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US-20260128318-A1 - COATING LIQUID FOR ELECTRODE FORMATION

US20260128318A1US 20260128318 A1US20260128318 A1US 20260128318A1US-20260128318-A1

Abstract

A carbon nanotube dispersion may have excellent dispersibility. Such a carbon nanotube dispersion may include at least carbon nanotubes, oxidized cellulose nanofibers, and water, wherein, of the oxidized cellulose nanofibers, 85% or more of the oxidized cellulose nanofibers have a fiber length in a range of from 50 to 250 nm.

Inventors

  • Takayuki Hayakawa
  • Ryosuke MATSUSHIMA
  • Satoshi Sakuma
  • Hiroshi Abe

Assignees

  • MITSUBISHI PENCIL COMPANY, LIMITED

Dates

Publication Date
20260507
Application Date
20231030
Priority Date
20221031

Claims (18)

  1. 1 . A coating liquid suitable for electrode layer formation, the coating liquid comprising: a carbon nanotube dispersion coating liquid comprising carbon nanotubes, oxidized cellulose nanofibers, an active material, a binder, and water, wherein the oxidized cellulose nanofibers have a C═O/C—O peak height ratio, of a peak height attributed to C═O, around 1610 cm −1 , to a peak height attributed to C—O, around 1062 cm −1 , of 0.70 or less in infrared spectroscopy, or wherein the oxidized cellulose nanofibers have a C═O/O—H peak height ratio, of a peak height attributed to C═O, around 1610 cm −1 , to a peak height attributed to O—H, around 3340 cm −1 , of 1.35 or less in infrared spectroscopy.
  2. 2 . The coating liquid claim 1 , wherein, of the oxidized cellulose nanofibers, 85% or more of the oxidized cellulose nanofibers have a fiber length in a range of from 50 to 250 nm.
  3. 3 . The coating liquid claim 1 , wherein the coating liquid structural resilience.
  4. 4 . The coating liquid of claim 1 , wherein the coating liquid has a thixotropic property and a ratio of structural resilience of 0.75 or more.
  5. 5 . The coating liquid of claim 1 , wherein the binder is a synthetic rubber.
  6. 6 . A composition suitable for an electrode produced from the coating liquid of claim 1 .
  7. 7 . The coating liquid of claim 1 , wherein the C═O/C—O peak height ratio of the oxidized cellulose nanofibers is 0.70 or less.
  8. 8 . The coating liquid of claim 1 , wherein the C═O/O—H peak height ratio of the oxidized cellulose nanofibers is 1.35 or less.
  9. 9 . The coating liquid of claim 1 , wherein, of the oxidized cellulose nanofibers, 85% or more of the oxidized cellulose nanofibers have a fiber length in a range of from 50 to 250 nm, and wherein the coating liquid has structural resilience.
  10. 10 . The coating liquid of claim 1 , wherein, of the oxidized cellulose nanofibers, 85% or more of the oxidized cellulose nanofibers have a fiber length in a range of from 50 to 250 nm, and wherein the coating liquid has a thixotropic property and a ratio of structural resilience of 0.75 or more.
  11. 11 . The coating liquid of claim 1 , wherein, of the oxidized cellulose nanofibers, 85% or more of the oxidized cellulose nanofibers have a fiber length in a range of from 50 to 250 nm, and wherein the binder is a synthetic rubber.
  12. 12 . The coating liquid of claim 1 , wherein, of the oxidized cellulose nanofibers, 85% or more of the oxidized cellulose nanofibers have a fiber length in a range of from 50 to 250 nm, wherein the coating liquid has a thixotropic property and a ratio of structural resilience of 0.75 or more, and wherein the binder is a synthetic rubber.
  13. 13 . The coating liquid of claim 1 , wherein, of the oxidized cellulose nanofibers, 85% or more of the oxidized cellulose nanofibers have a fiber length in a range of from 50 to 250 nm, wherein the coating liquid has structural resilience, and wherein the binder is a synthetic rubber.
  14. 14 . The coating liquid of claim 1 , wherein, of the oxidized cellulose nanofibers, 85% or more of the oxidized cellulose nanofibers have a fiber length in a range of from 50 to 250 nm, wherein the coating liquid has a thixotropic property and a ratio of structural resilience of 0.75 or more, wherein the binder is a synthetic rubber, and wherein the C═O/C—O peak height ratio of the oxidized cellulose nanofibers is 0.70 or less.
  15. 15 . The coating liquid of claim 1 , wherein the coating liquid has structural resilience, and wherein the binder is a synthetic rubber.
  16. 16 . The coating liquid of claim 1 , wherein the coating liquid has a thixotropic property and a ratio of structural resilience of 0.75 or more, and wherein the binder is a synthetic rubber.
  17. 17 . A composition suitable for an electrode produced from the coating liquid of claim 2 .
  18. 18 . A composition suitable for an electrode produced from the coating liquid of claim 3 .

Description

TECHNICAL FIELD The present invention relates to a coating liquid for electrode formation, the coating liquid serving as a production raw material of an electrode of a lithium ion battery or the like. BACKGROUND ART As electric vehicles became widespread and as mobile devices such as cellular phones and notebook computers became smaller and lighter and acquired higher performance, secondary batteries having high energy densities and higher capacities of the secondary batteries have been demanded. In such circumstances, many devices use lithium ion secondary batteries using non-aqueous electrolytes because of their characteristics such as high energy density and high voltage. Efficient formation of an electrically conductive network with good electrical conductivity performance and a reduced electrode resistance by using a small amount of a carbon nanotube dispersion or the like by using the carbon nanotube dispersion or the like as a negative electrode material and/or a positive electrode material used for these lithium ion secondary batteries and the like have been studied. Recently, a carbon nanotube dispersion using cellulose nanofibers as a dispersing agent and the like have been also known. For example, Patent Document 1 describes a carbon nanotube dispersion containing carbon nanotubes, cellulose nanofibers, and a dispersion medium to provide a carbon nanotube dispersion that suppresses aggregation of carbon nanotubes and that exhibits high dispersion stability, the cellulose nanofiber being fine cellulose fibers having a maximum fiber size of 1000 nm or less and a number average fiber size of 2 nm or more and 150 nm or less, some hydroxy groups of the fine cellulose fibers being substituted with at least one functional group selected from the group consisting of a carboxyl group and an aldehyde group, and a cellulose I type crystal structure being included. Patent Document 2 describes a nanomaterial composition containing a dispersion medium and cellulose nanofibers and carbon nanotubes dispersed in the dispersion medium to provide a nanomaterial composition that can improve a surface hardness when a molded article is formed. Furthermore, Patent Document 3 describes a dispersion stabilizer for an electrode coating liquid to provide a composition containing a dispersion stabilizer for an electrode coating liquid of a power storage device, the dispersion stabilizer exhibiting excellent dispersion stability of an electrode active material and an electrically conductive material and being capable of producing a homogeneous electrode even when a dispersing device with a weak shear force is used. The dispersion stabilizer for an electrode coating liquid of a power storage device contains cellulose fibers that has (a) a number average width of a short width of 2 to 200 nm, (b) an aspect ratio of 7.5 or more and 250 or less, and (C) a cellulose I type crystal, in which a degree of crystallinity is 70% or more and 95% or less, and a dispersion for electrode coating further contains (d) an anionic functional group, and (e) the anionic functional group being a carboxyl group, for which the content is 1.2 to 2.5 mmol/g. Furthermore, Patent Document 4 describes a binding agent composition for an electrode to provide a binding agent composition for an electrode that can provide an electrode having a high durability even in a case where an active material with a large volume change is used, an electrode for a power storage device produced by using the binding agent composition, and a power storage device including the electrode for a power storage device. The binding agent composition for an electrode contains (A) at least one type or two or more types of polymer components selected from the group consisting of a fluorine-based polymer, a butadiene-based polymer, and a thermoplastic elastomer, (B) a fibrous nanocarbon material having an average fiber size of 0.5 nm or more and 20 nm or less and a fiber length of 0.5 μm or more and 1 mm or less, (C) a cellulose material, (D) nanocellulose fibers, and (E) water, a mass ratio of the (A) and the (B) described above satisfies (A)/(B)=60/40 to 98/2. Patent Document 5 describes a dispersion containing a dispersion medium, metal-containing oxidized cellulose nanofibers containing a metal in a form of a salt other than sodium, and single-walled nanotubes. As oxidized cellulose nanofibers, carboxylated cellulose nanofibers obtained by TEMPO oxidation are described; however, the properties thereof are not described. For the TEMPO oxidation of the cellulose nanofibers, the oxidation reaction is typically performed as complete as possible. Furthermore, “Progress report for outsourced performance evaluation of cellulose nanofiber-applied products in 2017 (entrusted business from Ministry of the Environment in 2017) (identification of issues for practical use of lithium ion battery for vehicle with start-stop system to which cellulose nanofibers have been applied), Mar. 16, 2018: