CN114784260A - Modified silicon material for lithium ion battery and preparation method and application thereof - Google Patents
Modified silicon material for lithium ion battery and preparation method and application thereof Download PDFInfo
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- 239000002210 silicon-based material Substances 0.000 title claims abstract description 99
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 42
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 42
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 150000003376 silicon Chemical class 0.000 claims abstract description 53
- 238000000034 method Methods 0.000 claims abstract description 33
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 24
- 239000010439 graphite Substances 0.000 claims abstract description 24
- 239000010406 cathode material Substances 0.000 claims abstract description 18
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 30
- 239000011248 coating agent Substances 0.000 claims description 30
- 238000000576 coating method Methods 0.000 claims description 26
- 239000007773 negative electrode material Substances 0.000 claims description 24
- 239000011347 resin Substances 0.000 claims description 21
- 229920005989 resin Polymers 0.000 claims description 21
- 239000002356 single layer Substances 0.000 claims description 18
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 claims description 17
- 239000003729 cation exchange resin Substances 0.000 claims description 17
- 239000000377 silicon dioxide Substances 0.000 claims description 15
- 235000012239 silicon dioxide Nutrition 0.000 claims description 15
- 239000010410 layer Substances 0.000 claims description 13
- 239000002245 particle Substances 0.000 claims description 13
- 239000002002 slurry Substances 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000007254 oxidation reaction Methods 0.000 claims description 10
- 239000002243 precursor Substances 0.000 claims description 10
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 239000002910 solid waste Substances 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 7
- 239000003960 organic solvent Substances 0.000 claims description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 3
- 239000002202 Polyethylene glycol Substances 0.000 claims description 3
- 239000006185 dispersion Substances 0.000 claims description 3
- 229920001223 polyethylene glycol Polymers 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 231100001261 hazardous Toxicity 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 17
- 229910052710 silicon Inorganic materials 0.000 abstract description 17
- 239000010703 silicon Substances 0.000 abstract description 17
- 230000008901 benefit Effects 0.000 abstract description 7
- 230000008569 process Effects 0.000 abstract description 7
- 238000007599 discharging Methods 0.000 abstract description 4
- 238000013329 compounding Methods 0.000 abstract description 3
- 238000000713 high-energy ball milling Methods 0.000 abstract description 3
- 238000011161 development Methods 0.000 abstract description 2
- 230000014759 maintenance of location Effects 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 16
- 229910021383 artificial graphite Inorganic materials 0.000 description 6
- 238000000498 ball milling Methods 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 6
- 238000011065 in-situ storage Methods 0.000 description 6
- 238000002156 mixing Methods 0.000 description 5
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 4
- 238000011049 filling Methods 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
- 229910052863 mullite Inorganic materials 0.000 description 4
- 239000010405 anode material Substances 0.000 description 3
- 238000004146 energy storage Methods 0.000 description 3
- 238000005562 fading Methods 0.000 description 3
- 241000411851 herbal medicine Species 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000007873 sieving Methods 0.000 description 3
- 239000007921 spray Substances 0.000 description 3
- 238000001694 spray drying Methods 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000007888 film coating Substances 0.000 description 1
- 238000009501 film coating Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
Abstract
The invention discloses a preparation method of a modified silicon material for a lithium ion battery, which can effectively inhibit the volume expansion of micron silicon in the charging and discharging processes; a modified silicon material for lithium ion batteries, which can reduce internal resistance and improve the charging speed of the lithium ion batteries; a method for preparing a graphite cathode material by using a modified silicon material, which has simple and easy-to-realize process, and a method for preparing a graphite cathode material by using a modified silicon material with excellent electrochemical performance. The advantages are that: according to the invention, after the silicon material is modified and then is subjected to high-energy ball milling compounding with the graphite cathode material, the expansion rate of the pole piece can be effectively reduced, higher first discharge specific capacity, first charge specific capacity, first coulombic efficiency and capacity retention rate after 30-week circulation can be realized, and the method has a great promotion significance on the development of lithium ion batteries.
Description
The technical field is as follows:
the invention relates to the field of preparation of negative electrode materials, in particular to a modified silicon material for a lithium ion battery and a preparation method and application thereof.
The background art comprises the following steps:
with the problems of natural resource reduction, environmental pollution and the like, people are gradually exploring the application of renewable resources, but the renewable energy has the main characteristics of discontinuity, and the time and the place of energy generation are not in accordance with the actual requirements under the common conditions, so most renewable energy needs to be utilized by an energy storage device. Compared with the traditional lead-acid battery and nickel-hydrogen battery, the lithium ion battery has the advantages of high specific energy and long service life, and has the largest specific energy and specific power among all practical energy storage batteries, so the lithium ion battery is widely applied. The diversity of electrode material selection of the lithium ion battery also has great promotion space, and the lithium ion battery also becomes the best viewed energy storage battery. Currently, commercially available lithium ion batteries mainly use graphite as a negative electrode material. However, the specific capacity of the commercialized graphite anode material has been close to its theoretical value of 372mAh/g, and there is a limited space for further improvement, and therefore, it is necessary to develop a lithium ion battery anode material having a higher specific capacity. In the existing negative electrode material, the specific lithium storage capacity of silicon is the highest, and the theoretical value reaches 4200 mAh/g. However, when the silicon is used in a lithium ion battery for lithium intercalation and deintercalation in the charging and discharging processes, the silicon can generate violent volume effect (more than 300 percent), which leads to pulverization of active substances and shedding from a current collector. The powdered active substance can continuously break and rebuild a Solid Electrolyte Interface (SEI) film at a crack, and continuously consume electrolyte, so that the internal resistance is increased, the capacity attenuation is accelerated, and the application of the silicon material in the aspect of the lithium ion battery cathode material is seriously hindered.
The invention content is as follows:
in order to solve the above problems, a first object of the present invention is to provide a method for preparing a modified silicon material for lithium ion batteries, which can effectively inhibit the volume expansion of micron silicon during the charging and discharging processes; the second purpose of the invention is to provide a modified silicon material for lithium ion batteries, which can reduce internal resistance and improve the charging speed of the lithium ion batteries; the third purpose of the invention is to provide a method for preparing a graphite cathode material by using a modified silicon material, which has a simple and easy-to-implement process, and the fourth purpose of the invention is to provide a graphite cathode material prepared by using a modified silicon material, which has excellent electrochemical performance.
The first purpose of the invention is implemented by the following technical scheme:
a preparation method of a modified silicon material for a lithium ion battery comprises the following steps:
(1) coating a layer of silicon dioxide film on the surface of the silicon material to obtain a single-layer coated silicon material;
(2) and (2) coating a layer of resin film on the surface of the silicon material with the single-layer coating obtained in the step (1) to obtain the modified silicon material.
Preferably, in the step (1), the particle size of the silicon material is in the micron order.
Preferably, the silicon material D50 is 1.2-1.8 μm.
Preferably, in the step (1), the silicon material is subjected to an oxidation reaction at a medium temperature, so that a layer of silicon dioxide film is coated on the surface of the silicon material.
Preferably, in the step (1), the reaction temperature of the oxidation reaction is 400-600 ℃, and the reaction time is 30-90 minutes.
Preferably, in the step (2), the single-layer coated silicon material obtained in the step (1) is immersed in a resin solution to be uniformly dispersed to obtain precursor slurry, and the precursor slurry is dried to obtain the modified silicon material.
Preferably, in the step (2), the cation exchange resin is dissolved in an organic solvent to obtain the resin solution.
Preferably, in the step (2), the cation exchange resin is hazardous solid waste after boiler softened water treatment.
Preferably, in the step (2), the particle size of the cation exchange resin is 150 μm or less.
Preferably, in the step (2), the organic solvent is one of absolute ethyl alcohol, toluene and polyethylene glycol.
Preferably, in the step (2), the mass ratio of the cation exchange resin to the organic solvent is 3:100 to 8: 100.
Preferably, in the step (2), the dissolving is performed in a magnetic heating stirrer, the stirring speed is 300-500 r/min, the stirring time is 30-60 minutes, and the heating dissolving temperature is 40-60 ℃.
Preferably, in the step (2), the dispersion time of the silicon material of the single-layer coating in the resin solution is 60 to 120 minutes.
Preferably, in the step (2), the mass ratio of the silicon material of the single-layer coating film to the resin is 100:1 to 100: 5.
The second object of the invention is implemented by the following technical solution: the modified silicon material is prepared by the preparation method of the modified silicon material for the lithium ion battery.
The third object of the present invention is achieved by the following technical solutions:
the method for preparing the graphite cathode material by using the modified silicon material comprises the step of carrying out ball-milling compounding on the modified silicon material and the graphite cathode material according to a proportion to prepare the modified graphite cathode material.
Preferably, the mass ratio of the modified silicon material to the graphite negative electrode material is 3: 100-6: 100.
the fourth purpose of the invention is implemented by the following technical scheme:
the graphite cathode material is prepared by the method for preparing the graphite cathode material by using the modified silicon material.
The invention has the advantages that:
1. under the condition that no other substance is added, micron silicon is heated at medium temperature in the air, and an in-situ oxidation reaction is carried out to form a layer of silicon dioxide film on the surface of the micron silicon, so that the volume expansion of the micron silicon in the charge-discharge process is inhibited, and the compatibility with electrolyte is improved;
2. coating a layer of resin on the surface of the silicon dioxide film in a liquid phase coating manner to achieve the purposes of secondary coating and further inhibiting the volume expansion of the silicon dioxide film;
3. the used coating agent resin is a dangerous solid waste after boiler softened water treatment, and a new way can be provided for the recovery treatment of the dangerous solid waste, so that the coating agent resin has obvious advantages in the aspect of raw material cost;
4. the modified graphite negative electrode material which has good compatibility with electrolyte, high capacity, long cycle life, low expansion rate of a pole piece and good comprehensive performance is obtained by modifying a silicon material and then performing high-energy ball milling compounding with a graphite negative electrode material and combining the advantage of high specific capacity of silicon and the advantage of low volume expansion rate of graphite;
5. the D50 particle size of the negative electrode material obtained by the method is 13-17 mu m, the particle size is smaller, and the charging speed can be improved after the negative electrode material is used in a lithium ion battery; the specific surface area is 1-2 m2The first coulombic efficiency can be improved after the lithium ion battery is used; the compacted density of the pole piece is more than or equal to 1.5g/cm3After the lithium ion battery is used, the wettability of the electrolyte can be improved, the internal resistance can be reduced, and the charging speed can be improved; the final button cell has the first discharge specific capacity up to 463.2mAh/g, the first coulombic efficiency up to 90.8, the expansion rate of the pole piece reduced to 9.4%, and excellent electrochemical performance.
The specific implementation mode is as follows:
the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
a preparation method of a modified silicon material for a lithium ion battery comprises the following steps:
(1) and (2) loading 1.5-micron silicon of 500g D50 μm into a mullite crucible, carrying out in-situ oxidation reaction in a box-type resistance furnace at 450 ℃ for 60 minutes to coat a layer of silicon dioxide film on the surface of the silicon material to obtain a silicon material with a single-layer coating, and taking out for later use.
(2) Taking 200g of cation exchange resin treated by boiler softened water, putting the cation exchange resin into a multifunctional Chinese herbal medicine grinder, grinding for 1 minute, transferring the ground cation exchange resin into a square-hole sieve with the diameter of 150 mu m and the fineness of 300 meshes, and sieving for 30 minutes in an electronic vibration machine; adding 8g of the sieved material into 100g of absolute ethyl alcohol, and heating and dissolving for 60 minutes in a magnetic heating stirrer under the conditions that the stirring speed is 450r/min and the dissolving temperature is 40 ℃ to obtain a resin solution;
taking 200g of single-layer coated silicon material, adding the silicon material into 108g of resin solution, and dispersing for 80 minutes to obtain precursor slurry; and (3) instantly spray-drying the precursor slurry by a spray dryer under the conditions that the inlet temperature is 240-300 ℃ and the outlet temperature is 100-120 ℃ to obtain the modified silicon material.
The basic principle is as follows: under the condition of not adding any other substance, micron silicon is heated at medium temperature in air, and in-situ oxidation reaction is carried out to form a layer of silicon dioxide film on the surface of the micron silicon, so that the volume expansion of the micron silicon in the charging and discharging process is inhibited. Then, a layer of resin is coated on the surface of the silicon dioxide film in a liquid phase coating mode, so that the purposes of secondary coating and further inhibiting the volume expansion of the silicon dioxide film are achieved. Moreover, the used coating agent resin is a dangerous solid waste after boiler softened water treatment, and professional companies are required to perform centralized treatment in the past, so that the treatment cost is increased; the invention provides a new way for recycling the dangerous solid waste because of recycling the dangerous solid waste, thereby having obvious advantages in the aspect of raw material cost of the coating agent.
Example 2:
a preparation method of a modified silicon material for a lithium ion battery comprises the following steps:
(1) and (3) loading the micron silicon with the thickness of 1.3 mu m of 500g D50 into a mullite crucible, carrying out in-situ oxidation reaction in a box-type resistance furnace at the temperature of 500 ℃ for 45 minutes to coat a layer of silicon dioxide film on the surface of the silicon material to obtain a silicon material with a single-layer coating, and taking out the silicon material for later use.
(2) Taking 200g of cation exchange resin treated by boiler softened water, putting the cation exchange resin into a multifunctional Chinese herbal medicine crusher, crushing for 1 minute, transferring the crushed cation exchange resin into a square-hole sieve with the diameter of 150 mu m and the fineness of 300 meshes, and sieving for 30 minutes in an electronic vibration machine; adding 6g of the sieved material into 100g of polyethylene glycol, and heating and dissolving for 40 minutes in a magnetic heating stirrer under the conditions that the stirring speed is 400r/min and the dissolving temperature is 45 ℃ to obtain a resin solution;
taking 200g of single-layer coated silicon material, adding the silicon material into 108g of resin solution, and dispersing for 65 minutes to obtain precursor slurry; and (3) instantly spray-drying the precursor slurry by a spray dryer under the conditions that the inlet temperature is 240-300 ℃ and the outlet temperature is 100-120 ℃ to obtain the modified silicon material.
Example 3:
a preparation method of a modified silicon material for a lithium ion battery comprises the following steps:
(1) and (3) loading 1.8-micron silicon of 500g D50 into a mullite crucible, carrying out in-situ oxidation reaction in a box-type resistance furnace at 550 ℃, reacting for 35 minutes to coat a layer of silicon dioxide film on the surface of the silicon material to obtain a silicon material with a single-layer coating, and taking out for later use.
(2) Taking 200g of cation exchange resin treated by boiler softened water, putting the cation exchange resin into a multifunctional Chinese herbal medicine crusher, crushing for 1 minute, transferring the crushed cation exchange resin into a square-hole sieve with the diameter of 150 mu m and the fineness of 300 meshes, and sieving for 30 minutes in an electronic vibration machine; adding 6g of the sieved material into 100g of toluene, and heating and dissolving for 40 minutes in a magnetic heating stirrer at the stirring speed of 400r/min and the dissolving temperature of 45 ℃ to obtain a resin solution;
taking 100g of silicon material with a single-layer coating film, adding the silicon material into 108g of resin solution, and dispersing for 80 minutes to obtain precursor slurry; and (3) instantly spray-drying the precursor slurry by a spray dryer under the conditions that the inlet temperature is 240-300 ℃ and the outlet temperature is 100-120 ℃ to obtain the modified silicon material.
Example 4:
the method for preparing the graphite cathode material from the modified silicon material prepared in the example 1 comprises the steps of filling the modified silicon material and the artificial graphite into a planetary ball mill according to the mass ratio of 3:100, mixing and ball milling for 4.5 hours under the condition that the rotating speed of the ball mill is 450r/min to prepare the modified cathode material, wherein the D50 particle size is 14.8 mu m, and the specific surface area is 1.48m2The compacted density of the pole piece is 1.58g/cm based on the coating weight3。
Example 5:
the method for preparing the graphite cathode material from the modified silicon material prepared in the example 2 comprises the steps of filling the modified silicon material and the artificial graphite into a planetary ball mill according to the mass ratio of 4:100, mixing and ball milling for 4.5 hours under the condition that the rotating speed of the ball mill is 450r/min to prepare the modified cathode material, wherein the D50 particle size is 15.2 mu m, and the specific surface area is 1.64m2(g), the compacted density of the pole piece is 1.61g/cm based on the coating weight3。
Example 6:
the method for preparing the graphite negative electrode material from the modified silicon material prepared in the embodiment 3 comprises the steps of filling the modified silicon material and the artificial graphite into a planetary ball mill according to the mass ratio of 5:100, mixing and ball milling for 8 hours under the condition that the rotating speed of the ball mill is 300r/min, and preparing the modified negative electrode material, wherein the D50 particle size is 16.4 mu m, and the specific surface area is 1.72m2The compacted density of the pole piece is 1.65g/cm based on the coating weight3。
Comparative example 1:
the artificial graphite is directly used as a negative electrode material, the D50 particle size is 14.1 mu m, and the specific surface area is 1.39m2The compacted density of the pole piece is 1.51g/cm based on the coating weight3。
Comparative example 2:
charging micron silicon with the D50 of 1.5 mu m and artificial graphite according to the mass ratio of 3:100 into a planetary ball mill, mixing and ball milling for 4.5 hours under the condition that the rotating speed of the ball mill is 450r/min to prepare the negative electrode material, wherein the D50 particle size is 14.9 mu m, and the specific surface area is 1.46m2The compacted density of the pole piece is 1.56g/cm based on the coating weight3。
Comparative example 3:
firstly, loading 1.5 mu m micrometer silicon of 500g D50 into a mullite crucible, carrying out in-situ oxidation reaction in a box-type resistance furnace at 450 ℃ for 60 minutes to coat a layer of silicon dioxide film on the surface of the silicon material, thus obtaining the silicon material with a single-layer film.
Secondly, filling the silicon material with the single-layer film coating and the artificial graphite into a planetary ball mill according to the mass ratio of 3:100, mixing and ball milling for 4.5 hours under the condition that the rotating speed of the ball mill is 450r/min to prepare a negative electrode material, wherein D50 particles of the negative electrode materialThe degree is 15.0 mu m, the specific surface area is 1.45m2The compacted density of the pole piece is 1.53g/cm based on the coating weight3。
Comparative example 4:
first, a modified silicon material was prepared in the same manner as in example 1, with the only difference from example 1 that: the silicon material is a micron silicon material with D50 of 0.9 μm.
Next, in the same manner as in example 4, a modified anode material having a particle size of D50 of 12.8 μm and a specific surface area of 2.4m was produced2The compacted density of the pole piece is 1.48g/cm based on the coating weight3。
Comparative example 5:
the modified graphite negative electrode materials for lithium ion batteries prepared by the preparation methods of the modified graphite negative electrode materials for lithium ion batteries respectively provided in examples 4, 5 and 6 and the negative electrode materials respectively provided in comparative examples 1, 2, 3 and 4 were prepared into lithium ion batteries respectively by the same method, specifically:
preparing a negative electrode material, a conductive agent SP, a dispersion thickening agent CMC and a binder SBR (mass fraction of 50%) according to a mass ratio of 95.5:1.5:1.5:1.5, adding deionized water to prepare a slurry, coating the slurry on a copper foil, and drying the slurry in a vacuum drying oven for 12 hours to prepare a negative electrode sheet, wherein the electrolyte takes a mixture of EC, EMC and DEC according to a volume ratio of 1:1:1 as a solvent, and VC accounting for 3% of the volume of the solvent is added as an electrolyte modification additive; and assembling the anode plate and a conventional anode plate into a button cell. 7 negative electrode materials corresponding to the above example 4, example 5, example 6, comparative example 1, comparative example 2, comparative example 3 and comparative example 4 are selected as the negative electrode materials, so that 7 corresponding button cells are obtained.
In this comparative example, the electrochemical performance of 7 button cell batteries was tested and the results are shown in table 1. The electrochemical performance test is carried out on a blue charge-discharge tester (CT 2001A). All button cells were left for 12h after fabrication.
TABLE 17 electrochemical performance test results of button cell
Comparing the electrochemical performances of the two button cells corresponding to the comparative examples 1 and 2 shows that the initial discharge specific capacity and the initial charge specific capacity can be greatly improved by adding the silicon material, but the initial coulomb efficiency can be reduced, the expansion rate of the pole piece can be increased, and the capacity attenuation is serious.
Comparing the electrochemical performances of the two button cells corresponding to the comparative examples 2 and 3 shows that after the silicon material coated with the silicon dioxide film is added, the expansion rate of the pole piece can be obviously reduced while the high first discharge specific capacity and the high first charge specific capacity are maintained, the first coulombic efficiency can be improved, and the capacity fading condition can be improved.
Comparing the electrochemical performances of the two button cells corresponding to the comparative example 3 and the example 4 shows that when the modified silicon material coated with the secondary film provided by the invention is added, the expansion rate of the pole piece can be further reduced, the capacity fading condition can be further improved and the effect is obvious while the high first discharge specific capacity, first charge specific capacity and first coulombic efficiency are maintained.
Comparing the electrochemical performances of two button cells corresponding to the comparative example 4 and the example 4 shows that the cell with better capacity fading condition and pole piece expansion rate condition can be obtained by the grain size range of the silicon material provided by the invention.
In conclusion, after the silicon material is modified and then is compounded with the graphite negative electrode material through the high-energy ball milling, the expansion rate of the pole piece can be effectively reduced, higher first discharge specific capacity, first charge specific capacity, first coulombic efficiency and capacity retention rate after 30-week circulation can be realized, the comprehensive performance is obviously superior to that of the comparative examples 1, 2, 3 and 4, and the composite material has great promotion significance on the development of the lithium ion battery.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to cover any modifications, equivalents, improvements, etc. within the spirit and scope of the present invention.
Claims (18)
1. A preparation method of a modified silicon material for a lithium ion battery is characterized by comprising the following steps:
(1) coating a layer of silicon dioxide film on the surface of the silicon material to obtain a single-layer coated silicon material;
(2) and (2) coating a resin film on the surface of the single-layer coated silicon material obtained in the step (1) to obtain the modified silicon material.
2. The method according to claim 1, wherein in the step (1), the particle size of the silicon material is micron-sized.
3. The method for preparing the modified silicon material for the lithium ion battery according to claim 2, wherein the silicon material D50 is 1.2-1.8 μm.
4. The method according to claim 1, wherein in the step (1), the silicon material is subjected to an oxidation reaction at a medium temperature, so that a layer of silicon dioxide film is coated on the surface of the silicon material.
5. The method for preparing the modified silicon material for the lithium ion battery according to claim 4, wherein in the step (1), the reaction temperature of the oxidation reaction is 400-600 ℃, and the reaction time is 30-90 minutes.
6. The preparation method of the modified silicon material for the lithium ion battery according to claim 1, wherein in the step (2), the single-layer coated silicon material obtained in the step (1) is immersed in a resin solution and uniformly dispersed to obtain a precursor slurry, and the precursor slurry is dried to obtain the modified silicon material.
7. The method for preparing the modified silicon material for the lithium ion battery according to claim 6, wherein in the step (2), the cation exchange resin is dissolved in an organic solvent to obtain the resin solution.
8. The method for preparing the modified silicon material for lithium ion batteries according to claim 7, wherein in the step (2), the cation exchange resin is hazardous solid waste after boiler softened water treatment.
9. The method of claim 7, wherein in the step (2), the particle size of the cation exchange resin is not more than 150 μm.
10. The method for preparing the modified silicon material for lithium ion batteries according to claim 7, wherein in the step (2), the organic solvent is one of absolute ethyl alcohol, toluene and polyethylene glycol.
11. The preparation method of the modified silicon material for the lithium ion battery according to claim 7, wherein in the step (2), the mass ratio of the cation exchange resin to the organic solvent is 3: 100-8: 100.
12. The method for preparing the modified silicon material for the lithium ion battery according to claim 7, wherein in the step (2), the dissolving is performed in a magnetic heating stirrer, the stirring speed is 300-500 r/min, the stirring time is 30-60 minutes, and the heating and dissolving temperature is 40-60 ℃.
13. The method for preparing the modified silicon material for the lithium ion battery according to claim 6, wherein in the step (2), the dispersion time of the silicon material with the single-layer coating in the resin solution is 60-120 minutes.
14. The preparation method of the modified silicon material for the lithium ion battery according to claim 6, wherein in the step (2), the mass ratio of the silicon material of the single-layer coating film to the resin is 100: 1-100: 5.
15. A modified silicon material prepared by the method of any one of claims 1-14 for preparing a modified silicon material for lithium ion batteries.
16. The method for preparing the graphite cathode material by using the modified silicon material of claim 15, wherein the modified silicon material and the graphite cathode material are ball-milled and compounded according to a certain proportion to prepare the modified graphite cathode material.
17. The method for preparing the graphite negative electrode material by using the modified silicon material as claimed in claim 16, wherein the mass ratio of the modified silicon material to the graphite negative electrode material is 3: 100-6: 100.
18. a graphite negative electrode material prepared by the method for preparing a graphite negative electrode material from the modified silicon material as claimed in claim 16 or 17.
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