WO2022183445A1 - 卷绕型电化学装置及电子设备 - Google Patents

卷绕型电化学装置及电子设备 Download PDF

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Publication number
WO2022183445A1
WO2022183445A1 PCT/CN2021/079113 CN2021079113W WO2022183445A1 WO 2022183445 A1 WO2022183445 A1 WO 2022183445A1 CN 2021079113 W CN2021079113 W CN 2021079113W WO 2022183445 A1 WO2022183445 A1 WO 2022183445A1
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WIPO (PCT)
Prior art keywords
electrode
protective layer
current collector
electrochemical device
bending section
Prior art date
Application number
PCT/CN2021/079113
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English (en)
French (fr)
Inventor
刘晓欠
Original Assignee
宁德新能源科技有限公司
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Application filed by 宁德新能源科技有限公司 filed Critical 宁德新能源科技有限公司
Priority to PCT/CN2021/079113 priority Critical patent/WO2022183445A1/zh
Priority to CN202180001999.XA priority patent/CN115315842A/zh
Publication of WO2022183445A1 publication Critical patent/WO2022183445A1/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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound 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
    • H01M10/05—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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the embodiments of the present application relate to the technical field of energy storage devices, and in particular, to a wound electrochemical device and an electronic device.
  • lithium-ion batteries have become the preferred power source for consumer portable electronic products.
  • people have put forward higher and higher requirements for the performance of lithium-ion batteries used in these devices, especially the energy density of lithium-ion batteries, which requires lithium-ion batteries to have better performance.
  • High energy density providing maximum energy in the smallest possible space.
  • the electrodes of the battery need to be cold-pressed first.
  • the particles in the active layer of the electrode are easily squeezed between the current collector of the electrode and embedded in the current collector, resulting in the current collector. damage; in the subsequent winding process, due to the large stress on the bending section of the electrode, the bending section of the electrode is very prone to cracking, or even brittle fracture, and with the improvement of the electrode compaction, the electrode As the brittleness increases, the possibility of cracking and brittle fracture in the bending section of the electrode also increases.
  • the electrodes are prevented from becoming brittle, so as to prevent cracks and brittle fractures in the bending sections of the electrodes during the winding process, but this approach cannot achieve high energy density of the battery;
  • the brittleness of the electrode can be improved by mixing the main material particles with smaller roughness into the active material layer, but reducing the roughness will reduce the specific surface area of the main material, thereby deteriorating the kinetic performance of the battery.
  • the main technical problem solved by the embodiments of the present application is to provide a wound electrochemical device and electronic equipment that can prevent cracking and brittle fracture of the electrode during the winding process, so as to improve the compaction of the electrode and the stability of the electrochemical device. Energy Density.
  • a wound-type electrochemical device in one aspect, includes an electrode assembly.
  • the electrode assembly includes a first electrode.
  • the first electrode includes a current collector, a protective layer and an active material layer disposed on at least one surface of the current collector, and the protective layer is located between the current collector and the active material layer.
  • the first electrode is wound to form a straight section and a bent section, and the protective layer is arranged on the bent section of the first electrode.
  • the innermost circle of the first electrode includes a winding start end, a first bending section and a second bending section opposite to the first bending section, the first bending section is connected to the winding start end,
  • the protective layer is arranged on the first bending section and/or the second bending section.
  • the first electrode is wound to form a plurality of bending sections, and along the direction from the innermost circle of the first electrode to the outermost circle of the first electrode, at least two bending sections are respectively provided with protective layers.
  • the protective layer is disposed on at least one of the inner side and the outer side of the current collector at the bent section.
  • the length of the protective layer disposed on the inside of the bending section is the same as or different from the length of the protective layer disposed on the outside of the bending section.
  • the protective layer satisfies at least one of the following characteristics:
  • the thickness of the protective layer is 0.5 ⁇ m to 20 ⁇ m;
  • the length of the protective layer is 0.1 cm to 5 cm;
  • the width of the protective layer is 0.1 to 1 times the width of the current collector.
  • the protective layer is a conductive coating or conductive tape.
  • the conductive coating comprises a conductive agent and a binder
  • the mass of the conductive agent is 50% to 99% of the total mass of the conductive coating
  • the mass of the binder is 1% to 50% of the total mass of the conductive coating %.
  • the conductive agent includes at least one of lamellar, mesh, wire, or zero-dimensional conductive agents
  • the binder includes at least one of styrene-butadiene rubber, nitrile-butadiene rubber, carboxylated styrene-butadiene rubber, phenolic resin glue, polybutene, polypropylene, polyvinylidene fluoride, polyimide or polyvinyl acetate.
  • the conductive tape includes adhesive and conductive particles
  • the mass of the adhesive is 1% to 90% of the total mass of the conductive tape
  • the mass of the conductive particles is 10% of the total mass of the conductive tape to 99%.
  • the adhesive includes at least one of acrylic and polyester materials
  • the conductive particles are metal particles, and the particle size D50 of the metal particles is 0.001 ⁇ m to 500 ⁇ m.
  • the mechanical properties of the conductive tape satisfy at least one of the following characteristics:
  • the tensile strength of the conductive adhesive tape is greater than or equal to 50MPa
  • an electronic device is also provided, and the electronic device includes:
  • the electrode assembly of the wound electrochemical device further includes a protective layer, and the protective layer is arranged on the bent section of the first electrode and is located between the current collector and the active material layer,
  • the protective layer protects the current collector at the bending section, preventing the active material layer from being embedded in the current collector at the bending section during the cold pressing process and causing damage to the current collector, improving the current collection at the bending section.
  • the brittleness of the body thereby improving the winding performance of the bending section of the first electrode, preventing the cracking and brittle fracture of the bending section of the first electrode during the winding process, thereby improving the compaction and winding type of the electrode. Energy density of electrochemical devices.
  • FIG. 1 is a schematic structural diagram of an electrode assembly in a wound electrochemical device provided by one embodiment of the present application
  • FIG. 2 is a schematic diagram of a partially unfolded flat state of a first electrode of an electrode assembly according to an embodiment of the present application
  • FIG. 3 is a schematic structural diagram of an electrode assembly in a wound electrochemical device provided by an embodiment of the present application.
  • FIG. 4 is a schematic structural diagram of an electrode assembly in a wound electrochemical device provided by an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a partially unfolded flat state of the first electrode of the electrode assembly according to one embodiment of the present application.
  • the embodiments of the present application provide a wound electrochemical device, which converts chemical energy into electrical energy during discharge to supply power to a load, and converts electrical energy into chemical energy during charging to store energy.
  • the wound electrochemical device includes an electrode assembly 100 .
  • FIG. 1 shows an electrode assembly 100 according to one embodiment of the present application.
  • the electrode assembly 100 includes a first electrode 10 , and the first electrode 10 includes a current collector 11 , a protective layer 12 and a current collector 11 .
  • the active material layer 13 on at least one surface, the protective layer 12 is located between the current collector 11 and the active material layer 13, wherein, during the winding process of the electrode assembly 100, a part of the first electrode 10 occurs relative to another part of the first electrode 10 Bending so that the first electrode 10 is wound to form a straight section 101 and a bent section 102 .
  • the electrode assembly 100 is generally in a flat spiral structure after being wound for multiple turns, the first electrode 10 may be configured as the innermost electrode of the electrode assembly 100 , and the first electrode 10 may be configured as a cathode electrode of the electrode assembly 100 , which can also be configured as anode electrodes.
  • the active material particles in the active material layer are likely to be squeezed between the current collector and embedded in the current collector, resulting in damage to the current collector.
  • the bending section of the electrode is very prone to cracking and brittle fracture.
  • the electrode compaction increases, the brittleness of the electrode increases, and the The possibility of cracking and brittle fracture in the bending section also increases.
  • FIG. 2 shows that the bent section 102 of the first electrode 10 provided with the protective layer 12 is in a flat state.
  • a protective layer 12 is provided on the bending section 102 of the first electrode 10 , and the protective layer 12 is located between the current collector 11 and the active material layer 13 , and the protective layer 12 is used for the opposite bending
  • the current collector 11 at the bent section 102 plays a protective role, which prevents the active material layer 13 from being embedded in the current collector 11 at the bent section during the cold pressing process, resulting in damage to the current collector 11 and improves the bent section 102
  • the brittleness of the current collector 11 at the position of the first electrode 10 is improved, thereby improving the winding performance of the bending section 102 of the first electrode 10, preventing the bending section 102 of the first electrode 10 from cracking and brittle fracture during the winding process, thereby preventing Improve the compaction of electrodes and the energy density of wound electrochemical devices.
  • the present application In the electrochemical device provided by the embodiment, by disposing the protective layer 12 between the current collector 11 and the active material layer 13 at the bending section 102 of the first electrode 10, the bending section 102 of the electrode can be prevented from being wound during the winding process. Cracks and brittle fractures occur in the electrochemical device, which ensures the high energy density and kinetic performance of the electrochemical device.
  • the active material layer 13 is disposed on two opposite surfaces of the current collector 11 , it can be understood that in some other embodiments of the present application, the active material layer 13 only needs to be disposed
  • the active material layer 13 is not required to be provided on at least one surface of the current collector 11, and the active material layer 13 may be continuously provided on one surface of the current collector 11,
  • a blank area can also be reserved on the surface, the blank area is not provided with the active material layer 13, and the active material layer 13 is arranged outside the blank area, that is, a surface of the current collector 11 can be provided with active material in sections.
  • the bending section 13 does not need to be provided with the protective layer 12 .
  • the first electrode 10 is wound to form a plurality of bending sections 102 .
  • the stress generated by the winding is directed from the innermost circle of the first electrode 10 to the outermost circle of the first electrode 10 . Decrease in sequence and act on each bending section 102 respectively, that is, the bending section 102 closer to the center of the electrode assembly 100 is subjected to greater stress.
  • At least two bending sections 102 are respectively provided with protective layers 12, that is, the protective layers 12 are preferentially disposed on the center of the first electrode 10 close to the electrode assembly 100
  • the bent section 102 wherein the protective layer 12 is located between the current collector 11 and the active material layer 13 at the bent section 102.
  • Each bending section 102 is used to protect the bending section 102 with greater stress, which can effectively and targetedly prevent the bending section 102 of the first electrode 10 that is prone to cracking and brittle fracture during the winding process.
  • the protection is beneficial to the compaction of the electrode and the improvement of the energy density of the electrochemical device.
  • the innermost circle of the first electrode 10 refers to the first circle of the innermost edge formed during the winding process of the first electrode 10 ; the outermost circle of the first electrode 10 refers to the innermost circle of the first electrode 10 during the winding process The penultimate circle of the outermost edge formed.
  • the innermost circle of the first electrode 10 includes a winding starting end, a first bending section and a second bending section opposite to the first bending section, and the first bending section is connected to the winding starting end.
  • the number of the protective layers 12 can be selected according to actual needs, as long as the distribution rule of the protective layers 12 is to be respectively arranged on each bending section 102 of the first electrode 10 along a preset direction.
  • the number of the protective layers 12 is Four, along the direction from the innermost circle of the first electrode 10 to the outermost circle of the first electrode 10 , the four protective layers 12 are respectively disposed on the four bending sections 102 of the first electrode 10 , see FIG. 1 for details.
  • the protective layer 12 is disposed on the first bending section and/or the second bending section, wherein, the protective layer 12 is located between the current collector 11 and the active material layer 13 at the bending section 102 , as shown in FIG. 3, FIG. 3 shows the case where the protective layer 12 is disposed on the first bending section and the second bending section. It can be understood that the protective layer 12 can also be only disposed on the first bending section and the second bending section. One of the folds.
  • the winding performance of the bending section 102 of the first electrode 10 is improved, and While preventing cracking and brittle fracture of the bending section 102 of the first electrode 10 during the winding process, the adverse consequences of thickness increase and energy density loss caused by the provision of the protective layer 12 are further suppressed, and the pressure of the electrode is improved.
  • the energy density of the electrochemical device is improved, which further reduces the production cost caused by the provision of the protective layer 12 and improves the production efficiency.
  • the protective layer 12 is disposed on the first bending section.
  • the folded section 102 wherein the protective layer 12 is located between the current collector 11 and the active material layer 13 at the folded section 102 , as shown in FIG. 4 .
  • the folded section 102 When the folded section 102 is cracked and brittle during the winding process, it further suppresses the adverse consequences of thickness increase and energy density loss caused by the provision of the protective layer 12, and improves the compaction of the electrode and the durability of the electrochemical device.
  • the energy density further reduces the production cost caused by the provision of the protective layer 12 and improves the production efficiency.
  • the specific location of the protective layer 12 in the bending section 102 is that the protective layer 12 is disposed on at least one of the inner side and the outer side of the current collector 11 at the bending section 102, that is, the protective layer 12 can be installed as required.
  • the protective layer 12 can be provided as required.
  • the inside or outside of the current collector 11 disposed at the bending section 102 is specifically shown in FIG. 2 and FIG. 5 . 5 shows that the protective layer 12 is provided on one side of the current collector 11 at the bent section 102 .
  • the inner side of the current collector 11 at the bending section 102 refers to the side of the current collector 11 in the coiled state facing the center of the electrode assembly 100; the outer side of the current collector 11 at the bending section 102 refers to , the current collector 11 in the wound state faces the other side of the center of the electrode assembly 100 .
  • the protective layer 12 is provided on the current collector 11 at the bending section 102. The inner side and the outer side, so that the protective layer 12 can protect both the inner side and the outer side of the current collector 11 at the bending section 102 .
  • the protective layer 12 By arranging the protective layer 12 on the inside and outside of the current collector 11 at the bending section 102, the winding performance of the electrode under high pressure density is ensured, and the current collector at the bending section 102 is effectively prevented during the cold pressing process.
  • the two sides of 11 are stabbed by the active material layers 13 on the opposite sides of the collector 11 due to the extrusion stress, thereby preventing the bending section 102 of the electrode from cracking and brittle fracture during the winding process, ensuring that The feasibility of improving the compaction of the electrode and the energy density of the electrochemical device.
  • the protective layer 12 can be partially or completely covered on at least one of the inner side and the outer side of the current collector 11 at the bending section 102 , or can be arranged to extend to both ends of the bending section 102 .
  • Current collector 11 on straight section 101 is arranged to extend to both ends of the bending section 102 .
  • the protective layer 12 at least partially covers the top of the current collector 11 at the bending section 102 .
  • the structural dimension parameters of the protective layer 12 will be described below.
  • the protective layer 12 satisfies at least one of the following characteristics: (a) along the thickness direction of the current collector 11, the thickness of the protective layer 12 is 0.5 ⁇ m to 20 ⁇ m; (b) along the current collector In the winding direction of 11, the length of the protective layer 12 is 0.1 cm to 5 cm; (c) along the width direction of the current collector 11, the width of the protective layer 12 is 0.1 times to 1 times the width of the current collector 11, with 5 is an example illustration, the thickness direction of the protective layer 12 is consistent with the thickness direction of the first electrode 10, the length direction of the protective layer 12 is the length direction of the first electrode 10, and the length of the protective layer 12 is in the winding structure.
  • the arc length of the bending section is , and the width direction of the protective layer 12 is the direction perpendicular to the paper surface, which is consistent with the width direction of the first electrode 10 .
  • the above description of the structural dimension parameters (thickness, length and width) of the protective layer 12 is described for the protective layer 12 on the same side (inside or outside) of the current collector 11 .
  • the thickness of the protective layer 12 is less than 0.5 ⁇ m, it is difficult for the protective layer 12 to protect the current collector 11 at the bending section 102 , and the particles of the active material layer 13 can easily pass through the protective layer during the cold pressing process.
  • the layer 12 is embedded in the current collector 11 and the current collector 11 is damaged, which cannot effectively prevent the bending section 102 from cracking and brittle fracture during the winding process; if the thickness of the protective layer 12 is greater than 20 ⁇ m, the bending section 102 When the protective layer 12 is coated on the current collector 11 at the junction, there may be a risk of scratching and damage to the current collector 11.
  • the bending section 102 will avoid cracking and brittle fracture during the winding process, and will To a certain extent, the energy density of wound electrochemical devices is reduced. If the length of the protective layer 12 is less than 0.1 cm, it is also difficult for the protective layer 12 to protect the current collector 11 at the bending section 102 . During the cold pressing process, the particles of the active material layer 13 are easily embedded around the protective layer 12 . The current collector 11 is damaged, which cannot effectively prevent the bending section 102 from cracking and brittle fracture during the winding process; if the length of the protective layer 12 is greater than 5cm, the winding will be reduced to a certain extent. energy density of electrochemical devices.
  • the width of the protective layer 12 is less than 0.1 times the width of the current collector 11, it is also difficult for the protective layer 12 to protect the current collector 11 at the bent section 102. During the cold pressing process, the particles of the active material layer 13 are easily The current collector 11 is damaged by bypassing the protective layer 12 and embedded in the current collector 11, which cannot effectively prevent the bending section 102 from cracking and brittle fracture during the winding process; if the width of the protective layer 12 is greater than the width of the current collector 11 , it will reduce the energy density of the wound electrochemical device to a certain extent.
  • the sizes of the two protective layers 12 respectively located on the inner side and the outer side of the current collector 11 can be set according to actual needs , that is, the sizes of the two protective layers 12 located on the inner side and the outer side of the current collector 11 may be the same or different, as long as the above-mentioned features (a), (b) and (c) are satisfied At least one of them is sufficient.
  • the size of the protective layer 12 may all satisfy the above-mentioned features (a), (b) and (c).
  • the material of the protective layer 12 will be described below.
  • the protective layer 12 is made of a binder and a conductive material that is easy to slide or is not easy to stab the current collector 11 and has good electrical conductivity.
  • the protective layer 12 For conductive coating or conductive tape.
  • the conductive coating includes a conductive agent and a binder, the mass of the conductive agent is 50% to 99% of the total mass of the conductive coating, and the mass of the binder is 1% to 99% of the total mass of the conductive coating 50%. It should be noted that if the content of the conductive agent is lower than 50% of the total mass of the conductive coating, the internal resistance of the electrode assembly 100 will be deteriorated and the moving speed of electrons will be reduced; if the content of the binder is lower than 50% of the total mass of the conductive coating 1%, it will reduce the adhesion of the conductive coating, and there is a risk of delamination.
  • the conductive agent includes at least one of lamellar, reticulated, linear or zero-dimensional conductive agents.
  • the lamellar conductive agent releases the extrusion stress by sliding during the cold pressing process, so as to achieve a protective effect on the current collector 11 , the net-shaped, linear, zero-dimensional conductive agent can buffer the extrusion stress of the main material particles on the collector 11 during the cold pressing process, reduce the damage to the collector 11, and realize the protection of the collector 11. effect.
  • the sheet-like conductive agent can be, for example, graphene
  • the mesh-like conductive agent can be, for example, a graphite fiber mesh
  • the linear conductive agent can be, for example, carbon nanotubes and graphite fibers
  • the zero-dimensional conductive agent can be, for example, nanoparticle conductive carbon.
  • the binder includes at least one of styrene-butadiene rubber, nitrile-butadiene rubber, carboxylated styrene-butadiene rubber, phenolic resin glue, polybutene, polypropylene, polyvinylidene fluoride, polyimide or polyvinyl acetate, and the adhesive
  • the agent plays a role in buffering stress during the cold pressing process, and reduces the stab wound of the main material particles to the current collector 11 .
  • the manufacturing process of the conductive coating is exemplarily described below: add the solvent into the container, then add the conductive agent, mix the two evenly by stirring, add the binder, and mix the three evenly by stirring again.
  • the solvent can be an organic solvent, such as NMP, DMC, and the solvent can also be an inorganic solvent, such as deionized water.
  • the conductive tape includes adhesive and conductive particles, the mass of the adhesive is 1% to 90% of the total mass of the conductive tape, and the mass of the conductive particles is 10% of the total mass of the conductive tape % to 99%.
  • the adhesive includes at least one of acrylic and polyester materials.
  • the conductive particles are metal particles, and the particle size D50 of the metal particles is 0.001 ⁇ m to 500 ⁇ m.
  • the metal particles can be, for example, gold and silver.
  • the mechanical properties of the conductive tape must meet at least one of the following characteristics: (d) tensile strength ⁇ 50MPa; (e) elongation of the conductive tape ⁇ 3%. It should be noted that if the tensile strength of the conductive tape is ⁇ 50MPa and the elongation is ⁇ 3%, the conductive tape is easily stabbed by the particles of the active material layer 13 during the cold pressing process, and it is difficult to protect the current collector 11 effect. Of course, in order to make the conductive tape have a better protective effect, the mechanical properties of the conductive tape can both satisfy the features (d) and (e).
  • the electrode assembly 100 further includes a second electrode 20 and an isolation film 30 , and the first electrode 10 , the isolation film 30 and the second electrode 20 are stacked and wound in sequence to form an electrode assembly 100, the isolation film 30 is located between the first electrode 10 and the second electrode 20, and the second electrode 20 is opposite to the first electrode 10 in polarity.
  • the first electrode 10 may be a cathode electrode, then, the second electrode 20 is an anode electrode; correspondingly, the first electrode 10 may be an anode electrode, then, the second electrode 20 is a cathode electrode.
  • the structure of the second electrode 20 may be the same as the structure of the first electrode 10 in the above-mentioned respective embodiments, the difference is that the polarity of the second electrode 20 is the same as the polarity of the first electrode 10 Sex is the opposite.
  • the current collector 11 of the first electrode 10 is a cathode current collector
  • the active material layer 13 of the first electrode 10 is a cathode active material layer
  • the second electrode 20 The current collector is the anode current collector
  • the active material layer of the second electrode 20 is the anode active material layer
  • the first electrode 10 is the anode electrode
  • the current collector 11 of the first electrode 10 is the anode current collector
  • the first electrode 10 is the anode current collector.
  • the active material layer 13 of the first electrode 10 is an anode active material layer, correspondingly, the current collector of the second electrode 20 is a cathode current collector, and the active material layer of the second electrode 20 is a cathode active material layer.
  • the distribution law of the protective layer of the second electrode 20 in the second electrode 20 is the same as the distribution law of the protective layer 12 of the first electrode 10 in the first electrode 10
  • the material of the protective layer of the second electrode 20 is the same as that of the first electrode 10 .
  • the material of the protective layer 12 of 10 is the same.
  • the structure of the second electrode 20 may also be different from the structure of the first electrode 10 in the above embodiments, and the polarity of the second electrode 20 is opposite to that of the first electrode 10 .
  • the protective layer 12 is not provided on the bending section 102 of the second electrode 20; or the number of protective layers of the second electrode 20 is different from that of the first electrode 10, and at the same time, the protective layer of the second electrode 20 has priority
  • the bent section is disposed on the second electrode 20 near the center of the electrode assembly 100 .
  • the stress generated by winding is most likely to concentrate on the first or both bending sections 102 of the innermost ring of the innermost electrode, resulting in the occurrence of tortoises at the first or both of the innermost ring of the innermost electrode. Therefore, during the winding process of the electrode assembly 100 , the first electrode 10 is configured as the innermost electrode of the electrode assembly 100 .
  • first electrode 10 and the second electrode 20 are stacked and wound around the side where one of them faces away from the other, then the one is the innermost electrode, and the other is the innermost electrode. which is the outermost electrode.
  • the electrochemical device provided by the embodiment of the present application may be a lithium ion battery, and the lithium ion battery can prevent the electrode from cracking and brittle fracture during the winding process.
  • Lithium-ion batteries work primarily by the movement of lithium ions between cathode and anode electrodes.
  • lithium ions are intercalated and deintercalated back and forth between the cathode electrode and the anode electrode: during charging, lithium ions are deintercalated from the cathode electrode and intercalated into the anode electrode through the electrolyte, so that the anode electrode is in a lithium-rich state; during discharge, Lithium ions are extracted from the anode electrode and inserted into the cathode electrode through the electrolyte, so that the cathode electrode is in a lithium-rich state.
  • the first electrode 10 may be configured as the innermost electrode of the lithium ion battery
  • the second electrode 20 may be configured as the outermost electrode of the lithium ion battery
  • the first electrode 10 may be configured as a cathode electrode or an anode electrode
  • the second electrode 20 may be configured as an anode electrode or a cathode electrode.
  • the cathode electrode in the present application is not particularly limited as long as the purpose of the present application can be achieved.
  • the cathode current collector in the present application is not particularly limited, for example, aluminum foil, aluminum alloy foil, composite current collector, and the like.
  • the cathode active material layer includes a cathode active material, and the cathode active material in this application is not particularly limited, and any anode active material in the art can be used, for example, it can include nickel-cobalt lithium manganate (nickel-cobalt lithium manganate model can be NCM811, NCM622 , NCM523, NCM111), at least one of nickel-cobalt lithium aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganate, lithium manganese iron phosphate or lithium titanate.
  • nickel-cobalt lithium manganate nickel-cobalt lithium manganate model can be NCM811, NCM622 , NCM523, NCM111
  • nickel-cobalt lithium aluminate nickel-cobalt lithium aluminate
  • lithium iron phosphate lithium-rich manganese-based material
  • lithium cobalt oxide lithium manganate
  • the anode electrode in the present application is not particularly limited as long as the purpose of the present application can be achieved.
  • the anode current collector in the present application is not particularly limited, for example, copper foil, aluminum foil, aluminum alloy foil, composite current collector, and the like.
  • the anode active material layer includes an anode active material, and the anode active material in this application is not particularly limited, for example, it can include artificial graphite, natural graphite, mesocarbon microspheres, soft carbon, hard carbon, silicon, silicon carbon or lithium titanate at least one of them.
  • the manufacturing process of the cathode electrode is exemplified as follows: the cathode active material lithium cobalt oxide (LiCoO2), Super P, and polyvinylidene fluoride are mixed according to the weight ratio of 97:1.4:1.6, and N-methylpyrrolidone (NMP) is added. ), stir under the action of a vacuum mixer until the system is uniform, and obtain a cathode slurry, wherein the solid content of the cathode slurry is 72wt%; then, the cathode slurry is uniformly coated on the cathode current collector aluminum foil; The electrical aluminum foil is dried at 110°C, and then cold-pressed and slit to obtain a cathode electrode.
  • the cathode active material lithium cobalt oxide (LiCoO2), Super P, and polyvinylidene fluoride are mixed according to the weight ratio of 97:1.4:1.6, and N-methylpyrrolidone (NMP) is added. ), stir
  • the anode active material can be, for example, a mixture of artificial graphite and silicon
  • the anode active material, Super P, binder, and styrene-butadiene rubber (SBR) are mixed in a weight ratio of 96.2:1.5: Mixing at 0.5:1.8, adding deionized water, and obtaining anode slurry under the action of a vacuum mixer, wherein the solid content of the anode slurry is 54wt%; then, the anode slurry is uniformly coated on the anode current collector copper foil; Then, the anode current collector copper foil was dried at 85° C., and then subjected to cold pressing and slitting to obtain an anode electrode.
  • SBR styrene-butadiene rubber
  • the electrochemical device of the present application further includes an electrolyte, and the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte, wherein the electrolyte includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate one or more of.
  • LiPF6 can be selected as the lithium salt because it can give high ionic conductivity and improve cycle characteristics.
  • the non-aqueous solvent may be one or more of carbonate compounds, carboxylate compounds, ether compounds, and other organic solvents.
  • the above carbonate compound may be one or more of a chain carbonate compound, a cyclic carbonate compound, and a fluorocarbonate compound.
  • the above-mentioned carboxylate compound can be methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, One or more of caprolactone, valerolactone, mevalonolactone and caprolactone.
  • the above ether compound can be dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane One or more of ethyl ethane, 2-methyltetrahydrofuran and tetrahydrofuran.
  • the above-mentioned other organic solvents can be dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, methyl One or more of amide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate.
  • the above-mentioned chain carbonate compound can be dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl carbonate
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • DPC dipropyl carbonate
  • MPC methyl propyl carbonate
  • EPC ethyl propyl carbonate
  • MEC methyl carbonate
  • MEC methyl carbonate
  • MEC ethyl esters
  • the above-mentioned cyclic carbonate compound may be one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylethylene carbonate (VEC).
  • EC ethylene carbonate
  • PC propylene carbonate
  • BC butylene carbonate
  • VEC vinylethylene carbonate
  • the above-mentioned fluorocarbonate compound can be fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Ethyl carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-dicarbonate One or more of fluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate and trifluoromethylethylene carbonate.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Ethyl carbonate 1,1,2,2-tetrafluoroethylene carbonate
  • 1-fluoro-2-methylethylene carbonate 1-fluoro-1-methylethylene carbonate
  • 1,2-dicarbonate One or more of fluoro-1-methylethylene carbonate, 1,1,
  • the electrochemical device of the present application further includes an electrolyte, and the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte, wherein the electrolyte includes a lithium salt and a non-aqueous solvent.
  • the electrochemical device of the present application further includes a packaging bag for accommodating the electrode assembly 100 .
  • a lithium-ion battery can be manufactured by the following process: the cathode electrode and the anode electrode are stacked in sequence through a separator, and they are rolled, folded, etc., and placed in a packaging bag as needed, and the electrolyte is injected into the packaging bag and Sealing, wherein the cathode electrode used is the above-mentioned first electrode 10 or the second electrode 20 provided in the application, and the anode electrode used is the above-mentioned second electrode 20 or the first electrode 10 provided in the application.
  • an overcurrent preventing element, a guide plate, etc. can also be placed in the case as required, so as to prevent pressure rise and overcharge and discharge inside the lithium ion battery.
  • the electrochemical device provided in the embodiments of the present application may also be a lithium battery, a lithium ion polymer battery, or the like.
  • the wound-type electrochemical device in the above-mentioned embodiment and the wound-type electrochemical device of the comparative example were taken for experimental testing, and the experimental results in Table 1 below were obtained from the test.
  • the protective layer 12 was not provided in the current collector 11 of the wound electrochemical device of Comparative Example 1, and the entire current collector 11 of the wound electrochemical device of Comparative Example 2 was coated with the protective layer 12 .
  • An embodiment of the present application further provides an electronic device, the electronic device includes the wound electrochemical device provided in any of the above embodiments, and the wound electrochemical device has a higher energy density.
  • the electronic device of the present application is not particularly limited, and it may be used for any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets Stereo Headphones, VCRs, LCD TVs, Portable Cleaners, Portable CD Players, Mini CD-ROMs, Transceivers, Electronic Notepads, Calculators, Memory Cards, Portable Recorders, Radios, Backup Power, Motors, Automobiles, Motorcycles, Bicycles , bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

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Abstract

一种卷绕型电化学装置及电子设备，涉及储能器件技术领域，所述卷绕型电化学装置包括电极组件（100），电极组件（100）包括第一电极（10），第一电极（10）包括集电体（11）、保护层（12）和设置于集电体（11）至少一个表面的活性物质层（13），其中，保护层（12）位于集电体（11）和活性物质层（13）之间，第一电极（10）卷绕形成平直段（101）和弯折段（102），保护层（12）设置于第一电极（10）的弯折段（102）。通过以上设置，改善了弯折段（102）处的集电体（11）的脆性，提高了第一电极（10）的弯折段（102）的卷绕性能，防止第一电极（10）的弯折段（102）在卷绕过程中发生龟裂、脆断，从而提高了电极的压密以及电化学装置的能量密度。

Description

卷绕型电化学装置及电子设备 技术领域
本申请实施方式涉及储能器件技术领域，特别是涉及一种卷绕型电化学装置及电子设备。
背景技术
目前,锂离子电池已经成为消费类便携式电子产品的首选电源。伴随着移动通信设备、多媒体设备的快速发展,人们对应用在这些设备上的锂离子电池的性能提出了越来越高的要求,特别是锂离子电池的能量密度，要求锂离子电池要具有更高的能量密度,在尽可能小的空间内提供最大的能量。
在电池的生产过程中，需先对电池的电极进行冷压，冷压过程中，电极的活性层颗粒物质易与电极的集电体之间发生挤压而嵌入集电体，导致集电体受损；在后续的卷绕过程中，由于电极的弯折段受到的应力较大，导致电极的弯折段极容易发生龟裂，甚至脆断，且随着电极压密的提高，电极的脆性增加，电极的弯折段发生龟裂、脆断的可能性也随之增加。
在现有技术中，通过降低电极的压密，避免电极变脆，以防止电极的弯折段在卷绕过程中发生龟裂、脆断，但这种做法却无法实现电池的高能量密度；又或者，通过在活性物质层中混入粗糙度较小的主材颗粒，改善电极的脆性，但降低粗糙度会造成主材比表面积变小，从而恶化电池的动力学性能。
有鉴于此，确有必要提供一种能够解决上述问题的卷绕型电化学装置及电子设备。
发明内容
本申请实施方式主要解决的技术问题是提供一种能够防止电极在卷绕过程中发生龟裂和脆断的卷绕型电化学装置及电子设备，从而可提 高电极的压密以及电化学装置的能量密度。
为解决上述技术问题，本申请实施方式采用的一个技术方案是：
一方面，提供一种卷绕型电化学装置，卷绕型电化学装置包括电极组件。电极组件包括第一电极。第一电极包括集电体、保护层和设置于集电体至少一个表面的活性物质层，保护层位于集电体和活性物质层之间。第一电极卷绕形成平直段和弯折段，保护层设置于第一电极的弯折段。
在一些实施例中，第一电极的最内圈包括卷绕起始端、第一弯折段和相对于第一弯折段的第二弯折段，第一弯折段连接卷绕起始端，保护层设置于第一弯折段和/或所述第二弯折段。
在一些实施例中，第一电极卷绕形成多个弯折段，沿第一电极的最内圈向第一电极的最外圈的方向，至少两个弯折段分别设置有保护层。
在一些实施例中，保护层设置于弯折段处的集电体的内侧、外侧中的至少一者。
在一些实施例中，设置于弯折段内侧的保护层的长度与设置于弯折段外侧的保护层的长度相同或不同。
在一些实施例中，保护层满足以下特征中的至少一者：
(a)保护层的厚度为0.5μm至20μm；
(b)保护层的长度为0.1cm至5cm；
(c)保护层的宽度为集电体宽度的0.1倍至1倍。
在一些实施例中，保护层为导电涂层或导电胶纸。
在一些实施例中，导电涂层包括导电剂和粘结剂，导电剂的质量为导电涂层总质量的50％至99％，粘结剂的质量为导电涂层总质量的1％至50％。
在一些实施例中，导电剂包括片层状、网状、线状或零维导电剂中的至少一种；
粘结剂包括丁苯橡胶、丁腈橡胶、羧基丁苯橡胶、酚醛树脂胶、聚丁烯、聚丙烯、聚偏氟乙烯、聚酰亚胺或聚乙酸乙烯酯中的至少一种。
在一些实施例中，导电胶纸包括胶黏剂和导电颗粒，胶黏剂的质量为导电胶纸的总质量的1％至90％，导电颗粒的质量为导电胶纸的总质量 的10％至99％。
在一些实施例中，胶黏剂包括丙烯酸、聚酯类材料中的至少一种；
导电颗粒为金属颗粒，金属颗粒粒径D50为0.001μm至500μm。
在一些实施例中，导电胶纸的力学性能满足以下特征中的至少一者：
(d)导电胶纸的抗拉强度≥50MPa；
(e)导电胶纸延伸率≥3％。
另一方面，还提供一种电子设备，电子设备包括：
以上的卷绕型电化学装置。
与现有技术相比，本申请实施例的卷绕型电化学装置的电极组件还包括保护层，保护层设置于第一电极的弯折段，且位于集电体和活性物质层之间，保护层对弯折段处的集电体起保护作用，防止了冷压过程中活性物质层嵌入弯折段处的集电体而导致集电体受损，改善了弯折段处的集电体的脆性，从而提高了第一电极的弯折段的卷绕性能，防止第一电极的弯折段在卷绕过程中发生龟裂、脆断，进而可提高电极的压密以及卷绕型电化学装置的能量密度。
附图说明
一个或多个实施例通过与之对应的附图中的图片进行示例性说明，这些示例性说明且不构成对实施例的限定，附图中具有相同参考数字标号的元件表示为类似的元件，除非有特别申明，附图中的图不构成比例限制。
图1是本申请其中一实施例所提供的卷绕型电化学装置中的电极组件的结构示意图；
图2是本申请其中一实施例的电极组件的第一电极的部分展开的平坦状态的示意图；
图3是本申请其中一实施例所提供的卷绕型电化学装置中的电极组件的结构示意图；
图4是本申请其中一实施例所提供的卷绕型电化学装置中的电极组件的结构示意图；
图5是本申请其中一实施例的电极组件的第一电极的部分展开的平坦状态的示意图。
具体实施方式
为了便于理解本申请，下面结合附图和具体实施例，对本申请进行更详细的说明。需要说明的是，当元件被表述“固定于”/“设置于”另一个元件，它可以直接在另一个元件上、或者其间可以存在一个或多个居中的元件。当一个元件被表述“连接”另一个元件，它可以是直接连接到另一个元件、或者其间可以存在一个或多个居中的元件。本说明书所使用的术语“上”、“下”、“”、“外”、“垂直的”、“水平的”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。此外，术语“第一”、“第二”等仅用于描述目的，而不能理解为指示或暗示相对重要性。
除非另有定义，本说明书所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是用于限制本申请。本说明书所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。
此外，下面所描述的本申请不同实施例中所涉及的技术特征只要彼此之间未构成冲突就可以相互结合。
本申请实施例提供一种卷绕型电化学装置，其放电时将化学能转化成电能，以向负载供电，充电时将电能转化成化学能，以进行储能。其中，卷绕型电化学装置包括电极组件100。
请参阅图1，图1为根据本申请其中一实施例示出的电极组件100，电极组件100包括第一电极10，第一电极10包括集电体11、保护层12和设置于集电体11至少一个表面的活性物质层13，保护层12位于集电体11和活性物质层13之间，其中，在电极组件100的卷绕过程中，部分第一电极10相对另一部分第一电极10发生弯折，使得第一电极10卷绕形成平直段101和弯折段102，弯折段102位于平直段101的两端， 保护层12设置于第一电极10的弯折段102。
其中，电极组件100卷绕多圈后大致呈扁平螺旋状结构，第一电极10可被配置为电极组件100的最内圈电极，此外，第一电极10可被配置为电极组件100的阴极电极，也可被配置为阳极电极。
在电极的冷压过程中，活性物质层中的活性物质颗粒易与集电体之间发生挤压，而嵌入集电体，从而导致集电体受损。在后续卷绕过程中，由于电极的弯折段受到的应力较大，从而导致电极的弯折段极容易发生龟裂、脆断，随着电极压密的提高，电极的脆性增加，电极的弯折段发生龟裂、脆断的可能性也随之增加。
请结合图1和图2，图2示出了设置有保护层12的第一电极10的弯折段102处于展开的平坦状态，为了防止电极在卷绕过程中发生龟裂、脆断，本申请实施例的卷绕型电化学装置于第一电极10的弯折段102设置有保护层12，且保护层12位于集电体11和活性物质层13之间，保护层12用于对弯折段102处的集电体11起保护作用，其防止了冷压过程中活性物质层13嵌入弯折段处的集电体11，而导致集电体11受损，改善了弯折段102处的集电体11的脆性，从而提高了第一电极10的弯折段102的卷绕性能，防止第一电极10的弯折段102在卷绕过程中发生龟裂、脆断，进而可提高电极的压密以及卷绕型电化学装置的能量密度。
其中，相较通过降低电极的压密或在活性物质层中混入粗糙度较小的主材颗粒，以实现防止电极的弯折段在卷绕过程中发生龟裂、脆断的做法，本申请实施例提供的电化学装置，通过在第一电极10的弯折段102处的集电体11和活性物质层13之间设置保护层12，即可防止电极的弯折段102在卷绕过程中发生龟裂、脆断，保证了电化学装置的高能量密度以及动力学性能。
其中，只将保护层12设置于第一电极10的弯折段102，相对于将保护层12设置于第一电极10的整体，其简化了电极组件100的整体结构，可明显抑制因设置保护层12而产生的厚度增加、能量密度损失的不良后果，同时，可降低因设置保护层12所产生的生产成本，提高了生产效率。
其中，图1和图2示出了活性物质层13设置于集电体11的相背的两个表面，可以理解的是，在本申请的一些其他实施例中，活性物质层13只需设置于集电体11的至少一个表面即可，无需于集电体11的相背两面均设置有活性物质层13，此外，于集电体11的一表面上可以连续地设置活性物质层13，也可以在该一表面上预留空白区域，该空白区域不设置活性物质层13，活性物质层13设置于空白区域之外，也即，于集电体11的一表面可以分段地设置活性物质层13，其中，空白区域可以优先设置于弯折段13，则，在电极的冷压过程中，弯折段13可避免受到活性物质层13的刺伤，相应地，于设置有空白区域的弯折段13则无需设置保护层12。
以下对设置有保护层12的弯折段102的具体位置进行说明。
第一电极10卷绕形成多个弯折段102，在第一电极10的卷绕过程中，卷绕产生的应力由第一电极10的最内圈向第一电极10的最外圈的方向依序递减并分别作用于各个弯折段102，也即，越靠近电极组件100的中心的弯折段102所受应力越大，因此，在本申请的其中一实施例中，沿第一电极10的最内圈向第一电极10的最外圈的方向，至少两个弯折段102分别设置有保护层12，也即，保护层12优先设置于第一电极10靠近电极组件100的中心的弯折段102，其中，保护层12位于弯折段102处的集电体11和活性物质层13之间。通过以上对保护层12分布规律的设置，使得多个保护层12可被根据需要地沿第一电极10的最内圈向第一电极10的最外圈的方向分别配置于第一电极10的各个弯折段102，以对受应力较大的弯折段102进行保护，可有效地、针对性地对在卷绕过程中容易发生龟裂、脆断的第一电极10的弯折段102进行保护，有利于电极的压密和电化学装置的能量密度的提高。
其中，第一电极10的最内圈是指，第一电极10卷绕过程中形成的最内沿的第一圈；第一电极10的最外圈是指，第一电极10卷绕过程中形成的最外沿的倒数第一圈。第一电极10的最内圈包括卷绕起始端、第一弯折段和相对于第一弯折段的第二弯折段，第一弯折段连接卷绕起始端。
其中，保护层12的数量可以根据实际需要选择，只需保护层12的 分布规律为沿预设方向分别设置于第一电极10的各个弯折段102即可，例如，保护层12的数量为四个，沿第一电极10的最内圈向第一电极10的最外圈的方向，四个保护层12分别设置于第一电极10的四个弯折段102，具体可参阅图1。
由于卷绕产生的应力容易集中于第一弯折段和第二弯折段，而容易导致第一弯折段和第二弯折段发生龟裂、脆断，因此，在本申请的其中一实施例中，保护层12设置于第一弯折段和/或第二弯折段，其中，保护层12位于弯折段102处的集电体11和活性物质层13之间，具体如图3所示，图3示出了保护层12设置于第一弯折段和第二弯折段的情况，可以理解的是，保护层12也可以只设置于第一弯折段和第二弯折段中的一个。通过将保护层12的分布位置限制为第一电极10的最内圈的第一弯折段和/或第二弯折段，在提高第一电极10的弯折段102的卷绕性能，以及防止第一电极10的弯折段102在卷绕过程中发生龟裂、脆断的同时，进一步抑制了因设置保护层12而产生的厚度增加、能量密度损失的不良后果，提高了电极的压密和电化学装置的能量密度，进一步降低了因设置保护层12所产生的生产成本，提高了生产效率。
由于卷绕产生的应力最容易集中于第一弯折段，而导致第一弯折段发生龟裂、脆断，因此，在本申请的其中一实施例中，保护层12设置于第一弯折段102，其中，保护层12位于弯折段102处的集电体11和活性物质层13之间，具体如图4所示。通过将保护层12的分布位置限制为第一电极10的最内圈的最初的弯折段102，在提高第一电极10的弯折段102的卷绕性能，以及防止第一电极10的弯折段102在卷绕过程中发生龟裂、脆断的同时，更进一步抑制了因设置保护层12而产生的厚度增加、能量密度损失的不良后果，提高了电极的压密和电化学装置的能量密度，更进一步降低了因设置保护层12所产生的生产成本，提高了生产效率。
保护层12于弯折段102具体的所在位置为，保护层12设置于弯折段102处的集电体11的内侧、外侧中的至少一者，也即，保护层12可被根据需要地设置于弯折段102处的集电体11的一侧或两侧，当保护层12被设置于弯折段102处的集电体11的一侧时，该保护层12可被 根据需要地设置于弯折段102处的集电体11的内侧或外侧，具体如图2和图5所示，图2示出了保护层12被设置于弯折段102处的集电体11的两侧，图5示出了保护层12被设置于弯折段102处的集电体11的其中一侧。其中，弯折段102处的集电体11的内侧是指，处于卷绕状态的集电体11朝向电极组件100的中心的一侧；弯折段102处的集电体11的外侧是指，处于卷绕状态的集电体11背向电极组件100的中心的另一侧。
由于电极在冷压过程中，集电体11呈展开的平坦状态，集电体11的两侧面容易受活性物质层13的颗粒挤压而导致集电体11受损，从而恶化了集电体11的脆性，导致集电体11在卷绕过程中容易出现龟裂、脆断，因此，在本申请的其中一实施例中，保护层12设置于弯折段102处的集电体11的内侧和外侧，使得保护层12可对弯折段102处的集电体11的内侧和外侧两侧均起保护作用。通过将保护层12设置于弯折段102处的集电体11的内侧和外侧，保证了电极在高压密下的卷绕性能，有效防止在冷压过程中弯折段102处的集电体11的两侧因受挤压应力，而被集电体11相背两侧的活性物质层13刺伤，从而防止了电极的弯折段102在卷绕过程中发生龟裂、脆断，保证了提高电极的压密和电化学装置的能量密度的可行性。
需要说明的是，保护层12可局部地或完全覆盖地设置于弯折段102处的集电体11的内侧、外侧中的至少一者，也可以设置为扩展延伸到弯折段102两端的平直段101上的集电体11。其中，为更好地实现保护层12的保护作用，保护层12至少部分覆盖弯折段102处的集电体11的顶部。
以下对保护层12的结构尺寸参数进行说明。
对于上述的保护层12，保护层12满足以下特征中的至少一者：(a)沿集电体11的厚度方向上，保护层12的厚度为0.5μm至20μm；(b)沿集电体11的卷绕方向上，保护层12的长度为0.1cm至5cm；(c)沿集电体11的宽度方向上，保护层12的宽度为集电体11宽度的0.1倍至1倍，以图5的平面示意图为实例说明，保护层12的厚度方向与第一电极10的厚度方向一致，保护层12的长度方向为第一电极10的长 度方向，保护层12的长度为卷绕结构中的弯折段的弧长，保护层12的宽度方向为垂直指向纸面的方向，与第一电极10的宽度方向一致。以上对保护层12的结构尺寸参数(厚度、长度和宽度)的说明，是针对集电体11的同一侧上(内侧或外侧)的保护层12所描述的。
需要说明的是，如果保护层12的厚度小于0.5μm，则保护层12难以对弯折段102处的集电体11起保护作用，在冷压过程中，活性物质层13的颗粒容易通过保护层12嵌入集电体11而导致集电体11受损，不能有效防止弯折段102在卷绕过程中发生龟裂、脆断；如果保护层12的厚度大于20μm，则在弯折段102处的集电体11上涂布保护层12时，可能出现刮带风险而导致集电体11受损，不能保证弯折段102在卷绕过程中避免发生龟裂、脆断，且会在一定程度上降低卷绕型电化学装置的能量密度。如果保护层12的长度小于0.1cm，则保护层12同样难以对弯折段102处的集电体11起保护作用，在冷压过程中，活性物质层13的颗粒容易绕过保护层12嵌入集电体11而导致集电体11受损，不能有效防止弯折段102在卷绕过程中发生龟裂、脆断；如果保护层12的长度大于5cm，则会在一定程度上降低卷绕型电化学装置的能量密度。如果保护层12的宽度小于集电体11宽度的0.1倍，则保护层12同样难以对弯折段102处的集电体11起保护作用，在冷压过程中，活性物质层13的颗粒容易绕过保护层12嵌入集电体11而导致集电体11受损，不能有效防止弯折段102在卷绕过程中发生龟裂、脆断；如果保护层12的宽度大于集电体11宽度，则会在一定程度上降低卷绕型电化学装置的能量密度。
其中，当弯折段102处的集电体11的内侧和外侧均设置有保护层12时，分别位于集电体11的内侧和外侧上的两个保护层12的尺寸大小可以根据实际需要设置，也即，分别位于集电体11的内侧和外侧上的两个保护层12的尺寸大小可以一致，也可以存在差异，只需满足上述的(a)、(b)和(c)特征中的至少一者即可。当然，为了使得保护层12起到较好的保护效果，保护层12的尺寸大小可以均满足上述的(a)、(b)和(c)特征。
以下对保护层12的材料进行说明。
为实现保护层12较好的防护效果，保证弯折段102处的集电体11在冷压过程中不受损伤，以使得第一电极10的弯折段102在后续卷绕过程中不产生龟裂、脆断，保护层12由粘结剂及容易滑动或挤压过程中不易刺伤集电体11且导电性良好的导电物质制成，在本申请的一些实施例中，保护层12为导电涂层或导电胶纸。
对于上述的导电涂层，导电涂层包括导电剂和粘结剂，导电剂的质量为导电涂层总质量的50％至99％，粘结剂的质量为导电涂层总质量的1％至50％。需要说明的是，如果导电剂的含量低于导电涂层总质量的50％，则会恶化电极组件100内阻，降低电子的移动速率；如果粘结剂的含量低于导电涂层总质量的1％，则会降低导电涂层的粘结力，有脱膜风险。
导电剂包括片层状、网状、线状或零维导电剂中的至少一种，片层状导电剂在冷压过程中通过滑动释放挤压应力，从而实现对集电体11的保护作用，网状、线状、零维导电剂在冷压过程中可缓冲主材颗粒对集电体11产生的挤压应力，降低集电体11受损程度，从而实现对集电体11的保护作用。其中，片层状导电剂可以例如是石墨烯，网状导电剂可以例如是石墨纤维网，线状导电剂可以例如是碳纳米管、石墨纤维，零维导电剂可以例如是纳米颗粒导电碳。
粘结剂包括丁苯橡胶、丁腈橡胶、羧基丁苯橡胶、酚醛树脂胶、聚丁烯、聚丙烯、聚偏氟乙烯、聚酰亚胺或聚乙酸乙烯酯中的至少一种，粘结剂在冷压过程中起到缓冲应力的作用，降低主材颗粒对集电体11的刺伤。
以下对导电涂层的制作过程进行示例性说明：将溶剂加入容器，然后加入导电剂，通过搅拌将二者混合均匀后，加入粘结剂，再次通过搅拌将三者混合均匀。其中，溶剂可以为有机类溶剂，例如，NMP、DMC，溶剂也可以为无机类溶剂，例如，去离子水。
对于上述的导电胶纸，导电胶纸包括胶黏剂和导电颗粒，胶黏剂的质量为导电胶纸的总质量的1％至90％，导电颗粒的质量为导电胶纸的总质量的10％至99％。
胶黏剂包括丙烯酸、聚酯类材料中的至少一种。
导电颗粒为金属颗粒，金属颗粒粒径D50为0.001μm至500μm。 其中，金属颗粒可以例如是金、银。
为保证导电胶纸的防护效果，导电胶纸的力学性能需满足以下特征中的至少一者：(d)抗拉强度≥50MPa；(e)导电胶纸延伸率≥3％。需要说明的是，如果导电胶纸的抗拉强度≤50MPa以及延伸率≤3％，则在冷压过程中，导电胶纸容易被活性物质层13颗粒刺伤，难以起到保护集电体11的作用。当然，为了使得导电胶纸起到较好的防护效果，导电胶纸的力学性能可以均满足(d)和(e)特征。
请复参图1，在本申请实施例中，电极组件100还包括第二电极20和隔离膜30，第一电极10、隔离膜30和第二电极20依序叠置并卷绕形成电极组件100的结构主体，隔离膜30位于第一电极10和第二电极20之间，第二电极20与第一电极10极性相反。其中，第一电极10可以是阴极电极，则，第二电极20为阳极电极；相应地，第一电极10可以是阳极电极，则，第二电极20为阴极电极。
在本申请的一些实施例中，第二电极20的结构可以分别与上述各个实施例中的第一电极10的结构相同，不同的是，第二电极20的极性与第一电极10的极性相反。具体地，当第一电极10为阴极电极时，第一电极10的集电体11为阴极集电体，第一电极10的活性物质层13为阴极活性物质层，相应地，第二电极20的集电体为阳极集电体，第二电极20的活性物质层为阳极活性物质层；当第一电极10为阳极电极时，第一电极10的集电体11为阳极集电体，第一电极10的活性物质层13为阳极活性物质层，相应地，第二电极20的集电体为阴极集电体，第二电极20的活性物质层为阴极活性物质层。其中，第二电极20的保护层于第二电极20的分布规律与第一电极10的保护层12于第一电极10的分布规律相同，且第二电极20的保护层的材料与第一电极10的保护层12的材料相同。
在本申请的一些实施例中，第二电极20的结构也可以与上述各个实施例中的第一电极10的结构不同，且第二电极20的极性与第一电极10的极性相反。具体地，第二电极20的弯折段102不设置保护层12；或者第二电极20的保护层的数量与第一电极10的保护层的数量不同，同时，第二电极20的保护层优先设置于第二电极20靠近电极组件100 的中心的弯折段。其中，由于卷绕产生的应力最容易集中于最内圈电极的最内圈的最初或双方的弯折段102，而导致最内圈电极的最内圈的最初或双方的卷回部发生龟裂、脆断，因此，在电极组件100的卷绕过程中，将第一电极10配置为电极组件100的最内圈电极。
需要说明的是，第一电极10和第二电极20叠置且以其中一者背向另一者所在的一侧为中心进行卷绕，则该其中一者为最内圈电极，该另一者为最外圈电极。
本申请实施例提供的电化学装置可以是锂离子电池，该锂离子电池能够防止电极在卷绕过程中发生龟裂和脆断。锂离子电池主要依靠锂离子在阴极电极和阳极电极之间移动来工作。在充放电过程中，锂离子在阴极电极和阳极电极之间往返嵌入和脱嵌：充电时，锂离子从阴极电极脱嵌，经过电解质嵌入阳极电极，使得阳极电极处于富锂状态；放电时，锂离子从阳极电极脱出，经过电解质嵌入阴极电极，使得阴极电极处于富锂状态。其中，可将第一电极10配置为锂离子电池的最内圈电极，第二电极20配置为锂离子电池的最外圈电极，此外，第一电极10可被配置为阴极电极或阳极电极，相应地，第二电极20可被配置为阳极电极或阴极电极。
本申请中的阴极电极没有特别限制，只要能够实现本申请目的即可。其中，本申请中的阴极集电体没有特别限制，例如，铝箔、铝合金箔以及复合集电体等。阴极活性物质层包括阴极活性材料，本申请中的阴极活性材料没有特别限制，可以使用本领域任何阳极活性材料，例如，可以包括镍钴锰酸锂(镍钴锰酸锂型号可以是NCM811、NCM622、NCM523、NCM111)、镍钴铝酸锂、磷酸铁锂、富锂锰基材料、钴酸锂、锰酸锂、磷酸锰铁锂或钛酸锂中的至少一种。
本申请中的阳极电极没有特别限制，只要能够实现本申请目的即可。其中，本申请中的阳极集电体没有特别限制，例如，铜箔、铝箔、铝合金箔以及复合集电体等。阳极活性物质层包括阳极活性材料，本申请中的阳极活性材料没有特别限制，例如，可以包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、硅、硅碳或钛酸锂中的至少一种。
以下对阴极电极的制作过程进行示例性说明：将阴极活性物质钴酸 锂(LiCoO2)、Super P、聚偏二氟乙烯按照重量比97:1.4:1.6进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌至体系均匀，获得阴极浆料，其中阴极浆料的固含量为72wt％；接着，将阴极浆料均匀涂覆于阴极集电体铝箔上；然后，将阴极集电体铝箔在110℃下烘干，再经过冷压、分切后，从而得到阴极电极。
以下对阳极电极的制作过程进行示例性说明：阳极活性物质可以例如是人造石墨和硅的混合物，将阳极活性物质、Super P、粘结剂、丁苯橡胶(SBR)按照重量比96.2:1.5:0.5:1.8进行混合，加入去离子水，在真空搅拌机作用下获得阳极浆料，其中阳极浆料的固含量为54wt％；接着，将阳极浆料均匀涂覆在阳极集电体铜箔上；然后，将阳极集电体铜箔在85℃下烘干，再经过冷压、分切后，得到阳极电极。
本申请的电化学装置还包括电解质，电解质可以是凝胶电解质、固态电解质和电解液中的一种或多种，其中，电解液包括锂盐和非水溶剂。
在本申请一些实施例中，锂盐选自LiPF6、LiBF4、LiAsF6、LiClO4、LiB(C6H5)4、LiCH3SO3、LiCF3SO3、LiN(SO2CF3)2、LiC(SO2CF3)3、LiSiF6、LiBOB和二氟硼酸锂中的一种或多种。举例来说，锂盐可以选用LiPF6，因为它可以给出高的离子导电率并改善循环特性。
在本申请一些实施例中，非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂中的一种或多种。
上述碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物中的一种或多种。
上述羧酸酯化合物可为甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯中的一种或多种。
上述醚化合物可为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃中的一种或多种。
上述其它有机溶剂可为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯中的 一种或多种。
上述链状碳酸酯化合物可为碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)中的一种或多种。
上述环状碳酸酯化合物可为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)中的一种或多种。
上述氟代碳酸酯化合物可为碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯中的一种或多种。
本申请的电化学装置还包括电解质，电解质可以是凝胶电解质、固态电解质和电解液中的一种或多种，其中，电解液包括锂盐和非水溶剂。
本申请的电化学装置还包括包装袋，包装袋用于容纳电极组件100。
电化学装置的制备过程为本领域技术人员所熟知的，本申请没有特别的限制。例如，锂离子电池可以通过以下过程制造：将阴极电极和阳极电极经由隔离膜依序叠置，并根据需要将其卷绕、折叠等操作后放入包装袋内，将电解液注入包装袋并封口，其中所用的阴极电极为本申请提供的上述第一电极10或第二电极20，所用的阳极电极为本申请提供的上述第二电极20或第一电极10。此外，也可以根据需要将防过电流元件、导板等置于壳体中，从而防止锂离子电池内部的压力上升、过充放电。
当然，本申请实施例提供的电化学装置也可以是锂电池、锂离子聚合物电池等。
取上述实施例中的卷绕型电化学装置与对比例的卷绕型电化学装置进行实验测试，测试得出下表1中的实验结果。其中，对比例1的卷绕型电化学装置的集电体11中不设置保护层12，对比例2的卷绕型电化学装置的集电体11整体涂覆有保护层12。
表1 对比例1-2与实施例1-19
Figure PCTCN2021079113-appb-000001
Figure PCTCN2021079113-appb-000002
Figure PCTCN2021079113-appb-000003
Figure PCTCN2021079113-appb-000004
从表1可以看出，根据本申请提供的实施例1-20的卷绕型电化学装置于第一电极10的弯折段102设置保护层12后，第一电极10的极限压密和卷绕型电化学装置的能量密度均有所提高。在实施例13的卷绕型电化学装置中，对其第一弯折段和第二弯折段处的集电体11的内侧和外侧分别设置长度均为2cm的保护层12，且保护层12由占保护层12总质量85％的石墨烯和占保护层12总质量15％的丁苯橡胶制成，该实施例的卷绕型电化学装置的电极的压密和电化学装置能量密度提高幅度最大。因此，表1中的实验结果证明，本申请实施例提供的卷绕型电化学装置通过在弯折段102处的集电体11设置保护层12，可对对应的弯折段102起保护作用，提高了第一电极10的弯折段102的卷绕性能，防止第一电极10的弯折段102在卷绕过程中发生龟裂、脆断，从而提高了电极的压密和电化学装置的能量密度。
以下对压密测试方法进行示例性说明：取面积为S的极片(该极片包括集电体和涂布于集电体的活性物质层)，称出其膜层(活性物质层)质量为M，测量出其膜层厚度为T，则，膜层压密(极限压密)P.D.＝M/T/S。其中，膜层总质量M计算：涂布前取面积为S的空铝箔(集电体)，称其质量为m，向空铝箔涂布膜层形成极片并称极片质量为M0，则，M＝M0-m；膜层厚度T计算：用万分尺测出冷压后极片总厚度为T0，用万分尺测出所用空铝箔厚度为t，则，T＝T0-t。
以下对电化学装置的能量密度测试方法进行示例性说明：以0.5C 的电流对电化学装置充电至4.48V，再以4.48V的电压恒压充电至电流为0.05C，最后以0.5C的电流放电至3.0V，记录放电能量，则，能量密度E.D.＝放电能量/电化学装置体积(长度*宽度*厚度)。
以下对抗拉强度、延伸率测试方法进行示例性说明：空铝箔(样条宽15mm，标距50mm)：用高铁拉力机以5mm/min的速度沿长度方向拉伸，取断裂时的强度、延伸率为其测试结果；导电胶纸(样条宽15mm，标距20mm)：用高铁拉力机以5mm/min的速度，沿贴胶后，与极片长度平行的方向拉伸，取断裂时的强度、延伸率为其测试结果。
本申请实施例还提供一种电子设备，该电子设备包括上述任一实施例所提供的卷绕型电化学装置，该卷绕型电化学装置具有较高的能量密度。
本申请的电子设备没有特别限定，其可以是用于现有技术中已知的任何电子设备。在本申请的一些实施例中，电子设备可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
以上所述仅为本申请的实施方式，并非因此限制本申请的专利范围，凡是利用本申请说明书及附图容所作的等效结构或等效流程变换，或直接或间接运用在其他相关的技术领域，均同理包括在本申请的专利保护范围。
最后应说明的是：以上实施例仅用以说明本申请的技术方案，而非对其限制；在本申请的思路下，以上实施例或者不同实施例中的技术特征之间也可以进行组合，步骤可以以任意顺序实现，并存在如上所述的本申请的不同方面的许多其它变化，为了简明，它们没有在细节中提供；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改， 或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围。

Claims (13)

  1. 一种卷绕型电化学装置，包括电极组件，其特征在于，所述电极组件包括第一电极，所述第一电极包括集电体、保护层和设置于所述集电体至少一个表面的活性物质层，其中，所述保护层位于所述集电体和所述活性物质层之间，所述第一电极卷绕形成平直段和弯折段，所述保护层设置于所述第一电极的弯折段。
  2. 根据权利要求1所述的卷绕型电化学装置，其特征在于，所述第一电极的最内圈包括卷绕起始端、第一弯折段和相对于所述第一弯折段的第二弯折段，所述第一弯折段连接卷绕起始端，所述保护层设置于所述第一弯折段和/或所述第二弯折段。
  3. 根据权利要求1所述的卷绕型电化学装置，其特征在于，所述第一电极卷绕形成多个弯折段，沿所述第一电极的最内圈向所述第一电极的最外圈的方向，至少两个所述弯折段分别设置有所述保护层。
  4. 根据权利要求1-3任意一项所述的卷绕型电化学装置，其特征在于，所述保护层设置于所述弯折段处的集电体的内侧、外侧中的至少一者。
  5. 根据权利要求4所述的卷绕型电化学装置，其特征在于，设置于所述弯折段内侧的所述保护层的长度与设置于所述弯折段外侧的所述保护层的长度相同或不同。
  6. 根据权利要求1-3任意一项所述的卷绕型电化学装置，其特征在于，所述保护层满足以下特征中的至少一者：
    (a)所述保护层的厚度为0.5μm至20μm；
    (b)所述保护层的长度为0.1cm至5cm；
    (c)所述保护层的宽度为所述集电体宽度的0.1倍至1倍。
  7. 根据权利要求1-3任意一项所述的卷绕型电化学装置，其特征在于，所述保护层为导电涂层或导电胶纸。
  8. 根据权利要求7所述的卷绕型电化学装置，其特征在于，所述导电涂层包括导电剂和粘结剂，所述导电剂的质量为所述导电涂层总质量的50％至99％，所述粘结剂的质量为所述导电涂层总质量的1％至50％。
  9. 根据权利要求8所述的卷绕型电化学装置，其特征在于，所述导电剂包括片层状、网状、线状或零维导电剂中的至少一种；
    所述粘结剂包括丁苯橡胶、丁腈橡胶、羧基丁苯橡胶、酚醛树脂胶、聚丁烯、聚丙烯、聚偏氟乙烯、聚酰亚胺或聚乙酸乙烯酯中的至少一种。
  10. 根据权利要求7所述的卷绕型电化学装置，其特征在于，所述导电胶纸包括胶黏剂和导电颗粒，所述胶黏剂的质量为所述导电胶纸的总质量的1％至90％，所述导电颗粒的质量为所述导电胶纸的总质量的10％至99％。
  11. 根据权利要求10所述的卷绕型电化学装置，其特征在于，所述胶黏剂包括丙烯酸、聚酯类材料中的至少一种；
    所述导电颗粒为金属颗粒，所述金属颗粒粒径D50为0.001μm至500μm。
  12. 根据权利要求7所述的卷绕型电化学装置，其特征在于，所述导电胶纸的力学性能满足以下特征中的至少一者：
    (d)所述导电胶纸的抗拉强度≥50MPa；
    (e)所述导电胶纸延伸率≥3％。
  13. 一种电子设备，其特征在于，包括：
    如权利要求1-12任意一项所述的卷绕型电化学装置。
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