Active material for nonaqueous electrolyte secondary battery, negative electrode form, and nonaqueous electrolyte secondary battery

Patent metadata

Field	Value
Publication number	US-9972832-B2
Application number	US-201414309122-A
Country	US
Kind code	B2
Filing date	Jun 19, 2014
Priority date	Jun 20, 2013
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

An active material comprising silica-attached particles in the form of host particles of silicon or silicon compound having spherical silica nano-particles attached to surfaces thereof is suited for use in nonaqueous electrolyte secondary batteries. The spherical silica nano-particles have an average particle size of 5-1000 nm, a particle size distribution D 90 /D 10 of up to 3, and an average circularity of 0.8-1. The active material has high fluidity and exhibits improved cycle performance when used in nonaqueous electrolyte secondary batteries.

First claim

The invention claimed is:

1. An active material for nonaqueous electrolyte secondary batteries, comprising
silica-attached particles consisting of silicon or silicon compound particles and hydrophobic spherical silica nano-particles attached to surfaces of said silicon or silicon compound particles, wherein said hydrophobic spherical silica nano-particles are obtained by subjecting a tetrafunctional silane compound, a partial hydrolytic condensate thereof or a combination thereof to hydrolysis and condensation to form hydrophilic spherical silica nano-particles consisting essentially of SiO 2 units, and subjecting surfaces of the hydrophilic spherical silica nano-particles to hydrophobic treatment, the hydrophobic treatment including steps of introducing R 1 SiO 3/2 units wherein R 1 is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 20 carbon atoms and then introducing R 2 3 SiO 1/2 units wherein R 2 is independently a substituted or unsubstituted monovalent hydrocarbon group of 1 to 6 carbon atoms,
wherein said silica-attached particles are a mixture of said silicon or silicon compound particles and said hydrophobic spherical silica nano-particles, and said hydrophobic spherical silica nano-particles have an average particle size of 5 nm to 1.00 μm, a particle size distribution D 90 /D 10 of up to 3, and an average circularity of 0.8 to 1, and
wherein said silicon or silicon compound particles have a cumulative 50% by volume diameter D 50 of 3.2 to 30 μm.

2. The active material of claim 1 , wherein said hydrophobic spherical silica nano-particles are obtained through steps of (A1) forming hydrophilic spherical silica nano-particles, (A2) first hydrophobic surface treatment with trifunctional silane compound, (A3) concentration, and (A4) second hydrophobic surface treatment with monofunctional silane compound, wherein
the step (A1) of forming hydrophilic spherical silica nano-particles includes subjecting a tetrafunctional silane compound of general formula (I):
Si(OR 3 ) 4   (I)

wherein R 3 is each independently a monovalent hydrocarbon group of 1 to 6 carbon atoms, a partial hydrolyzate thereof or a mixture thereof to hydrolysis and condensation in a mixture of a hydrophilic organic solvent and water in a presence of a basic substance, thereby forming a dispersion of hydrophilic spherical silica nano-particles consisting essentially of SiO 2 units in the solvent mixture,
the first hydrophobic surface treatment (A2) includes adding a trifunctional silane compound of general formula (II):
R 1 Si(OR 4 ) 3   (II)

wherein R 1 is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 20 carbon atoms, and R 4 is each independently a monovalent hydrocarbon group of 1 to 6 carbon atoms, a partial hydrolyzate thereof or a mixture thereof to the dispersion from step (A1), for conducting surface treatment of the hydrophilic spherical silica nano-particles, thereby obtaining a dispersion of spherical silica nano-particles having R 1 SiO 3/2 units (wherein R 1 is as defined above) introduced on their surface in the solvent mixture,
the concentration step (A3) includes concentrating the dispersion from step (A2) by removing a portion of the hydrophilic organic solvent and water therefrom,
the second hydrophobic surface treatment (A4) includes adding a silazane compound of general formula (III):
R 2 3 SiNHSiR 2 3   (III)

wherein R 2 is each independently a substituted or unsubstituted monovalent hydrocarbon group of 1 to 6 carbon atoms, a monofunctional silane compound of general formula (IV):
R 2 3 SiX  (IV)

wherein R 2 is as defined above and X is an OH group or hydrolyzable group, or a mixture thereof to the concentrated dispersion from step (A3), for conducting surface treatment of the surface-treated hydrophilic spherical silica nano-particles having R 1 SiO 3/2 units introduced thereon, thereby introducing R 2 3 SiO 1/2 units (wherein R 2 is as defined above) on their surface.

3. The active material for nonaqueous electrolyte secondary batteries of claim 1 , wherein the silica-attached particles are secondary particles.

4. The active material for nonaqueous electrolyte secondary batteries of claim 1 , wherein the silica-attached particles have a cumulative 50% by volume diameter D 50 of 3.4 to 30 μm.

5. The active material for nonaqueous electrolyte secondary batteries of claim 1 , wherein the silica-attached particles have a BET specific surface area of 0.1 to 300 m 2 /g.

6. The active material for nonaqueous electrolyte secondary batteries of claim 1 , wherein said silicon or silicon compound particles are polycrystalline silica particles or silicon oxide particles.

7. The active material for nonaqueous electrolyte secondary batteries of claim 6 , wherein the hydrophobic spherical silica nano-particles have an average particle size of 11-238 nm, a particle size distribution D 90 /D 10 of 2.21-2.80, and an average circularity of 0.81-0.92.

8. The active material for nonaqueous electrolyte secondary batteries of claim 1 , wherein the amount of said silica nano-particles joined to said silicon or silicon compound particles is 0.1 to 3.0% by weight.

9. A negative electrode foam comprising the active material of claim 1 .

10. A nonaqueous electrolyte secondary battery comprising the negative electrode form of claim 9 , a positive electrode form, a separator, and a nonaqueous electrolyte.

Assignees

• Shinetsu Chemical Co

Inventors

• Nakanishi Tetsuo
• Matsumura Kazuyuki

Classifications

• H01M4/386

  Silicon or alloys based on silicon · CPC title

• C01P2004/32

  Spheres · CPC title

• H01M2004/021

  Physical characteristics, e.g. porosity, surface area · CPC title

• C01P2004/62

  Submicrometer sized, i.e. from 0.1-1 micrometer · CPC title

• C01B33/18

  Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof (preparation of aerogels by dehydrating gels C01B33/158; treatment to enhance the pigmenting or filling properties C09C) · CPC title