Negative electrode material and manufacturing method thereof, negative electrode and lithium ion battery

Abstract

The invention provides a manufacturing method of a negative electrode material, the negative electrode material, a negative electrode and a lithium ion battery, and the method comprises the following steps: adding a metal salt compound into a first solvent to form a first mixture; adding a silicon-based material into the first mixture to form a second mixture; performing first heat treatment on the second mixture to obtain an intermediate product; adding a carbon-based material and the intermediate product into a second solvent to form a third mixture; and performing a second heat treatment on the third mixture to obtain the negative electrode material, in which the negative electrode material comprises a metal silicide and a carbon coating layer coating the metal silicide, and both the metal silicide and the carbon coating layer are formed during the second heat treatment.

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 anodes have a higher theoretical specific capacity (~4200 mAh / g), effectively improving the energy density of lithium batteries. However, silicon-based anodes suffer from significant volume expansion, leading to a dramatic increase in the solid electrolyte interphase (SEI) film during charge and discharge, which degrades battery performance and severely impacts lithium battery performance. Therefore, new electrode materials are needed to improve the battery performance of the anode and reduce the volume expansion effect. Summary of the Invention

[0004] 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.

[0005] To address the aforementioned problems, the manufacturing method includes: adding a metal salt compound to a first solvent to form a first mixture; adding a silicon-based material to the first mixture to form a second mixture; subjecting the second mixture to a first heat treatment to obtain an intermediate product; adding a carbon-based material and the intermediate product to a second solvent to form a third mixture; and subjecting the third mixture to a second heat treatment to form the negative electrode material, wherein the negative electrode material includes a metal silicide and a carbon coating layer covering the metal silicide, and both the metal silicide and the carbon coating layer are formed during the second heat treatment.

[0006] In some embodiments, the metal silicide includes copper silicide (CuSi). a ) and nickel silicide (NiSi) b At least one of the following; and the values ​​a and b are any values ​​between 1 / 3 and 2.

[0007] In some embodiments, the metal salt compound includes at least one of aqueous copper nitrate and aqueous nickel nitrate; and the metal silicide includes at least one of copper silicide and nickel silicide.

[0008] In some embodiments, the first heat treatment includes: performing a first annealing treatment on a first precipitate produced by the second mixture at a first annealing temperature for a first annealing time to obtain the intermediate product; and the second heat treatment includes: performing a second annealing treatment on a second precipitate produced by the third mixture at a second annealing temperature for a second annealing time to obtain the negative electrode material.

[0009] In some embodiments, the second annealing time is longer than the first annealing time and is within a temperature range, so that both the metal silicide and the carbon coating are formed during the second annealing process.

[0010] In some embodiments, the first heat treatment further includes: after subjecting the second mixture to a first heating and stirring treatment for a first heating time at a first heating temperature, obtaining the first precipitate from the second mixture; and the second heat treatment further includes: after subjecting the third mixture to a second heating and stirring treatment for a second heating time at a second heating temperature, obtaining the second precipitate from the third mixture.

[0011] In some embodiments, the metal silicide is formed on the surface of the silicon-based material, making the metal silicide an alloy coating layer to coat the silicon-based material.

[0012] To solve the above problems, the negative electrode material is prepared using the aforementioned manufacturing method.

[0013] To address the aforementioned issues, the negative electrode of a lithium-ion battery includes the aforementioned negative electrode material.

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

[0015] The above method involves coating the surface of silicon nanoparticles with a compound containing metal cations. Then, through heat treatment, an alloy coating layer (e.g., CuSi) is formed on the silicon surface. x With NiSi x (etc.), and finally, surface carbon coating treatment is carried out to obtain a negative electrode material with high specific capacity and low expansion. Attached Figure Description

[0016] 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.

[0017] Figure 1 This is a flowchart of a method for manufacturing a negative electrode material according to an embodiment of the present invention.

[0018] Figure 2A and Figure 2B The images are X-ray diffractometer (XRD) spectra of the negative electrode material, pure silicon, and metal silicide according to embodiments of the present invention.

[0019] Figure 3A This is a transmission electron microscope (TEM) image of the negative electrode material according to an embodiment of the present invention.

[0020] Figure 3B It is according to the embodiments of the present invention. Figure 3A The illustrated high-magnification TEM image of region A.

[0021] Figure 3C It is according to the embodiments of the present invention. Figure 3A The illustrated high-magnification TEM image of region B.

[0022] Figure 4 This is a comparison diagram of the conductivity of the negative electrode material according to an embodiment of the present invention and pure silicon.

[0023] Figure 5A and Figure 5B This is a schematic diagram showing the specific capacity and coulombic efficiency of the negative electrode material and pure silicon under charge and discharge rates of 200 mA / g according to an embodiment of the present invention.

[0024] Figure 6 This is a schematic diagram of the specific capacity of the negative electrode material according to an embodiment of the present invention when charged and discharged at different charge and discharge rates. Detailed Implementation

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] Figure 1This 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.

[0031] In step S110, a metal salt compound is added to a first solvent to form a first mixture.

[0032] In some embodiments, the metal salt compound may include a metal cation. In some embodiments, the metal cation may be a transition metal cation. In some embodiments, the transition metal cation may include at least one of copper ions, nickel ions, iron ions, titanium ions, and cobalt ions. In some embodiments, the metal salt compound may include a metal salt anion. In some embodiments, the metal salt anion may include an acid radical ion. In some embodiments, the acid radical ion may include at least one of a nitrate ion, a sulfate ion, an acetate ion, and a halide acid radical ion (e.g., chloride ion of hydrochloric acid). In some embodiments, the metal salt compound may include a hydrated compound. In some embodiments, the metal salt compound may include a hydrated metal nitrate (M(NO3)3·nH3O). In some embodiments, M is the metal cation, and the value of n is between 0 and 6. In some embodiments, the metal salt compound may include at least one of hydrated copper nitrate (Cu(NO3)2·nH2O) and hydrated nickel nitrate (Ni(NO3)2·nH2O).

[0033] In some embodiments, the first solvent may include at least one of organic alcohols such as ethanol, organic ketones such as acetone, and other organic esters. In some embodiments, the metal salt compound is soluble in the first solvent to allow for sufficient mixing between the metal salt compound and the first solvent to produce the first mixture. In some embodiments, when the metal salt compound is a metal nitrate compound, the first solvent may be a solvent capable of dissolving the metal nitrate compound. In some embodiments, the first solvent may be pure ethanol.

[0034] In step S120, a silicon-based material is added to the first mixture to form a second mixture.

[0035] In some embodiments, the silicon-based material may include pure silicon and silicon oxide (SiO2). xAt least one of the following: (e.g., x). In some embodiments, the value of x is between 0 and 2. In some embodiments, the silicon-based material may be added to the first mixture in powder form. In some embodiments, after the silicon-based material is added to the first mixture, stirring may continue to produce the second mixture. In some embodiments, the silicon-based material may be insoluble in the first solvent.

[0036] In step S130, the second mixture is subjected to a first heat treatment to obtain an intermediate product.

[0037] In some embodiments, the first heat treatment may include a first heating and stirring process. In some embodiments, in the first heating and stirring process, the second mixture may be heated and stirred to a first heating temperature, and then stirred continuously at a constant temperature for a first heating time. In some embodiments, during the first heating and stirring process, the metal salt compound dissolved in the first solvent may be adsorbed onto the silicon-based material. In some embodiments, after heating for the first heating time, the second mixture is allowed to stand until a first precipitate is completely precipitated, and then the first precipitate is collected from the second mixture. In some embodiments, the first heating temperature is any temperature between 50°C and 80°C. In some embodiments, the first heating temperature may be, for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or any temperature between these values. In some embodiments, the first heating temperature is 65°C. In some embodiments, the first heating time is any time interval of 0.5 hours or more than 1 hour. In some embodiments, the first heating time can be, for example, 0.5 hours, 0.7 hours, 0.9 hours, 1 hour, 1.1 hours, 1.3 hours, 1.5 hours, or any time between them. In some embodiments, the first heating time is 1 hour.

[0038] In some embodiments, the first heating and stirring process can directly heat the second mixture until the first solvent is completely evaporated, leaving only the first precipitate. Therefore, the higher the first heating temperature, the faster the first solvent evaporates, and the shorter the first heating time. In some embodiments, the first heating temperature should not be too high to avoid unnecessary chemical reactions.

[0039] In some embodiments, the first heat treatment may include a first annealing treatment. In some embodiments, the first precipitate produced by the second mixture may be heated to a first annealing temperature and subjected to the first annealing treatment for a first annealing time to obtain the intermediate product. In some embodiments, during the first annealing treatment, the first precipitate may be first heated to the first annealing temperature and then held at that temperature for the first annealing time. In some embodiments, during the first annealing treatment, dry metal salt compounds may precipitate from the first precipitate and coat the surface of the silicon-based material. In some embodiments, the first annealing temperature is any temperature between 300°C and 400°C. In some embodiments, the first annealing temperature may be, for example, 300°C, 320°C, 340°C, 350°C, 360°C, 380°C, 400°C, or any temperature between them. In some embodiments, the first annealing temperature is 350°C. In some embodiments, the first annealing time is any time interval between 1.5 and 2.5 hours. In some embodiments, the first annealing time can be, for example, 1.5 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.5 hours, or any time in between. In some embodiments, the first annealing time is 2 hours.

[0040] In some embodiments, during the first heat treatment, the first heating and stirring treatment can be performed on the second mixture first, and after the first heating and stirring treatment is completed, the first precipitate in the second mixture can be collected, and then the first annealing treatment can be performed on the first precipitate to obtain the intermediate product.

[0041] In step S140, a carbon-based material and the intermediate product are added to a second solvent to form a third mixture.

[0042] In some embodiments, the carbon-based material may include at least one carbon-containing substance such as lignin, dopamine, resorcinol-formaldehyde resin or other resin derivatives, citric acid, or triethylene glycol (TEG). In some embodiments, after the carbon-based material and the intermediate product are added to the second solvent, stirring can be continued to produce the third mixture. In some embodiments, the second solvent may be an inorganic solvent. In some embodiments, the inorganic solvent does not react with the carbon-based material and allows the carbon-based material to be uniformly dispersed in the inorganic solvent. In some embodiments, the inorganic solvent may include water (e.g., deionized water, distilled water, or pure water). In some embodiments, the carbon-based material and the intermediate product may be insoluble in the second solvent.

[0043] In step S150, the third mixture is subjected to a second heat treatment to form the negative electrode material.

[0044] In some embodiments, the second heat treatment may include a second heating and stirring process. In some embodiments, in the second heating and stirring process, the third mixture may first be heated and stirred to a second heating temperature, and then continuously stirred at a constant temperature for a second heating time. In some embodiments, during the second heating and stirring process, the carbon-based material in the third mixture may adsorb onto the intermediate product in the third mixture. In some embodiments, after heating for the second heating time, the third mixture is allowed to stand until a second precipitate is completely precipitated, and then the second precipitate is collected from the third mixture. In some embodiments, the second heating temperature is any temperature between 50°C and 80°C. The second heating temperature may, for example, be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or any temperature between these temperatures. In some embodiments, the second heating temperature is 65°C. In some embodiments, the second heating time is any time interval of 0.5 hours or more than 1 hour. In some embodiments, the second heating time can be, for example, 0.5 hours, 0.7 hours, 0.9 hours, 1 hour, 1.1 hours, 1.3 hours, 1.5 hours, or any time in between. In some embodiments, the second heating time is 1 hour.

[0045] In some embodiments, the second heating and stirring process can directly heat the third mixture until the second solvent is completely evaporated, leaving only the second precipitate. Therefore, the higher the second heating temperature, the faster the second solvent evaporates, and the shorter the second heating time. In some embodiments, the second heating temperature should not be too high to avoid unnecessary chemical reactions.

[0046] In some embodiments, the second heat treatment may include a second annealing treatment. In some embodiments, the second precipitate produced by the third mixture may be heated to a second annealing temperature and subjected to a second annealing treatment for a second annealing time to obtain the negative electrode material. In some embodiments, during the second annealing treatment, the second precipitate may first be heated to the second annealing temperature and then held at a constant temperature for the second annealing time. In some embodiments, the third mixture may be placed in a high-temperature furnace for the second annealing treatment. In some embodiments, the third mixture may be placed in the high-temperature furnace at the second annealing temperature for the second annealing time. In some embodiments, a gaseous environment may be maintained inside the high-temperature furnace during heating and / or temperature control. In some embodiments, the gaseous environment is an inert gas environment. In some embodiments, the inert gas environment may be an environment composed of at least one inert gas, such as an argon (Ar) environment or a nitrogen (N2) environment. In some embodiments, the second mixture may also be placed in the high-temperature furnace or other heating device for the first annealing treatment.

[0047] The present invention also provides a negative electrode material comprising a metal silicide and a carbon coating layer covering the metal silicide. In some embodiments, when the metal cation in the metal salt compound includes at least one of copper ions and nickel ions, the metal silicide comprises copper silicide (CuSi). a ) and nickel silicide (NiSi) b At least one of the following. In some embodiments, the value a and the value b can each be any value between 1 / 3 and 2 (e.g., 1 / 3, 1 / 2, 1, and 2). In some embodiments, the value a can be 1 / 3, and the value b can be 2. In one specific embodiment, the copper silicide can be Cu3Si, and the nickel silicide can be NiSi2. In some embodiments, the metal cation in the metal salt compound can also include iron ions, titanium ions, and cobalt ions, therefore the metal silicide includes iron silicide, titanium silicide, and cobalt silicide.

[0048] In some embodiments, the second annealing temperature may be higher than the first annealing time, so that both the metal silicide and the carbon coating layer are formed simultaneously during the second annealing process. In some embodiments, the second annealing temperature may be higher than the reaction temperature between the metal salt compound and the silicon-based material, allowing the metal salt compound and the silicon-based material to react at the second annealing temperature to generate the metal silicide. In some embodiments, the second annealing temperature may be higher than the decomposition temperature of the carbon-based material, allowing the carbon-based material to decompose and release carbon atoms to coat the silicon-based material and the metal silicide, forming the carbon coating layer. In some embodiments, the second annealing temperature may be higher than both the reaction temperature and the decomposition temperature. In some embodiments, the first annealing temperature may be lower than the reaction temperature between the metal salt compound and the silicon-based material, so that the metal silicide may not form during the first annealing process, but instead form together with the carbon coating layer during the second annealing process.

[0049] In some embodiments, the second annealing temperature is any temperature between 700°C and 800°C. In some embodiments, the second annealing temperature can be, for example, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, or any value between them. In some embodiments, the second annealing temperature is 800°C. In some embodiments, the second annealing time is any time interval between 1.5 and 2.5 hours. In some embodiments, the second annealing time can be, for example, 1.5 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.5 hours, or any time between them. In some embodiments, the second annealing time is 2 hours.

[0050] In some embodiments, since the metal salt compound in the intermediate product is located on the surface of the silicon-based material in the intermediate product, during the second annealing process in the second heat treatment, the metal salt compound can react with silicon atoms or silicides located on the surface of the silicon-based material to form the metal silicide on the surface of the silicon-based material. Therefore, the metal silicide is an alloy coating layer to coat the silicon-based material.

[0051] In some embodiments, since the carbon-based material in the second precipitate is located on the surface of the metal salt compound in the intermediate product (i.e., on the outer surface of the intermediate product), during the second annealing process in the second heat treatment, the carbon-based material can be cleaved into carbon atoms on the surface of the metal salt compound, so that carbon atoms can be generated on the surface of the metal silicide also generated during the second annealing process. Therefore, the carbon atoms can form the carbon coating layer to coat the metal silicide. In some embodiments, since the metal silicide, as the alloy coating layer, coats the silicon-based material, and the carbon coating layer coats the metal silicide, as the alloy coating layer, the negative electrode material is a multilayer coated composite material.

[0052] In some embodiments, since both the metal silicide and the carbon coating are formed simultaneously during the second annealing process in the second heat treatment, the metal silicide and the carbon coating can enhance the bonding between the silicon-based material and the metal silicide at a first interface and between the metal silicide and the carbon coating at a second interface during the second annealing process, thereby enhancing the stability of the anode material. Furthermore, when the metal salt compound is reduced to a metallic state and forms an alloy phase with the silicon-based material (e.g., the metal silicide), the presence of the carbon-based material allows for a carbothermic reduction to alter the system's thermodynamics. This not only lowers the overall reaction temperature but also enables the carbon-based material to form a carbon coating on the outer layer of the metal silicide.

[0053] In some embodiments, the negative electrode of the lithium-ion battery can be prepared by the manufacturing method 100 of the negative electrode material.

[0054] Figure 2A and Figure 2B The images are X-ray diffractometer (XRD) spectra of the negative electrode material, pure silicon, and metal silicide according to embodiments of the present invention. Figure 2A The negative electrode material shown is manufactured using method 100 with hydrated nickel nitrate as the metal salt compound. Figure 2A The metal silicide shown is compared to nickel silicide (NiSi2). Figure 2B The negative electrode material shown is manufactured using method 100 with hydrated copper nitrate as the metal salt compound. Figure 2B The metal silicide shown is based on copper silicide (Cu3Si).

[0055] by Figure 2AAs can be seen from the comparison of the XRD patterns of pure silicon and nickel silicide, the diffraction peak positions of the two are extremely similar, making it difficult to distinguish between pure silicon and nickel silicide. Further analysis of the XRD patterns of this anode material with those of pure silicon and nickel silicide reveals that the diffraction peak positions of this anode material correspond to those of pure silicon and nickel silicide. Therefore, it can be concluded that the crystalline forms in this anode material are predominantly pure silicon and nickel silicide.

[0056] Furthermore, a comparison of the XRD patterns of pure silicon and nickel silicide reveals differences in the height ratio of the first and third diffraction peaks relative to the second diffraction peak. Regarding the first and second diffraction peaks, the heights of the first and second diffraction peaks in nickel silicide are similar, while the difference is larger in pure silicon. Relatively speaking, the height ratio of the first and second diffraction peaks in this anode material is lower than that in nickel silicide but slightly higher than that in pure silicon. Additionally, regarding the second and third diffraction peaks, the difference is larger in nickel silicide and smaller in pure silicon. Relatively speaking, the height ratio of the second and third diffraction peaks in this anode material is higher than that in nickel silicide but slightly lower than that in pure silicon. Therefore, it can be concluded that the crystalline composition of this anode material is still predominantly pure silicon, with an additional portion of nickel silicide.

[0057] by Figure 2B As can be seen from the comparison of the XRD patterns of pure silicon and copper silicide, the diffraction peak positions of the two are significantly different, clearly distinguishing pure silicon from copper silicide. Therefore, further analysis of the XRD patterns of this anode material with those of pure silicon and copper silicide reveals that the diffraction peak positions of this anode material clearly correspond to the diffraction peak positions of pure silicon and copper silicide. This indicates that the crystalline forms in this anode material are predominantly pure silicon and copper silicide.

[0058] XRD diffraction patterns confirmed that, after using the metal salt compound and the carbon-based material, the diffraction peaks of the anode material corresponded only to the diffraction peaks of pure silicon and the metal silicide. Therefore, the crystalline form of the anode material can be predominantly pure silicon and the metal silicide. In some embodiments, the anode material may still contain other amorphous elements or compounds.

[0059] Figure 3A This is a transmission electron microscope (TEM) image of 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 The illustrated high-magnification TEM image of region A. Figure 3C It is according to the embodiments of the present invention. Figure 3A The illustrated high-magnification TEM image of region B.

[0060] Figure 3A The nanoscale particles 300 of the negative electrode material produced by manufacturing method 100 are shown. Figure 3A The negative electrode material shown is manufactured using method 100 with hydrated nickel nitrate as the metal salt compound. Since the TEM sample made from this negative electrode material is a thin sheet, Figure 3A The nano-sized particle 300 can be considered a cross-section of a negative electrode material powder. Therefore, the internal region of the nano-sized particle 300 can be considered the interior of the negative electrode material powder. Figure 3A The left side of the medium-nano-scale particle 300 can be initially seen to show its multi-layer structure, which consists of a Si core, an alloy coating layer, and a carbon coating layer.

[0061] Figure 3B Showing Figure 3A A high-magnification TEM image of region A located inside nano-sized particles 300. Figure 3B The lattice arrangement of the Si core is clearly visible. The lattice spacing d of the Si core in region A is 0.313 nm, which corresponds to the Si (111) plane. Figure 3C Showing Figure 3A A high-magnification TEM image of region B, located inside and around the nano-sized particles 300. Figure 3C The lattice arrangement of the alloy coating is also clearly visible. The lattice spacing d of the metal silicide in region B is 0.191 nm, which corresponds to the NiSi2(220) plane. Therefore, from Figure 3B and Figure 3C It can be seen that the negative electrode material exhibits a layered structure of pure silicon and metal silicide in the internal region and the surrounding internal region, respectively. Please also refer to [further details omitted]. Figure 2A As shown in Figure 3, since there are no corresponding diffraction peaks for carbon atoms or carbon compounds in the XRD pattern, the carbon coating layer located in the outer surrounding area should be composed of amorphous carbon.

[0062] Figure 4 This is a comparison diagram of the conductivity of the negative electrode material according to an embodiment of the present invention and pure silicon. Figure 4 The measured negative electrode material is a negative electrode material made by manufacturing method 100 using hydrated nickel nitrate as the metal salt compound.

[0063] according to Figure 4As shown, with increasing voltage, the current increase of this negative electrode material is much greater than that of pure silicon. That is, the resistance of this negative electrode material is much lower than that of pure silicon, and the conductivity of this negative electrode material is much higher than that of pure silicon. Therefore, the negative electrode material manufactured by method 100, after coating the silicon-based material with the metal silicide, can significantly improve the conductivity of the negative electrode. In some embodiments, the conductivity of this negative electrode material can be approximately 100 times that of pure silicon.

[0064] Figure 5A and Figure 5B This is a schematic diagram showing the specific capacity and coulombic efficiency of the negative electrode material and pure silicon under charge and discharge rates of 200 mA / g according to an embodiment of the present invention. Figure 5A The negative electrode material shown is a negative electrode material made by manufacturing method 100 using hydrated nickel nitrate as the metal salt compound. Figure 5B The negative electrode material shown is a negative electrode material made by manufacturing method 100 using aqueous copper nitrate as the metal salt compound.

[0065] according to Figure 5A and Figure 5B As shown, both nickel silicide and copper silicide anode materials can stably perform more than 30 charge-discharge cycles, and their specific capacity can be stably maintained above 1000 mAh / g. In contrast, according to... Figure 5A As shown, the specific capacity of a pure silicon anode decreases rapidly with increasing charge-discharge cycles, dropping below 750 mAh / g after 30 cycles, and even below 250 mAh / g after 100 cycles. Therefore, after coating the silicon-based material with a metal silicide, the metal silicide can effectively improve the conductivity of the anode material, thereby giving the anode material better capacity performance.

[0066] In addition, according to Figure 5A and Figure 5B As shown, the coulombic efficiency of the negative electrode material, whether it has nickel silicide or copper silicide, increases with the number of charge-discharge cycles and gradually approaches 100%. In other words, with the increase of the number of charge-discharge cycles, under the dual effect of the carbon coating layer and the alloy coating layer, the negative electrode itself is less affected by the electrolyte and tends to be stable.

[0067] Figure 6 This is a schematic diagram of the specific capacity of the negative electrode material according to an embodiment of the present invention when charged and discharged at different charge and discharge rates. Figure 6 The negative electrode material shown is a negative electrode material made by manufacturing method 100 using hydrated nickel nitrate as the metal salt compound.

[0068] according to Figure 6As shown, the first 5 charge-discharge cycles were performed at a charge-discharge rate of 200 mA / g, the 6th to 10th cycles at a charge-discharge rate of 500 mA / g, the 11th to 15th cycles at a charge-discharge rate of 1000 mA / g, the 16th to 20th cycles at a charge-discharge rate of 2000 mA / g, the 21st to 25th cycles at a charge-discharge rate of 5000 mA / g, and the 26th to 45th cycles at a charge-discharge rate of 200 mA / g.

[0069] according to Figure 6 As shown, although the specific capacity of the negative electrode material decreases with increasing charge / discharge rate during the first 25 charge / discharge cycles, it still maintains a specific capacity of over 500 mAh / g even at a charge / discharge rate of 5000 mA / g. Therefore, after coating the silicon-based material with the metal silicide, the metal silicide effectively improves the conductivity of the negative electrode material, thereby giving it better capacity performance.

[0070] Furthermore, during the first five charge-discharge cycles at a charge-discharge rate of 200 mA / g, the anode material exhibits a specific capacity of approximately 1400 mAh / g or higher. Even at a high current density of 5000 mA / g, the anode material maintains a specific capacity of over 500 mAh / g. Subsequently, when the current density is reduced to a lower level (200 mA / g), the specific capacity of the anode material recovers and remains above 1300 mAh / g. This demonstrates that the dual coating of the carbon coating layer and the alloy layer prevents structural collapse of the anode material under high current density charge-discharge conditions. In other words, coating silicon-based materials with two protective layers (such as a carbon coating layer and an alloy layer) effectively alleviates the stress caused by volume expansion and contraction during charge-discharge, preventing structural collapse and cracking of the electrode surface.

[0071] 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.

[0072] 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 metal salt compound is added to a first solvent to form a first mixture; A silicon-based material is added to the first mixture to form a second mixture; After subjecting the second mixture to a first heat treatment, an intermediate product is obtained; A carbon-based material and the intermediate product are added to a second solvent to form a third mixture; and After subjecting the third mixture to a second heat treatment, the negative electrode material is formed, wherein: The anode material includes a metal silicide and a carbon coating layer covering the metal silicide, and Both the metal silicide and the carbon coating are formed during the second heat treatment.

2. The manufacturing method as described in claim 1, characterized in that, The metal silicide includes copper silicide (CuSi). a ) and nickel silicide (NiSi) b At least one of the following; and The values ​​a and b are any values ​​between 1 / 3 and 2.

3. The manufacturing method as described in claim 1, characterized in that, The metal salt compound includes at least one of hydrated copper nitrate and hydrated nickel nitrate; and The metal silicide includes at least one of copper silicide and nickel silicide.

4. The manufacturing method as described in claim 1, characterized in that, The first heat treatment includes: The intermediate product is obtained by subjecting a first precipitate from the second mixture to a first annealing treatment for a first annealing time at a first annealing temperature; and The second heat treatment includes: The anode material is obtained by subjecting a second annealing treatment of a second precipitate produced by the third mixture to a second annealing time at a second annealing temperature.

5. The manufacturing method as described in claim 4, characterized in that, The second annealing time is longer than the first annealing time and is within a temperature range, so that both the metal silicide and the carbon coating are formed during the second annealing process.

6. The manufacturing method as described in claim 4, characterized in that, This first heat treatment further includes: After subjecting the second mixture to a first heating and stirring treatment for a first heating time at a first heating temperature, the first precipitate is obtained from the second mixture; and This second heat treatment further includes: After subjecting the third mixture to a second heating and stirring treatment for a second heating time at a second heating temperature, the second precipitate is obtained from the third mixture.

7. The manufacturing method as described in claim 1, characterized in that, The metal silicide is formed on the surface of the silicon-based material, making the metal silicide an alloy coating layer to coat the silicon-based material.

8. A negative electrode material, wherein the negative electrode material is prepared by the method for manufacturing a 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.

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