Anode composite material, anode for lithium ion secondary battery, 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 and at least one lithium silicate selected from 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 wt% and less than 0.01wt %, and the content of LiOH is greater than 0 wt% and less than 0.01 wt%. 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 significantly improved, and the initial Coulombic efficiency and cycle characteristics of the lithium ion secondary battery can be improved.SELECTED DRAWING: Figure 2

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 manufacturing 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 support the energy supply of 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 widespread attention. Effective efforts have been made to improve the capacity and performance of lithium-ion secondary batteries. Lithium-ion secondary batteries have 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. While several types of negative electrode materials have been developed, silicon-based negative electrode materials are one type of negative electrode material with relatively high potential. 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, an anode including the anode composite material, and a lithium ion secondary battery, in order to solve the problems of the prior art, such as the excessively high residual lithium content of the anode material, difficulty in improving the processability of the slurry, and 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, there is provided a negative electrode active material comprising: negative electrode active material particles; and Li2CO3 and LiOH on the surfaces of the negative electrode active material particles, wherein the negative electrode active material particles are Granules containing silicon oxide and at least one lithium silicate selected from Li2SiO3 and Li2Si2O5; a carbon coating layer coated on at least a portion of the surface of the granule; Provided is a negative electrode composite material characterized in that, based on the weight of the negative electrode active material particles, the content of Li2CO3 is more than 0 wt% and less than 0.01 wt%, and the content of LiOH is more than 0 wt% and less than 0.01 wt%.

[0006] Furthermore, in the negative electrode composite material, the silicon oxide is SiO x (0.5≦x≦1.6).

[0007] 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.

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

[0009] 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; A method is provided in which the prelithiated product is washed and treated to form a negative electrode composite.

[0010] Furthermore, in the method for producing the negative electrode composite material, the washing treatment includes mixing the prelithiated product with water or acid, preferably to a solid content of 2 wt% to 10 wt%, to form a second mixture, ultrasonicating the second mixture to disperse it, then suction filtering, and finally drying the material after suction filtering.

[0011] 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.

[0012] 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 15:85.

[0013] Furthermore, in the method for producing the negative electrode composite material, the temperature of the first heat treatment is in the range of 500° C. to 750° C., and the time of the first heat treatment is in the range of 2 hours to 5 hours.

[0014] Furthermore, in the method for producing the negative electrode composite material, the temperature of the second heat treatment is in the range of 925°C to 1050°C, and the time of the second heat treatment is in the range of 3 hours to 6 hours.

[0015] Furthermore, in the method for producing the negative electrode composite material, the ultrasonic treatment time is in the range of 10 minutes to 30 minutes.

[0016] Furthermore, in the method for producing the negative electrode composite material, the dispersion time is in the range of 24 hours to 72 hours.

[0017] 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.

[0018] According to a further aspect of the present invention, there is provided a negative electrode for a lithium ion secondary battery comprising the aforementioned negative electrode composite material.

[0019] 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. [Effects of the Invention]

[0020] 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]

[0021] [Figure 1] 1 shows a photograph of the appearance of the negative electrode slurry in Comparative Example 4. [Figure 2] 1 shows Li 1s XPS (X-ray photoelectron spectrum) maps of the negative electrode composite materials in Examples 1 and 2, Comparative Examples 2 and 4. DETAILED DESCRIPTION OF THE INVENTION

[0022] 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.

[0023] 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. In response to the problems in 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 and at least one lithium silicate selected from Li2SiO3 and Li2SiO5, and a carbon coating layer coated on at least a portion of the surfaces of the granules, wherein the Li2CO3 content is greater than 0 wt% and less than 0.01 wt%, and the LiOH content is greater than 0 wt% and less than 0.01 wt%, based on the weight of the negative electrode active material particles.

[0024] A high residual lithium value affects the processability of a slurry containing a negative electrode composite material, making the slurry more likely to "jelly" during the process of producing the slurry using the negative electrode composite material. After extensive experiments, the inventors unexpectedly discovered that the present invention can significantly reduce the amount of residual lithium and produce a negative electrode composite material with an extremely low amount of residual lithium. The negative electrode composite material of the present invention has an extremely low amount of residual lithium, which effectively prevents the slurry from "jellying" during the process of producing the slurry using the negative electrode composite material, significantly improving the processability of the slurry and improving the initial coulombic efficiency and cycle characteristics of lithium-ion secondary batteries.

[0025] The silicon oxide according to the present application may be a silicon oxide generally used in the field for negative electrode materials. 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).

[0026] 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 is achieved between the capacity of the material and the coating uniformity.

[0027] 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, effectively reducing the amount of residual lithium, and improving the processability of the slurry.

[0028] In another exemplary embodiment of the present invention, a method for producing an anode composite material is provided, including the steps of: 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 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.

[0029] The method for producing a negative electrode composite material according to the present invention significantly reduces the amount of residual lithium, effectively prevents the slurry from becoming "jelly" during the process of producing a slurry using the negative electrode composite material, improves the processability of the slurry, and improves the initial coulombic efficiency and cycle performance of lithium ion secondary batteries, while also suppressing gas generation from the slurry. The negative electrode composite material obtained by the above method according to the present invention has an extremely low amount of residual lithium, significantly improves the processability of the slurry, and improves the initial coulombic efficiency and cycle performance of lithium ion secondary batteries.

[0030] 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 mass. The mass 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 mass silicon oxide precursor. The mass silicon oxide precursor is then placed in a crusher to be crushed to millimeter-scale particles. The millimeter-scale silicon oxide precursor is then placed in a jet mill to be crushed, and powders of different particle sizes are classified using an air classifier. Finally, the powders of different particle sizes are blended according to size to finally obtain a silicon oxide precursor of the desired particle size.

[0031] In some embodiments of the present invention, in the method for producing the above-described negative electrode composite material, the silicon oxide precursor is coated with carbon 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 carried out in an apparatus such as a rotary kiln, a fixed bed, or a fluidized bed.

[0032] In some embodiments of the present invention, in the method for preparing the above-described negative electrode composite material, the washing process includes mixing the prelithiated product with water or acid, preferably to a solids content of 2 wt% to 10 wt%, e.g., 2 wt% to 8 wt%, or 5 wt% to 10 wt%, to form a second mixture, ultrasonicating the second mixture, dispersing, suction filtering, and finally drying the filtered material. During the washing process, water can be used to dissolve alkaline substances such as Li2CO3 and LiOH, and acid can be used to neutralize the alkali generated on the surface of the prelithiated product during washing. Ultrasonication can clean the prelithiated product more thoroughly, ensuring a good washing effect and improving the cycle performance of lithium-ion secondary batteries. By performing cleaning treatments such as water washing and acid pickling, the amount of residual lithium can be significantly reduced to nearly zero, thereby effectively preventing the slurry from becoming "jelly" during the process of preparing a slurry using the anode composite material, significantly improving the processability of the slurry and further improving the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries. By maintaining the solids content within the above range, a sufficient amount of detergent can be used to clean a unit mass of pre-lithiated product, ensuring good cleaning results.

[0033] 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 2 wt% to 10 wt% to form a second mixture. The second mixture is ultrasonically treated at room temperature for 10 to 30 minutes, and then dispersed using a magnetic stirrer for 24 to 72 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 material after suction filtration is vacuum dried at 100°C to 120°C for 3 to 8 hours.

[0034] In some embodiments of the present invention, in the method for producing the above-described negative electrode composite material, the acid used to neutralize the alkali generated on the surface of the prelithiated product during washing 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.

[0035] 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 2 wt% to 10 wt%. The second mixture is then ultrasonically treated at room temperature for 10 to 30 minutes, and then dispersed using a magnetic stirrer for 24 to 72 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.

[0036] In some embodiments of the present invention, in the method for producing the above-mentioned 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 15:85. 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.

[0037] In some embodiments of the present invention, in the method for producing the above-mentioned negative electrode composite material, the temperature of the first heat treatment is in the range of 500°C to 750°C, and the time of the first heat treatment is in the range of 2 hours to 5 hours. By setting the temperature and time of the first heat treatment in the above ranges, it is possible to favor lithium diffusion in the solid-state reaction, ensure sufficient prelithiation of the silicon oxide, reduce the amount of residual lithium, and further improve the initial coulombic efficiency and cycle characteristics of the lithium-ion secondary battery.

[0038] In some embodiments of the present invention, in the method for producing the above-mentioned negative electrode composite material, the second heat treatment temperature is in the range of 925°C to 1050°C, and the second heat treatment time is in the range of 3 hours to 6 hours. Setting the second heat treatment temperature within this range is advantageous for the decomposition of Li2CO3 and LiOH (decomposition temperature is 924°C). The decomposition product Li2CO3 and LiOH, Li2O, begins to sublimate at temperatures above 1000°C, which is advantageous for significantly reducing the amount of residual lithium. Setting the temperature and time of the second heat treatment within this range ensures sufficient prelithiation of the silicon oxide, significantly reducing the amount of residual lithium, and further improving the initial coulombic efficiency and cycle characteristics of the lithium-ion secondary battery.

[0039] 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 15:85 under the protection of an inert argon atmosphere to form a first mixture, which is then placed in a rotary kiln and calcined at 500°C to 750°C for 2 to 5 hours under an argon atmosphere to fully react the carbon-coated silicon oxide with lithium metal, followed by heat treatment at 925°C to 1050°C for 3 to 6 hours to obtain a prelithiated product.

[0040] 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 10 to 30 minutes. By setting the ultrasonic treatment time in this range, it is possible to wash out the remaining lithium in the holes, to clean the prelithiated product more thoroughly, to ensure a good cleaning effect, and to avoid damage to the granules of the prelithiated product and to avoid affecting the particle size distribution.

[0041] In some embodiments of the present invention, in the method for producing the above-mentioned negative electrode composite material, the dispersion time may be controlled to a range of 24 to 72 hours, mainly taking into consideration energy consumption, time cost, and cleaning efficiency. If the dispersion time is too short, cleaning may not be performed properly, while if the dispersion time is too long, energy consumption and time cost are high. By controlling the dispersion time within the above range, not only can good cleaning efficiency be ensured, but energy consumption and time cost can also be reduced.

[0042] In some embodiments of the present invention, in the method for producing the above-mentioned negative electrode composite material, in order to coat at least a portion of the surface of the silicon oxide with carbon and achieve a good coating effect, the carbon source includes at least one of an alkane, an alkene, and an alkyne.

[0043] In a further exemplary embodiment of the present invention, a negative electrode for a lithium ion secondary battery is provided, which includes the above-described negative electrode composite material. Because the negative electrode for a lithium ion secondary battery of the present invention includes the above-described negative electrode composite material, the amount of residual lithium can be significantly reduced, the processability of the slurry can be significantly improved, and the initial coulombic efficiency and cycle characteristics of the lithium ion secondary battery can be improved.

[0044] The negative electrode sheet 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 dried in an oven to obtain a negative electrode sheet. 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.

[0045] 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 significantly improved, and the initial coulombic efficiency and cycle characteristics of the lithium ion secondary battery can be improved.

[0046] The positive electrode of the present invention includes a positive electrode 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 collector. The positive electrode collector can be made of a metal foil such as aluminum foil, nickel foil, or stainless steel foil.

[0047] The positive electrode active material layer may contain, as a positive electrode active material, one or more positive electrode materials capable of absorbing and releasing lithium ions, and may also contain other materials, such as a positive electrode binder and / or a positive electrode conductive agent, as necessary.

[0048] 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, and the like. 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, and the like.

[0049] Examples of the lithium-transition metal composite oxide may include, for example, LiCoO2, LiNiO2, and the like. Examples of the lithium-transition metal phosphate compound may include, for example, LiFePO4, LiFe 1-u Mn u PO4 (0 < u < 1), and the like.

[0050] 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, metal foils such as copper (Cu) foil, carbon-coated copper foil, nickel foil, and stainless steel foil can be used.

[0051] The separator of the present invention is for separating the positive electrode and the negative electrode of the battery, and can allow lithium ions to pass through and prevent a current short circuit due to contact between the positive electrode and the negative electrode. The separator is, for example, a porous membrane formed of a synthetic resin or a ceramic, or may be a laminated membrane in which two or more types of porous membranes are laminated. Examples of the synthetic resin include, for example, polytetrafluoroethylene, polypropylene, and polyethylene.

[0052] In an embodiment of the present invention, when charging the lithium-ion secondary battery, for example, lithium ions are released from the positive electrode and inserted into the negative electrode through the electrolytic solution immersed in the separator. When discharging the lithium-ion secondary battery, for example, lithium ions are released from the negative electrode and inserted into the positive electrode through the electrolytic solution immersed in the separator.

[0053] 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.

[0054] Example 1 Manufacture of anode composite materials At a pressure of 50 Pa and a temperature of 920 °C, 20 g of silicon oxide precursor SiO was dissolved in methane as the carbon source. x (x=1) Silicon oxide precursor SiO x (x=1) The material was carbon-coated, and 21 g of carbon-coated SiO x (x=1) material was formed.

[0055] Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the material were ground and mixed in a weight ratio of 10:90 to form a first mixture, which was then placed in a rotary kiln and calcined at 550°C for 3 hours under an argon atmosphere to produce a carbon-coated SiO x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 925°C for 3 hours to form prelithiated SiO x The material was obtained.

[0056] 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 8 wt%, and mixed together. The second mixture was first ultrasonicated at room temperature for 20 minutes, then dispersed using a magnetic stirrer for 48 hours, and then suction filtered. Pure water was then poured onto the material on the filter paper, and the material was washed twice by suction filtering. Finally, the material after suction filtering was vacuum dried at 120°C for 8 hours to obtain a negative electrode composite material.

[0057] Manufacture of negative electrode sheets 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, which was the negative electrode collector, and dried to obtain a negative electrode sheet.

[0058] Battery assembly The produced negative electrode sheet, 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.

[0059] Example 2 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the powder were ground and mixed in a weight ratio of 15:85 to form a first mixture, which was then placed in a rotary kiln and calcined at 600°C for 4 hours under an argon atmosphere to produce a carbon-coated SiO x The material was fully reacted with lithium metal, and then heat-treated at 1000°C for 4 hours to form prelithiated SiO x Obtaining the materials, Produced prelithiated SiO x The material and 1 mol / L hydrochloric acid were mixed in a beaker to form a second mixture with a solid content of 5 wt %. The second mixture was first ultrasonicated at room temperature for 15 minutes, then dispersed using a magnetic stirrer for 36 hours, and then suction filtered. Pure water was then poured onto the material on the filter paper, and the material was washed twice by suction filtering. Finally, the material after suction filtering 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:

[0060] Example 3 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x(x=1) material and the material were ground and mixed in a weight ratio of 5:95 to form a first mixture, which was then placed in a rotary kiln and calcined at 500°C for 2 hours under an argon atmosphere to produce a carbon-coated SiO x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 1050°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 2 wt %, and mixed together. The second mixture was first ultrasonicated at room temperature for 30 minutes, then dispersed using a magnetic stirrer for 72 hours, and then suction filtered. After that, pure water was poured onto the material on the filter paper, and the material was washed twice by suction filtering. Finally, the material after suction filtering 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:

[0061] 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 ground and mixed in a weight ratio of 15:85 to form a first mixture, which was then placed in a rotary kiln and calcined at 750°C for 5 hours under an argon atmosphere to produce a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 1025°C for 4 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:

[0062] Example 5 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the material were ground 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 650 °C for 2 h under an argon atmosphere to obtain a carbon-coated SiO x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 1050°C for 6 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 2 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 72 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:

[0063] 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 ground and mixed in a weight ratio of 15:85 to form a first mixture, which was then placed in a rotary kiln and calcined at 750°C for 5 hours under an argon atmosphere to produce a carbon-coated SiO2. x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 775°C for 4 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:

[0064] Comparative Example 2 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the powder were ground and mixed in a weight ratio of 2:98 to form a first mixture, which was then placed in a rotary kiln and calcined at 400°C for 2 hours under an argon atmosphere to produce a carbon-coated SiO x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 950°C for 7 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 10 minutes, 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:

[0065] Comparative Example 3 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the powder were ground and mixed in a weight ratio of 15:85 to form a first mixture, which was then placed in a rotary kiln and calcined at 600°C for 4 hours under an argon atmosphere to produce a carbon-coated SiO x The material was fully reacted with lithium metal, and then heat-treated at 1000°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 dispersed at room temperature for 36 hours using a magnetic stirrer, and then suction filtered. After that, pure water was poured onto the material on the filter paper, and the material was washed twice by suction filtering. Finally, the material after suction filtering 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:

[0066] Comparative Example 4 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the material were ground and mixed in a weight ratio of 10:90 to form a first mixture, which was then placed in a rotary kiln and calcined at 550°C for 3 hours under an argon atmosphere to produce a carbon-coated SiO x The material was allowed to react sufficiently with lithium metal, and then heat-treated at 925°C for 3 hours to form prelithiated SiO x Obtaining the materials, Prelithiated SiO x The material was prelithiated without any cleaning treatment. x A half cell was produced in the same manner as in Example 1, except that the material was used as it was for the negative electrode composite material.

[0067] Comparative Example 5 Under the protection of an inert argon atmosphere, a lithium ingot and carbon-coated SiO x (x=1) material and the powder were ground 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 for 5 hours under an argon atmosphere to produce a carbon-coated SiO 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 xThe 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:

[0068] Testing the physical properties of materials Tests were carried out on the negative electrode composite materials in Examples 1 to 5 and Comparative Examples 1 to 5, and the results of the Li2CO3 content and LiOH content were obtained.

[0069] Neutralization titration method: The negative electrode composite material and pure water were weighed into 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).

[0070] 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)] 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)].

[0071] Battery characteristics test Charge-discharge tests were conducted on the half-cells of Examples 1 to 5 and Comparative Examples 1 to 5 at a voltage of 0V to 1.5V in a 25°C environment. First, the half-cells of the above Examples and Comparative Examples were cycled once at a charge-discharge current of 0.1C (the charge-discharge voltage range was 0V to 1.5V) in a 25°C environment to measure the initial discharge capacity and initial coulombic efficiency of the battery. Then, the battery was cycled 50 times at a 1C current (the charge-discharge cutoff voltage was 0V to 1.5V) to obtain 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 1 and 2 below.

[0072] [Table 1]

[0073] As can be seen from the above test results, the above embodiments of the present invention have achieved the following technical effects:

[0074] A comparison of the results of Examples 1 to 5 with Comparative Examples 1 to 5 revealed that, compared to Comparative Examples 1 to 5 in which the Li2CO3 content and LiOH content relative to the weight of the negative electrode active material particles were outside the ranges of the present invention, the batteries in Examples 1 to 5 in which the Li2CO3 content relative to the weight of the negative electrode active material particles was more than 0 wt% and less than 0.01 wt% and the LiOH content was more than 0 wt% and less than 0.01 wt% had higher initial coulombic efficiency and higher discharge capacity retention rate after 50 cycles.

[0075] FIG. 2 shows Li 1s XPS (X-ray photoelectron spectroscopy) maps of the anode composite materials in Examples 1 and 2, Comparative Example 2, and Comparative Example 4. The XPS maps show a comparison of the amounts of lithium carbonate Li2CO3, which is one of the components of residual lithium, in the anode composite materials in Examples 1 and 2, Comparative Example 2, and Comparative Example 4. FIG. 2 reveals that there is no Li2CO3 peak in the XPS maps of the anode composite materials in Examples 1 and 2. This indicates that the amount of Li2CO3 in the anode composite materials in Examples 1 and 2 does not reach the amount required for XPS testing.

[0076] As a result of comparing the results of Example 1 and Comparative Example 4, it was found that the prelithiated SiO x By washing the material, a negative electrode composite material with extremely low Li2CO3 and LiOH contents was obtained, which significantly reduced the amount of residual lithium, significantly improved the processability of the slurry, and improved the battery's initial discharge capacity, initial coulombic efficiency, and discharge capacity retention rate after 50 cycles. Figure 1 shows a photograph of the appearance of the negative electrode slurry in Comparative Example 4. Figure 1 shows that the high amount of residual lithium in the negative electrode composite material in Comparative Example 4 caused the negative electrode slurry to gel.

[0077] Comparing the results of Example 2 and Comparative Example 3, it was found that when the cleaning treatment included ultrasonic treatment of the second mixture, a negative electrode composite material with an extremely low Li2CO3 content and an extremely low LiOH content was obtained, thereby reducing the amount of residual lithium, significantly improving the processability of the slurry, and improving the first discharge capacity, first coulombic efficiency, and discharge capacity retention rate after 50 cycles of the battery.

[0078] Comparing the results of Example 4 and Comparative Example 1, it was found that when the temperature of the second heat treatment was in the range of 925°C to 1050°C, a negative electrode composite material having an extremely low Li2CO3 content and an extremely low LiOH content was obtained, thereby reducing the amount of residual lithium, significantly improving the processability of the slurry, and improving the initial discharge capacity, initial coulombic efficiency, and discharge capacity retention rate after 50 cycles of the battery.

[0079] As can be seen from the above battery performance test results, the anode composite material, the method for manufacturing the anode composite material, and the anode and lithium ion secondary battery comprising the anode composite material according to the present invention can significantly reduce the amount of residual lithium, significantly improve the processability of the slurry, and improve the initial coulombic efficiency and cycle performance of the lithium ion secondary battery.

[0080] The above is only 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 principle of the present invention should 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 and Li ２ SiO ３ and Li ２ Si ２ O ５ Granules containing at least one lithium silicate selected from the group consisting of: 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 and the content of LiOH is more than 0 wt % and less than 0.01 wt %.

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

6.

3. 3. 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.

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

5. A negative electrode for a lithium ion secondary battery, comprising the negative electrode composite material according to claim 1 or 2.

6. 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 claim 1 or 2.

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