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CN-121986134-A - Release film for lithium transfer and method for producing same

CN121986134ACN 121986134 ACN121986134 ACN 121986134ACN-121986134-A

Abstract

The present invention relates to a release film for lithium transfer and a method of manufacturing the same, and more particularly, to a release film for transferring lithium (Li) to a battery current collector after depositing the same on the release film. By minimizing the generation of pinholes when lithium (Li) is deposited on a release film, not only is deposition efficiency excellent, but also the efficiency of transferring lithium deposited on the release film to a current collector is excellent, and a method for manufacturing the same.

Inventors

  • ZHANG NANYUN
  • HUANGFU KUI
  • Qian Chenghuan
  • JIN ZAILONG
  • Jin Longkui
  • Han Yinting

Assignees

  • 栗村化学株式会社

Dates

Publication Date
20260505
Application Date
20241010
Priority Date
20231113

Claims (15)

  1. 1. A release film for lithium transfer is formed by sequentially laminating a first release layer, a base film and a second release layer, The following condition (1) is satisfied: (1)A<B In the condition (1), a represents the release force of the first release layer, and B represents the release force of the second release layer.
  2. 2. The release film for lithium transfer according to claim 1, wherein, The following condition (2) is further satisfied: (2)A:B=1:1.1~5.0 In the condition (2), a represents the release force of the first release layer, and B represents the release force of the second release layer.
  3. 3. The release film for lithium transfer according to claim 1, wherein, When the first release layer is irradiated with white light after lithium is deposited on one surface of the second release layer at a thickness of 2 to 25 μm, the number of pinholes per 10cm×10cm unit area in the deposited lithium is 100 or less.
  4. 4. The release film for lithium transfer according to claim 3, wherein, When the first release layer is irradiated with white light after lithium is deposited on one surface of the second release layer at a thickness of 2-8 [ mu ] m, the number of pinholes per 10cm×10cm unit area in the deposited lithium is 100 or less.
  5. 5. The release film for lithium transfer according to claim 1, wherein, The second release layer comprises a resin composition, Wherein the resin composition comprises 10 to 70 wt% of a silicone resin based on the total weight%.
  6. 6. The release film for lithium transfer according to claim 5, wherein, The second release layer comprises 0.1-5 parts by weight of catalyst and 0.1-5 parts by weight of adhesion improver relative to 100 parts by weight of the resin composition.
  7. 7. The release film for lithium transfer according to claim 1, wherein, The first release layer comprises 2.2-25 wt% of silicon (Si) based on the total weight percent, The second release layer comprises 2-5 wt% of silicon (Si) based on the total weight percent.
  8. 8. The release film for lithium transfer according to claim 1, wherein, The base film includes 1 or more selected from polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyimide (PI), and Polyethylene (PE).
  9. 9. The release film for lithium transfer according to claim 5, wherein, The resin composition comprises a silicon-based resin and a non-silicon-based resin, The silicone resin comprises at least 1 selected from the group consisting of addition reaction type silicone resins, condensation reaction type silicone resins and UV reaction type silicone resins, The non-silicone resin includes at least 1 selected from cellulose resins, acrylate resins, melamine resins, and alkyd resins.
  10. 10. A method for manufacturing a release film for lithium transfer, comprising the steps of: a first step of preparing a base film, and A second step of coating a first release layer-forming composition on one surface of the base film, and coating a second release layer-forming composition on the other surface of the base film, and then curing the composition to form a first release layer on one surface of the base film and a second release layer on the other surface of the base film; the following condition (1) is satisfied: (1)A<B In the condition (1), a represents the release force of the first release layer, and B represents the release force of the second release layer.
  11. 11. The method for producing a release film for lithium transfer according to claim 10, wherein, The following condition (2) is further satisfied: (1)A:B=1:1.1~5.0 In the condition (2), a represents the release force of the first release layer, and B represents the release force of the second release layer.
  12. 12. The method for producing a release film for lithium transfer according to claim 10, wherein, When the first release layer is irradiated with white light after lithium is deposited on one surface of the second release layer at a thickness of 2 to 25 μm, the number of pinholes per 10cm×10cm unit area in the deposited lithium is 100 or less.
  13. 13. The method for producing a release film for lithium transfer according to claim 10, wherein, The second release layer forming composition is formed by mixing a resin composition, a catalyst, an adhesive force improver and a solvent, The resin composition comprises 10 to 70 wt% of a silicone resin based on the total weight%.
  14. 14. The method for producing a release film for lithium transfer according to claim 13, wherein, The second release layer forming composition is formed by mixing 0.1-5 parts by weight of a catalyst, 0.1-5 parts by weight of an adhesion improver and 800-1000 parts by weight of a solvent with respect to 100 parts by weight of the resin composition.
  15. 15. The method for producing a release film for lithium transfer according to claim 10, wherein, The curing is carried out at a temperature of 100-140 ℃ for 10-40 seconds.

Description

Release film for lithium transfer and method for producing same Technical Field The invention relates to a release film for lithium transfer and a manufacturing method thereof. More particularly, the present invention relates to a release film for lithium transfer, which is used to deposit lithium (Li) on a release film and transfer it to a current collector of a battery, and which is capable of minimizing the generation of pinholes (pin holes) when depositing lithium (Li), thereby having excellent deposition efficiency, and having excellent efficiency of transferring lithium deposited on the release film to the current collector, and a method for manufacturing the same. Background In a battery, particularly a secondary battery, a portion of lithium ions released from a positive electrode during the first charge is occluded in a negative electrode, resulting in a battery capacity lower than the theoretical capacity of the negative electrode material. In order to avoid such irreversible capacity loss, a technique has been disclosed in which lithium corresponding to the irreversible capacity loss is previously occluded in the negative electrode, and then the secondary battery is assembled and charge and discharge are started. By using this technique, lithium ions released from the positive electrode at the time of initial charge can be recovered to the negative electrode at a high rate, thereby increasing the battery capacity. On the other hand, as a general method of previously storing lithium in a negative electrode, a method of depositing lithium in a negative electrode is adopted. In order to increase the amount of lithium deposition corresponding to the irreversible capacity, it has been studied to increase the amount of lithium deposited by pre-treating a graphite material or a silicon-graphite material on a current collector. However, graphite materials have a limited capacity when lithium ions move, and silicon-graphite materials cause a sharp volume expansion when lithium ions move, thereby possibly affecting battery durability. For the above reasons, there is a need to develop a method of pre-charging a sufficient amount of lithium into a negative electrode and/or a new method capable of preventing volume expansion due to an increase in the amount of lithium, wherein one method is to deposit lithium metal on a release film and then transfer it to a current collector, preferably a negative electrode current collector. In view of the foregoing, with respect to a method of transferring lithium to a current collector after deposition of lithium on a release film, a solution for ensuring uniform deposition of lithium and obtaining high transfer efficiency is required. Disclosure of Invention Technical problem to be solved by the invention The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a release film for lithium transfer capable of ensuring uniform deposition performance and transfer efficiency, and a method for manufacturing the same. In addition, in order to facilitate use, it is an object of the present invention to provide a release film for lithium transfer and a method for producing the same, which have excellent release properties and can prevent transfer of lithium (Li) to other portions than the portion where lithium (Li) is deposited even when a plurality of release films for lithium transfer of the present invention are laminated and separated again. Means for solving the problems In order to solve the above problems, the release film for lithium transfer of the present invention may have a structure in which a first release layer, a base film, and a second release layer are laminated in this order. In a preferred embodiment of the present invention, a release film for lithium transfer according to the present invention may satisfy the following condition (1): (1)A<B In the condition (1), a represents the release force of the first release layer, and B represents the release force of the second release layer. In a preferred embodiment of the present invention, a release film for lithium transfer of the present invention may further satisfy the following condition (2): (2)A:B=1:1.1~5.0 In the condition (2), a represents the release force of the first release layer, and B represents the release force of the second release layer. In a preferred embodiment of the present invention, the base film and the first release layer may have a thickness ratio of 1:0.0014 to 0.0026. In a preferred embodiment of the present invention, the base film and the first release layer may have a thickness ratio of 2:0.001 to 0.0018. In a preferred embodiment of the present invention, after lithium is deposited on one side of the second release layer in a thickness of 2 to 25 μm, when white light (WHITE LIGHT) is irradiated to the first release layer, pinholes (pin holes) generated per 10cm×10cm unit area in the deposited lithium may be 100