Solid lithium ion secondary battery

Abstract

To provide a solid lithium ion secondary battery which can suppress reaction of aluminum as a negative electrode collector layer and lithium ions.SOLUTION: The solid lithium ion secondary battery sequentially includes a negative electrode collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode collector layer. The negative electrode collector layer has an aluminum layer, and at least a part on the negative electrode active material side of the aluminum layer is processed with nickel, and the negative electrode active material in the negative electrode active material layer reacts with lithium ions at 0.3 V or lower.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to solid-state lithium-ion secondary batteries. [Background technology]

[0002] In recent years, solid-state batteries using a solid electrolyte have been attracting attention. Solid-state batteries using a solid electrolyte are less susceptible to decomposition of the electrolyte due to overcharging of the battery, and have high cycle durability and energy density.

[0003] On the other hand, lithium-ion secondary batteries, which are a type of secondary battery, have characteristics such as high voltage and energy density and little memory effect, and are therefore used in various fields such as automobiles and portable devices. In addition to improving performance, lithium-ion secondary batteries are also required to be lightweight. In order to reduce the weight of batteries, a technology is known that uses aluminum foil, which has a smaller specific gravity than copper foil, as the negative electrode current collector layer.

[0004] For example, Patent Document 1 discloses an all-solid-state battery in which the negative electrode current collector layer is an aluminum foil or an aluminum alloy foil.

[0005] Patent Document 2 discloses a method for producing a negative electrode current collector, which includes forming a coating film made of nickel or copper on the surface of an aluminum foil, and a method for producing a liquid-based lithium-ion secondary battery, which includes producing such a negative electrode current collector. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2022-085523 [Patent Document 2] JP 2018-116910 A Summary of the Invention [Problem to be solved by the invention]

[0007] When aluminum foil is used as the negative electrode current collector layer of a battery, there is a problem that aluminum reacts with lithium ions to form an alloy, resulting in a decrease in battery performance.

[0008] An object of the present disclosure is to provide a solid-state lithium-ion secondary battery capable of suppressing reaction between aluminum as a negative electrode current collector layer and lithium ions. [Means for solving the problem]

[0009] The present inventors have found that the above problems can be solved by the following means. <Aspect 1> A solid-state lithium-ion battery including, in this order, a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer, the negative electrode current collector layer has an aluminum layer, At least a surface of the aluminum layer facing the negative electrode active material layer is nickel-plated, and The negative electrode active material contained in the negative electrode active material layer reacts with lithium ions at 0.3 V or less. Solid-state lithium-ion secondary battery. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a solid-state lithium-ion secondary battery capable of suppressing the reaction between aluminum as a negative electrode current collector layer and lithium ions. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a solid-state lithium-ion secondary battery of the present disclosure. [Diagram 2] FIG. 2 is a graph showing the current values ​​that flowed when a predetermined voltage was applied to the evaluation cell of each example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the present disclosure.

[0013] <Solid-state lithium-ion secondary battery> The solid-state lithium-ion secondary battery of the present disclosure includes, in this order, a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer. The negative electrode current collector layer has an aluminum layer, and at least the aluminum layer on the negative electrode active material layer side is nickel-plated, and the negative electrode active material contained in the negative electrode active material layer reacts with lithium at 0.3 V or less.

[0014] As described above, when aluminum foil is used as the negative electrode current collector layer of a battery, there is a problem that aluminum reacts with lithium ions to form an alloy, resulting in a decrease in battery performance. The present inventors have found that the reaction between aluminum and lithium ions can be suppressed by nickel plating at least the negative electrode active material layer side of the aluminum layer. The reason for this, without intending to be bound by any theory, is believed to be that the nickel layer formed on the surface of the aluminum layer prevents aluminum from coming into contact with lithium ions, thereby suppressing the reaction between aluminum and lithium ions.

[0015] Hereinafter, the solid-state lithium-ion secondary battery of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of the solid-state lithium-ion secondary battery of the present disclosure. As shown in Fig. 1, the solid-state lithium-ion secondary battery 1 of the present disclosure includes, in this order, a negative electrode current collector layer 10, a negative electrode active material layer 20, a solid electrolyte layer 30, a positive electrode active material layer 40, and a positive electrode current collector layer 50. Note that the dimensional relationships in Fig. 1 do not reflect the actual dimensional relationships.

[0016] <Negative electrode current collector layer> 1, the negative electrode current collector layer 10 has an aluminum layer 11, and at least the aluminum layer 11 on the side facing the negative electrode active material layer 20 is nickel-plated. A nickel layer 12 is formed on the surface of the aluminum layer 11 by this nickel plating process.

[0017] As the aluminum layer 11, a commercially available aluminum foil can be used.

[0018] The nickel plating may be performed, for example, by forming a coating film made of nickel on an aluminum foil, specifically, by immersing the aluminum foil in a plating solution.

[0019] The nickel plating may be performed by electrolytic plating or electroless plating.

[0020] The thickness of the nickel layer 12 may be more than 0 μm, 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more, and may be 3.0 μm or less, 2.7 μm or less, 2.5 μm or less, or 2.3 μm or less. When plating is performed by electrolytic plating, the thickness of the nickel layer 12 can be controlled by adjusting, for example, the current density and the current application time.

[0021] As the negative electrode current collector layer 10, a commercially available nickel-plated aluminum foil may be used.

[0022] <Negative electrode active material layer> The negative electrode active material layer 20 includes a negative electrode active material. The negative electrode active material reacts with lithium ions at 0.3 V or less. Examples of such a negative electrode active material include silicon-based active materials such as silicon, silicon alloys, and silicon oxide, and carbon-based active materials such as graphite and hard carbon.

[0023] When aluminum is used as the negative electrode current collector layer, the negative current collector current is 0.3 V (vs. Li / Li +) or lower is used, aluminum is alloyed with lithium. In contrast, the negative electrode current collector layer 10 of the present disclosure has the nickel layer 12 formed on the aluminum layer 11, and therefore, even when such a negative electrode active material is used, aluminum is prevented from being alloyed with lithium.

[0024] <Solid electrolyte layer, positive electrode active material layer, and positive electrode current collector layer> There are no particular limitations on the solid electrolyte layer 30, the positive electrode active material layer 40, and the positive electrode current collector layer 50, so long as they are commonly used in solid-state lithium ion secondary batteries. EXAMPLES

[0025] <<Preparation of evaluation cell>> Comparative Example 1 Li2S-P2S5 (100 mg) was placed as a sulfide-based solid electrolyte in a cylindrical container with a hole of φ11.28, and pressed with a pressure of 100 MPa using a SUS pin of φ11.28 to form a solid electrolyte layer. 2 The aluminum (Al) foil was placed on the other side of the solid electrolyte layer and pressed with a pressure of 600 MPa. 2 A lithium (Li) foil punched out was placed on the sheet to obtain a laminate. The laminate was sandwiched from both sides by a SUS pin and a restraining jig, in that order, and restrained at a pressure of 15 MPa. This produced an evaluation cell for Comparative Example 1.

[0026] Comparative Example 2 Vinyl resin and carbon were weighed and mixed to a mass ratio of 4:1. A solvent was added to this mixture and further mixed to obtain a resin slurry. The obtained resin slurry was applied onto an Al foil by a blade method, dried on a hot plate at 50°C for 20 minutes, and further dried on a hot plate at 150°C for 30 minutes. This resulted in an Al foil with a resin layer laminated thereon. The thickness of the resin layer was 6 μm. Thereafter, an evaluation cell for Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except that an Al foil with a resin layer laminated thereon was used instead of the Al foil.

[0027] Examples 1 to 4 Except for using nickel (Ni)-plated Al foil (Fukuda Metal Foil Powder Co., Ltd.) with a thickness of 0.6 μm, 1.2 μm, 1.6 μm, or 2.2 μm instead of Al foil, evaluation cells for Examples 1 to 4 were obtained in the same manner as in Comparative Example 1. The order in which the thicknesses are listed corresponds to the Example numbers.

[0028] "evaluation" Using an electrochemical measurement device, the voltage was changed at 0.5 mV / sec from the initial voltage to 0 V, from 0 V to 2 V, and from 2 V to 0 V. Then, the maximum current value that flowed when sweeping to 0 V in the second cycle was evaluated.

[0029] "result" The results are shown in FIG. 2. The current values ​​of each example are shown as relative values ​​with the value of Comparative Example 1 taken as 100. As shown in FIG. 2, the current value of the evaluation cell of the example in which the Ni-plated Al foil was used as the negative electrode current collector layer was smaller than the current value of the evaluation cell of Comparative Example 1 in which the non-Ni-plated Al foil was used as the negative electrode current collector layer. That is, it was confirmed that Al does not react easily with Li. In addition, the current value of the evaluation cell of Comparative Example 2 in which the Al foil laminated with the resin layer was used as the negative electrode current collector layer was approximately the same as the current value of the evaluation cell of the example, but the battery according to the configuration of Comparative Example 2 has a problem in that the resin softens in a high-temperature environment, and the shape change becomes large when the battery is used. [Explanation of symbols]

[0030] 1. Solid-state lithium-ion secondary battery 10 Negative electrode current collector layer 11 Aluminum layer 12 Nickel layer 20 Negative electrode active material layer 30 Solid electrolyte layer 40 Cathode active material layer 50 Positive electrode current collector layer

Claims

[Claim 1] A solid-state lithium-ion battery including, in this order, a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer, the negative electrode current collector layer has an aluminum layer, At least a surface of the aluminum layer facing the negative electrode active material layer is nickel-plated, and The negative electrode active material contained in the negative electrode active material layer reacts with lithium ions at 0.3 V or less. Solid-state lithium-ion secondary battery.

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