Anode composite material, lithium ion secondary battery anode, and lithium ion secondary battery

Abstract

To provide a negative electrode composite material, a preparation method thereof, a negative electrode, and a lithium ion secondary battery.SOLUTION: A negative electrode composite material includes negative electrode active material particles, and Li2CO3 and LiOH on surfaces of the negative electrode active material particles. The negative electrode active material particles include: granules containing a silicon oxide, Li2SiO3, and Li2Si2O5; and a carbon coating layer coating at least a part of surfaces of the granules. Based on the weight of the negative electrode active material particles, the content of Li2CO3 is greater than 0.001 wt% and less than 1wt %, the content of LiOH is greater than 0.01 wt% and less than 0.1 wt%, and the weight ratio of Li2Si2O5 to Li2SiO3, i.e. Li2Si2O5 / Li2SiO3 is within the range of 1.00-10.00. According to the negative electrode composite material, the preparation method thereof, the negative electrode, and the lithium-ion secondary battery of the present invention, the residual lithium amount can be reduced to a great extent, the processing performance of slurry can be improved, and the initial Coulombic efficiency and cycle characteristics of the lithium ion secondary battery can be improved.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of lithium ion secondary batteries, and in particular to an anode composite material, a method for producing the anode composite material, and an anode and a lithium ion secondary battery comprising the anode composite material. [Background technology]

[0002] In recent years, advances in electronic technology have led to an increasing demand for battery devices that provide energy for electronic devices. Currently, there is a need for batteries that can store more power and output higher power. Conventional lead-acid batteries and nickel-metal hydride batteries are no longer able to meet the requirements of new electronic devices, such as mobile devices like smartphones and stationary devices like energy storage systems. Therefore, lithium-ion secondary batteries have attracted attention. Effective efforts have been made to improve the capacity and performance of lithium-ion secondary batteries. Lithium-ion secondary batteries offer advantages such as high energy density, high operating voltage, long cycle life, and minimal environmental pollution, making them a new, environmentally friendly, high-energy chemical power source with great potential for development in the current world.

[0003] A lithium-ion secondary battery comprises a positive electrode, a negative electrode containing a negative electrode material, and an electrolyte. Several types of negative electrode materials have been developed, among which silicon-based negative electrode materials are one promising negative electrode material. Prior art has disclosed the use of prelithiation techniques to control the amount of residual lithium in silicon-based negative electrode materials to improve their performance. However, these techniques have high upper and lower limits for controlling the amount of residual lithium in silicon-based negative electrode materials, making it difficult to improve the processability of slurries containing the negative electrode material. This makes it difficult to effectively improve the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries. Therefore, there is a need for the development of new negative electrode composite materials, methods for producing these negative electrode composite materials, negative electrodes containing these negative electrode composite materials, and lithium-ion secondary batteries. Summary of the Invention [Problem to be solved by the invention]

[0004] The main objective of the present invention is to provide an anode composite material, a method for manufacturing the anode composite material, and an anode and a lithium ion secondary battery including the anode composite material, in order to solve the problems of the prior art, such as the excessively high residual lithium content of the anode material, the difficulty in improving the processability of the slurry, and the difficulty in effectively improving the initial coulombic efficiency and cycle characteristics of the lithium ion secondary battery. [Means for solving the problem]

[0005] In order to achieve the above object, according to one aspect of the present invention, Provided is an anode composite material comprising: anode active material particles; and Li2CO3 and LiOH on the surfaces of the anode active material particles, wherein the anode active material particles comprise granules containing silicon oxide, Li2SiO3, and Li2SiO5, and a carbon coating layer covering at least a portion of the surface of the granules, wherein, based on the weight of the anode active material particles, the Li2CO3 content is more than 0.01 wt% and less than 1 wt%, the LiOH content is more than 0.001 wt% and less than 0.1 wt%, and the weight ratio of Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, is in the range of 1.00 to 10.00.

[0006] Furthermore, in the negative electrode composite material, the content of Li2SiO3 is more than 1.0 wt% and less than 48.0 wt% based on the weight of the negative electrode active material particles.

[0007] Furthermore, in the negative electrode composite material, Li2SiO3 is distributed within the granule so that the amount thereof decreases from a position near the surface of the granule toward the center of the granule, and Li2Si2O5 is distributed closer to the center of the granule than Li2SiO3.

[0008] Furthermore, in the negative electrode composite material, the carbon coating layer covers the entire surface of the granule.

[0009] Furthermore, in the negative electrode composite material, the silicon oxide is SiOx (0.5≦x≦1.6).

[0010] Furthermore, in the negative electrode composite material, the silicon in the silicon oxide exists in the form of crystalline silicon having a size in the range of 5.0 nm to 12.0 nm.

[0011] Furthermore, in the negative electrode composite material, the intensity ratio I of the D peak to the G peak in the Raman spectrum of the negative electrode composite material D / I G is more than 0.8 and less than 2.0, preferably more than 1.5 and less than 1.8.

[0012] Furthermore, in the negative electrode composite material, the coating amount of the carbon coating layer is in the range of 1 wt % to 30 wt % based on the weight of the negative electrode active material particles.

[0013] According to another aspect of the present invention, there is provided a method for producing an anode composite, comprising the steps of: using a carbon source to perform a carbon coating process on the silicon oxide precursor to form a carbon-coated silicon oxide; combining a carbon-coated silicon oxide with a lithium source to form a first mixture, subjecting the first mixture to a first heat treatment to form a calcined product, and then subjecting the calcined product to a second heat treatment to form a prelithiated product; and washing the prelithiated product to form a negative electrode composite material.

[0014] Furthermore, in the method for producing the negative electrode composite material, the washing treatment includes mixing the prelithiated product with water, alcohol, or acid, preferably to a solid content of 5 wt% to 20 wt%, to form a second mixture, ultrasonicating the second mixture to disperse it, then suction filtering, and finally drying the material after suction filtering.

[0015] Furthermore, in the method for producing the negative electrode composite material, the acid is at least one selected from hydrochloric acid, citric acid, oxalic acid, phosphoric acid, sulfurous acid, acetic acid, chloric acid, hypochlorous acid, and boric acid.

[0016] Furthermore, in the method for producing the negative electrode composite material, the weight ratio of the lithium source to the carbon-coated silicon oxide is in the range of 5:95 to 40:60.

[0017] Furthermore, in the method for producing the negative electrode composite material, the temperature of the first heat treatment is in the range of 400° C. to 750° C., and the time of the first heat treatment is in the range of 1 hour to 5 hours.

[0018] Furthermore, in the method for producing the negative electrode composite material, the temperature of the second heat treatment is in the range of 800° C. or higher and lower than 925° C., and the time of the second heat treatment is in the range of 1 hour to 6 hours.

[0019] Furthermore, in the method for producing the negative electrode composite material, the ultrasonic treatment time is in the range of 1 minute to 30 minutes.

[0020] Furthermore, in the method for producing the negative electrode composite material, the dispersion time is in the range of 8 hours to 48 hours.

[0021] Furthermore, in the method for producing the negative electrode composite material, the carbon source includes at least one of an alkane, an alkene, and an alkyne.

[0022] Furthermore, in the method for producing the negative electrode composite material, the alcohol is at least one selected from ethanol, isopropanol, and butanol.

[0023] According to a further aspect of the present invention, there is provided a lithium ion secondary battery negative electrode comprising the aforementioned negative electrode composite material.

[0024] According to a further aspect of the present invention, there is provided a lithium ion secondary battery comprising a positive electrode, a negative electrode, and a separator, wherein the negative electrode comprises the above-described negative electrode composite material.

[0025] The negative electrode composite material of the present invention, the method for producing the negative electrode composite material, and the negative electrode and lithium ion secondary battery including the negative electrode composite material can significantly reduce the amount of residual lithium, improve the processability of the slurry, and improve the initial coulombic efficiency and cycle characteristics of the lithium ion secondary battery. [Brief explanation of the drawings]

[0026] [Figure 1] 1 shows a schematic structural diagram of a negative electrode composite material according to one embodiment of the present invention. [Figure 2] FIG. 1 shows a relationship diagram between the size of crystalline silicon in the negative electrode composite materials of Examples 1 to 10 and Comparative Examples 1 to 3, 5, 7, and 9 and the weight ratio of Li2Si2O5 to Li2SiO3, Li2Si2O5 / Li2SiO3, where the ordinate is the size of crystalline silicon in the negative electrode composite material and the abscissa is the weight ratio of Li2Si2O5 to Li2SiO3, Li2Si2O5 / Li2SiO3. [Figure 3] FIG. 1 shows a relationship diagram between the discharge capacity retention rate (%) after 50 cycles and the intensity ratio ID / IG of the D peak to the G peak in the Raman spectrum of the negative electrode composite material for Examples 1 to 8 and Comparative Examples 1, 3, 4, 6, 8, and 9, where the ordinate represents the discharge capacity retention rate (%) after 50 cycles and the abscissa represents the intensity ratio ID / IG of the D peak to the G peak in the Raman spectrum of the negative electrode composite material. [Figure 4] 1 shows Li 1s XPS (X-ray photoelectron spectrum) spectra at each etching depth in Example 2. [Figure 5] 1 shows Li 1s XPS (X-ray photoelectron spectrum) spectra at each etching depth in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0027] It should be noted that various embodiments and features of the embodiments of the present application may be combined with each other without contradiction. The present invention will be described in detail below with reference to the following examples. The following examples are for illustrative purposes only and do not limit the scope of protection of the present invention.

[0028] As described in the Background Art, in the prior art, the residual lithium content of the negative electrode material is too high, making it difficult to improve the processability of slurries containing the negative electrode material, and making it difficult to effectively improve the initial coulombic efficiency and cycle characteristics of lithium-ion secondary batteries. To address the problems of the prior art, a representative embodiment of the present invention provides a negative electrode composite material comprising: negative electrode active material particles; and Li2CO3 and LiOH on the surfaces of the negative electrode active material particles, the negative electrode active material particles comprising granules containing silicon oxide, Li2SiO3, and Li2SiO5, and a carbon coating layer covering at least a portion of the surfaces of the granules, wherein the Li2CO3 content is more than 0.01 wt% and less than 1 wt%, the LiOH content is more than 0.001 wt% and less than 0.1 wt%, and the weight ratio of Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, is in the range of 1.00 to 10.00, based on the weight of the negative electrode active material particles.

[0029] High residual lithium levels affect the processability of slurries containing anode composite materials, making them prone to "jelly" during the process of preparing the slurry using the anode composite materials. Prior art studies have not clarified the effects of the distribution of lithium-containing compounds and the weight ratio of Li2SiO5 to Li2SiO3 (Li2SiO5 / Li2SiO3) on controlling residual lithium. Through extensive experiments, the inventors unexpectedly found that designing the distribution of lithium-containing compounds in the anode composite materials and adjusting the weight ratio of Li2SiO5 to Li2SiO3 (Li2SiO5 / Li2SiO3) not only controls the size of crystalline silicon, but also favors the control and optimization of residual lithium. This significantly reduces the amount of residual lithium, prevents the "jelly" state during the process of preparing the slurry using the anode composite materials, improves the processability of the slurry, and improves the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries. Therefore, the negative electrode composite material of the present invention can significantly reduce the amount of residual lithium, improve the processability of the slurry, and improve the initial coulombic efficiency and cycle characteristics of the lithium ion secondary battery.

[0030] In some embodiments of the present invention, the negative electrode composite material of the present invention has a Li2SiO3 content of more than 1.0 wt% and less than 48.0 wt%, based on the weight of the negative electrode active material particles. In the prior art, the control of the amount of water-soluble Li2SiO3 is unclear, and the effect of the amount of water-soluble Li2SiO3 on the electrochemical properties has not been thoroughly studied. The inventors unexpectedly found that by adjusting the Li2SiO3 content within the above range, a sufficiently prelithiated negative electrode composite material can be obtained, and the initial coulombic efficiency and cycle performance of the lithium-ion secondary battery can be improved.

[0031] In some embodiments of the present invention, the anode composite material of the present invention has a distribution of Li2SiO3 within the granules, decreasing from positions near the surface to the center of the granules, and Li2SiO2O5 is distributed closer to the center of the granules than Li2SiO3. The distribution of water-soluble Li2SiO3 and water-insoluble Li2SiO2O5 in the anode composite material is advantageous for controlling and optimizing the residual lithium content, significantly reducing the amount of residual lithium, improving slurry processability, and improving the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries. Figure 1 shows a schematic diagram of the structure of an anode composite material according to one embodiment of the present invention.

[0032] In some embodiments of the present invention, in the negative electrode composite material of the present invention, the carbon coating layer may be coated on the entire surface of the granule, thereby improving the electrical conductivity of the negative electrode composite material, increasing the first coulomb efficiency, more effectively reducing the amount of residual lithium, and improving the processability of the slurry.

[0033] The silicon oxide in the present application may be any silicon oxide commonly used in negative electrode materials in the field. In some embodiments of the present invention, the silicon oxide in the negative electrode composite material of the present invention is SiO x (0.5≦x≦1.6, preferably 0.8≦x≦1.2, most preferably x=1.0).

[0034] In some embodiments of the present invention, in the negative electrode composite material of the present invention, the silicon in the silicon oxide is present in the form of crystalline silicon having a size in the range of 5.0 nm to 12.0 nm, preferably 5.0 nm to 11.5 nm. By setting the size of the crystalline silicon within this range, it is possible to reduce the volume expansion of the negative electrode composite material, thereby obtaining excellent cycle characteristics, and it is possible to simultaneously reduce the amount of residual lithium in the negative electrode composite material and improve the cycle characteristics of the lithium-ion secondary battery.

[0035] In some embodiments of the present invention, in the anode composite material of the present invention, the intensity ratio I of the D peak to the G peak in the Raman spectrum of the anode composite material is D / I G is greater than 0.8 and less than 2.0, preferably greater than 1.5 and less than 1.8. D / I G By setting the value of the carbon coating layer within the above range, the conductivity of the carbon coating layer can be improved, and the lithium ion secondary battery can have excellent cycle characteristics. -1 ) and G band (~1580cm -1 ) peak intensity I D and I G are obtained by Raman spectroscopy. The Raman spectroscopic device used is, for example, a Renishaw Qontor model, and the wavenumber range used is, for example, 100 to 1800 cm -1 and the laser wavelength used is, for example, 532 nm.

[0036] In some embodiments of the present invention, the coating amount of the carbon coating layer in the negative electrode composite material of the present invention is in the range of 1 wt% to 30 wt%, preferably 3 wt% to 20 wt%, and more preferably 5 wt% to 10 wt%, based on the weight of the negative electrode active material particles. By setting the coating amount of the carbon coating layer in this range, a good balance can be achieved between the capacity of the material and the coating uniformity.

[0037] In another exemplary embodiment of the present invention, there is provided a method for producing an anode composite material, the method including: performing a carbon-coating process on a silicon oxide precursor using a carbon source to form a carbon-coated silicon oxide; mixing the carbon-coated silicon oxide with a lithium source to form a first mixture; performing a first heat treatment on the first mixture to form a calcined product; and then performing a second heat treatment on the calcined product to form a prelithiated product; and washing the prelithiated product to form the anode composite material.

[0038] The method for producing a negative electrode composite material of the present invention is advantageous in controlling and optimizing residual lithium, significantly reducing the amount of residual lithium, preventing the slurry from becoming "jelly" during the process of producing a slurry using the negative electrode composite material, improving the processability of the slurry, improving the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries, and inhibiting gas generation from the slurry. The negative electrode composite material obtained by the above method of the present invention has an extremely low amount of residual lithium, improves the processability of the slurry, and improves the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries.

[0039] Silicon oxide precursors in the present invention, such as SiO x(0.5≦x≦1.6) can be prepared by conventional methods in the art. In some embodiments of the present invention, the silicon oxide precursor can be prepared by the following process: silicon powder and silica of a predetermined particle size are mixed in a molar ratio of about 1.1:1, and then the mixture is vibrated in a vibrator for about 12 hours to achieve uniform mixing. Approximately 1 kg of the uniformly mixed material is pressed into a block. The block is then placed in a vacuum sublimation furnace and heated to a temperature of 1200°C to 1500°C, with a vacuum of 0 to 30 Pa, a heating time of 8 to 10 hours, and a temperature at the collection end of 400°C to 800°C to produce a silicon oxide precursor. The silicon oxide precursor is then crushed into millimeter-scale particles in a crusher. The millimeter-scale silicon oxide precursor is then crushed in a jet mill and classified into powders with different particle sizes using an air classifier. Finally, the powders with different particle sizes are blended according to size to finally obtain a silicon oxide precursor with the desired particle size.

[0040] In some embodiments of the present invention, in the method for producing the above-described negative electrode composite material, carbon is coated on the silicon oxide precursor by chemical vapor deposition using at least one of an alkane, an alkene, and an alkyne as a carbon source at a pressure of 50 Pa to 10,000 Pa and a temperature of 600° C. to 1,000° C. to form a carbon-coated silicon oxide. In some embodiments of the present invention, the carbon coating is performed in an apparatus such as a rotary kiln, a fixed bed, or a fluidized bed.

[0041] In some embodiments of the present invention, in the method for preparing the anode composite material, the washing process includes mixing the prelithiated product with water, alcohol, or acid to a solids content of preferably 5 wt% to 20 wt%, e.g., 5 wt% to 10 wt%, 10 wt% to 15 wt%, or 15 wt% to 20 wt%, to form a second mixture, ultrasonicating the second mixture, dispersing, suction filtering, and finally drying the filtered material. In the washing process, water dissolves alkaline substances such as Li2CO3, LiOH, or Li2SiO3; alcohol slightly dissolves LiOH; and acid neutralizes the alkali generated on the surface of the prelithiated product during washing. Ultrasonication can more reliably wash the prelithiated product, ensuring a good washing effect and improving the cycle performance of lithium-ion secondary batteries. The washing process significantly reduces the amount of residual lithium, prevents the slurry from becoming "jelly" during the process of manufacturing the slurry using the anode composite, improves the processability of the slurry, and further improves the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries. Because Li2SiO5 is insoluble in water and Li2SiO3 is soluble in water, the washing process can also be used to adjust the weight ratio of Li2SiO5 to Li2SiO3 (Li2SiO5 / Li2SiO3).

[0042] In some embodiments of the present invention, the prelithiated product produced, e.g., prelithiated SiO x (0.5≦x≦1.6) The material is mixed with water to a solids content of 5 wt% to 20 wt% to form a second mixture. The second mixture is ultrasonically treated at room temperature for 1 to 30 minutes, and then dispersed using a magnetic stirrer for 8 to 48 hours. It is then suction filtered, and pure water is poured onto the material on the filter paper and washed twice by suction filtration. Finally, the material after suction filtration is vacuum dried at 100°C to 120°C for 3 to 8 hours.

[0043] In some embodiments of the present invention, in the method for producing the negative electrode composite material, the acid is at least one selected from hydrochloric acid, citric acid, oxalic acid, phosphoric acid, sulfurous acid, acetic acid, chloric acid, hypochlorous acid, and boric acid to further neutralize the alkali generated on the surface of the prelithiated product during washing.

[0044] In some embodiments of the present invention, the prelithiated product produced, e.g., prelithiated SiO x The (0.5≦x≦1.6) material is mixed with at least one of hydrochloric acid, citric acid, oxalic acid, phosphoric acid, sulfurous acid, acetic acid, chloric acid, hypochlorous acid, and boric acid, such as 1 mol / L citric acid, to form a second mixture with a solid content of 5 wt% to 20 wt%. The second mixture is then ultrasonically treated at room temperature for 1 to 30 minutes, and then dispersed using a magnetic stirrer for 8 to 48 hours. The second mixture is then suction filtered, and pure water is poured onto the material on the filter paper and washed twice by suction filtration. Finally, the suction-filtered material is vacuum dried at 100°C to 120°C for 3 to 8 hours.

[0045] In some embodiments of the present invention, in the method for producing the negative electrode composite material, the weight ratio of the lithium source to the carbon-coated silicon oxide is in the range of 5:95 to 40:60. By setting the weight ratio of the lithium source to the carbon-coated silicon oxide in this range, sufficient prelithiation of the silicon oxide can be ensured, the amount of residual lithium can be reduced, and the initial coulombic efficiency and cycle characteristics of the lithium-ion secondary battery can be further improved. In some embodiments of the present invention, the lithium source can include any of a lithium ingot, lithium metal powder, and lithium foil.

[0046] In some embodiments of the present invention, in the method for producing the negative electrode composite material, the temperature of the first heat treatment is in the range of 400°C to 750°C, and the time of the first heat treatment is in the range of 1 hour to 5 hours. By setting the temperature and time of the first heat treatment in the above ranges, sufficient prelithiation of the silicon oxide can be ensured, the amount of residual lithium can be reduced, and the initial coulombic efficiency and cycle characteristics of the lithium ion secondary battery can be further improved.

[0047] In some embodiments of the present invention, in the method for producing the negative electrode composite material, the temperature of the second heat treatment is in the range of 800°C or higher and lower than 925°C, and the time of the second heat treatment is in the range of 1 hour to 6 hours. By setting the temperature and time of the second heat treatment in the above ranges, sufficient prelithiation of the silicon oxide can be ensured, and the size of the crystalline silicon can be prevented from being too large, thereby significantly reducing the amount of residual lithium and further improving the initial coulombic efficiency and cycle characteristics of the lithium ion secondary battery.

[0048] In some embodiments of the present invention, a lithium source and carbon-coated silicon oxide are pulverized and mixed in a weight ratio of 5:95 to 40:60 under the protection of an inert argon atmosphere to form a first mixture, which is then placed in a rotary kiln and calcined at 400°C to 750°C for 1 to 5 hours under an argon atmosphere to fully react the carbon-coated silicon oxide with lithium metal, followed by heat treatment at 800°C to 924°C for 1 to 6 hours, thereby adjusting the depth of prelithiation and the amount of lithium-containing silicate to obtain a prelithiation product.

[0049] In some embodiments of the present invention, in the method for preparing the negative electrode composite material, the ultrasonic treatment time is in the range of 1 minute to 30 minutes. By setting the ultrasonic treatment time in this range, the prelithiated product can be thoroughly washed, ensuring a good washing effect while avoiding damage to the granules of the prelithiated product.

[0050] In some embodiments of the present invention, in the method for producing the negative electrode composite material, the dispersion time may be set to a range of 8 to 48 hours, mainly taking into consideration energy consumption, time cost, and cleaning efficiency. If the dispersion time is too short, cleaning may be insufficient, while if the dispersion time is too long, energy consumption is high and time is required. By setting the dispersion time within the above range, not only can a good cleaning effect be ensured, but energy consumption and time cost can also be reduced.

[0051] In some embodiments of the present invention, in the method for producing the anode composite material, the carbon source includes at least one of an alkane, an alkene, and an alkyne, in order to better coat at least a portion of the surface of the silicon oxide with carbon and achieve a good coating effect.

[0052] In some embodiments of the present invention, in the method for preparing the negative electrode composite material, the alcohol may be at least one selected from ethanol, isopropanol, and butanol, thereby achieving better cleaning effects. The alcohol is preferably ethanol, which slightly dissolves LiOH. When using ethanol for cleaning, ethanol is easily volatile, which is advantageous for drying in the subsequent step. Ethanol typically contains water, which can dissolve alkaline substances such as Li2CO3, LiOH, and Li2SiO3. Ethanol with a concentration of 75% is typically used.

[0053] In some embodiments of the present invention, the prelithiated product produced, e.g., prelithiated SiO x(0.5≦x≦1.6) The material is mixed with at least one of ethanol, isopropanol, butanol, etc. to a solids content of 5 wt% to 20 wt% to form a second mixture. The second mixture is ultrasonically treated at room temperature for 1 to 30 minutes, and then dispersed using a magnetic stirrer for 8 to 48 hours. It is then suction filtered, and pure water is poured onto the material on the filter paper and washed twice by suction filtration. Finally, the material after suction filtration is vacuum dried at 100°C to 120°C for 3 to 8 hours.

[0054] In a further exemplary embodiment of the present invention, a lithium ion secondary battery negative electrode is provided that includes the aforementioned negative electrode composite material. Because the lithium ion secondary battery negative electrode of the present invention includes the aforementioned negative electrode composite material, the amount of residual lithium can be significantly reduced, the processability of the slurry can be improved, and the initial coulombic efficiency and cycle characteristics of the lithium ion secondary battery can be improved.

[0055] The negative electrode plate of the present invention can be prepared by a conventional method in the art. For example, the negative electrode composite material of the present invention, a conductive agent, and a binder are dispersed in water as a solvent to form a uniform negative electrode slurry. The negative electrode slurry is then applied to a negative electrode collector and baked to obtain a negative electrode plate. The conductive agent can be conductive carbon black, conductive graphite, vapor-grown carbon fiber, carbon nanotubes, or any combination thereof. The binder can be one or more of styrene butadiene rubber (SBR), polyacrylic acid (PAA), polyimide (PI), etc., with polyacrylic acid (PAA) binder being preferred.

[0056] In a further exemplary embodiment of the present invention, there is provided a lithium ion secondary battery comprising a positive electrode, a negative electrode, and a separator, wherein the negative electrode comprises the aforementioned negative electrode composite material. Because the lithium ion secondary battery of the present invention comprises the aforementioned negative electrode composite material, the amount of residual lithium can be significantly reduced, the processability of the slurry can be improved, and the initial coulombic efficiency and cycle characteristics of the lithium ion secondary battery can be improved.

[0057] The positive electrode of the present invention includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material. The positive electrode active material layer is formed on two surfaces of the positive electrode current collector. As the positive electrode current collector, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil can be used.

[0058] The positive electrode active material layer may contain one or more positive electrode materials capable of occluding and releasing lithium ions as the positive electrode active material, and may contain other materials, for example, a positive electrode binder and / or a positive electrode conductive agent, as required.

[0059] Preferably, the positive electrode material is a lithium-containing compound. Examples of such lithium-containing compounds include lithium-transition metal composite oxides, lithium-transition metal phosphate compounds, etc. The lithium-transition metal composite oxide is an oxide containing Li and one or more transition metal elements as constituent elements, and the lithium-transition metal phosphate compound is a phosphate compound containing Li and one or more transition metal elements as constituent elements. The transition metal element is preferably one or more of Co, Ni, Mn, Fe, etc.

[0060] Examples of the lithium-transition metal composite oxide may include, for example, LiCoO2 and LiNiO2. Examples of the lithium-transition metal phosphate compound may include, for example, LiFePO4 and LiFe 1-u Mn u PO4(0 < u < 1), etc.

[0061] The negative electrode of the present invention includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode composite material. The negative electrode active material layer is formed on two surfaces of the negative electrode current collector. As the negative electrode current collector, for example, a metal foil such as a copper (Cu) foil, a carbon-coated copper foil, a nickel foil, or a stainless steel foil can be used.

[0062] The separator of the present invention separates the positive and negative electrodes of a battery, allowing lithium ions to pass through while preventing current short-circuiting due to contact between the positive and negative electrodes. The separator is, for example, a porous film made of synthetic resin or ceramic, and may also be a laminated film made by laminating two or more types of porous films. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene.

[0063] In an embodiment of the present invention, when a lithium ion secondary battery is charged, for example, lithium ions are released from the positive electrode and inserted into the negative electrode via the electrolyte solution impregnated in the separator. When a lithium ion secondary battery is discharged, for example, lithium ions are released from the negative electrode and inserted into the positive electrode via the electrolyte solution impregnated in the separator.

[0064] The present application will now be described in more detail with reference to specific examples, which do not limit the scope of protection claimed by the present application.

[0065] Example 1 Manufacture of anode composite materials At a pressure of 50 Pa and a temperature of 920°C, methane was used as the carbon source to produce the silicon oxide precursor SiO x (x=1) Silicon oxide precursor SiO was deposited by chemical vapor deposition on the surface of 20 g of material. x (x=1) The material is carbon-coated, and the carbon-coated SiO x (x=1) 21 g of material was formed.

[0066] Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 20:80 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 500°C under an argon atmosphere for 3 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 850°C for 3 hours to form prelithiated SiO x The material was obtained.

[0067] Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 5 wt%, and mixed together. The second mixture was then ultrasonically treated at room temperature for 30 minutes, and then dispersed using a magnetic stirrer for 48 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the material after suction filtration was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material.

[0068] Manufacture of negative electrode pieces 4 g of the negative electrode composite material produced by the above process was weighed, and the negative electrode composite material, conductive carbon black Super-P as a conductive agent, and polyacrylic acid PAA as a binder were mixed in a mass ratio of 82:8:10 with an appropriate amount of deionized water by thorough stirring, and the solid content was adjusted to 42 wt % to form a uniform negative electrode slurry. Thereafter, the negative electrode slurry was applied to the surface of copper foil as a negative electrode collector and dried to obtain a negative electrode plate.

[0069] Battery assembly The produced negative electrode plate, separator, lithium sheet, gasket, and battery case were stacked in this order, 100 μl of electrolyte was poured into the battery, and the battery was sealed with a sealing machine to assemble the desired half-cell.

[0070] Example 2 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 15:85 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 450°C under an argon atmosphere for 3 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 900°C for 4 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO xThe material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 5 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 10 minutes, and then dispersed using a magnetic stirrer for 48 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0071] Example 3 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 10:90 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 600°C under an argon atmosphere for 2 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 920°C for 5 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 15 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 5 minutes, and then dispersed using a magnetic stirrer for 16 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0072] Example 4 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 5:95 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 400°C under an argon atmosphere for 1 hour to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 924°C for 6 hours to form prelithiated SiO xObtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 20 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 1 minute, and then dispersed using a magnetic stirrer for 8 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0073] Example 5 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 25:75 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 600°C under an argon atmosphere for 4 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 850°C for 2 hours to form prelithiated SiO x Other than obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 5 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 20 minutes, and then dispersed using a magnetic stirrer for 36 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0074] Example 6 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 30:70 to form a first mixture, which was then placed in a rotary kiln and calcined at 600°C under an argon atmosphere for 5 hours to form a carbon-coated SiO2. xThe material was allowed to react sufficiently with lithium metal, and then heat-treated at 820°C for 2 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 10 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 30 minutes, and then dispersed using a magnetic stirrer for 40 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0075] Example 7 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 40:60 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 750°C under an argon atmosphere for 5 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 800°C for 1 hour to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 5 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 30 minutes, and then dispersed using a magnetic stirrer for 48 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0076] Example 8 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x(x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 20:80 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 550°C under an argon atmosphere for 4 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 900°C for 5 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 10 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 10 minutes, and then dispersed using a magnetic stirrer for 24 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0077] Example 9 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 30:70 to form a first mixture, which was then placed in a rotary kiln and calcined at 600°C under an argon atmosphere for 5 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 820°C for 2 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 75% ethanol were placed in a beaker to form a second mixture with a solid content of 5 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 30 minutes, and then dispersed using a magnetic stirrer for 40 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0078] Example 10 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 30:70 to form a first mixture, which was then placed in a rotary kiln and calcined at 600°C under an argon atmosphere for 5 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 820°C for 2 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and pure water were placed in a beaker to form a second mixture with a solid content of 5 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 30 minutes, and then dispersed using a magnetic stirrer for 48 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0079] Comparative Example 1 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 50:50 to form a first mixture. The first mixture was then placed in a rotary kiln and calcined at 750°C under an argon atmosphere for 5 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 800°C for 1 hour to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 5 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 30 minutes, and then dispersed using a magnetic stirrer for 48 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0080] Comparative Example 2 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 40:60 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 750°C under an argon atmosphere for 5 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 800°C for 1 hour to form prelithiated SiO x Obtaining the materials, Prelithiated SiO x The material was prelithiated without any cleaning treatment. x A half cell was fabricated in the same manner as in Example 1, except that the material was used as the negative electrode composite.

[0081] Comparative Example 3 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 5:95 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 400°C under an argon atmosphere for 1 hour to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 1000°C for 6 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 20 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 1 minute, and then dispersed using a magnetic stirrer for 8 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0082] Comparative Example 4 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x(x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 5:95 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 350°C under an argon atmosphere for 1 hour to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 924°C for 6 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 20 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 1 minute, and then dispersed using a magnetic stirrer for 8 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0083] Comparative Example 5 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 30:70 to form a first mixture, which was then placed in a rotary kiln and calcined at 600°C under an argon atmosphere for 5 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 820°C for 2 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and pure water were placed in a beaker to form a second mixture with a solid content of 5 wt %, and mixed together. The second mixture was dispersed at room temperature for 48 hours using a magnetic stirrer, and then filtered with suction. Pure water was then poured onto the material on the filter paper, and the material was washed twice with suction filtration. Finally, the material after suction filtration was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0084] Comparative Example 6 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiOx (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 2:98 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 400°C under an argon atmosphere for 1 hour to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 924°C for 6 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 20 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 1 minute, and then dispersed using a magnetic stirrer for 8 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0085] Comparative Example 7 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 40:60 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 750°C under an argon atmosphere for 5 hours to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 800°C for 1 hour to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 5 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 40 minutes, and dispersed using a magnetic stirrer for 48 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0086] Comparative Example 8 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the material were crushed and mixed in a weight ratio of 5:95 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 400°C under an argon atmosphere for 0.5 hours to produce a carbon-coated SiO x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 924°C for 6 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 20 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 1 minute, and then dispersed using a magnetic stirrer for 8 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0087] Comparative Example 9 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the SiO2 material were crushed and mixed in a weight ratio of 5:95 to form a first mixture, and then the first mixture was placed in a rotary kiln and calcined at 400°C under an argon atmosphere for 1 hour to form a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 924°C for 7 hours to form prelithiated SiO x Other than obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were placed in a beaker to form a second mixture with a solid content of 20 wt %, and mixed together. The second mixture was then ultrasonically treated at room temperature for 1 minute, and then dispersed using a magnetic stirrer for 8 hours. The second mixture was then suction filtered, and pure water was poured onto the material on the filter paper, followed by two suction filtration washes. Finally, the suction filtered material was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material. A half-cell was fabricated in the same manner as in Example 1, except that:

[0088] Testing the physical properties of materials Tests were carried out on the negative electrode composite materials in Examples 1 to 10 and Comparative Examples 1 to 9. D / I G The results of the Li2CO3 content, LiOH content, Li2SiO3 content, weight ratio of Li2Si2O5 to Li2SiO3 Li2Si2O5 / Li2SiO3, and size of crystalline silicon were obtained.

[0089] The mass percentages of Li2Si2O5 and Li2SiO3 were calculated from the XRD (Druker Advanced D8) test results, and the weight ratio of Li2Si2O5 to Li2SiO3, Li2Si2O5 / Li2SiO3, was obtained.

[0090] The content of Li2SiO3 was calculated from the XRD pattern.

[0091] The size of the crystalline silicon was calculated from the XRD (Druker Advanced D8) test results (calculated from the half-width of the crystalline silicon peak in the XRD spectrum using the Scherrer formula).

[0092] XRD test conditions: 10~80°, 1° / min.

[0093] Neutralization titration method: The negative electrode composite material and pure water were placed in a beaker in a mass ratio of 1:9, mixed, and dispersed at room temperature using a magnetic stirrer for 1 hour. The dispersion was then left to stand for 1 hour and filtered. 10 mL of the resulting filtrate was automatically titrated with 0.2 M hydrochloric acid using an automatic acid-alkali titrator to determine the first endpoint (a mL) and the second endpoint (b mL).

[0094] (Number 1) Li2CO3 content = [pure water volume (g) / filtrate volume (g)] × 2 × (b / 1000) × (equivalent concentration of hydrochloric acid titration volume × coefficient) × (1 / 2) × (molar mass of Li2CO3) × [100 (%) / sample volume (g)]

[0095] (Number 2) LiOH content = [amount of pure water (g) / amount of filtrate (g)] × [(ab) / 1000] × (equivalent concentration of hydrochloric acid titration amount × coefficient) × (1 / 2) × (molar mass of LiOH) × [100 (%) / amount of sample (g)].

[0096] Battery performance testing Charge-discharge tests were conducted on the half-cells of Examples 1 to 10 and Comparative Examples 1 to 9 at 25°C and voltages of 0V to 1.5V. First, the half-cells of the above Examples and Comparative Examples were cycled once at 25°C with a 0.1C charge-discharge current (charge-discharge voltage range: 0V to 1.5V) to measure the initial discharge capacity and initial coulombic efficiency of the battery. Then, the battery was cycled 50 times at 1C with a 1C current (charge-discharge cutoff voltage: 0V to 1.5V) to determine the capacity retention rate of the battery after 50 cycles. Initial coulombic efficiency (%) = initial discharge capacity / initial charge capacity × 100%. The experimental results are shown in Table 1 and Figures 2 to 5.

[0097] As can be seen from Figure 2, the crystalline silicon size in the negative electrode composite material and the weight ratio of Li2Si2O5 to Li2SiO3 (Li2Si2O5 / Li2SiO3) show a linear relationship. As can be seen from Figure 3, the intensity ratio I of the D peak to the G peak in the Raman spectrum of the negative electrode composite material D / I G When the ratio is greater than 0.8 and less than 2.0, preferably greater than 1.5 and less than 1.8, excellent cycle characteristics were obtained. In Figures 4 and 5, the direction from bottom to top is from the surface to the interior. As can be seen from Figures 4 and 5, water-soluble Li2CO3 and LiOH are mostly present on the surface of the granules (in Example 2, the signals in the XPS spectrum of the surface are very weak due to the very small amount of Li2CO3 and LiOH), and Li2SiO3 is distributed within the granules, decreasing from positions near the surface to the center of the granules. Another water-insoluble lithium silicate (Li2SiO5) is distributed closer to the center of the granules than Li2SiO3.

[0098] [Table 1]

[0099] As can be seen from the above test results, the above embodiments of the present invention achieve the following technical effects:

[0100] A comparison of the results of Examples 1 to 10 and Comparative Examples 1 to 9 revealed that, compared to Comparative Examples 1 to 9 in which the Li2CO3 content, LiOH content, and weight ratio of Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, based on the weight of the negative electrode active material particles, were not all within the ranges of the present invention, the batteries in Examples 1 to 10 in which the Li2CO3 content was more than 0.01 wt% and less than 1 wt%, the LiOH content was more than 0.001 wt% and less than 0.1 wt%, and the weight ratio of Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, was in the range of 1.00 to 10.00, had higher initial coulombic efficiency and higher discharge capacity retention rate after 50 cycles.

[0101] A comparison of the results of Examples 1 to 10 with Comparative Example 9 revealed that, compared to Comparative Example 9 in which the weight ratio Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, and the Li2SiO3 content, based on the weight of the negative electrode active material particles, were both outside the ranges of the present invention, the batteries in Examples 1 to 10 in which the weight ratio Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, based on the weight of the negative electrode active material particles, was in the range of 1.00 to 10.00 and the Li2SiO3 content was more than 1.0 wt% and less than 48.0 wt% had higher initial coulombic efficiency and higher discharge capacity retention rate after 50 cycles.

[0102] The results of Examples 6, 9, and 10 demonstrate that the negative electrode composite material of the present invention can be obtained by the production method of the present invention, which includes acid washing, alcohol washing, or water washing, thereby significantly reducing the amount of residual lithium, improving the processability of the slurry, and improving the initial coulombic efficiency of the battery and the discharge capacity retention rate after 50 cycles.

[0103] Comparing the results of Example 7 and Comparative Example 1, it was found that when the weight ratio of the lithium source to the carbon-coated silicon oxide was in the range of 5:95 to 40:60, a negative electrode composite material with an appropriate Li2CO3 content, LiOH content, Li2SiO3 content, and weight ratio of Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, could be obtained, thereby significantly reducing the amount of residual lithium, improving the processability of the slurry, and increasing the initial coulombic efficiency of the battery and the discharge capacity retention rate after 50 cycles.

[0104] As a result of comparing the results of Example 7 and Comparative Example 2, it was found that the prelithiated SiO x By washing the material, it was found that anode composites with appropriate Li2CO3 content, LiOH content, Li2SiO3 content, and weight ratio of Li2Si2O5 to Li2SiO3, Li2Si2O5 / Li2SiO3, could be obtained, which significantly reduced the amount of residual lithium, improved the processability of the slurry, and increased the initial coulombic efficiency of the battery and the discharge capacity retention rate after 50 cycles.

[0105] A comparison of the results of Example 4 and Comparative Example 3 revealed that when the temperature of the second heat treatment was in the range of 800°C or higher and lower than 925°C, a negative electrode composite material with an appropriate LiOH content, Li2SiO3 content, and weight ratio of Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, could be obtained, thereby controlling the size of the crystalline silicon and preventing the crystalline silicon from being too large, significantly reducing the amount of residual lithium, improving the processability of the slurry, and increasing the initial coulombic efficiency of the battery and the discharge capacity retention rate after 50 cycles.

[0106] A comparison of the results of Example 4 and Comparative Example 4 revealed that when the temperature of the first heat treatment is in the range of 400°C to 750°C, a negative electrode composite material with an appropriate Li2CO3 content, LiOH content, Li2SiO3 content, and weight ratio of Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, can be obtained, thereby ensuring a good prelithiation effect and improving the initial coulombic efficiency of the battery and the discharge capacity retention rate after 50 cycles. If the temperature of the first heat treatment is too low, prelithiation may not be possible, and further, the initial coulombic efficiency of the battery may decrease.

[0107] A comparison of the results of Example 10 and Comparative Example 5 revealed that when the cleaning treatment included ultrasonic treatment of the second mixture, a negative electrode composite material with an appropriate LiOH content, Li2SiO3 content, and weight ratio of Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, could be obtained, thereby improving the initial coulombic efficiency of the battery and the discharge capacity retention rate after 50 cycles.

[0108] A comparison of the results of Example 4 and Comparative Example 6 revealed that when the weight ratio of the lithium source to the carbon-coated silicon oxide was in the range of 5:95 to 40:60, a negative electrode composite with an appropriate Li2CO3 content, LiOH content, Li2SiO3 content, and weight ratio of Li2SiO5 to Li2SiO3 (Li2SiO5 / Li2SiO3) was obtained, thereby ensuring a good prelithiation effect and improving the initial coulombic efficiency of the battery and the discharge capacity retention rate after 50 cycles. If the weight ratio of the lithium source to the carbon-coated silicon oxide was too low, prelithiation would not be possible, lithium silicate would not be obtained, and the initial coulombic efficiency of the battery would be reduced.

[0109] Comparing the results of Example 7 and Comparative Example 7, it was found that when the ultrasonic treatment time was in the range of 1 min to 30 min, a negative electrode composite material with an appropriate weight ratio of Li2Si2O5 to Li2SiO3, Li2Si2O5 / Li2SiO3, was obtained, which prevented the granules from collapsing and improved the initial coulombic efficiency of the battery and the discharge capacity retention rate after 50 cycles.

[0110] Comparing the results of Example 4 and Comparative Example 8, it was found that when the first heat treatment time is 1 to 5 hours, a negative electrode composite material with an appropriate Li2CO3 content, LiOH content, Li2SiO3 content, and weight ratio of Li2SiO5 to Li2SiO3, Li2SiO5 / Li2SiO3, can be obtained, thereby ensuring a good prelithiation effect and improving the initial coulombic efficiency of the battery and the discharge capacity retention rate after 50 cycles.

[0111] A comparison of the results of Example 4 and Comparative Example 9 revealed that when the second heat treatment time is in the range of 1 hour to 6 hours, a negative electrode composite material with an appropriate Li2SiO3 content and an appropriate weight ratio of Li2Si2O5 to Li2SiO3, Li2Si2O5 / Li2SiO3, can be obtained, thereby controlling the size of the crystalline silicon and preventing the crystalline silicon from being too large, thereby improving the initial coulombic efficiency of the battery and the discharge capacity retention rate after 50 cycles.

[0112] The above battery performance test results clearly show that the anode composite material, the method for manufacturing the anode composite material, and the anode and lithium ion secondary battery including the anode composite material of the present invention can significantly reduce the amount of residual lithium, improve the processability of the slurry, and enhance the initial coulombic efficiency and cycle characteristics of the lithium ion secondary battery.

[0113] The above is merely a preferred embodiment of the present invention, and is not intended to limit the present invention. Those skilled in the art can make various modifications and changes to the present invention. Any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and principles of the present invention shall be included in the patent scope of the present invention.

Claims

1. Negative electrode active material particles and Li on the surface of the negative electrode active material particles ２ CO ３ and LiOH, and the negative electrode active material particles include Silicon oxide, Li ２ SiO ３ and Li ２ Si ２ O ５ and granules comprising: a carbon coating layer coated on at least a portion of the surface of the granule; Li based on the weight of the negative electrode active material particles ２ CO ３ The content of LiOH is more than 0.001 wt% and less than 0.1 wt%, and Li ２ Si ２ O ５ and Li ２ SiO ３ Weight ratio of Li ２ Si ２ O ５ / Li ２ SiO ３ is in the range of 1.00 to 10.

00.

2. Li based on the weight of the negative electrode active material particles ２ SiO ３ 2. The negative electrode composite material according to claim 1, wherein the content of is more than 1.0 wt% and less than 48.0 wt%.

3. Li ２ SiO ３ is distributed in the granule so as to decrease from a position close to the surface of the granule toward the center of the granule, and Li ２ Si ２ O ５ Li ２ SiO ３ 2. The negative electrode composite material according to claim 1, wherein the granules are distributed closer to the center than the granules.

4. 2. The negative electrode composite material according to claim 1, wherein the carbon coating layer covers the entire surface of the granule.

5. The silicon oxide is SiO ｘ 2. The negative electrode composite material according to claim 1, wherein x is 0.5≦x≦1.

6.

6. 2. The negative electrode composite material according to claim 1, wherein the silicon in the silicon oxide is present in the form of crystalline silicon having a size ranging from 5.0 nm to 12.0 nm.

7. The intensity ratio I between the D peak and the G peak in the Raman spectrum of the negative electrode composite material Ｄ / I Ｇ 2. The negative electrode composite material according to claim 1, wherein the ρ is greater than 0.8 and less than 2.0, preferably greater than 1.5 and less than 1.

8.

8. 2. The negative electrode composite material according to claim 1, wherein the amount of the carbon coating layer is in the range of 1 wt % to 30 wt % based on the weight of the negative electrode active material particles.

9. A lithium ion secondary battery negative electrode comprising the negative electrode composite material according to any one of claims 1 to 8.

10. A lithium ion secondary battery including a positive electrode, a negative electrode, and a separator, A lithium ion secondary battery, wherein the negative electrode comprises the negative electrode composite material according to any one of claims 1 to 8.

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