Anode material

Abstract

The present disclosure relates to anode materials, electrodes including the anode materials, batteries including the electrodes, methods of making the anode materials, and uses of the anode materials.

Description

[Technical Field]

[0001] This disclosure relates to an anode material, an electrode containing an anode material, a battery containing an electrode, a method for manufacturing an anode material, and the use of an anode material. [Background technology]

[0002] Lithium-ion batteries are rechargeable energy storage systems (secondary batteries) that currently have the highest energy density among chemical and electrochemical energy storage systems, with capacities of up to 250 Wh / kg. Lithium-ion batteries are primarily used in portable electronic devices such as laptops, computers, and mobile phones, as well as in transportation systems such as electric bicycles and automobiles.

[0003] Regarding electromobility, a higher energy density of lithium-ion batteries is needed to increase the range of vehicles, and regarding portable electronic devices, to extend the operating time on a single charge.

[0004] Current lithium-ion batteries cannot meet the high-speed charging requirements necessary to achieve the acceptable charging times for electric vehicles, for example. One factor limiting performance during fast charging is recognized as the low wettability between the electrodes and electrolyte during cell production. As the electrode density increases to maximize the energy targets of the energy density and power density required in automobiles, the wettability between the electrodes and electrolyte decreases further. Compared to the materials used for the cathode, graphite anode materials are particularly affected by the decrease in wettability that occurs with increasing electrode package size, mainly due to mechanical deformation caused by the electrode pressing process. [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, the object of this disclosure is to provide an anode material, a method of production, and a use that overcomes, or at least mitigates, the disadvantages of the prior art described above. [Means for solving the problem]

[0006] The inventors investigated how compaction of graphite fine particles affects wettability and, to their surprise, found that wettability can be suitably adjusted by appropriately selecting well-known physical parameters such as tap density (also called tapped density) and particle size distribution. Tapped density is a parameter well-known in the art and describes the increased bulk density obtained after mechanically tapping a container containing a powder sample. This discovery leads to the invention of an anode material for lithium-ion batteries containing carbon particles, wherein the anode material can be compressed onto a metal sheet to form a high-density and fast-wetting anode material layer, and the anode material layer has a density ρ (g / cm³). 3 (and), and the following equation (I) t w =x1 × (ρ-1,0) + x2 × e (x3×(ρ-1,7)) (I) The wetting time t described by w (with s) During the ceremony, ρ is the density of the anode material compressed on a metal sheet. It becomes possible to provide an anode material in which x1 is between 50 and 158, x2 is between 3 and 150, and x3 is between 13 and 45.

[0007] This means that the coefficients x1, x2, and x3 are in the following units ·x1[s cm 3 / g] x2[s] ·x3[s cm 3 / g] This means that it must have.

[0008] The above formula explains the wettability (more specifically, the rate of wetting) in relation to the density of the compressed anode material. Preferably, the density ρ (g / cm 3 3) of the anode material compressed on the metal sheet is between about 1.35 and 1.9, more specifically between 1.4 and 1.85, more specifically between 1.45 and 1.8, particularly between 1.5 and 1.75. Regarding these densities, the wetting time t w (in s) ranges from about 50 to about 600 seconds and is determined using standardized conditions and an electrolyte solution as further explained below.

[0009] The anode material is compressed by calendaring on the metal sheet to achieve the target density. The measurement of wettability is explained below. The wettability of the anode material is important for the overall quality of the battery. During the battery production process, the electrode material is wetted by the electrolyte. If the wetting time of the electrode material is very long, the electrode material is very non-uniform, and the mechanical time, and thus the production time, is undesirably high.

[0010] In some embodiments, the carbon particles contain graphite.

[0011] In some embodiments, the total number of all functional groups of the anode material is 10 μmol / g or less, preferably between 5.5 μmol / g and 0.05 μmol / g, more preferably between 1 μmol / g and 0.05 μmol / g.

[0012] The total number of all functional groups is defined as the algebraic sum of all acidic and alkaline chemical functional groups attached to the material surface. The total number of all functional groups is 10 μmol / g or less because side reactions increase and the interface is reduced when it exceeds 10 μmol / g. If there are more side reactions than the reversible capacity of the battery, it is reduced due to the formation of a larger amount of solid electrolyte interface.

[0013] In some embodiments, the anode material has a circularity-related distribution volume of 50% with a circularity of 0.85 to 1.0, preferably from 0.85 to 0.90 (s 50) has. Below 0.85, the tap density of the material decreases. Excessively low tap densities are generally undesirable because they limit the maximum electrode density that can be achieved by compression. Furthermore, the interface is reduced, and therefore, undesirable side reactions increase.

[0014] In some embodiments, the anode material has a distribution (s) that is 0.95 to 1, with respect to the circularity distribution covering 99% of the volume. 99 ) has.

[0015] In some embodiments, the anode material is in powder form, i.e., granular form.

[0016] In some embodiments, the anode material has a tap density ratio of 1500 taps / 30 taps, preferably 1.0 to 2.2, more preferably 1.0 to 1.8, and more preferably 1.2 to 1.6. If the tap density ratio is below 1.0, the electrode material packaging is not optimal, as it reduces the electrode properties. Poor packaging leads to a low tap density and negatively affects the density of the electrode layer.

[0017] Means for selecting and / or preparing graphite having desirable wettability are not particularly limited. It will be recognized that, according to the present disclosure, graphite parameters affecting pore formation may be investigated to identify further embodiments. For example, one skilled in the art can investigate the particle size (distribution) and tapping density. Means for selecting / preparing graphite having a suitable particle size distribution are well known in the art and are not particularly limited. For example, particles can be milled under conditions that result in smaller or larger graphite particles and wider or narrower particle size distributions. It is also possible to sort the graphite powder into size fractions and recombine the size fractions to obtain a desired particle size distribution. Means for achieving the target tap density are also well known in the art and are not particularly limited. The tap density (e.g., the tap density after 1500 taps) will depend inter alia on the size and shape factors of the graphite employed and is a parameter that is well classified for most commercial graphite materials. Thus, there is no impediment for one skilled in the art to select a suitable material.

[0018] The present disclosure also relates to an electrode comprising an anode material.

[0019] The present disclosure also relates to a battery comprising at least one of the aforementioned electrodes.

[0020] The present disclosure further relates to a) providing a graphitizable carbonaceous material and / or graphite material, and a graphitizable organic binder; b) preparing pitch; c) mixing the materials of step a) by using a coke / pitch (wt.-) ratio between 0.05 and 0.8, preferably between 0.15 and 0.7; d) heating to a maximum of 950 °C to obtain a carbonized material; e) heating the carbonized material of step e) to 3100 °C to obtain a graphitized material; f) mixing the powder of step g) with a graphitizable organic carbonaceous additive; g) A step of heating the mixture from step h) to a temperature between 800°C and 1100°C. The present invention relates to a method for manufacturing an anode material, including the above.

[0021] The graphitizable carbonaceous material is not particularly limited, but in particular, its true density, as measured by helium, must be at least 2.05 g / cm³. 3 Furthermore, the highest concentration is no more than 2.18 g / cm³. 3 As such, it can be a regular or needle-type coke.

[0022] The graphitizable organic carbonaceous additive is not particularly limited and can be any organic material that is graphitizable and / or can be carbonized at temperatures between 800°C and 1100°C. Suitable examples include any type of petroleum or plant-derived polymer, such as pitch, tar, bitumen or asphalt, epoxy resins, polystyrene, phenolic resins, polyurethanes, and polyvinyl alcohols.

[0023] For step f), the graphitizable organic carbonaceous additive is preferably added in an amount between 0.5 and 10 wt%, more preferably between 3 and 10 wt%, in relation to the powder in step g).

[0024] In some embodiments, after step b), step b1) a solid formation step can be performed, and after step d), step d1) a grinding step can be performed.

[0025] This disclosure also relates to the use of anodes for lithium-ion batteries for automobiles.

[0026] This disclosure is illustrated by the figures described below, which are for illustrative purposes only and do not limit the scope of the claims. [Brief explanation of the drawing]

[0027] [Figure 1] This is a scanning electron microscope (SEM) image showing a standard graphite anode material. It shows the material according to Comparative Example 1. [Figure 2] This is a scanning electron microscope (SEM) image showing the graphite anode material according to this disclosure. It shows the material according to Example 1. [Figure 3] This is a scanning electron microscope (SEM) image showing the graphite anode material according to this disclosure. It shows the material according to Example 2. [Figure 4] The wetting times achieved using the materials of Example 1, Example 2, and Comparative Example 1 are shown. [Modes for carrying out the invention]

[0028] This disclosure is illustrated by reference to embodiments described below, which are for illustrative purposes only and do not limit the scope of the claims.

[0029] measurement The following measurement methods apply (as needed: illustratively) to the description above and (again, as needed) to the examples below.

[0030] functional group The functional groups were determined by Bohm titration (based on DIN ISO 11352). All solutions used for the determination had a concentration of 0.001 mol / l.

[0031] Determination of basic functional groups: A few grams of the sample, for example 5 grams, was added dropwise to 200 ml of diluted HCl for 24 hours. Then, 3 × 20 ml was taken out and titrated with diluted NaOH.

[0032] Determination of acidic functional groups: A few grams, for example 5 grams, of the sample was added dropwise to 200 ml of a caustic alkali solution (diluted NaOH, Na2CO3, or NaHCO3) for 24 hours. Then, 20 or 30 ml of diluted HCl solution was added. Finally, the solution was titrated with diluted NaOH.

[0033] Tap density The tap density was measured using a Granupac apparatus adapted by Granutools®. The powder was placed in a metal tube with a rigorous automated initialization process. Subsequently, a lightweight, hollow cylinder was placed on top of the powder bed to maintain a flat powder / air interface during the packing dynamics process.

[0034] The tube containing the powder sample is raised to a fixed height AZ and then subjected to free fall. The free fall height is fixed at AZ = 1 mm. After each tap, the height h of the powder bed is automatically measured.

[0035] D10 value, D50 value, D90 value, and D99 value The measurement of the particle size distribution of an anode material is not particularly limited and can be performed using a laser diffraction particle size distribution analyzer, i.e., a device that provides a volume-based particle size distribution. Thus, the D10 value is the particle size at which the cumulative volume of particles reaches 10 vol%, starting from the smaller diameter side of the resulting particle size distribution. The D50, D90, and D99 values ​​are defined similarly.

[0036] Roundness, S50 value and S99 value The circularity of the particles may be measured by dynamic image analysis using a QICPIC measuring instrument equipped with a RODOS dry disperser from Sympatec, Germany. The measurement method should comply with ISO 13322-2:2021. For multiple particles, each with multiple circularities, the S50 and S99 values ​​of the resulting circularity distribution are as defined above.

[0037] Measuring Wetting Time 1. Sample preparation A sample for density measurement was obtained by punching out a circular disc of coated sheet material. 2. Determination of the density of the graphite anode material layer The density of the anode material on the circular disk was determined by measuring the thickness of the anode material layer on the circular disk, calculating the volume of the anode material layer from the thickness, weighing the disk, subtracting the mass of a circular metal sheet to obtain the mass of the graphite anode material layer, and then dividing the mass of the graphite anode material layer by the volume of the graphite anode material layer. 3. Determining the Wetting Time The wetting time was determined by placing a droplet of 1M LiPF6 (ethylene carbonate (EC) / ethylmethyl carbonate (EMC) (3 / 7 vol. ratio) with 0.5 wt% vinyl carbonate additive) in the center of the anode material layer of a circular disk, and then the time until the entire droplet adhered to the anode material layer was determined.

[0038] The droplet had a volume of 1 μl and was supplied at a flow rate of 1 μl per minute using a syringe with a hydrophobic blunt-end cannula, positioned vertically. A circular disc was placed on a stand. The stand on the circular disc was lifted in a controlled manner until the droplet suspended from the cannula touched the surface of the anode material layer. The stand was then quickly moved slightly downward. The time (in seconds [s]) from when the droplet is on the graphite anode material layer until the entire droplet is attached to the anode material layer is considered to be the wetting time in this specification. The entire droplet is considered to have been attached to the anode material layer when no reflection is observed on the surface of the layer.

[0039] Preparation of a calendered layer of graphite anode material on a metal sheet Graphite powder was added to an aqueous solution of carboxymethylcellulose (CMC). Styrene-butadiene rubber (SBR) polymer was added to this dispersion as a binder. The components were added in a ratio of graphite / CMC / SBR = 98 / 1 / 1 wt% to obtain the final dispersion (slurry). Electrodes were prepared by coating copper foil with the slurry using a laboratory coating machine KTF-S20412 (Werner Mathis AG). After coating, the electrodes were dried and then compressed by calendering using a laboratory calender CA9 (Sumet Systems GmbH) to achieve the desired final density in the electrode material layer. [Examples]

[0040] A uniform green mass is obtained by mixing pitch and coke at a pitch / coke ratio of 0.44. The selected coke has a true density of 2.149 g / cm³ as measured by helium. 3 As such, it is a needle type.

[0041] The green mass was formed into a solid form, and then the resulting block was fired at 800-950°C. The fired block was then graphitized at a temperature of at least 2750°C, but no more than 3100°C. After cooling to room temperature, the graphitized material was crushed and ground into a fine powder material, D 50 (50% between 10 and 20 μm was achieved.)

[0042] Using a mechanical mixing apparatus, a solid graphitizable organic carbonaceous additive in an amount between 0.1% and 10% was mixed with a fine powder material. The mixture of fine graphite powder and additive was heated at a temperature between 800°C and 1100°C for several hours.

[0043] The sum of all functional groups is below the detection limit. Tap density ratio: 1500 taps / 30 taps: 1.12 Circularity (S99) = 0.95 and (S50) = 0.86 [Examples]

[0044] A uniform green mass is obtained by mixing pitch and coke at a pitch / coke ratio of 0.8. The selected coke has a true density of 2.149 g / cm³ as measured by helium. 3 As such, it is needle coke. The green mass was sintered at 800-950°C, then graphitized at a temperature of at least 2750°C but no more than 3100°C, and then cooled to room temperature.

[0045] Tap density ratio: 1500 taps / 30 taps: 1.21 Circularity (S99) = 0.96 and (S50) = 0.88

[0046] Comparative Example 1 A uniform green mass is obtained by mixing pitch and coke at a pitch / coke ratio of 0.42. The selected coke is ordinary coke with a true density of 2.07 as measured by helium. The green mass is formed into a solid form, and the resulting block is then calcined at 800-950°C. The calcined block is then graphitized at a temperature of at least 2750°C, but no more than 3100°C. After cooling to room temperature, the graphitized material is crushed and formed into a fine powder material between 10 and 20 μm. 50 Achieved.

[0047] The total number of functional groups is 3.13 μmol / g. Tap density ratio: 1500 taps / 30 taps: 1.18 Circularity (S99) = 0.95 and (S50) = 0.87

[0048] As is clear from Figure 4, Examples 1 and 2 outperform Comparative Example 1 in terms of wettability (wetting rate). Equation (I) was derived from the regression analysis of the data shown in Figure 4. The slope of the regression is represented by the three solid lines in Figure 4. Equation (I) was derived from the regression analysis of the data for Example 1.

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