Current collector and preparation method and application thereof

Abstract

The invention relates to the technical field of lithium metal batteries, in particular to a current collector and a preparation method and application thereof.The current collector comprises a matrix, the surface of the matrix is coated with a coating layer, and the coating layer comprises strawberry DNA attached with cell wall polysaccharide; the preparation method comprises the following steps: S1, preparing a second mixed solution containing strawberry DNA; s2, preparing a dry mixture from the second mixed solution; s3, weighing the dried mixture, adding a Tris buffer solution, and adjusting the pH value by using the Tris buffer solution to prepare a third mixed solution; s4, putting the third mixed solution into a centrifugal machine for centrifugal rotation, and taking supernatant liquid as coating liquid; step S5, coating liquid is dropped on the surface of the ground substrate, and is baked in a baking oven to coat the surface of the substrate, so that the current collector is obtained; according to the current collector, the growth of lithium dendrites can be effectively inhibited, and the short-circuit risk of a lithium metal battery is greatly reduced; and the stability and coulombic efficiency of the battery can be remarkably improved, and the performance of the battery is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium metal battery, in particular to a current collector and a preparation method and use thereof. BACKGROUND

[0002] In lithium metal batteries, the current collector is a crucial component. On the one hand, the current collector serves as an adhesion carrier for the positive and negative active materials (such as ternary materials, lithium iron phosphate for the positive electrode, and graphite, silicon-based materials for the negative electrode), ensuring the stable fixation of the active materials and preventing them from falling off during charging and discharging, thus maintaining the structural integrity of the electrode. On the other hand, the current collector is used to uniformly guide the external current into the active materials and collect the current generated by the active materials during electrochemical reactions, thereby reducing the internal resistance of the battery and ensuring efficient transmission of electrical energy. The current collector is a key intermediary for the conversion of chemical energy into electrical energy.

[0003] The current collector of a lithium metal battery is usually made of metal materials. In traditional technology, aluminum foil and copper foil are commonly used for the current collector. Aluminum forms a dense oxide film (Al2O3) on its surface at high potentials (3-4.5 V), which has good corrosion resistance and is low in cost and light in weight. Copper has excellent chemical stability at low potentials (0-1 V) and is not easily corroded by electrolyte, and its electrical conductivity is higher than that of aluminum, which can reduce current transmission loss. To improve the energy density of the battery or adapt to new electrode materials, optimizing the structural design of the current collector is an important direction. As an example, some existing technical solutions construct the current collector into a 3D porous structure. For instance, Tsinghua University has constructed the current collector into a nanoporous structure, which can reduce the local current density and thus prolong the cycle life. As another example, some existing technical solutions modify the surface of the current collector. For instance, the University of California, Berkeley, has set a lithiumophilic coating (such as Au, ZnO nanoparticles) on the surface of the current collector to reduce the nucleation overpotential. For another example, a team from the Chinese Academy of Sciences has set a graphene layer (carbon material) on the surface of the current collector to enhance the electrical conductivity and homogenize the lithium ion flow. For yet another example, a negative electrode current collector disclosed in Chinese Patent CN 118198375 A forms an animal-derived DNA interface layer on the surface of the current collector by using animal-derived DNA raw materials, which is beneficial to simultaneously improving the coulombic efficiency and cycle performance of the negative electrode-free lithium metal battery.

[0004] Lithium dendrites are a tree-like, needle-like, or moss-like crystal structure formed by the irregular deposition of lithium metal on the surface of the negative electrode during the charging and discharging process of lithium-ion batteries (especially lithium metal batteries). The formation of lithium dendrites is essentially due to the non-uniformity of the lithium metal deposition process. The growth of lithium dendrites can severely damage the safety, cycle life, and energy density of the battery, and even cause catastrophic accidents. For example, when lithium dendrites grow to a certain length, they can pierce the separator inside the battery (used to separate the positive and negative electrodes to prevent electronic conduction but allow Li +By the porous membrane), directly connecting the positive and negative electrodes, triggering internal short circuit, a large amount of heat will be generated in the short circuit moment, leading to electrolyte decomposition, release of flammable gas, separator melting, electrode material combustion, eventually leading to battery fire and explosion, etc.; lithium dendrite is one of the core bottlenecks restricting the commercial application of lithium metal batteries.

[0005] In practical applications, the existing current collector will still have different degrees of tip effect and lithium dendrite formation due to uneven distribution of surface lithium ions, for example, the current collector provided with the animal-derived DNA interface layer in the above-mentioned prior art will still have significant growth of lithium dendrites in practical applications. How to more effectively control the growth of lithium dendrites and further improve the safety and performance of lithium metal batteries needs to be solved urgently. SUMMARY

[0006] The first aspect of the present application solves the above technical problems and provides a current collector capable of effectively inhibiting the growth of lithium dendrites, which can greatly reduce the risk of battery short circuit caused by lithium dendrite growth, improve safety, and further improve battery performance.

[0007] A current collector includes a substrate, and the surface of the substrate is coated with a coating layer containing strawberry DNA attached to cell wall polysaccharides. In this scheme, the surface of the substrate is coated with a coating layer containing strawberry DNA, which belongs to plant DNA. This scheme creatively uses strawberry DNA as a functional unit to construct the interface layer of a lithium metal battery. On the one hand, strawberry DNA has a high abundance of guanine-cytosine (GC) base pairs. The nitrogen atoms of the GC base pairs can establish a biomimetic ion channel through transient Li-N bonds, achieving spatial uniform distribution of lithium flux and inducing lithium to deposit along the crystal plane. On the other hand, during the extraction of strawberry DNA, strawberry cell wall polysaccharides (such as cellulose and hemicellulose) physically co-precipitate and entangle with the strawberry DNA, forming a viscous substance that is difficult to separate. These cell wall polysaccharide fragments are usually attached to the strawberry DNA, just like part of the phosphate backbone in the strawberry DNA. Therefore, the extracted strawberry DNA retains cell wall polysaccharide fragments (such as cellulose and hemicellulose) in its phosphate backbone. Cellulose can form an interconnected carbon fiber network after pyrolysis, equivalent to a thin film that effectively inhibits the growth of lithium metal. Not only can it mediate dynamic lithium ion solvation through hydroxyl groups, but also can act as a mechanical buffer layer to relieve stress caused by volume changes. Through the hydrogen bonding effect and self-adaptive viscoelastic properties between the cell wall polysaccharide residues in the strawberry DNA and the metal lithium, the interface stress accumulation can be synergistically inhibited, thereby effectively inhibiting the growth of lithium dendrites. This not only can greatly reduce the risk of lithium metal battery short circuit, improve safety, but also can provide a "molecular buffer-directional transport" dual-function solution for high-activity lithium metal interface dynamics regulation, and further improve battery performance.

[0008] Preferably, the thickness of the coating layer is 700-900 nm. If the thickness of the coating layer is less than 700 nm, the structure will fail due to insufficient coating; if the thickness of the coating layer is greater than 900 nm, the impedance will be significantly increased due to excessive coating.

[0009] Preferably, the substrate is a copper foil or an aluminum foil.

[0010] Preferably, the cell wall polysaccharide includes cellulose.

[0011] The second aspect of the present application provides a method for preparing a current collector, comprising the following steps: step S1, preparing a second mixture containing strawberry DNA and cell wall polysaccharide; step S2, preparing a dry mixture from the second mixture, the mixture containing strawberry DNA and cell wall polysaccharide; step S3, weighing the mixture and adding Tris buffer to adjust the pH and configure a third mixture; step S4, placing the third mixture in a centrifuge for centrifugal rotation, and taking the supernatant as a coating liquid containing strawberry DNA and cell wall polysaccharide; step S5, dropping the coating liquid onto the surface of a polished substrate and baking in an oven to coat the surface of the substrate, so as to form a coating layer on the surface of the substrate and obtain a current collector.

[0012] The third aspect of the present application aims to more effectively extract strawberry DNA. Further, the step S1 comprises the following steps: step S11, preparing strawberry juice from strawberries; step S12, mixing dishwashing detergent, edible salt and deionized water to prepare a DNA extraction solution; step S13, mixing the DNA extraction solution with the strawberry juice and standing to obtain a first mixture; and step S14, filtering the strawberry residues in the first mixture to obtain the second mixture. In this solution, the dishwashing detergent and the edible salt are mixed to prepare the DNA extraction solution, which innovatively uses the combination of dishwashing detergent and edible salt to extract strawberry DNA through the synergistic cooperation of ions and non-ions. This can significantly improve the extraction rate of strawberry DNA, and the extracted DNA extraction solution contains cell wall polysaccharide fragments (such as cellulose and hemicellulose) of strawberries, which is beneficial to effectively inhibit the growth of lithium dendrites.

[0013] Preferably, in step S11, a plurality of fresh strawberries are washed and placed in a plastic bag to be crushed to prepare the strawberry juice. By using a plastic bag, on the one hand, the inside of the strawberry can be crushed, and on the other hand, the strawberry pulp and strawberry juice can be prevented from leaking, so as to improve the utilization rate of strawberry DNA.

[0014] Preferably, the dishwashing liquid is APG dishwashing liquid. The hydrophobic alkyl chain of the APG dishwashing liquid breaks the DNA hydration layer by competitive hydrogen bond disruption, promotes the penetration of strawberry DNA single strand into the copper grain boundary micro gap, and effectively weakens the repulsion between the phosphate groups of strawberry DNA under the cooperation of edible salt (NaCl), induces the folding of strawberry DNA chain into a rigid conformation perpendicular to the copper substrate, thereby facilitating the inhibition of lithium dendrite growth and improving the battery performance.

[0015] The fourth aspect of the present application aims to further improve the battery performance. Preferably, the ratio of dishwashing liquid, edible salt and deionized water in the DNA extraction solution is 10ml:1g:30ml. In this scheme, by controlling the ratio of dishwashing liquid and edible salt in the DNA extraction solution to be 10ml:1g, the hydrophobic alkyl chain of the APG dishwashing liquid breaks the DNA hydration layer by competitive hydrogen bond disruption, promotes the penetration of strawberry DNA single strand into the copper grain boundary micro gap, and on this basis, strictly limits the edible salt (NaCl) to produce Debye shielding effect, thereby weakening the repulsion between the phosphate groups of strawberry DNA by 75% (ζ potential from-35mV to-12mV), inducing the folding of strawberry DNA chain into a rigid conformation perpendicular to the copper substrate, which not only facilitates the inhibition of lithium dendrite growth, but also improves the battery performance.

[0016] Preferably, in step S12, the amount of dishwashing liquid added is 50ml, the amount of edible salt added is 5g, and the amount of deionized water added is 150ml. This is conducive to further improving the battery performance.

[0017] The fifth aspect of the present application aims to improve the extraction efficiency of strawberry DNA. Further, the step S2 includes: step S21, adding alcohol to the second mixed solution and standing to make the strawberry DNA in the second mixed solution dehydrate and coagulate to form a flocculent precipitate, wherein the concentration of the alcohol is greater than or equal to 95%; step S22, separating the flocculent precipitate and washing it with alcohol to remove the remaining impurities to obtain a flocculent precipitate; and step S23, heating the flocculent precipitate to obtain a dry mixture, wherein the mixture includes strawberry DNA and cell wall polysaccharide. In this scheme, by adding alcohol with a concentration greater than or equal to 95% to the second mixed solution, the alcohol makes the strawberry DNA mixed with cell wall polysaccharide in the second mixed solution dehydrate and coagulate to form a flocculent precipitate, which not only ensures the optimal precipitation efficiency, but also effectively reduces the loss of strawberry DNA dissolution, thereby significantly improving the extraction efficiency of strawberry DNA. At the same time, the phosphate skeleton of the strawberry DNA retains fragments of the cell wall polysaccharide of the strawberry, which is conducive to more effectively inhibiting the growth of lithium dendrites.

[0018] Preferably, in step S21, the concentration of the alcohol is 95%.

[0019] The sixth aspect of the present application aims to further improve the performance of the battery, preferably, in step S21, the volume ratio of alcohol to the second mixed solution is 2:1 to 4:1. In this scheme, when the volume ratio of alcohol to the second mixed solution is less than 2:1, the impurities in the coating solution will increase significantly, which will seriously affect the performance of the battery; when the volume ratio of alcohol to the second mixed solution is greater than 4:1, the strawberry DNA in the coating solution is broken, which will also seriously affect the performance of the battery, therefore, the volume ratio of alcohol to the second mixed solution is controlled to be 2:1 to 4:1, which can not only reduce the impurity residue, but also prevent the strawberry DNA from being broken, thereby effectively improving the quality of the coating solution and achieving the purpose of further improving the performance of the battery.

[0020] Preferably, in step S21, the volume ratio of alcohol to the second mixed solution is 3:1. The problems of impurity residue and strawberry DNA breakage can be solved at the same time, the quality of the coating solution is effectively improved, and the performance of the battery can be significantly improved.

[0021] In order to solve the problem of faster drying of the flocculent precipitate without causing the strawberry DNA to be damaged, preferably, in step S23, the flocculent precipitate is baked in an oven, and the baking temperature is controlled to be 50℃. In this scheme, by controlling the baking temperature to be 50℃, the strawberry DNA mixed with cell wall polysaccharide can be effectively prevented from being damaged, and alcohol and water can be more efficiently removed, thereby achieving the purpose of drying the flocculent precipitate.

[0022] Preferably, in step S3, the pH of the third mixed solution is adjusted to 8.0 by using Tris buffer solution.

[0023] The seventh aspect of the present application aims to further improve the performance of the battery, preferably, in step S3, the concentration of strawberry DNA in the third mixed solution is 7mg / ml. This concentration is the maximum saturation degree of DNA dissolved in Tris solution, and at this concentration, the amount of DNA coated on the copper foil is the largest, which not only can greatly improve the performance of the battery, but also can achieve better effect of inhibiting the growth of lithium dendrites.

[0024] In order to solve the problem of faster drying of the coating layer without causing the strawberry DNA to be damaged, preferably, in step S5, the drying temperature in the oven is 50℃. In this scheme, by controlling the drying temperature in the oven to be 50℃, the strawberry DNA can be effectively prevented from being damaged, and the coating layer can be more efficiently dried, thereby obtaining the current collector with the strawberry DNA coating layer.

[0025] The eighth aspect of the present application provides the use of the current collector in a lithium metal battery. It is beneficial to further improve the performance of the battery.

[0026] Compared with the prior art, the current collector, the preparation method and the use thereof can effectively inhibit the growth of lithium dendrites, thereby greatly reducing the short circuit risk of the lithium metal battery due to the growth of lithium dendrites and improving the safety, and can improve the stability and coulombic efficiency of the lithium metal battery, thereby further improving the performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 The copper foil coated with strawberry DNA was plated with lithium at 1 mA cm -2 , 3 mAh cm -2 after plating lithium.

[0029] Figure 2 The copper foil coated with strawberry DNA was plated with lithium at 1 mA cm -2 , 3 mAh cm -2 after plating lithium.

[0030] Figure 3 The two groups of half batteries were cycled at 1 mA cm -2 , 1 mAh cm -2 , and the coulombic efficiency curves of the cycle number were obtained, i.e., the changes of the coulombic efficiency of the two batteries under long-time cycling.

[0031] Figure 4 The two groups of full batteries were cycled, and the coulombic efficiency curves of the cycle number and the specific capacity curves of the cycle number were obtained, i.e., the changes of the coulombic efficiency and the specific capacity of the two batteries under long-time cycling.

[0032] Figure 5 The animal DNA coating layer and the strawberry DNA coating layer were plated with lithium at 1 mA cm -2 , 3 mAh cm -2 , and the lithium dendrite microscope images at 30 min, 60 min and 120 min were obtained. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0034] Embodiment 1

[0035] A method for preparing a current collector is provided in the present embodiment, comprising the following steps: step S1, preparing a mixed solution containing strawberry DNA and cell wall polysaccharides.

[0036] In implementation, the present step specifically comprises step S11, washing a plurality of fresh strawberries and placing them in a plastic bag for sufficient kneading to obtain strawberry juice (including strawberry pulp and juice water). By using a plastic bag, on the one hand, the internal strawberries are facilitated to be kneaded, and on the other hand, the strawberry pulp and strawberry juice water are prevented from leaking, so as to improve the utilization rate of strawberry DNA (i.e., deoxyribonucleic acid). In implementation, the number of strawberries can be determined according to actual needs, and as a preferred, the number of strawberries can be 3-4. In the present embodiment, 3 strawberries are used. In the process of sufficient kneading of strawberries, the strawberry cell wall is damaged, and the strawberry cell wall polysaccharides (such as cellulose, hemicellulose, etc.) and the strawberry DNA are physically co-precipitated and entangled to form a viscous substance (i.e., mixed together) which is difficult to separate. These cell wall polysaccharide fragments (referred to as cell wall polysaccharides) are usually attached to the phosphate backbone of the strawberry DNA, like a part of the phosphate backbone of the strawberry DNA, and the two are not easily separated from each other.

[0037] Step S12, preparing a DNA extraction solution: adding a certain amount of detergent, edible salt and deionized water into a beaker and stirring thoroughly to obtain a DNA extraction solution. In implementation, the amounts of detergent, edible salt and deionized water can be determined according to actual needs, and as an example, the amount of detergent can be 50 ml, the amount of edible salt can be 5 g, and the amount of deionized water can be 150 ml. The three are stirred thoroughly in the beaker to obtain the DNA extraction solution. The DNA extraction solution composed of detergent, edible salt and deionized water can not only effectively extract the strawberry DNA in the strawberry juice, but also will not damage the strawberry cell wall polysaccharide fragments mixed (or attached) in the strawberry DNA, ensuring that the cell wall polysaccharide fragments are attached to the strawberry DNA.

[0038] Step S13, the DNA extraction solution is mixed with the strawberry juice and left to stand, to obtain a first mixed solution. In practice, the DNA extraction solution can be directly poured into a plastic bag, so that the DNA extraction solution is directly in contact with the strawberry juice and left to stand for a period of time, which can be 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, etc. as an example, in this embodiment, after the DNA extraction solution is mixed with the strawberry juice, it is left to stand for 5 minutes.

[0039] Step S14, the strawberry residue in the first mixed solution is filtered to obtain a second mixed solution, and the second mixed solution is placed in a beaker for later use. In practice, the strawberry residue in the first mixed solution can be filtered out with gauze, of course, steel mesh, filter membrane, etc. can also be used to filter the strawberry residue in the first mixed solution. It can be understood that the obtained second mixed solution includes strawberry DNA, and also includes strawberry cell wall polysaccharide fragments attached to the strawberry DNA.

[0040] Step S2, a dry mixture including strawberry DNA with cell wall polysaccharides is prepared from the second mixed solution.

[0041] As an example, alcohol is used to extract the mixture containing strawberry DNA and cell wall polysaccharides from the second mixed solution; in practice, this step specifically includes step S21, alcohol is added to the second mixed solution and left to stand, so that the strawberry DNA (essentially strawberry DNA with cell wall polysaccharides, which will not be described below) in the second mixed solution dehydrates and coagulates to form a flocculent precipitate. In practice, alcohol can be directly added to the beaker containing the second mixed solution; in this step, from a molecular level, alcohol can make the strawberry DNA in the second mixed solution dehydrate and coagulate to form a flocculent precipitate, so as to be separated from the second mixed solution; at the same time, alcohol can also effectively remove the lipid compounds in the second mixed solution, which can not only dissolve non-polar impurities, but also effectively avoid the harm of lipid compounds to the battery performance; and alcohol can also prevent the activity of deoxyribonuclease, so as to maintain the integrity of the DNA structure.

[0042] In practice, the concentration of alcohol can be determined according to actual needs, as an example, in this embodiment, the concentration of alcohol is 95%, which is conducive to achieving the best precipitation efficiency; accordingly, in practice, the amount of alcohol added can also be determined according to actual needs, as an example, in this embodiment, the volume ratio of alcohol to the second mixed solution can be 3:1, which can effectively reduce impurity residues, and also will not cause the strawberry DNA to be broken, ensuring the integrity of the strawberry DNA.

[0043] Step S22, separate the flocculation precipitate and rinse it with alcohol to remove the remaining impurities to obtain the flocculation precipitate. In the beaker, the flocculation precipitate is usually suspended in the upper layer of the beaker, so in the implementation, the suspended flocculation precipitate can be taken out by a glass rod to separate the flocculation precipitate from the liquid to obtain the flocculation precipitate only attached with alcohol and water.

[0044] In the rinsing, the flocculation precipitate is rinsed with alcohol, on the one hand, no new impurities are introduced, and on the other hand, the other impurities attached to the flocculation precipitate can be removed by rinsing to achieve the purpose of effectively purifying the flocculation precipitate.

[0045] Step S23, heat the flocculation precipitate to remove the alcohol and water attached to the flocculation precipitate to obtain dry strawberry DNA. In the implementation, the flocculation precipitate can be placed in an oven for baking to heat the flocculation precipitate by baking to separate the alcohol and water and dry the flocculation precipitate, and in other embodiments, the flocculation precipitate can also be heated by a warm water bath to effectively remove the alcohol and water, but the cell wall polysaccharide attached to the flocculation precipitate cannot be removed. Therefore, the heating temperature is an important indicator in the heating process. The essence of strawberry DNA is an organic macromolecule containing phosphate groups. If the heating temperature is too high, the deoxyribose phosphate backbone will be broken, the strawberry DNA will be damaged, and the cell wall polysaccharide will also be damaged, which will seriously affect the use effect of the current collector. If the heating temperature is too low, the combination of water molecules and hydrophilic groups (such as amine groups) cannot be easily broken, which is not conducive to drying the flocculation precipitate. In industrial applications, the drying temperature is usually 60-120°C. However, through the previous test, it is found that when the heating temperature is 60°C, the strawberry DNA has been broken. Therefore, to solve this technical problem, the influence of the heating temperature on this step is explored through comparative tests. It is found that when the heating temperature is greater than 52°C, the β-D-2 deoxyribose in the strawberry DNA begins to degrade and the strawberry DNA begins to be damaged. When the heating temperature is lower than 50°C, the combination of water molecules and hydrophilic groups (such as amine groups) is not easy to break. When the heating temperature is higher than 50°C, the combination of water molecules and hydrophilic groups (such as amine groups) is easier to break, indicating that 50°C is the critical point of the activation energy of high molecular thermal motion and the energy barrier of hydrolysis. Therefore, in the implementation, the temperature for heating the flocculation precipitate is preferably controlled to be 50-51°C, which can effectively prevent the strawberry DNA and cell wall polysaccharide from being damaged and more efficiently remove the alcohol and water. As an example, in this embodiment, the flocculation precipitate is baked in an oven with a heating temperature of 50°C. Of course, in other embodiments, the heating temperature can also be preferably controlled to be 50.5°C, 51°C, etc., which will not be illustrated one by one here.

[0046] In addition, the concentration of alcohol on the strawberry DNA is also explored in the previous experiment. The results of the previous experiment show that when the alcohol concentration is 97%, the amount of the mixture (mainly including strawberry DNA) obtained in this step is basically the same as that obtained when the alcohol concentration is 95% under the same second mixed solution. When the alcohol concentration is 90%, the amount of the mixture obtained in this step is significantly less than that obtained when the alcohol concentration is 95%. When the alcohol concentration is 85%, the amount of the mixture obtained in this step is much less than that obtained when the alcohol concentration is 90%, and is only about 60% of that obtained when the alcohol concentration is 95%. The test data show that the alcohol concentration below 85% will cause the loss of strawberry DNA dissolution to exceed 40%, and the high concentration of 95% alcohol can ensure the best precipitation efficiency.

[0047] In step S3, the obtained mixture is weighed, and Tris buffer solution is added to adjust the pH and configure the third mixed solution. In this step, the Tris buffer solution does not react with the strawberry DNA and the cell wall polysaccharide. On the one hand, the main purpose of adding the Tris buffer solution is to adjust the pH of the third mixed solution and maintain the stability of the pH value. For example, in this embodiment, the pH of the third mixed solution is adjusted to 8.0, which can not only protect the molecular mechanism of the integrity of the strawberry DNA structure, but also effectively improve the electrochemical matching degree of the copper foil interface. On the other hand, by mixing the strawberry DNA with the Tris buffer solution to form the third mixed solution, the strawberry DNA molecules can be uniformly dispersed in the solution, which is beneficial to realize more uniform coating in the subsequent process, thereby improving the performance of the battery.

[0048] In the implementation, the concentration of the strawberry DNA in the third mixed solution can be determined according to the actual needs. For example, in this embodiment, the concentration of the strawberry DNA in the third mixed solution is controlled to be 7 mg / ml. According to the previous experiment, this concentration is the maximum saturation of the strawberry DNA dissolved in the Tris solution. Under this concentration, the content of the strawberry DNA coated on the copper foil is the largest, and accordingly, the content of the cell wall polysaccharide is also the largest, which can not only greatly improve the performance of the battery, but also effectively inhibit the growth of lithium dendrites.

[0049] Step S4, the third mixed solution is placed in a centrifuge for centrifugal rotation, and the supernatant is taken as a coating solution, which includes strawberry DNA containing cell wall polysaccharides. In practice, the centrifuge is preferably a high-speed centrifuge, and the centrifugal force can be 10,000 rpm during centrifugal rotation, so that the third mixed solution is subjected to high-speed centrifugal rotation treatment to realize efficient separation of liquid-solid phases, remove impurities, but cannot remove cell wall polysaccharides attached to strawberry DNA, thereby improving the purity of strawberry DNA molecules and optimizing the performance of subsequent batteries. In practice, the centrifugal rotation time can be determined according to actual needs. In this embodiment, the centrifugal rotation treatment is 3 minutes.

[0050] The coating solution prepared by the above steps not only contains strawberry DNA, but also has cell wall polysaccharides attached to the strawberry DNA. Unlike animal DNA, strawberry DNA has a high abundance of guanine-cytosine (GC) base pairs, which can form a dense nitrogen coordination network, giving it unique lithium ion affinity. For example, the nitrogen atoms of GC base pairs can establish a biomimetic ion channel through transient Li-N bonds, enabling spatially uniform distribution of lithium flux, inducing lithium to deposit along the crystal plane; at the same time, the phosphoric acid skeleton retains fragments of strawberry cell wall polysaccharides (such as cellulose and hemicellulose), which can form an interconnected carbon fiber network after pyrolysis, equivalent to a thin film to effectively inhibit the growth of lithium dendrites. Not only can it mediate dynamic lithium ion solvation through hydroxyl groups, but also can act as a mechanical buffer layer to relieve electrode volume change stress.

[0051] Step S5, drop the coating solution onto the polished substrate surface and bake it in an oven to fully coat the substrate surface, so as to form a coating layer on the substrate surface to obtain a current collector. The current collector includes a substrate and a coating layer coated on the substrate surface, and the coating layer includes strawberry DNA mixed with (or attached to) cell wall polysaccharides.

[0052] In practice, the drying temperature in the oven can be determined according to actual needs. As mentioned earlier, when the temperature is greater than 52°C, β-D-2 deoxyribose in strawberry DNA begins to degrade, and strawberry DNA begins to be damaged. When the temperature is lower than 50°C, the combination of water molecules and hydrophilic groups (such as amine groups) is not easy to break. When the temperature is higher than 50°C, the combination of water molecules and hydrophilic groups (such as amine groups) is easier to break, indicating that 50°C is the critical point of the activation energy of high molecular thermal motion and the energy barrier of hydrolysis. Therefore, in this step, the drying temperature in the oven is preferably controlled at 50°C-51°C, which can effectively prevent the damage of strawberry DNA and more efficiently dry. As an example, in this embodiment, the drying temperature in the oven is 50°C. Of course, in other embodiments, the drying temperature in the oven can also be preferably controlled at 50.5°C, 51°C, etc., which will not be exemplified one by one here.

[0053] In practice, the substrate can adopt a copper foil or an aluminum foil, both of which can realize efficient transmission of current. As an example, in the present embodiment, the substrate adopts a copper foil.

[0054] In practice, the thickness of the coating layer can be determined according to the baking time, that is, in actual operation, the thickness of the coating layer is accurately controlled by accurately controlling the baking time, and after reaching the preset baking time, the excess coating liquid interface is washed away. At the same time, according to the previous test, it is found that if the thickness of the coating layer is too thin, the problem of insufficient coating leading to structural failure will occur, and if the thickness of the coating layer is too thick, the problem of significant impedance increase will occur. Research has found that when the thickness of the coating layer is less than 700 nm, structural failure will occur due to insufficient coating; when the thickness of the coating layer is greater than 900 nm, significant impedance increase will occur due to excessive coating. In practice, the thickness of the coating layer can be controlled to 700-900 nm first, since the size of the strawberry DNA molecule is about 2-3 nm (base pair length), when the thickness of the coating layer is 700-900 nm, there are 300-450 layers of DNA molecules stacked on the surface of the substrate, forming a continuous layered structure; more preferably, in practice, the thickness of the coating layer can be controlled to 750-800 nm first, when the thickness of the coating layer reaches 700-750 nm, the problem of structural failure due to insufficient coating is alleviated, and the impedance of the coating layer is relatively low; when the thickness of the coating layer reaches 750-800 nm, structural failure due to insufficient coating is basically not caused, and the impedance of the coating layer is relatively low; when the thickness of the coating layer reaches 800-900 nm, structural failure due to insufficient coating is not caused, but the impedance of the coating layer is relatively high. As an example, in the present embodiment, the thickness of the coating layer can be controlled to 750 nm or 760 nm or 770 nm, etc. first, which not only can improve the structural stability and improve the success rate of coating, but also can effectively control the impedance and further improve the battery performance.

[0055] For the convenience of testing, in the present embodiment, the prepared current collector is cut into a circular sheet with a diameter of 12 mm.

[0056] Comparative Example 1

[0057] The substrate with the same specifications as in Example 1 is taken as the current collector, since the substrate in Example 1 adopts a copper foil, therefore, in the present comparative example, the current collector adopts a copper foil without a coating layer, which is also cut into a circular sheet with a diameter of 12 mm.

[0058] Comparative test: 1, the circular sheet-shaped current collector prepared in Comparative Example 1 with a diameter of 12 mm is subjected to 1 mA cm -2 , 3 mAh cm -2The lithium plating process was performed, and then the surface of the current collector was observed under an electron microscope, such as... Figure 1 As shown; similarly, the 12mm diameter disc current collector prepared in Example 1 was subjected to 1 mA cm⁻¹ treatment. -2 3mAh cm -2 The lithium plating process was performed, and then the surface of the current collector was observed under an electron microscope, such as... Figure 2 As shown. From Figure 1 As can be seen, lithium dendrite growth is significant in the current collector (i.e., copper foil) after lithium plating; while from... Figure 2 As can be seen, under the same conditions, there is no obvious one-dimensional growth of lithium dendrites, which indicates that the current collector prepared in Example 1 can effectively suppress the growth of lithium dendrites, thereby greatly reducing the risk of short circuit in lithium metal batteries caused by the growth of lithium dendrites.

[0059] 2. Using the 12mm diameter circular current collector prepared in Example 1, a half-cell was assembled to obtain a half-cell that met the testing requirements. Similarly, using the 12mm diameter circular current collector prepared in Comparative Example 1, a half-cell was assembled under the same assembly conditions as the aforementioned half-cell to obtain a half-cell that met the testing requirements. Then, the two sets of half-cells were tested at 1mA cm⁻¹. -2 1mAh cm -2 Under the conditions of charge-discharge cycle experiment, two groups of half-cells were obtained at 1mA cm⁻¹. -2 1mAhcm -2 Coulombic efficiency curves under different charge-discharge cycles are shown in the figure. Figure 3 As shown, from Figure 3 As can be seen, the half-cell composed of the current collector in Comparative Example 1 showed a significant decrease in coulombic efficiency after 50 cycles, while the half-cell composed of the current collector in Example 1 did not show a significant decrease in coulombic efficiency after 350 cycles. This indicates that the current collector prepared in Example 1 can significantly improve the stability and coulombic efficiency of the battery.

[0060] 3. Using the 12mm diameter disc-shaped current collector prepared in Example 1, a full cell was assembled to obtain a full cell that met the testing requirements. Similarly, using the 12mm diameter disc-shaped current collector prepared in Comparative Example 1, a full cell was assembled under the same assembly conditions as the aforementioned full cell to obtain a full cell that met the testing requirements. Then, the two sets of full cells were tested at 1 mA cm⁻¹. -2 1mAh cm -2 Under certain conditions, charge-discharge cycle experiments were conducted on the batteries, and the specific capacity and coulombic efficiency curves of two sets of full cells under different charge-discharge cycles were obtained, as shown in the figure. Figure 4 As shown, from Figure 4It can be seen that the specific capacity of the full battery formed by the current collector in Comparative Example 1 decreases more obviously than that of the full battery formed by the current collector in Example 1 during the cycle process, thereby indicating that the current collector prepared in Example 1 can obtain better specific capacity retention rate and better battery stability.

[0061] Comparative Example 2

[0062] The substrate with the same specification as that in Example 1 is taken as the current collector. Since the substrate in Example 1 is a copper foil, in this comparative example, the current collector is a copper foil provided with a coating layer, which is also cut into a circular sheet with a diameter of 12 mm. In this example, the coating layer is a PVDF layer (i.e., polyvinylidene fluoride), and the thickness of the PVDF layer is the same as that of the strawberry DNA in Example 1.

[0063] Comparative Example 3

[0064] The substrate with the same specification as that in Example 1 is taken as the current collector. Since the substrate in Example 1 is a copper foil, in this comparative example, the current collector is a copper foil provided with a coating layer, which is also cut into a circular sheet with a diameter of 12 mm. In this example, the coating layer is Al2O3, and the thickness of the coating layer in this example is the same as that of the strawberry DNA in Example 1.

[0065] Comparative Test: The current collectors prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 are respectively subjected to the battery charge-discharge cycle experiment under the same conditions. The experimental conditions are the same, and the specific results are shown in Table 1. Through comparison, it can be known that the Coulomb efficiency of the current collector prepared in this example 1 decreases most slowly, which reveals that the corresponding battery has higher stability and Coulomb efficiency.

[0066] Table 1: Results of charge-discharge cycle experiment

[0067]

[0068] Comparative Example 4

[0069] It can be understood that, in the comparative experiment, a plurality of fresh strawberries are first selected, washed and then placed in a plastic bag for sufficient kneading to obtain strawberry juice. Then, the strawberry juice is divided into equal parts, and one part is selected to prepare the current collector by the method of Example 1, and one part of the strawberry juice is selected to prepare the current collector in each comparative example, which will not be described hereinafter.

[0070] In the present comparative example, first, 50 ml of dishwashing liquid, 5 g of edible salt and 150 ml of deionized water are used to configure a DNA extraction solution, then the DNA extraction solution is mixed with the selected strawberry juice, fully contacted and left for 5 minutes to obtain a first mixed solution; the strawberry residue in the first mixed solution is filtered to obtain a second mixed solution; 95% concentration alcohol is added to the second mixed solution, the volume ratio of alcohol to the second mixed solution is 1:1, so that the strawberry DNA in the second mixed solution is dehydrated and coagulated to form flocculent precipitate; the suspended flocculent precipitate is taken out by a glass rod to obtain flocculent precipitate; then the flocculent precipitate is baked in an oven, the heating temperature is controlled at 50°C, and a dry mixture containing strawberry DNA is obtained; an equal amount of the mixture of strawberry DNA is weighed and Tris buffer is added to configure a third mixed solution with a concentration of 7 mg / ml; then the third mixed solution is placed in a centrifuge for centrifugal rotation, the speed is 10000 revolutions per minute, the time is 3 minutes, and the upper clear liquid is taken as a coating liquid; finally, the coating liquid is dropped onto the polished substrate surface and dried in a 50°C oven to fully coat the substrate surface, so as to form a coating layer on the substrate surface to obtain a current collector.

[0071] Comparative Example 5

[0072] In the present comparative example, first, 50 ml of dishwashing liquid, 5 g of edible salt and 150 ml of deionized water are used to configure a DNA extraction solution, then the DNA extraction solution is mixed with the selected strawberry juice, fully contacted and left for 5 minutes to obtain a first mixed solution; the strawberry residue in the first mixed solution is filtered to obtain a second mixed solution; 95% concentration alcohol is added to the second mixed solution, the volume ratio of alcohol to the second mixed solution is 1:1, so that the strawberry DNA in the second mixed solution is dehydrated and coagulated to form flocculent precipitate; the suspended flocculent precipitate is taken out by a glass rod to obtain flocculent precipitate; then the flocculent precipitate is baked in an oven, the heating temperature is controlled at 50°C, and a dry mixture containing strawberry DNA is obtained; an equal amount of the mixture of strawberry DNA is weighed and Tris buffer is added to configure a third mixed solution with a concentration of 7 mg / ml; then the third mixed solution is placed in a centrifuge for centrifugal rotation, the speed is 10000 revolutions per minute, the time is 3 minutes, and the upper clear liquid is taken as a coating liquid; finally, the coating liquid is dropped onto the polished substrate surface and dried in a 50°C oven to fully coat the substrate surface, so as to form a coating layer on the substrate surface to obtain a current collector.

[0073] Comparative Example 6

[0074] In this comparative example, a DNA extraction solution was first prepared using 50 ml of dish soap, 5 g of table salt, and 150 ml of deionized water. This DNA extraction solution was then mixed with selected strawberry juice, allowed to fully contact, and allowed to stand for 5 minutes to obtain a first mixture. Strawberry residue was filtered from the first mixture to obtain a second mixture. 95% ethanol was added to the second mixture at a volume ratio of 4:1, causing the strawberry DNA in the second mixture to dehydrate and coagulate, forming a flocculent precipitate. The suspended flocculent precipitate was removed using a glass rod to obtain the flocculent precipitate. The flocculent precipitate was then dried in an oven at 50°C to obtain a dry mixture. An equal volume of the mixture was weighed and Tris buffer was added to prepare a third mixture with a concentration of 7 mg / ml. The third mixture was then centrifuged at 10,000 rpm for 3 minutes, and the supernatant was taken as the coating solution. Finally, the coating solution was dropped onto the polished substrate surface and dried in an oven at 50°C to fully coat the substrate surface, so as to form a coating layer on the substrate surface and obtain the current collector.

[0075] Comparative Example 7

[0076] In this comparative example, a DNA extraction solution was first prepared using 50 ml of dish soap, 5 g of table salt, and 150 ml of deionized water. This DNA extraction solution was then mixed with selected strawberry juice, allowed to fully contact, and allowed to stand for 5 minutes to obtain a first mixture. Strawberry residue was filtered from the first mixture to obtain a second mixture. 95% ethanol was added to the second mixture at a volume ratio of 5:1, causing the strawberry DNA in the second mixture to dehydrate and coagulate, forming a flocculent precipitate. The suspended flocculent precipitate was removed using a glass rod to obtain a flocculent precipitate. The flocculent precipitate was then baked in an oven at 50°C to obtain a dried mixture. An equal volume of the mixture was weighed and Tris buffer was added to prepare a third mixture with a concentration of 7 mg / ml. The third mixture was then centrifuged at 10,000 rpm for 3 minutes, and the supernatant was used as the coating solution. Finally, the coating solution was dropped onto the polished substrate surface and heated at 50°C. The material is dried in an oven to fully coat the substrate surface, thus forming a coating layer on the substrate surface to obtain a current collector.

[0077] Comparative testing: The current collectors prepared in Examples 1, 4, 5, 6, and 7 were assembled into half-cells for performance testing, including at 1 mA cm⁻¹. -2 1mAh cm -2The battery charging and discharging cycle experiment was carried out under the above conditions, and the test results showed that the stability and coulombic efficiency of the half battery corresponding to Example 1 were the highest, and the battery performance was the best; the stability and coulombic efficiency of the half battery corresponding to Comparative Example 4 were much lower than those of the half battery corresponding to Example 1, and the battery performance was not good; the stability and coulombic efficiency of the half battery corresponding to Comparative Example 5 were lower than those of the half battery corresponding to Example 1; the stability and coulombic efficiency of the half battery corresponding to Comparative Example 6 were lower than those of the half battery corresponding to Example 1; and the stability and coulombic efficiency of the half battery corresponding to Comparative Example 7 were much lower than those of the half battery corresponding to Example 1, and the battery performance was not good. Based on this, the coating liquid obtained in the preparation process was further detected, and it was found that the coating liquid prepared in Comparative Example 5 had impurity (the strawberry cell wall polysaccharide attached was not an impurity) residue, the coating liquid prepared in Comparative Example 4 not only had impurity residue, but also the impurity residue in Comparative Example 4 increased by about 80% compared with Comparative Example 5, which would seriously affect the performance of the battery; the coating liquid prepared in Comparative Example 5 was equivalent to the coating liquid prepared in Example 1, and there was basically no impurity residue (not including strawberry cell wall polysaccharide), but part of the strawberry DNA in the coating liquid prepared in Comparative Example 5 was broken, and the strawberry DNA breaking in the coating liquid prepared in Comparative Example 7 was more obvious, thereby seriously affecting the performance of the battery. Therefore, in the implementation, when the alcohol concentration is 95%, the volume ratio of alcohol to the second mixed liquid is preferably controlled to be 2:1-4:1, which can not only reduce impurity residue, but also can avoid strawberry DNA breaking as much as possible. Of course, in the implementation, the volume ratio of alcohol to the second mixed liquid can be preferably controlled to be 3:1, which can solve the problems of impurity residue and strawberry DNA breaking at the same time, effectively improve the quality of the coating liquid, and thereby can significantly improve the performance of the battery.

[0078] Comparative Example 8

[0079] In the present comparative example, first, 50 ml of dishwashing liquid, 5 g of edible salt and 150 ml of deionized water are used to configure a DNA extraction solution, then the strawberry DNA extraction solution is mixed with the selected strawberry juice, fully contacted and left for 5 minutes to obtain a first mixed solution; the strawberry residues in the first mixed solution are filtered to obtain a second mixed solution; 95% concentration alcohol is added to the second mixed solution, the volume ratio of alcohol to the second mixed solution is 3:1, so that the strawberry DNA in the second mixed solution is dehydrated and coagulated to form flocculent precipitate; the suspended flocculent precipitate is taken out by a glass rod to obtain flocculent precipitate; then the flocculent precipitate is baked in an oven, the heating temperature is controlled at 50°C to obtain a dry mixture; an equal amount of the mixture is weighed and Tris buffer solution is added to configure a third mixed solution with a concentration of 5 mg / ml; then the third mixed solution is placed in a centrifuge for centrifugal rotation, the speed is 10000 revolutions per minute, the time is 3 minutes, and the upper clear liquid is taken as a coating liquid; finally, the coating liquid is dropped onto the polished substrate surface and dried in a 50°C oven to fully coat the substrate surface, so as to form a coating layer on the substrate surface to obtain a current collector.

[0080] Comparative Example 9

[0081] In the present comparative example, first, 50 ml of dishwashing liquid, 5 g of edible salt and 150 ml of deionized water are used to configure a DNA extraction solution, then the strawberry DNA extraction solution is mixed with the selected strawberry juice, fully contacted and left for 5 minutes to obtain a first mixed solution; the strawberry residues in the first mixed solution are filtered to obtain a second mixed solution; 95% concentration alcohol is added to the second mixed solution, the volume ratio of alcohol to the second mixed solution is 3:1, so that the strawberry DNA in the second mixed solution is dehydrated and coagulated to form flocculent precipitate; the suspended flocculent precipitate is taken out by a glass rod to obtain flocculent precipitate; then the flocculent precipitate is baked in an oven, the heating temperature is controlled at 50°C to obtain a dry mixture; an equal amount of the mixture is weighed and Tris buffer solution is added to configure a third mixed solution with a concentration of 5 mg / ml; then the third mixed solution is placed in a centrifuge for centrifugal rotation, the speed is 10000 revolutions per minute, the time is 3 minutes, and the upper clear liquid is taken as a coating liquid; finally, the coating liquid is dropped onto the polished substrate surface and dried in a 50°C oven to fully coat the substrate surface, so as to form a coating layer on the substrate surface to obtain a current collector.

[0082] Comparative test; the current collectors prepared in Example 1, Comparative Example 8 and Comparative Example 9 are respectively assembled into half-batteries for performance test, including the specific capacity, the specific energy, the cycle life, the charge-discharge efficiency and the like. -2 , 1mAh cm -2The battery charging and discharging cycle experiment was carried out under the above conditions, and the test results showed that the stability and coulomb efficiency of the half battery corresponding to Example 1 were the highest, and the battery performance was the best; the stability and coulomb efficiency of the half battery corresponding to Comparative Example 8 were lower than that of the half battery corresponding to Comparative Example 9; the stability and coulomb efficiency of the half battery corresponding to Comparative Example 9 were lower than that of the half battery corresponding to Example 1. The reason is that when the concentration of the third mixed solution reaches about 7 mg / ml, the maximum saturation of strawberry DNA dissolved in the Tris solution is reached, and at this concentration, the amount of strawberry DNA contained in the coating solution is the most, and the amount of strawberry cell wall polysaccharide fragments carried is also the most, so that the amount of strawberry DNA coated on the substrate is the most, thereby greatly improving the performance of the battery; the amount of strawberry DNA in the coating solution in Comparative Example 9 is relatively small, and the amount of strawberry DNA in the coating solution in Comparative Example 8 is relatively smaller, thereby resulting in that the battery prepared in Example 1 has the best performance, and the battery prepared in Comparative Example 8 has the worst performance.

[0083] Comparative Example 10

[0084] In this comparative example, first, 150 ml of deionized water was used to prepare a DNA extraction solution, then the DNA extraction solution was mixed with the selected strawberry juice, fully contacted and stood for 5 minutes to obtain a first mixed solution; the strawberry residues in the first mixed solution were filtered to obtain a second mixed solution; 95% alcohol was added to the second mixed solution, and the volume ratio of alcohol to the second mixed solution was 3:1, so that the strawberry DNA in the second mixed solution was dehydrated and coagulated to form a flocculent precipitate; the flocculent precipitate was taken out by a glass rod to obtain a flocculent precipitate; then the flocculent precipitate was baked in an oven, and the heating temperature was controlled at 50°C to obtain dried strawberry DNA; an equal amount of strawberry DNA was weighed and added to Tris buffer solution to prepare a third mixed solution with a concentration of 7 mg / ml; then the third mixed solution was placed in a centrifuge for centrifugal rotation, the speed was 10000 revolutions per minute, and the time was 3 minutes, and the upper clear liquid was taken as a coating solution; finally, the coating solution was dropped onto the surface of the polished substrate, and was dried in a 50°C oven to fully coat the surface of the substrate, so as to form a coating layer on the surface of the substrate to obtain a current collector.

[0085] Comparative Example 11

[0086] In this comparative example, a DNA extraction solution was first prepared using 50 ml of dish soap and 150 ml of deionized water. This DNA extraction solution was then mixed with selected strawberry juice, allowed to fully contact, and allowed to stand for 5 minutes to obtain a first mixture. Strawberry residue was filtered from the first mixture to obtain a second mixture. 95% ethanol was added to the second mixture at a volume ratio of 3:1, causing the strawberry DNA in the second mixture to dehydrate and coagulate, forming a flocculent precipitate. The suspended flocculent precipitate was removed using a glass rod to obtain the flocculent precipitate. The flocculent precipitate was then baked in an oven at 50°C to obtain dried strawberry DNA. An equal amount of strawberry DNA was weighed and added to Tris buffer to prepare a third mixture with a concentration of 7 mg / ml. The third mixture was then centrifuged at 10,000 rpm for 3 minutes, and the supernatant was used as the coating solution. Finally, the coating solution was dropped onto the polished substrate surface and dried in an oven at 50°C to fully coat the substrate surface, so as to form a coating layer on the substrate surface and obtain the current collector.

[0087] Comparative Example 12

[0088] In this comparative example, a DNA extraction solution was first prepared using 5g of table salt and 150ml of deionized water. The DNA extraction solution was then mixed with selected strawberry juice, allowed to fully contact, and allowed to stand for 5 minutes to obtain a first mixture. Strawberry residue in the first mixture was filtered out to obtain a second mixture. 95% ethanol was added to the second mixture at a volume ratio of 3:1, causing the strawberry DNA in the second mixture to dehydrate and coagulate, forming a flocculent precipitate. The suspended flocculent precipitate was removed using a glass rod to obtain the flocculent precipitate. The flocculent precipitate was then baked in an oven at 50°C to obtain dried strawberry DNA. An equal amount of strawberry DNA was weighed and added to Tris buffer to prepare a third mixture with a concentration of 7 mg / ml. The third mixture was then centrifuged at 10,000 rpm for 3 minutes, and the supernatant was used as the coating solution. Finally, the coating solution was dropped onto the polished substrate surface and dried in an oven at 50°C to fully coat the substrate surface, so as to form a coating layer on the substrate surface and obtain the current collector.

[0089] Comparative testing: The current collectors prepared in Example 1, Comparative Example 10, Comparative Example 11, and Comparative Example 12 were assembled into half-cells for performance testing, including at 1 mA cm⁻¹. -2 1mAh cm -2The battery charging and discharging cycle test was carried out under the above conditions, and the test results showed that the stability and coulombic efficiency of the half battery prepared in Example 1 were the highest, and the battery performance was the best; the stability and coulombic efficiency of the half battery prepared in Comparative Example 10 were much lower than that of the half battery prepared in Example 1; the stability and coulombic efficiency of the half battery prepared in Comparative Example 11 were also much lower than that of the half battery prepared in Example 1; because, strawberry DNA is difficult to disperse in solution due to molecular entanglement and electrostatic repulsion of phosphate groups, it is difficult to effectively extract strawberry DNA by separately configuring dishwashing liquid in strawberry DNA extraction solution, and it is also difficult to effectively extract strawberry DNA by separately configuring edible salt in DNA extraction solution, in Example 1, food-grade alkyl glycoside (APG dishwashing liquid, a kind of surfactant) and edible salt (NaCl) were innovatively combined to break through this bottleneck through the synergistic cooperation of ion-nonion, which significantly improved the extraction rate of strawberry DNA, as shown in Table 2, the extraction rates of strawberry DNA extraction solutions in Example 1, Comparative Example 10, Comparative Example 11 and Comparative Example 12 were tested, among which the extraction rate of the DNA extraction solution used in Example 1 was the highest, and the fault was the leading; the hydrophobic alkyl chain of APG surfactant breaks down the DNA hydration layer by competitive hydrogen bond disruption, which promotes the penetration of strawberry DNA single strand into the copper grain boundary micro gap; at the same time, NaCl produces Debye shielding effect under strict concentration limitation (such as 0.65 mol / L, which can achieve the balance of the highest DNA purity and yield, and the co-precipitation of polysaccharides will occur above this concentration), which reduces the repulsion between strawberry DNA phosphate groups by 75% (ζ potential from-35 mV to-12 mV), induces strawberry DNA chain to fold into a rigid conformation perpendicular to the copper substrate, which not only helps to inhibit the growth of lithium dendrites, but also helps to improve the performance of the battery.

[0090] Table 2

[0091]

[0092] Comparative Example 13

[0093] In nature, deoxyribonucleic acid (DNA) provides a natural template for biomimetic interface design with its programmable double helix structure and multi-dimensional chemical activity. Unlike animal DNA, the high abundance of guanine-cytosine (GC) base pairs in plant DNA can form a dense nitrogen coordination network, giving it unique lithium ion affinity. At the same time, the plant cell wall polysaccharide fragments (such as cellulose and hemicellulose) retained in its phosphate backbone not only mediate dynamic lithium ion solvation through hydroxyl groups, but also act as a mechanical buffer layer to relieve stress from volume changes. Based on this, the application first proposes to use strawberry DNA as a functional unit to construct a lithium metal battery interface layer. The core scientific value lies in that, on the one hand, the nitrogen atoms of GC base pairs establish a biomimetic ion channel through transient Li-N bonds, which can achieve spatial uniform distribution of lithium flux and induce lithium deposition along the crystal plane. On the other hand, the hydrogen bonding effect and self-adaptive viscoelastic properties between plant polysaccharide residues and metal lithium can synergistically inhibit the accumulation of interfacial stress, effectively inhibit the growth of lithium dendrites, and provide a "molecular buffer-directional transport" dual-function solution for high-activity lithium metal interface dynamics regulation.

[0094] In this embodiment, an animal DNA coating layer (using the animal DNA coating layer disclosed in Chinese patent CN 118198375A) is arranged on the outer surface of the substrate to form a current collector coated with an animal DNA coating layer. The thickness of the animal DNA coating layer is the same as that of the coating layer in Example 1. Then, the current collector prepared in Example 1 and the current collector prepared in Comparative Example 13 are respectively subjected to 1 mA cm-2, 3 mAh cm-2lithium plating test, and the results are shown in Figure 5 Figure 5 The picture above the arrow in the test of the animal DNA coating layer in Comparative Example 13 is Figure 5 The picture below the arrow in the test of the strawberry DNA coating layer in Example 1 is; from Figure 5 It can be seen from the above that after the animal DNA coating layer undergoes 2h of lithium plating test, lithium dendrite growth is significant, while the lithium ion distribution on the surface of the strawberry DNA coating layer is still uniform, and no obvious lithium dendrite is observed. This is mainly because the plant cell wall polysaccharide fragments attached to the phosphate backbone of strawberry, including cellulose and hemicellulose, are unique to plant cells and cannot be possessed by animal cells. The interconnected carbon fiber network formed by pyrolysis of plant cellulose acts as a thin film to effectively inhibit the growth of lithium metal, achieving the purpose of inhibiting the growth of lithium dendrites. This not only can greatly reduce the risk of short circuit of lithium metal batteries and improve safety, but also is conducive to further improving the performance of the battery.

[0095] ​The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A current collector, characterized in that, It includes a matrix, the surface of which is covered with a coating layer, the coating layer including strawberry DNA with attached cell wall polysaccharides.

2. The current collector according to claim 1, characterized in that, The coating layer has a thickness of 700-900 nm; the substrate is made of copper foil or aluminum foil; the cell wall polysaccharide includes cellulose.

3. A method for preparing the current collector as described in claim 1, characterized in that, Includes the following steps: Step S1: Prepare a second mixture containing strawberry DNA and cell wall polysaccharides; Step S2: Prepare a dried mixture from the second mixture, the mixture comprising strawberry DNA and cell wall polysaccharides; Step S3: Weigh the dried mixture, add Tris buffer, adjust the pH using Tris buffer, and prepare the third mixture. Step S4: Place the third mixture in a centrifuge and centrifuge, and take the supernatant as the coating solution. The coating solution contains strawberry DNA and cell wall polysaccharides. Step S5: The coating liquid is dropped onto the polished substrate surface and baked in an oven to coat the substrate surface, thereby forming a coating layer on the substrate surface and obtaining a current collector.

4. The preparation method according to claim 3, characterized in that, Step S1 includes step S11, making strawberry juice using strawberries; Step S12: Mix dish soap, table salt and deionized water thoroughly to obtain DNA extraction solution; Step S13: Mix the DNA extract with strawberry juice and let it stand to obtain the first mixture; Step S14: Filter the strawberry residue in the first mixture to obtain the second mixture.

5. The preparation method according to claim 4, characterized in that, The dishwashing liquid used is APG dishwashing liquid.

6. The preparation method according to claim 4, characterized in that, The ratio of detergent, edible salt, and deionized water in the DNA extraction solution is 10ml:1g:30ml.

7. The preparation method according to claim 3, characterized in that, Step S2 includes step S21, adding alcohol to the second mixture and letting it stand, so that the strawberry DNA in the second mixture dehydrates and coagulates to form a flocculent precipitate, wherein the concentration of alcohol is greater than or equal to 95%; Step S22: Separate the flocculent precipitate and wash it with alcohol to remove the remaining impurities, thereby obtaining the flocculent precipitate; Step S23: Heat the flocculent precipitate to obtain a dry mixture.

8. The preparation method according to claim 7, characterized in that, In step S21, the volume ratio of alcohol to the second mixture is 2:1 to 4:

1.

9. The preparation method according to claim 8, characterized in that, In step S21, the concentration of alcohol is 95%; the volume ratio of alcohol to the second mixture is 3:

1.

10. Use of a current collector as described in claim 1 in a lithium metal battery.

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