All-solid-state tertiary batteries

Abstract

To provide an all-solid-state tertiary battery that exhibits excellent thermal responsiveness to temperature changes and excellent thermal durability against repeated temperature changes. [Solution] An all-solid-state tertiary battery 1 comprising a first electrode 2, a second electrode 3, and a solid electrolyte 4 located between the first electrode 2 and the second electrode 3.

Description

[Technical Field]

[0001] This invention relates to an all-solid-state tertiary battery. [Background technology]

[0002] In thermoelectric power generation technology, thermoelectric batteries (tertiary batteries) that continuously extract electrical energy by utilizing temperature changes have been developed. A tertiary battery uses two types of battery electrode materials with different oxidation-reduction potential temperature coefficients α (=dV / dT) for the positive and negative electrodes, and these positive and negative electrodes are placed in an electrolyte. By applying a temperature change, a difference in electromotive force is generated between the positive and negative electrodes, thereby generating thermoelectric power.

[0003] As an example of a tertiary battery, a thermoelectric element is known in which a first electrode and a second electrode face each other via a single electrolyte, and the first and second electrodes contain materials that allow the same metal ions to reversibly enter and exit. In tertiary batteries, a liquid electrolyte is generally used as the electrolyte (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-073596 [Overview of the project] [Problems that the invention aims to solve]

[0005] Since tertiary batteries generate electromotive force through temperature changes, the electrolyte needs to have high thermal responsiveness to temperature changes and thermal durability against repeated temperature changes. Conventional liquid electrolytes have the problem of low thermal responsiveness to temperature changes and low thermal durability against repeated temperature changes.

[0006] The present invention has been made in view of the above circumstances, and aims to provide an all-solid-state tertiary battery that has excellent thermal responsiveness to temperature changes and excellent thermal durability against repeated temperature changes. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] An all-solid-state rechargeable battery comprising a first electrode, a second electrode, and a solid electrolyte located between the first electrode and the second electrode. [2] The all-solid-state tertiary battery according to [1], wherein the solid electrolyte is at least one selected from polymer materials, oxides, and sulfides obtained by hygroscopically absorbing an aqueous solution of a sodium salt. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an all-solid-state tertiary battery that exhibits excellent thermal responsiveness to temperature changes and excellent thermal durability against repeated temperature changes. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of an all-solid-state tertiary battery in one embodiment of the present invention. [Figure 2] This figure shows the results of a thermal cycling test of a liquid-type tertiary battery in the comparative example. [Figure 3] This figure shows the results of a thermal cycling test of an all-solid-state tertiary battery in an example. [Modes for carrying out the invention]

[0010] Embodiments of the all-solid-state tertiary battery of the present invention will be described below. This embodiment is provided to give a better understanding of the spirit of the invention and does not limit the present invention unless otherwise specified.

[0011] [All-solid-state tertiary battery] Hereinafter, the all-solid-state secondary battery of the present embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the all-solid-state secondary battery of the present embodiment. As shown in FIG. 1, the all-solid-state secondary battery 1 of the present embodiment includes a unit 5 having a first electrode 2, a second electrode 3, and a solid electrolyte 4. The solid electrolyte 4 exists between the first electrode 2 and the second electrode 3. In the all-solid-state secondary battery 1, the first electrode 2 is provided on one surface 6a of the current collector 6, the second electrode 3 is provided on the other surface 6b of the current collector 6, and the first electrode 2 and the second electrode 3 are arranged to face each other via the current collector 6. Also, the first electrode 2 and the second electrode 3 are arranged to face each other. Further, the first electrode 2 and the second electrode 3 are arranged to face each other with a predetermined interval via a single solid electrolyte 4. Also, a plurality of units 5 having the first electrode 2, the second electrode 3, and the solid electrolyte 4 are stacked such that the first electrode 2 of one unit 5 and the second electrode 3 of the other unit 5 are adjacent to each other via the current collector 6. Also, the first electrode 2 and the second electrode 3 are electrically connected via a lead wire 7. Also, a circuit (not shown) or a device (not shown) for extracting the current generated in the all-solid-state secondary battery 1 may be provided in the middle of the lead wire 7. In the all-solid-state secondary battery 1, these components do not have to be sealed, and as shown in FIG. 1, these components may be sealed with a laminate film 8.

[0012] The first electrode 2 and the second electrode 3 contain a material in which the same metal ions can reversibly enter and exit. Also, the first electrode 2 and the second electrode 3 may contain a material in which the same metal ions are deposited or alloyed.

[0013] The material contained in the first electrode 2 includes Na x1 Co 1-y1 A z1 [Fe(CN)6] z1(However, A is at least one selected from the group consisting of Fe, Mn, Ni, and Zn, 0.8 < x1 < 2.0, 0.0 < y1 < 1.0, 0.7 < z1 < 1.0), and examples of the compound (cobalt Prussian blue analog (Co-PBA)) represented thereby include Na 1.60 Co 0.44 Mn 0.56 [Fe(CN)6] 0.90 and the like.

[0014] Examples of the material contained in the second electrode 3 include Na x2 M 1-y2 [Fe(CN)6] z2 (However, M = Ni, Mn, Cu, Cd, 0.8 < x2 < 2.0, 0.0 < y2 < 1.0, 0.7 < z2 < 1.0) (nickel Prussian blue analog (Ni-PBA), manganese Prussian blue analog (Mn-PBA), copper Prussian blue analog (Cu-PBA), cadmium Prussian blue analog (Cd-PBA)). Examples of such compounds include Na 1.76 Ni[Fe(CN)6] 0.94 and the like.

[0015] In addition to the above electrode materials, the first electrode 2 and the second electrode 3 may contain a binder resin (binder) and a conductive assistant. Examples of the binder resin include polyvinylidene fluoride (PVDF) resin, polytetrafluoroethylene (PTFE) resin, fluororubber, and the like. Examples of the conductive assistant include Ketjen black, acetylene black (AB), furnace black, vapor grown carbon fiber (VGCF), carbon nanotube, and the like.

[0016] The solid electrolyte 4 is a polymer material, an oxide, or a sulfide that has absorbed an aqueous solution of a sodium salt. These materials may be used alone or in combination of two or more.

[0017] When the solid electrolyte 4 is a polymer material that has absorbed an aqueous solution of sodium salt, the solid electrolyte 4 is a semi-solid electrolyte (including a gel-like electrolyte). The form of the semi-solid electrolyte may be film-like (sheet-like), plate-like, or gel-like. The creation of each state can be adjusted by controlling the concentration and water content of the aqueous solution of sodium salt to which the electrolyte is absorbed. Examples of polymer materials include polyacrylic acid-based polymer compounds (including sodium polyacrylate), polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride (PVDF)-hexafluoropropylene (HEP) copolymers, oxides such as β-alumina, and sulfides such as Na3PS4.

[0018] Examples of sodium salts include sodium nitrate (NaNO3), sodium chloride (NaCl), sodium sulfate (Na2SO4), sodium perchlorate (NaClO4), and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI).

[0019] The sodium salt content in the aqueous solution of sodium salt is preferably 0.1 mol / L or more, and more preferably a content at which the aqueous solution of sodium salt becomes a saturated solution. If the sodium salt content is above the lower limit, it will not adversely affect ion conduction when moisture is absorbed by the polymer material.

[0020] The content of the aqueous sodium salt solution relative to the total mass of the solid electrolyte 4 is preferably 66% by mass or more and 90% by mass or less. When the content of the aqueous sodium salt solution is above the lower limit, the hygroscopic polymer material can maintain its solid shape. When the content of the aqueous sodium salt solution exceeds the upper limit, the hygroscopic polymer material can no longer maintain its gel state and ceases to be a solid charged material.

[0021] Furthermore, Figure 1 illustrates a case in which multiple units 5, each having a first electrode 2, a second electrode 3, and a solid electrolyte 4, are stacked such that the first electrode 2 of one unit 5 and the second electrode 3 of the other unit 5 are adjacent to each other in an all-solid-state tertiary battery 1. However, this embodiment is not limited to this. The all-solid-state tertiary battery 1 of this embodiment may consist of a single unit 5 having a first electrode 2, a second electrode 3, and a solid electrolyte 4.

[0022] In this embodiment of the all-solid-state tertiary battery 1, since the first electrode 2 and the second electrode 3 are arranged facing each other via a solid electrolyte 4, it exhibits excellent thermal responsiveness to temperature changes and excellent thermal durability against repeated temperature changes. [Examples]

[0023] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0024] [Comparative Example] (Manufacturing of liquid-type tertiary batteries) Na is used as the electrode material, which is a cobalt-Prussian blue analog (Co-PBA). 1.48 Co[Fe(CN)6] 0.87 A positive electrode slurry was prepared by mixing acetylene black as a conductive additive and polyvinylidene fluoride (PVDF) resin as a binder resin in a mass ratio of 7:2:1. Na is used as the electrode material, which is a nickel-Prussian blue analog (Ni-PBA). 1.76 Ni[Fe(CN)6] 0.94 A cathode slurry was prepared by mixing acetylene black as a conductive additive and polyvinylidene fluoride (PVDF) resin as a binder resin in a mass ratio of 7:2:1. After applying the positive electrode slurry to one main surface of the SUS304 current collector, the positive electrode slurry was dried to form an electrode active material layer (positive electrode active material layer) consisting of the positive electrode slurry on one main surface of the SUS304 current collector, thereby obtaining the positive electrode. After applying the cathode slurry to one main surface of the SUS304 current collector, the cathode slurry was dried to form an electrode active material layer (cathode active material layer) consisting of the cathode slurry on one main surface of the SUS304 current collector, thereby obtaining the cathode. The obtained positive and negative electrodes were connected to a charge / discharge device (device name: HJ1001SD8, manufactured by Meiden Hokuto Co., Ltd.) and pre-oxidized to 0.53V. A 17 mol / kg aqueous solution of sodium perchlorate (NaClO4) was prepared as the liquid electrochemical substance. The obtained liquid electrochemical material was poured into a beaker, and the positive and negative electrodes were placed opposite each other in the liquid electrochemical material to obtain a liquid-type tertiary battery.

[0025] A thermal cycling test was performed on the resulting liquid-type tertiary battery. The thermal cycling test method involved heating the above-mentioned tertiary battery from 20°C to 40°C, maintaining the temperature at 40°C, and then applying a current of 1.0 μA to discharge the resulting electromotive force to 0V. After discharge, the temperature was lowered from 40°C to 20°C, maintained at 20°C, and then applying a current of 1.0 μA to discharge the resulting electromotive force to 0V. This process constituted one cycle, and the same process was repeated 10 times. The results are shown in Figure 2. As shown in Figure 2, the results confirm excellent reproducibility of electromotive force during both the heating and cooling processes for up to approximately 10 cycles.

[0026] [Examples] (Fabrication of all-solid-state tertiary batteries) Na is used as the electrode material, which is a cobalt-Prussian blue analog (Co-PBA). 1.48 Co[Fe(CN)6] 0.87 A positive electrode slurry was prepared by mixing acetylene black as a conductive additive and polyvinylidene fluoride (PVDF) resin as a binder resin in a mass ratio of 7:2:1. Na is used as the electrode material, which is a nickel-Prussian blue analog (Ni-PBA). 1.76 Ni[Fe(CN)6] 0.94A cathode slurry was prepared by mixing acetylene black as a conductive additive and polyvinylidene fluoride (PVDF) resin as a binder resin in a mass ratio of 7:2:1. After applying the positive electrode slurry to one main surface of the SUS304 current collector, the positive electrode slurry was dried to form an electrode active material layer (positive electrode active material layer) consisting of the positive electrode slurry on one main surface of the SUS304 current collector, thereby obtaining the positive electrode. After applying the cathode slurry to one main surface of the SUS304 current collector, the cathode slurry was dried to form an electrode active material layer (cathode active material layer) consisting of the cathode slurry on one main surface of the SUS304 current collector, thereby obtaining the cathode. The obtained positive and negative electrodes were connected to a charge / discharge device (device name: HJ1001SD8, manufactured by Meiden Hokuto Co., Ltd.) and pre-oxidized to 0.53V. A solid electrolyte (gel-like electrochemical substance) was prepared by impregnating 0.2 g of sodium polyacrylate with 400 μL of a 17 mol / kg aqueous solution of sodium perchlorate (NaClO4). By placing the positive and negative electrodes opposite each other through the obtained solid electrolyte, an all-solid-state tertiary battery was obtained.

[0027] (Thermal cycle test) Thermal cycling tests were performed on the obtained all-solid-state tertiary batteries. The thermal cycling test method was the same as that used for the comparative example. The results are shown in Figure 3. As shown in Figure 3, the results confirm excellent reproducibility of electromotive force during both the heating and cooling processes up to approximately 10 cycles. Furthermore, it was confirmed that electromotive force equivalent to that of the comparative example could be obtained. [Industrial applicability]

[0028] The thermal battery equipped with the electrolyte for thermal batteries of the present invention can be used in thermoelectric power generation elements, thermoelectric power generation systems, etc., that convert industrial waste heat, solar heat, human body heat, etc., into electrical energy. Specifically, the thermal battery of the present invention can be used as a stationary thermoelectric power generator, a mobile power generator, a hybrid solar energy power generator, etc. [Explanation of symbols]

[0029] 1 All-solid-state tertiary battery 2. First electrode 3. Second electrode 4 Solid electrolyte 5 units 6 Collector electrode 7 Lead wires 8. Laminating film

Claims

1. An all-solid-state rechargeable battery comprising a first electrode, a second electrode, and a solid electrolyte located between the first electrode and the second electrode.

2. The all-solid-state rechargeable battery according to claim 1, wherein the solid electrolyte is at least one selected from a polymer material that has absorbed an aqueous solution of a sodium salt, an oxide, and a sulfide.

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