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EP-4089760-B1 - ELECTROCHEMICAL DEVICE AND ELECTRONIC DEVICE

EP4089760B1EP 4089760 B1EP4089760 B1EP 4089760B1EP-4089760-B1

Inventors

  • FU, Ao

Dates

Publication Date
20260513
Application Date
20220331

Claims (8)

  1. An electrochemical device, comprising an electrode assembly; the electrode assembly comprises a first electrode plate (11), a second electrode plate (12) and a separator (13); the separator is provided between the first electrode plate and the second electrode plate; the first electrode plate comprises an active material layer; the active material layer comprises at least one first active material layer (111) and at least one second active material layer (112); the at least one first active material layer and the at least one second active material layer are provided along a length direction of the electrode plate; and the electrode assembly is formed by winding the first electrode plate, the second electrode plate and the separator; the electrode assembly includes a planar area (21) and a corner area (22); the first electrode plate is a positive electrode plate; the first active material layer is a first positive electrode active material layer; the second active material layer is a second positive electrode active material layer; at least a portion of the first positive electrode active material layer is located in the planar area; and at least a portion of the second positive electrode active material layer is located in the corner area; the first positive electrode active material layer comprises a first positive electrode conductive agent; the second positive electrode active material layer comprises a second positive electrode conductive agent; and the electrochemical device being characterized in that : a mass percentage of the first positive electrode conductive agent in the first positive electrode active material layer is greater than or equal to a mass percentage of the second positive electrode conductive agent in the second positive electrode active material layer and a lithium ion diffusion rate of the first active material layer is greater than or equal to 1.2 times that of a lithium ion diffusion rate of the second active material layer.
  2. The electrochemical device of claim 1, characterized in that , the mass percentage of the first positive electrode conductive agent in the first positive electrode active material layer is 0.5% to 5.5%; and the mass percentage of the second positive electrode conductive agent in the second positive electrode active material layer is 0.5% to 5%.
  3. The electrochemical device of claim 1, characterized in that , a compacted density of the second positive electrode active material layer is greater than or equal to a compacted density of the first positive electrode active material layer.
  4. An electrochemical device, comprising an electrode assembly; the electrode assembly comprises a first electrode plate (11), a second electrode plate (12) and a separator (13); the separator is provided between the first electrode plate and the second electrode plate; the first electrode plate comprises an active material layer; the active material layer comprises at least one first active material layer (111) and at least one second active material layer (112); the at least one first active material layer and the at least one second active material layer are provided along a length direction of the electrode plate; and the electrode assembly is formed by winding the first electrode plate, the second electrode plate and the separator; the electrode assembly comprises a planar area (21) and a corner area (22); the first electrode plate is a negative electrode plate; the first active material layer is a first negative electrode active material layer; the second active material layer is a second negative electrode active material layer; at least a portion of the first negative electrode active material layer is located in the corner area; and at least a portion of the second negative electrode active material layer is located in the planar area; the second negative electrode active material layer comprises a second negative electrode conductive agent; the first negative electrode active material layer comprises a first negative electrode conductive agent; and the electrochemical device being characterized in that : a mass percentage of the first negative electrode conductive agent in the first negative electrode active material layer is greater than or equal to a mass percentage of the second negative electrode conductive agent in the second negative electrode active material layer, and a lithium ion diffusion rate of the first active material layer is greater than or equal to 1.2 times that of a lithium ion diffusion rate of the second active material layer.
  5. The electrochemical device of claim 4, characterized in that , the first negative electrode active material layer comprises a first negative electrode active material; the second negative electrode active material layer comprises a second negative electrode active material; and at least one of the first negative electrode active material or the second negative electrode active material includes a graphite having a capacity per gram of 300 mAh/g to 380 mAh/g.
  6. The electrochemical device of any of claim 1 to 5, characterized in that , the first electrode plate comprises a plurality of first active material layers and a plurality of second active material layers.
  7. The electrochemical device of claim 6, characterized in that , the plurality of the first active material layers and the plurality of the second active material layers are provided at intervals along the length direction of the electrode plate.
  8. An electronic device, comprising an electrochemical device of any one of claims 1 to 7.

Description

BACKGROUND 1. Technical Field The application relates to the field of electrochemistry, and in particular to an electrochemical device and electronic device. 2. Description of the Related Art Electrochemical devices represented by lithium-ion batteries have the characteristics of high voltage, high energy density, long cycle life and no pollution, and are widely used in consumer electronic products such as mobile phones, computers, and digital cameras etc. With the development of electronic products, the requirements for electrochemical devices such as lithium-ion batteries become higher and higher, particularly in terms of high energy density and cycle life. During the charging and discharging process, ions (such as lithium ions) would be continuously deintercalated and intercalated on the electrode plate. However, due to the problems of the winding structure of the cell, such as local uneven compaction or local uneven CB (Cell balance, the ratio of directly opposite negative electrode capacity to positive electrode capacity), it leads to the problem of uneven distribution of ion transport kinetics in the cell during the cycle. In the area with insufficient kinetics, it would lead to lithium evolution in the cell, and lithium evolution would reduce the cycle performance of the cell. Prior art solutions are disclosed by CN 105 958 124 A that teaches a wound battery assembly where the electrodes have adjacent layers of materials having different "gram capacity", and by US 2020/144600 A1, which relates to an electrode for a secondary battery, the electrode having two overlapping layers of active material. SUMMARY In view of this, the present application provides an electrochemical device and electronic device in order to improve the problem of lithium evolution from an electrode plate. An electrochemical device provided by the present application, as defined in independent claim 1 comprises an electrode assembly, the electrode assembly comprises a first electrode plate, a second electrode plate and a separator. The separator is provided between the first electrode plate and the second electrode plate. The first electrode plate comprises an active material layer, the active material layer comprises at least one first active material layer and at least one second active material layer. The at least one first active material layer and the at least one second active material layer are provided along a length direction of the electrode plate, and the electrode assembly is formed by winding the first electrode plate, the second electrode plate and the separator. The electrode assembly comprises a planar area and a corner area, the first electrode plate is a positive electrode plate, the first active material layer is a first positive electrode active material layer, the second active material layer is a second positive electrode active material layer, at least a portion of the first positive electrode active material layer is located in the corner area, and at least a portion of the second positive electrode active material layer is located in the planar area. The second positive electrode active material layer comprises a second positive electrode conductive agent, the first positive electrode active material layer comprises a first positive electrode conductive agent. The electrochemical device of claim 1 is characterized in that a mass percentage of the first positive electrode conductive agent in the first positive electrode active material layer is greater than or equal to a mass percentage of the second positive electrode conductive agent in the second positive electrode active material layer, and a lithium ion diffusion rate of the first active material layer is greater than or equal to 1.2 times that of a lithium ion diffusion rate of the second active material layer. Optionally, the mass percentage of the first positive electrode conductive agent in the first positive electrode active material layer is 0.5% to 5.5%, and the mass percentage of the second positive electrode conductive agent in the second positive electrode active material layer is 0.5% to 5%. Optionally, the compacted density of the second positive electrode active material layer is greater than or equal to that of the first positive electrode active material layer. Another electrochemical device provided by the present application, as defined in independent claim 4, comprises an electrode assembly, the electrode assembly comprises a first electrode plate, a second electrode plate and a separator. The separator is provided between the first electrode plate and the second electrode plate. The first electrode plate comprises an active material layer, the active material layer comprises at least one first active material layer and at least one second active material layer. The at least one first active material layer and the at least one second active material layer are provided along a length direction of the electrode plate, and the electrode