Silicon-based layered porous negative electrode material, preparation method and silicon-based negative electrode and battery

Abstract

The application discloses a silicon-based layered porous negative material, a preparation method and a silicon-based negative electrode and a battery. The preparation method comprises the following steps: crushing, screening and drying boron-magnesium tailing raw materials; weighing the boron-magnesium tailing raw materials and magnesium powder, and performing magnesium hot reduction on SiO2 so as to convert SiO2 into silicon element, thereby obtaining a powder material in which silicon element layers and magnesium oxide layers are alternately distributed; performing acid activation on the powder material so as to remove magnesium ions between the silicon element layers; drying and grinding the powder material, thereby obtaining a layered porous material in which silicon element layers and magnesium oxide layers are alternately arranged; soaking the layered porous material in a glucose solution; and performing high-temperature treatment on the layered porous material soaked in the glucose solution, so as to pyrolyze and carbonize the glucose, thereby forming a carbon coating layer wrapped on the surface of the layered porous material, and finally obtaining the silicon-based layered porous negative material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicon-based negative electrode, and particularly relates to a silicon-based layered porous negative electrode material, a preparation method, a silicon-based negative electrode and a battery. BACKGROUND

[0002] Silicon material has become one of the most potential high-capacity silicon negative electrode materials due to its super-high theoretical specific capacity 4200mAh / g, low discharge voltage and lithium ion diffusion potential barrier, and high abundance of Si element in the earth's crust. Although the theoretical specific capacity of the silicon negative electrode material is more than 10 times that of the graphite negative electrode material, the volume expansion rate of the silicon negative electrode material during the delithiation and lithium intercalation process of charging and discharging can reach 300%, and the severe volume expansion will cause serious damage to the negative electrode structure during the multiple cycle discharge process, which seriously shortens the service life of the lithium battery.

[0003] At present, the mainstream scheme for solving the volume expansion problem of the silicon negative electrode material during lithium intercalation is to prepare Si nanospheres by chemical synthesis and ordered mesoporous Si materials by a template method. These schemes can solve the volume expansion problem of the silicon negative electrode material to a certain extent, but the cost is high and the process is complex, which is difficult to be applied on a large scale. This is because the silicon negative electrode material is mostly prepared by chemical synthesis using pure reagents as raw materials, which has a complex process, high production cost and low yield.

[0004] Therefore, there is an urgent need for a silicon negative electrode material preparation method which can solve the problem of severe volume expansion of the silicon negative electrode material during lithium intercalation and delithiation, and has a simple process and low production cost. SUMMARY

[0005] The present application aims to provide a silicon-based layered porous negative electrode material, a preparation method, a silicon-based negative electrode and a battery, which can solve the problem of severe volume expansion of the silicon negative electrode material during lithium intercalation and delithiation, and has a simple process and low production cost.

[0006] The present application discloses a silicon-based layered porous negative electrode material preparation method, which comprises the following steps:

[0007] The boron-magnesium tailings raw material is crushed, sieved and dried;

[0008] The boron-magnesium tailings raw material is weighed and blended with magnesium powder, and subjected to magnesium hot reduction of SiO2, so that the SiO2 is converted into silicon element, and a powder material in which silicon element layers and magnesium oxide layers are alternately distributed is obtained;

[0009] The powder material is subjected to acid activation to remove magnesium ions between the silicon element layers; and the powder material is dried and ground to obtain a layered porous material in which silicon element layers and magnesium oxide layers are alternately arranged;

[0010] The layered porous material is soaked in a glucose solution;

[0011] The layered porous material soaked by the glucose solution is treated at high temperature to pyrolyze and carbonize the glucose, so as to form a carbon coating layer wrapped on the surface of the layered porous material, thereby obtaining the silicon-based layered porous negative electrode material.

[0012] Optionally, in the step of magnesium hot reduction of SiO2, the magnesium hot reduction of SiO2 is carried out in a high-temperature ball mill under a reducing atmosphere.

[0013] Optionally, in the step of magnesium hot reduction of SiO2, the ball-to-material ratio is 10:1, the rotation speed is 200-400 r / min, and the ball milling temperature is increased to 600 DEG C at a temperature increasing rate of 5 DEG C / min; the magnesium hot reduction of SiO2 is carried out under a reducing atmosphere for 2-4 h.

[0014] Optionally, in the step of high-temperature treatment of the layered porous material soaked by the glucose solution, the inert gas is used as the protective gas in the muffle furnace, the temperature is increased to 350 DEG C at a two-stage temperature increasing rate, and then the glucose is pyrolyzed and carbonized for 5-10 min at constant temperature; and / or

[0015] In the step of crushing, screening and drying the boron-magnesium tailing raw material, the crushing time is 3-5 min; the screen mesh used is a 200-mesh screen; the constant-temperature drying temperature is 100-120 DEG C, and the drying time is 3 h.

[0016] Optionally, in the step of weighing the boron-magnesium tailing raw material and blending with magnesium powder, the mass ratio of the magnesium powder to the boron-magnesium tailing raw material is 6:25; and / or

[0017] In the step of acid activation of the powder material, sulfuric acid is used for acid activation, the sulfuric acid concentration is 2.16-2.71 mol / L, the acid activation temperature is 25-45 DEG C, and the acid activation time is 5-60 min; and / or

[0018] In the step of soaking the layered porous material with the glucose solution, the glucose solution concentration is 0.1 mol / L, and the soaking time is 60-120 min.

[0019] Optionally, the boron-magnesium tailing is selected from silicate minerals with a mass fraction of main components of B2O3 < 9%, SiO2 > 25%, and 25% < MgO < 49%, and the mineral powder has a particle size < 75 mu m.

[0020] Optionally, in the step of acid activation of the powder material, the layered porous material obtained has a magnesium oxide content of 8% < MgO < 15% and a particle size < 50 mu m.

[0021] The application further discloses a silicon-based layered porous negative electrode material prepared by the preparation method.

[0022] The present invention also discloses a silicon-based anode, comprising the silicon-based porous anode material as described above.

[0023] The present invention also discloses a battery comprising a silicon-based negative electrode as described above.

[0024] The present invention provides a method for preparing silicon-based porous anode materials, using boron-magnesium tailings as the silicon source. This method breaks away from the traditional chemical synthesis process that uses chemical reagents as the silicon source to prepare silicon anode materials. The manufacturing process is simple, significantly reducing the production cost of silicon anode materials and enabling mass production. Simultaneously, combined with… Figure 1 As shown, the prepared silicon-based porous anode material has an alternating Si-MgO layer structure with layered silicon monolayers as the framework and magnesium oxide layers as the support. Ions can freely intercalate and deintercalate between the porous layered structures, solving the serious volume expansion problem during lithium intercalation and deintercalation in silicon anode materials. Furthermore, after soaking in glucose solution and carbonizing, a carbon coating layer is formed on the surface of the layered porous material, creating a Si-Mg-C composite structure, which improves the conductivity of the prepared silicon-based porous anode material. Attached Figure Description

[0025] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the embodiments of the invention and illustrate implementation methods, and together with the textual description, explain the principles of the invention. Obviously, the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort. In the drawings:

[0026] Figure 1 This is a process flow diagram of the preparation process of silicon-based porous anode material according to an embodiment of the present invention. Detailed Implementation

[0027] It should be understood that the terminology, specific structural and functional details used herein are merely for describing particular embodiments and are representative. However, the invention can be implemented in many alternative forms and should not be construed as being limited to the embodiments set forth herein.

[0028] The present invention will now be described in detail with reference to the accompanying drawings and optional embodiments.

[0029] As an embodiment of the present invention, a method for preparing a silicon-based porous anode material is disclosed, comprising the following steps:

[0030] S100: Crushing, screening, and drying boron-magnesium tailings raw materials;

[0031] S200: Weigh boron-magnesium tailings raw material and blend it with magnesium powder, and perform magnesium thermal reduction of SiO2 to convert SiO2 into elemental silicon, so as to obtain a powder material with alternating layers of elemental silicon and magnesium oxide.

[0032] S300: Acid activation of powder materials to remove magnesium ions between silicon elemental layers; drying and grinding of powder materials to obtain layered porous materials with alternating silicon elemental layers and magnesium oxide layers;

[0033] S400: Layered porous materials are soaked in glucose solution;

[0034] S500: The layered porous material soaked in glucose solution is subjected to high temperature treatment to pyrolyze and carbonize the glucose, forming a carbon coating layer on the surface of the layered porous material to obtain a silicon-based layered porous anode material.

[0035] The present invention provides a method for preparing silicon-based porous anode materials, using boron-magnesium tailings as the silicon source. This method breaks away from the traditional chemical synthesis process that uses chemical reagents as the silicon source to prepare silicon anode materials. The manufacturing process is simple, significantly reducing the production cost of silicon anode materials and enabling mass production. Simultaneously, combined with… Figure 1 As shown, the prepared silicon-based porous anode material has an alternating Si-MgO layer structure with layered silicon monolayers as the framework and magnesium oxide layers as the support. Ions can freely intercalate and deintercalate between the porous layered structures, solving the serious volume expansion problem during lithium intercalation and deintercalation in silicon anode materials. Furthermore, after soaking in glucose solution and carbonizing, a carbon coating layer is formed on the surface of the layered porous material, creating a Si-Mg-C composite structure, which improves the conductivity of the prepared silicon-based porous anode material.

[0036] Specifically, combined Figure 1 As shown, in the preparation method of the present invention, magnesium thermal reduction is performed in step S200 to transform the SiO2 layer into a silicon elemental layer. Then, in step S300, the dissolution rate of magnesium ions is controlled by acid activation to prepare a layered porous material (Si-MgO layer structure) with alternating silicon elemental layers and magnesium oxide layers. Finally, in steps S400 and S500, the layered porous material (Si-MgO layer structure) is soaked in glucose solution and carbonized at high temperature to form a carbon coating layer (Si-Mg-C composite structure) on the surface of the layered porous material (Si-MgO layer structure), thereby improving the conductivity of the prepared silicon-based layered porous anode material.

[0037] Specifically, in the step of magnesothermic reduction of SiO2, a high-temperature ball mill is used to perform the magnesothermic reduction of SiO2 under a reducing atmosphere. This scheme involves performing the magnesothermic reduction of SiO2 under a reducing atmosphere, such as 95% Ar and 5% H2.

[0038] Specifically, in the step of magnesium hot reduction of SiO2, the ball-to-material ratio is 10:1, the rotation speed is 200-400 r / min, and the ball milling temperature is increased to 600℃ at a heating rate of 5℃ / min; the magnesium hot reduction of SiO2 is carried out under constant temperature ball milling for 2-4 h in a reducing atmosphere. Specifically, the rotation speed can be 200 r / min, 250 r / min, 300 r / min, 350 r / min, or 400 r / min. The constant temperature ball milling time can be 2 h, 2.5 h, 3 h, 3.5 h, or 4 h. Specifically, the magnesium powder and boron-magnesium tailings are fed in a mass ratio of 6:25; the grinding medium ratio is 5:3:2 of 1 cm medium ball:2 cm large ball:5 mm small ball.

[0039] Specifically, in the step of high temperature treatment of the layered porous material after soaking in the glucose solution, the inert gas is used as the protective gas in the muffle furnace, and the temperature is increased to 350℃ at a two-stage heating rate, and then the glucose is pyrolyzed and carbonized at constant temperature for 5-10 min. Specifically, the constant temperature carbonization time can be 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min. Specifically, the inert gas can be N2, and N2 is filled into the muffle furnace at a rate of 20 mL / min, and the temperature of the muffle furnace is increased to 180℃ at a heating rate of 20℃ / min under N2 protective atmosphere, and then the temperature is increased to 350℃ at a heating rate of 2℃ / min, and then constant temperature carbonization for 5-10 min.

[0040] Specifically, in the step of crushing, screening, and drying the boron-magnesium tailings raw material, the crushing time is 3-5 min; the screen used is a 200-mesh screen; the constant temperature drying temperature is 100-120℃, and the drying time is 3 h. Specifically, the crushing time can be 3 min, 3.5 min, 4 min, 4.5 min, or 5 min, and the constant temperature drying temperature can be 100℃, 105℃, 110℃, 115℃, or 120℃.

[0041] Specifically, in the step of weighing the boron-magnesium tailings raw material and blending with magnesium powder, the mass ratio of magnesium powder to boron-magnesium tailings raw material is 6:25.

[0042] Specifically, in the step of acid activating the powder material, sulfuric acid is used for acid activation, the concentration of sulfuric acid is 2.16-2.71 mol / L, the acid activation temperature is 25-45 DEG C, and the acid activation time is 5-60 min. Specifically, the concentration of sulfuric acid can be 2.16 mol / L, 2.2 mol / L, 2.25 mol / L, 2.3 mol / L, 2.35 mol / L, 2.4 mol / L, 2.5 mol / L, 2.6 mol / L, 2.7 mol / L, 2.71 mol / L. The acid activation temperature can be 25 DEG C, 30 DEG C, 35 DEG C, 40 DEG C, 45 DEG C. The acid activation time can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min. Specifically, after the sulfuric acid is used for acid activation, the sulfuric acid and the powder material solid-liquid mixture are separated by suction filtration.

[0043] In the step of soaking the layered porous material in the glucose solution, the concentration of the glucose solution is 0.1 mol / L, and the soaking time is 60-120 min. Specifically, the soaking time can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min.

[0044] Specifically, the boron-magnesium tailings are selected to be silicate minerals with the mass fraction of the main component content being B2O3 < 9%, SiO2 > 25%, and 25% < MgO < 49%, and the particle size of the mineral powder is < 75 mu m.

[0045] Specifically, in the step of acid activating the powder material, the obtained layered porous material has a magnesium oxide content of 8% < MgO < 15% and a particle size of < 50 mu m.

[0046] The application further discloses a silicon-based layered porous negative material prepared by the preparation method.

[0047] The application further discloses a silicon-based negative electrode comprising the silicon-based layered porous negative material.

[0048] The application further discloses a battery comprising the silicon-based negative electrode.

[0049] The application will be further described in detail below with reference to specific examples.

[0050] Example 1

[0051] (1) 200g of boron-magnesium tailings are placed in a mortar crusher for crushing for 3 min, and then sieved in a vibrating sieve machine using a 200-mesh screen, and the sieved raw materials are dried in a constant-temperature drying box at 110 DEG C for 3 h.

[0052] (2) Take 100 g of dried boron-magnesium tailings and 24 g of magnesium powder into a 2L hard alloy ball mill jar, add 1 kg of agate ball milling medium, the ratio of grinding medium is 1 cm medium ball, 2 cm large ball and 5 mm small ball, the ratio is 5:3:2. In the reducing atmosphere of mixed gas volume ratio Ar(95%) / H2(5%), ventilation rate 10 ml / min, the rotation speed is 150 r / min before the temperature rises to 600℃ at a heating rate of 5℃ / min, and the rotation speed of the ball mill is increased to 300 r / min when the temperature reaches 600℃, and the SiO2 magnesium reduction reaction is carried out under this condition for 3h, and the powder material with alternating distribution of silicon and magnesium oxide layers is obtained.

[0053] (3) Take 10 g of the powder material after magnesium reduction and place it in a 500 mL three-necked flask, add 80 mL of 2.16M sulfuric acid, and react at a temperature of 45℃ and a stirring speed of 400 r / min for 30 min, then filter and wash with distilled water for 3 times.

[0054] (4) Place the washed acid-activated layered porous material in a beaker, add 200 mL of 0.1 mol / L glucose solution, and soak the acid-activated layered porous material at room temperature for 60 min with a stirring speed of 400 r / min, then filter and dry in a constant temperature oven at 80℃ for 4h.

[0055] (5) Put the powder material treated with glucose solution into a muffle furnace, fill N2 into the muffle furnace at a rate of 20 mL / min, and raise the temperature of the muffle furnace to 180℃ at a heating rate of 20℃ / min, then raise the temperature to 350℃ at a heating rate of 2℃ / min, and then carbonize for 5 min at constant temperature, to obtain a carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material.

[0056] (6) The prepared carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material is made into a lithium ion battery for electrochemical test, and the thickness expansion rate is less than 10% after 800 cycles at room temperature.

[0057] Example 2

[0058] The difference between Example 2 and Example 1 is that the constant temperature carbonization in (5) is 10 min, which is as follows:

[0059] (1) Take 200 g of boron-magnesium tailings and place them in a grinding mill for 3 min, then use a 200 mesh screen in a vibrating screen machine to screen, and then dry the screened raw materials in a constant temperature drying oven at 110℃ for 3h.

[0060] (2) Take 100 g of dried boron-magnesium tailings and 24 g of magnesium powder into a 2L hard alloy ball mill jar, add 1 kg of agate ball milling medium, the ratio of grinding medium is 1 cm medium ball, 2 cm large ball and 5 mm small ball, the ratio is 5:3:2. In the reducing atmosphere of mixed gas volume ratio Ar(95%) / H2(5%), ventilation rate 10 ml / min, the rotation speed is 150 r / min before the temperature rises to 600℃ at a heating rate of 5℃ / min, and the rotation speed of the ball mill is increased to 300 r / min when the temperature reaches 600℃, and the SiO2 magnesium reduction reaction is carried out under this condition for 3h, and the powder material with alternating distribution of silicon and magnesium oxide layers is obtained.

[0061] (3) Take 10 g of the powder material after magnesium reduction and place it in a 500 mL three-necked flask, add 80 mL of 2.16M sulfuric acid, and react at a temperature of 45℃ and a stirring speed of 400 r / min for 30 min, then filter and wash with distilled water for 3 times.

[0062] (4) Place the washed acid-activated layered porous material in a beaker, add 200 mL of 0.1 mol / L glucose solution, and soak the acid-activated layered porous material at room temperature for 60 min at a stirring speed of 400 r / min, then filter and dry in a constant temperature oven at 80℃ for 4h.

[0063] (5) Put the powder material treated with glucose solution into a muffle furnace, fill N2 into the muffle furnace at a rate of 20 mL / min, and raise the temperature of the muffle furnace to 180℃ at a heating rate of 20℃ / min, then raise the temperature to 350℃ at a heating rate of 2℃ / min, and then carbonize for 10 min at constant temperature, to obtain a carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material.

[0064] (6) The prepared carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material is made into a lithium ion battery for electrochemical test, and the thickness expansion rate is less than 10% after 800 cycles at room temperature.

[0065] Example 3

[0066] The difference between Example 3 and Example 1 is that the sulfuric acid concentration in (3) is 2.71M, the temperature is 25℃, and the reaction time is 10 min, as follows:

[0067] (1) Take 200 g of boron-magnesium tailings and place them in a mill-type crusher for 3 min, then use a 200 mesh screen in a vibrating screen separator, and dry the screened raw material in a constant temperature drying oven at 110℃ for 3h.

[0068] (2) Take 100 g of dried boron-magnesium tailings and 24 g of magnesium powder into a 2L hard alloy ball mill jar, add 1 kg of agate ball milling medium, the ratio of grinding medium is 1 cm medium ball, 2 cm large ball and 5 mm small ball, the ratio is 5:3:2. In the reducing atmosphere of mixed gas volume ratio Ar(95%) / H2(5%), ventilation rate 10 ml / min, the rotation speed is 150 r / min before the temperature rises to 600℃ at a heating rate of 5℃ / min, and the rotation speed of the ball mill is increased to 300 r / min when the temperature reaches 600℃, and the SiO2 magnesium reduction reaction is carried out under this condition for 3h, and the powder material with alternating distribution of silicon and magnesium oxide layers is obtained.

[0069] (3) Take 10 g of the powder material after magnesium reduction and place it in a 500 mL three-necked flask, add 80 mL of 2.71 M sulfuric acid, and react at a temperature of 25℃ and a stirring speed of 400 r / min for 10 min, then filter and wash with distilled water for 3 times.

[0070] (4) Place the washed acid-activated layered porous material in a beaker, add 200 mL of 0.1 mol / L glucose solution, and soak the acid-activated layered porous material at room temperature for 60 min at a stirring speed of 400 r / min, then filter and dry in a constant temperature oven at 80℃ for 4h.

[0071] (5) Put the powder material treated with glucose solution into a muffle furnace, fill N2 into the muffle furnace at a rate of 20 mL / min, and raise the temperature of the muffle furnace to 180℃ at a heating rate of 20℃ / min, then raise the temperature to 350℃ at a heating rate of 2℃ / min, and then carbonize for 5 min at constant temperature, to obtain a carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material.

[0072] (6) The prepared carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material is made into a lithium ion battery for electrochemical test, and the thickness expansion rate is less than 10% after 800 cycles at room temperature.

[0073] Example 4

[0074] The difference between Example 4 and Example 1 is that the sulfuric acid concentration in (3) is 2.71 M, the temperature is 25℃, and the reaction time is 10 min, and the constant temperature carbonization in (5) is 10 min, as follows:

[0075] (1) Take 200 g of boron-magnesium tailings and place them in a grinding mill for 3 min, then use a 200 mesh screen in a vibrating screen machine to screen, and then dry the screened raw material in a 110℃ constant temperature drying oven for 3h.

[0076] (2) Take 100 g of dried boron-magnesium tailings and 24 g of magnesium powder into a 2L hard alloy ball mill jar, add 1 kg of agate ball milling medium, the ratio of grinding medium is 1 cm medium ball, 2 cm large ball and 5 mm small ball, the ratio is 5:3:2. In the reducing atmosphere of mixed gas volume ratio Ar(95%) / H2(5%), ventilation rate 10 ml / min, the rotation speed is 150 r / min before the temperature rises to 600℃ at a heating rate of 5℃ / min, and the rotation speed of the ball mill is increased to 300 r / min when the temperature reaches 600℃, and the SiO2 magnesium reduction reaction is carried out under the condition of keeping the temperature for 3h, and the powder material with alternating distribution of silicon and magnesium oxide layers is obtained.

[0077] (3) Take 10 g of the powder material after magnesium reduction and place it in a 500 mL three-necked flask, add 80 mL of 2.71 M sulfuric acid, and react under the conditions of temperature 25℃ and stirring speed 400 r / min for 10 min, then filter and wash with distilled water for 3 times.

[0078] (4) Place the washed acid-activated layered porous material in a beaker, add 0.1 mol / L glucose solution 200 mL, soak the acid-activated layered porous material for 60 min at room temperature with stirring speed 400 r / min, filter and dry in a constant temperature oven at 80℃ for 4h.

[0079] (5) Put the powder material treated with glucose solution into a muffle furnace, fill N2 into the muffle furnace at a rate of 20 mL / min, and raise the temperature of the muffle furnace to 180℃ at a heating rate of 20℃ / min under N2 protective atmosphere, then raise the temperature to 350℃ at a heating rate of 2℃ / min and keep carbonization for 10 min, to obtain Si-Mg-C composite structure silicon-based layered porous negative electrode material coated with carbon.

[0080] (6) The prepared Si-Mg-C composite structure silicon-based layered porous negative electrode material coated with carbon is made into lithium ion battery for electrochemical test, and the thickness expansion rate is less than 10% after 800 cycles at room temperature.

[0081] Example 5

[0082] The difference between Example 5 and Example 1 is that in (2), the temperature is kept constant at 600℃ and the rotation speed of the ball mill is increased to 400 r / min, and the reaction is kept for 2h, as follows:

[0083] (1) Take 200 g of boron-magnesium tailings and place them in a mill-type crusher for 3 min, then use a 200 mesh screen in a vibrating screen machine to screen, and dry the screened raw material in a 110℃ constant temperature drying oven for 3h.

[0084] (2) Take 100 g of dried boron-magnesium tailings and 24 g of magnesium powder and place them in a 2 L hard alloy ball mill jar. Add 1 kg of agate ball milling medium, and the ratio of the grinding medium is 1 cm medium ball, 2 cm large ball, and 5 mm small ball at a ratio of 5:3:2. In a reducing atmosphere with a mixed gas volume ratio of Ar (95%) / H2 (5%), aeration rate of 10 ml / min, the temperature is raised to 600°C at a rate of 5°C / min, and the rotation speed is 150 r / min before reaching 600°C. After the temperature reaches 600°C, keep the temperature constant and increase the rotation speed of the ball mill to 400 r / min. Keep the SiO2 magnesium reduction reaction under this condition for 2 h to obtain a powder material with alternating distribution of silicon and magnesium oxide layers.

[0085] (3) Take 10 g of the powder material after magnesium reduction and place it in a 500 mL three-necked flask. Add 80 mL of 2.16 M sulfuric acid. React at a temperature of 45°C and a stirring speed of 400 r / min for 30 min. Then filter and wash with distilled water for 3 times.

[0086] (4) Place the washed acid-activated layered porous material in a beaker and add 200 mL of 0.1 mol / L glucose solution. Soak the acid-activated layered porous material at room temperature for 60 min at a stirring speed of 400 r / min. After filtration, dry in a constant temperature oven at 80°C for 4 h.

[0087] (5) Put the powder material treated with glucose solution into a muffle furnace. Fill N2 into the muffle furnace at a rate of 20 mL / min. Under N2 protective atmosphere, raise the temperature of the muffle furnace to 180°C at a rate of 20°C / min, and then raise the temperature to 350°C at a rate of 2°C / min. Keep the temperature constant for 5 min to obtain a carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material.

[0088] (6) Prepare the carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material into a lithium ion battery for electrochemical testing. The thickness expansion rate is less than 10% after 800 cycles at room temperature.

[0089] Example 6

[0090] The difference between Example 6 and Example 1 is that in (2), the temperature is kept constant after reaching 600°C and the rotation speed of the ball mill is increased to 400 r / min, and the temperature is kept constant for 2 h. In (5), the constant temperature carbonization is 10 min, as follows:

[0091] (1) Take 200 g of boron-magnesium tailings and place them in a grinding disc crusher for 3 min. Then use a 200 mesh screen in a vibrating screen machine to screen the material. After screening, dry the raw material in a constant temperature drying oven at 110°C for 3 h.

[0092] (2) Take 100 g of dried boron-magnesium tailings and 24 g of magnesium powder and place them in a 2L hard alloy ball mill jar. Add 1 kg of agate ball milling medium, and the ratio of the grinding medium is 1 cm medium ball, 2 cm large ball and 5 mm small ball, with a ratio of 5:3:2. In a reducing atmosphere with a mixed gas volume ratio of Ar (95%) / H2 (5%), aeration rate of 10 ml / min, the temperature is raised to 600°C at a rate of 5°C / min, and the rotation speed is 150 r / min before reaching 600°C. After the temperature reaches 600°C, keep the temperature constant and increase the rotation speed of the ball mill to 400 r / min. Keep the conditions for 2h to carry out the magnesium reduction reaction of SiO2, and obtain a powder material with alternating distribution of silicon and magnesium oxide layers.

[0093] (3) Take 10 g of the powder material after magnesium reduction and place it in a 500 mL three-necked flask. Add 80 mL of 2.16M sulfuric acid, and react at a temperature of 45°C and a stirring speed of 400 r / min for 30 min. Then filter and wash with distilled water for 3 times.

[0094] (4) Place the washed acid-activated layered porous material in a beaker, add 200 mL of 0.1 mol / L glucose solution, and soak the acid-activated layered porous material at room temperature for 60 min at a stirring speed of 400 r / min. After filtration, dry in a constant temperature oven at 80°C for 4h.

[0095] (5) Put the powder material treated with glucose solution into a muffle furnace, fill N2 into the muffle furnace at a rate of 20 mL / min, and raise the temperature of the muffle furnace to 180°C at a rate of 20°C / min under N2 protective atmosphere. Then raise the temperature to 350°C at a rate of 2°C / min and keep carbonizing for 10 min at constant temperature to obtain Si-Mg-C composite structure silicon-based layered porous negative electrode material coated with carbon.

[0096] (6) The prepared Si-Mg-C composite structure silicon-based layered porous negative electrode material coated with carbon is made into a lithium ion battery for electrochemical test. The thickness expansion rate is less than 10% after 800 cycles at room temperature.

[0097] Example 7

[0098] The difference between Example 7 and Example 1 is that in (2), the temperature is kept constant after reaching 600°C and the rotation speed of the ball mill is increased to 400 r / min, and the conditions are kept for 2h. In (3), the concentration of sulfuric acid is 2.71M, the temperature is 25°C, and the reaction time is 10 min. The details are as follows:

[0099] (1) Take 200 g of boron-magnesium tailings and place them in a grinding mill for 3 min. Then use a 200 mesh screen in a vibrating screen to sieve the material. After sieving, dry the raw material in a constant temperature oven at 110°C for 3h.

[0100] (2) Take 100 g of dried boron-magnesium tailings and 24 g of magnesium powder into a 2L hard alloy ball mill jar, add 1 kg of agate ball milling medium, the ratio of grinding medium is 1 cm medium ball, 2 cm large ball and 5 mm small ball, the ratio is 5:3:2. In the reducing atmosphere of mixed gas volume ratio Ar(95%) / H2(5%), ventilation rate 10 ml / min, the rotation speed is 150 r / min before the temperature rises to 600℃ at a heating rate of 5℃ / min, and the temperature reaches 600℃. After that, keep the temperature constant and increase the rotation speed of the ball mill to 400 r / min, keep it for 2h under this condition to carry out the magnesium hot reduction reaction of SiO2, and get a powder material with alternating distribution of silicon single layer and magnesium oxide layer.

[0101] (3) Take 10 g of the powder material after magnesium reduction and put it into a 500 mL three-necked flask, add 80 mL of 2.71 M sulfuric acid, react at a temperature of 25℃ and a stirring speed of 400 r / min for 10 min, then filter and wash with distilled water for 3 times.

[0102] (4) Put the washed acid-activated layered porous material into a beaker, add 200 mL of 0.1 mol / L glucose solution, soak the acid-activated layered porous material at room temperature for 60 min at a stirring speed of 400 r / min, filter and dry in a constant temperature oven at 80℃ for 4h.

[0103] (5) Put the powder material treated with glucose solution into a muffle furnace, fill N2 into the muffle furnace at a rate of 20 mL / min, raise the temperature of the muffle furnace to 180℃ at a heating rate of 20℃ / min, then raise the temperature to 350℃ at a heating rate of 2℃ / min and keep it constant for 5 min, get the carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material.

[0104] (6) The prepared carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material is made into lithium ion battery for electrochemical test, the thickness expansion rate is less than 10% after 800 cycles at room temperature.

[0105] Example 8

[0106] The difference between Example 8 and Example 1 is that in (2), the temperature is kept constant after reaching 600℃ and the rotation speed of the ball mill is increased to 400 r / min, which is kept for 2h, in (3), the concentration of sulfuric acid is 2.71 M, the temperature is 25℃ and the reaction time is 10 min, in (5), the constant carbonization is 10 min, as follows:

[0107] (1) Take 200 g of boron-magnesium tailings and place them in a mill-type crusher for 3 min, then use a 200-mesh screen in a vibrating screen separator. After screening, the raw material is dried in a constant-temperature oven at 110°C for 3 h.

[0108] (2) Take 100 g of dried boron-magnesium tailings and 24 g of magnesium powder and place them in a 2L hard alloy ball mill jar. Add 1 kg of agate grinding media, with a ratio of 1 cm medium balls, 2 cm large balls, and 5 mm small balls at a ratio of 5:3:2. In a reducing atmosphere with a mixed gas volume ratio of Ar (95%) / H2 (5%) and a ventilation rate of 10 ml / min, the temperature is raised to 600°C at a rate of 5°C / min, and the rotation speed is 150 r / min before reaching 600°C. After reaching 600°C, the temperature is kept constant and the rotation speed of the ball mill is increased to 400 r / min. The SiO2 magnesium reduction reaction is carried out under these conditions for 2 h to obtain a powder material with alternating layers of silicon and magnesium oxide.

[0109] (3) Take 10 g of the powder material after magnesium reduction and place it in a 500 mL three-necked flask. Add 80 mL of 2.71 M sulfuric acid and react at a temperature of 25°C and a stirring speed of 400 r / min for 10 min. Then filter and wash with distilled water for 3 times.

[0110] (4) Place the washed acid-activated layered porous material in a beaker and add 200 mL of 0.1 mol / L glucose solution. Soak the acid-activated layered porous material in the solution at room temperature for 60 min at a stirring speed of 400 r / min. After filtration, dry the material in a constant-temperature oven at 80°C for 4 h.

[0111] (5) Place the powder material treated with the glucose solution in a muffle furnace. Fill the muffle furnace with N2 at a rate of 20 mL / min. Raise the temperature of the muffle furnace to 180°C at a rate of 20°C / min, then raise the temperature to 350°C at a rate of 2°C / min and keep the temperature constant for 10 min to obtain a carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material.

[0112] (6) Prepare the carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material into a lithium ion battery for electrochemical testing. The thickness expansion rate of the negative electrode sheet is less than 10% after 800 cycles at room temperature.

[0113] Comparative Example:

[0114] Prepare a traditional silicon-based negative electrode material into a lithium ion battery for electrochemical testing. The thickness expansion rate of the negative electrode sheet is as high as 25% after 300 cycles at room temperature.

[0115] Conclusion: The method for preparing the carbon-coated Si-Mg-C composite structure silicon-based layered porous negative electrode material greatly reduces the thickness expansion problem of the traditional silicon negative electrode material, reduces the material preparation cost, and has great practical significance for the industrial application of the silicon negative electrode material.

[0116] It should be noted that the limitations of each step involved in the present scheme do not constitute a limitation on the order of the steps without affecting the implementation of the specific scheme. The steps written in the front can be executed first, or executed later, or even executed simultaneously, as long as the present scheme can be implemented, it should be considered to belong to the protection scope of the present application.

[0117] The above content is a further detailed description of the present application in combination with specific optional embodiments, and cannot be considered as limiting the specific implementation of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered to belong to the protection scope of the present application.

Claims

1. A method for preparing a silicon-based layered porous negative electrode material, characterized in that, The method comprises the steps of: crushing, screening and drying the boron-magnesium tailing raw material, and the particle size of the mineral powder is less than 75 μm; weighing the boron-magnesium tailing raw material and magnesium powder, and performing magnesium thermal reduction of SiO2 under a reducing atmosphere by using a high-temperature ball mill to convert SiO2 into silicon element, thereby obtaining a powder material in which silicon element layers and magnesium oxide layers are alternately distributed; performing acid activation on the powder material by using sulfuric acid, the concentration of the sulfuric acid is 2.16-2.71 mol / L, the acid activation temperature is 25-45 ℃, and the acid activation time is 5-60 min, so as to remove magnesium ions between the silicon element layers; drying and grinding the powder material to obtain a layered porous material in which silicon element layers and magnesium oxide layers are alternately arranged; immersing the layered porous material in a glucose solution for 60-120 min; performing high-temperature treatment on the layered porous material after being immersed in the glucose solution, so that the glucose is pyrolyzed and carbonized to form a carbon coating layer wrapped on the surface of the layered porous material, thereby obtaining a silicon-based layered porous negative electrode material; wherein the silicon-based layered porous negative electrode material is a Si-MgO layer structure in which silicon element layers are arranged in layers and magnesium oxide layers are arranged alternately as supports.

2. The production method according to claim 1, wherein In the step of performing magnesium thermal reduction of SiO2, the ball-to-material ratio is 10:1, the rotation speed is 200-400 r / min, and the ball milling temperature is increased to 600 ℃ at a temperature increasing rate of 5 ℃ / min; the magnesium thermal reduction of SiO2 is performed under a constant temperature ball milling for 2-4 h under a reducing atmosphere.

3. The production method according to claim 1, wherein In the step of performing high-temperature treatment on the layered porous material after being immersed in the glucose solution, the glucose is pyrolyzed and carbonized by increasing the temperature to 350 ℃ in two stages in a muffle furnace with an inert gas as a protective gas, and then constant temperature carbonization is performed for 5-10 min; and / or In the step of crushing, screening and drying the boron-magnesium tailing raw material, the crushing time is 3-5 min, the screen mesh used is a 200-mesh screen, the constant temperature drying temperature is 100-120 ℃, and the drying time is 3 h.

4. The production method according to claim 1, wherein In the step of weighing the boron-magnesium tailing raw material and magnesium powder, the mass ratio of the magnesium powder to the boron-magnesium tailing raw material is 6:25; and / or In the step of immersing the layered porous material in a glucose solution, the concentration of the glucose solution is 0.1 mol / L.

5. The production method according to claim 1, wherein The boron-magnesium tailing is selected from silicate minerals with the mass fraction of the main components being B2O3 < 9%, SiO2 > 25%, and 25% < MgO < 49%.

6. The production method according to claim 1, wherein In the step of performing acid activation on the powder material, the layered porous material obtained has a magnesium oxide content of 8% < MgO < 15% and a particle size of less than 50 μm.

7. A silicon-based layered porous anode material, characterized in that, The silicon-based layered porous negative electrode material is prepared by the preparation method of any one of claims 1-6.

8. A silicon-based negative electrode, characterized by, The silicon-based layered porous negative electrode material of claim 7.

9. A battery, characterized by The silicon-based negative electrode of claim 8.

Images