A zinc metal negative electrode with defect region selective carbon nanoplague modification and a preparation method and application thereof

Abstract

The application relates to the technical field of battery material preparation, and discloses a zinc metal negative electrode selectively modified by carbon nanometer patches in defect regions and a preparation method and application thereof, the preparation method comprising the following steps: performing mechanical polishing or polishing pretreatment on a zinc metal substrate, adopting a carbon-containing flame to perform flame deposition treatment on the substrate, so that carbon nanometer particles are deposited on the surface; after cooling, weakly-attached particles are removed through cleaning, so that the carbon nanometer particles are selectively retained in the defect-rich area on the surface of the substrate; and after drying, the modified zinc metal negative electrode is obtained. The obtained modified zinc metal negative electrode comprises a zinc metal substrate, carbon nanometer particles are distributed in the defect-rich area on the surface of the substrate, and the carbon nanometer particles exist in the form of non-continuous local carbon nanometer patches. The modified zinc metal negative electrode is applied to a water-based zinc ion battery, can effectively stabilize the zinc negative electrode interface, and improves the cycle stability of the battery.

Description

Technical Field

[0001] This invention belongs to the field of battery material preparation technology, and particularly relates to the preparation of zinc metal anodes, specifically a zinc metal anode with selective carbon nanoparticle patch modification of defect areas, its preparation method and application. Background Technology

[0002] Aqueous zinc-ion batteries possess advantages such as high safety, low cost, environmental friendliness, and abundant zinc resources, making them promising candidates for large-scale energy storage. Zinc metal anodes, with their high theoretical capacity and low redox potential, are commonly used anode materials in aqueous zinc-ion batteries.

[0003] However, zinc metal anodes commonly suffer from interfacial instability in aqueous electrolytes. During rolling, cutting, grinding, and storage, the surface of the zinc anode is prone to the introduction of defect-rich regions such as grooves, depressions, scratches, localized protrusions, grain boundaries, and processing damage areas. During charge and discharge, these defective regions can induce localized electric field concentration and Zn... 2+ Uneven flux distribution induces non-uniform zinc deposition and zinc dendrite growth, while exacerbating hydrogen evolution reaction, corrosion reaction and by-product accumulation, ultimately leading to increased polarization voltage, decreased coulombic efficiency and shortened cycle life, and in severe cases even causing diaphragm puncture and battery short circuit.

[0004] To improve the interfacial stability of zinc anodes, various strategies have been proposed in existing technologies, including inorganic coatings, organic polymer coatings, carbon material coatings, alloying, and heat treatment. Among these, carbon materials have attracted much attention due to their combination of good conductivity, chemical stability, and cost advantages. However, conventional continuous carbon coatings or uniform carbon black coatings typically cover the entire zinc surface, which may not only increase interfacial transport impedance but also make it difficult to precisely control local defects such as micron-level grooves, depressions, and scratches on the zinc foil surface. Furthermore, if the coating adhesion is insufficient, it is prone to detachment during battery assembly or cycling; while if the coating is too thick, it will affect zinc ion transport and sacrifice electrode energy density.

[0005] There is an urgent need to develop a method for preparing a negative electrode that is simple to operate, low in cost, and capable of selectively modifying defect-rich areas on the zinc metal surface. This would effectively suppress zinc dendrites and side reactions while avoiding the formation of a continuous thick coating, thereby significantly improving the cycle stability of aqueous zinc-ion batteries. Summary of the Invention

[0006] In order to address the problems in the prior art where carbon coatings are usually in the form of full coverage, making it difficult to precisely control the micron-level defect areas on the surface of zinc anodes, and the problems of increased interfacial transport impedance, insufficient adhesion leading to easy detachment, or excessive coating thickness affecting ion transport and energy density, this invention provides a zinc metal anode with selective carbon nanoparticle modification of defect areas, its preparation method, and its application.

[0007] This invention is achieved using the following technical solution: This invention provides a method for preparing a zinc metal anode with selective carbon nanoparticle patch modification in defect areas, comprising the following steps: S1, Preprocessing Take the zinc metal substrate raw material and mechanically grind or polish it to remove surface contaminants and oxide layers. Then clean and dry it to prepare it as a pretreated zinc metal substrate for later use.

[0008] The zinc metal substrate raw materials are zinc foil, zinc sheet, zinc plate, zinc mesh, zinc powder sheet, zinc alloy foil, zinc alloy sheet or composite substrate containing zinc metal layer.

[0009] S2, Flame Deposition Processing A carbon-containing flame is used to perform flame deposition treatment on the pretreated zinc metal substrate for 5s to 10min, so that carbon nanoparticles generated by the carbon-containing flame are deposited on the surface of the zinc metal substrate to form an initial carbon deposition layer; the carbon-containing flame is a flame generated by one or more of the following: candle flame, paraffin flame, alcohol flame, and hydrocarbon fuel flame.

[0010] Specifically, the pretreated zinc metal substrate is placed above a carbon-containing flame with a gap of 0.5cm to 10cm, and the zinc metal substrate is moved relative to the carbon-containing flame at a speed of 0.5cm / s to 20cm / s.

[0011] Flame deposition treatment has the effect of heat treatment, which smooths the sharp morphological parts of the zinc metal substrate surface and promotes grain growth, thereby further improving the stability of the zinc anode interface.

[0012] S3, Cleaning treatment The zinc metal substrate treated in step S2 is cooled to room temperature and then cleaned with anhydrous ethanol or an ethanol solution to remove weakly attached carbon nanoparticles and selectively retain some carbon nanoparticles in the defect-rich areas on the surface of the zinc metal substrate. The defect-rich areas include one or more of the following on the surface of the zinc metal substrate: depressions, grooves, scratches, pits, cracks, processing damage areas, grain boundary-related irregular areas, local morphological abrupt change areas, and areas surrounding local protrusions.

[0013] S4, drying The cleaned zinc metal substrate was dried to obtain a zinc metal anode with selective carbon nanoparticle patch modification in the defect area; the drying temperature was 30℃~100℃ and the drying time was 5min~12h.

[0014] This invention provides a zinc metal anode modified with selective carbon nanoparticle patches in defect regions, comprising a zinc metal substrate, the surface of which includes a defect-enriched region, wherein carbon nanoparticles with an average particle size of 10 nm to 100 nm are distributed in the defect-enriched region, and the carbon nanoparticles exist in the form of discontinuous localized carbon nanoparticle patches; the carbon nanoparticles are carbon soot particles generated by carbon-containing flame pyrolysis, and the carbon nanoparticles include one or more of amorphous carbon, defect carbon, and locally graphitized carbon.

[0015] This invention provides an application of a zinc metal anode with selectively modified carbon nanoparticles in defect areas, used in the anode of an aqueous zinc-based battery. The aqueous zinc-based battery includes a positive electrode, a negative electrode, a separator, and an aqueous electrolyte. The aqueous electrolyte of the aqueous zinc-ion battery contains Zn. 2+ Specifically, the aqueous electrolyte includes one or more aqueous solutions of ZnSO4, Zn(CF3SO3)2, Zn(CH3COO)2, ZnCl2, and Zn(TFSI)2; the positive electrode of the aqueous zinc-ion battery includes one or more of manganese-based oxides, vanadium-based oxides, Prussian blue materials, organic positive electrode materials, and carbon-based positive electrode materials.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a zinc metal anode with selective carbon nanoparticle patch modification in defect areas, its preparation method, and its application. Through a process of flame deposition followed by cleaning, discontinuous localized carbon nanoparticle patches preferentially distributed in defect-rich areas such as trenches, depressions, scratches, and grain boundaries are constructed on the surface of the zinc anode. Compared with the existing technology that forms a continuous and uniform carbon black coating on the zinc metal surface, this invention transforms the initial loose carbon deposition layer into localized carbon nanoparticle patches with selective retention in defect-rich areas, achieving targeted modification of defect sites that are prone to inducing dendrites and side reactions.

[0017] The localized carbon nanoparticles of this invention can reduce the local electric field concentration in defect-rich regions and improve Zn 2+ The uniformity of the electrode / electrolyte distribution reduces local current density inhomogeneity, thereby inducing uniform nucleation and deposition of zinc and significantly inhibiting zinc dendrite growth.

[0018] The localized carbon nanoparticles of this invention can reduce the direct contact between the defect area on the zinc metal surface and the aqueous electrolyte, which helps to slow down the hydrogen evolution reaction, corrosion reaction and by-product accumulation. It solves the problem of interfacial instability of zinc metal anode in aqueous electrolyte. The localized carbon nanoparticles preferentially cover the defect-rich area, which can block the direct contact between the defect area and the electrolyte to a certain extent, thereby slowing down the occurrence of the above-mentioned side reactions.

[0019] The preparation method of this invention requires widely available raw materials, has a simple process, is easy to operate, does not require expensive special equipment or harsh conditions, has a cost advantage, is easy to scale up production, and is easy to realize large-scale production and practical application. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation process of the zinc metal anode with selective carbon nanoparticle patch modification in the defect region according to the present invention; Figure 2 A schematic diagram of the structure of a defect-rich region on the surface of an unmodified zinc metal substrate; Figure 3 This is a schematic diagram showing the changes in the distribution of carbonaceous nanoparticles on the zinc metal substrate before and after the cleaning treatment following flame deposition. Figure 4 This is a magnified schematic diagram of a localized carbon nanoparticle selectively distributed in a defect-rich region on a zinc metal substrate surface. Figure 5 This is a schematic diagram of the microstructure of carbon nanoparticles. Figure 6 A schematic diagram illustrating the surface morphology smoothing and grain growth of a zinc metal substrate induced by flame treatment; Figure 7 A schematic diagram comparing the interfacial behavior of the unmodified zinc anode and the carbon nanoparticle-modified zinc anode of the present invention during the zinc deposition process; Figure 8 A schematic diagram of an aqueous zinc-ion battery structure incorporating the carbon nanoparticle-modified zinc metal anode of this invention. Figure 9 The graph shows a comparison of the cycle performance of symmetrical batteries assembled with the unmodified zinc anode and the carbon nanoparticle-modified zinc anode of this invention.

[0021] In the figure: 1. Zinc metal substrate; 2. Defect-rich region; 3. Carbon-containing flame; 4. Carbonaceous nanoparticles; 5. Initial carbon deposition layer; 6. Anhydrous ethanol or ethanol solution; 7. Localized carbon nanoparticle patches; 8. Aqueous electrolyte; 9. Zinc dendrites or uneven deposition layer; 10. Zinc deposition layer; 11. Byproduct deposition; 12. Localized electric field concentration; 13. Zn 2+ Uneven flux. Detailed Implementation

[0022] The specific embodiments of the present invention will be described in detail below. Example 1

[0023] A zinc metal anode with selectively modified defect-region carbon nanoparticles, such as Figure 1 As shown, it includes the following steps: S1, Preprocessing like Figure 2As shown, the zinc metal substrate 1 raw material is unmodified, and its surface has defect-rich regions 2, such as depressions, grooves, scratches, pits, cracks, processing damage areas, irregular areas related to grain boundaries, areas of abrupt changes in local morphology, and areas surrounding local protrusions; the defect-rich regions 2 are more likely to generate local electric field concentration 12 and uneven Zn2+ flux 13 during the electrochemical deposition process.

[0024] Zinc foil was used as the raw material for zinc metal substrate 1. The zinc foil was 5cm×5cm in size. It was mechanically ground or polished to remove surface contaminants and oxide layers. It was then ultrasonically cleaned in anhydrous ethanol, rinsed with deionized water or ethanol, and dried. It was then used as the pretreated zinc metal substrate 1 for later use.

[0025] S2, Flame Deposition Processing A candle is lit to form a carbon-containing flame 3. The pre-treated zinc foil is placed above the candle flame with a 3cm gap. The zinc metal substrate 1 is moved relative to the stationary carbon-containing flame 3 at a speed of 5cm / s to perform flame deposition treatment for 30s. This allows the carbon nanoparticles 4 generated by the carbon-containing flame 3 to be deposited on the surface of the zinc metal substrate 1, forming an initial carbon deposition layer 5.

[0026] S3, Cleaning treatment like Figure 3 As shown, before the cleaning process, carbon nanoparticles 4 form a loose initial carbon deposition layer 5, which can cover the flat non-defect area and the defect-rich area 2 of the zinc metal substrate 1.

[0027] The zinc metal substrate 1 treated in step S2 is cooled to room temperature and then cleaned with anhydrous ethanol or ethanol solution 6. During the cleaning process, the weakly bonded carbon nanoparticles 4 are carried away by the cleaning solution. After cleaning, a large amount of the weakly attached carbon nanoparticles 4 in the flat, non-defect area are removed, while the remaining carbon nanoparticles 4 are mainly retained in the defect-rich area 2 on the surface of the zinc metal substrate 1 due to geometric confinement or adhesion, forming discontinuous local carbon nanoparticle patches 7.

[0028] S4, drying The cleaned zinc metal substrate 1 was dried at 60°C for 30 min to obtain a zinc metal anode with selective carbon nanoparticle modification in the defect area.

[0029] like Figure 4 As shown, discontinuous localized carbon nanoparticles 7 are selectively located within the defect-enriched region 2, forming dot-like, island-like, or cluster-like distributions within the defect-enriched region 2, while adjacent flat, non-defective regions remain exposed on the zinc surface. This differs from the uniform, dense carbon layer that continuously covers the entire zinc surface in existing technologies.

[0030] Structural characterization

[0031] The carbon nanoparticles in Example 1 were observed using transmission electron microscopy.

[0032] like Figure 5 As shown, the carbon nanoparticles exhibit a near-spherical morphology, and aggregates can form between them. High-resolution transmission electron microscopy reveals that the carbon nanoparticles may contain locally graphitized structures as well as amorphous / defective carbon structures without long-range order.

[0033] The surface morphology and microstructure of the zinc metal anode modified in Example 1 were analyzed.

[0034] like Figure 6 As shown, compared with the unmodified zinc metal substrate, the sharp grooves and protrusions on the surface of the zinc metal substrate after flame treatment and cleaning were partially smoothed, and the grain size was increased. This indicates that in addition to introducing carbon nanoparticles, flame treatment has a heat treatment effect, which helps to reduce the density of corrosion-sensitive grain boundaries and the degree of local interface abrupt changes.

[0035] Furthermore, the modified zinc metal anode can be characterized using methods such as scanning electron microscopy and energy dispersive spectroscopy, focused ion beam cross-section analysis, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and contact angle measurement. Preferably, in the Raman spectrum, the value at approximately 1350 cm⁻¹... -1 Approximately 1580cm -1 The presence of D and G bands at these locations indicates the presence of carbon materials; the detection of zinc signals in the X-ray photoelectron spectroscopy indicates that the localized carbon nanoparticles have not formed a continuous thick layer covering the entire zinc surface.

[0036] Interfacial behavior during zinc deposition

[0037] like Figure 7 As shown on the left, for unmodified zinc anodes, grooves, depressions, and localized protrusions on the zinc metal substrate surface can lead to Zn... 2+ Uneven flux and localized electric field concentration. During charging and discharging, Zn... 2+ Preferential deposition occurs at defect sites or local protrusions, causing the area to protrude further and inducing zinc dendrites or uneven deposition layers. Meanwhile, byproducts tend to accumulate in defect-rich areas and around uneven deposition layers.

[0038] like Figure 7 As shown on the right, for the zinc metal anode modified in this embodiment, the localized carbon nanoparticles are mainly located in the defect-rich region, which can reduce the local electric field concentration at the defect sites and improve the Zn... 2+ Flux distribution makes Zn 2+ This allows for more uniform deposition at the electrode / electrolyte interface, resulting in a smoother zinc deposit and reducing the probability of zinc dendrite and byproduct deposition. Example 2

[0039] An aqueous zinc-based battery includes a positive electrode, a negative electrode, a separator, and an aqueous electrolyte. like Figure 8 As shown, the negative electrode is a zinc metal negative electrode with defect-selective carbon nanoparticle patch modification prepared in Example 1; The positive electrode is a manganese-based oxide. In this embodiment, β-MnO2 is used as the positive electrode. The β-MnO2 positive electrode can be obtained by mixing β-MnO2, conductive carbon black and polyvinylidene fluoride and coating it onto carbon cloth or current collector. Specifically, β-MnO2, Super P and PVDF are mixed in a mass ratio of 7:2:1, N-methylpyrrolidone is added to make a slurry, which is then coated onto carbon cloth and dried to obtain the β-MnO2 positive electrode. The separator is a glass fiber separator or other porous separator suitable for aqueous zinc-ion batteries; Aqueous electrolyte contains Zn 2+ In this embodiment, a 2 mol / L ZnSO4 aqueous solution is used.

[0040] Comparative Example

[0041] A water-based zinc-based battery, in a comparative example, uses commercial zinc foil as the negative electrode, which is untreated by flame deposition and cleaning, i.e., unmodified zinc foil. The rest is the same as in Example 2.

[0042] Commercial zinc foil surface defects are directly exposed to aqueous electrolytes, making them more prone to localized Zn defects. 2+ Uneven flux, dendrite growth, corrosion, and byproduct accumulation lead to a decrease in the cycle stability of symmetric and full cells.

[0043] Comparing Example 2 and the Comparative Example, when subjected to long-cycle testing at a current density of 1 A / g, the Zn@CNPs||MnO2 full cell prepared in Example 2 exhibited a higher capacity retention rate; after 1000 cycles, the capacity retention rate was 74%, while the Comparative Example, under the same conditions, had a capacity retention rate of 28%.

[0044] The results demonstrate that the carbon nanoparticle-modified zinc metal anode of the present invention can improve the cycle stability of the full battery. Example 3

[0045] The zinc metal anode prepared in Example 1 was subjected to stability testing. In this example, a symmetrical battery cycle performance test was conducted. The zinc metal anode prepared in Example 1 was assembled into a symmetrical battery for zinc deposition / stripping testing. The symmetrical battery can adopt a CR2032 or CR2023 coin cell structure, with a 2 mol / L ZnSO4 aqueous solution as the electrolyte and a glass fiber membrane as the separator.

[0046] like Figure 9 As shown, at 1mA / cm2 Current density and 1mAh / cm 2 Under the given area and capacity conditions, the carbon nanoparticle-modified zinc anode symmetric battery of this embodiment can maintain stable cycling over a long period of time; at 5 mA / cm 2 Current density and 1mAh / cm 2 Under the given areal capacity conditions, it still exhibits stable zinc deposition / stripping behavior. Compared to the unmodified zinc anode, the zinc metal anode used in this embodiment has a more stable voltage plateau and a longer cycle life.

[0047] Specifically, the symmetrical cell prepared in this embodiment has an efficiency of 1 mA / cm². 2 1mAh / cm 2 Under certain conditions, the cycle life can reach 3450 hours at 5 mA / cm. 2 1mAh / cm 2 Under certain conditions, the cycle life can reach 3500 hours.

[0048] The above results demonstrate that the defect-selective carbon nanoparticles of the present invention can effectively stabilize the zinc anode interface.

[0049] The scope of protection claimed by this invention is not limited to the specific embodiments described above. Moreover, for those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a zinc metal anode with selectively modified carbon nanoparticles in defect regions, characterized in that, Includes the following steps: S1, Preprocessing Take the zinc metal substrate (1) raw material and mechanically grind or polish it to remove surface contaminants and oxide layer. Clean and dry it to prepare it as a pretreated zinc metal substrate (1) for later use. S2, Flame Deposition Processing The pretreated zinc metal substrate (1) was subjected to flame deposition treatment using a carbon-containing flame (3) for 5s to 10min, so that the carbon nanoparticles (4) generated by the carbon-containing flame (3) were deposited on the surface of the zinc metal substrate (1) to form an initial carbon deposition layer (5). S3, Cleaning treatment The zinc metal substrate (1) treated in step S2 is cooled to room temperature and then cleaned to remove weakly attached carbon nanoparticles (4) and to selectively retain some carbon nanoparticles (4) in the defect-rich region (2) on the surface of the zinc metal substrate (1). The defect-rich region (2) includes one or more of the following on the surface of the zinc metal substrate (1): depressions, grooves, scratches, pits, cracks, processing damage areas, grain boundary-related irregular areas, local morphological abrupt change areas, and areas surrounding local protrusions. S4, drying The cleaned zinc metal substrate (1) was dried to obtain a zinc metal anode with selective carbon nanoparticle patch modification in the defect area.

2. The method for preparing a zinc metal anode with selectively modified carbon nanoparticles in defect areas according to claim 1, characterized in that, In step S2, the flame deposition process includes placing the pretreated zinc metal substrate (1) above the carbon-containing flame (3) with a gap, so that the zinc metal substrate (1) moves relative to the carbon-containing flame (3); The carbon-containing flame (3) is a flame produced by one or more of the following: candle flame, paraffin flame, alcohol flame, and hydrocarbon fuel flame.

3. The method for preparing a zinc metal anode with selective carbon nanoparticle modification of defect regions according to claim 2, characterized in that, In step S2, the distance between the zinc metal substrate (1) and the carbon-containing flame (3) is 0.5cm~10cm, and the moving speed is 0.5cm / s~20cm / s.

4. The method for preparing a zinc metal anode with selectively modified carbon nanoparticles in defect regions according to claim 1, characterized in that, In step S3, anhydrous ethanol or ethanol solution (6) is used for cleaning.

5. A zinc metal anode with defect-selective carbon nanoparticle patch modification prepared by the preparation method according to claim 1, characterized in that, The zinc metal substrate (1) includes a defect enrichment region (2) on its surface. The defect enrichment region (2) is distributed with carbon nanoparticles (4) with an average particle size of 10 nm to 100 nm. The carbon nanoparticles (4) exist in the form of discontinuous local carbon nanoparticle patches (7).

6. The zinc metal anode with selective carbon nanoparticle patch modification for defect regions according to claim 5, characterized in that, The carbon nanoparticles (4) are carbon soot particles generated by the pyrolysis of a carbon-containing flame (3), and the carbon nanoparticles (4) include one or more of amorphous carbon, defective carbon, and locally graphitized carbon.

7. The application of the zinc metal anode modified with selective carbon nanoparticles in defect areas according to claim 5, characterized in that, Used in the negative electrode of an aqueous zinc-ion battery, wherein the aqueous electrolyte (8) of the aqueous zinc-ion battery contains Zn. 2+ .

8. The application of the zinc metal anode with selective carbon nanoparticle modification for defect regions as described in claim 5, characterized in that, The aqueous electrolyte (8) includes one or more aqueous solutions of ZnSO4, Zn(CF3SO3)2, Zn(CH3COO)2, ZnCl2, and Zn(TFSI)2.

9. The application of the zinc metal anode modified with selective carbon nanoparticles in defect areas according to claim 5, characterized in that, The positive electrode of the aqueous zinc-ion battery includes one or more of the following: manganese-based oxide, vanadium-based oxide, Prussian blue-based materials, organic positive electrode materials, and carbon-based positive electrode materials.

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