CN110048096A - For lithium/sodium-ion battery cathode tin oxide/carbon fibre composite and preparation method - Google Patents

Abstract

The invention provides a tin oxide/carbon fiber composite material and a preparation method for a negative electrode of a lithium/sodium ion battery. adding polyacrylonitrile to dimethylformamide and stirring to obtain a mixed solution; calcining zinc stannate hydroxide in a muffle furnace, and then adding the product Zn-Sn-O nanoparticles into the mixed solution and fully stirring uniform; transfer the obtained mixed solution into a syringe for electrospinning to obtain a composite material of Zn-Sn-O nanoparticles/polyacrylonitrile; firstly pre-calcinate the obtained composite material in air, and then calcine under an inert gas The Zn-Sn-O nanoparticle/carbon fiber composite material is obtained; finally, the porous tin oxide/carbon fiber composite material is obtained by etching with dilute hydrochloric acid, washing and drying. When used in sodium-ion batteries, at a current density of 100 mA g ^-1 , the specific capacity can reach more than 280 mA hg ^-1 after 200 cycles, and the Coulombic efficiency is close to 100%.

Description

Tin oxide/carbon fiber composites for lithium/sodium ion battery anodes and their preparation method

technical field

The invention belongs to the field of inorganic nanometer material synthesis. Specifically, it relates to a method for preparing a tin oxide/carbon fiber (SnO ₂ /CF) composite electrode material by electrospinning technology. In particular, a tin oxide/carbon fiber composite material and a preparation method for the negative electrode of a lithium/sodium ion battery.

Background technique

In the past few decades, in order to meet the increasing global energy demand, a large number of low-cost and renewable energy sources have been developed rapidly. Among them, lithium/sodium ion batteries are widely used in information technology, electric vehicles, aerospace and other fields due to their high specific energy density, high discharge voltage, high cycle life, no memory effect, and no pollution. In particular, flexible electrode materials have attracted extensive attention from researchers at home and abroad because they can be applied to wearable electronic devices.

In Li/Na-ion batteries, the anode material is one of the important factors affecting the battery capacity and service life. In the current research, the active material of the flexible electrode sheet using the coating process is easy to pulverize and fall off during the folding process, which greatly reduces the cycle life. Stable material. Among many metal oxides, tin dioxide has the advantages of high specific capacity (Li ⁺ : 1493mAh g ^-1 , Na ⁺ : 1378mAh g ^-1 ), high energy density, low lithium intercalation potential, non-toxicity and abundant resources. However, tin dioxide has a large volume expansion during the charge and discharge process, which reduces the cycle stability of the battery, and its low electrical conductivity and other factors limit its practical application. Wang C (Wang C, Zhou Y, Ge M, et al. Cheminform, 2010, 41(21):46.) et al. synthesized tin dioxide nanosheets by hydrothermal method and applied them in lithium-ion batteries , the nanosheets have large specific surface area and pore volume, which alleviates the volume expansion problem of tin dioxide during charging and discharging to a certain extent. However, with the increase of cycle times, the stability deteriorates and the capacity decays sharply, and The volume effect of tin dioxide during charge and discharge is not addressed. According to relevant literature reports, composite materials (such as carbon, graphene, carbon nanotubes, etc.) can effectively inhibit volume expansion and pulverization and shedding of active materials, and improve the cycle stability of batteries, but graphene, carbon nanotubes, etc. The preparation process requirements are high and the price is expensive, which is not conducive to the actual large-scale preparation of electrode materials. Xie W (Xie W, Gu L, Xia F, et al. Journal of Power Sources, 2016, 327: 21-28.) prepared tin dioxide/carbon composites by electrospinning and carbon coating, and used Its application in the negative electrode of lithium ion battery has improved the cycle stability, but because the composite material is a powder material, the cycle stability improvement is limited and it cannot be used in wearable devices without flexibility. Therefore, by designing a reasonable structure and preparing tin oxide and carbon fiber composite materials to improve the conductivity of the material, it can also alleviate the volume effect of the tin oxide negative electrode during the charge and discharge process, which is to improve the cycle of the tin oxide material as a negative electrode material for lithium/sodium ion batteries. It is one of the effective measures for stability, and the composite material is flexible and can be directly used in wearable devices as the negative electrode of lithium/sodium ion batteries.

SUMMARY OF THE INVENTION

The purpose of the present invention is to pre-calcinate zinc stannate hydroxide (ZnSn(OH) ₆ ), and then prepare tin oxide/carbon fibers which can be used as negative electrodes of lithium/sodium ion batteries through a series of processes such as electrospinning, post-calcination and etching. composite material. The composite material is formed by encapsulating nanoparticles in carbon fibers to form a three-dimensional network structure, and the composite material is flexible and can be directly used as the negative electrode of lithium/sodium ion batteries. When it is used as a negative electrode material for lithium/sodium ion batteries, the porous structure in tin oxide can alleviate the volume expansion of tin oxide. volume expansion, and at the same time, a stable solid electrolyte interfacial film can be formed on the fiber surface. Thus, this method improves the cycling stability of tin oxide as a negative electrode material for Li/Na-ion batteries.

The invention provides a tin oxide/carbon fiber composite material for a negative electrode of a lithium/sodium ion battery. The composite material is composed of porous tin oxide and carbon fiber, and the carbon fiber wraps the tin oxide to form a three-dimensional network structure.

The invention provides a tin oxide/carbon fiber composite material which can be used for the negative electrode of lithium/sodium ion battery to be synthesized by electrospinning method and then calcined and etched, and a method thereof.

The technical scheme of the present invention is as follows:

Preparation method of tin oxide/carbon fiber composite material for lithium/sodium ion battery negative electrode; the steps are as follows

1). Add polyacrylonitrile (PAN) into dimethylformamide (DMF), stir at 300-500r/min for 8-10h, so that PAN is uniformly dispersed in DMF;

2). The zinc stannate hydroxide (ZnSn(OH) ₆ ) is calcined in a muffle furnace, and then the product Zn-Sn-O nanoparticles are added to step 1). The obtained solution is sonicated for 0.5-1.5 h, stir at 300-500r/min for 8-10h;

3). Electrospinning the solution obtained in step 2) to obtain a Zn-Sn-O nanoparticle/PAN composite material;

4). The composite material obtained in step 3) is first put into a muffle furnace for calcination, and then transferred to a tubular furnace for calcination in argon;

5) soaking the obtained calcined product in dilute hydrochloric acid to etch away zinc oxide, washing and vacuum drying to obtain a porous SnO ₂ @C composite material;

The concentration of polyacrylonitrile in the step 1) is 0.06-0.12 g/ml.

In the step 2), the calcination temperature is 600°C, and the heating rate is 1-2°C/min.

In the step 2), the mass ratio of zinc hydroxide stannate (ZnSn(OH) ₆ ), Zn-Sn-O nanoparticles and polyacrylonitrile is 1.23:1:0.6-1.23:1:1.2.

The step 3) electrospinning conditions: the voltage is 13-18kv, the flow rate is set to 1.0-2.0ml/h, and the distance is 13-18cm.

Step 4) Muffle furnace calcination conditions: heating rate 2-5°C/min, keeping at 240-260°C for 2-4h, and then naturally cooled to room temperature. Tube furnace calcination conditions: the heating rate is 2-5°C/min, the temperature is kept at 600-650°C for 3-6h, and then naturally cooled to room temperature.

In the step 5), the concentration of hydrochloric acid is 1 mol/L, soaking for 6-12 hours, and washing with ethanol and deionized water for 6-8 times.

The step 6) drying conditions: vacuum drying at 60-80° C. for 10-12 hours.

In the present invention, polyacrylonitrile is added to dimethylformamide and stirred to obtain a uniform mixed solution; zinc stannate hydroxide is calcined in a muffle furnace, and then the product Zn-Sn-O nanoparticles are added to the mixed solution The obtained mixed solution was transferred into a syringe for electrospinning to obtain a Zn-Sn-O nanoparticle/polyacrylonitrile composite material; the obtained composite material was first pre-calcined in air, and then The Zn-Sn-O nanoparticle/carbon fiber composite material is obtained by calcination under inert gas; finally, the porous tin oxide/carbon fiber composite material is obtained by etching with dilute hydrochloric acid, washing and drying. The material is composed of tin oxide and carbon fibers to form a three-dimensional network structure, wherein tin oxide is a porous structure and is dispersed in carbon fibers. The porous structure can relieve the volume expansion of tin oxide. The carbon fiber can not only improve the conductivity of the material and shorten the ion and electron The transmission distance can also be suppressed, and the volume expansion and pulverization of tin oxide during the electrochemical reaction can be suppressed. Thus, the cycle stability of tin oxide as a negative electrode material for lithium/sodium ion batteries is improved. A tin oxide/carbon fiber composite material that can be used as a negative electrode for lithium/sodium ion batteries was prepared. Thus, this method improves the cycling stability of tin oxide as a negative electrode material for Li/Na-ion batteries. When used in a sodium-ion battery, its performance was tested at a current density of 100 mA g ^-1 . After 200 cycles, its specific capacity could reach more than 280 mA hg ^-1 , the Coulombic efficiency was close to 100%, and only 0.014% was lost per cycle.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of the tin oxide/carbon fiber composite material prepared in Example 1, the diffraction peaks at 26.6°, 33.9°, 37.9°, 51.7° and 54.7° in the diffraction pattern correspond to (110) of tin oxide, (101), (200), (211) and (220) crystal planes, while the carbon fiber is amorphous, so the prepared product is composed of tin oxide and carbon fiber, of which tin oxide has excellent crystallinity.

Figure 2 is a scanning electron microscope picture of the tin oxide/carbon fiber composite material prepared in Example 2. It can be seen from the figure that the product is composed of tin oxide nanoparticles and carbon fibers, and the carbon fibers wrap the tin oxide to form a three-dimensional network structure. -250nm.

Figure 3 is a long cycle test chart of the tin oxide/carbon fiber composite prepared in Example 2. It can be seen from the figure that when it is used in a sodium-ion battery, its performance is tested at a current density of 100mA g ^-1 , and the cycle is 200 After that, its specific capacity can reach more than 280mA hg ^-1 , and only lose 0.014% per lap.

Figure 4 is a transmission electron microscope picture of the tin oxide/carbon fiber composite material prepared in Example 3. It can be seen from the figure that the product is composed of tin oxide nanoparticles and carbon fibers, tin oxide is dispersed in the carbon fibers, and tin oxide has a porous structure.

Detailed ways

Example 1:

1). Add 0.9g of polyacrylonitrile (PAN) to 15ml of dimethylformamide (DMF), stir at 300r/min for 8h, so that PAN is uniformly dispersed in DMF, the concentration of PAN in the mixture is 0.06g /ml.

2). 1.85 g of zinc stannate hydroxide (ZnSn(OH) ₆ ) was calcined in a muffle furnace at 600° C. with a heating rate of 1° C./min to obtain Zn-Sn-O nanoparticles. Add 1.5 g of Zn-Sn-O nanoparticles to step 1). In the prepared solution (the mass ratio of zinc stannate hydroxide (ZnSn(OH) ₆ ), Zn-Sn-O nanoparticles to polyacrylonitrile 1.23:1.8:1:0.6), ultrasonic for 0.5h, stirring at 300r/min for 8h;

3). Electrospin the solution obtained in step 2). The voltage is 13kv, the flow rate is set to 1.0ml/h, and the distance is 13cm to obtain a Zn-Sn-O nanoparticle/PAN composite material;

4). The Zn-Sn-O nanoparticle/PAN composite material prepared in step 3) was first put into a muffle furnace at 240°C for 2 hours, and the heating rate was 2°C/min, and then transferred to a tube furnace under argon. The temperature was kept at 600 °C for 3 h in the air, and the heating rate was 2 °C/min. ;

5). The product obtained in step 4) was soaked in dilute hydrochloric acid with a concentration of 1 mol/L for 6 hours, washed with ethanol and deionized water for 6 times, and vacuum-dried at 60 °C for 10 hours to obtain SnO ₂ @C with pores composite material;

As shown in Figure 1, the prepared product is composed of tin oxide/carbon fibers, in which tin oxide has excellent crystallinity.

Example 2:

1). Add 1.5g of polyacrylonitrile (PAN) to 15ml of dimethylformamide (DMF), stir at 400r/min for 10h to make PAN evenly dispersed in DMF, the concentration of PAN in the mixture is 0.09g /ml.

2). 1.85 g of zinc stannate hydroxide (ZnSn(OH) ₆ ) was calcined in a muffle furnace at 600° C. with a heating rate of 1° C./min to obtain Zn-Sn-O nanoparticles. Add 1.5 g of Zn-Sn-O nanoparticles to step 1). In the prepared solution (the mass ratio of zinc stannate hydroxide (ZnSn(OH) ₆ ), Zn-Sn-O nanoparticles to polyacrylonitrile 1.23:1:0.9), ultrasonic for 1h, stirring at 400r/min for 9h;

3). Electrospin the solution obtained in step 2). The voltage is 15kv, the flow rate is set to 1.5ml/h, and the distance is 15cm to obtain a Zn-Sn-O nanoparticle/PAN composite material;

4). The Zn-Sn-O nanoparticle/PAN composite material prepared in step 3) was first put into a muffle furnace at 250°C for 3 hours, and the heating rate was 3°C/min, and then transferred to a tube furnace under argon. The temperature was kept at 650℃ for 4.5h in the air, and the heating rate was 3℃/min;

5). The product obtained in step 4) was soaked in dilute hydrochloric acid with a concentration of 1 mol/L for 9 hours, washed with ethanol and deionized water for 7 times, and vacuum-dried at 60 °C for 11 hours to obtain porous SnO ₂ @C composite material;

As shown in Fig. 2, the product is composed of tin oxide nanoparticles and carbon fibers. The carbon fibers wrap the tin oxide to form a three-dimensional network structure, and the carbon fibers have diameters ranging from 100 to 250 nm. As shown in Figure 3, when used in a sodium-ion battery, its performance was tested at a current density of 100 mA g ^-1 . After 50 cycles, its specific capacity could reach more than 296 mA hg ^-1 , and the Coulombic efficiency was close to 100%.

Example 3:

1). Add 1.8g of polyacrylonitrile (PAN) to 15ml of dimethylformamide (DMF), stir at 400r/min for 9h, so that PAN is uniformly dispersed in DMF, the concentration of PAN in the mixture is 0.12g /ml.

2). 1.85 g of zinc stannate hydroxide (ZnSn(OH) ₆ ) was calcined at 600° C. in a muffle furnace with a heating rate of 2° C./min to obtain Zn-Sn-O nanoparticles. Add 1.5 g of Zn-Sn-O nanoparticles to step 1). In the prepared solution (the mass ratio of zinc stannate hydroxide (ZnSn(OH) ₆ ), Zn-Sn-O nanoparticles to polyacrylonitrile 1.23:1:1.2), ultrasonic for 1.5h, stirring at 500r/min for 10h;

3). Electrospin the solution obtained in step 2). The voltage is 18kv, the flow rate is set to 2.0ml/h, and the distance is 18cm to obtain a Zn-Sn-O nanoparticle/PAN composite material;

4). The Zn-Sn-O nanoparticle/PAN composite material obtained in step 3) was firstly placed in a muffle furnace at 260°C for 4 hours, and the heating rate was 5°C/min, and then transferred to a tube furnace under argon. The temperature was kept at 650 °C for 6 h in the air, and the heating rate was 5 °C/min. ;

5). The product obtained in step 4) was soaked in dilute hydrochloric acid with a concentration of 1 mol/L for 12 h, washed with ethanol and deionized water for 8 times, and vacuum dried at 80 °C for 12 h to obtain porous SnO ₂ @C composite material;

As shown in Fig. 4, the product consists of tin oxide nanoparticles and carbon fibers, tin oxide is dispersed in the carbon fibers and the tin oxide is a porous structure.

It can also be clearly seen from the drawings of the above embodiments that the product prepared by the present invention is a tin oxide/carbon fiber composite material.

Claims (10)

1. it is a kind of for lithium/sodium-ion battery cathode tin oxide/carbon fibre composite, it is characterized in that composite material is by porous Tin oxide and carbon fiber composition, carbon fiber wrap up tin oxide formed three-dimensional net structure.

2. claim 1 is used for lithium/sodium-ion battery cathode tin oxide/carbon fibre composite preparation method, spy Sign is to include the following steps:

1) polyacrylonitrile (PAN) is added in dimethylformamide (DMF) by, is stirred 8-10h with 300-500r/min, is made PAN It is dispersed in DMF；

2) is by hydroxide zinc stannate (ZnSn (OH)₆) calcined in Muffle furnace, after by product Zn-Sn-O nano particle be added Into solution made from step 1), ultrasonic 0.5-1.5h stirs 8-10h with 300-500r/min；

3) solution made from step 2) is carried out electrostatic spinning by, obtains Zn-Sn-O nano particle/PAN composite material；

4) composite material made from step 3) is first put into Muffle furnace and calcines by, is then transferred in tube furnace in argon gas Calcining；

5) the obtained calcined product of step 4) is soaked in dilute hydrochloric acid and etches away zinc oxide by, and washing and vacuum drying are had There is porous SnO₂@C composite.

3. method according to claim 2, it is characterized in that the concentration of polyacrylonitrile is 0.06-0.12g/ in the step 1) ml。

4. method according to claim 2, it is characterized in that calcination temperature is 600 DEG C in the step 2), heating rate 1-2 ℃/min。

5. method according to claim 2, it is characterized in that hydroxide zinc stannate (ZnSn (OH) in the step 2)₆)、Zn-Sn- The mass ratio of O nano particle and polyacrylonitrile is 1.23:1:0.6-1.23:1:1.2.

6. method according to claim 2, it is characterized in that the step 3) electrospinning conditions: voltage 13-18kv, setting Flow is 1.0-2.0ml/h, and distance is 13-18cm.

7. method according to claim 2, it is characterized in that step 4) the Muffle furnace calcination condition: 2-5 DEG C of heating rate/ Then min naturally cools to room temperature in 240-260 DEG C of heat preservation 2-4h.

8. method according to claim 2, it is characterized in that tube furnace calcination condition: 2-5 DEG C of heating rate/min, in 600- 650 DEG C of heat preservation 3-6h, then naturally cool to room temperature.

9. method according to claim 2 is used it is characterized in that concentration of hydrochloric acid is that 1mol/L impregnates 6-12h in the step 5) Ethyl alcohol and deionized water are rinsed 6-8 times.

10. method according to claim 2, it is characterized in that the step 6) drying condition: being dried in vacuo 10- at 60-80 DEG C 12h。