Lithium ion secondary battery

Patent metadata

Field	Value
Publication number	US-10756337-B2
Application number	US-201615779660-A
Country	US
Kind code	B2
Filing date	Nov 29, 2016
Priority date	Nov 30, 2015
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

Abstract

When the particle size of a silicon material used for a negative electrode active material are small, a large surface area thereof easily causes a side reaction between the active material and an electrolyte solvent to occur, and the cycle characteristics of a lithium ion secondary battery decrease. In order to improve the cycle characteristics, a lithium ion secondary battery according to the present invention is characterized in comprising a negative electrode comprising a material comprising silicon as a constituent element and a polyacrylic acid, and an electrolyte solution comprising a fluoroethylene carbonate, wherein the 50% particle size of the material comprising silicon as a constituent element is 2 μm or less.

First claim

The invention claimed is:

1. A lithium ion secondary battery comprising
a negative electrode comprising a material comprising silicon and a polyacrylic acid, and
an electrolyte solution comprising a fluoroethylene carbonate,
wherein a 50% particle size of the material comprising silicon is 2μm or less,
the polyacrylic acid comprises a monomer unit based on an ethylenically unsaturated carboxylic acid, and a monomer unit based on an ethylenically unsaturated carboxylic ester and/or a monomer unit based on a aromatic vinyl, and
the material comprising silicon is selected from the group consisting of metal silicon, alloys comprising silicon, and silicon oxides.

2. The lithium ion secondary battery according to claim 1 , wherein a specific surface area (CS) of the material comprising silicon is 5 m 2 /cm 3 or more.

3. The lithium ion secondary battery according to claim 1 , wherein a content of the material comprising silicon is 5% by mass or more based on a total amount of a negative electrode active material.

4. The lithium ion secondary battery according to claim 1 , wherein the electrolyte solution comprises at least one additive selected from the group consisting of halogenated cyclic carbonates except for the fluoroethylene carbonate, carboxylic anhydrides, unsaturated cyclic carbonates, cyclic disulfonic acid esters, and open chain disulfonic acid esters.

5. The lithium ion secondary battery according to claim 1 , which satisfies inequality: A >B x C /15,
wherein A represents a concentration of the fluoroethylene carbonate in the electrolyte solution (unit: % by mass), B represents the specific surface area (CS) of the material comprising silicon (unit: m 2 /cm 3 ), and C represents the content of the material comprising silicon based on the total amount of the negative electrode active material (unit: % by mass).

6. A vehicle comprising the lithium ion secondary battery according to claim 1 .

7. The lithium ion secondary battery according to claim 1 , wherein the negative electrode comprises a graphite, and the polyacrylic acid binds the material comprising silicon to the graphite.

8. The lithium ion secondary battery according to claim 1 , wherein a content of the silicon material in the negative electrode active material is 5% by mass or more and 30% by mass or less, and
a content of the fluoroethylene carbonate in the electrolyte solution is 5% by mass or more and 30% by mass or less.

9. The lithium ion secondary battery according to claim 8 , wherein the 50% particle size of the material comprising silicon is 0.5 μm or more and 2 μm or less.

10. The lithium ion secondary battery according to claim 9 , wherein the polyacrylic acid comprises a monomer unit based on a conjugated diene and a monomer unit based on an ethylenically unsaturated carboxylic acid alkali metal salt.

11. The lithium ion secondary battery according to claim 10 , wherein the material comprising silicon is an alloy comprising silicon.

12. The lithium ion secondary battery according to claim 11 , wherein the battery comprises a positive electrode comprising a layered lithium nickel composite oxide represented by formula:
Li α Ni β Co γ Al δ O 2 ,
wherein 1 ≤α≤1.2, β≥0.7,γ≥0.2, and β+γ+δ=1.

13. The lithium ion secondary battery according to claim 12 , wherein the electrolyte solution comprises ethylene carbonate, diethyl carbonate and LiPF 6 .

14. A method for manufacturing a lithium ion secondary battery, comprising the steps of:
fabricating an electrode element by stacking a positive electrode and a negative electrode via a separator, and
encapsulating the electrode element and an electrolyte solution into an outer package,
wherein the electrolyte solution comprises a fluoroethylene carbonate, and the negative electrode comprises a material comprising silicon and a polyacrylic acid, wherein a 50% particle size of the material comprising silicon is 2μm or less,
the polyacrylic acid comprises a monomer unit based on an ethylenically unsaturated carboxylic acid, and a monomer unit based on an ethylenically unsaturated carboxylic ester and/or a monomer unit based on an aromatic vinyl, and
the material comprising silicon is selected from the group consisting of metal silicon, alloys comprising silicon, and silicon oxides.

Assignees

• Nec Corp

Inventors

• Shimanuki Ikiko
• Tamai Suguru
• Kawasaki Daisuke
• Ishikawa Hitoshi

Classifications

• Y02E60/10

  Energy storage using batteries · CPC title

• H01M2004/021

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

• H01M4/386

  Silicon or alloys based on silicon · CPC title

• H01M4/483

  for non-aqueous cells (H01M4/485 takes precedence) · CPC title

• H01M10/0569

  characterised by the solvents · CPC title