Preparation method and application of tellurium-containing graphite negative electrode material

Abstract

The invention belongs to the technical field of battery materials, and particularly relates to a preparation method and application of a tellurium-containing graphite negative electrode material. The preparation method comprises the following steps: mixing tellurium and graphite to obtain a mixed material, then adding a solid electrolyte, a conductive agent and a binder, mixing and forming to obtain the tellurium-containing graphite negative electrode material, the graphite does not include natural graphite. According to the preparation method disclosed by the invention, graphite and tellurium are mixed, relatively high specific capacity can be obtained and applied to a solid-state battery, tellurium and lithium can form a lithium-tellurium alloy, and the lithium conductivity of the negative electrode is improved, so that high-rate charging and discharging of the graphite negative electrode are realized, and the rate capability of the battery is improved. The voltage platform of the lithium telluride is high, so that the solid-state battery can keep stable voltage in the using process, and the stability and the safety of the battery are improved. Tellurium has certain lithium storage capacity, the short circuit problem is reduced, and the cycle life of the battery is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of battery materials, and in particular relates to a preparation method and application of a tellurium-containing graphite negative electrode material. Background Art

[0002] Traditional lithium-ion batteries use organic electrolytes. In abnormal situations such as overcharging and internal short circuits, the battery is prone to heat up, causing the electrolyte to swell, decompose, spontaneously combust, or even explode, posing serious safety hazards. All-solid-state batteries use solid electrolytes, which are non-volatile and leak-proof, greatly improving the safety performance of the battery, and therefore have received widespread attention. Currently, there are three types of all-solid-state battery electrolytes being studied: oxide electrolytes, polymer electrolytes, and sulfide electrolytes. Sulfide electrolytes have higher ionic conductivity than oxide and polymer electrolytes, reaching 10-3S / cm at room temperature, making them ideal solid-state battery electrolyte materials.

[0003] In addition, in the existing solid-state batteries, lithium deposition occurs on the negative electrode side during the lithiation process, and the growth of lithium dendrites causes internal short circuits in the battery, causing safety issues.

[0004] Graphite anode materials are the mainstream anode materials for lithium-ion batteries due to their good cycle stability, low price, wide source, and non-toxicity. Therefore, most sulfide solid-state battery research also uses graphite anodes, but graphite anodes also face many challenges, such as low theoretical capacity and poor rate performance.

[0005] Therefore, there is an urgent need to provide a graphite negative electrode with improved specific capacity and rate performance. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a preparation method and application of a tellurium-containing graphite negative electrode material. The graphite negative electrode material prepared by the preparation method of the present invention has high specific capacity and good rate performance.

[0007] The present invention provides a method for preparing a tellurium-containing graphite negative electrode material, wherein tellurium is mixed with graphite, and a solid electrolyte, a conductive agent and a binder are further added to obtain a graphite negative electrode material. Tellurium has a relatively high specific capacity and a certain lithium storage capacity, which can provide space for lithium deposition, reduce the growth of lithium dendrites during the deposition process, and ensure the safety of the battery; in addition, it can effectively increase the discharge specific capacity of the graphite negative electrode and improve the rate performance of the graphite negative electrode. This is of great significance for sulfide solid-state batteries to achieve high rate performance and improve safety.

[0008] A first aspect of the present invention provides a method for preparing a tellurium-containing graphite negative electrode material.

[0009] Specifically, a method for preparing a tellurium-containing graphite negative electrode material comprises the following steps:

[0010] Mixing tellurium and graphite to obtain a mixed material, then adding a solid electrolyte, a conductive agent and a binder, and mixing to obtain the tellurium-containing graphite negative electrode material;

[0011] The graphite does not include natural graphite.

[0012] Preferably, the tellurium is tellurium powder.

[0013] Preferably, the tellurium and graphite are mixed by ball milling.

[0014] Preferably, the ball mill is used for 10-30 hours, more preferably 20-25 hours.

[0015] Preferably, the rotation speed during ball milling is 200-600 rpm, more preferably 200-500 rpm.

[0016] Preferably, the solid electrolyte is a sulfide solid electrolyte, such as Li6PS5Cl.

[0017] Preferably, the conductive agent can be a conventional conductive agent, such as conductive carbon black SP, acetylene black, Ketjen black, conductive graphite, carbon fiber (VGCF) or carbon nanotubes.

[0018] Preferably, the binder can be a conventional binder, preferably a fluorine-based polymer and / or a synthetic rubber, more preferably one or a combination of at least two of polyvinyl fluoride, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, styrene butadiene rubber (SBR), fluorine-based rubber or ethylene propylene diene rubber.

[0019] Preferably, the conductive agent is selected from at least one of conductive carbon black SP, acetylene black, Ketjen black, conductive graphite, carbon fiber or carbon nanotube.

[0020] Preferably, the binder is selected from at least one of polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, fluorine-based rubber or ethylene propylene diene rubber.

[0021] Preferably, the graphite is artificial graphite, which is dried before use.

[0022] Preferably, the mass purity of the tellurium powder is >99.9%, and the particle size is 100-200 mesh.

[0023] Preferably, the mass ratio of graphite to tellurium is (6-9):(1-4), and more preferably (7-8):(2-3).

[0024] Preferably, the mass ratio of the mixed material, solid electrolyte, conductive agent and binder is (50-70): (30-50): (0.5-1.5): 1, and more preferably (55-60): (40-45): 1: 1.

[0025] Preferably, after the graphite negative electrode material is prepared, forming and shearing treatments are also included.

[0026] Preferably, the forming is performed by roll forming under heating conditions, for example, the heating temperature is 50-60°C.

[0027] A second aspect of the present invention provides a graphite negative electrode material.

[0028] Specifically, a graphite negative electrode material is prepared by the above preparation method.

[0029] A second aspect of the present invention provides an application of a graphite negative electrode material.

[0030] A solid-state battery comprises the above-mentioned graphite negative electrode material, or the graphite negative electrode material prepared by the above-mentioned preparation method.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The preparation method of the present invention mixes graphite with tellurium (Te) to obtain a higher specific capacity. When applied to solid-state batteries, tellurium (Te) can form a lithium-tellurium alloy with lithium, which increases the lithium conductivity of the negative electrode, thereby achieving high-rate charge and discharge of the graphite negative electrode and improving the rate performance of the battery. The voltage platform of lithium telluride is relatively high, which can enable the solid-state battery to maintain a relatively stable voltage during use, thereby improving the stability and safety of the battery. Tellurium (Te) has a certain lithium storage capacity, reduces short-circuit problems, and increases the cycle life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The cycle performance diagram of the battery assembled with the graphite negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0034] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0035] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0036] The tellurium powder used in the following examples has a mass purity of >99.9% and a particle size of 200 meshes.

[0037] Artificial graphite particles are uniform in size, with a particle size of D 50 =20μm, moisture content is less than 100ppm.

[0038] Example 1

[0039] A method for preparing a tellurium-containing graphite negative electrode material comprises the following steps:

[0040] (1) placing artificial graphite and tellurium powder in a ball mill at a mass ratio of 7:3 and milling for 20 hours at a speed of 500 rpm to obtain a mixed material;

[0041] (2) Take the mixed material prepared in step (1), add solid electrolyte Li6PS5Cl and conductive agent VGCF and mix for 2 hours, then add polytetrafluoroethylene (PTFE) for grinding, wherein the mass ratio of the mixed material, solid electrolyte Li6PS5Cl, conductive agent VGCF and polytetrafluoroethylene is 60:40:1:1, and a uniform graphite negative electrode material is obtained. The prepared graphite negative electrode material is roll-formed under heating conditions of 50°C, and then cut into small discs with a diameter of 8 mm for standby use.

[0042] Example 2

[0043] A method for preparing a tellurium-containing graphite negative electrode material comprises the following steps:

[0044] (1) placing artificial graphite and tellurium powder in a ball mill at a mass ratio of 8:2 and milling for 20 hours at a speed of 500 rpm to obtain a mixed material;

[0045] (2) Take the mixed material prepared in step (1), add solid electrolyte Li6PS5Cl and conductive agent VGCF and mix for 2 hours, then add polytetrafluoroethylene (PTFE) for grinding, wherein the mass ratio of the mixed material, solid electrolyte Li6PS5Cl, conductive agent VGCF and polytetrafluoroethylene is 60:40:1:1, and a uniform graphite negative electrode material is obtained. The prepared graphite negative electrode material is roll-formed under heating conditions of 50°C, and then cut into small discs with a diameter of 8 mm for standby use.

[0046] Example 3

[0047] A method for preparing a tellurium-containing graphite negative electrode material comprises the following steps:

[0048] (1) placing artificial graphite and tellurium powder in a ball mill at a mass ratio of 7:3 and milling for 10 h at a speed of 400 rpm to obtain a mixed material;

[0049] (2) Take the mixed material prepared in step (1), add solid electrolyte Li6PS5Cl and conductive agent VGCF and mix for 2 hours, then add polytetrafluoroethylene (PTFE) for grinding, wherein the mass ratio of the mixed material, solid electrolyte Li6PS5Cl, conductive agent VGCF and polytetrafluoroethylene is 60:40:1:1, and a uniform graphite negative electrode material is obtained. The prepared graphite negative electrode material is roll-formed under heating conditions of 50°C, and then cut into small discs with a diameter of 8 mm for standby use.

[0050] Comparative Example 1

[0051] Compared with Example 1, the difference of Comparative Example 1 is that tellurium powder is replaced with germanium telluride powder, and the other processes are the same as Example 1.

[0052] Comparative Example 2

[0053] Compared with Example 1, no tellurium powder is added in Comparative Example 2, and the other processes are the same as those in Example 1.

[0054] Comparative Example 3

[0055] Compared with Example 1, the difference of Comparative Example 3 is that the artificial graphite is replaced by natural graphite, and the other processes are the same as those of Example 1.

[0056] Performance Testing:

[0057] In an argon atmosphere, the graphite negative electrode materials prepared in the above embodiments and comparative examples were placed in a mold, sulfide electrolyte Li6PS5Cl was added, and Li-In alloy was used as the counter electrode. The solid-state battery was pressed at a pressure of 4T and packaged into a button battery with a CR2025 battery shell, and the battery was tested. The test method is: at 60°C, the voltage range is -0.62V-1.5V, and the rate performance of the battery is tested at 0.05C / 0.1C / 0.2C / 0.3C / 0.4C / 0.5C / 1C / 2C cycles.

[0058] The discharge specific capacity and 1C rate performance of the test battery are shown in Table 1 for detailed test data.

[0059] The battery cycle performance test method is: cycle test the battery rate performance at 60°C. The results are as follows Figure 1 shown.

[0060] Table 1: Electrochemical performance test results of the corresponding batteries of Examples 1-3 and Comparative Example 1

[0061]

[0062] It can be seen from Table 1 that Example 1 is the best solution. The amount of tellurium powder added has a significant effect on the discharge capacity of the battery. The mixing time of graphite and tellurium powder may affect the mixing uniformity, thereby affecting the rate performance of the battery. It can also be seen from Table 1 that replacing graphite with natural graphite or replacing tellurium powder with germanium telluride cannot achieve the experimental effect of Example 1.

[0063] Natural graphite is generally layered graphite with different particle sizes, many surface defects, serious side reactions, and high moisture content. It may be unevenly mixed with tellurium powder, so the performance is poor. The artificial graphite particles used in the present invention are uniform in size and have a particle size of D 50 =20μm, and the moisture content is less than 100ppm. Therefore, when applied in the technical solution of the present invention, the effect is outstanding.

[0064] Figure 1 The cycle performance diagram of the battery assembled with the graphite negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention. Figure 1 It can be seen that the batteries corresponding to Examples 1-3 have better cycle performance.

Claims

1. A method for preparing a graphite negative electrode material, characterized in that: The following steps are involved: Mixing tellurium and graphite to obtain a mixed material, then adding a solid electrolyte, a conductive agent and a binder, and mixing to obtain the tellurium-containing graphite negative electrode material; The graphite does not include natural graphite.

2. The preparation method according to claim 1, characterized in that: The tellurium is tellurium powder, the mass purity of the tellurium powder is greater than 99.9%, and the particle size is 100-200 meshes; and / or, the tellurium and graphite are mixed by ball milling.

3. The preparation method according to claim 1, characterized in that: The solid electrolyte is a sulfide solid electrolyte.

4. The preparation method according to claim 1, characterized in that: The conductive agent is selected from at least one of conductive carbon black SP, acetylene black, Ketjen black, conductive graphite, carbon fiber or carbon nanotube.

5. The preparation method according to claim 1, characterized in that: The binder is selected from at least one of polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, fluorine-based rubber or ethylene-propylene-diene rubber.

6. The preparation method according to claim 1, characterized in that: The graphite is artificial graphite.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The mass ratio of graphite to tellurium is (6-9):(1-4).

8. The preparation method according to any one of claims 1 to 6, characterized in that: The mass ratio of the mixed material, the solid electrolyte, the conductive agent and the binder is (50-70):(30-50):(0.5-1.5):

1.

9. A graphite negative electrode material, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. A solid-state battery, characterized in that: The invention comprises the graphite negative electrode material according to claim 9, or the graphite negative electrode material prepared by the preparation method according to any one of claims 1 to 8.

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