Lithium secondary battery including Si-based anode active material

Patent metadata

Field	Value
Publication number	US-12548854-B2
Application number	US-202318690992-A
Country	US
Kind code	B2
Filing date	Mar 31, 2023
Priority date	Jun 14, 2022
Publication date	Feb 10, 2026
Grant date	Feb 10, 2026

Abstract

Provided is a lithium secondary battery with reduced Hi-pot defects and improved capacity retention rate. According to one aspect of the present disclosure, there is provided a lithium secondary battery including an anode, a cathode, and a separator interposed between the anode and the cathode, in which the anode includes a Si-based anode active material, the separator includes a separator substrate having a plurality of pores and including a polyolefin resin, the polyolefin resin has a polydispersity index (PDI) of 2.5 to 4.2, an average pore size of 20 to 40 nm, and a maximum pore size of 50 nm or less.

First claim

The invention claimed is:

1 . A lithium secondary battery comprising:
an anode comprising a Si-based anode active material, a cathode, a separator interposed between the anode and the cathode, the separator comprising a separator substrate comprising a polyolefin resin having a polydispersity index (PDI) of 2.5 to 4.2, and an organic/inorganic composite coating layer on at least one surface of the separator substrate, the organic/inorganic composite coating layer comprising a crystalline binder and an amorphous binder, wherein the amorphous binder has an average particle size that is larger than an average particle size of the crystalline binder, wherein the separator substrate has a plurality of pores, wherein the plurality of pores have an average pore size of 20 to 40 nm and a maximum pore size of 50 nm or less, and wherein the separator substrate has: a strain of 25% or less when a tensile stress of 15 MPa is applied at 60° C. for 60 seconds and a recovery time of 200 seconds or less to reach a recovery rate of 70% when a tensile stress of 2 MPa is applied at 70° C. for 180 seconds and then removed.

2 . The lithium secondary battery according to claim 1 , wherein the polyolefin resin has a PDI of 2.5 to 4.0,
the plurality of pores have an average pore size of 20 to 39 nm and a maximum pore size of 48 nm or less, and the separator substrate has:
a strain of 23% or less when a tensile stress of 15 MPa is applied at 60° C. for 60 seconds, and
a recovery time of 190 seconds or less to reach a recovery rate of 70% when a tensile stress of 2 MPa is applied at 70° C. for 180 seconds and then removed.

3 . The lithium secondary battery according to claim 1 , wherein the polyolefin resin has a PDI of 2.6 to 3.9,
the plurality of pores have an average pore size of 21 to 38 nm and a maximum pore size of 46 nm or less, and the separator substrate has:
a strain of 21% or less when a tensile stress of 15 MPa is applied at 60° C. for 60 seconds, and
a recovery time of 180 seconds or less to reach a recovery rate of 70% when a tensile stress of 2 MPa is applied at 70° C. for 180 seconds and then removed.

4 . The lithium secondary battery according to claim 3 , wherein the plurality of pores have an average pore size of 22.2 to 36.1 nm, and
the separator substrate has:
a strain of 20.1% or less when a tensile stress of 15 MPa is applied at 60° C. for 60 seconds, and
a recovery time of 178 seconds or less to reach a recovery rate of 70% when a tensile stress of 2 MPa is applied at 70° C. for 180 seconds and then removed.

5 . The lithium secondary battery according to claim 1 , wherein the polyolefin resin has a weight average molecular weight of 500,000 to 1,500,000 g/mol.

6 . The lithium secondary battery according to claim 1 , wherein the separator substrate includes:
a core portion including a mixture of polyethylene and polypropylene, and a polyethylene skin portion on each of both surfaces of the core portion.

7 . The lithium secondary battery according to claim 1 , further comprising an electrolyte,
wherein the crystalline binder and the amorphous binder each independently has a concentration gradient in a thickness direction of the organic/inorganic composite coating layer.

8 . The lithium secondary battery according to claim 1 , wherein the organic/inorganic composite coating layer includes:
a first portion adjacent to the separator substrate, and a second portion opposite the first portion, and a concentration of the crystalline binder in the second portion is higher than a concentration of the crystalline binder in the first portion.

9 . The lithium secondary battery according to claim 1 , wherein the Si-based anode active material includes at least one selected from the group consisting of Si, SiO, and Si alloys.

10 . The lithium secondary battery according to claim 1 , wherein the anode further comprises a graphite.

11 . The lithium secondary battery according to claim 6 , wherein the organic/inorganic composite coating layer has a porosity of 30% to 70% by volume.

12 . The lithium secondary battery according to claim 6 , wherein the crystalline binder includes a copolymer comprising polyvinylidene fluoride.

13 . The lithium secondary battery according to claim 6 , wherein the crystalline binder includes one or more selected from the group consisting of polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-trichloroethylene (PVDF-TCE), and polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE).

14 . The lithium secondary battery according to claim 12 , wherein the amorphous binder includes a copolymer including acrylate as a monomer.

15 . The lithium secondary battery according to claim 14 , wherein the amorphous binder further includes one or more binder materials selected from the group consisting of styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber.

16 . The lithium secondary battery according to claim 15 , wherein the amorphous binder has a crystallinity of 30% or less, and
wherein the crystalline binder has a crystallinity of more than 30%.

17 . The lithium secondary battery according to claim 16 , wherein the crystalline binder has an average particle size in a range of from 200 nm to 350 nm, and
wherein the amorphous binder has an average particle size of from 350 nm to 500 nm.

18 . The lithium secondary battery according to claim 6 , wherein the organic/inorganic composite coating layer further comprises inorganic particles,
wherein the inorganic particles include alumina, wherein the crystalline binder includes a polyvinylidenefluoride-based polymer, and wherein the amorphous binder includes an acrylate-based polymer.

19 . The lithium secondary battery according to claim 18 , wherein the organic/inorganic composite coating layer comprises a binder resin comprising the crystalline binder and the amorphous binder, and the inorganic particles in a ratio of 1:99 to 30:70 by weight.

20 . The lithium secondary battery according to claim 1 , wherein the separator has a wet adhesion to the anode, the cathode, or both, in a range of from 10 to 15 gf/20 mm.

Assignees

• Lg Energy Solution Ltd

Inventors

• Bae Kyeong Hui
• Lee So Yeong
• Jeong So Mi
• Bae Won Sik

Classifications

• H01M4/587

  for inserting or intercalating light metals · CPC title

• H01M4/364

  as mixtures · CPC title

• H01M50/446

  Composite material consisting of a mixture of organic and inorganic materials · CPC title

• H01M50/457

  comprising three or more layers · CPC title

• H01M50/417 Primary

  Polyolefins · CPC title