Zirconium lithium chloride and aluminum lithium chloride double-coated graphite composite material and preparation method thereof

Abstract

The application discloses a zirconium lithium chloride and aluminum lithium chloride double-coated graphite composite material and a preparation method thereof. The preparation process comprises the following steps: dissolving an organic lithium salt in an organic solvent, adding zirconium aluminum hydroxide chloride and uniformly dispersing, adding graphite and uniformly dispersing through ultrasonic, to obtain solution A; meanwhile, an organic alkali solution B is prepared; then, the solution B is added dropwise into the solution A, a hydrothermal reaction is carried out at a temperature of (100-200) DEG C for (1-6) h, filter residues are filtered out, the filter residues are vacuum dried, then the filter residues are soaked in a resin solution, and then the filter residues are filtered and vacuum dried, and then the filter residues are transferred into a tube furnace and carbonized at a temperature of (700-1200) DEG C for (1-6) h, to obtain the zirconium lithium chloride and aluminum lithium chloride double-coated graphite composite material. The composite material utilizes the zirconium lithium chloride and the aluminum lithium chloride to improve the first efficiency of the material and the transmission rate of lithium ions in the charging and discharging process, and meanwhile, the synergistic effect between the zirconium lithium chloride and the aluminum lithium chloride is exerted, that is, the chemical bond effect between zirconium and aluminum between the two compounds, so that the structural stability of the material and the cycle performance of the material are improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material preparation, specifically a lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material and its preparation method. Background Technology

[0002] With increasing market demands for fast-charging performance in lithium-ion batteries, anode materials for lithium-ion batteries require excellent fast-charging capabilities. Many measures can improve the fast-charging performance of anode materials, such as reducing aggregate particle size, carbon coating, and surface modification, which can enhance lithium-ion intercalation / deintercalation channels and diffusion coefficients. Fast-ion conductors are compounds with high lithium-ion conductivity, enabling rapid lithium-ion exchange during charging and discharging, thus effectively improving fast-charging performance. While fast-ion conductors possess high ionic conductivity, they need to be combined with materials with good electronic conductivity to achieve optimal fast-charging performance. Patent CN114628659A discloses a graphite anode composite material for power batteries and its preparation method. This material has a graphite core and a Li5FeO4-doped fast-ion conductor monolayer structure, improving the rate performance of the anode material. However, the poor uniformity of the single-material coating results in low core integrity, making it prone to contact with the electrolyte, leading to numerous side reactions and reduced initial efficiency. To further improve the fast-charging performance and initial efficiency of the material, multiple coating processes are required to enhance its fast-charging performance. Summary of the Invention

[0003] The purpose of this invention is to provide a double-coated graphite composite material of lithium zirconium chloride and lithium aluminum chloride and its preparation method, thereby improving the fast-charging performance and cycle performance of the material.

[0004] The technical solution adopted by the present invention to solve its technical problem is as follows: it includes a core and a shell, the core being graphite and the shell being a composite of lithium zirconium chloride, lithium aluminum chloride, and amorphous carbon.

[0005] Preferably, in the composite material, the mass percentage of the outer shell is (5-10) wt%.

[0006] The present invention also provides a method for preparing the above-mentioned lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material, comprising the following steps:

[0007] S1. Dissolve the organic lithium salt in an organic solvent, then add zirconium aluminum hydroxide and disperse evenly, then add graphite and disperse evenly by ultrasonication to obtain solution A, wherein the mass ratio of organic lithium salt: organic solvent: zirconium aluminum hydroxide: graphite = (10-30): (100-500): (5-20): 100;

[0008] S2. Add the organic base to the organic solvent and disperse it evenly to prepare a solution B with a mass concentration of (1-10)wt%.

[0009] S3. Add solution A to a three-necked flask, then add solution B dropwise to solution A, and react hydrothermally at (100-200)℃ for (1-6)h. After that, filter out the residue, vacuum dry the residue, then soak it in a resin solution, filter out the residue again after soaking, vacuum dry the residue, then transfer it to a tube furnace and carbonize it at (700-1200)℃ for (1-6)h to obtain a graphite composite material with lithium zirconium chloride and lithium aluminum chloride double coating.

[0010] Preferably, the organic lithium salt in step S1 is one of lithium amino and lithium 2-hydroxypropionate.

[0011] Preferably, the organic solvent in step S1 is one of n-butanol, isobutanol, benzyl alcohol, and ethylene glycol.

[0012] Preferably, the organic base in step S2 is one of benzyltrimethylammonium chloride, benzyltriethylammonium chloride, tetraethylammonium chloride, tetramethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrabutylammonium chloride.

[0013] Preferably, in step S3, the mass ratio of solution A: solution B: resin solution is 100:(10-30):(1-10).

[0014] Preferably, the mass concentration of the resin solution in step S3 is 1-10 wt%, the solute of the resin solution is one of phenolic resin, epoxy resin, and furfural resin, and the solvent is one of diethyl ether and ethyl acetate.

[0015] The beneficial effects of this invention are:

[0016] 1. Using an organic alkaline solution, organic lithium salts react with aluminum zirconium chloride hydroxide at (100-200)℃ to generate lithium zirconium hydroxide and lithium aluminum hydroxide, followed by carbonization to obtain lithium zirconium chloride and lithium aluminum chloride materials, thereby improving the kinetic properties and first-pass efficiency of the materials.

[0017] 2. By coating the surface of graphite materials with lithium zirconium chloride and lithium aluminum chloride, the high lithium-ion conductivity of lithium zirconium chloride and lithium aluminum chloride can be utilized to improve rate performance. At the same time, zirconium doping can provide capacity, and aluminum doping can reduce the lithium ions consumed in the formation of SEI film, thereby improving the initial efficiency of the material and the lithium ion transport rate during charge and discharge. Furthermore, the synergistic effect between lithium zirconium chloride and lithium aluminum chloride, namely the chemical bond between the two compounds zirconium and aluminum, can be leveraged to enhance the structural stability of the material.

[0018] 3. Unreacted organic matter will carbonize to obtain amorphous carbon. The amorphous carbon coats the surface of lithium zirconium chloride and lithium aluminum chloride materials. The coating is complete and uniform, which improves the electronic conductivity and processing performance of the materials. It also exerts a synergistic effect among the three materials, improving the electronic and ionic conductivity of the materials, improving rate performance, and taking into account cycle performance and first-time efficiency. Attached Figure Description

[0019] Figure 1 The image shows a SEM image of the lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material prepared in Example 1. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0021] Example 1:

[0022] Step S1: Dissolve 20g of lithium amino acid in 300g of n-butanol organic solvent, then add 10g of aluminum zirconium chloride hydroxide and disperse evenly, then add 100g of artificial graphite and disperse evenly by ultrasonication to obtain solution A.

[0023] Step S2: Add 20g of benzyltrimethylammonium chloride to 400g of n-butanol organic solvent and disperse evenly to prepare a solution B with a mass concentration of 5wt%.

[0024] Step S3: Add 100g of solution A to a three-necked flask, then add 20g of solution B dropwise to solution A, and react via hydrothermal reaction at 150℃ for 3 hours. Filter out the residue and dry it in a vacuum environment at 80℃ for 24 hours. Then add the obtained material to 100g of a 3wt% phenolic resin solution in diethyl ether, filter out the residue, and dry it in a vacuum environment at 80℃ for 24 hours. Finally, transfer the obtained material to a tube furnace and carbonize it at 900℃ for 3 hours under an argon atmosphere to obtain a double-coated graphite composite material of lithium zirconium chloride and lithium aluminum chloride.

[0025] Example 2:

[0026] Step S1: Dissolve 10g of lithium 2-hydroxypropionate in 100g of isobutanol organic solvent, then add 5g of aluminum zirconium chloride hydroxide and disperse evenly, then add 100g of artificial graphite and disperse evenly by ultrasonication to obtain solution A.

[0027] Step S2: Add 10g of benzyltriethylammonium chloride to 1000g of isobutanol organic solvent and disperse evenly to prepare a solution B with a mass concentration of 1wt%.

[0028] Step S3: Add 100g of solution A to a three-necked flask, then add 10g of solution B dropwise to solution A, and react hydrothermally at 100℃ for 6 hours. Filter out the residue and dry it under vacuum at 80℃ for 24 hours. Then, immerse the obtained material in 100g of a 1wt% furfural resin solution in ethyl acetate, filter out the residue, and dry it under vacuum at 80℃ for 24 hours. Finally, transfer the obtained material to a tube furnace and carbonize it at 700℃ for 6 hours under an argon atmosphere to obtain a lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material.

[0029] Example 3:

[0030] Step S1: Dissolve 30g of lithium amino acid in 500g of benzyl alcohol organic solvent, then add 20g of aluminum zirconium chloride hydroxide and disperse evenly, then add 100g of artificial graphite and disperse evenly by ultrasonication to obtain solution A.

[0031] Step S2: Add 30g of tetraethylammonium chloride to 300g of benzyl alcohol organic solvent and disperse evenly to prepare a solution B with a mass concentration of 10wt%.

[0032] Step S3: Add 100g of solution A to a three-necked flask, then add 30g of solution B dropwise to solution A, and react via hydrothermal reaction at 200℃ for 1 hour. Filter out the residue and dry it in a vacuum environment at 80℃ for 24 hours. Then, immerse the obtained material in 100g of an ether solution of epoxy resin with a mass concentration of 5wt%, filter out the residue, and dry it in a vacuum environment at 80℃ for 24 hours. Finally, transfer the obtained material to a tube furnace and carbonize it at 1200℃ for 1 hour under an argon atmosphere to obtain a double-coated graphite composite material of lithium zirconium chloride and lithium aluminum chloride.

[0033] Comparative Example 1:

[0034] Step S1: Dissolve 20g of lithium amino acid in 300g of n-butanol organic solvent, then add 100g of artificial graphite and ultrasonically disperse it evenly to obtain solution A.

[0035] Step S2: Add 20g of tetraethylammonium chloride to 400g of n-butanol organic solvent and disperse evenly to prepare a solution B with a mass concentration of 5wt%.

[0036] Step S3: Add 100g of solution A to a three-necked flask, then add 20g of solution B dropwise to solution A, and react via hydrothermal reaction at 150℃ for 3 hours. Filter out the residue and dry it in a vacuum environment at 80℃ for 24 hours. Then transfer the obtained material to a tube furnace and carbonize it at 900℃ for 3 hours to obtain a graphite composite material.

[0037] Comparative Example 2:

[0038] Step S1: Dissolve 10g of aluminum zirconium chloride hydroxide in 300g of n-butanol organic solvent, then add 100g of artificial graphite and ultrasonically disperse it evenly to obtain solution A.

[0039] Step S2: Add 20g of benzyltrimethylammonium chloride to 400g of n-butanol organic solvent and disperse evenly to prepare a solution B with a mass concentration of 5wt%.

[0040] Step S3: Add 100g of solution A to a three-necked flask, then add 30g of solution B dropwise to solution A. React via hydrothermal reaction at 200℃ for 1 hour. Filter out the residue and dry it under vacuum at 80℃ for 24 hours. Then, immerse the resulting material in 100g of an ether solution containing 3wt% epoxy resin, filter out the residue, and dry it under vacuum at 80℃ for 24 hours. Transfer the resulting material to a tube furnace and carbonize it at 1200℃ for 1 hour to obtain the graphite composite material.

[0041] The materials prepared in the above embodiments and comparative examples were subjected to performance tests:

[0042] (1) SEM testing

[0043] The lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material prepared in Example 1 was subjected to SEM testing, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the obtained composite material has a granular structure with slight granulation and a particle size between 10-20 μm.

[0044] (2) Button cells and their physicochemical tests

[0045] The lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite materials prepared in Examples 1-3 and the graphite composite materials in Comparative Examples 1-2 were assembled into coin cells according to the following method: A binder, conductive agent, and solvent were added to the negative electrode material, and the mixture was stirred and mixed evenly to form a negative electrode slurry. The negative electrode slurry was coated onto copper foil, dried, rolled, and cut to obtain a negative electrode sheet. The binder was LA132 binder, the conductive agent was SP conductive agent, and the solvent was double-distilled water. The weight ratio of the negative electrode material, SP conductive agent, LA132 binder, and double-distilled water was 95:1:4:220. A lithium metal sheet was used as the counter electrode, a polyethylene (PE) film, a polypropylene (PP) film, or a polypropylene (PEP) composite film was used as the separator, and LiPF6 / EC+DEC (LiPF6 concentration was 1.3 mol / L, and the volume ratio of EC to DEC was 1:1) was used as the electrolyte. The battery assembly was carried out in an argon-filled glove box.

[0046] The fabricated button cells were installed on a Wuhan Landian CT2001A battery tester and charged and discharged at a rate of 0.1C, with a charging and discharging voltage range of 0.005V to 2.0V. The initial discharge capacity and initial discharge efficiency were measured. The 2C rate discharge capacity was also tested.

[0047] The powder conductivity and specific surface area of ​​the above-mentioned anode materials were tested according to the national standard GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries", and the coating integrity of the materials was tested by XPS. The powder diffusion coefficient was tested using the following method:

[0048] The negative electrode active material powder was assembled into a coin cell; all coin cells were in a completely delithiated state; cyclic voltammetry (CV) was performed at a scan rate of 0.1 mV / s; and calculations were performed according to Equation (I).

[0049] ip / m = 0.4463F (F / RT) 1 / 2 C*v 1 / 2 AeKS 1 / 2

[0050] In equation (I), ip is the peak current in A; m is the electrode mass in g; F = 96485 C / mol; R = 8.314 J / mol·K; T is the thermodynamic temperature in K; and C* is the initial lithium concentration in the LFP in mol / cm³. 3 v is the scanning speed, in V / s; Ae is the surface area of ​​the electrode, in m². 2 / g; KS is the diffusion coefficient, with units of cm⁻¹. 2 / s.

[0051] Table 1

[0052]

[0053] As can be seen from Table 1, the discharge capacity of the composite anode materials prepared in Examples 1-3 is significantly higher than that in Comparative Example 1. This shows that zirconium doping can improve capacity, aluminum doping can reduce the lithium ions consumed in the formation of the SEI film and improve the first-pass efficiency of the material, while amorphous carbon coating on the surface of lithium zirconium chloride and lithium aluminum chloride materials has good coating integrity, improves the electronic conductivity and processing performance of the material, and exerts a synergistic effect among the three to improve the electronic and ionic conductivity of the material, improve rate performance, and take into account the first-pass efficiency.

[0054] The discharge capacity of the composite negative electrode materials prepared in Examples 1-3 is significantly higher than that in Comparative Example 2. Comparative Example 2 uses an organic alkaline solution, where organic lithium salts react at 100-200°C and are then carbonized to obtain amorphous carbon-coated graphite materials. In contrast, the materials in the examples are lithium zirconium chloride and lithium aluminum chloride-coated graphite materials. The amorphous carbon is coated on the surface of the lithium zirconium chloride and lithium aluminum chloride materials, resulting in good coating integrity. Lithium compounds have advantages over amorphous carbon, such as higher lithium-ion conductivity and higher initial efficiency, thus improving the kinetic performance and initial efficiency of the materials.

[0055] (3) Pouch Battery Testing

[0056] The lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite materials prepared in Examples 1-3 and Comparative Examples 1-2 were used as negative electrodes, and ternary materials (LiNi) were used. 1 / 3 Co 1 / 3 Mn 1 / 3 A positive electrode was prepared using O2 as the positive electrode material, and a 2Ah soft-pack battery was prepared using LiPF6 (solvent EC+DEC, volume ratio 1:1, concentration 1.3mol / L) as the electrolyte and Celegard 2400 as the separator.

[0057] In the preparation of the negative electrode, a binder, a conductive agent, and a solvent are added to the negative electrode material and stirred to form a uniform negative electrode slurry. The negative electrode slurry is then coated onto copper foil, dried, rolled, and cut to obtain the negative electrode sheet. The binder is LA132 binder, the conductive agent is SP conductive agent, and the solvent is double-distilled water. The weight ratio of the negative electrode material, SP conductive agent, LA132 binder, and double-distilled water is 95:1:4:220.

[0058] In the preparation of the positive electrode, a binder, a conductive agent, and a solvent are added to the positive electrode material and stirred until homogeneous to form a positive electrode slurry. The positive electrode slurry is then coated onto aluminum foil, dried, rolled, and cut to obtain the positive electrode sheet. The binder is PVDF, the conductive agent is SP, and the solvent is N-methylpyrrolidone. The weight ratio of the positive electrode material, conductive agent, binder, and solvent is 93:3:4:140.

[0059] 3.1x Ratio Performance Test

[0060] The charge / discharge voltage range was 2.8V to 4.2V, and the test temperature was (25±3.0)℃. The battery was charged at 1.0C, 2.0C, 3.0C, and 5.0C, and discharged at 1.0C. The constant current ratio and temperature of the battery were tested under different charging modes, and the results are shown in Table 2.

[0061] Table 2

[0062]

[0063] As shown in Table 2, the rate charging performance of the battery pack in this embodiment is significantly better than that of the comparative example, and the charging time is shorter, indicating that the composite anode material of this invention has good fast charging performance. It is evident that the lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material with a high diffusion coefficient improves the lithium-ion transport rate during charging and discharging, thereby enhancing rate performance.

[0064] 3.2 Cyclic Performance Test

[0065] The soft-pack batteries prepared using the negative electrode materials in Examples 1-3 and Comparative Examples 1-2 were subjected to the following experiments: At a 2C / 2C charge / discharge rate and a voltage range of 2.8V-4.2V, they were subjected to 100, 300, and 500 charge / discharge cycles respectively, and their capacity retention was tested. The results are shown in Table 3.

[0066] Table 3

[0067]

[0068]

[0069] As can be seen from Table 3, the cycle performance of the lithium-ion battery prepared by the composite negative electrode material obtained in this invention is significantly better than that of the comparative example at all stages. This shows that the graphite composite material with lithium zirconium chloride and lithium aluminum chloride double coating plays a synergistic role between lithium zirconium chloride and lithium aluminum chloride, that is, the chemical bond between the two compounds zirconium and aluminum, which improves the surface structure stability of the material during charging and discharging, thereby improving the cycle performance.

[0070] It should be noted that the technical features not described in detail in the above embodiments are all prior art, and those skilled in the art can make reasonable selections from the prior art and apply them to the technical solutions of this application.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a graphite composite material with lithium zirconium chloride and lithium aluminum chloride double coating, characterized in that, Includes the following steps: S1. Dissolve the organic lithium salt in an organic solvent, then add zirconium chloride aluminum hydroxide and disperse evenly, then add graphite and disperse evenly by ultrasonication to obtain solution A, wherein the mass ratio of organic lithium salt: organic solvent: zirconium chloride aluminum hydroxide: graphite = (10-30): (100-500): (5-20): 100; S2. Add the organic base to the organic solvent and disperse it evenly to prepare a solution B with a mass concentration of (1-10) wt%. S3. Add solution A to a three-necked flask, then add solution B dropwise to solution A, and react with hydrothermal reaction at (100-200)℃ for (1-6) h. After that, filter out the residue, vacuum dry the residue, then soak the obtained material in a resin solution, filter out the residue again after soaking, vacuum dry the residue, then transfer the obtained material to a tube furnace and carbonize at (700-1200)℃ for (1-6) h to obtain a lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material. The lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material includes a core and a shell. The core is graphite, and the shell is a composite of lithium zirconium chloride, lithium aluminum chloride, and amorphous carbon. The organic base mentioned in step S2 is one of benzyltrimethylammonium chloride, benzyltriethylammonium chloride, tetraethylammonium chloride, tetramethylammonium chloride, and tetrabutylammonium chloride.

2. The preparation method of the lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material according to claim 1, characterized in that, The organic lithium salt mentioned in step S1 is one of lithium amino and lithium 2-hydroxypropionate.

3. The preparation method of the lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material according to claim 1, characterized in that, The organic solvent mentioned in step S1 is one of n-butanol, isobutanol, benzyl alcohol, and ethylene glycol.

4. The method for preparing the lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material according to claim 1, characterized in that, In step S3, the mass ratio of solution A: solution B: resin solution is 100: (10-30): (1-10).

5. The method for preparing the lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material according to claim 1, characterized in that, The resin solution in step S3 has a mass concentration of 1-10 wt%, the solute of the resin solution is one of phenolic resin, epoxy resin, and furfural resin, and the solvent is one of diethyl ether and ethyl acetate.

6. A graphite composite material with lithium zirconium chloride and lithium aluminum chloride double coating, characterized in that, It is prepared by any of the preparation methods described in claims 1-5.

7. The lithium zirconium chloride and lithium aluminum chloride double-coated graphite composite material according to claim 6, characterized in that, In the composite material, the mass percentage of the outer shell is (5-10) wt%.

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