WO2021068796A1 - 负极材料及其制备方法和应用以及锂离子电池 - Google Patents

负极材料及其制备方法和应用以及锂离子电池 Download PDF

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WO2021068796A1
WO2021068796A1 PCT/CN2020/118720 CN2020118720W WO2021068796A1 WO 2021068796 A1 WO2021068796 A1 WO 2021068796A1 CN 2020118720 W CN2020118720 W CN 2020118720W WO 2021068796 A1 WO2021068796 A1 WO 2021068796A1
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lithium
silicon
negative electrode
electrode material
temperature
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PCT/CN2020/118720
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English (en)
French (fr)
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孙赛
张丝雨
高焕新
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中国石油化工股份有限公司
中国石油化工股份有限公司上海石油化工研究院
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Priority claimed from CN201910953233.6A external-priority patent/CN112635719B/zh
Priority claimed from CN201910953279.8A external-priority patent/CN112652755B/zh
Application filed by 中国石油化工股份有限公司, 中国石油化工股份有限公司上海石油化工研究院 filed Critical 中国石油化工股份有限公司
Priority to BR112022005422A priority Critical patent/BR112022005422A2/pt
Priority to US17/754,742 priority patent/US20230148348A1/en
Priority to EP20874397.1A priority patent/EP4044285A4/en
Priority to AU2020363053A priority patent/AU2020363053A1/en
Priority to CA3155666A priority patent/CA3155666A1/en
Priority to JP2022521415A priority patent/JP2022552486A/ja
Priority to CN202080070420.0A priority patent/CN114467198A/zh
Priority to KR1020227015605A priority patent/KR20220078683A/ko
Publication of WO2021068796A1 publication Critical patent/WO2021068796A1/zh

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    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • 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 invention relates to the field of lithium ion batteries, in particular to a negative electrode material with a core-shell structure, a preparation method and application thereof, and a lithium ion battery.
  • the theoretical specific capacity of silicon is 4200mAh/g, which is currently the battery anode material with the highest gram capacity. Once successfully applied, it can significantly increase the energy density of lithium batteries, making it possible to reach 1,000 kilometers on a single charge.
  • the charging and discharging mechanism of silicon is different from that of graphite.
  • SEI solid electrolyte
  • the liberated Li causes the first coulombic efficiency (which can be referred to as the "first effect") of the silicon-based negative electrode material to be only between 65-85%, resulting in a great capacity loss.
  • the conductivity of silicon and the diffusion rate of lithium ions are lower than that of graphite, which will limit the performance of silicon under high current and high power conditions.
  • CN101179126B reports a doped silicon-based anode material for lithium-ion batteries.
  • the first Coulombic efficiency of the material is obtained by doping at least one element among boron, aluminum, gallium, antimony and phosphorus.
  • CN101179126B requires high-vacuum argon arc fusion welding during the preparation process, the reaction temperature is high (>1000°C), the reaction process is complicated (involving fusion welding, low-temperature blowing, rapid cooling, planetary ball milling and other operations), and the cost is relatively high.
  • CN108172775A reports a phosphorus-doped silicon-based negative electrode material.
  • the specific capacity of the phosphorus-doped silicon-based negative electrode is 610.1mAh/g
  • the first effect is 91.7%.
  • the CN108172775A preparation process requires spray drying, and the output is low-cost and high.
  • CN103400971A reported a negative electrode material doped with lithium silicate.
  • the addition amount of Si is 50% and the addition amount of Li 2 SiO 3 is 35%, the specific capacity of the material is 1156.2mAh/g, and the first effect is 88.2%.
  • the cycle of the material Stability and first-time coulombic efficiency still need to be improved.
  • CN111653738A reported an amorphous carbon-coated silicon carbon anode material.
  • the material has a core-shell structure.
  • the reversible charging capacity is 1765.54mAh/g
  • the first effect is 84.38%
  • the charging capacity retention rate for 50 cycles is 82.24%.
  • the purpose of the present invention is to overcome the problems of low reversible charging capacity and low first-time Coulombic efficiency of silicon-based negative electrode materials in the prior art, and to provide a negative electrode material with a core-shell structure, a preparation method of the negative electrode material, and a preparation method of the preparation method.
  • the obtained negative electrode material and a lithium-ion battery The negative electrode material provided by the present disclosure has improved reversible charging capacity (also referred to as "reversible charging specific capacity") and first-time coulombic efficiency, and is particularly suitable for lithium ion batteries.
  • the first aspect of the present invention provides a negative electrode material having a core-shell structure, the core includes a silicon-containing material, and the shell includes an organic lithium salt and a porous carbon film, wherein at least a portion of lithium ions are intercalated The layer is in the porous carbon film.
  • the organic lithium salt is selected from at least one of lithium polyacrylate, lithium polymethacrylate, lithium polymaleate, lithium polyfumarate, lithium carboxymethyl cellulose, and lithium alginate.
  • the second aspect of the present invention provides a method for preparing a negative electrode material, including the following steps:
  • step (3) The materials obtained by mixing in step (2) are subjected to vacuum freeze-drying.
  • the carbon source is pitch, preferably at least one selected from petroleum pitch, coal tar pitch, natural pitch and modified pitch.
  • the third aspect of the present invention provides a negative electrode material prepared by the above preparation method.
  • the fourth aspect of the present invention provides the application of the above-mentioned negative electrode material in a lithium ion battery.
  • a fifth aspect of the present invention provides a lithium ion battery, which includes the negative electrode material provided by the invention, the positive electrode material containing lithium element, a separator, and an electrolyte.
  • the present invention can be embodied as the following items:
  • a silicon-carbon anode material characterized in that the silicon-carbon anode material has a core-shell structure, the core includes a silicon-containing substance, and the shell includes an organic lithium salt and a porous carbon film.
  • the silicon-carbon anode material of item 1 wherein, based on the total amount of the silicon-carbon anode material, the content of the organic lithium salt is 5-34% by weight, and the content of the silicon-containing substance is 65-90% by weight %, the content of the porous carbon film is 1-10% by weight;
  • the content of the organic lithium salt is 10-30% by weight, the content of the silicon-containing substance is 68-86% by weight, and the content of the porous carbon film is 1- 6 wt%;
  • the silicon carbon negative electrode material further contains graphite; further preferably, the graphite is present in the core and/or shell;
  • the mass ratio of the total amount of the silicon-containing substance, the organic lithium salt and the porous carbon film to the graphite is 1:1-10, more preferably 1:1-5.
  • the silicon-containing substance is selected from at least one of elemental silicon, SiOx and silicon-containing alloys,
  • the silicon-containing alloy is selected from at least one of silicon-aluminum alloy, silicon-magnesium alloy, silicon-zirconium alloy, and silicon-boron alloy.
  • a preparation method of silicon carbon anode material characterized in that it comprises the following steps:
  • step (3) The materials obtained by mixing in step (2) are subjected to vacuum freeze-drying.
  • the silicon source is selected from at least one of elemental silicon, SiOx and silicon-containing alloys, wherein 0.6 ⁇ x ⁇ 1.5; preferably, the silicon-containing alloy is selected from silicon -At least one of aluminum alloy, silicon-magnesium alloy, silicon-zirconium alloy and silicon-boron alloy;
  • the carbon source is selected from at least one of petroleum pitch, coal tar pitch, natural pitch and modified pitch;
  • the mass ratio of the silicon source to the carbon source is 1: (0.04-0.12).
  • the silicon source and the carbon source to the organic solvent, and then perform ultrasonic stirring, preferably the ultrasonic stirring time is 10-100 min;
  • the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone;
  • the firing conditions include: in an inert atmosphere, a temperature of 600-1000°C, preferably 700-900°C; and a time of 10-240 min, preferably 20-60 min.
  • organic lithium salt is selected from the group consisting of lithium polyacrylate, lithium polymethacrylate, lithium polymaleate, lithium polyfumarate, carboxymethyl fiber At least one of lithium and lithium alginate;
  • the amount of the organic lithium salt is 0.05-0.5 parts by weight, preferably 0.1-0.4 parts by weight;
  • the mixing in step (2) includes: adding the calcined product and organic lithium salt obtained in step (1) into the solvent, and stirring for 4-48 hours.
  • the conditions of the vacuum freeze-drying include: the temperature is not higher than -65°C, the vacuum degree is not higher than 120pa, and the time is 4-48h.
  • step (4) comprises: mixing the product obtained by vacuum freeze-drying in step (3) with graphite;
  • the amount of graphite used is 1-15 parts by weight, preferably 1-5 parts by weight.
  • a lithium ion battery comprising the silicon carbon negative electrode material of any one of items 1-5 and 13, a positive electrode material containing lithium element, a separator, and an electrolyte;
  • the lithium ion battery is a liquid lithium ion battery, a semi-solid lithium ion battery or an all solid state lithium ion battery.
  • the negative electrode material with core-shell structure provided by the present invention contains lithium element, and at least a part of lithium element is intercalated in the porous carbon film in the form of ions, which can not only solve the problem of low reversible charging capacity and low first-time coulombic efficiency of traditional silicon-based negative electrodes
  • the problem can also suppress the problems of electrode material powdering and uncontrollable growth of SEI film caused by the "volume effect" in the charge and discharge process of traditional silicon-based negative electrodes.
  • the negative electrode material provided by the present invention does not require pre-lithiation treatment during use, which greatly increases the reversible charging capacity of the negative electrode material, and can significantly increase the energy density of the lithium battery.
  • Figure 1 is a TEM photograph of the negative electrode material S-1 prepared in Example 1, where A is a nano silicon core and B is a shell;
  • Example 2 is a full spectrum analysis diagram of the X-ray photoelectron spectroscopy of the anode material S-1 prepared in Example 1;
  • Example 3 is an X-ray photoelectron spectroscopy Li1s spectrum analysis diagram of the anode material S-1 prepared in Example 1;
  • Figure 6 is the first charge and discharge curve of the negative electrode material D-1 prepared in Comparative Example 1;
  • Figure 7 is a cycle stability test curve of the negative electrode material D-1 prepared in Comparative Example 1;
  • the core-shell structure refers to a material (such as the carbon source and organic lithium salt in the present invention) that uniforms another material (such as the silicon source in the present invention) through chemical bonds or other forces.
  • package and form an assembled structure Preferably, the anode material with a core-shell structure of the present invention has a nanometer scale.
  • the median particle size refers to the particle size corresponding to the cumulative particle size distribution percentage reaching 50%, and the median particle size is often used to indicate the average particle size of the powder.
  • the median particle size of the negative electrode material can be obtained by dynamic light scattering characterization.
  • the first aspect of the present invention provides a negative electrode material, the negative electrode material has a core-shell structure, the core includes a silicon-containing material, the shell includes an organic lithium salt and a porous carbon film, wherein at least a part of the lithium ion intercalation layer is Among the porous carbon membranes.
  • the adoption of this embodiment is not only beneficial to increase the transmission rate of lithium ions, but also can significantly improve the first coulombic efficiency of the material.
  • the negative electrode material further contains a phosphorus-containing coating layer.
  • the phosphorus-containing coating layer is located between the core and the shell.
  • the phosphorus-containing coating layer includes a polymer having a fused-ring aromatic structure segment.
  • the 13 C-NMR spectrum of the polymer with fused ring aromatic structure fragments has a signal peak at the position of 110 ppm to 140 ppm, thereby showing the presence of fused ring aromatic structure fragments.
  • 13 C-NMR spectra involving chemical shifts of fused ring aromatic hydrocarbons are disclosed in the following documents: Harris, KJ, Reeve ZEM, et al. Electrochemical Changes in Lithium-Battery Electrodes Studied Using 7 Li NMR and Enhanced 13 C NMR of Graphene and Graphitic Carbons[J].Chem.Mater.2015, 27, 9, 3299-3305, the full text of which is incorporated herein by reference.
  • the phosphorus in the phosphorus-containing coating layer and the silicon in the silicon-containing substance are connected by a chemical bond, preferably the chemical bond is P(O)-O-Si.
  • the connection of phosphorus and silicon through P(O)-O-Si can be characterized by X-ray photoelectron spectroscopy or 29 Si-NMR spectroscopy.
  • the negative electrode material further contains graphite.
  • the theoretical capacity of carbon is much lower than that of silicon
  • the introduction of graphite into the negative electrode material can compensate for the lower conductivity of silicon, and can also greatly improve the cycle charge capacity retention rate.
  • the use of graphite also does not have the problem of volume expansion experienced by silicon anode materials during charging and discharging.
  • the present invention does not specifically limit the location of graphite. During the preparation process, due to different preparation methods, it may exist in the core, in the shell, or in the core and the shell at the same time.
  • the graphite is present in the core and/or shell.
  • the silicon-containing substance is selected from at least one of elemental silicon, SiOx and silicon-containing alloy, wherein 0.6 ⁇ x ⁇ 1.5.
  • the silicon-containing material can be obtained commercially, or can be prepared by an existing method.
  • the silicon-containing alloy is selected from at least one of silicon-aluminum alloy, silicon-magnesium alloy, silicon-zirconium alloy, and silicon-boron alloy.
  • the present invention has a wide selection range for the content of silicon in the silicon-containing alloy. For example, based on the total amount of the silicon-containing alloy, the silicon content is 10-50% by weight.
  • the present invention does not specifically limit the preparation method of the silicon-containing alloy.
  • a specific preparation method of the silicon-containing alloy is now provided, and the present invention is not limited to this.
  • the preparation method of silicon-aluminum alloy preferably includes the following steps: 1) ball milling aluminum powder and silicon powder under the protection of an inert atmosphere for 30 minutes; 2) treating the above mixture at a high temperature at 900° C. for 10 hours.
  • the organic lithium salt is preferably a salt formed by a compound containing an organic acid functional group (preferably a carboxyl group) and a lithium-containing basic compound.
  • the organic lithium salt is selected from at least one of lithium polyacrylate, lithium polymethacrylate, lithium polymaleate, lithium polyfumarate, lithium carboxymethyl cellulose, and lithium alginate.
  • the present invention has a wide selection range for the molecular weight of the above-mentioned organic lithium salt.
  • the weight average molecular weight of the organic lithium salt is 2,000-5,000,000, more preferably 80,000-300,000.
  • the content of each component can be selected in a wide range.
  • the content of the organic lithium salt is 5-34% by weight.
  • the content of the porous carbon film is 65-90% by weight, and the content of the porous carbon film is 1-10% by weight; more preferably, based on the total amount of the negative electrode material, the content of the organic lithium salt is 10-30% by weight,
  • the content of the silicon-containing substance is 68-86 wt%, and the content of the porous carbon film is 1-6% by weight.
  • the negative electrode material further contains graphite; further preferably, the graphite is present in the core and/or shell, more preferably in the shell.
  • the present invention has a wide selection range for the content of the graphite.
  • the mass ratio of the total amount of the silicon-containing material, the organic lithium salt and the porous carbon film to the graphite is 1:1-10, more preferably 1:1-5 .
  • the median particle size of the negative electrode material is 0.1-20 ⁇ m, for example, 0.1 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, and any two of these values in the range constituted by Any value of.
  • the second aspect of the present invention provides a method for preparing a negative electrode material, including the following steps:
  • step (3) The materials obtained by mixing in step (2) are subjected to vacuum freeze-drying.
  • the silicon source is the above-mentioned silicon-containing material, or a silicon-containing precursor that can be converted into the above-mentioned silicon-containing material by the calcination. More preferably, the silicon source is the above-mentioned silicon-containing material.
  • the selection of specific types of silicon substances is as described above, and the present invention will not be repeated here.
  • the carbon source is pitch, preferably at least one selected from petroleum pitch, coal tar pitch, natural pitch, and modified pitch.
  • pitch preferably at least one selected from petroleum pitch, coal tar pitch, natural pitch, and modified pitch.
  • the petroleum pitch, coal tar pitch, natural pitch, and modified pitch of the present invention have the meaning conventionally understood by those skilled in the art, and are commercially available.
  • the amount of the carbon source added is related to the amount of the silicon source.
  • the mass ratio of the silicon source to the carbon source is 1:(0.04-0.12), for example, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.10, 1:0.11, 1:0.12, and any value in the range formed by any two of these values.
  • the mixing in step (1) includes: adding a silicon source and a carbon source to an organic solvent, and then performing ultrasonic stirring.
  • the adoption of this preferred embodiment is more conducive to the uniform coating of the carbon source on the silicon surface.
  • the time range for the ultrasonic stirring is relatively wide, and the silicon source and the carbon source can be dispersed in the organic solvent as the criterion.
  • the ultrasonic stirring time is 10-100 min, and more preferably 20-60min.
  • the organic solvent may be an organic solvent commonly used in the art, preferably at least one of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone .
  • the invention has a wide selection range for the addition amount of the organic solvent, for example, the solid content of the slurry obtained by mixing is 10-35 wt%.
  • the method further includes, after the mixing in step (1), separating the mixed materials, and subjecting the separated solid to the roasting.
  • the separation may be a conventional separation method in the art, such as centrifugal separation.
  • the method further includes drying the separated solid, and then performing the roasting.
  • the present invention has a wide selection range for the drying conditions.
  • the temperature is 80-150°C and the time is 1-10h.
  • the firing conditions include: in an inert atmosphere, a temperature of 600-1000°C, preferably 700-900°C; and a time of 10-240 min, preferably 20-60 min.
  • the inert atmosphere may be provided by at least one of nitrogen, helium, argon, and krypton.
  • the embodiment of the present invention takes nitrogen as an example for illustration, and the present invention is not limited to this.
  • the present invention does not specifically limit the heating rate of the calcination, for example, it can be 1-10°C/min. In the embodiment of the present invention, 5° C./min is taken as an example for illustrative description, and the present invention is not limited to this.
  • the method includes the step (2) after the calcined product obtained in step (1) is cooled (preferably below 50°C, for example, room temperature 25°C).
  • the cooling may be natural cooling.
  • the type of the organic lithium salt is selected as described above, and the present invention will not be repeated here.
  • the amount of the organic lithium salt is 0.05-0.5 parts by weight, preferably 0.1-0.4 parts by weight.
  • the specific method of mixing the calcined product obtained in step (1) of step (2) and the organic lithium salt is not particularly limited.
  • the mixing in step (2) includes: obtaining step (1)
  • the calcined product and the organic lithium salt are added to the solvent and stirred for 4-48h.
  • the present invention has a wide selection range for the addition amount of the solvent, for example, the solid content of the slurry obtained by mixing is 10-35 wt%.
  • the solvent is water.
  • the vacuum freeze-drying in step (3) of the present invention can ensure the structure of the porous carbon calcined in step (1), and at least a part of the lithium ion is intercalated in the porous carbon film.
  • the vacuum freeze-drying conditions in step (3) include: the temperature is not higher than -65°C, preferably -80°C to -65°C; the vacuum degree is not higher than 120pa, preferably 90-120pa.
  • the present invention has a wide selection range for the vacuum freeze-drying time.
  • the vacuum freeze-drying time is 4-48h, preferably 8-32h.
  • the method also preferably includes, before step (1), forming a phosphorus-containing coating layer, for example, by the following method: (a) contacting a silicon-containing substance, a phosphorus source and a solvent at 30-80°C, so that The phosphorus source is distributed on the periphery of the silicon-containing material; and (b) temperature-programmed roasting is performed to convert the phosphorus source on the periphery of the silicon-containing material into a polymer containing fused-ring aromatic structure fragments, wherein the temperature-programmed roasting includes:
  • the phosphorus source is any phosphorus-containing precursor that can be converted into a polymer containing fused ring aromatic structural fragments, for example, by condensation polymerization.
  • the phosphorus source is selected from organic polybasic phosphoric acid and its esters or salts, and the preferable organic polybasic phosphoric acid is phytic acid.
  • the solvent is at least one of toluene, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.
  • the amount of the solvent added is such that the solid content of the material in step (a) is 5-40% by weight.
  • the temperature programmed roasting includes: heating at a first temperature rise rate of 1-10°C/min, preferably 5-10°C/min to a first temperature of 450-500°C, such as 480°C; The temperature is increased to a second temperature of 600-650°C, such as 620°C at a second temperature increase rate of 1-3°C/min, preferably 1-3°C/min; the temperature is maintained at the second temperature for 1-8h, preferably 2-4h.
  • the method preferably also includes a step of introducing graphite.
  • the graphite can be introduced in step (1) and/or step (2), or can be introduced after step (3).
  • the preparation method further includes introducing graphite in step (1) and/or step (2).
  • the specific implementation introduced in step (1) includes, but is not limited to, mixing a silicon source, a carbon source, and graphite, and then firing.
  • the specific embodiments introduced in step (2) include, but are not limited to, mixing the calcined product obtained in step (1), organic lithium salt, and graphite.
  • the preparation method further includes step (4), and the step (4) includes: mixing the product obtained by vacuum freeze-drying in step (3) with graphite.
  • the graphite is introduced in step (4). With this preferred embodiment, it is easier to adjust the reversible charging capacity of the prepared negative electrode material.
  • the amount of graphite is 1-15 parts by weight, preferably 1-5 parts by weight.
  • the third aspect of the present invention provides a negative electrode material prepared by the above preparation method.
  • the structure and composition characteristics of the negative electrode material are as described above, and will not be repeated here.
  • the fourth aspect of the present invention provides the application of the above-mentioned negative electrode material in a lithium ion battery.
  • the above-mentioned anode materials Compared with traditional pure graphite anode materials, the above-mentioned anode materials contain silicon with a higher theoretical capacity, so that the reversible charging capacity is significantly improved. Therefore, when the above-mentioned anode materials are used in lithium-ion batteries, the energy density of the lithium battery can be improved.
  • a fifth aspect of the present invention provides a lithium ion battery, which includes the anode material provided by the present invention, a cathode material containing lithium element, a separator, and an electrolyte.
  • the structure of the lithium ion battery provided according to the present invention may be well known to those skilled in the art.
  • the separator is located between the positive electrode sheet and the negative electrode sheet.
  • the positive electrode sheet contains the positive electrode material
  • the negative electrode sheet contains the negative electrode material.
  • the present invention does not specifically limit the specific composition of the lithium element-containing cathode material, and it may be a lithium element-containing cathode material conventionally used in the art.
  • the separator can be selected from various separators used in lithium ion batteries known to those skilled in the art, such as polypropylene microporous membrane, polyethylene felt, glass fiber felt or ultrafine glass fiber paper.
  • the electrolyte may be various conventional electrolytes, such as non-aqueous electrolytes.
  • the non-aqueous electrolyte is a solution of electrolyte lithium salt in a non-aqueous solvent, and conventional non-aqueous electrolytes known to those skilled in the art can be used.
  • the electrolyte can be selected from lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate (LiClO 4 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ) and lithium hexafluorosilicate (LiSiF 6 ).
  • the non-aqueous solvent may be selected from linear acid esters, cyclic acid esters or mixtures thereof.
  • the chain ester may be at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) and dipropyl carbonate (DPC) .
  • the cyclic acid ester may be at least one of ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC).
  • a transmission electron microscope was used to characterize the morphology of the negative electrode material sample.
  • the transmission electron microscope was a transmission electron microscope model JEM-2100 manufactured by JEOL Ltd., and the test conditions: an acceleration voltage of 160KV, and the sample was placed on a copper support.
  • An electron microscope was inserted behind the net for observation, and a magnification of 800,000 times was used for the observation.
  • the negative electrode material samples were characterized by ESCALAB 250Xi X-ray photoelectron spectroscopy tester from ThermoFisher Scientific, USA.
  • the test conditions include: room temperature 25°C, vacuum degree less than 5 ⁇ 10 -10 mba, working voltage 15KV, and Al K ⁇ as radiation Source, full spectrum pass energy 100eV, step size 1.0eV.
  • the negative electrode material samples were characterized by ESCALAB 250Xi X-ray photoelectron spectroscopy tester from ThermoFisher Scientific, USA.
  • the test conditions include: room temperature 25°C, vacuum degree less than 5 ⁇ 10 -10 mba, working voltage 15KV, and Al K ⁇ as radiation Source, narrow spectrum pass energy is 30eV, step length is 0.05eV, beam spot is 500 ⁇ m.
  • the anode materials prepared in the following examples and comparative examples were assembled into lithium-ion battery samples, and the electrochemical performance of the assembled lithium-ion battery samples was tested using Wuhan blue battery test system (CT2001B). Test conditions include: voltage range 0.005V-3V. Assemble 10 samples in the form of button batteries for each negative electrode material sample, test the battery performance of the samples under the same voltage and current, and take the average value as the measurement value.
  • the battery test system (CT2001B) will give the first discharge capacity and the first charge capacity of the test battery sample.
  • the first discharge capacity is the specific capacity of the negative electrode material used, and the first charge capacity is the reversible charge capacity of the negative electrode material used.
  • the first Coulomb efficiency (referred to as "first effect") can be calculated through the two:
  • the first Coulomb efficiency the reversible charge capacity of the negative electrode material/the specific capacity of the negative electrode material.
  • Capacity retention rate At a rate of 0.2C, perform a selected number of times for the assembled lithium ion battery sample, such as 20, 50 or 100 charge and discharge cycles, measure the reversible charge capacity of the sample at each cycle, and calculate the cycle charge for each cycle. Capacity retention rate, where:
  • Cycle charge capacity retention rate reversible charge capacity under the corresponding cycle number/reversible charge capacity at the first charge ⁇ 100%
  • petroleum bitumen is commercially purchased from Tapco, under the brand name PMA.
  • the coal tar pitch was purchased from Longxin Material Trade Co., Ltd., and the grade is low temperature pitch (100-115).
  • the lithium polyacrylate is prepared by self-preparation, which specifically includes: taking 10 g of polyacrylic acid with a weight average molecular weight of 240,000 and adding it to 40 g of deionized water to prepare a polyacrylic acid solution with a mass fraction of 20%. Weigh 3.4 g of lithium hydroxide, add it to the above polyacrylic acid solution, heat and stir at 40°C until all solids are dissolved, and dry at 100°C for 4 hours to obtain lithium polyacrylate.
  • the lithium polymethacrylate is prepared by self-preparation, which specifically includes: taking 10 g of polymethacrylic acid with a weight average molecular weight of 240,000 and adding it to 40 g of deionized water to prepare a polymethacrylic acid solution with a mass fraction of 20%. Weigh 3.4 g of lithium hydroxide, add it to the above polymethacrylic acid solution, heat and stir at 40°C until all solids are dissolved, and dry at 100°C for 4 hours to obtain lithium polymethacrylate.
  • the lithium polymaleate is obtained by self-preparation, and specifically includes: taking 10 g of polymaleic acid with a weight average molecular weight of 240,000 and adding it to 40 g of deionized water to prepare a polymaleic acid solution with a mass fraction of 20%. Weigh 3.4 g of lithium hydroxide, add it to the polymaleic acid solution, heat and stir at 40°C until all solids are dissolved, and dry at 100°C for 4 hours to obtain polylithium maleate.
  • the lithium polyfumarate is prepared by itself, and specifically includes: taking 10 g of polyfumaric acid with a weight average molecular weight of 240,000 and adding it to 40 g of deionized water to prepare a polyfumaric acid solution with a mass fraction of 20%. Weigh 3.4g of lithium hydroxide, add it to the above polyfumaric acid solution, heat and stir at 40°C until all solids are dissolved, and dry at 100°C for 4h to obtain polylithium fumarate.
  • the lithium carboxymethyl cellulose is prepared by self-preparation, which specifically includes: taking 10 g of sodium carboxymethyl cellulose with a weight average molecular weight of 120,000 and adding it to 40 g of deionized water to prepare a 20% sodium carboxymethyl cellulose solution. Weigh 3.1 g of lithium hydroxide, add it to the above sodium carboxymethylcellulose solution, heat and stir at 40°C until all solids are dissolved, and dry at 100°C for 4 hours to obtain lithium carboxymethylcellulose.
  • Lithium alginate is obtained by self-preparation, which specifically includes: taking 10 g of sodium alginate with a weight average molecular weight of 80,000 and adding it to 40 g of deionized water to prepare a sodium alginate solution with a mass fraction of 20%. Weigh 1.2 g of lithium hydroxide, add it to the sodium alginate solution, heat and stir at 40°C until all solids are dissolved, and dry at 100°C for 4 hours to obtain lithium alginate.
  • polyacrylic acid polymethacrylic acid
  • polymaleic acid polymaleic acid
  • polyfumaric acid sodium carboxymethyl cellulose
  • sodium alginate commercially purchased from Aladdin Reagent Company.
  • the room temperature refers to 25°C.
  • step (3) Put the pitch-coated silicon obtained in step (2) in a tube furnace, raise the temperature to 800°C at a rate of 5°C/min, and keep it in a nitrogen atmosphere for 30 minutes. After the end, it is naturally cooled to room temperature to obtain carbon. Coated with silicon.
  • Fig. 1 is a TEM photograph of the lithium-containing negative electrode S-1. It can be seen from the figure that the nano silicon particles are evenly wrapped and have a core-shell structure, and the outer surface of the core is covered with a porous carbon film.
  • Figure 2 is a full spectrum analysis diagram of the X-ray photoelectron spectroscopy of the lithium-containing negative electrode material S-1. It can be seen from the figure that the negative electrode material contains lithium, carbon, and silicon elements.
  • Fig. 3 is a Li1s spectrum of the lithium-containing negative electrode material S-1. As shown in Figure 3, a significant signal peak appears at the binding energy of 64.1 eV. This signal peak corresponds to the LiC 6 complex.
  • the formation of the LiC 6 composite means that Li + migrates between the carbon atom sheets in the porous carbon film, that is, the lithium ion is intercalated in the porous carbon film.
  • the lithium-containing negative electrode material S-1 and the metal lithium sheet obtained in Example 1 were used as the positive electrode and the negative electrode, respectively, and a 1 mol/L LiPF 6 solution (ethylene carbonate and diethyl carbonate mixed in a 3:7 volume ratio as a solvent) It is an electrolyte and a polypropylene microporous membrane is a separator, assembled into a sample in the form of a CR2016 button battery.
  • the electrical properties of the battery sample are measured as described above to characterize the electrical properties of the lithium-containing negative electrode material S-1 of Example 1. .
  • FIG. 4 is the first charge and discharge curve of the coin battery based on the lithium-containing negative electrode material S-1 of Example 1.
  • FIG. As shown in the figure, the reversible charging capacity of the lithium-containing negative electrode material S-1 in Example 1 is 3000 mAh/g, and the first coulombic efficiency is 86.9%.
  • FIG. 5 is a cycle stability test curve of a button battery based on the lithium-containing negative electrode material S-1 of Example 1.
  • FIG. 5 As shown in the figure, the lithium-containing negative electrode material S-1 of Example 1 has a charge capacity retention rate of about 92% after 20 cycles at a charge-discharge rate of 0.2C.
  • step (3) Put the pitch-coated silicon obtained in step (2) in a tube furnace, raise the temperature to 800°C at a rate of 5°C/min, and keep it in a nitrogen atmosphere for 30 minutes. After the end, it is naturally cooled to room temperature to obtain carbon. Cover silicon and use it as negative electrode material D-1.
  • the battery was assembled and tested for electrical performance according to the method of Example 1, except that the lithium-containing anode material S-1 was replaced with the anode material D-1 prepared in Comparative Example 1.
  • FIG. 6 is the first charge and discharge curve of the coin battery based on the negative electrode material D-1 of Comparative Example 1.
  • FIG. 6 As shown in the figure, the reversible charging capacity of the negative electrode material of Comparative Example 1 is 908 mAh/g, and the first coulombic efficiency is 38.9%.
  • FIG. 7 is a cycle stability test curve of a coin battery based on the negative electrode material of Comparative Example 1.
  • FIG. As shown in the figure, the negative electrode material of Comparative Example 1 has a charge capacity retention rate of 6% after 12 cycles at a charge-discharge rate of 0.2C.
  • the difference is that the stirred slurry is placed in air for drying (temperature is 100° C.), and dried for 12 hours to obtain lithium-containing negative electrode material D-2.
  • Fig. 8 is a Li1s spectrum of the lithium-containing negative electrode material D-2. As shown in Figure 8, there is a signal peak at the binding energy of 56.3eV, where it is attributed to the signal peak of organic lithium salt (lithium polyacrylate), and there is no signal peak at the binding energy corresponding to the LiC 6 complex of 64.1eV. A significant signal peak was found. This means that no lithium ion intercalation has occurred in the porous carbon film.
  • the battery was assembled and tested for electrical performance according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Comparative Example 2.
  • the test results show that the reversible charging capacity of the material in Comparative Example 2 is 795mAh/g, and the first coulombic efficiency is 36.3%.
  • the material is at a charge-discharge rate of 0.2C and after 20 cycles, the charge capacity retention rate is about 30%.
  • the difference is that the lithium polyacrylate is replaced with the same mass of lithium carbonate to obtain the lithium-containing negative electrode material D-3.
  • the battery was assembled and tested for electrical performance according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Comparative Example 3.
  • the test results show that the reversible charging capacity of the material in Comparative Example 3 is 820mAh/g, and the first coulombic efficiency is 31%.
  • the material is at a charge-discharge rate of 0.2C and after 10 cycles, the charge capacity retention rate is about 10%.
  • step (3) Put the pitch-coated silicon obtained in step (2) in a tube furnace, raise the temperature to 800°C at a rate of 5°C/min, and keep it in a nitrogen atmosphere for 30 minutes. After the end, it is naturally cooled to room temperature to obtain carbon. Coated with silicon.
  • the TEM image of the lithium-containing anode material S-2, the full spectrum analysis chart of X-ray photoelectron spectroscopy, and the Li1s spectrum analysis chart of X-ray photoelectron spectroscopy are similar to Figures 1 to 3, respectively, indicating the prepared lithium-containing anode
  • the material S-2 has a core-shell structure, the outer surface of the core is covered with a porous carbon film, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled and tested for electrical performance according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 2.
  • the test results show that the reversible charge capacity of the material described in Example 2 is 2812mAh/g, the first coulombic efficiency is 87.6%, and the charge capacity retention rate of the material is about 0.2C after 15 cycles. 90%.
  • step (3) Put the pitch-coated silicon obtained in step (2) in a tube furnace, heat it up to 700°C at a rate of 5°C/min, and keep it in a nitrogen atmosphere for 30 minutes. After the end, it is naturally cooled to room temperature to obtain carbon Coated with silicon.
  • the TEM image, X-ray photoelectron spectroscopy full spectrum analysis graph and X-ray photoelectron spectroscopy Li1s spectrum analysis graph of the lithium-containing anode material S-3 are similar to Figures 1 to 3, respectively, indicating the prepared lithium-containing anode
  • the material S-3 has a core-shell structure, the outer surface of the core is covered with a porous carbon film, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled according to the method of Example 1 and the electrical performance test was performed, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 3.
  • the test results show that the reversible charge capacity of the material described in Example 3 is 2760mAh/g, the first coulombic efficiency is 89.3%, and the charge capacity retention rate of the material is about 0.2C after 15 cycles at a charge-discharge rate of 0.2C. 85%.
  • step (3) Place the pitch-coated silicon obtained in step (2) in a tube furnace, heat it up to 900°C at a rate of 5°C/min, and keep it in a nitrogen atmosphere for 30 minutes. After the end, it is naturally cooled to room temperature to obtain carbon. Coated with silicon.
  • the TEM image of the lithium-containing anode material S-4, the full spectrum analysis chart of X-ray photoelectron spectroscopy, and the Li1s spectrum analysis chart of X-ray photoelectron spectroscopy are similar to Figures 1 to 3, respectively, indicating the prepared lithium-containing anode
  • the material S-4 has a core-shell structure, the outer surface of the core is covered with a porous carbon film, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled according to the method of Example 1 and the electrical performance test was performed, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 4.
  • the test results show that the reversible charge capacity of the material described in Example 4 is 2720 mAh/g, the first coulombic efficiency is 87.9%, and the charge capacity retention rate of the material is about 0.2C after 15 cycles at a charge-discharge rate of 0.2C. 85%.
  • step (3) Put the pitch-coated silicon obtained in step (2) in a tube furnace, raise the temperature to 800°C at a rate of 5°C/min, and keep it in a nitrogen atmosphere for 30 minutes. After the end, it is naturally cooled to room temperature to obtain carbon. Coated with silicon.
  • the TEM image, X-ray photoelectron spectroscopy full spectrum analysis graph and X-ray photoelectron spectroscopy Li1s spectrum analysis graph of lithium-containing anode material S-5 are similar to Figures 1 to 3, respectively, indicating the prepared lithium-containing anode
  • the material S-5 has a core-shell structure, the outer surface of the core is covered with a porous carbon film, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled and the electrical performance test was performed according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 5.
  • the test results show that the reversible charge capacity of the material described in Example 5 is 2870mAh/g, and the first coulombic efficiency is 86.1%.
  • the material is charged and discharged at a rate of 0.2C and after 18 cycles, the charge capacity retention rate is about 91%.
  • step (3) Put the pitch-coated silicon obtained in step (2) in a tube furnace, raise the temperature to 800°C at a rate of 5°C/min, and keep it in a nitrogen atmosphere for 30 minutes. After the end, it is naturally cooled to room temperature to obtain carbon. Coated with silicon.
  • step (3) Take 0.15 g of lithium polyacrylate and place it in 3 mL of deionized water together with the carbon-coated silicon obtained in step (3), and stir for 12 hours at room temperature. Subsequently, the stirred slurry was placed in a freeze-vacuum drying box with a cold trap temperature of -80°C and a cavity vacuum of 100 Pa, and dried for 12 hours.
  • step (4) The product obtained by drying in step (4) is blended with artificial graphite in a mass ratio of 1:4 to obtain a lithium-containing negative electrode material S-6 with a design capacity of 900 mAh/g.
  • the median diameter of the lithium-containing negative electrode material S-6 and the content of each component are listed in Table 1.
  • the TEM image, X-ray photoelectron spectroscopy full spectrum analysis graph and X-ray photoelectron spectroscopy Li1s spectrum analysis graph of lithium-containing anode material S-6 are similar to Figures 1 to 3, respectively, indicating the prepared lithium-containing anode
  • the material S-6 has a core-shell structure, the outer surface of the core is covered with a porous carbon film and graphite, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled and tested for electrical performance according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 6.
  • the test results show that the reversible charging capacity of the material described in Example 6 is 912mAh/g, and the first coulombic efficiency is 90.6%.
  • the material is at a charge-discharge rate of 0.2C and after 100 cycles, the charge capacity retention rate is about 96%.
  • step (3) Put the pitch-coated silicon obtained in step (2) in a tube furnace, raise the temperature to 800°C at a rate of 5°C/min, and keep it in a nitrogen atmosphere for 30 minutes. After the end, it is naturally cooled to room temperature to obtain carbon. Coated with silicon.
  • step (3) Take 0.15 g of lithium polyacrylate and place it in 3 mL of deionized water together with the carbon-coated silicon obtained in step (3), and stir for 12 hours at room temperature. Subsequently, the stirred slurry was placed in a freeze-vacuum drying box with a cold trap temperature of -80°C and a cavity vacuum of 100 Pa, and dried for 12 hours.
  • step (4) The product obtained by drying in step (4) is blended with artificial graphite in a mass ratio of 1:5 to obtain a lithium-containing negative electrode material S-7 with a design capacity of 700 mAh/g.
  • the median diameter of the lithium-containing negative electrode material S-7 and the content of each component are listed in Table 1.
  • the TEM image, X-ray photoelectron spectroscopy full spectrum analysis graph and X-ray photoelectron spectroscopy Li1s spectrum analysis graph of lithium-containing anode material S-7 are similar to Figures 1 to 3, respectively, indicating the prepared lithium-containing anode
  • the material S-7 has a core-shell structure, the outer surface of the core is covered with a porous carbon film and graphite, and the lithium ion is intercalated in the porous carbon film.
  • the battery was assembled and tested for electrical performance according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 7.
  • the test results show that the reversible charge capacity of the material described in Example 7 is 752mAh/g, the first coulombic efficiency is 91.2%, and the charge capacity retention rate of the material is about 96%.
  • step (3) Put the pitch-coated silicon obtained in step (2) in a tube furnace, raise the temperature to 800°C at a rate of 5°C/min, and keep it in a nitrogen atmosphere for 30 minutes. After the end, it is naturally cooled to room temperature to obtain carbon. Coated with silicon.
  • step (3) Take 0.15 g of lithium polyacrylate and place it in 3 mL of deionized water together with the carbon-coated silicon obtained in step (3), and stir for 12 hours at room temperature. Subsequently, the stirred slurry was placed in a freeze-vacuum drying box with a cold trap temperature of -80°C and a cavity vacuum of 100 Pa, and dried for 12 hours.
  • step (4) The product obtained by drying in step (4) is blended with artificial graphite in a mass ratio of 1:1 to obtain a lithium-containing negative electrode material S-8 with a design capacity of 1500 mAh/g.
  • the median diameter of the lithium-containing negative electrode material S-8 and the content of each component are listed in Table 1.
  • the TEM image, X-ray photoelectron spectroscopy full spectrum analysis graph and X-ray photoelectron spectroscopy Li1s spectrum analysis graph of the lithium-containing anode material S-8 are similar to Figures 1 to 3, respectively, indicating the prepared lithium-containing anode
  • the material S-8 has a core-shell structure, the outer surface of the core is covered with a porous carbon film and graphite, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled and tested for electrical performance according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 8.
  • the test results show that the reversible charging capacity of the material described in Example 8 is 1512mAh/g, and the first coulombic efficiency is 88.9%.
  • the material is charged and discharged at a rate of 0.2C and after 150 cycles, the charge capacity retention rate is about 90%.
  • step (3) Put the pitch-coated silicon oxide obtained in step (2) in a tube furnace, raise the temperature to 750°C at a rate of 5°C/min, and keep the temperature in a nitrogen atmosphere for 30 minutes, and then naturally cool to room temperature after the end. Obtain carbon-coated silicon oxide.
  • the TEM image of the lithium-containing silicon oxide anode material S-9, the full spectrum analysis image of X-ray photoelectron spectroscopy, and the Li1s spectrum analysis image of X-ray photoelectron spectroscopy are similar to Figures 1 to 3, respectively.
  • the lithium silicon oxide negative electrode material S-9 has a core-shell structure, the outer surface of the core is covered with a porous carbon film, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled and tested for electrical performance according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 9.
  • the test results show that the reversible charge capacity of the material described in Example 9 is 1632mAh/g, the first coulombic efficiency is 83.1%, and the charge capacity retention rate of the material is about 0.2C after 200 cycles. 90%.
  • step (3) Place the pitch-coated silicon-aluminum alloy obtained in step (2) in a tube furnace, heat it up to 750°C at a rate of 5°C/min, and keep it in a nitrogen atmosphere for 30 minutes, and then naturally cool to room temperature after the end. Get carbon-coated silicon aluminum alloy.
  • the TEM image of the lithium-containing silicon aluminum anode material S-10, the full spectrum analysis image of X-ray photoelectron spectroscopy, and the Li1s spectrum analysis image of X-ray photoelectron spectroscopy are similar to Figures 1 to 3, respectively, indicating that the prepared lithium-containing The silicon-aluminum negative electrode material S-10 has a core-shell structure, the outer surface of the core is covered with a porous carbon film, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled and the electrical performance test was performed according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 10.
  • the test results show that the reversible charge capacity of the material described in Example 10 is 721mAh/g, the first coulombic efficiency is 84.1%, and the charge capacity retention rate of the material is about 0.2C after 200 cycles. 90%.
  • the difference is that the petroleum pitch is replaced with coal tar pitch of equal quality.
  • a lithium-containing negative electrode material S-11 was obtained.
  • the median diameter of the lithium-containing negative electrode material S-11 and the content of each component are listed in Table 1.
  • the TEM image, X-ray photoelectron spectroscopy full spectrum analysis graph and X-ray photoelectron spectroscopy Li1s spectrum analysis graph of the lithium-containing negative electrode material S-11 are similar to Figures 1 to 3, respectively, indicating the prepared lithium-containing negative electrode
  • the material S-11 has a core-shell structure, the outer surface of the core is covered with a porous carbon film, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled and tested for electrical performance according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 11.
  • the test results show that the reversible charge capacity of the material described in Example 11 is 2932mAh/g, the first coulombic efficiency is 88.7%, and the charge capacity retention rate of the material is about 0.2C after 30 cycles. 85%.
  • the difference is that the lithium polyacrylate is replaced with the same mass of lithium polymethacrylate.
  • the lithium-containing negative electrode material S-12 was obtained.
  • the median diameter of the lithium-containing negative electrode material S-12 and the content of each component are listed in Table 1.
  • the TEM image and X-ray photoelectron spectroscopy of the lithium-containing negative electrode material S-12 are similar to Figures 1 to 3, respectively, indicating that the prepared lithium-containing negative electrode material S-12 has a core-shell structure.
  • the outer surface of the core is covered with a porous carbon film, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled according to the method of Example 1 and the electrical performance test was performed, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 12.
  • the test results show that the reversible charge capacity of the material described in Example 12 is 2895mAh/g, the first coulombic efficiency is 87.1%, and the charge capacity retention rate of the material is about 0.2C after 30 cycles. 85%.
  • the difference is that the lithium polyacrylate is replaced with the same mass of lithium polymaleate.
  • a lithium-containing negative electrode material S-13 was obtained.
  • the median diameter of the lithium-containing negative electrode material S-13 and the content of each component are listed in Table 1.
  • the TEM image, X-ray photoelectron spectroscopy full spectrum analysis graph and X-ray photoelectron spectroscopy Li1s spectrum analysis graph of the lithium-containing anode material S-13 are similar to Figures 1 to 3, respectively, indicating the prepared lithium-containing anode
  • the material S-13 has a core-shell structure, the outer surface of the core is covered with a porous carbon film, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled and the electrical performance test was performed according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 13.
  • the test results show that the reversible charge capacity of the material described in Example 13 is 2925mAh/g, the first coulombic efficiency is 86.8%, and the charge capacity retention rate of the material is about 0.2C after 30 cycles. 85%.
  • the difference is that the lithium polyacrylate is replaced with the same mass of lithium polyfumarate.
  • the lithium-containing negative electrode material S-14 was obtained.
  • the median diameter of the lithium-containing negative electrode material S-14 and the content of each component are listed in Table 1.
  • the TEM image of the lithium-containing anode material S-14, the full spectrum analysis image of X-ray photoelectron spectroscopy, and the Li1s spectrum analysis image of X-ray photoelectron spectroscopy are similar to Figures 1 to 3, respectively, indicating the prepared lithium-containing anode
  • the material S-14 has a core-shell structure, the outer surface of the core is covered with a porous carbon film, and lithium ions are intercalated in the porous carbon film.
  • the battery was assembled and tested for electrical performance according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material prepared in Example 14.
  • the test results show that the reversible charge capacity of the material described in Example 14 is 2963mAh/g, the first coulombic efficiency is 86.5%, and the charge capacity retention rate of the material is about 0.2C after 30 cycles. 85%.
  • the battery was assembled and the electrical performance test was performed according to the method of Example 1, except that the lithium-containing negative electrode material S-1 was replaced with the material S-15 prepared in Example 15.
  • the test results show that the reversible charge capacity of the material described in Example 15 is 3480mAh/g, the first coulombic efficiency is 91.2%, and the charge capacity retention rate of the material is 94.8 after 30 cycles at a charge-discharge rate of 0.2C. %.
  • the negative electrode material provided by the present invention can increase the reversible charging capacity of the negative electrode material, and can increase the energy density of the lithium battery when applied to a lithium ion battery. More importantly, the negative electrode material provided by the present invention achieves both excellent first charging efficiency and cycle charging capacity retention rate, especially in a longer cycle period.

Abstract

本发明涉及锂离子电池领域。公开了负极材料及其制备方法和应用以及锂离子电池。所述负极材料具有核壳结构，所述核中包括含硅物质，所述壳中包括有机锂盐和多孔碳膜，并且至少一部分锂离子插层在所述多孔碳膜之中。其制备方法包括：(1)将硅源与碳源混合，然后焙烧；(2)将步骤(1)得到的焙烧产物与有机锂盐混合；(3)将步骤(2)混合得到的物料进行真空冷冻干燥。本发明所提供的负极材料具有提高的可逆充电容量，应用于锂离子电池中可以提高锂电池的能量密度。

Description

负极材料及其制备方法和应用以及锂离子电池 技术领域
本发明涉及锂离子电池领域，具体涉及具有核壳结构的负极材料及其制备方法和应用以及锂离子电池。
背景技术
硅的理论比容量为4200mAh/g，是目前克容量最高的电池负极材料，一旦成功应用，能显著提升锂电池的能量密度，使得一次充电续航1000公里成为可能。然而，硅的充放电机理和石墨的充放电机理不同，充放电过程中Si与电解液中Li+在界面处会不断生成固体电解质(SEI)薄膜，不可逆SEI的形成大量消耗了电解液和正极材料脱出的Li，导致硅基负极材料首次库伦效率(可以简称“首效”)仅在65-85％之间，造成极大的容量损失。另一方面，硅的电导率、锂离子扩散速度均低于石墨，这将限制硅在大电流大功率条件下的性能表现。
为解决上述问题，科研人员采用掺杂、纳米化等工艺来提高硅基负极材料的综合电性能。公开号为CN101179126B的中国专利报道了一种用于锂离子电池的掺杂型硅基负极材料，其通过掺杂硼、铝、镓、锑和磷中至少一种元素，材料的首次库伦效率得到提升。CN101179126B在制备过程中需要进行高真空氩弧熔融焊接，反应温度高(＞1000℃)，反应工艺复杂(涉及熔融焊接、低温吹炼、快速冷却，行星球磨等操作)，成本较高。CN108172775A报道了一种磷掺杂的硅基负极材料，实施例中磷掺杂的硅基负极比容量为610.1mAh/g时，首效为91.7％。CN108172775A制备过程需要喷雾干燥，产量低成本高。CN103400971A报道了硅酸锂掺杂的负极材料，Si添加量为50％，Li 2SiO 3添加量为35％时，材料的比容量为1156.2mAh/g，首效为88.2％，该材料的循环稳定性和首次库伦效率仍有待提高。CN111653738A报道了无定型碳包覆的硅碳负极材料，所述材料具有核壳结构，当可逆充电容量为1765.54mAh/g时，首效为84.38％，50次循环的充电容量保留率为82.24％，仍有待提高。
如上所述，虽然硅基负极材料的改造已经获得了一些进步，但是通常仅能提升硅基负极材料的一个性能，而不是提升其综合电性能。 而在可操作地用于高能量密度锂离子电池时，却希望负极材料同时具有优良的可逆充电容量、首效和循环充电容量保留率，特别是同时具有优良的首效和循环充电容量保留率。鉴于以上情况，仍然需要开发同时具有改善的首效、可逆充电容量、循环充电容量保留率和导电性的硅基负极材料。另外，还需要一种操作简单的制备硅基负极材料的方法。
发明内容
本发明的目的是为了克服现有技术存在的硅基负极材料可逆充电容量低、首次库伦效率低的问题，提供一种具有核壳结构的负极材料、该负极材料的制备方法和该制备方法制得的负极材料以及一种锂离子电池。本公开提供的负极材料具有提高的可逆充电容量(也称为“可逆充电比容量”)和首次库伦效率，特别适用于锂离子电池。
为了实现上述目的，本发明第一方面提供一种负极材料，其具有核壳结构，所述核中包括含硅物质，所述壳中包括有机锂盐和多孔碳膜，其中至少一部分锂离子插层在多孔碳膜之中。
优选地，所述有机锂盐选自聚丙烯酸锂、聚甲基丙烯酸锂、聚马来酸锂、聚富马酸锂、羧甲基纤维素锂和海藻酸锂中的至少一种。
本发明第二方面提供一种负极材料的制备方法，包括以下步骤：
(1)将硅源与碳源混合，然后焙烧；
(2)将步骤(1)得到的焙烧产物与有机锂盐混合；
(3)将步骤(2)混合得到的物料进行真空冷冻干燥。
优选地，所述碳源为沥青，优选选自石油沥青、煤焦沥青、天然沥青和改性沥青中的至少一种。
本发明第三方面提供上述制备方法制得的负极材料。
本发明第四方面提供上述负极材料在锂离子电池中的应用。
本发明第五方面提供一种锂离子电池，所述锂离子电池包括本发明提供的所述的负极材料、含有锂元素的正极材料、隔膜和电解液。
具体地说，本发明可以体现为以下项：
1、一种硅碳负极材料，其特征在于，所述硅碳负极材料具有核壳结构，所述核中包括含硅物质，所述壳中包括有机锂盐和多孔碳膜。
2、第1项的硅碳负极材料，其中，所述核的外表面包覆有多孔碳 膜，所述有机锂盐存在于所述多孔碳膜之中。
3、第1项的硅碳负极材料，其中，以所述硅碳负极材料的总量为基准，所述有机锂盐的含量为5-34重量％，含硅物质的含量为65-90重量％，多孔碳膜的含量为1-10重量％；
优选地，以所述硅碳负极材料的总量为基准，所述有机锂盐的含量为10-30重量％，含硅物质的含量为68-86重量％，多孔碳膜的含量为1-6重量％；
优选地，所述硅碳负极材料中还含有石墨；进一步优选地，所述石墨存在于所述核和/或壳中；
优选地，含硅物质、有机锂盐和多孔碳膜的总量与石墨的质量比为1∶1-10，进一步优选为1∶1-5。
4、第1项的硅碳负极材料，其中，所述硅碳负极材料的中值粒径为0.1-20μm。
5、第1-4项中任意一项的硅碳负极材料，其中，所述有机锂盐选自聚丙烯酸锂、聚甲基丙烯酸锂、聚马来酸锂、聚富马酸锂、羧甲基纤维素锂和海藻酸锂中的至少一种；
优选地，所述含硅物质选自单质硅、SiOx和含硅合金中的至少一种，
其中，0.6＜x＜1.5；优选地，所述含硅合金选自硅-铝合金、硅-镁合金、硅-锆合金和硅-硼合金中的至少一种。
6、一种硅碳负极材料的制备方法，其特征在于，包括以下步骤：
(1)将硅源与碳源混合，然后焙烧；
(2)将步骤(1)得到的焙烧产物与有机锂盐混合；
(3)将步骤(2)混合得到的物料进行真空冷冻干燥。
7、第6项的制备方法，其中，所述硅源选自单质硅、SiOx和含硅合金中的至少一种，其中，0.6＜x＜1.5；优选地，所述含硅合金选自硅-铝合金、硅-镁合金、硅-锆合金和硅-硼合金中的至少一种；
优选地，所述碳源选自石油沥青、煤焦沥青、天然沥青和改性沥青中的至少一种；
优选地，所述硅源与所述碳源的质量比为1∶(0.04-0.12)。
8、第6项的制备方法，其中，步骤(1)所述混合包括：
将硅源、碳源加入有机溶剂中，然后进行超声搅拌，优选超声搅 拌的时间为10-100min；
优选地，所述有机溶剂选自N，N-二甲基甲酰胺、N，N-二甲基乙酰胺和N-甲基吡咯烷酮中的至少一种；
优选地，所述焙烧的条件包括：在惰性气氛下，温度为600-1000℃，优选为700-900℃；时间为10-240min，优选为20-60min。
9、第6-8项中任意一项的制备方法，其中，所述有机锂盐选自聚丙烯酸锂、聚甲基丙烯酸锂、聚马来酸锂、聚富马酸锂、羧甲基纤维素锂和海藻酸锂中的至少一种；
优选地，相对于1重量份的硅源，所述有机锂盐的用量为0.05-0.5重量份，优选为0.1-0.4重量份；
优选地，步骤(2)所述混合包括：将步骤(1)得到的焙烧产物、有机锂盐加入溶剂中，搅拌4-48h。
10、第6-9项中任意一项的制备方法，其中，步骤(3)
所述真空冷冻干燥的条件包括：温度不高于-65℃，真空度不高于120pa，时间为4-48h。
11、第6-10项中任意一项的制备方法，其中，该制备方法还包括在步骤(1)和/或步骤(2)引入石墨。
12、第6-10项中任意一项的制备方法，其中，该制备方法还包括步骤(4)，所述步骤(4)包括：将步骤(3)真空冷冻干燥得到的产物与石墨混合；
优选地，相对于1重量份的步骤(3)真空冷冻干燥得到的产物，所述石墨的用量为1-15重量份，优选为1-5重量份。
13、第6-12项中任意一项的制备方法制得的硅碳负极材料。
14、第1-5和13项中任意一项的硅碳负极材料在锂离子电池中的应用。
15、一种锂离子电池，所述锂离子电池包括第1-5和13项中任意一项的硅碳负极材料、含有锂元素的正极材料、隔膜和电解液；
优选地，所述锂离子电池为液态锂离子电池、半固态锂离子电池或者全固态锂离子电池。
本发明提供的具有核壳结构的负极材料中含有锂元素，并且至少一部分锂元素以离子形式插层在多孔碳膜之中，不但可以解决传统硅基负极可逆充电容量低、首次库伦效率低的问题，还能够抑制传统硅 基负极在充放电过程中由于“体积效应”引发的电极材料粉化、SEI膜不可控增长等问题。本发明所提供的负极材料在使用过程中无需进行预锂化处理，大幅提高了负极材料的可逆充电容量，可显著提高锂电池的能量密度。
附图说明
图1是实施例1制得的负极材料S-1的TEM照片，其中A为纳米硅核，B为壳；
图2是实施例1制得的负极材料S-1的X射线光电子能谱的全谱分析图；
图3是实施例1制得的负极材料S-1的X射线光电子能谱的Li1s谱分析图；
图4是实施例1制得的负极材料S-1的首次充放电曲线；
图5是实施例1制得的负极材料S-1的循环稳定测试曲线；
图6是对比例1中制得的负极材料D-1的首次充放电曲线；
图7是对比例1中制得的负极材料D-1的循环稳定测试曲线；和
图8是对比例2中制得的负极材料D-2的X射线光电子能谱的Li1s谱分析图。
具体实施方式
在本文中所披露的范围的端点和任何值都不限于该精确的范围或值，这些范围或值应当理解为包含接近这些范围或值的值。对于数值范围来说，各个范围的端点值之间、各个范围的端点值和单独的点值之间，以及单独的点值之间可以彼此组合而得到一个或多个新的数值范围，这些数值范围应被视为在本文中具体公开。除了在实施例外，在本文中的所有数值都应理解为在所有情况下均由术语“约”修饰，无论“约”是否实际上出现在该数值之前。
在本说明书中，所述核壳结构，是指一种材料(如本发明中的碳源和有机锂盐)通过化学键或者其他作用力将另一种材料(如本发明中的硅源)均匀的包裹并形成的组装结构。优选地，本发明的具有核壳结构的负极材料具有纳米尺度。
在本说明书中，所述中值粒径，是指累计粒度分布百分数达到50％ 时所对应的粒径，中值粒径常用来表示粉体的平均粒度。在本发明中，无特殊说明情况下，所述负极材料的中值粒径可以通过动态光散射表征获得。
本发明第一方面提供一种负极材料，所述负极材料具有核壳结构，所述核中包括含硅物质，所述壳中包括有机锂盐和多孔碳膜，其中至少一部分锂离子插层在多孔碳膜之中。
采用该种实施方式既有利于提升锂离子的传输速率，又能够显著提高材料的首次库伦效率。根据本发明，优选地，所述负极材料还含有含磷包覆层。所述含磷包覆层位于所述核与所述壳之间。所述含磷包覆层包含具有稠环芳烃结构片段的聚合物。在一个变体中，具有稠环芳烃结构片段的聚合物的 13C-NMR谱图在110ppm-140ppm的位置存在信号峰，从而显示了稠环芳烃结构片段的存在。 13C-NMR谱图中涉及稠环芳烃的化学位移公开在以下文献中：Harris，K.J.，Reeve Z.E.M.，et al.Electrochemical Changes in Lithium-Battery Electrodes Studied Using  7Li NMR and Enhanced  13C NMR of Graphene and Graphitic Carbons[J].Chem.Mater.2015，27，9，3299-3305，在此将其全文引入作为参考。所述含磷包覆层中的磷和所述含硅物质中的硅通过化学键连接，优选所述化学键为P(O)-O-Si。磷与硅通过P(O)-O-Si连接可以通过X射线光电子能谱图来表征，或通过 29Si-NMR谱图来表征。
根据本发明，优选地，所述负极材料中还含有石墨。尽管碳的理论容量远低于硅，但是在负极材料引入石墨可以补偿硅的较低导电率，同时还可以大幅度改善循环充电容量保留率。使用石墨也不存在硅负极材料在充放电时所经历的体积膨胀问题。本发明对于石墨的存在位置没有特别的限定，在制备过程中，由于制备方法的不同，其可以存在于核中，也可以存在于壳中，还可以同时存在于核中和壳中。
根据本发明的一种优选实施方式，所述石墨存在于所述核和/或壳中。
根据本发明，优选地，所述含硅物质选自单质硅、SiOx和含硅合金中的至少一种，其中，0.6＜x＜1.5。所述含硅物质可以通过商购得到，也可以通过现有方法制备得到。
优选地，所述含硅合金选自硅-铝合金、硅-镁合金、硅-锆合金和硅-硼合金中的至少一种。本发明对所述含硅合金中硅的含量选择范围 较宽，例如，以所述含硅合金的总量为基准，硅的含量为10-50重量％。本发明对含硅合金的制备方法没有特别的限定，现提供一种含硅合金的具体制备方法，本发明并不限于此。例如，硅-铝合金的制备方法优选包括以下步骤：1)将铝粉、硅粉在惰性气氛保护下，球磨30min；2)将上述混合物在900℃下高温处理10h。
根据本发明，所述有机锂盐优选为含有机酸官能团(优选为羧基)的化合物与含锂的碱性化合物形成的一类盐。优选地，所述有机锂盐选自聚丙烯酸锂、聚甲基丙烯酸锂、聚马来酸锂、聚富马酸锂、羧甲基纤维素锂和海藻酸锂中的至少一种。本发明对上述有机锂盐的分子量选择范围较宽，优选地，所述有机锂盐的重均分子量为2000-5000000，进一步优选为80000-300000。
根据本发明，对于负极材料中，各组分的含量选择范围较宽，优选地，以所述负极材料的总量为基准，所述有机锂盐的含量为5-34重量％，含硅物质的含量为65-90重量％，多孔碳膜的含量为1-10重量％；更优选地，以所述负极材料的总量为基准，所述有机锂盐的含量为10-30重量％，含硅物质的含量为68-86重量％，多孔碳膜的含量为1-6重量％。
根据本发明的一种优选实施方式，所述负极材料中还含有石墨；进一步优选地，所述石墨存在于所述核和/或壳中，更优选存在于所述壳中。
本发明对所述石墨的含量选择范围较宽，优选地，含硅物质、有机锂盐和多孔碳膜的总量与石墨的质量比为1∶1-10，进一步优选为1∶1-5。
根据本发明，优选地，所述负极材料的中值粒径为0.1-20μm，例如为0.1μm、0.5μm、1μm、10μm、15μm、20μm，以及这些数值中的任意两个所构成的范围中的任意值。
本发明第二方面提供一种负极材料的制备方法，包括以下步骤：
(1)将硅源与碳源混合，然后焙烧；
(2)将步骤(1)得到的焙烧产物与有机锂盐混合；
(3)将步骤(2)混合得到的物料进行真空冷冻干燥。
根据本发明，优选地，所述硅源为上述的含硅物质，或者为通过所述焙烧能够转化为上述的含硅物质的含硅前体，进一步优选地，所 述硅源为上述的含硅物质，其具体种类的选择如上所述，本发明在此不再赘述。
根据本发明，优选地，所述碳源为沥青，优选选自石油沥青、煤焦沥青、天然沥青和改性沥青中的至少一种。采用该种优选实施方式，更有利于多孔碳的形成，更有利于进一步提高制得的负极材料的电化学性能。
本发明所述石油沥青、煤焦沥青、天然沥青和改性沥青具有本领域人员常规理解的含义，可以商购得到。
根据本发明，所述碳源的加入量与所述硅源的用量相关，优选地，所述硅源与所述碳源的质量比为1∶(0.04-0.12)，例如为1∶0.04、1∶0.05、1∶0.06、1∶0.07、1∶0.08、1∶0.09、1∶0.10、1∶0.11、1∶0.12，以及这些数值中的任意两个所构成的范围中的任意值。
根据本发明，优选地，步骤(1)所述混合包括：将硅源、碳源加入有机溶剂中，然后进行超声搅拌。采用该种优选实施方式，更有利于碳源均匀地包覆在硅表面。
根据本发明，对所述超声搅拌的时间选择范围较宽，以硅源与碳源能够分散于所述有机溶剂中为准，优选地，所述超声搅拌的时间为10-100min，进一步优选为20-60min。
根据本发明，所述有机溶剂可为本领域常规使用的有机溶剂，优选为N，N-二甲基甲酰胺、N，N-二甲基乙酰胺和N-甲基吡咯烷酮中的至少一种。
本发明对有机溶剂的加入量选择范围较宽，例如混合得到的浆液的固含量为10-35重量％。
根据本发明的一种具体实施方式，该方法还包括在步骤(1)所述混合之后，对混合得到的物料进行分离，将分离得到的固体进行所述焙烧。所述分离可以为本领域常规分离方法，例如离心分离。优选地，该方法还包括对所述分离得到的固体进行干燥，然后进行所述焙烧。本发明对所述干燥的条件选择范围较宽，优选地，温度为80-150℃，时间为1-10h。
根据本发明，优选地，所述焙烧的条件包括：在惰性气氛下，温度为600-1000℃，优选为700-900℃；时间为10-240min，优选为20-60min。所述惰性气氛可以由氮气、氦气、氩气和氪气中的至少一种 提供，本发明实施例部分以氮气为例进行示例性说明，本发明并不限于此。
本发明对所述焙烧的升温速率没有特别的限定，例如，可以为1-10℃/min。本发明实施例中以5℃/min为例进行示例性说明，本发明并不限于此。
根据本发明的一种具体实施方式，该方法包括待步骤(1)得到的焙烧产物降温(优选降至50℃以下，例如室温25℃)后进行所述步骤(2)。所述降温可以为自然降温。
根据本发明，所述有机锂盐的种类选择如上所述，本发明在此不再赘述。
根据本发明，优选地，相对于1重量份的硅源，所述有机锂盐的用量为0.05-0.5重量份，优选为0.1-0.4重量份。
本发明对步骤(2)所述的步骤(1)得到的焙烧产物和有机锂盐的混合的具体方式没有特别的限定，优选地，步骤(2)所述混合包括：将步骤(1)得到的焙烧产物、有机锂盐加入溶剂中，搅拌4-48h。本发明对溶剂的加入量选择范围较宽，例如混合得到的浆液的固含量为10-35重量％。优选地，所述溶剂为水。
本发明步骤(3)所述真空冷冻干燥可以保证步骤(1)焙烧得到的多孔碳的结构，并且至少一部分锂离子插层在多孔碳膜之中。
理论上，真空冷冻干燥的温度和真空度越低越好，但随着温度和真空度的降低，能耗会增大，且真空冷冻干燥设备也具有设备极限，从能耗和效果两方面考虑，优选地，步骤(3)所述真空冷冻干燥的条件包括：温度不高于-65℃，优选为-80℃至-65℃；真空度不高于120pa，优选为90-120pa。
本发明对于所述真空冷冻干燥的时间选择范围较宽，优选地，所述真空冷冻干燥的时间为4-48h，优选为8-32h。
根据本发明，该方法还优选包括，在步骤(1)之前，形成含磷包覆层，例如通过以下方法：(a)在30-80℃使含硅物质、磷源和溶剂接触，从而使磷源分布在含硅物质外周；和(b)进行程序升温焙烧，使在含硅物质外周的磷源转化为包含具有稠环芳烃结构片段的聚合物，其中所述程序升温焙烧包括：
以第一升温速率升温到400-500℃的第一温度，
以第二升温速率升温到600-800℃的第二温度，其中第二升温速率低于第一升温速率，和
在所述第二温度下保温。
所述磷源为可以转化为包含稠环芳烃结构片段的聚合物的任何含磷的前体，例如通过缩聚进行转化。优选磷源选自有机多元磷酸及其酯或盐，优选的有机多元磷酸为植酸。在步骤(a)中，优选所述溶剂为甲苯、N，N-二甲基甲酰胺、N，N-二甲基乙酰胺和N-甲基吡咯烷酮中的至少一种。优选溶剂的加入量使得，在步骤(a)中的物料的固含量为5-40重量％。优选地，所述程序升温焙烧包括：以1-10℃/min，优选5-10℃/min的第一升温速率升温至450-500℃的第一温度，例如480℃；再以1-5℃/min，优选1-3℃/min的第二升温速率升温至600-650℃的第二温度，例如620℃；在所述第二温度下保温1-8h，优选2-4h。
根据本发明，该方法还优选包括引入石墨的步骤。所述石墨可以在步骤(1)和/或步骤(2)中引入，也可以在步骤(3)之后引入。
根据本发明的一种优选实施方式，该制备方法还包括在步骤(1)和/或步骤(2)引入石墨。具体地，在步骤(1)中引入的具体实施方式包括但不限于将硅源、碳源和石墨混合，然后焙烧。具体地，在步骤(2)中引入的具体实施方式包括但不限于将步骤(1)得到的焙烧产物、有机锂盐与石墨混合。
根据本发明的另一种优选实施方式，该制备方法还包括步骤(4)，所述步骤(4)包括：将步骤(3)真空冷冻干燥得到的产物与石墨混合。
根据本发明，优选所述石墨在步骤(4)引入。采用该种优选实施方式更易于调整制得的负极材料的可逆充电容量。
根据本发明的一种优选实施方式，相对于1重量份的步骤(3)真空冷冻干燥得到的产物，所述石墨的用量为1-15重量份，优选为1-5重量份。
本发明第三方面提供上述制备方法制得的负极材料。所述负极材料的结构和组成特征如上所述，在此不再赘述。
本发明第四方面提供上述负极材料在锂离子电池中的应用。与传统纯石墨负极材料相比，上述负极材料由于含有理论容量更高的硅，从而可逆充电容量显著提升，因此在将上述负极材料用于锂离子电池 中时，可以提高锂电池的能量密度。
本发明第五方面提供一种锂离子电池，所述锂离子电池包括本发明提供的负极材料、含有锂元素的正极材料、隔膜和电解液。
根据本发明提供的锂离子电池的结构可以为本领域技术人员所公知，一般来说，隔膜位于正极片和负极片之间。正极片上含有所述正极材料，负极片含有所述负极材料。本发明对所述含有锂元素的正极材料的具体组成没有特别的限定，可以为本领域常规使用的含有锂元素的正极材料。
根据本发明提供的锂离子电池，所述隔膜可以选自本领域技术人员公知的锂离子电池中所用的各种隔膜，例如聚丙烯微孔膜、聚乙烯毡、玻璃纤维毡或超细玻璃纤维纸。
根据本发明提供的锂离子电池，所述电解液可为各种常规的电解液，例如非水电解液。所述非水电解液为电解质锂盐在非水溶剂中形成的溶液，可以使用本领域技术人员已知的常规的非水电解液。比如电解质可以选自六氟磷酸锂(LiPF 6)、高氯酸锂(LiClO 4)、四氟硼酸锂(LiBF 4)、六氟砷酸锂(LiAsF 6)和六氟硅酸锂(LiSiF 6)中的至少一种。非水溶剂可以选自链状酸酯、环状酸酯或其混合物。链状酸酯可以为碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸甲丙酯(MPC)和碳酸二丙酯(DPC)中的至少一种。环状酸酯可以为碳酸乙烯酯(EC)、碳酸丙烯酯(PC)和碳酸亚乙烯酯(VC)中的至少一种。
以下将通过实施例对本发明进行详细描述。实施例旨在描述而非以任何方式限制本发明。
测试方法
1.材料的确认
1.1透射电子显微镜图(TEM)
采用透射电子显微镜对负极材料样品的形貌进行表征，具体地，所述透射电子显微镜为日本电子株式会社的型号为JEM-2100的透射电子显微镜，测试条件：加速电压160KV，样品置于铜支持网后插入电镜进行观察，所述观察时使用80万倍的放大倍率。
1.2 X射线光电子能谱的全谱分析图
采用美国ThermoFisher Scientific公司的ESCALAB 250Xi型X射 线光电子能谱测试仪对负极材料样品进行表征，测试条件包括：室温25℃，真空度小于5×10 -10mba，工作电压15KV，采用Al Kα作为射线源，全谱通过能100eV，步长1.0eV。
1.3 X射线光电子能谱的Li1s谱分析图
采用美国ThermoFisher Scientific公司的ESCALAB 250Xi型X射线光电子能谱测试仪对负极材料样品进行表征，测试条件包括：室温25℃，真空度小于5×10 -10mba，工作电压15KV，采用Al Kα作为射线源，窄谱通过能30eV，步长0.05eV，束斑是500μm。
1.4中值粒径(D 50)
参照GB/T 19077-2016，通过动态光散射表征获得中值粒径。
2.材料的电性能
将以下实施例和对比例中制备的负极材料组装成锂离子电池样品，采用武汉蓝电电池测试系统(CT2001B)对装配得到的锂离子电池样品的电化学性能进行测试。测试条件包括：电压范围0.005V-3V。每个负极材料样品组装10个纽扣电池形式的样品，在同样的电压和电流下测试样品的电池性能，取平均值作为测量值。
2.1首次充放电曲线
在0.05V-3V的电压范围，以及0.1C倍率下，对组装的锂离子电池样品进行首次充放电，获得其首次充放电曲线。电池测试系统(CT2001B)将给出测试电池样品的首次放电容量和首次充电容量。首次放电容量为所用负极材料的比容量，首次充电容量为所用负极材料的可逆充电容量。通过两者可以计算出首次库伦效率(简称为“首效”)：
首次库伦效率＝负极材料的可逆充电容量/负极材料的比容量。
2.2循环稳定性测试
在0.2C的倍率下，对组装的锂离子电池样品进行选定次数，例如20、50或100次充放电循环，测量每次循环时样品的可逆充电容量，并由此计算各个循环的循环充电容量保留率，其中：
循环充电容量保留率＝相应循环序号下的可逆充电容量/首次充电时的可逆充电容量×100％
以循环次数为横坐标和循环充电容量保留率为纵坐标作图得到循环稳定性测试曲线。
3.试剂
以下实施例和对比例中，石油沥青商购自泰普克公司，牌号为PMA。煤焦沥青商购自隆鑫物贸有限公司，牌号为低温沥青(100-115)。
聚丙烯酸锂通过自行制备得到，具体包括：取重均分子量240000的聚丙烯酸10g加入到40g去离子水中，配制质量分数为20％的聚丙烯酸溶液。称取3.4g氢氧化锂，加入到上述聚丙烯酸溶液中，于40℃下加热搅拌直至所有固体全部溶解，100℃干燥4h，得聚丙烯酸锂。
聚甲基丙烯酸锂通过自行制备得到，具体包括：取重均分子量240000的聚甲基丙烯酸10g加入到40g去离子水中，配制质量分数为20％的聚甲基丙烯酸溶液。称取3.4g氢氧化锂，加入到上述聚甲基丙烯酸溶液中，于40℃下加热搅拌直至所有固体全部溶解，100℃干燥4h，得聚甲基丙烯酸锂。
聚马来酸锂通过自行制备得到，具体包括：取重均分子量240000的聚马来酸10g加入到40g去离子水中，配制质量分数为20％的聚马来酸溶液。称取3.4g氢氧化锂，加入到上述聚马来酸溶液中，于40℃下加热搅拌直至所有固体全部溶解，100℃干燥4h，得聚马来酸锂。
聚富马酸锂通过自行制备得到，具体包括：取重均分子量240000的聚富马酸10g加入到40g去离子水中，配制质量分数为20％的聚富马酸溶液。称取3.4g氢氧化锂，加入到上述聚富马酸溶液中，于40℃下加热搅拌直至所有固体全部溶解，100℃干燥4h，得聚富马酸锂。
羧甲基纤维素锂通过自行制备得到，具体包括：取重均分子量120000的羧甲基纤维素钠10g加入到40g去离子水中，配制质量分数为20％的羧甲基纤维素钠溶液。称取3.1g氢氧化锂，加入到上述羧甲基纤维素钠溶液中，于40℃下加热搅拌直至所有固体全部溶解，100℃干燥4h，得羧甲基纤维素锂。
海藻酸锂通过自行制备得到，具体包括：取重均分子量80000的海藻酸钠10g加入到40g去离子水中，配制质量分数为20％的海藻酸钠溶液。称取1.2g氢氧化锂，加入到上述海藻酸钠溶液中，于40℃下加热搅拌直至所有固体全部溶解，100℃干燥4h，得海藻酸锂。
其中，聚丙烯酸、聚甲基丙烯酸、聚马来酸、聚富马酸、羧甲基纤维素钠和海藻酸钠商购自阿拉丁试剂公司。
以下实施例和对比例中，所述室温是指25℃。
实施例1
(1)取D50为120nm的硅粉1g和0.12g石油沥青，加入到10g的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆硅置于管式炉中，以5℃/min速率升温至800℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆硅。
(4)取聚丙烯酸锂0.125g，与步骤(3)中所得碳包覆硅共同置于3mL去离子水中，室温下搅拌12h。随后，将搅拌好的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h即得含锂的负极材料S-1。含锂的负极材料S-1的中值粒径以及各组分的含量列于表1中。
对含锂的负极材料S-1进行取样，并如上所述进行材料的确定。图1是所述含锂的负极S-1的TEM照片。从图中可以看出纳米硅颗粒被均匀的包裹，具有核壳结构，所述核的外表面包覆有多孔碳膜。图2是所述含锂的负极材料S-1的X射线光电子能谱的全谱分析图，从图中可以看出所述负极材料中含有锂、碳、硅元素。图3为所述含锂的负极材料S-1的Li1s谱图。如图3所示，在结合能为64.1eV处出现显著的信号峰。该信号峰对应于LiC 6复合物。LiC 6复合物的形成意味着，有Li +迁移入多孔碳膜中碳原子片层之间，即锂离子插层在所述多孔碳膜之中。
分别以实施例1所得含锂的负极材料S-1、金属锂片为正极、负极，使用1mol/L的LiPF 6溶液(碳酸乙烯酯和碳酸二乙酯以3∶7体积比混合作为溶剂)为电解液，聚丙烯微孔膜为隔膜，组装为CR2016纽扣电池形式的样品，如上所述测定电池样品的电性能，以表征实施例1的所述含锂的负极材料S-1的电学性能。
图4为基于实施例1的所述含锂的负极材料S-1的纽扣电池的首次充放电曲线。如图所示，实施例1所述含锂的负极材料S-1的可逆充电容量为3000mAh/g，首次库伦效率为86.9％。
图5为基于实施例1的所述含锂的负极材料S-1的纽扣电池的循环稳定性测试曲线。如图所示，实施例1的所述含锂的负极材料S-1在 0.2C的充放电倍率下，经20次循环后，充电容量保留率约为92％。
对比例1
(1)取D50为120nm的硅粉1g和0.12g石油沥青，加入到10g的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆硅置于管式炉中，以5℃/min速率升温至800℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆硅，将其作为负极材料D-1。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为对比例1制得的负极材料D-1。
图6为基于对比例1的负极材料D-1的纽扣电池的首次充放电曲线。如图所示，对比例1的负极材料的可逆充电容量为908mAh/g，首次库伦效率为38.9％。
图7为基于对比例1的负极材料的纽扣电池的循环稳定性测试曲线。如图所示，对比例1的负极材料在0.2C的充放电倍率下，经12次循环后，充电容量保留率为6％。
对比例2
按照实施例1的方法，不同的是，将搅拌好的浆料置于空气中进行干燥(温度为100℃)，干燥12h即得含锂的负极材料D-2。
对含锂的负极材料D-2进行取样，并如上所述进行材料的确定。图8为所述含锂的负极材料D-2的Li1s谱图。如图8所示，在结合能为56.3eV处出现信号峰，此处归属于有机锂盐(聚丙烯酸锂)的信号峰，而在对应于LiC 6复合物的结合能为64.1eV处，没有发现显著的信号峰。这意味着，未发生锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为对比例2制得的材料。测试结果表明，对比例2所述材料的可逆充电容量为795mAh/g，首次库伦效率为36.3％，所述材料在0.2C的充放电倍率下，经20次循环后，充电容量保留率约为30％。
对比例3
按照实施例1的方法，不同的是，将聚丙烯酸锂替换为等质量的 碳酸锂，得到含锂的负极材料D-3。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为对比例3制得的材料。测试结果表明，对比例3所述材料的可逆充电容量为820mAh/g，首次库伦效率为31％，所述材料在0.2C的充放电倍率下，经10次循环后，充电容量保留率约为10％。
实施例2
(1)取D50为120nm的硅粉1g和0.04g石油沥青，加入到10g的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆硅置于管式炉中，以5℃/min速率升温至800℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆硅。
(4)取聚丙烯酸锂0.15g，与步骤(3)中所得碳包覆硅共同置于3mL去离子水中，室温下搅拌12h。随后，将搅拌好的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h即得含锂的负极材料S-2。含锂的负极材料S-2的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-2的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-2具有核壳结构，所述核的外表面包覆有多孔碳膜，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例2制得的材料。测试结果表明，实施例2所述材料的可逆充电容量为2812mAh/g，首次库伦效率为87.6％，所述材料在0.2C的充放电倍率下，经15次循环后，充电容量保留率约为90％。
实施例3
(1)取D50为120nm的硅粉1g和0.08g石油沥青，加入到10g的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm 转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆硅置于管式炉中，以5℃/min速率升温至700℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆硅。
(4)取聚丙烯酸锂0.3g，与步骤(3)中所得碳包覆硅共同置于3mL去离子水中，室温下搅拌12h。随后，将搅拌好的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h即得含锂的负极材料S-3。含锂的负极材料S-3的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-3的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-3具有核壳结构，所述核的外表面包覆有多孔碳膜，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例3制得的材料。测试结果表明，实施例3所述材料的可逆充电容量为2760mAh/g，首次库伦效率为89.3％，所述材料在0.2C的充放电倍率下，经15次循环后，充电容量保留率约为85％。
实施例4
(1)取D50为300nm的硅粉1g和0.08g石油沥青，加入到10g的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆硅置于管式炉中，以5℃/min速率升温至900℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆硅。
(4)取海藻酸锂0.32g，与步骤(3)中所得碳包覆硅共同置于3mL去离子水中，室温下搅拌12h。随后，将搅拌好的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h即得含锂的负极材料S-4。含锂的负极材料S-4的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-4的TEM图、X射线光电子能谱的全谱分析图 和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-4具有核壳结构，所述核的外表面包覆有多孔碳膜，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例4制得的材料。测试结果表明，实施例4所述材料的可逆充电容量为2720mAh/g，首次库伦效率为87.9％，所述材料在0.2C的充放电倍率下，经15次循环后，充电容量保留率约为85％。
实施例5
(1)取D50为300nm的硅粉1g和0.08g石油沥青，加入到10g的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆硅置于管式炉中，以5℃/min速率升温至800℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆硅。
(4)取羧甲基纤维素锂0.42g，与步骤(3)中所得碳包覆硅共同置于3mL去离子水中，室温下搅拌12h。随后，将搅拌好的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h即得含锂的负极材料S-5。含锂的负极材料S-5的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-5的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-5具有核壳结构，所述核的外表面包覆有多孔碳膜，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例5制得的材料。测试结果表明，实施例5所述材料的可逆充电容量为2870mAh/g，首次库伦效率为86.1％，所述材料在0.2C的充放电倍率下，经18次循环后，充电容量保留率约为91％。
实施例6
(1)取D50为120nm的硅粉1g和0.08g石油沥青，加入到10g 的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆硅置于管式炉中，以5℃/min速率升温至800℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆硅。
(4)取聚丙烯酸锂0.15g，与步骤(3)中所得碳包覆硅共同置于3mL去离子水中，室温下搅拌12h。随后，将搅拌好的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h。
(5)将步骤(4)干燥得到的产物与人造石墨按照1∶4的质量比共混，得到设计容量为900mAh/g的含锂的负极材料S-6。含锂的负极材料S-6的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-6的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-6具有核壳结构，所述核的外表面包覆有多孔碳膜和石墨，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例6制得的材料。测试结果表明，实施例6所述材料的可逆充电容量为912mAh/g，首次库伦效率为90.6％，所述材料在0.2C的充放电倍率下，经100次循环后，充电容量保留率约为96％。
实施例7
(1)取D50为120nm的硅粉1g和0.08g石油沥青，加入到10g的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆硅置于管式炉中，以5℃/min速率升温至800℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆硅。
(4)取聚丙烯酸锂0.15g，与步骤(3)中所得碳包覆硅共同置于3mL去离子水中，室温下搅拌12h。随后，将搅拌好的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h。
(5)将步骤(4)干燥得到的产物与人造石墨按照1∶5的质量比共混，得到设计容量为700mAh/g的含锂的负极材料S-7。含锂的负极材料S-7的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-7的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-7具有核壳结构，所述核的外表面包覆有多孔碳膜和石墨，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例7制得的材料。测试结果表明，实施例7所述材料的可逆充电容量为752mAh/g，首次库伦效率为91.2％，所述材料在0.2C的充放电倍率下，经150次循环后，充电容量保留率约为96％。
实施例8
(1)取D50为120nm的硅粉1g和0.08g石油沥青，加入到10g的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆硅置于管式炉中，以5℃/min速率升温至800℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆硅。
(4)取聚丙烯酸锂0.15g，与步骤(3)中所得碳包覆硅共同置于3mL去离子水中，室温下搅拌12h。随后，将搅拌好的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h。
(5)将步骤(4)干燥得到的产物与人造石墨按照1∶1的质量比共混，得到设计容量为1500mAh/g的含锂的负极材料S-8。含锂的负极材料S-8的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-8的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-8具有核壳结构，所述核的外表面包覆有多孔碳膜和石墨，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例8制得的材料。测试结果表明，实 施例8所述材料的可逆充电容量为1512mAh/g，首次库伦效率为88.9％，所述材料在0.2C的充放电倍率下，经150次循环后，充电容量保留率约为90％。
实施例9
(1)取D50为120nm的氧化亚硅粉(SiOx，x＝1)1g和0.08g石油沥青，加入到10g的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆氧化亚硅置于管式炉中，以5℃/min速率升温至750℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆氧化亚硅。
(4)取聚丙烯酸锂0.15g，与步骤(3)中所得碳包覆氧化亚硅共同置于3mL去离子水中，室温下搅拌12h。随后，将搅拌好的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h即得含锂的氧化亚硅负极材料S-9。含锂的氧化亚硅负极材料S-9的中值粒径以及各组分的含量列于表1中。
含锂的氧化亚硅负极材料S-9的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的氧化亚硅负极材料S-9具有核壳结构，所述核的外表面包覆有多孔碳膜，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例9制得的材料。测试结果表明，实施例9所述材料的可逆充电容量为1632mAh/g，首次库伦效率为83.1％，所述材料在0.2C的充放电倍率下，经200次循环后，充电容量保留率约为90％。
实施例10
(1)按质量比4∶1取D50为100nm的铝粉、D50为120nm的硅粉在氮气气氛保护下，球磨30min，将所得混合物置于氮气管式炉中，900℃焙烧10h，即得硅-铝合金粉(D50＝200nm，硅的含量为20重量％)。取上述硅铝合金1g和0.08g石油沥青，加入到10g的N，N-二甲基甲酰胺中，超声搅拌40分钟。
(2)搅拌结束后，将上述浆料转移至50mL离心管内，以5000rpm 转速，离心5分钟，收集下层固体，干燥(100℃，4h)。
(3)将步骤(2)所得沥青包覆硅铝合金置于管式炉中，以5℃/min速率升温至750℃，并在氮气气氛下保温30分钟，结束后自然冷却至室温，即得碳包覆硅铝合金。
(4)取聚丙烯酸锂0.15g，与步骤(3)中所得碳包覆硅铝合金共同置于3mL去离子水中，室温下搅拌12h。随后，将搅拌好的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h即得含锂的硅铝负极材料S-10。含锂的硅铝负极材料S-10的中值粒径以及各组分的含量列于表1中。
含锂的硅铝负极材料S-10的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的硅铝负极材料S-10具有核壳结构，所述核的外表面包覆有多孔碳膜，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例10制得的材料。测试结果表明，实施例10所述材料的可逆充电容量为721mAh/g，首次库伦效率为84.1％，所述材料在0.2C的充放电倍率下，经200次循环后，充电容量保留率约为90％。
实施例11
按照实施例1的方法，不同的是，将石油沥青替换为等质量的煤焦沥青。得到含锂的负极材料S-11。含锂的负极材料S-11的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-11的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-11具有核壳结构，所述核的外表面包覆有多孔碳膜，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例11制得的材料。测试结果表明，实施例11所述材料的可逆充电容量为2932mAh/g，首次库伦效率为88.7％，所述材料在0.2C的充放电倍率下，经30次循环后，充电容量保留率约为85％。
实施例12
按照实施例1的方法，不同的是，将聚丙烯酸锂替换为等质量的聚甲基丙烯酸锂。得到含锂的负极材料S-12。含锂的负极材料S-12的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-12的TEM图、X射线光电子能谱的全谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-12具有核壳结构，所述核的外表面包覆有多孔碳膜，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例12制得的材料。测试结果表明，实施例12所述材料的可逆充电容量为2895mAh/g，首次库伦效率为87.1％，所述材料在0.2C的充放电倍率下，经30次循环后，充电容量保留率约为85％。
实施例13
按照实施例1的方法，不同的是，将聚丙烯酸锂替换为等质量的聚马来酸锂。得到含锂的负极材料S-13。含锂的负极材料S-13的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-13的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-13具有核壳结构，所述核的外表面包覆有多孔碳膜，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例13制得的材料。测试结果表明，实施例13所述材料的可逆充电容量为2925mAh/g，首次库伦效率为86.8％，所述材料在0.2C的充放电倍率下，经30次循环后，充电容量保留率约为85％。
实施例14
按照实施例1的方法，不同的是，将聚丙烯酸锂替换为等质量的聚富马酸锂。得到含锂的负极材料S-14。含锂的负极材料S-14的中值粒径以及各组分的含量列于表1中。
含锂的负极材料S-14的TEM图、X射线光电子能谱的全谱分析图和X射线光电子能谱的Li1s谱分析图分别与图1-图3相似，说明制得的含锂的负极材料S-14具有核壳结构，所述核的外表面包覆有多孔 碳膜，并且锂离子插层在所述多孔碳膜之中。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例14制得的材料。测试结果表明，实施例14所述材料的可逆充电容量为2963mAh/g，首次库伦效率为86.5％，所述材料在0.2C的充放电倍率下，经30次循环后，充电容量保留率约为85％。
实施例15
1)取10gN，N’-二甲基甲酰胺和0.272g植酸混合形成混合溶液，向该混合溶液中加入0.54g硅粉(D50＝100nm)，在搅拌下升温到40℃并保持60min。反应结束后，抽滤洗涤所得固体粉末，并于80℃下真空干燥4h。
2)将上述固体置于管式炉中，并以5℃/min的第一升温速率升温至480℃，再以2℃/min的第二升温速率升温至620℃，在620℃下保温3小时。冷却到室温后，获得产物，称为磷包覆含硅材料S-15-1
3)取1.5g磷包覆含硅材料S-15-1，将其与0.18g石油沥青加入到15g的N，N-二甲基甲酰胺中，超声搅拌60分钟。将搅拌结束后获得的浆料转移至离心管内，以5000rpm的转速离心5分钟。收集下层固体，并在100℃干燥4h。得到沥青包覆的S-15-1。
4)将沥青包覆的S-15-1置于管式炉中，以5℃/min的速率升温至800℃，并在氮气气氛下保温30分钟。自然冷却至室温。得到碳包覆的S-15-1。
5)取聚丙烯酸锂0.188g，将其与碳包覆的S-15-1共同置于5mL去离子水中，并在室温下搅拌12h。随后，将获得的浆料置于冷阱温度-80℃、腔体真空度100pa的冷冻真空干燥箱中，干燥12h。得负极材料S-15。
按照实施例1的方法组装电池并进行电学性能测试，不同的是，将含锂的负极材料S-1替换为实施例15制得的材料S-15。测试结果表明，实施例15所述材料的可逆充电容量为3480mAh/g，首次库伦效率为91.2％，所述材料在0.2C的充放电倍率下，经30次循环后，充电容量保留率为94.8％。
表1
Figure PCTCN2020118720-appb-000001
通过上述实施例以及结果可以看出，本发明所提供的负极材料可以提高负极材料的可逆充电容量，应用于锂离子电池中可以提高锂电池的能量密度。更重要的是，本发明所提供的负极材料同时实现了优异的首次充电效率和循环充电容量保留率，特别是在更长的循环周期的优异充电容量保留率。
以上详细描述了本发明的优选实施方式，但是，本发明并不限于此。在本发明的技术构思范围内，可以对本发明的技术方案进行多种简单变型，包括各个技术特征以任何其它的合适方式进行组合，这些简单变型和组合同样应当视为本发明所公开的内容，均属于本发明的保护范围。

Claims (15)

  1. 一种负极材料，其特征在于，所述负极材料具有核壳结构，所述核中包括含硅物质，所述壳中包括有机锂盐和多孔碳膜，并且至少一部分锂离子插层在所述多孔碳膜之中。
  2. 根据权利要求1所述的负极材料，其中，所述负极材料还含有含磷包覆层，其位于核与壳之间；
    优选地，所述含磷包覆层含有具有稠环芳烃结构片段的聚合物；
    优选地，所述含磷包覆层由植酸制备形成。
  3. 根据权利要求1所述的负极材料，其中，以所述负极材料的总量为基准，所述有机锂盐的含量为5-34重量％，含硅物质的含量为65-90重量％，多孔碳膜的含量为1-10重量％；
    优选地，以所述负极材料的总量为基准，所述有机锂盐的含量为10-30重量％，含硅物质的含量为68-86重量％，多孔碳膜的含量为1-6重量％；
    任选地，所述负极材料中还含有石墨；
    优选地，所述石墨存在于所述核和/或壳中；
    优选地，含硅物质、有机锂盐和多孔碳膜的总量与石墨的质量比为1∶1-10，进一步优选为1∶1-5。
  4. 根据权利要求1所述的负极材料，其中，所述负极材料的中值粒径为0.1-20μm。
  5. 根据权利要求1-4中任意一项所述的负极材料，其中，所述有机锂盐选自聚丙烯酸锂、聚甲基丙烯酸锂、聚马来酸锂、聚富马酸锂、羧甲基纤维素锂和海藻酸锂中的至少一种；
    优选地，所述含硅物质选自单质硅、SiOx和含硅合金中的至少一种，其中，0.6＜x＜1.5；优选地，所述含硅合金选自硅-铝合金、硅-镁合金、硅-锆合金和硅-硼合金中的至少一种。
  6. 一种负极材料的制备方法，其特征在于，包括以下步骤：
    (1)将硅源与碳源混合，然后焙烧；
    (2)将步骤(1)得到的焙烧产物与有机锂盐混合；
    (3)将步骤(2)混合得到的物料进行真空冷冻干燥。
  7. 根据权利要求6所述的制备方法，其中，所述硅源选自单质硅、 SiOx和含硅合金中的至少一种，其中，0.6＜x＜1.5；优选地，所述含硅合金选自硅-铝合金、硅-镁合金、硅-锆合金和硅-硼合金中的至少一种；
    优选地，所述碳源为沥青，优选选自石油沥青、煤焦沥青、天然沥青和改性沥青中的至少一种；
    优选地，所述硅源与所述碳源的质量比为1∶(0.04-0.12)。
  8. 根据权利要求6所述的制备方法，其中，步骤(1)所述混合包括：
    将硅源、碳源加入有机溶剂中，然后进行超声搅拌，优选超声搅拌的时间为10-100min；
    优选地，所述有机溶剂选自N，N-二甲基甲酰胺、N，N-二甲基乙酰胺和N-甲基吡咯烷酮中的至少一种；
    优选地，所述焙烧的条件包括：在惰性气氛下，温度为600-1000℃，优选为700-900℃；时间为10-240min，优选为20-60min。
  9. 根据权利要求6-8中任意一项所述的制备方法，其中，所述有机锂盐选自聚丙烯酸锂、聚甲基丙烯酸锂、聚马来酸锂、聚富马酸锂、羧甲基纤维素锂和海藻酸锂中的至少一种；
    优选地，相对于1重量份的硅源，所述有机锂盐的用量为0.05-0.5重量份，优选为0.1-0.4重量份；
    优选地，步骤(2)所述混合包括：将步骤(1)得到的焙烧产物、有机锂盐加入溶剂中，搅拌4-48h。
  10. 根据权利要求6-9中任意一项所述的制备方法，其中，步骤(3)所述真空冷冻干燥的条件包括：温度不高于-65℃，真空度不高于120pa，时间为4-48h。
  11. 根据权利要求6-10中任意一项所述的制备方法，其中，该制备方法还包括在步骤(1)和/或步骤(2)引入石墨；
    优选地，该制备方法还包括步骤(4)，所述步骤(4)包括：将步骤(3)真空冷冻干燥得到的产物与石墨混合；
    优选地，相对于1重量份的步骤(3)真空冷冻干燥得到的产物，所述石墨的用量为1-15重量份，优选为1-5重量份。
  12. 根据权利要求6-10中任意一项所述的制备方法，其中，所述方法还包括：在步骤(1)之前，通过以下方法形成含磷包覆层：
    (a)在30-80℃使含硅物质、磷源和溶剂接触，从而使磷源分布 在含硅物质外周；和
    (b)进行程序升温焙烧，使在含硅物质外周的磷源转化为包含具有稠环芳烃结构片段的聚合物，其中所述程序升温焙烧包括：
    以第一升温速率升温到400-500℃的第一温度，
    以第二升温速率升温到600-800℃的第二温度，其中第二升温速率低于第一升温速率，和
    在所述第二温度下保温；
    优选地，所述磷源选自有机多元磷酸及其酯或盐，优选为植酸；
    优选地，所述溶剂为甲苯、N，N-二甲基甲酰胺、N，N-二甲基乙酰胺和N-甲基吡咯烷酮中的至少一种；
    优选地，所述程序升温焙烧包括：
    以1-10℃/min，优选5-10℃/min的第一升温速率升温至450-500℃的第一温度，例如480℃；再以1-5℃/min，优选1-3℃/min的第二升温速率升温至600-650℃的第二温度，例如620℃；在所述第二温度下保温1-8h，优选2-4h。
  13. 权利要求6-12中任意一项所述的制备方法制得的负极材料。
  14. 权利要求1-5和13中任意一项所述的负极材料在锂离子电池中的应用。
  15. 一种锂离子电池，所述锂离子电池包括权利要求1-5和13中任意一项所述的负极材料、含有锂元素的正极材料、隔膜和电解液；
    优选地，所述锂离子电池为液态锂离子电池、半固态锂离子电池或者全固态锂离子电池。
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