CN107834052A - A kind of method and its material that lithium ion battery silicon cathode material is prepared using flyash solid waste - Google Patents

Abstract

The invention discloses a method for preparing a silicon negative electrode material of a lithium ion battery by using fly ash solid waste, which comprises the following steps: 1) using fly ash as a raw material for alkali fusion treatment; The material is subjected to metallothermic reduction treatment; 3) the material treated in step 2) is uniformly dispersed in the binder; 4) the material treated in step 3) is coated on the copper foil, and further vacuum-dried to obtain lithium ion Battery silicon anode material. The present invention makes full use of the characteristics of high silicon dioxide content in fly ash, and develops a high-performance and cost-effective silicon negative electrode material for lithium-ion batteries by modifying and processing fly ash, which is different from traditional secondary lithium Compared with graphite, the negative electrode material of ion battery, it obviously shows better rate performance. This can not only greatly increase the commercial value of fly ash, but also reduce the pollution of fly ash solid waste to the environment, which has great social and economic benefits.

Description

A method of preparing silicon anode materials for lithium-ion batteries from fly ash solid waste method and material

technical field

The invention belongs to the field of recovery and utilization of fly ash solid waste, and in particular relates to a method for preparing a silicon negative electrode material of a lithium ion battery by using fly ash solid waste and the material thereof.

Background technique

With the rapid development of society, the challenges of environmental pollution and energy crisis are becoming increasingly severe, and green energy has become a research hotspot in countries all over the world. As a new type of clean rechargeable power source, lithium-ion batteries have the advantages of light weight, small size, high energy density, long service life and low environmental pollution. They have shown broad application prospects in the fields of national defense, electric vehicles and electronics. At present, commercialized secondary lithium-ion batteries mainly use graphite-like carbon as the negative electrode material, which has the advantage of better cycle performance and rate performance. However, the theoretical specific capacity of the traditional graphite anode is only 372mAh g ^-1 , and its lithium intercalation potential platform is close to that of metal lithium, so fast charging or low-temperature charging is prone to "lithium precipitation" phenomenon and cause safety hazards. With the rapid development of portable electronic devices and hybrid electric vehicles, graphite-based anode materials have been difficult to meet the urgent needs of the development of lithium-ion secondary batteries. As the most potential lithium-ion battery anode material that is expected to replace commercial graphite, silicon material has a high theoretical capacity (4200mAh g ^-1 ) and a suitable voltage platform. Apps get a lot of attention.

Fly ash is a kind of industrial waste discharged from coal-fired boilers in thermal power plants, and it is one of the largest industrial wastes in the world. At present, the utilization of fly ash in our country basically stays in the primary utilization stage, that is, as admixture of cement, mixing material of concrete, road construction and filling, etc. To study and solve the comprehensive utilization of fly ash, turn waste into treasure, and turn it into high value-added products has become a significant task before us.

At present, there are few reports and patents on the use of fly ash as a silicon negative electrode material for lithium-ion batteries. At this stage, it is still mainly focused on the fine utilization of fly ash, mainly for Al ₂ O ₃ and SiO in fly ash _2. Prepare high-purity polymeric aluminum, white carbon black, zeolite molecular sieve and other products. However, the articles and related patents on the use of fly ash as a negative electrode material for lithium-ion batteries are mainly used as carbon negative electrode materials.

Contents of the invention

The object of the present invention is to provide a method and material for preparing silicon negative electrode material of lithium ion battery by using fly ash solid waste.

In order to realize the above-mentioned purpose of the invention, the present invention specifically provides the following technical solutions:

1, a kind of method utilizing fly ash solid waste to prepare lithium-ion battery silicon negative electrode material, comprises the steps:

1) Carry out alkali fusion treatment with fly ash as raw material;

2) performing metal thermal reduction treatment on the material treated in step 1);

3) uniformly dispersing the material treated in step 2) in the binder;

4) coating the material treated in step 3) on a copper foil, and further vacuum drying to obtain a silicon negative electrode material for a lithium ion battery.

Further, step 3) includes adding conductive carbon black.

Further, the alkali fusion treatment in step 1) includes the following steps: mixing the fly ash raw material and alkali in a mass ratio of 1:1 and roasting in a box-type resistance furnace, the alkali being Na ₂ CO ₃ , NaOH or KOH

Further, the temperature of the step 1) alkali melting treatment is 600°C-1200°C, and the time is 4-12h.

Further, the metallothermic reduction treatment in step 2) includes the following steps: mixing the material after the alkali melting treatment in step 1) with the metal according to a mass ratio of 1: ₁ and then placing it in a tube furnace; Under protection, the temperature is 600°C-1200°C, after roasting for 5-12 hours, the calcined material is cooled, impregnated with 2-5M hydrochloric acid for 6-18 hours, and then washed with deionized water until neutral.

Further, the metal is one or more of magnesium, aluminum, sodium, potassium or lithium.

Further, in step 3) the binder is an aqueous solution of sodium alginate

Further, the mass fraction of the binder is 20%-50%.

Further, in step 3), the added mass percentage of the material treated in step 2) is 60-90%.

2. The lithium ion battery negative electrode material prepared according to any one of the methods.

The beneficial effect of the present invention is that: the present invention makes full use of the solid waste fly ash produced by coal-fired power plants, researches and solves the rational utilization of solid waste fly ash, turns waste into wealth, and makes it be used by traditional low-value-added It has become a high-value-added silicon anode material for lithium-ion batteries. By modifying and processing fly ash, a high-performance and cost-effective silicon anode material for lithium-ion batteries has been developed, which is different from traditional secondary lithium-ion battery anode materials. Compared with graphite, it obviously exhibits better rate capability. This will not only greatly increase the commercial value of fly ash, but also reduce the pollution of fly ash solid waste to the environment, which has great social and economic benefits. In addition, the process method is simple, highly efficient and energy-saving, and easy to industrialized production, and the whole process does not need to use expensive silicon precursors or chemical reagents.

Description of drawings

Fig. 1 is the XRD collection of illustrative plates of original fly ash;

Fig. 2 is the XRD spectrogram of fly ash treated by alkali fusion and metal thermal reduction;

Fig. 3 is the cycle performance curve at 1C of the lithium-ion battery silicon anode material prepared by fly ash;

Figure 4 is the charge and discharge curves of silicon anode materials for lithium ion batteries prepared from fly ash at different rates of 0.5C, 1C, 2C and 4C.

Detailed ways

In order to further understand the present invention and realize the beneficial effects of the present invention, the technical solutions provided by the present invention will be described in detail below in conjunction with specific embodiments.

Example 1 The pretreatment of fly ash

Mix fly ash and Na ₂ CO ₃ at a mass ratio of 1:1, put them into a box-type resistance furnace, and bake them at 800°C for 2 hours, then mix them with reduced metal magnesium at a mass ratio of 1:1 and place In a tube furnace, it was baked at 650°C for 6 hours under the protection of H ₂ /Ar mixed gas. After cooling, it was impregnated with 3M hydrochloric acid solution, and then washed with deionized water until neutral. The phase structure of fly ash solid waste before and after treatment is shown in Figure 1 and Figure 2. Figure 1 is the XRD diagram of the original fly ash. It can be seen from the curve that the phases in the original fly ash are mainly quartz and mullite, indicating that there are many types of impurities in the fly ash; Figure 2 is the original fly ash Compared with the original fly ash XRD spectrum of the phase structure after alkali fusion and metal thermal reduction treatment, the peaks of the curve are less and sharper, so it can be seen that after alkali fusion and metal thermal reduction treatment, the The impurities in the fly ash are significantly reduced and the characteristic diffraction peaks of crystalline silicon are obvious, indicating that the quartz and mullite in the fly ash have been completely transformed into a single crystalline silicon after the original fly ash has been processed by alkali melting and metal thermal reduction. Mutually.

Application example Application of treated fly ash as electric negative electrode material

Add 10% conductive agent Super-p (conductive carbon black) to the fly ash material after alkali fusion and metal thermal reduction treatment, and then mix it with the binder sodium alginate according to the mass ratio of 80:10:10 to make a slurry (the binder sodium alginate is pre-dissolved in water before use, and is configured as a solution with a mass fraction of 50%), and is evenly coated on the copper foil, and then dried in a vacuum environment at 70°C for 24 hours to obtain a lithium-ion battery. Silicon negative pole piece. Lithium sheet as the counter electrode, 1mol/LLiPF ₆ EC (ethylene carbonate) + DMC (dimethyl carbonate) + EMC (ethyl methyl carbonate) (volume ratio 1:1:1) solution as the electrolyte, model Cell separators for Celgard 2400 were assembled into coin cells in an argon-filled glove box.

Figure 3 is the cycle performance curve of the lithium-ion battery silicon anode material prepared from fly ash at 1C. It can be seen from Fig. 3 that the cycle capacity and coulombic efficiency of the silicon anode material prepared after the fly ash solid waste is processed by alkali melting and metallothermic reduction, at a current density of 0.1 (1C=1000mAh g ^-1 ), The first-cycle discharge capacity of the prepared silicon anode material reaches 3995.7mAh g ^-1 ; the first coulombic efficiency is as high as 80%, and the irreversible capacity is mainly due to the formation of the solid electrolyte interface (SEI) film on the surface of the Si material; and the coulombic efficiency is the first After the second cycle, it gradually increases, and after the third cycle, the Coulombic efficiency is as high as 97%. After the first cycle, the current density was increased to 1C, and after 100 charge-discharge cycles, the discharge capacity remained at about 1000mAh g ^-1 , showing good cycle performance.

Figure 4 is the charge and discharge curves of silicon anode materials for lithium ion batteries prepared from fly ash at different rates of 0.5C, 1C, 2C and 4C. It can be seen from Figure 4 that the discharge capacity reaches 2792.5mAh g ^-1 (0.5C), 2112.0mAh g ^-1 (1C), 1571.6mAh g ^-1 (2C) and 1450.3mAh g ^-1 (4C), respectively. Exceeding 7.5, 5.7, 5.0 and 4.2 times of the theoretical capacity (372mAh g ^-1 ) of graphite as the negative electrode material of the traditional secondary lithium ion battery, it exhibits excellent rate performance.

It can be illustrated from the above examples and application examples that the present invention makes full use of the high silicon dioxide content in the fly ash by modifying and processing the fly ash, uses it as a cheap silicon source, reclaims the silicon material therein and The application of it to lithium-ion battery anode materials shows high performance and high cost performance, and it obviously shows better rate performance compared with graphite, the traditional secondary lithium-ion battery anode material.

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it can be described in terms of form and Various changes may be made in the details without departing from the scope of the invention defined by the claims.

Claims (10)

1. A kind of 1. method that lithium ion battery silicon cathode material is prepared using flyash solid waste, it is characterised in that including Following steps：

   1) alkali fusion processing is carried out by raw material of flyash；

   2) metallothermic reduction processing will be carried out through the material after step 1) processing；

   3) material after step 2) processing is uniformly dispersed in a binder；

   4) material after step 3) processing is coated on copper foil, is further dried in vacuo to obtain lithium ion battery silicium cathode material Material.
2. A kind of 2. side that lithium ion battery silicon cathode material is prepared using flyash solid waste according to claim 1 Method, it is characterised in that step 3) includes adding conductive black.
3. A kind of 3. side that lithium ion battery silicon cathode material is prepared using flyash solid waste according to claim 1 Method, it is characterised in that step 1) the alkali fusion processing comprises the following steps：By powdered coal ash and alkali in mass ratio 1：1 is mixed It is calcined after conjunction in chamber type electric resistance furnace, the alkali is Na₂CO₃, NaOH or KOH.
4. A kind of 4. side that lithium ion battery silicon cathode material is prepared using flyash solid waste according to claim 1 Method, it is characterised in that the temperature of step 1) alkali fusion processing is 600 DEG C~1200 DEG C, and the time is 4~12h.
5. A kind of 5. side that lithium ion battery silicon cathode material is prepared using flyash solid waste according to claim 1 Method, it is characterised in that step 2) the metallothermic reduction processing comprises the following steps：By the material after alkali fusion processing in step 1) Material is with metal according to mass ratio 1：It is placed in after 1 mixing in tube furnace；In H₂Under Ar mixing gas shieldeds, temperature be 600 DEG C~ 1200 DEG C, be calcined 5~12h after, by after roasting material cooling after hydrochloric acid 6~18h of impregnation through 2~5M, then spend from Son is washed to neutrality.
6. 6. a kind of prepare lithium ion battery silicon cathode material using flyash solid waste according to claim 1 or 5 is described Method, it is characterised in that the metal is the one or more of magnesium, aluminium, sodium, potassium or lithium.
7. A kind of 7. side that lithium ion battery silicon cathode material is prepared using flyash solid waste according to claim 1 Method, it is characterised in that the step 3) binding agent is the aqueous solution of sodium alginate.
8. A kind of 8. side that lithium ion battery silicon cathode material is prepared using flyash solid waste according to claim 7 Method, it is characterised in that the mass fraction of the binding agent is 20~50%.
9. A kind of 9. side that lithium ion battery silicon cathode material is prepared using flyash solid waste according to claim 1 Method, it is characterised in that the material addition weight/mass percentage composition in step 3) after step 2) processing is 60~90%.
10. 10. according to lithium ion battery negative material made from the preparation method of any one of claim 1 to 9.