CN109004199A - A kind of preparation method of sodium-ion battery cathode biomass hard carbon material - Google Patents

Abstract

The invention discloses a kind of preparation methods of sodium-ion battery cathode biomass hard carbon material, use biomass cheap and easy to get for carbon source, are prepared into sodium-ion battery cathode hard carbon material with simple and convenient method, can be effectively reduced the cost of sodium-ion battery.Meanwhile the hard carbon material carbon-coating spacing is big, can accommodate the embedding de- of sodium ion, the sodium-ion battery of preparation has excellent chemical property, possesses good industrial prospect, is highly suitable to be applied for large-scale energy storage system.

Description

A kind of preparation method of biomass hard carbon material for sodium ion battery negative electrode

technical field

The invention relates to a preparation method of a negative electrode material of a sodium ion secondary battery, in particular to a preparation method of a biomass hard carbon material for a negative electrode of a sodium ion battery.

Background technique

Due to the advantages of high energy density, long service life, high rated voltage, good rate performance, low self-discharge, and environmental protection, lithium-ion secondary batteries have been widely used in mobile devices and electric vehicles in recent years. However, lithium reserves on Earth are limited and unevenly distributed. Half of the world's lithium ore resources are distributed in the Americas, and my country's lithium ore resources are not rich. With the development of lithium-ion batteries, it will inevitably cause the price of lithium mines to rise, and it will also deplete lithium mines, which is not conducive to the requirements of sustainable development. Therefore, there may be some problems in applying lithium-ion batteries to large-scale electrochemical energy storage systems. question.

As an element in the same family as lithium, sodium has similar physical and chemical properties with lithium, so sodium-ion batteries have attracted more and more attention. Sodium, as the sixth most abundant element in the earth's crust, is much more abundant than lithium on the earth, and its price is also lower. If sodium-ion batteries are used in large-scale electrochemical energy storage systems, the cost can be effectively reduced. However, in order to meet the requirements of large-scale energy storage devices, it is necessary to develop Na-ion battery materials with high energy density and sustainability.

Since the radius of sodium ions is larger than that of lithium ions, as the most commercially successful graphite material in lithium ion batteries, the sodium storage capacity shown in sodium ion batteries is not high. Hard carbon materials are considered to be the most promising negative electrode materials for commercialized sodium-ion batteries because they have a larger carbon layer spacing than graphite and can accommodate larger sodium ion deintercalation. Among them, biomass hard carbon materials have also received widespread attention due to their wide range of sources, green and pollution-free. At present, there are reports of using peanut shells, straw and weeds as carbon sources to prepare biomass hard carbon, but the capacity of prepared hard carbon materials is generally not high, which is difficult to meet the requirements of commercialization of sodium-ion batteries.

Therefore, it is urgent to develop a biomass hard carbon material with simple preparation method, low cost and high sodium storage capacity.

Contents of the invention

The primary purpose of the present invention is to provide a method for preparing the biomass hard carbon material for the negative electrode of the sodium ion battery with simple operation. The hard carbon material prepared by the invention has a large specific surface area, rich micropores, simple preparation process and excellent electrochemical performance, and is an excellent negative electrode material for a sodium ion battery.

To achieve the above object, the present invention adopts the following technical solutions:

(1) The biomass material is washed with deionized water and dried in a vacuum oven;

(2) Under a protective gas atmosphere, the material obtained in step (1) is carbonized at a high temperature in a high-temperature furnace; the temperature is 800-1400° C., the carbonization time is 2-5 hours, and the heating rate is 1-10° C./min;

(3) Grind the material obtained in step (2) into a powder, stir in an acid or alkali solution with a concentration of 0.5-2M for 6-12 hours, then wash with deionized water until neutral, and dry in a vacuum oven Vacuum drying to obtain the biomass hard carbon material for the negative electrode of the sodium ion battery.

Further, the biomass material used in step (1) is lotus plants, including lotus pods, lotus seeds, lotus leaves, lotus roots and other parts of lotus and yellow lotus.

Further, the vacuum drying temperature in step (1) is 60-120°C, and the time is 8-24 hours.

Further, the protective gas in step (2) is argon or nitrogen, and the flow rate of the protective gas is 100-300 sccm.

Preferably, the high-temperature carbonization in step (2) is divided into two-stage heat treatment, the heat treatment temperature of the first stage is 800°C to 1000°C, the heating rate is 5-10°C/min, and the constant temperature heat treatment time is 1-2 hours ; The heat treatment temperature of the second stage is 1200° C. to 1400° C., the heating rate is 1-2° C./min, and the constant temperature heat treatment time is 1-2 hours. During the first stage of heat treatment, the biomass undergoes pyrolysis and quickly releases a large number of organic molecules, which is conducive to the formation of rich pore structures; during the second stage of heat treatment, the biomass undergoes slow graphitization and crystallization, which improves the structural strength and conductivity.

Further, in step (3), it is preferable to use 1.0 mol/L hydrochloric acid to treat the obtained hard carbon powder material, thereby improving the cycle performance and rate performance of the material.

Further, the vacuum drying temperature in step (3) is 60-120°C, and the time is 8-24 hours.

According to another aspect of the present invention, a sodium-ion battery is provided, including the negative electrode prepared by the hard carbon negative electrode material prepared according to the above preparation method and the electrolyte, wherein the electrolyte contains NaClO ₄ , NaPF ₆ , NaTFSI and NaBF ₄ and a non-aqueous solvent selected from ethylene carbonate, diethyl carbonate, propylene carbonate, dimethyl carbonate, diglyme and ethylene glycol dimethyl ether.

According to the sodium ion battery of the present invention, the electrolytic solution is preferably ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1M _NaClO , wherein both ethylene carbonate (EC) and diethyl carbonate (DEC) have volume The ratio is 1:1.

According to the sodium-ion battery of the present invention, wherein the negative electrode is uniformly ground with the above-mentioned hard carbon negative electrode material, acetylene black and binding agent (such as polyvinylidene fluoride (PVDF)) with a mass ratio of 8:1:1 and solvent ( For example, nitrogen methyl pyrrolidone (NMP)) is mixed to prepare negative electrode slurry, which is coated on copper foil current collector.

Compared with prior art, the present invention has following advantage and technical effect:

The biomass hard carbon material prepared by the invention uses lotus pods as carbon sources. Lotus pods are common biomass in life, they are often discarded in large quantities, so using lotus pods as a carbon source can effectively save resources and avoid waste. Biomass hard carbon materials used as anode materials for sodium-ion batteries can effectively reduce the cost of batteries. The hard carbon material prepared by the invention has larger carbon layer spacing, larger specific surface area and more micropores, is beneficial to the deintercalation and adsorption of sodium ions, has higher capacity, and has good industrialization prospects.

Description of drawings

Fig. 1 is an SEM image of a biomass hard carbon material prepared in Example 1 of the present invention.

Fig. 2 is an XRD pattern of biomass hard carbon materials prepared in Examples 1-3 of the present invention.

Fig. 3 is a carbon dioxide adsorption-desorption curve graph of biomass hard carbon materials prepared in Examples 1-3 of the present invention.

Fig. 4 is a pore size distribution diagram of biomass hard carbon materials prepared in Examples 1-3 of the present invention.

Fig. 5 is a graph of cycle performance at a current density of 50mA/g of a battery made of a biomass hard carbon material prepared in Examples 1-3 of the present invention.

Detailed ways

In order to better understand the present invention, the present invention will be further described below through examples, which are only used to explain the present invention, and do not constitute a limitation to the present invention.

Example 1

A preparation method of biomass hard carbon material for sodium ion battery negative electrode, comprising the following steps:

1) Wash the lotus pods with deionized water and dry them in a vacuum oven at 80°C for 24 hours;

2) Under the argon atmosphere with a flow rate of 200 sccm, heat the material obtained in step 1) to 1000 °C at a rate of 5 °C/min in a tube furnace, keep it for 1 hour, and then increase the temperature at a rate of 2 °C/min to 1200°C, and keep warm for 1h;

3) Grind the material obtained in step 2) into powder, stir in 1M hydrochloric acid solution for 12 hours, then wash with deionized water until neutral, and vacuum dry in a vacuum oven at 80°C for 12 hours to obtain sodium ions Biomass hard carbon material for battery negative electrode, marked as LS1200H.

Figure 1 is the SEM image of the biomass hard carbon material prepared in this example. It can be seen that there are many micron-sized holes in the material, which is conducive to the infiltration of electrolyte and the shuttling of sodium ions.

Fig. 2 has shown the XRD figure of the biomass hard carbon material prepared in the present embodiment, can calculate carbon interlayer distance by Bragg equation as The carbon layer spacing is much larger than that of graphite, which can effectively accommodate the deintercalation of sodium ions.

Example 2

A preparation method of biomass hard carbon material for sodium ion battery negative electrode, comprising the following steps:

1) Wash the lotus pods with deionized water and dry them in a vacuum oven at 80°C for 24 hours;

2) Under an argon atmosphere with a flow rate of 200 sccm, heat the material obtained in step 1) to 1000°C at a rate of 5°C/min in a tube furnace, and keep it warm for 2h;

3) Grind the material obtained in step 2) into powder, stir in 1M hydrochloric acid solution for 12 hours, then wash with deionized water until neutral, and vacuum dry in a vacuum oven at 80°C for 12 hours to obtain sodium ions Biomass hard carbon material for battery negative electrode, marked as LS1000H.

Example 3

A preparation method of biomass hard carbon material for sodium ion battery negative electrode, comprising the following steps:

1) Wash the lotus pods with deionized water and dry them in a vacuum oven at 80°C for 24 hours;

2) Under an argon atmosphere with a flow rate of 200 sccm, heat the material obtained in step 1) to 1400°C at a rate of 5°C/min in a tube furnace, and keep it warm for 2h;

3) Grind the material obtained in step 2) into powder, stir in 1M hydrochloric acid solution for 12 hours, then wash with deionized water until neutral, and vacuum dry in a vacuum oven at 80°C for 12 hours to obtain sodium ions The biomass hard carbon material used for the negative electrode of the battery is marked as LS1400H.

Example 4

A preparation method of biomass hard carbon material for sodium ion battery negative electrode, comprising the following steps:

1) Wash the lotus pods with deionized water and dry them in a vacuum oven at 80°C for 24 hours;

2) Under a nitrogen atmosphere with a flow rate of 200 sccm, heat the material obtained in step 1) to 1200°C at a rate of 5°C/min in a tube furnace, and keep it warm for 2h;

3) Grind the material obtained in step 2) into powder, stir in 1M sulfuric acid solution for 12h, then wash with deionized water until neutral, and vacuum dry in a vacuum oven at 80°C for 12h to obtain sodium ion Biomass hard carbon material for battery negative electrode.

Example 5

A preparation method of biomass hard carbon material for sodium ion battery negative electrode, comprising the following steps:

1) Wash the lotus pods with deionized water and dry them in a vacuum oven at 80°C for 24 hours;

2) Under a nitrogen atmosphere with a flow rate of 200 sccm, heat the material obtained in step 1) to 1200°C at a rate of 2°C/min in a tube furnace, and keep it warm for 2 hours;

3) Grind the material obtained in step 2) into powder, stir in 1M hydrochloric acid solution for 12 hours, then wash with deionized water until neutral, and vacuum dry in a vacuum oven at 80°C for 12 hours to obtain sodium ions Biomass hard carbon material for battery negative electrode.

Example 6

A preparation method of biomass hard carbon material for sodium ion battery negative electrode, comprising the following steps:

1) Wash the lotus pods with deionized water and dry them in a vacuum oven at 80°C for 24 hours;

2) Under a nitrogen atmosphere with a flow rate of 200 sccm, heat the material obtained in step 1) to 1200°C at a rate of 5°C/min in a tube furnace, and keep it warm for 5h;

3) Grind the material obtained in step 2) into powder, stir in 1M hydrochloric acid solution for 12 hours, then wash with deionized water until neutral, and vacuum dry in a vacuum oven at 80°C for 12 hours to obtain sodium ions Biomass hard carbon material for battery negative electrode.

Example 7

A preparation method of biomass hard carbon material for sodium ion battery negative electrode, comprising the following steps:

1) Wash the lotus pods with deionized water and dry them in a vacuum oven at 80°C for 24 hours;

2) Under a nitrogen atmosphere with a flow rate of 200 sccm, heat the material obtained in step 1) to 1200°C at a rate of 2°C/min in a tube furnace, and keep it warm for 2 hours;

3) Grind the material obtained in step 2) into powder, stir in 1M potassium hydroxide solution for 12h, then wash with deionized water until neutral, and vacuum dry in a vacuum oven at 80°C for 12h to obtain Biomass hard carbon material for sodium ion battery negative electrode.

Example 8

A preparation method of biomass hard carbon material for sodium ion battery negative electrode, comprising the following steps:

1) Wash the lotus seeds with deionized water and dry them in a vacuum oven at 80°C for 24 hours;

2) Under an argon atmosphere with a flow rate of 200 sccm, heat the material obtained in step 1) to 1200°C at a rate of 5°C/min in a tube furnace, and keep it warm for 2h;

3) Grind the material obtained in step 2) into powder, stir in 1M hydrochloric acid solution for 12 hours, then wash with deionized water until neutral, and vacuum dry in a vacuum oven at 80°C for 12 hours to obtain sodium ions Biomass hard carbon material for battery negative electrode.

Fig. 2 is the XRD diagram of the biomass hard carbon material prepared in Examples 1-3 of the present invention, and the distance between carbon layers can be calculated by the Bragg equation. Figures 3-4 are carbon dioxide adsorption and desorption curves and pore size distribution diagrams of biomass hard carbon materials, respectively. The specific surface area and pore volume of the material are calculated by the BET equation. The calculation results are shown in Table 1. It can be seen that the material has a large specific surface area and abundant micropores, which is conducive to the adsorption of sodium ions and enhances the electrochemical performance of the material.

Table 1

Sodium-ion battery assembly and electrochemical performance testing

(1) The hard carbon powder material (LS1200H, LS1000H, LS1400H), acetylene black, and binder polyvinylidene fluoride (PVDF) obtained in Examples 1-3 were respectively mixed with a mass ratio of 8:1 by the smear method: The ratio of 1 is uniformly mixed with the solvent nitrogen methylpyrrolidone (NMP), and uniformly ground for 1 hour to prepare the negative electrode slurry, which is coated on the copper foil current collector and dried in a vacuum drying oven at 80°C for 12 hours ; After rolling and cutting, the hard carbon negative electrode sheet is obtained.

(2) Select the uniform and complete pole piece that has been partially cut, weigh it with a precision balance, and calculate the quality of the active material ((m total-m copper)*0.8); use the sodium sheet as the counter electrode and reference electrode, In the glove box under the atmospheric atmosphere, according to the correct operation steps, assemble the CR2032 button battery together with the positive electrode shell, negative electrode shell, glass fiber diaphragm, sodium sheet (diameter 12mm*thickness 1mm), and electrolyte. The electrolyte used was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1:1) dissolved with 1M NaClO ₄ , and the assembled battery was sealed using a button battery sealer. Seal it, take it out from the glove box, and let it stand at room temperature for 24 hours.

Electrochemical performance tests were carried out on the prepared sodium-ion batteries respectively. The instrument used in the test was a LAND CT2001A tester (Wuhan Landian Electronics Co., Ltd.). The test cycle was set to 200 weeks, specifically: in the voltage range of 0.01-2.5V and a current density of 50mA/g, the battery was charged and discharged for 200 cycles; the charge specific capacity (mAh/g) after activation and the charge specific capacity (mAh/g) after 200 cycles of charge and discharge were detected, and the charge and discharge cycle was calculated. The capacity retention rate of 200 cycles of discharge (= charge specific capacity after 200 cycles of charge and discharge ÷ charge specific capacity after activation completed × 100%).

Figure 5 is a graph of the cycle performance of the battery made of the biomass hard carbon material prepared in Example 1-3 at a current density of 50mA/g. It can be seen that the LS1200H material has a reversible capacity of 328.8mAh/g and is cycled for 200 cycles After that, the capacity of 295mAh/g is still maintained, reflecting good cycle performance.

Claims (8)

1. a preparation method of biomass hard carbon material for sodium ion battery negative pole, is characterized in that, comprises the following steps: (1) The biomass material is washed with deionized water and dried in a vacuum oven; (2) Under a protective gas atmosphere, the material obtained in step (1) is carbonized at a high temperature in a high-temperature furnace; the temperature is 800-1400° C., the carbonization time is 2-5 hours, and the heating rate is 1-10° C./min; (3) Grind the material obtained in step (2) into powder, stir in an acid or alkali solution with a concentration of 0.5-2M for 6-12 hours, then wash with deionized water until neutral, and dry in a vacuum oven Vacuum drying to obtain the biomass hard carbon material for the negative electrode of the sodium ion battery. 2. the preparation method of a kind of sodium ion battery negative pole biomass hard carbon material according to claim 1, is characterized in that, the biomass material used in step (1) is lotus family plant, comprises lotus and American yellow lotus Lotus pods, lotus seeds, lotus leaves, lotus roots and other parts. 3. The method for preparing a biomass hard carbon material for a negative electrode of a sodium ion battery according to claim 1, wherein the vacuum drying temperature in step (1) is 60-120° C., and the time is 8-24 hours. 4. the preparation method of a kind of sodium ion battery negative pole according to claim 1 uses biomass hard carbon material, it is characterized in that, the shielding gas in step (2) is argon or nitrogen, and shielding gas velocity is 100～300sccm . 5. the preparation method of a kind of sodium ion battery negative pole according to claim 1 uses biomass hard carbon material, it is characterized in that, the acid used in step (3) is one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid or Several kinds, the alkali is one or more of sodium hydroxide, potassium hydroxide and ammonia water. 6 . The method for preparing a biomass hard carbon material for a negative electrode of a sodium ion battery according to claim 1 , wherein the vacuum drying temperature in step (3) is 60 to 120° C. and the time is 8 to 24 hours. 7. A negative electrode material for a sodium ion battery, prepared by the preparation method according to any one of claims 1-6. 8. A sodium ion battery, comprising negative electrode and electrolytic solution prepared by negative electrode material according to claim 7, wherein electrolytic solution comprises sodium salt selected from NaClO ₄ , NaPF ₆ , NaTFSI and NaBF ₄ and selected from ethylene carbonate ester, diethyl carbonate, propylene carbonate, dimethyl carbonate, diglyme and ethylene glycol dimethyl ether as non-aqueous solvents.