Dual-core shell structure silicon-based microcapsule composite material, preparation method, semi-solid lithium-ion battery negative electrode paste and lithium-ion battery

Abstract

The present invention provides a dual-core shell structured silicon-based microcapsule composite material, a preparation method thereof, a semi-solid lithium-ion battery negative electrode paste, and a lithium-ion battery. Using Si@void@SnO2 nanospheres as the inner phase of the capsule, a dual-core shell structured silicon-based capsule composite material is prepared by a microfluidic technique and then formed into a microcapsule composite material after high-temperature carbonization. The abundant void structures existing inside can buffer volume changes, reduce the loss of active mass during the charge / discharge process, and thus improve the electrochemical performance in the negative electrode of a lithium-ion battery and the semi-solid lithium-ion battery negative electrode paste. Moreover, the dual-core shell structured silicon-based microcapsule composite material prepared by the microfluidic technique of the present invention has good controllability; the experimental process is simple and the yield is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, specifically to the technical field of semi-solid rechargeable batteries, and particularly relates to a dual-core shell structure silicon-based microcapsule composite material and a preparation method thereof, a semi-solid lithium-ion battery negative electrode slurry, and a lithium-ion battery. Background Art

[0002] The current commercial lithium-ion battery negative electrode is graphite. Problems such as its low capacity, poor stability, many side reactions caused by low purity, and poor rate performance have made it urgent to find a material with stable structure, high capacity, and capable of adapting to charge and discharge at high current density to replace natural graphite as the negative electrode of rechargeable lithium-ion batteries.

[0003] Among many materials, silicon-based composite materials can be used as alternative materials for the next-generation lithium-ion battery negative electrode due to their simple preparation process, stable structure, large theoretical capacity, and ability to adapt to high-current charge and discharge. The current preparation process of negative electrode materials is mostly the coating method. The prepared material is ground with conductive carbon black and then dispersed in carboxymethyl cellulose to form a slurry, which is then coated on the current collector copper foil with a certain thickness, dried, hot-rolled, and sliced to obtain the negative electrode sheet. The complex electrode sheet preparation process involves raw material ratio, slurry concentration, coating thickness, drying time, adhesion to the current collector, slicing process, etc., which increases the errors affecting the performance of the finally prepared electrode sheet and greatly increases the R & D and preparation costs of the electrode. Moreover, during the cycling process of the electrode sheet, due to the volume expansion of the material during charge and discharge, the surface of the electrode sheet will crack, resulting in the detachment of the electrode material from the current collector and causing irreversible attenuation of the battery capacity. Summary of the Invention

[0004] The purpose of the present invention is to provide a dual-core shell structure silicon-based microcapsule composite material and a preparation method thereof. Si@void@SnO 2 nanospheres are ultrasonically dispersed in a polyvinyl alcohol solution to form the inner phase of the capsule; through microfluidic technology, under the action of a polyvinyl alcohol driving liquid, a dual-core shell structure silicon-based microcapsule composite material is prepared.

[0005] Another purpose of the present invention is to provide a semi-solid lithium-ion battery negative electrode slurry. Using the above-mentioned dual-core shell structure silicon-based microcapsule composite material as the active material, without a current collector, it not only has a high capacity but also can avoid cracks in the electrode sheet during cycling and detachment from the current collector, thus having the characteristic of high stability.

[0006] Another purpose of the present invention is to provide a lithium-ion battery prepared using the semi-solid lithium-ion battery negative electrode slurry.

[0007] The specific technical solution of the present invention is as follows:

[0008] Preparation method of a dual-core shell structure silicon-based microcapsule composite material, comprising the following steps:

[0009] 1) Dispersing silicon particles in a mixed solution of ethanol and water, adding ammonia water and tetraethyl orthosilicate for reaction, and filtering, washing, and drying the product to obtain a Si@SiO 2 composite material;

[0010] 2) Dispersing the Si@SiO 2 composite material in a mixed solution of ethanol and water, adding urea and a tin source for hydrothermal reaction, centrifuging, washing, drying, and calcining the product to obtain a Si@void@SnO 2 composite material.

[0011] 3) Dispersing the Si@void@SnO 2 composite material in an aqueous solution of polyvinyl alcohol to form an inner phase solution A of the capsule;

[0012] 4) Preparing an outer phase solution B of the capsule;

[0013] 5) Synthesizing the inner phase solution A of the capsule prepared in step 3), the outer phase solution B of the capsule prepared in step 4), and the aqueous solution of polyvinyl alcohol through microfluidic technology to obtain a dual-core shell structure silicon-based microcapsule;

[0014] 6) Calcining the dual-core shell structure silicon-based microcapsule to obtain a dual-core shell structure silicon-based microcapsule composite material.

[0015] In step 1), the diameter of the silicon particles is 80 - 150 nanometers;

[0016] In step 1), the dosage ratio of the silicon particles to tetraethyl orthosilicate is 0.25 - 0.5:8 - 10 g / ml;

[0017] In step 1), the volume ratio of ethanol, water, ammonia water, and tetraethyl orthosilicate is 100 - 200:20 - 30:5 - 6:4 - 5; the mass concentration of the ammonia water is 22 - 25%; the water is preferably deionized water.

[0018] In step 1), the reaction conditions are: stirring continuously at a speed of 500 - 1500 r / min for 2 hours;

[0019] In step 1), the drying temperature is 60 - 80 °C, and the drying time is 10 - 12 hours.

[0020] In step 1), under the catalytic action of ammonia water, tetraethyl orthosilicate hydrolyzes and coats on the surface of the silicon particles, forming a composite material with silicon particles wrapped by silicon dioxide.

[0021] In step 2), the volume ratio of ethanol to water is 2:3;

[0022] Step 2) The dosage ratio of the Si@SiO 2 composite material to the mixed solution of ethanol and water is 0.01 - 0.04:30 g / ml.

[0023] In step 2), the mass ratio of the Si@SiO 2 composite material, urea and tin source is 0.02 - 0.04:0.45 - 0.9:0.06 - 0.12.

[0024] In step 2), the tin source is preferably potassium stannate trihydrate K 2 SnO 3 ·3H 2 O;

[0025] In step 2), the hydrothermal reaction conditions are reacting at 170 - 180 °C for 2 - 4 hours;

[0026] In step 2), the calcination conditions are calcining at 550 - 600 °C for 2 - 4 hours.

[0027] In step 2), the calcination is preferably carried out in an air atmosphere.

[0028] In step 2), the drying temperature is 60 - 80 °C and the drying time is 10 - 12 hours.

[0029] In step 2), under hydrothermal conditions, SiO 2 is gradually etched and dissolved, while the tin source gradually forms SnO 2 precursor adsorbed on the outer layer. As SiO 2 is completely etched, a shell of SnO 2 is formed on its surface, and the space originally occupied by the etched and dissolved SiO 2 becomes voids, thus forming a core - shell structure. Among them, the diameter of SnO 2 is related to the original diameter of Si@SiO 2 , and the thickness of the voids is related to the thickness of the SiO 2 layer. The size of the voids affects the ability of the product to buffer the volume change of the internal Si particles. Large voids contribute to completely buffering the volume expansion of Si; if the voids are too small, the volume expansion of silicon may break the outer layer of SnO 2 , causing it to rupture.

[0030] In step 3), the mass concentration of the polyvinyl alcohol aqueous solution is 2 - 20%.

[0031] In step 3), the dosage ratio of the Si@void@SnO 2 composite material to the polyvinyl alcohol aqueous solution is 0.05 - 0.2:1 g / mL.

[0032] Step 4) The specific preparation method is as follows: Add 2-hydroxy-2-methylpropiophenone to trimethylolpropane ethoxylate triacrylate and stir evenly to form the capsule outer phase solution B;

[0033] In step 4), the mass ratio of trimethylolpropane ethoxylate triacrylate to 2-hydroxy-2-methylpropiophenone is 10:(0.2 - 1.0). Trimethylolpropane ethoxylate triacrylate is used as the capsule outer phase material; 2-hydroxy-2-methylpropiophenone is used as the photocuring material to cure the capsule and make it not easy to break.

[0034] Step 5) is specifically as follows: Place the capsule inner phase solution A, the capsule outer phase solution B, and the polyvinyl alcohol aqueous solution in syringes according to the volume ratio (1 - 5):(1 - 5):(100 - 200) as the inner phase, outer phase, and driving phase respectively. Using microfluidic technology, the flow rate of the inner phase pump is 4 - 10 mL / h, the flow rate of the outer phase pump is 5 - 10 mL / h, and the flow rate of the outermost driving phase pump is 600 - 800 mL / h. Collect the product, wash it repeatedly with deionized water, and let it stand in deionized water for 2 - 3 days. After filtration, place it in an oven at 60 - 80 °C and dry it overnight for 10 - 12 hours.

[0035] The preparation method of the polyvinyl alcohol aqueous solution in step 5) is as follows: Disperse polyvinyl alcohol in deionized water, place it in a water bath at 60 - 80 °C and stir constantly until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol aqueous solution with a mass concentration of 0.02 - 0.04 g / mL;

[0036] The calcination in step 6) specifically has the following calcination conditions: the temperature is 400 - 450 °C, and the calcination time is 2 - 4 hours. Preferably, it is calcined in an argon atmosphere. Calcination carbonization makes the organic substances trimethylolpropane ethoxylate triacrylate and 2-hydroxy-2-methylpropiophenone in the capsule shell become inorganic carbon, and increases the conductivity. After high-temperature carbonization, a microcapsule composite material is formed. The rich void structure inside it can buffer the volume change and reduce the loss of active mass during the charge / discharge process, thereby improving the electrochemical performance in the negative electrode of lithium-ion batteries and the negative electrode paste of semi-solid lithium-ion batteries.

[0037] The dual-core-shell structure silicon-based microcapsule composite material provided by the present invention is prepared by the above method. The dual-core-shell structure silicon-based microcapsule composite material is spherical with an average diameter of 40 - 60 μm. Inside the spherical capsule, there is Si@void@SnO 2 composite material, Si@void@SnO 2 The size of the composite material is 200 - 400 nm. Si@void@SnO 2 is a core-shell structure, Si@void@SnO 2 is wrapped into the capsule and forms another core-shell structure. Therefore, the dual-core-shell structure is obtained in the present invention.

[0038] In the preparation method of the dual-core-shell structured silicon-based microcapsule composite material provided by the present invention, first, the core-shell structured Si@void@SnO 2 nanospheres are prepared, and then the Si@void@SnO 2 nanospheres are ultrasonically dispersed in a polyvinyl alcohol solution to form the inner phase of the capsule. Then, trimethylolpropane ethoxylate triacrylate (ETPTA) and 2-hydroxy-2-methylpropiophenone are used as photoinitiators and stirred evenly to form the outer phase of the capsule. Through microfluidic technology, under the action of a polyvinyl alcohol driving liquid, microcapsules encapsulating the Si@void@SnO 2 nanospheres are prepared; these microcapsules are dual-core-shell structured silicon-based microcapsule composite materials. The prepared microcapsules are subjected to high-temperature carbonization under argon protection to form the dual-core-shell structured silicon-based microcapsule composite material. In the present invention, the Si@void@SnO 2 nanospheres are used as the inner phase of the capsule, greatly improving the cycle stability of the capsule composite material. Single silicon particles have a high theoretical capacity but insufficient stability. The core-shell structure can effectively buffer the volume change of silicon nanoparticles. The Si@void@SnO 2 nanospheres not only have a high capacity but also high stability, thereby improving the capacity stability and fast charge-discharge performance. The loose and porous outer shell of the microcapsule has a large specific surface area, which is beneficial to accelerating electron transfer. At the same time, it also reduces the loss of active substances during the charge-discharge process and buffers the volume change, thereby improving the electrochemical performance of the anode material. The dual-core-shell structure synergistically stabilizes the solid electrolyte interface layer. The dual-core-shell structured silicon-based microcapsule composite material prepared by the present invention through microfluidic technology has good controllability; the experimental process is simple and the yield is high.

[0039] The semi-solid lithium-ion battery anode slurry provided by the present invention is prepared by using the above dual-core-shell structured silicon-based microcapsule composite material as the active material.

[0040] The preparation method of the semi-solid lithium-ion battery anode slurry is as follows: the dual-core-shell structured silicon-based microcapsule composite material is mixed with conductive carbon black and then ground. Under magnetic stirring, the ground powder is dispersed in the electrolyte, and then a polymer is added and stirred continuously to form a homogeneous slurry, thus obtaining it;

[0041] The mass ratio of the core-shell structured silicon-based microcapsule composite material to the conductive carbon black is 8:1, and the volume ratio of the total mass of the dual-core-shell structured silicon-based microcapsule composite material and the conductive carbon black to the electrolyte is 1:20 to 1:5 g / mL -1 , preferably 1:10 g / mL -1 ; the electrolyte serves both as a dispersant and as an electrolyte.

[0042] The ratio of the mass of the polymer to the mass of the core-shell structured silicon-based microcapsule composite material is preferably 8:1. The polymer is carboxymethyl cellulose CMC.

[0043] During the preparation, the stirring rate is 300 - 1300 r / min, and the stirring time is 2 - 12 h.

[0044] Compared with traditional solid electrodes, in semi-solid electrodes, since the active material is dispersed in the electrolyte, the steps such as slurry coating, drying, and hot rolling in the electrode preparation process are omitted, greatly reducing the preparation process and flow, and avoiding capacity attenuation caused by the detachment of the electrode material from the current collector. Moreover, during the charge and discharge process, the semi-solid electrode does not generate cracks compared with traditional electrodes, which can greatly improve the cycle life. The active material in the semi-solid slurry electrode is in a suspended state under stirring conditions. As the stirring stops, the material will precipitate at the bottom due to the influence of gravity. Therefore, the polymer added in the present invention can dissolve in the electrolyte environment and form a framework to form a conductive network to prevent the active material from precipitating. When the active material expands in volume during the charge and discharge process, since the active material is dispersed in the electrolyte, there will be no cracks and capacity attenuation compared with traditional electrodes, which is conducive to the rapid transmission of electrons and ions and can improve the performance of the battery.

[0045] The lithium-ion battery provided by the present invention is prepared by using a semi-solid lithium-ion battery negative electrode slurry.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] (1) The outer part of the prepared dual-core-shell structured silicon-based microcapsule composite material is a loose carbon layer, which is beneficial to improving the overall conductivity of the material;

[0048] (2) The prepared dual-core-shell structured silicon-based microcapsule composite material shows a high specific capacity and better capacity reversibility when applied to the negative electrode of a lithium-ion battery;

[0049] (3) The use of the semi-solid slurry electrode can avoid the shedding of active substances caused by the volume expansion of the material during the charge and discharge process, and is beneficial to regulating the content of active substances in the battery, which is conducive to the research and development of materials and the reduction of the battery process cost;

[0050] (4) The raw materials are inexpensive, the preparation process is simple, and large-scale production can be carried out. Description of the Drawings

[0051] Figure 1 SEM image of the Si@SiO 2 composite material prepared in step 1) of Example 1;

[0052] Figure 2The Si@SiO prepared in step 1) of Example 1 2 TEM image of the composite material

[0053] Figure 3 The Si@void@SnO prepared in step 2) of Example 1 2 SEM image of the composite material;

[0054] Figure 4 The Si@void@SnO prepared in step 2) of Example 1 2 TEM image of the composite material;

[0055] Figure 5 SEM image of the dual-core shell structure silicon-based microcapsule composite material prepared in step 5) of Example 1;

[0056] Figure 6 Optical picture of the dual-core shell structure silicon-based microcapsule composite material prepared in step 5) of Example 1;

[0057] Figure 7 SEM image of the dual-core shell structure silicon-based microcapsule composite material after calcination prepared in step 6) of Example 1;

[0058] Figure 8 XRD pattern of the dual-core shell structure silicon-based microcapsule composite material prepared in step 6) of Example 1;

[0059] Figure 9 Semi-solid slurry diagram prepared in Example 3;

[0060] Figure 10 Cycling performance diagram of the semi-solid slurry lithium-ion battery in Example 4;

[0061] Figure 11 Charge-discharge curve diagram of the semi-solid slurry lithium-ion battery in Example 4;

[0062] Figure 12 The lithium-ion battery assembled with the negative electrode of the lithium-ion battery prepared from the dual-core shell structure silicon-based microcapsule composite material prepared in Example 1 at 0.2 A g -1 Cycling performance diagram at the current density;

[0063] Figure 13 The charge-discharge curve diagram of the lithium-ion battery assembled with the negative electrode of the lithium-ion battery prepared from the composite material prepared in Example 1 at 0.2 A g -1 Charge-discharge curve diagram at the current density. Detailed implementation manners

[0064] The present invention will be described in detail below in conjunction with the embodiments and the accompanying drawings of the specification.

[0065] Example 1

[0066] A preparation method of a dual-core-shell structure silicon-based microcapsule composite material, comprising the following steps:

[0067] 1) Ultrasonically disperse 0.05 g of silicon particles (the diameter of the silicon particles is 80 - 150 nm) in a mixed solution of 40 mL of ethanol and 8 mL of water. While stirring, add 2 mL of ammonia water with a mass concentration of 22% and 1.6 mL of tetraethyl orthosilicate, and stir at a speed of 1000 r / min at room temperature for 2 hours. Then, after centrifugal filtration and washing, place it in an oven at 60 °C for 12 hours to obtain the Si@SiO 2 composite material, as Figure 1 and Figure 2 shown, the silicon particles are wrapped by SiO 2 ;

[0068] 2) Ultrasonically disperse 0.04 g of the Si@SiO 2 composite material in a mixed solution of 12 mL of ethanol and 18 mL of water, add 0.9 g of urea and 0.12 g of K 2 SnO 3 ·3H 2 O and stir for 10 minutes; carry out a hydrothermal reaction under the condition of reacting at 170 °C for 2 hours; centrifuge, wash, and place it in an oven at 70 °C for 12 hours, and calcine in an air atmosphere. The calcination temperature is 550 °C and the calcination time is 2 hours to obtain the Si@void@SnO 2 composite material, as Figure 3 and 4 shown, the silicon nanoparticles are wrapped by the outer layer of SnO 2 , and there is a void between the silicon and SnO 2 to facilitate buffering the volume change during the insertion and extraction of lithium ions and obtain stable lithium-ion battery performance;

[0069] 3) Ultrasonically disperse 0.5 g of the Si@void@SnO 2 composite material in 10 mL of an aqueous solution of polyvinyl alcohol with a mass concentration of 5% to obtain a mixed solution A;

[0070] 4) Stir and mix 0.4 mL of 2-hydroxy-2-methylpropiophenone and 10 g of trimethylolpropane ethoxylate triacrylate (ETPTA) evenly to obtain a mixed solution B;

[0071] 5) Disperse 20 g of polyvinyl alcohol in 1000 mL of deionized water, place it in a water bath at 70 °C, and stir constantly until the polyvinyl alcohol is completely dissolved to obtain an aqueous polyvinyl alcohol solution, which is mixed solution C; place mixed solution A, mixed solution B, and mixed solution C in syringes according to a volume ratio of 1:1:120 as the inner phase, outer phase, and driving phase respectively. Using microfluidic technology, the flow rate of the inner phase pump is 4 mL / h, the flow rate of the outer phase pump is 5 mL / h, and the flow rate of the outermost driving phase pump is 700 mL / h. Collect the product, wash it repeatedly with deionized water, and let it stand in deionized water for 2 days. After filtration, place it in an oven at 60 °C and dry it overnight for 12 hours to obtain the dual-core shell-structured silicon-based microcapsule composite material, as Figure 5 and Figure 6 shown, with uniform size and smooth surface;

[0072] 6) Place the obtained microcapsules in an argon atmosphere and calcine them at 420 °C for 2 hours to obtain carbonized capsules, namely dual-core shell-structured silicon-based microcapsule composite materials.

[0073] The dual-core shell-structured silicon-based microcapsule composite material prepared above is spherical with an average diameter of 40 - 60 μm. The inside of the spherical capsule is wrapped with Si@void@SnO 2 composite material, as Figure 7 shown, thus forming a unique morphology of core-shell structure wrapping core-shell structure (YSYS), which is conducive to electrolyte diffusion and ion transport, as well as buffering volume changes. The synergistic effect enables high capacity and long-term cycle stability as the anode of a lithium-ion battery.

[0074] Figure 8 XRD pattern of the dual-core shell-structured silicon-based microcapsule composite material prepared in step 6) of Example 1;

[0075] Example 2 (the prepared battery is used as a comparison)

[0076] Use the dual-core shell-structured silicon-based microcapsule composite material prepared in Example 1 as the active material to prepare the anode slurry, electrode sheet, and lithium-ion battery of the lithium-ion battery:

[0077] Modulation of the slurry: After uniformly mixing the prepared dual-core shell-structured silicon-based microcapsule composite material, conductive carbon black, and CMC in a ratio of 8:1:1, add 0.15 mL of SBR as a dispersant and stir magnetically for 10 hours to form a uniform slurry.

[0078] Prepare the electrode sheet using the above slurry: Coat the stirred slurry on a clean copper foil with a certain thickness by the coating method, and then dry it in a vacuum drying oven at 70 °C for 10 hours. Then use a cutting machine to cut it into small round electrodes of a certain size.

[0079] Preparation of lithium-ion battery using the above electrode sheets: The prepared electrode sheets were assembled into 2032-type button batteries in a glove box filled with high-purity argon (water value and oxygen value ≤ 0.01 ppm). The electrolyte consists of ethylene carbonate and diethyl carbonate (volume ratio 1:1), and the solvent contains 1M LiPF 6 . The specific method for assembling the battery is as follows: 0.05 mL of the electrolyte was dropped onto the electrode case, and then the above-prepared electrode sheet was placed. Then, 0.05 mL of the electrolyte was dropped to wet the electrode surface. A separator was placed on the electrode sheet, 0.05 mL of the electrolyte was dropped on the separator, and then a lithium sheet was placed as the counter electrode. Subsequently, a spacer and a spring piece were placed as supports, and the battery was tightly sealed with a hydraulic press.

[0080] Example 3

[0081] Preparation method of the negative electrode slurry for semi-solid lithium-ion battery. The specific preparation method is as follows: 0.08 g of the dual-core shell structure silicon-based microcapsule composite material prepared in Example 1 was ground and mixed with 0.01 g of conductive carbon black. Then, in the glove box, the evenly ground sample was magnetically stirred and dispersed in 1 mL of a binary electrolyte composed of ethylene carbonate and diethyl carbonate (volume ratio 1:1). After stirring and dispersing evenly, 0.01 g of CMC was added, and stirring continued for 10 hours to obtain the semi-solid slurry. It can be seen that the semi-solid slurry has good fluidity and homogeneity. Figure 9 It can be seen that the semi-solid slurry has good fluidity and homogeneity.

[0082] The prepared semi-solid lithium-ion battery negative electrode slurry was directly dropped onto the electrode case, and the content of the active material in the battery was calculated by the mass difference before and after dropping the slurry on the electrode case. Then, a glass fiber wetted with the binary electrolyte was placed as the separator, and then a lithium sheet was placed as the counter electrode. Then, a spacer and a spring piece were placed as supports. After placing the battery negative electrode case, the battery was pressed tightly with a hydraulic press.

[0083] Example 4

[0084] Electrochemical performance test of semi-solid lithium-ion battery:

[0085] After the semi-solid lithium-ion battery assembled in Example 3 was placed for 24 hours, cyclic performance and charge-discharge performance tests were carried out at a current density of 0.2 A g -1 . The results are as shown in Figure 10 、 Figure 11 . It can be seen from the figure that after 125 cycles, the capacity of the battery can still be stabilized at about 780 mAh g -1 , and the Coulomb efficiency is close to 100%.

[0086] Comparative Example 1

[0087] Electrochemical performance test of the electrode sheet lithium-ion battery:

[0088] After the battery assembled in Example 2 was placed for 12 to 24 hours, tests on the battery cycle performance and charge-discharge performance were carried out at a current density of 0.2 A g -1 . The results are as Figure 12 , Figure 13 shown, and excellent electrochemical performance is also demonstrated. Compared with the semi-solid state lithium-ion battery, although the capacity is increased, the Coulomb efficiency is unstable and fluctuates greatly, indicating that the charge-discharge energy loss of the battery is unstable, which is due to the fact that the solid electrode is difficult to buffer the large volume change of the active material during charge and discharge, resulting in poor structural stability of the electrode. Moreover, it can be seen that the capacity of the semi-solid state battery remains stable, while the capacity of the lithium-ion battery with a traditional solid electrode sheet decays significantly, which also reflects the significant superiority of the semi-solid state battery developed in this invention in terms of long-term cycle stability compared with the traditional solid electrode sheet battery.

[0089] This invention uses a silicon-based composite material with high capacity as the negative electrode to replace the currently commercialized graphite negative electrode. The simple preparation process makes the preparation cost lower, thus making the R & D process simpler. This invention provides a novel, high-capacity, low-cost and good-stability preparation process for semi-solid state lithium-ion batteries.

[0090] The above detailed description of a novel battery and its preparation technology for a dual-core shell structure silicon-based microcapsule composite material, its preparation method, rechargeable lithium-ion battery and semi-solid state lithium-ion battery with reference to the embodiments is illustrative rather than restrictive. Several embodiments can be listed within the defined scope. Therefore, changes and modifications without departing from the general concept of this invention should fall within the protection scope of this invention.

Claims

1. Preparation method of a dual-core shell structure silicon-based microcapsule composite material, characterized in that, the preparation method comprises the following steps: 1) Disperse silicon particles in a mixed solution of ethanol and water, add ammonia water and tetraethyl orthosilicate for reaction, and filter, wash, and dry the product to obtain the Si@SiO 2 composite material; 2) Disperse the Si@SiO 2 composite material in a mixed solution of ethanol and water, add urea and a tin source for hydrothermal reaction, centrifuge and wash the product, dry it, and calcine it to obtain the Si@void@SnO 2 composite material; 3) Disperse the Si@void@SnO 2 composite material in an aqueous solution of polyvinyl alcohol to form the inner phase solution A of the capsule; 4) Prepare the outer phase solution B of the capsule: Add 2-hydroxy-2-methylpropiophenone to trimethylolpropane ethoxylate triacrylate and stir evenly to form the outer phase solution B of the capsule; 5) Synthesize the inner phase solution A of the capsule prepared in step 3), the outer phase solution B of the capsule prepared in step 4), and the polyvinyl alcohol aqueous solution through microfluidic technology to obtain a dual-core shell structure silicon-based microcapsule; 6) Calcinate the dual-core shell structure silicon-based microcapsule to obtain a dual-core shell structure silicon-based microcapsule composite material.

2. The preparation method according to claim 1, characterized in that, in step 1), the dosage ratio of the silicon particles to tetraethyl orthosilicate is 0.25 - 0.5:8 - 10 g / ml; the volume ratio of ethanol, water, ammonia water and tetraethyl orthosilicate is 100 - 200:20 - 30:5 - 6:4 - 5.

3. The preparation method according to claim 1, characterized in that, Step 2) The volume ratio of ethanol to water is 2:3; the dosage ratio of the Si@SiO 2 composite material to the mixed solution of ethanol and water is 0.01 - 0.04:30 g / ml; the mass ratio of the Si@SiO 2 composite material, urea and tin source is 0.02 - 0.04:0.45 - 0.9:0.06 - 0.

12.

4. The preparation method according to claim 1 or 3, characterized in that, in step 2), the hydrothermal reaction conditions are to react at 170 - 180 °C for 2 - 4 hours.

5. The preparation method according to claim 1 or 3, characterized in that, in step 2), the calcination conditions are to calcine at 550 - 600 °C for 2 - 4 hours.

6. The preparation method according to claim 1 or 3, characterized in that, In step 3), the dosage ratio of the Si@void@SnO 2 composite material to the aqueous polyvinyl alcohol solution is 0.05 - 0.2: 1 g / mL.

7. The preparation method according to claim 1 or 3, characterized in that, the calcination in step 6) specifically has the following calcination conditions: the temperature is 400 - 450 °C, and the calcination time is 2 - 4 hours.

8. A dual-core shell structure silicon-based microcapsule composite material prepared by the preparation method according to any one of claims 1 - 7, characterized in that, The dual-core shell structure silicon-based microcapsule composite material is spherical with an average diameter of 40 - 60 μm, and the inside of the spherical capsule is wrapped with Si@void@SnO 2 composite material, and the size of the Si@void@SnO 2 composite material is 200 - 400 nm.

9. A semi-solid lithium-ion battery negative electrode slurry, characterized in that, the semi-solid lithium-ion battery negative electrode slurry is prepared by using the dual-core shell structure silicon-based microcapsule composite material according to claim 8 as an active material.

10. A lithium-ion battery, characterized in that, it is prepared by using the semi-solid lithium-ion battery negative electrode slurry according to claim 9.

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