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CN-122003753-A - Lithium secondary battery

CN122003753ACN 122003753 ACN122003753 ACN 122003753ACN-122003753-A

Abstract

A lithium secondary battery includes a positive electrode, a negative electrode, and an electrode group in which a separator (13) is wound so as to be disposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte. In the negative electrode, lithium metal is precipitated during charging, and lithium metal is dissolved in the nonaqueous electrolyte during discharging. The separator (13) comprises a base layer (13 a) and an adhesive layer (13 b), wherein the base layer (13 a) has a first main surface (13 a 1) arranged on the negative electrode side and a second main surface (13 a 2) arranged on the positive electrode side, and the adhesive layer (13 b) is formed on the first main surface (13 a 1) of the base layer. At least a part of the adhesive layer (13 b) is adhered to the negative electrode. In a 90% charged state, the average value Tn (μm) of the increase value of the thickness of one surface of the negative electrode caused by charging and the average thickness Ts (μm) of the separator (13) satisfy a relationship of 1.2< Ts/Tn.

Inventors

  • UCHIYAMA YOHEI
  • Wen Yecong

Assignees

  • 松下知识产权经营株式会社

Dates

Publication Date
20260508
Application Date
20240926
Priority Date
20230929

Claims (12)

  1. 1. A lithium secondary battery, comprising: an electrode group in which a positive electrode, a negative electrode, and a separator are wound so that the separator is disposed between the positive electrode and the negative electrode, and A non-aqueous electrolyte, which is a non-aqueous electrolyte, In the negative electrode, lithium metal is precipitated at the time of charging, the lithium metal is dissolved in the nonaqueous electrolyte at the time of discharging, The separator includes a base material layer having a first main surface arranged on the negative electrode side and a second main surface arranged on the positive electrode side, and an adhesive layer formed on the first main surface of the base material layer, At least a part of the adhesive layer is adhered to the negative electrode, In a state of charge of 90%, an average value Tn (μm) of an increase value of a thickness caused by charging of one face of the negative electrode and an average thickness Ts (μm) of the separator satisfy a relationship of 1.2< Ts/Tn.
  2. 2. The lithium secondary battery according to claim 1, wherein the adhesive layer contains a vinylidene fluoride polymer synthesized by polymerizing a monomer containing vinylidene fluoride.
  3. 3. The lithium secondary battery according to claim 1, wherein the adhesive layer contains a copolymer synthesized by polymerizing monomers including vinylidene fluoride and hexafluoropropylene.
  4. 4. The lithium secondary battery according to any one of claims 1 to 3, wherein the adhesive layer contains inorganic particles.
  5. 5. The lithium secondary battery according to any one of claims 1 to 3, wherein the adhesive layer is porous.
  6. 6. The lithium secondary battery according to any one of claim 1 to 3, wherein the nonaqueous electrolyte contains a nonaqueous solvent and a lithium salt, The non-aqueous solvent contains an ether and, The content of the ether in the nonaqueous solvent is 80 mass% or more.
  7. 7. The lithium secondary battery according to any one of claims 1 to 3, wherein the porosity of the base material layer is 40% or more and 90% or less.
  8. 8. The lithium secondary battery according to any one of claims 1 to 3, wherein the negative electrode includes a negative electrode current collector containing austenitic stainless steel.
  9. 9. The lithium secondary battery according to any one of claim 1 to 3, wherein the negative electrode comprises a negative electrode current collector, The negative electrode current collector includes a resin film and a transition metal layer laminated on the resin film, The resin film includes a base resin layer and a surface resin layer formed on the base resin layer, The surface resin layer contains a nitrogen-containing resin.
  10. 10. The lithium secondary battery according to claim 9, wherein the nitrogen-containing resin contains a nitrogen-hydrogen bond.
  11. 11. The lithium secondary battery according to claim 9, wherein the nitrogen-containing resin is a polymer having at least 1 selected from the group consisting of urea bond, melamine structure, triazine ring, amino group, amide bond, aromatic polyamide bond, imide bond, urethane bond, carbodiimide bond, uretdione structure, isocyanurate ring, nitrile group, and amide group.
  12. 12. The lithium secondary battery according to claim 9, wherein the nitrogen-containing resin is a polymer having at least 1 selected from the group consisting of aliphatic isocyanate groups, aromatic isocyanate groups, allophanate groups and biuret groups.

Description

Lithium secondary battery Technical Field The present disclosure relates to lithium secondary batteries. Background Lithium secondary batteries (lithium metal secondary batteries) are used for various purposes as high-capacity secondary batteries. During charging of a lithium secondary battery, lithium metal is deposited on the negative electrode. The precipitated lithium metal dissolves in the nonaqueous electrolyte upon discharge. As for lithium secondary batteries, various proposals have been made. Patent document 1 (japanese patent application laid-open No. 2020-95931) describes "a lithium secondary battery comprising a positive electrode, a negative electrode, and a polymer layer disposed on a surface of the negative electrode, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer, the negative electrode current collector has a planar size larger than that of the positive electrode, the negative electrode current collector has a first region overlapping the positive electrode and a second region not overlapping the positive electrode, the negative electrode active material layer is selectively disposed in the first region of the negative electrode current collector, the polymer layer includes a copolymer of polyvinylidene fluoride (PVDF) and Hexafluoropropylene (HFP) and an ionic liquid, the negative electrode current collector is covered on the first region with the negative electrode active material layer interposed therebetween, and the negative electrode current collector is not covered on the second region with the negative electrode active material layer interposed therebetween. Prior art literature Patent literature Patent document 1 Japanese patent laid-open No. 2020-95931 Disclosure of Invention Problems to be solved by the invention Lithium metal is precipitated in dendrite form during charging of a lithium secondary battery. Further, the expansion of the electrode group during charging of the lithium secondary battery is a great problem. These problems result in a decrease in charge-discharge cycle characteristics. Currently, improvement of charge-discharge cycle characteristics of lithium secondary batteries is demanded. An object of the present disclosure is to provide a lithium secondary battery having excellent charge-discharge cycle characteristics. Solution for solving the problem One aspect of the present disclosure relates to a lithium secondary battery, comprising: an electrode group in which a positive electrode, a negative electrode, and a separator are wound so that the separator is disposed between the positive electrode and the negative electrode, and A non-aqueous electrolyte, which is a non-aqueous electrolyte, In the negative electrode, lithium metal is precipitated at the time of charging, the lithium metal is dissolved in the nonaqueous electrolyte at the time of discharging, The separator includes a base material layer having a first main surface arranged on the negative electrode side and a second main surface arranged on the positive electrode side, and an adhesive layer formed on the first main surface of the base material layer, At least a part of the adhesive layer is adhered to the negative electrode, In a state of charge of 90%, an average value Tn (μm) of an increase value of a thickness caused by charging of one face of the negative electrode and an average thickness Ts (μm) of the separator satisfy a relationship of 1.2< Ts/Tn. ADVANTAGEOUS EFFECTS OF INVENTION According to the present disclosure, a lithium secondary battery having good charge-discharge cycle characteristics can be obtained. The novel features of the invention are set forth in the appended claims, but both the construction and the invention, together with other objects and features thereof, will be best understood from the following detailed description when read in connection with the accompanying drawings. Drawings Fig. 1 is a schematic diagram for explaining a method of measuring the thickness of a negative electrode. Fig. 2 is a cross-sectional view schematically showing an example of a lithium secondary battery according to the present disclosure. Fig. 3 is a cross-sectional view schematically showing an example of the separator. Detailed Description The embodiments according to the present disclosure will be described below by way of examples, but the present disclosure is not limited to the examples described below. In the following description, specific values and/or materials are sometimes exemplified, but other values and/or materials may be applied as long as the effects of the present disclosure can be obtained. In the present specification, the expression "a value a to B" includes a value a and B, and may be replaced with "a value a or more and B or less". In the following description, when the lower limit and the upper limit are exemplified by numerical values regarding specific physical properties, conditions,