A fast ion conductor coated graphite composite material and preparation method thereof

Abstract

The present invention relates to a fast ion conductor coated graphite composite material and a preparation method thereof. A fast ion conductor coated graphite composite material comprises an inner core and an outer shell coating the inner core; wherein the inner core is graphite; the outer shell is a double-layer structure, the inner layer is a first coating layer containing a fast ion conductor; the outer layer is a second coating layer, which is nitrogen-containing amorphous carbon. The present invention also discloses a preparation method of the graphite composite material. The fast ion conductor coated graphite composite material and the preparation method thereof described in the present invention utilize the synergistic effect between the first coating layer and the second coating layer, namely, the fast ion conductor has high lithium ion conductivity and stable structure, and the second coating layer has high electronic conductivity. At the same time, the first coating layer and the second coating layer are connected by a coupling agent to enhance the bonding force between the materials, reduce the impedance between the layers, and enhance the cycle performance and power performance.

Description

Technical Field

[0001] The present invention specifically relates to a fast ion conductor-coated graphite composite material and a preparation method thereof. Background Art

[0002] Currently, the negative electrode material for commercial lithium-ion batteries is primarily based on graphite (natural graphite and artificial graphite), which offers advantages such as good conductivity and high reversible specific capacity. However, graphite has poor structural stability, poor compatibility with electrolytes, and slow diffusion of lithium ions within its ordered layered structure, resulting in the material being unable to withstand high-rate charge and discharge.

[0003] The specific capacity of graphite composite materials has reached 360 mAh / g, which is close to the theoretical specific capacity of 372 mAh / g. The coating material is amorphous carbon formed by carbonizing asphalt or resin. However, the specific capacity of amorphous carbon materials is relatively low (around 300 mAh / g) and the initial efficiency is low (80-85%). Although the electronic conductivity is high, the ionic conductivity of the material is poor, which affects its fast charging performance and initial efficiency.

[0004] In view of this, the present invention proposes a new coating material for graphite composite materials and a preparation method thereof, and adopts a fast ion conductor as the coating material. The fast ion conductor is a lithium-containing metal inorganic compound with high lithium ion conductivity, stable structure, and does not react violently with the electrolyte. It can improve the dynamics of the material surface and its cycle performance. Coating it on the graphite surface is a measure to improve the fast charging performance. Summary of the Invention

[0005] The purpose of the present invention is to provide a fast ion conductor coated graphite composite material, which has a double-layer structure coated on the graphite surface, a fast ion conductor composite layer and a nitrogen-containing amorphous carbon layer, which is beneficial to improving the material's fast charging, initial efficiency and cycle performance.

[0006] In order to achieve the above objectives, the technical solutions adopted are:

[0007] A fast ion conductor-coated graphite composite material comprising a core and a shell coating the core;

[0008] Wherein, the core is graphite;

[0009] The shell is a double-layer structure, the inner layer is the first coating layer, which contains a fast ion conductor; the outer layer is the second coating layer, which is nitrogen-containing amorphous carbon.

[0010] Furthermore, the mass ratio of the core: the first coating layer: the second coating layer is 90-98: 1-5: 1-5.

[0011] Furthermore, the thickness of the first coating layer is 0.5-2 μm, and the thickness of the second coating layer is 0.1-0.5 μm.

[0012] Furthermore, the first coating layer is composed of: 80-90 wt% fast ion conductor, 1-5 wt% graphene, and the rest is amorphous carbon.

[0013] Furthermore, the fast ion conductor is LiAlSiO4, LiNbO3, Li7La3Zr2O 12 、Li 0.5 La 0.5 TiO3、Li 1.4 Al 0.4 Ti 1.6 One of (PO4)3.

[0014] Another object of the present invention is to provide a method for preparing the above-mentioned graphite composite material, which is simple.

[0015] In order to achieve the above objectives, the technical solutions adopted are:

[0016] The method for preparing the above-mentioned graphite composite material comprises the following steps:

[0017] (1) uniformly dispersing a fast ion conductor and graphene oxide N-methylpyrrolidone conductive liquid in an organic solvent, reacting at 100-200° C. and 1-5 MPa for 1-6 hours, filtering, and vacuum drying to obtain a coating material A;

[0018] (2) implanting the coating material A onto the surface of artificial graphite by a particle injection method to obtain material 1;

[0019] (3) Adding a conductive polymer and a 1-10 wt% hydrochloric acid solution to the coupling agent solution, mixing uniformly, adding the material B, dispersing uniformly, adding an organic solvent to dilute, spray drying, crushing, carbonizing, crushing, and classifying to obtain the graphite composite material.

[0020] Furthermore, in the step (1), the organic solvent is one of N-methylpyrrolidone, carbon tetrachloride, cyclohexane, xylene, and tetrahydrofuran;

[0021] In the step (2), the step is carried out under an atmosphere of at least one of argon, oxygen, nitrogen and ammonia;

[0022] In the step (3), the coupling agent is one of (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, (3-aminopropyl)dimethoxymethylsilane, (3-aminopropyl)diethoxymethylsilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-methylaminopropyltriethoxysilane;

[0023] The conductive polymer is one of polyaniline, polythiophene and polypyrrole.

[0024] Furthermore, in the step (1), the mass volume ratio of the fast ion conductor and the organic solvent is 100g:500-1000ml;

[0025] In the step (2), the reaction is carried out under an atmosphere of oxygen or ammonia.

[0026] In the step (3), the mass ratio of the coupling agent, the conductive polymer, and the material B is 0.5-2:1-10:100.

[0027] Furthermore, in the step (1), the mass fraction of graphene oxide in the graphene oxide N-methylpyrrolidone conductive liquid is 1-5 wt%;

[0028] In the step (2), the gas flow rate is 10-100 sccm, the gas pressure is 2×10 -4 -5×10 -4 Pa, time 1-60min;

[0029] In the step (3), the mass ratio of the solute to the organic solvent in the coupling agent solution is 1-5:100;

[0030] The carbonization temperature is 800-1200℃ and the time is 1-6h.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The technical solution of the present invention utilizes a double-layer structure coated on the graphite surface. The fast ion layer can increase the insertion and extraction rate of lithium ions in the material, and graphene doping between the fast ion layers can improve the electronic conductivity of the fast ion material. The outer nitrogen-containing carbon layer utilizes nitrogen atoms to enhance the electronic conductivity of the carbon coating layer and isolates the fast ion layer from the electrolyte, reducing side reactions.

[0033] 2. The technical solution of the present invention adopts the particle implantation method, which has the advantages of process controllability, controllable implantation depth, and good uniformity compared with the traditional physical and chemical coating methods. In addition, the particle implantation method has no effect on the structural properties of the implanting and implanted materials. At the same time, the depth and amount of implanted materials can be determined according to performance requirements.

[0034] 3. The technical solution of the present invention is that the outer layer conductive polymer has high electronic conductivity under hydrochloric acid conditions, and the synergistic effect with the alkaline coupling agent can be uniformly coated on the surface of the first coating layer, with strong bonding force and stable structure. At the same time, the amorphous carbon formed after the carbonization of the conductive polymer has good isotropic properties, which improves the fast charging performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the SEM image of the graphite composite material prepared in Example 1. DETAILED DESCRIPTION

[0036] To further illustrate the fast ion conductor-coated graphite composite material and its preparation method according to the present invention and achieve the intended purpose of the invention, the following, in conjunction with preferred embodiments, describes in detail the fast ion conductor-coated graphite composite material and its preparation method according to the present invention, its specific implementation, structure, characteristics, and efficacy. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable form.

[0037] The following is a detailed description of a fast ion conductor coated graphite composite material and its preparation method according to the present invention, in conjunction with specific embodiments:

[0038] The present invention discloses a fast ion conductor coated graphite composite material and its preparation method, wherein the composite material has graphite as the core and a double-layer structure as the outer shell, which is a first coating layer of fast ion conductor and a second coating layer of nitrogen-containing amorphous carbon from the inside to the outside. The fast ion conductor is LiAlSiO4, LiNbO3, Li7La3Zr2O 12 、Li 0.5 La 0.5 TiO3、Li 1.4 Al 0.4 Ti 1.6 (PO4)3. Its preparation process is as follows: a fast ion conductor composite material is prepared by a hydrothermal method, and then implanted into the graphite surface by a particle injection method. It is then added to a conductive polymer and coupling agent solution, spray-dried, and carbonized to obtain a graphite composite material. The composite material utilizes the synergistic effect between the first coating layer and the second coating layer, namely the high lithium ion conductivity and stable structure of the fast ion conductor, and the high electronic conductivity of the nitrogen-containing amorphous carbon in the second coating layer. At the same time, the first coating layer and the second coating layer are connected by a coupling agent to enhance the bonding strength between the materials, reduce the impedance between the layers, and improve the cycle performance and power performance.

[0039] The technical solution of the present invention is:

[0040] A fast ion conductor-coated graphite composite material comprising a core and a shell coating the core;

[0041] Wherein, the core is graphite;

[0042] The shell is a double-layer structure, the inner layer is the first coating layer, which contains a fast ion conductor; the outer layer is the second coating layer, which is nitrogen-containing amorphous carbon.

[0043] Preferably, the mass ratio of the core: the first coating layer: the second coating layer is 90-98: 1-5: 1-5.

[0044] Preferably, the thickness of the first coating layer is 0.5-2 μm, and the thickness of the second coating layer is 0.1-0.5 μm.

[0045] Preferably, the first coating layer is composed of: 80-90 wt% fast ion conductor, 1-5 wt% graphene, and the rest amorphous carbon.

[0046] Preferably, the fast ion conductor is LiAlSiO4, LiNbO3, Li7La3Zr2O 12 、Li 0.5 La 0.5 TiO3、Li 1.4 Al 0.4 Ti 1.6 One of (PO4)3.

[0047] The method for preparing the above-mentioned graphite composite material comprises the following steps:

[0048] (1) uniformly dispersing a fast ion conductor and graphene oxide N-methylpyrrolidone conductive liquid in an organic solvent, reacting at 100-200° C. and 1-5 MPa for 1-6 hours, filtering, and vacuum drying to obtain a coating material A;

[0049] (2) implanting the coating material A onto the surface of artificial graphite by a particle injection method to obtain material B;

[0050] (3) Adding a conductive polymer and a 1-10 wt% hydrochloric acid solution to the coupling agent solution, mixing uniformly, adding the material B, dispersing uniformly, spray drying, crushing, carbonizing, crushing, and classifying to obtain the graphite composite material.

[0051] Preferably, in the step (1), the organic solvent is one of N-methylpyrrolidone, carbon tetrachloride, cyclohexane, xylene, and tetrahydrofuran;

[0052] In the step (2), the step is carried out under an atmosphere of at least one of argon, oxygen, nitrogen and ammonia;

[0053] In the step (3), the coupling agent is one of (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, (3-aminopropyl)dimethoxymethylsilane, (3-aminopropyl)diethoxymethylsilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-methylaminopropyltriethoxysilane;

[0054] The conductive polymer is one of polyaniline, polythiophene and polypyrrole.

[0055] Further preferably, in the step (1), the mass volume ratio of the fast ion conductor and the organic solvent is 100 g: 500-1000 ml;

[0056] In the step (2), the reaction is carried out under an atmosphere of oxygen or ammonia.

[0057] In the step (3), the mass ratio of the coupling agent, the conductive polymer, and the material B is 0.5-2:1-10:100.

[0058] Further preferably, in the step (1), the mass fraction of graphene oxide in the graphene oxide N-methylpyrrolidone conductive liquid is 1-5 wt%;

[0059] In the step (2), the gas flow rate is 10-100 sccm, the gas pressure is 2×10 -4 -5×10 -4 Pa, time 1-60min;

[0060] In the step (3), the mass ratio of solute to solvent in the coupling agent solution is 1-5:100;

[0061] The carbonization temperature is 800-1200℃ and the time is 1-6h.

[0062] Example 1.

[0063] The specific steps are as follows:

[0064] (1) Preparation of coating materials:

[0065] 100g of LiAlSiO4 and 100ml of a 3wt% graphene oxide conductive solution in N-methylpyrrolidone were added to 800ml of N-methylpyrrolidone and ultrasonically dispersed. After uniform dispersion, the mixture was transferred to an autoclave and reacted at 150°C and 3 MPa for 3 hours. The mixture was then filtered, dried under vacuum at 80°C for 24 hours, and ground to obtain coating material A.

[0066] (2) In oxygen atmosphere, the gas flow rate is 50 sccm and the pressure is 3×10 -4Pa, using particle injection method, continuously bombarded with high-speed particle beams to implant the coating material A into the surface of artificial graphite for 30 min to obtain graphite composite material B;

[0067] (3) Add 1 g of (3-aminopropyl)trimethoxysilane to 20 ml of N-methylpyrrolidone to prepare a coupling agent solution, then add 5 g of polyaniline and 10 ml of 5 wt% dilute hydrochloric acid and disperse evenly;

[0068] Then add 100g of graphite composite material B and 500ml of N-methylpyrrolidone diluted solution, ultrasonically disperse them uniformly, spray dry them, crush them, and then heat them to 900℃ and carbonize them for 3h under an inert atmosphere of argon. Finally, crush them and classify them to obtain a graphite composite material.

[0069] The material was then cross-sectionally tested using TEM, and the mass ratio of the core: the first coating layer: the second coating layer was 95:4:1.

[0070] Example 2.

[0071] The specific steps are as follows:

[0072] (1) 100 g of LiNbO3 and 100 ml of 1 wt% graphene oxide N-methylpyrrolidone conductive liquid were added to 500 ml of carbon tetrachloride and ultrasonically dispersed. After uniform dispersion, the mixture was transferred to a high-pressure reactor and reacted at 100°C and 5 MPa for 6 h. The mixture was filtered, vacuum-dried at 80°C for 24 h, and ground to obtain coating material A.

[0073] (2) Under ammonia atmosphere, the gas flow rate is 10 sccm and the pressure is 2×10 -4 Pa, using particle injection method, continuously bombarded with high-speed particle beams to implant the coating material A into the surface of artificial graphite for 1 min to obtain graphite composite material B;

[0074] (3) 0.5 g of (3-aminopropyl)triethoxysilane was added to 50 ml of carbon tetrachloride to prepare a coupling agent solution. 1 g of polypyrrole and 10 ml of 1 wt% dilute hydrochloric acid were then added and uniformly dispersed. 100 ml of graphite composite material B was then added and uniformly dispersed by ultrasonication. 500 ml of the diluted carbon tetrachloride solution was then added. The mixture was then spray-dried and pulverized. The mixture was then carbonized at 800°C for 6 h under an inert atmosphere of argon, and then pulverized and classified to obtain a graphite composite material.

[0075] The material was then cross-sectionally tested using TEM, and the mass ratio of the core: the first coating layer: the second coating layer was 98:1:1.

[0076] At the same time, the coating thickness of the material was tested by TEM, and the thickness of the first coating layer was 0.5 μm, and the thickness of the second coating layer was 0.1 μm.

[0077] Example 3.

[0078] The specific steps are as follows:

[0079] (1) 100g Li7La3Zr2O 12 100 ml of 5 wt% graphene oxide N-methylpyrrolidone conductive liquid was added to 1000 ml of cyclohexane and ultrasonically dispersed. After uniform dispersion, the mixture was transferred to a high-pressure reactor, reacted at 200° C. and 1 MPa for 1 hour, filtered, vacuum-dried at 80° C. for 24 hours, and ground to obtain coating material A;

[0080] (2) Under argon atmosphere, the gas flow rate is 100 sccm and the pressure is 5×10 -4 Pa, using particle injection method, high-speed particle beam bombardment was used to implant the coating material A onto the surface of artificial graphite for 60 min to obtain graphite composite material B;

[0081] (3) 2 g of (3-aminopropyl)dimethoxymethylsilane was added to 20 ml of cyclohexane to prepare a coupling agent solution. 10 g of polythiophene and 10 ml of 10 wt% dilute hydrochloric acid were then added and dispersed uniformly. 100 g of graphite composite material B was then added and ultrasonically dispersed uniformly. 500 ml of the cyclohexane dilution solution was then added. The mixture was then spray-dried and pulverized. The mixture was then carbonized at 1200°C for 1 h under an inert atmosphere of argon, pulverized, and classified to obtain a graphite composite material.

[0082] The material was then cross-sectionally tested using TEM, and the mass ratio of the core: the first coating layer: the second coating layer was 93:5:2.

[0083] At the same time, the coating thickness of the material was tested by TEM, and the thickness of the first coating layer was 2 μm, and the thickness of the second coating layer was 0.2 μm.

[0084] Example 4.

[0085] The operating steps of Example 4 are the same as those of Example 1, except that:

[0086] The fast ion conductor is Li 0.5 La 0.5 TiO3, the organic solvent is tetrahydrofuran, and the coupling agent is (3-aminopropyl)diethoxymethylsilane.

[0087] The material was then cross-sectionally tested using TEM, and the mass ratio of the core: the first coating layer: the second coating layer was 95:4:1.

[0088] Example 5.

[0089] The operating steps of Example 5 are the same as those of Example 1, except that:

[0090] The fast ion conductor is Li 1.4 Al 0.4 Ti 1.6 (PO4)3, the organic solvent is xylene, and the coupling agent is N-methylaminopropyltriethoxysilane.

[0091] Comparative Example 1:

[0092] Weigh 10 g of the coating material A prepared in Example 1, add 100 g of artificial graphite to a ball mill and mix evenly, then add it to 500 ml of cyclohexane flux and disperse it evenly, spray dry it, and transfer it to a tube furnace. Under an argon inert atmosphere, heat it to 800 ° C and carbonize it for 6 h to obtain a graphite composite material.

[0093] Comparative Example 2:

[0094] The graphite composite material B prepared in steps (1) and (2) of Example 1 was used as the graphite negative electrode material.

[0095] Comparative Example 3:

[0096] 100 g of artificial graphite and 10 g of asphalt were weighed and mixed evenly, ball-milled for 24 h, then transferred to a tube furnace, heated to 800 ° C under an inert atmosphere and kept warm for 3 h, and then cooled to room temperature to obtain a graphite composite material.

[0097] Performance Testing

[0098] 1. Physical and chemical performance test

[0099] 1. SEM test

[0100] The graphite composite material prepared in Example 1 was subjected to SEM testing, and the test results are as follows: Figure 1 As shown. Figure 1 It can be seen that the graphite composite material prepared in Example 1 has a granular structure and is uniform in size, with a particle size ranging from 10 to 18 μm.

[0101] At the same time, the coating thickness of the material was tested by TEM, and the thickness of the first coating layer was 1 μm, and the thickness of the second coating layer was 0.2 μm.

[0102] 2. Powder conductivity test

[0103] The graphite composite materials prepared in Examples 1-5 and the graphite composite materials prepared in Comparative Examples 1-3 were subjected to powder conductivity tests. The powder conductivity test method was as follows: the powder was pressed into a block structure on a powder compaction density meter with a pressure of 2 T, and then the powder conductivity was tested using a four-probe tester. The test results are shown in Table 1.

[0104] 3. Tap density and specific surface area test

[0105] As above, the tap density and specific surface area were tested in accordance with GB / T 24533-2019 “Graphite Anode Materials for Lithium-ion Batteries”. The test results are shown in Table 1.

[0106] Table 1

[0107] project Conductivity (S / cm) <![CDATA[Tap density (g / cm 3 )]]> <![CDATA[Specific surface area (m 2 / g)]]> Example 1 4.11 1.11 1.45 Example 2 4.01 1.09 1.39 Example 3 3.81 1.03 1.37 Example 4 3.79 1.04 1.37 Example 5 4.01 1.01 1.36 Comparative Example 1 1.99 0.90 1.11 Comparative Example 2 2.21 0.87 1.24 Comparative Example 3 2.31 0.93 1.23

[0108] As can be seen from Table 1, the electrical conductivity of the fast ion-coated graphite composite material prepared by the particle injection method of the present invention is significantly higher than that of the comparative example. The reason is that the surface of the composite material is coated with a fast ion conductor material with higher conductivity, which improves the transmission rate of ions / electrons. At the same time, the amorphous carbon coated on the surface of the material and the effect of the coupling agent enhance the bonding strength and density between the materials, thereby improving the tap density of the material.

[0109] 2. Button Battery Test

[0110] The graphite composite materials prepared in Examples 1-5 and the graphite composite materials prepared in Comparative Examples 1-3 were assembled into button-type batteries a1, a2, a3, a4, a5, b1, b2, and b3, respectively. The assembly method was as follows: a binder, a conductive agent, and a solvent were added to the negative electrode material, stirred to form a slurry, and then the slurry was coated on copper foil. The negative electrode sheet was obtained by drying and rolling. The binder used was LA132, the conductive agent was SP, the negative electrode materials were the composite materials of Examples 1-5 and Comparative Examples 1-3, respectively, and the solvent was double-distilled water. The ratio of the components was: negative electrode material: SP: LA132: double-distilled water = 95g: 1g: 4g: 220mL; the electrolyte was LiPF6 / EC+DEC (LiPF6 concentration was 1.2 mol / L, EC:DEC volume ratio was 1:1), a metal lithium sheet was used as the counter electrode, and a celegard 2400 separator was used. The button cells were assembled in an argon-filled glove box, and the electrochemical performance tests were performed on a Wuhan Blue Power CT2001A battery tester. The charge and discharge voltage range was 0.005 V to 2.0 V, and the charge and discharge rate was 0.1 C. The discharge capacity at 3 C and 0.2 C rates was tested. The test results are shown in Table 2.

[0111] Table 2

[0112] project First discharge capacity (mAh / g) First efficiency (%) Magnification (3C / 0.2C) Button battery A1 367.3 96.8 93.5％ Button battery A2 366.4 96.5 92.6％ Button battery A3 364.5 96.1 91.3％ button battery a4 364.3 96.2 92.5％ button battery a5 364.1 96.0 92.3％ Button battery b1 354.4 93.2 83.9％ Button battery B2 353.8 91.8 85.1％ Button battery b3 354.1 92.3 86.2％

[0113] As can be seen in Table 2, the initial discharge capacity and initial charge-discharge efficiency of lithium-ion batteries prepared using the composite materials of Examples 1-5 of the present invention are significantly higher than those of the comparative example. This is due to the fact that the fast ion conductor is coated on the surface of the graphite core, utilizing the fast ion conductor's structural stability and large interlayer spacing to increase the lithium ion insertion rate, reduce the material's irreversible capacity loss, and improve the initial efficiency. Furthermore, the high lithium ion conductivity of the fast ion conductor improves the rate performance of the button cell.

[0114] 3. Soft pack battery test

[0115] The graphite composite materials prepared in Examples 1-5 and the graphite composite materials in Comparative Examples 1-3 were used as negative electrode materials to prepare negative electrode sheets; 1 / 3 Co 1 / 3 Mn 1 / 3 5Ah soft-pack batteries A1, A2, A3, A4, A5, B1, B2, and B3 were prepared using a LiPF6 solution (EC+DEC, 1:1 volume ratio, 1.3 mol / L LiPF6 concentration) as the positive electrode material, and a celegard 2400 separator. The soft-pack batteries were then tested for cycle performance, rate capability, and expansion performance under different conditions.

[0116] Cycle performance test conditions: charge and discharge current 1C / 1C, voltage range 2.8-4.2V, cycle number 500 times.

[0117] Rate performance test conditions: charge rate 1C / 3C / 5C / 8C, discharge rate 1C; voltage range 2.8-4.2V.

[0118] Expansion performance test conditions: 25℃, 1C / 1C, the negative electrode expands at full charge in the initial state, and expands at full charge after 500 cycles.

[0119] The test results are shown in Tables 3 and 4.

[0120] Table 3

[0121]

[0122] As can be seen from Table 3, the cycle performance of the soft-pack batteries prepared using the composite materials of Examples 1-5 is better than that of the comparative example. The reason is that in terms of 1C / 1C rate cycle performance, the fast ion conductor and amorphous carbon on the surface of the graphite core are injected by the particle method to improve the transmission rate of lithium ions; at the same time, the stable structure of the fast ion conductor itself is utilized to improve the cycle performance.

[0123] Table 4

[0124]

[0125]

[0126] As can be seen from Table 4, the soft-pack batteries prepared using the composite materials of Examples 1-5 have a better constant current ratio. The reason is that the fast ion conductor on the surface of the graphite core improves the lithium ion insertion rate of the material during rate charging, thereby improving the rate charging performance.

[0127] The above is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the embodiments of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the embodiments of the present invention are still within the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fast ion conductor coated graphite composite material, characterized in that: The graphite composite material comprises a core and a shell covering the core; Wherein, the core is graphite; The shell is a double-layer structure, the inner layer is the first coating layer, which contains a fast ion conductor; the outer layer is the second coating layer, which is nitrogen-containing amorphous carbon; The method for preparing the graphite composite material comprises the following steps: (1) After uniformly dispersing the fast ion conductor and graphene oxide N-methylpyrrolidone conductive liquid in an organic solvent, reacting at 100-200°C and 1-5 MPa for 1-6 hours, filtering, and vacuum drying to obtain coating material A; (2) implanting the coating material A onto the surface of artificial graphite by a particle injection method to obtain material B; (3) Adding a conductive polymer and a 1-10 wt% hydrochloric acid solution to the coupling agent solution, mixing them evenly, adding the material B, dispersing them evenly, adding an organic solvent to dilute them, spray drying, crushing, carbonizing, crushing, and classifying to obtain the graphite composite material; The coupling agent is a basic coupling agent, selected from one of (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, (3-aminopropyl)dimethoxymethylsilane, (3-aminopropyl)diethoxymethylsilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-methylaminopropyltriethoxysilane.

2. The graphite composite material according to claim 1, characterized in that The mass ratio of the core: the first coating layer: the second coating layer is 90-98: 1-5: 1-5.

3. The graphite composite material according to claim 1, characterized in that The thickness of the first coating layer is 0.5-2 μm, and the thickness of the second coating layer is 0.1-0.5 μm.

4. The graphite composite material according to claim 1, characterized in that The first coating layer is composed of: 80-90 wt% fast ion conductor, 1-5 wt% graphene, and the rest is amorphous carbon.

5. The graphite composite material according to claim 1, characterized in that The fast ion conductor is LiAlSiO4, LiNbO3, Li7La3Zr2O 12 、Li 0.5 La 0.5 TiO3、Li 1.4 Al 0.4 Ti 1.6 One of (PO4)3.

6. The method for preparing the graphite composite material according to claim 1, wherein The following steps are involved: (1) After uniformly dispersing the fast ion conductor and graphene oxide N-methylpyrrolidone conductive liquid in an organic solvent, reacting at 100-200°C and 1-5 MPa for 1-6 hours, filtering, and vacuum drying to obtain coating material A; (2) implanting the coating material A onto the surface of artificial graphite by a particle injection method to obtain material B; (3) Adding a conductive polymer and a 1-10 wt% hydrochloric acid solution to the coupling agent solution, mixing them evenly, adding the material B, dispersing them evenly, adding an organic solvent to dilute them, spray drying, crushing, carbonizing, crushing, and classifying them to obtain the graphite composite material.

7. The preparation method according to claim 6, characterized in that In the step (1), the organic solvent is one of N-methylpyrrolidone, carbon tetrachloride, cyclohexane, xylene, and tetrahydrofuran; In the step (2), the step is carried out under an atmosphere of at least one of argon, oxygen, nitrogen and ammonia; In the step (3), the coupling agent is one of (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, (3-aminopropyl)dimethoxymethylsilane, (3-aminopropyl)diethoxymethylsilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-methylaminopropyltriethoxysilane; The conductive polymer is one of polyaniline, polythiophene and polypyrrole.

8. The preparation method according to claim 6, characterized in that In the step (1), the mass volume ratio of the fast ion conductor and the organic solvent is 100g:500-1000ml; In the step (2), the reaction is carried out under an atmosphere of oxygen or ammonia. In the step (3), the mass ratio of the coupling agent, the conductive polymer, and the material B is 0.5-2:1-10:

100.

9. The preparation method according to claim 6, characterized in that In the step (1), the mass fraction of graphene oxide in the graphene oxide N-methylpyrrolidone conductive liquid is 1-5wt%; In step (2), the gas flow rate is 10-100 sccm and the gas pressure is 2×10 -4 -5×10 -4 Pa, time 1-60min; In the step (3), the mass ratio of the solute to the organic solvent in the coupling agent solution is 1-5:100; The carbonization temperature is 800-1200℃ and the time is 1-6h.

10. A fast ion conductor coated graphite composite material, characterized in that: The graphite composite material is prepared by the preparation method described in any one of claims 6 to 9.

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