WO2024243778A1 - 一种电化学装置和电子装置 - Google Patents

一种电化学装置和电子装置 Download PDF

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Publication number
WO2024243778A1
WO2024243778A1 PCT/CN2023/096914 CN2023096914W WO2024243778A1 WO 2024243778 A1 WO2024243778 A1 WO 2024243778A1 CN 2023096914 W CN2023096914 W CN 2023096914W WO 2024243778 A1 WO2024243778 A1 WO 2024243778A1
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Prior art keywords
electrode assembly
electrochemical device
oxide
layer
protrusion
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PCT/CN2023/096914
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English (en)
French (fr)
Inventor
侯天昊
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to CN202380012122.XA priority Critical patent/CN117480653A/zh
Priority to PCT/CN2023/096914 priority patent/WO2024243778A1/zh
Publication of WO2024243778A1 publication Critical patent/WO2024243778A1/zh
Anticipated expiration legal-status Critical
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of energy storage technology, and in particular to an electrochemical device and an electronic device.
  • Secondary batteries are widely used in the field of consumer electronics, and in recent years, the terminal market has increasingly higher requirements for their service life and energy density.
  • there are two mainstream packaging forms for secondary batteries namely soft-pack and metal shell packaging.
  • soft-pack secondary batteries are widely used due to their advantages such as good safety, high specific energy and flexible design.
  • secondary batteries such as lithium-ion batteries
  • formation treatment that is, the secondary batteries are charged and discharged for the first time to form an electrolyte interface film on the surface of the electrode material.
  • the electrolyte interface film can effectively prevent further loss of the electrolyte and has good ionic conductivity, electronic insulation, thermal stability and chemical stability, which has a very important influence on the subsequent performance of the secondary battery.
  • Applying pressure for formation treatment is an effective means to improve production efficiency and enhance electrode interface performance.
  • the inventors of the present application have found that due to the presence of structures such as the electrode ear welding in the bare cell, the surface is uneven and presents a concave-convex morphology.
  • the surface of the bare cell is subjected to uneven force, which can easily lead to the deterioration of the electrode interface, the precipitation of lithium dendrites, and even fire and explosion.
  • the present application provides an electrochemical device and an electronic device to improve the flatness of the surface of the electrochemical device, thereby improving the electrode interface formed by the electrochemical device during the pressurized formation process, and improving the cycle life and safety of the electrochemical device.
  • an electrochemical device comprising an electrode assembly and a shell, wherein the electrode assembly is accommodated in the shell, the shell comprises a packaging layer, one side surface of the electrode assembly has a protrusion, and one side surface of the packaging layer adjacent to the electrode assembly has a recess, wherein the protrusion is at least partially accommodated in the recess.
  • the present application provides a depression in the packaging layer of the electrochemical device shell, and the depression accommodates the protrusions on the surface of the electrode assembly, so that when the electrochemical device is subjected to pressurized formation treatment, all positions on the surface of the electrode assembly can be evenly stressed, avoiding the concentration of pressure on the protrusions on the surface of the electrode assembly, which leads to the deterioration of the electrode interface and further causes lithium dendrite precipitation and fire and explosion.
  • the depression in the packaging layer can also limit and fix the electrode assembly in the shell. The effect is that when the electrochemical device falls or is hit, the movement of the electrode assembly can be effectively suppressed, reducing the risk of the shell being broken.
  • the solution of the present application is conducive to improving the cycle life and safety performance of the electrochemical device.
  • the electrochemical device of the present application does not require the addition of an additional buffer structure, such as a silicone pad, the force of the electrode assembly during pressurized formation can be uniform, and therefore, it is also conducive to improving the energy density of the electrochemical device.
  • the protrusion is completely contained in the depression. In this way, uniform stress on the surface of the electrode assembly during the pressurized chemical formation process can be further promoted, the electrode interface can be improved, and the cycle life and safety of the electrochemical device can be increased.
  • the surface of the packaging layer facing away from the electrode assembly is a flat surface. In this way, when the electrochemical device is subjected to a pressurized chemical treatment, uniform stress can be further promoted on the surface of the electrode assembly, improving the electrode interface, thereby increasing the cycle life and safety of the electrochemical device.
  • the melting point of the encapsulation layer is 80° C. to 150° C. This is beneficial for encapsulating the housing and forming a concave surface on the inner side of the encapsulation layer.
  • the material of the encapsulation layer includes a thermoplastic polymer.
  • the material of the encapsulation layer includes at least one of polyethylene, polypropylene, ethylene-propylene copolymer, anhydride-modified polypropylene, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride, or derivatives thereof.
  • the depth of the recess is 3 ⁇ m to 150 ⁇ m.
  • the thickness of the packaging layer in the recess is 15 ⁇ m to 200 ⁇ m, so that the structural strength of the packaging layer in the recess can be improved, and the reliability of the housing can be improved.
  • the encapsulation layer further includes a body region adjacent to the recess, and a thickness of the body region is 20 ⁇ m to 250 ⁇ m.
  • the bonding strength between the packaging layer and the electrode assembly is greater than or equal to 2 N/m. In this way, the fixing effect of the shell on the electrode assembly can be further enhanced, the movement of the electrode assembly can be suppressed when the electrochemical device falls or is hit, the risk of the shell being broken is reduced, and the safety of the electrochemical device is improved.
  • the electrode assembly includes a pole piece and a pole lug
  • the electrode assembly includes a pole lug connection region
  • the pole lug is connected to the pole piece in the pole lug connection region
  • the protrusion is located in the pole lug connection region.
  • the electrode assembly is a wound structure
  • the wound structure includes a main body and a corner portion
  • the maximum value of the thickness difference of the electrochemical device at the main body is less than or equal to 20 ⁇ m.
  • the shell further includes a barrier layer, and the barrier layer is located on a surface of the packaging layer that is away from the electrode assembly.
  • the barrier layer has a thickness of 0.1 ⁇ m to 50 ⁇ m.
  • the material of the barrier layer includes at least one of metal, inorganic oxide, or inorganic nitride.
  • the housing further includes a protective layer, and the protective layer is located on a surface of the barrier layer facing away from the encapsulation layer.
  • the protective layer has a thickness of 2 ⁇ m to 50 ⁇ m.
  • the protective layer includes at least one of a polymer or a fiber.
  • the metal includes at least one of aluminum, copper, iron, titanium, or nickel.
  • the inorganic oxide includes at least one of titanium dioxide, aluminum oxide, hafnium dioxide, silicon dioxide, iron oxide, copper oxide, silver oxide, nickel oxide, manganese oxide, zinc oxide, tin oxide, zirconium titanium oxide, or vanadium oxide.
  • the inorganic nitride includes at least one of silicon nitride, silicon oxynitride, boron nitride, titanium nitride, or aluminum nitride.
  • the second aspect of the present application provides an electronic device, comprising the aforementioned electrochemical device. Therefore, the electronic device of the present application has good service life and safety.
  • FIG. 1 shows a cross-sectional view of an electrochemical device of the present application.
  • FIG. 2 shows an enlarged view of region A in FIG. 1 .
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range.
  • each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.
  • a list of connected items can mean any combination of the listed items.
  • the phrase “at least one of A and B” means only A; only B; or A and B.
  • the phrase “at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A can contain a single component or multiple components.
  • Item B can contain a single component or multiple components.
  • Item C can contain a single component or multiple components.
  • An embodiment of the present application provides an electrochemical device, including an electrode assembly and a shell, wherein the electrode assembly is accommodated in the shell, the shell includes a packaging layer, one side surface of the electrode assembly has a protrusion, and the side surface of the packaging layer adjacent to the electrode assembly has a depression, and the protrusion is at least partially accommodated in the depression.
  • the depression can accommodate the protrusions on the surface of the electrode assembly, so that when the electrochemical device is subjected to a pressurized formation treatment, each position on the surface of the electrode assembly can be uniformly stressed, avoiding the concentration of pressure on the protruding parts of the surface of the electrode assembly, which leads to the deterioration of the electrode interface, and then causes lithium dendrite precipitation and fire and explosion.
  • the depression of the packaging layer can also limit and fix the electrode assembly in the shell, and when the electrochemical device falls or is hit, it can effectively suppress the movement of the electrode assembly and reduce the risk of the shell being broken.
  • the scheme of the present application is conducive to improving the cycle life and safety performance of the electrochemical device.
  • the electrochemical device of the present application does not need to add an additional buffer structure, such as a silicone pad, it can achieve uniform force on the electrode assembly during pressurized formation, and therefore, it is also conducive to improving the energy density of the electrochemical device.
  • the protrusion is completely contained in the depression. In this way, the uniform force on the surface of the electrode assembly during the pressurized chemical formation process can be further promoted, the electrode interface can be improved, and the cycle life and safety of the electrochemical device can be increased.
  • the surface of the packaging layer facing away from the electrode assembly is a flat surface. In this way, when the electrochemical device is subjected to a pressurized chemical treatment, uniform stress can be further promoted on the surface of the electrode assembly, improving the electrode interface, thereby increasing the cycle life and safety of the electrochemical device.
  • the material of the encapsulation layer is a thermoplastic polymer.
  • the encapsulation layer can be heated and melted to form an electrochemical device by sealing the electrode assembly in the shell; at the same time, by performing a hot pressing treatment on the surface of the electrochemical device, the encapsulation layer can be softened by heat, and under the action of pressure, a depression is formed on the surface where the encapsulation layer contacts the protrusion, thereby accommodating the protrusion in the depression, thereby improving the uniformity of force on the surface of the electrode assembly when the electrochemical device is subjected to a pressurized chemical treatment.
  • the softened encapsulation layer can be tightly bonded to the surface of the electrode assembly, inhibiting the movement of the electrode assembly when the electrochemical device falls or is hit, reducing the risk of the shell being broken, and further improving the safety of the electrochemical device.
  • the material of the encapsulation layer includes polyethylene, polypropylene, ethylene propylene copolymer, anhydride modified poly At least one of propylene, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride or derivatives thereof.
  • the melting point of the encapsulation layer is 80°C to 150°C. This is conducive to encapsulating the shell and forming a recess on the inner surface of the encapsulation layer.
  • the melting point of the encapsulation layer is 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C or a range consisting of any two of the above values.
  • the depth of the recess is 3 ⁇ m to 150 ⁇ m.
  • the depth of the recess is 3 ⁇ m, 5 ⁇ m, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, 60 ⁇ m, 70 ⁇ m, 80 ⁇ m, 90 ⁇ m, 100 ⁇ m, 110 ⁇ m, 120 ⁇ m, 130 ⁇ m, 140 ⁇ m, 150 ⁇ m, or a range consisting of any two of the above values.
  • the depth of the depression is related to the height of the protrusion on the surface of the electrode assembly. For example, if the height of the protrusion on the surface of the electrode assembly is h and the depth of the depression is d, then 0.5h ⁇ d ⁇ h can be satisfied.
  • the thickness of the packaging layer in the recess is 15 ⁇ m to 200 ⁇ m. It is understandable that the thickness of the packaging layer in the recess is within the above range. On the one hand, it can ensure the structural strength of the packaging layer in the recess and the reliability of the shell; on the other hand, it is also conducive to forming a lightweight electrochemical device and improving the energy density of the electrochemical device.
  • the thickness of the packaging layer in the recess is 15 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, 60 ⁇ m, 70 ⁇ m, 80 ⁇ m, 90 ⁇ m, 100 ⁇ m, 110 ⁇ m, 120 ⁇ m, 130 ⁇ m, 140 ⁇ m, 150 ⁇ m, 160 ⁇ m, 170 ⁇ m, 180 ⁇ m, 190 ⁇ m, 200 ⁇ m or a range consisting of any two of the above values.
  • the encapsulation layer further includes a main body region adjacent to the recess, and the thickness of the main body region is 20 ⁇ m to 250 ⁇ m.
  • the thickness of the main body region is 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, 60 ⁇ m, 70 ⁇ m, 80 ⁇ m, 90 ⁇ m, 100 ⁇ m, 110 ⁇ m, 120 ⁇ m, 130 ⁇ m, 140 ⁇ m, 150 ⁇ m, 160 ⁇ m, 170 ⁇ m, 180 ⁇ m, 190 ⁇ m, 200 ⁇ m, 210 ⁇ m, 220 ⁇ m, 230 ⁇ m, 240 ⁇ m, 250 ⁇ m, or a range consisting of any two of the above values.
  • the thickness of the main region is equal to the sum of the depth of the depression and the thickness of the encapsulation layer at the depression. In this way, the uniformity of the force applied to the surface of the electrode assembly during the pressurized formation treatment of the electrochemical device can be further improved, the electrode interface can be improved, and the cycle life and safety of the electrochemical device can be improved.
  • the bonding strength between the packaging layer and the electrode assembly is greater than or equal to 2 N/m. It is understandable that the bonding between the packaging layer and the electrode assembly can further enhance the fixing effect of the shell on the electrode assembly, and when the electrochemical device falls or is hit, the movement of the electrode assembly can be suppressed, and the risk of the shell being broken can be reduced, thereby further improving the safety of the electrochemical device.
  • the electrode assembly includes a pole piece and a pole lug
  • the electrode assembly includes a pole lug connection area
  • the pole lug is connected to the pole piece in the pole lug connection area
  • the protrusion is located in the pole lug connection area.
  • the electrode assembly is a wound structure
  • the wound structure includes a main body and a corner portion
  • the maximum thickness difference of the electrochemical device at the main body is less than or equal to 20 ⁇ m.
  • the thickness difference within the above range is beneficial to improving the uniformity of force on the surface of the electrode assembly when the electrochemical device is subjected to pressurized formation treatment, thereby improving the electrode interface and increasing the cycle life and safety of the electrochemical device.
  • the shell further includes a barrier layer, which is located on the surface of the packaging layer facing away from the electrode assembly, and the thickness of the barrier layer is 0.1 ⁇ m to 50 ⁇ m.
  • the thickness of the barrier layer is 0.1 ⁇ m, 1 ⁇ m, 5 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, or a range consisting of any two of the above values. It is understood that the thickness of the barrier layer within the above range is conducive to preventing water vapor from penetrating into the shell and affecting the normal use of the electrochemical device.
  • the material of the barrier layer includes at least one of metal, inorganic oxide, or inorganic nitride.
  • the metal material includes, but is not limited to, at least one of aluminum, copper, iron, titanium, or nickel.
  • the inorganic oxide material includes at least one of titanium dioxide, aluminum oxide, hafnium dioxide, silicon dioxide, iron oxide, copper oxide, silver oxide, nickel oxide, manganese oxide, zinc oxide, tin oxide, zirconium titanium oxide, or vanadium oxide.
  • the inorganic nitride material includes at least one of silicon nitride, silicon oxynitride, boron nitride, titanium nitride, or aluminum nitride.
  • the housing further includes a protective layer, and the protective layer is located on a surface of the barrier layer facing away from the encapsulation layer.
  • the thickness of the protective layer is 2 ⁇ m to 50 ⁇ m.
  • the thickness of the protective layer is 2 ⁇ m, 5 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, or a range consisting of any two of the above values. It is understood that the thickness of the protective layer within the above range is conducive to preventing the external structure from damaging the shell and affecting the normal use of the electrochemical device.
  • the protective layer includes at least one of a polymer or a fiber.
  • the electrochemical device of the present application includes, but is not limited to, all kinds of primary batteries or secondary batteries.
  • the electrochemical device is a lithium secondary battery.
  • the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • An embodiment of the present application further provides an electronic device, comprising the electrochemical device of the aforementioned embodiment.
  • the electronic devices of the present application include but are not limited to: mobile phones, laptops, tablet computers, drones, smart watches, smart bracelets, VR glasses, electric cars or power tools, etc.
  • the embodiment of the present application also provides a method for preparing an electrochemical device, which is used to prepare the electrochemical device of the above embodiment, comprising: step 1, preparing an electrode assembly; step 2, wrapping the electrode assembly with a packaging layer, and heat-sealing the opening of the packaging layer; step 3, using a heating mold with a flat surface to heat the packaging layer on the surface of the electrode assembly.
  • the pressure treatment forms a depression at the protrusion of the packaging layer facing the surface of the electrode assembly; step 4, injecting electrolyte, and obtaining the electrochemical device of the present application through the processes of standing, pressurizing, and degassing.
  • the heat sealing temperature in step 2 is 80° C. to 150° C.
  • the heat sealing temperature is 80° C., 85° C., 90° C., 95° C., 100° C., 105° C., 110° C., 115° C., 120° C., 125° C., 130° C., 135° C., 140° C., 145° C., 150° C., or a range consisting of any two of the above values.
  • the heating temperature of the heating and pressurizing treatment in step 3 can soften the encapsulation layer.
  • the heating temperature of the heating and pressurizing treatment in step 3 is less than the melting point of the encapsulation layer, so that the risk of local film rupture can be reduced when the encapsulation layer is heated and pressurized.
  • the heating temperature of the heating and pressurizing treatment in step 3 is 80°C to 150°C.
  • the pressure of the heating and pressurizing treatment in step 3 is 0.1MPa to 1MPa.
  • the heating temperature of the heating and pressurizing treatment is 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C or a range consisting of any two of the above values.
  • the pressure of the heating and pressurizing treatment is 0.1MPa, 0.2MPa, 0.4MPa, 0.5MPa, 0.7MPa, 0.9MPa, 1MPa or a range consisting of any two of the above values.
  • the method for preparing an electrochemical device further includes: step 5, forming a barrier layer on the surface of the packaging layer facing away from the electrode assembly.
  • the process of forming the barrier layer includes at least one of coating, spraying, plating, evaporation or vapor deposition.
  • the method for preparing an electrochemical device further includes: step 6, forming a protective layer on the surface of the barrier layer facing away from the encapsulation layer.
  • the process of forming the protective layer includes at least one of coating, spraying, dipping or winding.
  • Preparation of negative electrode sheet Mix the negative electrode active materials graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) in a weight ratio of 96:1.5:2.5, add deionized water as a solvent, prepare a slurry with a solid content of 0.7, and stir evenly. The slurry is evenly coated on the negative electrode current collector copper foil, and the weight of the effective material on the electrode sheet is 95g/ m2 . Dry at 110°C to obtain a single-sided coated negative electrode sheet. After that, these steps are also completed on the back of the electrode sheet in exactly the same way, that is, a double-sided coated negative electrode sheet is obtained. After that, the negative electrode sheet is cold pressed to a compaction density of 1.7g/ cm3 , and the negative electrode sheet is obtained after cutting and welding the pole ears.
  • Super P conductive carbon black
  • SBR styrene-butadiene rubber
  • positive electrode sheet The positive electrode active material lithium cobalt oxide, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) is added as a solvent. Prepare a slurry with a solid content of 0.75 and stir evenly. Evenly coat the slurry on the positive electrode current collector aluminum foil, and the weight of the effective material on the electrode sheet is 180g/ m2 . Dry at 90°C to obtain a single-sided coated positive electrode sheet. After that, complete these steps on the back of the electrode sheet in exactly the same way to obtain a double-sided coated positive electrode sheet. After that, cold press the positive electrode sheet to a compaction density of 4.1g/ cm3 , and obtain the positive electrode sheet after cutting and welding the pole ears.
  • NMP N-methylpyrrolidone
  • bare cells Preparation of bare cells: The positive electrode sheet, separator and negative electrode sheet are stacked and wound in sequence to obtain a bare cell with a wound structure, wherein the positive electrode tab and the negative electrode tab are both located on the outside of the wound structure, and the separator is a porous polyethylene film with a thickness of 9 ⁇ m.
  • the size of the bare cell is 4.0 mm (thickness) ⁇ 19 mm (width) ⁇ 24 mm (length).
  • the end face of the bare cell is shown in Figures 1 and 2, and its surface is magnified with the characteristics of surface undulations, and the tab is 60 ⁇ m higher than the adjacent position.
  • Pre-packaging Wrap the electrode assembly with a packaging film with a thickness of 110 ⁇ m (three-layer co-extruded polyethylene film, the middle layer is a high-density polyethylene layer, the two sides are low-density polyethylene layers, and the melting point of the low-density polyethylene layers on both sides is 114°C), and perform hot-pressing packaging at the opening at a temperature of 110°C.
  • a packaging film with a thickness of 110 ⁇ m three-layer co-extruded polyethylene film, the middle layer is a high-density polyethylene layer, the two sides are low-density polyethylene layers, and the melting point of the low-density polyethylene layers on both sides is 114°C
  • Hot pressing and shaping Use a heating mold with a flat surface to hot press the surface of the bare cell and the packaging film. Keep it at 115°C and 0.1MPa pressure for 10s.
  • the low-density polyethylene layer in the packaging film melts and flows due to the heat, forming a complementary morphology with the surface of the bare cell, as shown in Figure 2.
  • the inner surface of the packaging film at the position of the pole ear is 60 ⁇ m recessed than the adjacent position.
  • the low-density polyethylene layer in the packaging film is heated and melted, it forms a bond with the diaphragm on the outer surface of the bare cell, and the bonding strength is 3N/m.
  • the flatness of the outer surface of the main body is the same as that of the mold, and the thickness difference does not exceed 3 ⁇ m.
  • Liquid injection packaging The above electrolyte is injected into the unpackaged open area and then packaged. After standing, pressurized formation, degassing and other processes, the lithium-ion battery is obtained.
  • Comparative Example 1 uses an aluminum-plastic film with a thickness of 100 ⁇ m for packaging, places the bare battery cell in an aluminum-plastic film packaging bag, heat-seales it on all sides, leaves a liquid injection port, seals the liquid injection port after liquid injection, and subsequently obtains a lithium-ion battery through processes such as standing, pressurized formation, and degassing.
  • Micro-drop test The experiment uses 10 groups of lithium-ion batteries.
  • the lithium-ion batteries are fixed with double-sided tape and assembled into the battery compartment of the watch model for a micro-drop test.
  • the drop height during the test is 7 cm.
  • the head and tail are dropped at 20 times/min for 20,000 times, and the four sides are dropped at 50 times/min for 500 times, for a total of 42,000 times.
  • the situation of package edge rupture or leakage is counted. If the package edge is ruptured or leaking, it is considered unpassed.
  • the pass rate of the micro-drop test the number of passes/10.
  • Example 1 of the present application uses a polyethylene packaging film for packaging and performs hot pressing shaping
  • the packaging film is connected to the tab.
  • a depression is formed at the corresponding position of the protrusion in the area, so as to better accommodate the protrusion on the surface of the bare battery cell, making the surface of the battery body smoother, and then improving the electrode interface during the pressurized formation process, so that the pass rate of the hot box safety test of the lithium-ion battery after 300 cycles is significantly improved, which greatly improves the safety of lithium-ion batteries.
  • the presence of depressions in the encapsulation layer and the bonding between the encapsulation layer and the outer surface of the bare battery cell can further improve the mechanical safety of the lithium-ion battery.
  • the bare battery cell will repeatedly impact the encapsulation edge of the aluminum-plastic film due to inertia, resulting in a low pass rate for the micro-drop test of the lithium-ion battery.
  • Example 1 since the depression in the encapsulation layer can limit the protrusions on the surface of the bare battery cell, and there is bonding with the bare battery cell, the inertia of the bare battery cell is greatly weakened, and the impact of the bare battery cell on the encapsulation edge is weakened, so the pass rate of the micro-drop test of the lithium-ion battery is significantly improved.
  • the depression of the packaging layer can accommodate the protrusions on the surface of the bare battery cell, the maximum thickness of the lithium-ion battery can be reduced, thereby further improving the volume energy density of the lithium-ion battery.

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  • Secondary Cells (AREA)

Abstract

本申请提供了一种电化学装置和电子装置，其中电化学装置包括电极组件和壳体，电极组件收容于壳体，壳体包括封装层，电极组件的一侧表面具有凸起，封装层与电极组件相邻的一侧表面具有凹陷，凸起至少部分容纳于凹陷。本申请的电化学装置中，封装层的凹陷和电极组件表面的凸起彼此互补，提高了加压化成处理时，电极组件的受力均匀性，进而改善了电极界面，提高了电化学装置的循环性能和使用安全性。

Description

一种电化学装置和电子装置 技术领域
本申请涉及储能技术领域，具体涉及一种电化学装置和电子装置。
背景技术
二次电池在消费电子领域具有广泛的应用，且近年来终端市场对其使用寿命和能量密度的要求越来越高。目前，二次电池的主流封装形式有两种，即软包和金属壳封装。其中，软包二次电池凭借安全性好、比能量高和设计灵活等优势而被广泛应用。
二次电池(如锂离子电池)在使用前，需要进行化成处理，即，对二次电池进行首次充放电，在电极材料表面形成电解质界面膜，电解质界面膜能够有效防止电解液的进一步损失，并且具有良好的离子导电性、电子绝缘性、热稳定性和化学稳定性，对后续二次电池性能的发挥具有十分重要的影响。施加压力进行化成处理，是提高生产效率、增强电极界面性能的有效手段。
发明内容
然而，本申请的发明人研究发现，裸电芯中由于存在极耳焊接等结构，导致其表面不平整，呈现凹凸形貌，在施加压力进行化成处理时，裸电芯表面受力不均匀，容易导致电极界面恶化、锂枝晶析出，甚至还可能会引起起火爆炸。鉴于现有技术存在的上述问题，本申请提供了一种电化学装置和电子装置，以提高电化学装置表面的平整性，进而改善电化学装置在加压化成过程中所形成的电极界面，提高电化学装置的循环寿命和使用安全性。
本申请的第一方面，提供一种电化学装置，包括电极组件和壳体，电极组件收容于壳体，壳体包括封装层，电极组件的一侧表面具有凸起，封装层与电极组件相邻的一侧表面具有凹陷，凸起至少部分容纳于凹陷。
本申请通过在电化学装置壳体的封装层设置凹陷，并且通过凹陷容纳电极组件表面上的凸起，使得在对电化学装置进行加压化成处理时，电极组件表面各个位置都能够均匀受力，避免由于压力在电极组件表面的凸起部位集中而导致电极界面恶化，进而造成锂枝晶析出以及起火爆炸。另一方面，封装层的凹陷还能够对壳体内的电极组件起到限位固定 作用，在电化学装置跌落或被撞击时，能够有效抑制电极组件的窜动，降低壳体被冲破的风险。综上，本申请的方案有利于提升电化学装置的循环寿命和使用安全性能。此外，由于本申请的电化学装置不需要增设额外的缓冲结构，例如硅胶垫，即可实现电极组件在加压化成时的受力均匀，因而，还有利于提升电化学装置的能量密度。
在一些实施方式中，所述凸起完全容纳于凹陷。如此，可进一步促进电极组件表面各处在加压化成处理时的均匀受力，改善电极界面，从而提高电化学装置的循环寿命和使用安全性。
在一些实施方式中，封装层背离电极组件的一侧表面为平坦表面。如此，在对电化学装置进行加压化成处理时，可以进一步促进电极组件表面各处的均匀受力，改善电极界面，从而提高电化学装置的循环寿命和使用安全性。
在一些实施方式中，封装层的熔点为80℃至150℃。如此，有利于对壳体进行封装以及封装层内侧表面凹陷的形成。
在一些实施方式中，封装层的材料包括热塑性聚合物。
在一些实施方式中，封装层的材料包括聚乙烯、聚丙烯、乙烯丙烯共聚物、酸酐改性聚丙烯、聚氯乙烯、聚醋酸乙烯酯、聚偏氟乙烯或上述物质的衍生物中的至少一种。
在一些实施方式中，凹陷的深度为3μm至150μm。
在一些实施方式中，凹陷处封装层的厚度为15μm至200μm。如此，可提高封装层于凹陷处的结构强度，提高壳体的可靠性。
在一些实施方式中，封装层还包括与凹陷相邻的主体区，主体区的厚度为20μm至250μm。
在一些实施方式中，封装层与电极组件之间的粘结强度大于或等于2N/m。如此，可进一步增强壳体对电极组件的固定作用，抑制在电化学装置跌落或被撞击时，电极组件的窜动，降低壳体被冲破的风险，提高电化学装置的使用安全性。
在一些实施方式中，电极组件包括极片和极耳，电极组件包括极耳连接区，极耳与极片于极耳连接区连接，凸起位于极耳连接区。
在一些实施方式中，电极组件为卷绕结构，卷绕结构包括主体部和拐角部，电化学装置于主体部处的厚度差的最大值小于或等于20μm。
在一些实施方式中，壳体还包括阻隔层，阻隔层位于封装层背离电极组件的一侧表面上。
在一些实施方式中，阻隔层的厚度为0.1μm至50μm。
在一些实施方式中，阻隔层的材料包括金属、无机氧化物或无机氮化物中的至少一种。
在一些实施方式中，壳体还包括保护层，保护层位于阻隔层背离封装层的一侧表面上。
在一些实施方式中，保护层的厚度为2μm至50μm。
在一些实施方式中，保护层包括聚合物或纤维中的至少一种。
在一些实施方式中，金属包括铝、铜、铁、钛或镍中的至少一种。
在一些实施方式中，无机氧化物包括二氧化钛、氧化铝、二氧化铪、二氧化硅、氧化铁、氧化铜、氧化银、氧化镍、氧化锰、氧化锌、氧化锡、氧化锆钛或氧化钒中的至少一种。
在一些实施方式中，无机氮化物包括氮化硅、氮氧化硅、氮化硼、氮化钛或氮化铝中的至少一种。
本申请的第二方面提供一种电子装置，包括前述电化学装置。由此，本申请的电子装置具有良好的使用寿命和安全性。
附图说明
图1示出了本申请的电化学装置的剖视图。
图2示出了图1中A区域的放大图。
具体实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合实施例对本申请的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。在此所描述的有关实施例为说明性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
为了简明，本文仅具体地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，除非另有说明，“以上”、“以下”包含本数。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。
术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所 连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个组分或多个组分。项目B可包含单个组分或多个组分。项目C可包含单个组分或多个组分。
一、电化学装置
本申请的实施例提供一种电化学装置，包括电极组件和壳体，电极组件收容于壳体，壳体包括封装层，电极组件的一侧表面具有凸起，封装层与电极组件相邻的一侧表面具有凹陷，凸起至少部分容纳于凹陷。
在本申请的电化学装置中，凹陷能够容纳电极组件表面上的凸起，使得在对电化学装置进行加压化成处理时，电极组件表面各个位置都能够均匀受力，避免由于压力在电极组件表面的凸起部位集中而导致电极界面恶化，进而造成锂枝晶析出以及起火爆炸。另一方面，封装层的凹陷还能够对壳体内的电极组件起到限位固定作用，在电化学装置跌落或被撞击时，能够有效抑制电极组件的窜动，降低壳体被冲破的风险。综上，本申请的方案有利于提升电化学装置的循环寿命和使用安全性能。此外，由于本申请的电化学装置不需要增设额外的缓冲结构，例如硅胶垫，即可实现电极组件在加压化成时的受力均匀，因而，还有利于提升电化学装置的能量密度。
在一些实施例中，凸起完全容纳于凹陷。如此，可进一步促进电极组件表面各处在加压化成处理时的均匀受力，改善电极界面，从而提高电化学装置的循环寿命和使用安全性。
在一些实施例中，封装层背离电极组件的一侧表面为平坦表面。如此，在对电化学装置进行加压化成处理时，可以进一步促进电极组件表面各处的均匀受力，改善电极界面，从而提高电化学装置的循环寿命和使用安全性。
在一些实施例中，封装层的材料为热塑性聚合物。在对壳体进行热封装时，封装层可以受热熔融连接，从而将电极组件密封在壳体中形成电化学装置；同时，通过对电化学装置表面进行热压处理，封装层可以受热软化，在压力的作用下，封装层与凸起接触的表面形成凹陷，从而将凸起容纳在凹陷中，进而提高电化学装置进行加压化成处理时，电极组件表面各处受力的均匀性。进一步的，软化的封装层可与电极组件表面紧密的粘结在一起，抑制电化学装置在跌落或被撞击时，电极组件的窜动，降低壳体被冲破的风险，从而进一步提高电化学装置的使用安全性。
在一些实施例中，封装层的材料包括聚乙烯、聚丙烯、乙烯丙烯共聚物、酸酐改性聚 丙烯、聚氯乙烯、聚醋酸乙烯酯、聚偏氟乙烯或上述物质的衍生物中的至少一种。
在一些实施例中，封装层的熔点为80℃至150℃。如此，有利于对壳体进行封装以及封装层内侧表面凹陷的形成。示例性的，封装层的熔点为80℃、85℃、90℃、95℃、100℃、105℃、110℃、115℃、120℃、125℃、130℃、135℃、140℃、145℃、150℃或上述任意两个数值组成的范围。
在一些实施例中，凹陷的深度为3μm至150μm。示例性的，凹陷的深度为3μm、5μm、10μm、20μm、30μm、40μm、50μm、60μm、70μm、80μm、90μm、100μm、110μm、120μm、130μm、140μm、150μm或上述任意两个数值组成的范围。
可以理解的是，凹陷的深度与电极组件表面凸起的高度相关。例如，电极组件表面凸起的高度为h，凹陷的深度为d，则可满足：0.5h≤d≤h。
在一些实施例中，凹陷处封装层的厚度为15μm至200μm。可以理解的是，凹陷处封装层的厚度在上述范围内，一方面能够保证凹陷处封装层的结构强度，保证壳体的可靠性；另一方面，也有利于形成轻薄化的电化学装置，提高电化学装置的能量密度。示例性的，凹陷处封装层的厚度为15μm、20μm、30μm、40μm、50μm、60μm、70μm、80μm、90μm、100μm、110μm、120μm、130μm、140μm、150μm、160μm、170μm、180μm、190μm、200μm或上述任意两个数值组成的范围。
在一些实施例中，封装层还包括与凹陷相邻的主体区，主体区的厚度为20μm至250μm。示例性的，主体区的厚度为20μm、30μm、40μm、50μm、60μm、70μm、80μm、90μm、100μm、110μm、120μm、130μm、140μm、150μm、160μm、170μm、180μm、190μm、200μm、210μm、220μm、230μm、240μm、250μm或上述任意两个数值组成的范围。
可以理解的是，在一些实施例中，主体区的厚度等于凹陷的深度与凹陷处封装层的厚度之和。如此，可进一步提高电化学装置进行加压化成处理时，电极组件表面各处受力的均匀性，改善电极界面，从而提高电化学装置的循环寿命和使用安全性。
在一些实施例中，封装层与电极组件之间的粘结强度大于或等于2N/m。可以理解的是，封装层与电极组件之间的粘结，可进一步增强壳体对电极组件的固定作用，在电化学装置跌落或被撞击时，可以抑制电极组件的窜动，降低壳体被冲破的风险，从而进一步提高电化学装置的使用安全性。
在一些实施例中，电极组件包括极片和极耳，电极组件包括极耳连接区，极耳与极片于极耳连接区连接，凸起位于极耳连接区。
在一些实施例中，电极组件为卷绕结构，卷绕结构包括主体部和拐角部，电化学装置于主体部处的厚度差的最大值小于或等于20μm。可以理解是，电化学装置于主体部处的 厚度差异在上述范围内，有利于提高电化学装置进行加压化成处理时，电极组件表面各处受力的均匀性，从而改善电极界面，提高电化学装置的循环寿命和使用安全性。
在一些实施例中，壳体还包括阻隔层，阻隔层位于封装层背离电极组件的一侧表面上，阻隔层的厚度为0.1μm至50μm。示例性的，阻隔层的厚度为0.1μm、1μm、5μm、10μm、15μm、20μm、25μm、30μm、35μm、40μm、45μm、50μm或上述任意两个数值组成的范围。可以理解的是，阻隔层的厚度在上述范围内，有利于防止水汽等渗入壳体内部，影响电化学装置的正常使用。
在一些实施例中，阻隔层的材料包括金属、无机氧化物或无机氮化物中的至少一种。
在一些实施例中，金属材料包括但不限于铝、铜、铁、钛或镍中的至少一种。
在一些实施例中，无机氧化物材料包括，二氧化钛、氧化铝、二氧化铪、二氧化硅、氧化铁、氧化铜、氧化银、氧化镍、氧化锰、氧化锌、氧化锡、氧化锆钛或氧化钒中的至少一种。
在一些实施例中，无机氮化物材料包括氮化硅、氮氧化硅、氮化硼、氮化钛或氮化铝中的至少一种。
在一些实施例中，壳体还包括保护层，保护层位于阻隔层背离封装层的一侧表面上。
在一些实施例中，保护层的厚度为2μm至50μm。示例性的，保护层的厚度为2μm、5μm、10μm、15μm、20μm、25μm、30μm、35μm、40μm、45μm、50μm或上述任意两个数值组成的范围。可以理解的是，保护层的厚度在上述范围内，有利于防止外部结构对壳体造成破坏，影响电化学装置的正常使用。
在一些实施例中，保护层包括聚合物或纤维中的至少一种。
本申请的电化学装置包括但不限于：所有种类的一次电池或二次电池。在一些实施例中，所述电化学装置是锂二次电池。在一些实施例中，锂二次电池包括，但不限于：锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
二、电子装置
本申请的实施例还提供一种电子装置，包括前述实施例的电化学装置。
本申请的电子装置包括但不限于：手机、笔记本电脑、平板电脑、无人机、智能手表、智能手环、VR眼镜、电动汽车或电动工具等。
三、电化学装置的制备方法
本申请的实施例还提供了一种电化学装置的制备方法，用于制备前述实施例的电化学装置，包括：步骤1，制备电极组件；步骤2，利用封装层包裹电极组件，对封装层的开口处进行热封；步骤3，使用表面平整的加热模具，对电极组件表面的封装层进行加热 加压处理，使封装层面向电极组件表面的凸起处形成凹陷；步骤4，注入电解液，经静置、加压化成、脱气等工序即得到本申请的电化学装置。
在一些实施例中，步骤2中热封的温度为80℃至150℃。示例性的，热封的温度为80℃、85℃、90℃、95℃、100℃、105℃、110℃、115℃、120℃、125℃、130℃、135℃、140℃、145℃、150℃或上述任意两个数值组成的范围。
可以理解的是，步骤3中加热加压处理的加热温度能够使封装层软化即可。在一些实施例中，步骤3中加热加压处理的加热温度小于封装层的熔点，如此，可降低在对封装层进行加热加压处理时，造成局部破膜的风险。在一些实施例中，步骤3中加热加压处理的加热温度为80℃至150℃。在一些实施例中，步骤3中加热加压处理的压力为0.1MPa至1MPa。示例性的，加热加压处理的加热温度为80℃、85℃、90℃、95℃、100℃、105℃、110℃、115℃、120℃、125℃、130℃、135℃、140℃、145℃、150℃或上述任意两个数值组成的范围。加热加压处理的压力为0.1MPa、0.2MPa、0.4MPa、0.5MPa、0.7MPa、0.9MPa、1MPa或上述任意两个数值组成的范围。
在一些实施例中，电化学装置的制备方法还包括：步骤5，在封装层背离电极组件的一侧表面形成阻隔层。形成阻隔层的工艺包括涂覆、喷涂、喷镀、蒸镀或气相沉积中的至少一种。
在一些实施例中，电化学装置的制备方法还包括：步骤6，在阻隔层背离封装层的一侧表面形成保护层。形成保护层的工艺包括涂覆、喷涂、浸渍或缠绕中的至少一种。
在下文中，将结合具体的实施例和对比例，并以锂离子电池为例进一步阐述本申请的电化学装置。
实施例及对比例
实施例1
1、负极极片的制备：将负极活性材料石墨、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，加入去离子水作为溶剂，调配成为固含量为0.7的浆料，并搅拌均匀。将浆料均匀涂覆在负极集流体铜箔上，极片上有效物质的重量为95g/m2。110℃下烘干，得到单面涂布的负极极片。之后，以完全一致的方法，在该极片背面也完成这些步骤，即得到双面涂布的负极极片。之后，将负极极片冷压至1.7g/cm3的压实密度，经裁切、焊接极耳后得到负极极片。
2、正极极片的制备：将正极活性材料钴酸锂、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的浆料，并搅拌均匀。将浆料均匀涂覆在正极集流体铝箔上，极片上有效物质的重量为180g/m2。90℃条件下烘干，得到单面涂布的正极极片。之后，以完全一致的方法，在该极片背面也完成这些步骤，即得到双面涂布的正极极片。之后，将正极极片冷压至4.1g/cm3的压实密度，经裁切、焊接极耳后得到正极极片。
3、电解液的制备：在干燥氩气气氛中，首先将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)以质量比EC:EMC:DEC＝30:50:20混合得到有机溶剂，然后向有机溶剂中加入锂盐六氟磷酸锂(LiPF6)溶解并混合均匀，得到锂盐浓度为1.15mol/L的电解液。
4、裸电芯的制备：将正极极片、隔膜和负极极片依次堆叠并卷绕的得到卷绕结构的裸电芯，其中，正极极耳和负极极耳均位于卷绕结构的外侧，隔膜选用厚度为9μm的多孔聚乙烯薄膜，裸电芯尺寸为4.0mm(厚)×19mm(宽)×24mm(长)。裸电芯的端面如图1和2所示，其表面放大具有表面凹凸起伏的特征，极耳处比相邻位置高出60μm。
5、预封装：用厚度为110μm的封装膜(三层共挤聚乙烯膜，中间层为高密度聚乙烯层，两侧为低密度聚乙烯层，两侧低密度聚乙烯层的熔点为114℃)包裹电极组件，开口处进行热压封装，热压温度为110℃。
6、热压整形：使用表面平整的加热模具，对裸电芯和封装膜的表面进行热压，在115℃和0.1MPa压力下，保持10s，封装膜中的低密度聚乙烯层受热熔融流动，形成与裸电芯表面互补的形貌，如图2。位于极耳处位置的封装膜内表面比相邻位置处凹陷60μm。同时封装膜中的低密度聚乙烯层在受热熔融时，和裸电芯外表面的隔膜形成粘结，粘结强度为3N/m。主体部的外表面平整度和模具持平，厚度差异不超过3μm。
8、注液封装：在未封装的敞口区域注入上述电解液后进行封装，经静置、加压化成、脱气等工序即得到锂离子电池。
对比例1
对比例1与实施例1的区别之处在于，对比例1使用厚度为100μm的铝塑膜进行封装，将裸电芯置于铝塑膜包装袋中，热封四周，留出注液口，注液后对注液口进行密封，后续经静置、加压化成、脱气等工序，得到锂离子电池。
测试方法
1、能量密度测试：室温(25℃±2℃)环境下，将锂离子电池静置不小于30分钟；以0.5C恒流充电至4.25V，再以4.25V恒压充电至电流为0.05C，使锂离子电池达到满充状态；然后以0.5C恒流放电至3.0V，计量放电能量E(以Wh计)；用千分尺测量锂离子电池的长宽高方向的最大值，计量体积V(以L计)；锂离子电池放电的体积能量密度 VED(Wh/L)＝E/V。
2、微跌测试：实验采用10组锂离子电池，将锂离子电池通过双面胶纸固定后组装入手表模型的电池舱中，进行微跌测试。测试过程中的跌落高度为7cm，头部朝下和尾部朝下以20次/min分别跌落20000次，四个侧面以50次/min分别跌落500次，总计跌落42000次，统计封装边冲开或漏液情况，封装边冲开或漏液即为未通过，微跌测试通过率＝通过数/10。
3、300圈循环后的热箱安全测试：实验采用3组锂离子电池，将锂离子电池在25±3℃下静置30分钟，以0.5C恒流充电至4.25V，再以4.25V恒压充电至电流为0.05C，然后以0.5C恒流放电至3.0V，重复上述步骤300次。将上述循环300圈的电池，以0.5C恒流充电至4.25V，再以4.25V恒压充电至电流为0.05C，使其处于满充状态进行热箱测试，测试过程是将上述满充状态的锂离子电池至于烘箱中，对烘箱进行5℃/min升温处理，升温至140℃保温1小时，观察电池情况。起火或爆炸视为未通过，未起火未爆炸即视为通过。300圈循环后的热箱安全测试通过率＝通过数/3。
4、封装层与裸电芯粘结强度测试：裁取一定尺寸的封装层与裸电芯之间粘结区域样条(宽20mm×长60mm)。将上述样条置于拉力机，两端用夹具夹紧。进行测试，得到拉力随移动距离的变化曲线，待拉力值稳定后，读取对应数值f(N)，粘结强度F＝f/0.02(N/m)。
表1
由表1可知，对比例1中，由于采用铝塑膜封装，且未进行热压整形，因而，其内侧的封装层不存在凹陷，无法有效容纳裸电芯中极耳连接区域的凸起，导致电池主体部的厚度差异较大，进而导致锂离子电池在加压化成过程中，电极界面形成不良，使得在后续的循环过程中容易形成锂枝晶，而锂枝晶相对不稳定，在受热条件下容易引发电池热失控。因而，对比例1中锂离子电池300圈循环后的热箱安全测试通过率较低。相比之下，由于本申请的实施例1采用聚乙烯封装膜进行封装，并进行了热压整形，在封装膜与极耳连接 区的凸起相对应处形成凹陷，从而更好地容纳裸电芯表面的凸起，使得电池主体部的表面更加平整，进而在加压化成过程中能够改善电极界面，使得锂离子电池在300圈循环后的热箱安全测试通过率显著提升，这大大提升了锂离子电池的使用安全性。
同时，封装层中凹陷的存在以及封装层与裸电芯外表面的粘结可进一步提高锂离子电池的机械安全性。对比例1中，铝塑膜内侧的封装层不存在凹陷，且和裸电芯不存在粘结，在微跌测试过程中，裸电芯会因惯性作用反复对铝塑膜的封装边造成冲击，从而导致锂离子电池的微跌测试通过率较低。而在实施例1中，由于封装层中的凹陷可对裸电芯表面的凸起进行限位，且和裸电芯之间存在粘结，大大削弱了裸电芯的惯性作用，减弱了裸电芯对封装边的冲击，因此锂离子电池的微跌测试通过率显著提升。
此外，由于封装层的凹陷可容纳裸电芯表面的凸起，进而能够降低锂离子电池的最大厚度，从而进一步提升锂离子电池的体积能量密度。
以上仅为本申请的较佳实施例而已，并不用以限制本申请，凡在本申请的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本申请的保护范围之内。

Claims (10)

  1. 一种电化学装置，包括电极组件和壳体，所述电极组件收容于所述壳体，所述壳体包括封装层，所述电极组件的一侧表面具有凸起，所述封装层与所述电极组件相邻的一侧表面具有凹陷，所述凸起至少部分容纳于所述凹陷。
  2. 根据权利要求1所述的电化学装置，其中，满足以下条件中的至少一者：
    (1)所述凸起完全容纳于所述凹陷；
    (2)所述封装层背离所述电极组件的一侧表面为平坦表面；
    (3)所述封装层的熔点为80℃至150℃；
    (4)所述封装层的材料包括热塑性聚合物；
    (5)所述封装层的材料包括聚乙烯、聚丙烯、乙烯丙烯共聚物、酸酐改性聚丙烯、聚氯乙烯、聚醋酸乙烯酯、聚偏氟乙烯或上述物质的衍生物中的至少一种。
  3. 根据权利要求1所述的电化学装置，其中，所述凹陷的深度为3μm至150μm。
  4. 根据权利要求1所述的电化学装置，其中，满足以下条件中的至少一者：
    (1)所述凹陷处所述封装层的厚度为15μm至200μm；
    (2)所述封装层还包括与所述凹陷相邻的主体区，所述主体区的厚度为20μm至250μm。
  5. 根据权利要求1所述的电化学装置，其中，所述封装层与所述电极组件之间的粘结强度大于或等于2N/m。
  6. 根据权利要求1所述的电化学装置，其中，所述电极组件包括极片和极耳，所述电极组件包括极耳连接区，所述极耳与所述极片于所述极耳连接区连接，所述凸起位于所述极耳连接区。
  7. 根据权利要求1所述的电化学装置，其中，所述电极组件为卷绕结构，所述卷绕结构包括主体部和拐角部，所述电化学装置于所述主体部处的厚度差的最大值小于或等于20μm。
  8. 根据权利要求1至7中任一项所述的电化学装置，其中，所述壳体还包括阻隔层，所述阻隔层位于所述封装层背离所述电极组件的一侧表面上，满足以下条件中的至少一者：
    (1)所述阻隔层的厚度为0.1μm至50μm；
    (2)所述阻隔层的材料包括金属、无机氧化物或无机氮化物中的至少一种；
    (3)所述壳体还包括保护层，所述保护层位于所述阻隔层背离所述封装层的一侧表面上。
  9. 根据权利要求8所述的电化学装置，其中，满足以下条件中的至少一者：
    (1)所述保护层的厚度为2μm至50μm；
    (2)所述保护层包括聚合物或纤维中的至少一种；
    (3)所述金属包括铝、铜、铁、钛或镍中的至少一种；
    (4)所述无机氧化物包括二氧化钛、氧化铝、二氧化铪、二氧化硅、氧化铁、氧化铜、氧化银、氧化镍、氧化锰、氧化锌、氧化锡、氧化锆钛或氧化钒中的至少一种；
    (5)所述无机氮化物包括氮化硅、氮氧化硅、氮化硼、氮化钛或氮化铝中的至少一种。
  10. 一种电子装置，包括权利要求1至9中任一项所述的电化学装置。
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