A nano-silicon-silicon monoxide negative electrode material with an inlay structure and a preparation method thereof

Abstract

The application belongs to the technical field of nanometer material preparation, and particularly relates to a kind of nanometer silicon-silicon monoxide negative electrode material with inlay structure and a preparation method thereof, wherein nanometer white carbon black is used as raw material, Al powder is used as reducing agent, NaCl, KCl and AlCl3 are used as auxiliary molten salt, the mixture is put into a tube furnace and heat treated in argon atmosphere, the heat treated product is soaked in hydrochloric acid to remove excess Al powder and molten salt, then repeatedly washed with distilled water and centrifuged, and vacuum dried to obtain the nanometer silicon-silicon monoxide negative electrode material with inlay structure. The preparation method is scientifically and reasonably designed, and the nanometer silicon is inlaid in silicon monoxide, which greatly limits the bulk expansion of nanometer silicon. When the material with this structure is used as battery negative electrode material, it can not only ensure that the theoretical specific capacity is higher than that of pure SiO x , but also can relieve the bulk expansion of pure silicon, so that the cycle stability and rate performance are more excellent.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation technology, specifically relating to an embedded structure nano-silicon-silicon suboxide anode material and its preparation method. Background Technology

[0002] The theoretical specific capacity of silicon materials is as high as 4200 mAh g. -1 (Li 22 Si(5) is considered the most promising next-generation lithium-ion battery anode material. However, elemental Si anode materials experience a volume change exceeding 300% during alloying / dealloying, leading to silicon particle cracking and pulverization, loss of effective contact with the conductive agent and current collector, and consequently, rapid capacity decay. Therefore, silicon materials have attracted increasing attention from scholars over the past few decades. To address the prominent issues in the commercial application of silicon-based anodes, various effective strategies have been explored to develop electrode materials with long cycle life and high rate performance.

[0003] silicon suboxide (SiO) x As a negative electrode material for lithium-ion batteries, it has a high theoretical specific capacity (2680 mAh g). -1 and low lithium intercalation potential (~0.5V vs. Li / Li) + Silicon suboxide (SiO₂) is a promising high-energy-density lithium-ion battery anode material. x As a negative electrode material for lithium-ion batteries, lithium silicate or lithium oxide is generated during lithiation, which reduces the overall volume expansion. At the same time, the generated lithium silicate or lithium oxide also acts as a buffer layer to reduce the impact of volume changes on the structure. It is considered to be a negative electrode material with a high degree of commercial use in the Si-based material family.

[0004] Industrial preparation of amorphous SiO x The main methods for material analysis can be divided into gas-phase methods, solid-phase methods, and wet chemical methods. The gas-phase method uses Si and SiO2 as raw materials. Under vacuum conditions, the temperature is raised to 1200–1500°C. The raw material powder sublimates into a gas, which is then rapidly cooled to deposit black amorphous SiO2. x By adjusting process conditions and raw material ratios, SiO₂ can be precisely controlled. x The method involves determining the oxygen content in the solution. While widely used industrially, this method requires stringent preparation conditions, demanding equipment, and incurring high production costs. The solid-state method uses SiO2 as a raw material, and under high temperature and an inert atmosphere, hydrogen gas is introduced to induce a redox reaction, reducing SiO2 to SiO2. xThis method involves high-temperature reduction reaction conditions and the use of hydrogen, making it highly dangerous and unsuitable for large-scale industrial production. Wet chemical methods mainly include solvothermal methods, sol-gel methods, and microemulsion methods, combined with carbothermal reduction heat treatment to prepare SiO₂. x These reactions are typically carried out at atmospheric pressure below 1000°C. Compared to gas-phase and solid-phase methods, wet chemical methods for preparing SiO2... x The reaction conditions for the material are relatively mild, and the prepared SiO x The material is uniformly dispersed, has a controllable morphology, and exhibits good electrochemical lithium storage performance.

[0005] When pure silicon is used as the negative electrode material for lithium-ion batteries, it will produce huge volume expansion during charging and discharging. However, when pure silicon suboxide is used as the negative electrode material for lithium-ion batteries, the volume expansion will be significantly reduced, but the initial theoretical specific capacity will be lower. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned problems existing in the conventional technology and provide an embedded structure nano-silicon-silicon suboxide anode material and its preparation method. This material maintains the high theoretical capacity of silicon and allows silicon suboxide to slow down the large volume change of silicon material. Furthermore, this embedded structure nano-silicon oxide / silicon suboxide powder has excellent electrochemical performance when used as a lithium-ion battery anode material.

[0007] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0008] This invention provides a method for preparing a nano-silicon-silicon suboxide anode material with an embedded structure, comprising the following steps:

[0009] 1) Mix nano-silica and Al powder evenly at a certain molar ratio to obtain powder A;

[0010] 2) Prepare a certain amount of ternary molten salt of NaCl, KCl and AlCl3, mix them evenly, and obtain powder B;

[0011] 3) Place the obtained powder A and powder B into an alumina crucible and mix them evenly. Place the crucible in a tube furnace and heat it to a certain temperature in an argon atmosphere for constant temperature and heat treatment.

[0012] 4) Soak the heat-treated product in excess hydrochloric acid to remove excess aluminum powder and molten salt;

[0013] 5) The product treated with hydrochloric acid was repeatedly washed with distilled water and centrifuged, and then dried in a vacuum drying oven to obtain the embedded structured nano-silicon-silicon suboxide anode material.

[0014] Furthermore, in the preparation method of the nano-silicon-silicon suboxide anode material with the inlaid structure as described above, in step 1), the molar ratio of nano-silica to Al powder is 1:1.2 to 1.5.

[0015] Furthermore, in the preparation method of the nano-silicon-silicon suboxide anode material with the above-described embedded structure, in step 2), when preparing the ternary molten salt, the molar percentage of the ternary chloride is:

[0016] AlCl3: 50%–64%

[0017] KCl: 9%–12.5%

[0018] The balance is NaCl.

[0019] Furthermore, in the preparation method of the nano-silicon-silicon suboxide anode material with the embedded structure as described above, in step 3), the molar ratio of powder A to powder B is 1.5 to 2.0:1.

[0020] Furthermore, in the preparation method of the nano-silicon-silicon suboxide anode material with the embedded structure as described above, in step 3), the temperature of the isothermal treatment is 300-450℃ and the time is 6-12h.

[0021] Furthermore, in the preparation method of the nano-silicon-silicon suboxide anode material with the embedded structure as described above, in step 3), the heating rate is 5℃ / min.

[0022] Furthermore, in the preparation method of the nano-silicon-silicon suboxide anode material with the inlaid structure as described above, in step 3), the flow rate of argon gas is 100-200 mL / min.

[0023] The present invention also provides an embedded structured nano-silicon-silicon suboxide anode material, which is prepared by the above-described preparation method.

[0024] The beneficial effects of this invention are:

[0025] 1. The preparation method of this invention is scientifically and rationally designed. The reaction generates nano-silicon embedded in silicon suboxide, which greatly limits the large volume expansion of nano-silicon. When this structured material is used as a battery anode material, it can ensure a theoretical specific capacity similar to that of pure SiO₂. x This method boasts high theoretical capacity and mitigates the significant volume expansion of pure silicon, resulting in superior cycle stability and rate performance. It is simple, easy to operate, and inexpensive, yielding high-yield nano-silicon-silicon suboxide anode materials.

[0026] 2. This invention utilizes Na in molten salt + Breaking the Si-O bonds in nano-SiO2, aluminum powder will break the Si... 4+The silicon is reduced to nano-Si, while the unreduced SiO2 reacts with the nano-silicon in a disproportionation reaction to form SiO2. x The method of coating nano-silicon surfaces is simple, low-cost, easy to operate, and has great commercial value.

[0027] Of course, any product implementing this invention does not necessarily need to achieve all of the above advantages at the same time. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is the XRD pattern of the nano-silicon-silicon suboxide anode material in Example 1;

[0030] Figure 2 This is the FESEM image of the nano-silicon-silicon suboxide anode material from Example 1;

[0031] Figure 3 This is a TEM image of the nano-silicon-silicon suboxide anode material from Example 1;

[0032] Figure 4 This is the XRD pattern of the nano-silicon-silicon suboxide anode material in Example 2;

[0033] Figure 5 The simulated battery sample assembled using nano-silicon-silicon suboxide anode material as the anode material in Example 1 was tested at 0.05 A g. -1 Constant current charge-discharge curves under these conditions;

[0034] Figure 6 Example 1 shows a simulated battery sample assembled using nano-silicon-silicon suboxide anode material as the anode material at a temperature of 0.5 Ag. -1 The following is a graph showing the cyclic performance. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention uses nano-SiO2 as raw material, Al powder as reducing agent, and NaCl, KCl, and AlCl3 as auxiliary molten salts. After mixing them evenly, they are placed in a tube furnace and heat-treated at a certain temperature in an argon atmosphere for 6-12 hours. The heat-treated product is then soaked in hydrochloric acid to remove excess aluminum powder and molten salt, and then repeatedly washed with distilled water and centrifuged. After vacuum drying, an embedded nano-silicon-silicon suboxide anode material is obtained.

[0037] Example 1

[0038] A method for preparing an embedded structured nano-silicon-silicon suboxide anode material includes the following steps:

[0039] 1) Weigh a certain amount of nano-carbon black and Al powder according to the molar ratio of nano-carbon black to aluminum powder of 1:1.5, mix them evenly in the preliminary stage, and obtain powder A;

[0040] 2) Weigh out 50% AlCl3, 37.5% NaCl, and 12.5% ​​KCl, mix them evenly to obtain powder B;

[0041] 3) Mix powder A and powder B in a molar ratio of 1.8:1 in a corundum crucible and mix them evenly again. Place the crucible in a tube furnace and heat it to 400°C at 5°C / min in an argon atmosphere for 12 hours.

[0042] 4) After heat treatment, the sample was soaked in 9wt% hydrochloric acid and stirred continuously for 12 hours before being washed out.

[0043] 5) Use distilled water to repeatedly wash and centrifuge to separate the nano-silicon suboxide, and dry it in a vacuum drying oven to obtain nano-silicon-silicon suboxide anode material.

[0044] The method of this invention prepares embedded silicon-silica suboxide nanoparticles for use as anode materials in lithium-ion batteries. This eliminates the need for carbon coating and significantly improves electrochemical performance compared to existing commercial silicon anode materials. At a current density of 0.05 Ag... -1 At that time, the reversible specific capacity was 3374–2562 mAh g. -1 The initial coulomb efficiency was 75.92%, at 0.5A g -1 The reversible specific capacity after 200 cycles at a given current density is 1470–1461 mAh g. -1 The capacity retention rate is 88.49%, and the current density is increased to 2A g. -1 At that time, the capacity was still 1172mAh g. -1 .

[0045] Example 2

[0046] A method for preparing an embedded structured nano-silicon-silicon suboxide anode material includes the following steps:

[0047] 1) Weigh a certain amount of nano-carbon black and Al powder according to the molar ratio of nano-carbon black to aluminum powder of 1:1.5, mix them evenly in the preliminary stage, and obtain powder A;

[0048] 2) Weigh out 60% AlCl3, 30% NaCl, and 10% KCl, mix them evenly to obtain powder B;

[0049] 3) Mix powder A and powder B in a molar ratio of 1.8:1 in a corundum crucible and mix them evenly again. Place the crucible in a tube furnace and heat it to 400°C at 5°C / min in an argon atmosphere for 6 hours.

[0050] 4) After heat treatment, the sample was soaked in 9wt% hydrochloric acid and stirred continuously for 12 hours before being washed out.

[0051] 5) Use distilled water to repeatedly wash and centrifuge to separate the nano-silicon suboxide, and dry it in a vacuum drying oven to obtain nano-silicon-silicon suboxide anode material.

[0052] Example 3

[0053] A method for preparing an embedded structured nano-silicon-silicon suboxide anode material includes the following steps:

[0054] 1) Weigh a certain amount of nano-carbon black and Al powder according to the molar ratio of nano-carbon black to aluminum powder of 1:1.2, mix them evenly in the preliminary stage, and obtain powder A;

[0055] 2) Weigh out 60% AlCl3, 30% NaCl, and 10% KCl, mix them evenly to obtain powder B;

[0056] 3) Mix powder A and powder B in a molar ratio of 1.8:1 in a corundum crucible and mix them evenly again. Place the crucible in a tube furnace and heat it to 350°C at 5°C / min in an argon atmosphere for 12 hours.

[0057] 4) After heat treatment, the sample was soaked in 9wt% hydrochloric acid and stirred continuously for 12 hours before being washed out.

[0058] 5) Use distilled water to repeatedly wash and centrifuge to separate the nano-silicon suboxide, and dry it in a vacuum drying oven to obtain nano-silicon-silicon suboxide anode material.

[0059] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. The application of an inlaid structured nano-silicon-silicon suboxide as a negative electrode material, characterized in that, The preparation method of the embedded structured nano-silicon-silicon suboxide anode material includes the following steps: 1) Mix nano-silica and Al powder evenly at a molar ratio of 1:1.2-1.5 to obtain powder A; 2) Prepare a certain amount of ternary molten salt of NaCl, KCl, and AlCl3, mix them evenly, and obtain powder B; when preparing the ternary molten salt, the molar percentage of the ternary chloride is: AlCl3: 50%–64% KCl: 9%~12.5% The balance is NaCl; 3) Mix the obtained powder A and powder B in an alumina crucible at a molar ratio of 1.5 to 2.0:

1. Place the crucible in a tube furnace and heat it to a certain temperature in an argon atmosphere. Perform constant temperature and heat treatment at a temperature of 300 to 450°C for 6 to 12 hours. 4) Soak the heat-treated product in excess hydrochloric acid to remove excess aluminum powder and molten salt; 5) The product treated with hydrochloric acid was repeatedly washed with distilled water and centrifuged, and then dried in a vacuum drying oven to obtain the embedded structured nano-silicon-silicon suboxide anode material.

2. The application according to claim 1, characterized in that: In step 3), the heating rate is 5℃ / min.

3. The application according to claim 1, characterized in that: In step 3), the flow rate of argon gas is 100-200 mL / min.

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