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CN-115528243-B - Polymer protective film, metallic lithium negative electrode, lithium secondary battery and vehicle

CN115528243BCN 115528243 BCN115528243 BCN 115528243BCN-115528243-B

Abstract

The application discloses a polymer protective film, a metal lithium anode, a lithium secondary battery and a vehicle, wherein the polymer protective film has the following structural formula: The polymer protective film has good flexibility, mechanical strength, ionic conductivity and electrical conductivity under the synergistic effect of the imidazole groups and the polyaniline chain segments, can effectively adapt to the expansion of lithium metal, improves the mobility and transmission of lithium ions, ensures uniform distribution of lithium ions, further inhibits the growth of lithium dendrites, and improves the cycle performance of a lithium secondary battery.

Inventors

  • YUAN TAO
  • XIE JING
  • MA YONGJUN
  • GUO ZIZHU

Assignees

  • 比亚迪股份有限公司
  • 上海比亚迪有限公司

Dates

Publication Date
20260505
Application Date
20210624

Claims (15)

  1. 1. A polymeric protective film characterized by the following structural formula: Wherein R 1 is selected from one of bis (trifluoromethylsulfonyl) imide, bis (fluorosulfonyl) imide, perchlorate, hexafluorophosphate, hexafluoroarsenate, tetrafluoroborate, dioxaborate, difluoroborate, trifluoroborate, and trifluoromethylsulfonate; R 2 is selected from- (CH 2 ) i -), 、 、 、 、-CH 2 -Y 1 -CH 2 -、-CH 2 -(CH 2 Y 2 CH 2 ) j -CH 2 - Wherein i is an integer from 2 to 100, Y 1 、Y 2 is each independently selected from O, NH or S, j is an integer from 1 to 100; p is the mole ratio of the reduced polyaniline chain segment to the polyaniline chain segment, p is any decimal between 0 and 1, m and n are the mole ratio of the polyimidazole chain segment and the polyaniline chain segment to the whole polymer respectively, m is more than or equal to 0.5 and less than or equal to 0.95, n is more than or equal to 0.05 and less than or equal to 0.5, and m+n is equal to 1.0; The- (CH 2 ) i -, the) The said The said The said The hydrogen atoms in the-CH 2 -Y 1 -CH 2 -, the-CH 2 -(CH 2 Y 2 CH 2 ) j -CH 2 -may be partially or fully substituted by substituents.
  2. 2. The polymer protective film according to claim 1, wherein 0.6≤m≤0.8, and 0.2≤n≤0.4.
  3. 3. The polymer protective film according to any one of claims 1 to 2, wherein the substituent is selected from halogen, hydroxy, amino, carbonyl, cyano, alkoxy of C 1 -C 6 , alkyl of C 1 -C 6 , aryl of C 6 -C 12 or cycloalkyl of C 6 -C 12 .
  4. 4. The polymer protective film according to claim 3, wherein the halogen is selected from one of fluorine, chlorine and bromine, the amine group is selected from primary amine of C 1 -C 6 , alkyl-substituted secondary amine or tertiary amine of C 1 -C 6 , the alkoxy group of C 1 -C 6 is selected from methoxy or ethoxy, the alkyl group of C 1 -C 6 is selected from methyl, ethyl, propyl and butyl, the aryl group of C 6 -C 12 is selected from phenyl, naphthyl and biphenyl, and the cycloalkyl group of C 6 -C 12 is selected from cyclohexyl and dicyclohexyl.
  5. 5. The polymer protective film according to claim 4, wherein the alkyl group of C 1 -C 6 is selected from isopropyl or tert-butyl.
  6. 6. The polymer protective film according to any one of claims 1 to 2, wherein the molecular weight of the polymer protective film is 10000 to 500000.
  7. 7. The polymer protective film according to claim 6, wherein the molecular weight of the polymer protective film is 100000 to 300000.
  8. 8. A method for producing the polymer protective film according to any one of claims 1 to 7, comprising the steps of: dissolving aniline and an initiator in water, and heating to react to obtain a mixed solution I; Adding acid liquor and a compound with double amino end caps into the mixed liquor I to obtain mixed liquor II; Dropwise adding a mixed solution of formaldehyde and acetaldehyde into the mixed solution II under the condition of ice water bath, and heating for reaction to obtain a mixed solution III; cooling the mixed solution III, and then dropwise adding the cooled mixed solution III into an aqueous solution of an anion exchanger to react to generate a precipitate; And washing and drying the precipitate to obtain the polymer protective film.
  9. 9. The method of claim 8, wherein the acid solution is any one of acetic acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid.
  10. 10. The method of claim 8, wherein the diamino-terminated compound is selected from the group consisting of substituted and unsubstituted NH 2 -R 2 -NH 2 , wherein R 2 is selected from the group consisting of- (CH 2 ) i - 、 、 、 、-CH 2 -Y 1 -CH 2 -、-CH 2 -(CH 2 Y 2 CH 2 ) j -CH 2 - I is an integer of 2-100, Y 1 、Y 2 is independently selected from O, NH or S, and j is an integer of 1-100.
  11. 11. The method according to claim 8, wherein the heating reaction is performed at a temperature of 40 ℃ to 100 ℃ for a reaction time of 0.5 to 12 hours.
  12. 12. The method of claim 8, wherein the anion exchanger is any one of lithium bis (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonyl) imide, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium dioxaoxalato borate, lithium difluorooxalato borate, or lithium trifluoromethylsulfonate.
  13. 13. A metallic lithium anode comprising a metallic lithium sheet and the polymer protective film according to any one of claims 1 to 7, the polymer protective film being provided on the metallic lithium sheet.
  14. 14. A lithium secondary battery comprising the metallic lithium anode of claim 13.
  15. 15. A vehicle comprising the lithium secondary battery of claim 14.

Description

Polymer protective film, metallic lithium negative electrode, lithium secondary battery and vehicle Technical Field The invention relates to the technical field of lithium batteries, in particular to a polymer protective film, a metal lithium negative electrode, a lithium secondary battery and a vehicle. Background Lithium metal has extremely high theoretical specific capacity (mAh/g) and extremely low electrochemical potential (-3.040 Vvs standard hydrogen electrode), and is an ideal negative electrode material for lithium secondary batteries. However, the barrier to limit the further development of the lithium secondary battery has two main aspects, namely (1) lithium dendrite is easily generated during the cycle of the lithium secondary battery, so that short circuit is easily generated in the battery, and (2) lithium metal is easily crushed and pulverized during the cycle, so that active lithium is lost, and the cycle life of the battery is shortened. Research shows that by constructing the protective film on the surface of lithium metal, the side reaction of lithium metal and electrolyte can be obviously reduced, the growth of dendrite is inhibited, and the cycle life of the battery is prolonged. The conventional protective films currently mainly include polymer films and inorganic/organic hybrid films. However, the existing polymer protective film has poor mechanical strength, can not well inhibit the growth of lithium dendrites, has poor acting force and wettability between the existing polymer protective film and lithium metal, and can not well conduct lithium ions between interfaces. The existing organic/inorganic hybrid protective film has poor toughness, and expansion and pulverization of lithium metal can lead the protective film to be broken, so that side reaction occurs between the lithium metal and electrolyte, and the protective effect is lost. The current conventional protective film cannot effectively improve the cycle performance of the lithium secondary battery. Disclosure of Invention In view of the above-described drawbacks or shortcomings in the prior art, it is desirable to provide a polymer protective film, a metallic lithium negative electrode, a lithium secondary battery, and a vehicle, which can effectively conduct lithium ions while suppressing growth of lithium dendrites, accommodate expansion of lithium, and further improve cycle performance of the lithium secondary battery. In a first aspect, the present invention provides a polymer protective film having the structural formula: Wherein R 1 is selected from one of bis (trifluoromethylsulfonyl) imide, bis (fluorosulfonyl) imide, perchlorate, hexafluorophosphate, hexafluoroarsenate, tetrafluoroborate, dioxaborate, difluoroborate, trifluoroborate, and trifluoromethylsulfonate; R 2 is selected from- (CH 2)i -), 、、、、-CH2-Y1-CH2-、-CH2-(CH2Y2CH2)j-CH2- Wherein i is an integer from 2 to 100, Y 1、Y2 is each independently selected from O, NH or S, j is an integer from 1 to 100; p is the mole ratio of the reduced polyaniline chain segment to the polyaniline chain segment, p is any decimal between 0 and 1, m and n are the mole ratios of the polyimidazole chain segment and the polyaniline chain segment to the whole polymer respectively, m and n are each independently any decimal between 0 and 1, and m+n is equal to 1.0; -(CH2)i-、、、、 、-CH2-Y1-CH2-、-CH2-(CH2Y2CH2)j-CH2- The hydrogen atoms of (c) may be partially or fully substituted with substituents. As an alternative to this, it is also possible, m is more than or equal to 0.5 and less than or equal to 0.95 and 0.05 n is more than or equal to 0.5. As an alternative to this, it is also possible, m is more than or equal to 0.6 and less than or equal to 0.8,0.2 n is more than or equal to 0.4. Alternatively, the substituents are selected from halogen, hydroxy, amino, carbonyl, cyano, alkoxy of C 1-C6, alkyl of C 1-C6, aryl of C 6-C12, or cycloalkyl of C 6-C12. Alternatively, halogen is selected from one of fluorine, chlorine and bromine, amine is selected from primary amine of C 1-C6 and alkyl substituted secondary amine or tertiary amine of C 1-C6, alkoxy of C 1-C6 is selected from methoxy or ethoxy, alkyl of C 1-C6 is selected from methyl, ethyl, propyl, isopropyl, butyl or tertiary butyl, aryl of C 6-C12 is selected from phenyl, naphthyl or biphenyl, and cycloalkyl of C 6-C12 is selected from cyclohexyl or dicyclohexyl. Alternatively, the molecular weight of the polymer protective film is 10000 to 500000, preferably 100000 to 300000. In a second aspect, the present invention provides a method for preparing the polymer protective film according to the first aspect, comprising the steps of: dissolving aniline and an initiator in water, and heating to react to obtain a mixed solution I; adding acid liquor and a compound with double amino end caps into the mixed liquor I to obtain mixed liquor II; Dropwise adding the mixture of formaldehyde and acetaldehyde into the mixed solution II under the