Negative electrode material and preparation method therefor, and lithium-ion battery

Abstract

A negative electrode material and a preparation method therefor, and a lithium-ion battery. The negative electrode material comprises an active substance; the active substance comprises an Si element, an O element, and a metal M element; the metal M comprises Mg, Ca, and Cu; and in the negative electrode material, the mass content of the Mg element is mMg, the mass content of the Ca element is mCa, and the mass content of the Cu element is mCu, wherein 0<mCa / mMg<0.1, and 0<mCu / mMg<0.01. In the negative electrode material, the Mg element, the Ca element and the Cu element are introduced into the active substance, and ratios of the Mg element, the Ca element and the Cu element are limited within a proper range, thereby improving the initial coulombic efficiency, electrical conductivity, cycle performance and lithium intercalation / de-intercalation rate of the negative electrode material.

Description

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

[0001] This application claims the benefit of Chinese patent application No. 2023118306082, filed on December 27, 2023. This application incorporates the entirety of the aforementioned Chinese patent application. Technical Field

[0002] The present application relates to the field of lithium battery technology, and in particular to negative electrode materials and preparation methods thereof, and lithium-ion batteries. Background Art

[0003] Silicon-based anode materials, with their highest lithium storage capacity and lowest voltage platform, are a hot topic in lithium-ion battery anode material research. However, silicon's significant volume expansion (>300%) and low electrical conductivity limit its commercial application. While SiO has a lower theoretical capacity than silicon, the Si-O bond is twice as strong as Si-Si, and the Li₂O compounds generated during the initial cycle of the reaction buffer the volume expansion, resulting in significantly superior cycling performance compared to silicon. However, excessive Li₂O increases the consumption of lithium ions in the cathode material during the initial charge, increasing the material's irreversible capacity and reducing the initial coulombic efficiency.

[0004] In existing technologies, silicon-based anode materials are doped with some reducing Mg elements to ensure a uniform distribution of Si, O, and Mg in the anode material to increase the irreversible capacity of the anode material. However, while the resulting silicon-based anode material has a certain improvement in its initial coulombic efficiency, it still suffers from low conductivity and poor cycling performance. Summary of the Invention

[0005] The present application provides a negative electrode material and a preparation method thereof, and a lithium-ion battery, which are conducive to comprehensively improving the first coulombic efficiency, electrical conductivity and cycle performance of the negative electrode material, so as to solve the problem in the prior art that the negative electrode material is difficult to achieve good first coulombic efficiency, electrical conductivity and cycle performance.

[0006] In a first aspect, an embodiment of the present application provides a negative electrode material, the negative electrode material includes an active substance, the active substance includes Si element, O element and metal M element, and the metal M includes Mg, Ca and Cu;

[0007] In the negative electrode material, the mass content of Mg element is m Mg , the mass content of Ca element is m Ca , the mass content of Cu element is m Cu , 0<m Ca / m Mg <0.1,0<m Cu / m Mg <0.01.

[0008] In a second aspect, the present application further proposes a method for preparing a negative electrode material, the preparation method comprising the following steps:

[0009] The raw materials of silicon-based active particles are mixed with a metal doping source containing an M element and heat-treated. The steam formed is mixed and then cooled to obtain an active material. The negative electrode material includes an active material. The active material includes Si element, O element and metal M element. The metal M includes Mg, Ca and Cu. In the negative electrode material, the mass content of Mg element is m Mg , the mass content of Ca element is m Ca , the mass content of Cu element is m Cu , 0<m Ca / m Mg <0.1,0<m Cu / m Mg <0.01.

[0010] In a third aspect, the present application further proposes a lithium-ion battery, comprising the negative electrode material as described above, or comprising the negative electrode material prepared by the preparation method as described above.

[0011] Compared with the existing technology, this technical solution has at least the following technical effects:

[0012] In the negative electrode material of the present application, by introducing Mg, Ca and Cu elements into the active material and limiting the ratio of Mg, Ca and Cu elements to an appropriate range, the first coulombic efficiency, electrical conductivity and cycle performance of the negative electrode material are comprehensively improved. In the present application, the introduced Mg and Ca elements are conducive to reducing the content of silicon oxide in the negative electrode material, so that the amount of lithium that can be consumed by silicon oxide in the negative electrode material is reduced, thereby improving the first coulombic efficiency of the negative electrode material. Compared with Mg atoms, Ca atoms have lower electronegativity and form larger bond energy with O and / or Si atoms, which is more conducive to stabilizing the atomic cluster structure, thereby improving the structural stability of the negative electrode material and improving the cycle performance. Ca / m Mg When it is greater than 0.1, the capacity of the negative electrode material decreases and the first coulombic efficiency decreases. Cu, as a doping element, may exist in the negative electrode material in the form of at least one compound such as copper oxide, cuprous oxide, copper silicate or copper silicide. Compared with Mg atoms, the number of electron layers of Cu atoms in Cu compounds is significantly more and the electron transition energy barrier is lower, that is, the ability to capture electrons is low and the mobility of the outermost free electrons is good. Cu / m Mg When the Cu content is greater than 0.01, the structural stability of the negative electrode material will decrease. Therefore, Cu doping can improve the conductivity of silicon-oxygen negative electrode materials and enhance the cycle performance of silicon-oxygen negative electrode materials.

[0013] In the preparation method of the present application, by doping appropriate amounts of Mg, Ca, and Cu into silicon-based active particles during the preparation of the active material of the negative electrode material, the ratio of Ca and Cu to Mg in the final negative electrode material is controlled within an ideal range, thereby enabling the prepared negative electrode material to have a high first coulombic efficiency, high electrical conductivity, relatively good cycle performance, and a faster lithium insertion and extraction rate. In the technical solution of the present application, the introduced Mg and Ca elements react with the silicon oxide in the silicon-based active particles to form elemental silicon, which is beneficial to reducing the content of silicon oxide in the negative electrode material, thereby reducing the amount of lithium that can be consumed by the silicon oxide in the negative electrode material, thereby improving the first coulombic efficiency of the negative electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings that constitute part of this application are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0015] FIG1 is a diagram showing the preparation process of the negative electrode material of the present application. DETAILED DESCRIPTION

[0016] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present application can be combined with each other. In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0017] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0018] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0019] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0020] In existing technologies, silicon-based anode materials are doped with some reducing Mg elements to ensure a uniform distribution of Si, O, and Mg in the anode material to increase the irreversible capacity of the anode material. However, while the resulting silicon-based anode material has a certain improvement in its initial coulombic efficiency, it still suffers from low conductivity and poor cycling performance.

[0021] In this regard, those skilled in the art have also attempted to comprehensively improve the conductivity and cycle performance of the negative electrode material by adjusting the content distribution of each element in the negative electrode material, but the above technical problems have not been solved. The main reason is that the elements in the negative electrode material are interrelated and synergistic with each other, and jointly affect the comprehensive performance of the material. However, for the influence of multiple parameters, it is difficult to obtain the appropriate control range of each parameter in the product through simple experimental means.

[0022] In response to the above technical problems, in the first aspect, the present application proposes a negative electrode material.

[0023] In the embodiment of the present application, the negative electrode material includes an active material, the active material includes Si element, O element, C element and metal M element, the metal M includes Mg, Ca and Cu; in the negative electrode material, the mass content of Mg element is m Mg , the mass content of Ca element is m Ca , the mass content of Cu element is m Cu , 0<m Ca / m Mg <0.1,0<m Cu / m Mg <0.01.

[0024] In the negative electrode material of the present application, by introducing Mg, Ca, and Cu elements into the active material and limiting the ratio of Mg, Ca, and Cu elements to an appropriate range, the first coulombic efficiency, electrical conductivity, and cycle performance of the negative electrode material are comprehensively improved. In the present application, the introduced Mg and Ca elements help reduce the content of silicon oxide in the negative electrode material, thereby reducing the amount of lithium that can be consumed by the silicon oxide in the negative electrode material, thereby improving the first coulombic efficiency of the negative electrode material.

[0025] It should be noted that, from the data of the embodiments and the analysis of the beneficial effects, the applicant can conclude that controlling the contents of Mg, Ca and Cu elements in the present application within the above-mentioned ranges can solve the technical problems of the present application, and there is no need to limit the specific existence forms of Mg, Ca and Cu elements.

[0026] In the negative electrode material provided herein, M (M = Mg, Ca, or Cu) is dispersed atomically in the silicon-oxygen material. Because the atomic electronegativity of M is lower than that of O and Si, M can form bonds with O or Si to form M-Si-O, MO, M-Si, etc., i.e., to form at least one of M silicates, M oxides, or M silicides. For example, Ca atoms can form at least one of calcium silicate, calcium oxide, and calcium silicide.

[0027] In the negative electrode material of the present application, the Mg element exists in the form of magnesium silicate; and compared with Mg atoms, Ca atoms have lower electronegativity and form larger bond energy with O and / or Si atoms, which is more conducive to stabilizing the atomic cluster structure, thereby improving the structural stability of the negative electrode material and enhancing the cycle performance.

[0028] Cu, as a doping element, may exist in the negative electrode material as at least one compound, including copper oxide, cuprous oxide, copper silicate, or copper silicide. Compared to Mg atoms, Cu atoms in Cu compounds have significantly more electron shells and lower electron transition energy barriers, meaning they have lower electron capture capabilities and better mobility of free electrons in their outermost shells. Therefore, Cu doping can improve the conductivity and cycling performance of silicon-oxygen negative electrode materials.

[0029] In the negative electrode material of the present application, by introducing appropriate amounts of Mg, Ca and Cu elements into the active material, the Mg element exists in the form of magnesium silicate, the Ca and Cu elements exist in the form of metal compounds, and the metal oxide includes at least one of metal silicates, metal oxides and silicides, thereby comprehensively improving the first coulombic efficiency, electrical conductivity and cycle performance of the negative electrode material.

[0030] In some embodiments, the Mg and Ca elements introduced in an appropriate mass content ratio exist in the negative electrode material in the form of magnesium silicate and calcium silicate. The stability of calcium silicate is better than that of magnesium silicate alone. Compared with single magnesium silicate, the co-existence of magnesium silicate and calcium silicate in an appropriate ratio can further improve the structural stability of the negative electrode material, and can enable the negative electrode sheet of the battery made of the negative electrode material to maintain a high electrical conductivity after long-term charging and discharging, that is, the cycle performance of the negative electrode material is improved; in addition, the Cu element introduced in an appropriate content can be combined with the Si element to exist in the form of copper silicide, and an appropriate amount of copper silicide has good conductivity and ductility, which can enhance the structural stability and electrical contact effect of the negative electrode material, thereby further improving the cycle performance and electrical conductivity of the negative electrode material.

[0031] In the negative electrode material of the present application, m Ca / m MgSpecifically, it can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.099, etc. Of course, it can also be other values ​​within the above range, which is not limited here. Ca / m Mg The value of is limited to the above range, which can control the size of silicon microcrystals generated by the silicon oxide reaction to be within 15nm or 15nm, thereby improving the cycle performance of the negative electrode material.

[0032] In the negative electrode material of the present application, m Cu / m Mg Specifically, the value may be 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.0099, etc. Of course, other values ​​within the above range are also possible and are not limited here. The above conditions are more conducive to controlling the content of copper silicide that may be produced and improving the capacity of the negative electrode material.

[0033] Based on similar reasons, it is further preferred that, in some embodiments, in the negative electrode material, 0.028≤m Ca / m Mg ≤0.099,0.0008≤m Cu / m Mg ≤0.0099.

[0034] In some embodiments, in the active material, Si element, O element, Mg element, Ca element and Cu element are uniformly distributed, which is beneficial to improving the structural stability of different parts of the negative electrode material, thereby being more beneficial to improving the overall cycle performance of the negative electrode material.

[0035] In some embodiments, in the negative electrode material, 0 < m Mg <25%, m Mg Specifically, it can be 0.01%, 1%, 5%, 10%, 15%, 20%, 24.99%, etc. Of course, it can also be other values ​​within the above range, which is not limited here. Mg The value of is limited to the above range, which is beneficial to improving the cycle performance and conductivity of the negative electrode material while maintaining the capacity of the negative electrode material without being greatly affected.

[0036] Based on similar reasons, it is further preferred that, in some embodiments, in the negative electrode material, 5%≤m Mg ≤15%, preferably 7.8%≤m Mg ≤8.7%.

[0037] In some embodiments, in the negative electrode material, 0 < m Ca <10%,mCa Specifically, it can be 0.01%, 1%, 2%, 4%, 6%, 8%, 9.99%, etc. Of course, it can also be other values ​​within the above range, which is not limited here. Ca The value of is limited to the above range, which is more conducive to slowing down the reaction process between Ca and silicon oxide in the material, so as to further reduce the Si grain size, so that the negative electrode material has better cycle performance.

[0038] Based on similar reasons, it is further preferred that, in some embodiments, in the negative electrode material, 0.2%≤m Ca ≤0.8%.

[0039] In some embodiments, in the negative electrode material, 0 < m Cu <0.5%,m Cu Specifically, it can be 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.499%, etc. Of course, it can also be other values ​​within the above range, which is not limited here. Cu The value of is limited to the above range, which is presumably beneficial for making the negative electrode material have a more appropriate amount of copper silicide, so as to utilize its good conductivity and ductility to improve the cycle performance and conductivity of the negative electrode material, and further reduce the capacity decrease caused by excessive copper silicide.

[0040] Based on similar reasons, it is further preferred that, in some embodiments, in the negative electrode material, 0.007%≤m Cu ≤0.08%.

[0041] In some embodiments, the mass content of silicon in the negative electrode material is 24% to 36%, specifically 24%, 28%, 30%, 32%, 34%, 36%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0042] In some embodiments, the mass content of oxygen in the negative electrode material is 44% to 59%, specifically 44%, 48%, 50%, 53%, 55%, 57%, 59, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0043] The present application further limits the mass content of silicon and oxygen elements in the negative electrode material to the above range, which is beneficial to fully react with the introduced Mg, Ca, and Cu elements to comprehensively improve the first coulombic efficiency, electrical conductivity, and cycle performance of the negative electrode material, while further reducing the lithium consumption of silicon oxide in the negative electrode material, thereby better improving the first coulombic efficiency of the negative electrode material.

[0044] In some embodiments, the Si element in the active material exists in the form of silicon and / or silicon oxide, and the Si crystallite size in the silicon and / or silicon oxide is ≤15 nm. A lower Si crystallite size is conducive to further improving the cycle performance of the negative electrode material.

[0045] In some embodiments, in the active material, the Si element exists in the form of at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and a composite of crystalline silicon and amorphous silicon.

[0046] In some embodiments, the active material comprises silicon oxide, the general formula of which is SiO x , 0<x≤2, specifically it can be 0.1, 0.5, 1, 1.5, 2, etc., of course it can also be other values ​​within the above range, which is not limited here.

[0047] In some embodiments, the metal M exists in the form of at least one of M silicate, M oxide, and M silicide.

[0048] In some embodiments, the active material includes at least one of calcium silicate, magnesium silicate, and copper silicide.

[0049] In some embodiments, the active material further includes elemental copper.

[0050] The above active materials in the present application are generated by introducing Mg, Ca and Cu elements, which are more conducive to improving the initial coulombic efficiency of the negative electrode material, and by improving the structural stability of the negative electrode material, it maintains a high conductivity during long-term charging and discharging, and further improves the cycle performance of the negative electrode material.

[0051] In some embodiments, the negative electrode material further comprises a carbon material, which is disposed on at least a portion of the surface of the active material. Providing a carbon layer on a portion of the surface of the active material can help reduce the formation of an SEI film caused by direct contact between the active material and the electrolyte, thereby reducing degradation of the material's cycling performance.

[0052] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, diamond-like carbon, carbon nanotubes, and carbon fibers. These carbon materials can protect the active material while providing good electrical conductivity, thereby further improving the conductivity of the negative electrode material. Amorphous carbon is a material formed by high-temperature decomposition of a carbon source and lacks characteristic peaks on an XRD pattern. For example, amorphous carbon can be obtained by decomposing acetylene at 750°C to 850°C.

[0053] In some embodiments, the carbon material forms a carbon layer on the surface of the active material.

[0054] In some embodiments, the carbon layer covers the active material, which can effectively reduce the volume expansion rate of the negative electrode material.

[0055] In some embodiments, the thickness of the carbon layer is between 50 nm and 200 nm, specifically 50 nm, 80 nm, 110 nm, 140 nm, 170 nm, 200 nm, etc., and other values ​​within the aforementioned range are also possible and are not limited herein. By limiting the thickness of the carbon layer to the aforementioned range, the carbon layer can completely encapsulate the active material, thereby preventing the active material from directly contacting the electrolyte and repeatedly forming an unstable SEI film, which would lead to excessive electrolyte consumption and reduced material cycle performance. However, the carbon layer is not susceptible to cracking due to internal particle stress caused by excessive thickness.

[0056] In some embodiments, the carbon content of the negative electrode material is 1% to 20% by weight, specifically 1%, 4%, 8%, 12%, 16%, 20%, etc., and other values ​​within the aforementioned range are also possible and are not limited herein. Under these conditions, a balance between active material protection and electrical conductivity can be achieved, thereby achieving a better balance between excellent electrical conductivity and cycle performance.

[0057] In some embodiments, the pH value of the negative electrode material is 8-10, specifically 8.00, 8.50, 9.00, 9.50, 10, etc., and other values ​​within the above range are also possible and are not limited here. Under the above conditions, the negative electrode material can be compatible with most electrolytes, thereby improving the universality of the negative electrode material.

[0058] In some embodiments, the average particle size D50 of the negative electrode material is 1 μm to 100 μm, specifically 1 μm, 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, or 100 μm, etc., and other values ​​within the above range are also possible and are not limited herein. A suitable particle size is beneficial for reducing agglomeration and facilitating material preparation.

[0059] In some embodiments, the specific surface area of ​​the negative electrode material is 1 m 2 / g~120m 2 / g, specifically 1m 2 / g、10m 2 / g, 20m 2 / g, 40m 2 / g、6m 2 / g、80m 2 / g、100m 2 / g or 120m 2 / g, etc., and of course other values ​​within the above range can also be used and are not limited here. An appropriate specific surface area is beneficial for further reducing the formation of SEI film during the first charge and discharge cycle, thereby further improving the first coulombic efficiency of the negative electrode material.

[0060] As described above, in the negative electrode material of the present application, by introducing Mg, Ca and Cu elements into the active material and limiting the ratio of Mg, Ca and Cu elements to an appropriate range, the first coulombic efficiency, electrical conductivity and cycle performance of the negative electrode material are comprehensively improved.

[0061] Specifically, in some embodiments, the first coulombic efficiency of the negative electrode material is 80% to 95%, preferably 80% to 85%.

[0062] In some embodiments, the conductivity of the negative electrode material is 0.5 S / cm to 7 S / cm, preferably 2 S / cm to 7 S / cm.

[0063] In some embodiments, the 50-cycle capacity retention rate of the negative electrode material is 80% to 90%.

[0064] In some embodiments, the electrode expansion rate of the negative electrode material after 50 cycles is 30% to 38%.

[0065] The negative electrode material with the above performance parameters is more suitable as a component of a lithium-ion battery to further improve the electrochemical performance of the entire battery.

[0066] Secondly, the present application also proposes a method for preparing a negative electrode material, as shown in FIG1 .

[0067] In the embodiment of the present application, the preparation method comprises the following steps:

[0068] S1. The raw material of silicon-based active particles is mixed with a metal doping source containing an M element and subjected to heat treatment. The resulting steam is mixed and then cooled to obtain an active material. The negative electrode material includes an active material, which includes Si element, O element and metal M element. The metal M includes Mg, Ca and Cu. In the negative electrode material, the mass content of Mg element is m Mg , the mass content of Ca element is m Ca , the mass content of Cu element is m Cu , 0<m Ca / m Mg <0.1,0<m Cu / m Mg <0.01.

[0069] In the preparation method of the present application, by doping appropriate amounts of Mg, Ca and Cu elements into silicon-based active particles during the preparation of the active material of the negative electrode material, the ratio of Ca and Cu elements to Mg in the final negative electrode material is controlled within an ideal range, thereby enabling the prepared negative electrode material to have a higher first coulombic efficiency, higher electrical conductivity, better cycle performance and faster lithium insertion and deinsertion rate.

[0070] In the technical solution of the present application, the introduced Mg and Ca elements react with the silicon oxide in the silicon-based active particles to form elemental silicon, which is beneficial to reducing the content of silicon oxide in the negative electrode material, so that the amount of lithium that can be consumed by the silicon oxide in the negative electrode material is reduced, thereby improving the first coulombic efficiency of the negative electrode material; and, after reducing the silicon in the silicon oxide, the introduced Mg and Ca elements will react with the silicon oxide to form corresponding magnesium silicate and calcium silicate. The stability of calcium silicate is better than that of magnesium silicate. Compared with a single magnesium silicate, the coexistence of magnesium silicate and calcium silicate in an appropriate ratio can further improve the structural stability of the negative electrode material, so that the negative electrode sheet of the battery made of the negative electrode material can still maintain a high electrical conductivity after long-term charge and discharge, that is, the cycle performance of the negative electrode material is improved; in addition, the introduced Cu element will further react with the generated elemental silicon to form a copper-silicon compound, reducing the amount of free silicon in the negative electrode material, enhancing the structural stability of the negative electrode material and the electrical contact effect between the negative electrode material particles, thereby further improving the cycle performance and electrical conductivity of the negative electrode material.

[0071] In the preparation method of the present application, m Ca / m Mg Specifically, it can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.099, etc. Of course, it can also be other values ​​within the above range, which is not limited here. Ca / m Mg The value of is limited to the above range, which can control the size of silicon microcrystals generated by silicon oxide reaction to be within 15nm or 15nm; when m Ca / m Mg When the value is too large, the reaction between Ca and silicon oxide will be more violent, and a large amount of heat will be released during the reaction, which will cause the generated Si grains to be larger, resulting in poor cycle performance of the negative electrode material.

[0072] In the preparation method of the present application, m Cu / m Mg Specifically, the value may be 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.0099, etc. Of course, other values ​​within the above range are also possible and are not limited here. When the mass content ratio of the Cu element to the Mg element is too large, the amount of copper silicide generated will be too much, and excessive copper silicide will lead to a decrease in the capacity of the material.

[0073] In some embodiments, the mass ratio of the metal doping source of the M element to the raw material of the silicon-based active particles is (1-35):100, specifically 1:100, 10:100, 20:100, 30:100, 35:100, etc., and of course other values ​​within the above range are also possible and are not limited here. The above mass ratio range is conducive to the introduction of Mg, Ca, and Cu elements to form appropriate amounts of magnesium silicate, calcium silicate, and copper silicon compound, thereby further improving the cycle performance and conductivity of the negative electrode material.

[0074] In some embodiments, the metal doping source includes at least one of a simple substance of metal M and a compound containing metal M.

[0075] In some embodiments, the metal doping source includes a mixture of an oxide containing a metal M and / or a salt containing a metal M and a reducing substance.

[0076] In some embodiments, the salt containing metal M includes at least one of MgCO3, MgCl2, CaCO3, dolomite, and copper-dyed dolomite.

[0077] The above-mentioned metal doping sources are lower in cost and easier to obtain, which is conducive to further reducing the preparation cost of negative electrode materials and making them more suitable for industrial production and application.

[0078] In some embodiments, the raw materials of silicon-based active particles include Si, SiO y A mixture of SiO2 and SiO y At least one of a mixture of Si and Si, and a mixture of Si and SiO2, wherein 0<y<2.

[0079] In some embodiments, the molar amount of the M element in the metal doping source is n M , 0<n Ca / n Mg <1.8,0<n Cu / n Mg By limiting the molar content ratio of calcium and copper to magnesium in the metal doping source to the above range, it is possible to ensure that the mass content ratio of calcium and copper to magnesium in the active material of the prepared negative electrode material satisfies the following conditions: 0 < m Ca / m Mg <0.1,0<m Cu / m Mg <0.01.

[0080] In some embodiments, the molar amount of the M element in the metal doping source is n M The molar amount of Si in the raw material of silicon-based active particles is n Si , and n M :n Si=(0.02-0.62):1, specifically 0.02:1, 0.1:1, 0.2:1, 0.4:1, 0.62:1 or any ratio therebetween; by limiting the molar ratio of the M element in the metal doping source to the silicon element in the raw material of the silicon-based active particles within the above range, the first coulombic efficiency, electrical conductivity and cycle performance of the prepared negative electrode material can be comprehensively improved to the greatest extent.

[0081] In some embodiments, the heat treatment includes heating and keeping the mixture of the raw materials of the silicon-based active particles and the metal doping source in a negative pressure environment.

[0082] In some embodiments, the vacuum degree of the negative pressure environment is 0.001 Pa to 100 Pa, specifically 0.001, 10, 40, 60, 80, 100 or any value therebetween.

[0083] In some embodiments, the heating temperature is 1100° C. to 1600° C., specifically 1100° C., 1200° C., 1300° C., 1400° C., 1500° C. or any value therebetween.

[0084] In some embodiments, the insulation time is 4 hours to 30 hours, specifically 4 hours, 12 hours, 20 hours, 25 hours, 30 hours or any value therebetween.

[0085] In some embodiments, the cooling temperature is ≤100°C, specifically 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 98°C or any value therebetween.

[0086] The above-mentioned heat treatment conditions are more conducive to introducing appropriate amounts of Mg, Ca and Cu elements into the silicon-based active particles, and making each element evenly distributed in the negative electrode material under the action of heat, thereby more fully exerting its effect on improving the first coulombic efficiency, electrical conductivity and cycle performance of the negative electrode material.

[0087] In some embodiments, the method further comprises pulverizing and / or classifying the active material obtained by cooling.

[0088] In some embodiments, the pulverization method is any one or more of ball milling, air flow milling, crushing or spheroidization.

[0089] In some embodiments, during the classification process, the average particle size D50 of 1 to 100 μm and the specific surface area of ​​1 to 120 m 2 / g of material.

[0090] In some embodiments, the active material obtained by cooling is first pulverized and then classified.

[0091] Through crushing and grading treatment, it is more conducive to obtaining negative electrode materials with suitable particle size and specific surface area, which makes it easier to prepare materials and further reduces the formation of SEI film during the first charge and discharge cycle to improve the first coulombic efficiency of the negative electrode material.

[0092] In some embodiments, the method further comprises: performing carbon coating treatment on the active material obtained by cooling to obtain a negative electrode material.

[0093] In some embodiments, the active material obtained by cooling is subjected to pulverization, classification and coating treatments in sequence.

[0094] In some embodiments, the carbon coating process includes any one of a vapor phase carbon coating process, a liquid phase carbon coating process, or a solid phase carbon coating process.

[0095] In some embodiments, the coating material used in the carbon coating treatment is a carbon material, and the carbon material includes at least one of graphite, graphene, amorphous carbon, diamond-like carbon, carbon nanotubes, and carbon fibers.

[0096] In some embodiments, the carbon coating has a coating thickness of 50 nm to 200 nm, specifically 50 nm, 100 nm, 150 nm, 200 nm, or any value therebetween.

[0097] In some embodiments, the carbon coating treatment includes: placing the active material in a CVD furnace, introducing argon gas as a protective gas from the outside, introducing acetylene gas as a carbon source from the inside, heating to 800°C to decompose acetylene, coating the surface of the active material with amorphous carbon, and obtaining a negative electrode material.

[0098] In some embodiments, the mass content ratio of carbon material to active substance is (1-20):(80-99), specifically 1:99, 1:80, 5:80, 10:80, 15:80, 20:80 or any ratio therebetween.

[0099] Using the above-mentioned carbon material to coat the surface of the active material is beneficial to reducing the formation of the SEI film caused by direct contact between the active material and the electrolyte, reducing excessive consumption of the electrolyte and degradation of the material's cycle performance. It can also provide good conductivity while protecting the active material, thereby further improving the conductivity of the negative electrode material and providing a suitable carbon layer to reduce its cracking caused by internal particle stress.

[0100] Thirdly, the present application also provides a lithium-ion battery comprising the above-described negative electrode material, or comprising the negative electrode material prepared using the above-described preparation method. The lithium-ion battery provided in the present application has the characteristics of high initial coulombic efficiency, high electrical conductivity, and excellent cycle performance.

[0101] 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.

[0102] Example 1

[0103] Preparation of negative electrode materials

[0104] (1) Preparation of active material: 5 kg of SiO, 0.48 kg of Mg, 0.2 kg of Ca, and 0.01 kg of Cu were mixed for 30 minutes and then placed in a vacuum furnace. The mixture was heated to 1350°C and held at this temperature for 20 hours under a vacuum of 1 Pa to generate SiO vapor, Mg vapor, Ca vapor, and Cu vapor in the furnace. After the vapors were evenly mixed, they were condensed to below 100°C to obtain 4 kg of active material. The active material included silicon, silicon oxide, calcium silicate, magnesium silicate, and copper silicide. The Si crystallite size was calculated to be 6 nm based on the XRD spectrum and the Scherrer equation.

[0105] (2) Powdering: 3 kg of the active material prepared in (1) was crushed, ball-milled, and classified to control the average particle size D50 to about 4 μm and the specific surface area to 30 m 2 / g.

[0106] (3) Carbon Coating Treatment: The active material, after the powderization treatment in (2) above, was placed in a CVD furnace. Argon gas was introduced as a shielding gas from the outer circuit, and acetylene gas was introduced as a carbon source from the inner circuit. The furnace was heated to 800°C to decompose the acetylene. A 5% carbon coating was formed on the surface of the active material to obtain a negative electrode material. The carbon material was amorphous carbon, and the pH value of the negative electrode material was 8.5.

[0107] The negative electrode material prepared in Example 1 was subjected to elemental quantitative analysis using an inductively coupled plasma emission spectrometer. The test results and the m calculated based on the test results were Ca / m Mg and m Cu / m Mg As shown in Table 1.

[0108] Furthermore, the electrochemical performance of the negative electrode material prepared in Example 1 was tested. The test results are shown in Tables 2 and 3.

[0109] Example 2

[0110] Preparation of negative electrode materials

[0111] (1) Preparation of active material: 3 kg of silicon powder, 6 kg of SiO2, 3 kg of calcined copper-dyed dolomite, and 3 kg of Mg were mixed for 30 min and then placed in a vacuum furnace. The mixture was heated to 1350°C under a vacuum degree of 1 Pa and kept at this temperature for 20 h to generate SiO vapor, Mg vapor, Ca vapor, and Cu vapor in the furnace. After the vapors were evenly mixed, they were condensed to below 100°C to obtain 4 kg of active material.

[0112] (2) Powdering: 3 kg of the active material prepared in (1) was crushed, ball-milled, and classified to control the average particle size D50 to about 4 μm and the specific surface area to 33 m 2 / g.

[0113] (3) Carbon Coating Treatment: The active material, after the powderization treatment in (2) above, was placed in a CVD furnace. Argon gas was introduced as a shielding gas from the outer circuit, and acetylene gas was introduced as a carbon source from the inner circuit. The furnace was heated to 800°C to decompose the acetylene. A 5% carbon coating was formed on the surface of the active material to obtain a negative electrode material. The carbon material was amorphous carbon, and the pH value of the negative electrode material was 8.9.

[0114] The negative electrode material prepared in Example 2 was subjected to elemental quantitative analysis using an inductively coupled plasma emission spectrometer. The test results and the m calculated based on the test results were Ca / m Mg and m Cu / m Mg As shown in Table 1.

[0115] Furthermore, the electrochemical performance of the negative electrode material prepared in Example 2 was tested. The test results are shown in Tables 2 and 3.

[0116] Example 3

[0117] Preparation of negative electrode materials

[0118] (1) Preparation of active material: 5 kg of SiO, 0.5 kg of Mg, 0.8 kg of Ca, and 0.1 kg of Cu were mixed for 30 min and then placed in a vacuum furnace. The mixture was heated to 1350°C under a vacuum degree of 1 Pa and kept at this temperature for 20 h to generate SiO vapor, Mg vapor, Ca vapor, and Cu vapor in the furnace. After the vapors were evenly mixed, they were condensed to below 100°C to obtain 4 kg of active material.

[0119] (2) Powdering: 3 kg of the active material prepared in (1) was crushed, ball-milled, and classified to control the average particle size D50 to about 4 μm and the specific surface area to 28 m 2 / g.

[0120] (3) Carbon Coating Treatment: The active material, after the powderization treatment in (2) above, was placed in a CVD furnace. Argon gas was introduced as a shielding gas from the outer circuit, and acetylene gas was introduced as a carbon source from the inner circuit. The furnace was heated to 800°C to decompose the acetylene. A 5% carbon coating was formed on the surface of the active material to obtain a negative electrode material. The carbon material was amorphous carbon, and the pH value of the negative electrode material was 8.6.

[0121] The negative electrode material prepared in Example 3 was subjected to elemental quantitative analysis using an inductively coupled plasma emission spectrometer. The test results and the m calculated based on the test results were Ca / m Mg and m Cu / m Mg As shown in Table 1.

[0122] Furthermore, the electrochemical performance of the negative electrode material prepared in Example 3 was tested. The test results are shown in Tables 2 and 3.

[0123] Example 4

[0124] Preparation of negative electrode materials

[0125] (1) Preparation of active material: 5 kg of SiO, 0.5 kg of Mg, 0.7 kg of Ca, and 0.01 kg of Cu were mixed for 30 min and then placed in a vacuum furnace. The mixture was heated to 1350°C under a vacuum degree of 1.5 Pa and kept at this temperature for 20 h to generate SiO vapor, Mg vapor, Ca vapor, and Cu vapor in the furnace. After the vapors were evenly mixed, they were condensed to below 100°C to obtain 4 kg of active material.

[0126] (2) Powdering: 3 kg of the active material prepared in (1) was crushed, ball-milled, and classified to control the average particle size D50 to about 4 μm and the specific surface area to 31 m 2 / g.

[0127] (3) Carbon Coating Treatment: The active material, after the powderization treatment in (2) above, was placed in a CVD furnace. Argon gas was introduced as a shielding gas from the outer circuit, and acetylene gas was introduced as a carbon source from the inner circuit. The furnace was heated to 800°C to decompose the acetylene. A 5% carbon coating was formed on the surface of the active material to obtain a negative electrode material. The carbon material was amorphous carbon, and the pH value of the negative electrode material was 8.6.

[0128] The negative electrode material prepared in Example 4 was subjected to elemental quantitative analysis using inductively coupled plasma emission spectrometry. The test results and m calculated based on the test results were Ca / m Mg and m Cu / m Mg As shown in Table 1.

[0129] Furthermore, the electrochemical performance of the negative electrode material prepared in Example 4 was tested. The test results are shown in Tables 2 and 3.

[0130] Example 5

[0131] Preparation of negative electrode materials

[0132] (1) Preparation of active material: 5 kg of SiO, 0.5 kg of Mg, 1.5 kg of Ca, and 0.06 kg of Cu were mixed for 30 min and then placed in a vacuum furnace. The mixture was heated to 1350°C under a vacuum degree of 1 Pa and kept at this temperature for 20 h to generate SiO vapor, Mg vapor, Ca vapor, and Cu vapor in the furnace. After the vapors were evenly mixed, they were condensed to below 100°C to obtain 4 kg of active material.

[0133] (2) Powdering: 3 kg of the active material prepared in (1) was crushed, ball-milled, and classified to control the average particle size D50 to about 4 μm and the specific surface area to 26 m 2 / g.

[0134] (3) Carbon Coating Treatment: The active material, after the powderization treatment in (2) above, was placed in a CVD furnace. Argon gas was introduced as a shielding gas from the outer circuit, and acetylene gas was introduced as a carbon source from the inner circuit. The furnace was heated to 800°C to decompose the acetylene. A 5% carbon coating was formed on the surface of the active material to obtain a negative electrode material. The carbon material was amorphous carbon, and the pH value of the negative electrode material was 8.8.

[0135] The negative electrode material prepared in Example 5 was subjected to elemental quantitative analysis using inductively coupled plasma emission spectrometry. The test results and m calculated based on the test results were Ca / m Mg and m Cu / m Mg As shown in Table 1.

[0136] Furthermore, the electrochemical performance of the negative electrode material prepared in Example 5 was tested. The test results are shown in Tables 2 and 3.

[0137] Example 6

[0138] Preparation of negative electrode materials

[0139] (1) Preparation of active material: 5 kg of SiO, 0.48 kg of Mg, 0.8 kg of Ca, and 0.4 kg of Cu were mixed for 30 min and then placed in a vacuum furnace. The mixture was heated to 1350°C under a vacuum degree of 1 Pa and kept at this temperature for 20 h to generate SiO vapor, Mg vapor, Ca vapor, and Cu vapor in the furnace. After the vapors were evenly mixed, they were condensed to below 100°C to obtain 4 kg of active material.

[0140] (2) Powdering: 3 kg of the active material prepared in (1) was crushed, ball-milled, and classified to control the average particle size D50 to about 4 μm and the specific surface area to 37 m 2 / g.

[0141] (3) Carbon Coating Treatment: The active material, after the powderization treatment in (2) above, was placed in a CVD furnace. Argon gas was introduced as a shielding gas from the outer circuit, and acetylene gas was introduced as a carbon source from the inner circuit. The furnace was heated to 800°C to decompose the acetylene. 5% carbon was coated on the surface of the active material to obtain a negative electrode material. The carbon material was amorphous carbon, and the pH value of the negative electrode material was 9.

[0142] The negative electrode material prepared in Example 6 was subjected to elemental quantitative analysis using inductively coupled plasma emission spectrometry. The test results and m calculated based on the test results were Ca / m Mg and m Cu / m Mg As shown in Table 1.

[0143] Furthermore, the electrochemical performance of the negative electrode material prepared in Example 6 was tested. The test results are shown in Tables 2 and 3.

[0144] Example 7

[0145] Preparation of negative electrode materials

[0146] (1) Preparation of active material: 5 kg of SiO, 0.48 kg of Mg, 0.2 kg of Ca, and 0.01 kg of Cu were mixed for 30 min and then placed in a vacuum furnace. The mixture was heated to 1100°C under a vacuum degree of 0.001 Pa and kept at this temperature for 30 h to generate SiO vapor, Mg vapor, Ca vapor, and Cu vapor in the furnace. After the vapors were evenly mixed, they were condensed to below 100°C to obtain 4 kg of active material.

[0147] (2) Powdering: 3 kg of the active material prepared in (1) was crushed, ball-milled, and classified to control the average particle size D50 to about 1 μm and the specific surface area to 120 m 2 / g.

[0148] (3) Carbon Coating Treatment: The active material, after the powderization treatment in (2) above, was placed in a CVD furnace. Argon gas was introduced as a shielding gas from the outer circuit, and acetylene gas was introduced as a carbon source from the inner circuit. The furnace was heated to 750°C to decompose the acetylene. 1% carbon was coated on the surface of the active material to obtain a negative electrode material. The carbon material comprised amorphous carbon, the thickness of the carbon layer was 50 nm, and the pH value of the negative electrode material was 8.

[0149] The negative electrode material prepared in Example 7 was subjected to elemental quantitative analysis using an inductively coupled plasma emission spectrometer. The test results and the m calculated based on the test results were Ca / m Mg and m Cu / m Mg As shown in Table 1.

[0150] Furthermore, the electrochemical performance of the negative electrode material prepared in Example 7 was tested. The test results are shown in Tables 2 and 3.

[0151] Example 8

[0152] Preparation of negative electrode materials

[0153] (1) Preparation of active material: 5 kg of SiO, 0.48 kg of Mg, 0.2 kg of Ca, and 0.01 kg of Cu were mixed for 30 min and then placed in a vacuum furnace. The mixture was heated to 1600°C under a vacuum degree of 100 Pa and kept at this temperature for 4 h to generate SiO vapor, Mg vapor, Ca vapor, and Cu vapor in the furnace. After the vapors were evenly mixed, they were condensed to below 100°C to obtain 4 kg of active material.

[0154] (2) Powdering: 3 kg of the active material prepared in (1) was crushed, ball-milled, and classified to control the average particle size D50 to about 100 μm and the specific surface area to 1 m 2 / g.

[0155] (3) Carbon Coating Treatment: The active material, after the powderization treatment in (2) above, was placed in a CVD furnace, argon gas was introduced as a shielding gas from the outer circuit, and acetylene gas was introduced as a carbon source from the inner circuit. The furnace was heated to 850°C to decompose the acetylene. A 20% carbon coating was formed on the surface of the active material to obtain a negative electrode material. The carbon material comprised amorphous carbon, the carbon layer had a thickness of 200 nm, and the pH value of the negative electrode material was 10.

[0156] The negative electrode material prepared in Example 8 was subjected to elemental quantitative analysis using inductively coupled plasma emission spectrometry. The test results and m calculated based on the test results were Ca / m Mg and m Cu / m Mg As shown in Table 1.

[0157] Furthermore, the electrochemical performance of the negative electrode material prepared in Example 8 was tested. The test results are shown in Tables 2 and 3.

[0158] Comparative Example 1

[0159] The difference from Example 1 is that the raw materials added in step (1) are 5 kg SiO and 0.5 kg Mg.

[0160] Comparative Example 2

[0161] The difference from Example 1 is that the raw materials added in step (1) are 5 kg SiO, 0.5 kg Mg and 0.2 kg Ca.

[0162] Comparative Example 3

[0163] The difference from Example 1 is that the raw materials added in step (1) are 5 kg SiO, 0.5 kg Mg, 0.2 kg Ca and 0.2 kg Cu.

[0164] Comparative Example 4

[0165] The difference from Example 1 is that the raw materials added in step (1) are 5 kg SiO, 0.5 kg Mg, 0.8 kg Ca and 0.01 kg Cu.

[0166] Comparative Example 5

[0167] The difference from Example 1 is that the raw materials added in step (1) are 5 kg SiO, 0.5 kg Mg and 0.6 kg Cu.

[0168] Test method:

[0169] 1. Element content: Inductively coupled plasma emission spectrometer and oxygen, nitrogen and hydrogen tester are used to perform element quantitative analysis on the negative electrode material.

[0170] 2. Si crystallite size: The negative electrode material is scanned and tested in the range of 10-90 degrees using an X-ray diffractometer, and the Si crystallite size is calculated using the Scherrer formula.

[0171] 3. Carbon material thickness: The negative electrode material is ground and cut using an ion mill, and then the cross-section of the negative electrode material is observed using a scanning electron microscope to confirm the thickness of the carbon material.

[0172] 4. pH value: Use a Mettler-Toledo pH meter to test the negative electrode material to obtain the pH value of the material.

[0173] 5. Average particle size D50: The average particle size of the negative electrode material was analyzed using a Malvern Panalytical Mastersizer 3000 laser particle size analyzer, and is the volume cumulative distribution.

[0174] 6. Specific surface area: The specific surface area of ​​the negative electrode material was analyzed using a Microbeam analyzer Tristar 3020 with nitrogen as the adsorption and desorption gas.

[0175] 7. Powder Conductivity: The volume resistivity of the negative electrode material powder was measured using the four-probe method. The instrument tested the resistance of the powder under five pressure points: 4kN, 8kN, 12kN, 16kN, and 20kN. The computer then automatically calculated the conductivity and resistivity of the negative electrode material powder. The data in Appendix 3 is the conductivity under a pressure of 20kN.

[0176] 8. Electrical performance test:

[0177] Referring to BTRTC / ZY / 01-020 "Button Battery Method Operation Instructions", button batteries are assembled as follows: the negative electrode material, conductive carbon black and polyacrylic acid binder are dissolved in deionized water at a mass percentage of 75:15:10, and then uniformly dispersed using a high-speed disperser. The stirring parameters are: first stirring at a speed of 800r / min for 20s, and then stirring at a speed of 2000r / min for 5min. Then use a dust-free cloth soaked in anhydrous ethanol to wipe the surface of the copper foil to remove oil stains, and use an automatic coating machine equipped with a 200μm coater to evenly coat the slurry on the copper foil at a speed of 20mm / s. After drying in a blast drying oven at 95°C for 0.5h, transfer to a vacuum drying oven at 130°C and dry for 8h. Use a punching machine to make it into The electrodes are weighed, packaged, and then transferred to an argon-filled glove box for battery assembly; the electrodes are made of metal lithium sheets, and the separator is a PP-PE-PP composite film with a diameter of 19.2 mm; the electrolyte component ratio is EC / EMC / DMC=1 / 1 / 1, and the lithium salt (LiPF6) concentration is 1.05 mol / L.

[0178] (1) Lithium insertion capacity: Under normal temperature conditions, 0.1C constant current charging, the charging voltage is limited to 0.005V~1.5V, and the corresponding capacity is the lithium insertion capacity.

[0179] (2) Delithiation capacity: Under normal temperature conditions, 0.1C constant current discharge, the discharge voltage is limited to 1.5V ~ 0.005V, and the corresponding capacity is the delithiation capacity.

[0180] (3) First coulombic efficiency: the ratio of the lithium insertion capacity obtained by the first charge to the lithium removal capacity obtained by the first discharge × 100%.

[0181] (4) Cyclic performance: The negative electrode materials prepared in the examples and comparative examples were prepared into batteries and tested using a button battery charging and discharging device. In the first week, the battery was discharged at 0.1C to 0.01V, then discharged at 0.01C in asymmetric decreasing order to 0.01V, then discharged at 0.01C to 0.005V, and then charged at 0.1C to 1.5V. In the second week, the battery was discharged at 0.2C to 0.01V, then discharged at 0.02C in asymmetric decreasing order to 0.01V, then discharged at 0.02C to 0.005V, and then charged at 0.2C to 1.5V. In the first week, the battery was discharged at 0.5C to 0.01V, discharged at 0.05C in a regularly decreasing manner to 0.01V, discharged at 0.05C to 0.005V and charged at 0.5C to 1.5V; from the 4th to the 50th week, the battery was discharged at 1C to 0.01V, discharged at a regularly decreasing manner to 0.01V, discharged at 0.1C to 0.005V and charged at 1C to 1.5V; in the 51st week, the battery was discharged at 0.1C to 0.01V, discharged at a regularly decreasing manner to 0.01V and discharged at 0.01C to 0.005V.

[0182] (5) Pole expansion rate: Under room temperature conditions, use a micrometer to test the thickness of the produced pole piece and record it, then assemble the pole piece into a battery for charge and discharge cycles; after a certain number of cycles, disassemble the battery and use a micrometer to test the thickness of the pole piece; the ratio of the increase in the thickness of the pole piece after the cycle compared to the thickness of the pole piece before the cycle to the thickness of the pole piece before the cycle is the pole piece expansion rate.

[0183] Test results:

[0184] The element content test results of the negative electrode materials prepared in Examples 1-8 and Comparative Examples 1-5 are shown in Table 1 below. In the negative electrode materials, the elements other than Ca, Mg, and Cu are Si, O, and C. The mass content of silicon is 24% to 36%, the mass content of oxygen is 44% to 59%, and the balance is carbon.

[0185] Table 1

[0186] The electrical performance test results of the negative electrode materials prepared in Examples 1-8 and Comparative Examples 1-5 are shown in Table 2 below:

[0187] Table 2

[0188] The test results of the electrical conductivity and cyclic expansion performance of the negative electrode materials prepared in Examples 1-8 and Comparative Examples 1-5 are shown in Table 3 below:

[0189] Table 3

[0190] Combined analysis of Table 1, Table 2 and Table 3:

[0191] By comparing Comparative Examples 1, 2, and 5 with Example 1, it can be seen that, compared to negative electrode materials whose active materials contain only one or two of the elements Ca, Mg, and Cu, the active materials of the negative electrode materials of the present application contain three elements at the same time, which is beneficial to reducing the volume expansion rate of the material and improving the ratio of lithium removal capacity to lithium insertion capacity, and can comprehensively improve the initial coulombic efficiency, conductivity, and cycle performance of the material. Among them, compared with Example 1, although the conductivity of Comparative Example 5 is higher, its cycle expansion rate is also significantly increased, and the application of the negative electrode material is greatly limited. The specific reason is that in Comparative Example 5, m Cu / m Mg There is a large increase, which makes the content of copper silicide in the negative electrode material also increase significantly, thereby improving the conductivity of the negative electrode material; at the same time, m Ca / m Mg The decrease in the content of the M element leads to an imbalance in the ratio of magnesium silicate to calcium silicate in the negative electrode material, which reduces the structural stability of the negative electrode material and significantly reduces the cycle performance of the negative electrode material. Examples 7 and 8 adjust the preparation process of the coating layer. Since the content of the M element is still adjusted within the range of this application, the performance of the negative electrode material is not significantly reduced, and the technical problem proposed in this application can still be solved.

[0192] By comparing Comparative Examples 3-4 with Examples 1-4, it can be seen that when the mass content ratios of calcium element, copper element and magnesium element in the prepared negative electrode material respectively meet the following requirements: 0<m Ca / m Mg <0.1, and 0<m Cu / m Mg When m is less than 0.01, the volume expansion rate of the negative electrode material and the ratio of lithium removal capacity to lithium insertion capacity can be improved, and the initial coulombic efficiency, conductivity and cycle performance of the material can be comprehensively improved without the situation where one or more of the performances are degraded due to the imbalance of element distribution. Among them, compared with Examples 1-4, although the conductivity of Comparative Example 3 is higher, its cycle expansion rate is also significantly increased, and the application of the negative electrode material is greatly limited. The reason is that in Comparative Example 3, m Cu / m Mg The large increase causes the content of copper silicide in the negative electrode material to increase, thereby improving the conductivity of the negative electrode material. However, the lack of calcium element significantly reduces the structural stability of the negative electrode material and significantly increases the cycle expansion rate.

[0193] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A negative electrode material, characterized in that: The negative electrode material includes an active substance, the active substance includes Si element, O element and metal M element, and the metal M includes Mg, Ca and Cu; In the negative electrode material, the mass content of Mg element is m Mg , the mass content of Ca element is m Ca , the mass content of Cu element is m Cu , 0<m Ca / m Mg <0.1,0<m Cu / m Mg <0.

01.

2. The negative electrode material according to claim 1, characterized in that The negative electrode material has at least one of the following characteristics: (1) In the active material, Mg, Ca and Cu are uniformly distributed; (2)0＜m Mg ＜25％； (3)0＜m Ca ＜10％； (4)0＜m Cu ＜0.5％。 3. The negative electrode material according to claim 1, characterized in that The negative electrode material has at least one of the following characteristics: (1) The mass content of silicon in the negative electrode material is 24% to 36%; (2) The mass content of oxygen element in the negative electrode material is 44% to 59%.

4. The negative electrode material according to claim 1, characterized in that The negative electrode material has at least one of the following characteristics: (1) In the active material, the Si element exists in the form of silicon element and / or silicon oxide, and the Si crystallite size in the silicon element and / or the silicon oxide is ≤15 nm; (2) In the active material, the Si element exists in the form of at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and a composite of crystalline silicon and amorphous silicon.

5. The negative electrode material according to claim 1, characterized in that The active material includes silicon oxide, and the general formula of the silicon oxide is SiO x , 0<x≤2.

6. The negative electrode material according to claim 1, characterized in that The metal M exists in the form of at least one of M silicate, M oxide and M silicide.

7. The negative electrode material according to claim 6, characterized in that The active material includes at least one of calcium silicate, magnesium silicate and copper silicide.

8. The negative electrode material according to claim 2, characterized in that The negative electrode material has at least one of the following characteristics: (1)0.028≤m Ca / m Mg ≤0.099,0.0008≤m Cu / m Mg ≤0.0099; (2)5％≤m Mg ≤15％； (3)0.2％≤m Ca ≤0.8％； (4)0.007％≤m Cu ≤0.08％。 9. The negative electrode material according to claim 1 or 2, characterized in that: The negative electrode material further includes a carbon material, and the carbon material is located on at least a portion of the surface of the active material.

10. The negative electrode material according to claim 9, characterized in that The negative electrode material has at least one of the following characteristics: (1) The carbon material comprises at least one of graphite, graphene, amorphous carbon, diamond-like carbon, carbon nanotubes and carbon fibers; (2) the carbon material forms a carbon layer on the surface of the active material; (3) The carbon material forms a carbon layer on the surface of the active material, and the thickness of the carbon layer is 50 nm to 200 nm; (4) The mass content of carbon element in the negative electrode material is 1% to 20%.

11. The negative electrode material according to claim 1, characterized in that The negative electrode material has at least one of the following characteristics: (1) The pH value of the negative electrode material is 8 to 10; (2) The average particle size D50 of the negative electrode material is 1 μm to 100 μm; (3) The specific surface area of ​​the negative electrode material is 1 m 2 / g~120m 2 / g; (4) The electrical conductivity of the negative electrode material is 0.5 S / cm to 7 S / cm.

12. A method for preparing a negative electrode material, characterized in that: The preparation method comprises the following steps: The raw material of the silicon-based active particles is mixed with a metal doping source containing an M element and subjected to heat treatment. The steam formed is mixed and then cooled to obtain an active material. The negative electrode material includes the active material. The active material includes Si element, O element and metal M element. The metal M includes Mg, Ca and Cu. In the negative electrode material, the mass content of Mg element is m Mg , the mass content of Ca element is m Ca , the mass content of Cu element is m Cu , 0<m Ca / m Mg <0.1,0<m Cu / m Mg <0.

01.

13. The preparation method according to claim 12, characterized in that: The preparation method includes at least one of the following features: (1) The mass ratio of the metal doping source to the raw material of the silicon-based active particles is (1-35):100; (2) the metal doping source comprises at least one of a simple substance of metal M and a compound containing metal M; (3) The raw materials of the silicon-based active particles include Si, SiO y Mixture of SiO2 and SiO y At least one of a mixture of Si and Si, and a mixture of Si and SiO2, wherein 0<y<2; (4) The molar amount of the M element in the metal doping source is n M The molar amount of Si in the raw material of the silicon-based active particles is n Si , and n M :n Si =(0.02~0.62):1; (5) The molar amount of the M element in the metal doping source is n M , 0<n Ca / n Mg <1.8,0<n Cu / n Mg <0.

3.

14. The preparation method according to any one of claims 12 to 13, characterized in that: The method further comprises: performing carbon coating treatment on the active material obtained by cooling to obtain a negative electrode material.

15. A lithium ion battery, characterized in that: The invention comprises the negative electrode material as claimed in any one of claims 1 to 11, or comprises the negative electrode material prepared by the preparation method as claimed in any one of claims 12 to 14.

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