Negative electrode and battery using same

Abstract

A negative electrode having a negative electrode current collector and a negative electrode layer that is arranged on the negative electrode current collector and contains solid electrolyte particles. The solid electrolyte particles have a value of (D90-D10) / D50 of less than 10.0, where D10, D50, and D90 are the volume cumulative particle diameters at 10 vol%, 50 vol%, and 90 vol% of the cumulative volume as determined by a laser diffraction scattering particle size distribution measurement method, respectively. The negative electrode does not contain a negative electrode active material. The solid electrolyte particles preferably have a volume cumulative particle diameter D95 of less than 65 [mu] m at a cumulative volume of 95 vol% by a laser diffraction / scattering particle size distribution measurement method.

Description

Technical Field

[0001] The present invention relates to a negative electrode and a battery using the same. Background Art

[0002] In recent years, secondary batteries have attracted widespread attention as a tool for reducing CO2 emissions and preventing global warming. Lithium-ion batteries, in particular, are widely used as power sources for portable electronic devices such as laptops and mobile phones due to their high energy density and ease of miniaturization and weight reduction. Furthermore, recent progress has been made in the development of high-power, high-capacity lithium-ion batteries for use in electric and hybrid vehicles.

[0003] However, the use of lithium foil in lithium-ion batteries can lead to poor contact between the solid electrolyte layer and the negative electrode, or to degradation of battery performance due to the oxide film formed on the surface of the lithium foil. A lithium-free battery has been proposed that uses LiCoO2 as the positive electrode material, Lipon as the solid electrolyte, and an in-situ deposition-type negative electrode. Instead of using lithium foil, the negative electrode utilizes lithium metal deposited on the current collector. However, the resulting battery capacity is insufficient, with a discharge current of only approximately 0.1 mAh.

[0004] To this end, Patent Document 1 proposes that a negative electrode comprising solid electrolyte particles and having a porosity of 0.05 to 0.8 is sandwiched between a solid electrolyte layer and arranged opposite to a positive electrode. Even if metallic lithium is precipitated during charging, the contact state between the solid electrolyte layer and the negative electrode can be improved, thereby increasing the discharge current.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-146553 Summary of the Invention

[0008] However, the battery having the negative electrode described in Patent Document 1 has problems such as frequent short circuits caused by dendritic deposition of metallic lithium and poor product yield.

[0009] Therefore, a technical problem of the present invention is to provide a negative electrode in which short circuiting of a battery, particularly a lithium ion battery, is suppressed, and a battery including the negative electrode.

[0010] The present inventors conducted intensive research to suppress short circuits in lithium-ion batteries and found that the technical problems can be solved by providing a negative electrode having solid electrolyte particles that meet specified conditions instead of the conventional in-situ precipitation type negative electrode, thereby conceiving of the present invention.

[0011] That is, the present invention provides a negative electrode comprising a negative electrode current collector and a negative electrode layer disposed on the negative electrode current collector and containing solid electrolyte particles.

[0012] The solid electrolyte particles are measured by laser diffraction scattering particle size distribution method, and the cumulative volume of 10%, 50% and 90% of the cumulative volume is respectively defined as D 10 、D 50 and D 90 When (D 90 -D 10 ) / D 50 The value of is less than 10.0,

[0013] The negative electrode does not contain a negative electrode active material.

[0014] Furthermore, the present invention provides a battery comprising a negative electrode, a positive electrode, and a solid electrolyte layer disposed between the negative electrode and the positive electrode.

[0015] The negative electrode comprises a negative electrode current collector and a negative electrode layer, wherein the negative electrode layer is disposed on the negative electrode current collector, contains solid electrolyte particles, and does not contain a negative electrode active material.

[0016] The solid electrolyte particles are measured by laser diffraction scattering particle size distribution method, and the cumulative volume of 10%, 50% and 90% of the cumulative volume is respectively defined as D 10 、D 50 and D 90 When (D 90 -D 10 ) / D 50 The value of is less than 10.0. DETAILED DESCRIPTION

[0017] Hereinafter, the present invention will be described based on preferred embodiments.

[0018] The negative electrode of the present invention and the battery using the negative electrode have the effect of suppressing short circuit. The specific reasons are as follows. First, the negative electrode of the present invention does not contain a negative electrode active material, but contains solid electrolyte particles. By using this negative electrode in the battery, the lithium ions migrated from the positive electrode during charging are precipitated in the form of metallic lithium, and the metallic lithium acts as a negative electrode active material. This is the so-called in-situ precipitation type negative electrode. One of the characteristics of the present invention is that solid electrolyte particles whose volume cumulative particle size is limited to a specified range are used. In the present invention having such a feature, compared with the conventional in-situ precipitation type negative electrode, the growth of metallic lithium crystals into dendrites can be suppressed, and as a result, the battery short circuit can be suppressed.

[0019] In the present invention, it is preferred that the growth of dendritic lithium metal can be suppressed to a degree that can suppress short circuits. Thus, short circuits caused by the growth of dendritic lithium metal penetrating the solid electrolyte layer and reaching the positive electrode layer can be suppressed. The specific allowed growth of dendritic lithium metal depends on the design of the battery, such as the thickness of the solid electrolyte layer disposed between the negative electrode and the positive electrode. For example, the growth of dendritic lithium metal allowed by the present invention, that is, the height of the protrusion on the surface of the negative electrode collector is preferably a height that does not penetrate the solid electrolyte layer from the negative electrode side to the positive electrode side, wherein it is preferably 15 μm or less, preferably 10 μm or less, and further 8 μm or less. By suppressing the height of the protrusion within the range, the battery short circuit can be effectively suppressed.

[0020] The negative electrode current collector used in the negative electrode of the present invention can be composed of metals such as stainless steel, gold, platinum, zinc, nickel, tin, aluminum, molybdenum, niobium, tantalum, tungsten, titanium, and alloys thereof. Its thickness can be set to, for example, 1 μm or greater, preferably 3 μm or greater, and more preferably 5 μm or greater. The thickness of the negative electrode current collector can be set to 50 μm or less, preferably 30 μm or less, or 15 μm or less.

[0021] In the negative electrode of the present invention, the solid electrolyte particles constituting the negative electrode layer have a cumulative volume of 10%, 50%, and 90% by volume, respectively, as determined by laser diffraction scattering particle size distribution measurement. 10 、D 50 and D 90 When (D 90 -D 10 ) / D 50 The value of needs to be less than 10.0, preferably less than 4.0, more preferably less than 3.8, and further preferably less than 2.2. (D 90 -D 10 ) / D 50 It is an indicator of the width of the particle size distribution. The closer this value is to 0, the more uniform the particle size distribution. By making the particle size distribution uniform, uniform gaps are formed between the solid electrolyte particles. During charging, lithium (Li) ions that migrate from the positive electrode are precipitated as metallic lithium within these gaps. Therefore, unlike conventional in-situ plating negative electrodes, the negative electrode according to the present invention can suppress the growth of lithium (Li) crystals into dendrites, which can prevent short circuits in batteries containing the negative electrode of the present invention.

[0022] (D 90 -D 10 ) / D 50 The lower limit of the value of is not particularly limited, and may be greater than 0, 0.5 or greater, or 0.8 or greater.

[0023] The determination of the particle size distribution of solid electrolyte particles based on the laser diffraction scattering particle size distribution determination method can be carried out, for example, according to the following steps. Using an automatic sampler for a laser diffraction particle size distribution determination device ("Microtorac SDC" manufactured by Nikkiso Co., Ltd.), 6 ml of the sample (slurry) is put into a non-aqueous solvent (toluene), the flow rate is set to 50%, and 30W ultrasonic waves are irradiated for 60 seconds. Then, the particle size distribution is determined using, for example, a laser diffraction particle size distribution determination machine "MT3000II" manufactured by Nikkiso Co., Ltd., and the volume cumulative particle size D at 10% by volume, 50% by volume, and 90% by volume can be determined from the obtained volume reference particle size distribution diagram. 10 、D 50 and D 90 The value of .

[0024] When measuring particle size distribution, the non-water-soluble solvent should be passed through a 60μm filter. The solvent refractive index is set to 1.50, the particle permeability is set to transparent, the particle refractive index is set to 1.59, the particle shape is set to non-spherical, the measurement range is set to 0.133μm to 704.0μm, the measurement time is set to 10 seconds, and the average value of the two measurements is set as D 10 、D 50 and D 90 .

[0025] The sample (slurry) can be prepared by manually mixing 0.3 g of the solid electrolyte and 5.7 g of the dispersion (mass ratio of toluene: SN-DISPERSANT 9228 manufactured by San Nopco Corporation = 19:1).

[0026] In the present invention, the solid electrolyte particles have a specific particle size distribution, and the cumulative volume 95% volume cumulative particle size D based on the laser diffraction scattering particle size distribution measurement method is 95 Preferably, it is less than 65 μm, more preferably less than 30 μm, and further preferably less than 10 μm. By having the particle size distribution of the solid electrolyte particles as described above and containing as few coarse particles as possible, the size of the gaps between the solid electrolyte particles is optimized, and as described above, the lithium (Li) ions migrating from the positive electrode during charging are efficiently precipitated in the form of metallic lithium in the gaps, which can inhibit the growth of metallic lithium into dendrites. Therefore, it is possible to prevent short circuits in batteries containing the negative electrode of the present invention.

[0027] From the perspective of easily forming gaps of appropriate size between solid electrolyte particles, the D 50 It is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. It is also preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less.

[0028] The BET specific surface area of the solid electrolyte particles is preferably 2 m 2 / g or more, more preferably 3m 2 / g or more, more preferably 4m 2 / g or more. Similarly, preferably 30m 2 / g or less, more preferably 20m 2 / g or less, more preferably 16m 2 / g or less, more preferably 10m 2 / g or less. As a result, lithium (Li) ions migrating from the positive electrode side during charging are more efficiently precipitated in the gaps between the solid electrolyte particles, which can inhibit the growth of metallic lithium into dendrites. Therefore, it is possible to prevent short circuits in batteries containing the negative electrode of the present invention.

[0029] The BET specific surface area was calculated using the following method. Using a surface area measurement device "BELSORP-miniII" manufactured by Microtrac BEL, adsorption and desorption isotherms were measured by the constant volume gas adsorption method, and the BET specific surface area was calculated using the multipoint method. Nitrogen was used as the gas.

[0030] In order to adjust the (D 90 -D 10 ) / D 50 The value and particle size of the solid electrolyte particles can be subjected to appropriate pulverization treatment. For example, the solid electrolyte particles manufactured by a known method can be coarsely pulverized using a ball mill or the like and then finely pulverized in a wet manner to adjust the particle size distribution and particle size. Specifically, by controlling the pulverization conditions during wet fine pulverization, such as pulverization time, rotation speed of the pulverization device, material of the pulverization medium, particle size of the pulverization medium, concentration of the slurry, liquid feeding amount of the slurry, mass ratio of solid electrolyte particles to pulverization medium, etc., solid electrolyte particles with a target particle size distribution can be obtained. The discovery of these pulverization conditions falls within the scope of technical common sense of those skilled in the art and is a matter that can be determined without placing an excessive burden on those skilled in the art.

[0031] In the negative electrode of the present invention, since the negative electrode layer is preferably formed on the negative electrode current collector by a coating method, the negative electrode layer does not go through the baking and sintering processes, and sintering does not occur between the solid electrolyte particles.

[0032] In addition, as described above, the negative electrode of the present invention does not contain a negative electrode active material. Specifically, the negative electrode layer in the negative electrode of the present invention does not contain a negative electrode active material, and the negative electrode current collector does not contain a negative electrode active material. The negative electrode of the present invention does not contain a negative electrode active material before the first charge. On the other hand, after the first charge, the metallic lithium (Li) precipitated in the negative electrode layer acts as a negative electrode active material. As a result, the negative electrode of the present invention acts as an in-situ precipitation type negative electrode.

[0033] From the perspective of suppressing the growth of dendritic lithium metal to a level sufficient to prevent short circuits, the solid electrolyte particles used in the negative electrode of the present invention are preferably composed of lithium (Li), sulfur (S), and M. The M element is preferably at least one of phosphorus (P), germanium (Ge), antimony (Sb), silicon (Si), tin (Sn), aluminum (Al), titanium (Ti), iron (Fe), nickel (Ni), cobalt (Co), and manganese (Mn). In particular, the M element preferably contains at least phosphorus (P), and more preferably, the M element is solely P.

[0034] Examples of compounds containing Li, S, and M include compounds containing only Li, S, and M, namely, Li7PS6, Li 7+3x (P 5+ 1-x Fe 2+ x )S6、Li 7+x (P 5+ 1-x Si 4+ x )S6, etc. (wherein x represents a number greater than or equal to 0.1 and less than or equal to 1.0). In addition, as a compound comprising a Li element, an S element, and an M element, a compound comprising other elements in addition to these three elements can also be used. As such other elements, for example, halogen (X) elements can be listed. By using a compound comprising an X element in addition to the Li element, the S element, and the M element, the battery having the negative electrode of the present invention is made more difficult to short-circuit. As the X element, at least one element selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I) can be used.

[0035] From the perspective of being able to suppress the growth of dendritic lithium metal to the extent that short circuit can be suppressed, the compound containing Li element, S element, M element and X element is preferably composed of the formula (1): Li a MS b X c Represents (wherein, M is at least one element selected from P, Ge, Sb, Si, Sn, Al, Ti, Fe, Ni, Co and Mn. X is at least one element selected from F, Cl, Br and I).

[0036] From the perspective of improving lithium ion conductivity, in the composition formula (1), a is preferably 3.0 or greater, more preferably 3.5 or greater. On the other hand, a is preferably 9.0 or less, more preferably 8.0 or less. In particular, when the M element is a P element, the atomic ratio of the Li element to the P element, i.e., the value of a, is preferably, for example, 5.0 or greater, preferably 5.5 or greater, and particularly preferably 6.0 or greater. On the other hand, a is preferably, for example, 8.0 or less, preferably 7.8 or less, and particularly preferably 7.5 or less.

[0037] Furthermore, b is preferably 4.0 or greater, more preferably 4.5 or greater, and even more preferably 5.0 or greater. On the other hand, b is preferably 7.5 or less, more preferably 7.0 or less, and even more preferably 6.5 or less.

[0038] Furthermore, c is preferably 0.1 or greater, more preferably 0.2 or greater. On the other hand, c is preferably less than 2.0, more preferably less than 1.0, more preferably 0.8 or less, and even more preferably 0.6 or less.

[0039] The M element in the composition formula (1) is particularly preferably at least one of P, Ge, Sb, Sn, and Si, particularly preferably contains P, and more preferably contains only P. This can suppress the growth of dendritic lithium metal to a degree sufficient to prevent short circuits.

[0040] When the M element is the P element, the atomic ratio of the X element to the P element, i.e., the value of c, is preferably, for example, greater than 0.1, and preferably greater than 0.2. On the other hand, the value of c is preferably, for example, less than 2.0, further preferably less than 1.0, and preferably less than 0.8, particularly less than 0.6. When the M element is the P element, the atomic ratio of the Li element to the P element is preferably, for example, greater than 5.0, and preferably greater than 5.5, and particularly preferably greater than 6.0. On the other hand, the atomic ratio of the Li element to the P element is preferably, for example, less than 9.0, and preferably less than 8.0, and more preferably less than 7.5. It should be noted that when the M element contains the P element and other elements, the atomic ratio of the Li element to the P element can be, for example, less than 20.0, less than 15.0, or less than 9.0.

[0041] The solid electrolyte particles are particularly preferably composed of the composition formula (2)Li 7-d MS 6-d X dThis is because the growth of dendritic lithium metal can be suppressed to a degree that can prevent short circuits. When the M element is a P element, the value of d, which is the atomic ratio of X to the P element, can be set to the same value as c in the above composition formula (1), and therefore is omitted here. In addition, when the M element is a P element, the atomic ratio of Li to the P element can also be set to the same value as in the above composition formula (1), and therefore is omitted here.

[0042] When the M element in the above composition formula (1) is an M1 element and an M2 element that are different from each other, the composition of the solid electrolyte particles can be Li a (M1 1-y M2 y )S b X c In addition, when the M element in the composition formula (2) is an M1 element and an M2 element that are different from each other, the composition of the solid electrolyte particles can be Li 7-d (M1 1-y M2 y )S 6-d X d y is preferably 0.010 or more, more preferably 0.020 or more, and even more preferably 0.050 or more. On the other hand, y is preferably 0.70 or less, more preferably 0.40 or less, and even more preferably 0.20 or less. It should be noted that the M1 element and the M2 element can be the same as the M element described in the composition formula (1), and therefore are omitted here.

[0043] The composition of each element in the solid electrolyte particles can be measured by, for example, ICP emission spectrometry.

[0044] In addition to the aforementioned elements, the solid electrolyte particles preferably also contain a crystalline phase having an argyrodite-type crystal structure. This further improves lithium ion conductivity. The solid electrolyte particles particularly preferably contain a crystalline phase having a cubic or orthorhombic argyrodite-type crystal structure. Whether the solid electrolyte particles contain a crystalline phase having an argyrodite-type crystal structure can be determined by analyzing the solid electrolyte particles using X-ray diffraction or total X-ray scattering. CuKα rays, such as CuKα1 rays, can be used as the radiation source in the X-ray diffraction method.

[0045] When the solid electrolyte particles have a cubic argyrodite-type crystal structure, they preferably have peaks at positions of 2θ=25.19°±1.00° and 29.62°±1.00° in an X-ray diffraction pattern measured using CuKα1 rays.

[0046] When the solid electrolyte particles have a cubic argyrodite-type crystal structure, in an X-ray diffraction pattern measured using CuKα1 radiation, it is further preferred that, in addition to positions of 2θ=25.19°±1.00° and 29.62°±1.00°, there are positions selected from the group consisting of 2θ=15.34°±1.00°, 17.74°±1.00°, 30.97°±1.00°, 44.37°±1.00°, 47.22°±1.00°, and 5 Preferably, the peaks are present at one or more positions within 1.70°±1.00°, and more preferably, the peaks are present at positions 2θ=15.34°±1.00°, 17.74°±1.00°, 30.97°±1.00°, 44.37°±1.00°, 47.22°±1.00° and 51.70°±1.00° in addition to the positions 2θ=25.19°±1.00° and 29.62°±1.00°.

[0047] In addition, when the solid electrolyte particles have an orthorhombic argyrodite-type crystal structure, in the X-ray diffraction pattern measured using CuKα1 rays, it is preferred that there are two peaks at 2θ=25.38°±1.00° and four peaks at 29.77°±1.00°.

[0048] In addition, when the solid electrolyte particles have an orthorhombic argyrodite-type crystal structure, in the X-ray diffraction pattern measured using CuKα1 rays, it is further preferred that, in addition to having two peaks at 2θ = 25.38° ± 1.00° and four peaks at 29.77° ± 1.00°, there are also peaks selected from 2θ = 15.40° ± 1.00° (2 peaks), 17.86° ± 1.00° (2 peaks), 31.25° ± 1.00° (2 peaks), 44.40° ± 1.00° (4 peaks), 47.20° ± 1.00° (4 peaks) and 52.0 It has peaks at one or more positions within 0°±1.00° (2 peaks), and more preferably, in addition to having 2 peaks at 2θ=25.38°±1.00° and 4 peaks at 29.77°±1.00°, it also has peaks at 2θ=15.40°±1.00° (2 peaks), 17.86°±1.00° (2 peaks), 31.25°±1.00° (2 peaks), 44.40°±1.00° (4 peaks), 47.20°±1.00° (4 peaks) and 52.00°±1.00° (2 peaks).

[0049] The peak position is expressed as ±1.00° from the center, but is preferably ±0.800° from the center, and more preferably ±0.500° from the center.

[0050] The solid electrolyte particles may contain other materials and other components as needed. Therefore, the solid electrolyte particles may be composed of a single phase, the single phase being composed of a crystalline phase of an argyrodite-type crystal structure, or may contain other phases in addition to this phase. For example, in addition to the crystalline phase of the argyrodite-type crystal structure, the solid electrolyte particles may also contain a Li2S phase, a Li3PS4 phase, a Li4P2S6 phase, a LiCl phase, or a LiBr phase. In particular, when the solid electrolyte particles contain a Li2S phase in addition to the crystalline phase of the argyrodite-type crystal structure, the lithium ion conductivity is further improved, which is preferred. It is particularly preferred that the solid electrolyte particles contain a compound containing Li, S, M, and X elements and containing a crystalline phase having an argyrodite-type crystal structure as the main material. In addition, in addition to the other materials and other components mentioned above, the solid electrolyte particles may also contain unavoidable impurities that have a small adverse effect on the effects of the present invention (for example, less than 5% by mass, wherein less than 3% by mass).

[0051] From the perspective of improving electronic conductivity, i.e., electron conductivity, the negative electrode of the present invention preferably contains a conductive material in the negative electrode layer. Examples of the conductive material include various metal materials and conductive non-metallic materials. Either the metal material or the conductive non-metallic material may be used alone, or both may be used in combination.

[0052] Examples of the metal material include various precious metal elements such as gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os). Examples of the metal material include various transition metal elements such as copper (Cu), iron (Fe), and tin (Sn). These metal elements may be used alone or in combination of two or more.

[0053] As the conductive non-metallic material, for example, a carbon material can be used. Examples thereof include graphite, acetylene black, carbon black, carbon nanofibers, carbon nanotubes, nanographene, and fullerene nanowhiskers. These carbon materials can be used alone or in combination of two or more. When carbon black among these carbon materials is used, the initial capacity and discharge rate characteristics of the battery can be further improved. From the perspective of making this advantage more significant, acetylene black or furnace black is preferably used as the carbon black. Among them, oil furnace black is preferably used, and Ketjen black is particularly preferably used.

[0054] The conductive material has a particle form, and its particle size D1 is, for example, preferably 1 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. Furthermore, D1 is, for example, preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less. The particle size D1 of the conductive material can be an average particle size (average value of 100 or more particles) of Feret diameter measured by direct observation of the particles using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0055] The particle size D1 of the conductive material is preferably smaller than the particle size (D 50 ).

[0056] It should be noted that, for example, when the conductive material is fibrous, such as the carbon nanotubes and carbon nanofibers described above, the fiber diameter can be used instead of the particle size. The fiber diameter D2 is, for example, preferably 50 nm or greater, more preferably 100 nm or greater, and even more preferably 150 nm or greater. Alternatively, D2 is, for example, preferably 10,000 nm or less, more preferably 5,000 nm or less, and even more preferably 2,000 nm or less.

[0057] In the present invention, the solid electrolyte particles and the conductive material can be compounded. The compounding of the solid electrolyte particles and the conductive material can be achieved by, for example, imparting mechanical energy to the particles of the solid electrolyte particles and the particles of the conductive material. For this purpose, it is preferred to apply a compressive force / impact force or a shear force / friction force to the solid electrolyte particles and the conductive material in their mixed state. Through this compounding, the increase in the viscosity of the slurry during the formation of the negative electrode is suppressed, and the solid electrolyte particles are uniformly dispersed in the slurry, thereby optimizing the size of the gaps between the solid electrolyte particles.

[0058] In order to impart mechanical energy such as compression / impact, shear / friction to the solid electrolyte particles and conductive material in a mixed state for compounding, it is preferred to use a device that is mainly used to stir, mix, knead, granulate, crush, disperse and / or surface modify the powder. For example, a planetary ball mill, a ball mill, a jet mill, a bead mill, a stirring type crusher, a vibration mill, a hammer mill, a roller mill and an atomizer can be used. The type of main mechanical energy that can be imparted using these devices varies depending on the device. For example, when a planetary ball mill is used, compression / impact is mainly applied to the solid electrolyte particles and the conductive material in a mixed state, thereby compounding the two. The centrifugal acceleration obtained when the device rotates is not particularly limited as long as it is a degree that can compound the solid electrolyte particles and the conductive material. For example, it is preferably 10G or more, more preferably 15G or more, and more preferably 18G or more. In addition, the centrifugal acceleration is, for example, preferably 40G or less, more preferably 30G or less, and more preferably 25G or less. By setting the centrifugal acceleration within the above range, the solid electrolyte particles can be easily and uniformly distributed in the negative electrode layer, thereby further suppressing battery short circuits.

[0059] Preferably, the solid electrolyte particles and the conductive material are "combined" to mean that the conductive material particles are inseparably integrated with the solid electrolyte particles and dispersed on the surface and within the solid electrolyte particles. Examples of "combination" include a method in which the conductive material particles are inseparably dispersed on the surface and / or within the solid electrolyte particles, and a method in which the solid electrolyte particles and the conductive material particles are chemically reacted and bonded.

[0060] The particles of conductive material are inseparably dispersed on the surface and inside of the solid electrolyte particles, which refers to the following state. For example, when a scanning electron microscope (SEM-EDS) equipped with an energy dispersive X-ray spectrometer is used to observe the solid electrolyte particles compounded with the particles of conductive material, and the constituent elements of the solid electrolyte (such as sulfur) and the constituent elements of the conductive material are mapped, the constituent elements of the solid electrolyte and the constituent elements of the conductive material exist in an overlapping manner. Or it refers to the following state. When a cross-section of a negative electrode layer containing solid electrolyte particles compounded with particles of conductive material is observed, the constituent elements of the solid electrolyte and the constituent elements of the conductive material exist in an overlapping manner on the surface and inside of the solid electrolyte particles. It should be noted that, for example, when the conductive material is a carbon material, the solid electrolyte particles and the conductive material particles undergo a chemical reaction and are compounded, which can also be confirmed by the presence or absence of C-S bonds using Raman spectroscopy or photoelectron spectroscopy.

[0061] In the negative electrode of the present invention, the conductive material is preferably contained in an amount of, for example, 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, relative to 100 parts by mass of the solid electrolyte. On the other hand, the conductive material is preferably contained in an amount of, for example, 50 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, even more preferably 13 parts by mass or less, and particularly preferably 10 parts by mass or less, relative to 100 parts by mass of the solid electrolyte.

[0062] The negative electrode can be made using the following methods: preparing a slurry containing solid electrolyte particles and no negative electrode active material, dropping the slurry onto the negative electrode current collector, and wiping it with a scraper or other method; placing the negative electrode current collector in contact with the slurry and then cutting it with an air knife; forming a coating by screen printing or other methods, and then removing the solvent by heating and drying. The slurry comprises solid electrolyte particles and a solvent. Examples of the solvent include, but are not limited to, non-polar solvents such as heptane, methylcyclohexane, and toluene; aprotic polar solvents such as methyl isobutyl ketone and cyclohexanone; or mixtures thereof.

[0063] The battery comprising the negative electrode of the present invention may be a solid-state battery having, for example, a positive electrode, the negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode. More specifically, it can be used for a lithium solid-state battery. A lithium solid-state battery may be a primary battery or a secondary battery, and preferably a lithium secondary battery. In addition to solid-state batteries that do not contain any liquid or gel-like substances as electrolytes, a method comprising, for example, less than 50% by mass, less than 30% by mass, or less than 10% by mass of a liquid or gel-like substance as an electrolyte is also included in the "solid-state battery". In this case, the negative electrode of the present invention does not contain a negative electrode active material. That is, it does not contain a negative electrode active material at the time of the first charge, but after the first charge, it functions as a so-called in-situ precipitation-type negative electrode containing a negative electrode active material (lithium).

[0064] Regarding the above-mentioned embodiment, the present invention further discloses the following negative electrode and battery.

[0065] [1] A negative electrode comprising a negative electrode current collector and a negative electrode layer disposed on the negative electrode current collector and containing solid electrolyte particles.

[0066] The solid electrolyte particles are measured by laser diffraction scattering particle size distribution method, and the cumulative volume of 10%, 50% and 90% of the cumulative volume is respectively defined as D 10 、D 50 and D 90 When (D 90 -D 10 ) / D 50The value of is less than 10.0,

[0067] The negative electrode does not contain a negative electrode active material.

[0068] [2] The negative electrode according to [1], wherein the solid electrolyte particles have a cumulative volume particle size D at 95% of the cumulative volume based on laser diffraction scattering particle size distribution measurement. 95 Less than 65μm.

[0069] [3] The negative electrode according to [1] or [2], further comprising a conductive material.

[0070] [4] The negative electrode according to any one of [1] to [3], wherein the solid electrolyte particles contain lithium (Li), sulfur (S) and M, and M is at least one of phosphorus (P), germanium (Ge), antimony (Sb), silicon (Si), tin (Sn), aluminum (Al), titanium (Ti), iron (Fe), nickel (Ni), cobalt (Co) and manganese (Mn).

[0071] [5] The negative electrode according to [4], wherein the solid electrolyte particles contain a crystal phase having an argyrodite-type crystal structure.

[0072] [6] The negative electrode according to [3], wherein the conductive material is a carbon material or a metal material.

[0073] [7] The negative electrode according to any one of [1] to [6], which is capable of depositing metallic lithium during charging.

[0074] [8] A battery comprising a negative electrode, a positive electrode, and a solid electrolyte layer disposed between the negative electrode and the positive electrode,

[0075] The negative electrode comprises a negative electrode current collector and a negative electrode layer, wherein the negative electrode layer is disposed on the negative electrode current collector, contains solid electrolyte particles, and does not contain a negative electrode active material.

[0076] The solid electrolyte particles are measured by laser diffraction scattering particle size distribution method, and the cumulative volume of 10%, 50% and 90% of the cumulative volume is respectively defined as D 10 、D 50 and D 90 When (D 90 -D 10 ) / D 50 The value of is less than 10.0.

[0077] Example 1

[0078] The present invention will be described in more detail below with reference to Examples. However, the scope of the present invention is not limited to these Examples. Unless otherwise specified, "%" means "mass %".

[0079] [Example 1]

[0080] Li2S powder, P2S5 powder, LiCl powder and LiBr powder were weighed to a total of 75 g, and mixed and pulverized using a planetary ball mill (P-7 manufactured by Fritsch) at a rotation speed of 600 rpm for 40 hours to obtain a composition of Li 5.8 PS 4.4 Br 0.8 Cl 0.8 Then, the sample was crushed using a mortar and pulverized using a ball mill, and then sized using a sieve with a mesh size of 53 μm to obtain a particle size of D 10 、D 50 and D 90 The solid electrolyte particles are 1.1μm, 3.1μm and 6.8μm. In addition, the particle size D 95 It is 8.3μm.

[0081] Acetylene black was used as the conductive material, and the particle size D1 of the conductive material was 0.4 μm.

[0082] Prepare an electrode slurry containing solid electrolyte particles, a conductive material, and a solvent. Specifically, prepare a slurry containing the solid electrolyte particles and the conductive material in a solvent at a mass ratio of 95:5. Apply this slurry to a 100 μm thickness on a negative electrode current collector made of SUS using a doctor blade method and then dry it to produce the negative electrode.

[0083] The above operations were all carried out in a glove box that had been purged with sufficiently dry Ar gas (dew point below -60°C).

[0084] [Example 2]

[0085] A negative electrode was produced in the same manner as in Example 1, except that the slurry was prepared by containing the solid electrolyte particles and the conductive material at a mass ratio of 90:10.

[0086] [Example 3]

[0087] In addition to making the particle size D of the solid electrolyte particles 10 、D 50 and D 90 A negative electrode was manufactured in the same manner as in Example 1 except that the thickness was 0.4 μm, 0.7 μm, and 1.3 μm.

[0088] [Comparative Example 1]

[0089] The slurry is prepared by containing solid electrolyte particles and conductive material in a mass ratio of 85:15. In addition, the particle size D of the solid electrolyte particles is 10 、D 50 and D 90 are 2.7 μm, 11.4 μm and 172.3 μm respectively, and the particle size D 95 A negative electrode was produced in the same manner as in Example 1 except for this.

[0090] [Evaluation of solid electrolyte particles]

[0091] The particle size distribution, particle diameter, and BET specific surface area of the solid electrolyte particles used in Examples and Comparative Examples were measured by the above-mentioned methods. The results are shown in Table 1.

[0092] [Evaluation of battery short circuit and electronic conductivity]

[0093] The above-mentioned negative electrode was punched into a size of 25mm×25mm. The punched negative electrode was overlapped with a 25mm×25mm solid electrolyte layer and a 20mm×20mm positive electrode, and then a pressure of 700MPa was applied by cold isostatic pressing (CIP) to make an all-solid-state battery. As the solid electrolyte layer, the same solid electrolyte as in the embodiment was used. As the positive electrode, a NCM622 (LiNi 0.6 Co 0.2 Mn 0.2 O2) is a positive electrode layer.

[0094] The resulting all-solid-state battery was charged and discharged at 25°C using a constant current and constant potential charge at 0.1C until it reached 4.3V, and then discharged at a constant current of 0.1C until it reached 2.5V. The battery was then inspected for short circuits. The final charge current was set at 0.05C. The results are shown in Table 1.

[0095] [Table 1]

[0096]

[0097] The results shown in Table 1 show that the batteries of each example, fabricated using a negative electrode containing solid electrolyte particles having a specific particle size distribution, did not short-circuit even after repeated charge and discharge. In contrast, the battery of Comparative Example 1 short-circuited during the first charge and discharge cycle.

[0098] Industrial applicability

[0099] As described above in detail, according to the present invention, there are provided a negative electrode in which short circuits in a battery, particularly a lithium ion battery, are suppressed, and a battery including the negative electrode.

Claims

1. A negative electrode comprising a negative electrode current collector and a negative electrode layer disposed on the negative electrode current collector and containing solid electrolyte particles, The solid electrolyte particles are measured by laser diffraction scattering particle size distribution method, and the cumulative volume of 10%, 50% and 90% of the cumulative volume is respectively defined as D 10 、D 50 and D 90 When (D 90 -D 10 ) / D 50 The value of is less than 10.0, The negative electrode does not contain a negative electrode active material.

2. The negative electrode according to claim 1, wherein The volume cumulative particle size D of the solid electrolyte particles at 95% of the cumulative volume based on the laser diffraction scattering particle size distribution measurement method is: 95 Less than 65μm. The negative electrode according to claim 1 or 2, further comprising a conductive material.

4. The negative electrode according to claim 1 or 2, wherein The solid electrolyte particles contain lithium (Li) element, sulfur (S) element and M element, and the M element is at least one of phosphorus (P), germanium (Ge), antimony (Sb), silicon (Si), tin (Sn), aluminum (Al), titanium (Ti), iron (Fe), nickel (Ni), cobalt (Co) and manganese (Mn).

5. The negative electrode according to claim 4, wherein The solid electrolyte particles include a crystal phase having an argyrodite-type crystal structure.

6. The negative electrode according to claim 3, wherein The conductive material is a carbon material or a metal material. The negative electrode according to claim 1 or 2, which can precipitate metallic lithium during charging.

8. A battery comprising a negative electrode, a positive electrode, and a solid electrolyte layer disposed between the negative electrode and the positive electrode. The negative electrode comprises a negative electrode current collector and a negative electrode layer, wherein the negative electrode layer is disposed on the negative electrode current collector, contains solid electrolyte particles, and does not contain a negative electrode active material. The solid electrolyte particles are measured by laser diffraction scattering particle size distribution method, and the cumulative volume of 10%, 50% and 90% of the cumulative volume is respectively defined as D 10 、D 50 and D 90 When (D 90 -D 10 ) / D 50 The value of is less than 10.0.

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