Current collector with three-dimensional porous structure on surface, preparation method and battery

Abstract

The invention provides a current collector with a three-dimensional porous structure on the surface, a preparation method and a battery. The preparation method comprises the following steps: firstly, obtaining a tin / copper foil with a three-dimensional structure on the surface through constant-current electrodeposition tin; then coating an indium tin seed layer on the tin surface of the three-dimensional structure through co-electrodeposition of indium tin, and on the basis, continuously performing constant-current electrodeposition of indium to obtain indium / indium tin / tin / copper foil with a three-dimensional porous structure on the surface; and finally, enabling the indium / indium tin / tin / copper foil to form an alloy by adopting a heat treatment technology so as to obtain the current collector with a walnut-shaped three-dimensional porous structure on the surface. Therefore, the lithium nucleation overpotential can be reduced, and the uniform deposition of lithium is guided, so that the growth of lithium dendrites and the volume expansion of lithium metal are effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of battery current collector technology, specifically to a current collector with a walnut-shaped three-dimensional porous structure on its surface, its preparation method, and a battery. Background Technology

[0002] As a core component of lithium anodes, current collectors are currently commonly made of copper foil, which has a smooth surface and stable chemical properties. However, this traditional copper foil current collector has limitations due to its smooth surface and poor lithium affinity, resulting in few and unevenly distributed nucleation sites for lithium ions during deposition. This can lead to localized preferential deposition of lithium metal, forming inhomogeneous morphologies such as dendrites and moss.

[0003] Surface modification of current collectors is an important means to enhance their function and improve the performance of lithium batteries. Constructing three-dimensional structures can increase specific surface area, reduce local current density, and accommodate deposited lithium metal, thereby suppressing dendrite growth and buffering volume expansion to some extent. However, these methods are often complex, costly, and have poor structural stability. Furthermore, if the resulting three-dimensional structure itself lacks lithium affinity, it is still difficult to fundamentally guide the uniform nucleation of lithium. Therefore, it is still necessary to find a current collector with good structural stability and lithium affinity. Summary of the Invention

[0004] In view of this, the present invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface, a preparation method thereof, and a battery. The indium tin alloy coating with the introduced walnut-shaped three-dimensional porous structure has good adhesion, and the current collector has excellent structural stability and lithium affinity. It can effectively alleviate problems such as uneven lithium deposition and disordered growth of lithium dendrites in lithium metal batteries during cycling, and is beneficial to improving the electrochemical performance of the battery.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, embodiments of the present invention provide a method for preparing a current collector with a walnut-shaped three-dimensional porous structure on its surface, the method comprising: Using copper foil as a substrate, tin / copper foil with a three-dimensional surface structure is obtained by constant current electrodeposition of tin. A three-dimensional tin / copper foil is immersed in an indium tin co-electrodeposition solution. An indium tin seed layer is deposited on the tin surface by constant current co-electrodeposition. Indium is then deposited by constant current electrodeposition. The deposition of indium is guided by the indium tin seed layer to obtain a three-dimensional porous indium / indium tin / tin / copper foil. The indium tin seed layer is porous and has a thickness of 0.05~0.15 μm. Heat treatment was performed on an indium / indium-tin / tin / copper foil with a three-dimensional porous surface structure to form a copper-tin alloy and an indium-tin alloy. The copper-tin alloy can improve the bonding force between the copper substrate and the tin plating layer. At the same time, during the interdiffusion formation of the alloy by indium and tin, the presence of an indium-tin seed layer leads to different degrees of interdiffusion at different locations, resulting in a current collector with a walnut-shaped three-dimensional porous surface structure. The walnut-shaped three-dimensional porous surface structure is a wrinkled quasi-spherical structure with pore channels. The pore channel diameter is 0.3~0.6 μm, and the wrinkled quasi-spherical structure diameter is 6~10 μm.

[0006] Preferably, the constant current electrodeposition to obtain a three-dimensional tin / copper foil with a surface structure includes: The copper foil was placed in the electrodeposition tin solution, and the current density was set to 1~3 A dm. -2 The electrodeposition time was 40–60 s, and the electrodeposition temperature was maintained at 25–30 °C. A magnetic stirrer was used to agitate the electrodeposition solution at a speed of 150–250 r / min. -1 This yields a tin / copper foil with a three-dimensional surface structure.

[0007] Preferably, the step of coating a tin surface with an indium tin seed layer by constant current co-electrodeposition of indium tin, followed by constant current electrodeposition of indium, includes: A 3D-structured tin / copper foil was immersed in a co-electrodeposition indium tin solution, with the co-electrodeposition current density set to 1~3 A dm. -2 The electrodeposition time was 7–11 s, and the stirring speed was 250–350 r / min. -1 The co-electrodeposited sample was placed in an indium electrodeposition solution, and the electrodeposition current density was set to 1~3 A dm. -2 The electrodeposition time was 60–120 s, and the stirring speed was 150–250 r / min. -1 This yields an indium / indium-tin / tin / copper foil with a three-dimensional porous surface structure.

[0008] Preferably, the heat treatment of the indium / indium-tin / tin / copper foil with a three-dimensional porous surface structure to obtain a current collector with a walnut-like three-dimensional porous surface includes: An indium / indium-tin / tin / copper foil with a three-dimensional porous surface is placed in an alumina crucible, and the alumina crucible is sealed in a quartz tube of a tube furnace. The heat treatment temperature is set to 110~130 ℃ and the heat treatment time is 7~9 h to obtain a current collector with a walnut-shaped three-dimensional porous surface.

[0009] Preferably, the thickness of the tin is 0.6~0.8 μm.

[0010] Preferably, the thickness of the indium tin seed layer is 0.05~0.15 μm.

[0011] Preferably, the thickness of the indium is 0.5~0.7 μm.

[0012] Preferably, the pore diameter of the pore channel is 0.3~0.6 μm, and the diameter of the wrinkled spherical structure is 6~10 μm.

[0013] Preferably, the roughness of the current collector is 0.539~0.644 μm.

[0014] Preferably, the current collector surface with a walnut-shaped three-dimensional porous structure includes two or more metals or alloys selected from copper, tin, indium, Cu3Sn, Cu6Sn5, In3Sn, and InSn4.

[0015] Secondly, embodiments of the present invention provide a current collector with a walnut-shaped three-dimensional porous structure on its surface, which is prepared by the current collector with a walnut-shaped three-dimensional porous structure on its surface as described in any embodiment of the present invention.

[0016] Thirdly, embodiments of the present invention provide a battery including a current collector having a walnut-shaped three-dimensional porous structure on its surface, as described in any embodiment of the present invention.

[0017] This invention provides a current collector with a walnut-like three-dimensional porous structure on its surface, a preparation method, and a battery. Using copper foil as a substrate, a tin / copper foil with a three-dimensional surface structure is obtained by constant current electrodeposition of tin. The tin / copper foil with the three-dimensional surface structure is immersed in an indium tin co-electrodeposition solution, and an indium tin seed layer is deposited on the tin surface by constant current co-electrodeposition. Subsequently, indium is deposited by constant current electrodeposition, and the indium deposition is guided by the indium tin seed layer to obtain an indium / indium tin / tin / copper foil with a three-dimensional porous surface structure. The indium / indium tin / tin / copper foil with the three-dimensional porous surface structure is then heat-treated to obtain a current collector with a walnut-like three-dimensional porous structure on its surface. The walnut-like three-dimensional porous structure is a wrinkled, spherical structure with pore channels.

[0018] The beneficial effects of this invention are: (1) In this invention, an ultrathin, porous indium-tin seed layer is introduced between the conventional tin plating and indium plating layers. On the one hand, the porous rough surface of the indium-tin seed layer improves the affinity for water, which is beneficial to the uniform deposition of indium in the subsequent process. On the other hand, the indium and tin in the seed layer have good bonding force with the indium layer above and the tin layer below, respectively, which can improve the overall bonding force of the plating layer. (2) The present invention forms a walnut-like structure through the induction and heat treatment technology of porous indium tin seed layer. The pore channels and wrinkled structure contained therein increase the electrochemical active surface area, provide more lithium-loving sites, and facilitate the penetration of electrolyte, improve the electrolyte wettability of current collector, and thus enable the battery to have better electrochemical performance. (3) The present invention contains a current collector with a walnut-shaped three-dimensional porous structure on its surface, which has excellent lithium affinity. It can not only reduce the nucleation overpotential of lithium, but also guide the uniform deposition of lithium metal and alleviate the uncontrollable growth of lithium dendrites on the surface of the current collector. At the same time, the formed copper-tin alloy improves the bonding force between the copper substrate and the tin plating layer, which is conducive to maintaining the stability of the overall structure. The three-dimensional porous structure can effectively alleviate the volume expansion of the indium tin alloy during cycling and the volume change during lithium deposition / stripping, which improves the stability of the electrode and is conducive to improving the cycle performance of the battery. Attached Figure Description

[0019] Figure 1 Scanning electron microscope (SEM) images at different magnifications of a current collector with a walnut-shaped three-dimensional porous structure on its surface, provided in an embodiment of the present invention. Figure 2 The contact angle of a current collector with a walnut-shaped three-dimensional porous structure on its surface, provided in an embodiment of the present invention, with respect to water; Figure 3 The contact angle of a current collector with a walnut-shaped three-dimensional porous structure on its surface to the electrolyte, as provided in an embodiment of the present invention; Figure 4 The electrochemically active surface area of ​​a current collector having a walnut-shaped three-dimensional porous structure is provided in one embodiment of the present invention; Figure 5 The lithium nucleation overpotential of a current collector having a walnut-shaped three-dimensional porous structure on its surface, as provided in an embodiment of the present invention; Figure 6 A graph showing the relationship between cycle number and coulombic efficiency of a lithium metal battery assembled with a current collector having a walnut-shaped three-dimensional porous structure on its surface, provided in an embodiment of the present invention; Figure 7 This is a graph showing the relationship between cycle time and polarization voltage of a lithium metal battery assembled with a current collector having a walnut-shaped three-dimensional porous structure on its surface, according to an embodiment of the present invention. Figure 8 The roughness of a current collector with a walnut-shaped three-dimensional porous structure is provided in an embodiment of the present invention. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0021] Example 1 A current collector with a walnut-shaped three-dimensional porous structure on its surface, prepared according to an embodiment of the present invention, is as follows: (1) Immerse the copper foil in a degreasing solution for 60 s at a temperature of 45 ℃; then immerse the degreased copper foil in an activation solution for 30 s at a temperature of 25 ℃; subsequently place the activated copper foil in an electrodeposition tin solution and set the current density to 2 A dm. -2 The electrodeposition time was 50 s, and the electrodeposition temperature was maintained at 25 ℃. A magnetic stirrer was used to stir the electrodeposition solution at a speed of 200 r / min. -1 This yields a tin / copper foil with a three-dimensional surface structure. (2) Place the three-dimensional tin / copper foil on the surface in a co-electrodeposition indium tin solution, and set the current density for co-electrodeposition of indium tin to 2 A dm³. -2 The co-electrodeposition time was 9 s, and the stirring speed was 300 r / min. -1 The electrodeposition temperature was maintained at 25℃ to obtain an indium tin / tin / copper foil with a three-dimensional porous surface. The contact angle of the foil with water was then tested, and the results are shown in [Figure number missing]. Figure 2 ; (3) Place the completed co-electrodeposition sample in the indium electrodeposition solution and set the indium electrodeposition current density to 2 A dm. -2 The electrodeposition time was 90 s, and the stirring speed was 200 r / min. -1 The electrodeposition temperature was kept at 25 °C to obtain an indium / indium tin / tin / copper foil with a three-dimensional porous structure on the surface, and the adhesion was tested. (4) An indium / indium-tin / tin / copper foil with a three-dimensional porous surface was placed in an alumina crucible, which was then placed in a tube furnace and sealed. The tube furnace was evacuated, and argon gas was introduced as a protective gas. The heat treatment temperature was set to 120℃, and the heat treatment time was 8 h. A current collector with a walnut-like three-dimensional porous surface was obtained. Scanning electron microscope images of the current collector at different magnifications were taken, and the contact angle and roughness of the electrolyte were tested. The results are shown in […]. Figure 1 , Figure 3 , Figure 8 ; (5) The current collector with a walnut-like three-dimensional porous structure obtained above was used in a lithium metal battery, i.e., lithium metal was used as the negative electrode active material, and lithium bis(trifluoromethanesulfonylimide) dissolved in 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) (v / v) = 1:1 with 2wt.% LiNO3 was used as the electrolyte in the battery. A Celgard 2400 separator was used to prepare the lithium metal battery. (The last sentence appears to be incomplete and possibly refers to a measurement or measurement method.) -2 The current density and 0.5 mAh cm⁻¹ -2The electrochemical active surface area, lithium nucleation overpotential, coulombic efficiency after 100 cycles, and polarization voltage after 300 hours of cycling were tested using the area capacity of this current collector. The results are shown in [Figure number missing]. Figure 4 , Figure 5 , Figure 6 , Figure 7 .

[0022] Example 2 This invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface, prepared according to an embodiment of the present invention. The specific implementation method is consistent with that of Example 1, except that the electrodeposition current density is changed to 1 A dm³ in the "electrodeposition of tin" step. -2 Conduct the experiment.

[0023] Example 3 This invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface, prepared according to an embodiment of the present invention. The specific implementation method is consistent with that of Example 1, except that the electrodeposition current density is changed to 3 A dm³ in the "electrodeposition of tin" step. -2 Conduct the experiment.

[0024] Example 4 The present invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface. The specific implementation method is consistent with that of Example 1, except that the co-deposition time in the "co-deposition of indium tin" step is changed to 7 s for the experiment.

[0025] Example 5 The present invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface. The specific implementation method is consistent with that of Example 1, except that the co-deposition time in the "co-deposition of indium tin" step is changed to 11 s for the experiment.

[0026] Example 6 The present invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface. The specific implementation method is consistent with that of Example 1, except that the electrodeposition time in the "indium electrodeposition" step is changed to 60 s for the experiment.

[0027] Example 7 The present invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface. The specific implementation method is consistent with that of Example 1, except that the electrodeposition time in the "indium electrodeposition" step is changed to 120 s for the experiment.

[0028] Comparative Example 1 The comparative example of this invention omits the co-electrodeposition step of indium tin, while the other steps remain consistent with those in Example 1.

[0029] Comparative Example 2 The present invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface, prepared as a comparative example. The specific implementation method is consistent with Example 1, except that the co-electrodeposition time of indium tin is changed to 20 s in the "co-electrodeposition of indium tin" step.

[0030] Comparative Example 3 The present invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface, prepared as a comparative example. The specific implementation method is consistent with Example 1, except that the co-electrodeposition time of indium tin is changed to 2 s in the "co-electrodeposition of indium tin" step.

[0031] Comparative Example 4 This invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface, prepared as a comparative example. The specific implementation method is consistent with Example 1, except that the electrodeposition current density is changed to 0.3 A dm³ in the "electrodeposition of tin" step. -2 Conduct the experiment.

[0032] Comparative Example 5 The present invention provides a current collector with a walnut-shaped three-dimensional porous structure on its surface, prepared as a comparative example. The specific implementation method is consistent with Example 1, except that the indium electrodeposition time is changed to 200 s in the "indium electrodeposition" step.

[0033] Comparative Example 6 The comparative example of this invention omits the heat treatment step, while the other steps remain consistent with those in Example 1.

[0034] Refer to Tables 1 and 2 for a comparative summary of the effects of electrodeposition tin current density, co-electrodeposition time of indium tin, electrodeposition time of indium, heat treatment on roughness, bonding strength, water contact angle, electrolyte contact angle, electrochemical active surface area, lithium nucleation overpotential, coulombic efficiency after 100 cycles, and polarization voltage after 300 hours of cycling in the embodiments of this invention. As can be seen from the tables: (1) In Example 1, the current density for electrodepositing tin was 2 A dm. -2 The optimal parameters for the current collector were obtained by co-depositing indium tin (INT) for 9 s, electrodepositing indium for 90 s, and heat treatment at 120 ℃. The current collector exhibited a walnut-like three-dimensional porous structure on its surface. It had a roughness of 0.644 μm, good adhesion, a water contact angle of 48.5°, an electrolyte contact angle of 26.4°, and an electrochemically active surface area of ​​3.35 mF / cm². -2 The lithium nucleation overpotential was 4.6 mV, the coulombic efficiency was 98.43% after 100 cycles, and the polarization voltage was 11.4 mV after 300 h of cycling.

[0035] (2) By comparing Example 1 with Comparative Examples 1, 2, 3 and Examples 4, 5, it can be concluded that the co-deposition time of indium tin has the greatest impact on the current collector with a three-dimensional porous structure with a lithiophilic surface. When the time is too short, the indium tin seed layer is too thin and cannot effectively guide the deposition of indium, thus failing to form a porous structure. On the other hand, if the time is too long, the indium tin seed layer will be too thick, resulting in the formation of a dense indium layer, which also lacks a porous structure. When the co-deposition step is missing, indium is directly deposited on tin to form a smooth and flat coating. Comparing the roughness, adhesion, water contact angle, electrolyte contact angle, electrochemical active surface area, lithium nucleation overpotential, coulombic efficiency after 100 cycles and polarization voltage after 300 h of cycles, both too thin and too thick indium tin seed layers will affect the performance of the current collector.

[0036] (3) By comparing Example 1 with Examples 2, 3, 6 and 7, it can be concluded that the current density of electrodeposited tin and the time of electrodeposited indium have little effect on the current collector with a three-dimensional porous structure with a lithiophilic surface. After comparing the roughness, gloss, contact angle, electrochemical active surface area, lithium nucleation overpotential, coulombic efficiency after 100 cycles and polarization voltage after 300 h of cycles, it can be concluded that the parameters in Example 1 are the best.

[0037] (4) By comparing Example 1 with Comparative Examples 4, 5 and 6, it can be concluded that in Comparative Example 4, due to the low current density, the grain growth rate was greater than the nucleation rate, the tin particles were too large, and the tin layer was too thick, which covered the three-dimensional structure of the copper foil, resulting in the formation of a planar coating. This could not effectively alleviate the volume expansion of the indium tin alloy and the volume change of the lithium deposition / stripping process during cycling. In Comparative Example 5, due to the long indium plating time, the indium layer was too thick and filled the porous structure, which reduced the electrochemical active surface area and reduced the affinity for water and electrolyte. In Comparative Example 6, due to the lack of heat treatment, the copper-tin alloy, indium-tin alloy and wrinkled morphology could not be formed. The absence of copper-tin alloy resulted in poor bonding force between the copper substrate and the tin coating, poor overall structural stability, reduced roughness and poor wettability of the current collector, and poor lithium affinity of the current collector due to the absence of indium-tin alloy, which was not conducive to improving the electrochemical performance of the battery.

[0038] Table 1 Table 2 In summary, the embodiments of the present invention provide a current collector with a walnut-like three-dimensional porous structure on its surface, a preparation method thereof, and a battery. Using copper foil as a substrate, a tin / copper foil with a three-dimensional surface structure is obtained by constant current electrodeposition of tin. The tin / copper foil with the three-dimensional surface structure is then immersed in a co-deposition solution of indium tin. An indium tin seed layer is deposited on the tin surface by constant current co-deposition of indium tin, followed by constant current electrodeposition of indium. The indium tin seed layer guides the deposition of indium to obtain a tin / indium tin / tin / copper foil with a three-dimensional porous surface structure. The tin / indium tin / tin / copper foil with the three-dimensional porous surface structure is then heat-treated to obtain a current collector with a walnut-like three-dimensional porous structure on its surface. The walnut-like three-dimensional porous structure is a wrinkled, spherical structure with pore channels.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for preparing a current collector with a three-dimensional porous structure on its surface, characterized in that, The method includes: Using copper foil as a substrate, tin / copper foil with a three-dimensional surface structure is obtained by constant current electrodeposition of tin. A three-dimensional tin / copper foil is immersed in an indium tin co-electrodeposition solution. An indium tin seed layer is deposited on the tin surface by constant current co-electrodeposition. Indium is then deposited by constant current electrodeposition. The deposition of indium is guided by the indium tin seed layer to obtain a three-dimensional porous indium / indium tin / tin / copper foil. The indium tin seed layer is porous and has a thickness of 0.05~0.15 μm. A current collector with a walnut-shaped three-dimensional porous structure is obtained by heat treatment of an indium / indium tin / tin / copper foil with a three-dimensional porous structure on the surface; wherein the walnut-shaped three-dimensional porous structure is a wrinkled spherical structure with pore channels, the pore diameter of the pore channels is 0.3~0.6 μm, and the diameter of the wrinkled spherical structure is 6~10 μm.

2. The method for preparing a current collector with a three-dimensional porous structure on its surface according to claim 1, characterized in that, The preparation method further includes: (1) Place the copper foil in the electrodeposition tin solution and set the current density to 1~3 A dm. -2 The electrodeposition time was 40–60 s, and the electrodeposition temperature was maintained at 25–30 °C. A magnetic stirrer was used to agitate the electrodeposition solution at a speed of 150–250 r / min. -1 This yields a tin / copper foil with a three-dimensional surface structure. (2) Immerse the three-dimensional tin / copper foil on the surface into a co-electrodeposition solution for indium tin, and set the current density for indium tin co-electrodeposition to 1~3 A dm. -2 The co-electrodeposition time was 7–11 s, and the stirring speed was 250–350 r / min. -1 The co-electrodeposited sample was placed in an indium electrodeposition solution, and the current density for indium electrodeposition was set to 1~3 A dm. -2 The electrodeposition time was 60–120 s, and the stirring speed was 150–250 r / min. -1 A three-dimensional porous indium / indium tin / tin / copper foil with a surface structure was obtained. (3) Place the indium / indium tin / tin / copper foil with a three-dimensional porous structure on the surface into the corundum crucible, and place the corundum crucible in the quartz tube of the tube furnace for sealing treatment. Set the heat treatment temperature to 110~130 ℃ and the heat treatment time to 7~9 h to obtain a current collector with a walnut-shaped three-dimensional porous structure on the surface.

3. The method for preparing a current collector with a three-dimensional porous structure on its surface according to claim 1, characterized in that, The thickness of the tin is 0.6~0.8 μm.

4. The method for preparing a current collector with a three-dimensional porous structure on its surface according to claim 1, characterized in that, The thickness of the indium tin seed layer is 0.05~0.15 μm.

5. The method for preparing a current collector with a three-dimensional porous structure on its surface according to claim 1, characterized in that, The thickness of the indium is 0.5~0.7 μm.

6. The method for preparing a current collector with a three-dimensional porous structure on its surface according to claim 1, characterized in that, The pore size of the pore channel is 0.3~0.6 μm.

7. The method for preparing a current collector with a three-dimensional porous structure on its surface according to claim 1, characterized in that, The roughness of the current collector is 0.539~0.644 μm.

8. A current collector with a walnut-shaped three-dimensional porous structure on its surface, characterized in that, The current collector includes the current collector obtained by the method for preparing a current collector with a three-dimensional porous structure on the surface as described in any one of claims 1 to 7.

9. The current collector with a three-dimensional porous structure on its surface according to claim 8, characterized in that, The current collector surface with a three-dimensional porous structure includes two or more metals or alloys selected from copper, tin, indium, Cu3Sn, Cu6Sn5, In3Sn, and InSn4.

10. A battery, characterized in that, Including a current collector with a three-dimensional porous structure on its surface as described in any one of claims 8 to 9.

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