Non-aqueous electrolyte secondary cell containing negative active material including scaly graphite particles and graphite particles coated with amorphous carbon particles and amorphous carbon layer and method of manufacturing the same

Patent metadata

Field	Value
Publication number	US-9577245-B2
Application number	US-201214129436-A
Country	US
Kind code	B2
Filing date	Jun 25, 2012
Priority date	Jun 30, 2011
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

Abstract

Disclosed is a non-aqueous electrolyte secondary cell excellent in capacity retention rate and I-V characteristics after repeated cycles. The secondary cell contains a negative electrode active material containing scaly graphite particles and coated graphite particles. The coated graphite particles contain graphite particles and a coating layer coating the surfaces of the graphite particles. The coating layer contains amorphous carbon particles and an amorphous carbon layer. It is preferable that the negative electrode active material contain 1 to 6% by mass of the scaly graphite particles and that the graphite particles, the amorphous carbon particles, and the amorphous carbon layer be in a mass ratio of 100:α:β where 1≦α≦10, 1≦β≦10, and α≦1.34β.

First claim

The invention claimed is:

1. A non-aqueous electrolyte secondary cell comprising:
a positive electrode containing a positive electrode active material;
a negative electrode containing a negative electrode active material; and
a non-aqueous electrolyte,
wherein
the negative electrode active material contains:
scaly graphite particles; and
coated graphite particles containing graphite particles and a coating layer coating surfaces of the graphite particles, the coating layer containing amorphous carbon particles and an amorphous carbon layer,

the coated graphite particles have a specific surface area of 4 to 6 m 2 /g,
the coated graphite particles have a tapped bulk density of not less than 0.9 g/cc,
the scaly graphite particles have a specific surface area of 5 to 15 m 2 /g,
the scaly graphite particles have a tapped bulk density of not less than 0.05 g/cc,
the negative electrode includes a negative electrode active material layer containing the negative electrode active material and a negative electrode binder for binding the negative electrode active material,
the negative electrode active material layer contains 1 to 6% by mass of the scaly graphite particles,
the negative electrode active material layer contains 92.7 to 97.7% by mass of the coated graphite particles, and
the negative electrode binder contains styrene-butadiene rubber.

2. The non-aqueous electrolyte secondary cell of claim 1 , wherein the coated graphite particles contain the graphite particles, the amorphous carbon particles, and the amorphous carbon layer in a mass ratio of 100:α:β where 1≦α≦10, 1≦β≦10, and α≦1.34β.

3. The non-aqueous electrolyte secondary cell of claim 1 , wherein the coated graphite particles have a median diameter of 12 to 16 μm when measured by laser diffraction.

4. The non-aqueous electrolyte secondary cell of claim 1 , wherein the scaly graphite particles have a median diameter of 5 to 10 μm when measured by laser diffraction.

5. The non-aqueous electrolyte secondary cell of claim 1 , wherein the positive electrode active material is a lithium-transition metal composite oxide having a layered structure expressed by Li 1+a (Ni x Co y Mn z ) 1−a O 2 where 0≦a≦0.15, 0.1≦x≦0.6, 0≦y≦0.5, x+y+z=1.

6. The non-aqueous electrolyte secondary cell of claim 1 , wherein the positive electrode active material is a lithium-transition metal composite oxide having a layered structure expressed by Li 1+a (Ni x Co y Mn z M b ) 1−a O 2 where M is at least one selected from the group consisting of Al, Ti, Zr, Nb, B, Mg, and Mo; and 0≦a≦0.15, 0≦b≦0.02, 0.1≦x≦0.6, 0≦y≦0.5, 0.2≦z≦0.4; x+y+z=1.

7. The non-aqueous electrolyte secondary cell of claim 1 has a capacity of not less than 4 Ah and an energy density of not less than 50 Wh/kg.

8. The non-aqueous electrolyte secondary cell of claim 1 has a capacity of not less than 20 Ah and an energy density of not less than 100 Wh/kg.

9. A method of manufacturing a non-aqueous electrolyte secondary cell, comprising the steps of:
mixing graphite particles, amorphous carbon particles, and a binder;
sintering a mixture obtained in the step of mixing the graphite particles, the amorphous carbon particles, and the binder at 900 to 1500° C. in a reducing atmosphere, thereby forming, on surfaces of the graphite particles, a coating layer containing the amorphous carbon particles and an amorphous carbon layer, the amorphous carbon layer being a carbonized product of the binder; and
preparing a negative electrode containing a negative electrode active material, the negative electrode active material at least containing the coated graphite particles prepared in the step of sintering and scaly graphite particles,
wherein,
the coated graphite particles have a specific surface area of 4 to 6 m 2 /g,
the coated graphite particles have a tapped bulk density of not less than 0.9 g/cc,
the scaly graphite particles have a specific surface area of 5 to 15 m 2 /g,
the scaly graphite particles have a tapped bulk density of not less than 0.05 g/cc,
the negative electrode includes a negative electrode active material layer containing the negative electrode active material and a negative electrode binder for binding the negative electrode active material,
the negative electrode active material layer contains 1 to 6% by mass of the scaly graphite particles,
the negative electrode active material layer contains 92.7 to 97.7% by mass of the coated graphite particles, and
the negative electrode binder contains styrene-butadiene rubber.

10. The method of claim 9 , wherein
the amorphous carbon particles are carbon black;
the binder is a pitch; and
in the step of mixture, the graphite particles, the carbon black, and the pitch are mixed in a mass ratio of 100:α:β where 1≦α≦β≦10.

Assignees

• YAMAMI Shinichi
• Tode Shingo
• Fujihara Toyoki
• Nohma Toshiyuki
• Sanyo Electric Co

Inventors

• YAMAMI Shinichi
• Tode Shingo
• Fujihara Toyoki
• Nohma Toshiyuki

Classifications

• H01M4/366

  as layered products · CPC title

• H01M4/505

  of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• H01M4/133 Primary

  Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx · CPC title

• H01M4/525

  of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy · CPC title