Flower-ball-shaped silicon-based negative electrode material for energy storage battery and preparation method of flower-ball-shaped silicon-based negative electrode material

Abstract

The invention provides a flower-ball-shaped silicon-based negative electrode material for an energy storage battery and a preparation method of the flower-ball-shaped silicon-based negative electrode material, and belongs to the field of composite materials. The method comprises the following steps: pretreating Si nanoparticles, pretreating the Si nanoparticles, treating commercial pure-phase Si with the diameter of 100nm by adopting piranha liquid so as to remove impurity adsorbates on the surfaces of the Si nanoparticles to enhance hydrophilicity, mixing concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) according to a certain proportion, adding the pure-phase Si, and stirring at a high temperature to react; and drying a Si (at) CS-MX precursor phase of a (Si (at) C-MX) composite structure by adopting a spray drying method on the Ti < 3 > C < 2 > T < x >-loaded C-coated Si nano-particles, and sintering at high temperature to prepare flower-ball-shaped Si (at) CS-MX composite material powder. The volume expansion of the Si nano-particles in the electrochemical reaction process can be effectively inhibited by the strong constraint effect of the amorphous C shell layer coated on the surfaces of the Si nano-particles, a compact and continuous 3D network can be formed in the Si-coated C-MX by adopting a dry spraying technology, the particle size distribution is uniform, the permeation of electrolyte into the 3D network is facilitated, and the electrochemical performance of the Si-coated C-MX is improved. And sufficient contact between the electrode active material and the electrolyte is ensured, and charge transmission of an interface is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-based negative electrode material preparation, and in particular to a flower-spherical silicon-based negative electrode material for energy storage batteries and a preparation method thereof. Background Art

[0002] In addition to metal oxides, Si anode is another type of lithium-ion battery anode material with development potential. Compared with metal oxides, silicon anode has ultra-high lithium storage capacity (~4200mAh g -1 ) and low lithium redox potential have attracted great attention from researchers. The ultra-high lithium storage capacity of silicon (Si) is due to the Li 4.4 Si alloys, so the Si negative electrode also has a 300% volume expansion during the lithiation process. Therefore, when used as the negative electrode material of lithium-ion batteries, the Si negative electrode will continuously consume lithium ions to form a SEI film due to structural pulverization, causing rapid capacity decay.

[0003] To address the volume expansion of silicon anode materials during lithium insertion and extraction, researchers generally use carbon coating to suppress this expansion, shorten the lithium ion diffusion path, increase the contact area between the active material and the electrolyte, and improve electrochemical cycling performance. However, the thickness of the coating layer is difficult to control. Excessive coating thickness can easily lead to lower capacity and initial coulombic efficiency, further reducing the energy density of lithium secondary batteries prepared with Si anode materials. These shortcomings have seriously hindered their commercial application.

[0004] In summary, there is an urgent need to develop a Si negative electrode material that is simple to synthesize, low in cost, safe and stable, which will help overcome the limitations of current technology and improve the electrochemical performance of lithium secondary batteries. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention discloses a flower-spherical silicon-based negative electrode material for energy storage batteries and a preparation method thereof. The synthesis process of the flower-spherical Si negative electrode material of the present invention is simple, low-cost, safe and stable. The prepared flower-spherical Si negative electrode material has a uniform particle size distribution, which helps the electrolyte to penetrate into it, so that the Si-based negative electrode material is in full contact with the electrode liquid, facilitates charge transfer at the interface, and effectively inhibits volume expansion.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a spherical silicon-based negative electrode material for an energy storage battery and a preparation method thereof, comprising the following steps:

[0008] Step S1: Pretreatment of Si nanoparticles: Commercially pure Si nanoparticles are treated with piranha solution to remove impurities adsorbed on the surface of the Si nanoparticles and enhance their hydrophilicity. Specifically, concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) are mixed in a certain proportion, and then pure Si nanoparticles are added and reacted with stirring at high temperature.

[0009] Step S2: preparing an acetic acid aqueous solution, adding chitosan (CS) to the acetic acid solution, and stirring until the CS is completely dissolved;

[0010] Step S3: Add an appropriate amount of Si nanoparticles washed with piranha solution to the completely dissolved CS obtained in step S2, stir evenly, and then add an appropriate amount of single-layer Ti3C2T x The suspension is stirred rapidly until it is evenly dispersed;

[0011] Step S4: spray-dry the mixed solution using a spray drying technique, collect the powder, and obtain a Si@CS-MX precursor phase.

[0012] Step S5: sintering the Si@CS-MX precursor phase obtained in step S4 at a high temperature in a tube furnace under the protection of an inert atmosphere to obtain a Si@CS-MX composite material.

[0013] Preferably, in step S1, the diameter of the commercially pure Si phase is 100 nm;

[0014] Preferably, in step S1, the ratio of concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) is (7-9):(3-5);

[0015] Preferably, in step S1, the stirring temperature after mixing is 80-100°C, and the reaction time is 40-60 minutes;

[0016] Preferably, in step S2, chitosan (CS) is used as a carbon source;

[0017] Preferably, in step S2, 200 ml of 1-3% acetic acid aqueous solution is prepared;

[0018] Preferably, in step S3, the single layer Ti3C2T x (Ti3C2T x NSs) as a conductive / flexible substrate;

[0019] Preferably, in step S3, the mixture is rapidly stirred for 12 to 24 hours until uniformly dispersed;

[0020] Preferably, in step S4, the gas flow rate during the spray drying process is 500-700 L / h, and the hot air temperature is 200-250° C.;

[0021] Preferably, in step S5, the inert gas is a H2 / Ar mixed gas, the heating rate is 1-5°C / min, the sintering temperature is 340-650°C, and the sintering time is 2-5h.

[0022] The present invention also provides a spherical Si@CS-MX composite material prepared by the preparation method described in the above technical solution.

[0023] The present invention also provides the use of the flower-spherical Si@CS-MX composite material described in the above technical solution as a negative electrode material for a lithium secondary battery.

[0024] The present invention provides a method for preparing a Ti3C2T x The preparation method and application of Si-based negative electrode materials include the following steps: first, pre-treating Si nanoparticles to remove impurities and adsorbents on the surface of the Si nanoparticles to enhance their hydrophilicity; second, preparing a composite structure of chitosan (CS) and Si nanoparticles to obtain a Si@C solution; third, drying the mixed solution in the second step using a spray dryer to obtain a Si@C precursor; and fourth, drying the Si@C precursor obtained in the third step at high temperature under an inert atmosphere to obtain a Si@C composite material.

[0025] The beneficial effects of the present invention are:

[0026] 1. The strong confinement effect of the amorphous C shell coating on the surface of the Si nanoparticles in the present invention can effectively inhibit the volume expansion of the Si nanoparticles during the electrochemical reaction;

[0027] 2. The present invention uses dry spray technology to form a tight and continuous 3D network in Si@C-MX, accelerating the ion / electron transport of the electrode material during the cycle;

[0028] 3. The "double insurance" advantage of the spherical shape of 3D Si@C-MX demonstrates ultra-high lithium storage capacity and excellent cycle stability when applied to negative electrode materials for lithium secondary batteries.

[0029] In summary, the flower-spherical Si-based composite material of the present invention is simple to synthesize, safe and stable, and has the potential for commercial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute undue limitations thereon. It is obvious that one of ordinary skill in the art could derive other drawings based on these drawings without inventive effort.

[0031] Figure 1This is a surface scanning electron microscope image of the flower-shaped Si@C-MX electrode material prepared in Example 1 of the present invention;

[0032] Figure 2 This is a surface scanning electron microscope image of the Si@C electrode material prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0033] To further illustrate the present invention, a flower-spherical silicon-based negative electrode material for an energy storage battery and a preparation method thereof provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of protection of the present invention.

[0034] In the present invention, the spherical Si@CS-MX composite material powder is preferably prepared by a method comprising the following steps:

[0035] Si nanoparticles were pretreated by mixing concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) in a ratio of (7-9): (3-5), and then pure Si was added. The stirring temperature was 80-100°C and the reaction time was 40-60 min.

[0036] In the present invention, the ratio of concentrated sulfuric acid (H2SO4) to hydrogen peroxide (H2O2) is (7-9): (3-5), more preferably 7:3;

[0037] In the present invention, the stirring temperature is preferably controlled at 80-100°C, and the reaction time is controlled at 40-60 min, more preferably at 80°C and 40 min.

[0038] Prepare 200 ml of 1-3% acetic acid aqueous solution, add chitosan (CS) to the acetic acid solution, and stir until CS is completely dissolved;

[0039] In the present invention, the 200 ml of acetic acid aqueous solution having a concentration of 1 to 3%, more preferably an acetic acid aqueous solution having a concentration of 1%;

[0040] The mixed solution is spray dried using a spray drying technique, and the powder is collected to obtain a Si@CS-MX precursor phase.

[0041] In the present invention, the gas flow rate during the spray drying process is 500-700 L / h, and the hot air temperature is 200-250°C. Preferably, the gas flow rate is 600 L / h, and the hot air temperature is 220°C.

[0042] The obtained Si@CS-MX precursor phase was sintered at high temperature in a tube furnace under inert atmosphere protection to obtain a Si@CS-MX composite material.

[0043] In the present invention, the inert atmosphere is at least one of hydrogen, nitrogen, argon and helium, more preferably a hydrogen / argon mixed gas.

[0044] In the present invention, the high temperature sintering in the tube furnace has a heating rate of 1 to 5°C / min, a sintering temperature of 340 to 650°C, and a sintering time of 2 to 5 hours, more preferably a heating rate of 1°C / min, a sintering temperature of 600°C, and a sintering time of 2 hours;

[0045] Example 1

[0046] (1) Pretreatment of Si nanoparticles: 100 nm diameter commercial pure Si is treated with piranha solution to remove impurities adsorbed on the surface of Si nanoparticles and enhance hydrophilicity;

[0047] (2) After mixing concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) in a certain proportion, add pure Si and stir at high temperature to react;

[0048] (3) Prepare 200 ml of 1% acetic acid aqueous solution;

[0049] (4) Add chitosan (CS) to the acetic acid solution and stir until CS is completely dissolved;

[0050] (5) Add 50 mg of Si nanoparticles treated with piranha wash solution to the CS solution, stir evenly, and then add 30 mg of single-layer Ti3C2T x The suspension was stirred rapidly for 12 h until uniformly dispersed;

[0051] (6) spray drying the mixed solution using a spray dryer. During the spray drying process, the gas flow rate is 600 L / h and the hot air temperature is 220°C to obtain the Si@CS-MX precursor phase;

[0052] (7) The Si@CS-MX precursor was placed in a H2 / Ar mixed atmosphere for 1 ℃ min -1 The temperature was raised to 600 °C at a heating rate of 1000 ℃ and kept for 2 h to obtain Si@C-MX composite material.

[0053] Comparative Example 1

[0054] The steps are the same as those in Example 1, except that the prepared Si-based composite material does not contain a single layer of Ti3C2T x (Ti3C2T x NSs) flexible substrate, denoted as Si@C.

[0055] (1) Pretreatment of Si nanoparticles: 100 nm diameter commercial pure Si is treated with piranha solution to remove impurities adsorbed on the surface of Si nanoparticles and enhance hydrophilicity;

[0056] (2) After mixing concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) in a certain proportion, add pure Si and stir at high temperature to react;

[0057] (3) Prepare 200 ml of 1% acetic acid aqueous solution;

[0058] (4) Add chitosan (CS) to the acetic acid solution and stir until CS is completely dissolved;

[0059] (5) Add 50 mg of Si nanoparticles treated with piranha wash solution to the CS solution and stir evenly;

[0060] (6) The mixed solution was spray dried using a spray dryer. During the spray drying process, the gas flow rate was 600 L / h and the hot air temperature was 220 °C to obtain the S@CS precursor phase;

[0061] (7) The Si@CS-MX precursor was placed in a H2 / Ar mixed atmosphere for 1 ℃ min -1 The temperature was raised to 600 °C at a heating rate of 10000 ℃ and kept for 2 h to obtain Si@C composite material.

[0062] The morphology and structure of the flower-shaped Si@C-MX and Si@C prepared in Example 1 and Comparative Example 1 are as follows: Figure 1 The morphology is a flower ball Si@C-MX. Figure 2 The Si@C morphology shows that the Si@C-MX prepared by the present invention is a micron-sized flower ball, and most of the SiNPs are tightly wrapped in a single layer of Ti3C2T x The wrinkled flower ball is beneficial to the ion / electron transport of the electrode material during the cycle.

[0063] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A spherical silicon-based negative electrode material for energy storage batteries and a preparation method thereof, characterized in that: The following steps are involved: Pre-treat Si nanoparticles by treating 100nm diameter commercial pure Si with piranha solution to remove impurities adsorbed on the surface of Si nanoparticles and enhance their hydrophilicity; after mixing concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) in a certain proportion, add pure Si and stir at high temperature to react; Ti3C2T x The C-coated Si nanoparticles were loaded and spray-dried to dry the Si@CS-MX precursor phase of the composite structure (Si@C-MX), and then sintered at high temperature to obtain the flower-spherical Si@CS-MX composite powder. The Si nanoparticle pretreatment method according to claim 1 is characterized in that the molar ratio of concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) is (7-9):(3-5).

2. The Si nanoparticles for removing surface impurity adsorbates according to claim 2, characterized in that: After mixing, the stirring temperature is 80-100° C., and the reaction time is 40-60 minutes.

3. The acetic acid aqueous solution according to claim 3, characterized in that Aqueous solution of acetic acid with a concentration of 1 to 3%.

4. The conductive / flexible matrix material according to claim 4, wherein the MXene is Ti3C2T x , Ti2CT x , Ti4C3T x At least one of .

5. The method of claim 5 , wherein the mixed solution is spray-dried using a spray dryer, During the spray drying process, the gas flow rate is 500-700 L / h, and the hot air temperature is 200-250°C.

6. The high temperature sintered Si@CS-MX according to claim 6, characterized in that Under the protection of H2 / Ar mixed atmosphere, the heating rate is 1-5°C / min, the sintering temperature is 340-650°C, and the sintering time is 2-5h.

7. Use of the flower-spherical Si@CS-MX composite material according to claim 7 as an electrode material for a lithium secondary battery.

Images