CN110838574A - High-capacity composite negative electrode material for lithium ion battery, preparation method of high-capacity composite negative electrode material and lithium ion battery comprising composite material - Google Patents
High-capacity composite negative electrode material for lithium ion battery, preparation method of high-capacity composite negative electrode material and lithium ion battery comprising composite material Download PDFInfo
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Abstract
The invention discloses a high-capacity composite negative electrode material for a lithium ion battery, a preparation method of the high-capacity composite negative electrode material and the lithium ion battery comprising the composite material. The method comprises the following steps: 1) dispersing the modified nano-silicon alloy in a raw material of the mesocarbon microbeads, carrying out polymerization reaction and separation to obtain a precursor; 2) and coating, modifying and sintering the obtained precursor to obtain the composite negative electrode material. The invention has simple process and is easy for large-scale production. The prepared composite negative electrode material has excellent electrochemical performance, and when the composite negative electrode material is applied to a lithium ion battery, the composite negative electrode material has high specific capacity, high efficiency and excellent cycle life.
Description
Technical Field
The invention belongs to the field of application of lithium ion battery cathode materials, and relates to a composite cathode material, a preparation method thereof and a lithium ion battery containing the composite cathode material, in particular to a high-capacity composite cathode material for a lithium ion battery, a preparation method thereof and a lithium ion battery containing the composite material.
Background
Lithium ion batteries have the advantages of high energy density, long cycle life, good safety and the like, are widely applied to portable electronic equipment, and are rapidly increased in the fields of electric vehicles and the like. The mesocarbon microbeads are applied to the lithium ion battery cathode material due to the advantages of high stacking density, small specific surface, good rate capability, good safety performance and the like, but the mesocarbon microbeads have low specific capacity of only 340mAh/g and cannot meet the increasing demands of the current market on the high-energy density lithium ion battery. The silicon material as the negative electrode material has high theoretical specific capacity (4200mA h/g), but the silicon negative electrode is accompanied with large volume expansion (up to 300%) in the process of lithium removal/insertion, so that silicon particles are crushed and pulverized, the material loses activity, and finally the cycle performance is seriously attenuated; in addition, silicon has low conductivity and poor rate capability.
CN107768671A discloses a preparation method of silicon mesocarbon microbeads for lithium ion batteries, which comprises the following steps: adding simple substance silicon or silicon-containing oxide into the raw materials, uniformly mixing, carrying out thermal polycondensation reaction, separating to obtain mesocarbon microbeads with silicon as the core, and carbonizing to obtain the mesocarbon microbeads with silicon as the core for the lithium ion battery. Although the method improves the capacity of the mesocarbon microbeads, the dispersion effect of silicon and silicon-containing oxide in the mesocarbon microbeads is poor, and the conductivity and the expansion of the silicon and the silicon-containing oxide are poor, so that the capacity of the material cannot be further improved, and the expansion of the material is large.
Disclosure of Invention
In view of the above problems in the prior art, an object of the present invention is to provide a composite negative electrode material, a preparation method thereof, and a lithium ion battery comprising the composite negative electrode material, and in particular, to provide a high-capacity composite negative electrode material for a lithium ion battery, a preparation method thereof, and a lithium ion battery comprising the composite material.
The high capacity in the high capacity composite negative electrode material of the invention refers to: the first reversible capacity of 0.1C is 800-1100 mAh/g.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a composite anode material (see fig. 1 for a schematic structural diagram), which includes mesocarbon microbeads, modified nano-silicon alloy dispersed inside the mesocarbon microbeads, and a carbon material coating layer coated outside the mesocarbon microbeads.
The invention adopts the nano silicon alloy material as the active substance, has better conductivity and lower expansion compared with pure silicon, further reduces the expansion of the silicon alloy after nanoscale treatment, and improves the cycle performance. The lipophilicity of the nano silicon alloy can be effectively improved by carbon coating modification of the nano silicon alloy, so that the dispersion effect and the associativity of the nano silicon alloy in the mesocarbon microbeads are improved, and the material performance reduction caused by local agglomeration of the nano silicon alloy material is avoided. The modified nano silicon alloy is dispersed in the mesocarbon microbeads, so that the capacity of the mesocarbon microbeads can be effectively improved, and the expansion of the nano silicon alloy is further reduced. And finally, carrying out carbon coating modification on the surfaces of the mesocarbon microbeads, further reducing the expansion performance and the specific surface area of the material and improving the performance of the material.
The term "comprising" as used herein may also be replaced by the term "comprising" or "consisting of … …" as used herein. When the composite negative electrode material is composed of the mesocarbon microbeads, the modified nano-silicon alloy dispersed in the mesocarbon microbeads and the carbon material coating layer coated outside the mesocarbon microbeads, the composite negative electrode material has better electrochemical performance, including high specific capacity, high efficiency and excellent cycle life.
As a preferred technical scheme of the composite cathode material, the dispersion of the modified nano alloy in the mesocarbon microbeads is realized in the process of preparing the mesocarbon microbeads.
Preferably, the modified nano-silicon alloy is a carbon-coated modified nano-silicon alloy. The carbon coating modification can better improve the lipophilicity of the nano silicon alloy and increase the binding property and the dispersibility of the nano silicon alloy dispersed in the mesocarbon microbeads.
Preferably, the modified nano-silicon alloy is composed of a nano-silicon alloy and a carbon-coated modified layer coated on the surface of the nano-silicon alloy.
Preferably, the nano-silicon alloy is any 1 or at least 2 combinations of ferrosilicon, silicon-nickel alloy, silicon-titanium alloy, silicon-tin alloy, silicon-copper alloy or silicon-aluminum alloy, which are typical but non-limiting examples of the combinations: a combination of a silicon-iron alloy and a silicon-nickel alloy, a combination of a silicon-iron alloy and a silicon-titanium alloy, a combination of a silicon-nickel alloy and a silicon-tin alloy, a combination of a silicon-titanium alloy and a silicon-aluminum alloy, a combination of a silicon-iron alloy, a silicon-nickel alloy and a silicon-copper alloy, a combination of a silicon-nickel alloy, a silicon-titanium alloy and a silicon-aluminum alloy, a combination of a silicon-nickel alloy, a silicon-titanium alloy, a silicon-tin alloy and a silicon-aluminum alloy, and the like.
As a preferred technical scheme of the composite negative electrode material, the composite negative electrode material comprises, by weight, 10-60% of the nano silicon alloy, 1-8% of the carbon-coated modified layer, 30-80% of the mesocarbon microbeads and 3-20% of the carbon material coating layer, wherein the total mass of the composite negative electrode material is 100%.
In the preferred embodiment, the nano-silicon alloy is, for example, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, or 60 wt%; the carbon-coated modified layer is, for example, 1 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 5 wt%, 5.5 wt%, 6 wt%, 7 wt%, 8 wt%, or the like; the content of the mesocarbon microbeads by mass is, for example, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 60 wt%, 65 wt%, 70 wt%, 80 wt%, or the like; the carbon material coating layer is, for example, 3 wt%, 5 wt%, 7 wt%, 10 wt%, 12 wt%, 15 wt%, 16 wt%, 18 wt%, or 20 wt%.
More preferably, the composite negative electrode material comprises, by mass, 20% to 50% of the nano silicon alloy, 2% to 6% of the carbon-coated modified layer, 40% to 70% of the mesocarbon microbeads and 5% to 15% of the carbon material coating layer, based on 100% of the total mass of the composite negative electrode material.
Preferably, the composite negative electrode material has a median particle diameter of 1 to 45 μm, for example, 1 to 3, 5, 8, 10, 15, 17.5, 20, 22 or 25 μm, preferably 5 to 25 μm.
Preferably, the nano-silicon alloy has a median particle size of 50nm to 800nm, for example 50nm, 60nm, 80nm, 100nm, 150nm, 200nm, 300nm, 350nm, 400nm, 450nm, 500nm, 600nm, 650nm, 700nm, 800nm, or the like, preferably 100nm to 500 nm.
In a second aspect, the present invention provides a method for preparing a composite anode material according to the first aspect, the method comprising the steps of:
(1) dispersing the modified nano-silicon alloy in a raw material of the mesocarbon microbeads, and carrying out polymerization reaction to obtain a first precursor;
(2) separating the first precursor to obtain a second precursor;
(3) coating and modifying the second precursor to obtain a third precursor;
(4) and sintering the third precursor to obtain the composite anode material.
In the method of the present invention, the separation in step (2) is an essential step because: raw materials (such as pitch, coal tar, synthetic resin and the like) of the mesocarbon microbeads in the step (1) are converted into molten state through polymerization reaction, the mesocarbon microbeads containing the nano silicon alloy are dispersed in the mother liquor in the obtained first precursor, and the mesocarbon microbeads containing the nano silicon alloy are separated out through the separation in the step (2) so as to carry out the subsequent coating step.
According to the method, the modified nano silicon alloy is introduced in the process of preparing the mesocarbon microbeads through high-temperature polymerization reaction, so that a structure that the modified nano silicon alloy is dispersed in the mesocarbon microbeads can be formed, the lipophilicity of nano silicon is improved by the modified nano silicon alloy, the modified nano silicon alloy can be well dispersed in the mesocarbon microbeads, the binding property is high, the expansion of the silicon alloy can be well relieved by the unique internal dispersion structure (the structure is equivalent to the modified nano silicon alloy embedded in the mesocarbon microbeads), meanwhile, the side reaction between the material and the electrolyte is effectively inhibited, a carbon material coating layer is further coated outside the mesocarbon microbeads, a composite negative electrode material is obtained, and when the composite negative electrode material is applied to a lithium ion battery, the composite negative electrode material has high specific capacity, high efficiency and excellent cycle life.
As a preferable technical scheme of the method, the modified nano-silicon alloy in the step (1) is carbon-coated modified nano-silicon alloy.
Preferably, the preparation method of the carbon-coated modified nano-silicon alloy is a gas-phase coating method, and comprises the following steps: and (2) placing the nano silicon alloy in a reaction furnace, taking organic carbon source gas as a coating source, and carrying out carbon coating modification on the surface of the nano silicon alloy under the condition of introducing protective gas.
As a preferable technical scheme of the preparation method of the carbon-coated modified nano silicon alloy, the method comprises the following steps: and (2) placing the nano silicon alloy in a rotary furnace, adjusting the rotating speed of the rotary furnace to be 0.1 r/min-5 r/min, introducing protective gas, heating to 500-1200 ℃, introducing organic carbon source gas, and preserving heat to obtain the carbon-coated modified nano silicon alloy.
In the preferred technical scheme, the rotating speed of the rotary furnace is 0.1 r/min-5 r/min, such as 0.1r/min, 0.5 r/min, 1r/min, 2r/min, 3r/min, 4r/min or 5r/min and the like; the temperature is raised to 500 to 1200 deg.C, for example, 500 deg.C, 600 deg.C, 700 deg.C, 800 deg.C, 900 deg.C, 1000 deg.C, 1100 deg.C or 1200 deg.C.
Preferably, in the preparation process of the carbon-coated modified nano-silicon alloy, the protective gas comprises any 1 or at least 2 of nitrogen, helium, neon, argon, krypton or xenon;
preferably, in the preparation process of the carbon-coated modified nano silicon alloy, the heating rate of heating to 500-1200 ℃ is 0.5-20 ℃/min, such as 0.5 ℃/min, 1 ℃/min, 3 ℃/min, 5 ℃/min, 8 ℃/min, 10 ℃/min, 12.5 ℃/min, 15 ℃/min or 20 ℃/min, and the like.
Preferably, in the preparation process of the carbon-coated modified nano silicon alloy, the organic carbon source gas is any 1 or at least 2 combinations of hydrocarbons and/or aromatic hydrocarbon derivatives with 1-3 benzene rings, preferably any 1 or at least 2 combinations of methane, ethylene, acetylene, benzene, toluene, xylene, acetone, styrene or phenol.
Preferably, in the preparation process of the carbon-coated modified nano silicon alloy, the introduction flow rate of the organic carbon source gas is 0.1L/min to 20L/min, such as 0.1L/min, 0.5L/min, 1L/min, 5L/min, 7L/min, 10L/min, 12L/min, 14L/min, 16L/min, 18L/min or 20L/min, and the like, and preferably 2L/min to 10L/min.
Preferably, in the preparation process of the carbon-coated modified nano silicon alloy, the heat preservation time is 0.1h to 10h, for example, 0.1h, 0.5h, 1h, 3h, 5h, 6h, 8h or 10h, and the like, and preferably 1h to 5 h.
In the method, the nano silicon alloy is preferably subjected to carbon coating modification by adopting a gas phase coating method, and parameters such as the rotating speed of a rotary furnace, the reaction temperature, the introduction flow rate of organic carbon source gas, the heat preservation time and the like are controlled, so that a carbon coating modification layer with proper thickness and uniform coating is formed on the surface of the nano silicon alloy, the lipophilicity of the surface of the nano silicon alloy is favorably improved, the dispersibility and the associativity of the carbon coating modification layer dispersed in the mesocarbon microbeads are improved, and the electrochemical performance of the composite negative electrode material is improved.
As a preferred embodiment of the method of the present invention, the raw material of the mesocarbon microbeads in step (1) is any 1 or at least 2 combinations of coal pitch, coal tar, petroleum pitch, petroleum residue, synthetic pitch, synthetic resin or heavy oil, and the combinations are typically but not limited to: a combination of coal pitch and coal tar, a combination of coal pitch and petroleum pitch, a combination of coal tar and petroleum residual oil, a combination of coal pitch and heavy oil, a combination of coal pitch, coal tar and petroleum pitch, a combination of coal tar, petroleum residual oil and synthetic pitch, a combination of petroleum pitch, petroleum residual oil and synthetic resin, a combination of coal pitch, coal tar, petroleum residual oil and heavy oil, and the like.
Preferably, step (1) comprises:
(A) placing the raw materials of the modified nano silicon alloy and the mesocarbon microbeads in a reaction kettle, introducing protective gas, heating to 200-350 ℃, and stirring to uniformly disperse the modified nano silicon alloy in the raw materials of the mesocarbon microbeads;
(B) then heating to 400-550 ℃, controlling the pressure to be 0.1-12 MPa, preserving the heat, and carrying out thermal polycondensation on the raw materials of the mesocarbon microbeads to obtain a first precursor.
In the preferred technical scheme, the reaction kettle in the step (A) is a high-temperature high-pressure reaction kettle.
In this preferred embodiment, the temperature in step (A) is raised to 200-350 deg.C, such as 200 deg.C, 220 deg.C, 245 deg.C, 265 deg.C, 285 deg.C, 300 deg.C, 320 deg.C or 350 deg.C.
In this preferred embodiment, the temperature in step (B) is raised to 400-550 deg.C, such as 400 deg.C, 420 deg.C, 430 deg.C, 440 deg.C, 460 deg.C, 480 deg.C, 500 deg.C, 525 deg.C or 550 deg.C.
In this preferred embodiment, the control pressure in step (B) is 0.1MPa to 12MPa, for example, 0.1MPa, 0.5MPa, 1MPa, 3MPa, 5MPa, 7MPa, 10MPa, 11MPa or 12 MPa.
Preferably, the temperature raising rate in step (A) is 0.5 ℃/min to 15 ℃/min, such as 0.5 ℃/min, 1 ℃/min, 2 ℃/min, 3 ℃/min, 5 ℃/min, 7 ℃/min, 8 ℃/min, 10 ℃/min, 12 ℃/min, 14 ℃/min or 15 ℃/min, and the like.
Preferably, the stirring speed of step (A) is 500rpm to 2500rpm, such as 500rpm, 650rpm, 800rpm, 900rpm, 1000rpm, 1100rpm, 1250rpm, 1500rpm, 1700 rpm, 2000rpm, 2200rpm, 2500rpm, or the like; the stirring time is preferably 1 to 2 hours, for example 1 hour, 1.2 hours, 1.5 hours, 1.7 hours, 2 hours or the like.
Preferably, in the step (a), the modified nano silicon alloy accounts for 20 to 55% by mass, for example, 20%, 22.5%, 25%, 30%, 33%, 36%, 40%, 45%, 47%, 50%, 52%, 54% or 55% by mass, and preferably 30 to 50% by mass, based on 100% by mass of the total mass of the raw materials of the modified nano silicon alloy and the mesocarbon microbeads.
Preferably, the temperature raising rate in step (B) is 0.5 ℃/min to 15 ℃/min, such as 0.5 ℃/min, 1.5 ℃/min, 3 ℃/min, 5 ℃/min, 8 ℃/min, 10 ℃/min, 12 ℃/min, 13 ℃/min or 15 ℃/min, and the like.
Preferably, the pressure in step (B) is controlled to be 1MPa to 8MPa, such as 1MPa, 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa or 8 MPa.
Preferably, the incubation time in step (B) is 1h to 15h, such as 1h, 3h, 5h, 7h, 8h, 10h, 12h, 13h, 14h or 15h, etc.
As a preferable technical scheme of the method, the separation method in the step (2) comprises the following steps: any one of precipitation separation, centrifugation separation and solvent separation.
Preferably, the method for coating modification in step (3) is as follows: either a liquid phase coating method or a solid phase coating method.
Preferably, the process steps of the liquid phase coating method comprise: and dispersing the second precursor and the organic matter in an organic solvent system, and drying to obtain a third precursor.
Preferably, in the liquid phase coating process, the organic solvent is any 1 or a combination of at least 2 of ether, alcohol or ketone.
Preferably, the process steps of the solid phase coating method comprise: and (3) placing the second precursor and the organic matter in a VC high-efficiency mixer, and mixing for at least 0.5h to obtain a third precursor.
Preferably, during the solid phase coating, the rotating speed of the VC high-efficiency mixer is adjusted to be 500 r/min-3000 r/min, such as 500r/min, 650r/min, 800r/min, 1000r/min, 1200r/min, 1500 r/min, 2000r/min, 2200r/min, 2600r/min or 3000 r/min.
Preferably, in the liquid phase coating method and the solid phase coating method, the organic matter is independently any 1 or a combination of at least 2 of polyesters, saccharides, organic acids or asphalt.
In the liquid phase coating method and the solid phase coating method, the organic material is in a powder form, and the median particle diameter is independently 0.1 to 25 μm, for example, 0.1 to 1, 3, 6, 10, 15, 18, 20, 22, or 25 μm, preferably 0.5 to 8 μm.
As a preferred embodiment of the method of the present invention, the sintering in step (4) comprises: and (3) placing the third precursor in a reactor, introducing protective gas, heating to 500-1200 ℃, and preserving heat to obtain the composite cathode material.
In this preferred embodiment, the temperature is raised to 500 ℃ to 1200 ℃, for example, 500 ℃, 600 ℃, 700 ℃, 750 ℃, 800 ℃, 900 ℃, 950 ℃, 1000 ℃, 1100 ℃, 1200 ℃, or the like.
Preferably, in the sintering process in the step (4), the reactor comprises any 1 of a vacuum furnace, a box furnace, a rotary furnace, a roller kiln, a pushed slab kiln and a tubular furnace.
Preferably, during the sintering in step (4), the protective gas includes any 1 or at least 2 of nitrogen, helium, neon, argon or xenon.
Preferably, during the sintering process in step (4), the temperature raising rate is 0.5 ℃/min to 20 ℃/min, such as 0.5 ℃/min, 1 ℃/min, 3 ℃/min, 5 ℃/min, 7 ℃/min, 10 ℃/min, 12 ℃/min, 13 ℃/min or 15 ℃/min, etc.
Preferably, in the sintering process in the step (4), the holding time is 0.5h to 10h, for example, 0.5h, 1h, 3h, 5h, 6h, 8h or 10 h.
As a further preferred technical solution of the method of the present invention, the method comprises the steps of:
(1) placing the nano silicon alloy with the median particle size of 100-500 nm in a rotary furnace, adjusting the rotation speed of the rotary furnace to 0.1-5 r/min, introducing protective gas, heating to 500-1200 ℃ at the speed of 0.5-20 ℃/min, introducing organic carbon source gas with the introduction flow of 2-10L/min, preserving the heat for 1-5 h, and naturally cooling to obtain the carbon-coated modified nano silicon alloy;
placing the raw materials of the carbon-coated modified nano silicon alloy and the mesocarbon microbeads in a high-temperature high-pressure reaction kettle, introducing protective gas, heating to 200-350 ℃ at the speed of 0.5-15 ℃/min, stirring for 1-2 h at the speed of 500-2500 rpm, and uniformly dispersing the modified nano silicon alloy in the raw materials of the mesocarbon microbeads; then heating to 400-550 ℃ at the speed of 0.5-15 ℃/min, controlling the pressure to be 2-5 MPa, keeping the temperature for 1-15 h, and carrying out thermal polycondensation on the raw materials of the mesocarbon microbeads to obtain a first precursor;
(2) separating the first precursor to obtain a second precursor;
(3) coating the second precursor with an organic matter as a carbon source by adopting a liquid phase coating method or a solid phase coating method to obtain a third precursor;
(4) placing the third precursor in a reactor, heating to 500-1200 ℃ at the speed of 0.5-20.0 ℃/min, preserving the heat for 0.5-10 h, and naturally cooling to obtain the composite cathode material with the median particle size of 1-45 mu m;
wherein the modified nano silicon alloy accounts for 20-55% of the total mass of the raw materials of the modified nano silicon alloy and the mesocarbon microbeads, which is 100%;
the mass percentage of the second precursor is 75-95%, such as 75%, 80%, 82%, 85%, 87.5%, 90%, 915%, 93% or 95%, and the like, based on 100% of the total mass of the second precursor and the organic matter;
the nano silicon alloy is any 1 or combination of at least 2 of ferrosilicon, silicon-nickel alloy, silicon-titanium alloy, silicon-tin alloy, silicon-copper alloy or silicon-aluminum alloy;
the raw material of the mesocarbon microbeads is any 1 or the combination of at least 2 of coal pitch, coal tar, petroleum pitch, petroleum residual oil, synthetic pitch, synthetic resin or heavy oil;
the organic matter is any 1 or combination of at least 2 of polyester, saccharide, organic acid or asphalt.
In the preferred technical scheme, the carbon coating layer with proper thickness and uniform coating is formed on the surface of the nano silicon alloy by controlling the parameters of the gas phase coating process in the step (1), and the parameters such as the consumption of the raw materials of the modified nano silicon alloy and the mesocarbon microbeads in the step (2) and the consumption of the organic matters in the step (3) are further matched, so that good dispersion and effective coating can be formed, and the first reversible capacity, the first coulombic efficiency and the cycle performance of the material can be greatly improved.
In a third aspect, the present invention provides a lithium ion battery comprising the composite anode material of the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) the composite negative electrode material has a novel structure, the modified nano silicon alloy improves the lipophilicity of nano silicon, and the bonding property and the dispersibility of the nano silicon dispersed in the mesocarbon microbeads are improved, the unique structure can well relieve the expansion of the silicon alloy, simultaneously effectively inhibit the side reaction between the material and electrolyte, further coat a carbon material coating layer outside the mesocarbon microbeads to obtain the composite negative electrode material, and when the composite negative electrode material is applied to a lithium ion battery, the composite negative electrode material has high specific capacity, high efficiency and excellent cycle life.
(2) According to the method, the modified nano silicon alloy is introduced in the process of preparing the mesocarbon microbeads through the polymerization reaction, so that a structure that the modified nano silicon alloy is dispersed in the mesocarbon microbeads can be formed, the lipophilicity of the nano silicon is improved by the modified nano silicon alloy, the modified nano silicon alloy can be well dispersed in the mesocarbon microbeads and has high binding property, the unique structure can well relieve the expansion of the silicon alloy, and meanwhile, the side reaction between the material and the electrolyte is effectively inhibited.
According to the invention, the carbon coating modification is preferably carried out on the nano silicon alloy by adopting a gas phase coating method, and parameters such as the rotating speed of a rotary kiln, the reaction temperature, the introduction flow rate of organic carbon source gas, the heat preservation time and the like are controlled, so that a carbon coating modification layer with proper thickness and uniform coating is formed on the surface of the nano silicon alloy, thus the lipophilicity of the surface of the nano silicon alloy is favorably improved, the dispersibility and the associativity of the nano silicon alloy dispersed in the mesocarbon microbeads are improved, and the electrochemical performance of the composite negative electrode material is further improved.
(3) The invention has simple process and is easy for large-scale production.
Drawings
FIG. 1 is a schematic structural diagram of a composite anode material provided by the invention, wherein the composite anode material comprises 1-mesocarbon microbeads, 2-modified silicon nano-alloy and a 3-carbon material coating layer;
fig. 2 is a cycle curve obtained by forming a battery using the anode material of example 1 and testing it.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
The anode materials of the respective examples and comparative examples were tested by the following methods:
① first charge and discharge performance was tested using the following method:
dispersing the negative electrode material, the conductive agent and the binder of each embodiment and the comparative example in a solvent according to the mass percentage of 90:5:5, mixing, coating the obtained mixed slurry on a copper foil current collector, and drying in vacuum to obtain a negative electrode piece; then 1mol/L LiPF6The electrolyte of/EC + DMC + EMC (v/v is 1:1:1), SK (12 μm) diaphragm and shell are assembled into a CR2016 button cell by adopting a conventional process, the current density of electrochemical performance test is 0.1C and is equal to 800-1100mA h/g, and the test results are shown in Table 1.
② cycling performance was tested using the following method:
dispersing and mixing a negative electrode material, a conductive agent and a binder in a solvent according to the mass percentage of 95:2:3, coating the mixture on a copper foil current collector, and drying in vacuum to obtain a negative electrode plate; then preparing a ternary positive pole piece prepared by a traditional mature process and 1mol/L LiPF6The 18650 cylindrical single-cell battery is assembled by adopting a conventional production process through an electrolyte of/EC + DMC + EMC (v/v is 1:1:1), an SK (12 mu m) diaphragm and a shell. The charging and discharging test of the cylindrical battery is carried out on a LAND battery test system of Wuhanjinnuo electronic Co., Ltd, constant current charging and discharging are carried out under the normal temperature condition and the multiplying power of 1C, the charging and discharging voltage is limited to 2.75-4.2V, and the test result is shown in table 1.
Example 1
(1) Putting the ferrosilicon with the particle size of 150nm into a rotary furnace, adjusting the rotary speed to be 1.5r/min, introducing nitrogen, heating to 850 ℃ at the heating rate of 5.0 ℃/min, introducing acetylene gas with the flow of 2.0L/min, preserving the temperature for 1h, and naturally cooling to the room temperature to obtain the modified nano ferrosilicon;
(2) placing the modified nano ferrosilicon alloy and coal pitch into a high-temperature high-pressure reaction kettle according to the mass ratio of 50:50, introducing nitrogen, heating to 250 ℃ at the heating rate of 5.0 ℃/min, stirring for 1h in the reaction kettle at the stirring speed of 2200rpm, heating to 500 ℃ at the heating rate of 3.0 ℃/min, controlling the pressure to be 2MPa, and preserving the heat for 5h to obtain a first precursor; separating the solvent to obtain a second precursor;
(3) putting the second precursor and the asphalt into a VC high-efficiency mixer according to the ratio of 90:10, adjusting the rotating speed to 2000.0r/min, and mixing for 0.5h to obtain a third precursor; and (3) placing the third precursor in a box-type furnace, introducing nitrogen gas, heating to 900 ℃ at the heating rate of 5.0 ℃/min, preserving the heat for 1.0h, and naturally cooling to room temperature to obtain the high-capacity composite anode material.
Fig. 2 is a cycle curve obtained by testing a battery made of the anode material of the embodiment, and it can be seen that the battery has very excellent cycle performance, and the capacity retention rate is still as high as 89.3% after 1C/1C cycle for 500 times.
Example 2
(1) Placing the silicon-titanium alloy with the particle size of 200nm in a rotary furnace, adjusting the rotary speed to 3r/min, introducing argon, heating to 950 ℃ at the heating rate of 3.0 ℃/min, introducing methane gas with the flow of 5.0L/min, preserving the temperature for 3h, and naturally cooling to room temperature to obtain the modified nano silicon-titanium alloy;
(2) placing the silicon-titanium alloy and coal tar in a high-temperature high-pressure reaction kettle according to a mass ratio of 30:70, introducing argon, heating to 200 ℃ at a heating rate of 3.0 ℃/min, stirring for 2h in the reaction kettle at a stirring speed of 1500rpm, heating to 450 ℃ at a heating rate of 5.0 ℃/min, controlling the pressure to be 5MPa, and preserving heat for 7h to obtain a first precursor; obtaining a second precursor through centrifugal separation;
(3) dispersing the second precursor and glucose in ethanol according to a ratio of 85:15, and drying to obtain a third precursor; and (3) placing the third precursor in a rotary furnace, introducing nitrogen gas, heating to 700 ℃ at the heating rate of 3.0 ℃/min, preserving the heat for 2.0h, and naturally cooling to room temperature to obtain the high-capacity composite anode material.
Example 3
(1) Placing the silicon-copper alloy with the particle size of 300nm in a rotary furnace, adjusting the rotary speed to 5r/min, introducing nitrogen, heating to 700 ℃ at the heating rate of 2.0 ℃/min, introducing ethylene gas at the flow rate of 7.0L/min, preserving the heat for 5h, and naturally cooling to room temperature to obtain the modified nano silicon-copper alloy;
(2) placing the modified nano silicon-copper alloy and petroleum asphalt in a high-temperature high-pressure reaction kettle according to the mass ratio of 40:60, introducing nitrogen, heating to 300 ℃ at the heating rate of 10.0 ℃/min, stirring for 2h in the reaction kettle at the stirring speed of 800rpm, heating to 480 ℃ at the heating rate of 6.0 ℃/min, controlling the pressure to be 10MPa, and preserving the heat for 10h to obtain a first precursor; obtaining a second precursor through precipitation separation;
(3) placing the second precursor and glucose in a VC high-efficiency mixer according to the ratio of 82:18, adjusting the rotating speed to 3000.0r/min, and mixing for 0.5h to obtain a third precursor; and (3) placing the third precursor in a box-type furnace, introducing nitrogen gas, heating to 1100 ℃ at the heating rate of 10.0 ℃/min, preserving the heat for 3.0h, and naturally cooling to room temperature to obtain the high-capacity composite anode material.
Example 4
(1) Placing the silicon-nickel alloy with the particle size of 500nm in a rotary furnace, adjusting the rotary speed to be 2.5r/min, introducing argon, heating to 1100 ℃ at the heating rate of 15.0 ℃/min, introducing styrene gas at the flow rate of 15.0L/min, preserving the temperature for 0.5h, and naturally cooling to room temperature to obtain the modified nano silicon-nickel alloy;
(2) placing the silicon-nickel alloy and the synthetic asphalt in a high-temperature high-pressure reaction kettle according to a mass ratio of 45:55, introducing argon, heating to 350 ℃ at a heating rate of 7.0 ℃/min, stirring in the reaction kettle at a stirring speed of 1000rpm for 1.8h, heating to 550 ℃ at a heating rate of 10.0 ℃/min, controlling the pressure to be 8MPa, and keeping the temperature for 12h to obtain a first precursor; obtaining a second precursor through centrifugal separation;
(3) dispersing the second precursor and citric acid in acetone according to a ratio of 78:22, and drying to obtain a third precursor; and (3) placing the third precursor in a rotary furnace, introducing nitrogen gas, heating to 600 ℃ at the heating rate of 1.0 ℃/min, preserving the temperature for 10.0h, and naturally cooling to room temperature to obtain the high-capacity composite anode material.
Example 5
(1) Placing the silicon-aluminum alloy with the grain size of 750nm in a rotary furnace, adjusting the rotary speed to 4r/min, introducing nitrogen, heating to 600 ℃ at the heating rate of 6.0 ℃/min, introducing benzene gas with the flow of 3.5L/min, preserving the heat for 7.5h, and naturally cooling to room temperature to obtain the modified nano silicon-aluminum alloy;
(2) placing the modified nano silicon-aluminum alloy and the petroleum residue oil in a high-temperature high-pressure reaction kettle according to a mass ratio of 42:58, introducing nitrogen, heating to 275 ℃ at a heating rate of 5.0 ℃/min, stirring for 1.5h in the reaction kettle at a stirring speed of 2250rpm, heating to 400 ℃ at a heating rate of 8.0 ℃/min, controlling the pressure to be 12MPa, and preserving heat for 3h to obtain a first precursor; separating the solvent to obtain a second precursor;
(3) putting the second precursor and the asphalt into a VC high-efficiency mixer according to the ratio of 95:5, adjusting the rotating speed to 1500.0 r/min, and mixing for 4h to obtain a third precursor; and (3) placing the third precursor in a box-type furnace, introducing nitrogen gas, heating to 600 ℃ at the heating rate of 5.0 ℃/min, preserving the temperature for 10.0h, and naturally cooling to room temperature to obtain the high-capacity composite anode material.
Example 6
(1) Placing the silicon-tin alloy with the particle size of 80nm in a rotary furnace, adjusting the rotary speed to be 2r/min, introducing argon, heating to 1000 ℃ at the heating rate of 10.0 ℃/min, introducing acetone gas at the flow rate of 1.0L/min, preserving the temperature for 8h, and naturally cooling to room temperature to obtain the modified nano silicon-tin alloy;
(2) placing the silicon-tin alloy and heavy oil in a high-temperature high-pressure reaction kettle according to a mass ratio of 35:65, introducing argon, heating to 200 ℃ at a heating rate of 4.0 ℃/min, stirring for 2h in the reaction kettle at a stirring speed of 2000rpm, heating to 500 ℃ at a heating rate of 8.0 ℃/min, controlling the pressure to be 6.5MPa, and preserving heat for 3h to obtain a first precursor; obtaining a second precursor through centrifugal separation;
(3) dispersing the second precursor and glucose in dimethyl ether according to a ratio of 80:20, and drying to obtain a third precursor; and (3) placing the third precursor in a rotary furnace, introducing helium gas, heating to 800 ℃ at the heating rate of 8.0 ℃/min, preserving the heat for 7.0h, and naturally cooling to room temperature to obtain the high-capacity composite anode material.
Comparative example 1
A high capacity composite anode material was prepared in substantially the same manner as in example 1, except that: replacing the modified nano ferrosilicon alloy with nano silicon without modification treatment, and not coating the third precursor; a battery was fabricated in the same manner as in example 1.
TABLE 1
The anode material of the embodiments of the invention has high specific capacity, high efficiency and excellent cycle life. In the comparative example 1, nano silicon with poor expansion and conductivity is used as an active substance, and modification treatment is not performed, so that the silicon has poor dispersion effect in the mesocarbon microbeads, and the material has large expansion and poor cycle performance due to particle agglomeration; comparative example 1 no carbon coating is performed on the surface of the mesocarbon microbeads, and because nano-silicon has poor dispersibility in the mesocarbon microbeads, part of the nano-silicon may be exposed on the surface of the mesocarbon microbeads, thereby increasing the specific surface area, increasing the side reactions of the electrolyte, lowering the coulombic efficiency of the material, preventing the silicon from expanding well, and further deteriorating the cycle performance.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. The composite negative electrode material is characterized by comprising mesocarbon microbeads, modified nano-silicon alloy dispersed in the mesocarbon microbeads and a carbon material coating layer coated on the outer portions of the mesocarbon microbeads.
2. The composite anode material of claim 1, wherein in the process of preparing the mesocarbon microbeads, the modified nano-alloy is dispersed in the mesocarbon microbeads;
preferably, the modified nano-silicon alloy is a carbon-coated modified nano-silicon alloy;
preferably, the modified nano-silicon alloy consists of a nano-silicon alloy and a carbon-coated modified layer coated on the surface of the nano-silicon alloy;
preferably, the nano silicon alloy is any 1 or at least 2 of ferrosilicon, silicon-nickel alloy, silicon-titanium alloy, silicon-tin alloy, silicon-copper alloy or silicon-aluminum alloy.
3. The composite anode material according to claim 1 or 2, wherein the mass percentage of the nano silicon alloy is 10 to 60 wt%, the mass percentage of the carbon-coated modified layer is 1 to 8 wt%, the mass percentage of the mesocarbon microbeads is 30 to 80 wt%, and the mass percentage of the carbon material coating layer is 3 to 20 wt%, based on 100 wt% of the total mass of the composite anode material;
preferably, the composite negative electrode material comprises, by weight, 20% to 50% of the nano silicon alloy, 2% to 6% of the carbon-coated modified layer, 40% to 70% of the mesocarbon microbeads and 5% to 15% of the carbon material coating layer, wherein the total mass of the composite negative electrode material is 100%;
preferably, the median particle diameter of the composite negative electrode material is 1 to 45 μm, preferably 5 to 25 μm;
preferably, the nano silicon alloy has a median particle size of 50nm to 800nm, preferably 100nm to 500 nm.
4. A method for preparing a composite anode material according to any one of claims 1 to 3, characterized in that the method comprises the steps of:
(1) dispersing the modified nano-silicon alloy in a raw material of the mesocarbon microbeads, and carrying out polymerization reaction to obtain a first precursor;
(2) separating the first precursor to obtain a second precursor;
(3) coating and modifying the second precursor to obtain a third precursor;
(4) and sintering the third precursor to obtain the composite anode material.
5. The method according to claim 4, wherein the modified nano-silicon alloy of step (1) is a carbon-coated modified nano-silicon alloy;
preferably, the preparation method of the carbon-coated modified nano-silicon alloy is a gas-phase coating method, and comprises the following steps: placing the nano silicon alloy in a reaction furnace, taking organic carbon source gas as a coating source, and carrying out carbon coating modification on the surface of the nano silicon alloy under the condition of introducing protective gas;
preferably, the preparation process of the carbon-coated modified nano silicon alloy comprises the following steps: placing the nano silicon alloy in a rotary furnace, adjusting the rotating speed of the rotary furnace to be 0.1 r/min-5 r/min, introducing protective gas, heating to 500-1200 ℃, introducing organic carbon source gas, and preserving heat to obtain carbon-coated modified nano silicon alloy;
preferably, in the preparation process of the carbon-coated modified nano-silicon alloy, the protective gas comprises any 1 or at least 2 of nitrogen, helium, neon, argon, krypton or xenon;
preferably, in the preparation process of the carbon-coated modified nano silicon alloy, the temperature rise rate of the nano silicon alloy is 0.5-20 ℃/min when the nano silicon alloy is heated to 500-1200 ℃;
preferably, in the preparation process of the carbon-coated modified nano silicon alloy, the organic carbon source gas is any 1 or at least 2 combinations of hydrocarbons and/or aromatic hydrocarbon derivatives with 1-3 benzene rings, preferably any 1 or at least 2 combinations of methane, ethylene, acetylene, benzene, toluene, xylene, acetone, styrene or phenol;
preferably, in the preparation process of the carbon-coated modified nano silicon alloy, the introduction flow rate of the organic carbon source gas is 0.1-20L/min, preferably 2-10L/min;
preferably, in the preparation process of the carbon-coated modified nano silicon alloy, the heat preservation time is 0.1-10 hours, preferably 1-5 hours.
6. The method according to claim 4 or 5, wherein the raw material of the mesocarbon microbeads of step (1) is any 1 or a combination of at least 2 of coal pitch, coal tar, petroleum pitch, petroleum residue, synthetic pitch, synthetic resin or heavy oil;
preferably, step (1) comprises:
(A) placing the raw materials of the modified nano silicon alloy and the mesocarbon microbeads in a reaction kettle, introducing protective gas, heating to 200-350 ℃, and stirring to uniformly disperse the modified nano silicon alloy in the raw materials of the mesocarbon microbeads;
(B) then heating to 400-550 ℃, controlling the pressure to be 0.1-12 MPa, preserving the heat, and carrying out thermal polycondensation on the raw materials of the mesocarbon microbeads to obtain a first precursor;
preferably, the heating rate of the step (A) is 0.5 ℃/min to 15 ℃/min;
preferably, the stirring speed of the step (A) is 500 rpm-2500 rpm, and the stirring time is preferably 1 h-2 h;
preferably, in the step (a), the modified nano-silicon alloy accounts for 20 to 55 percent by mass, and preferably 30 to 50 percent by mass, based on 100 percent by mass of the total mass of the raw materials of the modified nano-silicon alloy and the mesocarbon microbeads;
preferably, the heating rate of the step (B) is 0.5 ℃/min to 15 ℃/min;
preferably, the pressure in the step (B) is controlled to be 1MPa to 8 MPa;
preferably, the heat preservation time in the step (B) is 1-15 h.
7. The method according to any one of claims 4 to 6, wherein the separation method of step (2) comprises: any one of a precipitation separation method, a centrifugal separation method or a solvent separation method;
preferably, the method for coating modification in step (3) is as follows: any one of a liquid phase coating method and a solid phase coating method;
preferably, the process steps of the liquid phase coating method comprise: dispersing the second precursor and the organic matter in an organic solvent system, and drying to obtain a third precursor;
preferably, in the liquid phase coating process, the organic solvent is any 1 or a combination of at least 2 of ether, alcohol or ketone;
preferably, the process steps of the solid phase coating method comprise: placing the second precursor and the organic matter in a VC high-efficiency mixer, and mixing for at least 0.5h to obtain a third precursor;
preferably, in the process of solid-phase coating, the rotating speed of the VC high-efficiency mixer is adjusted to be 500 r/min-3000 r/min;
preferably, in the liquid phase coating method and the solid phase coating method, the organic matter is independently any 1 or combination of at least 2 of polyesters, saccharides, organic acids or asphalt;
preferably, in the liquid phase coating method and the solid phase coating method, the organic material is in a powder form, and the median particle diameter is independently 0.1 to 25 μm, preferably 0.5 to 8 μm.
8. The method according to any one of claims 4-7, wherein the sintering of step (4) comprises: placing the third precursor in a reactor, introducing protective gas, heating to 500-1200 ℃, and preserving heat to obtain a composite anode material;
preferably, in the sintering process in the step (4), the reactor comprises any 1 of a vacuum furnace, a box furnace, a rotary furnace, a roller kiln, a pushed slab kiln or a tubular furnace;
preferably, during the sintering in step (4), the protective gas comprises any 1 or a combination of at least 2 of nitrogen, helium, neon, argon or xenon;
preferably, in the sintering process in the step (4), the temperature rise rate is 0.5 ℃/min-20 ℃/min;
preferably, in the sintering process in the step (4), the heat preservation time is 0.5-10 h.
9. Method according to any of claims 4-8, characterized in that the method comprises the steps of:
(1) placing the nano silicon alloy with the median particle size of 100-500 nm in a rotary furnace, adjusting the rotation speed of the rotary furnace to 0.1-5 r/min, introducing protective gas, heating to 500-1200 ℃ at the speed of 0.5-20 ℃/min, introducing organic carbon source gas with the introduction flow of 2-10L/min, preserving the heat for 1-5 h, and naturally cooling to obtain the carbon-coated modified nano silicon alloy;
placing the raw materials of the carbon-coated modified nano silicon alloy and the mesocarbon microbeads in a high-temperature high-pressure reaction kettle, introducing protective gas, heating to 200-350 ℃ at the speed of 0.5-15 ℃/min, stirring for 1-2 h at the speed of 500-2500 rpm, and uniformly dispersing the modified nano silicon alloy in the raw materials of the mesocarbon microbeads; then heating to 400-550 ℃ at the speed of 0.5-15 ℃/min, controlling the pressure to be 2-5 MPa, keeping the temperature for 1-15 h, and carrying out thermal polycondensation on the raw materials of the mesocarbon microbeads to obtain a first precursor;
(2) separating the first precursor to obtain a second precursor;
(3) coating the second precursor with an organic matter as a carbon source by adopting a liquid phase coating method or a solid phase coating method to obtain a third precursor;
(4) placing the third precursor in a reactor, heating to 500-1200 ℃ at the speed of 0.5-20.0 ℃/min, preserving the heat for 0.5-10 h, and naturally cooling to obtain the composite cathode material with the median particle size of 1-45 mu m;
wherein the modified nano silicon alloy accounts for 20-55% of the total mass of the raw materials of the modified nano silicon alloy and the mesocarbon microbeads, which is 100%;
the mass percentage of the second precursor is 75-95% based on the total mass of the second precursor and the organic matter as 100%;
the nano silicon alloy is any 1 or combination of at least 2 of ferrosilicon, silicon-nickel alloy, silicon-titanium alloy, silicon-tin alloy, silicon-copper alloy or silicon-aluminum alloy;
the raw material of the mesocarbon microbeads is any 1 or the combination of at least 2 of coal pitch, coal tar, petroleum pitch, petroleum residual oil, synthetic pitch, synthetic resin or heavy oil;
the organic matter is any 1 or combination of at least 2 of polyester, saccharide, organic acid or asphalt.
10. A lithium ion battery comprising the composite anode material according to any one of claims 1 to 3.
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