WO2021120155A1 - Nano-tin-silicon composite negative electrode material, and preparation method therefor and use thereof - Google Patents

Abstract

Disclosed are a nano-tin-silicon composite negative electrode material, a preparation method therefor, a negative electrode containing the nano-tin-silicon composite negative electrode material, and a lithium ion battery. The nano-tin-silicon composite negative electrode material comprises: a linear, dendritic or beaded nano-tin, nano-silicon material particles embedded in the nano-tin, and a conductive covering layer covering the outer surface of the nano-tin. The nano-tin-silicon composite negative electrode material can remedy the respective defects of silicon and tin, and improve the conductivities and electrochemical cycling characteristics of silicon and tin negative electrode materials. The tin-silicon composite negative electrode material has an excellent electrochemical performance when used as a lithium ion battery negative electrode material, and has potential application prospects in portable mobile devices and electric vehicles.

Description

Nano tin-silicon composite negative electrode material and preparation method and application thereof Technical field

The invention relates to the field of negative electrode materials for lithium ion batteries, in particular to a nano tin-silicon composite negative electrode material and a preparation method and application thereof.

Background technique

Due to the rapid development and wide application of portable electronic devices and electric vehicles, there is an urgent need for lithium-ion batteries with high specific energy and long cycle life. Currently, commercial lithium-ion batteries mainly use graphite as the negative electrode material. However, the theoretical specific capacity of graphite is only 372mAh/g, which limits the further improvement of the specific energy of lithium-ion batteries.

Silicon, because of its extremely high theoretical specific capacity for lithium insertion (up to 4200mAh/g) and low lithium storage potential, has attracted great attention from researchers and is one of the ideal candidates for new high-capacity lithium storage materials. However, the silicon material is a semiconductor, so its conductivity is not as good as that of the graphite anode, which limits its rate performance and low temperature performance. The volume expansion of silicon during lithium storage exceeds 200%. Because of its lack of ductility, silicon particles are easily broken and cause loss of electrical contact. At the same time, the newly exposed surface reacts with the electrolyte to form a solid electrolyte (SEI) to consume active lithium. Tin has good electrical conductivity, good ductility, is not easy to break during the process of deintercalating lithium, and has fast charge-discharge capability and good low-temperature performance. But its specific capacity is much lower (up to 994mAh/g), and there is also a certain volume expansion.

Therefore, if the advantages of tin and silicon can be combined and the problem of volume expansion can be solved, it is expected that a high-capacity negative electrode material with excellent performance can be obtained. The Chinese patent with the authorized announcement number CN 101510601B prepares a silicon-tin alloy anode material used in lithium-ion batteries, which can solve the problem of volume expansion of silicon-tin to a certain extent and improve the electrochemical performance of tin-silicon alloy , Its specific capacity can reach 600-700mAh/g. However, this material cannot solve the problems of crack generation or fracture caused by volume expansion when lithium is released, pole piece cracking, inability to form a stable SEI, and poor electrical contact. At the same time, the silicon oxide material used in this patent is difficult to remove oxygen on the silicon surface, which affects the battery cycle.

Summary of the invention

An object of the present invention is to provide a nano tin-silicon composite negative electrode material with high specific capacity and good cycle performance, which can well improve the problem of tin-silicon volume expansion.

Another object of the present invention is to provide a method for preparing the nano-tin-silicon composite negative electrode material of the present invention.

Another object of the present invention is to provide an application of the nano-tin-silicon composite negative electrode material of the present invention.

The purpose of the present invention is achieved by providing the following technical solutions:

In one aspect, the present invention provides a nano-tin-silicon composite negative electrode material, which comprises: linear, dendritic or beaded nano-tin, nano-silicon material particles embedded in the nano-tin, and coated on the nano-tin Conductive coating on the outer surface. Preferably, the conductive coating layer is a carbon layer.

In some embodiments of the present invention, the nano-silicon material accounts for 5 to 80 wt% of the nano-tin-silicon composite negative electrode material based on the elemental silicon; preferably 10-50 wt%; the nano-tin based on the elemental tin accounts for 5 to 80 wt% 15-90wt% of the nano-tin-silicon composite negative electrode material, preferably 40-80wt%; the conductive coating layer accounts for 1-15wt% of the nano-tin-silicon composite negative electrode material, more preferably 3-10wt%.

In some embodiments of the present invention, the nano-silicon material is one or more of silicon nano-materials, silicon-carbon nano-materials, and silicon alloy nano-materials. In some embodiments of the present invention, the particle size of the silicon nano-material particles is 5-1000 nm, preferably 10-200 nm.

On the other hand, the present invention provides a method for preparing the nano-tin-silicon composite negative electrode material of the present invention, which includes the following steps:

(1) Add the nano silicon material to the solvent to obtain a suspension, and then perform ultrasonic dispersion treatment on the suspension;

(2) Add soluble tin salt to the suspension after ultrasonic dispersion, then conduct hydrothermal reaction or add co-precipitation agent for co-precipitation, and finally filter, wash, and vacuum dry to obtain nano-tin compound or oxide coating Nano-silicon composite materials;

(3) The nano-tin compound or oxide-coated nano-silicon composite material obtained in step (2) is reduced and coated to obtain the nano-tin-silicon composite negative electrode material.

In some embodiments of the present invention, the solvent in step (1) of the method for preparing the nano-tin-silicon composite negative electrode material of the present invention is water, methanol, ethanol, propanol, isopropanol, butanol and ethyl alcohol. One or more of the glycols, preferably water and/or ethanol; preferably, in the ultrasonic dispersion treatment step, a dispersing agent can also be added, and the dispersing agent is methanol, ethanol, ethylene glycol, propylene One or more of alcohol and isopropanol, preferably methanol and/or ethanol.

In some embodiments of the present invention, the soluble tin salt in step (2) of the method for preparing the nano-tin-silicon composite negative electrode material of the present invention is SnCl ₂ , SnSO ₄ , Sn(NO ₃ ) ₂ , Na ₂ SnO ₂ , K ₂ SnO ₂ , SnCl ₄ , Sn(SO ₄ ) ₂ , Sn(NO ₃ ) ₄ , Na ₂ SnO ₃ , SnC ₂ O ₄ or K ₂ SnO ₃ ; and/or of the co-precipitating agent The type is determined according to the tin salt, which is ammonia, sodium hydroxide, potassium hydroxide or urea; preferably, the amount of the co-precipitating agent added is just enough to completely precipitate the tin.

In an alternative embodiment of the present invention, the nano-tin-silicon composite negative electrode material of the present invention can also be prepared by a method including the following steps:

The nano-silicon material and the tin salt that can decompose to generate tin oxide at high temperature are mixed and subjected to high-energy ball milling, and the ball-milled mixed material is reduced and coated to obtain the nano-tin-silicon composite negative electrode material. Preferably, the tin salt that can decompose to produce tin oxide at high temperature is tin oxide, stannous oxide, tin hydroxide, stannous oxalate, stannous sulfate, or stannous acetate.

In some embodiments of the present invention, the reduction coating in the method for preparing the nano-tin-silicon composite anode material of the present invention is chemical vapor deposition coating (CVD coating), and the chemical vapor deposition coating The gas used can be acetylene, methane, toluene, or ethylene; preferably, the chemical vapor deposition coating adopts C ₂ H ₂ gas for carbon coating, and the coating conditions include: C ₂ H ₂ flow rate of 1 to 300 sccm , Preferably 10-100sccm; temperature is 500-800°C, preferably 650-750°C; time is 5min-10h, preferably 2-6h.

In another aspect, the present invention provides a negative electrode, which includes the negative electrode material provided by the present invention or the negative electrode material prepared according to the method of the present invention; preferably, the negative electrode further includes a current collector, a conductive additive, and a binder , Wherein the negative electrode material, conductive additive and binder are supported on the current collector.

In another aspect, the present invention provides a lithium ion battery, the battery includes a battery case, an electrode group and an electrolyte, the electrode group and the electrolyte are sealed in the battery case, the electrode group includes a positive electrode, a separator, and The negative electrode, wherein the negative electrode is the negative electrode provided by the present invention.

The invention adopts composite coating. The coating layer on the surface of the nano silicon material is composed of a tin coating layer and a conductive coating layer. The tin coating layer is wrapped on the outside of the nano silicon material particles, and the conductive coating layer is then wrapped in the tin coating. The outside of the layer. Silicon material is a semiconductor with poor conductivity, but has a very high capacity; tin also has a higher capacity, and has good processing properties, good conductivity, rapid charge and discharge capabilities during the process of deintercalating lithium, and good low temperature Performance: The conductive coating layer on the outer surface can effectively avoid the direct contact between the nano-silicon material and the electrolyte to form a stable SEI, so it can alleviate the volume expansion of the nano-silicon and keep the nano-silicon particles from breaking. In the process of charging and discharging and deintercalating lithium, due to the poor conductivity of silicon, the slow deintercalation of lithium leads to slow charging and discharging. However, the nano-tin-silicon composite negative electrode material of the present invention first conducts lithium ions through tin, and the conduction speed increases rapidly. . Generally, volume expansion will cause the pole piece to crack, but the tin coating layer and the conductive coating layer in the nano-tin-silicon composite negative electrode material of the present invention have a certain length, and have good flexibility and elasticity, and have a certain degree of flexibility. The expansion and contraction function can ensure that the linear, dendritic or beaded nano tin is not broken, and the linear, dendritic or beaded nano tin-silicon composite negative electrode material is in contact with the surface through the surface, and the contact area is larger, thereby Able to achieve good electrical contact. During the first charge, due to the presence of the conductive coating on the outer surface, although the whole swells, it does not break, and the swelling rate is significantly lower than 200%, about 30% to 60%. It will not change when lithium is removed again, and holes are formed inside. Therefore, when lithium is removed again later, the entire nanotube will not expand again, and the long-term cycle shell structure can still remain stable. Moreover, the synthesis method of the nano tin-silicon composite negative electrode material of the present invention is simple and convenient, and can be produced on a large scale.

In summary, the nano-tin-silicon composite anode material of the present invention has the following advantages and beneficial effects:

1. The nano tin-silicon composite negative electrode material has excellent electrochemical performance, the specific capacity after 100 cycles of cycles is above 1000 mAh/g, and at the same time has excellent rate performance.

2. The ductility of tin helps to alleviate the cracks or fractures caused by the volume expansion when the material is intercalated with lithium.

3. It can effectively avoid the direct contact between nano tin and silicon and the electrolyte, and the SEI formed on the coating layer is thin and stable.

4. During the first charge, the expanded shell can be maintained without cracking due to the existence of the external conductive coating layer, and will not change when the lithium is removed again, and holes are formed inside. Therefore, when the lithium is released again later, the entire nanotube will not be broken. Will expand again, and the long-term circulation shell structure can still remain stable.

5. The linear, dendritic or beaded nano-tin in the nano-tin-silicon composite anode material of the present invention has high electrical conductivity before and after lithium insertion. When the volume expansion of the electrode lithium insertion causes the pole piece to crack, the active material remains It can maintain good electrical contact with the electrode.

6. In the process of charging and discharging and deintercalating lithium, due to the poor conductivity of silicon, the slow deintercalation of lithium leads to slow charging and discharging. However, the nano-tin-silicon composite negative electrode material of the present invention first conducts lithium ions through tin. Rapid increase, and its magnification performance is greatly improved.

Description of the drawings

Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which:

FIG. 1 is an XRD pattern of the nano-tin-silicon composite anode material of Example 1 of the present invention.

2A is an SEM image of a tin-silicon composite anode material including linear nano-tin of the present invention; FIG. 2B is an SEM image of a tin-silicon composite anode material including beaded nano-tin of the present invention; FIG. 2C is an SEM image of the present invention including dendrites SEM image of the tin-silicon composite anode material of nano-tin; Figure 2D is the TEM image of the tin-silicon composite anode material including linear nano-tin of the present invention; Figure 2E is the SEM image of the tin-silicon composite anode material prepared in Comparative Example 3 .

3 is a graph showing the charge-discharge cycle performance of the lithium-ion battery of the tin-silicon composite anode material of Example 1 of the present invention.

Fig. 4 is a graph showing the rate performance of a lithium-ion battery of the tin-silicon composite anode material of Example 1 of the present invention.

FIG. 5 shows a schematic longitudinal cross-sectional view of an embodiment of the nano-tin-silicon composite negative electrode material including linear nano-tin according to the present invention.

FIG. 6 shows a schematic diagram of the charging and discharging process of deintercalating lithium in one embodiment of the nano-tin-silicon composite negative electrode material including linear nano-tin according to the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, and the examples given are only to illustrate the present invention, not to limit the scope of the present invention.

Example 1

(1) Weigh 2g of silicon powder with a particle size of 100nm into 1000ml of water, add 20ml of ethanol to obtain a nano-silicon suspension, and then place the nano-silicon suspension in an ultrasonic machine for 2 hours;

(2) after the ultrasonic dispersion silicon nano suspension was stirred constantly with a magnetic stirrer, followed by addition of 10ml 37% hydrochloric acid and 6g of SnCl ₂ in the solution, and then slowly adding ammonia to adjust pH to about 7. Finally, after filtering, washing and drying, the nano-silicon composite material coated with nano-tin compound is obtained;

(3) Put the nano-silicon composite material coated with nano-tin compound into a tube furnace under nitrogen atmosphere for C ₂ H ₂ carbon-coated, N ₂ flow rate is 300 sccm, C ₂ H ₂ flow rate is 100 sccm, and the heating rate is 50 ℃/min, maintained at 680℃ for 60 min, to obtain nano tin-silicon composite anode material.

It has been determined that the nano-tin-silicon composite negative electrode material includes linear nano-tin, nano-silicon particles embedded in the nano-tin, and a carbon coating layer coated on the outer surface of the nano-tin. In the nano-tin-silicon composite negative electrode material, nano-silicon accounts for 63% by weight of the nano-tin-silicon composite negative electrode material based on elemental silicon; nano-tin takes up 33% by weight of the nano-tin-silicon composite negative electrode material based on elemental tin; carbon The coating layer accounts for 4wt% of the nano-tin-silicon composite negative electrode material.

Example 2

(1) Weigh 2g of silicon powder with a particle size of 100nm into 500ml of water, add 20ml of ethanol to obtain a nano-silicon suspension, and then place the nano-silicon suspension in an ultrasonic machine for 2h;

(2) Stir the ultrasonically dispersed nano-silicon suspension with a magnetic stirrer, then add 5ml 37% hydrochloric acid and 6g SnCl _{2 to the solution} , then put it into a 300ml reactor at 180℃ Reaction for 12h. Finally, after filtering, washing and drying, the nano-silicon composite material coated with nano-tin compound is obtained;

(3) Put the nano-silicon composite material coated with nano-tin compound into a tube furnace under nitrogen atmosphere for C ₂ H ₂ carbon-coated, N ₂ flow rate is 300 sccm, C ₂ H ₂ flow rate is 100 sccm, and the heating rate is 50 ℃/min, maintained at 680℃ for 60 min, to obtain nano tin-silicon composite anode material.

It has been determined that the nano-tin-silicon composite negative electrode material includes linear nano-tin, nano-silicon particles embedded in the nano-tin, and a carbon coating layer coated on the outer surface of the nano-tin. In the nano-tin-silicon composite anode material, nano-silicon accounts for 64% of the nano-tin-silicon composite anode material in terms of silicon element; nano-tin accounts for 31 wt% of the nano-tin-silicon composite anode material in terms of elemental tin; carbon The coating layer accounts for 5 wt% of the nano-tin-silicon composite negative electrode material.

Example 3

(1) Weigh 2g of silicon powder with a particle size of 100nm into 1000ml of water, add 20ml of ethanol to obtain a nano-silicon suspension, and then place the nano-silicon suspension in an ultrasonic machine for 2 hours;

(2) Stir the ultrasonically dispersed nano-silicon suspension with a magnetic stirrer, then add 2g NaOH and 7g Na ₂ SnO ₃ ·3H ₂ O to the solution, then slowly add acetic acid to adjust the pH to about 7 . Finally, after filtering, washing, and drying, the nano-silicon composite material coated with nano-tin compound is obtained;

(3) Put the nano-silicon composite material coated with nano-tin compound into a tube furnace under nitrogen atmosphere for C ₂ H ₂ carbon-coated, N ₂ flow rate is 300 sccm, C ₂ H ₂ flow rate is 100 sccm, and the heating rate is 50 ℃/min, maintained at 680℃ for 60 min, to obtain nano tin-silicon composite anode material.

It has been determined that the nano-tin-silicon composite negative electrode material includes linear nano-tin, nano-silicon particles embedded in the nano-tin, and a carbon coating layer coated on the outer surface of the nano-tin. In the nano-tin-silicon composite anode material, nano-silicon accounts for 59wt% of the nano-tin-silicon composite anode material based on silicon; nano-tin accounts for 35wt% of the nano-tin-silicon composite anode material based on tin; carbon The coating layer accounts for 6 wt% of the nano-tin-silicon composite negative electrode material.

Example 4

(1) Weigh 2g of silicon powder with a particle size of 30nm into 1000ml of water, add 20ml of ethanol to obtain a nano-silicon suspension, and then place the nano-silicon suspension in an ultrasonic machine for 2h;

(2) after the ultrasonic dispersion silicon nano suspension was stirred constantly with a magnetic stirrer, followed by addition of 10ml 37% hydrochloric acid and 6g of SnCl ₂ in the solution, and then slowly adding ammonia to adjust pH to about 7. Finally, after filtering, washing and drying, the nano-silicon composite material coated with nano-tin compound is obtained;

(3) Put the nano-silicon composite material coated with nano-tin compound into a tube furnace under nitrogen atmosphere for C ₂ H ₂ carbon-coated, N ₂ flow rate is 300 sccm, C ₂ H ₂ flow rate is 50 sccm, and the heating rate is 50 ℃/min, maintained at 650℃ for 90min, to obtain nano tin-silicon composite anode material.

It has been determined that the nano-tin-silicon composite negative electrode material includes dendritic nano-tin, nano-silicon particles embedded in the nano-tin, and a carbon coating layer coated on the outer surface of the nano-tin. In the nano-tin-silicon composite negative electrode material, nano-silicon accounts for 64% by weight of the nano-tin-silicon composite negative electrode material based on silicon element; nano-tin takes up 33% by weight of the nano-tin-silicon composite negative electrode material based on elemental tin; carbon The coating layer accounts for 3%wt of the nano-tin-silicon composite negative electrode material.

Example 5

(1) Weigh 2g of silicon powder with a particle size of 20nm into 1000ml of water, add 20ml of ethanol to obtain a nano-silicon suspension, and then place the nano-silicon suspension in an ultrasonic machine for 2h;

(2) after the ultrasonic dispersion silicon nano suspension was stirred constantly with a magnetic stirrer, followed by addition of 10ml 37% hydrochloric acid and 6g of SnCl ₂ in the solution, and then slowly adding ammonia to adjust pH to about 7. Finally, after filtering, washing and drying, the nano-silicon composite material coated with nano-tin compound is obtained;

(3) Put the nano-tin compound coated nano-silicon composite material into a tube furnace under nitrogen atmosphere for C ₂ H ₂ carbon-coated, N ₂ flow rate is 300 sccm, C ₂ H ₂ flow rate is 30 sccm, and the heating rate is 50 ℃/min, maintain at 650℃ for 120min to obtain nano tin-silicon composite anode material.

It has been determined that the nano-tin-silicon composite negative electrode material includes beaded nano-tin, nano-silicon particles embedded in the nano-tin, and a carbon coating layer coated on the outer surface of the nano-tin. In the nano-tin-silicon composite anode material, nano-silicon accounts for 65 wt% of the nano-tin-silicon composite anode material based on silicon; nano-tin accounts for 32% of the nano-tin-silicon composite anode material based on tin; carbon The coating layer accounts for 3 wt% of the nano-tin-silicon composite negative electrode material.

Example 6

(1) Mix 20g of 100nm silicon powder and 45g of 5μm stannous oxide, then carry out high-energy ball milling for 8 hours, then sieving and drying;

(2) Take 2g of the dried material and put it into a tube furnace under nitrogen atmosphere for C ₂ H ₂ carbon coating, N ₂ flow rate is 300 sccm, C ₂ H ₂ flow rate is 100 sccm, heating rate is 50 ℃/min, at 680 The temperature is maintained for 60 minutes to obtain a nano-tin-silicon composite anode material.

It has been determined that the nano-tin-silicon composite negative electrode material includes linear nano-tin, nano-silicon particles embedded in the nano-tin, and a carbon coating layer coated on the outer surface of the nano-tin. In the nano-tin-silicon composite anode material, nano-silicon accounts for 65 wt% of the nano-tin-silicon composite anode material based on silicon; nano-tin accounts for 32 wt% of the nano-tin-silicon composite anode material based on tin; carbon The coating layer accounts for 3 wt% of the nano-tin-silicon composite negative electrode material.

Example 7

(1) Mix 20g of 100nm silicon powder and 70g of stannous oxalate and perform high-energy ball milling for 8 hours, then sieving and drying;

(2) Take 2g of the dried material and put it into a tube furnace under nitrogen atmosphere for C ₂ H ₂ carbon coating, N ₂ flow rate is 300 sccm, C ₂ H ₂ flow rate is 100 sccm, heating rate is 50 ℃/min, at 680 The temperature is maintained for 60 minutes to obtain a nano tin-silicon composite anode material.

It has been determined that the nano-tin-silicon composite negative electrode material includes linear nano-tin, nano-silicon particles embedded in the nano-tin, and a carbon coating layer coated on the outer surface of the nano-tin. In the nano-tin-silicon composite negative electrode material, nano-silicon accounts for 64% by weight of the nano-tin-silicon composite negative electrode material based on elemental silicon; nano-tin takes up 32% by weight of the nano-tin-silicon composite negative electrode material based on the elemental tin; carbon The coating layer accounts for 4wt% of the nano-tin-silicon composite negative electrode material.

Example 8

(1) Mix 20g of 100nm silicon powder and 50g of tin oxide and perform high-energy ball milling for 8 hours, then sieving and drying;

(2) Take 2g of the dried material and put it into a tube furnace under nitrogen atmosphere for C ₂ H ₂ carbon coating, N ₂ flow rate is 300 sccm, C ₂ H ₂ flow rate is 100 sccm, heating rate is 50 ℃/min, at 680 The temperature is maintained for 60 minutes to obtain a nano tin-silicon composite anode material.

It has been determined that the nano-tin-silicon composite negative electrode material includes linear nano-tin, nano-silicon particles embedded in the nano-tin, and a carbon coating layer coated on the outer surface of the nano-tin. In the nano-tin-silicon composite negative electrode material, nano-silicon accounts for 65% of the nano-tin-silicon composite negative electrode material based on elemental silicon; nano-tin takes up 32wt% of the nano-tin-silicon composite negative electrode material based on elemental tin; carbon The coating layer accounts for 3 wt% of the nano-tin-silicon composite negative electrode material.

The XRD pattern of the nano-tin-silicon composite negative electrode material of the present invention is shown in FIG. 1. The SEM images of the nano-tin-silicon composite negative electrode material of the present invention including linear, bead-shaped, and dendritic nano-tin are shown in FIG. 2A, FIG. 2B, and FIG. 2C, respectively. The TEM image of the nano-tin-silicon composite negative electrode material including linear nano-tin of the present invention is shown in FIG. 2D. The charge-discharge cycle performance diagram of the lithium-ion battery of the tin-silicon composite anode material of Example 1 of the present invention is shown in FIG. 3. The rate performance diagram of the lithium ion battery of the tin-silicon composite anode material of Example 1 of the present invention is shown in FIG. 4.

FIG. 5 shows a schematic longitudinal cross-sectional view of an embodiment of the nano-tin-silicon composite negative electrode material including linear nano-tin according to the present invention. FIG. 6 shows a schematic diagram of the charging and discharging process of deintercalating lithium in one embodiment of the nano-tin-silicon composite negative electrode material including linear nano-tin according to the present invention. During the first charge, the expanded shell can be maintained without cracking due to the presence of the external conductive coating layer, and will not change when lithium is removed again, and holes are formed in the interior (shown in white), so when lithium is removed again later , The entire nanotube will not expand any more, and the long-term circulating shell structure can still remain stable.

Example 9

1. Preparation of button cell

The nano-tin-silicon composite anode material prepared in Examples 1-8, super-p (conductive carbon black) and sodium alginate were mixed uniformly with a mixer at a mass ratio of 8:1:1, and then evenly coated on the copper foil Put it in a vacuum drying oven, vacuum dry at 120°C for 12 hours, and take it out to make a pole piece.

Lithium sheet is used as the counter electrode, the electrolyte is 1mol/l LiPF ₆ EC+DMC (volume ratio is 1:1) solution, and the PP/PE/PP three-layer membrane is used as the diaphragm (purchased from Celgard in the United States), Assemble CR2032 button cell in a glove box filled with argon atmosphere.

2. Electrochemical performance test

The electrochemical performance test of the assembled battery was carried out with a Landian tester (purchased from Wuhan Landian Electronics Co., Ltd.). The battery was cycled at a rate of 0.05C for 1 week and then cycled at a rate of 0.2C for 99 weeks, charging and discharging. The cut-off voltage range is 0.01V～1.0V. The test results are shown in Table 1.

Comparative example 1

A button cell was prepared in the same manner as in Example 9 except that 100 nm silicon particles were used instead of the nano-tin-silicon composite negative electrode material. According to the electrochemical performance test conditions of Example 9, the battery was subjected to a charge-discharge cycle performance test, and the results are shown in Table 1.

Comparative example 2

A button cell was prepared in the same manner as in Example 9 except that 100 nm tin particles were used instead of the nano-tin-silicon composite negative electrode material. According to the electrochemical performance test conditions of Example 9, the battery was subjected to a charge-discharge cycle performance test, and the results are shown in Table 1.

Comparative Example 3 A negative electrode material was prepared according to the method of Example 1 of patent CN101510601B

(1) Take 5 mL of ^{1.0 mol·L -1} ammonia solution, 100 mL of methanol and 20 mL of water and mix them for 0.5 h. Add 6.25 mL of methyl silicate to the mixture and stir for 3 h. The resulting suspension is separated by centrifugation , After washing with deionized water and drying, silica balls are obtained.

(2) 11.46 g of urea and 1.7 g of Na ₂ SnO ₃ ·3H ₂ O were dissolved in 200 mL of deionized water, and then 18 mL of ethanol was added thereto and stirred to obtain a milky suspension. 3.82g of the product of step (1), molar ratio Sn:Si:urea=1:10:30, ultrasonically dispersed in 4mL deionized water for 0.5h to obtain a suspension. The mixture obtained by mixing the two suspensions is transferred to a 300 mL high-pressure furnace, heated at 2 atmospheres at 100° C. for 2 h, cooled, centrifuged, washed, and dried. Of dried product was 240mg, and 1.3ml, 2mol / L KOH solution in a molar ratio ^{(Sn + Si) :OH - =} 1:2, 2 hours, 60% etched in step (1) of the product, centrifuged, The hollow spheres of silicon tin oxide are obtained, centrifuged, washed, and dried in a microwave oven at a temperature of 110°C.

(3) Take 87.5 mg of the product of step (2) and stir and disperse it in 10 mL of deionized water to obtain a suspension. Dissolve this suspension with 16 mL of deionized water to dissolve 600 mg of maltose solution by molar ratio (Sn+Si). ): Maltose=1:4, mixed and stirred, transferred to a pressure cooker and heated at 1 atmosphere pressure and 200°C for 8 hours, the product was centrifuged, washed, and dried.

(4) Transfer the product of step (3) to a tube furnace and heat it in an argon atmosphere at 500°C for 12 hours. Centrifugal separation can obtain a gray-black product. The product is washed with deionized water and then dried at 110°C. Dry to obtain a negative electrode material.

After measurement, the SEM image of the negative electrode material is shown in 2E, which is spherical particles.

A button cell was prepared in the same manner as in Example 9 except that the anode material of step (4) was used instead of the nano-tin-silicon composite anode material. According to the electrochemical performance test conditions of Example 9, the battery was subjected to a charge-discharge cycle performance test, and the results are shown in Table 1.

Comparative example 4

(1) Mix 20g of 100nm silicon powder and 37.5g of tin powder and perform high-energy ball milling, then sieving and drying;

(2) Take 2g of the dried material and put it into a tube furnace under nitrogen atmosphere for C ₂ H ₂ carbon coating, N ₂ flow rate is 300 sccm, C ₂ H ₂ flow rate is 100 sccm, heating rate is 50 ℃/min, at 680 The temperature is maintained for 60 minutes to obtain a nano tin-silicon composite anode material.

It is determined that the nano-tin-silicon composite negative electrode material is spherical particles ranging from tens of micrometers to hundreds of micrometers, with little carbon coating on the outside.

Except that the nano-tin-silicon composite negative electrode material obtained in step (2) of this comparative example was used as the negative electrode material, a button cell was prepared in the same manner as in Example 9. According to the electrochemical performance test conditions of Example 9, the battery was subjected to a charge-discharge cycle performance test, and the results are shown in Table 1.

Test results and analysis

It can be seen from the XRD pattern of FIG. 1 that the nano-tin-silicon composite negative electrode material of the present invention only has elemental tin and elemental silicon, and no other impurity peaks.

It can be seen from the SEM images of FIGS. 2A to 2C that the nano-tin-silicon composite negative electrode material of the present invention has a linear, beaded, or dendritic shape. It can be seen from the TEM image of FIG. 2D that the coating structure of the linear nano-tin-silicon composite anode material is very complete and uniform. It can be seen from the SEM image of FIG. 2E that the negative electrode material prepared by the method of Comparative Example 3 has a different structure from the negative electrode material of the present invention, and is spherical particles.

It can be seen from the charge-discharge cycle diagram of FIG. 3 that the nano-tin-silicon composite negative electrode material of the present invention has high capacity, stable cycle performance, and excellent electrochemical performance.

It can be seen from the rate performance graph of FIG. 4 that the nano-tin-silicon composite negative electrode material of the present invention has excellent rate performance.

Table 1

It can be seen from the data in Table 1 that compared with the button battery made of elemental silicon or elemental tin as the negative electrode material of Comparative Example 1-2, and the button battery made of the negative electrode material of Comparative Example 3-4, The button battery made of the nano-tin-silicon composite negative electrode material of the present invention exhibits more excellent electrochemical performance, and its capacity is above 1000 mAh/g. Compared with the button battery of Comparative Examples 1-4, the capacity is greatly improved. In addition, the coulombic efficiency and capacity retention rate of the button cell made of the nano-tin-silicon composite anode material of the present invention are very high, and both are significantly higher than those of the button cell of Comparative Examples 1-4.

The particle size of the silicon powder, the mass of silicon-tin element, and _{the flow rate of C 2} H ₂ were changed, and other conditions were unchanged. The nano-tin-silicon composite negative electrode material was prepared according to the method of Example 1, and then the nano-tin-silicon composite negative electrode Materials 1-20 size batteries were prepared according to the method for preparing button batteries in Example 9, and the battery was subjected to charge-discharge cycle performance test according to the electrochemical performance test method of Example 9. The results are shown in Table 2.

Table 2

It can be seen from the data in Table 2 that the particle size of silicon is preferably below 200 nm. Although low tin content is conducive to battery capacity, the battery stability is poor and the capacity retention rate decreases. Considering comprehensively, the tin content is preferably 40 to 80 wt%. Too high or too low content of the outer conductive coating layer also has an adverse effect on battery performance, and the weight percentage of the carbon coating layer is preferably controlled within 3-10 wt%.

The types of solvent, tin salt and nano-silicon material were changed respectively, and other conditions were unchanged, the nano-tin-silicon composite anode material was prepared according to the method of Example 1, and then the nano-tin-silicon composite anode material was prepared according to Example 9 The button battery method was used to prepare No. 21-33 batteries, and the battery was subjected to the charge-discharge cycle performance test according to the electrochemical performance test method of Example 9. The results are shown in Table 3.

table 3

From the data in Table 3, it can be seen that changing the types of solvents, tin salts and nano-silicon materials within the scope of the present invention can produce composite materials with excellent electrochemical performance.

The silicon powder particle size, tin type, and ball milling time were changed, and other conditions were unchanged. The nano-tin-silicon composite negative electrode material was prepared according to the method of Example 8, and then the nano-tin-silicon composite negative electrode material was prepared according to Example 9. The button battery method was used to prepare No. 34-52 batteries, and the battery was subjected to a charge-discharge cycle performance test according to the electrochemical performance test method of Example 9. The results are shown in Table 4.

Table 4

It can be seen from the data in Table 4 that the particle size of silicon particles during ball milling is preferably below 200 nm. Changing the type of tin compound within the scope of the present invention has little effect on battery performance. The milling time is preferably 6h or more.

Claims (10)

1. A nano tin-silicon composite negative electrode material, comprising: linear, dendritic or beaded nano tin, nano silicon material particles embedded in the nano tin, and a conductive package coated on the outer surface of the nano tin Coating; Preferably, the conductive coating is a carbon layer.
2. The nano-tin-silicon composite negative electrode material according to claim 1, wherein the nano-silicon material accounts for 5 to 80 wt% of the nano-tin-silicon composite negative electrode material based on silicon element, preferably 10 to 50 wt%; Tin is 15-90wt%, preferably 40-80wt% of the nano-tin-silicon composite anode material based on tin element; the conductive coating layer accounts for 1-15wt% of the nano-tin-silicon composite anode material, preferably 3～10wt%.
3. The nano-tin-silicon composite anode material according to claim 1 or 2, wherein the nano-silicon material is one or more of silicon nano-materials, silicon-carbon nano-materials and silicon alloy nano-materials; preferably, the The particle size of the nano silicon material particles is 5-1000 nm, preferably 10-200 nm.
4. A method for preparing the nano-tin-silicon composite negative electrode material according to any one of claims 1 to 3, comprising the following steps:

   (1) Add the nano silicon material to the solvent to obtain a suspension, and then perform ultrasonic dispersion treatment on the suspension;

   (2) Add soluble tin salt to the suspension after ultrasonic dispersion, then conduct hydrothermal reaction or add co-precipitation agent for co-precipitation, and finally filter, wash, and vacuum dry to obtain nano-tin compound or oxide coating Nano-silicon composite materials;

   (3) The nano-tin compound or oxide-coated nano-silicon composite material obtained in step (2) is reduced and coated to obtain the nano-tin-silicon composite negative electrode material.
5. The method according to claim 4, wherein the solvent in step (1) is one or more of water, methanol, ethanol, propanol, isopropanol, butanol and ethylene glycol, preferably water And/or ethanol; preferably, in the ultrasonic dispersion treatment step, a dispersant is also added, and the dispersant is one or more of methanol, ethanol, ethylene glycol, propanol and isopropanol, preferably Methanol and/or ethanol.
6. The method according to claim 4, wherein the soluble tin salt in step (2) is SnCl ₂ , SnSO ₄ , Sn(NO ₃ ) ₂ , Na ₂ SnO ₂ , K ₂ SnO ₂ , SnCl ₄ , Sn (SO ₄ ) ₂ , Sn(NO ₃ ) ₄ , Na ₂ SnO ₃ , SnC ₂ O ₄ or K ₂ SnO ₃ ; and/or

   The type of the co-precipitating agent is determined according to the tin salt, which is ammonia, sodium hydroxide, potassium hydroxide, or urea; preferably, the amount of the co-precipitating agent added is an amount just to completely precipitate tin.
7. A method for preparing the nano-tin-silicon composite negative electrode material according to any one of claims 1 to 3, comprising the following steps:

   The nano-silicon material and the tin salt that can decompose to produce tin oxide at high temperature are mixed for high-energy ball milling, and the ball-milled mixed material is reduced and coated to obtain the nano-tin-silicon composite negative electrode material; preferably, the The tin salt that can decompose to produce tin oxide at high temperature is tin oxide, stannous oxide, tin hydroxide, stannous oxalate, stannous sulfate or stannous acetate.
8. The method according to any one of claims 4 to 7, wherein the reduction coating method is chemical vapor deposition coating, and the gas used for the chemical vapor deposition coating is acetylene, methane, toluene or ethylene; preferably Preferably, the chemical vapor deposition coating adopts C ₂ H ₂ gas for carbon coating, and the coating conditions include: the _{flow rate of C 2} H ₂ is 1 to 300 sccm, preferably 10 to 100 sccm; and the temperature is 500 to 800° C., preferably 650～750℃; time is 5min～10h, preferably 2～6h.
9. A negative electrode comprising the negative electrode material according to any one of claims 1 to 3 or the negative electrode material prepared by the method according to any one of claims 4 to 8; preferably, the negative electrode further comprises a collector Fluid, conductive additive and binder, wherein the negative electrode material, conductive additive and binder are supported on the current collector.
10. A lithium ion battery, the battery includes a battery case, an electrode group and an electrolyte, the electrode group and the electrolyte are sealed in the battery case, the electrode group includes a positive electrode, a separator and a negative electrode, wherein the negative electrode is The negative electrode of claim 9.

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