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

Abstract

To provide a negative electrode material, a manufacturing method thereof, and a lithium ion battery.SOLUTION: A negative electrode material includes a carbon material and a nanosilicon-based material dispersed in the carbon material, and contains elemental fluorine, and when the total mass content of elemental fluorine contained in the negative electrode material is A0 ppm, and the mass content of elemental fluorine contained inside the nanosilicon-based material in the negative electrode material is A1 ppm, A0 and A1 satisfy A0-2A1≥30 ppm. The negative electrode material, the manufacturing method thereof, and the lithium ion battery according to the present application are advantageous in reducing the volume expansion of the negative electrode material and maintaining the structural integrity of the negative electrode material during charge and discharge cycles, and thus in improving cycle characteristics.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present application relates to the technical field of anode materials, and more particularly to anode materials and methods for producing the same, and lithium ion batteries. [Background technology]

[0002] Conventional lithium-ion batteries have advantages such as high energy density, high power output, long cycle life, and minimal environmental pollution, making them widely used in electric vehicles and consumer electronics. There is a clear trend toward developing lithium-ion batteries with higher energy densities. The cathode and anode materials are key to determining the battery's operating efficiency. Currently, the only anode material in practical use is graphite, whose capacity is already close to its theoretical limit, limiting further improvement. Therefore, there is a strong demand for the development of next-generation anode materials with high energy density.

[0003] Silicon-based anode materials are considered as next-generation battery anode materials due to their advantages of high capacity, abundant supply, and relative safety. However, silicon-based anode materials suffer from a severe volume expansion phenomenon during cycling, which causes the materials to pulverize, shatter, and rapidly decay with cycling. Multiple solutions have been proposed to address this issue, including structural engineering of silicon through technological means such as nanosizing and porousization, and improving the performance through composite coatings.

[0004] However, conventional silicon-carbon anode materials undergo large volume changes during charge and discharge, which leads to capacity fading and deterioration of cycle characteristics. Summary of the Invention [Problem to be solved by the invention]

[0005] The present application provides a negative electrode material that can effectively suppress volume expansion of the negative electrode material and improve battery cycle characteristics, a method for manufacturing the same, and a lithium-ion battery, and the manufacturing method can reduce manufacturing costs. [Means for solving the problem]

[0006] In a first aspect, there is provided a negative electrode material comprising: the negative electrode material has aggregates containing a carbon material and a nanosilicon-based material dispersed in the carbon material, and contains elemental fluorine; When the total mass content of the fluorine element contained in the negative electrode material is A0 ppm and the mass content of the fluorine element contained inside the nanosilicon-based material in the negative electrode material is A1 ppm, A0 and A1 provide a negative electrode material that satisfies the following formula: A0-2A1≧30ppm

[0007] In one embodiment, when the total mass content of the fluorine element contained in the negative electrode material is A0 ppm, the range of values ​​that A0 can take is 100 to 10,000. In one embodiment, the average particle size D of the nanosilicon based material 50 is 1 nm to 500 nm. In one embodiment, the content of the nanosilicon-based material in the negative electrode material is 10% by mass to 80% by mass. In one embodiment, the nanosilicon-based material comprises at least one selected from the group consisting of elemental silicon, silicon alloys, and silicon-oxygen-containing materials. In one embodiment, the content of the carbon material in the negative electrode material is 10% by mass to 50% by mass. In one embodiment, the carbon material comprises at least one selected from the group consisting of hard carbon and soft carbon. In one embodiment, the negative electrode material has a particle crush strength of 300 MPa or more. In one embodiment, the negative electrode material further comprises a coating layer present on at least a portion of the surface of the nanosilicon based material. In one embodiment, the coating layer comprises amorphous carbon and a lithium salt dispersed within the amorphous carbon.

[0008] In one embodiment, the lithium salt comprises at least one selected from the group consisting of lithium hydroxide, lithium chloride, lithium carbonate, lithium fluoride, lithium oxide, lithium borohydride, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide. In one embodiment, the coating layer has a thickness of 1 nm to 3000 nm. In one embodiment, the median diameter of the negative electrode material is 0.5 μm to 30 μm. In one embodiment, the specific surface area of ​​the negative electrode material is 5 m 2 / g or more.

[0009] In a second aspect, there is provided a method for producing a negative electrode material, comprising: The negative electrode material is Producing a first precursor comprising a nanosilicon based material; producing a second precursor comprising the first precursor and a carbon source; and carbonizing the second precursor to obtain a negative electrode material, the first precursor and / or the second precursor contains a fluorine-containing compound, The negative electrode material contains elemental fluorine, and when the total mass content of the elemental fluorine contained in the negative electrode material is A0 ppm and the mass content of the elemental fluorine contained inside the nanosilicon-based material in the negative electrode material is A1 ppm, A0 and A1 satisfy the following formula: A0-2A1≧30ppm

[0010] In some embodiments, the fluorine-containing compound includes at least one selected from the group consisting of calcium fluoride, cryolite, aluminum fluoride, sodium fluoride, sodium silicofluoride, magnesium fluoride, potassium fluoride, lithium fluoride, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium difluoro(oxalato)borate, fluoroethylene carbonate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0011] In some embodiments, at least one of the first precursor, the second precursor, and the nano silicon based material comprises a lithium salt.

[0012] In some embodiments, at least one of the first precursor, the second precursor, and the nanosilicon-based material comprises a lithium salt, and the lithium salt comprises at least one selected from the group consisting of lithium hydroxide, lithium chloride, lithium carbonate, lithium fluoride, lithium oxide, lithium borohydride, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide. In some embodiments, the average particle size D of the nanosilicon based material 50 is 1 nm to 500 nm.

[0013] In some embodiments, the method further comprises, prior to the step of producing the first precursor, wet-milling and drying a mixture comprising a silicon-based material and a solvent to obtain a nano silicon-based material. In some embodiments, the step of producing the first precursor includes wet-grinding a mixture containing a silicon-based material, a fluorine-containing compound, and a solvent, and drying the mixture to obtain the first precursor. In some embodiments, the step of producing the first precursor includes wet-grinding a mixture containing a silicon-based material, a fluorine-containing compound, and a solvent, and drying the mixture to obtain a first precursor, and the content of the fluorine-containing compound added to the first precursor is 0.01% by mass to 3.00% by mass.

[0014] In some embodiments, the step of producing the first precursor includes mixing the nanosilicon-based material, the fluorine-containing compound, and a solvent, and then removing the solvent to obtain the first precursor. In some embodiments, the nanosilicon-based material comprises at least one selected from the group consisting of elemental silicon, silicon alloys, and silicon-oxygen-containing materials. In some embodiments, the solvent comprises an organic solvent. In some embodiments, the organic solvent comprises at least one selected from the group consisting of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, pentanol, trifluoroethanol, and trifluoromethanol. In some embodiments, the mixing method includes at least one selected from the group consisting of mechanical stirring, ultrasonic dispersion, and abrasive dispersion. In some embodiments, the step of producing the first precursor comprises mixing a nanosilicon-based material, a fluorine-containing compound and a solvent, followed by drying to obtain the first precursor.

[0015] In some embodiments, the drying temperature is 40°C to 600°C. In some embodiments, the drying time is 1 hour to 15 hours. In some embodiments, the drying process comprises at least one of spray drying and freeze drying. In some embodiments, the content of the lithium salt added to the first precursor is 0.05% by mass to 1% by mass. In some embodiments, the step of producing the second precursor includes mixing the first precursor, a carbon source, and a fluorine-containing compound, and then obtaining the second precursor.

[0016] In some embodiments, the mass ratio of the first precursor to the carbon source is 100:(10 to 100). In some embodiments, the carbon source comprises at least one selected from the group consisting of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt. In some embodiments, the content of the fluorine-containing compound added to the second precursor is 0.05% by mass to 3.00% by mass. In some embodiments, the content of the lithium salt added to the second precursor is 0.01% by mass to 0.1% by mass. In some embodiments, the carbonization temperature is 600°C to 1200°C. In some embodiments, the carbonization treatment time is 1 hour to 10 hours. In some embodiments, the temperature rise rate in the carbonization treatment is 1° C. / min to 30° C. / min. In some embodiments, a protective gas is passed through during the carbonization treatment, and the protective gas includes at least one selected from the group consisting of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas.

[0017] In a third aspect, there is provided a lithium ion battery including the above-mentioned negative electrode material or a negative electrode material produced by the above-mentioned production method. [Effects of the Invention]

[0018] The technical solution of the present application can achieve at least the following beneficial effects: The negative electrode material according to the present application comprises a carbon material and a nanosilicon-based material dispersed in the carbon material, and contains elemental fluorine. When the total mass content of the elemental fluorine contained in the negative electrode material is A0 ppm and the mass content of the elemental fluorine contained inside the nanosilicon-based material in the negative electrode material is A1 ppm, by controlling the mass content of the elemental fluorine in the nanosilicon-based material to satisfy A0-2A1≧30 ppm, it is possible to ensure that the mass content of the elemental fluorine in the nanosilicon-based material is smaller than the mass content in negative electrode materials other than the nanosilicon-based material, and that more elemental fluorine is present in the negative electrode materials other than the nanosilicon-based material. Since fluorine, which has strong electronegativity, can be reduced at a low reduction potential, the content of fluorine inside the nanosilicon-based material is smaller than the mass content in the negative electrode material other than the nanosilicon-based material. This concentration gradient allows the fluorine in the negative electrode material other than the nanosilicon-based material to be preferentially involved in the formation of a solid electrolyte film on the surface of the negative electrode material during charging and discharging, optimizing the solid electrolyte film, reducing the reaction activity between the negative electrode material and the electrolyte, protecting the negative electrode material, and reducing the occurrence of side reactions, thereby improving the cycle characteristics of the negative electrode material, especially the long-term cycle characteristics, and preventing the formation of a solid electrolyte film inside the particles of the negative electrode material, thereby improving the specific capacity of the material.

[0019] The method for producing a negative electrode material according to the present application involves first producing a first precursor containing a nanosilicon-based material, and then carbonizing the first precursor and a second precursor containing a carbon source to produce a negative electrode material, wherein a fluorine-containing compound is added to the first precursor and / or the second precursor so that the majority of elemental fluorine is located in the negative electrode material other than the nanosilicon-based material, and A0 and A1 satisfy the relationship A0-2A1≧30 ppm. By controlling the content within the above range, it is possible to ensure that the mass content of elemental fluorine in the nanosilicon-based material is smaller than the mass content in the negative electrode material other than the nanosilicon-based material, and that a greater amount of elemental fluorine is present in the negative electrode material other than the nanosilicon-based material.

[0003] The present invention relates to a method for manufacturing a negative electrode material, and a method for manufacturing the same. ... [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a flowchart of a method for producing a negative electrode material according to an embodiment of the present invention. [Figure 2] 1 is a scanning electron microscope (SEM) photograph of the negative electrode material prepared in Example 1 of the present invention. [Figure 3] 1 is an X-ray diffraction pattern of the negative electrode material prepared in Example 1 of the present invention. [Figure 4] 1 shows the initial charge-discharge curve of the negative electrode material prepared in Example 1 of the present invention. [Figure 5] 1 shows the cycle characteristic curve of the negative electrode material prepared in Example 1 of the present invention. [Figure 6] 1 is a scanning transmission electron microscope (SEM-EDX) image of the negative electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0021] The following are preferred embodiments of the present invention, and those skilled in the art will recognize that some improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications are also within the scope of protection of the present invention.

[0022] An anode material according to one embodiment includes a carbon material and a nanosilicon-based material dispersed in the carbon material, the anode material containing elemental fluorine, When the total mass content of the fluorine element contained in the negative electrode material is A0 ppm and the mass content of the fluorine element contained inside the nanosilicon-based material in the negative electrode material is A1 ppm, A0 and A1 satisfy the following formula. A0-2A1≧30ppm

[0023] The mass content of the fluorine element is measured by the following measurement method. The total mass content of fluorine element in the negative electrode material is measured by ion chromatography, atomic absorption spectrometry, elemental analysis, or inductively coupled plasma atomic emission spectrometry, A0 ppm; The negative electrode material is then immersed in an 8 mol / L sodium hydroxide solution until the silicon-based material is removed. The remaining material is washed with deionized water and then dried to obtain a composite from which the silicon-based material has been removed. The mass content of fluorine element A2 ppm in the composite from which the silicon has been removed is measured using ion chromatography, atomic absorption spectroscopy, elemental analysis, or inductively coupled plasma atomic emission spectroscopy. By calculation, the mass content of the fluorine element contained inside the nanosilicon in the negative electrode material is A1 ppm. A2-A1=A0-A1-A1=A0-2A1

[0024] The negative electrode material of this embodiment includes a carbon material and a nanosilicon-based material dispersed therein. By controlling the content of fluorine in the nanosilicon-based material to satisfy A0-2A1≧30 ppm, the fluorine content in the nanosilicon-based material is lower than that in the other negative electrode materials, ensuring a higher fluorine content in the other negative electrode materials. Because fluorine has a strong electronegativity and can be reduced at a low reduction potential, the fluorine content in the nanosilicon-based material is lower than that in the other negative electrode materials. This concentration gradient allows the fluorine in the other negative electrode materials to preferentially participate in the formation of a solid electrolyte film on the surface of the negative electrode material during charging and discharging. This optimizes the solid electrolyte film, reduces the reactivity between the negative electrode material and the electrolyte, protects the negative electrode material, and reduces the occurrence of side reactions, thereby improving the cycle performance, particularly the long-term cycle performance, of the negative electrode material. This also reduces the formation of a solid electrolyte film within the particles of the negative electrode material, thereby improving the specific capacity of the material.

[0025] In some embodiments, the carbon material includes at least one selected from the group consisting of hard carbon and soft carbon. Examples of soft carbon include amorphous carbon and porous carbon. Examples of hard carbon include, but are not limited to, activated carbon for capacitors and activated carbon. The nanosilicon-based material is located on the surface of the carbon material, between particles of the carbon material, or embedded within the carbon material. When the carbon material is porous carbon, the nanosilicon-based material may be located within the pores of the porous carbon. In some embodiments, 30 ppm ≤ A0 - 2A1 ≤ 7000 ppm. Specifically, the value of "A0 - 2A1" may be, for example, 30 ppm, 50 ppm, 100 ppm, 150 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm, 6000 ppm, or 7000 ppm, etc., and is not limited thereto. Preferably, 100 ppm ≤ A0 - 2A1 ≤ 1000 ppm. When controlled within the above range, the content of fluorine element on the surface of the nano-silicon-based material is low, indicating that most of the fluorine element exists in the anode material other than the nano-silicon-based material. Thereby, a solid electrolyte film is formed on the surface of the anode material particles, which further contributes to the further optimization of the cycle retention rate of the anode material.

[0026] In one embodiment, when the total mass content of the fluorine element contained in the anode material is A0 ppm, the range of possible values of A0 is 100 to 10000, specifically, it may be 100, 200, 500, 1000, 2000, 5000, 8000, 9000, or 10000, etc., and of course, other values within the above range are also possible and are not limited thereto. Specifically, the total mass content of the fluorine element in the anode material can be measured by ion chromatography, atomic absorption spectrometry, elemental analysis, or inductively coupled plasma optical emission spectrometry.

[0027] In some embodiments, the nano-silicon-based material includes at least one selected from the group consisting of elemental silicon, silicon-oxygen-containing materials, and silicon alloys. Examples of the silicon alloy include silicon-lithium alloy, silicon-magnesium alloy, etc. The silicon-oxygen-containing material may be a silicon-oxygen composite in which the molar ratio of silicon atoms to oxygen atoms is in the range of 0.1 to 1.9. The silicon-oxygen composite may be a composite of Si and SiO2, a substance containing SiO represented by the general formula (0 < x < 2), or a silicate-based substance. x (0 < x < 2), or a silicate-based substance.

[0028] In some embodiments, the average particle size D of the nano-silicon-based material 50is 1 nm to 500 nm. Specifically, it may be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm, and of course, it may be other values ​​within the above range, but is not limited to these. Nanosilicon-based materials have high structural stability and can suppress volume expansion. By controlling the average particle diameter of the nanosilicon-based material within the above range, it is possible to reduce aggregation of the nanosilicon-based material during charge and discharge, and reduce production costs. Preferably, the average particle diameter D of the nanosilicon-based material is 50 The thickness is 1 nm to 200 nm, and more preferably 1 nm to 100 nm.

[0029] In some embodiments, the particles of the negative electrode material have a fracture strength of 300 MPa or more. The fracture strength of the particles of the negative electrode material may be, but is not limited to, 300 MPa, 310 MPa, 320 MPa, 350 MPa, 380 MPa, 390 MPa, 400 MPa, 450 MPa, 480 MPa, or 500 MPa, and may also be other values ​​within the above range. Because of its strong rigidity, the particle structure is highly stable and can resist a certain volume expansion stress, thereby reducing expansion and improving the cycle stability of the battery.

[0030] In some embodiments, the content of the nanosilicon-based material in the negative electrode material is 10% by mass to 80% by mass, and specifically may be, but is not limited to, 10% by mass, 20% by mass, 30% by mass, 40% by mass, 50% by mass, 60% by mass, 70% by mass, or 80% by mass.

[0031] In some embodiments, the content of the carbon material in the negative electrode material is 10% by mass to 50% by mass, and may be specifically, but is not limited to, 10% by mass, 20% by mass, 25% by mass, 30% by mass, 35% by mass, 40% by mass, 45% by mass, or 50% by mass. Furthermore, the negative electrode material further comprises a coating layer present on at least a portion of the surface of the nanosilicon-based material. Preferably, the coating layer is distributed on the surface of the nanosilicon-based material.

[0032] In some embodiments, the coating layer comprises amorphous carbon. In some embodiments, the thickness of the coating layer is 1 nm to 3000 nm. It is understood that the coating layer covering the surface of the nanosilicon-based material can reduce contact between the nanosilicon-based material and the electrolyte, reduce the generation of a passivation film, and improve the reversible capacity of the battery.

[0033] Specifically, the coating layer is a carbon layer, and the thickness of the carbon layer may be 1 nm, 50 nm, 180 nm, 200 nm, 350 nm, 400 nm, 550 nm, 850 nm, 950 nm, 1050 nm, 1500 nm, 2000 nm, 2500 nm, or 3000 nm, or other values ​​within the above ranges, but is not limited thereto. If the carbon layer is too thick, the carbon content will be too high, which is disadvantageous in obtaining a composite material with a high specific capacity. If the carbon layer is too thin, it will be disadvantageous in increasing the conductivity of the negative electrode material and will be unable to suppress the volume expansion of the material, resulting in poor long-term cycle characteristics. Preferably, the carbon layer thickness is 50 nm to 800 nm, and more preferably, the carbon layer thickness is 100 nm to 500 nm.

[0034] In some embodiments, the coating layer comprises amorphous carbon and a lithium salt dispersed within the amorphous carbon, and the lithium salt present in the coating layer increases the content of active lithium ions and participates in the formation of a solid electrolyte during the first charge / discharge cycle, thereby compensating for the loss of active lithium ions in the electrolyte, thereby compensating for irreversible capacity loss and effectively improving the first coulombic efficiency of the material. In some embodiments, the lithium salt comprises at least one selected from the group consisting of lithium hydroxide, lithium chloride, lithium carbonate, lithium fluoride, lithium oxide, lithium borohydride, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0035] In some embodiments, the median diameter of the negative electrode material is 0.5 μm to 30 μm. Specifically, the median diameter may be 0.5 μm, 1 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 25 μm, or 30 μm, and may of course be other values ​​within the above range, but is not limited thereto. It is understood that controlling the median diameter of the negative electrode material within the above range contributes to improving the cycle characteristics of the negative electrode material.

[0036] In some embodiments, the specific surface area of ​​the negative electrode material is 5 m 2 / g or less. Specifically, 5m 2 / g, 4.5m 2 / g, 4m 2 / g, 3.5m 2 / g, 3m 2 / g, 2m 2 / g, 1m 2 / g or 0.5m 2 / g, etc., and of course, other values ​​within the above range may also be used, but are not limited to these. It is understood that controlling the specific surface area of ​​the negative electrode material within the above range contributes to suppressing volume expansion and contributing to improving the cycle characteristics of the negative electrode material.

[0037] In some embodiments, the negative electrode material particles have a fracture strength of 300 MPa or greater. Specifically, the fracture strength of the negative electrode material particles may be, but is not limited to, 300 MPa, 310 MPa, 320 MPa, 350 MPa, 380 MPa, 390 MPa, 400 MPa, 450 MPa, 480 MPa, or 500 MPa, and may also be other values ​​within the above range. Because of its strong rigidity, the particle structure is highly stable and can resist certain volume expansion stress, thereby reducing expansion and improving the cycling stability of the battery.

[0038] The negative electrode materials of the above embodiments can be combined in any manner as long as they are not inconsistent with each other. For example, it is possible to combine and limit the breaking strength and specific surface area of ​​the particles of the negative electrode material.

[0039] In another aspect, a method for producing a negative electrode material, comprising: As shown in FIG. 1, the manufacturing method includes: A step S10 of producing a first precursor comprising a nanosilicon-based material; a step S20 of producing a second precursor comprising the first precursor and a carbon source; and a step S30 of carbonizing the second precursor to obtain a negative electrode material, the first precursor and / or the second precursor contains a fluorine-containing compound, The negative electrode material contains elemental fluorine, and when the total mass content of the elemental fluorine contained in the negative electrode material is A0 ppm and the mass content of the elemental fluorine contained inside the nanosilicon-based material in the negative electrode material is A1 ppm, A0 and A1 satisfy the following formula: A0-2A1≧30 ppm.

[0040] In this embodiment, a first precursor containing a nanosilicon-based material is produced, and then the first precursor and a second precursor containing a carbon source are carbonized to produce a negative electrode material, wherein a fluorine-containing compound is added to the first precursor and / or the second precursor so that the majority of elemental fluorine is located in the negative electrode material other than the nanosilicon-based material, and A0 and A1 satisfy A0-2A1≧30 ppm. By controlling the fluorine content within the above range, it is possible to ensure that the fluorine content in the nanosilicon-based material is lower than the content in the negative electrode material other than the nanosilicon-based material, and that more elemental fluorine is present in the negative electrode material other than the nanosilicon-based material.

[0003] The present invention relates to a method for manufacturing a negative electrode material, and a method for manufacturing the same. ...

[0041] The production method of the present invention will be specifically described below with reference to examples. In the manufacturing method, before step S10, The method further includes wet-grinding a mixture containing a silicon-based material and a solvent, followed by drying to obtain a nanosilicon-based material.

[0042] In some embodiments, the solvent comprises at least one selected from the group consisting of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, pentanol, trifluoroethanol, and trifluoromethanol. In some embodiments, the temperature of the drying treatment is 40°C to 600°C. Specifically, it may be 40°C, 50°C, 80°C, 100°C, 120°C, 250°C, 380°C, 400°C, 500°C, 580°C, 600°C, etc. The time of the drying treatment is 1 h to 15 h. Specifically, it may be 1 h, 3 h, 5 h, 7 h, 9 h, 10 h, 12 h, 15 h, etc. The drying treatment method may be, for example, in-furnace drying, freeze drying, stirring evaporation to dryness, spray drying, etc. In this embodiment, through the drying treatment, the solvent in the mixture can be removed as much as possible.

[0043] In step S10, a first precursor containing a nanosilicon-based material is produced. In some embodiments, step S10 includes subjecting a mixture containing a silicon-based material, a fluorine-containing compound, and a solvent to wet grinding treatment, drying, and obtaining a first precursor. The content of the fluorine-containing compound added to the first precursor is 0.01% by mass to 3.00% by mass. Specifically, the content of the fluorine-containing compound added to the first precursor may specifically be 0.01% by mass, 0.02% by mass, 0.06% by mass, 0.10% by mass, 0.20% by mass, 0.40% by mass, 0.50% by mass, 0.60% by mass, 0.80% by mass, 1.00% by mass, 1.50% by mass, 2.00% by mass, 2.50% by mass, or 3.00% by mass, etc. Of course, it may also be other values within the above range and is not limited thereto.

[0044] In some embodiments, the nanosilicon-based material includes at least one selected from the group consisting of elemental silicon, silicon oxygen-containing materials, and silicon alloys. Examples of the silicon alloy include silicon lithium alloy, silicon magnesium alloy, etc. The silicon oxygen-containing material may be a silicon oxygen composite in which the molar ratio of silicon atoms to oxygen atoms is within the range of 0.1 to 1.9. The silicon oxygen composite may be a composite of Si and SiO2, or a substance containing a compound represented by the general formula SiO x (0 < x < 2), or a silicate-based substance. The silicon oxygen-containing material may have the general formula SiO x (0 < x < 2). The silicon oxygen-containing material may be SiO, SiO0.2 , SiO 0.5 , SiO 0.7 , SiO 0.9 , SiO 1.5 , SiO1 .6 or SiO 1.9 etc. may also be used. In some embodiments, step S10 includes mixing the nanosilicon-based material, the fluorine-containing compound, and a solvent, and then removing the solvent to obtain a first precursor.

[0045] In some embodiments, the nanosilicon-based material is a particle, and the average particle diameter of the nanosilicon-based material is 1 nm to 500 nm. Specifically, the average particle diameter may be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm, and of course, other values ​​within the above range are also possible, but are not limited to these. Through extensive testing, it has been found that nanosilicon-based materials have high surface energy, tend to aggregate during charging and discharging, have high particle structure, and can suppress the volume expansion of silicon. Silicon-based materials have too small particle diameters, which increases the manufacturing cost. Preferably, the median diameter of the nanosilicon-based material is 1 nm to 200 nm, more preferably 1 nm to 100 nm.

[0046] In some embodiments, the solvent comprises an organic solvent, the organic solvent comprising at least one selected from the group consisting of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, pentanol, trifluoroethanol, and trifluoromethanol. In some embodiments, the mixing method includes at least one selected from the group consisting of mechanical stirring, ultrasonic dispersion, and abrasive dispersion.

[0047] In some embodiments, a specific step of preparing the first precursor includes mixing a nanosilicon-based material, a fluorine-containing compound and a solvent, followed by drying to obtain the first precursor.

[0048] In some embodiments, the mixing method includes at least one selected from the group consisting of mechanical stirring, ultrasonic dispersion, and abrasive dispersion. Preferably, abrasive dispersion is used to disperse the nanosilicon-based material, reduce aggregation of the nanosilicon-based material, and disperse the nanosilicon-based material into relatively small nanoparticles. Preferably, a wet ball mill is used, with a dispersion time of 0.5 to 10 hours, to achieve a more uniform mixing of the components with sufficient abrasion, resulting in a nanosilicon-based material particle size of 1 to 500 nm.

[0049] In some embodiments, the dried first precursor may be dispersed, and the dispersion may be a grinding dispersion, and the dispersion time may be 0.5 hours to 9 hours, specifically 0.5 hours, 1.5 hours, 2.5 hours, 3.5 hours, 4.5 hours, 5.5 hours, 7.5 hours, or 9 hours, etc. In this embodiment, the particle size of the dispersed first precursor is controlled by grinding dispersion.

[0050] In some embodiments, the fluorine-containing compound includes at least one selected from the group consisting of calcium fluoride, cryolite, aluminum fluoride, sodium fluoride, sodium silicofluoride, magnesium fluoride, potassium fluoride, lithium fluoride, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium difluoro(oxalato)borate, fluoroethylene carbonate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0051] In some embodiments, the content of the fluorine-containing compound added to the first precursor is 0.01% by mass to 3.00% by mass, and specifically may be 0.01%, 0.02%, 0.06%, 0.10%, 0.20%, 0.40%, 0.50%, 0.60%, 0.80%, 1.00%, 1.50%, 2.00%, 2.50%, or 3.00% by mass, or may be other values ​​within the above range, but is not limited thereto. Preferably, the content of the fluorine-containing compound added to the first precursor is 0.01% by mass to 0.09% by mass. When the fluorine-containing compound is simultaneously a lithium salt, such as lithium fluoride, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium difluoro(oxalato)borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide, the range of the amount added is controlled based on the fluorine-containing compound.

[0052] In some embodiments, the lithium salt comprises at least one selected from the group consisting of lithium hydroxide, lithium chloride, lithium carbonate, lithium fluoride, lithium oxide, lithium borohydride, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0053] In some embodiments, the content of the lithium salt added to the first precursor is 0.05% by weight to 1% by weight, and may be specifically, but is not limited to, 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, or 1% by weight, or may be any other value within the above range.

[0054] In step S20, a second precursor containing the first precursor and a carbon source is produced. In some embodiments, the carbon source comprises at least one selected from the group consisting of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt.

[0055] In some embodiments, the mass ratio of the first precursor to the carbon source is 100:(10 to 100), and may be specifically 100:100, 100:94, 100:80, 100:75, 100:70, 100:50, 100:30, 100:20, or 100:10, etc. If the mass ratio of the first precursor to the carbon source is too high, the capacity of the material will decrease, which is undesirable. Also, in some embodiments, if the proportion of non-graphitic carbon is too high, the initial efficiency of the material may decrease.

[0056] In some embodiments, the step of producing the second precursor may specifically include mixing the first precursor, a carbon source, and a fluorine-containing compound, and then obtaining the second precursor. In some embodiments, the mixing method includes at least one selected from the group consisting of a fusion process, a kneading extrusion process, and VC mixing. In some embodiments, the content of the fluorine-containing compound added to the second precursor is 0.05% by mass to 0.9% by mass, and specifically may be 0.05%, 0.1%, 0.2%, 0.5%, 0.6%, 0.7%, 0.8%, or 0.9% by mass, or may be any other value within the above range, but is not limited to these. In some embodiments, the total mass content of the fluorine-containing compounds added to the second precursor and / or the first precursor is higher than the mass content of the fluorine-containing compounds contained in the nanosilicon-based material. By controlling the amount of fluorine-containing compounds added, the mass content of elemental fluorine in the negative electrode material other than the nanosilicon-based material becomes higher than the mass content inside the nanosilicon-based material, which contributes to the formation of a concentration gradient of elemental fluorine. This allows the elemental fluorine in the negative electrode material other than the nanosilicon-based material to preferentially participate in the formation of a solid electrolyte film on the surface of the negative electrode material during charge and discharge, thereby optimizing the solid electrolyte film.

[0057] In some embodiments, the second precursor further comprises a lithium salt, and the content of the lithium salt added to the second precursor is 0.01% by weight to 0.1% by weight, specifically, 0.01%, 0.02%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1% by weight, and may of course be other values ​​within the above range, but is not limited thereto. When the fluorine-containing compound is also a lithium salt, such as lithium fluoride, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium difluoro(oxalato)borate, lithium bis(difluorosulfonyl)imide, or lithium bis(trifluoromethanesulfonyl)imide, the range of the amount added is controlled based on the fluorine-containing compound.

[0058] In some embodiments, the mixing method is mechanofusion, which improves the fracture strength of the negative electrode material particles, and further carbonization can strengthen the stability of the particle structure, improve the connection stability between the nanosilicon-based material and the carbon source, and reduce the porosity. Of course, in other embodiments, other methods of mixing can be used, and are not limited to these.

[0059] In some embodiments, the crush strength of the negative electrode material particles is 300 MPa or greater. In step S30, the second precursor is carbonized to obtain a negative electrode material. In some embodiments, the carbonization temperature is 600°C to 1200°C, such as 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc. Preferably, the carbonization temperature is 600°C to 1000°C. In some embodiments, the carbonization time may be 1 hour to 10 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0060] In some embodiments, the temperature rise rate during the carbonization treatment is 1°C / min to 30°C / min, and specifically may be 1°C / min, 5°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, 30°C / min, etc. For example, the temperature rise rate during the carbonization treatment is preferably 1°C / min to 15°C / min. In some embodiments, a protective gas is passed through during the carbonization process, and the protective gas includes at least one selected from the group consisting of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas. In some embodiments, after step S30, at least one selected from the group consisting of pulverization, sieving, and demagnetization is further performed, and preferably, after the carbonization treatment, pulverization, sieving, and demagnetization are further performed in this order.

[0061] In some embodiments, the milling is performed using any one selected from a mechanical mill, an airflow mill, and a cryogenic mill. In some embodiments, the sieving is performed using any one selected from a fixed sieve, a drum screen, a resonating sieve, a roller sieve, a vibrating sieve, and a chain grizzly sieve, and the mesh number of the sieve is 500 mesh or more. Specifically, the mesh number of the sieve may be 500 mesh, 600 mesh, 700 mesh, 800 mesh, etc. Controlling the particle size of the negative electrode material within the above range contributes to improving the cycle characteristics of the negative electrode material.

[0062] In some embodiments, the demagnetizing device is any one selected from a permanent magnet drum magnetic separator, an electromagnetic iron remover, and a pulsating high gradient magnetic separator, and the demagnetizing is performed to ultimately control the content of magnetic materials in the negative electrode material so as to avoid the discharge effect of magnetic materials on the lithium ion battery and its impact on safety during use. In this application, the median diameter refers to the average particle diameter, and its physical meaning is the particle diameter corresponding to the cumulative particle size distribution percentage of particles reaching 50%, which is measured using a Malvern particle size analyzer. The Malvern particle size analyzer utilizes the phenomenon of light scattering by particles to comprehensively convert the particle size distribution of the measured particles based on the distribution of scattered light energy.

[0063] In one embodiment, when the total mass content of the elemental fluorine contained in the negative electrode material is A0 ppm, A0 can have a value in the range of 100 to 10,000. Specifically, A0 can have a value of 100, 200, 500, 1,000, 2,000, 5,000, 8,000, 9,000, or 10,000, or can have other values ​​within the above range, but is not limited thereto. Specifically, the total mass content of elemental fluorine in the negative electrode material can be measured by ion chromatography, atomic absorption spectrometry, elemental analysis, or inductively coupled plasma atomic emission spectrometry.

[0064] The present application further provides a lithium ion battery having the above negative electrode material. The present application will be further explained below with reference to several examples. However, the present application is not limited to the specific examples below. Modifications may be made as appropriate within the scope of the present invention.

[0065] Example 1 The method for producing the negative electrode material of this example includes the following steps. (1) 100 μm metallic silicon was wet-pulverized in a ball mill, and the solvent was n-hexane. Nanosilicon was 100 mass %. 0.03 mass % lithium tetrafluoroborate was added and mixed. The rotation speed was set to 500 rpm, and the time was set to 18 hours. Nanosilicon (D 50A slurry containing 180 nm of fluorine-containing silica and lithium tetrafluoroborate is obtained. (2) The slurry is freeze-dried and granulated to obtain the first precursor. (3) The first precursor, asphalt, and lithium hexafluoroarsenate are mixed in a mass ratio of 100:49:0.1 to obtain a second precursor. (4) The second precursor is placed in a heat treatment furnace, carbonized at a temperature of 1000°C, kept at that temperature for 4 hours, and then crushed and sieved to obtain the negative electrode material.

[0066] The negative electrode material prepared in this example includes a carbon material and nanosilicon dispersed in the carbon material, and the performance test data of the negative electrode material is shown in Table 1. Figure 2 is a scanning electron microscope (SEM) image of the negative electrode material prepared in Example 1 of the present application.

[0067] Example 2 (1) 20 μm metallic silicon was wet-ground in a planetary ball mill using butanol as the solvent, at a rotation speed of 600 rpm, for 30 h, to obtain nanosilicon (D 50 A slurry containing 130 nm of ZnO is obtained. (2) The slurry is adjusted to 100% by mass, and 0.4% by mass of lithium hexafluoroarsenate is added to the slurry, mixed, and then spray-dried and granulated to obtain a first precursor. (3) The first precursor and the phenolic resin are mixed in a mass ratio of 100:33 to obtain a second precursor. (4) The second precursor is placed in a heat treatment furnace, carbonized at a temperature of 800°C, kept at that temperature for 3 hours, and then crushed and sieved to obtain the negative electrode material.

[0068] The negative electrode material prepared in this example includes a carbon material and nanosilicon dispersed in the carbon material, and the performance test data of the negative electrode material is shown in Table 1.

[0069] Example 3 (1) 10 μm metallic silicon was wet-ground in an agitation mill, the solvent was methanol, the rotation speed was 400 rpm, and the time was 25 h to obtain nanosilicon (D 50A slurry containing 120 nm of ZnO is obtained. (2) The slurry is adjusted to 100% by mass, and 0.09% by mass of lithium difluoro(oxalato)borate is added to the slurry, mixed, and spray-dried to granulate to obtain a first precursor. (3) The first precursor, phenolic resin, and lithium difluoro(oxalato)borate are mixed in a mass ratio of 100:33:0.08 to obtain a second precursor. (4) The second precursor is placed in a heat treatment furnace, carbonized at a temperature of 800°C, kept at that temperature for 3 hours, and then crushed and sieved to obtain the negative electrode material.

[0070] The negative electrode material prepared in this example includes a carbon material and nanosilicon dispersed in the carbon material, and the performance test data of the negative electrode material is shown in Table 1.

[0071] Example 4 (1) 100 μm metallic silicon was wet-ground in a sand mill, the solvent was t-butyl alcohol, the rotation speed was 900 rpm, and the time was 33 h. Nanosilicon (D 50 A slurry containing 80 nm of ZnO is obtained. (2) The slurry is adjusted to 100% by mass, and 0.08% by mass of lithium fluoride is added to the slurry, mixed, and then spray-dried and granulated to obtain a first precursor. (3) The first precursor, sucrose, and lithium bis(difluorosulfonyl)imide are mixed in a mass ratio of 100:88:0.1 to obtain a second precursor. (4) The second precursor is placed in a heat treatment furnace, carbonized at a temperature of 780°C, kept at this temperature for 8 hours, and then crushed and sieved to obtain the negative electrode material.

[0072] The negative electrode material prepared in this example includes a carbon material and nanosilicon dispersed in the carbon material, and the performance test data of the negative electrode material is shown in Table 1.

[0073] Example 5 (1) 40 μm metallic silicon was wet-ground in a sand mill, and the solvent was methanol, nanosilicon was 100 mass%, and 0.06 mass% lithium difluoro(oxalato)borate was added and mixed. The rotation speed was set to 1700 rpm, and the time was set to 28 hours to obtain nanosilicon (D 50 A slurry containing 1000 nm of ZnO (having a particle size of 60 nm) and lithium difluoro(oxalato)borate is obtained. (2) The slurry is adjusted to 100% by mass, and 0.08% by mass of fluoroethylene carbonate is added to the slurry, mixed, and freeze-dried to granulate, thereby obtaining a first precursor. (3) The first precursor and fructose are mixed in a mass ratio of 100:94 to obtain a second precursor. (4) The second precursor is placed in a heat treatment furnace, carbonized at a temperature of 880°C, kept at that temperature for 4 hours, and then crushed and sieved to obtain the negative electrode material. The negative electrode material prepared in this example includes a carbon material and nanosilicon dispersed in the carbon material, and the performance test data of the negative electrode material is shown in Table 1.

[0074] Example 6 In step (1), 10 μm silicon-oxygen-containing material (SiO) is wet-pulverized in a ball mill, the solvent is n-hexane, the nano silicon-oxygen-containing material is 100 mass%, 0.05 mass% magnesium fluoride is added and mixed, the rotation speed is 500 rpm, the time is 18 hours, and the nano silicon-oxygen-containing material (D 50 This example differs from Example 1 in that a slurry containing lithium tetrafluoroborate is obtained.

[0075] Example 7 In step (1), 10 μm silicon magnesium alloy is wet-pulverized in a ball mill, the solvent is n-hexane, the nano silicon magnesium alloy is 100 mass%, 0.03 mass% lithium tetrafluoroborate is added and mixed, the rotation speed is 500 rpm, the time is 18 hours, and the nano silicon magnesium alloy (D 50 This example differs from Example 1 in that a slurry containing lithium tetrafluoroborate is obtained.

[0076] Example 8 In step (2), the slurry is adjusted to 100% by mass, and 0.08% by mass of fluoroethylene carbonate is added to the slurry, mixed, and freeze-dried to granulate, thereby obtaining a first precursor, which is different from Example 1.

[0077] Example 9 This example differs from Example 1 in that in step (3), the first precursor, asphalt, and lithium carbonate are mixed in a mass ratio of 100:49:0.05 to obtain a second precursor.

[0078] Example 10 (1) 100 μm metallic silicon was wet-ground in a ball mill, the solvent was trifluoroethanol, nanosilicon was 100 mass%, and 1.00 mass% lithium tetrafluoroborate was added and mixed, the rotation speed was set to 500 rpm, and the time was set to 18 hours to obtain nanosilicon (D 50 A slurry containing 180 nm of fluorine-containing silica and lithium tetrafluoroborate is obtained. (2) The slurry is freeze-dried and granulated to obtain the first precursor. (3) The first precursor, asphalt, and lithium hexafluoroarsenate are mixed in a mass ratio of 100:49:3 to obtain a second precursor. (4) The second precursor is placed in a heat treatment furnace, carbonized at a temperature of 1000°C, kept at that temperature for 4 hours, and then crushed and sieved to obtain the negative electrode material. The negative electrode material prepared in this example includes a carbon material and nanosilicon dispersed in the carbon material, and the performance test data of the negative electrode material is shown in Table 1.

[0079] Comparative Example 1 The method for producing the negative electrode material of this comparative example includes the following steps. (1) 100 μm metallic silicon was wet-ground in a ball mill using n-hexane as the solvent, at a rotation speed of 500 rpm for 18 h to obtain nanosilicon (D 50 A slurry containing 180 nm of ZnO is obtained. (2) The slurry is freeze-dried and granulated to obtain the first precursor. (3) The first precursor and asphalt are mixed in a mass ratio of 100:49 to obtain a second precursor. (4) The second precursor is placed in a heat treatment furnace, carbonized at a temperature of 1000°C, kept at that temperature for 4 hours, and then crushed and sieved to obtain the negative electrode material.

[0080] The negative electrode material prepared in this comparative example includes a carbon material and nanosilicon dispersed in the carbon material, and the performance test data of the negative electrode material is shown in Table 1.

[0081] Comparative Example 2 The method for producing the negative electrode material of this comparative example includes the following steps. (1) 100 μm metallic silicon was wet-pulverized in a ball mill, and the solvent was n-hexane. Nanosilicon was 100 mass %. 0.03 mass % lithium tetrafluoroborate was added and mixed. The rotation speed was set to 500 rpm, and the time was set to 18 hours. Nanosilicon (D 50 A slurry containing 180 nm of fluorine-containing silica and lithium tetrafluoroborate is obtained. (2) The slurry is freeze-dried and granulated to obtain the first precursor. (3) The first precursor and asphalt are mixed in a mass ratio of 100:49 to obtain a second precursor. (4) The second precursor is placed in a heat treatment furnace, carbonized at a temperature of 1000°C, kept at that temperature for 4 hours, and then crushed and sieved to obtain the negative electrode material. The negative electrode material prepared in this comparative example includes a carbon material and nanosilicon dispersed in the carbon material, and the performance test data of the negative electrode material is shown in Table 1.

[0082] Comparative Example 3 The method for producing the negative electrode material of this comparative example includes the following steps. (1) 100 μm metallic silicon was wet-pulverized in a ball mill, and the solvent was n-hexane. Nanosilicon was 100 mass %. 0.02 mass % lithium tetrafluoroborate was added and mixed. The rotation speed was set to 500 rpm, and the time was set to 18 hours. Nanosilicon (D 50 A slurry containing 180 nm of fluorine-containing silica and lithium tetrafluoroborate is obtained. (2) The slurry is freeze-dried and granulated to obtain the first precursor. (3) The first precursor, asphalt, and lithium difluoro(oxalato)borate are mixed in a mass ratio of 100:39:0.02 to obtain a second precursor. (4) The second precursor is placed in a heat treatment furnace, carbonized at a temperature of 1000°C, kept at that temperature for 4 hours, and then crushed and sieved to obtain the negative electrode material. The negative electrode material prepared in this comparative example includes a carbon material and nanosilicon dispersed in the carbon material, and the performance test data of the negative electrode material is shown in Table 1.

[0083] Measurement method (1) Measurement of the fluorine content in the negative electrode material 10 g of the negative electrode material is weighed out, and the total mass content of fluorine element in the negative electrode material, A0 ppm, is measured by ion chromatography, atomic absorption spectrometry, elemental analysis, or inductively coupled plasma atomic emission spectrometry. The negative electrode material is then immersed in an 8 mol / L sodium hydroxide solution until the silicon-based material is removed. The remaining material is washed with deionized water and dried to obtain a composite from which the silicon-based material has been removed. The fluorine content (A2 ppm) of the composite from which the silicon-based material has been removed is measured using ion chromatography, atomic absorption spectroscopy, elemental analysis, or inductively coupled plasma atomic emission spectroscopy. By calculation, the mass content of the fluorine element contained inside the nanosilicon material in the negative electrode material is A1 ppm. A2=A0-A1, so A2-A1=A0-A1-A1=A0-2A1 The above method is measured five times, and the average value of the mass content of elemental fluorine inside the nanosilicon-based material is calculated.

[0084] (2) Method for measuring the median diameter of negative electrode materials The particle size measurement method is in accordance with GB / T19077-2016, where the median diameter, which is the average particle size of the negative electrode material, is measured using a laser particle size analyzer (Mastersizer 3000).

[0085] (3) Measurement of the breaking strength of negative electrode material particles The negative electrode material is extruded, and the breaking strength of each of 50 or more negative electrode material particles is measured, and the average value is taken as the breaking strength of the particle.

[0086] (4) Measurement method for the specific surface area of ​​negative electrode materials The specific surface area of ​​the negative electrode material was measured using a Micromeritics TriStar 3020 specific surface area / pore size analyzer. A certain mass of powder was weighed and thoroughly degassed under vacuum and heating to remove adsorbates from the surface. The specific surface area of ​​the particles was then calculated from the amount of adsorbed nitrogen gas using the nitrogen gas adsorption method.

[0087] (5) Method for measuring the thickness of the coating layer of the negative electrode material The material is cross-sectioned using a focused ion beam scanning electron microscope (FIB-SEM) device, and the average thickness of the coating layer is measured in the scanning electron microscope photograph.

[0088] (6) Measurement of the mass content of carbon materials in the anode material A sample of anode material is heated to high temperatures in a high-frequency furnace under oxygen-rich conditions, causing carbon to oxidize and become carbon dioxide. After the gas is processed, it enters a corresponding absorption cell, absorbs the corresponding infrared light, and is converted into a corresponding signal by a probe. This signal is sampled and linearly corrected by a computer to convert it into a value directly proportional to the carbon dioxide concentration. The values ​​are then integrated throughout the analysis process. After the analysis is complete, the integrated value is divided by the weight value in the computer, multiplied by a correction factor, and the blank is subtracted to obtain the carbon material content (mass%) in the sample. The sample was measured using a high-frequency infrared carbon / sulfur analyzer (model: Shanghai Dekai HCS-140).

[0089] (7) Electrochemical measurements The electrochemical cycle characteristics were measured using the following method. The prepared negative electrode material, conductive agent, and adhesive were dissolved and mixed in deionized water in a mass ratio of 94:1:5 to achieve a 50% solids content. The mixture was applied to a copper foil current collector and vacuum dried to produce a negative electrode sheet. Then, a layered nickel-cobalt-manganese oxide (NCM) ternary positive electrode sheet manufactured using conventional, mature technology, a 1 mol / L LiPF6 / ethylene carbonate + dimethyl carbonate + methyl ethyl carbonate (v / v = 1:1:1) electrolyte, a Celgard 2400 separator, and a case were assembled into a button-type lithium-ion battery using conventional manufacturing techniques. The initial thickness (H0) of the electrode sheet of the lithium-ion battery was measured using a micrometer. The charge and discharge tests for lithium-ion batteries were carried out using a LAND battery measurement system from WuhanLANDelectronics (original Chinese: Wuhan Jinnuo Electronics Co., Ltd.), with constant current charging and discharging at 0.2C at room temperature, and the charge and discharge voltage was set to 2.75 to 4.2V, and the initial reversible capacity, first cycle charge capacity, and first cycle discharge capacity were obtained. First coulomb efficiency = 1st cycle discharge capacity / 1st cycle charge capacity

[0090] After 50 cycles, measure the thickness H1 of the electrode sheet of the lithium-ion battery with a micrometer. Expansion rate after 50 cycles = (H1-H0) / H0 x 100% Repeat 100 cycles and record the discharge capacity as the remaining capacity of the lithium-ion battery. Capacity maintenance rate = remaining capacity / initial capacity x 100%

[0091] [Table 1]

[0092] FIG. 3 shows the X-ray diffraction pattern of the negative electrode material produced in Example 1 of the present application. As shown in FIG. 3, the X-ray diffraction pattern of the negative electrode material contains peaks characteristic of silicon. FIG. 4 shows the initial charge / discharge curve of the negative electrode material produced in Example 1 of the present application. As shown in FIG. 4, the initial charge / discharge capacity of the negative electrode material is high, and the initial coulombic efficiency is also high at 88.1%. FIG. 5 shows the cycle characteristic curve of the negative electrode material produced in Example 1 of the present application. As shown in FIG. 5, the negative electrode material has excellent cycle characteristics, with a 300-cycle capacity retention rate of 90.5%. FIG. 6 shows a scanning transmission electron microscope (SEM-EDX) image of the negative electrode material produced in Example 1 of the present application. As shown in FIG. 6, elemental fluorine is mainly distributed in the carbon material on the surface of the nanosilicon, specifically, as elemental fluorine represented by (1) to (6) in FIG. 6. Elemental fluorine in the carbon material is preferentially involved in the formation of the solid electrolyte membrane and optimizes the solid electrolyte membrane.

[0093] The measurement data of Examples 1 to 10 indicate that a larger amount of elemental fluorine is present in the anode materials other than the nanosilicon-based materials. Because fluorine, with its strong electronegativity, can be reduced at a low reduction potential, the elemental fluorine in the anode materials other than the nanosilicon-based materials can participate in the formation of a solid electrolyte film during charge and discharge, optimizing the solid electrolyte film, reducing the reaction activity between the anode material and the electrolyte, protecting the anode material, and reducing the occurrence of side reactions, thereby improving the cycle performance of the anode material. Furthermore, the measurement data of Examples 1 to 5 indicate that the larger difference between A0 and 2A1 indicates that a larger proportion of elemental fluorine is present in the anode materials other than the nanosilicon-based materials. This allows a solid electrolyte film to form on the surface of the anode material particles, further contributing to optimizing the cycle retention rate of the anode material.

[0094] In Comparative Example 1, no fluorine-containing compound was added during the production of the negative electrode material, and the trace amount of fluorine was mainly derived from the small amount of fluorine doped into the asphalt. As a result, the total content of the fluorine element in the produced negative electrode material was insufficient, and the fluorine element involved in the formation of the solid electrolyte membrane was insufficient. As a result, the side reaction between the negative electrode material and the electrolyte increased, and the cycle retention rate of the material was significantly reduced.

[0095] In Comparative Example 2, the amount of fluorine-containing compound added during the production of the negative electrode material was insufficient, resulting in an insufficient total content of fluorine element in the produced negative electrode material. Moreover, most of the fluorine element was distributed on the surface of the nanosilicon and was involved in the formation of the solid electrolyte film. The fluorine element on the surface of the negative electrode material was insufficient, which increased the side reaction between the negative electrode material and the electrolyte, and significantly reduced the cycle retention rate of the material. In Comparative Example 3, in the process of producing the negative electrode material, the amount of fluorine-containing compound added when producing the nanosilicon-based material was higher than the amount of fluorine-containing compound added when producing the second precursor.As a result, in the final product, the fluorine content in the nanosilicon and the fluorine content in the carbon material were relatively close, and no concentration gradient of the fluorine content was formed.As a result, there was insufficient fluorine on the surface of the negative electrode material, which is involved in the formation of the solid electrolyte membrane, and side reactions between the negative electrode material and the electrolyte increased, resulting in a lower cycle retention rate of the material than in Example 1.

[0096] As described above, the present application has been disclosed in terms of preferred embodiments, but these embodiments do not limit the scope of the claims. Those skilled in the art can make various possible modifications and variations without departing from the spirit of the present application. Therefore, the scope of protection of the present application should be limited to the scope defined by the claims.

Claims

1. A negative electrode material, the negative electrode material includes a carbon material and a nanosilicon-based material dispersed in the carbon material, and contains elemental fluorine; The nanosilicon-based material has an average particle diameter D 50 of 1 nm to 100 nm; The nanosilicon-based material substantially contains elemental fluorine, The total mass content of the fluorine element contained in the negative electrode material is A 0 ppm, and the mass content of fluorine element contained inside the nanosilicon-based material in the negative electrode material is A 1 In ppm, A 0 and A 1 A negative electrode material characterized by satisfying the following formula: A 0 -2A 1 ≧30ppm

2. The negative electrode material according to claim 1, wherein at least one of the following (1) to (6) is satisfied: (1) The total mass content of the fluorine element contained in the negative electrode material is A 0 In ppm, A 0 The range of possible values ​​of is 100 to 10,000; (2) The content of the nanosilicon-based material in the negative electrode material is 10% by mass to 80% by mass; (3) The nanosilicon-based material includes at least one selected from the group consisting of silicon elemental material, silicon alloy, and silicon-oxygen-containing material; (4) The content of the carbon material in the negative electrode material is 10% by mass to 50% by mass; (5) The carbon material includes at least one selected from the group consisting of hard carbon and soft carbon; (6) The particles of the negative electrode material have a breaking strength of 300 MPa or more.

3. 2. The negative electrode material according to claim 1, further comprising a coating layer present on at least a portion of the surface of the nanosilicon-based material.

4. The negative electrode material according to claim 3, wherein at least one of the following (1) to (6) is satisfied: (1) the coating layer contains amorphous carbon; (2) the coating layer contains amorphous carbon and a lithium salt dispersed in the amorphous carbon; (3) The coating layer contains a lithium salt, and the lithium salt includes at least one selected from the group consisting of lithium hydroxide, lithium chloride, lithium carbonate, lithium fluoride, lithium oxide, lithium borohydride, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide; (4) The thickness of the coating layer is 1 nm to 3000 nm; (5) The median diameter of the negative electrode material is 0.5 μm to 30 μm; (6) The specific surface area of ​​the negative electrode material is 5 m 2 / g or less.

5. A method for producing the negative electrode material of claim 1, comprising: The manufacturing method includes: A step of producing a first precursor containing a nanosilicon-based material and a fluorine-containing compound, the content of the fluorine-containing compound being 0.01% by mass to 3.00% by mass; a step of producing a second precursor by mixing the first precursor, a carbon source, and a fluorine-containing compound so that the content of the fluorine-containing compound is 0.05% by mass to 3.00% by mass; and carbonizing the second precursor to obtain a negative electrode material, The negative electrode material contains elemental fluorine, The total mass content of the fluorine element contained in the negative electrode material is A 0 ppm, and the mass content of fluorine element contained inside the nanosilicon-based material in the negative electrode material is A 1 In ppm, A 0 and A 1 A manufacturing method characterized in that the following formula is satisfied: A 0 -2A 1 ≧30ppm

6. 6. The method for producing an anode material according to claim 5, wherein at least one of the following conditions (1) to (2) is satisfied: (1) The fluorine-containing compound includes at least one selected from the group consisting of calcium fluoride, cryolite, aluminum fluoride, sodium fluoride, sodium silicofluoride, magnesium fluoride, potassium fluoride, lithium fluoride, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium difluoro(oxalato)borate, fluoroethylene carbonate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide; (2) At least one of the first precursor, the second precursor, and the nanosilicon-based material contains a lithium salt, and the lithium salt includes at least one selected from the group consisting of lithium hydroxide, lithium chloride, lithium carbonate, lithium fluoride, lithium oxide, lithium borohydride, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

7. 6. The method for producing an anode material according to claim 5, wherein at least one of the following conditions (1) to (7) is satisfied: (1) The manufacturing method further includes, before the step of manufacturing the first precursor, wet-grinding and drying a mixture containing a silicon-based material and a solvent to obtain a nano-silicon-based material, wherein the solvent comprises at least one selected from the group consisting of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, pentanol, trifluoroethanol, and trifluoromethanol, the temperature of the drying process is 40°C to 600°C, the time of the drying process is 1 hour to 15 hours, and the method of the drying process includes at least one of spray drying and freeze drying; (2) The step of producing the first precursor includes wet-grinding and drying a mixture containing a silicon-based material, a fluorine-containing compound, and a solvent to obtain a first precursor, wherein the solvent includes at least one selected from the group consisting of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, pentanol, trifluoroethanol, and trifluoromethanol, the temperature of the drying treatment is 40°C to 600°C, the time of the drying treatment is 1 hour to 15 hours, and the method of the drying treatment includes at least one of spray drying and freeze drying; (3) The step of producing the first precursor includes mixing a nanosilicon-based material, a fluorine-containing compound, and a solvent, and then removing the solvent to obtain the first precursor, wherein the solvent includes at least one selected from the group consisting of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, pentanol, trifluoroethanol, and trifluoromethanol; (4) The nanosilicon-based material includes at least one selected from the group consisting of silicon elemental material, silicon alloy, and silicon-oxygen-containing material; (5) The mixing method includes at least one selected from the group consisting of mechanical stirring, ultrasonic dispersion, and abrasive dispersion; (6) The step of preparing the first precursor includes mixing a nanosilicon-based material, a fluorine-containing compound, and a solvent, followed by drying to obtain the first precursor, wherein the solvent includes at least one selected from the group consisting of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, pentanol, trifluoroethanol, and trifluoromethanol, the temperature of the drying is 40°C to 600°C, the time of the drying is 1 hour to 15 hours, and the method of the drying includes at least one of spray drying and freeze drying; (7) The first precursor contains a lithium salt, and the content of the lithium salt is 0.05% by mass to 1% by mass.

8. 6. The method for producing an anode material according to claim 5, wherein at least one of the following conditions (1) to (3) is satisfied: (1) the mass ratio of the first precursor to the carbon source is 100:(10-100); (2) The carbon source includes at least one selected from sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt; (3) The second precursor contains a lithium salt, and the content of the lithium salt is 0.01% by mass to 0.1% by mass.

9. 6. The method for producing an anode material according to claim 5, wherein at least one of the following conditions (1) to (4) is satisfied: (1) The temperature of the carbonization treatment is 600°C to 1200°C; (2) The carbonization treatment time is 1 hour to 10 hours; (3) The temperature rising rate in the carbonization treatment is 1°C / min to 30°C / min; (4) A protective gas is passed through the carbonization treatment, and the protective gas includes at least one gas selected from the group consisting of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas.

10. A lithium ion battery comprising the negative electrode material according to any one of claims 1 to 4.

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