Method for manufacturing electrode material, and electrode material

Abstract

Provided are a method for manufacturing an electrode material and the electrode material. The method is a method for manufacturing an electrode material composed of an electrode active material, a conductive assistant, and an electrolyte solution, the method comprising: a step for generating a processed conductive assistant by performing, on the conductive assistant, processing for reducing the bulk density thereof; a step for generating an electrode mixture by mixing the processed conductive assistant and the electrode active material; and a step for creating an electrode material by mixing the electrode mixture and the electrolyte solution. The processed conductive assistant has a bulk density of 55% or less based on the bulk density of the conductive assistant before processing.

Description

Electrode material manufacturing method and electrode material

[0001] The present disclosure relates to a method for producing an electrode material and the electrode material.

[0002] In recent years, demand for secondary batteries, such as lithium-ion batteries (LIBs), has grown significantly due to the widespread use of mobile devices and their installation in hybrid vehicles. The applications of secondary batteries are expected to expand further, including to electric vehicles and stationary storage batteries. Therefore, development of secondary batteries is being conducted to achieve higher energy density, larger capacity, higher output, longer life, and larger size.

[0003] For example, the electrode materials in LIBs are mainly composed of powders such as active materials, conductive additives, and binders, as well as electrolyte solutions, and are manufactured through processes such as dispersion / mixing, coating, drying, pressing, and liquid injection. Quasi-solid-state batteries have been developed that can be manufactured without the drying and liquid injection processes. Quasi-solid-state batteries are also called semi-solid batteries.

[0004] In quasi-solid-state batteries, the electrode material itself forms the electrode layer, so battery performance is affected by the constituent materials, amount, homogeneity, etc. of the electrode material. A method for preparing a semi-solid electrode has been disclosed, which aims to improve battery performance by increasing the homogeneity of the constituent materials, by combining an active material and an electrolyte to form an intermediate material, and then kneading the suspension of the intermediate material and a conductive additive until it reaches a specific apparent viscosity (Patent Document 1).

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-521783

[0006] In a method of kneading a suspension of the electrode material to increase the homogeneity of the electrode material, excessive kneading reduces the conductivity of the electrode material, and further improvement in conductivity cannot be expected.

[0007] An object of the present disclosure is to provide a method for producing an electrode material with improved conductivity, and the electrode material.

[0008] Specific means for solving the problems include the following aspects. <1> A method for producing an electrode material comprising an electrode active material, a conductive additive, and an electrolyte solution, the method comprising the steps of: producing a treated conductive additive by treating the conductive additive to reduce its bulk density; producing an electrode mixture by mixing the treated conductive additive with the electrode active material; and producing an electrode material by mixing the electrode mixture with the electrolyte solution, wherein the treated conductive additive has a bulk density of 55% or less based on the bulk density of the conductive additive before treatment. <2> A method for producing an electrode material according to <1>, wherein the treatment for reducing the bulk density is a dry crushing treatment. <3> A method for producing an electrode material according to <2>, wherein the crushing treatment is a treatment using an airflow. <4> A method for producing an electrode material according to <2> or <3>, wherein the crushing treatment is a treatment using a jet mill. <5> The method for producing an electrode material according to any one of <1> to <4>, wherein the treated conductive additive has a bulk density of 25% or less, based on the bulk density of the conductive additive before treatment. <6> The method for producing an electrode material according to any one of <1> to <5>, wherein the conductive additive is carbon black. <7> An electrode material produced by the method for producing an electrode material according to any one of <1> to <6>. <8> An electrode material comprising an electrode active material, a treated conductive additive that has been treated to reduce its bulk density, and electrolysis, wherein the electrode material simultaneously satisfies all of the following formulas (1) to (3), where y is the yield stress (unit: kPa) measured with a rotational viscometer and x is the electrical conductivity (unit: mS / cm) measured with an electrical resistance meter: y≦4.8x−7.4 (1) 10≦y≦100 (2) 2≦x≦23 (3) <9> The electrode material according to <8>, which is for an electrode layer of a quasi-solid-state battery. <10> The electrode material according to <8> or <9>, wherein the treated conductive additive is carbon black that has been treated to reduce its bulk density.

[0009] According to an embodiment of the present disclosure, a method for producing an electrode material and an electrode material having improved conductivity can be provided.

[0010] FIG. 1 is an image of a conductive additive before and after bulk density reduction treatment. FIG. 2 is a graph showing the relationship between x and y, with x on the horizontal axis and y on the vertical axis, where y is the yield stress (unit: kPa) measured by a rotational viscometer and x is the electrical conductivity (unit: mS / cm) measured by an electrical resistance meter, when the amount of conductive additive is changed. FIG. 3 is an explanatory diagram explaining the estimated relationship between the electrode active material and the conductive additive in the electrode material of the present disclosure. FIG. 4 is an explanatory diagram explaining the estimated relationship between the electrode active material and the conductive additive in a conventional electrode material. FIG. 5 is a graph showing the relationship between x and y, with x on the horizontal axis and y on the vertical axis, when the amount of conductive additive is changed, with y being the yield stress (unit: kPa) measured by a rotational viscometer and x being the electrical conductivity (unit: mS / cm) measured by an electrical resistance meter, when the amount of conductive additive is changed in Examples and Comparative Examples.

[0011] The electrode material and the manufacturing method of the electrode material according to the present disclosure will be described below. However, the present disclosure is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present disclosure.

[0012] When describing embodiments of the present disclosure with reference to the drawings, descriptions of overlapping components and reference numerals may be omitted. Components indicated by the same reference numerals in the drawings are the same components. The dimensional ratios in the drawings do not necessarily represent the actual dimensional ratios.

[0013] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​described before and after "to" as the lower and upper limits. In numerical ranges described in stages in the present disclosure, the upper limit value described in a certain numerical range may be replaced with the upper limit value of another numerical range described in stages, and the lower limit value described in a certain numerical range may be replaced with the lower limit value of another numerical range described in stages. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0014] In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In this specification, "mass %" and "weight %" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

[0015] The method for producing an electrode material according to the present disclosure is a method for producing an electrode material comprising an electrode active material, a conductive additive, and an electrolyte solution, and includes the steps of: generating a treated conductive additive by treating the conductive additive to reduce its bulk density (hereinafter also referred to as a bulk density reduction treatment step); generating an electrode mixture by mixing the treated conductive additive and the electrode active material (hereinafter also referred to as an electrode mixture production step); and mixing the electrode mixture with an electrolyte solution to produce an electrode material (hereinafter also referred to as an electrode material production step), wherein the treated conductive additive has a bulk density of 55% or less based on the bulk density of the conductive additive before treatment.

[0016] Furthermore, the electrode material of the present disclosure includes an electrode active material, a treated conductive additive that has been treated to reduce its bulk density, and an electrolyte solution, and satisfies all of the following formulas (1) to (3), where y is the yield stress (unit: kPa) measured with a rotational viscometer and x is the electrical conductivity (unit: mS / cm) measured with an electrical resistance meter.

[0017] y≦4.8x-7.4 (1) 10≦y≦100 (2) 2≦x≦23 (3)

[0018] The background to the present disclosure will be explained. In quasi-solid-state batteries, the electrode layer is formed from a clay-like electrode material itself, so battery performance is influenced by the constituent materials and amounts of the electrode material. Increasing the solid content of the active material and increasing the amount of conductive additive added are conceivable ways to improve battery performance. However, increasing the solid content of the active material, conductive additive, etc. increases the viscosity of the electrode material. In quasi-solid-state batteries, the electrode layer itself is formed from the electrode material, so the electrode material must have an appropriate viscosity range. Therefore, it is preferable to improve battery performance without increasing the solid content of the electrode material for quasi-solid-state batteries.

[0019] In particular, carbon black, which is generally used as a conductive additive in quasi-solid-state batteries, is in the form of fine particles and has a large specific surface area, so that the effect of increasing the viscosity of the electrode material is significantly large relative to the amount added.

[0020] Therefore, as a method for achieving high conductivity without increasing the amount of conductive additive, a method for improving the homogeneity of the electrode material by applying shear force of a fluid in the state of the electrode material including the electrolyte solution is known (Patent Document 1). However, with this method, the conductivity may decrease due to the high kneading energy, and further improvement of the conductivity by kneading cannot be expected.

[0021] The inventors have investigated how to improve the conductivity of electrode materials for quasi-solid-state batteries, and have found that, when mixing electrode materials, even when the conductivity is reduced due to high mixing energy, agglomerates of the conductive additive remain in the electrode material after mixing and are not sufficiently disintegrated, that high mixing energy is expected to destroy the network formed by the conductive additive, and that electrode materials for quasi-solid-state batteries, which have high viscosity, are prone to wear at parts where high shear is applied, such as the stirring blades of the mixer, and that this may cause new problems such as the possibility of metal foreign matter being mixed in.

[0022] Based on the above findings, the present inventors conducted extensive research into improving the conductivity of electrode materials. Focusing on the form of the conductive additive before mixing, the present inventors performed a process to reduce the bulk density of the conductive additive before mixing. This process increases the bulkiness of the conductive additive, and the conductive additive that has been treated to reduce the bulk density is mixed with an active material. An electrolyte solution is then added and mixed. The present inventors discovered that this method makes it possible to produce an electrode material with high electrical conductivity, which led to the completion of the present disclosure.

[0023] The electrode material manufacturing method and electrode material disclosed herein enable the formation of electrodes with high electrical conductivity without increasing the amount of conductive additive. That is, with the same amount of conductive additive, the electrode material disclosed herein can exhibit higher electrical conductivity than conventional electrode materials different from the electrode material disclosed herein. Furthermore, by not increasing the amount of conductive additive, the increase in viscosity of the electrode material due to the conductive additive is suppressed. That is, compared to conventional electrode materials with equivalent electrical conductivity, the electrode material disclosed herein can be made to have a lower viscosity. While the detailed mechanism by which this effect is achieved is unknown, it is presumed that the conductive additive, which has been specifically treated before mixing, effectively forms a network in the electrode material produced by a specific process.

[0024] <Method for manufacturing electrode material> The method for manufacturing an electrode material according to the present disclosure is a method for manufacturing an electrode material comprising an electrode active material, a conductive additive, and an electrolyte solution, and includes the steps of: generating a treated conductive additive by treating the conductive additive to reduce its bulk density (hereinafter also referred to as a "bulk density reduction treatment step"); generating an electrode mixture by mixing the treated conductive additive and the electrode active material (hereinafter also referred to as an "electrode mixture generation step"); and creating an electrode material by mixing the electrode mixture and an electrolyte solution (hereinafter also referred to as an "electrode material generation step"). The treated conductive additive has a bulk density of 55% or less based on the bulk density of the conductive additive before treatment.

[0025] (Bulk density reduction treatment step) The bulk density reduction treatment step is a step of producing a treated conductive additive by performing a treatment (bulk density reduction treatment) to reduce the bulk density of the conductive additive. Bulk density means the mass per unit bulk volume occupied by the powder. A method for measuring bulk density will be described later.

[0026] The conductive additive to be subjected to bulk density reduction treatment may be a conductive additive before being mixed with other materials. Any conductive additive can be used, including commercially available conductive additives as they are and those that have undergone some kind of treatment. For example, when the conductive additive is carbon black, the form may be a primary aggregate formed by the aggregation of primary particles with a diameter of 30 nm to 50 nm, a secondary aggregate formed by connecting primary aggregates, or agglomerates formed by the aggregation of secondary aggregates. In carbon black, primary aggregates are also called aggregates, with each aggregate having a length of approximately 100 nm to 500 nm, and secondary aggregates are also called agglomerates, with each agglomerate having a length of approximately several μm. Commercially available carbon black is often in the form of agglomerates aggregated together. Such aggregates, agglomerates, etc. are subjected to bulk density reduction treatment.

[0027] Any treatment that can reduce the bulk density of the conductive additive can be used to reduce the bulk density of the conductive additive. The treatment to reduce the bulk density is preferably a crushing treatment. Crushing treatment is a treatment that breaks up aggregates, agglomerates, etc. without changing the size of the primary particles. Furthermore, since the conductive additive is preferably used in a dry state, a dry crushing treatment is preferred.

[0028] The crushing treatment can be performed using a conventionally known method, and either crushing by airflow or physical crushing can be used. Specific examples of crushing by airflow include treatment using a jet mill. Specific examples of physical crushing include treatment using a ball mill, bead mill, or the like. Crushing treatment using airflow is preferred because it causes less destruction of primary particles. Crushing treatment using airflow is preferred because it is highly effective in reducing the bulk density of the conductive additive.

[0029] The treated conductive additive produced by the bulk density reduction treatment has a bulk density of 55% or less, based on the bulk density of the conductive additive before treatment. In the present disclosure, the bulk density is measured by calculating the bulk density from the volume of a powder sample measured when a known mass of powder is passed through a sieve and placed in a measuring cylinder. In the present disclosure, the bulk density is a value calculated from the volume of a powder sample measured when a known mass of powder is passed through a sieve and placed in a measuring cylinder, and is also called loose bulk density. For loose bulk density, reference can be made to the "initial bulk density" in JIS R 1628-1997 "Method for measuring the bulk density of fine ceramic powders" or the "loose bulk density" in the Japanese Pharmacopoeia "3.01 Bulk Density Measurement Method."

[0030] In the present disclosure, the treated conductive assistant has a bulk density of 55% or less, based on the bulk density of the conductive assistant before treatment. The bulk density reduction treatment reduces the bulk density of the conductive assistant and increases its bulkiness compared to the conductive assistant before treatment. When the bulk density of the treated conductive assistant is 55% or less, the bulkiness of the treated conductive assistant is 1.8 times or more, compared to the conductive assistant before treatment. More preferably, the treated conductive assistant has a bulk density of 25% or less, based on the bulk density of the conductive assistant before treatment. When the bulk density of the treated conductive assistant is 25% or less, the bulkiness of the treated conductive assistant is 4.0 times or more.

[0031] The lower limit of the bulk density is not limited because it depends on the type of conductive additive, the method of bulk density reduction treatment, etc., but when a jet mill is used, the lower limit of the bulk density of the treated conductive additive is 22%, which is 4.5 times the bulk density of the conductive additive before treatment. A treated conductive additive with a bulk density of 22% can also be used.

[0032] The degree of bulk density can be controlled by adjusting the operation of the equipment used for the bulk density reduction treatment.

[0033] The bulk density of the treated conductive additive is measured based on the bulk density of the conductive additive before treatment. For example, when measuring the bulk density using the same method with the same mass of the untreated conductive additive and the treated conductive additive, the bulk density can also be measured by comparing the height of the conductive additive when placed in a measuring cylinder of the same shape.

[0034] As shown in Figure 1, for the same amount of conductive additive, the measuring cylinder on the left side of the page contains conductive additive A before bulk density reduction treatment after passing it through a sieve, and the other measuring cylinder on the right side of the page contains treated conductive additive B after bulk density reduction treatment after passing it through a sieve. In this way, when measuring cylinders of the same shape are used, the bulk density of the treated conductive additive can be easily measured as a ratio to the conductive additive before bulk density reduction treatment by measuring the height of each conductive additive.

[0035] The treated conductive additive is in a state of secondary agglomeration, and is thought to be in a state in which a network is formed by branched particles entangled at the branched portions. The formation of an effective network by the conductive additive is thought to improve the conductivity of the electrode material. An effective network by the conductive additive means a network formed by the connection of conductive additives, which improves conductivity. Since much of the added conductive additive is used to form an effective network in the treated conductive additive, it is thought that the conductivity of the electrode material is maintained even when a smaller amount of conductive additive is added than conventionally.

[0036] The conductive additive may be a conventionally known conductive additive. For example, the conductive additive may be various carbon materials, metal powders, or carbides. The conductive additive is preferably a carbon material, and more preferably carbon black, as this more preferably exhibits the effect of improving conductivity. Preferred examples of carbon black include acetylene black and ketjen black.

[0037] The conductive additive may be a single substance or a mixture. In the case of a mixture, the mixture may be subjected to a bulk density reduction treatment, or each of the materials constituting the mixture may be subjected to a bulk density reduction treatment and then mixed to produce a treated conductive additive.

[0038] (Electrode mixture production step) In the manufacturing method of the electrode material of the present disclosure, after the bulk density reduction treatment step, an electrode mixture production step is carried out in which the treated conductive assistant and the electrode active material are mixed to produce an electrode mixture. The electrode mixture production step can be carried out by a conventionally known method as long as the treated conductive assistant can be used as the conductive assistant.

[0039] In the electrode mixture, the mixing ratio of the electrode active material and the conductive additive may be the same as conventional, depending on the electrode to be produced, or a smaller amount of conductive additive may be used than conventional. For example, in order to produce an electrode having the same conductivity as conventional electrodes, the method for producing an electrode material of the present disclosure can achieve the same conductivity even if a smaller amount of conductive additive is added. In this case, the smaller amount of conductive additive added can reduce the viscosity of the electrode material, making electrode production easier. Furthermore, in order to produce an electrode having better conductivity than conventional electrodes, the method for producing an electrode material of the present disclosure can obtain an electrode material with higher conductivity by adding the same amount of conductive additive as conventional. In this case, since the amount of conductive additive added is the same as conventional, the viscosity of the electrode material is the same as conventional, but by employing the same manufacturing method as conventional, an electrode material with improved conductivity can be obtained without requiring additional equipment, etc.

[0040] (Electrode material producing step) In the method for producing an electrode material according to the present disclosure, the electrode material producing step is carried out after the electrode mixture producing step. The electrode material producing step is a step of producing an electrode material by mixing the electrode mixture with an electrolytic solution. The electrode material producing step can be carried out by a conventionally known method as long as the electrode mixture contains a treated conductive assistant.

[0041] As a method for mixing the electrode mixture produced in the electrode mixture production step with the electrolyte solution, a conventionally known method can be adopted. The type of electrolyte solution, the mixing ratio of the electrode mixture and the electrolyte solution, and the mixing method can also be the same as those in the past.

[0042] <Electrode Material> The electrode material of the present disclosure includes an electrode active material, a treated conductive additive that has been treated to reduce its bulk density, and an electrolyte solution, and satisfies all of the following formulas (1) to (3), where y is the yield stress (unit: kPa) measured with a rotational viscometer and x is the electrical conductivity (unit: mS / cm) measured with an electrical resistance meter.

[0043] y≦4.8x-7.4 (1) 10≦y≦100 (2) 2≦x≦23 (3)

[0044] In the electrode material of the present disclosure, the conductive additive is a treated conductive additive that has been treated to reduce its bulk density. The treatment to reduce the bulk density is the same as that described above for the bulk density reduction treatment, and therefore a description thereof will be omitted. The treated conductive additive, electrode active material, and electrolyte solution are also the same as those described above, and therefore a description thereof will be omitted. The electrode material of the present disclosure can be obtained by the manufacturing method of the electrode material of the present disclosure.

[0045] The electrode material of the present disclosure satisfies all of the above formulas (1) to (3), where y is the yield stress (hereinafter also referred to as the yield value, unit: kPa) when the electrode material is measured using a rotational viscometer, and x is the electrical conductivity (unit: mS / cm) measured using an electrical resistance meter.

[0046] The yield value of an electrode material is measured as follows: The mixed electrode material is placed in a container (e.g., a cylindrical cup) and pressed down from above using a jig or the like at a pressure of approximately 0.1 MPa to 1 MPa to solidify the electrode material so that there are no gaps between the material particles, thereby preparing a measurement sample. Using a precision rotational viscometer with a blade-type spindle (e.g., Brookfield Soft Solid Tester, RST-SST), a probe is inserted into the measurement sample (i.e., the solidified electrode material), and the change in stress when rotated at a constant speed is read to measure the yield value (yield stress).

[0047] The electrical conductivity of the electrode material is measured as follows: Using an electrical resistance measuring meter with a four-point probe (for example, a Loresta-GXII MCP-T710 low-resistance resistivity meter manufactured by Nitto Seiko Analytech), the probe is inserted into the measurement sample, the electrical resistance value is read, and the value is converted into electrical conductivity.

[0048] Equation (1) shows that when the conductivity of an electrode material is changed by changing the mixing ratio of the conductive additive, the yield stress and the conductivity are in a substantially proportional relationship. Equation (2) shows the range of the yield stress value of the electrode material, and Equation (3) shows the range of the conductivity of the electrode material.

[0049] As shown in FIG. 2, the linear graph shows the relationship between electrical conductivity and yield stress when only the amount of treated conductive additive is changed in an example of an electrode material of the present disclosure, and represents the linear line of the above formula (1). The above example is an example of the composition of Example 2, which will be described later. Plot c is for the case where the content of the treated conductive additive is 0.8 mass% (yield stress is 31.8 kPa, electrical conductivity is 8.0 mS / cm), plot d is for the case where it is 1.0% (yield stress is 57.7 kPa, electrical conductivity is 13.8 mS / cm), and plot e is for the case where it is 1.2% (yield stress is 97.9 kPa, electrical conductivity is 21.8 mS / cm). Note that in the case of the linear graph of the present disclosure and the conventional dashed line graph, the type and amount of materials used, the manufacturing method of the electrode material, the yield stress, the electrical conductivity measurement method, etc. are all the same, except that in the case of the present disclosure, a bulk density reduction treatment was performed as a conductive additive.

[0050] 2, even in conventional electrode materials using a conductive additive that has not been treated to reduce bulk density (hereinafter also referred to as an untreated additive), when the conductivity is changed by changing the mixing ratio of the untreated additive, as shown in the dashed line graph, the yield stress and the conductivity are approximately proportional to each other. Plot f is for the case where the content of the untreated additive is 0.8 mass% (yield stress: 41.6 kPa, conductivity: 5.8 mS / cm), plot g is for the case where the content of the untreated additive is 1.0% (yield stress: 65.3 kPa, conductivity: 6.0 mS / cm), and plot h is for the case where the content of the untreated additive is 1.2% (yield stress: 124.0 kPa, conductivity: 7.3 mS / cm), based on the total amount of the electrode material.

[0051] The linear graph showing formula (1) for the electrode material of the present disclosure has a smaller slope than the dashed line graph showing the relationship between yield stress and electrical conductivity for a conventional electrode material. By satisfying all of formulas (1) to (3) above, the electrode material of the present disclosure exhibits a viscosity-reducing effect, such as a lower yield stress at the same electrical conductivity, compared to conventional electrode materials using untreated auxiliary agents, and exhibits a conductivity-improving effect, such as a higher electrical conductivity at the same yield stress. The value of the yield stress corresponds to the viscosity of the electrode material. Adjustments to satisfy formulas (1) to (3) can be made by performing or not performing a treatment to reduce bulk density, preferably by changing the method or conditions of the crushing treatment.

[0052] As shown in Figure 3, the reason why the electrode material 10 of the present disclosure has higher electrical conductivity than conventional electrode materials is not clear, but it is presumed that the electrode active material 11 is connected by a network formed by the conductive additive 12. That is, in the electrode material 10 of the present disclosure, it is thought that the conductive additive 12 having an effective network makes the electrical network between the electrode active material 11 and the like that constitute the electrode material dense. On the other hand, as shown in Figure 4, in the electrode material 15 using an untreated additive, the conductive additive 12 tends to be locally unevenly distributed, and it is presumed that it does not form an effective network compared to the electrode material 10 of the present disclosure.

[0053] The electrode material of the present disclosure can be used in various electrode materials that use a conductive additive. Any electrode material that uses a conductive additive can be applied to the present disclosure, regardless of other compositions, such as the presence or absence of a binder. For example, the electrode material of the present disclosure can be applied to dry electrodes such as those of lithium-ion batteries, which are created by heating a mixed powder of an electrode active material, a conductive additive, and a binder powder to form an electrode layer, and then injecting an electrolyte solution. Furthermore, the electrode material of the present disclosure can be applied to electrodes for quasi-solid-state batteries that contain a binder, as well as electrodes for quasi-solid-state batteries that do not contain a binder. The electrode material of the present disclosure is preferably used because it exhibits a viscosity-reducing effect and also exhibits a conductivity-improving effect in various electrode materials.

[0054] The electrode material etc. of the present disclosure can be applied to any type of electrode, including positive electrodes, negative electrodes, reference electrodes, etc. Therefore, the electrode material etc. of the present disclosure can be applied not only as an electrode material for positive electrodes but also as an electrode material for negative electrodes.

[0055] The electrode material of the present disclosure is suitable as an electrode material for the electrode layer of a quasi-solid battery. The electrode layer for a quasi-solid battery is often composed of an electrode material that does not contain a binder, and the viscosity tends to be high in order to improve the energy density. Therefore, when the electrode material of the present disclosure is used for the electrode layer of a quasi-solid battery, the above-mentioned viscosity-reducing effect is preferable in terms of manufacturing, and in addition, the effect of improving conductivity is also exhibited, which is preferable. Note that the "quasi-solid battery" in the present disclosure is a secondary battery having an electrode layer formed using an electrode material in which an electrolytic solution is mixed with an electrode active material and a conductive additive.

[0056] The electrode material of the present disclosure can use various conductive additives, but is suitable for an electrode material in which the conductive additive is carbon black, because when the conductive additive is carbon black, an effective network is preferably formed by the conductive additive through treatment to reduce the bulk density, and the effects of improving conductivity and reducing viscosity are more effectively exhibited.

[0057] The electrode material of the present disclosure can be formed into an electrode layer by a conventionally known method. Because the electrode material of the present disclosure has the effect of improving conductivity and reducing viscosity, it can form, for example, an electrode layer with a higher energy density. Therefore, a battery using the electrode material of the present disclosure in an electrode layer has a high energy density and can reduce the battery size. Furthermore, the manufacturing method of the electrode material of the present disclosure uses a conductive additive that has been treated to reduce the bulk density, and requires only one additional step compared to conventional manufacturing methods. Furthermore, conventional manufacturing methods can be used in subsequent steps, and the electrode material, electrode layer, battery, and the like can be manufactured without changing the manufacturing equipment. Furthermore, the type of conductive additive used can be a conventional one. Therefore, the electrode material of the present disclosure is useful not only in terms of electrode material performance but also in terms of manufacturing costs.

[0058] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0059] Example 1 A mixture of ethylene carbonate, propylene carbonate, and diethyl carbonate was mixed with LiPF as an electrolyte. ６ After mixing, vinylene carbonate was further mixed. 69 g of the resulting mixture was extracted and designated as electrolyte solution X1. 2 g of carbon ECP (Ketjen black, manufactured by Lion Chemical Co., Ltd.) was used as a conductive additive, and a crushing process was performed using a dry jet mill (manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to reduce the bulk density. The jet mill discharge pressure was set to 0.6 MPa as the crushing treatment condition. Before and after the crushing treatment, bulk density measurements were performed using a 20 mL measuring cylinder using the method described above. As a result of the bulk density measurement, the bulk height of the treated conductive additive after the crushing treatment was 3.9 times higher. This bulk density was 26% (1 / 3.9) of the bulk density of the conductive additive before treatment.

[0060] 3 g of the treated conductive additive and 168 g of a positive electrode active material (lithium iron phosphate, M121, manufactured by Aleees Corporation) were stirred for 30 seconds at 1500 rpm (revolutions per minute) in a mixer (Thinky Mixer ARE-310, manufactured by Thinky Corporation) to prepare a mixture Y1 (171 g).

[0061] 69 g of the electrolyte solution X1 was added to 171 g of the mixture Y1, and the mixture was stirred at 1500 rpm for 120 seconds in a mixer (Thinky Mixer ARE-310, manufactured by Thinky Corporation) to obtain a positive electrode material P1. The volume ratio of the solid component to the liquid component in the obtained positive electrode material P1 was 46:54.

[0062] In order to measure the performance of the positive electrode material P1, the yield stress and electrical conductivity were measured. The yield stress and electrical conductivity were measured by the methods described above.

[0063] Positive electrode material P1 satisfied all of the following formulas (1) to (3), where y is the yield stress (unit: kPa) measured with a rotational viscometer and x is the electrical conductivity (unit: mS / cm) measured with an electrical resistance meter. y≦4.8x−7.4 (1) 10≦y≦100 (2) 2≦x≦23 (3) Positive electrode material P1 had a yield stress of 40.1 kPa and an electrical conductivity of 14.9 mS / cm. Formula (1) and this result are plotted as plot P1 in the graph of FIG. 5.

[0064] Example 2 A mixture of ethylene carbonate, propylene carbonate, and diethyl carbonate was mixed with LiPF as an electrolyte. ６After mixing, vinylene carbonate was further mixed. 64 g of the resulting mixture was extracted and designated as electrolyte solution X1. 2 g of Ketjen black carbon ECP600JD (manufactured by Lion Chemical Co., Ltd.) was used as a conductive additive, and a crushing process was performed using a dry jet mill (manufactured by Hosokawa Micron Corporation) to reduce the bulk density. The crushing process was performed under conditions of a jet mill discharge pressure of 0.5 MPa. Before and after the crushing process, bulk density measurements were performed using a 20 mL measuring cylinder using the method described above. As a result of the bulk density measurement, the bulk height of the treated conductive additive after the crushing process was 4.2 times higher. This bulk density was 24% (1 / 4.2) of the bulk density of the conductive additive before treatment.

[0065] 3 g of the treated conductive additive and 174 g of a positive electrode active material (lithium iron phosphate, M121, manufactured by Aleees Corporation) were stirred for 30 seconds at 1500 rpm (revolutions per minute) in a mixer (Thinky Mixer ARE-310, manufactured by Thinky Corporation) to prepare a mixture Y1 (176 g).

[0066] 64 g of the electrolyte solution X1 was added to 176 g of the mixture Y1, and the mixture was stirred at 1500 rpm for 120 seconds in a mixer (Thinky Mixer ARE-310, manufactured by Thinky Corporation), to obtain a positive electrode material P2. The volume ratio of the solid component to the liquid component in the obtained positive electrode material P2 was 48:52.

[0067] Positive electrode material P2 satisfied all of the following formulas (1) to (3), where y is the yield stress (unit: kPa) measured with a rotational viscometer and x is the electrical conductivity (unit: mS / cm) measured with an electrical resistance meter. y≦4.8x−7.4 (1) 10≦y≦100 (2) 2≦x≦23 (3) Positive electrode material P2 had a yield stress of 57.7 kPa and an electrical conductivity of 13.8 mS / cm. Formula (1) and this result are plotted as plot P2 in the graph of FIG. 5.

[0068] <Example 3> In the crushing treatment, a dry bead mill (ZrO２ , φ0.5mm) was used. Otherwise, a treated conductive additive was produced in the same manner as in Example 1, and positive electrode material P3 was manufactured. The conditions for the crushing treatment were as follows: 2 g of conductive additive and 70 g of beads were placed in a 500 ml vial, and the mixture was stirred 500 times. As a result of measuring the bulk density, the bulk height of the treated conductive additive after the crushing treatment was 1.9 times. When converted to bulk density, the bulk density was 53% (1 / 1.9) of the bulk density of the conductive additive before treatment.

[0069] Positive electrode material P3 satisfied all of the following formulas (1) to (3), where y is the yield stress (unit: kPa) measured with a rotational viscometer and x is the electrical conductivity (unit: mS / cm) measured with an electrical resistance meter. y≦4.8x−7.4 (1) 10≦y≦100 (2) 2≦x≦23 (3) Positive electrode material P3 had a yield stress of 36.2 kPa and an electrical conductivity of 9.5 mS / cm. Formula (1) and this result are plotted as plot P3 in the graph of FIG. 5.

[0070] Comparative Example 1 A positive electrode material Q1 was produced in the same manner as in Example 1, except that the conductive additive was not subjected to a crushing treatment and was used as a raw material.

[0071] The yield stress (unit: kPa) and electrical conductivity (unit: mS / cm) of positive electrode material Q1 were measured in the same manner as in Example 1. The positive electrode material Q1 had a yield stress of 35.8 kPa and an electrical conductivity of 7.4 mS / cm. The results were plotted as plot Q1 in the graph of FIG. 5. Plot Q1 clearly indicated that positive electrode material Q1 did not satisfy all of the above formulas (1) to (3).

[0072] Comparative Example 2 A positive electrode material Q2 was produced in the same manner as in Example 2, except that the conductive additive was not subjected to a crushing treatment and was used as a raw material.

[0073] The yield stress (unit: kPa) and electrical conductivity (unit: mS / cm) of positive electrode material Q2 were measured in the same manner as in Example 1. The positive electrode material Q1 had a yield stress of 65.3 kPa and an electrical conductivity of 6.0 mS / cm. The results were plotted as plot Q2 in the graph of FIG. 5. Plot Q2 clearly indicated that positive electrode material Q2 did not satisfy all of the above formulas (1) to (3).

[0074] <Evaluation> In Examples 1 to 3, which used the electrode material of the present disclosure, the yield stress corresponding to the amount of conductive material added was low, but the electrical conductivity was high. In Comparative Examples 1 and 2, which did not use the electrode material of the present disclosure, the yield stress was high and the electrical conductivity was low. Therefore, it was demonstrated that the electrode material of the present disclosure is an electrode material with improved electrical conductivity.

[0075] The disclosure of Japanese Patent Application No. 2024-058210, filed on March 29, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A method for producing an electrode material comprising an electrode active material, a conductive additive, and an electrolyte, comprising the steps of: producing a treated conductive additive by treating the conductive additive to reduce its bulk density; producing an electrode mixture by mixing the treated conductive additive with the electrode active material; and obtaining an electrode material by mixing the electrode mixture with the electrolyte, wherein the treated conductive additive has a bulk density of 55% or less based on the bulk density of the conductive additive before the treatment.

2. The method for producing an electrode material according to claim 1, wherein the treatment for reducing the bulk density is a dry crushing treatment.

3. The method for producing an electrode material according to claim 2, wherein the crushing treatment is a treatment using an air current.

4. The method for producing an electrode material according to claim 2, wherein the crushing treatment is a treatment using a jet mill.

5. The method for producing an electrode material according to claim 1, wherein the bulk density of the treated conductive additive is 25% or less based on the bulk density of the conductive additive before the treatment.

6. The method for producing an electrode material according to claim 1, wherein the conductive additive is carbon black.

7. An electrode material produced by the method for producing an electrode material according to any one of claims 1 to 6.

8. An electrode material comprising an electrode active material, a conductive additive that has been treated to reduce its bulk density, and an electrolyte, wherein the electrode material satisfies all of the following formulas (1) to (3), where y is the yield stress (unit: kPa) measured with a rotational viscometer and x is the electrical conductivity (unit: mS / cm) measured with an electrical resistance meter: y≦4.8x-7.4 (1) 10≦y≦100 (2) 2≦x≦23 (3) 9. The electrode material according to claim 8, which is used for an electrode layer of a quasi-solid battery.

10. The electrode material according to claim 8, wherein the treated conductive additive is carbon black that has been treated to reduce its bulk density.

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