CN114824178A - Composite modification method for lithium metal negative electrode - Google Patents
Composite modification method for lithium metal negative electrode Download PDFInfo
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- CN114824178A CN114824178A CN202210423294.3A CN202210423294A CN114824178A CN 114824178 A CN114824178 A CN 114824178A CN 202210423294 A CN202210423294 A CN 202210423294A CN 114824178 A CN114824178 A CN 114824178A
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 178
- 239000002131 composite material Substances 0.000 title claims abstract description 44
- 238000002715 modification method Methods 0.000 title claims abstract description 21
- AGBQKNBQESQNJD-UHFFFAOYSA-N lipoic acid Chemical compound OC(=O)CCCCC1CCSS1 AGBQKNBQESQNJD-UHFFFAOYSA-N 0.000 claims abstract description 94
- 235000019136 lipoic acid Nutrition 0.000 claims abstract description 47
- 229960002663 thioctic acid Drugs 0.000 claims abstract description 47
- 238000006243 chemical reaction Methods 0.000 claims abstract description 23
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 30
- 238000012986 modification Methods 0.000 claims description 30
- 230000004048 modification Effects 0.000 claims description 30
- 239000000243 solution Substances 0.000 claims description 20
- 238000003756 stirring Methods 0.000 claims description 20
- 150000002641 lithium Chemical class 0.000 claims description 19
- 239000011259 mixed solution Substances 0.000 claims description 18
- ODNBVEIAQAZNNM-UHFFFAOYSA-N 1-(6-chloroimidazo[1,2-b]pyridazin-3-yl)ethanone Chemical compound C1=CC(Cl)=NN2C(C(=O)C)=CN=C21 ODNBVEIAQAZNNM-UHFFFAOYSA-N 0.000 claims description 15
- GUNJVIDCYZYFGV-UHFFFAOYSA-K Antimony trifluoride Inorganic materials F[Sb](F)F GUNJVIDCYZYFGV-UHFFFAOYSA-K 0.000 claims description 15
- 229910052786 argon Inorganic materials 0.000 claims description 15
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 14
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 12
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 11
- 238000005498 polishing Methods 0.000 claims description 10
- 238000005406 washing Methods 0.000 claims description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 238000002360 preparation method Methods 0.000 claims description 6
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 230000001681 protective effect Effects 0.000 claims description 5
- 239000007789 gas Substances 0.000 claims description 4
- 239000003960 organic solvent Substances 0.000 claims description 4
- 239000003795 chemical substances by application Substances 0.000 claims description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 55
- 229910052751 metal Inorganic materials 0.000 abstract description 30
- 239000002184 metal Substances 0.000 abstract description 30
- 239000011248 coating agent Substances 0.000 abstract description 13
- 238000000576 coating method Methods 0.000 abstract description 13
- 238000000034 method Methods 0.000 abstract description 10
- 229910001439 antimony ion Inorganic materials 0.000 abstract description 4
- 230000015572 biosynthetic process Effects 0.000 abstract description 4
- 239000011247 coating layer Substances 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 239000007784 solid electrolyte Substances 0.000 abstract description 3
- 239000000463 material Substances 0.000 abstract 1
- 239000007773 negative electrode material Substances 0.000 abstract 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 12
- 210000001787 dendrite Anatomy 0.000 description 6
- 230000008021 deposition Effects 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 4
- 230000001680 brushing effect Effects 0.000 description 4
- 210000004027 cell Anatomy 0.000 description 4
- 238000002484 cyclic voltammetry Methods 0.000 description 4
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- 229910001245 Sb alloy Inorganic materials 0.000 description 2
- JDZCKJOXGCMJGS-UHFFFAOYSA-N [Li].[S] Chemical compound [Li].[S] JDZCKJOXGCMJGS-UHFFFAOYSA-N 0.000 description 2
- 239000002140 antimony alloy Substances 0.000 description 2
- BZHNHDOWFCBZNK-UHFFFAOYSA-N antimony lithium Chemical compound [Li].[Sb] BZHNHDOWFCBZNK-UHFFFAOYSA-N 0.000 description 2
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
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- 239000010406 cathode material Substances 0.000 description 1
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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
- H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
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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
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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
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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Abstract
The invention relates to a composite modification method for a lithium metal negative electrode, and the material is applied to the manufacture of the negative electrode of a lithium metal battery, belonging to the field of negative electrode materials of the lithium metal battery. According to the invention, metal antimony ions and alpha-lipoic acid molecules are introduced into a reaction system, and an organic/inorganic coating layer is constructed on the surface of metal lithium by utilizing the reaction among the metal antimony ions, the alpha-lipoic acid molecules and the metal lithium, so that the formation of an artificial solid electrolyte interface SEI on the surface of the metal lithium is realized; the method is simple and easy to implement, can effectively control the forming speed of the coating layer on the surface of the lithium metal, improves the surface coating uniformity, and combines the high ionic conductivity of the inorganic SEI film and the flexibility of the organic SEI film, thereby effectively improving the cycle and rate performance of the lithium metal battery.
Description
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a composite modification method for a lithium metal negative electrode.
Background
The lithium metal anode has the highest theoretical specific capacity (3860mAh g) -1 ) And a lower electrochemical potential (-3.045V relative to a standard hydrogen electrode), have gained widespread attention from next generation lithium battery developers. Lithium metal anodes can broaden the range of options for battery cathodes, enabling the use of high capacity cathode materials that are free of lithium, such as sulfur, oxygen, and high potential fluorides, in batteries. However, practical application of lithium metal secondary batteries (including lithium sulfur batteries) has been hampered by poor cycle stability and safety problems. During continuous charging and discharging, the non-uniform deposition of lithium metal can create non-uniform electric fields and nucleation sites, thereby creating lithium dendrites. In addition, the reaction of the electrolyte with the highly reactive lithium metal can result in depletion of the electrolyte. The lithium metal anode surface forms a fragile and non-uniform Solid Electrolyte Interface (SEI), cannot withstand the volume change of the anode, and induces the growth of lithium dendrites. The continued formation and growth of lithium dendrites can cause internal micro-shorts in the battery, greatly shortening the battery life. Therefore, suppression of lithium dendrites is critical for practical application of metallic lithium in batteries.
In recent years, various methods have been proposed in an attempt to solve the lithium dendrite problem. For example, uniform deposition of lithium metal on the current collector is promoted by structuring a porous current collector or performing functional group modification on the surface of the current collector. By developing a novel electrolyte additive, the stability, ionic conductivity and flexibility of the SEI film on the surface of the metal lithium are improved in the electrochemical cycle process. Patent CN110071284A by antimony trifluoride (SbF) 3 ) The lithium-antimony alloy is formed on the surface of the metal lithium through the reaction between the lithium-antimony alloy and the metal lithium, so that the uniform deposition/stripping of lithium ions on the surface of the metal lithium can be effectively promoted, the formation of lithium dendrites is further inhibited, and the cycle stability of the metal lithium is improved. Patent CN113346045A discloses that SbF 3 The inorganic SEI film generated by the reaction with the metallic lithium has high mechanical strength, and can promote the transmission kinetics of lithium ions in the SEI film, thereby stabilizing the deposition/stripping process of the metallic lithium. However, SbF 3 The reaction speed with the metallic lithium is high, and the inevitable local oxidation of the surface of the metallic lithium can cause the uneven reaction process, which can cause the inorganic SEI film on the surface of the anodeIs difficult to control effectively.
In addition, it is difficult to satisfy the performance requirements of the lithium metal anode in terms of flexibility, elasticity, and the like only by constructing an inorganic SEI film on the surface of the lithium metal anode. The lithium metal anode interface needs to have certain flexibility to improve the adaptability of the anode interface to the volume change of lithium metal, prevent the cracking of the SEI film, and slow down the consumption of the electrolyte (patent CN 111416156A). Therefore, the interfacial modification technology of organic-inorganic composite of metal lithium anode has become an important research and development direction for surface modification of lithium metal anode (patent CN 111009650A). For example, alpha-lipoic acid has strong adsorption performance on the surface of lithium metal and is combined with lithium ions to form an organic SEI layer (patent CN112740460A), but the scheme needs to heat the alpha-lipoic acid to a temperature higher than the melting point temperature to enable the alpha-lipoic acid to perform a ring-opening reaction and a free radical polymerization reaction to form a polymer serving as a protective film, so that the manufacturing energy consumption is greatly increased, and the low-carbon manufacturing is not facilitated.
In addition, in the field, modification of alpha-lipoic acid on the surface of metal lithium is generally realized by an electrochemical process after being added into an electrolyte, and the alpha-lipoic acid cannot directly react with the metal lithium alone, but no report is found about modification of organic-inorganic composite of the alpha-lipoic acid on the surface of the metal lithium, so that the inventor researches and explores the direction to form an organic-inorganic composite SEI film on the surface of a metal lithium negative electrode, sufficiently exerts high ionic conductivity of the inorganic SEI film and flexibility of the organic SEI film, and realizes improvement of the lithium metal battery in the aspects of cycle and rate performance.
Disclosure of Invention
The invention provides a lithium metal negative electrode composite modification method aiming at the defects of the prior art.
The method is realized by the following technical scheme:
a lithium metal negative electrode composite modification method comprises the following steps:
(1) preparation of alpha-lipoic acid solution:
dissolving alpha-lipoic acid in an organic solvent in a glove box, and stirring at room temperature to prepare an alpha-lipoic acid solution;
(2) dissolving antimony trifluoride:
dissolving antimony trifluoride in an alpha-lipoic acid solution in a glove box, and stirring at room temperature to prepare a mixed solution;
(3) pretreatment of the lithium metal sheet:
placing the lithium metal sheet in a glove box, polishing the surface of the lithium metal sheet, and drying after polishing;
(4) modification of lithium metal sheets:
placing the pretreated lithium metal sheet into the mixed solution until the lithium metal sheet is completely immersed, and stirring for reaction;
(5) post-treatment of the lithium metal sheet:
and taking out the modified lithium metal sheet, and washing and drying the modified lithium metal sheet in sequence to obtain the organic/inorganic composite modified lithium metal sheet.
In the steps (1) to (3), the glove box is filled with protective gas to control the oxygen content and the water content in the environment to be less than or equal to 0.1 ppm.
The protective gas is argon.
In the step (1), the organic solvent is one or two of dimethyl ether and propylene carbonate.
In the step (1), the concentration of the alpha-lipoic acid solution is 0.01-0.05 mol/L.
In the step (2), SbF in the mixed solution 3 The concentration is 0.02-0.2 mol/L.
In the present invention, it is considered that the reaction of antimony trifluoride with lithium is the main reaction, and thus the concentration of antimony trifluoride is generally higher than that of alpha-lipoic acid.
In the step (3), the polishing is to brush the lithium metal sheet in tetrahydrofuran by using a brush until the surface gloss is reached.
In the step (4), the stirring reaction is carried out at the temperature of 5-35 ℃ for 2-10 h.
In the step (5), the drying temperature is 5-35 ℃.
In the step (5), the washing agent adopted for washing is any one or two of dimethyl ether and propylene carbonate.
The technical principle is as follows:
according to the invention, metal antimony ions and alpha-lipoic acid molecules are introduced into a reaction system at the same time, and an organic/inorganic coating layer is constructed on the surface of metal lithium by utilizing the reaction among the metal antimony ions, the alpha-lipoic acid molecules and the metal lithium, so that the formation of an artificial Solid Electrolyte Interface (SEI) on the surface of the metal lithium is realized.
In SbF 3 During the reaction with the lithium metal surface, alpha-lipoic acid molecules are introduced. On the one hand, the alpha-lipoic acid can effectively regulate SbF 3 The chemical reaction speed with lithium metal realizes more uniform coating of inorganic precipitates on the surface of the lithium metal; on the other hand, in SbF 3 In the reaction with lithium metal, SbF 3 The chemical reaction of alpha-lipoic acid and metallic lithium can be promoted, the organic modification of the alpha-lipoic acid on the surface of a metallic lithium cathode is realized, an organic/inorganic composite SEI film is further generated, and the effective combination of an inorganic SEI film with high ionic conductivity and an organic SEI film with flexibility is realized, so that the cycle performance and the rate capability of the lithium metal battery are obviously improved.
Has the advantages that:
the composite coating modification method of the lithium metal sheet is simple and easy to implement, has low condition requirement, does not need to control pH and reaction temperature, and can realize composite coating on the surface of the lithium metal sheet by one-step reaction at room temperature.
The invention realizes the control of the reaction speed of the surface of the metal lithium, and effectively inhibits the excessive deposition and the non-uniform growth of a coating layer on the surface of the metal lithium, mainly because the introduction of the alpha-lipoic acid can effectively inhibit SbF 3 The method can realize the SbF only by controlling the concentration of the alpha-lipoic acid 3 The reaction speed with the metallic lithium is effectively controlled.
The lithium metal sheet has excellent ionic conductivity and flexibility, and the surface of the lithium metal sheet is coated with the organic SEI and inorganic SEI composite membrane, so that the lithium metal sheet can be used as a negative electrode of a lithium metal battery to remarkably improve the cycle performance and rate capability of the lithium metal battery (such as a lithium sulfur battery and a lithium battery).
Drawings
FIG. 1: multiplying power performance graphs of the lithium sheets before and after surface modification in the symmetrical battery;
FIG. 2: the lithium sheets before and after surface modification are 0.5mA/cm in a symmetrical battery 2 A graph of cyclic performance of time;
FIG. 3: the lithium sheets before and after surface modification are respectively assembled with the lithium iron phosphate anode to form an electrochemical impedance spectrum of the battery;
FIG. 4: the lithium sheets before and after surface modification and the lithium iron phosphate anode are respectively assembled into a battery cyclic voltammetry spectrum;
FIG. 5: multiplying power performance diagrams of batteries assembled by the lithium sheets before and after surface modification and the lithium iron phosphate positive electrode at 0.1-5 ℃ respectively;
FIG. 6: and the lithium sheets before and after surface modification and the lithium iron phosphate anode are respectively assembled into a battery with a cycle performance diagram at 0.5 ℃.
Detailed Description
The following is a detailed description of the embodiments of the present invention, but the present invention is not limited to these embodiments, and any modifications or substitutions in the basic spirit of the embodiments are included in the scope of the present invention as claimed in the claims.
Example 1
A lithium metal negative electrode composite modification method comprises the following steps:
(1) preparation of alpha-lipoic acid solution:
dissolving alpha-lipoic acid in propylene carbonate in a glove box protected by argon, and stirring at room temperature to prepare an alpha-lipoic acid solution;
(2) dissolving antimony trifluoride:
dissolving antimony trifluoride in an alpha-lipoic acid solution in a glove box protected by argon, and stirring at room temperature to prepare a mixed solution; the concentration of alpha-lipoic acid in the mixed solution is 0.05mol/L, and SbF 3 The concentration of (A) is 0.1 mol/L;
(3) pretreatment of the lithium metal sheet:
placing the lithium metal sheet in a glove box protected by argon, brushing the lithium metal sheet in tetrahydrofuran by a brush until the surface gloss is achieved to obtain a polished lithium metal sheet, and drying at 25 ℃ after polishing;
(4) modification of lithium metal sheets:
placing the pretreated lithium metal sheet into the mixed solution at 25 ℃ until the lithium metal sheet is completely immersed, and stirring for reaction for 5 hours;
(5) post-treatment of the lithium metal sheet:
taking out the modified lithium metal sheet, washing with propylene carbonate, and drying at 25 ℃ to obtain an organic/inorganic composite modified lithium metal sheet;
the steps (1) to (4) are all finished in an argon-protected glove box, and the oxygen content and the water content in the glove box are both less than or equal to 0.1 ppm.
And (3) performance detection:
the surface of the lithium metal sheet modified by the embodiment is dark red; the modified lithium sheet of the embodiment is used as a negative electrode, the Celgard 2325 diaphragm and the lithium iron phosphate are used as positive active materials, and a CR2025 battery shell is adopted to assemble the button cell; meanwhile, the lithium sheet before modification in the embodiment is used as a control group, and the button cell is assembled by adopting the same assembly design;
FIG. 1 shows that the symmetrical battery assembled by the metal lithium before and after the composite coating modification is carried out on the metal lithium is at 0.2mA/cm 2 And 0.5mA/cm 2 Charge and discharge performance in time. Two modified metal lithium sheets are adopted to be assembled into a symmetrical battery, and the polarization voltage is lower than that of a Li | Li symmetrical battery in the charging and discharging processes. The two symmetrical batteries are subjected to 1200-hour charge-discharge cycle performance test, and the comparison result further proves the improvement of the electrochemical stability of the lithium metal negative electrode after composite modification (figure 2). As can be seen from the electrochemical impedance spectroscopy result in fig. 3, after the lithium metal is subjected to composite coating modification, the modified lithium sheet and the lithium iron phosphate positive electrode are used for battery assembly, and the electrochemical impedance is smaller, so that the modified lithium metal sheet promotes lithium ion transmission in the battery, which is beneficial to improving the rate capability of the battery. As can be seen from the cyclic voltammetry curve result in fig. 4, after the metal lithium is subjected to composite coating modification, the area of the graph surrounded by the cyclic voltammetry curve is larger, which indicates that the electrochemical activity of the metal lithium negative electrode subjected to composite coating modification is stronger. Furthermore, the distance between the cathode peak and the anode peak was decreased from 0.425V before modificationAs little as 0.345V shows that the surface composite coating of the metallic lithium can reduce the polarization of the battery and improve the electrochemical cycle reversibility. It can be known from the comparison of the rate performance test results in fig. 5 that the discharge capacities of the lithium iron phosphate battery prepared by using the composite coated and modified metal lithium at 0.1C, 0.2C, 0.5C, 1C, 2C and 5C are 160.3mAh/g, 157.1mAh/g, 148.0mAh/g, 124.6mAh/g, 104.3mAh/g and 70.1mAh/g, respectively, and the discharge capacity is greatly improved compared with the discharge capacity of the metal lithium negative electrode before the composite coating modification. The discharge capacities of the lithium iron phosphate battery prepared by the metal lithium before composite coating modification at 0.1C, 0.2C, 0.5C, 1C, 2C and 5C are 150.1mAh/g, 143.3mAh/g, 133.5mAh/g, 118.0mAh/g, 90.2mAh/g and 47.5mAh/g respectively. This shows that the composite coating modification of the surface of the lithium metal is beneficial to improving the discharge performance of the lithium iron phosphate under high rate. After the lithium sheets before and after modification are respectively assembled with lithium iron phosphate into a battery, a cycle charge and discharge test is carried out for 250 weeks at 0.5 ℃, and the result shows that compared with the unmodified lithium metal | lithium iron phosphate battery (133.6mAh/g, 92.8%), the composite coating modification of the lithium metal not only improves the discharge capacity of the lithium iron phosphate battery at 0.5 ℃ but also improves the capacity retention capacity (148.7mAh/g, 98.4%).
Example 2
A lithium metal negative electrode composite modification method comprises the following steps:
(1) preparation of alpha-lipoic acid solution:
dissolving alpha-lipoic acid in propylene carbonate in a glove box protected by argon, and stirring at room temperature to prepare an alpha-lipoic acid solution;
(2) dissolving antimony trifluoride:
dissolving antimony trifluoride in an alpha-lipoic acid solution in a glove box protected by argon, and stirring at room temperature to prepare a mixed solution; the concentration of alpha-lipoic acid in the mixed solution is 0.01mol/L, and SbF 3 The concentration of (A) is 0.02 mol/L;
(3) pretreatment of lithium metal sheets:
placing the lithium metal sheet in a glove box protected by argon, brushing the lithium metal sheet in tetrahydrofuran by a brush until the surface gloss is achieved to obtain a polished lithium metal sheet, and drying at 25 ℃ after polishing;
(4) modification of lithium metal sheets:
placing the pretreated lithium metal sheet into the mixed solution at the temperature of 5 ℃ until the lithium metal sheet is completely immersed, and stirring for reaction for 2 hours;
(5) post-treatment of the lithium metal sheet:
taking out the modified lithium metal sheet, washing with propylene carbonate, and drying at 25 ℃ to obtain an organic/inorganic composite modified lithium metal sheet;
the steps (1) to (4) are all finished in an argon-protected glove box, and the oxygen content and the water content in the glove box are both less than or equal to 0.1 ppm.
Example 3
A lithium metal negative electrode composite modification method comprises the following steps:
(1) preparation of alpha-lipoic acid solution:
dissolving alpha-lipoic acid in a mixed solvent of propylene carbonate and dimethyl ether with equal molar ratio in a glove box protected by argon, and stirring at room temperature to prepare an alpha-lipoic acid solution;
(2) dissolving antimony trifluoride:
dissolving antimony trifluoride in an alpha-lipoic acid solution in a glove box protected by argon, and stirring at room temperature to prepare a mixed solution; the concentration of alpha-lipoic acid in the mixed solution is 0.02mol/L and SbF 3 The concentration of (A) is 0.2 mol/L;
(3) pretreatment of lithium metal sheets:
placing the lithium metal sheet in a glove box protected by argon, brushing the lithium metal sheet in tetrahydrofuran by a brush until the surface gloss is achieved to obtain a polished lithium metal sheet, and drying at 25 ℃ after polishing;
(4) modification of lithium metal sheets:
placing the pretreated lithium metal sheet into the mixed solution at 15 ℃ until the lithium metal sheet is completely immersed, and stirring for reaction for 10 hours;
(5) post-treatment of the lithium metal sheet:
taking out the modified lithium metal sheet, washing the lithium metal sheet by using a mixed detergent with the mol ratio of propylene carbonate to dimethyl ether and the like in sequence, and drying the lithium metal sheet at 25 ℃ to obtain an organic/inorganic composite modified lithium metal sheet;
the steps (1) to (4) are all finished in a glove box protected by argon, and the oxygen content and the water content in the glove box are both less than or equal to 0.1 ppm.
Example 4
A lithium metal negative electrode composite modification method comprises the following steps:
(1) preparation of alpha-lipoic acid solution:
dissolving alpha-lipoic acid in propylene carbonate in a glove box protected by argon, and stirring at room temperature to prepare an alpha-lipoic acid solution;
(2) dissolving antimony trifluoride:
dissolving antimony trifluoride in an alpha-lipoic acid solution in a glove box protected by argon, and stirring at room temperature to prepare a mixed solution; the concentration of alpha-lipoic acid in the mixed solution is 0.05mol/L and SbF 3 The concentration of (A) is 0.03 mol/L;
(3) pretreatment of the lithium metal sheet:
placing the lithium metal sheet in a glove box protected by argon, brushing the lithium metal sheet in tetrahydrofuran by a brush until the surface gloss is achieved to obtain a polished lithium metal sheet, and drying at 25 ℃ after polishing;
(4) modification of lithium metal sheets:
placing the pretreated lithium metal sheet into the mixed solution at the temperature of 20 ℃ until the lithium metal sheet is completely immersed, and stirring for reaction for 8 hours;
(5) post-treatment of the lithium metal sheet:
taking out the modified lithium metal sheet, sequentially washing with dimethyl ether and drying at 25 ℃ to obtain an organic/inorganic composite modified lithium metal sheet;
the steps (1) to (4) are all finished in an argon-protected glove box, and the oxygen content and the water content in the glove box are both less than or equal to 0.1 ppm.
And (3) performance detection:
the surfaces of the lithium metal sheets modified in the embodiments 2 to 4 are all dark red; the lithium sheets modified in the embodiments 2, 3 and 4 are respectively used as negative electrodes, and the button cells are assembled according to the assembly method of the embodiment 1;
the results are shownThe following steps: examples 2-4 symmetrical cells assembled at 0.2mA/cm 2 And 0.5mA/cm 2 Under the condition, lower polarization voltage is shown in the charging and discharging process, and the result of a 1200-hour charging and discharging cycle performance test shows that the electrochemical stability of the modified lithium metal negative electrode is more excellent.
Examples 2-4 show a smaller electrochemical impedance compared to unmodified modified lithium metal sheets. And the area surrounded by the cyclic voltammetry curve is larger, and the distance between the cathode peak and the anode peak is reduced.
The rate performance of the assembled batteries of examples 2-4 is as follows, and the discharge capacity of each group at different currents is shown in table 1:
TABLE 1
| Intensity of current | Example 2(mAh/g) | Example 3(mAh/g) | Example 4(mAh/g) |
Capacity retention capacity is shown in table 2 for 250 weeks on 0.5C cycle:
| example 2 | Example 3 | Example 4 | |
| Capacity retention (%) | 96.3 | 98.1 | 94.7 |
Claims (10)
1. A lithium metal negative electrode composite modification method is characterized by comprising the following steps:
(1) preparation of alpha-lipoic acid solution:
dissolving alpha-lipoic acid in an organic solvent in a glove box, and stirring at room temperature to prepare an alpha-lipoic acid solution;
(2) dissolving antimony trifluoride:
dissolving antimony trifluoride in an alpha-lipoic acid solution in a glove box, and stirring at room temperature to prepare a mixed solution;
(3) pretreatment of the lithium metal sheet:
placing the lithium metal sheet in a glove box, polishing the surface of the lithium metal sheet, and drying after polishing;
(4) modification of lithium metal sheets:
placing the pretreated lithium metal sheet into the mixed solution until the lithium metal sheet is completely immersed, and stirring for reaction;
(5) post-treatment of the lithium metal sheet:
and taking out the modified lithium metal sheet, and sequentially washing and drying to obtain the organic/inorganic composite modified lithium metal sheet.
2. The composite modification method for the lithium metal negative electrode as claimed in claim 1, wherein in the steps (1) to (3), the glove box is filled with protective gas to control the oxygen content and the water content in the environment to be less than or equal to 0.1 ppm.
3. The composite modification method for the lithium metal negative electrode as claimed in claim 1, wherein the protective gas is argon.
4. The composite modification method for the lithium metal negative electrode as claimed in claim 2, wherein in the step (1), the organic solvent is one or both of dimethyl ether and propylene carbonate.
5. The composite modification method for the lithium metal negative electrode as claimed in claim 1, wherein in the step (1), the concentration of the alpha-lipoic acid solution is 0.01-0.05 mol/L.
6. The composite modification method for lithium metal negative electrode as claimed in claim 1, wherein in the step (2), SbF is contained in the mixed solution 3 The concentration is 0.02-0.2 mol/L.
7. The composite modification method for the lithium metal negative electrode as claimed in claim 1, wherein in the step (3), the polishing is to brush the lithium metal sheet in tetrahydrofuran by using a brush until the surface gloss is reached.
8. The composite modification method for the lithium metal negative electrode as claimed in claim 1, wherein in the step (4), the stirring reaction is carried out at a temperature of 5-35 ℃ for 2-10 h.
9. The composite modification method for the lithium metal negative electrode as claimed in claim 1, wherein in the step (5), the drying temperature is 5-35 ℃.
10. The composite modification method for the lithium metal negative electrode as claimed in claim 1, wherein in the step (5), the washing agent used for washing is any one or two of dimethyl ether and propylene carbonate.
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