Electrochemical Equipment

Abstract

The present invention relates to a negative electrode active material and an electrochemical device including the same. Some embodiments of the present invention provide an electrochemical device, the electrochemical device includes a negative electrode, the negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a magnesium-doped carbon silicon oxygen material, and a carbon nanotube coating layer is provided on the surface of the crystalline oxide of the magnesium-doped carbon silicon oxygen material. The electrochemical device of the present invention uses the magnesium-doped carbon silicon oxygen material with a carbon nanotube coating layer to improve the initial coulombic efficiency of the electrochemical device, improve the structural stability during the cycle process of the electrochemical device, and further improve the cycle retention rate and cycle characteristics of the electrochemical device.

Description

[Technical Field]

[0001] The present invention relates to the field of energy storage, and in particular to negative electrode active materials and electrochemical devices containing the same, especially lithium ion batteries. [Background technology]

[0002] With the development of technology and the increasing demand for mobile devices, the demand for electrochemical devices (e.g., lithium-ion batteries) has increased significantly. In order to provide electrochemical devices with high energy density, high discharge characteristics, and high cycle performance, one of the main research directions in the field of electrochemical energy storage is the research and improvement of electrode materials in electrochemical devices.

[0003] Currently, many commercial electrochemical devices use graphite as the negative electrode active material, but graphite has a low gram capacity. Silicon-based materials have a higher theoretical gram capacity than graphite as a negative electrode active material and are therefore a key negative electrode active material for the development of future electrochemical devices with high volumetric energy density. However, in practical applications, such high-energy-density negative electrode active materials experience a large volume change during the lithium absorption / desorption process, which can lead to poor cycling performance and poor initial coulombic efficiency in electrochemical devices. Improvements to silicon-based materials still have various shortcomings.

[0004] In view of these circumstances, it is necessary to continue research and improvement of negative electrode materials and negative electrode active materials in order to improve the battery capacity, cycle characteristics, and rate characteristics of electrochemical devices. Summary of the Invention

[0005] SUMMARY OF THE INVENTION To at least partially solve at least one of the problems existing in the related art, embodiments of the present invention provide a negative electrode active material having a substrate-free adhesive film and an electrochemical device including the same.

[0006] According to one aspect of the present invention, some embodiments of the present invention provide a negative electrode active material, which includes a magnesium-doped carbon silicon oxygen material. By using carbon nanotubes to coat the particles of the magnesium-doped carbon silicon oxygen material, the magnesium-doped carbon silicon oxygen material further includes a carbon nanotube coating layer, and the carbon nanotube coating layer is provided on the particle surface of the crystalline oxide of the magnesium-doped carbon silicon oxygen material. The negative electrode active material according to the present invention can improve the initial Coulomb efficiency of the carbon silicon oxygen material and enhance the rate performance of the carbon silicon oxygen material by using the magnesium-doped carbon silicon oxygen material. In addition, by providing a carbon nanotube coating layer on the particle surface of the crystalline oxide of the magnesium-doped carbon silicon oxygen material, a network conductive structure can be formed, and the electrical conductivity of the negative electrode active material can be improved.

[0007] According to another aspect of the present invention, some embodiments of the present invention provide an electrochemical device, which includes a negative electrode. The negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a magnesium-doped carbon silicon oxygen material. The magnesium-doped carbon silicon oxygen material includes a carbon nanotube coating layer, and the carbon nanotube coating layer is provided on the surface of the crystalline oxide of the magnesium-doped carbon silicon oxygen material. The electrochemical device according to the present invention can improve the initial Coulomb efficiency of the electrochemical device, improve the structural stability during the cycle process of the electrochemical device, and further improve the cycle retention rate and cycle characteristics of the electrochemical device by using the magnesium-doped carbon silicon oxygen material with a carbon nanotube coating layer.

[0008] According to some embodiments of the present invention, the general formula of the crystalline oxide of the magnesium-doped carbon silicon oxygen material is Mg z SiC x O y where x, y, and z satisfy 0 < x < 0.3, 0.4 < y < 1.0, and 0.1 < z < 0.2.

[0009] According to some embodiments of the present invention, in the magnesium-doped carbon silicon oxygen material, the molar silicon content is 40%-70%, the molar carbon content is 3.5%-24%, and the molar magnesium content is 7.0%-7.5%.

[0010] According to some embodiments of the present invention, in the magnesium-doped carbon silicon oxygen material, the molar ratio of magnesium to silicon is 0.1-0.2, and the molar ratio of magnesium to carbon is 0.2-10.0.

[0011] According to some embodiments of the present invention, the I in the Raman spectrum of the magnesium-doped carbon silicon oxygen material D / I G The value is 0.023 to 0.32.

[0012] According to some embodiments of the present invention, the I in the Raman spectrum of magnesium-doped carbon silicon oxygen materials versus the molar carbon content D / I G The value of the ratio of values ​​is 0.095 to 6.78.

[0013] According to some embodiments of the present invention, the carbon nanotube coating layer has a thickness of 0.5 nm to 5.0 μm.

[0014] According to some embodiments of the present invention, the carbon nanotube coating layer includes carbon nanotube clusters, which extend from the surface of the carbon nanotube coating layer, and the length of the carbon nanotube clusters is 0.1 μm to 1.0 μm.

[0015] According to some embodiments of the present invention, the negative electrode active material layer further includes a binder, and the binder includes synthetic rubber. The binder includes one or more binders selected from the group consisting of polyacrylic acid ester, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium hydroxymethylcellulose, and potassium hydroxymethylcellulose.

[0016] According to some embodiments of the present invention, the weight percentage of the binder is 2% to 6% based on the total weight of the negative electrode active material layer.

[0017] According to some embodiments of the present invention, an electrolyte for an electrochemical device includes an organic solvent and a lithium salt, the organic solvent including one or more selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, vinylene carbonate, propyl propionate, and ethyl propionate, and the lithium salt is lithium hexafluorophosphate. The compound may include one or more selected from the group consisting of lithium tetrafluoroborate (LiPF), lithium tetrafluoroborate (LiBF), lithium difluorophosphate (LiPOF), lithium bis(trifluoromethanesulfonyl)imide (LiN(CFSO)), lithium bis(fluorosulfonyl)imide (Li(N(SOF))), lithium bis(oxalato)borate (LiB(C0)), and lithium difluoro(oxalato)borate (LiBF(C0)).

[0018] Other aspects and advantages of embodiments of the present invention are set forth in part in the description that follows, and in part are illustrated by, or may be learned by, the practice of the embodiments of the present application. [Brief explanation of the drawings]

[0019] In the following, in order to explain the embodiments of the present application, necessary drawings for explaining the embodiments of the present application or the prior art will be briefly described. Obviously, the drawings described below are only some of the embodiments in the present application. Those skilled in the art can still obtain drawings of other embodiments based on the structures illustrated in these drawings without creative work.

[0020] [Figure 1] FIG. 1 is a schematic diagram of the particle structure of negative electrode active materials according to some embodiments of the present invention. [Figure 2] FIG. 2 is the XRD diffraction spectrum of the magnesium-doped carbon silicon oxygen material of Example 1 of the present invention. [Figure 3] FIG. 3 is a microscopic image of the negative electrode active material of Example 1 of the present invention taken by a scanning electron microscope at 5000 magnifications. [Figure 4] FIG. 4 is a graph showing cycle capacity curves of the electrochemical devices of Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0021] The embodiments of the present invention are described in detail below, and should not be construed as limitations on the present application.

[0022] As used herein, the following terms have the meanings indicated below unless otherwise specified.

[0023] As used herein, the terms "substantially," "roughly," "substantially," and "about" are intended to indicate and describe small variations. When used in conjunction with an instance or circumstance, the terms can refer to instances in which the instance or circumstance occurred exactly as well as instances in which the instance or circumstance occurred very approximately. For example, when used in conjunction with a numerical value, the terms can refer to a range of variation of ±10% or less of the numerical value, e.g., ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.1%, or ±0.05%. For example, two numerical values ​​are considered to be "approximately" the same if the difference between them is ±10% or less of the mean value of the values ​​(e.g., ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.1%, or ±0.05%).

[0024] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "one or more selected from the group consisting of," "at least one or more of," or other similar terminology can refer to any combination of the listed items. For example, if items A and B are listed, the phrase "one or more of A and B" means A only, B only, or A and B. In another example, if items A, B, and C are listed, the phrase "one or more of A, B, and C" means A only, B only, C only, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A may include one element or multiple elements. Item B may include one element or multiple elements. Item C may include one element or multiple elements.

[0025] Also, for convenience of description, terms such as "first," "second," "third," etc. may be used herein to distinguish between different components in a figure or series of figures. "First," "second," "third," etc. are not intended to describe corresponding components unless otherwise specified or limited.

[0026] In the field of electrochemical energy storage, attempts have been made to replace conventional graphite anode active materials with high-energy-density anode active materials to achieve optimal energy density. However, these high-energy-density anode active materials have different material properties and require further processing. For example, silicon-based materials have a high theoretical gram capacity of 4200 mAh / g, making them the mainstream anode active material for the development of future high-volume energy-density electrochemical devices (e.g., lithium-ion batteries). These high-energy-density anode active materials exhibit a large volume change effect (e.g., over 300%) during the lithium absorption / desorption process. Significant expansion of the anode leads to deformation and separation of the interface between the anode and the separator, further degrading the cycle performance of lithium-ion batteries. At the same time, the unstable lithium ion pathways in silicon-based materials during the lithium absorption / desorption process make them prone to non-uniform lithium metal deposition, known as the "dead lithium" phenomenon. This results in a poor initial coulombic efficiency of an electrochemical device using a silicon-based material as the negative electrode active material. The initial charge / discharge coulombic efficiency can directly reflect the electrochemical performance of the electrochemical device.

[0027] Chinese Patent CN108767241A discloses a negative electrode material that uses magnesium-doped silicon oxide formed by doping magnesium into a silicon-oxygen material, which can improve the rate characteristics and initial coulombic efficiency of lithium-ion batteries. However, during the charge-discharge cycle, the magnesium-doped silicon oxide has insufficient electrical conductivity and a high volume expansion rate during the lithium absorption / release process, so the magnesium-doped silicon oxide as a negative electrode active material still cannot effectively form uniform lithium metal deposition, resulting in a reduced cycle efficiency and a shortened service life of the magnesium-doped silicon oxide.

[0028] In view of the above, according to one aspect of the present invention, as shown in Figure 1, some embodiments of the present invention provide an anode active material, which includes a composite material, i.e., a magnesium-doped carbon silicon oxygen material, formed by doping silicon oxide with carbon and magnesium through a high-temperature manufacturing process. The anode active material further includes a carbon nanotube coating layer 102 on the surface of the crystalline oxide 101 of the magnesium-doped carbon silicon oxygen material. The carbon nanotube coating layer 102 is formed on the particle surface of the crystalline oxide 101 of the magnesium-doped carbon silicon oxygen material through a carbon nanotube coating process.

[0029] By doping silicon-oxygen materials with magnesium, magnesium silicon oxides can be formed, which can improve the initial Coulomb efficiency of electrochemical devices. At the same time, by doping carbon, carbon-containing magnesium silicon oxides can be further formed in the composite magnesium-doped carbon silicon-oxygen materials. The carbon-containing magnesium silicon oxides have a low volume expansion rate and excellent cycle structure stability during the lithium absorption and release process. The magnesium-doped carbon silicon-oxygen materials can effectively form uniform lithium metal precipitation during the cycle process, improve the cycle characteristics of electrochemical devices, and extend their service life. In addition, the present invention can further improve the conductivity of the anode active material by coating the particle surface of the magnesium-doped carbon silicon-oxygen material with carbon nanotubes.

[0030] The magnesium-doped carbon silicon-oxygen material is a composite material comprising a crystalline oxide composed of magnesium, carbon, silicon and oxygen, and carbon nanotubes coated on its surface. In some embodiments, the crystalline oxide of the magnesium-doped carbon silicon-oxygen material can be represented by the general formula Mg z SiC x O y . In some embodiments, the stoichiometry of the general formula Mg z SiC x O y of the crystalline oxide of the magnesium-doped carbon silicon-oxygen material is 0 < x < 0.3, 0.4 < y < 1.0, and 0.1 < z < 0.2. In some embodiments, 0.15 < x < 0.28, 0.6 < y < 0.8, and 0.1 < z < 0.2. In some embodiments, 0.2 < x < 0.25, 0.7 < y < 0.78, and 0.1 < z < 0.2.

[0031] The components and crystalline structure of the magnesium-doped carbon silicon oxygen material have a certain effect on the cycling characteristics, gram capacity, and structural stability of the magnesium-doped carbon silicon oxygen material in an electrochemical device. In some embodiments, the molar content of elemental silicon (Si) in the magnesium-doped carbon silicon oxygen material is 40% to 70%. If the silicon content is too low, the gram capacity of the negative electrode active material will be low, and if the silicon content is too high, the volume expansion rate of the negative electrode active material will be high. In some embodiments, the molar content of elemental silicon (Si) in the magnesium-doped carbon silicon oxygen material is 60%.

[0032] In some embodiments, the magnesium-doped carbon silicon oxygen material has a molar content of elemental magnesium (Mg) of 7.00% to 7.5%. This range of elemental magnesium can effectively form a carbon-containing magnesium silicon oxide while avoiding the formation of highly active magnesium oxide or magnesium metal between elemental magnesium and oxygen, thereby improving the initial coulombic efficiency of the magnesium-doped carbon silicon oxygen material as a negative electrode active material and reducing safety risks during electrochemical cycling of the magnesium-doped carbon silicon oxygen material.

[0033] In some embodiments, the molar content of carbon element C in the magnesium-doped carbon silicon oxygen material is 3.5% to 24%. The carbon element source in the magnesium-doped carbon silicon oxygen material includes carbon doped into a crystalline oxide and carbon nanotubes coated with a crystalline oxide. If the carbon doping amount is too low, the structural stability of the negative electrode active material decreases and the volume expansion rate increases, while if the carbon doping amount is too high, the gram capacity of the negative electrode active material decreases. In some embodiments, the molar content of carbon element C in the magnesium-doped carbon silicon oxygen material is 4.5% to 10%. In some embodiments, the molar content of carbon element C in the magnesium-doped carbon silicon oxygen material is about 6%.

[0034] It should be understood that the content of each element in the magnesium-doped carbon-silicon-oxygen material of the present invention can be detected using any suitable detection method known in the art, but is not limited to this. In some embodiments, the magnesium content and silicon content in the magnesium-doped carbon-silicon-oxygen material can be measured by X-ray diffraction analysis. In some embodiments, the carbon content of the magnesium-doped carbon-silicon-oxygen material can be measured by the following carbon content test. Under oxygen-enriched conditions, a sample is heated to high temperatures in a high-frequency furnace to combust, oxidizing carbon and sulfur to carbon dioxide and sulfur dioxide, respectively. After processing, the gas enters a corresponding absorption cell, absorbs corresponding infrared radiation, and is converted into a corresponding signal by a detector. This signal is sampled by a computer, linearly corrected, and converted into a value proportional to the carbon dioxide and sulfur dioxide concentrations. The values ​​throughout the analysis are then accumulated. After the analysis is completed, the accumulated value is divided by the weight, multiplied by a correction factor, and the blank is subtracted to obtain the carbon and sulfur contents of the sample. A high frequency infrared sulfur carbon analyzer (Shanghai Dekai Instrument Co., Ltd. HCS-140) is used for sample testing.

[0035] FIG. 2 shows an XRD diffraction spectrum of the magnesium-doped carbon silicon oxygen material of Example 1 of the present invention. As shown in FIG. 2, in one example, X-ray diffraction analysis was performed on the magnesium-doped carbon silicon oxygen material. The XRD diffraction spectrum shows that the magnesium-doped carbon silicon oxygen material contains one or more characteristic peaks selected from Si, SiO2, MgSiO3, and Mg2SiO4. In some examples, the magnesium-doped carbon silicon oxygen material has a molar ratio of magnesium to silicon of 0.1 to 0.2 and a molar ratio of magnesium to carbon of 0.2 to 10.0. This improves the cycle performance and first coulombic efficiency of the magnesium-doped carbon silicon oxygen material in an electrochemical device. In some examples, the magnesium-doped carbon silicon oxygen material has a molar ratio of magnesium to silicon of about 0.12.

[0036] Figure 3 is a 5000x scanning electron microscope image of the magnesium-doped carbide silicon oxygen material of Example 1 of the present invention. As can be seen from Figure 3, the carbon nanotube coating layer on the surface of the crystalline oxide particles of the magnesium-doped carbide silicon oxygen material can form a network conductive structure, which can make the distribution of lithium metal deposition more uniform during cycling and improve the volume expansion distribution of the magnesium-doped carbide silicon oxygen material, resulting in better structural stability of the negative electrode active material during cycling.

[0037] In some embodiments, the thickness of the carbon nanotube coating layer can affect the electrical conductivity and energy density of the magnesium-doped carbon silicon oxygen material in an electrochemical device. If the carbon nanotube coating layer is too thick, the gram capacity of the magnesium-doped carbon silicon oxygen material decreases, while if the carbon nanotube coating layer is too thin, the electrical conductivity decreases and the structural stability of the magnesium-doped carbon silicon oxygen material cannot be improved. In some embodiments, the thickness of the carbon nanotube coating layer is about 0.5 nm, 1.0 nm, 5 nm, 10 nm, 50 nm, 100 nm, 250 nm, 500 nm, 1.0 μm, or 5.0 μm, or a range consisting of any two of the foregoing values. In some embodiments, the thickness of the carbon nanotube coating layer is 0.5 nm to 5.0 μm. In some embodiments, the thickness of the carbon nanotube coating layer is 2.0 nm to 150 nm.

[0038] In some embodiments, the carbon nanotube coating layer comprises carbon nanotube clusters. The carbon nanotube clusters extend outward from the surface of the magnesium-doped carbon silicon oxygen material particles and contact the carbon nanotube coating layers on other particle surfaces, forming an effective conductive network and improving the conductivity of the magnesium-doped carbon silicon oxygen material. In some embodiments, the carbon nanotube clusters extend for a length of 0.1 μm to 1.0 μm. In some embodiments, the carbon nanotube clusters have a thickness of about 0.5 μm.

[0039] In this specification, the thickness of the carbon nanotube coating layer and the extension length of the carbon nanotube clusters are not particularly limited and can be detected using any suitable detection method in the art. In some embodiments, the thickness of the carbon nanotube coating layer and the extension length of the carbon nanotube clusters are evaluated using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). In some embodiments, the evaluation using the scanning electron microscope was recorded using a Philips XL-30 field emission scanning electron microscope, and was performed under conditions of 10 kV and 10 mA.

[0040] In some embodiments, the particle size (Dv50) of the magnesium-doped carbide silicon oxygen material particles is 2.5 μm to 10.0 μm. In some embodiments, the particle size (Dv50) of the magnesium-doped carbide silicon oxygen material particles is 2.7 μm to 5.3 μm, thereby improving the coating distribution of the magnesium-doped carbide silicon oxygen material in the negative electrode active material layer. In some embodiments, the particle size distribution of the magnesium-doped carbide silicon oxygen material particles satisfies the relationship: 0.3≦Dn10 / Dv50≦0.6.

[0041] As used herein, the term "particle size," unless otherwise specified, includes characteristic particle characteristics of a sample obtained by particle size testing, such as Dn10 or Dv50. Here, Dn10 refers to the particle size at which the cumulative particle number of the smallest particle size in the particle size-based particle distribution of the material is 10%. Dv50 refers to the particle size at which the cumulative volume of the smallest particle size in the volume-based particle distribution of the material is 50%. In some examples, the particle size test method used a Mastersizer 2000 laser particle size distribution analyzer to analyze the particle size of the sample. The sample was dispersed in 100 mL of dispersant (deionized water) to a light blocking level of 8-12%. The sample was then sonicated for 5 minutes at 40 kHz and 180 watts. After sonication, the sample was subjected to laser particle size distribution analysis to obtain particle size distribution data.

[0042] In some embodiments, the magnesium doped carbon silicon oxygen material particles have a specific surface area of ​​1 m 2 / g~50m 2 In some embodiments, the specific surface area of ​​the magnesium doped carbon silicon oxygen material particles is 5 m 2 / g~20m 2 / g, the reaction rate between the magnesium-doped silicon carbide and oxygen material and the electrolyte is maintained.

[0043] In some embodiments, the coverage and structural stability of the carbon nanotube coating layer in the magnesium-doped carbon silicon oxygen material can be evaluated by Raman spectroscopy. -1 and 1580cm -1 The D peak and G peak in the vicinity are characteristic peaks in the Raman spectrum of carbon crystals. In some embodiments, the ratio of the value of the characteristic D peak to the value of the characteristic G peak in the Raman spectrum of the magnesium-doped carbon silicon oxygen material, i.e., I D / I GThe I value can be used to evaluate the network-like conductive structure due to the carbon nanotube coating layer in the magnesium-doped carbon silicon oxygen material particles. D / I G A low value indicates that the network conductive structure of the carbon nanotube coating is relatively complete. In some embodiments, the I D / I G In some embodiments, the I value in the Raman spectrum of the magnesium-doped carbon silicon oxygen material is 0.32 or less. D / I G By setting the value to 0.023 to 0.32, the network conductive structure of the carbon nanotube coating layer is improved.

[0044] In some embodiments, the I in the Raman spectrum of magnesium-doped carbon silicon oxygen materials versus the molar carbon content D / I G The ratio of the carbon content to the carbon nanotube coating layer can be further evaluated by the ratio of the carbon content to the carbon nanotube coating layer. D / I G If the ratio of the carbon content to the carbon content is too low, the gram capacity of the magnesium-doped carbon silicon oxygen material will be low. D / I G If the ratio of the carbon content to the carbon nanotube coating is too high, the carbon nanotube coating layer on the magnesium-doped carbon silicon oxygen material will be poorly coated. D / I G The ratio of the values ​​is 0.095 to 6.78.

[0045] According to another aspect of the present invention, some embodiments of the present invention provide a method for preparing the magnesium-doped carbon silicon oxygen material, the specific process is as follows:

[0046] (1) A carbon nanotube raw material is mixed with ethanol to prepare an ethanol dispersion having a predetermined carbon nanotube concentration. In some embodiments, the weight percent concentration of the carbon nanotubes in the ethanol dispersion is 1.5% to 10.0%. In some embodiments, the weight percent concentration of the carbon nanotubes in the ethanol dispersion is 1.6% to 6.6%.

[0047] (2) The precursor of the magnesium-doped carbon silicon oxygen material is mixed with the ethanol dispersion and stirred uniformly. The mixture of the precursor of the magnesium-doped carbon silicon oxygen material and the ethanol dispersion is evaporated to dryness, and the dry powder is collected.

[0048] (3) The collected dry powder is subjected to high temperature treatment under an argon atmosphere to obtain a magnesium-doped silicon carbide (SiC) material. In some embodiments, the high temperature treatment temperature is 400°C to 800°C. In some embodiments, the high temperature treatment temperature is about 600°C. In some embodiments, the high temperature treatment time is 1 hour to 5 hours. In some embodiments, the high temperature treatment time is about 3 hours.

[0049] The present invention provides a magnesium-doped carbon silicon oxygen material having a carbon nanotube coating by coating a precursor of the magnesium-doped carbon silicon oxygen material with carbon nanotubes using an ethanol dispersion. The magnesium-doped carbon silicon oxygen material having a carbon nanotube coating not only has improved electrical conductivity compared to simple carbon-coated or carbon-doped negative electrode active materials, but also reduces the impact of the carbon material on the electrical performance and gram capacity of the magnesium-doped carbon silicon oxygen material, improves the lithium deposition absorption / desorption mechanism of the magnesium-doped carbon silicon oxygen material, and further improves the electrical performance and cycle characteristics of the magnesium-doped carbon silicon oxygen material in electrochemical devices. In some embodiments, adjusting the temperature and reaction time of the high-temperature treatment further improves the electrical conductivity and coating structure of the carbon nanotube coating in the magnesium-doped carbon silicon oxygen material, allowing the magnesium-doped carbon silicon oxygen material to exhibit excellent cycle characteristics and initial coulombic efficiency as a negative electrode active material.

[0050] According to another aspect of the present invention, some embodiments of the present invention provide an electrochemical device, the electrochemical device including a negative electrode, the negative electrode including a negative electrode active material layer, the negative electrode active material layer including a negative electrode active material, and the negative electrode active material including the magnesium-doped carbon silicon oxygen material of the above embodiments. The electrochemical device uses the magnesium-doped carbon silicon oxygen material with a carbon nanotube coating layer to improve the initial coulombic efficiency of the electrochemical device, improve the structural stability of the electrochemical device during cycling, and further improve the cycle retention rate and cycling characteristics of the electrochemical device. In some embodiments, the weight percentage of the magnesium-doped carbon silicon oxygen material is 20% or more relative to the total weight of the negative electrode active material. In some embodiments, the weight percentage of the magnesium-doped carbon silicon oxygen material is 60% or more. In some embodiments, the negative electrode active material is formed from the magnesium-doped carbon silicon oxygen material of the above embodiments.

[0051] In some embodiments, the negative electrode active material further includes graphite, and the graphite may include one or more types selected from the group consisting of natural graphite, artificial graphite, and mesocarbon microbeads. This can improve the conductivity and cycle characteristics of the negative electrode active material. The negative electrode active material may include other common negative electrode active materials in the art that can absorb and release lithium (Li), as long as they are not contrary to the spirit of the present invention. Examples of other common negative electrode active materials include, but are not limited to, one or more types selected from carbon materials, metal compounds, oxides, sulfides, lithium nitrides such as LiN3, lithium metal, metal elements and metalloid elements alloyed with lithium, polymer materials, and combinations thereof.

[0052] In some embodiments, the powder electrical conductivity of the negative electrode active material can be controlled by adjusting the content of the magnesium-doped carbon silicon oxygen material, thereby improving the cycle characteristics of the negative electrode active material layer. In some embodiments, the powder electrical conductivity of the negative electrode active material is 2.0 S / cm to 30 S / cm. In some embodiments, the powder electrical conductivity of the negative electrode active material is 5.0 S / cm to 10 S / cm. In this specification, the powder electrical conductivity of the negative electrode active material is not particularly limited and can be detected using any appropriate detection method in the art. In some embodiments, the powder electrical conductivity of the negative electrode active material is detected as follows. Using a resistivity measuring device (Suzhou Jingge Electronic Co., Ltd., ST-2255A), 5 g of powder sample was taken and pressed in an electronic press at a constant pressure of 5000 kg ± 2 kg for 15-25 s. The sample was placed between the electrodes of the measuring device, and the powder electronic conductivity was calculated using the formula δ = h / (S * R) / 1000, where h is the height of the sample (cm), R is the resistance (KΩ), and S is the area of ​​the powder sample after pressing it into a sheet, i.e., 3.14 cm. 2 is.

[0053] In some embodiments, the resistance range of the negative electrode active material layer is 0.2Ω to 1Ω.

[0054] In some embodiments, the negative electrode active material layer further includes a binder to improve the structural stability of the negative electrode active material layer. In some embodiments, the binder includes a synthetic rubber, and the binder includes one or more selected from the group consisting of polyacrylic acid ester, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium hydroxymethylcellulose, and potassium hydroxymethylcellulose. In some embodiments, the weight percentage of the binder is 2% to 6% of the total weight of the negative electrode active material layer. In other embodiments, the weight percentage of the binder is, for example, about 2%, about 3%, about 4%, about 5%, or about 6% of the total weight of the negative electrode active material, or a range consisting of any two of these values.

[0055] In some embodiments, the negative electrode active material layer further includes a conductive agent to improve the conductivity of the negative electrode active material layer. The conductive agent may include one or more selected from the group consisting of carbon nanotubes, conductive carbon black, acetylene black, graphene, and ketjen black. Those skilled in the art can select common conductive agents according to their needs, but the present invention is not limited to these. In some embodiments, the weight percentage of the conductive agent is 1% to 10% relative to the total weight of the negative electrode active material layer. In other embodiments, the weight percentage of the conductive agent is, for example, about 1%, about 2%, about 3%, about 5%, or about 10%, or a range consisting of any two of these values, relative to the total weight of the negative electrode active material.

[0056] In some embodiments, the negative electrode further includes a negative electrode current collector, which may be a copper foil or a nickel foil, but may also be any other negative electrode current collector commonly used in the art, without limitation.

[0057] In some embodiments, the electrochemical device further includes a positive electrode and a separator, and the positive electrode, the separator, and the negative electrode in the above embodiments can be wound or stacked to form an electrode assembly. The electrode assembly in the present invention can be any suitable electrode assembly in the art as long as it does not deviate from the spirit of the present invention, but is not limited thereto. In some embodiments, the electrode assembly has a wound structure. In some embodiments, the electrode assembly can have a stacked structure or a multi-tab structure. In some embodiments, the electrochemical device is a lithium ion battery.

[0058] In some embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector may be aluminum foil or nickel foil, but other positive electrode current collectors commonly used in the art may also be used, including, but not limited to, these. In some embodiments, the positive electrode active material layer includes a positive electrode active material capable of absorbing and desorbing lithium (Li) (hereinafter, sometimes referred to as a "positive electrode active material capable of absorbing / desorbing lithium Li"). Examples of positive electrode active materials capable of absorbing / desorbing lithium (Li) include one or more selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxygen phosphate, lithium iron phosphate, lithium titanate, and lithium-rich manganese-based materials.

[0059] In some embodiments, the positive electrode active material layer may further include at least one of a binder and a conductive agent. The binder may include one or more selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The conductive agent may include one or more selected from the group consisting of carbon nanotubes, conductive carbon black, acetylene black, graphene, and ketjen black. Those skilled in the art may select conventional binders and conductive agents according to their needs, but the binders and conductive agents are not limited thereto.

[0060] In some embodiments, the separator may include, but is not limited to, at least one selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid. For example, the polyethylene may include at least one component selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene. Among these, polyethylene and polypropylene are effective in preventing short circuits and can improve battery stability through the off-state effect. Those skilled in the art can select conventional separators according to their needs, but the separator may be selected from among these.

[0061] In some embodiments, the electrochemical device of the present invention further comprises an electrolyte, the electrolyte comprising a lithium salt and an organic solvent.

[0062] In some embodiments, the lithium salt includes one or more selected from the group consisting of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium difluorophosphate (LiPOF), lithium bis(trifluoromethanesulfonyl)imide (LiN(CFSO)), lithium bis(fluorosulfonyl)imide (Li(N(SOF)), lithium bis(oxalato)borate (LiB(CO)), and lithium difluoro(oxalato)borate (LiBF(CO)). For example, lithium hexafluorophosphate (LiPF) is selected as the lithium salt because of its high ionic conductivity and ability to improve cycle characteristics.

[0063] In some embodiments, the organic solvent comprises one or more selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, vinylene carbonate, propyl propionate, and ethyl propionate. The lithium salt comprises one or more selected from the group consisting of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium difluorophosphate (LiPOF), lithium bis(trifluoromethanesulfonyl)imide (LiN(CFSO)), lithium bis(fluorosulfonyl)imide (Li(N(SOF)), lithium bis(oxalato)borate (LiB(CO)), and lithium difluoro(oxalato)borate (LiBF(CO)).

[0064] In some embodiments, the electrolyte further comprises an additive, which may be any suitable additive known in the art, but is not limited thereto, as long as it does not contradict the spirit of the present invention.

[0065] The methods for manufacturing the positive electrode, separator, negative electrode, and electrolyte in the examples of the present invention may be any suitable conventional method in the art according to specific needs, as long as they do not deviate from the spirit of the present invention, but are not limited thereto. In one embodiment of the method for manufacturing an electrochemical device, the method for manufacturing a lithium ion battery includes the following steps: The negative electrode, separator, and positive electrode in the examples are wound, folded, or stacked in order to form an electrode assembly, and then the electrode assembly is placed in a case such as an aluminum plastic film case, and an electrolyte is injected. The lithium ion battery with the electrode assembly attached is then subjected to subsequent processes such as vacuum sealing, standing, formation, and shaping to obtain a lithium ion battery.

[0066] Although the above description has been given using a lithium ion battery as an example, those skilled in the art will appreciate that the adhesive film of the negative electrode active material of the present invention can be applied to other suitable electrochemical devices. Such electrochemical devices include any device that generates an electrochemical reaction, and specific examples thereof include all types of primary batteries, secondary batteries, fuel cells, solar cells, and capacitors. In particular, the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0067] Some embodiments of the present invention further provide an electronic device, the electronic device including an electrochemical device according to an embodiment of the present invention.

[0068] The electronic device of the present invention is not particularly limited and may be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, a laptop computer, a pen-based computer, a mobile computer, an electronic book player, a mobile phone, a portable facsimile machine, a portable copier, a portable printer, a stereo headset, a video recorder, an LCD television, a portable vacuum cleaner, a portable CD player, a mini CD player, a walkie-talkie, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household storage battery, and a lithium ion capacitor.

[0069] Specific Examples Below, some specific examples and comparative examples are given, and the test methods and results of the Raman test, cycle test, rate characteristic test, and expansion coefficient test for the electrochemical device (lithium ion battery) are described to better explain the technical solution of the present invention.

[0070] 1. Test method 1.1 Raman Testing: A Raman spectrometer (Jobin Yvon LabRAM HR) was used, the wavelength of the light source was 532 nm, and the test range was 0 cm. -1 ~4000cm -1 The test was carried out on a negative electrode active material measuring 100 μm × 100 μm, and the result was 1350 cm -1 and 1580 cm -1 The peak intensity around the peak was recorded. 100 values ​​were taken for each group, and the average value of the ratio of the characteristic peak values ​​of the D peak and the G peak, i.e., I D / I G The value was calculated.

[0071] 1.2 Rate characteristic test: The lithium-ion batteries formed in the following examples and comparative examples were placed in an incubator at 45°C ± 2°C for 2 hours, charged to 4.45 V at a constant current of 0.5 C, charged to 0.025 C at a constant voltage of 4.45 V, left for 5 minutes, and then discharged to 3.0 V at a constant current of 0.2 C. This was the initial capacity, and the discharge capacity of the first cycle of the lithium-ion battery was recorded. The battery was then charged to 4.45 V at a constant current of 0.5 C and discharged to 3.0 V at a constant current of 2 C, and the discharge capacity was recorded. The gram capacity of the negative electrode active material was calculated from the initial capacity, and the ratio of the 2 C discharge capacity to the initial capacity was calculated as the initial efficiency of the negative electrode active material.

[0072] 1.3 Cycle characteristic test: The lithium-ion batteries prepared in the following examples and comparative examples were placed in a thermostatic chamber at 25°C ± 2°C for 2 hours, charged to 4.45V at a constant current of 0.5C, charged to 0.025C at a constant voltage of 4.45V, left for 5 minutes, and then discharged to 3.0V at a constant current of 0.3C. This constitutes one charge-discharge cycle, and the discharge capacity of the first cycle of the lithium-ion battery was recorded. The charge-discharge cycle was then repeated according to the above method, and the ratio of the discharge capacity to the initial discharge capacity was recorded to obtain a capacity change curve.

[0073] Four lithium-ion batteries were taken from each group, and the average capacity retention rate of the lithium-ion batteries was calculated. The cycle capacity retention rate of a lithium-ion battery = discharge capacity (mAh) at the 400th cycle / discharge capacity (mAh) after the first cycle × 100%.

[0074] 1.4 Cyclic Thickness Swelling Test: The thickness of the lithium-ion battery was measured using a 600g flat plate thickness gauge (ELASTOCON, EV01).

[0075] The lithium-ion batteries formed in the following examples and comparative examples were placed in an incubator at 25°C ± 2°C for 2 hours, charged to 4.45V at a constant current of 0.7C, then charged to 0.05C at a constant voltage of 4.45V and left for 15 minutes. The thickness of the fully charged lithium-ion battery was recorded, and the battery was then discharged to 3.0V at a constant current of 0.5C. This constitutes one charge-discharge cycle, and the thickness of the lithium-ion battery after the first cycle was recorded. The charge-discharge cycle was then repeated 400 times according to the above method, and the thickness of the lithium-ion battery after 400 cycles was recorded.

[0076] Four lithium-ion batteries were taken from each group, and the average cycling thickness expansion rate of the lithium-ion batteries was calculated: cycling thickness expansion rate of lithium-ion batteries = (thickness of lithium-ion battery at the 400th cycle / thickness of lithium-ion battery at the first cycle - 1) x 100%.

[0077] 2. Manufacturing method 2.1 Cathode production The positive electrode active material, lithium cobalt oxide (LiCoO2), conductive carbon black (SuperP), and polyvinylidene fluoride (PVDF), were mixed in a mass ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solids content of 0.75. The slurry was then uniformly mixed. The positive electrode current collector, aluminum foil, was uniformly coated with the slurry and dried at 90°C. The cathode was then obtained after cold pressing, cutting, and slitting.

[0078] 2.2 Preparation of electrolyte In an environment with a water content of less than 150 ppm (dry argon atmosphere), a solution prepared by mixing the lithium salt LiPF6 with an organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): vinylene carbonate (VC) = 20:30:20:28:2, mass ratio) in a mass ratio of 8:92 was used as the electrolyte for the lithium-ion battery.

[0079] 2.3 Manufacture of the negative electrode Using copper foil as the negative electrode current collector, the negative electrode active material provided in the following examples or comparative examples was mixed with graphite in an equal mass ratio (1:1) to obtain a mixed powder with a designed mixed gram capacity of 850 mAh / g. The mixed powder, acetylene black, and polyacrylic acid (PAA) were thoroughly mixed in a deionized water solvent system in a weight ratio of 95:1.2:3.8 until homogeneous, forming a negative electrode active material slurry. One layer of the negative electrode active material slurry was then uniformly coated on the surface of the copper foil and dried at 90°C. After cold pressing, cutting, and slitting, the mixture was dried in a vacuum at 85°C for 4 hours to produce a negative electrode.

[0080] 2.4 Lithium-ion battery manufacturing A 15 μm-thick polyethylene film was used as the separator, and the positive electrode, separator, and negative electrode were stacked in this order so that the separator was interposed between the positive and negative electrodes to act as an insulator. The stacked electrode assembly was heated to 80°C to remove moisture, resulting in a dried electrode assembly. The dried electrode assembly was placed in a packaging, the prepared electrolyte was injected, sealed, and then subjected to processes such as formation, degassing, and side cutting to obtain a lithium-ion battery.

[0081] 2.5 Preparation of negative electrode active material Example 1 (1) Carbon nanotube raw material and ethanol were mixed to prepare an ethanol dispersion having a carbon nanotube concentration of 3.3 wt %.

[0082] (2) The precursor of the magnesium-doped carbon silicon oxygen material and the ethanol dispersion are uniformly mixed and stirred, and the precursor is dissolved in the magnesium-doped carbon silicon oxygen material according to the general formula: Mg 0.14 SiC 0.25 O 0.77The magnesium raw material (magnesium powder), carbon raw material (acetylene gas), and silicon / oxygen raw material were mixed in a stoichiometric ratio of 2:1:10 by weight. The mixture of the magnesium-doped carbon / silicon / oxygen material precursor and ethanol dispersion was evaporated to dryness, and the dry powder was collected.

[0083] (3) The collected dried powder was subjected to high-temperature treatment under argon atmosphere to obtain magnesium-doped carbon silicon oxygen material, where the high-temperature treatment temperature was about 600°C and the time was 3 h.

[0084] Examples 2 and 3 In step (1), the manufacturing method is almost the same as that in Example 1 except that the carbon nanotube concentration in the ethanol dispersion is different, and for specific details, see the table of examples below.

[0085] Examples 4 to 7 In step (3), the manufacturing method is almost the same as that in Example 1 except that the temperature of the high-temperature treatment is different, and for specific details, see the table of examples below.

[0086] Examples 8 and 9 In step (3), the manufacturing method is almost the same as that in Example 3 except for the time of the high-temperature treatment, and for specific details, see the table of examples below.

[0087] Comparative Example 1 The precursor of the magnesium-doped carbon silicon oxygen material was treated at high temperature under an argon atmosphere to obtain the magnesium-doped carbon silicon oxygen material. The precursor has the general formula of the magnesium-doped carbon silicon oxygen material: Mg 0.14 SiC 0.18 O 0.8 The magnesium raw material (magnesium powder), carbon raw material (acetylene gas), and silicon-oxygen raw material were mixed in a stoichiometric ratio of 2:1:10 by weight, and the high-temperature treatment was carried out at a temperature of approximately 600°C for 3 hours.

[0088] 3. Comparison results 3.1 Comparison of negative electrode active material compositions The lithium ion batteries of Examples 1 to 9 and Comparative Example 1 are distinguished from each other by the composition of the negative electrode active material (after the carbon nanotube coating layer is disposed) and its precursor (without the carbon nanotube coating layer disposed) used therein. The composition of the negative electrode active material precursor and the results of component tests and Raman tests on the magnesium-doped carbon silicon oxygen material are shown in Table 1 below.

[0089] [Table 1]

[0090] N / A indicates that no corresponding value is available.

[0091] As can be seen from Table 1, the present invention can effectively form a carbon nanotube coating layer on the surface of the crystalline oxide of the negative electrode active material particles through a manufacturing process using an ethanol dispersion. As a result, the manufactured negative electrode active material powder has a higher carbon content than the negative electrode active material before manufacturing. As can be seen from Examples 1 to 3, the thickness of the carbon nanotube coating layer can be controlled by adjusting the carbon nanotube concentration in the ethanol dispersion. Furthermore, as can be seen from the results of Raman analysis, the thickness of the carbon nanotube coating layer affects the stability and conductivity of its carbon structure.

[0092] As can be seen from Examples 1 and 4 to 9, the coating structure of the carbon nanotube coating layer can be affected by the temperature and time of the high-temperature treatment. As can be seen from the results of the Raman test, as the temperature of the high-temperature treatment decreases, the degree of carbonization of the carbon nanotube coating layer decreases, and the degree of disorder and defects in the carbon structure of the carbon nanotube coating layer increase. As the temperature of the high-temperature treatment increases, the degree of carbonization of the carbon nanotube coating layer increases, and the degree of disorder and defects in the carbon structure of the carbon nanotube coating layer decrease.

[0093] 3.2 Comparison of electrochemical device performance The results of the rate test, cycle characteristic test, and cycle thickness expansion rate test for the lithium ion batteries of Examples 1 to 9 and Comparative Example 1 are shown in Table 2 below.

[0094] [Table 2]

[0095] Referring to Table 2, the magnesium-doped carbide silicon oxygen material according to the present invention has excellent initial coulombic efficiency and cycle characteristics. By further doping the magnesium-doped silicon oxide with carbon, the present invention can improve the cycle effect of the negative electrode active material, reduce its cycle thickness expansion rate after a high number of cycles, and extend its cycle life. Further comparing the present invention with Comparative Example 1, FIG. 4 compares the cycle capacity curve 201 of Example 1 of the present invention with the cycle capacity curve 202 of the electrochemical device of Comparative Example 1. As shown in FIG. 4, Example 1 of the present invention includes a magnesium-doped carbide silicon oxygen material with a carbon nanotube coating layer. The specific carbon nanotube coating layer improves the cycle capacity retention rate of the negative electrode active material and significantly reduces its cycle thickness expansion rate, thereby enabling the electrochemical device to have excellent initial coulombic efficiency and cycle characteristics.

[0096] As can be seen from Examples 1 to 3, when the carbon nanotube coating layer is too thin, the coating layer is not dense enough to effectively form a continuous and uniform conductive network, resulting in a decrease in the cycle retention rate of the material.When the carbon nanotube coating layer is too thick, the accumulation of by-products increases, and the consumption of electrolyte and active lithium increases, resulting in a decrease in the cycle retention rate of the material and a decrease in the initial conductive efficiency of the material.

[0097] As can be seen from Examples 4 to 9, when the calcination temperature is decreased, the carbonization degree of the magnesium-doped silicon-carbon-oxygen material decreases, which increases the defects in the coating layer and leads to the formation of I D / I GAs the calcination temperature increases, the carbonization degree of the magnesium-doped silicon-carbon oxide material increases, which reduces the defects in the coating layer and decreases the I D / I G The value of SiO2 decreases, improving the electron conduction performance of the conductive network. However, as the temperature increases, the silicate phase in the carbon-doped silicon material increases, reducing the initial efficiency. Furthermore, the increase in the silicate phase deteriorates the structural stability of the material, resulting in a decrease in cycle retention.

[0098] Throughout the specification, references to "in some embodiments," "some embodiments," "one embodiment," "another embodiment," "an example," "particular example," or "some examples" mean that at least one embodiment or example of the invention includes a particular feature, structure, material, or characteristic described in that embodiment or example. Thus, references to, for example, "in some embodiments," "in an embodiment," "in another embodiment," "in one example," "in a particular example," or "an example" in various places in the specification are not necessarily all referring to the same embodiment or example throughout the specification. Furthermore, particular features, structures, materials, or characteristics described herein may be incorporated in any suitable manner into one or more embodiments or examples.

[0099] Although exemplary embodiments have been shown and described, those skilled in the art should not construe the above-described embodiments as limitations on the present application, and may change, substitute, or modify the embodiments without departing from the spirit, principle, and scope of the present application.

Claims

1. a negative electrode including a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a magnesium-doped silicon carbide oxygen material; a carbon nanotube coating layer is provided on a surface of the crystalline oxide of the magnesium-doped carbon silicon oxygen material; The magnesium-doped carbon silicon oxygen material has an ID / IG value in a Raman spectrum of 0.023 to 0.

32.

2. 2. The electrochemical device of claim 1, wherein the crystalline oxide of the magnesium-doped carbon silicon oxygen material has a general formula of MgSiCO, where x, y, and z satisfy the following conditions: 0<x<0.3, 0.4<y<1.0, and 0.1<z<0.

2.

3. 2. The electrochemical device of claim 1, wherein the magnesium-doped carbon silicon oxygen material has a molar silicon content of 40% to 70%, a molar carbon content of 3.5% to 24%, and a molar magnesium content of 7.0% to 7.5%.

4. 2. The electrochemical device of claim 1, wherein the magnesium-doped carbon silicon oxygen material has a molar ratio of magnesium to silicon of 0.1 to 0.2 and a molar ratio of magnesium to carbon of 0.2 to 10.

0.

5. 4. The electrochemical device of claim 1, wherein the ratio of the ID / IG value in the Raman spectrum of the magnesium-doped carbon silicon oxygen material to the molar carbon content is between 0.095 and 6.

78.

6. The carbon nanotube coating layer is (1) The thickness of the carbon nanotube coating layer is 0.5 nm to 5.0 μm; (2) The electrochemical device of claim 1, wherein the carbon nanotube coating layer contains carbon nanotube clusters, the carbon nanotube clusters extend from the surface of the carbon nanotube coating layer, and the length of the carbon nanotube clusters is 0.1 μm to 1.0 μm.

7. The magnesium-doped carbon silicon oxygen material comprises: (1) the particle size Dv50 of the magnesium-doped carbon silicon oxygen material is 2.5 μm to 10.0 μm; (2) the particle size distribution of the magnesium-doped carbon silicon oxygen material satisfies 0.3≦Dn10 / Dv50≦0.6; (3) The magnesium-doped carbon silicon oxygen material has a specific surface area of ​​1 m2 / g to 50 m2 / g. The electrochemical device according to claim 1 , wherein at least one of the following is satisfied:

8. the negative electrode active material layer further contains a binder, the binder comprises a synthetic rubber, the binder comprises one or more selected from the group consisting of polyacrylic acid ester, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium hydroxymethylcellulose, and potassium hydroxymethylcellulose; 2. The electrochemical device according to claim 1, wherein the weight percentage of the binder is 2% to 6% with respect to the total weight of the negative electrode active material layer.

9. the electrolyte of the electrochemical device comprises an organic solvent and a lithium salt; the organic solvent comprises one or more selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, vinylene carbonate, propyl propionate, and ethyl propionate; 2. The electrochemical device of claim 1, wherein the lithium salt comprises one or more selected from the group consisting of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium difluorophosphate (LiPOF), lithium bis(trifluoromethanesulfonyl)imide (LiN(CFSO)), lithium bis(fluorosulfonyl)imide (Li(N(SOF)), lithium bis(oxalato)borate (LiB(CO)), and lithium difluoro(oxalato)borate (LiBF(CO)).

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