CN113629253B - Porous silicon@carbon core-shell nanosphere for lithium ion battery cathode and preparation and application thereof - Google Patents

Porous silicon@carbon core-shell nanosphere for lithium ion battery cathode and preparation and application thereof Download PDF

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CN113629253B
CN113629253B CN202110870376.8A CN202110870376A CN113629253B CN 113629253 B CN113629253 B CN 113629253B CN 202110870376 A CN202110870376 A CN 202110870376A CN 113629253 B CN113629253 B CN 113629253B
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lithium ion
porous silicon
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CN113629253A (en
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赵东元
张威
李伟
杨东
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Fudan University
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Abstract

The invention relates to a porous silicon@carbon core-shell nanosphere for a lithium ion battery cathode, and preparation and application thereof, wherein the preparation process of the nanosphere specifically comprises the following steps: dissolving a base catalyst, a carbon precursor and a silica precursor in an organic solvent/water mixed solution; the carbon precursor and the silicon dioxide precursor are hydrolyzed and polymerized under the action of base catalysis, and phase separation and precipitation are carried out to form the silicon dioxide@high molecular core-shell nanospheres; then carbonizing at high temperature to form silicon dioxide@carbon core-shell nanospheres; further reducing by molten salt to obtain the porous silicon@carbon nanospheres. Compared with the prior art, the material provided by the invention has excellent performance when being applied to the negative electrode of a lithium ion battery, the first-circle coulomb efficiency is up to 86%, the capacity is kept at 800mAh/g after 150 times of circulation under the current density of 500mA/g, the raw materials are easy to obtain in the preparation process, the method is simple, the cost is low, and the material is expected to be widely applied to the field of lithium ion batteries.

Description

Porous silicon@carbon core-shell nanosphere for lithium ion battery cathode and preparation and application thereof
Technical Field
The invention belongs to the technical field of lithium ion battery materials, and relates to a porous silicon@carbon core-shell nanosphere for a lithium ion battery cathode, and preparation and application thereof.
Background
In the existing energy storage equipment, the lithium ion battery has the advantages of high energy density, small volume, no memory effect, small self-discharge point effect and the like, and has been widely applied to portable electronic equipment and plays an important role in the fields of electric power energy storage systems and aerospace. However, the current commercial lithium ion battery has an energy density of about 150-180Wh/Kg, which makes it difficult to meet the endurance requirements of consumer electronics, especially electric automobiles. Therefore, there is an urgent need to develop a lithium ion battery system with high energy density. From the viewpoint of the anode material, silicon has a high theoretical specific capacity (4200 mA h g -1 ) And low voltage platforms, are considered ideal negative electrode materials for next generation lithium ion batteries. However, the low intrinsic conductivity of silicon and the huge volume change in the charge and discharge process limit the application of the silicon in the field of lithium ion batteries, and the modification of the silicon-based negative electrode overcomes the defectsSaid disadvantages have a very important significance.
The modification modes of the silicon-based negative electrode commonly used at present mainly comprise nanocrystallization, porosification and silicon-carbon recombination. Compounding with carbon can significantly increase the conductivity of silicon materials and mitigate the volumetric expansion of silicon, and is considered the most potential direction. Currently, some silicon-carbon negative electrode materials have been industrialized, but are limited by capacity and cycling stability, and these materials can only be used on portable electronic devices and electric tools. Development of high capacity, long stability silicon carbon anode materials for electric vehicles remains a challenge.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a porous silicon@carbon core-shell nanosphere for a lithium ion battery cathode as well as preparation and application thereof.
The aim of the invention can be achieved by the following technical scheme:
the invention provides a preparation method of porous silicon@carbon core-shell nanospheres for a lithium ion battery cathode, which comprises the following steps:
(1): dissolving a base catalyst, a carbon precursor and a silicon dioxide precursor in a mixed solvent of an organic solvent and water to obtain a mixed solution;
(2): stirring the mixed solution obtained in the step (1), washing and drying the precipitate obtained by the reaction, and roasting to obtain the silicon dioxide@carbon core-shell nanospheres;
(3): and (3) mixing the silicon dioxide@carbon core-shell nanospheres obtained in the step (2) with molten salt, and carrying out reduction treatment to obtain the target product porous silicon@carbon core-shell nanospheres.
Further, the base catalyst is selected from one or more of organic base or inorganic base. The base here serves to catalyze the hydrolytic polymerization of the silica precursor and the carbon precursor.
Further, the inorganic base is at least one of ammonia water, sodium hydroxide, potassium hydroxide and the like.
Further, the organic base is at least one of methylamine, ethylamine, octylamine, dodecylamine, triethanolamine, diethanolamine, and the like. Preferably, the base catalyst is ammonia or sodium hydroxide.
Further, the carbon precursor is prepared from phenolic substances and aldehyde substances according to a molar ratio of 1: (0.8 to 10), preferably in a molar ratio of 1:2.5. further, the phenolic substance is selected from one or more of phenol, resorcinol, catechol, hydroquinone, o-methylphenol, p-methylphenol and m-methylphenol. Resorcinol is preferred.
Further, the aldehyde substance is selected from one or more of formaldehyde, acetaldehyde, propionaldehyde or salicylaldehyde. Formaldehyde is preferred.
Further, the silicon dioxide precursor is one or more of sodium silicate, tetraethoxysilane, methyl orthosilicate, fumed silica, trichlorosilane, tetrachlorosilane, sodium metasilicate, aluminosilicate, 1, 4-bis (triethoxysilyl) benzene, bis (triethoxysilyl) ethylene, methoxydimethylbenzene silane, (diphenylmethyl) trichlorosilane, bis (p-bromophenyl) dimethyl silane and ethoxytriethyl silane. Ethyl orthosilicate is preferred.
Further, in the step (1), the volume ratio of the organic solvent to the water is (0.5-5): 1, preferably 2:1.
further, the organic solvent is used for uniformly mixing the silicon dioxide precursor and the carbon precursor, and the silicon dioxide precursor and the carbon precursor can be one or more of methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, cyclohexane or n-hexane. Preferably, the organic solvent is ethanol.
Further, in step (1), the molar ratio of the base catalyst, the carbon precursor, and the silica precursor is (5-50): (1.8-11): (1-10), preferably, the molar ratio of the base catalyst, the phenolic substance, the aldehyde substance, the silica precursor and the organic solvent is (5-50): 1: (0.8-10): (1-10): (80-500). More preferably 12:1:2:4:260.
further, in the step (2), the stirring is performed at room temperature for 12 to 120 hours, preferably 24 hours.
Further, in the step (2), the calcination is performed under an inert atmosphere at a temperature of 500 to 1500 ℃, preferably 1000 ℃, for a time of 2 to 24 hours, preferably 6 hours.
Further, in the step (3), the molten salt is one or more of a binary molten salt system and a ternary molten salt system; wherein the binary molten salt system is Al-AlCl 3 、Mg-AlCl 3 At least one of the following; the ternary molten salt system is Al-AlCl 3 -NaCl、Al-AlCl 3 -ZnCl 2 、Mg-AlCl 3 -NaCl、Mg-AlCl 3 -ZnCl 2 Or CaCl 2 -MgCl 2 -at least one of NaCl, etc.
Further, in the step (3), the temperature of the reduction treatment is 100 to 500 ℃, preferably 230 ℃, and the time is 2 to 30 hours, preferably 12 hours.
The second technical proposal of the invention provides a porous silicon@carbon core-shell nanosphere for the lithium ion battery cathode, which is prepared by adopting the preparation method, wherein the size of the porous silicon@carbon core-shell nanosphere is 20-5000nm, and the specific surface area is 100-2000m 2 And/g, the carbon content is 5-90wt%.
The third technical scheme of the invention provides an application of the porous silicon@carbon core-shell nanospheres for the negative electrode of the lithium ion battery as a negative electrode material of the lithium ion battery. In particular, it shows when used as lithium ion battery electrode material: the initial coulomb efficiency is up to 86% at a current density of 500mA/g, and the capacity is kept at 800mAh/g after 150 cycles. Therefore, the porous silicon@carbon core-shell nanosphere has a wide application prospect in the aspect of lithium ion batteries.
Compared with the prior art, the invention has the following advantages:
1) Because the porous silicon@carbon nanospheres provided by the invention have a porous structure, space and buffer can be provided for volume expansion in the silicon charge and discharge process;
2) Because the porous silicon@carbon provided by the invention is wrapped by the carbon layer, the conductivity of the electrode material can be improved, and the transmission of electrons is ensured;
drawings
FIG. 1 is a flow chart of the preparation of porous silicon @ carbon core-shell nanospheres in accordance with an embodiment of the present invention;
FIG. 2 is a transmission electron microscope image of the porous silicon@carbon core-shell nanospheres provided in example 1 of the present invention;
FIG. 3 is a scanning electron microscope image of the porous silicon@carbon core-shell nanospheres provided in example 1 of the present invention;
FIG. 4 is a thermal weight loss diagram of the porous silicon@carbon core-shell nanospheres provided in example 1 of the present invention;
FIG. 5 is an X-ray diffraction pattern of the porous silicon@carbon core-shell nanospheres provided in example 1 of the present invention;
FIG. 6 is a drawing showing nitrogen adsorption and desorption of porous silicon@carbon core-shell nanospheres provided in example 1 of the present invention;
FIG. 7 is a graph showing pore size distribution of the porous silica@carbon core-shell nanospheres provided in example 1 of the present invention;
FIG. 8 is a charge-discharge curve of the porous silicon@carbon core-shell nanospheres provided in example 1 of the present invention as a negative electrode material of a lithium ion battery at a current density of 500 mA/g;
FIG. 9 is a charge-discharge curve at a current density of 500mA/g when porous silicon provided in comparative example 1 of the present invention is used as a negative electrode material for a lithium ion battery;
fig. 10 is a charge-discharge curve at a current density of 500mA/g when silica @ carbon provided in comparative example 2 of the present invention is used as a negative electrode material for a lithium ion battery.
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples. The present embodiment is implemented on the premise of the technical scheme of the present invention, and a detailed implementation manner and a specific operation process are given, but the protection scope of the present invention is not limited to the following examples.
In the following description of the various embodiments of the present invention,
the remainder, unless specifically stated, is indicative of a conventional commercially available feedstock or conventional processing technique in the art.
Example 1
The preparation method of the porous silicon@carbon core-shell nanospheres comprises the following steps:
first 1.25ml ammonia was added to 40ml of ethanol/water (volume ratio 2:1) mixed solution. After stirring for 30 minutes and mixing uniformly, 1.6ml of ethyl orthosilicate, 0.20g of resorcinol and 0.28ml of formaldehyde solution were added respectively, and the mixture was reacted at room temperature for 24 hours. And then, after centrifugal washing, placing the sample in a tube furnace protected by argon atmosphere, and roasting for 6 hours at 1000 ℃ to obtain the silicon dioxide@carbon nanospheres. Mixing the obtained nanospheres with aluminum powder, aluminum trichloride and sodium chloride according to the mass ratio of 1:0.8:8:0.45, placing the mixture in a tube furnace, reducing the mixture for 12 hours at 230 ℃, washing the mixture by hydrochloric acid, centrifuging the mixture to obtain the nano-spheres with the size of 280nm, the carbon content of 25wt% and the specific surface area of 132m 2 Samples per gram.
Referring to fig. 1, in this embodiment, tetraethyl orthosilicate is used as a silicon source, a polymer produced by polymerizing resorcinol and formaldehyde is used as a carbon source, ammonia water is used as a catalyst, and the silica@polymer core-shell nanospheres are formed by crosslinking and polymerization of precursors. And then reducing silicon dioxide into porous silicon by high-temperature carbonization and molten salt reduction, and carbonizing the high polymer layer into carbon to obtain the porous silicon@carbon nanospheres.
Specifically, referring to fig. 2-3, the transmission electron microscope of fig. 2 shows that the porous silicon @ carbon nanospheres obtained in example 1 have a size of about-280 nm and a carbon layer thickness of about-30 nm. Fig. 3 shows that the porous silicon @ carbon nanospheres obtained in example 1 have uniform spherical morphology and good dispersibility.
FIG. 4 is a graph of thermal weight loss of the porous silicon @ carbon nanosphere material obtained in example 1, with a carbon content of about 25% by weight.
FIG. 5 is a powder X-ray diffraction pattern of the porous silicon@carbon nanosphere material obtained in example 1, corresponding to the X-ray diffraction peaks of elemental silicon, showing that magnesia reduction can successfully convert silicon dioxide to elemental silicon.
Fig. 6 is a nitrogen adsorption/desorption isotherm of the porous silicon @ carbon nanosphere material obtained in example 1. The adsorption curve is an IV curve, a typical mesoporous material adsorption isotherm. The corresponding mesoporous is obviously adsorbed at the relative pressure of 0.5-0.8. The specific surface area of the material is 132m 2 /g
FIG. 7 is a pore size distribution curve of the porous silicon@carbon nanosphere material obtained in example 1. The curve shows that the material has a uniform pore size, about 5.6nm in size.
Fig. 8 is a lithium ion battery performance test of the porous silicon @ carbon nanosphere material obtained in example 1. The initial coulomb efficiency of the obtained material reaches 86%, and 1000mAh g still exists after 180 times of circulation -1 Is a capacity retention of (c).
Example 2
A preparation method of porous silicon@carbon comprises the following steps:
first, 1.25ml of ammonia water was added to 40ml of a mixed solution of ethanol/water (volume ratio 2:1). After stirring for 30 minutes and mixing uniformly, 1.6ml of ethyl orthosilicate, 0.30g of resorcinol and 0.42ml of formaldehyde solution were added respectively, and reacted at room temperature for 24 hours. And then, after centrifugal washing, placing the sample in a tube furnace protected by argon atmosphere, and roasting for 6 hours at 1000 ℃ to obtain the silicon dioxide@carbon nanospheres. Mixing the obtained nanospheres with aluminum powder, aluminum trichloride and sodium chloride according to the mass ratio of 1:0.8:8:0.45, placing the mixture in a tube furnace, reducing the mixture at 230 ℃ for 12 hours, washing the mixture by hydrochloric acid, centrifuging the mixture to obtain the nano-spheres with the size of 350nm, the carbon content of 40wt% and the specific surface area of 160m 2 Samples per gram.
Comparative example 1:
in comparison with example 1, the same was carried out for the most part, except that resorcinol and formaldehyde were not added as high molecular sources.
Fig. 9 shows that the simple porous silicon spheres lost capacity quickly without the protection of the carbon layer.
Comparative example 2:
in comparison with example 1, the vast majority are identical, except that no molten salt reduction is performed.
Fig. 10 shows that the capacity of the material is low when the silica is not reduced to porous silicon.
Example 3:
in comparison with example 1, the molar ratio of the base catalyst, the phenol, the aldehyde, the silica precursor and the organic solvent was adjusted to 5 by adjusting the addition amount of the raw materials other than resorcinol in this example: 1:0.8:1:80.
example 4:
in comparison with example 1, the molar ratio of the base catalyst, the phenol, the aldehyde, the silica precursor and the organic solvent was 50 by adjusting the addition amount of the raw materials other than resorcinol in this example: 1:10:10:500.
example 5:
in comparison with example 1, the molar ratio of the base catalyst, the phenol, the aldehyde, the silica precursor and the organic solvent was 12 by adjusting the addition amount of the raw materials other than resorcinol in this example: 1:2:4:260.
example 6:
compared to example 1, the vast majority are identical, except in this example: after adding formaldehyde solution, the reaction time is 12 hours at room temperature;
roasting is carried out in inert atmosphere, the roasting temperature is 1500 ℃, and the roasting time is 2 hours;
the reduction treatment was carried out at 100℃for 30 hours.
Example 7:
compared to example 1, the vast majority are identical, except in this example: after adding formaldehyde solution, the reaction time is 120h at room temperature;
roasting is carried out in inert atmosphere, the roasting temperature is 500 ℃, and the roasting time is 2 hours;
the temperature of the reduction treatment was 500℃and the time was 2 hours.
Examples 8 to 15:
compared to example 1, the vast majority are identical, except in this example: the alkali catalyst ammonia water is replaced by sodium hydroxide, potassium hydroxide, methylamine, ethylamine, octylamine, dodecylamine, triethanolamine and diethanolamine with equal molar amounts respectively.
Example 16:
compared to example 1, the vast majority are identical, except in this example: the carbon precursor is prepared from phenolic substances and aldehyde substances according to a molar ratio of 1: 0.8.
Example 17:
compared to example 1, the vast majority are identical, except in this example: the carbon precursor is prepared from phenolic substances and aldehyde substances according to a molar ratio of 1: 10.
Example 18:
compared to example 1, the vast majority are identical, except in this example: the carbon precursor is prepared from phenolic substances and aldehyde substances according to a molar ratio of 1:2.5.
Examples 19 to 24:
compared to example 1, the vast majority are identical, except in this example: the phenolic substance resorcinol is replaced by equimolar amounts of phenol, catechol, hydroquinone, o-methylphenol, p-methylphenol, m-methylphenol respectively.
Examples 25 to 27:
compared to example 1, the vast majority are identical, except in this example: the aldehydes are replaced by equimolar amounts of acetaldehyde, propionaldehyde or salicylaldehyde, respectively.
Examples 28 to 40:
compared to example 1, the vast majority are identical, except in this example: the silica precursor ethyl orthosilicate is replaced by equimolar amounts of sodium silicate, methyl orthosilicate, fumed silica, trichlorosilane, tetrachlorosilane, sodium metasilicate, aluminosilicate, 1, 4-bis (triethoxysilyl) benzene, bis (triethoxysilyl) ethylene, methoxydimethylbenzene silane, (diphenylmethyl) trichlorosilane, bis (p-bromophenyl) dimethyl silane, ethoxytriethyl silane, respectively.
Example 41:
compared to example 1, the vast majority are identical, except in this example: the volume ratio of the organic solvent to the water is 0.5:1.
Example 42:
compared to example 1, the vast majority are identical, except in this example: the volume ratio of the organic solvent to the water is 5:1.
Examples 43 to 49:
compared to example 1, the vast majority are identical, except in this example: the organic solvent is replaced with an equal volume amount of methanol, propanol, isopropanol, n-butanol, sec-butanol, cyclohexane or n-hexane.
In the above examples, the molten salt used may be replaced with Al-AlCl 3 、Mg-AlCl 3 Equal binary system or Al-AlCl 3 -NaCl、Al-AlCl 3 -ZnCl 2 、Mg-AlCl 3 -NaCl、Mg-AlCl 3 -ZnCl 2 Or CaCl 2 -MgCl 2 Any one or a mixture of a plurality of ternary systems such as NaCl.
The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present invention.

Claims (3)

1. The preparation method of the porous silicon@carbon core-shell nanospheres for the lithium ion battery cathode is characterized by comprising the following steps of:
(1): dissolving a base catalyst, a carbon precursor and a silicon dioxide precursor in a mixed solvent of an organic solvent and water to obtain a mixed solution;
(2): stirring the mixed solution obtained in the step (1), washing and drying the precipitate obtained by the reaction, and roasting to obtain the silicon dioxide@carbon core-shell nanospheres;
(3): mixing the silicon dioxide@carbon core-shell nanospheres obtained in the step (2) with molten salt, and carrying out reduction treatment to obtain a target product porous silicon@carbon core-shell nanosphere;
the base catalyst is selected from one or more of organic base or inorganic base;
wherein the inorganic alkali is at least one of ammonia water, sodium hydroxide and potassium hydroxide;
the organic base is at least one of methylamine, ethylamine, octylamine, dodecylamine, triethanolamine and diethanolamine;
the carbon precursor is prepared from phenolic substances and aldehyde substances according to a molar ratio of 1: (0.8-10);
the phenolic substances are selected from one or more of phenol, resorcinol, catechol, hydroquinone, o-methylphenol, p-methylphenol and m-methylphenol;
the aldehyde substance is selected from one or more of formaldehyde, acetaldehyde, propionaldehyde or salicylaldehyde;
the silicon dioxide precursor is one or more of sodium silicate, tetraethoxysilane, methyl orthosilicate, fumed silica, trichlorosilane, tetrachlorosilane, sodium metasilicate, aluminosilicate oxide, 1, 4-bis (triethoxysilyl) benzene, bis (triethoxysilyl) ethylene, methoxydimethylbenzene silane, (diphenylmethyl) trichlorosilane, bis (p-bromophenyl) dimethylsilane and ethoxytriethylsilane;
in the step (1), the volume ratio of the organic solvent to the water is (0.5-5): 1;
in step (1), the molar ratio of the base catalyst, the carbon precursor and the silica precursor is (5-50): (1.8-11): (1-10);
in the step (2), stirring is carried out at room temperature, and the stirring time is 12-120h;
roasting is carried out in inert atmosphere, the roasting temperature is 500-1500 ℃, and the roasting time is 2-24h;
in the step (3), the molten salt is one or more of a binary molten salt system and a ternary molten salt system; wherein the binary molten salt system is Al-AlCl 3 、Mg-AlCl 3 At least one of (a) and (b); the ternary molten salt system is Al-AlCl 3 -NaCl、Al-AlCl 3 -ZnCl 2 、Mg-AlCl 3 -NaCl、Mg-AlCl 3 -ZnCl 2 Or CaCl 2 -MgCl 2 -at least one of NaCl;
the temperature of the reduction treatment is 100-500 ℃ and the time is 2-30h.
2. A porous silicon@carbon core-shell nanosphere for a lithium ion battery cathode, which is prepared by the preparation method as claimed in claim 1, is characterized in that the size of the porous silicon@carbon core-shell nanosphere is 20-5000nm, and the specific surface area is 100-2000m 2 Per g, the carbon content is 5-90wt%.
3. The use of a porous silicon @ carbon core-shell nanosphere for a lithium ion battery negative electrode as claimed in claim 2 as a lithium ion battery negative electrode material.
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CN109755482A (en) * 2017-11-01 2019-05-14 同济大学 Silicon/carbon composite and preparation method thereof

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