Anode material

Abstract

The present application 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, higher energy density of lithium-ion batteries is needed to increase the range of vehicles. Regarding portable electronic devices, it is necessary to extend the operating time on a single battery 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 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 particles affects wettability and, to their surprise, found that tap density (also called tapped density) and particle size distribution are important parameters influencing the wettability of graphite anode materials. Tapped density is a well-known parameter in the art and describes the increased bulk density obtained after mechanically tapping a container containing a powder sample. Details of its measurement are described below. Particle size distribution is also a well-known parameter and is described in further detail below. The inventors found that a combination of relatively small particle size and relatively low packing density, reflected by a low tapping density, significantly improves the wettability of granular anode materials. While not wishing to be bound by theory, these findings can be rationalized as follows: a low tapped density means the material is not as compacted and contains more space for electrolyte contact. Smaller particle size (such as that reflected by a low D99 value of particle size distribution) means a larger surface area. The combination of a larger surface area and lower tapped density, given to smaller particle sizes, means that the compacted anode material exhibits high capillary action, due to the presence of more hollow spaces and a larger surface area within the compacted material. This capillary action is presumably responsible for promoting wettability of the particle surface.

[0007] Accordingly, in a first aspect of this disclosure, a granular anode material for a lithium-ion battery comprising graphite particles, wherein the particle size distribution has a D99 value of 20 to 75 μm and 0.7 to 1.2 g / cm³ 3 It has a tap density after 1500 tamping cycles, and the tap density and particle size after 1500 tamping cycles are given by formula (I) Tap density after 1500 tamps * D99 < 55 (g / cm³) 3 )*μm (I) A granular anode material that satisfies the relationship is provided.

[0008] The aforementioned tap density is defined as the tap density after 1500 tamps, that is, after being subjected to 1500 mechanical tapping events. A large number of tamps ensures that the material has achieved its maximum possible tap density, which gradually increases with each tamp until a constant value is reached. As mentioned above, details of the measurement are discussed below.

[0009] In some embodiments, the D99 value is 20 to 60 μm, more specifically 25 to 50 μm, particularly 30 to 45 μm.

[0010] In some embodiments, the tap density after 1500 tamps is 0.75 to 1.15 g / cm 3 , more specifically 0.80 to 1.10 g / cm 3 , particularly 0.85 to 1.00 g / cm 3 Excessively low tap density is generally undesirable because it limits the maximum electrode density that can be achieved by compression. Furthermore, the interfacial area is reduced, therefore undesired side reactions increase.

[0011] In some embodiments, the tap density after 1500 tamps and the particle size satisfy the relationship of formula (II) Tap density after 1500 tamps * D99 < x (g / cm 3 )*μm (II) wherein x is 50, more specifically 45, even more specifically 40, particularly 35. The above formula (II) is used for convenience to further limit formula (I).

[0012] In some embodiments, the product of the numerical operation obtained by multiplying the tap density after 1500 tamps by the D99 value is between 10 and 55 (g / cm 3 )*μm, more specifically between 15 and 50 (g / cm 3 )*μm, even more specifically between 20 and 45 (g / cm 3 )*μm, particularly between 25 and 40 (g / cm 3 )*μm. ​

[0013] In some embodiments, the granular anode material has a D50 value of its particle size distribution, which is between 8 and 25 μm, more specifically between 10 and 22 μm, and particularly between about 12 and 20 μm.

[0014] In some embodiments, the difference between the D99 value and the D50 value is 40 μm or less, more specifically 35 μm or less, even more specifically 30 μm or less, and particularly 25 μm or less. This relationship explains a relatively narrow particle size distribution in absolute value.

[0015] In some embodiments, the ratio of the D90 value of the particle size distribution to the D10 value of the particle size distribution is less than 4.2, more specifically less than 4.0, more specifically less than 3.7, and especially less than 3.5. This relationship explains a relatively narrow particle size distribution in relative terms.

[0016] In some embodiments, the granular anode material is characterized by a total functional group of the material of 10 μmol / g or less. The total functional group is defined as the algebraic sum of all acidic and alkaline chemical functional groups attached to the material surface. The total functional group is favorably 10 μmol / g or less because exceeding 10 μmol / g increases side reactions and reduces the interface. If there are more side reactions than the reversible capacity of the battery, it is reduced to form a larger amount of solid electrolyte interface. In some embodiments, the total functional group of the anode material is between 5.5 μmol / g and 0.05 μmol / g, more specifically between 1 μmol / g and 0.05 μmol / g.

[0017] In some embodiments, the granular anode material has a particle roundness distribution, wherein the S50 value of the distribution is 0.85 to 1.0 and / or the S99 value of the distribution is 0.95 to 1. In the art, this parameter is used to characterize the shape of graphite particles.

[0018] In some embodiments, the xylol density of the material is 2.2 to 2.26 g / cm³. 3is between. The measurement of xylene density is established in the art and can be performed, for example, in accordance with DIN 51901 (2006-11).

[0019] According to a second aspect of the present disclosure, there is provided an electrode comprising a particulate anode material. The particulate anode material may be as defined in relation to the first aspect of the present disclosure.

[0020] According to a third aspect of the present disclosure, there is provided a battery comprising at least one electrode according to the second aspect.

[0021] According to a fourth aspect of the present disclosure, there is provided a method for producing an anode material according to the first aspect of the present disclosure, comprising: a) providing a graphitizable carbonaceous material and / or graphite material, and a graphitizable organic binder; b) mixing the materials of step a) by using a coke / pitch ratio of from 0.05 to 0.8; c) heating to a maximum of 950°C to obtain a carbonized material; d) heating the carbonized material of step c) to 3100°C to obtain a graphitized material; e) mixing the powder of step d) with a graphitizable organic carbonaceous additive; and f) heating the mixture of step e) to a temperature between 800°C and 1100°C. The particulate anode material may be as defined in relation to the first aspect of the present disclosure.

[0022] In some embodiments, after step b), step b1) forming a solid is performed, and after step d), step d1) pulverizing is performed.

[0023] According to a fifth aspect of the present disclosure, there is provided use of the particulate anode material according to the first aspect of the present disclosure, particularly for lithium ion batteries for automobiles. The particulate anode material may be as defined in relation to the first aspect of the present disclosure.

[0024] The findings discussed above also provide a granular anode material for lithium-ion batteries containing graphite 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 (III) t w =x1 × (ρ-1,0) + x2 × e (x3×(ρ-1,7)) (III) The wetting time t described by w (with s) During the ceremony, It becomes possible to provide a granular anode material in which ρ is the density of the anode material compressed on a metal sheet, x1 is between 50 and 158, x2 is between 3 and 150, and x3 is between 13 and 45.

[0025] 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.

[0026] The above equation describes wettability (more specifically, the rate of wetting) in relation to the density of the compressed anode material. Preferably, the density ρ (g / cm³) of the compressed anode material on the metal sheet is... 3 The wetting time t is approximately between 1.35 and 1.9, more specifically between 1.4 and 1.85, more specifically between 1.45 and 1.8, and especially between 1.5 and 1.75. With respect to these densities, the wetting time t w (in s) ranges from approximately 50 to 600 seconds and is determined using standardized conditions and electrolyte solutions, as further described below.

[0027] The anode material is compressed onto a metal sheet by calendering to achieve the target density. Wettability measurement is described 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. Furthermore, if the wetting time of the electrode material is very long, the electrode material becomes highly non-uniform, resulting in undesirably high machine time and therefore, high production time.

[0028] In some embodiments, the anode material has a tap density ratio of 1500 / 30 taps of 1.0 to 2.2, preferably 1.0 to 1.8, and more preferably 1.2 to 1.6. Tap 1500 refers to the density after 1500 tamps, and tap 30 refers to the density after 30 tamps. If the tap density ratio is below 1.0, the electrode material packaging is suboptimal, reducing the electrode's properties. Poor packaging leads to low tap density and negatively impacts the density of the electrode layer.

[0029] Means for selecting and / or preparing graphite having a desirable particle size distribution are well known in the art and are not particularly limited. For example, particles can be ground under conditions that result in smaller or larger graphite particles and a wider or narrower particle size distribution. It is also possible to separate graphite powder into size fractions and rearrange the size fractions to obtain a desired particle size distribution.

[0030] The means for achieving the target tap density are well known in the art and are not particularly limited. The tap density (e.g., tap density after 1500 tamping cycles) depends particularly on the size and shape factors of the graphite used, and these are parameters that are well classified for most commercial graphite materials. Therefore, those skilled in the art will not have difficulty selecting a suitable material.

[0031] Turning to the method according to the fourth aspect of this disclosure, The easily graphitizable carbonaceous material is not particularly limited, but in particular, its true density, as measured by helium, is at least 2.05 g / cm³. 3Furthermore, the highest concentration is 2.18 g / cm³. 3 As such, it can be a regular or needle-type coke.

[0032] The organic easily graphitizable carbonaceous additive is not particularly limited and can be an organic material that is easily 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.

[0033] For step f), the organic easily graphitizable carbonaceous additive is advantageously added in an amount between 0.5 and 10 wt%, more specifically in the range of 3 to 10 wt%, in relation to the powder in step g).

[0034] 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.

[0035] The concepts of this disclosure are illustrated with reference to the diagrams described below. The diagrams are for illustrative purposes only and do not limit the scope of the claims. [Brief explanation of the drawing]

[0036] [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]

[0037] 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.

[0038] measurement The following measurement methods apply (as needed: illustratively) to the description above and (again, as needed) to the examples below.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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]

[0049] Coke was mixed with pitch to obtain a uniform green mass. The green mass was formed into a solid form, and the resulting block was then 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 to achieve a D50 between 10 and 20 μm.

[0050] Using a mechanical mixing apparatus, 10 wt% of a solid graphitizable organic carbonaceous additive 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. [Examples]

[0051] Finely powdered coke was mixed with pitch to obtain a uniform green mass. The granular green mass was calcined at 800-950°C, then graphitized at a temperature of at least 2750°C but no more than 3100°C, and subsequently cooled to room temperature. The graphitized material had a D50 that was somewhat smaller than that of Example 1, and a narrower particle size distribution than that of Example 1.

[0052] Comparative Example 1: Similar to Example 1, coke was mixed with pitch to obtain a uniform green mass. The green mass was formed into a solid form, and the resulting block was then 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 under different conditions than in Example 1, achieving a D50 between 10 and 20 μm, although the particle size distribution was broader than in Example 1.

[0053] Using a mechanical mixing device, 10 wt% of a solid organic easily graphitizable carbonaceous additive was mixed with a fine powder material. The mixture of fine graphite powder and the additive was heated at a temperature between 800°C and 1100°C for several hours.

[0054] The prepared material had the following properties:

[0055] [Table 1]

[0056] For the materials of Example 1, Example 2, and Comparative Example 1, the wetting times shown in Figure 4 were obtained.

[0057] As can be seen from the table above, the graphite of Examples 1 and 2 and Comparative Example 1 have different tapping densities despite having similar morphologies (see Figures 1 to 3). However, as is evident from the comparison of tapping densities of Examples 1 and 2 at 1500 tamps, tapping density alone does not affect the achievable wetting performance. As is evident from Figure 4, in this respect, Example 2, despite having a higher tapping density, surpasses Example 1. However, once surface area via particle size (distribution) is additionally taken into consideration, the wetting time correlates with the product of tapping densities at D99*1500 tamps, which is consistent with the aforementioned interpretation that the product of tapping densities at D99*1500 tamps is a descriptor of space and capillary action within the compacted graphite powder. Furthermore, the relatively narrow particle size distribution, particularly as suggested by the ratio D90 / D10 of Examples 1 and 2, also appears to promote wettability.

[0058] Equation (III) 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 (III) was derived from the regression analysis of the data in Example 1.

Claims

1. A granular anode material for lithium-ion batteries containing graphite particles, wherein the particle size distribution has a D99 value of 20 to 75 μm and a particle size of 0.7 to 1.2 g / cm³. ３ The tap density after 1500 tamping cycles is given by formula (I). Tap density after 25 ≤ 1500 tamps * D99 ≤ 40 (g / cm³) ３ ) *μm Satisfying the relationship, The D99 value is 30 to 45 μm. The tap density after 1500 taps is 0.85 to 1.00 g / cm³. ３ And, A granular anode material in which the difference between the D99 value and the D50 value of the particle size distribution is 25 μm or less.

2. The tap density after 1500 taps and the particle size distribution are given by equation (II) Tap density after 1500 taps * D99 < x (g / cm²) ３ ) *μm (II) Satisfying the relationship, The granular anode material according to claim 1, wherein x is 35 in the formula.

3. The granular anode material according to claim 1, wherein the D50 value of the particle size distribution is between 8 and 25 μm.

4. The granular anode material according to claim 1, wherein the ratio of the D90 value of the particle size distribution to the D10 value of the particle size distribution is less than 4.

2.

5. The granular anode material according to claim 1, wherein the total amount of all functional groups in the granular anode material is 10 μmol / g or less.

6. The granular anode material according to claim 1, wherein the granular anode material has a particle circularity distribution, the S50 value of the distribution is 0.85 to 1.0, and / or the S99 value of the distribution is 0.95 to 1.

7. The xylol density of the granular anode material is 2.2 to 2.26 g / cm³. ３ The granular anode material according to claim 1, which is between [the specified range].

8. An electrode comprising the granular anode material according to any one of claims 1 to 7.

9. A battery comprising at least one electrode as described in claim 8.

10. Use of the granular anode material according to any one of claims 1 to 7 for a lithium-ion battery for an automobile.

Images