Antimony-based alloy negative electrode material and preparation method thereof, negative electrode sheet and lithium ion battery

Abstract

This application relates to the field of lithium-ion batteries and discloses a CoFe3Sb... 12 Alloy anode materials, their preparation methods, anode sheets, and lithium-ion batteries. The anode materials described in this application include CoFe3Sb. 12 Alloy, graphitized carbon coating layer and amorphous carbon coating layer; wherein the graphitized carbon coating layer coats one or more CoFe3Sb. 12 Alloy particles, wherein the amorphous carbon coating layer is coated with a graphitized carbon coating layer. In this application, suitable graphitized carbon materials are selected and coated onto CoFe3Sb using a vapor deposition method. 12 The surface is then coated with amorphous carbon, forming a double-layer coating structure that effectively prevents CoFe3Sb from being absorbed. 12 The cracking of the alloy improves its cycle performance, rate performance, and first charge / discharge performance, and further enhances its capacity and conductivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a CoFe3Sb 12 alloy negative electrode material, a preparation method thereof, a negative electrode sheet and a lithium ion battery. BACKGROUND

[0002] Lithium ion batteries have the advantages of high voltage, large energy density, good safety performance, etc., and are widely used. The research on the negative electrode materials thereof is becoming more and more active. Graphite and various carbon negative electrode materials taking graphite as a precursor have the disadvantages of large energy loss and poor high-rate charge-discharge performance, while the electrochemical mechanism of the multiphase compound of tin is that lithium ions and tin reversibly react to form Li x Sn, so that lithium ions can be reversibly extracted and embedded in the electrode; similarly, CoFe3Sb 12 alloy has high capacity and good electrical conductivity, and can also be used as a good negative electrode material.

[0003] Although the CoFe3Sb 12 alloy has the advantages of high capacity and good electrical conductivity as a negative electrode material, when lithium ions are embedded and extracted in the CoFe3Sb 12 alloy negative electrode material, dendrites will be formed, and the alloy molecules will be oxidized and cracked to form a passivation film, which affects the cycle performance, rate performance, electrical conductivity and the like. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a CoFe3Sb 12 alloy negative electrode material and a preparation method thereof, so that the negative electrode material can improve the cycle performance, rate performance, first charge-discharge performance and electrical conductivity;

[0005] Another purpose of the present application is to provide a negative electrode sheet and a lithium ion battery based on the above negative electrode material.

[0006] In order to solve the above technical problems / achieve the above purposes or at least partially solve the above technical problems / achieve the above purposes, as a first aspect of the present application, a CoFe3Sb 12 alloy negative electrode material is provided, which comprises CoFe3Sb 12 alloy, a graphitized carbon coating layer and an amorphous carbon coating layer; the graphitized carbon coating layer coats one or more CoFe3Sb 12 alloy particles, and the amorphous carbon coating layer coats the graphitized carbon coating layer.

[0007] Optionally, the mass percentage of the CoFe3Sb 12 alloy is 90-99%, and the mass percentage of the graphitized carbon coating layer and the amorphous carbon coating layer is 1-10%.

[0008] Optionally, the graphitized carbon coating layer comprises a graphitized carbon material, and the graphitized carbon material comprises one or more than two of mesocarbon microbeads (MCMB), carbon fiber and carbon nanotube.

[0009] Optionally, the amorphous carbon coating layer comprises an amorphous carbon material formed by a carbon source; further optionally, the carbon source comprises a gaseous carbon source and / or a solid carbon source, wherein the gaseous carbon source comprises one or more than two of C1-C4 alkane, C2-C4 alkene and C2-C4 alkyne.

[0010] Optionally, the gaseous carbon source further comprises borane or phosphine.

[0011] As a second aspect of the present application, a preparation method of the negative electrode material is provided, comprising:

[0012] CoFe3Sb 12 alloy as a matrix and a graphitized carbon material as a target material to perform atomic vapor deposition to obtain a CoFe3Sb 12 composite material coated with graphitized carbon;

[0013] carbonizing the CoFe3Sb 12 composite material coated with graphitized carbon at high temperature in a carbon source environment to form an amorphous carbon coating layer to obtain the negative electrode material.

[0014] As a third aspect of the present application, a negative electrode sheet is provided, taking the negative electrode material described in the present application as an active material.

[0015] As a fourth aspect of the present application, a lithium ion battery is provided, comprising a positive electrode sheet, a separator, an electrolyte and the negative electrode sheet described in the present application.

[0016] Compared with a conventional CoFe3Sb 12 alloy negative electrode material, the present application selects a suitable graphitized carbon material to coat the surface of CoFe3Sb 12 alloy by vapor deposition, and then coats the surface with amorphous carbon, so that the double-layer coating structure effectively prevents the cracking of CoFe3Sb 12 alloy, improves the cycle performance, rate performance, initial charge-discharge performance and the like, and further improves the capacity and conductivity of the alloy. BRIEF DESCRIPTION OF DRAWINGS

[0017] The drawings accompanying the specification of the present application serve to provide further understanding of the present application, and the schematic embodiments of the present application and the description thereof serve to explain the present application, and do not constitute an improper limitation on the present application;

[0018] Figure 1 The structure of the negative electrode material described in the present application is shown.

[0019] Figure 2 SEM image of the negative electrode material described in the present application is shown. DETAILED DESCRIPTION

[0020] The present application discloses a CoFe3Sb 12 alloy negative electrode material, a preparation method thereof, a negative electrode sheet and a lithium ion battery. Those skilled in the art can refer to the content herein and appropriately improve the process parameters for implementation. It is particularly pointed out that all similar substitutions and changes are obvious to those skilled in the art, and they are considered to be included in the present application. The products, processes and applications described in the present application have been described by the preferred embodiments, and the relevant personnel can obviously make changes or appropriate changes and combinations to the methods described herein without departing from the content, spirit and scope of the present application, to realize and apply the technology of the present application. Obviously, the described embodiments are 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 skilled in the art without creative labor are within the scope of protection of the present application.

[0021] It should be noted that in the present text, relational terms such as "first" and "second", "step 1" and "step 2", and "(1)" and "(2)" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or equipment including the element. Meanwhile, the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0022] In the first aspect of the present application, a CoFe3Sb 12 alloy negative electrode material is provided, which comprises CoFe3Sb 12 alloy, a graphitized carbon coating layer and an amorphous carbon coating layer; the graphitized carbon coating layer coats one or more CoFe3Sb 12 alloy particles, and the amorphous carbon coating layer coats the graphitized carbon coating layer; in some other embodiments of the present application, the negative electrode material has a granular structure with uniform size distribution and a particle size of 1-5 μm, and a structural schematic diagram thereof is shown inFigure 1 SEM images are shown in Figure 2 .

[0023] In some embodiments of the present application, the mass percentage of the CoFe3Sb 12 alloy is 90-99%, and can also be 94-97%, such as 94.1%, 95.1%, 96.1%, etc., and the mass percentage of the graphitized carbon coating layer and the amorphous carbon coating layer is 1-10%, and can also be 3-6%, such as 3.9%, 4.9%, 5.9%, etc.; in some other embodiments of the present application, the mass ratio of the amorphous carbon coating layer:graphitized carbon coating layer = 1:(1-2), such as 1:1, 1:1.5, 1:2, etc.

[0024] In some embodiments of the present application, the graphitized carbon coating layer comprises a graphitized carbon material, and the graphitized carbon material comprises one or more of mesocarbon microbeads, carbon fibers and carbon nanotubes.

[0025] In some embodiments of the present application, the amorphous carbon coating layer comprises an amorphous carbon material formed from a carbon source; in some other embodiments of the present application, the carbon source comprises a gaseous carbon source and / or a solid carbon source; in some other embodiments of the present application, the gaseous carbon source comprises one or more of C1-C4 alkanes, C2-C4 alkenes and C2-C4 alkynes, such as methane, ethane, acetylene, etc.; in some other embodiments of the present application, the gaseous carbon source further comprises boranes or phosphines, such as B2H6 or PH3; and the volume ratio of the carbon source to boranes or phosphines in the gaseous carbon source is 10:1-5, and can be selected from 10:1, 10:2, 10:3, 10:4 or 10:5.

[0026] In a second aspect of the present application, a preparation method of the negative electrode material is provided, comprising:

[0027] using the CoFe3Sb 12 alloy as a substrate and a graphitized carbon material as a target material to perform atomic vapor deposition, to obtain a graphitized carbon-coated CoFe3Sb 12 alloy material;

[0028] carbonizing the graphitized carbon-coated CoFe3Sb 12 alloy material in a carbon source environment at high temperature to form an amorphous carbon coating layer, to obtain the negative electrode material.

[0029] In some embodiments of the present application, less than 5 parts by weight of the graphitized carbon material and CoFe3Sb 12atomic vapor deposition; in some other embodiments of the present application, 2 parts by weight, 3 parts by weight or 4 parts by weight of graphitized carbon material and 98 parts by weight, 97 parts by weight or 96 parts by weight of CoFe3Sb 12 atomic vapor deposition.

[0030] In some embodiments of the present application, the atomic vapor deposition procedure can refer to the following:

[0031] ① Introducing graphitized carbon material;

[0032] ② Inert gas purging;

[0033] ③ Introducing oxygen source;

[0034] ④ Inert gas purging;

[0035] ⑤ Introducing water;

[0036] ⑥ Inert gas purging;

[0037] ⑦ Cycles from step ① until the requirement is reached;

[0038] The required time for each stage and the number of cycles are determined according to actual requirements, for example, 10-100 cycles; the inert gas can be selected from nitrogen, argon, etc.

[0039] In some other embodiments of the present application, the atomic vapor deposition procedure can refer to the following:

[0040] ① Introducing graphitized carbon material for 1s;

[0041] ② Nitrogen purging for 60s;

[0042] ③ Introducing oxygen source for 5s;

[0043] ④ Nitrogen purging for 5s;

[0044] ⑤ Introducing water for 0.05s;

[0045] ⑥ Nitrogen purging for 50s;

[0046] ⑦ Cycles from step ① for 10-100 times.

[0047] In some embodiments of this application, the carbon source environment is selected as a gaseous carbon source atmosphere, specifically including one or more of C1-C4 alkanes, C2-C4 alkenes, and C2-C4 alkynes, such as methane, ethane, and acetylene. In other embodiments of this application, the gaseous carbon source further includes borane or phosphine, such as B2H6 or PH3. The volume ratio of the carbon source to borane or phosphine in the gaseous carbon source is 10:1-5, specifically selected from 10:1, 10:2, 10:3, 10:4, or 10:5. In other embodiments of this application, the gas flow rate of the gaseous carbon source is 100-500 mL / min.

[0048] In some embodiments of this application, the high-temperature carbonization is a heat treatment at 800-1200℃ for 1-6 hours; in other embodiments of this application, the high-temperature carbonization is a heat treatment at 800-1200℃ for 1-6 hours with a heating rate of 1-10℃ / min.

[0049] In some embodiments of this application, a preparation process for the negative electrode material is provided, including:

[0050] S1: Graphitized carbon materials and CoFe3Sb 12 The alloys were ball-milled separately, with CoFe3Sb 12 Using graphitized carbon as the matrix and graphitized carbon as the target, atomic vapor deposition was performed according to the following procedure:

[0051] ① Graphitized carbon material for 1 second; ② Nitrogen purging for 60 seconds; ③ Introduce oxygen source for 5 seconds; ④ Nitrogen purging for 5 seconds; ⑤ Introduce water for 0.05 seconds; ⑥ Nitrogen purging for 50 seconds; ⑦ Cycle 10-100 times starting from step ①.

[0052] In CoFe3Sb 12 Graphitized carbon material was deposited on the substrate to obtain CoFe3Sb coated with graphitized carbon. 12 Composite materials;

[0053] S2: CoFe3Sb coated with graphitized carbon 12 The material is transferred to a carbon source gas atmosphere and heated to 800-1200℃ at a heating rate of 1-10℃ / min and held at that temperature for 1-6 hours to obtain the amorphous carbon / graphitized carbon-coated CoFe3Sb described in this application. 12 Alloy anode material.

[0054] In a third aspect of this application, a negative electrode sheet is provided, using the negative electrode material described in this application as the active material.

[0055] In some embodiments of this application, the negative electrode sheet includes a current collector and an active material coated on the current collector; wherein, the current collector may be selected from a metal foil with good conductivity, such as copper foil or aluminum foil; the active material includes the negative electrode material described in this application, as well as a binder, a conductive agent and a solvent, wherein the binder, conductive agent and solvent and their amounts are selected in accordance with conventional methods, and this application does not impose specific limitations.

[0056] In a fourth aspect of this application, a lithium-ion battery is provided, comprising a positive electrode, a separator, an electrolyte, and the negative electrode described in this application; in some embodiments of this application, the lithium-ion battery is a pouch cell or a button cell.

[0057] In some embodiments of this application, the positive electrode uses a ternary material as the active material, such as LiNi. 1 / 3Co 1 / 3 Mn 1 / 3 O2; the diaphragm is a Celegard series diaphragm, such as Celegard 2400; the electrolyte is a LiPF6 solution, such as an electrolyte with a volume ratio of 1:1 of ethylene carbonate (EC) and diethyl carbonate (DEC) as solvents and a LiPF6 concentration of 1.0-1.5 mol / L.

[0058] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials remain consistent to ensure comparability. Furthermore, all materials used in this application are commercially available.

[0059] The following describes a CoFe3Sb provided in this application. 12 The alloy anode material, its preparation method, anode sheet, and lithium-ion battery are further explained.

[0060] Example 1:

[0061] S1: Place 3g of mesophase carbon microspheres (MCMB) in a ball mill and ball mill at 300 rpm for 1 hour, along with 97g of CoFe3Sb. 12 CoFe3Sb was ball-milled at 1000 rpm for 2 hours using atomic vapor deposition. 12 The material was transferred to a vacuum chamber and used as a substrate, with MCMB as the target. The following parameters were applied: (① MCMB material for 1 second; ② Nitrogen purging for 60 seconds; ③ Oxygen source introduction for 5 seconds; ④ Nitrogen purging for 5 seconds; ⑤ Water introduction for 0.05 seconds; ⑥ Nitrogen purging for 50 seconds; ⑦ 60 cycles starting from step ①) to target CoFe3Sb. 12 MCMB was deposited on the substrate to obtain MCMB-coated CoFe3Sb. 12 Composite materials;

[0062] S2: CoFe3Sb coated with MCMB 12 transferred into a tube furnace, and argon gas was introduced to remove air in the tube, then methane mixed gas (volume ratio, methane:PH3=10:4, flow rate 300 ml / min) was introduced, and heated to 1000°C at a heating rate of 10°C / min and kept for 2h, to obtain amorphous carbon / MCMB coated CoFe3Sb 12 alloy negative electrode material (amorphous carbon coating layer: MCMB coating layer: CoFe3Sb 12 alloy = 1:1.5:48.5).

[0063] Example 2:

[0064] S1: 4g carbon fiber material was placed in a ball mill at 400rpm for 1 hour, 96g CoFe3Sb 12 CoFe3Sb was coated with carbon fiber by atomic vapor deposition method at 900rpm for 2.5 hours 12 transferred into a vacuum chamber and used as a substrate, and carbon fiber was used as a target material, and carbon fiber was deposited on the CoFe3Sb 12 substrate according to the following parameters (① carbon fiber material for 1 second; ② nitrogen gas purging for 60 seconds; ③ oxygen source for 5 seconds; ④ nitrogen gas purging for 5 seconds; ⑤ water for 0.05 seconds; ⑥ nitrogen gas purging for 50 seconds; ⑦ 80 cycles from step ①), to obtain carbon fiber coated CoFe3Sb 12 composite material;

[0065] S2: CoFe3Sb coated with carbon fiber 12 transferred into a tube furnace, and argon gas was introduced to remove air in the tube, then ethane mixed gas (volume ratio, ethane:B2H6=10:2, flow rate 200 ml / min) was introduced, and heated to 800°C at a heating rate of 7°C / min and kept for 3h, to obtain amorphous carbon / carbon fiber coated CoFe3Sb 12 alloy negative electrode material (amorphous carbon coating layer: carbon fiber coating layer: CoFe3Sb 12 alloy = 1:2:48).

[0066] Example 3:

[0067] S1: 2g carbon nanotube was placed in a ball mill at 500rpm for 1.5 hours, 98g CoFe3Sb 12 CoFe3Sb was coated with carbon nanotube by atomic vapor deposition method at 1100rpm for 1.5 hours 12The CoFe3Sb alloy was transferred into a vacuum chamber and used as a substrate, and carbon nanotubes were used as a target material. The carbon nanotubes were deposited on the CoFe3Sb alloy substrate according to the following parameters: (1) carbon nanotubes for 1 second; (2) nitrogen purge for 60 seconds; (3) introduction of oxygen source for 5 seconds; (4) nitrogen purge for 5 seconds; (5) introduction of water for 0.05 seconds; (6) nitrogen purge for 50 seconds; and (7) cycle 55 times from step (1). 12 The carbon nanotubes were deposited on the CoFe3Sb alloy substrate to obtain a carbon nanotube-coated CoFe3Sb alloy composite material. 12 The carbon nanotubes were deposited on the CoFe3Sb alloy substrate to obtain a carbon nanotube-coated CoFe3Sb alloy composite material.

[0068] S2: The carbon nanotubes were deposited on the CoFe3Sb alloy substrate to obtain a carbon nanotube-coated CoFe3Sb alloy composite material. 12 The CoFe3Sb alloy was transferred into a tube furnace and purged with helium gas to remove air in the tube. Then, acetylene mixed gas (volume ratio, acetylene:PH3=10:4, flow rate 200 ml / min) was introduced, and the temperature was raised to 800°C at a rate of 8°C / min and maintained for 2.5 hours to obtain an amorphous carbon / carbon nanotube-coated CoFe3Sb alloy negative electrode material. 12 The CoFe3Sb alloy was transferred into a tube furnace and purged with helium gas to remove air in the tube. Then, acetylene mixed gas (volume ratio, acetylene:PH3=10:4, flow rate 200 ml / min) was introduced, and the temperature was raised to 800°C at a rate of 8°C / min and maintained for 2.5 hours to obtain an amorphous carbon / carbon nanotube-coated CoFe3Sb alloy negative electrode material. 12 The CoFe3Sb alloy was transferred into a tube furnace and purged with helium gas to remove air in the tube. Then, acetylene mixed gas (volume ratio, acetylene:PH3=10:4, flow rate 200 ml / min) was introduced, and the temperature was raised to 800°C at a rate of 8°C / min and maintained for 2.5 hours to obtain an amorphous carbon / carbon nanotube-coated CoFe3Sb alloy negative electrode material.

[0069] Comparative Example 1:

[0070] The CoFe3Sb alloy was transferred into a tube furnace and purged with helium gas to remove air in the tube. Then, acetylene mixed gas (volume ratio, acetylene:PH3=10:4, flow rate 200 ml / min) was introduced, and the temperature was raised to 800°C at a rate of 8°C / min and maintained for 2.5 hours to obtain an amorphous carbon / carbon nanotube-coated CoFe3Sb alloy negative electrode material. 12 The CoFe3Sb alloy was transferred into a tube furnace and purged with helium gas to remove air in the tube. Then, acetylene mixed gas (volume ratio, acetylene:PH3=10:4, flow rate 200 ml / min) was introduced, and the temperature was raised to 800°C at a rate of 8°C / min and maintained for 2.5 hours to obtain an amorphous carbon / carbon nanotube-coated CoFe3Sb alloy negative electrode material. 12 The CoFe3Sb alloy was transferred into a tube furnace and purged with helium gas to remove air in the tube. Then, acetylene mixed gas (volume ratio, acetylene:PH3=10:4, flow rate 200 ml / min) was introduced, and the temperature was raised to 800°C at a rate of 8°C / min and maintained for 2.5 hours to obtain an amorphous carbon / carbon nanotube-coated CoFe3Sb alloy negative electrode material.

[0071] Comparative Example 2:

[0072] S1: 3g of artificial graphite material was placed in a ball mill and ball milled at 300 revolutions / min for 1 hour, and 97g of CoFe3Sb alloy was ball milled at 1000 revolutions / min for 2 hours. 12 S1: 3g of artificial graphite material was placed in a ball mill and ball milled at 300 revolutions / min for 1 hour, and 97g of CoFe3Sb alloy was ball milled at 1000 revolutions / min for 2 hours. 12 The CoFe3Sb alloy was transferred into a tube furnace and purged with helium gas to remove air in the tube. Then, acetylene mixed gas (volume ratio, acetylene:PH3=10:4, flow rate 200 ml / min) was introduced, and the temperature was raised to 800°C at a rate of 8°C / min and maintained for 2.5 hours to obtain an amorphous carbon / carbon nanotube-coated CoFe3Sb alloy negative electrode material. 12 The CoFe3Sb alloy was transferred into a tube furnace and purged with helium gas to remove air in the tube. Then, acetylene mixed gas (volume ratio, acetylene:PH3=10:4, flow rate 200 ml / min) was introduced, and the temperature was raised to 800°C at a rate of 8°C / min and maintained for 2.5 hours to obtain an amorphous carbon / carbon nanotube-coated CoFe3Sb alloy negative electrode material. 12 The CoFe3Sb alloy was transferred into a tube furnace and purged with helium gas to remove air in the tube. Then, acetylene mixed gas (volume ratio, acetylene:PH3=10:4, flow rate 200 ml / min) was introduced, and the temperature was raised to 800°C at a rate of 8°C / min and maintained for 2.5 hours to obtain an amorphous carbon / carbon nanotube-coated CoFe3Sb alloy negative electrode material.

[0073] S2: The carbon nanotubes were deposited on the CoFe3Sb alloy substrate to obtain a carbon nanotube-coated CoFe3Sb alloy composite material. 12The MCMB-coated CoFe3Sb prepared in S1 of Example 1 is transferred into a tube furnace, and xenon inert gas is introduced to remove air in the tube, followed by introduction of a methane mixed gas (volume ratio, methane:PH3=10:4, flow rate 300 ml / min), and heated to 1000℃ at a heating rate of 10℃ / min and kept for 2h to obtain amorphous carbon / MCMB-coated CoFe3Sb alloy negative electrode material. 12 MCMB-coated CoFe3Sb alloy negative electrode material (amorphous carbon coating layer: MCMB coating layer: CoFe3Sb alloy=1:1:48.5). 12 MCMB-coated CoFe3Sb alloy=1:1:48.5).

[0074] Comparative Example 3:

[0075] S1: 3g of mesocarbon microbead (MCMB) material is placed in a ball mill for ball milling at 300r / min for 1h, 97g of silicon nanoparticles is deposited on the silicon nanoparticle substrate by atomic vapor deposition method, the silicon nanoparticles are transferred into a vacuum chamber and used as a substrate, and the MCMB is used as a target material, and the MCMB is deposited on the silicon nanoparticle substrate according to the following parameters (①MCMB material for 1s; ②nitrogen purging for 60s; ③introduction of oxygen source for 5s; ④nitrogen purging for 5s; ⑤introduction of water for 0.05s; ⑥nitrogen purging for 50s; ⑦recycle from step ① for 60 cycles) to obtain MCMB-coated silicon nanoparticle composite material;

[0076] S2: The MCMB-coated silicon nanoparticle is transferred into a tube furnace, and xenon inert gas is introduced to remove air in the tube, followed by introduction of a methane mixed gas (volume ratio, methane:PH3=10:4, flow rate 300 ml / min), and heated to 1000℃ at a heating rate of 10℃ / min and kept for 2h to obtain amorphous carbon / MCMB-coated silicon nanoparticle negative electrode material.

[0077] Comparative Example 4:

[0078] The MCMB-coated CoFe3Sb prepared in S1 of Example 1 is transferred into a tube furnace, and xenon inert gas is introduced to remove air in the tube, followed by introduction of a methane mixed gas (volume ratio, methane:PH3=10:4, flow rate 300 ml / min), and heated to 1000℃ at a heating rate of 10℃ / min and kept for 2h to obtain amorphous carbon / MCMB-coated CoFe3Sb alloy negative electrode material. 12 The composite material is directly used as a negative electrode material.

[0079] Experimental Example 1:

[0080] 1.1, SEM test

[0081] The alloy negative electrode material prepared in Example 1 is subjected to SEM test, and the test results are shown in FIG. 1. Figure 2 As can be seen from the figure, the alloy negative electrode material presents a granular structure with uniform size distribution, and the particle size is between (1-5) μm.

[0082] 1.2, Powder physical and chemical property test

[0083] The tap density, specific surface area, and specific capacity of each negative electrode material prepared in Examples 1-3 and Comparative Examples 1-4 were tested. According to GB / T 24533-2019 “Graphite-based negative electrode material for lithium ion batteries”. The test results are shown in Table 1.

[0084] Table 1 Physical and chemical properties of negative electrode materials in examples and comparative examples

[0085] Item Conductivity (S / cm) Tap density (g / cm3) 3 )]]> Specific surface area (m 2 / g) Example 1 20.64 2.87 1.91 Example 2 20.36 2.84 1.84 Example 3 20.22 2.81 1.82 Comparative Example 1 19.53 2.74 1.23 Comparative Example 2 19.42 2.76 1.47 Comparative Example 3 19.88 1.84 2.14 Comparative Example 4 19.31 2.83 1.85

[0086] As can be seen from Table 1, the electrical conductivity and tap density of the alloy negative electrode material prepared in Examples 1-3 of the present application are slightly improved compared to the comparative examples. This shows that the two-layer coating material of the present application has little effect on the electrical conductivity, and the densities of the two are quite different from the alloy, so the tap density is not much affected. The graphitized carbon material shows a corresponding improvement for the alloy negative electrode material, which can be seen from Comparative Example 4, whose tap density is comparable to the present application. The tap density of Comparative Example 3 is quite different from that of the other groups, which may be due to the difference in density between silicon and alloy.

[0087] 1.3, first charge-discharge performance test

[0088] The negative electrode materials in Examples 1-3 and Comparative Examples 1-4 were assembled into button cells, respectively. The assembly method was as follows: a binder, a conductive agent and a solvent (consistent for each group) were added to the negative electrode material, stirred to make a slurry, coated on a copper foil, and then dried and rolled to obtain a negative electrode sheet. The assembly of the button cell was carried out in a hydrogen-filled glove box, and the electrochemical performance test was carried out on a Wuhan LanDian CT2001A battery tester. The charge-discharge voltage range was 0.005V to 2.0V, and the charge-discharge rate was 0.1C. The test results are shown in Table 2.

[0089] Table 2 Comparison of first charge-discharge performance of examples and comparative examples

[0090]

[0091] As can be seen from Table 2, the first discharge capacity and first charge-discharge efficiency of the lithium ion battery using the negative electrode material obtained in Examples 1-3 are significantly higher than those of the comparative examples. The double coating of amorphous carbon and graphitized carbon can reduce the generation of side reactions and prevent the oxidation of alloy particles, thereby reducing the irreversible capacity and improving the first efficiency.

[0092] 1.4, cycle performance and rate performance test

[0093] The negative electrode materials in Examples 1-3 and Comparative Examples 1-4 were used to prepare negative electrode sheets. The negative electrode sheets were assembled into lithium ion batteries with ternary materials (LiNi 1 / 3Co 1 / 3 Mn 1 / 3O2) is a positive electrode, LiPF6 solution (solvent is EC+DEC, volume ratio 1:1, LiPF6 concentration 1.3 mol / L) is an electrolyte, and celegard2400 is a separator, to prepare a 5 Ah soft package battery. Then, the cycle performance and rate performance of the soft package battery are tested.

[0094] The cycle performance test conditions are: charge-discharge current 1C / 1C, voltage range 2.8-4.2 V, cycle number 500 times, and the test results are shown in Table 3.

[0095] The rate performance test conditions are: charge rate 1C / 3C / 5C / 8C, discharge rate 1C; voltage range: 2.8-4.2 V, and the test results are shown in Table 4.

[0096] Table 3: Comparison of cycle performance of examples and comparative examples

[0097]

[0098]

[0099] As can be seen from Table 3, the cycle performance of the soft package battery prepared from the alloy negative electrode material of the application is better than that of the comparative examples. The reason is that, in terms of 1C / 1C rate cycle performance, the double-coating of the outer layer of the alloy negative electrode material can form a stable structure of the negative electrode material, reduce the formation of dendrites during lithium ion intercalation and deintercalation, and reduce impedance to improve cycle performance.

[0100] Table 4: Comparison of rate performance of examples and comparative examples

[0101]

[0102] As can be seen from Table 4, the soft package battery prepared from the alloy negative electrode material of Examples 1-3 of the application has better constant current ratio, i.e., the charge time of the soft package battery of Examples 1-3 is better.

[0103] The above description is merely a specific implementation of the application, which enables those skilled in the art to understand or implement the application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A CoFe3Sb 12 alloy negative material characterized by, CoFe3Sb 12 alloy, graphitized carbon coating layer and amorphous carbon coating layer, the CoFe3Sb 12 alloy is 90-99%, the mass percentage of the graphitized carbon coating layer and the amorphous carbon coating layer is 1-10%, the mass ratio of the amorphous carbon coating layer to the graphitized carbon coating layer is 1:(1-2); the graphitized carbon coating layer coats one or more than two CoFe3Sb 12 alloy particles, the amorphous carbon coating layer coats the graphitized carbon coating layer; the graphitized carbon coating layer comprises a graphitized carbon material, the graphitized carbon material comprises one or more than two of mesocarbon microbeads, carbon fibers and carbon nanotubes; the amorphous carbon coating layer comprises an amorphous carbon material formed by a gaseous carbon source, the gaseous carbon source comprises one or more than two of C1-C4 alkane, C2-C4 alkene and C2-C4 alkyne, and borane or phosphine; The negative electrode material is prepared according to the following preparation method: CoFe3Sb 12 CoFe3Sb 12 composite The graphitized carbon-coated CoFe3Sb is prepared in a gaseous carbon source environment 12 The composite is carbonized at high temperature to form an amorphous carbon coating layer, and the negative electrode material is obtained.

2. The method for preparing the negative electrode material according to claim 1, characterized in that, Comprise: CoFe3Sb 12 CoFe3Sb 12 composite The graphitized carbon-coated CoFe3Sb is prepared in a gaseous carbon source environment 12 The composite is carbonized at high temperature to form an amorphous carbon coating layer, and the negative electrode material is obtained.

3. A negative electrode sheet characterized by comprising: The negative electrode material of claim 1 is used as an active material.

4. A lithium-ion battery, characterized by, Comprise a positive electrode sheet, a separator, an electrolyte and the negative electrode sheet of claim 3.

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