Negative electrode material and preparation method thereof, and battery

Abstract

The present application provides a negative electrode material and a preparation method thereof, a battery, and a negative electrode material. The negative electrode material includes a silicon-based material and a carbon material. In the Raman spectrum of the negative electrode material, the negative electrode material has a Raman spectrum of 450 cm ‑1 ~530cm ‑1 The double peaks in the range are the first peak and the second peak according to the peak position from low to high, and the peak position difference between the first peak and the second peak is P1, 20 cm ‑1 ≤P1≤60cm ‑1 ; The negative electrode material at 1550cm ‑1 ~1650cm ‑1 There are two peaks in the range, which are the third peak and the fourth peak from low to high, and the peak position difference between the third peak and the fourth peak is P2,40cm ‑1 ≤P2≤80cm ‑1 The peak area of ​​the fourth peak is B2, the peak area of ​​the second peak is A2, and 0.2≤B2 / A2≤100. The negative electrode material and preparation method provided in this application can increase the bonding strength between the silicon-based material and the carbon material, enhance the conductivity of the silicon-based material, and improve the specific capacity and cycle performance of the negative electrode material.

Description

Technical Field

[0001] The present application relates to the technical field of negative electrode materials, and in particular, to a negative electrode material, a preparation method thereof, and a battery. Background Art

[0002] Electric new energy vehicles are the future of the automotive market, and their core component is the lithium-ion battery. As the market develops, the demand for high-capacity batteries is increasing. Using new high-specific-capacity cathode and cathode materials is one of the key methods for increasing battery energy density.

[0003] More and more new materials such as metals, oxides, and metal alloys are being used as active materials in negative electrode materials to continuously explore various ways to improve the energy density of batteries. Taking silicon-based negative electrode materials as an example, silicon-based negative electrode materials, as one of the above-mentioned active materials, are generally considered to be the next generation of negative electrode materials. They have ultra-high theoretical specific capacity (4200mAh / g) and low delithiation potential (<0.5V). In addition, the voltage platform of silicon is slightly higher than that of graphite, and it is difficult to cause surface lithium deposition during charging. It has better safety performance and other advantages, which make it highly praised. However, the silicon negative electrode has a severe volume expansion effect during the cycle process, which causes the material to pulverize and break, and the battery cycle decays rapidly.

[0004] In the prior art, silicon-based materials are simply mixed with graphite. However, since there is no binding force between the silicon-based materials and the graphite, it is difficult to comprehensively improve the performance of the composite material by simply mixing the two. Summary of the Invention

[0005] This application proposes a negative electrode material, a preparation method thereof, and a battery, which can increase the bonding strength between silicon-oxygen material and carbon material, enhance the conductivity of silicon-oxygen material, and improve the specific capacity and cycle performance of the negative electrode material.

[0006] In a first aspect, the present application provides a negative electrode material, wherein the negative electrode material comprises a silicon-based material and a carbon material;

[0007] In the Raman spectrum of the negative electrode material, the negative electrode material has a Raman spectrum of 450 cm -1 ~530cm -1 The double peaks in the range are the first peak and the second peak according to the peak position from low to high, and the peak position difference between the first peak and the second peak is P1, 20 cm -1 ≤P1≤60cm -1 ; The negative electrode material at 1550cm -1 ~1650cm -1 There are two peaks in the range, which are the third peak and the fourth peak from low to high, and the peak position difference between the third peak and the fourth peak is P2,40cm -1 ≤P2≤80cm-1 ; and the peak area of ​​the fourth peak is B2, the peak area of ​​the second peak is A2, 0.2≤B2 / A2≤100.

[0008] In some embodiments, the silicon-based material further comprises a metal M element, and the metal M is selected from at least one metal having an electronegativity less than 1.8.

[0009] In some embodiments, the metal M exists in the form of a single substance M or a compound containing M.

[0010] In some embodiments, the metal M is selected from at least one of Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn.

[0011] In some embodiments, the metal M includes Mg and / or Li.

[0012] In some embodiments, the silicon-based material includes at least one of amorphous silicon, crystalline silicon, silicon-oxygen materials, and silicates.

[0013] In some embodiments, the carbon material includes at least one of natural graphite, artificial graphite, expanded graphite, graphite oxide, carbon nanoparticles, carbon nanotubes, and graphene.

[0014] In some embodiments, the mass content of silicon in the negative electrode material is m Si %,The mass content of oxygen element in the negative electrode material is m O %, 10%≤m O / (m Si +m O )≤53%.

[0015] In some embodiments, the mass content of carbon in the negative electrode material is m C %, 50≤m C ≤99.

[0016] In some embodiments, the median particle size D of the negative electrode material is 50 1μm~10μm.

[0017] In some embodiments, the specific surface area of ​​the negative electrode material is ≤20m 2 / g.

[0018] In some embodiments, the negative electrode material has pores, wherein the volume of micropores with a pore diameter of less than 2 nm accounts for 1% to 5% of the total pore volume of all pores.

[0019] In some embodiments, the compaction density of the negative electrode material is ≤2 g / cm 3 .

[0020] In some embodiments, the compaction density of the negative electrode material is ≤2 g / cm 3 When the negative electrode material has a powder conductivity of ≥5S / cm.

[0021] In some embodiments, in the Raman spectrum of the negative electrode material, the peak area of ​​the first peak is A1, the peak area of ​​the second peak is A2, and A1 / A2>0.5.

[0022] In some embodiments, in the Raman spectrum of the negative electrode material, the peak area of ​​the third peak is B1, the peak area of ​​the fourth peak is B2, 0.05 <B2 / B1<1。

[0023] In some embodiments, the silicon-based material includes silicon oxide, and the silicon oxide includes silicon and oxygen. The atomic ratio of the silicon to oxygen is 0 to 2, excluding 0.

[0024] In some embodiments, the silicon-based material comprises silicon oxide, the chemical formula of which is SiO x , where 0<x≤2.

[0025] In a second aspect, the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0026] preparing a mixture comprising a carbon material, a silicon raw material, asphalt, and a polysiloxane-type asphalt defoamer;

[0027] The mixture is subjected to a hot pressing process, and the hot pressing product is subjected to a carbonization process to obtain a negative electrode material.

[0028] In some embodiments, the carbon material includes graphite.

[0029] In some embodiments, the carbon material includes at least one of natural graphite, artificial graphite, expanded graphite, graphite oxide, carbon nanoparticles, carbon nanotubes, and graphene.

[0030] In some embodiments, the mixture further includes at least one of amorphous silicon, crystalline silicon, and silicate.

[0031] In some embodiments, the asphalt includes at least one of coal tar pitch, petroleum pitch, and natural asphalt.

[0032] In some embodiments, in the mixture, based on the total mass of the silicon-oxygen raw material and the carbon material being 100%, the mass content of the silicon-oxygen raw material is 1% to 45%.

[0033] In some embodiments, in the mixture, based on the total mass of the silicon-oxygen raw material, the carbon material and the asphalt being 100%, the mass content of the asphalt is 1% to 40%.

[0034] In some embodiments, based on 100% by mass of the mixture, 0.5% to 3% by mass of a polysiloxane asphalt defoamer is added to the mixture.

[0035] In some embodiments, the temperature of the hot pressing treatment is 200°C to 500°C.

[0036] In some embodiments, the heat pressing treatment lasts for 10 minutes to 12 hours.

[0037] In some embodiments, the pressure of the hot pressing treatment is 1T to 50T.

[0038] In some embodiments, the carbonization treatment temperature is 800°C to 1000°C.

[0039] In some embodiments, the carbonization treatment time is 0.5 h to 24 h.

[0040] In some embodiments, the carbonization treatment is performed under a protective atmosphere.

[0041] In some embodiments, the carbonization treatment is performed under a protective atmosphere comprising at least one of nitrogen, helium, neon, argon, krypton, and xenon.

[0042] In a third aspect, the present application provides a battery, comprising the negative electrode material as described in the first aspect or the negative electrode material prepared by the preparation method as described in the second aspect.

[0043] The technical solution of this application has at least the following beneficial effects:

[0044] First, the negative electrode material provided by the present application includes a silicon-based material and a carbon material; -1 ~530cm -1 The double peaks in the range are the first peak and the second peak according to the peak position from low to high. The first peak is the characteristic peak of amorphous silicon, and the second peak is the characteristic peak of crystalline silicon. The peak position difference between the two peaks is controlled at 20cm -1 ~60cm -1 The range of the content ratio of amorphous silicon to crystalline silicon in the negative electrode material can be effectively controlled, the distribution uniformity of amorphous silicon and crystalline silicon can be improved, the silicon lattice distortion caused by excessive crystalline silicon can be reduced, and the structural stability of silicon-based material particles can be improved during the cycle. In addition, the negative electrode material has a high conductivity at 1550 cm -1 ~1650cm -1There are two peaks in the range, which are the third peak and the fourth peak from low to high. The third peak is the characteristic peak of graphitized carbon material, and the fourth peak is the characteristic peak of graphitized carbon edge defects. The peak position difference between these two peaks is controlled at 40cm -1 ~80cm -1 Within this range, the ratio of the compressive stress of the lattice defects generated by the combination of the carbon material and the silicon-based material in the negative electrode material to the compressive stress of the graphite lattice can be effectively controlled, which can improve the lithium ion transmission rate of the negative electrode material; and the peak area ratio of the fourth peak to the second peak can be controlled to enhance the conductivity of the silicon oxide material, so that the negative electrode material has excellent electrical conductivity.

[0045] The preparation method of the negative electrode material provided in the present application first prepares a mixture comprising a carbon material, a silicon oxide raw material, asphalt and a polysiloxane-type asphalt defoamer. The asphalt in the mixture can be fully liquefied after hot pressing treatment, and at the same time, under the action of the polysiloxane-type asphalt defoamer, the asphalt can be in good and close contact with the silicon oxide raw material and the carbon material; then, during the heat treatment process, the C-Si-O structure produced by the thermal decomposition of the defoamer can combine with the Si-O bond in the silicon oxide raw material and the CC bond at the edge of the carbon material, so that the silicon oxide raw material and the carbon material are combined together through chemical bonds. Compared with simple mixing, the bonding ability of the silicon oxide raw material and the carbon material can be improved, so that the silicon-based material has stronger conductivity. Finally, through carbonization treatment, a carbon material with a larger degree of defects can be formed at the bonding connection between the silicon-based material and the carbon material, which can enhance the electrical conductivity of the negative electrode material while improving the particle structure stability of the negative electrode material and improving the cycle performance of the negative electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic flow chart of the method for preparing the negative electrode material provided in the embodiments of the present application.

[0047] Figure 2 This is the Raman spectrum of the negative electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0048] The following is a preferred implementation of the embodiments of the present application. It should be noted that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the embodiments of the present application. These improvements and modifications are also considered to be within the scope of protection of the embodiments of the present application.

[0049] In a first aspect, the present application provides a negative electrode material, the negative electrode material comprising a silicon-based material and a carbon material;

[0050] In the Raman spectrum of the negative electrode material, the negative electrode material has a Raman spectrum of 450 cm -1 ~530cm -1The double peaks in the range are the first peak and the second peak according to the peak position from low to high, and the peak position difference between the first peak and the second peak is P1, 20 cm -1 ≤P1≤60cm -1 ; The negative electrode material at 1550cm -1 ~1650cm -1 There are two peaks in the range, which are the third peak and the fourth peak from low to high, and the peak position difference between the third peak and the fourth peak is P2,40cm -1 ≤P2≤80cm -1 ; and the peak area of ​​the fourth peak is B2, the peak area of ​​the second peak is A2, 0.2≤B2 / A2≤100.

[0051] The negative electrode material provided in this application includes silicon-based materials and carbon materials; -1 ~530cm -1 The double peaks in the range are the first peak and the second peak according to the peak position from low to high. The first peak is the characteristic peak of amorphous silicon, and the second peak is the characteristic peak of crystalline silicon. The peak position difference between the two peaks is controlled at 20cm -1 ~60cm -1 The range of the content ratio of amorphous silicon to crystalline silicon in the negative electrode material can be effectively controlled, the distribution uniformity of amorphous silicon and crystalline silicon can be improved, the silicon lattice distortion caused by excessive crystalline silicon can be reduced, and the structural stability of silicon-based material particles can be improved during the cycle. In addition, the negative electrode material has a high conductivity at 1550 cm -1 ~1650cm -1 There are two peaks in the range, which are the third peak and the fourth peak from low to high. The third peak is the characteristic peak of graphitized carbon material, and the fourth peak is the characteristic peak of graphitized carbon edge defects. The peak position difference between these two peaks is controlled at 40cm -1 ~80cm -1 Within this range, the ratio of the compressive stress of the lattice defects generated by the combination of the carbon material and the silicon-based material in the negative electrode material to the compressive stress of the graphite lattice can be effectively controlled, which can improve the lithium ion transmission rate of the negative electrode material; and the peak area ratio of the fourth peak to the second peak can be controlled to enhance the conductivity of the silicon oxide material, so that the negative electrode material has excellent electrical conductivity.

[0052] In some embodiments, 20 cm -1 ≤P1≤60cm -1 , P1 can be 20cm -1 , 30cm -1 , 40cm -1 , 45cm -1 , 50cm -1 , 55cm -1 or 60cm-1 Of course, it can also be other values ​​within the above range, which is not limited here. -1 , indicating that the amorphous silicon content is too much and the crystalline silicon content is too little, which will lead to a decrease in the conductivity of the negative electrode material and a decrease in the rate performance of the negative electrode material; when P1>60cm -1 , indicating that the crystalline silicon content is too much and the amorphous silicon content is too little, which will increase the size of the silicon microcrystals in the negative electrode material, easily causing large silicon lattice distortion, resulting in increased local expansion stress during the charge and discharge process, and a decrease in the conductivity and cycle performance of the negative electrode material. Therefore, in this application, P1 is controlled at 20cm -1 ~60cm -1 Within this range, the content ratio of amorphous silicon to crystalline silicon in the negative electrode material can be effectively controlled, the distribution uniformity of amorphous silicon and crystalline silicon can be improved, and the silicon lattice distortion caused by excessive crystalline silicon can be reduced, which is beneficial to improving the structural stability of the negative electrode material particles during the cycle.

[0053] In some embodiments, 40 cm -1 ≤P2≤80cm -1 , P2 can be 40cm -1 , 50cm -1 、60cm -1 、65cm -1 , 70cm -1 , 75cm -1 or 80cm -1 Of course, it can also be other values ​​within the above range, which is not limited here. -1 , indicating that the lattice compressive stress of graphite is too large; when P2>80cm -1 , indicating that the compressive stress of the lattice defects at the junction of the carbon material and the silicon-based material is too large, which will also lead to a decrease in the comprehensive conductivity of the negative electrode material. Therefore, in this application, P2 is controlled at 40cm -1 ~80cm -1 Within this range, the content ratio of non-graphite carbon material to graphitized carbon in the negative electrode material can be effectively controlled, the lithium ion transmission rate of the negative electrode material can be improved, and the non-graphite carbon material can effectively connect the silicon-based material and the graphite carbon material, which can enhance the conductivity of the silicon-based material, so that the negative electrode material has excellent electrical conductivity.

[0054] In some embodiments, the peak area of the fourth peak is B2, and the peak area of the second peak is A2, and the following relationship is satisfied: 0.2 ≤ B2 / A2 ≤ 100. Specifically, B2 / A2 can be, for example, 0.2, 0.21, 0.22, 0.25, 0.3, 0.5, 1, 1.5, 2.0, 5, 10, 20, 30, 40, 50, 80, or 100, etc. Of course, it can also be other values within the above range, which are not limited herein. The ratio of the peak areas of the fourth peak to the second peak can reflect the degree of defects at the junction of the silicon-based material and the carbon material, and can effectively improve the conductivity of the composite anode material. When the ratio of B2 / A2 is too large, the structural framework instability of the carbon material and the silicon-based material increases; when the ratio of B2 / A2 is too small, the degree of defects at the junction of the carbon material and the silicon-based material is too small, and the improvement of the conductivity of the silicon-based material is not obvious. Preferably, 1 ≤ B2 / A2 ≤ 100.

[0055] In some embodiments, in the Raman spectrum of the anode material, the peak area of the first peak is A1, and the peak area of the second peak is A2, and A1 / A2 > 0.5; specifically, A1 / A2 can be, for example, 0.51, 0.52, 0.55, 0.6, 0.7, 0.8, 0.92, 1, 1.1, or 1.2, etc. Of course, it can also be other values within the above range, which are not limited herein. If the ratio of A1 / A2 is too small, it indicates that the crystallization degree of Si in the silicon-based material is too large, and the expansion effect of the silicon-based material is aggravated, which is not conducive to improving the cycle stability of the anode material.

[0056] In some embodiments, in the Raman spectrum of the anode material, the peak area of the third peak is B1, and the peak area of the fourth peak is B2, 0.05 < B2 / B1 < 1; specifically, B2 / B1 can be, for example, 0.051, 0.06, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, or 1, etc. Of course, it can also be other values within the above range, which are not limited herein. If the ratio of B2 / B1 is too large, it indicates that the defects of the carbon material are too large, and the stability of the structural framework at the junction of the carbon material and the silicon-based material decreases; if the ratio of B2 / B1 is too small, it indicates that the defects of the carbon material are too small, and the improvement of the conductivity of the silicon-based material is not obvious, and the conductivity of the anode material decreases. Preferably, 0.05 < B2 / B1 < 0.15.

[0057] In some embodiments, the silicon-based material includes at least one of amorphous silicon, crystalline silicon, silicon oxide material, and silicate.

[0058] In some embodiments, the silicon oxide includes silicon and oxygen elements, and the atomic ratio of silicon to oxygen elements is 0 to 2, excluding 0. The atomic ratio of silicon to oxygen elements can specifically be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2, etc., which are not limited herein. Preferably, the atomic ratio of silicon to oxygen elements is 0 to 1, excluding 0.

[0059] In some embodiments, the chemical general formula of the silicon oxide is SiO x , where 0 < x ≤ 2, and x can specifically be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2, etc., which are not limited herein. Preferably, 0 < x < 1. The silicon-oxygen material can be a material formed by silicon particles dispersed in SiO2, or a material having a tetrahedral structural unit, with silicon atoms located at the center of the tetrahedral structural unit and oxygen atoms located at the four vertices of the tetrahedral structural unit.

[0060] In some embodiments, the carbon material includes at least one of natural graphite, artificial graphite, expanded graphite, graphite oxide, carbon nanoparticles, carbon nanotubes, and graphene. Preferably, the carbon material includes graphite, which is a material with high conductivity, small volume expansion, high first efficiency, and stable cycling performance. By combining graphite and the silicon-based material, the conductivity of the anode material can be comprehensively improved and the expansion can be reduced.

[0061] In some embodiments, the silicon-based material is dispersed in the carbon material, and the carbon material constructs a conductive network for the silicon-based material, overcoming the disadvantage of poor conductivity of the silicon-based material (such as the silicon oxide SiO x ), which is beneficial to the capacity utilization and cycling stability of the silicon-based material.

[0062] In some embodiments, the silicon-based material further includes a metal M element, and the metal M is selected from at least one of metals with an electronegativity < 1.8.

[0063] In some embodiments, the metal M exists in the form of a single substance M or a compound containing M, and the single substance M or the compound containing M is amorphous; the single substance M or the compound containing M has more non-bridging oxygen, and the non-bridging oxygen is more easily reduced, reducing the excessive conversion of amorphous silicon into crystalline silicon, and can effectively control the size of Si crystallites in silicon oxide, effectively inhibiting the volume expansion of the negative electrode material, and the amorphous metal M silicate is dispersed in the silicon oxide, and can also play a role in buffering and stress dispersion. The metal M silicate has more non-bridging oxygen and a low degree of silicate polymerization, which can improve the rate performance and cycle stability of the negative electrode material.

[0064] In some embodiments, the metal M is selected from at least one of Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn; preferably, the metal M includes Mg and / or Li.

[0065] In some embodiments, the metal M is magnesium, and the silicate of the metal M includes MgSiO3 and Mg2SiO4. When the metal M is magnesium, the size of Si crystallites can be further reduced, thereby reducing the expansion of the material.

[0066] In some embodiments, the mass content of the metal element M in the digestion solution of the negative electrode material is 1% to 20%, specifically 1%, 2%, 3%, 5%, 8%, 10%, 12%, 15%, 18% or 20%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0067] It should be noted that the preparation method of the negative electrode material digestion solution includes: calcining the negative electrode material at 750°C in an oxygen-containing atmosphere to constant weight, then dissolving it with a mixed acid composed of concentrated HF, concentrated HCl, and concentrated HNO3 until the solution no longer produces bubbles. The mixed acid is then repeatedly added in double the amount. When the solution still does not produce bubbles, solid-state separation is performed to obtain the negative electrode material digestion solution. The mass content of element M in the digestion solution is determined by electrically coupled plasma atomic emission spectrometry.

[0068] In some embodiments, the mass content of silicon in the negative electrode material is m Si %,The mass content of oxygen in the negative electrode material is m O %, 10%≤m O / (m Si +m O )≤53%. m O / (m Si +m O ) can specifically be 10%, 20%, 30%, 35%, 40%, 45%, 50% or 53%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0069] In some embodiments, the mass content of carbon in the negative electrode material is m C %, 50≤m C ≤99, the mass content of carbon element can specifically be 50%, 55%, 60%, 65%, 69%, 70%, 80%, 90% or 99%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0070] In some embodiments, the non-graphite carbon material is disposed on the surface of the silicon-based material to form a carbon layer. The non-graphite carbon material can be disposed on the surface of silicon-based material particles, or on the surface of carbon material particles, or the silicon-based material particles and carbon material particles can be secondary granulated and coated to form secondary particles, without limitation herein.

[0071] In some embodiments, the thickness of the carbon layer is 1 nm to 1000 nm, and can specifically be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 400 nm, 500 nm, 700 nm, 800 nm, 900 nm, 1000 nm, etc., without limitation herein. A carbon layer that is too thick and has too high a carbon content is not conducive to obtaining a negative electrode material with a high specific capacity; a carbon layer that is too thin is not conducive to increasing the conductivity of the negative electrode material and has poor performance in suppressing the volume expansion of the material, resulting in poor long-cycle performance. Preferably, the thickness of the carbon layer is 50 nm to 800 nm; more preferably, the thickness of the carbon layer is 100 nm to 500 nm.

[0072] In some embodiments, the median particle size D of the negative electrode material is 50 It is 1μm to 10μm, and specifically can be 1μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 5μm, 6μm, 8μm, 9μm or 10μm, etc., which is not limited here.

[0073] In some embodiments, the specific surface area of ​​the negative electrode material is ≤ 20 m 2 / g; specifically, 1.0m 2 / g, 1.5m 2 / g, 1.8m 2 / g, 2.0m 2 / g, 2.5m 2 / g, 3.0m 2 / g, 3.6m 2 / g, 4.0m 2 / g、5m 2 / g, 5.5m 2 / g, 6.0m 2 / g, 7.0m 2 / g, 8.0m 2 / g、8.5m 2 / g, 10.0m 2 / g, 12.0m 2 / g, 15.0m 2 / g, 18.0m 2 / g or 20.0m 2 / g, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. Controlling the specific surface area of ​​the negative electrode material within the above range is beneficial to improving the first coulombic efficiency of the negative electrode material. When the specific surface area of ​​the negative electrode material is too large, the side reactions between the negative electrode material and the electrolyte increase, which will consume more active lithium ions and reduce the first coulombic efficiency of the negative electrode material. Preferably, the specific surface area of ​​the negative electrode material is ≤10m 2 / g.

[0074] In some embodiments, the compacted density of the negative electrode material is ≤ 2 g / cm 3 The tap density of the negative electrode material can be specifically 2g / cm 3 , 1.89g / cm 3 , 1.8g / cm 3 , 1.6g / cm 3 , 1.5g / cm 3 , 1.4g / cm 3 , 1.3g / cm 3 , 125g / cm 3 , 1.2g / cm 3 , 1.18g / cm 3 or 1.0g / cm 3 etc., not limited here.

[0075] In some embodiments, the compacted density of the negative electrode material is ≤ 2 g / cm 3 When the negative electrode material has a powder conductivity of ≥5 S / cm, specifically 5 S / cm, 5.5 S / cm, 6 S / cm, 6.5 S / cm, 7 S / cm, 7.5 S / cm, or 8 S / cm, and other values ​​within the above range are also possible and are not limited here. Good powder conductivity of the negative electrode material is beneficial to improving the cycle performance of the negative electrode material. When the powder conductivity of the negative electrode material is too low, the structure of the negative electrode material becomes looser or the conductive network becomes poorer, resulting in reduced cycle stability.

[0076] In some embodiments, the negative electrode material has pores, wherein the volume proportion of micropores with a pore size of <2 nm in the total pore volume of all pores is 1% to 5%, specifically 1.1%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5% or 5.0%, etc., which are not limited here. When the volume proportion of micropores is too large, the particle structure of the negative electrode material is loose, the conductive network is incomplete, and the cycle stability of the negative electrode material decreases. The present application controls the presence of an appropriate amount of micropores in the negative electrode material. On the premise of ensuring the conductivity of the negative electrode material, it can also provide a buffer space for the volume expansion of the silicon-based material, reduce the particle breakage caused by excessive local stress, and improve the cycle stability of the negative electrode material.

[0077] In a second aspect, the present application provides a method for preparing a negative electrode material, such as Figure 1 As shown, the following steps are included:

[0078] Step S10, preparing a mixture comprising a carbon material, a silicon-oxygen raw material, and asphalt, wherein, based on the mass of the mixture being 100%, a polysiloxane-type asphalt defoamer having a mass content of 0.5% to 3% is added to the mixture;

[0079] Step S20: hot-pressing the mixture and carbonizing the hot-pressed product to obtain a negative electrode material.

[0080] The preparation method of the negative electrode material provided in the present application first prepares a mixture comprising a carbon material, a silicon oxide raw material, asphalt and a polysiloxane-type asphalt defoamer. The asphalt in the mixture can be fully liquefied after hot pressing treatment, and at the same time, under the action of the polysiloxane-type asphalt defoamer, the asphalt can be in good and close contact with the silicon oxide raw material and the carbon material; then, during the heat treatment process, the C-Si-O structure produced by the thermal decomposition of the defoamer can combine with the Si-O bond in the silicon oxide raw material and the CC bond at the edge of the carbon material, so that the silicon oxide raw material and the carbon material are combined together through chemical bonds. Compared with simple mixing, the bonding ability of the silicon oxide raw material and the carbon material can be improved, so that the silicon-based material has stronger conductivity. Finally, through carbonization treatment, a carbon material with a larger degree of defects can be formed at the bonding connection between the silicon-based material and the carbon material, which can enhance the electrical conductivity of the negative electrode material while improving the particle structure stability of the negative electrode material and improving the cycle performance of the negative electrode material.

[0081] The following is a detailed introduction to this plan:

[0082] Step S10: preparing a mixture comprising a carbon material, a silicon-oxygen raw material and asphalt, wherein, based on the mass of the mixture being 100%, a polysiloxane-type asphalt defoamer having a mass content of 0.5% to 3% is added to the mixture.

[0083] In some embodiments, the carbon material includes at least one of natural graphite, artificial graphite, expanded graphite, graphite oxide, carbon nanoparticles, carbon nanotubes, and graphene. Preferably, the carbon material includes graphite, which has high conductivity, low volume expansion, high initial efficiency, and stable cycling performance. By combining graphite with a silicon-based material, the conductivity of the negative electrode material can be comprehensively improved and its expansion can be reduced.

[0084] In some embodiments, the median particle size of the carbon material is 1 μm to 10 μm, specifically 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or 10 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0085] In some embodiments, in the mixture, the mass content of the silicon-oxygen raw material is 1% to 45%, based on the total mass of the silicon-oxygen raw material and the carbon material being 100%. The mass content of the silicon-oxygen raw material can specifically be 1%, 5%, 10%, 20%, 30%, 35%, 40%, or 45%, etc., and of course, other values ​​within the above range can also be used, which is not limited here. In this application, by controlling the mass content of the silicon raw material and the carbon material, the negative electrode material can have both the high conductivity of the carbon material and the high specific capacity of the silicon-based material.

[0086] In some embodiments, the mass content of the asphalt is 1% to 40%, based on the total mass of the silicon-oxygen raw material, carbon material, and asphalt as 100%. The mass content of the silicon-oxygen raw material can specifically be 1%, 5%, 10%, 20%, 30%, 35%, or 40%, and other values ​​within the aforementioned range are also possible and are not limited herein. It is understood that the addition of an appropriate amount of asphalt can ensure that the final negative electrode material contains an appropriate amount of conductive carbon material, thereby improving the conductivity of the negative electrode material.

[0087] In some embodiments, based on the mass of the mixture as 100%, a polysiloxane-type asphalt defoamer having a mass content of 0.5% to 3% is added to the mixture. The mass content of the polysiloxane-type asphalt defoamer can specifically be 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2.0%, 2.5%, 2.8% or 3%, etc., and of course it can also be other values ​​within the above range, which are not limited here. The C-Si-O structure produced by the thermal decomposition of the defoamer can be combined with the Si-O bond in the silicon-oxygen raw material and the CC bond at the edge of the carbon material, so that the silicon-oxygen raw material and the carbon material are combined together through chemical bonds. Compared with the reduced mixing, the bonding ability of the silicon-oxygen raw material and the carbon material can be improved, so that the prepared silicon-based material has stronger electrical conductivity. The bonding connection between the silicon-based material and the carbon material can form a carbon material with a greater degree of defects, which can enhance the electrical conductivity of the negative electrode material while improving the particle structure stability of the negative electrode material and improving the cycle performance of the negative electrode material.

[0088] In some embodiments, the asphalt includes at least one of coal tar pitch, petroleum pitch, and natural asphalt.

[0089] Step S20: hot-pressing the mixture and carbonizing the hot-pressed product to obtain a negative electrode material.

[0090] In some embodiments, the temperature of the hot pressing treatment is 200°C to 500°C. The temperature of the hot pressing treatment can be 200°C, 220°C, 230°C, 250°C, 270°C, 280°C, 300°C, 320°C, 350°C, 400°C, 420°C, 450°C, or 500°C, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the temperature of the hot pressing treatment is 250°C to 350°C.

[0091] In some embodiments, the time for hot pressing treatment is 10 minutes to 12 hours; the time for hot pressing treatment can be 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 1 hour, 2 hours, 3 hours, 5 hours, 6 hours, 8 hours, 10 hours or 12 hours, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0092] In some embodiments, the pressure of the hot pressing treatment is 1T to 50T. The pressure of the hot pressing treatment can be 1T, 5T, 10T, 15T, 20T, 25T, 30T, 35T, 40T, 45T, or 50T, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the pressure of the hot pressing treatment is 10T to 20T.

[0093] In the present application, by controlling the temperature, time and pressure of the hot pressing treatment, the asphalt can be fully integrated with the graphite and silicon-based materials, thereby improving the mixing uniformity.

[0094] In some embodiments, the carbonization temperature is 800°C to 1000°C; the carbonization temperature can be 800°C, 820°C, 850°C, 880°C, 900°C, 920°C, 950°C, 980°C or 1000°C, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0095] In some embodiments, the carbonization treatment time is 0.5h to 24h; the carbonization treatment time can be 0.5h, 1h, 2h, 3h, 5h, 6h, 8h, 10h, 12h, 15h, 18h, 20h, 22h or 24h, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0096] In some embodiments, the carbonization process is performed under a protective atmosphere.

[0097] In this application, by controlling the temperature and time of the carbonization treatment, the asphalt, asphalt defoamer, etc. can be fully carbonized. The connection between the silicon-oxygen raw material and the carbon material can form a carbon material with a greater degree of defects. This enhances the conductivity of the negative electrode material while improving the particle structure stability of the negative electrode material and the cycle performance of the negative electrode material. In some embodiments, the protective atmosphere includes at least one of nitrogen, helium, neon, argon, krypton, and xenon.

[0098] Furthermore, the method further comprises: screening and demagnetizing the carbonized material to obtain a negative electrode material.

[0099] In some embodiments, the screening method is any one of a fixed screen, a drum screen, a resonance screen, a roller screen, a vibrating screen and a chain screen, and the screening mesh number is 100 to 500 meshes. Specifically, the screening mesh number can be 100 mesh, 200 mesh, 250 mesh, 325 mesh, 400 mesh, 500 mesh, etc. Preferably, the screening mesh number is 250 mesh, and the particle size of the negative electrode material is controlled within the above range, which is beneficial to improving the processing performance of the negative electrode material.

[0100] In some embodiments, the demagnetization equipment is any one of a permanent magnetic drum magnetic separator, an electromagnetic iron remover, and a pulsating high gradient magnetic separator. The purpose of demagnetization is to ultimately control the magnetic material content of the negative electrode material, avoid the discharge effect of the magnetic material on the lithium-ion battery, and the safety of the battery during use.

[0101] The present application also provides a battery using the negative electrode material provided in the above-mentioned embodiments of the present application or using the negative electrode material preparation method provided in the above-mentioned embodiments of the present application. The battery can be a lithium-ion battery or a sodium-ion battery. The battery provided in the present application has the advantages of excellent rate performance and low expansion.

[0102] Test method:

[0103] 1) Particle size of negative electrode material:

[0104] The particle size test method refers to GB / T 19077-2016. The volume-based cumulative particle size distribution is measured using laser diffraction. D10 represents the particle size at which the cumulative volume-based particle size distribution reaches 10%, D50 represents the particle size at which the cumulative volume-based particle size distribution reaches 50%, and D90 represents the particle size at which the cumulative volume-based particle size distribution reaches 90%.

[0105] 2) Test method for specific surface area of ​​negative electrode material:

[0106] At constant temperature and low temperature, after measuring the adsorption amount of gas on the solid surface at different relative pressures, the monolayer adsorption amount of the sample is obtained based on the Brownauer-Ettel-Taylor adsorption theory and its formula (BET formula), thereby calculating the specific surface area of ​​the material.

[0107] 3) Test method for mass content of carbon element in negative electrode material:

[0108] The mass content of amorphous carbon was determined by thermogravimetric analysis.

[0109] 4) Test method for the mass content of oxygen in negative electrode materials:

[0110] An oxygen, nitrogen and hydrogen analyzer was used to test the oxygen mass content in the negative electrode material.

[0111] 5) Test method for mass content of M element in negative electrode material:

[0112] The negative electrode material was burned at 750℃ in an oxygen-containing atmosphere to constant weight, and then dissolved with a mixed acid consisting of concentrated HF, concentrated HCl, and concentrated HNO3 until the solution no longer produced bubbles. The mixed acid was then added twice as much. When the solution still had no bubbles, solid separation was performed to obtain the digestion solution of the negative electrode material. The mass content of element M in the digestion solution was measured by electrically coupled plasma atomic emission spectrometry. M .

[0113] 6) Test method for mass content of silicon in negative electrode materials:

[0114] According to the measured mass content of carbon element in the negative electrode material m C , oxygen element mass content m O And the mass content of element M m M , calculate the mass content of silicon element, m Si =1-m C -m O -m M .

[0115] 7) Raman testing method in negative electrode materials:

[0116] The negative electrode material was tested using a laser confocal Raman spectrometer with a laser wavelength of 532 nm and a test range of 100 cm -1 Up to 3000cm -1 , randomly select no less than 15 points and test to obtain multiple Raman spectrum curves.

[0117] When processing the data, LabSpec software was used to remove the baseline of the Raman spectrum curves of all the points, and then to search for peaks. By adjusting the peak search parameters, the peak at 480 cm -1 ~530cm -1There is a single peak or doublet at 1550cm -1 ~1650cm -1 The peaks can be separated into two peaks. If the peaks separated exceed two, the impurity peaks that do not meet the peak spacing are deleted. After fixing the peak position and performing fitting, the peak height I of each specified peak position of each curve can be obtained. Then, at each peak position, the peak height I obtained by all curve fitting is averaged. The average peak height value of the peak position is the average peak height of the first, second, third, and fourth peaks.

[0118] Directly read the peak areas of the first, second, third and fourth peaks from the test software LabSpec. 8) Test method for residual carbon rate of asphalt:

[0119] Weigh a certain amount of pitch, record the weight as m(A), heat treat it at 1000°C in an Ar atmosphere for 12 hours, remove the product and weigh it, record the weight as m(B). Residual carbon rate = m(B) / m(A).

[0120] The asphalt carbon residue in this application has a weight m 沥青残碳 With asphalt weight m 沥青 The relationship is: m 沥青残碳 =m 沥青 *Carbon residue rate.

[0121] 9) Button battery test

[0122] The prepared negative electrode material, conductive carbon black, and polyacrylic acid binder were dissolved in a solvent at a mass ratio of 75:15:10. The mixture was then coated onto a copper foil current collector and dried under vacuum to produce the negative electrode sheet. A lithium metal sheet was used as the counter electrode, and button-type batteries were assembled in an argon-filled glove box. Charge and discharge tests were conducted at a current density of 0.1C over a range of 0.01-1.5V.

[0123] 10) Electrochemical performance test

[0124] The prepared negative electrode material was mixed with graphite in a ratio of 10:90, then mixed with sodium carboxymethyl cellulose (CMC), binder styrene-butadiene rubber (SBR), conductive agent Super-P, and conductive agent KS-6 in a mass ratio of 92:2:2:2 to form a slurry. The mixture was coated on copper foil, vacuum dried, and roll-pressed to produce the negative electrode. A ternary positive electrode prepared using a conventional process was then assembled with a 1 mol / L LiPF6 / ethylene carbonate + dimethyl carbonate + methyl ethyl carbonate (v / v = 1:1:1) electrolyte, a Celgard 2400 separator, and a casing using conventional production processes to create a CR2016 simulated battery. Cycling performance was tested using a constant current charge-discharge experiment at 30 mA, with the charge and discharge voltage limited to 0-1.5 V. Testing was performed using the LAND battery testing system from Wuhan Jinnuo Electronics Co., Ltd. Charge and discharge tests were conducted at a current density of 0.1C over a charge and discharge range of 0.005 V to 1.5 V.

[0125] First coulombic efficiency = first cycle discharge capacity / first cycle charge capacity.

[0126] Repeat the cycle for 50 times, and use a micrometer to measure the thickness of the lithium-ion battery electrode at this time, which is H1. The expansion rate after 50 cycles = (H1-H0) / H0×100%.

[0127] Repeat 100 cycles and record the discharge capacity as the remaining capacity of the lithium-ion battery; capacity retention rate = remaining capacity / initial capacity*100%.

[0128] The following further illustrates the embodiments of the present application in multiple embodiments. The embodiments of the present application are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0129] Example 1

[0130] A method for preparing a negative electrode material comprises the following steps:

[0131] (1) 1 kg of SiO material was mixed with 9 kg of graphite and 1.852 kg of asphalt to obtain a mixture. 1% of a polysiloxane type asphalt defoamer was also added to the mixture. The residual carbon rate of the asphalt used was 60%, and the m SiO / (m SiO +m 石墨 )=10%,m 沥青残碳 / (m SiO +m 石墨 +m 沥青残碳 )=10%.

[0132] (2) The following mixture was placed into a mold and hot pressed at 400°C and 30T pressure for 1 h to obtain a hot pressed product.

[0133] (3) The hot-pressed product was placed in a kiln at 900°C for heat treatment for 12 hours under an Ar atmosphere to obtain a negative electrode material.

[0134] The negative electrode material prepared in the embodiment of the present application includes an active substance and a carbon material located on at least a portion of the surface of the active substance, wherein the active substance includes silicon oxide and graphite.

[0135] Figure 2 This is a Raman spectrum of the negative electrode material prepared in Example 1 of the present application. The parameters of the negative electrode material are detailed in Table 1.

[0136] Example 2

[0137] A method for preparing a negative electrode material comprises the following steps:

[0138] (1) 1 kg of SiO material was mixed with 0.0877 kg of asphalt to obtain a mixture. 1% of a polysiloxane type asphalt defoamer was also added to the mixture. The residual carbon rate of the asphalt used was 60%, and the m 沥青残碳 / (m SiO +m 沥青残碳 )=5%.

[0139] (2) The mixture was placed in an Ar atmosphere and heat treated in a kiln at 900 °C for 12 h to obtain carbon-coated SiO.

[0140] (3) 1 kg of carbon-coated SiO2 was mixed with 9 kg of graphite and 1.852 kg of asphalt to obtain a mixture. 1% of a polysiloxane-type asphalt defoamer was also added to the mixture. The residual carbon rate of the asphalt used was 60%, and the m SiO / (m SiO +m 石墨 )=10%,m 沥青残碳 / (m SiO +m 石墨 +m 沥青残碳 )10%.

[0141] (4) The following mixture was placed into a mold and hot pressed at 400°C and 30T pressure for 1 h to obtain a hot pressed product.

[0142] (5) The hot-pressed product was placed in a kiln at 900°C for heat treatment for 12 hours under an Ar atmosphere to obtain a negative electrode material.

[0143] The negative electrode material prepared in the embodiment of the present application includes an active substance and a carbon material located on at least a portion of the surface of the active substance, wherein the active substance includes silicon oxide and graphite.

[0144] The parameters of the negative electrode materials are detailed in Table 1.

[0145] Example 3

[0146] The difference from Example 1 is that:

[0147] (1) 1 kg of SiO material was mixed with 9 kg of graphite and 1.852 kg of asphalt to obtain a mixture. 0.5% of a polysiloxane type asphalt defoamer was also added to the mixture. The residual carbon rate of the asphalt used was 60%, and the m SiO / (m SiO +m 石墨 )=10%,m 沥青残碳 / (m SiO +m 石墨 +m 沥青残碳 )10%.

[0148] Example 4

[0149] The difference from Example 1 is that

[0150] (1) 1 kg of SiO material was mixed with 9 kg of graphite and 1.852 kg of asphalt to obtain a mixture. 1% of ether-modified silicone oil asphalt defoamer was also added to the mixture. The residual carbon rate of the asphalt used was 60%, and the m SiO / (m SiO +m 石墨 )=10%,m 沥青残碳 / (m SiO +m 石墨 +m 沥青残碳 )10%.

[0151] Example 5

[0152] The difference from Example 1 is that

[0153] (1) 1 kg of SiO / Mg2SiO4 composite material was mixed with 9 kg of graphite and 1.852 kg of asphalt to obtain a mixture. 1% of an ether-modified silicone oil asphalt defoamer was also added to the mixture. The residual carbon rate of the asphalt used was 60%, and the m SiO / (m SiO / Mg2SiO4 +m 石墨 )=10%,m 沥青残碳 / (m SiO / Mg2SiO4 +m 石墨 +m 沥青残碳 )10%.

[0154] Example 6

[0155] The difference from Example 1 is that

[0156] (1) 1 kg of SiO material was mixed with 9 kg of graphite and 1.852 kg of asphalt to obtain a mixture. 1% of ether-modified silicone oil asphalt defoamer was also added to the mixture. The residual carbon rate of the asphalt used was 60%, and the m SiO / (m SiO +m 石墨 )=10%,m 沥青残碳 / (m SiO +m 石墨 +m 沥青残碳 )=40%.

[0157] Example 7

[0158] The difference from Example 1 is that

[0159] (4) The following mixture was placed into a mold and hot pressed at 400°C and 10T pressure for 12 h to obtain a hot pressed product.

[0160] Example 8

[0161] The difference from Example 1 is that

[0162] (4) The following mixture was placed into a mold and hot pressed at 300°C and 30T pressure for 1 h to obtain a hot pressed product.

[0163] Example 9

[0164] The difference from Example 1 is that:

[0165] (1) 1 kg of SiO material was mixed with 9 kg of graphite and 1.852 kg of asphalt to obtain a mixture. 5% of a polysiloxane type asphalt defoamer was also added to the mixture. The residual carbon rate of the asphalt used was 60%, and the m SiO / (m SiO +m 石墨 )=10%,m 沥青残碳 / (m SiO +m 石墨 +m 沥青残碳 )=10%.

[0166] Comparative Example 1

[0167] A method for preparing a negative electrode material comprises the following steps:

[0168] (1) 1 kg of SiO material was mixed with 0.1852 kg of asphalt to obtain a mixture, wherein the residual carbon content of the asphalt was 60%, m 沥青残碳 / (m SiO +m 沥青残碳 )=10%.

[0169] (2) The mixture was placed in an Ar atmosphere and heat treated in a kiln at 900 °C for 12 h to obtain carbon-coated SiO.

[0170] (3) 1 kg of carbon-coated SiO2 was mixed with 9 kg of graphite to obtain the negative electrode material, wherein m 碳包覆SiO / (m 碳包覆SiO +m 石墨 )=10%.

[0171] The negative electrode material prepared in the embodiment of the present application includes carbon-coated silicon oxide and graphite.

[0172] The parameters of the negative electrode materials are detailed in Table 1.

[0173] Comparative Example 2

[0174] The difference from Example 1 is that:

[0175] (2) The following mixture was placed into a mold and cold pressed at room temperature and 30°C for 1 h to obtain a cold pressed product.

[0176] Comparative Example 3

[0177] A method for preparing a negative electrode material comprises the following steps:

[0178] (1) 1 kg of SiO material was mixed with 9 kg of graphite and 1.852 kg of asphalt to obtain a mixture. 1% of a polysiloxane type asphalt defoamer was also added to the mixture. The residual carbon rate of the asphalt used was 60%, and the m SiO / (m SiO +m 石墨 )=10%,m 沥青残碳 / (m SiO +m 石墨 +m 沥青残碳 )=10%.

[0179] (2) The mixture was placed in an Ar atmosphere and heat treated in a kiln at 900°C for 12 hours to obtain a negative electrode material.

[0180] The negative electrode material prepared in the embodiment of the present application includes an active substance and a carbon material located on at least a portion of the surface of the active substance, wherein the active substance includes silicon oxide and graphite.

[0181] The parameters of the negative electrode materials are detailed in Table 1.

[0182] The performance tests were conducted on the negative electrode materials obtained in the examples and comparative examples. The results of the above performance tests are shown in Tables 1 to 3:

[0183] Table 1. Summary of performance test results of negative electrode materials

[0184]

[0185]

[0186] Table 2. Summary of performance test results of negative electrode materials

[0187] sample A1 B1 A2 B2 B2 / A2 A1 / A2 B2 / B1 Example 1 3904.2 39420.2 4906.62 4172.01 0.85 0.796 0.106 Example 2 2928.3 15440.0 3039.81 1286.36 0.42 0.963 0.083 Example 3 3051 34805.4 2562.3 4003.16 1.56 1.191 0.115 Example 4 1333.4 41241.3 1363.2 3042.80 2.23 0.978 0.074 Example 5 2428.9 16163.5 4149.3 1114.83 0.27 0.585 0.069 Example 6 3861.0 22231.7 3542.8 2327.32 0.66 1.090 0.105 Example 7 4145.3 42585.3 5012.2 3041.4 0.61 0.827 0.071 Example 8 3542.5 16174.2 4045.1 1818.0 0.45 0.876 0.112 Example 9 1311.8 16383.3 1271.9 868.3 0.68 1.031 0.053 Comparative Example 1 992.4 15183.0 1052.3 none none none none Comparative Example 2 174.8 43142.4 352.3 2088.44 5.9 0.496 0.048 Comparative Example 3 1109.6 30283.6 1499.0 114.38 0.07 0.74 0.004

[0188] Table 3. Summary of the electrochemical performance results of the battery

[0189]

[0190]

[0191] According to the data in Tables 1 and 2, by preparing a mixture comprising graphite, silicon oxide raw material, asphalt and polysiloxane-type asphalt defoaming agent, the mixture can be fully liquefied after hot pressing treatment, and at the same time, under the action of the polysiloxane-type asphalt defoaming agent, the asphalt can be in good and close contact with the silicon oxide material and graphite; finally, during the heat treatment process, the C-Si-O structure produced by the thermal decomposition of the defoaming agent can be combined with the Si-O bond in the silicon oxide material and the CC bond at the edge of the graphite, so that the silicon-based material and the graphite are combined together through chemical bonds. Compared with the reduced mixing, the bonding ability of the silicon-based material and the graphite can be improved, so that the silicon-based material has stronger conductivity. The bonding connection between the silicon-based material and the graphite can form a carbon material with a greater degree of defects, which can enhance the electrical conductivity of the negative electrode material while improving the particle structure stability of the negative electrode material and improving the cycle performance of the negative electrode material.

[0192] During the preparation process of Comparative Example 1, no polysiloxane-type asphalt defoaming agent was added, the bonding ability between the silicon-based material and the graphite decreased, the degree of carbon material defects at the bonding connection between the silicon-based material and the graphite decreased, and the conductive performance of the negative electrode material also decreased accordingly.

[0193] During the preparation process of Comparative Examples 2 and 3, no hot pressing process was used, or the cold pressed products obtained by cold pressing were carbonized. The asphalt was difficult to fully liquefy, and the contact tightness between the asphalt and the silicon-based material and graphite decreased, and the conductive performance of the negative electrode material also decreased accordingly; and due to the decrease in bonding strength, the expansion effect of the negative electrode material was aggravated, and the cycle performance of the negative electrode material also decreased accordingly.

[0194] Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the claims. Any person skilled in the art may make several possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

Claims

1. A negative electrode material, characterized in that The negative electrode material includes silicon-based materials and carbon materials; In the Raman spectrum of the negative electrode material, the negative electrode material has a Raman spectrum of 450 cm -1 ~530cm -1 The double peaks in the range are the first peak and the second peak according to the peak position from low to high, and the peak position difference between the first peak and the second peak is P1, 20 cm -1 ≤P1≤60cm -1 ; The negative electrode material is at 1550 cm -1 ~1650cm -1 There are two peaks in the range, which are the third peak and the fourth peak from low to high, and the peak position difference between the third peak and the fourth peak is P2,40cm -1 ≤P2≤80cm -1 ; The peak area of ​​the fourth peak is B2, the peak area of ​​the third peak is B1, the peak area of ​​the second peak is A2, the peak area of ​​the first peak is A1, 0.05 <B2 / B1<1,A1 / A2> 0.5, 0.2≤B2 / A2≤100.

2. The negative electrode material according to claim 1, characterized in that The silicon-based material further includes a metal M element, and the metal M is selected from at least one metal with an electronegativity less than 1.

8.

3. The negative electrode material according to claim 2, characterized in that The negative electrode material satisfies at least one of the following characteristics: (1) The metal M exists in the form of a single substance M or a compound containing M; (2) The metal M is at least one selected from Li, K, Na, Mg, Ca, Al, La, Zn, Ti and Mn; (3) The metal M includes Mg and / or Li.

4. The negative electrode material according to any one of claims 1 to 3, characterized in that The negative electrode material satisfies at least one of the following characteristics: (1) The silicon-based material includes at least one of amorphous silicon, crystalline silicon, silicon-oxygen material and silicate; (2) The carbon material includes at least one of natural graphite, artificial graphite, carbon nanotubes and graphene; (3) The mass content of silicon in the negative electrode material is m Si %, the mass content of oxygen element in the negative electrode material is m O %,10%≤m O / (m Si +m O )≤53%; (4) The mass content of carbon in the negative electrode material is m C %,50≤m C ≤99; (5) Median particle size D of the negative electrode material 50 1μm~10μm; (6) The specific surface area of ​​the negative electrode material is ≤20 m 2 / g; (7) The negative electrode material has pores, wherein the volume of micropores with a pore diameter of less than 2 nm accounts for 1% to 5% of the total pore volume of all pores; (8) The compaction density of the negative electrode material is ≤ 2 g / cm 3 ; (9) The compaction density of the negative electrode material is ≤2 g / cm 3 When the negative electrode material has a powder conductivity of ≥5S / cm.

5. The negative electrode material according to any one of claims 1 to 3, characterized in that The negative electrode material satisfies at least one of the following characteristics: (1) The silicon-based material includes silicon oxide, and the silicon oxide includes silicon and oxygen, and the atomic ratio of the silicon to oxygen is 0 to 2, excluding 0; (2) The silicon-based material includes silicon oxide, and the chemical formula of the silicon oxide is SiO x , where 0<x≤2.

6. A method for preparing the negative electrode material according to any one of claims 1 to 5, characterized in that: The following steps are involved: preparing a mixture comprising a carbon material, a silicon raw material, asphalt, and a polysiloxane-type asphalt defoamer; The mixture is subjected to a hot pressing process, and the hot pressing product is subjected to a carbonization process to obtain a negative electrode material.

7. The preparation method according to claim 6, characterized in that The method satisfies at least one of the following characteristics: (1) The carbon material includes at least one of natural graphite, artificial graphite, carbon nanotubes and graphene; (2) The carbon material includes graphite; (3) The mixture further comprises at least one of amorphous silicon, crystalline silicon and silicate; (4) The asphalt includes at least one of coal tar asphalt and petroleum asphalt.

8. The preparation method according to claim 6, characterized in that The method satisfies at least one of the following characteristics: (1) In the mixture, the mass content of the silicon-oxygen raw material is 1% to 45%, based on the total mass of the silicon-oxygen raw material and the carbon material being 100%; (2) In the mixture, the mass content of the asphalt is 1% to 40%, based on the total mass of the silicon-oxygen raw material, the carbon material and the asphalt being 100%; (3) Based on the mass of the mixture being 100%, a polysiloxane asphalt defoamer having a mass content of 0.5% to 3% is added to the mixture.

9. The preparation method according to claim 6, characterized in that The method satisfies at least one of the following characteristics: (1) The temperature of the hot pressing treatment is 200°C to 500°C; (2) The heat pressing treatment time is 10 minutes to 12 hours; (3) The pressure of the hot pressing treatment is 1T~50T; (4) The carbonization treatment temperature is 800°C to 1000°C; (5) The carbonization treatment time is 0.5h~24h; (6) The carbonization treatment is carried out under a protective atmosphere; (7) The carbonization treatment is carried out under a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, helium, neon, argon, krypton and xenon.

10. A battery, characterized in that: The negative electrode material comprises the negative electrode material according to any one of claims 1 to 5 or the negative electrode material prepared by the preparation method according to any one of claims 6 to 9.

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