Negative electrode for nonaqueous secondary battery and nonaqueous secondary battery, negative electrode active material and method for producing same, complex including nano silicon, carbon layer, and cationic polymer layer, and method for producing complex formed of nano silicon and carbon layer

Patent metadata

Field	Value
Publication number	US-10446838-B2
Application number	US-201415115320-A
Country	US
Kind code	B2
Filing date	Aug 27, 2014
Priority date	Jan 31, 2014
Publication date	Oct 15, 2019
Grant date	Oct 15, 2019

Abstract

An active material including: a first active material that contains a nano silicon produced by heating a layered polysilane represented by a composition formula (SiH)n and having a structure in which multiple six-membered rings formed from silicon atoms are connected; and a second active material that contains a graphite, is used in a negative electrode. With this, expansion and contraction due to stress during charging and discharging can be mitigated, and thereby cycle characteristics improve.

First claim

The invention claimed is:

1. A negative electrode active material comprising a complex including:
nano silicon aggregated particles each having a structure in which multiple layers of a plate-like silicon body, having a structure in which nano-sized silicon particles are arranged as layers, are overlaid in a thickness direction thereof; and
a carbon layer having a thickness within a range of 1 nm to 100 nm and at least formed on a surface of the plate-like silicon body, and satisfying following relational formula (1) regarding average thickness (R) and standard deviation (σ) of the thickness:
R/ 3σ>1.  Relational formula (1):

2. A negative electrode for nonaqueous secondary batteries, the negative electrode comprising a current collector and a negative electrode active material layer bound to the current collector, wherein
the negative electrode active material layer includes a first active material that is the negative electrode active material according to claim 1 , and a second active material containing a graphite.

3. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein at least one portion of the aggregated particles is covered with the carbon layer, and the carbon layer has a thickness within a range of 1 nm to 100 nm and satisfies following relational formula (1) regarding average thickness (R) and standard deviation (σ) of the thickness:
R/ 3σ>1.  Relational formula (1):

4. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein
a nano silicon of the nano silicon aggregated particles is produced by heating a layered polysilane represented by a composition formula (SiH) n and having, as a basic structure, a structure in which multiple six-membered rings formed from silicon atoms are connected.

5. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein
the graphite is contained by 10 to 90 mass % with respect to a total amount of the first active material and the second active material.

6. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein
the graphite is contained by 10 to 40 mass % with respect to a total amount of the first active material and the second active material.

7. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein
the graphite is contained by 40 to 90 mass % with respect to a total amount of the first active material and the second active material.

8. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein
the complex contains carbon by 1 to 40 mass %.

9. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein
the complex contains a matrix including carbon, and the aggregated particles dispersed in the matrix.

10. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein
the complex contains carbon by 1 to 30 mass %.

11. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein
the plate-like silicon body has a thickness of 20 nm to 50 nm and a long axis direction length of 0.1 μm to 50 μm.

12. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein
the plate-like silicon body has a structure in which flat nano silicon particles are arranged in layers.

13. The negative electrode for nonaqueous secondary batteries according to claim 12 , wherein
the flat nano silicon particles each have a long axis direction length of 5 nm to 20 nm and a short axis direction length of 2 nm to 5 nm.

14. The negative electrode for nonaqueous secondary batteries according to claim 12 , wherein
a ratio (long axis/short axis) between lengths of a long axis and a short axis of the flat nano silicon particles is 2.5 to 10.

15. The negative electrode for nonaqueous secondary batteries according to claim 2 , wherein
the carbon layer is interposed between layers of the silicon particles arranged in layers, or between layers of flat nano silicon particles arranged in layers.

16. A nonaqueous secondary battery comprising the negative electrode according to claim 2 .

17. The nonaqueous secondary battery according to claim 16 , wherein the nonaqueous secondary battery is a lithium ion secondary battery.

18. A method for producing a negative electrode active material, the method, with which the complex according to claim 1 is formed, comprising the following steps to be performed in the following order:
an aggregated particle formation step of obtaining nano silicon aggregated particles in which multiple layers of a plate-like silicon body, having a structure in which nano-sized silicon particles are arranged as layers, are overlaid in a thickness direction thereof, by heating a layered polysilane represented by a composition formula (SiH) n and having, as a basic structure, a structure in which multiple six-membered rings formed from silicon atoms are connected; and
a carbonization step of forming a carbon layer at least on a surface of the plate-like silicon body by bringing the nano silicon aggregated particles in contact with an organic gas in a non-oxidizing atmosphere and applying heat thereto to carbonize the organic gas.

19. An electrical storage device comprising a negative electrode including the negative electrode active material according to claim 1 .

20. The method for producing the negative electrode active material according to claim 18 , wherein
the organic gas is propane.

21. A complex comprising:
nano silicon aggregated particles each having a structure in which multiple layers of a plate-like silicon body, having a structure in which nano-sized silicon particles are arranged as layers, are overlaid in a thickness direction thereof;
a carbon layer covering the silicon aggregated particles; and
a cationic polymer layer including a cationic polymer covering the carbon layer.

22. A method for producing a complex formed of nano silicon aggregated particles and a carbon layer, the method comprising
mixing CaSi 2 and a halogen-containing polymer to obtain a mixture thereof, and heating the mixture at a temperature not lower than a carbonization temperature of the halogen-containing polymer.

Assignees

• Toyota Jidoshokki Kk

Inventors

• Kondo Takeshi
• Sugiyama Yusuke
• Mohri Takashi
• Oshima Hiroki
• Niimi Tomohiro
• Takahashi Mutsumi
• Goda Nobuhiro
• Sugioka Takahiro
• Kawamoto Yuta

Classifications

• H01M4/364

  as mixtures · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M4/366 Primary

  as layered products · CPC title

• H01M4/587

  for inserting or intercalating light metals · CPC title

• H01M10/0525

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