CN114843473A - Composite slurry applied to lithium iron battery and preparation method thereof - Google Patents
Composite slurry applied to lithium iron battery and preparation method thereof Download PDFInfo
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- 239000002131 composite material Substances 0.000 title claims abstract description 62
- 239000002002 slurry Substances 0.000 title claims abstract description 40
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 238000002360 preparation method Methods 0.000 title claims description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 53
- 239000006258 conductive agent Substances 0.000 claims abstract description 30
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 30
- 239000002041 carbon nanotube Substances 0.000 claims abstract description 23
- 229910021393 carbon nanotube Inorganic materials 0.000 claims abstract description 23
- 229920000767 polyaniline Polymers 0.000 claims abstract description 17
- 239000007784 solid electrolyte Substances 0.000 claims abstract description 16
- 239000006229 carbon black Substances 0.000 claims abstract description 10
- 238000002156 mixing Methods 0.000 claims description 25
- 239000000243 solution Substances 0.000 claims description 19
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 claims description 18
- 239000011259 mixed solution Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 15
- 239000000463 material Substances 0.000 claims description 13
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 12
- 238000009210 therapy by ultrasound Methods 0.000 claims description 12
- 239000011230 binding agent Substances 0.000 claims description 11
- 239000007787 solid Substances 0.000 claims description 11
- 239000000126 substance Substances 0.000 claims description 11
- 239000002270 dispersing agent Substances 0.000 claims description 10
- 239000002904 solvent Substances 0.000 claims description 10
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 9
- 239000002202 Polyethylene glycol Substances 0.000 claims description 7
- 229910003002 lithium salt Inorganic materials 0.000 claims description 7
- 159000000002 lithium salts Chemical class 0.000 claims description 7
- 239000005457 ice water Substances 0.000 claims description 6
- 229910001867 inorganic solvent Inorganic materials 0.000 claims description 6
- 239000003049 inorganic solvent Substances 0.000 claims description 6
- 239000003960 organic solvent Substances 0.000 claims description 6
- 239000005518 polymer electrolyte Substances 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- 239000000853 adhesive Substances 0.000 claims description 4
- 230000001070 adhesive effect Effects 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 238000003760 magnetic stirring Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 239000004570 mortar (masonry) Substances 0.000 claims description 4
- 238000007500 overflow downdraw method Methods 0.000 claims description 4
- 238000001291 vacuum drying Methods 0.000 claims description 4
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 3
- 229910013063 LiBF 4 Inorganic materials 0.000 claims description 3
- 229910013188 LiBOB Inorganic materials 0.000 claims description 3
- 229910013684 LiClO 4 Inorganic materials 0.000 claims description 3
- 229910010941 LiFSI Inorganic materials 0.000 claims description 3
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 3
- 239000002033 PVDF binder Substances 0.000 claims description 3
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 3
- 229920006184 cellulose methylcellulose Polymers 0.000 claims description 3
- 229910003480 inorganic solid Inorganic materials 0.000 claims description 3
- 229910003473 lithium bis(trifluoromethanesulfonyl)imide Inorganic materials 0.000 claims description 3
- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 claims description 3
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 claims description 3
- 229920001223 polyethylene glycol Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 3
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 3
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 3
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 239000004020 conductor Substances 0.000 claims 1
- 239000007774 positive electrode material Substances 0.000 abstract description 7
- 230000000052 comparative effect Effects 0.000 description 10
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 238000010297 mechanical methods and process Methods 0.000 description 2
- 238000000527 sonication Methods 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000011244 liquid electrolyte Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000002195 synergetic effect Effects 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
- H01M4/362—Composites
- H01M4/364—Composites as mixtures
-
- 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
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention discloses a composite slurry applied to a lithium iron battery, which comprises a positive electrode composite material, a high-solid-content conductive agent and a solid electrolyte, wherein the positive electrode composite material is a composite material with a net structure of graphene/carbon nano tube/lithium iron phosphate @ PANI formed through structural design, and the high-solid-content conductive agent is a composite material formed by combining carbon black, CNT and graphene into a point-line-surface combination. The graphene/carbon nanotube/lithium iron phosphate @ PANI composite material disclosed by the invention forms a net-shaped porous structure, and the carbon nanotube has excellent conductivity, so that the conductivity of a positive electrode material is improved.
Description
Technical Field
The invention relates to the technical field of lithium iron batteries, in particular to a composite slurry applied to a lithium iron battery and a preparation method thereof.
Background
During the working process of the lithium ion battery, the reconstruction of the surface of the de-lithiated anode can occur on the interface of the electrode/electrolyte to release oxygen, the decomposition of the electrolyte, and the formation and decomposition of a solid electrolyte interface layer (SEI) can all cause gas generation. The generated gas can cause battery gas expansion, deformation, thermal runaway and other safety disasters, and serious threats are caused to the safety performance of the lithium ion battery. In recent years, there are a lot of reports about safety disasters of lithium ion batteries, and especially under the condition that the energy density is continuously improved, the safety problem becomes more prominent. How to further increase the energy density on the basis of ensuring good safety is crucial to improving the competitiveness of lithium ion batteries in various energy storage devices.
In the lithium ion battery electrode material, the conductive agent provides an electron moving channel, so that the electron conductivity of the electrode material is increased, and the electrode has good charge and discharge performance. Solid state lithium batteries are considered a reliable option for substantially improving the safety of lithium batteries by replacing organic liquid electrolytes with nonflammable solid electrolytes. The invention provides a composite slurry applied to a lithium iron battery and a preparation method thereof based on the facts that a solid electrolyte is matched with a high-efficiency conductive agent, the interface stability of a positive electrode material and a negative electrode material in a circulation process is guaranteed, a metal lithium negative electrode with high energy density is matched to be used, and higher energy density is achieved.
Disclosure of Invention
The invention aims to provide a composite slurry applied to a lithium iron battery and a preparation method thereof, so as to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme:
the composite slurry applied to the lithium iron battery comprises a positive electrode composite material, a high-solid-content conductive agent and a solid electrolyte, wherein the positive electrode composite material is a net-shaped structure composite material formed by graphene/carbon nano tubes/lithium iron phosphate @ PANI through structural design, and the high-solid-content conductive agent is a composite material formed by comprehensively combining carbon black, CNT and graphene into a point-line-surface combination mode.
Preferably, the solid electrolyte is one or more of a combination of an Inorganic Solid Electrolyte (ISE), a Solid Polymer Electrolyte (SPE) and a Composite Polymer Electrolyte (CPE).
The invention also provides a preparation method of the composite slurry applied to the lithium iron battery, which is characterized by comprising the following steps of:
the method comprises the following steps: mixing lithium iron phosphate, graphene and carbon nano tubes according to a certain mass ratio, uniformly mixing the three by using a mechanical fusion method, and heating the mixture at the temperature of 120-150 ℃ for 3-5h under vacuum to form a mixed material.
Step two: placing the mixed material in ethanol, mixing by ultrasonic treatment to disperse the mixed material uniformly, adding HCl solution with a certain concentration and aniline for mixing, and adding HCl and (NH) with a certain concentration 4 ) 2 S 2 O 8 The temperature of the mixed solution is controlled by an ice-water bath, the mixed solution is stirred for 12-15 hours, the obtained mixed solution is subjected to centrifugal treatment, and vacuum drying is carried out for 12-15 hours at the temperature of 60 ℃, so that the graphene/carbon nano tube/lithium iron phosphate @ PANI composite material is obtained;
step three: mixing the conductive substance and the solvent, performing magnetic stirring at the stirring speed of 200-600rpm for 2-3h, performing ultrasonic treatment for 0.5-1h to disperse the conductive substance, adding the dispersing agent into the solution, and performing ultrasonic treatment for 1-1.5h to obtain conductive agent slurry with high solid content;
step four: PEO and a binder in a certain mass ratio were dissolved in NMP to prepare a binder solution, followed by addition of a lithium salt. Preparing a graphene/carbon nanotube/lithium iron phosphate @ PANI composite material, high-solid-content conductive agent slurry and an adhesive solution into slurry according to a certain mass ratio, and uniformly mixing in an agate mortar to obtain the composite slurry.
Preferably, the high-solid-content conductive agent slurry contains 15-20% of conductive substances, 0.1-5% of dispersing agents and 75-85% of solvents.
Preferably, the high-solid-content conductive agent comprises 40-50% of CNT, 8-10% of graphene and 40-50% of carbon black.
Preferably, the dispersing agent is selected from one or more of polyvinylpyrrolidone, polyethylene glycol and polyvinyl alcohol.
Preferably, the solvent comprises an organic solvent and an inorganic solvent, wherein the organic solvent is one or two of N, N-dimethylformamide and N, N-dimethylacetamide, and the inorganic solvent is water.
Preferably, the binder is one or more of PTFE, PVDF, CMC, GA, CG and XG.
Preferably, the lithium salt is LiFP 6 、LiBF 4 、LiBOB、LiTFSI、LiFSI、LiDFOB、LiClO 4 、LiAsO 4 One or more of (a).
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention provides a graphene/carbon nanotube/lithium iron phosphate @ PANI composite material which forms a net-shaped porous structure, has excellent conductivity of a carbon nanotube and improves the conductivity of a positive electrode material.
(2) The invention provides a high-solid-content conductive agent, the solid content of which exceeds 5% of the total mass fraction, and the CNT, the graphene and the carbon black are adopted for the first time to form perfect combination of points, lines and surfaces, so that the conductivity is effectively improved, and when the conductive agent is used as a lithium battery conductive agent, the compaction performance can be effectively improved, and the rate capability and the cycle performance of a battery are improved.
(3) The invention provides an all-solid-state battery and a preparation method thereof, wherein a solid electrolyte containing a high-solid-content conductive agent and a composite positive electrode material have good interface stability, and in the circulating process, the excellent circulating stability is kept, and the circulating performance of the all-solid-state battery is improved.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to specific embodiments, 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 obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The composite slurry applied to the lithium iron battery comprises a positive electrode composite material, a high-solid-content conductive agent and a solid electrolyte, wherein the positive electrode composite material is a composite material with a net structure of graphene/carbon nano tube/lithium iron phosphate @ PANI formed through structural design, and the high-solid-content conductive agent is a composite material formed by comprehensively combining carbon black, CNT and graphene into a point-line-surface combination mode.
The solid electrolyte of the present embodiment is one or more of a combination of an Inorganic Solid Electrolyte (ISE), a Solid Polymer Electrolyte (SPE) and a Composite Polymer Electrolyte (CPE).
The invention also provides a preparation method of the composite slurry applied to the lithium iron battery, which is characterized by comprising the following steps of:
the method comprises the following steps: mixing lithium iron phosphate, graphene and carbon nano tubes according to a certain mass ratio, uniformly mixing the three by using a mechanical fusion method, and heating the mixture at the temperature of 120-150 ℃ for 3-5h under vacuum to form a mixed material.
Step two: putting the mixed material into ethanol, mixing by ultrasonic treatment to disperse the mixed material evenly, then adding HCl solution with certain concentration and aniline for mixing, and then adding HCl and (NH) with certain concentration 4 ) 2 S 2 O 8 The temperature of the mixed solution is controlled by an ice-water bath, the mixed solution is stirred for 12-15 hours, the obtained mixed solution is subjected to centrifugal treatment, and vacuum drying is carried out for 12-15 hours at the temperature of 60 ℃, so that the graphene/carbon nano tube/lithium iron phosphate @ PANI composite material is obtained;
step three: mixing a conductive substance and a solvent, performing magnetic stirring at the stirring speed of 200-600rpm for 2-3h, performing ultrasonic treatment for 0.5-1h to disperse the conductive substance, adding a dispersing agent into the solution, and performing ultrasonic treatment for 1-1.5h to obtain conductive agent slurry with high solid content;
step four: PEO and a binder in a certain mass ratio were dissolved in NMP to prepare a binder solution, followed by addition of a lithium salt. Preparing a graphene/carbon nanotube/lithium iron phosphate @ PANI composite material, high-solid-content conductive agent slurry and an adhesive solution into slurry according to a certain mass ratio, and uniformly mixing in an agate mortar to obtain the composite slurry.
In the high-solid-content conductive agent slurry, the conductive substance is 15-20%, the dispersant is 0.1-5%, and the solvent is 75-85%.
The high-solid-content conductive agent of the embodiment contains 40-50% of CNT, 8-10% of graphene and 40-50% of carbon black.
The dispersant of this embodiment is selected from one or more of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol.
The solvent of this embodiment includes an organic solvent and an inorganic solvent, the organic solvent is one or two of N, N-dimethylformamide and N, N-dimethylacetamide, and the inorganic solvent is water.
The binder of the present embodiment is one or more of PTFE, PVDF, CMC, GA, CG and XG.
The lithium salt in this example is LiFP 6 、LiBF 4 、LiBOB、LiTFSI、LiFSI、LiDFOB、LiClO 4 、LiAsO 4 One or more of (a).
Example 1
A preparation method of composite slurry applied to a lithium iron battery comprises the following steps:
(1) mixing 30g of lithium iron phosphate, 15g of graphene and 5g of carbon nano tube by a mechanical method, uniformly mixing the three by using a mechanical fusion method, and heating the mixture at the temperature of 120-150 ℃ for 3-5h under vacuum to form a mixed material;
(2) placing the mixed material in 50ml ethanol, mixing by ultrasonic treatment to disperse uniformly, adding 2.5g of 15ml 2M HCl solution and aniline, mixing, adding 5g of 15ml 2M HCl and (NH) 4 ) 2 S 2 O 8 The temperature of the mixed solution is controlled by an ice-water bath, the mixed solution is stirred for 12-15 hours, the obtained mixed solution is subjected to centrifugal treatment, and vacuum drying is carried out for 12-15 hours at the temperature of 60 ℃, so that the graphene/carbon nano tube/lithium iron phosphate @ PANI composite material is obtained;
(3) uniformly mixing 45% of CNT, 10% of graphene and 45% of carbon black by a mechanical method to form a conductive substance, mixing the conductive substance with a solvent, carrying out magnetic stirring, carrying out ultrasonic treatment for 0.5-1h after stirring at the rotating speed of 400rpm for 2-3h, dispersing the conductive substance, adding a dispersing agent into the solution, and carrying out ultrasonic treatment for 1-1.5h to obtain the conductive agent slurry with high solid content.
(4) PEO and a binder were dissolved in NMP at a mass ratio of 2: 1 to prepare a binder solution, followed by addition of a lithium salt. Preparing a graphene/carbon nanotube/lithium iron phosphate @ PANI composite material, high-solid-content conductive agent slurry and an adhesive solution into slurry according to a mass ratio of 75: 10: 15, and uniformly mixing in an agate mortar to obtain the composite slurry.
Example 2
Example 2 was prepared according to the method of example 1, except that in step (2), the mixed material was placed in 50ml of ethanol, mixed by sonication to disperse it uniformly, then 5g of 15ml of 2M HCl solution and aniline were added to mix, and 10g of 15ml of 2M HCl and (NH) were added 4 ) 2 S 2 O 8 And (3) stirring the mixed solution for 12-15h by controlling the temperature through an ice-water bath, centrifuging the obtained mixed solution, and drying the mixed solution for 12-15h in vacuum at 60 ℃ to obtain the graphene/carbon nano tube/lithium iron phosphate @ PANI composite material.
Example 3
Example 3 was prepared according to the method of example 1, except that in step (2), the mixed material was placed in 50ml of ethanol, mixed by sonication to disperse it uniformly, then 10g of 15ml of 2M HCl solution and aniline were added to mix, and 20g of 15ml of 2M HCl and (NH) were added 4 ) 2 S 2 O 8 And (3) stirring the mixed solution for 12-15h by controlling the temperature through an ice-water bath, centrifuging the obtained mixed solution, and drying the mixed solution for 12-15h in vacuum at 60 ℃ to obtain the graphene/carbon nano tube/lithium iron phosphate @ PANI composite material.
Comparative example 1
Comparative example 1 was prepared according to the method of example 1, except that steps (1) and (2) were not required, and a lithium iron phosphate positive electrode material was used instead of the graphene/carbon nanotube/lithium iron phosphate @ PANI composite material.
Comparative example 2
Comparative example 2 was prepared according to the method of example 1 except that step (3) was not required and a carbon black conductive agent was used instead of the high-solid content conductive agent slurry.
Comparative example 3
Comparative example 3 was prepared according to the method of example 1, except that in step (4), an electrolyte having an EC: EMC of 3: 7 was used instead of the solid electrolyte.
(1) Cycle testing
The batteries of examples 1 to 3 and comparative examples 1 to 3 were each charged at 25 ℃ to 3.65V with a constant current and a constant voltage of 1C and a cutoff current of 0.05C, and then the battery 1C was constant-current discharged to 2.0V, and the discharge capacity Q0, which is the cycle first discharge capacity, was recorded. This is a complete cycle, and the cell was cycled for 500, 1000 weeks in this manner, and the discharge capacity Q500, Q1000 was recorded for 500, 1000 cycles. Wherein, the cycle capacity retention rate of 1000 cycles is Q1000/Q0 100%.
(2) High temperature shelf test
The cells of examples 1-3 and comparative examples 1-3 were charged with 1C constant current and constant voltage to 3.65V at 25C, respectively, with a cutoff current of 0.05C, and then the cell volume was measured by the drainage method and recorded as V0. The fully charged battery was then transferred to a 60 ℃ incubator and stored for 28 days. After 28 days of storage, the cells were removed and the cells were again tested for post-storage volume by draining, which was designated V28. Wherein, the volume expansion rate of the storage at 60 ℃ for 28 days is (V28-V0)/V0 for 100 percent.
The batteries of examples 1-3 and comparative examples 1-3 were respectively charged to 3.65V with a 1C constant current and constant voltage at 25 ℃ and a cutoff current of 0.05C, and then the battery 1C was constant current discharged to 2.0V, and the discharge capacity Q0 was recorded. The fully charged battery was then transferred to a 60 ℃ incubator and stored for 28 days. After 28 days of storage, the cells were removed and again discharged at 1C constant current to 2.0V, and the discharge capacity Q28 was recorded. Wherein, the capacity retention rate is Q28/Q0 × 100%.
TABLE 1
From the results of the comprehensive experimental tests, it can be seen from examples 1 to 3 that as the mass fraction of aniline increases, a more stable network structure is facilitated to be formed, and a better cycle capacity retention rate is shown on the battery performance, but when the aniline content exceeds a certain amount, the aniline content alone exists in the positive electrode material, and ion transmission is hindered, thereby affecting the battery performance.
In combination with the experimental test results, the composite slurry of the present invention showed more excellent properties in example 1 and comparative examples 1 to 3. The positive electrode composite material has a stable net structure and the performance of the composite conductive paste is improved, and the positive electrode composite material has a synergistic effect when used as a solid battery positive electrode material, so that the positive electrode composite material has excellent performance.
In summary, the composite slurry of the invention can greatly improve the performance of the lithium iron battery, wherein the solid electrolyte can also better solve the problems of gas generation and the like of the high-temperature battery, and still shows excellent capacity retention rate and cycle performance at high temperature.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (9)
1. The composite slurry applied to the lithium iron battery is characterized by comprising a positive electrode composite material, a high-solid-content conductive agent and a solid electrolyte, wherein the positive electrode composite material is a composite material with a net structure of graphene/carbon nano tube/lithium iron phosphate @ PANI formed through structural design, and the high-solid-content conductive agent is a composite material formed by comprehensively combining carbon black, CNT and graphene into a point-line-surface combination mode.
2. The composite slurry applied to the lithium iron battery according to claim 1, wherein the solid electrolyte is one or more of an Inorganic Solid Electrolyte (ISE), a Solid Polymer Electrolyte (SPE) and a Composite Polymer Electrolyte (CPE).
3. A method for preparing a composite paste applied to an lithium iron battery according to any one of claims 1 to 2, comprising the steps of:
the method comprises the following steps: mixing lithium iron phosphate, graphene and carbon nano tubes according to a certain mass ratio, uniformly mixing the three by using a mechanical fusion method, and heating the mixture at the temperature of 120-150 ℃ for 3-5h under vacuum to form a mixed material.
Step two: placing the mixed material in ethanol, mixing by ultrasonic treatment to disperse the mixed material uniformly, adding HCl solution with a certain concentration and aniline for mixing, and adding HCl and (NH) with a certain concentration 4 ) 2 S 2 O 8 The temperature of the mixed solution is controlled by an ice-water bath, the mixed solution is stirred for 12-15 hours, the obtained mixed solution is subjected to centrifugal treatment, and vacuum drying is carried out for 12-15 hours at the temperature of 60 ℃, so that the graphene/carbon nano tube/lithium iron phosphate @ PANI composite material is obtained;
step three: mixing the conductive substance and the solvent, performing magnetic stirring at the stirring speed of 200-600rpm for 2-3h, performing ultrasonic treatment for 0.5-1h to disperse the conductive substance, adding the dispersing agent into the solution, and performing ultrasonic treatment for 1-1.5h to obtain conductive agent slurry with high solid content;
step four: PEO and a binder were dissolved in NMP in a certain mass ratio to prepare a binder solution, followed by addition of a lithium salt. Preparing a graphene/carbon nanotube/lithium iron phosphate @ PANI composite material, high-solid-content conductive agent slurry and an adhesive solution into slurry according to a certain mass ratio, and uniformly mixing in an agate mortar to obtain the composite slurry.
4. The preparation method of the composite slurry applied to the lithium iron battery, according to claim 3, characterized in that the conductive material in the high-solid-content conductive agent slurry is 15-20%, the dispersant is 0.1-5%, and the solvent is 75-85%.
5. The preparation method of the composite slurry applied to the lithium iron battery, according to claim 3, wherein the high-solid-content conductive agent comprises 40-50% of CNT, 8-10% of graphene and 40-50% of carbon black.
6. The method for preparing a composite slurry for an iron-lithium battery according to claim 3, wherein the dispersing agent is one or more selected from polyvinylpyrrolidone, polyethylene glycol and polyvinyl alcohol.
7. The preparation method of the composite slurry applied to the lithium iron battery according to claim 6, wherein the solvent comprises an organic solvent and an inorganic solvent, the organic solvent is one or two of N, N-dimethylformamide and N, N-dimethylacetamide, and the inorganic solvent is water.
8. The preparation method of the composite slurry applied to the lithium iron battery, according to claim 7, wherein the binder is one or more of PTFE, PVDF, CMC, GA, CG and XG.
9. The method of claim 8, wherein the lithium salt is LiFP 6 、LiBF 4 、LiBOB、LiTFSI、LiFSI、LiDFOB、LiClO 4 、LiAsO 4 One or more of (a).
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