Liquid composition for forming electrode active material layer

Abstract

To provide a liquid composition for electrode active material layer formation, which enables the increase in adhesion of an electrode active material layer containing a metal active material including Cu to a current collector.SOLUTION: A liquid composition for electrode active material layer formation disclosed herein comprises: over 5.0 mass% to 99.0 mass% of metal active material particles containing a metal active material including Cu and / or occluding and releasing metal ions; a binding agent; and a solvent, in which an aggregate including a plurality of the metal active material particles is 60 μm or smaller in particle diameter.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a liquid composition for forming an electrode active material layer for use in secondary batteries, such as non-aqueous electrolyte secondary batteries and all-solid-state secondary batteries. [Background technology]

[0002] In recent years, small electronic devices such as home video cameras, laptops, and smartphones have become widespread. These small electronic devices use non-aqueous electrolyte secondary batteries, typified by lithium-ion batteries. As small electronic devices become smaller and more powerful, secondary batteries, including non-aqueous electrolyte secondary batteries, are required to have high charge / discharge capacities.

[0003] Currently, graphite-based active materials are used for the negative electrodes of secondary batteries, but these materials have technical issues with regard to charge / discharge capacity.

[0004] Therefore, metal-based active materials, which have higher capacities than graphite-based active materials, have been attracting attention. Known examples of metal-based active materials include silicon (Si)-based active materials.

[0005] However, metal-based active materials repeatedly expand and contract significantly during charging and discharging. This makes their capacity prone to degradation. For example, the volume expansion rate of graphite during charging is approximately 12%. In contrast, the volume expansion rate of silicon (Si) during charging is approximately 400%. Therefore, when an electrode plate made of silicon (Si) undergoes repeated charging and discharging, significant expansion and contraction occur. In this case, the electrode active material layer formed on the current collector of the electrode plate cracks. As a result, the capacity of the electrode plate drops sharply. This is mainly due to the volume expansion and contraction causing some of the electrode active material to peel off, causing the electrode plate to lose its electronic conductivity.

[0006] Therefore, new metal-based active materials have been proposed as alternatives to silicon (Si)-based active materials.

[0007] International Publication No. 2017 / 213147 (Patent Document 1), International Publication No. 2019 / 017349 (Patent Document 2), and Japanese Patent Application Laid-Open No. 2017-091662 (Patent Document 3) propose metal-based active materials containing alloy particles containing copper (Cu).

[0008] The negative electrode active material disclosed in Patent Document 1 includes an alloy having a chemical composition containing, in at %, 10.0 to 22.5% Sn and 10.5 to 23.0% Si, with the remainder being Cu and impurities. The alloy has at least one phase selected from the group consisting of the η' phase, the ε phase, and the Sn phase in a Cu—Sn binary phase diagram. The microstructure of the alloy includes a network region and island regions surrounded by the network region, with the average size of the island regions being 900 nm or less in equivalent circle diameter. Patent Document 1 states that this results in a negative electrode active material that can improve capacity per volume and charge / discharge cycle characteristics.

[0009] The negative electrode active material disclosed in Patent Document 2 includes alloy particles containing, in atomic composition percentages excluding oxygen, 13.0 to 40.0 at% Sn and 6.0 to 40.0 at% Si, with the remainder being Cu and impurities, and 0.50 to 3.00 mass% oxygen. The alloy particles contain one or two phases selected from the group consisting of a phase having a D03 structure in Strukturbericht notation with a Si content of 0 to 5.0 at% and a δ phase with a Si content of 0 to 5.0 at%, one or two phases selected from the group consisting of an ε phase with a Si content of 0 to 5.0 at% and an η' phase with a Si content of 0 to 5.0 at%, and a SiOx phase (x = 0.50 to 1.70). In an X-ray diffraction profile, the alloy particles have a peak with a maximum integrated diffraction intensity in the diffraction angle 2θ range of 42.0 to 44.0 degrees, and the half-width of the peak is 0.15 to 2.50 degrees, which results in a negative electrode active material with excellent capacity per volume and capacity retention, as described in Patent Document 2.

[0010] The negative electrode active material disclosed in Patent Document 3 contains a Cu—Sn-based alloy containing a ζ phase, which results in a negative electrode active material with excellent charge / discharge capacity and cycle characteristics, as described in Patent Document 3.

[0011] In addition to the negative electrode active material disclosed in the above-mentioned Patent Documents 1 to 3, metal-based active material containing alloy particles containing Cu is disclosed in, for example, WO 2014 / 034104 (Patent Document 4), WO 2015 / 129264 (Patent Document 5), WO 2015 / 129265 (Patent Document 6), WO 2015 / 129266 (Patent Document 7), WO 2015 / 129267 (Patent Document 8), WO 2015 / 129270 (Patent Document 9), and WO 2017 / 200046 (Patent Document 10). [Prior art documents] [Patent documents]

[0012] [Patent Document 1] International Publication No. 2017 / 213147 [Patent Document 2] International Publication No. 2019 / 017349 [Patent Document 3] Japanese Patent Application Publication No. 2017-091662 [Patent Document 4] International Publication No. 2014 / 034104 [Patent Document 5] International Publication No. 2015 / 129264 [Patent Document 6] International Publication No. 2015 / 129265 [Patent Document 7] International Publication No. 2015 / 129266 [Patent Document 8] International Publication No. 2015 / 129267 [Patent Document 9] International Publication No. 2015 / 129270 [Patent Document 10] International Publication No. 2017 / 200046 Summary of the Invention [Problem to be solved by the invention]

[0013] An electrode plate is produced by applying an electrode active material layer-forming liquid composition to a current collector such as a Cu ribbon and drying the composition. The electrode active material layer-forming liquid composition contains an electrode active material, a binder, and a solvent. The electrode active material layer is formed by drying the electrode active material layer-forming liquid composition. When charge and discharge are repeated, the electrode active material repeatedly expands and contracts in volume, causing the volume of the electrode active material layer to repeatedly expand and contract. If the electrode active material layer has low adhesion to the current collector, the volume expansion and contraction during repeated charge and discharge easily causes part of the electrode active material layer to peel off from the current collector. If the electrode active material layer peels off from the current collector, the electrode plate loses its electronic conductivity. Therefore, it is preferable that the electrode active material layer has high adhesion to the current collector.

[0014] For example, the use of metal-based active materials containing Cu-containing alloy particles, as disclosed in the above-mentioned Patent Documents 1 to 10, can improve the charge / discharge capacity and cycle characteristics of secondary batteries. However, the above-mentioned Patent Documents 1 to 10 do not consider the adhesion of electrode active material layers containing Cu-containing alloy particles to current collectors. Therefore, when electrode active material layers are formed using the techniques disclosed in the above-mentioned Patent Documents 1 to 10, the adhesion to current collectors is sometimes low.

[0015] An object of the present disclosure is to provide a liquid composition for forming an electrode active material layer that can improve the adhesion of an electrode active material layer containing a metal active material containing Cu to a current collector. [Means for solving the problem]

[0016] The liquid composition for forming an electrode active material layer according to the present disclosure comprises: More than 5.0% by mass to 99.0% by mass of metal active material particles containing Cu and a metal active material that occludes and / or releases metal ions; A binder; a solvent; The particle diameter of the aggregate containing the plurality of metal active material particles is 60 μm or less. [Effects of the Invention]

[0017] The liquid composition for forming an electrode active material layer according to the present disclosure can improve the adhesion of an electrode active material layer containing a metal active material containing Cu to a current collector. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a cross section of an electrode plate provided with an electrode active material layer produced using a conventional liquid composition for forming an electrode active material layer. [Figure 2] FIG. 2 is a schematic diagram of a cross section of an electrode plate provided with an electrode active material layer produced using the electrode active material layer-forming liquid composition of this embodiment. [Figure 3] FIG. 3 is a diagram showing the reading position of the gauge when measuring the particle size of the aggregate. [Figure 4] FIG. 4 is a schematic diagram of a manufacturing apparatus for metal active material particles. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present inventors first formed an electrode plate using a metal active material containing Cu. Specifically, a liquid composition for forming an electrode active material layer was formed by kneading metal active material particles containing Cu, a binder, and a solvent. The liquid composition for forming an electrode active material layer was applied to a current collector, which was a Cu thin ribbon. The applied liquid composition for forming an electrode active material layer was heated and dried. In this way, an electrode plate having an electrode active material layer containing a metal active material containing Cu was produced. For comparison, an electrode plate having an electrode active material layer containing conventional metal active material particles containing Si was produced using a similar method.

[0020] The adhesion of each electrode active material layer to the current collector was evaluated. As a result, the electrode active material layer containing Cu-containing metal active material had lower adhesion to the current collector than the electrode active material layer containing conventional Si-containing metal active material particles. The inventors conducted a detailed investigation into the cause of this.

[0021] If the adhesion to the current collector is low, the electrode active material layer will easily peel off from the current collector. There are two possible patterns for the electrode active material layer to peel off from the current collector. One is when the electrode active material layer itself is damaged, causing parts to fall off and peel off from the current collector. The other is when the electrode active material layer peels off from the interface between the electrode active material layer and the current collector.

[0022] As a result of investigations by the present inventors, it was found that an electrode active material layer containing metal active material particles containing Cu has poor adhesion at the interface between the electrode active material layer and a current collector. Therefore, the present inventors investigated the cause of this in detail. As a result, they were unable to identify the cause of the poor adhesion of the electrode active material layer containing metal active material particles containing Cu. However, the following possibility was considered.

[0023] The specific gravity of copper (Cu) is 8.93 g / cm 3 The specific gravity of silicon (Si) is 2.33 g / cm 3 The Cu-containing metal active material particles contain Cu, which has a large specific gravity. Therefore, the Cu-containing metal active material particles have a larger specific gravity than conventional Si-containing metal active material particles.

[0024] Due to their high specific gravity, Cu-containing metal active material particles tend to precipitate in a solvent. The precipitated Cu-containing metal active material particles accumulate. In the precipitate of the accumulated Cu-containing metal active material particles, the Cu-containing metal active material particles adhere to each other. The liquid composition for forming an electrode active material layer contains a binder in addition to the metal active material particles and a solvent. When the Cu-containing metal active material particles precipitate, the binder is caught in the Cu-containing metal active material particles and incorporated into the accumulated precipitate. Here, if a binder is present on the surface of a Cu-containing metal active material particle, it will bind to other Cu-containing metal active material particles that have deposited on top of it. In other words, the Cu-containing metal active material particles are bound to each other by the binder. This results in the formation of an aggregate containing multiple Cu-containing metal active material particles. The higher the specific gravity of the metal active material particles, the more likely they are to precipitate in a solvent. Therefore, aggregates are more likely to form.

[0025] The techniques disclosed in Patent Documents 1 to 10 do not consider aggregates in liquid compositions for forming electrode active material layers. Therefore, when a liquid composition for forming an electrode active material layer is produced using the conventional electrode active material materials disclosed in Patent Documents 1 to 10, it is thought that metal active material particles containing Cu may precipitate, resulting in the formation of coarse aggregates. The present inventors have considered the case where coarse aggregates are formed in a liquid composition for forming an electrode active material layer.

[0026] FIG. 1 is a schematic diagram of a cross section of an electrode plate including an electrode active material layer produced using a conventional liquid composition for forming an electrode active material layer. Referring to FIG. 1, the electrode plate 1 includes a current collector 2 and an electrode active material layer 3. The electrode active material layer 3 is formed on the current collector 2. Conventional liquid compositions for forming an electrode active material layer contain coarse aggregates 4. Therefore, the electrode active material layer 3 formed using the conventional liquid composition for forming an electrode active material layer contains the coarse aggregates 4. The electrode active material layer 3 is adhered to the current collector 2 via the adhesive surfaces 5 between the coarse aggregates 4 and the current collector 2. There are many voids within the electrode active material layer 3 containing the coarse aggregates 4. Therefore, the adhesive area between the electrode active material layer 3 containing the coarse aggregates 4 and the current collector 2 is small. This is thought to result in poor adhesion of the electrode active material layer 3 to the current collector 2.

[0027] Therefore, the present inventors thought that if the particle size of the aggregates in the electrode active material layer-forming liquid composition could be reduced, the voids in the electrode active material layer 3 could be reduced, as shown in Fig. 2. In this case, the adhesion area between the electrode active material layer 3 and the current collector 2 increases. As a result, it is believed that the adhesion of the electrode active material layer 3 to the current collector 2 can be improved.

[0028] The present inventors further investigated the particle size of the aggregates 4 that can improve the adhesion of the electrode active material layer 3 to the current collector 2. As a result, it was found that in the case of aggregates 4 containing metal active material particles containing a Cu-containing metal active material, if the particle size is 60 μm or less, the electrode active material layer 3 exhibits excellent adhesion to the current collector 2.

[0029] The liquid composition for forming an electrode active material layer of this embodiment, which has been completed based on the above findings, has the following composition.

[0030] [1] More than 5.0% by mass to 99.0% by mass of metal active material particles containing Cu and a metal active material that occludes and / or releases metal ions; A binder; a solvent; The particle diameter of the aggregate containing the plurality of metal active material particles is 60 μm or less. Liquid composition for forming an electrode active material layer.

[0031] [2] The liquid composition for forming an electrode active material layer according to [1], The metal active material further comprises Contains one or more elements selected from the group consisting of Sn and Si, Liquid composition for forming an electrode active material layer.

[0032] [3] [2] The liquid composition for forming an electrode active material layer according to the present invention, The metal active material is Sn: 10 to 40 at% Cu: 50 to 90 at %, Liquid composition for forming an electrode active material layer.

[0033] [4] [2] The liquid composition for forming an electrode active material layer according to the present invention, The metal active material is Sn: 10 to 35 at% containing one or more elements selected from the group consisting of Ti: 9 at% or less, V: 49 at% or less, Cr: 49 at% or less, Mn: 9 at% or less, Fe: 49 at% or less, Co: 49 at% or less, Ni: 9 at% or less, Zn: 29 at% or less, Al: 49 at% or less, Si: 49 at% or less, B: 5 at% or less, and C: 5 at% or less; The balance consists of Cu and impurities. Liquid composition for forming an electrode active material layer.

[0034] [5] The liquid composition for forming an electrode active material layer according to any one of [1] to [4], The median diameter (d50) of the metal active material particles is 0.5 to 50.0 μm. Liquid composition for forming an electrode active material layer.

[0035] [6] The liquid composition for forming an electrode active material layer according to any one of [1] to [5], further comprising: Contains carbon black, Liquid composition for forming an electrode active material layer.

[0036] [7] [6] The liquid composition for forming an electrode active material layer according to [6], Contains 0.1 to 15.0 mass% carbon black, Liquid composition for forming an electrode active material layer.

[0037] [8] [7] The liquid composition for forming an electrode active material layer according to [7], When the total of the content of the metal active material particles in mass% and the content of the carbon black in mass% is taken as 100%, the content of the carbon black in mass% is 1% or more. Liquid composition for forming an electrode active material layer.

[0038] The liquid composition for forming an electrode active material layer of this embodiment will be described in detail below.

[0039] [Liquid composition for forming electrode active material layer] The liquid composition for forming an electrode active material layer of this embodiment contains metal active material particles, a binder, and a solvent.

[0040] [Metal active material particles] The metal active material particles contain a metal active material, which contains Cu and absorbs and / or releases metal ions.

[0041] The metal ion absorbed and / or released by the metal active material is, for example, one selected from the group consisting of lithium ion, magnesium ion, aluminum ion and sodium ion, with the preferred metal ion being lithium ion.

[0042] Preferably, the metal active material contains one or more selected from the group consisting of metals, alloys, intermetallic compounds, and metal oxides, with the balance consisting of impurities. More preferably, the metal active material contains one or more selected from the group consisting of metals, alloys, and intermetallic compounds, with the balance consisting of impurities. Preferably, the metal active material is a Cu alloy. More preferably, the metal active material contains a Cu alloy and the balance consisting of impurities.

[0043] The metal active material particles may contain a carbonaceous material in addition to the metal active material. That is, the metal active material particles may be metal active material particles composed of a metal active material and a carbonaceous material. The carbonaceous material may be, for example, one or more selected from the group consisting of graphite and carbon black. The graphite functions as an active material. The carbon black functions as a conductive additive. The carbon black may be one or more selected from the group consisting of acetylene black and ketjen black. The metal active material accounts for 5% by volume or more of the metal active material particles. The content of the metal active material in the metal active material particles is preferably 10% by volume or more, more preferably 20% by volume or more, more preferably 50% by volume or more, even more preferably 70% by volume or more, even more preferably 80% by volume or more, and even more preferably 90% by volume or more. More preferably, the metal active material particles are composed of a metal active material. The metal active material may contain impurities within a range that does not detract from the gist of the present invention.

[0044] [Chemical composition of metal active material] The metal active material contains Cu. Copper (Cu) has a high discharge capacity per volume and reduces the electrode resistance of an electrode including the electrode active material layer 3. The preferred Cu content is 50 to 90 at %.

[0045] Cu: 50 to 90 at% Copper (Cu) has a high discharge capacity per volume and reduces the electrode resistance of an electrode including an electrode active material layer 3. If the Cu content is 50 at% or more, the discharge capacity of an electrode including an electrode active material layer 3 increases and the electrode resistance decreases. On the other hand, if the Cu content is 90 at% or less, the discharge capacity per volume increases. Therefore, the Cu content is preferably 50 to 90 at%. A more preferable lower limit of the Cu content is 55 at% and even more preferably 60 at%. A more preferable upper limit of the Cu content is 80 at% and even more preferably 70 at%.

[0046] Preferably, the elements contained in the metal active material other than Cu are one or more elements selected from the group consisting of metal elements, metalloid elements, oxygen, and carbon. That is, the chemical composition of the metal active material is preferably a chemical composition consisting of Cu, one or more elements selected from the group consisting of metal elements, metalloid elements, oxygen, and carbon, and impurities.

[0047] The metal element may be, for example, one or more elements selected from the group consisting of tin (Sn), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), and aluminum (Al). The metalloid element may be, for example, one or more elements selected from the group consisting of silicon (Si) and boron (B). In other words, the chemical composition of the metal active material may be one or more elements selected from the group consisting of Sn, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Al, Si, B, O, and C, with the balance being Cu and impurities.

[0048] [Preferable components of metal active material (1)] More preferably, the metal active material contains one or more elements selected from the group consisting of Sn and Si, with the balance consisting of Cu and impurities.More preferably, the metal active material contains 10 to 40 at % Sn and 50 to 90 at % Cu, with the balance consisting of impurities.

[0049] Sn: 10 to 40 at% Tin (Sn) increases the discharge capacity per volume. If the Sn content is 10 at% or more, this effect is effectively obtained. If the Sn content is 40 at% or less, the discharge capacity per volume is further increased. Therefore, the preferred Sn content is 10 to 40 at%. A more preferred lower limit of the Sn content is 13 at%, more preferably 18.5 at%, and even more preferably 21 at%. A more preferred upper limit of the Sn content is 35 at%, and even more preferably 30 at%.

[0050] [Preferable components of metal active material (2)] The metal active material may also contain one or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Al, Si, B and C, and Sn, with the balance being Cu and impurities.

[0051] When the metal active material contains Sn and one or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Al, Si, B, and C, with the balance consisting of Cu and impurities, the metal active material preferably contains 10 to 35 at% Sn and one or more elements selected from the group consisting of Ti: 9 at% or less, V: 49 at% or less, Cr: 49 at% or less, Mn: 9 at% or less, Fe: 49 at% or less, Co: 49 at% or less, Ni: 9 at% or less, Zn: 29 at% or less, Al: 49 at% or less, Si: 49 at% or less, B: 5 at% or less, and C: 5 at% or less, with the balance consisting of Cu and impurities.

[0052] As described above, the preferred upper limit of the Ti content is 9 at%. A more preferred upper limit of the Ti content is 6 at%, and even more preferably 5 at%. A preferred lower limit of the Ti content is 0.1 at%, and even more preferably 0.5 at%, and even more preferably 1 at%. Ti suppresses excessive oxidation of Cu and Sn and reduces the electrode resistance of the electrode.

[0053] As described above, the preferred upper limit of the V content is 49 at%. A more preferred upper limit of the V content is 30 at%, more preferably 15 at%, and even more preferably 10 at%. A preferred lower limit of the V content is 0.1 at%, more preferably 0.5 at%, and even more preferably 1 at%. V suppresses excessive oxidation of Cu and Sn and reduces the electrode resistance of the electrode.

[0054] As described above, the preferred upper limit of the Cr content is 49 at%. A more preferred upper limit of the Cr content is 30 at%, more preferably 15 at%, and even more preferably 10 at%. A preferred lower limit of the Cr content is 0.1 at%, more preferably 0.5 at%, and even more preferably 1 at%. Cr suppresses excessive oxidation of Cu and Sn and reduces the electrode resistance of the electrode.

[0055] As described above, the preferred upper limit of the Mn content is 9 at%. A more preferred upper limit of the Mn content is 6 at%, and even more preferably 5 at%. A preferred lower limit of the Mn content is 0.1 at%, and even more preferably 0.5 at%, and even more preferably 1 at%. Mn suppresses excessive oxidation of Cu and Sn and reduces the electrode resistance of the electrode.

[0056] As described above, the preferred upper limit of the Fe content is 49 at%. A more preferred upper limit of the Fe content is 30 at%, more preferably 15 at%, and even more preferably 10 at%. A preferred lower limit of the Fe content is 0.1 at%, more preferably 0.5 at%, and even more preferably 1 at%. Fe suppresses excessive oxidation of Cu and Sn and reduces the electrode resistance of the electrode.

[0057] As described above, the preferred upper limit of the Co content is 49 at%. A more preferred upper limit of the Co content is 30 at%, more preferably 15 at%, and even more preferably 10 at%. A preferred lower limit of the Co content is 0.1 at%, more preferably 0.5 at%, and even more preferably 1 at%. Co suppresses excessive oxidation of Cu and Sn and reduces the electrode resistance of the electrode.

[0058] As described above, the preferred upper limit of the Ni content is 9 at%. A more preferred upper limit of the Ni content is 5 at%, and even more preferably 2 at%. A preferred lower limit of the Ni content is 0.1 at%, and even more preferably 0.5 at%, and even more preferably 1 at%. Ni suppresses excessive oxidation of Cu and Sn and reduces the electrode resistance of the electrode.

[0059] As described above, the preferred upper limit of the Zn content is 29 at%. A more preferred upper limit of the Zn content is 27 at%, and even more preferably 25 at%. A preferred lower limit of the Zn content is 0.1 at%, and even more preferably 0.5 at%, and even more preferably 1 at%. Zn suppresses excessive oxidation of Cu and Sn and reduces the electrode resistance of the electrode.

[0060] As described above, the preferred upper limit of the Al content is 49 at%. A more preferred upper limit of the Al content is 30 at%, more preferably 15 at%, and even more preferably 10 at%. A preferred lower limit of the Al content is 0.1%, more preferably 0.5 at%, and even more preferably 1 at%. Al suppresses excessive oxidation of Cu and Sn and reduces the electrode resistance of the electrode.

[0061] As described above, the preferred upper limit of the Si content is 49 at%. A more preferred upper limit of the Si content is 30 at%, more preferably 15 at%, and even more preferably 10 at%. A preferred lower limit of the Si content is 0.1 at%, more preferably 0.5 at%, and even more preferably 1 at%. Si can increase the discharge capacity per volume.

[0062] The upper limit of the B content is preferably 5 at%. The lower limit of the B content is preferably 0.01 at%, more preferably 0.1 at%, even more preferably 0.5 at%, and still more preferably 1 at%. B suppresses excessive oxidation of Cu and Sn and reduces the electrode resistance of the electrode.

[0063] The upper limit of the C content is preferably 5 at%. The lower limit of the C content is preferably 0.01 at%, more preferably 0.1 at%, even more preferably 0.5 at%, and even more preferably 1 at%. C can reduce the volume expansion coefficient (when occluding metal ions) of the metal active material.

[0064] [Preferable components of metal active material (3)] The metal active material may further contain Sn and a Group 2 element and / or a rare earth element (REM) for the purpose of increasing discharge capacity, with the balance being Cu and impurities. Examples of Group 2 elements include magnesium (Mg) and calcium (Ca). Examples of REM include one or more elements selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd).

[0065] [Metal active material particle content] The electrode active material layer-forming liquid composition of this embodiment contains more than 5.0 mass % to 99.0 mass % of metal active material particles. If the content of metal active material particles is 5.0 mass % or less, the discharge capacity of the electrode active material layer 3 decreases. On the other hand, if the content of metal active material particles exceeds 99.0 mass %, the amount of binder relative to the metal active material particles becomes too small, resulting in poor formation of the electrode active material layer 3. Therefore, the content of metal active material particles is more than 5.0 mass % to 99.0 mass %. The lower limit of the content of metal active material particles is preferably 10.0 mass %, more preferably 20.0 mass %, more preferably 30.0 mass %, even more preferably 40.0 mass %, even more preferably 50.0 mass %, even more preferably 60.0 mass %, and even more preferably 65.0 mass %. The upper limit of the content of the metal active material particles is preferably 98.0 mass%, more preferably 95.0 mass%, more preferably 90.0 mass%, more preferably 85.0 mass%, more preferably 80.0 mass%, and even more preferably 70.0 mass%.

[0066] The content of metal active material particles refers to the content of metal active material particles when the total content, in mass %, of components other than the solvent in the liquid composition for forming an electrode active material layer is taken as 100 mass %.

[0067] [Median diameter of metal active material particles] The median diameter (d50) of the metal active material particles of this embodiment is not particularly limited. When the median diameter (d50) of the metal active material particles is 0.5 μm or more, the specific surface area of ​​the metal active material particles can be prevented from becoming too large. Therefore, the irreversible capacity can be effectively suppressed, and further, the discharge capacity per volume can be improved. When the median diameter (d50) of the metal active material particles is 50.0 μm or less, it is easy to manufacture a flat and thin electrode. Therefore, the median diameter (d50) of the metal active material particles is preferably 0.5 to 50.0 μm. The lower limit of the median diameter (d50) of the metal active material particles is more preferably 1.0 μm, and even more preferably 1.5 μm. The upper limit of the median diameter (d50) of the metal active material particles is more preferably 40.0 μm, and even more preferably 20.0 μm.

[0068] [Method for measuring the median diameter of metal active material particles] The median diameter (d50) of the metal active material particles is determined by the following method: 2 ml of the liquid composition for forming an electrode active material layer is taken and centrifuged at 3000 rpm for 10 minutes. After centrifugation, the supernatant is discarded. 1 ml of solvent (water or N-methyl-2-pyrrolidone) is added to the remaining precipitate and stirred thoroughly. The mixture is again centrifuged at 3000 rpm for 10 minutes. The addition of the solvent and centrifugation are repeated three more times. This separates the metal active material particles from the liquid composition for forming an electrode active material layer. The median diameter (d50) of the obtained metal active material particles is measured by laser diffraction scattering.

[0069] The median diameter (d50) of metal active material particles is measured by the laser diffraction scattering method using a laser diffraction / scattering particle size distribution analyzer in accordance with JIS Z 8825 (2013). The dispersion medium used in the measurement is water to which 0.1% by mass of a surfactant containing alkylglycoxide has been added. The dispersion method is ultrasonic dispersion for 5 minutes. The particle size at which the cumulative volume of all metal active material particles is 50% (volume average particle size measured by the laser diffraction scattering method) is taken as the average particle size (median diameter (d50)) of the metal active material particles.

[0070] [Binder] The liquid composition for forming an electrode active material layer of this embodiment contains a binder. The binder is scattered on the surfaces of the metal active material particles and binds the metal active material particles together. The type of binder is not particularly limited. For example, the binder is one or more selected from the group consisting of a water-insoluble resin that is insoluble in a solvent used in the non-aqueous electrolyte of the battery, a water-soluble resin, and styrene butadiene rubber (SBR). The water-insoluble resin that is insoluble in a solvent used in the non-aqueous electrolyte of the battery is one or more selected from the group consisting of polyimide (PI), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), and polytetrafluoroethylene (PTFE). The water-soluble resin is one or more selected from the group consisting of carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA). Two or more of these binders may be mixed and used. That is, the binder is, for example, one or more selected from the group consisting of polyimide (PI), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and styrene butadiene rubber (SBR).

[0071] Preferably, the binder is one or more selected from the group consisting of carboxymethyl cellulose (CMC), polyimide (PI), and polyvinylidene fluoride (PVDF). These binders have excellent electrode adhesion, making it more difficult for the electrode active material layer 3 to peel off from the current collector 2 during electrode production.

[0072] [Binder content] The content of the binder in the liquid composition for forming an electrode active material layer can be set appropriately. When the content of the binder is 1.0% by mass or more, the adhesion of the electrode active material layer 3 to the current collector 2 is stably improved. When the content of the binder is 1.0% by mass or more, the battery characteristics, particularly the cycle characteristics, are further stably improved. On the other hand, when the content of the binder is 20.0% by mass or less, the volume resistivity of the electrode active material layer 3 is stably reduced. Therefore, the rapid chargeability of the non-aqueous electrolyte secondary battery is further stably improved. Therefore, the content of the binder is preferably 1.0 to 20.0% by mass or less. The lower limit of the content of the binder is more preferably 2.0% by mass, even more preferably 5.0% by mass, and even more preferably 10.0% by mass.

[0073] The content of the binder refers to the content of the binder when the total content of the components other than the solvent in the electrode active material layer-forming liquid composition is taken as 100 mass %.

[0074] [solvent] The liquid composition for forming an electrode active material layer of this embodiment contains a solvent. The solvent is at least one selected from the group consisting of organic solvents and water. The solvent is preferably at least one selected from the group consisting of N-methyl-2-pyrrolidone, ethanol, methanol, N,N-dimethylacetamide, ethylene glycol mono-normal-butyl ether, and water. More preferably, the solvent is at least one selected from the group consisting of N-methyl-2-pyrrolidone and water.

[0075] [Solvent content] The content of the solvent in the liquid composition for forming an electrode active material layer can be set as appropriate. The content of the solvent is preferably 30 to 100% by mass. In this case, the viscosity of the liquid composition for forming an electrode active material layer is likely to be suitable for producing the electrode plate 1. The lower limit of the solvent content is more preferably 40% by mass, more preferably 50% by mass, even more preferably 60% by mass, and even more preferably 70% by mass. The upper limit of the solvent content is more preferably 90% by mass, and even more preferably 80% by mass.

[0076] The content of the solvent refers to the content of the solvent relative to the total content of the components other than the solvent in the liquid composition for forming an electrode active material layer, taken as 100 mass %.

[0077] [Method for measuring the content of metal active material particles, binder, solvent, and carbon black] The contents of metal active material particles, binder, solvent, and carbon black in the liquid composition for forming an electrode active material layer are measured using the following method. 2 ml of the liquid composition for forming an electrode active material layer is weighed and then centrifuged in a centrifuge. The centrifugation conditions are 3000 rpm for 10 minutes. The supernatant after centrifugation is recovered and the precipitate is separated. The weight of the recovered supernatant is also measured. 1 ml of solvent (water or N-methyl-2-pyrrolidone) is added to the precipitate and stirred well. The mixture is centrifuged again for 10 minutes at 3000 rpm. The supernatant after centrifugation is combined with the previously recovered supernatant and placed in the same container. The addition of the solvent, centrifugation, and supernatant recovery are repeated three more times. All recovered supernatants are placed in the same container. This separates the metal active material particles from other components. After a total of five centrifugations, the weight of the precipitate is measured. The precipitate was also analyzed by energy dispersive X-ray spectroscopy (SEM-EDX) using a scanning electron microscope (SEM). This confirmed that the precipitate contained Cu. The measured weight of the precipitate was taken as the metal active material particle content (% by mass). The container containing all the supernatants collected after the five centrifugations was depressurized to evaporate the solvent inside the container. The weight (% by mass) of the residue after the solvent had evaporated was measured. The weight change of this residue with respect to temperature was measured using a thermogravimetric analyzer (TGA). Specifically, the temperature was raised from room temperature (25°C) to 600°C under a nitrogen atmosphere, and the weight loss from room temperature to 600°C was measured. The weight loss was taken as the binder content (% by mass). The difference between the weight (% by mass) of the residue after the solvent had evaporated and the binder content (% by mass) was taken as the carbon black content (% by mass). The solvent content (% by mass) is calculated by subtracting the contents of the metal active material particles, binder, and carbon black from the weight of 2 ml of the electrode active material layer-forming liquid composition measured initially. The total of the metal active material particles, binder, and carbon black contents is set to 100% by mass, and the metal active material particle content (% by mass), binder content (% by mass), and carbon black content (% by mass) are calculated.

[0078] The electrode active material layer forming liquid composition of this embodiment may be a liquid composition for forming an electrode active material layer comprising metal active material particles, a binder, and a solvent.

[0079] [Carbon black] The liquid composition for forming an electrode active material layer of this embodiment may further contain carbon black. Carbon black acts as a conductive additive and reduces the electrical resistance of the electrode active material layer 3.

[0080] [Carbon black content] Carbon black is optionally contained. That is, the carbon black content may be 0% by mass. When the carbon black content is 0.1% by mass or more, the electrical resistance of the electrode active material layer 3 can be stably reduced. On the other hand, when the carbon black content is 15.0% by mass or less, the content of the metal active material particles and / or the content of the binder increases relatively, thereby further improving the discharge capacity and / or adhesion of the electrode active material layer 3. Therefore, the carbon black content in the liquid composition for forming an electrode active material layer is preferably 0.1 to 15.0% by mass. The lower limit of the carbon black content is more preferably 0.2% by mass, even more preferably 0.5% by mass, even more preferably 0.8% by mass, and even more preferably 1.0% by mass. The upper limit of the carbon black content is more preferably 13.0% by mass, even more preferably 10.0% by mass, even more preferably 8.0% by mass, even more preferably 5.0% by mass, and even more preferably 3.0% by mass.

[0081] The carbon black content refers to the carbon black content when the total content of the components other than the solvent in the electrode active material layer-forming liquid composition is taken as 100 mass %.

[0082] Preferably, the electrode active material layer forming liquid composition of this embodiment is a liquid composition for forming an electrode active material layer comprising metal active material particles, a binder, carbon black, and a solvent.

[0083] [Ratio of metal active material particles to carbon black content] Carbon black is present between metal active material particles precipitated in the liquid composition for forming an electrode active material layer, suppressing adhesion between the metal active material particles. Therefore, when carbon black is contained in the liquid composition for forming an electrode active material layer, the carbon black suppresses the formation of coarse aggregates 4. The higher the carbon black content relative to the metal active material particle content, the more easily the formation of coarse aggregates 4 is suppressed. Therefore, when the sum of the metal active material particle content in mass% and the carbon black content in mass% is taken as 100%, the carbon black content in mass% is preferably 1% or more. When the sum of the metal active material particle content in mass% and the carbon black content in mass% is taken as 100%, the carbon black content in mass% is more preferably 2% or more, and even more preferably 3% or more.

[0084] [Agglomerate particle size] The metal active material particles contained in the liquid composition for forming an electrode active material layer of this embodiment contain Cu and have a high specific gravity. Therefore, aggregates 4 containing multiple metal active material particles are easily formed. However, in the liquid composition for forming an electrode active material layer of this embodiment, the particle diameter of aggregates 4 containing multiple metal active material particles is 60 μm or less. Therefore, the electrode active material layer 3 formed using the liquid composition for forming an electrode active material layer of this embodiment has high adhesion to the current collector 2. The upper limit of the particle diameter of aggregates 4 containing multiple metal active material particles is preferably 55 μm or less, more preferably 50 μm or less, even more preferably 45 μm or less, and even more preferably 40 μm or less. The lower limit of the particle diameter of aggregates 4 containing multiple metal active material particles is not particularly limited, but is, for example, 10 μm. In the present disclosure, aggregates 4 refer to aggregates containing multiple metal active material particles including a metal active material containing Cu.

[0085] [Method for measuring particle size of aggregates] The particle size of the aggregate 4 containing a plurality of metal active material particles is measured as follows. The measurement is performed using a method conforming to the dispersity measurement method described in JIS K5600-2-5 (1990). Here, the gauge reading is performed according to the following method, rather than the method described in JIS K5600-2-5 (1990). Specifically, according to the method described in JIS K5600-2-5 (1990), the electrode active material layer-forming liquid composition is poured into the gauge groove, a scraper is pulled, and the electrode active material layer-forming liquid composition is observed. The gauge is read at the position where the first line appears in the electrode active material layer-forming liquid composition. Figure 3 shows the gauge reading position when measuring the particle size of the aggregate 4. In the gauge shown in Figure 3, the starting point of the first line 6 that appears is within the reading position range of 55 to 60 μm. In this case, the maximum reading of 60 μm within the reading position range of 55 to 60 μm is taken as the reading result. The average value of the readings from the three measurements is calculated, and the average value with the same accuracy as the original reading result (5 μm units for 100 μm gauge, 2 μm units for 50 μm gauge, 1 μm units for 25 μm gauge, and 0.5 μm units for 15 μm gauge) is used as the particle size of aggregate 4.

[0086] Next, the starting point of the first line that appears is scooped up with a spatula, and aggregate 4 is collected. A mesh is used to prevent aggregate 4 from flowing away, and the binder (and carbon black) adhering to aggregate 4 is washed off with a solvent. For example, if aggregate 4 has a particle size of 60 μm, it is placed on a 30 μm polyethylene mesh and solvent is poured over it. In this way, aggregate 4 is extracted. The obtained aggregate 4 is observed and analyzed by SEM-EDX, and it is confirmed that it contains multiple particles. Furthermore, it is confirmed that each of the multiple particles contains Cu.

[0087] As described above, the electrode active material layer-forming liquid composition of this embodiment contains more than 5.0 mass % to 99.0 mass % of metal active material particles containing a metal active material that contains Cu and occludes and / or releases metal ions, a binder, and a solvent. The electrode active material layer-forming liquid composition of this embodiment further contains aggregates 4 containing a plurality of metal active material particles, each having a particle diameter of 60 μm or less. Therefore, the electrode active material layer 3 formed using the electrode active material layer-forming liquid composition of this embodiment has high adhesion to the current collector 2.

[0088] [Battery Using Liquid Composition for Forming Electrode Active Material Layer of the Present Embodiment] An example of an electrode and a battery produced using the liquid composition for forming an electrode active material layer of this embodiment will be shown below.

[0089] [electrode] FIG. 2 is a schematic cross-sectional view of an electrode plate including an electrode active material layer produced using the liquid composition for forming an electrode active material layer of this embodiment. Referring to FIG. 2, the electrode plate 1 is an electrode plate 1 for a secondary battery, and includes an electrode active material layer 3 formed using the liquid composition for forming an electrode active material layer described above, and a current collector 2 made of metal foil. In this embodiment, the electrode plate 1 may be a positive electrode or a negative electrode. The electrode active material layer 3 is formed by applying the liquid composition for forming an electrode active material layer of this embodiment to the surface of the current collector 2 and drying it. The current collector 2 is in the form of a thin film or plate and supports the electrode active material layer 3. The current collector 2 is made of metal foil. The current collector 2 is made of well-known materials such as Cu, Ni, Ni-plated copper, and stainless steel. In the case of an electrode plate 1 for a lithium-ion secondary battery, the current collector 2 is preferably made of Cu. This is because Cu is less likely to form an alloy with lithium and has excellent formability. The thickness of the current collector 2 is, for example, 10 to 20 μm.

[0090] [Secondary battery] The secondary battery of this embodiment includes the above-described electrode plate 1. The secondary battery includes the above-described electrode plate 1, a positive electrode or a negative electrode, a separator, and an electrolyte. The shape of the secondary battery is not particularly limited, and may be cylindrical, prismatic, coin-shaped, or sheet-shaped. The secondary battery may be selected from the group consisting of lithium-ion batteries, sodium-ion batteries, magnesium-ion batteries, aluminum-ion batteries, all-solid-state batteries, and lithium-sulfur batteries.

[0091] When the electrode plate 1 is used as a negative electrode, the positive electrode may have a known structure. Preferably, the positive electrode contains a transition metal compound containing a metal ion as an active material. More preferably, the positive electrode contains a lithium (Li)-containing transition metal compound as an active material. For example, the Li-containing transition metal compound is LiM1-xM' x O2 and / or LiM2yM'O4, where 0≦x, y≦1, and M and M' are each one or more elements selected from the group consisting of barium (Ba), cobalt (Co), nickel (Ni), manganese (Mn), chromium (Cr), titanium (Ti), vanadium (V), iron (Fe), zinc (Zn), aluminum (Al), indium (In), tin (Sn), scandium (Sc), and yttrium (Y).

[0092] The secondary battery of this embodiment may include, as the positive electrode having the above-described configuration, other well-known positive electrodes such as transition metal chalcogenides, vanadium oxides and their lithium (Li) compounds, niobium oxides and their lithium compounds, conjugated polymers using organic conductive substances, Schoepler phase compounds, activated carbon, and activated carbon fibers.

[0093] When the electrolyte is an electrolytic solution, the electrolytic solution may be a nonaqueous electrolytic solution in which a lithium salt serving as a supporting electrolyte is dissolved in an organic solvent. Examples of the lithium salt include lithium perchlorate (LiClO), lithium fluoroborate (LiBF), lithium hexafluorophosphate (LiPF), LiAsF, LiB(CH), LiCFSO, LiCHSO, Li(CFSO)N, LiCFSO, Li(CFSO), LiCl, LiBr, and LiI. These may be used alone or in combination. The organic solvent may be a carbonate ester such as propylene carbonate, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate. However, various other organic solvents, including carboxylic acid esters and ethers, may also be used. These organic solvents may be used alone or in combination. When the electrolyte is a solid electrolyte, the secondary battery may be, for example, a polymer battery or an all-solid-state battery.

[0094] The separator is placed between the positive and negative electrodes. It acts as an insulator. It also plays a major role in retaining the electrolyte. The separator can have a well-known structure. For example, the separator can be a polyolefin-based material such as polypropylene or polyethylene, or a mixture of both, or a porous material such as a glass filter.

[0095] [Method of manufacturing a liquid composition for forming an electrode active material layer] An example of a method for producing the electrode active material layer-forming liquid composition of this embodiment will be described below. The production method described below is one example for producing the electrode active material layer-forming liquid composition of this embodiment. Therefore, the electrode active material layer-forming liquid composition having the above-mentioned configuration may be produced by a production method other than the production method described below. However, the production method described below is a preferred example of a method for producing the electrode active material layer-forming liquid composition of this embodiment.

[0096] The method for producing the electrode active material layer-forming liquid composition of this embodiment includes a metal active material particle preparation step, a preliminary kneading step, a main kneading step, and a reduced pressure kneading step. Each step will be described below.

[0097] [Metal active material particle preparation process] In the metal active material particle preparation step, metal active material particles are prepared. The metal active material particles may be supplied by a third party or may be manufactured. When manufactured, the metal active material particles are produced, for example, by rapidly cooling a molten metal. Methods for rapidly cooling a molten metal include, for example, roll cooling, gas atomization, submerged spinning, and melt spinning.

[0098] Preferably, the metal active material particles are produced by the following method: A molten metal containing the components of the metal active material is produced by melting raw materials using a known melting method such as arc melting or resistance heating melting.

[0099] The molten metal is used to produce a metal active material. Examples of methods for producing a metal active material include an ingot casting method, a strip casting method, and a melt spinning method. When producing a metal active material by quenching, a metal ribbon 600 is produced using a manufacturing apparatus 100 shown in FIG. 4, for example, in consideration of production efficiency. FIG. 4 is a schematic diagram of the manufacturing apparatus 100 for producing a metal active material of metal active material particles. The manufacturing apparatus 100 includes a cooling roll 200, a tundish 300, and a blade member 400.

[0100] The chill roll 200 has an outer circumferential surface, and cools and solidifies the molten metal 500 on the outer circumferential surface while rotating. The chill roll 200 is rotated around its central axis by a drive source. RD shown in FIG. 4 is the rotation direction of the chill roll 200. When the metal ribbon 600 is produced, the chill roll 200 rotates in the rotation direction RD. As a result, in FIG. 4, the molten metal 500 that comes into contact with the chill roll 200 is partially solidified on the outer circumferential surface of the chill roll 200 and moves as the chill roll 200 rotates. The tundish 300 is capable of storing the molten metal 500 and supplies the molten metal 500 onto the outer circumferential surface of the chill roll 200.

[0101] The blade member 400 is disposed downstream of the tundish 300 in the direction of rotation of the chill roll 200, with a gap provided between it and the outer circumferential surface of the chill roll 200. The blade member 400 is a separate member from the tundish 300, and is disposed away from the tundish 300 and downstream in the direction of rotation RD of the chill roll 200. The blade member 400 restricts the thickness of the molten metal 500 on the outer circumferential surface of the chill roll 200 to the thickness of the gap between the outer circumferential surface of the chill roll 200 and the blade member 400, thereby producing a metal ribbon 600. The thickness of the molten metal 500 is restricted to the thickness of the gap between the blade member 400 and the chill roll 200, and the molten metal 500 is cooled by the chill roll 200 and the blade member 400. This causes the molten metal 500 to be rapidly cooled, producing a metal ribbon 600.

[0102] The produced metal ribbon 600 is subjected to a mechanical alloying treatment (MA treatment) to produce a metal active material. The mechanical alloying device is, for example, a high-speed planetary mill. Examples of high-speed planetary mills include a Hi-G BX (product name) manufactured by Kurimoto Iron Works Co., Ltd., a Turbula Shaker Mixer (Model T2F manufactured by Shinmaru Enterprises Co., Ltd.), and a small vibration rod mill (Model 1045 manufactured by Yoshida Manufacturing Co., Ltd.). The obtained metal active material may be used as metal active material particles. When producing metal active material particles containing a metal active material and a carbonaceous material, the metal ribbon 600 and the carbonaceous material may be mixed during the MA treatment to composite the metal active material and the carbonaceous material. Apart from the MA treatment, a composite treatment may be performed in which the metal ribbon 600 and the carbonaceous material are mixed and composited. From the viewpoint of reducing the number of manufacturing steps, when the metal active material and the carbonaceous material are composited, it is preferable to composite them simultaneously during the MA treatment. The carbonaceous material is, for example, one or more selected from the group consisting of graphite, carbon black, acetylene black, and ketjen black.Thereby, metal active material particles containing a metal active material containing Cu are produced.

[0103] [Kneading process] In conventional methods for producing a liquid composition for forming an electrode active material layer, metal active material particles, a binder, and a solvent are kneaded in a single kneading step to produce the liquid composition for forming an electrode active material layer. However, in the method for producing a liquid composition for forming an electrode active material layer of the present embodiment, three kneading steps are performed in this order: preliminary kneading, main kneading, and reduced pressure kneading. By performing the three kneading steps under appropriate conditions, the particle diameter of the aggregates 4 containing a plurality of metal active material particles in the liquid composition for forming an electrode active material layer can be reduced to 60 μm or less.

[0104] While the reason for this is unclear, the following may be considered. As described below, the rotation speed of the rotating blade in the preliminary kneading step is 300 to 700 rpm. This rotation speed of the rotating blade corresponds to a peripheral speed of 0.9 to 2.2 m / s. Meanwhile, the rotation speed of the stirrer in the main kneading step is 30 to 40 m / s. That is, in the method for producing a liquid composition for forming an electrode active material layer according to this embodiment, the stirring speed in the preliminary kneading step is slower than the stirring speed in the main kneading step. By kneading at a slow stirring speed in advance in the preliminary kneading step, the metal active material particles, the binder, and the solvent are kneaded to a certain extent while suppressing the formation of clumps of the metal active material particles, which tend to settle. Furthermore, in the main kneading step, the kneading is performed at a stirring speed faster than that in the preliminary kneading step. This allows the metal active material particles to be highly dispersed, and the liquid composition for forming an electrode active material layer can be produced while suppressing the formation of coarse aggregates 4. If the preliminary kneading step is not performed and only the main kneading step and the reduced pressure kneading step are performed, the metal active material particles, the binder, and the solvent are kneaded at a high stirring speed from the beginning. In this case, the metal active material particles form lumps. In this case, it is thought that coarse aggregates 4 are formed.

[0105] [Pre-mixing process] In the preliminary kneading step, the metal active material particles prepared in the metal active material particle preparation step are kneaded with a binder, a solvent, and, if necessary, carbon black. First, the metal active material particles, binder, solvent, and, if necessary, carbon black are placed in a stirring vessel. Next, a rotating bladed stirrer is inserted into the stirring vessel, and the mixture is kneaded by rotating the rotating blades. The rotating bladed stirrer is, for example, a high-power general-purpose stirrer BLh600 manufactured by Shinto Scientific Co., Ltd.

[0106] The rotation speed of the rotating blade in the preliminary kneading step is 300 to 700 rpm. If the rotation speed of the rotating blade is less than 300 rpm, the energy required to disperse the metal active material particles is not obtained, and the metal active material particles adhere to each other to form aggregates 4. On the other hand, if the rotation speed of the rotating blade exceeds 700 rpm, the temperature of the mixture in the stirring vessel increases locally, causing the solvent to volatilize. This causes a local increase in the solids concentration of the mixture in the stirring vessel, resulting in the formation of coarse aggregates 4.

[0107] The kneading time in the preliminary kneading step is 60 to 120 seconds. If the kneading time is less than 60 seconds, the energy required to disperse the metal active material particles is not obtained, and the metal active material particles adhere to each other to form aggregates 4. On the other hand, if the kneading time exceeds 120 seconds, the temperature of the mixture in the stirring vessel increases locally, causing the solvent to volatilize. This causes the solids concentration of the mixture in the stirring vessel to increase locally, resulting in the formation of coarse aggregates 4.

[0108] The content of each component in the preliminary kneading step is the same as the content of each component in the liquid composition for forming an electrode active material layer. In other words, in the manufacturing method of this embodiment, instead of adding the metal active material particles, binder, solvent, and carbon black separately in each kneading step, all components are kneaded in the preliminary kneading step, which is the first kneading step. Thereafter, the main kneading step and the reduced-pressure kneading step are carried out without adding any of the components.

[0109] [Main kneading process] In this kneading step, the mixture containing the metal active material particles, binder, and solvent produced in the preliminary kneading step is further kneaded. Specifically, the mixture produced in the preliminary kneading step is placed in a membrane swirl type high-speed mixer and kneaded. An example of a membrane swirl type high-speed mixer is the membrane swirl type high-speed mixer Filmix (trademark) 40-40 model manufactured by Primix Corporation.

[0110] The rotation speed of the stirrer (cylindrical thin film) in this kneading step is 30 to 40 m / s. If the rotation speed of the stirrer is less than 30 m / s, sufficient shear stress cannot be applied to the mixture, resulting in the formation of aggregates 4. On the other hand, if the rotation speed of the stirrer exceeds 40 m / s, the temperature of the mixture in the mixer rises, causing the solvent to volatilize. This increases the viscosity of the liquid composition for forming an electrode active material layer, resulting in the formation of coarse aggregates 4.

[0111] The kneading time in this kneading step is 60 to 120 seconds. If the kneading time is less than 60 seconds, the energy required to disperse the metal active material particles is not obtained, and the metal active material particles adhere to each other to form aggregates 4. On the other hand, if the kneading time exceeds 120 seconds, the temperature of the mixture in the mixer rises and the solvent volatilizes. This increases the viscosity of the liquid composition for forming an electrode active material layer, and coarse aggregates 4 are formed.

[0112] The content of metal active material particles, the content of binder, and the content of solvent in the mixture in the preliminary kneading step are the same as the content of metal active material particles, the content of binder, and the content of solvent in the mixture in the main kneading step, respectively.

[0113] [Decompression mixing process] In the reduced pressure kneading step, the mixture containing the metal active material particles, binder, and solvent produced in the main kneading step is further kneaded. Specifically, the mixture produced in the main kneading step is placed in a kneader. The kneader is, for example, a Hivismix (trademark) 2P-03 kneader manufactured by Primix Corporation.

[0114] In the reduced pressure kneading step, the mixture is kneaded under reduced pressure, for example, at a pressure of 0.01 MPa, to remove minute bubbles formed in the electrode active material layer-forming liquid composition in the preliminary kneading step and main kneading step.

[0115] The rotation speed of the stirrer (blade) in the reduced pressure kneading step is 1 to 40 rpm. The kneading time in the reduced pressure kneading step is 30 minutes to 12 hours. In this case, minute bubbles in the liquid composition for forming an electrode active material layer are sufficiently removed. The minute bubbles in the liquid composition for forming an electrode active material layer may also be incorporated into the deposited metal active material particles. In this case, the aggregates become coarse. By carrying out the reduced pressure kneading step, minute bubbles in the liquid composition for forming an electrode active material layer are removed, thereby suppressing the formation of coarse aggregates 4.

[0116] The electrode active material layer-forming liquid composition of this embodiment can be produced by the above steps. The electrode active material layer-forming liquid composition of this embodiment produced by the above production method contains more than 5.0 mass % to 99.0 mass % metal active material particles containing a metal active material that contains Cu and occludes and / or releases metal ions, a binder, and a solvent. The electrode active material layer-forming liquid composition of this embodiment further contains aggregates containing a plurality of metal active material particles, each having a particle diameter of 60 μm or less. Therefore, the electrode active material layer 3 produced using the electrode active material layer-forming liquid composition of this embodiment has high adhesion to the current collector 2.

[0117] [Electrode manufacturing method] An example of a method for manufacturing an electrode and a battery using the liquid composition for forming an electrode active material layer of this embodiment is as follows: The liquid composition for forming an electrode active material layer is applied to the surface of a current collector 2 and dried to form an electrode active material layer 3 on the current collector 2. Furthermore, if necessary, the dried current collector 2 and electrode active material layer 3 are pressed. An electrode is manufactured through the above steps.

[0118] [Battery manufacturing method] The above-mentioned electrode, separator, and counter electrode are stacked together to produce a laminate by a known method, and the laminate is placed in a case to produce a battery. [Example]

[0119] The effects of the liquid composition for forming an electrode active material layer of this embodiment will be explained in more detail using examples. The conditions in the following examples are one example of conditions adopted to confirm the feasibility and effects of the liquid composition for forming an electrode active material layer of this embodiment. Therefore, the liquid composition for forming an electrode active material layer of this embodiment is not limited to this one example of conditions.

[0120] [Metal active material particle preparation process] Metal active material particles with the composition shown in Table 1 were prepared. Specifically, molten metal was produced so that the metal active material particles had the chemical composition shown in the "Composition" column in Table 1. For example, "Cu-18Sn-17Si" in the "Composition (mass%)" column of the "Metal Active Material Particles" column in Table 1 means that the metal active material of the corresponding test number contains 18 at% Sn and 17 at% Si, with the remainder consisting of Cu and impurities. The "Carbonaceous Material" column in Table 1 indicates whether the metal active material particles are metal active material particles made of a metal active material or metal active material particles made of a metal active material and a carbonaceous material. When the "Carbonaceous Material" column in Table 1 states "Yes," the metal active material particles are made of a metal active material and a carbonaceous material. When the metal active material particles are made of a metal active material and a carbonaceous material, the volume percent content of the metal active material and the carbonaceous material in the metal active material particles is shown in the "Metal:Carbon Ratio" column in Table 1. When "19:1" is entered in the "Metal:Carbon" column of Table 1, the metal active material particles of the corresponding test number contain metal active material:carbonaceous material in a mass ratio of 19:1.

[0121] [Table 1]

[0122] After stabilizing the molten metal temperature at 1200°C, the molten metal was rapidly cooled by strip casting to cast a metal strip 600 with a thickness of 75 μm. For strip casting, a manufacturing apparatus 100 shown in FIG. 4 was used. Specifically, a water-cooled copper chill roll 200 was used, and the rotation speed of the chill roll 200 was set to a peripheral speed of the roll surface of 300 meters per minute. In an argon atmosphere, the molten metal 500 was supplied to the rotating chill roll 200 via a horizontal tundish 30 (made of alumina). The molten metal 500 was rapidly solidified by being pulled up onto the rotating chill roll 200. The gap width between the blade member 400 and the chill roll 200 was 80 μm. The blade member 400 was made of alumina.

[0123] The obtained metal ribbon 600 was further pulverized to produce metal active material particles. A high-speed planetary mill (Hi-G BX, manufactured by Kurimoto Iron Works) was used for the pulverization. The rotation speed was 200 rpm. The pulverization time was 20 minutes. When the metal active material particles contained a carbonaceous material, the metal active material and the carbonaceous material were mixed in the pulverization process so that the mass ratio of the metal active material and the carbonaceous material was as shown in the "Metal:Carbon" column in Table 1, and then pulverized. The carbonaceous material was conductive carbon black (SUPER C65, manufactured by Imerys Graphite & Carbon). In this way, metal active material particles were produced. The median diameter (d50) of the metal active material particles was as shown in Table 1.

[0124] [Kneading process] In test numbers 1 to 2 and 4 to 22, the components were mixed in the amounts shown below, and a preliminary kneading step, a main kneading step, and a reduced-pressure kneading step were carried out under the conditions shown in Table 1. In this way, liquid compositions for forming an electrode active material layer were produced. In the preliminary kneading step, the rotating blades were rotated at the rotation speeds (rpm) shown in Table 1. The rotation speeds (rpm) of the rotating blades in the preliminary kneading step converted into peripheral speeds (m / s) are shown in the "Converted peripheral speed (m / s)" column in Table 1. Metal active material particles: 16.5g Carbon black: 0.2g (binder) Polyimide: 0.9g Polyvinylidene fluoride: 0.4g (solvent) N-methylpyrrolidone: 16.0g

[0125] In test numbers 1 to 2 and 4 to 22, polyimide (DREAMBOND DB100 manufactured by IST Co., Ltd.) and polyvinylidene fluoride (PVdF#9100 manufactured by Kureha Co., Ltd., solid content concentration 10 wt%) were used as binders, and N-methyl-2-pyrrolidone was used as a solvent.

[0126] In Test No. 3, the components were mixed in the amounts shown below, and a preliminary kneading step, a main kneading step, and a reduced-pressure kneading step were carried out under the conditions shown in Table 1. In this way, a liquid composition for forming an electrode active material layer was produced. Metal active material particles: 16.5g Carbon black: 0.2g (binder) Styrene butadiene rubber: 0.2g Carboxymethylcellulose: 0.2g (solvent) Water: 13.0g

[0127] In test number 3, styrene butadiene rubber (TRD2001 manufactured by JSR Corporation) and carboxymethyl cellulose (CMC2200 manufactured by Daicel FineChem Co., Ltd.) were used as binders.

[0128] In the preliminary kneading step, a high-power general-purpose mixer BLh600 manufactured by Shinto Scientific Co., Ltd. was used as the rotary blade mixer. In the main kneading step, a membrane rotation type high-speed mixer Filmix (trademark) 40-40 model manufactured by Primix Corporation was used as the membrane rotation type high-speed mixer. In the reduced pressure kneading step, a kneader Hivismix (trademark) 2P-03 model manufactured by Primix Corporation was used as the kneader.

[0129] [Agglomerate particle size measurement test] The particle size of the aggregates containing multiple metal active material particles in the liquid composition for forming an electrode active material layer of each test number was measured using the following method. According to the method described in JIS K5600-2-5 (1990), the liquid composition for forming an electrode active material layer was poured into the groove of the gauge, and the scraper was used to observe the liquid composition for forming an electrode active material layer. The reading position was determined from the starting point of the first line that appeared in the liquid composition for forming an electrode active material layer in the groove. The maximum value within the range of the reading position was recorded as the reading result. The reading results of three measurements were averaged, and the average value with the same accuracy as the original reading result (5 μm units for a 100 μm gauge, 2 μm units for a 50 μm gauge, 1 μm units for a 25 μm gauge, and 0.5 μm units for a 15 μm gauge) was recorded as the particle size of the aggregates. The results are shown in Table 1.

[0130] [Electrode plate manufacturing] The liquid composition for forming an electrode active material layer of each test number was applied to a Cu foil having a thickness of 20 μm, a length of 15 cm, and a width of 15 cm. The applied area was 10 cm in length and 8 cm in width. The liquid composition for forming an electrode active material layer applied to the Cu foil was dried at 100°C for 20 minutes. A load of 500 kgf / cm was applied to the dried electrode active material layer. 2 The mixture was pressed at 100°C to produce an electrode plate.

[0131] [Adhesion evaluation test] The adhesion strength of the electrode active material layer to the current collector produced using the liquid composition for forming an electrode active material layer with each test number was evaluated. Specifically, a 180-degree peel test was performed using a high-speed peel tester (IMADA Co., Ltd., IPTS-20N / 50N). The 180-degree peel test was performed at a measurement speed of 50 mm / min, and the peel load (N) was read using a force gauge. The average value of the peel load (N) at 300 points was divided by the peel width (10 mm) to calculate the adhesion strength (mN / mm). The results are shown in Table 1.

[0132] [Evaluation results] Referring to Table 1, the electrode active material layer-forming liquid compositions of Test Nos. 1 to 9 contained more than 5.0 mass % to 99.0 mass % metal active material particles containing a metal active material that contains Cu and occludes and / or releases metal ions, a binder, and a solvent. The electrode active material layer-forming liquid compositions of Test Nos. 1 to 9 further contained aggregates containing a plurality of metal active material particles with a particle size of 60 μm or less. As a result, the electrode active material layers produced using the electrode active material layer-forming liquid compositions of Test Nos. 1 to 9 had a high adhesion strength to the current collector of 10 mN / mm or more.

[0133] On the other hand, the electrode active material layer-forming liquid composition of Test No. 10 had an excessively low rotation speed of the rotor blades in the preliminary kneading step. As a result, the particle diameter of the aggregates containing multiple metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the electrode active material layer-forming liquid composition of Test No. 10 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0134] For the liquid composition for forming an electrode active material layer of Test No. 11, the rotation speed of the stirrer in the kneading step was too low, and the kneading time was too short. As a result, the particle diameter of the aggregates containing multiple metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the liquid composition for forming an electrode active material layer of Test No. 11 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0135] The electrode active material layer-forming liquid composition of Test No. 12 had a pre-kneading step in which the kneading time was too long. As a result, the particle diameter of the aggregates containing multiple metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the electrode active material layer-forming liquid composition of Test No. 12 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0136] For the electrode active material layer-forming liquid composition of Test No. 13, the rotation speed of the rotary blades in the preliminary kneading step was too high. As a result, the particle diameter of the aggregates containing multiple metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the electrode active material layer-forming liquid composition of Test No. 13 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0137] Furthermore, in test number 13, the rotation speed of the rotating blade in the preliminary kneading step was 10,000 rpm. This rotation speed of the rotating blade corresponds to a peripheral speed of 31.4 m / s. The rotation speed of the stirrer in the main kneading step in test number 13 was 30 m / s. In other words, in test number 13, the stirring speed in the preliminary kneading step was faster than the stirring speed in the main kneading step.

[0138] The electrode active material layer-forming liquid composition of Test No. 14 had an excessively short kneading time in the preliminary kneading step. As a result, the particle diameter of the aggregates containing a plurality of metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the electrode active material layer-forming liquid composition of Test No. 14 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0139] For the liquid composition for forming an electrode active material layer of Test No. 15, the rotation speed of the stirrer in the kneading step was too high. As a result, the particle diameter of the aggregates containing multiple metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the liquid composition for forming an electrode active material layer of Test No. 15 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0140] The electrode active material layer-forming liquid composition of Test No. 16 had a kneading time that was too long in the main kneading step. As a result, the particle diameter of the aggregates containing multiple metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the electrode active material layer-forming liquid composition of Test No. 16 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0141] For the liquid composition for forming an electrode active material layer of Test No. 17, the rotation speed of the stirrer in the kneading step was too slow. As a result, the particle diameter of the aggregates containing multiple metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the liquid composition for forming an electrode active material layer of Test No. 17 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0142] For the electrode active material layer-forming liquid composition of Test No. 18, the kneading time in the main kneading step was too short. As a result, the particle diameter of the aggregates containing multiple metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the electrode active material layer-forming liquid composition of Test No. 18 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0143] The electrode active material layer-forming liquid composition of Test No. 19 was not subjected to the preliminary kneading step and the main kneading step. As a result, the particle diameter of the aggregates containing a plurality of metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the electrode active material layer-forming liquid composition of Test No. 19 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0144] The electrode active material layer-forming liquid composition of Test No. 20 was not subjected to a preliminary kneading step. As a result, the particle diameter of the aggregates containing a plurality of metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the electrode active material layer-forming liquid composition of Test No. 20 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0145] The electrode active material layer-forming liquid composition of Test No. 21 was not subjected to a reduced pressure kneading step. As a result, the particle diameter of the aggregates containing a plurality of metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the electrode active material layer-forming liquid composition of Test No. 21 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0146] For the electrode active material layer-forming liquid composition of Test No. 22, the solvent was added after the preliminary kneading step and before the main kneading was started, and the main kneading was then performed. Therefore, the content of the solvent relative to the metal active material particles and binder differed between the preliminary kneading step and the main kneading step. In Test No. 22, the particle diameter of the aggregate containing multiple metal active material particles exceeded 60 μm. As a result, the electrode active material layer produced using the electrode active material layer-forming liquid composition of Test No. 22 had a low adhesion strength to the current collector of less than 10 mN / mm.

[0147] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure. [Explanation of symbols]

[0148] 4 Aggregates

Claims

1. A metal active material containing Cu and occluding and / or releasing metal ions, the metal active material particles having a median diameter (d50) of 0.5 to 20.0 μm, in an amount of more than 5.0 mass% to 99.0 mass%; A binder; a solvent; The particle diameter of the aggregate containing the plurality of metal active material particles is 60 μm or less. Liquid composition for forming an electrode active material layer.

2. The liquid composition for forming an electrode active material layer according to claim 1, The metal active material further comprises Contains one or more elements selected from the group consisting of Sn and Si, Liquid composition for forming an electrode active material layer.

3. The liquid composition for forming an electrode active material layer according to claim 2, The metal active material is Sn: 10 to 40 at%; Cu: 50 to 90 at%; Liquid composition for forming an electrode active material layer.

4. The liquid composition for forming an electrode active material layer according to claim 2, The metal active material is Sn: 10 to 35 at%; containing one or more elements selected from the group consisting of Ti: 9 at% or less, V: 49 at% or less, Cr: 49 at% or less, Mn: 9 at% or less, Fe: 49 at% or less, Co: 49 at% or less, Ni: 9 at% or less, Zn: 29 at% or less, Al: 49 at% or less, Si: 49 at% or less, B: 5 at% or less, and C: 5 at% or less; The balance consists of Cu and impurities. Liquid composition for forming an electrode active material layer.

5. The liquid composition for forming an electrode active material layer according to any one of claims 1 to 4, further comprising: Contains carbon black, Liquid composition for forming an electrode active material layer.

6. The liquid composition for forming an electrode active material layer according to claim 5, Contains 0.1 to 15.0 mass% of carbon black, Liquid composition for forming an electrode active material layer.

7. The liquid composition for forming an electrode active material layer according to claim 6, the content of the carbon black in mass% is 1% or more when the total of the content of the metal active material particles in mass% and the content of the carbon black in mass% is 100%; Liquid composition for forming an electrode active material layer.

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