CN112786313A - Electrode slurry containing lithium nitride and preparation and application thereof - Google Patents
Electrode slurry containing lithium nitride and preparation and application thereof Download PDFInfo
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- IDBFBDSKYCUNPW-UHFFFAOYSA-N lithium nitride Chemical compound [Li]N([Li])[Li] IDBFBDSKYCUNPW-UHFFFAOYSA-N 0.000 title claims abstract description 110
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 239000011267 electrode slurry Substances 0.000 title claims description 17
- 239000002904 solvent Substances 0.000 claims abstract description 72
- 238000000034 method Methods 0.000 claims abstract description 33
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 23
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 23
- 239000000463 material Substances 0.000 claims abstract description 5
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 55
- 239000002033 PVDF binder Substances 0.000 claims description 34
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 26
- 238000003756 stirring Methods 0.000 claims description 22
- 239000006258 conductive agent Substances 0.000 claims description 20
- 239000007787 solid Substances 0.000 claims description 20
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 19
- 239000002002 slurry Substances 0.000 claims description 15
- 239000013543 active substance Substances 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 12
- 238000005303 weighing Methods 0.000 claims description 11
- 239000011230 binding agent Substances 0.000 claims description 9
- 238000000576 coating method Methods 0.000 claims description 6
- 239000003990 capacitor Substances 0.000 claims description 5
- 239000007774 positive electrode material Substances 0.000 claims description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 2
- 239000002003 electrode paste Substances 0.000 claims 2
- YWJVFBOUPMWANA-UHFFFAOYSA-H [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O Chemical compound [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O YWJVFBOUPMWANA-UHFFFAOYSA-H 0.000 claims 1
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 claims 1
- 239000006230 acetylene black Substances 0.000 claims 1
- 229910021389 graphene Inorganic materials 0.000 claims 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 33
- 229910052744 lithium Inorganic materials 0.000 abstract description 33
- 238000000265 homogenisation Methods 0.000 abstract description 10
- 239000000654 additive Substances 0.000 abstract description 6
- 230000000996 additive effect Effects 0.000 abstract description 6
- 238000009835 boiling Methods 0.000 abstract description 5
- 231100000053 low toxicity Toxicity 0.000 abstract description 5
- 230000009257 reactivity Effects 0.000 abstract description 5
- 238000004364 calculation method Methods 0.000 abstract description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 51
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 31
- MHABMANUFPZXEB-UHFFFAOYSA-N O-demethyl-aloesaponarin I Natural products O=C1C2=CC=CC(O)=C2C(=O)C2=C1C=C(O)C(C(O)=O)=C2C MHABMANUFPZXEB-UHFFFAOYSA-N 0.000 description 14
- 239000000203 mixture Substances 0.000 description 11
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 10
- 239000003292 glue Substances 0.000 description 9
- 239000000843 powder Substances 0.000 description 9
- 239000003153 chemical reaction reagent Substances 0.000 description 8
- 238000009830 intercalation Methods 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 238000005056 compaction Methods 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 6
- 230000002687 intercalation Effects 0.000 description 6
- 229910014282 N-NMP Inorganic materials 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000006356 dehydrogenation reaction Methods 0.000 description 4
- 239000002798 polar solvent Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000003775 Density Functional Theory Methods 0.000 description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 101150047356 dec-1 gene Proteins 0.000 description 3
- 230000002427 irreversible effect Effects 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 229910010710 LiFePO Inorganic materials 0.000 description 2
- 229910013191 LiMO2 Inorganic materials 0.000 description 2
- 229910013100 LiNix Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000013557 residual solvent Substances 0.000 description 2
- 238000007581 slurry coating method Methods 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 238000005815 base catalysis Methods 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- -1 lithium hexafluorophosphate Chemical compound 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000004660 morphological change Effects 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 238000009702 powder compression Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/50—Electrodes characterised by their material specially adapted for lithium-ion capacitors, e.g. for lithium-doping or for intercalation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
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- 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
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention relates to a method for preparing a lithium nitride-containing electrode, which firstly selects and optimizes a DMF solvent which does not react with lithium nitride through a method combining theoretical calculation and experimental research, and the solvent has the characteristics of low toxicity and high boiling point. The invention firstly proposes to use the lithium nitride as a homogenizing solvent and adopt a homogenizing method to prepare the lithium nitride-containing electrode. Compared with the reported preparation method of the lithium nitride, the electrode prepared by the homogenization method has the advantages that the material distribution is uniform, the specific capacity exerted by the lithium nitride is high, and the electrode containing the lithium nitride can be coated on a large scale. The invention solves the problem of reactivity of lithium nitride and a solvent from the aspect of an electrode preparation process, can promote further research of a lithium nitride-containing electrode, and has important significance for a lithium ion super container taking the lithium nitride as a pre-lithium additive from basic research to large-scale commercialization.
Description
Technical Field
The invention relates to the technical field of lithium ion super capacitors and batteries, in particular to a lithium ion super capacitor electrode.
Background
In a lithium ion supercapacitor and a lithium ion battery system, for a carbonaceous lithium intercalation negative electrode, a certain degree of irreversible lithium intercalation (a part of lithium is consumed by an SEI film formed on the surface of the negative electrode) exists in the first charge-discharge process, and the electrochemical behavior can cause irreversible adsorption of electrolyte anions with the same molar number on the surface of an active carbon positive electrode or cause positive electrode loss of lithium, finally cause reduction of electrolyte ion concentration and attenuation of positive electrode capacity, and influence the charge-discharge performance and capacity of the lithium ion supercapacitor and the lithium ion battery system. Aiming at the problem, a lithium source can be found from the outside of the anode material, and the formation of the SEI film consumes lithium ions of the outside lithium source, so that the lithium ions extracted from the anode can not be wasted in the formation process, and finally, the full battery capacity can be improved. This process of providing an external source of lithium is prelithiation.
Currently, the prelithiation methods are: the method is not suitable for practical application due to the limitations of the former three methods on equipment and process; the method of the positive electrode lithium-rich material is to introduce a non-metallic lithium third electrode (i.e. a lithium-rich compound with certain irreversible lithium removal property, such as LiFePO) into the positive electrode4、LiMO2Where M is Co, Ni, Mn, etc. and LiNixZ1-xO2Wherein Z is Mn, Co, Fe, La, V, Al, Mg, Zn, 0<x>1) The method of (1) pre-intercalating lithium into the negative electrode has a disadvantage that inactive products or unreacted lithium-rich compounds are generated along with intercalation of lithium in the lithium-rich compounds into the negative electrode, and these substances remain in the positive electrode and affect the electrochemical performance of the lithium ion supercapacitor.
The lithium nitride is used as an anode additive and is subjected to first-circle activation, then the lithium nitride is decomposed, lithium enters a negative electrode to complete pre-lithium intercalation of the negative electrode, nitrogen is generated at the same time, the nitrogen is stored in a battery gas bag, and the nitrogen is discharged after first-circle formation. By nitridingAfter lithium is used as an anode additive to complete the pre-intercalation of lithium on a cathode, substances can not be remained in the anode to influence the electrochemical performance of a lithium ion super capacitor and a lithium ion battery system, and meanwhile, lithium nitride has ultrahigh theoretical specific capacity and is added with LiFePO in the anode4、LiMO2Where M is Co, Ni, Mn, etc. and LiNixZ1-xO2Compared with the prior art, the same pre-lithium intercalation effect can be achieved by only adding a small amount of lithium nitride. However, Li3N has an inherent problem of poor compatibility with an aprotic polar solvent during electrode fabrication because it has high reactivity with a common solvent such as N-methyl-2-pyrrolidone (NMP). This is a significant impediment to the large-scale commercialization of lithium ion supercapacitors with lithium nitride as a pre-lithium additive from basic research. In the prior art, lithium nitride-containing electrodes were prepared by dry and powder compression methods due to the reaction of lithium nitride with commonly used homogenization reagents, which have the following problems: on one hand, the electrode material is unevenly distributed in the electrode, so that the performance of the electrode is poor; on the other hand, these methods of making lithium nitride-containing electrodes are difficult to employ in commercial battery electrode preparation.
In the present invention, the electrode containing Li3N was prepared by a commercially available route by first homogenizing an electrode slurry using a strongly polar solvent N, N-Dimethylformamide (DMF) having low toxicity and high boiling point, and preparing an electrode containing lithium nitride by a slurry coating method. The molecular stability mechanism of DMF is proved by experimental analysis and DFT simulation, which shows that the dehydrogenation energy of DMF is obviously larger than that of other common solvents (such as NMP and the like).
Disclosure of Invention
The present invention is directed to Li3The inherent problems of N, namely poor compatibility with aprotic polar solvents in the electrode manufacturing process and high reactivity with common solvents such as N-methyl-2-pyrrolidone (NMP) and the like, firstly proposes a solvent which is N, N-Dimethylformamide (DMF) compatible with lithium nitride, is a strong polar solvent with low toxicity and high boiling point, and firstly realizes the preparation of the electrode containing lithium nitride by adopting a slurry coating method.
The specific technical scheme provided by the invention is as follows:
on the aspect of theoretical calculation: according to the theory of base catalysis, the reaction mechanism of lithium nitride and each solvent (including N, N-Dimethylformamide (DMF), N-Dimethylformamide (DMAC), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO)) is to dehydrogenate the solvent first, so the dehydrogenation energy of each solvent is calculated by DFT first in the invention, and the calculation result shows (as shown in fig. 4): the dehydrogenation energy of the solvent N, N-Dimethylformamide (DMF) is the greatest compared to the others, indicating that the solvent DMF is the most difficult to dehydrogenate, i.e. to react. Further analysis of the molecular formula of solvent DMF revealed: since hydrogen in DMF is aldehyde hydrogen and α -hydrogen contained in other solvents, it is assumed that lithium nitride easily reacts with the α -hydrogen-containing solvent but does not react with the aldehyde hydrogen-containing solvent.
The preparation of the electrode slurry mainly comprises the following steps:
(1) respectively measuring a certain volume of each solvent (comprising DMF, DMAC, NMP and DMSO) and a beaker, adding a certain amount of polyvinylidene fluoride (PVDF) into each solvent, and stirring for 3-5 hours, wherein the solid content of the PVDF is 2-10 wt%.
(2) The active material (active carbon or battery positive electrode material such as lithium cobaltate, lithium iron phosphate, ternary material and the like): lithium nitride: conductive agent: and (2) respectively weighing active substances, lithium nitride and a conductive agent according to the proportion of 68:12:10:10 of the binder PVDF, respectively adding the active substances, the lithium nitride and the conductive agent into the mixture (1), stirring the mixture simultaneously, adjusting the solid content of the electrode slurry by adopting the corresponding solvent in the mixture (1), and stirring the mixture until the substances are uniformly mixed and the slurry has good fluidity, wherein the stirring time is 10 minutes to 3 hours.
(3) And (3) coating the electrode by using an automatic coating machine, and removing the corresponding solvent to obtain the lithium nitride-containing electrode.
In the preparation process of the electrode slurry, since lithium nitride reacts with the solvent (DMAC, NMP, DMSO) and emits a large amount of heat, when the above-mentioned solvents are used as the homogenizing agent, the binder (PVDF) system is polymerized by the large amount of heat emitted from the reaction, resulting in non-fluidity of the electrode slurry and finally, the electrode slurry is unusable.
The beneficial results of the invention are:
the invention preferably selects a low-toxicity high-boiling point homogenizing solvent which does not react with lithium nitride, so that the electrode containing lithium nitride can be prepared by adopting a homogenizing coating method. From the aspect of an electrode preparation process, the problem of reactivity of lithium nitride and a solvent is solved, further research on the lithium nitride-containing electrode can be promoted, and the method has important significance for a lithium ion super container with the lithium nitride as a pre-lithium additive from basic research to large-scale commercialization.
Drawings
FIG. 1 XRD patterns of lithium nitride and Solid residue (Solid-Li)3N-DMF、Solid-Li3N-DMAC Solid-Li3N-NMP Solid-Li3N-DMSO represents respectively: lithium nitride is mixed and fully reacted with solvents DMAC, NMP, DMSO and DMF respectively, and solid residue obtained after removing residual solvent).
FIG. 2 Li3SEM images of N powder (a) and its solid residue after mixing with DMF, DMAC, NMP and DMSO.
FIG. 3 Li3Photographs of the powder of N (a) and its solid residue after mixing with DMF, DMAC, NMP and DMSO.
FIG. 4 DFT calculation: dehydrogenation energy of each solvent.
Detailed Description
The technical solution of the present invention is not limited to the specific embodiments listed below, and includes any combination of the specific embodiments.
In the experimental aspect, we first added lithium nitride to each solvent at a mass ratio of lithium nitride to solvent of 1:50, and after sufficient reaction (10 minutes), removed the residual solvent. Phase analysis of the solid residue by XRD: as can be seen from FIG. 1, solid-Li3The XRD peak in N-DMF coincided with the characteristic peak of lithium nitride, indicating that lithium nitride reacts with DMF as solvent and solid residue solid-Li3N-DMAC，solid-Li3N-NMP，solid-Li3The characteristic peak of lithium nitride is found in N-NMP, which shows that the lithium nitride reacts with solvents DMAC, NMP and DMSO to generate a new substance. And (3) performing morphology observation and analysis on the lithium nitride and the solid residues treated by the solvents by adopting a scanning electron microscope: from the morphology photographs (see FIG. 2), solid residue solid-Li3The N-DMF had a granular morphology essentially corresponding to that of the untreated lithium nitride, while the solid residue solid-Li3N-DMAC appeared to be obviously pulverized and solid residue solid-Li3N-NMP presents the morphology of lamellar stacking, while solid residue solid-Li3N-NMP is in cluster shape, in conclusion, DMAC, NMP and DMSO-treated lithium nitride all have obvious morphological changes, and combined with the photo (shown in figure 3) of the reaction product and the XRD result, the conclusion is drawn that: lithium nitride chemically reacts with the DMAC, NMP, DMSO solvents described above. The above-mentioned solvent cannot be used for the preparation of lithium nitride-containing electrode slurry, and the solvent DMF can be used as a homogenizing solvent for the preparation of lithium nitride-containing electrodes.
Comparative examples 1 and 2 are methods of preparing lithium nitride containing electrodes that have been used in previous studies.
Comparative example 1: mixing materials by dry method
According to the active substance (active carbon): lithium nitride: conductive agent: 0.34g of activated carbon, 0.06g of lithium nitride, 0.05g of conductive agent and 0.05g of binder, PTFE being 68:12:10:10, were weighed out in a mortar in sequence, and ground to mix homogeneously, after 20min, 0.02g of the ground mixture was weighed out between two cut pieces of carbon paper (. phi.14 mm), and the mixture was pressed onto the carbon paper with a powder tablet press, using it as the working electrode, the lithium piece as the counter electrode, and 1 iPF of (MLDEC) in which Ethylene Carbonate (EC) and diethyl carbonate are used as solvents6(EC/DEC 1:1) is used as electrolyte, a 2016 type button cell is assembled, the charge-discharge performance of the button cell is tested, and the specific capacity exerted by the lithium nitride is calculated according to the charge capacity of the first circle and the proportion of the lithium nitride in the electrode.
Comparative example 2: mechanical compaction
Weighing 0.95g of NMP solvent, placing in a reagent bottle, weighing0.05g of PVDF binder was added to the above NMP solvent while stirring, and after stirring for 3 hours, a uniformly dispersed PVDF gel was obtained. According to the active substance (active carbon): conductive agent: 0.34g of activated carbon and 0.05g of conductive agent are respectively weighed and sequentially added into the PVDF glue according to the proportion of 68:10:10, the PVDF glue is stirred simultaneously, and the solid content of the PVDF glue is regulated and controlled by adopting a solvent NMP so as to obtain a slurry system with the solid content of 30%. And stirring the slurry for 3 hours, coating an electrode, drying to remove the solvent, weighing 0.006g of lithium nitride powder, uniformly spreading the lithium nitride powder on the coated electrode, and pressing the lithium nitride powder on the electrode by adopting a mechanical compaction method to obtain the lithium nitride-containing electrode. Cutting the electrode containing lithium nitride prepared by mechanical compaction method into electrode plate with diameter of 14mm, using the electrode plate as working electrode, lithium sheet as counter electrode, and 1MLiPF prepared from Ethylene Carbonate (EC) and diethyl carbonate as solvent (DEC)6(EC/DEC 1:1) is used as electrolyte, a 2016 type button cell is assembled, the charge-discharge performance of the button cell is tested, and the specific capacity exerted by the lithium nitride is calculated according to the charge capacity of the first circle and the proportion of the lithium nitride in the electrode.
Example 1: homogenization method-DMF
Weighing 0.95g of DMF solvent, placing the DMF solvent in a reagent bottle, weighing 0.05g of PVDF binder, adding the PVDF binder into the DMF solvent, stirring the mixture simultaneously, and stirring the mixture for 3 hours to obtain the PVDF glue with uniform dispersion. According to the active substance (active carbon): lithium nitride: conductive agent: 0.34g of activated carbon, 0.06g of lithium nitride and 0.05g of conductive agent are respectively weighed and sequentially added into the PVDF gel according to the proportion of 68:12:10:10, and the PVDF gel is stirred and regulated and controlled in solid content by adopting a solvent DMF so as to obtain a slurry system with the solid content of 30%. And stirring the slurry for 3 hours, coating an electrode, and drying to remove the solvent to obtain the lithium nitride-containing electrode. Cutting the electrode containing lithium nitride prepared by the homogenization method into an electrode plate with the size of phi 14mm, taking the electrode plate as a working electrode, taking a lithium sheet as a counter electrode, and taking Ethylene Carbonate (EC) and diethyl carbonate as solvent (DEC) 1MLiPF6(EC/DEC 1:1) as electrolyte, assembling 2016 type button cell, testing its charge-discharge performance, and calculating the charge capacity of the first circle and the proportion of lithium nitride in the electrodeThe specific capacity exhibited by the lithium nitride was calculated.
Example 2:
weighing 0.95g of NMP solvent, placing in a reagent bottle, weighing 0.05g of PVDF binder, adding into the NMP solvent, stirring simultaneously, and stirring for 3 hours to obtain the uniformly dispersed PVDF glue. According to the active substance (active carbon): lithium nitride: conductive agent: 0.34g of activated carbon, 0.05g of conductive agent and 0.06g of lithium nitride are respectively weighed according to the proportion of PVDF (polyvinylidene fluoride) as a binder, and are sequentially added into the PVDF glue, and are stirred simultaneously, the solid content of the PVDF glue is regulated and controlled by adopting a solvent NMP (N-methyl pyrrolidone), and after the slurry is stirred for 10 minutes, the slurry is in a shape of a lump, because the lithium nitride reacts with the solvent NMP along with the stirring and is accompanied with a large amount of heat release, so that the PVDF binder is polymerized. The slurry in "dough" cannot be used to coat the electrodes. That is, lithium nitride containing electrodes cannot be homogenized with NMP, a solvent commonly used in commercial cell preparation.
Example 3:
weighing 0.95g of DMAC solvent, placing the DMAC solvent in a reagent bottle, adding 0.05g of PVDF binder into the DMAC solvent, stirring simultaneously, and stirring for 3 hours to obtain the PVDF glue with uniform dispersion. According to the active substance (active carbon): lithium nitride: conductive agent: 0.34g of activated carbon, 0.05g of conductive agent and 0.06g of lithium nitride are respectively weighed according to the proportion of the PVDF binder, and are sequentially added into the PVDF binder, and are stirred simultaneously, the solid content of the PVDF binder is regulated and controlled by adopting a solvent NMP, and after the slurry is stirred for 10 minutes, the slurry is also in a shape of a lump, because the lithium nitride reacts with a solvent DMAC along with the stirring and is released along with a large amount of heat, so that the PVDF binder is polymerized. The slurry in "dough" cannot be used to coat the electrodes. That is, lithium nitride containing electrodes cannot be homogenized with DMAC, a solvent commonly used in commercial cell preparation.
Example 4:
weighing 0.95g of DMSO solvent, placing the DMSO solvent in a reagent bottle, adding 0.05g of PVDF binder into the DMSO solvent, stirring the mixture at the same time, and stirring the mixture for 3 hours to obtain uniformly dispersed PVDF glue. According to the active substance (active carbon): lithium nitride: conductive agent: 0.34g of activated carbon, 0.05g of conductive agent and 0.06g of lithium nitride are respectively weighed and sequentially added into the PVDF adhesive according to the proportion of the PVDF binder, the mixture is stirred simultaneously, after the slurry is stirred for 2 minutes, the slurry is immediately in a shape of a lump, and the lithium nitride reacts with a DMSO solvent violently and is released along with a large amount of heat, so that the PVDF binder is polymerized. The slurry in "dough" cannot be used to coat the electrodes. That is, electrodes containing lithium nitride cannot be homogenized with the solvent DMSO, which is commonly used in commercial cell preparation.
TABLE 1 lithium nitride performance and number of delithiations in lithium nitride-containing electrodes prepared by different methods
And (3) analyzing an experimental result: comparative example 1 a reported powder compaction method was used to prepare a lithium nitride containing electrode; comparative example 2 an electrode containing lithium nitride was prepared using a reported mechanical compaction method, i.e., an electrode containing an electrode active material was prepared using a homogenization method (a homogenization reagent is commonly used NMP, which does not add lithium nitride when preparing an electrode slurry because it reacts with lithium nitride), and then lithium nitride powder was spread over the electrode and compacted. The examples are lithium nitride-containing electrodes prepared by the homogenization method proposed by the present invention (the homogenization reagent is the DMF solvent screened by theoretical calculation and experiments in the present invention).
The prepared electrode is used as a positive electrode, metal lithium is used as a negative electrode, a 1M lithium hexafluorophosphate (EC/DMC ═ 1:1) system is used as an electrolyte, Cellgard2400 is used as a diaphragm, a button cell is assembled and charged under the current density of 14mA/g, and the charge cut-off voltage is 4.2V vs+and/Li. After the charging is finished, the specific capacity exerted by the lithium nitride is calculated according to the charging capacity and the proportion of the lithium nitride to the active carbon. The theoretical specific capacity of the lithium nitride is 2308.5mAh/g, namely 769mAh/g is the capacity for lithium extraction.
Table 1 lists the specific capacity and the number of lithium ions removed exhibited by the lithium nitride in the lithium nitride-containing electrode prepared by the above three methods, respectively. As can be seen from the table, in the lithium nitride-containing electrode prepared by the homogenization method by using the DMF provided by the invention as the homogenization solvent, the specific capacity of the lithium nitride is up to 1999.4mAh/g, the lithium removal number is up to 2.6, and is much higher than the specific capacity of the lithium nitride in the lithium nitride-containing electrode prepared by the reported powder tabletting method and mechanical compaction method, namely 922.1mAh/g (the lithium removal number is 1.2) and 655.7mAh/g (the lithium removal number is 0.9). In conclusion, the beneficial results of the invention can be seen: the low-toxicity high-boiling point DMF solvent which is preferably selected by the invention is a homogenizing solvent, can be used for preparing the lithium nitride-containing electrode in a large scale, and compared with the reported preparation method of the lithium nitride, the specific capacity exerted by the lithium nitride in the electrode prepared by the homogenizing method is obviously improved. From the aspect of an electrode preparation process, the problem of reactivity of lithium nitride and a solvent is solved, and further research on the lithium nitride-containing electrode can be promoted. The method has important significance for lithium ion super containers with lithium nitride as a pre-lithium additive from basic research to large-scale commercialization.
Claims (8)
1. The electrode slurry containing the lithium nitride is characterized by adopting N, N-Dimethylformamide (DMF) as a solvent.
2. The electrode slurry according to claim 1, wherein:
the lithium ion battery comprises DMF (dimethyl formamide), lithium nitride, a positive active substance, a conductive agent and a binder PVDF (polyvinylidene fluoride).
3. The electrode slurry according to claim 1 or 2, wherein the mass ratio of lithium nitride to DMF is (1-8): (30-240); the preferable mass ratio is (2-4): (60-120); more preferably, the mass ratio is (2-3): (60-100).
4. The electrode slurry according to claim 1 or 2, further comprising,
the positive active substance is one or more than two of ternary positive materials of active carbon, lithium vanadium phosphate, lithium iron phosphate and nickel cobalt manganese;
the conductive agent is one or more of acetylene black, Super P and graphene
PVDF as a binder;
positive electrode active material: lithium nitride: conductive agent: the mass ratio of the binder is (68-78): (2-12): (5-10).
5. A method for preparing an electrode slurry according to any one of claims 1 to 4, characterized in that:
weighing the binder, adding the binder into a DMF solvent, stirring simultaneously, and stirring for more than 2 hours to obtain uniformly dispersed sol; and respectively weighing active substances, lithium nitride and a conductive agent, sequentially adding the active substances, the lithium nitride and the conductive agent into the sol, adjusting the electrode slurry to the required solid content by adopting a DMF solvent, and uniformly stirring (usually stirring for 10 minutes to 3 hours) to obtain a slurry system.
6. Use of an electrode slurry according to any one of claims 1 to 4 in the preparation of a positive electrode for a lithium ion supercapacitor or lithium ion battery.
7. The application of the lithium ion super capacitor or lithium ion battery positive electrode paste as claimed in claim 6, wherein the positive electrode paste is used for preparing the lithium ion super capacitor or lithium ion battery positive electrode by a coating method.
8. The use according to claim 6, wherein the positive electrode active material content is 3 to 10mg/cm2。
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| CN113929061A (en) * | 2021-10-12 | 2022-01-14 | 深圳高能时代科技有限公司 | Method for recovering lithium nitride waste |
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