Zinc electrode with boron-based protective film formed and zinc secondary battery containing the same

Abstract

The present invention relates to an electrode having a boron-based protective film formed thereon and a zinc secondary battery including the same. By forming a boron-based protective film on the surface of a zinc electrode, side reactions caused by water electrolysis during electrodeposition can be suppressed and dendrite formation can be prevented, thereby improving the lifespan characteristics of the zinc secondary battery.

Description

Technology Field

[0001] The present invention relates to a zinc secondary battery, and more specifically, to a zinc electrode having a boron-based protective film formed thereon that can improve electrical performance by suppressing dendrite growth and side reactions during electrodeposition, and a zinc secondary battery including the same. Background Technology

[0002] Lithium-ion batteries are one of the most promising technologies for the small and medium-to-large battery markets. However, analyses suggest that limited lithium reserves may not be able to meet increasing demand, and accordingly, the development of next-generation rechargeable batteries is expected to play a significant role in the future energy market.

[0003] In accordance with these market trends, next-generation secondary batteries using sodium (Na) and potassium (K), which are more cost-competitive than lithium, are being developed as alternatives. However, there is a demand for the development of batteries using multivalent cations capable of accepting one or more electrons to increase the amount of charge reversibly stored in a narrow voltage range. In other words, divalent or trivalent multivalent ions, such as zinc, magnesium, calcium, and aluminum, are expected to achieve higher capacity and energy density than monovalent ions.

[0004] Zinc secondary batteries are being actively researched and developed for use as energy storage batteries because they can fundamentally resolve the risks of fire and explosion, enable low-cost implementation, and possess low toxicity. A zinc secondary battery is a system that utilizes zinc metal as the negative electrode active material and manganese dioxide as the positive electrode active material; it utilizes the oxidation / reduction reaction between zinc metal and zinc ions at the negative electrode, and the oxidation / reduction reaction of manganese through the insertion / extraction reaction between zinc ions and hydrogen ions at the positive electrode.

[0005] In zinc secondary batteries, the zinc electrode used as the negative electrode is made of zinc metal, and due to side reactions between the zinc metal and the aqueous electrolyte, the surface of the zinc electrode corrodes, the electrolyte is depleted, and serious performance degradation in terms of lifespan and stability is caused by dendrite formation and / or growth.

[0006] To address these problems, a protective film of polymer or inorganic material has conventionally been formed on the surface of the zinc electrode. While such a protective film can inhibit dendrite growth, it has been observed that electrochemical performance deteriorates rapidly because it fails to provide sufficient space for ion movement. Furthermore, even if the protective film secures space for ion movement, hydrogen gas is generated, causing electrochemical reactions within the electrode's operating range and degrading the battery's performance. Prior art literature

[0007] Registered Patent Publication No. 10-2536312 (Registered on May 19, 2023) The problem to be solved

[0008] Therefore, the objective of the present invention is to provide a zinc electrode having a boron-based protective film formed thereon that can improve electrical performance by suppressing dendrite growth and side reactions during electrodeposition, and a zinc secondary battery including the same.

[0009] Meanwhile, the objectives of the present invention are not limited to the above objectives, and other unmentioned objectives will be clearly understood from the description below. means of solving the problem

[0010] To achieve the above objective, the present invention provides a zinc electrode for a zinc secondary battery comprising: a zinc metal; and a boron-based protective film formed on the surface of the zinc metal.

[0011] The above boron-based protective film comprises a boron-based material and a binder.

[0012] The above boron-based material includes at least one of BN, B3N3Cl3, B3N3F3, and B2O3.

[0013] The above binder includes PVDF.

[0014] The above boron-based material has a particle size of 100 to 400 nm.

[0015] The weight ratio of the above boron-based material and binder is 9:1 to 8:2.

[0016] The thickness of the above boron-based protective film is 5 to 20 μm.

[0017] The present invention also provides a zinc secondary battery comprising the zinc electrode described above. Effects of the invention

[0018] According to the present invention, by forming a boron-based protective film on the surface of a zinc electrode, side reactions caused by water electrolysis during electrodeposition and dendrite formation can be suppressed, thereby improving the lifespan characteristics of a zinc secondary battery. That is, in a water-based zinc secondary battery, the boron-based protective film formed on the surface of the zinc electrode can suppress side reactions caused by water electrolysis and suppress dendrite growth, thereby improving the lifespan characteristics of the battery.

[0019] Meanwhile, the effects of the present invention are not limited to those described above, and other unmentioned effects may be disclosed directly or implicitly in the detailed description according to the embodiments of the present invention to be described below. Brief explanation of the drawing

[0020] Figure 1 is a flowchart showing a method for forming a boron-based protective film on the surface of a zinc electrode of a zinc secondary battery. Figure 2 is a diagram showing an SEM image of a zinc electrode according to Example 1. Figure 3 is an SEM image showing the state of zinc electrodeposited after charging and discharging of the zinc electrode according to Comparative Example 1 and Example 1. Figure 4 is a graph showing the cycle characteristics of a symmetric cell including a zinc electrode according to Comparative Example 1 and Example 1. Figure 5 is a graph showing the cycle characteristics of a full cell including a zinc electrode according to Comparative Example 1 and Example 1. Specific details for implementing the invention

[0021] It should be noted that in the following description, only the parts necessary for understanding the embodiments of the present invention are explained, and the description of other parts will be omitted to the extent that it does not deviate from the gist of the present invention.

[0022] The terms and words used in the specification and claims described below should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. Accordingly, the embodiments described in this specification and the configurations illustrated in the drawings are merely preferred embodiments of the invention and do not represent all aspects of the technical spirit of the invention; therefore, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0023] Hereinafter, embodiments of the present invention will be described in more detail with reference to the attached drawings.

[0024] The zinc secondary battery according to the present invention includes a zinc electrode.

[0025] The zinc electrode of the zinc secondary battery according to the present invention comprises zinc metal and a boron-based protective film formed on the surface of the zinc metal.

[0026] Here, the boron-based protective film comprises a boron-based material and a binder. That is, a boron-based protective film can be formed by coating and drying a boron-based slurry containing a boron-based material and a binder onto zinc metal. Alternatively, a boron-based protective film can be formed by coating and drying a boron-based slurry onto a sacrificial substrate to form a boron-based film, and then attaching the boron-based film separated by the sacrificial substrate to zinc metal.

[0027] The boron-based material includes at least one of BN, B3N3Cl3, B3N3F3, and B2O3.

[0028] PVDF may be used as a binder, but is not limited to this.

[0029] The boron-based material has a particle size of 100 to 400 nm. If the particle size of the boron-based material exceeds 400 nm, the effect of suppressing dendrite growth and side reactions during electrodeposition may decrease.

[0030] The weight ratio of the boron-based material to the binder is 9:1 to 8:2. If the weight ratio of the boron-based material exceeds 9, the binder content is insufficient, which may reduce the adhesion of the boron-based protective film to zinc metal and prevent the boron-based protective film from being properly formed. If the weight ratio of the binder in the boron-based protective film exceeds 2, dendrite growth can be inhibited, but electrochemical performance may be degraded because sufficient space for ion movement is not secured.

[0031] A method for manufacturing a zinc electrode of a zinc secondary battery according to the present invention is described below with reference to FIG. 1. FIG. 1 is a flowchart showing a method for forming a boron-based protective film on the surface of a zinc electrode of a zinc secondary battery.

[0032] First, in step S10, a boron-based material and a binder are mixed to prepare a boron-based slurry.

[0033] Next, in step S20, a boron-based slurry is coated onto the surface of zinc metal to form a boron-based coating film. Here, at least one of slit coating, spin coating, dip coating, spray coating, slot die coating, roll coating, and bar coating may be used as the coating method.

[0034] Then, the boron-based coating film coated in step S30 is dried to form a boron-based protective film on the surface of the zinc metal.

[0035] [Examples and Comparative Examples]

[0036] In order to confirm the electrochemical characteristics of the zinc electrode formed with a boron-based coating film according to the present invention, zinc electrodes according to the examples and comparative examples were prepared, and the charge / discharge characteristics and SEM images of the surface of the zinc electrode after charge / discharge were confirmed.

[0037] Example 1

[0038] A boron-based slurry was prepared using BN powder as the boron-based material and PVDF as the binder. The particle size of the BN powder is 100–400 nm. The boron-based slurry was prepared by mixing BN and PVDF in a weight ratio of 9:1. Then, a zinc electrode with a boron-based protective film was prepared by applying the boron-based slurry onto zinc metal and drying it. The thickness of the boron-based protective film is 5–20 μm.

[0039] Comparative Example 1

[0040] Zinc metal without a boron-based protective film was used as the zinc electrode.

[0041] Figure 2 is a diagram showing an SEM image of a zinc electrode according to Example 1.

[0042] Referring to FIG. 2, it can be seen that the zinc electrode according to Example 1 has a boron-based protective film uniformly formed on the surface of the zinc metal.

[0043] FIG. 3 is an SEM image showing the state of zinc electrodeposited after charging and discharging of the zinc electrode according to Comparative Example 1 and Example 1. Here, FIG. 3(a) is an SEM image showing the state of zinc electrodeposited after charging and discharging of the zinc electrode according to Comparative Example 1. FIG. 3(b) is an SEM image showing the state of zinc electrodeposited after charging and discharging of the zinc electrode according to Example 1.

[0044] As shown in FIG. 3, when comparing the electrodeposition shape after charging and discharging of the zinc electrode according to Comparative Example 1, in which no boron-based protective film is formed, and the zinc electrode according to Example 1, in which a boron-based protective film is formed, it can be seen that a zinc electrodeposition layer containing relatively irregular and large protrusions is formed on the surface of the zinc electrode according to Comparative Example 1, as shown in FIG. 3 (a).

[0045] On the other hand, as shown in Fig. 3(b), it can be seen that the zinc electrode according to Example 1 has a flat and uniformly formed zinc electrodeposited layer.

[0046] It can be confirmed that the zinc electrodeposited layer, as illustrated in FIG. 3, affects the zinc charge / discharge performance of the zinc electrode as shown in FIG. 4, thereby influencing the cycle characteristics. Here, FIG. 4 is a graph showing the cycle characteristics of a symmetric cell containing a zinc electrode according to Comparative Example 1 and Example 1. In FIG. 4, the cycle characteristic is 3 mA / cm² 2 Current and 3 mAh / cm 2 It was measured under reaction capacity conditions.

[0047] Referring to FIG. 4, it can be seen that the zinc electrode according to Example 1 exhibits better cycle characteristics than Comparative Example 1.

[0048] Examples 2 to 4

[0049] In addition to Example 1, which used BN as the boron-based material, B3N3Cl3 (Example 2), B3N3F3 (Example 3), and B2O3 (Example 4) were also coated on zinc metal under the same conditions and methods as Example 1, and the cycle characteristics for the symmetric cell as shown in Fig. 4 were measured, and the measurement results are as shown in Table 1 below.

[0050] Boron-based protective film Charge / Discharge Duration (Time) BN (Example 1) 194 B3N3Cl3 (Example 2) 112 B3N3F3 (Example 3) 126 B2O3 (Example 4) 152 No protective layer (Comparative Example 1) 63

[0051] Referring to Table 1, it can be seen that the zinc electrodes according to Examples 1 to 4 exhibit improved charge-discharge cycle characteristics compared to Comparative Example 1.

[0052] Figure 5 is a graph showing the cycle characteristics of a full cell including a zinc electrode according to Comparative Example 1 and Example 1.

[0053] Referring to FIG. 5, a full cell including a zinc electrode according to Comparative Example 1 and Example 1 was manufactured. Specifically, after fabricating a zinc-manganese oxide aqueous secondary battery using the zinc electrode according to Comparative Example 1 and Example 1, the charge-discharge cycle (lifetime) characteristics of the secondary battery were verified. The manganese oxide electrode used contained 70 wt% beta-phase MnO2, and carbon black was used as the conductive material and PTFE as the binder. The capacity per electrode area was 4 mAh / cm² 2 It corresponds to. 2M ZnSO4 and 0.5M MnSO4 were used as the electrolyte.

[0054] After manufacturing a Zn-MnO2 full cell with a zinc electrode according to Example 1 and Comparative Example 1 applied as the cathode and checking the cycle characteristics after 400 charge-discharge cycles, it can be confirmed that the Zn-MnO2 full cell according to Example 1 shows a significantly higher capacity retention rate than Comparative Example 1.

[0055] In addition to Example 1 using BN as the boron-based material, B3N3Cl3 (Example 2), B3N3F3 (Example 3), and B2O3 (Example 4) were also prepared under the same conditions and methods as Example 1, and the capacity retention rates of the Zn-MnO2 full cells are as shown in Table 2.

[0056] Boron-based protective film 400-cycle dose retention rate (%) of Zn-MnO2 full cell BN (Example 1) 80 B3N3Cl3 (Example 2) 63 B3N3F3 (Example 3) 65 B2O3 (Example 4) 70 No protective layer (Comparative Example 1) 47

[0057] Referring to Table 2, it can be seen that the Zn-MnO2 full cells according to Examples 2 to 4 also show a significantly higher capacity retention rate than Comparative Example 1.

[0058] As such, the improvement in the reversible efficiency, electrodeposition shape, and lifespan characteristics in a full cell of the zinc electrodes according to Examples 1 to 4 is attributed to the boron-based protective film. That is, it is believed that the improved results are produced by suppressing the interfacial movement of anions and water in the electrolyte and inhibiting side reactions through the acid-base properties of the boron-based protective film, and by relatively promoting the movement of only zinc ions.

[0059] Meanwhile, the embodiments disclosed in this specification and drawings are merely specific examples provided to aid understanding and are not intended to limit the scope of the invention. It is obvious to those skilled in the art that other variations based on the technical concept of the invention are possible in addition to the embodiments disclosed herein.

Claims

Claim 1 A zinc electrode for a zinc secondary battery, comprising: a zinc metal; and a boron-based protective film formed on the surface of the zinc metal; wherein the boron-based protective film comprises a boron-based material and a binder, wherein the boron-based material comprises at least one of B3N3Cl3, B3N3F3, and B2O3, wherein the boron-based material has a particle size of 100 to 400 nm, and the weight ratio of the boron-based material to the binder is 9:1 to 8:

2. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A zinc electrode for a zinc secondary battery according to claim 1, characterized in that the binder comprises PVDF. Claim 6 delete Claim 7 A zinc electrode for a zinc secondary battery according to claim 1, characterized in that the thickness of the boron-based protective film is 5 to 20 μm. Claim 8 A zinc secondary battery comprising a zinc electrode, wherein the zinc electrode comprises a zinc metal; and a boron-based protective film formed on the surface of the zinc metal; wherein the boron-based protective film comprises a boron-based material and a binder, wherein the boron-based material comprises at least one of B3N3Cl3, B3N3F3, and B2O3, wherein the boron-based material has a particle size of 100 to 400 nm, and the weight ratio of the boron-based material to the binder is 9:1 to 8:2.

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