WO2023137708A1 - 电化学装置 - Google Patents

电化学装置 Download PDF

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WO2023137708A1
WO2023137708A1 PCT/CN2022/073239 CN2022073239W WO2023137708A1 WO 2023137708 A1 WO2023137708 A1 WO 2023137708A1 CN 2022073239 W CN2022073239 W CN 2022073239W WO 2023137708 A1 WO2023137708 A1 WO 2023137708A1
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magnesium
negative electrode
lithium
electrochemical device
carbon
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French (fr)
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李鑫
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to JP2024523468A priority Critical patent/JP7762801B2/ja
Priority to PCT/CN2022/073239 priority patent/WO2023137708A1/zh
Priority to CN202280007611.1A priority patent/CN116941060A/zh
Publication of WO2023137708A1 publication Critical patent/WO2023137708A1/zh
Priority to US18/622,217 priority patent/US20240266518A1/en
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    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of energy storage, in particular to a negative electrode active material and an electrochemical device containing it, especially a lithium ion battery.
  • electrochemical devices such as lithium-ion batteries
  • electrochemical devices such as lithium-ion batteries
  • one of the main research directions in the field of electrochemical energy storage is to study and improve electrode materials in electrochemical devices.
  • the embodiments of the present application solve at least one problem existing in the related field to at least some extent by providing a negative electrode active material with a substrate-free adhesive film and an electrochemical device comprising the same.
  • some embodiments of the present application provide a negative electrode active material, the negative electrode active material includes a magnesium-doped carbon silicon oxide material, wherein the magnesium doped carbon silicon oxygen material further includes a carbon nanotube coating layer by coating the particles of the magnesium doped carbon silicon oxygen material with carbon nanotubes, and the carbon nanotube coating layer is disposed on the particle surface of the crystal oxide of the magnesium doped carbon silicon oxygen material.
  • the negative electrode active material of the present application adopts magnesium-doped carbon silicon oxygen material, doping magnesium can optimize the first coulombic efficiency of carbon silicon oxygen material, improve the rate performance of carbon silicon oxygen material, and form a network conductive structure by setting a carbon nanotube coating layer on the particle surface of the crystal oxide of magnesium doped carbon silicon oxygen material, which can improve the conductivity of the negative electrode active material.
  • some embodiments of the present application provide an electrochemical device, which includes a negative electrode, wherein 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, wherein the magnesium doped carbon silicon oxygen material includes a carbon nanotube coating layer, and the carbon nanotube coating layer is disposed on the surface of the crystal oxide of the magnesium doped carbon silicon oxygen material.
  • the electrochemical device of the present application can improve the first Coulombic efficiency of the electrochemical device and optimize the structural stability of the electrochemical device during the cycle by using the magnesium-doped carbon silicon oxide material with a carbon nanotube coating layer, thereby improving the cycle retention rate and cycle performance of the electrochemical device.
  • the general formula of the crystalline oxide of Mg-doped carbon silicon oxide material is Mg z SiC x O y , wherein 0 ⁇ x ⁇ 0.3, 0.4 ⁇ y ⁇ 1.0, and 0.1 ⁇ z ⁇ 0.2.
  • the molar content of silicon is 40% to 70%
  • the molar content of carbon is 3.5% to 24%
  • the molar content of magnesium is 7.0% to 7.5%.
  • the molar ratio of magnesium to silicon in the magnesium-doped carbon silicon oxygen material is 0.1 to 0.2, and the molar ratio of magnesium to carbon is 0.2 to 10.0.
  • the I D / IG value in the Raman spectrum of the magnesium-doped carbon silicon oxide material is 0.023 to 0.32.
  • the ratio of the ID / IG value to the carbon molar content in the Raman spectrum of the magnesium-doped carbon silicon oxide material is 0.095 to 6.78.
  • the carbon nanotube coating layer has a thickness of 0.5 nm to 5.0 ⁇ m.
  • the carbon nanotube coating layer includes carbon nanotube clusters, wherein 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 ⁇ m to 1.0 ⁇ m.
  • the negative electrode active material layer further includes a binder, wherein the binder includes synthetic rubber including one or more of polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium hydroxymethylcellulose, and potassium hydroxymethylcellulose.
  • the binder includes synthetic rubber including one or more of polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium hydroxymethylcellulose, and potassium hydroxymethylcellulose.
  • the mass of the binder is 2% to 6%.
  • the electrolyte solution of the electrochemical device includes an organic solvent and a lithium salt
  • the organic solvent includes one or more of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, vinylene carbonate, propyl propionate, and ethyl propionate
  • the lithium salt includes lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 f 2 ), lithium bistrifluoromethanesulfonylimide (LiN(CF 3 SO 2 ) 2 ), lithium bis(fluorosulfonyl)imide (Li(N(SO 2 F) 2 )), lithium bisoxalate borate (LiB(C 2 o 4 ) 2 ) and lithium difluor
  • FIG. 1 is a schematic diagram of a particle structure of an anode active material according to some embodiments of the present application.
  • FIG. 2 is an XRD diffraction pattern of the magnesium-doped carbon silicon oxide material according to Example 1 of the present application.
  • FIG. 3 is a 5,000-fold microscopic image of the negative electrode active material according to Example 1 of the present application under a scanning electron microscope.
  • FIG. 4 is a graph of the cycle capacity of the electrochemical devices of Example 1 and Comparative Example 1 of the present application.
  • the terms “approximately,” “substantially,” “substantially,” and “about” are used to describe and account for minor variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurred exactly as well as instances in which the event or circumstance occurred with close approximation.
  • the term when used in conjunction with a numerical value, can refer to a range of variation of less than or equal to ⁇ 10% of the stated value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • two numerical values are considered to be “substantially" the same if the difference between the two numerical values is less than or equal to ⁇ 10% of the mean of the values (e.g., less than or equal to ⁇ 5% or less, less than or equal to ⁇ 4%, or less than or equal to ⁇ 3%, or less than or equal to ⁇ 2%, or less than or equal to 1%, or less than or equal to ⁇ 0.5%, or less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%).
  • a list of items linked by the terms “at least one of”, “at least one of”, “one or more of”, “one or more of” or other similar terms may mean any combination of the listed items.
  • the phrase “one or more of A and B” means A only; only B; or A and B.
  • the phrase “one or more of A, B, and C” means only A; or only B; only C; 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 contain a single element or multiple elements.
  • Item B may contain a single element or multiple elements.
  • Item C may contain a single element or multiple elements.
  • Severe expansion of the negative electrode will cause deformation or even separation of the interface between the negative electrode and the separator, resulting in a decrease in the cycle performance of the lithium-ion battery.
  • due to the unstable lithium ion path in the process of lithium intercalation of silicon-based materials it is easy to cause uneven deposition of lithium metal, or even dead lithium, which makes the first Coulombic efficiency of electrochemical devices using silicon-based negative electrode active materials poor, and the first charge-discharge Coulombic efficiency can directly reflect the electrochemical performance of the electrochemical device.
  • Chinese patent CN108767241A discloses a negative electrode material that uses magnesium-doped silicon oxide formed by doping magnesium in a silicon-oxygen material to improve the rate performance and first Coulombic efficiency of lithium-ion batteries.
  • magnesium-doped silicon oxide as the negative electrode active material still cannot effectively form uniform lithium metal deposition, resulting in low cycle efficiency and low service life of magnesium-doped silicon oxide.
  • some embodiments of the present application provide a negative electrode active material
  • the negative electrode active material includes a composite material formed by carbon-doping and magnesium-doping silicon oxide through a high-temperature preparation process, that is, a magnesium-doped carbon silicon oxide material, wherein the surface of the magnesium-doped carbon silicon oxide material crystalline oxide 101 further includes a carbon nanotube coating layer 102, and the carbon nanotube coating layer 102 is provided on the magnesium-doped carbon silicon oxygen material crystal oxide 101 through a carbon nanotube coating process on the particle surface.
  • magnesium-silicon oxides can be formed to improve the first Coulombic efficiency of electrochemical devices.
  • carbon-containing magnesium-silicon oxides can be further formed in composite magnesium-doped carbon-silicon-oxygen materials.
  • Carbon-containing magnesium-silicon oxides have a lower volume expansion rate and better cycle structure stability in the lithium-deintercalation process.
  • Magnesium-doped carbon-silicon-oxygen materials can effectively form uniform lithium metal deposition in the cycle process, so as to improve the cycle performance of electrochemical devices and extend their service life.
  • the present application can further improve the conductivity of the negative electrode active material by coating the particle surface of the magnesium-doped carbon silicon oxide material with carbon nanotubes.
  • the magnesium-doped carbon-silicon-oxygen material is a composite material comprising crystalline oxide composed of magnesium, carbon, silicon and oxygen and carbon nanotubes coated on its surface.
  • the crystalline oxide of magnesium doped carbon silicon oxygen material can be represented by the general formula Mg z SiC x O y .
  • 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.
  • the various components and crystal structure composition of magnesium-doped carbon-silicon-oxygen materials have a certain influence on the cycle performance, gram capacity and structural stability in electrochemical devices.
  • the molar content of silicon element Si in the magnesium-doped carbon silicon oxygen material is 40% to 70%. If the content of silicon element is too low, the gram capacity of the negative electrode active material will decrease, and if it is too high, the volume expansion rate of the negative electrode active material will increase.
  • the molar content of Si in the magnesium-doped carbon-silicon-oxygen material is 60%.
  • the magnesium element Mg molar content in the magnesium-doped carbon silicon oxygen material is 7.00% to 7.5%, and the content range of the magnesium element can effectively form carbon-containing magnesium silicon oxide, and avoid magnesium element and oxygen to form highly active magnesium oxide or magnesium metal, so as to improve the first coulombic efficiency of the magnesium-doped carbon silicon oxygen material as the negative electrode active material, and reduce the safety risk of the magnesium-doped carbon silicon oxygen material in the electrochemical cycle reaction.
  • the molar content of carbon element C in the magnesium-doped carbon silicon oxygen material is 3.5% to 24%, wherein the source of carbon element in the magnesium doped carbon silicon oxygen material includes carbon doped in crystalline oxide and carbon nanotubes covering the crystalline oxide. If the doping amount of carbon element is too low, the structural stability of the negative electrode active material will decrease and the volume expansion rate will increase. If it is too high, the gram capacity of the negative electrode active material will decrease. 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 oxide material is about 6%.
  • the content of each element component in the magnesium-doped carbon-silicon-oxygen material of the present application can be detected by any suitable detection method in the art, without being limited thereto.
  • the magnesium content and silicon content of the magnesium-doped carbon silicon oxygen material can be determined by X-ray diffraction analysis.
  • the carbon content of the magnesium-doped carbon-silicon-oxygen material can be measured by the following carbon content test (please provide the standard number if available): the sample is heated and burned in a high-frequency furnace under oxygen-enriched conditions to oxidize carbon and sulfur into carbon dioxide and sulfur dioxide respectively.
  • the signal is sampled by the computer, and converted into a value proportional to the concentration of carbon dioxide and sulfur dioxide after linear correction, and then the value of the entire analysis process is accumulated. After the analysis is completed, the accumulated value is divided by the weight value in the computer, multiplied by the correction coefficient, and the percentage content of carbon and sulfur in the sample can be obtained by deducting the blank. Sample testing was performed using a high-frequency infrared carbon-sulfur analyzer (Shanghai Dekai HCS-140).
  • FIG. 2 is an XRD diffraction pattern of the magnesium-doped carbon silicon oxide material according to Example 1 of the present application. As shown in FIG. 2 , in one embodiment, the magnesium-doped carbon silicon oxide material is analyzed by X-ray diffraction. In the XRD diffraction pattern, the magnesium-doped carbon silicon oxygen material contains one or more characteristic peaks of Si, SiO 2 , MgSiO 3 , and Mg 2 SiO 4 .
  • the molar ratio of magnesium to silicon in the magnesium-doped carbon silicon oxygen material is 0.1 to 0.2, and the molar ratio of magnesium to carbon is 0.2 to 10.0, so as to optimize the cycle performance and the first coulombic efficiency of the magnesium doped carbon silicon oxygen material in an electrochemical device.
  • the magnesium doped carbon silicon oxygen material has a magnesium to silicon molar ratio of about 0.12.
  • FIG. 3 is a 5,000-magnification microscopic image of the magnesium-doped carbon silicon oxide material according to Example 1 of the present application under a scanning electron microscope.
  • the carbon nanotube coating layer arranged on the particle surface of the crystalline oxide of the magnesium-doped carbon-silicon-oxygen material can form a network conductive structure to further improve the distribution of lithium metal deposition during the cycle, and optimize the volume expansion distribution of the magnesium-doped carbon-silicon-oxygen material, so that the negative electrode active material has excellent structural stability during the cycle.
  • the thickness of the carbon nanotube coating layer can affect the conductivity and energy density of the magnesium-doped carbon silicon oxide material in the electrochemical device. If the thickness of the carbon nanotube coating layer is too thick, the gram capacity of the magnesium-doped carbon silicon oxygen material will be reduced. If the thickness of the carbon nanotube coating layer is too low, the electrical conductivity will be reduced, 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 approximately: 0.5nm, 1.0nm, 5nm, 10nm, 50nm, 100nm, 250nm, 500nm, 1.0 ⁇ m, 5.0 ⁇ m or a numerical range formed by any two of the above values. In some embodiments, the carbon nanotube coating layer has a thickness of 0.5 nm to 5.0 ⁇ m. In some embodiments, the carbon nanotube coating layer has a thickness of 2.0 nm to 150 nm.
  • the carbon nanotube coating includes carbon nanotube clusters, and the carbon nanotube clusters can extend outward from the particle surface of the magnesium-doped carbon silicon oxide material and contact the carbon nanotube coating layer on the surface of other particles to further form an effective conductive network to optimize the conductivity of the magnesium doped carbon silicon oxygen material.
  • the carbon nanotube clusters have an extension length of 0.1 ⁇ m to 1.0 ⁇ m. In some embodiments, the carbon nanotube clusters have an extended length of about 0.5 ⁇ m.
  • the thickness of the carbon nanotube coating layer and the extension length of the carbon nanotube clusters can be detected by any suitable detection method in the art, without being limited thereto.
  • the thickness of the carbon nanotube coating and the extension length of the carbon nanotube clusters are characterized by scanning electron microscopy (SEM) or transmission electron microscopy (TEM).
  • scanning electron microscopy characterizations were recorded by a Philips XL-30 field emission scanning electron microscope with detection at 10 kV and 10 mA.
  • the particle size (Dv50) of the magnesium-doped carbon silicon oxygen material particles is 2.5 ⁇ m to 10.0 ⁇ m. In some embodiments, the particle size (Dv50) of the magnesium-doped carbon silicon oxide material particles is 2.7 ⁇ m to 5.3 ⁇ m, so as to optimize the coating distribution of the magnesium doped carbon silicon oxygen material in the negative electrode active material layer. In some embodiments, the particle size distribution of the magnesium-doped carbon-silicon-oxygen material particles satisfies the following conditions:
  • the term "particle size”, when not specifically referred to, includes the characterizing particle characteristics of the sample obtained by the particle size test, for example, Dn10 or Dv50, wherein Dn10 indicates the particle size of the material in the particle size-based particle distribution, starting from the small particle size, reaching 10% of the cumulative number of particles;
  • the particle size test method is to use a Mastersizer 2000 laser particle size distribution tester to analyze the particle size of the sample: the sample is dispersed in 100mL of dispersant (deionized water), so that the shading reaches 8-12%. The sample was then sonicated for 5 minutes at an ultrasonic intensity of 40KHz and 180w. After ultrasonic treatment, the sample will be analyzed by laser particle size distribution to obtain particle size distribution data.
  • the magnesium-doped carbon-silicon-oxygen material particles have a specific surface area of 1 m 2 /g to 50 m 2 /g. In some embodiments, the specific surface area of the magnesium-doped carbon silicon oxide material particle is 5 m 2 /g to 20 m 2 /g, so as to maintain the reaction rate of the magnesium doped carbon silicon oxygen material and the electrolyte.
  • the coating degree and structural stability of the carbon nanotube coating layer in the magnesium-doped carbon silicon oxygen material can be characterized by Raman spectroscopy detection, wherein the D peaks and G peaks around 1350 cm -1 and 1580 cm -1 in the Raman spectrum are characteristic peaks of the Raman spectrum of carbon atom crystals.
  • the ratio of characteristic peaks of the D peak and G peak in the Raman spectrum of the magnesium-doped carbon silicon oxygen material: ID / I G value can characterize the network conductive structure of the carbon nanotube coating layer to the magnesium doped carbon silicon oxygen material particles.
  • the ID / IG value of the magnesium doped carbon silicon oxygen material in the Raman spectrum is low, it means that the network conductive structure of the carbon nanotube coating layer is relatively complete.
  • the I D / IG value of the magnesium-doped carbon silicon oxide material in the Raman spectrum is less than or equal to 0.32.
  • the I D / IG value of the magnesium-doped carbon silicon oxide material in the Raman spectrum is 0.023 to 0.32, so as to optimize the network conductive structure of the carbon nanotube coating layer.
  • the ratio of the ID / IG value of the magnesium-doped carbon silicon oxygen material in the Raman spectrum to the carbon molar content can further characterize the coating degree of the carbon nanotube coating layer on the magnesium-doped carbon silicon oxygen material. When it is high , it will make the coating of the carbon nanotube coating layer on the magnesium-doped carbon silicon oxygen material poor. In some embodiments, the ratio of the ID / IG value to the carbon molar content in the Raman spectrum of the magnesium-doped carbon silicon oxide material is 0.095 to 6.78.
  • some embodiments of the present application provide a method for preparing the above magnesium-doped carbon silicon oxide material, and the specific process is as follows:
  • the weight concentration of carbon nanotubes in the ethanol dispersion is 1.5% to 10.0%. In some embodiments, the weight concentration of carbon nanotubes in the ethanol dispersion is 1.6% to 6.6%. .
  • the collected dry powder is subjected to high-temperature treatment under an argon atmosphere to obtain a magnesium-doped carbon silicon oxide material.
  • the temperature of the high temperature treatment is 400°C to 800°C. In some embodiments, the temperature of the high temperature treatment is about 600°C. In some embodiments, the time for the high temperature treatment is 1 h to 5 h. In some embodiments, the time of high temperature treatment is about 3 hours.
  • the precursor of the magnesium-doped carbon silicon oxide material can be coated with carbon nanotubes by using the ethanol dispersion liquid to form the magnesium doped carbon silicon oxide material with a carbon nanotube coating layer.
  • the magnesium-doped carbon-silicon-oxygen material with a carbon nanotube coating in the present application can not only improve the electrical conductivity, but also reduce the influence of carbon materials on the electrical performance and gram capacity of the magnesium-doped carbon-silicon-oxygen material, optimize the lithium precipitation and deintercalation mechanism of the magnesium-doped carbon-silicon-oxygen material, and further optimize the electrical performance and cycle performance of the magnesium-doped carbon-silicon-oxygen material in electrochemical devices.
  • the conductivity and coating structure of the carbon nanotube coating layer in the magnesium-doped carbon silicon oxide material can be further optimized, so that it can have excellent cycle performance and the first Coulomb effect as an anode active material.
  • some embodiments of the present application provide an electrochemical device, the electrochemical device includes a negative electrode, wherein 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 the magnesium-doped carbon silicon oxide material in the above embodiment.
  • the electrochemical device can improve the first Coulombic efficiency of the electrochemical device and optimize the structural stability of the electrochemical device during the cycle by using the magnesium-doped carbon silicon oxide material with a carbon nanotube coating layer, thereby improving the cycle retention rate and cycle performance of the electrochemical device.
  • the weight ratio of the magnesium-doped carbon silicon oxide material is greater than or equal to 20%.
  • the weight ratio of magnesium-doped carbon silicon oxide material is greater than or equal to 60%.
  • the negative electrode active material is composed of the magnesium-doped carbon silicon oxide material in the above embodiments.
  • the negative electrode active material further includes graphite, wherein the graphite includes one or more of natural graphite, artificial graphite, and mesocarbon microspheres, so as to improve the conductivity and cycle performance of the negative electrode active material.
  • the negative electrode active material can also include other common negative electrode active materials capable of absorbing and releasing lithium (Li) in the art, such as, but not limited to, one or more of carbon materials, metal compounds, oxides, sulfides, lithium nitrides such as LiN 3 , lithium metal, metal elements and semimetal elements that form alloys with lithium, polymer materials, and combinations thereof.
  • the negative electrode active material can control the powder conductivity of the negative electrode active material by adjusting the content of the magnesium-doped carbon silicon oxide material, so as to optimize the cycle performance of the negative electrode active material layer.
  • the powder conductivity of the negative active material is 2.0 S/cm to 30 S/cm.
  • the powder conductivity of the negative active material is 5.0 S/cm to 10 S/cm.
  • the powder conductivity of the negative electrode active material can be detected by any suitable detection method in the art, without being limited thereto.
  • the resistance of the negative electrode active material layer ranges from 0.2 ⁇ to 1 ⁇ .
  • the negative active material layer further includes a binder to improve the structural stability of the negative active material layer.
  • the binder comprises synthetic rubber comprising one or more of polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sodium hydroxymethyl cellulose, and potassium hydroxymethyl cellulose.
  • the mass of the binder is 2% to 6%.
  • the weight ratio of the binder is approximately, for example, about 2%, about 3%, about 4%, about 5%, about 6%, or a range consisting of any two of these values.
  • the negative active material layer further includes a conductive agent to improve the conductivity of the negative active material layer.
  • the conductive agent includes one or more of carbon nanotubes, conductive carbon black, acetylene black, graphene, and Ketjen black. It should be understood that those skilled in the art can select conventional conductive agents in the field according to actual needs, without being limited thereto. In some embodiments, based on the total weight of the negative electrode active material layer, the mass of the conductive agent is 1% to 10%.
  • the weight ratio of the conductive agent is approximately, for example, about 1%, about 2%, about 3%, about 5%, about 10%, or a range consisting of any two of these values.
  • the negative electrode further includes a negative electrode current collector.
  • the negative electrode current collector may be copper foil or nickel foil, however, other negative electrode current collectors commonly used in the art may be used without limitation.
  • 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 laminated to form an electrode assembly.
  • the electrode assembly in the present application may be any suitable electrode assembly in the art, without being limited thereto.
  • the electrode assembly is a wound structure.
  • the electrode assembly can be a lamination structure or a multi-tab structure.
  • the electrochemical device is a lithium ion battery.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material layer.
  • the positive current collector may be aluminum foil or nickel foil, however, other positive current collectors commonly used in the art may be used without limitation.
  • the cathode active material layer includes a cathode active material capable of absorbing and releasing lithium (Li) (hereinafter, sometimes referred to as “a cathode active material capable of absorbing/releasing lithium Li”).
  • Examples of the positive electrode active material capable of absorbing/releasing lithium (Li) may include one or more of lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium iron phosphate, lithium titanate, and lithium-rich manganese-based materials.
  • the positive electrode active material layer can further include at least one of a binder and a conductive agent.
  • the binder includes one or more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the conductive agent includes one or more of carbon nanotubes, conductive carbon black, acetylene black, graphene, and Ketjen black. It should be understood that those skilled in the art may select conventional binders and conductive agents in the art according to actual needs, without being limited thereto.
  • the isolation film includes, but is not limited to, at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid.
  • polyethylene includes at least one component selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene.
  • polyethylene and polypropylene which have a good effect on preventing short circuits and can improve the stability of the battery through the shutdown effect. It should be understood that those skilled in the art may select conventional separators in the art according to actual needs, without being limited thereto.
  • the electrochemical device of the present application also includes an electrolyte, which includes a lithium salt and an organic solvent.
  • the lithium salt comprises lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ), lithium bistrifluoromethanesulfonyl imide (LiN(CF 3 SO 2 ) 2 ), lithium bis(fluorosulfonyl)imide (Li(N(SO 2 F) 2 )), lithium bisoxalate borate (LiB(C 2 O 4 ) 2 ) and one or more of lithium difluorooxalate borate (LiBF 2 (C 2 O 4 )).
  • lithium hexafluorophosphate (LiPF 6 ) is selected as the lithium salt because it can give high ion conductivity and improve cycle characteristics.
  • the organic solvent includes one or more of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, vinylene carbonate, propyl propionate, and ethyl propionate;
  • the lithium salt includes lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 f 2 ), lithium bistrifluoromethanesulfonimide (LiN(CF 3 SO 2 ) 2 ), lithium bis(fluorosulfonyl)imide (Li(N(SO 2 F) 2 )), lithium bisoxalate borate (LiB(C 2 o 4 ) 2 ) and lithium difluorooxalate borate (LiBF 2 (C 2 o 4 )) in one or more.
  • EC
  • the electrolyte solution further includes additives, and without departing from the spirit of the present application, the additives may be any suitable additives in the art without limitation.
  • the preparation method of the lithium-ion battery includes: winding, folding or stacking the negative electrode, the separator and the positive electrode in the examples in order to form an electrode assembly, and then putting the electrode assembly into a casing, such as an aluminum-plastic film, and injecting an electrolyte, and then the lithium-ion battery loaded into the electrode assembly is subjected to subsequent processes such as vacuum packaging, standing, forming, and shaping to obtain a lithium-ion battery.
  • the adhesive film of the negative electrode active material of the present application can be used in other suitable electrochemical devices after reading the application.
  • Such an electrochemical device includes any device in which an electrochemical reaction occurs, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • 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.
  • Some embodiments of the present application further provide an electronic device, which includes the electrochemical device in the embodiments of the present application.
  • the electronic device in the embodiment of the present application is not particularly limited, and it may be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen-based computers, mobile computers, electronic book players, cellular phones, portable fax machines, portable copiers, portable printers, headsets, video recorders, LCD televisions, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting appliances, toys, game consoles, watches, power tools, Flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • the wavelength of the light source is 532nm, and the test range is 0cm -1 to 4000cm -1 .
  • the negative electrode active material with a size of 100 ⁇ m ⁇ 100 ⁇ m is tested, and the peak intensity near 1350cm -1 and 1580cm -1 is recorded. Each set of values is taken 100 times and the average ratio of the characteristic peaks of D peak and G peak is calculated: ID / I G value.
  • the cycle capacity retention rate of the lithium-ion battery the discharge capacity (mAh) of the 400th cycle/the discharge capacity (mAh) after the first cycle ⁇ 100%.
  • a 600g flat plate thickness gauge (ELASTOCON, EV 01) was used to test the thickness of lithium-ion batteries.
  • the formed lithium-ion batteries of the following examples and comparative examples in a constant temperature box at 25°C ⁇ 2°C for 2 hours, charge them with a constant current of 0.7C to 4.45V, then charge them with a constant voltage of 4.45V to 0.05C and let them stand for 15 minutes to record the thickness of the lithium-ion batteries in the fully charged state; then discharge them at a constant current of 0.5C to 3.0V. Perform 400 charge-discharge cycles, and record the thickness of the lithium-ion battery after 400 cycles.
  • Cycle thickness expansion ratio of the lithium ion battery (thickness of the lithium ion battery at the 400th cycle/thickness of the lithium ion battery at the first cycle ⁇ 1) ⁇ 100%.
  • the positive electrode active material lithium cobalt oxide (LiCoO 2 ), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed according to a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.75, and stirred evenly.
  • NMP N-methylpyrrolidone
  • the slurry was evenly coated on the positive electrode current collector aluminum foil, and dried at 90°C. Afterwards, the positive electrode is obtained after cold pressing, cutting, and slitting procedures.
  • Copper foil is used as the negative electrode current collector, and the negative electrode active material provided in the following examples or comparative examples is mixed with graphite in an equal mass ratio (1:1) to obtain a mixed powder with a designed mixed gram capacity of 850mAh/g.
  • PAA polyacrylic acid
  • a polyethylene film is used as the separator, wherein the thickness of the polyethylene film is 15 ⁇ m, and the above-mentioned positive electrode, separator and negative electrode are stacked in sequence, so that the separator is in the middle of the positive electrode and the negative electrode to play the role of isolation.
  • the stacked electrode assembly is dehydrated at 80°C, the dry electrode assembly is obtained.
  • the dry electrode assembly is placed in the outer packaging, injected with the prepared electrolyte, and then packaged. After chemical formation, degassing, and edge trimming, the lithium-ion battery is obtained.
  • the precursor is formed by mixing the magnesium doped carbon silicon oxygen material with a stoichiometric ratio of the general formula: Mg 0.14 SiC 0.25 O 0.77 , wherein the weight ratio of magnesium raw material (magnesium powder), carbon raw material (acetylene gas), and silicon oxygen raw material is 2:1:10.
  • the mixture of the precursor of the carbon silicon oxygen material and the ethanol dispersion liquid is evaporated to dryness at high temperature, and the dry powder is collected.
  • the collected dry powder is subjected to high-temperature treatment in an argon atmosphere, wherein the temperature of the high-temperature treatment is about 600° C. for 3 hours, and then a magnesium-doped carbon silicon oxide material is obtained.
  • the preparation method is roughly the same as in Example 1, except that in step (1), the concentration of carbon nanotubes in the ethanol dispersion is different.
  • step (1) the concentration of carbon nanotubes in the ethanol dispersion is different.
  • the preparation method is substantially the same as in Example 1, except that in step (3), the temperature of the high-temperature treatment is different.
  • the temperature of the high-temperature treatment is different.
  • the preparation method is substantially the same as that of Example 3, except that in step (3), the time of high temperature treatment is different.
  • the time of high temperature treatment is different.
  • the precursor of the magnesium-doped carbon silicon oxygen material is subjected to high temperature treatment in an argon atmosphere.
  • the precursor is formed by mixing the magnesium doped carbon silicon oxygen material with a stoichiometric ratio of the general formula: Mg 0.14 SiC 0.18 O 0.8 , wherein the weight ratio of magnesium raw material (magnesium powder), carbon raw material (acetylene gas), and silicon oxygen raw material is 2:1:10.
  • Examples 1-9 and the lithium-ion battery of Comparative Example 1 lies in the composition of the negative electrode active material (after the carbon nanotube coating layer is provided) and its precursor (without the carbon nanotube coating layer) used in it.
  • N/A indicates no corresponding value.
  • the present application can effectively form a carbon nanotube coating on the surface of the crystal oxide of the negative electrode active material particles by adopting the preparation process of the ethanol dispersion, so that the prepared negative electrode active material powder has a carbon content higher than that of the negative electrode active material before preparation.
  • the thickness of the carbon nanotube coating can be controlled by adjusting the concentration of carbon nanotubes in the ethanol dispersion. At the same time, according to the results of the Lyman test, the thickness of the carbon nanotube coating will affect the stability and conductivity of its carbon structure.
  • the coating structure of the carbon tube coating can be affected by the temperature and time of high-temperature treatment. According to the results of the Lehman test, when the temperature of the high-temperature treatment is reduced, the degree of carbonization of the carbon tube coating will be reduced, increasing the degree of disorder of the carbon tube coating and the defects of the carbon structure.
  • the magnesium-doped carbon-silicon-oxygen material of the embodiment of the present application has excellent first-time coulombic efficiency and cycle performance.
  • the present application can improve the cycle effect of the negative electrode active material by further carbon doping the magnesium-doped silicon oxide, reduce the cycle thickness expansion rate of its high cycle number, and prolong its cycle life.
  • FIG. 4 is a comparison chart of the cycle capacity curve 201 of the embodiment 1 of the present application and the cycle capacity curve 202 of the electrochemical device of the comparative example 1.
  • Example 1 of the present application includes a magnesium-doped carbon silicon oxide material with a carbon nanotube coating layer. By setting a specific carbon nanotube coating layer, the cycle capacity retention rate of the negative electrode active material can be improved, and the cycle thickness expansion rate can be greatly reduced, so that the electrochemical device has excellent first-time Coulombic efficiency and cycle performance.
  • the coating layer when the thickness of the carbon nanotube coating layer is low, 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 thickness of the carbon nanotube coating layer is high, 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 at the same time reducing the initial conductivity of the material.

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Abstract

本申请涉及一种负极活性材料及包含其的电化学装置。本申请部分实施例提供一种电化学装置，该电化学装置包括负极，其中负极包含负极活性材料层，该负极活性材料层包含负极活性材料，且负极活性材料包含镁掺杂碳硅氧材料，其中镁掺杂碳硅氧材料的晶体氧化物的表面上设置有碳纳米管包覆层。本申请的电化学装置通过采用具备碳纳米管包覆层的镁掺杂碳硅氧材料，能够提高电化学装置的首次库仑效率并优化电化学装置在循环过程中的结构稳定性，进而提高电化学装置的循环保持率及循环性能。

Description

电化学装置 技术领域
本申请涉及储能领域，具体涉及一种负极活性材料及包含其的电化学装置，特别是锂离子电池。
背景技术
随着技术的发展和对移动装置的需求的增加，人们对电化学装置(例如，锂离子电池)的需求显著增加。为了提供高能量密度、高放电性能及高循环性能的电化学装置，电化学储能领域中主要的研究方向之一是对电化学装置中的电极材料进行研究及改进。
目前，商用电化学装置多半采用石墨作为电极的负极活性材料，然而石墨的克容量较低。相较于石墨，硅基材料作为负极活性材料具有更高的理论克容量，是未来高体积能量密度的电化学装置开发的主流负极活性材料。然而，在实际使用中，此类高能量密度的负极活性材料在脱嵌锂过程中存在巨大的体积变化效应，会导致电化学装置的循环性能降低，首次库仑效率表现不佳。而对于硅基材料的改进方案中，依然存在多种不同形式的缺陷。
有鉴于此，确有必要持续对负极材料负极活性材料进行研究与改进，以提升电化学装置的电池容量、循环性能及倍率性能。
发明内容
本申请实施例通过提供一种具有无基材胶膜的负极活性材料及包含其的电化学装置以在至少某种程度上解决至少一种存在于相关领域中的问题。
根据本申请的一方面，本申请部分实施例提供了一种负极活性材料，该负极活性材料包含镁掺杂碳硅氧材料，其中通过采用碳纳米管包覆镁掺杂碳硅氧材料的颗粒，使镁掺杂碳硅氧材料进一步包含碳纳米管包覆层，该碳纳米管包覆层设置在镁掺杂碳硅氧材料的晶体氧化物的颗粒表面上。本申请的负极活性材料通过采用镁掺杂碳硅氧材料，掺杂镁能够优化碳硅氧材料的首次库仑效率，提升碳硅氧材料的倍率性能，并且通过设置碳纳米管包覆层在镁 掺杂碳硅氧材料的晶体氧化物的颗粒表面以形成网状导电结构，其能够提升负极活性材料的电导率。
根据本申请的另一方面，本申请部分实施例提供一种电化学装置，该电化学装置包括负极，其中负极包含负极活性材料层，该负极活性材料层包含负极活性材料，且负极活性材料包含镁掺杂碳硅氧材料，其中镁掺杂碳硅氧材料包含碳纳米管包覆层，碳纳米管包覆层设置在所述镁掺杂碳硅氧材料的晶体氧化物的表面上。本申请的电化学装置通过采用具备碳纳米管包覆层的镁掺杂碳硅氧材料，能够提高电化学装置的首次库仑效率并优化电化学装置在循环过程中的结构稳定性，进而提高电化学装置的循环保持率及循环性能。
根据本申请的一些实施例，镁掺杂碳硅氧材料的晶体氧化物的通式为Mg zSiC xO y，其中0<x<0.3，0.4<y<1.0，且0.1<z<0.2。
根据本申请的一些实施例，镁掺杂碳硅氧材料中，硅的摩尔含量为40％至70％，碳的摩尔含量为3.5％至24％，且镁的摩尔含量为7.0％至7.5％。
根据本申请的一些实施例，镁掺杂碳硅氧材料的镁与硅的摩尔比为0.1至0.2，镁与碳的摩尔比为0.2至10.0。
根据本申请的一些实施例，镁掺杂碳硅氧材料的拉曼光谱中的I D/I G值为0.023至0.32。
根据本申请的一些实施例，镁掺杂碳硅氧材料的拉曼光谱中的I D/I G值与碳摩尔含量的比值为0.095至6.78。
根据本申请的一些实施例，碳纳米管包覆层的厚度为0.5nm至5.0μm,。
根据本申请的一些实施例，碳纳米管包覆层包含碳纳米管团簇，其中所述碳纳米管团簇自所述碳纳米管包覆层的表面延伸，所述碳纳米管团簇的长度为0.1μm至1.0μm。
根据本申请的一些实施例，负极活性材料层进一步包含粘结剂，其中所述粘结剂包含合成橡胶包含聚丙烯酸酯、聚酰亚胺、聚酰胺、聚酰胺酰亚胺、聚偏氟乙烯、丁苯橡胶、海藻酸钠、聚乙烯醇、聚四氟乙烯、聚丙烯腈、羧甲基纤维素钠、羧甲基纤维素钾、羟甲基纤维素钠及羟甲基纤维素钾中的一种或多种。
根据本申请的一些实施例，以负极活性材料层的总重计，粘结剂的质量为2％至6％。
根据本申请的一些实施例，电化学装置的电解液包含有机溶剂及锂盐，其中 有机溶剂包含碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、碳酸亚丙酯、碳酸亚乙烯酯、丙酸丙酯及丙酸乙酯中的一种或多种；锂盐包含六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、二氟磷酸锂(LiPO 2F 2)、双三氟甲烷磺酰亚胺锂(LiN(CF 3SO 2) 2)、双(氟磺酰)亚胺锂(Li(N(SO 2F) 2))、双草酸硼酸锂(LiB(C 2O 4) 2)及二氟草酸硼酸锂(LiBF 2(C 2O 4))中的一种或多种。
本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1为根据本申请一些实施例的负极活性材料的颗粒结构示意图。
图2为根据本申请实施例1的镁掺杂碳硅氧材料的XRD衍射图谱。
图3为根据本申请实施例1的负极活性材料于扫描式电子显微镜下的5千倍显微图像。
图4为本申请实施例1与对比例1的电化学装置的循环容量曲线图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。本申请的实施例不应该被解释为对本申请的限制。
除非另外明确指明，本文使用的下述术语具有下文指出的含义。
如本文中所使用，术语“大致”、“大体上”、“实质”及“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数值使用时，术语可指代小于或等于所述数值的±10％的变化范围， 例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％。举例来说，如果两个数值之间的差值小于或等于所述值的平均值的±10％(例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％)，那么可认为所述两个数值“大体上”相同。
在具体实施方式及权利要求书中，由术语“中的至少一者”、“中的至少一个”、“中的一种或多种”、“中的一者或多者”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的一者或多者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的一者或多者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
再者，为便于描述，“第一”、“第二”、“第三”等等可在本文中用于区分一个图或一系列图的不同组件。除非经特别指定或限定之外，“第一”、“第二”、“第三”等等不意欲描述对应组件。
在电化学储能领域中，为了追求最佳的能量密度，已尝试将传统负极活性材料中的石墨替换为具有高能量密度的负极活性材料，但是在应用此类高能量密度负极活性材料时，由于不同的材料特性还需要对其做进一步的工艺处理。举例来说，硅基材料由于理论克容量高达4200m Ah/g，是未来高体积能量密度的电化学装置(例如，锂离子电池)开发的主流负极活性材料。此类高能量密度的负极活性材料在脱嵌锂过程中存在巨大的体积变化效应(例如，大于约300％)，负极严重膨胀会造成负极与隔离膜的界面变形甚至分离，进而造成锂离子电池的循环性能降低。同时，由于硅基材料脱嵌锂过程中的锂离子路径不稳定，容易造成锂金属沉积不均匀，甚至死锂的现象，这使得采用硅基材料的负极活性材料的电化学装置的首次库仑效率不佳，而首次充放电库仑效率可以直接反映该电化学装置的电化学性能。
中国专利CN108767241A公开了一种负极材料，该负极材料采用了对硅氧材料中掺杂镁所形成的镁掺杂硅氧化物，以提升锂离子电池的倍率性能以及首次库 仑效率。然而，在充放电循环过程中，由于镁掺杂硅氧化物的导电性不足及脱嵌锂过程中的体积膨胀率较高，镁掺杂硅氧化物作为负极活性材料依然无法有效的形成均匀的锂金属沉积，导致镁掺杂硅氧化物的循环效率低下，使用寿命较低。
有鉴于上述问题，根据本申请的一个方面，如图1所示，本申请部分实施例提供了一种负极活性材料，该负极活性材料包含通过高温制备工艺对硅氧化物进行碳掺杂及镁掺杂所形成的复合材料，即镁掺杂碳硅氧材料，其中镁掺杂碳硅氧材料的晶体氧化物101的表面上进一步包含碳纳米管包覆层102，该碳纳米管包覆层102通过碳纳米管包覆工艺设置于镁掺杂碳硅氧材料的晶体氧化物101的颗粒表面上。
本申请通过对硅氧材料进行镁掺杂，能够形成镁硅氧化物以提高电化学装置的首次库仑效率，同时，通过碳掺杂，能够进一步于复合镁掺杂碳硅氧材料中形成含碳的镁硅氧化物，含碳的镁硅氧化物于脱嵌锂过程中具有较低的体积膨胀率及较佳的循环结构稳定性，镁掺杂碳硅氧材料能够有效的在循环过程中形成均匀的锂金属沉积，以提高电化学装置的循环性能并延长其使用寿命。此外，本申请通过使用碳纳米管包覆镁掺杂碳硅氧材料的颗粒表面，能够进一步提高负极活性材料的导电性。
镁掺杂碳硅氧材料为包含镁、碳、硅与氧所构成的晶体氧化物以及其表面包覆的碳纳米管的复合材料。在一些实施例中，镁掺杂碳硅氧材料的晶体氧化物能够由通式Mg zSiC xO y表示。在一些实施例中，镁掺杂碳硅氧材料的晶体氧化物的通式Mg zSiC xO y,的化学计量为：0<x<0.3，0.4<y<1.0，且0.1<z<0.2。在一些实施例中，0.15<x<0.28，0.6<y<0.8，且0.1<z<0.2。在一些实施例中，0.2<x<0.25，0.7<y<0.78，且0.1<z<0.2。
镁掺杂碳硅氧材料中各个成分及其晶体结构组成对其于电化学装置中的循环表现、克容量及结构稳定性具有一定影响。在一些实施例中，镁掺杂碳硅氧材料中的硅元素Si摩尔含量为40％至70％，硅元素的含量过低会导致负极活性材料的克容量减少，过高则会导致负极活性材料的体积膨胀率上升。在一些实施例中，镁掺杂碳硅氧材料中的硅元素Si摩尔含量为60％。
在一些实施例中，镁掺杂碳硅氧材料中的镁元素Mg摩尔含量为7.00％至7.5％，镁元素的含量范围能够有效形成含碳的镁硅氧化物，并避免镁元素与氧形成高活性的氧化镁或镁金属，以提高镁掺杂碳硅氧材料作为负极活性材 料的首次库仑效率，并降低镁掺杂碳硅氧材料于电化学循环反应中的安全风险。
在一些实施例中，镁掺杂碳硅氧材料中的碳元素C摩尔含量为3.5％至24％，其中镁掺杂碳硅氧材料中的碳元素来源包含掺杂于晶体氧化物中的碳以及包覆晶体氧化物的碳纳米管，碳元素的掺杂量过低会导致负极活性材料的结构稳定性降低使得体积膨胀率上升，过高则会导致负极活性材料的克容量减少。在一些实施例中，镁掺杂碳硅氧材料中的碳元素C摩尔含量为4.5％至10％。在一些实施例中，镁掺杂碳硅氧材料中的碳元素C摩尔含量为约6％。
应理解，本申请的镁掺杂碳硅氧材料中的各个元素成分含量可以采用本领域中任何合适的检测方式进行检测，而不受其限制。在一些实施例中，镁掺杂碳硅氧材料的镁含量及硅含量能够通过X射线衍射分析进行测定。在一些实施例中，镁掺杂碳硅氧材料的碳含量能够通过以下碳含量测试(如有标准号请提供)进行测定：样品在富氧条件下由高频炉高温加热燃烧使碳和硫分别氧化成二氧化碳和二氧化硫，该气体经处理后进入相应的吸收池，对相应的红外辐射进行吸收再由探测器转化成对应的信号。此信号由计算机采样，经线性校正后转换成与二氧化碳、二氧化硫浓度成正比的数值，然后把整个分析过程的取值累加，分析结束后，此累加值在计算机中除以重量值，再乘以校正系数，扣除空白，即可获得样品中碳、硫百分含量。利用高频红外碳硫分析仪(上海徳凯HCS-140)进行样品测试。
图2为根据本申请实施例1的镁掺杂碳硅氧材料的XRD衍射图谱。如图2所示，在一实施例中，镁掺杂碳硅氧材料经过X射线衍射分析，于XRD衍射图谱中，镁掺杂碳硅氧材料包含的Si、SiO 2、MgSiO 3、Mg 2SiO 4中的一种或多种特征峰。在一些实施例中，镁掺杂碳硅氧材料的镁与硅的摩尔比为0.1至0.2，镁与碳的摩尔比为0.2至10.0，以优化镁掺杂碳硅氧材料于电化学装置中的循环表现及首次库仑效率。在一些实施例中，镁掺杂碳硅氧材料的镁与硅的摩尔比为约0.12。
图3为根据本申请实施例1的镁掺杂碳硅氧材料于扫描式电子显微镜下的5千倍显微图像。参见图3可知，于镁掺杂碳硅氧材料的晶体氧化物的颗粒表面上设置的碳纳米管包覆层能够形成网状导电结构，以进一步提高循环过程中锂金属沉积的分布，并优化镁掺杂碳硅氧材料的体积膨胀分布，使得负极活 性材料在循环过程具有跟优异的结构稳定性。
在一些实施例中，碳纳米管包覆层的厚度能够影响镁掺杂碳硅氧材料于电化学装置中的导电性能及能量密度，碳纳米管包覆层的厚度过厚会降低镁掺杂碳硅氧材料的克容量，而碳纳米管包覆层的厚度过低则会导致其导电性降低，并无法提高镁掺杂碳硅氧材料的结构稳定性。在一些实施例中，碳纳米管包覆层的厚度大致为：0.5nm、1.0nm、5nm、10nm、50nm、100nm、250nm、500nm、1.0μm、5.0μm或上述任两者数值所构成的数值范围。在一些实施例中，碳纳米管包覆层的厚度为0.5nm至5.0μm。在一些实施例中，碳纳米管包覆层的厚度为2.0nm至150nm。
在一些实施例中，碳纳米管包覆层包含碳纳米管团簇，碳纳米管团簇能够自镁掺杂碳硅氧材料的颗粒表面向外延伸，并与其他颗粒表面的碳纳米管包覆层接触，以进一步形成的有效导电网络，优化镁掺杂碳硅氧材料的导电性。在一些实施例中，碳纳米管团簇的延伸长度为0.1μm至1.0μm。在一些实施例中，碳纳米管团簇的延伸长度为约0.5μm。
在本文中，碳纳米管包覆层的厚度及碳纳米管团簇的延伸长度可以采用本领域中任何合适的检测方式进行检测，而不受其限制。在一些实施例中，碳纳米管包覆层的厚度及碳纳米管团簇的延伸长度是通过扫描电子显微镜(SEM)或透射电子显微镜(TEM)进行表征。在一些实施例中，扫描电子显微镜表征由PhilipsXL-30型场发射扫描电子显微镜记录，在10kV及10mA条件下进行检测。
在一些实施例中，镁掺杂碳硅氧材料颗粒的颗粒度(Dv50)为2.5μm至10.0μm。在一些实施例中，镁掺杂碳硅氧材料颗粒的颗粒度(Dv50)为2.7μm至5.3μm，以优化镁掺杂碳硅氧材料在负极活性材料层中的涂覆分布。在一些实施例中，镁掺杂碳硅氧材料颗粒的粒径分布满足以下条件：
0.3≤Dn10/Dv50≤0.6。
在本文中，术语“颗粒度”，在未特别指代时，包含样品通过颗粒度测试所得到的表征颗粒特性例如，Dn10或Dv50，其中Dn10表示材料在粒径基准的颗粒分布中，从小粒径测起、达到颗粒数量累积10％的粒径；Dv50表示材料在体积基准的颗粒分布中，从小粒径测起、达到体积累积50％的粒 径。在一些实施例中，颗粒度测试方法为采用Mastersizer 2000激光粒度分布测试仪分析样品的颗粒的粒径：将样品分散在100mL的分散剂(去离子水)中，使遮光度达到8～12％。随后在超声强度为40KHz及180w下对样品进行超声处理5分钟。待超声处理后，将对样品进行激光粒径分布分析，得到粒径分布数据。
在一些实施例中，镁掺杂碳硅氧材料颗粒的比表面积为1m 2/g至50m 2/g。在一些实施例中，镁掺杂碳硅氧材料颗粒的比表面积为5m 2/g至20m 2/g，以维持镁掺杂碳硅氧材料与电解液的反应速率。
在一些实施例中，镁掺杂碳硅氧材料中的碳纳米管包覆层的包覆度及结构稳定性能够通过拉曼光谱检测进行表征，其中拉曼光谱中大约1350cm -1和1580cm -1附近的D峰及G峰是碳原子晶体的拉曼光谱特征峰。在一些实施例中，镁掺杂碳硅氧材料于拉曼光谱中D峰及G峰特征峰值的比值：I D/I G值能够表征的碳纳米管包覆层对镁掺杂碳硅氧材料颗粒的网状导电结构，当镁掺杂碳硅氧材料在拉曼光谱中的I D/I G值较低时，代表其碳纳米管包覆层的网状导电结构较为完整。在一些实施例中，镁掺杂碳硅氧材料在拉曼光谱中的I D/I G值小于或等于0.32。在一些实施例中，镁掺杂碳硅氧材料在拉曼光谱中的I D/I G值为0.023至0.32，以优化碳纳米管包覆层的网状导电结构。
在一些实施例中，镁掺杂碳硅氧材料在拉曼光谱中的I D/I G值与碳摩尔含量的比值能够进一步表征碳纳米管包覆层对镁掺杂碳硅氧材料的包覆程度，当镁掺杂碳硅氧材料在拉曼光谱中的I D/I G值与碳摩尔含量的比值过低时，会导致镁掺杂碳硅氧材料的克容量降低；而镁掺杂碳硅氧材料在拉曼光谱中的I D/I G值与碳摩尔含量的比值过高时，会使得碳纳米管包覆层对镁掺杂碳硅氧材料的包覆不佳。在一些实施例中，镁掺杂碳硅氧材料的拉曼光谱中的I D/I G值与碳摩尔含量的比值为0.095至6.78。
根据本申请的另一方面，本申请部分实施例提供一种制备上述镁掺杂碳硅氧材料的方法，具体流程如下：
(1)将碳纳米管原料与乙醇混合，以配置成具有一定碳纳米管浓度的乙醇分散液。在一些实施例中，乙醇分散液中的碳纳米管重量浓度为1.5％至10.0％。在一些实施例中，乙醇分散液中的碳纳米管重量浓度为1.6％至6.6％。。
(2)将镁掺杂碳硅氧材料的前驱体与乙醇分散液混合，并搅拌均匀。将碳硅氧材料的前驱体与乙醇分散液的混合液蒸干，并收集干燥粉末。
(3)将收集的干燥粉末在氩气环境下进行高温处理，以得到镁掺杂碳硅氧材料。在一些实施例中，高温处理的温度为400℃至800℃。在一些实施例中，高温处理的温度为约600℃。在一些实施例中，高温处理的时间为1h至5h。在一些实施例中，高温处理的时间为约3h。
本申请通过采用乙醇分散液能够使碳纳米管包覆镁掺杂碳硅氧材料的前驱体以形成具有碳纳米管包覆层的镁掺杂碳硅氧材料。相较于单纯的碳包覆或碳掺杂处理的负极活性材料，本申请具有碳纳米管包覆层的镁掺杂碳硅氧材料不仅能够提高电导性能，还可以降低碳材料对镁掺杂碳硅氧材料的电性表现及克容量影响，并优化镁掺杂碳硅氧材料的锂沉淀的脱嵌机制，进而优化镁掺杂碳硅氧材料在电化学装置中的电性表现及循环表现。在一些实施例中，通过调整高温处理的温度与反应时间，能够进一步优化镁掺杂碳硅氧材料中碳纳米管包覆层的导电与包覆结构，使其作为负极活性材料能够具有优异的循环性能及首次库仑效果。
根据本申请的另一方面，本申请部分实施例提供一种电化学装置，该电化学装置包括负极，其中负极包含负极活性材料层，该负极活性材料层包含负极活性材料，且负极活性材料包含上述实施例中的镁掺杂碳硅氧材料。电化学装置通过采用具备碳纳米管包覆层的镁掺杂碳硅氧材料，能够提高电化学装置的首次库仑效率并优化电化学装置在循环过程中的结构稳定性，进而提高电化学装置的循环保持率及循环性能。在一些实施例中，以负极活性材料的总重计，镁掺杂碳硅氧材料的重量比大于或等于20％。在一些实施例中，镁掺杂碳硅氧材料的重量比大于或等于60％。在一些实施例中，负极活性材料由上述实施例中的镁掺杂碳硅氧材料所构成。
在一些实施例中，负极活性材料还包括石墨，其中石墨包括天然石墨、人造石墨、中间相碳微球中的一种或多种，以提高负极活性材料的导电性及循环性能。在不违背本申请的精神下，负极活性材料还能够包括本领域中其他常见的能够吸收和释放锂(Li)的负极活性材料，例如，但不限于，碳材料、金属化合物、氧化物、硫化物、锂的氮化物例如LiN 3、锂金属、与锂一起形成合金的金属元素和半金属元素、聚合物材料及其组合中的一种或多 种。
在一些实施例中，负极活性材料能够通过调整镁掺杂碳硅氧材料的含量控制负极活性材料的粉末电导率，以优化负极活性材料层的循环性能。在一些实施例中，负极活性材料的粉末电导率为2.0S/cm至30S/cm。在一些实施例中，负极活性材料的粉末电导率为5.0S/cm至10S/cm。在本文中，负极活性材料的粉末电导率可以采用本领域中任何合适的检测方式进行检测，而不受其限制。在一些实施例中，负极活性材料的粉末电导率的检测方法如下：采用电阻率测试仪(苏州晶格电子ST-2255A)，取5g粉末样品，用电子压力机恒压至5000kg±2kg，维持15-25s，将样品置于测试仪电极间，根据公式δ＝h/(S*R)/1000计算得到粉末电子电导率，其中h为样品高度(cm)，R为电阻(KΩ)，S为粉末样品压片后的面积3.14cm 2。
在一些实施例中，负极活性材料层的电阻范围为0.2Ω至1Ω。
在一些实施例中，负极活性材料层进一步包含粘结剂，以提高负极活性材料层的结构稳定性。在一些实施例中，粘结剂包含合成橡胶包含聚丙烯酸酯、聚酰亚胺、聚酰胺、聚酰胺酰亚胺、聚偏氟乙烯、丁苯橡胶、海藻酸钠、聚乙烯醇、聚四氟乙烯、聚丙烯腈、羧甲基纤维素钠、羧甲基纤维素钾、羟甲基纤维素钠及羟甲基纤维素钾中的一种或多种。在一些实施例中，以负极活性材料层的总重计，粘结剂的质量为2％至6％。在另一些实施例中，以负极活性材料的总重量计，粘结剂的重量比大致为，例如，约2％、约3％、约4％、约5％、约6％或这些数值中任意两者组成的范围。
在一些实施例中，负极活性材料层进一步包含导电剂，以提高负极活性材料层的导电性。导电剂包含碳纳米管、导电炭黑、乙炔黑、石墨烯、科琴黑中的一种或多种。应理解，本领域技术人员可以根据实际需要选择本领域常规的导电剂，而不受其限制。在一些实施例中，以负极活性材料层的总重计，导电剂的质量为1％至10％。在另一些实施例中，以负极活性材料的总重量计，导电剂的重量比大致为，例如，约1％、约2％、约3％、约5％、约10％或这些数值中任意两者组成的范围。
在一些实施例中，负极还包含负极集流体。负极集流体可为铜箔或镍箔， 然而，可以采用本领域常用的其他负极集流体，而不受其限制。
在一些实施例中，电化学装置还包含正极及隔离膜，正极、隔离膜与上述实施例中的负极能够通过卷绕或叠合的方式形成电极组件。在不违背本申请的精神下，本申请中的电极组件可以是本领域中任何合适的电极组件，而不受其限制。在一些实施例中，电极组件为卷绕结构。在一些实施例中，电极组件能够为叠片结构或多极耳结构。在一些实施例中，电化学装置为锂离子电池。
在一些实施例中，正极包含正极集流体及正极活性材料层。正极集流体可以为铝箔或镍箔，然而，可以采用本领域常用的其他正极集流体，而不受其限制。在一些实施例中，正极活性材料层包括能够吸收和释放锂(Li)的正极活性材料(下文中，有时称为“能够吸收/释放锂Li的正极活性材料”)。能够吸收/释放锂(Li)的正极活性材料的实例可以包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、磷酸铁锂、钛酸锂和富锂锰基材料中的一种或多种。
在一些实施例中，正极活性材料层能够进一步包含粘结剂及导电剂中的至少一种。粘结剂包含聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素钠、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯及聚六氟丙烯中的一种或多种。导电剂包含碳纳米管、导电炭黑、乙炔黑、石墨烯、科琴黑中的一种或多种。应理解，本领域技术人员可以根据实际需要选择本领域常规的粘结剂及导电剂，而不受其限制。
在一些实施例中，隔离膜包括，但不限于，选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺和芳纶中的至少一种。举例来说，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯和超高分子量聚乙烯中的至少一种组分。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。应理解，本领域技术人员可以根据实际需要选择本领域常规的隔离膜，而不受其限制。
在一些实施例中，本申请的电化学装置还包括电解液，该电解液包括锂 盐和有机溶剂。
在一些实施例中，锂盐包含六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、二氟磷酸锂(LiPO 2F 2)、双三氟甲烷磺酰亚胺锂(LiN(CF 3SO 2) 2)、双(氟磺酰)亚胺锂(Li(N(SO 2F) 2))、双草酸硼酸锂(LiB(C 2O 4) 2)及二氟草酸硼酸锂(LiBF 2(C 2O 4))中的一种或多种。举例来说，锂盐选用六氟磷酸锂(LiPF 6)，因为它可以给出高的离子导电率并改善循环特性。
在一些实施例中，有机溶剂包含碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、碳酸亚丙酯、碳酸亚乙烯酯、丙酸丙酯及丙酸乙酯中的一种或多种；锂盐包含六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、二氟磷酸锂(LiPO 2F 2)、双三氟甲烷磺酰亚胺锂(LiN(CF 3SO 2) 2)、双(氟磺酰)亚胺锂(Li(N(SO 2F) 2))、双草酸硼酸锂(LiB(C 2O 4) 2)及二氟草酸硼酸锂(LiBF 2(C 2O 4))中的一种或多种。
在一些实施例中，电解液还包含添加剂，在不违背本申请的精神下，添加剂可以是本领域中任何合适的添加剂，而不受其限制。
应理解，本申请实施例中的正极、隔离膜、负极以及电解液的制备方法，在不违背本申请的精神下，可以根据具体需要选择本领域任何合适的常规方法，而不受其限制。在制造电化学装置的方法的一个实施方案中，锂离子电池的制备方法包括：将实施例中的负极、隔膜及正极按顺序卷绕、折叠或堆叠成电极组件，随后电极组件装入外壳，例如，铝塑膜，并注入电解液，随后对装入电极组件的锂离子电池通过后续真空封装、静置、化成、整形等工序，以获得锂离子电池。
虽然上面以锂离子电池进行了举例说明，但是本领域技术人员在阅读本申请之后，能够想到由本申请的负极活性材料的胶膜可以用于其他合适的电化学装置。这样的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容。特别地，该电化学装置是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
本申请的一些实施例进一步提供了一种电子装置，电子装置包含本申请实施例中的电化学装置。
本申请实施例的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
具体实施例
下面列举了一些具体实施例及对比例并分别对其电化学装置(锂离子电池)进行拉曼测试、循环测试、倍率性能测试、膨胀率测试的测试方法与结果以更好地对本申请的技术方案进行说明。
一、测试方法
1.1拉曼测试：
采用拉曼光谱仪(Jobin Yvon LabRAM HR)，光源波长为532nm，测试范围为0cm -1至4000cm -1，对100μm×100μm大小的负极活性材料进行测试，并记录1350cm -1和1580cm -1附近的峰值强度，每组数值取100次并计算平均的D峰及G峰特征峰值的比值：I D/I G值。
1.2倍率性能测试：
将以下实施例及对比例中化成后的锂离子电池置于45℃±2℃的恒温箱中静置2小时，以0.5C恒流充电至4.45V，然后以4.45V恒压充电至0.025C并静置5分钟；再以0.2C恒流放电至3.0V，此为首次容量，记录锂离子电池首次循环的放电容量，后以0.5C恒流充电至4.45V，然后以2C恒流放电至3.0V，记录放电容量。以首次容量计算负极活性材料的克容量，并以2C放电容量与首次容量的比值计算负极活性材料的首次效率。
1.3循环性能测试：
将以下实施例及对比例中化成后的锂离子电池置于25℃±2℃的恒温箱 中静置2小时，以0.5C恒流充电至4.45V，然后以4.45V恒压充电至0.025C并静置5分钟；再以0.3C恒流放电至3.0V，此为一次充放电循环过程，记录锂离子电池首次循环的放电容量；而后按上述方法重复进行充放电循环过程，并记录放电容量与初次放电容量的比值得到容量变化曲线。
每组取4块锂离子电池，计算锂离子电池的容量保持率的平均值。锂离子电池的循环容量保持率＝第400次循环的放电容量(mAh)/首次循环后的放电容量(mAh)×100％。
1.4循环厚度膨胀率测试：
采用600g平板测厚仪(ELASTOCON,EV 01)测试锂离子电池的厚度。
将以下实施例及对比例的化成后锂离子电池置于25℃±2℃的恒温箱中静置2小时，以0.7C恒流充电至4.45V，然后以4.45V恒压充电至0.05C并静置15分钟，纪录满充状态下的锂离子电池厚度；再以0.5C恒流放电至3.0V，此为一次充放电循环过程，记录锂离子电池首次循环的锂离子电池厚度；而后按上述方法重复进行400次的充放电循环过程，并记录400次循环后的锂离子电池厚度。
每组取4块锂离子电池，计算锂离子电池的循环厚度膨胀率的平均值。锂离子电池的循环厚度膨胀率＝(第400次循环的锂离子电池厚度/首次循环的锂离子电池厚度-1)×100％。
二、制备方法
2.1正极的制备
将正极活性材料钴酸锂(LiCoO 2)、导电炭黑(Super P)、聚偏二氟乙烯(PVDF)按照重量比97.5:1.0:1.5进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成为固含量为0.75的浆料，并搅拌均匀。将浆料均匀涂覆在正极集流体铝箔上，90℃条件下烘干。随后经过冷压、裁片、分切程序后得到正极。
2.2电解液的制备
在含水量小于150ppm的环境(干燥氩气气氛中)下，将锂盐LiPF6与 有机溶剂(碳酸乙烯酯(EC)：碳酸二乙酯(DEC)：碳酸亚丙酯(PC)：丙酸丙酯(PP)：碳酸亚乙烯酯(VC)＝20:30:20:28:2，质量比)按质量比8：92配制而成的溶液作为锂离子电池的电解液。
2.3负极的制备
采用铜箔作为负极集流体，采用以下实施例或对比例提供的负极活性材料与石墨按等质量比例(1:1)混合，得到设计混合克容量为850mAh/g的混合粉末，将混合粉末、乙炔黑、聚丙烯酸(PAA)按照重量比95：1.2：3.8在去离子水溶剂体系中充分搅拌混合均匀形成负极活性材料浆料后，在铜箔表面均匀的涂布一层负极活性材料浆料，并于90℃条件下烘干。随后经过冷压、裁片、分切程序后，在85℃的真空条件下干燥4h，制备得到负极。
2.4锂离子电池的制备
采用聚乙烯膜作为隔离膜，其中聚乙烯膜的厚度为15μm，将上述正极、隔离膜与负极依顺序堆叠，使隔离膜处于正极与负极中间起到隔离的作用。将堆叠的电极组件在80℃下脱去水分后，获得干电极组件，将干电极组件置于外包装中，注入配好的电解液后进行封装，经过化成，脱气，切边等工艺流程得到锂离子电池。
2.5负极活性材料的制备
实施例1
(1)将碳纳米管原料与乙醇混合，以配置成具有3.3wt％碳纳米管浓度的乙醇分散液，其中，碳纳米管的平均粒径为(如果有请提供)。
(2)将镁掺杂碳硅氧材料的前驱体与乙醇分散液混合搅拌均匀，该前驱体以镁掺杂碳硅氧材料通式：Mg 0.14SiC 0.25O 0.77的化学计量比混合形成，其中镁原料(镁粉)、碳原料(乙炔气)、硅氧原料的重量比例为2：1：10。将碳硅氧材料的前驱体与乙醇分散液的混合液在温度下蒸干，并收集干燥粉末。
(3)将收集的干燥粉末在氩气环境下进行高温处理，其中高温处理的温度为约600℃，时间为3h，随后得到镁掺杂碳硅氧材料。
实施例2及3
与实施例1的制备方式大致上相同，其区别在于第(1)步骤中，乙醇分散液中的碳纳米管浓度不同，具体请参见以下实施例表格。
实施例4-7
与实施例1的制备方式大致上相同，其区别在于第(3)步骤中，高温处理的温度不同，具体请参见以下实施例表格。
实施例8及9
与实施例3的制备方式大致上相同，其区别在于第(3)步骤中，高温处理的时间不同，具体请参见以下实施例表格。
对比例1
将镁掺杂碳硅氧材料的前驱体在氩气环境下进行高温处理，该前驱体以镁掺杂碳硅氧材料通式：Mg 0.14SiC 0.18O 0.8的化学计量比混合形成，其中镁原料(镁粉)、碳原料(乙炔气)、硅氧原料的重量比例为2：1：10其中高温处理的温度为约600℃，时间为3h，随后得到镁掺杂碳硅氧材料。
三、比较结果
3.1负极活性材料组成比较
实施例1-9与对比例1的锂离子电池的区别在于其使用的负极活性材料(设置碳纳米管包覆层后)及其前驱体(未设置碳纳米管包覆层)的组成不同，负极活性材料的前驱体的组成及镁掺杂碳硅氧材料通过成分测试、拉曼测试的结果记载于下表1中。
表1
Figure PCTCN2022073239-appb-000001
Figure PCTCN2022073239-appb-000002
N/A表示无对应数值。
参考表1可知，本申请通过采用乙醇分散液的制备工艺，能够有效的在负极活性材料颗粒的晶体氧化物的表面，形成碳纳米管包覆层，使得制备后的负极活性材料粉末具有高于制备前的负极活性材料的碳含量。参考实施例1-3可知，碳纳米管包覆层的厚度能够通过调整乙醇分散液中的碳纳米管浓度来控制，同时，根据莱曼测试的结果可知，碳管包覆层的厚度会影响其碳结构的稳定性及导电性。
参考实施例1及4-9可知，碳管包覆层的包覆结构能够受到高温处理的温度及时间影响，根据莱曼测试的结果可知，当高温处理的温度降低时，会导致碳管包覆层的碳化程度减少，提高其碳管包覆层的无序度和碳结构的缺陷，当高温处理的温度提高时，会提升碳管包覆层的碳化程度，降低其碳管包覆层的无序度和碳结构缺陷。
3.2电化学装置性能比较
实施例1-9与对比例1的锂离子电池通过倍率测试、循环性能测试及循环厚度膨胀率测试的结果记载于下表2中。
表2
Figure PCTCN2022073239-appb-000003
Figure PCTCN2022073239-appb-000004
参考表2，本申请实施例的镁掺杂碳硅氧材料，具有优异的首次库仑效率以及循环性能，本申请通过进一步于镁掺杂硅氧化物进行碳掺杂能够提升负极活性材料的循环效果，降低其高循环次数的循环厚度膨胀率，延长其循环寿命。而进一步比较实施例与对比例1，图4为本申请实施例1的循环容量曲线201与对比例1的电化学装置的循环容量曲线202的对比图。如图4所示，本申请实施例1包含具有碳纳米管包覆层的镁掺杂碳硅氧材料，通过设置特定的碳纳米管包覆层，能够提升负极活性材料的循环容量保持率，并大幅降低循环厚度膨胀率，使得电化学装置具有优异的首次库仑效率及循环性能。
参考实施例1-3可知，当碳纳米管包覆层厚度较低时，会使得包覆层不够致密，而无法有效形成连续均匀的导电网络，导致材料的循环保持率降低；当碳纳米管包覆层厚度较高时，副产物积累增多，电解液消耗和活性锂消耗增多，导致材料的循环保持率降低，同时降低材料的首次导电效率。
参考实施例4-9可知，当烧结温度降低，镁掺杂碳硅氧材料的碳化度降低时，会使得包覆层缺陷增多，I D/I G值升高，导电网络的电子传导能力降低，导致循环保持率降低；当纳结温度题升，镁掺杂碳硅氧材料的碳化度提高时，会使得包覆层缺陷降低，I D/I G值降低，导电网络的电子传导能力提升，然而，温度升高会导致碳掺杂硅材料中的硅酸盐相增多，进而导致首效降低，硅酸盐相的增多也恶化了材料的结构稳定性，从而导致循环保持率降低。
整个说明书中对“实施例、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例”，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实 施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (10)

  1. 一种电化学装置，其包括负极，其中所述负极包含负极活性材料层，所述负极活性材料层包含负极活性材料，且所述负极活性材料包含镁掺杂碳硅氧材料，其中所述镁掺杂碳硅氧材料的晶体氧化物的表面上设置有碳纳米管包覆层。
  2. 根据权利要求1所述的电化学装置，其中所述镁掺杂碳硅氧材料的所述晶体氧化物的通式为Mg zSiC xO y，其中0<x<0.3，0.4<y<1.0，且0.1<z<0.2。
  3. 根据权利要求1所述的电化学装置，其中，在所述镁掺杂碳硅氧材料中，硅的摩尔含量为40％至70％，碳的摩尔含量为3.5％至24％，且镁的摩尔含量为7.0％至7.5％。
  4. 根据权利要1所述的电化学装置，其中所述镁掺杂碳硅氧材料的镁与硅的摩尔比为0.1至0.2，镁与碳的摩尔比为0.2至10.0。
  5. 根据权利要求1所述的电化学装置，其中所述镁掺杂碳硅氧材料的拉曼光谱中的I D/I G值为0.023至0.32。
  6. 根据权利要求3或5所述的电化学装置，其中所述镁掺杂碳硅氧材料的拉曼光谱中的I D/I G值与碳摩尔含量的比值为0.095至6.78。
  7. 根据权利要求1所述的电化学装置，其中所述碳纳米管包覆层满足以下至少一者：
    (1)所述碳纳米管包覆层的厚度为0.5nm至5.0μm，或
    (2)所述碳纳米管包覆层包含碳纳米管团簇，其中所述碳纳米管团簇自所述碳纳米管包覆层的表面延伸，所述碳纳米管团簇的长度为0.1μm至1.0μm。
  8. 根据权利要求1所述的电化学装置，其中所述镁掺杂碳硅氧材料满足以下至少一者：
    (1)所述镁掺杂碳硅氧材料的颗粒度Dv50为2.5μm至10.0μm，
    (2)所述镁掺杂碳硅氧材料的粒径分布满足：0.3≤Dn10/Dv50≤0.6，或
    (3)所述镁掺杂碳硅氧材料的比表面积为1m 2/g至50m 2/g。
  9. 根据权利要求1所述的电化学装置，其中所述负极活性材料层进一步包含粘结剂，其中所述粘结剂包含合成橡胶包含聚丙烯酸酯、聚酰亚胺、聚酰胺、聚酰胺酰亚胺、聚偏氟乙烯、丁苯橡胶、海藻酸钠、聚乙烯醇、聚四氟乙烯、聚丙烯腈、羧甲基纤维素钠、羧甲基纤维素钾、羟甲基纤维素钠及羟甲基纤维素钾中的一种或多种,其中，以所述负极活性材料层的总重计，所述粘结剂的质量为2％至6％。
  10. 根据权利要求1所述的电化学装置，其中，所述电化学装置的电解液包含有机溶剂及锂盐，其中所述有机溶剂包含碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、碳酸亚丙酯、碳酸亚乙烯酯、丙酸丙酯及丙酸乙酯中的一种或多种；所述锂盐包含六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、二氟磷酸锂(LiPO 2F 2)、双三氟甲烷磺酰亚胺锂(LiN(CF 3SO 2) 2)、双(氟磺酰)亚胺锂(Li(N(SO 2F) 2))、双草酸硼酸锂(LiB(C 2O 4) 2)及二氟草酸硼酸锂(LiBF 2(C 2O 4))中的一种或多种。
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