High-performance silicon negative electrode material prepared from modified photovoltaic crystalline silicon waste and preparation method of high-performance silicon negative electrode material

Abstract

The invention provides a high-performance silicon negative electrode material prepared from modified photovoltaic crystalline silicon waste and a preparation method of the high-performance silicon negative electrode material, and belongs to the technical field of lithium ion battery silicon negative electrodes. The method comprises the following steps: adding the photovoltaic crystalline silicon waste into acid liquor for acid leaching and impurity removal, and drying to obtain pretreated silicon powder; transferring into a fluidized bed ALD reaction cavity, regulating and controlling the air flow fluidization speed, alternately introducing a metal precursor source and an oxygen source, and purging redundant products to obtain silicon / metal oxide powder; and alternately introducing a lithium source and a fluorine source, and purging redundant products to obtain silicon / metal oxide / lithium fluoride powder. And the deposited metal oxide not only can slow down the volume expansion of the silicon waste material in the charging and discharging process, but also can effectively stabilize the SEI layer and slow down the crushing and reconstruction of the SEI layer and the consumption of lithium, so that the cycling stability of the lithium ion silicon-based negative electrode is improved. The lithium fluoride coating can be beneficial to construction of stable SEI, and the SEI layer rich in lithium fluoride can provide a fast ion channel, so that the material has excellent rate capability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery silicon negative electrode, and particularly relates to a modified photovoltaic crystalline silicon waste material for preparing high-performance silicon negative electrode material and a preparation method thereof. BACKGROUND

[0002] In recent years, the photovoltaic industry has developed rapidly, promoting the transformation of clean energy while also producing a large amount of photovoltaic crystalline silicon waste in the process of silicon wafer cutting. According to industry statistics, about 300-500 tons of silicon waste are generated for every 1 GW of silicon wafer production, which not only causes resource waste but also brings severe environmental pressure. Research has found that preparing it into a lithium ion battery silicon negative electrode is an excellent technical route for the high-value utilization of crystalline silicon waste. However, this technical route faces two difficulties: on the one hand, silicon material has a volume expansion effect of up to 300% during lithium intercalation / deintercalation, leading to mechanical damage to the electrode structure; on the other hand, the solid electrolyte interface film (SEI) is difficult to maintain stable under repeated volume changes, causing continuous electrolyte decomposition and active lithium consumption. These problems together cause the cycle life of the electrode to decay sharply and the interfacial impedance to increase significantly, which seriously restricts the practical application of photovoltaic crystalline silicon waste in the field of lithium battery negative electrodes.

[0003] Current research mainly improves the performance of silicon negative electrodes through strategies such as material nanocrystallization, carbon compounding, and electrolyte optimization, but these methods have obvious limitations when applied to photovoltaic crystalline silicon waste. Therefore, developing a preparation scheme for photovoltaic crystalline silicon waste silicon negative electrodes that can effectively inhibit the volume expansion of silicon negative electrodes and stabilize the SEI interface has become a key to effectively improving its practicality. Recycling and preparing lithium ion battery silicon-based negative electrodes not only reduces the manufacturing cost of lithium ion batteries but also achieves economic benefits of photovoltaic solid waste recycling and reuse. SUMMARY

[0004] The present application aims to provide a modified photovoltaic crystalline silicon waste material for preparing high-performance silicon negative electrode material and a preparation method thereof, which solves the above technical problems.

[0005] In order to achieve the above application purposes, the present application provides the following technical solutions:

[0006] The present application provides a method for preparing high-performance silicon negative electrode material from modified photovoltaic crystalline silicon waste, comprising the following steps:

[0007] Step 1), mixing the photovoltaic crystalline silicon waste and acid solution for pretreatment, then sequentially washing and drying to obtain silicon waste;

[0008] Step 2), sending the silicon waste into a fluidized bed ALD reaction chamber, alternately introducing a metal precursor source and an oxygen source to obtain a silicon / metal oxide powder;

[0009] Step 3), the silicon / metal oxide powder is purged, and then a lithium source and a fluorine source are alternately introduced to obtain the high-performance silicon negative electrode material.

[0010] Further, in step 1), the acid solution is composed of components including 10-80 vol% of an acidic substance, 5-30 vol% of hydrogen peroxide, and the balance of water;

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

[0012] Further, in step 1), the pretreatment time is 0.1-10 h, and the pretreatment temperature is 20-38℃.

[0013] Further, in step 2), the temperature in the fluidized bed ALD reaction cavity is 50-500℃, and the fluidization velocity of the gas flow is 0.01-0.1 m / s.

[0014] Further, in step 2), the heating temperature of the metal precursor source is 80-200℃, and the heating temperature of the oxygen source is 30-100℃.

[0015] Further, 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] Further, in step 2), the number of alternations is 10-500.

[0018] Further, in step 3), the purge gas for purging is one or more of nitrogen, argon, and helium;

[0019] The lithium source includes tert-butyl lithium, lithium hexamethyldisilylamide, or lithium tetramethylheptanedionate;

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

[0021] Further, in step 3), the heating temperature of the lithium source is 60-200℃, and the heating temperature of the fluorine source is 100-300℃.

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

[0023] The application also provides a high-performance silicon negative electrode material prepared by the above preparation method.

[0024] The beneficial effects of the present application are as follows:

[0025] The present application proposes to use fluidized bed powder ALD to modify silicon materials, which not only can realize uniform deposition on the surface of high defect silicon waste materials, but also can precisely control the thickness of the coating layer.

[0026] The present application deposits a metal oxide layer and a lithium fluoride layer on the surface of photovoltaic cutting silicon waste materials, the metal oxide layer effectively inhibits the volume expansion of internal silicon particles, and improves the material structure stability. The lithium fluoride layer can guide the construction of a stable SEI layer, thereby improving the cycle stability.

[0027] The present application not only effectively solves the problem of recycling photovoltaic cutting silicon waste materials, but also proposes a simple and direct operation scheme using green raw materials to modify and prepare lithium ion silicon-based negative electrodes. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The cycle performance diagram of the high-performance silicon negative electrode material obtained in Example 1 of the present application;

[0029] Figure 2 The XPS analysis diagram of the high-performance silicon negative electrode material obtained in Example 2 of the present application;

[0030] Figure 3 The electrochemical impedance diagram of the high-performance silicon negative electrode material obtained in Example 3 of the present application;

[0031] Figure 4 The XPS analysis diagram of the high-performance silicon negative electrode material obtained in Example 4 of the present application after electrical cycling. DETAILED DESCRIPTION

[0032] The present application provides a method for preparing a high-performance silicon negative electrode material by modifying photovoltaic crystalline silicon waste materials, comprising the following steps:

[0033] Step 1), the photovoltaic crystalline silicon waste materials and acid solution are mixed for pretreatment, and then sequentially washed and dried to obtain silicon waste materials;

[0034] Step 2), the silicon waste materials are sent into a 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 source and fluorine source are alternately introduced to obtain a high-performance silicon negative electrode material.

[0036] In the present application, a mechanical buffer layer and an artificial SEI layer are sequentially constructed on the surface of silicon waste by powder atomic layer deposition gradient coating process. According to the characteristics of the cut silicon waste, the surface impurities are first removed by acid immersion; then metal oxide and lithium fluoride are sequentially deposited on the surface of the silicon material by fluidized bed atomic layer deposition (ALD) technology. The present application can realize precise control and uniform deposition of the coating layer, not only inhibits the volume expansion of silicon, but also helps to build a stable SEI layer.

[0037] In the present application, the metal oxide with a certain mechanical strength inner layer can bind the volume expansion of the internal silicon in the cycle process. Due to repeated silicon rupture, a large amount of electrolyte is contacted on the surface to trigger the repeated generation of SEI layer, consuming active materials and active lithium. Therefore, lithium fluoride is introduced into the outermost layer, which not only can induce the formation of a relatively stable SEI layer, but also can improve the overall ion transport capacity of the material.

[0038] In the present application, the photovoltaic crystalline silicon waste is the waste silicon powder generated in the cutting process of photovoltaic industry silicon wafer.

[0039] In the present application, in step 1), the acid solution is composed of the following components by volume fraction: 10-80 vol% of acidic substance, preferably 20-50 vol%, further preferably 30 vol%; 5-30 vol% of hydrogen peroxide, preferably 10-20 vol%, further preferably 15 vol%; and the balance is 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, further preferably hydrofluoric acid and / or hydrochloric acid.

[0041] In the present application, in step 1), the pretreatment time is 0.1-10 h, preferably 1-8 h, further preferably 3-5 h; and the pretreatment temperature is 20-38℃, preferably 25-32℃.

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

[0043] In the present application, in step 1), the washing is sequentially rinsed with deionized water and ethanol, and then dried with nitrogen.

[0044] In the present application, in step 2), the temperature in the fluidized bed ALD reaction chamber is 50-500℃, preferably 100-300℃, further preferably 200℃; and the fluidization speed of the gas flow is 0.01-0.1 m / s, preferably 0.03-0.08 m / s, further preferably 0.04 m / s.

[0045] In the present application, in step 2), the heating temperature of the metal precursor source is 80-200℃, preferably 120-180℃, further preferably 150℃; the heating temperature of the oxygen source is 30-100℃, preferably 50-80℃, further preferably 60℃.

[0046] In the present application, 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, further preferably H2O and / or oxygen.

[0048] In the present application, in step 2), the number of alternations is 10-500, preferably 100-300, further preferably 200.

[0049] In the present application, in step 3), the purge gas for purging is one or more of nitrogen, argon and helium, preferably nitrogen and / or argon.

[0050] The lithium source is preferably tert-butyl lithium, lithium hexamethyldisilylamide or lithium tetramethylheptanedionate, further preferably tert-butyl lithium or lithium hexamethyldisilylamide.

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

[0052] In the present application, in step 3), the heating temperature of the lithium source is 60-200℃, preferably 100-150℃, further preferably 130℃; the heating temperature of the fluorine source is 100-300℃, preferably 120-250℃, further preferably 150-220℃.

[0053] The number of alternations is 10-500, preferably 100-300, further preferably 200.

[0054] The present application also provides a high-performance silicon negative electrode material prepared by the above preparation method.

[0055] The technical solutions provided by the present application will be described in detail below in conjunction with the examples, but they should not be understood as limiting the scope of protection of the present application.

[0056] Example 1

[0057] A silicon waste material with a particle size of 240 nm was mixed with an acid solution with a volume fraction of 5 vol% hydrofluoric acid, 5 vol% nitric acid, 10 vol% hydrogen peroxide, and the balance being deionized water, stirred at 28℃ for 1h, then immersed in an acid solution containing 10 vol% hydrofluoric acid and 20 vol% hydrochloric acid, stirred for 2h, then sequentially washed with deionized water, ethanol, and dried with nitrogen to obtain a silicon waste material;

[0058] The silicon waste material was transferred to a fluidized bed ALD chamber, the fluidization speed was controlled to be 0.01 m / s, the chamber temperature was 250℃, then the Al(CH3)3 precursor with a temperature of 120℃ was introduced, then the excess byproduct was purged with nitrogen, then the H2O with a temperature of 50℃ was introduced, then the byproduct was purged with nitrogen. This was alternated for 50 cycles, and the thickness of the obtained aluminum oxide layer was 5nm;

[0059] The chamber temperature was maintained at 250℃, the fluidization speed was controlled to be 0.04 m / s, the excess byproduct was first purged with nitrogen, then the tert-butyllithium precursor with a temperature of 120℃ was introduced, then nitrogen was purged, then the titanium tetrafluoride with a temperature of 180℃ was introduced, then nitrogen was purged, and this was alternated for 30 cycles, and the thickness of the obtained lithium fluoride layer was 3nm, thereby obtaining a high-performance silicon negative electrode material.

[0060] The silicon-carbon negative electrode material obtained in Example 1 was subjected to electrochemical performance testing, and the test method was carried out according to the method in Appendix D of national standard GB / T38823-2020. Figure 1 The cycle performance graph of the high-performance silicon negative electrode material obtained in Example 1 is shown in the figure, and the results show that the cycle performance of the battery in this embodiment is the best, and compared with the other electrodes, the capacity after 300 cycles still maintains 800mAhg -1 above.

[0061] Example 2

[0062] A silicon waste material with a particle size of 240 nm was mixed with an acid solution with a volume fraction of 10 vol% hydrofluoric acid, 10 vol% nitric acid, 10 vol% hydrogen peroxide, and the balance being deionized water, stirred at 28℃ for 2h, then immersed in an acid solution containing 10 vol% hydrofluoric acid and 20 vol% hydrochloric acid, stirred for 3h, then sequentially washed with deionized water, ethanol, and dried with nitrogen to obtain a silicon waste material;

[0063] The silicon waste material was transferred to a fluidized bed ALD chamber, the fluidization speed was controlled to be 0.02 m / s, the chamber temperature was 250℃, then the Ti(NMe2)4 precursor with a temperature of 120℃ was introduced, then the excess byproduct was purged with nitrogen, then the H2O with a temperature of 60℃ was introduced, then the byproduct was purged with nitrogen. This was alternated for 50 cycles, and the thickness of the obtained titanium oxide layer was 5nm;

[0064] The cavity temperature is maintained at 250 DEG C, the fluidization speed is regulated at 0.05 m / s, the excess by-product is first purged by nitrogen, then the lithium hexamethyldisilazide precursor with a temperature of 140 DEG C is introduced, nitrogen is purged, then titanium tetrafluoride with a temperature of 180 DEG C is introduced, nitrogen is purged, and the above steps are alternately repeated for 50 times, the thickness of the obtained lithium fluoride layer is 5 nm, and a high-performance silicon negative electrode material is obtained.

[0065] The silicon-carbon negative electrode material obtained in Example 2 is subjected to electrochemical performance test, and the test method is carried out according to the method in Appendix D of national standard GB / T38823-2020. Figure 2 The XPS analysis diagram of the high-performance silicon negative electrode material obtained in Example 2 is shown in the figure, and the results show that the XPS spectrum in this embodiment shows that the corresponding peak of titanium is observed, which proves the successful preparation of the titanium oxide coating.

[0066] Example 3

[0067] An acid solution with a volume fraction of 15 vol% hydrofluoric acid, 15 vol% nitric acid, 20 vol% hydrogen peroxide and the balance being deionized water is prepared, the photovoltaic crystalline silicon waste with a particle size of 240 nm is mixed with the acid solution, stirred at 28 DEG C for 3 h, then filtered and immersed in an acid solution containing 10 vol% hydrofluoric acid and 30 vol% hydrochloric acid, stirred for 4 h, and then sequentially subjected to deionized water washing, ethanol washing, and nitrogen blowing to obtain the silicon waste;

[0068] The silicon waste is transferred to the fluidized bed ALD cavity, the fluidization speed is regulated at 0.05 m / s, the cavity temperature is 200 DEG C, then the Zr(NMe2)4 precursor with a temperature of 140 DEG C is introduced, then the excess by-product is purged by nitrogen, then H2O with a temperature of 80 DEG C is introduced, and then the by-product is purged by nitrogen. The above steps are alternately repeated for 80 times, and the thickness of the obtained zirconium oxide layer is 7 nm.

[0069] The cavity temperature is maintained at 200 DEG C, the fluidization speed is regulated at 0.07 m / s, the excess by-product is first purged by nitrogen, then the lithium hexamethyldisilazide precursor with a temperature of 140 DEG C is introduced, nitrogen is purged, then ammonium fluoride with a temperature of 120 DEG C is introduced, and nitrogen is purged, and the above steps are alternately repeated for 50 times, the thickness of the obtained lithium fluoride layer is 5 nm, and a high-performance silicon negative electrode material is obtained.

[0070] The silicon-carbon negative electrode material obtained in Example 3 is subjected to electrochemical performance test, and the test method is carried out according to the method in Appendix D of national standard GB / T38823-2020. Figure 3 The electrochemical impedance diagram of the high-performance silicon negative electrode material obtained in Example 3 is shown in the figure, and the results show that the Nyquist spectrum in this embodiment verifies that although the zirconium oxide coating improves the mechanical stress, the too thick coating will reduce the conductivity, and the overall resistance of the material will increase.

[0071] Example 4

[0072] The acid solution with a volume fraction of 20vol% hydrofluoric acid, 20vol% nitric acid, 20vol% hydrogen peroxide and the balance being deionized water was prepared, the photovoltaic crystalline silicon waste with a particle size of 240nm was mixed with the acid solution, stirred at 28℃ for 1h, then immersed in the acid solution containing 20vol% hydrofluoric acid and 30vol% hydrochloric acid, stirred for 1h, then sequentially washed with deionized water, ethanol, and dried with nitrogen to obtain the silicon waste;

[0073] The silicon waste was transferred into the fluidized bed ALD cavity, the fluidization speed was controlled to be 0.1m / s, the cavity temperature was 350℃, then the Zn(N(CH3)2)2 precursor with a temperature of 160℃ was introduced, then the excess by-product was purged with nitrogen, then the H2O with a temperature of 50℃ was introduced, then the by-product was purged with nitrogen. This alternating cycle was performed for 100 times, and the thickness of the obtained zinc oxide layer was 8nm;

[0074] The cavity temperature was maintained at 200℃, the fluidization speed was controlled to be 0.2m / s, the excess by-product was purged with nitrogen, then the tert-butyllithium precursor with a temperature of 120℃ was introduced, then nitrogen was purged, then the ammonium fluoride with a temperature of 120℃ was introduced, then nitrogen was purged, and this alternating cycle was performed for 90 times, and the thickness of the obtained lithium fluoride layer was 8nm, thereby obtaining the high-performance silicon negative electrode material.

[0075] The silicon-carbon negative electrode material obtained in Example 4 was subjected to electrochemical performance test, and the test method was carried out according to the method in Appendix D of national standard GB / T38823-2020, Figure 4 The XPS analysis diagram of the high-performance silicon negative electrode material obtained in Example 4 after the electric cycle, the results showed that the XPS diagram after the cycle of the material in this embodiment was rich in LiF at the interface after the cycle, and had a stable SEI layer.

[0076] From the above examples, the present application provides a high-performance silicon negative electrode material prepared by modifying photovoltaic crystalline silicon waste and a preparation method thereof. First, the surface impurities are removed by acid immersion, then the metal oxide and lithium fluoride are deposited on the surface of the silicon material in sequence by fluidized bed atomic layer deposition (ALD) technology, the metal oxide with certain mechanical strength in the inner layer can bind the volume expansion of the internal silicon during the cycle. The present application can realize precise control and uniform deposition of the coating layer, not only inhibits the volume expansion of silicon, but also helps to build a stable SEI layer, improves the overall ion transmission capacity of the material, and has important significance.

[0077] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

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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