CN110589796B - A kind of molten salt chemically synthesized carbon powder and its preparation method and application - Google Patents

Abstract

A fused salt chemical synthesis carbon powder and a preparation method and application thereof belong to the field of carbon material chemical synthesis. The preparation method of the fused salt chemical synthesis carbon powder comprises weighing dry CaC according to the proportion₂Powdered, dried CaCO₃Putting the powder and the dehydrated molten salt raw material into a crucible, putting the crucible into a closed reactor, and introducing inert gas for protection; heating the closed reactor to the reaction temperature, and preserving the temperature for 5 min-10 h to carry out carbonization reaction to obtain a carbon product; and (3) carrying out ultrasonic cleaning on the carbon product, carrying out solid-liquid separation, removing molten salt, and drying to obtain carbon powder. The carbon powder material is used as a negative electrode carbon material of a lithium ion electrode, and has the advantages of improving the battery capacity and the cycle performance. The product of the method only generates calcium oxide except carbon, does not generate other toxic and harmful substances, and has green and environment-friendly process, and simple and easy operation.

Description

A kind of molten salt chemically synthesized carbon powder and its preparation method and application

technical field

The invention belongs to the field of chemical synthesis of carbon materials, and particularly relates to a molten salt chemically synthesized carbon powder and a preparation method and application thereof.

Background technique

Carbon materials include graphite, amorphous carbon, diamond, carbon nanotubes, graphene and other forms. The preparation of corresponding carbon materials also requires different synthesis methods, such as high temperature sintering of natural graphite, high temperature cracking of organic carbon, vapor deposition, epitaxy growth, electrolysis, etc. The above methods all have certain advantages, but there are also some technical problems to be overcome. For example, high-temperature sintering of natural graphite and high-temperature pyrolysis of organic carbon generally require a high temperature above 1800 °C, which requires high heating equipment and high energy consumption; vapor deposition and epitaxial growth require sophisticated and expensive equipment and complex operations; Electrolysis is less efficient and has more side reactions. Therefore, it is of great practical significance to develop a simple, feasible, and low-cost preparation method for carbon materials.

Calcium carbide is widely used in PVC, vinyl acetate, rubber, acetylene and other chemical fields. Calcium carbide is the main component of natural calcium carbide. In addition, industrial calcium carbide is mainly formed by the high temperature reaction of coke and calcium oxide. Calcium carbonate is also an important inorganic chemical raw material and is often used in many industries such as coatings, rubber, plastics and paper making. Calcium carbonate can be obtained from natural limestone through mechanical grinding, crushing and other processes (heavy calcium carbonate); it can also be prepared by chemical methods such as calcination, separation, and precipitation (light calcium carbonate, activated calcium carbonate and nano-calcium carbonate).

Lithium-ion batteries (LIBs) have the advantages of high energy density, no memory effect, long cycle life, and environmental friendliness. They are widely used in portable machinery, electronics, automobiles, aviation and other fields. one of the secondary batteries. The negative electrode material is a major component of Li-ion batteries, and the intercalation and deintercalation reactions of Li ⁺ ions occur during the charging and discharging of the battery. Commonly used anode materials for lithium-ion batteries include carbon-based, silicon-based, tin-based, titanium-based oxides, transition metal oxides, and transition metal sulfides. Among them, the carbon-based negative electrode material represented by graphite is a typical intercalation material, which has the characteristics of good electrical conductivity, low lithium intercalation potential, and low price. It is the earliest and most widely used commercial negative electrode material. Although the theoretical specific capacity of graphite is 372mAh·g ^-1 , which is lower than that of other anode materials such as silicon (silicon is 4200mAh·g ^-1 ), it also has the advantages of small volume expansion and good stability. At present, the carbon negative electrodes of lithium-ion batteries mainly include graphite (including modified graphite, artificial graphite, etc.), amorphous carbon (including soft carbon, hard carbon, etc.), and nanocarbon (including carbon nanotubes, graphite, etc.) alkene, C ₆₀ , etc.). However, the preparation of these carbon materials generally requires complex synthesis processes and harsh conditions such as high temperature and high vacuum.

SUMMARY OF THE INVENTION

Based on the prior art, the purpose of the present invention is to provide a molten salt chemically synthesized carbon powder, a preparation method and application thereof, and the molten salt chemically synthesized carbon powder is a multi-morphological and multi-structure composite carbon powder. In the invention, calcium carbide and calcium carbonate are used as raw materials, and molten Ca-based halide molten salt is used as reaction medium, and carbonization reaction is carried out at a certain temperature and time to prepare carbon powder material. The reacted product and the molten salt mixture are removed from the melt, cooled, washed with ultrasonic water, and dried to obtain a carbon powder material. Using this carbon powder material as a negative electrode carbon material for lithium ion electrodes has the advantages of improving battery capacity and cycle performance. In addition to carbon, the product of the method only generates calcium oxide, and does not generate other toxic and harmful substances, and the process is environmentally friendly, simple and easy to implement.

A preparation method of a molten salt chemically synthesized carbon powder of the present invention comprises the following steps:

Step 1: Molten Salt Dehydration Treatment

The raw material of the molten salt is vacuum-dried, and cooled to room temperature with the furnace to obtain the dehydrated molten salt raw material; the molten salt is a calcium-based halide molten salt, and when the molten salt is a mixture, the mixing ratio is a mixed material the mixing ratio to form the eutectic salt;

Step 2: Preparation of calcium carbide and calcium carbonate

(1) Weigh the CaC ₂ , crush it under an inert atmosphere, and dry it to obtain a dry CaC ₂ powder with a particle size of 1 μm-5mm;

( ₂ ) take by weighing CaCO powder, dry, obtain dry CaCO powder _;

Step 3: Molten salt chemical synthesis of carbon powder

(1) According to the proportion, weigh the dry CaC ₂ powder, the dry CaCO ₃ powder, the dehydrated molten salt raw material, place it in a crucible, put it into a closed reactor, and pass it into an inert gas for protection; wherein, according to CaCO ₃ Complete reaction, the chemical formula of CaCO ₃ +2CaC ₂ →3CaO+5C, the amount of CaC ₂ added is 1-100wt.% in excess of the stoichiometric ratio, the mass of CaCO ₃ accounts for the mass percentage of calcium halide in the dehydrated molten salt raw material is 0.1 ~20%, preferably 5~10%;

(2) heating the closed reactor to the reaction temperature, keeping the temperature for 5min～10h to carry out carbonization reaction to obtain a carbon product; wherein, the reaction temperature is greater than the melting point of the dehydrated molten salt raw material;

Step 4: Post-processing

The carbon product is subjected to ultrasonic cleaning, solid-liquid separation, removal of molten salt, and drying to obtain carbon powder.

In the step 1, the vacuum drying process is as follows: the drying temperature is 200-400° C., and the drying time is 24-48 h.

In the described step 1, the calcium-based halide molten salt is calcium halide, a mixture of calcium halide and an alkali metal halide compound, or a mixture of calcium halide and an alkaline earth metal halide compound, or a calcium halide and an alkaline earth metal halide compound and One of a mixture of alkali metal halide compounds.

In the calcium-based halide molten salt, the calcium-based halide is preferably one or more of CaCl ₂ , CaBr ₂ and CaF ₂ , preferably CaCl ₂ .

The alkali metal halide compound is one or more of NaCl, KCl, LiCl, NaBr, KBr, LiBr, NaF, KF and LiF.

The alkaline earth metal halide compound is one or more of MgCl ₂ , MgF ₂ , CaCl ₂ , CaF ₂ , SrCl ₂ , SrF ₂ , BaCl ₂ , and BaF ₂ .

In the step 2(1), CaC ₂ is analytically pure calcium carbide or industrial calcium carbide, preferably analytically pure calcium carbide.

In the step 2(1), the crushing methods of CaC ₂ are manual crushing and mechanical grinding, preferably mechanical crushing.

In the step 2(1), the particle size of the dried CaC ₂ powder is preferably 50 μm-200 μm.

In the step 2(1), the drying temperature is 80-120°C.

In the step 2(2), the CaCO ₃ is heavy calcium carbonate, light calcium carbonate, active calcium carbonate and nano-calcium carbonate, preferably light calcium carbonate and nano-calcium carbonate.

In the step 2(2), the particle size of the CaCO ₃ powder is 0.05 μm-200 μm, preferably 0.1-20 μm.

In the step 2(2), the drying temperature is 100-300°C, preferably 120-150°C.

In the step 3(1), preferably, in a molar ratio, CaCO ₃ :CaC ₂ =(1~2):(2~4).

In the described step 3(1), the dry CaC ₂ powder, the dry CaCO ₃ powder, and the dehydrated molten salt raw material are placed in the crucible, and the following five methods are selected:

The first: mix all the raw materials evenly and place them in a crucible;

The second is to lay each raw material layer by layer and place it in the crucible; the layer-by-layer tiling is preferably from the bottom of the crucible to the top and the distribution order is dry CaC ₂ powder, dehydrated molten salt raw material and dry CaCO ₃ powder tiling method;

The third type, in which two kinds of raw materials are mixed evenly, and then spread layer by layer with another raw material;

The fourth method is to repeatedly lay some raw materials layer by layer and place them in the crucible;

The fifth method is to use at least two of the above four mixing methods to be placed in the crucible.

In the step 3(2), the temperature increase rate is 0.5-15°C/min.

In the step 3(2), the reaction temperature is higher than the melting point of the dehydrated molten salt raw material, and the reaction temperature is preferably 600°C to 1000°C.

In the step 4, in the ultrasonic cleaning, the unreacted CaC ₂ is removed by cleaning with hydrochloric acid, and then the molten salt after the reaction is removed by cleaning with water, and the ultrasonic frequency is 10-30 KHz.

The pH value of the clear water is 5-7, and the hydrochloric acid is a hydrochloric acid solution with a substance concentration of 0.5-2 mol/L.

In the step 4, the solid-liquid separation is preferably centrifugal separation, and the rotational speed of the centrifugal separation is preferably 200-1000 r/min.

A molten salt chemically synthesized carbon powder is prepared by the above-mentioned preparation method.

The molten salt chemically synthesized carbon powder prepared by the invention has an average particle size of 0.1-50 μm. With the increase of the reaction temperature, the carbon powder has at least two morphologies of flower shape, tube shape, flake shape and spherical shape. The composite structure tends towards a single structure with spherical morphology.

The application of the molten salt chemically synthesized carbon powder of the present invention is to use the molten salt chemically synthesized carbon powder as the negative electrode carbon material of the lithium ion battery, and the lithium ion battery prepared by the molten salt chemically synthesized carbon powder has a cyclic charge-discharge specific capacity greater than 400mAh g ^-1 , and The specific capacity of cycle charge and discharge is better than that of ordinary graphite material (theoretical capacity of ordinary graphite is 372mAh g ^-1 ).

A lithium ion battery negative electrode material, comprising the above-mentioned molten salt chemically synthesized carbon powder.

An electrode pole piece is prepared by using the above-mentioned negative electrode material of a lithium ion battery.

A lithium ion battery, comprising the above-mentioned electrode pole piece.

A kind of molten salt chemical synthesis carbon powder of the present invention and its preparation method and application, its principle is as follows:

离子和

以溶解态存在于熔盐中，可通过控制反应物浓度、比例和分布、熔盐组成、反应时间等方式对反应过程进行有效调控，从而控制产物结构和形貌。Calcium carbonate and calcium carbide are two kinds of inorganic substances containing carbon, and they are also commonly used chemical raw materials. Among them, the carbon element in calcium carbonate is in an oxidized state and has a positive tetravalence; the carbon element in calcium carbide is in a reduced state and has a negative univalent valence. It can be seen from thermodynamic calculations that in the range of 600-1000 °C, calcium carbonate and calcium carbide can react to generate elemental carbon and calcium oxide. The standard Gibbs free energies of this reaction are all less than -400kJ/mol. However, since both the reactants and the products are pure solids, after the contact reaction, the diffusion of elemental carbon and calcium carbide in the products will block the contact of the reactants and prevent the reaction from proceeding fully. The calcium-based halide molten salt is used as the reaction medium, which has a great solubility for the product CaO, so that the generated calcium oxide can be rapidly dissolved, and the liquid molten salt can be suspended in it with carbon element, thereby removing the reactant calcium carbide The barrier between calcium carbonate and calcium carbonate makes the reaction proceed rapidly. In addition, calcium carbonate and calcium oxide have high solubility in calcium-based halide molten salts, which can make

ions and

Existing in molten salt in a dissolved state, the reaction process can be effectively regulated by controlling the concentration, proportion and distribution of reactants, composition of molten salt, reaction time, etc., thereby controlling the structure and morphology of the product.

The present invention is a molten salt chemically synthesized carbon powder and a preparation method thereof, and the beneficial effects are as follows:

1. The method of the present invention can realize the efficient and high-quality preparation of carbon powder at a lower temperature, and the equipment is easy to operate.

2. The use of industrial raw materials calcium carbonate and calcium carbide as reaction raw materials can broaden the source of carbon materials, reduce the transition consumption of natural graphite and the complex process of high temperature cracking, and can prepare carbon powder with controllable structure and morphology The raw materials are abundant and readily available, and no toxic and harmful substances are produced during the reaction, which is beneficial to recycling.

3. The melting environment of calcium-based halide molten salt has a high solubility for calcium oxide, one of the products, so that the reaction product can be removed in time, which can provide kinetic conditions for the reaction to proceed fully.

4. Melting can endow the carbon-containing ions in the reactants in the molten salt, so as to realize the regulation of chemical reactions and products.

5. The present invention uses calcium carbide and calcium carbonate as raw materials, uses the molten salt medium environment, and uses chemical methods to prepare carbon powder materials, and can prepare high-quality carbon powder materials at lower temperatures. The reaction product is that in addition to carbon, only calcium oxide is generated, and other toxic and harmful substances are not produced, and it has the characteristics of low cost, green process, environmental friendliness, and high product quality, and the present invention utilizes calcium carbonate and calcium carbide in calcium-based molten salt. It has a certain solubility in the carbonation reaction, which changes the carbonization reaction from the solid phase to the liquid phase reaction, making the reaction easier to carry out.

Description of drawings

Fig. 1 is the XRD pattern of carbon powder body chemically synthesized by molten salt in Example 1 of the present invention;

Fig. 2 is the SEM image of molten salt chemically synthesized carbon powder in Example 1 of the present invention;

Fig. 3 is the XRD pattern of molten salt chemically synthesized carbon powder in Example 2 of the present invention;

Fig. 4 is the SEM image of the carbon powder body chemically synthesized by molten salt in Example 2 of the present invention

Fig. 5 is the flow chart of the chemical synthesis of lithium ion battery carbon negative electrode material by molten salt in the embodiment 15 of the present invention;

6 is the cycle performance of the chemically synthesized lithium-ion battery carbon negative electrode material by molten salt in Example 15 of the present invention;

7 is the rate performance of the chemically synthesized lithium-ion battery carbon negative electrode material in molten salt in Example 15 of the present invention;

Detailed ways

The present invention will be further described in detail below in conjunction with the examples.

In the embodiment of the present invention, the calcium-based halide molten salt is analytically pure, and the purity is 99%;

The alumina crucible used in the embodiment of the present invention is a commercially available product, the purity is 99%, and the diameter is 40-200 mm, and the alumina crucible used in this embodiment is 50 mm and 100 mm;

The Ar argon used in the example of the present invention is commercially available high-purity argon with a purity of 99.999%;

In the embodiment of the present invention, the molten salt used is CaCl ₂ , CaCl ₂ -NaCl, CaCl ₂ -LiCl, CaCl ₂ -LiCl-KCl molten salt system, and the working temperature of CaCl ₂ is 800±5°C-1000±5°C _; In the NaCl molten salt system, the molar ratio is CaCl ₂ : NaCl=52:48, and the working temperature is 600±5°C-1000±5°C; in the CaCl ₂ -LiCl molten salt system, the molar ratio CaCl ₂ : LiCl=36 : 64; in the CaCl ₂ -LiCl-KCl system, the molar ratio of CaCl ₂ : LiCl : KCl=35:52:13, and the working temperature is 500±5℃-950±5℃.

In the embodiment of the present invention, the mass of molten salt used is 50-1000g;

In the embodiment of the present invention, the applied ultrasonic field frequency is 10-30KHz;

In the embodiment of the present invention, the pH of the water used for ultrasonic cleaning is between 5 and 7;

In the embodiment of the present invention, the frequency of ultrasonic cleaning is 10-30KHZ;

In the embodiment of the present invention, the centrifugal separation speed is 600 r/min.

Comparative Example 1

A preparation method of molten salt chemically synthesized carbon powder, comprising the following steps:

Step 1. Preparation of calcium carbide and calcium carbonate raw materials and assembly of the reaction device

10g CaCO ₃ was weighed and dried at 300°C for 24h. 13g CaC ₂ was weighed, crushed in an inert atmosphere, and dried at 80°C.

Step 2. Carbon powder synthesis reaction

(1) Spread CaC ₂ and CaCO ₃ into a crucible with a diameter of 50mm layer by layer in the order starting from the bottom of the crucible, close the reactor, pass high-purity argon gas, and at the same time pass into the sealing flange of the closed reactor Circulating cooling water.

(2) The temperature is raised at 3°C/min, the temperature is raised to 850°C, and the temperature is maintained for 4 hours to obtain a reaction product.

Step 3. Post-processing

The cooled product was removed from the reactor, and the salt was removed by repeated ultrasonic cleaning with clean water with a pH of 7, and the ultrasonic oscillation frequency was 20kHZ. Then, use 2 mol/L hydrochloric acid to wash, and use clean water to wash off the residual acid, and obtain the product after centrifugation and drying. After the reaction, there were very few black substances in the crucible, and the yield of carbon elements was found to be less than 10% after cleaning and recovery, indicating that the reactants basically did not react.

Example 1

A preparation method of molten salt chemically synthesized carbon powder, comprising the following steps:

Step 1, molten salt dehydration treatment

Weigh 50g of CaCl ₂ molten salt, and dry it in a 300°C crucible furnace for 24 hours to obtain a dried and dehydrated molten salt;

Step 2. Preparation of calcium carbide and calcium carbonate raw materials and assembly of the reaction device

Weigh 10 g of CaCO ₃ , and dry it at 300° C. for 24 h to obtain dry molten salt. 13g CaC ₂ was weighed, crushed in an inert atmosphere, and dried at 80°C.

Step 3. Carbon powder synthesis reaction

(1) Spread CaC ₂ , CaCl ₂ and CaCO ₃ layer by layer into a crucible with a diameter of 50 mm in the order starting from the bottom of the crucible, close the reactor, pass high-purity argon gas, and at the same time to the sealing flange of the closed reactor Introduce circulating cooling water.

(2) the temperature is increased at 3°C/min, the temperature is increased to 700°C, and the temperature is maintained for 4 hours to obtain a reaction product.

Step 4. Post-processing

The cooled product was removed from the reactor, and the salt was removed by repeated ultrasonic cleaning with clean water with a pH of 7, and the ultrasonic oscillation frequency was 20kHZ. Then, use 2 mol/L hydrochloric acid to wash insolubles such as CaO, and wash off residual acid with clean water, and obtain the product after centrifugation and drying. The phase and morphology of the obtained product are shown in Figure 1 and Figure 2, respectively. The product obtained by the reaction is mainly composed of amorphous carbon, and the morphology of the product is composed of tubular, flaky and granular structures. The yield of carbon element is above 85%.

Example 2

A preparation method of molten salt chemically synthesized carbon powder, the same as Embodiment 1, the difference is:

(1) The temperature used in step 2 was 900°C.

The structure of the obtained product is a composite structure comprising amorphous carbon and graphite phases, its XRD is shown in Figure 3, and its SEM is shown in Figure 4, it can be seen from Figure 4 that its morphology is uniform spherical particles.

Example 3

A preparation method of molten salt chemically synthesized carbon powder, the same as Embodiment 1, the difference is:

(1) the molten salt used in the step 1 is CaCl ₂ -NaCl eutectic mixed molten salt, the quality is 500g, and the two kinds of molten salts before drying are evenly mixed;

( ₂ ) in step ₂ , CaCO quality is 70g, CaC quality is 91g;

(3) in step 3 (1), the diameter of corundum crucible is 100mm;

(4) in step 3 (1), the mixing mode of CaC ₂ , CaCl ₂ -NaCl and CaCO ₃ is uniform mixing;

(4) In step 3 (2), the reaction temperature is 650° C., and the reaction time is 6 h.

Example 4

A preparation method of molten salt chemically synthesized carbon powder, the same as Embodiment 1, the difference is:

(1) The molten salt used in step 1 is CaCl ₂ -LiCl eutectic mixed molten salt, and the molten salt is evenly mixed before drying;

(2) in step ₂ , CaCO quality is _2g , CaC quality is 2.6g;

(3) In step 3(1), CaC ₂ , CaCl ₂ -LiCl and CaCO ₃ are spread layer by layer from the bottom of the crucible.

(4) In step 3 (2), the reaction temperature is 750° C., and the reaction time is 4 h.

Example 5

A preparation method of molten salt chemically synthesized carbon powder, the same as Embodiment 1, the difference is:

(1) the molten salt used in step 1 is CaCl ₂ -LiCl-KCl eutectic mixed molten salt, the quality is 100g, and the molten salt is evenly mixed before drying;

(2) in step ₂ , CaCO 3.5g, CaC _4.55g ;

(3) In step 3(1), CaC ₂ , CaCl ₂ -LiCl-KCl and CaCO ₃ are uniformly mixed.

(4) In step 3 (2), the reaction temperature is 700° C., and the reaction time is 5 h.

Example 6

A preparation method of molten salt chemically synthesized carbon powder, the same as Embodiment 1, the difference is:

(1) the molten salt quality used in step 1 is 1000g;

( ₂ ) in step ₂ , CaCO is 40g, and CaC is 64g;

(3) in step 3 (1), the diameter of corundum crucible is 150mm;

(3) In step 3(1), CaC ₂ , CaCl ₂ and CaCO ₃ are uniformly mixed.

Example 7

A preparation method of molten salt chemically synthesized carbon powder, the same as Embodiment 1, the difference is:

(1) In step 3 (1), CaCO ₃ , CaCl ₂ and CaC ₂ are laid out layer by layer from the bottom of the crucible.

Example 8

A preparation method of molten salt chemically synthesized carbon powder, the same as Embodiment 1, the difference is:

(1) Starting from the bottom of the crucible in step 3 (1), add CaC ₂ (0.5 part of the total mass), CaCl ₂ (one-third part of the total mass), CaCO ₃ (0.5 part of the total mass), CaCl ₂ (one-third part of the total mass) One part total mass), CaC2 (0.5 part total mass), _{CaCl2 (} one- _third total mass) and CaCO3 (0.5 part total mass) were tiled layer by layer.

Example 9

A preparation method of molten salt chemically synthesized carbon powder, the same as in Embodiment 3, the difference is:

(1) In step 3 (1), CaCO ₃ , CaCl ₂ -NaCl and CaC ₂ are laid out layer by layer from the bottom of the crucible.

Example 10

A preparation method of molten salt chemically synthesized carbon powder, the same as in Embodiment 3, the difference is:

(1) In step 3 (1), starting from the bottom of the crucible, add CaC ₂ (0.5 part of the total mass), CaCl ₂ -NaCl (one-third part of the total mass), CaCO ₃ (0.5 part of the total mass), CaCl ₂ -NaCl (one-third total mass), CaC2 (0.5 total mass), _{CaCl2 -} NaCl (one- _third total mass), and CaCO3 (0.5 total mass) were tiled in the order.

Example 11

A preparation method of molten salt chemically synthesized carbon powder, the same as in Example 4, the difference is:

(1) In step 3 (1), CaCO ₃ , CaCl ₂ -LiCl and CaC ₂ are laid out layer by layer from the bottom of the crucible.

Example 12

A preparation method of molten salt chemically synthesized carbon powder, the same as in Example 4, the difference is:

(1) In step 3(1), starting from the bottom of the crucible, add CaC ₂ (0.5 part of the total mass), CaCl ₂ -LiCl (one third of the total mass), CaCO ₃ (0.5 part of the total mass), CaCl ₂ -LiCl (one-third total mass), CaC2 (0.5 total mass), _{CaCl2 -} LiCl (one- _third total mass), and CaCO3 (0.5 total mass) were tiled layer by layer in the order.

Example 13

A preparation method of molten salt chemically synthesized carbon powder, the same as in Embodiment 3, the difference is:

(1) In step 3 (1), CaCO ₃ , CaCl ₂ -LiCl-KCl and CaC ₂ are laid out layer by layer from the bottom of the crucible.

Example 14

A preparation method of molten salt chemically synthesized carbon powder, the same as in Embodiment 3, the difference is:

(1) In step 3(1), starting from the bottom of the crucible, add CaC ₂ (0.5 part of the total mass), CaCl ₂ -LiCl-KCl (one-third part of the total mass), CaCO ₃ (0.5 part of the total mass), CaCl ₂ - LiCl-KCl (one-third total mass), CaC2 (0.5 total mass), _{CaCl2 -} LiCl-KCl (one- _third total mass) and CaCO3 (0.5 total mass) in order Layer tiling.

Example 15

A method for preparing a lithium ion battery carbon negative electrode material in molten salt, the process flow is shown in Figure 5, including the following steps

Step 1: take the carbon powder obtained in Example 1 as the carbon material;

Step 2: Assembly and Testing of Batteries

The obtained carbon material, acetylene black and PVDF are made into a slurry in NMP medium at a mass ratio of 8:1:1 to obtain a lithium ion battery negative electrode material;

The negative electrode material of the lithium ion battery was coated on the copper foil and dried in a vacuum at 80° C. for 12 hours to obtain an electrode pole piece.

The electrode pole piece and lithium piece are used as the counter electrode, the polypropylene film is used as the separator, the electrolyte is 1MLLiPF6/(EC:DEC=1:1), the battery shell model is 2025, and the battery is charged and discharged at a current density of 0.5C. The cycle life test is carried out within the voltage range of V.

Figure 6 and Figure 7 are the cycle performance and rate performance of the carbon anode material, respectively. It can be seen that the material has good cycle and rate performance, and the capacity is significantly higher than that of ordinary graphite (the theoretical capacity of ordinary graphite is 372mAh g ^-1 ). Although the stability of the battery needs to be improved, because the materials are currently amorphous carbon, graphite and composites, and the microscopic morphology is a mixture of various particles such as fibers, spheres, and petals, this problem can be adjusted by regulating the reaction. structure and morphology to obtain materials with high cycle performance and better stability.

Example 16

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 15, except that:

(1) The molten salt used in step 1 (1) is CaCl ₂ -NaCl eutectic mixed molten salt, the quality is 200g, and CaCl ₂ and NaCl are uniformly mixed before drying;

(2) in step 1 (2), CaCO ₃ is nano-CaCO ₃ , and the quality is 14g;

( ₃ ) CaC mass is 18.2g in step 1 (3);

(4) in step 2 (1), the mixing mode of CaC ₂ , CaCl ₂ -NaCl and CaCO ₃ is uniform mixing;

(4) In step 2 (2), the reaction temperature is 650° C., and the reaction time is 6 h.

Example 17

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 15, except that:

(1) The molten salt used in step 1 (1) is CaCl ₂ -LiCl eutectic mixed molten salt, and the molten salt is uniformly mixed before drying;

(2) in step 1 ( ₂ ), light CaCO mass is 2g,

( ₃ ) CaC mass is 2.6g in step 1 (3);

(4) in step 2 (1), CaC ₂ , CaCl ₂ -LiCl and CaCO ₃ are tiled layer by layer from the bottom of the crucible;

(4) In step 2 (2), the reaction temperature is 750° C., and the reaction time is 4 h.

Example 18

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 15, except that:

(1) CaCl used in step 1 ( ₁ ) Quality is 800g;

(2) CaCO in step 1 ( ₂ ) is heavy calcium carbonate, and the quality is 160g,

(3) in step 1 ( ₃ ), CaC quality is 60g;

(4) in step 2 (1), the diameter of corundum crucible is 150mm;

(5) In step 2(1), CaC ₂ , CaCl ₂ and CaCO ₃ are uniformly mixed.

(6) In step 2 (2), the reaction temperature is 950° C., and the reaction time is 8 h.

Example 19

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 15, except that:

(1) CaCl used in step 1 ( ₁ ) Quality is 800g;

(2) CaCO in step 1 ( ₂ ) is heavy calcium carbonate, and the quality is 160g,

(3) in step 1 ( ₃ ), CaC quality is 60g;

(4) in step 2 (1), the diameter of corundum crucible is 150mm;

(5) In step 2 (1), CaCl ₂ and CaCO ₃ are uniformly mixed, and then spread layer by layer from bottom to top from the bottom of the crucible according to the CaC ₂ and the mixture.

(6) In step 2 (2), the reaction temperature is 1000° C., and the reaction time is 4 h.

Example 20

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 15, except that:

(1) In step 2(1), starting from the bottom of the crucible, add CaC ₂ (0.5 part of the total mass), CaCl ₂ (one-third part of the total mass), CaCO ₃ (0.5 part of the total mass), CaCl ₂ (one-third part of the total mass) One part total mass), CaC2 (0.5 part total mass), _{CaCl2 (} one- _third total mass) and CaCO3 (0.5 part total mass) were tiled layer by layer.

(2) In step 2 (2), the reaction temperature is 900° C., and the reaction time is 2 h.

Example 21

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 16, except that:

(1) the molten salt used in step 1 (1) is CaCl ₂ -NaCl eutectic mixed molten salt quality is 1000g;

(2) nano-CaCO ₃ in step 1 (2), the quality is 280g;

( ₃ ) CaC mass is 109.2g in step 1 (3);

(4) in step 2(1), CaC ₂ , CaCl ₂ -NaCl and CaCO ₃ are mixed in a layer-by-layer tiling manner;

(4) In step 2 (2), the reaction temperature is 800° C., and the reaction time is 10 h.

Example 22

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 16, except that:

(1) In step 2 (1), CaCl ₂ -NaCl and CaCO ₃ are uniformly mixed, and then spread layer by layer from bottom to top according to the CaC ₂ and the mixture from the bottom of the crucible.

(2) In step 2 (2), the reaction temperature is 900° C., and the reaction time is 7 h.

Example 23

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 16, except that:

(1) In step 2(1), starting from the bottom of the crucible, add CaC ₂ (0.5 part of the total mass), CaCl ₂ (one-third part of the total mass), CaCO ₃ (0.5 part of the total mass), CaCl ₂ (one-third part of the total mass) One part total mass), CaC2 (0.5 part total mass), _{CaCl2 (} one- _third total mass) and CaCO3 (0.5 part total mass) were tiled layer by layer.

(2) The reaction time in step 2 (2) is 3h.

Example 24

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 17, except that:

(1) the molten salt used in step 1 (1) is CaCl ₂ -LiCl eutectic mixed molten salt quality is 500g;

(2) the active CaCO ₃ in step 1 (2), the mass is 140g;

(3) in step 1 ( ₃ ), CaC quality is 65g;

(4) in step 2(1), CaC ₂ , CaCl ₂ -LiCl and CaCO ₃ are uniformly mixed;

(4) In step 2 (2), the reaction temperature is 850° C., and the reaction time is 8 h.

Example 25

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 17, except that:

(1) In step 2 (1), CaCl ₂ -LiCl and CaCO ₃ are uniformly mixed, and then spread layer by layer from bottom to top according to CaC ₂ and the mixture from the bottom of the crucible.

(2) The reaction time in step 2 (2) is 5h.

Example 26

A method for preparing a carbon negative electrode material for a lithium ion battery in a molten salt is the same as in Example 17, except that:

(1) In step 2(1), starting from the bottom of the crucible, add CaC ₂ (0.5 part of the total mass), CaCl ₂ -LiCl (one-third of the total mass), CaCO ₃ (0.5 part of the total mass), CaCl ₂ -LiCl (one-third total mass), CaC2 (0.5 total mass), _{CaCl2 -} LiCl (one- _third total mass), and CaCO3 (0.5 total mass) were tiled layer by layer in the order.

(2) In step 2 (2), the reaction time is 2h.

Claims (10)

1. a preparation method of molten salt chemical synthesis carbon powder, is characterized in that, comprises the following steps: Step 1: Molten Salt Dehydration Treatment The raw material of the molten salt is vacuum-dried, and cooled to room temperature with the furnace to obtain the dehydrated molten salt raw material; the molten salt is a mixture of calcium halide, calcium halide and alkali metal halide compound, or calcium halide and alkaline earth metal halide One of the mixture of calcium halide and alkaline earth metal halide compound and the mixture of alkali metal halide compound; when the molten salt is a mixture, its mixing ratio is the mixing ratio of the mixed substances to form a eutectic salt; Step 2: Preparation of calcium carbide and calcium carbonate (1) Weigh the CaC ₂ , crush it under an inert atmosphere, and dry it to obtain a dry CaC ₂ powder with a particle size of 1 μm-5mm; ( ₂ ) take by weighing CaCO powder, dry, obtain dry CaCO powder _; Step 3: Molten Salt Chemical Synthesis of Carbon Powder (1) According to the proportion, weigh the dry CaC ₂ powder, the dry CaCO ₃ powder, the dehydrated molten salt raw material, place it in a crucible, put it into a closed reactor, and pass it into an inert gas for protection; wherein, according to CaCO ₃ Complete reaction, the chemical formula of CaCO ₃ +2CaC ₂ →3CaO+5C, the amount of CaC ₂ added is 1~100 wt.% in excess of the stoichiometric ratio, and the mass of CaCO ₃ accounts for the mass percentage of calcium halide in the dehydrated molten salt raw material: 0.1~20%; (2) the airtight reactor is heated up to the reaction temperature, and the thermal insulation is carried out for 5min～10h to carry out the carbonization reaction to obtain a carbon product; wherein, the reaction temperature is greater than the melting point of the dehydrated molten salt raw material; Step 4: Post-processing The carbon product is subjected to ultrasonic cleaning, solid-liquid separation, removal of molten salt, and drying to obtain carbon powder. 2. The preparation method of chemically synthesized carbon powder in molten salt according to claim 1, characterized in that, in the molten salt, calcium halide is one or more of CaCl ₂ , CaBr ₂ , CaF ₂ ; Described alkali metal halide compound is one or more in NaCl, KCl, LiCl, NaBr, KBr, LiBr, NaF, KF, LiF; The alkaline earth metal halide compound is one or more of MgCl ₂ , MgF _{2 ,} CaCl ₂ , CaF ₂ , SrCl ₂ , SrF ₂ , BaCl ₂ , and BaF ₂ . 3. the preparation method of molten salt chemical synthesis carbon powder body according to claim 1, is characterized in that, in described step 2 (1), CaC ₂ is analytically pure calcium carbide or industrial calcium carbide; drying temperature is 80- 120°C. 4. the preparation method of molten salt chemical synthesis carbon powder body according to claim 1, is characterized in that, in described step 2 (2), described CaCO ₃ is heavy calcium carbonate, light calcium carbonate, Activated calcium carbonate and nano-calcium carbonate; the particle size of the CaCO ₃ powder is 0.05 μm-200 μm; the drying temperature is 100-300° C. 5 . The method for preparing carbon powder by molten salt chemical synthesis according to claim 1 , wherein, in the step 3 (2), the reaction temperature is 600° C.˜1000° C. 6 . 6. A molten salt chemically synthesized carbon powder, characterized in that, it is obtained by the preparation method described in any one of claims 1 to 5. 7. The molten salt chemically synthesized carbon powder according to claim 6, wherein the prepared molten salt chemically synthesized carbon powder has an average particle size of 0.1 to 50 μm. The chemically synthesized carbon powder tends to have a single structure with a spherical shape from a composite structure with at least two morphologies among flower-like, tubular, flake-like and spherical. 8 . A negative electrode material for lithium ion batteries, characterized in that the negative electrode material for lithium ion batteries comprises the chemically synthesized carbon powder of molten salt according to claim 6 . 9 . An electrode pole piece, characterized in that, it is prepared by using the negative electrode material of a lithium ion battery according to claim 8 . 10 . A lithium ion battery, characterized in that the lithium ion battery comprises the electrode plate of claim 9 , and the prepared lithium ion battery has a specific capacity of cyclic charge and discharge greater than 400 mAh g ⁻¹ .

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