A high-performance silicon negative electrode material prepared from modified photovoltaic crystalline silicon waste and a preparation method thereof

Abstract

This invention provides a high-performance silicon anode material prepared from modified photovoltaic crystalline silicon waste and its preparation method, belonging to the field of lithium-ion battery silicon anode technology. The invention involves adding photovoltaic crystalline silicon waste to an acid solution for acid leaching to remove impurities, followed by drying to obtain pretreated silicon powder. This powder is then transferred to a fluidized bed ALD reaction chamber, where the airflow velocity is controlled, and metal precursor and oxygen sources are alternately introduced while excess products are purged to obtain silicon / metal oxide powder. Subsequently, lithium and fluorine sources are alternately introduced, and excess products are purged to obtain silicon / metal oxide / lithium fluoride powder. The deposited metal oxide not only slows down the volume expansion of the silicon waste during charge and discharge but also effectively stabilizes the SEI layer, reducing its breakage and reconstruction, as well as lithium consumption, thereby improving the cycle stability of the lithium-ion silicon-based anode. The lithium fluoride coating helps to construct a stable SEI, and the lithium fluoride-rich SEI layer provides fast ion channels, giving the material excellent rate performance.

Description

Technical Field

[0001] This invention relates to the field of silicon anode technology for lithium-ion batteries, and in particular to a high-performance silicon anode material prepared from modified photovoltaic crystalline silicon waste and its preparation method. Background Technology

[0002] In recent years, the photovoltaic industry has flourished. While promoting the transformation to clean energy, the silicon wafer cutting process also generates a large amount of photovoltaic crystalline silicon waste. According to industry statistics, approximately 300-500 tons of silicon waste are generated for every 1GW of silicon wafers produced, causing not only resource waste but also severe environmental pressure. Research has found that preparing it into silicon anodes for lithium-ion batteries is an excellent technical route for realizing the high-value utilization of crystalline silicon waste. However, this technical route faces two challenges: on the one hand, silicon materials exhibit a volume expansion effect of up to 300% during lithium insertion / extraction, leading to mechanical damage to the electrode structure; on the other hand, the solid electrolyte interphase (SEI) film is difficult to maintain stability under repeated volume changes, causing continuous electrolyte decomposition and active lithium consumption. These problems together lead to a sharp decline in electrode cycle life and a significant increase in interfacial impedance, severely restricting the practical application of photovoltaic crystalline silicon waste in the field of lithium-ion battery anodes.

[0003] Current research mainly focuses on improving the performance of silicon anodes through strategies such as material nanostructuring, carbon composites, and electrolyte optimization. However, these methods have significant limitations when applied to photovoltaic crystalline silicon waste. Therefore, proposing a silicon anode preparation scheme from photovoltaic crystalline silicon waste that can effectively suppress silicon anode volume expansion and stabilize the SEI interface has become crucial for improving its practicality. Recycling and using this material to prepare silicon-based anodes for lithium-ion batteries not only reduces the manufacturing cost of lithium-ion batteries but also achieves the economic benefits of recycling and reusing photovoltaic solid waste. Summary of the Invention

[0004] The purpose of this invention is to provide a high-performance silicon anode material prepared from modified photovoltaic crystalline silicon waste and its preparation method, in order to solve the above-mentioned technical problems.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste, comprising the following steps:

[0007] Step 1) After pretreatment by mixing photovoltaic crystalline silicon waste with acid, the waste is washed and dried sequentially to obtain silicon waste.

[0008] Step 2) The silicon waste is fed into the fluidized bed ALD reaction chamber, and metal precursor source and oxygen source are alternately introduced to obtain silicon / metal oxide powder.

[0009] Step 3) The silicon / metal oxide powder is purged, and then lithium and fluorine sources are alternately introduced to obtain high-performance silicon anode material.

[0010] Furthermore, in step 1), the acid solution is composed of components comprising the following volume fractions: 10-80 vol% acidic substances, 5-30 vol% hydrogen peroxide, and the remainder being water;

[0011] The acidic substances include one or more of hydrofluoric acid, hydrochloric acid, nitric acid, and sulfuric acid.

[0012] Furthermore, in step 1), the pretreatment time is 0.1 to 10 hours, and the pretreatment temperature is 20 to 38°C.

[0013] Furthermore, in step 2), the temperature in the fluidized bed ALD reaction chamber is 50–500°C, and the fluidization velocity of the gas flow is 0.01–0.1 m / s.

[0014] Furthermore, in step 2), the heating temperature of the metal precursor source is 80–200°C, and the heating temperature of the oxygen source is 30–100°C.

[0015] Furthermore, in step 2), the metal precursor source includes one of Al(CH3)3, Ti(NMe2)4, Zr(NMe2)4, Zn(N(CH3)2)2, Hf(N(CH3)2)4, Ta(N(CH3)2)5, and Ni(C5H5)2;

[0016] The oxygen source includes one or more of H2O, oxygen, plasma oxygen, and ozone.

[0017] Furthermore, in step 2), the number of alternations is 10 to 500 times.

[0018] Furthermore, in step 3), the purging gas is one or more of nitrogen, argon, and helium.

[0019] The lithium source includes tert-butyllithium, hexamethyldisilamide lithium, or lithium tetramethylheptanedione salt;

[0020] The fluorine source includes titanium tetrafluoride, ammonium fluoride, tantalum pentafluoride, or hydrogen fluoride.

[0021] Furthermore, in step 3), the heating temperature of the lithium source is 60–200°C, and the heating temperature of the fluorine source is 100–300°C.

[0022] The number of alternations is 10 to 500.

[0023] The present invention also provides a high-performance silicon anode material prepared by the above-described preparation method.

[0024] The beneficial effects of this invention are:

[0025] This invention proposes using fluidized bed powder ALD to modify silicon materials, which can not only achieve uniform deposition on the surface of high-defect silicon waste, but also precisely control the coating thickness.

[0026] This invention deposits a metal oxide layer and a lithium fluoride layer on the surface of photovoltaic-cut silicon waste. The metal oxide layer effectively suppresses the volume expansion of internal silicon particles, improving the structural stability of the material. The lithium fluoride layer guides the construction of a stable SEI layer, thereby enhancing cycle stability.

[0027] This invention not only effectively solves the problem of recycling silicon waste from photovoltaic industry cutting, but also proposes a simple and direct solution that uses green raw materials to modify and prepare lithium-ion silicon-based anodes. Attached Figure Description

[0028] Figure 1 This is a cycle performance diagram of the high-performance silicon anode material obtained in Example 1 of the present invention;

[0029] Figure 2 XPS analysis diagram of the high-performance silicon anode material obtained in Example 2 of this invention;

[0030] Figure 3 The electrochemical impedance spectroscopy diagram of the high-performance silicon anode material obtained in Example 3 of this invention is shown.

[0031] Figure 4 This is an XPS analysis diagram of the high-performance silicon anode material obtained in Example 4 of the present invention after electrical cycling. Detailed Implementation

[0032] This invention provides a method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste, comprising the following steps:

[0033] Step 1) After pretreatment by mixing photovoltaic crystalline silicon waste with acid, the waste is washed and dried sequentially to obtain silicon waste.

[0034] Step 2) The silicon waste is fed into the fluidized bed ALD reaction chamber, and metal precursor source and oxygen source are alternately introduced to obtain silicon / metal oxide powder.

[0035] Step 3) The silicon / metal oxide powder is purged, and then lithium and fluorine sources are alternately introduced to obtain high-performance silicon anode material.

[0036] In this invention, a mechanical buffer layer and an artificial SEI layer are sequentially constructed on the surface of silicon waste using a gradient coating process via atomic layer deposition (ALD). Based on the characteristics of diced silicon waste, surface impurities are first removed by acid leaching; then, metal oxides and lithium fluoride are sequentially deposited on the silicon surface using fluidized bed atomic layer deposition (ALD). This invention enables precise control and uniform deposition of the coating layer, not only suppressing silicon volume expansion but also contributing to the construction of a stable SEI layer.

[0037] In this invention, the inner metal oxide layer, possessing a certain mechanical strength, can restrain the volume expansion of the internal silicon during cycling. Repeated silicon breakage leads to extensive contact between the silicon surface and the electrolyte, causing repeated formation of the SEI layer and consuming active materials and active lithium. Therefore, lithium fluoride is introduced into the outermost layer, which not only induces the formation of a more stable SEI layer but also enhances the overall ion transport capability of the material.

[0038] In this invention, the photovoltaic crystalline silicon waste is waste silicon powder generated during the silicon wafer cutting process in the photovoltaic industry.

[0039] In this invention, in step 1), the acid solution is composed of the following components in volume fractions: 10-80 vol% acidic substance, preferably 20-50 vol%, more preferably 30 vol%; 5-30 vol% hydrogen peroxide, preferably 10-20 vol%, more preferably 15 vol%; the balance being water;

[0040] The acidic substance includes one or more of hydrofluoric acid, hydrochloric acid, nitric acid and sulfuric acid, preferably one or more of hydrofluoric acid, hydrochloric acid and nitric acid, and more preferably hydrofluoric acid and / or hydrochloric acid.

[0041] In this invention, in step 1), the pretreatment time is 0.1 to 10 hours, preferably 1 to 8 hours, and more preferably 3 to 5 hours; the pretreatment temperature is 20 to 38°C, preferably 25 to 32°C.

[0042] In this invention, the purpose of the pretreatment in step 1) is to remove the oxide layer and embedded metal ions from the surface of photovoltaic crystalline silicon waste.

[0043] In this invention, in step 1), the washing is performed by rinsing with deionized water and ethanol in sequence, followed by drying with nitrogen.

[0044] In this invention, in step 2), the temperature in the fluidized bed ALD reaction chamber is 50-500°C, preferably 100-300°C, and more preferably 200°C; the fluidization velocity of the gas flow is 0.01-0.1 m / s, preferably 0.03-0.08 m / s, and more preferably 0.04 m / s.

[0045] In this invention, in step 2), the heating temperature of the metal precursor source is 80-200°C, preferably 120-180°C, and more preferably 150°C; the heating temperature of the oxygen source is 30-100°C, preferably 50-80°C, and more preferably 60°C.

[0046] In this invention, in step 2), the metal precursor source is preferably one of Al(CH3)3, Ti(NMe2)4, Zr(NMe2)4, Zn(N(CH3)2)2, Hf(N(CH3)2)4, Ta(N(CH3)2)5 and Ni(C5H5)2;

[0047] The oxygen source includes one or more of H2O, oxygen, plasma oxygen, and ozone, preferably one or more of H2O, oxygen, and plasma oxygen, and more preferably H2O and / or oxygen.

[0048] In this invention, in step 2), the number of alternations is 10 to 500 times, preferably 100 to 300 times, and more preferably 200 times.

[0049] In this invention, in step 3), the purging gas is one or more of nitrogen, argon and helium, preferably nitrogen and / or argon;

[0050] The lithium source is preferably tert-butyllithium, hexamethyldisilamide lithium or lithium tetramethylheptanedione salt, and more preferably tert-butyllithium or hexamethyldisilamide lithium;

[0051] The fluorine source includes titanium tetrafluoride, ammonium fluoride, tantalum pentafluoride, or hydrogen fluoride, preferably titanium tetrafluoride, ammonium fluoride, or tantalum pentafluoride, and more preferably titanium tetrafluoride and / or ammonium fluoride.

[0052] In this invention, in step 3), the heating temperature of the lithium source is 60-200°C, preferably 100-150°C, and more preferably 130°C; the heating temperature of the fluorine source is 100-300°C, preferably 120-250°C, and more preferably 150-220°C.

[0053] The number of alternations is 10 to 500 times, preferably 100 to 300 times, and more preferably 200 times.

[0054] The present invention also provides a high-performance silicon anode material prepared by the above-described preparation method.

[0055] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] Prepare an acid solution with volume fractions of 5 vol% hydrofluoric acid, 5 vol% nitric acid, 10 vol% hydrogen peroxide, and the balance being deionized water. Mix photovoltaic silicon waste with a particle size of 240 nm with the acid solution and stir at 28°C for 1 hour. After filtration, immerse it in an acid solution containing 10 vol% hydrofluoric acid and 20 vol% hydrochloric acid and stir for 2 hours. Then, wash it sequentially with deionized water and ethanol, and dry it with nitrogen to obtain silicon waste.

[0058] Silicon waste was transferred to a fluidized bed ALD chamber, with the fluidization velocity controlled at 0.01 m / s and the chamber temperature at 250 °C. First, an Al(CH3)3 precursor at 120 °C was introduced, followed by nitrogen purging of excess byproducts. Then, H2O at 50 °C was introduced, and nitrogen purging of byproducts was repeated. This process was repeated 50 times, resulting in an alumina layer with a thickness of 5 nm.

[0059] The chamber temperature was maintained at 250℃, and the fluidization rate was controlled at 0.04m / s. Excess byproducts were first purged with nitrogen gas, followed by the introduction of tert-butyllithium precursor at 120℃ and purging with nitrogen gas. Then, titanium tetrafluoride at 180℃ was introduced and purged with nitrogen gas. This alternating cycle was repeated 30 times. The resulting lithium fluoride layer had a thickness of 3nm, thus obtaining a high-performance silicon anode material.

[0060] The silicon-carbon anode material obtained in Example 1 was subjected to electrochemical performance testing, and the testing method was carried out in accordance with the method in Appendix D of the national standard GB / T38823-2020. Figure 1 The graph shows the cycling performance of the high-performance silicon anode material obtained in Example 1. The results indicate that the battery in this example exhibits the best cycling performance, maintaining a capacity of 800 mAh g after 300 cycles, compared to the other electrodes. -1 above.

[0061] Example 2

[0062] Prepare an acid solution with volume fractions of 10 vol% hydrofluoric acid, 10 vol% nitric acid, 10 vol% hydrogen peroxide, and the balance being deionized water. Mix photovoltaic silicon waste with a particle size of 240 nm with the acid solution and stir at 28°C for 2 hours. After filtration, immerse it in an acid solution containing 10 vol% hydrofluoric acid and 20 vol% hydrochloric acid and stir for 3 hours. Then, wash it sequentially with deionized water and ethanol, and dry it with nitrogen to obtain silicon waste.

[0063] Silicon waste was transferred to a fluidized bed ALD chamber, with the fluidization velocity controlled at 0.02 m / s and the chamber temperature at 250 °C. First, a Ti(NMe2)4 precursor at 120 °C was introduced, followed by nitrogen purging of excess byproducts. Then, H2O at 60 °C was introduced, and nitrogen purging of byproducts was repeated. This process was repeated 50 times, resulting in a titanium oxide layer with a thickness of 5 nm.

[0064] The chamber temperature was maintained at 250℃, and the fluidization rate was controlled at 0.05m / s. Excess byproducts were first purged with nitrogen gas, followed by the introduction of a hexamethyldisilamide lithium precursor at 140℃ and purging with nitrogen gas. Then, titanium tetrafluoride at 180℃ was introduced and purged with nitrogen gas. This alternating cycle was repeated 50 times. The resulting lithium fluoride layer had a thickness of 5nm, thus obtaining a high-performance silicon anode material.

[0065] The silicon-carbon anode material obtained in Example 2 was subjected to electrochemical performance testing, and the testing method was carried out in accordance with the method in Appendix D of the national standard GB / T38823-2020. Figure 2 The XPS analysis results of the high-performance silicon anode material obtained in Example 2 show that the XPS spectrum in this example shows the corresponding peak of titanium, proving the successful preparation of the titanium oxide coating.

[0066] Example 3

[0067] An acid solution was prepared with volume fractions of 15 vol% hydrofluoric acid, 15 vol% nitric acid, 20 vol% hydrogen peroxide, and the balance being deionized water. Photovoltaic silicon waste with a particle size of 240 nm was mixed with the acid solution and stirred at 28°C for 3 hours. After filtration, it was immersed in an acid solution containing 10 vol% hydrofluoric acid and 30 vol% hydrochloric acid and stirred for 4 hours. Then, it was washed with deionized water and ethanol in sequence, and dried with nitrogen to obtain silicon waste.

[0068] Silicon waste was transferred to a fluidized bed ALD chamber, with the fluidization velocity controlled at 0.05 m / s and the chamber temperature at 200 °C. Then, a Zr(NMe2)4 precursor at 140 °C was introduced, followed by nitrogen purging of excess byproducts. Next, H2O at 80 °C was introduced, followed by nitrogen purging of byproducts. This process was repeated for 80 cycles, resulting in a zirconia layer with a thickness of 7 nm.

[0069] The chamber temperature was maintained at 200℃, and the fluidization rate was controlled at 0.07m / s. Excess byproducts were first purged with nitrogen gas, followed by the introduction of hexamethyldisilamide lithium precursor at 140℃ and purging with nitrogen gas. Then, ammonium fluoride at 120℃ was introduced and purged with nitrogen gas. This alternating cycle was repeated 50 times. The resulting lithium fluoride layer had a thickness of 5nm, thus obtaining a high-performance silicon anode material.

[0070] The silicon-carbon anode material obtained in Example 3 was subjected to electrochemical performance testing, and the testing methods were carried out in Appendix D of the national standard GB / T38823-2020. Figure 3 The electrochemical impedance spectroscopy (EIS) of the high-performance silicon anode material obtained in Example 3 shows that the Nyquist spectrum in this example verifies that although the zirconium oxide coating increases mechanical stress, an excessively thick coating will reduce conductivity, resulting in an increase in the overall resistance of the material.

[0071] Example 4

[0072] Prepare an acid solution with volume fractions of 20 vol% hydrofluoric acid, 20 vol% nitric acid, 20 vol% hydrogen peroxide, and the balance being deionized water. Mix photovoltaic silicon waste with a particle size of 240 nm with the acid solution and stir at 28°C for 1 hour. After filtration, immerse it in an acid solution containing 20 vol% hydrofluoric acid and 30 vol% hydrochloric acid and stir for 1 hour. Then, wash it sequentially with deionized water and ethanol, and dry it with nitrogen to obtain silicon waste.

[0073] Silicon waste was transferred to a fluidized bed ALD chamber, with the fluidization velocity adjusted to 0.1 m / s and the chamber temperature set to 350 °C. Then, a Zn(N(CH3)2)2 precursor at 160 °C was introduced, followed by nitrogen purging of excess byproducts. Next, H2O at 50 °C was introduced, and then nitrogen purging was repeated. This process was repeated 100 times, resulting in a zinc oxide layer with a thickness of 8 nm.

[0074] The chamber temperature was maintained at 200℃, and the fluidization rate was controlled at 0.2m / s. Excess byproducts were first purged with nitrogen gas, followed by the introduction of tert-butyllithium precursor at 120℃ and purging with nitrogen gas. Then, ammonium fluoride at 120℃ was introduced and purged with nitrogen gas. This alternating cycle was repeated 90 times. The resulting lithium fluoride layer had a thickness of 8nm, thus obtaining a high-performance silicon anode material.

[0075] The silicon-carbon anode material obtained in Example 4 was subjected to electrochemical performance testing. The testing methods were carried out in Appendix D of the national standard GB / T38823-2020. Figure 4 The XPS analysis diagram of the high-performance silicon anode material obtained in Example 4 after electrical cycling shows that the XPS diagram after cycling in this example shows that the material interface after cycling is rich in LiF and has a stable SEI layer.

[0076] As shown in the above embodiments, this invention provides a high-performance silicon anode material prepared from modified photovoltaic crystalline silicon waste and its preparation method. First, surface impurities are removed by acid leaching. Then, metal oxide and lithium fluoride are sequentially deposited on the silicon surface using fluidized bed atomic layer deposition (ALD) technology. The inner metal oxide layer, possessing a certain mechanical strength, can restrain the volume expansion of the internal silicon during cycling. This invention enables precise control and uniform deposition of the coating layer, not only suppressing silicon volume expansion but also contributing to the construction of a stable SEI layer, thereby enhancing the overall ion transport capability of the material, which is of significant importance.

[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste, characterized in that, Includes the following steps: Step 1) After pretreatment by mixing photovoltaic crystalline silicon waste with acid, the waste is washed and dried sequentially to obtain silicon waste. Step 2) The silicon waste is fed into the fluidized bed ALD reaction chamber, and metal precursor source and oxygen source are alternately introduced to obtain silicon / metal oxide powder. Step 3) The silicon / metal oxide powder is purged, and then lithium and fluorine sources are alternately introduced to obtain high-performance silicon anode material.

2. The method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste according to claim 1, characterized in that, In step 1), the acid solution is composed of the following components in volume fractions: 10-80 vol% acidic substance, 5-30 vol% hydrogen peroxide, and the remainder is water; The acidic substances include one or more of hydrofluoric acid, hydrochloric acid, nitric acid, and sulfuric acid.

3. A method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste according to claim 1 or 2, characterized in that, In step 1), the pretreatment time is 0.1 to 10 hours and the pretreatment temperature is 20 to 38°C.

4. The method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste according to claim 3, characterized in that, In step 2), the temperature in the fluidized bed ALD reaction chamber is 50 to 500°C, and the fluidization velocity of the gas flow is 0.01 to 0.1 m / s.

5. A method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste according to claim 1, 2, or 4, characterized in that, In step 2), the heating temperature of the metal precursor source is 80-200°C, and the heating temperature of the oxygen source is 30-100°C.

6. The method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste according to claim 5, characterized in that, In step 2), the metal precursor source includes one of Al(CH3)3, Ti(NMe2)4, Zr(NMe2)4, Zn(N(CH3)2)2, Hf(N(CH3)2)4, Ta(N(CH3)2)5 and Ni(C5H5)2; The oxygen source includes one or more of H2O, oxygen, plasma oxygen, and ozone.

7. A method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste according to claim 1 or 6, characterized in that, In step 2), the number of alternations is 10 to 500.

8. The method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste according to claim 7, characterized in that, In step 3), the purging gas is one or more of nitrogen, argon and helium; The lithium source includes tert-butyllithium, hexamethyldisilamide lithium or lithium tetramethylheptanedione salt, and cyclopentadienyllithium; The fluorine source includes titanium tetrafluoride, ammonium fluoride, tantalum pentafluoride, or hydrogen fluoride.

9. A method for preparing high-performance silicon anode materials from modified photovoltaic crystalline silicon waste according to claim 1, 6, or 8, characterized in that, In step 3), the heating temperature of the lithium source is 60-200°C, and the heating temperature of the fluorine source is 100-300°C. The number of alternations is 10 to 500.

10. The high-performance silicon anode material prepared by the preparation method according to any one of claims 1 to 9.

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