Positive electrode mixture and battery

Abstract

The present disclosure relates to a positive electrode mixture and a battery. The positive electrode mixture of the present disclosure contains Li2S, a P-containing sulfide, and carbon. The G / 2D band ratio calculated from a Raman spectrum on the positive electrode mixture is 6.00 or less. By using the positive electrode mixture of the present disclosure to constitute a battery, the battery easily becomes a battery having excellent cycle characteristics.

Description

Technical Field

[0001] This application discloses a positive electrode composite and a battery. Background Technology

[0002] Japanese Patent Application Publication No. 2019-212615 discloses a battery using a cathode composite material containing a sulfur-based cathode active material. Summary of the Invention

[0003] Batteries using cathode composites containing sulfur-based cathode active materials have room for improvement in cycle characteristics.

[0004] This application discloses several solutions as a means to solve the above problems.

[0005] <Option 1>

[0006] The cathode composite material contains Li₂S, phosphorus-containing sulfides, and carbon.

[0007] The G / 2D band ratio (band ratio) determined from the Raman spectrum of the aforementioned cathode composite is below 6.00.

[0008] <Option 2>

[0009] According to the positive electrode composite material described in Scheme 1, the D / G band ratio determined from the Raman spectrum of the positive electrode composite material is 1.10 or higher.

[0010] <Option 3>

[0011] According to the positive electrode composite material described in Scheme 1 or 2, the BET specific surface area of ​​the carbon is 1500 m². 2 / g or more.

[0012] <Option 4>

[0013] A battery having a positive electrode composite layer, an electrolyte layer, and a negative electrode, wherein the positive electrode composite layer comprises a positive electrode composite of any one of schemes 1 to 3.

[0014] <Option 5>

[0015] According to the battery of embodiment 4, the electrolyte layer comprises a solid electrolyte.

[0016] When a battery is constructed using the positive electrode composite material disclosed herein, the battery is likely to become a battery with excellent cycle characteristics. Attached Figure Description

[0017] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein like symbols denote like elements, and wherein:

[0018] Figure 1 An example of the structure of a battery having the positive electrode composite of the present disclosure is shown schematically;

[0019] Figure 2 The X-ray diffraction pattern of the positive electrode composite material of Example 1 is shown;

[0020] Figure 3 Raman spectra of the comparative examples and embodiments with respect to carbon before mixing and Raman spectra of the cathode composite after mixing are shown respectively.

[0021] Figure 4 The configuration of the respective compressed cells of the comparative examples and embodiments is schematically shown; and

[0022] Figure 5 The cycle characteristics of the respective compressed cells of the comparative examples and embodiments are shown. Detailed Implementation

[0023] Hereinafter, one embodiment of the positive electrode composite and battery of the present disclosure will be described, but the positive electrode composite and battery of the present disclosure are not limited to the embodiment described below.

[0024] 1. Positive electrode composite material

[0025] The cathode composite material involved in this embodiment comprises Li₂S, a P-containing sulfide, and carbon. The G / 2D band ratio in the Raman spectrum of the cathode composite material is 6.00 or less.

[0026] 1.1 Li2S

[0027] The cathode composite material involved in this embodiment contains Li₂S. A portion of the Li₂S functions as a sulfide-based active material, while another portion can form an ion-conducting phase through reactions with P-containing sulfides (described later). The shape of the Li₂S contained in the cathode composite material is not particularly limited; for example, it can be granular. Whether the cathode composite material contains Li₂S can be determined by performing various analyses such as XRD, XAFS, or NMR on the cathode composite material.

[0028] The amount of Li2S contained in the cathode composite (the amount added) can be, for example, 30% by mass or more and 70% by mass or less, 40% by mass or more and 60% by mass or less, or 45% by mass or more and 50% by mass or less. Alternatively, the amount of Li2S contained in the cathode composite can be adjusted to meet the molar ratios Li / P or Li / S described later.

[0029] 1.2 P-containing sulfides

[0030] The cathode composite material involved in this embodiment includes a phosphorus-containing sulfide. The phosphorus-containing sulfide facilitates the formation of the ion-conducting phase in the cathode composite material. The phosphorus-containing sulfide is a compound containing phosphorus and other elements as constituent elements. The phosphorus-containing sulfide can be a substance containing at least phosphorus and sulfur as constituent elements, and further containing other elements M. Examples of other elements M include one or more of Ge, Sn, Si, B, and Al. Alternatively, the phosphorus-containing sulfide can be a substance containing phosphorus and sulfur as constituent elements and optionally element M, but without phosphorus. One embodiment of the cathode composite material may contain, for example, P₂S₅ as a phosphorus-containing sulfide. Furthermore, the phosphorus-containing sulfide can be a substance having an orthorhombic structure of phosphorus (PS₄ structure). Additionally, the phosphorus-containing sulfide can be amorphously formed as PS₄ by, for example, combining with a portion of the aforementioned Li₂S. 3- or P2S6 4- or P2S7 4- It exists in the form of.

[0031] There are no particular limitations on the shape of the phosphorus-containing sulfides contained in the cathode material; for example, they can be granular or amorphous. Whether the cathode material contains phosphorus-containing sulfides can be determined by various analyses, such as XAFS, XRD, or NMR.

[0032] The amount (filled amount) of phosphorus-containing sulfides contained in the cathode material can be, for example, 10% by mass or more and 50% by mass or less, 20% by mass or more and 40% by mass or less, or 25% by mass or more and 35% by mass or less. Alternatively, the amount of phosphorus-containing sulfides contained in the cathode material can be adjusted to satisfy the molar ratio Li / P described later.

[0033] 1.3 Carbon

[0034] The cathode composite material involved in this embodiment contains carbon. Carbon functions as a conductive material in the cathode composite material. The carbon is, for example, elemental carbon. The carbon can be one or more of the following: carbon nanotubes, vapor-grown carbon fibers (VGCF), acetylene black, furnace black, Ketjen black, activated carbon, and graphene. Alternatively, the carbon contained in the cathode composite material can be porous carbon such as activated carbon.

[0035] The carbon contained in the cathode material can be a substance with a certain specific surface area. For example, the BET specific surface area of ​​this carbon can be 1000 m². 2 / g or more, 1300m 2 / g or more or 1500m 2 / g or more, can be 2500m 2 / g or less, 2000m 2 / g or less or 1700m 2Below / g. It is believed that the larger the BET specific surface area of ​​this carbon, the better the conductivity of the cathode composite, ensuring superior cycle characteristics. Specifically, the BET specific surface area of ​​this carbon is 1500m². 2 With a concentration of / g or higher, it is easier to ensure superior cycle characteristics. In one embodiment, the carbon contained in the cathode composite may have a carbon content of 1500 μm. 2 Porous carbon with a specific surface area of ​​1100 μm or more. Alternatively, in one embodiment, the carbon contained in the cathode composite may be porous carbon with a specific surface area of ​​1100 μm or more. 2 Monolayer carbon nanotubes with a specific surface area of ​​over / g. Furthermore, the BET specific surface area of ​​the carbon contained in the cathode material can be obtained using the BET method with nitrogen as the adsorbed gas. Specifically, the carbon used in the cathode material is vacuum dried at 120°C for 12 hours, and then, for example, the BET specific surface area (m²) of the carbon is measured using a specific surface area measuring device (BERSORP-MAX (MicrotracBEL Co., Ltd.)) according to JIS Z8830:2013. 2 / g).

[0036] There is no particular limitation on the amount of carbon contained in the cathode material, as long as it is appropriately determined according to the required battery performance. In one embodiment, the carbon content in the cathode material can be more than 0% by mass and less than 50% by mass, more than 5% by mass and less than 40% by mass, or more than 10% by mass and less than 30% by mass. Alternatively, the amount of carbon contained in the cathode material can be adjusted to satisfy the molar ratio C / S described later.

[0037] 1.4 Other components

[0038] The cathode material may contain other components besides those described above. There is no particular limitation on the content of other components in the cathode material. The cathode material may contain 90% or more, 95% or more, or 99% or more by mass of the above-mentioned Li-containing sulfide, P-containing sulfide, and carbon. Furthermore, the cathode material according to this embodiment may not contain elemental sulfur as a sulfur-based active material. For example, the amount of elemental sulfur contained in the cathode material may be 1.0% or less by mass.

[0039] 1.5 molar ratios of Li / P, Li / S, and C / S

[0040] In this embodiment, the molar ratio of Li to P in the cathode composite (Li / P) can be, for example, 3.0 or more and 30.0 or less, 4.0 or more and 20.0 or less, or 5.0 or more and 10.0 or less. Furthermore, the molar ratio of Li to S in the cathode composite (Li / S) can be, for example, 0.5 or more and 2.0 or less, 0.7 or more and 1.7 or less, or 1.0 or more and 1.5 or less. Additionally, the molar ratio of C to S in the cathode composite (C / S) can be, for example, 0.50 or more and 1.50 or less, 0.60 or more and 1.40 or less, 0.70 or more and 1.30 or less, 0.80 or more and 1.20 or less, or 0.90 or more and 1.10 or less. Moreover, these molar ratios Li / P, Li / S, and C / S can be determined by analyzing the types and amounts of elements contained in the cathode composite.

[0041] 1.6 Raman Spectroscopy

[0042] 1.6.1 G / 2D band ratio

[0043] The G / 2D band ratio determined from the Raman spectrum of the cathode composite material according to this embodiment is 6.00 or less. Given this small G / 2D band ratio, it is considered that the carbon contained in the cathode composite material, even with sp... 2 While the graphene structure contains disordered or defective bonds, the diverse layer structure of graphene facilitates the establishment of conductive pathways in the cathode composite. This improves the overall conductivity of the cathode composite, ensuring excellent cycle performance. The G / 2D band ratio can be controlled by adjusting the type of carbon used in the cathode composite and the conditions during its manufacture (the mechanical energy imparted to the carbon). As described later, the cathode composite can be manufactured by imparting mechanical energy to a mixture containing Li₂S, a P-containing sulfide, and carbon. Here, the carbon used as a mixture with Li₂S and P-containing sulfides is a material with predetermined properties (G / 2D band ratio, etc.) before mixing. Furthermore, by controlling the amount of mechanical energy imparted to the mixture (in the case of imparting mechanical energy via a ball mill, the rotational speed of the ball mill, processing time, number of processing cycles, etc.), the carbon can be physically or chemically combined with Li₂S or P-containing sulfides. This allows for diversification of the graphene layer structure within the carbon while simultaneously dispersing the carbon throughout the cathode composite, resulting in a cathode composite that satisfies the aforementioned G / 2D band ratio. By constructing a battery using such a cathode composite, the utilization rate of the active material is increased, making it easier to ensure excellent cycle characteristics.

[0044] As described above, a smaller G / 2D band ratio in the cathode composite is considered to ensure superior cycle characteristics. This G / 2D band ratio can be 5.50 or less, 5.00 or less, 4.90 or less, 4.80 or less, 4.70 or less, 4.60 or less, 4.50 or less, 4.40 or less, or 4.30 or less. There is no particular limitation on the lower limit of this G / 2D band ratio; for example, it can be 3.00 or more, 3.50 or more, 4.00 or more, 4.10 or more, or 4.20 or more. In one embodiment, the G / 2D band ratio can be, for example, 4.00 or more and 5.00 or less, 4.10 or more and 4.90 or less, or 4.20 or more and 4.80 or less.

[0045] 1.6.2 D / G Belt Ratio

[0046] The D / G band ratio obtained from the Raman spectrum of the cathode composite material involved in this embodiment can be, for example, 1.10 or higher. A large D / G band ratio indicates significant disorder or defects in the graphene structure of the carbon contained in the cathode composite material. In other words, a D / G band ratio of 1.10 or higher means that energy is imparted to the carbon during the manufacture of the cathode composite material to the extent that the graphene structure of the carbon collapses, and the carbon is sufficiently mixed with Li₂S and the P-containing sulfide active material (the carbon in the cathode composite material is well-mixed). As described later, the cathode composite material can be manufactured by imparting mechanical energy to a mixture containing Li₂S, P-containing sulfides, and carbon nanotubes. Here, by controlling the amount of mechanical energy imparted to the mixture (in the case of imparting mechanical energy via a ball mill, the rotational speed of the ball mill, processing time, number of processing cycles, etc.), and by thoroughly mixing Li₂S, P-containing sulfides, and carbon to satisfy the aforementioned D / G band ratio, carbon can be physically or chemically bonded to Li₂S or P-containing sulfides, and carbon can be dispersed throughout the cathode composite, thereby improving the electronic conductivity of the cathode composite as a whole. As a result, in the case of a battery, the utilization rate of the active material increases, and excellent cycle characteristics are easily ensured.

[0047] As mentioned above, a higher D / G ratio in the cathode composite material is considered to ensure superior cycle characteristics. This D / G ratio can be 1.15 or higher, 1.20 or higher, 1.25 or higher, 1.30 or higher, 1.35 or higher, 1.40 or higher, or 1.45 or higher. There is no particular upper limit to this D / G ratio; for example, it can be 2.00 or lower, 1.90 or lower, 1.80 or lower, 1.70 or lower, or 1.60 or lower. In one embodiment, the D / G ratio can be, for example, 1.10 or higher and 1.70 or lower, or 1.30 or higher and 1.60 or lower.

[0048] 1.6.3 Conditions and methods for obtaining Raman spectra

[0049] The conditions for obtaining the Raman spectrum of the cathode composite are as follows.

[0050] (I) For the powder of the positive electrode composite, Raman spectrometry was performed at room temperature under Ar atmosphere using an XploRAPLUS manufactured by Horiba Corporation, under the following conditions.

[0051] Raster: 1200

[0052] Laser wavelength: 532nm

[0053] Laser power: 1%

[0054] (II) In the Raman spectrum obtained by Raman spectrometry, the source appearing at 1590 cm⁻¹ was identified. -1 The maximum intensity of the peak in the nearby G-band and the peak that appears at 2700 cm⁻¹ -1 The maximum intensity of the peak in the nearby 2D band was determined, and the peak intensity of the G band relative to the peak intensity of the 2D band was defined as the G / 2D band ratio. Additionally, in this Raman spectrum, the peak intensity appearing at 1590 cm⁻¹ was identified. -1 The maximum intensity of the peak in the nearby G-band and the peak that appears at 1350 cm⁻¹ -1 The maximum intensity of the peak in the nearby D band is determined, and the peak intensity of the D band relative to the peak intensity of the G band is defined as the D / G band ratio.

[0055] 2. Manufacturing method of positive electrode composite material

[0056] The positive electrode composite of this embodiment can be manufactured by, for example, the following method. Specifically, a method for manufacturing the positive electrode composite of one embodiment includes:

[0057] S1: Obtain a mixture containing Li2S, a P-containing compound, and carbon, and

[0058] S2: Imparting mechanical energy to the mixture

[0059] Specifically, by controlling the type of carbon contained in the mixture and the mechanical energy imparted to the mixture, the G / 2D band ratio obtained from the Raman spectrum of the mixture after imparting the mechanical energy is 6.00 or less. For example, using carbon with a G / 2D band ratio of 6.00 or less obtained from Raman spectroscopy to form a mixture, mechanically grinding the mixture using a ball mill at a speed of, for example, 400 rpm for a total of 36 hours, it is easy to obtain a G / 2D band ratio of 6.00 or less in the Raman spectrum of the mechanically ground mixture. There are no particular limitations on the specific conditions of the ball mill (speed, processing time, number of processing times, etc.), as long as conditions are adopted that result in a G / 2D band ratio of 6.00 or less in the cathode composite.

[0060] 3. Battery

[0061] By using the positive electrode alloy described in this embodiment to construct a battery, the battery becomes a battery with excellent cycle characteristics. For example... Figure 1 As shown, a battery 100 according to one embodiment has a positive electrode composite layer 11, an electrolyte layer 20, and a negative electrode 30. The positive electrode composite layer 11 contains a positive electrode composite according to the above embodiment.

[0062] 3.1 Positive electrode

[0063] There are no particular limitations on the shape or thickness of the positive electrode composite layer 11 in the positive electrode 10; it can be appropriately determined considering factors such as the desired battery performance. The positive electrode composite layer 11 can be a sheet with a generally flat surface. The thickness of the positive electrode composite layer 11 can be, for example, 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, and can be less than 2 mm, less than 1 mm, less than 500 μm, or less than 100 μm. Furthermore, as... Figure 1 As shown, the positive electrode 10 of the battery 100 may have a positive current collector 12 that is in contact with the positive electrode composite layer 11. There are no particular limitations on the constituent materials, shape, size, etc. of the positive current collector 12.

[0064] 3.2 Electrolyte layer

[0065] An electrolyte layer 20 is disposed between the positive electrode composite layer 11 and the negative electrode 30. The electrolyte layer 20 contains at least an electrolyte. The electrolyte layer 20 may contain at least one of a solid electrolyte and a liquid electrolyte (electrolyte), and may optionally contain a binder, etc. In particular, when the electrolyte layer 20 contains a solid electrolyte, it is easier to ensure higher performance. The electrolyte layer 20 may also be a solid electrolyte layer that does not contain a liquid electrolyte. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, inorganic solid electrolytes are excellent in terms of ionic conductivity and heat resistance. Examples of inorganic solid electrolytes include, for example, oxide solid electrolytes, sulfide solid electrolytes, and ion-binding inorganic solid electrolytes. Among inorganic solid electrolytes, sulfide solid electrolytes have high performance; more specifically, sulfide solid electrolytes containing at least Li, S, and P as constituent elements have high performance. Alternatively, among inorganic solid electrolytes, ion-binding solid electrolytes have high performance; more specifically, solid electrolytes containing at least Li, Y, and a halogen (at least one of Cl, Br, I, and F) as constituent elements have high performance. Solid electrolytes can be amorphous or crystalline. Solid electrolytes can also be in particle form.

[0066] 3.3 Negative electrode

[0067] The negative electrode 30 may include, for example, a negative electrode active material layer 31 and a negative electrode current collector 32 in contact with the negative electrode active material layer 31. In one embodiment, the negative electrode 30 may be a negative electrode in which lithium metal is deposited during charging and dissolved during discharging. In this case, lithium metal is considered to constitute the negative electrode active material layer 31. In this case, "lithium metal" refers to the concept of lithium alloy in addition to elemental lithium. That is, in the battery 100, lithium metal may be deposited as elemental lithium or as an alloy with other metals. Examples of lithium alloys include Li-Mg, Li-Sn, Li-Al, Li-B, Li-C, Li-Si, Li-Ca, Li-Ga, Li-Ge, Li-As, Li-Se, Li-Ru, Li-Rh, Li-Pd, Li-Ag, Li-Au, Li-Cd, Li-In, Li-Sb, Li-Ir, Li-Pt, Li-Hg, Li-Pb, Li-Bi, Li-Zn, Li-Tl, Li-Te, and Li-At. There can be only one lithium alloy or two or more. Furthermore, in this case, an intermediate layer may be present between the electrolyte layer 20 and the negative electrode 30 for purposes such as homogenizing the deposition and dissolution of metallic lithium. The type of intermediate layer is not particularly limited; it can be a layer containing elements capable of alloying with metallic lithium. The amount of metallic lithium deposited between the electrolyte layer 20 and the negative electrode current collector 32 is not particularly limited; it can be determined appropriately considering the target battery performance. Alternatively, the negative electrode active material layer 31 may comprise a negative electrode active material, and optionally may also comprise an electrolyte, conductive additives, binders, and various additives. The content of each component in the negative electrode active material layer 31 can be appropriately determined considering the desired battery performance. In this case, the shape of the negative electrode active material layer 31 is not particularly limited; for example, it may be a sheet with a generally planar shape. In this case, the thickness of the negative electrode active material layer 31 is not particularly limited; for example, it may be 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, or it may be 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less. The negative electrode active material may be any material known as a negative electrode active material for batteries. For example, silicon-based active materials such as Si, Si alloys, and silicon oxide may be used; carbon-based active materials such as graphite and hard carbon may be used; various oxide-based active materials such as lithium titanate may be used; and the aforementioned metallic lithium or lithium alloys may also be used. Alternatively, the negative electrode active material may also be metallic lithium in foil or film form as described above. That is, the negative electrode active material layer 31 can be made of a sheet of negative electrode active material. There are no particular limitations on the electrolyte or other substances that can be included in the negative electrode active material layer 31. The negative electrode current collector 32 can be made of any material that can function as a negative electrode current collector in a battery.

[0068] 3.4 Other

[0069] Regarding battery 100, in addition to the above-described configuration, it may also have a general battery configuration, such as tabs and terminals. Battery 100 may be a battery in which the above-described configurations are housed within an outer casing. Furthermore, multiple batteries 100 may be arbitrarily electrically connected and may be arbitrarily stacked to form a battery pack. Examples of battery 100 shapes include coin-shaped, laminated, cylindrical, and angular shapes. Battery 100 may have a constraint member in the thickness direction for constraining the above-described configurations. Battery 100 may be a rechargeable battery. Alternatively, battery 100 may be a lithium-sulfur battery (LiS battery). Furthermore, battery 100 may be an all-solid-state battery that substantially does not contain a liquid electrolyte. Additionally, battery 100 may be an all-solid-state lithium-sulfur battery. Regarding battery 100, in addition to the above-described positive electrode composite, it may be manufactured using known methods.

[0070] As described above, one embodiment of the positive electrode composite and battery has been explained. However, the technology of this disclosure can be modified in various ways without departing from its spirit, and is not limited to the above-described embodiment. Hereinafter, the technology of this disclosure will be described in further detail while showing embodiments, but the technology of this disclosure is not limited to the embodiments described below.

[0071] 1. Preparation of positive electrode composite material

[0072] Weigh Li2S, P2S5 (a P-containing sulfide), and various carbons (vacuum dried at 120°C) to make a Li2S:P2S5:C mass ratio of 50.9:29.6:19.5. Mix them in a mortar to obtain mixture (1). Then, add 1.7g of mixture (1) and 80g of carbon to each ball mill jar. Zirconia balls of 4 mm were mixed in a planetary ball mill at 400 rpm for 36 hours to obtain mixture (2). After mixing in a planetary ball mill, mixture (2) was dry-graded using a 38 μm sieve to obtain the cathode material for evaluation.

[0073] In Comparative Example 1, the cathode material used was porous carbon (A) (G / 2D band ratio: 7.96, D / G band ratio: 1.06, BET specific surface area: 1082 m²). 2 / g), the cathode material of Comparative Example 2 uses porous carbon (B) (G / 2D band ratio: 9.32, D / G band ratio: 1.05, BET specific surface area: 1351 m²). 2 / g), the cathode composite material in Example 1 uses monolayer carbon nanotubes (G / 2D band ratio: 4.81, D / G band ratio: 0.01, BET specific surface area: 1188m²). 2 / g), the positive electrode material in Example 2 uses porous carbon (C) (G / 2D band ratio: 4.29, D / G band ratio: 1.75, BET specific surface area: 1517m²). 2 / g).

[0074] 2. X-ray diffraction measurement of positive electrode composite material

[0075] The positive electrode composite material prepared as described above was placed in a non-exposed fixture to avoid exposure to the atmosphere, and X-ray diffraction patterns were obtained under CuKα radiation in the range of 2θ = 10 to 50° using Rigaku's Ultima IV. Figure 2 The X-ray diffraction pattern of the positive electrode composite involved in Example 1 is shown. Furthermore, Comparative Examples 1, 2 and Example 2 also have similar X-ray diffraction patterns.

[0076] 3. Raman spectroscopy determination

[0077] Raman spectroscopy was performed on the carbon before mixing in the planetary ball mill and the cathode composite material after mixing in the planetary ball mill to determine the G / 2D band ratio and D / G band ratio. The measurement conditions were as described in the embodiment of this specification. Furthermore, the G / 2D band ratio and D / G band ratio of the cathode composite material after mixing in the planetary ball mill were substantially the same as those of the cathode composite material contained in the cathode prepared by the pressing unit. Figure 3 Raman spectra of the various cathode composites of Comparative Examples 1 and 2, and Examples 1 and 2 are shown.

[0078] 4. Fabrication of the pressing unit (cell)

[0079] Using the positive electrode composite material prepared as described above, prepare according to the following steps. The pressing unit is 11.28 mm thick. The fabricated pressing unit is configured as follows: Figure 4 As shown.

[0080] (1) Add 100 mg of sulfide solid electrolyte into the unit and press it with a pressure of 1 ton.

[0081] (2) 7.6 mg of positive electrode material was added to the upper side of the sulfide solid electrolyte layer in the unit and pressed with a pressure of 1 ton.

[0082] (3) Apply the positive electrode composite material to the upper side of the unit. 11.28mm thick Al foil is pressed under 6 tons of pressure.

[0083] (4) The sulfide solid electrolyte layer in the unit is sequentially added to the lower side. 11.28mm stamped Li-10wt%Mg alloy foil (100μm thick) and Ni foil, pressed with a pressure of 1 ton.

[0084] (5) The size constraint is fixed by a constraint pressure of 2 Nm (equivalent to about 30 MPa) to obtain the pressing unit for evaluation.

[0085] 5. Electrochemical Measurement

[0086] For the compression unit prepared as described above, the upper limit cutoff potential for charging is set to 3.1V, and the lower limit cutoff potential for discharging is set to 1.2V vsLi. + / Li, setting 1C to 5.84mA / cm 2 A constant current charge-discharge test was conducted at 60°C according to the following scheme. Table 1 below shows the discharge capacity C1 of the first cycle and the discharge capacity C of the 50th cycle after modulation in this constant current charge-discharge test. 50 The discharge capacities are all calculated based on a Li-free baseline; that is, the weight of the cathode material after removing the weight of Li from the Li₂S in the preparation composition is used to calculate the specific capacity. Additionally, Figure 5 The discharge capacity of each suppression unit in the comparative examples and embodiments is shown for each cycle.

[0087] (1) Modulation (1.2V discharge) and cycles 1-3: current density 0.584 mA / cm 2 0.1C equivalent

[0088] (2) Cycles 4-22: Current density 1.168 mA / cm 2 0.2C equivalent

[0089] (3) 23rd cycle: current density 0.584 mA / cm 2 0.1C equivalent

[0090] (4) Cycles 24-42: Current density 1.168 mA / cm 2 0.2C equivalent

[0091] (5) 43rd cycle: current density 0.584 mA / cm 2 0.1C equivalent

[0092] (6) Cycles 44-50: Current density 1.168 mA / cm 2 0.2C equivalent

[0093] 6. Evaluation Results

[0094] Table 1 below shows the types of carbon contained in the cathode composite and their BET specific surface area (m²). 2 / g), G / 2D band ratio and D / G band ratio obtained from Raman spectra of the mixture (1) before ball milling, G / 2D band ratio and D / G band ratio obtained from Raman spectra of the positive electrode composite after ball milling, discharge capacity C1 (mAh / g) of the pressing unit in the first cycle and discharge capacity C in the 50th cycle. 50 (mAh / g) and capacity retention C 50 / C1×100 (%).

[0095] (Table 1)

[0096]

[0097] From Table 1 above, Figure 2 , 3 The results shown in Figure 5 indicate the following:

[0098] from Figure 2 The X-ray diffraction patterns shown indicate that the cathode composites involved in the comparative examples and embodiments contain Li₂S, and constitute an amorphous phase other than Li₂S. Furthermore, as... Figure 3 As shown in Table 1, the G / 2D band ratios obtained from the Raman spectra of the cathode composites involved in Examples 1 and 2 are 6.00 or less, while the G / 2D band ratios obtained from the Raman spectra of the cathode composites involved in Comparative Examples 1 and 2 exceed 6.00. That is, it is considered that in Examples 1 and 2, although the carbon contained in the cathode composite has sp... 2 Although the graphene structure exhibits disorder or defects in its bonds, the diverse layer structure of graphene easily ensures conductive pathways. Therefore, it is believed that the overall conductivity of the positive electrode composite is improved compared to Comparative Examples 1 and 2. Thus, as... Figure 5 As shown in Table 1, the pressing unit using the positive electrode composite material of Examples 1 and 2 has superior cycle characteristics compared to the pressing unit using the positive electrode composite material of Comparative Examples 1 and 2.

[0099] 7. Summary

[0100] The results above show that when a positive electrode composite material that satisfies (A) and (B) is used to construct a battery, the battery becomes a battery with excellent cycle characteristics.

[0101] (A) The cathode composite material contains Li2S, P-containing sulfides and carbon.

[0102] (B) The G / 2D band ratio determined from the Raman spectrum of the positive electrode composite is below 6.00.

Claims

1. The cathode composite material comprises Li₂S, a phosphorus-containing sulfide, and carbon, wherein, The G / 2D band ratio determined from the Raman spectrum of the aforementioned cathode composite is below 6.

00.

2. The positive electrode composite material according to claim 1, wherein, The D / G band ratio determined from the Raman spectrum of the aforementioned cathode composite is greater than 1.

10.

3. The positive electrode composite material according to claim 1, wherein, The BET specific surface area of ​​the carbon is 1500 m². 2 / g or more.

4. A battery, which has a positive electrode composite layer, an electrolyte layer, and a negative electrode, wherein, The positive electrode composite layer comprises the positive electrode composite as described in any one of claims 1-3.

5. The battery according to claim 4, wherein, The electrolyte layer contains a solid electrolyte.

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