A dual-ion doped hard carbon composite material, a preparation method and application thereof

Abstract

The application relates to the field of secondary battery material preparation, in particular to a dual-ion doped hard carbon composite material and a preparation method and application thereof, the preparation method comprises the following steps: combining a hard carbon precursor with a mixed solution of an organic sodium salt and an organic cerium salt in an alkaline solution, and obtaining the dual-ion doped hard carbon composite material after carbonization. The obtained hard carbon composite material utilizes the doping of sodium ions and cerium ions to improve the transmission rate of sodium ions in the charging and discharging process and improve the rate, and the cerium doping improves the electronic conductivity of the material and the cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of secondary battery material preparation, in particular to a dual-ion doped hard carbon composite material and a preparation method and application thereof. BACKGROUND

[0002] Hard carbon refers to carbon that is difficult to graphitize, has a highly disordered stable structure and a large interlayer spacing, can allow lithium ions / sodium ions to diffuse quickly, has good compatibility with electrolyte, has a high diffusion coefficient and a wide lithium intercalation potential interval, is conducive to the rapid intercalation of ions, prevents the precipitation of dendritic lithium, and is suitable for large-current charging and discharging. However, due to the turbostratic structure of hard carbon itself, the poor electronic conductivity of the material affects its rate performance, and the formation of SEI film during the charging and discharging process consumes lithium ions / sodium ions, reducing the initial efficiency. One of the measures to improve the electronic conductivity and initial efficiency of hard carbon material is electronic or ionic doping, such as doping nitrogen, boron and their metal elements to improve the electronic conductivity of the material, or doping ionic compounds to improve the ionic conductivity of the material and reduce the irreversible capacity to improve the initial efficiency. Sodium ion compounds have a fast sodium ion transmission rate during charging and discharging, which can make up for the loss of sodium ions consumed by the formation of SEI film during the charging and discharging process of hard carbon, thereby improving the initial efficiency, but sodium ion doping will reduce the specific capacity of the material; cerium dioxide belongs to the cubic system, has high thermal stability, good chemical stability, a large interlayer spacing, and high specific capacity, and is widely used in lithium ion / sodium ion batteries to provide specific capacity and improve the cycle performance by virtue of its structural stability.

[0003] Patent application number CN202211042344.X discloses a hard carbon material and a preparation method and application thereof. The hard carbon material is doped with heteroatoms, the heteroatoms include N atoms and M atoms, the M atoms include a combination of at least two of As, Se, Sb or Te, the obtained material can increase the interlayer spacing of the hard carbon material and introduce defect sites through the synergistic effect between the heteroatoms, thereby causing a large distortion of the structure of the hard carbon material, increasing the intercalation capacity and adsorption capacity of sodium ions, and enabling the hard carbon material to have high specific capacity and high rate performance, but doping only improves the electronic conductivity of the material, and does not improve the ionic conductivity and initial efficiency of the material.

[0004] Therefore, it is of great application prospect to develop a material that can balance electronic conductivity, ionic conductivity and initial efficiency. SUMMARY

[0005] The first aspect of the present application provides a preparation method of a dual-ion doped hard carbon composite material, the preparation method comprising: combining a hard carbon precursor with a mixed solution of organic sodium salt and organic cerium salt in an alkaline solution, and obtaining a dual-ion doped hard carbon composite material after carbonization.

[0006] Further, the preparation method comprises: combining the hard carbon precursor with a mixed solution of organic sodium salt and organic cerium salt in an alkaline solution, reacting at a temperature of 100-200℃ for 1-6h, filtering, vacuum drying, carbonizing at 700-1000℃ for 1-6h, and crushing to obtain a hard carbon composite material doped with two ions.

[0007] In some embodiments, the mass ratio of the hard carbon precursor, the mixed solution, and the alkaline solution is 100:100:(100-500).

[0008] In some embodiments, the mixed solution comprises organic sodium salt, organic cerium salt, and propionic acid, and the mass ratio is (1-10):(1-10):100.

[0009] In some embodiments, the organic sodium salt comprises at least one of sodium acetate, sodium acetate, sodium valproate, sodium hypochlorite phosphate, sodium pyrosuccinate, sodium p-hydroxybenzoate, and sodium p-toluenesulfonate, and / or the organic cerium salt comprises at least one of cerium oxalate, cerium neodecanoate, cerium acetate, and cerium 2-ethylhexanoate.

[0010] The organic sodium salt contains carbon, hydrogen, oxygen, and sodium ions, and after carbonization, sodium-doped porous carbon is formed, the porous structure can store sodium ions to improve the specific capacity, and doping sodium reduces the defects of the material and improves the transmission rate of sodium ions during charging and discharging; and the organic cerium salt is carbonized to form cerium-doped porous carbon, which relies on the high specific capacity of cerium to improve the specific capacity of the material and the adsorption of sodium ions by the porous structure to also improve the specific capacity of the material. If the organic sodium salt and the organic cerium salt are too high, the hard carbon composite material will expand and the cycle performance will be poor, and if they are too low, the specific capacity of the material will be low and the rate performance will be poor.

[0011] Further, the alkaline solution is not specially limited and can be selected from the commonly used types in the art, such as at least one of dimethylamine, N,N-diethylethylenediamine, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, tetraethylammonium chloride, and tetramethylammonium chloride.

[0012] In some embodiments, the preparation method of the hard carbon precursor comprises: uniformly mixing oxidized pitch with an imidazole crosslinking agent, and obtaining the hard carbon precursor after carbonization.

[0013] In some embodiments, the preparation method of the oxidized pitch comprises: uniformly mixing pitch with phosphorus pentoxide, and oxidizing at a temperature to obtain the oxidized pitch.

[0014] Further, the preparation method of the hard carbon precursor comprises: uniformly mixing pitch with phosphorus pentoxide, and oxidizing at a temperature of 250-350℃ at a temperature increasing rate of 1-10℃ / min for 1-6h in an air atmosphere,

[0015] The oxidized pitch is mixed with the imidazole crosslinking agent uniformly, and is carbonized at 1200-1500 DEG C under an inert atmosphere for 1-6 h, and a hard carbon precursor is obtained after carbonization.

[0016] In some embodiments, the mass ratio of the pitch, the phosphorus pentoxide, and the imidazole crosslinking agent is 100:(1-5):(10-30).

[0017] In some embodiments, the imidazole crosslinking agent comprises at least one of 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 2-(thiazol-4-yl)benzimidazole, 2-undecylimidazole, N-(trimethylsilyl)imidazole, 2-heptadecylimidazole, 2-methyl-4-ethylimidazole, and 4-formylimidazole.

[0018] The imidazole crosslinking agent is used in the present application to prevent the formation of a lamellar structure of carbon material during carbonization of the pitch, to facilitate the formation of a turbostratic structure and nano / micropores, and to facilitate sodium storage.

[0019] A second aspect of the present application provides a dual-ion-doped hard carbon composite material obtained by the above preparation method.

[0020] A third aspect of the present application provides the use of the above dual-ion-doped hard carbon composite material in the preparation of a secondary battery negative electrode material.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] (1) The hard carbon composite material obtained by the present application improves the transmission rate of sodium ions in the charging and discharging process, improves the rate, and improves the electronic conductivity and cycle performance of the material by doping sodium ions and cerium ions.

[0023] (2) The present application generates a stable compound by chemical reaction of the hydroxyl and carboxyl groups on the surface of the oxidized pitch and the amino groups on the surface of the organic sodium salt / organic cerium salt under alkaline conditions, thereby improving the cycle performance of the material.

[0024] (3) The present application improves the specific capacity of the hard carbon by using the specific capacity of cerium dioxide formed by carbonization of the organic cerium salt. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 SEM image of the dual-ion-doped hard carbon composite material prepared in Example 1. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0027] Embodiment 1

[0028] The embodiment provides a dual-ion doped hard carbon composite material, and a preparation method thereof includes the following steps.

[0029] S1. 100 g of pitch is uniformly mixed with 3 g of phosphorus pentoxide, oxidized at an air atmosphere at a temperature increasing rate of 5 ℃ / min to 300 ℃ for 3 h to obtain oxidized pitch, and then uniformly mixed with 20 g of 1-benzyl-2-methylimidazole, and carbonized at an argon inert atmosphere to 1300 ℃ for 3 h to obtain a hard carbon precursor;

[0030] S2. 5 g of sodium acetate and 5 g of cerous oxalate are dissolved in 100 g of propionic acid to obtain a mixed solution;

[0031] S3. 100 g of the hard carbon precursor is added to 100 g of the mixed solution and uniformly dispersed, and then 300 g of dimethylamine solution is added, uniformly mixed, and then transferred to a high-pressure reaction kettle, reacted at a temperature of 150 ℃ for 3 h, filtered, vacuum dried at 80 ℃ for 24 h, carbonized at 850 ℃ for 3 h, and crushed to obtain the dual-ion doped hard carbon composite material.

[0032] Embodiment 2

[0033] The embodiment provides a dual-ion doped hard carbon composite material, and a preparation method thereof includes the following steps.

[0034] S1. 100 g of pitch is uniformly mixed with 1 g of phosphorus pentoxide, oxidized at an air atmosphere at a temperature increasing rate of 1 ℃ / min to 250 ℃ for 6 h to obtain oxidized pitch, and then uniformly mixed with 10 g of 1-cyanoethyl-2-methylimidazole, and carbonized at an argon inert atmosphere to 1200 ℃ for 6 h to obtain a hard carbon precursor;

[0035] S2. 1 g of sodium acetate and 1 g of cerous acetate are dissolved in 100 g of propionic acid to obtain a mixed solution;

[0036] S3. 100 g of the hard carbon precursor is added to 100 g of the mixed solution and uniformly dispersed, and then 100 g of N,N-diethylethylenediamine solution is added, uniformly mixed, and then transferred to a high-pressure reaction kettle, reacted at a temperature of 100 ℃ for 6 h, filtered, vacuum dried at 80 ℃ for 24 h, carbonized at 700 ℃ for 6 h, and crushed to obtain the dual-ion doped hard carbon composite material.

[0037] Example 3

[0038] The embodiment provides a dual-ion doped hard carbon composite material, and a preparation method thereof, which comprises the following steps:

[0039] S1. 100 g of pitch is uniformly mixed with 5 g of phosphorus pentoxide, and is subjected to oxidation treatment at 350 DEG C for 1 h at an air atmosphere and at a temperature increasing rate of 10 DEG C / min, to obtain oxidized pitch, which is then uniformly mixed with 30 g of 2-(thiazol-4-yl) benzimidazole, and is subjected to carbonization treatment at 1500 DEG C for 1 h under an argon inert atmosphere, to obtain a hard carbon precursor;

[0040] S2. 10 g of sodium pyrogallate and 10 g of cerium neodecanoate are dissolved in 100 g of propionic acid to obtain a mixed solution;

[0041] S3. 100 g of the hard carbon precursor is added into 100 g of the mixed solution and is uniformly dispersed, and then 500 g of a benzyltrimethylammonium chloride solution is added, and after being uniformly mixed, the mixture is transferred into a high-pressure reaction kettle, and is reacted at 200 DEG C for 1 h, and is filtered, vacuum dried at 80 DEG C for 24 h, carbonized at 1000 DEG C for 1 h, and crushed, to obtain the dual-ion doped hard carbon composite material.

[0042] Comparative Example 1

[0043] The comparative example provides a dual-ion doped hard carbon composite material, and the specific implementation manner is the same as that in Example 3, except that in step S3, 100 g of the hard carbon precursor is transferred into a high-pressure reaction kettle, and is reacted at 150 DEG C for 3 h, and is filtered, vacuum dried at 80 DEG C for 24 h, carbonized at 850 DEG C for 3 h, and crushed, to obtain the dual-ion doped hard carbon composite material.

[0044] Comparative Example 2

[0045] The comparative example provides a dual-ion doped hard carbon composite material, and the specific implementation manner is the same as that in Example 3, except that in step S1, 100 g of pitch is subjected to carbonization treatment at 1300 DEG C for 3 h under an argon inert atmosphere, to obtain the hard carbon precursor.

[0046] Comparative Example 3

[0047] The comparative example provides a dual-ion doped hard carbon composite material, and the specific implementation manner is the same as that in Example 3, except that 15 g of sodium acetate and 15 g of cerous oxalate are used.

[0048] Comparative Example 4

[0049] The comparative example provides a dual-ion doped hard carbon composite material, and the specific implementation manner is the same as that in Example 3, except that 5 g of sodium acetate and 0 g of cerous oxalate are used.

[0050] Performance test

[0051] (1) SEM test

[0052] The double-ion doped hard carbon composite material prepared in Example 1 was subjected to SEM test, and the test results are shown in FIG. 1. Figure 1 As can be seen from FIG. 1, the hard carbon composite material prepared in Example 1 is in a granular form, and the particle size D50 thereof is between (1-5) μm. Figure 1

[0053] (2) Physicochemical properties and button cell test

[0054] Physicochemical property test:

[0055] The double-ion doped hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to interlayer spacing (D002), specific surface area, tap density, particle size D50, and powder conductivity determination. The test method was tested according to the method of national standard GBT-24533-2019 "Lithium ion battery graphite negative material". The test results are shown in Table 1.

[0056] Button cell test:

[0057] The double-ion doped hard carbon composite materials in Examples 1-3 and Comparative Examples 1-4 were assembled into button cells as lithium ion battery negative materials. The specific preparation method of the negative material was as follows: the negative electrode sheet was prepared by mixing the hard carbon composite material, CMC, SBR, SP and H2O in a mass ratio of 94:2.5:1.5:2:150; sodium sheet was used as the counter electrode; NaPF6(solvent EC:DEC:PC:propylene glycol polyoxypropylene ether = 1:2:1:0.05, concentration 1.3 mol / L) was used as the electrolyte; and the composite film of polyethylene PE, polypropylene PP and polyethylene propylene PEP was used as the separator. The button cell was assembled in an argon-filled glove box. The electrochemical performance was tested on a Wuhan Lan Dian CT2001A battery tester, the charge and discharge voltage range was 0.00V to 2.0V, the charge and discharge rate was 0.1C, and the first discharge capacity and first efficiency of the button cell, and the rate performance (1C / 0.1C) were tested. The test results are shown in Table 1.

[0058] Table 1

[0059]

[0060] As can be seen from Table 1, the double-ion doped hard carbon composite material of the examples is superior to the comparative examples in specific capacity and first efficiency. The reason is that the doping of heteroatoms in the material improves the specific capacity of the material, and the doping of organic sodium salt in the material reduces the irreversible capacity and improves the first efficiency. At the same time, the organic sodium salt improves the number of sodium ion insertion and extraction during the charge and discharge process, thereby improving the rate performance.​

[0061] (3) Soft pack battery test:

[0062] The double-ion doped hard carbon composite materials in Examples 1-3 and Comparative Examples 1-4 were prepared into negative electrode sheets by slurry mixing and coating, and 5 Ah soft pack batteries were prepared with layered oxides as positive electrodes and NaPF6 (solvent: EC: DEC: PC: propylene glycol polyoxypropylene ether = 1:2:1:0.05, concentration 1.3 mol / L) as electrolyte.

[0063] Test cycle performance: charge-discharge current 1.0C / 1.0C, voltage range 1-4.0V, cycle number 500 times.

[0064] Test rate performance: test the initial cycle DCR of the soft pack battery, and the constant current ratio under 2C charging condition.

[0065] The test results are shown in Table 2.

[0066] Table 2

[0067]

[0068]

[0069] As can be seen from Table 2, the rate and cycle performance of the negative electrode sheet in Examples 1-3 are significantly better than those of the comparative examples. The reason is that the material in the examples has a large interlayer spacing and improves the rate performance of the powder conductivity improving material; at the same time, the hydroxyl and carboxyl groups on the surface of the oxidized pitch and the amino groups on the surface of the organic sodium salt / organic cerium salt chemically react under alkaline conditions to form a stable compound, thereby improving the cycle performance of the material.

[0070] The above describes preferred embodiments of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A method for preparing a dual-ion doped hard carbon composite material, characterized in that: The preparation method comprises: combining a hard carbon precursor with a mixed solution of an organic sodium salt and an organic cerium salt in an alkaline solution, and carbonizing the mixture to obtain a dual-ion doped hard carbon composite material; the alkaline solution comprises at least one of dimethylamine, N,N-diethylethylenediamine, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, tetraethylammonium chloride, and tetramethylammonium chloride; The preparation method of the hard carbon precursor comprises: uniformly mixing oxidized asphalt and an imidazole cross-linking agent, and carbonizing the mixture to obtain the hard carbon precursor.

2. The preparation method according to claim 1, characterized in that The mass ratio of the hard carbon precursor, the mixed solution and the alkaline solution is 100:100:(100-500).

3. The preparation method according to claim 2, characterized in that The mixed solution comprises an organic sodium salt, an organic cerium salt and propionic acid in a mass ratio of (1-10):(1-10):

100.

4. The preparation method according to claim 1, characterized in that The preparation method of the oxidized asphalt comprises: uniformly mixing asphalt and phosphorus pentoxide, and performing oxidation treatment at elevated temperature to obtain the oxidized asphalt.

5. The preparation method according to claim 4, characterized in that The mass ratio of the asphalt, phosphorus pentoxide and imidazole cross-linking agent is 100: (1-5): (10-30).

6. The preparation method according to claim 5, characterized in that The imidazole crosslinking agent includes at least one of 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 2-(thiazol-4-yl)benzimidazole, 2-undecylimidazole, N-(trimethylsilyl)imidazole, 2-heptadecylimidazole, 2-methyl-4-ethylimidazole, and 4-formylimidazole.

7. The preparation method according to claim 1, characterized in that The organic sodium salt includes at least one of sodium acetate, sodium acetate, sodium valproate, sodium hypochlorite phosphate, sodium pyrogluconate, sodium p-hydroxybenzoate, and sodium p-toluenesulfonate, and / or the organic cerium salt includes at least one of cerium oxalate, cerium neodecanoate, cerium acetate, and cerium 2-ethylhexanoate.

8. A dual-ion doped hard carbon composite material, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the dual-ion doped hard carbon composite material according to claim 8 in preparing negative electrode materials for secondary batteries.

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