Preparation method of high-performance oxygen-controlled silicon-based negative electrode material as well as product and application thereof

Abstract

The invention relates to the technical field of silicon composite materials, in particular to a preparation method of a high-performance oxygen-controlled silicon-based negative electrode material as well as a product and application of the high-performance oxygen-controlled silicon-based negative electrode material. Comprising the following steps: S1, mixing silicon with surface-heavy-oxidized silicon particles, adding ball milling auxiliary materials, and putting into a high-energy ball mill for ball milling; s2, putting the ball-milled powder into a tubular furnace, and performing high-temperature calcination in an anoxic environment; and S3, the cooled material is taken out and sieved. Compared with the prior art, the prepared SiOx negative electrode material is high in silicon content, the silicon oxide layer wrapped outside the SiOx negative electrode material inhibits volume deformation of silicon in electrochemical reaction, negative electrode damage is avoided, and the material performance is more stable; the obtained SiOx material has the characteristics of high specific capacity and high initial coulombic efficiency (gt, 76%), has great application prospects, and is suitable for industrial production of high-capacity lithium batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon composite materials, and in particular to a preparation method of a high-performance oxygen-controlled silicon-based negative electrode material, and a product and application thereof. Background Art

[0002] In recent years, the country has encouraged the development of battery negative electrode materials with a specific capacity ≥ 500mAh / g. The specific capacity of lithium-ion batteries is determined by the specific capacity of the positive electrode and the specific capacity of the negative electrode, and the larger the specific capacity of the negative electrode, the better. The specific capacity of traditional graphite negative electrode products is around 350-370mAh / g, which has basically reached the theoretical limit. Silicon negative electrode is considered to be the most promising next-generation negative electrode material. The theoretical specific capacity of silicon can reach up to 4200mAh / g, and it has the advantages of low working potential (lithium insertion potential is about 0.5 V vs. Li / Li+), rich reserves (silicon is the second most abundant element in the earth's crust), etc., and has significant application advantages.

[0003] However, silicon will expand by 300% in volume during the charge and discharge process, which can easily cause the formation of a solid interface SEI film between the negative electrode and the electrolyte, Si pulverization, and loss of electrical contact, resulting in rapid capacity decay of the negative electrode, low initial coulombic efficiency and cycle life. When silicon is partially oxidized, byproducts such as lithium oxide and lithium silicate will be produced on the surface of the negative electrode during the electrochemical lithium storage process, which can buffer the large volume changes caused by the direct alloying of lithium and silicon, thereby improving the stability of the negative electrode. Its theoretical specific capacity is in the range of 1400-4000mAh / g, which has significant advantages. When the oxygen content is high and there are many defects, silicon dioxide is easily produced. Although it can also carry lithium ions, the irreversible lithium ion loss of silicon dioxide in the first cycle is large, so the first efficiency will be relatively low. In addition, silicon dioxide has poor conductivity, and the electrochemical impedance of the negative electrode will increase, which is not conducive to the transmission and diffusion of ions. While reducing the specific capacity of the negative electrode, it also reduces the rate characteristics of the battery.

[0004] At present, in order to improve the stability of silicon-based negative electrodes, a Chinese invention patent with application number CN202210942076.0 discloses a high-performance silicon-oxygen negative electrode material, a preparation method and application thereof, and a Chinese invention patent with application number CN202210959559.1 discloses a silicon-oxygen negative electrode material, a preparation method and application thereof, and proposes to prepare silicon-oxygen compounds by liquid phase exfoliation, chemical vapor deposition and other methods. However, the liquid phase exfoliation method requires the use of organic solutions, which is not environmentally friendly, and has low preparation efficiency and is prone to agglomeration. Most chemical vapor deposition methods use flammable and explosive gases such as silane, which are costly, slow to prepare, and have poor thermal stability. They cannot be mass-produced and are difficult to directly apply to actual production. Based on the deficiencies of the above-mentioned technologies, the present invention proposes a preparation method for a high-performance oxygen-controlled silicon-based negative electrode material, its products and applications. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a method for preparing a high-performance oxygen-controlled silicon-based negative electrode material, a product thereof and an application thereof, and the obtained oxygen-controlled silicon-based negative electrode material has a quantitative oxygen content and is a silicon-oxygen composite material with high specific capacity and high stability. While ensuring that the silicon content in the material is large enough to ensure the high specific capacity of the lithium battery, the silicon material is wrapped with silicon oxide that is not easily deformed to alleviate the volume deformation of silicon in the electrochemical reaction, and the thickness of the oxide layer can be changed by regulating the oxygen content in SiOx.

[0006] To achieve the above purpose, a method for preparing a high-performance oxygen-controlled silicon-based negative electrode material is designed, comprising the following steps: S1, mixing silicon with heavily oxidized silicon particles, adding ball milling auxiliary materials, and putting them into a high-energy ball mill for ball milling; S2, placing the ball-milled powder into a tube furnace and calcining it at high temperature in an oxygen-deficient environment; S3, taking out the cooled material and sieving it.

[0007] In the step S1, silicon particles cleaned from photovoltaic industry cutting waste are used as silicon source, wherein the silicon content is >99%.

[0008] In the step S1, the silicon particles in the silicon source are crystalline silicon particles of any shape and have a size of 300-800 nm.

[0009] In the step S1, the surface of the heavily oxidized silicon particles is a thicker silicon dioxide film layer, and the thickness of the silicon dioxide film layer is 10-200 nm.

[0010] In the step S1, the mass ratio of silicon to surface oxidized silicon dioxide is 1:0.5-1:5.

[0011] In the step S1, the added ball milling auxiliary material is a one-dimensional or two-dimensional carbon nanomaterial, including one or two of carbon nanotubes, carbon nanofibers, graphene, graphene oxide, diamond-like particles, etc., and the added weight accounts for 1-15% of the silicon oxide material.

[0012] In the step S1, a high-energy ball mill is used for physical mixing, wherein the medium during ball milling is large and small agate beads, the ratio of large and small agate beads is 1:2, covering 70-80% of the material, and the ball milling is carried out at 400 r / min for 4 hours.

[0013] In the step S2, the solid material after ball milling is placed in a vacuum furnace and kept warm at 800-900° C. under normal pressure for 3-5 hours in a nitrogen or argon atmosphere.

[0014] To achieve the above purpose, a high-performance oxygen-controlled silicon-based negative electrode material is designed, which has a core-shell structure, with a core of silicon and an outer shell of amorphous silicon oxide.

[0015] To achieve the above purpose, a high-performance oxygen-controlled silicon-based negative electrode material is designed. The oxygen-controlled silicon-based negative electrode material is mixed with conductive carbon black particles through a binder, and then coated on a copper sheet to form a film to prepare a lithium-ion battery negative electrode.

[0016] Compared with the prior art, the SiOx negative electrode material prepared by the present invention has a high silicon content, and the silicon oxide layer wrapped outside the negative electrode inhibits the volume deformation of silicon in the electrochemical reaction, avoids damage to the negative electrode, and the material performance is more stable; the obtained SiOx material has the characteristics of high specific capacity and high first coulomb efficiency (>76%), has great application prospects, and is suitable for the industrial production of high-capacity lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The graphs are charge and discharge cycle diagrams of the oxygen-controlled silicon-based negative electrode materials prepared in different proportions in the present invention when applied to the negative electrode of a lithium-ion battery, wherein 1-0 to 1-5 represent the mass ratio of silicon to surface oxidized silicon dioxide.

[0018] Figure 2 It is a schematic diagram of the structure of the silicon-oxygen negative electrode material in the present invention and a simulation diagram of its reaction during the cycle process.

[0019] Figure 3 This is the XRD spectrum after oxygen in the active material silicon oxide is regulated in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings.

[0021] The preparation method of the high-performance oxygen-controlled silicon-based negative electrode material in this embodiment includes the following steps: S1, mixing silicon with heavily oxidized silicon particles, adding ball milling auxiliary materials, and putting them into a high-energy ball mill for ball milling; S2, placing the ball-milled powder into a tube furnace and calcining it at high temperature in an oxygen-deficient environment; S3, taking out the cooled material and sieving it, and using a sieve with a mesh size of 250-350.

[0022] In step S1, silicon particles cleaned from photovoltaic industry cutting waste are used as silicon source, wherein the silicon content is >99%. The silicon particles in the silicon source are crystalline silicon particles of any shape, with a size of 300-800nm.

[0023] The surface of the heavily oxidized silicon particles is a thicker silicon dioxide film layer, and the thickness of the silicon dioxide film layer is 10-200nm. When used specifically, the silicon dioxide film layer is obtained by oxidation of silicon in an oxygen environment at 850°C.

[0024] The mass ratio of silicon to surface oxidized silicon dioxide is 1:0.5~1:5.

[0025] The ball milling auxiliary material is a one-dimensional or two-dimensional carbon nanomaterial, including one or two of carbon nanotubes, carbon nanofibers, graphene, graphene oxide, diamond-like particles, etc., and the added weight accounts for 1-15% of the silicon oxide material.

[0026] When physical mixing is performed by a high-energy ball mill, the ball milling media are large and small agate beads, the ratio of large and small agate beads is 1:2, covering 70~80% of the material, and the ball milling is carried out at 400r / min for 4h.

[0027] In step S2, the solid material after ball milling is placed in a vacuum furnace, and kept at 800-900° C. under normal pressure for 3-5 hours in a nitrogen or argon atmosphere to ensure that the raw materials are fully reacted.

[0028] The oxygen-controlled silicon-based negative electrode material prepared by the above steps S1 to S3 is as follows Figure 2 As shown in (a), it has a core-shell structure, with the core being silicon and the shell being amorphous silicon oxide.

[0029] When the above oxygen-controlled silicon-based negative electrode material is used, the oxygen-controlled silicon-based negative electrode material is mixed with conductive carbon black particles SP through a binder PAA-Li, and then coated on a copper sheet to form a film to prepare a lithium-ion battery negative electrode. When the battery undergoes an electrochemical reaction, SP assists the negative electrode in conducting electricity. Compared with existing spherical particles, the oxygen-controlled silicon-based negative electrode material of the present invention is irregular particles and disorderly agglomerated, and the gaps between the materials are small, which is conducive to the SP being tightly filled between the two silicon oxygen material particles to form a good conductive network.

[0030] like Figure 2As shown, in the first stage of the electrochemical reaction, lithium ions combine with silicon oxide in the outer shell of the oxygen-controlled silicon-based negative electrode material to generate electrochemically inert lithium oxide, lithium silicate and active nano-silicon clusters, and then the nano-silicon clusters uniformly buried in the inert components undergo further alloying reaction with lithium. In this stage, the irreversible lithium silicate and the like generated are all coated on the surface of the active material, and the generated silicon nanoclusters participate in the electrochemical reaction again, resulting in their own volume deformation, which is manifested in the cyclic charge and discharge curve as a high first discharge specific capacity but a low cycle life, and a rapid decrease in specific capacity. In the second stage of the electrochemical reaction, lithium ions combine with silicon particles inside the material to undergo an alloying reaction. However, the outside of silicon is coated with silicon oxide and the electrochemically inert substances produced in the first stage. The presence of these substances alleviates the overall volume expansion of the negative electrode and avoids damage to the negative electrode, showing that the battery discharge specific capacity continues to rise in the cyclic charge and discharge curve until it stabilizes. As shown Figure 1 As shown in the figure, the first cycle discharge specific capacity and the first coulombic efficiency of the battery are both high, and its discharge specific capacity shows a trend of first decreasing and then continuously increasing during the cycle process. Embodiment 1

[0031] The original mass ratio of silicon to silicon dioxide in this example is 1.5:1, and the specific steps are as follows: S1, weigh silicon and silicon dioxide at a mass ratio of 1.5:1 respectively, and add 10% carbon nanofibers, mix and put into a high-energy ball mill for ball milling, wherein the coverage rate of agate beads is 70%~80%, to ensure that the raw materials are physically mixed evenly.

[0032] S2, the ball-milled powder is placed in a vacuum furnace, nitrogen is used as the protective gas, and calcined at 850℃ for 3h.

[0033] S3, after the above materials are cooled to room temperature, take them out and sieve them through a 280-mesh sieve. Embodiment 2

[0034] The original mass ratio of silicon to silicon dioxide in this example is 1:3, and the specific preparation steps are as follows: S1, weigh silicon and silicon dioxide at a mass ratio of 1:3, add 5% carbon nanotubes, mix and put into a high-energy ball mill for ball milling, wherein the coverage rate of agate beads is 70%~80%, to ensure that the raw materials are physically mixed evenly and the particle size reaches submicron level.

[0035] S2, the ball-milled powder is placed in a vacuum furnace, nitrogen is used as the protective gas, and calcined at 850℃ for 3h.

[0036] S3, after the above materials are cooled to room temperature, take them out and sieve them through a 300-mesh sieve.

[0037] Figure 3The XRD spectra of two silicon-oxygen negative electrodes with different oxygen contents in Example 1 and Example 2 are shown in Figure 1. The product prepared in Example 1 is a mixture of single crystal silicon and amorphous silicon oxide, and the test result is curve (a) in the figure. Specifically, the weight ratio of each phase is Si:SiO=45:55, the peak between 20-22° in the curve is relatively low, and the interplanar spacing obtained by the 2θ angle value is about 3.1411Å.

[0038] In Example 2, the original silicon dioxide has a larger mass ratio and a higher oxygen content. By analyzing the XRD diffraction spectrum, it is found that the weight ratio of the silicon-oxygen composite material selected in Example 2 after sintering is Si:SiO=41.8:58.2. The interplanar spacing is about 3.1473Å, the silicon-oxygen bond spacing in the silicon-oxygen composite material is large, and the concentration is high, corresponding to Figure 3 The peak between 20-22° in (b) is relatively high, with an obvious bulge-shaped diffraction peak.

[0039] The silicon-oxygen composite materials obtained in Example 1 and Example 2 were used as active materials to prepare button-type lithium-ion batteries. The cycle charge and discharge performance of the batteries was as follows: Figure 1 As shown. It can be seen that in Example 1, the first discharge specific capacity is high and the specific capacity decrease rate is slow, the cycle life is high, and the overall performance in the first stage is good. The oxygen content of the negative electrode material obtained in Example 2 is slightly higher, and the silicon oxide content obtained is higher, and a stable solid electrolyte interface film is easily formed at the beginning of the cycle. Silicon oxide has high charging and discharging lithium storage stability, small body expansion, and the discharge specific capacity can be steadily increased.

Claims

1. A method for preparing a high-performance oxygen-controlled silicon-based negative electrode material, characterized in that: The steps include: S1, mixing silicon with heavily oxidized silicon particles, adding ball milling auxiliary materials, and putting them into a high-energy ball mill for ball milling; S2, placing the ball-milled powder into a tube furnace and calcining it at high temperature in an oxygen-deficient environment; S3, taking out the cooled material and sieving it.

2. The method for preparing a high-performance oxygen-controlled silicon-based negative electrode material according to claim 1, characterized in that: In the step S1, silicon particles cleaned from photovoltaic industry cutting waste are used as silicon source, wherein the silicon content is >99%.

3. A method for preparing a high-performance oxygen-controlled silicon-based negative electrode material according to claim 1 or 2, characterized in that: In the step S1, the silicon particles in the silicon source are crystalline silicon particles of any shape and have a size of 300-800 nm.

4. The method for preparing a high-performance oxygen-controlled silicon-based negative electrode material according to claim 1, characterized in that: In the step S1, the surface of the heavily oxidized silicon particles is a thicker silicon dioxide film layer, and the thickness of the silicon dioxide film layer is 10-200 nm.

5. The method for preparing a high-performance oxygen-controlled silicon-based negative electrode material according to claim 1, characterized in that: In the step S1, the mass ratio of silicon to surface oxidized silicon dioxide is 1:0.5-1:

5.

6. The method for preparing a high-performance oxygen-controlled silicon-based negative electrode material according to claim 1, characterized in that: In the step S1, the added ball milling auxiliary material is a one-dimensional or two-dimensional carbon nanomaterial, including one or two of carbon nanotubes, carbon nanofibers, graphene, graphene oxide, diamond-like particles, etc., and the added weight accounts for 1-15% of the silicon oxide material.

7. The method for preparing a high-performance oxygen-controlled silicon-based negative electrode material according to claim 1, characterized in that: In the step S1, a high-energy ball mill is used for physical mixing, wherein the medium during ball milling is large and small agate beads, the ratio of large and small agate beads is 1:2, covering 70-80% of the material, and the ball milling is carried out at 400 r / min for 4 hours.

8. The method for preparing a high-performance oxygen-controlled silicon-based negative electrode material according to claim 1, characterized in that: In the step S2, the solid material after ball milling is placed in a vacuum furnace and kept warm at 800-900° C. under normal pressure for 3-5 hours in a nitrogen or argon atmosphere.

9. A high-performance oxygen-controlled silicon-based negative electrode material prepared by the method according to any one of claims 1 to 8, characterized in that: It has a core-shell structure, with the core being silicon and the shell being amorphous silicon oxide.

10. An application of the high-performance oxygen-controlled silicon-based negative electrode material according to claim 9, characterized in that: The oxygen-controlled silicon-based negative electrode material is mixed with conductive carbon black particles through a binder and then coated on a copper sheet to form a film to prepare a lithium-ion battery negative electrode.

Images