WO2022198677A1 - 电化学装置及电子装置 - Google Patents

电化学装置及电子装置 Download PDF

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Publication number
WO2022198677A1
WO2022198677A1 PCT/CN2021/083425 CN2021083425W WO2022198677A1 WO 2022198677 A1 WO2022198677 A1 WO 2022198677A1 CN 2021083425 W CN2021083425 W CN 2021083425W WO 2022198677 A1 WO2022198677 A1 WO 2022198677A1
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WIPO (PCT)
Prior art keywords
isolation layer
lithium
pole piece
region
electrochemical device
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PCT/CN2021/083425
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English (en)
French (fr)
Inventor
张益博
翁秋燕
魏红梅
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宁德新能源科技有限公司
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Priority to PCT/CN2021/083425 priority Critical patent/WO2022198677A1/zh
Priority to CN202180006433.6A priority patent/CN114730856A/zh
Publication of WO2022198677A1 publication Critical patent/WO2022198677A1/zh

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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
    • 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
    • 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
    • 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
    • H01M10/058—Construction or manufacture
    • H01M10/0583—Construction or manufacture of accumulators with folded construction elements except wound ones, i.e. folded positive or negative electrodes or separators, e.g. with "Z"-shaped electrodes or separators
    • 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/463—Separators, membranes or diaphragms characterised by their shape
    • H01M50/466—U-shaped, bag-shaped or folded

Definitions

  • the present application relates to the field of battery technology, and in particular, to an electrochemical device and an electronic device.
  • Electrochemical devices eg, lithium-ion batteries
  • the length and/or width of the negative pole piece is greater than the length and/or width of the positive pole piece, and along the length and/or width of the negative pole piece, the area of the negative pole piece beyond the positive pole piece produces Extension (overhang), also known as A/C overhang.
  • Extension also known as A/C overhang.
  • the capacity of the positive electrode is smaller than that of the negative electrode, so as to improve the reliability of the battery and avoid too much lithium ions released from the positive electrode during the charging process, which cannot be completely inserted into the negative electrode active material. As a result, lithium precipitation occurs on the surface of the negative pole piece, which brings a safety risk.
  • the present application provides an electrochemical device to solve at least one of the above problems.
  • an electrochemical device comprising a positive pole piece, a first isolation layer and a negative pole piece; along the first direction, the negative pole piece includes a protruding portion beyond the positive pole piece, so
  • the first isolation layer includes a first area located between the positive pole piece and the negative pole piece, a second area located on the surface of the protruding portion, extending beyond the negative pole piece along the first direction and extending beyond the negative pole piece.
  • the width of the first isolation layer is greater than the width of the negative pole piece, and the portion beyond the edge of the negative pole piece is folded toward the surface of the negative pole piece to form an end including the fourth region.
  • the ends of the separator are limited between the protruding parts of the negative pole pieces, which can prevent the occurrence of problems such as short circuit between the positive and negative electrodes caused by the wrinkling or backturning of the first separator.
  • the fourth area It is located above the protruding part where the positive pole piece is not provided, which can reduce the thickness difference of the electrode assembly in the protruding part region and the non-protruding part region, thereby reducing the risk of lithium precipitation.
  • the width of the protruding portion in the first direction is A
  • the width of the first end portion in the first direction is C, where C ⁇ A. C ⁇ A, that is, in the first direction, it is ensured that the width of the turned-back portion is less than or equal to the width of the protruding portion, so that the first isolation layer cannot be turned back to the positive pole piece area.
  • C ⁇ 0.25A is beneficial to improve the filling degree of the space above the extension, improve the uniformity of pressure at the edge, and at the same time, it is also beneficial to firmly restrict the end of the first isolation layer to the space above the extension , reduce the risk of short circuit.
  • C ranges from 0.05 mm to 20 mm and A ranges from 0.5 mm to 20 mm.
  • the width of the third region in the first direction is B, and the range of B is 0.5 mm to 20 mm.
  • B value is too small, the edge of the negative pole piece is easily damaged when folded, causing problems such as powder falling; when the B value is too large, it may cause a loss of energy density.
  • the third region includes a curved portion bent toward the negative electrode pole piece, and the curvature radius of the curved portion is R, and R ranges from 10 ⁇ m to 5000 ⁇ m.
  • the thickness of the fourth region is H1, and H1 ranges from 2 ⁇ m to 60 ⁇ m.
  • the thickness of the positive electrode sheet is Hc, which satisfies: 0.3Hc ⁇ H1 ⁇ Hc.
  • H1 ⁇ 0.3Hc is beneficial to improve the filling degree of the space above the overhang, improve the uniformity of pressure at the edge, and reduce the risk of lithium precipitation.
  • the first direction is the width direction of the negative pole piece.
  • the length of the fourth region accounts for more than 50% of the length of the protruding portion.
  • the second area and the fourth area are bonded, and the end of the first isolation layer is fixed by the bonding between the second area and the fourth area, and the wrinkle or Risk of short circuit caused by rollback.
  • the electrochemical device further includes a second isolation layer, and the negative pole piece is located between the second isolation layer and the first isolation layer; the second isolation layer includes a A fifth area on the surface of the pole piece, a sixth area extending beyond the negative pole piece along the first direction and bent, and a second end connected to the sixth area, the second end including The seventh region of the four-region surface.
  • the width of the second end portion in the first direction is D, where D ⁇ A.
  • 0.25A ⁇ D ⁇ A 0.25A ⁇ D ⁇ A.
  • the thickness of the seventh region is H2, and H2 ranges from 2 ⁇ m to 60 ⁇ m.
  • 0.3Hc ⁇ H1+H2 ⁇ Hc In some embodiments, 0.4Hc ⁇ H1+H2 ⁇ Hc. In some embodiments, 0.5Hc ⁇ H1+H2 ⁇ Hc.
  • the seventh region and the fourth region are bonded together, and by the bonding between the seventh region and the fourth region, the stability of filling the space above the protruding portion is improved, and the separation of the second end portion is reduced. risks of.
  • the porosity of the first isolation layer is 30% to 95%. In some embodiments, the porosity of the second isolation layer is 30% to 95%. In some embodiments, the thickness of the first isolation layer is 1 ⁇ m ⁇ 20 ⁇ m. In some embodiments, the thickness of the second isolation layer is 1 ⁇ m ⁇ 20 ⁇ m. If the porosity of the isolation layer is too small, the ion transport path will be blocked and the normal cycle of the electrochemical device will be hindered; if the porosity is too large, the structure will be unstable and the mechanical strength will be too poor to resist the puncture of the particles on the surface of the pole piece. The thickness of the isolation layer ranges from 1 ⁇ m to 20 ⁇ m, which is beneficial to improve the energy density of the electrochemical device on the premise of ensuring the mechanical strength.
  • the first isolation layer and/or the second isolation layer includes polymer fibers, and optionally further includes particles; the particles include at least one of inorganic matter and organic matter.
  • the polymer fibers include polyvinylidene fluoride (PVDF), polyimide (PI), polyamide (PA), polyacrylonitrile (PAN), polyethylene glycol (PEG), polyoxyethylene Ethylene (PEO), Polyphenylene Oxide (PPO), Polypropylene carbonate (PPC), Polymethylmethacrylate (PMMA), Polyethylene terephthalate (PET), Poly(vinylidene fluoride) - At least one of hexafluoropropylene) (PVDF-HFP), poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) and derivatives thereof.
  • PVDF polyvinylidene fluoride
  • PI polyimide
  • PA polyamide
  • PAN polyacrylonitrile
  • PEG polyethylene glycol
  • PEO polyoxyethylene Ethylene
  • PPO Polyphenylene Oxide
  • PPC Polypropylene carbonate
  • PMMA Polymethylmethacrylate
  • the inorganic substances include HfO 2 (hafnium dioxide), SrTiO 3 (strontium titanate), SnO 2 (tin dioxide), CeO 2 (cerium oxide), MgO (magnesium oxide), NiO (oxide Nickel), CaO (calcium oxide), BaO (barium oxide), ZnO (zinc oxide), ZrO 2 (zirconia), Y 2 O 3 (yttrium trioxide), Al 2 O 3 (alumina), TiO 2 (titanium dioxide), SiO 2 (silicon dioxide), boehmite ( ⁇ -AlOOH, hydrated alumina), Mg(OH) 2 (magnesium hydroxide), Al(OH) 3 (aluminum hydroxide), lithium phosphate ( Li 3 PO 4 ), lithium titanium phosphate ((Li x Ti y (PO 4 ) 3 , where 0 ⁇ x ⁇ 2 and 0 ⁇ y ⁇ 3), lithium aluminum titanium phosphate ((Li x A y T z (
  • the organic matter includes polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyphenylene At least one of ether (PPO), polypropylene carbonate (PPC), polyethylene oxide (PEO) and derivatives thereof.
  • PVDF-HFP polyvinylidene fluoride-hexafluoropropylene
  • PVDF polyvinylidene fluoride
  • PVDF polyacrylonitrile
  • PMMA polymethyl methacrylate
  • PPO polypropylene carbonate
  • PEO polyethylene oxide
  • the present application also provides an electronic device including the electrochemical device as described above.
  • the first isolation layer and/or the second isolation layer are constructed on the surface of the pole piece, and the part of the width of the isolation layer that exceeds the width of the pole piece is turned back, so that the end of the isolation layer is located at In the space above the protrusion of the negative pole piece, the uniformity of the pressure at the edge is improved and the risk of lithium precipitation is reduced.
  • FIG. 1 is a schematic diagram of an electrochemical device provided by an embodiment of the present application.
  • FIG. 2 is a schematic diagram of an electrochemical device provided by another embodiment of the present application.
  • FIG. 3 is a schematic diagram of an electrochemical device provided by another embodiment of the present application.
  • FIG. 4 is a schematic diagram of an electrochemical device provided by another embodiment of the present application.
  • FIG. 5 is a schematic diagram of preparing a first isolation layer or a second isolation layer according to an embodiment of the present application.
  • FIG. 6 is a microstructure diagram of the first isolation layer or the second isolation layer prepared in the embodiment in FIG. 5 .
  • FIG. 7 is a schematic diagram of preparing a first isolation layer or a second isolation layer according to another embodiment of the present application.
  • FIG. 8 is a microstructure diagram of the first isolation layer or the second isolation layer prepared in the embodiment of FIG. 7 .
  • FIG. 9 is a schematic diagram of an electrochemical device in Comparative Example 3.
  • FIG. 9 is a schematic diagram of an electrochemical device in Comparative Example 3.
  • FIG. 10 is a schematic diagram of the electrochemical device in Comparative Example 4.
  • FIG. 10 is a schematic diagram of the electrochemical device in Comparative Example 4.
  • the third area 33 is the third area 33
  • the sixth area 72 is the sixth area 72
  • the present application provides an electrochemical device 100 , which includes a positive pole piece 10 , a first isolation layer 30 and a negative pole piece 50 .
  • the negative pole piece 50 includes an extension 51 that extends beyond the positive pole piece
  • the first isolation layer 30 includes a portion located in the positive pole piece.
  • the width of the first isolation layer 30 is greater than the width of the negative pole piece, and the part beyond the edge of the negative pole piece 50 (that is, the third region 33 and the first end 34) is folded toward the surface of the negative pole piece, And the fourth area 35 in the first end is located on the surface of the second area 32.
  • the first end is limited between the protruding parts 51 of the negative pole pieces, which can prevent the occurrence of the first isolation caused by the
  • the fourth area 35 is arranged in the space where the positive pole piece is not arranged above the extension part, which can reduce the problem of the electrode assembly in the extension part area. Thickness differences in non-protrusion regions, thereby reducing the risk of lithium precipitation.
  • the width of the protruding portion 51 in the first direction X is A, and the width of the first end portion 34 in the first direction X is C, where C ⁇ A.
  • AC overhang refers to the part of the negative pole piece that exceeds the positive pole piece in the length and width directions.
  • C ⁇ A that is, in the first direction X, it is ensured that the width of the rolled-back portion is less than or equal to the width of AC overhang, so that the first isolation layer 30 will not be rolled back to the area of the positive pole piece 10 .
  • C ⁇ 0.25A is beneficial to improve the filling degree of the space above the extension, improve the uniformity of pressure at the edge, and at the same time, it is also beneficial to firmly restrict the end of the first isolation layer to the space above the extension , reduce the risk of short circuit.
  • C ranges from 0.05 mm to 20 mm and A ranges from 0.5 mm to 20 mm. If the value of A is too small, lithium may be easily precipitated at the edge of the negative pole piece; if the value of A is too large, the loss of energy density may be caused.
  • the width of the third region 33 in the first direction X is B, and the range of B is 0.5 mm to 20 mm.
  • B the width of the third region 33 in the first direction X is B
  • the range of B is 0.5 mm to 20 mm.
  • the third region 33 includes a curved portion bent toward the negative electrode pole piece 50 , and the curvature radius of the curved portion is R, and R ranges from 10 ⁇ m to 5000 ⁇ m.
  • the thickness of the fourth region 35 is H1 , and the range of H1 is 2 ⁇ m to 60 ⁇ m.
  • the thickness of the positive electrode sheet 10 is Hc, which satisfies: 0.3Hc ⁇ H1 ⁇ Hc.
  • H1 ⁇ 0.3Hc is beneficial to improve the filling degree of the space above the overhang, improve the uniformity of pressure at the edge, and reduce the risk of lithium precipitation.
  • the direction perpendicular to the thickness direction Y and the first direction X at the same time is the length direction of the negative pole piece 50 (that is, the extension direction of the negative pole piece 50 ), along the length of the negative pole piece 50 direction, the length of the fourth region 35 accounts for more than 50% of the length of the protruding portion.
  • the second area 32 and the fourth area 35 are bonded, and the end of the first isolation layer 30 is fixed by the bonding between the second area 32 and the fourth area 35, thereby reducing the Risk of short circuit caused by a wrinkle or rollback of the isolation layer 30 .
  • the electrochemical device 100 further includes a second isolation layer 70 , and the negative electrode plate 50 is located between the second isolation layer 70 and the first isolation layer 30 .
  • the second isolation layer 70 includes a fifth region 71 located on the surface of the negative pole piece 50 , a sixth region 72 extending beyond the negative pole piece 50 and bent along the first direction X, and connecting the sixth region
  • the second end portion 73 of the fourth region 35 is located in the seventh region 74 of the surface of the fourth region 35 .
  • the width of the second end portion 73 in the first direction is D, where D ⁇ A.
  • 0.25A ⁇ D ⁇ A 0.25A ⁇ D ⁇ A.
  • the thickness of the seventh region 74 is H2, and H2 ranges from 2 ⁇ m to 60 ⁇ m.
  • 0.3Hc ⁇ H1+H2 ⁇ Hc In some embodiments, 0.4Hc ⁇ H1+H2 ⁇ Hc. In some embodiments, 0.5Hc ⁇ H1+H2 ⁇ Hc.
  • the seventh region 74 and the fourth region 35 are bonded. Through the bonding between the seventh region 74 and the fourth region 35, the stability of filling the space above the protruding portion is improved, and the first region is reduced. Risk of detachment of the two ends.
  • FIG. 2 shows the situation where the first isolation layer 30 and the second isolation layer 70 are reversed after overlapping the area beyond the negative pole piece 50 , that is, the third area 33 and the sixth area 72 partially overlap, and the fourth area 35 and The seventh region 74 overlaps. It can be understood that the first isolation layer 30 and the second isolation layer 70 can also be maintained independently and then turned back, as shown in FIG. 3 .
  • the second isolation layer 70 may not be turned back, and may be selected from common isolation films, such as PE (polyethylene) or PP (polypropylene) isolation films, and the like.
  • PE polyethylene
  • PP polypropylene
  • the porosity of the first isolation layer is 30%-95%. In some embodiments, the porosity of the second isolation layer is 30% to 95%. In some embodiments, the thickness of the first isolation layer is 1 ⁇ m ⁇ 20 ⁇ m. In some embodiments, the thickness of the second isolation layer is 1 ⁇ m ⁇ 20 ⁇ m. If the porosity of the isolation layer is too small, the ion transport path will be blocked and the normal cycle of the electrochemical device will be hindered; if the porosity is too large, the structure will be unstable and the mechanical strength will be too poor to resist the puncture of the particles on the surface of the pole piece. The thickness of the isolation layer ranges from 1 ⁇ m to 20 ⁇ m, which is beneficial to improve the energy density of the electrochemical device on the premise of ensuring the mechanical strength.
  • the first barrier layer and/or the second barrier layer includes polymer fibers.
  • the first isolation layer and/or the second isolation layer may further comprise particles, and the mass fraction of the particles ranges from 5% to 80%. If the mass fraction is too small, the filler particles cannot effectively fill the pores, improve the mechanical strength, and optimize the pore size distribution; if the mass fraction is too large, it is difficult for the gaps of the polymer fibers to accommodate so many filler particles, and the filler particles are easy to fall off. Also affects the overall thickness and consistency of the first isolation layer (second isolation layer).
  • the particles include at least one of inorganic oxides, lithium ion conductive inorganics, and organics.
  • the polymer fibers include polyvinylidene fluoride (PVDF), polyimide (PI), polyamide (PA), polyacrylonitrile (PAN), polyethylene glycol (PEG), polyethylene oxide ( PEO), polyphenylene oxide (PPO), polypropylene carbonate (PPC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), poly(vinylidene fluoride-hexa) At least one of fluoropropene) (PVDF-HFP), poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) and derivatives thereof.
  • PVDF polyvinylidene fluoride
  • PI polyimide
  • PA polyamide
  • PAN polyacrylonitrile
  • PEG polyethylene glycol
  • PEO polyethylene oxide
  • PPO polyphenylene oxide
  • PPC polypropylene carbonate
  • PMMA polymethyl methacrylate
  • PET polyethylene terephthalate
  • the inorganic substances include HfO 2 (hafnium dioxide), SrTiO 3 (strontium titanate), SnO 2 (tin dioxide), CeO 2 (cerium oxide), MgO (magnesium oxide), NiO (nickel oxide) , CaO (calcium oxide), BaO (barium oxide), ZnO (zinc oxide), ZrO 2 (zirconia), Y 2 O 3 (yttrium oxide), Al 2 O 3 (alumina), TiO 2 (titanium dioxide) ), SiO 2 (silicon dioxide), boehmite ( ⁇ -AlOOH, hydrated alumina), Mg(OH) 2 (magnesium hydroxide), Al(OH) 3 (aluminum hydroxide), lithium phosphate (Li 3 PO 4 ), lithium titanium phosphate ((Li x Ti y (PO 4 ) 3 , where 0 ⁇ x ⁇ 2 and 0 ⁇ y ⁇ 3), lithium aluminum titanium phosphate ((Li x A y T z (
  • the organic matter includes polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyphenylene ether ( At least one of PPO), polypropylene carbonate (PPC), polyethylene oxide (PEO) and derivatives thereof.
  • PVDF-HFP polyvinylidene fluoride-hexafluoropropylene
  • PVDF polyvinylidene fluoride
  • PVDF polyacrylonitrile
  • PMMA polymethyl methacrylate
  • PPO polyphenylene ether
  • PPC polypropylene carbonate
  • PEO polyethylene oxide
  • one or more protective layers may be provided on the surface of the first isolation layer 30 facing away from the negative pole piece 50 , and the second isolation layer 70 is away from the negative pole piece 50 .
  • the surface can also be provided with one or more protective layers (not shown) to further improve the mechanical strength and ensure insulation properties.
  • the thickness of the protective layer is 0.1 ⁇ m-20 ⁇ m, too thin can not improve the mechanical strength and inhibit particle puncture and inhibit the growth of lithium dendrites; too thick will inhibit lithium ion conduction, battery polarization will increase, and performance will be affected. inhibition.
  • the porosity of the protective layer is 10%-40%, and the average pore size is 0.1 ⁇ m-1 ⁇ m.
  • the material of the protective layer includes at least one of inorganic oxides, lithium ion conductive inorganic substances and organic substances.
  • the types of the inorganic oxides, the lithium ion conductive inorganic substances and the organic substances are as described above. It will not be repeated here.
  • the present application also provides an electronic device including the electrochemical device 100 as described above.
  • the negative electrode active material graphite (Graphite), conductive carbon black (Super P), and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 96:1.5:2.5, and deionized water was added to prepare a negative electrode active material slurry with a solid content of 0.7. ingredients and mix well.
  • the negative electrode active material slurry is uniformly coated on one surface of the negative electrode current collector copper foil, and dried at 110°C to obtain a negative electrode active material layer, and then another surface is formed on the other surface of the negative electrode current collector by the same process. Anode active material layer. Further, through cutting pieces and welding tabs, a negative pole piece is obtained.
  • electrospinning on the surface of the negative pole piece (each raw material is added to the solvent, heated and stirred to form a uniform spinning solution, the spinning solution is prepared into nanofibers on the surface of the pole piece by electrospinning equipment, and dried to remove solvent) method to prepare a PVDF first isolation layer with a thickness of 15 ⁇ m.
  • the prepared first isolation layer had an average pore diameter of 500 nm and a porosity of 80%.
  • a second isolation layer is arranged on the back of the negative pole piece, and dried at 90° C. to obtain a negative electrode coated on both sides and provided with the first isolation layer and the second isolation layer. pole piece.
  • the positive active material lithium cobalt oxide (LiCoO 2 ), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) was added as a solvent.
  • NMP N-methylpyrrolidone
  • the positive electrode active material slurry is uniformly coated on the positive electrode current collector aluminum foil, and dried at 90° C. to obtain a positive electrode active material layer.
  • another positive electrode active material layer is formed on the other surface of the positive electrode current collector using the same process. Further, after cutting pieces and welding tabs, a positive pole piece with a thickness Hc of 100 ⁇ m was obtained.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the coated negative pole piece and positive pole piece are stacked opposite to each other, and then guided by guide rollers and local airflow, the first isolation layer and the second isolation layer beyond the area of the negative pole piece are directed toward the
  • the surface direction of the negative pole piece is folded to the state shown in Figure 2 or Figure 3, and its position is fixed by hot pressing, wherein the sum H of the thickness H1 of the fourth region and the thickness H2 of the seventh region is the same as the positive electrode.
  • Example 2 The difference between Example 2 and Example 1 is that A is 0.5 mm.
  • Example 3 The difference between Example 3 and Example 1 is that A is 0.8 mm.
  • Example 4 The difference between Example 4 and Example 1 is that A is 0.8 mm and B is 20 mm.
  • Example 5 The difference between Example 5 and Example 1 is that A is 0.8 mm and B is 0.5 mm.
  • Example 6 The difference between Example 6 and Example 1 is that A is 0.8 mm and B is 0.7 mm.
  • Example 7 The difference between Example 7 and Example 1 is that A is 0.8 mm, B is 0.7 mm, and C is 0.05 mm.
  • Example 8 The difference between Example 8 and Example 1 is that B is 0.7 mm and C is 20 mm.
  • Example 9 The difference between Example 9 and Example 1 is that A is 0.8 mm, B is 0.7 mm, and C is 0.5 mm.
  • Example 10 The difference between Example 10 and Example 9 is that H/Hc is 0.8.
  • Example 11 The difference between Example 11 and Example 9 is that H/Hc is 0.3.
  • Example 12 The difference between Example 12 and Example 9 is that H/Hc is 1.
  • Example 13 The difference between Example 13 and Example 9 is that H/Hc is 0.5.
  • Example 14 The difference between Example 14 and Example 1 is that A is 0.8 mm, B is 0.7 mm, C is 0.5 mm, and R is 100 ⁇ m.
  • a protective layer is respectively provided on the surface of the first isolation layer and the second isolation layer, and the specific steps are: the inorganic ceramic particles aluminum oxide (Al 2 O 3 ) and polyvinylidene fluoride (PVDF) , mix according to the weight ratio of 95:5, add N-methylpyrrolidone (NMP) as a solvent, prepare a slurry with a solid content of 0.8, stir evenly, and coat the slurry evenly on the first isolation layer and the second On isolation, drying at 90°C to obtain a protective layer.
  • the thickness of the protective layer is 3 ⁇ m, the porosity is 30%, and the pore diameter is less than 1 ⁇ m.
  • A is 0.8 mm
  • B is 0.7 mm
  • C is 0.5 mm
  • R 100 ⁇ m.
  • the rest of the settings are the same as those in Embodiment 1, and are not repeated here.
  • the alumina ceramic particles are added with N-methylpyrrolidone (NMP) by the electrospraying process.
  • NMP N-methylpyrrolidone
  • a slurry with a solid content of 0.7 was prepared and sprayed onto the surface of the negative electrode pole piece to obtain a first separator or a second separator filled with particles as shown in FIG. 8 .
  • A is 0.8 mm
  • B is 0.7 mm
  • C is 0.5 mm
  • R 100 ⁇ m.
  • the rest of the settings are the same as those in Embodiment 1, and are not repeated here.
  • a primer coating is applied on the negative electrode current collector copper foil.
  • the slurry is uniformly coated on the negative electrode current collector copper foil, and dried at 110 °C to obtain a negative electrode primer coating.
  • the remaining preparation steps of the negative pole piece are the same as those in Example 1, and will not be repeated here.
  • A is 0.8 mm
  • B is 0.7 mm
  • C is 0.5 mm
  • R is 100 ⁇ m.
  • Comparative Example 1 A is 0.8 mm, and a conventional PE separator is used.
  • Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the first isolation layer and the second isolation layer are arranged on the surface of the positive electrode sheet, and the isolation layer is not folded.
  • Comparative Example 3 the difference between Comparative Example 3 and Example 1 is that A is 0.8 mm and C is 1.2 mm, that is, A ⁇ C.
  • the rest of the settings are the same as those in Embodiment 1, and are not repeated here.
  • Comparative Example 4 Please refer to FIG. 10 , the difference between Comparative Example 4 and Example 1 is that the back turn does not reach the AC overhang area, and A is 0.8mm.
  • the rest of the settings are the same as those in Embodiment 1, and are not repeated here.
  • volume energy density at 25°C, charge the lithium-ion battery to 4.45V with a constant current of 0.5C, then charge it with a constant voltage of 4.45V to a current of 0.05C, and then discharge it to 3.0V with a constant current of 1C to obtain a discharge capacity of 1C .
  • 1C discharge volume energy density 1C discharge capacity/volume of lithium ion battery.
  • Ratio of lithium ionization Take 20 lithium-ion batteries and carry out the above 200 cycles, disassemble the lithium ion battery after the cycle, observe the surface of the negative pole piece, and count the number of lithium ion batteries that have undergone lithium ionization.
  • the ratio of lithium ionization the number of lithium ionization /20.
  • the present application can improve the energy density of the battery, improve the problem of lithium precipitation at the edge after cycling, and improve the cycle capacity retention rate.
  • the isolation layer without folding treatment Comparative Example 2 in the present application, since the end of the isolation layer is turned back to the space above the protrusion of the negative pole piece, the uniformity of pressure at the edge can be improved, and further Improve the problem of lithium precipitation at the edge after cycling, and improve the cycle capacity retention rate.
  • the present application can greatly reduce the phenomenon that the separator is inwardly embedded in the edge of the positive electrode, which can improve the energy density of the battery and improve the edge segregation after cycling.
  • the present application greatly reduces the phenomenon that the isolation layer accumulates wrinkles on the edge of the negative pole piece, which can improve the problem of lithium precipitation at the edge after cycling and improve the retention of cycle capacity. Rate.
  • the stiffness of the battery can be improved, and the cycle performance of the battery can be further improved; at the same time, the anti-self-discharge ability can be further optimized. , that is, to improve the overall performance of the battery.

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Abstract

本申请提供一种电化学装置及电子装置，所述电化学装置包括正极极片、第一隔离层以及负极极片，沿第一方向，所述负极极片包括超出所述正极极片的伸出部，所述第一隔离层包括位于所述正极极片与所述负极极片之间的第一区域、位于所述伸出部表面的第二区域、沿所述第一方向超出所述负极极片并弯曲的第三区域、与所述第三区域连接的第一端部，所述第一端部包括位于所述第二区域表面的第四区域。本申请提供的电化学装置及电子装置，通过在极片表面构建第一隔离层和/或第二隔离层，并通过热压将隔离层位置固定，从而防止发生因其褶皱或回翻等现象引发的诸多问题。

Description

电化学装置及电子装置 技术领域
本申请涉及电池技术领域，尤其涉及一种电化学装置及电子装置。
背景技术
电化学装置(例如，锂离子电池)具有电压高、体积小、质量轻、比容量高、无记忆效应、无污染、自放电小和循环寿命长等优点，已广泛应用于众多领域。随着电化学装置的广泛应用，其性能也受到越来越多的关注。
在目前的电化学装置中，负极极片的长度和/或宽度大于正极极片的长度和/或宽度，沿负极极片的长度和/或宽度方向，负极极片超出正极极片的区域产生伸出部(overhang)，又称A/C overhang。研究人员认为，电池设计中增加overhang区域可调节正负极容量，一般正极容量小于负极容量，以提升电池可靠性，避免充电过程中正极脱出的锂离子过多，无法完全插入负极活性材料中，从而在负极极片表面出现析锂，带来安全风险。但是，电极组件在overhang区域和其他区域(非overhang区域)存在厚度差异(结构层的厚度之和不同)，在热压化成过程中，电极组件受到的压力不均匀，导致电池界面恶化，充电时容易在overhang表面出现析锂现象，影响充放电性能。
发明内容
有鉴于此，本申请提供一种电化学装置以解决上述存在的至少一个问题。
本申请的技术方案是：一种电化学装置，包括正极极片、第一隔离层以及负极极片；沿第一方向，所述负极极片包括超出所述正极极片的伸出部，所述第一隔离层包括位于所述正极极片与所述负极极片之间的第一区域、位于所述伸出部表面的第二区域、沿所述第一方向超出所述负极极片并弯曲的第三区域、以及与所述第三区域连接的第一端部，所述第一端部包括位于所述第二区域表面的第四区域。
所述第一隔离层的宽度大于负极极片的宽度，并将超出所述负极极片边缘的部分，向负极极片表面方向翻折，形成包括第四区域的端部，一方面，第一隔离层的端部被限制在负极极片的伸出部之间，可防止发生因所述第一隔离层褶皱或回翻等现象引发的正负极短路等问题，另一方面，第四区域位于未设置正极极片的伸出部上方，能够降低电极组件在伸出部区域和非伸出部区域存在的厚度差异，从而降低析锂风险。
一些实施方式中，所述伸出部在所述第一方向上的宽度为A，所述第一端部在所述第一方向上的宽度为C，C≤A。C≤A，即在第一方向上保证回翻部分的宽度小于等于伸出部的宽度，使第一隔离层不会回翻至正极极片区域。
一些实施方式中，0.25A≤C≤A。其中，C≥0.25A，有利于提高伸出部上方空间的填充程度，提高边缘处受压的均匀性，同时，也有利于将第一隔离层的端 部牢固限制在伸出部上方的空间中，降低短路风险。
一些实施方式中，C的范围为0.05mm至20mm，A的范围为0.5mm至20mm。
一些实施方式中，所述第三区域在所述第一方向上的宽度为B，B的范围为0.5mm至20mm。B数值过小时，翻折时容易破坏负极极片边缘，引发掉粉等问题；B数值过大时，可能会带来能量密度损失。
一些实施方式中，所述第三区域包括朝向所述负极极片弯曲的弯曲部，所述弯曲部的曲率半径为R，R的范围为10μm至5000μm。
一些实施方式中，所述第四区域的厚度为H1，H1的范围为2μm至60μm。
一些实施方式中，所述正极极片的厚度为Hc，满足：0.3Hc≤H1≤Hc。其中，H1≥0.3Hc，有利于提高伸出部上方空间的填充程度，提高边缘处受压的均匀性，降低析锂风险。
一些实施方式中，所述第一方向为所述负极极片的宽度方向。
一些实施方式中，沿所述负极极片的长度方向，所述第四区域的长度占所述伸出部长度的50％以上。
一些实施方式中，第二区域与第四区域之间粘接，通过第二区域与第四区域之间的粘接，从而将第一隔离层的端部固定，降低因第一隔离层褶皱或回翻引发的短路风险。
一些实施方式中，所述电化学装置还包括第二隔离层，所述负极极片位于所述第二隔离层与所述第一隔离层之间；所述第二隔离层包括位于所述负极极片表面的第五区域、沿所述第一方向超出所述负极极片并弯曲的第六区域、连接所述第六区域的第二端部，所述第二端部包括位于所述第四区域表面的第七区域。
一些实施方式中，所述第二端部在所述第一方向上的宽度为D，D≤A。
一些实施方式中，0.25A≤D≤A。
一些实施方式中，所述第七区域的厚度为H2，H2的范围为2μm至60μm。
一些实施方式中，0.3Hc≤H1+H2≤Hc。一些实施方式中，0.4Hc≤H1+H2≤Hc。一些实施方式中，0.5Hc≤H1+H2≤Hc。
一些实施方式中，第七区域与第四区域之间粘接，通过第七区域与第四区域之间的粘接，提高了在伸出部上方空间填充的稳定性，降低第二端部脱离的风险。
一些实施方式中，所述第一隔离层的孔隙率为30％～95％。一些实施方式中，所述第二隔离层的孔隙率为30％～95％。一些实施方式中，所述第一隔离层的厚度为1μm～20μm。一些实施方式中，所述第二隔离层的厚度为1μm～20μm。隔离层的孔隙率过小，会导致离子传输通路堵塞，阻碍电化学装置正常循环；孔隙率过大，会导致结构不稳定，机械强度太差，无法抵抗极片表面颗粒的穿刺。隔离层的厚度范围为1μm至20μm，在保证机械强度的前提下，有利于提高电化学装置的能量密度。
一些实施方式中，所述第一隔离层和/或所述第二隔离层包括聚合物纤维，以及可选地进一步包括颗粒；所述颗粒包括无机物以及有机物中的至少一种。
一些实施方式中，所述聚合物纤维包括聚偏氟乙烯(PVDF)、聚酰亚胺(PI)、 聚酰胺(PA)、聚丙烯腈(PAN)、聚乙二醇(PEG)、聚氧化乙烯(PEO)、聚苯醚(PPO)、聚碳酸亚丙酯(PPC)、聚甲基丙烯酸甲酯(PMMA)、聚对苯二甲酸乙二醇酯(PET)，聚(偏二氟乙烯-六氟丙烯)(PVDF-HFP)、聚(偏二氟乙烯-共-三氟氯乙烯)(PVDF-CTFE)及其衍生物中的至少一种。
一些实施方式中，所述无机物包括HfO 2(二氧化铪)、SrTiO 3(钛酸锶)、SnO 2(二氧化锡)、CeO 2(氧化铈)、MgO(氧化镁)、NiO(氧化镍)、CaO(氧化钙)、BaO(氧化钡)、ZnO(氧化锌)、ZrO 2(氧化锆)、Y 2O 3(三氧化二钇)、Al 2O 3(氧化铝)、TiO 2(二氧化钛)、SiO 2(二氧化硅)、勃姆石(γ-AlOOH，水合氧化铝)、Mg(OH) 2(氢氧化镁)、Al(OH) 3(氢氧化铝)、磷酸锂(Li 3PO 4)、锂钛磷酸盐((Li xTi y(PO 4) 3，其中0<x<2且0<y<3)、锂铝钛磷酸盐((Li xAl yTi z(PO 4) 3，其中0<x<2，0<y<1，且0<z<3)、锂镧钛酸盐(Li xLa yTiO 3，其中0<x<2且0<y<3)、锂锗硫代磷酸盐(Li xGe yP zS w，其中0<x<4，0<y<1，0<z<1，且0<w<5)、锂氮化物(Li xN y，其中0<x<4，0<y<2)、SiS 2玻璃(Li xSi yS z，其中0≤x<3，0<y<2且0<z<4)、P 2S 5玻璃(Li xP yS z，其中0≤x<3，0<y<3且0<z<7)、氧化锂(Li 2O)、氟化锂(LiF)、氢氧化锂(LiOH)、碳酸锂(Li 2CO 3)、偏铝酸锂(LiAlO 2)、锂锗磷硫陶瓷(Li 2O-Al 2O 3-SiO 2-P 2O 5-TiO 2-GeO 2)和石榴石陶瓷(Li 3+xLa 3M 2O 12，其中0≤x≤5，且M为Te碲、Nb铌或Zr锆)中的至少一种。
一些实施方式中，所述有机物包括聚偏氟乙烯-六氟丙烯(PVDF-HFP)、聚偏氟乙烯(PVDF)、聚丙烯腈(PAN)、聚甲基丙烯酸甲酯(PMMA)、聚苯醚(PPO)、聚碳酸亚丙酯(PPC)、聚环氧乙烷(PEO)及其衍生物中的至少一种。
本申请还提供一种电子装置，包括如上所述的电化学装置。
本申请提供的电化学装置及电子装置，通过在极片表面构建第一隔离层和/或第二隔离层，并将隔离层宽度超出极片宽度的部分回翻，使隔离层的端部位于负极极片伸出部上方的空间中，从而提高边缘处受压的均匀性，降低析锂风险。
附图说明
下面结合附图和具体实施方式对本申请作进一步详细的说明。
图1为本申请一实施方式提供的电化学装置的示意图。
图2为本申请另一实施方式提供的电化学装置的示意图。
图3为本申请另一实施方式提供的电化学装置的示意图。
图4为本申请另一实施方式提供的电化学装置的示意图。
图5为本申请一实施方式提供的制备第一隔离层或第二隔离层的示意图。
图6为图5中实施方式制得的第一隔离层或第二隔离层的微观结构图。
图7为本申请另一实施方式提供的制备第一隔离层或第二隔离层的示意图。
图8为图7中实施方式制得的第一隔离层或第二隔离层的微观结构图。
图9为对比例3中电化学装置的示意图。
图10为对比例4中电化学装置的示意图。
主要元件符号说明：
电化学装置               100
正极极片                 10
第一隔离层               30
第一区域                 31
第二区域                 32
第三区域                 33
第一端部                 34
第四区域                 35
负极极片                 50
伸出部                   51
第二隔离层               70
第五区域                 71
第六区域                 72
第二端部                 73
第七区域                 74
第一方向(宽度方向)       X
厚度方向                 Y
如下具体实施方式将结合上述附图进一步说明本申请实施例。
具体实施方式
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请实施例的技术领域的技术人员通常理解的含义相同。本文中所使用的术语只是为了描述具体的实施方式的目的，不是旨在于限制本申请实施例。
请参阅图1，本申请提供一种电化学装置100，其包括正极极片10、第一隔离层30以及负极极片50。沿第一方向X(所述负极极片50的宽度方向)，所述负极极片50包括超出所述正极极片的伸出部51，所述第一隔离层30包括位于所述正极极片10与所述负极极片50之间的第一区域31、位于所述伸出部51表面的第二区域32、沿所述第一方向X超出所述负极极片50并弯曲的第三区域33、以及与所述第三区域33连接第一端部34，所述第一端部34包括位于所述第二区域32表面的第四区域35。
所述第一隔离层30的宽度大于负极极片的宽度，并将超出所述负极极片50边缘的部分(即第三区域33和第一端部34)向负极极片表面方向翻折，并使第一端部中的第四区域35位于第二区域32的表面，一方面，第一端部被限制在负极极片的伸出部51之间，可防止发生因所述第一隔离层30褶皱或回翻等现象引发的正负极短路等问题，另一方面，第四区域35设置在伸出部上方未设置正极极片的空间中，能够降低电极组件在伸出部区域和非伸出部区域存在的厚度差 异，从而降低析锂风险。
所述伸出部51在所述第一方向X上的宽度为A，所述第一端部34在所述第一方向X上的宽度为C，C≤A。在电池技术领域，AC overhang指负极极片长度和宽度方向上多出正极极片之外的部分。C≤A，即在第一方向X上保证回翻部分的宽度小于或等于AC overhang的宽度，使第一隔离层30不会回翻至正极极片10的区域。
一些实施方式中，0.25A≤C≤A。其中，C≥0.25A，有利于提高伸出部上方空间的填充程度，提高边缘处受压的均匀性，同时，也有利于将第一隔离层的端部牢固限制在伸出部上方的空间中，降低短路风险。
一些实施方式中，C的范围为0.05mm至20mm，A的范围为0.5mm至20mm。A数值过小时，负极极片边缘可能容易析锂；A数值过大时，可能会造成能量密度损失。
一些实施方式中，所述第三区域33在所述第一方向X上的宽度为B，B的范围为0.5mm至20mm。B数值过小时，翻折时容易破坏负极极片50的边缘，引发掉粉等问题；B数值过大时，可能会带来能量密度损失。
如图1所示，所述第三区域33包括朝向所述负极极片50弯曲的弯曲部，所述弯曲部的曲率半径为R，R的范围为10μm至5000μm。
一些实施方式中，在厚度方向Y(所述厚度方向Y垂直于所述第一方向X)上，所述第四区域35的厚度为H1，H1的范围为2μm至60μm。
一些实施方式中，所述正极极片10的厚度为Hc，满足：0.3Hc≤H1≤Hc。其中，H1≥0.3Hc，有利于提高伸出部上方空间的填充程度，提高边缘处受压的均匀性，降低析锂风险。
一些实施方式中，同时垂直于所述厚度方向Y和所述第一方向X的方向为负极极片50的长度方向(即负极极片50的延伸方向)，沿所述负极极片50的长度方向，所述第四区域35的长度占所述伸出部长度的50％以上。
一些实施方式中，第二区域32与第四区域35之间粘接，通过第二区域32与第四区域35之间的粘接，从而将第一隔离层30的端部固定，降低因第一隔离层30褶皱或回翻引发的短路风险。
如图2所示，所述电化学装置100还包括第二隔离层70，所述负极极片50位于所述第二隔离层70与所述第一隔离层30之间。所述第二隔离层70包括位于所述负极极片50表面的第五区域71、沿所述第一方向X超出所述负极极片50并弯曲的第六区域72、连接所述第六区域72的第二端部73，所述第二端部73位于所述第四区域35表面的第七区域74。
一些实施方式中，所述第二端部73在所述第一方向上的宽度为D，D≤A。
一些实施方式中，0.25A≤D≤A。
一些实施方式中，所述第七区域74的厚度为H2，H2的范围为2μm至60μm。
一些实施方式中，0.3Hc≤H1+H2≤Hc。一些实施方式中，0.4Hc≤H1+H2≤Hc。一些实施方式中，0.5Hc≤H1+H2≤Hc。
一些实施方式中，第七区域74与第四区域35之间粘接，通过第七区域74与第四区域35之间的粘接，提高了在伸出部上方空间填充的稳定性，降低第二端部脱离的风险。
图2示出了第一隔离层30和第二隔离层70在超出负极极片50的区域重叠后再回翻的情况，即第三区域33和第六区域72部分重叠，第四区域35和第七区域74重叠。可以理解，所述第一隔离层30和第二隔离层70也可各自保持独立再回翻，如图3所示。
如图4所示，所述第二隔离层70还可以不回翻，其可以选自普通隔离膜，例如，PE(聚乙烯)或PP(聚丙烯)隔离膜等。
进一步地，一些实施方式中，所述第一隔离层的孔隙率为30％～95％。一些实施方式中，所述第二隔离层的孔隙率为30％～95％。一些实施方式中，所述第一隔离层的厚度为1μm～20μm。一些实施方式中，所述第二隔离层的厚度为1μm～20μm。隔离层的孔隙率过小，会导致离子传输通路堵塞，阻碍电化学装置正常循环；孔隙率过大，会导致结构不稳定，机械强度太差，无法抵抗极片表面颗粒的穿刺。隔离层的厚度范围为1μm至20μm，在保证机械强度的前提下，有利于提高电化学装置的能量密度。
如图6所示，所述第一隔离层和/或所述第二隔离层包括聚合物纤维。如图8所示，所述第一隔离层和或所述第二隔离层可地进一步包括颗粒，所述颗粒的质量分数范围为5％-80％。质量分数过小，则填充颗粒无法起到有效填充孔隙、改善机械强度、优化孔径分布的作用；质量分数过大，聚合物纤维的间隙难以容纳如此多的填充颗粒，填充颗粒易脱落掉粉，同时影响第一隔离层(第二隔离层)的整体厚度和一致性。所述颗粒包括无机氧化物、锂离子传导性无机物以及有机物中的至少一种。
进一步地，所述聚合物纤维包括聚偏氟乙烯(PVDF)、聚酰亚胺(PI)、聚酰胺(PA)、聚丙烯腈(PAN)、聚乙二醇(PEG)、聚氧化乙烯(PEO)、聚苯醚(PPO)、聚碳酸亚丙酯(PPC)、聚甲基丙烯酸甲酯(PMMA)、聚对苯二甲酸乙二醇酯(PET)，聚(偏二氟乙烯-六氟丙烯)(PVDF-HFP)、聚(偏二氟乙烯-共-三氟氯乙烯)(PVDF-CTFE)及其衍生物中的至少一种。
进一步地，所述无机物包括HfO 2(二氧化铪)、SrTiO 3(钛酸锶)、SnO 2(二氧化锡)、CeO 2(氧化铈)、MgO(氧化镁)、NiO(氧化镍)、CaO(氧化钙)、BaO(氧化钡)、ZnO(氧化锌)、ZrO 2(氧化锆)、Y 2O 3(三氧化二钇)、Al 2O 3(氧化铝)、TiO 2(二氧化钛)、SiO 2(二氧化硅)、勃姆石(γ-AlOOH，水合氧化铝)、Mg(OH) 2(氢氧化镁)、Al(OH) 3(氢氧化铝)、磷酸锂(Li 3PO 4)、锂钛磷酸盐((Li xTi y(PO 4) 3，其中0<x<2且0<y<3)、锂铝钛磷酸盐((Li xAl yTi z(PO 4) 3，其中0<x<2，0<y<1，且0<z<3)、锂镧钛酸盐(Li xLa yTiO 3，其中0<x<2且0<y<3)、锂锗硫代磷酸盐(Li xGe yP zS w，其中0<x<4，0<y<1，0<z<1，且0<w<5)、锂氮化物(Li xN y，其中0<x<4，0<y<2)、SiS 2玻璃(Li xSi yS z，其中0≤x<3，0<y<2且0<z<4)、P 2S 5玻璃(Li xP yS z，其中0≤x<3，0<y<3且0<z<7)、 氧化锂(Li 2O)、氟化锂(LiF)、氢氧化锂(LiOH)、碳酸锂(Li 2CO 3)、偏铝酸锂(LiAlO 2)、锂锗磷硫陶瓷(Li 2O-Al 2O 3-SiO 2-P 2O 5-TiO 2-GeO 2)和石榴石陶瓷(Li 3+xLa 3M 2O 12，其中0≤x≤5，且M为Te碲、Nb铌或Zr锆)中的至少一种。
进一步地，所述有机物包括聚偏氟乙烯-六氟丙烯(PVDF-HFP)、聚偏氟乙烯(PVDF)、聚丙烯腈(PAN)、聚甲基丙烯酸甲酯(PMMA)、聚苯醚(PPO)、聚碳酸亚丙酯(PPC)、聚环氧乙烷(PEO)及其衍生物中的至少一种。
一些实施方式中，所述第一隔离层30背离所述负极极片50的表面可设置一层或多层保护层(图未示)，所述第二隔离层70背离所述负极极片50的表面也可设置一层或多层保护层(图未示)，用于进一步提高机械强度并确保绝缘性能。所述保护层厚度为0.1μm-20μm，太薄起不到提高机械强度并抑制颗粒刺穿和抑制锂枝晶生长的作用；太厚会抑制锂离子传导，电池极化增大，性能发挥受到抑制。所述保护层的孔隙率10％-40％，平均孔径为0.1μm-1μm。所述保护层的材质包括无机氧化物、锂离子传导性无机物以及有机物中的至少一种，所述无机氧化物、所述锂离子传导性无机物以及所述有机物的种类如前所述，此处不再赘述。
本申请还提供一种电子装置，包括如上所述的电化学装置100。
以下将结合具体实施例对本申请作进一步说明。
实施例1
(1)负极极片的制备
将负极活性材料石墨(Graphite)、导电炭黑(Super P)、丁苯橡胶(SBR)按照重量比96:1.5:2.5进行混合，加入去离子水，调配成为固含量为0.7的负极活性物质浆料，并搅拌均匀。将负极活性物质浆料均匀涂覆在负极集流体铜箔的一表面上，110℃条件下烘干，得到一负极活性物质层，接着采用相同工艺在负极集流体的另一表面上形成另一负极活性物质层。进一步地，再经过裁片和焊接极耳，得到负极极片。
(2)隔离层的制备
如图5所示，在负极极片表面通过电纺丝(各原料加入溶剂中，加热搅拌形成均纺丝溶液，纺丝溶液通过电纺丝设备制备成纳米纤维到极片表面，烘干去除溶剂)的方法，制备一层厚度为15μm的PVDF第一隔离层。如图6所示，制备的所述第一隔离层的平均孔径为500nm，孔隙率为80％。
之后，以完全一致的方法，在该负极极片的背面设置第二隔离层，并在90℃条件下烘干，即得到双面涂布并设有第一隔离层和第二隔离层的负极极片。
(3)正极极片的制备
将正极活性材料钴酸锂(LiCoO 2)、导电炭黑(Super P)、聚偏二氟乙烯(PVDF)按照重量比97.5:1.0:1.5进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成为固含量为0.75的正极活性物质浆料，并搅拌均匀。将正极活性物质浆料均匀涂覆在正极集流体铝箔上，90℃条件下烘干，得到一正极活性物质层。接着采用相同工艺在正极集流体的另一表面上形成另一正极活性物质层。 进一步地，再经过裁片和焊接极耳，得到厚度Hc为100μm的正极极片。
(3)电解液的制备
在干燥氩气气氛中，首先将有机溶剂碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)以质量比EC:EMC:DEC＝30:50:20混合，然后向有机溶剂中加入锂盐六氟磷酸锂(LiPF 6)溶解并混合均匀，得到锂盐的浓度为1.15M的电解液。
(4)锂离子电池的制备
如图2所示，将涂布好的负极极片和正极极片相对并叠好，随后利用导辊和局部气流引导，将该超出负极极片区域的第一隔离层和第二隔离层向负极极片表面方向翻折至如图2或图3所示的状态，并通过热压将其位置固定，其中，第四区域的厚度H1与第七区域的厚度H2之和H，与正极极片的厚度Hc的关系满足H/Hc＝0.4，伸出部在所述负极极片宽度方向上的宽度A为20mm，第三区域在所述负极极片宽度方向上的宽度B为0.8mm，第一端部在所述负极极片宽度方向上的宽度C为0.2mm，第三区域的弯曲部的曲率半径R为500μm。卷绕后置入铝塑膜中，最后经顶侧封、注液、封装后，最终得到锂离子电池。
实施例2
实施例2与实施例1的区别在于：A为0.5mm。
实施例3
实施例3与实施例1的区别在于：A为0.8mm。
实施例4
实施例4与实施例1的区别在于：A为0.8mm，B为20mm。
实施例5
实施例5与实施例1的区别在于：A为0.8mm，B为0.5mm。
实施例6
实施例6与实施例1的区别在于：A为0.8mm，B为0.7mm。
实施例7
实施例7与实施例1的区别在于：A为0.8mm，B为0.7mm，C为0.05mm。
实施例8
实施例8与实施例1的区别在于：B为0.7mm，C为20mm。
实施例9
实施例9与实施例1的区别在于：A为0.8mm，B为0.7mm，C为0.5mm。
实施例10
实施例10与实施例9的区别在于：H/Hc为0.8。
实施例11
实施例11与实施例9的区别在于：H/Hc为0.3。
实施例12
实施例12与实施例9的区别在于：H/Hc为1。
实施例13
实施例13与实施例9的区别在于：H/Hc为0.5。
实施例14
实施例14与实施例1的区别在于：A为0.8mm，B为0.7mm，C为0.5mm，R为100μm。
实施例15
本实施例中，在第一隔离层和第二隔离层的表面分别设置一层保护层，具体步骤为：将无机陶瓷颗粒三氧化二铝(Al 2O 3)和聚偏氟乙烯(PVDF)，按照重量比95:5进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成为固含量为0.8的浆料，并搅拌均匀，将浆料均匀涂覆在第一隔离层和第二隔离上，90℃条件下烘干，得到保护层。所述保护层的厚度为3μm，孔隙率为30％，孔径<1μm。并且，本实施例中，A为0.8mm，B为0.7mm，C为0.5mm，R为100μm。其余设置均与实施例1相同，此处不再赘述。
实施例16
本实施例中，如图7所示，在利用电纺丝制备第一隔离层或第二隔离层的同时，利用电喷涂的工艺，将氧化铝陶瓷颗粒，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成为固含量为0.7的浆料，喷射到负极极片表面，进而得到如图8所示的包含颗粒填充的第一隔离层或第二隔离层。本实施例中，A为0.8mm，B为0.7mm，C为0.5mm，R为100μm。其余设置均与实施例1相同，此处不再赘述。
实施例17
本实施例中，在涂覆负极活性物质浆料前，在负极集流体铜箔上涂覆底涂层，具体步骤为：将导电炭黑(Super P)、丁苯橡胶(SBR)按照重量比95:5进行混合，加入去离子水作为溶剂，调配成为固含量为0.8的浆料，将浆料均匀涂覆在负极集流体铜箔上，110℃条件下烘干，得到负极底涂层。负极极片的其余制备步骤与实施例1相同，此处不再赘述。本实施例中，A为0.8mm，B为0.7mm，C为0.5mm，R为100μm。
对比例1
对比例1中，A为0.8mm，用的是常规PE隔离膜。
对比例2
对比例2与实施例1的区别在于：在正极极片的表面设置第一隔离层和第二隔离层，隔离层无翻折处理。
对比例3
请参阅图9，对比例3与实施例1的区别在于：A为0.8mm，C为1.2mm，即A＜C。其余设置均与实施例1相同，此处不再赘述。
对比例4
请参阅图10，对比例4与实施例1的区别在于：回翻未上至AC overhang区域，A为0.8mm。其余设置均与实施例1相同，此处不再赘述。
性能测试
褶皱比例：取20支锂离子电池，拆解，观察超出负极极片边缘的隔离层是否发生褶皱(例如，超出部分呈波形延伸)，统计发生褶皱的锂离子电池个数，褶皱比例＝发生褶皱的个数/20。
体积能量密度：在25℃下，将锂离子电池以0.5C恒流充电至4.45V，然后以4.45V恒压充电至电流为0.05C，再以1C恒流放电至3.0V，得到1C放电容量。1C放电体积能量密度＝1C放电容量/锂离子电池的体积。
循环容量保持率：在25℃下，将锂离子电池以0.5C恒流充电至4.45V，然后以4.45V恒压充电至电流为0.05C，再以0.5C恒流放电至3.0V，得到放电容量，即为首次放电容量。将上述步骤重复200次，记录第200次的放电容量。200次循环容量保持率＝第200次的放电容量/首次放电容量。
析锂比例：取20支锂离子电池进行上述200次循环，将循环后的锂离子电池拆解，观察负极极片表面，统计析锂的锂离子电池个数，析锂比例＝析锂个数/20。
上述实施例1-17以及对比例1-4的各项参数及测试结果见表1。
表1
Figure PCTCN2021083425-appb-000001
Figure PCTCN2021083425-appb-000002
本申请相比对比例1中常规隔离膜的设置，可以提升电池能量密度，并改善循环后边缘析锂问题，提高循环容量保持率。本申请相比于无翻折处理的隔离层(对比例2)，由于隔离层的端部回翻至负极极片伸出部的上方空间中，可以提高边缘处受压的均匀性，进而可以改善循环后边缘析锂问题，提高循环容量保持率。本申请相比于A＜C的翻折处理的隔离层(对比例3)，由于大幅减少了隔离层内翻嵌入正极极片边缘的现象，可以提升电池能量密度，并可以改善循环后边缘析锂问题，提高循环容量保持率。本申请相比于未回翻至AC overhang区域的隔离层(对比例4)，由于大幅减少了隔离层在负极极片边缘堆积褶皱的现象，可以改善循环后边缘析锂问题，提高循环容量保持率。另外，通过底涂层、保护层和填充颗粒的引入(实施例15至实施例17)，一方面可以提高电池的刚度，进一步提升电池的循环性能；同时可以使抗自放电能力得到进一步的优化，即改善电池的综合性能。

Claims (14)

  1. 一种电化学装置，包括正极极片、第一隔离层以及负极极片；沿第一方向，所述负极极片包括超出所述正极极片的伸出部，所述第一隔离层包括位于所述正极极片与所述负极极片之间的第一区域、位于所述伸出部表面的第二区域、沿所述第一方向超出所述负极极片并弯曲的第三区域、以及与所述第三区域连接的第一端部，所述第一端部包括位于所述第二区域表面的第四区域。
  2. 如权利要求1所述的电化学装置，其中，所述伸出部在所述第一方向上的宽度为A，所述第一端部在所述第一方向上的宽度为C，C≤A。
  3. 如权利要求2所述的电化学装置，其中，0.25A≤C≤A。
  4. 如权利要求1所述的电化学装置，其中，所述第三区域在所述第一方向上的宽度为B，B的范围为0.5mm至20mm。
  5. 如权利要求1所述的电化学装置，其中，所述第三区域包括朝向所述负极极片弯曲的弯曲部，所述弯曲部的曲率半径为R，R的范围为10μm至5000μm。
  6. 如权利要求1所述的电化学装置，其中，所述第四区域的厚度为H1，所述正极极片的厚度为Hc，满足：0.3Hc≤H1≤Hc。
  7. 如权利要求1所述的电化学装置，其中，所述第一方向为所述负极极片的宽度方向，沿所述负极极片的长度方向，所述第四区域的长度占所述伸出部长度的50％以上。
  8. 如权利要求2所述的电化学装置，其中，所述电化学装置还包括第二隔离层，所述负极极片位于所述第二隔离层与所述第一隔离层之间；所述第二隔离层包括位于所述负极极片表面的第五区域、沿所述第一方向超出所述负极极片并弯曲的第六区域、连接所述第六区域的第二端部，所述第二端部包括位于所述第四区域表面的第七区域。
  9. 如权利要求8所述的电化学装置，其中，所述第二端部在所述第一方向上的宽度为D，D≤A。
  10. 如权利要求9所述的电化学装置，其中，满足以下条件的至少一者：
    i)0.25A≤D≤A；
    ii)所述第四区域的厚度为H1，所述正极极片的厚度为Hc，所述第七区域的厚度为H2，0.3Hc≤H1+H2≤Hc。
  11. 如权利要求8所述的电化学装置，其中，满足以下条件的至少一者：
    a)所述第一隔离层的孔隙率为30％～95％；
    b)所述第二隔离层的孔隙率为30％～95％；
    c)所述第一隔离层的厚度为1μm～20μm；
    d)所述第二隔离层的厚度为1μm～20μm。
  12. 如权利要求8所述的电化学装置，其中，所述第一隔离层和/或所述第二隔离层包括聚合物纤维，以及可选地进一步包括颗粒；所述颗粒包括无机物以及有机物中的至少一种。
  13. 如权利要求12所述的电化学装置，其中，
    所述聚合物纤维包括聚偏氟乙烯、聚酰亚胺、聚酰胺、聚丙烯腈、聚乙二醇、聚氧化乙烯、聚苯醚、聚碳酸亚丙酯、聚甲基丙烯酸甲酯、聚对苯二甲酸乙二醇酯，聚(偏二氟乙烯-六氟丙烯)、聚(偏二氟乙烯-共-三氟氯乙烯)及其衍生物中的至少一种；
    所述无机物包括二氧化铪、钛酸锶、二氧化锡、氧化铈、氧化镁、氧化镍、氧化钙、氧化钡、氧化锌、氧化锆、三氧化二钇、氧化铝、二氧化钛、二氧化硅、勃姆石、氢氧化镁、氢氧化铝、磷酸锂、锂钛磷酸盐、锂铝钛磷酸盐、锂镧钛酸盐、锂锗硫代磷酸盐、锂氮化物、SiS 2玻璃、P 2S 5玻璃、氧化锂、氟化锂、氢氧化锂、碳酸锂、偏铝酸锂、锂锗磷硫陶瓷和石榴石陶瓷中的至少一种；
    所述有机物包括聚偏氟乙烯-六氟丙烯、聚偏氟乙烯、聚丙烯腈、聚甲基丙烯酸甲酯、聚苯醚、聚碳酸亚丙酯、聚环氧乙烷及其衍生物中的至少一种。
  14. 一种电子装置，包括如权利要求1-13任一项所述的电化学装置。
PCT/CN2021/083425 2021-03-26 2021-03-26 电化学装置及电子装置 WO2022198677A1 (zh)

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