Negative electrode material and battery

Abstract

The invention relates to a negative electrode material and a battery, the negative electrode material comprises an active substance, the active substance comprises silicon, a silicon oxide and a compound of a metal element M, the compaction density of the negative electrode material is P g / cm < 3 >, the true density is T g / cm < 3 >, the desorption accumulated total pore volume is V cm < 3 > / g, the energy storage index of the negative electrode material is X, X = T-1 * (P-1-T-1-V)-1, 1.1 < = X < = 1.5. The negative electrode material disclosed by the invention has proper compaction density, so that the negative electrode material has relatively high energy density, and meanwhile, the cycle performance, the charge-discharge efficiency and the rate capability of the negative electrode material can also be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of negative electrode materials, in particular to a negative electrode material and a battery. BACKGROUND

[0002] Lithium ion batteries have the advantages of high energy density, small self-discharge, good safety performance, long cycle life, high working voltage and the like, and are widely used in the fields of consumer electronics, electric vehicles, energy storage materials and the like. The negative electrode material is an important component of the lithium ion battery, which directly affects the key indicators of the battery such as energy density, cycle life and safety performance. At present, the commercialized lithium ion battery mainly uses graphite-based negative electrode material, but its theoretical specific capacity is only 372 mAh / g, which is difficult to meet the demand of high energy density lithium ion battery. Silicon-based negative electrode material containing Si and silicon oxide (general formula: SiO x x≤2) has a very high specific capacity and is one of the candidate materials for the next generation of high energy density lithium ion batteries. However, the silicon-based negative electrode material will produce a huge volume change during the charge and discharge cycle, which will lead to the deterioration of the material / pole piece structure and the instability of the solid electrolyte interface film (SEI), thereby causing the sharp decline of the electrochemical performance.

[0003] At present, the silicon-based negative electrode material is often compounded with metal-doped materials to improve the volume expansion of the silicon-based negative electrode material through the doping of metal elements, so as to improve the electrochemical performance of the silicon-based negative electrode material. However, the existing compounding method is often to simply mix the silicon-based negative electrode material with the metal-doped material, which leads to loose combination between the negative electrode material particles and cannot meet the market demand for obtaining negative electrode materials with high tap density and good cycle performance. Therefore, it is necessary to explore the action mechanism of the synergistic effect of various factors and develop negative electrode materials that meet the market demand. SUMMARY

[0004] The present application provides a negative electrode material and a battery. The negative electrode material has a suitable tap density, which can make the negative electrode material have a high energy density, and can also improve the cycle performance, charge and discharge efficiency and rate performance of the negative electrode material.

[0005] In a first aspect, the present application provides a negative electrode material, which comprises an active substance, the active substance comprises silicon, silicon oxide and a compound of a metal element M, the tap density of the negative electrode material is P g / cm 3 , the true density is T g / cm 3 , the cumulative total pore volume of desorption is V cm 3 / g, the energy storage index of the negative electrode material is X, X=T -1 *(P -1 -T -1 -V) -1, 1.1≤X≤1.5.

[0006] In some embodiments, the silicon oxide has a general formula of SiO x , 0<x≤2.

[0007] In some embodiments, the compound of the metal element M includes at least one of an oxide of the metal element M or a silicate of the metal element M.

[0008] In some embodiments, the metal element M includes at least one of Mg, Li, Fe, Al, Mn and Cu.

[0009] In some embodiments, the mass content of the metal element M in the negative electrode material is 5% to 20%.

[0010] In some embodiments, the compaction density of the negative electrode material is P g / cm 3 , 1.2≤P≤1.5.

[0011] In some embodiments, the true density of the negative electrode material is T g / cm 3 , T≥2.4.

[0012] In some embodiments, the cumulative total pore volume of the negative electrode material is V cm 3 / g, 0.02≤V≤0.04.

[0013] In some embodiments, the negative electrode material is tested by Raman spectrum, and the negative electrode material has a characteristic peak of Si-Si bond in a range of 500 cm -1 to 540 cm -1 , the highest peak intensity of the characteristic peak of Si-Si bond is I1, has a characteristic peak of Si-O bond in a range of 900 cm -1 to 1000 cm -1 , the highest peak intensity of the characteristic peak of Si-O bond is I2, and I1 / I2≥4.

[0014] In some embodiments, the average desorption pore diameter of the negative electrode material is 6 nm to 9 nm.

[0015] In some embodiments, the negative electrode material further includes a carbon material, and the carbon material is between the active substances and / or on the surface of the active substances.

[0016] In some embodiments, the carbon material includes amorphous carbon.

[0017] In some embodiments, the carbon material on the surface of the active substances forms a carbon layer, and the mass content of the carbon element in the negative electrode material is 0.5% to 10%.

[0018] In some embodiments, the tap density of the negative electrode material is ≥ 0.87 g / cm 3 .

[0019] In some embodiments, the specific surface area of the negative electrode material is ≤ 10 cm 2 / g.

[0020] In some embodiments, the pH of the negative electrode material is 6-10.

[0021] In some embodiments, the moisture content of the negative electrode material is ≤ 0.5 wt%.

[0022] In some embodiments, the mass content of oxygen element in the negative electrode material is 26%-33%.

[0023] In some embodiments, the particle size of the negative electrode material satisfies: 1.0 μm ≤ D 10 ≤ 3.0 μm, 4.5 μm ≤ D 50 ≤ 7.0 μm, and 8.0 μm ≤ D 90 ≤ 12.0 μm.

[0024] In a second aspect, the present application provides a battery comprising the negative electrode material of the first aspect.

[0025] Compared with the prior art, the technical scheme of the present application has at least the following beneficial effects:

[0026] The negative electrode material provided by the present application comprises an active substance, the active substance comprises silicon, silicon oxide and a compound of a metal element M, the tap density of the negative electrode material is P g / cm 3 , the true density is T g / cm 3 , and the cumulative total pore volume of desorption is V cm 3 / g; the energy storage index of the negative electrode material is defined as X, X = T -1 *(P -1 -T -1 -V) -11.1≤X≤1.5. The true density of the negative electrode material can reflect the compactness of its structure and internal pore structure. The compaction density of the negative electrode material can reflect the tightness of the bonding between the particles and the consistency of the surface morphology of the particles. At the same time, the internal pore structure of the negative electrode material is related to the cumulative total pore volume of the desorption of the negative electrode material. In this application, the energy storage index X of the negative electrode material can be used to measure the volumetric energy density of the negative electrode material. By controlling the balance between the compaction density, true density, and cumulative total pore volume of the negative electrode material, the energy storage index X of the negative electrode material is controlled within the range of 1.1 to 1.5. This reduces the interfacial repulsion between negative electrode material particles, allowing the particles to bond tightly together, thus giving the negative electrode material a suitable compaction density. This results in the electrode sheet made from the negative electrode material having a high energy density. At the same time, the negative electrode material particles have a suitable pore structure. During charge and discharge, these pore structures can be used to provide buffer space for the volume expansion of the active material in the negative electrode material, reducing the volume expansion of the negative electrode material and thus improving the cycle performance of the negative electrode material. Furthermore, these pore structures can also improve the lithium-ion transport efficiency between negative electrode material particles, thereby improving the rate performance of the negative electrode material. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Figure 1 Raman spectra of the negative electrode material provided in the embodiments of this application;

[0029] Figure 2 This is a schematic diagram of the discharge state of a battery provided in an embodiment of this application.

[0030] Figure 2 middle:

[0031] 1-Positive electrode sheet; 11-Positive current collector; 12-Positive active layer; 2-Negative electrode sheet; 21-Negative current collector; 22-Negative active material layer; 3-Separating membrane. Detailed Implementation

[0032] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0033] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0035] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0036] In a first aspect, this application provides a negative electrode material, which includes an active material comprising silicon, silicon oxide, and a compound of metal element M. The compaction density of the negative electrode material is P g / cm³. 3 The true density is T g / cm³. 3 The cumulative total pore volume of desorption is V cm³. 3 / g, the energy storage index of the negative electrode material is X, X=T -1 *(P -1 -T -1 -V) -1 , 1.1≤X≤1.5.

[0037] In the above-described scheme, the negative electrode material provided in this application includes an active material, which comprises compounds of silicon, silicon oxide, and metal element M. The compaction density of the negative electrode material is P g / cm³. 3 The true density is T g / cm³. 3 The cumulative total pore volume of desorption is V cm³. 3 / g; Define the energy storage index of the negative electrode material as X, X = T -1 *(P -1 -T -1 -V) -11.1≤X≤1.5. The true density of the negative electrode material can reflect the compactness of its structure and internal pore structure. The compaction density of the negative electrode material can reflect the tightness of the bonding between the particles and the consistency of the surface morphology of the particles. At the same time, the internal pore structure of the negative electrode material is related to the cumulative total pore volume of the desorption of the negative electrode material. In this application, the energy storage index X of the negative electrode material can be used to measure the volumetric energy density of the negative electrode material. By controlling the balance between the compaction density, true density, and cumulative total pore volume of the negative electrode material, the energy storage index X of the negative electrode material is controlled within the range of 1.1 to 1.5. This reduces the interfacial repulsion between negative electrode material particles, allowing the particles to bond tightly together, thus giving the negative electrode material a suitable compaction density. This results in the electrode sheet made from the negative electrode material having a high energy density. At the same time, the negative electrode material particles have a suitable pore structure. During charge and discharge, these pore structures can be used to provide buffer space for the volume expansion of the active material in the negative electrode material, reducing the volume expansion of the negative electrode material and thus improving the cycle performance of the negative electrode material. Furthermore, these pore structures can also improve the lithium-ion transport efficiency inside the negative electrode material particles, thereby improving the charge and discharge efficiency and rate performance of the negative electrode material.

[0038] In some embodiments, the energy storage index of the negative electrode material is X, where 1.1 ≤ X ≤ 1.5. Specifically, it can be 1.1, 1.11, 1.15, 1.2, 1.21, 1.23, 1.25, 1.28, 1.3, 1.35, 1.36, 1.4, 1.42, 1.47, or 1.5, etc., and of course, other values ​​within the above range are also possible, without limitation. The energy storage index X of the negative electrode material can be used to measure the volumetric energy density of the negative electrode material. The larger the X value, the greater the true density of the negative electrode material particles themselves, the smaller the cumulative total pore volume of desorption on the surface of the negative electrode material particles, the smaller the interfacial repulsion between the negative electrode material particles, the tighter the bonding between the negative electrode material particles, the higher the compaction density of the negative electrode material, and the higher the lithium storage capacity per unit volume of the negative electrode material, which is beneficial to improving the energy density of the battery made from the negative electrode material. However, when X is greater than 1.5, the true density of the negative electrode material itself is too high, and there are fewer pores inside and on the surface of the negative electrode material particles. The internal structure of the negative electrode material particles does not have a certain buffer space to alleviate the volume expansion of the active material. The negative electrode material is prone to large expansion deformation during battery charging and discharging. In addition, the interfacial repulsion force between the negative electrode material particles is too small, which makes the negative electrode material particles too tightly bound and prone to agglomeration. This is not conducive to the insertion and extraction of lithium ions, resulting in poor charge and discharge efficiency and rate performance of the battery made from this negative electrode material. The smaller the X value, the greater the interfacial repulsion between the negative electrode material particles, making it less likely for the particles to agglomerate. This helps to increase the overall contact area between lithium ions and the negative electrode material. Furthermore, the true density of the negative electrode material particles is also smaller, indicating that the particles themselves have a certain porosity. At the same time, the cumulative total pore volume of desorption on the surface of the negative electrode material particles is larger. The surface and interior of the negative electrode material particles have sufficient pores, which can provide buffer space for the volume expansion of the active material, reducing the volume expansion of the negative electrode material and thus improving the cycle performance of the negative electrode material. It can also improve the lithium ion transport efficiency inside the negative electrode material particles, thereby improving the charge and discharge efficiency and rate performance of the negative electrode material. However, when X < 1.1, the interfacial repulsion between the negative electrode material particles is too large. At this time, the fluidity between the negative electrode material particles increases, their mechanical properties decrease, and the negative electrode material particles are difficult to bond tightly together, resulting in a decrease in the compaction density of the negative electrode material. The electrode sheet made from this negative electrode material is prone to powdering during cycling. In addition, the true density of the negative electrode material particles is too small, and the unit lithium storage capacity of the negative electrode material itself is low, which reduces the energy density of the negative electrode material. At the same time, the structural strength of the negative electrode material particles themselves decreases, and the total pore volume accumulated by desorption on the surface of the negative electrode material particles is too large. During the cycling expansion process, the supporting skeleton is prone to breakage and structural damage, resulting in a decrease in the electrochemical performance of the negative electrode material.When 1.36 ≤ X ≤ 1.5, the anode material possesses suitable compaction density, true density, and cumulative total pore volume due to desorption. On one hand, the anode material particles themselves have a relatively compact structure, and the particles are tightly bonded together, resulting in a high energy density in the electrode sheet. On the other hand, the interfacial repulsion between the particles is low, and the appropriate porosity between the particles is beneficial for improving lithium-ion transport efficiency. Furthermore, the small cumulative total pore volume due to desorption on the particle surface facilitates accelerated lithium-ion insertion and extraction within the particles. Simultaneously, the presence of a certain amount of porosity within the particles reduces volume expansion during cycling, thus resulting in good cycle performance and rate performance. When 1.1 ≤ X < 1.36, the true density of the anode material particles further decreases, and the particles possess even more porosity, leading to higher lithium-ion transport efficiency and further reducing volume expansion during cycling. This significantly improves the cycle performance and rate performance of the anode material.

[0039] In some embodiments, the general formula for silicon oxide is SiO. x , 0 < x ≤ 2. Specifically, SiO x Specifically, it could be SiO 0.5 SiO 0.7 SiO 0.9 SiO, SiO 1.2 SiO 1.5 SiO 1.8 SiO 1.9 etc. are not specified here.

[0040] In some embodiments, the compound of metal element M includes at least one of the oxide of metal element M and the silicate of metal element M.

[0041] In some embodiments, the metal element M includes at least one selected from Mg, Li, Fe, Al, Mn, and Cu.

[0042] In some embodiments, the mass content of metal element M in the negative electrode material is 5% to 20%, specifically 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, 16%, 18%, or 20%, etc., and of course, other values ​​within the above range are also possible, which are not limited here. The mass content of metal element M in the negative electrode material (i.e., the doping amount) is an important indicator affecting the internal structural characteristics of the negative electrode material. After metal element M is doped, it reacts with silicon oxide SiO2. xThe formation of a certain Si-OM bond structure during the reaction affects the overall structural strength and structural distribution characteristics of the anode material. When the mass content of metal element M in the anode material is <5%, the Si-OM bond structure formed after M doping is less, and the structure of the anode material is mainly composed of silicon oxide (SiO2). x The main issue is that the elements in the anode material are tightly bonded together, and the silicon crystals in the anode material itself are relatively small, which is not conducive to the transport and adsorption / desorption of lithium ions. When the mass ratio of metal element M in the anode material is >20%, excessive doping of metal element M will lead to the silicon oxide (SiO) in the anode material being concentrated. x The structure is damaged, making the internal structure of the negative electrode material more loose. Furthermore, the bond structure of the negative electrode material itself will generate a large number of breakpoints due to excessive metal element M doping, which will reduce the structural stability of the negative electrode material. The negative electrode material is prone to cracking and breaking during cycling, thus leading to a decrease in the electrochemical performance of the negative electrode material.

[0043] In some embodiments, the compaction density of the negative electrode material is P g / cm³. 3 The value of P is 1.2 ≤ P ≤ 1.5, specifically it can be 1.2, 1.25, 1.28, 1.3, 1.36, 1.38, 1.4, 1.45, 1.47, or 1.5, or other values ​​within the above range, which are not limited here. The compaction density of the negative electrode material reflects the tightness of the bonding between the negative electrode material particles and the consistency of their surface morphology. It is related to the interfacial repulsion between the negative electrode material particles and is one of the important indicators for measuring the energy storage index of the negative electrode material. When P < 1.2 g / cm³... 3 At this point, the surface morphology uniformity between the negative electrode material particles is poor, and the interfacial repulsion between the particles is too large, making it difficult for the particles to form a tight bond. Large gaps exist between the particles, resulting in a low energy storage index and a low energy density in the battery made from this negative electrode material. When 1.2 g / cm³... 3 ≤P≤1.5g / cm 3 When P > 1.5 g / cm³, the negative electrode material has a suitable compaction density, good surface morphology uniformity, and low interfacial repulsion between particles, allowing for tight particle bonding and a high energy storage index, resulting in a battery with high capacity. 3When the interfacial repulsion between the negative electrode material particles is too small, the electrode structure obtained after the negative electrode material is compacted is too dense. Although this can give the negative electrode material a large energy storage index, there are fewer lithium ion transport channels reserved in the negative electrode material, which is not conducive to the insertion / extraction of lithium ions. At the same time, there are fewer gaps between the negative electrode material particles, and the volume expansion generated by the negative electrode material during cycling is difficult to be effectively alleviated, thus leading to a decrease in the charge and discharge efficiency and cycle performance of the negative electrode material.

[0044] In some embodiments, the true density of the negative electrode material is T g / cm³. 3 T ≥ 2.4, specifically it can be 2.4, 2.41, 2.42, 2.45, 2.5, 2.56, 2.6, 2.67, 2.73, 2.78, or 2.8, etc., and of course, other values ​​within the above range are also possible, without limitation here. True density is the actual density of the powder anode material after removing the internal pores or voids between particles. It is one of the indicators for measuring the compactness of the anode material's own structure and the internal pore structure of the particles. When T ≥ 2.4 g / cm³ 3 This indicates that the negative electrode material contains silicon (Si) and silicon oxide (SiO). x With uniform doping of the metallic element M, the internal void volume of the anode material particles is small and the particle structure is relatively compact, which improves the structural stability of the anode material. This helps to disperse the expansion stress generated during cycling, reduces the probability of structural damage during cycling, and thus improves the cycling performance of the anode material. When T < 2.4 g / cm³ 3 When the time is right, it indicates that there is a large pore space inside the negative electrode material, and the structure of the negative electrode material itself is not very compact, which is not conducive to maintaining the cycle stability of the negative electrode material.

[0045] In some embodiments, the cumulative total pore volume of the negative electrode material after desorption is V cm⁻¹. 3 / g, 0.02≤V≤0.04, specifically can be 0.02, 0.021, 0.023, 0.025, 0.03, 0.032, 0.035, 0.037, or 0.04, etc., and of course, other values ​​within the above range are also possible, without limitation here. The cumulative total pore volume of desorption in the negative electrode material is related to the uniformity of doping of the metal element M in the negative electrode material and the surface morphology and structure of the negative electrode material, and is one of the indicators for measuring the internal pore structure of the negative electrode material particles. When V < 0.02cm 3 At / g, the doping uniformity of metal element M in the negative electrode material is poor. The compound of metal element M is usually aggregated into a bulk and then embedded in silicon oxide (SiO). x Furthermore, the two are clearly distinct and incompatible. At this point, the compound of metal element M and silicon oxide SiO in the negative electrode material... xUneven structural distribution leads to increased potential differences at different locations within the negative electrode material, resulting in decreased rate performance, cycle stability, and safety. Furthermore, the reduced internal porosity due to the doping of the metal element M makes it difficult to mitigate volume expansion during cycling, making the negative electrode material prone to breakage and pulverization, further degrading its cycle performance. (When 0.02cm...) 3 / g≤V≤0.04cm 3 / g, the negative electrode material has a suitable pore volume on its surface, providing lithium-ion channels from the surface to the interior for easy lithium-ion transport. Furthermore, the pores on both the surface and interior of the negative electrode material are small, resulting in good structural strength and a certain buffering capacity against volume expansion during cycling. When V > 0.04cm 3 At / g, the pores on the surface of the negative electrode material are too large. Although the large number of pores from the surface to the interior of the negative electrode material is beneficial for the insertion and extraction of lithium ions and for improving the charge and discharge efficiency and rate performance of the negative electrode material, the structure of the negative electrode material is relatively loose and the material structure is unstable. The negative electrode material has poor tolerance to cycle expansion, which makes the negative electrode material prone to structural fracture during cycling, thus leading to a decrease in the electrochemical performance of the negative electrode material.

[0046] In some implementations, Raman spectroscopy is used to test the negative electrode material. Figure 1 The Raman spectrum of the negative electrode material provided in the embodiments of this application is as follows: Figure 1 As shown, the negative electrode material was measured at 500 cm⁻¹. -1 ~540cm -1 The characteristic peaks of Si-Si bonds are present within the range, with the highest peak intensity of the Si-Si bond being I1, at 900 cm⁻¹. -1 ~1000cm -1 The spectrum contains characteristic peaks of Si-O bonds, with the highest peak intensity being I2, and I1 / I2 ≥ 4. Understandably, in Raman spectroscopy results, peak intensities at different positions characterize the intensity of different bond sites on the surface of the anode material. When I1 / I2 ≥ 4, it indicates a reduction in oxygen-containing functional groups on the surface of the anode material, which improves interfacial repulsion, promotes tighter bonding between particles, and ultimately increases the energy storage index and volumetric energy density of the anode material.

[0047] In some embodiments, the average desorption pore size of the negative electrode material is 6nm to 9nm, specifically 6nm, 6.5nm, 7nm, 7.5nm, 8nm, 8.5nm, or 9nm, or other values ​​within the above range, which are not limited here. It is understood that an average desorption pore size within the above range ensures smooth lithium ion insertion and extraction, improving the charge / discharge efficiency and rate performance of the negative electrode material, while also enhancing its structural stability and reducing breakage and pulverization during cycling, thereby improving the cycle performance of the negative electrode material.

[0048] In some embodiments, the negative electrode material also includes carbon material, and carbon material is present on the surface of the active material and / or between the active material.

[0049] In some implementations, the carbon material includes amorphous carbon.

[0050] In some embodiments, a carbon layer is formed on the surface of the active material, and the mass content of carbon in the anode material is 0.5% to 10%, specifically 0.5%, 1%, 2%, 5%, 9%, 9.5%, or 10%, etc., and other values ​​within the above range are also possible, without limitation. It is understood that by limiting the mass content of carbon within the above range, it can be ensured that the carbon layer completely coats the active material, reducing direct contact between the active material and the electrolyte, thereby reducing the formation of the SEI film, reducing the consumption of active lithium ions, and improving the first coulombic efficiency of the anode material.

[0051] In some embodiments, the tap density of the negative electrode material is ≥0.87 g / cm³. 3 Specifically, it could be 0.87 g / cm³. 3 0.89 g / cm 3 0.9g / cm 3 0.95g / cm 3 1.0g / cm 3 1.5g / cm 3 1.8g / cm 3 2.0g / cm 3 Or 2.1g / cm 3 Of course, other values ​​within the above range are also possible and are not limited here. The tap density of the negative electrode material reflects the particle distribution of the powder negative electrode material before it is pressed. It is related to the surface characteristics of the negative electrode material and is an important characteristic for measuring the interfacial repulsion between particles. When the tap density of the negative electrode material is ≥0.87 g / cm³... 3When the surface morphology of the negative electrode material particles is relatively uniform, the interfacial repulsion between the particles is small, which is conducive to promoting the tight bonding between the particles and improving the volumetric energy density of the negative electrode material; when the tap density of the negative electrode material is <0.87 g / cm³ 3 This indicates that there are significant differences in the surface morphology between the negative electrode material particles, and the functional groups on the surface of the negative electrode material particles are not uniform. This results in a large interfacial repulsion force between the negative electrode material particles, making it difficult for the negative electrode material particles to achieve tight bonding. Consequently, there are many pores between the negative electrode material particles, and the overall structure of the negative electrode material is loose.

[0052] In some embodiments, the specific surface area of ​​the negative electrode material is ≤10cm². 2 / g, specifically 10cm 2 / g、9cm 2 / g、8cm 2 / g、7cm 2 / g、6cm 2 / g, 5cm 2 / g、4cm 2 / g, 3cm 2 / g、2cm 2 / g or 1cm 2 / g, etc., and of course, other values ​​within the above range are also possible, and are not limited here. The specific surface area of ​​the negative electrode material is related to the doping process of the metal element M during the preparation of the negative electrode material. During the doping process, the metal element M needs to react with SiO2. x The reaction forms a certain MO-Si bond structure within the negative electrode material, and the doping of the metal element M further affects the overall SiO₂ content of the negative electrode material. x Structure. A high specific surface area of ​​the negative electrode material results in larger mesopore volumes on its surface, which is detrimental to the overall structural uniformity of the negative electrode material. It also leads to a loose and porous outer layer structure, resulting in poor expansion resistance. When the specific surface area of ​​the negative electrode material is ≤10cm²... 2 At a specific surface area of ​​10 cm² / g, the negative electrode material possesses a suitable surface pore structure, which helps to disperse the expansion stress generated during cycling, reduces the probability of structural damage, and thus improves the cycling performance of the negative electrode material. 2 / g, the surface of the negative electrode material has a lot of pores, which makes the surface structure of the negative electrode material loose and the structural strength of the material poor. The negative electrode material is prone to structural fracture and breakage during cycling, which leads to a decrease in the electrochemical performance of the negative electrode material.

[0053] In some embodiments, the pH of the negative electrode material is 6–10, specifically 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10, or other values ​​within the above range, which are not limited here. Maintaining the pH of the negative electrode material within the above range can increase its compatibility with the electrolyte, thereby reducing irreversible capacity and improving the rate performance of the negative electrode material.

[0054] In some embodiments, the moisture content of the negative electrode material is ≤0.5wt%, specifically 0.5wt%, 0.4wt%, 0.3wt%, 0.25wt%, 0.2wt%, 0.1wt%, or 0.05wt%, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0055] In some embodiments, the oxygen content in the negative electrode material is 26% to 33% by mass, specifically 26%, 27%, 28%, 29%, 30%, 31%, 32%, or 33%, etc. Of course, other values ​​within the above range are also possible, and no limitation is made here.

[0056] In some implementations, the particle size of the negative electrode material satisfies: 1.0 μm ≤ D 10 ≤3.0μm, 4.5μm≤D 50 ≤7.0μm, 8.0μm≤D 90 ≤12.0μm. D 10 Specifically, it can be 1.0μm, 1.5μm, 1.8μm, 2.0μm, 2.5μm, 2.7μm, or 3.0μm, etc., D 50 Specifically, it can be 4.5μm, 4.8μm, 5.0μm, 5.5μm, 6.0μm, 6.5μm, or 7.0μm, etc., D 90 Specifically, the particle size distribution can be 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10.0 μm, 10.5 μm, 11 μm, 11.5 μm, or 12 μm, etc., and is not limited here. It should be noted that the volumetric cumulative particle size distribution D, determined by laser diffraction, is used to measure the particle size distribution. 10 D represents the particle size at which the cumulative particle size distribution percentage of the powder reaches 10%. 50 D represents the particle size at which the cumulative particle size distribution percentage reaches 50%. 90 This indicates the particle size corresponding to a cumulative particle size distribution percentage of 90%.

[0057] Secondly, this application provides a method for preparing a negative electrode material, the method comprising the following steps:

[0058] Step S100: The raw materials of silicon-oxygen material and the raw materials of metal element M are mixed evenly to form a mixture, wherein the mass ratio of the raw materials of silicon-oxygen material to the raw materials of metal element M is (9.25~8):(0.75~2);

[0059] Step S200: Under vacuum conditions, the above mixture is added, and an inert gas is introduced at the same time. The initial pressure of the inert gas is controlled to be 10 Pa to 1000 Pa, so that the above mixture is heated and vaporized under the partial pressure generated by the inert gas to form a mixed gas containing silicon, oxygen and M elements, which is then co-deposited to obtain the precursor.

[0060] Step S300: The precursor is pulverized to its maximum particle size D. max The thickness is 10μm to 20μm;

[0061] In step S400, the pulverized precursor product is subjected to plasma treatment at 1800℃~2000℃, followed by acid washing in an acid solution with a mass fraction of 2%~10% to obtain the active substance.

[0062] Step S500: The above active material is subjected to carbon coating treatment to obtain the negative electrode material.

[0063] In the above-mentioned method for preparing anode materials, the raw materials of silicon-oxygen materials and metal element M are first mixed evenly to form a mixture. The mass ratio of the raw materials of silicon-oxygen materials to the raw materials of metal element M is controlled at (9.25~8):(0.75~2). This allows control over the mass content of metal element M doping in the anode material. On the one hand, it enables metal element M to form a suitable pore structure in the anode material, increasing the lithium-ion transport channels and thus improving the charge-discharge efficiency and rate performance of the anode material. On the other hand, the true density of the anode material can be controlled by metal element M, improving the structural stability of the anode material and reducing the breakage and pulverization of the anode material during cycling, thereby improving the cycle performance of the anode material. Secondly, by adding the above mixture under vacuum conditions, the introduction of impurities can be reduced, and the evaporation temperature of the silicon-oxygen material and the metal element M in the mixture can be lowered. Simultaneously, an inert gas is introduced, and the initial pressure of the inert gas is controlled at 10 Pa to 1000 Pa. This allows the mixture to be heated and vaporized under the partial pressure generated by the inert gas, forming a mixed gas containing silicon, oxygen, and M, which is then co-deposited to obtain the precursor. By controlling the initial pressure of the inert gas, the partial pressure generated by the inert gas can regulate the evaporation rate of the silicon-oxygen material and the metal element M in the mixture, as well as the deposition rate and morphology of silicon, oxygen, and metal element M in the mixed gas. At this point, under the inert gas... Under the influence of the partial pressure generated by the reactive gas, silicon, oxygen, and metal element M tend to grow selectively rather than simply fill the substrate during deposition. This growth pattern conforms to the principle of energy minimization, meaning that the growth direction of the deposited products is consistent. This allows for a uniform distribution of silicon, silicon oxide, and metal element M compounds in the precursor, improving the uniformity and consistency of the anode material's distribution. Simultaneously, metal element M can form certain pores in the precursor during deposition, facilitating the formation of channels conducive to lithium-ion transport in the anode material. Furthermore, metal element M can regulate the true density of the anode material during deposition, thereby improving its structural stability, reducing breakage and pulverization during cycling, and enhancing its cycle performance. Secondly, pre-construction pulverization further improves the uniformity of active material coating. The pre-crushed precursor is then subjected to plasma treatment and acid washing to obtain the active material. In particular, plasma treatment at 800℃~2000℃ to melt and cast the surface of the precursor particles can control the surface morphology of the precursor particles and improve their sphericity. At the same time, it can improve the surface morphology consistency of the negative electrode material, improve the interfacial repulsion between the negative electrode material particles, and enable the negative electrode material particles to be tightly bonded, thereby increasing the compaction density and volumetric energy density of the negative electrode material. Moreover, the pores on the surface of the precursor can be filled in the above melting and casting process, thereby improving the structural stability of the negative electrode material.Further acid pickling reduces free radicals on the surface of the negative electrode material, thereby improving the interfacial repulsion between particles and increasing the compaction density. Simultaneously, acid pickling in a 2%–10% (by mass) acid solution creates pores in the negative electrode material, resulting in suitable surface pore volume. The smaller pore size of these pores improves lithium-ion transport rate, charge / discharge efficiency, and rate performance. It also enhances surface structural strength, improving the material's resistance to pressure during cyclic expansion. Finally, carbon coating of the active material forms a carbon layer on its surface, increasing conductivity and reducing direct contact between the active material and the electrolyte, thus minimizing surface side reactions and further improving cycle performance.

[0064] The preparation method provided in this scheme is described in detail below:

[0065] Step S100: The raw materials of silicon-oxygen material and the raw materials of metal element M are mixed evenly to form a mixture, wherein the mass ratio of the raw materials of silicon-oxygen material to the raw materials of metal element M is (9.25~8):(0.75~2).

[0066] In the above scheme, by uniformly mixing the raw materials of silicon-oxygen material and the raw materials of metal element M, the contact area between the raw materials of silicon-oxygen material and the raw materials of metal element M can be increased, which is beneficial to improving the reaction efficiency between the raw materials of silicon-oxygen material and the raw materials of metal element M, improving the spatial distribution uniformity of silicon-oxygen material and metal element M in the reaction system, thereby improving the uniformity and consistency of the negative electrode material.

[0067] In some embodiments, the mass ratio of the silicon-oxygen material raw material to the metal element M raw material is (9.25-8):(0.75-2), specifically 9.25:0.75, 9:1, 8.75:1.25, 8.5:1.5, 7.25:1.75, or 8:2, etc., and other values ​​within the above range are also possible, without limitation. It is understood that a mass ratio of the silicon-oxygen material raw material to the metal element M raw material within the above range is beneficial for controlling the mass content of metal element M doping in the negative electrode material. On the one hand, it allows metal element M to form a suitable porous structure in the negative electrode material, increasing the lithium-ion transport channels and thus improving the charge-discharge efficiency and rate performance of the negative electrode material. On the other hand, it can regulate the true density of the negative electrode material through metal element M, improving the structural stability of the negative electrode material, thereby reducing the breakage and pulverization of the negative electrode material during cycling and improving its cycle performance.

[0068] In some embodiments, the raw material for the silicon-oxygen material includes SiO2. yA mixture of y and Si, where 0 < y < 2.

[0069] In some implementations, SiO y The molar ratio of Si to Si is 1:1.

[0070] In some embodiments, the raw material for the metal element M is elemental metal M.

[0071] In some embodiments, the metal element M includes at least one selected from Mg, Li, Fe, Al, Mn, and Cu.

[0072] In step S200, under vacuum conditions, the above mixture is added, and an inert gas is introduced at the same time. The initial pressure of the inert gas is controlled to be 10 Pa to 1000 Pa, so that the above mixture is heated and vaporized under the partial pressure generated by the inert gas to form a mixed gas containing silicon, oxygen and metal M, which is then co-deposited to obtain the precursor.

[0073] In some embodiments, the initial pressure of the inert gas is 10 Pa to 1000 Pa, specifically 10 Pa, 50 Pa, 100 Pa, 200 Pa, 500 Pa, 600 Pa, 800 Pa, 900 Pa, or 1000 Pa, etc., and of course, other values ​​within the above range are also possible, without limitation. It is understood that when the initial pressure of the inert gas is within the above range, the partial pressure generated by the inert gas can control the evaporation rate of the silicon-oxygen material raw materials and the raw materials of metal M in the mixture. This is beneficial for controlling the deposition rate and deposition uniformity of silicon, oxygen, and metal M elements in the mixed gas, and can improve the distribution uniformity of silicon, silicon oxide, and metal M element compounds in the negative electrode material, thereby improving the structural stability of the negative electrode material.

[0074] In some embodiments, the inert gas includes at least one of argon, helium, neon, or krypton.

[0075] In some embodiments, the heating and vaporization temperature of the mixture is 1100℃ to 1400℃, specifically 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃ or 1400℃, and of course other values ​​within the above range are also possible, which are not limited here.

[0076] In some embodiments, the heat preservation time of the mixture is 4h to 20h, specifically 4h, 6h, 8h, 10h, 12h, 15h, 16h, 18h or 20h, etc., and of course other values ​​within the above range are also possible, which are not limited here.

[0077] Step S300: The precursor is crushed to the maximum particle size D. max The size ranges from 10μm to 20μm.

[0078] D max Specifically, the particle size can be 10μm, 12μm, 15μm, 16μm, 17μm, 18μm, 19μm, or 20μm, etc., and of course, other values ​​within the above range are also possible; no limitation is made here. Understandably, the maximum particle size D of the precursor powder is... max Within the above range, the uniformity of coating of active materials and carbon can be improved.

[0079] In step S400, the pulverized precursor product is subjected to plasma treatment at 1800℃~2000℃, followed by acid washing in an acid solution with a mass fraction of 2%~10% to obtain the active substance.

[0080] In some embodiments, the plasma treatment temperature is 1800℃~2000℃, specifically 1800℃, 1850℃, 1880℃, 1900℃, 1920℃, 1950℃, 1980℃ or 2000℃, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0081] In some embodiments, the heat treatment time for plasma treatment is 5s to 30s, specifically 5s, 8s, 10s, 12s, 15s, 18s, 20s, 25s, 28s or 30s, etc. Of course, other values ​​within the above range are also possible, and no limitation is made here.

[0082] In some embodiments, the pickling process includes immersing and grinding the plasma-treated product in an acid solution for 1 to 3 hours. The immersion and grinding time can be 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, 2.3 hours, 2.6 hours, 2.8 hours, or 3 hours, or other values ​​within the above range, and is not limited here.

[0083] In some embodiments, the acid used in the pickling process includes at least one of hydrofluoric acid, hydrochloric acid, nitric acid, and sulfuric acid.

[0084] In some embodiments, the acid solution used in the pickling process has a mass fraction of 2% to 10%, specifically 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, etc. Of course, other values ​​within the above range are also possible, and no limitation is made here.

[0085] In some embodiments, the acid-washed product is further washed with water and dried to obtain the active substance.

[0086] Step S500: The above active material is subjected to carbon coating treatment to obtain the negative electrode material.

[0087] Understandably, carbon coating can increase the conductivity of active materials, buffer the huge volume changes of active materials during lithium insertion / extraction, and the carbon layer can optimize the conductive network of the negative electrode material. It can also minimize the direct contact between the surface of the negative electrode material particles and the electrolyte, thereby reducing side reactions between the electrolyte and the negative electrode material and improving the cycle performance of the battery.

[0088] In some embodiments, the carbon coating process includes mixing the active material with a carbon source and heat-treating it to form a carbon layer on the surface of the active material.

[0089] In some embodiments, the carbon coating treatment includes at least one of gas-phase carbon coating treatment, solid-phase carbon coating treatment, and liquid-phase carbon coating treatment. Preferably, the carbon coating treatment is a gas-phase carbon coating treatment.

[0090] In some embodiments, the gaseous carbon source used in the gaseous carbon coating process includes at least one of methane, propane, butane, acetylene, ethylene, benzene, and toluene.

[0091] In some embodiments, the flow rate of the gaseous carbon source is 2L / min to 10L / min, specifically 2L / min, 3L / min, 4L / min, 5L / min, 6L / min, 7L / min, 8L / min or 10L / min, etc. Of course, other values ​​within the above range are also possible, and no limitation is made here.

[0092] In some embodiments, the heat treatment temperature is 700℃ to 1000℃, specifically 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0093] In some embodiments, the heat treatment holding time is 2h to 8h, specifically 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, etc., and of course other values ​​within the above range are also possible, which are not limited here.

[0094] In some embodiments, the solid carbon source used in the solid carbon coating treatment includes at least one of sucrose, fructose, glucose, pitch, phenolic resin, polyimide, citric acid, epoxy resin, amino resin, polystyrene, polyacrylic acid, carboxymethyl cellulose, and cellulose acetate butyrate.

[0095] Thirdly, this application provides a battery comprising the above-described negative electrode material or a negative electrode material prepared by the above-described method for preparing the negative electrode material.

[0096] The battery provided in this application can be a secondary battery (such as a lithium-ion battery, sodium-ion battery, etc.), including a casing, electrode assembly, and electrolyte. Both the electrode assembly and electrolyte are located inside the casing. The casing can be a packaging bag sealed with an encapsulating film (such as an aluminum-plastic film), such as a pouch battery for secondary batteries.

[0097] In other embodiments, the secondary battery may also be a steel-cased battery, an aluminum-cased battery, etc.

[0098] Figure 2 This is a schematic diagram of the discharge state of the battery provided in the embodiments of this application, such as... Figure 2 As shown, the battery includes a casing and an electrode assembly. The electrode assembly includes a positive electrode 1, a negative electrode 2, and a separator 3, with the separator 3 disposed between the positive electrode 1 and the negative electrode 2. The electrode assembly can be a stacked structure, formed by alternately stacking the positive electrode 1, the separator 3, and the negative electrode 2. In other embodiments, the electrode assembly can also be a wound structure, formed by sequentially stacking and winding the positive electrode, the separator, and the negative electrode.

[0099] In some embodiments, the positive electrode 1 includes a positive current collector 11 and a positive active layer 12 disposed on at least one surface of the positive current collector 11.

[0100] In some embodiments, the positive current collector 11 can be made of aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, current collectors formed by combining the aforementioned conductive foil (aluminum foil or nickel foil, etc.) with a polymer substrate. The positive active layer 12 contains a positive active material, which includes compounds that can reversibly insert and deintercalate metal ions.

[0101] In some embodiments, the positive electrode active material may include lithium transition metal composite oxides, sodium transition metal composite oxides, etc. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel.

[0102] In some embodiments, the positive electrode active material may include, but is not limited to, lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt ternary materials (NCM), and lithium manganese oxide (LiMn2O3). 4) Lithium nickel manganese oxide (LiNi) 0.5 Mn 1.5 At least one of lithium iron phosphate (LiFePO4) or lithium iron phosphate (LiFePO4).

[0103] In some embodiments, the negative electrode 2 includes a negative electrode current collector 21 and a negative electrode active material layer 22 disposed on at least one surface of the negative electrode current collector.

[0104] In some embodiments, the negative electrode current collector 21 can be at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or carbon-based current collector, or any composite current collector disclosed in the prior art, such as, but not limited to, the current collector formed by combining the aforementioned conductive foil and polymer substrate. The negative electrode active material layer 22 includes a negative electrode material, which is the negative electrode material described in the first aspect or the negative electrode material prepared by the above preparation method.

[0105] Example 1

[0106] (1) Mix 900g of Si and SiO2 mixed powder with a molar ratio of 1:1 and 100g of metallic Mg powder evenly to obtain a mixture;

[0107] (2) The above mixture is put into a vacuum device and heated at 1300℃, while argon gas is introduced and the initial pressure of argon gas is controlled to be 100Pa, so that the above mixture generates a mixed gas containing silicon, oxygen and metal element Mg under the partial pressure of inert gas and then co-deposits it. The heat preservation time of the vacuum device is controlled to be 10h to obtain the precursor.

[0108] (3) The above precursor is pulverized to obtain the maximum particle size D. max The powder is 20 μm in size, and the powder is placed in a plasma device for treatment. The reaction temperature is set to 1900℃ and the holding time is 10s.

[0109] (4) The plasma-treated product was placed in a 4% hydrofluoric acid solution and soaked and ground for 2 hours. Then it was washed with water and dried to obtain the active substance.

[0110] (5) Place the active material in a reactor, introduce methane gas, control the flow rate of methane gas to 5L / min, perform heat treatment at 800℃ and keep it at that temperature for 5h to obtain the negative electrode material.

[0111] The negative electrode material prepared in this embodiment includes active materials, which include silicon, silicon oxide (SiO) and magnesium silicate.

[0112] Other parameters of the negative electrode material are detailed in Table 1.

[0113] Example 2

[0114] (1) Mix 850g of Si and SiO2 mixed powder with a molar ratio of 1:1 and 150g of metallic Mg powder evenly to obtain a mixture.

[0115] (2) The above mixture is put into a vacuum device and heated at 1300℃, while argon gas is introduced and the initial pressure of argon gas is controlled to be 100Pa, so that the above mixture generates a mixed gas containing silicon, oxygen and metal element Mg under the partial pressure of inert gas and then co-deposits it. The heat preservation time of the vacuum device is controlled to be 10h to obtain the precursor.

[0116] (3) The above precursor is pulverized to obtain the maximum particle size D. max The powder is 20 μm in size, and the powder is placed in a plasma device for treatment. The reaction temperature is set to 1900℃ and the holding time is 10s.

[0117] (4) The plasma-treated product was placed in a 4% hydrofluoric acid solution and soaked and ground for 2 hours. Then it was washed with water and dried to obtain the active substance.

[0118] (5) Place the active material in a reactor, introduce methane gas, control the flow rate of methane gas to 5L / min, perform heat treatment at 800℃ and keep it at that temperature for 5h to obtain the negative electrode material.

[0119] The negative electrode material prepared in this embodiment includes active materials, which include silicon, silicon oxide (SiO) and magnesium silicate.

[0120] Other parameters of the negative electrode material are detailed in Table 1.

[0121] Example 3

[0122] The difference from Example 1 is:

[0123] (1) Mix 800g of Si and SiO2 mixed powder with a molar ratio of 1:1 and 200g of metallic Mg powder evenly to obtain a mixture.

[0124] The negative electrode material prepared in this embodiment includes active materials, which include silicon, silicon oxide (SiO) and magnesium silicate.

[0125] Other parameters of the negative electrode material are detailed in Table 1.

[0126] Example 4

[0127] The difference from Example 2 is:

[0128] (2) The above mixture is put into a vacuum device and heated at 1400°C. Argon gas is introduced at the same time, and the initial pressure of argon gas is controlled to be 100Pa, so that the above mixture generates a mixed gas containing silicon, oxygen and Mg under the partial pressure of inert gas and then co-deposits. The heat preservation time of the vacuum device is controlled to be 10h to obtain the precursor.

[0129] The negative electrode material prepared in this embodiment includes active materials, which include silicon, silicon oxide (SiO) and magnesium silicate.

[0130] Other parameters of the negative electrode material are detailed in Table 1.

[0131] Example 5

[0132] The difference from Example 2 is:

[0133] (2) The above mixture is put into a vacuum device and heated at 1100°C. At the same time, argon gas is introduced and the initial pressure of argon gas is controlled to be 100Pa, so that the above mixture generates a mixed gas containing silicon, oxygen and metal element Mg under the partial pressure of inert gas and then co-deposits. The heat preservation time of the vacuum device is controlled to be 10h to obtain the precursor.

[0134] The negative electrode material prepared in this embodiment includes active materials, which include silicon, silicon oxide (SiO) and magnesium silicate.

[0135] Example 6

[0136] The difference from Example 2 is:

[0137] (1) Mix 850g of Si and SiO2 mixed powder with a molar ratio of 1:1 and 150g of metallic Li powder evenly to obtain a mixture.

[0138] The negative electrode material prepared in this embodiment includes active materials, including silicon, silicon oxide (SiO) and lithium silicate.

[0139] Other parameters of the negative electrode material are detailed in Table 1.

[0140] Example 7

[0141] The difference from Example 2 is:

[0142] (1) Mix 850g of Si and SiO2 mixed powder with a molar ratio of 1:1 and 150g of metallic Al powder evenly to obtain a mixture.

[0143] The negative electrode material prepared in this embodiment includes active materials, including silicon, silicon oxide (SiO) and aluminum silicate.

[0144] Example 8

[0145] The difference from Example 2 is:

[0146] (2) The above mixture is put into a vacuum device and heated at 1300°C. Argon gas is introduced at the same time, and the initial pressure of argon gas is controlled to be 1000Pa, so that the above mixture generates a mixed gas containing silicon, oxygen and Mg under the partial pressure of inert gas and then co-deposits. The heat preservation time of the vacuum device is controlled to be 10h to obtain the precursor.

[0147] The negative electrode material prepared in this embodiment includes active materials, which include silicon, silicon oxide (SiO) and magnesium silicate.

[0148] Other parameters of the negative electrode material are detailed in Table 1.

[0149] Example 9

[0150] The difference from Example 2 is:

[0151] (2) The above mixture is put into a vacuum device and heated at 1300°C. Argon gas is introduced at the same time, and the initial pressure of argon gas is controlled to be 10Pa, so that the above mixture generates a mixed gas containing silicon, oxygen and Mg under the partial pressure of inert gas and then co-deposits. The heat preservation time of the vacuum device is controlled to be 10h to obtain the precursor.

[0152] The negative electrode material prepared in this embodiment includes active materials, which include silicon, silicon oxide (SiO) and magnesium silicate.

[0153] Other parameters of the negative electrode material are detailed in Table 1.

[0154] Example 10

[0155] The difference from Example 2 is:

[0156] (3) The above precursor is pulverized to obtain the maximum particle size D. max The powder is 20 μm in size and is placed in a plasma device for processing. The reaction temperature is set to 2000℃ and the holding time is 10s.

[0157] The negative electrode material prepared in this embodiment includes active materials, which include silicon, silicon oxide (SiO) and magnesium silicate.

[0158] Example 11

[0159] The difference from Example 2 is:

[0160] (3) The above precursor is pulverized to obtain the maximum particle size D. max The powder is 20 μm in size and is placed in a plasma device for processing. The reaction temperature is set to 1800℃ and the holding time is 10 s.

[0161] The negative electrode material prepared in this embodiment includes active materials, which include silicon, silicon oxide (SiO) and magnesium silicate.

[0162] Other parameters of the negative electrode material are detailed in Table 1.

[0163] Example 12

[0164] The difference from Example 2 is:

[0165] (1) Take 925g of Si and SiO with a molar ratio of 1:1. x The mixed powder and 75g of metallic Mg powder were mixed evenly to obtain a mixture.

[0166] The negative electrode material prepared in this embodiment includes active materials, which include silicon, silicon oxide (SiO) and magnesium silicate.

[0167] Other parameters of the negative electrode material are detailed in Table 1.

[0168] Comparative Example 1

[0169] The difference from Example 2 is:

[0170] No Mg powder is added in step (1).

[0171] Comparative Example 2

[0172] The difference from Example 2 is:

[0173] (1) Mix 750g of Si and SiO2 mixed powder with a molar ratio of 1:1 and 250g of metallic Mg powder evenly to obtain a mixture.

[0174] Comparative Example 3

[0175] The difference from Example 2 is:

[0176] (1) Mix 750g of Si and SiO2 mixed powder with a molar ratio of 1:1 and 250g of metallic Mg powder evenly to obtain a mixture.

[0177] (2) The above mixture is put into a sintering equipment and heated at 1300°C while argon gas is introduced. The initial pressure of the argon gas is 100 Pa and the holding time is 10 h to obtain the precursor.

[0178] Comparative Example 4

[0179] The difference from Example 2 is:

[0180] (2) The above mixture is put into a vacuum device and heated at 1300°C to generate a mixed gas containing silicon, oxygen and Mg, and then co-deposited. The heat preservation time of the vacuum device is controlled to be 10h to obtain the precursor.

[0181] Comparative Example 5

[0182] The difference from Example 2 is:

[0183] Step (3) The above precursor is crushed to obtain the maximum particle size D. max After the powder is 20μm in size, no plasma treatment is performed.

[0184] Test methods

[0185] (1) Compaction density test of negative electrode material:

[0186] Measured according to GB / T 24533-2019 "Appendix L of Graphite Anode Materials for Lithium-ion Batteries" or the equipment manual. Measured using an automatic powder compaction density meter (UTM7305).

[0187] (2) True density test of negative electrode material:

[0188] The measurement was performed according to GB / T 24533-2019, Appendix D, "Determination of True Density" or the equipment instruction manual. A true density meter (Bestde 3H-2000TD) was used. Helium was used as the gas.

[0189] (3) Test of cumulative total pore volume and average pore size of desorption of negative electrode material:

[0190] The measurement was performed according to GB / T 19587-2017 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method" or the equipment manual. A specific surface area and pore size analyzer (Micromeritics TriStar 3000) was used for measurement. Nitrogen gas was used.

[0191] (4) Tap density test of negative electrode material:

[0192] The measurement was performed according to GB / T 5162-2006 / ISO 3953:1993 "Determination of tap density of metal powders" or the equipment manual. A tap density meter (Kunta DAT-4-220) was used for measurement. The number of vibrations was 3000.

[0193] (5) Specific surface area test of negative electrode material:

[0194] The measurement was performed according to GB / T 19587-2004 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method" or the equipment manual. A specific surface area and pore size analyzer (McASAP2460-2) was used for measurement. The adsorbed gas used was N2.

[0195] (6) Raman spectroscopy test:

[0196] Measurements were performed according to GB / T 40219-2021 "General Specifications for Raman Spectrometers" or the equipment manual. Measurements were taken using a microconfocal Raman spectrometer (in Via).

[0197] (7) Test of the mass content of metallic element M in the negative electrode material:

[0198] Take 0.1g of negative electrode material, add a certain concentration of aqua regia and stir until completely dissolved, then dilute 100 times and make up the volume. Finally, use an ICP spectrometer (Agilent 5800VDVICP-OES) to test and calculate the mass content of metal element M.

[0199] (8) pH test of negative electrode material:

[0200] Take 10g of negative electrode material, add 10g of water, stir for 30 minutes, and then measure the pH value of the solution.

[0201] (9) Moisture content test of negative electrode material:

[0202] The moisture content was measured according to GB / T 6283-2008 "Determination of Moisture Content in Chemical Products - Karl Fischer Method (General Method)" or the equipment manual. A coulometric moisture analyzer (Mettler-Toledo C30S-Inmotion KF) was used for measurement.

[0203] (10) Test of oxygen content in negative electrode material:

[0204] 10mg to 13mg of negative electrode material was weighed and wrapped in nickel foil, and then sent into the graphite crucible of the ONH elemental analyzer (ONH-2000) for testing to obtain the total oxygen content of the negative electrode material.

[0205] (11) Particle size testing of negative electrode materials:

[0206] The particle size distribution was measured according to GB / T 19077.1-2008 "Particle Size Analysis - Laser Diffraction - Part 1: General Rules" or the equipment manual. A Malvern Panaco MS3000 laser particle size analyzer was used. The volumetric cumulative particle size distribution D, determined by laser diffraction, was calculated. 10 D represents the particle size at which the cumulative particle size distribution percentage of the powder reaches 10%. 50D represents the particle size at which the cumulative particle size distribution percentage reaches 50%. 90 This indicates the particle size corresponding to a cumulative particle size distribution percentage of 90%.

[0207] (12) Test of carbon content in negative electrode material:

[0208] Measurements were taken according to GB / T 20123-2006 "Determination of Total Carbon and Sulfur Content in Iron and Steel - Infrared Absorption Method After Combustion in a High-Frequency Induction Furnace (Conventional Method)" or the equipment manual. An infrared carbon and sulfur analyzer (Ertex CS i, Germany) was used for measurement.

[0209] (13) Electrochemical performance testing:

[0210] The negative electrode materials obtained in Examples 1-12 and Comparative Examples 1-5 were used as negative electrode active materials. They were mixed uniformly at a mass ratio of active material: conductive agent (Super P): sodium carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) = 92:2:2:2, and then coated onto a copper foil current collector. After drying, negative electrode sheets were obtained for later use. The dried electrode sheets were rolled under a pressure of 3 MPa to obtain negative electrode sheets with a certain compaction density. Button cell tests were performed on the rolled negative electrode sheets. Battery assembly was carried out in an argon glove box, using lithium metal sheets as the negative electrode, a 1 mol / L LiPF6 + ethylene carbonate (EC) + methyl ethyl carbonate (EMC) electrolyte, and a polyethylene / propylene composite microporous membrane as the separator. Electrochemical performance was tested on a battery testing instrument with a charge / discharge voltage of 0.01–1.5 V. Battery cycle life was defined as the number of charge / discharge cycles performed before the capacity retention rate decreased to 80%.

[0211] The test results are detailed in Tables 1 to 3.

[0212] Table 1. Test results of physicochemical properties of anode materials

[0213]

[0214]

[0215] Table 2. Test results of physicochemical properties of anode materials

[0216]

[0217] Table 3 Electrochemical performance test results of negative electrode materials

[0218]

[0219]

[0220] According to the test data in Tables 1 to 3, the negative electrode materials prepared in Examples 1 to 12 of this application, by controlling the balance between the compaction density, true density, and cumulative total pore volume of the negative electrode material, can keep the energy storage index X of the negative electrode material within the range of 1.1 to 1.5. This reduces the interfacial repulsion between negative electrode material particles, allowing the particles to bond tightly together, thus giving the negative electrode material a suitable compaction density. This results in the electrode sheet made from the negative electrode material having a high energy density. At the same time, the negative electrode material particles have a suitable pore structure. During the charge and discharge process, these pore structures can provide buffer space for the volume expansion of the active material in the negative electrode material, reducing the volume expansion of the negative electrode material and thus improving the cycle performance of the negative electrode material. Furthermore, these pore structures can improve the lithium-ion transport efficiency inside the negative electrode material particles, thereby improving the charge and discharge efficiency and rate performance of the negative electrode material.

[0221] According to the test data of Example 2 and Comparative Example 1, the negative electrode material of Example 12 has a lower content of Mg metal added during the preparation process, resulting in a larger energy storage index X value. The interfacial repulsion between negative electrode material particles is smaller, and the bonding between negative electrode material particles is tighter, resulting in a higher compaction density of the negative electrode material. Therefore, the specific capacity of the battery made from this negative electrode material is increased. However, the true density of the negative electrode material is increased, the total pore volume accumulated by desorption is reduced, and the pore structure inside the negative electrode material particles is reduced. During the charging and discharging process, the buffer space when the active material undergoes volume expansion is reduced, and the lithium ion transport channels are also reduced, resulting in a decrease in the cycle life and rate performance of the negative electrode material.

[0222] According to the test data of Example 2 and Comparative Example 1, the negative electrode material of Comparative Example 1 was not doped with the metal element Mg during the preparation process. The compaction density P and true density T of the prepared negative electrode material increased, and the cumulative total pore volume V of desorption decreased. The relationship between the compaction density P, true density T and cumulative total pore volume V of the negative electrode material was unbalanced, resulting in the energy storage index X of the negative electrode material being greater than 1.5. The interfacial repulsion between the negative electrode material particles was too small, the bonding between the negative electrode material particles was too tight, and the compaction density of the negative electrode material was too large. Therefore, the specific capacity of the battery made from this negative electrode material increased. However, the pore structure in the negative electrode material was too small, and the volume expansion of the negative electrode material was difficult to suppress during the charging and discharging process. In addition, the lithium ion transport efficiency inside the negative electrode material particles decreased, which led to a decrease in the cycle life, cumulative release capacity and rate performance of the negative electrode material.

[0223] According to the test data of Example 2 and Comparative Example 2, the negative electrode material of Comparative Example 2 had too much Mg metal added during the preparation process. The compaction density P and true density T of the prepared negative electrode material decreased, and the cumulative total pore volume V increased. The relationship between the compaction density P, true density T and cumulative total pore volume V of the negative electrode material was unbalanced. The energy storage index X of the prepared negative electrode material was less than 1.1. The interfacial repulsion between the negative electrode material particles was too large, and the negative electrode material particles were difficult to bond tightly together, which led to a decrease in the compaction density of the negative electrode material. In addition, there were too many pore structures in the negative electrode material, which reduced the structural stability of the negative electrode material. The negative electrode material was prone to cracking and breaking during cycling, which led to a decrease in the electrochemical performance of the negative electrode material.

[0224] According to the test data of Example 2 and Comparative Example 3, the negative electrode material of Comparative Example 3 had too much Mg metal added during the preparation process and was not heated and vaporized and deposited under vacuum conditions. At the same heating temperature, the silicon oxide raw material and Mg metal were not heated and vaporized into vapor, resulting in poor mixing uniformity between silicon oxide and Mg metal. The energy storage index X of the prepared negative electrode material was less than 1.1. The interfacial repulsion between the negative electrode material particles was too large, making it difficult for the particles to bond tightly together. This led to a significant decrease in the compaction density of the negative electrode material. Furthermore, the negative electrode material had too many pore structures, resulting in a decrease in the structural stability of the negative electrode material. The negative electrode material was prone to cracking and breaking during cycling, which led to the deterioration of the electrochemical performance of the negative electrode material.

[0225] According to the test data of Example 2 and Comparative Example 4, no argon gas was added during the heating, vaporization and deposition process of the raw material in Comparative Example 4. The energy storage index X of the prepared negative electrode material was greater than 1.5. The interfacial repulsion between the negative electrode material particles was too small, the bonding between the negative electrode material particles was too tight, and the pore structure in the negative electrode material was too small. During the charging and discharging process, the volume expansion of the negative electrode material was difficult to suppress, and the lithium ion transport efficiency between the negative electrode material particles decreased, which resulted in a decrease in the cycle life, cumulative release capacity and rate performance of the negative electrode material.

[0226] According to the test data of Example 2 and Comparative Example 5, the negative electrode material of Comparative Example 5 was not subjected to plasma treatment during preparation. The surface morphology uniformity and sphericity of the negative electrode material were poor. The energy storage index X of the prepared negative electrode material was less than 1.1. The interfacial repulsion between the negative electrode material particles could not be improved. The negative electrode material particles were difficult to bond tightly together. The compaction density and true density of the negative electrode material decreased. In addition, the porosity of the negative electrode material increased, the structural stability of the negative electrode material decreased, and the negative electrode material was easy to break and pulverize during cycling. This increased the side reactions between the negative electrode material and the electrolyte, resulting in a decrease in the electrochemical performance of the negative electrode material.

[0227] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A negative electrode material, characterized in that, The negative electrode material includes an active substance, which comprises a compound of silicon, silicon oxide, and metal element M. The compaction density of the negative electrode material is P g / cm³. 3 The true density is T g / cm³. 3 The cumulative total pore volume of desorption is V cm³. 3 / g, the energy storage index of the negative electrode material is X, X = T -1 *(P -1 -T -1 -V) -1 , 1.1≤X≤1.

5.

2. The negative electrode material according to claim 1, characterized in that, The negative electrode material includes at least one of the following characteristics: (1) The general formula of the silicon oxide is SiO x , 0 < x ≤ 2; (2) The compound of the metal element M includes at least one of the oxide of the metal element M and the silicate of the metal element M; (3) The metallic element M includes at least one of Mg, Li, Fe, Al, Mn and Cu; (4) The mass content of metal element M in the negative electrode material is 5% to 20%.

3. The negative electrode material according to claim 1, characterized in that, The negative electrode material includes at least one of the following characteristics: (1) The compaction density of the negative electrode material is P g / cm³. 3 , 1.2≤P≤1.5; (2) The true density of the negative electrode material is T g / cm³. 3 T≥2.4; (3) The cumulative total pore volume of the desorption of the negative electrode material is V cm. 3 / g, 0.02≤V≤0.

04.

4. The negative electrode material according to any one of claims 1 to 3, characterized in that, The negative electrode material was tested using Raman spectroscopy, and the results were obtained at 500 cm⁻¹. -1 ~540cm -1 The range contains characteristic peaks of Si-Si bonds, with the highest peak intensity of the Si-Si bond characteristic peak being I1, at 900 cm⁻¹. -1 ~1000cm -1 The range contains characteristic peaks of Si-O bonds, and the highest peak intensity of the characteristic peaks of the Si-O bonds is I2, I1 / I2≥4.

5. The negative electrode material according to any one of claims 1 to 3, characterized in that, The average pore size of the desorption material is 6 nm to 9 nm.

6. The negative electrode material according to claim 1, characterized in that, The negative electrode material further includes carbon material, and the carbon material is present on the surface of the active material and / or between the active material.

7. The negative electrode material according to claim 6, characterized in that, The negative electrode material includes at least one of the following characteristics: (1) The carbon material includes amorphous carbon; (2) A carbon layer is formed on the surface of the active material; (3) The carbon content in the negative electrode material is 0.5% to 10% by mass.

8. The negative electrode material according to any one of claims 1, characterized in that, The negative electrode material includes at least one of the following characteristics: (1) The tap density of the negative electrode material is ≥0.87 g / cm³. 3 ; (2) The specific surface area of ​​the negative electrode material is ≤10cm². 2 / g; (3) The pH of the negative electrode material is 6 to 10; (4) The moisture content of the negative electrode material is ≤0.5wt%; (5) The mass content of oxygen in the negative electrode material is 26% to 33%.

9. The negative electrode material according to any one of claims 1, characterized in that, The particle size of the negative electrode material satisfies: 1.0 μm ≤ D 10 ≤3.0μm, 4.5μm≤D 50 ≤7.0μm, 8.0μm≤D 90 ≤12.0μm.

10. A battery, characterized in that, The battery comprises the negative electrode material as described in any one of claims 1 to 9.

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