Positive electrode active material for chloride ion batteries and method for producing the same, positive electrode composite material for chloride ion batteries, chloride ion battery
Strontium ruthenium oxide with a layered perovskite structure addresses the cycle degradation issue in chloride ion batteries by promoting intercalation reactions, enhancing battery stability and capacity retention.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2024-11-11
- Publication Date
- 2026-05-21
AI Technical Summary
Conventional metal chloride-based positive electrode active materials for chloride ion batteries suffer from poor cycle characteristics due to solubility in the electrolyte and significant expansion and contraction during charging and discharging, leading to reduced contact with the electrolyte and decreased battery performance.
Employing strontium ruthenium oxide with a layered perovskite structure as the positive electrode active material, which facilitates intercalation reactions, minimizing expansion and contraction, and improving cycle characteristics.
Strontium ruthenium oxide enhances the cycle stability of chloride ion batteries by maintaining effective contact with the electrolyte during charge-discharge cycles, resulting in high capacity retention rates.
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Abstract
Description
[Technical Field]
[0001] This disclosure relates to a positive electrode active material for chloride ion batteries, a method for producing the same, a positive electrode composite material for chloride ion batteries, and a chloride ion battery. [Background technology]
[0002] As disclosed in Non-Patent Documents 1 and 2, and in Patent Document 1, metal chlorides are known as positive electrode active materials for chloride ion batteries. [Prior art documents] [Non-patent literature]
[0003] [Non-Patent Document 1] Xiangyu Zhao et al., “Chloride ION BATTERY: a new member in the rechargeable BATTERY family”, Journal of Power Sources 245 (2014) 706-711 [Non-Patent Document 2] Ryo SAKAMOTO er al., “Room-temperature Operation of All-SOLID-STATE Chloride-ION Battery with Perovskite-type CsSn0.95Mn0.05Cl3 as a Solid Electrolyte”, Electrochemistry, 91(7), 077003 (2023) [Patent Documents]
[0004] [Patent Document 1] Japanese Patent Publication No. 2022-126132 [Overview of the project] [Problems that the invention aims to solve]
[0005] This disclosure aims to provide a novel positive electrode active material for chloride ion batteries, a method for producing the same, a positive electrode composite material for chloride ion batteries containing such a positive electrode active material, and a chloride ion battery containing such a positive electrode composite material. [Means for solving the problem]
[0006] The Disclosing Party has found that the above-mentioned problems can be solved by the following means. <Aspect 1> A strontium ruthenium oxide having a layered perovskite structure, which is a positive electrode active material for chloride ion batteries. <Aspect 2> The strontium ruthenium oxide is Sr3Ru2O x A positive electrode active material for a chloride ion battery according to embodiment 1, wherein (5 ≤ x ≤ 7). <Aspect 3> A positive electrode composite material for a chloride ion battery, comprising the positive electrode active material for a chloride ion battery described in Embodiment 1 or 2. <Aspect 4> It has a positive electrode active material layer, and The positive electrode active material layer contains the positive electrode composite material for chloride ion batteries described in Embodiment 3. Chloride ion battery. <Aspect 5> A method for producing a positive electrode active material for a chloride ion battery according to embodiment 1 or 2, comprising the following steps: (a) Mixing strontium carbonate and ruthenium oxide to prepare a raw material mixture. (b) Pelleting the raw material mixture to form pellets, and (c) Calcining the pellets. [Effects of the Invention]
[0007] According to this disclosure, it is possible to provide a novel positive electrode active material for chloride ion batteries and a method for producing the same, a positive electrode composite material for chloride ion batteries containing such a positive electrode active material, and a chloride ion battery containing such a positive electrode composite material. [Brief explanation of the drawing]
[0008] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a chloride ion battery of the present disclosure. [Figure 2] Figure 2(a) is an XRD pattern of the battery of the example, and Figure 2(b) is an enlarged view of the region of 8° to 38° of the XRD pattern of Figure 2(a). [Figure 3] Figure 3 is a charge-discharge curve of the battery of the example. [Figure 4] Figure 4 is a charge-discharge curve of the battery of the comparative example. [Figure 5] Figure 5 is a graph showing the cycle characteristics of the battery of the comparative example, that is, the relationship between the number of charge-discharge cycles and the capacity.
Mode for Carrying Out the Invention
[0009] 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 gist of the disclosure.
[0010] <<Positive Electrode Active Material for Chloride Ion Battery>> The positive electrode active material for a chloride ion battery of the present disclosure is strontium ruthenium oxide having a layered perovskite structure.
[0011] The present inventors unexpectedly found that strontium ruthenium oxide having a layered perovskite structure functions as a positive electrode active material for a chloride ion battery.
[0012] In addition, the present inventors found that such a positive electrode active material for a chloride ion battery can improve the cycle characteristics of the battery.
[0013] The present inventors considered that in a battery containing a conventional positive electrode active material for a chloride ion battery, which is a metal chloride, the cycle characteristics deteriorate for the following reasons, for example: · The positive electrode active material, which is a metal chloride, is easily soluble in the electrolyte In batteries containing a positive electrode active material that is a metal chloride, charging and discharging occur via a conversion reaction, resulting in significant expansion and contraction during charging and discharging. This can easily reduce the contact between the positive electrode active material and the electrolyte during the charge-discharge cycle.
[0014] In contrast, the reason why a strontium ruthenium oxide positive electrode active material for chloride ion batteries, which has a layered perovskite structure, can improve the battery's cycle characteristics is presumed to be as follows, although this is not intended to be constrained by any theory. That is, batteries containing the chloride ion battery positive electrode active material of this disclosure are charged and discharged by an intercalation reaction (insertion reaction), so it is thought that the expansion and contraction associated with charging and discharging are small. And it is thought that this can suppress the decrease in contact between the positive electrode active material and the electrolyte during the charge-discharge cycle, thereby improving the battery's cycle characteristics.
[0015] Strontium ruthenium oxide is Sr3Ru2O x (5≦x≦7) is acceptable. Typically, strontium ruthenium oxide having a layered perovskite structure is represented as Sr3Ru2O7. In contrast, strontium ruthenium oxide is represented as Sr3Ru2O x The expression (5≦x≦7) means that strontium ruthenium oxide has an oxygen-deficient layered perovskite structure. In this compositional formula, x may be 5.5 or greater, 6.0 or greater, 6.3 or greater, 6.5 or greater, 6.6 or greater, 6.7 or greater, 6.8 or greater, or 6.9 or greater, and may also be 7.0 or less, 6.9 or less, 6.8 or less, 6.7 or less, 6.6 or less, or 6.5 or less. x may be between 6.5 and 7. Also, x may be 7, meaning that strontium ruthenium oxide may be Sr3Ru2O7.
[0016] Strontium ruthenium oxide may have a Ruddlesden-popper type layered perovskite structure.
[0017] The shape, size, etc., of the positive electrode active material for chloride ion batteries disclosed herein are not particularly limited as long as they can function as a positive electrode active material for chloride ion batteries.
[0018] The positive electrode active material for chloride ion batteries of this disclosure may be manufactured by the manufacturing method described later, or by another method.
[0019] <<Method for manufacturing positive electrode active material for chloride ion batteries>> A method for producing a positive electrode active material for a chloride ion battery, as disclosed herein, includes the following steps: (a) Mixing strontium carbonate and ruthenium oxide to prepare a raw material mixture (raw material mixing step), (b) Pelleting the raw material mixture to form pellets (pellet formation process), and (c) Firing the pellets (firing process).
[0020] In other words, the positive electrode active material for chloride ion batteries of this disclosure, which is strontium ruthenium oxide having a layered perovskite structure, can be produced by solid-phase synthesis.
[0021] <Mixing process> The method disclosed herein comprises (a) mixing strontium carbonate and ruthenium oxide to prepare a raw material mixture.
[0022] The molar ratio of strontium carbonate to ruthenium oxide to be mixed may be 3:2.
[0023] The method for mixing strontium carbonate and ruthenium oxide is not particularly limited, and one example is mixing them in a mortar. The mixing conditions, such as the mixing time, are not particularly limited.
[0024] <Pellet Formation Process> The method disclosed herein includes (b) pelletizing a raw material mixture to form pellets.
[0025] The method for pelletizing the raw material mixture is not particularly limited, and a conventional method in solid-phase synthesis can be used.
[0026] <Firing Process> The method disclosed herein includes (c) firing the pellets.
[0027] The firing conditions, such as firing temperature and firing time, are not particularly limited. The firing temperature may be, for example, 500°C or higher, 750°C or higher, 1000°C or higher, 1100°C or higher, 1200°C or higher, or 1300°C or higher, and may be 2000°C or lower, 1750°C or lower, 1500°C or lower, or 1400°C or lower, or 1350°C. The firing time may be, for example, 1 hour or more, 5 hours or more, 10 hours or more, 15 hours or more, or 20 hours or more, and may be 50 hours or less, 40 hours or less, 30 hours or less, 25 hours or less, or 20 hours or less, or 20 hours.
[0028] The apparatus used in the firing process is not particularly limited and may be, for example, an electric furnace.
[0029] The method disclosed herein may further include the following steps: (d) Crushing the calcined pellets to obtain crushed material (crushing process), (e) Mixing the crushed material to prepare a crushed material mixture (crushed material mixing step), (f) Pelleting the crushed mixture to form pellets (pellet formation step), and (g) Calcining the pellets (pellet calcination process).
[0030] If the method disclosed herein further includes steps (d) to (g), steps (a) to (f) may be denoted as follows: (a') Mixing strontium carbonate and ruthenium oxide to prepare a raw material mixture (raw material mixing step), (b') Pelletizing the raw material mixture to form the first pellet (first pellet formation step), (c') Firing the first pellet (first firing process), (d') The first pellet that has been fired is crushed to obtain the crushed material (crushing process), (e') Mix the crushed material to obtain a crushed material mixture (crushed material mixing step), (f') Pelleting the crushed mixture to form a second pellet (second pellet formation step), and (g') Firing the second pellet (second firing process).
[0031] For processes (a') to (c'), refer to the above description regarding processes (a) to (c).
[0032] <Crushing process> The method of this disclosure may include crushing the first calcined pellet to obtain a crushed material.
[0033] The method for crushing the first pellets after firing is not particularly limited, and a conventional method can be used.
[0034] <Crushed material mixing process> The method disclosed herein may include mixing the pulverized material to obtain a pulverized mixture.
[0035] The method for mixing the crushed material is not particularly limited and may be the same as the raw material mixing process, or it may be a different method.
[0036] <Second Pellet Forming Process> The method disclosed herein may include pelletizing the crushed mixture to form a second pellet.
[0037] The method for pelletizing the mixture obtained by mixing the crushed material is not particularly limited, and a conventional method in solid-phase synthesis can be used.
[0038] <Second firing process> The method of this disclosure may include firing the second pellet.
[0039] The firing conditions for the second firing process and the apparatus used for firing are not particularly limited and may be the same as those for the first firing process, or they may be different, but they may be the same.
[0040] Steps (d) to (g) ((d') to (g')) may be repeated until the positive electrode active material for the chloride ion battery of this disclosure is sufficiently prepared. In this case, the "first" in steps (d') to (g') can be read as "n," and the "second" can be read as "n+1." n is not particularly limited and may be, for example, 1 or more, 4 or less, 3 or less, or 2 or less, or 1.
[0041] <<Positive electrode composite material for chloride ion batteries>> The positive electrode composite material for chloride ion batteries of this disclosure includes a positive electrode active material and may optionally include a solid electrolyte, a conductive additive, etc.
[0042] In this disclosure, “positive electrode mixture” means a composition that can constitute a positive electrode active material layer, either on its own or by further containing other components. In this disclosure, “positive electrode mixture slurry” means a slurry that, in addition to the “positive electrode mixture,” contains a dispersion medium, thereby forming a positive electrode active material layer when applied and dried.
[0043] The following describes the elements that may constitute the positive electrode composite material for chloride ion batteries of this disclosure.
[0044] <Cathode active material> The positive electrode composite material for chloride-ion batteries of this disclosure includes the positive electrode active material for chloride-ion batteries of this disclosure. For the positive electrode active material for chloride-ion batteries of this disclosure, please refer to the above description relating to the positive electrode active material for chloride-ion batteries of this disclosure.
[0045] The content of the positive electrode active material in the positive electrode composite material may be, for example, 1% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, or 30% by mass or more, and may also be 100% by mass or less, 80% by mass or less, 60% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, or 30% by mass or less. This content may also be 10% by mass or more and 50% by mass or less, 15% by mass or more and 45% by mass or less, or 20% by mass or more and 40% by mass or less.
[0046] The positive electrode active material contained in the positive electrode composite material may consist solely of the positive electrode active material of this disclosure, or it may be a combination of the positive electrode active material of this disclosure and other positive electrode active materials. The positive electrode active material other than the positive electrode active material of this disclosure is not particularly limited and may be, for example, a metal chloride. The metal chloride is not particularly limited and may be, for example, a poor metal chloride such as bismuth chloride (BiCl3), gallium chloride (GaCl3), indium chloride (InCl3); a noble metal chloride such as copper chloride (CuCl), silver chloride (AgCl); an iron group element chloride such as nickel chloride (NiCl2), cobalt chloride (CoCl2), iron chloride (FeCl2); or vanadium chloride (VCl3), which are known as positive electrode active materials for chloride ion batteries.
[0047] The proportion of the positive electrode active material of this disclosure to the total (100% by mass) of positive electrode active material contained in the positive electrode mixture may be, for example, 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, 99% by mass or more and 100% by mass or less, or 100% by mass. In other words, all of the positive electrode active material contained in the positive electrode mixture may be the positive electrode active material of this disclosure.
[0048] <Solid electrolyte> The positive electrode composite may contain a solid electrolyte. The solid electrolyte assists in the conduction of chloride ions.
[0049] The solid electrolyte is not particularly limited and may be at least one selected from, for example, tin chloride (SnCl2), strontium chloride (SrCl2), barium chloride (BaCl2), etc.
[0050] The solid electrolyte may be the above chloride doped with potassium (K), for example, Sr 1-x K x C 2-x (0 < x ≤ 0.1) may be applicable.
[0051] Sr 1-x K x C 2-x (0 < x ≤ 0.1) can be produced, for example, by applying mechanical shock to strontium chloride (SrCl2) and potassium chloride (KCl) in a predetermined molar ratio. As such a method, the mechanical milling method is exemplified. Specifically, a method of mixing raw materials using a ball mill device can be mentioned. The operating method of the ball mill device may be any of planetary, vibration, rotation, etc. By using a planetary ball mill device, the mixing of the sample can be efficiently performed. This step may be carried out under an inert gas atmosphere.
[0052] When mixing raw materials using a planetary ball mill device, the table rotation speed is not particularly limited, but may be, for example, 300 rpm or more, 400 rpm or more, 500 rpm or more, or 600 rpm or more, and may also be 1000 rpm or less, 900 rpm or less, 800 rpm or less, 700 rpm or less, or 600 rpm or less. The table rotation speed may be 600 rpm.
[0053] When mixing raw materials using a planetary ball mill device, the mixing time is not particularly limited, but may be 0.5 hours or more, 1 hour or more, 2 hours or more, or 3 hours or more, and may also be 10 hours or less, 8 hours or less, 6 hours or less, 4 hours or less, or 3 hours or less. The mixing time may be 3 hours.
[0054] The solid electrolyte content in the positive electrode composite material may be, for example, 1% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, and may also be 99% by mass or less, 95% by mass or less, 90% by mass or less, 80% by mass or less, or 70% by mass or less. This content may be 40% by mass or more and 90% by mass or less, 50% by mass or more and 80% by mass or less, or 60% by mass or more and 70% by mass or less.
[0055] The shape, size, etc., of the solid electrolyte are not particularly limited, as long as it can function as a solid electrolyte for a chloride ion battery.
[0056] <Conductive additive> The positive electrode composite material may contain a conductive additive. The conductive additive is not particularly limited as long as it has electronic conductivity.
[0057] The conductive additive may be, for example, a carbon material, a single metal or a metal compound, or a combination thereof.
[0058] The carbon material may be at least one selected from, for example, carbon black such as acetylene black, Ketjen black, or furnace black, graphite powder, or fibrous carbon materials such as vapor-grown carbon fiber (VGCF).
[0059] The content of the conductive additive in the positive electrode composite material is not particularly limited and may be, for example, 1% by mass or more, 5% by mass or more, or 10% by mass or more, or 30% by mass or less, 20% by mass or less, or 10% by mass or less.
[0060] <Other ingredients> The positive electrode composite material may or may not contain various additives other than the components listed above. Other components are not particularly limited and include, for example, binders. The binder only needs to be chemically and electrically stable in a chloride ion battery. The types and amounts of other components can be set as appropriate.
[0061] <<Manufacturing Method for Cathode Compound Material for Chloride Ion Batteries>> A method for manufacturing a positive electrode composite material for chloride ion batteries may include the following steps: To provide a raw material containing strontium ruthenium oxide, and Applying mechanical impact to raw materials.
[0062] One example of a method for applying mechanical impact to raw materials is mechanical milling. Specifically, this involves mixing the raw materials using a ball mill. The ball mill can be operated by any of the following methods: planetary, vibration, or rotation. Using a planetary ball mill allows for efficient mixing of the sample. This process may be carried out under an inert gas atmosphere.
[0063] When mixing raw materials using a planetary ball mill apparatus, the rotation speed of the base plate is not particularly limited, but may be, for example, 1 rpm or more, 10 rpm or more, 50 rpm or more, or 100 rpm or more, or 300 rpm or less, 200 rpm or less, 150 rpm or less, or 100 rpm or less. The rotation speed of the base plate may be 100 rpm.
[0064] When mixing raw materials using a planetary ball mill apparatus, the mixing time is not particularly limited, but may be 1 hour or more, 3 hours or more, 5 hours or more, or 10 hours or more, and may be 30 hours or less, 20 hours or less, 15 hours or less, or 10 hours or less. The mixing time may be 10 hours.
[0065] For other blendable raw materials besides strontium ruthenium oxide, refer to the above description regarding the cathode composite material for chloride ion batteries in this disclosure.
[0066] <<Chloride ion battery>> As illustrated in Figure 1, the chloride-ion battery 1 of the present disclosure has a positive electrode active material layer 20, and the positive electrode active material layer contains the positive electrode composite material for chloride-ion batteries of the present disclosure. Because the chloride-ion battery of the present disclosure contains the positive electrode composite material for chloride-ion batteries of the present disclosure, it has improved cycle characteristics.
[0067] As illustrated in Figure 1, the chloride ion battery 1 of this disclosure may have a positive electrode active material layer 20, an electrolyte layer 30, and a negative electrode active material layer 40 in this order.
[0068] The chloride ion battery of this disclosure may be a liquid-type battery containing an electrolyte as an electrolyte layer, or it may be a solid-state battery having a solid electrolyte layer as an electrolyte layer. In this disclosure, "solid-state battery" means a battery using at least a solid electrolyte as an electrolyte, and therefore a solid-state battery may use a combination of a solid electrolyte and a liquid electrolyte as its electrolyte. Furthermore, the solid-state battery of this disclosure may be an all-solid-state battery, i.e., a battery using only a solid electrolyte as its electrolyte.
[0069] A chloride ion battery may be a primary battery or a secondary battery.
[0070] The shape of the chloride ion battery may be, for example, coin-type, laminated (pouch-type), cylindrical, or rectangular.
[0071] Chloride ion batteries can be manufactured by molding each of the above layers using a dry or wet method.
[0072] The chloride-ion battery of this disclosure can be suitably used in, for example, at least one type of vehicle selected from hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs).
[0073] In the following, as an example, the elements constituting the chloride ion battery of this disclosure will be described in the case where the chloride ion battery of this disclosure is an all-solid-state battery.
[0074] <Cathode active material layer> The positive electrode active material layer contains the positive electrode composite material for chloride ion batteries of this disclosure. For the positive electrode composite material for chloride ion batteries of this disclosure, refer to the above description relating to the positive electrode composite material for chloride ion batteries of this disclosure.
[0075] The positive electrode active material layer may be, for example, a compacted powder of the positive electrode composite material for chloride ion batteries of the present disclosure itself.
[0076] The shape of the positive electrode active material layer is not particularly limited and may be, for example, a sheet with a substantially flat surface.
[0077] The thickness of the positive electrode active material layer is not particularly limited and can be any appropriate thickness depending on the configuration of the chloride ion battery. For example, the thickness of the positive electrode active material layer may be between 100 nm and 1 mm.
[0078] <Electrolyte layer> The electrolyte layer may be a solid electrolyte layer containing a solid electrolyte. For the solid electrolyte, refer to the above description of the positive electrode composite material for chloride ion batteries in this disclosure.
[0079] The shape of the electrolyte layer is not particularly limited and may, for example, be in the form of a sheet with a substantially flat surface.
[0080] The thickness of the electrolyte layer is not particularly limited and can be any appropriate thickness depending on the configuration of the chloride ion battery. For example, the thickness of the electrolyte layer may be between 100 nm and 1 mm.
[0081] <Negative electrode active material layer> The negative electrode active material layer contains a negative electrode active material and may optionally contain a solid electrolyte, a conductive additive, etc.
[0082] The negative electrode active material is not particularly limited as long as it has a lower potential than the positive electrode active material. Examples of such active materials include elemental metals such as lead (Pb) and tin (Sn), alloys thereof, oxides thereof, and chlorides thereof.
[0083] The negative electrode active material may be, for example, CsSnCl3, which is CsSn doped with yttrium (Y). 1-x Y x Cl 3+x (0 <x≦0.1)であってもよい。
[0084] CsSnCl3 can be produced, for example, by applying mechanical shock to cesium chloride (CsCl) and tin chloride (SnCl2) in a predetermined molar ratio. Mechanical milling is an example of such a method. Specifically, a method of mixing the raw materials using a ball mill is employed. The ball mill can be operated by any of the following methods: planetary, vibration, or rotation. Using a planetary ball mill allows for efficient mixing of the sample. This process may be carried out under an inert gas atmosphere.
[0085] When mixing raw materials using a planetary ball mill apparatus, the rotation speed of the base plate is not particularly limited, but may be, for example, 300 rpm or more, 400 rpm or more, 500 rpm or more, or 600 rpm or more, and may also be 1000 rpm or less, 900 rpm or less, 800 rpm or less, 700 rpm or less, or 600 rpm or less. The rotation speed of the base plate may be 600 rpm.
[0086] When mixing raw materials using a planetary ball mill apparatus, the mixing time is not particularly limited, but may be 1 hour or more, 3 hours or more, 5 hours or more, or 10 hours or more, and may be 30 hours or less, 20 hours or less, 15 hours or less, or 10 hours or less. The mixing time may be 10 hours.
[0087] <Solid electrolytes and conductive additives> For solid electrolytes and conductive additives, refer to the above description regarding positive electrode composite materials for chloride ion batteries in this disclosure.
[0088] The shape of the negative electrode active material layer is not particularly limited and may be, for example, a sheet with a substantially flat surface.
[0089] The thickness of the negative electrode active material layer is not particularly limited and can be any appropriate thickness depending on the configuration of the chloride ion battery. For example, the thickness of the negative electrode active material layer may be between 100 nm and 1 mm.
[0090] <Other configurations> The chloride-ion battery of this disclosure may further include a positive electrode current collector layer 10 and a negative electrode current collector layer 50, as shown in Figure 1. The material, shape, thickness, etc., of the positive electrode current collector layer and the negative electrode current collector layer are not particularly limited, as long as they can function as current collector layers for a chloride-ion battery. Furthermore, the chloride-ion battery of this disclosure may further include other configurations. [Examples]
[0091] <<Example 1>> <Synthesis of positive electrode active material for chloride ion batteries> (Raw material mixing process) Strontium carbonate (SrCO3) and ruthenium oxide (RuO2) were weighed out in a 3:2 molar ratio and mixed in a mortar to obtain a raw material mixture.
[0092] (First pellet formation process) The obtained raw material mixture was pelletized using a conventional method in solid-phase synthesis to form the first pellet.
[0093] (First firing process) The resulting first pellet was fired in an electric furnace at 1350°C for 20 hours.
[0094] (Crushing process) The first pellet, which had been fired, was crushed by a conventional method to obtain the crushed material.
[0095] (Crushed material mixing process) The resulting pulverized material was mixed in a mortar to obtain a pulverized mixture.
[0096] (Second pellet formation process) The resulting crushed mixture was pelletized using a conventional method in solid-phase synthesis to form a second pellet.
[0097] (Second firing process) The obtained first pellet was calcined in an electric furnace at 1350°C for 20 hours. This yielded strontium ruthenium oxide (Sr3Ru2O7) having a layered perovskite structure, which is a positive electrode active material for chloride ion batteries.
[0098] <Fabrication of chloride ion batteries> Sr3Ru2O7 is used as the positive electrode active material, and potassium (K) is used as the solid electrolyte in SrCl2(Sr 0.97 K 0.03 Cl 1.97 The raw materials, along with vapor-grown carbon fiber (VGCF) (manufactured by Showa Denko) as a conductive additive, were weighed in a mass ratio of 30:60:10. The above raw materials were mixed using a ball mill at 100 rpm for 10 hours to obtain a positive electrode mixture for chloride ion batteries. A positive electrode active material layer was formed by compacting this mixture.
[0099] Sr as a solid electrolyte 0.97 K 0.03 Cl 1.97 It was synthesized by mechanically milling strontium chloride (SrCl2) and potassium chloride (KCl) using a ball mill at 600 rpm for 3 hours.
[0100] The solid electrolyte layer contains Sr as the solid electrolyte. 0.97 K 0.03 Cl 1.97 It was formed by compacting and molding the powder.
[0101] The negative electrode active material layer was formed by placing a tin foil on one side (the side where the negative electrode current collector layer would later be placed) of a layer formed using CsSnCl3. CsSnCl3 was synthesized by weighing cesium chloride (CsCl) and tin chloride (SnCl2) in a predetermined molar ratio and mechanically milling them in a ball mill at 600 rpm for 10 hours.
[0102] A solid-state chloride ion battery was fabricated by stacking a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer in this order.
[0103] <Rating> (XRD measurement) XRD measurements were performed on samples of the positive electrode active material layer formed from the positive electrode composite material in the initial state before operation, the charged state, and the discharged state of the battery. The XRD measurements were performed using a concentrated method with CuKα radiation irradiated under conditions of a tube voltage of 40kV and a tube current of 40mA in an inert gas atmosphere using a Rigaku Ultima IV X-ray diffractometer. The samples were sealed on an airtight sample stage in an argon atmosphere and measured without exposure to air. A glass sample holder was used as the substrate for mounting the samples. The obtained XRD patterns are shown in Figure 2. Figure 2(a) is the XRD pattern of the battery of Example 1, and Figure 2(b) is an enlarged view of the 8° to 38° region of the XRD pattern in Figure 2(a).
[0104] As shown in Figure 2, and particularly in Figure 2(b), it was confirmed that Sr3Ru2O7 was generated in the battery of Example 1 in its initial state. Furthermore, in the charged state, Sr3Ru2O7Cl x However, it was confirmed that the layered perovskite structure of Sr3Ru2O7 was being formed, i.e., maintained. This suggests that in batteries containing the positive electrode active material for chloride ion batteries of this disclosure, charging and discharging occur via intercalation reactions.
[0105] (Charge / Discharge Test) For the chloride ion battery in the example, the test was conducted in a sealed container under vacuum at a test temperature of 140°C and a current density of 0.03 mA / cm². 2 The battery was charged and discharged 10 times. The charging termination conditions were set to an upper voltage of 1.4V and a lower current of 0.001mA / cm² for constant voltage charging. 2 The test was conducted as follows. The discharge termination condition was set to a lower voltage limit of -1.0V. For the charge-discharge test, an electrochemical measurement system equipped with a frequency response analyzer (VMP-300 high-performance electrochemical measurement system, manufactured by Biologic Inc.) was used.
[0106] The charge-discharge curve of the battery in Example 1 is shown in Figure 3. The initial discharge capacity, the discharge capacity after 10 cycles, and the capacity retention rate are shown in Table 1. Note that "capacity retention rate" refers to the discharge capacity after 10 cycles divided by the initial discharge capacity.
[0107] <<Comparative Example 1>> <Fabrication of chloride ion batteries> An all-solid-state chloride ion battery was fabricated in the same manner as in Example 1, except that bismuth chloride (BiCl3) was used as the positive electrode active material.
[0108] <Rating> The evaluation was carried out in the same manner as in Example 1, except that the charging termination condition was set to an upper voltage limit of 0.8V, constant voltage charging was not performed, and the discharge termination condition was set to a lower voltage limit of 0V. The discharge curve of the battery of Comparative Example 1 is shown in Figure 4, and the cycle characteristics, i.e., the relationship between the number of charge / discharge cycles and capacity, is shown in Figure 5.
[0109] [Table 1]
[0110] As shown in Figure 3 and Table 1, the battery in the example containing strontium ruthenium oxide having a layered perovskite structure as the positive electrode active material showed a high capacity retention rate, with almost no capacity reduction after 10 charge-discharge cycles. In contrast, as shown in Figures 4 and 5 and Table 1, the battery in the comparative example showed a significant decrease in capacity retention rate. [Explanation of Symbols]
[0111] 1. Chloride ion battery 10 Positive electrode current collector layer 20 Cathode active material layer 30 Electrolyte layer 40 Negative electrode active material layer 50 Negative electrode current collector layer
Claims
1. A strontium ruthenium oxide having a layered perovskite structure, which is a positive electrode active material for chloride ion batteries.
2. The strontium ruthenium oxide mentioned above is Sr ３ Ru ２ O ｘ The positive electrode active material for a chloride ion battery according to claim 1, wherein (5 ≤ x ≤ 7).
3. A positive electrode composite material for a chloride ion battery, comprising the positive electrode active material for a chloride ion battery described in claim 1 or 2.
4. It has a positive electrode active material layer, and The positive electrode active material layer contains the positive electrode composite material for chloride ion batteries described in claim 3. Chloride ion battery.
5. A method for producing a positive electrode active material for a chloride ion battery according to claim 1 or 2, comprising the following steps: (a) Mixing strontium carbonate and ruthenium oxide to prepare a raw material mixture. (b) Pelleting the raw material mixture to form pellets, and (c) Calcining the pellets.