CN117623317A - Purification method of micro-nano silicon powder - Google Patents
Purification method of micro-nano silicon powder Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 155
- 238000000746 purification Methods 0.000 title claims abstract description 78
- 238000000034 method Methods 0.000 title claims abstract description 47
- 239000005543 nano-size silicon particle Substances 0.000 title claims abstract description 47
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 47
- 239000012535 impurity Substances 0.000 claims abstract description 42
- 229910052751 metal Inorganic materials 0.000 claims abstract description 30
- 239000002184 metal Substances 0.000 claims abstract description 30
- 238000000926 separation method Methods 0.000 claims abstract description 22
- 238000007885 magnetic separation Methods 0.000 claims abstract description 19
- 238000005406 washing Methods 0.000 claims abstract description 14
- 238000001035 drying Methods 0.000 claims abstract description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 118
- 239000011863 silicon-based powder Substances 0.000 claims description 94
- 239000000843 powder Substances 0.000 claims description 59
- 239000000377 silicon dioxide Substances 0.000 claims description 59
- 239000002002 slurry Substances 0.000 claims description 59
- 238000003756 stirring Methods 0.000 claims description 43
- 239000011261 inert gas Substances 0.000 claims description 30
- 238000003825 pressing Methods 0.000 claims description 28
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 24
- 239000002245 particle Substances 0.000 claims description 24
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 23
- 239000001301 oxygen Substances 0.000 claims description 23
- 229910052760 oxygen Inorganic materials 0.000 claims description 23
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical group OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 18
- 239000002904 solvent Substances 0.000 claims description 18
- 230000008569 process Effects 0.000 claims description 17
- 238000006243 chemical reaction Methods 0.000 claims description 14
- 238000001914 filtration Methods 0.000 claims description 11
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 10
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- 238000004806 packaging method and process Methods 0.000 claims description 9
- 238000004140 cleaning Methods 0.000 claims description 8
- 230000018044 dehydration Effects 0.000 claims description 8
- 238000006297 dehydration reaction Methods 0.000 claims description 8
- 239000007800 oxidant agent Substances 0.000 claims description 8
- 230000001590 oxidative effect Effects 0.000 claims description 8
- 230000035484 reaction time Effects 0.000 claims description 8
- 238000005086 pumping Methods 0.000 claims description 7
- 238000001291 vacuum drying Methods 0.000 claims description 7
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 6
- 238000011049 filling Methods 0.000 claims description 6
- 239000006148 magnetic separator Substances 0.000 claims description 6
- 150000007522 mineralic acids Chemical class 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 239000003153 chemical reaction reagent Substances 0.000 claims description 5
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 18
- 239000000047 product Substances 0.000 description 17
- 229910052710 silicon Inorganic materials 0.000 description 14
- 239000010703 silicon Substances 0.000 description 14
- 238000000227 grinding Methods 0.000 description 8
- 238000011085 pressure filtration Methods 0.000 description 8
- 238000005520 cutting process Methods 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- 239000002253 acid Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000006227 byproduct Substances 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 229910001873 dinitrogen Inorganic materials 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
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- 230000008859 change Effects 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 229910003460 diamond Inorganic materials 0.000 description 2
- 239000010432 diamond Substances 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 239000000696 magnetic material Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 229910021419 crystalline silicon Inorganic materials 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
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- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 239000011858 nanopowder Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- XJKVPKYVPCWHFO-UHFFFAOYSA-N silicon;hydrate Chemical compound O.[Si] XJKVPKYVPCWHFO-UHFFFAOYSA-N 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention discloses a purification method of micro-nano silicon powder, which utilizes magnetic separation, centrifugal separation, organic purification, metal purification, deoxidization purification, water washing and drying to comprehensively purify the micro-nano silicon powder, controls the impurity content of a micro-nano silicon powder product to be below 1000PPM, and is suitable for purifying micro-nano silicon powder from different sources.
Description
Technical Field
The invention belongs to the technical field of silicon materials, and particularly relates to a purification method of micro-nano silicon powder.
Background
Silicon is widely used as a semiconductor material, not only as a material of an integrated circuit, but also as a main raw material of the photovoltaic industry, and is also a raw material for producing silicon nitride, silicon carbide and some organic silicon; with the development of energy storage industry, silicon has great application potential as a negative electrode material.
Compared with the graphite material widely used at present, the silicon material has very high theoretical specific capacity (4200 mAh/g) and lower electrochemical lithium intercalation potential, has excellent quick charge performance, and is an excellent negative electrode material of a lithium ion battery; the silicon cathode is an urgent need for development of a series of new technical fields such as portable electronic products, unmanned aerial vehicles, new energy automobiles, energy storage battery systems and the like.
The sources of the existing micro-nano silicon powder for preparing the silicon cathode mainly comprise the following three types:
(1) gas phase synthesis: comprises preparing nanometer silicon powder by a plasma enhanced chemical vapor deposition method, a laser induced vapor deposition method and a fluidized bed method;
(2) mechanical ball milling method: grinding the silicon material with larger size into micro-nano size powder by utilizing mechanical rolling force and shearing force generated by mechanical rotation and interaction between particles; grinding aid is added in the grinding process, impurities are easy to introduce, and the purity of the product is low.
(3) By-product of silicon wafer cutting link: in the diamond wire cutting process of monocrystalline silicon or polycrystalline silicon, silicon powder generated when a silicon rod is cut by a diamond wire is deposited into cutting slurry together with other impurities to form silicon mud byproducts;
however, the three sources of micro-nano silicon powder have different degrees of pollution. The surface of the silicon powder can be corroded and polluted by water and oxygen in a contacted device or atmosphere, and impurities of metals and organic matters can be adhered to the silicon powder; the contamination of the metal in the silicon can affect the self-discharge of the cathode or the high content of the metal can increase the risk of safety problems such as short circuit, overheat and the like of the battery, and the oxygen content is somewhat related to the capacity loss and the internal resistance of the battery; in addition, too low an oxygen content may also lead to a decrease in the energy density of the battery, limiting the service life of the battery. Therefore, the purification of the surface of the silicon powder directly influences the subsequent processing technology and the application direction.
At present, great technical difficulty exists in purifying micro-nano silicon powder; this is because micro-nano silicon powder has a small particle size and a large specific surface area, and thus is extremely easily contaminated by corrosion and clamps or adheres impurities, and thus it is difficult to remove various impurities therein cleanly, and there is a problem of secondary pollution during the purification process.
In the prior art, no report is made on purification of silicon powder from different sources, and the silicon powder is generally byproduct silicon mud related to a cutting link. For example, CN106865552a discloses a method for recovering high purity silicon powder from cutting waste slurry of crystalline silicon, which performs magnetic separation, solid-liquid separation, acid leaching, drying and screening on the collected waste slurry to obtain high purity silicon powder; but this method does not take into account organic and oxygen contamination in the silicon powder. For another example, patent CN115353112a discloses a method for sorting and purifying photovoltaic silicon mud, comprising: removing organic auxiliary agents, adding mixed acid liquor with a certain concentration, stirring and immersing, gravity separation, press filtration or centrifugal dehydration; however, the method does not process the oxygen pollution in the silicon mud.
Therefore, the purified micro-nano silicon powder in the prior art still has impurities with oxygen and metal content, in other words, a method for effectively controlling the purified micro-nano silicon powder is not available in the prior art.
Disclosure of Invention
The invention aims to provide a purification method of micro-nano silicon powder, which controls the impurity content of a micro-nano silicon powder product to be below 1000 PPM.
The invention is realized by the following technical scheme:
the purifying process of micro nanometer silica powder includes the following steps:
dispersing micro-nano silicon powder to be treated in a solvent to obtain silicon powder slurry, carrying out one or more of magnetic separation treatment, centrifugal purification treatment, organic purification treatment and metal purification treatment on the silicon powder slurry according to the impurity composition in the micro-nano silicon powder to be treated, carrying out deoxidation purification treatment, and finally washing and drying to obtain a purified micro-nano silicon powder product; or directly deoxidizing and purifying the silica powder slurry to be treated, and then washing and drying to obtain a purified micro-nano silica powder product;
wherein,
the magnetic separation treatment comprises the following steps: carrying out magnetic separation on the silica powder slurry by a magnetic separator, and removing magnetic impurities in the silica powder slurry to obtain treated silica powder slurry;
the centrifugal purification treatment is as follows: centrifugally separating the silica powder slurry to separate heterogeneous particles in the silica powder to obtain classified concentrated silica powder slurry, and then performing filter pressing to remove solvent from the classified concentrated silica powder slurry to obtain treated silica powder;
the organic purification treatment comprises the following steps: adding an oxidant into the silicon powder slurry to perform stirring reaction, and performing centrifugal separation and desolventizing to obtain treated silicon powder;
the metal purification treatment comprises the following steps: adding inorganic acid into the silica powder slurry to perform stirring reaction so as to remove metal impurities, and then performing filter pressing to remove solvent to obtain treated silica powder;
the deoxidization and purification treatment comprises the following steps: adding a chemical reagent containing hydrofluoric acid into the silica powder slurry to perform stirring reaction so as to remove oxygen-containing impurities, and then performing filter pressing and desolventizing to obtain treated silica powder;
the water washing and drying steps are as follows: and stirring, cleaning, press-filtering and dehydrating the deoxidized and purified silicon powder by pure water, and then removing water by vacuum drying.
When the micro-nano silicon powder to be treated is subjected to multistage treatment, the silicon powder after the previous stage treatment is firstly dispersed into silicon powder slurry by using a solvent, and then the next stage treatment is performed.
The invention is based on micro-nano silicon powder with different sources, and summarizes main pollution sources in the micro-nano silicon powder as follows: metals, oxygen, organics, heterogeneous particles and moisture; the invention aims at the characteristics of the pollution source and the micro-nano silicon powder, and a method for purifying the micro-nano silicon powder in an omnibearing way by utilizing a wet chemical method is determined through long-time research, and the method specifically combines magnetic separation, centrifugal purification, organic purification, metal purification and deoxidization purification.
The specific principle of the invention is as follows:
(1) removing the magnetic material by magnetic separation, and facilitating the subsequent purification process;
(2) adopting a centrifugal separation process, removing heterogeneous particles with different particle diameters and densities, such as plastic particles, silicon carbide and other impurity particles brought by a cutting or grinding device by controlling the rotating speed, and classifying and concentrating the silicon powder; the invention applies centrifugal separation technology to the separation of heterogeneous particles in silicon powder for the first time;
(3) in the organic purification step, an oxidant is utilized to effectively remove organic matters adhered to the surface of the silicon powder;
(4) the inorganic acid is utilized to effectively remove metal impurities in the metal purification step;
(5) the invention finally uses hydrofluoric acid to deoxidize and purify, on one hand, oxygen-containing impurities (such as silicon dioxide) are removed, and on the other hand, oxygen pollution caused by the subsequent purification procedure is avoided;
the invention not only can effectively purify pollutants such as metal, oxygen-containing impurities, moisture, heterogeneous particles, organic matters and the like in the micro-nano silicon powder, but also does not change the microstructure and the property of the main body of the micro-nano silicon powder in the process of purifying the micro-nano silicon powder, thereby being beneficial to the application of products.
There is no limitation on the operation sequence of the magnetic separation treatment, the centrifugal purification treatment, the organic purification treatment, and the metal purification treatment, but when the magnetic separation treatment and the metal purification treatment are adopted, it is preferable to perform the magnetic separation treatment first and then the metal purification treatment.
The solvent is pure water or ethanol; when the organic purification treatment, the metal purification treatment or the deoxidization purification treatment is performed, the solvent of the silica powder slurry is pure water.
As a specific embodiment of the invention, the purification method of the micro-nano silicon powder comprises the following steps:
(1) Dispersing: placing micro-nano silicon powder to be treated in a solvent for stirring and dispersing to obtain silicon powder slurry;
(2) Magnetic separation: carrying out magnetic separation on the silica powder slurry through a magnetic separator, and removing magnetic materials in the silica powder slurry;
(3) And (3) centrifugal purification treatment: centrifugally separating the silica powder slurry treated in the step (2) to separate heterogeneous particles in the silica powder, thereby obtaining concentrated slurry of the silica powder which is classified and concentrated; then, carrying out filter pressing to remove solvent on the classified concentrated silica powder slurry to obtain treated silica powder;
(4) Organic purification treatment: adding pure water into the silicon powder treated in the step (3) for dispersion, adding an oxidant for stirring reaction, and then performing centrifugal separation and desolventizing to obtain treated silicon powder;
(5) And (3) metal purification treatment: adding pure water into the silicon powder treated in the step (4) for dispersion, adding inorganic acid for stirring reaction to remove metal impurities, and then performing filter pressing and desolventizing to obtain treated silicon powder;
(6) Deoxidizing and purifying: adding pure water into the silicon powder treated in the step (5) for dispersion, adding a chemical reagent containing hydrofluoric acid for stirring reaction to remove oxygen-containing impurities, and then performing filter pressing and desolventizing to obtain treated silicon powder;
(7) Washing and drying: and (3) stirring, cleaning, press-filtering and dehydrating the silicon powder treated in the step (6) by using pure water, and then removing water through vacuum drying to obtain a purified micro-nano silicon powder product.
Preferably, the silicon powder micro-nano silicon powder to be treated is placed in a solvent for stirring and dispersing, and the stirring rotating speed is 300-2000 RPM; further, ultrasonic waves can be superimposed during the stirring and dispersing process to assist in the dispersion of the silicon powder.
Further, before purification, the impurity composition in the micro-nano silicon powder to be treated is detected and analyzed, including the components, states and contents thereof.
Preferably, during the centrifugal purification treatment, the rotating speed of a centrifugal separator is adjusted according to the density and the particle size of heterogeneous particles clamped by micro-nano silicon powder to carry out multistage centrifugal separation on the silicon powder slurry so as to remove various heterogeneous particles; that is, the rotational speed of the centrifuge depends on the density and particle size of the foreign particles.
Preferably, the rotational speed of the centrifugal separator during the centrifugal cleaning treatment is 1000 to 9000RPM.
Preferably, the oxidant used in the organic purification treatment is hydrogen peroxide, and the dosage of the oxidant is equivalent or excessive needed for removing organic impurities in the silicon powder; in the organic purification treatment, an oxidant is added into the silica powder slurry, and the mixture is stirred for reaction for more than or equal to 15 minutes at 120-1600 RPM; the reaction is carried out for 15 minutes to substantially complete the removal of impurities, and the specific reaction time is 15 to 60 minutes.
Preferably, the specific operation of the organic purification treatment is as follows: after the silicon powder is dispersed, firstly adding hydrogen peroxide to carry out mixing and stirring reaction, then carrying out centrifugal separation, taking a part with high silicon powder content, and finally carrying out desolventizing treatment through filter pressing to obtain concentrated silicon powder slurry or silicon powder mud (i.e. treated silicon powder); the rotational speed of the centrifugal separation is 1000-9000 RPM.
Preferably, in the metal purifying treatment, the inorganic acid is one or more of hydrochloric acid, acetic acid and hydrofluoric acid, and the reaction time is more than or equal to 15 minutes, and the specific reaction time is 15-60 minutes, with stirring at more than or equal to 60 RPM. The amount of mineral acid is the equivalent or excess required to remove the metal-containing impurities.
Preferably, the filter press employed in the metal purification treatment is a cross-flow filter press; compared with forward pressure filtration, the cross-flow pressure filtration is used for concentrating and separating silica powder slurry, accumulation of filter materials is avoided, impurities dissolved in a solution or a solvent can be thoroughly filtered through the filter membrane, the filter materials are prevented from clamping the impurities, and efficient separation of the impurities and the filter materials is realized.
Preferably, in the deoxidation and purification treatment, the stirring reaction time after the chemical reagent is added is more than or equal to 15 minutes, and the specific reaction time is 15-60 minutes. The dosage of the hydrofluoric acid is equivalent or excessive needed for removing oxygen-containing impurities from the silicon powder.
The deoxidation and purification treatment adopts the conventional forward pressure filtration operation; preferably, inert gas is filled in the filter pressing process for protection. The inert gas adopted by the invention is nitrogen.
Preferably, the washing operation is as follows: adding pure water into the deoxidized and purified silicon powder, stirring and cleaning, performing filter pressing and dehydration, adding water and stirring, performing filter pressing and dehydration, and repeating the processes of adding water, stirring and filter pressing for a plurality of times; the stirring speed is not more than 2000RPM.
Preferably, the last filter pressing in the washing operation is performed by adopting an ultrahigh pressure filter press so as to quickly filter out the moisture in the silicon powder and reduce the residual moisture in the silicon powder as much as possible, thereby reducing the risk of secondary pollution of the silicon powder by oxygen in the process.
Preferably, inert gas is introduced in the process of washing to protect, so that the pollution caused by introducing oxygen in the operation process is avoided.
More preferably, in the centrifugal separation and filter pressing processes, inert gas can be introduced to protect, so that silicon powder is prevented from contacting oxygen, and the risk of introducing oxygen pollution is reduced.
Preferably, the drying is vacuum drying, that is, under low vacuum, the moisture in the silicon powder is evaporated at the temperature of not more than 60 ℃, and preferably, inert gas or inert gas and IPA (isopropyl alcohol) steam are introduced in the drying process to carry out auxiliary heat transfer.
Further, the invention also comprises packaging protection, in particular to vacuum air-pumping packaging or vacuum air-pumping inert gas-filling packaging for the purified micro-nano silicon powder product.
The inert gas and IPA (isopropyl alcohol) used in the invention all need to have purity of more than 99.99%, and the inert gas and IPA are subjected to purification treatment, water removal, oil removal, pressurization and temperature control treatment before use.
Compared with the prior art, the invention has the following advantages:
the method of the invention utilizes magnetic separation, centrifugal purification, organic purification, metal purification, deoxidization purification, water washing and drying, can comprehensively purify the micro-nano silicon powder, effectively remove metal, heterogeneous particles, organic matters and oxygen-containing impurities clamped or adhered in the micro-nano silicon powder, does not change the microstructure and the property of the micro-nano silicon powder main body in the purification process, and is suitable for purifying micro-nano silicon powder from different sources.
The inventor selects proper technological parameters such as stirring speed, reaction time, centrifugal separation rotating speed and the like during reaction through repeated experiments so as to ensure that impurities can be effectively removed and oxygen pollution caused by long operation time can be avoided; and adopting inert gas protection and ultra-high pressure filter pressing to control the contact concentration and time of the micro-nano silicon powder, water and oxygen in the purification process, so as to avoid secondary pollution by oxygen in the purification process.
After the purified micro-nano silicon powder product is placed for 45 days, the impurity content of the micro-nano silicon powder product is still kept below 1000PPM, the requirement of the silicon as a battery cathode raw material for the purity is met, and the product is ensured to have high quality when being applied to downstream industries.
In addition, the method is an omnibearing purification method, and a person skilled in the art can select the treatment steps of the micro-nano silicon powder to be treated according to the requirement of downstream industry on the purity of the micro-nano powder so as to adapt to the requirement.
Detailed Description
The following examples are only for illustration of the invention, and the scope of the invention is not limited to the following examples. The object of the present invention can be achieved by those skilled in the art based on the above disclosure of the present invention and the ranges taken by the parameters.
Example 1
TABLE 1
(1) And (3) taking silicon powder mud as a byproduct in the silicon wafer cutting process, detecting and analyzing impurity components, states and contents (the main impurity contents are shown in the table 1), adding the silicon powder mud into pure water (the resistivity is more than 10 megaohms) with the weight of 5 times, dispersing the silicon powder mud for 60 minutes by using stirring paddles at the rotating speed of 1000-1800 RPM, and controlling the temperature below 50 ℃ to form silicon powder slurry.
(2) And (3) carrying out magnetic separation on the silica powder slurry by a magnetic separator.
(3) The silicon powder slurry passes through a centrifugal separator and is subjected to multistage separation at a rotating speed of 1000-9000 RPM (specific rotating speed is determined according to the particle size and density of the impurity content of the silicon powder slurry); and (3) carrying out desolventizing on the classified concentrated silica powder slurry through a forward filter press to obtain treated silica powder.
(4) Adding 5 times of pure water into the silicon powder treated in the step (3), adding hydrogen peroxide (the concentration of the hydrogen peroxide reaches 8% of the total solution concentration), and stirring at 120-1600 RPM for 15-60 minutes; and then, performing solid-liquid separation by using a centrifugal separator at a rotating speed of 1000-9000 RPM, and then performing solvent removal by press filtration to obtain the treated silicon powder.
(5) Adding 5 times of pure water by weight into the silicon powder treated in the step (4), adding hydrochloric acid (the concentration of the silicon powder reaches 8% of the total solution concentration), stirring at the rotating speed of 60-150 RPM for 15-60 minutes, and controlling the temperature to be not more than 60 ℃; and pumping the silica powder slurry, and performing cross-flow filter pressing to obtain treated silica powder, wherein water can be added simultaneously in the process, and the PH value is adjusted to be more than 4.
(6) Adding pure water into the silicon powder treated in the step (5), wherein the total capacity is not lower than the total capacity before cross-flow filter pressing concentration;
adding hydrofluoric acid (the concentration of which reaches 8% of the total solution concentration), stirring for 15 minutes at the rotating speed of 60-150 RPM, filling inert gas for protection, and carrying out forward pressure filtration for deacidification.
(7) Adding pure water into silicon powder under the protective atmosphere of inert gas, stirring and cleaning, forward pressure filtering again to remove acid, adding pure water again, repeating for a plurality of times until the PH is near neutral (6-7), and performing ultra-high pressure plate filtration to perform rapid pressure filtration to obtain silicon powder blocks; placing the silicon powder blocks into a vacuum drying oven for dehydration, wherein the temperature is not more than 60 ℃, the vacuum pressure is not more than-0.090 MPA, and introducing inert gas for auxiliary heat transfer; then, crushing is carried out under the atmosphere of inert gas, and then air-grinding crushing is carried out under the atmosphere of inert gas protection, so as to obtain the purified silicon powder product.
(8) Vacuum nitrogen gas filling and packaging are carried out. Table 2 shows the measured values after 45 days of product placement.
TABLE 2
Example 2
TABLE 3 Table 3
(1) The silicon powder prepared by mechanical grinding is taken, the impurity components, states and contents (the main impurity contents are shown in the table 3) in the silicon powder are detected and analyzed, the silicon powder is added into ethanol with the weight of 5 times of the silicon powder, and the silicon powder is dispersed for 60 minutes at the rotating speed of 1000-1800 RPM through stirring paddles, and the temperature is controlled below 50 ℃ to form silicon powder slurry.
(2) And (3) carrying out magnetic separation on the silica powder slurry by a magnetic separator.
(3) The silicon powder slurry passes through a centrifugal separator and is subjected to multistage separation (specific rotation speed is determined according to the particle size and density of the impurity content) at the rotation speed of 1000-9000 RPM; and (3) carrying out desolventizing on the classified concentrated silica powder slurry through a forward filter press to obtain treated silica powder.
(4) Adding 5 times of pure water into the silicon powder treated in the step (3), adding hydrogen peroxide (the concentration of the hydrogen peroxide reaches 15% of the total solution concentration), and stirring at 120-1600 RPM for 15-60 minutes; and then, performing solid-liquid separation by using a centrifugal separator at a rotating speed of 1000-9000 RPM, and then performing filter pressing to remove solvent to obtain the treated silicon powder.
(5) Adding 5 times of pure water by weight to the silicon powder treated in the step (4), simultaneously adding hydrochloric acid (the concentration is more than 8 percent calculated according to the total solution) and hydrofluoric acid (the concentration is more than 5 percent calculated according to the total solution), stirring at the rotating speed of 60-150 RPM for 15-60 minutes, and controlling the temperature to be not more than 60 ℃.
And pumping silica powder slurry, and carrying out cross-flow filter pressing on the silica powder slurry by a filter rod to obtain treated silica powder, wherein water can be added simultaneously in the process, and the PH value is adjusted to be more than 4.
(6) Adding pure water into the silicon powder treated in the step (5), wherein the total capacity is not lower than the total capacity before cross-flow filter pressing; adding hydrofluoric acid (the concentration of which reaches 5% of the total solution concentration) and ethanol (the concentration of which reaches 0.5% of the total solution concentration), stirring for 15 minutes at the rotating speed of 60-2000 RPM, and charging inert gas for protection to perform forward pressure filtration and deacidification.
(7) Adding pure water into silicon powder under the protective atmosphere of inert gas, stirring and cleaning, forward pressure filtering again to remove acid water, adding pure water again, repeating for many times until the PH is nearly neutral, and performing ultra-high pressure filtering to obtain silicon powder cake; putting the silicon powder cake into a vacuum drying oven, dehydrating at a temperature of not more than 60 ℃ and a vacuum pressure of not more than-0.094 MPA, and controlling the water content below 0.1%; then crushing under the atmosphere of inert gas, and then grinding under the atmosphere of inert gas protection to obtain the purified silicon powder product.
(8) Vacuum nitrogen gas filling and packaging are carried out. Table 4 shows the measured values after 45 days of product placement.
TABLE 4 Table 4
Example 3
TABLE 5
(1) The silicon powder collected by the vapor synthesis method is taken, the impurity components, states and contents (the main impurity contents are shown in the table 5) in the silicon powder are detected and analyzed, the silicon powder is added into ethanol with the weight of 5 times of the silicon powder, and the silicon powder is dispersed at 1000-1800 RPM through stirring paddles for 60 minutes, and the temperature is controlled below 50 ℃ to form silicon powder slurry.
(2) And (3) carrying out magnetic separation on the silica powder slurry by a magnetic separator.
(3) The silicon powder slurry passes through a centrifugal separator, and simultaneously inert gas is filled into the centrifugal separator at a rotating speed of 1000-9000 RPM (specific rotating speed is determined according to the particle size and density of the impurity content) to carry out multistage separation; and (3) introducing inert gas into the classified concentrated silica powder slurry, and passing through a forward filter press to remove solvent to obtain treated silica powder.
(4) Adding 5 times of pure water into the silicon powder treated in the step (3), adding hydrogen peroxide (the concentration of the hydrogen peroxide reaches 2% of the total solution concentration), and stirring at 120-1600 RPM for 15-60 minutes;
then, inert gas is introduced into a centrifugal separator, and solid-liquid separation and desolventizing are carried out at the rotating speed of 1000-9000 RPM, so that the treated silicon powder is obtained.
(5) Adding 5 times of pure water by weight to the silicon powder treated in the step (4), adding hydrochloric acid (the concentration is more than 8% calculated by the total solution) and hydrofluoric acid (the concentration is more than 1% calculated by the total solution) to stir, rotating at 60-150 RPM for 15-60 minutes, and controlling the temperature to be not more than 60 ℃.
And pumping silica powder slurry, and carrying out cross-flow filter pressing on the silica powder slurry by a filter rod to obtain treated silica powder, wherein water can be added simultaneously in the process, and the PH value is adjusted to be more than 4.
(6) And (3) adding pure water into the silicon powder treated in the step (5), wherein the total capacity is not lower than the total capacity before cross-flow filter pressing concentration.
Adding hydrofluoric acid (the concentration of which reaches 5 percent of the total solution concentration), stirring for 15 minutes, and introducing inert gas to carry out forward pressure filtration for deacidification at the rotating speed of 60-150 RPM.
(7) Adding pure water into the silicon powder, stirring and cleaning, introducing inert gas again to perform forward pressure filtration for deacidification, adding pure water again, repeating for a plurality of times until the PH is approximately neutral 7 (6-7), and stirring at the same time; and carrying out plate filtration and press filtration to obtain the silica powder cake.
The silicon powder cake is put into a vacuum drying oven for dehydration, inert gas is introduced for carrying out the dehydration at the temperature of not more than 60 ℃ and the vacuum pa degree of not less than-0.080 Mpa, and the inert gas and IPA vapor are introduced for auxiliary heat transfer. Then crushing under the atmosphere of inert gas, and then grinding under the atmosphere of inert gas protection to obtain the purified silicon powder product.
(8) Vacuum nitrogen gas filling and packaging are carried out. Table 6 shows the measured values after 45 days of product placement.
TABLE 6
The present invention may be summarized in other specific forms without departing from the spirit or essential characteristics thereof. The above-described embodiments of the present invention are to be considered in all respects only as illustrative and not restrictive. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments according to the essential technology of the present invention fall within the scope of the present invention.
Claims (10)
1. The purification method of the micro-nano silicon powder is characterized by comprising the following steps of:
dispersing micro-nano silicon powder to be treated in a solvent to obtain silicon powder slurry, carrying out one or more of magnetic separation treatment, centrifugal purification treatment, organic purification treatment and metal purification treatment on the silicon powder slurry according to the impurity composition in the micro-nano silicon powder to be treated, carrying out deoxidation purification treatment, and finally washing and drying to obtain a purified micro-nano silicon powder product; or directly deoxidizing and purifying the silica powder slurry to be treated, and then washing and drying to obtain a purified micro-nano silica powder product;
wherein,
the magnetic separation treatment comprises the following steps: carrying out magnetic separation on the silica powder slurry by a magnetic separator, and removing magnetic impurities in the silica powder slurry to obtain treated silica powder slurry;
the centrifugal purification treatment is as follows: centrifugally separating the silica powder slurry to separate heterogeneous particles in the silica powder to obtain classified concentrated silica powder slurry, and then performing filter pressing to remove solvent from the classified concentrated silica powder slurry to obtain treated silica powder;
the organic purification treatment comprises the following steps: adding an oxidant into the silicon powder slurry to perform stirring reaction, and performing centrifugal separation and desolventizing to obtain treated silicon powder;
the metal purification treatment comprises the following steps: adding inorganic acid into the silica powder slurry to perform stirring reaction so as to remove metal impurities, and then performing filter pressing to remove solvent to obtain treated silica powder;
the deoxidization and purification treatment comprises the following steps: adding a chemical reagent containing hydrofluoric acid into the silica powder slurry to perform stirring reaction so as to remove oxygen-containing impurities, and then performing filter pressing and desolventizing to obtain treated silica powder;
the water washing and drying steps are as follows: and stirring, cleaning, press-filtering and dehydrating the deoxidized and purified silicon powder by pure water, and then removing water by vacuum drying.
2. The method according to claim 1, wherein the rotational speed of the centrifugal separator is adjusted to perform multistage centrifugal separation on the silicon powder slurry according to the density and the particle size of the heterogeneous particles clamped by the micro-nano silicon powder during the centrifugal purification treatment, so as to remove various heterogeneous particles.
3. The purification method according to claim 2, wherein the oxidant used in the organic purification treatment is hydrogen peroxide, and the reaction is stirred for not less than 15 minutes at 120RPM to 1600 RPM.
4. The method according to claim 3, wherein the inorganic acid used in the metal purifying treatment is one or more of hydrochloric acid, acetic acid and hydrofluoric acid, and the reaction time is not less than 15 minutes at not less than 60 RPM.
5. The purification process of claim 4, wherein the filter press employed in the metal purification treatment is a cross-flow filter press.
6. The purification method according to claim 5, wherein in the deoxidation purification treatment, the reaction time is 15 minutes or more after the chemical reagent is added; and (5) filling inert gas in the filter pressing process for protection.
7. The method of claim 6, wherein the washing is performed by: after being stirred and cleaned by pure water, the mixture is subjected to filter pressing dehydration, then water is added for stirring, then the mixture is subjected to filter pressing dehydration, and the processes of water addition, stirring and filter pressing are repeated for a plurality of times.
8. The purification method according to claim 7, wherein the inert gas is introduced during the washing process to protect the process from oxygen introduced during the operation.
9. The purification method according to claim 8, wherein the solvent is pure water or ethanol; when the organic purification treatment, the metal purification treatment or the deoxidization purification treatment is performed, the solvent of the silica powder slurry is pure water.
10. Purification method according to any one of claims 1 to 9, characterized in that it further comprises packaging protection, in particular vacuum-pumping packaging or vacuum-pumping inert gas-filled packaging of the purified micro-nano silicon powder product.
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