CN107611406B - Preparation method of silicon/graphene/carbon composite negative electrode material - Google Patents

Preparation method of silicon/graphene/carbon composite negative electrode material Download PDF

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CN107611406B
CN107611406B CN201710856163.3A CN201710856163A CN107611406B CN 107611406 B CN107611406 B CN 107611406B CN 201710856163 A CN201710856163 A CN 201710856163A CN 107611406 B CN107611406 B CN 107611406B
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graphene
dispersion liquid
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喻万景
易旭
张宝
何文洁
赵子涵
童汇
郑俊超
张佳峰
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Central South University
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Abstract

A preparation method of a silicon/graphene/carbon composite negative electrode material comprises the following steps: (1) uniformly dispersing silicon nanoparticles into absolute ethyl alcohol under ultrasonic treatment; (2) adding aminopropyl trimethoxy silane by stirring to perform surface modification treatment on silicon; (3) centrifuging and drying the dispersion to obtain APS modified silicon nanoparticles, dispersing the APS modified silicon nanoparticles in absolute ethyl alcohol to form dispersion, dropwise adding a graphene solution under stirring, centrifuging, washing, and freeze-drying; (4) uniformly mixing the polyvinylidene fluoride and the mixed solution, coating the mixture on a copper current collector to form a composite material with consistent thickness, and drying the composite material in a vacuum drying oven; (5) and carrying out high-temperature heat treatment in an inert atmosphere. The obtained negative electrode material has high discharge specific capacity, good charge-discharge characteristics and high cycle stability; the process flow is simple, the silicon content in the material is large, and the method is easy to implement and suitable for large-scale production.

Description

一种硅/石墨烯/碳复合负极材料的制备方法A kind of preparation method of silicon/graphene/carbon composite negative electrode material

技术领域technical field

本发明涉及锂离子电池技术领域,具体涉及一种硅/石墨烯/碳复合负极材料的制备方法。The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of a silicon/graphene/carbon composite negative electrode material.

背景技术Background technique

锂离子电池由于具有高电压、高比能量、长循环寿命和对环境友好等特点,成为便携式电子、移动产品、电动汽车的理想配套电源。由于电子产品小型化、高能量密度化、便携化的发展需求,尤其是智能手机和新能源电池的发展,对锂离子电池的能量密度要求越来越高,对锂离子电池性能的改善主要取决于嵌锂材料能量密度和循环寿命的提高,而目前以石墨等材料为负极的锂离子电池的理论容量仅有372 mAh/g,远远不能满足人们日常生活中对储能设备的需求,开发新型高性能负极材料已成当务之急。研究发现,将硅基材料应用于锂离子电池负极具有极高的比容量,其中理论容量可以达到3579 mAh/g,因此,将硅基材料作为锂离子电池负极材料受到越来越多的关注。Due to its high voltage, high specific energy, long cycle life and environmental friendliness, lithium-ion batteries have become an ideal supporting power source for portable electronics, mobile products, and electric vehicles. Due to the development needs of miniaturization, high energy density and portability of electronic products, especially the development of smart phones and new energy batteries, the energy density of lithium-ion batteries is getting higher and higher. The improvement of lithium-ion battery performance mainly depends on Due to the improvement of energy density and cycle life of lithium intercalation materials, the theoretical capacity of lithium-ion batteries with graphite and other materials as negative electrodes is only 372 mAh/g, which is far from meeting the needs of energy storage devices in people's daily life. New high-performance anode materials have become a top priority. Studies have found that the application of silicon-based materials to lithium-ion battery anodes has extremely high specific capacity, of which the theoretical capacity can reach 3579 mAh/g. Therefore, silicon-based materials are used as lithium-ion battery anode materials. More and more attention.

但是,在采用硅材料作为锂离子电池的负极,在电池充放电的循环过程中,Li-Si合金的可逆生成与分解将会伴随着巨大的体积变化,从而会引起硅负极材料的分化和裂缝,导致材料结构的崩塌和电极材料的脱落,进而导致电极材料与导电网络脱离,内阻增加,导致可逆容量迅速衰减,造成硅负极锂离子电池的循环性能的急剧下降。同时由于副反应的发生,在充放电过程会产生大量的气体,容易导致电池的内部胀气。针对上述问题,研究者们积极探索提高硅负极材料循环性能的方法,如降低硅材料颗粒粒径、形成多孔材料、硅薄膜材料、硅纳米线、硅复合材料等。其中比较有效的方法是制备成硅基复合材料来缓解在充放电过程中的体积膨胀,此方法已经广泛应用于锂离子电池负极材料的改性研究中。However, when silicon material is used as the negative electrode of lithium-ion battery, the reversible formation and decomposition of Li-Si alloy will be accompanied by huge volume changes during the cycle process of battery charge and discharge, which will cause the differentiation and cracks of silicon negative electrode material. , resulting in the collapse of the material structure and the detachment of the electrode material, which in turn leads to the separation of the electrode material from the conductive network, the internal resistance increases, and the reversible capacity rapidly decays, resulting in a sharp decline in the cycle performance of the silicon anode lithium-ion battery. At the same time, due to the occurrence of side reactions, a large amount of gas will be generated during the charging and discharging process, which may easily lead to the internal flatulence of the battery. In response to the above problems, researchers are actively exploring methods to improve the cycle performance of silicon anode materials, such as reducing the particle size of silicon materials, forming porous materials, silicon thin film materials, silicon nanowires, and silicon composite materials. One of the more effective methods is to prepare silicon-based composite materials to alleviate the volume expansion during charging and discharging. This method has been widely used in the modification of lithium-ion battery anode materials.

CN180094A公开了一种石墨烯包覆硅负极材料及制备方法,采用静电自组装的方法将石墨烯包覆在硅负极材料表面,提高了石墨烯包覆硅负极锂离子电池的储锂比容量和电池循环性能。但是石墨烯并不能很好的保护纳米硅颗粒的粉化。CN180094A discloses a graphene-coated silicon negative electrode material and a preparation method. The graphene is coated on the surface of the silicon negative electrode material by the electrostatic self-assembly method, which improves the lithium storage specific capacity and the lithium ion battery of the graphene-coated silicon negative electrode lithium ion battery. Battery cycle performance. However, graphene cannot protect the pulverization of nano-silicon particles well.

CN105024076A公开了一种锂离子电池负极材料及其制备方法和应用,材料分为两层:碳核心层和硅包覆层,可以有效的缓解硅材料的膨胀,从而提高了电池材料的循环性能,但是单纯的碳包覆对提高复合材料导电性的能力还是有限。CN105024076A discloses a lithium ion battery negative electrode material and its preparation method and application. The material is divided into two layers: a carbon core layer and a silicon coating layer, which can effectively relieve the expansion of the silicon material, thereby improving the cycle performance of the battery material. However, the ability of pure carbon coating to improve the electrical conductivity of composites is still limited.

以上所述的方法均不能从根本上解决硅材料负极锂离子电池在充放电过程中体积的急剧膨胀问题。None of the above-mentioned methods can fundamentally solve the problem of the rapid volume expansion of the lithium-ion battery of the silicon material negative electrode during the charging and discharging process.

发明内容SUMMARY OF THE INVENTION

本发明所要解决的技术问题是,提供一种硅/石墨烯/碳复合负极材料的制备方法,该方法制备的硅/石墨烯/碳复合负极材料,能从根本上解决硅材料负极锂离子电池在充放电过程中体积的急剧膨胀问题,从而提高硅负极锂离子电池的充放电效率,延长使用寿命。The technical problem to be solved by the present invention is to provide a method for preparing a silicon/graphene/carbon composite negative electrode material, and the silicon/graphene/carbon composite negative electrode material prepared by the method can fundamentally solve the problem of a silicon material negative electrode lithium ion battery The rapid expansion of the volume during the charging and discharging process improves the charging and discharging efficiency of the silicon anode lithium-ion battery and prolongs the service life.

本发明解决其技术问题所采用的技术方案是:一种硅/石墨烯/碳复合负极材料的制备方法,包括以下步骤:The technical solution adopted by the present invention to solve the technical problem is: a preparation method of silicon/graphene/carbon composite negative electrode material, comprising the following steps:

(1)将硅纳米颗粒在超声处理下均匀分散到无水乙醇中,形成硅纳米颗粒分散液;(1) Uniformly disperse silicon nanoparticles into absolute ethanol under ultrasonic treatment to form a silicon nanoparticle dispersion;

(2)向步骤(1)所得的硅纳米颗粒分散液中通过搅拌加入氨基丙基三甲氧基硅烷(APS)进行硅的表面修饰处理;(2) adding aminopropyltrimethoxysilane (APS) to the silicon nanoparticle dispersion obtained in step (1) by stirring to perform surface modification treatment of silicon;

(3)将步骤(2)中得到的分散液通过离心和烘干后得到APS修饰的硅纳米颗粒,将APS修饰的硅纳米颗粒分散于无水乙醇形成分散液,在搅拌下滴加入石墨烯溶液,经离心洗涤、冷冻干燥处理后得到硅纳米颗粒/石墨烯复合材料;(3) centrifuging and drying the dispersion obtained in step (2) to obtain APS-modified silicon nanoparticles, dispersing the APS-modified silicon nanoparticles in absolute ethanol to form a dispersion, and adding graphene dropwise under stirring The solution is centrifugally washed and freeze-dried to obtain a silicon nanoparticle/graphene composite material;

(4)将步骤(3)所得的硅纳米颗粒/石墨烯复合材料与聚偏氟乙稀(PVDF)混合均匀后一起涂覆在铜集流体上形成厚度一致的复合材料,并在真空干燥箱中烘干;(4) The silicon nanoparticle/graphene composite material obtained in step (3) is mixed with polyvinylidene fluoride (PVDF) and then coated together on the copper current collector to form a composite material with uniform thickness, and dried in a vacuum drying oven. medium drying;

(5)将步骤(4)烘干后的复合材料在惰性气氛中进行高温热处理,得到硅/石墨烯/碳复合负极材料。(5) The composite material after drying in step (4) is subjected to high temperature heat treatment in an inert atmosphere to obtain a silicon/graphene/carbon composite negative electrode material.

优选的,步骤(1)中,所述的硅纳米颗粒的粒径范围为30 nm~70 nm。Preferably, in step (1), the particle size of the silicon nanoparticles ranges from 30 nm to 70 nm.

优选的,步骤(1)中,所述的硅纳米颗粒分散液的浓度为0.5 mg/mL~2 mg/mL。Preferably, in step (1), the concentration of the silicon nanoparticle dispersion liquid is 0.5 mg/mL to 2 mg/mL.

优选的,步骤(2)中,加入的APS的体积百分比(APS的体积与硅纳米颗粒分散液的体积之比)为0.5%~2%。Preferably, in step (2), the volume percentage of the APS added (the ratio of the volume of the APS to the volume of the silicon nanoparticle dispersion) is 0.5% to 2%.

优选的,步骤(3)中,APS修饰的硅纳米颗粒的分散液的浓度为0.5 mg/mL~2 mg/mL。Preferably, in step (3), the concentration of the dispersion liquid of the APS-modified silicon nanoparticles is 0.5 mg/mL to 2 mg/mL.

优选的,步骤(3)中,所述加入的石墨烯溶液浓度为1 mg/mL~2.5 mg/mL。Preferably, in step (3), the added graphene solution has a concentration of 1 mg/mL to 2.5 mg/mL.

优选的,步骤(3)中,加入石墨烯溶液时,控制分散液中硅纳米颗粒与石墨烯的质量比为9~11:1。Preferably, in step (3), when adding the graphene solution, the mass ratio of silicon nanoparticles to graphene in the dispersion liquid is controlled to be 9-11:1.

优选的,步骤(4)中,所述的硅纳米颗粒/石墨烯复合材料与聚偏氟乙稀的质量比为1~3:1。Preferably, in step (4), the mass ratio of the silicon nanoparticle/graphene composite material to polyvinylidene fluoride is 1-3:1.

优选的,步骤(4)中,所述的真空干燥的温度为60℃~120℃。Preferably, in step (4), the temperature of the vacuum drying is 60°C to 120°C.

优选的,步骤(5)中,所述的惰性气氛为氩氢混合气、氩气、氮气中的一种或几种。Preferably, in step (5), the inert atmosphere is one or more of argon-hydrogen mixture, argon, and nitrogen.

优选的,步骤(5)中,所述的高温热处理温度为500℃~850℃。Preferably, in step (5), the high temperature heat treatment temperature is 500°C to 850°C.

本发明所制备的硅/石墨烯/碳复合负极材料放电比容量高(0.5 A g-1的循环电流下,首次放电容量3932.5mAh/g)、充放电特性好(0.5 A g-1的循环电流下,首次库伦效率为81.47%)、循环稳定性较高(0.5 A g-1的循环电流下,充放电30次,仍然保持有2010 mAh/g的比容量)。The silicon/graphene/carbon composite negative electrode material prepared by the invention has a high specific discharge capacity (the first discharge capacity is 3932.5mAh/g at a cycle current of 0.5 A g -1 ), and has good charge-discharge characteristics (a cycle of 0.5 A g -1 ). Under the current, the first Coulombic efficiency is 81.47%), and the cycle stability is high (under the cycle current of 0.5 A g -1 , the specific capacity of 2010 mAh/g is still maintained after being charged and discharged 30 times).

利用本发明制备的硅负极锂离子电池,与现有技术相比,一方面,包括直接使用粘结剂聚偏氟乙稀(PVDF)作为碳源对硅粒子进行表面包覆,在硅粒子表面形成一层全封装的碳包覆层,使得在电池充放电过程中,电极材料锂化速率提高3-4.5倍,提高了充放电效率;且此有弹性的、非晶形态碳结构包覆层将硅粒子在充放电过程中的“多裂纹粉化”过程转变为“单裂纹粉化”过程,增加了电池使用寿命。另一方面,包括石墨烯包覆硅粒子能够增加材料的导电性,从而进一步增加硅负极锂离子电池的充放电效率。该硅负极锂离子电池在0.5A g-1的循环电流下,充放电30次,仍然保持有2010 mAh/g的比容量;在4 A g-1 的循环电流下,充放电100次,仍然保持有750 mAh/g的比容量。Compared with the prior art, the silicon negative electrode lithium ion battery prepared by the invention, on the one hand, includes directly using the binder polyvinylidene fluoride (PVDF) as a carbon source to coat the silicon particles on the surface, A fully encapsulated carbon coating layer is formed, so that the lithiation rate of the electrode material is increased by 3-4.5 times during the charging and discharging process of the battery, and the charging and discharging efficiency is improved; and this flexible, amorphous carbon structure coating layer The process of "multi-crack pulverization" of silicon particles during the charging and discharging process is transformed into a "single crack pulverizing" process, which increases the service life of the battery. On the other hand, the inclusion of graphene-coated silicon particles can increase the electrical conductivity of the material, thereby further increasing the charge-discharge efficiency of lithium-ion batteries with silicon anodes. The silicon anode lithium - ion battery was charged and discharged 30 times at a cycle current of 0.5A g -1 , and still maintained a specific capacity of 2010 mAh/g; A specific capacity of 750 mAh/g is maintained.

附图说明Description of drawings

图1为本发明实施例1制备的硅负极电极片的SEM电镜图;Fig. 1 is the SEM electron microscope picture of the silicon negative electrode sheet prepared in Example 1 of the present invention;

图2为本发明实施例1制备的硅/石墨烯/碳复合负极材料在0.5 A g-1电流密度下的前3次充放电性能;2 is the first three charge-discharge performances of the silicon/graphene/carbon composite negative electrode material prepared in Example 1 of the present invention at a current density of 0.5 A g −1 ;

图3为本发明实施例1制备的硅/石墨烯/碳复合负极材料在0.5 A g-1电流密度下的循环性能曲线。3 is a cycle performance curve of the silicon/graphene/carbon composite negative electrode material prepared in Example 1 of the present invention at a current density of 0.5 A g −1 .

具体实施方式Detailed ways

以下所述是本发明实施例的优选实施方式,应当指出,对于本技术领域的普通技术人员来说,在不脱离本发明实施例原理的前提下,还可以做出若干改进和润饰,这些改进和润饰也视为本发明实施例的保护范围。The following descriptions are preferred implementations of the embodiments of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principles of the embodiments of the present invention. These improvements and retouching are also regarded as the protection scope of the embodiments of the present invention.

实施例1Example 1

(1)将80 mg硅纳米颗粒(40 nm~60 nm)在超声处理下均匀分散到100 ml无水乙醇中,形成浓度为0.8mg/mL的硅纳米颗粒分散液;(1) Disperse 80 mg of silicon nanoparticles (40 nm~60 nm) uniformly into 100 ml of absolute ethanol under ultrasonication to form a silicon nanoparticle dispersion with a concentration of 0.8 mg/mL;

(2)向步骤(1)所得的硅纳米颗粒分散液中通过磁力搅拌加入0.8 mL氨基丙基三甲氧基硅烷(APS)进行硅的表面修饰处理;(2) adding 0.8 mL of aminopropyltrimethoxysilane (APS) to the silicon nanoparticle dispersion obtained in step (1) by magnetic stirring to perform surface modification treatment of silicon;

(3)将步骤(2)中得到的分散液通过离心和烘干后得到APS修饰的硅纳米颗粒,将APS修饰的硅纳米颗粒分散于无水乙醇形成浓度为0.8 mg/mL的分散液,在磁力搅拌下滴加入石墨烯溶液(1.26mg/mL),使硅纳米颗粒与石墨烯的质量比为10:1,经离心洗涤、冷冻干燥处理后得到硅纳米颗粒/石墨烯复合材料;(3) centrifuging and drying the dispersion obtained in step (2) to obtain APS-modified silicon nanoparticles, and dispersing the APS-modified silicon nanoparticles in absolute ethanol to form a dispersion with a concentration of 0.8 mg/mL, Graphene solution (1.26 mg/mL) was added dropwise under magnetic stirring, so that the mass ratio of silicon nanoparticles to graphene was 10:1, and the silicon nanoparticles/graphene composite material was obtained after centrifugal washing and freeze drying;

(4)将硅纳米颗粒/石墨烯复合材料与聚偏氟乙稀(PVDF)按质量比6:4为比例混合均匀后一起涂覆在铜集流体上形成厚度一致的复合材料,并在真空干燥箱中120℃烘干;(4) The silicon nanoparticle/graphene composite material and polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 6:4 and then coated together on the copper current collector to form a composite material with the same thickness, and vacuum Dry at 120°C in a drying oven;

(5)将烘干后的复合材料在氩气气氛中550℃进行热处理,得到硅/石墨烯/碳复合负极材料。(5) heat-treating the dried composite material at 550° C. in an argon atmosphere to obtain a silicon/graphene/carbon composite negative electrode material.

本实施例所得的硅/石墨烯/碳复合负极材料制备的硅负极电极片的SEM电镜图,如图1所示。图中可以观察到石墨烯和纳米Si粒子均匀混合,并且石墨烯对纳米Si粒子有很好的包覆。The SEM image of the silicon negative electrode sheet prepared by the silicon/graphene/carbon composite negative electrode material obtained in this example is shown in FIG. 1 . In the figure, it can be observed that graphene and nano-Si particles are uniformly mixed, and graphene has a good coating on nano-Si particles.

电池组装:将煅烧处理后的复合材料在真空干燥箱中烘干,在充氩气的密闭手套箱中以金属锂为对极,以微孔聚丙烯膜作为隔膜,1.0 M LiPF6 的溶于体积比为1:1的碳酸乙烯酯(EC)和碳酸二甲酯(DMC)混合溶剂作为电解液,金属锂作为对电极,组装成CR2025的扣式电池。将电池在0.02~1 V电压范围内,测试其充放电性能。Battery assembly: The calcined composites were dried in a vacuum drying oven, and in an argon-filled airtight glove box, metal lithium was used as the counter electrode, microporous polypropylene film was used as the separator, and 1.0 M LiPF 6 dissolved in A 1:1 volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) mixed solvent was used as the electrolyte, and metal lithium was used as the counter electrode to assemble a CR2025 button battery. Test the charge and discharge performance of the battery within the voltage range of 0.02 to 1 V.

在0.5 A g-1电流密度下的前3次充放电性能,如图2所示,由图2可知,硅/石墨烯碳/复合负极材料比容量高(0.5 A g-1的循环电流下,首次放电比容量可达3932.5 mAh/g,首次库伦效率为81.47%。)Figure 2 shows the first three charge - discharge performances at a current density of 0.5 A g , the first discharge specific capacity can reach 3932.5 mAh/g, and the first Coulomb efficiency is 81.47%.)

在0.5 A g-1电流密度下的循环性能曲线,如图3所示,0.5 A g-1的循环电流下,充放电30次,仍然保持有2010 mAh/g的比容量。The cycle performance curve at the current density of 0.5 A g -1 is shown in Figure 3. Under the cycle current of 0.5 A g -1 , the specific capacity of 2010 mAh/g is still maintained after 30 times of charge and discharge.

实施例2Example 2

(1)将80 mg硅纳米颗粒(40 nm~55 nm)在超声处理下均匀分散到100 ml无水乙醇中,形成浓度为0.8 mg/mL的硅纳米颗粒分散液;(1) Disperse 80 mg of silicon nanoparticles (40 nm~55 nm) uniformly into 100 ml of absolute ethanol under ultrasonication to form a silicon nanoparticle dispersion with a concentration of 0.8 mg/mL;

(2)向硅纳米颗粒分散液中通过磁力搅拌加入0.8 mL氨基丙基三甲氧基硅烷(APS)进行硅的表面修饰处理;(2) Add 0.8 mL of aminopropyltrimethoxysilane (APS) to the silicon nanoparticle dispersion by magnetic stirring for surface modification of silicon;

(3)将步骤(2)中得到的分散液通过离心和烘干后得到APS修饰的硅纳米颗粒,将APS修饰的硅纳米颗粒分散于无水乙醇形成浓度为0.8 mg/mL的分散液,在磁力搅拌下滴加入石墨烯溶液(1.26mg/mL),使硅纳米颗粒与石墨烯的质量比为10:1,经离心洗涤、冷冻干燥处理后得到硅纳米颗粒/石墨烯复合材料;(3) centrifuging and drying the dispersion obtained in step (2) to obtain APS-modified silicon nanoparticles, and dispersing the APS-modified silicon nanoparticles in absolute ethanol to form a dispersion with a concentration of 0.8 mg/mL, Graphene solution (1.26 mg/mL) was added dropwise under magnetic stirring, so that the mass ratio of silicon nanoparticles to graphene was 10:1, and the silicon nanoparticles/graphene composite material was obtained after centrifugal washing and freeze drying;

(4)将硅纳米颗粒/石墨烯复合材料与聚偏氟乙稀(PVDF)按质量比为6:4比例混合均匀后一起涂覆在铜集流体上形成厚度一致的复合材料,并在真空干燥箱中120℃烘干;(4) The silicon nanoparticle/graphene composite material and polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 6:4, and then coated on the copper current collector to form a composite material with the same thickness, and vacuum Dry at 120°C in a drying oven;

(5)将复合材料在氩氢气氛中800℃进行热处理,得到硅/石墨烯/碳复合负极材料。(5) The composite material is heat-treated at 800° C. in an argon-hydrogen atmosphere to obtain a silicon/graphene/carbon composite negative electrode material.

电池组装:将煅烧处理后的复合材料在真空干燥箱中烘干,在充氩气的密闭手套箱中以金属锂为对极,以微孔聚丙烯膜作为隔膜,1.0 M LiPF6 的溶于体积比为1:1的碳酸乙烯酯(EC)和碳酸二甲酯(DMC)混合溶剂作为电解液,金属锂作为对电极,组装成CR2025的扣式电池。将电池在0.02~1 V电压范围内,测试其充放电性能。Battery assembly: The calcined composites were dried in a vacuum drying oven, and in an argon-filled airtight glove box, metal lithium was used as the counter electrode, microporous polypropylene film was used as the separator, and 1.0 M LiPF 6 dissolved in A 1:1 volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) mixed solvent was used as the electrolyte, and metal lithium was used as the counter electrode to assemble a CR2025 button battery. Test the charge and discharge performance of the battery within the voltage range of 0.02 to 1 V.

本实施例所得的硅/石墨烯碳/复合负极材料比容量高(0.5 A g-1的循环电流下,首次放电比容量可达3234.5 mAh/g,首次库伦效率为80.47%);0.5 A g-1的循环电流下,充放电30次,仍然保持有1845 mAh/g的比容量。The silicon/graphene carbon/composite negative electrode material obtained in this example has a high specific capacity (at a cycle current of 0.5 A g -1 , the first discharge specific capacity can reach 3234.5 mAh/g, and the first coulombic efficiency is 80.47%); 0.5 A g Under the cycle current of -1 , it still maintains a specific capacity of 1845 mAh/g after being charged and discharged 30 times.

实施例3Example 3

(1)将80 mg硅纳米颗粒(45 nm~60 nm)在超声处理下均匀分散到100 ml无水乙醇中,形成浓度为0.8 mg/mL的硅纳米颗粒分散液;(1) Disperse 80 mg of silicon nanoparticles (45 nm~60 nm) uniformly in 100 ml of absolute ethanol under ultrasonication to form a silicon nanoparticle dispersion with a concentration of 0.8 mg/mL;

(2)向硅纳米颗粒分散液中通过磁力搅拌加入0.8 mL氨基丙基三甲氧基硅烷(APS)进行硅的表面修饰处理;(2) Add 0.8 mL of aminopropyltrimethoxysilane (APS) to the silicon nanoparticle dispersion by magnetic stirring for surface modification of silicon;

(3)将步骤(2)中得到的分散液通过离心和烘干后得到APS修饰的硅纳米颗粒,将APS修饰的硅纳米颗粒分散于无水乙醇形成浓度为0.8 mg/mL的分散液,在磁力搅拌下滴加入石墨烯溶液(1.26 mg/mL),使硅纳米颗粒与石墨烯的质量比为10:1,经离心洗涤、冷冻干燥处理后得到硅纳米颗粒/石墨烯复合材料;(3) centrifuging and drying the dispersion obtained in step (2) to obtain APS-modified silicon nanoparticles, and dispersing the APS-modified silicon nanoparticles in absolute ethanol to form a dispersion with a concentration of 0.8 mg/mL, Graphene solution (1.26 mg/mL) was added dropwise under magnetic stirring, so that the mass ratio of silicon nanoparticles to graphene was 10:1, and the silicon nanoparticles/graphene composite material was obtained after centrifugal washing and freeze drying;

(4)将硅纳米颗粒/石墨烯复合材料与聚偏氟乙稀(PVDF)按质量比为6:4的比例混合均匀后一起涂覆在铜集流体上形成厚度一致的复合材料,并在真空干燥箱中120℃烘干;(4) The silicon nanoparticle/graphene composite material and polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 6:4 and then coated on the copper current collector to form a composite material with the same thickness, and the composite material with the same thickness is formed on the copper collector. Dry at 120°C in a vacuum drying oven;

(5)将复合材料在氮气气氛中850℃进行高温热处理,得到硅/石墨烯/碳复合负极材料。(5) The composite material is subjected to high temperature heat treatment at 850° C. in a nitrogen atmosphere to obtain a silicon/graphene/carbon composite negative electrode material.

电池组装:将煅烧处理后的复合材料在真空干燥箱中烘干,在充氩气的密闭手套箱中以金属锂为对极,以微孔聚丙烯膜作为隔膜,1.0 M LiPF6 的溶于体积比为1:1的碳酸乙烯酯(EC)和碳酸二甲酯(DMC)混合溶剂作为电解液,金属锂作为对电极,组装成CR2025的扣式电池。将电池在0.02~1 V电压范围内,测试其充放电性能。Battery assembly: The calcined composites were dried in a vacuum drying oven, and in an argon-filled airtight glove box, metal lithium was used as the counter electrode, microporous polypropylene film was used as the separator, and 1.0 M LiPF 6 dissolved in A 1:1 volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) mixed solvent was used as the electrolyte, and metal lithium was used as the counter electrode to assemble a CR2025 button battery. Test the charge and discharge performance of the battery within the voltage range of 0.02 to 1 V.

本实施例所得的硅/石墨烯/碳复合负极材料比容量高负极材料比容量高(0.5 Ag-1的循环电流下,首次放电比容量可达3136.5mAh/g,首次库伦效率为79.7%);0.5 A g-1的循环电流下,充放电30次,仍然保持有1789 mAh/g的比容量。The silicon/graphene/carbon composite negative electrode material obtained in this example has a high specific capacity and a high specific capacity (at a cycle current of 0.5 Ag -1 , the specific capacity of the first discharge can reach 3136.5mAh/g, and the first Coulomb efficiency is 79.7%) ; Under the cyclic current of 0.5 A g -1 , the specific capacity of 1789 mAh/g is still maintained after being charged and discharged for 30 times.

Claims (5)

1. A preparation method of a silicon/graphene/carbon composite negative electrode material is characterized by comprising the following steps:
(1) uniformly dispersing silicon nanoparticles into absolute ethyl alcohol under ultrasonic treatment to form silicon nanoparticle dispersion liquid, wherein the particle size range of the silicon nanoparticles is 30-70 nm, and the concentration of the silicon nanoparticle dispersion liquid is 0.5mg/m L-2 mg/m L;
(2) adding aminopropyl trimethoxy silane into the silicon nanoparticle dispersion liquid obtained in the step (1) by stirring to perform surface modification treatment on silicon; the volume percentage of the added aminopropyl trimethoxy silane is 0.5-2%, and the volume percentage refers to the volume ratio of the aminopropyl trimethoxy silane to the volume of the silicon nanoparticle dispersion liquid;
(3) centrifuging and drying the dispersion liquid obtained in the step (2) to obtain APS modified silicon nanoparticles, dispersing the APS modified silicon nanoparticles in absolute ethyl alcohol to form a dispersion liquid, dropwise adding a graphene solution under stirring, and carrying out centrifugal washing and freeze drying treatment to obtain a silicon nanoparticle/graphene composite material; when the graphene solution is added, controlling the mass ratio of the silicon nanoparticles to the graphene in the dispersion liquid to be 9-11: 1;
(4) uniformly mixing the silicon nanoparticle/graphene composite material obtained in the step (3) with polyvinylidene fluoride, coating the mixture on a copper current collector to form a composite material with consistent thickness, and drying the composite material in a vacuum drying oven; the mass ratio of the silicon nano-particle/graphene composite material to the PVDF is 0.25-4.5;
(5) and (4) carrying out high-temperature heat treatment on the dried composite material in the step (4) in an inert atmosphere to obtain the silicon/graphene/carbon composite anode material.
2. The method for preparing the silicon/graphene/carbon composite anode material according to claim 1, wherein in the step (3), the concentration of the APS-modified silicon nanoparticle dispersion liquid is 0.5mg/m L-2 mg/m L.
3. The preparation method of the silicon/graphene/carbon composite anode material as claimed in claim 1 or 2, wherein in the step (3), the concentration of the added graphene is 1mg/m L-2.5 mg/m L.
4. The method for preparing a silicon/graphene/carbon composite anode material according to claim 1 or 2, characterized in that: in the step (4), the temperature of the vacuum drying is 60-120 ℃.
5. The method for preparing a silicon/graphene/carbon composite anode material according to claim 1 or 2, characterized in that: in the step (5), the high-temperature heat treatment temperature is 500-850 ℃.
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