Negative electrode material, method for manufacturing the same, negative electrode, and lithium ion battery

Abstract

The present invention provides a negative electrode material and a manufacturing method thereof, a negative electrode, and a lithium ion battery. The manufacturing method of the negative electrode material includes: adding a silicon-based compound to an adhesive solution and mixing to form a first mixture, wherein the adhesive solution comprises a first adhesive, and the first adhesive is an olefinic acid polymer; adding a second adhesive to the first mixture and mixing to form a second mixture, wherein the second adhesive is different from the first adhesive; adding a conductive material to the second mixture and mixing to form a third mixture; and adding a third adhesive to the third mixture and mixing to form the negative electrode material, wherein the third adhesive is different from the first adhesive and the second adhesive.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a negative electrode material and its manufacturing method, a negative electrode, and a lithium-ion battery. Background Technology

[0002] The importance of lithium-ion batteries in various applications such as 3C products and electric vehicles is increasing daily, and improving the energy density of individual cells is a crucial development direction for lithium-ion batteries. The main approaches to improving cell energy density include developing positive electrode materials with high specific capacity and high discharge voltage platforms, high specific capacity negative electrode materials, and developing binders with high adhesion and excellent conductivity. Currently, the main negative electrode material for lithium-ion batteries on the market is composed of graphite; however, the theoretical capacity of graphite is only 372 mAh / g, therefore, negative electrode materials with higher specific capacity are needed.

[0003] Compared to graphite, silicon-based anodes have a high specific capacity (~3750mAh / g), which can effectively improve the energy density of lithium batteries. However, due to the large volume expansion effect, silicon-based anodes cause a sharp increase in the solid electrolyte interphase (SEI) film during charging and discharging, which in turn deteriorates battery performance and seriously affects the performance of lithium batteries.

[0004] To address this issue, nanostructures are currently used to solve the expansion problem. However, these technologies are characterized by high cost and complex processes, hindering mass production. Furthermore, even with adjustments to the adhesive selection, it remains difficult to reduce problems such as significant volume expansion, cracking during coating, and numerous streaks after cold pressing. Summary of the Invention

[0005] The present invention was made in view of the above-mentioned problems, and provides a method for manufacturing a negative electrode material, a negative electrode material prepared by the manufacturing method, and a negative electrode or lithium-ion battery including the negative electrode material.

[0006] To address the aforementioned problems, the manufacturing method includes: adding a silicon-based compound to an adhesive solution and mixing to form a first mixture, wherein the adhesive solution contains a first adhesive, the first adhesive being an acrylic polymer; adding a second adhesive to the first mixture and mixing to form a second mixture, wherein the second adhesive is different from the first adhesive; adding a conductive material to the second mixture and mixing to form a third mixture; and adding a third adhesive to the third mixture and mixing to form the negative electrode material, wherein the third adhesive is different from both the first and second adhesives.

[0007] In some embodiments, the first adhesive is a poly(acrylic acid) (PAA) adhesive, the second adhesive is a carboxymethyl cellulose (CMC) adhesive, and the third adhesive is a styrene-butadiene rubber (SBR) adhesive.

[0008] In some embodiments, the first mixture includes a first adhesive formed by the silicon-based compound and the first adhesive, and the second mixture includes a second adhesive formed by coating the first adhesive with the second adhesive.

[0009] In some embodiments, the third mixture includes a third adhesive formed by coating the second adhesive with the conductive material.

[0010] In some embodiments, when the third adhesive is added to the third mixture and mixed, a negative electrode slurry is formed, wherein: the negative electrode slurry contains the negative electrode material; the negative electrode material is generated by the third adhesive and the third adhesive.

[0011] In some embodiments, the negative electrode slurry is coated onto an electrode sheet to form a negative electrode sheet, and a drying process is performed to remove moisture from the negative electrode sheet.

[0012] In some implementations, the drying process may include two stages of temperature control.

[0013] To solve the above problems, the negative electrode material is prepared using the aforementioned manufacturing method.

[0014] To address the aforementioned issues, the negative electrode of a lithium-ion battery includes the aforementioned negative electrode material.

[0015] To address the aforementioned issues, a lithium-ion battery includes a negative electrode, wherein the negative electrode uses the aforementioned negative electrode material.

[0016] By using the above method and selecting three different adhesives in a specific order of addition, in addition to compensating for the shortcomings of each adhesive, the specific order also enhances the interaction between the adhesives or between the adhesives and other additives, thereby obtaining a negative electrode material with high specific capacity, strong bonding force and mechanical strength, and low deformation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a method for manufacturing a negative electrode material according to an embodiment of the present invention.

[0019] Figure 2 This is a scanning electron microscope (SEM) image of the composite material produced by the negative electrode material according to an embodiment of the present invention.

[0020] Figure 3A This is a transmission electron microscope (TEM) image of the composite material produced by the negative electrode material according to an embodiment of the present invention.

[0021] Figure 3B It is according to the embodiments of the present invention. Figure 3A Image of the diffraction pattern of the illustrated region A.

[0022] Figure 4 It is an X-ray diffractometer (XRD) pattern of the composite material produced by the negative electrode material according to an embodiment of the present invention. Detailed Implementation

[0023] The following description contains specific information relating to exemplary embodiments of the invention. The accompanying drawings and detailed description are merely exemplary embodiments. However, the invention is not limited to these exemplary embodiments. Other variations and embodiments of the invention will occur to those skilled in the art. Unless otherwise stated, the same or corresponding components in the drawings are indicated by the same or corresponding reference numerals. Furthermore, the drawings and illustrations in this invention are generally not drawn to scale and are not intended to correspond to actual relative dimensions.

[0024] For the purposes of consistency and ease of understanding, the same features are indicated by reference numerals in the exemplary drawings (although not in some examples). However, features in different embodiments may differ in other respects, and therefore should not be narrowly limited to the features shown in the drawings.

[0025] The terms "at least one embodiment," "one embodiment," "multiple embodiments," "different embodiments," "some embodiments," and "this embodiment" indicate that the embodiments of the invention described herein may include specific features, structures, or characteristics, but not every possible embodiment of the invention must include those specific features, structures, or characteristics. Furthermore, the repeated use of the phrases "in one embodiment" and "in this embodiment" does not necessarily refer to the same embodiment, although they may be identical. Moreover, the use of phrases such as "embodiment" in connection with "the invention" does not imply that all embodiments of the invention must include the specific features, structures, or characteristics, and should be understood as "at least some embodiments of the invention" including the stated specific features, structures, or characteristics. When the term "comprising" is used, it means "including but not limited to," which explicitly indicates an open inclusion or relationship of combinations, groups, series, and equivalents. In some examples, detailed descriptions of well-known methods, techniques, systems, architectures, etc., are omitted to avoid obscuring the descriptive narrative with unnecessary detail.

[0026] The terms "first," "second," and "third," etc., used in the specification and accompanying drawings of this invention are used to distinguish different objects, not to describe a specific order. Furthermore, the term "comprising," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps is not limited to the steps listed, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products, or apparatuses.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] Figure 1 This is a flowchart of a method 100 for manufacturing a negative electrode material according to an embodiment of the present invention. Because there are various ways to perform the manufacturing method 100, therefore... Figure 1 The manufacturing method 100 shown is merely an example. Figure 1 Each step shown in the diagram may represent one or more processes, methods or subroutines being performed, and more steps may be added between each step without causing the essence of manufacturing method 100 to deviate from the scope of the technical solution of manufacturing method 100.

[0029] In step S110, a silicon-based compound is added to an adhesive solution and mixed to form a first mixture.

[0030] In some embodiments, the adhesive solution comprises a first adhesive. In some embodiments, the first adhesive may be a solute and added to a solvent. In some embodiments, the solvent may be a liquid solvent such as deionized water or distilled water. In some embodiments, the first adhesive may be an acrylic polymer. In some embodiments, the first adhesive may be a polyacrylic acid (PAA) adhesive. For example, the first adhesive may be a PAA adhesive or a salt formed by PAA and metal ions.

[0031] In some embodiments, the silicon-based compound may be silicon oxide (SiO2). x In some embodiments, the value of x is between 0 and 2. In some embodiments, the silicon-based compound may also be pure silicon (Si). In some embodiments, the silicon-based compound may be silicon monoxide (SiO1) or silicon dioxide (SiO2), etc. In some embodiments, after the silicon-based compound is added to the adhesive solution and mixed, the first mixture can be formed. The first mixture may be a first slurry. In some embodiments, the first slurry, as the first mixture, may include a first adhesive formed by the silicon-based compound and the first adhesive.

[0032] In some embodiments, because the silicon-based compound has the property of modifying oxides on its surface, when deionized water is used as the solvent, -OH (i.e., hydroxyl groups) will form between the oxide and the deionized water. In some embodiments, the molecular chain of the first adhesive (e.g., PAA-type adhesive) may include a large number of -COOH (i.e., carboxyl groups), which can form hydrogen bonds with the surface of the silicon-based compound to impart strong bonding force and mechanical strength to both. In other words, the first adhesive can stabilize the silicon-based compound, giving the bonding energy between the silicon-based compounds a better structure, and can simultaneously alleviate the volume expansion problem of the silicon-based compound. Therefore, the first adhesive, as an adhesive for the silicon-based compound in the first stage of bonding, can improve the cycle performance of the battery and increase its lifespan.

[0033] In step S120, a second adhesive is added to the first mixture and mixed to form a second mixture.

[0034] In some embodiments, the second adhesive is different from the first adhesive. In some embodiments, the second adhesive may be a carboxymethyl cellulose (CMC) adhesive. For example, the second adhesive may be a CMC adhesive or a salt formed by CMC and metal ions.

[0035] In some embodiments, the second adhesive is added to the first mixture and mixed to form the second mixture. The second mixture may be a second slurry. In some embodiments, the second slurry, as the second mixture, may include a second adhesive formed by coating the first adhesive with the second adhesive.

[0036] In some embodiments, when the second adhesive is added to the first mixture, the solvent may be added to the first mixture for dilution. In some embodiments, the function of the second adhesive is to coat the outer layer of the first adhesive (e.g., PAA and SiO2). x The outer layer (formed together) is a coating structure formed by the second adhesive, which inhibits SiO2 formation. x The expansion that occurs during charge-discharge cycles. In some embodiments, in subsequent processes (e.g., heat treatment such as drying), the combination of the first adhesive (e.g., PAA-type adhesive) and the second adhesive (e.g., CMC-type adhesive) can be cross-linked due to dehydration condensation between the carboxyl groups of the first adhesive and the hydroxyl groups of the second adhesive. The cross-linked adhesive can effectively limit the change in electrode thickness and further improve the cycle performance of the electrode. In some embodiments, since the first adhesive (e.g., PAA-type adhesive) can form an inner protective layer and the second adhesive (e.g., CMC-type adhesive) can form an outer protective layer, the volume change of the silicon-based compound during charge-discharge cycles can be significantly suppressed under the dual influence of the inner and outer protective layers.

[0037] In step S130, a conductive material is added to the second mixture and mixed to form a third mixture.

[0038] In some embodiments, the conductive material may include at least one of the following carbon materials: single-walled carbon nanotubes, multi-walled carbon nanotubes, nano-carbon black, acetylene black, graphene, graphite, conductive carbon black (SuperP, SP), and vapor-grown carbon fiber (VGCF). In some embodiments, when the conductive material is a mixture of at least two carbon materials (e.g., graphite anode with conductive carbon black SP or vapor-grown carbon fiber VGCF), the active material of the conductive material can be uniformly distributed on the anode material surface by dry mixing and stirring beforehand to improve the overall conductivity.

[0039] In some embodiments, the conductive material is added to the second mixture and mixed to form the third mixture. The third mixture may be a third slurry. In some embodiments, the third slurry, as the third mixture, may include a third adhesive formed by coating the second adhesive with the conductive material.

[0040] In some embodiments, since the second adhesive (e.g., a CMC-type adhesive) coating the outer layer of the second adhesive can be mutually adsorbed with the conductive material, and the carbon material, as the conductive material, repels each other due to the influence of electrostatic forces, the conductive material can be uniformly distributed on the surface of the active material of the second adhesive.

[0041] In some embodiments, the conductive material may be coated with a carbon layer in a subsequent process (e.g., drying process) to completely coat the silicon-based compound, thereby improving the conductivity of the negative electrode.

[0042] In step S140, a third adhesive is added to the third mixture and mixed to form the negative electrode material.

[0043] In some embodiments, the third adhesive differs from both the first and second adhesives. In some embodiments, the third adhesive is a styrene-butadiene rubber (SBR) adhesive. For example, the first adhesive may be an SBR adhesive. In some embodiments, when the third adhesive is added to the mixture, it should be stirred slowly to avoid generating excessive stress that could cause demulsification.

[0044] In some embodiments, the third adhesive is added to the third mixture and mixed to form a negative electrode slurry. In some embodiments, the negative electrode slurry may include the negative electrode material, and the negative electrode material is generated by the third adhesive and the third adhesive. In some embodiments, the third adhesive may coat the third adhesive to form the negative electrode material.

[0045] In some embodiments, the negative electrode slurry can be coated onto an electrode sheet to form a negative electrode sheet. Furthermore, the negative electrode sheet can be subjected to a drying process to remove the solvent from the negative electrode sheet, followed by further machining to form a negative electrode. In some embodiments, the machining is rolling. In some embodiments, the drying process may include at least one stage of temperature control. In some embodiments, the drying process may include two stages of temperature control. In some embodiments, during the first stage of temperature control, the negative electrode sheet can be heated to a first temperature. Through this first stage of temperature control, the solvent in the negative electrode sheet can be gradually evaporated to reduce the solvent content in the negative electrode sheet, while simultaneously ensuring that the negative electrode material adheres reliably to the electrode sheet. In some embodiments, the first temperature should not be too high to avoid premature sealing of the surface of the negative electrode material, which would affect the dissipation of the solvent. In some embodiments, if the solvent is water, the first temperature can be any temperature between 65°C and 75°C. In some embodiments, if the solvent is water, the first temperature can be, for example, 65°C, 67°C, 69°C, 70°C, 71°C, 73°C, 75°C, or any temperature between them. In some embodiments, if the solvent is water, the first temperature can be 70°C. In some embodiments, during the second stage of temperature control, the negative electrode sheet can be heated to a second temperature. Through this second stage of temperature control, the solvent in the negative electrode sheet can be completely evaporated, and the surface of the negative electrode material can be sealed to completely remove the solvent and form the negative electrode. In some embodiments, if the solvent is water, the second temperature can be any temperature between 90°C and 95°C. In some embodiments, if the solvent is water, the second temperature can be, for example, 90°C, 92°C, 94°C, 95°C, or any temperature between them. In some embodiments, if the solvent is water, the second temperature can be 92°C. In some embodiments, after the negative electrode material in the negative electrode slurry is dried to remove moisture, it can form a composite material adhered to the electrode sheet. Therefore, the negative electrode may include the electrode sheet and the composite material. In some embodiments, the negative electrode may be disposed in a lithium-ion battery.

[0046] In some embodiments, since the third adhesive can be located on the outermost layer of the negative electrode material, when the negative electrode slurry is coated onto the electrode sheet to form the negative electrode sheet, the third adhesive can fully adhere the negative electrode material to the electrode sheet through a point-to-point bonding mechanism. Furthermore, after the solvent is removed through the drying process, the third adhesive can reliably adhere the silicon-based compound coated with the carbon coating layer to the electrode sheet.

[0047] Figure 2This is a scanning electron microscope (SEM) image of the composite material produced by the negative electrode material according to an embodiment of the present invention.

[0048] Figure 2 The composite material can be a powder obtained by subjecting the negative electrode material produced by manufacturing method 100 to heat treatment such as drying. In some embodiments, the particle size of the composite material powder is about 0.5 μm to 10 μm. In some embodiments, the particle size of the conductive material powder added in manufacturing method 100 is about 4 μm to 40 μm. In other words, under the influence of heat treatment such as drying, the conductive material powder has been further refined and dispersed around the silicon-based compound.

[0049] Figure 3A This is a transmission electron microscope (TEM) image of the composite material produced by the negative electrode material according to an embodiment of the present invention. Figure 3B It is according to the embodiments of the present invention. Figure 3A Image of the diffraction pattern of the illustrated region A.

[0050] Figure 3A The image shows particles 300 produced after heat treatment, such as drying, of the negative electrode material manufactured by method 100. Since the TEM sample made from this composite material is a thin sheet, Figure 3A Particle 300 can be considered a cross-section of a composite material powder. Therefore, the interior region of particle 300 can be considered the interior of the composite material powder. (Regarding...) Figure 3A TEM diffraction pattern analysis of the illustrated region A reveals that the material in region A has three main diffraction rings. These three diffraction rings indicate the Si(111) plane, the Si(311) plane, and the Si(220) plane, respectively. Since there are no other obvious diffraction rings in the diffraction pattern of region A, it can be concluded that the interior of this composite powder (even at the interior boundaries) contains only some pure-phase Si nanocrystals, and no other pure-phase crystals are produced. Instead, the silicon-based compound is mainly composed of amorphous phases.

[0051] against Figure 3AIn the high-magnification TEM image of region B, it is clear that the structure of the interior of particle 300 differs from that at its outermost boundary. Conversely, the outermost boundary of particle 300 is characterized by a carbon coating layer formed by the conductive material. This carbon coating layer helps the silicon-based compound maintain sufficient conductivity while retaining a high specific capacity (~3750 mAh / g).

[0052] Figure 4 It is an X-ray diffractometer (XRD) pattern of the composite material produced by the negative electrode material according to an embodiment of the present invention. Figure 4 The XRD pattern of the powder produced after heat treatment such as drying of the negative electrode material manufactured by manufacturing method 100 is shown. Comparison of the XRD patterns of this composite material with those of the amorphous silicon-based compound reveals that the XRD pattern of this composite material exhibits three distinct diffraction peaks compared to the amorphous silicon-based compound. The positions of the three diffraction rings, from left to right, correspond to the Si(111) plane, the Si(220) plane, and the Si(311) plane, respectively. Therefore, please refer to both images. Figure 3B and Figure 4 During the drying and other heat treatment processes, the Si atoms in the silicon-based compound diffuse and rearrange, thereby generating pure-phase Si nanocrystals inside the composite material.

[0053] In summary, the first adhesive forms hydrogen bonds with the surface of the silicon-based compound, thereby imparting strong bonding and mechanical strength between them. Furthermore, the first adhesive stabilizes the silicon-based compound, resulting in a better structure for the bonding energy between the silicon-based compounds, and simultaneously alleviates the volume expansion problem of the silicon-based compound. Therefore, the first adhesive, as the adhesive for the silicon-based compound in the first stage of bonding, can improve the battery's cycle performance and extend its lifespan. Subsequently, in subsequent processes (e.g., heat treatment such as drying), the addition of a second adhesive allows the combination of the first and second adhesives to undergo dehydration condensation, resulting in crosslinking. The crosslinked adhesive effectively limits the change in electrode thickness and further improves the electrode's cycle performance and cycle life. Moreover, since the first adhesive forms an inner protective layer and the second adhesive forms an outer protective layer, the combined effect of these two protective layers can significantly suppress the volume change of the silicon-based compound during charge-discharge cycles. Furthermore, since the second adhesive coating the outer layer of the second adhesive can adsorb onto the conductive material, and the carbon material, as the conductive material, repels each other due to electrostatic forces, the conductive material can be uniformly distributed on the surface of the active material of the second adhesive. Additionally, the negative electrode is formed after coating with the third adhesive and bonding it to the electrode sheet, followed by drying. Finally, even after layering with three different adhesives and undergoing heat treatment such as drying, a carbon coating layer encapsulating the silicon-based compound can still be obtained, and the function of the negative electrode is not affected by the stacking of multiple different adhesives.

[0054] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0055] In conclusion, this invention meets the requirements for an invention patent, and therefore a patent application is filed in accordance with the law. However, the above description is only a preferred embodiment of this invention, and any equivalent modifications or variations made by those skilled in the art in accordance with the spirit of this invention should be included within the scope of the following patent application.

Claims

1. A method for manufacturing a negative electrode material, characterized in that, The manufacturing method includes: A silicon-based compound is added to an adhesive solution and mixed to form a first mixture, wherein the adhesive solution contains a first adhesive, the first adhesive being an acrylic polymer; A second adhesive is added to the first mixture and mixed to form a second mixture, wherein the second adhesive is different from the first adhesive; A conductive material is added to the second mixture, and the mixture is then combined to form a third mixture; and A third adhesive is added to the third mixture and mixed to form the negative electrode material, wherein the third adhesive is different from the first adhesive and the second adhesive.

2. The manufacturing method as described in claim 1, characterized in that, The first adhesive is a polyacrylic acid (PAA) type adhesive. The second adhesive is a carboxymethyl cellulose (CMC) adhesive, and The third adhesive is a styrene-butadiene rubber (SBR) type adhesive.

3. The manufacturing method as described in claim 1, characterized in that, The first mixture comprises a first adhesive formed by the silicon-based compound and the first adhesive, and The second mixture includes a second adhesive formed by coating the first adhesive with the second adhesive.

4. The manufacturing method as described in claim 3, characterized in that, The third mixture includes a third adhesive formed by coating the second adhesive with the conductive material.

5. The manufacturing method as described in claim 4, characterized in that, When the third adhesive is added to the third mixture and mixed, a negative electrode slurry is formed, wherein: The negative electrode slurry contains the negative electrode material; and The negative electrode material is produced by the third adhesive and the third binder.

6. The manufacturing method as described in claim 5, characterized in that, The negative electrode paste is coated onto an electrode sheet to form a negative electrode sheet, and A drying process is used to remove moisture from the negative electrode.

7. The manufacturing method as described in claim 6, characterized in that, The drying process may include two stages of temperature control.

8. A negative electrode material, wherein the negative electrode material is prepared by the manufacturing method of the negative electrode material as described in any one of claims 1-7.

9. A negative electrode for a lithium-ion battery, wherein the negative electrode uses the negative electrode material as described in claim 8.

10. A lithium-ion battery comprising a negative electrode, wherein the negative electrode uses the negative electrode material as described in claim 8.

Images