carbon coating, and the suppression of dendrite penetration.

[0062] First-round coulomb efficiency: The three-dimensional porous structure and lithium-loving metal particles provide abundant nucleation sites, guiding the uniform deposition of lithium metal and reducing side reactions with the electrolyte and the formation of dead lithium. Therefore, the first-round efficiency is significantly higher than that of bright copper foil.

[0063] Expansion rate after 100 cycles: The grooves on the copper foil provide space for lithium deposition, and the composite carbon layer has good mechanical strength and toughness, which can effectively restrain the volume expansion during the lithium deposition process.

[0064] Capacity retention after 100 cycles: Lithophile metal guides uniform deposition, grooves suppress particle agglomeration and volume change, and composite carbon layer optimizes interface contact and suppresses dendrites. The three work together to ensure excellent cycling stability.

[0065] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A current collector, characterized in that, include: A grooved current collector substrate, wherein at least one surface is provided with a regularly arranged array of grooves; Lithophilic nanoparticles, wherein the lithophilic nanoparticles are fixed in the groove by in-situ deposition; And a composite carbon layer, wherein the composite carbon layer is laminated and bonded to the surface of the groove current collector substrate having the groove array.

2. The current collector according to claim 1, characterized in that, The composite carbon layer includes: porous carbon cloth and conductive carbon material and binder distributed on the porous carbon cloth.

3. The current collector according to claim 2, characterized in that, The porous carbon cloth has a porosity of 4% to 80% and a pore size of 1 to 10 μm.

4. The current collector according to claim 2, characterized in that, The conductive carbon material includes carbon nanotubes and / or graphene.

5. The current collector according to claim 1, characterized in that, The thickness of the composite carbon layer is 3~20μm.

6. The current collector according to claim 1, characterized in that, The groove array includes: an axisymmetric regular polygon array or a circular array.

7. The current collector according to claim 1, characterized in that, The groove has a depth of 0.8~1.2μm and an inscribed circle diameter of 4.5~5.5μm.

8. The current collector according to claim 1, characterized in that, The particle size of the lithium-loving nanoparticles is 10~100nm; And / or, the material of the lithium-loving nanoparticles includes at least one of magnesium, zinc, indium, silicon, silver, aluminum or tin.

9. The method for preparing a current collector according to any one of claims 1 to 8, characterized in that, Includes the following steps: A grooved current collector matrix is ​​obtained by forming a regularly arranged array of grooves on the surface of a metal substrate. Lithophilic nanoparticles are deposited within the groove; Conductive carbon material and binder are coated onto porous carbon cloth to form a composite carbon layer; The composite carbon layer is combined with the surface of a grooved current collector substrate on which the lithium-loving nanoparticles are deposited.

10. A negative electrode-free lithium metal battery, characterized in that, Includes the current collector as described in any one of claims 1 to 8.

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