Nonaqueous electrolyte secondary cell and method for producing same

Patent metadata

Field	Value
Publication number	US-2016294006-A1
Application number	US-201414392275-A
Country	US
Kind code	A1
Filing date	May 27, 2014
Priority date	Jul 2, 2013
Publication date	Oct 6, 2016
Grant date	—

Abstract

A nonaqueous electrolyte secondary cell 10 provided by the present invention includes a nonaqueous electrolyte solution, and an electrode unit 50 that includes a positive electrode 64 and a negative electrode 84. The negative electrode 84 includes a negative electrode current collector 82 and a negative electrode mixture layer 86 that contains at least a negative electrode active material and is formed on a surface of the negative electrode current collector 82. A coating film containing at least boron (B) and sodium (Na) is formed on a surface of the negative electrode active material in the negative electrode mixture layer 86, and the ratio A/B is less than 0.1 where A is the amount [μg/cm 2 ] of sodium (Na) and B is the amount [μg/cm 2 ] of boron (B) that are contained in the coating film per unit area of the negative electrode mixture layer 86.

First claim

1 . A nonaqueous electrolyte secondary cell comprising a nonaqueous electrolyte solution, and an electrode unit that includes a positive electrode and a negative electrode, wherein
the negative electrode includes a negative electrode current collector and a negative electrode mixture layer that contains at least a negative electrode active material and is formed on a surface of the negative electrode current collector, a coating film containing at least boron (B) and sodium (Na) is formed on a surface of the negative electrode active material in the negative electrode mixture layer, and a ratio A/B is less than 0.1 where A is the amount [μg/cm 2 ] of sodium (Na) and B is the amount [μg/cm 2 ] of boron (B) that are contained in the coating film per unit area of the negative electrode mixture layer.

2 . The nonaqueous electrolyte secondary cell according to claim 1 , wherein
the positive electrode includes a positive electrode current collector and a positive electrode mixture layer that contains at least a positive electrode active material and is formed on a surface of the positive electrode current collector, and the positive electrode active material is a lithium transition metal composite oxide.

3 . The nonaqueous electrolyte secondary cell according to claim 1 , wherein the negative electrode contains a binder in the negative electrode mixture layer, and the binder is a styrene-butadiene rubber.

4 . The nonaqueous electrolyte secondary cell according to claim 1 , wherein the electrode unit further includes a separator disposed between the positive electrode and the negative electrode.

5 . The nonaqueous electrolyte secondary cell according to claim 1 , wherein the nonaqueous electrolyte solution contains lithium bis(oxalato)borate.

6 . A method for producing a nonaqueous electrolyte secondary cell, the method comprising:
a step of preparing a positive electrode that contains a positive electrode active material, and a negative electrode that contains a negative electrode active material, a sodium (Na) component being present as an unavoidable impurity in at least one of the prepared positive electrode and negative electrode; a step of removing at least a portion of the sodium (Na) component by washing, with a nonaqueous electrolyte solution, the electrode containing the sodium (Na) component selected from the positive electrode and negative electrode; a step of fabricating an electrode unit using the positive electrode and/or negative electrode that has been subjected to the removal step; a step of fabricating an assembly in which the electrode unit is housed within a cell case; a step of injecting, into the cell case, a nonaqueous electrolyte solution to which lithium bis(oxalato)borate has been added; and a step of charging the assembly to a prescribed charge voltage and thereafter discharging the assembly to a prescribed discharge voltage.

7 . The production method according to claim 6 , wherein the sodium (Na) component is removed in the removal step so as to bring a ratio C/D to less than 0.1 where C is the dissolved amount [mmol/L] of the sodium ion that dissolves from the electrode unit into the nonaqueous electrolyte solution to which lithium bis(oxalato)borate has been added, and D is the amount of addition [mmol/L] of the lithium bis(oxalato)borate.

8 . The production method according to claim 6 , wherein, in the removal step, the positive electrode and/or the negative electrode is immersed in a nonaqueous electrolyte solution that contains at least a lithium salt, and the positive electrode and negative electrode are thereafter washed using a nonaqueous electrolyte solution that does not contain a lithium salt.

9 . The production method according to claim 6 , wherein a separator that is to be disposed between the positive electrode and the negative electrode is additionally prepared in the preparation step, the removal step is carried out on the separator, and the electrode unit is fabricated using the separator after the removal step, and the positive electrode and/or negative electrode having been subjected to the removal step.

10 . The production method according to claim 6 , wherein a lithium transition metal composite oxide is used as the positive electrode active material.

11 . The production method according to claim 6 , wherein a styrene-butadiene rubber is used as a binder contained in the negative electrode.

12 . The production method according to claim 6 , wherein a wound electrode unit is used as the electrode unit, the wound electrode unit being provided by winding an electrode unit in which a positive electrode formed in a sheet shape and a negative electrode formed in a sheet shape are stacked, the electrode unit being wound in a longitudinal direction thereof.

Assignees

• Toyota Motor Co Ltd

Inventors

• Onizuka Hiroshi
• Kondo Hiroki
• Muraoka Hiroki
• Sano Hideki

Classifications

• H01M4/366

  as layered products · CPC title

• H01M10/0587

  of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators · CPC title

• H01M4/485

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title

• H01M10/0567 Primary

  characterised by the additives · CPC title

• H01M2004/027

  Negative electrodes · CPC title